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anie.20170218810.1002/anie.201702188C-C bond cleavageShihong8-Febhttps://onlinelibrary.wiley.com/doi/full/10.1002/anie.201702188#N/A
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ja410718r10.1021/ja410718rFALSEhttps://doi.org/10.1021/ja410718rRobert H. MorrisJ. Am. Chem. Soc.A simple equation (pK(a)(THF) = Sigma A(L) + C-charge + C-nd + C-d6) can be used to obtain an estimate of the pK(a) of diamagnetic transition metal hydride and dihydrogen complexes in tetrahydrofuran, and, by use of conversion equations, in other solvents. It involves adding acidity constants A(L) for each of the ligands in the 5-, 6-, 7-, or 8-coordinate conjugate base complex of the hydride or dihydrogen complex along with a correction for the charge (C-charge = -15, 0 or 30 for x = +1, 0 or -1 charge, respectively) and the periodic row of the transition metal (C-nd = 0 for 3d or 4d metal, 2 for 5d metal) as well as a correction for d(6) octahedral acids (C-d6 = 6 for d(6) metal ion in the acid, 0 for others) that are not dihydrogen complexes. Constants A(L) are provided for 13 commonly occurring ligand types; of these, nine neutral ligands are correlated with Lever's electrochemical ligand parameters E-L. This method gives good estimates of the over 170 literature pK(a) values that range from less than zero to 50 with a standard deviation of 3 pK(a) units for complexes of the metals chromium to nickel, molybdenum, ruthenium to palladium, and tungsten to platinum in the periodic table. This approach allows a quick assessment of the acidity of hydride complexes found in nature (e.g., hydrogenases) and in industry (e.g., catalysis and hydrogen energy applications). The pK(a) values calculated for acids that have bulky or large bite angle chelating ligands deviate the most from this correlation. The method also provides an estimate of the base strength of the deprotonated form of the complex.Estimating the Acidity of Transition Metal Hydride and Dihydrogen Complexes by Adding Ligand Acidity Constantsx201496#N/AFALSE
133
jacs.9b0593410.1021/jacs.9b05934?FALSEhttps://doi.org/10.1021/jacs.9b05934Skrydstrup, TJ. Am. Chem. Soc.A series of 4-membered azametallacyCles have been prepared by the oxidative addition of Ni(0) with aziridines. Stoichiometric C-13-labeled carbon monoxide could be efficiently incorporated via Ni-C bond insertion to generate air stable and isolable cyClic Ni-acyl complexes. Upon subjection to a range of C-, N-, O-, and S-nuCleophiles, C-13-labeled beta-amino acids and derivatives thereof, as well as beta-aminoketones, could be rapidly accessed. The methodology proved highly adaptable for the synthesis of the antidiabetic drug, sitagliptin, with a single carbon isotope label.Carbon Isotope Labeling Strategy for beta-Amino Acid Derivatives via Carbonylation of AzanickellacyCles8201962#N/ATRUE
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jacs.7b0274210.1021/jacs.7b02742?FALSEhttps://doi.org/10.1021/jacs.7b02742Zhou, JSJ. Am. Chem. Soc.Nickel-catalyzed addition of Arylboron reagents to ketones results in Aryl olefins directly. The neutral condition, allows acidic protons of alcohols, phenols, and malonates to be present, and fragile structures are also tolerated.Nickel-Catalyzed Direct Synthesis of Aryl Olefins from Ketones and OrganB(OH)2ron Reagents under Neutral Conditions24201764#N/ATRUE
135
jacs.0c1033310.1021/jacs.0c10333?FALSEhttps://doi.org/10.1021/jacs.0c10333Hong, SJ. Am. Chem. Soc.Reported herein is a modular, NiH-catalyzed system capable of proximal-selective hydroamination of unactivated alkenes with diverse amine sources. The key to the successful implementation of this approach is the promotion of NiH insertion into even highly substituted olefins via coordination of the bidentate directing group to the nickel complex. A wide range of primary and secondary amines can be installed in both internal and terminal unactivated alkenes with excellent regiocontrol under the optimized reaction conditions. This protocol is flexible and general for the preparation of a variety of valuable beta- and gamma-amino acid building blocks that would otherwise be difficult to synthesize. The utility of this transformation was further demonstrated by the site-selective late-stage modification of complex and medicinally relevant molecules. Combined experimental and computational studies illuminate the detailed reaction mechanism.NiH-Catalyzed Proximal-Selective Hydroamination of Unactivated Alkenes102020108#N/ATRUE
136
ja990750c10.1021/ja990750c?FALSEhttps://doi.org/10.1021/ja990750cKotora, MJ. Am. Chem. Soc.ZirconacyClopentadienes, prepared from two alkynes or a diyne, reacted with the Alkyl-, trimethylsilyl-, or alkoxy-substituted third alkyne as well as an alkyne with an electron-withdrawing group in the presence of a stoichiometric amount of NiBr2(PPh3)(2) to give benzene derivatives in good yields. Heteroatom-containing a diynes such as dipropargylBenzylamine and propargyl-homopropargylBenzylamine gave ispindoline and tetrahydroisoquinoline derivatives in good to high yields. This procedure was also used for the selective preparation of benzene derivatives from three different alkynes. The use of trimethylsilyl-substituted alkyne as the first, second or third alkyne afforded desilylated benzene derivatives. The reaction of zirconacyClopentadienes with allenes gave benzene derivatives as a mixture of two isomers.Carbon-carbon bond formation reaction of zirconacyClopentadienes with alkynes in the presence of Ni(II)-complexes135199963#N/ATRUE
137
ja903175g10.1021/ja903175g?FALSEhttps://doi.org/10.1021/ja903175gOgoshi, SJ. Am. Chem. Soc.AzaaluminacyClopentenes, which serve as useful precursors for gamma-substituted attylamines, were catalytically prepared from novel Ni-mediated three-component cyClocondensation of an alkyne, an imine, and AlMe3.Ni(O)-Catalyzed Formation of AzaaluminacyClopentenes via AzanickelacyClopentenes: A Unique Nickel/Aluminum Double Transmetalation Reaction37200937#N/ATRUE
138
ja901028210.1021/ja9010282?FALSEhttps://doi.org/10.1021/ja9010282Hiyama, TJ. Am. Chem. Soc.Cyanoformate esters add across 1,2-dienes in the presence of a nickel/PMe2Ph catalyst to afford beta-cyano-alpha-methylenealkanoates regioselectively, which are kinetically favored and readily isomerize to thermodynamically favored alpha-cyanomethyl-alpha,beta-unsaturated Carbonylates at high temperature under the nickel catalysis, possibly through oxidative addition of the C-CN bond. Similar cyanoesterification products are produced from chloroformate esters, trimethylsilyl cyanide, and 1,2-dienes in the presence of a nickel/dppp catalyst. The resulting cyanoesterification products have a structure of allylic cyanide and thus undergo further allyl cyanation reaction across alkynes with the aid of a nickel/P(4-CF3-C6H4)(3) catalyst to afford highly substituted acrylonitrile derivatives.Cyanoesterification of 1,2-Dienes Catalyzed by Nickel64200966#N/ATRUE
139
ja806113v10.1021/ja806113v?FALSEhttps://doi.org/10.1021/ja806113vMorken, JPJ. Am. Chem. Soc.The nickel-catalyzed reaction of Carbonyls and dienes was accomplished in a regio- and stereoselective fashion employing a stoichiometric amount of bis(pinacolato)diboron. This reductive Coupling furnishes an allyl boronic ester as the reaction product, a Compound which was readily converted to the derived allylic alcohol by oxidative workup.Diastereoselective Construction of Functionalized Homoallylic Alcohols by Ni-Catalyzed Diboron-Promoted Coupling of Dienes and Aldehydes64200861#N/ATRUE
142
ja060683410.1021/ja0606834?FALSEhttps://doi.org/10.1021/ja0606834Hiyama, TJ. Am. Chem. Soc.Cyanoesterification of 1,2-dienes: Synthesis and transformations of highly functionalized alpha-cyanomethylacrylate esters82200642#N/ATRUE
143
ja047580a10.1021/ja047580a?FALSEhttps://doi.org/10.1021/ja047580aOdashima, KJ. Am. Chem. Soc.A Ni(O)/ZnX2 system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyClization of Ni(O) species on enones across the alkyne part followed by ZnX2-promoted Cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyClization. When the resulting sigma-Alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyClopentane derivatives. On the other hand, a sigma-Alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the Cleavage of one C-C bond.Ni-catalyzed, ZnX2-assisted domino coupling of enones, alkynes, and alkenes23200455#N/ATRUE
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ja038191410.1021/ja0381914?FALSEhttps://doi.org/10.1021/ja0381914Hillhouse, GLJ. Am. Chem. Soc.Group transfer from nickel imido, phosphinidene, and carbene complexes to ethylene with formation of aziridine, phosphirane, and cyClopropane products138200339#N/ATRUE
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ja00413a01410.1021/ja00413a014?FALSEhttps://doi.org/10.1021/ja00413a014YAMAMOTO, AJ. Am. Chem. Soc.INTERACTION OF NICKEL(0) COMPLEXES WITH ALLYL CarbonylATES, ALLYL ETHERS, ALLYLIC ALCOHOLS, AND Vinyl-ACETATE - PI-COMPLEX FORMATION AND OXIDATIVE ADDITION TO NICKEL INVOLVING ClEAVAGE OF THE ALKENYL-OXYGEN BOND112198164#N/ATRUE
146
ja00341a064?FALSEhttps://pubs.acs.org/doi/10.1021/ja00341a064Susan M. CliftJ. Am. Chem. Soc.Synthesis of carbene complexes of Group IV metals from Alkylidene-bridged heterobimetallic precursors1001983Added by Yizhou#N/ATRUE
147
ja002480010.1021/ja0024800?FALSEhttps://doi.org/10.1021/ja0024800Skrydstrup, TJ. Am. Chem. Soc.A mild and simple method for the selective introduction of carbinol side chains onto glycine residues in peptides is presented as a potential route for the preparation of peptide libraries. A series of di- and tripeptides, as well as one tetrapeptide, each possessing one glycine residue, were first selectively functionalized at this amino acid unit by a two-step sequence involving bromination with N-bromosuccinimide and then sulfide formation by treatment of the unstable glycyl bromide with 2-mercaptopyridine. These modified peptides were then reduced with samarium diiodide at room temperature in the presence of Alkyl aldehydes and ketones, affording a series of peptides in yields of 40-65% containing serine/threonine derivatives as new functionalities. These reactions are quite efficient, considering the presence of as many as four amide protons in the enolate intermediate. The diastereoselectivities of these reactions are low or nonexistent, which is ascribed to either (a) the formation of single enolate, where the neighboring chiral centers impart no influence in the Alkylation step or (b) the generation of an enolate mixture, where each stereoisomer leads to opposite enantiomers with respect to the newly formed amino acid upon Alkylation. The successful nonselective double Alkylation of the tripeptide, Bz-Gly-Val-Gly-OMe, suggests the possibility that the reductive samariation approach to the C-Alkylation of peptides may be a viable route for the preparation of peptide libraries based on multiple serine/threonine derivatives. Finally, a preliminary investigation on one peptide has shown that the addition of Ilo of nickel(II) iodide to these condensation reactions has a significant effect on the coupling yields.Selective side chain introduction onto small peptides mediated by samarium diiodide: A potential route to peptide libraries592000107#N/ATRUE
149
ja00100a02110.1021/ja00100a021?FALSEhttps://doi.org/10.1021/ja00100a021SCHWARZ, HJ. Am. Chem. Soc.Fourier-transform ion cyClotron resonance mass spectrometry has been used to study the gas-phase oxidation of benzene mediated by ''bare'' MO(+) cations (M = Sc, Ti, V, Cr, Mn, Co, and Ni). Oxidation reactions by the oxides of Sc, Ti, and V were not observed, consistent with the stability of the MO(+) bond for the early-transition-metal oxides, and only condensation products, i.e., MO(C6H6)(+), were formed. For Cr through Ni oxide cations, the most abundant process corresponds to the exothermic conversion of benzene to phenol. All oxidation reactions are kinetically efficient; i.e., k(f)/k(C) approximate to 1. The reactivity of each metal oxide cation is examined, and mechanistic details for various processes have been uncovered based an mass spectrometric evidence and labeling studies by using [D-6]benzene and [1,3,5-D-3]benzene. The operation of an intramolecular isotope effect of k(H)/k(D) = 3.7 for MnO+ was evaluated from the relative product intensities of MnOH+ and MnOD+ generated from the reaction with [1,3,5-D-3]benzene. BDE-(Mn+-OH) = 82 +/- 7 kcal/mol has been derived from H-atom-transfer reactions.OXIDATION OF BENZENE MEDIATED BY FIRST-ROW TRANSITION-METAL OXIDE CATIONS - THE REACTIVITY OF SCO plus THROUGH NIO plus IN COMPARISON73199481#N/ATRUE
150
ja00037a00610.1021/ja00037a006?FALSEhttps://doi.org/10.1021/ja00037a006DEMEIJERE, ANEW CYClOPROPYL BUILDING BLOCKS FOR ORGANIC SYNTHESIS .9. NUClEOPHILIC SUBSTITUTIONS OF 1-ALKENYLCYClOPROPYL ESTERS AND 1-ALKYNYLCYClOPROPYL CHLORIDES CATALYZED BY PALLADIUM(O)1992#N/ATRUE
151
c9sc00226j10.1039/c9sc00226j?FALSEhttps://doi.org/10.1039/c9sc00226jChen, MChem. Sci.Stereoselective synthesis of (Z)--boryl-crotylboronate is developed. Ni-catalyzed Z-selective alkene isomerization of -boryl substituted homoallylboronate provided the targeted (Z)-crotylboronate with high selectivity. Stereoselective addition of the novel crotylboron reagent to aldehydes gave (E)--boryl-substituted syn-homoallylic alcohols with excellent diastereoselectivities. The Vinyl boronate unit in the products can be directly used for a subsequent C-C bond-forming transformation as illustrated in the synthesis of the C1-7 fragment of the natural products nannocystin A and nannocystin Ax.(Z)-alpha-Boryl-crotylboron reagents via Z-selective alkene isomerization and application to stereoselective syntheses of (E)--boryl-syn-homoallylic alcohols25201976#N/ATRUE
152
anie.20200174210.1002/anie.202001742?FALSEhttps://doi.org/10.1002/anie.202001742Zhu, SLAngew. Chem.-Int. Edit.A redox-relay migratory hydroArylation of isomeric mixtures of olefins with Arylboronic acids catalyzed by nickel complexes bearing diamine ligands is described. A range of structurally diverse 1,1-diArylalkanes, inCluding those containing a 1,1-diArylated quaternary carbon, were obtained in excellent yields and with high regioselectivity. Preliminary experimental evidence supports the proposed non-dissociated chainwalking of Aryl-nickel(II)-hydride species along the Alkyl chain of alkenes before selective reductive elimination at a Benzylic position. A catalyst loading as low as 0.5 mol % proved to be sufficient in large-scale synthesis while retaining high reactivity, highlighting the practical value of this transformation.Ligand-Enabled Nickel-Catalyzed Redox-Relay Migratory HydroArylation of Alkenes with ArylboronsC-H Activation; cross-coupling; isomerization; nickel catalysis; regioselectivity252020100#N/ATRUE
153
anie.20190107410.1002/anie.201901074?FALSEhttps://doi.org/10.1002/anie.201901074Qin, YAngew. Chem.-Int. Edit.Strictamine and rhazinoline are representative methanoquinolizidine-containing akuammiline alkaloids that possess different stereochemistry at the C16 position. A unified approach to the enantioselective total syntheses of these two molecules is described. The key steps in this synthesis inClude a photocatalytic intra/intermolecular type II radical cascade reaction, a Tsuji-Trost allylation, a palladium- or nickel-mediated cyClization, and a late-stage intramolecular N-Alkylation reaction.Asymmetric Total Syntheses of the Akuammiline Alkaloids (-)-Strictamine and (-)-Rhazinolinealkaloids; cascade reaction; photoredox catalysis; total synthesis; transition metal18201976#N/ATRUE
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anie.20190080110.1002/anie.201900801?FALSEhttps://doi.org/10.1002/anie.201900801Maulide, NAngew. Chem.-Int. Edit.A flexible redox-neutral coupling of aldehydes and alkenes enables rapid access to stereotriads starting from a single stereocenter with perfect levels of enantio- and diastereoselectivity under mild conditions. The versatility of the method is highlighted by the installation of heteroatoms along the tether, which enables a route to structurally diverse building blocks. The formal synthesis of (+)-neopeltolide further demonstrates the synthetic utility of this approach.Diastereo- and Enantioselective Access to Stereotriads through a Flexible Coupling of Substituted Aldehydes and Alkenes5201952#N/ATRUE
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anie.20180557810.1002/anie.201805578?FALSEhttps://doi.org/10.1002/anie.201805578Lam, HWAngew. Chem.-Int. Edit.The enantioselective synthesis of highly functionalized chiral cyClopent-2-enones by the reaction of alkynyl malonate esters with Arylboronic acids is described. These desymmetrizing Arylative cyClizations are catalyzed by a chiral phosphinooxazoline/nickel complex, and cyClization is enabled by the reversible E/Zisomerization of alkenylnickel species. The general methodology is also applicable to the synthesis of 1,6-dihydropyridin-3(2H)-ones.Enantioselective Synthesis of Chiral CyClopent-2-enones by Nickel-Catalyzed Desymmetrization of Malonate Estersasymmetric catalysis; carbocyCles; cyClization; isomerization; nickel28201857#N/ATRUE
156
anie.20171129610.1002/anie.201711296?FALSEhttps://doi.org/10.1002/anie.201711296Sparr, CAngew. Chem.-Int. Edit.Despite the manifold use of heterocyClic fluorophores, only a fraction of the desired dye diversity can be accessed by contemporary synthetic approaches. Herein, we describe a modular method that converts various Carbonylic acid esters directly into a broad spectrum of heteroanthrylium fluorophores. The double addition of heteroatom-bridged 1,5-bifunctional organomagnesium reagents to esters leads to the formation of acridinium, xanthylium, and SiR fluorophores after dehydrative acidic work-up. This one-step synthetic method provides access to organophotoredox catalysts for dual catalysis with nickel and dyes amenable to fluorescence enhancement.Direct Transformation of Esters into HeterocyClic FluorophoresCarbonylic acid esters; fluorophores; Grignard reaction; organomagnesium reagents; photoredox catalysis38201870#N/ATRUE
157
anie.20170753110.1002/anie.201707531?FALSEhttps://doi.org/10.1002/anie.201707531Bower, JFAngew. Chem.-Int. Edit.Nickel-catalyzed coupling of Benzyl acrylates with activated ketones and imines provides gamma-butyrolactones and lactams, respectively. The Benzyl alcohol byproduct released during the lactonization/lactamization event is relayed to the next cyCle where it serves as the reductant for C-C bond formation. This strategy represents a conceptually unique approach to transfer-hydrogenative C-C bond formation, thus providing examples of reductive heterocyClizations where hydrogen embedded within an alcohol leaving group facilitates turnover.Reductive Coupling of Acrylates with Ketones and Ketimines by a Nickel-Catalyzed Transfer-Hydrogenative Strategyalcohols; lactones; nickel; spiro compounds; transfer hydrogenation13201742#N/ATRUE
158
anie.20160170110.1002/anie.201601701?FALSEhttps://doi.org/10.1002/anie.201601701Feng, XMAngew. Chem.-Int. Edit.A highly efficient asymmetric cascade reaction between keto esters and alkynyl alcohols and amides is reported. The success of the reaction was attributed to the combination of chiral Lewis acid N,N-dioxide nickel(II) catalysis with achiral -acid gold(I) catalysis working as an asymmetric relay catalytic system. The corresponding spiroketals and spiroaminals were synthesized in up to 99% yield, 19:1 d.r., and more than 99% ee under mild reaction conditions. Control experiments suggest that the N,N-dioxide ligand was essential for the formation of the spiro products.Bimetallic Gold(I)/Chiral N,N-Dioxide Nickel(II) Asymmetric Relay Catalysis: Chemo- and Enantioselective Synthesis of Spiroketals and Spiroaminalsasymmetric catalysis; cascade reactions; gold; nickel; relay catalysis72201661#N/ATRUE
159
anie.20140464310.1002/anie.201404643?FALSEhttps://doi.org/10.1002/anie.201404643Feng, XMAngew. Chem.-Int. Edit.Highly efficient catalytic asymmetric Claisen rearrangements of O-propargyl -ketoesters and O-allyl -ketoesters have been accomplished under mild reaction conditions. In the presence of the chiral N,N-dioxide/Ni-II complex, a wide range of allenyl/allyl-substituted all-carbon quaternary -ketoesters was obtained in generally good yield (up to 99%) and high diastereoselectivity (up to 99:1 d.r.) with excellent enantioselectivity (up to 99% ee).Nickel(II)-Catalyzed Asymmetric Propargyl and Allyl Claisen Rearrangements to Allenyl-and Allyl-Substituted beta-Ketoestersallenic compounds; asymmetric catalysis; heterocyCles; nickel; rearrangement42201464#N/ATRUE
160
anie.20110542310.1002/anie.201105423?FALSEhttps://doi.org/10.1002/anie.201105423Goossen, LJAngew. Chem.-Int. Edit.Selective Crossed-Tishchenko Reaction-A Waste-Free Synthesis of Benzyl Esters19201127#N/ATRUE
161
acscatal.9b0504910.1021/acscatal.9b05049?FALSEhttps://doi.org/10.1021/acscatal.9b05049Hu, XLACS Catal.A nickel-catalyzed reductive amidation of unactivatedesters recently reported, employing readily available and low-cost nitroarenes as nitrogen sources. Here, we describe a comprehensive experimental and computational study, which reveals an intricate mechanism of this process. The reaction profile indicated azoarene as the terminal nitrogen intermediate formed from the reduction of nitroarene. The Activation of azoarene en route to amidation was probed by kinetics, Hammett plots, and density functional theory (DFT) calculations. The Activation likely involves Ni-catalyzed, ZnX2-promoted, reductive Cleavage of the N=N double bond in an azoarene to form a bridging imido species, which then reacts in a rate-determining step with an ester to give an amide. Besides the nickel catalyst, ZnX2 has an important influence on the rates and orders of the reaction. DFT computations suggest ZnX2 stabilizes many of the intermediates in the reaction pathway of azoarene Activation, inCluding forming the key Ni-Zn heterobimetallic imido intermediate. The mechanistic insights revealed in this study lay the foundation for the development of synthetic methods employing azoarenes as stable and easily accessible nitrogen sources.Reductive Cleavage of Azoarene as a Key Step in Nickel-Catalyzed Amidation of Esters with Nitroarenesnickel catalysis; mechanism; azobenzene; amidation; kinetics7202043#N/ATRUE
162
acscatal.8b0393010.1021/acscatal.8b03930?FALSEhttps://doi.org/10.1021/acscatal.8b03930Wang, CACS Catal.By merging cross-electrophile coupling and C-C bond Cleavage, we developed a Ni-catalyzed electrophilic ring opening of cyCloketone oxime esters with aromatic acid chlorides in assistance of Mn as reductant. Notably, complete regioselectivity can be achieved in this C-C bond Cleavage reaction, providing an efficient access to a variety of cyanoketones under cyanide-free conditions. A radical reaction pathway was proposed on the basis of the results of the mechanistic probing experiments.Nickel-Catalyzed Reductive Electrophilic Ring Opening of CyCloketone Oxime Esters with Aroyl Chloridesring opening cross-electrophile; C-C bond Cleavage; Ni-catalysis; cyanoketones38201887#N/ATRUE
163
acscatal.1c0037910.1021/acscatal.1c00379?https://doi.org/10.1021/acscatal.1c00379Huang, KWACS Catal.The traditional Staudinger/aza-Wittig reaction represents one of the most powerful tools for imine formation. However, for this multistep procedure, the sacrificial phosphine has to be used, resulting in difficulties in the purification process and waste disposal at the same time. Here, we report a redox-neutral azide-alcohol imination methodology enabled by a base-metal nickel PN3 pincer catalyst. The one-step, waste-free, and high atom-economical features highlight its advantages further. Moreover, mechanistic insight suggests a non-metal-ligand cooperation pathway based on the observation of an intermediate and density functional theory calculations.Redox-Neutral Imination of Alcohol with Azide: A Sustainable Alternative to the Staudinger/Aza-Wittig Reactionimination; redox-neutral process; base-metal catalysis; atom and step economy; PN3 pincerY12021x37#N/AFALSE
164
science.113089510.1126/science.1130895?FALSEhttps://doi.org/10.1126/science.1130895Wachterschauser, GScienceTo test the theory of a chemoautotrophic origin of life in a volcanic, hydrothermal setting, we explored mechanisms for the buildup of bio-organic compounds by carbon fixation on catalytic transition metal precipitates. We report the carbon monoxide - dependent formation of carbon-fixation products, inCluding an ordered series of alpha-hydroxy and alpha-amino acids of the general formula R-CHA-COOH (where R is H, CH3, C2H5, or HOCH2 and A is OH or NH2) by carbon fixation at 80 degrees to 120 degrees C, catalyzed by nickel or nickel, iron precipitates with Carbonyl, cyano, and methylthio ligands as carbon sources, with or without sulfido ligands. Calcium or magnesium hydroxide was added as a pH buffer. The results narrow the gap between biochemistry and volcanic geochemistry and open a new gateway for the exploration of a volcanic, hydrothermal origin of life.alpha-hydroxy and alpha-amino acids under possible hadean, volcanic origin-of-life conditions135200631#N/ATRUE
165
anie.20190125510.1002/anie.201901255?FALSEhttps://doi.org/10.1002/anie.201901255Ho, CYAngew. Chem.-Int. Edit.A cross-hydroalkenylation/rearrangement cascade (HARC), using a cyClopropene and alkyne as substrate pairs, was achieved for the first time by using new [(NHC) Ni(allyl)]BArF catalysts (NHC=N-heterocyClic carbenes). By controlling the (NHC) (NiH)-H-II relative insertion reactivity with cyClopropene and alkyne, a broad scope of cyClopentadienes was obtained with highly selectively. The structural features of the new (NHC)Ni-II catalyst were important for the success of the reaction. The mild reaction conditions employed may serve as an entry for exploring (NHC)Ni-II-assisted VinylcyClopropane rearrangement reactivity.[(NHC)(NiH)-H-II]-Catalyzed Cross-Hydroalkenylation of CyClopropenes with Alkynes: CyClopentadiene Synthesis by [(NHC)Ni-II]-Assisted C-C Rearrangementalkynes; dienes; N-heterocyClic carbenes; nickel; rearrangements14201973#N/ATRUE
166
acs.orglett.0c0064910.1021/acs.orglett.0c00649?FALSEhttps://doi.org/10.1021/acs.orglett.0c00649Feng, XMKinetic Resolution of Propargylic Ethers via [2,3]-Wittig Rearrangement to Synthesize Chiral alpha-Hydroxyallenes2020#N/ATRUE
167
acscatal.1c0090810.1021/acscatal.1c00908AdditionElaineFALSEhttps://doi.org/10.1021/acscatal.1c00908Ogoshi, SACS Catal.A stereoselective alkene isomerization and sequential hydroArylation with Arylboronic acid using a nickel(0) catalyst has been developed. The bulky monophosphine PAd(2)(n-Bu) is an effective ligand in these reactions to furnish both various stereo-defined internal alkenes and hydroArylation products (isomerization: up to 98%, E/Z = 98:2; tandem hydroArylation: up to 82%). Mechanistic studies based on experiments and computational calculations suggested that the isomerization proceeds via an intra- or intermolecular hydrogen shift. Furthermore, a concerted multibond recombination with boronic acid-assisted oxidative protometallation of the alkene was found to be a reasonable mechanism for the formation of the Alkylnickel(II) species from the alkene, nickel(0), alcohol, and boronic acid in the hydroArylation.Development and Mechanistic Studies of (E)-Selective Isomerization/Tandem HydroArylation Reactions of Alkenes with a Nickel(0)/Phosphine Catalystnickel catalyst; alkene isomerization; hydroArylation; concerted protometallation; DFT calculationsyY02021xx67#N/AFALSE
168
jacs.0c0712610.1021/jacs.0c07126AdditionElaineFALSEhttps://doi.org/10.1021/jacs.0c07126Chen, YFJ. Am. Chem. Soc.Herein, we report a nickel-catalyzed reductive cross-coupling reaction of easily accessible 3-butenyl carbamoyl chloride with primary Alkyl iodide to access the chiral a-Alkylated pyrrolidinone with broad substrate scope and high enantiomeric excess. The current art of synthesis still remains challenging on the enantioselective alpha-monoAlkylation of pyrrolidinones. The newly designed chiral 8-quinoline imidazoline ligand (Quinim) is crucial for maintaining the reactivity and enantioselectivity to ensure the reductive cyClization of monosubstituted alkenes for unprecedented synthesis of chiral non-aromatic heterocyCles.Quinim: A New Ligand Scaffold Enables Nickel-Catalyzed Enantioselective Synthesis of alpha-Alkylated gamma-Lactam2 stepy182020ring formation90#N/AFALSE
169
ja00279a06810.1021/ja00279a068AdditionImanuelFALSEhttps://doi.org/10.1021/ja00279a068NOZAKI, HJ. Am. Chem. Soc.REACTIONS OF ALKENYLCHROMIUM REAGENTS PREPARED FROM ALKENYL TRIFLUOROMETHANESULFONATES (TRIFLATES) WITH CHROMIUM(II) CHLORIDE UNDER NICKEL CATALYSIS412198621#N/ATRUE
170
anie.20200632210.1002/anie.202006322AdditionImanuelFALSEhttps://doi.org/10.1002/anie.202006322Zhao, YAngew. Chem.-Int. Edit.We present herein an unprecedented allylative dicarbofunctionalization of alkynes with allylic alcohols. This simple catalytic procedure utilizes commercially available Ni(COD)(2), triphenylphosphine, and inexpensive reagents, and delivers valuable skipped dienes and trienes with an all-carbon tetrasubstituted alkene unit in a highly stereoselective fashion. Preliminary mechanistic studies support the reaction pathway of allylnickelation followed by transmetalation in this dicarbofunctionalization of alkynes.Nickel-Catalyzed Allylmethylation of Alkynes with Allylic Alcohols and AlMe3: Facile Access to Skipped Dienes and Trienesalkynes; allylic alcohols; dicarbofunctionalization; multicomponent reactions; nickel6202084#N/ATRUE
171
ja036140110.1021/ja0361401AdditionFALSEdoi.org/10.1021/ja0361401Jamison, TF1142003#N/ATRUE
172
j.tetlet.2008.03.035
10.1016/j.tetlet.2008.03.035
AdditionFALSEhttps://doi.org/10.1016/j.tetlet.2008.03.035Chen, C372008xxxx#N/A
173
s41467-020-19717-610.1038/s41467-020-19717-6AdditionFALSEhttps://doi.org/10.1038/s41467-020-19717-6Koh, MJNat. Commun.Among the plethora of catalytic methods developed for hydrocarbofunctionalization of olefins to date, reactions that regioselectively install a functionalized Alkyl unit at the 2-position of a terminal unactivated C=C bond to afford branched products are scarce. Here, we show that a Ni-based catalyst in conjunction with a stoichiometric reducing agent promote Markovnikov-selective hydroAlkylation of unactivated alkenes tethered to a recyClable 8-aminoquinaldine directing auxiliary. These mild reductive processes employ readily available primary and secondary haloalkanes as both the hydride and Alkyl donor. Reactions of alkenyl amides with >= five-carbon chain length regioselectively afforded beta -Alkylated products through remote hydroAlkylation, underscoring the fidelity of the catalytic process and the directing group's capability in stabilizing five-membered nickelacyCle intermediates. The operationally simple protocol exhibits exceptional functional group tolerance and is amenable to the synthesis of bioactive molecules as well as regioconvergent transformations. Methods that regioselectively install a functionalized Alkyl unit at the 2-position of a terminal unactivated C=C bond are scarce. Here, the authors report a Markovnikov-selective hydroAlkylation of unactivated amide-tethered alkenes catalyzed by nickel in conjunction with a stoichiometric reductant.Alkyl halides as both hydride and Alkyl sources in catalytic regioselective reductive olefin hydroAlkylation5202071#N/ATRUE
174
ol901776n10.1021/ol901776nAdditionFALSEhttps://doi.org/10.1021/ol901776nXia, CGAn Efficient Synthesis of Chiral Diamines with Rigid Backbones: Application in Enantioselective Michael Addition of Malonates to Nitroalkenes492009#N/ATRUE
175
ol201927c10.1021/ol201927cAdditionFALSEhttps://doi.org/10.1021/ol201927cYuan, WCDiastereo- and Enantioselective Conjugate Addition of 3-Substituted Oxindoles to Nitroolefins Catalyzed by a Chiral Ni(OAc)(2)-Diamine Complex under Mild Conditions662011#N/ATRUE
176
ol025731d10.1021/ol025731dAdditionFALSEhttps://doi.org/10.1021/ol025731dCheng, CHHighly stereoselective ring-opening addition of terminal acetylenes to bicyClic olefins catalyzed by nickel complexes902002#N/ATRUE
177
jacs.9b0748910.1021/jacs.9b07489AdditionFALSEhttps://pubs.acs.org/doi/10.1021/jacs.9b07489Martin, RJ. Am. Chem. Soc.
A catalytic deaminative Alkylation of unactivated olefins is described. The protocol is characterized by its mild conditions, wide scope, inCluding the use of ethylene as substrate, and exquisite site-selectivity pattern for both α-olefins and internal olefins, thus unlocking a new catalytic platform to forge sp3–sp3 linkages, even in the context of late-stage functionalization.
Site-Selective Catalytic Deaminative Alkylation of Unactivated Olefins772019Added by Yizhou#N/ATRUE
178
jacs.8b1370910.1021/jacs.8b13709AdditionFALSEhttps://doi.org/10.1021/jacs.8b13709Weix, DJJ. Am. Chem. Soc.Transition-metal-catalyzed addition of Aryl halides across Carbonyls remains poorly developed, especially for aliphatic aldehydes and hindered substrate combinations. We report here that simple nickel complexes of bipyridine and Pybox can catalyze the addition of Aryl halides to both aromatic and aliphatic aldehydes using zinc metal as the reducing agent. This convenient approach tolerates acidic functional groups that are not compatible with Grignard reactions, yet sterically hindered substrates still couple in high yield (33 examples, 70% average yield). Mechanistic studies show that an Arylnickel, and not an Arylzinc, adds efficiently to cyClohexanecarboxaldehyde, but only in the presence of a Lewis acid co-catalyst (ZnBr2).Nickel-Catalyzed Addition of Aryl Bromides to Aldehydes To Form Hindered Secondary Alcohols14201939#N/ATRUE
179
jacs.8b1203510.1021/jacs.8b12035AdditionFALSEhttps://doi.org/10.1021/jacs.8b12035Baran, PSJ. Am. Chem. Soc.A two-step degradation reconstruction approach to the carbon-14 radiolabeling of Alkyl Carbonylic acids is presented. Simple Activation via redox-active ester formation was followed by nickel mediated deCarbonylative Carbonylation to afford a range of complex compounds with ample isotopic incorporations for drug metabolism and pharmacokinetic studies. The practicality and operational simplicity of the protocol were demonstrated by its use in an industrial carbon-14 radiolabeling setting.Direct Carbon Isotope Exchange through DeCarbonylative Carbonylation26201976#N/ATRUE
180
jacs.8b0463710.1021/jacs.8b04637AdditionFALSEhttps://doi.org/10.1021/jacs.8b04637Montgomery, JJ. Am. Chem. Soc.Nickel-catalyzed cross-electrophile couplings have recently emerged as highly effective and practical methods for the formation of C-C bonds. By merging this process with well-established pi-pi coupling chemistry, a new method for the synthesis of tetrasubstituted alkenes has been developed. The procedure relies on the use of chlorosilanes as a means of generating reactive Vinylnickel intermediates, which are capable of undergoing a reductive cross-electrophile coupling with Alkyl halides. The method not only generates highly substituted allylic alcohol derivatives but also obviates the need for stoichiometric organometallic nuCleophiles and provides greatly improved scope and functional group tolerance compared with previously developed methods.Synthesis of Tetrasubstituted Alkenes by Tandem MetallacyCle Formation/Cross-Electrophile Coupling23201861#N/ATRUE
181
jacs.6b0876710.1021/jacs.6b08767AdditionFALSEhttps://doi.org/10.1021/jacs.6b08767Nakao, YJ. Am. Chem. Soc.We report a method that ensures the selective Alkylation of benzamides and aromatic ketones at the para-position via cooperative nickel/aluminum catalysis. Using a bulky catalyst/cocatalyst system allows reactions between benzamides and alkenes to afford the corresponding para-Alkylated products. The origin of the high para-selectivity has also been investigated by density functional theory calculations.para-Selective Alkylation of Benzamides and Aromatic Ketones by Cooperative Nickel/Aluminum Catalysis86201626#N/ATRUE
182
jacs.5b0227210.1021/jacs.5b02272AdditionFALSEhttps://doi.org/10.1021/jacs.5b02272Zhao, PJJ. Am. Chem. Soc.A Modular and atom-efficient synthesis of 2-aza-1,3-butadiene:,derivatives, has been developed via nickel-Catalyzed intermolecular coupling between internal alkynes. and aromatic N-H ketimines. This novel alkyne hydroimination process, is promoted by a catalyst system of a Ni(0) precursor ([Ni(cod)(2)]), N-heterocyClic carbene (NHC) ligand (IPr), and Cs2CO3 additive. The exClusive formation of (Z)-enamine stereoisoimers is Consistent with a proposed anti-iminometalation of alkyne by pi-complexation with Ni(0) and subsequent attack by the N-H ketimine nuCleophile. An NHC-ligated,Ni(0) pi-imine complex, [(IPr)(eta(1)-HN=CPh2)(eta(2)-HN=CPh2)], Was independently synthesized and displayed improved re-activity as the catalyst precursor.Nickel-Catalyzed Hydroimination of Alkynes30201560#N/ATRUE
183
jacs.1c0322810.1021/jacs.1c03228AdditionFALSEhttps://doi.org/10.1021/jacs.1c03228Koh, MJJ. Am. Chem. Soc.Alkene hydrocarbofunctionalization represents one of the most important Classes of chemical transformations, but related branched-selective examples with unactivated olefins are scarce. Here, we report that catalytic amounts of a dimeric Ni(I) complex and an exogenous alkoxide base promote Markovnikov-selective hydroArylation(alkenylation) of unactivated and activated olefins using organo bromides or triflates derived from widely available phenols and ketones. Products bearing Aryl- and alkenyl-substituted tertiary and quaternary centers could be isolated in up to 95% yield and >99:1 regioisomeric ratios. Contrary to previous dual-catalytic methods that rely on metal-hydride atom transfer (MHAT) to the olefin prior to carbofunctionalization with a cocatalyst, our mechanistic evidence points toward a nonradical reaction pathway that begins with site-selective carbonickelation across the C=C bond followed by hydride transfer using alkoxide as the hydride source. Utility of the single-catalyst protocol is highlighted through the synthesis of medicinally relevant scaffolds.Catalytic Regioselective Olefin HydroArylation(alkenylation) by Sequential Carbonickelation-Hydride Transfer0202153#N/ATRUE
184
jacs.1c0191610.1021/jacs.1c01916AdditionFALSEhttps://doi.org/10.1021/jacs.1c01916Martin, RJ. Am. Chem. Soc.A Ni-catalyzed reductive Carbonylation of N-substituted aziridines with CO2 at atmospheric pressure is disClosed. The protocol is characterized by its mild conditions, experimental ease, and exquisite chemo- and regioselectivity pattern, thus unlocking a new catalytic blueprint to access beta-amino acids, important building blocks with considerable potential as peptidomimetics.Ni-Catalyzed Carbonylation of Aziridines en Route to beta-Amino Acids0202155#N/ATRUE
185
jacs.1c0014210.1021/jacs.1c00142AdditionFALSEhttps://doi.org/10.1021/jacs.1c00142Shu, XZJ. Am. Chem. Soc.The regiocontrolled functionalization of 1,3-dienes has become a powerful tool for divergent synthesis, yet it remains a long-standing challenge for aliphatic substrates. Herein, we report a reductive approach for a branch-selective 1,2-hydroVinylation of aliphatic 1,3-dienes with R-X electrophiles, which represents a new selectivity pattern for diene functionalization. Simple butadiene, aromatic 1,3-dienes, and highly conjugated polyene were also tolerated. The combination of Ni(0) and the phosphine-nitrile ligand generally resulted in >20:1 regioselectivity with the retention of the geometry of the C3-C4 double bonds. This reaction proceeds with a broad substrate scope, and it allows for the conjugation of two biologically active units to form more complex polyene molecules, such as tetraene and pentaene as well as heptaene.Regiocontrolled Reductive Vinylation of Aliphatic 1,3-Dienes with Vinyl Triflates by Nickel Catalysis3202161#N/ATRUE
186
jacs.0c0212610.1021/jacs.0c02126AdditionFALSEhttps://doi.org/10.1021/jacs.0c02126Betley, TAJ. Am. Chem. Soc.A dipyrrin-supported nickel catalyst (L-AdF) Ni(py) (L-AdF: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine) displays productive intramolecular C-H bond amination to afford N-heterocyClic products using aliphatic azide substrates. The catalytic amination conditions are mild, requiring 0.1-2 mol% catalyst loading and operational at room temperature. The scope of C-H bond substrates was explored and Benzylic, tertiary, secondary, and primary C-H bonds are successfully aminated. The amination chemoselectivity was examined using substrates featuring multiple activatable C-H bonds. Uniformly, the catalyst showcases high chemoselectivity favoring C-H bonds with lower bond dissociation energy as well as a wide range of functional group tolerance (e.g., ethers, halides, thioetheres, esters, etc.). Sequential cyClization of substrates with ester groups could be achieved, providing facile preparation of an indolizidine framework commonly found in a variety of alkaloids. The amination cyClization reaction mechanism was examined employing nuClear magnetic resonance (NMR) spectroscopy to determine the reaction kinetic profile. A large, primary intermolecular kinetic isotope effect (KIE = 31.9 +/- 1.0) suggests H-atom abstraction (HAA) is the rate-determining step, indicative of H-atom tunneling being operative. The reaction rate has first order dependence in the catalyst and zeroth order in substrate, consistent with the resting state of the catalyst as the corresponding nickel iminyl radical. The presence of the nickel iminyl was determined by multinuClear NMR spectroscopy observed during catalysis. The Activation parameters (Delta H double dagger = 13.4 +/- 0.5 kcal/mol; Delta S double dagger = -24.3 +/- 1.7 cal/mol.K) were measured using Eyring analysis, implying a highly ordered transition state during the HAA step. The proposed mechanism of rapid iminyl formation, rate-determining HAA, and subsequent radical recombination was corrB(OH)2rated by intramolecular isotope labeling experiments and theoretical calculations.Efficient C-H Amination Catalysis Using Nickel-Dipyrrin Complexes13202060#N/ATRUE
187
ja991064g10.1021/ja991064gAdditionFALSE
doi.org/10.1021/ja991064g
Wada, EAsymmetric conjugate addition of thiols to a 3-(2-alkenoyl)-2-oxazolidinone catalyzed by the DBFOX/Ph aqua complex of nickel(II) perchlorate1261999#N/ATRUE
188
ja980499l10.1021/ja980499lAdditionFALSEhttps://doi.org/10.1021/ja980499lHoveyda, AHJ. Am. Chem. Soc.Ni-catalyzed asymmetric addition of Grignard reagents to unsaturated cyClic acetals. The influence of added phosphine on enantioselectivity58199820#N/ATRUE
189
ja910305p10.1021/ja910305pAdditionFALSEhttps://doi.org/10.1021/ja910305pDriess, MJ. Am. Chem. Soc.The strikingly different behavior of the ylide-like, N-heterocyClic silylene LSi: (5: L = CH[(C=CH2)CMe(NAr)(2)]; Ar = 2,6-(PrC6H3)-Pr-i) versus its LSi -> Ni(CO)(3) complex 13 to activate E-H bonds (E = S, N) of small molecules is reported. Remarkably, conversion of 5 with hydrogen sulfide leads exClusively to the first isolable silathioformamide, L'Si(=S)H (16: L' = CH[C(Me)NAr](2); Ar = 2,6-iPrC(6)H(3)) with a donor-supported Si=S double bond and four-coordinate silicon. The latter result demonstrates the unusual ambivalent reactivity of 5 by combining two modes of reactivity involving S-H bond Activation and subsequent 1,4- and 1,1-addition, respectively. In addition, 5 can serve as a ligand with well-balanced sigma-donor and pi-acceptor capabilities toward transition metals. This has been demonstrated by the isolable [Ni-0(arene)] complexes 12a-e (arene = MenC6H6-n, n = 0-3), which are ideal precursors for the formation of the corresponding Ni(CO)(3) complex 13. The latter activates a S-H bond in hydrogen sulfide, too, but the presence of the Ni(CO)(3) moiety governs the formation of the complex 17, bearing an unprecedented beta-diketiminate silicon(II) thiol ligand: L'Si(SH): (L' = CH[C(Me)NAr](2); Ar 2,6-(PrC6H3)-Pr-i). Likewise, the Si(II)-> Ni(CO)(3) coordination in 13 steers exClusively 1,4-addition of ammonia, isopropylamine, and phenylhydrazine onto the silylene ligand 5, leading to the corresponding beta-diketiminate silicon(II) amide or hydrazide complexes L'Si(NHR)-> Ni(CO)(3) (23a-c: R = H, Pr-i, N(H)Ph). IR measurements reveal that the Carbonyl stretching frequencies of the Ni(CO)(3) moiety in 23a-c are shifted to even lower wavenumbers in comparison to those of NHCs or phosphines. In other words, the beta-diketiminate silicon(II) amide ligands in 23a-c represent the strongest donors in the series of N-heterocyClic silylenes reported as yet.Steering S-H and N-H Bond Activation by a Stable N-HeterocyClic Silylene: Different Addition of H2S, NH3, and Organoamines on a Silicon(II) Ligand versus Its Si(II)-> Ni(CO)(3) Complex143201070#N/ATRUE
190
ja909457b10.1021/ja909457bAdditionFALSEhttps://doi.org/10.1021/ja909457bSodeoka, MJ. Am. Chem. Soc.A highly efficient, catalytic, diastereo- and enantiosetective conjugate addition of aketoesters to nitroatkenes has been devised. The reaction was applicable to various substrates. Notably, the combination of endogenous and exogenous bases was effective, allowing a small amount of the catalyst (0.1-1 mol % Ni) to promote the reaction efficiently. The synthetic utility of this reaction was demonstrated in the synthesis of substituted pyrrolidine derivatives, whose stereochemistry is Closely related to biologically important natural products such as kainic acid.Diastereo- and Enantioselective Conjugate Addition of alpha-Ketoesters to Nitroalkenes Catalyzed by a Chiral Ni(OAc)(2) Complex under Mild Conditions95201018#N/ATRUE
191
ja905853710.1021/ja9058537AdditionFALSEhttps://doi.org/10.1021/ja9058537Morken, JPJ. Am. Chem. Soc.The nickel-catalyzed enantioselective addition of allylboronic acid pinacol ester [allylB(pin)] to alpha,beta,gamma,delta-unsaturated aldehydes is described. This reaction results in a remarkable inversion of substrate otefin geometry, providing the Z,E-configured reaction product in good enantioselectivity and olefin stereoselectivity. The reaction appears to proceed by conversion of the dienal to an unsaturated pi-allyl complex followed by reductive elimination via transition state II. Enantioselectivities range from 73-94% ee for a range of Omega-substituted dienals when chiral ligand L3 is employed.Catalytic Enantioselective Allylation of Dienals through the Intermediacy of Unsaturated pi-Allyl Complexes53200936#N/ATRUE
192
ja903510u10.1021/ja903510uAdditionFALSEhttps://doi.org/10.1021/ja903510uOhashi, MJ. Am. Chem. Soc.A direct conjugate addition of simple alkenes to enones has been achieved in the presence of a Ni(O)/PCy(3) catalyst.Nickel-Catalyzed Direct Conjugate Addition of Simple Alkenes to Enones55200921#N/ATRUE
193
ja901374v10.1021/ja901374vAdditionFALSEhttps://doi.org/10.1021/ja901374vHiyama, TJ. Am. Chem. Soc.Allyl cyanides are found to add across alkynes in the presence of a nickel/P(4-CF3-C6H4)(3) catalyst to give polysubstituted 2,5-hexadienenitriles with defined stereo- and regiochemistry. Use of AlMe2Cl or AlMe3 as a Lewis acid cocatalyst accelerates the reaction and expands the substrate scope significantly. The cyano group in the allylcyanation products can be transformed to a hydroxymethyl or aminomethyl group to afford highly substituted allylic alcohols or amines. alpha-Siloxyallyl cyanides also add across alkynes selectively at the less hindered gamma-carbon to allow introduction of 3-oxo-propyl functionality after hydrolysis of the resulting silyl enol ethers. This particular carbocyanation reaction has been applied to the stereoselective construction of the trisubstituted double bond of plaunotol, an antibacterial natural product active against Helicobacter pylori.Nickel-Catalyzed Carbocyanation of Alkynes with Allyl Cyanides90200999#N/ATRUE
194
ja901153s10.1021/ja901153sAdditionFALSEhttps://doi.org/10.1021/ja901153sHiyama, TJ. Am. Chem. Soc.Formamides are found to undergo addition reactions across alkynes and 1,3-dienes by nickel/Lewis acid catalysis to give a variety of alpha,beta- and beta,gamma-unsaturated amides with stereo- and regioselectivity. Intramolecular insertion reactions of olefins into the C-H bonds of formamides also proceed under similar conditions. The presence of Lewis acid cocatatysts is crucial, and formamide coordination to the Lewis acid is considered to be responsible for the Activation of their Carbonyl C-H bonds probably through oxidative addition to nickel(0).Hydrocarbamoylation of Unsaturated Bonds by Nickel/Lewis-Acid Catalysis118200926#N/ATRUE
195
ja806569h10.1021/ja806569hAdditionFALSEhttps://doi.org/10.1021/ja806569hMatsubara, SJ. Am. Chem. Soc.An intermolecular nickel-catalyzed addition reaction has been developed where phthalic anhydrides react with alkynes to afford substituted isocoumarins. A mechanistic rationale is proposed, implying reductive elimination of Ni(0) promoted by ZnX2 cocatalyst as the key step of the catalytic cyCle.Nickel-Catalyzed DeCarbonylative Addition of Anhydrides to Alkynes107200835#N/ATRUE
196
ja802844v10.1021/ja802844vAdditionFALSEhttps://doi.org/10.1021/ja802844vMontgomery, JJ. Am. Chem. Soc.Three-component nickel-catalyzed couplings of enals, alkynes, and silanes have been developed as a new entry to enol silanes. The enol silane and a trisubstituted alkene are both formed with > 98:2 stereoselectively, and the reaction tolerates a broad range of functionality inCluding aldehydes, ketones, esters, free hydroxyls, and basic secondary amines. A mechanistic pathway involving the formation of a metallacyCle that possesses and eta(1) nickel O-enolate motif explains the high level of stereoselection.Highly chemoselective and stereoselective synthesis of Z-enol silanes29200831#N/ATRUE
197
ja801213x10.1021/ja801213xAdditionFALSEhttps://doi.org/10.1021/ja801213xKrische, MJJ. Am. Chem. Soc.Under the conditions of ruthenium-catalyzed transfer hydrogenation, commercially available acyClic 1,3dienes, butadiene, isoprene, and 2,3-dimethylbutadiene, couple to Benzylic alcohols la -6a to furnish products of Carbonyl crotylation 1b -6b, Carbonyl isoprenylation 1c-6c, and Carbonyl reverse 2-methyl prenylation 1d-6d. Under related transfer hydrogenation conditions employing isopropanol as terminal reductant, isoprene couples to aldehydes 7a-9a to furnish identical products of Carbonyl isoprenylation 1c-3c. Thus, Carbonyl allylation is achieved from the alcohol or the aldehyde oxidation level in the absence of preformed allyl metal reagents. Coupling to aliphatic alcohols (isoprene to 1-nonanol, 65% isolated yield) and allylic alcohols (isoprene to geraniol, 75% isolated yield) also is demonstrated. Isotopic labeling studies corrB(OH)2rate a mechanism involving hydrogen donation from the reactant alcohol or sacrificial alcohol (i-PrOH).Ruthenium-catalyzed C-C bond forming transfer hydrogenation: Carbonyl allylation from the alcohol or aldehyde oxidation level employing acyClic 1,3-dienes as surrogates to preformed allyl metal reagents135200857#N/ATRUE
198
ja800997j10.1021/ja800997jAdditionFALSEhttps://doi.org/10.1021/ja800997jSuginome, MJ. Am. Chem. Soc.The C-H bond of a terminal alkyne adds to a carbon-carbon double bond of 1,3-dienes, styrenes, and norbornene at room temperature in the presence of a nickel catalyst in regio- and stereoselective manners. Reaction of triisopropylsilylacetylene with 1-substituted 1,3-butadinene derivatives afforded hydroalkynylation products via introduction of a hydrogen atom and a triisopropylsilylethynyl group to 4- and 3-positions of the dienes, respectively. Likewise, 1-triisopropylsiloxy-1,3-butadiene, 1,3-pentadiene, 1-cyClohexen-1-yl-1,3-butadiene, and 1,3-cyClohexadiene underwent the hydroalkynylation reaction, giving the corresponding 1,4-enyne derivatives in good yields at room temperature. Reaction of p-substituted styrene with triisopropylsilylacetylene also proceeded in the presence of the nickel catalyst, giving the branched hydroalkynylation products in good yields. Norbornene gave a exo-addition product in good yield under the same reaction conditions.Nickel-catalyzed addition of C-H bonds of terminal alkynes to 1,3-dienes and styrenes78200828#N/ATRUE
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ja711442610.1021/ja7114426AdditionFALSEhttps://doi.org/10.1021/ja7114426Kurahashi, TJ. Am. Chem. Soc.An intermolecular nickel-catalyzed addition reaction has been developed where N-Arylphthalimides react with alkynes to afford substituted isoquinolones. A mechanistic rationale is proposed, implying nuCleophilic attack of Ni(0) to an amide as the primary step of the catalytic cyCle.Nickel-catalyzed deCarbonylative addition of phthalimides to alkynes149200850#N/ATRUE
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ja511964k10.1021/ja511964kAdditionFALSEhttps://doi.org/10.1021/ja511964kMashima, KJ. Am. Chem. Soc.Tris[N,N-bis(trimethylsilyl)amido] complexes of group 3 metals, especially yttrium and gadolinium, served as catalysts for ortho-C-H bond addition of pyridine derivatives and N-Hets into the C=N double bond of nonactivated imines to afford the corresponding aminomethylated products. Addition of catalytic amounts of secondary amines, such as diBenzylamine, dramatically improved the catalytic activity through the formation of a mixed ligated complex such as [(Me3Si)2N](2)Y(NBn2)(THF) (4). Furthermore, kinetic studies using the isolated complex 4 provided a plausible reaction mechanism by which coordination of two pyridine derivatives afforded a penta-coordinated species as a key step.Aminomethylation Reaction of ortho-Pyridyl C-H Bonds Catalyzed by Group 3 Metal Triamido Complexes39201539#N/ATRUE
201
ja500666h10.1021/ja500666hAdditionFALSEhttps://doi.org/10.1021/ja500666hMatsubara, SJ. Am. Chem. Soc.We have developed a redox-economical coupling reaction of alcohols and alkynes to form allylic alcohols under mild conditions. The reaction is redox-neutral as well as redox-economical and thus free from any additives such as a reductant or an oxidant. This atom-economical coupling can be applied for the conversion of both aliphatic and Benzylic alcohols to the corresponding substituted allylic alcohols in a single synthetic operation.Nickel-Catalyzed Redox-Economical Coupling of Alcohols and Alkynes to Form Allylic Alcohols50201444#N/ATRUE
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ja410883p10.1021/ja410883pAdditionFALSEhttps://doi.org/10.1021/ja410883pMartin, RJ. Am. Chem. Soc.In recent years a significant progress has been made for the Carbonylation of Aryl and Benzyl halides with CO2, becoming convenient alternatives to the use of stoichiometric amounts of well-defined metal species. Still, however, most of these processes require the use of pyrophoric and air-sensitive reagents and the current methods are mostly restricted to organic halides. Therefore, the discovery of a mild, operationally simple alternate Carbonylation that occurs with a wide substrate scope employing readily available coupling partners will be highly desirable. Herein, we report a new protocol that deals with the development of a synergistic Activation of CO2 and a rather challenging Activation of inert C(sp(2))-O and C(sp(3))-O bonds derived from simple and cheap alcohols, a previously unrecognized opportunity in this field. This unprecedented Carbonylation event is characterized by its simplicity, mild reaction conditions, remarkable selectivity pattern and an excellent chemoselectivity profile using air-, moisture-insensitive and easy-to-handle nickel precatalysts. Our results render our method a powerful alternative, practicality and novelty aside, to commonly used organic halides as counterparts in Carbonylation protocols. Furthermore, this study shows, for the first time, that traceless directing groups allow for the reductive coupling of substrates without extended pi-systems, a typical requisite in many C-O bond-Cleavage reactions. Taking into consideration the limited knowledge in catalytic Carbonylative reductive events, and the prospective impact of providing a new tool for accessing valuable Carbonylic acids, we believe this work opens up new vistas and allows new tactics in reductive coupling events.Ni-Catalyzed Carbonylation of C(sp(2))- and C(sp(3))-O Bonds with CO2y211201498#N/AFALSE
203
ja400650m10.1021/ja400650mAdditionFALSEhttps://doi.org/10.1021/ja400650mJia, YXJ. Am. Chem. Soc.A highly enantioselective Friedel-Crafts Alkylation reaction of indoles with beta-CF3-beta-disubstituted nitroalkenes was achieved using a Ni(ClO4)(2)-bisoxazoline complex as a catalyst, which afforded indole-bearing chiral compounds with trifluoromethylated all-carbon quaternary stereocenters in good yields with excellent enantioselectivities (up to 97% ee). The transformation of one of the products into first a trifluoromethylated tryptamine and then a trifluoromethylated tetrahydro-beta-carboline by sequential nitro reduction and Pictet-Spengler cyClization were realized with complete preservation of enantiopurity.Highly Enantioselective Construction of Trifluoromethylated All-Carbon Quaternary Stereocenters via Nickel-Catalyzed Friedel-Crafts Alkylation Reaction162201376#N/ATRUE
204
ja109908x10.1021/ja109908xAdditionFALSEhttps://doi.org/10.1021/ja109908xOgoshi, SJ. Am. Chem. Soc.In the presence of a Ni(0)/NHC catalyst, an equimolar mixture of aliphatic and Aryl aldehydes can be employed to selectively yield a single cross-coupled ester. This reaction can be applied to a variety of aliphatic (1 degrees, 2 degrees, cyc-2 degrees, and 3 degrees) and Aryl aldehyde combinations. The reaction represents 100% atom efficiency and generates no waste. Mechanistic studies have revealed that the striking feature of the reaction is the simultaneous coordination of two aldehydes to Ni(0).Nickel-Catalyzed Selective Conversion of Two Different Aldehydes to Cross-Coupled Esters88201141#N/ATRUE
205
ja102346v10.1021/ja102346vAdditionFALSEhttps://doi.org/10.1021/ja102346vOgoshi, SJ. Am. Chem. Soc.Cyanoformates and cyanoformannides are found to add across alkynes by nickel/Lewis acid (LA) cooperative catalysis to give beta-cyano-substituted acrylates and acrylamides, respectively, in highly stereoselective and regioselective manners. The resulting adducts serve as versatile synthetic building blocks through chemoselective transformations of the ester, amide, and cyano groups as demonstrated by the synthesis of typical structures of beta-cyano ester, beta-amino nitrile, gamma-lactam, disubstituted maleic anhydride, and gamma-aminobutyric acid. The related reactions of cyanoformate thioester and benzoyl cyanide, on the other hand, are found to add across alkynes with deCarbonylation in the presence of a palladium/LA catalyst.Nickel/Lewis Acid-Catalyzed Cyanoesterification and Cyanocarbamoylation of Alkynes1452010145#N/ATRUE
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ja101513d10.1021/ja101513dAdditionFALSEhttps://doi.org/10.1021/ja101513dMorken, JPJ. Am. Chem. Soc.The nickel-catalyzed reaction of Carbonyls and dienes was accomplished in a regio- and stereoselective fashion employing a stoichiometric amount of bis(pinacolato)diboron. In the presence of P(SiMe3)(3), this reductive coupling furnishes allyl boronic esters which are regioisomeric to those obtained with PCy3 as the ligand. The coupling product may be subject to oxidation, which furnishes the derived 1,3-diol, or allytation with an additional aldehyde, which furnishes the derived 1,6-diol in a stereoselective fashion.Ni-Catalyzed Borylative Diene-Aldehyde Coupling: The Remarkable Effect of P(SiMe3)(3)42201042#N/ATRUE
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ja072992f10.1021/ja072992fAdditionFALSEhttps://doi.org/10.1021/ja072992fMontgomery, JJ. Am. Chem. Soc.A new chiral N-heterocyClic carbene ligand has been prepared and examined in nickel-catalyzed, asymmetric reductive couplings of aldehydes and alkynes. In comparison with related structures that have been largely examined in asymmetric ring-Closing metathesis reactions, the new ligand provides superior yields and enantioselectivities in the nickel-catalyzed reductive couplings. The scope of asymmetric couplings in intermolecular variants as well as a 14-membered macrocyClization is illustrated.New N-heterocyClic carbene ligand and its application in asymmetric nickel-catalyzed aldehyde/alkyne reductive couplings138200730#N/ATRUE
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ja069318310.1021/ja0693183AdditionFALSEhttps://doi.org/10.1021/ja0693183Zhou, QLJ. Am. Chem. Soc.A highly efficient nickel-catalyzed asymmetric reductive coupling of dienes and aldehydes has been realized by using bulky spirobiindane phosphoramidite ligands, affording bishomoallylic alcohols in high yields with excellent diastereoselectivities and enantioselectivities.Asymmetric reductive coupling of dienes and aldehydes catalyzed by nickel complexes of spiro phosphoramidites: Highly enantioselective synthesis of chiral bishomoallylic alcohols90200730#N/ATRUE
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ja067878w10.1021/ja067878wAdditionFALSEhttps://doi.org/10.1021/ja067878wMorken, JPJ. Am. Chem. Soc.Conjugate addition of pinacolato(allyl)boron to BenzylideneAlkylidene ketones is remarkably facile when catalyzed by Ni(0) and Pd(0) complexes. Simple enones are inert to the reaction conditions, suggesting a significant activating effect by the auxiliary Benzylidene unit. A comparison of different catalysts and substrates is provided, as is a mechanistic rationale, and an example of asymmetric catalysis.Catalytic conjugate addition of allyl groups to styryl-activated enones84200745#N/ATRUE
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ja064970j10.1021/ja064970jAdditionFALSEhttps://doi.org/10.1021/ja064970jYamamoto, AJ. Am. Chem. Soc.Nickel-catalyzed addition of alkynylboranes to alkynes136200632#N/ATRUE
211
ja058652g10.1021/ja058652gAdditionFALSE
doi.org/10.1021/ja058652g
Sevov, SCDeltahedral germanium Clusters: Insertion of transition-metal atoms and addition of organometallic fragments1132006#N/ATRUE
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ja057741q10.1021/ja057741qAdditionFALSEhttps://doi.org/10.1021/ja057741qMontgomery, JJ. Am. Chem. Soc.A new nickel-catalyzed procedure for the [4+2+1] cyCloaddition of (trimethylsilyl)diazomethane with alkynes tethered to dienes has been developed. A broad range of unsaturated substrates participate in the sequence, and stereoselectivities are generally excellent. Stereochemical studies provided evidence for a mechanism that involves the [3,3] sigmatropic rearrangement of diVinylcyClopropanes.Synthetic studies and mechanistic insight in nickel-catalyzed [4+2+1] cyCloadditions78200655#N/ATRUE
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ja055516310.1021/ja0555163AdditionFALSEhttps://doi.org/10.1021/ja0555163Togni, AJ. Am. Chem. Soc.A highly enantioselective intermolecular hydrophosphination reaction is described. The (Pigiphos)nickel (II)-catalyzed reaction of secondary phosphines and methacrylonitrile gives chiral 2-cyanopropy-lphosphines in good yield and high enantiomeric excess (ee's up to 94%; (R)-(S)-Pigiphos = bis{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}cyClohexylphos phine). We propose a mechanism involving coordination of methacrylonitrile to the dicationic nickel catalyst followed by 1,4-addition of the phosphine, and then, rate-determining proton transfer. This mechanism is supported by (a) the experimentally determined rate law (rate = k'[Ni][methacrylonitrile][t-Bu2PH]), (b) a large primary deuterium isotope effect k(H)/k(D) = 4.6(1) for the addition of t-Bu2PH(D) at 28.3 degrees C in toluene-d(8), (c) the isolation and characterization of the species [Ni(kappa(3)-Pigiphos)(kappa N-methacrylonitrile)](2+), and (d) DFT calculations of model compounds.Enantioselective addition of secondary phosphines to methacrylonitrile: Catalysis and mechanism125200557#N/ATRUE
214
ja049429710.1021/ja0494297AdditionFALSEhttps://doi.org/10.1021/ja0494297Shimada, SJ. Am. Chem. Soc.Efficient and selective nickel-catalyzed addition of H-P(O) and H-S bonds to alkynes205200424#N/ATRUE
215
ja046903010.1021/ja0469030AdditionFALSEhttps://doi.org/10.1021/ja0469030Tamaru, YJ. Am. Chem. Soc.In the presence of 10 mol % of Ni(acac)(2), four components comprising Me2Zn, alkynes, 1,3butadiene, and Carbonyl compounds combine in this order in 1:1:1:1 ratio to furnish (3E,6-7)-octadien-1-ols 1 in good yields. Similarly, the coupling reaction of Me2Zn, 1,omega-dienynes 5, and Carbonyls furnishes 1-Alkylidene-2-(4'-hydroxy-(1'E)-alkenyl)cyClopentanes and -cyClohexanes 6 and their oxygen and nitrogen heterocyCle derivatives in good yield and an excellent level of 1,5-diastereoselectivity with respect to the cyCloalkane methine carbon and the OH-bearing carbon of the C2 side chain. The reaction is completed in most cases within 1 h at room temperature under nitrogen, tolerates an ester, a hydroxy, an allyl and propargyl ethers, an allylamino, and a pyridyl functionalities, and accommodates a variety of aromatic and aliphatic alkynes and Carbonyls (alClehydes and ketones).Nickel-catalyzed addition of dimethylzinc to aldehydes across alkynes and 1,3-butadiene: An efficient four-component connection reaction74200557#N/ATRUE
217
ja044588b10.1021/ja044588bAdditionFALSEhttps://doi.org/10.1021/ja044588bRovis, TJ. Am. Chem. Soc.A nickel-catalyzed Alkylation of succinic and glutaric anhydrides with Alkyl- and Arylzinc reagents has been developed. A dramatic olefin effect has been investigated resulting in the identification of several styrene-based promoters which show pronounced enhancements in reaction rate. The substrate scope with respect to electrophilic and nuCleophilic coupling partners has been examined and found to be remarkably broad, allowing for rapid introduction of molecular complexity through the use of functionalized coupling partners. Regioselective Alkylation of an unsymmetrical succinic anhydride and a profound effect of pendent coordinating olefins on reaction rate suggest a mechanism involving discrete oxidative addition of the nickel complex into the cyClic anhydride followed by a transmetalation event.Highly efficient nickel-catalyzed cross-coupling of succinic and glutaric anhydrides with organozinc reagents542005x74#N/ATRUE
218
ja020179910.1021/ja0201799AdditionFALSEhttps://doi.org/10.1021/ja0201799Raabe, GJ. Am. Chem. Soc.Selective addition of the chiral, sulfonimldoyl substituted bis(allyl)titanium complexes 5a-d, which are configurationally labile in regard to the Calpha-atoms, to N-toluenesulfonyl (Ts)-, N-2-trimethylsilylethanesulfonyl (SES)-, and N-tert-butylsulfonyl (Bus) alpha-imino ester (9a-c) in the presence of Ti(OiPr)(4) and ClTj(OiPr)(3) afforded with high regio- and diastereoselectivities in good yields the (syn, E)-configured beta-Alkyl-gamma,delta-unsaturated alpha-amino acid derivatives 2a-g, which carry a chiral, electron-withdrawing nuCleofuge at the delta-position and a cyClohexyl, an isopropyl, a phenyl, and a methyl group at the beta-position. Addition of the cyClic bis(allyl)titanium complex 14 to N-Bus alpha-imino ester 9c afforded with similar high regio- and diastereoselectivities the (E)- and (Z)-configured amino acid derivatives (E)-8 and (Z)-8. Reaction of complexes 5a-d with alpha-imino esters 9a-c in the presence of Ti(OiPr)(4) occurs stepwise to give first the mono(allyl)titanium complexes containing 2a-g as ligands, which react in the presence of CITi(OiPr)(3) with a second molecule of 9a-c with formation of two molecules of 2a-g. Formation of (S,R,E)-configured homoallylic amines 2a-g entails SiRe,E processes of alpha-imino esters 9a-c with the (R,R)-configured bis(allyl)titanium complexes (R,R)-5a-d and (R)-configured mono(allyl)titanium complexes (R)-17a-d, both of which are most likely in rapid equilibrium with their (S,S)-diastereomers and (S)-diastereomers, respectively, Interestingly, in the reaction of 5a-d with aldehydes, the (S,S)-configured complexes (S,S)5a-d are the ones which react faster. Reaction of the N-titanated amino acid derivatives Ti-2a and Ti-2b with N-Ts alpha-imino ester 9a led to the highly diastereoselective formation of imidazoldinones 15a and 15b, respectively. Cleavage of the sulfonamide group of the N-Bus amino acid derivative 2d with CF3SO3H gave quantitatively the sulfonimidoyl functionalized amino acid H-2d. A Ni-catalyzed cross-coupling reaction of the amino acid derivative 2e with ZnPh2 led to a substitution of the sulfonimidoyl group by a phenyl group and furnished the enantiomerically pure protected alpha-amino acid Bus-1. Two new N-sulfonyl alpha-imino esters, the SES and the Bus alpha-imino esters 9b and 9c, respectively, have been synthesized from the corresponding sulfonamides by the Kresze method in medium to good yields. The N-SES alpha-imino ester 9b and the N-Bus alpha-imino ester 9c should find many synthetic applications, in particular, in cases where the N-Ts alpha-imino ester 9a had been used before.Highly selective addition of chiral, sulfonimidoyl substituted bis(allyl)titanium complexes to N-sulfonyl alpha-imino esters: Asymmetric synthesis of gamma,delta-unsaturated alpha-amino acids bearing a chiral, electron-withdrawing nuCleofuge at the delta-position382002153#N/ATRUE
219
ja00524a01710.1021/ja00524a017AdditionFALSEhttps://doi.org/10.1021/ja00524a017KOSUGI, HJ. Am. Chem. Soc.NICKEL-CATALYZED CONJUGATE ADDITION OF ALKENYL ZIRCONIUM SPECIES TO ALPHA,BETA-UNSATURATED KETONES117198037#N/ATRUE
220
ja00475a052AdditionFALSEhttps://doi.org/SCHWARTZ, JJ. Am. Chem. Soc.NICKEL-CATALYZED CONJUGATE ADDITION OF ORGANOALUMINUM ACETYLIDES TO ALPHA,BETA-ENONES#N/A22197818#N/ATRUE
221
ja00466a04410.1021/ja00466a044AdditionFALSEhttps://doi.org/10.1021/ja00466a044SCHWARTZ, JJ. Am. Chem. Soc.NICKEL-CATALYZED CONJUGATE ADDITION OF ZIRCONIUM ALKENYLS TO ALPHA, BETA-UNSATURATED KETONES77197712#N/ATRUE
222
ja00039a03010.1021/ja00039a030AdditionFALSEhttps://doi.org/10.1021/ja00039a030MACKENZIE, PBJ. Am. Chem. Soc.Alpha,beta-unsaturated aldehydes R1CH=CR2CHO (R1 = H, Me, n-Pr; R2 = H, Me) react with ethenyl-, (1-ethoxyethenyl)-, (2-phenylethenyl)-, and 1-propenyltriAlkyltin reagents and chlorotriAlkylsilanes (Me3SiCl or t-BuMe2SiCl) in the presence of Ni(COD)2 (COD = 1,5-cyClooctadiene) or 1-((triAlkylsilyl)oxy)allylnickel(II) chloride catalyst precursors to afford the corresponding triAlkylsilyl (E)-enol ethers in 48-79% yield. High C(3)-regioselectivities (greater-than-or-equal-to 15:1 crude, greater-than-or-equal-to 50:1 purified) are observed when R1 = H; moderate C(3)-regioselectivities (2-12:1 crude, 2->50:1 purified) are observed when R1 = Me or n-Pr. High (E)-enol ether selectivities (5->19:1 crude, 10->50:1 purified) are observed in all cases save the addition of (1-ethoxyethenyl)tributyltin to 2-propenal, for which case a 2:1 E/Z ratio is observed. Stoichiometric model reaction and kinetic studies strongly support a Ni(0)/Ni(II) mechanism involving 1-((triAlkylsilyl)oxy)allylnickel(II) intermediates and turnover-limiting alkenyl group transmetalation.NICKEL-CATALYZED, CHLOROTRIAlkylSILANE-ASSISTED CONJUGATE ADDITION OF ALKENYLTRIBUTYLTIN REAGENTS TO ALPHA,BETA-UNSATURATED ALDEHYDES - EVIDENCE FOR A [1-((TRIAlkylSILYL)OXY)ALLYL]NICKEL(II) MECHANISM69199221#N/ATRUE
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d1sc02625a10.1039/d1sc02625aAdditionFALSEhttps://doi.org/10.1039/d1sc02625aKong, WQChem. Sci.Methanol is an abundant and renewable chemical raw material, but its use as a C1 source in C-C bond coupling reactions still constitutes a big challenge, and the known methods are limited to the use of expensive and noble metal catalysts such as Ru, Rh and Ir. We herein report nickel-catalyzed direct coupling of alkynes and methanol, providing direct access to valuable allylic alcohols in good yields and excellent chemo- and regioselectivity. The approach features a broad substrate scope and high atom-, step- and redox-economy. Moreover, this method was successfully extended to the synthesis of [5,6]-bicyClic hemiacetals through a cascade cyClization reaction of alkynones and methanol.Allylic alcohol synthesis by Ni-catalyzed direct and selective coupling of alkynes and methanol0202162#N/ATRUE
224
d0sc02054k10.1039/d0sc02054kAdditionFALSEhttps://doi.org/10.1039/d0sc02054kCONN, RSEJ. Am. Chem. Soc.NICKEL-CATALYZED ADDITION OF GRIGNARD-REAGENTS TO SILYLACETYLENES - SYNTHESIS OF TETRASUBSTITUTED ALKENES79197836#N/ATRUE
225
cs501495g10.1021/cs501495gAdditionFALSEhttps://doi.org/10.1021/cs501495gPeters, RACS Catal.Transition-metal-catalyzed cross-coupling reactions between sp(2)-hybridized C atoms are of prime importance in both target and diversity oriented synthesis. Ideal cross-coupling reactions would neither require any leaving groups nor stoichiometric reagents. In this artiCle, we report the first direct dehydrogenative cross-couplings between aromatic C-H bonds (in most cases using indole substrates) and allylic alcohols, which do not require an additional Classical stoichiometric oxidizing agent and provide beta-Arylketones as value-added products. Ruthenocene- or ferrocene-based bismetallacyCles, in which either Pd(II) or Pt(II) are the catalytically active centers, were found to be particularly efficient catalysts. Control experiments suggest that the bismetallacyCles initially transform the allylic alcohols into Vinylketones, which then Alkylate the aromatic substrate in the presence of the catalyst. The fact that the dehydrogenative coupling does not require a Classical stoichiometric oxidizing agent is explained either by protonolysis of a metallacyClic M(II)-H intermediate or by a mechanism in which an excess of the allylic alcohol substrate serves as a sacrificial hydrogen acceptor. The title reaction is supported by cocatalytic amounts of Ni(OAc)(2). In preliminary studies, it was observed that the title reaction can as well be applied to prochiral CH-acidic pronuCleophiles such as alpha-cyanoacetates, representing the first examples for direct enantioselective, beta-ketoAlkylations via allylic alcohols in the absence of an additional oxidant.Catalytic Direct Dehydrogenative Cross-Couplings of C-H (Pro)NuCleophiles and Allylic Alcohols without an Additional Oxidantbimetallic catalysts; bispalladacyCles; alpha-cyanoacetate; dehydrogenative cross-coupling; direct cross-coupling; ferrocene; indole; beta-ketoAlkylations; oxidant-free; platinacyCle; ruthenocene32201565#N/ATRUE
227
cs501267h10.1021/cs501267hAdditionFALSEhttps://doi.org/10.1021/cs501267hShimazu, SACS Catal.Intercalation of an in situ prepared [Rh(OH)(6)](3) complex into an anion exchangeable NiZn layered hydroxy double salt (Rh/NiZn) was demonstrated. The resulting Rh/NiZn effectively catalyzed the 1,4-addition of diverse enones and phenylboronic acids to their corresponding beta-substituted Carbonyl compounds. In the case of 2-cyClohexen-1-one and phenylboronic acid, a turnover frequency (TOF) of 920 h1 based on Rh was achieved. The [Rh(OH)(6)](3) complex maintained its original monomeric trivalent state within the NiZn interlayer following catalysis, attributable to a strong electrostatic interaction between the NiZn host and anionic Rh(III) complex.Efficient 1,4-Addition of Enones and Boronic Acids Catalyzed by a Ni-Zn Hydroxyl Double Salt-Intercalated Anionic Rhodium(III) ComplexNi-Zn hydroxyl double salt; anion exchange; intercalation rhodium; rhodium; 1,4-addition16201468#N/ATRUE
228
c7cc03263c10.1039/c7cc03263cAdditionFALSEhttps://doi.org/10.1039/c7cc03263cYao, YMRegioselective addition of C(sp(3))-H bonds of Alkyl pyridines to olefins catalysed by cationic zirconium complexes152017#N/ATRUE
229
anie.20201669010.1002/anie.202016690AdditionFALSEhttps://doi.org/10.1002/anie.202016690Shibasaki, MAngew. Chem.-Int. Edit.A direct catalytic asymmetric addition of acetonitrile to aldehydes that realizes over 90 % ee is the ultimate challenge in Alkylnitrile addition chemistry. Herein, we report achieving high enantioselectivity by the strategic use of a sterically demanding Ni-II pincer carbene complex, which afforded highly enantioenriched beta-hydroxynitriles. This highly atom-economical process paves the way for exploiting inexpensive acetonitrile as a promising C2 building block in a practical synthetic toolbox for asymmetric catalysis.Direct Catalytic Asymmetric Addition of Alkylnitriles to Aldehydes with Designed Nickel-Carbene Complexesaldehydes; enantioselectivity; homogeneous catalysis; nickel; nitriles2202152#N/ATRUE
230
anie.20191305710.1002/anie.201913057AdditionFALSEhttps://doi.org/10.1002/anie.201913057Hong, SAngew. Chem.-Int. Edit.Cation-binding salen nickel catalysts were developed for the enantioselective alkynylation of trifluoromethyl ketones in high yield (up to 99 %) and high enantioselectivity (up to 97 % ee). The reaction proceeds with substoichiometric quantities of base (10-20 mol % KOt-Bu) and open to air. In the case of trifluoromethyl Vinyl ketones, excellent chemo-selectivity was observed, generating 1,2-addition products exClusively over 1,4-addition products. UV-vis analysis revealed the pendant oligo-ether group of the catalyst strongly binds to the potassium cation (K+) with 1:1 binding stoichiometry (K-a=6.6x10(5) m(-1)).Enantioselective Alkynylation of Trifluoromethyl Ketones Catalyzed by Cation-Binding Salen Nickel Complexesalkynylation; bifunctional catalysis; nickel; trifluoromethylketones11202084#N/ATRUE
231
anie.20190257610.1002/anie.201902576AdditionFALSEhttps://doi.org/10.1002/anie.201902576Zhang, WBAngew. Chem.-Int. Edit.An efficient nickel-catalyzed asymmetric hydrogenation of N-tBu-sulfonyl imines was developed with excellent yields and enantioselectivities using (R,R)-QuinoxP* as a chiral ligand. The use of a much lower catalyst loading (0.0095mol%, S/C=10500) represents the highest catalytic activity for the Ni-catalyzed asymmetric hydrogenations reported so far. Mechanistic studies suggest that a coordination equilibrium exists between the nickel salt and its complex, and that excess nickel salt promotes the formation of the active Ni-complex, and therefore improved the efficiency of the hydrogenation. The catalytic cyCle was also investigated by calculations to determine the origin of the enantioselectivity. An extensive network of numerous weak attractive interactions was found to exist between the catalyst and substrate in the transition state and may also contribute to the high catalytic activity.Nickel-Catalyzed Asymmetric Hydrogenation of N-Sulfonyl Iminesamines; asymmetric catalysis; hydrogenation; nickel; reaction mechanisms44201958#N/ATRUE
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anie.20180181710.1002/anie.201801817AdditionFALSEhttps://doi.org/10.1002/anie.201801817Zhou, QLAngew. Chem.-Int. Edit.A BrOnsted acid enabled nickel-catalyzed hydroalkenylation of aldehydes and styrene derivatives has been developed. The BrOnsted acid acts as a proton shuttle to transfer a proton from the alkene to the aldehyde, thereby leading to an economical and byproduct-free coupling. A series of synthetically useful allylic alcohols were obtained through one-step reactions from readily available styrene derivatives and aliphatic aldehydes in up to 88% yield and with high linear selectivity.BrOnsted Acid Enabled Nickel-Catalyzed Hydroalkenylation of Aldehydes with Styrene and its Derivativesaldehydes; alkenes; BrOnsted acids; hydroalkenylation; nickel10201878#N/ATRUE
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anie.20170594310.1002/anie.201705943AdditionFALSEhttps://doi.org/10.1002/anie.201705943Feng, XMAngew. Chem.-Int. Edit.The first enantioselective conjugate addition of silyl ketene imines to in situ generated indol-2-ones was performed in the presence of a chiral N,N'-dioxide/Ni-II catalyst. This method provides efficient access to chiral beta-Alkyl nitriles bearing congested vicinal all-carbon quaternary stereocenters in up to 90% yield with 23:1 d.r. and 98% ee. The products enable facile transformations to chiral pyrroloindoline frameworks and spirocyClohexane oxindole derivatives. A possible transition state was also proposed to explain the origin of the asymmetric induction.Nickel-Catalyzed Conjugate Addition of Silyl Ketene Imines to In Situ Generated Indol-2-ones: Highly Enantioselective Construction of Vicinal All-Carbon Quaternary Stereocenters3-bromooxindoles; asymmetric catalysis; conjugate addition; quaternary stereocenters; silyl ketene imines37201776#N/ATRUE
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anie.20160069710.1002/anie.201600697AdditionFALSEhttps://doi.org/10.1002/anie.201600697Martin, RAngew. Chem.-Int. Edit.A user-friendly Ni-catalyzed reductive Carbonylation of Benzylic C-N bonds with CO2 is described. This procedure outperforms state-of-the-art techniques for the Carbonylation of Benzyl electrophiles by avoiding commonly observed parasitic pathways, such as homodimerization or -hydride elimination, thus leading to new knowledge in cross-electrophile reactions.Nickel-Catalyzed Carbonylation of Benzylic C-N Bonds with CO2Carbonylation; C-N Activation; homogeneous catalysis; nickel; reductive coupling132201689#N/ATRUE
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anie.20150293010.1002/anie.201502930AdditionFALSEhttps://doi.org/10.1002/anie.201502930Peters, RAngew. Chem.-Int. Edit.Diastereodivergency is a challenge for catalytic asymmetric synthesis. For many reaction types, the generation of one diastereomer is inherently preferred, while the other diastereomers are not directly accessible with high efficiency and require circuitous synthetic approaches. Overwriting the inherent preference by means of a catalyst requires control over the spatial positions of both reaction partners. We report a novel polyfunctional catalyst type in which a Ni-II-bis(phen-oxyimine) unit, free hydroxy groups, and an axially chiral bisimidazolium entity participate in the stereocontrol of the direct 1,4-addition of oxindoles to nitroolefins. Both epimers of the 1,4-adduct are accessible in excess on demand by changes to the ligand constitution and configuration. As the products have been reported to be valuable precursors to indole alkaloids, this method should allow access to their epimeric derivatives.Diastereodivergent Asymmetric 1,4-Addition of Oxindoles to Nitroolefins by Using Polyfunctional Nickel-Hydrogen-Bond-Azolium Catalystsaxial chirality; cooperative catalysis; hydrogen bonds; imidazolium; oxindolesx46201541#N/AFALSE
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anie.20100118810.1002/anie.201001188AdditionFALSEhttps://doi.org/10.1002/anie.201001188Suginome, MAngew. Chem.-Int. Edit.Nickel-Catalyzed Asymmetric Addition of Alkyne C-H Bonds across 1,3-Dienes Using Taddol-Based Chiral Phosphoramidite Ligandsalkynes; asymmetric catalysis; C-H Activation; 1,3-dienes; nickel65201066#N/ATRUE
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anie.20080332610.1002/anie.200803326AdditionFALSEhttps://doi.org/10.1002/anie.200803326Feng, XMAsymmetric Intramolecular Oxa-Michael Addition of Activated alpha,beta-Unsaturated Ketones Catalyzed by a Chiral N,N '-Dioxide Nickel(II) Complex: Highly Enantioselective Synthesis of Flavanonesx2008#N/AFALSE
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anie.20070375810.1002/anie.200703758AdditionFALSEhttps://doi.org/10.1002/anie.200703758Hiyama, TAngew. Chem.-Int. Edit.Nickel-catalyzed addition of pyridine-N-oxides across alkynesalkynes; C-C coupling; C-H Activation; nickel; pyridine-N-oxides229200722#N/ATRUE
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anie.19800128110.1002/anie.198001281AdditionFALSEhttps://doi.org/10.1002/anie.198001281BLANK, HAngew. Chem.-Int. Edit. Engl.DIRECT SYNTHESIS OF THE PERFLUOROALKANESULFINATES OF IRON(II), COBALT(II), AND NICKEL(II) - SO2-ASSISTED ADDITION OF Alkyl-HALIDES TO TRANSITION-METALS219809#N/ATRUE
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acscatal.8b0419810.1021/acscatal.8b04198AdditionFALSEhttps://doi.org/10.1021/acscatal.8b04198Shi, SLACS Catal.The nickel-catalyzed enantioselective redox-neutral coupling of alcohols and alkynes to access chiral allylic alcohols is reported. The reaction proceeds via a hydrogen transfer process under ambient temperature, converting abundant feedstock alcohols and alkynes to chiral allylic alcohols with high stereoselectivities in one chemical step. Key to the success of this process was the development of a bulky chiral N-heterocyClic carbene, (R,R,R,R)-SIPE, a chiral version of SIPr, as the ligand for nickel. Notably, we found that the utilization of P(OPh)(3) as secondary ligand for nickel was crucial to inhibit the isomerization of products.Nickel/N-HeterocyClic Carbene Complex-Catalyzed Enantioselective Redox-Neutral Coupling of Benzyl Alcohols and Alkynes to Allylic Alcoholsasymmetric catalysis; nickel; ligand design; N-heterocyClic carbenes; transfer hydrogenation; redox-neutral coupling; alkynes; alcohols36201976#N/ATRUE
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acscatal.1c0197110.1021/acscatal.1c01971AdditionFALSEhttps://doi.org/10.1021/acscatal.1c01971Fang, XJACS Catal.A nickel-catalyzed enantioselective hydrocyanation of N-Aryl 5-norbornene-endocis-2,3-dicarboximides was reported. This desymmetrization process allows for a quick construction of both continuous stereogenic carbon centers and remote N-C-Ar atropisomeric chirality. Mechanism studies indicated that the resident Carbonyl group of the substrates plays a key role in the enantioselectivity.Enantioselective Nickel-Catalyzed Hydrocyanative Desymmetrization of Norbornene DerivativesC-N chiral axis; norbornene derivatives; hydrocyanation; Carbonyl effect; desymmetrization0202154#N/ATRUE
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acscatal.0c0181910.1021/acscatal.0c01819AdditionFALSEhttps://doi.org/10.1021/acscatal.0c01819Voituriez, AACS Catal.A chiral phosphathiahelicene scaffold displaying a CI phosphole and a thiophene unit as the terminal rings of the helical sequence has been synthesized and characterized by spectroscopic methods and X-ray diffraction studies. The phosphine oxides (HelPhos-V oxides) have been obtained following a robust and scalable synthetic approach, based on a nickel-promoted alkyne cyClotrimerization reaction. Then, late-stage functionalization has been carried out via a bromination/palladium coupling reaction sequence. The HelPhos-V gold(I) complexes have been used as catalysts in the unprecedented enantioselective [2 + 2] cyClization of N-homoallenyl tryptamine derivatives, to afford indolenine-fused cyClobutanes in good isolated yields, with enantiomeric excesses up to 93%.Chiral Phosphathiahelicenes: Improved Synthetic Approach and Uses in Enantioselective Gold(I)-Catalyzed [2+2] CyCloadditions of N-Homoallenyl Tryptaminesphosphorus ligands; helicenes; gold catalysis; spirofused compounds; tryptamines; indolinecyClobutanes6202085#N/ATRUE
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acscatal.0c0010510.1021/acscatal.0c00105AdditionFALSEhttps://doi.org/10.1021/acscatal.0c00105Elbaz, LTernary NiFeTiOOH Catalyst for the Oxygen Evolution Reaction: Study of the Effect of the Addition of Ti at Different Loadings2020#N/ATRUE
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acs.orglett.9b0162510.1021/acs.orglett.9b01625AdditionFALSEhttps://doi.org/10.1021/acs.orglett.9b01625Lee, SNi/Cu-Catalyzed DeCarbonylative Addition of Alkynoic Acids to Terminal Alkynes for the Synthesis of gem-1,3-Enynes2019#N/ATRUE
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1521-3773(20020802)41:15<2784::AID-ANIE2784>3.0.CO;2-A10.1002/1521-3773(20020802)41:15<2784::AID-ANIE2784>3.0.CO;2-AAdditionFALSEhttps://doi.org/10.1002/1521-3773(20020802)41:15<2784::AID-ANIE2784>3.0.CO;2-ATamaru, YAngew. Chem.-Int. Edit.Remarkably high 1,5-diastereoselectivity in a nickel-catalyzed conjugate addition of Me2Zn and Carbonyl compounds to 1,omega-dienynes with through-space couplingaldehydes; alkynes; dienes; ketones; nickel; zinc36200236#N/ATRUE
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jacs.9b1252910.1021/jacs.9b12529AdditionFALSEhttps://doi.org/10.1021/jacs.9b12529Murakami, MJ. Am. Chem. Soc.A photoinduced Carbonylation reaction of Benzylic and aliphatic C-H bonds with CO2 is developed. toluene derivatives capture gaseous CO2 at the Benzylic position to produce phenylacetic acid derivatives when irradiated with UV light in the presence of an aromatic ketone, a nickel complex, and potassium tert-butoxide. CyClohexane reacts with CO2 to furnish cyClohexaneCarbonylic acid under analogous reaction conditions. The present photoinduced Carbonylation reaction provides a direct access from readily available hydrocarbons to the corresponding Carbonylic acids with one carbon extension.Carbonylation of Benzylic and Aliphatic C-H Bonds with CO2 Induced by Light/Ketone/Nickel37201947#N/ATRUE
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jacs.8b0770810.1021/jacs.8b07708AdditionFALSEhttps://doi.org/10.1021/jacs.8b07708Love, JAJ. Am. Chem. Soc.We report a mechanistic study of C(sp(3))-H bond Activation mediated by nickel. CyClometalated Ni(II) ureate [(PEt3)Ni(kappa(3)-C,N,N-((C) under barH(2))N(Cy)(CO)(N) under bar(((N) under bar)-quinolin-8-y1))] was synthesized and isolated from the urea precursor, (Me)(Cy)N(CO)N(H)(quinolin-8-yl), via C(sp(3))-H Activation. We investigated the effects of solvents and base additives on the rate of C-H Activation. Kinetic isotope effect experiments showed that C-H Activation is rate determining. Through deuterium labeling and protonation studies, we also showed that C-H Activation can be reversible. We extended this reaction to a range of ureas with primary and secondary C(sp(3))-H bonds, which activate readily to form analogous nickelated products. Finally, we showed that Carbonylate additives assist with both ligand dissociation and initial N-H bond Activation, consistent with a concerted metalation-deprotonation mechanism.Understanding Ni(II)-Mediated C(sp(3))-H Activation: Tertiary Ureas as Model Substrates22201883#N/ATRUE
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jacs.6b1196210.1021/jacs.6b11962AdditionFALSEhttps://doi.org/10.1021/jacs.6b11962Zhu, SLJ. Am. Chem. Soc.The synergistic combination of NiH-catalyzed alkene isomerization with nickel-catalyzed cross-coupling has yielded a general protocol for the synthesis of a wide range of structurally diverse 1,1-diArylalkanes in excellent yields and high regioselectivities from readily accessible olefin starting materials. Furthermore, the practicality and synthetic flexibility of this approach is highlighted by the successful employment of isomeric mixtures of olefins for regioconvergent Arylation.Mild and Regioselective Benzylic C-H Functionalization: Ni-Catalyzed Reductive Arylation of Remote and Proximal Olefins132201742#N/ATRUE
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jacs.5b0454810.1021/jacs.5b04548AdditionFALSEhttps://doi.org/10.1021/jacs.5b04548Montgomery, JJ. Am. Chem. Soc.An inhibitory role of 1,5-cyClooctadiene (COD) in nickel-catalyzed,C-H functionalization processes as identified and studied. The bound COD participates in C-H Activation by capturing the hydride, leading to a stable off-cyCle pi-allyl complex that greatly diminished overall catalytic efficiency. Computational studies elucidated the origin of the effect and enabled identification of a 1,5-hexadiene-derived pre-catalyst that avoids the off-cyCle intermediate and provides catalytic efficiencies that are superior to those of catalysts derived from Ni(COD)(2).Highly Active Nickel Catalysts for C-H Functionalization Identified through Analysis of Off-CyCle Intermediates52201546#N/ATRUE
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jacs.0c0881010.1021/jacs.0c08810AdditionFALSEhttps://doi.org/10.1021/jacs.0c08810Martin, RJ. Am. Chem. Soc.A remote catalytic reductive sp(2.) C-H Carbonylation of arenes with CO2 (1 bar) via 1,4-Ni migration is disClosed. This protocol constitutes the first catalytic 1,4-Ni migration reported to date, thus offering new vistas in the Ni-catalyzed reductive coupling arena while providing an unconventional new platform for incorporating electrophilic sites at remote sp(2) C-H linkages.Remote sp(2) C-H Carbonylation via Catalytic 1,4-Ni Migration with CO23202075#N/ATRUE
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ja800021610.1021/ja8000216AdditionFALSEhttps://doi.org/10.1021/ja8000216Jones, WDJ. Am. Chem. Soc.The reaction of [(dippe)NiH](2) with 2-methyl-3-butenenitrile (2M3BN) in solvents spanning a wide range of polarities shows significant differences in the ratio of C-H and C-CN activated products. C-H Cleavage is favored in polar solvents, whereas C-C Cleavage is favored in nonpolar solvents. This variation is attributed to the differential solvation of the transition states, which was further supported through the use of sterically bulky solvents and weakly coordinating solvents. Variation of the temperature of reaction of [(dippe)NiH](2) with 2M3BN in decane and N,N-dimethylformamide (DMF) allowed for the calculation of Eyring Activation parameters for the C-CN Activation and C-H Activation mechanisms. The Activation parameters for the C-H Activation pathway were Delta H-double dagger = 11.4 +/- 5.3 kcal/mol and Delta S-double dagger = -45 +/- 15 e.u., compared with Delta H-double dagger = 17.3 +/- 2.6 kcal/mol and Delta S-double dagger = -29 +/- 7 e:u. for the C-CN Activation pathway. These parameters indicate that C-H Activation is favored enthalpically, but not entropically, over C-C Activation, implying a more ordered transition state for the former.Solvent effects and Activation parameters in the competitive Cleavage of C-CN and C-H bonds in 2-methyl-3-butenenitrile using [(dippe)NiH](2)59200823#N/ATRUE
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ja710766j10.1021/ja710766jAdditionFALSEhttps://doi.org/10.1021/ja710766jHiyama, TJ. Am. Chem. Soc.The C-2 selective alkenylation of pyridine derivatives is achieved with a catalyst consisting of nickel and Lewis acid. Use of diorganozinc compounds as the Lewis acid catalyst gives C-2 monoalkenylation products, whereas AIMe(3) changes the reaction course to afford C-2 dienylated products, which are derived from double insertion of alkynes into the C(2)-H bond. The reaction demonstrates a broad substrate scope and proceeds with high chemo-, regio-, and stereoselectivities under mild conditions compared with previous examples of direct GM functionalization of pyridines.A strategy for C-H Activation of pyridines: Direct C-2 selective alkenylation of pyridines by Nickel/Lewis acid catalysis328200823#N/ATRUE
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ja106124610.1021/ja1061246AdditionFALSEhttps://doi.org/10.1021/ja1061246Yap, GPAJ. Am. Chem. Soc.We have presented new amino-NHC Ni-Al complex mediated para C-H bond Activation for pyridine and quinolin, and isolated for the first time the intermediate structure of a bimetallic eta(2),eta(1)-pyridine pyridine nickel aluminum complex prior to its C-H Activation, which serves as key evidence for bimetallic catalysis.Bimetallic Nickel Aluminun Mediated Para-Selective Alkenylation of Pyridine: Direct Observation of eta(2),eta(1)-Pyridine Ni(0)-Al(III) Intermediates Prior to C-H Bond Activation195201032#N/ATRUE
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anie.20190738710.1002/anie.201907387AdditionFALSEhttps://doi.org/10.1002/anie.201907387Shi, SLAngew. Chem.-Int. Edit.Chiral polyfluoroarene derivatives are an important scaffold in chemistry. An unprecedented enantioselective C-H Alkylation of polyfluoroarenes with alkenes is described. The reaction employs bulky chiral N-heterocyClic carbene (NHC) ligands for nickel catalysts to enable exClusive Activation of C-H bonds over C-F bonds and complete endo-selective C-H annulation and excellent enantioselectivity. A wide variety of chiral fluorotetralins, compounds otherwise difficultly accessed but serve as important bioisosteric analogs of both tetralin and heterocyCle units for drug design, are expediently synthesized from easily available substrates. To our knowledge, this is the first example of catalytic enantioselective C-H functionalization of polyfluoroarenes.Nickel/NHC-Catalyzed Asymmetric C-H Alkylation of Fluoroarenes with Alkenes: Synthesis of Enantioenriched Fluorotetralinsasymmetric hydroArylation; C-H Alkylation; chiral NHC ligand; fluoroarenes; nickel catalysis30201979#N/ATRUE
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anie.20190477410.1002/anie.201904774AdditionFALSEhttps://doi.org/10.1002/anie.201904774Cramer, NAngew. Chem.-Int. Edit.An enantioselective nickel(0)-catalyzed C-H functionalization of indoles and pyrroles that does not require the typical Lewis basic directing groups is disClosed. The reaction provides access to valuable tetrahydropyridoindoles and tetrahydroindolizines in high yields and enantioselectivity under mild reaction conditions. The process is characterized by a Clear endo-cyClization preference to yield the sought-after six-membered-ring products. Key for the success of the Activation and selectivity in the cyClization was the development of a novel chiral SIPr carbene ligand analogue with very bulky flanking groups.A Bulky Chiral N-HeterocyClic Carbene Nickel Catalyst Enables Enantioselective C-H Functionalizations of Indoles and Pyrrolesasymmetric catalysis; C-H Activation; chiral NHC ligands; heterocyCles; nickel33201991#N/ATRUE
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anie.20181319110.1002/anie.201813191AdditionFALSEhttps://doi.org/10.1002/anie.201813191Ackermann, LAngew. Chem.-Int. Edit.Highly enantioselective nickel-catalyzed alkene endo-hydroArylations were accomplished with full selectivity by organometallic C-H Activation. The asymmetric assembly of chiral six-membered scaffolds proved viable in the absence of pyrophoric organoaluminum reagents within an unprecedented nickel/JoSPOphos manifold.Enantioselective Aluminum-Free Alkene HydroArylations through C-H Activation by a Chiral Nickel/JoSPOphos Manifoldaluminum-free; asymmetric catalysis; C-H Activation; nickel; SPOs292019101#N/ATRUE
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anie.20100712810.1002/anie.201007128AdditionFALSEhttps://doi.org/10.1002/anie.201007128Ma, SMAngew. Chem.-Int. Edit.Highly Regio- and Stereoselective Three-Component Nickel-Catalyzed syn-HydroCarbonylation of Alkynes with Diethyl Zinc and Carbon Dioxidealkynes; carbon dioxide; hydroCarbonylation; inorganic fluoride; nickel162201159#N/ATRUE
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acscatal.7b0291910.1021/acscatal.7b02919AdditionFALSEhttps://doi.org/10.1021/acscatal.7b02919Zimmerman, PMACS Catal.A detailed mechanistic investigation of N-heterocyClic carbene-nickel-catalyzed hydroArylation via C-H functionalization is described. These catalysts are complicated, in part, by undesired reactivity stemming from common olefinic ligands such as cyClooctadiene (COD) that stabilize the precatalyst. This reaction adds diversity to the overall reactive landscape by permitting multiple types of ligand-to-ligand hydrogen transfer (LLHT) steps to activate the substrate arene C-H bonds. In one case, stable pi-ally1 complexes can be formed via LLHT to the olefin, hindering catalysis, and in the other, LLHT to the alkyne substrate leads to productive catalysis. Here, a useful map is built from extensive computational and experimental studies to guide subsequent investigations on the productive use of Ni catalysis. In addition to showing the details of catalyst deActivation, Activation, and operating regimes, this artiCle suggests the following: 1. Reductive elimination is rate-limiting and assisted by an additional alkyne ligand; 2. The resting state for catalysis is an alkyne-ligated Ni center; and 3. The reaction rate is under thermodynamic control, showing a good correlation with thermodynamics of C-H addition to the metal center (R-2 = 0.95).Entrances, Traps, and Rate-Controlling Factors for Nickel-Catalyzed C-H Functionalizationnickel catalysis; C-H functionalization; chain walking; off-cyCle activity; linear free energy relationships24201753#N/ATRUE
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acscatal.1c0075010.1021/acscatal.1c00750AdditionFALSEhttps://doi.org/10.1021/acscatal.1c00750Ye, MCACS Catal.Conventional C-H alkenylation with alkynes via low-valent transition-metal catalysis occurs at the C6 or C4 position of 2-pyridone with electron-deficient C-H bonds. A bifunctional ligand-bonded Ni-Al bimetallic catalyst resulted in a reversed selectivity, providing a series of C3-alkenylated 2-pyridones in up to 99% yields.Ligand-Controlled Ni(0)-Al(III) Bimetal-Catalyzed C3-H Alkenylation of 2-Pyridones by Reversing Conventional Selectivitynickel; aluminum; site-selective; 2-pyridone; alkenylation1202190#N/ATRUE
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s41467-019-08631-110.1038/s41467-019-08631-1AdditionFALSEhttps://doi.org/10.1038/s41467-019-08631-1Li, CJNat. Commun.Alkenes are fundamental functionalities in nature and highly useful intermediates in organic synthesis, medicinal chemistry and material sciences. Transition-metal-catalyzed Heck couplings with organic halides as electrophiles have been established as a powerful protocol for the synthesis of this valuable building block. However, the requirement of organic halides and the generation of stoichiometric hazardous halide wastes may cause significant sustainable concerns. The halide-free oxidative Heck alkenylations involving organometallics or arenes as the coupling partners provide a facile and alternative pathway. Nonetheless, stoichiometric amounts of extra oxidant are essential in most cases. Herein, we present a direct dehydrogenative Alkyl Heck-coupling reaction under oxidant-free conditions, liberating hydrogen, nitrogen and water as the side products. Excellent regioselectivity is achieved via neighboring oxygen atom coordination. Broad substrate scope, great functional group (ketone, ester, phenol, free amine, amide etc) tolerance and modification of pharmaceutical candidates and biological molecules exemplified its generality and practicability.Direct dehydrogenative Alkyl Heck-couplings of Vinylarenes with umpolung aldehydes catalyzed by nickely242019xx65#N/AFALSE
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jacs.9b0941510.1021/jacs.9b09415AdditionFALSEhttps://doi.org/10.1021/jacs.9b09415Fu, YJ. Am. Chem. Soc.Substantial advances in enantioconvergent C(sp(3))-C(sp(3)) bond formation reactions have been made in recent years through the use of transition-metal-catalyzed cross-coupling reactions of racemic secondary Alkyl electrophiles with organometallic reagents. Herein, we report a general process for the asymmetric construction of Alkyl-Alkyl bonds adjacent to heteroatoms, namely, a nickel-catalyzed enantioconvergent reductive hydroAlkylation of olefins with alpha-heteroatom phosphorus or sulfur Alkyl electrophiles. InCluding the use of readily available olefins, this reaction has considerable advantages, such as mild reaction conditions, a broad substrate scope, and good functional group compatibility, making it a desirable alternative to traditional electrophile-nuCleophile cross-coupling reactions.Nickel-Catalyzed Enantioconvergent Reductive HydroAlkylation of Olefins with alpha-Heteroatom Phosphorus or Sulfur Alkyl Electrophiles30202068#N/ATRUE
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ja807258m10.1021/ja807258mAdditionFALSEhttps://doi.org/10.1021/ja807258mHiyama, TJ. Am. Chem. Soc.Nickel/P(c-C(5)H(9))(3) (PCyp(3)) catalyst effects the addition reactions of fluoroarenes across alkynes, 1,3-dienes, and Vinylarenes via the Activation of C-H bonds over C-F bonds. The acidic C-H bonds located ortho to fluorine are exClusively activated to afford a range of alkenylated and Alkylated fluoroarenes.Nickel-Catalyzed Alkenylation and Alkylation of Fluoroarenes via Activation of C-H Bond over C-F Bondy230200838#N/AFALSE
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c9cc05385a10.1039/c9cc05385aAdditionFALSEhttps://pubs.rsc.org/en/content/artiClepdf/2019/cc/c9cc05385aLiu, FNi-Catalyzed deaminative hydroalkylation of internal alkynes†17#N/A
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anie.20200501910.1002/anie.202005019AdditionFALSEhttps://doi.org/10.1002/anie.202005019Guo, CCooperative Ni/Cu-Catalyzed Asymmetric Propargylic Alkylation of Aldimine Estersy2020#N/AFALSE
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anie.20170317410.1002/anie.201703174AdditionTRUEhttps://onlinelibrary.wiley.com/doi/full/10.1002/anie.201703174Garg, NKANGEWANDTE CHEMIE-INTERNATIONAL EDITIONWe report non-deCarbonylative Mizoroki-Heck reactions of amide derivatives. The transformation relies on the use of nickel catalysis and proceeds using sterically hindered tri- and tetrasubstituted olefins to give products containing quaternary centers. The resulting polycyclic or spirocyclic products can be obtained in good yields. Moreover, a diastereoselective variant of this method gives access to an adduct bearing vicinal, highly substituted sp3 stereocenters. These results demonstrate that amide derivatives can be used as building blocks for the assembly of complex scaffolds.Mizoroki-Heck Cyclizations of Amide Derivatives for the Introduction of Quaternary Centers
amides ; homogeneous catalysis ; Mizoroki-Heck reactions ; nickel ; quaternary centers
#N/A#N/A#N/A#N/A6420175/11/2022
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jacs.9b0093110.1021/jacs.9b00931Additionhttps://pubs.acs.org/doi/10.1021/jacs.9b00931Shi, SL#N/A
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acscatal.5b0179310.1021/acscatal.5b01793Addition of StyrenesFALSEhttps://doi.org/10.1021/acscatal.5b01793Jia, YXACS Catal.Enantioselective addition of styrenes to cyClic N-sulfonyl alpha-ketiminoesters was developed using the complex of Ni(ClO4)(2) with chiral phosphine complex as a catalyst. A range of chiral benzofused 5-membered sultams bearing alkenylated or allylated alpha-tetrasubstituted amino ester framework were afforded in excellent enantioselectivities (up to 99% ee) as potential biologically active compounds for drug research.Nickel-Catalyzed Enantioselective Addition of Styrenes to CyClic N-Sulfonyl alpha-Ketiminoestersasymmetric catalysis; nickel; styrene; quaternary stereocenter; sultam28201570#N/ATRUE
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anie.20191137210.1002/anie.201911372addition reactionhttps://doi.org/10.1002/anie.201911372Newman, SGAngew. Chem.-Int. Edit.While esters are frequently used as traditional electrophiles in substitution chemistry, their application in cross-coupling chemistry is still in its infancy. This work demonstrates that methyl esters can be used as coupling electrophiles in Ni-catalyzed Heck-type reactions through the challenging Cleavage of the C(acyl)-O bond under relatively mild reaction conditions at either 80 or 100 degrees C. With the sigma-Ni-II intermediate generated from the insertion of acyl Ni-II species into the tethered C=C bond, Carbonyl-retentive products were formed by domino Heck/Suzuki-Miyaura coupling and Heck/reduction pathways when organB(OH)2ron and mild hydride nuCleophiles are used.Nickel-Catalyzed Domino Heck-Type Reactions Using Methyl Esters as Cross-Coupling Electrophilesesters; cross-coupling; cyClizations; homogeneous catalysis; nickeladdition reaction212019xxxring formation96#N/AFALSE
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ja073591310.1021/ja0735913Additions FALSEhttps://doi.org/10.1021/ja0735913Seidel, DJ. Am. Chem. Soc.Readily prepared Ni(II)-bis[(RR)-N,N-diBenzylcyClohexane-1,2-diamine]Br-2 was shown to catalyze the Michael addition of 1,3-diCarbonyl compounds to nitroalkenes at room temperature in good yields with high enantioselectivities. The two diamine ligands in this system each play a distinct role: one serves as a chiral ligand to provide stereoinCluction in the addition step while the other functions as a base for substrate enolization. Ligand modification within the catalyst was also investigated to facilitate the reaction of aliphatic nitroalkenes, 1,3-diketones, and beta-ketoacids. Ni(II)-bis[(R,R)-N,N-di-p-bromo-BenzylcyClohexane-1,2diamine]Br-2 was found to be an effective catalyst in these instances. Furthermore, monodiamine complex, Ni(II)-[(R,R)-N,N-diBenzylcyClohexane-1,2-diamine]Br-2, catalyzed the addition reaction in the presence of water. The proposed model for stereochernical induction is shown to be consistent with X-ray structure analysis.Scope and mechanism of enantioselective Michael additions of 1,3-diCarbonyl compounds to nitroalkenes catalyzed by nickel(II)-diamine complexes2542007109#N/ATRUE
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jacs.8b1325110.1021/jacs.8b13251Alkenyl ExchangeTRUEhttps://doi.org/10.1021/jacs.8b13251Zhou, QLJ. Am. Chem. Soc.A functional group exchange reaction between allylamines and alkenes via nickel -catalyzed C-C bond Cleavage and formation was developed. This reaction provides a novel protocol, which does not require the use of unstable imine substrates, for the synthesis of allylamines, which are widely used in the production of fine chemicals, pharmaceuticals, and agrochemicals.Alkenyl Exchange of Allylamines via Nickel(0)-Catalyzed C-C Bond CleavageCsp2-Csp3E-NuHHVinylVinylNo baseNo Base162019354/15/2022TRUE
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anie.20200608210.1002/anie.202006082AlkylidenecyClopropanationsFALSEhttps://doi.org/10.1002/anie.202006082Cramer, NAngew. Chem.-Int. Edit.A novel Class of chiral naphthyridine diimine ligands (NDI*) readily accessible fromC(2)-symmetric 2,6-di-(1-Arylethyl)anilines is described. The utility of these ligands, particularly one with fluorinated Aryl side arms, is demonstrated by a reductive Ni-catalyzed enantioselective Alkylidene transfer reaction from 1,1-dichloroalkenes to olefins. This transformation provides direct access to a broad range of synthetically valuable AlkylidenecyClopropanes in high yields and enantioselectivities.A Chiral Naphthyridine Diimine Ligand Enables Nickel-Catalyzed Asymmetric AlkylidenecyClopropanationsAlkylidene transfer; asymmetric catalysis; cyClopropanes; naphthyridine diimine (NDI) ligands; nickel2202064#N/ATRUE
273
ja017575w10.1021/ja017575wAminationTRUEhttps://doi.org/10.1021/ja017575wHartwig, JFJ. Am. Chem. Soc.A simple colorimetric assay of various transition-metal catalysts showed that the combination of DPPF, Ni(COD)(2), and acid is a highly active catalyst system for the hydroamination of dienes by Alkylamines to form allylic amines. The scope of the reaction is broad; various primary and secondary Alkylamines react with 1,3-dienes in the presence of these catalysts. Detailed mechanistic studies revealed the individual steps involved in the catalytic process. These studies uncovered unexpected thermodynamics for the addition of amines to pi-allyl nickel complexes: instead of the thermodynamics favoring the reaction of a nickel allyl with an amine to form an allylic amine, the thermodynamics favored reaction of a nickel(0) complex with allylic amine in the presence of acid to form a Nj(II) allyl. The realization of these thermodynamics led us to the discovery that nickel and some palladium complexes in the presence or absence of acid catalyze the exchange of the amino groups of allylic amines with free amines. This exchange process was used to reveal the relative thermodynamic stabilities of various allylic amines. In addition, this exchange reaction leads to racemization of allylic amines. Therefore, the relative rate for C-N bond formation and Cleavage influences the enantioselectivity of diene hydroaminations.A general nickel-catalyzed hydroamination of 1,3-dienes by Alkylamines: Catalyst selection, scope, and mechanism#N/A#N/A#N/A#N/A1902002495/11/2022TRUE
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jacs.0c0851210.1021/jacs.0c08512AnnulationFALSEhttps://doi.org/10.1021/jacs.0c08512Chatani, NJ. Am. Chem. Soc.The Ni-catalyzed reaction of ortho-fluoro-substituted aromatic amides with alkynes results in C-F/N-H annulation to give 1(2H) isoquinolinones. A key to the success of the reaction is the use of (KOBu)-Bu-t or even weak base, such as Cs2CO3. The reaction proceeds in the absence of a ligand and under mild reaction conditions (40-60 degrees C). DFT calculations suggest that the pathway for this Ni-catalyzed C-F/N-H annulation involves N-H deprotonation, oxidative addition of a C-F bond, migratory insertion of an alkyne, and reductive elimination to form 1(2H)-isoquinolinone derivatives.Nickel-Catalyzed C-F/N-H Annulation of Aromatic Amides with Alkynes: Activation of C-F Bonds under Mild Reaction Conditions14202044#N/ATRUE
275
c8sc05063e10.1039/c8sc05063eannulationFALSEhttps://doi.org/10.1039/c8sc05063eChatani, NChem. Sci.The reaction of N-Het compounds, such as 2-Aryl-pyrrole, benzimidazole, imidazole, indole, and pyrazole derivatives, with alkynes in the presence of a catalytic amount of a nickel complex results in C-H/N-H oxidative annulation. The reaction shows a high functional group compatibility. While both Ni(0) and Ni(II) complexes show a high catalytic activity, Ni(0) is proposed as a key catalytic species in the main catalytic cyCle. In the case of the Ni(II) system, the presence of a catalytic amount of a strong base, such as KOBut, is required for the reaction to proceed. In sharp contrast, a base is not required in the case of the Ni(0) system. The proposed mechanism is supported by DFT studies.Nickel-catalyzed oxidative C-H/N-H annulation of N-Het compounds with alkynes262019103#N/ATRUE
276
anie.20100759810.1002/anie.201007598annulationFALSEhttps://doi.org/10.1002/anie.201007598Harrity, JPAAngew. Chem.-Int. Edit.A Nickel-Catalyzed Benzannulation Approach to Aromatic Boronic Estersalkynylboronates; boronic esters; cyCloadditions; cyClobutenones; quinones74201133#N/ATRUE
277
ja909603j10.1021/ja909603jAnnulation FALSEhttps://doi.org/10.1021/ja909603jMurakami, MJ. Am. Chem. Soc.A denitrogenative annulation reaction of 1,2,3-benzotriazin-4(3H)-ones with allenes catalyzed by a nickel-phosphine complex to produce a variety of substituted 3,4-dihydroisoquinolin-1(2H)-ones in a regioselective manner is described. A highly enantioselective version, as well as structural evidence for the mechanistic course of this reaction, is also presented.Enantioselective Synthesis of 3,4-Dihydroisoquinolin-1(2H)-ones by Nickel-Catalyzed Denitrogenative Annulation of 1,2,3-Benzotriazin-4(3H)-ones with Allenes96201021#N/ATRUE
278
c7sc01750b10.1039/c7sc01750bannulation FALSEhttps://doi.org/10.1039/c7sc01750bChatani, NChem. Sci.The Ni-catalyzed reaction of aromatic amides with alkynes in the presence of KOBut involves C-H/N-H oxidative annulation to give 1(2H)-isoquinolinones. A key to the success of the reaction is the use of a catalytic amount of strong base, such as KOBut. The reaction shows a high functional group compatibility. The reaction with unsymmetrical alkynes, such as 1-Arylalkynes, gives the corresponding 1(2H)-isoquinolinones with a high level of regioselectivity. This discovery would lead to the development of Nicatalyzed chelation-assisted C-H functionalization reactions without the need for a specific chelation system.Nickel-catalyzed C-H/N-H annulation of aromatic amides with alkynes in the absence of a specific chelation system42201765#N/ATRUE
279
anie.20200126710.1002/anie.202001267Annulation FALSEhttps://doi.org/10.1002/anie.202001267Ye, MCEnantioselective Twofold C-H Annulation of Formamides and Alkynes without Built-in Chelating Groups2020#N/ATRUE
280
anie.20140836410.1002/anie.201408364AnnulationsFALSEhttps://doi.org/10.1002/anie.201408364Cramer, NAngew. Chem.-Int. Edit.CyClopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel-catalyzed reductive [3+2] cyCloaddition of alpha,beta-unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C-1-symmetric N-heterocyClic carbene ligand were shown to enable an efficient asymmetric synthesis of cyClopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyClopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.Nickel(0)-Catalyzed Enantioselective Annulations of Alkynes and Arylenoates Enabled by a Chiral NHC Ligand: Efficient Access to CyClopentenonesannulation; asymmetric catalysis; carbenes; cyClopentenones; nickel39201477#N/ATRUE
281
acscatal.0c0458510.1021/acscatal.0c04585Bimetallic CatalysisFALSEhttps://doi.org/10.1021/acscatal.0c04585Ye, MCACS Catal.Previously reported direct C-H functionalization reactions of enamides mainly occurred at Vinylic C(sp(2))-H bonds because of their relatively high reactivity, while less reactive beta'-C(sp(3))-H Activation has been rarely explored. Herein we report a selective C(sp(3))-H Cleavage of N-Carbonyl enamides without backbone modification, providing a series of 2-pyridones in 58-99% yields. A bifunctional phosphine oxide (PO) ligand-bridging Ni-Al bimetallic catalyst played key role in the reaction.Selective C(sp(3))-H Cleavage of Enamides for Synthesis of 2-Pyridones via Ligand-Enabled Ni-Al Bimetallic Catalysisnickel; aluminum; C(sp(3))-H; enamide; alkyne62021115#N/ATRUE
282
d1sc00900a10.1039/d1sc00900aC-B AcouplingFALSEhttps://doi.org/10.1039/d1sc00900aBrown, MKChem. Sci.Through the combination of a Ni-catalyzed alkene alkenylboration followed by hydrogenation, the synthesis of congested Csp(3)-Csp(3)-bonds can be achieved. Conditions have been identified that allow for the use of both alkenyl-bromides and -triflates. In addition, the hydrogenation creates another opportunity for stereocontrol, thus allowing access to multiple stereoisomers of the product. Finally, the method is demonstrated in the streamlined synthesis of a biologically relevant molecule.Construction of congested Csp(3)-Csp(3) bonds by a formal Ni-catalyzed Alkylboration0202152#N/ATRUE
283
ja204868210.1021/ja2048682C-B CouplingFALSEhttps://doi.org/10.1021/ja2048682Krauss, IJJ. Am. Chem. Soc.A simple method for addition of homoallylic fragments to aldehydes is described. Cydopropanated allylboration reagents react with aldehydes in the presence of PhBCl2 to give high yields of bishomoallyl alcohols. CyClopropanated cis- and trans-crotyl reagents afford the corresponding 1,3-anti- and 1,3-syn-methyl-substituted homocrotylated alcohols with high selectivity, consistent with a Zimmerman-Traxler transition state. Accordingly, the optically active alpha-substituted reactant affords the E-substituted product in 97:3 er.Homoallylboration and Homocrotylboration of Aldehydes22201153#N/ATRUE
284
anie.20170671910.1002/anie.201706719C-B couplingFALSEhttps://doi.org/10.1002/anie.201706719Morken, JPAngew. Chem.-Int. Edit.Catalytic enantioselective conjunctive cross-coupling between 9-BBN borate complexes and Aryl electrophiles can be accomplished with Ni salts in the presence of a chiral diamine ligand. The reactions furnish chiral 9-BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or engaged in other stereospecific C-C bond forming reactions.Nickel-Catalyzed Enantioselective Conjunctive Cross-Coupling of 9-BBN Boratesasymmetric catalysis; boron; cross coupling; nickel39201765#N/ATRUE
285
jacs.9b01886
10.1021/jacs.9b01886C-Br ActivationTRUEhttps://pubs.acs.org/doi/10.1021/jacs.9b01886Baran, PSElectrochemically Driven, Ni-Catalyzed Aryl Amination: Scope, Mechanism, and ApplicationsElectrochemistry#N/AXHArylNo baseNo Base7/28/2022FALSE
286
jacs.1c0850210.1021/jacs.1c08502C-C ActivationLongTRUEhttps://pubs.acs.org/doi/10.1021/jacs.1c08502Song, SLCsp2_ar-Csp2_arE-NuOOMsB(OH)2ArylIonic-PO4020213/11/2022
287
science.aaf612310.1126/science.aaf6123C-C ActivationFALSEhttps://doi.org/10.1126/science.aaf6123Baran, PSScienceAlkyl Carbonylic acids are ubiquitous in all facets of chemical science, from natural products to polymers, and represent an ideal starting material with which to forge new connections. This study demonstrates how the same activating principles used for decades to make simple C-N (amide) bonds from Carbonylic acids with loss of water can be used to make C-C bonds through coupling with diAlkylzinc reagents and loss of carbon dioxide. This disconnection strategy benefits from the use of a simple, inexpensive nickel catalyst and exhibits a remarkably broad scope across a range of substrates (> 70 examples).A general Alkyl-Alkyl cross-coupling enabled by redox-active esters and Alkylzinc reagents3682016xx32#N/ATRUE
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jo00070a02210.1021/jo00070a022C-C ActivationFALSEhttps://pubs.acs.org/doi/10.1021/jo00070a022Scott, W. J.J. Org. Chem.Nickel-mediated cross-coupling of unactivated neopentyl iodides with organozincs341993#N/A
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anie.20161181910.1002/anie.201611819C-C Activationhttps://onlinelibrary.wiley.com/doi/10.1002/anie.201611819Rueping, M#N/A
290
acscatal.8b0281510.1021/acscatal.8b02815C-Carbonyl ActivationKellyFALSEhttps://doi.org/10.1021/acscatal.8b02815Szostak, MACS Catal.We report the Pd-catalyzed acyl and the Ni-catalyzed biAryl Suzuki-Miyaura cross-coupling of N-acetyl-amides with Arylboronic acids by selective N-C(O) Cleavage. Activation of the amide bond by N-acylation provides electronically destabilized, acyClic, nonplanar amide, which readily undergoes cross-coupling with a wide range of boronic acids to produce biAryl ketones or biAryls in a highly efficient manner. Most crucially, the presented results introduce N-acetyl-amides as reactive acyClic amides in the emerging manifold of transition-metal-catalyzed amide cross-coupling. The scope and origin of high selectivity are discussed. Mechanistic studies point to remodeling of amidic resonance and amide bond twist as selectivity determining features in a unified strategy for cross-coupling of acyClic amides. Structural studies, mechanistic investigations as well as beneficial effects of the N-acyl substitution on cross-coupling of amides are reported.Acyl and DeCarbonylative Suzuki Coupling of N-Acetyl Amides: Electronic Tuning of Twisted, AcyClic Amides in Catalytic Carbon-Nitrogen Bond Cleavageamides; N-C Activation; cross-coupling; Suzuki-Miyaura coupling; deCarbonylation; biAryl coupling582018xxx89#N/ATRUE
291
jacs.6b0717210.1021/jacs.6b07172C-Carbonyl ActivationFALSEhttps://doi.org/10.1021/jacs.6b07172Baran, PSJ. Am. Chem. Soc.Cross-couplings of Alkyl halides and organometallic species based on single electron transfer using Ni and Fe catalyst systems have been studied extensively, and separately, for decades. Here we demonstrate the first couplings of redox-active esters (both isolated and derived in situ from Carbonylic acids) with organozinc and organo-magnesium species using an Fe-based catalyst system originally developed for Alkyl halides. This work is placed in context by showing a direct comparison with a Ni catalyst for >40 examples spanning a range of primary, secondary, and tertiary substrates. This new C-C coupling is scalable and sustainable, and it exhibits a number of Clear advantages in several cases over its Ni-based counterpart.Redox-Active Esters in Fe-Catalyzed C-C Coupling151201637#N/ATRUE
292
jacs.6b0025010.1021/jacs.6b00250C-Carbonyl ActivationFALSEhttps://doi.org/10.1021/jacs.6b00250Baran, PSJ. Am. Chem. Soc.A new transformation is presented that enables chemists to couple simple Alkyl Carbonylic acids with Aryl zinc reagents under Ni-catalysis. The success of this reaction hinges on the unique use of redox-active esters that allow one to employ such derivatives as Alkyl halides surrogates. The chemistry exhibits broad substrate scope and features a high degree of practicality. The simple procedure and extremely inexpensive nature of both the substrates and pre-catalyst (NiCl2 center dot 6H(2)O, ca. $9.5/mol) bode well for the immediate widespread adoption of this method.Practical Ni-Catalyzed Aryl-Alkyl Cross-Coupling of Secondary Redox-Active Esters237201660#N/ATRUE
293
anie.20160546310.1002/anie.201605463C-Carbonyl ActivationFALSEhttps://doi.org/10.1002/anie.201605463Baran, PSAngew. Chem.-Int. Edit.A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross-coupling between Alkyl-Carbonylic acids and boronic acids is described. This Ni-catalyzed reaction relies upon the Activation of Alkyl Carbonylic acids as their redox-active ester derivatives, specifically N-hydroxy-tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl2 center dot 6H(2)O-$9.5mol(-1), Et3N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption.Nickel-Catalyzed Cross-Coupling of Redox-Active Esters with Boronic AcidsdeCarbonylation; homogeneous catalysis; nickel catalysts; redox-active esters; Suzuki cross-coupling123201635#N/ATRUE
294
anie.20200239210.1002/anie.202002392C-Cl ActivationTRUEhttps://doi.org/10.1002/anie.202002392Stradiotto, MAngew. Chem.-Int. Edit.Nickel-Catalyzed Cross-Coupling of Sulfonamides With (Hetero)Aryl Chloridesamination; cross-coupling; ligand design; nickel; sulfonamidesCsp2_ar-Nsp3E-NuO
OCONEt2
HHetNo baseNo Base132020572/7/2022TRUE
295
anie.20190009510.1002/anie.201900095C-Cl ActivationFALSEhttps://doi.org/10.1002/anie.201900095Stradiotto, MAngew. Chem.-Int. Edit.Base-metal catalysts capable of enabling the assembly of heteroatom-dense molecules by cross-coupling of primary heteroArylamines and (hetero)Aryl chlorides, while sought-after given the ubiquity of unsymmetrical di(hetero)Arylamino fragments in pharmacophores, are unknown. Herein, we disClose the new double cage bisphosphine PAd2-DalPhos (L2). The derived air-stable Ni-II pre-catalyst C2 functions well at low loadings in challenging test C-N cross-couplings with established substrates, and facilitates the first Ni-catalyzed C-N cross-couplings of primary five- or six-membered ring heteroArylamines and activated (hetero)Aryl chlorides, with synthetically useful scope that is competitive with Pd catalysis.PAd2-DalPhos Enables the Nickel-Catalyzed C-N Cross-Coupling of Primary HeteroArylamines and (Hetero)Aryl Chloridesamination; bisphosphines; cross-coupling; ligand design; nickel24201933#N/ATRUE
296
d0sc06056a10.1039/d0sc06056aC-CN ActivationFALSEhttps://doi.org/10.1039/d0sc06056aChatani, NChem. Sci.The Ni-catalyzed reaction of ortho-phenoxy-substituted aromatic amides with alkynes in the presence of (LiOBu)-Bu-t as a base results in C-O/N-H annulation with the formation of 1(2H)-isoquinolinones. The use of a base is essential for the reaction to proceed. The reaction proceeds, even in the absence of a ligand, and under mild reaction conditions (40 degrees C). An electron-donating group on the aromatic ring facilitates the reaction. The reaction was also applicable to carbamate (C-O bond Activation), methylthio (C-S bond Activation), and cyano (C-CN bond Activation) groups as leaving groups.Nickel-catalyzed C-O/N-H, C-S/N-H, and C-CN/N-H annulation of aromatic amides with alkynes: C-O, C-S, and C-CN Activation4202156#N/ATRUE
297
c8sc04437f10.1039/c8sc04437fC-CN ActivationFALSEhttps://doi.org/10.1039/c8sc04437fMashima, KChem. Sci.We developed a non-toxic cyanation reaction of various Aryl halides and triflates in acetonitrile using a catalyst system of [Ni(MeCN)(6)](BF4) 2, 1,10-phenanthroline, and 1,4-bis(trimethylsilyl)-2,3,5,6-tetramethyl-1,4-dihydropyrazine (Si-Me-4-DHP). Si-Me-4-DHP was found to function as a reductant for generating nickel(0) species and a silylation reagent to achieve the catalytic cyanation via C-CN bond Cleavage.Nickel-catalyzed cyanation of Aryl halides and triflates using acetonitrile via C-CN bond Cleavage assisted by 1,4-bis(trimethylsilyl)-2,3,5,6-tetramethyl-1,4-dihydropyrazine30201975#N/ATRUE
298
c6sc01191h10.1039/c6sc01191hC-CN ActivationFALSEhttps://doi.org/10.1039/c6sc01191hLiu, YHChem. Sci.A nickel-catalyzed regioselective addition/cyClization of o-(cyano) phenyl propargyl ethers with Arylboronic acids has been developed, which provides an efficient protocol for the synthesis of highly functionalized 1-naphthylamines with wide structural diversity. The reaction is characterized by a regioselective and anti-addition of the Arylboronic acids to the alkyne and subsequent facile nuCleophilic addition of the resulting alkenylmetal to the tethered cyano group. Mechanistic studies reveal that a Ni(I) species might be involved in the catalytic process.Nickel-catalyzed cyClization of alkyne-nitriles with organB(OH)2ronic acids involving anti-carbometalation of alkynes42201655#N/ATRUE
299
acscatal.5b0034810.1021/acscatal.5b00348C-CN ActivationFALSEhttps://doi.org/10.1021/acscatal.5b00348Garcia, JJACS Catal.Amidines and 2-substituted benzoxazoles were synthesized from N-heterocyClic nitriles under mild conditions (50 degrees C, 48 h, two steps) in an atom-economical process that involves addition of methanol, the solvent, to a nitrile moiety to yield a methyl imidate and the subsequent extrusion of solvent in the presence of amines to afford the title compounds. Methyl imidate formation was achieved by developing a new catalytic pathway using [(dippe)Ni(H)](2) (dippe = 1,2-bis(diisopropylphosphino)ethane), [Ni(cod)(2)]/dppe, or [Ni(cod)(2)]/P(OPh)(3) (cod = 1,5-cyClooctadiene, dppe = 1,2-bis(diphenylphosphino)ethane, P(OPh)(3) = triphenyl phosphite) as the catalyst precursor. Regarding the ligands, for a given substrate, namely 4-cyanopyridine, the best performance for the Ni(0)-catalyzed system was found for the sigma-donor bidentate dippe, whereas the monodentate p acceptor P(OPh)(3) was less efficient. In relation to the substrates, for a given Ni-dippe system, steric hindrance and, more importantly, substrate electron-withdrawing character control imidate formation and thus the yield of amidines and benzoxazoles.Synthesis of Annidines and Benzoxazoles from Activated Nitriles with Ni(0) CatalystsN-heteroArylcarbonitrile; methanol; nickel; catalysis; methyl imidate; amidine; benzoxazole17201544#N/ATRUE
300
acs.orglett.7b0190510.1021/acs.orglett.7b01905C-CN Activationhttps://pubs.acs.org/doi/pdf/10.1021/acs.orglett.7b01905Rueping, M#N/A
301
acs.orglett.7b0118810.1021/acs.orglett.7b01188C-F CouplingFALSEhttps://doi.org/10.1021/acs.orglett.7b01188Baxter, RDRadical C-H Fluorination Using Unprotected Amino Acids as Radical Precursors2017#N/ATRUE
302
c5sc00305a10.1039/C5SC00305AC-H couplingFALSEhttps://doi.org/10.1039/C5SC00305AChatani, N802015
303
jacs.0c0240510.1021/jacs.0c02405C-H CouplingFALSEhttps://doi.org/10.1021/jacs.0c02405Newman, SGJ. Am. Chem. Soc.We report a one-step procedure to directly reduce unactivated Aryl esters into their corresponding tolyl derivatives. This is achieved by an organosilane-mediated ester hydrosilylation reaction and subsequent Ni/NHC-catalyzed hydrogenolysis. The resulting conditions provide a direct and efficient alternative to multi-step procedures for this transformation that often require the use of hazardous metal hydrides. Applications in the synthesis of -CD3-containing products, derivatization of bioactive molecules, and chemoselective reduction in the presence of other C-O bonds are demonstrated.Exhaustive Reduction of Esters Enabled by Nickel Catalysis3202085#N/ATRUE
304
ja311940s10.1021/ja311940sC-H CouplingFALSEhttps://doi.org/10.1021/ja311940sMartin, RJ. Am. Chem. Soc.A mechanistic and computational study on the reductive Cleavage of C-OMe bonds catalyzed by Ni(COD)(2)/PCy3 with silanes as reducing agents is reported herein. Specifically, we demonstrate that the mechanism for this transformation does not proceed via oxidative addition of the Ni(0) precatalyst into the C-OMe bond. In the absence of an external reducing agent, the in-situ-generated oxidative addition complexes rapidly undergo beta-hydride elimination at room temperature, ultimately leading to either Ni(0)-Carbonyl- or Ni(0)-aldehyde-bound complexes. Characterization of these complexes by X-ray crystallography unambiguously suggested a different mechanistic scenario when silanes are present in the reaction media. Isotopic-labeling experiments, kinetic isotope effects, and computational studies Clearly reinforced this perception. Additionally, we also found that water has a deleterious effect by deactivating the Ni catalyst via formation of a new Ni-bridged hydroxo species that was characterized by X-ray crystallography. The order in each component was determined by plotting the initial rates of the C-OMe bond Cleavage at varying concentrations. These data together with the in-situ-monitoring experiments by H-1 NMR, EPR, IR spectroscopy, and theoretical calculations provided a mechanistic picture that involves Ni(I) as the key reaction intermediates, which are generated via comproportionation of initially formed Ni(II) species. This study strongly supports that a Classical Ni(0)/Ni(II) for C-OMe bond Cleavage is not operating, thus opening up new perspectives to be implemented in other related C-O bond-Cleavage reactions.Combined Experimental and Theoretical Study on the Reductive Cleavage of Inert C-O Bonds with Silanes: Ruling out a Classical Ni(0)/Ni(II) Catalytic Couple and Evidence for Ni(I) Intermediates2622013109#N/ATRUE
305
ja106943q10.1021/ja106943qC-H CouplingFALSEhttps://doi.org/10.1021/ja106943qMartin, RJ. Am. Chem. Soc.An efficient Ni-catalyzed protocol for the reductive Cleavage of inert C-O bonds has been developed. The method is characterized by its simplicity and wide scope, thereby allowing the use of Aryl ethers as easily removable directing groups in organic synthesis.Ni-Catalyzed Reduction of Inert C-O Bonds: A New Strategy for Using Aryl Ethers as Easily Removable Directing Groups194201033#N/ATRUE
306
c5sc00305a10.1039/c5sc00305aC-H CouplingFALSEhttps://doi.org/10.1039/c5sc00305aChatani, NChem. Sci.The reductive Cleavage of the C-O bonds of Aryl ethers has great potential in organic synthesis. Although several catalysts that can promote the reductive Cleavage of Aryl ethers have been reported, all such systems require the use of an external reductant, e.g., hydrosilane or hydrogen. Here, we report the development of a new nickel-based catalytic system that can Cleave the C-O bonds of ethers in the absence of an external reductant. The hydrogen atom required in this new reductive Cleavage reaction is provided by the alkoxy group of the substrate, which serves as an internal reductant. The absence of an external reductant enables the unique chemoselectivity, i.e., the selective reduction of an alkoxy group over alkenes and ketones.Nickel-catalyzed reductive Cleavage of Aryl Alkyl ethers to arenes in absence of external reductant78201546#N/ATRUE
307
anie.20180766410.1002/anie.201807664C-H CouplingFALSEhttps://doi.org/10.1002/anie.201807664Miura, MAngew. Chem.-Int. Edit.A Ni(OAc)(2)-catalyzed C-H coupling of 8-amino-quinoline-derived benzamides with epoxides has been developed. The reaction proceeds with concomitant removal of the 8-aminoquinoline auxiliary to form the corresponding 3,4-dihydroisocoumarins directly. Additionally, the nickel catalysis is stereospecific, and the cis- and trans-epoxides are converted into the corresponding cis- and trans-dihydroisocoumarins with retention of configuration, which is complementary to previously reported palladium catalysis. Moreover, while still preliminary, the C-sp3-H functionalization is also achieved in the presence of modified NiCl2 catalysts.Nickel-Catalyzed Stereospecific C-H Coupling of Benzamides with EpoxidesC-H coupling; epoxides; lactones; nickel; stereospecificity20201845#N/ATRUE
308
acscatal.8b0200910.1021/acscatal.8b02009C-H CouplingFALSEhttps://doi.org/10.1021/acscatal.8b02009Tobisu, MACS Catal.The catalytic removal of a methoxy group on an aromatic ring allows this group to be used as a traceless activating and directing group for aromatic functionalization reactions. Although several catalytic methods for the reductive Cleavage of anisole derivatives have been reported, all are applicable only to pi-extended Aryl ethers, such as naphthyl and biphenyl ethers, while monocyClic Aryl ethers cannot be reduced. Herein, we report a nickel-catalyzed reductive Cleavage reaction of C-O bonds in Aryl ethers using diisopropylaminB(OH)2rane as the reducing agent. Unlike previously reported methods, this reducing reagent allows effective C-O bond reduction in a much wider range of Aryl ether substrates, inCluding monocyClic and heterocyClic ethers bearing various functional groups.Nickel-Catalyzed Reductive Cleavage of Carbon-Oxygen Bonds in Anisole Derivatives Using DiisopropylaminB(OH)2ranenickel catalyst; carbon-oxygen bond Cleavage; reduction; aminB(OH)2rane; anisole15201872#N/ATRUE
309
ja004195m10.1021/ja004195mC-In ActivationFALSEhttps://doi.org/10.1021/ja004195mSarandeses, LAJ. Am. Chem. Soc.The novel metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles is described. Triorganoindium compounds (R3In) containing Alkyl, Vinyl, Aryl, and alkynyl groups are efficiently prepared from the corresponding Lithium or magnesium organometallics by reaction with indium trichloride. The cross-coupling reaction of R3In with Aryl halides and pseudohalides (iodide 2, bromide 5; and triflate 4), Vinyl triflates, Benzyl bromides, and acid chlorides proceeds under palladium catalysis in excellent yields and with high chemoselectivity. Indium organometallics also react with Aryl chlorides as under nickel catalysis. In the cross-coupling reaction the triorganoindium compounds transfer; in a Clear example of atom economy, all three of the organic groups attached to the metal, as shown by the necessity of using only 34 mol % of indium. The feasibility of using R3In in reactions with different electrophiles, along with the high yields and chemoselectivities obtained, reveals indium organometallics to be useful alternatives to other organometallics in cross-coupling reactions.Atom-efficient metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles2492001104#N/ATRUE
310
ja203352510.1021/ja2033525C-N Activation
C-H, C-B Coupling		FALSEhttps://doi.org/10.1021/ja2033525Mori, AJ. Am. Chem. Soc.Polymerization of 2-chloro-3-substituted thiophenes proceeded with a stoichiometric amount of magnesium amide, TMPMgX center dot LiCl, or a combination of a Grignard reagent and a catalytic amount of secondary amine in the presence of a nickel catalyst. Although the nickel-catalyzed polymerization with NiCl(2)dppe, which exhibited high catalytic activity in the reaction of bromothiophenes, was less effective, use of a nickel catalyst bearing N-heterocyClic carbene as a ligand was found to induce polymerization with controlled molecular weight and molecular weight distribution.C-H Functionalization Polycondensation of Chlorothiophenes in the Presence of Nickel Catalyst with Stoichiometric or Catalytically Generated Magnesium Amidex123201174#N/AFALSE
311
ja501649a10.1021/ja501649aC-N Activation
(C-H, C-B Coupling)		FALSEhttps://doi.org/10.1021/ja501649aChatani, NJ. Am. Chem. Soc.The nickel-catalyzed reaction of N-Aryl amides with hydrB(OH)2rane or diboron reagents resulted in the formation of the corresponding reduction or borylation products, respectively. Mechanistic studies revealed that these reactions proceeded via the Activation of the C(Aryl)-N bonds of simple, electronically neutral substrates and did not require the presence of an ortho directing group.Nickel-Catalyzed Reductive and Borylative Cleavage of Aromatic Carbon-Nitrogen Bonds in N-Aryl Amides and Carbamates127201439#N/ATRUE
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c6sc03902b10.1039/c6sc03902bC-N Activation ?TRUEhttps://doi.org/10.1039/c6sc03902bFeng, XMChem. Sci.A highly efficient asymmetric Mannich-type reaction between alpha-tetralone-derived beta-keto esters/amides and 1,3,5-triAryl-1,3,5-triazinanes was realized in the presence of chiral N,N'-dioxide-Ni(II) or Mg(II) complex. A variety of optically active beta-amino compounds with all-carbon quaternary stereocenters were obtained in good yields with excellent enantioselectivities. A possible transition state was proposed based on these experiments and previous reports.A new approach to the asymmetric Mannich reaction catalyzed by chiral N, N-dioxide-metal complexes#N/A#N/AHAlkyl#N/A#N/A522017xx513/10/2022TRUE
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anie.20201204810.1002/anie.202012048C-N Activation (Addition)TRUEhttps://doi.org/10.1002/anie.202012048Garg, NKAngew. Chem.-Int. Edit.We report a means to achieve the addition of two disparate nuCleophiles to the amide Carbonyl carbon in a single operational step. Our method takes advantage of non-precious-metal catalysis and allows for the facile conversion of amides to chiral alcohols via a one-pot Suzuki-Miyaura cross-coupling/transfer-hydrogenation process. This study is anticipated to promote the development of new transformations that allow for the conversion of Carbonylic acid derivatives to functional groups bearing stereogenic centers via cascade processes.Reductive Arylation of Amides via a Nickel-Catalyzed Suzuki-Miyaura-Coupling and Transfer-Hydrogenation Cascadeamides; base metal catalysis; cascade reactions; Suzuki&#8211; Miyaura coupling; transfer hydrogenationCsp2-Csp2_arE-NuN
N(Bn)Boc
Bpin
Carbonyl
Ionic-PO4220211122/17/2022TRUE
314
acscatal.7b0285910.1021/acscatal.7b02859C-N Activation (Addition) FALSEhttps://doi.org/10.1021/acscatal.7b02859Hu, XLACS Catal.Transmidation is an attractive method for amide synthesis. However, transamidation of secondary amides is challenging. Here, we describe a reductive transamidation method that employs readily available nitro(hetero)arenes as the nitrogen sources, zinc or manganese as reductant, and simple nickel salt and ligand as a catalyst system. The scope of amides inCludes both Alkyl and Aryl secondary amides, with high functional group compatibility.Nickel-Catalyzed Reductive Transamidation of Secondary Amides with Nitroarenestransamidation; nickel catalysis; reductive coupling; amide synthesis; nitroarenesy53201735#N/AFALSE
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jacs.1c0062210.1021/jacs.1c00622C-N CouplingFALSEhttps://doi.org/10.1021/jacs.1c00622Shi, HJ. Am. Chem. Soc.Chiral alpha-branched amines are common structural motifs in functional materials, pharmaceuticals, and chiral catalysts. Therefore, developing efficient methods for preparing compounds with these privileged scaffolds is an important endeavor in synthetic chemistry. Herein, we describe an atom-economical, modular method for a nickel-catalyzed enantioselective alpha-alkenylation of readily available linear N-sulfonyl amines with alkynes to afford a wide variety of allylic amines without the need for exogenous oxidants, reductants, or activating reagents. The method provides a platform for constructing chiral alpha-branched amines as well as derivatives such as alpha-amino amides and beta-amino alcohols, which can be conveniently accessed from the newly introduced alkene. Given the generality, versatility, and high atom economy of this method, we anticipate that it will have broad synthetic utility.Nickel-Catalyzed Enantioselective alpha-Alkenylation of N-Sulfonyl Amines: Modular Access to Chiral alpha-Branched Amines1202167#N/ATRUE
316
jacs.0c1163010.1021/jacs.0c11630C-N CouplingFALSEhttps://doi.org/10.1021/jacs.0c11630Hu, XLJ. Am. Chem. Soc.Chiral Alkyl amines are omnipresent as bioactive molecules and synthetic intermediates. The catalytic and enantioselective synthesis of Alkyl amines from readily accessible precursors is challenging. Here we develop a nickel-catalyzed hydroAlkylation method to assemble a wide range of chiral Alkyl amines from enecarbamates (N-Cbz-protected enamines) and Alkyl halides with high regio- and enantioselectivity. The method works for both nonactivated and activated Alkyl halides and is able to produce enantiomerically enriched amines with two minimally differentiated alpha-Alkyl substituents. The mild conditions lead to high functional group tolerance, which is demonstrated in the postproduct functionalization of many natural products and drug molecules, as well as the synthesis of chiral building blocks and key intermediates to bioactive compounds.Chiral Alkyl Amine Synthesis via Catalytic Enantioselective HydroAlkylation of Enecarbamates11202162#N/ATRUE
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ja411911s10.1021/ja411911sC-N CouplingFALSEhttps://doi.org/10.1021/ja411911sHartwig, JFJ. Am. Chem. Soc.First-row metal complexes often undergo undesirable one-electron redox processes during two-electron steps of catalytic cyCles. We report the amination of Aryl chlorides and bromides with primary aliphatic amines catalyzed by a well-defined, single-component nickel precursor (BINAP)Ni(eta(2)-NC-Ph) (BINAP = 2,2'-bis (biphenylphosphino)- 1,1'-binaphthalene) that Minimizes the formation of Ni(l) species and (BINAP)(2)Ni. The scope of the reaction encompasses electronically varied Aryl chlorides and nitrogen-containing heteroAryl chlorides, inCluding pyridine, quinoline, and isoquinoline derivatives. Mechanistic studies support the catalytic cyCle involving a Ni(0)/Ni(II) couple for this nickel-catalyzed amination and are inconsistent with a Ni(I) halide intermediate. Monitoring the reaction mixture by P-31 NMR spectroscopy identified (BINAP)Ni(eta(2)-NC-Ph) as the resting state of the catalyst in the amination of both Aryl chlorides and bromides. Kinetic studies showed that the amination of Aryl chlorides and bromides is first order in both catalyst and Aryl halide and zero order in base and amine. The reaction of a representative Aryl chloride is inverse first order in PhCN, but the reaction of a representative Aryl bromide is zero order in PhCN. This difference in the order of the reaction in PhCN indicates that the Aryl chloride reacts with (BINAP)Ni(0), formed by dissociation PhCN from (BINAP)Ni(eta(2)-NC-Ph), but the Aryl bromide directly reacts with (BINAP)Ni(eta(2)-NC-Ph). The overall kinetic behavior is consistent with turnover-limiting oxidative addition of the Aryl halide to Ni(0). Several pathways for catalyst decomposition were identified, such as the formation of the catalytically inactive bis(amine)-ligated Arylnickel(II) chloride, (BINAP)(2)Ni(0), and the Ni(I) species [(BINAP)Ni(mu-Cl)](2). By using a well-defined nickel complex as catalyst, the formation of (BINAP)(2)Ni(0) is avoided and the formation of the Ni(l) species [(BINAP)Ni(mu-Cl)](2) is minimized.Controlling First-Row Catalysts: Amination of Aryl and HeteroAryl Chlorides and Bromides with Primary Aliphatic Amines Catalyzed by a BINAP-Ligated Single-Component Ni(0) Complex149201449#N/ATRUE
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ja051520310.1021/ja0515203C-N CouplingFALSEhttps://doi.org/10.1021/ja0515203Parra, AJ. Am. Chem. Soc.The Benzylation of N-sulfinyl ketimines with 2-(p-tolylsulfinyl)ethylbenzene and LDA afford t-Alkylamines in good yields. The configuration at each one of the new chiral centers simultaneously created in this reaction is controlled by the configuration of the sulfinyl groups at the nuCleophile and electrophile, respectively. Thus, the reactions of the (S)-sulfoxide 6 with the N-(S)-sulfinylketimines 3 only yield the anti diastereoisomers 18, whereas the syn diastereoisomers 19 are exClusively formed in reactions of (S)-6 with N-(R)-sulfinylketimines 3. After a two-step desulfinylation process ((i) TFA, (ii) Ra-Ni), this reaction provides a procedure for synthesizing any epimer of alpha,alpha-dibranched beta-AlkylArylamines in optically pure form by choosing the configuration of the starting materials. A similar behavior is observed for carbanions derived from the O-protected 2-(p-tolylsulfinyl) Benzyl alcohol 7 thus allowing the synthesis of the optically pure anti- and syn-1,2-amino alcohols containing a chiral quaternary carbon adjacent to the nitrogen.Highly stereoselective Benzylation of N-sulfinylketimines39200549#N/ATRUE
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ja035465e10.1021/ja035465eC-N CouplingFALSEhttps://doi.org/10.1021/ja035465eVyskocil, SJ. Am. Chem. Soc.Achiral, diamagnetic Ni(II) complexes 1 and 3 have been synthesized from Ni(II) salts and the Schiff bases, generated from glycine and PBP (7) and PBA (11), respectively, in MeONa/MeOH solutions. The requisite Carbonyl-derivatizing agents pyridine-2-Carbonylic acid (2-benzoyi-phenyl)-amide 7 (Pl3P) and pyridine-2-Carbonylic acid (2-Carbonyl-phenyl)-amide 11 (PBA) were readily prepared from picolinic acid and o-aminobenzophenone or picolinic acid and methyl o-anthranilate, respectively. The structure of 1 was established by X-ray crystallography. Complexes 1 and 3 were found to undergo C-Alkylation with Alkyl halides under PTC conditions in the presence of beta-naphthol or Benzyltriethylammonium bromide as catalysts to give mono- and bis-Alkylated products, respectively. Decomposition of the complexes with aqueous HCl under mild conditions gave the required amino acids, and PBP and PBA were recovered. Alkylation of 1 with highly reactive Alkyl halides, carried out under the PTC conditions in the presence of 10% mol of (S) or (R)-2-hydroxy-2'-amino-1,1'-binaphthyl 31a (NOBIN)-and/or its N-acyl derivatives and by (S)- or (R)-2-hydroxy-8'-amino-1,1'-binaphthyI 32a (iso-NOBIN) and its N-acyl derivatives, respectively, gave rise to a-amino acids with high enantioselectivities (90-98.5% ee) in good-to-excel lent chemical yields at room temperature within several minutes. An unusually large positive nonlinear effect was observed in these reactions. The Michael addition of acrylic derivatives 37 to 1 was conducted under similar conditions with up to 96% ee. The H-1 NIVIR and IR spectra of a mixture of the sodium salt of NOBIN and 1 indicated formation of a complex between the two components. Implications of the association and self-association of NOBIN for the observed sense of asymmetric induction and nonlinear effects are discussed.Synthesis of alpha-amino acids via asymmetric phase transfer-catalyzed Alkylation of achiral nickel(II) complexes of glycine-derived Schiff bases101200375#N/ATRUE
320
d1sc00972a10.1039/d1sc00972aC-N CouplingFALSEhttps://doi.org/10.1039/d1sc00972aWalsh, PJChem. Sci.A unique enantioselective nickel-catalyzed Vinylation of 2-azaallyl anions is advanced for the first time. This method affords diverse Vinyl Aryl methyl amines with high enantioselectivities, which are frequently occurring scaffolds in natural products and medications. This C-H functionalization method can also be extended to the synthesis of enantioenriched 1,3-diamine derivatives by employing suitably elaborated Vinyl bromides. Key to the success of this process is the identification of a Ni/chiraphos catalyst system and a less reducing 2-azaallyl anion, all of which favor an anionic Vinylation route over a background radical reaction. A telescoped gram scale synthesis and a product derivatization study confirmed the scalability and synthetic potential of this method.Nickel-catalyzed enantioselective Vinylation of Aryl 2-azaallyl anions0202167#N/ATRUE
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anie.20201134210.1002/anie.202011342C-N CouplingFALSEhttps://doi.org/10.1002/anie.202011342Nevado, CAngew. Chem.-Int. Edit.A nickel-catalyzed asymmetric reductive hydroArylation of Vinyl amides to produce enantioenriched alpha-Arylbenzamides is reported. The use of a chiral bisimidazoline (BIm) ligand, in combination with diethoxymethylsilane and Aryl halides, enables the regioselective introduction of Aryl groups to the internal position of the olefin, forging a new stereogenic center alpha to the N atom. The use of neutral reagents and mild reaction conditions provides simple access to pharmacologically relevant motifs present in anticancer, SARS-CoV PLpro inhibitors, and KCNQ channel openers.Nickel-Catalyzed Asymmetric Synthesis of alpha-Arylbenzamidesasymmetric synthesis; hydroArylation; nickel; Vinyl amides; &#945; -Aryl amides14202178#N/ATRUE
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anie.20180993010.1002/anie.201809930C-N CouplingFALSEhttps://doi.org/10.1002/anie.201809930Zhou, JSAngew. Chem.-Int. Edit.Asymmetric reductive amination of poorly nuCleophilic sulfonamides was realized in the presence of nickel catalysts and titanium alkoxide. A wide range of ketones, inCluding enolizable ketones and some biAryl ones, were converted into sulfonamides in excellent enantiomeric excess. The cyClization of sulfamates and intermolecular reductive amination of a diArylphosphinamide were also successful. Formic acid was used as a safe and economic surrogate of high-pressure hydrogen gas.Asymmetric Stepwise Reductive Amination of Sulfonamides, Sulfamates, and a Phosphinamide by Nickel Catalysischiral Alkylamines; nickel catalysis; reductive amination; sulfonamides; transfer hydrogenation21201984#N/ATRUE
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anie.20160682110.1002/anie.201606821C-N CouplingFALSEhttps://doi.org/10.1002/anie.201606821Zhou, JAngew. Chem.-Int. Edit.An asymmetric reductive amination of ketones using both Arylamines and benzhydrazide in the presence of nickel catalysts was developed. A one-pot synthesis of tetrahydroquinoxalines was also developed starting directly from alpha-ketoaldehydes and 1,2-diaminobenzene. Formic acid was used as a safe and economic surrogate for high-pressure hydrogen gas. Strongly sigma-donating bis(Alkylphosphine)s are crucial ancillary ligands for both stereoselective hydride insertion and deCarbonylation of the formate.Nickel-Catalyzed Enantioselective Reductive Amination of Ketones with Both Arylamines and Benzhydrazidechiral Alkylamines; nickel; reductive amination; synthetic methods; transfer hydrogenation532016116#N/ATRUE
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acscatal.8b0194110.1021/acscatal.8b01941C-N CouplingFALSEhttps://doi.org/10.1021/acscatal.8b01941Stavropoulos, PACS Catal.Selective amination of sigma and pi entities such as C-H and C=C bonds of substrates remains a challenging endeavor for current catalytic methodologies devoted to the synthesis of abundant nitrogen-containing chemicals. The present work addresses an approach toward discriminating aromatic over aliphatic alkenes in aziridination reactions, relying on the use of anionic metal reagents (M = Mn, Fe, Co, Ni) to attenuate reactivity in a metal-dependent manner. A family of Mn-II reagents bearing a triphenylamido-amine scaffold and various pendant arms has been synthesized and characterized by various techniques, inCluding cyClic voltammetry. Aziridination of styrene by PhI=NTs in the presence of each Mn-II catalyst establishes a trend of increasing yield with increasing Mn-II/III anodic potential. The Fe-II, Co-II, and Ni-II congeners of the highest-yielding Mn-II catalyst have been synthesized and explored in the aziridination of aromatic and aliphatic alkenes, exhibiting good to high yields with para-substituted styrenes, low to modest yields with sterically congested styrenes, and invariably low yields with aliphatic olefins. Co-II aziridination in comparison to Mn-II but is less selective than Mn-II in competitive aziridinations of nonconjugated olefins. Indeed, Mn-II proved to be highly selective even versus well-established copper and rhodium aziridination reagents. Mechanistic investigations and computational studies indicate that all metals follow a two-step styrene aziridination pathway (successive formation of two N-C bonds), featuring a turnover-limiting metal-nitrene addition to an olefinic carbon, followed by product-determining ring Closure. Both steps exhibit Activation barriers in the order Fe > Mn > Co, most likely stemming from relevant metal-nitrene electrophilicities and M-II/III redox potentials. The aziridination of aliphatic olefins follows the same stepwise path, albeit with a considerably higher Activation barrier and a weaker driving force for the formation of the initial N-C bond, succeeded by ring Closure with a miniscule barrier.Comparative Nitrene-Transfer Chemistry to Olefinic Substrates Mediated by a Library of Anionic Mn(II) Triphenylamido-Amine Reagents and M(II) Congeners (M = Fe, Co, Ni) Favoring Aromatic over Aliphatic Alkenesmanganese; iron; cobalt; trisamido-amine ligands; nitrene-transfer catalysis; electrochemistry; mechanistic studies; computational studies172018277#N/ATRUE
325
anie.20090089210.1002/anie.200900892C-N FormationFALSEhttps://doi.org/10.1002/anie.200900892Kuwano, RAngew. Chem.-Int. Edit.Nickel-Catalyzed Formation of a Carbon-Nitrogen Bond at the beta Position of Saturated Ketonesamination; beta-enaminones; ketones; nickel catalysis; oxidation72200928#N/ATRUE
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jacs.1c04215
10.1021/jacs.1c04215C-S couplingFALSEhttps://pubs.acs.org/doi/10.1021/jacs.1c04215Yamaguchi, J12021xx#N/A
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anie.20150320410.1002/anie.201503204C-O Activation (but not suitable)https://onlinelibrary.wiley.com/doi/10.1002/anie.201503204Chen, TQANGEWANDTE CHEMIE-INTERNATIONAL EDITIONNickel-Catalyzed CO/CH Cross-Coupling Reactions for CC Bond Formation
asymmetric catalysis ; CH Activation ; CO Activation ; cross-coupling ; nickel catalysis
Small reviewx192015#N/A
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anie.20120884310.1002/anie.201208843C-O Activation (but not suitable)https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201208843Martin, RSmall review#N/A
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nchem.150410.1038/nchem.1504C-O Activation (but not suitable)https://www.nature.com/articles/nchem.1504Garg, NK2 steps#N/A
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ja00502a07410.1021/ja00502a074C-O Activation (but not suitable)https://pubs.acs.org/doi/pdf/10.1021/ja00502a074SWINDELL, CSSmall review3071979
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ejoc.20130057310.1002/ejoc.201300573C-O Activation (but not suitable)https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.201300573Sheppard, TDChem. Eur. JRecent Developments in Amide Synthesis: Direct Amidation of Carbonylic Acids and Transamidation ReactionsReviewno nickel catalysts2052013Added by LongFALSE
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D1CC00913C10.1039/D1CC00913CC-O Activation (but not suitable)https://doi.org/10.1039/D1CC00913CNolan, SPChem. Com.Ni-Catalyzed α-Arylation of esters and amides with phenol derivatives†Review682015Long added#N/AFALSE
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cr100259t10.1021/cr100259tC-O Activation (but not suitable)https://pubs.acs.org/doi/10.1021/cr100259tPercec, VReview1046
334
ar500345f10.1021/ar500345fC-O Activation (but not suitable)https://doi.org/10.1021/ar500345fShi, ZJReview y 4852021shihong added#N/AFALSE
335
ar100082d10.1021/ar100082dC-O Activation (but not suitable)https://doi.org/10.1021/ar100082dShi, ZJReview467shihong added#N/AFALSE
336
ar100082d10.1021/ar100082dC-O Activation (but not suitable)https://pubs.acs.org/doi/10.1021/ar100082dShi, ZJReview artiCle455
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anie.20170672410.1002/anie.201706724C-O Activation (but not suitable)https://doi.org/10.1002/anie.201706724Konig, BAngew. Chem.-Int. Edit.We report the efficient Carbonylation of bromides and triflates with K2CO3 as the source of CO2 in the presence of an organic photocatalyst in combination with a nickel complex under visible light irradiation at room temperature. The reaction is compatible with a variety of functional groups and has been successfully applied to the synthesis and derivatization of biologically active molecules. In particular, the Carbonylation of unactivated cyClic Alkyl bromides proceeded well with our protocol, thus extending the scope of this transformation. Spectroscopic and spectroelectrochemical investigations indicated the generation of a Ni-0 species as a catalytic reactive intermediate.Carbonylation of Aromatic and Aliphatic Bromides and Triflates with CO2 by Dual Visible-Light-Nickel Catalysiscarbon dioxide; Carbonylation; nickel catalysis; photocatalysis; visible lightphotocatalysis99201760#N/AFALSE
338
ja507117410.1021/ja50711741C-O Activation DFThttps://pubs.acs.org/doi/10.1021/ja5071174Musaev, DGJ. Am. Chem. Soc.The mechanism of the Ni-dcype-catalyzed C-H/C-O coupling of benzoxazole and naphthalen-2-yl pivalate was studied. Special attention was devoted to the base effect in the C-O oxidative addition and C-H Activation steps as well as the C-H substrate effect in the C-H Activation step. No base effect in the C(Aryl)-O oxidative addition to Ni-dcype was found, but the nature of the base and C-H substrate plays a crucial role in the following C-H Activation. In the absence of base, the azole C-H Activation initiated by the C-O oxidative addition product Ni(dcype)(Naph)(PivO), 1B, proceeds via Delta G = 34.7 kcal/mol barrier. Addition of Cs2CO3 base to the reaction mixture forms the Ni(dcype)(Naph)[PivOCs.CsCO3], 3_Cs_Clus, Cluster complex rather than undergoing PivO(-) -> CsCO3(-) ligand exchange. Coordination of azole to the resulting 3_Cs_Clus complex forms intermediate with a weak Cs-heteroatom(azole) bond, the existence of which increases acidity of the activated C-H bond and reduces C-H Activation barrier. This conClusion from computation is consistent with experiments showing that the addition of Cs2CO3 to the reaction mixture of 1B and benzoxazole increases yield of C-H/C-O coupling from 32% to 67% and makes the reaction faster by 3-fold. This emerging mechanistic knowledge was validated by further exploring base and C-H substrate effects via replacing Cs2CO3 with K2CO3 and benzoxazole (1a) with 1H-benzo[d]imidazole (1b) or quinazoline (1c). We proposed the modified catalytic cyCle for the Ni(cod)(dcype)-catalyzed C-H/C-O coupling of benzoxazole and naphthalen-2-yl pivalate.Key Mechanistic Features of Ni-Catalyzed C-H/C-O BiAryl Coupling of Azoles and Naphthalen-2-yl PivalatesDFT Calculation120201473#N/AFALSE
339
ja411841310.1021/ja4118413C-O Activation DFThttps://doi.org/10.1021/ja4118413Houk, KNJ. Am. Chem. Soc.Many experiments have shown that nickel with monodentate phosphine ligands favors the C(Aryl)-O Activation over the C(acyl)-O Activation for Aryl esters. However, Itami and co-workers recently discovered that nickel with bidentate phosphine ligands can selectively activate the C(acyl)-O bond of Aryl esters of aromatic Carbonylic acids. The chemoselectivity with bidentate phosphine ligands can be switched back to C(Aryl)-O Activation when Aryl pivalates are employed.To understand the mechanisms and origins of this switchable chemoselectivity, density functional theory (DFT) calculations have been conducted. For Aryl esters, nickel with bidentate phosphine ligands Cleaves C(acyl)-O and C(Aryl)-O bonds via three-centered transition states. The C(acyl)-O Activation is more favorable due to the lower bond dissociation energy (BDE) of C(acyl)-O bond, which translates into a lower transition-state distortion energy. However, when monodentate phosphine ligands are used, a vacant coordination site on nickel creates an extra Ni-O bond in the five-centered C(Aryl)-O Cleavage transition state. The additional interaction energy between the catalyst and substrate makes C(Aryl)-O Activation favorable. In the case of Aryl pivalates, nickel with bidentate phosphine ligands still favors the C(acyl)-O Activation over the C(Aryl)-O Activation at the Cleavage step. However, the subsequent deCarbonylation generates a very unstable tBu-Ni(II) intermediate, and this unfavorable step greatly increases the overall barrier for generating the C(acyl)-O Activation products. Instead, the subsequent C-H Activation of azoles and C-C coupling in the C(Aryl)-O Activation pathway are much easier, leading to the observed C(Aryl)-O Activation products.Mechanisms and Origins of Switchable Chemoselectivity of Ni-Catalyzed C(Aryl)-O and C(acyl)-O Activation of Aryl Esters with Phosphine LigandsDFT Calculation166201497#N/AFALSE
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acscatal.6b0296410.1021/acscatal.6b02964C-O Activation Reviewhttps://doi.org/10.1021/acscatal.6b02964Li, CJACS Catal.Aryl halides are very useful electrophiles for synthesizing various substituted aromatic compounds via metal-catalyzed cross-coupling reactions. Because of the high cost associated with their synthesis and the stoichiometric halide waste produced when using Aryl halide feedstocks, cheaper and more sustainable alternatives have been explored, such as phenols. However, phenols have a very reactive hydroxyl group and a C-O bond with high dissociation energy. To overcome such challenges, earlier studies focused on finding ways to reduce the energy of the C-O bond while removing the active proton by transforming phenols into phenol derivatives (e.g., sulfonates, esters, carbamates, ethers, and metal salts). A greater ambition is to directly cross-couple phenols with nuCleophiles via C-O Cleavage. In this Perspective, we briefly summarize efforts and accomplishments concerning the cross-coupling of phenol derivatives and phenols.An Adventure in Sustainable Cross-Coupling of Phenols and Derivatives via Carbon-Oxygen Bond Cleavagecross-coupling; phenol; C-O Cleavage; phenol derivatives; nickel; iron; ruthenium; palladiumReview1412017Extracted ref:
36 (jo00041a004)
41(c1sc00230a)
42(ja907700e)
43(acs.orglett.6b02265)
45 (acs.orglett.6b00819)
46(ja8056503)
48(anie.200803814)
49 (ol203322v)
50 (D1CC00913C,anie.201403823,anie.201412051)
51 (ja412107b)
52 (ja410883p)
54 (acscatal.6b00801)
59 (jo00199a030)		162#N/AFALSE
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acs.accounts.5b00051
10.1021/acs.accounts.5b00051
C-O Activation Reviewhttps://doi.org/10.1021/acs.accounts.5b00051Chatani, NReviewy453shihong added7/28/2022FALSE
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(SICI)1521-3773(19980817)37:15<2046::AID-ANIE2046>3.3.CO;2-C10.1002/(SICI)1521-3773(19980817)37:15<2046::AID-ANIE2046>3.3.CO;2-CC-O Activation Reviewhttps://doi.org/10.1002/(SICI)1521-3773(19980817)37:15<2046::AID-ANIE2046>3.3.CO;2-CJohn F. HartwigAngew. Chem.-Int. Edit.Transition metal catalyzed synthesis of Arylamines and Aryl ethers from Aryl halides and triflates: Scope and mechanismaminations; Arylations; ethers; nickel; palladiumreview, no nickle catalyst19371998183#N/AFALSE
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jacs.8b0984910.1021/jacs.8b09849C-O Activation but orange complexhttps://pubs.acs.org/doi/pdf/10.1021/jacs.8b09849Cornella, J#N/A
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c5sc02942b10.1039/c5sc02942bC-O Activation
C-H Activation		LongTRUEhttps://doi.org/10.1039/c5sc02942bItami, KChem. Sci.The first nickel-catalyzed C-H Arylations and alkenylations of imidazoles with phenol and enol derivatives are described. Under the influence of Ni(OTf)(2)/dcype/K3PO4 (dcype: 1,2-bis(dicyClohexylphosphino) ethane) in t-amyl alcohol, imidazoles can undergo C-H Arylation with phenol derivatives. The C-H Arylation of imidazoles with chloroarenes as well as that of thiazoles and oxazoles with phenol derivatives can also be achieved with this catalytic system. By changing the ligand to dcypt (3,4-bis(dicyClohexylphosphino) thiophene), enol derivatives could also be employed as coupling partners achieving the C-H alkenylation of imidazoles as well as thiazoles and oxazoles. Thus, a range of C2-Arylated and alkenylated azoles can be synthesized using this newly developed nickel-based catalytic system. The key to the success of the C-H coupling of imidazoles is the use of a tertiary alcohol as solvent. This also allows the use of an air-stable nickel(II) salt as the catalyst precursor.C-H Arylation and alkenylation of imidazoles by nickel catalysis: solvent-accelerated imidazole C-H ActivationCsp2_ar-Csp2_arE-NuOH
OCONMe2
HArylK3PO4Ionic-PO47820157511/4/2021TRUE
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jacs.0c0738110.1021/jacs.0c07381C-O CouplingFALSEhttps://doi.org/10.1021/jacs.0c07381Cornella, JJ. Am. Chem. Soc.In this artiCle, we investigated the I-2-promoted cyClic diAlkyl ether formation from 6-membered oxanickelacyCles originally reported by Hillhouse. A detailed mechanistic investigation based on spectroscopic and crystallographic analysis revealed that a putative reductive elimination to forge C(sp(3))-OC(sp(3)) using I-2 might not be operative. We isolated a paramagnetic bimetallic Ni-III intermediate featuring a unique Ni-2(OR)(2) (OR = alkoxide) diamond-like core complemented by a mu-iodo bridge between the two Ni centers, which remains stable at low temperatures, thus permitting its characterization by NMR, EPR, X-ray, and HRMS. At higher temperatures (>-10 degrees C), such bimetallic intermediate thermally decomposes to afford large amounts of elimination products together with iodoalkanols. Observation of the latter suggests that a C(sp(3))-I bond reductive elimination occurs preferentially to any other challenging C-O bond reductive elimination. Formation of cyClized THF rings is then believed to occur through cyClization of an alcohol/alkoxide to the recently forged C(sp(3))-I bond. The results of this artiCle indicate that the use of F+ oxidants permits the challenging C(sp(3))-OC(sp(3)) bond formation at a high-valent nickel center to proceed in good yields while minimizing deleterious elimination reactions. Preliminary investigations suggest the involvement of a high-valent bimetallic NiIII intermediate which rapidly extrudes the C-O bond product at remarkably low temperatures. The new set of conditions permitted the elusive synthesis of diethyl ether through reductive elimination, a remarkable feature currently beyond the scope of Ni.DiAlkyl Ether Formation at High-Valent Nickel12020134#N/ATRUE
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ja512498u10.1021/ja512498uC-P couplingFALSEhttps://doi.org/10.1021/ja512498uHan, LBJ. Am. Chem. Soc.The first Ni-catalyzed C-O/P-H cross-coupling producing organophosphorus compounds is disClosed. This method features wide generality in regard to both C-O and P-H compounds: for C-O compounds, the readily available alcohol derivatives of Aryl, alkenyl, Benzyl, and allyl are applicable, and for P-H compounds, both >P-V(O)H compounds (secondary phosphine oxide, H-phosphinate, and H-phosphonate) and hydrogen phosphines (>(PH)-H-III) can be used as the substrates. Thus, a variety of valuable C(sp(2))-P and C(sp(3))-P compounds can be readily obtained in good to excellent yields by this new strategy.C-P Bond-Forming Reactions via C-O/P-H Cross-Coupling Catalyzed by Nickel163201567#N/ATRUE
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jacs.9b0231210.1021/jacs.9b02312C-S ActivationFALSEhttps://doi.org/10.1021/jacs.9b02312Niu, DWJ. Am. Chem. Soc.We demonstrate that readily available and bench-stable alpha-oxo-Vinylsulfones are competent electrophiles in Ni-catalyzed Suzuki-Miyaura cross-coupling reactions. The C-sulfone bond in the alpha-oxo-Vinylsulfone motif is Cleaved chemoselectively in these reactions, furnishing C-Aryl glycals or acyClic Vinyl ethers in high yields. These reactions proceed under mild conditions and tolerate a remarkable scope of heterocyCles and functional groups. Preliminary mechanistic studies revealed the importance of an alpha-heteroatom in facilitating these transformations.Ni-Catalyzed Suzuki-Miyaura Cross-Coupling of alpha-Oxo-Vinylsulfones To Prepare C-Aryl Glycals and AcyClic Vinyl Ethers31201988#N/ATRUE
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ja00099a00910.1021/ja00099a009C-S ActivationFALSEhttps://doi.org/10.1021/ja00099a009LUH, TYJ. Am. Chem. Soc.An unprecedented chelation approach to activate C(sp)3-S bonds in nickel-catalyzed cross-coupling reactions is described. Our theme was based on the formation of a chelation complex which results in the enhancement of the reactivity of aliphatic carbon-sulfur bonds. When two dithioacetal functionalities are located in Close proximity, selective olefination of one of these two dithioacetal groups can thus be achieved conveniently. Depending on the relative positions of the newly formed double bond and the remaining dithioacetal group, tandem olefination occurs to give the corresponding 1,5-bis-silyl-substituted pentadienes. Various neighboring heteroatom substituents (OR, OH, NR(2) as well as SR groups) can facilitate the olefination of a dithioacetal group. Poly(thioether) linkage afforded the corresponding degradation products via a B-sulfur elimination process. 1,3-Dimercapto- and 1,3-dithiolatopropanes furnish the cyClopropane formation under nickel-catalyzed reaction conditions. The reaction of a dihydrothiopyran with MeMgX in the presence of the nickel catalyst proceeds via a sulfur-coordinated ir-allyl complex, which can further activate the CS bond to give VinylcyClopropane.CHELATION ASSISTANCE IN THE Activation OF C(SP(3))-S BONDS IN NICKEL-CATALYZED CROSS-COUPLING REACTIONS28199447#N/ATRUE
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anie.20190600010.1002/anie.201906000C-S ActivationFALSEhttps://doi.org/10.1002/anie.201906000Weix, DJAngew. Chem.-Int. Edit.Synthesis of the C-C bonds of ketones relies upon one high-availability reagent (Carbonylic acids) and one low-availability reagent (organometallic reagents or Alkyl iodides). We demonstrate here a ketone synthesis that couples two different Carbonylic acid esters, N-hydroxyphthalimide esters and S-2-pyridyl thioesters, to form Aryl Alkyl and diAlkyl ketones in high yields. The keys to this approach are the use of a nickel catalyst with an electron-poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnX2 to enhance the reactivity of the NHP ester. The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with alpha-heteroatoms. The conditions can be employed in the coupling of complex fragments, inCluding a 20-mer peptide fragment analog of Exendin(9-39) on solid support.Ketones from Nickel-Catalyzed DeCarbonylative, Non-Symmetric Cross-Electrophile Coupling of Carbonylic Acid Esterscross-electrophile coupling; ketones; nickel catalysis; peptide modification; redox-active esters36201957#N/ATRUE
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c5sc03359d10.1039/c5sc03359dC-S couplingFALSEhttps://pubs.rsc.org/en/content/articlelanding/2016/SC/C5SC03359DSchoenebeck, F#N/A
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jacs.1c0421510.1021/jacs.1c04215C-S CouplingFALSEhttps://doi.org/10.1021/jacs.1c04215Yamaguchi, JJ. Am. Chem. Soc.A Ni-catalyzed Aryl sulfide synthesis through an Aryl exchange reaction between Aryl sulfides and a variety of Aryl electrophiles was developed. By using 2-pyridyl sulfide as a sulfide donor, this reaction achieved the synthesis of Aryl sulfides without using odorous and toxic thiols. The use of a Ni/dcypt catalyst capable of Cleaving and forming Aryl-S bonds was important for the Aryl exchange reaction between 2-pyridyl sulfides and Aryl electrophiles, which inClude aromatic esters, arenol derivatives, and Aryl halides. Mechanistic studies revealed that Ni/dcypt can simultaneously undergo oxidative additions of Aryl sulfides and aromatic esters, followed by ligand exchange between the generated Aryl-Ni-SR and Aryl-Ni-OAr species to furnish Aryl exchanged compounds.Ni-Catalyzed Aryl Sulfide Synthesis through an Aryl Exchange Reaction0202168#N/ATRUE
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ja505576g10.1021/ja505576gC-S CouplingFALSEhttps://doi.org/10.1021/ja505576gOzerov, OVJ. Am. Chem. Soc.This artiCle describes a well-defined pincer-Rh catalyst for C-S cross-coupling reactions. (POCOP)Rh(H)(Cl) serves as an active precatalyst for the coupling of Aryl chlorides and bromides with Aryl and Alkyl thiols under reasonable conditions (3% mol cat., 110 degrees C, 2-24 h, >90% yield). For select substrates, >90% yields were obtained with catalyst loading as low as 0.1%. Key mechanistic intermediates have been isolated and fully characterized, inCluding (POCOP)Rh(Ph)(SPh) (6a) and (POCOP)Rh(SPh2) (6b). The Aryl/bis(phosphinite) (POCOP)Rh system has been shown to favor Aryl thiolate reductive elimination at elevated temperatures and in some cases at room temperature, compared with the analogous diArylamido/bis(phosphine) (PNP)Rh pincer system. Concerted reductive elimination has been studied with 6a directly and in the presence of Aryl bromide and Aryl chloride traps. This investigation demonstrates a Clear rate dependence on Aryl chloride concentration during catalysis, a dependence that is absent when using Aryl bromides. The rate of catalysis is dramatically reduced or brought to zero for ortho-tolyl halides, which can be traced to slower C-S coupling and slower carbon-halogen oxidative addition for ortho-substituted Aryls. The influence of the sterics in the thiol component is less straightforward. The S-H oxidative addition product (POCOP)Rh(H)(SPh) (16) has been fully characterized and its reactivity has been examined, resulting in the isolation of the sodium-thiolate adduct (POCOP)Rh(NaSPh) (19). The solid-state structure of 19 shows Na interactions not only with sulfur, but also with a neighboring Rh and the chelating Aryl carbon of the pincer framework. The reactivity of 16 and 19 indicates that these potential side products should not hinder catalysis.A Well-Defined (POCOP)Rh Catalyst for the Coupling of Aryl Halides with Thiols59201468#N/ATRUE
353
c5sc03359d10.1039/c5sc03359dC-S CouplingFALSEhttps://doi.org/10.1039/c5sc03359dSchoenebeck, FChem. Sci.While nickel catalysts have previously been shown to activate even the least reactive Csp(2)-O bonds, i.e. Aryl ethers, in the context of C-C bond formation, little is known about the reactivity limits and molecular requirements for the introduction of valuable functional groups under homogeneous nickel catalysis. We identified that due to the high reactivity of Ni-catalysts, they are also prone to react with existing or installed functional groups, which ultimately causes catalyst deActivation. The scope of the Ni-catalyzed coupling protocol will therefore be dictated by the reactivity of the functional groups towards the catalyst. Herein, we showed that the application of computational tools allowed the identification of matching functional groups in terms of suitable leaving groups and tolerated functional groups. This allowed for the development of the first efficient protocol to trifluoromethylthiolate Csp(2)-O bonds, giving the mild and operationally simple C-SCF3 coupling of a range of Aryl, Vinyl triflates and nonaflates. The novel methodology was also applied to biologically active and pharmaceutical relevant targets, showcasing its robustness and wide applicability.Nickel-catalyzed trifluoromethylthiolation of Csp(2)-O bonds64201693#N/ATRUE
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acscatal.0c0295010.1021/acscatal.0c02950C-S CouplingFALSEhttps://doi.org/10.1021/acscatal.0c02950Sanford, MSACS Catal.This report describes the development of a nickel-catalyzed deCarbonylative reaction for the synthesis of fluoroAlkyl thioethers (RFSR) from the corresponding thioesters. Readily available, inexpensive, and stable fluoroAlkyl Carbonylic acids (RFCO2H) serve as the fluoroAlkyl (R-F) source in this transformation. Stoichiometric organometallic studies reveal that R-F-S bond-forming reductive elimination is a challenging step in the catalytic cyCle. This led to the identification of diphenylphosphinoferrocene as the optimal ligand for this transformation. Ultimately, this method was applied to the construction of diverse fluoroAlkyl thioethers (RFSR), with R = both Aryl and Alkyl.Nickel-Catalyzed DeCarbonylative Synthesis of FluoroAlkyl Thioethersnickel-catalysis; deCarbonylation; fluoroAlkyl Carbonylic acids; thioether synthesis; fluoroAlkylationy12202068#N/AFALSE
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c6sc03236b10.1039/c6sc03236bC-Si ActivationFALSEhttps://doi.org/10.1039/c6sc03236bMolander, GAChem. Sci.The attractive field of iterative cross-coupling has seen numerous advances, although almost exClusively in the union of sp(2)-hybridized partners. Conspicuously absent from this useful synthetic manifold is the inClusion of sp(3)-hybridized pronuCleophiles that can undergo transmetalation under mild conditions. Described here is the use of primary and secondary ammonium Alkylsilicates, which undergo facile C(sp(3))-C(sp(2)) cross-coupling with borylated Aryl bromide partners under photoredox/nickel dual catalysis conditions. This operationally simple procedure allows the production of Alkylated small molecules possessing boronate ester (BPin, Bneopentyl, BMIDA) functional handles. Because of the extremely mild reaction conditions and the innocuous byproduct generated upon fragmentative oxidation of silicates, the corresponding borylated compounds were isolated in good to excellent yields. Aryl bromides bearing unprotected boronic acids are also generally tolerated for the first time and prove useful in multistep syntheses. Unlike many previously reported photoredox/Ni dual cross-couplings, the C(sp(3))-C(sp(2)) bonds were forged using a transition metal-free photocatalyst, allowing a substantial increase in sustainability as well as a cost reduction. Because the developed Ni-catalyzed cross-coupling does not require discrete boron speciation control, as in many popular orthogonal Pd-based methods, this protocol represents a significant advance in atom-and step-economy.C(sp(3))-C(sp(2)) cross-coupling of Alkylsilicates with borylated Aryl bromides - an iterative platform to Alkylated Aryl- and heteroAryl boronates34201746#N/ATRUE
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jacs.8b0447910.1021/jacs.8b04479C-Si bond formationFALSEhttps://doi.org/10.1021/jacs.8b04479Martin, RJ. Am. Chem. Soc.Monodentate phosphine ligands are frequently employed in the Ni-catalyzed C-O functionalization of Aryl esters. However, the extensive body of preparative work on such reactions contrasts with the lack of information concerning the structure and reactivity of the relevant nickel intermediates. In fact, experimental evidence for a seemingly trivial oxidative addition into the C-O bond of Aryl esters with monodentate phosphines and low-valent nickel complexes still remains elusive. Herein, we report a combined experimental and theoretical study on the Ni(0)/PCy3-catalyzed silylation of Aryl pivalates with CuF2/CsF additives that reveals the involvement of unorthodox dinickel oxidative addition complexes in C-O bond Cleavage and their relevance in C-Si bond formation. We have obtained a mechanistic picture that Clarifies the role of the additives and demonstrates that dinickel complexes act as reservoirs of the propagating monomeric nickel complexes by disproportionation. We believe this study will serve as a useful entry point to unravelling the mechanistic underpinnings of other related Ni-catalyzed C-O functionalization reactions employing monodentate phosphines.Intermediacy of Ni-Ni Species in sp(2) C-O Bond Cleavage of Aryl Esters: Relevance in Catalytic C-Si Bond Formation44201878#N/ATRUE
357
s41467-020-20392-w10.1038/s41467-020-20392-wC-Si CouplingFALSEhttps://doi.org/10.1038/s41467-020-20392-wZhao, DBNat. Commun.1,2-Bis-silyl alkenes have exciting synthetic potential for programmable sequential synthesis via manipulation of the two vicinal silyl groups. Transition metal-catalyzed bis-silylation of alkynes with disilanes is the most straightforward strategy to access such useful building blocks. However, this process has some limitations: (1) symmetric disilanes are frequently employed in most of the reactions to assemble two identical silyl groups, which makes chemoselective differentiation for stepwise downstream transformations difficult; (2) the main catalysts are low-valent platinum group transition metal complexes, which are expensive; and (3) internal alkynes remain challenging substrates with low inherent reactivity. Thus, the development of abundant metal-catalyzed bis-silylation of internal alkynes with unsymmetrical disilanes is of significance. Herein, we solve most of the aforementioned limitations in bis-silylation of unsaturated bonds by developing a strongly coordinating disilane reagent and a Ni(0) catalytic system. Importantly, we sufficiently realize the stepwise recognition of the two silyl groups, making this synthetic protocol of wide potential utility. Bis-silylated alkenes offer the advantage of two functional handles with distinguished reactivity for downstream functionalization. Here, the authors report a nickel-catalyzed bis-silylation of internal alkynes to versatile silylated alkene intermediates which can be chemoselectively manipulated.Bis-silylation of internal alkynes enabled by Ni(0) catalysis1202152#N/ATRUE
358
s41467-018-06830-w10.1038/s41467-018-06830-wC-Si CouplingFALSEhttps://doi.org/10.1038/s41467-018-06830-wShibata, NNat. Commun.Direct Activation of carbon-fluorine bonds (C-F) to introduce the silyl or boryl groups and generate valuable carbon-silicon (C-Si) or carbon-boron (C-B) bonds is important in the development of synthetically useful reactions, owing to the unique opportunities for further derivatization to achieve more complex molecules. Despite considerable progress of C-F bond Activation to construct carbon-carbon (C-C) and carbon-heteroatom (C-X) bond formation, the defluorosilylation via C-F Cleavage has been rarely demonstrated. Here, we report an ipso-silylation of Aryl fluorides via Cleavage of unactivated C-F bonds by a Ni catalyst under mild conditions and without the addition of any external ligand. Alkyl fluorides are also directly converted into the corresponding Alkyl silanes under similar conditions, even in the absence of the Ni catalyst. Applications of this protocol in late-stage defluorosilylation of potentially bioactive pharmaceuticals and in further derivatizations are also carried out.Defluorosilylation of fluoroarenes and fluoroalkanes38201839#N/ATRUE
359
d0cc07916b10.1039/d0cc07916bC-Si CouplingFALSEKomatsu, THydrosilylation of Carbonyls over electron-enriched Ni sites of intermetallic compound Ni3Ga heterogeneous catalyst daggerx2021#N/AFALSE
360
jacs.7b0255310.1021/jacs.7b02553C-Si CouplingFALSEhttps://doi.org/10.1021/jacs.7b02553Iwasawa, NJ. Am. Chem. Soc.Efficient synthesis and catalysis of a series of palladium complexes having a group 13 metalloligand Ga, In) are reported utilizing 6,6 ''-bis(phosphino)terpyridine as a new scaffold for Pd-E bonds (E = Al, Ga, In). Systematic investigation revealed unique character, istics of the Al-metalloligand in both structure and reactivity, which exhibited the highest catalytic activity for hydrosilylation of CO2 ever reported (TOF = 19 300 h(-1)). This study demonstrated fine-tuning of catalyst activity by the precisely designed metalloligand is a promising approach for new catalyst development in synthetic organometallic chemistry.Synthesis, Structure, and Catalysis of Palladium Complexes Bearing a Group 13 Metalloligand: Remarkable Effect of an Aluminum-Metalloligand in Hydrosilylation of CO2100201744#N/ATRUE
361
jacs.6b1099810.1021/jacs.6b10998C-Si CouplingFALSEhttps://doi.org/10.1021/jacs.6b10998Martin, RJ. Am. Chem. Soc.Metal-catalyzed transformations that forge carbon heteroatom bonds are of central importance in organic synthesis. Despite the formidable potential of Aryl methyl ethers as coupling partners, the scarcity of metal-catalyzed C-heteroatom bond formations via C-OMe Cleavage is striking, with isolated precedents requiring specialized, yet expensive, ligands, high temperatures, and pi-extended backbones. We report an unprecedented catalytic ipso-silylation of Aryl methyl ethers under mild conditions and without recourse to external ligands. The method is distinguished by its wide scope, which inCludes the use of Benzyl methyl ethers, Vinyl methyl ethers, and unbiased anisole derivatives, thus representing a significant step forward for designing new C-heteroatom bond formations via C-OMe scission. Applications of this transformation in orthogonal silylation techniques as well as in further derivatizations are also described. Preliminary mechanistic experiments suggest the intermediacy of Ni(0)-ate complexes, leaving some doubt that a canonical catalytic cyCle consisting of an initial oxidative addition of the C-OMe bond to Ni(0) species comes into play.A Mild and Ligand-Free Ni-Catalyzed Silylation via C-OMe Cleavage79201782#N/ATRUE
362
ja407749w10.1021/ja407749wC-Si CouplingFALSEhttps://doi.org/10.1021/ja407749wMontgomery, JJ. Am. Chem. Soc.Regioselective methods for allene hydrosilylation have been developed, with regioselectivity being governed primarily by the choice of metal. Alkenylsilanes are produced via nickel catalysis with larger N-heterocyClic carbene (NHC) ligands, and allylsilanes are produced via palladium catalysis with smaller NHC ligands. These complementary methods allow either regioisomeric product to be obtained with exceptional regiocontrol.Regioselective Allene Hydrosilylation Catalyzed by N-HeterocyClic Carbene Complexes of Nickel and Palladium74201353#N/ATRUE
363
ja070938t10.1021/ja070938tC-Si CouplingFALSEhttps://doi.org/10.1021/ja070938tOshima, KJ. Am. Chem. Soc.Treatment of terminal alkenes with silacyClobutanes under nickel catalysis resulted in silylation of the alkenes and yielded the corresponding Vinylsilanes in a highly regio- and stereoselective fashion. The reaction provides a facile access to Vinylsilanes starting from trivial terminal alkenes as well as styrenes, 1,3-dienes, and acrylate esters.Nickel-catalyzed regio- and stereoselective silylation of terminal alkenes with silacyClobutanes: Facile access to Vinylsilanes from alkenes46200742#N/ATRUE
364
ja062745w10.1021/ja062745wC-Si CouplingFALSEhttps://doi.org/10.1021/ja062745wChatani, NJ. Am. Chem. Soc.Rh(I)-catalyzed silylation of Aryl and alkenyl cyanides involving the Cleavage of c-c and si-si bonds129200632#N/ATRUE
365
ja00852a05910.1021/ja00852a059C-Si CouplingFALSEhttps://doi.org/10.1021/ja00852a059KUMADA, MJ. Am. Chem. Soc.NOVEL DEHYDROGENATIVE CIS DOUBLE SILYLATION OF INTERNAL ACETYLENES WITH HYDROSILANES - CATALYSIS BY DIETHYL(BIPYRIDYL)NICKEL(II)48197518#N/ATRUE
366
d1cc02683f10.1039/d1cc02683fC-Si CouplingFALSEhttps://doi.org/10.1039/d1cc02683fYorimitsu, HSodium silylsilanolate enables nickel-catalysed silylation of Aryl chlorides2021#N/ATRUE
367
c9sc00126c10.1039/c9sc00126cC-Si CouplingFALSEhttps://doi.org/10.1039/c9sc00126cHu, XLChem. Sci.We report the first Ni MOF catalysts for anti-Markovnikov hydrosilylation of alkenes. These catalysts are bench-stable and easily-assembled from simple Ni salts and Carbonylic acids. The best catalyst gives turnover numbers up to 9500 and is robust even after 10 recyCling runs. The catalyst can be applied for the hydrosilylation of a wide range of alkenes, achieving good synthetic utility and functional group tolerance.Alkene hydrosilylation catalyzed by easily assembled Ni(II)-Carbonylate MOFs12201969#N/ATRUE
368
c7sc04687a10.1039/c7sc04687aC-Si CouplingFALSEhttps://doi.org/10.1039/c7sc04687aMandal, SKChem. Sci.In this report, a ligand-redox assisted catalytic hydrosilylation has been investigated. A phenalenyl ligand coordinated nickel complex has been utilized as an electron reservoir to develop a base metal-assisted catalyst, which very efficiently hydrosilylates a wide variety of olefin substrates under ambient conditions. A mechanistic investigation revealed that a two-electron reduced phenalenyl based biradical nickel complex plays the key role in such catalysis. The electronic structure of the catalytically active biradical species has been interrogated using EPR spectroscopy, magnetic susceptibility measurements, and electronic structure calculations using a DFT method. Inhibition of the reaction by a radical quencher, as well as the mass spectrometric detection of two intermediates along the catalytic loop, suggest that a single electron transfer from the ligand backbone initiates the catalysis. The strategy of utilising the redox reservoir property of the ligand ensures that the nickel is not promoted to an unfavorable oxidation state, and the fine tuning between the ligand and metal redox orbitals elicits smooth catalysis.Tuning the redox non-innocence of a phenalenyl ligand toward efficient nickel-assisted catalytic hydrosilylation22201869#N/ATRUE
369
c3sc52626g10.1039/c3sc52626gC-Si CouplingFALSEhttps://doi.org/10.1039/c3sc52626gPeters, JCChem. Sci.Metal-borane complexes are emerging as promising systems for study in the context of bifunctional catalysis. Herein we describe diphosphineborane nickel complexes that activate Si-H bonds and catalyze the hydrosilylation of aldehydes. Treatment of [(DPBPh)-D-Mes]Ni (1) ([MesDPBPh] MesB(o-Ph2PC6H4)(2)) with organosilanes affords the complexes [(DPBPh)-D-Mes](m-H) NiE (E SiH2Ph (3), SiHPh2 (4)). Complex 4 is in solution equilibrium with 1 and the thermodynamic and kinetic parameters of their exchange have been characterized by NMR spectroscopy. Complex 1 is a catalyst for the hydrosilylation of a range of parasubstituted benzaldehydes. Mechanistic studies on this reaction via multinuClear NMR spectroscopy are consistent with the intermediacy of a borohydrido-Ni-siloxyAlkyl species.Facile Si-H bond Activation and hydrosilylation catalysis mediated by a nickel-borane complex93201478#N/ATRUE
370
anie.20200872910.1002/anie.202008729C-Si CouplingFALSEhttps://doi.org/10.1002/anie.202008729Beller, MAngew. Chem.-Int. Edit.Hydrosilylation reactions, which allow the addition of Si-H to C=C/C equivalent to C bonds, are typically catalyzed by homogeneous noble metal catalysts (Pt, Rh, Ir, and Ru). Although excellent activity and selectivity can be obtained, the price, purification, and metal residues of these precious catalysts are problems in the silicone industry. Thus, a strong interest in more sustainable catalysts and for more economic processes exists. In this respect, recently disClosed hydrosilylations using catalysts based on earth-abundant transition metals, for example, Fe, Co, Ni, and Mn, and heterogeneous catalysts (supported nanopartiCles and single-atom sites) are noteworthy. This minireview describes the recent advances in this field.Recent Advances in Catalytic Hydrosilylations: Developments beyond Traditional PlatinumCatalystsalkenes; alkynes; hydrosilylation; silanes122021123#N/ATRUE
371
anie.20170661110.1002/anie.201706611C-Si CouplingFALSEhttps://doi.org/10.1002/anie.201706611Oestreich, MAngew. Chem.-Int. Edit.A deCarbonylative silylation of aliphatic N-hydroxyphthalimide (NHPI) esters using Si-B reagents as silicon pronuCleophiles is reported. This C(sp(3))-Si cross-coupling is catalyzed by copper(I) and follows a radical mechanism, even with exClusion of light. Both primary and secondary Alkyl groups couple effectively, whereas tertiary Alkyl groups are probably too sterically hindered. The functional-group tolerance is generally excellent, and alpha-heteroatom-substituted substrates also participate well. This enables, for example, the synthesis of alpha-silylated amines starting from NHPI esters derived from alpha-amino acids. The new method extends the still limited number of C(sp(3))-Si cross-couplings of unactivated Alkyl electrophiles.Copper-Catalyzed DeCarbonylative Radical Silylation of Redox-Active Aliphatic Carbonylic Acid Derivativescopper; cross-coupling; deCarbonylation; radical reactions; silicon74201748#N/ATRUE
372
anie.20161246010.1002/anie.201612460C-Si CouplingFALSE#REF!Lee, KL(Aminomethyl)pyridine Complexes for the Cobalt-Catalyzed Anti-Markovnikov Hydrosilylation of Alkoxy- or Siloxy(Vinyl)silanes with Alkoxy- or Siloxyhydrosilanes2017#N/ATRUE
373
anie.20160469610.1002/anie.201604696C-Si CouplingFALSEhttps://doi.org/10.1002/anie.201604696Rueping, MAngew. Chem.-Int. Edit.An efficient nickel/copper-catalyzed deCarbonylative silylation reaction of Carbonylic acid esters with silylboranes is described. This reaction provides access to structurally diverse silanes with high efficiency and excellent functional-group tolerance starting from readily available esters.DeCarbonylative Silylation of Esters by Combined Nickel and Copper Catalysis for the Synthesis of Arylsilanes and HeteroArylsilanesdeCarbonylative cross-couplings; copper; esters; nickel; silylation88201679#N/ATRUE
374
anie.20150782910.1002/anie.201507829C-Si CouplingFALSEhttps://doi.org/10.1002/anie.201507829Hu, XLAngew. Chem.-Int. Edit.Chemoselective hydrosilylation of functionalized alkenes is difficult to achieve using base-metal catalysts. Reported herein is that well-defined bis(amino) amide nickel pincer complexes are efficient catalysts for anti-Markovnikov hydrosilylation of terminal alkenes with turnover frequencies of up to 83000 per hour and turnover numbers of up to 10000. Alkenes containing amino, ester, amido, ketone, and Carbonyl groups are selectively hydrosilylated. A slight modification of reaction conditions allows tandem isomerization/hydrosilylation reactions of internal alkenes using these nickel catalysts.Chemoselective Alkene Hydrosilylation Catalyzed by Nickel Pincer Complexesalkenes; chemoselectivity; nickel; pincer ligands; silanes144201547#N/ATRUE
375
anie.20150352110.1002/anie.201503521C-Si CouplingFALSEhttps://doi.org/10.1002/anie.201503521Montgomery, JAngew. Chem.-Int. Edit.Methods for the highly stereoselective and regiodivergent hydrosilylation of 1,3-disubstituted allenes have been developed. The synthesis of Eallylsilanes is accomplished with palladium NHC catalysts, and trisubstituted Zalkenylsilanes are accessed with nickel NHC catalysts. Unsymmetrically substituted allenes are well tolerated with nickel catalysis and afford Zalkenylsilanes. Evidence for a plausible mechanism was obtained through an isotopic double-labeling crossover study.Regiodivergent and Stereoselective Hydrosilylation of 1,3-Disubstituted Alleneshydrosilylation; regioselectivity; silanes; stereoselectivity; transition-metal catalysis41201573#N/ATRUE
376
anie.20110572210.1002/anie.201105722C-Si CouplingFALSEhttps://doi.org/10.1002/anie.201105722Driess, MHydrosilylation of Alkynes by Ni(CO)3-Stabilized Silicon(II) Hydride2012#N/ATRUE
377
anie.20035157910.1002/anie.200351579C-Si CouplingFALSEhttps://doi.org/10.1002/anie.200351579Kambe, NAngew. Chem.-Int. Edit.Nickel-catalyzed dimerization and carbosilylation of 1,3-butadienes with chlorosilanes and Grignard reagentsdienes; Grignard reagents; multicomponent reactions; nickel; silanes41200325#N/ATRUE
378
acscatal.9b0087910.1021/acscatal.9b00879C-Si CouplingFALSEhttps://doi.org/10.1021/acscatal.9b00879Ke, ZFACS Catal.Lewis acid transition-metal-complex-catalyzed hydrosilylation of CO2 has attracted vast interests. Yet, the Si-H bond Activation mechanism is still ambiguous and needs further elucidation. Herein, DFT studies were performed to study the reaction mechanism of CO2 hydrosilylation catalyzed by the PBP-Ni-OCHO center dot B(C6F5)(3). Different from previously proposed B-Ni-bond-assisted nonlinear Si-H Cleavage and boron-promoted Si-H bond Activation, two other patterns of linear S(N)2 type Si-H bond Activation were proposed: the B Ni-bond-assisted Si-H bond Cleavage and the Ni-promoted Si-H bond Cleavage. Our results demonstrate the important role of the linear S(N)2 type cooperation in Si-H bond Activation. As for the Si-H Cleavage assisted by the B-Ni bond, the linear S(N)2 type proposed in this work is more favored than the nonlinear S(N)2 type. Specifically, the Ni-center-promoted linear S(N)2 type Si-H Cleavage is the most plausible mechanism for Si-H bond Activation because of its linear geometry, small deformation energy, and avoidance of B-O bond dissociation in the transition state. With regard to the whole hydrosilylation reaction, four steps are involved: initial Si-H Activation, hydride transfer, second Si-H Activation, and reduction of CO2. The C=O reductions of both hydride transfer and CO2 are preferred to be promoted by the B-H via the cooperation of the PBP-Ni center dot center dot center dot HB(C6F5)(3) Lewis pairs. The initial Si-H Activation with the free-energy barrier of similar to 28 kcal/mol is the rate-determining step in the whole reaction. This research highlights the important role of the linear S(N)2 type cooperation in Si-H bond Activation by Lewis acid transition-metal systems, which should provide important guidance to mechanistic understanding and catalyst design in the future.Mechanism of Si-H Bond Activation for Lewis Acid PBP-Ni-Catalyzed Hydrosilylation of CO2: The Role of the Linear S(N)2 Type CooperationCO2 hydrosilylation; Si-H Activation; Lewis acid; transition metal; DFT; mechanism; nickel; boron11201946#N/ATRUE
379
acscatal.8b0310410.1021/acscatal.8b03104C-Si CouplingFALSEhttps://doi.org/10.1021/acscatal.8b03104Pawluc, PACS Catal.Over the years, hydrosilylation of terminal alkenes has emerged as one of the most prominent applications of homogeneous catalysis. While most of the relevant reports concern fi-selective hydrosilylation, yielding linear products which are of industrial importance, the opposite selectivity is also gaining increasing interest and sets the scene for the next challenges. Markovnikov hydrosilylation of alkenes, especially in its asymmetric variant, has become the aim of development of new catalytic systems successfully implementing base -metal complexes one of the most prominent trends in contemporary catalysis. In this Perspective, we present the current state of this topic and the way it has been achieved, with special emphasis put on the issues still unresolved and prospective directions of development based on the trends present in the literature, but without unnecessary attention to some details of only historical significance.Markovnikov Hydrosilylation of Alkenes: How an Oddity Becomes the Goalhydrosilylation; Markovnikov selectivity; asymmetric catalysis; base-metal complexes; transition-metal catalysis; catalyst design40201861#N/ATRUE
380
acscatal.6b0299010.1021/acscatal.6b02990C-Si CouplingFALSEhttps://doi.org/10.1021/acscatal.6b02990Huang, ZACS Catal.This review covers the advance in the development of Fe, Co, and Ni catalysts for the alkene hydrosilylation reaction, as well as the related dehydrogenative silylation reaction. The hydrosilylation of alkene is an important reaction for the synthesis of Alkylsilanes that has widespread applications in numerous silicon based materials, and for decades, this transformation has been relying on the use of Pt catalysts. Recently, the high abundance and low cost, coupled with the environmentally benign nature of the base metals have stimulated enormous research on the development of first-row transition-metal catalysts as replacements for the precious Pt catalysts. Several base-metal catalysts which have emerged during the past 5 years offer high activity, broad substrate scope, and excellent regioselectivity. Both of the anti-Markovnikov and the unusual Markovnikov additions can be achieved in a high degree of regioselectivity. The reactions of acyClic internal olefins catalyzed by the base-metal catalysts reported to date yield linear Alkylsilanes via a tandem olefin-isomerization and hydrosilylation process. A few catalysts enable the dehydrogenative silylation of alkenes to form Vinylsilanes and/or allylsilanes.Advances in Base-Metal-Catalyzed Alkene Hydrosilylationiron; cobalt; nickel; alkene; hydrosilylation; dehydrogenative silylation221201798#N/ATRUE
381
acscatal.6b0226910.1021/acscatal.6b02269C-Si CouplingFALSEhttps://doi.org/10.1021/acscatal.6b02269Albrecht, MACS Catal.A set of nickel(II) Cp complexes with triazolylidenes containing various different wingtip groups (Aryl, Alkyl, pyridyl, CH2OH) have been synthesized by direct metalation of the corresponding triazolium salt with nickelocene. Distinct effects of the substituents on electronic and steric properties of the formed complexes are demonstrated by NMR spectroscopy and single crystal structural analysis, as well as by the catalytic activity of the complexes in the hydrosilylation of aldehydes. While all complexes display appreciable catalytic performance, the cyClometalated pyridyl-functionalized triazolylidene nickel complex 2e is highly active and reaches turnover frequencies of >20 000 h(-1) with good catalyst stability (full conversion at 0.05 mol % catalyst, maximum turnovers of similar to 6000). A variety of functional groups on the benzaldehyde are tolerated. Ketones are not converted, which identifies complex 2e as a highly selective precatalyst for the hydrosilylation of aldehydes in the presence of ketones.Synthesis of Triazolylidene Nickel Complexes and Their Catalytic Application in Selective Aldehyde Hydrosilylationnickel; triazolylidene; hydrosilylation; N-heterocyClic carbene; aldehyde conversion402016142#N/ATRUE
382
acscatal.6b0030410.1021/acscatal.6b00304C-Si CouplingFALSEhttps://doi.org/10.1021/acscatal.6b00304Chirik, PJACS Catal.High-spin pyridine diimine cobalt(II) bis(Carbonylate) complexes have been synthesized and exhibit high activity for the hydrosilylation of a range of commercially relevant alkenes and tertiary silanes. Previously observed dehydrogenative silylation is suppressed with the use of sterically unencumbered ligands, affording exClusive hydrosilylation with up to 4000 TON. The cobalt precatalysts were readily prepared and handled on the benchtop and underwent substrate Activation, obviating the need for external reductants. The cobalt catalysts are tolerant of epoxide, amino, Carbonyl, and Alkyl halide functional groups, broadening the scope of alkene hydrosilylation with earth-abundant metal catalysts.Bench-Stable, Substrate-Activated Cobalt Carbonylate Pre-Catalysts for Alkene Hydrosilylation with Tertiary Silanescobalt; hydrosilylation; alkenes; tertiary silanes; redox active; silicone91201651#N/ATRUE
383
acs.orglett.8b0274610.1021/acs.orglett.8b02746C-Si CouplingFALSEhttps://doi.org/10.1021/acs.orglett.8b02746Yang, YAn NNN-Pincer-Cobalt Complex Catalyzed Highly Markovnikov-Selective Alkyne Hydrosilylation2018#N/ATRUE
384
ol702499h10.1021/ol702499hC-Si CouplingTRUE
https://doi.org/10.1021/ol702499h
Knochel, POrg. Lett.A direct room-temperature Ni-catalyzed cross-coupling of aminoalkylzinc halides, readily available from the corresponding aminoalkyl chlorides via Grignard reagents, with aryl and hetaryl electrophiles, allows a convenient one-step preparation of aminoalkyl (het)arenes, bearing a basic tertiary nitrogen in the side chain, including piperidine and tropane derivatives. Such aminoalkylarene scaffolds are widely present in various biologically active molecules.Direct Aminoalkylation of Arenes and Hetarenes via Ni-Catalyzed Negishi Cross-Coupling ReactionsCsp2_ar-Csp3E-NuOOTfMgXArylNo baseNo Base492007x3/10/2022
385
ja412107b10.1021/ja412107bC-Si CouplingFALSEja412107bMartin, Ry1502014xx#N/A
386
ja992597s10.1021/ja992597sC-Sn CouplingFALSEhttps://doi.org/10.1021/ja992597sHiyama, TJ. Am. Chem. Soc.Nickel-catalyzed carbostannylation of alkynes with allyl-, acyl-, and alkynylstannanes: Stereoselective synthesis of trisubstituted Vinylstannanes121199910#N/ATRUE
387
ja002040910.1021/ja0020409C-Sn CouplingFALSEhttps://doi.org/10.1021/ja0020409Hiyama, TJ. Am. Chem. Soc.Nickel-catalyzed acylstannylation of 1,3-dienes: Synthesis and reaction of epsilon-oxoallylstannanes46200014#N/ATRUE
388
anie.20161172010.1002/anie.201611720C-Sn CouplingFALSEhttps://doi.org/10.1002/anie.201611720Martin, RAngew. Chem.-Int. Edit.A Ni-catalyzed stannylation of Aryl esters with air- and moisture-insensitive silylstannyl reagents via C-sp2-O Cleavage is described. This protocol is characterized by its wide scope, inCluding challenging combinations, thus enabling access to versatile building blocks and orthogonal C-heteroatom bond formations.Ni-Catalyzed Stannylation of Aryl Esters via C-O Bond CleavageAryl esters; C-O Cleavage; cross-coupling; nickel44201771#N/ATRUE
389
anie.20035364910.1002/anie.200353649C-Sn CouplingFALSEhttps://doi.org/10.1002/anie.200353649Hiyama, TAngew. Chem.-Int. Edit.Nickel-catalyzed tandem carbostannylation of alkynes and 1,2-dienes with alkynylstannanesC-C coupling; metalation multicomponent reactions; nickel; tin31200422#N/ATRUE
390
acs.orglett.7b0366910.1021/acs.orglett.7b03669C-Sn CouplingFALSEhttps://doi.org/10.1021/acs.orglett.7b03669Rueping, MCatalytic Ester to Stannane Functional Group Interconversion via DeCarbonylative Cross-Coupling of Methyl Esters2018#N/ATRUE
391
ja105588v10.1021/ja105588vC-Sn CouplingFALSEhttps://doi.org/10.1021/ja105588vJohnson, SAJ. Am. Chem. Soc.The ubiquitous Stille coupling reaction utilizes Sn-C bonds and is of great utility to organic chemists. Unlike the B-C bonds used in the Miyaura-Suzuki coupling reaction, which are readily obtained via direct borylation of C-H bonds, routes to organotin compounds via direct C-H bond functionalization are lacking. Here we report that the nickel-catalyzed reaction of fluorinated arenes and pyridines with Vinyl stannanes does not provide the expected Vinyl compounds via C-F Activation but rather provides new Sn-C bonds via C-H functionalization with the loss of ethylene. This mechanism provides a new unanticipated methodology for the direct conversion of C-H bonds to carbon-heteroatom bonds.Catalytic C-H Bond Stannylation: A New Regioselective Pathway to C-Sn Bonds via C-H Bond Functionalization73201038#N/ATRUE
392
ja909395610.1021/ja9093956C-X ActivationTRUEhttps://doi.org/10.1021/ja9093956Weix, DJJ. Am. Chem. Soc.The direct reductive cross-coupling of Alkyl halides with Aryl halides is described. The transformation is efficient (equimolar amounts of the starting materials are used), generally high-yielding (all but one between 55 and 88% yield), highly functional-group-tolerant [OH, NHBoc, NHCbz, Bpin, C(O)Me, CO2Et, and CN are all tolerated], and easy to perform (uses only benchtop-stable reagents, tolerates small amounts of water and oxygen, changes color when complete, and uses filtration workup). The reaction appears to avoid the formation of intermediate organomanganese species, and a synergistic effect was found when a mixture of two ligands was employed.Nickel-Catalyzed Reductive Cross-Coupling of Aryl Halides with Alkyl HalidesCsp2_ar-Csp3XXXArylNo baseNo Base2532010247/28/2022TRUE
393
acscatal.0c0342810.1021/acscatal.0c03428C-X ActivationFALSEhttps://doi.org/10.1021/acscatal.0c03428Tan, WHACS Catal.The development of strategies to access 2,2'-diammobiAryl derivatives via a transition-metal-catalyzed coupling reaction from protecting-group-free starting materials is a challenging task to accomplish, owing to the easy occurrence of undesired side reactions. The exploitation of Ni-catalyzed direct homocoupling of unprotected 2-haloaniline analogues to produce 2,2'-diaminobiAryls with a readily available and inexpensive bipyridine ligand has been described. This approach was highlighted by its high chemoselectivity, broad substrate scope, and functional group compatibility. The mechanistic and calculation studies indicated that Ni(0), Ni(I), Ni(II), and Ni(III) species might be involved in the catalytic cyCle.Highly Chemoselective Access to 2,2 '-DiaminobiAryls via Ni-Catalyzed Protecting-Group-Free Coupling of 2-HaloanilinesNi-catalyzed; chemoselective; protecting-group-free coupling; 2-haloaniline; 2,2&PRIME-diaminobiArylsyy220200#N/AFALSE
394
jo970784810.1021/jo9707848C-X ActivationFALSEhttps://pubs.acs.org/doi/10.1021/jo9707848Miyaura, N195#N/A
395
bcsj.63.8010.1246/bcsj.63.80C-X ActivationFALSEhttps://doi.org/10.1246/bcsj.63.80ODA, M257#N/A
396
jo970784810.1021/jo9707848C-X ActivationFALSEhttps://doi.org/10.1021/jo9707848Miyaura, N195#N/A
397
bcsj.49.195810.1246/bcsj.49.1958C-X ActivationTRUEhttps://doi.org/10.1246/bcsj.49.1958KUMADA, MCsp3-Csp2_arXClMgXAlkylNo baseNo Base6527/28/2022
398
C3976000596B
10.1039/C3976000596BC-X ActivationFALSEhttps://doi.org/10.1039/C3976000596BBABA, S138#N/A
399
science.aai861110.1126/science.aai8611C-X ActivationFALSEhttps://doi.org/10.1126/science.aai8611Fu, GCScienceAlkylboron compounds are an important family of target molecules, serving as useful intermediates, as well as end points, in fields such as pharmaceutical science and organic chemistry. Facile transformation of carbon-boron bonds into a wide variety of carbon-X bonds (where X is, for example, carbon, nitrogen, oxygen, or a halogen), with stereochemical fidelity, renders the generation of enantioenriched Alkylboronate esters a powerful tool in synthesis. Here we report the use of a chiral nickel catalyst to achieve stereoconvergent Alkyl-Alkyl couplings of readily available racemic alpha-halB(OH)2ronates with organozinc reagents under mild conditions. We demonstrate that this method provides straightforward access to a diverse array of enantioenriched Alkylboronate esters, in which boron is bound to a stereogenic carbon, and we highlight the utility of these compounds in synthesis.A general, modular method for the catalytic asymmetric synthesis of Alkylboronate esters107201627#N/ATRUE
400
s41467-018-05946-310.1038/s41467-018-05946-3C-X ActivationFALSEhttps://doi.org/10.1038/s41467-018-05946-3Gandelman, MNat. Commun.Methods for synthesis of chiral organic compounds bearing trifluoromethyl-substituted stereocenters are of great interest for agrochemical and pharmaceutical labs and industries in their search for new bioactive materials. We report on employment of bisfunctionalized electrophiles, bearing both a trifluoromethyl and a functional group as direct substituents of the reactive center, in cross-coupling reactions. We exemplify this concept in the asymmetric synthesis of enantioenriched alpha-trifluoromethyl- and perfluoroAlkyl-containing Benzylic and allylic ethers and alcohols by nickel-catalyzed stereoconvergent Hiyama cross-coupling reaction. Substrate electrophiles are conveniently prepared in few steps from trifluoroacetic acid. The method represents a conceptually different approach to chiral CF3-substituted alcohols and ethers and allows for a rapid catalytic preparation of a wide range of these valuable compounds in high yields and enantioselectivity.Synthesis of chiral alpha-trifluoromethyl alcohols and ethers via enantioselective Hiyama cross-couplings of bisfunctionalized electrophiles18201827#N/ATRUE
401
jacs.9b0417510.1021/jacs.9b04175C-X ActivationTRUEhttps://doi.org/10.1021/jacs.9b04175Watson, DAJ. Am. Chem. Soc.A general catalytic method for asymmetric C-Alkylation of nitroalkanes using nickel catalysis is described. This method enables the formation of highly enantioenriched beta-nitroamides from readily available alpha-bromoamides using mild reaction conditions that are compatible with a wide range of functional groups. When combined with subsequent reactions, this method allows access to highly enantioenriched products with nitrogen bearing fully substituted carbon centers.Nickel-Catalyzed Asymmetric C-Alkylation of Nitroalkanes: Synthesis of Enantioenriched beta-NitroamidesCsp3-Csp2HHBrAlkylNaOMeIonic-OR52019456/29/2022TRUE
402
jacs.5b0047310.1021/jacs.5b00473C-X ActivationFALSEhttps://doi.org/10.1021/jacs.5b00473Gandelman, MJ. Am. Chem. Soc.The incorporation of fluorine atom into a stereogenic center is a highly challenging transformation with current methodologies offering access mainly to chiral alpha- and beta-fluoroalkanes. In this artiCle, the development of a novel general approach to construct beta-, gamma-, delta-, and epsilon- fluoroalkanes with good enantioselectivity is described. Different directing groups, such as Benzyl, ketone, and sulfonyl, were shown to give good enantioselectivity under Suzuki cross-coupling conditions in the presence of a Ni catalyst and chiral diamine ligand. It inCludes the first examples of enantioselective synthesis of chiral fluorine-containing centers at as distant as delta or epsilon positions from the functional groups.Enantioselective Suzuki Cross-Couplings of Unactivated 1-Fluoro-1-haloalkanes: Synthesis of Chiral beta-, gamma-, delta-, and epsilon-Fluoroalkanes51201559#N/ATRUE
403
ja508718m10.1021/ja508718mC-X ActivationFALSEhttps://doi.org/10.1021/ja508718mFu, GCJ. Am. Chem. Soc.Although nickel-catalyzed stereoconvergent couplings of racemic Alkyl electrophiles are emerging as a powerful tool in organic chemistry, to date there have been no systematic mechanistic studies of such processes. Herein, we examine the pathway for enantioselective Negishi Arylations of secondary propargylic bromides, and we provide evidence for an unanticipated radical chain pathway wherein oxidative addition of the C-Br bond occurs through a bimetallic mechanism. In particular, we have crystallographically characterized a diamagnetic Arylnickel(II) complex, [(i-Pr-pybox)(NiPh)-Ph-II]BArF4, and furnished support for [(i-Pr-pybox)(NiPh)-Ph-II](+) being the predominant nickel-containing species formed under the catalyzed conditions as well as a key player in the cross-coupling mechanism. On the other hand, our observations do not require a role for an organonickel(I) intermediate (e.g., (i-Pr-pybox)(NiPh)-Ph-I), which has previously been suggested to be an intermediate in nickel-catalyzed cross-couplings, oxidatively adding Alkyl electrophiles through a monometallic pathway.Nickel-Catalyzed Negishi Arylations of Propargylic Bromides: A Mechanistic Investigation231201426#N/ATRUE
404
anie.20201261410.1002/anie.202012614C-X ActivationFALSEhttps://doi.org/10.1002/anie.202012614Zhu, SLAngew. Chem.-Int. Edit.A NiH-catalyzed migratory hydroalkenylation reaction of olefins with alkenyl bromides has been developed, affording Benzylic alkenylation products with high yields and excellent chemoselectivity. The mild conditions of the reaction preClude olefinic products from undergoing further isomerization or subsequent alkenylation. Catalytic enantioselective hydroalkenylation of styrenes was achieved by using a chiral bisoxazoline ligand.Nickel-Catalyzed, Regio- and Enantioselective Benzylic Alkenylation of Olefins with Alkenyl Bromidealkenes; alkenylation; asymmetric catalysis; isomerization; nickel82021104#N/ATRUE
405
anie.20180271310.1002/anie.201802713C-X ActivationFALSEhttps://doi.org/10.1002/anie.201802713Zhang, XGAngew. Chem.-Int. Edit.Although iron-catalyzed cross-coupling of Grignard reagents with Alkyl halides has been well established, the adoption of the reaction for fluoroAlkylations has not been reported because traditional catalytic systems often lead to defluorination reactions. Described herein is the investigation of an iron-catalyzed cross-coupling between Arylmagnesium bromides and difluoroAlkyl bromides with modified N,N,N',N'-tetramethyl-ethane-1,2-diamine (TMEDA) as a ligand. The use of this bulky diamine, in which a butylene is substituted at one carbon atom of the ethylene backbone in TMEDA, enables the iron-catalyzed difluoroAlkylation under mild reaction conditions with a wide range of difluoroAlkyl bromides, inCluding vulnerable bromodifluoromethane, thus providing a general and cost-efficient route for applications in medicinal chemistry.Bulky Diamine Ligand Promotes Cross-Coupling of DifluoroAlkyl Bromides by Iron Catalysis46201868#N/ATRUE
406
acscatal.8b0100510.1021/acscatal.8b01005C-X ActivationFALSEhttps://doi.org/10.1021/acscatal.8b01005Stradiotto, MACS Catal.We report herein on the synthesis and catalytic application of a family of o-phenylene-bridged bisphosphine ancillary ligands featuring a bulky N-heterocyClic phosphine (NHP) donor fragment paired with an adjacent PR2 donor group (R = Alkyl, Aryl), whereby the incorporation of phosphorus into either a saturated or unsaturated heterocyClic ring serves as a means of modulating the donicity of the NHP fragment. Screening of these ancillary ligands in representative nickel-catalyzed C(sp(2)) N cross-coupling test reactions allowed for the identification of one variant, featuring a saturated NHP structure and an adjacent diphenylphosphino donor group (i.e., NHP-DalPhos), as being particularly effective in reactions involving primary Alkylamines. Notably, application of the derived precatalyst (NHP-DalPhos)NiCl(o-tolyl) (C1) enabled the typically challenging monoArylation of structurally diverse primary Alkylamines with (hetero)Aryl chlorides or bromides at room temperature. Also described are the results of our comparative density functional theory computational analysis of nickel-catalyzed primary Alkylamine C(sp(2)) N cross-couplings employing PAd-DalPhos or NHP-DalPhos.Application of Diazaphospholidine/Diazaphospholene-Based Bisphosphines in Room-Temperature Nickel-Catalyzed C(sp(2))-N Cross-Couplings of Primary Alkylamines with (Hetero)Aryl Chlorides and Bromidesnickel; C-N cross-coupling; amination; ligand design; density functional theory20201855#N/ATRUE
407
acscatal.5b0232410.1021/acscatal.5b02324C-X ActivationFALSEhttps://doi.org/10.1021/acscatal.5b02324Hu, XLACS Catal.Replacement of a dimethyl amino group of the amidobis(amine) nickel(II) pincer complex (1), [((N2N)-N-Me)-Ni-Cl], by a pyrrolidino group resulted in a new nickel(II) pincer complex (2), [((PNNN)-N-yr-N-Me)Ni-Cl]. Complex 2 is an efficient catalyst for Kumada and Suzuki-Miyaura cross-coupling of nonactivated secondary Alkyl halides, while complex 1 is largely inactive. The significant activity difference is tentatively attributed to a minimal structural difference, which leads to a more hemilabile ligand.From Dimethylamine to Pyrrolidine: The Development of an Improved Nickel Pincer Complex for Cross-Coupling of Nonactivated Secondary Alkyl Halidesnickel; pincer ligands; Kumada coupling; Suzuki-Miyaura coupling secondary Alkyl halide28201639#N/ATRUE
408
acscatal.5b0146310.1021/acscatal.5b01463C-X ActivationFALSEhttps://doi.org/10.1021/acscatal.5b01463Ichikawa, JACS Catal.The nickel-catalyzed defluorinative coupling of 2-trifluoromethyl-1-alkenes and alkynes with the aid of Et3SiH provides 1,1-difluoro-1,4-dienes under mild reaction conditions. This reaction involves selective allylic C(sp(3))-F bond Activation via beta-fluorine elimination from nickelacyClopentenes.Nickel-Catalyzed Allylic C(sp(3))-F Bond Activation of Trifluoromethyl Groups via beta-Fluorine Elimination: Synthesis of Difluoro-1,4-dienesC-F bond Activation; nickel catalysis; trifluoromethylalkenes; alkynes; 1,4-dienes; beta-fluorine eliminationy101201555#N/AFALSE
409
ja903928910.1021/ja9039289C-X ActivationFALSEhttps://doi.org/10.1021/ja9039289Nakamura, MJ. Am. Chem. Soc.Combinations of N-heterocyClic carbenes (NHCs) and fluoride salts of the iron-group metals (Fe, Co, and Ni) have been shown to be excellent catalysts for the cross-coupling reactions of Aryl Grignard reagents ((ArMgX)-Mg-1) with Aryl and heteroAryl halides ((ArX)-X-2) to,give unsymmetrical biAryls (Ar-1-Ar-2). Iron fluorides in combination with SIPr, a saturated NHC ligand, catalyze the biAryl cross-coupling between various Aryl chlorides and Aryl Grignard reagents in high yield and high selectivity. On the other hand, cobalt and nickel fluorides in combination with IPr, an unsaturated NHC ligand, exhibit interesting complementary reactivity in the coupling of Aryl bromides or iodides; in contrast, with these substrates the iron catalysts show a lower selectivity. The formation of homocoupling byproducts is suppressed markedly to less than 5% in most cases by choosing the appropriate metal fluoride/NHC combination. The present catalyst combinations offer several synthetic advantages over existing methods: practical synthesis of a broad range of unsymmetrical biAryls without the use of palladium catalysts and phosphine ligands. On the basis of stoichiometric control experiments and theoretical studies, the origin of the unique catalytic effect of the fluoride counterion can be ascribed to the formation of a higher-valent heteroleptic metalate [(ArMF2)-M-1]MgX as the key intermediate in our proposed catalytic cyCle. First, stoichiometric control experiments revealed the stark differences in chemical reactivity between the metal fluorides and metal chlorides. Second, DFT calculations indicate that the initial reduction of di- or trivalent metal fluoride in the wake of transmetalation with PhMgX is energetically unfavorable and that formation of a divalent heteroleptic metalate complex, [PhMF2]MgX (M = Fe, Co, Ni), is dominant in the metal fluoride system. The heteroleptic ate-complex serves as a key reactive intermediate, which undergoes oxidative addition with PhCl and releases the biAryl cross-coupling product Ph-Ph with reasonable energy barriers. The present cross-coupling reaction catalyzed by iron-group metal fluorides and an NHC ligand provides a highly selective and practical method for the synthesis of unsymmetrical biAryls as well as the opportunity to gain new mechanistic insights into the metal-catalyzed cross-coupling reactions.Highly Selective BiAryl Cross-Coupling Reactions between Aryl Halides and Aryl Grignard Reagents: A New Catalyst Combination of N-HeterocyClic Carbenes and Iron, Cobalt, and Nickel Fluorides2572009186#N/ATRUE
410
anie.20080604810.1002/anie.200806048C-X ActivationFALSEhttps://doi.org/10.1002/anie.200806048Johnson, SAAngew. Chem.-Int. Edit.Selective C-F Bond Activation of Tetrafluorobenzenes by Nickel(0) with a Nitrogen Donor Analogous to N-HeterocyClic Carbenesamides; C-F Activation; fluorides; nickel; zwitterions67200935#N/ATRUE
411
anie.20190681510.1002/anie.201906815C-X CouplingFALSEhttps://doi.org/10.1002/anie.201906815Reisman, SEAngew. Chem.-Int. Edit.A Ni-catalyzed halogenation of enol triflates was developed and it enables the synthesis of a broad range of alkenyl iodides, bromides, and chlorides under mild reaction conditions. The reaction utilizes inexpensive, bench-stable Ni(OAc)(2).4 H2O as a precatalyst and proceeds at room temperature in the presence of sub-stoichiometric Zn and either 1,5-cyClooctadiene or 4-(N,N-dimethylamino)pyridine.Nickel-Catalyzed Conversion of Enol Triflates into Alkenyl Halidesalkenes; halides; kinetics; nickel; reaction mechanisms16201950#N/ATRUE
412
ja806292510.1021/ja8062925CarbonylationFALSEhttps://doi.org/10.1021/ja8062925Rovis, TJ. Am. Chem. Soc.A nickel-catalyzed reductive Carbonylation of styrenes using CO2 has been developed. The reaction proceeds under mild conditions using diethylzinc as the reductant. Preliminary data suggests the mechanism involves two discrete nickel-mediated catalytic cyCles, the first involving a catalyzed hydrozincation of the alkene followed by a second, slower nickel-catalyzed Carbonylation of the in situ formed organozinc reagent. Importantly, the catalyst system is very robust and will fixate CO2 in good yield even if exposed to only an equimolar amount introduced into the headspace above the reaction.Nickel-Catalyzed Reductive Carbonylation of Styrenes Using CO2284200837#N/ATRUE
413
jacs.8b0979010.1021/jacs.8b09790CB CouplingFALSEhttps://doi.org/10.1021/jacs.8b09790Marder, TBJ. Am. Chem. Soc.A highly selective and general photocatalytic C-F borylation protocol that employs a rhodium biphenyl complex as a triplet sensitizer and the nickel catalyst [Ni(IMes)(2)] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the C-F bond Activation and defluorB(OH)2rylation process is reported. This tandem catalyst system operates with visible (blue, 400 nm) light and achieves borylation of a wide range of fluoroarenes with B(2)pin(2) at room temperature in excellent yields and with high selectivity. Direct irradiation of the intermediary C-F bond oxidative addition product trans-[NiF(Ar-F)(IMes)(2)] leads to very fast decomposition when B(2)pin(2) is present. This destructive pathway can be bypassed by indirect excitation of the triplet states of the nickel(II) complex via the photoexcited rhodium biphenyl complex. Mechanistic studies suggest that the exceptionally long-lived triplet excited state of the Rh biphenyl complex used as the photosensitizer allows for efficient triplet energy transfer to trans-[NiF(Ar-F)(IMes)(2)], which leads to dissociation of one of the NHC ligands. This contrasts with the majority of current photocatalytic transformations, which employ transition metals as excited state single electron transfer agents. We have previously reported that C(arene)-F bond Activation with [Ni(IMes)(2)] is facile at room temperature, but that the transmetalation step with B(2)pin(2) is associated with a high energy barrier. Thus, this triplet energy transfer ultimately leads to a greatly enhanced rate constant for the transmetalation step and thus for the whole borylation process. While addition of a fluoride source such as CsF enhances the yield, it is not absolutely required. We attribute this yield-enhancing effect to (i) formation of an anionic adduct of B(2)pin(2), i.e., FB(2)pin(2)(-), as an efficient, much more nuCleophilic {Bpin(-)} transfer reagent for the borylation/transmetalation process, and/or (ii) trapping of the Lewis acidic side product FBpin by formation of [F(2)Bpin](-) to avoid the formation of a significant amount of NHC-FBpin and consequently decomposition of {Ni(NHC)(2)} species in the reaction mixture.Selective Photocatalytic C-F Borylation of Polyfluoroarenes by Rh/Ni Dual Catalysis Providing Valuable Fluorinated Arylboronate EstersPhotocatalyst722018102#N/AFALSE
414
jacs.8b0710310.1021/jacs.8b07103CB CouplingFALSEhttps://doi.org/10.1021/jacs.8b07103Aggarwal, VKJ. Am. Chem. Soc.An operationally simple deaminative borylation reaction of primary Alkylamines has been developed. The formation of electron-donor acceptor complexes between N-Alkylpyridinium salts and bis-(catecholato)diboron enables photoinduced single-electron transfer and fragmentation to carbon-centered radicals, which are subsequently borylated. The mild conditions allow a diverse range of readily available Alkylamines to be efficiently converted into synthetically valuable Alkylboronic esters under catalyst-free conditions.Photoinduced Deaminative Borylation of AlkylaminesPhotocatalyst168201879#N/AFALSE
415
jacs.6b0233710.1021/jacs.6b02337CB CouplingFALSEhttps://doi.org/10.1021/jacs.6b02337Radius, UJ. Am. Chem. Soc.The [Ni(IMes)(2)]-catalyzed transformation of fluoroarenes into Arylboronic acid pinacol esters via C-F bond Activation and transmetalation with bis(pinacolato)diboron (B(2)pin(2)) is reported. Various partially fluorinated arenes with different degrees of fluorination were converted into their corresponding boronate esters.Preparing (Multi)Fluoroarenes as Building Blocks for Synthesis: Nickel-Catalyzed Borylation of Polyfluoroarenes via C-F Bond Cleavagex115201645#N/AFALSE
416
jacs.6b0137610.1021/jacs.6b01376CB CouplingFALSEhttps://doi.org/10.1021/jacs.6b01376Larionov, OVJ. Am. Chem. Soc.We report herein a simple, metal- and additive-free, photoinduced borylation of haloarenes, inCluding electron-rich fluoroarenes, as well as Arylammonium salts directly to boronic acids. This borylation method has a broad scope and functional group tolerance. We show that it can be further extended to boronic esters and carried out on gram scale as well as under flow conditions.Scalable, Metal- and Additive-Free, Photoinduced Borylation of Haloarenes and Quaternary Arylammonium SaltsPhotocatalyst1532016110#N/AFALSE
417
science.aam735510.1126/science.aam7355CB CouplingFALSEhttps://doi.org/10.1126/science.aam7355Baran, PSScienceThe widespread use of Alkyl boronic acids and esters is frequently hampered by the challenges associated with their preparation. We describe a simple and practical method to rapidly access densely functionalized Alkyl boronate esters from abundant Carbonylic substituents. This broad-scope nickel-catalyzed reaction uses the same activating principle as amide bond formation to replace a Carbonylic acid moiety with a boronate ester. Application to peptides allowed expedient preparations of alpha-amino boronic acids, often with high stereoselectivity, thereby facilitating synthesis of the Alkyl boronic acid drugs Velcade and Ninlaro as well as a boronic acid version of the iconic antibiotic vancomycin. The reaction also enabled the discovery and extensive biological characterization of potent human neutrophil elastase inhibitors, which offer reversible covalent binding properties.DeCarbonylative borylation212201754#N/ATRUE
418
ol902155e10.1021/ol902155eCB CouplingFALSEhttps://doi.org/10.1021/ol902155ePercec, VNeopentylglycolborylation of Aryl Chlorides Catalyzed by the Mixed Ligand System NiCl2(dppp)/dppf2009#N/ATRUE
419
jacs.9b0896110.1021/jacs.9b08961CB CouplingFALSEhttps://doi.org/10.1021/jacs.9b08961Sanford, MSJ. Am. Chem. Soc.This ArtiCle describes the development of a base-free, nickel-catalyzed deCarbonylative coupling of Carbonylic acid fluorides with diboron reagents to selectively afford Aryl boronate ester products. Detailed studies were conducted to assess the relative rates of direct transmetalation between Aryl boronate esters and diboron reagents and a bisphosphine nickel(Aryl)(fluoride) intermediate. These investigations revealed that diboron reagents undergo transmetalation with this Ni(Aryl)(fluoride) intermediate at rates significantly faster than their Aryl boronate ester congeners. Furthermore, the reactivity of both boron reagents toward transmetalation is enhanced with increasing electrophilicity of the boron center. These mechanistic insights were leveraged to develop a catalytic deCarbonylative borylation of acid fluorides that proved applicable to a variety of (hetero)Aryl Carbonylic acid fluorides as well as diverse diboron reagents. The acid fluorides can be generated in situ directly from Carbonylic acids. Furthermore, the mechanistic studies directed the identification of various air-stable Ni pre-catalysts for this transformation.Mechanism and Scope of Nickel-Catalyzed DeCarbonylative Borylation of Carbonylic Acid Fluorides41201979#N/ATRUE
420
jacs.6b0739610.1021/jacs.6b07396CB CouplingFALSEhttps://doi.org/10.1021/jacs.6b07396Watson, MPJ. Am. Chem. Soc.We have developed a stereospecific, nickel-catalyzed Miyaura borylation of allylic pivalates, which delivers highly enantioenriched alpha-stereogenic gamma-Aryl allylboronates with good yields and regioselectivities. Our complementary sets of conditions enable access to either enantiomer of allylboronate product from a single enantiomer of readily prepared allylic pivalate substrate. Excellent functional group tolerance, yields, regioselectivities, and stereochemical fidelities are observed. The stereochemical switch from stereoretention to stereoinversion largely depends upon solvent and can be explained by competitive pathways for the oxidative addition step. Our mechanistic investigations support a stereoretentive pathway stemming from a directed oxidative addition and a stereoinvertive pathway that is dominant when MeCN blocks coordination of the directing group by binding the nickel catalyst.Accessing Both Retention and Inversion Pathways in Stereospecific, Nickel-Catalyzed Miyaura Borylations of Allylic Pivalates47201658#N/ATRUE
421
jacs.6b0614410.1021/jacs.6b06144CB CouplingFALSEhttps://doi.org/10.1021/jacs.6b06144Chirik, PJCobalt-Catalyzed C(sp(2))-H Borylation: Mechanistic Insights Inspire Catalyst Design2016#N/ATRUE
422
jacs.5b1224910.1021/jacs.5b12249CB CouplingFALSEhttps://doi.org/10.1021/jacs.5b12249Chirik, PJJ. Am. Chem. Soc.Cobalt diAlkyl and bis(Carbonylate) complexes bearing a-diimine ligands have been synthesized and demonstrated as active for the C(sp(3))-H borylation of a range of substituted Alkyl arenes using B(2)Pin(2) (Pin = pinacolate) as the boron source. At longer reaction times, rare examples of polyborylation were observed, and in the case of toluene, all three Benzylic C-H positions were functionalized. Coupling Benzylic C-H Activation with Alkyl isomerization enabled a base-metal-catalyzed method for the borylation of remote, unactivated C(sp(3))-H bonds.Cobalt-Catalyzed Benzylic Borylation: Enabling Polyborylation and Functionalization of Remote, Unactivated C(sp(3))-H Bonds111201665#N/ATRUE
423
jacs.5b1011910.1021/jacs.5b10119CB CouplingFALSEhttps://doi.org/10.1021/jacs.5b10119Hosoya, TJ. Am. Chem. Soc.Ni/Cu-catalyzed transformation of fluroarenes to Arylboronic acid pinacol esters via C-F bond Cleavage has been achieved. Further versatile derivatization of an Arylboronic ester has allowed for the facile two-step conversion of a fluoroarene to diverse functionalized arenes, demonstrating the synthetic utility of the method.Ni/Cu-Catalyzed DefluorB(OH)2rylation of Fluoroarenes for Diverse C-F Bond Functionalizations124201594#N/ATRUE
424
jacs.5b0810310.1021/jacs.5b08103CB CouplingFALSEhttps://doi.org/10.1021/jacs.5b08103Martin, RJ. Am. Chem. Soc.A Ni-catalyzed borylation via C-F Activation is described. This protocol is distinguished by a wide scope, inCluding unactivated fluoroarenes, without compromising its efficiency and scalability, thus representing a significant step-forward toward the implementation of C-F Activation protocols.Ni-Catalyzed Borylation of Aryl Fluorides via C-F Cleavage141201579#N/ATRUE
425
jacs.5b0395510.1021/jacs.5b03955CB CouplingFALSEhttps://doi.org/10.1021/jacs.5b03955Martin, RJ. Am. Chem. Soc.A Ni-catalyzed ipso-borylation of Aryl ethers via C(sp(2))-OMe and C(sp(3))-OMe Cleavage is described. The transformation is characterized by its wide substrate scope tinder mild conditions and an exquisite divergence in Site selectivity that can be easily switched by selecting the appropriate, boron reagent.Ipso-Borylation of Aryl Ethers via Ni-Catalyzed C-OMe Cleavage137201567#N/ATRUE
426
jacs.1c0303810.1021/jacs.1c03038CB CouplingFALSEhttps://doi.org/10.1021/jacs.1c03038Nakao, YSelective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex2021#N/ATRUE
427
jacs.0c0883410.1021/jacs.0c08834CB CouplingFALSEhttps://doi.org/10.1021/jacs.0c08834Marder, TBJ. Am. Chem. Soc.A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)(2)] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B(2)pin(2) at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)(2)] undergoes very fast chlorine atom abstraction from Aryl chlorides to give [Ni-I(IMes)(2)Cl] and Aryl radicals. Control experiments indicate that light promotes the reaction of [Ni-I(IMes)(2)Cl] with Aryl chlorides generating additional Aryl radicals and [Ni-II(IMes)(2)Cl-2]. The Aryl radicals react with an anionic sp(2)-sp(3) diborane [B(2)pin(2)(OMe)](-) formed from B(2)pin(2) and KOMe to yield the corresponding borylation product and the [Bpin(OMe)](center dot-) radical anion, which reduces [Ni-II(IMes)(2)Cl-2] under irradiation to regenerate [Ni-I(IMes)(2)Cl] and [Ni(IMes)(2)] for the next catalytic cyCle.Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes102020114#N/ATRUE
428
jacs.0c0543410.1021/jacs.0c05434CB CouplingFALSEhttps://doi.org/10.1021/jacs.0c05434Marder, TBJ. Am. Chem. Soc.A highly efficient and general protocol for traceless, directed C3-selective C-H borylation of indoles with [Ni(IMes)(2)] as the catalyst is reported. Activation and borylation of N-H bonds by [Ni(IMes)(2)] is essential to install a Bpin moiety at the N-position as a traceless directing group, which enables the C3-selective borylation of C-H bonds. The N-Bpin group which is formed is easily converted in situ back to an N-H group by the oxidative addition product of [Ni(IMes)(2)] and in situ-generated HBpin. The catalytic reactions are operationally simple, allowing borylation of a variety of substituted indoles with B(2)pin(2) in excellent yields and with high selectivity. The C-H borylation can be followed by Suzuki-Miyaura cross-coupling of the C-borylated indoles in an overall two-step, one-pot process providing an efficient method for synthesizing C3-functionalized heteroarenes.Ni-Catalyzed Traceless, Directed C3-Selective C-H Borylation of Indoles212020109#N/ATRUE
429
ja910808x10.1021/ja910808xCB CouplingFALSEhttps://doi.org/10.1021/ja910808xPercec, VJ. Am. Chem. Soc.The mixed-ligand system NiCl2(dppp)/dppf is shown to be an effective catalyst for the neopentylglycolborylation of ortho-, meta-, and para- substituted electron-rich and electron-deficient Aryl mesylates and tosylates. The addition of Zn powder as a reductant dramatically increases the reaction yield and reduces the reaction time by more than an order of magnitude, providing complete conversion in 1-3 hNeopentylglycolborylation of Aryl Mesylates and Tosylates Catalyzed by Ni-Based Mixed-Ligand Systems Activated with Zn127201034#N/ATRUE
430
d1sc01440d10.1039/d1sc01440dCB CouplingFALSEhttps://doi.org/10.1039/d1sc01440dIto, HChem. Sci.The synthesis of a series of hydrosilylboronates via the selective iridium- or nickel-catalyzed monB(OH)2rylation of dihydrosilane Si-H bonds is described. The synthesized silylboronates, which bear a single Si-H bond, can be used as novel silicon nuCleophiles in the presence of transition-metal catalysts or bases. The first Si-29{H-1} NMR spectroscopic evidence for the formation of (t-Bu)(2)HSiLi, generated by the reaction of (t-Bu)(2)HSi-B(pin) with MeLi, is reported as the first example of a diAlkylhydorosilyl lithium species.Synthesis of hydrosilylboronates via the monB(OH)2rylation of a dihydrosilane Si-H bond and their application for the generation of diAlkylhydrosilyl anions038#N/ATRUE
431
c8cc08504h10.1039/c8cc08504hCB CouplingFALSEhttps://doi.org/10.1039/c8cc08504hNishihara, YNickel-catalysed deCarbonylative borylation of aroyl fluorides2018#N/ATRUE
432
anie.20210635610.1002/anie.202106356CB CouplingFALSEhttps://doi.org/10.1002/anie.202106356Su, WPAngew. Chem.-Int. Edit.The Ni-catalyzed deCarbonylative borylation of (hetero)Aryl Carbonylic acids with B(2)cat(2) has been achieved without recourse to any additives. This Ni-catalyzed method exhibits a broad substrate scope covering poorly reactive non-ortho-substituted (hetero)Aryl Carbonylic acids, and tolerates diverse functional groups inCluding some of the groups active to Ni-0 catalysts. The key to achieve this deCarbonylative borylation reaction is the choice of B(2)cat(2) as a coupling partner that not only acts as a borylating reagent, but also chemoselectively activates Aryl Carbonylic acids towards oxidative addition of their C(acyl)-O bond to Ni-0 catalyst via the formation of acyloxyboron compounds. A combination of experimental and computational studies reveals a detailed plausible mechanism for this reaction system, which involves a hitherto unknown concerted deCarbonylation and reductive elimination step that generates the Aryl boronic ester product. This mode of boron-promoted Carbonylic acid Activation is also applicable to other types of reactions.Activation of Aryl Carbonylic Acids by Diboron Reagents towards Nickel-Catalyzed Direct DeCarbonylative Borylationborylation; Carbonylic acid Activation; deCarbonylative cross-coupling; DFT studies; nickel catalysis0120#N/ATRUE
433
anie.20180960810.1002/anie.201809608CB CouplingFALSEhttps://doi.org/10.1002/anie.201809608Shi, ZZAngew. Chem.-Int. Edit.An efficient method for the metal-free deaminative borylation of Alkylamines, using bis(catecholato) diboron as the boron source, to directly synthesize various Alkyl potassium trifluorB(OH)2rate salts is introduced. The key to this high reactivity is the utilization of pyridinium salt activated Alkylamines, with a catalytic amount of a bipyridine-type Lewis base as a promoter. This transformation shows good functional-group compatibility (e.g., it is unimpeded by the presence of a ketone, indole, internal alkene, or unactivated Alkyl chloride) and can serve as a powerful synthetic tool for borylation of amine groups in complex compounds. Mechanistic experiments and computations suggest a mechanism in which the Lewis base activated B(2)cat(2) unit intercepts an Alkyl radical generated by single-electron transfer (SET) from a boron-based reductant.Selective C-N Borylation of Alkyl Amines Promoted by Lewis Baseamines; borylation; C-N Activation; Lewis bases; radicalsyy82201875#N/AFALSE
434
anie.20180601510.1002/anie.201806015CB CouplingFALSEhttps://doi.org/10.1002/anie.201806015Fu, GCAngew. Chem.-Int. Edit.Nickel-catalyzed cross-coupling has emerged as the most versatile approach to date for achieving enantioconvergent carbon-carbon bond formation using racemic Alkyl halides as electrophiles. In contrast, there have not yet been reports of the application of chiral nickel catalysts to the corresponding reactions with heteroatom nuCleophiles to produce carbon-heteroatom bonds with good enantioselectivity. Herein, we establish that a chiral nickel/pybox catalyst can borylate racemic secondary Benzylic chlorides to provide enantioenriched Benzylic boronic esters, a highly useful family of compounds in organic synthesis. The method displays good functional group compatibility (e.g., being unimpeded by the presence of an indole, a ketone, a tertiary amine, or an unactivated Alkyl bromide), and both of the catalyst components (NiCl2-glyme and the pybox ligand) are commercially available.Nickel-Catalyzed Enantioconvergent Borylation of Racemic Secondary Benzylic Electrophilesasymmetric catalysis; boron; borylation; cross-coupling; nickel26201827#N/ATRUE
435
anie.20170123810.1002/anie.201701238CB CouplingFALSEhttps://doi.org/10.1002/anie.201701238Nakao, YAngew. Chem.-Int. Edit.para-Selective C-H borylation of benzamides and pyridines has been achieved by cooperative iridium/aluminum catalysis. A combination of iridium catalysts commonly employed for arene C-H borylation and bulky aluminum-based Lewis acid catalysts provides an unprecedented strategy for controlling the regioselectivity of C-H borylation to give variously substituted (hetero)Arylboronates, which are versatile synthetic intermediates for complex multi-substituted aromatic compounds.para-Selective C-H Borylation of (Hetero)Arenes by Cooperative Iridium/Aluminum Catalysis76201768#N/ATRUE
436
anie.20160306810.1002/anie.201603068CB CouplingFALSEhttps://doi.org/10.1002/anie.201603068Shi, ZZAngew. Chem.-Int. Edit.A nickel/N-heterocyClic carbene catalytic system has been established for deCarbonylative borylation of amides with B(2)nep(2) by C-N bond Activation. This transformation shows good functional-group compatibility and can serve as a powerful synthetic tool for late-stage borylation of amide groups in complex compounds. More importantly, as a key intermediate, the structure of an acyl nickel complex was first confirmed by X-ray analysis. Furthermore, the deCarbonylative process was also observed. These findings confirm the key mechanistic features of the acyl C-N bond Activation process.Nickel-Catalyzed DeCarbonylative Borylation of Amides: Evidence for Acyl C-N Bond Activationamides; boron; deCarbonylation; nickel; structure elucidation164201684#N/ATRUE
437
anie.20120820310.1002/anie.201208203CB CouplingFALSEhttps://doi.org/10.1002/anie.201208203Hartwig, JFAngew. Chem.-Int. Edit.Sterically Controlled Alkylation of Arenes through Iridium-Catalyzed C?H Borylation63201362#N/ATRUE
438
anie.20100718210.1002/anie.201007182CB CouplingFALSEhttps://doi.org/10.1002/anie.201007182Ito, HCopper(I)-Catalyzed Regioselective MonB(OH)2rylation of 1,3-Enynes with an Internal Triple Bond: Selective Synthesis of 1,3-Dienylboronates and 3-Alkynylboronates2011#N/ATRUE
439
acscatal.9b0263610.1021/acscatal.9b02636CB CouplingFALSEhttps://doi.org/10.1021/acscatal.9b02636Hong, XACS Catal.Solvents act as a powerful control of stereospecificity in Ni-catalyzed Miyaura borylation of allylic pivalates. Low polar solvents lead to stereoretentive borylation, whereas highly polar solvents deliver low stereoselectivity for retention and acetonitrile produces stereoinversion products. We explored the reaction mechanism and origins of stereospecificity with density functional theory calculations. The Ni-catalyzed allylic C-O bond Activation determines the stereospecificity of borylation. A zwitterionic S(N)2-type transition state inverts the allylic stereogenic center, whereas a neutral cyClic transition state Cleaves the C-O bond with stereoretention. This difference in charge separation results in the control of stereospecificity by solvent polarity. Low polar solvents demonstrate the intrinsic selectivity for retention, whereas highly polar solvents lower such selectivity by stabilizing the zwitterionic stereoinvertive transition state. Distinctive from other solvents, acetonitrile further promotes stereoinversion by replacing the coordination of the phosphine ligand and reverses the intrinsic stereoselectivity. We proved this solvent-promoted Ni-catalyzed C-O bond Activation with a designed experimental verification of ligandless Ni-catalyzed borylation of allylic pivalates in acetonitrile.How Solvents Control the Stereospecificity of Ni-Catalyzed Miyaura Borylation of Allylic Pivalatessolvents; stereospecificity; Miyaura borylation; allylic pivalates10201953#N/ATRUE
440
acscatal.7b0144810.1021/acscatal.7b01448CB CouplingFALSEhttps://doi.org/10.1021/acscatal.7b01448Hosoya, TCopper-Catalyzed ipso-Borylation of Fluoroarenes2017#N/ATRUE
441
acscatal.6b0195610.1021/acscatal.6b01956CB CouplingFALSEhttps://doi.org/10.1021/acscatal.6b01956Shi, ZZACS Catal.The nickel-catalyzed direct borylation and silylation of phenolic esters has been established. The key to this highly efficient acyl C-O bond borylative and silylative Cleavage depends on the appropriate choice of different ligands and additives in the presence of nickel catalyst. Both transformations exhibit good functional group compatibility and can serve as powerful synthetic tools for late-stage functionalization of complex compounds. The elucidation of key mechanistic features of this newly developed acyl C-O bond Activation in esters was confirmed by two well-characterized organonickel(II) intermediates.Nickel-Catalyzed DeCarbonylative Borylation and Silylation of Estersnickel; borylation; silylation; esters; deCarbonylation1242016111#N/ATRUE
442
acscatal.5b0297310.1021/acscatal.5b02973CB CouplingFALSEhttps://doi.org/10.1021/acscatal.5b02973Yoshida, HACS Catal.Alkenylboranes have been vital reagents in modern synthetic organic chemistry, whose carbon boron bond is transformable into a carbon carbon bond stereoretentively to give such invaluable mutisubstituted alkenes as natural products, biologically active molecules, and functional materials. Introduction of a boryl moiety across a carbon carbon triple bond of alkynes (borylation of alkynes) is one of the most direct and potent methods for synthesizing alkenylboranes, and this field has thus far experienced remarkable progress mainly with group 10 transition metal catalysts (Ni, Pd, Pt), which enables highly functionalized alkenylboranes to be constructed stereoselectively. On the other hand, much attention has recently been focused on the appealing catalysis of base (Fe, Co) and coinage (Cu, Ag, Au) metals toward the borylation of alkynes, which is summarized in this perspective.Borylation of Alkynes under Base/Coinage Metal Catalysis: Some Recent Developmentsalkenylborane synthesis; alkynes; base metal catalysis; boron; coinage metal catalysis; regioselectivity; stereoselectivity2122016103#N/ATRUE
443
acscatal.1c0018510.1021/acscatal.1c00185CB CouplingFALSEhttps://doi.org/10.1021/acscatal.1c00185Yamaguchi, KC(sp(3))-H Selective Benzylic Borylation by In Situ Reduced Ultrasmall Ni Species on CeO22021#N/ATRUE
444
c8sc04335c10.1039/c8sc04335cCeavaged C-C bondFALSEhttps://doi.org/10.1039/c8sc04335cFu, YChem. Sci.Herein, we report a nickel-catalyzed allylic defluorinative Alkylation of trifluoromethyl alkenes through reductive deCarbonylation of redox-active esters. The present reaction enables the preparation of functionalized gem-difluoroalkenes with the formation of sterically hindered C(sp(3))-C(sp(3)) bonds under very mild reaction conditions, while tolerating many sensitive functional groups and requiring minimal substrate protection. Therefore, this method provides an efficient and convenient approach for late-stage modification of biologically interesting molecules.Nickel-catalyzed allylic defluorinative Alkylation of trifluoromethyl alkenes with reductive deCarbonylation of redox-active estersy732019xxxxnot C-O Activation95#N/AFALSE
445
acscatal.8b0434810.1021/acscatal.8b04348CF and CO Activation(both)FALSEhttps://pubs.acs.org/doi/pdf/10.1021/acscatal.8b04348Jamison, TF
446
acscatal.0c0388410.1021/acscatal.0c03884CF CouplingFALSEhttps://doi.org/10.1021/acscatal.0c03884Zhu, SLACS Catal.We report the hydrofluorination of unactivated alkenes using N-fluorobenzenesulfonimide as a fluorination reagent. The reaction produces exClusively Markovnikov hydrofluorination products under mild conditions. It is not affected by air or moisture and uses an inexpensive and readily available nickel compound as a catalyst. Distinct from the previously reported ionic pathway of the NiH-catalyzed hydrofunctionalization of olefins, this reaction was shown to proceed through a hydrogen atom transfer pathway.Nickel-Catalyzed Hydrofluorination of Unactivated Alkenes through a HAT Pathwayalkenes; fluorine; hydrofluorination; nickel; nickel hydridey4202083#N/AFALSE
447
C0CC05169A 10.1039/C0CC05169ACH CouplingFALSEhttps://doi.org/10.1039/C0CC05169AChen, C143#N/A
448
anie.20161262410.1002/anie.201612624CH CouplingFALSEhttps://doi.org/10.1002/anie.201612624Rueping, MAngew. Chem.-Int. Edit.An inexpensive nickel(II) catalyst and a hydrosilane were used for the efficient reductive defunctionalization of Aryl and heteroAryl esters through a deCarbonylative pathway. This versatile method could be used for the removal of ester and amide functional groups from various organic molecules. Moreover, a scale-up experiment and a synthetic application based on the use of a removable Carbonylic acid directing group highlight the usefulness of this reaction.Selective Reductive Removal of Ester and Amide Groups from Arenes and Heteroarenes through Nickel-Catalyzed C-O and C-N Bond Activationamides; Cleavage reactions; esters; nickel catalysis; reductiony110201796#N/AFALSE
449
acscatal.6b0304010.1021/acscatal.6b03040CH CouplingFALSEhttps://doi.org/10.1021/acscatal.6b03040Maiti, DACS Catal.To date, Cleavage of the C-N bond in aromatic amides has been achieved in molecules with a distorted constitutional framework around the nitrogen atom. In this report, a nickel-catalyzed reduction of planar amides to the corresponding lower hydrocarbon homologue has been reported. This involves a one-pot reductive Cleavage of the C-N bond followed by a tandem C-CO bond break in the presence of a hydride source. Substrate scope circumscribes deamidation examples which proceed via oxidative addition of nickel in the amide bonds of nontwisted amides. Mechanistic studies involving isolation and characterization of involved intermediates via different spectroscopic techniques reveal a deeper introspection into the plausible catalytic cyCle for the methodology.Nickel-Catalyzed Deamidative Step-Down Reduction of Amides to Aromatic Hydrocarbonsnickel; amides; deamidation; C-N bond; catalysis; reductiony83201759#N/AFALSE
450
anie.20110682510.1002/anie.201106825Cleavaged double bondFALSEhttps://doi.org/10.1002/anie.201106825Miura, MAngew. Chem.-Int. Edit.Nickel- and Cobalt-Catalyzed Direct Alkylation of Azoles with N-Tosylhydrazones Bearing Unactivated Alkyl GroupsAlkylation; azoles; C?H functionalization; cobalt; nickel1772012113#N/ATRUE
451
anie.20210380310.1002/anie.202103803CN CouplingFALSEhttps://doi.org/10.1002/anie.202103803Shi, SLAngew. Chem.-Int. Edit.The transition-metal-catalyzed C-N cross-coupling has revolutionized the construction of amines. Despite the innovations of multiple generations of ligands to modulate the reactivity of the metal center, ligands for the low-temperature enantioselective amination of Aryl halides remain a coveted target of catalyst engineering. Designs that promote one elementary reaction often create bottlenecks at other steps. We here report an unprecedented low-temperature (as low as -50 degrees C), enantioselective Ni-catalyzed C-N cross-coupling of Aryl chlorides with sterically hindered secondary amines via a kinetic resolution process (s factor up to >300). A bulky yet flexible chiral N-heterocyClic carbene (NHC) ligand is leveraged to drive both oxidative addition and reductive elimination with low barriers and control the enantioselectivity. Computational studies indicate that the rotations of multiple sigma-bonds on the C-2-symmetric chiral ligand adapt to the changing needs of catalytic processes. We expect this design would be widely applicable to diverse transition states to achieve other challenging metal-catalyzed asymmetric cross-coupling reactions.Low-Temperature Nickel-Catalyzed C-N Cross-Coupling via Kinetic Resolution Enabled by a Bulky and Flexible Chiral N-HeterocyClic Carbene Ligandasymmetric catalysis; C-N coupling; low-temperature reactions; NHC ligands; nickel32021107#N/ATRUE
452
anie.20170894910.1002/anie.201708949CN CouplingFALSEhttps://doi.org/10.1002/anie.201708949Zhou, JRSAngew. Chem.-Int. Edit.A borrowing-hydrogen reaction between amines and alcohols is an atom-economic way to prepare Alkylamines, ideally with water as the sole byproduct. Herein, nickel catalysts are used for direct N-Alkylation of hydrazides and Arylamines using racemic alcohols. Moreover, a nickel catalyst of (S)-binapine was used for an asymmetric N-Alkylation of benzohydrazide with racemic Benzylic alcohols.Nickel-Catalyzed N-Alkylation of Acylhydrazines and Arylamines Using Alcohols and Enantioselective ExamplesAlkylation; amination; hydrogen transfer; nickel; Pligands682017106#N/ATRUE
453
acscatal.9b0371510.1021/acscatal.9b03715CN CouplingFALSEhttps://doi.org/10.1021/acscatal.9b03715Stradiotto, MACS Catal.The Ni(II) precatalyst (C1) featuring the phosphonite ancillary ligand Phen-DalPhos (L1) was employed in the cross-coupling of (hetero)anilines with (hetero)Aryl chlorides and in the diArylation of ammonia with (hetero)Aryl chlorides to afford heteroatom-dense di(hetero)Arylamines. The PAd2-DalPhos precatalyst C4 provided complementary reactivity in cross-couplings of indoles with (hetero)Aryl chlorides. Taken together, the demonstration of room-temperature reactivity within each of the reaction Classes examined and the observation of useful chemoselectivity at low loading (<= 0.5 mol % Ni) and on gram-scale distinguishes C1 and C4 from other metal catalysts (i.e., copper, palladium, nickel, or other) within the field of C-N cross-coupling chemistry.Nickel-Catalyzed C-N Cross-Coupling of Ammonia, (Hetero)anilines, and Indoles with Activated (Hetero)Aryl Chlorides Enabled by Ligand Designamination; ammonia; chemoselectivity; heteroanilines; heteroAryl chlorides; indole; ligand design; nickel`201961#N/ATRUE
454
acscatal.8b0218710.1021/acscatal.8b02187CN CouplingFALSEhttps://doi.org/10.1021/acscatal.8b02187Montgomery, JACS Catal.The synthesis and catalytic activity of several Classes of NHC-Ni(0) precatalysts stabilized by electron withdrawing alkenes are described. Variations in the structure of fumarate and acrylate ligands modulate the reactivity and stability of the NHC-Ni(0) precatalysts and lead to practical and versatile catalysts for a variety of transformations. The catalytic activity and efficiency of representative members of this Class of catalysts have been evaluated in reductive couplings of aldehydes and alkynes and in N-Arylations of amines.Stable, Well-Defined Nickel(0) Catalysts for Catalytic C-C and C-N Bond Formationprecatalyst; amination; reductive coupling; N-heterocyClic carbenes; catalysis19201846#N/ATRUE
455
ja710922h10.1021/ja710922hConjugationFALSEhttps://doi.org/10.1021/ja710922hMorken, JPJ. Am. Chem. Soc.The nickel-catalyzed enantioselective addition of allylboronic acid pinacol ester, allyIB(pin), is described. This reaction is highly effective with diAlkylidene ketones and favors the allylation of the Benzylidene site in nonsymmetric substrates. The reaction appears to proceed by conversion of the diAlkylidene ketone substrate to an unsaturated pi-allyl complex (1), followed by reductive elimination. Enantioselectivities range from 91 to 94% ee for a range of substrates when chiral ligand 14 is employed.Asymmetric Ni-catalyzed conjugate allylation of activated enones78200855#N/ATRUE
456
anie.20191545410.1002/anie.201915454
Conjunctive Cross-Coupling
FALSEhttps://doi.org/10.1002/anie.201915454Engle, KMAngew. Chem.-Int. Edit.Allylation and conjunctive cross-coupling represent two useful, yet largely distinct, reactivity paradigms in catalysis. The union of these two processes would offer exciting possibilities in organic synthesis but remains largely unknown. Herein, we report the use of allyl electrophiles in nickel-catalyzed conjunctive cross-coupling with a non-conjugated alkene and dimethylzinc. The transformation is enabled by weakly coordinating, monodentate aza-heterocyCle directing groups that are useful building blocks in synthesis, inCluding saccharin, pyridones, pyrazoles, and triazoles. The reaction occurs under mild conditions and is compatible with a wide range of allyl electrophiles. High chemoselectivity through substrate directivity is demonstrated by the facile reactivity of the beta-gamma alkene of the starting material, whereas the epsilon-zeta alkene of the product is preserved. The generality of this approach is further illustrated through the development of an analogous method with alkyne substrates. Mechanistic studies reveal the importance of the dissociation of the weakly coordinating directing group to allow the allyl moiety to bind and facilitate C(sp(3))-C(sp(3)) reductive elimination.Integrating Allyl Electrophiles into Nickel-Catalyzed Conjunctive Cross-Couplingallylation; conjunctive cross-coupling; dicarbofunctionalization; heterocyCles; nickel catalysis11202058#N/ATRUE
457
jacs.0c0132410.1021/jacs.0c01324Convergent FALSEhttps://doi.org/10.1021/jacs.0c01324Fu, GCJ. Am. Chem. Soc.Because chiral diAlkyl carbinols, as well as their derived esters, are significant as intermediates and end points in fields such as organic, pharmaceutical, and biological chemistry, the development of efficient approaches to their asymmetric synthesis is an important endeavor. In this report, we describe a method for the direct catalytic enantioselective synthesis of such esters, beginning with an Alkyl halide (derived from an aldehyde and an acyl bromide), an olefin, and a hydrosilane, catalyzed by nickel, an earth-abundant metal. The method is versatile, tolerating substituents that vary in size and that bear a range of functional groups. We further describe a four-component variant of this process, wherein the Alkyl halide is generated in situ, thus obviating the need to isolate either an Alkyl electrophile or an Alkylmetal, while still effecting an Alkyl-Alkyl coupling. Finally, we apply our convergent method to the efficient catalytic enantioselective synthesis of three esters that are bioactive themselves or that have been utilized in the synthesis of bioactive compounds.Convergent Catalytic Asymmetric Synthesis of Esters of Chiral DiAlkyl Carbinols21202023#N/ATRUE
458
d1sc00822f10.1039/d1sc00822fCross-E both halogenFALSEhttps://doi.org/10.1039/d1sc00822fReisman, SEChem. Sci.An asymmetric reductive cross-coupling of alpha-chloroesters and (hetero)Aryl iodides is reported. This nickel-catalyzed reaction proceeds with a chiral BiOx ligand under mild conditions, affording alpha-Arylesters in good yields and enantioselectivities. The reaction is tolerant of a variety of functional groups, and the resulting products can be converted to pharmaceutically-relevant chiral building blocks. A multivariate linear regression model was developed to quantitatively relate the influence of the alpha-chloroester substrate and ligand on enantioselectivity.Nickel-catalyzed asymmetric reductive cross-coupling of alpha-chloroesters with (hetero)Aryl iodides2202127#N/ATRUE
459
anie.20171242810.1002/anie.201712428Cross-E Both HalogenFALSEhttps://doi.org/10.1002/anie.201712428Martin, RAngew. Chem.-Int. Edit.A nickel-catalyzed reductive Arylation of ambiphilic -bromoAlkyl boronic esters with Aryl halides is described. This platform provides an unrecognized opportunity to promote the catalytic umpolung reactivity of ambiphilic reagents with Aryl halides, thus unlocking a new cross-coupling strategy that complements existing methods for the preparation of densely functionalized Alkyl-substituted organometallic reagents from simple and readily accessible precursors.Nickel-Catalyzed Umpolung Arylation of Ambiphilic -BromoAlkyl Boronic Estersboron; C-C bond formation; cross-coupling; nickel; umpolung24201872#N/ATRUE
460
jacs.7b0170510.1021/jacs.7b01705Cross-E: Both HalogenFALSEhttps://doi.org/10.1021/jacs.7b01705Reisman, SEJ. Am. Chem. Soc.An asymmetric Ni-catalyzed reductive cross-coupling of (hetero)Aryl iodides and Benzylic chlorides has been developed to prepare enantioenriched 1,1-diArylalkanes. As part of these studies, a new chiral BiOxazoline ligand, 4-heptyl-BiOx (L1), was developed in order to obtain products in synthetically useful yield and enantioselectivity. The reaction tolerates a variety of heterocyClic coupling partners, inCluding pyridines, pyrimidines, indoles, and piperidines.Nickel-Catalyzed Asymmetric Reductive Cross-Coupling To Access 1,1-DiArylalkanes107201763#N/ATRUE
461
jacs.5b0625510.1021/jacs.5b06255Cross-E: both halogenFALSEhttps://doi.org/10.1021/jacs.5b06255Gong, HGJ. Am. Chem. Soc.A mild Ni-catalyzed reductive Arylation of tertiary Alkyl halides with Aryl bromides has been developed that delivers products bearing all-carbon quaternary centers in moderate to excellent yields with excellent functional group tolerance. Electron-deficient arenes are generally more effective in inhibiting Alkyl isomerization. The reactions proceed successfully with pyridine or 4-(dimethylamino)pyridine, while imidazolium salts slightly enhance the coupling efficiency.Nickel-Catalyzed Reductive Coupling of Aryl Bromides with Tertiary Alkyl Halides142201554#N/ATRUE
462
ja402922w10.1021/ja402922wCross-E: both halogenFALSEhttps://doi.org/10.1021/ja402922wReisman, SEJ. Am. Chem. Soc.The first enantioselective Ni-catalyzed reductive acyl cross-coupling has been developed. Treatment of acid chlorides and racemic secondary Benzyl chlorides with a Ni-II/bis(oxazoline) catalyst in the presence of Mn-0 as a stoichiometric reductant generates acyClic alpha,alpha-disubstituted ketones in good yields and high enantioselectivity without requiring stoichiometric chiral auxiliaries or pregeneration of organometallic reagents. The mild, base-free reaction conditions are tolerant of a variety of functional groups on both coupling partners.Catalytic Asymmetric Reductive Acyl Cross-Coupling: Synthesis of Enantioenriched AcyClic alpha,alpha-Disubstituted Ketones169201374#N/ATRUE
463
acscatal.0c0323710.1021/acscatal.0c03237Cross-E: HalogenFALSEhttps://doi.org/10.1021/acscatal.0c03237Zultanski, SLACS Catal.A dual catalytic system for cross-electrophile coupling reactions between Aryl halides and Alkyl halides that features a Ni catalyst, a Co cocatalyst, and a mild homogeneous reductant is described. Mechanistic studies indicate that the Ni catalyst activates the Aryl halide, while the Co cocatalyst activates the Alkyl halide. This allows the system to be rationally optimized for a variety of substrate Classes by simply modifying the loadings of the Ni and Co catalysts based on the reaction product profile. For example, the coupling of Aryl bromides and Aryl iodides with Alkyl bromides, Alkyl iodides, and Benzyl chlorides is demonstrated using the same Ni and Co catalysts under similar reaction conditions but with different optimal catalyst loadings in each case. Our system is tolerant of numerous functional groups and is capable of coupling heteroAryl halides, di-ortho-substituted Aryl halides, pharmaceutically relevant druglike Aryl halides, and a diverse range of Alkyl halides. Additionally, the dual catalytic platform facilitates a series of selective one-pot three-component cross-electrophile coupling reactions of bromo(iodo)arenes with two distinct Alkyl halides. This demonstrates the unique level of control that the platform provides and enables the rapid generation of molecular complexity. The system can be readily utilized for a wide range of applications as all reaction components are commercially available, the reaction is scalable, and toxic amide-based solvents are not required. It is anticipated that this strategy, as well as the underlying mechanistic framework, will be generalizable to other cross-electrophile coupling reactions.A Widely Applicable Dual Catalytic System for Cross-Electrophile Coupling Enabled by Mechanistic Studiescross-electrophile coupling; nickel; medicinal chemistry; synthetic methods; mechanism52020134#N/ATRUE
464
jacs.8b0947310.1021/jacs.8b09473Cross-Electrophile: both halogenFALSEhttps://doi.org/10.1021/jacs.8b09473Gong, HGJ. Am. Chem. Soc.This work illustrates the reductive coupling of electron-rich Aryl halides with tertiary Alkyl halides under Ni-catalyzed cross-electrophile coupling conditions, which offers an efficient protocol for the construction of all carbon quaternary stereogenic centers. The mild and easy-to-operate reaction tolerates a wide range of functional groups. The utility of this method is manifested by the preparation of cyClotryptamine derivatives, wherein successful incorporation of 7-indolyl moieties is of particular interest as numerous naturally occurring products are composed of these key scaffolds. DFT calculations have been carried out to investigate the proposed radical chain and double oxidative addition pathways, which provide useful mechanistic insights into the part of the reaction that takes place in solution.Ni-Catalyzed Reductive Coupling of Electron-Rich Aryl Iodides with Tertiary Alkyl Halides77201853#N/ATRUE
465
acscatal.0c0303610.1021/acscatal.0c03036crystal materialFALSEhttps://doi.org/10.1021/acscatal.0c03036Sasaki, KHigh-Performance Nitrogen-Doped Intermetallic PtNi Catalyst for the Oxygen Reduction Reaction2020#N/ATRUE
466
ja982053a10.1021/ja982053acrystal researchFALSEhttps://doi.org/10.1021/ja982053aDarensbourg, MYJ. Am. Chem. Soc.The observation of nearly identical infrared spectra in the diatomic (2000 cm(-1)) region of oxidized forms of [NiFe]hydrogenases, as isolated from Chromatium vinosum (Happe et al. Nature 1997, 385, 126) and Desulfovibrio gigas (Volbeda et al. J. Am. Chem. Sec. 1996, 118, 12989) and the anion (eta(5)-C5H5)Fe(CN)(2)(CO)(-) (Darensbourg et al. J. Am. Chem Sec. 1997, 119, 7903), inCluding isotopic label shifts, has prompted further development of the organometallic model complex as a spectroscopic reference. The vibrational spectroscopy of the pyramidal Fe(CN)(2)(CO) unit found in the salts of (eta(5)-C5H5)Fe(CN)(2)(Co)(-) and (eta(5)-C-5- Me-5)Fe(CN)2(CO)(-) is thoroughly investigated with respect to band positions and intensity ratios as influenced by counterion and solvent. The neutral analogues (eta(5)-C5H5)- and (eta(5)-C5Me5)Fe(CN)(CO)(2) as well as the protonated H[(eta(5)-C5H5)Fe(CN)(2)(CO)] are inCluded for comparison. The X-ray crystal structure of the latter finds short interionic N ... N distances of 2.55 Angstrom indicative of CN-nitrogen protonation and strong II-bonding as similarly seen in the attachment of Fe(CN)(2)(CO) to the protein found in the crystal structure of [NiFe]H-2-ase enzyme isolated from the D. gigas bacteria. For a series of nine complexes that covers a broad range of electronic effects las confirmed by electrochemical studies) within a constant hexacoordinate structure and medium (CH3CN), there is an excellent linearity in the correlation between nu(CO) (or F-CO) and nu(CN) (or F-CN) The enzyme states that are not in the catalytic cyCle reasonably fit the model complex correlation and are expected to maintain hexacoordination about iron. The possibile source(s) of deviations from this correlation both in the model tin aqueous media) and in the enzyme system are discussed.Responses of the Fe(CN)(2)(CO) unit to electronic changes as related to its role in [NiFe]hydrogenase82199850#N/ATRUE
467
ja011047310.1021/ja0110473crystal researchFALSEhttps://doi.org/10.1021/ja0110473Long, JRJ. Am. Chem. Soc.Face-capped octahedral [Re6Se8(CN)(6)](3-/4-) Clusters are used in place of octahedral [M(CN)(6)](3-/4-) complexes for the synthesis of microporous Prussian blue type solids with adjustable porosity. The reaction between [Fe(H2O)(6)](3+) and [Re6Se8(CN)(6)](4-) in aqueous solution yields, upon heating, Fe-4[Re6Se8(CN)(6)](3). 36H(2)O (4). A single-crystal X-ray analysis confirms the structure of 4 to be a direct expansion of Prussian blue (Fe-4[Fe(CN)(6)](3). 14H(2)O), with [Re6Se8(CN)(6)](4-) Clusters connected through octahedral Fe3+ ions in a cubic three-dimensional framework. As in Prussian blue, one out of every four hexacyanide units is missing from the structure, creating sizable, water-filled cavities within the neutral framework. Oxidation of (Bu4N)(4)[Re6Se8(CN)(6)] (1) with iodine in methanol produces (Bu4N)(3)[Re6Se8(CN)(6)] (2), which is then metathesized to give the water-soluble salt Na-3[Re6Se8(CN)(6)] (3). Reaction of [Co(H2O)(6)](2+) or [Ni(H2O)(6)](2+) with 3 in aqueous solution affords CO3[Re6Se8(CN)(6)](2). 25H(2)O (5) or Ni-3[Re6Se8(CN)(6)](2). 33H(2)O (6). Powder X-ray diffraction data show these compounds to adopt structures based on the same cubic framework present in 4, but with one out of every three Cluster hexacyanide units missing as a consequence of charge balance. In contrast, reaction of [Ga(H2O)(6)](3+) with 3 gives Ga[Re6Se8(CN)(6)]. 6H(2)O (7), wherein charge balance dictates a fully occupied cubic framework enClosing much smaller cavities. The expanded Prussian blue analogues 4-7 can be fully dehydrated, and retain their crystallinity with extended heating at 250 degreesC. Consistent with the trend in the frequency of framework vacancies, dinitrogen sorption isotherms show porosity to increase along the series of representative compounds 7, Ga-4[Re6Se8(CN)(6)](3). 38H(2)O, and 6. Furthermore, all of these phases display a significantly higher sorption capacity and surface area than observed in dehydrated Prussian blue. Despite incorporating paramagnetic [Re6Se8(CN)(6)](3-) Clusters, no evidence for magnetic ordering in compound 6 is apparent at temperatures down to 5 K. Reactions related to those employed in preparing compounds 4-6, but carried out at lower pH, produce the isostructural phases H[cis-M(H2O)(2)][Re6Se8(CN)(6)]. 2H(2)O (M = Fe (8). Co (9), Ni (10)). The crystal structure of 8 reveals a densely packed three-dimensional framework in which [Re6Se8(CN)(6)](4-) Clusters are interlinked through a combination of protons and Fe3+ ions.Expanded Prussian blue analogues incorporating [Re6Se8(CN)(6)](3-/4-) Clusters: Adjusting porosity via charge balance2322001123#N/ATRUE
468
acscatal.6b0057210.1021/acscatal.6b00572cyClizaiton(computational)FALSEhttps://doi.org/10.1021/acscatal.6b00572Liu, XYACS Catal.The mechanism of Ni(0)-catalyzed denitrogenative transannulation of 1,2,3-benzotriazin-4(3H)-ones with alkynes to access isoquinolones has been comprehensively studied by a density functional theory (DFT) calculation and control experimental investigation. The results indicate that the transformations proceed via a sequential nitrogen extrusion, carbometalation, Ni C bond insertion, and reductive elimination process. A frontier molecular orbital (FMO) theory and natural bond orbital (NBO) analysis reveals that the advantages of substituents on chemical reactivity and regioselectivity exist for multiple reasons: (1) Phenyl groups on the N atom of benzotriazinone and/or unsymmetrical alkynes mainly account for the high reactivity and regioselectivity via its electronic effect. (2) The pi center dot center dot center dot pi-interaction between the phenyl substituent on the alkyne and triazole ring might partially contribute to the high regioselectivity when unsymmetrical alkynes were employed as the substrates. Furthermore, DFT calculations successfully explain the origin of enantioselectivity and discrepancy of reactivities between different N-substituted benzotriazinones for the asymmetric construction of axially chiral isoquinolones in an atroposelective manner. The calculated results indicate that high enantioselectivity is mainly determined by the structural difference between these two transition states of the key annulation step, which lies in the orientation of the naphthyl substituent relative to the chiral ligand.Nickel(0)-Catalyzed Denitrogenative Transannulation of Benzotriazinones with Alkynes: Mechanistic Insights of Chemical Reactivity and Regio- and Enantioselectivity from Density Functional Theory and Experimentdenitrogenative annulations; density functional theory; heterocyCles; axially chiral isoquinolones; nickel20201644#N/ATRUE
469
s41467-021-23371-x10.1038/s41467-021-23371-xcyClizationFALSEhttps://doi.org/10.1038/s41467-021-23371-xYe, MCNat. Commun.The construction of 7-membered ring via direct C7-H cyClization of benzoimidazoles with alkenes would provide a more atom- and step-economical route to tricyClic imidazoles and derivatives that widely exist in a broad range of bioactive molecules. However, transition metal-catalyzed C-H cyClization for medium-ring synthesis has been limited to reactive C-H bonds, instead, the Activation of unreactive C-H bonds towards medium synthesis still remains an elusive challenge. Herein, we report a direct construction of 7-membered rings via Ni-Al co-catalyzed unreactive C7-H cyClization of benzoimidazoles with alkenes, providing a series of tricyClic imidazoles in 40-98% yield and with up to 95:5 er. Transition metal-catalyzed C-H cyClization for medium-ring synthesis has been limited to reactive C-H bonds, the Activation of unreactive C-H bonds still remains a challenge. Here the authors show the direct construction of 7-membered rings via Ni-Al co-catalyzed unreactive C-H cyClization of benzoimidazoles with alkenes, providing a series of tricyClic imidazoles.Construction 7-membered ring via Ni-Al bimetal-enabled C-H cyClization for synthesis of tricyClic imidazoles0202151#N/ATRUE
470
jacs.8b0696610.1021/jacs.8b06966CyClizationFALSEhttps://doi.org/10.1021/jacs.8b06966Lautens, MJ. Am. Chem. Soc.A novel nickel-catalyzed cyCloisomerization reaction forming a new carbon-carbon bond while preserving the carbon-halogen bond has been developed. A cheap and readily available Ni-catalyst is employed to generate nitrogen containing heterocyCles in good to excellent yields and the procedure is readily scalable. The more readily available Aryl bromides were also cyClized with the addition of potassium iodide to generate the respective Alkyl iodides. A rare dual ligand system employing a bisphosphine and bisphosphine monoxide was used to achieve enantioenriched products.Carboiodination Catalyzed by Nickel48201871#N/ATRUE
471
jacs.8b0254710.1021/jacs.8b02547cyClizationFALSEhttps://doi.org/10.1021/jacs.8b02547Ye, MCJ. Am. Chem. Soc.A Ni-Al bimetallic catalyzed enantioselective C-H exo-selective cyClization of imidazoles with alkenes has been developed. A series of bi- or polycyClic imidazoles with beta-stereocenter were obtained in up to 98% yield and >99% ee. The bifunctional SPO ligand-promoted bimetallic catalysis proved to be critical to this challenging stereocontrol.Enantioselective Ni-Al Bimetallic Catalyzed exo-Selective C-H CyClization of Imidazoles with Alkenes51201886#N/ATRUE
472
acs.orglett.5b0302310.1021/acs.orglett.5b03023CyClizationFALSEhttps://doi.org/10.1021/acs.orglett.5b03023Yamada, TSilver Catalyzed Cascade Carbonylation and CyClization of Trimethyl(2-methylenebut-3-yn-1-yl)silane Derivatives2015#N/ATRUE
473
jacs.6b0420610.1021/jacs.6b04206cyClizationsFALSEhttps://doi.org/10.1021/jacs.6b04206Lam, HWJ. Am. Chem. Soc.Nickel-catalyzed additions of Arylboronic acids to alkynes, followed by enantioselective cyClizations of the alkenylnickel species onto tethered ketones or enones, are reported. These reactions are reliant upon the formal anti-carbonickelation of the alkyne, which is postulated to occur by the reversible E/Z isomerization of an alkenylnickel species.Enantioselective Nickel-Catalyzed anti-Carbometallative CyClizations of Alkynyl Electrophiles Enabled by Reversible Alkenylnickel E/Z Isomerization96201646#N/ATRUE
474
ja993069j10.1021/ja993069jcyClizationsFALSEhttps://doi.org/10.1021/ja993069jMontgomery, JJ. Am. Chem. Soc.A formal synthesis of (+)-alpha-allokainic acid and a total synthesis of (-)-alpha-kainic acid were carried out using a short, efficient, and highly stereoselective approach. From an alkyne precursor, a nickel-catalyzed cyClization and a palladium-catalyzed rearrangement were utilized in the synthesis of (+)-alpha-allokainic acid. From an allene precursor, a nickel-catalyzed cyClization was utilized in the synthesis of (-)-alpha-kainic acid. The allene cyClization used in the latter sequence was the first example of a metal-catalyzed cyClization of this type.A stereodivergent approach to (-)-alpha-kainic acid and (+)-alpha-allokainic acid utilizing the complementarity of alkyne and allene cyClizations100199964#N/ATRUE
475
ja970212510.1021/ja9702125cyClizationsFALSEhttps://doi.org/10.1021/ja9702125Savchenko, AVJ. Am. Chem. Soc.A nickel-catalyzed method for cyClizations of electron-deficient alkenes with tethered unsaturation in the presence of organozincs was developed. Considerable flexibility in the structure of each reactive component was observed. Enones, Alkylidene malonates, unsaturated beta-ketoesters, and nitroalkenes participated as the electron-deficient alkene; alkynes, enones, 1,3-dienes, and aldehydes participated as the tethered unsaturation; and a variety of sp(2) and sp(3)-hybridized organozincs, inCluding those that possess beta-hydrogens, participated as the nuCleophilic component. Substrate structure, organozinc structure, and ligand structure all played a significant role in determining product selectivities. Of particular synthetic significance was the opportunity to prepare either E or Z tri- or tetrasubstituted alkenes from a common alkyne. A discussion of probable mechanisms is provided.Nickel-catalyzed organozinc-promoted carbocyClizations of electron-deficient alkenes with tethered unsaturation120199776#N/ATRUE
476
ja952026+10.1021/ja952026+cyClizationsFALSEhttps://doi.org/10.1021/ja952026+Savchenko, AVJ. Am. Chem. Soc.Nickel-catalyzed cyClizations of alkynyl enones with concomitant stereoselective tri- or tetrasubstituted alkene introduction87199639#N/ATRUE
477
ja201337x10.1021/ja201337xcyClizationsFALSEhttps://doi.org/10.1021/ja201337xTanaka, KJ. Am. Chem. Soc.It has been established that a cationic rhodium(I)/(R)-H-8-BINAP or (R)-Segphos complex catalyzes two modes of enantioselective cyClizations of gamma-alkynylaldehydes with acyl phosphonates via C-P or C-H bond Cleavage. The ligands of the Rh(I) complexes and the substitutents of both gamma-alkynylaldehydes and acyl phosphonates control these two different pathways.Rhodium-Catalyzed Enantioselective CyClizations of gamma-Alkynylaldehydes with Acyl Phosphonates: Ligand- and Substituent-Controlled C-P or C-H Bond Cleavage36201148#N/ATRUE
478
ja200867d10.1021/ja200867dcyClizationsFALSEhttps://doi.org/10.1021/ja200867dMontgomery, JJ. Am. Chem. Soc.The mechanism of nickel-catalyzed, silane-mediated reductive cyClization of ynals has been evaluated. The cyClizations are first-order in [Ni] and [ynal] and zeroth-order in [silane]. These results, in combination with the lack of rapid silane consumption upon reaction initiation, are inconsistent with mechanisms involving reaction initiation by oxidative addition of Ni(0) to the silane. Silane consumption occurs only when both the alkyne and aldehyde are present. Mechanisms involving rate-determining oxidative cyClization to a metallacyCle followed by rapid reaction with the silane are consistent with the data obtained.Mechanistic Study of Nickel-Catalyzed Ynal Reductive CyClizations through Kinetic Analysis26201134#N/ATRUE
479
ja077562410.1021/ja0775624cyClizationsFALSEhttps://doi.org/10.1021/ja0775624Lam, HWJ. Am. Chem. Soc.In the presence of diethylzinc as a stoichiometric reductant, Ni(acac)(2) functions as an efficient. precatalyst for the reductive aldol cyClization of alpha,beta-unsaturated Carbonyl compounds tethered to a ketone electrophile through an amide or an ester linkage. The reactions are tolerant of a wide range of substitution at both alpha,beta-unsaturated Carbonyl and ketone components and proceed smoothly to furnish beta-hydroxylactams and beta-hydroxylactones with generally high diastereoselectivities. A series of experiments, inCluding deuterium-labeling studies, was carried out in an attempt to gain some insight into the possible reaction mechanisms that might be operative.Diastereoselective nickel-catalyzed reductive aldol cyClizations using diethylzinc as the stoichiometric reductant: Scope and mechanistic insight27200865#N/ATRUE
480
ja042733f10.1021/ja042733fcyClizationsFALSEhttps://doi.org/10.1021/ja042733fJamison, TFJ. Am. Chem. Soc.Described in this work are total syntheses of amphidinolides T1 and T4 using two nickel-catalyzed reductive coupling reactions of alkynes, with an epoxide in one case (intermolecular) and with an aldehyde in another (intramolecular). The latter was used to effect a macrocyClization, form a C-C bond, and install a stereogenic center with > 10:1 selectivity in both natural product syntheses. Alternative approaches in which intermolecular alkyne-aldehyde reductive coupling reactions would serve to join key fragments were investigated and are also discussed; it was found that macrocyClization (i.e. intramolecular alkyne-aldehyde coupling) was superior in several respects (diastereoselectivity, yield, and length of syntheses). Alkyne-epoxide reductive couplings were instrumental in the construction of key fragments corresponding to approximately half of the molecule of both natural products. In one case (T4 series), the alkyne-epoxide coupling exhibited very high site selectivity in a coupling of a diyne. A model for the stereoselectivity observed in the macrocyClizations is also proposed.Total syntheses of amphidinolides T1 and T4 via catalytic, stereoselective, reductive macrocyClizations83200567#N/ATRUE
481
ja037423w10.1021/ja037423wcyClizationsFALSEhttps://doi.org/10.1021/ja037423wMontgomery, JJ. Am. Chem. Soc.A new strategy for effecting cascade cyClization processes using nickel enolates has been developed. Nickel enolates may be Cleanly generated by the oxidative cyClization of an enal and alkyne with Ni(0), and the resulting enolate may be functionalized by a variety of Alkylation processes. Partially and fully intramolecular versions of the process allow the rapid synthesis of complex polycyClics from simple achiral, acyClic precursors.Cascade cyClizations and couplings involving nickel enolates43200361#N/ATRUE
482
anie.20130321110.1002/anie.201303211cyClizationsFALSEhttps://doi.org/10.1002/anie.201303211Alexanian, EJAngew. Chem.-Int. Edit.Stereoselective Nickel-Catalyzed [2+2+2] CyCloadditions and Alkenylative CyClizations of Ene-Allenes and Alkenesalkenes; allenes; carbocyCles; cyCloaddition; nickel24201332#N/ATRUE
483
anie.20030063410.1002/anie.200300634cyClizationsFALSEhttps://doi.org/10.1002/anie.200300634Martin, RAngew. Chem.-Int. Edit.Nickel-catalyzed reductive cyClizations and couplingsmetallacyCles; multicomponent reactions; nickel; reductive coupling; reductive cyClization5372004135#N/ATRUE
484
ol016082t10.1021/ol016082tCyCloadditionFALSEhttps://doi.org/10.1021/ol016082tItoh, KRuthenium(II)-catalyzed cyCloaddition of 1,6-diynes with isocyanates leading to bicyClic pyridones2001#N/ATRUE
485
jacs.9b0794810.1021/jacs.9b07948CyCloadditionFALSEhttps://doi.org/10.1021/jacs.9b07948Matsubara, SJ. Am. Chem. Soc.The nickel-catalyzed formal [5+2] cyCloaddition of five-membered benzothiophenes and alkynes giving seven-membered benzothiepines via unprecedented dearomatization is reported. The reaction involves the carbothiolation of alkynes with sulfur-containing aromatic heterocyCles affording sulfur-containing heterocyClic compounds via ring expansion. As a result, this method facilitates divergent access to thermally metastable benzothiepines. The structure of the thianickelacyCle intermediate, which is formed via oxidative addition of the C-S bond in benzothiophenes to nickel(0), was confirmed by in situ X-ray absorption fine structure spectroscopy and density functional theory calculation.Nickel-Catalyzed [5+2] CyCloaddition of 10 pi-Electron Aromatic Benzothiophenes with Alkynes To Form Thermally Metastable 12 pi-Electron Nonaromatic Benzothiepines10201935#N/ATRUE
486
jacs.8b0967710.1021/jacs.8b09677CyCloadditionFALSEhttps://doi.org/10.1021/jacs.8b09677Pericas, MKJ. Am. Chem. Soc.The nickel-catalyzed synthesis of tetrasubstituted cyClobutenes from alkynes is reported. This transformation is uniquely promoted by the use of a primary aminophosphine, an unusual ligand in nickel catalysis. Mechanistic insights for this new transformation are provided, and postreaction modifications of the cyClobutene products to stereodefined cyClic and acyClic compounds are reported, inCluding the synthesis of epitruxillic acid.Nickel-Catalyzed Reductive [2+2] CyCloaddition of Alkynes10201890#N/ATRUE
487
jacs.8b0467310.1021/jacs.8b04673CyCloadditionFALSEhttps://doi.org/10.1021/jacs.8b04673Shinokubo, HJ. Am. Chem. Soc.A nickel-mediated tandem double cyClization of ethynylene-linked dibromodiporphyrins afforded highly reactive etheno-fused diporphyrins, which undergo a thermal [2+2] cyCloaddition at the fused C-C double bond to afford the cyClobutane moiety in X-shaped cyClobutane-linked tetraporphyrins. During the reaction of a Zn(II) complex precursor, the initial double cyClization product was converted into the diketodiporphyrin, which exhibits red chemiluminescence under ambient conditions.X-Shaped CyClobutane-Linked Tetraporphyrins through a Thermal [2+2] CyCloaddition of Etheno-Fused Diporphyrins4201836#N/ATRUE
488
jacs.7b0994710.1021/jacs.7b09947CyCloadditionFALSEYe, MCNi-Al Bimetallic Catalyzed Enantioselective CyCloaddition of CyClopropyl Carboxamide with Alkyne2017#N/ATRUE
489
jacs.7b0633810.1021/jacs.7b06338CyCloadditionFALSEhttps://doi.org/10.1021/jacs.7b06338Hong, SYJ. Am. Chem. Soc.Transition-metal-catalyzed or metal-free azide alkyne cyCloadditions are methods to access 1,4 or 1,5-disubstituted 1,2,3-triazoles. Although the copper catalyzed cyCloaddition to access 1,4-disubstituted products has been applied to biomolecular reaction systems, the azide alkyne cyCloaddition to access the complementary 1,5-regioisomers under aqueous and ambient conditions remains a challenge due to limited substrate scope or moisture-/air-sensitive catalysts. Herein, we report a method to access 1,5-disubstituted 1,2,3-triazoles using a Cp2Ni/Xantphos catalytic system. The reaction proceeds both in water and organic solvents at room temperature. This protocol is simple and scalable with a broad substrate scope inCluding both aliphatic and aromatic substrates. Moreover, triazoles attached with carbohydrates or amino acids are prepared via this cyCloaddition.Nickel-Catalyzed Azide-Alkyne CyCloaddition To Access 1,5-Disubstituted 1,2,3-Triazoles in Air and Water64201749#N/ATRUE
490
jacs.1c0135410.1021/jacs.1c01354CyCloadditionFALSEhttps://doi.org/10.1021/jacs.1c01354Topczewski, JJJ. Am. Chem. Soc.The triazole heterocyCle has been widely adopted as an isostere for the amide bond. Many native amides are a-chiral, being derived from amino acids. This makes a-N-chiral triazoles attractive building blocks. This report describes the first enantioselective triazole synthesis that proceeds via nickel-catalyzed alkyne-azide cyCloaddition (NiAAC). This dynamic kinetic resolution is enabled by a spontaneous [3,3]-sigmatropic rearrangement of the allylic azide. The 1,4,5-trisubstituted triazole products, derived from internal alkynes, are complementary to those commonly obtained by the related CuAAC reaction. Initial mechanistic experiments indicate that the NiAAC reaction proceeds through a monometallic Ni complex, which is distinct from the CuAAC manifold.Enantioselective Nickel-Catalyzed Alkyne-Azide CyCloaddition by Dynamic Kinetic Resolution1202172#N/ATRUE
491
ja904068p10.1021/ja904068pCyCloadditionFALSEhttps://doi.org/10.1021/ja904068pMatsubara, SJ. Am. Chem. Soc.An intermolecular nickel-catalyzed addition reaction has been developed where salicylic acid ketals react with alkynes to afford substituted chromones. A mechanistic rationale is proposed, implying beta-elimination of ketone from ring strained seven-membered nickelacyCle to generate a five-membered oxa-nickelacyCle intermediate.Nickel-Catalyzed CyCloaddition of Salicylic Acid Ketals to Alkynes via Elimination of Ketones44200930#N/ATRUE
492
ja809389k10.1021/ja809389kCyCloadditionFALSEhttps://doi.org/10.1021/ja809389kXie, ZWJ. Am. Chem. Soc.Transition metal mediated multicomponent cross-coupling reactions are a powerful strategy to assemble complex molecules from very simple precursors in a single operation. This Communication reports a nickel-mediated three-component cyCloaddition reaction of carboryne with alkenes and alkynes giving dihydrobenzocarborane derivatives with excellent chemo- and regioselectivity. A reaction mechanism involving sequential alkene and alkyne insertion, followed by reductive elimination, is proposed. The key intermediate of nickelacyClopentane was isolated and confirmed by single-crystal X-ray analyses. This work furnishes a new method for the preparation of substituted dihydrobenzocarboranes that are difficult to obtain by other methods.Nickel-Mediated Three-Component CyCloaddition Reaction of Carboryne, Alkenes, and Alkynes59200940#N/ATRUE
493
ja807952r10.1021/ja807952rCyCloadditionFALSEhttps://doi.org/10.1021/ja807952rMatsubara, SJ. Am. Chem. Soc.A nickel-catalyzed [4 + 2] cyCloaddition reaction has been developed where enones react with alkynes to afford polysubstituted pyrans. A mechanistic rationale is proposed, implying oxa-nickela cyCle formation by oxidative cyClization of nickel to enone, followed by alkyne insertion.Nickel-Catalyzed [4+2] CyCloaddition of Enones with Alkynes36200951#N/ATRUE
494
ja510520610.1021/ja5105206CyCloadditionFALSEhttps://doi.org/10.1021/ja5105206Louie, JJ. Am. Chem. Soc.A Ni/N-heterocyClic carbene catalyst couples diynes to the C(alpha)-C(beta) double bond of tropone, a type of reaction that is unprecedented for metal-catalyzed cyCloadditions with aromatic tropone. Many different diynes were efficiently coupled to afford [5-6-7] fused tricyClic products, while [5-7-6] fused tricyClic compounds were obtained as minor byproducts in a few cases. The reaction has broad substrate scope and tolerates a wide range of functional groups, and excellent regioselectivity is found with unsymmetrical diynes. Theoretical calculations show that the apparent enone cyCloaddition occurs through a distinctive 8 pi insertion of tropone. The initial intramolecular oxidative cyClization of diyne produces the nickelacyClopentadiene intermediate. This intermediate undergoes an 8p insertion of tropone, and subsequent reductive elimination generates the [5-6-7] fused tricyClic product. This initial product undergoes two competing isomerizations, leading to the observed [5-6-7] and [5-7-6] fused tricyClic products.Ni(NHC)]-Catalyzed CyCloaddition of Diynes and Tropone: Apparent Enone CyCloaddition Involving an 8 pi Insertion28201498#N/ATRUE
495
ja509171a10.1021/ja509171aCyCloadditionFALSEhttps://doi.org/10.1021/ja509171aOgoshi, SJ. Am. Chem. Soc.The first nickel(0)-catalyzed [2 + 2 + 1] Carbonylative cyCloaddition reaction of imines and alkynes or norbornene has been achieved by employing phenyl formate as a CO source. With this method, a variety of N-benzenesulfonyl, -tosyl, and -phosphoryl-substituted gamma-lactams can be prepared in good to high yields.Nickel(0)-Catalyzed [2+2+1] Carbonylative CyCloaddition of Imines and Alkynes or Norbornene Leading to gamma-Lactams63201454#N/ATRUE
496
ja307592410.1021/ja3075924CyCloadditionFALSEhttps://doi.org/10.1021/ja3075924Louie, JThe Discovery of [Ni(NHC)RCN](2) Species and Their Role as CyCloaddition Catalysts for the Formation of Pyridines2012#N/ATRUE
497
ja307477510.1021/ja3074775CyCloadditionFALSEhttps://doi.org/10.1021/ja3074775Ogoshi, SJ. Am. Chem. Soc.A nickel-catalyzed intermolecular [2 + 2] cyCloaddition of conjugated enynes with alkenes has been developed. A variety of electron-deficient alkenes as well as electronically neutral norbornene and 1-decene were applicable to this reaction. The use of conjugated enynes circumvented possible side rections, such as oligomerizations and cyClotrimerizations. The isolation of reaction intermediate complexes revealed that the eta(3)-butadienyl coordination is the key for the selective formation of cyClobutene.Nickel-Catalyzed Intermolecular [2+2] CyCloaddition of Conjugated Enynes with Alkenes95201256#N/ATRUE
498
ja208162w10.1021/ja208162wCyCloadditionFALSEhttps://doi.org/10.1021/ja208162wOgoshi, SJ. Am. Chem. Soc.Pyridines, which comprise one of the most important Classes of the six-membered heterocyClic compounds, are widely distributed in nature, and the transition-metal-catalyzed [2 + 2 + 2] cyCloaddition reaction of two alkynes and a nitrile is one of the most powerful methods for preparing versatile, highly substituted pyridine derivatives. However, the lack of chemo- and regioselectivity is still a crucial issue associated with fully intermolecular [2 + 2 + 2] cyCloaddition. The present study developed the Ni(0)-catalyzed intermolecular dehydrogenative [4 + 2] cyCloaddition reaction of 1,3-butadienes with nitrites to give a variety of pyridines regioselectively.Nickel-Catalyzed Dehydrogenative [4+2] CyCloaddition of 1,3-Dienes with Nitriles98201149#N/ATRUE
499
ja205999910.1021/ja2059999CyCloadditionFALSEhttps://doi.org/10.1021/ja2059999Ogoshi, SJ. Am. Chem. Soc.Oxygen-containing organic compounds, such as ethers, Carbonylates, and carbamates, have recently received increasing attention because of their newly discovered applications as electrophiles in cross-coupling reactions via transition metal-catalyzed C-O bond Activation. However, no cyCloaddition reaction involving their C-O bond Activation has been demonstrated thus far. The present study developed a Ni(O)-catalyzed unique [3+2] cyCloaddition reaction of alpha,beta-unsaturated phenyl esters with alkynes in (PrOH)-Pr-i to yield cydopentenone derivatives.Nickel-Catalyzed Formation of CyClopentenone Derivatives via the Unique CyCloaddition of alpha,beta-Unsaturated Phenyl Esters with Alkynes43201155#N/ATRUE
500
ja203829j10.1021/ja203829jCyCloadditionFALSEhttps://doi.org/10.1021/ja203829jMatsubara, SJ. Am. Chem. Soc.An intermolecular cyCloaddition reaction has been developed, where o-Arylcarboxybenzonitriles react with alkynes to afford coumarins in the presence of Ni(0)/P(CH(2)Ph)(3)/MAD as a catalyst. The reaction process displays an unusual mechanistic feature the Cleavage of two independent C-CN and C-CO bonds.Nickel-Catalyzed CyCloaddition of o-Arylcarboxybenzonitriles and Alkynes via Cleavage of Two Carbon-Carbon sigma Bonds83201130#N/ATRUE
501
ja105878910.1021/ja1058789CyCloadditionFALSEhttps://doi.org/10.1021/ja1058789Xie, ZWJ. Am. Chem. Soc.o-Carboryne (1,2-dehydro-o-carborane) has been reported as a very reactive intermediate and regarded as a three-dimensional relative of benzyne, whereas the 1,3-dehydro-o-carborane has remained elusive. In this artiCle, we present the preparation of 1,3-dehydro-o-carborane from 3-iodo-1-lithio-o-carborane mediated by palladium(0). This reactive intermediate can be trapped by alkynes via Pd/Ni-cocatalyzed [2 + 2 + 2] cyCloaddition reaction, leading to the formation of C,B-substituted-o-carborane derivatives. The possible reaction mechanism involving the formation of metal-1,3-dehydro-o-carborane followed by stepwise insertions of 2 equiv of alkyne and reductive elimination is proposed, and the relative reactivity of M-C versus M-B bond in metal-1,3-dehydro-o-carborane complexes is also discussed. This work offers a new methodology for B-functionalization of carboranes and demonstrates that metal-1,3-dehydro-o-carborane can be viewed as a new kind of boron nuCleophile.Palladium/Nickel-Cocatalyzed CyCloaddition of 1,3-Dehydro-o-Carborane with Alkynes. Facile Synthesis of C,B-Substituted Carboranes41201055#N/ATRUE
502
ja105541r10.1021/ja105541rCyCloadditionFALSEhttps://doi.org/10.1021/ja105541rMurakami, MJ. Am. Chem. Soc.The enantioselective intermolecular [2 + 2 + 2] cyCloaddition reaction of two molecules of isocyanate and one molecule of allene is catalyzed by a nickel(0)/(S,S)-i-Pr-FOXAP complex, providing an efficient access to enantiomerically enriched dihydropyrimidine-2,4-diones.Enantioselective [2+2+2] CyCloaddition Reaction of Isocyanates and Allenes Catalyzed by Nickel53201038#N/ATRUE
503
ja061605j10.1021/ja061605jCyCloadditionFALSEhttps://doi.org/10.1021/ja061605jXie, ZWJ. Am. Chem. Soc.Nickel-mediated regioselective [2+2+2] cyCloaddition of carboryne with alkynes63200631#N/ATRUE
504
ja046854r10.1021/ja046854rCyCloadditionFALSEhttps://doi.org/10.1021/ja046854rTekavec, TNJ. Am. Chem. Soc.Efficient nickel-catalyzed [2+2+2] cyCloaddition of CO2 and diynes (vol 124, pg 15188, 2002)320041#N/ATRUE
505
ja046477i10.1021/ja046477iCyCloadditionFALSEhttps://doi.org/10.1021/ja046477iLouie, JJ. Am. Chem. Soc.Nickel-catalyzed cyCloaddition of alkynes and isocyanates144200420#N/ATRUE
506
ja035014u10.1021/ja035014uCyCloadditionFALSEhttps://doi.org/10.1021/ar500345fMurai, SA GaCl3-catalyzed [4+1] cyCloaddition of alpha,beta-unsaturated Carbonyl compounds and isocyanides leading to unsaturated gamma-lactone derivatives2003#N/ATRUE
507
ja027438e10.1021/ja027438eCyCloadditionFALSEhttps://doi.org/10.1021/ja027438eTekavec, TNJ. Am. Chem. Soc.Efficient nickel-catalyzed [2+2+2] cyCloaddition of CO2 and diynes280200230#N/ATRUE
508
ja016510q10.1021/ja016510qCyCloadditionFALSEhttps://doi.org/10.1021/ja016510qItoh, KJ. Am. Chem. Soc.Ruthenium-catalyzed cyCloaddition of 1,6-diynes with isothiocyanates and carbon disulfide: First transition-metal catalyzed [2+2+2] cocyClotrimerization involving C=S double bond75200227#N/ATRUE
509
ja00052a04710.1021/ja00052a047CyCloadditionFALSEhttps://doi.org/10.1021/ja00052a047MORETO, JMJ. Am. Chem. Soc.The title Carbonylative cyCloaddition of five- to eight-member ring 3-halo- and 1-(halomethyl)cyCloalkenes with different acetylenes was studied. From moderate to good yields of ring-fused and spiro cyClopentenone derivatives were obtained, especially in the reaction with acetylenes bearing electron-withdrawing substituents by proper selection of the reaction conditions to avoid the acetylene polyinsertion and/or other side reactions from the organonickel intermediates. In this context, the beneficial role of acetate ion on the outcome of the reaction is rationalized. This process leading to the formation of bicyCloadducts with the concomitant formation of up to six C-C bonds, with high regio- and stereoselectivity, can be useful in the synthesis of natural products as exemplified by the easy preparation of [5-5-5] tricyClic compound 14 from a 1:1 cis and trans isomeric mixture of 6-acetoxy-3-bromocyClooctene (11). A plausible general reaction mechanism is proposed that is consistent with all the products obtained.RING-FUSED AND SPIRO CYClOPENTENONES BY NI(CO)4-PROMOTED INTERMOLECULAR CarbonylATIVE CYClOADDITION OF ACETYLENES WITH 3-HALOCYClOALKENES AND 1-(HALOMETHYL)CYClOALKENES571992105#N/ATRUE
510
d1sc02681j10.1039/d1sc02681jCyCloadditionFALSEhttps://doi.org/10.1039/d1sc02681jFeng, XMChem. Sci.Efficient asymmetric synthesis of a collection of small molecules with structural diversity is highly important to drug discovery. Herein, three distinct types of chiral cyClic compounds were accessible by enantioselective catalysis and sequential transformations. Highly regio- and enantioselective [2+2] cyCloaddition of (E)-alkenyloxindoles with the internal C=C bond of N-allenamides was achieved with N,N'-dioxide/Ni(OTf)(2) as the catalyst. Various optically active spirocyClobutyl oxindole derivatives were obtained under mild conditions. Moreover, formal [4+2] cyCloaddition products occurring at the terminal C=C bond of N-allenamides, dihydropyran-fused indoles, were afforded by a stereospecific sequential transformation with the assistance of a catalytic amount of Cu(OTf)(2). In contrast, performing the conversion under air led to the formation of gamma-lactones via the water-involved deprotection and rearrangement process. Experimental studies and DFT calculations were performed to probe the reaction mechanism.Catalytic asymmetric synthesis of spirocyClobutyl oxindoles and beyond via [2+2] cyCloaddition and sequential transformations0202198#N/ATRUE
511
cs501653s10.1021/cs501653sCyCloadditionFALSEhttps://doi.org/10.1021/cs501653sMatsubara, SACS Catal.Two nonstrained C-C sigma-bonds are Cleaved in a novel nickel(0)/LA-catalyzed decyanative [4 + 2] cyCloaddition of o-Arylcarboxybenzonitrile with alkyne, where LA represents a Lewis acid such as methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide). The catalytic cyCle of this reaction is systematically investigated here by DFT method to Clarify the reasons two nonstrained C-C sigma-bonds are successfully Cleaved in this reaction. DFT calculations indicate that this reaction occurs via the oxidative addition of the C-CN sigma-bond of o-Arylcarboxybenzonitrile to the Ni(0) center, alkyne insertion into the Ni(II) Aryl bond, C-C coupling between the Vinyl carbon and the Carbonyl carbon atoms, and beta-Aryl elimination followed by reductive elimination. One LA interacts with the cyano nitrogen atom of o-Arylcarboxybenzonitrile to accelerate the oxidative addition by stabilizing the unoccupied sigma* + pi* C-CN antibonding orbital. One more LA interacts with the Carbonyl oxygen of o-Arylcarboxybenzonitrile. This LA enhances the electrophilic nature of the Carbonyl carbon to accelerate the C C coupling, because this step occurs through the nudeophilic attack of the Vinyl carbon at the Carbonyl carbon atom. The second C-C sigma-bond Activation occurs via beta-Aryl elimination, the transition state of which is stabilized by the interaction between LA and the Carbonyl oxygen atom. These results lead to the dear conClusion that the presence of two LA molecules is crucial to achieve the dual C-C sigma-bond Cleavages. The reasons LA accelerates the oxidative addition of the C-CN sigma-bond to the nickel(0) center and the C-C coupling followed by the beta-Aryl elimination are discussed in detail.Reasons Two Nonstrained C-C sigma-Bonds Can Be Easily Cleaved in Decyanative [4+2] CyCloaddition Catalyzed by Nickel(0)/Lewis Acid Systems. Theoretical InsightC-C bond Activation; nickel complex; Lewis acid; density functional theory calculation; synergy effect33201598#N/ATRUE
512
c7sc02576a10.1039/c7sc02576aCyCloadditionFALSEhttps://doi.org/10.1039/c7sc02576aCui, XChem. Sci.Catalytic [2 + 2 + 2] cyCloaddition with imines has, for the first time, been developed as a practical and selective approach for direct construction of hexahydropyrimidine derivatives from various alkenes. With formaldimines as reagents and simple InCl3 as the catalyst, this ionic [2 + 2 + 2] approach is applicable for a wide scope of alkenes and allenes with various electronic and steric properties, as well as substitution patterns. Through facile hydrolysis of the resulting hexahydropyrimidines, this catalytic process also provides a new synthetic strategy for the aminomethylamination of alkenes and allenes to practically access 1,3-diamine derivatives.Catalytic [2+2+2] cyCloaddition with indium(III)-activated formaldimines: a practical and selective access to hexahydropyrimidines and 1,3-diamines from alkenes13201759#N/ATRUE
513
anie.20161060510.1002/anie.201610605CyCloadditionFALSEhttps://doi.org/10.1002/anie.201610605Shibata, NCatalytic Asymmetric 1,3-Dipolar CyCloaddition of beta-FluoroAlkylated alpha,beta-Unsaturated 2-Pyridylsulfones with Nitrones for Chiral FluoroAlkylated Isoxazolidines and gamma-Amino Alcohols2017#N/ATRUE
514
anie.20140269510.1002/anie.201402695CyCloadditionFALSEhttps://doi.org/10.1002/anie.201402695Ichikawa, JAngew. Chem.-Int. Edit.The nickel-mediated [3+2] cyCloaddition of 2-trifluoromethyl-1-alkenes with alkynes afforded fluorine-containing multi-substituted cyClopentadienes in a regioselective manner. This reaction involves the consecutive two C-F bond Cleavage of a trifluoromethyl or a pentafluoroethyl group through beta-fluorine elimination.Double C-F Bond Activation through beta-Fluorine Elimination: Nickel-Mediated [3+2] CyCloaddition of 2-Trifluoromethyl-1-alkenes with Alkynesalkynes; C-F bond Activation; cyCloaddition; cyClopentadienes; fluoroalkenes; nickel88201498#N/ATRUE
515
anie.20130686910.1002/anie.201306869CyCloadditionFALSEhttps://doi.org/10.1002/anie.201306869Louie, JAngew. Chem.-Int. Edit.Nickel-Catalyzed CyCloaddition of 1,3-Dienes with 3-Azetidinones and 3-Oxetanonesazetidinones; CC Activation; cyCloaddition; nickel; oxetanones472013116#N/ATRUE
516
anie.20110621210.1002/anie.201106212CyCloadditionFALSEhttps://doi.org/10.1021/acscatal.6b02964Xie, ZWThree-Component [2+2+2] CyCloaddition of Carboryne, Unactivated Alkene, and Alkyne via ZirconacyClopentane Mediated by Nickel: One-Pot Synthesis of Dihydrobenzocarboranes2012#N/ATRUE
517
anie.20110617410.1002/anie.201106174CyCloadditionFALSEhttps://doi.org/10.1002/anie.201106174Ogoshi, SAngew. Chem.-Int. Edit.[3+2] CyCloaddition Reaction of CyClopropyl Ketones with Alkynes Catalyzed by Nickel/Dimethylaluminum ChloridecarbocyCles; cyCloaddition; homogeneous catalysis; nickel; transition metals53201150#N/ATRUE
518
anie.20110447510.1002/anie.201104475CyCloadditionFALSEhttps://doi.org/10.1002/anie.201104475Louie, JAngew. Chem.-Int. Edit.A Serendipitous Discovery: Nickel Catalyst for the CyCloaddition of Diynes with Unactivated Nitrilesalkynes; cyCloaddition; heterocyCles; nickel; synthetic methods89201162#N/ATRUE
519
anie.20110428610.1002/anie.201104286CyCloadditionFALSEhttps://doi.org/10.1002/anie.201104286Matsubara, SAngew. Chem.-Int. Edit.Nickel-Catalyzed CyCloaddition of alpha,beta,gamma,delta-Unsaturated Ketones with AlkynescyCloaddition; homogeneous catalysis; isomerization; nickel; transition metals9201127#N/ATRUE
520
anie.20110362110.1002/anie.201103621CyCloadditionFALSEhttps://doi.org/10.1002/anie.201103621Louie, JAngew. Chem.-Int. Edit.Nickel-Mediated CyCloaddition by Two Sequential C-H ActivationsC-H Activation; cross-dehydrogenative coupling; cyClometalation; dihydropyridone; nickel13201132#N/ATRUE
521
anie.20100124910.1002/anie.201001249CyCloadditionFALSEhttps://doi.org/10.1002/anie.201001249Xie, ZWAngew. Chem.-Int. Edit.Nickel-Catalyzed Regioselective [2+2+2] CyCloaddition of Carboryne with Alkynesalkynes; carboryne; cyCloaddition; nickel; regioselectivity53201050#N/ATRUE
522
anie.20090705210.1002/anie.200907052CyCloadditionFALSEhttps://doi.org/10.1002/anie.200907052Masu, HAngew. Chem.-Int. Edit.Synthesis of Nine-Membered CarbocyCles by the [4+3+2] CyCloaddition Reaction of Ethyl CyClopropylideneacetate and DienynesC-C coupling; cyCloaddition; medium-ring compounds; nickel; synthetic methods47201086#N/ATRUE
523
anie.20090200610.1002/anie.200902006CyCloadditionFALSEhttps://doi.org/10.1002/anie.200902006Xie, ZWAngew. Chem.-Int. Edit.Nickel-Catalyzed Three-Component [2+2+2] CyCloaddition Reaction of Arynes, Alkenes, and Alkynesarynes; cyClization; homogeneous catalysis; nickel; three-component reactions57200960#N/ATRUE
524
acscatal.8b0348210.1021/acscatal.8b03482CyCloadditionFALSEhttps://doi.org/10.1021/acscatal.8b03482Pidko, EAACS Catal.The Diels-Alder cyCloaddition (DAC) is a powerful tool to construct C-C bonds. The DAC reaction can be accelerated in several ways, one of which is reactant confinement as observed in supramolecular complexes and Diels-Alderases. Another method is altering the frontier molecular orbitals (FMOs) of the reactants by using homogeneous transition-metal complexes whose active sites exhibit d-orbitals suitable for net-bonding orbital interactions with the substrates. Both features can be combined in first row d-block (TM) exchanged faujasite catalysts where the zeolite framework acts as a stabilizing ligand for the active site while confining the reactants. Herein, we report on a mechanistic and periodic DFT study on TM-(Cu(I), Cu(II), Zn(II), Ni(II), Cr(III), Sc(III), V(V))exchanged faujasites to elucidate the effect of d-shell filling on the DAC reaction between 2,5-dimethylfuran and ethylene. Two pathways were found: one being the concerted one-step and the other being the stepwise two-step pathway. A decrease in d-shell filling results in a concomitant increase in reactant Activation as evidenced by increasingly narrow energy gaps and lower Activation barriers. For models holding relatively small d-block cations, the zeolite framework was found to bias the DAC reaction toward an asynchronous one-step pathway instead of the two-step pathway. This work is an example of how the active site properties and the surrounding chemical environment influence the reaction mechanism of chemical transformations.Mechanistic Insight into the [4+2] Diels-Alder CyCloaddition over First Row d-Block Cation-Exchanged FaujasitesDFT calculations; zeolite catalysis; 2,5-dimethylfuran; ethylene; property-activity relations32019100#N/ATRUE
525
acs.orglett.6b0061910.1021/acs.orglett.6b00619CyCloadditionFALSEhttps://doi.org/10.1021/acs.orglett.6b00619Shibata, TIridium-Catalyzed Formal [4+1] CyCloaddition of Biphenylenes with Alkenes Initiated by C-C Bond Cleavage for the Synthesis of 9,9-Disubstituted Fluorenes2016#N/ATRUE
526
ja206850s10.1021/ja206850sCyCloaddition FALSEhttps://doi.org/10.1021/ja206850sChatani, NJ. Am. Chem. Soc.Although the pioneering example of ortho metalation involving Cleavage of C-H bonds was achieved using a nickel complex (Kleiman, J. P.; Dubeck, M. J. Am. Chem. Soc. 1963, 85, 1544), no examples of catalysis using nickel complexes have been reported. In this work, the Ni-catalyzed transformation of ortho C-H bonds utilizing chelation assistance, such as oxidative cyCloaddition of aromatic amides with alkynes, has been achieved.Nickel-Catalyzed Chelation-Assisted Transformations Involving Ortho C-H Bond Activation: Regioselective Oxidative CyCloaddition of Aromatic Amides to Alkynes292201153#N/ATRUE
527
jacs.1c0283310.1021/jacs.1c02833CyCloadditionsFALSEhttps://doi.org/10.1021/jacs.1c02833Sodeoka, MJ. Am. Chem. Soc.Reaction design in asymmetric catalysis has traditionally been predicated on a structurally robust scaffold in both substrates and catalysts, to reduce the number of possible diastereomeric transition states. Herein, we present the stereo-chemical dynamics in the Ni(II)-catalyzed diastereoconvergent (3 + 2) cyCloadditions of isomerizable nitrile-conjugated nitrones with alpha-keto ester enolates. Even in the presence of multiple equilibrating species, the catalytic protocol displays a wide substrate scope to access a range of CN-containing building blocks bearing adjacent stereocenters with high enantio- and diastereoselectivities. Our computational investigations suggest that the enantioselectivity is governed in the deprotonation process to form (Z)-Ni-enolates, while the unique syn addition is mainly controlled by weak noncovalent bonding interactions between the nitrone and ligand.Dynamics in Catalytic Asymmetric Diastereoconvergent (3+2) CyCloadditions with Isomerizable Nitrones and alpha-Keto Ester Enolates0202189#N/ATRUE
528
anie.20201160210.1002/anie.202011602
CyClopropanation
FALSEhttps://doi.org/10.1002/anie.202011602Uyeda, CAngew. Chem.-Int. Edit.(NDI)Ni-2 catalysts (NDI=naphthyridine-diimine) promote cyClopropanation reactions of 1,3-dienes using (Me3Si)CHN2. Mechanistic studies reveal that a metal carbene intermediate is not part of the catalytic cyCle. The (NDI)Ni-2(CHSiMe3) complex was independently synthesized and found to be unreactive toward dienes. Based on DFT models, we propose an alternative mechanism that begins with a Ni-2-mediated coupling of (Me3Si)CHN2 and the diene. N-2 extrusion followed by radical C-C bond formation generates the cyClopropane product. This model reproduces the experimentally observed regioselectivity and diastereoselectivity of the reaction.A Dinickel Catalyzed CyClopropanation without the Formation of a Metal Carbene Intermediatecarbenes; cyClopropane; homogeneous catalysis; metal&#8211; metal interactions; nickel2202139#N/ATRUE
529
anie.20161092410.1002/anie.201610924
CyClopropanation
FALSEhttps://doi.org/10.1002/anie.201610924Suero, MGAngew. Chem.-Int. Edit.The first stereoconvergent cyClopropanation reaction by means of photoredox catalysis using diiodomethane as the methylene source is described. This transformation exhibits broad functional group tolerance and it is characterized by an excellent stereocontrol enroute to trans-cyClopropanes regardless of whether E- or Z-styrene substrates were utilized.A Stereoconvergent CyClopropanation Reaction of Styrenes28201755#N/ATRUE
530
c9sc02035g10.1039/c9sc02035g
deCarbonylation
FALSEhttps://doi.org/10.1039/c9sc02035gTobisu, MChem. Sci.Nickel-catalyzed deCarbonylation of N-acylated N-heteroarenes is developed. This method can be used to produce a variety of N-Aryl heteroarenes, inCluding pyrroles, indoles, carbazoles and phenoxazines, using benzoic acid derivatives as Arylating reagents. Arylnickelamide intermediates that are relevant to the catalytic reaction were characterized by X-ray crystallography. When N-acylated benzimidazoles are used as substrates, deCarbonylation accompanied 1,2-migration to form 2-Arylated benzimidazoles.Nickel-catalyzed deCarbonylation of N-acylated N-heteroarenes15201934#N/ATRUE
531
DeCarbonylation FALSETobisu, MJ. Am. Chem. Soc.Herein, we describe a new catalytic approach to accessing aromatic amines from an abundant feedstock, namely phenols. The most reliable catalytic method for converting phenols to aromatic amines uses an activating group, such as a trifluoromethane sulfonyl group. However, this activating group is eliminated as a leaving group during the amination process, resulting in significant waste. Our nickel-catalyzed deCarbonylation reaction of Aryl carbamates forms aromatic amines with carbon dioxide as the only byproduct. As this amination proceeds in the absence of free amines, a range of functionalities, inCluding a Carbonyl group, are compatible. A bisphosphine ligand immobilized on a polystyrene support (PS-DPPBz) is key to the success of this reaction, generating a catalytic species that is significantly more active than simple nonsupported variants.Nickel-Catalyzed DeCarbonylation of Aryl Carbamates for Converting Phenols into Aromatic Amines21201928#N/ATRUE
532
anie.20170510710.1002/anie.201705107DeCarbonylativeFALSEhttps://doi.org/10.1002/anie.201705107Baran, PSAngew. Chem.-Int. Edit.The development of a new deCarbonylative cross-coupling method that affords terminal and substituted alkynes from various Carbonylic acids is described using both nickel- and iron-based catalysts. The use of N-hydroxytetrachlorophthalimide (TCNHPI) esters is crucial to the success of the transformation, and the reaction is amenable to insitu Carbonylic acid Activation. Additionally, an inexpensive, commercially available alkyne source is employed in this formal homologation process that serves as a surrogate for other well-established alkyne syntheses. The reaction is operationally simple and broad in scope while providing succinct and scalable avenues to previously reported synthetic intermediates.DeCarbonylative Alkynylationalkynylation; homologation; iron catalysis; nickel catalysis; redox-active esters83201773#N/ATRUE
533
anie.20141032210.1002/anie.201410322DehydrogenativeTRUEhttps://doi.org/10.1002/anie.201410322Dong, VMAngew. Chem.-Int. Edit.By exploring a new mode of nickel-catalyzed cross-coupling, a method to directly transform both aromatic and aliphatic aldehydes into either esters or amides has been developed. The success of this oxidative coupling depends on the appropriate choice of catalyst and organic oxidant, inCluding the use of either ,,-trifluoroacetophenone or excess aldehyde. Mechanistic data that supports a catalytic cyCle involving oxidative addition into the aldehyde CH bond is also presented.Nickel-Catalyzed Dehydrogenative Cross-Coupling: Direct Transformation of Aldehydes into Esters and Amidesamides; cross-coupling; dehydrogenation; esters; nickelCsp2-Csp3HHH
Carbonyl
No baseNo Base1132015867/6/2022TRUE
534
acscatal.0c0211510.1021/acscatal.0c02115Dicarbofunctionalizationhttps://doi.org/10.1021/acscatal.0c02115Diao, TNACS Catal.1,2-Dicarbofunctionalization of alkenes has emerged as an efficient synthetic strategy for preparing substituted molecules by coupling readily available alkenes with electrophiles and/or nuCleophiles. Nickel complexes serve as effective catalysts owing to their tendency to undergo facile oxidative addition and slow beta-hydride elimination, and their capability to access both two-electron and radical pathways. Two-component alkene functionalization reactions have achieved high chemo-, regio-, and stereoselectivities by tethering one of the coupling partners to the alkene substrate. Three-component reactions, however, often incorporate directing groups to control the selectivity. Only a few examples of directing-group-free difunctionalizations of unactivated alkenes have been reported. Therefore, great opportunities exist for the development of three-component difunctionalization reactions stereoselectivities.Nickel-Catalyzed Dicarbofunctionalization of Alkenesdicarbofunctionalization; nickel catalysis; alkenes; selectivity332020136#N/ATRUE
535
jacs.9b0924510.1021/jacs.9b09245DifunctionalizationFALSEhttps://doi.org/10.1021/jacs.9b09245Newhouse, TRJ. Am. Chem. Soc.This report demonstrates the possibility of a nickel-catalyzed difunctionalization of unactivated alkenes initiated by an unstabilized enolate nuCleophile. The process tolerates a diverse range of electrophiles, inCluding Aryl, heteroAryl, alkenyl, and amino electrophiles. An electron-deficient phosphine ligand and a tetrabutylammonium salt additive were crucial for promoting efficient vicinal difunctionalization.Nickel-Catalyzed Difunctionalization of Unactivated Alkenes Initiated by Unstabilized Enolates16201962#N/ATRUE
536
jacs.7b1248610.1021/jacs.7b12486Doyle–Kirmse ReactionFALSEhttps://doi.org/10.1021/jacs.7b12486Feng, XMJ. Am. Chem. Soc.Although high enantioselectivity of [2,3]-sigmatropic rearrangement of sulfonium ylides (Doyle-Kirmse reaction) has proven surprisingly elusive using Classic chiral Rh(II) and Cu(I) catalysts, in principle it is due to the difficulty in fine discrimination of the heterotopic lone pairs of sulfur and chirality inversion at sulfur of sulfonium ylides. Here, we show that the synergistic merger of new alpha-diazo pyrazoleamides and a chiral N, N'-dioxide-nickel(II) complex catalyst enables a highly enantioselective Doyle-Kirmse reaction. The pyrazoleamide substituent serves as both an activating and a directing group for the ready formation of a metal-carbene- and Lewis-acid-bonded ylide intermediate in the assistance of a dual-tasking nickel(II) complex. An alternative chiral Lewis-acid-bonded ylide pathway greatly improves the product enantiopurity even for the reaction of a symmetric diallylsulfane. The majority of transformations over a series of Aryl- or Vinyl-substituted a-diazo pyrazoleamindes and sulfides proceed rapidly (within 5-20 min in most cases) with excellent results (up to 99% yield and 96% ee), providing a breakthrough in enantioselective Doyle-Kirmse reaction.Chiral Nickel(II) Complex Catalyzed Enantioselective Doyle-Kirmse Reaction of alpha-Diazo Pyrazoleamides60201849#N/ATRUE
537
jacs.9b0689610.1021/jacs.9b06896EliminationFALSEhttps://doi.org/10.1021/jacs.9b06896Sanford, MSJ. Am. Chem. Soc.The treatment of pyridine- and pyrazole-ligated Ni-II sigma-Aryl complexes with Selectfluor results in C(sp(2))-F bond formation under mild conditions. With appropriate design of supporting ligands, diamagnetic Ni-IV sigma-Aryl fluoride intermediates can be detected spectroscopically and/or isolated during these transformations. These studies demonstrate for the first time that Ni-IV sigma-Aryl fluoride complexes participate in challenging C(sp(2))-F bond-forming reductive elimination to yield Aryl fluoride products.Aryl-Fluoride Bond-Forming Reductive Elimination from Nickel(IV) Centers15201969#N/ATRUE
538
jacs.8b0940110.1021/jacs.8b09401EliminationFALSEhttps://doi.org/10.1021/jacs.8b09401Giri, RJ. Am. Chem. Soc.We disClose unprecedented synergistic bimetallic Ni/Ag and Ni/Cu catalysts for regioselective ykdiArylation of unactivated alkenes in simple ketimines with Aryl halides and Arylzinc reagents. The bimetallic synergy, which generates cationic Ni(II) species during reaction, promotes migratory insertion and transmetalation steps and suppresses beta-H elimination and cross coupling, the major side reactions that cause serious problems during alkene difunctionalization. This diArylation reaction proceeds at remote locations to imines to afford, after simple H+ workup, diversely substituted gamma,delta-diAryl ketones that are otherwise difficult to access readily with existing methods.Synergistic Bimetallic Ni/Ag and Ni/Cu Catalysis for Regioselective gamma,delta-DiArylation of Alkenyl Ketimines: Addressing beta-H Elimination by in Situ Generation of Cationic Ni(II) Catalysts55201868#N/ATRUE
539
jacs.7b0557410.1021/jacs.7b05574EliminationFALSEhttps://doi.org/10.1021/jacs.7b05574Johnson, SAJ. Am. Chem. Soc.The reaction of C6F5H and H2C CHSiMe3 with catalytic [(i)Pr(2)Im]Ni(eta(2)-H2C CHSiMe3)(2) (1b) exClusively forms the C-H silylation product C6F5SiMe3 with ethylene as a byproduct ([(i)Pr(2)Im] = 1,3-di(isopropyl)imidazole-2-ylidene). Catalytic C-H bond silylation is facile with partially fluorinated aromatic substrates containing two ortho fluorine substituents adjacent to the C-H bond and 1,2,3,4-tetrafluorobenzene. Less fluorinated substrates react slower. Under the same reaction conditions, catalytic [IPr]Ni(eta(2)-H2C=CHSiMe3)(2) (1a) ([IPr] = 1,3-bis [2,6-diisopropylphenyl]-1,3-dihydro-2H-imidazol-2-ylidene) provided only the alkene hydroArylation product C6F5CH2CH2SiMe3. Mechanistic studies reveal that the C-H Activation and beta-Si elimination steps are reversible under catalytic conditions with both catalysts la and 1b. With catalytic la, reversible ethylene loss after beta-Si elimination was also observed despite its inability to catalyze C-H silylation; the reductive elimination step to form the silylation product is much slower than reductive elimination to form the alkene hydroArylation product. Reversible ethylene loss was not observed with 1b, which suggests that the rate-limiting step in the reaction is neither C-H Activation nor beta-Si elimination but either ethylene loss or reductive elimination of cis-disposed Aryl and SiMe3 moieties.Nickel-Catalyzed C-H Silylation of Arenes with Vinylsilanes: Rapid and Reversible beta-Si Elimination25201792#N/ATRUE
540
jacs.6b1035010.1021/jacs.6b10350EliminationFALSEhttps://doi.org/10.1021/jacs.6b10350Sanford, MSJ. Am. Chem. Soc.This manuscript describes the design, synthesis, characterization, and reactivity studies of organometallic Ni-III complexes of general structure TpNi(III)(R)(R-1) (Tp = tris(pyrazolyl)borate). With appropriate selection of the R and R-1 ligands, the complexes are stable at room temperature and can be characterized by cyClic voltammetry, EPR spectroscopy, and X-ray crystallography. Upon heating, many of these Ni-III compounds undergo C(sp(2))-C(sp(2)) or C(sp(3))-C(sp(2)) bond-forming reactions that are challenging at lower oxidation states of nickel.Carbon-Carbon Bond-Forming Reductive Elimination from Isolated Nickel(III) Complexes62201655#N/ATRUE
541
jacs.6b0001610.1021/jacs.6b00016EliminationFALSEhttps://doi.org/10.1021/jacs.6b00016Diao, TNJ. Am. Chem. Soc.Ni-catalyzed cross-coupling reactions have found important applications in organic synthesis. The fundamental characterization of the key steps in cross-coupling reactions, inCluding C-C bond-forming reductive elimination, represents a significant challenge. Bimolecular pathways were invoked in early proposals, but the experimental evidence was limited. We present the preparation of well-defined (pyridine-pyrrolyl)Ni monomethyl and monophenyl complexes that allow the direct observation of bimolecular reductive elimination to generate ethane and biphenyl, respectively. The sp(3)-sp(3) and sp(2)-sp(2) couplings proceed via two distinct pathways. Oxidants promote the fast formation of Ni(III) from (pyridine-pyrrolyl)Ni-methyl, which dimerizes to afford a bimetallic Ni(III) intermediate. Our data are most consistent with the subsequent methyl coupling from the bimetallic Ni(III) to generate ethane as the rate-determining step. In contrast, the formation of biphenyl is facilitated by the coordination of a bidentate donor ligand.Bimetallic C-C Bond-Forming Reductive Elimination from Nickel44201669#N/ATRUE
542
jacs.0c0330410.1021/jacs.0c03304EliminationFALSEhttps://doi.org/10.1021/jacs.0c03304Shen, QLJ. Am. Chem. Soc.The reductive elimination from a high-valent late-transition-metal complex for the formation of a carbon-carbon or carbon heteroatom bond represents a fundamental product-forming step in a number of catalytic processes. Wbile reductive eliminations from well-defined Pt(IV), Pd(IV), Ni(III)/Ni(IV), and Au(III) complexes have been studied, the analogous reactions from neutral Cu(III) complexes remain largely unexplored. Herein, we report the isolation of a stable, five-coordinate, neutral square pyramidal Cu(III) complex that gives CH3-CF3 in quantitative yield via reductive elimination. Mechanistic studies suggest that the reaction occurs through a synchronous bond-breaking/bond-forming process via a three-membered ring transition state.C(sp(3))-CF3 Reductive Elimination from a Five -Coordinate Neutral Copper(III) Complex15202048#N/ATRUE
543
ja971499910.1021/ja9714999EliminationFALSEhttps://doi.org/10.1021/ja9714999Hillhouse, GLCarbon-oxygen reductive-elimination from nickel(II) oxametallacyCles and factors that control formation of ether, aldehyde, alcohol, or ester products1997#N/ATRUE
544
ja903833u10.1021/ja903833uEliminationFALSEhttps://doi.org/10.1021/ja903833uLei, AWJ. Am. Chem. Soc.For a direct quantitative investigation of the Csp(2)-Csp(2) reductive elimination rate within a catalytic cyCle, a novel oxidative coupling system in the presence of a Ni catalyst and desyl chloride as the oxidant is devised. The reaction progress profiles of Arylzinc reagents exhibit zero-order kinetic behavior, and a reductive elimination step is confirmed as the rate-determining step. This allows direct measurement of the Csp(2)-Csp(2) reductive elimination rate constant within a catalytic cyCle. The rate constants of p-MePhZnX are obtained in the range 0.23 to 3.5 s(-1) from 0 to -35 degrees C, which are unusually fast reaction rates. According to the Arhenius equation, the values of Delta H-double dagger and Delta S-double dagger (Delta H-double dagger = 9.7 kcal mo(-1), Delta S-double dagger = 35 J mo(-1) K-1) are obtained. The small value of Delta H-double dagger reveals that the reductive elimination step of Csp(2)-Ni-Csp(2) is an extremely facile process.What is the Rate of the Csp(2)-Csp(2) Reductive Elimination Step? Revealing an Unusually Fast Ni-Catalyzed Negishi-Type Oxidative Coupling Reaction31200921#N/ATRUE
545
ja408084j10.1021/ja408084jEliminationFALSEhttps://doi.org/10.1021/ja505576gZhou, HCConstruction of Ultrastable Porphyrin Zr Metal-Organic Frameworks through Linker Elimination2013#N/ATRUE
546
ja067845g10.1021/ja067845gEliminationFALSEhttps://doi.org/10.1021/ja067845gRovis, TJ. Am. Chem. Soc.Results from a mechanistic study on the Ni(COD)(2)-bipy-catalyzed Alkylation of anhydrides are consistent with turnover-limiting reductive elimination at high Et2Zn concentrations. While the presence of styrene does not affect the initial rate of Alkylation, it appears to inhibit catalyst decomposition and provides higher product yield at long reaction times. In contrast, Ni(COD)(2)-(PrPHOX)-Pr-i-catalyzed anhydride Alkylation proceeds through two competing catalytic cyCles differentiated by the presence of styrene. The presence of styrene in this system appears to accelerate rate-limiting oxidative addition and promotes the cyCle which proceeds 4 times more rapidly and with much higher enantioselectivity than its styrene-lacking counterpart.Ligand-dependent catalytic cyCle and role of styrene in nickel-catalyzed anhydride cross-coupling: Evidence for turnover-limiting reductive elimination60200757#N/ATRUE
547
ja036751t10.1021/ja036751tEliminationFALSEhttps://doi.org/10.1021/ja036751tMarek, IJ. Am. Chem. Soc.Several dienyl zirconocene derivatives were easily prepared, as unique geometrical isomers, from simple non-conjugated unsaturated enol ethers with (1-butene)ZrCP2 complexes. This new methodology is based on a tandem allylic C-H bond Activation-elimination sequence and the mechanism has been mapped out by deuterium labeling experiments. The stereochemical outcome of this process was determined by addition of several electrophiles. Moreover, when the organometallic derivative is Vinylic as well as allylic such as in 44-47Zr, an unexpected reversal of the stereochemistry has been found during the zirconium to copper transmetalation step.Stereoselective preparation of dienyl zirconocene complexes via a tandem allylic C-H bond Activation-elimination sequence65200374#N/ATRUE
548
ja00277a02210.1021/ja00277a022EliminationFALSEhttps://doi.org/10.1021/ja00277a022ROE, DCJ. Am. Chem. Soc.THE MECHANISM OF NICKEL-CATALYZED ETHYLENE HYDROCYANATION - REDUCTIVE ELIMINATION BY AN ASSOCIATIVE PROCESS46198658#N/ATRUE
549
ja00226a06710.1021/ja00226a067EliminationFALSEhttps://doi.org/10.1021/ja00226a067MURAI, SJ. Am. Chem. Soc.AN UNUSUALLY LOWER BARRIER TO REDUCTIVE ELIMINATION OF AN 18-ELECTRON ETA-3-ALLYL(ORGANO)NICKEL(II) COMPLEX THAN THOSE OF A 16-ELECTRON ETA-3-ALLYL COUNTERPART AND A 16-ELECTRON ETA-1-ALLYL ISOMER33198829#N/ATRUE
550
c5sc02553b10.1039/c5sc02553bEliminationFALSEhttps://doi.org/10.1039/c5sc02553bOsuka, AChem. Sci.2-Borylated porphyrins reacted with Pt(cod)Cl-2 to give beta-to-beta platinum-bridged porphyrin dimers, which were converted to beta-to-beta directly linked porphyrin dimers through triphenylphosphine-mediated reductive elimination. Similar reactions of 2,18-diborylated Ni(II)-porphyrin and Zn(II)-porphyrin gave the corresponding doubly beta-to-beta platinum-bridged porphyrin dimers. Treatment of the doubly beta-to-beta platinum-bridged Ni(II)-porphyrin dimer with triphenylphosphine caused a single reductive elimination to produce a Ni(II)-porphyrin dimer possessing a beta-to-beta platinum bridge and a beta-to-beta direct C-C bond.Singly and doubly beta-to-beta platinum-bridged porphyrin dimers and their reductive eliminations9201534#N/ATRUE
551
anie.20191393010.1002/anie.201913930EliminationFALSEhttps://doi.org/10.1002/anie.201913930Ackermann, LAngew. Chem.-Int. Edit.Nickela-electrooxidative C-H alkoxylations with challenging secondary alcohols were accomplished in a fully dehydrogenative fashion, thereby avoiding stoichiometric chemical oxidants, with H-2 as the only stoichiometric byproduct. The nickela-electrocatalyzed oxygenation proved viable with various (hetero)arenes, inCluding naturally occurring secondary alcohols, without racemization. Detailed mechanistic investigation, inCluding DFT calculations and cyClovoltammetric studies of a well-defined C-H activated nickel(III) intermediate, suggest an oxidation-induced reductive elimination at nickel(III).Nickela-electrocatalyzed C-H Alkoxylation with Secondary Alcohols: Oxidation-Induced Reductive Elimination at Nickel(III)C-H alkoxylation; electrocatalysis; electrochemistry; nickel; oxygenation392020146#N/ATRUE
552
anie.20170155210.1002/anie.201701552EliminationFALSEhttps://doi.org/10.1002/anie.201701552Ritter, TAngew. Chem.-Int. Edit.We report a C-F reductive elimination from a characterized first-row Aryl metal fluoride complex. Reductive elimination from the presented nickel(III) complexes is faster than C-F bond formation from any other characterized Aryl metal fluoride complex.Carbon-Fluorine Reductive Elimination from Nickel(III) ComplexesAryl fluorides; fluorination; nickel; reductive elimination28201748#N/ATRUE
553
anie.20160256610.1002/anie.201602566EliminationFALSEhttps://doi.org/10.1002/anie.201602566Diao, TNAngew. Chem.-Int. Edit.Natural products containing N-N bonds exhibit important biological activity. Current methods for constructing N-N bonds have limited scope. An advanced understanding of the fundamental N-N bond formation/Cleavage processes occurring at the transition-metal center would facilitate the development of catalytic reactions. Herein we present an N-N bond-forming reductive elimination, which proceeds via a mixed-valent Ni-II-Ni-III intermediate with a Ni-Ni bond order of zero. The discrete Ni-II-Ni-III oxidation states contrast with the cationic dimeric Ni analogue, in which both Ni centers are equivalent with an oxidation state of 2.5. The electronic structures of these mixed-valent complexes have implications for the fundamental understanding of metal-metal bonding interactions.N-N Bond Forming Reductive Elimination via a Mixed-Valent Nickel(II)-Nickel(III) Intermediatemetal-metal bonding; mixed-valent compounds; nickel; N-N bond formation; reductive elimination22201666#N/ATRUE
554
anie.20070068810.1002/anie.200700688EliminationFALSEhttps://doi.org/10.1002/anie.200700688Kurosawa, HAngew. Chem.-Int. Edit.Formation of an aza-nickelacyCle by reaction of an imine and an alkyne with nickel(0): Oxidative cyClization, insertion, and reductive eliminationalkynes; cyCloaddition; imines; metallacyCles; nickel76200723#N/ATRUE
555
anie.19891035110.1002/anie.198910351EliminationFALSEhttps://doi.org/10.1002/anie.198910351GUHL, DAngew. Chem.-Int. Edit. Engl.NICKEL(0)-CATALYZED PREPARATION OF ISOMERIC CARboxAMIDES - LIGAND-CONTROLLED BETA-H OR BETA'-H ELIMINATION1719893#N/ATRUE
556
acscatal.9b0382710.1021/acscatal.9b03827EliminationFALSEhttps://doi.org/10.1021/acscatal.9b03827Chen, HACS Catal.Reactivity of electronically excited base transition metals is an emerging frontier wherein mechanistic understanding is highly desired but mostly lacking. To reveal how C-O bond coupling reductive elimination (RE) is stimulated by excited Ni-II [Welin, E. R.; Le, C.; Arias-Rotondo, D. M.; McCusker, J. K.; MacMillan, D. W. C. Science 2017, 355, 380], we report here high-level theoretical modellings based on a combined ab initio protocol (CASSCF, CASPT2, DLPNO-CCSD(T)). In contrast to the experimental proposal of the d-d excited state, we find that the metal-to-ligand charge transfer (MLCT) excited state is most likely to stimulate the C-O coupling RE. This unprecedented assignment of the reactive excited state not only obviates the known thermodynamic prohibition of C-O coupling by ground state Ni-II, but also matches the experimental triplet energy requisite for energy transfer. In addition, the enhanced RE reactivity in excited Ni-II can be well rationalized by the Ni-III character of the MLCT state. The resolution of this intriguing mechanistic puzzle in the excited-state chemistry of a Ni-II complex underscores the potential of multireference methods in this field.Reactivity of Transition-Metal Complexes in Excited States: C-O Bond Coupling Reductive Elimination of a Ni(II) Complex Is Elicited by the Metal-to-Ligand Charge Transfer Statephotocatalysis; energy transfer; nickel catalysis; excited state; reductive elimination; metal-to-ligand charge transfer state; d-d excited state; C-O coupling12202071#N/ATRUE
557
acscatal.0c0061810.1021/acscatal.0c00618EliminationFALSEhttps://doi.org/10.1021/acscatal.0c00618Jugovic, TMEACS Catal.Quantum chemical models of reaction pathways can provide deep insight into the inner workings of transition metal complexes. Often, these simulations have relied on atomistic models where a single or a few conformational isomers of the complex are investigated. This ArtiCle will show that, for bisphosphine Ni complexes used to forge C-C bonds, a large number of conformers must be studied to provide confidence that the overall model is meaningful. Not only do conformer effects modify particular reaction barriers, but often the lowest barrier reaction pathway proceeds from a conformer that is not the lowest energy conformer. This finding suggests that errors on the order of more than a few kcal/mol could be present in single-conformer studies. The particular reaction pathway and conformer preferences for a series of eight common Ni bisphosphine complexes will provide some guidance as to when the effects of the conformer will be large or small.Revealing the Strong Relationships between Ligand Conformers and Activation Barriers: A Case Study of Bisphosphine Reductive Eliminationquantum chemical model; reaction pathway; transition metal complexes; bisphosphine nickel complex; conformer effects6202088#N/ATRUE
558
ja101707810.1021/ja1017078elimination (no C-N Activation inCluded)FALSEhttps://doi.org/10.1021/ja1017078Hiyama, TJ. Am. Chem. Soc.Alkanenitriles having a heteroatom such as nitrogen, oxygen, and sulfur at the gamma-position are found to add across alkynes stereo- and regioselectively by nickel/Lewis acid catalysis to give highly substituted acrylonitriles. The heteroatom functionalities likely coordinate to the nickel center to make oxidative addition of the C-CN bonds of the Alkyl cyanides kinetically favorable, forming a five-membered nickelacyCle intermediate and, thus, preventing beta-hydride elimination to allow the Alkylcyanation reaction.Heteroatom-Directed Alkylcyanation of Alkynes94201028#N/ATRUE
559
jacs.0c1303410.1021/jacs.0c13034EnantioconvergentFALSEhttps://doi.org/10.1021/jacs.0c13034Fu, GCJ. Am. Chem. Soc.Chiral diAlkyl carbinamines are important in fields such as organic chemistry, pharmaceutical chemistry, and bio-chemistry, serving for example as bioactive molecules, chiral ligands, and chiral catalysts. Unfortunately, most catalytic asymmetric methods for synthesizing diAlkyl carbinamines do not provide general access to amines wherein the two Alkyl groups are of similar size (e.g., CH2R versus CH2R1). Herein, we report two mild methods for the catalytic enantioconvergent synthesis of protected diAlkyl carbinamines, both of which use a chiral nickel catalyst to couple an Alkylzinc reagent (1.1-1.2 equiv) with a racemic partner, specifically, an a-phthalimido Alkyl chloride or an N-hydroxyphthalimide (NHP) ester of a protected alpha-amino acid. The methods are versatile, providing diAlkyl carbinamine derivatives that bear an array of functional groups. For couplings of NHP esters, we further describe a one-pot variant wherein the NHP ester is generated in situ, allowing the generation of enantioenriched protected diAlkyl carbinamines in one step from commercially available amino acid derivatives; we demonstrate the utility of this method by applying it to the efficient catalytic enantioselective synthesis of a range of interesting target molecules.The Asymmetric Synthesis of Amines via Nickel-Catalyzed Enantioconvergent Substitution Reactions3202145#N/ATRUE
560
acscatal.6b0202810.1021/acscatal.6b02028
Fragmentation
FALSEhttps://doi.org/10.1021/acscatal.6b02028Hartwig, JFACS Catal.We report the reagentless Cleavage of prevalent beta-O-4 linkages in lignin model compounds, as well as the Cleavage of several types of organosolv lignins, catalyzed by commercially available Pd/C. Such lignin fragmentation occurred without added reagent if the indigenous double bonds were reduced first or it occurred under conditions in which just 1 atm of hydrogen was added to the system to reduce C=C bonds of the original lignin sample in situ prior to fragmentation. A detailed view of the sites of Cleavage of lignin samples from various sources was gained by HSQC NMR experiments. Complex model compounds were prepared and shown to form simpler arenes and substituted phenols HO under catalytic conditions without added reagents. The hydrogen generated in situ from alcohol functionalities provides the reductant for concomitant hydrogenolysis of C-O bonds in beta Aryl ethers. DeCarbonylation of primary alcohols also occurred, and this process resulted in significant amounts of aromatic products containing substituents bearing one fewer carbon atom than the original linkages in lignin. The fragmentations of synthetic lignin and several organosolv lignins derived from Miscanthus giganteus and pine tree were conducted. Because the lignins contain alkenes that accept the hydrogen, two procedures involving reduction of the alkenes prior to C-O bond Cleavage were developed. The first procedure involves reduction of the alkenes, followed by catalytic Cleavage of C-O bonds after saturation of the C-C bonds; a second involves Cleavage of lignin samples in the presence of 1 atm of hydrogen to saturate the alkenes before Cleavage in situ. These protocols convert solid lignin to monomeric phenolic compounds with 20 mol % catalyst or to an oil (with 5 mol % Pd/C loading) having favorable viscosity parameters upon blending with a renewable organic solvent.Fragmentation of Lignin Samples with Commercial Pd/C under Ambient Pressure of Hydrogenheterogeneous catalysis; palladium on carbon; lignin; Miscanthus giganteus; beta-O-4 linkages51201657#N/ATRUE
561
s41467-018-04645-310.1038/s41467-018-04645-3G: AdditionFALSEhttps://doi.org/10.1038/s41467-018-04645-3Zhang, WBNat. Commun.Chiral allylic amines are not only present in many bioactive compounds, but can also be readily transformed to other chiral amines. Therefore, the asymmetric synthesis of chiral allylic amines is highly desired. Herein, we report two types of Ni(II)-catalyzed asymmetric alkenylation of cyClic ketimines for the preparation of chiral allylic amines. When ketimines bear Alkyl or alkoxyCarbonyl groups, the alkenylation gives five-and six-membered cyClic atertiary allylic amine products with excellent yields and enantioselectivities under mild reaction conditions. A variety of ketimines can be used and the method tolerates some variation in alkenylboronic acid scope. Furthermore, with alkenyl five-membered ketimine substrates, an alkenylation/ rearrangement reaction occurs, providing seven-membered chiral sulfamide products bearing a conjugated diene skeleton with excellent yields and enantioselectivities. Mechanistic studies reveal that the ring expansion step is a stereospecific siteselective process, which can be catalyzed by acid (Lewis acid or Bronsted acid).Ni(II)-catalyzed asymmetric alkenylations of ketimines27201870#N/ATRUE
562
jacs.7b0634010.1021/jacs.7b06340G: AdditionFALSEhttps://doi.org/10.1021/jacs.7b06340Giri, RJ. Am. Chem. Soc.We disClose a strategy for Ni-catalyzed dicarbofunctionalization of olefins in styrenes by intercepting Heck C(sp(3))-NiX intermediates with Arylzinc reagents. This approach utilizes a readily removable imine as a coordinating group that plays a dual role of intercepting oxidative addition species derived from Aryl halides and triflates to promote Heck carbometalation and stabilizing the Heck C(sp(3))-NiX intermediates as transient metallacyCles to suppress beta-hydride elimination and facilitate transmetalation/reductive elimination steps. This method affords diversely substituted 1,1,2-triArylethyl products that occur as structural motifs in various natural products.Ni-Catalyzed Regioselective 1,2-Dicarbofunctionalization of Olefins by Intercepting Heck Intermediates as Imine-Stabilized Transient MetallacyCles110201765#N/ATRUE
563
jacs.7b0271010.1021/jacs.7b02710G: AdditionFALSEhttps://doi.org/10.1021/jacs.7b02710Mashima, KJ. Am. Chem. Soc.A d(0) niobium(V) complex, NbCl3(alpha-diimine) (1a), supported by a dianionic redox-active N,Ni-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene (alpha-diimine) ligand (ene-diamido ligand) served as a catalyst for radical addition reactions of CC14 to alpha-olefins and cyClic alkenes, selectively affording 1:1 radical addition products in a regioselective manner. During the catalytic reaction, the alpha-diimine ligand smoothly released and stored an electron to control the oxidation state of the niobium center by changing between an eta(4)-(sigma(2),pi) coordination mode with a folded MN2C2 metallacyCle and a kappa(2)-(N,N') coordination mode with a planar MN2C2 metallacyCle. Kinetic studies of the catalytic reaction elucidated the reaction order in the catalytic cyCle: the radical addition reaction rate obeyed first-order kinetics that were dependent on the concentrations of the catalyst, styrene, and CCl4, while a saturation effect was observed at a high CCl4 concentration. In the presence of excess amounts of styrene, styrene coordinated in an eta(2)-olefmic manner to the niobium center to decrease the reaction rate. No observation of oligomers or polymers of styrene and high stereoselectivity for the radical addition reaction of CCl4 to cyClopentene suggested that the C-C bond formation proceeded inside the coordination sphere of niobium, which was in good accordance with the negative entropy value of the radical addition reaction. Furthermore, reaction of la with (bromomethyl)cyClopropane confirmed that both the C Br bond Activation and formation proceeded on the alpha-diimine-coordinated niobium center during transformation of the cyClopropylmethyl radical to a homoallyl radical. With regard to the reaction mechanism, we detected and isolated NbCl4(adiimine) (6a) as a transient one-electron oxidized species of la during reductive Cleavage of the C-X bonds; in addition, the monoanionic a-diimine ligand of 6a adoptedStructural and Electronic Noninnocence of alpha-Diimine Ligands on Niobium for Reductive C-Cl Bond Activation and Catalytic Radical Addition Reactions352017176#N/ATRUE
564
jacs.6b1035110.1021/jacs.6b10351G: AdditionFALSEhttps://doi.org/10.1021/jacs.6b10351Martin, RJ. Am. Chem. Soc.A catalytic hydroamidation of alkynes with isocyanates using Alkyl bromides as hydride sources has been developed. The method turns parasitic beta-hydride elimination into a strategic advantage, rapidly affording acrylamides with excellent chemo- and regioselectivity.Alkyl Bromides as Mild Hydride Sources in Ni-Catalyzed Hydroamidation of Alkynes with Isocyanates49201657#N/ATRUE
565
ja052935r10.1021/ja052935rG: AdditionFALSESeidel, DNi(II)-bis[(R,R)-N,N '-diBenzylcyClohexane-1,2-diamine]Br-2 catalyzed enantioselective Michael additions of 1,3-diCarbonyl compounds to conjugated nitroalkenes2005#N/ATRUE
566
c9sc04177j10.1039/c9sc04177jG: AdditionFALSEhttps://doi.org/10.1039/c9sc04177jZhou, QLChem. Sci.Transition-metal-catalyzed hydrofunctionalization of 1,3-dienes is a useful and atom-economical method for constructing allylic compounds. Although substantial progress on hydroAlkylation of dienes with stabilized carbon nuCleophiles has been made, hydroAlkylation of dienes with unstabilized carbon nuCleophiles has remained a challenge. In this artiCle, we report a protocol for nickel-catalyzed hydroAlkylation of dienes with hydrazones, which serve as equivalents of Alkyl carbon nuCleophiles. In addition, we developed a protocol for hydroalkenylation of dienes with alpha,beta-unsaturated hydrazones, providing a new method for the synthesis of 1,4-dienes. These hydroAlkylation and hydroalkenylation reactions feature mild conditions and a wide substrate scope, and the utility of the reaction products is demonstrated by the preparation of an activator of soluble guanylate cyClase.Nickel-catalyzed hydroAlkylation and hydroalkenylation of 1,3-dienes with hydrazones12201955#N/ATRUE
567
anie.20171333310.1002/anie.201713333G: AdditionFALSEhttps://doi.org/10.1002/anie.201713333Zhou, QLAngew. Chem.-Int. Edit.A nickel(0)-catalyzed hydroalkenylation of imines with styrene and its derivatives is described. A wide range of aromatic and aliphatic imines directly coupled with styrene and its derivatives, thus providing various synthetically useful allylic amines with up to 95% yield. The reaction offers a new atom- and step-economical approach to allylic amines by using alkenes instead of alkenyl-metallic reagents. Experiments and DFT calculations showed that TsNH2 promotes the proton transfer from the coordinated olefin to the imine, accompanied by a new C-C bond formation.Nickel(0)-Catalyzed Hydroalkenylation of Imines with Styrene and Its Derivativesalkenes; allylic compounds; imines; nickel; reaction mechanisms21201872#N/ATRUE
568
anie.20080082510.1002/anie.200800825G: AdditionFALSEhttps://doi.org/10.1002/anie.200800825Cheng, CHAngew. Chem.-Int. Edit.Regioselective synthesis of gamma-amino esters, nitriles, sulfones, and pyrrolidinones by nickel-catalyzed reductive coupling of aldimines and activated alkenescross-coupling; homogeneous catalysis; N ligands; nickel; pyrrolidinones40200865#N/ATRUE
569
acscatal.9b0159710.1021/acscatal.9b01597G: AdditionFALSEhttps://doi.org/10.1021/acscatal.9b01597Zhang, ZHACS Catal.A heterogeneous Ni catalyst was discovered to be active in the synthesis of secondary cross-imines via hydrogenative coupling of nitriles and amines. The mesoporous Al2O3-supported Ni nanopartiCles (abbreviated as Ni/m-Al2O3-600, where 600 represents the reduction temperature) were active in hydrogenative coupling of nitriles and amines reaction at 80 degrees C and 1 bar H-2, affording corresponding cross-imines with yields in the range 64.1-98.1%. Density functional theory calculations reveal the hydrogenation of benzonitrile (PhCN) to Benzylamine (PhCH2NH2) has higher Activation energy than that for hydrogenative cross-coupling of PhCN and RNH2 on the Ni/m-Al2O3-600 catalyst, suggesting the latter reaction is more favorable. The theoretical calculations are in good agreement with our experimental results.Synthesis of Secondary Aldimines from the Hydrogenative Cross-Coupling of Nitriles and Amines over Al2O3-Supported Ni Catalystsnickel catalysts; synthesis of secondary amines; cross-coupling; DFT calculations5201929#N/ATRUE
570
anie.20170318710.1002/anie.201703187G: AnnulationFALSEhttps://doi.org/10.1002/anie.201703187Ogoshi, SAngew. Chem.-Int. Edit.The nickel(0)-catalyzed Carbonylative cyCloaddition of 1,5- and 1,6-ene-imines with carbon monoxide (CO) is reported. Key to this reaction is the efficient regeneration of the catalytically active nickel(0) species from nickel Carbonyl complexes such as [Ni(CO)(3)L]. Avariety of tri-and tetracyClic gamma-lactams were thus prepared in excellent yields with 100% atom efficiency. Preliminary results on asymmetric derivatives promise potential in the synthesis of enantioenriched polycyClic gamma-lactams.Efficient Synthesis of PolycyClic gamma-Lactams by Catalytic Carbonylation of Ene-Imines via NickelacyCle IntermediatesCarbonylation; cyClization; enantioselectivity; heterocyCles; nickelx23201750#N/AFALSE
571
anie.20191313010.1002/anie.201913130G: AnnulationFALSEhttps://doi.org/10.1002/anie.201913130Li, XWAngew. Chem.-Int. Edit.Ni-0-catalyzed chemo- and enantioselective [3+2] cyCloaddition of cyClopropenones and alpha,beta-unsaturated ketones/imines is described. This reaction integrates C-C bond Cleavage of cyClopropenones and enantioselective functionalization by Carbonyl/imine group, offering a mild approach to gamma-alkenyl butenolides and lactams in excellent enantioselectivity (88-98 % ee) through intermolecular C-C Activation.Nickel(0)-Catalyzed Enantioselective [3+2] Annulation of CyClopropenones and alpha,beta-Unsaturated Ketones/IminescyClopropenones; enantioselective C-C Activation; enones; lactones; nickel13202084#N/ATRUE
572
anie.20150040410.1002/anie.201500404G: C-X ActivationFALSEhttps://doi.org/10.1002/anie.201500404Hartwig, JFAngew. Chem.-Int. Edit.The nickel-catalyzed amination of Aryl chlorides to form primary Arylamines occurs with ammonia or ammonium sulfate and a well-defined single-component nickel(0) precatalyst containing a Josiphos ligand and an eta(2)-bound benzonitrile ligand. This system also catalyzes the coupling of Aryl chlorides with gaseous amines in the form of their hydrochloride salts.Nickel-Catalyzed Amination of Aryl Chlorides with Ammonia or Ammonium Saltsamination; ammonia; Arylation; cross-coupling; nickel94201543#N/ATRUE
573
ja909689t10.1021/ja909689tG: CC couplingTRUEhttps://doi.org/10.1021/ja909689tFu, GCJ. Am. Chem. Soc.The first asymmetric Kumada reactions of Alkyl electrophiles are described, specifically, cross-couplings of racemic alpha-bromoketones with Aryl Grignard reagents. Several features of this investigation are of interest. First, the couplings proceed at remarkably low temperature (-40 or -60 degrees C), which enables the asymmetric synthesis of racemization-prone alpha-Arylketones. Second, diAlkyl ketones undergo enantioselective Coupling in good ee and yield. Third, readily available bis(oxazolines) are shown for the first time to be effective ligands for cross-couplings of Alkyl electrophiles, thereby opening the door to new opportunities in asymmetric catalysis.Nickel/Bis(oxazoline)-Catalyzed Asymmetric Kumada Reactions of Alkyl Electrophiles: Cross-Couplings of Racemic alpha-BromoketonesCsp3-Csp2_arXXMgXAllylNo baseNo Base1712010357/28/2022TRUE
574
c3sc52199k10.1039/c3sc52199kG: CC couplingFALSEhttps://doi.org/10.1039/c3sc52199kItami, KChem. Sci.A programmed synthesis of privileged Arylthiazoles via sequential C-H couplings catalyzed by palladium or nickel catalysts has been accomplished. This versatile protocol can supply all possible Arylthiazole substitution patterns (2-Aryl, 4-Aryl, 5-Aryl, 2,4-diAryl, 2,5-diAryl, 4,5-diAryl, and 2,4,5-triAryl) from an unfunctionalized thiazole platform by 11 distinct synthetic routes. We have generated over 150 Arylthiazoles by using this methodology. We have applied this method to the rapid synthesis of fatostatin (SREBP inhibitor), and the gram-scale synthesis of triArylthiazoles has been demonstrated.Programmed synthesis of Arylthiazoles through sequential C-H couplings160201473#N/ATRUE
575
anie.20170678110.1002/anie.201706781G: CC couplingFALSEhttps://doi.org/10.1002/anie.201706781Weix, DJAngew. Chem.-Int. Edit.A new method for the synthesis of terminal and internal alkynes from the nickel-catalyzed deCarbonylative coupling of N-hydroxyphthalimide esters and bromoalkynes is presented. This reductive cross-electrophile coupling is the first to use a C(sp)-X electrophile, and appears to proceed via an alkynylnickel intermediate. The internal alkyne products are obtained in yields of 41-95% without the need for a photocatalyst, light, or a strong oxidant. The reaction displays a broad scope of Carbonylic acid and alkyne coupling partners, and can tolerate an array of functional groups, inCluding carbamate NH, halogen, nitrile, olefin, ketone, and ester moieties. Mechanistic studies suggest that this process does not involve an alkynylmanganese reagent and instead proceeds through nickel-mediated bond formation.Reductive DeCarbonylative Alkynylation of N-Hydroxyphthalimide Esters with BromoalkynesAlkylation; alkynes; cross-coupling; cross-electrophile coupling; homogeneous catalysis60201798#N/ATRUE
576
ol800086s10.1021/ol800086sG: CyCloadditionFALSEhttps://doi.org/10.1021/ol800086sRovis, TEnantioselective synthesis of indolizidines bearing quaternary substituted stereocenters via rhodium-catalyzed [2+2+2] cyCloaddition of alkenyl isocyanates and terminal alkynes2008#N/ATRUE
577
ja982254e10.1021/ja982254eG: CyCloadditionFALSEhttps://doi.org/10.1021/ol702499hWada, EHighly endo- and enantioselective asymmetric nitrone cyCloadditions catalyzed by the aqua complex of 4,6-dibenzofurandiyl-2,2 '-bis (4-phenyl-oxazoline)-nickel(II) perchlorate. Transition structure based on dramatic effect of MS 4A on selectivities1998#N/ATRUE
578
ja903899c10.1021/ja903899cG: CyCloadditionFALSEhttps://doi.org/10.1021/ja903899cRovis, TJ. Am. Chem. Soc.A regioselective, rhodium-catalyzed cyCloaddition between a variety of internal, unsymmetrical alkynes is described. We document the impact of both steric and electronic properties of the alkyne on reaction course, efficiency, and enantioselectivity. The substituent that better stabilizes a positive charge or the larger group, all else being equal, inserts distal to the Carbonyl moiety in a predictable and controllable fashion. The reaction scope is broad and the enantioselectivities are high, providing an instruction manual for substrate choice when utilizing this reaction as a synthetic tool.Predictable and Regioselective Insertion of Internal Unsymmetrical Alkynes in Rhodium-Catalyzed CyCloadditions with Alkenyl Isocyanates61200953#N/ATRUE
579
ja200766k10.1021/ja200766kG: CyCloadditionFALSEhttps://doi.org/10.1021/ja200766kRovis, TEnantioselective Rhodium-Catalyzed [4+2] CyCloaddition of alpha,beta-Unsaturated Imines and Isocyanates2011#N/ATRUE
580
acscatal.8b0145410.1021/acscatal.8b01454G: CyCloadditionFALSEhttps://doi.org/10.1021/acscatal.8b01454Huang, YYACS Catal.The intermolecular [2 + 2] cyCloaddition/isomerization between allenyl imides and N-(2-methoxyphenyl) aldimine counterparts catalyzed by a Ni(ClO4)(2)center dot 6H(2)O Lewis acid at room temperature was discovered, providing a facile access to 1-azadiene derivatives with high atom economy. The incorporation of an 2-oxazolidinone group into allene amides resulted in unusual reactivity for the imine-metathesis and synthetic application to a chiral gamma,delta-unsaturated beta-ketoimide. A mechanistic experiment using density functional theory (DFT) computation in CH2Cl2 with the B3LYP functional rationalized the proposed catalytic pathway involving initial stepwise [2 + 2] cyCloaddition to provide an azetidine species, two-time proton transfer to form a 2-azetine intermediate, and final conrotatory ring opening for trans-1-azadiene-based substances.Intermolecular [2+2] CyCloaddition/lsomerization of Allenyl Imides and Unactivated Imines for the Synthesis of 1-Azadienes Catalyzed by a Ni(ClO4)(2)center dot 6H(2)O Lewis Acid[2+2] cyCloaddition; isomerization; allene; imine; azadiene; proton transfer; DFT calculations; gamma,delta-unsaturated beta-ketoester11201897#N/ATRUE
581
jacs.6b0153310.1021/jacs.6b01533G: DeCarbonylative AlkylidenationFALSEhttps://doi.org/10.1021/jacs.6b01533Weix, DJJ. Am. Chem. Soc.A new method for the deCarbonylative coupling of Alkyl N-hydroxyphthalimide esters (NHP esters) with Aryl iodides is presented. In contrast to previous studies that form Alkyl radicals from Carbonylic acid derivatives, no photocatalyst, light, or Arylmetal reagent is needed, only nickel and a reducing agent (Zn). Methyl, primary, and secondary Alkyl groups can all be coupled in good yield (77% ave yield). One coupling with an acid chloride is also presented. Stoichiometric reactions of (dtbbpy)Ni(2-tolyl)I with an NHP ester show for the first time that Arylnickel(II) complexes can directly react with NHP esters to form Alkylated arenes.DeCarbonylative Cross-Electrophile Coupling of N-Hydroxyphthalimide Esters with Aryl Iodides210201643#N/ATRUE
582
ja406817210.1021/ja4068172G: DeCarbonylative AlkylidenationFALSEhttps://doi.org/10.1021/ja4068172Matsubara, SJ. Am. Chem. Soc.We have developed a nickel-catalyzed transformation, in which phthalimides react with trimethylsilyl-substituted alkynes in the presence of Ni(0)/PMe3/MAD catalyst to provide isoindolinones. The reaction process displays an unusual mechanistic feature-deCarbonylation and Alkylidenation. The use of both trimethylsilyl-substiuted alkynes and MAD was found to be essential for the transformation with high selectivities.Nickel-Catalyzed DeCarbonylative Alkylidenation of Phthalimides with Trimethylsilyl-Substituted Alkynes45201337#N/ATRUE
583
s41467-021-23105-z10.1038/s41467-021-23105-zG:AdditionFALSEhttps://doi.org/10.1038/s41467-021-23105-zFeng, XMNat. Commun.Intermolecular addition of enols and enolates to unactivated alkynes was proved to be a simple and powerful method for carbon-carbon bond formation. Up to date, a catalytic asymmetric version of alkyne with 1,3-diCarbonyl compound has not been realized. Herein, we achieve the catalytic asymmetric intermolecular addition of 1,3-diCarbonyl compounds to unactivated 1-alkynes attributing to the synergistic Activation of chiral N,N-dioxide-indium(III) or nickel(II) Lewis acid and achiral gold(I) pi -acid. A range of beta -ketoamides, beta -ketoesters and 1,3-diketones transform to the corresponding products with a tetra-substituted chiral center in good yields with good e.r. values. Besides, a possible catalytic cyCle and a transition state model are proposed to illustrate the reaction process and the origin of chiral induction based on the experimental investigations.Although enols and enolates addition to unactivated alkynes is used for carbon-carbon bond modification a catalytic asymmetric alkyne with 1,3-diCarbonyl compound has been elusive. Here, the authors achieve this using the synergistic Activation of chiral N,N ' -dioxide-indium(III) or nickel(II) Lewis acid and achiral gold(I) pi -acid.Catalytic asymmetric Nakamura reaction by gold(I)/chiral N,N'-dioxide-indium(III) or nickel(II) synergistic catalysis0202152#N/ATRUE
584
jacs.0c0992210.1021/jacs.0c09922G:AdditionFALSEhttps://doi.org/10.1021/jacs.0c09922Koh, MJJ. Am. Chem. Soc.Multicomponent catalytic processes that can generate multiple C(sp(3))-C(sp(3)) bonds in a single step under mild conditions, particularly those that employ inexpensive catalysts and substrates, are highly sought-after in chemistry research for complex molecule synthesis. Here, we disClose an efficient Ni-catalyzed reductive protocol that chemoselectively merges alkenyl amides with two different aliphatic electrophiles. Starting materials are readily accessible from stable and abundant feedstock, and products are furnished in up to >98:2 regioisomeric ratios. The present strategy eliminates the use of sensitive organometallic reagents, tolerates a wide array of complex functionalities, and enables regiodivergent addition of two primary Alkyl groups bearing similar electronic and steric attributes across aliphatic C=C bonds with exquisite control of site selectivity. Utility is underscored by the concise synthesis of bioactive compounds and postreaction functionalizations leading to structurally diverse scaffolds. DFT studies revealed that the regiochemical outcome originates from the orthogonal reactivity and chemoselectivity profiles of in situ generated organonickel species.Chemoselective Union of Olefins, Organohalides, and Redox-Active Esters Enables Regioselective Alkene DiAlkylation5202075#N/ATRUE
585
jacs.0c0525410.1021/jacs.0c05254G:AdditionFALSEhttps://doi.org/10.1021/jacs.0c05254Nevado, CJ. Am. Chem. Soc.Alkene dicarbofunctionalizations enable the stream- lined construction of aliphatic structures and have thus been the subject of intense research efforts. Despite significant progress, catalytic asymmetric variants remain scarce. Inspired by the advantages of reductive cross-coupling approaches, we present here a highly efficient asymmetric intermolecular Ni-catalyzed reductive dicarbofunctionalization of alkenes. Two distinct readily available electrophiles, namely, Csp(2)- and Csp(3)-halides, are added simultaneously across a variety of olefins (Vinyl amides, Vinyl boranes, Vinyl phosphonates) at room temperature in a highly regioand enantioselective manner. The reaction, devoid of sensitive organometallic reagents, takes advantage of an in situ generated chiral Alkyl Ni(III)-intermediate to ensure a stereodefined outcome in the Csp(3)-Csp(2) bond-forming reaction. An (L)-(+)-isoleucine chiral bisoxazoline ligand and the presence of coordinating sites on the alkene are key for the successful outcome in these asymmetric radical relayed reductive couplings (ARRRCs). Further, multiple transformations of the chiral amides obtained in this process showcase the potential of this new methodology for the straightforward assembly of chiral building blocks such as primary and secondary amines and oxazolines, highlighting its synthetic utility.Asymmetric Ni-Catalyzed Radical Relayed Reductive Coupling41202084#N/ATRUE
586
ja309176h10.1021/ja309176hG:AdditionFALSEhttps://doi.org/10.1021/ja309176hWeix, DJJ. Am. Chem. Soc.An alternative method to copper-catalyzed conjugate addition followed by enolate silylation for the synthesis of beta-disubstituteCl silyl enol ether products (R-1(R-2)HCCH=C(OSiR34)R-3) is presented. This method uses haloarenes instead of nuCleophilic Aryl reagents. Nickel ligated to either neocuproine or bipyridine couples an alpha-beta-unsaturated ketone or aldehyde ((RHC)-H-2=CHC(O)R-3) with an organic halide (R-1-X) in the presence of a triAlkylchlorosilane reagent (Cl-SiR34). Reactions are assembled on the benchtop and tolerate a variety of functional groups (aldehyde, ketone, nitrile, sulfone, pentafluorosulfur, and N-Aryltrifluoroacetamide), electron-rich iodoarenes, and electron-poor haloarenes. Mechanistic studies have confirmed the first example of a catalytic reductive conjugate addition of organic halides that proceeds via an allylnickel intermediate. Selectivity is attributed to (1) rapid, selective reaction of LNi0 with chlorotriethylsilane and enone in the presence of other organic electrophiles, and (2) minimization of enone dimerization by ligand steric effects.Nickel-Catalyzed Reductive Conjugate Addition to Enones via Allylnickel Intermediates672013127#N/ATRUE
587
ja00482a06610.1021/ja00482a066G:AdditionFALSEhttps://doi.org/10.1021/ja00482a066Kong, WQACS Catal.Transition-metal-catalytic domino reactions represent important advances in synthetic organic chemistry. Their development benefits synthesis by providing highly efficient and step-economical methods to complex molecules with impressive selectivity. Herein, a Ni-catalyzed domino reductive cyClization of acrylamides with alkynyl bromides is reported, enabling rapid assembly of a range of substituted 2,3-fused cyClopentannulated indolines. Preliminary mechanistic studies revealed that tricyClic indolines are afforded through a highly regioselective migratory insertion of 1,3-diynes, which are formed from the homocoupling of alkynyl bromides, into the in situ generated sigma-Alkyl-Ni(II) species, followed by nuCleophilic addition of the resulting alkenyl nickel to unactivated amides. Most importantly, a highly regio- and enantioselective reductive cyClization of acrylamides and internal alkynes has also been developed. This transformation takes place under mild conditions with high efficiency, providing a rapid access to structurally diverse cyClopentannulated indolines in synthetically useful yields with high regioselectivity (>20/1) and enantioselectivity (27 examples, 82-96% ee).Ni-Catalyzed Regio- and Enantioselective Domino Reductive CyClization: One-Pot Synthesis of 2,3-Fused CyClopentannulated IndolinesNi catalysis; reductive cross-coupling; cyClization; enantioselectivity; 2,3-fused cyClopentannulated indoline; regioselectivity24201967#N/ATRUE
588
d1sc03121j10.1039/d1sc03121jG:AdditionFALSEhttps://doi.org/10.1039/d1sc03121jEngle, KMChem. Sci.We report a full account of our research on nickel-catalyzed Markovnikov-selective hydroArylation and hydroalkenylation of non-conjugated alkenes, which has yielded a toolkit of methods that proceed under mild conditions with alkenyl sulfonamide, ketone, and amide substrates. Regioselectivity is controlled through catalyst coordination to the native Lewis basic functional groups contained within these substrates. To maximize product yield, reaction conditions were fine-tuned for each substrate Class, reflecting the different coordination properties of the directing functionality. Detailed kinetic and computational studies shed light on the mechanism of this family of transformations, pointing to transmetalation as the turnover-limiting step.Directed Markovnikov hydroArylation and hydroalkenylation of alkenes under nickel catalysis067#N/ATRUE
589
c7sc03149a10.1039/c7sc03149aG:AdditionFALSEhttps://doi.org/10.1039/c7sc03149aZhao, YChem. Sci.Efficient difunctionalization of alkenes allows the rapid construction of molecular complexity from simple building blocks in organic synthesis. We present herein a nickel-catalyzed dicarbofunctionalization of alkenes using readily available organB(OH)2ronic acids and organic halides in a three-component fashion. In particular, an unprecedented regioselectivity of the 1,3-dicarbofunctionalization of N-allylpyrimidin-2-amine is achieved when Aryl and methyl iodides are utilized. In contrast, the use of Alkyl bromides with beta-hydrogens results in 1,3-hydroArylation or oxidative 1,3-diArylation. Preliminary mechanistic studies suggest an isomerization involving nickel hydride in the 1,3-difunctionalization reactions. On the other hand, the use of alkenyl or alkynyl halides promotes alternative regioselectivities to deliver 1,2-alkenylcarbonation or intriguing 2,1-alkynylcarbonation products. Such 2,1-alkynylArylation is also applicable to N-allylbenzamide as a different Class of substrates. Overall, this nickel-catalyzed process proves to be powerful in delivering versatile difunctionalized compounds using readily available reagents/catalysts and a simple procedure.Nickel-catalyzed difunctionalization of allyl moieties using organB(OH)2ronic acids and halides with divergent regioselectivities99201865#N/ATRUE
590
anie.20201502110.1002/anie.202015021G:AdditionFALSEhttps://doi.org/10.1002/anie.202015021Shi, SLAngew. Chem.-Int. Edit.A general, efficient, highly enantio- and chemoselective N-heterocyClic carbene (NHC)/Ni-catalyzed addition of readily available and stable Arylboronic esters to ketones is reported. This protocol provides unexpectedly fast access (usually 10 min) to various chiral tertiary alcohols with exceptionally broad substrate scope and excellent functional group tolerance (76 examples, up to 98 % ee). This process is orthogonal to other known Ni-mediated Suzuki-Miyaura couplings, as it tolerates Aryl chlorides, fluorides, ethers, esters, amides, nitriles, and Alkyl chlorides. The reaction is applied to late-stage modifications of various densely functionalized medicinally relevant molecules. Preliminary mechanistic studies suggest that a rare enantioselective eta(2)-coordinating Activation of ketone Carbonyls is involved. This cross-coupling-like mechanism is expected to enable other challenging transformations of ketones.Fast Enantio- and Chemoselective Arylation of Ketones with OrganB(OH)2ronic Esters Enabled by Nickel/N-HeterocyClic Carbene CatalysisArylboronic esters; chiral NHC ligands; chiral tertiary alcohols; nickel catalysis6202168#N/ATRUE
591
anie.20190389010.1002/anie.201903890G:AlkylborationFALSEhttps://doi.org/10.1002/anie.201903890Yin, GYAngew. Chem.-Int. Edit.An unprecedented nickel-catalyzed 1,1-Alkylboration of electronically unbiased alkenes has been developed, providing straightforward access to secondary aliphatic boronic esters from readily available materials under very mild reaction conditions. The regioselectivity of this reaction is governed by a unique pyridyl carboxamide ligated catalyst, rather than the substrates. Moreover, this transformation shows excellent chemo- and regio-selectivity and remarkably good functional-group tolerance. We also demonstrate that under balloon pressure, ethylene can also be utilized as a substrate. Additionally, competence experiments indicate that selective bond formation is favored at the alpha-position of boron and preliminary mechanistic studies indicate that the key step in this three-component reaction involves a 1,2-nickel migration.Nickel-Catalyzed 1,1-Alkylboration of Electronically Unbiased Terminal Alkenesalkenes; Alkylboration; coupling reactions; nickel; regioselectivity23201974#N/ATRUE
592
science.aaz385510.1126/science.aaz3855G:C-C couplingFALSEhttps://doi.org/10.1126/science.aaz3855Fu, GCScienceStereochemical control in the construction of carbon-carbon bonds between an Alkyl electrophile and an Alkyl nuCleophile is a persistent challenge in organic synthesis. Classical substitution reactions via S(N)1 and S(N)2 pathways are limited in their ability to generate carbon-carbon bonds (inadequate scope, due to side reactions such as rearrangements and eliminations) and to control stereochemistry when beginning with readily available racemic starting materials (racemic products). Here, we report a chiral nickel catalyst that couples racemic electrophiles (propargylic halides) with racemic nuCleophiles (beta-zincated amides) to form carbon-carbon bonds in doubly stereoconvergent processes. affording a single stereoisomer of the product from two stereochemical mixtures of reactants.Catalyst-controlled doubly enantioconvergent coupling of racemic Alkyl nuCleophiles and electrophiles33202040#N/ATRUE
593
jacs.9b1392010.1021/jacs.9b13920G:C-C couplingTRUEhttps://doi.org/10.1021/jacs.9b13920Murakami, MJ. Am. Chem. Soc.A photoinduced dehydrogenative coupling reaction between Benzylic and aldehydic C-H bonds is reported. When a solution of an Alkylbenzene and an aldehyde in ethyl acetate is irradiated with visible light in the presence of iridium and nickel catalysts, a coupled alpha-Aryl ketone is formed with evolution of dihydrogen. An analogous C-C bond forming reaction occurs between a C-H bond next to the nitrogen of an N-methylamide and an aldehydic C-H bond to produce an a-amino ketone. These reactions provide a straightforward pathway from readily available materials leading to valued structural motifs of pharmacological relevance.Dehydrogenative Coupling of Benzylic and Aldehydic C-H BondsCsp3-Csp2HHHAlkylNo baseNo Base282020476/29/2022TRUE
594
jacs.0c1047110.1021/jacs.0c10471G:C-C couplingTRUEhttps://doi.org/10.1021/jacs.0c10471Huo, HHJ. Am. Chem. Soc.A direct enantioselective acylation of alpha-amino C(sp(3))-H bonds with Carbonylic acids has been achieved via the merger of transition metal and photoredox catalysis. This straightforward protocol enables cross-coupling of a wide range of Carbonylic acids, one Class of feedstock chemicals, with readily available N-Alkyl benzamides to produce highly valuable alpha-amino ketones in high enantioselectivities under mild conditions. The synthetic utility of this method is further demonstrated by gram scale synthesis and application to late-stage functionalization. This method provides an unprecedented solution to address the challenging stereocontrol in metallaphotoredox catalysis and C(sp(3))-H functionalization. Mechanistic studies suggest the alpha-C(sp(3))-H bond of the benzamide coupling partner is Cleavage by photocatalytically generated bromine radicals to form a-amino Alkyl radicals, which subsequently engages in nickel-catalyzed asymmetric acylation.Direct Enantioselective C(sp(3))-H Acylation for the Synthesis of alpha-Amino KetonesCsp3-Csp3E-NuOOHHAlkylNa2HPO4112020876/1/2022TRUE
595
ja907930810.1021/ja9079308G:C-C couplingFALSEhttps://doi.org/10.1021/ja9079308Kishi, YJ. Am. Chem. Soc.Two new ligands 1a,b are reported. Upon treatment with 1 equiv of NiCl2 center dot(MeOCH2)(2), 1a,b give the corresponding Ni complexes. X-ray analysis of 1a-NiCl2 established that the NiCl2 is selectively coordinated to the phenanthroline nitrogens. Ni/Cr heterobimetallic catalysts 1a,b center dot CrCl2/NiCl2, prepared from 1a,b center dot NiCl2, have been shown to behave exceptionally well in catalytic asymmetric Ni/Cr-mediated couplings, with highlights inCluding the following: (1) 1-2 mol % catalyst is sufficient to complete the coupling; (2) only negligible amounts of the dimers, byproducts formed through the alkenyl Ni species, are observed; (3) the coupling goes to completion even with a 1:1 molar ratio of the coupling partners; and (4) the asymmetric induction is practically identical with that obtained from the coupling with the Cr catalysts prepared from (S)-sulfonamides 2a,b. The scope of the new Ni/Cr heterobimetallic catalysts was briefly studied using four additional aldehydes. The applicability of the new catalysts to polyfunctional substrates was demonstrated by two C-C bond formations chosen from the hatichondrin/E7389 synthesis as examples.Dramatic Improvement in Catalyst Loadings and Molar Ratios of Coupling Partners for Ni/Cr-Mediated Coupling Reactions: Heterobimetallic Catalysts45200918#N/ATRUE
596
ja902737810.1021/ja9027378G:C-C couplingFALSEhttps://doi.org/10.1021/ja9027378Hu, XLJ. Am. Chem. Soc.A nickel(II) pincer complex [((NN2)-N-Me)NiCl] (1) catalyzes Kumada-Corriu-Tamao cross coupling of nonactivated Alkyl halides with Aryl and heteroAryl Grignard reagents. The coupling of octyl bromide with phenylmagnesium chloride was used as a test reaction. Using 3 mol % of 1 as the precatalyst and THF as the solvent, and in the presence of a catalytic amount of TMEDA, the coupling product was obtained in a high yield. The reaction conditions could be applied to cross coupling of other primary and secondary Alkyl bromides and iodides. The coupling is tolerant to a wide range of functional groups. Therefore, Alkyl halides containing ester, amide, ether, thioether, alcohol, pyrrole, indole, furan, nitrile, conjugated enone, and Aryl halide moieties were coupled to give high isolated yields of products in which these units stay intact. For the coupling of ester-containing substrates, O-TMEDA is a better additive than TMEDA. The reaction protocol proves to be efficient for the coupling of Knochel-type functionalized Grignard reagents. Thus Aryl Grignard reagents containing electron-deficient and/or sensitive ester, nitrile, amide, and CF3 substituents could be successfully coupled to nonactivated and functionalized Alkyl iodides. The catalysis is also efficient for the coupling of Alkyl iodides with functionalized heteroAryl Grignard reagents, giving rise to pyridine-, thiophene-, pyrazole-, furan-containing molecules with additional functionalities. Concerning the mechanism of the catalysis, [((NN2)-N-Me)Ni-(hetero)Ar] was identified as an intermediate, and the Activation of Alkyl halides was found to take place through a radical-rebound process.Functional Group Tolerant Kumada-Corriu-Tamao Coupling of Nonactivated Alkyl Halides with Aryl and HeteroAryl NuCleophiles: Catalysis by a Nickel Pincer Complex Permits the Coupling of Functionalized Grignard Reagents192200996#N/ATRUE
597
ja301612y10.1021/ja301612yG:C-C couplingFALSEhttps://doi.org/10.1021/ja301612yFu, GCJ. Am. Chem. Soc.The ability of two common protected forms of amines (carbamates and sulfonamides) to serve as directing groups in Ni-catalyzed Suzuki reactions has been exploited in the development of catalytic asymmetric methods for cross-coupling unactivated Alkyl electrophiles. Racemic secondary bromides and chlorides undergo C-C bond formation in a stereoconvergent process in good ee at room temperature in the presence of a commercially available Ni complex and chiral ligand. Structure enantioselectivity studies designed to elucidate the site of binding to Ni (the oxygen of the carbamate and of the sulfonamide) led to the discovery that sulfones also serve as useful directing groups for asymmetric Suzuki cross-couplings of racemic Alkyl halides. To our knowledge, this investigation provides the first examples of the use of sulfonamides or sulfones as effective directing groups in metal-catalyzed asymmetric C-C bond-forming reactions. A mechanistic study established that transmetalation occurs with retention of stereochemistry and that the resulting Ni-C bond does not undergo homolysis in subsequent stages of the catalytic cyCle.New Directing Groups for Metal-Catalyzed Asymmetric Carbon-Carbon Bond-Forming Processes: Stereoconvergent Alkyl-Alkyl Suzuki Cross-Couplings of Unactivated Electrophiles175201224#N/ATRUE
598
ja207951510.1021/ja2079515G:C-C couplingFALSEhttps://doi.org/10.1021/ja2079515Fu, GCJ. Am. Chem. Soc.With the aid of a chiral nickel catalyst, enantioselective gamma- (and delta-) Alkylations of Carbonyl compounds can be achieved through the coupling of gamma-haloamides with Alkylboranes. In addition to primary Alkyl nuCleophiles, for the first time for an asymmetric cross-coupling of an unactivated Alkyl electrophile, an Arylmetal, a boronate ester, and a secondary (cyClopropyl) Alkylmetal compound are shown to couple with significant enantioselectivity. A mechanistic study indicates that Cleavage of the carbon-halogen bond of the electrophile is irreversible under the conditions for asymmetric carbon-carbon bond formation.Catalytic Asymmetric gamma-Alkylation of Carbonyl Compounds via Stereoconvergent Suzuki Cross-Couplings139201116#N/ATRUE
599
ja200270k10.1021/ja200270kG:C-C couplingFALSEhttps://doi.org/10.1021/ja200270kHu, XLJ. Am. Chem. Soc.A structure-activity study was carried out for Ni catalyzed Alkyl-Alkyl Kumada-type cross coupling reactions. A series of new nickel(II) complexes inCluding those with tridentate pincer bis(amino)amide ligands ((R)N(2)N) and those with bidentate mixed amino-amide ligands ((R)NN) were synthesized and structurally characterized. The coordination geometries of these complexes range from square planar, tetrahedral, to square pyramidal. The complexes had been examined as precatalysts for cross coupling of nonactivated Alkyl halides, particularly secondary Alkyl iodides, with Alkyl Grignard reagents. Comparison was made to the results obtained with the previously reported Ni pincer complex [((Me)N(2)N)NiCl]. A transmetalation site in the precatalysts is necessary for the catalysis. The coordination geometries and spin-states of the precatalysts have a small or no influence. The work led to the discovery of several well-defined Ni catalysts that are significantly more active and efficient than the pincer complex [((Me)N(2)N)NiCl] for the coupling of secondary Alkyl halides. The best two catalysts are [((H)NN)Ni(PPh(3))Cl] and [((H)NN)Ni(2,4-lutidine)Cl]. The improved activity and efficiency was attributed to the fact that phosphine and lutidine ligands in these complexes can dissociate from the Ni center during catalysis. The Activation of Alkyl halides was shown to proceed via a radical mechanism.A Structure-Activity Study of Ni-Catalyzed Alkyl-Alkyl Kumada Coupling. Improved Catalysts for Coupling of Secondary Alkyl Halides93201157#N/ATRUE
600
c9sc05444h10.1039/c9sc05444hG:C-C couplingFALSEhttps://doi.org/10.1039/c9sc05444hNelson, DJChem. Sci.The energetically-favorable coordination of aldehydes and ketones - but not esters or amides - to Ni-0 during Suzuki-Miyaura reactions can lead either to exquisite selectivity and enhanced reactivity, or to inhibition of the reaction. Aryl halides where the C-X bond is connected to the same pi-system as an aldehyde or ketone undergo unexpectedly rapid oxidative addition to [Ni(COD)(dppf)] (1), and are selectively cross-coupled during competition reactions. When aldehydes and ketones are present in the form of exogenous additives, the cross-coupling reaction is inhibited to an extent that depends on the strength of the coordination of the pendant Carbonyl group to Ni-0. This work advances our understanding of how common functional groups interact with Ni-0 catalysts and how these interactions affect workhorse catalytic reactions in academia and industry.Aldehydes and ketones influence reactivity and selectivity in nickel-catalysed Suzuki-Miyaura reactions9202049#N/ATRUE
601
anie.20200495810.1002/anie.202004958G:C-C couplingFALSEhttps://doi.org/10.1002/anie.202004958Ackermann, LAngew. Chem.-Int. Edit.Direct Alkylations of Carbonylic acid derivatives are challenging and particularly nickel catalysis commonly requires high reaction temperatures and strong bases, translating into limited substrate scope. Herein, nickel-catalyzed C-H Alkylations of unactivated 8-aminoquinoline amides have been realized under exceedingly mild conditions, namely at room temperature, with a mild base and a user-friendly electrochemical setup. This electrocatalyzed C-H Alkylation displays high functional group tolerance and is applicable to both the primary and secondary Alkylation. Based on detailed mechanistic studies, a nickel(II/III/I) catalytic manifold has been proposed.Nickela-electrocatalyzed Mild C-H Alkylations at Room TemperatureC-H Alkylation; electrosynthesis; homogeneous catalysis; nickel; redox-neutral reactions152020120#N/ATRUE
602
anie.20200495810.1002/anie.202004958G:C-C couplingFALSEhttps://doi.org/10.1002/anie.202004958Ackermann, LAngew. Chem.-Int. Edit.Direct Alkylations of Carbonylic acid derivatives are challenging and particularly nickel catalysis commonly requires high reaction temperatures and strong bases, translating into limited substrate scope. Herein, nickel-catalyzed C-H Alkylations of unactivated 8-aminoquinoline amides have been realized under exceedingly mild conditions, namely at room temperature, with a mild base and a user-friendly electrochemical setup. This electrocatalyzed C-H Alkylation displays high functional group tolerance and is applicable to both the primary and secondary Alkylation. Based on detailed mechanistic studies, a nickel(II/III/I) catalytic manifold has been proposed.Nickela-electrocatalyzed Mild C-H Alkylations at Room TemperatureC-H Alkylation; electrosynthesis; homogeneous catalysis; nickel; redox-neutral reactions152020120#N/ATRUE
603
acscatal.9b0357410.1021/acscatal.9b03574G:C-C coupling + additionFALSEhttps://doi.org/10.1021/acscatal.9b03574Giri, RACS Catal.We disClose a transmetalation-initiated Ni(I)-catalyzed regioselective beta,delta-VinylArylation of gamma,delta-alkenyl alpha-cyanoCarbonylic esters with Vinyl triflates and Arylzinc reagents. This reaction proceeds via contraction of six-membered nickellacyCles to five-membered nickellacyCles to form carbon-carbon bonds at the nonClassical homovicinal sites, and it provides expeditious access to a wide range of complex aliphatic alpha-cyanoesters, alpha-cyanoCarbonylic acids, diCarbonylic acids, diCarbonylic acid monoamides, monoCarbonylic acids, nitriles, and spirolactones. Control, deuterium labeling, and crossover experiments indicate that (i) the nickellacyCle contraction occurs by beta-H elimination, followed by hydronickellation on transiently formed alkenes, and (ii) the Ni species are stabilized as Ni-enolates.Ni(I)-Catalyzed beta,delta-VinylArylation of gamma,delta-Alkenyl alpha-CyanoCarbonylic Esters via Contraction of Transient NickellacyClesmetallacyCle contraction; nickel(1)-catalyzed; nickel enolates; regioselective; transmetalation; beta,delta-VinylArylation13201971#N/ATRUE
604
jacs.9b1353110.1021/jacs.9b13531G:C-N couplingFALSEhttps://doi.org/10.1021/jacs.9b13531Sanford, MSJ. Am. Chem. Soc.The reaction of Carbonylic acid derivatives with amines to form amide bonds has been the most widely used transformation in organic synthesis over the past century. Its utility is driven by the broad availability of the starting materials as well as the kinetic and thermodynamic driving force for amide bond formation. As such, the invention of new reactions between Carbonylic acid derivatives and amines that strategically deviate from amide bond formation remains both a challenge and an opportunity for synthetic chemists. This report describes the development of a nickel-catalyzed deCarbonylative reaction that couples (hetero)aromatic esters with a broad scope of amines to form (hetero)Aryl amine products. The successful realization of this transformation was predicated on strategic design of the cross-coupling partners (phenol esters and silyl amines) to preClude conventional reactivity that forms inert amide byproducts.Nickel-Catalyzed DeCarbonylative Amination of Carbonylic Acid Esters11202041#N/ATRUE
605
d0sc04525j10.1039/d0sc04525jFALSEhttps://doi.org/10.1039/d0sc04525jApfel, UPChem. Sci.In recent years, metal-rich sulfides of the pentlandite type (M9S8) have attracted considerable attention for energy storage applications. However, common synthetic routes towards pentlandites either involve energy intensive high temperature procedures or solvothermal methods with specialized precursors and non-sustainable organic solvents. Herein, we demonstrate that ball milling is a simple and efficient method to synthesize nanosized bimetallic pentlandite partiCles (Fe4.5Ni4.5S8, Pn) with an average size of ca. 250 nm in a single synthetic step from elemental- or sulfidic mixtures. We herein highlight the effects of the milling ball quantity, precursor types and milling time on the product quality. Along this line, Raman spectroscopy as well as temperature/pressure monitoring during the milling processes provide valuable insights into mechanistic differences between the mechanochemical Pn-formation. By employing the obtained Pn-nanosized partiCles as cathodic electrocatalysts for water splitting in a zero-gap PEM electrolyzer we provide a comprehensive path for a potential sustainable future process involving non-noble metal catalysts.Sustainable and rapid preparation of nanosized Fe/Ni-pentlandite partiCles by mechanochemistryx2202045#N/AFALSE
606
cs500874z10.1021/cs500874zG:C-S couplingFALSEhttps://doi.org/10.1021/cs500874zTonzetich, ZJACS Catal.A series of catalytic C-S coupling reactions utilizing well-defined Ni(II) PNP pincer complexes as precatalysts are reported (PNP = anion of 2,5-bisadiAlkyl/Aryl-phosphino)methyl]pyrrole, abbreviated as P(2)(R)Pyr). Coupling reactions employing a variety of Aryl iodides and thiols in the presence of base and DMF proceed in good to excellent yield at 80 degrees C with low catalyst loadings. Aryl bromides were found to result in substantially lower yields, and Aryl chlorides were found to be unreactive under the catalytic conditions. In an effort to further understand the reactivity of the nickel PNP precatalysts, complexes of Ni(II) containing amide, alkmdde, hydroxide, thiolate, and hydrosulfide ligands have been prepared and examined in stoichiometric reactions relevant to carbon-heteroatom coupling. Full characterization of each nickel complex is provided, inCluding solid-state structures. The results of stoichiometric reactions implicate a reduced Ni(I) species as the active catalyst, which forms by reduction of the Ni(II) precatalyst in the presence of excess thiolate. The facility in forming Ni(I) species is invoked to rationalize the observed activity among different Ni PNP precatalysts.Catalytic C-S Cross-Coupling Reactions Employing Ni Complexes of Pyrrole-Based Pincer LigandsC-S cross-coupling; nickel catalysis; PNP ligands; nickel(II); mechanistic studies78201451#N/ATRUE
607
acscatal.9b0436310.1021/acscatal.9b04363G:C-S couplingFALSEhttps://doi.org/10.1021/acscatal.9b04363Willis, MCACS Catal.We report a redox-neutral Ni(II)-catalyzed sulfination of readily available Aryl and heteroAryl boronic acids. Using the combination of commercially available, airstable NiBr2 center dot(glyme), a commercially available phenanthroline ligand, and DABSO, boronic acids are efficiently converted to the corresponding sulfinate salts, which can be further elaborated to valuable sulfonyl-containing groups, inCluding sulfones, sulfonamides, sulfonyl fluorides, and sulfonate esters. The catalyst loading can be reduced to 2.5 mol % on a gram scale. This practically simple protocol tolerates an unprecedented range of pharmaceutically relevant and electron-poor (hetero)Aryl boronic acids, allowing the direct synthesis of active pharmaceutical ingredients.Nickel(II)-Catalyzed Synthesis of Sulfinates from Aryl and HeteroAryl Boronic Acids and the Sulfur Dioxide Surrogate DABSOnickel; catalysis; sulfinates; boronic acids; sulfones; sulfonamides; sulfonyl fluorides; sulfur dioxide19201966#N/ATRUE
608
acscatal.9b0514110.1021/acscatal.9b05141G:CarbonylationFALSEhttps://doi.org/10.1021/acscatal.9b05141Yorimitsu, HACS Catal.Nickel-catalyzed reductive Carbonylation reactions of Aryl electrophiles typically require the use of metallic reducing agents. At present, the prevailing perception is that these serve as both a source of electrons and as a source of Lewis acids that may aid CO2 insertion into the Ni-C bond. Herein, we provide evidence for the in situ formation of organometallic species from the metallic reductant, a step that has either been ruled out or has been unexplored in catalytic Carbonylation reactions with metal powder reductants. Specifically, we demonstrate that Zn(O) acts as a reductant and that Zn(II) generates Arylzinc species that might play a role in the C(sp(2))-S Carbonylation of Arylsulfonium salts. Overall, the reductive Ni-catalyzed C(sp(2))-S Carbonylation reaction proceeds under mild conditions in a non-amide solvent, displays a wide substrate scope, and can be applied to the formal para C-H Carbonylation of arenes.Ni-Catalyzed Carbonylation of C(sp(2))-S Bonds with CO2: Evidence for the Multifaceted Role of ZnCarbonylation; nickel; C-S Cleavage; carbon dioxide; zinc15202079#N/ATRUE
609
acscatal.9b0056610.1021/acscatal.9b00566G:CarbonylationFALSEhttps://doi.org/10.1021/acscatal.9b00566Saydjari, AKACS Catal.The nickel-catalyzed Carbonylation of organic halides or pseudohalides using carbon dioxide is an emerging method to prepare synthetically valuable Carbonylic acids. Here, we report a detailed mechanistic investigation of these reactions using the Carbonylation of Aryl halides with (PPh3)(2)(NiCl2)-Cl-II as a model reaction. Our studies allow us to understand several general features of nickel-catalyzed Carbonylation reactions. For example, we demonstrate that both a Lewis acid and halide source are beneficial for catalysis. To this end, we establish that heterogeneous Mn(0) and Zn(0) reductants are multifaceted reagents that generate noninnocent Mn(II) or Zn(II) Lewis acids upon oxidation. In a key result, a rare example of a well-defined nickel(I) Aryl complex is isolated, and it is demonstrated that its reaction with carbon dioxide results in the formation of a Carbonylic acid in high yield (after workup). The carbon dioxide insertion product undergoes rapid decomposition, which can be circumvented by a ligand metathesis reaction with a halide source. Our studies have led to both a revised mechanism and the development of a broadly applicable strategy to improve reductive Carbonylation reactions. A critical component of this strategy is that we have replaced the heterogeneous Mn(0) reductant typically used in catalysis with a well-defined homogeneous organic reductant. Through its use, we have increased the range of ancillary ligands, additives, and substrates that are compatible with the reaction. This has enabled us to perform reductive Carbonylations at low catalyst loadings. Additionally, we demonstrate that reductive Carbonylations of organic (pseudo)halides can be achieved in high yields in more practically useful, non-amide solvents. Our results describe a mechanistically guided strategy to improve reductive Carbonylations through the use of a homogeneous organic reductant, which may be broadly translatable to a wide range of cross-electrophile coupling reactions.Development of an Improved System for the Carbonylation of Aryl Halides through Mechanistic Studiescarbon dioxide; nickel; cross-electrophile coupling; homogeneous organic reductant; catalysis; mechanism382019110#N/ATRUE
610
anie.20210276910.1002/anie.202102769G:Reductive Carbo-CarbonylationFALSEhttps://doi.org/10.1002/anie.202102769Yu, DGAngew. Chem.-Int. Edit.Reductive Carbonylation of organo (pseudo)halides with CO2 is a powerful method to provide Carbonylic acids quickly. Notably, the catalytic reductive carbo-Carbonylation of unsaturated hydrocarbons via CO2 fixation is a highly challenging but desirable approach for structurally diverse Carbonylic acids. There are only a few reports and no examples of alkenes via transition metal catalysis. We report the first asymmetric reductive carbo-Carbonylation of alkenes with CO2 via nickel catalysis. A variety of Aryl (pseudo)halides, such as Aryl bromides, Aryl triflates and inert Aryl chlorides of particular note, undergo the reaction smoothly to give important oxindole-3-acetic acid derivatives bearing a C3-quaternary stereocenter. This transformation features mild reaction conditions, wide substrate scope, facile scalability, good to excellent chemo-, regio- and enantioselectivities. The method highlights the formal synthesis of (-)-Esermethole, (-)-Physostigmine and (-)-Physovenine, and the total synthesis of (-)-Debromoflustramide B, (-)-Debromoflustramine B and (+)-Coixspirolactam A; thereby, opening an avenue for the total synthesis of chiral natural products with CO2.Nickel-Catalyzed Asymmetric Reductive Carbo-Carbonylation of Alkenes with CO2alkenes; carbo-Carbonylation; carbon dioxide; nickel32021155#N/ATRUE
611
acscatal.9b0208110.1021/acscatal.9b02081G:Reductive CyClizationFALSEhttps://doi.org/10.1021/acscatal.9b02081Cramer, NJ. Am. Chem. Soc.Chiral trivalent phosphorus species are the dominant Class of ligands and the key controlling element in asymmetric homogeneous transition-metal catalysis. Here, novel chiral diaminophosphine oxide ligands are described. The arising catalyst system with nickel(0) and trimethylaluminum efficiently activates formamide C-H bonds under mild conditions providing pyrrolidones via intramolecular hydrocarbamoylation in a highly enantioselective manner with as little as 0.25% mol catalyst loading. Mechanistically, the secondary phosphine oxides behave as bridging ligands for the nickel center and the Lewis acidic organoaluminum center to give a heterobimetallic catalyst with superior reactivity.Diaminophosphine Oxide Ligand Enabled Asymmetric Nickel-Catalyzed Hydrocarbamoylations of Alkenes87201357#N/ATRUE
612
ja903123b10.1021/ja903123bGlycosidesFALSEhttps://doi.org/10.1021/ja903123bNguyen, HMJ. Am. Chem. Soc.The development of a new method for the stereoselective synthesis of alpha-2-deoxy-2-amino glycosides is described. This methodology relies on the nature of the cationic nickel catalyst, generated in situ from L0NiCl2 and AgOTf, to direct the anomeric stereoselectivity. The new glycosylation reaction is highly a-selective and proceeds under mild conditions with 5-10 mol % of the nickel catalyst Loading at ambient temperature. This new method has been applied to both D-glucosamine and galactosamine trichloroacetimidate donors as well as an array of primary, secondary, and tertiary alcohol nuCleophiles to provide the desired glycoconjugates in good yields with excellent alpha-selectivity. Mechanistic studies of the present reaction are underway and will be reported in due course.Nickel-Catalyzed Stereoselective Formation of alpha-2-Deoxy-2-Amino Glycosides61200930#N/ATRUE
613
ja106682m10.1021/ja106682mGlycosylation FALSEhttps://doi.org/10.1021/ja106682mNguyen, HMJ. Am. Chem. Soc.The 1,2-cis-2-amino glycosides are key components found within a variety of biologically important oligosaccharides and glycopeptides. Although there are remarkable advances in the synthesis of 1,2-cis-2-amino glycosides, disadvantages of the current state-of-the-art methods inClude limited substrate scope, low yields, long reaction times, and anomeric mixtures. We have developed a novel method for the synthesis of 1,2-cis-2-amino glycosides via nickel-catalyzed alpha-selective glycosylation with C(2)-N-substituted Benzylidene D-glucosamine and galactosamine trichloroacetimidates. These glycosyl donors are capable of coupling to a wide variety of alcohols to provide glycoconjugates in high yields with excellent levels of alpha-selectivity. Additionally, only a substoichiometric amount of nickel (5-10 mol %) is required for the reaction to occur at 25 degrees C. The current nickel method relies on the nature of the nickel-ligand complex to control the alpha-selectivity. The reactive sites of the nuCleophiles or the nature of the protecting groups have little effect on the alpha-selectivity. This methodology has also been successfully applied to both disaccharide donors and acceptors to provide the corresponding oligosaccharides in high yields and alpha-selectivity. The efficacy of the nickel procedure has been further applied toward the preparation of heparin disaccharides, GPI anchor pseudodisaccharides, and alpha-GluNAc/GalNAc. Mechanistic studies suggest that the presence of the substituted Benzylidene functionality at the C(2)-amino position of glycosyl donors is crucial for the high alpha-selectivity observed in the coupling products. Additionally, the alpha-orientation of the C(1)-trichloro-acetimidate group on glycosyl donors is necessary for the coupling process to occur.Nickel-Catalyzed Stereoselective Glycosylation with C(2)-N-Substituted Benzylidene D-Glucosamine and Galactosamine Trichloroacetimidates for the Formation of 1,2-cis-2-Amino Glycosides. Applications to the Synthesis of Heparin Disaccharides, GPI Anchor Pseudodisaccharides, and alpha-GalNAc75201081#N/ATRUE
614
ja061376110.1021/ja0613761Halide SuzukiFALSEhttps://doi.org/10.1021/ja0613761Fu, GCJ. Am. Chem. Soc.Amino alcohols as ligands for nickel-catalyzed Suzuki reactions of unactivated Alkyl halides, inCluding secondary Alkyl chlorides, with Arylboronic acids221200614#N/ATRUE
615
ja804156410.1021/ja8041564Halogen NegishiFALSEhttps://doi.org/10.1021/ja8041564Gagne, MRJ. Am. Chem. Soc.A Ni-catalyzed Negishi cross-coupling approach to C-glycosides is described with an emphasis on C-Aryl glycosides. The combination of NiCl2/Pybox in N,N'-dimethylimidazolidinone (DMI) enabled the synthesis of C-Alkyl glycosides under mild reaction conditions. Moderate yields and beta-selectivities were obtained for C-glucosides, and good yields and high alpha-selectivities were the norm for C-mannosides. For C-Aryl glycosides, reactions employing Ni(COD)(2)/Bu-t-Terpy in N,N-dimethylformamide (DMF) were typically high yielding and provided C glucosides with high beta-selectivities (1:> 10 alpha:beta) and C-mannosides in moderate alpha-selectivities (3:1 alpha:beta); alpha-C-Aryl glycosides could be obtained by the combination of Ni(COD)(2)/Pybox in DIM F (> 20:1 alpha:beta). The collective studies suggest that stereochemical control of the C glycosides is dependent on the substrate and catalysts combination. The Negishi protocol displays excellent functional group tolerance, as demonstrated by its use in the first total synthesis of the natural product salmochelin SX.Diastereoselective Ni-catalyzed Negishi cross-coupling approach to saturated, fully oxygenated C-Alkyl and C-Aryl glycosides155200854#N/ATRUE
616
ja501815p10.1021/ja501815pHalogen NegishiFALSEhttps://doi.org/10.1021/ja501815pFu, GCJ. Am. Chem. Soc.The development of new approaches to the construction of fluorine-containing target molecules is important for a variety of scientific disciplines, inCluding medicinal chemistry. In this ArtiCle, we describe a method for the catalytic enantioselective synthesis of tertiary Alkyl fluorides through Negishi reactions of racemic alpha-halo-alpha-fluoroketones, which represents the first catalytic asymmetric cross-coupling that employs geminal dihalides as electrophiles. Thus, selective reaction of a C-Br (or C-Cl) bond in the presence of a C-F bond can be achieved with the aid of a nickel/bis(oxazoline) catalyst. The products of the stereoconvergent cross-couplings, enantioenriched tertiary alpha-fluoroketones, can be converted into an array of interesting organofluorine compounds.Catalytic Asymmetric Synthesis of Tertiary Alkyl Fluorides: Negishi Cross-Couplings of Racemic alpha,alpha-Dihaloketones107201452#N/ATRUE
617
ja303442q10.1021/ja303442qHalogen NegishiFALSEhttps://doi.org/10.1021/ja303442qFu, GCJ. Am. Chem. Soc.The first method for the stereoconvergent cross-coupling of racemic alpha-halonitriles is described, specifically, nickel-catalyzed Negishi Arylations and alkenylations that furnish an array of enantioenriched alpha-Arylnitriles and allylic nitriles, respectively. Noteworthy features of this investigation inClude: the highly enantioselective synthesis of alpha-Alkyl-alpha-Aryl nitriles that bear secondary alpha-Alkyl substituents; the first examples of the use of allcenylzinc reagents in stereoconvergent Negishi reactions of Alkyl electrophiles; demonstration of the utility of a new family of ligands for asymmetric Negishi crosscouplings (a bidentate bis(oxazoline), rather than a tridentate pybox); in the case of Arylzinc reagents, carbon-carbon bond formation at a remarkably low temperature (-78 degrees C), the lowest reported to date for an enantioselective cross-coupling of an Alkyl electrophile; a mechanistic dichotomy between Negishi reactions of an unactivated versus an activated secondary Alkyl bromide.Catalytic Asymmetric Synthesis of Secondary Nitriles via Stereoconvergent Negishi Arylations and Alkenylations of Racemic alpha-Bromonitriles116201236#N/ATRUE
618
ja308460z10.1021/ja308460zHalogen SuzukiFALSEhttps://doi.org/10.1021/ja308460zFu, GCJ. Am. Chem. Soc.We have developed a nickel-catalyzed method for the asymmetric cross-coupling of secondary electrophiles with secondary nuCleophiles, specifically, stereoconvergent Negishi reactions of racemic Benzylic bromides with achiral cyCloAlkylzinc reagents. In contrast to most previous studies of enantioselective Negishi cross-couplings, tridentate pybox ligands are ineffective in this process; however, a new, readily available bidentate isoquinoline-oxazoline ligand furnishes excellent ee's and good yields. The use of acyClic Alkylzinc reagents as coupling partners led to the discovery of a highly unusual isomerization that generates a significant quantity of a branched cross-coupling product from an unbranched nuCleophile.Catalytic Enantioselective Cross-Couplings of Secondary Alkyl Electrophiles with Secondary Alkylmetal NuCleophiles: Negishi Reactions of Racemic Benzylic Bromides with Achiral Alkylzinc Reagents126201236#N/ATRUE
619
ja207759e10.1021/ja207759eHalogen SuzukiFALSEhttps://doi.org/10.1021/ja207759eChatani, NJ. Am. Chem. Soc.Two protocols for the nickel-catalyzed cross-coupling of Aryl fluorides with Aryl boronic esters have been developed. The first employs metal fluoride cocatalysts, such as ZrF4 and TiF4, which enable Suzuki-Miyaura reactions of Aryl fluorides bearing electron-withdrawing (ketones, esters, and CF3), Aryl and alkenyl groups as well as those comprising fused aromatic rings, such as fluoronaphthalenes and fluoroquinolines. The second protocol employs Aryl fluorides bearing ortho-directing groups, which facilitate the difficult C-F bond Activation process via cyClometalation. N-heterocyCles, such as pyridines, quinolines, pyrazoles, and oxazolines, can successfully promote cross-coupling with an array of organB(OH)2ronic esters. A study into the substituent effects with respect to both coupling components has provided fundamental insights into the mechanism of the nickel-catalyzed cross-coupling of Aryl fluorides.Nickel-Catalyzed Suzuki-Miyaura Reaction of Aryl Fluorides1972011118#N/ATRUE
620
ja074008l10.1021/ja074008lHalogen SuzukiFALSEhttps://doi.org/10.1021/ja074008lFu, GCJ. Am. Chem. Soc.A commercially available 1,2-diamine serves as an effective ligand for metal-catalyzed cross-couplings of unactivated Alkyl electrophiles at room temperature. In particular, Ni/trans-N,N'-dimethyl-1,2-cyClohexanediamine provides the first method for achieving Alkyl-Alkyl Suzuki reactions of unactivated secondary Alkyl halides with Alkylboranes; earlier success in Suzuki couplings of such electrophiles had been restricted to reactions with Aryl- and Vinylboron reagents at elevated temperature.Alkyl-Alkyl Suzuki cross-couplings of unactivated secondary Alkyl halides at room temperature196200714#N/ATRUE
621
anie.20170686810.1002/anie.201706868Halogen SuzukiFALSEhttps://doi.org/10.1002/anie.201706868Shen, QLAngew. Chem.-Int. Edit.Trifluoromethoxy-substituted stereogenic centers can be constructed with high enantioselectivity by a nickel-catalyzed Suzuki-Miyaura coupling of readily available alpha-bromoBenzyl trifluoromethyl ethers with a variety of Aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups, such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino, and Vinyl moieties, were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without a decrease in enantioselectivity.Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers by a Nickel-Catalyzed Asymmetric Suzuki-Miyaura Coupling of Secondary Benzyl Bromidesasymmetric catalysis; cross-coupling; fluorine; nickel; trifluoromethoxy groups39201777#N/ATRUE
622
ja060890410.1021/ja0608904HomoallylationFALSEhttps://doi.org/10.1021/ja0608904Tamaru, YJ. Am. Chem. Soc.Ni(acac)(2) catalyzes homoallylation of aldehydes with 1,3-dienes in the presence of triethylborane. Triethylborane serves as a reducing agent delivering a formal hydride to the C2 position of 1,3-dienes, thus generating a formal homoallyl anion species and enabling the novel homoallylation of aldehydes. The reaction proceeds smoothly at room temperature in the absence of any phosphane or nitrogen ligands and is highly regioselective and stereoselective for a wide variety combination of aldehydes and 1,3-dienes: e. g., isoprene and benzaldehyde combine to give a mixture of anti- and syn-1-phenyl-3-methyl-4-penten-1-ol (2.2) in a ratio of 15:1 in 90% yield. Under the conditions, sterically congested aliphatic aldehydes and ketones show low yields. In such cases, diethylzinc serves as a substitute for triethylborane and yields the expected products in good yields with similarly high regio- and stereoselectivity. 1,3-CyClohexadiene is one exception among 24 kinds of dienes examined and undergoes allylation (not homoallylation) selectively.Regio- and stereoselective nickel-catalyzed homoallylation of aldehydes with 1,3-dienes115200658#N/ATRUE
623
1521-3773(20011001)40:19<3600::AID-ANIE3600>3.0.CO;2-N10.1002/1521-3773(20011001)40:19<3600::AID-ANIE3600>3.0.CO;2-NHomoallylationFALSEhttps://doi.org/10.1002/1521-3773(20011001)40:19<3600::AID-ANIE3600>3.0.CO;2-NTamaru, YAngew. Chem.-Int. Edit.Nickel-catalyzed homoallylation of aldehydes in the presence of water and alcoholsaldehydes; allylation; boron; dienes; nickel69200121#N/ATRUE
624
acscatal.8b0498810.1021/acscatal.8b04988HydrB(OH)2ration FALSEhttps://doi.org/10.1021/acscatal.8b04988Shimizu, KACS Catal.This study describes our development of a Cu-based heterogeneous catalytic system for additive-free hydrB(OH)2ration of alkenes. Surveying monometallic Cu supported on various oxides revealed that Al2O3 provided the best catalytic support with respect to this reaction. A typical volcano-type relationship between the TOF and isoelectric point of the support was observed, which suggests that both acidic and basic properties were necessary to promote this reaction. The catalytic activity of Cu/Al2O3 was further enhanced by the addition of Ni, whereas the selectivity decreased as Ni content increased. The combination of X-ray diffraction, high-angle annular dark-field scanning transmission electron microscopy energy-dispersive system, and extended X-ray absorption fine structure analyses demonstrated the homogeneous formation of a Cu-Ni solid-solution alloy on Al2O3. The optimized Cu5Ni/Al2O3 catalyst exhibited high catalytic performance for styrene hydrB(OH)2ration (98% yield at 25 degrees C for 6 h). A mechanistic study revealed that (1) ethanol adsorbed on a Lewis acid site of Al2O3 released a proton to the alkene, generating a carbocation intermediate, (2) diboron was activated by a basic site in the Al2O3 structure, which was followed by a nuCleophilic attack on the carbocation to form the final product, and (3) Ni acted as an efficient adsorption site for alkene, which facilitated the protonation of alkene as the rate-determining step. The catalysis was assisted by acid-base properties and an alloying effect, which resulted in a unique reaction mechanism and an efficient catalytic system for hydrB(OH)2ration.Heterogeneous Additive-Free HydrB(OH)2ration of Alkenes Using Cu-Ni/Al2O3: Concerted Catalysis Assisted by Acid- Base Properties and Alloying EffectshydrB(OH)2ration; alkene; acid-base; alloy; copperx5201940#N/AFALSE
625
ja910750b10.1021/ja910750bHydrB(OH)2ration FALSEhttps://doi.org/10.1021/ja910750bMorken, JPJ. Am. Chem. Soc.A catalytic regio- and stereoselective 1,4-hydrB(OH)2ration of 1,3-dienes was accomplished with pinacolborane in the presence of Ni(cod)(2) and PCy(3). This reaction exhibits broad substrate scope operating oil a range of Substituted dienes and Occurs with generally high levels of selectivity and efficiency. Reactivity patterns Suggest that the reactive conformation of the diene is the S-cis form. The intermediate allylboronate call be oxidized to stereodefined allylic alcohols or can be used in stereoselective Carbonyl addition reactions.Regio- and Stereoselective Ni-Catalyzed 1,4-HydrB(OH)2ration of 1,3-Dienes: Access to Stereodefined (Z)-Allylboron Reagents and Derived Allylic Alcohols86201019#N/ATRUE
626
d0cc05246a10.1039/d0cc05246aHydrB(OH)2ration FALSEYamaguchi, YBottleable NiCl2(dppe) as a catalyst for the Markovnikov-selective hydrB(OH)2ration of styrenes with bis(pinacolato)diboron2020#N/ATRUE
627
cs501639r10.1021/cs501639rHydrB(OH)2ration FALSEhttps://doi.org/10.1021/cs501639rChirik, PJACS Catal.Cobalt Alkyl complexes bearing readily available and redox-active 2,2':6',2-terpyridine and a-diimine ligands have been synthesized, and their electronic structures have been elucidated. In each case, the supporting chelate is reduced to the monoanionic, radical form that is engaged in antiferromagnetic coupling with the cobalt(II) center. Both Classes of cobalt Alkyls proved to be effective for the isomerization hydrB(OH)2ration of sterically hindered alkenes. An a-diimine-substituted cobalt allyl complex proved exceptionally active for the reduction of hindered tri-, tetra-, and limonene, formation of an eta(3)-allyl complex with a C-H agostic interaction was identified and accounts for the sluggish reactivity observed with diene substrates. For the terpyridine derivative, unique Markovnikov selectivity with styrene was also observed with HBPin.High-Activity Cobalt Catalysts for Alkene HydrB(OH)2ration with Electronically Responsive Terpyridine and alpha-Diimine Ligandscobalt; hydrB(OH)2ration; catalysis; redox-active ligands; boronates108201552#N/ATRUE
628
c4sc01110d10.1039/c4sc01110dHydrB(OH)2ration FALSEhttps://doi.org/10.1039/c4sc01110dHazari, NChem. Sci.The Carbonylation of allenes with CO2 represents a potentially important method for the synthesis of unsaturated Carbonylic acids. Here, we describe a detailed mechanistic study of the catalytic Carbonylation of allenes using (PSiP)-P-Cy ((PSiP)-P-Cy = Si(Me)(2-PCy2-C6H4)(2)) supported Pd complexes. As part of this work we have identified, characterized and isolated all of the proposed intermediates in the catalytic cyCle and shown that they are kinetically competent catalysts. In addition, we have isolated several off-cyCle species, which are in equilibrium with complexes in the catalytic cyCle, and established that they are also active catalysts. Several of these off-cyCle species are formed through an unusual ligand rearrangement of the (PSiP)-P-Cy pincer ligand, in which a Si-C bond is reversibly Cleaved. The major catalyst deActivation pathway has been identified. Furthermore, our mechanistic study has allowed us to develop a new catalyst for the hydrB(OH)2ration of carbon dioxide, which gives a maximum turnover number (TON) greater than 60 000; the highest reported to date.A mechanistic study of allene Carbonylation with CO2 resulting in the development of a Pd(II) pincer complex for the catalytic hydrB(OH)2ration of CO2762014130#N/ATRUE
629
acscatal.8b0513610.1021/acscatal.8b05136HydrB(OH)2ration FALSEhttps://doi.org/10.1021/acscatal.8b05136Wang, WGACS Catal.An air-stable half-sandwich nickel(II) complex bearing a phosphinophenolato ligand, Cp*Ni(1,2-Ph2PC6H4O) (1), has been designed and synthesized for Activation of HBpin and catalytic hydrB(OH)2ration of N-heteroarenes such as pyridine. Through addition of the H- B bond across the Ni-O bond, 1 reacts with HBpin to afford an 18-electron Ni(II)-1-1 intermediate [H1(Bpin)] featuring an oxygen-stabilized boron moiety, which readily reduces pyridine analogues to give the 1,2-hydrB(OH)2rated product, thus accomplishing the catalytic cyCle under mild conditions. The necessity of the phosphinophenolato ligand to deliver the boryl group was manifested by the Clear difference in the activity of 1 and Cp*NiH(PPh3) (3H) in catalytic hydrB(OH)2rations. The latter lacks a functional oxygen atom and is inert to process the catalysis.Ni-O Cooperation versus Nickel(II) Hydride in Catalytic HydrB(OH)2ration of N-Heteroarenesmetal-ligand cooperation; nickel(II) catalyst; B-H bond Cleavage; nickel hydride; hydrB(OH)2ration18201967#N/ATRUE
630
acscatal.8b0389410.1021/acscatal.8b03894HydrB(OH)2ration FALSEhttps://doi.org/10.1021/acscatal.8b03894Hazari, NACS Catal.The factors that influence the selectivity of pincer supported group 10 transition metal hydride catalysts for CO2 hydrB(OH)2ration are investigated. We demonstrate that selective CO2 reduction to either the two-electron boryl formate reduction product, the four-electronbis(boryl)acetal reduction product, or the six-electron methoxy borane reduction product can be achieved by varying either the identity and concentration of the organB(OH)2rane reductant, the nature and loading of the catalyst, or the presence of a Lewis acid cocatalyst. In fact, using one specific catalyst, ((PCP)-P-tBu)-NiH ((PCP)-P-tBu = 2,6-C6H3((CH2PBu2)-Bu-t)(2)), we can selectively form either the two-, four-, or six-electron CO2 reduction products by changing either the nature of the reductant or the reaction conditions. Additionally, we show that Lewis acid cocatalysts can be used to alter the selectivity of CO2 hydrB(OH)2ration, which is a new method to control the selectivity of this type of hydrB(OH)2ration reaction. All of our results on selectivity are consistent with CO2 hydrB(OH)2ration being a tandem reaction, in which it is possible to either trap the kinetic two- or four electron reduction products or form the thermodynamic six-electron reduction product. We also explore the formation of off cyCle K-2-borohydride species through the reaction of the transition metal hydride with the borane reductant and show that this can impact selectivity. Overall, our work provides detailed guidelines for designing even more active and selective catalysts for CO2 hydrB(OH)2ration and may also be relevant for the improvement of catalysts for related reactions such as CO2 hydrosilylation.Controlling Selectivity in the HydrB(OH)2ration of Carbon Dioxide to the Formic Acid, Formaldehyde, and Methanol Oxidation LevelshydrB(OH)2ration; carbon dioxide reduction; pincer complexes; mechanism; transition metal catalysis29201964#N/ATRUE
631
acscatal.8b0197210.1021/acscatal.8b01972HydrB(OH)2ration FALSEhttps://doi.org/10.1021/acscatal.8b01972Turculet, LACS Catal.We describe the results of our combined experimental and computational investigation of structurally analogous (N-phosphinoamidinate)metal(N(SiMe3)(2)) precatalysts ((PN)M; M = Mn2+, Fe2+, Co2+, and Ni2+; Cls d(8)) in the isomerization hydrB(OH)2ration of 1-octene, cis-4-octene, or trans-4-octene (la-c) with HBPin. As part of this investigation, the synthesis and crystallographic characterization of diamagnetic (PN)Ni, ((PN)NiH)(2), (PN)NiH(L) (L = pyridine or DMAP), and (PN)Ni(NHdipp) (dipp = 2,6iPr(2)C(6)H(3)) are reported. Divergent catalytic reactivity and selectivity was noted for members of the (PN)M series; (PN)Mn and (PN)Ni afforded poor hydrB(OH)2ration yields, whereas the use of (PN)Fe or (PN)Co afforded high conversion and selectivity for the terminal borylation product, (n-octyl)BPin (2a). DFT calculations involving (PN)M as well as stoichiometric reactivity studies featuring (PN)Ni confirmed that (PN)MH intermediates generated upon reaction of (PN)M with HBPin represent viable catalytic species whereby formation of putative (PN)Ni(H(2)BPin) is reversible. Conversely, poor catalytic performance was noted for ((PN)NiH)(2) and (PN)NiH(L) (L = pyridine or DMAP). Using DFT calculations, the relative reactivity of (PN)M precatalysts was found to be a function of their spin-state energy gaps. For reaction of (PN)MnH with trans-4-octene (1c) there is no viable spin crossover mechanism and migratory insertion is slow, resulting in poor reaction yields. In contrast, (PN)FeH can access a lower barrier through spin crossover, whereas (PN)CoH has a very low migratory insertion barrier from its low spin state. While (PN)NiH has a reasonable migratory insertion barrier, it is plausible that off-catalytic cyCle intermediates are responsible for the diminished reaction rate and product yields that are observed experimentally. On the basis of the computed isomerization and borylation energy landscapes, a Curtin Hammett-type scenario with fast isomerization through beta-hydride elimination and migratory insertion steps is proposed, giving rise to a catalytic equilibrium of isomeric (PN)M(octyl) resting states, followed by slow product-forming borylation. The significantly lower barriers calculated for borylation of terminal (PN)M(n-octyl) species versus isomeric internal (PN)M(CHR2) intermediates provides a rationale for the experimentally observed terminal isomerization hydrB(OH)2ration selectivity.Alkene Isomerization-HydrB(OH)2ration Catalyzed by First-Row Transition-Metal (Mn, Fe, Co, and Ni) N-Phosphinoamidinate Complexes: Origin of Reactivity and Selectivityfirst-row transition metal; density functional theory; spin crossover; hydrB(OH)2ration; olefin isomerization; remote functionalization19201880#N/ATRUE
632
acscatal.8b0116610.1021/acscatal.8b01166
HydrB(OH)2ration
FALSEhttps://doi.org/10.1021/acscatal.8b01166Findlater, MACS Catal.Combinations of Ni(acac)(2) with phosphine ligands were found to catalyze the regioselective hydrB(OH)2ration of N-heteroarenes with pinacolborane, affording N-borylated 1,4-reduction products. Preliminary mechanistic studies have focused on the isolation and study of potential intermediates in the catalytic cyCle.Nickel-Catalyzed Regioselective 1,4-HydrB(OH)2ration of N-Heteroarenes1,4-regioselective; dearomatization; N-heteroarene; pyridine; nickel30201863#N/ATRUE
633
anie.20201133910.1002/anie.202011339HydroAlkylationFALSEhttps://doi.org/10.1002/anie.202011339Shu, WAngew. Chem.-Int. Edit.The development of enantioselective Alkyl-Alkyl cross-couplings with coinstantaneous formation of a stereogenic center without the use of sensitive organometallic species is attractive yet challenging. Herein, we report the intermolecular regio- and enantioselective formal hydrofunctionalizations of acrylamides, forging a stereogenic center alpha-position to the newly formed C-sp3-C-sp3 bond for the first time. The use of a newly developed chiral ligand enables the electronically-reversed formal hydrofunctionalizations, inCluding hydroAlkylation, hydroBenzylation, and hydropropargylation, offering an efficient way to access diverse enantioenriched amides with a tertiary alpha-stereogenic carbon center which is facile to racemize. This operationally simple protocol allows for the anti-Markovnikov enantioselective hydroAlkylation, and unprecedented hydroBenzylation, hydropropargylation under mild conditions with excellent functional group compatibility, delivering a wide range of amides with excellent levels of enantioselectivity.Regio- and Enantioselective Ni-Catalyzed Formal HydroAlkylation, HydroBenzylation, and Hydropropargylation of Acrylamides to alpha-Tertiary AmidesAlkyl&#8211; Alkyl cross-coupling; enantioselectivety; hydroAlkylation; hydroBenzylation; hydropropargylation11202139#N/ATRUE
634
anie.20181322210.1002/anie.201813222HydroAlkylationFALSEhttps://doi.org/10.1002/anie.201813222Zhu, SLAngew. Chem.-Int. Edit.Reported here is a terminal-selective, remote asymmetric hydroAlkylation of olefins with racemic -bromo amides. The reaction proceeds by NiH-catalyzed alkene isomerization and subsequent Alkylation reaction, and can enantioconvergently introduce an unsymmetrical secondary Alkyl group from a racemic -bromo amide onto a terminal C(sp(3))-H position along the hydrocarbon chain of the alkene. This mild process affords a range of structurally diverse chiral -Alkylalkanoic amides in excellent yields, and high regio- and enantioselectivities. In addition, the synthetic utility of this protocol is further highlighted by the regioconvergent conversion of industrial raw materials of isomeric olefin mixtures into enantioriched -Alkylalkanoic amides on large scale.NiH-Catalyzed Remote Asymmetric HydroAlkylation of Alkenes with Racemic -Bromo AmidesAlkylation; C-H Activation; enantioselectivity; isomerization; nickel52201992#N/ATRUE
635
acscatal.1c0229910.1021/acscatal.1c02299HydroAlkylation FALSEhttps://doi.org/10.1021/acscatal.1c02299Zhu, SLACS Catal.Here, we report an enantioselective nickel-hydride catalyzed hydroAlkylation of readily accessible beta-Alkyl-alpha,beta-unsaturated amides to form structurally diverse beta-chiral amides. This process was proposed to proceed through an enantiodifferentiating syn-hydrometalation of nickel hydride, forming chiral Alkylnickel at the beta-position in which the regioselectivity is different from that with copper hydride. This regio-reversed hydronickellation process provides a complementary approach to access enantioenriched beta-functionalization amides with a stereocenter at the beta-position.Catalytic Asymmetric HydroAlkylation of alpha,beta-Unsaturated Amides Enabled by Regio-Reversed and Enantiodifferentiating syn-Hydronickellationalkenes; Alkylation; asymmetric catalysis; nickel; nickel-hydride0202177#N/ATRUE
636
s41467-021-22983-710.1038/s41467-021-22983-7hydroAlkylationsFALSEhttps://doi.org/10.1038/s41467-021-22983-7Shu, WNat. Commun.Chiral aliphatic amine and alcohol derivatives are ubiquitous in pharmaceuticals, pesticides, natural products and fine chemicals, yet difficult to access due to the challenge to differentiate between the spatially and electronically similar Alkyl groups. Herein, we report a nickel-catalyzed enantioselective hydroAlkylation of acyl enamines and enol esters with Alkyl halides to afford enantioenriched alpha -branched aliphatic acyl amines and esters in good yields with excellent levels of enantioselectivity. The operationally simple protocol provides a straightforward access to chiral secondary Alkyl-substituted amine and secondary Alkyl-substituted alcohol derivatives from simple starting materials with great functional group tolerance. Chiral aliphatic amine and alcohol derivatives are difficult to access due to the challenge to differentiate between spatially and electronically similar Alkyl groups. Here the authors show a nickel-catalyzed enantioselective hydroAlkylation of acyl enamines and enol esters with Alkyl halides to afford enantioenriched alpha -branched aliphatic acyl amines and esters in good yields with excellent enantioselectivity.Enantioselective access to chiral aliphatic amines and alcohols via Ni-catalyzed hydroAlkylations5202155#N/ATRUE
637
s41467-021-24032-910.1038/s41467-021-24032-9hydroaminoAlkylationFALSEhttps://doi.org/10.1038/s41467-021-24032-9Ye, MCNat. Commun.Allylic amines are versatile building blocks in organic synthesis and exist in bioactive compounds, but their synthesis via hydroaminoAlkylation of alkynes with amines has been a formidable challenge. Here, we report a late transition metal Ni-catalyzed hydroaminoAlkylation of alkynes with N-sulfonyl amines, providing a series of allylic amines in up to 94% yield. Double ligands of N-heterocyClic carbene (IPr) and tricyClohexylphosphine (PCy3) effectively promote the reaction. Allylic amines are versatile building blocks in organic synthesis and exist in bioactive compounds, but efficient catalytic systems for hydroaminoAlkylation of alkynes are needed. Here, the authors report a late transition metal-catalyzed hydroaminoAlkylation of alkynes with N-sulfonyl amines, providing a series of allylic amines in up to 94% yield.Ni-catalyzed hydroaminoAlkylation of alkynes with amines0202149#N/ATRUE
638
acscatal.8b0511110.1021/acscatal.8b05111HydrocyanationaFALSEhttps://doi.org/10.1021/acscatal.8b05111Chang, SACS Catal.The in situ generation of a cyano unit from readily available organic precursors is of high interest in synthetic chemistry. Herein, we report the first example of Ni-mediated dehydration of formamide to form CN and its subsequent catalytic applications in the hydrocyanation of alkynes and cyanation of Aryl halides. Formamide can serve as a convenient source for the nitrile unit, in that it releases water as the only byproduct.Ni-Mediated Generation of CN Unit from Formamide and Its Catalysis in the Cyanation Reactionscyano source; formamide; Ni catalyst; hydrocyanation; alkynes; Aryl halides27201965#N/ATRUE
639
s41467-020-19807-510.1038/s41467-020-19807-5HydrogenationFALSEhttps://doi.org/10.1038/s41467-020-19807-5Zhang, WBNat. Commun.Chiral alpha -Aryl glycines play a key role in the preparation of some bioactive products, however, their catalytic asymmetric synthesis is far from being satisfactory. Herein, we report an efficient nickel-catalyzed asymmetric hydrogenation of N-Aryl imino esters, affording chiral alpha -Aryl glycines in high yields and enantioselectivities (up to 98% ee). The hydrogenation can be conducted on a gram scale with a substrate/catalyst ratio of up to 2000. The obtained chiral N-p-methoxyphenyl alpha -Aryl glycine derivatives are not only directly useful chiral secondary amino acid esters but can also be easily deprotected by treatment with cerium ammonium nitrate for further transformations to several widely used molecules inCluding drug intermediates and chiral ligands. Formation of a chiral Ni-H species in hydrogenation is detected by H-1 NMR. Computational results indicate that the stereo selection is determined during the approach of the substrate to the catalyst. Chiral alpha -amino acids find application in the fields of pharmaceutical, biological and synthetic chemistry. Here, the authors report a nickel-catalyzed asymmetric hydrogenation of N-Aryl imino esters affording chiral alpha -Aryl glycines in high yields and enantioselectivities.Ni-catalyzed asymmetric hydrogenation of N-Aryl imino esters for the efficient synthesis of chiral alpha-Aryl glycines2202054#N/ATRUE
640
s41467-020-17188-310.1038/s41467-020-17188-3HydrogenationFALSEhttps://doi.org/10.1038/s41467-020-17188-3Zhang, BSNat. Commun.Light elements in the interstitial site of transition metals have strong influence on heterogeneous catalysis via either expression of surface structures or even direct participation into reaction. Interstitial atoms are generally metastable with a strong environmental dependence, setting up giant challenges in controlling of heterogeneous catalysis. Herein, we show that the desired carbon atoms can be manipulated within nickel (Ni) lattice for improving the selectivity in acetylene hydrogenation reaction. The radius of octahedral space of Ni is expanded from 0.517 to 0.524 angstrom via formation of Ni3Zn, affording the dissociated carbon atoms to readily dissolve and diffuse at mild temperatures. Such incorporated carbon atoms coordinate with the surrounding Ni atoms for generation of Ni3ZnC0.7 and thereof inhibit the formation of subsurface hydrogen structures. Thus, the selectivity and stability are dramatically improved, as it enables suppressing the pathway of ethylene hydrogenation and restraining the accumulation of carbonaceous species on surface. Design and synthesis of non-noble metal catalysts is crucial for highly-efficient hydrogenation. Here, the interstitial sites in nickel are manipulated with zinc and filled by dissociated carbon atoms, which drastically improve the selectivity/stability in acetylene hydrogenation reaction.Manipulating interstitial carbon atoms in the nickel octahedral site for highly efficient hydrogenation of alkyne10202047#N/ATRUE
641
jacs.9b1387610.1021/jacs.9b13876HydrogenationFALSEhttps://doi.org/10.1021/jacs.9b13876Chirik, PJJ. Am. Chem. Soc.The asymmetric hydrogenation of alpha,beta-unsaturated Carbonylic acids using readily prepared bis(phosphine) cobalt(0) 1,5-cyClooctadiene precatalysts is described. Di-, tri-, and tetrasubstituted acrylic acid derivatives with various substitution patterns as well as dehydro-a-amino acid derivatives were hydrogenated with high yields and enantioselectivities, affording chiral Carbonylic acids inCluding Naproxen, (S)-Flurbiprofen, and a D-DOPA precursor. Turnover numbers of up to 200 were routinely obtained. Compatibility with common organic functional groups was observed with the reduced cobalt(0) precatalysts, and protic solvents such as methanol and isopropanol were identified as optimal. A series of bis(phosphine) cobalt(II) bis(pivalate) complexes, which bear structural similarity to state-of-the-art ruthenium(II) catalysts, were synthesized, characterized, and proved catalytically competent. X-band EPR experiments revealed bis(phosphine)cobalt(II) bis(Carbonylate)s were generated in catalytic reactions and were identified as catalyst resting states. Isolation and characterization of a cobalt(II)-substrate complex from a stoichiometric reaction suggests that alkene insertion into the cobalt hydride occurred in the presence of free Carbonylic acid, producing the same alkane enantiomer as that from the catalytic reaction. Deuterium labeling studies established homolytic H-2 (or D-2) Activation by Co(0) and cis addition of H-2 (or D-2) across alkene double bonds, reminiscent of rhodium(I) catalysts but distinct from ruthenium(II) and nickel(II) Carbonylates that operate by heterolytic H-2 Cleavage pathways.Cobalt-Catalyzed Asymmetric Hydrogenation of alpha,beta-Unsaturated Carbonylic Acids by Homolytic H-2 Cleavage18202074#N/ATRUE
642
jacs.9b1270610.1021/jacs.9b12706HydrogenationFALSEhttps://doi.org/10.1021/jacs.9b12706Newhouse, TRJ. Am. Chem. Soc.This manuscript describes the first practical Benzylic dehydrogenation of electron-deficient heteroarenes, inCluding pyridines, pyrazines, pyrimidines, pyridazines, and triazines. This transformation allows for the efficient Benzylic oxidation of heteroarenes to afford heterocyClic styrenes by the action of nickel catalysis paired with an unconventional bromothiophene oxidant.Aryl-Nickel-Catalyzed Benzylic Dehydrogenation of Electron-Deficient Heteroarenes10202040#N/ATRUE
643
jacs.9b0795710.1021/jacs.9b07957HydrogenationFALSEhttps://doi.org/10.1021/jacs.9b07957Zhang, XMJ. Am. Chem. Soc.Nickel-catalyzed desymmetric hydrogenation has been achieved. With the Ni(OTf)(2)/(S,S)-Ph-BPE system, a series of gamma,gamma-disubstituted cyClohexadienones were transformed to the corresponding cyClohexenones with a chiral all-carbon quaternary center at the gamma position in high yields (92-98%) and excellent enantioselectivities (92%-99% ee). This catalytic system can also tolerate the desymmetric reaction of spirocarbocyClic cyClohexadienones to produce the corresponding cyClohexenones bearing a chiral spiro quaternary carbon with high yields (94%-98%) and ee values (96%-99% ee). Furthermore, this methodology provides an efficient and concise synthetic route to the intermediate of natural products cannabispirenones A and B.Nickel-Catalyzed Desymmetric Hydrogenation of CyClohexadienones: An Efficient Approach to All-Carbon Quaternary Stereocenters18201961#N/ATRUE
644
jacs.9b0336110.1021/jacs.9b03361HydrogenationFALSEhttps://doi.org/10.1021/jacs.9b03361Li, LDJ. Am. Chem. Soc.The selective hydrogenation of alkynes to alkenes is an important type of organic transformation with large-scale industrial applications. This transformation requires efficient catalysts with precise selectivity control, and palladium-based metallic catalysts are currently employed. Here we show that four-coordinated cationic nickel(II) confined in zeolite can efficiently catalyze the selective hydrogenation of acetylene to ethylene, a key process for trace acetylene removal prior to the polymerization process. Under optimized conditions, 100% acetylene conversion and an ethylene selectivity up to 97% are simultaneously achieved. This catalyst system also exhibits good stability and recyClability for potential applications. Spectroscopy investigations and density functional theory calculations reveal the heterolytic dissociation of hydrogen molecules and the importance of hydride and protons in the selective hydrogenation of acetylene to ethylene. This work provides an efficient strategy toward active and selective zeolite catalysts by utilizing the local electrostatic field within the zeolite confined space for small-molecule Activation and by linking heterogeneous and homogeneous catalysis.Acetylene-Selective Hydrogenation Catalyzed by Cationic Confined in Zeolite26201954#N/ATRUE
645
jacs.0c0019910.1021/jacs.0c00199HydrogenationFALSEhttps://doi.org/10.1021/jacs.0c00199Jackson, JEMultiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
Electrocatalytic
2020#N/AFALSE
646
jacs.9b0255210.1021/jacs.9b02552HydrogenationFALSEhttps://doi.org/10.1021/jacs.9b02552Newhouse, TRJ. Am. Chem. Soc.We herein disClose the first report of a first-row transition metal-catalyzed alpha,beta-dehydrogenation of Carbonyl compounds using allyl-nickel catalysis. This development overcomes several limitations of previously reported allyl-palladium-catalyzed oxidation, and is further leveraged for the development of an oxidative cyCloalkenylation reaction that provides access to bicyCloalkenones with fused, bridged, and spirocyClic ring systems using unactivated ketone and alkene precursors.Allyl-Nickel Catalysis Enables Carbonyl Dehydrogenation and Oxidative CyCloalkenylation of Ketones16201946#N/ATRUE
647
jacs.8b0778910.1021/jacs.8b07789HydrogenationFALSEhttps://doi.org/10.1021/jacs.8b07789Datye, AJ. Am. Chem. Soc.Since the discovery that ceria is an active catalyst for selective hydrogenation of alkynes, there has been much debate on the catalytic mechanism. In this work, we propose, based on density functional theory (DFT) investigations, a mechanism that involves the heterolytic dissociation of H-2 at oxygen vacancies of CeO2(111), facilitated by frustrated Lewis pairs consisting of spatially separated O and Ce sites. The resulting O-H and Ce-H species effectively catalyze the hydrogenation of acetylene, avoiding the overstabilization of the C2H3* intermediate in a previously proposed mechanism. On the basis of our mechanism, we propose the doping of ceria by Ni as a means to create oxygen vacancies. Interestingly, the Ni dopant is not directly involved in the catalytic reaction, but serves as a single-atom promoter. Experimental studies confirm the design principles and demonstrate much higher activity for Ni-doped ceria in selective hydrogenation of acetylene. The combined results from DFT calculations and experiment provide a basis to further develop selective hydrogenation catalysts based on earth-abundant materials.Design of Effective Catalysts for Selective Alkyne Hydrogenation by Doping of Ceria with a Single-Atom Promotor75201871#N/ATRUE
648
jacs.8b0506010.1021/jacs.8b05060HydrogenationFALSEhttps://doi.org/10.1021/jacs.8b05060Laursen, SJ. Am. Chem. Soc.A non-noble intermetallic compound catalyst consisting of Ni3Ga nanopartiCles supported on Al2O3 that exhibits high selectivity (similar to 94%), comparable activity (TOF = 4.7 X 10(-2) s(-1)), good stability (similar to 94% to 81% over the 82 h test), and regenerability in the direct dehydrogenation of propane to propylene at 600 degrees C has been developed. Through synthesis techniques that stabilize the Ni3Ga phase, the surface composition of the catalytic nanopartiCles could be tuned by Ni and Ga loading such that improved selectivity toward propylene may be achieved. Comparisons with well-defined silica supported Ni3Ga and NiGa catalysts and Ni3Ga/Al2O3 with a range of Ni:Ga loading suggested that a specific surface composition range was most promising for propylene production. The presence of Ni at the active partiCle surface was also found to be critical to drive dehydrogenation and enhance conversion, whereas the presence of Ga was necessary to attenuate the reactivity of the surface to improve selectivity and catalyst stability.Selective and Stable Non-Noble-Metal Intermetallic Compound Catalyst for the Direct Dehydrogenation of Propane to Propylene29201839#N/ATRUE
649
jacs.7b0936510.1021/jacs.7b09365HydrogenationFALSEhttps://doi.org/10.1021/jacs.7b09365Farha, OKJ. Am. Chem. Soc.Few-atom cobalt-oxide Clusters, when dispersed on a Zr-based metal-organic framework (MOF) NU-1000, have been shown to be active for the oxidative dehydrogenation (ODH) of propane at low temperatures (<230 degrees C), affording a selective and stable propene production catalyst. In our current work, a series of promoter ions with varying Lewis acidity, inCluding Ni(II), Al(III), Ti(IV) and Mo(VI), are anchored as metal-oxide,hydroxide Clusters to NU-1000 followed by Co(II) ion deposition, yielding a series of NU-1000-supported bimetallic-oxo,hydroxo,aqua Clusters. Using difference envelope density (DED) analyses, the spatial locations of the promoter ions and catalytic cobalt ions are determined. For all samples, the promoter ions are sited between pairs of Zr-6 nodes along the MOF c-axis, whereas the location of the cobalt ions varies with the promoter ions. These NU-1000 supported bimetallic-oxide Clusters are active for propane ODH after thermal Activation under 02 to open a cobalt coordination site and to oxidize Co(II) to Co(III), as evidenced by operando X-ray absorption spectroscopy at the Co K-edge. In accord with the decreasing Lewis acidity of the promoter ion, catalytic activity increases in the following order: Mo(VI) < Ti(IV) < Al(III) < Zn(II) < Ni(II). The finding is attributed to increasing ease of formation of Co(III)-O species and stabilization of a cobalt(III)oxyl/propane transition state as the Lewis acidity of the promoter ions decreases. The results point to an increasing ability to fine-tune the structure-dependent activity of MOF-supported heterogeneous catalysts. Coupled with mechanistic studies computational or experimental this ability may translate into informed prediction of improved catalysts for propane ODH and other chemical reactions.Fine-Tuning the Activity of Metal-Organic Framework-Supported Cobalt Catalysts for the Oxidative Dehydrogenation of Propane79201758#N/ATRUE
650
jacs.7b0791110.1021/jacs.7b07911HydrogenationFALSEhttps://doi.org/10.1021/jacs.7b07911Lu, CCJ. Am. Chem. Soc.Large-scale CO2 hydrogenation could offer a renewable stream of industrially important C-1 chemicals while reducing CO2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)-> Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h(-1)), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, inCluding a rare anionic d(10) Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.A Bimetallic Nickel-Gallium Complex Catalyzes CO2 Hydrogenation via the Intermediacy of an Anionic d(10) Nickel Hydride69201765#N/ATRUE
651
jacs.7b0716710.1021/jacs.7b07167HydrogenationFALSEhttps://doi.org/10.1021/jacs.7b07167Driess, MJ. Am. Chem. Soc.The first chelating bis(N-heterocyClic silylene)-xanthene ligand [Si-II(Xant)Si-II] as well as its Ni complexes [Si-II(Xant)Si-II]Ni(eta(2)-1,3-cod) and [Si-II(Xant)Si-II]Ni(PMe3)(2) were synthesized and fully characterized. Exposing [Si-II(Xant)si(II)]Ni (eta(2)-1,3-cod) to 1 bar H-2 at room temperature quantitatively generated an unexpected dinuClear hydrido Ni complex with a four-membered planar Ni2Si2 core. Exchange of the 1,3-COD ligand by PMe3 led to [Si-II(Xant)Si-II]Ni(PMe3)(2), which could activate H-2 reversibly to afford the first Si-II-stabilized mononuClear dihydrido Ni complex characterized by multi-nuClear NMR and single-crystal X-ray diffraction analysis. [Si-II(Xant)Si-II]Ni(eta(2)-1,3-cod) is a strikingly efficient precatalyst for homogeneous hydrogenation of olefins with a wide substrate scope under 1 bar H-2 pressure at room temperature. DFT calculations reveal a novel mode of H-2 Activation, in which the Sin atoms of the [Si-II(Xant)Si-II] ligand are involved in the key step of H-2 Cleavage and hydrogen transfer to the olefin.Divalent Silicon-Assisted Activation of Dihydrogen in a Bis(N-heterocyClic silylene)xanthene Nickel(0) Complex for Efficient Catalytic Hydrogenation of Olefins51201795#N/ATRUE
652
jacs.6b0051910.1021/jacs.6b00519HydrogenationFALSEhttps://doi.org/10.1021/jacs.6b00519Chirik, PJJ. Am. Chem. Soc.A highly active and enantioselective phosphine-nickel catalyst for the asymmetric hydrogenation of alpha,beta-unsaturated esters has been discovered. The coordination chemistry and catalytic behavior of nickel halide, acetate, and mixed halide-acetate with chiral bidentate phosphines have been explored and deuterium labeling studies, the method of continuous variation, nonlinear studies, and kinetic measurements have provided mechanistic understanding. Activation of molecular hydrogen by a trimeric (Me-DuPhos)(3)Ni-3(OAc)(5)I complex was established as turnover limiting followed by rapid conjugate addition of a nickel hydride and nonselective protonation to release the substrate. In addition to reaction discovery and optimization, the previously unreported utility high throughput experimentation for mechanistic elucidation is also described.Nickel-Catalyzed Asymmetric Alkene Hydrogenation of alpha,beta-Unsaturated Esters: High-Throughput Experimentation-Enabled Reaction Discovery, Optimization, and Mechanistic Elucidation93201660#N/ATRUE
653
jacs.0c1268910.1021/jacs.0c12689HydrogenationFALSEhttps://doi.org/10.1021/jacs.0c12689Rossi, LMJ. Am. Chem. Soc.Controlling the selectivity of CO2 hydrogenation catalysts is a fundamental challenge. In this study, the selectivity of supported Ni catalysts prepared by the traditional impregnation method was found to change after a first CO2 hydrogenation reaction cyCle from 100 to 800 degrees C. The usually high CH4 formation was suppressed leading to full selectivity toward CO. This behavior was also observed after the catalyst was treated under methane or propane atmospheres at elevated temperatures. In situ spectroscopic studies revealed that the accumulation of carbon species on the catalyst surface at high temperatures leads to a nickel carbide-like phase. The catalyst regains its high selectivity to CH4 production after carbon depletion from the surface of the Ni partiCles by oxidation. However, the selectivity readily shifts back toward CO formation after exposing the catalysts to a new temperature-programmed CO2 hydrogenation cyCle. The fraction of weakly adsorbed CO species increases on the carbide-like surface when compared to a Clean nickel surface, explaining the higher selectivity to CO. This easy protocol of changing the surface of a common Ni catalyst to gain selectivity represents an important step for the commercial use of CO2 hydrogenation to CO processes toward high-added-value products.Optimizing Active Sites for High CO Selectivity during CO2 Hydrogenation over Supported Nickel Catalysts2202167#N/ATRUE
654
jacs.0c0012310.1021/jacs.0c00123HydrogenationFALSEhttps://doi.org/10.1021/jacs.0c00123Kanai, MJ. Am. Chem. Soc.We developed the first acceptorless dehydrogenation of aliphatic secondary alcohols to ketones under visible light irradiation at room temperature by devising a ternary hybrid catalyst system comprising a photoredox catalyst, a thiophosphate organocatalyst, and a nickel catalyst. The reaction proceeded through three main steps: hydrogen atom transfer from the alpha-C-H bond of an alcohol substrate to the thiyl radical of the photooxidized organocatalyst, interception of the generated carbon-centered radical with a nickel catalyst, and beta-hydride elimination. The reaction proceeded in high yield under mild conditions without producing side products (except H-2 gas) from various alcohols, inCluding sterically hindered alcohols, a steroid, and a pharmaceutical derivative. This catalyst system also promoted acceptorless cross-dehydrogenative esterification from aldehydes and alcohols through hemiacetal intermediates.Catalytic Acceptorless Dehydrogenation of Aliphatic Alcohols28202065#N/ATRUE
655
ja991218s10.1021/ja991218sHydrogenationFALSEhttps://doi.org/10.1021/ja991218sHo, WJ. Am. Chem. Soc.The dynamics and chemistry of individual ethylene molecules adsorbed on the Ni(110) surface at 13 K have been studied with a variable temperature scanning tunneling microscope (STM). By applying a voltage pulse to a single ethylene molecule, the tunneling electrons cause the molecule to reversibly hop away from and back under the tip. The five ethylene isotopes hop at different rates. A larger voltage pulse (1.1-1.5 V) induces dehydrogenation, and a strong primary isotope effect is observed. By using inelastic electron tunneling spectroscopy (IETS) with the STM, we identified the dehydrogenated products from the characteristic vibrational energies as acetylene. This identification is further supported with STM-IETS on single acetylene molecules adsorbed directly from the gas phase. Two different types of acetylene exist on the surface. They can be distinguished in the regular STM image, and they exhibit shifted vibrational peaks. Applying another voltage pulse (1.0-4.8 V) further dehydrogenates acetylene to carbon atoms.Vibrational analysis of single molecule chemistry: Ethylene dehydrogenation on Ni(110)69199954#N/ATRUE
656
ja802554g10.1021/ja802554gHydrogenationFALSEhttps://doi.org/10.1021/ja802554gComelli, GJ. Am. Chem. Soc.We demonstrate that the key step for the reaction of CO2 with hydrogen on Ni(110) is a change of the activated molecule coordination to the metal surface. At 90 K, CO2 is negatively charged and chemically bonded via the carbon atom. When the temperature is increased and H approaches, the H-CO2 complex flips and binds to the surface through the two oxygen atoms, while H binds to the carbon atom, thus yielding formate. We provide the atomic-level description of this process by means of conventional ultrahigh vacuum surface science techniques combined with density functional theory calculations and corrB(OH)2rated by high pressure reactivity tests. Knowledge about the details of the mechanisms involved in this reaction can yield a deeper comprehension of heterogeneous catalytic organic synthesis processes involving carbon dioxide as a reactant. We show why on Ni the CO2 hydrogenation barrier is remarkably smaller than that on the common Cu metal-based catalyst. Our results provide a possible interpretation of the observed high catalytic activity of NiCu alloys.Carbon dioxide hydrogenation on Ni(110)129200843#N/ATRUE
657
ja501592y10.1021/ja501592yHydrogenationFALSEhttps://doi.org/10.1021/ja501592yLercher, JAJ. Am. Chem. Soc.The effect of an aqueous phase on phenol hydrogenation over Pt and Ni catalysts was investigated using density functional theory-based ab initio molecular dynamics calculations. The adsorption of phenol and the addition of the first and second hydrogen adatoms to three, ring carbon positions (ortho, meta, and para with respect to the phenolic OH group) were explored in both vacuum and liquid water. The major change in the electronic structure of both Pt(111) and Ni(111) surfaces, between a gaseous and liquid phase environment, results from a repulsion between the electrons of the liquid water and the diffuse tail of electron density emanating from the metal surface. The redistribution of the metal's electrons toward the subsurface layer lowers the metal work function by about 1 eV. The lower work function gives the liquid-covered metal a higher chemical reduction strength and, in consequence, a lower oxidation strength, which, in turn lowers the phenol adsorption energy, despite the stabilizing influence of the solvation of the partly positively charged adsorbate. At both the solid/vapor and the solid/water interface, H adatom addition involves neutral H atom transfer hence the reaction barriers for adding H adatoms to phenol are lowered by only 10-20 kJ/mol, due to a small stabilizing at the transition state. More importantly, the liquid environment significantly influences the relative energetics of charged, surface-bound intermediates and of proton-transfer reactions like keto/enol isomerization. For phenol hydrogenation, solvation in water results in an energetic preference to form ketones as a result of tautomerization of surface-bound enol intermediates.First-Principles Study of Phenol Hydrogenation on Pt and Ni Catalysts in Aqueous Phase155201460#N/ATRUE
658
ja206924610.1021/ja2069246HydrogenationFALSEhttps://doi.org/10.1021/ja2069246Han, LBJ. Am. Chem. Soc.A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disClosed for the first time from a reaction of alkyne, Carbonylic acid, and a zerovalent group 10 transition metal complex M(PEt3)(4) (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a Carbonylic acid with Pt(PEt3)(4), but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding Clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Bronsted acid and Pd(0) complex. This finding also leads to the disClosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.Facile Regio- and Stereoselective Hydrometalation of Alkynes with a Combination of Carbonylic Acids and Group 10 Transition Metal Complexes: Selective Hydrogenation of Alkynes with Formic Acid1472011129#N/ATRUE
659
ja075132810.1021/ja0751328HydrogenationFALSEHall, MBThe catalytic dehydrogenation of ammonia-borane involving an unexpected hydrogen transfer to ligated carbene and subsequent carbon-hydrogen Activation2008#N/ATRUE
660
ja066860i10.1021/ja066860iHydrogenationFALSEhttps://doi.org/10.1021/ja066860iBaker, RTJ. Am. Chem. Soc.We report here the first example of a homogeneous first row transition-metal-based catalyst which is active for dehydrogenation of ammonia-borane, H3NBH3, a promising chemical hydrogen storage material. Addition of ammonia-borane to an active catalyst formed in situ from the reaction of Ni(cod)(2) and 2 equiv of an appropriate N-heterocyClic carbene (NHC) rapidly evolves hydrogen at 60 degrees C. Using a gas burette to quantify the gas evolved, 29 of a possible 31 mL of H-2 for 3 equiv of H-2 was produced, equating to > 2.5 equiv of H-2 from ammonia-borane. Kinetic isotope effects of deuterated derivatives of ammonia-borane suggest that both N-H and B-H bonds are being broken in the rate-determining step(s).Base metal catalyzed dehydrogenation of ammonia-borane for chemical hydrogen storage577200718#N/ATRUE
661
ja00845a01410.1021/ja00845a014HydrogenationFALSEhttps://doi.org/10.1021/ja00845a014HOLM, RHJ. Am. Chem. Soc.SYNTHETIC TRANSFORMATIONS OF TETRAAZA MACROCYClIC METAL-COMPLEXES - PREPARATION OF CORRINOID AND OTHER UNSATURATED RING-SYSTEMS BY OXIDATIVE DEHYDROGENATION REACTIONS OF NICKEL(II), COPPER(II), AND COBALT(II) MACROCYLES25197555#N/ATRUE
662
ja00472a05810.1021/ja00472a058HydrogenationFALSEhttps://doi.org/10.1021/ja00472a058RADONOVICH, LJJ. Am. Chem. Soc.PI-ARENE COMPLEXES OF NICKEL(II) STABILIZED BY SIGMA-BONDED PENTAFLUOROPHENYL LIGANDS - HOMOGENEOUS ARENE HYDROGENATION CATALYSIS AND UNUSUALLY LABILE PI-ARENE LIGANDS53197815#N/ATRUE
663
d0sc06471h10.1039/d0sc06471hHydrogenationFALSEhttps://doi.org/10.1039/d0sc06471hDriess, MChem. Sci.The isolable chelating bis(N-heterocyClic silylenyl)-substituted terphenyl ligand [Si-II(Terp)Si-II] as well as its bis(phosphine) analogue [P-III(Terp)P-III] have been synthesised and fully characterised. Their reaction with Ni(cod)(2) (cod = cyCloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecular eta(2)-arene coordination of Ni, [E(Terp)E]Ni(eta(2)-arene) (E = P-III, Si-II; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H-2 Activation and H atom transfer, [Si-II(Terp)Si-II]Ni(eta(2)-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H-2 pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the eta(2)-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [Si-II(Terp)Si-II]Ni(eta(2)-arene). The mechanism has been established by kinetic measurements, inCluding kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h(-1)) could be realised.Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst1202169#N/ATRUE
664
d0sc00247j10.1039/d0sc00247jHydrogenationFALSEhttps://doi.org/10.1039/d0sc00247jJitsukawa, KChem. Sci.The study of metal phosphide catalysts for organic synthesis is rare. We present, for the first time, a well-defined nano-cobalt phosphide (nano-Co2P) that can serve as a new Class of catalysts for the hydrogenation of nitriles to primary amines. While earth-abundant metal catalysts for nitrile hydrogenation generally suffer from air-instability (pyrophoricity), low activity and the need for harsh reaction conditions, nano-Co2P shows both air-stability and remarkably high activity for the hydrogenation of valeronitrile with an excellent turnover number exceeding 58000, which is over 20- to 500-fold greater than that of those previously reported. Moreover, nano-Co2P efficiently promotes the hydrogenation of a wide range of nitriles, which inClude di- and tetra-nitriles, to the corresponding primary amines even under just 1 bar of H-2 pressure, far milder than the conventional reaction conditions. Detailed spectroscopic studies reveal that the high performance of nano-Co2P is attributed to its air-stable metallic nature and the increase of the d-electron density of Co near the Fermi level by the phosphidation of Co, which thus leads to the accelerated Activation of both nitrile and H-2. Such a phosphidation provides a promising method for the design of an advanced catalyst with high activity and stability in highly efficient and environmentally benign hydrogenations.A cobalt phosphide catalyst for the hydrogenation of nitriles13202060#N/ATRUE
665
cs300051j10.1021/cs300051jHydrogenationFALSEhttps://doi.org/10.1021/cs300051jMarin, GBACS Catal.The Single-Event Micro Kinetic (SEMK) methodology, which had been successfully applied to benzene hydrogenation on a Pt catalyst, has now been extended toward substituted monoaromatics, that is, toluene and o-xylene. The single event concept Combined with thermodynamic constraints. allowed to significantly reduce the number of adjustable parameters. In addition to the number of unsaturated nearest neighbor carbon atoms, H-atom addition rate and equilibrium coefficients were assumed to depend on the carbon atom type, that is, secondary or tertiary. This leads to three additional :reaction families compared to benzene hydrogenation: Gas. phase toluene and o-xylene hydrogenation experiments were performed on 0.5 wt % Pt/ZSM-22 in a temperature range from 423 to 498 K, a total pressure range from 1 to 3 MPa, H-2 inlet partial pressures between 100 and 600 kPa and aromatic inlet partial pressures between 10 and 60 kPa. A simultaneous regression of the :SEMK,Model to an experimental data set consisting of 39 toluene and 37 o-xylene hydrogenation experiments resulted in Activation energies of H additions to tertiary:carbon:atoms:that are 10.5 kJ mol(-1) higher than to secondary carbon atoms. This can be related to the steric hindrance experienced during H addition to a carbon atom bearing a substituent. The presence of a substituent on the aromatic king was found not to affect the Chemisorption enthalpies. The reaction path analysis has been carried out via differential contribution analysis and identified that the hydrogenation first, occurs at secondary carbon atoms, prior to the hydrogenation of the tertiary carbon atoms in the hydrogenation Sequence. This is in line with the distribution of hydrocarbon species on the catalyst surfaceExtension of the Single-Event Microkinetic Model to Alkyl Substituted Monoaromatics Hydrogenation on a Pt Catalysthydrogenation; monoaromatics; toluene; o-xylene; platinum; noble metal; single event microkinetic modeling15201251#N/ATRUE
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chem.20070182210.1002/chem.200701822HydrogenationFALSEhttps://doi.org/10.1002/chem.200701822Yu, SHControllable synthesis of VSB-5 micirospheres and microrods: Growth mechanism and selective hydrogenation catalysis2008#N/ATRUE
667
c8sc05230a10.1039/c8sc05230aHydrogenationFALSEhttps://doi.org/10.1039/c8sc05230aKlankermayer, JChem. Sci.Herein a highly active non-precious transition metal catalyst system for homogeneous hydrogenation of carbon dioxide to formate is presented. The application of selected nickel(ii) salts in combination with tailored multidentate ligands enabled the effective transformation of carbon dioxide with an exceptional TON of up to 4.65 x 10(6). This unprecedented productivity based on the novel nickel catalyst not only outmatches that of existing systems containing first row transition metals, but also established catalysts based on precious transition metals.A highly active non-precious transition metal catalyst for the hydrogenation of carbon dioxide to formates12201935#N/ATRUE
668
c8sc04712j10.1039/c8sc04712jHydrogenationFALSEhttps://doi.org/10.1039/c8sc04712jLu, CCChem. Sci.We present three heterobimetallic complexes containing an isostructural nickel center and a lutetium ion in varying coordination environments. The bidentate (Pr2PCH2NHPh)-Pr-i and nonadentate ((Pr2PCH2NHAr)-Pr-i)(3)tacn ligands were used to prepare the Lu metalloligands, Lu((Pr2PCH2NPh)-Pr-i) 3 (1) and Lu{((Pr2PCH2NAr)-Pr-i)(3)tacn} (2), respectively. Reaction of Ni(COD) 2 (where COD is 1,5-cyClooctadiene) and 1 afforded NiLu((Pr2PCH2NPh)-Pr-i)(3) (3), with a Lu coordination number (CN) of 4 and a Ni-Lu distance, d(Ni-Lu), of 2.4644(2) degrees A. Complex 3 can further bind THF to form 3-THF, increasing both the Lu CN to 5 and d(Ni-Lu) to 2.5989(4) degrees A. On the other hand, incorporation of Ni(0) into 2 provides NiLu{((Pr2PCH2NAr)-Pr-i)(3)tacn} (4), in which the Lu coordination environment is more saturated (CN = 6), and the d(Ni-Lu) is substantially elongated at 2.9771(5) angstrom. CyClic voltammetry of the three Ni-Lu complexes shows an overall similar to 410 mV shift in the Ni(0/I) redox couple, suggesting tunability of the Ni electronics across the series. Computational studies reveal polarized bonding interactions between the Ni 3d(z2) (major) and the Lu 5d(z2) (minor) orbitals, where the percentage of Lu character increases in the order: 4 (6.0% Lu 5d(z2)) < 3-THF (8.5%) < 3 (9.3%). All three Ni-Lu complexes bind H-2 at low temperatures (-30 to -80 degrees C) and are competent catalysts for styrene hydrogenation. Complex 3 outperforms 4 with a four-fold faster rate. Additionally, adding increasing THF equivalents to 3, which would favor build-up of 3-THF, decreases the rate. We propose that altering the coordination sphere of the Lu support can influence the resulting properties and catalytic activity of the active Ni(0) metal center.Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment24201980#N/ATRUE
669
anie.20190393610.1002/anie.201903936HydrogenationFALSEhttps://doi.org/10.1002/anie.201903936Sun, LCAngew. Chem.-Int. Edit.The use of water as an oxygen and hydrogen source for the paired oxygenation and hydrogenation of organic substrates to produce valuable chemicals is of utmost importance as a means of establishing green chemical syntheses. Inspired by the active Ni3+ intermediates involved in electro-catalytic water oxidation by nickel-based materials, we prepared NiBx as a catalyst and used water as the oxygen source for the oxygenation of various organic compounds. NiBx was further employed as both an anode and a cathode in a paired electrosynthesis cell for the respective oxygenation and hydrogenation of organic compounds, with water as both the oxygen and hydrogen source. Conversion efficiency and selectivity of >= 99% were observed during the oxygenation of 5-hydroxy-methylfurfural to 2,5-furandiCarbonylic acid and the simultaneous hydrogenation of p-nitrophenol to p-aminophenol. This paired electrosynthesis cell has also been coupled to a solar cell as a stand-alone reactor in response to sunlight.Paired Electrocatalytic Oxygenation and Hydrogenation of Organic Substrates with Water as the Oxygen and Hydrogen Sourceelectrochemistry; green chemical synthesis; hydrogenation; oxygenation; water
Electrocatalytic
47201931#N/AFALSE
670
c8sc02864h10.1039/c8sc02864hHydrogenationFALSEhttps://doi.org/10.1039/c8sc02864hGrutzmacher, HChem. Sci.The dinuClear ruthenium complex [Ru2H(mu-H)(Me(2)dad)(dbcot)(2)] contains a 1,4-dimethyl-diazabuta-1,3-diene (Me(2)dad) as a non-innocent bridging ligand between the metal centers to give a [Ru-2(Me(2)dad)] core. In addition, each ruthenium is bound to one dibenzo[a,e]cyClooctatetraene (dbcot) ligand. This Ru dimer converts H-2 to protons and electrons. It also catalyzes reversibly under mild conditions the selective hydrogenation of vitamins K-2 and K-3 to their corresponding hydroquinone equivalents without affecting the C=C double bonds. Mechanistic studies suggest that the [Ru-2(Me(2)dad)] moiety, like hydrogenases, reacts with H-2 and releases electrons and protons stepwise.A low-valent dinuClear ruthenium diazadiene complex catalyzes the oxidation of dihydrogen and reversible hydrogenation of quinones2201958#N/ATRUE
671
c8cc03829e10.1039/c8cc03829eHydrogenationFALSE#REF!Chen, JGGHigh selectivity of CO2 hydrogenation to CO by controlling the valence state of nickel using perovskite2018#N/ATRUE
672
c7sc02073b10.1039/c7sc02073bHydrogenationFALSEhttps://doi.org/10.1039/c7sc02073bZhang, JLChem. Sci.Fine-tuning of the porphyrin beta-periphery is important for naturally occurring metal tetrapyrroLes to exert diverse biological roles. Here we describe how this approach is also applied to design molecular cataLysts, as exemplified by Ni(u) porphyrinoids catalyzing the hydrogen evolution reaction (HER). We found that beta-hydrogenation of porphyrin remarkably enhances the eLectrocataLytic HER reactivity (turnover frequencies of 6287 vs. 265 s(-1) for Ni(ii) chlorin (Ni-2) and porphyrin (Ni-1), and of 1737 vs. 342 s(-1) for Ni(u) hydroporphoLactone (Ni-4) and porphoLactone (Ni-3), respectively) using trifluoroacetic acid (TFA) as the proton source. DFT calculations suggested that after two-electron reduction, beta-hydrogenation renders more electron density Located on the Ni center and thus prefers to generate a highly reactive nickel hydride intermediate. To demonstrate this, decamethyLcobaLtocene Co(Cp*)(2) was used as a chemical reductant. [Ni-2](2-) reacts ca. 30 times faster than [Ni-1](2-) with TFA, which is in Line with the eLectrocataLysis and computational results. Thus, such subtle structural changes inducing the distinctive reactivity of Ni(u) not only test the fundamental understanding of naturaL Ni tetrapyrroLes but also provide a valuable due to design metal porphyrinoid cataLysts.Enhancing the reactivity of nickel(II) in hydrogen evolution reactions (HERs) by beta-hydrogenation of porphyrinoid ligands32201761#N/ATRUE
673
c7cc06116a10.1039/c7cc06116aHydrogenationFALSEZhao, CA nickel-phyllosilicate core-echinus catalyst via a green and base additive free hydrothermal approach for hydrogenation reactions2017#N/ATRUE
674
c0sc00483a10.1039/c0sc00483aHydrogenationFALSEhttps://doi.org/10.1039/c0sc00483aGrutzmacher, HChem. Sci.A rare paramagnetic organometallic nickel(I) olefin complex can be isolated using the ligand bis(5H-dibenzo[a,d]cyClohepten-5-yl)amine. This complex and related nickel(0) hydride complexes show very high catalytic activity in the dehydrogenation of dimethylamino borane with release of one equivalent of dihydrogen.Amino olefin nickel(I) and nickel(0) complexes as dehydrogenation catalysts for amine boranes79201186#N/ATRUE
675
anie.20191653410.1002/anie.201916534HydrogenationFALSEhttps://doi.org/10.1002/anie.201916534Zhang, WBAngew. Chem.-Int. Edit.Earth-abundant nickel, coordinated with a suitable chiral bisphosphine ligand, was found to be an efficient catalyst for the asymmetric hydrogenation of 2-amidoacrylates, affording the chiral alpha-amino acid esters in quantitative yields and excellent enantioselectivity (up to 96 % ee). The active catalyst component was studied by NMR and HRMS, which helped us to realize high catalytic efficiency on a gram scale with a low catalyst loading (S/C=2000). The hydrogenated products could be simply converted into chiral alpha-amino acids, beta-amino alcohols, and their bioactive derivatives. Furthermore, the catalytic mechanism was investigated using deuterium-labeling experiments and computational calculations.Nickel-Catalyzed Asymmetric Hydrogenation of 2-Amidoacrylates2-amidoacrylates; asymmetric hydrogenation; chiral alpha-amino acids; homogeneous catalysis; nickel20202081#N/ATRUE
676
anie.20191638510.1002/anie.201916385HydrogenationFALSEhttps://doi.org/10.1002/anie.201916385Leitner, WAngew. Chem.-Int. Edit.Rhodium nanopartiCles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh@SILP(Ph-3-P-NTf2)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO2, ionic liquid, nanopartiCles) led to outstanding catalytic properties. In particular, intimate contact between the nanopartiCles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh@SILP(Ph-3-P-NTf2) catalyst was active for the hydrodeoxygenation of Benzylic ketones under mild conditions, and the product distribution for non-Benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh@SILP(Ph-3-P-NTf2) catalyst opens the way to the production of a wide range of high-value cyClohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel-Crafts acylation products and lignin-derived aromatic ketones.Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to CyClohexane Derivatives Using a Rh@SILP Catalysthydrodeoxygenation; ionic liquids; nanopartiCles; rhodium; supported ionic liquid phases11202076#N/ATRUE
677
anie.20190748710.1002/anie.201907487HydrogenationFALSEhttps://doi.org/10.1002/anie.201907487Gronert, SAngew. Chem.-Int. Edit.A gas-phase anionic nickel(0) fluorenyl complex is shown to effect the dehydrogenation of linear, branched, and cyClic alkanes via C-H Activation. It performs dehydrogenations via a C-H insertion followed by beta-hydride elimination. When given energy via collision-induced dissociation, the system is capable of second and third dehydrogenations to form dienes and aromatics such as benzene. Kinetic isotope effects and DFT calculations completed at the M06/6-311+G** level support the proposed mechanism. The metal complex can act as an experimental model for graphene-supported nickel single-atom catalysts and suggests that these catalysts are capable of alkane dehydrogenation via C-H Activation.Gas-Phase Dehydrogenation of Alkanes: C-H Activation by a Graphene-Supported Nickel Single-Atom Catalyst Modelalkanes; C-H Activation; dehydrogenation; gas-phase reactions; nickel11201939#N/ATRUE
678
anie.20190332710.1002/anie.201903327HydrogenationFALSEhttps://doi.org/10.1002/anie.201903327Zhang, BAngew. Chem.-Int. Edit.Exploring an alternative anodic reaction to produce value-added chemicals with high selectivity, especially integrated with promoted hydrogen generation, is desirable. Herein, a selective semi-dehydrogenation of tetrahydroisoquinolines (THIQs) is demonstrated to replace the oxygen evolution reaction (OER) for boosting H-2 evolution reaction (HER) in water over a Ni2P nanosheet electrode. The value-added semi-dehydrogenation products, dihydroisoquinolines (DHIQs), can be selectively obtained with high yields at the anode. The controllable semi-dehydrogenation is attributed to the in situ formed Ni-II/Ni-III redox active species. Such a strategy can deliver a variety of DHIQs bearing electron-withdrawing/donating groups in good yields and excellent selectivities, and can be applied to gram-scale synthesis. A two-electrode Ni2P bifunctional electrolyzer can produce both H-2 and DHIQs with robust stability and high Faradaic efficiencies at a much lower cell voltage than that of overall water splitting.Integrating Hydrogen Production with Aqueous Selective Semi-Dehydrogenation of Tetrahydroisoquinolines over a Ni2P Bifunctional Electrodeelectrocatalysis; hydrogen evolution reaction (HER); nickel; Raman spectroscopy; semi-dehydrogenation84201950#N/ATRUE
679
anie.20180842810.1002/anie.201808428HydrogenationFALSEhttps://doi.org/10.1002/anie.201808428Lercher, JAAngew. Chem.-Int. Edit.Hydrogenation on Mo and W sulfides occurs at the edges of the sulfide slabs. The rate of hydrogen addition is directly proportional to the concentration of sulfhydryl (SH) groups at the slab edge and the metal atom attached to it. Sulfhydryl groups vicinal to edge-incorporated Ni hydrogenate with much higher rates than SH Close to Mo and W. Each subset of SH groups, however, exhibits nearly identical intrinsic activity and selectivity, independent of the sulfide composition. The higher activity of Ni-WS2 compared to Ni-MoS2 stems from a higher concentration of SH groups on the former sulfide associated with a higher tendency of its surface vacancies to react with H-2.Active Sites on Nickel-Promoted Transition-Metal Sulfides That Catalyze Hydrogenation of Aromatic Compoundsactive sites; aromatic compounds; hydrogenation; nickel; transition-metal sulfides17201844#N/ATRUE
680
anie.20180223110.1002/anie.201802231HydrogenationFALSEhttps://doi.org/10.1002/anie.201802231Zhang, TAngew. Chem.-Int. Edit.Hydrothermally stable, acid-resistant nickel catalysts are highly desired in hydrogenation reactions, but such a catalyst remains absent owing to the inherent vulnerability of nickel under acidic conditions. An ultra-durable Ni-N-C single-atom catalyst (SAC) has now been developed that possesses a remarkable Ni content (7.5wt%) required for practical usage. This SAC shows not only high activities for hydrogenation of various unsaturated substrates but also unprecedented durability for the one-pot conversion of cellulose under very harsh conditions (245 degrees C, 60bar H-2, presence of tungstic acid in hot water). Using integrated spectroscopy characterization and computational modeling, the active site structure is identified as (Ni-N4)N, where significantly distorted octahedral coordination and pyridinic N constitute a frustrated Lewis pair for the heterolytic dissociation of dihydrogen, and the robust covalent chemical bonding between Ni and N atoms accounts for its ultrastability.A Durable Nickel Single-Atom Catalyst for Hydrogenation Reactions and Cellulose Valorization under Harsh Conditionsactive sites; biomass conversion; nickel; single-atom catalysts; XANES simulation111201849#N/ATRUE
681
anie.20150101810.1002/anie.201501018HydrogenationFALSEhttps://doi.org/10.1002/anie.201501018Zhou, JRAngew. Chem.-Int. Edit.We report the use of nickel catalysts for the catalytic transfer hydrogenation of hydrazones and other ketimines with formic acid. Strongly donating bisphosphines must be used to support the catalysts. As in enzymatic catalysis, attractive weak interactions may be important for stereochemical control by the nickel/binapine catalyst.Nickel-Catalyzed Asymmetric Transfer Hydrogenation of Hydrazones and Other Ketiminesasymmetric catalysis; hydrazones; hydride insertion; nickel; transfer hydrogenation782015130#N/ATRUE
682
anie.20140774410.1002/anie.201407744HydrogenationFALSEhttps://doi.org/10.1002/anie.201407744Zhou, JRAngew. Chem.-Int. Edit.The field of asymmetric (transfer) hydrogenation of prochiral olefins has been dominated by noble metal catalysts based on rhodium, ruthenium, and iridium. Herein we report that a simple nickel catalyst is highly active in the transfer hydrogenation using formic acid. Chiral alpha- and beta-amino acid derivatives were obtained in good to excellent enantioselectivity. The key toward success was the use of the strongly donating and sterically demanding bisphosphine Binapine.Nickel-Catalyzed Asymmetric Transfer Hydrogenation of Olefins for the Synthesis of alpha- and beta-Amino Acidsamino acids; hydride insertion; formic acid; nickel; transfer hydrogenation74201457#N/ATRUE
683
anie.20140508010.1002/anie.201405080HydrogenationFALSEhttps://doi.org/10.1002/anie.201405080Nguyen, STAngew. Chem.-Int. Edit.Five different first-row transition metal precursors (V-III, Cr-III, Mn-II, Co-II, Ni-II) were successfully incorporated into a catechol porous organic polymer (POP) and characterized using ATR-IR and XAS analysis. The resulting metallated POPs were then evaluated for catalytic alkyne hydrogenation using high-throughput screening techniques. All POPs were unexpectedly found to be active and selective catalysts for alkyne semihydrogenation. Three of the metallated POPs (V, Cr, Mn) are the first of their kind to be active single-site hydrogenation catalysts. These results highlight the advantages of using a POP platform to develop new catalysts which are otherwise difficult to achieve through traditional heterogeneous and homogeneous routes.Discovery of Highly Selective Alkyne Semihydrogenation Catalysts Based on First-Row Transition-Metallated Porous Organic Polymersheterogeneous catalysis; high-throughput screening; hydrogenation; polymers; transition metals40201444#N/ATRUE
684
acscatal.9b0540210.1021/acscatal.9b05402HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b05402Chandler, BDACS Catal.Bimetallic NiAu catalysts have garnered broad interest for a variety of reactions inCluding automotive emissions, selective hydrogenation, selective oxidation, hydrodechlorination, and biomass conversion. However, the bulk immiscibility of the two metals, complicating catalyst synthesis, has limited studies of this bimetallic system. We report a solution-phase synthesis for Ni and bimetallic NiAu heterogeneous catalysts. Using oleylamine as a capping agent, an optimized synthesis for Ni catalysts led to supported partiCles with a narrow size distribution (4.7 +/- 0.4 nm). Gold was added to the Ni nanopartiCles via galvanic displacement of Ni in organic solution, the partiCles were deposited onto commercial alumina, and oleylamine capping agent was removed. The catalytic activity of the bimetallic materials in 1-octyne partial hydrogenation was in between the activity of monometallic Ni and Au catalysts. At high space velocity, the bimetallic catalysts largely maintained the high alkene selectivity associated with Au catalysts (>90% alkene selectivity at a 95% conversion). At lower space velocities, the NiAu catalysts also had a reduced propensity to overhydrogenate the alkene (relative to Ni). A simple catalyst performance parameter, which combined activity, selectivity, and space velocity, was developed and used to describe the overall performance of each catalyst under varying reaction conditions. By this metric, the bimetallic catalysts had considerably better performance than monometallic Ni. The most active bimetallic catalyst was examined with a week-long stability test; it showed no activity loss with a 100% carbon balance. Catalysts were characterized by transmission electron microscopy, X-ray diffraction, H-2 and N-2 adsorption, and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The reactivity and characterization studies suggest the active catalysts are likely composed of bimetallic NiAu surfaces. The incorporation of Au into the catalysts suppresses H-2 adsorption on Ni, leading to lower hydrogen coverage during catalysis; this contributes to slowing undesirable alkene hydrogenation and improving catalyst selectivity.Supported Ni-Au Colloid Precursors for Active, Selective, and Stable Alkyne Partial Hydrogenation Catalystsalkyne semihydrogenation; colloid synthesis; Ni-Au; bimetallic catalyst; catalyst deActivation; reaction kinetics; catalyst performance; hydrogen adsorption42020101#N/ATRUE
685
acscatal.9b0533810.1021/acscatal.9b05338HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b05338Vela, JACS Catal.Motivated by increased awareness about nitrate contamination of surface waters and its deleterious effects in human and animal health, we sought an alternative, non-noble metal catalyst for the chemical degradation of nitrate. First row transition metal phosphides recently emerged as excellent alternatives for hydrogen evolution and hydrotreating reactions. We demonstrate that a key member of this family, Ni2P, readily hydrogenates nitrate (NO3-) to ammonia (NH3) near ambient conditions with very high selectivity (96%). One of the few non-precious metal-based catalysts for this transformation, and among ca. 1% of catalysts with NH3 selectivity, Ni2P can be recyCled multiple times with limited loss of activity. Both nitrite (NO2-) and nitric oxide (NO) intermediates are also hydrogenated. Density functional theory (DFT) indicates that.in the absence of a catalyst.nitrite hydrogenation is the reaction bottleneck. A variety of adsorbates (H, O, N, NO) induce surface reconstruction with top-layer Ni-rich surface stoichiometry. Critically, H saturation coverage on Ni2P(001) is only ca. 3 nm(-2), significantly less than that on Pd(111) and Ni(111) of ca. 15-18 nm(-2), which may play a key role in allowing coadsorption of NOx-. The ability of Earth-abundant, binary metal phosphides such as Ni2P to catalyze nitrate hydrogenation could transform and help us to better understand the basic science behind catalytic hydrogenation and, in turn, advance the next generation of oxyanion removal technologies.Mild and Selective Hydrogenation of Nitrate to Ammonia in the Absence of Noble Metalsnitrate removal; nitrate reduction; catalytic hydrogenation; Ni2P catalysts; non-precious metal; noble metal-free; high selectivity; ammonia7202084#N/ATRUE
686
acscatal.9b0503110.1021/acscatal.9b05031HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b05031Li, QBACS Catal.Selective hydrogenation of cinnamaldehyde (CAL) is an important reaction because the main products, cinnamic alcohol (COL) and hydrocinnamaldehyde (HCAL), are used in various fields, such as production of pharmaceutical intermediates, chemicals, perfumes, and fragrances. In recent years, numerous metal-based catalysts and significant study achievements have been reported. Thus, this Review focuses on selective hydrogenation of CAL to target products in terms of metal-based catalysts and summarizes recent developments in this reaction with different catalysts, inCluding Pt-, Pd-, Ru-, Ni-, Co-, and Cu-based catalysts. In addition, the reaction mechanisms of different catalysts, the effects of catalyst substrates, the different catalyst structures, and the synergistic effects in bimetallic catalysts are discussed. Lastly, the limitations and barriers encountered for noble metal and non-noble metal catalysts in the current study as well as potential research trends are discussed.Recent Advances in Selective Hydrogenation of Cinnamaldehyde over Supported Metal-Based Catalystscinnamaldehyde (CAL); selective hydrogenation; metal-based catalysts; cinnamyl alcohol (COL); hydrocinnamaldehyde (HCAL)212020155#N/ATRUE
687
acscatal.9b0292110.1021/acscatal.9b02921HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b02921Holladay, JDACS Catal.Electrocatalytic hydrogenation is increasingly studied as an alternative to integrate the use of recyCled carbon feedstocks with renewable energy sources. However, the abundant empiric observations available have not been correlated with fundamental properties of substrates and catalysts. In this study, we investigated electrocatalytic hydrogenation of a homologues series of Carbonylic acids, ketones, phenolics, and aldehydes on a variety of metals (Pd, Rh, Ru, Cu, Ni, Zn, and Co). We found that the rates of Carbonyl reduction in aldehydes correlate with the corresponding binding energies between the aldehydes and the metals according to the Sabatier principle. That is, the highest rates are obtained at intermediate binding energies. The rates of H-2 evolution that occur in parallel to hydrogenation also correlate with the H-metal binding energies, following the same volcano-type behavior. Within the boundaries of this model (e.g., compounds reactive at room temperature and without important steric effects over the Carbonyl group), the reported correlations help to explain the complex trends derived from the experimental observations, allowing for the correlation of rates with binding energies and the differentiation of mechanistic routes.Understanding the Role of Metal and Molecular Structure on the Electrocatalytic Hydrogenation of Oxygenated Organic Compoundselectrocatalytic hydrogenation; H-2 evolution; theoretical thermodynamic descriptors; Sabatier principle
Electrocatalytic
22201960#N/AFALSE
688
acscatal.9b0486310.1021/acscatal.9b04863HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b04863Stockenhuber, MACS Catal.The promoting effect of manganese on the Ni/Al2O3 catalyst for the hydrogenation of carbon oxides, in the presence of light hydrocarbons, was studied. Ni/Al2O3 displayed a high activity for the complete conversion of CO and CO2 to methane and C2+ hydrocarbons. Moreover, over a discrete and relatively narrow temperature range, the net concentration of light C2+ hydrocarbons was elevated, with the exit stream containing a higher concentration of C2+ species than was present in the feed stream and the product stream being virtually free of carbon oxides. It is found that the addition of manganese can enhance the selectivity toward the production of light hydrocarbons. A series of Ni-Mn/Al2O3 catalysts, prepared with different Ni/Mn ratios, were studied. Various characterization techniques such as X-ray diffraction (XRD) analysis, CO and H-2 chemisorption, in situ nitric oxide adsorption Fourier transform infrared spectroscopy (NO-FTIR), and temperature-programmed reduction (TPR) were performed to gain an insight into how the addition of Mn to the primary catalyst enhances the yield of light hydrocarbons. The origin of Mn promotion was demonstrated through density functional theory (DFT) calculations, which revealed the favorable Mn substitution at the Ni(211) step edge sites under reducing conditions. The affinity of these Mn species toward oxidation stabilizes the CO dissociation product and thus provides a thermodynamic driving force that promotes C-O bond Cleavage compared to the Mn-unmodified catalyst surface.Effect of Manganese on the Selective Catalytic Hydrogenation of COx in the Presence of Light Hydrocarbons Over Ni/Al2O3: An Experimental and Computational StudyCO and CO2 hydrogenation; bimetallic catalysts; nickel; manganese; density functional theory2202080#N/ATRUE
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acscatal.9b0485510.1021/acscatal.9b04855HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b04855Qin, YACS Catal.Precise control of selectivity in hydrogenation reactions is a long-standing challenge. Surface decoration of nanocatalysts with transition-metal oxide nanopartiCles (NPs) is an effective strategy to tailor the catalytic selectivity but generally at the expense of activity due to the blocking of active sites. Here, we report that constructing single-site metal oxide modifiers (NiO, CoOx, or FeOx), on supported Au NPs by atomic layer deposition (ALD) can regulate their catalytic selectivity for nitroaromatic hydrogenation. The coverage of single-site metal oxide can be precisely tuned by altering the number of ALD cyCles. The Au/TiO2 decorated with five cyCles of NiO (Ni: 0.32 wt %) in the style of a single site can efficiently change the product selectivity from azo to azoxy compounds without significantly blocking the surface active sites. The density functional theory calculations indicate that the azoxybenzene bonded to the single-site NiO-decorated Au(111) with a larger adsorption energy, which inhibits the overhydrogenation of azoxybenzene and results in high azoxybenzene selectivity. Our work has demonstrated a general and efficient way to regulate the reaction selectivity of metal nanocatalysts by anchoring single-site metal oxide promoters.Selectivity Regulation in Au-Catalyzed Nitroaromatic Hydrogenation by Anchoring Single-Site Metal Oxide Promotershydrogenation selectivity; single-site promoter; atomic layer deposition; reduction coupling of nitroarenes; Au-NiO6202050#N/ATRUE
690
acscatal.9b0418710.1021/acscatal.9b04187HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b04187Xiao, FSACS Catal.Selective hydrogenation of CO2 into valuable ethanol proceeds by the coupling of appropriate C-1 intermediates to form C-2-oxygenates. Matching the different C-1 intermediates is crucial for this process but is difficult to control. We found that incorporation of nickel species into the cobalt catalyst could boost the formation of relatively stable *CHx intermediate from CO2 hydrogenation, which significantly avoids an occurrence of methanation. The *CHx species subsequently insert into the *HCOO, another intermediate that is easily formed, to produce C-2-oxygenates. Following this pathway, the optimized catalyst, Co0.52Ni0.48AlOx, gives the ethanol yield at 15.8 mmol g(cat)(-1) with selectivity at 85.7% in the CO2 hydrogenation at 200 degrees C for 12 h, which even outperforms those of noble metal catalysts.Cobalt-Nickel Catalysts for Selective Hydrogenation of Carbon Dioxide into EthanolCO2 hydrogenation; cobalt catalyst; nickel; ethanol; reaction intermediate; C-C coupling16201948#N/ATRUE
691
acscatal.9b0396310.1021/acscatal.9b03963HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b03963Kirchner, KACS Catal.An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable Alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)(3)(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-Alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)(2)(H)]. A range of mono- and disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 degrees C, while 1,2-disubstituted alkenes require a reaction temperature of 60 degrees C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexeshydrogenation; alkenes; manganese; bisphosphine complexes; Alkyl complexes; DFT calculations9201933#N/ATRUE
692
acscatal.9b0393210.1021/acscatal.9b03932HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b03932Snurr, RQACS Catal.The modular structure of metal organic frameworks (MOFs) makes them promising platforms for catalyst design and for elucidating structure/performance relationships in catalysis. In this work, we systematically varied the composition of the metal nodes (Fe2M) of the MOF PCN-250 and used density functional theory (DFT) to identify promising catalysts for light alkane C-H bond Activation. Oxidative dehydrogenation (ODH) of alkanes was studied using N2O as the oxidant to understand the reactivity of the oxocentered Fe2M nodes found in PCN-250, where the Fe ions are in the +3 oxidation state and M is a metal with the oxidation state of +2. We show that the N2O Activation barrier is positively correlated with the oxygen-binding energy at the metal center, and the C-H Activation barrier is negatively correlated with this same quantity. For Clusters containing early transition metals, oxygen binds strongly, facilitating N2O Activation but hindering C-H Activation. To validate the DFT predictions, we synthesized and tested PCN-250(Fe2M) with M = Mn, Fe, Co, and Ni and found that PCN-250(Fe2Mn) and PCN-250(Fe-3) are more active than PCN-250(Fe2Co) and PCN-250(Fe2Ni) in agreement with the DFT predictions, demonstrating the power of DFT calculations to predict and identify promising MOF catalysts for alkane C-H bond Activation in advance of experiments.Computational Predictions and Experimental Validation of Alkane Oxidative Dehydrogenation by Fe2M MOF Nodesmetal-organic frameworks; C-H bond Activation; oxidation catalysis; structure-function relationships; density functional theory; PCN-250; oxidative dehydrogenation17202062#N/ATRUE
693
acscatal.9b0353410.1021/acscatal.9b03534HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b03534Lu, CCACS Catal.The Co(-I) dihydrogen complexes, [(eta(2)-H-2)CoML](-), where ML is the group 13 metalloligand, N(o-((NCH2PPr2)-Pr-i)C6H4)(3)M, and M is Al, Ga, or In, were previously reported (J. Am. Chem. Soc. 2017, 139, 6570-6573). In this work, the related Co(-I) end-on dinitrogen adducts, [(N-2)CoML](-), were isolated and investigated as precatalysts for CO2 hydrogenation. The Co-Ga catalyst was highly active, achieving 19,200 formate turnovers with an initial turnover frequency of 27,000 h(-1) under 34 atm of 1:1 CO2/H-2 and using Verkades proazaphosphatrane as a base at ambient temperature. The Co-Al catalyst was moderately active, while the Co-In complex was inactive. Hence, tuning the group 13 ion greatly influences the catalytic activity at the Co site. To elucidate the role of the group 13 support, experimental and theoretical mechanistic studies of the Co-Ga and Co-Al catalysts were conducted. The Co(-I) H-2 species are potent hydride donors with estimated thermodynamic hydricities (Delta G degrees(H-)) of 32.0(1) and 37.4(1) kcal/mol in CH3CN for M = Al and Ga, respectively. By acting as masked Co(I) dihydrides, the Co(-I) H-2 species operate via an unusual Co(-I)/Co(I) redox cyCle. After hydride transfer to CO2, the resulting intermediate is the Co(I) hydride complex, HCoML, which was independently synthesized and structurally characterized for M = Al and Ga. The Gibbs free energy for H-2 binding, Delta G degrees(bind) (1 atm), to generate (eta(2)-H-2)HCoML was slightly more favorable for HCoGaL (-4.2(1) kcal/mol) than for HCoAlL (-2.7(1) kcal/mol). In the subsequent step, the deprotonation reaction to regenerate the initial catalyst was much more favorable for (eta(2)-H-2)HCoGaL (pK(a) of 31.4, CH3CN) than for (eta(2)-H-2)HCoAlL (pK(a) of 34.3). The straightforward substitution of Al with Ga perturbs the energy profile of the catalytic reaction (vertical bar Delta Delta G degrees(H-)vertical bar = 5.4 kcal/mol, vertical bar Delta G degrees(bind)vertical bar = 1.5 kcal/mol, and vertical bar Delta Delta G degrees(Ka)vertical bar = 4.0 kcal/mol) and thus provides a thermodynamic rationale for the higher catalytic efficiency of Co-Ga over Co-Al.Cobalt-Group 13 Complexes Catalyze CO2 Hydrogenation via a Co(-I)/Co(I) Redox CyClecobalt; gallium; carbon dioxide; hydrogenation; Z ligand; hydricity17202086#N/ATRUE
694
acscatal.9b0344910.1021/acscatal.9b03449HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b03449Li, CACS Catal.Hydrogenation of CO2 to methanol utilizing the hydrogen from renewable energy sources offers a promising way to reduce CO2 emissions through the CO2 utilization as a carbon source. However, it is a challenge to convert CO2 to methanol with high activity and high methanol selectivity. Herein, we report a Class of metal-oxide solid-solution catalysts: MaZrOx (M-a = Cd, Ga), which show a methanol selectivity up to 80% with the CO2 single pass conversion reaching 4.3%-12.4% under the reaction conditions of H-2/CO2 = 3/1, 24 000 h(-1), 5 MPa. Structural and electronic characterizations combined with denisty functional theory calculations suggest that the M-a and Zr components in MaZrOx (M-a = Cd, Ga) solid-solution catalysts show a strong synergetic effect, which enhances the H-2 heterolytic dissociation and results in high activity and high methanol selectivity. The solid-solution catalyst with dual metal oxide components offers an approach for the selective hydrogenation of CO2 to chemicals.High-Performance MaZrOx (M-a = Cd, Ga) Solid-Solution Catalysts for CO2 Hydrogenation to MethanolCO2 hydrogenation; methanol synthesis; solid solution catalyst; dual active sites; H-2 heterolytic dissociation33201951#N/ATRUE
695
acscatal.9b0330510.1021/acscatal.9b03305HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b03305Perez-Ramirez, JACS Catal.MonoClinic zirconia has been uncovered as a carrier able to substantially boost the activity of indium oxide for CO2 hydrogenation to methanol. Here, electronic, geometric, and interfacial phenomena associated with this peculiar effect are investigated. Generating mixed In-Zr oxides by coprecipitation does not improve performance, exCluding a primary role of electronic parameters. Because even only 1 mol % of indium stabilizes the metastable tetragonal phase of zirconia, the relevance of its crystalline structure is explored in impregnated solids. Both tetragonal and monoClinic ZrO2 permit epitaxial growth of In2O3, but a more pronounced lattice mismatching leads to a lower dispersion of the oxide on the second, which is observed in the form of subnanometric islands on the carrier, and to more pronounced tensile forces. The latter triggers the formation of a surplus of oxygen vacancies only in this system, which is in line with its greatly enhanced indium-specific activity. Hence, a deposition synthesis method is essential to unlock the role of monoClinic zirconia. According to kinetic analyses, the monoClinic ZrO2-based catalyst can also better activate both reactants, likely because of a superior character of oxygen vacancies on supported In2O3 and a direct contribution of zirconia to CO2 Activation on its own oxygen vacancies, which was investigated in comparison with In2O3 supported on alumina and ceria. Elucidating the nature of the active sites at the phase boundary and the impact of the defect chemistry of zirconia are identified as aspects to be prioritized in upcoming studies to shed further light on interfacial effects in this relevant catalytic system.Role of Zirconia in Indium Oxide-Catalyzed CO2 Hydrogenation to MethanolCO2 hydrogenation; methanol synthesis; indium oxide; zirconium oxide polymorphs; epitaxial growth; interfacial effects46202058#N/ATRUE
696
acscatal.9b0023810.1021/acscatal.9b00238HydrogenationFALSEhttps://doi.org/10.1021/acscatal.9b00238Wei, MACS Catal.Selective hydrogenation of biomass to value-added products plays a crucial role in the development of renewable energy resources. Herein, two heterogonous Ni catalysts supported on mixed metal oxides (MMO) were prepared via structural topological transformation from hydrotalcites (LDHs) precursors with carbonate or nitrate in interlayer region (denoted as Ni/MMO-CO3 and Ni/MMO-NO3), which were featured by highly exposed Ni(111) facets as well as multifacets with abundant steps/vacancies, respectively. Interestingly, the selectivity of furfural hydrogenation can be switched by using these two catalysts: Ni/MMO-NO3 exhibits a high selectivity (97%) to furfural alcohol (FOL) (hydrogenation product of C=O bond), whereas Ni/MMO-CO3 shows an exClusive selectivity (99%) toward tetrahydrofurfuryl alcohol (THFOL, hydrogenation product of both C=O and furan ring). A combination study inCluding high-resolution transmission electron microscopy (HRTEM), extended X-ray analysis fine structure (EXAFS), and in situ CO-IR confirms a large proportion of steps/edges of Ni nanopartiCles in Ni/ MMO-NO3 catalyst, which suppresses the adsorption of the furan ring and only facilitates activated adsorption of the C=O group. In contrast, a high exposure of Ni(111) plane in Ni/MMO-CO3 promotes activated adsorption of both furan ring and C=O group, resulting in the production of THFOL. In situ FT-IR measurements and DFT calculations reveal that the adsorption configuration of substrate plays a key role in determining the hydrogenation pathway and selectivity. This work provides a feasible approach for a control over hydrogenation selectivity of biomass molecules by tuning the surface microstructure of metal catalysts.A Control over Hydrogenation Selectivity of Furfural via Tuning Exposed Facet of Ni CatalystsNi catalysts; layered double hydroxides; surface structure; selective hydrogenation; furfural47201947#N/ATRUE
697
acscatal.8b0289210.1021/acscatal.8b02892HydrogenationFALSEhttps://doi.org/10.1021/acscatal.8b02892Gaston, JACS Catal.We report the synthesis of a highly active, selective, and stable catalyst for the hydrogenation of CO2 to short chain olefins in one single step by using a metal organic framework as catalyst precursor. By studying the promotion of the resulting Fe(41 wt %)-carbon composites with different elements (Cu, Mo, Li, Na, K, Mg, Ca, Zn, Ni, Co, Mn, Fe, Pt, and Rh), we have found that only K is able to enhance olefin selectivity. Further catalyst optimization in terms of promoter loading results in catalysts displaying unprecedented C-2-C-4 olefin space time yields of 33.6 mmol.gcat(-1).h(-1) at X-CO2 = 40%, 320 degrees C, 30 bar, H-2/CO2 = 3, and 24 000 mL.g(-1).h(-1). Extensive characterization demonstrates that K promotion affects catalytic performance by (i) promoting a good balance between the different Fe active phases playing a role in CO2 hydrogenation, namely, iron oxide and iron carbides and by (ii) increasing CO2 and CO uptake while decreasing H-2 affinity, interactions responsible for boosting olefin selectivity.Metal Organic Framework-Derived Iron Catalysts for the Direct Hydrogenation of CO2 to Short Chain OlefinsCO2 hydrogenation; olefins; metal organic framework; Fe catalysts; MOF-mediated synthesis64201862#N/ATRUE
698
acscatal.8b0275510.1021/acscatal.8b02755HydrogenationFALSEhttps://doi.org/10.1021/acscatal.8b02755Wei, MACS Catal.Selective hydrogenation of unsaturated Carbonyl compounds plays a key role in the production of fine chemicals and pharmaceutical agents. In this work, two kinds of intermetallic compounds (IMCs: CoIn3 and CoGa3) were prepared via structural topotactic transformation from layered double hydroxide (LDH) precursors, which exhibited surprisingly high catalytic activity and selectivity toward hydrogenation reaction of alpha,beta-unsaturated aldehydes (C=O vs C=C). Notably, the CoGa3 catalyst shows a hydrogenation selectivity of 96% from cinnamaldehyde (CAL) to cinnamyl alcohol (COL), significantly higher than CoIn3 (80%) and monometallic Co catalyst (42%). A combination study inCluding XANES, XPS, and CO-IR spectra verifies electron transfer from Ga (or In) to Co, leading to the formation of Co-Ga (or Co-In) coordination. FT-IR measurements and DFT calculation studies substantiate that the electropositive element (Ga or In) in IMCs serves as an active site and facilitates the adsorption of polarized C=O, while C=C adsorption on the Co site is extremely depressed, which is responsible for the markedly enhanced selectivity toward hydrogenation of C=O. This work reveals the key role of functional group adsorption in determining the hydrogenation selectivity of alpha,beta-unsaturated aldehydes, which gives an in-depth understanding on the structureproperty correlation and reaction mechanism.Selective Hydrogenation of Cinnamaldehyde over Co-Based Intermetallic Compounds Derived from Layered Double Hydroxidesintermetallic compounds; layered double hydroxides; selective hydrogenation; cinnamaldehyde; FT-IR; DFT42201850#N/ATRUE
699
acscatal.7b0390910.1021/acscatal.7b03909HydrogenationFALSEhttps://doi.org/10.1021/acscatal.7b03909Chirik, PJACS Catal.Treatment of a mixture of air-stable nickel(II) bis(octanoate), Ni(O2CC7H15)(2), and alpha-diimine ligand, (DI)-D-iPr or (Cy)ADI ((DI)-D-iPr = [2,6-Pr-i(2)-C6H3N=C(CH3)](2), (Cy)ADI = [C6H11N=C(CH3)](2)) with pinacolborane (HBPin) generated a highly active catalyst for the hydrogenation of hindered, essentially unfunctionalized alkenes. A range of tri- and tetrasubstituted alkenes was hydrogenated and a benchtop procedure for the hydrogenation of 1-phenyl-1-cyClohexene on a multigram scale was demonstrated and represents an advance in catalyst activity and scope for the nickel-catalyzed hydrogenation of this challenging Class of alkenes. Deuteration of 1,2-dimethylindene with the in situ-generated nickel catalyst with (DI)-D-iPr exClusively furnished the 1,2-syn-d(2)-dimethylindane. With cyClic trisubstituted alkenes, such as 1-methyl-indene and methylcyClohexene, deuteration with the in situ generated nickel catalyst under 4 atm of D-2 produced multiple deuterated isotopologues of the alkanes, signaling chain running processes that are competitive with productive hydrogenation. Stoichiometric studies, titration, and deuterium labeling experiments identified that the borane reagent served the dual role of reducing nickel(II) bis(Carbonylate) to the previously reported nickel hydride dimer [((DI)-D-iPr)NiH](2) and increasing the observed hydrogenation activity. Performing the catalyst Activation procedure with D-2 gas and HBPin generated both HD and DBPin, establishing that the borane is involved in H-2 Activation as judged by H-1 and B-11 nuClear magnetic resonance spectroscopies.Air-Stable alpha-Diimine Nickel Precatalysts for the Hydrogenation of Hindered, Unactivated Alkeneshydrogenation; nickel; alkene; borane; Carbonylate41201859#N/ATRUE
700
acscatal.7b0273610.1021/acscatal.7b02736HydrogenationFALSEhttps://doi.org/10.1021/acscatal.7b02736Butt, JNACS Catal.Photocatalytic chemical synthesis by coupling abiotic photosensitizers to purified enzymes provides an effective way to overcome the low conversion efficiencies of natural photosynthesis while exploiting the high catalytic rates and selectivity of enzymes as renewable, earth-abundant electrocatalysts. However, the selective synthesis of multiple products requires more versatile approaches and should avoid the time-consuming and costly processes of enzyme purification. Here we demonstrate a cell-based strategy supporting light-driven H-2 evolution or the hydrogenation of C=C and C=O bonds in a nonphotosynthetic microorganism. Methylviologen shuttles photoenergized electrons from water-soluble photosensitizers to enzymes that catalyze H-2 evolution and the reduction of fumarate, pyruvate, and CO2 in Shewanella oneidensis. The predominant reaction is selected by the experimental conditions, and the results allow rational development of cell-based strategies to harness nature's intrinsic catalytic diversity for selective light driven synthesis of a wide range of products.Light-Driven H-2 Evolution and C=C or C=O Bond Hydrogenation by Shewanella oneidensis: A Versatile Strategy for Photocatalysis by Nonphotosynthetic Microorganismsproton reduction; CO2 reduction; photocatalysis; hydrogenase; formate dehydrogenase; visible light28201771#N/ATRUE
701
acscatal.7b0084810.1021/acscatal.7b00848HydrogenationFALSEhttps://doi.org/10.1021/acscatal.7b00848Fan, MHACS Catal.The overall objective of this research is to convert the increasingly concerning CO2 and renewable H-2 to highly demanded methanol (CH3OH), which creates a win-win scenario for simultaneous Climate change prevention and sustainable economic development. The key to the success of this targeted CO2 utilization technology is the development of low-pressure methanol synthesis catalysts (NiaInbAl/SiO2; a = 0-8.3, b = 0-9.1) by means of a phyllosilicate precursor, allowing for formation of well-dispersed metallic partiCles with an average diameter of 2.5-3.5 nm. The catalysts were characterized with various methods inCluding ICP-OES, N-2 physisorption, XRD, SEM, TEM, TGA, H-2 TPR, DRIFTS, and XPS. The performances of the NiaInbAl/SiO2 catalysts and conventional catalyst were compared under various evaluation temperatures at ambient pressure. It was found that catalysts with Ni/In ratios of 0.4-0.7 showed the highest activity. Ni3.5In5.3Al/SiO2 (NIA-0.7) with 15% metal loading was the best among the tested NiaInbAl/SiO2 catalysts with an activity of 0.33 mol h(-1) (mol catalyst metal)(-1) in comparison to the benchmark Cu/ZnO/Al2O3 (CZA) catalyst at 0.17. Several NiaInbAl/SiO2 catalysts also showed similar CO2 conversions in comparison to the CZA catalyst. Infrared studies using DRIFTS determined that CO2 hydrogenation on NiaInbAl/SiO2 catalysts proceeds through monodentate carbonate before further conversion to monodentate and bidentate formate. With a feed of CO/H-2 instead of CO2/H-2 the primary hydrocarbon product changes from methanol to propane, accompanied by a lack of formate and monodentate carbonate IR signals.Low-Pressure Hydrogenation of CO2 to CH3OH Using Ni-In-Al/SiO2 Catalyst Synthesized via a Phyllosilicate Precursormethanol synthesis; CO2 hydrogenation; heterogeneous catalysis; phyllosilicate; nickel indium catalyst47201797#N/ATRUE
702
acscatal.7b0035010.1021/acscatal.7b00350HydrogenationFALSEhttps://doi.org/10.1021/acscatal.7b00350Appel, AMACS Catal.The water-soluble Ni bis(diphosphine) complex [NiL2](BF4)(2) (L = 1,2-[bis(dimethoxypropyl)phosphino]ethane and the corresponding hydride, [HNiL2]BF4, were synthesized and characterized. These complexes were specifically designed for CO2 hydrogenation. For HNiL2+, the hydricity (Delta G(H-)(o)) was determined to be 23.2(3) kcal/mol in aqueous solution. On the basis of the hydricity of formate, 24.1 kcal/mol, the transfer of a hydride from HNiL2+ to CO2 to produce formate is favorable by 1 kcal/mol. Starting from either NiL22+ or HNiL2+ in water, catalytic hydrogenation of CO2 was observed with NaHCO3 (0.8 M) as the only additive. A maximum turnover frequency of [4.0(5)] x 10(-1) h(-1) was observed at 80 degrees C and 34 atm of a 1:1 mixture of CO2 and H-2. This report demonstrates the use of a homogeneous first-row transition-metal catalyst for CO2 hydrogenation in water using NaHCO3 as an inexpensive, readily available base.Hydrogenation of CO2 in Water Using a Bis(diphosphine) Ni-H ComplexCO2 hydrogenation; hydricity; homogeneous catalysis; nickel; aqueous bicarbonate48201780#N/ATRUE
703
acscatal.6b0349410.1021/acscatal.6b03494HydrogenationFALSEhttps://doi.org/10.1021/acscatal.6b03494Duan, XACS Catal.In a number of heterogeneous catalysis processes, synergic catalysis of metal and acid-base sites of supports is of vital importance and remains a challenge to obtain largely improved catalytic performance. Herein, an acid-base-promoted Ni nanocatalyst supported on Ni/Al mixed metal oxide (denoted as Ni/NiAl-MMO) was prepared on the basis of the in situ structural topotactic transformation of NiAl-layered double hydroxide (NiAl-LDH) precursor. In situ studies inCluding XRD, Raman, and EXAFS verify that the cubic NiO-like phase (Al3+-doped NiO species), with medium-strong acid-base sites (Ni delta+-O delta- pair), are well-distributed in the amorphous Al2O3 to form NiAl-MMO support. The concentration of Ni active site and acid-base sites can be simultaneously enhanced by precisely tuning the in situ structural topotactic transformation parameters of LDH precursor as revealed by CO pulse chemisorption, CO2-TPD, and NH3-TPD, so as to achieve a promoted synergic catalysis between metal Ni and acid-base sites. The resulting Ni/NiAl-MMO(400) shows largely enhanced catalytic performance (formation rate of 2-octanone: 78.5 mmol g(-1) h(-1)) toward oxidant-free dehydrogenation of 2-octanol to 2-octanone, which is 3.9 times larger than the conventional Ni/Al2O3 catalyst (formation rate of 2-octanone: 20.1 mmol g(-1) h(-1)). Studies on the structure-property correlation based on operando time-resolved EXAFS spectra and kinetic isotope effect (KIE) measurements reveal that such an excellent catalytic performance is attributed to the optimized synergic catalysis between Ni0 and medium-strong acid-base sites of support, which accelerates the bond Cleavage of kinetically key steps: alpha-C-H and O-H, respectively.Promoted Synergic Catalysis between Metal Ni and Acid-Base Sites toward Oxidant-Free Dehydrogenation of Alcoholslayered double hydroxide; synergic catalysis; acid-base sites; dehydrogenation; structure-activity correlation67201738#N/ATRUE
704
acscatal.6b0329910.1021/acscatal.6b03299HydrogenationFALSEhttps://doi.org/10.1021/acscatal.6b03299Takanabe, KACS Catal.Liquid organic chemical hydrides are effective hydrogen storage media for easy and safe transport. The chemical couple of methylcyClohexane (MCH) and toluene (TOL) has been considered one of the feasible cyCles for a hydrogen carrier, but the selective dehydrogenation of MCH to TOL has been reported using only Pt-based noble metal catalysts. This study reports MCH dehydrogenation to TOL using supported NiZn as a selective, non-noble-metal catalyst. A combined experimental and computational study was conducted to provide insight into the site requirements and reaction mechanism for MCH dehydrogenation to TOL, which were compared with those for cyClohexane (CH) dehydrogenation to benzene (BZ). The kinetic measurements carried out at 300-360 degrees C showed an almost zero order with respect to MCH pressure in the high-pressure region (>= 10 kPa) and nearly a positive half order with respective to H-2 pressure (<= 40 kPa). These kinetic data for the dehydrogenation reaction paradoxically indicate that hydrogenation of a strongly chemisorbed intermediate originating from TOL is the rate-determining step. Density functional theory (DFT) calculation confirms that the dehydrogenated TOL species at the aliphatic (methyl) position group (C6H5CH2) were strongly adsorbed on the surface, which must be hydrogenated to desorb as TOL. This hydrogen-assisted desorption mechanism explains the essential role of excess H-2 present in the feed in maintaining the activity of the metallic surface for hydrogenation. The rate of the CH to BZ reaction was less sensitive to H-2 pressure than that of MCH to TOL, which can be explained by the absence of a methyl group in the stnicture, which in turn reduces the binding energy of the adsorbed species. DFT suggests that the improved TOL selectivity by adding Zn to Ni was due to Zn atoms preferentially occupying low-coordination sites on the surface (the corner and edge sites), which are likely the unselective sites responsible for the C-C dissociation of the methyl group of TOL.Kinetics on NiZn Bimetallic Catalysts for Hydrogen Evolution via Selective Dehydrogenation of MethylcyClohexane to toluenedehydrogenation; methylcyClohexane; toluene; NiZn; density functional theory29201745#N/ATRUE
705
acscatal.6b0236910.1021/acscatal.6b02369HydrogenationFALSEhttps://doi.org/10.1021/acscatal.6b02369Wilson, KACS Catal.Aqueous-phase hydrogenation of n-glucose to D-sorbitol was systematically investigated over silica-supported Pt nanopartiCles to elucidate structure reactivity relations and mechanistic insight. D-Glucose hydrogenation over large Pt partiCles competes with its isomerization to D-fructose over low-coordination (electron-deficient) Pt sites; D-sorbitol production by the former process was structure insensitive for nanopartiCles spanning 3-17 nm, whereas isomerization was favored by smaller partiCles, with both pathways independent of the choice of fumed silica or mesoporous SBA-15 support. While n-fructose was readily hydrogenated to D-mannitol under the same reaction conditions, the latter underwent minimal isomerization to D-sorbitol, which is, therefore, a direct product of D-glucose ring opening and subsequent hydrogenation of the aldose conformer. D-Sorbitol production was favored by low D-glucose concentrations (<10 wt %), high H-2 pressures (>40 bar), and low reaction temperatures (<140 degrees C), which suppressed undesired polymerization side reactions.Platinum-Catalyzed Aqueous-Phase Hydrogenation of D-Glucose to D-Sorbitolglucose; hydrogenation; platinum; sorbitol; SBA-1552201664#N/ATRUE
706
acscatal.6b0129510.1021/acscatal.6b01295HydrogenationFALSE#REF!Bentrup, UMechanistic Study of Low-Temperature CO2 Hydrogenation over Modified Rh/Al2O3 Catalysts2016#N/ATRUE
707
acscatal.6b0052010.1021/acscatal.6b00520HydrogenationFALSEhttps://doi.org/10.1021/acscatal.6b00520Zhao, CACS Catal.A tandem process involving the dehydroaromatization of the terpene limonene and the hydrodeoxygenation of stearic acid has been found to be efficiently catalyzed by Pd-Ni/HZSM-5. The process involves the generation of p-cymene from terpene with concomitant formation of H-2, which leads to the one-pot hydrodeoxygenation of stearic acid to C-17 and C-18 alkanes; these products can be used as kerosene additives for aviation fuel. Screening a wide range of catalysts, the bimetallic Pd-Ni/HZSM-5 catalyst is the most efficient, leading to quantitative conversion of stearic acid to alkanes in limonene at 280 degrees C at a H-2 pressure of 2 bar after 120 min. It has been found that single Ni or Pd catalysts lead to a poor conversion of stearic acid in limonene at a H-2 pressure of 2 bar. The combination of physically mixed Pd- and Ni-sites onto different supports (Pd/HZSM-5 or Pd/C, and Ni/HZSM-S, Ni/HY, or Ni/HBEA) leads to catalysts which show satisfactory conversion to p-cymene but generally have very low stearic acid conversion rates. Directly incorporating Pd and Ni onto the HZSM-5 scaffold forms the bimetallic catalyst, which demonstrates a remarkable improvement in stearic acid conversion to C-17 and C-18 alkane products. In this catalyst system, Pd is shown to be the active site for limonene dehydroaromatization, while Ni catalyzes the separate stearic acid hydrodeoxygenation. The acidity of HZSM-5 (modified by the Si/Al ratios) influences the performance of the Pd-Ni bimetallic catalyst, and the proper pore size of HZSM-5 prevents side-reactions from limonene condensation. In addition, the alloyed Pd-Ni nanopartiCles (optimized with higher Pd/Ni ratios) on the external surface of HZSM-5 enhance internal H-center dot transfer between the two metals, thereby increasing the rate of stearic acid hydrodeoxygenation. The catalytic compatibility of the Pd and Ni sites, coupled with the proper pore sizes and optimized level of Bronsted acid sites in HZSM-5, result in the design of a multifunctional catalyst that is efficient for both steps of the cascade reaction. Hence, a bimetallic 5%Pd-10%Ni/HZSM-5 catalyst has been developed that allows for a simple approach for producing aromatics and hydrocarbon components present in biojet fuel derived from two biomass resources.Development of a Bimetallic Pd-Ni/HZSM-5 Catalyst for the Tandem Limonene Dehydrogenation and Fatty Acid Deoxygenation to Alkanes and Arenes for Use as Biojet Fuelterpene dehydroaromatization; stearic acid HDO; green biofuels; bimetallic catalysis; cascade reactions68201648#N/ATRUE
708
acscatal.6b0004410.1021/acscatal.6b00044HydrogenationFALSEhttps://doi.org/10.1021/acscatal.6b00044Basset, JMNi-M-O (M = Sn, Ti, W) Catalysts Prepared by a Dry Mixing Method for Oxidative Dehydrogenation of Ethane2016#N/ATRUE
709
acscatal.5b0267410.1021/acscatal.5b02674HydrogenationFALSEhttps://doi.org/10.1021/acscatal.5b02674Jones, WDACS Catal.Hydrogenation of alkenes containing polarized C=C double bonds has been achieved with iron-based homogeneous catalysts bearing a bis(phosphino)amine pincer ligand. Under standard catalytic conditions (5 mol % of (PNHPiPr)Fe(H)(2)(CO) (PNHPiPr = NH(CH(2)CH(2)PiPr(2))(2)), 23 degrees C, 1 atm of H-2), styrene derivatives containing electron-withdrawing para substituents reacted much more quickly than both the parent styrene and substituted styrenes with an electron-donating group. Selective hydrogenation of C=C double bonds occurs in the presence of other reducible functionalities such as -CO2Me, -CN, and N-heterocyCles. For the alpha,beta-unsaturated ketone benzalacetone, both C=C and C=O bonds have been reduced in the final product, but NMR analysis at the initial stage of catalysis demonstrates that the C=O bond is reduced much more rapidly than the C=C bond. Although Hanson and co-workers have proposed a nonbifunctional alkene hydrogenation mechanism for related nickel and cobalt catalysts, the iron system described here operates via a stepwise metal-ligand cooperative pathway of Fe-H hydride transfer, resulting in an ionic intermediate, followed by N-H proton transfer from the pincer ligand to form the hydrogenated product. Experimental and computational studies indicate that the polarization of the C=C bond is imperative for hydrogenation with this iron catalyst.Iron-Catalyzed Homogeneous Hydrogenation of Alkenes under Mild Conditions by a Stepwise, Bifunctional Mechanismolefin/alkene hydrogenation; iron catalysis; bifunctional mechanism; metal-ligand cooperativity; DFT calculations75201644#N/ATRUE
710
acscatal.5b0168610.1021/acscatal.5b01686HydrogenationFALSEhttps://doi.org/10.1021/acscatal.5b01686Vlachos, DGACS Catal.We employ electronic structure calculations to elucidate the catalytic pathways on bifunctional metal/zeolite catalysts by modeling a HZSM-5-supported nickel tetramer Cluster (Ni-4-ZSM-S). Hydrogenation of acetone to 2-propanol followed by dehydration to propene have been investigated as model reactions. In Ni-4-ZSM-5, we observe reverse hydrogen spillover, whereby the Bronsted hydrogen migrates from the zeolite active site to the metal Cluster. Consequently, the zeolite-supported metal Cluster becomes electron-deficient, facilitating the hydrogenation reaction. In contrast, studies conducted on the dehydration reaction pathways indicate that the Bronsted acid catalysis in HZSM-5 is preferred over the metal catalyzed pathway in the Ni-4-ZSM-S system, again as a result of the electron-deficient nature of the metal species.Computational Insights into the Role of Metal and Acid Sites in Bifunctional Metal/Zeolite Catalysts: A Case Study of Acetone Hydrogenation to 2-Propanol and Subsequent Dehydration to Propenebifunctional catalysts; zeolites; hydrodeoxygenation; density functional theory; reaction mechanisms26201667#N/ATRUE
711
acscatal.0c0228310.1021/acscatal.0c02283HydrogenationFALSEhttps://doi.org/10.1021/acscatal.0c02283Garcia, JJACS Catal.Mn-, Fe-, Co-, and Ni-based catalytic precursors have been reported for the homogeneous 3d transition-metal-catalyzed hydrogenation of nitriles. We present herein a critical assessment of such reports, emphasizing experimental setups, selectivity patterns, and mechanistic aspects fashioning this growing field. Moreover, its successes, drawbacks, and challenges are highlighted to outline what is next in the design of catalytic systems for future years.Toward Amines, Imines, and Imidazoles: A Viewpoint on the 3d Transition-Metal-Catalyzed Homogeneous Hydrogenation of Nitrilesnitriles; amines; imines; first-row transition metals; catalysis; homogeneous; hydrogenationReview5202064#N/AFALSE
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acscatal.5b0152210.1021/acscatal.5b01522HydrogenationFALSEhttps://doi.org/10.1021/acscatal.5b01522Wang, LACS Catal.Heterogeneous hydrogenation is one of the most important industrial operations, and reduced metals (mostly noble metals and a few inexpensive metals) generally serve as the catalyst to activate molecular H-2. Herein we report oxygen-deficient tungsten oxide, such as WO2.72, is a versatile and efficient catalyst for the hydrogenation of linear olefins, cyClic olefins, and Aryl nitro groups, with obvious advantages compared with non-noble metal nickel catalyst from the aspect of activity and selectivity. Density functional theory calculations prove the oxygen-deficient surface activates H-2 very easily in both kinetics and thermodynamics. Testing on several oxygen-deficient tungsten oxides shows a linear dependence between the hydrogenation activity and oxygen vacancy concentration. Tungsten is earth-abundant, and WO2.72 can be synthesized in large scale using a low-cost procedure, which provides an ideal catalyst for industrial application. Because oxygen vacancy is a common characteristic of many metal oxides, the findings in this work may be extended to other metal oxides and thus provide the possibility for exploring a new type of hydrogenation catalyst.Oxygen-Deficient Tungsten Oxide as Versatile and Efficient Hydrogenation Catalystheterogeneous catalysis; hydrogenation; oxygen vacancy; tungsten oxide; molecular H-2 activatation158201540#N/ATRUE
713
acscatal.5b0146410.1021/acscatal.5b01464HydrogenationFALSEhttps://doi.org/10.1021/acscatal.5b01464Szanyi, JACS Catal.The hydrogenation of CO2 was investigated over a wide range of reaction conditions, using two Pd/gamma-Al2O3 catalysts with different Pd loadings (5% and 0.5%) and dispersions (similar to 11% and similar to 100%, respectively). Turnover rates for CO and CH4 formation were both higher over 5% Pd/Al2O3 with a larger average Pd partiCle size than those over 0.5% Pd/Al2O3 with a smaller average partiCle size. The selectivity to methane (22-40%) on 5% Pd/Al2O3 was higher by a factor of 2-3 than that on 0.5% Pd/Al2O3. The drastically different rate expressions and apparent energies of Activation for CO and CH4 formation led us to conClude that reverse water gas shift and CO2 methanation do not share the same rate-limiting step on Pd and that the two pathways are probably catalyzed at different surface sites. Measured reaction orders in CO2 and H-2 pressures were similar over the two catalysts, suggesting that the reaction mechanism for each pathway does not change with partiCle size. In accordance, the DRIFTS results reveal that the prevalent surface species and their evolution patterns are comparable on the two catalysts during transient and steady-state experiments, switching feed gases among CO2, H-2 and CO2 + H-2. The DRIFTS and MS results also demonstrate that no direct dissociation of CO2 takes place over the two catalysts and that CO2 has to first react with surface hydroxyls on the oxide support. The thus-formed bicarbonates react with dissociatively adsorbed hydrogen on Pd partiCles to produce adsorbed formate species (bifunctional catalyst: CO2 Activation on the oxide support and H-2 dissociation on the metal partiCles). Formates near the Pd partiCles (most likely at the metal/oxide interface) can react rapidly with adsorbed H to produce CO, which then adsorbs on the metallic Pd partiCles. Two types of Pd sites are identified: one has a weak interaction with CO, which easily desorbs into gas phase at reaction temperatures, whereas the other interacts more strongly with CO, which is mainly in multibound forms and remains stable in He flow at high temperatures, but is reactive toward adsorbed H atoms on Pd leading eventually to CH4 formation. 5% Pd/Al2O3 contains a larger fraction of terrace sites favorable for forming these more multibound and stable CO species than 0.5% Pd/Al2O3. Consequently, we propose that the difference in the formation rate and selectivity to CH4 on different Pd partiCle sizes stems from the different concentrations of the reactive intermediate for the methanation pathway on the Pd surface.Mechanism of CO2 Hydrogenation on Pd/Al2O3 Catalysts: Kinetics and Transient DRIFTS-MS StudiesCO2 reduction; Pd/Al2O3; partiCle size; reaction mechanism; CO/CH4 selectivity187201541#N/ATRUE
714
acscatal.5b0142910.1021/acscatal.5b01429HydrogenationFALSEhttps://doi.org/10.1021/acscatal.5b01429Duan, XACS Catal.We report a new synthetic strategy for the fabrication of several supported nickel phosphides (Ni12P5, Ni2P, and NiP2) with partiCle size ranging from 5 to 15 nm via a two-step procedure: preparation of supported Ni partiCles from layered double hydroxide precursors, followed by a further reaction with a certain amount of red phosphorus. The selective hydrogenation of phenylacetylene over these metal phosphides was evaluated, and the as-prepared Ni2P/Al2O3 catalyst shows a much higher selectivity to styrene (up to 88.2%) than Ni12P5/Al2O3 (48.0%), NiP2/Al2O3 (65.9%), and Ni/Al2O3 (0.7%) catalysts. EXAFS and in situ IR measurements reveal that the incorporation of P increases the bond length of Ni-Ni, which imposes a key influence on the adsorption state of alkene intermediates: as the Ni-Ni bond length extends to 0.264 nm, the alkene intermediate undergoes di-pi(C=C) adsorption, facilitating its desorption and the resulting enhanced selectivity. Moreover, electron transfer occurs from Ni to P, as confirmed by EXAFS, XPS, and in situ CO-IR experiment, in which the positively charged Ni reduces the desorption energy of alkene and thus improves the reaction selectivity.Metal Phosphides Derived from Hydrotalcite Precursors toward the Selective Hydrogenation of Phenylacetylenemetal phosphides; LDHs; selective hydrogenation; EXAFS; in situ IR83201565#N/ATRUE
715
acscatal.5b0134610.1021/acscatal.5b01346HydrogenationFALSEhttps://doi.org/10.1021/acscatal.5b01346Davis, BHACS Catal.A series of Co-Fe bimetallic catalysts was prepared, characterized, and studied for the hydrogenation of carbon dioxide. The catalyst precursors were prepared via an oxalate coprecipitation method. Monometallic (Co or Fe) and bimetallic (Co-Fe) oxalate precursors were decomposed under a N-2 flow at 400 degrees C and further pretreated under a CO flow at 250 degrees C. The catalysts (before decomposition of the oxalates or after Activation) were characterized by BET, TGA-MS, X-ray diffraction, CO-TPR, SEM, HR-TEM, and Mossbauer spectroscopy techniques. The hydrogenation reaction of CO2 was performed using Co-Fe bimetallic catalysts pretreated in situ in a fixed-bed catalytic microreactor operating in the temperature range of 200-270 degrees C and a pressure of 0.92 MPa. With increasing Fe fraction, the selectivity to C-2-C-4 for Co-Fe catalyst increased under all operating conditions. The alcohol selectivity was found to increase with increasing iron content of the Co-Fe catalyst up to 50%, but then it dropped with further addition of iron. Among the three different Activation conditions, the CO pretreated Co-Fe (50Co50Fe) catalyst exhibited a much lower selectivity for methane. Addition of 1 wt % Na or 1.7 wt % K to 50Co50Fe catalyst increases its olefinic (C-2-C-4) and oxygenate selectivities.Hydrogenation of Carbon Dioxide over Co-Fe Bimetallic CatalystsCo-Fe bimetallic catalyst; oxalates coprecipitation method; carbon dioxide (CO2) hydrogenation; iron carbides; Mossbauer spectroscopy; thermogravimetry; cobalt carbide; oxygenates88201636#N/ATRUE
716
acscatal.0c0418610.1021/acscatal.0c04186HydrogenationFALSEhttps://doi.org/10.1021/acscatal.0c04186Hellman, AACS Catal.Glycerol is a byproduct of biodiesel production and an abundant feedstock that can be used for the synthesis of high-value chemicals. There are many approaches for glycerol valorization, but, due to the complicated reaction mechanism, controlling which products are produced is challenging. Here, we describe glycerol's chemical selectivity for different metallic catalysts using descriptors for carbon (mainly *C, *CH2OH) and oxygen (mainly *O, CH3O*). The quality of these descriptors and the weighted combinations thereof are validated based on their fit, via linear regression, to the binding energies of all reaction intermediates generated in the first two glycerol dehydrogenation steps on a number of Close-packed Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au surfaces. We show that *CH2OH is a better descriptor than *C for the studied carbon-bound intermediates, which is attributed to the observation that the adjacent *OH group interacts with the surface. This leads to a negative oxygen dependence, which can be generalized to similar alcohol-derived adsorbates. Furthermore, we show that CH3O* is a better oxygen descriptor than *0 for the studied intermediates. This is mainly attributed to the difference between the single and double bonds, as we show that *OH is Closer to the accuracy of CH3O*. Multilinear regression with different combinations of *C, *O, and *OH is comparable in accuracy to that of *CH2OH and CH3O*. Scaling relationships are used to determine the selectivity map for glycerol dehydrogenation. The results show that the first dehydrogenation is selective toward two different intermediates (one bonded via the secondary carbon and the other via the secondary oxygen) depending on the relative bond strength of the carbon and oxygen descriptors. The second dehydrogenation step results in five intermediates, again depending primarily on the relative bond strength of carbon and oxygen to the surface. The selectivity maps can be used together with kinetic considerations and experimental data to find catalyst candidates for glycerol dehydrogenation.Selectivity of the First Two Glycerol Dehydrogenation Steps Determined Using Scaling Relationshipsscaling; glycerol; CH2OH; CH3O; first principles; selectivity; transition metals0202163#N/ATRUE
717
acscatal.0c0366510.1021/acscatal.0c03665HydrogenationFALSEhttps://doi.org/10.1021/acscatal.0c03665Song, CSACS Catal.Carbon dioxide (CO2) hydrogenation to methanol with H-2 produced with renewable energy represents a promising path for the effective utilization of a major anthropogenic greenhouse gas, in which catalysts play a key role for CO2 conversion and methanol selectivity. Although still under development, indium oxide (In2O3)-based catalysts have attracted great attention in recent years due to the excellent selectivity to methanol along with high activity for CO2 conversion. In this review, we discuss recent advances of In2O3-based catalysts for CO2 hydrogenation based on both experimental and computational studies. Various strategies have been adopted to improve the catalytic performance by facilitating the formation of surface oxygen vacancies (In2O3-x) as active sites, the Activation of CO2 and H-2 toward hydrogenation to methanol to mitigate reverse water-gas shift reaction, and the stabilization of the key intermediates. Mechanistic insights are gained from combining catalytic kinetic studies, in situ characterization, and theoretical investigations involving CO2 conversion via the formate HCOO* pathway versus the Carbonyl COOH* pathway. Strategies to further promote selective CO2 hydrogenation to methanol inClude adding a metal component such as Pd or Ni on In2O3 (which may also involve formation of bimetallic In-M catalysts) to promote H-2 Activation and oxygen vacancy formation, combining In2O3 with an oxide promoter such as ZrO2 to enhance CO2 adsorption and Activation, controlling the concentration of CO and H2O to enhance methanol formation, and adopting a second catalytic component to enhance CO2 conversion to other desired products such as olefins or aromatics on an acid catalyst such as zeolites. Through a comprehensive overview of the recent advances in In2O3 related catalysts, the present review paves the way for future development in In2O3-based selective catalysts for CO2 hydrogenation to methanol.CO2 Hydrogenation to Methanol over In2O3-Based Catalysts: From Mechanism to Catalyst DevelopmentIn2O3-based catalysts; CO(2 )hydrogenation; methanol; oxygen vacancies; reaction mechanism52021116#N/ATRUE
718
acscatal.0c0332810.1021/acscatal.0c03328HydrogenationFALSEChen, JSAtomically Dispersed Ni-Based Anti-Coking Catalysts for Methanol Dehydrogenation in a Fixed-Bed Reactor2020#N/ATRUE
719
acscatal.0c0256910.1021/acscatal.0c02569HydrogenationFALSEhttps://doi.org/10.1021/acscatal.0c02569Zhang, XMACS Catal.Cheap transition metal Ni-catalyzed asymmetric hydrogenation of 2-oxazolones was successfully developed, which provided an efficient synthetic strategy to prepare various chiral 2-oxazolidinones with 95%-99% yields and 97%->99% ee. The gram-scale hydrogenation could be proceeded well with >99% ee in the presence of low catalyst loading (up to 3350 TON). This Ni-catalyzed hydrogenation protocol demonstrated great synthetic utility, and the chiral 2-oxazolidinone product was easily converted to a variety of other important molecules in good yields and without loss of ee values, such as chiral dihydrothiophene-2(3H)-thione, amino alcohol, oxazoline ligand, and allenamide. Moreover, a series of deuterium labeling experiments, control experiments, and DFT calculations were conducted to illustrate a reasonable catalytic mechanism for this Ni-catalyzed asymmetric hydrogenation, which involved a tautomerization between the enamine and its isomer imine and then went through asymmetric 1,2-addition of Ni(II)-H to the preferred imine.Efficient Access to Chiral 2-Oxazolidinones via Ni-Catalyzed Asymmetric Hydrogenation: Scope Study, Mechanistic Explanation, and Origin of Enantioselectivityasymmetric hydrogenation; nickel catalytic system; chiral 2-oxazolidinones; enantioselectivity; chiral phosphine ligand92020109#N/ATRUE
720
c8sc04002h10.1039/c8sc04002hhydrogenation FALSEhttps://doi.org/10.1039/c8sc04002hZhang, XMChem. Sci.Nickel-catalyzed asymmetric hydrogenation of challenging tetrasubstituted fluorinated enamides has been achieved, affording chiral -fluoro--amino esters in high yields with excellent diastereo- and enantioselectivities (up to 98% yield, >99:1 dr, up to >99% ee). Deuterium-labeling experiments and control experiments were conducted to probe the mechanism, and the results indicated that the acidity of the solvent plays a critical role in the control of diastereoselectivity by trapping the adduct of nickel hydride to C?C bonds via protonolysis, giving the hydrogenation product with stereospecific syn-selectivity. This protocol provides efficient access to chiral -fluoro--amino esters which have important potential applications in organic synthesis and medicinal chemistry.A cheap metal for a challenging task: nickelcatalyzed highly diastereo- and enantioselective hydrogenation of tetrasubstituted fluorinated enamides28201973#N/ATRUE
721
c7sc02669b10.1039/c7sc02669bhydrogenation FALSEhttps://doi.org/10.1039/c7sc02669bZhang, XMChem. Sci.An efficient approach for synthesizing chiral beta-amino nitroalkanes has been developed via the Ni-catalyzed asymmetric hydrogenation of challenging beta-amino nitroolefins under mild conditions, affording the desired products in excellent yields and with high enantioselectivities. This protocol had good compatibility with the wide substrate scope and a range of functional groups. The synthesis of chiral beta-amino nitroalkanes on a gram scale has also been achieved. In addition, the reaction mechanism was elucidated using a combined experimental and computational study, and it involved acetate-assisted heterolytic H-2 Cleavage followed by 1,4-hydride addition and protonation to achieve the nitroalkanes.Nickel-catalyzed asymmetric hydrogenation of beta-acylamino nitroolefins: an efficient approach to chiral amines40201750#N/ATRUE
722
anie.20160213010.1002/anie.201602130HydrogenativeFALSEhttps://doi.org/10.1002/anie.201602130Ye, MCAngew. Chem.-Int. Edit.An FeBr3-catalyzed reductive coupling of various aldehydes with alkenes that proceeds through a direct hydride transfer pathway has been developed. With (PrOH)-Pr-i as the hydrogen donor under mild conditions, previously challenging coupling reactions of unactivated Alkyl and Aryl aldehydes with simple alkenes, such as styrene derivatives and alpha-olefins, proceeded smoothly to furnish a diverse range of functionalized alcohols with complete linear regioselectivity.Iron-Catalyzed Regioselective Transfer Hydrogenative Couplings of Unactivated Aldehydes with Simple Alkenesaldehydes; alkenes; hydride transfer; iron; transfer hydrogenative couplings24201654#N/ATRUE
723
anie.20190752510.1002/anie.201907525HydrogenolysisFALSEhttps://doi.org/10.1002/anie.201907525Grutzmacher, HAngew. Chem.-Int. Edit.The dehydrogenation of organosilanes (RxSiH4-x) under the formation of Si-Si bonds is an intensively investigated process leading to oligo- or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si-Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo- and polysilanes that is highly selective and proceeds under mild conditions. New low-valent nickel hydride complexes are used as catalysts and secondary silanes, RR ' SiH2, are obtained as products in high purity.Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexeshydrogenolysis; hydrosilanes; nickel hydrides; polysilanes; silane complexesx1202059#N/AFALSE
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science.1200437HydrogenolysisFALSEhttps://doi.org/Hartwig, JFScienceSelective, nickel-catalyzed hydrogenolysis of Aryl ethers (vol 332, pg 439, 2011)220111#N/ATRUE
725
science.120043710.1126/science.1200437HydrogenolysisFALSEhttps://doi.org/10.1126/science.1200437Hartwig, JFScienceSelective hydrogenolysis of the aromatic carbon-oxygen (C-O) bonds in Aryl ethers is an unsolved synthetic problem important for the generation of fuels and chemical feedstocks from biomass and for the liquefaction of coal. Currently, the hydrogenolysis of aromatic C-O bonds requires heterogeneous catalysts that operate at high temperature and pressure and lead to a mixture of products from competing hydrogenolysis of aliphatic C-O bonds and hydrogenation of the arene. Here, we report hydrogenolyses of aromatic C-O bonds in Alkyl Aryl and diAryl ethers that form exClusively arenes and alcohols. This process is catalyzed by a soluble nickel carbene complex under just 1 bar of hydrogen at temperatures of 80 to 120 C; the relative reactivity of ether substrates scale as Ar-OAr>>Ar-OMe>ArCH(2)-OMe (Ar, Aryl; Me, Methyl). Hydrogenolysis of lignin model compounds highlights the potential of this approach for the conversion of refractory Aryl ether biopolymers to hydrocarbons.Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers588201128#N/ATRUE
726
ja300326t10.1021/ja300326tHydrogenolysisFALSEhttps://doi.org/10.1021/ja300326tAgapie, TJ. Am. Chem. Soc.Mechanistic studies of the hydrogenolysis of Aryl ethers by nickel were undertaken with (diphosphine)Aryl methyl ethers. A Ni(0) complex containing Ni arene interactions adjacent to the Aryl-O bond was isolated. Heating led to Aryl-O bond Activation and generation of a nickel Aryl methoxide complex. Formal beta-H elimination from this species produced a nickel Aryl hydride which can undergo reductive elimination in the presence of formaldehyde to generate a carbon monoxide adduct of Ni(0). The reported complexes map out a plausible mechanism of Aryl ether hydrogenolysis catalyzed by nickel. Investigations of a previously reported catalytic system using isotopically labeled substrates are consistent with the mechanism proposed in the stoichiometric system, involving beta-H elimination from a nickel alkoxide rather than Cleavage of the Ni-O bond by H-2.Nickel-Mediated Hydrogenolysis of C-O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?114201247#N/ATRUE
727
cs401199f10.1021/cs401199fHydrogenolysisFALSEhttps://doi.org/10.1021/cs401199fYan, NA Series of NiM (M = Ru, Rh, and Pd) Bimetallic Catalysts for Effective Lignin Hydrogenolysis in Water2014#N/ATRUE
728
c9sc01018a10.1039/c9sc01018aHydrogenolysisFALSEhttps://doi.org/10.1039/c9sc01018aAllendorf, MDChem. Sci.Metal-Organic Frameworks (MOFs) that catalyze hydrogenolysis reactions are rare and there is little understanding of how the MOF, hydrogen, and substrate molecules interact. In this regard, the isoreticular IRMOF-74 series, two of which are known catalysts for hydrogenolysis of aromatic C-O bonds, provides an unusual opportunity for systematic probing of these reactions. The diameter of the 1D open channels can be varied within a common topology owing to the common secondary building unit (SBU) and controllable length of the hydroxy-Carbonylate struts. We show that the first four members of the IRMOF-74(Mg) series are inherently catalytic for aromatic C-O bond hydrogenolysis and that the conversion varies non-monotonically with pore size. These catalysts are recyClable and reusable, retaining their crystallinity and framework structure after the hydrogenolysis reaction. The hydrogenolysis conversion of phenylethylphenyl ether (PPE), Benzylphenyl ether (BPE), and diphenyl ether (DPE) varies as PPE > BPE > DPE, consistent with the strength of the C-O bond. Counterintuitively, however, the conversion also follows the trend IRMOF-74(III) > IRMOF-74(IV) > IRMOF-74(II) > IRMOF-74(I), with little variation in the corresponding selectivity. DFT calculations suggest the unexpected behavior is due to much stronger ether and phenol binding to the Mg(ii) open metal sites (OMS) of IRMOF-74(III), resulting from a structural distortion that moves the Mg2+ ions toward the interior of the pore. Solid-state Mg-25 NMR data indicate that both H-2 and ether molecules interact with the Mg(ii) OMS and hydrogen-deuterium exchange reactions show that these MOFs activate dihydrogen bonds. The results suggest that both confinement and the presence of reactive metals are essential for achieving the high catalytic activity, but that subtle variations in pore structure can significantly affect the catalysis. Moreover, they challenge the notion that simply increasing MOF pore size within a constant topology will lead to higher conversions.IRMOF-74(n)-Mg: a novel catalyst series for hydrogen Activation and hydrogenolysis of C-O bonds10201979#N/ATRUE
729
anie.20190955110.1002/anie.201909551HydrogenolysisFALSEhttps://doi.org/10.1002/anie.201909551Lercher, JAAngew. Chem.-Int. Edit.The hydrogenolysis of the aromatic C-O bond in Aryl ethers catalyzed by Ni was studied in decalin and water. Observations of a significant kinetic isotope effect (k(H)/k(D)=5.7) for the reactions of diphenyl ether under H-2 and D-2 atmosphere and a positive dependence of the rate on H-2 chemical potential in decalin indicate that addition of H to the aromatic ring is involved in the rate-limiting step. All kinetic evidence points to the fact that H addition occurs concerted with C-O bond scission. DFT calculations also suggest a route consistent with these observations involving hydrogen atom addition to the ipso position of the phenyl ring concerted with C-O scission. Hydrogenolysis initiated by H addition in water is more selective (ca. 75 %) than reactions in decalin (ca. 30 %).The Critical Role of Reductive Steps in the Nickel-Catalyzed Hydrogenolysis and Hydrolysis of Aryl Ether C-O Bondscatalysis; C-O bond Cleavage; hydrogenolysis; nickel; reaction mechanisms11202035#N/ATRUE
730
acscatal.7b0440310.1021/acscatal.7b04403HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.7b04403Flaherty, DWACS Catal.Nickel phosphide catalysts (Ni12P5 and Ni2P) preferentially Cleave sterically hindered (CO)-C-3 bonds over unhindered (CO)-C-2 bonds, and Ni2P is up to 50 times more selective toward (CO)-C-3 bond Cleavage than Ni. Here, we combine kinetic measurements, in situ infrared spectroscopy, and density functional theory (DFT) calculations to describe the mechanism for CO bond rupture over Ni, Ni12P5, and Ni2P catalysts. Steady-state rate measurements and DFT calculations of CO bond rupture within 2-methyltetrahydrofuran (MTHF) show that quasi-equilibrated MTHF adsorption and dehydrogenation steps precede kinetically relevant CO bond rupture at these conditions (150 kPa MTHF; 0.16 MPa H-2; 543 K). Rates for (CO)-C-3 and (CO)-C-2 bond rupture are inhibited by H-2, and the ratio of these rates increases with [H2]1/2, suggesting that the composition of the reactive intermediates for (CO)-C-3 and (CO)-C-2 rupture differs by one H atom. Site-blocking CO*, NH3*, and H* inhibit rates without altering the ratio of (CO)-C-3 to (CO)-C-2 bond rupture, indicating that these CO bond rupture precursors and transition states bind to identical active sites. DFT-based predictions suggest that these sites are exposed ensembles of 3 Ni atoms on Ni(111) and Ni2P(001) and 4 Ni atoms on Ni12P5(001) and that the incorporation of P disrupts extended Ni ensembles and alters the reactivity of the Ni. Increasing the phosphorus to nickel ratio (P:Ni) decreases measured and DFT-predicted Activation enthalpies (Delta H-double dagger, 473583 K) for (CO)-C-3 bond rupture relative to that of (CO)-C-2 bond rupture. Selectivity differences between specific CO bonds within MTHF reflect differences in the H content of reactive intermediates, Activation enthalpy barriers, and P:Ni of Ni, Ni12P5, and Ni2P nanopartiCles.Mechanisms and Active Sites for C-O Bond Rupture within 2-Methyltetrahydrofuran over Ni, Ni12P5, and Ni2P Catalystsnickel phosphide; reaction mechanism; hydrogenolysis; kinetics; 2-methyltetrahydrofuran; active site; DFT11201887#N/ATRUE
731
acscatal.7b0409710.1021/acscatal.7b04097HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.7b04097Zhu, XLACS Catal.Understanding the effect of metal partiCle size on the reactions during hydrodeoxygenation of phenolics is of great importance for rational design of a catalyst for selective control of a desirable reaction. To this end, vapor phase hydrodeoxygenation of m-cresol was studied over 5% Ni/SiO2 catalysts with varying Ni partiCle sizes (2-22 nm) at 300 degrees C and 1 atm H-2. The Ni partiCle sizes were confirmed by several characterization techniques, and the varying surface concentration of terrace, step, and corner sites with Ni partiCle sizes was verified by H-2 temperature-programmed desorption. Decreasing the Ni partiCle size from 22 to 2 nm improves the intrinsic reaction rate by 24 times and the turnover frequency (TOF) by 3 times. The TOFs for toluene and methylcyClohexanone/methylcyClohexanol formation increase by 6 and 4 times, respectively, while the TOF for CH, formation decreases by 3/4, indicating that smaller partiCles with more defect sites (step and corner) favor deoxygenation and hydrogenation while larger partiCles with more terrace sites favor C-C hydrogenolysis. Density functional theory study shows that the barrier for direct dehydroxylation of phenol on Ni(111), Ni(211), and defected Ni(211) decreases from 175.6 to 145.6 and then to 120.5 kJ/mol. The results indicate that a highly coordinatively unsaturated surface Ni site is responsible for C-O Cleavage through facile adsorption and stabilization of -OH in the transition state, thus facilitating deoxygenation toward toluene. Our results indicate that tuning the metal partiCle size is an effective approach to control reactions during hydrodeoxygenation.Size Dependence of Vapor Phase Hydrodeoxygenation of m-Cresol on Ni/SiO2 Catalystsm-cresol; hydrodeoxygenation; Ni; partiCle size; deoxygenation; C-C hydrogenolysis; hydrogenation58201865#N/ATRUE
732
acscatal.7b0231710.1021/acscatal.7b02317HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.7b02317Zhao, CACS Catal.Aqueous-phase hydrogenolysis of renewable biomass at low H-2 pressures is an attractive route to selectively produce renewable fuels and valuable chemicals. Here, we show that Ru and Ni nanopartiCles (NPs) dispersed on HZSM-5 with an optimum H-center dot radical transfer catalyzed a rapid rate (152 mmol g(-1) h(-1)) of hydrogenolysis of C-O bonds in lignin-derived guaiacol at 240 degrees C and 2 bar H-2 pressure in water. The coimpregnated individual Ru and Ni nanopartiCles (NPs) on HZSM-5 were highly dispersed and did not present an alloy structure, but the individual Ru and Ni NPs were in Close proximity. The guaiacol hydrogenolysis rates were proportional to the amounts of the adjacent RuO2 and NiO NPs on the calcined samples, suggesting that the Closely contacted Ru and Ni NPs on HZSM-5 are the active sites. In phase at low H-2 pressures, Ru dissociated the hydrogen molecules to H-center dot radicals (H-center dot), and then such radicals were transferred to adjacent Ni atoms to activate the capability of inert Ni centers. The adjustment of the H-center dot transfer length between Ru and Ni NPs led to shorter transfer lengths, which resulted in activities as high as 118 mmol g(-1) h(-1). The transferring and anchoring of H-center dot radicals was considered to be achieved by the Si-OH groups and their defects on HZSM-5, as demonstrated by a temperature programmed desorption of hydrogen coupled with mass spectroscopy (TPD/H-2-MS) experiment. To further shorten the H-center dot transfer length over uniformly formed Ru and Ni nanopartiCles, the isolated Ni islands were removed through the incorporation of a Ru precursor that initially occupied the Bronsted acid sites on HZSM-5. By fully activating the two metals in the aqueous phase via an H-center dot transfer mechanism at low H-2 pressures, the rational design of bimetallic Ru-Ni catalysts provides a promising approach for achieving substantially high rates in selective hydrogenolysis steps. the waterBimetallic Ru-Ni Catalyzed Aqueous-Phase Guaiacol Hydrogenolysis at Low H-2 Pressuresbimetallic Ru-Ni; XAFS; H-center dot radical transfer; aqueous-phase hydrogenolysis; lignin70201734#N/ATRUE
733
acscatal.6b0245710.1021/acscatal.6b02457HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.6b02457Jackson, BACS Catal.The heat of adsorption and sticking probability of methyl iodide were measured on Ni(111) at 100 and 160 K using single-crystal adsorption calorimetry (SCAC). At 100 K, methyl iodide adsorbs molecularly with a heat of 102 kJ/mol on terrace sites in the low-coverage limit, giving a standard enthalpy of formation (Delta H-f degrees) of CH3I(ad) of -87 kJ/mol. A heat of 122 kJ/mol is also measured on defect sites, probably step edges. Calorimetry of the dissociative adsorption of methyl iodide on Ni(111) at 160 K yielded an integral heat of adsorption of -270 kJ/mol at 0.04 ML, providing the energetics of adsorbed methyl, with Delta H-f degrees [CH3(ad)] = -71 kJ/mol and a CH3-Ni(111) bond enthalpy of 218 kJ/mol. This is 22 kJ/mol stronger than the reported value for H3C-Pt(111) bonds, explaining the greater activity of Ni catalysts for hydrogenolysis in comparison to Pt. The energetics for methyl were compared to density functional theory (DFT) calculations from previous literature, showing that these methods systematically underestimate the bond energy of methyl to Ni(111). measuredEnergetics of Adsorbed Methyl and Methyl Iodide on Ni(111) by Calorimetry: Comparison to Pt(111) and Implications for Catalysisadsorbed methyl; nickel; platinum; heat of adsorption; hydrogenolysis; methane Activation; steam reforming; partial oxidation12201769#N/ATRUE
734
acscatal.5b0218010.1021/acscatal.5b02180HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.5b02180Guan, NJACS Catal.The selective scission of chemical bonds is always of great significance in organic chemistry. The Cleavage of strong carbon carbon sigma bonds in the unstrained systems remains challenging. Here, we report the selective hydrogenolysis of carbon-carbon sigma bonds in primary aliphatic alcohols catalyzed by supported metals under relatively mild conditions. In the case of 1-hexadecanol hydrogenolysis over Ru/TiO2 as a model reaction system, the selective scission of carbon-carbon bonds over carbon oxygen bonds is observed, resulting in n-pentadecane as the dominant product with a small quantity of n-hexadecane. Theoretical calculations reveal that the 1-hexadecanol hydrogenolysis on flat Ru (0001) undergoes two parallel pathways: i.e. carbon-carbon bond scission to produce n-pentadecane and carbon-oxygen bond scission to produce n-hexadecane. The removal of adsorbed CO on a flat Ru (0001) surface is a crucial step for the 1-hexadecanol hydrogenolysis. It contributes to the largest energy barrier in n-pentadecane production and also retards the rate for n-hexadecane production by covering the active Ru (0001) surface. The knowledge presented in this work has significance not just for a fundamental understanding of strong carbon-carbon sigma bond scission but also for practical biomass conversion to fuels and chemical feedstocks.Selective Catalytic Hydrogenolysis of Carbon-Carbon sigma Bonds in Primary Aliphatic Alcohols over Supported Metalsruthenium catalyst; primary aliphatic alcohols; hydrogenolysis; carbon-carbon bond scission; theoretical calculations14201536#N/ATRUE
735
acscatal.5b0208910.1021/acscatal.5b02089HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.5b02089Wu, YDACS Catal.The transformation of aromatic carbon oxygen (C-Ar-O) bonds in lignin to useful chemical building blocks has great potential in biomass conversion. A Ni-NHC (N-heterocyClic carbene) catalyzed selective hydrogenolysis of Aryl ethers has recently been developed by Hartwig and co-worker, but the reaction mechanism, inCluding the role of different additives found to accelerate the reaction and the origin of the selectivity, remains unClear. DFT calculations of several possible pathways for this useful and important transformation suggest a new mechanistic pathway which involves coordination of the excess base ((BuO-)-Bu-t) to facilitate the rate-determining C-O Activation step, dissociation of the ArO- ligand, H-2 Activation through a Ni-(OBu)-Bu-t bond to give (HOBu)-Bu-t, and finally reductive elimination to afford the arene product. Another new ion-pair (SNAr-like) pathway for the base-assisted C-O bond Activation could compete with the above base-assisted oxidative addition pathway for some diAryl ethers. The regioselective Cleavage of different ethers and the effects of the Lewis acid were also examined and compared. The results demonstrate that bulkiness and strong donating ability of the NHC ligand and the presence of excess base are the keys to a Ni(O)/Ni(II) catalytic cyCle.Mechanism of Ni-NHC Catalyzed Hydrogenolysis of Aryl Ethers: Roles of the Excess Basenickel; N-heterocyClic carbene; hydrogenolysis; C-O Activation; biomass; H-2 Activation502016100#N/ATRUE
736
acscatal.5b0206110.1021/acscatal.5b02061HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.5b02061Allendorf, MDACS Catal.We demonstrate that metal organic frameworks (MOFs) can catalyze hydrogenolysis of Aryl ether bonds under mild conditions. Mg-IRMOF-74(I) and Mg-IRMOF-74(II) are stable under reducing conditions and can Cleave phenyl ethers containing beta-O-4, alpha-O-4, and 4-O-5 linkages to the corresponding hydrocarbons and phenols. Reaction occurs at 10 bar H-2 and 120 degrees C without added base. DFT-optimized structures and charge transfer analysis suggest that the MOF orients the substrate near Mg2+ ions on the pore walls. Ti and Ni doping further increase conversions to as high as 82% with 96% selectivity for hydrogenolysis versus ring hydrogenation. Repeated cyCling induces no loss of activity, making this a promising route for mild Aryl-ether bond scission.MOF-Based Catalysts for Selective Hydrogenolysis of Carbon Oxygen Ether Bondsmetal-organic frameworks; catalysis; C-O bond Cleavage; hydrogenolysis; aromatic ethers58201630#N/ATRUE
737
acscatal.5b0205810.1021/acscatal.5b02058HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.5b02058Surawatanawong, PACS Catal.The catalytic C-O bond Activation of Aryl ethers attracts substantial interest as it is significant for the lignin degradation process. A nickel complex with N-heterocyClic carbene (Ni-SIPr) has been shown to selectively catalyze C-O bond hydrogenolysis of Aryl methyl ether to obtain arene and alcohol as the only products. Here, the reaction mechanism of Ni-SIPr catalyzed C-O bond hydrogenolysis of methyl phenyl ether (PhOMe) was studied using density functional theory. In the presence of H-2, the catalytic cyCle involves the following: (i) aromatic C-O bond oxidative addition of Ni(SIPr)(eta(2)-PhOMe) to form Ni(SIPr)-(OMe)(Ph), (ii) beta-H transfer from the methoxy to phenyl group in Ni(SIPr)(OMe)(Ph) via sigma-complex-assisted metathesis (sigma-CAM), which eliminates benzene and forms Ni(SIPr)(eta(2)-CH2O), (iii) H-2 binding to form Ni(SIPr)(H-2)(eta(2)-CH2O) prior to H-transfer from H-2 to the formaldehyde carbon via sigma-CAM to generate Ni(SIPr)(H)(OMe), and (iv) reductive elimination to form methanol and the binding of methyl phenyl ether to regenerate Ni(SIPr)(eta(2)-PhOMe). The tert-butoxide base could play a role to assist with the formation of Ni(SIPr)(eta(2)-PhOMe), the catalytically active species, and could bind to Ni(SIPr)(H)(OMe) before reductive elimination. A similar mechanism was found for the C-O bond hydrogenolysis of 2-methoxynaphthalene. Our study showed that the C-O bond oxidative addition is the rate-determining step and that the aromatic C-O bond Cleavage to form Ni(SIPr)(OMe)(Ph) is more favorable than the aliphatic C-O bond Cleavage to form Ni(SIPr)(OPh)(Me), consistent with the arene and alcohol products obtained from the experiment. Notably, the beta-H transfer from the methoxy to phenyl group on Ni-SIPr is not a stepwise beta-H elimination as generally perceived, but rather a concerted process that occurs via sigma-CAM. This leads to benzene elimination before H-2 binding, in accordance with the results of the isotope labeling experiment of C-O bond hydrogenolysis of 2-methoxynaphthalene. In the absence of H-2, Ni(SIPr)(eta(2)-CH2O) tends to undergo C-H bond Activation and alpha-H elimination to release H-2 and generate a nickel Carbonyl complex, the catalytically inactive species. This was reflected by experimental results which demonstrated low conversion of 2-methoxynaphthalene in the absence of H-2. Thus, H-2 is crucial to the catalytic reaction through its role in suppressing the formation of the inactive nickel Carbonyl species. Insights into the mechanisms of Ni-SIPr catalyzed conversion of methyl phenyl ether should benefit the development of catalysts for C-O bond Activation.Density Functional Study of Nickel N-HeterocyClic Carbene Catalyzed C-O Bond Hydrogenolysis of Methyl Phenyl Ether: The Concerted beta-H Transfer MechanismC-O bond Activation; beta-H transfer; nickel; N-heterocyClic carbene; density functional theory; Aryl ether20201665#N/ATRUE
738
acscatal.0c0556010.1021/acscatal.0c05560HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.0c05560Resasco, DEACS Catal.As a non-noble metal, Ni could offer significant economic advantages if used as a catalyst for hydrodeoxygenation (HDO) of lignin-derived phenolics to produce aromatics. However, on unmodified Ni catalysts, the desirable direct deoxygenation reaction must compete with high rates of phenylring hydrogenation and C- C hydrogenolysis reactions, which lead to low aromatics yields. Here, we report on a bimetallic NiW/SiO2 (W/Ni = 1) prepared by coimpregnation that shows an HDO reaction rate of m-cresol almost an order of magnitude higher than that on Ni/SiO2 at 350 degrees C and 1 atm H-2. More importantly, under these conditions, this catalyst exhibits a complete inhibition of CH4 formation, while at a temperature as low as 250 degrees C, the dominant product is still toluene, with minimal formation of ring-saturation products. To elucidate the structure of this catalyst, a detailed characterization was performed by combination of several techniques. It was found that the calcined NiW/SiO2 exhibits a large extent of Ni-W oxide interaction. After reduction at 500 degrees C, a thin NiW alloy shell with a small Ni core and WOx in Close proximity are formed, with a strong interaction between Ni and adjacent W species. The electronic modifications of Ni and W species were monitored by X-ray photoelectron spectroscopy and it was found that these interactions alter the surface properties of the alloy, resulting in significantly weakened CO chemisorption. This unique structure provides a balanced hydrogenation, oxophilicity, and C-O Cleavage activity, which result in a significantly improved rate and selectivity toward toluene with inhibition of CH4 and hydrogenation product formation.Elucidating the Structure of Bimetallic NiW/SiO2 Catalysts and Its Consequences on Selective Deoxygenation of m-Cresol to toluenehydrodeoxygenation; m-cresol; nickel; NiW/SiO2 bimetallic catalyst; C-C hydrogenolysis0202167#N/ATRUE
739
acscatal.0c0237510.1021/acscatal.0c02375HydrogenolysisFALSEhttps://doi.org/10.1021/acscatal.0c02375Ma, LLACS Catal.Keto-alcohols, which are traditionally produced from fossil resources with multisteps, are considered as important intermediates for diversified high-value-added fine chemical synthesis due to their involved Carbonyl and hydroxyl groups. Herein, direct cellulose hydrogenolysis to C-3-C-4 keto-alcohol products (hydroxyacetone and 1(3)hydroxy-2-butanone) was achieved over Ni-WOx/C catalysts with an W/Ni atom ratio of 1.0-5.0. The keto-alcohol yield was proposed to strongly depend on the W/Ni ratio and the catalyst annealing temperature. The highest keto-alcohol yield of 63% was obtained at the optimal balance of basic/acidic WOx species and metallic Ni. The introduction of Ni facilitated the formation of the basic W5+ sites, which enhanced the formation of basic sites at the Ni-WOx interface. The synergistic effect between the basic W5+ and acidic oxygen vacancy (Vo) could activate the target C-O/C=O bonds, promoting the isomerization of glucose and C-3-C-4 aldehyde intermediates with the assistance of the interfacial Ni. The cooperative adsorption of the -OH and -C=O groups at the Ni-O-W-Vo interface stabilized the adjacent ketone and hydroxyl groups and kept the other hydroxyl groups for hydrogenolysis, obtaining the final C-3-C-4 keto-alcohols. This work expanded the application of cellulosic biomass, enabling the green and sustainable synthesis of the high-value C-3-C-4 keto-alcohol products using lignocellulosic biomass as a raw material.Selective C-3-C-4 Keto-Alcohol Production from Cellulose Hydrogenolysis over Ni-WOx/C Catalystsbiomass; cellulose; keto-alcohols; Ni-WOx/C catalyst; hydrogenolysis2202076#N/ATRUE
740
acscatal.7b0162410.1021/acscatal.7b01624inorganicFALSEhttps://doi.org/10.1021/acscatal.7b01624Deguchi, TACS Catal.Developing an ammonia synthesis process from N-2 and H-2 is of interest in the catalysis and hydrogen research community. Wool-like metal electrodes used to produce nonthermal plasma were determined to serve as efficient catalysts for ammonia synthesis under atmospheric pressure without heating. The catalytic activity of Pt, Pd, Ag, Cu, and Ni wools increased as the experiment was repeated, while that of Au, Fe, Mo, Ti, W, and Al was almost constant. The activity change was mainly due to migration of metals from the electrode to the inner wall of a silica reactor or increases in surface areas of metal catalysts. The order of the activity at each initial experiment was Au > Pt > Pd > Ag > Cu > Fe > Mo > Ni > W > Ti > Al. DFT calculations using Gaussian 09 and CASTEP were applied for energy changes in a reaction M-3 + 1/2 N-2 -> M3N and in adsorption of a nitrogen atom on metal surface, in which M3 was a virtual minimum unit of the metal surface. The reactions were assumed to be an essential step in the ammonia production after plasma Activation of N-2. The resulting values correlated with the respective initial catalytic activity, indicating that a more unstable M3N surface intermediate produced higher catalytic activity. Emission spectra in the plasma process using various electrodes were measured and showed that the efficiency of electrodes for plasma Activation of nitrogen molecules was almost independent of the metals, while the reactivity of the activated species to form ammonia depended greatly on the metal used. The N-2/H-2 ratio dependence and formation/decomposition rate constants of ammonia were finally determined on Au and Cu, which were different from those for the conventional Haber-Bosch process. The decomposition of produced ammonia was suggested to proceed in a plasma-irradiated gas phase.Ammonia Synthesis on Wool-Like Au, Pt, Pd, Ag, or Cu Electrode Catalysts in Nonthermal Atmospheric-Pressure Plasma of N-2 and H-2ammonia synthesis; plasma; nonthermal; catalysis; gold; platinum; palladium; copper82201736#N/ATRUE
741
acscatal.0c0232510.1021/acscatal.0c02325inorganicFALSEhttps://doi.org/10.1021/acscatal.0c02325Joo, SHACS Catal.Atomically dispersed nickel sites complexed on nitrogen-doped carbon (Ni-N/C) have demonstrated considerable activity for the selective electrochemical carbon dioxide reduction reaction (CO2RR) to CO. However, the high-temperature treatment typically involved during the Activation of Ni-N/C catalysts makes the origin of the high activity elusive. In this work, Ni(II) phthalocyanine molecules grafted on carbon nanotube (NiPc/CNT) and heat-treated NiPc/CNT (H-NiPc/CNT) are exploited as model catalysts to investigate the impact of thermal Activation on the structure of active sites and CO2RR activity. H-NiPc/CNT exhibits a similar to 4.7-fold higher turnover frequency for CO2RR to CO in comparison to NiPc/CNT. Extended X-ray absorption fine structure analysis and density functional theory (DFT) calculations reveal that the heat treatment transforms the molecular Ni2+-N-4 sites of NiPc into Ni+-N3V (V: vacancy) and Ni+-N-3 sites incorporated in the graphene lattice that concomitantly involves breakage of Ni-N bonding, shrinkage in the Ni-N-C local structure, and decrease in the oxidation state of the Ni center from +2 to +1. DFT calculations combined with microkinetic modeling suggest that the Ni-N3V site appears to be responsible for the high CO2RR activity because of its lower barrier for the formation of * COOH intermediate and optimum *CO binding energy. In situ/operando X-ray absorption spectroscopy analyses further corrB(OH)2rate the importance of reduced Ni+ species in boosting the CO2RR activity.Thermal Transformation of Molecular Ni2+-N-4 Sites for Enhanced CO2 Electroreduction ActivityNi-N/C catalyst; electrochemical CO2 reduction; heat treatment; local structure; oxidation state11202069#N/ATRUE
742
jacs.6b1025510.1021/jacs.6b10255InsertionFALSEhttps://doi.org/10.1021/jacs.6b10255Yorimitsu, HJ. Am. Chem. Soc.Treatment of benzofurans with bis(pinacolato)diboron and Cs2CO3 under nickel-NHC catalysis resulted in the insertion of a boron atom into the C-2-O bond of benzofurans to afford the corresponding oxaborins. The scope of benzofuran substrates is wide, and the reactions proceeded without loss of functional groups such as fluoro, methoxy, and ester that are potentially reactive under nickel catalysis. The boron inserted products proved to be useful building blocks and subsequently underwent a series of transformations, one of which led to the synthesis of fluorescent pi-expanded oxaborins.Nickel-Catalyzed Boron Insertion into the C-2-O Bond of Benzofurans42201699#N/ATRUE
743
acscatal.0c0471310.1021/acscatal.0c04713Insertionshttps://doi.org/10.1021/acscatal.0c04713Uyeda, CACS Catal.A (pybox)Ni catalyst (where pybox = pyridine-bis(oxazoline)) promotes the reductive cyClization of beta-hydroxy 1,1-dichloroalkenes to form 2,3-dihydrofurans. The substrates for this reaction are conveniently prepared by an aldol addition, followed by one-carbon homologation. Chiral substrates are accessible in highly enantioenriched form, allowing for the synthesis of stereochemically complex 2,3,4-trisubstituted products. Mechanistic studies support a Vinylidene O-H insertion rather than a C-O cross-coupling pathway.Nickel-Catalyzed Vinylidene Insertions into O-H BondsVinylidenes; O-H bond insertion; cyClization; oxygen heterocyCles; nickel catalysis0202141#N/ATRUE
744
anie.20161181910.1002/anie.201611819InterconversionFALSEhttps://doi.org/10.1002/anie.201611819Rueping, MAngew. Chem.-Int. Edit.An efficient nickel-catalyzed deCarbonylative amination reaction of Aryl and heteroAryl esters has been achieved for the first time. The new amination protocol allows the direct interconversion of esters and amides into the corresponding amines and represents a good alternative to Classical rearrangements as well as cross coupling reactions.Catalytic Ester and Amide to Amine Interconversion: Nickel-Catalyzed DeCarbonylative Amination of Esters and Amides by C-O and C-C Bond Activationamination; arenes; esters; nickel; reaction mechanisms116201759#N/ATRUE
745
ja073300q10.1021/ja073300qIntermolecularFALSEhttps://doi.org/10.1021/ja073300qMontgomery, JJ. Am. Chem. Soc.A nickel-catalyzed intermolecular reductive coupling of enones and alkynes has been developed as a novel entry to gamma,delta-unsaturated ketones. The process does not require formation of a Vinyl organometallic, and a variety of functional groups inCluding free hydroxyls and esters are tolerated. A number of features that complement existing copper-mediated processes are highlighted.Catalytic intermolecular reductive coupling of enones and alkynes44200719#N/ATRUE
746
acscatal.0c0098010.1021/acscatal.0c00980Intermolecularhttps://doi.org/10.1021/acscatal.0c00980Matsubara, SACS Catal.Organohalogen compounds such as alkenyl bromides are versatile and essential building blocks in organic synthesis. Herein, we describe the nickel-catalyzed intermolecular carbobrominations of alkynes with Aryl bromides to form highly substituted and functionalized alkenyl bromides. The reductive elimination of the carbon-bromine bond from a Ni(II) species, which is usually a disfavored process, is achieved from a high-valent Ni(III) species in this reaction. This transformation not only expands the scope of transition-metal-complex-promoted bond-forming reactions but also, more particularly, accomplishes the formation of labile bonds, which is as challenging to achieve as the Cleavage of inert bonds, such as C-O or C-H bonds.Nickel-Catalyzed Intermolecular Carbobromination of Alkynescarbobromination; odd valent nickel; reductive elimination; carbon-bromine bond; alkyne5202063#N/ATRUE
747
jacs.9b0093110.1021/jacs.9b00931intermoleculeFALSEhttps://doi.org/10.1021/jacs.9b00931Shi, SLJ. Am. Chem. Soc.Annulated pyridines are ubiquitous scaffolds in many bioactive molecules. A highly regio- and enantioselective Ni(0) - catalyzed endo-selective C-H cyClization of pyridines with alkenes has been developed. An unprecedented enantioselective C-H Activation at pyridyl 3- or 4-positions was enabled by bulky chiral N-heterocyClic carbene ligands. This protocol provides expedient access to a series of optically active 5,6,7,8-tetrahydroquinolines and 5,6,7,8-tetrahydroisoquinolines, compounds otherwise accessed with difficulty, in moderate to high yields (up to 99% yield) and enantioselectivities (up to 99% ee). To our knowledge, this is the first example of enantioselective C-H cyClization of pyridines to chiral annulated products.Regio- and Enantioselective C-H CyClization of Pyridines with Alkenes Enabled by a Nickel/N-HeterocyClic Carbene Catalysis51201991#N/ATRUE
748
jacs.8b0118110.1021/jacs.8b01181intermoleculeFALSEhttps://doi.org/10.1021/jacs.8b01181Cramer, NJ. Am. Chem. Soc.Annulated pyridones are an important scaffold found in many biologically active compounds. A Ni(0)-catalyzed C-H functionalization of 2- and 4-pyridones is disClosed, providing access to annulated pyridones via enantioselective intramolecular olefin hydroArylation. Key to the success of the transformation was the development of a sterically hindered and tunable N-heterocyClic carbene ligand resembling a chiral version of IPr. This ligand allows for mild reaction temperatures, and leads to the annulated pyridones in excellent yields and enantioselectivities.Nickel-Catalyzed Enantioselective Pyridone C-H Functionalizations Enabled by a Bulky N-HeterocyClic Carbene Ligand76201862#N/ATRUE
749
anie.20181075710.1002/anie.201810757IntermoleculeTRUEhttps://doi.org/10.1002/anie.201810757Alexanian, EJAngew. Chem.-Int. Edit.The development of a general, nickel-catalyzed Alkyl-Mizoroki-Heck reaction of unactivated Alkyl bromides is described. The mild reaction proceeds efficiently using a wide range of primary and secondary Alkyl bromides, and examples of intermolecular cross-couplings are provided. Reaction alkene regioselectivity is significantly enhanced over prior carbocyClizations using palladium catalysis. Mechanistic investigations are consistent with a direct carbocyClization in contrast to the auto-tandem atom-transfer cyClization and halide elimination previously observed with palladium catalysis.Nickel-Catalyzed Mizoroki-Heck-Type Reactions of Unactivated Alkyl BromidesAlkyl halides; cross-coupling; nickel; radical reactions; synthetic methodsCsp2-Csp3HHBrVinylEt3NNitrogenNitrogen(neutral)202018303/17/2022TRUE
750
ja902202g10.1021/ja902202gIsomerizationFALSEhttps://doi.org/10.1021/ja902202gToda, YJ. Am. Chem. Soc.Highly anti- and enantioselective synthesis of beta-amino aldehydes having an aliphatic substituent. at the beta-position was accomplished by a combination of two catalytic reactions, that is, an initial Ni(II) complex-catalyzed isomerization of a double bond followed by a chiral phosphoric acid catalyzed aza-Petasis-Ferrier rearrangement, using hemiaminal allyl ethers as the initial substrate. The chiral phosphoric acid also functioned as an efficient resolving catalyst of racemic hemiaminal Vinyl ethers.Double Bond Isomerization/Enantioselective Aza-Petasis-Ferrier Rearrangement Sequence as an Efficient Entry to Anti- and Enantioenriched beta-Amino Aldehydes121200914#N/ATRUE
751
anie.20046237110.1002/anie.200462371Kumadahttps://doi.org/10.1002/anie.200462371Born, RAngew. Chem.-Int. Edit.Modular diamino- and dioxophosphine oxides and chlorides as ligands for transition-metal-catalyzed C-C and C-N couplings with Aryl chlorides119200542#N/ATRUE
752
acscatal.7b0428610.1021/acscatal.7b04286ligand materialFALSEhttps://doi.org/10.1021/acscatal.7b04286Shi, JLACS Catal.With ever-increasing severe environment pollutions and energy demand, it is becoming greatly important to develop sustainable energy resources as alternatives to traditional fossil fuels. As one of the ultimate Clean energy sources, hydrogen (H-2) energy produced by water splitting using electricity from solar radiation, wind, tide, and nuClear fusion, among other sources, has attracted more and more public attention since the late 18th century. Although noble-metal based electrocatalysts perform well, they suffer severely from the high cost and rarity from the viewpoint of practical applications. Recently, various kinds of non-noble-metal electrocatalysts based on low cost and earth-abundant transition metals have been developed for both hydrogen evolution reaction (HER) and oxygen (O-2) evolution reaction (OER). Among them, non-noble-metal bifunctional electrocatalysts (NHOBEs), showing high performances in both HER and OER, are therefore of great significance and importance in future applications. With NHOBEs, one will be able to significantly simplify the fabrication procedures of electrolyzers, and more importantly, elevate the efficiency of all in one electrocatalytic water-splitting systems, which will greatly favor their industrial applications by demanding substantially lowered the production costs. While the laws of NHOBEs from the same main group anionic elements such as oxygen, nitrogen, carbon, and boron families have not been well-reported so far. Herein, the recent significant progresses of NHOBEs Classified by different main group anionic elements are summarized, and emphases are placed to the designs, syntheses, electrocatalytic performances in water-splitting, and future possible applications of NHOBEs. Moreover, the prospects of a number of vigorously investigated NHOBE catalysts and the possible trends of future developments are also evaluated. In addition, current challenges facing research with respect to electrocatalysts for water-splitting are discussed.Anion-Containing Noble-Metal-Free Bifunctional Electrocatalysts for Overall Water Splittinganion-containing; noble-metal-free; bifunctional electrocatalyst; overall water-splitting; energy conversion1032018128#N/ATRUE
753
ja207944c10.1021/ja207944c
Modular Route
FALSEhttps://doi.org/10.1021/ja207944cZard, SZJ. Am. Chem. Soc.A recently discovered radical fragmentation of 2-fluoro-6-pyridinoxy derivatives allows a new highly stereoselective and convergent route to (E)-Vinylsulfones from allylic alcohols. Reductive desulfonylation or nickel-catalyzed couplings furnish di- and trisubstituted (E)- and (Z)-alkenes.A Highly Stereoselective, Modular Route to (E)-Vinylsulfones and to (Z)- and (E)-Alkenes31201187#N/ATRUE
754
ja908906n10.1021/ja908906nN-H ActivationFALSEhttps://doi.org/10.1021/ja908906nShibasaki, MJ. Am. Chem. Soc.A highly enantioselective catalytic asymmetric access to 3-aminooxindoles with a tetrasubstituted carbon stereocenter is described. 1-2 mol % of homobimetallic (R)-Ni-2-Schiff base 1 catalyzed the asymmetric amination of 3-substituted oxindoles with azodiCarbonylates to give (R)-products in 99-89% yield and 99-87% ee. Reversal of enantiofacial selectivity was observed between bimetallic and monometallic Schiff base complexes, and monometallic (R)-Ni-Schiff base 2c gave (S)-products in 98-80% ee. Transformation of the products into an optically active oxindole with a spiro-beta-lactam unit and a known key intermediate for AG-041R synthesis is also described.Catalytic Asymmetric Synthesis of 3-Aminooxindoles: Enantiofacial Selectivity Switch in Bimetallic vs Monometallic Schiff Base Catalysisx230201049#N/AFALSE
755
ncomms1107310.1038/ncomms11073N-H ActivationTRUEhttps://doi.org/10.1038/ncomms11073Stradiotto, MNat. Commun.Palladium-catalysed C(sp(2))-N cross-coupling (that is, Buchwald-Hartwig amination) is employed widely in synthetic chemistry, inCluding in the pharmaceutical industry, for the synthesis of (hetero) aniline derivatives. However, the cost and relative scarcity of palladium provides motivation for the development of alternative, more Earth-abundant catalysts for such transformations. Here we disClose an operationally simple and air-stable ligand/nickel(II) pre-catalyst that accommodates the broadest combination of C(sp(2))-N coupling partners reported to date for any single nickel catalyst, without the need for a precious-metal co-catalyst. Key to the unprecedented performance of this pre-catalyst is the application of the new, sterically demanding yet electron-poor bisphosphine PAd-DalPhos. Featured are the first reports of nickel-catalysed room temperature reactions involving challenging primary Alkylamine and ammonia reaction partners employing an unprecedented scope of electrophiles, inCluding transformations involving sought-after (hetero) Aryl mesylates for which no capable catalyst system is known.Challenging nickel-catalysed amine Arylations enabled by tailored ancillary ligand designCsp2_ar-Nsp3E-NuOOTsHArylIonic-OtBu852016613/10/2022TRUE
756
ja964391m10.1021/ja964391mN-H ActivationFALSEhttps://doi.org/10.1021/ja964391mBuchwald, SLJ. Am. Chem. Soc.Aryl chlorides are converted to aniline derivatives using catalytic amounts of Ni(COD)(2) (COD 1,5-cyClooctadiene) and DPPF (DPPF = 1,1'-bis(diphenylphosphino)ferrocene) or 1,10-phenanthroline in the presence of sodium tert-butoxide. This procedure has a broad substrate scope: electron-rich or electron-poor Aryl chlorides, as well as chloropyridine derivatives, can be combined with primary and secondary amines to give the desired Aryl amine products in moderate to excellent yields. Additionally, a procedure which utilizes the air-stable precatalysts (DPPF)NiCl2 or (1,10-phenanthroline)NiCl2 is also described.Nickel-catalyzed amination of Aryl chlorides260199734#N/ATRUE
757
ja302691r10.1021/ja302691rN-H ActivationFALSEhttps://doi.org/10.1021/ja302691rTang, YJ. Am. Chem. Soc.A Ni-catalyzed asymmetric ring-opening reaction of 2-substituted cyClopropane-1,1-diCarbonylates with aliphatic amines has been accomplished using the chiral indane-trisoxazoline (In-TOX) ligand. This highly enantioselective reaction provides an efficient approach to a variety of chiral gamma-substituted gamma-amino acid derivatives, which are readily transformed into multifunctionalized piperidines and gamma-lactams. The single-crystal X-ray structure of the TOX-Ni complex is provided, and the role of the side arm in the chiral ligand is discussed.Side-Arm-Promoted Highly Enantioselective Ring-Opening Reactions and Kinetic Resolution of Donor-Acceptor CyClopropanes with Amines113201272#N/ATRUE
758
acscatal.8b0085610.1021/acscatal.8b00856N-H ActivationFALSEhttps://doi.org/10.1021/acscatal.8b00856Nicasio, MCACS Catal.Nickel catalysis is gaining in popularity in recent years, mostly within the area of cross-coupling. However, unlike Pd, the mechanisms of Ni-catalyzed C-C and C-heteroatom bond forming reactions have been much less studied, in particular when N-heterocyClic carbenes are used as ligands. Here, we present a thorough study of the mechanism of C-N cross-coupling reactions catalyzed by an NHC-Ni complex. Focusing on the coupling of 2-chloropyridines with indole catalyzed by [(IPrNi(styrene)(2)] (IPr = N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), we have examined each of the elementary steps: i.e., oxidative addition, ligand substitution, and reductive elimination. All relevant catalytic intermediates have been isolated and structurally characterized by both spectroscopic and crystallographic methods. Kinetic studies have revealed that the reductive elimination is the rate-limiting step. Catalyst deActivation is related to the formation of unproductive dinuClear pyridyl-bridged NHC-Ni-II species, which can be prevented by increasing the size of the heteroAryl chloride. These investigations support a neutral Ni(0)/Ni(II) catalytic cyCle. Calculations corrB(OH)2rate the experimental evidence and confirm the influence exerted by the ligands in each of the elementary steps.Elucidating the Mechanism of Aryl Aminations Mediated by NHC-Supported Nickel Complexes: Evidence for a Nonradical Ni(0)/Ni(II) Pathwayamination; C-N bond formation; mechanism; cross-coupling; nickel; NHC; indole282018107#N/ATRUE
759
acs.orglett.9b0299010.1021/acs.orglett.9b02990N-H ActivationFALSEhttps://doi.org/10.1021/acs.orglett.9b02990Balaraman, EGeneral Synthesis of N-Alkylation of Amines with Secondary Alcohols via Hydrogen Autotransfer2019#N/ATRUE
760
anie.20035263410.1002/anie.200352634N-H CouplingFALSEhttps://doi.org/10.1002/anie.200352634Snieckus, VAngew. Chem.-Int. Edit.ortho-anisylsulfonyl as a protecting group for secondary amines: Mild Ni-0-catalyzed hydrodesulfortylationamines; magnesium; nickel; protecting groups; sulfonamidesx38200470#N/AFALSE
761
anie.20160502610.1002/anie.201605026N-N CouplingFALSEhttps://doi.org/10.1002/anie.201605026Warren, THAngew. Chem.-Int. Edit.Nitrosobenzene (PhNO) serves as a stable analogue of nitroxyl (HNO), a biologically relevant, redox-active nitric oxide derivative. Capture of nitrosobenzene at the electron-deficient beta-diketiminato nickel(I) complex [(Pr2NNF6)-Pr-i]Ni results in reduction of the PhNO ligand to a (PhNO)(./-) species coordinated to a square planar Ni-II center in [iPr(2)NN(F6)] Ni(eta(2)-ONPh). Ligand centered reduction leads to the (PhNO)(2-) moiety bound to NiII supported by XAS studies. Systematic investigation of structure-reactivity patterns of (PhNO)(./-) and (PhNO)(2-) ligands reveals parallels with superoxo (O-2)(./-) and peroxo (O-2)(2-) ligands, respectively, and forecasts reactivity patterns of the more transient HNO ligand.Redox Non-Innocence of Nitrosobenzene at Nickelnickel; nitric oxide; nitrosobenzene; redox-active ligands; X-ray spectroscopy22201640#N/ATRUE
762
anie.20190051010.1002/anie.201900510N-O Activationhttps://doi.org/10.1002/anie.201900510Leonori, DAngew. Chem.-Int. Edit.Herein, we report a strategy for the generation of nitrogen-radicals by ground-state single electron transfer with organyl-Ni-I species. Depending on the philicity of the N-radical, two types of processes have been developed. In the case of nuCleophilic aminyl radicals direct N-Arylation with Aryl organozinc, organB(OH)2ron, and organosilicon reagents was achieved. In the case of electrophilic amidyl radicals, cascade processes involving intramolecular cyClization, followed by reaction with both Aryl and Alkyl organometallics have been developed. The N-cyClization-Alkylation cascade introduces a novel retrosynthetic disconnection for the assembly of substituted lactams and pyrrolidines with its potential demonstrated in the short total synthesis of four venom alkaloids.Reaction of Nitrogen-Radicals with Organometallics Under Ni-Catalysis: N-Arylations and Amino-Functionalization Cascadesalkaloid; Arylation; nitrogen radicals; radical cyClization; single electron transfer19201966#N/ATRUE
763
ja300473310.1021/ja3004733N-O ActivationFALSEhttps://doi.org/10.1021/ja3004733RajanBabu, TVJ. Am. Chem. Soc.Vinylindoles undergo Ni(II)-catalyzed asymmetric hydroVinylation under very mild conditions (-78 degrees C, 1 atm ethylene, 4 mol% catalyst) to give the corresponding 2-but-3-enyl derivatives in excellent yields and enantioselectivities. HydrB(OH)2ration of the alkene and oxidation to an acid, followed by Friedel-Crafts annulation, gives an indole-annulated cyClopentanone that is a suitable precursor for the syntheses of cis-trikentrins and all known herbindoles. For example, the cyClopentanone from 4-ethyl-7-Vinylindole is converted into (+)-cis-trikentin A in four steps (Wittig reaction, alkene isomerization, diastereoselective hydrogenation, and nitrogen deprotection). The previous synthesis of this molecule from (S)-(-)-malic acid involved more than 20 steps and a preparative HPLC separation of diastereomeric intermediates.Asymmetric HydroVinylation of Vinylindoles. A Facile Route to CyClopenta[g]indole Natural Products (+)-cis-Trikentrin A and (+)-cis-Trikentrin B49201252#N/ATRUE
764
anie.20191374310.1002/anie.201913743N-O ActivationFALSEhttps://doi.org/10.1002/anie.201913743Zhu, SLAngew. Chem.-Int. Edit.Starting from diverse alkene-tethered Aryl iodides and O-benzoyl-hydroxylamines, the enantioselective reductive cross-electrophilic 1,2-carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of beta-chiral amines with an enantioenriched Aryl-substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.Nickel-Catalyzed Asymmetric Reductive 1,2-Carboamination of Unactivated Alkenesalkenes; asymmetric catalysis; carboamination; nickel; synthetic methods21202099#N/ATRUE
765
acscatal.7b0343210.1021/acscatal.7b03432N-O ActivationFALSEhttps://doi.org/10.1021/acscatal.7b03432Selander, NACS Catal.A nickel-catalyzed 1,2-aminoArylation of oximeester-tethered alkenes with boronic acids was developed. A variety of pyrroline derivatives were synthesized in good yields via the successive formation of C(sp(3))-N and C(sp(3))-C(sp(2)) bonds. For cyClobutanone-derived oxime esters, the reaction provided aliphatic nitriles incorporating an aromatic group in the gamma-position. A mechanism involving iminyl radical and carbon-centered radical intermediates was proposed.Nickel-Catalyzed 1,2-AminoArylation of Oxime Ester-Tethered Alkenes with Boronic AcidsaminoArylation; nickel catalysis; oximes; pyrrolines; radicals64201770#N/ATRUE
766
d1sc02846d10.1039/d1sc02846dN–N bond formationFALSEhttps://doi.org/10.1039/d1sc02846dCaulton, KGChem. Sci.The syntheses of (DIM)Ni(NO3)(2) and (DIM)Ni(NO2)(2), where DIM is a 1,4-diazadiene bidentate donor, are reported to enable testing of bis boryl reduced N-heterocyCles for their ability to carry out stepwise deoxygenation of coordinated nitrate and nitrite, forming O(Bpin)(2). Single deoxygenation of (DIM)Ni(NO2)(2) yields the tetrahedral complex (DIM)Ni(NO)(ONO), with a linear nitrosyl and kappa(1)-ONO. Further deoxygenation of (DIM)Ni(NO)(ONO) results in the formation of dimeric [(DIM)Ni(NO)](2), where the dimer is linked through a Ni-Ni bond. The lost reduced nitrogen byproduct is shown to be N2O, indicating N-N bond formation in the course of the reaction. Isotopic labelling studies establish that the N-N bond of N2O is formed in a bimetallic Ni-2 intermediate and that the two nitrogen atoms of (DIM)Ni(NO)(ONO) become symmetry equivalent prior to N-N bond formation. The [(DIM)Ni(NO)](2) dimer is susceptible to oxidation by AgX (X = NO3-, NO2-, and OTf-) as well as nitric oxide, the latter of which undergoes nitric oxide disproportionation to yield N2O and (DIM)Ni(NO)(ONO). We show that the first step in the deoxygenation of (DIM)Ni(NO)(ONO) to liberate N2O is outer sphere electron transfer, providing insight into the organic reductants employed for deoxygenation. Lastly, we show that at elevated temperatures, deoxygenation is accompanied by loss of DIM to form either pyrazine or bipyridine bridged polymers, with retention of a BpinO(-) bridging ligand.Nickel-mediated N-N bond formation and N2O liberation via nitrogen oxyanion reduction0202170#N/ATRUE
767
jacs.5b0472510.1021/jacs.5b04725NegishiFALSEhttps://doi.org/10.1021/jacs.5b04725Fu, GCJ. Am. Chem. Soc.In this report; we establish that a readily available nickel/bis(oxazoline) catalyst accomplishes a Wide array of enantioconvergent cross-couplings of Arylzinc reagents with CF3-substituted racemic secondary Alkyl halides, a process that necessitate that the chiral catalyst be able to effectively distinguish between a CF3 and an Alkyl group in order to provide good ee. We further demonstrate that this method can be applied without modification to the catalytic asymmetric synthesis of other families of fluorinated organic compounds.Stereoconvergent Negishi Arylations of Racemic Secondary Alkyl Electrophiles: Differentiating between a CF3 and an Alkyl Group71201537#N/ATRUE
768
ja050650910.1021/ja0506509NegishiFALSEhttps://doi.org/10.1021/ja0506509Fu, GCJ. Am. Chem. Soc.Asymmetric nickel-catalyzed negishi cross-couplings of secondary alpha-bromo amides with organozinc reagents225200520#N/ATRUE
769
ja506885s10.1021/ja506885sNegishi FALSEhttps://doi.org/10.1021/ja506885sFu, GCJ. Am. Chem. Soc.The development of efficient methods for the generation of enantioenridied sulfonamides and sulfones is an important objective for fields such as organic synthesis and medicinal chemistry; however, there have been relatively few reports of direct catalytic asymmetric approaches to controlling the stereochemistry of the sulfur-bearing carbon of such targets. In this report, we describe nickel-catalyzed stereo-convergent Negishi Arylations and alkenylations of racemic alpha-bromosulfonamides and -sulfones that furnish the desired cross-coupling product in very good ee and yield for an array of reaction partners. Mechanistic studies are consistent with the generation of a radical intermediate that has a sufficient lifetime to diffuse out of the solvent cage and to cyClize onto a pendant olefin.Stereoconvergent Arylations and Alkenylations of Unactivated Alkyl Electrophiles: Catalytic Enantioselective Synthesis of Secondary Sulfonamides and Sulfones81201451#N/ATRUE
770
cs501492710.1021/cs5014927NHC catalystFALSEhttps://doi.org/10.1021/cs5014927Chetcuti, MJACS Catal.The chemistry of nickel N-heterocyClic carbene complexes is a research area that has blossomed over the last 10 years, and a large number of new complexes with a variety of architectural motifs are now known. The evolution of this chemistry has led to increasing applications of these complexes in catalytic bond formation. The rapid expansion of this field now calls for a review of the kinds of reactions that are catalyzed and a summary of the state of the art at this time. As the breadth of reactions catalyzed by such complexes is vast, this review specifically targets catalytic C-C bond formation, in particular C-C cross-couplings and C-C couplings via C-H bond Activation, mediated by nickel-N-heterocyClic carbene complexes. A special emphasis is placed on mechanistic data, because this allows possible new insights into catalyst improvement.Nickel N-HeterocyClic Carbene-Catalyzed C-C Bond Formation: Reactions and Mechanistic Aspectsnickel; N-heterocyClic carbene; catalysis; C-C bond formation; reaction mechanismReview1122015165#N/AFALSE
771
ja312087x10.1021/ja312087xNi(0)FALSEhttps://pubs.acs.org/doi/pdf/10.1021/ja312087xLiu, F2142013x#N/ATRUE
772
d1sc02210e10.1039/d1sc02210eNI(0)?FALSEhttps://doi.org/10.1039/d1sc02210eLee, YChem. Sci.A dinickel(0)-N-2 complex, stabilized with a rigid acridane-based PNP pincer ligand, was studied for its ability to activate C(sp(2))-H and C(sp(2))-O bonds. Stabilized by a Ni-mu-N-2-Na+ interaction, it activates C-H bonds of unfunctionalized arenes, affording nickel-Aryl and nickel-hydride products. Concomitantly, two sodium cations get reduced to Na(0), which was identified and quantified by several methods. Our experimental results, inCluding product analysis and kinetic measurements, strongly suggest that this C(sp(2))-H Activation does not follow the typical oxidative addition mechanism occurring at a low-valent single metal centre. Instead, via a bimolecular pathway, two powerfully reducing nickel ions cooperatively activate an arene C-H bond and concomitantly reduce two Lewis acidic alkali metals under ambient conditions. As a novel synthetic protocol, nickel(ii)-Aryl species were directly synthesized from nickel(ii) precursors in benzene or toluene with excess Na under ambient conditions. Furthermore, when the dinickel(0)-N-2 complex is accessed via reduction of the nickel(ii)-phenyl species, the resulting phenyl anion deprotonates a C-H bond of glyme or 15-crown-5 leading to C-O bond Cleavage, which produces Vinyl ether. The dinickel(0)-N-2 species then Cleaves the C(sp(2))-O bond of Vinyl ether to produce a nickel(ii)-Vinyl complex. These results may provide a new strategy for the Activation of C-H and C-O bonds mediated by a low valent nickel ion supported by a structurally rigidified ligand scaffold.Ni(0)-promoted Activation of C-O bonds0202165#N/ATRUE
773
acscatal.1c0053610.1021/acscatal.1c00536O-H CouplingFALSEhttps://doi.org/10.1021/acscatal.1c00536Cho, EJACS Catal.While organB(OH)2ron compound is one of the most attractive and widely used nuCleophiles in transition-metal-catalyzed coupling processes, they require sacrificial reagents for transmetalation (TM) processes. Herein, we report an unprecedented exogenous base-free procedure of a stereoselective Ni-catalyzed ArylVinylation of alkynes. It was revealed that Ni(0) species generated in situ from an air-stable Ni(II) precursor by a P<^>N ligand undergoes oxidative cyClization with an unactivated enyne to afford a nickellacyCle intermediate, where a B-assisted C-O bond Cleavage results in the formation of a TM-active boronate complex affording tetrasubstituted 1,3-diene products stereoselectively. A series of controlled experiments and density functional studies have been carried out to support the mechanistic proposal. The highly functionalized product comprising the stereoselective 1,3-diene system shows potential as an important building block in the synthesis of complex organic architectures.Synergistic Effects of Boron and Oxygen Interaction Enabling Nickel-Catalyzed Exogenous Base-Free Stereoselective ArylVinylation of Alkynes through Vinyl TranspositionC-O bond Cleavage; base-free transmetalation; nickel catalysis; Vinyl migration; 1,3-dienes1202162#N/ATRUE
774
(SICI)1521-3773(19980504)37:8<1136::AID-ANIE1136>3.0.CO;2-Z10.1002/(SICI)1521-3773(19980504)37:8<1136::AID-ANIE1136>3.0.CO;2-ZO-H CouplingFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980504)37:8<1136::AID-ANIE1136>3.0.CO;2-ZOgasawara, KAngew. Chem.-Int. Edit.Extremely facile and selective nickel-catalyzed allyl ether Cleavageallyl ethers; aluminum; Cleavage reactions; nickel; protecting groups63199815#N/ATRUE
775
ja062866w10.1021/ja062866wO-Si CouplingFALSEhttps://doi.org/10.1021/ja062866wJamison, TFJ. Am. Chem. Soc.A full account of two recently developed nickel-catalyzed coupling reactions of alkenes, aldehydes, and silyl triflates is presented. These reactions provide either allylic alcohol or homoallylic alcohol derivatives selectively, depending on the ligand employed. These processes are believed to be mechanistically distinct from Lewis acid-catalyzed Carbonyl-ene reactions, and several lines of evidence supporting this hypothesis are discussed.Nickel-catalyzed coupling of alkenes, aldehydes, and silyl triflates56200697#N/ATRUE
776
acscatal.6b0171510.1021/acscatal.6b01715O-Si CouplingFALSEhttps://doi.org/10.1021/acscatal.6b01715Lopez-Serrano, JACS Catal.This work describes a thorough investigation of the mechanism of a highly selective hydrosilylation of CO2 to the formaldehyde level catalyzed by a bis(phosphino)boryl (PBP)Ni(II) complex in the presence of B(C6F5)(3). CO2 Activation by insertion into the Ni-H bond of the catalyst precursor 2 is shown to occur very easily, because of the trans influence exerted by the boryl ligand. During catalysis, the limiting step is B(C6F5)(3) dissociation from the active species (PBP)Ni-OCHO center dot B(C5F6)(3) (4), which controls the amount of free borane that can lead to over -reduction to methane. Free borane activates the silane by formation of [R3Si-H center dot center dot center dot B(C6F5)(3)], which can then transfer the silylium (R3Si+) fragment to the oxygen atoms of the Ni formate and Ni acetal intermediates. The ion pair [(PBP)Ni][HB(C6F5)(3)] (5) is the key species that activates CO2 in the catalytic cyCle (and silylformate in a second step) with [HB(C6F5)(3)](-) as the source of hydride. Hydride transfer to [(PBP)Ni-OCO](+) is virtually barrierless, whereas hydride transfer to [(PBP)Ni-OCHOSiR3](+) has the second -highest energy barrier of the process (25.2 kcal mol(-1)). Therefore, the (PBP)Ni framework is instrumental in both reduction steps of the catalysis and controls the selectivity of the reaction by sequestering B(C6F5)(3).Mechanistic Studies on the Selective Reduction of CO2 to the Aldehyde Level by a Bis(phosphino)boryl (PBP)-Supported Nickel ComplexCO2; nickel complexes; boryl ligands; hydrosilylation; mechanisms; DFT calculations36201691#N/ATRUE
777
jacs.1c0179710.1021/jacs.1c01797O-Si forming bondFALSEhttps://doi.org/10.1021/jacs.1c01797Schoenebeck, FJ. Am. Chem. Soc.We report a remote functionalization strategy, which allows the Z-selective synthesis of silyl enol ethers of (hetero)aromatic and aliphatic ketones via Ni-catalyzed chain walking from a distant olefin site. The positional selectivity is controlled by the directionality of the chain walk and is independent of thermodynamic preferences of the resulting silyl enol ether. Our mechanistic data indicate that a Ni-(I) dimer is formed under these conditions, which serves as a catalyst resting state and, upon reaction with an Alkyl bromide, is converted to [Ni-(II)-H] as an active chain-walking/functionalization catalyst, ultimately generating a stabilized eta(3)-bound Ni-(II) enolate as the key selectivity-controlling intermediate.Selective Synthesis of Z-Silyl Enol Ethers via Ni-Catalyzed Remote Functionalization of Ketones0202154#N/ATRUE
778
anie.20070216010.1002/anie.200702160Oxidation of AlkenesFALSEhttps://doi.org/10.1002/anie.200702160Nunez, AAngew. Chem.-Int. Edit.Exploring the nickel-catalyzed oxidation of alkenes: A diamination by sulfamide transferdiamines; homogeneous catalysis; nickel; oxidation; sulfamides112200735#N/ATRUE
779
jacs.0c0915710.1021/jacs.0c09157OxidationsFALSEhttps://doi.org/10.1021/jacs.0c09157Hartwig, JFJ. Am. Chem. Soc.The Ni-catalyzed oxidation of unactivated alkanes, inCluding the oxidation of polyethylenes, by meta-chloroperbenzoic acid (mCPBA) occur with high turnover numbers under mild conditions, but the mechanism of such transformations has been a subject of debate. Putative, high-valent nickel-oxo or nickel-oxyl intermediates have been proposed to Cleave the C-H bond, but several studies on such complexes have not provided strong evidence to support such reactivity toward unactivated C(sp(3))-H bonds. We report mechanistic investigations of Ni-catalyzed oxidations of unactivated C-H bonds by mCPBA. The lack of an effect of ligands, the formation of carbon-centered radicals with long lifetimes, and the decomposition of mCPBA in the presence of Ni complexes suggest that the reaction occurs through free Alkyl radicals. Selectivity on model substrates and deuterium-labeling experiments imply that the m-chlorobenzoyloxy radical derived from mCPBA Cleaves C-H bonds in the alkane to form an Alkyl radical, which subsequently reacts with mCPBA to afford the alcohol product and regenerate the aroyloxy radical. This free-radical chain mechanism shows that Ni does not Cleave the C(sp(3))-H bonds as previously proposed; rather, it catalyzes the decomposition of mCPBA to form the aroyloxy radical.Mechanism of Ni-Catalyzed Oxidations of Unactivated C(sp(3))-H Bonds4202048#N/ATRUE
780
acs.orglett.6b0175810.1021/acs.orglett.6b01758Parafin capsuleFALSEhttps://doi.org/10.1021/acs.orglett.6b01758Garg, NKBenchtop Delivery of Ni(cod)(2) using Paraffin Capsules2016#N/ATRUE
781
anie.20170710210.1002/anie.201707102Phosphorylationhttps://doi.org/10.1002/anie.201707102Szostak, MAngew. Chem.-Int. Edit.Considering the ubiquity of organophosphorus compounds in organic synthesis, pharmaceutical discovery agrochemical crop protection and materials chemistry, new methods for their construction hold particular significance. A conventional method for the synthesis of C-P bonds involves cross-coupling of Aryl halides and diAlkyl phosphites (the Hirao reaction). We report a catalytic deamidative phosphorylation of a wide range of amides using a palladium or nickel catalyst giving Aryl phosphonates in good to excellent yields. The present method tolerates a wide range of functional groups. The reaction constitutes the first example of a transition-metal-catalyzed generation of C-P bonds from amides. This redox-neutral protocol can be combined with site-selective conventional cross-coupling for the regioselective synthesis of potential pharmacophores. Mechanistic studies suggest an oxidative addition/transmetallation pathway. In light of the importance of amides and phosphonates as synthetic intermediates, we envision that this Pd and Ni-catalyzed C-P bond forming method will find broad application.DeCarbonylative Phosphorylation of Amides by Palladium and Nickel Catalysis: The Hirao Cross-Coupling of Amide Derivativesamides; Carbonylic acids; cross-coupling; N-C Activation; phosphonates1102017103#N/ATRUE
782
anie.20150548210.1002/anie.201505482PropanationFALSEhttps://doi.org/10.1002/anie.201505482Chen, PAngew. Chem.-Int. Edit.Nickel was identified as a catalyst for the cyClopropanation of unactivated olefins by using insitu generated lithiomethyl trimethylammonium triflate as a methylene donor. A mechanistic hypothesis is proposed in which the generation of a reactive nickel carbene explains several interesting observations. Additionally, our findings shed light on a report by Franzen and Wittig published in 1960 that had been retracted later owing to irreproducibility, and provide a rational basis for the systematic development of the reaction for preparative purposes as an alternative to diazomethane or Simmons-Smith conditions.Nickel-Catalyzed CyClopropanation with NMe4OTf and nBuLicarbenes; cyClopropanation; nickel; ylides19201543#N/ATRUE
783
anie.20191415110.1002/anie.201914151Radical-Polar Crossover FALSEhttps://doi.org/10.1002/anie.201914151Feng, XMEnantioselective Radical-Polar Crossover Reactions of Indanonecarboxamides with Alkenes2020#N/ATRUE
784
c7sc05216b10.1039/c7sc05216brearrangementShihonghttps://doi.org/10.1039/c7sc05216bStoltz, BMChem. Sci.The first nickel-catalyzed enantioselective allylic Alkylation of lactone and lactam substrates to deliver products bearing an all-carbon quaternary stereocenter is reported. The reaction, which utilizes a commercially available chiral bisphosphine ligand, proceeds in good yield with a high level of enantioselectivity (up to 90% ee) on a range of unactivated allylic alcohols for both lactone and lactam nuCleophiles. The utility of this method is further highlighted via a number of synthetically useful product transformations.Nickel-catalyzed enantioselective allylic Alkylation of lactones and lactams with unactivated allylic alcoholselectron rearrangement272018x3/15/2022FALSE
785
ja065876610.1021/ja0658766rearrangementFALSEhttps://doi.org/10.1021/ja0658766Carretero, JCJ. Am. Chem. Soc.An efficient chiral Lewis acid-catalyzed inverse-electron-demand Diels-Alder reaction of 1-azadienes is described. This procedure is based on the combination of Ni-II-DBFOX complex as catalyst and the use of a metal-coordinating (8-quinolyl) sulfonyl moiety at the iminic nitrogen of the N-sulfonyl 1-aza-1,3-diene, providing highly functionalized piperidine derivatives in good yields with excellent endoselectivity, and enantioselectivities typically in the range of 77-92% ee.Catalytic asymmetric inverse-electron-demand Diels-Alder reaction of N-sulfonyl-1-aza-1,3-dienes158200723#N/ATRUE
786
anie.20160933810.1002/anie.201609338RearrangementFALSEhttps://doi.org/10.1002/anie.201609338Kimura, MAngew. Chem.-Int. Edit.4-Methylene-1,3-dioxolan-2-ones underwent oxidative addition of a Ni-0 catalyst in the presence of Me2Al(OMe), followed by a coupling reaction with alkynes, to form delta,epsilon-unsaturated beta-ketoCarbonylic acids with high regio- and stereoselectivity. The reaction proceeds by [1,3] rearrangement of an enol metal carbonate intermediate and the formal reinsertion of CO2.Nickel-Catalyzed CO2 Rearrangement of Enol Metal Carbonates for the Efficient Synthesis of beta-KetoCarbonylic Acidsalkynes; aluminum; cyClic carbonates; multicomponent reactions; nickel16201792#N/ATRUE
787
anie.20160695510.1002/anie.201606955RearrangementFALSEhttps://onlinelibrary.wiley.com/doi/10.1002/anie.201606955Shi, SL#N/A
788
anie.20190716410.1002/anie.201907164Rearrangements FALSEhttps://doi.org/10.1002/anie.201907164Feng, XMAsymmetric Catalytic [2,3] Stevens and Sommelet-Hauser Rearrangements of alpha-Diazo Pyrazoleamides with Sulfides2019#N/ATRUE
789
jo00057a05510.1021/jo00057a055Reduction FALSEhttps://sci-hub.yncjkj.com/10.1021/jo00057a055Baran, PS#N/A
790
c6sc01457g10.1039/c6sc01457gRing ClosingFALSEhttps://doi.org/10.1039/c6sc01457gSenanayake, CHChem. Sci.The direct Arylation of pyridine substrates using non-precious catalysts is underdeveloped but highly desirable due to its efficiency to access important motifs while being extremely cost-effective. The first nickel-catalyzed C-3 direct Arylation of pyridine derivatives to provide a new approach to valuable 1-azafluorene pharmacophore frameworks was developed. This transformation is accomplished using air-stable nickel catalyst precursors combined with phenanthroline ligands and tolerates a variety of substituents. Computational studies suggest facile oxidative addition via the pyridinium form, deprotonation, and a subsequent carbo-nickelation cyClization. Nickel homolysis/recombination permits isomerization to the stereochemical array needed for the final elimination.Nickel-catalyzed C-3 direct Arylation of pyridinium ions for the synthesis of 1-azafluorenes12201659#N/ATRUE
791
anie.20190901510.1002/anie.201909015Ring ClosingFALSEhttps://doi.org/10.1002/anie.201909015Cho, EJAngew. Chem.-Int. Edit.An unconventional nickel-catalyzed reaction was developed for the synthesis of multifunctionalized benzofurans from alkyne-tethered phenolic esters. The transformation involves the generation of a nuCleophilic Vinyl Ni-II species by the regioselective syn-Aryl nickelation of an alkyne, which then undergoes an intramolecular cyClization with phenol ester to yield highly functionalized 1,1-disubstituted alkenes with 3-benzofuranyl and (hetero)Aryl substituents. The methodology can be used for the late-stage benzofuran incorporation of various drug molecules and natural products, such as 2-propylvaleric acid, gemfibrozil, biotin, and lithocholic acid. Furthermore, this Arylative cyClization method was successfully applied for the efficient synthesis of the anti-arrhythmic drug amiodarone.Access to Multifunctionalized Benzofurans by Aryl Nickelation of Alkynes: Efficient Synthesis of the Anti-Arrhythmic Drug AmiodaronecyClizations; heterocyCles; nickel; reaction mechanisms; synthetic methods15201977#N/ATRUE
792
anie.20120433310.1002/anie.201204333Ring ExpansionFALSEhttps://doi.org/10.1002/anie.201204333Radius, UAngew. Chem.-Int. Edit.C?N Bond Cleavage and Ring Expansion of N-HeterocyClic Carbenes using Hydrosilanes912012105#N/ATRUE
793
ja964361j10.1021/ja964361jRing OpeningFALSEhttps://doi.org/10.1021/ja964361jChiu, PJ. Am. Chem. Soc.The reductive ring opening of oxabicyClic compounds has been achieved. While RMgX/MgX2 works in a few Limited substrates, diisobutylaluminum hydride reacts with oxabicyClic[3.2.1]- and -[2.2.1]alkenes to provide cyCloheptenols and cyClohexenols in good yield and in some cases in good regioselectivity. With some substrates further reduction of the alkene was observed which led us to examine transition metals such as nickel which are known to accelerate the hydroalumination reaction. The reaction with Ni(COD)(2) (COD = cyClooctadiene) gave the best reactivity-selectivity profile, and significantly higher yields were obtained with minimal overreduction of the alkene. Phosphine ligands were shown to dramatically improve the regioselectivity of ring opening of bridgehead-substituted oxabicyClic compounds. The best ligand was 1,4-bis(diphenylphosphino)butane which gave up to 380:1 selectivity. A series of deuterium quenching experiments showed that the selectivity of the hydroalumination varies according to the reaction protocol and ligand-metal ratio.Synthesis of cyClohexenols and cyCloheptenols via the regioselective reductive ring opening of oxabicyClic compounds40199742#N/ATRUE
794
acscatal.0c0544910.1021/acscatal.0c05449Silylacylationhttps://doi.org/10.1021/acscatal.0c05449Brown, MKACS Catal.A Ni-catalyzed silylacylation of alkenes is presented. The reaction combines alkenes, CIZnSiR3, and acid chlorides to provide rapid access to beta-silyl ketones. Importantly, the method involves a [Ni]-SiR3 complex as a catalytic intermediate, which is rarely described for three-component alkene functionalization. Finally, the synthetic utility of the products is demonstrated, and the mechanistic details are described.Three-Component Ni-Catalyzed Silylacylation of Alkenesnickel; alkene; silylation; acylation; zinc0202159#N/ATRUE
795
acscatal.7b0202510.1021/acscatal.7b02025SilyloxyarenesFALSEhttps://doi.org/10.1021/acscatal.7b02025Montgomery, JACS Catal.Silyloxyarenes are demonstrated to be a versatile substrate Class in a variety of nickel-catalyzed coupling processes. The C(sp(2))-O bond of Aryl silyl ethers is directly transformed into C-H or C-Si bonds using Ti(O-i-Pr)(4) or triAlkylsilanes as reagents using nickel catalysts with N-heterocyClic carbene (NHC) ligands. Paired with the useful characteristics of silyl protecting groups, these methods enable protected hydroxyls to directly participate in high-value bond-forming steps rather than requiring deprotection-Activation strategies that conventional approaches require. These processes of silyloxyarenes provide reactivity complementary to widely used phenol derivatives such as Aryl pivalates, carbamates, and methyl ethers, thus enabling a powerful strategy for sequential chemoselective derivatization of complex substrates without protecting group and activating group manipulations.Silyloxyarenes as Versatile Coupling Substrates Enabled by Nickel-Catalyzed C-O Bond Cleavagenickel; catalysis; silyloxyarenes; cross-coupling; C-O bond Activation; silane18201730#N/ATRUE
796
acscatal.8b0093310.1021/acscatal.8b00933SuzukiFALSEhttps://doi.org/10.1021/acscatal.8b00933Grimaud, LACS Catal.The mechanism of boron-to-nickel transmetalation, the key step of the nickel-catalyzed Suzuki-Miyaura (S-M) coupling, was examined both experimentally and theoretically. DinuClear p-hydroxo-bridged complexes formed by reaction of trans-[ArNi(PR3)(2)X] with hydroxide are not directly involved in transmetalation, but they rather act as a resting state for the catalyst. The base/boronic acid ratio is the crucial parameter, as it modulates the extent of formation of these dinuClear species and thus tunes the catalytic activity. These findings explain some limitations encountered in practical applications of nickel-catalyzed S-M couplings and suggest how to tailor the experimental conditions in order to overcome these difficulties.Taming Nickel-Catalyzed Suzuki-Miyaura Coupling: A Mechanistic Focus on Boron-to-Nickel Transmetalationnickel; Suzuki-Miyaura coupling; reaction mechanism; boronic acids; cross-couplingyy402018107#N/AFALSE
797
ja105148g10.1021/ja105148gSuzuki FALSEhttps://doi.org/10.1021/ja105148gFu, GCJ. Am. Chem. Soc.A nickel-catalyzed stereoconvergent method for the enantioselective Suzuki Arylation of racemic alpha-chloroamides has been developed. This process provides a unique example of an asymmetric Arylation of an alpha-haloamide, an enantioselective Arylation of an alpha-chloroCarbonyl compound, and an asymmetric Suzuki reaction with an activated Alkyl electrophile or an Arylboron reagent. The method is also applicable to the corresponding enantioselective cross-coupling of alpha-bromoamides. The coupling products can be transformed without racemization into enantio-enriched alpha-ArylCarbonylic acids and primary alcohols. A modest kinetic resolution of the alpha-chloroamide was observed; a mechanistic study indicated that the selectivity may reflect discrimination by the chiral catalyst of the two enantiomeric alpha-chloroamides in an irreversible oxidative-addition process.Asymmetric Suzuki Cross-Couplings of Activated Secondary Alkyl Electrophiles: Arylations of Racemic alpha-Chloroamides152201024#N/ATRUE
798
chem.20150244810.1002/chem.201502448SynthesisFALSEFeng, XMAsymmetric Synthesis of Furo[3,4-b]indoles by Catalytic [3+2] CyCloaddition of Indoles with Epoxides2015#N/ATRUE
799
acs.orglett.6b0337310.1021/acs.orglett.6b03373SynthesisFALSEhttps://doi.org/10.1021/acs.orglett.6b03373Svenda, JEnantioselective Synthesis of Cephalimysins B and C2017#N/ATRUE
800
acs.orglett.6b0142810.1021/acs.orglett.6b01428SynthesisFALSEhttps://doi.org/10.1021/acs.orglett.6b01428Urpi, FStereoselective Synthesis of the C9-C19 Fragment of Peloruside A2016#N/ATRUE
801
ja016333t10.1021/ja016333tSynthesis artiCleFALSEhttps://doi.org/10.1021/ja016333tVollhardt, KPCJ. Am. Chem. Soc.Five synthetic approaches to racemic strychnine (1), with the cobalt-mediated [2 + 2 + 2] cyCloaddition of alkynes to indoles as the key step, are described. These inClude the generation and attempted cyClization of macrocyCle 8 and the synthesis of dihydrocarbazoles 15, 22, and 26 and their elaboration to pentacyClic structures via a conjugate addition, dipolar cyCloaddition, and propellane-to-spirofused skeletal rearrangement, respectively. Finally, the successful total synthesis of 1 is discussed. The development of a short, highly convergent route (14 steps in the longest linear sequence) is highlighted by the cyClization of enynoylindole 40 with acetylene and the formal intramolecular 1,8-conjugate addition of amine 49 to form pentacyCle 50. Numerous attempts toward the formation of the piperidine ring of 1 from Vinyl iodide 56 were made and its successful formation via palladium-, nickel-, and radical-mediated processes is described.Approaches to the synthesis of (+/-)-strychnine via the cobalt-mediated [2+2+2] cyCloaddition: Rapid assembly of a Classic framework1032001175#N/ATRUE
802
jacs.7b0986910.1021/jacs.7b09869Synthetic RouteFALSEhttps://doi.org/10.1021/jacs.7b09869Herzon, SBJ. Am. Chem. Soc.We describe the development of an enantioselective synthetic route to (+)-pleuromutilin (1), (+)-12-epi-mutilin, and related derivatives. A key hydrindanone was prepared in three steps and 48% overall yield from cyClohex-2-en-1-one. 1,4-Hydrocyanation provided a nitrile (53%, or 85% based on recovered starting material) that was converted to the eneimide 57 in 80% yield by the 1,2-addition of methyllithium to the nitrile function, cyClization, and in situ acylation with di-tert-butyldicarbonate. The eneimide 57 was employed in a 2-fold neopentylic coupling reaction with an organolithium reagent derived from the Alkyl iodides (R)- or (S)-30, which contain the C11-C13 atoms of the target, to provide diastereomeric diketones in 60% or 48% yield (for coupling with (R)- or (S)-30, respectively). The diketone derived from (S)-30 contains the (S)-C12 stereochemistry found in pleuromutilin and was elaborated to an alkynylaldehyde. Nickel-catalyzed reductive cyClization of this alkynylaldehyde, to construct the eight-membered ring of the target, unexpectedly provided a cyClopentene (67%), which arises from participation of the C12-alpha-olefin in the transformation. The diketone derived from the enantiomeric C12-fragment (R)-30 underwent reductive cyClization to provide the desired product in 60% yield. This was elaborated to 12-epi-mutilin by a four-step sequence (39% overall). Installation of the glycolic acid residue followed by C12 epimerization (Berner et al. Monatsh. Chem. 1986, 117, 1073) generated (+)-pleuromutilin (1). (+)-12-epi-Pleuromutilin and (+)-11,12-di-epi-pleuromutilin were prepared by related sequences. This work establishes a convergent entry to the pleuromutilins and provides a foundation for the production of novel antibiotics to treat drug-resistant and Gram-negative infections.Development of a Modular Synthetic Route to (+)-Pleuromutilin, (+)-12-epi-Mutilins, and Related Structures29201789#N/ATRUE
803
ja991241d10.1021/ja991241dTetheredFALSEhttps://doi.org/10.1021/ja991241dMori, MJ. Am. Chem. Soc.A nickel-promoted intramolecular cyClization of 1,3-diene with the tethered Carbonyl group was developed using the catalyst generated by reduction of Ni(acac)(2) with DIBAL-H in the presence of PPh3. It was found that the addition of 1,3-CHD to the reaction mixture affected the regiochemistry of olefin on the side chain of the cyClized product. The reaction course of this cyClization can he accounted for by tno possible mechanisms. In one mechanism, a nickel hydride complex plays a kev role and the cyClization proceeds via pi-allylnickel intermediate. In the other mechanism, a zero-valent nickel complex is the active species and the cyClization proceeds via nickelacyCle intermediates. These mechanistic considerations led to finding two nickel-(0)-catalyzed zed cyClizations of 1,3-diene and the tethered aldehyde, in which the five- to seven-membered ring products were produced in a regio- and stereoselective manner via pi-allylnickel intermediate or via a transmetalation process of nickelacyCle intermediates with Bu-i(2)-ALAC.Further studies on nickel-promoted or -catalyzed cyClization of 1,3-diene and a tethered Carbonyl group85200055#N/ATRUE
804
ja044679910.1021/ja0446799TetheredFALSEhttps://doi.org/10.1021/ja0446799Jamison, TFJ. Am. Chem. Soc.Ligand-switchable directing effects of tethered alkenes in nickel-catalyzed additions to alkynes92200427#N/ATRUE
805
anie.20110146810.1002/anie.201101468Three componentFALSEhttps://doi.org/10.1002/anie.201101468Fukuzawa, SAngew. Chem.-Int. Edit.Nickel-Catalyzed Three-Component Coupling between Aryl Aldehydes, Norbornenes, and Silanes Leading to Indanols through Aromatic C-H Bond Activation of Aryl AldehydesC-H Activation; cyCloalkenes; indanols; nickel; synthetic methods39201131#N/ATRUE
806
acscatal.6b0354310.1021/acscatal.6b03543Three-Component Couplinghttps://doi.org/10.1021/acscatal.6b03543Bi, SWACS Catal.Density functional theory (DFT) calculations have been performed to unravel the mechanism of Lewis-acid-induced Ni(cod)(2)-catalyzed selective coupling reactions of one diketene and two alkynes. Complex mixtures (unsymmetrical phenylacetic acid P1, symmetrical phenylacetic acid P2 and (3E)-4-ethyl-5-methylene-3-heptenoic acid P3) were obtained in the absence of Et2Al(OEt). P1 formation involves C(sp(2))-O oxidative addition of diketene, twice alkyne insertion, intramolecular C=C insertion, acidolysis, and beta-H elimination. For P2/P3 formation, the common key issue related to the C=C double bond Cleavage of the substrate diketene was explored and found that it was accomplished via a four-membered-ring-Closure/four-membered-ring-opening process. And then, P2 was produced via the second alkyne insertion while P3 was accessed by a stoichiometric reaction with HCI. The Et2Al(OEt)-induced chemoselectivity was also probed. It is found that the Ni-O (from Al reagent) bonding facilitates the second alkyne insertion, and the Al-O (from Carbonylate) bonding weakens the four-membered ring-Closure step, which consequently leads to the formation of P1 exClusively. Additionally, HCI plays a promoting role as a cocatalyst in producing P1 and P2. The theoretical results not only well rationalize the experimental observations but provide insights into the mechanism of the Ni-catalyzed multicomponent coupling reactions.Mechanism and Origin of Et2Al(OEt)-Induced Chemoselectivity of Nickel-Catalyzed Three-Component Coupling of One Diketene and Two Alkynesnickel; multicomponent coupling DFT; organoaluminum; selectivity; diketene; alkynes31201756#N/ATRUE
807
jacs.9b0397810.1021/jacs.9b03978Total synthesisFALSEhttps://doi.org/10.1021/jacs.9b03978Li, CJ. Am. Chem. Soc.Structurally complex and bioactive ent-kaurane diterpenoids have well-characterized biological functions and have drawn widespread attention from chemists for many decades. However, construction of highly oxidized forms of such diterpenoids still presents considerable challenges to synthetic chemists. Herein, we report the first total syntheses of C19 oxygenated spiro-lactone ent-kauranoids, inCluding longirabdiol, longirabdolactone, and effusin. A concise synthesis of the common intermediate used for all three syntheses was enabled via three free-radical-based reactions: (1) a newly devised tandem deCarbonylative cyClization/alkenylation sequence that forges the cis-19, 6-lactone concomitantly with vicinal alkenylation, (2) a Ni-catalyzed deCarbonylative Giese reaction that constructs C10 quaternary center stereoselectively, and (3) a Vinyl radical cyClization that generates a rigid bicyClo[3.2.1]octane. A series of late-stage oxidations from the common intermediate then provided each of the natural products in turn. Further biological evaluation of these synthetic natural products reveals broad anticancer activities.Tandem DeCarbonylative CyClization/Alkenylation Strategy for Total Syntheses of (+)-Longirabdiol, (-)-Longirabdolactone, and (-)-Effusin17201974#N/ATRUE
808
jacs.9b0375110.1021/jacs.9b03751Total synthesisFALSEhttps://doi.org/10.1021/jacs.9b03751Newhouse, TRJ. Am. Chem. Soc.The total synthesis of principinol D, a rearranged kaurane diterpenoid, is reported. This grayanane natural product is constructed via a convergent fragment coupling approach, wherein the central seven-membered ring is synthesized at a late stage. The bicyClo[3.2.1]octane fragment is accessed by a Ni-catalyzed alpha-Vinylation reaction. Strategic reductions inClude a diastereoselective SmI2-mediated ketone reduction with PhSH and a new protocol for selective ester reduction in the presence of ketones. The convergent strategy reported herein may be an entry point to the larger Class of kaurane diterpenoids.Convergent Total Synthesis of Principinol D, a Rearranged Kaurane Diterpenoid17201962#N/ATRUE
809
jacs.7b0146310.1021/jacs.7b01463total synthesisFALSEhttps://doi.org/10.1021/jacs.7b01463Hartwig, JFJ. Am. Chem. Soc.Controlling First-Row Catalysts: Amination of Aryl and HeteroAryl Chlorides and Bromides with Primary Aliphatic Amines Catalyzed by a BINAP-Ligated Single-Component Ni(0) Complex120170#N/ATRUE
810
jacs.0c0030210.1021/jacs.0c00302Total synthesisFALSEhttps://doi.org/10.1021/jacs.0c00302Li, CZJ. Am. Chem. Soc.We report herein the first enantioselective total synthesis of akuammiline alkaloids (+)-corymine and (-)-deCarbonylcorymine. Starting from commercially available N-nosyltryptamine, the target molecules are both achieved in 11 steps. Key elements of the design inClude (a) a copper-catalyzed enantioselective addition of dimethyl malonate to a 3-bromooxindole to secure the C7 all-carbon quaternary stereocenter, (b) a one-step construction of cyClohexyl and pyrrolidinyl rings via intramolecular nuCleophilic C- and N-addition, and (c) a nickel-promoted 7-endo cyClization of alkenyl bromide to furnish the azepanyl ring. The strategy is further extended to the synthesis of another three members of the akuammiline family, namely, (-)-10- demethoxyvincorine, (-)-2(S)-cathafoline, and (-)-3-epi-dihydrocorymine 17-acetate.Enantioselective Total Synthesis of (+)-Corymine and (-)-DeCarbonylcorymine5202084#N/ATRUE
811
ja907931u10.1021/ja907931uTotal synthesisFALSEhttps://doi.org/10.1021/ja907931uMontgomery, JJ. Am. Chem. Soc.A unified approach to the pyrrolidine triacid natural products isodomoic acids G and H has been developed. Total syntheses of both natural products were completed, and determination of the correct stereostructure of isodomoic acid G was established by comparing 5'-(R) and 5'-(S) isomers to a sample of authentic material. A nickel-catalyzed cyClization constructs the pyrrolidine ring while simultaneously establishing either the E or Z stereochemistry of an exocyClic tetrasubstituted alkene. Stereoselective assembly of both the E- and Z-alkenes,of the natural products is made possible by a predictable strategy that alters the timing of substituent introduction to control alkene stereochemistry.Total Syntheses of Isodomoic Acids G and H: An Exercise in Tetrasubstituted Alkene Synthesis32200958#N/ATRUE
812
ja107004310.1021/ja1070043Total synthesisFALSEhttps://doi.org/10.1021/ja1070043Qin, YJ. Am. Chem. Soc.The first asymmetric total synthesis of (+)-perophoramidine has been achieved in 17 steps with similar to 11% overall yield. The key step relies on an asymmetric biomimetic Die Is Alder reaction between the in situ-generated chiral diene T-24 and the substituted tryptamine 23 to assemble the core structure 27a in a highly efficient way. An acid-catalyzed thermodynamic equilibrium results in C=N double-bond migration of the amidine moiety in 37, which guarantees a regioselective methylation on NI at the end of the synthesis. The absolute configuration of (+)-perophoramidine was determined by X-ray crystallographic analysis of the chiral intermediate 32 and comparison of the rotation of synthetic (+)-perophoramidine with that of the natural product.Total Synthesis of (+)-Perophoramidine and Determination of the Absolute Configuration101201024#N/ATRUE
813
ja00341a05110.1021/ja00341a051total synthesisFALSEhttps://doi.org/10.1021/ja00341a051WATT, DSJ. Am. Chem. Soc.PARTIAL SYNTHESIS OF (20R)-25-HYDROXYCHOLESTEROL INVOLVING A NICKEL(II)-PROMOTED DIENOL REARRANGEMENT20198342#N/ATRUE
814
ja001440t10.1021/ja001440tTotal synthesisFALSEhttps://doi.org/10.1021/ja001440tMontgomery, JJ. Am. Chem. Soc.A new method for the reductive cyClization of ynals involving a Ni(COD)(2)/PBu3 catalyst system to produce allylic alcohols was developed. The triethylsilane-mediated procedure allows preparation of functionally rich pyrrolizidine, indolizidine, and quinolizidine alkaloid frameworks. The method allows the direct introduction of an allylic alcohol moiety with completely stereoselective creation of an exocyClic double bond and highly diastereoselective alcohol introduction relative to preexisting chirality. The total syntheses of (+)-allopumiliotoxin 267A, (+)-allopumiliotoxin 339A, and (+)-allopumiliotoxin 339B were accomplished utilizing an ynal cyClization as the key step. These syntheses provide short and efficient entries to the allopumiliotoxins and highlight the utility of nickel-catalyzed ynal cyClizations in complex synthetic strategies.Nickel-catalyzed preparation of bicyClic heterocyCles: Total synthesis of (+)-allopumiliotoxin 267A, (+)-allopumiliotoxin 339A, and (+)-allopumiliotoxin 339B95200047#N/ATRUE
815
c7sc03293e10.1039/c7sc03293eTotal synthesisFALSEhttps://doi.org/10.1039/c7sc03293eTang, PPChem. Sci.The first total syntheses of schilancidilactones A and B, schilancitrilactone A, and 20-epi-schilancitrilactone A have been accomplished using a nickel-catalyzed cross coupling of Alkyl bromide with Vinyl stannane as the final step. The other key steps inClude late-stage C( sp(3))-H bromination, the oxidative Cleavage of a diol to provide the requisite ketone and ester for schilancidilactones A and B, and Dieckmann-type condensation to generate the A ring of schilancitrilactone A and 20-epi-schilancitrilactone A.Total syntheses of schilancidilactones A and B, schilancitrilactone A, and 20-epi-schilancitrilactone A via late-stage nickel-catalyzed cross coupling19201764#N/ATRUE
816
acscatal.5b0096910.1021/acscatal.5b00969
Transfer reactions
FALSEhttps://doi.org/10.1021/acscatal.5b00969Liang, XHACS Catal.A recyClable highly dispersed Ni/SiO2 catalyst was prepared by atomic layer deposition. Chemoselective reduction of nitroarenes was studied using the prepared Ni/SiO2 as the catalyst and hydrazine hydrate as a hydrogen donor. Different kinds of nitroarenes were converted to the corresponding anilines with high yields. The high activity of the catalysts could be a result of the highly dispersed Ni nanopartiCles.Chemoselective Transfer Hydrogenation of Nitroarenes Catalyzed by Highly Dispersed, Supported Nickel NanopartiClesatomic layer deposition (ALD); nickel nanopartiCles; heterogeneous catalysis; chemoselective; transfer hydrogenation; nitroarenesx96201533#N/AFALSE
817
jacs.6b1289610.1021/jacs.6b12896triboronatesFALSEhttps://doi.org/10.1021/jacs.6b12896Chirik, PJJ. Am. Chem. Soc.A highly diastereoselective carbon-carbon bond-forming reaction involving the tandem coupling of Benzyltriboronates, enoates, and Alkyl halides is described. This method was enabled by the discovery of alpha-diimine nickel catalysts that promote the chemoselective tribor-ylation of Benzylic C(sp(3))-H bonds using B(2)Pin(2) (Pin = pinacolate). The C-H functionalization method is effective with methylarenes and for the diborylation of secondary Benzylic C-H bonds, providing direct access to polyboron building blocks from readily available hydrocarbons. Combination of the Benzylic perborylation with a new deborylative conjugate addition Alkylation method enables a one-pot procedure in which multiple simple precursors are combined to generate diastereopure products containing quaternary stereocenters.Benzyltriboronates: Building Blocks for Diastereoselective Carbon-Carbon Bond Formation60201759#N/ATRUE
818
anie.200501860
10.1002/anie.200501860FALSEhttps://doi.org/10.1002/anie.200501860Song, SL2062005xxx#N/A
819
anie.20160966210.1002/anie.201609662https://doi.org/10.1002/anie.201609662Baran, PSAngew. Chem.-Int. Edit.Two named reactions of fundamental importance and paramount utility in organic synthesis have been reinvestigated, the Barton deCarbonylation and Giese radical conjugate addition. N-hydroxyphthalimide (NHPI) based redox-active esters were found to be convenient starting materials for simple, thermal, Ni-catalyzed radical formation and subsequent trapping with either a hydrogen atom source (PhSiH3) or an electron-deficient olefin. These reactions feature operational simplicity, inexpensive reagents, and enhanced scope as evidenced by examples in the realm of peptide chemistry.Nickel-Catalyzed Barton DeCarbonylation and Giese Reactions: A Practical Take on Classic Transformsconjugate addition; deCarbonylation; esters; nickel catalysis; redox-activex140201754#N/AFALSE
820
anie.20180243410.1002/anie.201802434https://doi.org/10.1002/anie.201802434Marek, IAngew. Chem.-Int. Edit.The combined ruthenium-catalyzed chain walking with the nickel-catalyzed cross-coupling reaction of -alkenyl ethers provide a unique entry to functionalized Vinyl species. This transformation illustrates the power and flexibility of remote functionalization by demonstrating the compatibility of two independent reactions involving unrelated sites.Metal-Catalyzed Remote Functionalization of omega-Ene Unsaturated Ethers: Towards Functionalized Vinyl Speciescross-coupling; isomerization; nickel; remote functionalization; zirconium2 stepsx22201883#N/AFALSE
821
acs.orglett.5b0164510.1021/acs.orglett.5b01645https://doi.org/10.1021/acs.orglett.5b01645Kobayashi, SVisible Light-Mediated Ullmann-Type C-N Coupling Reactions of Carbazole Derivatives and Aryl IodidesPhotocatalyst2015#N/AFALSE
822
ncomms940410.1038/ncomms9404https://doi.org/10.1038/ncomms9404You, JSNat. Commun.The past decade has witnessed significant advances in C-H bond functionalizations with the discovery of new mechanisms. Non-precious transition-metal-catalysed radical oxidative coupling for C(sp(3))-H bond transformations is an appealing strategy for C-C bond formations. The radical oxidative C(sp(3))-H/C(sp(3))-H cross-coupling reactions of alpha-C(sp(3))-H bonds of amines with free radicals represent a conceptual and practical challenge. We herein develop the coordinating Activation strategy to illustrate the nickel-catalysed radical oxidative cross-coupling between C(sp(3))-H bonds and (hetero)Arylmethyl free radicals. The protocol can tolerate a rich variety of alpha-amino acids and (hetero)Arylmethanes as well as Arylmethylenes and Arylmethines, affording a large library of alpha-tertiary and alpha-quaternary beta-aromatic alpha-amino acids. This process also features low-cost metal catalyst, readily handled and easily removable coordinating group, synthetic simplicity and gram-scale production, which would enable the potential for economical production at commercial scale in the future.Coordinating Activation strategy for C(sp(3))-H/C(sp(3))-H cross-coupling to access beta-aromatic alpha-amino acidsx602015no ligand?413/15/2022FALSE
823
jacs.9b0910910.1021/jacs.9b09109https://doi.org/10.1021/jacs.9b09109Sanford, MSJ. Am. Chem. Soc.This ArtiCle describes the synthesis and characterization of cyClometalated aminoquinoline Ni-II sigma-Aryl and sigma-Alkyl complexes that have been proposed as key intermediates in Ni-catalyzed C-H functionalization reactions. These Ni-II complexes serve as competent catalysts for the C-H functionalization of aminoquinoline derivatives with I-2. They also react stoichiometrically with I-2 to form either Aryl iodides or beta-lactams within minutes at room temperature. Furthermore, they react with Ag-I salts at -30 degrees C to afford isolable five-coordinate Ni-III species. The Ni-II sigma-Aryl complexes proved inert toward C(sp(2))-I bond-forming reductive elimination under all conditions examined (up to 140 degrees C in DMF). In contrast, a Ni-III sigma-Alkyl analogue underwent C(sp(3))-N bond-forming reductive elimination at 140 degrees C in DMF to afford a beta-lactam product. However, despite the ability of this latter Ni-III species to participate in stoichiometric product formation, the complex was not a competent catalyst for beta-lactam formation. Overall, these results suggest against the intermediacy of Ni-III species in these C-H functionalization reactions.Catalytically Relevant Intermediates in the Ni-Catalyzed C(sp(2))-H and C(sp(3))-H Functionalization of Aminoquinoline Substratesx112019corrected artiCle51#N/AFALSE
824
jacs.8b0399810.1021/jacs.8b03998https://doi.org/10.1021/jacs.8b03998Mashima, KJ. Am. Chem. Soc.A mixed ligated amidoyttrium complex, Y(NBn2)(L1)-(THF)(2) (8, LI = N,N'-bis(2,6-diisopropylphenyl)ethylenediamine), served as a catalyst for addition of the ortho-pyridyl C(sp(2))-H bond of 2-substituted pyridines to nonactivated imines; complex 8 showed superior catalytic performance compared with Y[N(SiMe3)(2)](3) (1) and Y[N(SiMe3)(2)](2)(NBn2)(THF) (2). Concerning the reaction mechanism, we conducted a stoichiometric reaction of an Alkylyttrium complex, Y(CH2SiMe3)(L1)(THF)2 (7), with 2-ethylpyridine (4e), giving a mixture of (eta(3) -pyridylmethyl)yttrium complex 9 and (eta(2)-pyridyl)yttrium complex 10 along with elimination of SiMe4. Furthermore, addition of N-(tert-butyl)-2-methylpropan-l-imine (Si) to the mixture of 9 and 10 afforded (pyridylmethylamido)yttrium complex 11 as a single product, and the catalytic activity of 11 was comparable to that of complex 8. Kinetic analysis of the aminoAlkylation reaction in the presence/absence of HNBn2 revealed that the reaction rate in the presence of HNBn2 was four times faster than that without HNBn2 due to acceleration of the product-eliminating step from complex 11 by HNBn2 to regenerate amidoyttrium complex 8 and the product. In addition, we determined that the catalytic reaction obeyed a first-order rate dependence on the catalyst concentration, independent of the imine concentration, and a second-order rate dependence on the concentration of the pyridine substrate in the reaction system, both with and without HNBn2. An enantiomerically pure N,N'-diAryl-1,2-diphenylethylenediamido ligand was applied for the C(sp(2))-H aminoAlkylation reaction in combination with Lu(CH2SiMe3)(3)(THF)(2) to give chiral aminoAlkylated products in moderate yield with good enantioselectivity.Direct ortho-C-H AminoAlkylation of 2-Substituted Pyridine Derivatives Catalyzed by Yttrium Complexes with N,N '-DiArylethylenediamido LigandsNot Nickel catalyst25201888#N/AFALSE
825
acscatal.7b0024510.1021/acscatal.7b00245https://doi.org/10.1021/acscatal.7b00245Newman, SGACS Catal.A palladium-catalyzed cross-coupling between Aryl esters and anilines is reported, enabling access to diverse amides. The reaction takes place via Activation of the C-O bond by oxidative addition with a Pd-NHC complex, which enables the use of relatively non-nuCleophilic anilines that otherwise require stoichiometric Activation with strong bases in order to react. High yields of aromatic, aliphatic, and heterocyClic products are obtained. A range of activated esters are evaluated in the presence and absence of catalyst, demonstrating that the catalytic methodology substantially increases the types of electrophiles that can be utilized for amide bond formation the absence of harsh bases.A Cross-Coupling Approach to Amide Bond Formation from Esterscross-coupling amides; palladium catalysis; C-O bond Activation; C-N couplingx80201775#N/AFALSE
826
jacs.9b1199910.1021/jacs.9b11999https://doi.org/10.1021/jacs.9b11999Sanford, MSJ. Am. Chem. Soc.This ArtiCle demonstrates a mild oxidatively induced C(sp(3))-H Activation at a high-valent Ni center. In contrast with most C(sp(3))-H Activation reactions at Ni-II, the transformation proceeds at room temperature and generates an isolable Ni-IV sigma-Alkyl complex. Density functional theory studies show two plausible mechanisms for this C-H Activation process involving triflate-assisted C-H Cleavage at either a Ni-IV or a Ni-III intermediate. The former pathway is modestly favored over the latter (by similar to 3 kcal/mol). The Ni-IV sigma-Alkyl product of C-H Cleavage reacts with a variety of nuCleophiles to form C(sp(3))-X bonds (X = halide, oxygen, nitrogen, sulfur, or carbon). These stoichiometric transformations can be coupled using N-fluoro-2,4,6-trimethylpyridinium triflate as a terminal oxidant in conjunction with chloride as a nuCleophile to achieve a proof-of-principle Ni-II/IV-catalyzed C(sp(3))-H functionalization reaction.Nickel(II/IV) Manifold Enables Room-Temperature C(sp(3))-H Functionalizationxyy11201946#N/AFALSE
827
ja412745510.1021/ja4127455FALSEhttps://doi.org/10.1021/ja4127455Fu, YJ. Am. Chem. Soc.Itami et al. recently reported the C-O electrophile-controlled chemoselectivity of Ni-catalyzed coupling reactions between azoles and esters: the deCarbonylative C H coupling product was generated with the Aryl ester substrates, while C H/C-O coupling product was generated with the phenol derivative substrates (such as phenyl pivalate). With the aid of DFT calculations (MO6L/6-311+G(2d,p)SDD//B3LYP/6-31G(d)-LANL2DZ), the present study systematically investigated the mechanism of the aforementioned chemoselective reactions. The deCarbonylative C H coupling mechanism involves oxidative addition of C(acy1)-0 bond, base-promoted C H Activation of azole, CO migration, and reductive elimination steps (C H/Decar mechanism). This mechanism is partially different from Itami's previous proposal (Decar/C H mechanism) because the C H Activation step is unlikely to occur after the CO migration step. Meanwhile, C H/ C-O coupling reaction proceeds through oxidative addition of C(phenyl)-O bond, base-promoted C H Activation, and reductive elimination steps. It was found that the C-0 electrophile significantly influences the overall energy demand of the deCarbonylative C H coupling mechanism, because the rate-determining step (i.e., CO migration) is sensitive to the steric effect of the acyl substituent. In contrast, in the C H/C-0 coupling mechanism, the release of the Carbonylates occurs before the ratedetermining step (i.e., base-promoted C H Activation), and thus the overall energy demand is almost independent of the acyl substituent. Accordingly, the deCarbonylative C H coupling product is favored for less-bulky group substituted C-0 electrophiles (such as Aryl ester), while C H/C-0 coupling product is predominant for bulky group substituted C-0 electrophiles (such as phenyl pivalate).Mechanistic Study of Chemoselectivity in Ni-Catalyzed Coupling Reactions between Azoles and Aryl CarbonylatesNo reaction figyy104201451#N/AFALSE
828
ja206745w10.1021/ja206745whttps://doi.org/10.1021/ja206745wHayashi, TJ. Am. Chem. Soc.Iron-copper cooperative catalysis is shown to be effective for an alkene-Grignard exchange reaction and Alkylmagnesiation of alkynes. The Grignard exchange between terminal alkenes (RCH=CH2) and cyClopentylmagnesium bromide was catalyzed by FeCl3 (2.5 mol %) and CuBr (5 mol %) in combination with PBu3 (10 mol %) to give RCH2CH2MgX in high yields. 1-Alkyl Grignard reagents add to alkynes in the presence of a catalyst system consisting of Fe(acac)(3), CuBr, PBu3, and N,N,N',N'-tetramethylethylenediamine to give beta-AlkylVinyl Grignard reagents. The exchange reaction and carbometalation take place on iron, whereas copper assists with the exchange of organic groups between organoiron and organomagnesium species through transmetalation with these species. Sequential reactions consisting of the alkene-Grignard exchange and the Alkylmagnesiation of alkynes were successfully conducted by adding an alkyne to a mixture of the first reaction. Isomerization of Grignard reagents from 2-Alkyl to 1-Alkyl catalyzed by Fe-Cu also is applicable as the first 1-Alkyl Grignard formation step.Iron-Copper Cooperative Catalysis in the Reactions of Alkyl Grignard Reagents: Exchange Reaction with Alkenes and Carbometalation of AlkynesNot Nickel catalyst108201240#N/AFALSE
829
anie.20201024410.1002/anie.202010244https://doi.org/10.1002/anie.202010244Wei, HAngew. Chem.-Int. Edit.Highly selective divergent coupling reactions of benzocyClobutenones and indoles, in which the chemoselectivity is controlled by catalysts, are reported herein. The substrates undergo C2(indole)-C8(benzocyClobutenone) coupling to produce Benzylated indoles and benzo[b]carbazoles in the Ni- and Ru-catalyzed reactions. A completely different selectivity pattern C2(indole)-C2(benzocyClobutenone) coupling to form Arylated indoles is observed in the Rh-catalyzed reaction. Preliminary mechanistic studies suggest C-H and C-C Activations in the reaction pathway. Synthetic utility of this protocol is demonstrated by the selective synthesis of three different types of carbazoles from the representative products.Divergent Coupling of BenzocyClobutenones with Indoles via C-H and C-C ActivationsbenzocyClobutenone; carbazole; catalyst-control; C-C Activation; divergent synthesisNot Nickel catalyst7202087#N/AFALSE
830
anie.20170340010.1002/anie.201703400FALSEhttps://doi.org/10.1002/anie.201703400Buchwald, SLAngew. Chem.-Int. Edit.We report an efficient means of sp(2)-sp(3) cross coupling for a variety of terminal monosubstituted olefins with Aryl electrophiles using Pd and CuH catalysis. In addition to its applicability to a range of Aryl bromide substrates, this process was also suitable for electron-deficient Aryl chlorides, furnishing higher yields than the corresponding Aryl bromides in these cases. The optimized protocol does not require the use of a glovebox and employs air-stable Cu and Pd complexes as precatalysts. A reaction on 10 mmol scale further highlighted the practical utility of this protocol. Employing a similar protocol, a series of cyClic alkenes were also examined. CyClopentene was shown to undergo efficient coupling under these conditions. Lastly, deuterium-labeling studies indicate that deuterium scrambling does not take place in this sp(2)-sp(3) cross coupling, implying that beta-hydride elimination is not a significant process in this transformation.A Dual Palladium and Copper Hydride Catalyzed Approach for Alkyl-Aryl Cross-Coupling of Aryl Halides and Olefinsalkenes; copper; cross-coupling; homogeneous catalysis; palladiumNot Nickel catalyst68201766#N/AFALSE
831
acscatal.8b0044010.1021/acscatal.8b00440FALSEhttps://doi.org/10.1021/acscatal.8b00440Kanai, MACS Catal.We developed a palladium-catalyzed C-H transformation that enabled the synthesis of ketones from aldehydes and (hetero)Aryl halides. The use of picolinamide ligands was key to achieving the transformation. HeteroAryl ketones, as well as diAryl ketones, were synthesized in good to excellent yields, even in gram-scale, using this reaction. Results of density functional theory (DFT) calculations support the C-H bond Activation pathway.Palladium-Catalyzed Synthesis of DiAryl Ketones from Aldehydes and (Hetero)Aryl Halides via C-H Bond ActivationNot Nickel catalyst41201864#N/AFALSE
832
acscatal.0c0210510.1021/acscatal.0c02105https://doi.org/10.1021/acscatal.0c02105Zheng, CACS Catal.Herein, we report that merging palladium catalysis with hydrogen atom transfer (HAT) photocatalysis enabled direct Arylations and Aralkenylations of aldehyde C-H bonds, facilitating visible light-catalyzed construction of a variety of ketones. Tetrabutylammonium decatungstate and anthraquinone were found to act as synergistic HAT photocatalysts. Density PC isolated yield functional theory calculations suggested a Pd-0-Pd-II-Pd-III-Pd-I-Pd-0 pathway and revealed that regeneration of the Pd-0 catalyst and the photocatalyst occurs simultaneously in the presence of KHCO3. This regeneration features a low energy barrier, promoting efficient coupling of the palladium catalytic cyCle with the photocatalytic cyCle. The work reported herein suggests great promise for further applications of HAT photocatalysis in palladium-catalyzed cross-coupling and C-H functionalization reactions to be successful.Direct C-H Arylation of Aldehydes by Merging Photocatalyzed Hydrogen Atom Transfer with Palladium Catalysispalladium catalysis; HAT photocatalyst; hydrogen-atom transfer; C-H functionalization; ketone synthesis; DFT calculationPhotocatalystUnrelatedyy14202054#N/AFALSE
833
acscatal.0c0089810.1021/acscatal.0c00898https://doi.org/10.1021/acscatal.0c00898Yin, GYACS Catal.Divergent catalysis represents a powerful strategy for increasing molecular complexity and exploring catalytic modes in organic synthesis. Herein, we report, a nickel-catalyzed, chemodivergent 1,1-alkynylboration, and 1,1-dialkynylation of unactivated alpha-olefins. This study not only provides an efficient and modular protocol for the divergent synthesis of propargylic boronic esters and gem-dialkynylalkanes, but also achieves a controllable, single or double cross-coupling of Ni/B bimetallic intermediates. Mechanistic studies reveal that the diboron reagent (B-2 pin(2)) plays a significant role in the dialkynylation reaction, serving as both the reductant and transient assisting group. Notably, both reactions show high regioselectivities and good functional group tolerance. In addition, the synthetic value of the products has been demonstrated with several downstream transformations.Nickel-Catalyzed Chemodivergent 1,1-Difunctionalization of Unactivated alpha-Olefins with Alkynyl Electrophiles and B(2)pin(2)divergent catalysis; nickel catalysis; 1,1-regioselectivity; difunctionalization; alpha-olefinsUnrelatedy1020203 reactants56#N/AFALSE
834
acs.orglett.5b0170110.1021/acs.orglett.5b01701https://doi.org/10.1021/acs.orglett.5b01701Glorius, FCobalt(III)-Catalyzed Directed C-H AllylationNot Nickel catalyst2015#N/AFALSE
835
ja307936210.1021/ja3079362https://doi.org/10.1021/ja3079362Doyle, AGJ. Am. Chem. Soc.The mechanism of a recently reported Suzuki coupling reaction of quinoline-derived allylic N,O-acetals has been studied using a combination of structural, stereochemical, and kinetic isotope effect experiments. The data indicate that C-O Activation is facilitated by Lewis acid assistance from the boronic acid coupling partner and an ionic S(N)1-like mechanism accounts for oxidative addition. In this context, we demonstrate the first direct observation of oxidative addition to a quinolinium salt. Notably, this mechanism is distinct from the more commonly described S(N)2(')-type oxidative addition of low-valent transition metals to most allylic electrophiles.Mechanistic Investigation of the Nickel-Catalyzed Suzuki Reaction of N,O-Acetals: Evidence for Boronic Acid Assisted Oxidative Addition and an Iminium Activation PathwayxY50201245#N/AFALSE
836
anie.20150675110.1002/anie.201506751https://doi.org/10.1002/anie.201506751Li, CJAngew. Chem.-Int. Edit.The transition-metal-catalyzed amination of Aryl halides has been the most powerful method for the formation of Aryl amines over the past decades. Phenols are regarded as ideal alternatives to Aryl halides as coupling partners in cross-couplings. An efficient palladium-catalyzed formal cross-coupling of phenols with various amines and anilines has now been developed. A variety of substituted phenols were compatible with the standard reaction conditions. Secondary and tertiary Aryl amines could thus be synthesized in moderate to excellent yields.Formal Direct Cross-Coupling of Phenols with AminesAryl amines; dehydrogenation; hydrogen borrowing; palladium; phenolsx97201575#N/AFALSE
837
acscatal.8b0444410.1021/acscatal.8b04444https://doi.org/10.1021/acscatal.8b04444Nguyen, HMACS Catal.Metal triflates have been utilized to catalytically facilitate numerous glycosylation reactions under mild conditions. In some methods, the metal triflate system provides stereocontrol during the glycosylation, rather than the nature of protecting groups on the substrate. Despite these advances, the true activating nature of metal triflates remains unClear. Our findings indicated that the in situ generation of trace amounts of triflic acid from metal triflates can be the active catalyst species in the glycosylation. This fact has been mentioned previously in metal-triflate-catalyzed glycosylation reactions; however, a thorough study on the subject and its implications on stereoselectivity has yet to be performed. Experimental evidence from control reactions and F-19 NMR spectroscopy have been obtained to confirm and quantify the triflic acid released from nickel triflate, for which it is of paramount importance in achieving a stereoselective 1,2-cis-2-amino glycosidic bond formation via a transient anomeric triflate. A putative intermediate resembling that of a glycosyl triflate has been detected using variable temperature NMR (H-1 and C-13) experiments. These observations, together with density functional theory calculations and a kinetic study, corrB(OH)2rate a mechanism involving triflicacid-catalyzed stereoselective glycosylation with N-substituted trifluoromethylBenzylideneamino-protected electrophiles. Specifically, triflic acid facilitates formation of a glycosyl triflate intermediate which then undergoes isomerization from the stable a-anomer to the more reactive beta-anomer. Subsequent S(N)2-like displacement of the reactive anomer by a nuCleophile is highly favorable for the production of 1,2-cis-2-aminoglycosides. Although there is a previously reported work regarding glycosyl triflates, none of these reports have been confirmed to come from the counterion of the metal center. Our work provides supporting evidence for the induction of a glycosyl triflate through the role of triflic acid in metal-triflate-catalyzed glycosylation reactions.Are Bronsted Acids the True Promoter of Metal-Triflate-Catalyzed Glycosylations? A Mechanistic Probe into 1,2-cis-Aminoglycoside Formation by Nickel Triflateglycosylation mechanism; hidden Bronsted acid; kinetics; 1,2-cis-aminoglycosides; nickel triflatexy22201978#N/AFALSE
838
1521-3773(20010202)40:3<534::AID-ANIE534>3.0.CO;2-C
10.1002/1521-3773(20010202)40:3<534::AID-ANIE534>3.0.CO;2-C
https://doi.org/10.1002/1521-3773(20010202)40:3<534::AID-ANIE534>3.0.CO;2-CRueping, MAngew. Chem.-Int. Edit.Olefin polymerization by late transition metal complexes - A root of Ziegler catalysts gains new groundx434200183#N/AFALSE
839
to be filled 5FALSEhttps://doi.org/SALTSBURG, HScienceNickel metal catalysts composed of nanometer by micrometer strips have been produced with solid-state microfabrication techniques. The strips are actually the edges of nickel-catalyst thin films, which are sandwiched between separating support layers, which are also nanometers thick. These linear nanostructures constitute well-defined and well-controlled catalytic entities that reproduce the size of traditional supported metal Clusters in one dimension, thus separating size from total number of atoms in the catalyst. Examination of their catalytic activity showed that they duplicate the behavior of conventional supported Clusters. A specific rate maximum was observed for the hydrogenolysis of ethane at a nanoscale dimension similar to the Cluster size at which the rate is maximum in the case of the supported Cluster studies, whereas the hydrogenation of ethylene shows no such size dependency. The results suggest that the surface-to-volume ratio or the number of atoms in the catalytic entity cannot be the source of these size effects and that either support effects or nonequilibrium surface structures are the determining factors.LINEAR METAL NANOSTRUCTURES AND SIZE EFFECTS OF SUPPORTED METAL-CATALYSTS#N/Ax71199212#N/AFALSE
840
to be filled 4FALSEhttps://doi.org/WITTE, JAngew. Chem.-Int. Edit. Engl.CONTROL OF THE MOLECULAR-WEIGHT OF POLYETHENE IN SYNTHESES WITH BIS(YLIDE)NICKEL CATALYSTS#N/Ax75198713#N/AFALSE
841
to be filled 25FALSEhttps://doi.org/GEIGER, WEJ. Am. Chem. Soc.STABILIZATION OF PARAMAGNETIC METAL(I) COMPLEXES OF NICKEL SUBGROUP - ELECTROCHEMICAL AND ELECTRON-SPIN RESONANCE STUDIES OF METAL DITHIOLENE COMPLEXES AND THEIR AMINO ANALOGS#N/Ax35197514#N/AFALSE
842
to be filled 23https://doi.org/MILCHEREIT, AAngew. Chem.-Int. Edit.CC BOND FORMATION OF ALKENES WITH ISOCYANATES ON NI-0 COMPLEXES - A NEW SYNTHESIS OF ACRYLAMIDES#N/ABook ? 019859#N/AFALSE
843
to be filled 2https://doi.org/Bansleben, DAScienceScope of olefin polymerization nickel catalysts - Response#N/Ax13200023#N/AFALSE
844
to be filled 18FALSEhttps://doi.org/MAY, JJ. Am. Chem. Soc.PROTON NUClEAR MAGNETIC-RESONANCE CONTACT SHIFTS OF OCTAHEDRAL IRON(II), COBALT(II), AND NICKEL(II) IMIDAZOLE COMPLEXES#N/Ax5197525#N/AFALSE
845
to be filled 15FALSEhttps://doi.org/CRABTREE, RHAngew. Chem.-Int. Edit. Engl.In the solid state an octahedral while in solution probably a square-planar coordination geometry is found for the central metal atom in the Ni(II) thiosemicarbazone complex cation 1. The dissociation of the phenol groups lends 1 hydrogenase-like activity. Dissolved in EtOH through which a stream of D2 gas is bubbled, 1-Cl2 undergoes H/D exchange with a turnover of 7.5, a reaction which corresponds to the Activation of H-2.FUNCTIONAL-MODELING OF NI,FE HYDROGENASES - A NICKEL-COMPLEX IN AN N,O,S ENVIRONMENT#N/ABook68199133#N/AFALSE
846
to be filled 14https://doi.org/Verdaguer, MJ. Am. Chem. Soc.CoFe Prussian blue analogue Rb1.8Co4[Fe(CN)(6)](3.3). 13H(2)O was synthesized, which presents an important photomagnetic effect. The electronic structure and the local structure of the ground and of the excited states have been investigated. X-ray absorption spectroscopy measurements at the Co and Fe L-2.3 edges and cobalt K-edge (XANES and EXAFS) evidence the local electronic transfer and the spin change of the cobalt ions induced by irradiation. We observed a 0.19 Angstrom increase of the Co-N bond length, associated with the transformation of Co-III low spin to Co-II high spin. The Co-II/Co-III ratio has been evaluated as a function of the irradiation time and revealed as an important parameter to understanding the bulk magnetic properties. The combined role of the diamagnetic Fe-II-Co-III pairs and hexacyanoferrate(III) vacancies is locally evidenced. This work is a new step in the understanding of the photoinduced electron transfer.Photoinduced ferrimagnetic systems in Prussian blue analogues C-x(I)Co-4[Fe(CN)(6)](y) (C-I = alkali cation). 2. X-ray absorption spectroscopy of the metastable state#N/APhotocatalystx131200032#N/AFALSE
847
to be filled 13FALSE#REF!Mukherjee, AKLow-temperature superplasticity in nanostructured nickel and metal alloys#N/Ax1999#N/AFALSE
848
to be filled 11https://doi.org/KLEIN, HFJ. Am. Chem. Soc.SYNTHESIS OF NOVEL POLYFUNCTIONAL NICKEL(II) NICKEL(II) DIMER NI2Cl2[C(SIME3)(PME3)]2 BY PHOTOLYSIS OF THE 1ST [(TRIMETHYLSILYL)DIAZOMETHYL]NICKEL(II) COMPLEX NI[C(N2)SIME3]Cl(PME3)2#N/APhotocatalystx25199016#N/AFALSE
849
s-1981-2968010.1055/s-1981-29680FALSEhttps://sci-hub.yncjkj.com/10.1055/s-1981-29680Kumada, MSYNTHESIS-STUTTGARTCross-Coupling of Enol Phosphates with Trimethylsilylmethylmagnesium Halides Catalyzed by Nickel or Palladium Complexes; A Selective Synthesis of AllylsilanesNi(0) complex901981#N/A
850
to be filled 1https://www.jstor.org/stable/3075410Rueping, MScienceScope of olefin polymerization nickel catalysts#N/Ax8200013#N/AFALSE
851
science.abh262310.1126/science.abh2623https://doi.org/10.1126/science.abh2623Stahl, SSScienceThe magic methyl effect describes the change in potency, selectivity, and/or metabolic stability of a drug candidate associated with addition of a single methyl group. We report a synthetic method that enables direct methylation of C(sp(3))-H bonds in diverse drug-like molecules and pharmaceutical building blocks. Visible light-initiated triplet energy transfer promotes homolysis of the O-O bond in di-tert-butyl or dicumyl peroxide under mild conditions. The resulting alkoxyl radicals undergo divergent reactivity, either hydrogen-atom transfer from a substrate C-H bond or generation of a methyl radical via beta-methyl scission. The relative rates of these steps may be tuned by varying the reaction conditions or peroxide substituents to optimize the yield of methylated product arising from nickel-mediated cross-coupling of substrate and methyl radicals.C(sp(3))-H methylation enabled by peroxide photosensitization and Ni-mediated radical couplingPhotocatalyst32021556/1/2022FALSE
852
science.abg552610.1126/science.abg5526FALSEhttps://doi.org/10.1126/science.abg5526Dong, GBScienceMild methods to Cleave the carbon-oxygen (C-O) bond in Alkyl ethers could simplify chemical syntheses through the elaboration of these robust, readily available precursors. Here we report that dibromB(OH)2ranes react with Alkyl ethers in the presence of a nickel catalyst and zinc reductant to insert boron into the C-O bond. Subsequent reactivity can effect oxygen-to-nitrogen substitution or one-carbon homologation of cyClic ethers and more broadly streamline preparation of bioactive compounds. Mechanistic studies reveal a Cleavage-then-rebound pathway via zinc/nickel tandem catalysis.Boron insertion into Alkyl ether bonds via zinc/nickel tandem catalysisx02021101#N/AFALSE
853
science.abg176510.1126/science.abg1765FALSEhttps://doi.org/10.1126/science.abg1765Wagner, TScienceEthane, the second most abundant hydrocarbon gas in the seafloor, is efficiently oxidized by anaerobic archaea in syntrophy with sulfate-reducing bacteria. Here, we report the 0.99-angstrom-resolution structure of the proposed ethane-activating enzyme and describe the specific traits that distinguish it from methane-generating and -consuming methyl-coenzyme M reductases. The widened catalytic chamber, harboring a dimethylated nickel-containing F-430 cofactor, would adapt the chemistry of methyl-coenzyme M reductases for a two-carbon substrate. A sulfur from methionine replaces the oxygen from a canonical glutamine as the nickel lower-axial ligand, a feature conserved in thermophilic ethanotrophs. Specific loop extensions, a four-helix bundle dilatation, and posttranslational methylations result in the formation of a 33-angstrom-long hydrophobic tunnel, which guides the ethane to the buried active site as confirmed with xenon pressurization experiments.Crystal structure of a key enzyme for anaerobic ethane Activationx0202159#N/AFALSE
854
to be filled 6FALSEhttps://doi.org/ClAUSE, OJ. Am. Chem. Soc.The adsorption of Co(II) or Ni(II) ammine complexes from aqueous solutions onto gamma-alumina at neutral or near neutral pH (7 < pH < 8.2) and ambient temperature is investigated as a function of the ion concentration in the impregnating solutions, the contact and aging times, and the drying conditions. The formation of coprecipitates inCluding Al(III) ions extracted from the support is demonstrated by EXAFS and IR spectroscopy for contact times and Ni or Co loadings higher than 0.5 h and about 2.0 wt %, respectively. The EXAFS technique makes it possible to distinguish the Ni or Co hydroxides and basic nitrates from coprecipitates with the hydrotalcite-type structure. In other words, EXAFS is shown to be sensitive to the presence of aluminum in the coprecipitates. Furthermore, in most cases, the M(II)/Al(III) ratio (M = Ni or Co) in the supported coprecipitates can be estimated. Infrared spectroscopy can also be used as a fingerprint of coprecipitate formation through lattice octahedral modes characteristic of the NiAl and CoAl hydrotalcite-type compounds in the 400-450 cm(-1) region. Thus, alumina should not be considered systematically as inert even at pH values Close to its isoelectric point. Possible mechanisms responsible for the formation of coprecipitates at pH values nonaggressive for alumina are discussed. Dialysis experiments leading to the observation of hydrotalcite crystallites at a distance from alumina suggest that a dissolution-precipitation mechanism is possibly involved and that the rate of alumina dissolution is promoted by adsorbed Ni(II) or Co(II) ions. Three phenomer a are suggested to occur at the same time at the oxide/water interface; the adsorption of ions, as described by the site binding models; the alumina dissolution, promoted by the adsorbed ions and kinetically limited; the coprecipitation of M(II) with Al(III) ions extracted from the support. Site binding models have a considerable value for the early stages of impregnation, whereas approaches which use geochemistry as a basis and involve surface rehydration and coprecipitate formation have probably a greater validity for the later stages.IMPREGNATION OF GAMMA-ALUMINA WITH NI(II) OR CO(II) IONS AT NEUTRAL PH - HYDROTALCITE-TYPE COPRECIPITATE FORMATION AND CHARACTERIZATION#N/A144199559#N/ATRUE
855
science.abb568010.1126/science.abb5680FALSEhttps://doi.org/10.1126/science.abb5680Yavuz, CTScienceHu and Ruckenstein state that our findings were overClaimed and not new, despite our presentation of evidence for the Nanocatalysts on Single Crystal Edges (NOSCE) mechanism. Their arguments do not take into account fundamental differences between our Ni-Mo/MgO catalyst and their NiO/MgO preparations.Response to Comment on Dry reforming of methane by stable Ni-Mo nanocatalysts on single-crystalline MgOx0202015#N/AFALSE
856
science.abb545910.1126/science.abb5459FALSEhttps://doi.org/10.1126/science.abb5459Ruckenstein, EComment on Dry reforming of methane by stable Ni-Mo nanocatalysts on single-crystalline MgOx2020#N/AFALSE
857
science.aba611810.1126/science.aba6118FALSEhttps://doi.org/10.1126/science.aba6118Mogensen, MBScienceIn a world powered by intermittent renewable energy, electrolyzers will play a central role in converting electrical energy into chemical energy, thereby decoupling the production of transport fuels and chemicals from today's fossil resources and decreasing the reliance on bioenergy. Solid oxide electrolysis cells (SOECs) offer two major advantages over alternative electrolysis technologies. First, their high operating temperatures result in favorable thermodynamics and reaction kinetics, enabling unrivaled conversion efficiencies. Second, SOECs can be thermally integrated with downstream chemical syntheses, such as the production of methanol, dimethyl ether, synthetic fuels, or ammonia. SOEC technology has witnessed tremendous improvements during the past 10 to 15 years and is approaching maturity, driven by advances at the cell, stack, and system levels.Recent advances in solid oxide cell technology for electrolysisx39202084#N/AFALSE
858
to be filled 29FALSEhttps://doi.org/BLOMBERG, MRAJ. Am. Chem. Soc.Calculations inCluding electron correlation have been performed for the insertion of a number of first and second row transition metal atoms (Cr, Co, Fe, Ni, Cu, Mo, Ag) into the C-O bond of ethene oxide. It is found that for all these metals, except silver, a metallacyCle is more stable than the [metal + epoxide]. The energy of [metal + epoxide] is also compared to [metal oxide + ethene] and it is found that only for copper and silver is [metal + epoxide] lower in energy than [metal oxide + ethene]. The difference between the metals in this respect is explained by the difference in binding energy of the diatomic metal oxides. Silver and copper have much weaker M = O bonds than the rest of the metals studied, and this favors an epoxidation reaction.METALLAOXETANES AS POSSIBLE INTERMEDIATES IN METAL-PROMOTED DEOXYGENATION OF EPOXIDES AND EPOXIDATION OF OLEFINS#N/A54199249#N/ATRUE
859
to be filled 28FALSEhttps://doi.org/Ringe, DNatureThe virulent phenotype of the pathogenic bacterium Corynebacterium diphtheriae is conferred by diphtheria toxin, whose expression is an adaptive response to low concentrations of iron. The expression of the toxin gene (tox) is regulated by the repressor DtxR (ref. 1), which is activated by transition metal ions. X-ray crystal structures of DtxR with(2-5) and without (apo-form(2)) its coordinated transition metal ion have established the general architecture of the repressor, identified the location of the metal-binding sites, and revealed a metal-ion-triggered subunit-subunit 'caliper-like' conformational change, Here we report the three-dimensional crystal structure of the complex between a biologically active Ni(II)-bound DtxR(C102D) mutant, in which a cysteine is replaced by an aspartate at residue 102, and a 33-base-pair DNA segment containing the toxin operator toxO. This structure shows that DNA interacts with two dimeric repressor proteins bound to opposite sides of the tox operator. We propose that a metal-ion-induced helix-to-coil structural transition in the amino-terminal region of the protein is partly responsible for the unique mode of repressor Activation by transition metal ions.Structure of the metal-ion-activated diphtheria toxin repressor tox operator complex#N/A138199830#N/ATRUE
860
to be filled 27FALSEhttps://doi.org/Leitner, AAngew. Chem.-Int. Edit.Iron-catalyzed cross-coupling reactions of Alkyl-grignard reagents with Aryl chlorides, tosylates, and triflates354200257#N/ATRUE
861
science.aaw749310.1126/science.aaw7493FALSEhttps://doi.org/10.1126/science.aaw7493Xia, BYScienceDevelopment of efficient and robust electrocatalysts is critical for practical fuel cells. We report one-dimensional bunched platinum-nickel (Pt-Ni) alloy nanocages with a Pt-skin structure for the oxygen reduction reaction that display high mass activity (3.52 amperes per milligram platinum) and specific activity (5.16 milliamperes per square centimeter platinum), or nearly 17 and 14 times higher as compared with a commercial platinum on carbon (Pt/C) catalyst. The catalyst exhibits high stability with negligible activity decay after 50,000 cyCles. Both the experimental results and theoretical calculations reveal the existence of fewer strongly bonded platinum-oxygen (Pt-O) sites induced by the strain and ligand effects. Moreover, the fuel cell assembled by this catalyst delivers a current density of 1.5 amperes per square centimeter at 0.6 volts and can operate steadily for at least 180 hours.Engineering bunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cellsx310201954#N/AFALSE
862
science.aav241210.1126/science.aav2412FALSEhttps://doi.org/10.1126/science.aav2412Yavuz, CTScienceLarge-scale carbon fixation requires high-volume chemicals production from carbon dioxide. Dry reforming of methane could provide an economically feasible route if coke- and sintering-resistant catalysts were developed. Here, we report a molybdenum-doped nickel nanocatalyst that is stabilized at the edges of a single-crystalline magnesium oxide (MgO) support and show quantitative production of synthesis gas from dry reforming of methane. The catalyst runs more than 850 hours of continuous operation under 60 liters per unit mass of catalyst per hour reactive gas flow with no detectable coking. Synchrotron studies also show no sintering and reveal that during Activation, 2.9 nanometers as synthesized crystallites move to combine into stable 17-nanometer grains at the edges of MgO crystals above the Tammann temperature. Our findings enable an industrially and economically viable path for carbon reClamation, and the Nanocatalysts On Single Crystal Edges technique could lead to stable catalyst designs for many challenging reactions.Dry reforming of methane by stable Ni-Mo nanocatalysts on single-crystalline MgOx81202093#N/AFALSE
863
(SICI)1521-3773(19980518)37:9<1198::AID-ANIE1198>3.0.CO;2-Y
10.1002/(SICI)1521-3773(19980518)37:9<1198::AID-ANIE1198>3.0.CO;2-Y
FALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980518)37:9<1198::AID-ANIE1198>3.0.CO;2-YZhang, YCAngew. Chem.-Int. Edit.Transition metal catalysis in the Baeyer-Villiger oxidation of ketones320199890#N/ATRUE
864
to be filled 22FALSEhttps://doi.org/ROJO, TAngew. Chem.-Int. Edit.ALTERNATING FERROMAGNETIC AND ANTIFERROMAGNETIC INTERACTIONS IN A MN-II CHAIN WITH ALTERNATING END-ON AND END-TO-END BRIDGING AZIDO LIGANDS64199424#N/ATRUE
865
science.aap788310.1126/science.aap7883FALSEhttps://doi.org/10.1126/science.aap7883Kobayashi, SScienceThe development of highly reactive and stereoselective catalytic systems is required not only to improve existing synthetic methods but also to invent distinct chemical reactions. Herein, a homogenized combination of nickel-based Lewis acid-surfactant-combined catalysts and single-walled carbon nanotubes is shown to exhibit substantial activity in water. In addition to the enhanced reactivity, stereoselective performance and long-term stability were demonstrated in asymmetric conjugate addition reactions of aldoximes to furnish chiral nitrones in high yields with excellent selectivities. The practical and straightforward application of the designed catalysts in water provides an expedient, environmentally benign, and highly efficient pathway to access optically active compounds.Chiral Lewis acids integrated with single-walled carbon nanotubes for asymmetric catalysis in waterx17201836#N/AFALSE
866
science.aao653810.1126/science.aao6538FALSEhttps://doi.org/10.1126/science.aao6538Regalbuto, JRScienceSupported nanopartiCles containing more than one metal have a variety of applications in sensing, catalysis, and biomedicine. Common synthesis techniques for this type of material often result in large, unalloyed nanopartiCles that lack the interactions between the two metals that give the partiCles their desired characteristics. We demonstrate a relatively simple, effective, generalizable method to produce highly dispersed, well-alloyed bimetallic nanopartiCles. Ten permutations of noble and base metals (platinum, palladium, copper, nickel, and cobalt) were synthesized with average partiCle sizes from 0.9 to 1.4 nanometers, with tight size distributions. High-resolution imaging and x-ray analysis confirmed the homogeneity of alloying in these ultrasmall nanopartiCles.Synthesis of ultrasmall, homogeneously alloyed, bimetallic nanopartiCles on silica supportsx146201733#N/AFALSE
867
to be filled 19FALSEhttps://doi.org/Sievers, CAngew. Chem.-Int. Edit.RETRACTION: Conversion of Methane into Methanol and Ethanol over Nickel Oxide on Ceria-Zirconia Catalysts in a Single Reactor (Retraction of Vol 56, Pg 13876, 2017)#N/A020191#N/ATRUE
868
science.aan878210.1126/science.aan8782FALSEhttps://doi.org/10.1126/science.aan8782Comelli, GScienceSingle adatoms are expected to participate in many processes occurring at solid surfaces, such as the growth of graphene on metals. We demonstrate, both experimentally and theoretically, the catalytic role played by single metal adatoms during the technologically relevant process of graphene growth on nickel (Ni). The catalytic action of individual Ni atoms at the edges of a growing graphene flake was directly captured by scanning tunneling microscopy imaging at the millisecond time scale, while force field molecular dynamics and density functional theory calculations rationalize the experimental observations. Our results unveil the mechanism governing the activity of a single-atom catalyst at work.Real-time imaging of adatom-promoted graphene growth on nickelx74201825#N/AFALSE
869
science.aan449710.1126/science.aan4497FALSEhttps://doi.org/10.1126/science.aan4497Higuchi, YScienceNAD(+) (oxidized form of NAD: nicotinamide adenine dinuCleotide)-reducing soluble [ NiFe]hydrogenase (SH) is phylogenetically related to NADH (reduced form of NAD(+)): quinone oxidoreductase (complex I), but the geometrical arrangements of the subunits and Fe-S Clusters are unClear. Here, we describe the crystal structures of SH in the oxidized and reduced states. The Cluster arrangement is similar to that of complex I, but the subunits orientation is not, which supports the hypothesis that subunits evolved as prebuilt modules. The oxidized active site inCludes a six-coordinate Ni, which is unprecedented for hydrogenases, whose coordination geometry would prevent O-2 from approaching. In the reduced state showing the normal active site structure without a physiological electron acceptor, the flavin mononuCleotide cofactor is dissociated, which may be caused by the oxidation state change of nearby Fe-S Clusters and may suppress production of reactive oxygen species.Structural basis of the redox switches in the NAD(+)-reducing soluble [NiFe]-hydrogenasex21201728#N/AFALSE
870
ja00197a02910.1021/ja00197a029FALSEhttps://pubs.acs.org/doi/pdf/10.1021/ja00197a029Hartwig, JFJ. Am. Chem. Soc.MONO(ETHYNE)NICKEL(O) AND BIS(ETHYNE)NICKEL(0) COMPLEXES#N/A38198969#N/ATRUE
871
science.aam815810.1126/science.aam8158FALSEhttps://doi.org/10.1126/science.aam8158Itami, KScienceThe synthesis of a carbon nanobelt, comprising a Closed loop of fully fused edge-sharing benzene rings, has been an elusive goal in organic chemistry for more than 60 years. Here we report the synthesis of one such compound through iterative Wittig reactions followed by a nickel-mediated Aryl-Aryl coupling reaction. The cylindrical shape of its belt structure was confirmed by x-ray crystallography, and its fundamental optoelectronic properties were elucidated by ultraviolet-visible absorption, fluorescence, and Raman spectroscopic studies, as well as theoretical calculations. This molecule could potentially serve as a seed for the preparation of structurally well-defined carbon nanotubes.Synthesis of a carbon nanobeltx224201732#N/AFALSE
872
science.aal516610.1126/science.aal5166FALSEhttps://doi.org/10.1126/science.aal5166Lu, KMETALLURGY Grain boundary stability governs hardening and softening in extremely fine nanograined metalsx2017#N/AFALSE
873
science.aal249010.1126/science.aal2490https://doi.org/10.1126/science.aal2490MacMillan, DWCScienceTransition metal catalysis has traditionally relied on organometallic complexes that can cyCle through a series of ground-state oxidation levels to achieve a series of discrete yet fundamental fragment-coupling steps. The viability of excited-state organometallic catalysis via direct photoexcitation has been demonstrated. Although the utility of triplet sensitization by energy transfer has long been known as a powerful Activation mode in organic photochemistry, it is surprising to recognize that photosensitization mechanisms to access excited-state organometallic catalysts have lagged far behind. Here, we demonstrate excited-state organometallic catalysis via such an Activation pathway: Energy transfer from an iridium sensitizer produces an excited-state nickel complex that couples Aryl halides with Carbonylic acids. Detailed mechanistic studies confirm the role of photosensitization via energy transfer.PHOTOCHEMISTRY Photosensitized, energy transfer-mediated organometallic catalysis through electronically excited nickel(II)Photocatalyst211201741#N/AFALSE
874
to be filled 16FALSEhttps://doi.org/SCHNOCKEL, HAngew. Chem.-Int. Edit.[(CPNI)(2)(CP-ASTERISK-AL)(2)] - CP-ASTERISK-AL AS A BRIDGING 2-ELECTRON LIGAND#N/A54199429#N/ATRUE
875
to be filled 12FALSE#REF!Castedo, LEfficient palladium-catalyzed cyClotrimerization of arynes: Synthesis of triphenylenes1998#N/ATRUE
876
to be filled 10FALSEhttps://doi.org/SCHUCHARDT, UAngew. Chem.-Int. Edit. Engl.NICKEL(II)-CATALYZED SYNTHESIS OF PYRROLES FROM 2H-AZIRINES AND ACTIVATED KETONES#N/A419774#N/ATRUE
877
science.abe575710.1126/science.abe5757FALSEhttps://doi.org/10.1126/science.abe5757Parkinson, GSUnraveling CO adsorption on model single-atom catalystsx2021#N/AFALSE
878
science.aba382310.1126/science.aba3823FALSEhttps://doi.org/10.1126/science.aba3823Jensen, KFScienceElectrochemistry offers opportunities to promote single-electron transfer (SET) redox-neutral chemistries similar to those recently discovered using visible-light photocatalysis but without the use of an expensive photocatalyst. Herein, we introduce a microfluidic redox-neutral electrochemistry (mRN-eChem) platform that has broad applicability to SET chemistry, inCluding radical-radical cross-coupling, Minisci-type reactions, and nickel-catalyzed C(sp(2))-O cross-coupling. The cathode and anode simultaneously generate the corresponding reactive intermediates, and selective transformation is facilitated by the rapid molecular diffusion across a microfluidic channel that outpaces the decomposition of the intermediates. mRN-eChem was shown to enable a two-step gram-scale electrosynthesis of a nematic liquid crystal compound, demonstrating its practicality.Microfluidic electrochemistry for single-electron transfer redox-neutral reactionsx44202057#N/AFALSE
879
science.aag020910.1126/science.aag0209https://doi.org/10.1126/science.aag0209MacMillan, DWCScienceOver the past two decades, there have been major developments in transition metal-catalyzed aminations of Aryl halides to form anilines, a common structure found in drug agents, natural product isolates, and fine chemicals. Many of these approaches have enabled highly efficient and selective coupling through the design of specialized ligands, which facilitate reductive elimination from a destabilized metal center. We postulated that a general and complementary method for carbon-nitrogen bond formation could be developed through the destabilization of a metal amido complex via photoredox catalysis, thus providing an alternative approach to the use of structurally complex ligand systems. Here, we report the development of a distinct mechanistic paradigm for Aryl amination using ligand-free nickel(II) salts, in which facile reductive elimination from the nickel metal center is induced via a photoredox-catalyzed electron-transfer event.Aryl amination using ligand-free Ni(II) salts and photoredox catalysisPhotocatalyst264201630#N/AFALSE
880
science.aay844710.1126/science.aay8447FALSEhttps://doi.org/10.1126/science.aay8447Li, LDScienceThe efficient removal of alkyne impurities for the production of polymer-grade lower olefins remains an important and challenging goal for many industries. We report a strategy to control the pore interior of faujasite (FAU) zeolites by the confinement of isolated open nickel(II) sites in their six-membered rings. Under ambient conditions, Ni@FAU showed remarkable adsorption of alkynes and efficient separations of acetylene/ethylene, propyne/propylene. and butyne/1,3-butadiene mixtures, with unprecedented dynamic separation selectivities of 100, 92, and 83, respectively. In situ neutron diffraction and inelastic neutron scattering revealed that confined nickel(II) sites enabled chemoselective and reversible binding to acetylene through the formation of metastable [Ni(II)(C2H2)(3)] complexes. Control of the chemistry of pore interiors of easily scalable zeolites has unlocked their potential in challenging industrial separations.Control of zeolite pore interior for chemoselective alkyne/olefin separationsx30202055#N/AFALSE
881
science.aax584310.1126/science.aax5843FALSEhttps://doi.org/10.1126/science.aax5843Mirkin, CAScienceTetrahexahedral partiCles (similar to 10 to similar to 500 nanometers) composed of platinum (Pt), palladium, rhodium, nickel, and cobalt, as well as a library of bimetallic compositions, were synthesized on silicon wafers and on catalytic supports by a ligand-free, solid-state reaction that used trace elements [antimony (Sb), bismuth (Bi), lead, or tellurium] to stabilize high-index facets. Both simulation and experiment confirmed that this method stabilized the {210} planes. A study of the PtSb system showed that the tetrahexahedron shape resulted from the evaporative removal of Sb from the initial alloy-a shape-regulating process fundamentally different from solution-phase, ligand-dependent processes. The current density at a fixed potential for the electro-oxidation of formic acid with a commercial Pt/carbon catalyst increased by a factor of 20 after transformation with Bi into tetrahexahedral partiCles.Shape regulation of high-index facet nanopartiCles by dealloyingx43201942#N/AFALSE
882
science.aav161010.1126/science.aav1610FALSEhttps://doi.org/10.1126/science.aav1610Schoenebeck, FE-Olefins through intramolecular radical relocationx2019#N/AFALSE
883
science.aae042710.1126/science.aae0427FALSEhttps://doi.org/10.1126/science.aae0427Morandi, BScienceNitriles and alkenes are important synthetic intermediates with complementary reactivity that play a central role in the preparation of materials, pharmaceuticals, cosmetics, and agrochemicals. Here, we report a nickel-catalyzed transfer hydrocyanation reaction between a wide range (60 examples) of Alkyl nitriles and alkenes. This strategy not only overcomes the toxicity challenge posed by the use of HCN in traditional approaches, but also encompasses distinct chemical advances, inCluding retro-hydrocyanation and anti-Markovnikov regioselectivity. In a broader context, this work highlights an approach to the reversible hydrofunctionalization of alkenes through thermodynamically controlled transfer reactions to circumvent the use of volatile and hazardous reagents in the laboratory.ORGANIC CHEMISTRY Catalytic reversible alkene-nitrile interconversion through controllable transfer hydrocyanationx146201639#N/AFALSE
884
science.aar733510.1126/science.aar7335FALSEhttps://doi.org/10.1126/science.aar7335Baran, PSScienceCross-coupling chemistry is widely applied to carbon-carbon bond formation in the synthesis of medicines, agrochemicals, and other functional materials. Recently, single-electron-induced variants of this reaction Class have proven particularly useful in the formation of C(sp(2))-C(sp(3)) linkages, although certain compound Classes have remained a challenge. Here, we report the use of sulfones to activate the Alkyl coupling partner in nickel-catalyzed radical cross-coupling with Aryl zinc reagents. This method's tolerance of fluoroAlkyl substituents proved particularly advantageous for the streamlined preparation of pharmaceutically oriented fluorinated scaffolds that previously required multiple steps, toxic reagents, and nonmodular retrosynthetic blueprints. Five specific sulfone reagents facilitate the rapid assembly of a vast set of compounds, many of which contain challenging fluorination patterns.Modular radical cross-coupling with sulfones enables access to sp(3)-rich (fluoro)Alkylated scaffoldsx84201840#N/AFALSE
885
science.aac834310.1126/science.aac8343FALSEhttps://doi.org/10.1126/science.aac8343Chang, CJScienceConversion of carbon dioxide (CO2) to carbon monoxide (CO) and other value-added carbon products is an important challenge for Clean energy research. Here we report modular optimization of covalent organic frameworks (COFs), in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO. The catalysts exhibit high Faradaic efficiency (90%) and turnover numbers (up to 290,000, with initial turnover frequency of 9400 hour(-1)) at pH 7 with an overpotential of -0.55 volts, equivalent to a 26-fold improvement in activity compared with the molecular cobalt complex, with no degradation over 24 hours. X-ray absorption data reveal the influence of the COF environment on the electronic structure of the catalytic cobalt centers.Covalent organic frameworks comprising cobalt porphyrins for catalytic CO2 reduction in waterx1264201547#N/AFALSE
886
science.aao502310.1126/science.aao5023FALSEhttps://doi.org/10.1126/science.aao5023McFarland, EWScienceMetals that are active catalysts for methane (Ni, Pt, Pd), when dissolved in inactive low-melting temperature metals (In, Ga, Sn, Pb), produce stable molten metal alloy catalysts for pyrolysis of methane into hydrogen and carbon. All solid catalysts previously used for this reaction have been deactivated by carbon deposition. In the molten alloy system, the insoluble carbon floats to the surface where it can be skimmed off. A 27% Ni-73% Bi alloy achieved 95% methane conversion at 1065 degrees C in a 1.1-meter bubble column and produced pure hydrogen without CO2 or other by-products. Calculations show that the active metals in the molten alloys are atomically dispersed and negatively charged. There is a correlation between the amount of charge on the atoms and their catalytic activity.Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbonx119201727#N/AFALSE
887
science.aaa452610.1126/science.aaa4526FALSEhttps://doi.org/10.1126/science.aaa4526Sanford, MSScienceHomogeneous nickel catalysis is used for the synthesis of pharmaceuticals, natural products, and polymers. These reactions generally proceed via nickel intermediates in the Ni-O, Ni-I, Ni-II, and/or Ni-III oxidation states. In contrast, Ni-IV intermediates are rarely accessible. We report herein the design, synthesis, and characterization of a series of organometallic Ni-IV complexes, accessed by the reaction of Ni-II precursors with the widely used oxidant S-(trifluoromethyl) dibenzothiophenium triflate. These Ni-IV complexes undergo highly selective carbon(sp(3))-oxygen, carbon(sp(3))-nitrogen, and carbon(sp(3))-sulfur coupling reactions with exogenous nuCleophiles. The observed reactivity has the potential for direct applications in the development of nickel-catalyzed carbon-hetero-atom coupling reactions.Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexesx153201539#N/AFALSE
888
science.aan156810.1126/science.aan1568FALSEhttps://doi.org/10.1126/science.aan1568Hartwig, JFScienceWe present an approach to multidimensional high-throughput discovery of catalytic coupling reactions that integrates molecular design with automated analysis and interpretation of mass spectral data. We simultaneously assessed the reactivity of three pools of compounds that shared the same functional groups (halides, boronic acids, alkenes, and alkynes, among other groups) but carried inactive substituents having specifically designed differences in masses. The substituents were chosen such that the products from any Class of reaction in multiple reaction sets would have unique differences in masses, thus allowing simultaneous identification of the products of all transformations in a set of reactants. In this way, we easily distinguished the products of new reactions from noise and known couplings. Using this method, we discovered an alkyne hydroallylation and a nickel-catalyzed variant of alkyne diArylation.Snap deconvolution: An informatics approach to high-throughput discovery of catalytic reactionsx44201737#N/AFALSE
889
science.aal130310.1126/science.aal1303FALSEhttps://doi.org/10.1126/science.aal1303Wang, WYScienceThe redox state of Earth's convecting mantle, masked by the lithospheric plates and basaltic magmatism of plate tectonics, is a key unknown in the evolutionary history of our planet. Here we report that large, exceptional gem diamonds like the Cullinan, Constellation, and Koh-i-Noor carry direct evidence of crystallization from a redox-sensitive metallic liquid phase in the deep mantle. These sublithospheric diamonds contain inClusions of solidified iron-nickel-carbon-sulfur melt, accompanied by a thin fluid layer of methane +/- hydrogen, and sometimes majoritic garnet or former calcium silicate perovskite. The metal-dominated mineral assemblages and reduced volatiles in large gem diamonds indicate formation under metal-saturated conditions. We verify previous predictions that Earth has highly reducing deep mantle regions capable of precipitating a metallic iron phase that contains dissolved carbon and hydrogen.Large gem diamonds from metallic liquid in Earth's deep mantle175201631#N/ATRUE
890
science.817133410.1126/science.8171334FALSEhttps://doi.org/10.1126/science.8171334SPIRO, TGScienceCarbon monoxide dehydrogenase catalyzes the synthesis of acetyl-coenzyme A from coenzyme A, a methyl group, and carbon monoxide. The carbon monoxide binds to a mixed metal center of the enzyme, which contains nickel bridged to an iron-sulfur Cluster. Resonance Raman spectroscopy has been used to identify both C-O stretching and metal-CO stretching vibrations of the carbon monoxide adduct of the enzyme. This adduct was shown by isotopic exchange to be on the pathway for acetyl-coenzyme A synthesis. The metal to which carbon monoxide is bound was established to be iron, not nickel, by preparation of enzyme from bacteria grown on iron-54 and nickel-64. The Fe-CO frequency is low, 360 wave numbers, implying a weak bond, probably because of electron donation from sulfide and thiolate ligands of the iron. A bimetallic mechanism is proposed, in which carbon monoxide binds to an iron atom and is subsequently attacked by a methyl group on a nearby nickel atom, forming an acetyl ligand, which is then transferred to coenzyme A.NATURES CarbonylATION CATALYST - RAMAN-SPECTROSCOPIC EVIDENCE THAT CARBON-MONOXIDE BINDS TO IRON, NOT NICKEL, IN CO DEHYDROGENASEx58199424#N/AFALSE
891
science.aak999110.1126/science.aak9991FALSEhttps://doi.org/10.1126/science.aak9991Rolison, DRScienceThe next generation of high-performance batteries should inClude alternative chemistries that are inherently safer to operate than nonaqueous lithium-based batteries. Aqueous zinc-based batteries can answer that challenge because monolithic zinc sponge anodes can be cyCled in nickel-zinc alkaline cells hundreds to thousands of times without undergoing passivation or macroscale dendrite formation. We demonstrate that the three-dimensional (3D) zinc form-factor elevates the performance of nickel-zinc alkaline cells in three fields of use: (i) > 90% theoretical depth of discharge (DODZn) in primary (single-use) cells, (ii) > 100 high-rate cyCles at 40% DODZn at lithium-ion-commensurate specific energy, and (iii) the tens of thousands of power-demanding duty cyCles required for start-stop microhybrid vehiCles.Rechargeable nickel-3D zinc batteries: An energy-dense, safer alternative to lithium-ion488201730#N/ATRUE
892
science.aah716110.1126/science.aah7161FALSEhttps://doi.org/10.1126/science.aah7161Marin, GBScienceEfficient CO2 transformation from a waste product to a carbon source for chemicals and fuels will require reaction conditions that effect its reduction. We developed a super-dry CH4 reforming reaction for enhanced CO production from CH4 and CO2. We used Ni/MgAl2O4 as a CH4-reforming catalyst, Fe2O3/MgAl2O4 as a solid oxygen carrier, and CaO/Al2O3 as a CO2 sorbent. The isothermal coupling of these three different processes resulted in higher CO production as compared with that of conventional dry reforming, by avoiding back reactions with water. The reduction of iron oxide was intensified through CH4 conversion to syngas over Ni and CO2 extraction and storage as CaCO3. CO2 is then used for iron reoxidation and CO production, exploiting equilibrium shifts effected with inert gas sweeping (Le Chatelier's principle). Super-dry reforming uses up to three CO2 molecules per CH4 and offers a high CO space-time yield of 7.5 millimole CO per second per kilogram of iron at 1023 kelvin.Super-dry reforming of methane intensifies CO2 utilization via Le Chatelier's principle177201622#N/ATRUE
893
science.aah613310.1126/science.aah6133FALSE#REF!Huang, XQBiaxially strained PtPb/Pt core/shell nanoplate boosts oxygen reduction catalysis2016#N/ATRUE
894
science.aag294710.1126/science.aag2947FALSEhttps://doi.org/10.1126/science.aag2947Mansoorabadi, SOThe biosynthetic pathway of coenzyme F430 in methanogenic and methanotrophic archaea2016#N/ATRUE
895
science.287.5452.46010.1126/science.287.5452.460FALSEhttps://doi.org/10.1126/science.287.5452.460Bansleben, DANeutral, single-component nickel (II) polyolefin catalysts that tolerate heteroatomsx2000#N/AFALSE
896
science.aaf632310.1126/science.aaf6323FALSEhttps://doi.org/10.1126/science.aaf6323Eddaoudi, MScienceThe chemical industry is dependent on the olefin/paraffin separation, which is mainly accomplished by using energy-intensive processes. We report the use of reticular chemistry for the fabrication of a chemically stable fluorinated metal-organic framework (MOF) material (NbOFFIVE-1-Ni, also referred to as KAUST-7). The bridging of Ni(II)-pyrazine square-grid layers with (NbOF5)(2-) pillars afforded the construction of a three-dimensional MOF, enClosing a periodic array of fluoride anions in contracted square-shaped channels. The judiciously selected bulkier (NbOF5)(2-) caused the looked-for hindrance of the previously free-rotating pyrazine moieties, delimiting the pore system and dictating the pore aperture size and its maximum opening. The restricted MOF window resulted in the selective molecular exClusion of propane from propylene at atmospheric pressure, as evidenced through multiple cyClic mixed-gas adsorption and calorimetric studies.A metal-organic framework-based splitter for separating propylene from propane529201630#N/ATRUE
897
science.285.5430.105510.1126/science.285.5430.1055FALSEhttps://doi.org/10.1126/science.285.5430.1055Berndt, MEScienceRecently, methane (CH4) of possible abiogenic origin has been reported from many Localities within Earth's crust, However, little is known about the mechanisms of abiogenic methane formation, or about isotopic fractionation during such processes. Here, a hydrothermally formed nickel-iron alloy was shown to catalyze the otherwise prohibitively slow formation of abiogenic CH4 from dissolved bicarbonate (HCO3-) under hydrothermal conditions. Isotopic fractionation by the catalyst resulted in delta(13)C values of the CH4 formed that are as Low as those typically observed for microbial methane, with similarly high CH4/(C2H6 + C3H8) ratios. These results, combined with the increasing recognition of nickel-iron alloy occurrence in oceanic crusts, suggest that abiogenic methane may be more widespread than previously thought.Abiogenic methane formation and isotopic fractionation under hydrothermal conditionsx433199949#N/AFALSE
898
science.aaf152510.1126/science.aaf1525FALSEhttps://doi.org/10.1126/science.aaf1525Sargent, EHScienceEarth-abundant first-row (3d) transition metal-based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing nearoptimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 millivolts) reported at 10 milliamperes per square centimeter in alkaline electrolyte. The catalyst shows no evidence of degradation after more than 500 hours of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER.Homogeneously dispersed multimetal oxygen-evolving catalysts1157201629#N/ATRUE
899
science.aaf061610.1126/science.aaf0616FALSEhttps://doi.org/10.1126/science.aaf0616Ragsdale, SWScienceMethyl-coenzyme M reductase, the rate-limiting enzyme in methanogenesis and anaerobic methane oxidation, is responsible for the biological production of more than 1 billion tons of methane per year. The mechanism of methane synthesis is thought to involve either methyl-nickel(III) or methyl radical/Ni(II)-thiolate intermediates. We employed transient kinetic, spectroscopic, and computational approaches to study the reaction between the active Ni(I) enzyme and substrates. Consistent with the methyl radical-based mechanism, there was no evidence for a methyl-Ni(III) species; furthermore, magnetic circular dichroism spectroscopy identified the Ni(II)-thiolate intermediate. Temperature-dependent transient kinetics also Closely matched density functional theory predictions of the methyl radical mechanism. Identifying the key intermediate in methanogenesis provides fundamental insights to develop better catalysts for producing and activating an important fuel and potent greenhouse gas.The radical mechanism of biological methane synthesis by methyl-coenzyme M reductase76201648#N/ATRUE
900
science.aad551310.1126/science.aad5513FALSEhttps://doi.org/10.1126/science.aad5513Rudnick, RLScienceThe Archean Eon witnessed the production of early continental crust, the emergence of life, and fundamental changes to the atmosphere. The nature of the first continental crust, which was the interface between the surface and deep Earth, has been obscured by the weathering, erosion, and tectonism that followed its formation. We used Ni/Co and Cr/Zn ratios in Archean terrigenous sedimentary rocks and Archean igneous/metaigneous rocks to track the bulk MgO composition of the Archean upper continental crust. This crust evolved from a highly mafic bulk composition before 3.0 billion years ago to a felsic bulk composition by 2.5 billion years ago. This compositional change was attended by a fivefold increase in the mass of the upper continental crust due to addition of granitic rocks, suggesting the onset of global plate tectonics at similar to 3.0 billion years ago.Archean upper crust transition from mafic to felsic marks the onset of plate tectonics216201631#N/ATRUE
901
science.280.5368.142710.1126/science.280.5368.1427FALSEhttps://doi.org/10.1126/science.280.5368.1427Nolte, RJMScienceAmphiphilic block copolymers containing a poly(styrene) tail and a charged helical poly(isocyanide) headgroup derived from isocyano-L-alanine-L-alanine and isocyano-L-alanine-L-histidine were prepared. Analogous to low-molecular mass surfactants, these block copolymers self-assembled in aqueous systems to form micelles, vesiCles, and bilayer aggregates. The morphology of these aggregates can be controlled by variation of the length of the poly(isocyanide) block, the pH, and the anion-headgroup interactions. The chirality of the macromolecules results in the formation of helical superstructures that have a helical sense opposite to that of the constituent block copolymers. The great variety of morphologies displayed by these block copolymers and the fact that they are easily accessible from poly(styrene) and different types of peptides open new opportunities for applications in the fields of life and materials sciences.Helical superstructures from charged poly(styrene)-poly(isocyanodipeptide) block copolymersx552199832#N/AFALSE
902
science.aaa876510.1126/science.aaa8765FALSEhttps://doi.org/10.1126/science.aaa8765Huang, YScienceBimetallic platinum-nickel (Pt-Ni) nanostructures represent an emerging Class of electrocatalysts for oxygen reduction reaction (ORR) in fuel cells, but practical applications have been limited by catalytic activity and durability. We surface-doped Pt3Ni octahedra supported on carbon with transition metals, termed M-Pt3Ni/C, where M is vanadium, chromium, manganese, iron, cobalt, molybdenum (Mo), tungsten, or rhenium. The Mo-Pt3Ni/C showed the best ORR performance, with a specific activity of 10.3 mA/cm(2) and mass activity of 6.98 A/mg(Pt), which are 81- and 73-fold enhancements compared with the commercial Pt/C catalyst (0.127 mA/cm(2) and 0.096 A/mg(Pt)). Theoretical calculations suggest that Mo prefers subsurface positions near the partiCle edges in vacuum and surface vertex/edge sites in oxidizing conditions, where it enhances both the performance and the stability of the Pt3Ni catalyst.High-performance transition metal-doped Pt3Ni octahedra for oxygen reduction reaction1111201538#N/ATRUE
903
science.279.5358.191310.1126/science.279.5358.1913FALSEhttps://doi.org/10.1126/science.279.5358.1913Stensgaard, IScienceDetailed studies of elementary chemical processes on well-characterized single crystal surfaces have contributed substantially to the understanding of heterogeneous catalysis. insight into the structure of surface alloys combined with an understanding of the relation between the surface composition and reactivity is shown to lead directly to new ideas for catalyst design, The feasibility of such an approach is illustrated by the synthesis, characterization, and tests of a high-surface area gold-nickel catalyst for steam reforming.Design of a surface alloy catalyst for steam reformingx840199828#N/AFALSE
904
science.278.5345.193110.1126/science.278.5345.1931FALSEhttps://doi.org/10.1126/science.278.5345.1931Ertl, GScienceThe catalytic oxidation of carbon monoxide (CO) on a platinum (111) surface was studied by scanning tunneling microscopy. The adsorbed oxygen atoms and CO molecules were imaged with atomic resolution, and their reactions to carbon dioxide (CO2) were monitored as functions of time. The results allowed the formulation of a rate law that takes the distribution of the reactants in separate domains into account. From temperature-dependent measurements, the kinetic parameters were obtained. Their values agree well with data from macroscopic measurements. In this way, a kinetic description of a chemical reaction was achieved that is based solely on the statistics of the underlying atomic processes.Atomic and macroscopic reaction rates of a surface-catalyzed reactionx287199727#N/AFALSE
905
science.276.5315.109710.1126/science.276.5315.1097FALSEhttps://doi.org/10.1126/science.276.5315.1097Wark, JSScienceA saturated nickel-like samarium x-ray laser beam at 7 nanometers has been demonstrated with an output energy of 0.3 millijoule in 50-picosecond pulses, demonstrating that saturated operation of a laser at wavelengths shorter than 10 nanometers can be achieved. The narrow divergence, short wavelength, short pulse duration, high efficiency, and high brightness of this samarium laser make it an ideal candidate for many x-ray laser applications.A saturated X-ray laser beam at 7 nanometersx202199727#N/AFALSE
906
science.273.5274.48310.1126/science.273.5274.483FALSEhttps://doi.org/10.1126/science.273.5274.483Smalley, REScienceFullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200 degrees C. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and thai they self-organize into ''ropes,'' which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C-5v symmetry and an open edge stabilized by triple bonds.Crystalline ropes of metallic carbon nanotubesx5012199631#N/AFALSE
907
science.841849910.1126/science.8418499FALSEhttps://doi.org/10.1126/science.8418499KATER, SBScienceA myelin-associated protein from the central nervous system, the neurite growth inhibitor NI-35, inhibits regeneration of lesioned neuronal fiber tracts in vivo and growth of neurites in vitro. Growth cones of cultured rat dorsal root ganglion neurons arrested their growth and collapsed when exposed to liposomes containing NI-35. Before morphological changes, the concentration of free intracellular calcium ([Ca2+]i) showed a rapid and large increase.in growth cones exposed to liposomes containing NI-35. Neither an increase in [Ca2+]i nor collapse of growth cones was detected in the presence of antibodies to NI-35. Dantrolene, an inhibitor of calcium release from caffeine-sensitive intracellular calcium stores, protected growth cones from collapse evoked by NI-35. Depletion of these caffeine-sensitive intracellular calcium stores prevented the increase in [Ca2+]i evoked by NI-35. The NI-35-evoked cascade of intracellular messengers that mediates collapse of growth cones inCludes the crucial step of calcium release from intracellular stores.ROLE OF INTRACELLULAR CALCIUM IN NI-35-EVOKED COLLAPSE OF NEURONAL GROWTH CONES247199361#N/ATRUE
908
science.838812510.1126/science.8388125FALSEhttps://doi.org/10.1126/science.8388125SNUTCH, TPScienceOscillatory firing patterns are an intrinsic property of some neurons and have an important function in information processing. In some cells, low voltage-activated calcium channels have been proposed to underlie a depolarizing potential that regulates bursting. The sequence of a rat brain calcium channel alpha1 subunit (rbE-II) was deduced. Although it is structurally related to high voltage-activated calcium channels, the rbE-II channel transiently activated at negative membrane potentials, required a strong hyperpolarization to deinactivate, and was highly sensitive to block by nickel. In situ hybridization showed that rbE-II messenger RNA is expressed in regions throughout the central nervous system. The electrophysiological properties of the rbE-II current are consistent with a type of low voltage-activated calcium channel that,requires membrane hyperpolarization for maximal activity, which suggests that rbE-II may be involved in the modulation of firing patterns.STRUCTURE AND FUNCTIONAL EXPRESSION OF A MEMBER OF THE LOW-VOLTAGE ACTIVATED CALCIUM-CHANNEL FAMILY480199341#N/ATRUE
909
science.785559310.1126/science.7855593FALSEhttps://doi.org/10.1126/science.7855593HAUSINGER, RPREQUIREMENT OF CARBON-DIOXIDE FOR IN-VITRO ASSEMBLY OF THE UREASE NICKEL METALLOCENTER1995#N/ATRUE
910
science.291.5502.28510.1126/science.291.5502.285FALSEhttps://doi.org/10.1126/science.291.5502.285Kobayashi, AScienceMolecular metals normally require charge transfer between two different chemical species. We prepared crystals of [Ni(tmdt)(2)] (tmdt, trimethylenetetrathiafulvalenedithiolate) and carried out crystal structure analyses and resistivity measurements. The analyses and measurements revealed that these single-component molecular crystals are metallic from room temperature down to 0.6 kelvin. Ab initio molecular orbital calculations suggested that pi molecular orbitals form conduction bands. The compact molecular arrangement, intermolecular overlap integrals of the highest occupied and Lowest unoccupied molecular orbitals, and tight-binding electronic band structure calculation revealed that [Ni(tmdt)(2)] is a three-dimensional synthetic metal composed of planar molecules.A three-dimensional synthetic metallic crystal composed of single-component molecules430200114#N/ATRUE
911
science.291.5501.10610.1126/science.291.5501.106FALSEhttps://doi.org/10.1126/science.291.5501.106Stiefel, EIScienceThe complex Ni[S2C2(CF3)(2)](2) reacts with tight olefins, inCluding ethylene and propylene, selectively and reversibly. The reaction is not poisoned by hydrogen gas, carbon monoxide, acetylene, or hydrogen sulfide, which are commonly present in olefin streams, presumably because olefin binding occurs through the sulfur Ligand rather than the metal center. The reversible reaction of olefins with Ni[S2C2(CN)(2)](2)(n) (n = 0, -1, -2) can be controlled electrochemically, where the oxidation state-dependent binding and release of olefins are fast on the electrochemical time scale. The observed tolerance to poisons and controllable electrochemical reactivity present an alternative approach to the separation of olefins from complex streams.Toward separation and purification of olefins using dithiolene complexes: An electrochemical approach205200123#N/ATRUE
912
science.216.4552.1324
10.1126/science.216.4552.1324
FALSEhttps://doi.org/10.1126/science.216.4552.1324Wojtczak, AScienceNEW BIOLOGICAL PARAMAGNETIC CENTER - OCTAHEDRALLY COORDINATED NICKEL(III) IN THE METHANOGENIC BACTERIAx59198217#N/AFALSE
913
science.288.5467.83910.1126/science.288.5467.839FALSEhttps://doi.org/10.1126/science.288.5467.839Keil, KScienceChemical zoning patterns in some iron, nickel metal grains from CH carbonaceous chondrites imply formation at temperatures from 1370 to 1270 kelvin by condensation from a solar nebular gas cooling at a rare of similar to 0.2 kelvin per hour. This cooling rate requires a Large-scale thermal event in the nebula, in contrast to the localized, transient heating events inferred for chondrule formation. In our model, mass accretion through the protoplanetary disk caused Large-scale evaporation of precursor dust near its midplane inside of a few astronomical units. Gas convectively moved from the midplane to cooler regions above it, and the metal grains condensed in these parcels of rising gas.Large-scale thermal events in the solar nebula: Evidence from Fe,Ni metal grains in primitive meteorites67200027#N/ATRUE
914
science.287.5451.28210.1126/science.287.5451.282FALSEhttps://doi.org/10.1126/science.287.5451.282Fisher, NSScienceUnderstanding how animals are exposed to the Large repository of metal pollutants in aquatic sediments is complicated and is important in regulatory decisions. Experiments with four types of invertebrates showed that feeding behavior and dietary uptake control bioaccumulation of cadmium, silver, nickel, and zinc. Metal concentrations in animal tissue correlated with metal concentrations extracted from sediments, but not with metal in porewater, across a range of reactive sulfide concentrations, from 0.5 to 30 micromoles per gram. These results contradict the notion that metal bioavailability in sediments is controlled by geochemical equilibration of metals between porewater and reactive sulfides, a proposed basis for regulatory criteria for metals.Influences of dietary uptake and reactive sulfides on metal bioavailability from aquatic sediments210200023#N/ATRUE
915
science.125364710.1126/science.1253647https://doi.org/10.1126/science.1253647Molander, GAScienceThe routine application of C-sp3-hybridized nuCleophiles in cross-coupling reactions remains an unsolved challenge in organic chemistry. The sluggish transmetalation rates observed for the preferred organB(OH)2ron reagents in such transformations are a consequence of the two-electron mechanism underlying the standard catalytic approach. We describe a mechanistically distinct single-electron transfer-based strategy for the Activation of organB(OH)2ron reagents toward transmetalation that exhibits complementary reactivity patterns. Application of an iridium photoredox catalyst in tandem with a nickel catalyst effects the cross-coupling of potassium alkoxyAlkyl- and BenzyltrifluorB(OH)2rates with an array of Aryl bromides under exceptionally mild conditions (visible light, ambient temperature, no strong base). The transformation has been extended to the asymmetric and stereoconvergent cross-coupling of a secondary BenzyltrifluorB(OH)2rate.Single-electron transmetalation in organB(OH)2ron cross-coupling by photoredox/nickel dual catalysisPhotocatalyst6882014337/28/2022FALSE
916
science.125142810.1126/science.1251428https://doi.org/10.1126/science.1251428Lewis, NSScienceAlthough semiconductors such as silicon (Si), gallium arsenide (GaAs), and gallium phosphide (GaP) have band gaps that make them efficient photoanodes for solar fuel production, these materials are unstable in aqueous media. We show that TiO2 coatings (4 to 143 nanometers thick) grown by atomic layer deposition prevent corrosion, have electronic defects that promote hole conduction, and are sufficiently transparent to reach the light-limited performance of protected semiconductors. In conjunction with a thin layer or islands of Ni oxide electrocatalysts, Si photoanodes exhibited continuous oxidation of 1.0 molar aqueous KOH to O-2 for more than 100 hours at photocurrent densities of >30 milliamperes per square centimeter and similar to 100% Faradaic efficiency. TiO2-coated GaAs and GaP photoelectrodes exhibited photovoltages of 0.81 and 0.59 V and light-limiting photocurrent densities of 14.3 and 3.4 milliamperes per square centimeter, respectively, for water oxidation.Amorphous TiO2 coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidationPhotocatalyst911201430#N/AFALSE
917
science.285.5424.8510.1126/science.285.5424.85FALSEhttps://doi.org/10.1126/science.285.5424.85Fifield, LKScienceTwo main types of material survive from the Canyon Diablo impactor, which produced Meteor Crater in Arizona: iron meteorites, which did not melt during the impact; and spheroids, which did. Ultrasensitive measurements using accelerator mass spectrometry show that the meteorites contain about seven times as much nickel-59 as the spheroids. Lower average nickel-59 contents in the spheroids indicate that they typically came from 0.5 to 1 meter deeper in the impactor than did the meteorites. Numerical modeling for an impact velocity of 20 kilometers per second shows that a shell 1.5 to 2 meters thick, corresponding to 16 percent of the projectile volume, remained solid on the rear surface; that most of the projectile melted; and that little, if any, vaporized.Shock melting of the Canyon Diablo Impactor: Constraints from nickel-59 contents and numerical modeling17199939#N/ATRUE
918
science.282.5391.110510.1126/science.282.5391.1105FALSE#REF!Provencio, PNSynthesis of large arrays of well-aligned carbon nanotubes on glass1998#N/ATRUE
919
science.124132710.1126/science.1241327https://doi.org/10.1126/science.1241327Dai, HJScienceSilicon's sensitivity to corrosion has hindered its use in photoanode applications. We found that deposition of a similar to 2-nanometer nickel film on n-type silicon (n-Si) with its native oxide affords a high-performance metal-insulator-semiconductor photoanode for photoelectrochemical (PEC) water oxidation in both aqueous potassium hydroxide (KOH, pH = 14) and aqueous borate buffer (pH = 9.5) solutions. The Ni film acted as a surface protection layer against corrosion and as a nonprecious metal electrocatalyst for oxygen evolution. In 1 M aqueous KOH, the Ni/n-Si photoanodes exhibited high PEC activity with a low onset potential (similar to 1.07 volts versus reversible hydrogen electrode), high photocurrent density, and durability. The electrode showed no sign of decay after similar to 80 hours of continuous PEC water oxidation in a mixed lithium borate-potassium borate electrolyte. The high photovoltage was attributed to a high built-in potential in a metal-insulator-semiconductor-like device with an ultrathin, incomplete screening Ni/NiOx layer from the electrolyte.High-Performance Silicon Photoanodes Passivated with Ultrathin Nickel Films for Water OxidationPhotocatalyst485201329#N/AFALSE
920
science.124014810.1126/science.1240148FALSEhttps://doi.org/10.1126/science.1240148Murray, CBScienceInteractions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions. However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts. We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals. We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, Clarifying the pivotal role played by the support.Control of Metal Nanocrystal Size Reveals Metal-Support Interface Role for Ceria Catalystsx785201326#N/AFALSE
921
science.122821110.1126/science.1228211FALSEhttps://doi.org/10.1126/science.1228211Williams, QScienceThe size of nanocrystals provides a limitation on dislocation activity and associated stress-induced deformation. Dislocation-mediated plastic deformation is expected to become inactive below a critical partiCle size, which has been proposed to be between 10 and 30 nanometers according to computer simulations and transmission electron microscopy analysis. However, deformation experiments at high pressure on polycrystalline nickel suggest that dislocation activity is still operative in 3-nanometer crystals. Substantial texturing is observed at pressures above 3.0 gigapascals for 500-nanometer nickel and at greater than 11.0 gigapascals for 20-nanometer nickel. Surprisingly, texturing is also seen in 3-nanometer nickel when compressed above 18.5 gigapascals. The observations of pressure-promoted texturing indicate that under high external pressures, dislocation activity can be extended down to a few-nanometers-length scale.Texture of Nanocrystalline Nickel: Probing the Lower Size Limit of Dislocation Activityx82201226#N/AFALSE
922
science.122777510.1126/science.1227775https://doi.org/10.1126/science.1227775Krauss, TDScienceHomogeneous systems for light-driven reduction of protons to H-2 typically suffer from short lifetimes because of decomposition of the light-absorbing molecule. We report a robust and highly active system for solar hydrogen generation in water that uses CdSe nanocrystals capped with dihydrolipoic acid (DHLA) as the light absorber and a soluble Ni2+-DHLA catalyst for proton reduction with ascorbic acid as an electron donor at pH = 4.5, which gives >600,000 turnovers. Under appropriate conditions, the precious-metal-free system has undiminished activity for at least 360 hours under illumination at 520 nanometers and achieves quantum yields in water of over 36%.Robust Photogeneration of H-2 in Water Using Semiconductor Nanocrystals and a Nickel CatalystPhotocatalystx587201227#N/AFALSE
923
science.281.5377.67010.1126/science.281.5377.670FALSEhttps://doi.org/10.1126/science.281.5377.670Wachtershauser, GScienceIn experiments modeling volcanic or hydrothermal settings amino acids were converted into their peptides by use of coprecipitated (Ni,Fe)S and CO in conjunction with H2S (or CH3SH) as a catalyst and condensation agent at 100 degrees C and pH 7 to 10 under anaerobic, aqueous conditions. These results demonstrate that amino acids can be activated under geochemically relevant conditions. They support a thermophilic origin of Life and an early appearance of peptides in the evolution of a primordial metabolism.Peptides by Activation of amino acids with CO on (Ni,Fe)S surfaces: Implications for the origin of life441199816#N/ATRUE
924
science.280.5368.141810.1126/science.280.5368.1418FALSEhttps://doi.org/10.1126/science.280.5368.1418El Goresy, AScienceOptical and scanning electron microscopy of a chondrule-free Clast in the unequilibrated L3 chondrite Khohar revealed a spherical object consisting of an aggregate of small (similar to 2-micrometer diameter), Ni-poor (0.5 to 2.89 weight percent) metal partiCles and fine-grained graphite (< 1-micrometer diameter). The graphite has large D and N-15 excesses (delta D similar to 1500 per mil and delta(15)N similar to 1300 per mil) with two isotopically distinct signatures: N rich with a high D/H ratio and N poor with a high N-15/N-14 ratio. These excesses are the largest D and N-15 excesses observed in situ in a well-characterized phase in a meteorite. The isotopic characteristics are suggestive of an interstellar origin, probably by ion-molecule reactions at low temperature in the interstellar molecular Cloud from which the solar system formed. The structure and nonchondritic composition of the metal partiCles suggest they did not form under equilibrium conditions in the solar nebula.In situ discovery of graphite with interstellar isotopic signatures in a chondrule-free Clast in an L3 chondrite17199818#N/ATRUE
925
science.272.5266.131410.1126/science.272.5266.1314FALSEhttps://doi.org/10.1126/science.272.5266.1314Lewis, RSType II supernova matter in a silicon carbide grain from the Murchison meteorite1996#N/ATRUE
926
science.120586410.1126/science.1205864FALSEhttps://doi.org/10.1126/science.1205864DuBois, DLScienceReduction of acids to molecular hydrogen as a means of storing energy is catalyzed by platinum, but its low abundance and high cost are problematic. Precisely controlled delivery of protons is critical in hydrogenase enzymes in nature that catalyze hydrogen (H-2) production using earth-abundant metals (iron and nickel). Here, we report that a synthetic nickel complex, [Ni((P2NPh)-N-Ph)(2)](BF4)(2), ((P2NPh)-N-Ph = 1,3,6-triphenyl-1-aza-3,6-diphosphacyCloheptane), catalyzes the production of H2 using protonated dimethylformamide as the proton source, with turnover frequencies of 33,000 per second (s(-1)) in dry acetonitrile and 106,000 s(-1) in the presence of 1.2 M of water, at a potential of -1.13 volt (versus the ferrocenium/ferrocene couple). The mechanistic implications of these remarkably fast catalysts point to a key role of pendant amines that function as proton relays.A Synthetic Nickel Electrocatalyst with a Turnover Frequency Above 100,000 s(-1) for H-2 Productionx814201129#N/AFALSE
927
science.120223210.1126/science.1202232FALSEhttps://doi.org/10.1126/science.1202232Ishida, KScienceIn superelastic alloys, large deformation can revert to a memorized shape after removing the stress. However, the stress increases with increasing temperature, which limits the practical use over a wide temperature range. Polycrystalline Fe-Mn-Al-Ni shape memory alloys show a small temperature dependence of the superelastic stress because of a small transformation entropy change brought about by a magnetic contribution to the Gibbs energies. For one alloy composition, the superelastic stress varies by 0.53 megapascal/degrees C over a temperature range from -196 to 240 degrees C.Superelastic Effect in Polycrystalline Ferrous Alloysx234201126#N/AFALSE
928
science.269.5222.37110.1126/science.269.5222.371FALSEhttps://doi.org/10.1126/science.269.5222.371Schnurch, MScienceSwitching behavior between electron tunneling and ballistic transport states was induced by repeatedly bringing a sharpened nickel wire into contact with a gold surface. The high-conductivity ballistic state had a quantized conductance of 0.977 +/- 0.015 (2e(2)/h). Switching was accomplished by moving the electrodes with a piezoelectric actuator over a distance of 2 angstroms. The two electrodes and the actuator form a three-terminal device that is demonstrated to be a reliable digital and analog switch; it shows good discrimination between high and low states and possesses the important property of power gain. The conductance channel is most likely only one atom wide and possibly consists of a single atom.QUANTUM POINT-CONTACT SWITCHES100199512#N/ATRUE
929
science.262.5131.22910.1126/science.262.5131.229FALSEhttps://doi.org/10.1126/science.262.5131.229COMBES, JMScienceX-ray absorption spectroscopy (XAS) of Fe2+ in Fe2SiO4 liquid at 1575 kelvin and 10(-4) gigapascal (1 bar) shows that the Fe2+-O bond length is 1.98 +/- 0.02 angstroms compared with almost-equal-to 2.22 angstroms in crystalline Fe2SiO4 (fayalite) at the melting point (1478 kelvin), which indicates a decrease in average Fe2+ coordination number from six in fayalite to four in the liquid. Anharmonicity in the liquid was accounted for using a data analysis procedure. This reduction in coordination number is similar to that observed on the melting of certain ionic salts. These results are used to develop a model of the medium-range structural environment of Fe2+ in olivine-composition melts, which helps explain some of the properties of Fe2SiO4 liquid, inCluding density, viscosity, and the partitioning of iron and nickel between silicate melts and crystalline olivines. Some of the implications of this model for silicate melts in the Earth's crust and mantle are discussed.HIGH-TEMPERATURE XAS STUDY OF FE2SIO4 LIQUID - REDUCED COORDINATION OF FERROUS IRON68199353#N/ATRUE
930
science.115666010.1126/science.1156660FALSEhttps://doi.org/10.1126/science.1156660Norskov, JKScienceThe removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts ( often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces. This analysis not only verified the facility of known catalysts but identified nickel- zinc alloys as alternatives. Experimental studies demonstrated that these alloys dispersed on an oxide support were selective for acetylene hydrogenation at low pressures.Identification of non-precious metal alloy catalysts for selective hydrogenation of acetylenex718200826#N/AFALSE
931
science.259.5101.159210.1126/science.259.5101.1592FALSEhttps://doi.org/10.1126/science.259.5101.1592YAMAOKA, SScienceAs diamond-producing catalysts, 12 transition metals such as iron, cobalt, and nickel were first reported by General Electric researchers more than 30 years ago. Since then, no additional elemental catalyst has been reported. An investigation of the catalytic action of group V elements is of great interest from the viewpoint of producing an n-type semiconducting diamond crystal. In the present study, diamond was synthesized from graphite in the presence of elemental phosphorus at high pressure and temperature (7.7 gigapascals and 1800-degrees-C). Furthermore, single-crystal diamond was grown on a diamond seed crystal.PHOSPHORUS - AN ELEMENTAL CATALYST FOR DIAMOND SYNTHESIS AND GROWTH85199310#N/ATRUE
932
science.257.5067.22310.1126/science.257.5067.223FALSE#REF!CEYER, STTHE CHEMISTRY OF BULK HYDROGEN - REACTION OF HYDROGEN EMBEDDED IN NICKEL WITH ADSORBED CH31992#N/ATRUE
933
science.126121210.1126/science.1261212FALSEhttps://doi.org/10.1126/science.1261212Strasser, PScienceMorphological shape in chemistry and biology owes its existence to anisotropic growth and is Closely coupled to distinct functionality. Although much is known about the principal growth mechanisms of monometallic shaped nanocrystals, the anisotropic growth of shaped alloy nanocrystals is still poorly understood. Using aberration-corrected scanning transmission electron microscopy, we reveal an element-specific anisotropic growth mechanism of platinum (Pt) bimetallic nano-octahedra where compositional anisotropy couples to geometric anisotropy. A Pt-rich phase evolves into precursor nanohexapods, followed by a slower step-induced deposition of an M-rich (M = Ni, Co, etc.) phase at the concave hexapod surface forming the octahedral facets. Our finding explains earlier reports on unusual compositional segregations and chemical degradation pathways of bimetallic polyhedral catalysts and may aid rational synthesis of shaped alloy catalysts with desired compositional patterns and properties.Element-specific anisotropic growth of shaped platinum alloy nanocrystals230201432#N/ATRUE
934
science.110738910.1126/science.1107389FALSEhttps://doi.org/10.1126/science.1107389Mao, SXScienceResponse to comment on grain boundary-mediated plasticity in nanocrystalline nickelx1320059#N/AFALSE
935
science.110714310.1126/science.1107143FALSEhttps://doi.org/10.1126/science.1107143Yan, XQScienceComment on grain boundary-mediated plasticity in nanocrystalline nickelx13200512#N/AFALSE
936
science.109874110.1126/science.1098741FALSEhttps://doi.org/10.1126/science.1098741Mao, SXScienceThe plastic behavior of crystalline materials is mainly controlled by the nuCleation and motion of lattice dislocations. We report in situ dynamic transmission electron microscope observations of nanocrystalline nickel films with an average grain size of about 10 nanometers, which show that grain boundary-mediated processes have become a prominent deformation mode. Additionally, trapped lattice dislocations are observed in individual grains following deformation. This change in the deformation mode arises from the grain size-dependent competition between the deformation controlled by nuCleation and motion of dislocations and the deformation controlled by diffusion-assisted grain boundary processes.Grain boundary-mediated plasticity in nanocrystalline nickelx724200427#N/AFALSE
937
science.109507110.1126/science.1095071FALSEhttps://doi.org/10.1126/science.1095071Schmitt, BPlastic deformation with reversible peak broadening in nanocrystalline nickelx2004#N/AFALSE
938
science.109384610.1126/science.1093846https://doi.org/10.1126/science.1093846Neuhauser, DScienceRotary motion around a molecular axis has been controlled by simple electron transfer processes and by photoexcitation. The basis of the motion is intramolecular rotation of a carborane cage ligand ( 7,8-dicarbollide) around a nickel axle. The Ni(III) metallacarborane structure is a transoid sandwich with two pairs of carbon vertices reflected through a center of symmetry, but that of the Ni(IV) species is cisoid. The interconversion of the two provides the basis for controlled, rotational, oscillatory motion. The energies of the Ni(III) and Ni(IV) species are calculated as a function of the rotation angle.Electrical or photocontrol of the rotary motion of a metallacarboranePhotocatalyst251200429#N/AFALSE
939
science.108899610.1126/science.1088996FALSEhttps://doi.org/10.1126/science.1088996Rizzo, TRScienceThe dissociation of methane on a nickel catalyst is a key step in steam reforming of natural gas for hydrogen production. Despite substantial effort in both experiment and theory, there is still no atomic-scale description of this important gas-surface reaction. We report quantum state-resolved studies, using pulsed laser and molecular beam techniques, of vibrationally excited methane reacting on the nickel (100) surface. For doubly deuterated methane (CD2H2), we observed that the reaction probability with two quanta of excitation in one C-H bond was greater (by as much as a factor of 5) than with one quantum in each of two C-H bonds. These results Clearly exClude the possibility of statistical models correctly describing the mechanism of this process and attest to the importance of full-dimensional calculations of the reaction dynamics.Vibrational mode-specific reaction of methane on a nickel surfacex207200327#N/AFALSE
940
science.108559710.1126/science.1085597FALSEhttps://doi.org/10.1126/science.1085597Dumesic, JAScienceHydrogen (H-2) was produced by aqueous-phase reforming of biomass-derived oxygenated hydrocarbons at temperatures near 500 kelvin over a tin-promoted Raney-nickel catalyst. The performance of this non - precious metal catalyst compares favorably with that of platinum-based catalysts for production of hydrogen from ethylene glycol, glycerol, and sorbitol. The addition of tin to nickel decreases the rate of methane formation from C-O bond Cleavage while maintaining the high rates of C-C bond Cleavage required for hydrogen formation.Raney Ni-Sn catalyst for H-2 production from biomass-derived hydrocarbonsx798200325#N/AFALSE
941
science.125473810.1126/science.1254738FALSEhttps://doi.org/10.1126/science.1254738Taubenberger, SScienceType Ia supernovae result from binary systems that inClude a carbon-oxygen white dwarf, and these thermonuClear explosions typically produce 0.5 solar mass of radioactive Ni-56. The Ni-56 is commonly believed to be buried deeply in the expanding supernova Cloud. In SN2014J, we detected the lines at 158 and 812 kiloelectron volts from Ni-56 decay (time similar to 8.8 days) earlier than the expected several-week time scale, only similar to 20 days after the explosion and with flux levels corresponding to roughly 10% of the total expected amount of Ni-56. Some mechanism must break the spherical symmetry of the supernova and at the same time create a major amount of Ni-56 at the outskirts. A plausible explanation is that a belt of helium from the companion star is accreted by the white dwarf, where this material explodes and then triggers the supernova event.Early Ni-56 decay gamma rays from SN2014J suggest an unusual explosion74201444#N/ATRUE
942
science.106414810.1126/science.1064148FALSEhttps://doi.org/10.1126/science.1064148Watkins, JJDeposition of conformal copper and nickel films from supercritical carbon dioxidex2001#N/AFALSE
943
science.125127710.1126/science.1251277FALSEhttps://doi.org/10.1126/science.1251277Beck, RDScienceWater dissociation on transition-metal catalysts is an important step in steam reforming and the water-gas shift reaction. To probe the effect of translational and vibrational Activation on this important heterogeneous reaction, we performed state-resolved gas/surface reactivity measurements for the dissociative chemisorption of D2O on Ni(111), using molecular beam techniques. The reaction occurs via a direct pathway, because both the translational and vibrational energies promote the dissociation. The experimentally measured initial sticking probabilities were used to calibrate a first-principles potential energy surface based on density functional theory. Quantum dynamical calculations on the scaled potential energy surface reproduced the experimental results semiquantitatively. The larger increase of the dissociation probability by vibrational excitation than by translation per unit of energy is consistent with a late barrier along the O-D stretch reaction coordinate.Vibrationally Promoted Dissociation of Water on Ni(111)132201445#N/ATRUE
944
science.105706310.1126/science.1057063https://doi.org/10.1126/science.1057063Hessler, JPScienceThe determination of the structure of transient molecules, such as photoexcited states, in disordered media (such as in solution) usually requires methods with high temporal resolution. The transient molecular structure of a reaction intermediate produced by photoexcitation of NiTPP-L-2 (NiTPP, nickeltetraphenylporphyrin; L, piperidine) in solution was determined by x-ray absorption fine structure (XAFS) data obtained on a 14-nanosecond time scale from a third-generation synchrotron source. The XAFS measurements confirm that photoexcitation Leads to the rapid removal of both axial Ligands to produce a transient square-planar intermediate, NiTPP, with a lifetime of 28 nanoseconds. The transient structure of the photodissociated intermediate is nearly identical to that of the ground state NiTPP, suggesting that the intermediate adopts the same structure as the ground state in a noncoordinating solvent before it recombines with two Ligands to form the more stable octahedrally coordinated NiTPP-L-2.Capturing a photoexcited molecular structure through time-domain X-ray absorption fine structurePhotocatalyst235200132#N/AFALSE
945
s41929-017-0023-z#citeas10.1038/s41929-017-0023-zFALSEhttps://doi.org/10.1038/s41929-017-0023-zRao, YPhotocatalystErik M. Carreira #N/AFALSE
946
science.124906110.1126/science.1249061FALSEhttps://doi.org/10.1126/science.1249061Stamenkovic, VRHighly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces2014#N/ATRUE
947
science.121193410.1126/science.1211934FALSEhttps://doi.org/10.1126/science.1211934Markovic, NMEnhancing Hydrogen Evolution Activity in Water Splitting by Tailoring Li+-Ni(OH)(2)-Pt Interfaces2011#N/ATRUE
948
s41586-020-2908-210.1038/s41586-020-2908-2FALSEhttps://doi.org/10.1038/s41586-020-2908-2Jones, TENatureThe oxygen evolution reaction has an important role in many alternative-energy schemes because it supplies the protons and electrons required for converting renewable electricity into chemical fuels(1-3). Electrocatalysts accelerate the reaction by facilitating the required electron transfer(4), as well as the formation and rupture of chemical bonds(5). This involvement in fundamentally different processes results in complex electrochemical kinetics that can be challenging to understand and control, and that typically depends exponentially on overpotential(1,2,6,7). Such behaviour emerges when the applied bias drives the reaction in line with the phenomenological Butler-Volmer theory, which focuses on electron transfer(8), enabling the use of Tafel analysis to gain mechanistic insight under quasi-equilibrium(9-11) or steady-state assumptions(12). However, the charging of catalyst surfaces under bias also affects bond formation and rupture(13-15), the effect of which on the electrocatalytic rate is not accounted for by the phenomenological Tafel analysis(8) and is often unknown. Here we report pulse voltammetry and operando X-ray absorption spectroscopy measurements on iridium oxide to show that the applied bias does not act directly on the reaction coordinate, but affects the electrocatalytically generated current through charge accumulation in the catalyst. We find that the Activation free energy decreases linearly with the amount of oxidative charge stored, and show that this relationship underlies electrocatalytic performance and can be evaluated using measurement and computation. We anticipate that these findings and our methodology will help to better understand other electrocatalytic materials and design systems with improved performance. Spectroscopic studies and theoretical calculations of the electrocatalytic oxygen evolution reaction establish that reaction rates depend on the amount of charge stored in the electrocatalyst, and not on the applied potential.Key role of chemistry versus bias in electrocatalytic oxygen evolution
Electrocatalytic
57202027#N/AFALSE
949
s41586-020-2464-910.1038/s41586-020-2464-9FALSEhttps://doi.org/10.1038/s41586-020-2464-9Hosono, HNatureAmmonia (NH3) is pivotal to the fertilizer industry and one of the most commonly produced chemicals(1). The direct use of atmospheric nitrogen (N-2) had been challenging, owing to its large bond energy (945 kilojoules per mole)(2,3), until the development of the Haber-Bosch process. Subsequently, many strategies have been explored to reduce the Activation barrier of the N equivalent to N bond and make the process more efficient. These inClude using alkali and alkaline earth metal oxides as promoters to boost the performance of traditional iron- and ruthenium-based catalysts(4-6)via electron transfer from the promoters to the antibonding bonds of N(2)through transition metals(7,8). An electride support further lowers the Activation barrier because its low work function and high electron density enhance electron transfer to transition metals(9,10). This strategy has facilitated ammonia synthesis from N(2)dissociation(11)and enabled catalytic operation under mild conditions; however, it requires the use of ruthenium, which is expensive. Alternatively, it has been shown that nitrides containing surface nitrogen vacancies can activate N-2(refs.(12-15)). Here we report that nickel-loaded lanthanum nitride (LaN) enables stable and highly efficient ammonia synthesis, owing to a dual-site mechanism that avoids commonly encountered scaling relations. Kinetic and isotope-labelling experiments, as well as density functional theory calculations, confirm that nitrogen vacancies are generated on LaN with low formation energy, and efficiently bind and activate N-2. In addition, the nickel metal loaded onto the nitride dissociates H-2. The use of distinct sites for activating the two reactants, and the synergy between them, results in the nickel-loaded LaN catalyst exhibiting an activity that far exceeds that of more conventional cobalt- and nickel-based catalysts, and that is comparable to that of ruthenium-based catalysts. Our results illustrate the potential of using vacancy sites in reaction cyCles, and introduce a design concept for catalysts for ammonia synthesis, using naturally abundant elements. Ammonia is synthesized using a dual-site approach, whereby nitrogen vacancies on LaN activate N-2, which then reacts with hydrogen atoms produced over the Ni metal to give ammonia.Vacancy-enabled N(2)Activation for ammonia synthesis on an Ni-loaded catalystx44202036#N/AFALSE
950
science.121164910.1126/science.1211649FALSEhttps://doi.org/10.1126/science.1211649Carter, WBUltralight Metallic Microlattices2011#N/ATRUE
951
science.120792210.1126/science.1207922FALSEhttps://doi.org/10.1126/science.1207922Hartwig, JFScienceTransition metal complexes catalyze many important reactions that are employed in medicine, materials science, and energy production. Although high-throughput methods for the discovery of catalysts that would mirror related approaches for the discovery of medicinally active compounds have been the focus of much attention, these methods have not been sufficiently general or accessible to typical synthetic laboratories to be adopted widely. We report a method to evaluate a broad range of catalysts for potential coupling reactions with the use of simple laboratory equipment. Specifically, we screen an array of catalysts and ligands with a diverse mixture of substrates and then use mass spectrometry to identify reaction products that, by design, exceed the mass of any single substrate. With this method, we discovered a copper-catalyzed alkyne hydroamination and two nickel-catalyzed hydroArylation reactions, each of which displays excellent functional-group tolerance.A Simple, Multidimensional Approach to High-Throughput Discovery of Catalytic Reactions160201137#N/ATRUE
952
science.118328110.1126/science.1183281FALSEhttps://doi.org/10.1126/science.1183281Wieghardt, KScienceRadical Ligands Confer Nobility on Base-Metal Catalysts635201020#N/ATRUE
953
science.117977310.1126/science.1179773FALSEhttps://doi.org/10.1126/science.1179773Fontecave, MScienceInterconversion of water and hydrogen in unitized regenerative fuel cells is a promising energy storage framework for smoothing out the temporal fluctuations of solar and wind power. However, replacement of presently available platinum catalysts by lower-cost and more abundant materials is a requisite for this technology to become economically viable. Here, we show that the covalent attachment of a nickel bisdiphosphine-based mimic of the active site of hydrogenase enzymes onto multiwalled carbon nanotubes results in a high-surface area cathode material with high catalytic activity under the strongly acidic conditions required in proton exchange membrane technology. Hydrogen evolves from aqueous sulfuric acid solution with very low overvoltages (20 millivolts), and the catalyst exhibits exceptional stability ( more than 100,000 turnovers). The same catalyst is also very efficient for hydrogen oxidation in this environment, exhibiting current densities similar to those observed for hydrogenase-based materials.From Hydrogenases to Noble Metal-Free Catalytic Nanomaterials for H-2 Production and Uptake682200925#N/ATRUE
954
s41586-018-0366-x10.1038/s41586-018-0366-xTRUEhttps://doi.org/10.1038/s41586-018-0366-xMacMillan, DWCNatureDespite the widespread success of transition-metal-catalysed cross-coupling methodologies, considerable limitations still exist in reactions at sp(3)-hybridized carbon atoms, with most approaches relying on prefunctionalized Alkylmetal or bromide coupling partners(1-2). Although the use of native functional groups (for example, Carbonylic acids, alkenes and alcohols) has improved the overall efficiency of such transformations by expanding the range of potential feedstocks(3-5), the direct functionalization of carbon-hydrogen (C-H) bonds-the most abundant moiety in organic molecules-represents a more ideal approach to molecular construction. In recent years, an impressive range of reactions that form C(sp(3))-heteroatom bonds from strong C-H bonds has been reported(6-7). Additionally, valuable technologies have been developed for the formation of carbon-carbon bonds from the corresponding C(sp(3))-H bonds via substrate-directed transitionmetal C-H insertion(8), undirected C-H insertion by captodative rhodium carbenoid complexes', or hydrogen atom transfer from weak, hydridic C-H bonds by electrophilic open-shell species(10-14). Despite these advances, a mild and general platform for the coupling of strong, neutral C(sp(3))-H bonds with Aryl electrophiles has not been realized. Here we describe a protocol for the direct C(sp(3)) Arylation of a diverse set of aliphatic, C-H bond-containing organic frameworks through the combination of light-driven, polyoxometalate-facilitated hydrogen atom transfer and nickel catalysis. This dual-catalytic manifold enables the generation of carbon-centred radicals from strong, neutral C-H bonds, which thereafter act as nuCleophiles in nickel-mediated cross-coupling with Aryl bromides to afford C(sp(3))-C(sp(2)) cross-coupled products. This technology enables unprecedented, single-step access to a broad array of complex, medicinally relevant molecules directly from natural products and chemical feedstocks through functionalization at sites that are unreactive under traditional methods.Direct Arylation of strong aliphatic C-H bondsphotoCsp3-Csp2_arHBrAlkylK3PO4Ionic-PO41742018336/1/2022FALSE
955
science.115281910.1126/science.1152819FALSEhttps://doi.org/10.1126/science.1152819Utz, ALScienceEnergy redistribution, inCluding the many phonon- assisted and electronically assisted energy- exchange processes at a gas- metal interface, can hamper vibrationally mediated selectivity in chemical reactions. We establish that these limitations do not prevent bond- selective control of a heterogeneously catalyzed reaction. State- resolved gas- surface scattering measurements show that the nu(1) C-H stretch vibration in trideuteromethane ( CHD3) selectively activates C-H bond Cleavage on a Ni( 111) surface. Isotope- resolved detection reveals a CD3: CHD2 product ratio > 30: 1, which contrasts with the 1: 3 ratio for an isoenergetic ensemble of CHD3 whose vibrations are statistically populated. Recent studies of vibrational energy redistribution in the gas and condensed phases suggest that other gas- surface reactions with similar vibrational energy flow dynamics might also be candidates for such bond- selective control.Bond-selective control of a heterogeneously catalyzed reaction163200840#N/ATRUE
956
s41557-021-00734-x10.1038/s41557-021-00734-xFALSEhttps://doi.org/10.1038/s41557-021-00734-xWang, HTNat. Chem.Transition-metal single-atom catalysts present extraordinary activity per metal atomic site, but suffer from low metal-atom densities (typically less than 5 wt% or 1 at.%), which limits their overall catalytic performance. Here we report a general method for the synthesis of single-atom catalysts with high transition-metal-atom loadings of up to 40 wt% or 3.8 at.%, representing several-fold improvements compared to benchmarks in the literature. Graphene quantum dots, later interweaved into a carbon matrix, were used as a support, providing numerous anchoring sites and thus facilitating the generation of high densities of transition-metal atoms with sufficient spacing between the metal atoms to avoid aggregation. A significant increase in activity in electrochemical CO2 reduction (used as a representative reaction) was demonstrated on a Ni single-atom catalyst with increased Ni loading.General synthesis of single-atom catalysts with high metal loading using graphene quantum dotsx045#N/AFALSE
957
s41557-020-0473-910.1038/s41557-020-0473-9FALSEhttps://doi.org/10.1038/s41557-020-0473-9Li, YDNat. Chem.Single-atom catalysts not only maximize metal atom efficiency, they also display properties that are considerably different to their more conventional nanopartiCle equivalents, making them a promising family of materials to investigate. Herein we developed a general host-guest strategy to fabricate various metal single-atom catalysts on nitrogen-doped carbon (M-1/CN, M = Pt, Ir, Pd, Ru, Mo, Ga, Cu, Ni, Mn). The iridium variant Ir-1/CN electrocatalyses the formic acid oxidation reaction with a mass activity of 12.9 Amg(Ir)(-1) whereas an Ir/C nanopartiCle catalyst is almost inert (similar to 4.8 x 10(-3) Amg(Ir)(-1)). The activity of Ir-1/CN is also 16 and 19 times greater than those of Pd/C and Pt/C, respectively. Furthermore, Ir-1/CN displays high tolerance to CO poisoning. First-principle density functional theory reveals that the properties of Ir-1/CN stem from the spatial isolation of iridium sites and from the modified electronic structure of iridium with respect to a conventional nanopartiCle catalyst.Iridium single-atom catalyst on nitrogen-doped carbon for formic acid oxidation synthesized using a general host-guest strategyx58202059#N/AFALSE
958
science.114848110.1126/science.1148481FALSEhttps://doi.org/10.1126/science.1148481Dobbek, HScienceAnaerobic CO dehydrogenases catalyze the reversible oxidation of CO to CO2 at a complex Ni-, Fe-, and S-containing metal center called Cluster C. We report crystal structures of CO dehydrogenase II from Carboxydothermus hydrogenoformans in three different states. In a reduced state, exogenous CO2 supplied in solution is bound and reductively activated by Cluster C. In the intermediate structure, CO2 acts as a bridging ligand between Ni and the asymmetrically coordinated Fe, where it completes the square-planar coordination of the Ni ion. It replaces a water/hydroxo ligand bound to the Fe ion in the other two states. The structures define the mechanism of CO oxidation and CO2 reduction at the Ni-Fe site of Cluster C.Carbon dioxide Activation at the Ni,Fe-Cluster of anaerobic carbon monoxide dehydrogenase319200722#N/ATRUE
959
science.113594110.1126/science.1135941FALSEhttps://doi.org/10.1126/science.1135941Markovic, NMScienceThe slow rate of the oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cell ( PEMFC) is the main limitation for automotive applications. We demonstrated that the Pt3Ni( 111) surface is 10-fold more active for the ORR than the corresponding Pt(111) surface and 90-fold more active than the current state-of-the- art Pt/C catalysts for PEMFC. The Pt3Ni( 111) surface has an unusual electronic structure (d-band center position) and arrangement of surface atoms in the near-surface region. Under operating conditions relevant to fuel cells, its near-surface layer exhibits a highly structured compositional oscillation in the outermost and third layers, which are Pt-rich, and in the second atomic layer, which is Ni-rich. The weak interaction between the Pt surface atoms and nonreactive oxygenated species increases the number of active sites for O-2 adsorption.Improved oxygen reduction activity on Pt3Ni(111) via increased surface site availability3187200729#N/ATRUE
960
science.108234210.1126/science.1082342FALSEhttps://doi.org/10.1126/science.1082342Eichhorn, BWInterpenetrating As-20 fullerene and Ni-12 icosahedra in the onion-skin [As@Ni-12@As-20](3-) ion2003#N/ATRUE
961
s41557-019-0357-z10.1038/s41557-019-0357-zFALSEhttps://doi.org/10.1038/s41557-019-0357-zHerbert, DENat. Chem.Replacing current benchmark rare-element photosensitizers with ones based on abundant and low-cost metals such as iron would help facilitate the large-scale implementation of solar energy conversion. To do so, the ability to extend the lifetimes of photogenerated excited states of iron complexes is critical. Here, we present a sensitizer design in which iron(II) centres are supported by frameworks containing benzannulated phenanthridine and quinoline heterocyCles paired with amido donors. These complexes exhibit panchromatic absorption and nanosecond charge-transfer excited state lifetimes, enabled by the combination of vacant, energetically accessible heterocyCle-based acceptor orbitals and occupied molecular orbitals destabilized by strong mixing between amido nitrogen atoms and iron. This finding shows how ligand design can extend metal-to-ligand charge-transfer-type excited state lifetimes of iron(II) complexes into the nanosecond regime and expand the range of potential applications for iron-based photosensitizers.Iron(II) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimesx41201951#N/AFALSE
962
s41557-019-0353-310.1038/s41557-019-0353-3https://doi.org/10.1038/s41557-019-0353-3Ritter, TNat. Chem.Photoredox catalysis, especially in combination with transition metal catalysis, can produce redox states of transition metal catalysts to facilitate challenging bond formations that are not readily accessible in conventional redox catalysis. For arene functionalization, metallophotoredox catalysis has successfully made use of the same leaving groups as those valuable in conventional cross-coupling catalysis, such as bromide. Yet the redox potentials of common photoredox catalysts are not sufficient to reduce most Aryl bromides, so synthetically useful Aryl radicals are often not directly available. Therefore, the development of a distinct leaving group more appropriately matched in redox potential could enable new reactivity manifolds for metallophotoredox catalysis, especially if Arylcopper(iii) complexes are accessible, from which the most challenging bond-forming reactions can occur. Here we show the conceptual advantages of Aryl thianthrenium salts for metallophotoredox catalysis, and their utility in site-selective late-stage aromatic fluorination.Photoredox catalysis with Aryl sulfonium salts enables site-selective late-stage fluorinationPhotocatalyst43202036#N/AFALSE
963
s41557-019-0342-610.1038/s41557-019-0342-6FALSEhttps://doi.org/10.1038/s41557-019-0342-6Addison, DNat. Chem.Next-generation lithium-battery cathodes often involve the growth of lithium-rich phases, which enable specific capacities that are 2-3 times higher than insertion cathode materials, such as lithium cobalt oxide. Here, we investigated battery chemistry previously deemed irreversible in which lithium oxide, a lithium-rich phase, grows through the reduction of the nitrate anion in a lithium nitrate-based molten salt at 150 degrees C. Using a suite of independent characterization techniques, we demonstrated that a Ni nanopartiCle catalyst enables the reversible growth and dissolution of micrometre-sized lithium oxide crystals through the effective catalysis of nitrate reduction and nitrite oxidation, which results in high cathode areal capacities (similar to 12 mAh cm(-2)). These results enable a rechargeable battery system that has a full-cell theoretical specific energy of 1,579 Wh kg(-1), in which a molten nitrate salt serves as both an active material and the electrolyte.Rechargeable-battery chemistry based on lithium oxide growth through nitrate anion redoxx8201927#N/AFALSE
964
science.106150010.1126/science.1061500FALSEhttps://doi.org/10.1126/science.1061500Meyer, OScienceThe homodimeric nickel-containing CO dehydrogenase from the anaerobic bacterium Carboxydothermus hydrogenoformans catalyzes the oxidation of CO to CO2. A crystal structure of the reduced enzyme has been solved at 1.6 angstrom resolution. This structure represents the prototype for Ni-containing CO dehydrogenases from anaerobic bacteria and archaea. It contains five metal Clusters of which Clusters B, B', and a subunit-bridging, surface-exposed Cluster D are cubane-type [4Fe-4S] Clusters. The active-site Clusters C and C' are novel, asymmetric [Ni-4Fe-5S] Clusters. Their integral Ni ion, which is the likely site of CO oxidation, is coordinated by four sulfur ligands with square planar geometry.Crystal structure of a carbon monoxide dehydrogenase reveals a [Ni-4Fe-5S] Cluster363200136#N/ATRUE
965
s41557-019-0218-910.1038/s41557-019-0218-9FALSEhttps://doi.org/10.1038/s41557-019-0218-9Tezcan, FANat. Chem.The bottom-up design and construction of functional metalloproteins remains a formidable task in biomolecular design. Although numerous strategies have been used to create new metalloproteins, pre-existing knowledge of the tertiary and quaternary protein structure is often required to generate suitable platforms for robust metal coordination and activity. Here we report an alternative and easily implemented approach (metal active sites by covalent tethering or MASCoT) in which folded protein building blocks are linked by a single disulfide bond to create diverse metal coordination environments within evolutionarily naive protein-protein interfaces. Metalloproteins generated using this strategy uniformly bind a wide array of first-row transition metal ions (Mn-II, Fe-II, Co-II, Ni-II, Cu-II, Zn-II and vanadyl) with physiologically relevant thermodynamic affinities (dissociation constants ranging from 700 nM for Mn-II to 50 fM for Cu-II). MASCoT readily affords coordinatively unsaturated metal centres-inCluding a penta-His-coordinated non-haem Fe site-and well-defined binding pockets that can accommodate modifications and enable coordination of exogenous ligands such as nitric oxide to the interfacial metal centre.An efficient, step-economical strategy for the design of functional metalloproteinsx25201973#N/AFALSE
966
s41586-021-03485-410.1038/s41586-021-03485-4FALSEDrahus, MGaseous atomic nickel in the coma of interstellar comet 2I/Borisov2021#N/ATRUE
967
s41557-018-0150-410.1038/s41557-018-0150-4https://doi.org/10.1038/s41557-018-0150-4Wang, JYNat. Chem.Photosensitizers, which harness light energy to upgrade weak reductants to strong reductants, are pivotal components of the natural and artificial photosynthesis machineries. However, it has proved difficult to enhance and expand their functions through genetic engineering. Here we report a genetically encoded, 27 kDa photosensitizer protein (PSP), which facilitates the rational design of miniature photocatalytic CO2-reducing enzymes. Visible light drives PSP efficiently into a long-lived triplet excited state (PSP*), which reacts rapidly with reduced nicotinamide adenine dinuCleotide to generate a super-reducing radical (PSP center dot), which is strong enough to reduce many CO2-reducing catalysts. We determined the three-dimensional structure of PSP center dot at 1.8 A resolution by X-ray crystallography. Genetic engineering enabled the site-specific attachment of a nickel-terpyridine complex and the modular optimization of the photochemical properties of PSP, the chromophore/catalytic centre distance and the catalytic centre microenvironment, which culminated in a miniature photocatalytic CO2-reducing enzyme that has a CO2/CO conversion quantum efficiency of 2.6%.A genetically encoded photosensitizer protein facilitates the rational design of a miniature photocatalytic CO2-reducing enzymePhotocatalyst37201836#N/AFALSE
968
s41557-018-0110-z10.1038/s41557-018-0110-zFALSEhttps://doi.org/10.1038/s41557-018-0110-zEngle, KMActivation of diverse carbon-heteroatom and carbon-carbon bonds via palladium(II)-catalysed beta-X eliminationx2018#N/AFALSE
969
s41467-021-25095-410.1038/s41467-021-25095-4FALSEhttps://doi.org/10.1038/s41467-021-25095-4Liu, LZNat. Commun.Oxygen evolution reaction (OER) plays a determining role in electrochemical energy conversion devices, but challenges remain due to the lack of effective low-cost electrocatalysts and insufficient understanding about sluggish reaction kinetics. Distinguish from complex nano-structuring, this work focuses on the spin-related charge transfer and orbital interaction between catalysts and intermediates to accelerate catalytic reaction kinetics. Herein, we propose a simple magnetic-stimulation approach to rearrange spin electron occupation in noble-metal-free metal-organic frameworks (MOFs) with a feature of thermal-differentiated superlattice, in which the localized magnetic heating in periodic spatial distribution makes the spin flip occur at particular active sites, demonstrating a spin-dependent reaction pathway. As a result, the spin-rearranged Co0.8Mn0.2 MOF displays mass activities of 3514.7 A g(metal)(-1) with an overpotential of similar to 0.27 V, which is 21.1 times that of pristine MOF. Our findings provide a new paradigm for designing spin electrocatalysis and steering reaction kinetics.Spin-sate reconfiguration induced by alternating magnetic field for efficient oxygen evolution reactionx0202139#N/AFALSE
970
s41586-021-03435-010.1038/s41586-021-03435-0FALSEhttps://doi.org/10.1038/s41586-021-03435-0Jehin, EIron and nickel atoms in cometary atmospheres even far from the Sun2021#N/ATRUE
971
s41467-021-24589-510.1038/s41467-021-24589-5FALSEhttps://doi.org/10.1038/s41467-021-24589-5Pell, AJNat. Commun.Structural and morphological control of crystalline nanopartiCles is crucial in the field of heterogeneous catalysis and the development of reaction specific catalysts. To achieve this, colloidal chemistry methods are combined with ab initio calculations in order to define the reaction parameters, which drive chemical reactions to the desired crystal nuCleation and growth path. Key in this procedure is the experimental verification of the predicted crystal facets and their corresponding electronic structure, which in case of nanostructured materials becomes extremely difficult. Here, by employing P-31 solid-state nuClear magnetic resonance aided by advanced density functional theory calculations to obtain and assign the Knight shifts, we succeed in determining the crystal and electronic structure of the terminating surfaces of ultrafine Ni2P nanopartiCles at atomic scale resolution. Our work highlights the potential of ssNMR nanocrystallography as a unique tool in the emerging field of facet-engineered nanocatalysts. Structural and morphological control of crystalline nanopartiCles is crucial in heterogeneous catalysis. Applying DFT-assisted solid-state NMR spectroscopy, we determine the surface crystal and electronic structure of Ni2P nanopartiCles, unveiling NMR nanocrystallography as an emerging tool in facet-engineered nanocatalysts.Crystal and electronic facet analysis of ultrafine Ni2P partiCles by solid-state NMR nanocrystallographyx0202154#N/AFALSE
972
s41586-020-2036-z10.1038/s41586-020-2036-zFALSEhttps://doi.org/10.1038/s41586-020-2036-zChen, BHigh-pressure strengthening in ultrafine-grained metals2020#N/ATRUE
973
s41586-019-1776-010.1038/s41586-019-1776-0FALSEhttps://doi.org/10.1038/s41586-019-1776-0Long, JRNatureThe size-dependent and shape-dependent characteristics that distinguish nanoscale materials from bulk solids arise from constraining the dimensionality of an inorganic structure(1-3). As a consequence, many studies have focused on rationally shaping these materials to influence and enhance their optical, electronic, magnetic and catalytic properties(4-6). Although a select number of stable Clusters can typically be synthesized within the nanoscale regime for a specific composition, isolating Clusters of a predetermined size and shape remains a challenge, especially for those derived from two-dimensional materials. Here we realize a multidentate coordination environment in a metal-organic framework to stabilize discrete inorganic Clusters within a porous crystalline support. We show confined growth of atomically defined nickel(ii) bromide, nickel(ii) chloride, cobalt(ii) chloride and iron(ii) chloride sheets through the peripheral coordination of six chelating bipyridine linkers. Notably, confinement within the framework defines the structure and composition of these sheets and facilitates their precise characterization by crystallography. Each metal(ii) halide sheet represents a fragment excised from a single layer of the bulk solid structure, and structures obtained at different precursor loadings enable observation of successive stages of sheet assembly. Finally, the isolated sheets exhibit magnetic behaviours distinct from those of the bulk metal halides, inCluding the isolation of ferromagnetically coupled large-spin ground states through the elimination of long-range, interlayer magnetic ordering. Overall, these results demonstrate that the pore environment of a metal-organic framework can be designed to afford precise control over the size, structure and spatial arrangement of inorganic Clusters.Confinement of atomically defined metal halide sheets in a metal-organic framework32202043#N/ATRUE
974
s41586-018-0669-y10.1038/s41586-018-0669-yFALSEhttps://doi.org/10.1038/s41586-018-0669-yFu, GCNatureCarbon-carbon bonds, inCluding those between sp(3)-hybridized carbon atoms (Alkyl-Alkyl bonds), typically comprise much of the framework of organic molecules. In the case of sp(3)-hybridized carbon, the carbon can be stereogenic and the particular stereochemistry can have implications for structure and function(1-3). As a consequence, the development of methods that simultaneously construct Alkyl-Alkyl bonds and control stereochemistry is important, although challenging. Here we describe a strategy for enantioselective Alkyl-Alkyl bond formation, in which a racemic Alkyl electrophile is coupled with an olefin in the presence of a hydrosilane, rather than via a traditional electrophile-nuCleophile cross-coupling, through the action of a chiral nickel catalyst. We demonstrate that families of racemic Alkyl halides-inCluding secondary and tertiary electrophiles, which have not previously been shown to be suitable for enantioconvergent coupling with Alkyl metal nuCleophiles-cross-couple with olefins with good enantioselectivity and yield under very mild reaction conditions. Given the ready availability of olefins, our approach opens the door to developing more general methods for enantioconvergent Alkyl-Alkyl coupling.Catalytic enantioconvergent coupling of secondary and tertiary electrophiles with olefins110201831#N/ATRUE
975
s41467-021-24079-810.1038/s41467-021-24079-8FALSEhttps://doi.org/10.1038/s41467-021-24079-8Yan, HNat. Commun.Single-atom catalysts provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of the catalysts for alkaline water dissociation has hampered advances in highly efficient hydrogen production. Herein, we develop a single-atom platinum immobilized NiO/Ni heterostructure (Pt-SA-NiO/Ni) as an alkaline hydrogen evolution catalyst. It is found that Pt single atom coupled with NiO/Ni heterostructure enables the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy and promotes the H* conversion for accelerating alkaline hydrogen evolution reaction. A further enhancement is achieved by constructing Pt-SA-NiO/Ni nanosheets on Ag nanowires to form a hierarchical three-dimensional morphology. Consequently, the fabricated Pt-SA-NiO/Ni catalyst displays high alkaline hydrogen evolution performances with a quite high mass activity of 20.6Amg(-1) for Pt at the overpotential of 100mV, significantly outperforming the reported catalysts. While H-2 evolution from water may represent a renewable energy source, there is a strong need to improve catalytic efficiencies while maximizing materials utilization. Here, authors examine single-atom Pt on nickel-based heterostructures as highly active electrocatalysts for alkaline H-2 evolution.Platinum single-atom catalyst coupled with transition metal/metal oxide heterostructure for accelerating alkaline hydrogen evolution reactionx0202167#N/AFALSE
976
s41467-021-24052-510.1038/s41467-021-24052-5FALSEhttps://doi.org/10.1038/s41467-021-24052-5Chen, PNat. Commun.While inheriting the exceptional merits of single atom catalysts, diatomic site catalysts (DASCs) utilize two adjacent atomic metal species for their complementary functionalities and synergistic actions. Herein, a DASC consisting of nickel-iron hetero-diatomic pairs anchored on nitrogen-doped graphene is synthesized. It exhibits extraordinary electrocatalytic activities and stability for both CO2 reduction reaction (CO2RR) and oxygen evolution reaction (OER). Furthermore, the rechargeable Zn-CO2 battery equipped with such bifunctional catalyst shows high Faradaic efficiency and outstanding rechargeability. The in-depth experimental and theoretical analyses reveal the orbital coupling between the catalytic iron center and the adjacent nickel atom, which leads to alteration in orbital energy level, unique electronic states, higher oxidation state of iron, and weakened binding strength to the reaction intermediates, thus boosted CO2RR and OER performance. This work provides critical insights to rational design, working mechanism, and application of hetero-DASCs. Diatomic site catalysts utilize two adjacent atomic metal species for their complementary functionalities and synergistic actions. Here, the authors report the orbital coupling of hetero-diatomic nickel-iron site boosts CO2 reduction reaction and oxygen evolution reaction.Orbital coupling of hetero-diatomic nickel-iron site for bifunctional electrocatalysis of CO2 reduction and oxygen evolutionx0202153#N/AFALSE
977
s41467-021-23971-710.1038/s41467-021-23971-7FALSEhttps://doi.org/10.1038/s41467-021-23971-7Li, CJNat. Commun.Aldehydes and ketones are widely found in biomass resources and play important roles in organic synthesis. However, the direct deoxygenative coupling of aldehydes or ketones to construct C(sp(3))-C(sp(3)) bond remains a scientific challenge. Here we report a nickel-catalyzed reductive homo-coupling of moisture- and air-stable hydrazones generated in-situ from naturally abundant aldehydes and ketones to construct challenging C(sp(3))-C(sp(3)) bond. This transformation has great functional group compatibility and can suit a broad substrate scope with innocuous H2O, N-2 and H-2 as the by-products. Furthermore, the application in several biological molecules and the transformation of PEEK model demonstrate the generality, practicability, and applicability of this novel methodology. The direct deoxygenative coupling of aldehydes or ketones to construct C(sp(3))-C(sp(3)) bond remains a scientific challenge. Here the authors use a nickel-catalyzed reductive homo-coupling of moisture- and air-stable hydrazones generated in-situ from naturally abundant aldehydes and ketones to construct challenging C(sp(3))-C(sp(3)) bonds.C(sp(3))-C(sp(3)) bond formation via nickel-catalyzed deoxygenative homo-coupling of aldehydes/ketones mediated by hydrazinex1202135#N/AFALSE
978
s41467-021-23887-210.1038/s41467-021-23887-2https://doi.org/10.1038/s41467-021-23887-2Huo, HHNat. Commun.Asymmetric C(sp(3))-H functionalization is a persistent challenge in organic synthesis. Here, we report an asymmetric Benzylic C-H acylation of Alkylarenes employing Carbonylic acids as acyl surrogates for the synthesis of alpha -Aryl ketones via nickel and photoredox dual catalysis. This mild yet straightforward protocol transforms a diverse array of feedstock Carbonylic acids and simple Alkyl benzenes into highly valuable alpha -Aryl ketones with high enantioselectivities. The utility of this method is showcased in the gram-scale synthesis and late-stage modification of medicinally relevant molecules. Mechanistic studies suggest a photocatalytically generated bromine radical can perform Benzylic C-H Cleavage to activate Alkylarenes as nuCleophilic coupling partners which can then engage in a nickel-catalyzed asymmetric acyl cross-coupling reaction. This bromine-radical-mediated C-H Activation strategy can be also applied to the enantioselective coupling of Alkylarenes with chloroformate for the synthesis of chiral alpha -Aryl esters. Chiral alpha -Aryl ketones are versatile building blocks, and represent important pharmacophores existing in many drug molecules such as ibuprofen and naproxen. Here the authors for such ketones but using nickel and photoredox dual catalysis in asymmetric Benzylic C-H acylation of Alkylarenes and employing Carbonylic acids as acyl surrogates.Asymmetric Benzylic C(sp(3))-H acylation via dual nickel and photoredox catalysisPhotocatalyst02021656/21/2022FALSE
979
s41467-021-23750-410.1038/s41467-021-23750-4FALSEhttps://doi.org/10.1038/s41467-021-23750-4Ma, YYNat. Commun.Hydrogen spillover phenomenon of metal-supported electrocatalysts can significantly impact their activity in hydrogen evolution reaction (HER). However, design of active electrocatalysts faces grand challenges due to the insufficient understandings on how to overcome this thermodynamically and kinetically adverse process. Here we theoretically profile that the interfacial charge accumulation induces by the large work function difference between metal and support (Phi) and sequentially strong interfacial proton adsorption construct a high energy barrier for hydrogen transfer. Theoretical simulations and control experiments rationalize that small Phi induces interfacial charge dilution and relocation, thereby weakening interfacial proton adsorption and enabling efficient hydrogen spillover for HER. Experimentally, a series of Pt alloys-CoP catalysts with tailorable Phi show a strong Phi -dependent HER activity, in which PtIr/CoP with the smallest Phi =0.02eV delivers the best HER performance. These findings have conClusively identified Phi as the criterion in guiding the design of hydrogen spillover-based binary HER electrocatalysts. Despite the significance of hydrogen spillover on metal-supported electrocatalysts for hydrogen evolution, fundamental understandings on such a process are insufficient. Here the authors show that small work function difference between metal and support facilitates hydrogen spillover and enhances activity.A fundamental viewpoint on the hydrogen spillover phenomenon of electrocatalytic hydrogen evolution
Electrocatalytic
0202178#N/AFALSE
980
s41586-018-0628-710.1038/s41586-018-0628-7FALSEhttps://doi.org/10.1038/s41586-018-0628-7Sanford, MSNatureThe Suzuki-Miyaura cross-coupling of organB(OH)2ron nuCleophiles with Aryl halide electrophiles is one of the most widely used carbon-carbon bond-forming reactions in organic and medicinal chemistry(1,2). A key challenge associated with these transformations is that they generally require the addition of an exogenous base, the role of which is to enable transmetallation between the organB(OH)2ron nuCleophile and the metal catalyst(3). This requirement limits the substrate scope of the reaction because the added base promotes competitive decomposition of many organB(OH)2ron substrates(3-5). As such, considerable research has focused on strategies for mitigating base-mediated side reactions(6-12). Previous efforts have primarily focused either on designing strategically masked organB(OH)2ron reagents (to slow base-mediated decomposition)(6-8) or on developing highly active palladium precatalysts (to accelerate cross-coupling relative to base-mediated decomposition pathways)(10-12). An attractive alternative approach involves identifying combinations of catalyst and electrophile that enable Suzuki-Miyaura-type reactions to proceed without an exogenous base(12-14). Here we use this approach to develop a nickel-catalysed coupling of Aryl boronic acids with acid fluorides(15-17), which are formed in situ from readily available Carbonylic acids(18-22). This combination of catalyst and electrophile enables a mechanistic manifold in which a 'transmetallation-active' Aryl nickel fluoride intermediate is generated directly in the catalytic cyCle(13,16). As such, this transformation does not require an exogenous base and is applicable to a wide range of base-sensitive boronic acids and biologically active Carbonylic acids.Base-free nickel-catalysed deCarbonylative Suzuki-Miyaura coupling of acid fluorides102201833#N/ATRUE
981
s41467-021-22996-210.1038/s41467-021-22996-2FALSEhttps://doi.org/10.1038/s41467-021-22996-2Gao, MRNat. Commun.Operating fuel cells in alkaline environments permits the use of platinum-group-metal-free (PGM-free) catalysts and inexpensive bipolar plates, leading to significant cost reduction. Of the PGM-free catalysts explored, however, only a few nickel-based materials are active for catalyzing the hydrogen oxidation reaction (HOR) in alkali; moreover, these catalysts deactivate rapidly at high anode potentials owing to nickel hydroxide formation. Here we describe that a nickel-tungsten-copper (Ni5.2WCu2.2) ternary alloy showing HOR activity rivals Pt/C benchmark in alkaline electrolyte. Importantly, we achieved a high anode potential up to 0.3V versus reversible hydrogen electrode on this catalyst with good operational stability over 20h. The catalyst also displays excellent CO-tolerant ability that Pt/C catalyst lacks. Experimental and theoretical studies uncover that nickel, tungsten, and copper play in synergy to create a favorable alloying surface for optimized hydrogen and hydroxyl bindings, as well as for the improved oxidation resistance, which result in the HOR enhancement. The lack of efficient and cost-effective catalysts for H-2 oxidation reaction (HOR) hinders the application of anion exchange membrane fuel cells. Here, authors report a ternary nickel-tungsten-copper nanoalloy with marked HOR activity and stability that rivals the benchmark platinum catalyst.Ternary nickel-tungsten-copper alloy rivals platinum for catalyzing alkaline hydrogen oxidationx0202163#N/AFALSE
982
s41586-018-0082-610.1038/s41586-018-0082-6FALSEhttps://doi.org/10.1038/s41586-018-0082-6O'Hayre, RNatureProtonic ceramic fuel cells, like their higher-temperature solid-oxide fuel cell counterparts, can directly use both hydrogen and hydrocarbon fuels to produce electricity at potentially more than 50 per cent efficiency(1,2). Most previous direct-hydrocarbon fuel cell research has focused on solid-oxide fuel cells based on oxygen-ion-conducting electrolytes, but carbon deposition (coking) and sulfur poisoning typically occur when such fuel cells are directly operated on hydrocarbon-and/or sulfur-containing fuels, resulting in severe performance degradation over time(3-6). Despite studies suggesting good performance and anti-coking resistance in hydrocarbon-fuelled protonic ceramic fuel cells(2,7,8), there have been no systematic studies of long-term durability. Here we present results from long-term testing of protonic ceramic fuel cells using a total of 11 different fuels (hydrogen, methane, domestic natural gas (with and without hydrogen sulfide), propane, n-butane, i-butane, iso-octane, methanol, ethanol and ammonia) at temperatures between 500 and 600 degrees Celsius. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (less than 1.5 per cent degradation per 1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. Large fluctuations in temperature are tolerated, and coking is not observed even after thousands of hours of continuous operation. Finally, sulfur, a notorious poison for both low-temperature and high-temperature fuel cells, does not seem to affect the performance of protonic ceramic fuel cells when supplied at levels consistent with commercial fuels. The fuel flexibility and long-term durability demonstrated by the protonic ceramic fuel cell devices highlight the promise of this technology and its potential for commercial application.Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells197201852#N/ATRUE
983
s41467-021-22690-310.1038/s41467-021-22690-3https://doi.org/10.1038/s41467-021-22690-3Gong, LNat. Commun.The direct and selective C(sp(3))-H functionalization of cyCloalkanes and alkanes is a highly useful process in organic synthesis owing to the low-cost starting materials, the high step and atom economy. Its application to asymmetric catalysis, however, has been scarcely explored. Herein, we disClose our effort toward this goal by incorporation of dual asymmetric photocatalysis by a chiral nickel catalyst and a commercially available organophotocatalyst with a radical relay strategy through sulfur dioxide insertion. Such design leads to the development of three-component asymmetric sulfonylation involving direct functionalization of cyCloalkanes, alkanes, toluene derivatives or ethers. The photochemical reaction of a C(sp(3))-H precursor, a SO2 surrogate and a common alpha,beta-unsaturated Carbonyl compound proceeds smoothly under mild conditions, delivering a wide range of biologically interesting alpha-C chiral sulfones with high regio- and enantioselectivity (>50 examples, up to >50:1 rr and 95% ee). This method is applicable to late-stage functionalization of bioactive molecules, and provides an appealing access to enantioenriched compounds starting from the abundant hydrocarbon compounds. The direct and selective C(sp(3))-H functionalization of cyCloalkanes and alkanes is useful in organic synthesis but its application to asymmetric catalysis has been less explored. Here, the authors demonstrate the incorporation of a dual asymmetric photocatalyst which leads to the development of asymmetric sulfonylation involving direct functionalization of cyCloalkanes, alkanes, toluene derivatives or ethers.Photocatalytic three-component asymmetric sulfonylation via direct C(sp(3))-H functionalizationPhotocatalyst1202180#N/AFALSE
984
s41557-020-0469-510.1038/s41557-020-0469-5FALSEhttps://doi.org/10.1038/s41557-020-0469-5Lin, SNat. Chem.Chiral nitriles and their derivatives are prevalent in pharmaceuticals and bioactive compounds. Enantioselective alkene hydrocyanation represents a convenient and efficient approach for synthesizing these molecules. However, a generally applicable method featuring a broad substrate scope and high functional group tolerance remains elusive. Here, we address this long-standing synthetic problem using dual electrocatalysis. Using this strategy, we leverage electrochemistry to seamlessly combine two canonical radical reactions-cobalt-mediated hydrogen-atom transfer and copper-promoted radical cyanation-to accomplish highly enantioselective hydrocyanation without the need for stoichiometric oxidants. We also harness electrochemistry's unique feature of precise potential control to optimize the chemoselectivity of challenging substrates. Computational analysis uncovers the origin of enantio-induction, for which the chiral catalyst imparts a combination of attractive and repulsive non-covalent interactions to direct the enantio-determining C-CN bond formation. This work demonstrates the power of electrochemistry in accessing new chemical space and providing solutions to pertinent challenges in synthetic chemistry.Dual electrocatalysis enables enantioselective hydrocyanation of conjugated alkenes34202067#N/ATRUE
985
s41557-020-00609-710.1038/s41557-020-00609-7FALSEhttps://doi.org/10.1038/s41557-020-00609-7Fu, GCNat. Chem.The development of efficient methods, particularly catalytic and enantioselective processes, for the construction of all-carbon quaternary stereocentres is an important (and difficult) challenge in organic synthesis due to the occurrence of this motif in a range of bioactive molecules. One conceptually straightforward and potentially versatile approach is the catalytic enantioconvergent substitution reaction of a readily available racemic tertiary Alkyl electrophile by an organometallic nuCleophile; however, examples of such processes are rare. Here we demonstrate that a nickel-based chiral catalyst achieves enantioconvergent couplings of a variety of tertiary electrophiles (cyClic and acyClic alpha-haloCarbonyl compounds) with alkenylmetal nuCleophiles to form quaternary stereocentres with good yield and enantioselectivity under mild conditions in the presence of a range of functional groups. These couplings, which probably proceed via a radical pathway, provide access to an array of useful families of organic compounds, inCluding intermediates in the total synthesis of two natural products, (-)-eburnamonine and madindoline A.Quaternary stereocentres via catalytic enantioconvergent nuCleophilic substitution reactions of tertiary Alkyl halides5202143#N/ATRUE
986
s41467-021-22403-w10.1038/s41467-021-22403-wFALSEhttps://doi.org/10.1038/s41467-021-22403-wKim, YJNat. Commun.The energy storage performance of lithium-ion batteries (LIBs) depends on the electrode capacity and electrode/cell design parameters, which have previously been addressed separately, leading to a failure in practical implementation. Here, we show how conformal graphene (Gr) coating on Ni-rich oxides enables the fabrication of highly packed cathodes containing a high content of active material (similar to 99 wt%) without conventional conducting agents. With 99 wt% LiNi0.8Co0.15Al0.05O2 (NCA) and electrode density of similar to 4.3 g cm(-3), the Gr-coated NCA cathode delivers a high areal capacity, similar to 5.4 mAh cm(-2) (similar to 38% increase) and high volumetric capacity, similar to 863 mAh cm(-3) (similar to 34% increase) at a current rate of 0.2 C (similar to 1.1 mA cm(-2)); this surpasses the bare electrode approaching a commercial level of electrode setting (96 wt% NCA; similar to 3.3 g cm(-3)). Our findings offer a combinatorial avenue for materials engineering and electrode design toward advanced LIB cathodes.Graphene collage on Ni-rich layered oxide cathodes for advanced lithium-ion batteriesx4202148#N/AFALSE
987
s41467-021-22224-x10.1038/s41467-021-22224-xFALSEhttps://doi.org/10.1038/s41467-021-22224-xPerez-Ramirez, JNanostructure of nickel-promoted indium oxide catalysts drives selectivity in CO2 hydrogenationx2021#N/AFALSE
988
s41557-019-0409-410.1038/s41557-019-0409-4FALSEhttps://doi.org/10.1038/s41557-019-0409-4Hartwig, JFNat. Chem.The anti-Markovnikov hydroArylation of unactivated alkenes with unactivated arenes has been achieved with high selectivity by using nickel catalysts bearing large N-heterocyClic carbene ligands. Energy decomposition analysis indicates that the high activity of the catalysts with large carbene ligands arises from stabilizing non-covalent interactions rather than steric effects. Anti-Markovnikov additions to alkenes have been a longstanding goal of catalysis, and anti-Markovnikov addition of arenes to alkenes would produce Alkylarenes that are distinct from those formed by acid-catalysed processes. Existing hydroArylations are either directed or occur with low reactivity and low regioselectivity for the n-Alkylarene. Herein, we report the first undirected hydroArylation of unactivated alkenes with unactivated arenes that occurs with high regioselectivity for the anti-Markovnikov product. The reaction occurs with a nickel catalyst ligated by a highly sterically hindered N-heterocyClic carbene. Catalytically relevant arene- and alkene-bound nickel complexes have been characterized, and the rate-limiting step was shown to be reductive elimination to form the C-C bond. Density functional theory calculations, combined with second-generation absolutely localized molecular orbital energy decomposition analysis, suggest that the difference in activity between catalysts containing large and small carbenes results more from stabilizing intramolecular non-covalent interactions in the secondary coordination sphere than from steric hindrance.Nickel-catalysed anti-Markovnikov hydroArylation of unactivated alkenes with unactivated arenes facilitated by non-covalent interactions40202052#N/ATRUE
989
s41467-021-21947-110.1038/s41467-021-21947-1https://doi.org/10.1038/s41467-021-21947-1Xu, TDual Ni/photoredox-catalyzed asymmetric cross-coupling to access chiral Benzylic boronic estersPhotocatalyst2021#N/AFALSE
990
s41557-019-0303-010.1038/s41557-019-0303-0FALSEhttps://doi.org/10.1038/s41557-019-0303-0Wang, XNat. Chem.Nanomaterials are known to display chemical and physical behaviours that are different from those of their bulk counterparts, but assembly processes in the sub-nanometre region are difficult to control. The early growth of nanomaterials is typically thought to involve two separate steps: nuCleation and the growth stage, as described by the LaMer model. Control of the shape and size of the final structure is typically determined during the growth stage by interactions between the nuClei and surrounding monomers. Here, we show that Clusters with well-defined structures, such as polyoxometalates, can intervene at the nuCleation stage of nickel oxysulfide and nickel-cobalt hydroxide by co-assembling with nuClei to produce uniform binary assemblies. Those can, in turn, incorporate a third, or also a fourth, type of nanoCluster to form ternary or quaternary assemblies, respectively. Both binary and ternary assemblies are shown to serve as efficient atomic-site catalysts for room-temperature gasoline desulfurization and stereoselective catalytic reactions.Incorporation of Clusters within inorganic materials through their addition during nuCleation steps27201931#N/ATRUE
991
s41557-018-0195-410.1038/s41557-018-0195-4FALSEhttps://doi.org/10.1038/s41557-018-0195-4Zhu, CQTransition-metal-bridged bimetallic Clusters with multiple uranium-metal bonds2019#N/ATRUE
992
s41467-021-24828-910.1038/s41467-021-24828-9FALSEhttps://doi.org/10.1038/s41467-021-24828-9Hou, JGNat. Commun.Rational design of single atom catalyst is critical for efficient sustainable energy conversion. However, the atomic-level control of active sites is essential for electrocatalytic materials in alkaline electrolyte. Moreover, well-defined surface structures lead to in-depth understanding of catalytic mechanisms. Herein, we report a single-atomic-site ruthenium stabilized on defective nickel-iron layered double hydroxide nanosheets (Ru-1/D-NiFe LDH). Under precise regulation of local coordination environments of catalytically active sites and the existence of the defects, Ru-1/D-NiFe LDH delivers an ultralow overpotential of 18mV at 10mAcm(-2) for hydrogen evolution reaction, surpassing the commercial Pt/C catalyst. Density functional theory calculations reveal that Ru-1/D-NiFe LDH optimizes the adsorption energies of intermediates for hydrogen evolution reaction and promotes the O-O coupling at a Ru-O active site for oxygen evolution reaction. The Ru-1/D-NiFe LDH as an ideal model reveals superior water splitting performance with potential for the development of promising water-alkali electrocatalysts. Rational design of single atom catalyst is critical for efficient sustainable energy conversion. Single-atomic-site ruthenium stabilized on defective nickel-iron layered double hydroxide nanosheets achieve superior HER and OER performance in alkaline media.Engineering single-atomic ruthenium catalytic sites on defective nickel-iron layered double hydroxide for overall water splitting0202167#N/ATRUE
993
s41467-021-24284-510.1038/s41467-021-24284-5FALSEhttps://doi.org/10.1038/s41467-021-24284-5Yan, NNat. Commun.Electrochemical water splitting is one of the most sustainable approaches for generating hydrogen. Because of the inherent constraints associated with the architecture and materials, the conventional alkaline water electrolyzer and the emerging proton exchange membrane electrolyzer are suffering from low efficiency and high materials/operation costs, respectively. Herein, we design a membrane-free flow electrolyzer, featuring a sandwich-like architecture and a cyClic operation mode, for decoupled overall water splitting. Comprised of two physically-separated compartments with flowing H-2-rich catholyte and O-2-rich anolyte, the cell delivers H-2 with a purity >99.1%. Its low internal ohmic resistance, highly active yet affordable bifunctional catalysts and efficient mass transport enable the water splitting at current density of 750mAcm(-2) biased at 2.1V. The eletrolyzer works equally well both in deionized water and in regular tap water. This work demonstrates the opportunity of combining the advantages of different electrolyzer concepts for water splitting via cell architecture and materials design, opening pathways for sustainable hydrogen generation. Seawater electrolysis is promising for grid-scale H-2 production without freshwater reliance, but high energy costs and detrimental Cl chemistry reduce its practical potential. Here, authors developed an energy-saving hybrid seawater electrolyzer for chlorine-free H-2 production and N2H4 degradation.A membrane-free flow electrolyzer operating at high current density using earth-abundant catalysts for water splitting0202157#N/ATRUE
994
s41467-020-20485-610.1038/s41467-020-20485-6FALSEhttps://doi.org/10.1038/s41467-020-20485-6Luecke, HNat. Commun.Infection of the human stomach by Helicobacter pylori remains a worldwide problem and greatly contributes to peptic ulcer disease and gastric cancer. Without active intervention approximately 50% of the world population will continue to be infected with this gastric pathogen. Current eradication, called triple therapy, entails a proton-pump inhibitor and two broadband antibiotics, however resistance to either Clarithromycin or metronidazole is greater than 25% and rising. Therefore, there is an urgent need for a targeted, high-specificity eradication drug. Gastric infection by H. pylori depends on the expression of a nickel-dependent urease in the cytoplasm of the bacteria. Here, we report the 2.0 angstrom resolution structure of the 1.1 MDa urease in complex with an inhibitor by cryo-electron microscopy and compare it to a beta -mercaptoethanol-inhibited structure at 2.5 angstrom resolution. The structural information is of sufficient detail to aid in the development of inhibitors with high specificity and affinity. Infection by Helicobacter pylori is associated with peptic ulcers and gastric cancer. H. pylori urease is required for colonization of the stomach and thus an attractive antimicrobial drug target. Cryo-EM analyses of the H. pylori urease with inhibitors bound reveal structural details useful in rational drug design.Cryo-EM structure of Helicobacter pylori urease with an inhibitor in the active site at 2.0 angstrom resolutionx2202145#N/AFALSE
995
s41467-021-24275-610.1038/s41467-021-24275-6FALSEhttps://doi.org/10.1038/s41467-021-24275-6Rabbia, ONat. Commun.Primitive olivines from the monogenetic cones Los Hornitos, Central-South Andes, preserve dendritic, skeletal, and polyhedral growth textures. Consecutive stages of textural maturation occur along compositional gradients where high Fo-Ni cores of polyhedral olivines (Fo(92.5), Ni similar to 3500ppm) contrast with the composition of dendritic olivines (Fo<91.5, Ni<3000ppm), indicating sequential nuCleation. Here we present a new growth model for oscillatory Fo-Ni olivine zoning that contrasts with the standard interpretation of continuous, sequential core-to-rim growth. Olivine grows rapidly via concentric addition of open-structured crystal frames, leaving behind compositional boundary layers that subsequently fill-in with Fo-Ni-depleted olivine, causing reversals. Elemental diffusion modeling reveals growth of individual crystal frames and eruption at the surface occurred over 3.5-40 days. Those timescales constrain magma ascent rates of 40-500m/h (0.011 to 0.14m/s) from the deep crust. Compared to ocean island basalts, where dendritic and skeletal olivines have been often described, magmas erupted at arc settings, experiencing storage and degassing, may lack such textures due to fundamentally different ascent histories. Arc olivines are commonly explained through a paradigm of core-to-rim sequential growth and oscillatory zoning is interpreted to represent magma mixing. Here the authors show Fo-Ni-P oscillatory zoned olivines can grow as out-of-sequence crystal frames and complex zoning can occur in Closed systems.Out-of-sequence skeletal growth causing oscillatory zoning in arc olivines0202171#N/ATRUE
996
s41467-021-24093-w10.1038/s41467-021-24093-wFALSEhttps://doi.org/10.1038/s41467-021-24093-wChen, MWNat. Commun.Glass transition is one of the unresolved critical issues in solid-state physics and materials science, during which a viscous liquid is frozen into a solid or structurally arrested state. On account of the uniform arrested mechanism, the calorimetric glass transition temperature (T-g) always follows the same trend as the dynamical glass transition (or alpha -relaxation) temperature (T-alpha) determined by dynamic mechanical analysis (DMA). Here, we explored the correlations between the calorimetric and dynamical glass transitions of three prototypical high-entropy metallic glasses (HEMGs) systems. We found that the HEMGs present a depressed dynamical glass transition phenomenon, i.e., HEMGs with moderate calorimetric T-g represent the highest T-alpha and the maximum Activation energy of alpha -relaxation. These decoupled glass transitions from thermal and mechanical measurements reveal the effect of high configurational entropy on the structure and dynamics of supercooled liquids and metallic glasses, which are associated with sluggish diffusion and decreased dynamic and spatial heterogeneities from high mixing entropy. The results have important implications in understanding the entropy effect on the structure and properties of metallic glasses for designing new materials with plenteous physical and mechanical performances. Here the authors study thermodynamic and dynamic glass transition of high entropy metallic glasses. Results show retarded alpha -relaxation and distinct crystallization resistance attributed to their sluggish diffusion and high-entropy mixing that is different from the traditional metallic glasses.Decoupling between calorimetric and dynamical glass transitions in high-entropy metallic glasses0202153#N/ATRUE
997
s41467-021-23182-010.1038/s41467-021-23182-0FALSEhttps://doi.org/10.1038/s41467-021-23182-0Moddel, GNat. Commun.Although the effect of resonant tunneling in metal-double-insulator-metal ((MIM)-M-2) diodes has been predicted for over two decades, no experimental demonstrations have been reported at the low voltages needed for energy harvesting rectenna applications. Using quantum-well engineering, we demonstrate the effects of resonant tunneling in a Ni/NiO/Al2O3/Cr/Au (MIM)-M-2 structures and achieve the usually mutually exClusive desired characteristics of low resistance (R-0(DC) similar to 13 k Omega for 0.035 mu m(2)) and high responsivity (beta(o) = 0.5 A W-1) simultaneously. By varying the thickness of insulators to modify the depth and width of the (MIM)-M-2 quantum well, we show that resonant quasi-bound states can be reached at near zero-bias, where diodes self-bias when driven by antennas illuminated at 30 THz. We present an improvement in energy conversion efficiency by more than a factor of 100 over the current state-of-the-art, offering the possibility of engineering efficient energy harvesting rectennas.Demonstration of resonant tunneling effects in metal-double-insulator-metal ((MIM)-M-2) diodes1202129#N/ATRUE
998
s41467-021-22707-x10.1038/s41467-021-22707-xFALSEhttps://doi.org/10.1038/s41467-021-22707-xRabkin, EThe impact of alloying on defect-free nanopartiCles exhibiting softer but tougher behavior2021#N/ATRUE
999
s41467-020-19420-610.1038/s41467-020-19420-6FALSEhttps://doi.org/10.1038/s41467-020-19420-6Seneor, PNat. Commun.We report on spin transport in state-of-the-art epitaxial monolayer graphene based 2D-magnetic tunnel junctions (2D-MTJs). In our measurements, supported by ab-initio calculations, the strength of interaction between ferromagnetic electrodes and graphene monolayers is shown to fundamentally control the resulting spin signal. In particular, by switching the graphene/ferromagnet interaction, spin transport reveals magneto-resistance signal MR>80% in junctions with low resistance x area products. Descriptions based only on a simple K-point filtering picture (i.e. MR increase with the number of layers) are not sufficient to predict the behavior of our devices. We emphasize that hybridization effects need to be taken into account to fully grasp the spin properties (such as spin dependent density of states) when 2D materials are used as ultimately thin interfaces. While this is only a first demonstration, we thus introduce the fruitful potential of spin manipulation by proximity effect at the hybridized 2D material / ferromagnet interface for 2D-MTJs. 2D materials are foreseen as an opportunity to tailor spintronics devices interfaces, a.k.a spinterfaces. Here, using state-of-the-art large-scale integration in spin-valves, authors demonstrate that hybridization of graphene with a metallic spin source results in strong spin filtering effects.Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriersx3202046#N/AFALSE
1000
s41467-021-22523-310.1038/s41467-021-22523-3FALSEhttps://doi.org/10.1038/s41467-021-22523-3Chen, JNat. Commun.Layered transition-metal oxides have attracted intensive interest for cathode materials of sodium-ion batteries. However, they are hindered by the limited capacity and inferior phase transition due to the gliding of transition-metal layers upon Na+ extraction and insertion in the cathode materials. Here, we report that the large-sized K+ is riveted in the prismatic Na+ sites of P2-Na0.612K0.056MnO2 to enable more thermodynamically favorable Na+ vacancies. The Mn-O bonds are reinforced to reduce phase transition during charge and discharge. 0.901 Na+ per formula are reversibly extracted and inserted, in which only the two-phase transition of P2 <-> P'2 occurs at low voltages. It exhibits the highest specific capacity of 240.5 mAh g(-1) and energy density of 654 Wh kg(-1) based on the redox of Mn3+/Mn4+, and a capacity retention of 98.2% after 100 cyCles. This investigation will shed lights on the tuneable chemical environments of transition-metal oxides for advanced cathode materials and promote the development of sodium-ion batteries. High-capacity and structural stable cathode materials are challenges for sodium-ion batteries. Here, the authors report a layered P2-Na0.612K0.056MnO2 with large-sized K+ riveted in the Na-layers to enable 0.9 Na+ (de)insertion with a reversible phase transition of P2-P'2.Tuning local chemistry of P2 layered-oxide cathode for high energy and long cyCles of sodium-ion battery0202149#N/ATRUE
1001
s41467-021-22512-610.1038/s41467-021-22512-6FALSEhttps://doi.org/10.1038/s41467-021-22512-6Miller, JTNat. Commun.In heterogeneous catalysis, olefin oligomerization is typically performed on immobilized transition metal ions, such as Ni2+ and Cr3+. Here we report that silica-supported, single site catalysts containing immobilized, main group Zn2+ and Ga3+ ion sites catalyze ethylene and propylene oligomerization to an equilibrium distribution of linear olefins with rates similar to that of Ni2+. The molecular weight distribution of products formed on Zn2+ is similar to Ni2+, while Ga3+ forms higher molecular weight olefins. In situ spectroscopic and computational studies suggest that oligomerization unexpectedly occurs by the Cossee-Arlman mechanism via metal hydride and metal Alkyl intermediates formed during olefin insertion and beta-hydride elimination elementary steps. Initiation of the catalytic cyCle is proposed to occur by heterolytic C-H dissociation of ethylene, which occurs at about 250 degrees C where oligomerization is catalytically relevant. This work illuminates new chemistry for main group metal catalysts with potential for development of new oligomerization processes.Olefin oligomerization by main group Ga3+ and Zn2+ single site catalysts on SiO21202168#N/ATRUE
1002
s41467-020-19329-010.1038/s41467-020-19329-0https://doi.org/10.1038/s41467-020-19329-0Jang, JWNat. Commun.Considering their superior charge-transfer characteristics, easy tenability of energy levels, and low production cost, organic semiconductors are ideal for photoelectrochemical (PEC) hydrogen production. However, organic-semiconductor-based photoelectrodes have not been extensively explored for PEC water-splitting because of their low stability in water. Herein, we report high-performance and stable organic-semiconductors photoanodes consisting of p-type polymers and n-type non-fullerene materials, which is passivated using nickel foils, GaIn eutectic, and layered double hydroxides as model materials. We achieve a photocurrent density of 15.1 mA cm(-2) at 1.23 V vs. reversible hydrogen electrode (RHE) with an onset potential of 0.55 V vs. RHE and a record high half-cell solar-to-hydrogen conversion efficiency of 4.33% under AM 1.5 G solar simulated light. After conducting the stability test at 1.3 V vs. RHE for 10 h, 90% of the initial photocurrent density are retained, whereas the photoactive layer without passivation lost its activity within a few minutes.High-performance and stable photoelectrochemical water splitting cell with organic-photoactive-layer-based photoanodePhotocatalyst9202066#N/AFALSE
1003
s41467-021-22066-710.1038/s41467-021-22066-7FALSEhttps://doi.org/10.1038/s41467-021-22066-7Shen, YNNat. Commun.The end-Permian mass extinction (EPME) was the most severe extinction event in the past 540 million years, and the Siberian Traps large igneous province (STLIP) is widely hypothesized to have been the primary trigger for the environmental catastrophe. The killing mechanisms depend critically on the nature of volatiles ejected during STLIP eruptions, initiating about 300 kyr before the extinction event, because the atmosphere is the primary interface between magmatism and extinction. Here we report Ni isotopes for Permian-Triassic sedimentary rocks from Arctic Canada. The delta Ni-60 data range from -1.09 to 0.35 parts per thousand, and exhibit the lightest delta Ni-60 compositions ever reported for sedimentary rocks. Our results provide strong evidence for global dispersion and loading of Ni-rich aerosol partiCles into the Panthalassic Ocean. Our data demonstrate that environmental degradation had begun well before the extinction event and provide a link between global dispersion of Ni-rich aerosols, ocean chemistry changes, and the EPME. The end-Permian mass extinction was the most severe extinction event in the past 540 million years, and the Siberian Traps large igneous province is widely hypothesized to have been the primary trigger for the environmental catastrophe. In this study, Ni isotopes provide the link between Siberian Traps magmatism and early environmental degradation, ultimately leading to the end-Permian extinction.Nickel isotopes link Siberian Traps aerosol partiCles to the end-Permian mass extinction0202154#N/ATRUE
1004
s41467-021-21083-w10.1038/s41467-021-21083-wFALSEhttps://doi.org/10.1038/s41467-021-21083-wShu, WNat. Commun.The development of straightforward synthesis of regio- and stereodefined alkenes with multiple aliphatic substituents under mild conditions is an unmet challenge owing to competitive beta -hydride elimination and selectivity issues. Herein, we report the nickel-catalyzed intermolecular cross-diAlkylation of alkynes devoid of directing or activating groups to afford multiple aliphatic substituted alkenes in a syn-selective fashion at room temperature. The combination of two-electron oxidative cyClometallation and single-electron cross-electrophile coupling of nickel enables the syn-cross-diAlkylation of alkynes at room temperature. This reductive protocol enables the sequential installation of two different Alkyl substituents onto alkynes in a regio- and stereo-selective manner, circumventing the tedious preformation of sensitive organometallic reagents. The synthetic utility of this protocol is demonstrated by efficient synthesis of multi-substituted unfunctionalized alkenes and diverse transformations of the product. The synthesis of regio- and stereo-defined alkenes with multiple Alkyl substituents is an unmet challenge. Here, the authors report a nickel-catalyzed intermolecular cross-diAlkylation of alkynes devoid of directing or activating groups to afford multiple aliphatic substituted alkenes in a syn-selective fashion.Ni-catalyzed regio- and stereo-defined intermolecular cross-electrophile diAlkylation of alkynes without directing group2202162#N/ATRUE
1005
s41467-020-19133-w10.1038/s41467-020-19133-wFALSEhttps://doi.org/10.1038/s41467-020-19133-wNam, KTNat. Commun.High-valent metal-oxo moieties have been implicated as key intermediates preceding various oxidation processes. The critical O-O bond formation step in the Kok cyCle that is presumed to generate molecular oxygen occurs through the high-valent Mn-oxo species of the water oxidation complex, i.e., the Mn4Ca Cluster in photosystem II. Here, we report the spectroscopic characterization of new intermediates during the water oxidation reaction of manganese-based heterogeneous catalysts and assign them as low-spin Mn(IV)-oxo species. Recently, the effects of the spin state in transition metal catalysts on catalytic reactivity have been intensely studied; however, no detailed characterization of a low-spin Mn(IV)-oxo intermediate species currently exists. We demonstrate that a low-spin configuration of Mn(IV), S=1/2, is stably present in a heterogeneous electrocatalyst of Ni-doped monodisperse 10-nm Mn3O4 nanopartiCles via oxo-ligand field engineering. An unprecedented signal (g=1.83) is found to evolve in the electron paramagnetic resonance spectrum during the stepwise transition from the Jahn-Teller-distorted Mn(III). In-situ Raman analysis directly provides the evidence for Mn(IV)-oxo species as the active intermediate species. Computational analysis confirmed that the substituted nickel species induces the formation of a z-axis-compressed octahedral C-4v crystal field that stabilizes the low-spin Mn(IV)-oxo intermediates. Understanding reaction intermediates provides a foundation for active electrocatalysts' design, but it remains elusive for heterogeneous electrocatalysts. Here, the authors report the spectroscopic characterization of low-spin Mn(IV)-oxo as the active intermediates during electrochemical water oxidation.Spectroscopic capture of a low-spin Mn(IV)-oxo species in Ni-Mn3O4 nanopartiCles during water oxidation catalysisx2202061#N/AFALSE
1006
s41467-021-21017-610.1038/s41467-021-21017-6FALSEhttps://doi.org/10.1038/s41467-021-21017-6Zhong, CJNat. Commun.Alloying noble metals with non-noble metals enables high activity while reducing the cost of electrocatalysts in fuel cells. However, under fuel cell operating conditions, state-of-the-art oxygen reduction reaction alloy catalysts either feature high atomic percentages of noble metals (>70%) with limited durability or show poor durability when lower percentages of noble metals (<50%) are used. Here, we demonstrate a highly-durable alloy catalyst derived by alloying PtPd (<50%) with 3d-transition metals (Cu, Ni or Co) in ternary compositions. The origin of the high durability is probed by in-situ/operando high-energy synchrotron X-ray diffraction coupled with pair distribution function analysis of atomic phase structures and strains, revealing an important role of realloying in the compressively-strained single-phase alloy state despite the occurrence of dealloying. The implication of the finding, a striking departure from previous perceptions of phase-segregated noble metal skin or complete dealloying of non-noble metals, is the fulfilling of the promise of alloy catalysts for mass commercialization of fuel cells. Durability of catalysts under fuel cell reaction conditions is challenging for active nanoalloy electrocatalysts derived from platinum group metals and other transition metals. Here, the authors show that realloying in certain multimetallic nanoalloys plays a major role in enabling the high durability.Alloying-realloying enabled high durability for Pt-Pd-3d-transition metal nanopartiCle fuel cell catalysts5202157#N/ATRUE
1007
s41467-020-20644-910.1038/s41467-020-20644-9FALSE#REF!Guo, CCollective synthesis of acetylenic pharmaceuticals via enantioselective Nickel/Lewis acid-catalyzed propargylic Alkylation2021#N/ATRUE
1008
s41467-020-18870-210.1038/s41467-020-18870-2FALSEhttps://doi.org/10.1038/s41467-020-18870-2Stahlberg, HNat. Commun.Urease converts urea into ammonia and carbon dioxide and makes urea available as a nitrogen source for all forms of life except animals. In human bacterial pathogens, ureases also aid in the invasion of acidic environments such as the stomach by raising the surrounding pH. Here, we report the structure of urease from the pathogen Yersinia enterocolitica at 2 angstrom resolution from cryo-electron microscopy. Y. enterocolitica urease is a dodecameric assembly of a trimer of three protein chains, ureA, ureB and ureC. The high data quality enables detailed visualization of the urease bimetal active site and of the impact of radiation damage. The obtained structure is of sufficient quality to support drug development efforts. Urease is a nickel enzyme responsible for catalyzing the conversion of urea into ammonia and carbon dioxide. Here the authors report a high resolution cryo-EM structure of urease from the bacterial pathogen Yersinia enterocolitica, providing a detailed visualization of the urease bimetal active site and a basis for drug development.High-resolution cryo-EM structure of urease from the pathogen Yersinia enterocoliticax2202058#N/AFALSE
1009
s41467-020-20503-710.1038/s41467-020-20503-7FALSEhttps://doi.org/10.1038/s41467-020-20503-7Ito, YNat. Commun.Graphene-covering is a promising approach for achieving an acid-stable, non-noble-metal-catalysed hydrogen evolution reaction (HER). Optimization of the number of graphene-covering layers and the density of defects generated by chemical doping is crucial for achieving a balance between corrosion resistance and catalytic activity. Here, we investigate the influence of charge transfer and proton penetration through the graphene layers on the HER mechanisms of the non-noble metals Ni and Cu in an acidic electrolyte. We find that increasing the number of graphene-covering layers significantly alters the HER performances of Ni and Cu. The proton penetration explored through electrochemical experiments and simulations reveals that the HER activity of the graphene-covered catalysts is governed by the degree of proton penetration, as determined by the number of graphene-covering layers. Graphene-covering technology provides a promising approach for achieving a non-noble-metal-catalyst with corrosion protection and catalytic activity under acidic media. Here, the authors unveil that the electrochemical hydrogen evolution mechanism is governed by the proton penetration phenomenon.Catalytic activity of graphene-covered non-noble metals governed by proton penetration in electrochemical hydrogen evolution reaction6202143#N/ATRUE
1010
s41467-020-18585-410.1038/s41467-020-18585-4FALSEhttps://doi.org/10.1038/s41467-020-18585-4Yu, SHNat. Commun.Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi4 catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction. The lack of efficient and cost-effective catalysts for hydrogen oxidation reaction (HOR) hampers the application of hydroxide exchange membrane fuel cells. Here, authors reported bimetallic MoNi4 and WNi4 nanoalloys with marked HOR activity in alkali, among which MoNi4 outperforms the Pt/C catalyst.Bimetallic nickel-molybdenum/tungsten nanoalloys for high-efficiency hydrogen oxidation catalysis in alkaline electrolytesx15202054#N/AFALSE
1011
s41467-020-18459-910.1038/s41467-020-18459-9FALSEhttps://doi.org/10.1038/s41467-020-18459-9Xue, JMNat. Commun.Achieving a functional and durable non-platinum group metal-based methanol oxidation catalyst is critical for a cost-effective direct methanol fuel cell. While Ni(OH)(2) has been widely studied as methanol oxidation catalyst, the initial process of oxidizing Ni(OH)(2) to NiOOH requires a high potential of 1.35V vs. RHE. Such potential would be impractical since the theoretical potential of the cathodic oxygen reduction reaction is at 1.23V. Here we show that a four-coordinated nickel atom is able to form charge-transfer orbitals through delocalization of electrons near the Fermi energy level. As such, our previously reported periodically arranged four-six-coordinated nickel hydroxide nanoribbon structure (NR-Ni(OH)(2)) is able to show remarkable methanol oxidation activity with an onset potential of 0.55V vs. RHE and suggests the operability in direct methanol fuel cell configuration. Thus, this strategy offers a gateway towards the development of high performance and durable non-platinum direct methanol fuel cell. Development of suitable methanol oxidation reaction catalysts for direct methanol fuel cells is challenging due to sluggish kinetics. Herein, authors show that four-coordinate nickel atoms form charge-transfer orbitals near the Fermi energy level, leading to remarkable methanol oxidation activity.Materializing efficient methanol oxidation via electron delocalization in nickel hydroxide nanoribbonx9202026#N/AFALSE
1012
s41467-020-18017-310.1038/s41467-020-18017-3FALSEhttps://doi.org/10.1038/s41467-020-18017-3Zhong, CJNat. Commun.The need for active and stable oxidation catalysts is driven by the demands in production of valuable chemicals, remediation of hydrocarbon pollutants and energy sustainability. Traditional approaches focus on oxygen-activating oxides as support which provides the oxygen Activation at the catalyst-support peripheral interface. Here we report a new approach to oxidation catalysts for total oxidation of hydrocarbons (e.g., propane) by surface oxygenation of platinum (Pt)-alloyed multicomponent nanopartiCles (e.g., platinum-nickel cobalt (Pt-NiCo)). The in-situ/operando time-resolved studies, inCluding high-energy synchrotron X-ray diffraction and diffuse reflectance infrared Fourier transform spectroscopy, demonstrate the formation of oxygenated Pt-NiOCoO surface layer and disordered ternary alloy core. The results reveal largely-irregular oscillatory kinetics associated with the dynamic lattice expansion/shrinking, ordering/disordering, and formation of surface-oxygenated sites and intermediates. The catalytic synergy is responsible for reduction of the oxidation temperature by similar to 100 degrees C and the high stability under 800 degrees C hydrothermal aging in comparison with Pt, and may represent a paradigm shift in the design of self-supported catalysts.Surface oxygenation of multicomponent nanopartiCles toward active and stable oxidation catalystsx6202035#N/AFALSE
1013
s41467-020-20124-010.1038/s41467-020-20124-0FALSEhttps://doi.org/10.1038/s41467-020-20124-0van Hest, JCMNat. Commun.The cell cytosol is crowded with high concentrations of many different biomacromolecules, which is difficult to mimic in bottom-up synthetic cell research and limits the functionality of existing protocellular platforms. There is thus a Clear need for a general, biocompatible, and accessible tool to more accurately emulate this environment. Herein, we describe the development of a discrete, membrane-bound coacervate-based protocellular platform that utilizes the well-known binding motif between Ni2+-nitrilotriacetic acid and His-tagged proteins to exercise a high level of control over the loading of biologically relevant macromolecules. This platform can accrete proteins in a controlled, efficient, and benign manner, culminating in the enhancement of an encapsulated two-enzyme cascade and protease-mediated cargo secretion, highlighting the potency of this methodology. This versatile approach for programmed spatial organization of biologically relevant proteins expands the protocellular toolbox, and paves the way for the development of the next generation of complex yet well-regulated synthetic cells. Mimicking the crowded cytosol of cells in synthetic cells has been a major limitation to the functionality. Here, the authors used the interaction between nickel, nitrilotriacetic acid and histidine tagged proteins to control loading of macromolecules into spatially programmed coacervate-based protocells.Programmed spatial organization of biomacromolecules into discrete, coacervate-based protocells6202054#N/ATRUE
1014
s41467-020-20004-710.1038/s41467-020-20004-7FALSESargent, EHPromoting CO2 methanation via ligand-stabilized metal oxide Clusters as hydrogen-donating motifs2020#N/ATRUE
1015
s41467-020-19908-110.1038/s41467-020-19908-1FALSEhttps://doi.org/10.1038/s41467-020-19908-1Wen, HHNat. Commun.The pairing mechanism in cuprates remains as one of the most challenging issues in condensed matter physics. Recently, superconductivity was discovered in thin films of the infinite-layer nickelate Nd1-xSrxNiO2 (x=0.12-0.25) which is believed to have the similar 3d(9) orbital electrons as that in cuprates. Here we report single-partiCle tunneling measurements on the superconducting nickelate thin films. We find predominantly two types of tunneling spectra, one shows a V-shape feature which can be fitted well by a d-wave gap function with gap maximum of about 3.9meV, another one exhibits a full gap of about 2.35meV. Some spectra demonstrate mixed contributions of these two components. Combining with theoretical calculations, we attribute the d-wave gap to the pairing potential of the Ni-3dx2-y2 orbital. Several possible reasons are given for explaining the full gap feature. Our results indicate both similarities and distinctions between the newly found Ni-based superconductors and cuprates.Single partiCle tunneling spectrum of superconducting Nd1-xSrxNiO2 thin films17202029#N/ATRUE
1016
s41467-020-19729-210.1038/s41467-020-19729-2FALSEhttps://doi.org/10.1038/s41467-020-19729-2Diaz-Morales, ONat. Commun.Efficient oxygen evolution reaction (OER) electrocatalysts are pivotal for sustainable fuel production, where the Ni-Fe oxyhydroxide (OOH) is among the most active catalysts for alkaline OER. Electrolyte alkali metal cations have been shown to modify the activity and reaction intermediates, however, the exact mechanism is at question due to unexplained deviations from the cation size trend. Our X-ray absorption spectroelectrochemical results show that bigger cations shift the Ni2+/(3+delta)+ redox peak and OER activity to lower potentials (however, with typical discrepancies), following the order CsOH>NaOH approximate to KOH>RbOH>LiOH. Here, we find that the OER activity follows the variations in electrolyte pH rather than a specific cation, which accounts for differences both in basicity of the alkali hydroxides and other contributing anomalies. Our density functional theory-derived reactivity descriptors confirm that cations impose negligible effect on the Lewis acidity of Ni, Fe, and O lattice sites, thus strengthening the conClusions of an indirect pH effect. It is commonly accepted that electrolyte alkali metal cations modify the catalytic activity for oxygen evolution reaction. Here the authors challenge this assumption, showing that the activity is actually affected by a change in the electrolyte pH rather than a specific alkali cation.Key activity descriptors of nickel-iron oxygen evolution electrocatalysts in the presence of alkali metal cations2202075#N/ATRUE
1017
s41467-020-17904-z10.1038/s41467-020-17904-zFALSEhttps://doi.org/10.1038/s41467-020-17904-zHuang, JENat. Commun.1T-MoS2 and single-atom modified analogues represent a highly promising Class of low-cost catalysts for hydrogen evolution reaction (HER). However, the role of single atoms, either as active species or promoters, remains vague despite its essentiality toward more efficient HER. In this work, we report the unambiguous identification of Ni single atom as key active sites in the basal plane of 1T-MoS2 (Ni@1T-MoS2) that result in efficient HER performance. The intermediate structure of this Ni active site under catalytic conditions was captured by in situ X-ray absorption spectroscopy, where a reversible metallic Ni species (Ni-0) is observed in alkaline conditions whereas Ni remains in its local structure under acidic conditions. These insights provide crucial mechanistic understanding of Ni@1T-MoS2 HER electrocatalysts and suggest that the understanding gained from such in situ studies is necessary toward the development of highly efficient single-atom decorated 1T-MoS2 electrocatalysts. While single atom catalysis combines heterogeneous materials with molecular understanding, the role of the single atoms remains vague. Here, authors examine single Ni on MoS2 via in situ X-ray absorption spectroscopy to reveal the intermediate and catalytically active species.Dynamic evolution and reversibility of single-atom Ni(II) active site in 1T-MoS2 electrocatalysts for hydrogen evolutionx10202054#N/AFALSE
1018
s41467-020-19413-510.1038/s41467-020-19413-5FALSEhttps://doi.org/10.1038/s41467-020-19413-5Zhuang, ZBNat. Commun.The development of cost-effective hydroxide exchange membrane fuel cells is limited by the lack of high-performance and low-cost anode hydrogen oxidation reaction catalysts. Here we report a Pt-free catalyst Ru7Ni3/C, which exhibits excellent hydrogen oxidation reaction activity in both rotating disk electrode and membrane electrode assembly measurements. The hydrogen oxidation reaction mass activity and specific activity of Ru7Ni3/C, as measured in rotating disk experiments, is about 21 and 25 times that of Pt/C, and 3 and 5 times that of PtRu/C, respectively. The hydroxide exchange membrane fuel cell with Ru7Ni3/C anode can deliver a high peak power density of 2.03Wcm(-2) in H-2/O-2 and 1.23Wcm(-2) in H-2/air (CO2-free) at 95 degrees C, surpassing that using PtRu/C anode catalyst, and good durability with less than 5% voltage loss over 100h of operation. The weakened hydrogen binding of Ru by alloying with Ni and enhanced water adsorption by the presence of surface Ni oxides lead to the high hydrogen oxidation reaction activity of Ru7Ni3/C. By using the Ru7Ni3/C catalyst, the anode cost can be reduced by 85% of the current state-of-the-art PtRu/C, making it highly promising in economical hydroxide exchange membrane fuel cells. Development of hydroxide exchange membrane fuel cells (HEMFCs) requires high-performance and low-cost catalysts for hydrogen oxidation reaction at the anode. Here the authors report Ru7Ni3/C as anode catalysts, delivering high power density and good durability in alkaline media for HEMFCs.A highly-active, stable and low-cost platinum-free anode catalyst based on RuNi for hydroxide exchange membrane fuel cells9202049#N/ATRUE
1019
s41467-020-19391-810.1038/s41467-020-19391-8FALSEhttps://doi.org/10.1038/s41467-020-19391-8Jung, YNat. Commun.Phase separation of specific biomolecules into liquid droplet-like condensates is a key mechanism to form membrane-less organelles, which spatio-temporally organize diverse biochemical processes in cells. To investigate the working principles of these biomolecular condensates as dynamic reaction centers, precise control of diverse condensate properties is essential. Here, we design a strategy for metal ion-induced Clustering of minimal protein modules to produce liquid protein condensates, the properties of which can be widely varied by simple manipulation of the protein Clustering systems. The droplet forming-minimal module contains only a single receptor protein and a binding ligand peptide with a hexahistidine tag for divalent metal ion-mediated Clustering. A wide range of protein condensate properties such as droplet forming tendency, droplet morphology, inside protein diffusivity, protein recruitment, and droplet density can be varied by adjusting the nature of receptor/ligand pairs or used metal ions, metal/protein ratios, incubation time, binding motif variation on recruited proteins, and even spacing between receptor/ligand pairs and the hexahistidine tag. We also demonstrate metal-ion-induced protein phase separation in cells. The present phase separation strategy provides highly versatile protein condensates, which will greatly facilitate investigation of molecular and structural codes of droplet-forming proteins and the monitoring of biomolecular behaviors inside diverse protein condensates. Mimetic membrane-less organelles are of interest for the range of biochemical processes which can be spatio-temporally organized using them. Here, the authors report on a protein condensate system formed by metal ion induced Clustering and demonstrate control over condensate properties.Behavior control of membrane-less protein liquid condensates with metal ion-induced phase separation2202058#N/ATRUE
1020
s41467-020-16715-610.1038/s41467-020-16715-6FALSEhttps://doi.org/10.1038/s41467-020-16715-6Jiang, HLNat. Commun.Single-atom catalysts (SACs) have sparked broad interest recently while the low metal loading poses a big challenge for further applications. Herein, a dual protection strategy has been developed to give high-content SACs by nanocasting SiO2 into porphyrinic metal-organic frameworks (MOFs). The pyrolysis of SiO2@MOF composite affords single-atom Fe implanted N-doped porous carbon (Fe-SA-N-C) with high Fe loading (3.46wt%). The spatial isolation of Fe atoms centered in porphyrin linkers of MOF sets the first protective barrier to inhibit the Fe agglomeration during pyrolysis. The SiO2 in MOF provides additional protection by creating thermally stable FeN4/SiO2 interfaces. Thanks to the high-density Fe-SA sites, Fe-SA-N-C demonstrates excellent oxygen reduction performance in both alkaline and acidic medias. Meanwhile, Fe-SA-N-C also exhibits encouraging performance in proton exchange membrane fuel cell, demonstrating great potential for practical application. More far-reaching, this work grants a general synthetic methodology toward high-content SACs (such as Fe-SA, Co-SA, Ni-SA). Single-atom catalysts (SACs) with high metal loading are highly desired to improve catalytic performance. Here, the authors report a dual protection strategy by nanocasting SiO2 into metal-organic frameworks to prepare high-loading SACs with excellent catalytic performance toward oxygen reduction.Nanocasting SiO2 into metal-organic frameworks imparts dual protection to high-loading Fe single-atom electrocatalystsx66202047#N/AFALSE
1021
s41467-020-19214-w10.1038/s41467-020-19214-wFALSEhttps://doi.org/10.1038/s41467-020-19214-wHou, JGNat. Commun.Rational design of the catalysts is impressive for sustainable energy conversion. However, there is a grand challenge to engineer active sites at the interface. Herein, hierarchical transition bimetal oxides/sulfides heterostructure arrays interacting two-dimensional MoOx/MoS2 nanosheets attached to one-dimensional NiOx/Ni3S2 nanorods were fabricated by oxidation/hydrogenation-induced surface reconfiguration strategy. The NiMoOx/NiMoS heterostructure array exhibits the overpotentials of 38mV for hydrogen evolution and 186mV for oxygen evolution at 10mAcm(-2), even surviving at a large current density of 500mAcm(-2) with long-term stability. Due to optimized adsorption energies and accelerated water splitting kinetics by theory calculations, the assembled two-electrode cell delivers the industrially relevant current densities of 500 and 1000mAcm(-2) at record low cell voltages of 1.60 and 1.66V with excellent durability. This research provides a promising avenue to enhance the electrocatalytic performance of the catalysts by engineering interfacial active sites toward large-scale water splitting. While water splitting is an appealing carbon-neutral strategy for renewable energy generation, there is a need to develop new active, cost-effective catalysts. Here, authors prepare a nickel-molybdenum oxide/sulfide heterojunctions as bifunctional H-2 and O-2 evolution electrocatalysts.Engineering active sites on hierarchical transition bimetal oxides/sulfides heterostructure array enabling robust overall water splitting21202077#N/ATRUE
1022
s41467-020-16139-210.1038/s41467-020-16139-2FALSEhttps://doi.org/10.1038/s41467-020-16139-2Ho, CYNat. Commun.Enantioenriched 1,4-dienes are versatile building blocks in asymmetric synthesis, therefore their efficient synthesis directly from chemical feedstock is highly sought after. Here, we show an enantioselective cross-hydroalkenylation of cyClic 1,3-diene and hetero-substituted terminal olefin by using a chiral [NHC-Ni(allyl)]BArF catalyst. Using a structurally flexible chiral C-2 NHC-Ni design is key to access a broad scope of chiral 1,4-diene 3 or 3 with high enantioselectivity. This study also offers insights on how to regulate chiral C-2 NHC-Ni(II) 1,3-allylic shift on cyClic diene 1 and to build sterically more hindered endocyClic chiral allylic structures on demand. p id=Par Chiral 1,4-dienes are versatile building blocks in asymmetric synthesis, therefore their production is highly sought after. Here, the authors report an efficient enantioselective cross-hydroalkenylation of cyClic 1,3-dienes and terminal olefins affording chiral 1,4-dienes by using a chiral NHC-Ni(allyl)]BArF catalyst.NHC-Ni catalyzed enantioselective synthesis of 1,4-dienes by cross-hydroalkenylation of cyClic 1,3-dienes and heterosubstituted terminal olefinsx7202046#N/AFALSE
1023
s41467-020-19194-x10.1038/s41467-020-19194-xFALSEhttps://doi.org/10.1038/s41467-020-19194-xMao, JYNat. Commun.The catalytic generation of homoenolates and their higher homologues has been a long-standing challenge. Like the generation of transition metal enolates, which have been used to great affect in synthesis and medicinal chemistries, homoenolates and their higher homologues have much potential, albeit largely unrealized. Herein, a nickel-catalyzed generation of homoenolates, and their higher homologues, via deCarbonylation of readily available cyClic anhydrides has been developed. The utility of nickel-bound homoenolates and their higher homologues is demonstrated by cross-coupling with unactivated Alkyl bromides, generating a diverse array of aliphatic acids. A broad range of functional groups is tolerated. Preliminary mechanistic studies demonstrate that: (1) oxidative addition of anhydrides by the catalyst is faster than oxidative addition of Alkyl bromides; (2) nickel bound metallocyCles are involved in this transformation and (3) the catalyst undergoes a single electron transfer (SET) process with the Alkyl bromide. Homoenolates and their higher homologs have much potential, albeit largely unrealized, in transition metal catalysis. Here, the authors report the nickel-catalyzed generation of homoenolates, and their higher homologs, via deCarbonylation of cyClic anhydrides, which then undergo cross-coupling with Alkyl bromides.Nickel-catalyzed reductive coupling of homoenolates and their higher homologues with unactivated Alkyl bromides1202075#N/ATRUE
1024
s41467-020-16085-z10.1038/s41467-020-16085-zFALSEhttps://doi.org/10.1038/s41467-020-16085-zHuang, EWNat. Commun.Alloys with ultra-high strength and sufficient ductility are highly desired for modern engineering applications but difficult to develop. Here we report that, by a careful controlling alloy composition, thermomechanical process, and microstructural feature, a Co-Cr-Ni-based medium-entropy alloy (MEA) with a dual heterogeneous structure of both matrix and precipitates can be designed to provide an ultra-high tensile strength of 2.2GPa and uniform elongation of 13% at ambient temperature, properties that are much improved over their counterparts without the heterogeneous structure. Electron microscopy characterizations reveal that the dual heterogeneous structures are composed of a heterogeneous matrix with both coarse grains (10 similar to 30 mu m) and ultra-fine grains (0.5 similar to 2 mu m), together with heterogeneous L1(2)-structured nanoprecipitates ranging from several to hundreds of nanometers. The heterogeneous L1(2) nanoprecipitates are fully coherent with the matrix, minimizing the elastic misfit strain of interfaces, relieving the stress concentration during deformation, and playing an active role in enhanced ductility. Improving both strength and ductility simultaneously in structural metals and alloys remains a challenge. Here, the authors design a heterogeneous structure in a Co-Cr-Ni alloy that results in ultrahigh strength and significant uniform elongation.Dual heterogeneous structures lead to ultrahigh strength and uniform ductility in a Co-Cr-Ni medium-entropy alloyx21202038#N/AFALSE
1025
s41467-020-18943-210.1038/s41467-020-18943-2FALSEhttps://doi.org/10.1038/s41467-020-18943-2Ozin, GANat. Commun.Akin to single-site homogeneous catalysis, a long sought-after goal is to achieve reaction site precision in heterogeneous catalysis for chemical control over patterns of activity, selectivity and stability. Herein, we report on metal phosphides as a Class of material capable of realizing these attributes and unlock their potential in solar-driven CO2 hydrogenation. Selected as an archetype, Ni12P5 affords a structure based upon highly dispersed nickel nanoClusters integrated into a phosphorus lattice that harvest light intensely across the entire solar spectral range. Motivated by its panchromatic absorption and unique linearly bonded nickel-Carbonyl-dominated reaction route, Ni12P5 is found to be a photothermal catalyst for the reverse water gas shift reaction, offering a CO production rate of 96012mmolg(cat)(-1)h(-1), near 100% selectivity and long-term stability. Successful extension of this idea to Co2P analogs implies that metal phosphide materials are poised as a universal platform for high-rate and highly selective photothermal CO2 catalysis. There exists an urgent need to develop new materials to convert CO2 to useful products. Here, authors demonstrate metal phosphide nanopartiCles to enable light-driven CO2 hydrogenation with high activities and near-unity selectivity.High-performance light-driven heterogeneous CO2 catalysis with near-unity selectivity on metal phosphides6202047#N/ATRUE
1026
s41467-020-18891-x10.1038/s41467-020-18891-xFALSEhttps://doi.org/10.1038/s41467-020-18891-xXia, BYNat. Commun.Nickel-iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel-iron hydroxides. The anaerobic sulfate-reducing bacteria, using sulfate as the electron acceptor, play a significant role in the formation of iron sulfide decorated nickel-iron hydroxides, which exhibit excellent electrocatalytic performance for oxygen evolution. Experimental and theoretical investigations suggest that the synergistic effect between oxyhydroxides and sulfide species accounts for the high activity. This microorganism corrosion strategy not only provides efficient candidate electrocatalysts but also bridges traditional corrosion engineering and emerging electrochemical energy technologies. Developing facile strategies to realize the precise construction of Ni-Fe structures is of significance for water oxidation. Here, the authors demonstrate a universal microorganism-assisted corrosion strategy for preparing highly efficient Ni-Fe composites towards oxygen evolution.Preparation of nickel-iron hydroxides by microorganism corrosion for efficient oxygen evolution39202043#N/ATRUE
1027
s41467-020-18658-410.1038/s41467-020-18658-4FALSEhttps://doi.org/10.1038/s41467-020-18658-4Feng, CNat. Commun.Despite remarkable recent advances in transition-metal-catalyzed C(sp(3))-C cross-coupling reactions, there remain challenging bond formations. One Class of such reactions inClude the formation of tertiary-C(sp(3))-C bonds, presumably due to unfavorable steric interactions and competing isomerizations of tertiary Alkyl metal intermediates. Reported herein is a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated Alkyl bromides at remote tertiary centers. This approach enables the facile construction of otherwise difficult to prepare all-carbon quaternary centers. Key to the success of this transformation is an unusual remote functionalization via chain walking to the most sterically hindered tertiary C(sp(3)) center of the substrate. Preliminary mechanistic and radical trapping studies with primary Alkyl bromides suggest a unique mode of tertiary C-radical generation through chain-walking followed by Ni-C bond homolysis. This strategy is complementary to the existing coupling protocols with tert-Alkyl organometallic or -Alkyl halide reagents, and it enables the expedient formation of quaternary centers from easily available starting materials. Formation of tertiary C(sp(3))-C bonds is a formidable challenge due to steric interactions and low barriers for isomerization of intermediates. Here, the authors show a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated Alkyl bromides at remote tertiary carbon centers.Migratory functionalization of unactivated Alkyl bromides for construction of all-carbon quaternary centers via transposed tert-C-radicals9202076#N/ATRUE
1028
s41467-020-17941-810.1038/s41467-020-17941-8FALSEhttps://doi.org/10.1021/ja3079362Tsubaki, NMetal 3D printing technology for functional integration of catalytic system2020#N/ATRUE
1029
s41467-020-17939-210.1038/s41467-020-17939-2FALSEhttps://doi.org/10.1038/s41467-020-17939-2Li, YHNat. Commun.Cyano-containing compounds constitute important pharmaceuticals, agrochemicals and organic materials. Traditional cyanation methods often rely on the use of toxic metal cyanides which have serious disposal, storage and transportation issues. Therefore, there is an increasing need to develop general and efficient catalytic methods for cyanide-free production of nitriles. Here we report the reductive cyanation of organic chlorides using CO2/NH3 as the electrophilic CN source. The use of tridentate phosphine ligand Triphos allows for the nickel-catalyzed cyanation of a broad array of Aryl and aliphatic chlorides to produce the desired nitrile products in good yields, and with excellent functional group tolerance. Cheap and bench-stable urea was also shown as suitable CN source, suggesting promising application potential. Mechanistic studies imply that Triphos-Ni(I) species are responsible for the reductive C-C coupling approach involving isocyanate intermediates. This method expands the application potential of reductive cyanation in the synthesis of functionalized nitrile compounds under cyanide-free conditions, which is valuable for safe synthesis of (isotope-labeled) drugs.Reductive cyanation of organic chlorides using CO2 and NH3 via Triphos-Ni(I) species2202061#N/ATRUE
1030
s41467-020-17935-610.1038/s41467-020-17935-6FALSEhttps://doi.org/10.1038/s41467-020-17935-6Turchinovich, DNat. Commun.A material's magnetic state and its dynamics are of great fundamental research interest and are also at the core of a wide plethora of modern technologies. However, reliable access to magnetization dynamics in materials and devices on the technologically relevant ultrafast timescale, and under realistic device-operation conditions, remains a challenge. Here, we demonstrate a method of ultrafast terahertz (THz) magnetometry, which gives direct access to the (sub-)picosecond magnetization dynamics even in encapsulated materials or devices in a contact-free fashion, in a fully calibrated manner, and under ambient conditions. As a showcase for this powerful method, we measure the ultrafast magnetization dynamics in a laser-excited encapsulated iron film. Our measurements reveal and disentangle distinct contributions originating from (i) incoherent hot-magnon-driven magnetization quenching and (ii) coherent acoustically-driven modulation of the exchange interaction in iron, paving the way to technologies utilizing ultrafast heat-free control of magnetism. High sensitivity and relative ease of experimental arrangement highlight the promise of ultrafast THz magnetometry for both fundamental studies and the technological applications of magnetism.Ultrafast terahertz magnetometry10202058#N/ATRUE
1031
s41467-020-17934-710.1038/s41467-020-17934-7FALSEhttps://doi.org/10.1038/s41467-020-17934-7Chai, YNat. Commun.Anodic oxygen evolution reaction (OER) is recognized as kinetic bottleneck in water electrolysis. Transition metal sites with high valence states can accelerate the reaction kinetics to offer highly intrinsic activity, but suffer from thermodynamic formation barrier. Here, we show subtle engineering of highly oxidized Ni4+ species in surface reconstructed (oxy)hydroxides on multicomponent FeCoCrNi alloy film through interatomically electronic interplay. Our spectroscopic investigations with theoretical studies uncover that Fe component enables the formation of Ni4+ species, which is energetically favored by the multistep evolution of Ni2+-> Ni3+-> Ni4+. The dynamically constructed Ni4+ species drives holes into oxygen ligands to facilitate intramolecular oxygen coupling, triggering lattice oxygen Activation to form Fe-Ni dual-sites as ultimate catalytic center with highly intrinsic activity. As a result, the surface reconstructed FeCoCrNi OER catalyst delivers outstanding mass activity and turnover frequency of 3601A g(metal)(-1) and 0.483s(-1) at an overpotential of 300mV in alkaline electrolyte, respectively. Electrocatalytic water oxidation is facilitated by high valence states, but these are challenging to achieve at low applied potentials. Here, authors report a multicomponent FeCoCrNi alloy with dynamically formed Ni4+ species to offer high catalytic activity via lattice oxygen Activation mechanism.Lattice oxygen Activation enabled by high-valence metal sites for enhanced water oxidation32202068#N/ATRUE
1032
s41467-020-17627-110.1038/s41467-020-17627-1FALSEhttps://doi.org/10.1038/s41467-020-17627-1Park, AHANat. Commun.Current thermochemical methods to generate H-2 inClude gasification and steam reforming of coal and natural gas, in which anthropogenic CO2 emission is inevitable. If biomass is used as a source of H-2, the process can be considered carbon-neutral. Seaweeds are among the less studied types of biomass with great potential because they do not require freshwater. Unfortunately, reaction pathways to thermochemically convert salty and wet biomass into H-2 are limited. In this study, a catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H-2 with substantially suppressed CO2 formation making the overall biomass conversion not only carbon-neutral but also potentially carbon-negative. High-purity 69.69 mmol-H-2/(dry-ash-free)g-brown seaweed is produced with a conversion as high as 71%. The hydroxide is involved in both H-2 production and in situ CO2 capture, while the Ni/ZrO2 catalyst enhanced the secondary H-2 formation via steam methane reforming and water-gas shift reactions.Alkaline thermal treatment of seaweed for high-purity hydrogen production with carbon capture and storage potential3202060#N/ATRUE
1033
s41467-020-17018-610.1038/s41467-020-17018-6FALSEhttps://doi.org/10.1038/s41467-020-17018-6Mao, LQNat. Commun.Nitric oxide (NO) has been implicated in a variety of physiological and pathological processes. Monitoring cellular levels of NO requires a sensor to feature adequate sensitivity, transient recording ability and biocompatibility. Herein we report a single-atom catalysts (SACs)-based electrochemical sensor for the detection of NO in live cellular environment. The system employs nickel single atoms anchored on N-doped hollow carbon spheres (Ni SACs/N-C) that act as an excellent catalyst for electrochemical oxidation of NO. Notably, Ni SACs/N-C shows superior electrocatalytic performance to the commonly used Ni based nanomaterials, attributing from the greatly reduced Gibbs free energy that are required for Ni SACs/N-C in activating NO oxidation. Moreover, Ni SACs-based flexible and stretchable sensor shows high biocompatibility and low nanomolar sensitivity, enabling the real-time monitoring of NO release from cells upon drug and stretch stimulation. Our results demonstrate a promising means of using SACs for electrochemical sensing applications.Single-atom Ni-N-4 provides a robust cellular NO sensor85202047#N/ATRUE
1034
s41467-019-13941-510.1038/s41467-019-13941-5FALSEhttps://doi.org/10.1038/s41467-019-13941-5Geng, BYNat. Commun.Selective reduction of ketone/aldehydes to alcohols is of great importance in green chemistry and chemical engineering. Highly efficient catalysts are still demanded to work under mild conditions, especially at room temperature. Here we present a synergistic function of single-atom palladium (Pd-1) and nanopartiCles (Pd-NPs) on TiO2 for highly efficient ketone/aldehydes hydrogenation to alcohols at room temperature. Compared to simple but inferior Pd-1/TiO2 and Pd-NPs/TiO2 catalysts, more than twice activity enhancement is achieved with the Pd1+NPs/TiO2 catalyst that integrates both Pd-1 and Pd NPs on mesoporous TiO2 supports, obtained by a simple but large-scaled spray pyrolysis route. The synergistic function of Pd-1 and Pd-NPs is assigned so that the partial Pd-1 dispersion contributes enough sites for the Activation of C=O group while Pd-NPs site boosts the dissociation of H-2 molecules to H atoms. This work not only contributes a superior catalyst for ketone/aldehydes hydrogenation, but also deepens the knowledge on their hydrogenation mechanism and guides people to engineer the catalytic behaviors as needed.Titania supported synergistic palladium single atoms and nanopartiCles for room temperature ketone and aldehydes hydrogenationx40202057#N/AFALSE
1035
s41467-020-16554-510.1038/s41467-020-16554-5FALSEhttps://doi.org/10.1038/s41467-020-16554-5Zhao, CNat. Commun.Nickel-based catalysts are most commonly used in industrial alkaline water electrolysis. However, it remains a great challenge to address the sluggish reaction kinetics and severe deActivation problems of hydrogen evolution reaction (HER). Here, we show a Cu-doped Ni catalyst implanted with Ni-O-VOx sites (Ni(Cu)VOx) for alkaline HER. The optimal Ni(Cu)VOx electrode exhibits a near-zero onset overpotential and low overpotential of 21mV to deliver -10mAcm(-2), which is comparable to benchmark Pt/C catalyst. Evidence for the formation of Ni-O-VOx sites in Ni(Cu)VOx is established by systematic X-ray absorption spectroscopy studies. The VOx can cause a substantial dampening of Ni lattice and create an enlarged electrochemically active surface area. First-principles calculations support that the Ni-O-VOx sites are superactive and can promote the charge redistribution from Ni to VOx, which greatly weakens the H-adsorption and H-2 release free energy over Ni. This endows the Ni(Cu)VOx electrode high HER activity and long-term durability.Implanting Ni-O-VOx sites into Cu-doped Ni for low-overpotential alkaline hydrogen evolution28202041#N/ATRUE
1036
s41467-019-13415-810.1038/s41467-019-13415-8FALSEhttps://doi.org/10.1038/s41467-019-13415-8Zhao, CNat. Commun.Efficient generation of hydrogen from water-splitting is an underpinning chemistry to realize the hydrogen economy. Low cost, transition metals such as nickel and iron-based oxides/ hydroxides have been regarded as promising catalysts for the oxygen evolution reaction in alkaline media with overpotentials as low as similar to 200 mV to achieve 10 mA cm(-2), however, they are generally unsuitable for the hydrogen evolution reaction. Herein, we show a Janus nanopartiCle catalyst with a nickel-iron oxide interface and multi-site functionality for a highly efficient hydrogen evolution reaction with a comparable performance to the benchmark platinum on carbon catalyst. Density functional theory calculations reveal that the hydrogen evolution reaction catalytic activity of the nanopartiCle is induced by the strong electronic coupling effect between the iron oxide and the nickel at the interface. Remarkably, the catalyst also exhibits extraordinary oxygen evolution reaction activity, enabling an active and stable bi-functional catalyst for whole cell water-splitting with, to the best of our knowledge, the highest energy efficiency (83.7%) reported to date.Overall electrochemical splitting of water at the heterogeneous interface of nickel and iron oxidex111201960#N/AFALSE
1037
s41467-019-13375-z10.1038/s41467-019-13375-zFALSEhttps://doi.org/10.1038/s41467-019-13375-zHe, MYNat. Commun.Hydrogen production by electrocatalytic water splitting is an efficient and economical technology, however, is severely impeded by the kinetic-sluggish and low value-added anodic oxygen evolution reaction. Here we report the nickel-molybdenum-nitride nanoplates loaded on carbon fiber Cloth (Ni-Mo-N/CFC), for the concurrent electrolytic productions of high-purity hydrogen at the cathode and value-added formate at the anode in low-cost alkaline glycerol solutions. Especially, when equipped with Ni-Mo-N/CFC at both anode and cathode, the established electrolyzer requires as low as 1.36 V of cell voltage to achieve 10 mA cm(-2), which is 260 mV lower than that in alkaline aqueous solution. Moreover, high Faraday efficiencies of 99.7% for H-2 evolution and 95.0% for formate production have been obtained. Based on the excellent electrochemical performances of Ni-Mo-N/CFC, electrolytic H-2 and formate productions from the alkaline glycerol solutions are an energy-efficient and promising technology for the renewable and Clean energy supply in the future.Nickel-molybdenum nitride nanoplate electrocatalysts for concurrent electrolytic hydrogen and formate productionsx58201966#N/AFALSE
1038
s41467-020-16119-610.1038/s41467-020-16119-6FALSEhttps://doi.org/10.1038/s41467-020-16119-6Luo, ZTNat. Commun.Experiments have shown that graphene-supported Ni-single atom catalysts (Ni-SACs) provide a promising strategy for the electrochemical reduction of CO2 to CO, but the nature of the Ni sites (Ni-N2C2, Ni-N3C1, Ni-N-4) in Ni-SACs has not been determined experimentally. Here, we apply the recently developed grand canonical potential kinetics (GCP-K) formulation of quantum mechanics to predict the kinetics as a function of applied potential (U) to determine faradic efficiency, turn over frequency, and Tafel slope for CO and H-2 production for all three sites. We predict an onset potential (at 10mAcm(-2)) U-onset=-0.84V (vs. RHE) for Ni-N2C2 site and U-onset=-0.92V for Ni-N3C1 site in agreement with experiments, and U-onset=-1.03V for Ni-N-4. We predict that the highest current is for Ni-N-4, leading to 700mAcm(-2) at U=-1.12V. To help determine the actual sites in the experiments, we predict the XPS binding energy shift and CO vibrational frequency for each site. Single atom catalysts (SACs) are promising in electrocatalysis but challenging to characterize. Here, the authors apply a recently developed quantum mechanical grand canonical potential kinetics method to predict reaction mechanisms and rates for CO2 reduction at different sites of graphene-supported Ni-SACs.Reaction mechanism and kinetics for CO2 reduction on nickel single atom catalysts from quantum mechanics21202070#N/ATRUE
1039
s41467-020-15837-110.1038/s41467-020-15837-1FALSEhttps://doi.org/10.1038/s41467-020-15837-1Kong, WQNat. Commun.The restricted availability, expense and toxicity of precious metal catalysts such as rhodium and palladium challenge the sustainability of synthetic chemistry. As such, nickel catalysts have garnered increasing attention as replacements for enyne cyClization reactions. On the other hand, bridged tricyClo[5.2.1.0(1,5)]decanes are found as core structures in many biologically active natural products; however, the synthesis of such frameworks with high functionalities from readily available precursors remains a significant challenge. Herein, we report a nickel-catalyzed asymmetric domino cyClization reaction of enynones, providing rapid and modular synthesis of bridged tricyClo[5.2.1.0(1,5)]decane skeletons with three quaternary stereocenters in good yields and remarkable high levels of regio- and enantioselectivities (92-99% ee). TricyClo[5.2.1.0(1,5)]decanes are often found in bioactive natural products; however, their synthesis poses significant challenges. Here, the authors report a nickel-catalyzed asymmetric domino cyClization of enynones, providing a rapid and modular synthesis of bridged tricyClo[5.2.1.0(1,5)]decane skeletons.Synthesis of bridged tricyClo[5.2.1.0(1,5)]decanes via nickel-catalyzed asymmetric domino cyClization of enynones10202064#N/ATRUE
1040
s41467-020-14917-610.1038/s41467-020-14917-6FALSEhttps://doi.org/10.1038/s41467-020-14917-6Zeng, JNat. Commun.Single-atom catalysts (SACs) exhibit intriguing catalytic performance owing to their maximized atom utilizations and unique electronic structures. However, the reported strategies for synthesizing SACs generally have special requirements for either the anchored metals or the supports. Herein, we report a universal approach of electrochemical deposition that is applicable to a wide range of metals and supports for the fabrication of SACs. The depositions were conducted on both cathode and anode, where the different redox reactions endowed the SACs with distinct electronic states. The SACs from cathodic deposition exhibited high activities towards hydrogen evolution reaction, while those from anodic deposition were highly active towards oxygen evolution reaction. When cathodically- and anodically-deposited Ir single atoms on Co0.8Fe0.2Se2@Ni foam were integrated into a two-electrode cell for overall water splitting, a voltage of 1.39V was required at 10mAcm(-2) in alkaline electrolyte. While single-atom catalysts exhibit intriguing catalytic performances and electronic structures, syntheses are often tailored to a particular system. Here, authors report electrochemical deposition as a universal approach for the fabrication of single-atom catalysts over range of metals and supports.Electrochemical deposition as a universal route for fabricating single-atom catalysts60202034#N/ATRUE
1041
s41467-019-13052-110.1038/s41467-019-13052-1FALSEhttps://doi.org/10.1038/s41467-019-13052-1Sun, LCNat. Commun.First-row transition metal-based catalysts have been developed for the oxygen evolution reaction (OER) during the past years, however, such catalysts typically operate at overpotentials (eta) significantly above thermodynamic requirements. Here, we report an iron/ nickel terephthalate coordination polymer on nickel form (NiFeCP/NF) as catalyst for OER, in which both coordinated and uncoordinated Carbonylates were maintained after electrolysis. NiFeCP/NF exhibits outstanding electro-catalytic OER activity with a low overpotential of 188 mV at 10 mA cm(-2) in 1.0 KOH, with a small Tafel slope and excellent stability. The pH-independent OER activity of NiFeCP/NF on the reversible hydrogen electrode scale suggests that a concerted proton-coupled electron transfer (c-PET) process is the rate-determining step (RDS) during water oxidation. Deuterium kinetic isotope effects, proton inventory studies and atom-proton-transfer measurements indicate that the uncoordinated Carbonylates are serving as the proton transfer relays, with a similar function as amino acid residues in photosystem II (PSII), accelerating the proton-transfer rate.A bio-inspired coordination polymer as outstanding water oxidation catalyst via second coordination sphere engineeringx50201962#N/AFALSE
1042
s41467-019-13051-210.1038/s41467-019-13051-2FALSEhttps://doi.org/10.1038/s41467-019-13051-2Li, GQNat. Commun.Metal-organic frameworks (MOFs) have been recognized as compelling platforms for the development of miscellaneous applications because of their structural diversity and functional tunability. Here, we propose that the electrocatalytic properties could be well modified by incorporating missing linkers into the MOF. Theoretical calculations suggest the electronic structure of MOFs can be tuned by introducing missing linkers, which improves oxygen evolution reaction (OER) performance of the MOF. Inspired by these aspects, we introduced various missing linkers into a layered-pillared MOF Co-2(OH)(2)(C8H4O4) (termed as CoBDC) to prepare missing-linker MOFs. Transmission electron microscope and synchrotron X-ray measurements confirmed that the missing linkers in the MOF could be introduced and well controlled by our strategy. The self-supported MOF nanoarrays with missing linkers of carboxyferrocene exhibit excellent OER performance with ultralow overpotential of 241 mV at 100 mA cm(-2). This work opens a new prospect to develop efficient MOF-based electro-catalysts by introducing missing linkers.Missing-linker metal-organic frameworks for oxygen evolution reactionx112201956#N/AFALSE
1043
s41467-020-14799-810.1038/s41467-020-14799-8https://doi.org/10.1038/s41467-020-14799-8Huang, WNat. Commun.Amides are among the most fundamental functional groups and essential structural units, widely used in chemistry, biochemistry and material science. Amide synthesis and transformations is a topic of continuous interest in organic chemistry. However, direct catalytic asymmetric Activation of amide C-N bonds still remains a long-standing challenge due to high stability of amide linkages. Herein, we describe an organocatalytic asymmetric amide C-N bonds Cleavage of N-sulfonyl biAryl lactams under mild conditions, developing a general and practical method for atroposelective construction of axially chiral biAryl amino acids. A structurally diverse set of axially chiral biAryl amino acids are obtained in high yields with excellent enantioselectivities. Moreover, a variety of axially chiral unsymmetrical biAryl organocatalysts are efficiently constructed from the resulting axially chiral biAryl amino acids by our present strategy, and show competitive outcomes in asymmetric reactions. Asymmetric Activation of amide bonds remains a challenge due to the high stability of amide linkages. Here, the authors show an organocatalytic asymmetric C-N bond Cleavage of N-sulfonyl biAryl lactams under mild conditions, to access axially chiral biAryl amino acids.Organocatalytic asymmetric N-sulfonyl amide C-N bond Activation to access axially chiral biAryl amino acids31202070#N/ATRUE
1044
s41467-019-12993-x10.1038/s41467-019-12993-xFALSEhttps://doi.org/10.1038/s41467-019-12993-xLu, JLNat. Commun.Hydrogenation of nitriles represents as an atom-economic route to synthesize amines, crucial building blocks in fine chemicals. However, high redox potentials of nitriles render this approach to produce a mixture of amines, imines and low-value hydrogenolysis byproducts in general. Here we show that quasi atomic-dispersion of Pd within the outermost layer of Ni nanopartiCles to form a Pd1Ni single-atom surface alloy structure maximizes the Pd utilization and breaks the strong metal-selectivity relations in benzonitrile hydrogenation, by prompting the yield of diBenzylamine drastically from similar to 5 to 97% under mild conditions (80 degrees C; 0.6 MPa), and boosting an activity to about eight and four times higher than Pd and Pt standard catalysts, respectively. More importantly, the undesired carcinogenic toluene by-product is completely prohibited, rendering its practical applications, especially in pharmaceutical industry. Such strategy can be extended to a broad scope of nitriles with high yields of secondary amines under mild conditions.Quasi Pd1Ni single-atom surface alloy catalyst enables hydrogenation of nitriles to secondary aminesx23201972#N/AFALSE
1045
s41467-019-12977-x10.1038/s41467-019-12977-xhttps://doi.org/10.1038/s41467-019-12977-xHe, JHNat. Commun.Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in photoelectrochemical (PEC) water splitting applications. Here, we present a simple and efficient strategy for III-V-based photoelectrodes that functionally and spatially decouples the light harvesting component of the device from the electrolysis part that eliminates parasitic light absorption, reduces the cost, and enhances the stability without any compromise in efficiency. The monolithically integrated PEC cell was fabricated by an epitaxial lift-off and transfer of inversely grown InGaP/GaAs to a robust Ni-substrate and the resultant photoanode exhibits an STH efficiency of similar to 9% with stability similar to 150 h. Moreover, with the ability to access both sides of the device, we constructed a fully-integrated, unassisted-wireless artificial leaf system with an STH efficiency of similar to 6%. The excellent efficiency and stability achieved herein are attributed to the light harvesting/catalysis decoupling scheme, which concurrently improves the optical, electrical, and electrocatalytic characteristics.An efficient and stable photoelectrochemical system with 9% solar-to-hydrogen conversion efficiency via InGaP/GaAs double junctionPhotocatalyst31201957#N/AFALSE
1046
s41467-020-14462-210.1038/s41467-020-14462-2FALSEhttps://doi.org/10.1126/science.abh2623Li, YCarbon doping switching on the hydrogen adsorption activity of NiO for hydrogen evolution reaction2020#N/ATRUE
1047
s41467-020-14402-010.1038/s41467-020-14402-0FALSEhttps://doi.org/10.1038/s41467-020-14402-0He, CXNat. Commun.Carbon dioxide electroreduction provides a useful source of carbon monoxide, but comparatively few catalysts could be sustained at current densities of industry level. Herein, we construct a high-yield, flexible and self-supported single-atom nickel-decorated porous carbon membrane catalyst. This membrane possesses interconnected nanofibers and hierarchical pores, affording abundant effective nickel single atoms that participate in carbon dioxide reduction. Moreover, the excellent mechanical strength and well-distributed nickel atoms of this membrane combines gas-diffusion and catalyst layers into one architecture. This integrated membrane could be directly used as a gas diffusion electrode to establish an extremely stable three-phase interface for high-performance carbon dioxide electroreduction, producing carbon monoxide with a 308.4mAcm(-2) partial current density and 88% Faradaic efficiency for up to 120h. We hope this work will provide guidance for the design and application of carbon dioxide electro-catalysts at the potential industrial scale. Here the authors deploy Ni single atom-decorated carbon membranes as integrated gas diffusion electrodes to construct an extremely stable three-phase interface for CO2 electroreduction, producing CO with a partial current density of 308.4mAcm(-2) and a Faradaic efficiency of 88% for up to 120h.Carbon dioxide electroreduction on single-atom nickel decorated carbon membranes with industry compatible current densities74202035#N/ATRUE
1048
s41467-020-14320-110.1038/s41467-020-14320-1FALSEhttps://doi.org/10.1038/s41467-020-14320-1Chen, YFNat. Commun.Transition metal-catalyzed Carbonylation with carbon nuCleophiles is one of the most prominent methods to construct ketones, which are highly versatile motifs prevalent in a variety of organic compounds. In comparison to the well-established palladium catalytic system, the nickel-catalyzed Carbonylative coupling is much underdeveloped due to the strong binding affinity of CO to nickel. By leveraging easily accessible tert-butyl isocyanide as the CO surrogate, we present a nickel-catalyzed allylic Carbonylative coupling with Alkyl zinc reagent, allowing for the practical and straightforward preparation of synthetically important beta,gamma-unsaturated ketones in a linear-selective fashion with excellent trans-selectivity under mild conditions. Moreover, the undesired polyCarbonylation process which is often encountered in palladium chemistry could be completely suppressed. This nickel-based method features excellent functional group tolerance, even inCluding the active Aryl iodide functionality to allow the orthogonal derivatization of beta,gamma-unsaturated ketones. Preliminary mechanistic studies suggest that the reaction proceeds via a pi-allylnickel intermediate.Nickel-catalyzed allylic Carbonylative coupling of Alkyl zinc reagents with tert-butyl isocyanide17202067#N/ATRUE
1049
s41467-019-14211-010.1038/s41467-019-14211-0FALSEhttps://doi.org/10.1038/s41467-019-14211-0Chen, ClNat. Commun.The development of high-performance transition metal catalysts has long been a major driving force in academic and industrial polyolefin research. Late transition metal-based olefin polymerization catalysts possess many unique properties, such as the ability to generate variously branched polyolefins using only ethylene as the feedstock and the capability of incorporating polar functionalized comonomers without protecting agents. Here we report the synthesis and (co)polymerization studies of a simple but extremely versatile alpha-imino-ketone nickel system. This type of catalyst is easy to synthesize and modify, and it is thermally stable and highly active during ethylene polymerization without the addition of any cocatalysts. Despite the sterically open nature, these catalysts can generate branched Ultra-High-Molecular-Weight polyethylene and copolymerize ethylene with a series of polar comonomers. The versatility of this platform has been further demonstrated through the synthesis of a dinuClear nickel catalyst and the installation of an anchor for catalyst heterogenization.A simple and versatile nickel platform for the generation of branched high molecular weight polyolefins53202070#N/ATRUE
1050
s41467-019-14157-310.1038/s41467-019-14157-3FALSEhttps://doi.org/10.1038/s41467-019-14157-3Yu, HQEfficient electrochemical production of glucaric acid and H-2 via glucose electrolysis2020#N/ATRUE
1051
s41467-019-11432-110.1038/s41467-019-11432-1https://doi.org/10.1038/s41467-019-11432-1Ababou-Girard, SNat. Commun.Apart from being key structures of modern microelectronics, metal-insulator-semiconductor (MIS) junctions are highly promising electrodes for artificial leaves, i.e. photoelectrochemical cells that can convert sunlight into energy-rich fuels. Here, we demonstrate that homogeneous Si/SiOx/Ni MIS junctions, employed as photoanodes, can be functionalized with a redox-active species and simultaneously converted into high-photovoltage inhomogeneous MIS junctions by electrochemical dissolution. We also report on the considerable enhancement of performance towards urea oxidation, induced by this process. Finally, we demonstrate that both phenomena can be employed synergistically to design highly-efficient Si-based photoanodes. These findings open doors for the manufacturing of artificial leaves that can generate H-2 under solar illumination using contaminated water.Tailoring the photoelectrochemistry of catalytic metal-insulator-semiconductor (MIS) photoanodes by a dissolution methodPhotocatalyst12201937#N/AFALSE
1052
s41467-019-13701-510.1038/s41467-019-13701-5https://doi.org/10.1038/s41467-019-13701-5Song, QLNat. Commun.Cross-coupling reactions involving metal carbene intermediates play an increasingly important role in C-C bond formation. Expanding the carbene precursors to a broader range of starting materials and more diverse products is an ongoing challenge in synthetic organic chemistry. Herein, we report a Suzuki-Miyaura coupling reaction of in situ-generated Pd-carbene complexes via desulfurization of thioureas or thioamides. This strategy enables the preparation of a broad array of substituted amidinium salts and unsymmetrical diAryl ketones. The reaction is readily scalable, compatible with bromo groups on aromatic rings, tolerant to moisture and air and has a broad substrate scope. Furthermore, a single crystal structure of Pd-diaminocarbene complex is obtained and proven to be the key intermediate in both catalytic and stoichiometric reactions. Preliminary mechanistic studies demonstrate the dual role of the silver salt as a desulfurating reagent assisting the elimination of sulfur and as oxidant facilitating the Pd-II/Pd-0/Pd(II )catalytic cyCle.Palladium-catalyzed Suzuki-Miyaura coupling of thioureas or thioamides11201968#N/ATRUE
1053
s41467-019-10698-910.1038/s41467-019-10698-9FALSEhttps://doi.org/10.1038/s41467-019-10698-9Yu, SHNat. Commun.The incorporation of defects, such as vacancies, into functional materials could substantially tailor their intrinsic properties. Progress in vacancy chemistry has enabled advances in many technological applications, but creating new type of vacancies in existing material system remains a big challenge. We show here that ionized nitrogen plasma can break bonds of iron-carbon-nitrogen-nickel units in nickel-iron Prussian blue analogues, forming unconventional carbon-nitrogen vacancies. We study oxygen evolution reaction on the carbon-nitrogen vacancy-mediated Prussian blue analogues, which exhibit a low overpotential of 283 millivolts at 10 milliamperes per square centimeter in alkali, far exceeding that of original Prussian blue analogues and previously reported oxygen evolution catalysts with vacancies. We ascribe this enhancement to the in-situ generated nickel-iron oxy(hydroxide) active layer during oxygen evolution reaction, where the Fe leaching was significantly suppressed by the unconventional carbon-nitrogen vacancies. This work opens up opportunities for producing vacancy defects in nanomaterials for broad applications.Unconventional CN vacancies suppress iron-leaching in Prussian blue analogue pre-catalyst for boosted oxygen evolution catalysisx66201946#N/AFALSE
1054
s41467-019-10692-110.1038/s41467-019-10692-1https://doi.org/10.1038/s41467-019-10692-1Mecking, SUniform shape monodisperse single chain nanocrystals by living aqueous catalytic polymerizationx2019#N/AFALSE
1055
s41467-019-10464-x10.1038/s41467-019-10464-xFALSEhttps://doi.org/10.1038/s41467-019-10464-xOzin, GANickel@Siloxene catalytic nanosheets for high-performance CO2 methanationx2019#N/AFALSE
1056
s41467-019-13300-410.1038/s41467-019-13300-4FALSEhttps://doi.org/10.1038/s41467-019-13300-4Li, ZXNat. Commun.Plate tectonics and mantle plumes are two of the most fundamental solid-Earth processes that have operated through much of Earth history. For the past 300 million years, mantle plumes are known to derive mostly from two large low shear velocity provinces (LLSVPs) above the core-mantle boundary, referred to as the African and Pacific superplumes, but their possible connection with plate tectonics is debated. Here, we demonstrate that transition elements (Ni, Cr, and Fe/Mn) in basaltic rocks can be used to trace plume-related magmatism through Earth history. Our analysis indicates the presence of a direct relationship between the intensity of plume magmatism and the supercontinent cyCle, suggesting a possible dynamic coupling between supercontinent and superplume events. In addition, our analysis shows a consistent sudden drop in MgO, Ni and Cr at similar to 3.2-3.0 billion years ago, possibly indicating an abrupt change in mantle temperature at the start of global plate tectonics.Global geochemical fingerprinting of plume intensity suggests coupling with the supercontinent cyCle10201954#N/ATRUE
1057
s41467-019-09845-z10.1038/s41467-019-09845-zFALSEhttps://doi.org/10.1038/s41467-019-09845-zMa, TYNat. Commun.Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction. Here, we report one single atom W6+ doped Ni(OH)(2) nanosheet sample (w-Ni(OH)(2)) with an outstanding oxygen evolution reaction (OER) performance that is, in a 1 M KOH medium, an overpotential of 237 mV is obtained reaching a current density of 10 mA/cm(2). Moreover, at high current density of 80 mA/cm(2), the overpotential value is 267 mV. The corresponding Tafel slope is measured to be 33 mV/dec. The d(0) W6+ atom with a low spin-state has more outermost vacant orbitals, resulting in more water and OH- groups being adsorbed on the exposed W sites of the Ni(OH)(2) nanosheet. Density functional theory (DFT) calculations confirm that the O radical and O-O coupling are both generated at the same site of W6+. This work demonstrates that W6+ doping can promote the electrocatalytic water oxidation activity of Ni(OH)(2) with the highest performance.Single atom tungsten doped ultrathin alpha-Ni(OH)(2) for enhanced electrocatalytic water oxidation
Electrocatalytic
130201960#N/AFALSE
1058
s41467-019-13092-710.1038/s41467-019-13092-7FALSEhttps://doi.org/10.1038/s41467-019-13092-7Ren, ZFNat. Commun.Seawater is one of the most abundant natural resources on our planet. Electrolysis of seawater is not only a promising approach to produce Clean hydrogen energy, but also of great significance to seawater desalination. The implementation of seawater electrolysis requires robust and efficient electrocatalysts that can sustain seawater splitting without chloride corrosion, especially for the anode. Here we report a three-dimensional core-shell metal-nitride catalyst consisting of NiFeN nanopartiCles uniformly decorated on NiMoN nanorods supported on Ni foam, which serves as an eminently active and durable oxygen evolution reaction catalyst for alkaline seawater electrolysis. Combined with an efficient hydrogen evolution reaction catalyst of NiMoN nanorods, we have achieved the industrially required current densities of 500 and 1000 mA cm(-2) at record low voltages of 1.608 and 1.709 V, respectively, for overall alkaline seawater splitting at 60 degrees C. This discovery significantly advances the development of seawater electrolysis for large-scale hydrogen production.Non-noble metal-nitride based electrocatalysts for high-performance alkaline seawater electrolysis139201955#N/ATRUE
1059
s41467-019-13061-010.1038/s41467-019-13061-0FALSEhttps://doi.org/10.1126/science.aap7883Durrant, JRSpectroelectrochemical study of water oxidation on nickel and iron oxyhydroxide electrocatalysts2019#N/ATRUE
1060
s41467-019-09394-510.1038/s41467-019-09394-5FALSEhttps://doi.org/10.1038/s41467-019-09394-5Feng, XLNat. Commun.Developing low-cost electrocatalysts to replace precious Ir-based materials is key for oxygen evolution reaction (OER). Here, we report atomically dispersed nickel coordinated with nitrogen and sulfur species in porous carbon nanosheets as an electrocatalyst exhibiting excellent activity and durability for OER with a low overpotential of 1.51 V at 10 mA cm(-2) and a small Tafel slope of 45 mV dec(-1) in alkaline media. Such electrocatalyst represents the best among all reported transition metal- and/or heteroatom-doped carbon electrocatalysts and is even superior to benchmark Ir/C. Theoretical and experimental results demonstrate that the well-dispersed molecular S vertical bar NiNx species act as active sites for catalyzing OER. The atomic structure of S vertical bar NiNx centers in the carbon matrix is Clearly disClosed by aberration-corrected scanning transmission electron microscopy and synchrotron radiation X-ray absorption spectroscopy together with computational simulations. An integrated photoanode of nanocarbon on a Fe2O3 nanosheet array enables highly active solar-driven oxygen production.Atomically dispersed nickel-nitrogen-sulfur species anchored on porous carbon nanosheets for efficient water oxidationx200201960#N/AFALSE
1061
s41467-019-09290-y10.1038/s41467-019-09290-yFALSEhttps://doi.org/10.1038/s41467-019-09290-yWan, LJNat. Commun.Although single-atomically dispersed metal-N-x on carbon support (M-NC) has great potential in heterogeneous catalysis, the scalable synthesis of such single-atom catalysts (SACs) with high-loading metal-Nx is greatly challenging since the loading and single-atomic dispersion have to be balanced at high temperature for forming metal-Nx. Herein, we develop a general cascade anchoring strategy for the mass production of a series of M-NC SACs with a metal loading up to 12.1 wt%. Systematic investigation reveals that the chelation of metal ions, physical isolation of chelate complex upon high loading, and the binding with N-species at elevated temperature are essential to achieving high-loading M-NC SACs. As a demonstration, high-loading Fe-NC SAC shows superior electrocatalytic performance for O-2 reduction and Ni-NC SAC exhibits high electrocatalytic activity for CO2 reduction. The strategy paves a universal way to produce stable M-NC SAC with high-density metal-N-x sites for diverse high-performance applications.Cascade anchoring strategy for general mass production of high-loading single-atomic metal-nitrogen catalystsx213201969#N/AFALSE
1062
s41467-019-12994-w10.1038/s41467-019-12994-wFALSEhttps://doi.org/10.1038/s41467-019-12994-wGarcia-Melchor, MNat. Commun.A major roadblock in realizing large-scale production of hydrogen via electrochemical water splitting is the cost and inefficiency of current catalysts for the oxygen evolution reaction (OER). Computational research has driven important developments in understanding and designing heterogeneous OER catalysts using linear scaling relationships derived from computed binding energies. Herein, we interrogate 17 of the most active molecular OER catalysts, based on different transition metals (Ru, Mn, Fe, Co, Ni, and Cu), and show they obey similar scaling relations to those established for heterogeneous systems. However, we find that the conventional OER descriptor underestimates the activity for very active OER complexes as the standard approach neglects a crucial one-electron oxidation that many molecular catalysts undergo prior to O-O bond formation. Importantly, this additional step allows certain molecular catalysts to circumvent the overpotential wall, leading to enhanced performance. With this knowledge, we establish fundamental principles for the design of ideal molecular OER catalysts.Universal scaling relations for the rational design of molecular water oxidation catalysts with near-zero overpotential47201981#N/ATRUE
1063
s41467-019-08763-410.1038/s41467-019-08763-4FALSEhttps://doi.org/10.1038/s41467-019-08763-4Dunand, DCNat. Commun.Additive manufacturing of high-entropy alloys combines the mechanical properties of this novel family of alloys with the geometrical freedom and complexity required by modern designs. Here, a non-beam approach to additive manufacturing of high-entropy alloys is developed based on 3D extrusion of inks containing a blend of oxide nanopowders (Co3O4 + Cr2O3 + Fe2O3 + NiO), followed by co-reduction to metals, inter-diffusion and sintering to near-full density CoCrFeNi in H-2. A complex phase evolution path is observed by in-situ X-ray diffraction in extruded filaments when the oxide phases undergo reduction and the resulting metals inter-diffuse, ultimately forming face-centered-cubic equiatomic CoCrFeNi alloy. Linked to the phase evolution is a complex structural evolution, from loosely packed oxide partiCles in the green body to fully-annealed, metallic CoCrFeNi with 99.6 +/- 0.1% relative density. CoCrFeNi micro-lattices are created with strut diameters as low as 100 mu m and excellent mechanical properties at ambient and cryogenic temperatures.3D ink-extrusion additive manufacturing of CoCrFeNi high-entropy alloy micro-latticesx41201957#N/AFALSE
1064
s41467-019-08416-610.1038/s41467-019-08416-6FALSEhttps://doi.org/10.1038/s41467-019-08416-6Liu, YNat. Commun.The search for porous materials with strong Bronsted acid sites for challenging reactions has long been of significant interest, but it remains a formidable synthetic challenge. Here we demonstrate a cage extension strategy to construct chiral permanent porous hydrogen-bonded frameworks with strong Bronsted acid groups for heterogeneous asymmetric catalysis. We report the synthesis of two octahedral coordination cages using enantiopure 4,4', 6,6'-tetra(benzoate) ligand of 1,1'-spirobiindane-7,7'-phosphoric acid and Ni-4/Co-4-p-tert-butylsulfonylcalix[4]arene Clusters. Intercage hydrogen-bonds and hydrophobic interactions between tert-butyl groups direct the hierarchical assembly of the cages into a permanent porous material. The chiral phosphoric acid-containing frameworks can be high efficient and recyClable heterogeneous Bronsted acid catalysts for asymmetric [3+2] coupling of indoles with quinone monoimine and Friedel-Crafts Alkylations of indole with Aryl aldimines. The afforded enantioselectivities (up to 99.9% ee) surpass those of the homogeneous counterparts and compare favorably with those of the most enantioselective homogeneous phosphoric acid catalysts reported to date.Permanent porous hydrogen-bonded frameworks with two types of Bronsted acid sites for heterogeneous asymmetric catalysisx52201970#N/AFALSE
1065
s41467-019-08309-810.1038/s41467-019-08309-8FALSEhttps://doi.org/10.1038/s41467-019-08309-8Daugulis, ONat. Commun.Here we report that the tri-1-adamantylphosphine- nickel complex [Ad(3)PNiBr(3)](-)[Ad(3)PH](+) upon Activation with an Alkylaluminoxane catalyzes the polymerization of ethylene to ultra-high-molecular-weight, nearly linear polyethylene (M-n up to 1.68 x 10(6) g mol(-1)) with initial activities reaching 3.7 million turnovers per h(-1) at 10 degrees C. Copolymerizations of ethylene with alpha-olefins such as 1-hexene and 1-octadecene, as well as tert-butyldimethyl(dec-9-en-1-yloxy) silane give the corresponding copolymers with no decrease in activity.A highly active Ni(II)-triadamantylphosphine catalyst for ultrahigh-molecular-weight polyethylene synthesisx33201931#N/AFALSE
1066
s41467-018-07380-x10.1038/s41467-018-07380-xFALSEhttps://doi.org/10.1038/s41467-018-07380-xZheng, GFNat. Commun.Solar-driven electrochemical carbon dioxide (CO2) reduction is capable of producing value-added chemicals and represents a potential route to alleviate carbon footprint in the global environment. However, the ever-changing sunlight illumination presents a substantial impediment of maintaining high electrocatalytic efficiency and stability for practical applications. Inspired by green plant photosynthesis with separate light reaction and (dark) carbon fixation steps, herein, we developed a redox-medium-assisted system that proceeds water oxidation with a nickel-iron hydroxide electrode under light illumination and stores the reduction energy using a zinc/zincate redox, which can be controllably released to spontaneously reduce CO2 into carbon monoxide (CO) with a gold nanocatalyst in dark condition. This redox-medium-assisted system enables a record-high solar-to-CO photoconversion efficiency of 15.6% under 1-sun intensity, and an outstanding electric energy efficiency of 63%. Furthermore, it allows a unique tuning capability of the solar-to-CO efficiency and selectivity by the current density applied during the carbon fixation.Efficient solar-driven electrocatalytic CO2 reduction in a redox-medium-assisted system
Electrocatalytic
38201830#N/AFALSE
1067
s41467-019-12858-310.1038/s41467-019-12858-3FALSEhttps://doi.org/10.1038/s41467-019-12858-3Weckhuysen, BMNat. Commun.Carbon dioxide is a desired feedstock for platform molecules, such as carbon monoxide or higher hydrocarbons, from which we will be able to make many different useful, value-added chemicals. Its catalytic hydrogenation over abundant metals requires the amalgamation of theoretical knowledge with materials design. Here we leverage a theoretical understanding of structure sensitivity, along with a library of different supports, to tune the selectivity of methanation in the Power-to-Gas concept over nickel. For example, we show that carbon dioxide hydrogenation over nickel can and does form propane, and that activity and selectivity can be tuned by supporting different nickel partiCle sizes on various oxides. This theoretical and experimental toolbox is not only useful for the highly selective production of methane, but also provides new insights for carbon dioxide Activation and subsequent carbon-carbon coupling towards value-added products thereby reducing the deleterious effects of this environmentally harmful molecule.Understanding carbon dioxide Activation and carbon-carbon coupling over nickel34201947#N/ATRUE
1068
s41467-018-07069-110.1038/s41467-018-07069-1https://doi.org/10.1038/s41467-018-07069-1Zeng, XMNat. Commun.Selective creation of quaternary carbon centers has been a long-standing challenge in synthetic chemistry. We report here the chromium-catalyzed, para-selective formation of Arylated quaternary carbon centers by Alkylative reactions of benzamide derivatives with tertiary Alkylmagnesium bromides at room temperature. The reaction, which was enabled by a low-cost chromium(III) salt combined with trimethylsilyl bromide, introduces a sterically bulky tertiary Alkyl scaffold on the para-position of benzamide derivatives in a highly selective fashion without either isomerization of the tertiary Alkyl group or formation of ortho-Alkylated byproducts. Forming low-valent Cr species in situ by reaction of CrCl3 with t-BuMgX accompanied by evolution of hydrogen can be considered, which serves as reactive species to promote the reaction. The para-Alkylation likely occurs via a radical-type nuCleophilic substitution of imino-coordination benzimidate intermediate.Chromium-catalyzed para-selective formation of quaternary carbon centers by Alkylation of benzamide derivativesx11201853#N/AFALSE
1069
s41467-018-07050-y10.1038/s41467-018-07050-yFALSEhttps://doi.org/10.1038/s41467-018-07050-yJung, WNat. Commun.Supported metal nanopartiCles hold great promise for many fields, inCluding catalysis and renewable energy. Here we report a novel methodology for the in situ growth of architecturally tailored, regenerative metal nanocatalysts that is applicable to a wide range of materials. The main idea underlying this strategy is to selectively diffuse catalytically active metals along the grain boundaries of host oxides and then to reduce the diffused metallic species to form nanoClusters. As a case study, we choose ceria and zirconia, the most recognized oxide supports, and spontaneously form various metal partiCles on their surface with controlled size and distribution. Metal atoms move back and forth between the interior (as cations) and the exterior (as Clusters) of the host oxide lattice as the reductive and oxidative atmospheres repeat, even at temperatures below 700 degrees C. Furthermore, they exhibit excellent sintering/coking resistance and reactivity toward chemical/electrochemical reactions, demonstrating potential to be used in various applications.In situ synthesis of supported metal nanocatalysts through heterogeneous dopingx34201859#N/AFALSE
1070
s41467-019-12843-w10.1038/s41467-019-12843-wFALSEZhang, TAtomically dispersed nickel as coke-resistant active sites for methane dry reforming2019#N/ATRUE
1071
s41467-018-06904-910.1038/s41467-018-06904-9https://doi.org/10.1038/s41467-018-06904-9Chu, LLNat. Commun.Substituted alkenes are pivotal structural motifs found in pharmaceuticals and agrochemicals. Although numerous methods have been developed to construct substituted alkenes, a generally efficient, mild, catalytic platform for the conversion of alkynes to this highly functionalized scaffold via successive C-C bond forming steps remains in high demand. Here we describe an intermolecular, regio- and syn-stereoselective AlkylArylation of terminal alkynes with tertiary Alkyl oxalates via photoredox-Ni dual catalysis. This catalytic protocol, synergistically combining Ir/Ni-catalyzed alkyne difunctionalization with photoinduced alkene isomerization, affords trisubstituted alkenes with excellent efficiency and syn-stereo-selectivity. The mild conditions tolerate many functional groups, allowing for a broad scope with respect to terminal alkynes, Aryl bromides, and Alkyl oxalates.syn-Selective AlkylArylation of terminal alkynes via the combination of photoredox and nickel catalysisPhotocatalyst45201871#N/AFALSE
1072
s41467-019-12510-010.1038/s41467-019-12510-0FALSEhttps://doi.org/10.1038/s41467-019-12510-0Zhang, TRNat. Commun.There is interest in metal single atom catalysts due to their remarkable activity and stability. However, the synthesis of metal single atom catalysts remains somewhat ad hoc, with no universal strategy yet reported that allows their generic synthesis. Herein, we report a universal synthetic strategy that allows the synthesis of transition metal single atom catalysts containing Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pt or combinations thereof. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and extended X-ray absorption fine structure spectroscopy confirm that the transition metal atoms are uniformly dispersed over a carbon black support. The introduced synthetic method allows the production of carbon-supported metal single atom catalysts in large quantities (>1 kg scale) with high metal loadings. A Ni single atom catalyst exhibits outstanding activity for electrochemical reduction of carbon dioxide to carbon monoxide, achieving a 98.9% Faradaic efficiency at -1.2 V.A universal ligand mediated method for large scale synthesis of transition metal single atom catalysts97201934#N/ATRUE
1073
s41467-018-06728-710.1038/s41467-018-06728-7FALSEhttps://doi.org/10.1038/s41467-018-06728-7Sun, YJInterfacing nickel nitride and nickel boosts both electrocatalytic hydrogen evolution and oxidation reactions
Electrocatalytic
2018#N/AFALSE
1074
s41467-019-11765-x10.1038/s41467-019-11765-xFALSEhttps://doi.org/10.1038/s41467-019-11765-xYang, XRNat. Commun.Herein, ruthenium (Ru) and iridium (Ir) are introduced to tailor the atomic and electronic structure of self-supported nickel-vanadium (NiV) layered double hydroxide to accelerate water splitting kinetics, and the origin of high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities are analyzed at atomic level. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy studies reveal synergistic electronic interactions among Ni, V, and Ru (Ir) cations. Raman spectra and Fourier and wavelet transform analyses of the extended X-ray absorption fine structure indicate modulated local coordination environments around the Ni and V cations, and the existence of V vacancies. The Debye-Waller factor suggests a severely distorted octahedral V environment caused by the incorporation of Ru and Ir. Theoretical calculations further confirm that Ru or Ir doping could optimize the adsorption energy of intermediates in the Volmer and Heyrovsky steps for HER and accelerate the whole kinetic process for OER.Atomic and electronic modulation of self-supported nickel-vanadium layered double hydroxide to accelerate water splitting kinetics112201977#N/ATRUE
1075
s41467-018-06324-910.1038/s41467-018-06324-9https://doi.org/10.1038/s41467-018-06324-9Kennepohl, PNat. Commun.Nickel-catalyzed catalyst transfer polycondensation (CTP) of thiophenes is an efficient strategy for the controlled synthesis of polythiophenes. However, a detailed view of its reaction mechanism has remained elusive with unresolved questions regarding the geometry and bonding of critical Ni(0) thiophene intermediates. Herein, we provide experimental and computational evidence of structurally characterized square planar eta(2)-Ni(0)-thiophene species and their relevance to the mechanism of CTP. These results confirm the viability of C, C-eta(2) bound intermediates in CTP of thiophenes, providing an electronic rationale for the stability of such species, and thus that such processes can proceed as living polymerizations. We further show that C,S-kappa(2) species may also be relevant in nickel-catalyzed CTP of thiophenes, providing new avenues for exploitation and optimization.Identifying the missing link in catalyst transfer polymerizationx12201842#N/AFALSE
1076
s41467-019-11352-010.1038/s41467-019-11352-0FALSEhttps://doi.org/10.1038/s41467-019-11352-0Chen, JGGNat. Commun.The electrochemical carbon dioxide reduction reaction to syngas with controlled CO/H-2 ratios has been studied on Pd-based bimetallic hydrides using a combination of in situ characterization and density functional theory calculations. When compared with pure Pd hydride, the bimetallic Pd hydride formation occurs at more negative potentials for Pd-Ag, Pd-Cu, and Pd-Ni. Theoretical calculations show that the choice of the second metal has a more significant effect on the adsorption strength of *H than *HOCO, with the free energies between these two key intermediates (i.e., Delta G(*H)-Delta G(*HOCO)) correlating well with the carbon dioxide reduction reaction activity and selectivity observed in the experiments, and thus can be used as a descriptor to search for other bimetallic catalysts. The results also demonstrate the possibility of alloying Pd with non-precious transition metals to promote the electrochemical conversion of CO2 to syngas.Tuning the activity and selectivity of electroreduction of CO2 to synthesis gas using bimetallic catalysts57201957#N/ATRUE
1077
s41467-018-06106-310.1038/s41467-018-06106-3FALSEhttps://doi.org/10.1038/s41467-018-06106-3Schuhmann, WA fully protected hydrogenase/polymer-based bioanode for high-performance hydrogen/glucose biofuel cellsx2018#N/AFALSE
1078
s41467-019-10851-410.1038/s41467-019-10851-4FALSEhttps://doi.org/10.1038/s41467-019-10851-4Shen, QLNat. Commun.Nickel-catalyzed asymmetric cross-coupling of secondary Alkyl electrophiles with different nuCleophiles represents a powerful strategy for the construction of chiral tertiary carbon centers. Yet, the use of Aryl Grignard reagents or Aryl zinc halides in many reactions typically resulted in low enantioselectivity, mainly due to their slow transmetalation step in the catalytical cyCle and consequently the requirement of relatively high temperature. Here we report that the use of lithium Aryl zincate [Ph2ZnBr]Li facilitates the transmetalation step of the nickel-catalyzed cross-coupling reaction. Based on this discovery, a highly enantioselective construction of fluoroAlkyl-substituted stereogenic center by a nickel-catalyzed asymmetric Suzuki-Miyaura coupling of alpha-bromoBenzyl trifluoro-/difluoro-/mono- fluoromethanes with a variety of lithium Aryl zincates [Ph2ZnBr]Li that were in situ generated from the reaction of lithium orgaB(OH)2ronate with 1.0 equivalent of ZnBr2 was described.Facilitating the transmetalation step with Aryl-zincates in nickel-catalyzed enantioselective Arylation of secondary Benzylic halides16201942#N/ATRUE
1079
s41467-019-10304-y10.1038/s41467-019-10304-yFALSEhttps://doi.org/10.1038/s41467-019-10304-yYe, JHNat. Commun.Ambient sunlight-driven CO2 methanation cannot be realized due to the temperature being less than 80 degrees C upon irradiation with dispersed solar energy. In this work, a selective light absorber was used to construct a photothermal system to generate a high temperature (up to 288 degrees C) under weak solar irradiation (1 kW m(-2)), and this temperature is three times higher than that in traditional photothermal catalysis systems. Moreover, ultrathin amorphous Y2O3 nanosheets with confined single nickel atoms (SA Ni/Y2O3) were synthesized, and they exhibited superior CO2 methanation activity. As a result, 80% CO2 conversion efficiency and a CH4 production rate of 7.5 L m(-2) h(-1) were achieved through SA Ni/Y2O3 under solar irradiation (from 0.52 to 0.7 kW m(-2)) when assisted by a selective light absorber, demonstrating that this system can serve as a platform for directly harnessing dispersed solar energy to convert CO2 to valuable chemicals.Selective light absorber-assisted single nickel atom catalysts for ambient sunlight-driven CO2 methanation63201946#N/ATRUE
1080
s41467-019-09766-x10.1038/s41467-019-09766-xFALSEhttps://doi.org/10.1038/s41467-019-09766-xRueping, MNat. Commun.Transition-metal-catalyzed cross-couplings have been extensively used in the pharmaceutical and agrochemical industries for the construction of diverse C-C bonds. Conventional cross-coupling reactions require reactive electrophilic coupling partners, such as organohalides or sulfonates, which are not environmentally friendly and not naturally abundant. Another disadvantage associated with these transformations is the need for an exogenous base to facilitate the key transmetalation step, and this reagent inevitably induces side reactions and limits the substrate scope. Here, we report an unconventional Suzuki-type approach to the synthesis of biAryls, through nickel-catalyzed deCarbonylative cross coupling of aldehydes with organB(OH)2ron reagents under base-free conditions. The transformation tolerates structurally diverse (hetero)Aryl substituents on both coupling partners and shows high reactivity and excellent functional group tolerance. Furthermore, the protocol was carried out on gram scale and successfully applied to the functionalization of complex biologically active molecules. Mechanistic investigations support a catalytic cyCle involving the oxidative addition of the nickel into the aldehyde C(acyl)-H bond with subsequent hydride transfer, transmetalation, deCarbonylation and reductive elimination processes.Nickel-catalyzed Suzuki-Miyaura cross-couplings of aldehydes28201930#N/ATRUE
1081
s41467-018-05600-y10.1038/s41467-018-05600-yFALSEhttps://doi.org/10.1038/s41467-018-05600-yStevenson, KJNat. Commun.The electrolysis of water is of global importance to store renewable energy and the methodical design of next-generation oxygen evolution catalysts requires a greater understanding of the structural and electronic contributions that give rise to increased activities. Herein, we report a series of Ruddlesden-Popper La0.5Sr1.5Ni1-xFexO4 +/-delta oxides that promote charge transfer via cross-gap hybridization to enhance electrocatalytic water splitting. Using selective substitution of lanthanum with strontium and nickel with iron to tune the extent to which transition metal and oxygen valence bands hybridize, we demonstrate remarkable catalytic activity of 10 mA cm(-2) at a 360 mV overpotential and mass activity of 1930 mA mg(-1) ox at 1.63 V via a mechanism that utilizes lattice oxygen. This work demonstrates that Ruddlesden-Popper materials can be utilized as active catalysts for oxygen evolution through rational design of structural and electronic configurations that are unattainable in many other crystalline metal oxide phases.Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1-xFexO4 +/-delta Ruddlesden-Popper oxides
Electrocatalytic
80201852#N/AFALSE
1082
s41467-018-05542-510.1038/s41467-018-05542-5https://doi.org/10.1038/s41467-018-05542-5Lee, HEnergy-efficient CO2 hydrogenation with fast response using photoexcitation of CO2 adsorbed on metal catalystsPhotocatalyst2018#N/AFALSE
1083
s41467-018-05350-x10.1038/s41467-018-05350-xFALSEhttps://doi.org/10.1126/science.aak9991Ananikov, VPExploring the performance of nanostructured reagents with organic-group-defined morphology in cross-coupling reactionx2018#N/AFALSE
1084
s41467-018-05341-y10.1038/s41467-018-05341-yFALSEhttps://doi.org/10.1038/s41467-018-05341-yWang, MNat. Commun.It is of great importance to understand the origin of high oxygen-evolving activity of state-of the-art multimetal oxides/(oxy)hydroxides at atomic level. Herein we report an evident improvement of oxygen evolution reaction activity via incorporating iron and vanadium into nickel hydroxide lattices. X-ray photoelectron/absorption spectroscopies reveal the synergistic interaction between iron/vanadium dopants and nickel in the host matrix, which subtly modulates local coordination environments and electronic structures of the iron/vanadium/nickel cations. Further, in-situ X-ray absorption spectroscopic analyses manifest contraction of metal-oxygen bond lengths in the activated catalyst, with a short vanadium-oxygen bond distance. Density functional theory calculations indicate that the vanadium site of the iron/ vanadium co-doped nickel (oxy)hydroxide gives near-optimal binding energies of oxygen evolution reaction intermediates and has lower overpotential compared with nickel and iron sites. These findings suggest that the doped vanadium with distorted geometric and disturbed electronic structures makes crucial contribution to high activity of the trimetallic catalyst.Atomic-level insight into super-efficient electrocatalytic oxygen evolution on iron and vanadium co-doped nickel (oxy)hydroxide
Electrocatalytic
256201870#N/AFALSE
1085
s41467-019-09666-010.1038/s41467-019-09666-0FALSEhttps://doi.org/10.1038/s41467-019-09666-0Sun, XMNat. Commun.Single atom catalyst, which contains isolated metal atoms singly dispersed on supports, has great potential for achieving high activity and selectivity in hetero-catalysis and electrocatalysis. However, the activity and stability of single atoms and their interaction with support still remains a mystery. Here we show a stable single atomic ruthenium catalyst anchoring on the surface of cobalt iron layered double hydroxides, which possesses a strong electronic coupling between ruthenium and layered double hydroxides. With 0.45 wt.% ruthenium loading, the catalyst exhibits outstanding activity with overpotential 198 mV at the current density of 10 mA cm(-2) and a small Tafel slope of 39 mV dec(-1) for oxygen evolution reaction. By using operando X-ray absorption spectroscopy, it is disClosed that the isolated single atom ruthenium was kept under the oxidation states of 4+ even at high overpotential due to synergetic electron coupling, which endow exceptional electrocatalytic activity and stability simultaneously.Boosting oxygen evolution of single-atomic ruthenium through electronic coupling with cobalt-iron layered double hydroxides156201970#N/ATRUE
1086
s41467-019-08877-910.1038/s41467-019-08877-9FALSEhttps://doi.org/10.1038/s41467-019-08877-9Gu, JAtomically engineering Activation sites onto metallic 1T-MoS2 catalysts for enhanced electrochemical hydrogen evolution2019#N/ATRUE
1087
s41467-019-08473-x10.1038/s41467-019-08473-xFALSEhttps://doi.org/10.1126/science.287.5452.460Liu, LCatalytic enantioselective oxidative coupling of saturated ethers with Carbonylic acid derivatives2019#N/ATRUE
1088
s41467-018-07371-y10.1038/s41467-018-07371-yFALSEhttps://doi.org/10.1038/s41467-018-07371-yPriya, SColossal tunability in high frequency magnetoelectric voltage tunable inductors2018#N/ATRUE
1089
s41467-018-04646-210.1038/s41467-018-04646-2FALSEhttps://doi.org/10.1038/s41467-018-04646-2Ji, SJNat. Commun.Chalcogen-containing compounds have received considerable attention because of their manifold applications in agrochemicals, pharmaceuticals, and material science. While many Classical methods have been developed for preparing organic sulfides, most of them exploited the transition-metal-catalyzed cross-couplings of Aryl halides or pseudo halides with thiols or disulfides, with harsh reaction conditions usually being required. Herein, we present a user-friendly, nickel-catalyzed reductive thiolation of unactivated primary and secondary Alkyl bromides with thiosulfonates as reliable thiolation reagents, which are easily prepared and bench-stable. Furthermore, a series of selenides is also prepared in a similar fashion with selenosulfonates as selenolation reagents. This catalytic method offers a facile synthesis of a wide range of unsymmetrical Alkyl-Aryl or Alkyl-Alkyl sulfides and selenides under mild conditions with an excellent tolerance of functional groups. Likewise, the use of sensitive and stoichiometric organometallic reagents can be avoided.Nickel-catalyzed reductive thiolation and selenylation of unactivated Alkyl bromidesx41201857#N/AFALSE
1090
s41467-018-07046-810.1038/s41467-018-07046-8FALSEhttps://doi.org/10.1038/s41467-018-07046-8Beale, AMNat. Commun.We report the results from the first 5D tomographic diffraction imaging experiment of a complex Ni-Pd/CeO2-ZrO2/Al2O3 catalyst used for methane reforming. This fivedimensional (three spatial, one scattering and one dimension to denote time/imposed state) approach enabled us to track the chemical evolution of many partiCles across the catalyst bed and relate these changes to the gas environment that the partiCles experience. Rietveld analysis of some 2 x 10(6) diffraction patterns allowed us to extract heterogeneities in the catalyst from the A to the nm and to the pm scale (3D maps corresponding to unit cell lattice parameters, crystallite sizes and phase distribution maps respectively) under different chemical environments. We are able to capture the evolution of the Ni-containing species and gain a more complete insight into the multiple roles of the CeO2-ZrO2 promoters and the reasons behind the partial deActivation of the catalyst during partial oxidation of methane.5D operando tomographic diffraction imaging of a catalyst bed42201864#N/ATRUE
1091
s41467-018-03928-z10.1038/s41467-018-03928-zhttps://doi.org/10.1038/s41467-018-03928-zUchiyama, MNat. Commun.pi-Conjugated polymers are widely used in optoelectronics for fabrication of organic photovoltaic devices, organic light-emitting diodes, organic field effect transistors, and so on. Here we describe the protocol for polycondensation of bifunctional Aryl ethers or Aryl ammonium salts with aromatic dimetallic compounds through Cleavage of inert C-O/C-N bonds. This reaction proceeds smoothly in the presence of commercially available Ni/Pd catalyst under mild conditions, affording the corresponding pi-conjugated polymers with high molecular weight. The method is applicable to monomers that are unreactive in other currently employed polymerization procedures, and opens up the possibility of transforming a range of naturally abundant chemicals into useful functional compounds/polymers.Cross-coupling polycondensation via C-O or C-N bond Cleavagex22201870#N/AFALSE
1092
s41467-018-06900-z10.1038/s41467-018-06900-zFALSEhttps://doi.org/10.1038/s41467-018-06900-zPeng, ZMNat. Commun.Understanding the growth pathway of faceted alloy nanopartiCles at the atomic level is crucial to morphology control and property tuning. Yet, it remains a challenge due to complexity of the growth process and technical limits of modern characterization tools. We report a combinational use of multiple cutting-edge in situ techniques to study the growth process of octahedral Pt3Ni nanopartiCles, which reveal the partiCle growth and facet formation mechanisms. Our studies confirm the formation of octahedral Pt3Ni initiates from Pt nuClei generation, which is followed by continuous Pt reduction that simultaneously catalyzes Ni reduction, resulting in mixed alloy formation with moderate elemental segregation. Carbon monoxide molecules serve as a facet formation modulator and induce Ni segregation to the surface, which inhibits the (111) facet growth and causes the partiCle shape to evolve from a spherical Cluster to an octahedron as the (001) facet continues to grow.Deconvolution of octahedral Pt3Ni nanopartiCle growth pathway from in situ characterizations20201831#N/ATRUE
1093
s41467-018-03879-510.1038/s41467-018-03879-5https://doi.org/10.1038/s41467-018-03879-5Tong, RNat. Commun.Biodegradable polyesters with various tacticities have been synthesized by means of stereoselective ring-opening polymerization of racemic lactide and beta-lactones but with limited side-chain groups. However, stereoselective synthesis of functional polyesters remains challenging from O-carboxyanhydrides that have abundant pendant side-chain functional groups. Herein we report a powerful strategy to synthesize stereoblock polyesters by stereoselective ring-opening polymerization of racemic O-carboxyanhydrides with the use of photoredox Ni/Ir catalysts and a selected Zn complex with an achiral ligand. The obtained stereoblock copolymers are highly isotactic with high molecular weights (> 70 kDa) and narrow molecular weight distributions (M-w/M-n < 1.1), and they display distinct melting temperatures that are similar to their stereocomplex counterparts. Furthermore, in one-pot photoredox copolymerization of two different O-carboxyanhydrides, the use of such Zn complex mediates kinetic resolution of the comonomers during enchainment and shows a chirality preference that allows for the synthesis of gradient copolymers.Stereoselective photoredox ring-opening polymerization of O-carboxyanhydridesPhotocatalystx32201870#N/AFALSE
1094
s41467-018-03810-y10.1038/s41467-018-03810-yFALSEhttps://doi.org/10.1038/s41467-018-03810-yXiao, FSSingle-site catalyst promoters accelerate metal-catalyzed nitroarene hydrogenationx2018#N/AFALSE
1095
s41467-018-03721-y10.1038/s41467-018-03721-yFALSEhttps://doi.org/10.1038/s41467-018-03721-yKhursheed, ANat. Commun.There have been several long-standing problems of cold field emission sources for electron microscopy and lithography that have prevented their widespread use, such as their inherent ultrahigh vacuum condition requirement (<10(-9) torr), relatively poor current stability and rapid emission decay. This paper presents a cold field emission electron source which overcomes these problems based upon using a graphene-coated nickel point cathode. Preliminary experiments demonstrate that it provides stable emission for relatively large tip diameters (micron sizes), can operate in high vacuum conditions (>10(-8) torr) and has an ultralow work function value of 1.10 +/- 0.07 eV. It has an estimated reduced brightness value of 1.46 x 10(9) Am-2 sr(-1) V-1 for cathode tip-radius of 170 nm and the measured energy spread ranges from 0.246 eV to 0.420 eV for a tip radii range of 260 nm to 500 nm, which is comparable to state-of-the-art conventional cold field emission sources.A high-brightness large-diameter graphene coated point cathode field emission electron sourcex36201841#N/AFALSE
1096
s41467-018-03650-w10.1038/s41467-018-03650-wFALSEhttps://doi.org/10.1038/s41467-018-03650-wZhou, XNat. Commun.Effective transfection of genetic molecules such as DNA usually relies on vectors that can reversibly uptake and release these molecules, and protect them from digestion by nuClease. Non-viral vectors meeting these requirements are rare due to the lack of specific interactions with DNA. Here, we design a series of four isoreticular metal-organic frameworks (Ni-IRMOF-74-II to -V) with progressively tuned pore size from 2.2 to 4.2 nm to precisely inClude single-stranded DNA (ssDNA, 11-53 nt), and to achieve reversible interaction between MOFs and ssDNA. The entire nuCleic acid chain is completely confined inside the pores providing excellent protection, and the geometric distribution of the confined ssDNA is visualized by Xray diffraction. Two MOFs in this series exhibit excellent transfection efficiency in mammalian immune cells, 92% in the primary mouse immune cells (CD4+ T cell) and 30% in human immune cells (THP-1 cell), unrivaled by the commercialized agents (Lipo and Neofect).Metal-organic frameworks for precise inClusion of single-stranded DNA and transfection in immune cellsx87201848#N/AFALSE
1097
s41467-018-06478-610.1038/s41467-018-06478-6FALSEhttps://doi.org/10.1038/s41467-018-06478-6Jiang, BNat. Commun.Controlling product branching ratios in a chemical reaction represents a desired but difficult achievement in chemistry. In this work, we demonstrate the first example of altering the branching ratios in a multichannel reaction, i.e., methanol dissociative chemisorption on Cu(111), via selectively exciting specific vibrational modes. To this end, we develop a globally accurate full-dimensional potential energy surface for the CH3OH/Cu(111) system and perform extensive vibrational state-selected molecular dynamics simulations. Our results show that O-H/C-H/C-O stretching vibrational excitations substantially enhance the respective bond scission processes, representing extraordinary bond selectivity. At a given total energy, the branching ratio of C-O/C-H dissociation can increase by as large as 100 times by exciting the C-O stretching mode which possesses an unprecedentedly strong vibrational efficacy on reactivity. This vibrational control can be realized by the well-designed experiment using a linearly polarized laser.Vibrational control of selective bond Cleavage in dissociative chemisorption of methanol on Cu(111)23201860#N/ATRUE
1098
s41467-018-06296-w10.1038/s41467-018-06296-wFALSEhttps://doi.org/10.1038/s41467-018-06296-wLi, YDNat. Commun.Development of single-site catalysts supported by ultrathin two-dimensional (2D) porous matrix with ultrahigh surface area is highly desired but also challenging. Here we report a cocoon silk chemistry strategy to synthesize isolated metal single-site catalysts embedded in ultrathin 2D porous N-doped carbon nanosheets (M-ISA/CNS, M = Fe, Co, Ni). X-ray absorption fine structure analysis and spherical aberration correction electron microscopy demonstrate an atomic dispersion of metal atoms on N-doped carbon matrix. In particular, the Co-ISA/CNS exhibit ultrahigh specific surface area (2105 m(2) g(-1)) and high activity for C-H bond Activation in the direct catalytic oxidation of benzene to phenol with hydrogen peroxide at room temperature, while the Co species in the form of phthalocyanine and metal nanopartiCle show a negligible activity. Density functional theory calculations discover that the generated O = Co = O center intermediates on the single Co sites are responsible for the high activity of benzene oxidation to phenol.A cocoon silk chemistry strategy to ultrathin N-doped carbon nanosheet with metal single-site catalysts90201870#N/ATRUE
1099
s41467-018-03239-310.1038/s41467-018-03239-3https://doi.org/10.1038/s41467-018-03239-3Schneider, SNat. Commun.Direct hydrogenation of CO2 to CO, the reverse water-gas shift reaction, is an attractive route to CO2 utilization. However, the use of molecular catalysts is impeded by the general reactivity of metal hydrides with CO2. Insertion into M-H bonds results in formates (MO(O) CH), whereas the abnormal insertion to the hydroxyCarbonyl isomer (MC(O) OH), which is the key intermediate for CO-selective catalysis, has never been directly observed. We here report that the selectivity of CO2 insertion into a Ni-H bond can be inverted from normal to abnormal insertion upon switching from thermal to photochemical conditions. Mechanistic examination for abnormal insertion indicates photochemical N-H reductive elimination as the pivotal step that leads to an umpolung of the hydride ligand. This study conceptually introduces metal-ligand cooperation for selectivity control in photochemical transformations.The elusive abnormal CO2 insertion enabled by metal-ligand cooperative photochemical selectivity inversionPhotocatalyst31201829#N/AFALSE
1100
s41467-018-03011-710.1038/s41467-018-03011-7FALSEhttps://doi.org/10.1038/s41467-018-03011-7Rudiger, ONat. Commun.The Ni(P2N2)(2) catalysts are among the most efficient non-noble-metal based molecular catalysts for H-2 cyCling. However, these catalysts are O-2 sensitive and lack long term stability under operating conditions. Here, we show that in a redox silent polymer matrix the catalyst is dispersed into two functionally different reaction layers. Close to the electrode surface is the active layer where the catalyst oxidizes H-2 and exchanges electrons with the electrode generating a current. At the outer film boundary, insulation of the catalyst from the electrode forms a protection layer in which H-2 is used by the catalyst to convert O-2 to H2O, thereby providing the active layer with a barrier against O-2. This simple but efficient polymer-based electrode design solves one of the biggest limitations of these otherwise very efficient catalysts enhancing its stability for catalytic H-2 oxidation as well as O-2 tolerance.Dual properties of a hydrogen oxidation Ni-catalyst entrapped within a polymer promote self-defense against oxygenx22201830#N/AFALSE
1101
s41467-017-02429-910.1038/s41467-017-02429-9FALSEhttps://doi.org/10.1038/s41467-017-02429-9Sun, LCNat. Commun.Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm(-2). The core-shell NiFeCu electrode exhibits pH-dependent oxygen evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation
Electrocatalytic
193201849#N/AFALSE
1102
s41467-018-06019-110.1038/s41467-018-06019-1FALSEhttps://doi.org/10.1038/s41467-018-06019-1Zhu, CJNat. Commun.The construction of an Aryl ketone structural unit by means of catalytic carbon-carbon coupling reactions represents the state-of-the-art in organic chemistry. Herein we achieved the direct deoxygenative ketone synthesis in aqueous solution from readily available aromatic Carbonylic acids and alkenes, affording structurally diverse ketones in moderate to good yields. Visible-light photoredox catalysis enables the direct deoxygenation of acids as acyl sources with triphenylphosphine and represents a distinct perspective on Activation. The synthetic robustness is supported by the late-stage modification of several pharmaceutical compounds and complex molecules. This ketone synthetic strategy is further applied to the synthesis of the drug zolpidem in three steps with 50% total yield and a concise construction of cyClophane-braced 18-20 membered macrocyCloketones. It represents not only the advancement for the streamlined synthesis of aromatic ketones from feedstock chemicals, but also a photoredox radical Activation mode beyond the redox potential of Carbonylic acids.A general deoxygenation approach for synthesis of ketones from aromatic Carbonylic acids and alkenes78201851#N/ATRUE
1103
s41467-018-05999-410.1038/s41467-018-05999-4FALSEhttps://doi.org/10.1038/s41467-018-05999-4Zhu, DDNat. Commun.Organic materials are emerging thermoelectric candidates for flexible power generation and solid-cooling applications. Although the Peltier effect is a fundamental thermoelectric effect that enables site-specific and on-demand cooling applications, the Peltier effect in organic thermoelectric films have not been investigated. Here we experimentally observed and quasi-quantitatively evaluated the Peltier effect in a poly(Ni-ett) film through the fabrication of thermally suspended devices combined with an infrared imaging technique. The experimental and simulation results confirm effective extraction of the Peltier effect and verify the Thomson relations in organic materials. More importantly, the working device based on poly (Ni-ett) film yields maximum temperature differences as large as 41 K at the two contacts and a cooling of 0.2 K even under heat-insulated condition. This exploration of the Peltier effect in organic thermoelectric films predicts that organic materials hold the ultimate potential to enable flexible solid-cooling applications.Exploring Peltier effect in organic thermoelectric films34201826#N/ATRUE
1104
s41467-017-01910-910.1038/s41467-017-01910-9FALSEhttps://doi.org/10.1038/s41467-017-01910-9Gascon, JNat. Commun.The development of synthetic protocols for the preparation of highly loaded metal nanopartiCle-supported catalysts has received a great deal of attention over the last few decades. Independently controlling metal loading, nanopartiCle size, distribution, and accessibility has proven challenging because of the Clear interdependence between these crucial performance parameters. Here we present a stepwise methodology that, making use of a cobalt-containing metal organic framework as hard template (ZIF-67), allows addressing this long-standing challenge. Condensation of silica in the Co-metal organic framework pore space followed by pyrolysis and subsequent calcination of these composites renders highly loaded cobalt nanocomposites (similar to 50 wt.% Co), with cobalt oxide reducibility in the order of 80% and a good partiCle dispersion, that exhibit high activity, C5 + selectivity and stability in Fischer-Tropsch synthesis.Manufacture of highly loaded silica-supported cobalt Fischer-Tropsch catalysts from a metal organic frameworkx62201753#N/AFALSE
1105
s41467-017-01545-w10.1038/s41467-017-01545-whttps://doi.org/10.1038/s41467-017-01545-wAlberto, RNat. Commun.Atomically dispersed supported catalysts can maximize atom efficiency and minimize cost. In spite of much progress in gas-phase catalysis, applying such catalysts in the field of renewable energy coupled with electrochemistry remains a challenge due to their limited durability in electrolyte. Here, we report a robust and atomically dispersed hybrid catalyst formed in situ on a hematite semiconductor support during photoelectrochemical oxygen evolution by electrostatic adsorption of soluble monomeric [Ir(OH)(6)](2-) coupled to positively charged NiOx sites. The alkali-stable [Ir(OH)(6)](2-) features synergistically enhanced activity toward water oxidation through NiOx that acts as a movable bridge of charge transfer from the hematite surface to the single iridium center. This hybrid catalyst sustains high performance and stability in alkaline electrolyte for > 80 h of operation. Our findings provide a promising path for soluble catalysts that are weakly and reversibly bound to semiconductor-supported hole-accumulation inorganic materials under catalytic reaction conditions as hybrid active sites for photoelectrocatalysis.Atomically dispersed hybrid nickel-iridium sites for photoelectrocatalysisPhotocatalyst25201744#N/AFALSE
1106
s41467-018-05951-610.1038/s41467-018-05951-6FALSEhttps://doi.org/10.1038/s41467-018-05951-6Chu, LLNat. Commun.The development of catalytic carboacylation of simple olefins, which would enable the rapid construction of ketones with high levels of complexity and diversity, is very challenging. To date, the vast majority of alkene carboacylation reactions are typically restricted to single and two-component methodologies. Here we describe a three-component carboacylation of alkenes via the merger of radical chemistry with nickel catalysis. This reaction manifold utilizes a radical relay strategy involving radical addition to an alkene followed by Alkyl radical capture by an acyl-nickel complex to forge two vicinal C-C bonds under mild conditions. Excellent chemoselectivity and regioselectivity have been achieved by utilizing a pendant weakly chelating group. This versatile protocol allows for facile access to a wide range of important beta-fluoroAlkyl ketones from simple starting materials.Intermolecular selective carboacylation of alkenes via nickel-catalyzed reductive radical relay72201872#N/ATRUE
1107
s41467-018-05210-810.1038/s41467-018-05210-8FALSEhttps://doi.org/10.1038/s41467-018-05210-8Chen, NNat. Commun.Unsupported non-bridged uranium-carbon double bonds have long been sought after in actinide chemistry as fundamental synthetic targets in the study of actinide-ligand multiple bonding. Here we report that, utilizing I-h(7)-C-80 fullerenes as nanocontainers, a diuranium carbide Cluster, U=C=U, has been encapsulated and stabilized in the form of UCU@I-h(7)-C-80 . This endohedral fullerene was prepared utilizing the Kratschmer-Huffman arc discharge method, and was then co-crystallized with nickel(II) octaethylporphyrin (Ni-II-OEP) to produce UCU@I-h(7)-C-80 center dot[ Ni-II-OEP] as single crystals. X-ray diffraction analysis reveals a cage-stabilized, carbide-bridged, bent UCU Cluster with unexpectedly short uranium-carbon distances (2.03 angstrom) indicative of covalent U=C double-bond character. The quantum-chemical results suggest that both U atoms in the UCU unit have formal oxidation state of +5. The structural features of UCU@I-h(7)-C-80 and the covalent nature of the U(f(1))=C double bonds were further affirmed through various spectroscopic and theoretical analyses.A diuranium carbide Cluster stabilized inside a C-80 fullerene cage33201868#N/ATRUE
1108
s41467-017-01035-z10.1038/s41467-017-01035-zFALSEhttps://doi.org/10.1038/s41467-017-01035-zStrasser, PNat. Commun.Direct electrochemical reduction of CO2 to fuels and chemicals using renewable electricity has attracted significant attention partly due to the fundamental challenges related to reactivity and selectivity, and partly due to its importance for industrial CO2-consuming gas diffusion cathodes. Here, we present advances in the understanding of trends in the CO2 to CO electrocatalysis of metal-and nitrogen-doped porous carbons containing catalytically active M-N-x moieties (M = Mn, Fe, Co, Ni, Cu). We investigate their intrinsic catalytic reactivity, CO turnover frequencies, CO faradaic efficiencies and demonstrate that Fe-N-C and especially Ni-N-C catalysts rival Au- and Ag-based catalysts. We model the catalytically active M-N-x moieties using density functional theory and correlate the theoretical binding energies with the experiments to give reactivity-selectivity descriptors. This gives an atomic-scale mechanistic understanding of potential-dependent CO and hydrocarbon selectivity from the M-N-x moieties and it provides predictive guidelines for the rational design of selective carbon-based CO2 reduction catalysts.Understanding activity and selectivity of metal-nitrogen-doped carbon catalysts for electrochemical reduction of CO2x445201763#N/AFALSE
1109
s41467-017-00776-110.1038/s41467-017-00776-1FALSEhttps://doi.org/10.1038/s41467-017-00776-1Kepert, CJNat. Commun.External control over the mechanical function of materials is paramount in the development of nanoscale machines. Yet, exploiting changes in atomic behaviour to produce controlled scalable motion is a formidable challenge. Here, we present an ultra-flexible coordination framework material in which a cooperative electronic transition induces an extreme abrupt change in the crystal lattice conformation. This arises due to a change in the preferred coordination character of Fe(II) sites at different spin states, generating scissor-type flexing of the crystal lattice. Diluting the framework with transition-inactive Ni(II) sites disrupts long-range communication of spin state through the lattice, producing a more gradual transition and continuous lattice movement, thus generating colossal positive and negative linear thermal expansion behaviour, with coefficients of thermal expansion an order of magnitude greater than previously reported. This study has wider implications in the development of advanced responsive structures, demonstrating electronic control over mechanical motion.Spin crossover-induced colossal positive and negative thermal expansion in a nanoporous coordination framework materialx46201736#N/AFALSE
1110
s41467-017-00519-210.1038/s41467-017-00519-2FALSEhttps://doi.org/10.1038/s41467-017-00519-2Gogotsi, YNat. Commun.Lithium metal has been regarded as the future anode material for high-energy-density rechargeable batteries due to its favorable combination of negative electrochemical potential and high theoretical capacity. However, uncontrolled lithium deposition during lithium plating/stripping results in low Coulombic efficiency and severe safety hazards. Herein, we report that nanodiamonds work as an electrolyte additive to co-deposit with lithium ions and produce dendrite-free lithium deposits. First-principles calculations indicate that lithium prefers to adsorb onto nanodiamond surfaces with a low diffusion energy barrier, leading to uniformly deposited lithium arrays. The uniform lithium deposition morphology renders enhanced electrochemical cyCling performance. The nanodiamond-modified electrolyte can lead to a stable cyCling of lithium vertical bar lithium symmetrical cells up to 150 and 200 h at 2.0 and 1.0 mA cm(-2), respectively. The nanodiamond co-deposition can significantly alter the lithium plating behavior, affording a promising route to suppress lithium dendrite growth in lithium metal-based batteries.Nanodiamonds suppress the growth of lithium dendritesx242201751#N/AFALSE
1111
s41467-018-05019-510.1038/s41467-018-05019-5FALSEhttps://doi.org/10.1038/s41467-018-05019-5Chen, JSNat. Commun.Although a number of nonprecious materials can exhibit catalytic activity approaching (sometimes even outperforming) that of iridium oxide catalysts for the oxygen evolution reaction, their catalytic lifetimes rarely exceed more than several hundred hours under operating conditions. Here we develop an energy-efficient, cost-effective, scaled-up corrosion engineering method for transforming inexpensive iron substrates (e.g., iron plate and iron foam) into highly active and ultrastable electrodes for oxygen evolution reaction. This synthetic method is achieved via a desired corrosion reaction of iron substrates with oxygen in aqueous solutions containing divalent cations (e.g., nickel) at ambient temperature. This process results in the growth on iron substrates of thin film nanosheet arrays that consist of iron-containing layered double hydroxides, instead of rust. This inexpensive and simple manufacturing technique affords iron-substrate-derived electrodes possessing excellent catalytic activities and activity retention for over 6000 hours at 1000 mA cm(-2) current densities.Corrosion engineering towards efficient oxygen evolution electrodes with stable catalytic activity for over 6000 hours192201844#N/ATRUE
1112
s41467-018-04746-z10.1038/s41467-018-04746-zFALSERen, ZFHigh-performance bifunctional porous non-noble metal phosphide catalyst for overall water splitting2018#N/ATRUE
1113
s41467-018-04682-y10.1038/s41467-018-04682-yFALSEhttps://doi.org/10.1038/s41467-018-04682-yShao, ZPNat. Commun.An efficient and cost-effective oxygen evolution reaction (OER) electrocatalyst is key for electrochemical energy generation and storage technologies. Here, the rational design and in situ formation of an antiperovskite-based hybrid with a porous conductive Cu1-xNNi3-y (x and y represent defect) core and amorphous FeNiCu (oxy) hydroxide shell is reported as a promising water oxidation electrocatalyst, showing outstanding performance. Benefiting from the unique advantage of core-shell structure, as well as the synergistic effect of Fe, Ni, and Cu and the highly porous hierarchical structure, the hybrid catalyst exhibits highly efficient and robust OER performance in alkaline environments, outperforming the benchmark IrO2 catalyst in several aspects. Our findings demonstrate the application potential of antiperovskite-based materials in the field of electrocatalysis, which may inspire insights into the development of novel materials for energy generation and storage applications.A surface-modified antiperovskite as an electrocatalyst for water oxidation44201844#N/ATRUE
1114
s41467-018-04123-w10.1038/s41467-018-04123-wFALSEhttps://doi.org/10.1038/s41467-018-04123-wFeng, XMNat. Commun.Although great success has been achieved in asymmetric Claisen rearrangement for the synthesis of chiral gamma,delta-unsaturated Carbonyl compounds bearing vicinal tertiary-quaternary stereocenters, the development of asymmetric versions for stereodivergent construction of adjacent quaternary-quaternary stereocenters remains a formidable challenge because of the high steric hindrance. Here we report a catalytic enantioselective dearomatization Claisen rearrangement of allyl furyl ethers catalyzed by chiral N,N'-dioxide-Ni-II complex catalysts. A variety of chiral gamma,delta-unsaturated Carbonyl compounds bearing vicinal quaternary-quaternary stereocenters were obtained with excellent outcomes under mild conditions. Furthermore, we disClosed that by matching the configuration of the catalysts and the alkene unit of the substrates, four stereoisomers of the products could be prepared in excellent yields and stereoselectivities. Finally, the fascination of this strategy was demonstrated by stereodivergent synthesis of bioactive natural products hyperolactones B, C, and their epimers. A possible catalytic model was proposed to explain the origin of the asymmetric induction.Stereodivergent synthesis of vicinal quaternary-quaternary stereocenters and bioactive hyperolactones27201851#N/ATRUE
1115
s41467-018-03896-410.1038/s41467-018-03896-4FALSEhttps://doi.org/10.1038/s41467-018-03896-4Li, YLNat. Commun.Electrocatalysis by atomic catalysts is a major focus of chemical and energy conversion effort. Although transition-metal-based bulk electrocatalysts for electrochemical application on energy conversion processes have been reported frequently, anchoring the stable transitionmetal atoms (e. g. nickel and iron) still remains a practical challenge. Here we report a strategy for fabrication of ACs comprising only isolated nickel/iron atoms anchored on graphdiyne. Our findings identify the very narrow size distributions of both nickel (1.23 angstrom) and iron (1.02 angstrom), typical sizes of single-atom nickel and iron. The precision of this method motivates us to develop a general approach in the field of single-atom transition-metal catalysis. Such atomic catalysts have high catalytic activity and stability for hydrogen evolution reactions.Anchoring zero valence single atoms of nickel and iron on graphdiyne for hydrogen evolution348201862#N/ATRUE
1116
s41467-018-03532-110.1038/s41467-018-03532-1FALSEhttps://doi.org/10.1038/s41467-018-03532-1Zhang, XGNat. Commun.Relatively low reactivity hinders using chlorodifluoromethane (ClCF2H) for general difluoromethylation with organic molecules, despite its availability as an inexpensive industrial chemical. To date, transformations of ClCF2H are very limited and most of them involve difluorocarbene intermediate. Here, we describe a strategy for difluoromethylation of aromatics through nickel-catalyzed cross-coupling of ClCF2H with readily accessible (hetero)Aryl chlorides. The reaction proceeds under mild reaction conditions with high efficiency and features synthetic simplicity without preformation of Arylmetals and broad substrate scope, inCluding a variety of Hets and commercially available pharmaceuticals. The reliable practicability and scalability of the current nickel-catalyzed process has also been demonstrated by several 10-g scale reactions without loss of reaction efficiency. Preliminary mechanistic studies reveal that the reaction starts from the oxidative addition of Aryl chlorides to Ni(0) and a difluoromethyl radical is involved in the reaction, providing a route for applications of ClCF2H in organic synthesis and related chemistry.Difluoromethylation of (hetero)Aryl chlorides with chlorodifluoromethane catalyzed by nickel73201845#N/ATRUE
1117
s41467-018-03380-z10.1038/s41467-018-03380-zFALSEhttps://doi.org/10.1038/s41467-018-03380-zLi, YDNat. Commun.Development of single-atomic-site catalysts with high metal loading is highly desirable but proved to be very challenging. Although utilizing defects on supports to stabilize independent metal atoms has become a powerful method to fabricate single-atomic-site catalysts, little attention has been devoted to cation vacancy defects. Here we report a nickel hydroxide nanB(OH)2ard with abundant Ni2+ vacancy defects serving as the practical support to achieve a single-atomic-site Pt catalyst (Pt-1/Ni(OH)(x)) containing Pt up to 2.3 wt% just by a simple wet impregnation method. The Ni2+ vacancies are found to have strong stabilizing effect of single-atomic Pt species, which is determined by X-ray absorption spectrometry analyses and density functional theory calculations. This Pt-1/Ni(OH)(x) catalyst shows a high catalytic efficiency in diboration of a variety of alkynes and alkenes, yielding an overall turnover frequency value upon reaction completion for phenylacetylene of similar to 3000 h(-1), which is much higher than other reported heterogeneous catalysts.Cation vacancy stabilization of single-atomic-site Pt-1/Ni(OH)(x) catalyst for diboration of alkynes and alkenes121201861#N/ATRUE
1118
s41467-017-02095-x10.1038/s41467-017-02095-xFALSEhttps://doi.org/10.1038/s41467-017-02095-xHazen, RMNat. Commun.The mineralogy and geochemistry associated with Rodinian assembly (similar to 1.3-0.9 Ga) are significantly different from those of other supercontinents. Compared to other supercontinents, relatively more Nb-bearing minerals, Y-bearing minerals, and zircons formed during Rodinian assembly, with corresponding enrichments of Nb, Y, and Zr concentrations in igneous rocks. By contrast, minerals bearing many other elements (e.g., Ni, Co, Au, Se, and platinum group elements) are significantly less abundant, without corresponding depletion of Ni and Co concentrations in igneous rocks. Here we suggest that the Nb, Y, and Zr enrichments in igneous rocks and relatively more occurrences of corresponding Nb-bearing minerals, Y-bearing minerals, and zircons result from significant non-arc magmatism during the mid-Proterozoic, while fewer occurrences of many other minerals suggest enhanced erosion of Rodinian volcanic arcs and orogens. The prolonged, extrovert assembly of Rodinia from thickened mid-Proterozoic continental crust via two-sided subduction can account for both the prevalence of non-arc magmatism and the enhanced erosion.Geochemical and mineralogical evidence that Rodinian assembly was unique13201769#N/ATRUE
1119
s41467-017-01949-810.1038/s41467-017-01949-8FALSEhttps://doi.org/10.1038/s41467-017-01949-8Dau, HNat. Commun.The emergence of disordered metal oxides as electrocatalysts for the oxygen evolution reaction and reports of amorphization of crystalline materials during electrocatalysis reveal a need for robust structural models for this Class of materials. Here we apply a combination of low-temperature X-ray absorption spectroscopy and time-resolved in situ X-ray absorption spectroelectrochemistry to analyze the structure and electrochemical properties of a series of disordered iron-cobalt oxides. We identify a composition-dependent distribution of di-mu-oxo bridged cobalt-cobalt, di-mu-oxo bridged cobalt-iron and corner-sharing cobalt structural motifs in the composition series. Comparison of the structural model with (spectro) electrochemical data reveals relationships across the composition series that enable unprecedented assignment of voltammetric redox processes to specific structural motifs. We confirm that oxygen evolution occurs at two distinct reaction sites, di-mu-oxo bridged cobalt-cobalt and di-mu-oxo bridged iron-cobalt sites, and identify direct and indirect modesof- action for iron ions in the mixed-metal compositions.Spectroscopic identification of active sites for the oxygen evolution reaction on iron-cobalt oxides73201745#N/ATRUE
1120
ol501180q10.1021/ol501180qhttps://doi.org/10.1021/ol501180qChatani, NOrg. Lett
A new, catalytic, and general methodology for the synthesis of biAryls and heterobiAryls by the cross coupling of anthranilamide derivatives (o-NMe2 benzamides) with Aryl boroneopentylates is described. The reaction proceeds under catalytic RuH2(CO)(PPh3)3 conditions driven by the Activation of the unreactive C–N bond by amide directing group (DG)-Ru catalyst chelation. High regioselectivity, orthogonality with the Suzuki–Miyaura reaction, operational simplicity, and convenient scale-up are features of these reactions which may lend themselves to industrial applications.
Beyond Directed Ortho Metalation: Ruthenium-Catalyzed Amide-Directed CAr–N Activation/C–C Coupling Reaction of Anthranilamides with Organoboronatesx422014Added by Shihong#N/A
1121
s41467-017-01540-110.1038/s41467-017-01540-1FALSEhttps://doi.org/10.1038/s41467-017-01540-1Zhang, XGNat. Commun.In spite of the important applications of difluoroAlkylated molecules in medicinal chemistry, to date, the reaction of difluoroAlkylating reagents with unactivated, aliphatic substrates through a controllable manner remains challenging and has not been reported. Here we describe an efficient nickel-catalyzed cross-coupling of unactivated Alkylzinc reagen\ts with gem-difluoropropargyl bromides. The reaction proceeds under mild reaction conditions with high efficiency and excellent regiochemical selectivity. Transformations of the resulting difluoroAlkylated alkanes lead to a variety of biologically active molecules, providing a facile route for applications in drug discovery and development. Preliminary mechanistic studies reveal that an Alkyl nickel intermediate [Ni(tpy)Alkyl] (tpy, terpyridine) is involved in the catalytic cyCle.Highly selective nickel-catalyzed gem-difluoropropargylation of unactivated Alkylzinc reagents30201756#N/ATRUE
1122
s41467-017-01507-210.1038/s41467-017-01507-2FALSEhttps://doi.org/10.1038/s41467-017-01507-2Kempe, RNat. Commun.The catalytic synthesis of linear alpha-olefins from ethylene is a technologically highly important reaction. A synthesis concept allowing the formation of selective products and various linear a-olefin product distributions with one catalyst system is highly desirable. Here, we describe a trimetallic catalyst system (Y-Al-Ni) consisting of a rare earth metal polymerization catalyst which can mediate coordinative chain transfer to triethylaluminum combined with a simultaneously operating nickel beta-hydride elimination/transfer catalyst. This nickel catalyst displaces the grown Alkyl chains forming linear alpha-olefins and recyCles the aluminum-based chain transfer agent. With one catalyst system, we can synthesize product spectra ranging from selective 1-butene formation to a-olefin distributions centered at 850 gmol(-1) with a low polydispersity. The key to this highly flexible linear alpha-olefin synthesis is the easy tuning of the rates of the Y and Ni catalysis independently of each other. The reaction is substoichiometric or formally catalytic regarding the chain transfer agent.A broadly tunable synthesis of linear alpha-olefins18201723#N/ATRUE
1123
s41467-017-00363-410.1038/s41467-017-00363-4FALSEhttps://doi.org/10.1038/s41467-017-00363-4Fu, YNat. Commun.OrganB(OH)2ron compounds play an irreplaceable role in synthetic chemistry and the related transformations based on the unique reactivity of C-B bond are potentially the most efficient methods for the synthesis of organic molecules. The synthetic importance of multiboron compounds in C-C bond formation and function transformation reactions is growing and the related borations of activated or nonactivated alkenes have been developed recently. However, introducing directly two boron moieties into the terminal sites of alkenes giving 1,1-diborylalkanes in a catalytic fashion has not been explored yet. Here we describe a synthetic strategy of 1,1-diborylalkanes via a Ni-catalyzed 1,1-diboration of readily available terminal alkenes. This methodology shows high level of chemoselectivity and regioselectivity and can be used to convert a large variety of terminal alkenes, such as Vinylarenes, aliphatic alkenes and lower alkenes, to 1,1-diborylalkanes.Nickel-catalyzed synthesis of 1,1-diborylalkanes from terminal alkenes44201759#N/ATRUE
1124
s41467-017-00068-810.1038/s41467-017-00068-8FALSEhttps://doi.org/10.1038/s41467-017-00068-8Ogoshi, SNat. Commun.TricyClic furan derivatives with multiple chiral centers are ubiquitous in natural products. Construction of such tricyClic scaffolds in a stereocontrolled, step-economic, and atom-economic manner is a key challenge. Here we show a nickel-catalyzed highly enantioselective synthesis of hydronaphtho[1,8-bc]furans with five contiguous chiral centers via desymmetrization of alkynyl-cyClohexadienone by oxidative cyClization and following formal [4 + 2] cyCloaddition processes. Alkynyl-cyClohexadienone was synthesized in one step from easily accessible phenols. This reaction represents excellent chemo-selectivity, regio-selectivity, diastereo-selectivity, and enantio-selectivity (single diastereomer, up to 99% ee). An extraordinary regioselectivity in the formal [4 + 2] cyCloaddition step with enones revealed the diverse reactivity of the nickelacyCle intermediate. Desymmetrization of alkynyl-cyClohexadienones via oxidative cyClization on nickel was supported by the isolation of a nickelacyCle from a stoichiometric reaction. Enantioenriched tricyClic products contain various functional groups such as C=O and C=C. The synthetic utility of these products was demonstrated by derivatization of these functional groups.Two-step synthesis of chiral fused tricyClic scaffolds from phenols via desymmetrization on nickel84201746#N/ATRUE
1125
ol990288110.1021/ol9902881FALSEhttps://doi.org/10.1021/ol9902881Sasai, HDesign and synthesis of the first spiro bis(isoxazoline) derivatives as asymmetric ligands1999#N/ATRUE
1126
ol990280r10.1021/ol990280rFALSEhttps://doi.org/10.1021/ol990280rYu, JWOlefin-mediated interaction observed for nickel tetraphenylporphyrins with an acceptor substituted on the beta-carbon1999#N/ATRUE
1127
ol902970z10.1021/ol902970zFALSEhttps://doi.org/10.1021/ol902970zDaugulis, ONickel, Manganese, Cobalt, and Iron-Catalyzed Deprotonative Arene Dimerization2010#N/ATRUE
1128
ol901052w10.1021/ol901052wFALSEhttps://doi.org/10.1021/ol901052wChen, QYUnprecedented Degradation of Nickel(II) 2,3,12,13-Tetrabromo-5,10,15,20-tetraArylporphyrins by the Anion of E-Benzaldoxime: A Novel Approach to Nickel(II) Chlorophins and Bacteriophins2009#N/ATRUE
1129
ol802351r10.1021/ol802351rFALSEhttps://doi.org/10.1021/ol802351rSrinivasan, A9,10,19,20-TetraArylporphycenes2008#N/ATRUE
1130
ol070287610.1021/ol0702876FALSEhttps://doi.org/10.1021/ol0702876Oshima, KPalladium-catalyzed anti-hydrothiolation of 1-alkynylphosphinesx2007#N/AFALSE
1131
ol800225t10.1021/ol800225tFALSEhttps://doi.org/10.1021/ol800225tBuono, GLooking for a synergic effect between NHCs and chiral P-ligands2008#N/ATRUE
1132
ol503395g10.1021/ol503395gFALSEhttps://doi.org/10.1126/science.1085597Yoshikai, NIron-Catalyzed Directed C2-Alkylation and Alkenylation of Indole with Vinylarenes and Alkynes2015#N/ATRUE
1133
ol401540k10.1021/ol401540kFALSEhttps://doi.org/10.1021/ol401540kShi, BFRhodium(III)-Catalyzed Oxidative Olefination of Pyridines and Quinolines: Multigram-Scale Synthesis of Naphthyridinones2013#N/ATRUE
1134
ol302891310.1021/ol3028913FALSEhttps://doi.org/10.1021/ol3028913Cuerva, JMWater Control over the Chemoselectivity of a Ti/Ni Multimetallic System: Heck- or Reductive-Type CyClization Reactions of Alkyl Iodides2012#N/ATRUE
1135
ol300348w10.1021/ol300348wFALSEhttps://doi.org/10.1021/ol300348wHu, XLCopper-Catalyzed Alkylation of Benzoxazoles with Secondary Alkyl Halides2012#N/ATRUE
1136
ol300207810.1021/ol3002078TRUEShibasaki, MCatalytic Enantioselective Desymmetrization of meso-Glutaric Anhydrides Using a Stable Ni-2-Schiff Base CatalystCsp2-Csp3E-NuO
O(Ring-Opening)
H
Carbonyl
No baseNo Base20123/24/2022TRUE
1137
ol300203w10.1021/ol300203wFALSEhttps://doi.org/10.1021/ol300203wJun, CHIr(I)/HCl Catalyzed Head-to-Tail Homocoupling Reactions of Vinylsilanes2012#N/ATRUE
1138
ol202878v10.1021/ol202878vFALSEhttps://doi.org/10.1021/ol202878vKishi, YAir-Stable Heterobimetallic Catalysts to Effect Ni/Cr-Mediated Couplings with a ca. 1:1 Molar Ratio of Coupling Partners at Low Catalyst Loadings2012#N/ATRUE
1139
ol035587b10.1021/ol035587bFALSEhttps://doi.org/10.1021/ol035587bStang, PJA self-assembled supramolecular optical sensor for Ni(II), Cd(II), and Cr(III)x2004#N/AFALSE
1140
ol201141m10.1021/ol201141mFALSEhttps://doi.org/10.1021/ol201141mZhao, YFNi(II)/Zn Catalyzed Reductive Coupling of Aryl Halides with Diphenylphosphine Oxide in Water2011#N/ATRUE
1141
ol200881v10.1021/ol200881vFALSEhttps://doi.org/10.1021/ol200881vWeix, DJReductive Conjugate Addition of Haloalkanes to Enones To Form Silyl Enol Ethers2011#N/ATRUE
1142
ol071326g10.1021/ol071326gFALSEInoue, YPalladium-catalyzed selective cross-addition of triisopropylsilylacetylene to internal and terminal unactivated alkynes2007#N/ATRUE
1143
ol015807q10.1021/ol015807qFALSEhttps://doi.org/10.1126/science.1211649Maleczka, REA Nozaki-Hiyama-Kishi Ni(II)/Cr(II) coupling approach to the phomactinsx2001#N/AFALSE
1144
ol062807n10.1021/ol062807nFALSERyu, IRu-catalyzed intermolecular [3+2+1] cyCloaddition of alpha,beta-unsaturated ketones with silylacetylenes and carbon monoxide leading to alpha-pyrones2007#N/ATRUE
1145
ol061579u10.1021/ol061579uFALSEhttps://doi.org/10.1021/ol061579uMontgomery, JHighly diastereoselective preparation of anti-1,2-diols by catalytic addition of alkynylsilanes to alpha-silyloxyaldehydes2006#N/ATRUE
1146
ncomms961910.1038/ncomms9619FALSEhttps://doi.org/10.1038/ncomms9619Vlachos, DGNat. Commun.Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanopartiCles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N - H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.Patched bimetallic surfaces are active catalysts for ammonia decompositionx46201551#N/AFALSE
1147
ol060752j10.1021/ol060752jFALSEhttps://doi.org/10.1021/ol060752jGunnlaugsson, TSupramolecular self-assembly of mixed f-d metal ion conjugates2006#N/ATRUE
1148
ol060454m10.1021/ol060454mFALSEhttps://doi.org/10.1021/ol060454mHocek, MSynthesis of C-Aryldeoxyribosides by [2+2+2]-cyClotrimerization catalyzed by Rh, Ni, Co, and Ru complexes2006#N/ATRUE
1149
ncomms917710.1038/ncomms9177FALSEhttps://doi.org/10.1038/ncomms9177Koper, MTMNat. Commun.The electrochemical conversion of carbon dioxide and water into useful products is a major challenge in facilitating a Closed carbon cyCle. Here we report a cobalt protoporphyrin immobilized on a pyrolytic graphite electrode that reduces carbon dioxide in an aqueous acidic solution at relatively low overpotential (0.5 V), with an efficiency and selectivity comparable to the best porphyrin-based electrocatalyst in the literature. While carbon monoxide is the main reduction product, we also observe methane as by-product. The results of our detailed pH-dependent studies are explained consistently by a mechanism in which carbon dioxide is activated by the cobalt protoporphyrin through the stabilization of a radical intermediate, which acts as Bronsted base. The basic character of this intermediate explains how the carbon dioxide reduction circumvents a concerted proton-electron transfer mechanism, in contrast to hydrogen evolution. Our results and their mechanistic interpretations suggest strategies for designing improved catalysts.Electrocatalytic reduction of carbon dioxide to carbon monoxide and methane at an immobilized cobalt protoporphyrin
Electrocatalytic
288201537#N/AFALSE
1150
ol050063s10.1021/ol050063sFALSEhttps://doi.org/10.1021/ol050063sRobins, MJFluoro, Alkylsulfanyl, and Alkylsulfonyl leaving groups in Suzuki cross-coupling reactions of purine 2 '-deoxynuCleosides and nuCleosides2005#N/ATRUE
1151
ncomms889010.1038/ncomms8890FALSEhttps://doi.org/10.1038/ncomms8890Cramer, SPNat. Commun.The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the Fe-57-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique 'wagging' mode involving H- motion perpendicular to the Ni(mu-H)Fe-57 plane was studied using Fe-57-specific nuClear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(mu-D)Fe-57 deuteride substitution, this wagging causes a characteristic perturbation of Fe-CO/CN bands. Spectra have been interpreted by comparison with Ni(mu-H/D)Fe-57 enzyme mimics [(dppe)Ni(mu-pdt)(mu-H/D)Fe-57(CO) 3](+) and DFT calculations, which collectively indicate a low-spin Ni(II)(mu-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe-H moieties in other important natural and synthetic catalysts.Hydride bridge in [NiFe]-hydrogenase observed by nuClear resonance vibrational spectroscopyx57201563#N/AFALSE
1152
ol049506310.1021/ol0495063FALSERajanbabu, TVFine-tuning monophosphine ligands for enhanced enantioselectivity. Influence of chiral hemilabile pendant groups2004#N/ATRUE
1153
ol047872g10.1021/ol047872gFALSEhttps://doi.org/10.1021/ol047872gKanemasa, SEnantioselective enol lactone synthesis under double catalytic conditions2005#N/ATRUE
1154
ol036326510.1021/ol0363265FALSEhttps://doi.org/10.1021/ol0363265Colby, DACarbaporphyrinoid chemistry has a silver lining! Silver(III) oxybenzi-, oxynaphthi-, tropi-, and benzocarbaporphyrins2004#N/ATRUE
1155
ncomms761610.1038/ncomms7616FALSEhttps://doi.org/10.1038/ncomms7616Zhao, CANat. Commun.Large-scale industrial application of electrolytic splitting of water has called for the development of oxygen evolution electrodes that are inexpensive, robust and can deliver large current density (>500 mA cm(-2)) at low applied potentials. Here we show that an efficient oxygen electrode can be developed by electrodepositing amorphous mesoporous nickel-iron composite nanosheets directly onto macroporous nickel foam substrates. The as-prepared oxygen electrode exhibits high catalytic activity towards water oxidation in alkaline solutions, which only requires an overpotential of 200 mV to initiate the reaction, and is capable of delivering current densities of 500 and 1,000 mA cm(-2) at overpotentials of 240 and 270 mV, respectively. The electrode also shows prolonged stability against bulk water electrolysis at large current. Collectively, the as-prepared three-dimensional structured electrode is the most efficient oxygen evolution electrode in alkaline electrolytes reported to the best of our knowledge, and can potentially be applied for industrial scale water electrolysis.Electrodeposition of hierarchically structured three-dimensional nickel-iron electrodes for efficient oxygen evolution at high current densitiesx1198201544#N/AFALSE
1156
ncomms743010.1038/ncomms7430FALSEhttps://doi.org/10.1038/ncomms7430Tang, ZYNat. Commun.Design and synthesis of effective electrocatalysts for hydrogen evolution reaction in alkaline environments is critical to reduce energy losses in alkaline water electrolysis. Here we report a hybrid nanomaterial comprising of one-dimensional ultrathin platinum nanowires grown on two-dimensional single-layered nickel hydroxide. Judicious surface chemistry to generate the fully exfoliated nickel hydroxide single layers is explored to be the key for controllable growth of ultrathin platinum nanowires with diameters of about 1.8 nm. Impressively, this hybrid nanomaterial exhibits superior electrocatalytic activity for hydrogen evolution reaction in alkaline solution, which outperforms currently reported catalysts, and the obviously improved catalytic stability. We believe that this work may lead towards the development of single-layered metal hydroxide-based hybrid materials for applications in catalysis and energy conversion.Ultrathin platinum nanowires grown on single-layered nickel hydroxide with high hydrogen evolution activityx627201556#N/AFALSE
1157
ol035232s10.1021/ol035232sFALSEhttps://doi.org/10.1021/ol035232sLatos-Grazynski, LRegioselective pyridination of m-benziporphyrin2003#N/ATRUE
1158
ncomms600310.1038/ncomms6003FALSEhttps://doi.org/10.1038/ncomms6003Sparks, DNat. Commun.Reactions at the mineral-water interface are central to numerous geochemical processes and have consequences at local, regional and global scales. They are also important in materials science research. Kinetics greatly influences mineral-water interface reactions; however, there are few kinetic data in real-time and at the molecular scale. Here we report real-time data illustrating the rapid formation of nickel aluminium-layered double hydroxide precipitates at the mineral-water interface in a flow environment in as little as 31-40 min. Layered double hydroxides have a variety of applications in environmental remediation and materials science. The real-time data shown here enhance our fundamental understanding of the kinetics of mineral-water interface processes, such as adsorption, dissolution and precipitation, by illustrating their rapid and simultaneous occurrence in a dynamic environment. Both precipitation and adsorption can occur on the same rapid timescale.Real-time QEXAFS spectroscopy measures rapid precipitate formation at the mineral-water interfacex35201442#N/AFALSE
1159
ol034227l10.1021/ol034227lFALSEhttps://doi.org/10.1021/ol034227lFuruta, HN-confused porphyrin-bearing meso-perfluorophenyl groups: A potential agent that forms stable square-planar complexes with Cu(II) and Ag(III)2003#N/ATRUE
1160
ol034141s10.1021/ol034141sFALSEReiser, OFacile asymmetric synthesis of the core nuClei of xanthanolides, guaianolides, and eudesmanolides2003#N/ATRUE
1161
ol005956t10.1021/ol005956tFALSENolan, SPEfficient cross-coupling reactions of Aryl chlorides and bromides with phenyl- or Vinyltrimethoxysilane mediated by a palladium/imidazolium chloride system2000#N/ATRUE
1162
ncomms966210.1038/ncomms9662FALSEhttps://doi.org/10.1038/ncomms9662Kong, JNat. Commun.Although hexagonal boron nitride (h-BN) is a good candidate for gate-insulating materials by minimizing interaction from substrate, further applications to electronic devices with available two-dimensional semiconductors continue to be limited by flake size. While monolayer h-BN has been synthesized on Pt and Cu foil using chemical vapour deposition (CVD), multilayer h-BN is still absent. Here we use Fe foil and synthesize large-area multilayer h-BN film by CVD with a borazine precursor. These films reveal strong cathodoluminescence and high mechanical strength (Young's modulus: 1.16 +/- 0.1 TPa), reminiscent of formation of high-quality h-BN. The CVD-grown graphene on multilayer h-BN film yields a high carrier mobility of similar to 24,000 cm(2)V(-1) s(-1) at room temperature, higher than that (similar to 13,000(2)V(-1) s(-1)) with exfoliated h-BN. By placing additional h-BN on a SiO2/Si substrate for a MoS2 (WSe2) field-effect transistor, the doping effect from gate oxide is minimized and furthermore the mobility is improved by four (150) times.Synthesis of large-area multilayer hexagonal boron nitride for high material performance250201564#N/ATRUE
1163
ncomms325610.1038/ncomms3256FALSEhttps://doi.org/10.1038/ncomms3256Paltiel, YNat. Commun.Several technologies are currently in use for computer memory devices. However, there is a need for a universal memory device that has high density, high speed and low power requirements. To this end, various types of magnetic-based technologies with a permanent magnet have been proposed. Recent charge-transfer studies indicate that chiral molecules act as an efficient spin filter. Here we utilize this effect to achieve a proof of concept for a new type of chiral-based magnetic-based Si-compatible universal memory device without a permanent magnet. More specifically, we use spin-selective charge transfer through a self-assembled monolayer of polyalanine to magnetize a Ni layer. This magnitude of magnetization corresponds to applying an external magnetic field of 0.4 T to the Ni layer. The readout is achieved using low currents. The presented technology has the potential to overcome the limitations of other magnetic-based memory technologies to allow fabricating inexpensive, high-density universal memory-on-chip devices.A chiral-based magnetic memory device without a permanent magnetx88201325#N/AFALSE
1164
ncomms311410.1038/ncomms3114FALSEhttps://doi.org/10.1038/ncomms3114Han, SMNat. Commun.Graphene is a single-atomic-layer material with excellent mechanical properties and has the potential to enhance the strength of composites. Its two-dimensional geometry, high intrinsic strength and modulus can effectively constrain dislocation motion, resulting in the significant strengthening of metals. Here we demonstrate a new material design in the form of a nanolayered composite consisting of alternating layers of metal (copper or nickel) and monolayer graphene that has ultra-high strengths of 1.5 and 4.0 GPa for copper-graphene with 70-nm repeat layer spacing and nickel-graphene with 100-nm repeat layer spacing, respectively. The ultra-high strengths of these metal-graphene nanolayered structures indicate the effectiveness of graphene in blocking dislocation propagation across the metal-graphene interface. Ex situ and in situ transmission electron microscopy compression tests and molecular dynamics simulations confirm a build-up of dislocations at the graphene interface.Strengthening effect of single-atomic-layer graphene in metal-graphene nanolayered compositesx419201333#N/AFALSE
1165
ncomms930410.1038/ncomms9304FALSEhttps://doi.org/10.1038/ncomms9304Hupp, JTNat. Commun.The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200mV at a benchmark current density of 10mAcm (-2). Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution176201563#N/ATRUE
1166
ncomms924810.1038/ncomms9248FALSEhttps://doi.org/10.1038/ncomms9248Li, YDPlatinum-nickel frame within metal-organic framework fabricated in situ for hydrogen enrichment and molecular sieving2015#N/ATRUE
1167
ncomms912010.1038/ncomms9120FALSEhttps://doi.org/10.1038/ncomms9120Irvine, JTSNat. Commun.Metal partiCles supported on oxide surfaces are used as catalysts for a wide variety of processes in the chemical and energy conversion industries. For catalytic applications, metal partiCles are generally formed on an oxide support by physical or chemical deposition, or less commonly by exsolution from it. Although fundamentally different, both methods might be assumed to produce morphologically and functionally similar partiCles. Here we show that unlike nickel partiCles deposited on perovskite oxides, exsolved analogues are socketed into the parent perovskite, leading to enhanced stability and a significant decrease in the propensity for hydrocarbon coking, indicative of a stronger metal-oxide interface. In addition, we reveal key surface effects and defect interactions critical for future design of exsolution-based perovskite materials for catalytic and other functionalities. This study provides a new dimension for tailoring partiCle-substrate interactions in the context of increasing interest for emergent interfacial phenomena.Nano-socketed nickel partiCles with enhanced coking resistance grown in situ by redox exsolution345201531#N/ATRUE
1168
ncomms1596710.1038/ncomms15967FALSEhttps://doi.org/10.1038/ncomms15967Kim, GNat. Commun.In perovskites, exsolution of transition metals has been proposed as a smart catalyst design for energy applications. Although there exist transition metals with superior catalytic activity, they are limited by their ability to exsolve under a reducing environment. When a doping element is present in the perovskite, it is often observed that the surface segregation of the doping element is changed by oxygen vacancies. However, the mechanism of co-segregation of doping element with oxygen vacancies is still an open question. Here we report trends in the exsolution of transition metal (Mn, Co, Ni and Fe) on the PrBaMn2O5-delta layered perovskite oxide related to the co-segregation energy. Transmission electron microscopic observations show that easily reducible cations (Mn, Co and Ni) are exsolved from the perovskite depending on the transition metal-perovskite reducibility. In addition, using density functional calculations we reveal that co-segregation of B-site dopant and oxygen vacancies plays a central role in the exsolution.Exsolution trends and co-segregation aspects of self-grown catalyst nanopartiCles in perovskitesx154201737#N/AFALSE
1169
ncomms879810.1038/ncomms8798FALSEhttps://doi.org/10.1038/ncomms8798Hu, PNat. Commun.It is crucial to develop a catalyst made of earth-abundant elements highly active for a complete oxidation of methane at a relatively low temperature. NiCo2O4 consisting of earth-abundant elements which can completely oxidize methane in the temperature range of 350-550 degrees C. Being a cost-effective catalyst, NiCo2O4 exhibits activity higher than precious-metal-based catalysts. Here we report that the higher catalytic activity at the relatively low temperature results from the integration of nickel cations, cobalt cations and surface lattice oxygen atoms/oxygen vacancies at the atomic scale. In situ studies of complete oxidation of methane on NiCo2O4 and theoretical simulations show that methane dissociates to methyl on nickel cations and then couple with surface lattice oxygen atoms to form -CH3O with a following dehydrogenation to -CH2O; a following oxidative dehydrogenation forms CHO; CHO is transformed to product molecules through two different sub-pathways inCluding dehydrogenation of OCHO and CO oxidation.Understanding complete oxidation of methane on spinel oxides at a molecular level158201548#N/ATRUE
1170
ncomms826110.1038/ncomms8261FALSEhttps://doi.org/10.1038/ncomms8261Cui, YNat. Commun.Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, inCluding oxygen evolution reaction and hydrogen evolution reaction, is important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanopartiCles (similar to 20 nm) are electrochemically transformed into ultra-small diameter (2-5 nm) nanopartiCles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanopartiCles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanopartiCles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10mAcm(-2) water-splitting current at only 1.51V for over 200 h without degradation in a two-electrode configuration and 1M KOH, better than the combination of iridium and platinum as benchmark catalysts.Bifunctional non-noble metal oxide nanopartiCle electrocatalysts through lithium-induced conversion for overall water splitting613201532#N/ATRUE
1171
ncomms153910.1038/ncomms1539FALSEhttps://doi.org/10.1038/ncomms1539Liu, ZFNat. Commun.Controlled growth of high-quality graphene is still the bottleneck of practical applications. The widely used chemical vapour deposition process generally suffers from an uncontrollable carbon precipitation effect that leads to inhomogeneous growth and strong correlation to the growth conditions. Here we report the rational design of a binary metal alloy that effectively suppresses the carbon precipitation process and activates a self-limited growth mechanism for homogeneous monolayer graphene. As demonstrated by an Ni-Mo alloy, the designed binary alloy contains an active catalyst component for carbon source decomposition and graphene growth and a black hole counterpart for trapping the dissolved carbons and forming stable metal carbides. This type of process engineering has been used to grow strictly single-layer graphene with 100% surface coverage and excellent tolerance to variations in growth conditions. With simplicity, scalability and a very large growth window, the presented approach may facilitate graphene research and industrial applications.Rational design of a binary metal alloy for chemical vapour deposition growth of uniform single-layer graphenex206201128#N/AFALSE
1172
ncomms769410.1038/ncomms7694FALSEhttps://doi.org/10.1038/ncomms7694Lou, XWNat. Commun.While the synthesis of hollow structures of transition metal oxides is well established, it is extremely challenging to fabricate complex hollow structures for mixed transition metal sulfides. Here we report an anion exchange method to synthesize a complex ternary metal sulfides hollow structure, namely nickel cobalt sulfide ball-in-ball hollow spheres. Uniform nickel cobalt glycerate solid spheres are first synthesized as the precursor and subsequently chemically transformed into nickel cobalt sulfide ball-in-ball hollow spheres. When used as electrode materials for electrochemical capacitors, these nickel cobalt sulfide hollow spheres deliver a specific capacitance of 1,036 F g(-1) at a current density of 1.0 A g(-1). An asymmetric supercapacitor based on these ball-in-ball structures shows long-term cyCling performance with a high energy density of 42.3 Wh kg(-1) at a power density of 476 W kg(-1), suggesting their potential application in high-performance electrochemical capacitors.Formation of nickel cobalt sulfide ball-in-ball hollow spheres with enhanced electrochemical pseudocapacitive properties883201559#N/ATRUE
1173
ncomms1513110.1038/ncomms15131FALSEhttps://doi.org/10.1038/ncomms15131Zheng, LSNat. Commun.Crystal phase regulations may endow materials with enhanced or new functionalities. However, syntheses of noble metal-based allomorphic nanomaterials are extremely difficult, and only a few successful examples have been found. Herein, we report the discovery of hexagonal Close-packed Pt-Ni alloy, despite the fact that Pt-Ni alloys are typically crystallized in face-centred cubic structures. The hexagonal Close-packed Pt-Ni alloy nano-multipods are synthesized via a facile one-pot solvothermal route, where the branches of nano-multipods take the shape of excavated hexagonal prisms assembled by six nanosheets of 2.5 nm thickness. The hexagonal Close-packed Pt-Ni excavated nano-multipods exhibit superior catalytic property towards the hydrogen evolution reaction in alkaline electrolyte. The overpotential is only 65mV versus reversible hydrogen electrode at a current density of 10 mA cm(-2), and the mass current density reaches 3.03 mA mu gPt(-1) at -70 mV versus reversible hydrogen electrode, which outperforms currently reported catalysts to the best of our knowledge.Platinum-nickel alloy excavated nano-multipods with hexagonal Close-packed structure and superior activity towards hydrogen evolution reactionx226201751#N/AFALSE
1174
ncomms663310.1038/ncomms6633FALSEhttps://doi.org/10.1038/ncomms6633Lee, MJDirect cellular delivery of human proteasomes to delay tau aggregation2014#N/ATRUE
1175
ncomms14993
10.1038/ncomms14993https://doi.org/10.1038/ncomms14993Chatani, NNat. Commun.
Amide and olefins are important synthetic intermediates with complementary reactivity which play a key role in the construction of natural products, pharmaceuticals and manmade materials. Converting the normally highly stable aliphatic amides into olefins directly is a challenging task. Here we show that a Ni/NHC-catalytic system has been established for deCarbonylative elimination of aliphatic amides to generate various olefins via C-N and C-C bond Cleavage. This study not only overcomes the acyl C-N bond Activation in aliphatic amides, but also encompasses distinct chemical advances on a new type of elimination reaction called retro-hydroamidoCarbonylation. This transformation shows good functional group compatibility and can serve as a powerful synthetic tool for late-stage olefination of amide groups in complex compounds.
Nickel-catalysed retro-hydroamidoCarbonylation of aliphatic amides to olefins
Hu, JF; Wang, MY; Pu, XH; Shi, ZZ
Condensation reaction
y592017
Added by Imanuel
#N/AFALSE
1176
ncomms547710.1038/ncomms5477FALSEhttps://doi.org/10.1038/ncomms5477Hu, XLNat. Commun.The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chemical compositions and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compositions or structures. Specifically, liquid phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alkaline conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a commercial iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic conductivity. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction.Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis1405201438#N/ATRUE
1177
ncomms534510.1038/ncomms5345FALSEhttps://doi.org/10.1038/ncomms5345Cui, YNat. Commun.Searching for low-cost and efficient catalysts for the oxygen evolution reaction has been actively pursued owing to its importance in Clean energy generation and storage. While developing new catalysts is important, tuning the electronic structure of existing catalysts over a wide electrochemical potential range can also offer a new direction. Here we demonstrate a method for electrochemical lithium tuning of catalytic materials in organic electrolyte for subsequent enhancement of the catalytic activity in aqueous solution. By continuously extracting lithium ions out of LiCoO2, a popular cathode material in lithium ion batteries, to Li0.5CoO2 in organic electrolyte, the catalytic activity is significantly improved. This enhancement is ascribed to the unique electronic structure after the delithiation process. The general efficacy of this methodology is demonstrated in several mixed metal oxides with similar improvements. The electrochemically delithiated LiCo0.33Ni0.33Fe0.33O2 exhibits a notable performance, better than the benchmark iridium/carbon catalyst.Electrochemical tuning of layered lithium transition metal oxides for improvement of oxygen evolution reaction322201439#N/ATRUE
1178
ncomms508510.1038/ncomms5085FALSEhttps://doi.org/10.1038/ncomms5085Strasser, GNat. Commun.The increasing demand of rapid sensing and diagnosis in remote areas requires the development of compact and cost-effective mid-infrared sensing devices. So far, all miniaturization concepts have been demonstrated with discrete optical components. Here we present a monolithically integrated sensor based on mid-infrared absorption spectroscopy. A bi-functional quantum cascade laser/detector is used, where, by changing the applied bias, the device switches between laser and detector operation. The interaction with chemicals in a liquid is resolved via a dielectric-loaded surface plasmon polariton waveguide. The thin dielectric layer enhances the confinement and enables efficient end-fire coupling from and to the laser and detector. The unamplified detector signal shows a slope of 1.8-7 mu V per p.p.m., which demonstrates the capability to reach p.p.m. accuracy over a wide range of concentrations (0-60%). Without any hybrid integration or subwavelength patterning, our approach allows a straightforward and cost-saving fabrication.Monolithically integrated mid-infrared lab-on-a-chip using plasmonics and quantum cascade structures113201433#N/ATRUE
1179
ncomms341310.1038/ncomms3413FALSEhttps://doi.org/10.1038/ncomms3413Han, XDIn situ atomic-scale observation of continuous and reversible lattice deformation beyond the elastic limit2013#N/ATRUE
1180
ncomms1417810.1038/ncomms14178FALSEhttps://doi.org/10.1038/ncomms14178Li, XCNat. Commun.Effective control of melting and solidification behaviours of materials is significant for numerous applications. It has been a long-standing challenge to increase the melted zone (MZ) depth while shrinking the heat-affected zone (HAZ) size during local melting and solidification of materials. In this paper, nanopartiCle-induced unusual melting and solidification behaviours of metals are reported that effectively solve this long-time dilemma. By introduction of Al2O3 nanopartiCles, the MZ depth of Ni is increased by 68%, while the corresponding HAZ size is decreased by 67% in laser melting at a pulse energy of 0.18 mJ. The addition of SiC nanopartiCles shows similar results. The discovery of the unusual melting and solidification of materials that contain nanopartiCles will not only have impacts on existing melting and solidification manufacturing processes, such as laser welding and additive manufacturing, but also on other applications such as pharmaceutical processing and energy storage.NanopartiCle-induced unusual melting and solidification behaviours of metalsx38201726#N/AFALSE
1181
ncomms1413610.1038/ncomms14136FALSEhttps://doi.org/10.1038/ncomms14136Wang, LYNat. Commun.Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. However, effects of the distance between the noble metal and oxophilic metal active sites on the catalytic performance have rarely been investigated. Herein, we report on ultrasmall (similar to 5 nm) Pd-Ni-P ternary nanopartiCles for ethanol electrooxidation. The activity is improved up to 4.95A per mg(Pd), which is 6.88 times higher than commercial Pd/C (0.72A per mgPd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni-P heterodimers into Pd-Ni-P nanopartiCles and tuning the Ni/Pd atomic ratio to 1:1. Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals (on Ni active sites) which facilitate the oxidative removal of carbonaceous poison and combination with CH3CO radicals on adjacent Pd active sites.Improved ethanol electrooxidation performance by shortening Pd-Ni active site distance in Pd-Ni-P nanocatalystsx214201744#N/AFALSE
1182
ncomms1387010.1038/ncomms13870FALSEhttps://doi.org/10.1038/ncomms13870Brechin, EKNat. Commun.Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the 'transformation' from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuClear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with T-c controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, 'squeezing' the molecules Closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of T-c with pressure.Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomersx23201652#N/AFALSE
1183
ncomms1364610.1038/ncomms13646FALSEhttps://doi.org/10.1038/s41557-019-0303-0Mallah, TEngineering the magnetic coupling and anisotropy at the molecule-magnetic surface interface in molecular spintronic devicesx2016#N/AFALSE
1184
ncomms135910.1038/ncomms1359FALSEhttps://doi.org/10.1038/ncomms1359Liu, MLNat. Commun.The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deActivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C(3)H(8), CO and gasified carbon fuels at 750 degrees C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H(2)O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity.Promotion of water-mediated carbon removal by nanostructured barium oxide/nickel interfaces in solid oxide fuel cellsx226201143#N/AFALSE
1185
ncomms1287910.1038/ncomms12879FALSEhttps://doi.org/10.1038/ncomms12879Zboril, RNat. Commun.Superparamagnetism is a phenomenon caused by quantum effects in magnetic nanomaterials. Zero-valent metals with diameters below 5 nm have been suggested as superior alternatives to superparamagnetic metal oxides, having greater superspin magnitudes and lower levels of magnetic disorder. However, synthesis of such nanometals has been hindered by their chemical instability. Here we present a method for preparing air-stable superparamagnetic iron nanopartiCles trapped between thermally reduced graphene oxide nanosheets and exhibiting ring-like or core-shell morphologies depending on iron concentration. Importantly, these hybrids show superparamagnetism at room temperature and retain it even at 5 K. The corrected saturation magnetization of 185 Am-2 kg(-1) is among the highest values reported for iron-based superparamagnets. The synthetic concept is generalized exploiting functional groups of graphene oxide to stabilize and entrap cobalt, nickel and gold nanopartiCles, potentially opening doors for targeted delivery, magnetic separation and imaging applications.Air-stable superparamagnetic metal nanopartiCles entrapped in graphene oxide matrixx45201646#N/AFALSE
1186
ncomms1276510.1038/ncomms12765FALSEhttps://doi.org/10.1038/ncomms12765Ren, ZFNat. Commun.With the massive consumption of fossil fuels and its detrimental impact on the environment, methods of generating Clean power are urgent. Hydrogen is an ideal carrier for renewable energy; however, hydrogen generation is inefficient because of the lack of robust catalysts that are substantially cheaper than platinum. Therefore, robust and durable earth-abundant and cost-effective catalysts are desirable for hydrogen generation from water splitting via hydrogen evolution reaction. Here we report an active and durable earth-abundant transition metal dichalcogenide-based hybrid catalyst that exhibits high hydrogen evolution activity approaching the state-of-the-art platinum catalysts, and superior to those of most transition metal dichalcogenides (molybdenum sulfide, cobalt diselenide and so on). Our material is fabricated by growing ternary molybdenum sulfoselenide partiCles on self-standing porous nickel diselenide foam. This advance provides a different pathway to design cheap, efficient and sizable hydrogen-evolving electrode by simultaneously tuning the number of catalytic edge sites, porosity, heteroatom doping and electrical conductivity.Efficient hydrogen evolution by ternary molybdenum sulfoselenide partiCles on self-standing porous nickel diselenide foamx209201638#N/AFALSE
1187
ncomms1236210.1038/ncomms12362FALSEhttps://doi.org/10.1038/ncomms12362Li, YDNat. Commun.The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reactionx123201638#N/AFALSE
1188
ncomms281210.1038/ncomms2812FALSEhttps://doi.org/10.1038/ncomms2812Dai, HJAdvanced zinc-air batteries based on high-performance hybrid electrocatalysts2013#N/ATRUE
1189
ncomms251810.1038/ncomms2518FALSEhttps://doi.org/10.1038/ncomms2518Amine, KNat. Commun.Long-life and safe lithium-ion batteries have been long pursued to enable electrification of the transportation system and for grid applications. However, the poor safety characteristics of lithium-ion batteries have been the major bottleneck for the widespread deployment of this promising technology. Here, we report a novel nonaqueous Li2B12F12-xHx electrolyte, using lithium difluoro(oxalato) borate as an electrolyte additive, that has superior performance to the conventional LiPF6-based electrolyte with regard to cyCle life and safety, inCluding tolerance to both overcharge and thermal abuse. Cells tested with the Li2B12F9H3-based electrolyte maintained about 70% initial capacity when cyCled at 55 degrees C for 1,200 cyCles, and the intrinsic overcharge protection mechanism was active up to 450 overcharge abuse cyCles. Results from in situ high-energy X-ray diffraction showed that the thermal decomposition of the delithiated Li1-x[Ni(1/3M)n(1/3)Co(1/3)](0.9)O-2 cathode was delayed by about 20 degrees C when using the Li2B12F12-based electrolyte.New Class of nonaqueous electrolytes for long-life and safe lithium-ion batteries89201324#N/ATRUE
1190
ncomms235110.1038/ncomms2351FALSEhttps://doi.org/10.1038/ncomms2351Suenaga, KNat. Commun.The alloying behaviour of materials is a well-known problem in all kinds of compounds. Revealing the heteroatomic distributions in two-dimensional crystals is particularly critical for their practical use as nano-devices. Here we obtain statistics of the homo-and heteroatomic coordinates in single-layered Mo1-xWxS2 from the atomically resolved scanning transmission electron microscope images and successfully quantify the degree of alloying for the transition metal elements (Mo or W). The results reveal the random alloying of this mixed dichalcogenide system throughout the chemical compositions (x = 0 to 1). Such a direct route to gain an insight into the alloying degree on individual atom basis will find broad applications in characterizing low-dimensional heterocompounds and become an important complement to the existing theoretical methods.Visualization and quantification of transition metal atomic mixing in Mo1-xWxS2 single layers153201337#N/ATRUE
1191
ncomms1206710.1038/ncomms12067FALSEhttps://doi.org/10.1038/ncomms12067Glezakou, VANat. Commun.Technetium (Tc-99) is an abundant, long-lived radioactive fission product whose mobility in the subsurface is largely governed by its oxidation state. Tc immobilization is crucial for radioactive waste management and environmental remediation. Tc(IV) incorporation in spinels has been proposed as a novel method to increase Tc retention in glass waste forms during vitrification. However, experiments under high-temperature and oxic conditions show reoxidation of Tc(IV) to volatile pertechnetate, Tc(VII). Here we examine this problem with ab initio molecular dynamics simulations and propose that, at elevated temperatures, doping with first row transition metal can significantly enhance Tc retention in magnetite in the order Co>Zn>Ni. Experiments with doped spinels at 700 degrees C provide quantitative confirmation of the theoretical predictions in the same order. This work highlights the power of modern, state-of-the-art simulations to provide essential insights and generate theory-inspired design criteria of complex materials at elevated temperatures.Impeding Tc-99(IV) mobility in novel waste formsx59201643#N/AFALSE
1192
ncomms1570210.1038/ncomms15702FALSEhttps://doi.org/10.1038/ncomms15702Folco, LNat. Commun.Molten I-type cosmic spherules formed by heating, oxidation and melting of extraterrestrial Fe, Ni metal alloys. The entire oxygen in these spherules sources from the atmosphere. Therefore, I-type cosmic spherules are suitable tracers for the isotopic composition of the upper atmosphere at altitudes between 80 and 115 km. Here we present data on I-type cosmic spherules collected in Antarctica. Their composition is compared with the composition of tropospheric O-2. Our data suggest that the Earth's atmospheric O-2 is isotopically homogenous up to the thermosphere. This makes fossil I-type micrometeorites ideal proxies for ancient atmospheric CO2 levels.Tracing the oxygen isotope composition of the upper Earth's atmosphere using cosmic spherules21201754#N/ATRUE
1193
ncomms1543710.1038/ncomms15437FALSEhttps://doi.org/10.1038/ncomms15437Feng, XLNat. Commun.Various platinum-free electrocatalysts have been explored for hydrogen evolution reaction in acidic solutions. However, in economical water-alkali electrolysers, sluggish water dissociation kinetics (Volmer step) on platinum-free electrocatalysts results in poor hydrogen-production activities. Here we report a MoNi4 electrocatalyst supported by MoO2 cuboids on nickel foam (MoNi4/MoO2@Ni), which is constructed by controlling the outward diffusion of nickel atoms on annealing precursor NiMoO4 cuboids on nickel foam. Experimental and theoretical results confirm that a rapid Tafel-step-decided hydrogen evolution proceeds on MoNi4 electrocatalyst. As a result, the MoNi4 electrocatalyst exhibits zero onset overpotential, an overpotential of 15 mV at 10 mA cm(-2) and a low Tafel slope of 30 mV per decade in 1M potassium hydroxide electrolyte, which are comparable to the results for platinum and superior to those for state-of-the-art platinum-free electrocatalysts. Benefiting from its scalable preparation and stability, the MoNi4 electrocatalyst is promising for practical water-alkali electrolysers.Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics459201746#N/ATRUE
1194
ncomms1537710.1038/ncomms15377FALSEhttps://doi.org/10.1038/ncomms15377Wang, XNat. Commun.Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS2) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70mV for hydrogen evolution and 235mV for oxygen evolution at 10 mA cm(-2) with long-term stability, which have superior kinetics for hydrogen-and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec(-1). Moreover, we achieve 10 mA cm(-2) at a low voltage of 1.44V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS2 to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS2.Amorphous nickel-cobalt complexes hybridized with 1T-phase molybdenum disulfide via hydrazine-induced phase transformation for water splitting186201749#N/ATRUE
1195
ncomms1502010.1038/ncomms15020FALSEhttps://doi.org/10.1038/ncomms15020Dai, SSolid-state synthesis of ordered mesoporous carbon catalysts via a mechanochemical assembly through coordination cross-linking2017#N/ATRUE
1196
ncomms1487510.1038/ncomms14875FALSEhttps://doi.org/10.1038/ncomms14875Sodeoka, MNat. Commun.Chiral metal catalysts have been widely applied to asymmetric transformations. However, the electronic structure of the catalyst and how it contributes to the Activation of the substrate is seldom investigated. Here, we report an empirical approach for providing insights into the catalytic Activation process in the distorted Ni(II)-catalysed asymmetric [3+2] cyCloaddition of alpha-ketoesters. We quantitatively characterize the bonding nature of the catalyst by means of electron density distribution analysis, showing that the distortion around the Ni(II) centre makes the dz(2) orbital partially 'naked', wherein the labile acetate ligand is coordinated with electrostatic interaction. The electron-deficient dz(2) orbital and the acetate act together to deprotonate the alpha-ketoester, generating the (Lambda)-Ni(II)-enolate. The solid and solution state analyses, together with theoretical calculations, strongly link the electronic structure of the centrochiral octahedral Ni(II) complex and its catalytic activity, depicting a cooperative mechanism of enolate binding and outer sphere hydrogen-bonding Activation.Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cyCloaddition26201764#N/ATRUE
1197
ncomms1472310.1038/ncomms14723FALSEhttps://doi.org/10.1038/ncomms14723Lee, DNat. Commun.The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanoCluster. The catalytic activity of the resulting bimetallic nanoCluster, PtAu24(SC6H13)(18), for the hydrogen production is found to be significantly higher than reported catalysts. It is even better than the benchmarking platinum catalyst. The molecule-like bimetallic nanoCluster represents a Class of catalysts that bridge homogeneous and heterogeneous catalysis and may provide a platform for the discovery of finely optimized catalysts.A molecule-like PtAu24(SC6H13)(18) nanoCluster as an electrocatalyst for hydrogen production151201750#N/ATRUE
1198
ncomms1437710.1038/ncomms14377FALSEhttps://doi.org/10.1038/ncomms14377Lin, JFNat. Commun.The +0.1 parts per thousand elevated Fe-56/Fe-54 ratio of terrestrial basalts relative to chondrites was proposed to be a fingerprint of core-mantle segregation. However, the extent of iron isotopic fractionation between molten metal and silicate under high pressure-temperature conditions is poorly known. Here we show that iron forms chemical bonds of similar strengths in basaltic glasses and iron-rich alloys, even at high pressure. From the measured mean force constants of iron bonds, we calculate an equilibrium iron isotope fractionation between silicate and iron under core formation conditions in Earth of similar to 0-0.02 parts per thousand, which is small relative to the +0.1 parts per thousand shift of terrestrial basalts. This result is unaffected by small amounts of nickel and candidate core-forming light elements, as the isotopic shifts associated with such alloying are small. This study suggests that the variability in iron isotopic composition in planetary objects cannot be due to core formation.Iron isotopic fractionation between silicate mantle and metallic core at high pressure27201756#N/ATRUE
1199
ncomms1014110.1038/ncomms10141FALSEhttps://doi.org/10.1038/ncomms10141Yan, YSNat. Commun.The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanopartiCles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanopartiCles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanopartiCles. Density functional theory calculations indicate that the nitrogen-doped support stabilizes the nanopartiCle against reconstruction, while nitrogen located at the edge of the nanopartiCle tunes local adsorption sites by affecting the d-orbitals of nickel. Owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells.Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolytex211201658#N/AFALSE
1200
ncomms1003510.1038/ncomms10035FALSEhttps://doi.org/10.1038/ncomms10035Dai, HJNat. Commun.Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum-nickel hydroxide-graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reActivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts.Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphenex293201544#N/AFALSE
1201
NCHEM.62610.1038/NCHEM.626FALSEhttps://doi.org/10.1038/NCHEM.626Chen, JGGNat. Chem.The facile decomposition of ammonia to produce hydrogen is critical to its use as a hydrogen storage medium in a hydrogen economy, and although ruthenium shows good activity for catalysing this process, its expense and scarcity are prohibitive to large-scale commercialization. The need to develop alternative catalysts has been addressed here, using microkinetic modelling combined with density functional studies to identify suitable monolayer bimetallic (surface or subsurface) catalysts based on nitrogen binding energies. The Ni-Pt-Pt(111) surface, with one monolayer of Ni atoms residing on a Pt(111) substrate, was predicted to be a catalytically active surface. This was verified using temperature-programmed desorption and high-resolution electron energy loss spectroscopy experiments. The results reported here provide a framework for complex catalyst discovery. They also demonstrate the critical importance of combining theoretical and experimental approaches for identifying desirable monolayer bimetallic systems when the surface properties are not a linear function of the parent metals.Using first principles to predict bimetallic catalysts for the ammonia decomposition reactionx281201039#N/AFALSE
1202
ncomms1430910.1038/ncomms14309FALSEhttps://doi.org/10.1038/ncomms14309Chen, GYNat. Commun.Understanding the reaction pathway and kinetics of solid-state phase transformation is critical in designing advanced electrode materials with better performance and stability. Despite the first-order phase transition with a large lattice mismatch between the involved phases, spinel LiMn1.5Ni0.5O4 is capable of fast rate even at large partiCle size, presenting an enigma yet to be understood. The present study uses advanced two-dimensional and three-dimensional nano-tomography on a series of well-formed LixMn(1.5)Ni(0.5)O(4) (0 <= x <= 1) crystals to visualize the mesoscale phase distribution, as a function of Li content at the sub-partiCle level. Inhomogeneity along with the coexistence of Li-rich and Li-poor phases are broadly observed on partially delithiated crystals, providing direct evidence for a concurrent nuCleation and growth process instead of a shrinking-core or a partiCle-by-partiCle process. Superior kinetics of (100) facets at the vertices of truncated octahedral partiCles promote preferential delithiation, whereas the observation of strain-induced cracking suggests mechanical degradation in the material.Phase transformation mechanism in lithium manganese nickel oxide revealed by single-crystal hard X-ray microscopy65201750#N/ATRUE
1203
ncomms1232410.1038/ncomms12324FALSEhttps://doi.org/10.1038/ncomms12324Hu, XLNat. Commun.Efficient oxygen-evolution reaction catalysts are required for the cost-effective generation of solar fuels. Metal selenides have been reported as promising oxygen-evolution catalysts; however, their active forms are yet to be elucidated. Here we show that a representative selenide catalyst, nickel selenide, is entirely converted into nickel hydroxide under oxygen-evolution conditions. This result indicates that metal selenides are unstable during oxygen evolution, and the in situ generated metal oxides are responsible for their activity. This knowledge inspired us to synthesize nanostructured nickel iron diselenide, a hitherto unknown metal selenide, and to use it as a templating precursor to a highly active nickel iron oxide catalyst. This selenide-derived oxide catalyses oxygen evolution with an overpotential of only 195 mV for 10 mA cm(-2). Our work underscores the importance of identifying the active species of oxygen-evolution catalysts, and demonstrates how such knowledge can be applied to develop better catalysts.A nickel iron diselenide-derived efficient oxygen-evolution catalyst551201631#N/ATRUE
1204
NCHEM.291510.1038/NCHEM.2915FALSEhttps://doi.org/10.1038/NCHEM.2915Sykes, ECHNat. Chem.The recent availability of shale gas has led to a renewed interest in C-H bond Activation as the first step towards the synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu-based catalysts are not practical due to high C-H Activation barriers, but their weaker binding to adsorbates offers resilience to coking. Using Pt/Cu single-atom alloys (SAAs), we examine C-H Activation in a number of systems inCluding methyl groups, methane and butane using a combination of simulations, surface science and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke-resistant C-H Activation chemistry, with the added economic benefit that the precious metal is diluted at the atomic limit.Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C-H Activationx234201852#N/AFALSE
1205
ncomms1226910.1038/ncomms12269FALSEhttps://doi.org/10.1038/ncomms12269Apfel, UPPentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation2016#N/ATRUE
1206
ncomms1209910.1038/ncomms12099FALSEhttps://doi.org/10.1038/ncomms12099Sumant, AVMetal-induced rapid transformation of diamond into single and multilayer graphene on wafer scale2016#N/ATRUE
1207
ncomms1198110.1038/ncomms11981FALSEhttps://doi.org/10.1038/ncomms11981Sun, LCNickel-vanadium monolayer double hydroxide for efficient electrochemical water oxidation2016#N/ATRUE
1208
NCHEM.207510.1038/NCHEM.2075https://doi.org/10.1038/NCHEM.2075Stupp, SINat. Chem.Integration into a soft material of all the molecular components necessary to generate storable fuels is an interesting target in supramolecular chemistry. The concept is inspired by the internal structure of photosynthetic organelles, such as plant chloroplasts, which colocalize molecules involved in light absorption, charge transport and catalysis to create chemical bonds using light energy. We report here on the light-driven production of hydrogen inside a hydrogel scaffold built by the supramolecular self-assembly of a perylene monoimide amphiphile. The charged ribbons formed can electrostatically attract a nickel-based catalyst, and electrolyte screening promotes gelation. We found the emergent phenomenon that screening by the catalyst or the electrolytes led to two-dimensional crystallization of the chromophore assemblies and enhanced the electronic coupling among the molecules. Photocatalytic production of hydrogen is observed in the three-dimensional environment of the hydrogel scaffold and the material is easily placed on surfaces or in the pores of solid supports.Self-assembling hydrogel scaffolds for photocatalytic hydrogen productionPhotocatalyst264201434#N/AFALSE
1209
ncomms1174110.1038/ncomms11741FALSEhttps://doi.org/10.1038/ncomms11741Xia, YYNat. Commun.Low-cost alkaline water electrolysis has been considered a sustainable approach to producing hydrogen using renewable energy inputs, but preventing hydrogen/oxygen mixing and efficiently using the instable renewable energy are challenging. Here, using nickel hydroxide as a redox mediator, we decouple the hydrogen and oxygen production in alkaline water electrolysis, which overcomes the gas-mixing issue and may increase the use of renewable energy. In this architecture, the hydrogen production occurs at the cathode by water reduction, and the anodic Ni(OH)(2) is simultaneously oxidized into NiOOH. The subsequent oxygen production involves a cathodic NiOOH reduction (NiOOH -> Ni(OH)(2)) and an anodic OH- oxidization. Alternatively, the NiOOH formed during hydrogen production can be coupled with a zinc anode to form a NiOOH-Zn battery, and its discharge product (that is, Ni(OH)(2)) can be used to produce hydrogen again. This architecture brings a potential solution to facilitate renewables-to-hydrogen conversion.Separating hydrogen and oxygen evolution in alkaline water electrolysis using nickel hydroxide185201652#N/ATRUE
1210
ncomms1125810.1038/ncomms11258FALSEhttps://doi.org/10.1038/ncomms11258Gauzzi, ANat. Commun.There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here by means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eV angstrom, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2. This is explained by a huge staggered crystal field of 1.4V angstrom(-1), produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. This unexpected result in the absence of heavy elements demonstrates an effective mechanism of Rashba coupling amplification that may foster spin-orbit band engineering.Rashba coupling amplification by a staggered crystal field23201631#N/ATRUE
1211
nature2367410.1038/nature23674FALSEhttps://doi.org/10.1038/nature23674Long, JRNatureCooperative binding, whereby an initial binding event facilitates the uptake of additional substrate molecules, is common in biological systems such as haemoglobin(1,2).It was recently shown that porous solids that exhibit cooperative binding have substantial energetic benefits over traditional adsorbents(3), but few guidelines currently exist for the design of such materials. In principle, metal-organic frameworks that contain coordinatively unsaturated metal centres could act as both selective(4-7) and cooperative adsorbents if guest binding at one site were to trigger an electronic transformation that subsequently altered the binding properties at neighbouring metal sites(8-10). Here we illustrate this concept through the selective adsorption of carbon monoxide (CO) in a series of metal-organic frameworks featuring coordinatively unsaturated iron(ii) sites. Functioning via a mechanism by which neighbouring iron(ii) sites undergo a spin-state transition above a threshold CO pressure, these materials exhibit large CO separation capacities with only small changes in temperature. The very low regeneration energies that result may enable more efficient Fischer-Tropsch conversions and extraction of CO from industrial waste feeds, which currently underutilize this versatile carbon synthon(11). The electronic basis for the cooperative adsorption demonstrated here could provide a general strategy for designing efficient and selective adsorbents suitable for various separations.A spin transition mechanism for cooperative adsorption in metal-organic frameworksx108201733#N/AFALSE
1212
ncomms1112910.1038/ncomms11129FALSEhttps://doi.org/10.1038/ncomms11129Liu, LNat. Commun.New carbon-carbon bond formation reactions expand our horizon of retrosynthetic analysis for the synthesis of complex organic molecules. Although many methods are now available for the formation of C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bonds via transition metal-catalyzed cross-coupling of Alkyl organometallic reagents, direct use of readily available olefins in a formal fashion of hydrocarbonation to make C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bonds remains to be developed. Here we report the discovery of a general process for the intermolecular reductive coupling of unactivated olefins with Alkyl or Aryl electrophiles under the promotion of a simple nickel catalyst system. This new reaction presents a conceptually unique and practical strategy for the construction of C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bonds without using any organometallic reagent. The reductive olefin hydrocarbonation also exhibits excellent compatibility with varieties of synthetically important functional groups and therefore, provides a straightforward approach for modification of complex organic molecules containing olefin groups.Practical carbon-carbon bond formation from olefins through nickel-catalyzed reductive olefin hydrocarbonation120201655#N/ATRUE
1213
nature2203210.1038/nature22032FALSEhttps://doi.org/10.1038/nature22032Lu, ZPNatureNext-generation high-performance structural materials are required for lightweight design strategies and advanced energy applications. Maraging steels, combining a martensite matrix with nanoprecipitates, are a Class of high-strength materials with the potential for matching these demands(1-3). Their outstanding strength originates from semi-coherent precipitates(4,5), which unavoidably exhibit a heterogeneous distribution that creates large coherency strains, which in turn may promote crack initiation under load(6-8). Here we report a counterintuitive strategy for the design of ultrastrong steel alloys by high-density nanoprecipitation with minimal lattice misfit. We found that these highly dispersed, fully coherent precipitates (that is, the crystal lattice of the precipitates is almost the same as that of the surrounding matrix), showing very low lattice misfit with the matrix and high anti-phase boundary energy, strengthen alloys without sacrificing ductility. Such low lattice misfit (0.03 +/- 0.04 per cent) decreases the nuCleation barrier for precipitation, thus enabling and stabilizing nanoprecipitates with an extremely high number density (more than 10(24) per cubic metre) and small size (about 2.7 +/- 0.2 nanometres). The minimized elastic misfit strain around the partiCles does not contribute much to the dislocation interaction, which is typically needed for strength increase. Instead, our strengthening mechanism exploits the chemical ordering effect that creates backstresses (the forces opposing deformation) when precipitates are cut by dislocations. We create a Class of steels, strengthened by Ni(Al, Fe) precipitates, with a strength of up to 2.2 gigapascals and good ductility (about 8.2 per cent). The chemical composition of the precipitates enables a substantial reduction in cost compared to conventional maraging steels owing to the replacement of the essential but high-cost alloying elements cobalt and titanium with inexpensive and lightweight aluminium. Strengthening of this Class of steel alloy is based on minimal lattice misfit to achieve maximal precipitate dispersion and high cutting stress (the stress required for dislocations to cut through coherent precipitates and thus produce plastic deformation), and we envisage that this lattice misfit design concept may be applied to many other metallic alloys.Ultrastrong steel via minimal lattice misfit and high-density nanoprecipitationx531201743#N/AFALSE
1214
ncomms1094210.1038/ncomms10942FALSEhttps://doi.org/10.1038/ncomms10942Dinca, MNat. Commun.Control over the architectural and electronic properties of heterogeneous catalysts poses a major obstaCle in the targeted design of active and stable non-platinum group metal electrocatalysts for the oxygen reduction reaction. Here we introduce Ni-3(HITP)(2) (HITP = 2, 3, 6, 7, 10, 11-hexaiminotriphenylene) as an intrinsically conductive metal-organic framework which functions as a well-defined, tunable oxygen reduction electrocatalyst in alkaline solution. Ni-3(HITP)(2) exhibits oxygen reduction activity competitive with the most active non-platinum group metal electrocatalysts and stability during extended polarization. The square planar Ni-N-4 sites are structurally reminiscent of the highly active and widely studied non-platinum group metal electrocatalysts containing M-N-4 units. Ni-3(HITP)(2) and analogues thereof combine the high crystallinity of metal-organic frameworks, the physical durability and electrical conductivity of graphitic materials, and the diverse yet well-controlled synthetic accessibility of molecular species. Such properties may enable the targeted synthesis and systematic optimization of oxygen reduction electrocatalysts as components of fuel cells and electrolysers for renewable energy applications.Electrochemical oxygen reduction catalysed by Ni-3(hexaiminotriphenylene)(2)357201649#N/ATRUE
1215
ncomms1066710.1038/ncomms10667FALSEYao, XDAtomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis2016#N/ATRUE
1216
nature1905610.1038/nature19056https://doi.org/10.1038/nature19056MacMillan, DWCNatureIn the past 50 years, cross-coupling reactions mediated by transition metals have changed the way in which complex organic molecules are synthesized. The predictable and chemoselective nature of these transformations has led to their widespread adoption across many areas of chemical research(1). However, the construction of a bond between two sp(3)-hybridized carbon atoms, a fundamental unit of organic chemistry, remains an important yet elusive objective for engineering cross-coupling reactions(2). In comparison to related procedures with sp(2)-hybridized species, the development of methods for sp(3)-sp(3) bond formation via transition metal catalysis has been hampered historically by deleterious side-reactions, such as beta-hydride elimination with palladium catalysis or the reluctance of Alkyl halides to undergo oxidative addition(3,4.) To address this issue, nickel-catalysed cross-coupling processes can be used to form sp(3)-sp(3) bonds that utilize organometallic nuCleophiles and Alkyl electrophiles(5-7). In particular, the coupling of Alkyl halides with pre-generated organozinc(8,9), Grignard(10) and organB(OH)2rane(11) species has been used to furnish diverse molecular structures. However, the manipulations required to produce these activated structures is inefficient, leading to poor step-and atom-economies. Moreover, the operational difficulties associated with making and using these reactive coupling partners, and preserving them through a synthetic sequence, has hindered their widespread adoption. A generically useful sp(3)-sp(3) coupling technology that uses bench-stable, native organic functional groups, without the need for pre-functionalization or substrate derivatization, would therefore be valuable. Here we demonstrate that the synergistic merger of photoredox and nickel catalysis enables the direct formation of sp(3)-sp(3) bonds using only simple Carbonylic acids and Alkyl halides as the nuCleophilic and electrophilic coupling partners, respectively. This metallaphotoredox protocol is suitable for many primary and secondary Carbonylic acids. The merit of this coupling strategy is illustrated by the synthesis of the pharmaceutical tirofiban in four steps from commercially available starting materials.Metallaphotoredox-catalysed sp(3)-sp(3) cross-coupling of Carbonylic acids with Alkyl halidesPhotocatalyst243201630#N/AFALSE
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nature1894810.1038/nature18948FALSEhttps://doi.org/10.1038/nature18948
Sankaranarayanan, SKRS
NatureMoving mechanical interfaces are commonly lubricated and separated by a combination of fluid films and solid 'tribofilms', which together ensure easy slippage and long wear life(1). The efficacy of the fluid film is governed by the viscosity of the base oil in the lubricant; the efficacy of the solid tribofilm, which is produced as a result of sliding contact between moving parts, relies upon the effectiveness of the lubricant's anti-wear additive (typically zinc diAlkyldithiophosphate)(2). Minimizing friction and wear continues to be a challenge, and recent efforts have focused on enhancing the anti-friction and anti-wear properties of lubricants by incorporating inorganic nanopartiCles and ionic liquids(3,4). Here, we describe the in operando formation of carbon-based tribofilms via dissociative extraction from base-oil molecules on catalytically active, sliding nanometre-scale crystalline surfaces, enabling base oils to provide not only the fluid but also the solid tribofilm. We study nanocrystalline catalytic coatings composed of nitrides of either molybdenum or vanadium, containing either copper or nickel catalysts, respectively. Structurally, the resulting tribofilms are similar to diamond-like carbon(5). Ball-on-disk tests at contact pressures of 1.3 gigapascals reveal that these tribofilms nearly eliminate wear, and provide lower friction than tribofilms formed with zinc diAlkyldithiophosphate. Reactive and ab initio molecular-dynamics simulations show that the catalytic action of the coatings facilitates dehydrogenation of linear olefins in the lubricating oil and random scission of their carbon-carbon backbones; the products recombine to nuCleate and grow a compact, amorphous lubricating tribofilm.Carbon-based tribofilms from lubricating oilsx186201629#N/AFALSE
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nature1800810.1038/nature18008FALSEhttps://doi.org/10.1038/nature18008Stahl, SSNatureThe electrochemical oxidation of alcohols is a major focus of energy and chemical conversion efforts, with potential applications ranging from fuel cells to biomass utilization and fine-chemical synthesis(1-7). Small-molecule electrocatalysts for processes of this type are promising targets for further development(8), as demonstrated by recent advances in nickel catalysts for electrochemical production and oxidation of hydrogen(9-11). Complexes with tethered amines that resemble the active site of hydrogenases(12) have been shown both to catalyse hydrogen production (from protons and electrons) with rates far exceeding those of such enzymes(11,13) and to mediate reversible electrocatalytic hydrogen production and oxidation with enzyme-like performance(14). Progress in electrocatalytic alcohol oxidation has been more modest. Nickel complexes similar to those used for hydrogen oxidation have been shown to mediate efficient electrochemical oxidation of Benzyl alcohol, with a turnover frequency of 2.1 per second. These compounds exhibit poor reactivity with ethanol and methanol, however(15). Organic nitroxyls, such as TEMPO (2,2,6,6-tetramethyl-1-piperidine N-oxyl), are the most widely studied electrocatalysts for alcohol oxidation(5-7,16-19). These catalysts exhibit good activity (1-2 turnovers per second) with a wide range of alcohols(18) and have great promise for electro-organic synthesis(7). Their use in energy-conversion applications, however, is limited by the high electrode potentials required to generate the reactive oxoammonium species. Here we report (2,2'-bipyridine) Cu/nitroxyl co-catalyst systems for electrochemical alcohol oxidation that proceed with much faster rates, while operating at an electrode potential a half-volt lower than that used for the TEMPO-only process. The (2,2'-bipyridine) Cu(II) and TEMPO redox partners exhibit cooperative reactivity and exploit the low-potential, proton-coupled TEMPO/TEMPOH redox process rather than the high-potential TEMPO/TEMPO+ process. The results show how electron-proton-transfer mediators, such as TEMPO, may be used in combination with first-row transition metals, such as copper, to achieve efficient two-electron electrochemical processes, thereby introducing a new concept for the development of non-precious-metal electrocatalysts.Cooperative electrocatalytic alcohol oxidation with electron-proton-transfer mediators
Electrocatalytic
200201630#N/AFALSE
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nature1487510.1038/nature14875https://doi.org/10.1038/nature14875MacMillan, DWCNatureTransition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings(1,2). Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cyCle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and Aryl bromides. More notably, we have developed a general strategy to 'switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts.Switching on elusive organometallic mechanisms with photoredox catalysisPhotocatalyst2952015307/28/2022FALSE
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ncomms105710.1038/ncomms1057FALSEhttps://doi.org/10.1038/ncomms1057Ballav, NControlling spins in adsorbed molecules by a chemical switch2010#N/ATRUE
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NCHEM.50510.1038/NCHEM.505FALSEhttps://doi.org/10.1038/NCHEM.505Knochel, PNat. Chem.Stereoselective functionalizations of organic molecules are of great importance to modern synthesis. A stereoselective preparation of pharmaceutically active molecules is often required to ensure the appropriate biological activity. Thereby, diastereoselective methods represent valuable tools for an efficient set-up of multiple stereocentres. In this artiCle, highly diastereoselective Csp(3) Negishi cross-couplings of various cyCloAlkylzinc reagents with Aryl halides are reported. In all cases, the thermodynamically most-stable stereoisomer was obtained. Remarkably, this diastereoselective coupling was successful not only for 1,2-substituted cyClic systems, but also for 1,3- and 1,4-substituted cyClohexylzinc reagents. The origin of this remote stereocontrol was investigated by NMR experiments and density functional theory calculations. A detailed mechanism based on these experimental and theoretical data is proposed.Highly diastereoselective Csp(3)-Csp(2) Negishi cross-coupling with 1,2-, 1,3-and 1,4-substituted cyCloAlkylzinc compounds95201047#N/ATRUE
1222
NCHEM.36610.1038/NCHEM.366FALSEhttps://doi.org/10.1038/NCHEM.366Nam, WNat. Chem.Metal-dioxygen adducts, such as metal-superoxo and -peroxo species, are key intermediates often detected in the catalytic cyCles of dioxygen Activation by metalloenzymes and biomimetic compounds. The synthesis and spectroscopic characterization of an end-on nickel(II)-superoxo complex with a 14-membered macrocyClic ligand was reported previously. Here we report the isolation, spectroscopic characterization, and high-resolution crystal structure of a mononuClear side-on nickel(III)-peroxo complex with a 12-membered macrocyClic ligand, [Ni(12-TMC)(O(2))](+) (1) (12-TMC = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyClododecane). In contrast to the end-on nickel(II)-superoxo complex, the nickel(III)-peroxo complex is not reactive in electrophilic reactions, but is capable of conducting nuCleophilic reactions. The nickel(III)-peroxo complex transfers the bound dioxygen to manganese(II) complexes, thus affording the corresponding nickel(II) and manganese(III)peroxo complexes. Our results demonstrate the significance of supporting ligands in tuning the geometric and electronic structures and reactivities of metal-O(2) intermediates that have been shown to have biological as well as synthetic usefulness in biomimetic reactions.Geometric and electronic structure and reactivity of a mononuClear 'side-on' nickel(III)-peroxo complex113200938#N/ATRUE
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nature0990110.1038/nature09901FALSEhttps://doi.org/10.1038/nature09901Kimel, AVNatureFerromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism(1-4). Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technology. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, that is, spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behaviour of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), that is, in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic circular dichroism to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 picoseconds, which is substantially slower than the Fe reversal time of 300 femtoseconds. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.Transient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spinsx557201118#N/AFALSE
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nature0989910.1038/nature09899FALSEhttps://doi.org/10.1038/nature09899Schmidt, MWNatureVery low seismic velocity anomalies in the Earth's mantle(1,2) may reflect small amounts of melt present in the peridotite matrix, and the onset of melting in the Earth's upper mantle is likely to be triggered by the presence of small amounts of carbonate(3). Such carbonates stem from subducted oceanic lithosphere in part buried to depths below the 660-kilometre discontinuity and remixed into the mantle. Here we demonstrate that carbonate-induced melting may occur in deeply subducted lithosphere at near-adiabatic temperatures in the Earth's transition zone and lower mantle. We show experimentally that these carbonatite melts are unstable when infiltrating ambient mantle and are reduced to immobile diamond when recyCled at depths greater than similar to 250 kilometres, where mantle redox conditions are determined by the presence of an (Fe,Ni) metal phase(4-6). This 'redox freezing' process leads to diamond-enriched mantle domains in which the Fe-0, resulting from Fe2+ disproportionation in perovskites and garnet, is consumed but the Fe3+ preserved. When such carbon-enriched mantle heterogeneities become part of the upwelling mantle, diamond will inevitably react with the Fe3+ leading to true carbonatite redox melting at similar to 660 and similar to 250 kilometres depth to form deep-seated melts in the Earth's mantle.Redox freezing and melting in the Earth's deep mantle resulting from carbon-iron redox couplingx295201153#N/AFALSE
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nature0957910.1038/nature09579FALSEhttps://doi.org/10.1038/nature09579Tour, JMNatureMonolayer graphene was first obtained(1) as a transferable material in 2004 and has stimulated intense activity among physicists, chemists and material scientists(1-4). Much research has been focused on developing routes for obtaining large sheets of monolayer or bilayer graphene. This has been recently achieved by chemical vapour deposition (CVD) of CH4 or C2H2 gases on copper or nickel substrates(5-7). But CVD is limited to the use of gaseous raw materials, making it difficult to apply the technology to a wider variety of potential feedstocks. Here we demonstrate that large area, high-quality graphene with controllable thickness can be grown from different solid carbon sources-such as polymer films or small molecules-deposited on a metal catalyst substrate at temperatures as low as 800 degrees C. Both pristine graphene and doped graphene were grown with this one-step process using the same experimental set-up.Growth of graphene from solid carbon sourcesx1070201031#N/AFALSE
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nature0705810.1038/nature07058FALSEhttps://doi.org/10.1038/nature07058Mandrus, DNatureThe recent synthesis of the superconductor LaFeAsO0.89F0.11 with transition temperature T-c approximate to 26 K ( refs 1 - 4) has been quickly followed by reports of even higher transition temperatures in related compounds: 41 K in CeFeAsO0.84F0.16 ( ref. 5), 43 K in SmFeAsO0.9F0.1 ( ref. 6), and 52 K in NdFeAsO0.89F0.11 and PrFeAsO0.89F0.11 ( refs 7, 8). These discoveries have generated much interest(9,10) in the mechanisms and manifestations of unconventional superconductivity in the family of doped quaternary layered oxypnictides LnOTMPn ( Ln: La, Pr, Ce, Sm; TM: Mn, Fe, Co, Ni; Pn: P, As), because many features of these materials set them apart from other known superconductors. Here we report resistance measurements of LaFeAsO0.89F0.11 at high magnetic fields, up to 45 T, that show a remarkable enhancement of the upper critical field B-c2 compared to values expected from the slopes dB(c2)/ dT approximate to 2 T K-1 near Tc, particularly at low temperatures where the deduced B-c2(0) approximate to 63 - 65 T exceeds the paramagnetic limit. We argue that oxypnictides represent a new Class of high-field superconductors with B-c2 values surpassing those of Nb3Sn, MgB2 and the Chevrel phases, and perhaps exceeding the 100 T magnetic field benchmark of the high- T-c copper oxides.Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fieldsx450200826#N/AFALSE
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nature0597110.1038/nature05971FALSEhttps://doi.org/10.1038/nature05971Oppermann, UNaturePost-translational histone modification has a fundamental role in chromatin biology and is proposed to constitute a 'histone code' in epigenetic regulation(1,2). Differential methylation of histone H3 and H4 lysyl residues regulates processes inCluding heterochromatin formation, X-chromosome inActivation, genome imprinting, DNA repair and transcriptional regulation(3). The discovery of lysyl demethylases using flavin (amine oxidases)(4) or Fe( II) and 2-oxoglutarate as cofactors (2OG oxygenases)(5-7) has changed the view of methylation as a stable epigenetic marker. However, little is known about how the demethylases are selective for particular lysyl-containing sequences in specific methylation states, a key to understanding their functions. Here we reveal how human JMJD2A ( jumonji domain containing 2A), which is selective towards tri- and dimethylated histone H3 lysyl residues 9 and 36 (H3K9me3/me2 and H3K36me3/me2), discriminates between methylation states and achieves sequence selectivity for H3K9. We report structures of JMJD2A - Ni( II) - Zn( II) inhibitor complexes bound to tri-, di- and monomethyl forms of H3K9 and the trimethyl form of H3K36. The structures reveal a lysyl-binding pocket in which substrates are bound in distinct bent conformations involving the Zn-binding site. We propose a mechanism for achieving methylation state selectivity involving the orientation of the substrate methyl groups towards a ferryl intermediate. The results suggest distinct recognition mechanisms in different demethylase subfamilies and provide a starting point to develop chemical tools for drug discovery and to study and dissect the complexity of reversible histone methylation and its role in chromatin biology.Crystal structures of histone demethylase JMJD2A reveal basis for substrate specificityx251200717#N/AFALSE
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NCHEM.269710.1038/NCHEM.2697FALSEhttps://doi.org/10.1038/NCHEM.2697Thomas, SPNat. Chem.First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air-and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general Activation with sodium tert-butoxide. Using only robust air-and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydrB(OH)2ration, hydroVinylation, hydrogenation and [2 pi+2 pi] alkene cyCloaddition. This Activation method allows for the easy use of earth-abundant metals, inCluding iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis.Activation and discovery of earth-abundant metal catalysts using sodium tert-butoxide170201741#N/ATRUE
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NCHEM.257510.1038/NCHEM.2575FALSEhttps://doi.org/10.1038/NCHEM.2575Duboc, CNickel-centred proton reduction catalysis in a model of [NiFe] hydrogenase2016#N/ATRUE
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NCHEM.20810.1038/NCHEM.208FALSEhttps://doi.org/10.1038/NCHEM.208Kanatzidis, MGNat. Chem.Aerogels are low-density porous materials, made mostly of air, for which hundreds of applications have been found in recent years. Inorganic oxide-based aerogels have been known for a long time, carbon aerogels were discovered in the early 1990s and sulfur- and selenium-based aerogels (chalcogels) are the most recent additions to this family. Here we present new aerogels made of Co(Ni)-Mo(W)-S networks with extremely large surface areas and porosity. These systems are formed by the coordinative reactions of (MoS4)(2-) and (WS4)(2-) with Co2+ and Ni2+ salts in non-aqueous solvents. We show that these low-density sponge-like networks can absorb conjugated organic molecules and mercury ions, and preferentially adsorb CO2 over H-2, which illustrates their high potential as gas-separation media. The chalcogels are shown to be twice as active as the conventional sulfided Co-Mo/Al2O3 catalyst for the hydrodesulfurization of thiophene.Spongy chalcogels of non-platinum metals act as effective hydrodesulfurization catalysts90200924#N/ATRUE
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NCHEM.187310.1038/NCHEM.1873FALSENorskov, JKDiscovery of a Ni-Ga catalyst for carbon dioxide reduction to methanol2014#N/ATRUE
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nchem.162110.1038/nchem.1621FALSEhttps://doi.org/10.1038/nchem.1621Cronin, LNat. Chem.Hydrogen is essential to several key industrial processes and could play a major role as an energy carrier in a future 'hydrogen economy'. Although the majority of the world's hydrogen supply currently comes from the reformation of fossil fuels, its generation from water using renewables-generated power could provide a hydrogen source without increasing atmospheric CO2 levels. Conventional water electrolysis produces H-2 and O-2 simultaneously, such that these gases must be generated in separate spaces to prevent their mixing. Herein, using the polyoxometalate H3PMo12O40, we introduce the concept of the electron-coupled-proton buffer (ECPB), whereby O-2 and H-2 can be produced at separate times during water electrolysis. This could have advantages in preventing gas mixing in the headspaces of high-pressure electrolysis cells, with implications for safety and electrolyser degradation. Furthermore, we demonstrate that temporally separated O-2 and H-2 production allows greater flexibility regarding the membranes and electrodes that can be used in water-splitting cells.Decoupling hydrogen and oxygen evolution during electrolytic water splitting using an electron-coupled-proton buffer287201345#N/ATRUE
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nature2231610.1038/nature22316FALSEhttps://doi.org/10.1038/nature22316Martin, RNatureCatalytic carbon-carbon bond formation has enabled the streamlining of synthetic routes when assembling complex molecules(1). It is particularly important when incorporating saturated hydrocarbons, which are common motifs in petrochemicals and biologically relevant molecules. However, cross-coupling methods that involve Alkyl electrophiles result in catalytic bond formation only at specific and previously functionalized sites(2). Here we describe a catalytic method that is capable of promoting Carbonylation reactions at remote and unfunctionalized aliphatic sites with carbon dioxide at atmospheric pressure. The reaction occurs via selective migration of the catalyst along the hydrocarbon side-chain(3) with excellent regio- and chemoselectivity, representing a remarkable reactivity relay when compared with Classical cross-coupling reactions. Our results demonstrate that site-selectivity can be switched and controlled, enabling the functionalization of less-reactive positions in the presence of a priori more reactive ones. Furthermore, we show that raw materials obtained in bulk from petroleum processing, such as alkanes and unrefined mixtures of olefins, can be used as substrates. This offers an opportunity to integrate a catalytic platform en route to valuable fatty acids by transforming petroleum-derived feedstocks directly(4).Remote Carbonylation of halogenated aliphatic hydrocarbons with carbon dioxide214201726#N/ATRUE
1234
nature2142710.1038/nature21427FALSEhttps://doi.org/10.1038/nature21427Warren, MJNatureMethane biogenesis in methanogens is mediated by methyl-coenzyme M reductase, an enzyme that is also responsible for the utilization of methane through anaerobic methane oxidation. The enzyme uses an ancillary factor called coenzyme F-430, a nickel-containing modified tetrapyrrole that promotes catalysis through a methyl radical/Ni( ii)-thiolate intermediate. However, it is unClear how coenzyme F-430 is synthesized from the common primogenitor uroporphyrinogen iii, incorporating 11 steric centres into the macrocyCle, although the pathway must involve chelation, amidation, macrocyClic ring reduction, lactamization and carbocyClic ring formation. Here we identify the proteins that catalyse the biosynthesis of coenzyme F-430 from sirohydrochlorin, termed CfbA-CfbE, and demonstrate their activity. The research completes our understanding of how the repertoire of tetrapyrrole-based pigments are constructed, permitting the development of recombinant systems to use these metalloprosthetic groups more widely.Elucidation of the biosynthesis of the methane catalyst coenzyme F-43051201742#N/ATRUE
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nature2083010.1038/nature20830FALSEhttps://doi.org/10.1038/nature20830Pan, YNatureThe Earth formed by accretion of Moon-to Mars-size embryos coming from various heliocentric distances. The isotopic nature of these bodies is unknown. However, taking meteorites as a guide, most models assume that the Earth must have formed from a heterogeneous assortment of embryos with distinct isotopic compositions(1-3). High-precision measurements, however, show that the Earth, the Moon and enstatite meteorites have almost indistinguishable isotopic compositions(4-10). Models have been proposed that reconcile the Earth-Moon similarity with the inferred heterogeneous nature of Earth-forming material, but these models either require specific geometries for the Moon-forming impact(11,12) or can explain only one aspect of the Earth-Moon similarity (that is, O-17)(1-3). Here I show that elements with distinct affinities for metal can be used to decipher the isotopic nature of the Earth's accreting material through time. I find that the mantle signatures of lithophile O, Ca, Ti and Nd, moderately siderophile Cr, Ni and Mo, and highly siderophile Ru record different stages of the Earth's accretion; yet all those elements point to material that was isotopically most similar to enstatite meteorites. This isotopic similarity indicates that the material accreted by the Earth always comprised a large fraction of enstatite-type impactors (about half were E-type in the first 60 per cent of the accretion and all of the impactors were E-type after that). Accordingly, the giant impactor that formed the Moon probably had an isotopic composition similar to that of the Earth, hence relaxing the constraints on models of lunar formation. Enstatite meteorites and the Earth were formed from the same isotopic reservoir but they diverged in their chemical evolution owing to subsequent fractionation by nebular and planetary processes(13).The isotopic nature of the Earth's accreting material through time152201732#N/ATRUE
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nature1411010.1038/nature14110FALSEhttps://doi.org/10.1038/s41467-020-14799-8Lubitz, WHydrogens detected by subatomic resolution protein crystallography in a [NiFe] hydrogenase2015#N/ATRUE
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nature1367210.1038/nature13672FALSEhttps://doi.org/10.1038/nature13672Renaud, MNatureA type Ia supernova is thought to be a thermonuClear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive Ni-56 (refs 1-3). After the explosion, the decay chain from Ni-56 to Co-56 to Fe-56 generates gamma-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of Co-56 lines at energies of 847 and 1,238 kiloelectronvolts and a gamma-ray continuum in the 200-400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 +/- 0.1 solar masses of radioactive Ni-56 were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 +/- 3,000 kilometres per second. The observed gamma-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exClude merger scenarios that fuse comparable amounts of Ni-56.Cobalt-56 gamma-ray emission lines from the type Ia supernova 2014J110201442#N/ATRUE
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jacs.9b1340210.1021/jacs.9b13402FALSEhttps://doi.org/10.1021/jacs.9b13402Mirica, KAJ. Am. Chem. Soc.This paper describes the first implementation of an array of two-dimensional (2D) layered conductive metal-organic frameworks (MOFs) as drop-tasted film electrodes that facilitate voltammetric detection of redox active neurochemicals in a multianalyte solution. The device configuration comprises a glassy carbon electrode modified with a film of conductive MOF (M3HXTP2; M = Ni, Cu; and X = NH, 2,3,6,7,10,11-hexaiminotriphenylene (HITP) or 0, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP)). The utility of 2D MOFs in voltammetric sensing is measured by the detection of ascorbic acid (AA), dopamine (DA), uric acid (UA), and serotonin (5-HT) in 0.1 M PBS (pH = 7.4). In particular, Ni3HHTP2 MOFs demonstrated nanomolar detection limits of 63 +/- 11 nM for DA and 40 +/- 17 nM for 5-HT through a wide concentration range (40 nM-200 mu M). The applicability in biologically relevant detection was further demonstrated in simulated urine using Ni3HHTP2 MOFs for the detection of 5-HT with a nanomolar detection limit of 63 +/- 11 nM for 5-HT through a wide concentration range (63 nM-200 mu M) in the presence of a constant background of DA. The implementation of conductive MOFs in voltammetric detection holds promise for further development of highly modular, sensitive, selective, and stable electroanalytical devices.Employing Conductive Metal-Organic Frameworks for Voltammetric Detection of Neurochemicalsx372020192#N/AFALSE
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jacs.9b1334710.1021/jacs.9b13347FALSEhttps://doi.org/10.1021/jacs.9b13347Sargent, EHJ. Am. Chem. Soc.Electrochemical conversion of nitrate (NO3-) into ammonia (NH3) recyCles nitrogen and offers a route to the production of NH3, which is more valuable than dinitrogen gas. However, today's development of NO3- electroreduction remains hindered by the lack of a mechanistic picture of how catalyst structure may be tuned to enhance catalytic activity. Here we demonstrate enhanced NO3- reduction reaction (NO3-RR) performance on Cu50Ni50 alloy catalysts, inCluding a 0.12 V upshift in the half-wave potential and a 6-fold increase in activity compared to those obtained with pure Cu at 0 V vs reversible hydrogen electrode (RHE). Ni alloying enables tuning of the Cu d-band center and modulates the adsorption energies of intermediates such as *NO3-, *NO2, and *NH2. Using density functional theory calculations, we identify a NO3-RR-to-NH3 pathway and offer an adsorption energy-activity relationship for the CuNi alloy system. This correlation between catalyst electronic structure and NO3-RR activity offers a design platform for further development of NO3-RR catalysts.Enhanced Nitrate-to-Ammonia Activity on Copper-Nickel Alloys via Tuning of Intermediate Adsorptionx49202031#N/AFALSE
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jacs.9b1316510.1021/jacs.9b13165https://doi.org/10.1021/jacs.9b13165Ellman, JAJ. Am. Chem. Soc.We report a photoredox-catalyzed alpha-amino C-H Arylation reaction of highly substituted piperidine derivatives with R electron-deficient cyano(hetero)arenes. The scope and limitations of the reaction were explored, with piperidines bearing multiple substitution patterns providing the Arylated products in good yields and with high diastereoselectivity. To probe the mechanism of the overall transformation, optical and fluorescent spectroscopic methods were used to investigate the reaction. By employing flash-quench transient absorption spectroscopy, we were able to observe electron transfer processes associated with radical formation beyond the initial excited-state Ir(ppy)(3) oxidation. Following the rapid and unselective C-H Arylation reaction, a slower epimerization occurs to provide the high diastereomer ratio observed for a majority of the products. Several stereoisomerically pure products were resubjected to the reaction conditions, each of which converged to the experimentally observed diastereomer ratios. The observed distribution of diastereomers corresponds to a thermodynamic ratio of isomers based upon their calculated relative energies using density functional theory (DFT).Highly Diastereoselective Functionalization of Piperidines by Photoredox-Catalyzed alpha-Amino C-H Arylation and EpimerizationPhotocatalyst15202063#N/AFALSE
1241
nature1256910.1038/nature12569FALSEhttps://doi.org/10.1038/nature12569Waters, CNatureSuper-luminous supernovae(1-4) that radiate more than 1044 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae(5,6). Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuClear explosions. Many solar masses of Ni-56 are synthesized; this isotope decays to Fe-56 via Co-56, powering bright light curves(7,8). Such massive progenitors are expected to have formed from metal-poor gas in the early Universe(9). Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova(1,10). Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra Closely resemble typical fast-deClining super-luminous supernovae(2,11,12), which are not powered by radio-activity. Modelling our observations with 10-16 solar masses of magnetar-energized(13,14) ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 x 10(-6) times that of the core-collapse rate.Slowly fading super-luminous supernovae that are not pair-instability explosions179201331#N/ATRUE
1242
jacs.9b1283510.1021/jacs.9b12835FALSEhttps://doi.org/10.1021/jacs.9b12835Scholes, GDJ. Am. Chem. Soc.We report mechanistic insights into an iridium/nickel photocatalytic C-O cross-coupling reaction from timeresolved spectroscopic studies. Using transient absorption spectroscopy, energy transfer from an iridium photocatalyst to a catalytically relevant Ni(II)(Aryl) acetate acceptor was observed. Concentration-dependent lifetime measurements suggest the mechanism of the subsequent reductive elimination is a unimolecular process occurring on the long-lived excited state of the Ni(II) complex. We envision that our study of the productive energy-transfer-mediated pathway would encourage the development of new excited-state reactivities in the field of metallaphotocatalysis that are enabled by light harvesting.Transient Absorption Spectroscopy Offers Mechanistic Insights for an Iridium/Nickel-Catalyzed C-O CouplingPhotocatalstx28202029#N/AFALSE
1243
jacs.9b1282410.1021/jacs.9b12824https://doi.org/10.1021/jacs.9b12824Rose, MJJ. Am. Chem. Soc.We report here the remarkable and non-catalytic beneficial effects of a Ni(II) ion binding to a Si|PNP type surface as a result of significant thermodynamic band bending induced by ligand attachment and Ni(II) binding. We unambiguously deconvolute the thermodynamic flat band potentials (V-FB) from the kinetic onset potentials (V-on) by synthesizing a specialized bis-PNP macrochelate that enables one-step Ni(II) binding to a p-Si(111) substrate. XPS analysis and rigorous control experiments confirm covalent attachment of the designed ligand and its resulting Ni(II) complex. Illuminated J-V measurements under catalytic conditions show that the Si|BisPNP-Ni substrate exhibits the most positive onset potential for the hydrogen evolution reaction (HER) (-0.55 V vs Fc/Fc(+)) compared to other substrates herein. Thermodynamic flat band potential measurements in the dark reveal that Si|BisPNP-Ni also exhibits the most positive VFB value (-0.02 V vs Fc/Fc+) by a wide margin. Electrochemical impedance spectroscopy data generated under illuminated, catalytic conditions demonstrate a surprising lack of correlation evident between Von and equivalent circuit element parameters commonly associated with HER. Overall, the resulting paradigm comprises a system wherein the extent of band bending induced by metal ion binding is the primary driver of photoelectrochemical (PEC)-HER benefits, while the kinetic (catalytic) effects of the PNP-Ni(II) are minimal. This suggests that dipole and band-edge engineering must be a primary design consideration (not secondary to catalyst) in semiconductor|catalyst hybrids for PEC-HER.Non-Catalytic Benefits of Ni(II) Binding to an Si(111)-PNP Construct for Photoelectrochemical Hydrogen Evolution Reaction: Metal Ion Induced Flat Band Potential ModulationPhotocatalyst4202057#N/AFALSE
1244
nature0573510.1038/nature05735FALSEhttps://doi.org/10.1038/nature05735Scott, ERDNatureIn our Solar System, the planets formed by collisional growth from smaller bodies. Planetesimals collided to form Moon-to-Mars-sized protoplanets in the inner Solar System in 0.1 - 1 Myr, and these collided more energetically to form planets(1). Insights into the timing and nature of collisions during planetary accretion can be gained from meteorite studies. In particular, iron meteorites offer the best constraints on early stages of planetary accretion because most are remnants of the oldest bodies, which accreted and melted in < 1.5 Myr, forming silicate mantles and iron-nickel metallic cores(2-4). Cooling rates for various groups of iron meteorites suggest that if the irons cooled isothermally in the cores of differentiated bodies, as conventionally assumed, these bodies were 5 -200 km in diameter(5,6). This picture is incompatible, however, with the diverse cooling rates observed within certain groups, most notably the IVA group(7,8), but the large uncertainties associated with the measurements do not preClude it. Here we report cooling rates for group IVA iron meteorites that range from 100 to 6,000 K Myr(-1), increasing with decreasing bulk Ni. Improvements in the cooling rate model, smaller error bars, and new data from an independent cooling rate indicator(9) show that the conventional interpretation is no longer viable. Our results require that the IVA meteorites cooled in a 300-km-diameter metallic body that lacked an insulating mantle. This body probably formed similar to 4,500 Myr ago in a 'hit-and-run' collision between Moon-to-Mars-sized protoplanets(10). This demonstrates that protoplanets of similar to 10(3) km size accreted within the first 1.5 Myr, as proposed by theory, and that fragments of these bodies survived as asteroids.Iron meteorite evidence for early formation and catastrophic disruption of protoplanets91200730#N/ATRUE
1245
jacs.9b1249310.1021/jacs.9b12493FALSEhttps://doi.org/10.1021/jacs.9b12493Ogoshi, SJ. Am. Chem. Soc.gamma-Lactam derivatives with multiple contiguous stereogenic carbon centers are ubiquitous in physiologically active compounds. The development of straightforward and reliable synthetic routes to such chiral structural motifs in a stereocontrolled manner should thus be of importance. Herein, we report a strategy to construct polycyClic gamma-lactam derivatives that contain more than two contiguous stereogenic centers in an enantioselective as well as atom-economic manner. Moreover, we have achieved the first enantioselective synthesis of strigolactam derivative GR-24, a racemic variant of which is a potential seed germination stimulator and plantgrowth regulator. A key of the procedure presented here is a nickel(0)/chiral phosphoramidite-catalyzed asymmetric [2+2+1] Carbonylative cyCloaddition between readily accessible ene-imines and carbon monoxide, which proceeded enantioselectively to furnish up to 90% ee (>99% ee after recrystallization). The results of mechanistic studies, inCluding the isolation of a chiral heteronickelacyCle, support that the enantioselectivity on the two contiguous carbon atoms of the gamma-lactams is determined during the oxidative cyClization on nickel(0).Enantioselective Synthesis of PolycyClic gamma-Lactams with Multiple Chiral Carbon Centers via Ni(0)-Catalyzed Asymmetric Carbonylative CyCloadditions without Stirringx15202075#N/AFALSE
1246
jacs.9b1249010.1021/jacs.9b12490FALSEhttps://doi.org/10.1021/jacs.9b12490Rueping, MJ. Am. Chem. Soc.Cross-coupling reactions for carbon-carbon and carbon-heteroatom bond formation are of great importance in modern chemical synthesis. In addition to Classical cross-couplings involving preformed or preactivated coupling partners, more recently breakthroughs have been made in the selective, direct coupling of abundant aliphatic carbon-hydrogen bonds using hydrogen atom transfer reactions in which the bond-dissociation energy is the thermodynamic driving force. The more challenging carbon-carbon bond Activation is still rather underdeveloped due to the bond inertness. Herein, we report a mild and general strategy for the Activation of a diverse set of readily available cyClic alcohols for the remote and site-specific Arylation of ketones via the combination of photoredox-mediated multisite concerted proton-electron transfer (MS-PCET) and nickel catalysis. The current cross-coupling proceeds with the generation of an alkoxy radical utilizing bond-dissociation free energy (BDFE) as the thermodynamic driving force. Subsequently, the resulting remote carbon-centered radicals formed by C-C Cleavage merge with the nickel catalytic cyCle to create the challenging C(sp(3))-C(sp(2)) bonds.Remote Nickel-Catalyzed Cross-Coupling Arylation via Proton-Coupled Electron Transfer-Enabled C-C Bond Cleavagex38202065#N/AFALSE
1247
jacs.9b1244310.1021/jacs.9b12443https://doi.org/10.1021/jacs.9b12443Xiong, YJJ. Am. Chem. Soc.Harvesting solar energy for catalytic conversion of CO2 into valuable chemical fuels/feedstocks is an attractive yet challenging strategy to realize a sustainable carbon-cyCle utilization. Homogeneous catalysts typically exhibit higher activity and selectivity as compared with heterogeneous counterparts, benefiting from their atomically dispersed catalytic sites and versatile coordination structures. However, it is still a black box how the coordination and electronic structures of catalysts dynamically evolve during the reaction, forming the bottleneck for understanding their reaction pathways. Herein, we demonstrate to track the mechanistic pathway of photocatalytic CO2 reduction using a terpyridine nickel(II) complex as a catalyst model. Integrated with a typical homogeneous photosensitizer, the catalytic system offers a high selectivity of 99% for CO2-to-CO conversion with turnover number and turnover frequency as high as 2.36 x 10(7) and 385.6 s(-1), respectively. We employ operando and time-resolved X-ray absorption spectroscopy, in combination with other in situ spectroscopic techniques and theoretical computations, to track the intermediate species of Ni catalyst in the photocatalytic CO2 reduction reaction for the first time. Taken together with the charge dynamics resolved by optical transient absorption spectroscopy, the investigation elucidates the full mechanistic reaction pathway inCluding some key factors that have been often overlooked. This work opens the black box for CO2 reduction in the system of homogeneous catalysts and provides key information for developing efficient catalysts toward artificial photosynthesis.Tracking Mechanistic Pathway of Photocatalytic CO2 Reaction at Ni Sites Using Operando, Time-Resolved SpectroscopyPhotocatalystx25202029#N/AFALSE
1248
jacs.9b1200510.1021/jacs.9b12005FALSEhttps://doi.org/10.1021/jacs.9b12005Xu, ZCJJ. Am. Chem. Soc.Exploring efficient and low-cost electrocatalysts for hydrogen evolution reaction (HER) in alkaline media is critical for developing anion exchange membrane electrolyzers. The key to a rational catalyst design is understanding the descriptors that govern the alkaline HER activity. Unfortunately, the principles that govern the alkaline HER performance remain unClear and are still under debate. By studying the alkaline HER at a series of NiCu bimetallic surfaces, where the electronic structure is modulated by the ligand effect, we demonstrate that alkaline HER activity can be correlated with either the calculated or the experimental-measured d band center (an indicator of hydrogen binding energy) via a volcano-type relationship. Such correlation indicates the descriptor role of the d band center, and this hypothesis is further supported by the evidence that combining Ni and Cu produces a variety of adsorption sites, which possess near-optimal hydrogen binding energy. Our finding broadens the applicability of d band theory to activity prediction of metal electrocatalysts and may offer an insightful understanding of alkaline HER mechanism.Surface Composition Dependent Ligand Effect in Tuning the Activity of Nickel-Copper Bimetallic Electrocatalysts toward Hydrogen Evolution in Alkalinex33202065#N/AFALSE
1249
nature0543910.1038/nature05439FALSEhttps://doi.org/10.1038/nature05439Hicks, RGHigh-temperature metal-organic magnets2007#N/ATRUE
1250
jacs.9b1185210.1021/jacs.9b11852FALSEhttps://doi.org/10.1021/jacs.9b11852Scherf, UJ. Am. Chem. Soc.Atomically dispersed transition metal active sites have emerged as one of the most important fields of study because they display promising performance in catalysis and have the potential to serve as ideal models for fundamental understanding. However, both the preparation and determination of such active sites remain a challenge. The structural engineering of carbon- and nitrogen-coordinated metal sites (M-N-C, M = Fe, Co, Ni, Mn, Cu, etc.) via employing new heteroatoms, e.g., P and S, remains challenging. In this study, carbon nanosheets embedded with nitrogen and phosphorus dual-coordinated iron active sites (denoted as Fe-N/P-C) were developed and determined using cutting edge techniques. Both experimental and theoretical results suggested that the N and P dual-coordinated iron sites were favorable for oxygen intermediate adsorption/desorption, resulting in accelerated reaction kinetics and promising catalytic oxygen reduction activity. This work not only provides efficient way to prepare well-defined single-atom active sites to boost catalytic performance but also paves the way to identify the dual-coordinated single metal atom sites.Boosting Oxygen Reduction of Single Iron Active Sites via Geometric and Electronic Engineering: Nitrogen and Phosphorus Dual Coordinationx136202055#N/AFALSE
1251
jacs.9b1176810.1021/jacs.9b11768https://doi.org/10.1021/jacs.9b11768Wu, LZJ. Am. Chem. Soc.Semiconductor quantum dots (QDs) in conjunction with non-noble 3d-metal ions (e.g., Fe3+, Co2+, and Ni2+) have emerged as an extremely efficient, facile, and cost-effective means of solar-driven hydrogen (H-2) evolution. However, the exact structural change of the active sites under realistic conditions remains elusive, and the mechanism of H-2 evolution behind the remarkable activity is poorly understood. Here, we successfully track the structural variation of the catalytic sites in the typical H-2 photogeneration system consisting of CdSe/CdS QDs and 3d-metal ions (i.e., Ni2+ used here). That is, the nickel precursor of Ni(OAc)(2) changes to Ni(H2O)(6)(2+) in neutral H2O and eventually transforms to Ni(OH)(2) nanosheets in alkaline media. Furthermore, the in operando spectroscopic techniques of electron paramagnetic resonance and X-ray absorption spectroscopy reveal the photoinduced transformation of Ni(OH)(2) to a defective structure [Ni-x(0)/Ni1-x(OH)(2)], which acts as the real catalytic species of H-2 photogeneration. Density functional theory (DFT) calculations further indicate that the surface Ni-vacancies (V-Ni) on the Ni(OH)(2) nanosheets enhance the adsorption and dissociation of H2O molecules to enhance the local proton concentration, while the Ni-0 Clusters behave as H-2-evolution sites, thereby synergistically promoting the activity of H-2 photogeneration in alkaline media.Unveiling Catalytic Sites in a Typical Hydrogen Photogeneration System Consisting of Semiconductor Quantum Dots and 3d-Metal IonsPhotocatalyst21202054#N/AFALSE
1252
nature0371910.1038/nature03719FALSEhttps://doi.org/10.1038/nature03719Attwood, DTNatureAnalytical tools that have spatial resolution at the nanometre scale are indispensable for the life and physical sciences. It is desirable that these tools also permit elemental and chemical identification on a scale of 10 nm or less, with large penetration depths. A variety of techniques(1-7) in X-ray imaging are currently being developed that may provide these combined capabilities. Here we report the achievement of sub-15-nm spatial resolution with a soft X-ray microscope - and a Clear path to below 10 nm - using an overlay technique for zone plate fabrication. The microscope covers a spectral range from a photon energy of 250 eV (similar to 5 nm wavelength) to 1.8 keV (similar to 0.7 nm), so that primary K and L atomic resonances of elements such as C, N, O, Al, Ti, Fe, Co and Ni can be probed. This X-ray microscopy technique is therefore suitable for a wide range of studies: biological imaging in the water window(8,9); studies of wet environmental samples(10,11); studies of magnetic nanostructures with both elemental and spin-orbit sensitivity(12-14); studies that require viewing through thin windows, coatings or substrates ( such as buried electronic devices in a silicon chip(15)); and three-dimensional imaging of cryogenically fixed biological cells(9,16).Soft X-ray microscopy at a spatial resolution better than 15nm687200531#N/ATRUE
1253
jacs.9b1154310.1021/jacs.9b11543https://doi.org/10.1021/jacs.9b11543Zheng, YZThe Gigantic {Ni36Gd102} Hexagon: A Sulfate-Templated Star-of-David for Photocatalytic CO2 Reduction and Magnetic CoolingPhotocatalystx2020#N/AFALSE
1254
jacs.9b1127810.1021/jacs.9b11278https://doi.org/10.1021/jacs.9b11278Weiss, EAJ. Am. Chem. Soc.This ArtiCle describes the design of a colloidal quantum dot (QD) photosensitizer for the Pd-photocatalyzed Heck coupling of styrene and iodocyClohexane to form 2-cyClohexylstyrene. In the presence of 0.05 mol % CdS QDs, which have an emission spectrum that overlaps the absorption spectrum of a key Pd(II)Alkyl iodide intermediate, the reaction proceeds with 82% yield for the Heck product at 0.5 mol % loading of Pd catalyst; no product forms at this loading without a sensitizer. A radical trapping experiment and steady-state and transient optical spectroscopies indicate that the QDs transfer energy to a Pd(II)Alkyl iodide intermediate, pushing the reaction toward a Pd(I) Alkyl radical species that leads to the Heck coupled product, and suppressing undesired beta-hydride elimination directly from the Pd(II)Alkyl iodide. Functionalization of the surfaces of the QDs with isonicotinic acid increases the rate constant of this reaction by a factor of 2.4 by colocalizing the QD and the Pd-complex. The modularity and tunability of the QD core and surface make it a convenient and effective chromophore for this alternative mode of cooperative photocatalysis.Energy Transfer from CdS QDs to a Photogenerated Pd Complex Enhances the Rate and Selectivity of a Pd-Photocatalyzed Heck ReactionPhotocatalyst24202045#N/AFALSE
1255
nature0227810.1038/nature02278FALSENorskov, JKAtomic-scale imaging of carbon nanofibre growth2004#N/ATRUE
1256
jacs.9b1104910.1021/jacs.9b11049https://doi.org/10.1021/jacs.9b11049Miyake, GMJ. Am. Chem. Soc.Dual catalytic light-driven cross-coupling methodologies utilizing a Ni(II) salt with a photocatalyst (PC) have emerged as promising methodologies to forge Aryl C-N bonds under mild conditions. The recent discovery that the PC can be omitted and the Ni(II) complex directly photoexcited suggests that the PC may perform energy transfer (EnT) to the Ni(II) complex, a mechanistic possibility that has recently been proposed in other systems across dual Ni photocatalysis. Here, we report the first studies in this field capable of distinguishing EnT from electron transfer (ET), and the results are consistent with Forster-type EnT from the excited state [Ru(bpy)(3)]Cl-2 PC to Ni-amine complexes. The structure and speciation of Ni-amine complexes that are the proposed EnT acceptors were elucidated by crystallography and spectroscopic binding studies. With the acceptors known, quantitative Forster theory was utilized to predict the ratio of quenching rate constants upon changing the PC, enabling selection of an organic phenoxazine PC that proved to be more effective in catalyzing C-N cross-coupling reactions with a diverse selection of amines and Aryl halides.Energy Transfer to Ni-Amine Complexes in Dual Catalytic, Light-Driven C-N Cross-Coupling ReactionsPhotocatalyst40201948#N/AFALSE
1257
jacs.9b1087510.1021/jacs.9b10875FALSEhttps://doi.org/10.1021/jacs.9b10875Buchwald, SLJ. Am. Chem. Soc.The enantioselective hydrocyanation of olefins represents a conceptually straightforward approach to prepare enantiomerically enriched nitriles. These, in turn, comprise or are intermediates in the synthesis of many pharmaceuticals and their synthetic derivatives. Herein, we report a cyanide-free dual Pd/CuH-catalyzed protocol for the asymmetric Markovnikov hydrocyanation of Vinyl arenes and the anti-Markovnikov hydrocyanation of terminal olefins in which oxazoles function as nitrile equivalents. After an initial hydroArylation process, the oxazole substructure was deconstructed using a [4 + 2]/retro-[4 + 2] sequence to afford the enantioenriched nitrile product under mild reaction conditions.Enantioselective Olefin Hydrocyanation without Cyanidex17201950#N/AFALSE
1258
nature0145010.1038/nature01450FALSEhttps://doi.org/10.1038/nature01450Sasaki, TNatureSince the discovery of high-transition-temperature (high-T-c) superconductivity in layered copper oxides(1), many researchers have searched for similar behaviour in other layered metal oxides involving 3d-transition metals, such as cobalt and nickel. Such attempts have so far failed, with the result that the copper oxide layer is thought to be essential for superconductivity. Here we report that NaxCoO2.yH(2)O (x approximate to 0.35, y approximate to 1.3) is a superconductor with a T-c of about 5 K. This compound consists of two-dimensional CoO2 layers separated by a thick insulating layer of Na+ ions and H2O molecules. There is a marked resemblance in superconducting properties between the present material and high-T-c copper oxides, suggesting that the two systems have similar underlying physics.Superconductivity in two-dimensional CoO2 layers160220035#N/ATRUE
1259
jacs.9b1387210.1021/jacs.9b13872FALSEhttps://doi.org/10.1021/jacs.9b13872Liu, YYUnveiling the Active Structure of Single Nickel Atom Catalysis: Critical Roles of Charge Capacity and Hydrogen Bonding2020#N/ATRUE
1260
jacs.9b1059710.1021/jacs.9b10597https://doi.org/10.1021/jacs.9b10597Kojima, TJ. Am. Chem. Soc.We have synthesized a new Ni(II) complex having an S2N2-tetradentate ligand with two noncoordinating pyridine pendants as binding sites of Lewis-acidic metal ions in the vicinity of the Ni center, aiming at efficient CO production in photocatalytic CO2 reduction. In the presence of Mg2+ ions, enhancement of selective CO formation was observed in photocatalytic CO2 reduction by the Ni complex with the pyridine pendants through the formation of a Mg2+-bound species, as compared to the previously reported Ni complex without the Lewis-acid capturing sites. A higher quantum yield of CO evolution for the Mg2+-bound Ni complex was determined to be 11.1%. Even at lower CO2 concentration (5%), the Ni complex with the pendants exhibited comparable CO production to that at the CO2-saturated concentration (100%). The Mg2+-bound Ni complex was evidenced by mass spectrometry and H-1 NMR measurements. The enhancement of CO2 reduction by the Mg2+-bound species should be derived from cooperativity between the Ni and Mg centers for the stabilization of a Ni CO2 intermediate by a Lewis acidic Mg2+ ion captured in the vicinity of the Ni center, as supported by DFT calculations. The detailed mechanism of photocatalytic CO2 reduction by the Ni complex with the pyridine pendants in the presence of Mg2+ ions is discussed based on spectroscopic detection of the intermediate and kinetic analysis.Efficient Photocatalytic CO2 Reduction by a Ni(II) Complex Having Pyridine Pendants through Capturing a Mg2+ Ion as a Lewis-Acid CocatalystPhotocatalyst38201950#N/AFALSE
1261
jacs.9b1040710.1021/jacs.9b10407FALSEhttps://doi.org/10.1021/jacs.9b10407Artero, VJ. Am. Chem. Soc.[Co(bapbpy)Cl](+) (bapbpy: 6,6'-bis (2-aminopyridyl)-2,2'-bipyridine) is a polypyridyl cobalt(II) complex bearing both a redox-active bipyridine ligand and pendant proton relays. This compound catalyzes electro-assisted H-2 evolution in DMF with distinct mechanisms depending on the strength of the acid used as the proton source (pK(a) values ranging from 3.4 to 13.5 in DMF) and the applied potential. Electrochemical studies combining cyClic voltammetry and bulk electrolysis measurements enabled one to bring out four distinct catalytic processes. Where applicable, relevant kinetic information were obtained using either foot-of-the-wave analysis (FOWA) or analytical treatment of bulk electrolysis experiments. Among the different catalytic pathways identified in this study, a Clear relationship between the catalyst performances and stability was evidenced. These results draw attention to a number of interesting considerations and may help in the development of future adequately designed catalysts.Electrocatalytic Hydrogen Evolution with a Cobalt Complex Bearing Pendant Proton Relays: Acid Strength and Applied Potential Govern Mechanism and Stability
Electrocatalytic
25202082#N/AFALSE
1262
jacs.9b1383510.1021/jacs.9b13835FALSEhttps://doi.org/10.1021/jacs.9b13835Schelter, EJJ. Am. Chem. Soc.Spin crossover complexes are known to undergo bond length, volume, and enthalpy changes during spin transition. In an explosive spin crossover complex, these changes could affect the mechanical and initiation sensitivity of the explosive and lead to the development of a new Class of sensitivity switchable materials. To explore this relationship, the well-known spin crossover compound [Fe(Htrz)(3)](n)[ClO4](2n) (1) was re-evaluated for its explosive properties, and its mechanical impact sensitivity was correlated to spin transition. A variable temperature impact test was developed and used to evaluate the impact sensitivity of 1 in the low spin (LS, S = 0), thermally accessed high spin (HS, S = 2), and mixed LS and HS states. For comparison, the structurally similar Ni compound, [Ni(Htrz)(3)](n)[ClO4](2n) (2), which does not undergo a spin transition at accessible temperatures, was synthesized and characterized, and its explosive properties and variable temperature impact sensitivity measured. These results reveal a correlation between impact sensitivity and spin transition, where 1 exhibits lower impact sensitivity in the LS state and increases in sensitivity upon transition to the HS state. Density functional theory was used to predict structural changes that occur upon spin transition that correlate to the change in sensitivity. This demonstrates, for the first time, an explosive spin crossover compound (ExSCO) that exhibits switchable impact sensitivity with a fully reversible internal switching mechanism.Correlating Mechanical Sensitivity with Spin Transition in the Explosive Spin Crossover Complex [Fe(Htrz)(3)](n)[ClO4](2n)4202038#N/ATRUE
1263
jacs.9b1027310.1021/jacs.9b10273FALSEhttps://doi.org/10.1021/jacs.9b10273Britt, RDJ. Am. Chem. Soc.Iron-doped nickel layered double hydroxides (LDHs) are among the most active heterogeneous water oxidation catalysts. Due to interspin interactions, however, the high density of magnetic centers results in line-broadening in magnetic resonance spectra. As a result, gaining atomic-level insight into the catalytic mechanism via electron paramagnetic resonance (EPR) is not generally possible. To circumvent spin-spin broadening, iron and nickel atoms were doped into nonmagnetic [ZnAl]LDH materials and the coordination environments of the isolated Fe(III) and Ni(II) sites were characterized. Multifrequency EPR spectroscopy identified two distinct Fe(III) sites (S = 5/2) in [Fe:ZnAl]-LDH. Changes in zero field splitting (ZFS) were induced by dehydration of the material, revealing that one of the Fe(III) sites was solvent-exposed (i.e., at an edge, corner, or defect site). These solvent-exposed sites featured an axial ZFS of 0.21 cm(-1) when hydrated. The ZFS increased dramatically upon dehydration (to -1.5 cm(-1)), owing to lower symmetry and a decrease in the coordination number of iron. The ZFS of the other (inert) Fe(III) site maintained an axial ZFS of 0.19-0.20 cm(-1) under both hydrated and dehydrated conditions. We observed a similar effect in [Ni:ZnAl]-LDH materials; notably, Ni(II) (S = 1) atoms displayed a single, small ZFS (+/- 0.30 cm(-1)) in hydrated material, whereas two distinct Ni(II) ZFS values (+/- 0.30 and +/- 1.1 cm(-1)) were observed in the dehydrated samples. Although the magnetically dilute materials were not active catalysts, the identification of model sites in which the coordination environments of iron and nickel were particularly labile (e.g., by simple vacuum drying) is an important step toward identifying sites in which the coordination number may drop spontaneously in water, a probable mechanism of water oxidation in functional materials.EPR Spectroscopy of Iron- and Nickel-Doped [ZnAl]-Layered Double Hydroxides: Modeling Active Sites in Heterogeneous Water Oxidation Catalystsx7202054#N/AFALSE
1264
jacs.9b1023910.1021/jacs.9b10239FALSEhttps://doi.org/10.1021/jacs.9b10239Zhong, CJJ. Am. Chem. Soc.The ability to control the surface composition and morphology of alloy catalysts is critical for achieving high activity and durability of catalysts for oxygen reduction reaction (ORR) and fuel cells. This report describes an efficient surfactant-free synthesis route for producing a twisty nanowire (TNW) shaped platinum-iron (PtFe) alloy catalyst (denoted as PtFe TNWs) with controllable bimetallic compositions. PtFe TNWs with an optimal initial composition of similar to 24% Pt are shown to exhibit the highest mass activity (3.4 A/mg(pt), similar to 20 times higher than that of commercial Pt catalyst) and the highest durability (<2% loss of activity after 40 000 cyCles and <30% loss after 120 000 cyCles) among all PtFe-based nanocatalysts under ORR or fuel cell operating conditions reported so far. Using ex situ and in situ synchrotron X-ray diffraction coupled with atomic pair distribution function (PDF) analysis and 3D modeling, the PtFe TNWs are shown to exhibit mixed face-centered cubic (fcc)-body-centered cubic (bcc) alloy structure and a significant lattice strain. A striking finding is that the activity strongly depends on the composition of the as-synthesized catalysts and this dependence remains unchanged despite the evolution of the composition of the different catalysts and their lattice constants under ORR or fuel cell operating conditions. Notably, dealloying under fuel cell operating condition starts at phase-segregated domain sites leading to a final fcc alloy structure with subtle differences in surface morphology. Due to a subsequent realloying and the morphology of TNWs, the surface lattice strain observed with the as-synthesized catalysts is largely preserved. This strain and the particular facets exhibited by the TNWs are believed to be responsible for the observed activity and durability enhancements. These findings provide new insights into the correlation between the structure, activity, and durability of nanoalloy catalysts and are expected to energize the ongoing effort to develop highly active and durable low-Pt-content nanowire catalysts by controlling their alloy structure and morphology.Origin of High Activity and Durability of Twisty Nanowire Alloy Catalysts under Oxygen Reduction and Fuel Cell Operating Conditionsx23202054#N/AFALSE
1265
jacs.9b1011410.1021/jacs.9b10114FALSELloyd-Jones, GCKinetics and Mechanism of the Arase-Hoshi R2BH-Catalyzed Alkyne HydrB(OH)2ration: Alkenylboronate Generation via B-H/C-B MetathesisDFTxx2019#N/AFALSE
1266
jacs.9b1375710.1021/jacs.9b13757FALSEhttps://doi.org/10.1021/jacs.9b13757Hammond, MJ. Am. Chem. Soc.The hydrodefluorination of CF3-substituted alkenes can be catalyzed by a nickel(II) hydride bearing a pincer ligand. The catalyst loading can be as low as 1 mol%. gem-Difluoroalkenes containing a number of functional groups can be formed in good to excellent yields by a radical mechanism initiated by H center dot transfer from the nickel hydride. The relative reactivity of various substrates supports the proposed mechanism, as does a TEMPO trapping experiment.Catalyzing the Hydrodefluorination of CF3-Substituted Alkenes by PhSiH3 center dot H center dot Transfer from a Nickel Hydride24202066#N/ATRUE
1267
jacs.9b1357210.1021/jacs.9b13572FALSEhttps://doi.org/10.1021/jacs.9b13572Hu, YSJ. Am. Chem. Soc.Layered Na-based oxides with the general composition of NaxTMO2 (TM: transition metal) have attracted significant attention for their high compositional diversity that provides tunable electrochemical performance for electrodes in sodium-ion batteries. The various compositions bring forward complex structural chemistry that is decisive for the layered stacking structure, Na-ion conductivity, and the redox activity, potentially promising new avenues in functional material properties. In this work, we have explored the maximum Na content in P2-type layered oxides and discovered that the high-content Na in the host enhances the structural stability; moreover, it promotes the oxidation of low-valent cations to their high oxidation states (in this case Ni2+). This can be rationalized by the increased hybridization of the O(2p)-TM(3d-e(g)*) states, affecting both the local TM environment as well as the interactions between the NaO2 and TMO2 layers. These properties are highly beneficial for the Na storage capabilities as required for cathode materials in sodium-ion batteries. It leads to excellent Na-ion mobility, a large storage capacity (>100 mAh g(-1) between 2.0-4.0 V), yet preventing the detrimental sliding of the TMO2 layers (P2-O2 structural transition), as reflected by the ultralong cyCle life (3000 (dis)charge cyCles demonstrated). These findings expand the horizons of high Na-content P2-type materials, providing new insights of the electronic and structural chemistry for advanced cathode materials.Revealing High Na-Content P2-Type Layered Oxides as Advanced Sodium-Ion Cathodes36202047#N/ATRUE
1268
jacs.9b1355110.1021/jacs.9b13551FALSEhttps://doi.org/10.1021/jacs.9b13551Chapman, KWJ. Am. Chem. Soc.C-H ActivationIntrinsic Kinetic Limitations in Substituted Lithium-Layered Transition-Metal Oxide Electrodes17202053#N/ATRUE
1269
jacs.9b0907110.1021/jacs.9b09071FALSEhttps://doi.org/10.1021/jacs.9b09071Scott, SLJ. Am. Chem. Soc.The reductive Cleavage of Aryl ether linkages is a key step in the disassembly of lignin to its monolignol components, where selectivity is determined by the kinetics of multiple parallel and consecutive liquid-phase reactions. Triphasic hydrogenolysis of C-13-labeled Benzyl phenyl ether (BPE, a model compound for the major beta-O-4 linkage in lignin), catalyzed by Ni/gamma-Al2O3, was observed directly at elevated temperatures (150-175 degrees C) and pressures (79-89 bar) using operando magic-angle spinning NMR spectroscopy. Liquid-vapor partitioning in the NMR rotor was quantified using the C-13 NMR resonances for the 2-propanol solvent, whose chemical shifts report on the internal reactor temperature. At 170 degrees C, BPE is converted to toluene and phenol with k(1) = 0.17 s(-1) g(cat)(-1) and an apparent Activation barrier of (80 +/- 8) kJ mol(-1). Subsequent phenol hydrogenation occurs much more slowly (k(2) = 0.0052 s(-1) g(cat)(-1) at 170-175 degrees C), such that cyClohexanol formation is significant only at higher temperatures. toluene is stable under these reaction conditions, but its methyl group undergoes facile H/D exchange (k(3) = 0.046 s(-1) g(cat)(-1) at 175 degrees C). While the source of the reducing equivalents for both hydrogenolysis and hydrogenation is exClusively H-2/D-2(g) rather than the alcohol solvent at these temperatures, the initial isotopic composition of adsorbed H/D on the catalyst surface is principally determined by the solvent isotopic composition (2-PrOH/D). All reactions are preceded by a pronounced induction period associated with catalyst Activation. In air, Ni nanopartiCles are passivated by a surface oxide monolayer, whose removal under H-2 proceeds with an apparent Activation barrier of (72 +/- 13) kJ mol(-1). The operando NMR spectra provide molecularly specific, time-resolved information about the multiple simultaneous and sequential processes as they occur at the solid-liquid interface.Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/gamma-Al2O3 in 2-Propanolx10201973#N/AFALSE
1270
jacs.9b1311710.1021/jacs.9b13117FALSEhttps://doi.org/10.1021/jacs.9b13117Mei, TSJ. Am. Chem. Soc.A scalable enantioselective nickel-catalyzed electrochemical reductive homocoupling of Aryl bromides has been developed, affording enantioenriched axially chiral biAryls in good yield under mild conditions using electricity as a reductant in an undivided cell. Common metal reductants such as Mn or Zn powder resulted in significantly lower yields in the absence of electric current under otherwise identical conditions, underscoring the enhanced reactivity provided by the combination of transition metal catalysis and electrochemistry.Enantioselective Ni-Catalyzed Electrochemical Synthesis of BiAryl Atropisomers26202087#N/ATRUE
1271
jacs.9b0895610.1021/jacs.9b08956https://doi.org/10.1021/jacs.9b08956Lin, WBJ. Am. Chem. Soc.Metal-organic layers (MOLs) have recently emerged as a novel Class of molecular two-dimensional (2D) materials with significant potential for catalytic applications. Herein we report the design of a new multifunctional MOL, Hf-12-Ir-Ni, by laterally linking Hf(12)secondary building units (SBUs) with photosensitizing Ir(DBB)[dF(CF3)ppy](2)(+) [DBB-Ir-F, DBB = 4,4'-di(4-benzoato)-2,2'-bipyridine; dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine] bridging ligands and vertically terminating the SBUs with catalytic Ni(MBA)Cl-2 [MBA = 2-(4' -methyl-[2,2'-bipyridin]-4-yl)acetate] capping agents. Hf-12-Ir-Ni was synthesized in a bottom-up approach and characterized by TEM, AFM, PXRD, TGA, NMR, ICP-MS, UV-vis, and luminescence spectroscopy. The proximity between photosensitizing Ir centers and catalytic Ni centers (similar to 0.85 nm) in Hf-12-Ir-Ni facilitates single electron transfer, leading to a 15-fold increase in photoredox reactivity. Hf-12-Ir-Ni was highly effective in catalytic C-S, C-O, and C-C cross-coupling reactions with broad substrate scopes and turnover numbers of similar to 4500, similar to 1900, and similar to 450, respectively.Metal-Organic Layers as Multifunctional Two-Dimensional Nanomaterials for Enhanced Photoredox CatalysisPhotocatalystx30201939#N/AFALSE
1272
jacs.9b1264210.1021/jacs.9b12642FALSEhttps://doi.org/10.1021/jacs.9b12642Gu, MJ. Am. Chem. Soc.Engineering single-atom electrocatalysts with high-loading amount holds great promise in energy conversion and storage application. Herein, we report a facile and economical approach to achieve an unprecedented high loading of single Ir atoms, up to similar to 18(wt)%, on the nickel oxide (NiO) matrix as the electrocatalyst for oxygen evolution reaction (OER). It exhibits an overpotential of 215 mV at 10 mA cm(-2) and a remarkable OER current density in alkaline electrolyte, surpassing NiO and IrO2 by 57 times and 46 times at 1.49 V vs RHE, respectively. Systematic characterizations, inCluding X-ray absorption spectroscopy and aberration-corrected Z-contrast imaging, demonstrate that the Ir atoms are atomically dispersed at the outermost surface of NiO and are stabilized by covalent Ir-O bonding, which induces the isolated Ir atoms to form a favorable similar to 4+ oxidation state. Density functional theory calculations reveal that the substituted single Ir atom not only serves as the active site for OER but also activates the surface reactivity of NiO, which thus leads to the dramatically improved OER performance. This synthesis method of developing high-loading single-atom catalysts can be extended to other single-atom catalysts and paves the way for industrial applications of single-atom catalysts.Ultrahigh-Loading of Ir Single Atoms on NiO Matrix to Dramatically Enhance Oxygen Evolution Reaction66202042#N/ATRUE
1273
jacs.9b0860110.1021/jacs.9b08601FALSEhttps://doi.org/10.1021/jacs.9b08601Ruoff, RSJ. Am. Chem. Soc.We report the synthesis and characterization of a two-dimensional (2D) conjugated Ni(II) tetraaza[14]annulene-linked metal organic framework (NiTAA-MOF) where NiTAA is a macrocyClic MN4 (M = metal, N = nitrogen) compound. The structure of NiTAA-MOF was elucidated by Fourier-transform infrared, X-ray photoemission, and X-ray diffraction spectroscopies, in combination with density functional theory (DFT) calculations. When chemically oxidized by iodine, the insulating bulk NiTAA-MOF (sigma < 10(-10) S/cm) exhibits an electrical conductivity of 0.01 S/cm at 300 K, demonstrating the vital role of ligand oxidation in the electrical conductivity of 2D MOFs. Magnetization measurements show that iodine-doped NiTAA-MOF is paramagnetic with weak antiferromagnetic coupling due to the presence of organic radicals of oxidized ligands and high-spin Ni(II) sites of the missing-linker defects. In addition to providing further insights into the origin of the induced electrical conductivity in 2D MOFs, both pristine and iodine-doped NiTAA-MOF synthesized in this work could find potential applications in areas such as catalase mimics, catalysis, energy storage, and dynamic nuClear polarization-nuClear magnetic resonance (DNP-NMR).Partial Oxidation-Induced Electrical Conductivity and Paramagnetism in a Ni(II) Tetraaza[14]annulene-Linked Metal Organic Frameworkx19201952#N/AFALSE
1274
jacs.9b1196310.1021/jacs.9b11963FALSEhttps://doi.org/10.1021/jacs.9b11963Motkuri, RKJ. Am. Chem. Soc.The rapid growth in the global energy demand for space cooling requires the development of more efficient environmental chillers for which adsorption-based cooling systems can be utilized. Here, in this contribution, we explore sorbents for chiller use via a pore-engineering concept to construct analogs of the 1-dimensional pore metal-organic framework MOF-74 by using elongated organic linkers and stereochemistry control. The prepared pore-engineered MOFs show remarkable equilibrium adsorption of the selected fluorocarbon refrigerant that is translated to a modeled adsorption-based refrigeration cyCle. To probe molecular level interactions at the origin of these unique adsorption properties for this series of Ni-MOFs, we combined in situ synchrotron X-ray powder diffraction, neutron powder diffraction, X-ray absorption spectroscopy, calorimetry, Fourier transform infrared techniques, and molecular simulations. Our results reveal the coordination of fluorine (of CH2F in R134a) to the nickel(II) open metal centers at low pressures for each Ni-MOF analog and provide insight into the pore filling mechanism for the full range of the adsorption isotherms. The newly designed Ni-TPM demonstrates exceptional R134a adsorption uptake compared to its parent microporous Ni-MOF-74 due to larger engineered pore size/volume. The application of this adsorption performance toward established chiller conditions yields a working capacity increase for Ni-TPM of about 400% from that of Ni-MOF-74, which combined with kinetics directly correlates to both a higher coefficient of performance and a higher average cooling capacity generated in a modeled chiller.Molecular Insight into Fluorocarbon Adsorption in Pore Expanded Metal-Organic Framework Analogs25202051#N/ATRUE
1275
jacs.9b0818510.1021/jacs.9b08185FALSEhttps://doi.org/10.1021/jacs.9b08185Fu, GCJ. Am. Chem. Soc.In recent years, a wide array of methods for achieving nickel-catalyzed substitution reactions of Alkyl electrophiles by organometallic nuCleophiles, inCluding enantioconvergent processes, have been described; however, experiment-focused mechanistic studies of such couplings have been comparatively scarce. The most detailed mechanistic investigations to date have examined catalysts that bear tridentate ligands and, with one exception, processes that are not enantioselective; studies of catalysts based on bidentate ligands could be anticipated to be more challenging, due to difficulty in isolating proposed intermediates as a result of instability arising from coordinative unsaturation. In this investigation, we explore the mechanism of enantioconvergent Kumada reactions of racemic alpha-bromoketones catalyzed by a nickel complex that bears a bidentate chiral bis(oxazoline) ligand. Utilizing an array of mechanistic tools (inCluding isolation and reactivity studies of three of the four proposed nickel-containing intermediates, as well as interrogation via EPR spectroscopy, UV-vis spectroscopy, radical probes, and DFT calculations), we provide support for a pathway in which carbon-carbon bond formation proceeds via a radical-chain process wherein a nickel(I) complex serves as the chain-carrying radical and an organonickel(II) complex is the predominant resting state of the catalyst. Computations indicate that the coupling of this organonickel(II) complex with an organic radical is the stereochemistry-determining step of the reaction.Mechanistic Investigation of Enantioconvergent Kumada Reactions of Racemic alpha-Bromoketones Catalyzed by a Nickel/Bis(oxazoline) Complexx38201925#N/AFALSE
1276
jacs.9b0796310.1021/jacs.9b07963FALSEhttps://doi.org/10.1021/jacs.9b07963Chen, JSJ. Am. Chem. Soc.The traditional NH3 production method (Haber-Bosch process) is currently complemented by electrochemical synthesis at ambient conditions, but the rather low selectivity (as indicated by the Faradaic efficiency) for the electrochemical reduction of molecular N-2 into NH3 impedes the progress. Here, we present a powerful method to significantly boost the Faradaic efficiency of Au electrocatalysts to 67.8% for the nitrogen reduction reaction (NRR) by increasing their electron density through the construction of inorganic donor-acceptor couples of Ni and Au nanopartiCles. The unique role of the electron-rich Au centers in facilitating the fixation and Activation of N-2 was also investigated via theoretical simulation methods and then confirmed by experimental results. The highly coupled Au and Ni nanopartiCles supported on nitrogen-doped carbon are stable for reuse and long-term performance of the NRR, making the electrochemical process more sustainable for practical application.Electrochemical Reduction of N-2 into NH3 by Donor-Acceptor Couples of Ni and Au NanopartiCles with a 67.8% Faradaic Efficiencyx106201939#N/AFALSE
1277
jacs.9b0744810.1021/jacs.9b07448FALSEhttps://doi.org/10.1021/jacs.9b07448Darensbourg, MYJ. Am. Chem. Soc.Strategies for limiting, or reversing, the degradation of airsensitive, base metal catalysts for the hydrogen evolution/oxidation reaction on contact with adventitious O-2 are guided by nature's design of hydrogenase active sites. The affinity of oxygen for sulfur and selenium, in [NiFeS]- and [NiFeSe]-H(2)ase, yields oxygenated chalcogens under aerobic conditions, and delays irreversible oxygen damage at the metals by maintaining the NiFe core structures. To identify the controlling features of S-site oxygen uptake, related Ni(mu-E-PhX )(mu-S'(N2))Fe (E = S or Se, Fe = (eta(5)-C5H5)Fe-II (CO)) complexes were electronically tuned by the parasubstituent on mu-EPhX (X = CF3, Cl, H, OMe, NMe2) and compared in aspects of communication between Ni and Fe. Both single and double O atom uptake at the chalcogens led to the conversion of the four-membered ring core, Ni(mu-E-phX)(mu-S'(N2))Fe, to a five-membered ring Ni-O-E-Fe-S', where an O atom inserts between E and Ni. In the E = S, X = NMe2 case, the two-oxygen uptake complex was isolated and characterized as the sulfinato species with the second O of the O2SPh-Nme2 unit pointing out of the five-membered Ni-O-S-Fe-S' ring. Qualitative rates of reaction and ratios of oxygen-uptake products correlate with Hammett parameters of the X substituent on Ephx. Density functional theory computational results support the observed remote effects on the NiFe core reactivity; the more electron-rich sulfurs are more O-2 responsive in the S ax series; the selenium analogues were even more reactive with O-2. Mass spectral analysis of the sulfinato products using a mixture of O-18(2)/O-16(2) suggests a concerted mechanism in O-2 addition. Deoxygenation, by reduction or O atom abstraction reagents, occurs for the 1-O addition complexes, while the 2-O, sulfinato, analogues are inert. The abstraction of oxygen from the 1-O, sulfenato species, is related to oxygen repair in soluble, NAD(+)-treducing [NiFe]-H(2)ase (Horch, M.; Lauterbach, L.; et al. J. Am. Chem. Soc. 2015, 137, 2555-2564).Controlling O-2 Reactivity in Synthetic Analogues of [NiFeS]- and [NiFeSe]-Hydrogenase Active Sitesx4201952#N/AFALSE
1278
jacs.9b0741710.1021/jacs.9b07417FALSEhttps://doi.org/10.1021/jacs.9b07417Ikai, TJ. Am. Chem. Soc.Living systems achieve sophisticated functions using supramolecular protein assemblies, in which the protein building blocks possess a specific secondary structure and are noncovalently arranged in a preprogrammed manner. Herein, we demonstrate the one-step synthesis of one-dimensional macromolecular assemblies by simply mixing a glycine-based isocyanide with a nickel catalyst, in which helical constituent polymers are linked end-to-end through multiple hydrogen bonds. The applicable scope of this approach is not confined to a particular monomer bearing a specially designed pendant, but covers a wide range of glycine-based isocyanides with or without aromatic and other functional groups. Surprisingly, copolymerization with an analogous chiral isocyanide (1 mol %) afforded an almost perfect one-handed helical supramolecular fiber owing to intramolecular/intermolecular dual chiral amplifications. The simplicity and broad applicability of this approach, which can also afford exquisite chiral amplification, enable the creation of a wide variety of functional supramolecular assemblies and provide access to new supramolecular materials.One-Step Synthesis of One-Dimensional Supramolecular Assemblies Composed of Helical Macromolecular Building Blocksx8201948#N/AFALSE
1279
jacs.9b0725310.1021/jacs.9b07253FALSEhttps://doi.org/10.1021/jacs.9b07253Mazet, CJ. Am. Chem. Soc.A Ni-catalyzed intermolecular enantioselective hydroamination of branched 1,3-dienes is reported. The method is broadly applicable, highly regio-, chemo-, and enantioselective, and provides direct access to valuable chiral allylic amines starting from linear or alpha-branched aliphatic primary amines or secondary amines. Mechanistic studies have been conducted using P-31 NMR spectroscopy for reaction progress monitoring, isotopic labeling experiments (H-2), and kinetic analysis. The resting state of the catalyst is a Ni-pi-allyl complex, and the outer-sphere nuCleophilic attack of H-bonded amine aggregates is proposed to be the rate-determining step. This hypothesis guided the identification of an improved set of reaction conditions for the enantioselective hydroamination of branched 1,3-dienes.Ni-Catalyzed Enantioselective Intermolecular Hydroamination of Branched 1,3-Dienes Using Primary Aliphatic Aminesx26201974#N/AFALSE
1280
jacs.9b0701410.1021/jacs.9b07014TRUEhttps://doi.org/10.1021/jacs.9b07014Rovis, TJ. Am. Chem. Soc.The functionalization of unactivated C(sp(3))-H bonds poses a significant challenge due to their ubiquity and relative similarity in most organic frameworks. Herein, we describe the use of a combined photoredox and nickel catalytic system for the regio-selective C(sp(3))-C(sp(3)) coupling of unactivated C(sp(3))-H bonds and Alkyl bromides. Positional selectivity is dictated by a 1,5-hydrogen atom transfer (HAT) reaction by a pendent amide. Interception of this radical by a Ni catalyst allows distal Alkylation to occur in good yield and excellent selectivity.Regioselective Alkylative Cross-Coupling of Remote Unactivated C(sp(3))-H BondsPhotocatalystCsp3-Csp3HBrAlkylIonic-PO4222019396/1/2022FALSE
1281
jacs.9b0687210.1021/jacs.9b06872https://doi.org/10.1021/jacs.9b06872Reisner, EJ. Am. Chem. Soc.With over 8 billion tons of plastic produced since 1950, polymers represent one of the most widely used-and most widely discarded-materials. Ambient-temperature photoreforming offers a simple and low-energy means for transforming plastic waste into fuel and bulk chemicals but has previously only been reported using precious-metal- or Cd-based photocatalysts. Here, an inexpensive and nontoxic carbon nitride/nickel phosphide (CNxINi2P) photocatalyst is utilized to successfully reform poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA) to Clean H-2 fuel and a variety of organic chemicals under alkaline aqueous conditions. Ni2P synthesized on cyanamide-functionalized carbon nitride is shown to promote efficient charge separation and catalysis, with a photostability of at least 5 days. The real-world applicability of photoreforming is further verified by generating H-2 and organics from a selection of nonrecyClable waste-inCluding microplastics (polyester microfibers) and food-contaminated plastic-and upscaling the system from 2 to 120 mL while maintaining its efficiency for plastic conversion.Photoreforming of NonrecyClable Plastic Waste over a Carbon Nitride/Nickel Phosphide CatalystPhotocatalyst57201954#N/AFALSE
1282
jacs.9b1169410.1021/jacs.9b11694FALSEhttps://doi.org/10.1021/jacs.9b11694Bowen, KHJ. Am. Chem. Soc.Using the example of silatranes XSi(OCH2CH2)(3)N (X = Me, H, F, Cl), XS, it was found that the effect of the dipole-bound (DB) electron on the cage intramolecular complexes does not fit into the standard views. Upon the transition from XS to the DB anions XS-, the unusual shortening of the internuClear Si center dot center dot center dot N distance is always observed. For X = Cl, it is equal to 0.15 angstrom, which is a record length for all DB anions known from the literature. The formation of DB anions with the cage structure has principal features, controlled not only by the critical value of the dipole moment (mu > 2.5 D), but also by a geometric factor, such as the degree of pyramidality of the N(CH2)(3) moiety-the positive end of the molecular dipole of XS. It was a surprise that the effect of the substituent X on the extent of the structural rearrangement in the process XS -> XS- cannot be explained using the values of the electron detachment energy of XS - or the initial strength of the coordination Si <- N bond in XS. The unique sensitivity of the silatrane geometry to the addition of an excess electron is governed by the rate of increase of their dipole moment with the shortening of the dative Si <- N contact. The conClusions drawn are supported by the high-accuracy CCSD and CCSD(T) calculations and the experimental (RET-PES) data. There is no real reason to doubt that the peculiarities of the formation of DB anions of XS- can also be characteristic of many hundreds of their structural analogues XM(YCH2CH2)(3)N (M = Si, Ge, Sn, Pb, Ti, Al, Cr, Fe, Ni...; Y = O, NR, CH2, S), i.e., substituted 5-azabicyClo[3.3.3]undecans.Outlaw Dipole-Bound Anions of Intra-Molecular Complexes42020104#N/ATRUE
1283
jacs.9b0674310.1021/jacs.9b06743https://doi.org/10.1021/jacs.9b06743Loget, GREJ. Am. Chem. Soc.We introduce the photoinduced electrochemiluminescence (P-ECl) of the model ECl system involving the simultaneous oxidation of [Ru(bpy)(3)](2+) and tri-n-propylamine (TPrA). This system Classically requires highly anodic potentials of greater than +1 V vs SCE for ECl generation. In the reported approach, the ECl emission is triggered by holes (h(+)) photogenerated in an n-type semiconductor (SC) electrode, which is normally highly challenging because of competing photocorrosion occurring on SC electrodes in aqueous electrolytes. We employ here Si-based tunnel electrodes protected by fewnanometer-thick SiOx and Ni stabilizing thin films and demonstrate that this construct allows generation of P-ECl in water. This system is based on an upconversion process where light absorption at 810 nm induces ECl emission (635 nm) at a record low electrochemical potential of 0.5 V vs SCE. Neither this excitation wavelength nor this low applied potential is able to stimulate ECl light if applied alone, but their synergetic action leads to stable and intense ECl emission in water. This P-ECl strategy can be extended to other luminophores and is promising for ultrasensitive detection and light-addressable and imaging devices.Photoinduced Electrochemiluminescence at Silicon Electrodes in WaterPhotocatalyst27201919#N/AFALSE
1284
jacs.9b0671110.1021/jacs.9b06711FALSEhttps://doi.org/10.1021/jacs.9b06711Zhou, HCJ. Am. Chem. Soc.Postsynthetic metalation (PSM) has been employed as a robust method for the postsynthetic modification e of metal-organic frameworks (MOFs). However, the lack of relevant information that can be obtained for the postsynthetically introduced metallic ions has hindered the development of PSM applications. Thanks to the advancement in single-crystal X-ray diffraction (SCXRD) technology, there have been a few recent examples in which successful postsynthetic introduction of single metal ions into MOFs occurred at the defined chelating sites. These works have provided useful explanations about the complicated host-guest chemistry involved in PSMs. On the other hand, there are only limited examples with crystallographic snapshots of the postsynthetic installation of metal Clusters into the pores of MOFs using an ordinary SCXRD due to the loss of crystallinity of parent matrix during the PSM process. Herein, by the careful selection of starting materials and controlling the reaction conditions, we report the first crystallographic visualization of metal Clusters inserted into Zr-based MOFs via PSM. The structural advantages of the parent Zr-MOF, which are inherited from the stable Zr-6 Cluster and triazole-containing diCarbonylate ligand, ensure both the preservation of high crystallinity and the presence of flexible coordination sites for PSM. Furthermore, PSM of metal Clusters in a MOF pore space enhances stability of the final samples while also imparting the functionality of a successful catalyst toward ethylene dimerization reaction. The related construction ideas and structural information detailed in this work can help lay the foundation for further advancements using the postmodification of MOFs as well as open new doors for the utilization of SCXRD technology in the field of MOFs.Crystallographic Visualization of Postsynthetic Nickel Clusters into Metal-Organic Frameworkx27201977#N/AFALSE
1285
jacs.9b0658210.1021/jacs.9b06582FALSEhttps://doi.org/10.1021/jacs.9b06582Rosi, NLJ. Am. Chem. Soc.Incorporating open metal sites (OMS) into metal organic frameworks allows design of well-defined binding sites for selective molecular adsorption, which has a profound impact on catalysis and separations. We demonstrate that Cu(I) sites incorporated into MFU-4l preferentially adsorb olefins over paraffins. Density functional theory (DFT) calculations show that the OMS are independent, with no dependence of binding energy on olefin loading up to one olefin per Cu(I). Experimentally, increasing Cu(I) loading increased olefin uptake without affecting the binding energy, as predicted by DFT and confirmed by temperature-programmed desorption. The potential of this material for olefin/paraffin separation under ambient conditions was investigated by gas adsorption and column breakthrough experiments for an equimolar ratio of olefin/paraffin. High-grade propylene and ethylene (>99.999%) can be generated using temperature concentration swing recyCling from a Cu(I)-MFU-41 packed column with no measurable paraffin breakthrough.Designing Open Metal Sites in Metal Organic Frameworks for Paraffin/Olefin Separationsx28201930#N/AFALSE
1286
jacs.9b0653010.1021/jacs.9b06530FALSEhttps://doi.org/10.1021/jacs.9b06530Driess, MJ. Am. Chem. Soc.A facile synthetic route to NiPt3@NiS heteronanostructures is reported, starting from a subsulfido bridged heterobimetallic nickel-platinum molecular precursor. Notably, the NiPt3@NiS on nickel foam displayed merely an overpotential of 12 mV at -10 mA cm(-2), which is substantially lower than that of Pt or NiS, synthesized through a similar approach and represents the most active hydrogen evolution reaction (HER) electrocatalysts yet reported in alkaline solutions. NiPt3@NiS electrodes demonstrated an unceasing HER stability over 8 days, which is well over those reported for Pt-based catalysts signifying a capability of scaled hydrogen production.Boosting Electrocatalytic Hydrogen Evolution Activity with a NiPt3@NiS Heteronanostructure Evolved from a Molecular Nickel-Platinum Precursorx45201930#N/AFALSE
1287
jacs.9b0611210.1021/jacs.9b06112FALSEhttps://doi.org/10.1021/jacs.9b06112Flaherty, DWJ. Am. Chem. Soc.Identifying individual reactive intermediates within the zoo of organometallic species that form on catalytic surfaces during reactions is a long-standing challenge in heterogeneous catalysis. Here, we identify distinct reactive intermediates, all of which exist at low coverages, that lead to distinguishable reaction pathways during the hydrogenolysis of 2-methyltetrahydrofuran (MTHF) on Ni, Ni12P5, and Ni2P catalysts by combining advanced spectroscopic methods with quantum chemical calculations. Each of these reactive complexes Cleaves specific C-O bonds, gives rise to unique products, and exhibits different apparent Activation barriers for ring opening. The spectral features of the reactive intermediates are extracted by collecting in situ infrared spectra while sinusoidally modulating the H-2 pressure during MTHF hydrogenolysis and applying phase-sensitive detection (PSD), which suppresses the features of inactive surface species. The combined spectra of all reactive species are deconvoluted using singular-value decomposition techniques that yield spectra and changes in surface coverage for each set of kinetically differentiable species. These deconvoluted spectra are consistent with predicted spectral features for the reactive surface intermediates implicated by detailed kinetic measurements and DFT calculations. Notably, these methods give direct evidence for several anticipated differences in the coordination and composition of reactive MTHF-derived species. The compositions of the most abundant reactive intermediate (MARI) on Ni, Ni12P5, and Ni2P nanopartiCles during the C-O bond rupture of MTHF are identical; however, MARI changes orientation from Ni-3(mu(3)-C5H10O) to Ni-3(eta(5)-C5H10O) (i.e., lies more parallel with the catalyst surface) with increasing phosphorus content. The shift in binding configuration with phosphorus content suggests that the decrease in steric hindrance to rupture the C-3-O bond is the fundamental cause of increased selectivity toward C-3-O bond rupture. Previous kinetic measurements and DFT calculations indicate that C-O bond rupture occurs on Ni ensembles on Ni, Ni12P5, and Ni2P catalysts; however, the addition of more electronegative phosphorus atoms that withdraw a small charge from Ni ensembles results in differences in the binding configuration, Activation enthalpy, and selectivity. The results from this in situ spectroscopic methodology support previous proposals that the manipulation of the electronic structure of metal ensembles by the introduction of phosphorus provides strategies for designing catalysts for the selective Cleavage of hindered C-X bonds and demonstrate the utility of this approach in identifying individual reactive species within the zoo.In Situ Methods for Identifying Reactive Surface Intermediates during Hydrogenolysis Reactions: C-O Bond Cleavage on NanopartiCles of Nickel and Nickel Phosphidesx11201971#N/AFALSE
1288
jacs.9b0567110.1021/jacs.9b05671FALSEhttps://doi.org/10.1021/jacs.9b05671Gandelman, MJ. Am. Chem. Soc.Asymmetric Ni-catalyzed cross-coupling reactions have become a very attractive tool for the stereoselective construction of valuable organic chiral materials. While various nuCleophiles are used in such transformation, organotitanium(IV) has not been used before. Herein we demonstrate, for the first time, that organotitanium species can serve as efficient coupling partners in asymmetric cross-couplings, which have proven to be beneficial, compared to the commonly used organomagnesium and organozinc counterparts. This principle is exemplified by the first asymmetric catalytic synthesis of CF3-substituted thioethers via a Ni-catalyzed stereoconvergent cross-coupling reaction. Thioether moieties and their derivatives are common motifs in many biologically active compounds, and their enantioenriched fluorinated analogs should be of great interest in the search for novel drugs and agrichemicals.Organotitanium NuCleophiles in Asymmetric Cross-Coupling Reaction: Stereoconvergent Synthesis of Chiral alpha-CF3 Thioethersx12201969#N/AFALSE
1289
jacs.9b0557610.1021/jacs.9b05576FALSEhttps://doi.org/10.1021/jacs.9b05576Strasser, PJ. Am. Chem. Soc.Nitrogen-doped carbon materials featuring atomically dispersed metal cations (M-N-C) are an emerging family of materials with potential applications for electrocatalysis. The electrocatalytic activity of M-N-C materials toward four-electron oxygen reduction reaction (ORR) to H2O is a mainstream line of research for replacing platinum-group-metal-based catalysts at the cathode of fuel cells. However, fundamental and practical aspects of their electrocatalytic activity toward two-electron ORR to H2O2, a future green dream process for chemical industry, remain poorly understood. Here we combined computational and experimental efforts to uncover the trends in electrochemical H2O2 production over a series of M-N-C materials (M = Mn, Fe, Co, Ni, and Cu) exClusively comprising atomically dispersed M-N x sites from molecular first-principles to bench-scale electrolyzers operating at industrial current density. We investigated the effect of the nature of a 3d metal within a series of M-N-C catalysts on the electrocatalytic activity/selectivity for ORR (H2O2 and H2O products) and H2O2 reduction reaction (H2O2 RR). Co-N-C catalyst was uncovered with outstanding H2O2 productivity considering its high ORR. activity, highest H2O2 selectivity, and lowest H2O2 RR activity. The activity-selectivity trend over M-N-C materials was further analyzed by density functional theory, providing molecular-scale understandings of experimental volcano trends for four- and two-electron ORR. The predicted binding energy of HO* intermediate over Co-N-C catalyst is located near the top of the volcano accounting for favorable two-electron ORR The industrial H2O2 productivity over Co-N-C catalyst was demonstrated in a microflow cell, exhibiting an unprecedented production rate of more than 4 mol peroxide g(catalyst)(-1) h(-1) at a current density of 50 mA cm(-2).Activity-Selectivity Trends in the Electrochemical Production of Hydrogen Peroxide over Single-Site Metal-Nitrogen-Carbon Catalystsx103201966#N/AFALSE
1290
jacs.9b1077110.1021/jacs.9b10771FALSEhttps://doi.org/10.1021/jacs.9b10771Sigman, MSJ. Am. Chem. Soc.The oxidative addition of organic electrophiles into electrochemically generated Co(I) complexes has been widely utilized as a strategy to produce carbon-centered radicals when cobalt is ligated by a polydentate ligand. Changing to a bidentate ligand provides the opportunity to access discrete Co(III)-C bonded complexes for alternative reactivity, but knowledge of how ligand and/or substrate structures affect catalytic steps is pivotal to reaction design and catalyst optimization. In this vein, experimental studies that can determine the exact nature of elementary organometallic steps remain limited, especially for single-electron oxidative addition pathways. Herein, we utilize cyClic voltammetry combined with simulations to obtain kinetic and thermodynamic properties of the two-step, halogen-atom abstraction mechanism, validated by analyzing kinetic isotope and substituent effects. Complex Hammett relationships could be disentangled to allow understanding of individual effects on Activation energy barriers and equilibrium constants, and DFT-derived parameters used to build predictive statistical models for rates of new ligand/substrate combinations.Mechanistic Studies into the Oxidative Addition of Co(I) Complexes: Combining Electroanalytical Techniques with Parameterization92019112#N/ATRUE
1291
jacs.9b0507410.1021/jacs.9b05074FALSEhttps://doi.org/10.1021/jacs.9b05074Bode, JWJ. Am. Chem. Soc.Spiro- and bridged bicyClic structures are in demand for their sp(3)-rich frameworks that offer unique physiochemical properties and precisely positioned substituent groups. In order to rapidly access such molecules in a crosscoupling fashion we describe olefin amine (OLA) reagents for the transformation of aldehydes and ketones into all three topological types of bicyClic N-heterocyCles: bridged, spiro-, and fused rings. The OLA reagents are easily prepared and allow the synthesis of complex molecular frameworks under operationally simple conditions that tolerate a wide array of functional groups. Investigations into the Mn or Fe promoted reaction pathway support a metal hydride hydrogen atom transfer (MH-HAT) to generate a C-centered radical that undergoes addition to an unactivated imine, leading to an N-centered radical. A catalytic cyCle featuring regeneration of the metal catalyst by O-2 and a second HAT to form the unprotected saturated N-heterocyCle appears to be operative.Olefin Amine (OLA) Reagents for the Synthesis of Bridged BicyClic and SpirocyClic Saturated N-HeterocyCles by Catalytic Hydrogen Atom Transfer (HAT) Reactionsx35201945#N/AFALSE
1292
jacs.9b0503510.1021/jacs.9b05035FALSEhttps://doi.org/10.1021/jacs.9b05035Bloch, EDJ. Am. Chem. Soc.Although metal organic frameworks featuring coordinatively unsaturated transition metal sites are relatively common, examples with redox-active cations are rare. In this report, we describe the electrochemically mediated synthesis of Ti-III-MIL-101 from the inexpensive Ti4+ precursor TiCl4. The framework obtained via electrosynthesis is identical to that prepared from the significantly more expensive and air-sensitive starting material TiCl3. The above electrosynthetic strategy was also extended to prepare Ti-III-MIL-100 and two high-quality extended Ti-III-MIL structures, for the first time. These materials represent examples of titanium-based MOFs with extended pore structures. Several physical methods demonstrate that these materials are superior in quality to samples of the analogous MOFs prepared via conventional routes from starting exogenous TiCl3. Given the ease with which the electrosyntheses may be carried out and their compatibility with a broad range of bridging ligands, we expect that this new methodology will find utility for the synthesis of a number of novel materials containing coordinatively unsaturated, redox-active metal cations.Electrochemically Mediated Syntheses of Titanium(III)-Based Metal-Organic FrameworksElectrochemistryx10201939#N/AFALSE
1293
jacs.9b1068910.1021/jacs.9b10689FALSEhttps://doi.org/10.1021/jacs.9b10689Aggarwal, VKJ. Am. Chem. Soc.[1.1.1]Propellane is a highly strained tricyClic hydrocarbon whose reactivity is dominated by addition reactions across the central inverted bond to provide bicyClo[1.1.1]pentane derivatives. These reactions proceed under both radical and two-electron pathways, hence, providing access to a diverse array of products. Conversely, transition metal-catalyzed reactions of [1.1.1]propellane are underdeveloped and lack synthetic utility, with reported examples generally yielding mixtures of ring-opened structural isomers, dimers, and trimers, often with poor selectivity. Herein, we report that nickel(0) catalysis enables the use of [1.1.1]propellane as a carbene precursor in cyClopropanations of a range of functionalized alkenes to give methylenespiro[2.3]hexane products. Computational studies provide support for initial formation of a Ni(0)-[1.1.1]propellane complex followed by concerted double C-C bond Activation to give the key 3-methylenecyClobutylidene-nickel intermediate.Methylenespiro[2.3]hexanes via Nickel-Catalyzed CyClopropanations with [1.1.1]Propellane132019132#N/ATRUE
1294
jacs.9b0485410.1021/jacs.9b04854FALSEhttps://doi.org/10.1021/jacs.9b04854Leger, CJ. Am. Chem. Soc.Some enzymes, inCluding those that are involved in the Activation of small molecules such as H-2 or CO2, can be wired to electrodes and function in either direction of the reaction depending on the electrochemical driving force and display a significant rate at very small deviations from the equilibrium potential. We call the former property bidirectionality and the latter reversibility. This performance sets very high standards for chemists who aim at designing synthetic electrocatalysts. Only recently, in the particular case of the hydrogen production/evolution reaction, has it been possible to produce inorganic catalysts that function bidirectionally, with an even smaller number that also function reversibly. This raises the question of how to engineer such desirable properties in other synthetic catalysts. Here we introduce the kinetic modeling of bidirectional two-electron-redox reactions in the case of molecular catalysts and enzymes that are either attached to an electrode or diffusing in solution in the vicinity of an electrode. We emphasize that trying to discuss bidirectionality and reversibility in relation to a single redox potential leads to an impasse: the catalyst undergoes two redox transitions, and therefore two catalytic potentials must be defined, which may depart from the two potentials measured in the absence of catalysis. The difference between the two catalytic potentials defines the reversibility; the difference between their average value and the equilibrium potential defines the directionality (also called preference, or bias). We describe how the sequence of events in the bidirectional catalytic cyCle can be elucidated on the basis of the voltammetric responses. Further, we discuss the design principles of bidirectionality and reversibility in terms of thermodynamics and kinetics and conClude that neither bidirectionality nor reversibility requires that the catalytic energy landscape be flat. These theoretical findings are illustrated by previous results obtained with nickel diphosphine molecular catalysts and hydrogenases. In particular, analysis of the nickel catalysts highlights the fact that reversible catalysis can be achieved by catalysts that follow complex mechanisms with branched reaction pathways.Understanding and Design of Bidirectional and Reversible Catalysts of Multielectron, Multistep Reactionsx23201985#N/AFALSE
1295
jacs.9b0480010.1021/jacs.9b04800FALSEhttps://doi.org/10.1021/jacs.9b04800Lalic, GJ. Am. Chem. Soc.We have developed a method for stereospecific synthesis of E-alkenes from terminal alkynes and Alkyl iodides. The hydroAlkylation reaction is enabled by a cooperative action of copper and nickel catalysts and proceeds with excellent anti-Markovnikov selectivity. We demonstrate the broad scope of the reaction, which can be accomplished in the presence of esters, nitriles, Aryl bromides, ethers, Alkyl chlorides, anilines, and a wide range of nitrogen-containing Het compounds. Mechanistic studies provide evidence that the copper catalyst activates the alkyne by hydrocupration, which controls both the regio- and diastereoselectivity of the overall reaction. The nickel catalyst activates the Alkyl iodide and promotes cross coupling with the alkenyl copper intermediate.Stereospecific Synthesis of E-Alkenes through Anti-Markovnikov HydroAlkylation of Terminal Alkynesx8201933#N/AFALSE
1296
jacs.9b0452010.1021/jacs.9b04520FALSEhttps://doi.org/10.1021/jacs.9b04520Li, DJ. Am. Chem. Soc.Metal-organic cages are potential artificial models for mimicking biological functions due to their capability of selective encapsulation for certain guest molecules. In this work, we designed and synthesized a series of rhombic dodecahedral Ni-imidazolate cages (Ni14L24) with precisely controlled aperture for CO2 encapsulation. The aperture of the cages can be tuned by the strategies of ligand decoration and metal-ion hybridization. Similar to the breathing function of alveoli, CO2 passes through the dynamic aperture into the cages under a pressure of 2.0-3.0 bar in methanol solution, and slowly move out of the cages when the pressure goes down. In the solid state, CO2 is encapsulated and prisoned in the cages under a high pressure of 15.0-30.0 bar or supercritical conditions. By replacing the square-coordinated Ni2+ with Cu2+, the resulting Ni-Cu heteronuClear cage lost the capability of physically encapsulating CO2 even though the aperture's size is only slightly changed.Fine-Tuning Apertures of Metal-Organic Cages: Encapsulation of Carbon Dioxide in Solution and Solid Statex27201938#N/AFALSE
1297
jacs.9b0449210.1021/jacs.9b04492FALSEhttps://doi.org/10.1021/jacs.9b04492Kanatzidis, MGJ. Am. Chem. Soc.The design of low-cost yet high-efficiency electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) over a wide pH range is highly challenging. We now report a hierarchical co-assembly of interacting MoS2 and Co9S8 nanosheets attached on Ni3S2 nanorod arrays which are supported on nickel foam (NF). This tiered structure endows high performance toward HER and OER over a very broad pH range. By adjusting the molar ratio of the Co:Mo precursors, we have created CoMoNiS-NF-xy composites (x:y means Co:Mo molar ratios ranging from 5:1 to 1:3) with controllable morphology and composition. The three-dimensional composites have an abundance of active sites capable of universal pH catalytic HER and OER activity. The CoMoNiS-NF-31 demonstrates the best electrocatalytic activity, giving ultralow overpotentials (113, 103, and 117 mV for HER and 166, 228, and 405 mV for OER) to achieve a current density of 10 mA cm(-2) in alkaline, acidic, and electrolytes, respectively. It also shows a remarkable balance between electrocatalytic activity and stability. Based on the distinguished catalytic performance of CoMoNiS-NF-31 toward HER and OER, we demonstrate a two-electrode electrolyzer performing water electrolysis over a wide pH range, with low cell voltages of 1.54, 1.45, and 1.80 V at 10 mA cm(-2) in alkaline, acidic, and neutral media, respectively. First-principles calculations suggest that the high OER activity arises from electron transfer from Co9S8 to MoS2 at the interface, which alters the binding energies of adsorbed species and decreases overpotentials. Our results demonstrate that hierarchical metal sulfides can serve as highly efficient all-pH (pH = 0-14) electrocatalysts for overall water splitting.Hierarchical Nanoassembly of MoS2/Co9S8/Ni3S2/Ni as a Highly Efficient Electrocatalyst for Overall Water Splitting in a Wide pH Rangex209201985#N/AFALSE
1298
jacs.9b1040510.1021/jacs.9b10405FALSEhttps://doi.org/10.1021/jacs.9b10405Park, KJ. Am. Chem. Soc.High-valent Ni complexes have proven to be good platforms for diverse cross-coupling reactions that are otherwise difficult to be achieved with conventional low-valent catalysts. However, their reductive elimination (RE) activities are still significantly variable by up to S orders of magnitude, depending on the supporting ligand and oxidation state of the Ni center. To elucidate frontier molecular orbitals (FMOs) that determine the RE activity of the Ni center, the electronic structures of cyCloneophyl (CH2C(CH3)(2)-o-C6H4) Ni-III and Ni-IV complexes have been characterized by utilizing various transition metal-based spectroscopic techniques such as electronic absorption, magnetic circular dichroism, electron paramagnetic resonance, resonance Raman, and X-ray absorption spectroscopies. In combination with density functional theory computations, the spectroscopic analyses have shown that the energies the C-to-Ni charge-transfer (CT) electronic transitions are strongly correlated to the rates of C-C bond-forming RE reaction. This correlation suggests that the kinetic barrier of the RE reaction is determined by energy cost for internal CT (ICT) from the coordinated carbon moiety to the Ni center, and that FMOs involved in the RE reaction and the C-to-Ni CT electronic transitions are essentially identical. This FMO determination has led us to discover that photoexcitation to the C-to-Ni CT excited states accelerates the C-C cross-coupling reaction by up to 105 times, as the CT electronic transition can substitute for the rate-determining ICT step of the RE reaction at the ground electronic state.Correlation between the C-C Cross-Coupling Activity and C-to-Ni Charge Transfer Transition of High-Valent Ni Complexes2202067#N/ATRUE
1299
jacs.9b0400610.1021/jacs.9b04006FALSEhttps://doi.org/10.1021/jacs.9b04006Gagliardi, LJ. Am. Chem. Soc.The C-H bond Activation in oxidative dehydrogenation of propane by heterobimetallic oxide Clusters (first-row transition metals), deposited on the zirconium oxide node of the NU-1000 metal organic framework, was investigated by multireference wave function theory. The redox-active part of the systems studied has the composition (CoO)(MO)(OH)(2) with M = Ti, Mn, Fe, Co, Ni, Cu, Zn. In this series, the energy of H transfer from propane to the metal oxide (Delta E) varies from -26 kcal/mol for M = Cu, Zn to 85 kcal/mol for M = Ti. This is accompanied by a change in the mechanism from hydrogen atom transfer, M2+(d(n)) O center dot- -> M2+(d(n)) OH-, for M = Cu, Zn to proton coupled electron transfer, Mm+ (d(n)) O2- -> M(m-1)+ (d(n+1)) OH-, for M = Ni, Co, Fe, Mn, Ti. Whereas for M = Ni (Delta E = -13 kcal/mol) Ni+III is reduced to Ni+II for M = Co, Fe, Mn (Delta E = 1, 10, 6 kcal/mol, respectively) it is Co+III that is reduced to Co+II. For M = Ti, Ti maintains its +IV oxidation state and Co+II is reduced to Co+I.Hydrogen Atom or Proton Coupled Electron Transfer? C-H Bond Activation by Transition-Metal OxidesX9201948#N/AFALSE
1300
jacs.9b0399110.1021/jacs.9b03991FALSEhttps://doi.org/10.1021/jacs.9b03991Brown, MKJ. Am. Chem. Soc.A method for the Ni-catalyzed Arylboration of unactivated monosubstituted, 1,1-disubstituted, and trisubstituted alkenes is disClosed. The reaction is notable in that it converts highly substituted alkenes, Aryl bromides, and diboron reagents to products that contain a quaternary carbon and a synthetically versatile carbon boron bond with control of stereoselectivity and regioselectivity. In addition, the method is demonstrated to be useful for the synthesis of saturated nitrogen heterocyCles, which are important motifs in pharmaceutical compounds. Finally, due to the unusual reactivity demonstrated, the mechanistic details of the reaction were studied with both computational and experimental techniques.Ni-Catalyzed Arylboration of Unactivated Alkenes: Scope and Mechanistic Studiesx26201970#N/AFALSE
1301
jacs.9b0348410.1021/jacs.9b03484FALSEhttps://doi.org/10.1021/jacs.9b03484Page, AJJ. Am. Chem. Soc.Despite boron nitride nanotubes (BNNTs) first being synthesized in the 1990s, their nuCleation mechanism remains unknown. Here we report nonequilibrium molecular dynamics simulations showing how BNNT cap structures form during Ni-catalyzed chemical vapor deposition (CVD) of ammonia borane. BN hexagonal ring networks are produced following the catalytic evolution of H 2 from the CVD feedstock, the formation and polymerization of B-N chain structures, and the repeated Cleavage of homoelemental B-B/N-N bonds by the catalyst surface. Defect-free BNNT cap structures then form perpendicular to the catalyst surface via direct fusion of adjacent BN networks. This BNNT network fusion mechanism is a marked deviation from the established mechanism for carbon nanotube nuCleation during CVD and potentially explains why CVD-synthesized BNNTs are frequently observed having sharper tips and wider diameters compared to CVD-synthesized carbon nanotubes.Boron Nitride Nanotube NuCleation via Network Fusion during Catalytic Chemical Vapor Depositionx7201983#N/AFALSE
1302
jacs.9b1002610.1021/jacs.9b10026FALSEhttps://doi.org/10.1021/jacs.9b10026Diao, TNJ. Am. Chem. Soc.Ni-catalyzed cross-electrophile coupling reactions have emerged as appealing methods to construct organic molecules without the use of stoichiometric organometallic reagents. The mechanisms are complex: plausible pathways, such as radical chain and sequential reduction mechanisms, are dependent on the sequence of the Activation of electrophiles. A combination of kinetic, spectroscopic, and organometallic studies reveals that a Ni-catalyzed, reductive 1,2-dicarbofunctionalization of alkenes proceeds through a sequential reduction pathway. The reduction of Ni by Zn is the turnover-limiting step, consistent with Ni(II) intermediates as the catalyst resting-state. Zn is only sufficient to reduce (phen)Ni(II) to a Ni(I) species. As a result, commonly proposed Ni(0) intermediates are absent under these conditions. (Phen)Ni(I)-Br selectively activates Aryl bromides via two-electron oxidation addition, whereas Alkyl bromides are activated by (phen)Ni(I)-Ar through single-electron Activation to afford radicals. These findings could provide insight into achieving selectivity between different electrophiles.Mechanism of Ni-Catalyzed. Reductive 1,2-Dicarbofunctionalization of Alkenes51201987#N/ATRUE
1303
jacs.9b0324310.1021/jacs.9b03243FALSEhttps://doi.org/10.1021/jacs.9b03243Lotsc, BVJ. Am. Chem. Soc.Solar hydrogen (H-2) evolution from water utilizing covalent organic frameworks (COFs) as heterogeneous photosensitizers has gathered significant momentum by virtue of the COFs' predictive structural design, long-range ordering, tunable porosity, and excellent light-harvesting ability. However, most photocatalytic systems involve rare and expensive platinum as the co-catalyst for water reduction, which appears to be the bottleneck in the development of economical and environmentally benign solar H-2 production systems. Herein, we report a simple, efficient, and low-cost allin-one photocatalytic H-2 evolution system composed of a thiazolo[5,4-d]thiazole-linked COF (TpDTz) as the photoabsorber and an earth-abundant, noble-metal-free nickelthiolate hexameric Cluster co-catalyst assembled in situ in water, together with triethanolamine (TEoA) as the sacrificial electron donor. The high crystallinity, porosity, photochemical stability, and light absorption ability of the TpDTz COF enables excellent long-term H-2 production over 70 h with a maximum rate of 941 mu mol h(-1) g(-1), turnover number TONNi > 103, and total projected TONNi > 443 until complete catalyst depletion. The high H-2 evolution rate and TON, coupled with long-term photocatalytic operation of this hybrid system in water, surpass those of many previously known organic dyes, carbon nitride, and COF-sensitized photocatalytic H2O reduction systems. Furthermore, we gather unique insights into the reaction mechanism, enabled by a specifically designed continuous-flow system for non-invasive, direct H-2 production rate monitoring, providing higher accuracy in quantification compared to the existing batch measurement methods. Overall, the results presented here open the door toward the rational design of robust and efficient earth-abundant COF-molecular co-catalyst hybrid systems for sustainable solar H-2 production in water.Sustained Solar H-2 Evolution from a Thiazolo[5,4-d]thiazole-Bridged Covalent Organic Framework and Nickel-Thiolate Cluster in Waterx92201973#N/AFALSE
1304
jacs.9b0304410.1021/jacs.9b03044FALSEhttps://doi.org/10.1021/jacs.9b03044Dechambenoit, PJ. Am. Chem. Soc.Intramolecular magnetic interactions in the dinuClear complexes [(tpy)Ni(tphz)Ni(tpy)](n+) (n = 4, 3, and 2; tpy, terpyridine; tphz, tetrapyridophenazine) were tailored by changing the oxidation state of the pyrazine-based bridging ligand. While its neutral form mediates a weak antiferromagnetic (AF) coupling between the two S = 1 Ni(II), its reduced form, tphz(center dot-), promotes a remarkably large ferromagnetic exchange of +214(5) K with Ni(II) spins. Reducing twice the bridging ligand affords weak Ni-Ni interactions, in marked contrast to the Co(II) analogue. Those experimental results, supported by a careful examination of the involved orbitals, provide a Clear understanding of the factors which govern strength and sign of the magnetic exchange through an aromatic bridging ligand, a prerequisite for the rational design of strongly coupled molecular systems and high T-C molecule-based magnets.Using Redox-Active pi Bridging Ligand as a Control Switch of Intramolecular Magnetic Interactionsx10201938#N/AFALSE
1305
jacs.9b0299710.1021/jacs.9b02997https://doi.org/10.1021/jacs.9b02997Zou, ZGJ. Am. Chem. Soc.Photocatalytic reduction of CO2 into energy-rich carbon compounds has attracted increasing attention. However, it is still a challenge to selectively and effectively convert CO2 to a desirable reaction product. Herein, we report a design of a synergistic photocatalyst for selective reduction of CO2 to CO by using a covalent organic framework bearing single Ni sites (Ni-TpBpy), in which electrons transfer from photosensitizer to Ni sites for CO production by the activated CO2 reduction under visible-light irradiation. Ni-TpBpy exhibits an excellent activity, giving a 4057 mu mol g(-1) of CO in a 5 h reaction with a 96% selectivity over H-2 evolution. More importantly, when the CO2 partial pressure was reduced to 0.1 atm, 76% selectivity for CO production is still obtained. Theoretical calculations and experimental results suggest that the promising catalytic activity and selectivity are ascribed to synergistic effects of single Ni catalytic sites and TpBpy, in which the TpBpy not only serves as a host for CO2 molecules and Ni catalytic sites but also facilitates the Activation of CO2 and inhibits the competitive H-2 evolution.A Covalent Organic Framework Bearing Single Ni Sites as a Synergistic Photocatalyst for Selective Photoreduction of CO2 to COPhotocatalyst167201943#N/AFALSE
1306
jacs.9b0949710.1021/jacs.9b09497FALSEhttps://doi.org/10.1021/jacs.9b09497Li, XPJ. Am. Chem. Soc.In coordination-driven self-assembly, 2,2':6',2 ''-terpyridine (tpy) has gained extensive attention in constructing supramolecular architectures on the basis of < tpy-M-tpy > connectivity. In direct self-assembly of large discrete structures, however, the metal ions were mainly limited to Cd(II), Zn(II), and Fe(II) ions. Herein, we significantly broaden the spectrum of metal ions with seven divalent transition metal ions M(II) (M = Mn, Fe, Co, Ni, Cu, Zn, Cd) to assemble a series of supramolecular fractals. In particular, Mn(II), Co(II), Ni(II), and Cu(II) were reported for the first time to form such large and discrete structures with (tpy-M-tpy) connectivity. In addition, the structural stabilities of those supramolecules in the gas phase and the kinetics of the ligand exchange process in solution were investigated using mass spectrometry. Such a fundamental study gave the relative order of structural stability in the gas phase and revealed the inertness of coordination in solution depending on the metal ions. Those results would guide the future study in tpy-based supramolecular chemistry in terms of self-assembly, characterization, property, and application.Introducing Seven Transition Metal Ions into Terpyridine-Based Supramolecules: Self-Assembly and Dynamic Ligand Exchange Study142020138#N/ATRUE
1307
jacs.9b0293610.1021/jacs.9b02936FALSEhttps://doi.org/10.1021/jacs.9b02936Li, YDJ. Am. Chem. Soc.Exploring high-performance zeolite-supported metal catalysts is of great significance. Herein, we develop a strategy for fabricating isolated single metal atomic site catalysts in Y zeolite (M-ISAS@Y, M = Pt, Pd, Ru, Rh, Co, Ni, Cu) by in situ separating and confining a metal-ethanediamine complex into beta-cages during the crystallization process followed by thermal treatment. The M-ISAS are stabilized by skeletal oxygens of Y zeolite, and the crystallinity, porosity, and large surface area are well inherited in m-ISASp Y. As a demonstration, acidic Pt-ISAS@Y is used for n-hexane isomerization involving consecutive catalytic dehydrogenation/hydrogenation on Pt-ISAS and isomerization on Bronsted acid sites. The turnover frequency value of Pt-ISAS reaches 727 h(-1), 5 times more than Pt nanopartiCles (similar to 3.5 nm), with a total isomer selectivity of more than 98%. This strategy provides a convenient route to fabricate promising zeolite-based M-ISAS catalysts for industrial applications.A General Strategy for Fabricating Isolated Single Metal Atomic Site Catalysts in Y Zeolitex73201943#N/AFALSE
1308
jacs.9b0252710.1021/jacs.9b02527FALSEhttps://doi.org/10.1021/jacs.9b02527Yu, SHJ. Am. Chem. Soc.The design of highly efficient non-noble-metal electro-catalysts for large-scale hydrogen production remains an ongoing challenge. We report here a Ni2P nanoarray catalyst grown on a commercial Ni foam substrate, which demonstrates an outstanding electrocatalytic activity and stability in basic electrolyte. The high catalytic activity can be attributed to the favorable electron transfer, superior intrinsic activity, and the intimate connection between the nanoarrays and their substrate. Moreover, the unique superaerophobic surface feature of the Ni2P nanoarrays enables a remarkable capability to withstand internal and external forces and release the in situ generated H-2 bubbles in a timely manner at large current densities (such as >1000 mA cm(-2)) where the hydrogen evolution becomes vigorous. Our results highlight that an aerophobic structure is essential to catalyze gas evolution for large-scale practical applications.Superaerophobic Nickel Phosphide Nanoarray Catalyst for Efficient Hydrogen Evolution at Ultrahigh Current Densitiesx145201948#N/AFALSE
1309
jacs.9b0252110.1021/jacs.9b02521https://doi.org/10.1021/jacs.9b02521Artero, VJ. Am. Chem. Soc.A push-pull organic dye and a cobaloxime catalyst were successfully cografted on NiO and CuGaO2 to form efficient molecular photocathodes for H-2 production with >80% Faradaic efficiency. CuGaO2 is emerging as a more effective p-type semiconductor in photoelectrochemical cells and yields a photocathode with 4-fold higher photocurrent I so densities and 400 mV more positive onset photocurrent potential compared to the one based on NiO. Such an optimized CuGaO2 photocathode was combined with a TaON vertical bar CoOx photoanode in a photoelectrochemical cell. Operated in this Z-scheme configuration, the two photo-electrodes produced H-2 and O-2 from water with 87% and 88% Faradaic efficiency, respectively, at pH 7 under visible light and in the absence of an applied bias, equating to a solar to hydrogen conversion efficiency of 5.4 X 10(-3)%. This is, to the best of our knowledge, the highest efficiency reported so far for a molecular-based noble metal-free water splitting Z-scheme.Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-SplittingPhotocatalyst46201947#N/AFALSE
1310
jacs.9b0935210.1021/jacs.9b09352FALSEhttps://doi.org/10.1021/jacs.9b09352Wang, GXJ. Am. Chem. Soc.Designing atomically dispersed metal catalysts for oxygen reduction reaction (ORR) is a promising approach to achieve efficient energy conversion. Herein, we develop a template-assisted method to synthesize a series of single metal atoms anchored on porous N,S-codoped carbon (NSC) matrix as highly efficient ORR catalysts to investigate the correlation between the structure and their catalytic performance. The structure analysis indicates that an identical synthesis method results in distinguished structural differences between Fe-centered single-atom catalyst (Fe-SAs/NSC) and Co-centered/Ni-centered single-atom catalysts (Co-SAs/NSC and Ni-SAs/NSC) because of the different trends of each metal ion in forming a complex with the N,S-containing precursor during the initial synthesis process. The Fe-SAs/NSC mainly consists of a well-dispersed FeN4S2 center site where S atoms form bonds with the N atoms. The S atoms in Co-SAs/NSC and Ni-SAs/NSC, on the other hand, form metal-S bonds, resulting in CoN3S1 and NiN3S1 center sites. Density functional theory (DFT) reveals that the FeN4S2 center site is more active than the CoN3S1 and NiN3S1 sites, due to the higher charge density, lower energy barriers of the intermediates, and products involved. The experimental results indicate that all three single-atom catalysts could contribute high ORR electrochemical performances, while Fe-SAs/NSC exhibits the highest of all, which is even better than commercial Pt/C. Furthermore, Fe-SAs/NSC also displays high methanol tolerance as compared to commercial Pt/C and high stability up to 5000 cyCles. This work provides insights into the rational design of the definitive structure of single-atom catalysts with tunable electrocatalytic activities for efficient energy conversion.Tuning the Coordination Environment in Single-Atom Catalysts to Achieve Highly Efficient Oxygen Reduction Reactions170201946#N/ATRUE
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jacs.9b0233810.1021/jacs.9b02338https://doi.org/10.1021/jacs.9b02338Xiao, WJJ. Am. Chem. Soc.The first asymmetric propargylic radical cyanation was realized through a dual photoredox and copper catalysis. An organic photocatalyst serves to both generate propargyl radicals and oxidize Cu(I) species to Cu(II) species. A chiral Cu complex functions as an efficient organometallic catalyst to resemble the propargyl radical and cyanide in an enantio-controlled manner. Thus, a diverse range of optically active propargyl cyanides were produced with high reaction efficiency and enantioselectivities (28 examples, 57-97% yields and 83-98% ee). Moreover, mechanistic investigations inCluding experiments and density functional theory calculations were performed to illustrate on the reaction pathway and stereochemical results.Asymmetric Propargylic Radical Cyanation Enabled by Dual Organophotoredox and Copper CatalysisPhotocatalyst79201952#N/AFALSE
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jacs.9b0896810.1021/jacs.9b08968FALSEhttps://doi.org/10.1021/jacs.9b08968Dinca, MJ. Am. Chem. Soc.RuNi nanopartiCles supported on a metal-organic framework (RuNi@MOF) and formed in situ from a ruthenium complex enClosed inside a nickel-based MOF act as a highly active catalyst for the Guerbet reaction of ethanol to I-butanol, providing turnover numbers up to 725 000 Ru-1. Negligible activity of the RuNi@MOF ethanol upgrading catalyst system toward chemically similar 1-butanol makes it possible to synthesize the competent Guerbet substrate 1-butanol with >99% selectivity.Metal-Organic Framework-Derived Guerbet Catalyst Effectively Differentiates between Ethanol and Butanol13201933#N/ATRUE
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jacs.9b0167610.1021/jacs.9b01676FALSEhttps://doi.org/10.1021/jacs.9b01676Arnoux, PJ. Am. Chem. Soc.Enzymatic regulations are central processes for the adaptation to changing environments. In the particular case of metallophore-dependent metal uptake, there is a need to quickly adjust the production of these metallophores to the metal level outside the cell, to avoid metal shortage or overload, as well as waste of metallophores. In Staphylococcus aureus, CntM catalyzes the last biosynthetic step in the production of staphylopine, a broad-spectrum metallophore, through the reductive condensation of a pathway intermediate (xNA) with pyruvate. Here, we describe the chemical synthesis of this intermediate, which was instrumental in the structural and functional characterization of CntM and confirmed its opine synthase properties. The three-dimensional structure of CntM was obtained in an open form, in the apo state or as a complex with substrate or product. The xNA substrate appears mainly stabilized by its imidazole ring through a pi-pi interaction with the side chain of Tyr240. Intriguingly, we found that metals exerted various and sometime antagonistic effects on the reaction catalyzed by CntM: zinc and copper are moderate activators at low concentration and then total inhibitors at higher concentration, whereas manganese is only an activator and cobalt and nickel are only inhibitors. We propose a model in which the relative affinity of a metal toward xNA and an inhibitory binding site on the enzyme controls Activation, inhibition, or both as a function of metal concentration. This metal-dependent regulation of a metallophore-producing enzyme might also take place in vivo, which could contribute to the adjustment of metallophore production to the internal metal level.Control by Metals of Staphylopine Dehydrogenase Activity during Metallophore Biosynthesisx10201936#N/AFALSE
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jacs.9b0873410.1021/jacs.9b08734FALSEhttps://doi.org/10.1021/jacs.9b08734Zhang, QWJ. Am. Chem. Soc.A nickel-catalyzed asymmetric allylation of secondary phosphine oxides (SPO) for the synthesis of tertiary phosphine oxides (TPO) was realized with high enantioselectivity. The dynamic kinetic asymmetric transformation of SPO was accomplished in the presence of nickel complex. By elucidating the absolute configurations of the reacted SPO starting material and the TPO product, we confirmed that the allylation reaction proceeded through a P-stereo retention process. The protocol represents the first example of synthesizing P-stereogenic phosphine oxides by allylation reaction.Ni-Catalyzed Asymmetric Allylation of Secondary Phosphine Oxides20201978#N/ATRUE
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jacs.9b0858610.1021/jacs.9b08586FALSEhttps://doi.org/10.1021/jacs.9b08586Knochel, PChromium(II)-Catalyzed Diastereoselective and Chemoselective Csp(2)-Csp(3) Cross-Couplings Using Organomagnesium Reagents2019#N/ATRUE
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jacs.9b0680810.1021/jacs.9b06808FALSEhttps://doi.org/10.1021/jacs.9b06808Li, JJ. Am. Chem. Soc.Single-atom catalysts (SACs) and single-Cluster catalysts (SCCs) are the new frontier of heterogeneous catalysis, which exhibit high activity, selectivity, stability, and atomic efficiency as well as precise tunability. However, the lack of efficient methods for producing high-loading and high-purity SACs and SCCs hinders their industrial applications. In this work, we propose a general and efficient strategy for the production of high-loading and high-purity SACs and SCCs anchored on suitable substrates. Our strategy relies on the existence of an electrochemical potential window (EcPW) we predict within which any aggregate forms of the target metal on the substrate are leached away by electrochemical oxidation, while the strongly bound single atoms or single Clusters remain at the substrate. We demonstrate the applicability of this strategy with modeling the production of Pt, Pd, and Ni SACs anchored on N-doped graphene and Fe2O3 as well as Pt-3 and Ni-3 SCCs anchored on graphdiyne.Constructing High-Loading Single-Atom/Cluster Catalysts via an Electrochemical Potential Window Strategy33202081#N/ATRUE
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jacs.9b0093910.1021/jacs.9b00939FALSEhttps://doi.org/10.1021/jacs.9b00939Chirik, PJJ. Am. Chem. Soc.The synthesis and spectroscopic characterization of a family of Ni X (X = Cl, Br, I, H) complexes supported by the bulky alpha-diimine chelate N,N'-bis(1R,2R,3R,5S)-(-)-iso-pinocampheyl-2,3-butanediimine ((ipc)ADI) are described. Diimine-supported, three-coordinate nickel(I)-X complexes have been proposed as key intermediates in a host of catalytic transformations such as C-C and C-heteroatom cross coupling and C-H functionalization but have until now remained synthetically elusive. A combination of structural, spectroscopic, electrochemical, and computational studies were used to establish the electronic structure of each monomeric [((ipc)ADI)NiX] (X = Cl, Br, I) complex as a nickel(I) derivative supported by a redox-neutral alpha-diimine chelate. The dimeric nickel hydride, [((ipc)ADI)Ni(mu(2)-H)](2), was prepared and characterized by X-ray diffraction; however, magnetic measurements and 'H NMR spectroscopy support monomer formation at ambient temperature in THE solution. This nickel hydride was used as a precatalyst for the hydrogen isotope exchange (HIE) of C-H bonds in arenes and pharmaceuticals. By virtue of the multisite reactivity and high efficiency, the new nickel precatalyst provided unprecedented high specific activities (50-99 C-i/mmol) in radiolabeling, meeting the threshold required for radioligand binding assays. Use of air-stable and readily synthesized nickel precursor, [((ipc)ADI)NiBr2], broad functional group tolerance, and compatibility with polar protic solvents are additional assets of the nickel-catalyzed HIE method.Ni(I)-X Complexes Bearing a Bulky alpha-Diimine Ligand: Synthesis, Structure, and Superior Catalytic Performance in the Hydrogen Isotope Exchange in Pharmaceuticalsx392019101#N/AFALSE
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jacs.9b0638310.1021/jacs.9b06383FALSEhttps://doi.org/10.1021/jacs.9b06383Sanford, MSJ. Am. Chem. Soc.This ArtiCle describes the development of a stable Ni-IV complex that mediates C(sp(2)) - H trifluoromethylation reactions. This reactivity is first demonstrated stoichiometrically and then successfully translated to a Ni-IV-catalyzed C-H trifluoromethylation of electron-rich arene and heteroarene substrates. Both experimental and computational mechanistic studies support a radical chain pathway involving Ni-IV, Ni-III, and Ni-II intermediates.Nickel(IV)-Catalyzed C-H Trifluoromethylation of (Hetero)arenes20201942#N/ATRUE
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jacs.9b0066910.1021/jacs.9b00669https://doi.org/10.1021/jacs.9b00669Molander, GAJ. Am. Chem. Soc.DNA-encoded library (DEL) technology is a powerful tool commonly used by the pharmaceutical industry for the identification of compounds with affinity to biomolecular targets. Success in this endeavor lies in sampling diverse chemical libraries. However, current DELs tend to be deficient in C(sp(3)) carbon counts. We report unique solutions to the challenge of increasing both the chemical diversity of these libraries and their C(sp(3)) carbon counts by merging Ni/photoredox dual catalytic C(sp(2))-C(sp(3)) cross-coupling as well as photoredox-catalyzed radical/polar crossover Alkylation protocols with DELs. The successful integration of multiple Classes of radical sources enables the rapid incorporation of a diverse set of Alkyl fragments.Open-Air Alkylation Reactions in Photoredox-Catalyzed DNA-Encoded Library SynthesisPhotocatalyst113201995#N/AFALSE
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jacs.9b0054910.1021/jacs.9b00549FALSEhttps://doi.org/10.1021/jacs.9b00549Fischer, RAJ. Am. Chem. Soc.The oxygen evolution reaction (OER) is a key process for renewable energy storage. However, developing non-noble metal OER electrocatalysts with high activity, long durability and scalability remains a major challenge. Herein, high OER activity and stability in alkaline solution were discovered for mixed nickel/cobalt hydroxide electrocatalysts, which were derived in one-step procedure from oriented surface-mounted metal-organic framework (SURMOF) thin films that had been directly grown layer-by-layer on macro- and microelectrode substrates. The obtained mass activity of similar to 2.5 mA.mu g(-1) at the defined overpotential of 300 mV is 1 order of magnitude higher than that of the benchmarked IrO2 electrocatalyst and at least 3.5 times higher than the mass activity of any state-of-the-art NiFe-, FeCoW-, or NiCo-based electrocatalysts reported in the literature. The excellent morphology of the SURMOF-derived ultrathin electrocatalyst coating led to a high exposure of the most active Ni- and Co-based sites.Unprecedented High Oxygen Evolution Activity of Electrocatalysts Derived from Surface-Mounted Metal-Organic Frameworksx60201960#N/AFALSE
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jacs.9b0015910.1021/jacs.9b00159FALSEhttps://doi.org/10.1021/jacs.9b00159Driess, MJ. Am. Chem. Soc.The synthesis and tautomerization of a half-parent aminosilylene and its heavy P- and As-analogues ((LSi)-L-TMS-EH2; E = N, P, As; L-TMS = N(SiMe3)(2,6-(Pr2C6H3)-Pr-i)) in the coordination sphere of nickel(0) to give the corresponding side-on eta(2)-RSi(H)=EH and RH2Si-E (silylpnictinidene) nickel complexes are reported. These complexes can be accessed through salt metathesis reactions of the lithium dihydropnictides LiEH2 with the acyClic chlorosilylene nickel(0) complex 1, [L-TMS(Cl)Si -> Ni(NHC)(2); NHC = :C[(Pr-i)NC(Me)](2)). In addition, we report the facile E-H bond Activation reactions of EH3 with 1, which furnished a silyl nickel(II) complex through NH3 Activation, but phosphido and arsenido complexes in the Activation of PH3 and AsH3, respectively. Notably, reaction of 1 with LiNH2 leads to the acyClic bis(amido)silylene complex [L-TMS(H2N)Si -> Ni(NHC)(2)] 5, which does not undergo N-H proton migration to silicon(II) under ambient conditions. The transformation of the P- and As-analogues of 1 furnishes directly the respective side-on Si=E Ni complexes (nickelacyCles), [eta(2)-{L-TMS(H) Si=E(H)}Ni(NHC)(2)] (E = P, 6; E = As, 9). These nickelacyCles show a vastly different stability in solutions. While 6 is stable for several days at ambient temperature, 9 undergoes further rearrangement processes within minutes of its formation. Given the high acidity of the As-H proton in 9, however, this moiety can be trapped as a highly charge separated metalated-eta(2)-silaarsene nickel complex 12 that is best described as an [AsSiNi] nickelacyCle with Si-As multiple bond character. Taken as a whole, these results give, for the first time, insights into the relative stability of the tautomeric forms of side-on silaldimine transition metal complexes. The electronic nature and the rearrangement processes of these compounds were also investigated by quantum chemical calculations.Versatile Tautomerization of EH2-Substituted Silylenes (E = N, P, As) in the Coordination Sphere of Nickelx4201960#N/AFALSE
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jacs.9b0014410.1021/jacs.9b00144https://doi.org/10.1021/jacs.9b00144Shankar, KJ. Am. Chem. Soc.Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nuCleus due to the aromatic pi network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR Clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr(3) based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C(3)N(5 )blended with MA(x)FA(1-x)Pb(I0.85Br0.15)(3) perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intrasheet cavity make it an attractive supramolecular adsorbent for environmental applications.C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Framework for Photocatalytic, Photovoltaic and Adsorbent ApplicationsPhotocatalyst1062019174#N/AFALSE
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jacs.960765910.1021/jacs.9607659FALSEhttps://doi.org/10.1021/jacs.9607659Tilley, RDJ. Am. Chem. Soc.The direct growth of Pt islands on lattice mismatched Ni nanopartiCles is a major synthetic challenge and a promising strategy to create highly strained Pt atoms for electrocatalysis. By using very mild reaction conditions, Pt islands with tunable strain were formed directly on Ni branched partiCles. The highly strained 1.9 nm Pt-island on branched Ni nanopartiCles exhibited high specific activity and the highest mass activity for hydrogen evolution (HER) in a pH 13 electrolyte. These results show the ability to synthetically tune the size of the Pt islands to control the strain to give higher HER activity.Direct Growth of Highly Strained Pt Islands on Branched Ni NanopartiCles for Improved Hydrogen Evolution Reaction Activityx41201948#N/AFALSE
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jacs.9b0523010.1021/jacs.9b05230FALSEhttps://doi.org/10.1021/jacs.9b05230Solomon, EIJ. Am. Chem. Soc.High potential multicopper oxidases (MCOs) have T1 reduction potentials >600 mV (vs normal hydrogen electrode), making them important catalysts for O-2 reduction in various biotechnological applications. The oxygen reduction mechanism for the low potential MCOs is well-characterized; however, O-2 reactivity of high potential MCOs is not well understood. In this study, we have shown that laccase from Trametes versicolor, where the T1 redox potential is increased by similar to 350 mV over that of the low potential MCOs corresponding to an 8 kcal/mol decrease in the driving force, exhibits a slower intramolecular electron transfer (IET) rate to the trinuClear Cu Cluster (TNC) in the native intermediate (NI), relative to the low potential MCO from Rhus vernicifera laccase. This IET rate is, however, >10(2) times faster than the decay rate of the NI, demonstrating that this intermediate form of the enzyme is catalytically relevant enabling fast turnover. However, in contrast to the low potential MCOs where T1 reduction by substrate is rate limiting, the rate limiting step in turnover of high potential MCOs is the first IET to NI. Part of the reduction potential difference of the T1 sites in high vs low potential MCOs is balanced by an similar to 100 mV higher reduction potential of NI due to the more positive protein environment in the vicinity of the TNC.O-2 Reduction to Water by High Potential Multicopper Oxidases: Contributions of the T1 Copper Site Potential and the Local Environment of the TrinuClear Copper Cluster14201954#N/ATRUE
1325
jacs.8b1355210.1021/jacs.8b13552FALSEhttps://doi.org/10.1021/jacs.8b13552Illas, FRoom Temperature Methane Capture and Activation by Ni Clusters Supported on TiC(001): Effects of Metal-Carbide Interactions on the Cleavage of the C-H Bondx2019#N/AFALSE
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jacs.9b0493710.1021/jacs.9b04937FALSEhttps://doi.org/10.1021/jacs.9b04937Kitagawa, HJ. Am. Chem. Soc.We first demonstrate the influence of d-elements on the electronic-state alternation of molecules coupled with proton transfer in d-pi hybridized electron systems. Compact and planar metal complexes with protonated 2,3-pyrazinedithiolates (L), M(HL)(2) (M = Ni, Pd, and Pt), were synthesized and subsequently determined to be assembled by hydrogen bond (H-bond) interactions between pyrazine moieties. Structural and theoretical investigations revealed that these complexes are regarded as d-pi hybridized electron systems based on a M(S2C2)(2) core, especially, significant d-pi hybridization in the Pt(S2C2)(2) core was indicated. The pH-dependent optical and electrochemical measurements revealed that the Ni complex has a higher proton-accepting character and a stronger pH dependence for redox potential compared with the Pt complex. This indicates that the Ni complex has a larger amount of pi-electron density on ligands than the Pt complex because the significant d-pi hybridization in the Pt complex could reduce the amount of pi-electron reconstructed by attaching/detaching proton. CyClic voltammetry of Ni and Pt complexes that form an H-bonded multimer showed a potential splitting at the first redox wave (Delta E-1/2 = 0.28 V for M = Ni and 0.17 V for M = Pt) corresponding to a mixed-valence state coupled with proton transfer. The Delta E-1/2 values indicate that the change in electronic states by proton transfer is remarkable in the Ni complex, but moderate in the Pt complex. These experimental results lead that the d-element substitution plays a role in controlling the degree of proton-electron coupling in d-pi hybridized electron systems.Role of d-Elements in a Proton-Electron Coupling of d-pi Hybridized Electron Systems9201940#N/ATRUE
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jacs.9b0412310.1021/jacs.9b04123FALSEhttps://doi.org/10.1021/jacs.9b04123Shionoya, MJ. Am. Chem. Soc.Hetero-multinuClear metal complexes are a promising Class of compounds applicable to photoluminescence, magnetism, and catalysis. In this work, we have developed a synthetic method for hetero-tetranuClear metal complexes by combining advantages of site-selective redox switching and transmetalation. First, a homo-tetranuClear (Co4I)-I-II complex was converted to a mixed-valence (CoCo3II)-Co-III complex by site-selective oxidation, which was then transmetalated from Co-II to N-II to form a heterometallic (CoCo3II)-Co-III complex. Finally, a (CoCo3II)-Co-III complex was synthesized by metal-selective reduction on the Co' site. The basic structural frameworks of the main products in the whole process starting from the Co-4(II) complex are isostructural. Notably, the (CoCo3II)-Co-III complex was not accessible by direct mixing of ligand, Co-II, and Ni-II. This method would provide an alternative strategy for highly selective synthesis of hetero-multinuClear metal complexes.Synthesis of Hetero-multinuClear Metal Complexes by Site-Selective Redox Switching and Transmetalation on a Homo-multinuClear Complex19201943#N/ATRUE
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jacs.8b1349910.1021/jacs.8b13499FALSEhttps://doi.org/10.1021/jacs.8b13499Diao, TNJ. Am. Chem. Soc.Ni(I)-mediated single-electron oxidative Activation of Alkyl halides has been extensively proposed as a key step in Ni-catalyzed cross-coupling reactions to generate radical intermediates. There are four mechanisms through which this step could take place: oxidative addition, outer-sphere electron transfer, inner-sphere electron transfer, and concerted halogen atom abstraction. Despite considerable computational studies, there is no experimental study to evaluate all four pathways for Ni(I)-mediated Alkyl radical formation. Herein, we report the isolation of a series of (Xantphos)Ni(I)-Ar complexes that selectively activate Alkyl halides over Aryl halides to eject radicals and form Ni(II) complexes. This observation allows the application of kinetic studies on the steric, electronic, and solvent effects, in combination with DFT calculations, to systematically assess the four possible pathways. Our data reveal that (Xantphos)Ni(I)-mediated Alkyl halide Activation proceeds via a concerted halogen-atom abstraction mechanism. This result corrB(OH)2rates previous DFT studies on (terpy)Ni(I)- and (py)Ni(I)-mediated Alkyl radical formation, and contrasts with the outer-sphere electron transfer pathway observed for (PPh3)(4)Ni(O)-mediated Aryl halide Activation. This study of a model system provides insight into the overall mechanism of Ni-catalyzed cross-coupling reactions and offers a basis for differentiating electrophiles in cross-electrophile coupling reactions.Mechanistic Characterization of (Xantphos)Ni(I)-Mediated Alkyl Bromide Activation: Oxidative Addition, Electron Transfer, or Halogen-Atom Abstractionx50201965#N/AFALSE
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jacs.9b0344110.1021/jacs.9b03441FALSEhttps://doi.org/10.1021/jacs.9b03441Mirica, KAJ. Am. Chem. Soc.This paper describes the synthesis of a novel intrinsically conductive two-dimensional (2D) covalent organic framework (COF) through the aromatic annulation of 2,3,9,10,16,17,23,24-octa-aminophthalocyanine nickel(II) and pyrene-4,5,9,10-tetraone. The intrinsic bulk conductivity of the COF material (termed COF-DC-8) reached 2.51 X 10(-3) S/m, and increased by 3 orders of magnitude with I-2 doping. Electronic calculations revealed an anisotropic band structure, with the possibility for significant contribution from out-of-plane charge-transport to the intrinsic bulk conductivity. Upon integration into chemiresistive devices, this conductive COF showed excellent responses to various reducing and oxidizing gases, inCluding NH3, H2S, NO, and NO2, with parts-per-billion (ppb) limits of detection (for NH3 = 70 ppb, for H2S = 204 ppb, for NO = 5 ppb, and for NO2 = 16 ppb based on 1.5 min exposure). Electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy studies suggested that the chemiresistive response of the COF-DC-8 involves charge transfer interactions between the analyte and nickelphthalocyanine component of the framework.Two-Dimensional Chemiresistive Covalent Organic Framework with High Intrinsic Conductivity99201996#N/ATRUE
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jacs.9b0297310.1021/jacs.9b02973FALSEhttps://doi.org/10.1021/jacs.9b02973Nevado, CJ. Am. Chem. Soc.Olefins devoid of directing or activating groups have been dicarbofunctionalized here with two electrophilic carbon sources under reductive conditions. Simultaneous formation of one C(sp(3))-C(sp(3)) and one C(sp(3))-C(sp(2)) bond across a variety of unbiased pi-systems proceeds with exquisite selectivity by the combination of a Ni catalyst with TDAE as sacrificial reductant. Control experiments and computational studies revealed the feasibility of a radical-based mechanism involving, formally, two interconnected Ni(I)/Ni(III) processes and demonstrated the different ability of Ni(I) species (Ni(I)I vs PhNi(I)) to reduce the C(sp(3))-I bond. The role of the reductant was also investigated in depth, suggesting that a one-electron reduction of Ni(II) species to Ni(I) is thermodynamically favored. Further, the preferential Activation of Alkyl vs Aryl halides by ArNi(I) complexes as well as the high affinity of ArNi(II) for secondary over tertiary C-centered radicals explains the lack of undesired homo- and direct coupling products (Ar-Ar, Ar-Alk) in these transformations.Ni-Catalyzed Reductive Dicarbofunctionalization of Nonactivated Alkenes: Scope and Mechanistic Insights68201976#N/ATRUE
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jacs.9b0241110.1021/jacs.9b02411FALSEhttps://doi.org/10.1021/jacs.9b02411Sanford, MSJ. Am. Chem. Soc.This paper describes the one-electron interconversions of isolable Ni-III and Ni-IV complexes through their reactions with carbon-centered radicals (R center dot). First, model Ni-III complexes are shown to react with Alkyl and Aryl radicals to afford Ni-IV products. Preliminary mechanistic studies implicate a pathway involving direct addition of a carbon-centered radical to the Ni-III center. This is directly analogous to the known reactivity of Ni-II complexes with R center dot, a step that is commonly implicated in catalysis. Second, a Ni-IV-CH3 complex is shown to react with Aryl and Alkyl radicals to afford C-C bonds via a proposed S(H)2-type mechanism. This pathway is leveraged to enable challenging H3C-CF3 bond formation under mild conditions. Overall, these investigations suggest that Ni-II/III/IV sequences may be viable redox pathways in high-oxidation-state nickel catalysis.Connecting Organometallic Ni(III) and Ni(IV): Reactions of Carbon-Centered Radicals with High-Valent Organonickel Complexes16201961#N/ATRUE
1332
jacs.8b1249510.1021/jacs.8b12495https://doi.org/10.1021/jacs.8b12495Yin, SFJ. Am. Chem. Soc.Functional group substituted 1-naphthylamines, especially N-methylated ones, play important roles in numerous chemical and biological processes. However, these compounds' general and step economic syntheses are highly limited, which seriously restricts efforts to improve the properties and develop new functions for this kind of compound. In this report, we describe the development of an efficient, convenient, and general method for the synthesis of valuable functionalized 1-naphthylamines directly from readily available terminal alkynes, 2-bromoAryl ketones, and amides via Cu(I)-catalyzed benzannulation in a green solvent (i.e., water) under Pd- and ligand-free conditions. A total of 82 functionalized 1-naphthylamines, especially synthetically and biologically useful N-methylated compounds, are synthesized in isolated yields up to 95%. Some unique features of the reaction are as follows: (1) exClusive 6-endo-dig selectivity, (2) ready incorporation of a broad range of functional groups directly from easily available substrates, and (3) amides that can be used as aminating agents and that are excellent alternatives to toxic and/or odorous amines. Due to facile tuning of functional groups for the reaction, the products possess good electronic donor-acceptor structures and exhibit intriguing photophysical properties, such as tunable and polarity-sensitive fluorescence emission and large Stokes shifts (up to 258 nm). Utilizing the products' unique polarity sensitive fluorescence response, we successfully applied the 1-naphthylamine derivatives, such as compound 91, to image lipid droplets (LDs) and monitor cellular LDs growth. The previously mentioned advantages of this methodology, along with the mild conditions, simple operation, and scalable synthesis, may allow this novel reaction to be extended to varied applications in chemistry, biology, and materials science.Cu(I)-Catalyzed 6-endo-dig CyClization of Terminal Alkynes, 2-BromoAryl Ketones, and Amides toward 1-Naphthylamines: Applications and Photophysical PropertiesPhotocatalyst222019104#N/AFALSE
1333
jacs.9b0228610.1021/jacs.9b02286FALSEhttps://doi.org/10.1021/jacs.9b02286Peng, ZMJ. Am. Chem. Soc.Designing highly active oxygen reduction reaction (ORR) catalysts is crucial to boost the fuel cell economy. Previous research has mainly focused on Pt-based alloy catalysts in which surface Pt is the solely active site and the activity improvement was challenged by the discovered scaling relationship. Herein we report a new concept of utilizing dual active sites for the ORR and demonstrate its effectiveness by synthesizing a SnOx/Pt-Cu-Ni heterojunctioned catalyst. A maximum of 40% enhancement in the apparent specific activity, which corresponds to 10-fold enhancement on interface sites, is measured compared with pure Pt-Cu-Ni. Detailed investigations suggest an altered dual-site cascade mechanism wherein the first two steps occur on SnO, sites and the remaining steps occur on adjacent Pt sites, allowing a significant decrease in the energy barrier. This study with the suggested dual-site cascade mechanism shows the potential to overcome the ORR energy barrier bottleneck to develop highly active catalysts.Dual-Site Cascade Oxygen Reduction Mechanism on SnOx/Pt-Cu-Ni for Promoting Reaction Kinetics23201937#N/ATRUE
1334
jacs.9b0154110.1021/jacs.9b01541FALSEMuraoka, TFormation of Giant and Small CyClic Complexes from a Flexible Tripeptide Ligand Controlled by Metal Coordination and Hydrogen Bonds2019#N/ATRUE
1335
jacs.8b1202510.1021/jacs.8b12025https://doi.org/10.1021/jacs.8b12025MacMillan, DWCJ. Am. Chem. Soc.A strategy for the installation of small Alkyl fragments onto pharmaceutically relevant aliphatic structures has been established via metallaphotoredox catalysis. Herein, we report that tris(trimethylsilyl)silanol can be employed as an effective halogen abstraction reagent that, in combination with photoredox and nickel catalysis, allows a generic approach to C-sp(3)-c(sp)(3) cross-electrophile coupling. In this study, we demonstrate that a variety of aliphatic drug-like groups can be successfully coupled with a number of commercially available small Alkyl electrophiles, inCluding methyl tosylate and strained cyClic Alkyl bromides. Moreover, the union of two secondary aliphatic carbon centers, a long-standing challenge for organic molecule construction, has been accomplished with a wide array of structural formats. Last, this technology can be selectively merged with C-sp(2)-C-sp(3) Aryl-Alkyl couplings to build drug-like systems in a highly modular fashion.Metallaphotoredox-Catalyzed Cross-Electrophile C-sp(3)-C-sp(3) Coupling of Aliphatic BromidesPhotocatalyst562018616/15/2022FALSE
1336
jacs.8b1194210.1021/jacs.8b11942https://doi.org/10.1021/jacs.8b11942Engle, KMJ. Am. Chem. Soc.A nickel-catalyzed conjunctive cross-coupling of simple alkenyl amides with Aryl iodides and Aryl boronic esters is reported. The reaction is enabled by an electron-deficient olefin (EDO) ligand, dimethyl fumarate, and delivers the desired 1,2-diArylated products with excellent regiocontrol. Under optimized conditions, a wide range of amides derived from 3-butenoic acid, 4-pentenoic acid, and allyl amine are compatible substrates. This method represents the first example of regiocon-trolled 1,2-diArylation directed by a native amide functional group. Computational analysis sheds light on the potential substrate binding mode and the role of the EDO ligand in the reductive elimination step.Nickel-Catalyzed 1,2-DiArylation of Simple Alkenyl Amidesx82201836#N/AFALSE
1337
jacs.8b1173410.1021/jacs.8b11734FALSEhttps://doi.org/10.1021/jacs.8b11734Yu, JHJ. Am. Chem. Soc.Hierarchical nanozeolites are highly desired for heavy oil conversion because of their fast mass transfer, good site accessibility, and short diffusion length compared with their conventional counterparts. Here, we provide a facile amino acid-assisted strategy to synthesize hierarchical ZSM-5 (MFI) zeolite nanocrystals by two-step crystallization in a concentrated gel system. Strikingly, each virus-like zeolite nanopartiCle with abundant interconnected intracrystalline mesopores is a high-quality single crystal that is defect-free as confirmed by electron diffraction and NMR analysis. By utilizing advanced electron microscopy techniques, we have studied the evolution process of single-crystalline hierarchical ZSM-5 nanocrystals that involves oriented aggregation of protozeolitic nanopartiCles formed at low temperature followed by intrapartiCle ripening at high temperature. The as-prepared hierarchical Ni@ZSM-5 catalysts exhibit superior catalytic performance in hydro-deoxygenation of stearic acid and palm oil.Amino Acid-Assisted Construction of Single-Crystalline Hierarchical Nanozeolites via Oriented-Aggregation and IntrapartiCle Ripeningx52201933#N/AFALSE
1338
jacs.9b0135610.1021/jacs.9b01356FALSEhttps://doi.org/10.1038/ncomms9619Patzke, GRMechanistically Driven Control over Cubane Oxo Cluster Catalysts2019#N/ATRUE
1339
jacs.9b0121410.1021/jacs.9b01214FALSEhttps://doi.org/10.1021/ol060752jWan, LJSe-Doping Activates FeOOH for Cost-Effective and Efficient Electrochemical Water Oxidation2019#N/ATRUE
1340
jacs.8b1141310.1021/jacs.8b11413FALSEhttps://doi.org/10.1021/jacs.8b11413Tarascon, JMJ. Am. Chem. Soc.Disordered rock salt cathodes showing both anionic and cationic redox are being extensively studied for their very high energy storage capacity. Mn-based disordered rock salt compounds show much higher energy efficiency compared to the Ni-based materials as a result of the different voltage hysteresis, 0.5 and 2 V, respectively. To understand the origin of this difference, we herein report the design of two model compounds, Li1.3Ni0.27Ta0.43O2 and Li1.3Mn0.4Ta0.3O2, and study their charge compensation mechanism through the uptake and removal of Li via an arsenal of analytical techniques. We show that the different voltage hysteresis with Ni or Mn substitution is due to the different reduction potential for anionic redox. We rationalized such a finding by DFT calculations and propose this phenomenon to be nested in the smaller charge transfer band gap of the Ni-based compounds compared to that of the Mn ones. Altogether, these findings provide vital guidelines for designing high-capacity disordered rock salt cathode materials based on anionic redox activity for the next generation of Li ion batteries.Charge Transfer Band Gap as an Indicator of Hysteresis in Li-Disordered Rock Salt Cathodes for Li-Ion Batteriesx28201946#N/AFALSE
1341
jacs.9b0093710.1021/jacs.9b00937FALSEhttps://doi.org/10.1021/jacs.9b00937Delcamp, JHJ. Am. Chem. Soc.Photocatalytic conversion of CO, to reduced carbon states using sunlight and an earth-abundant catalyst could provide a critically needed source of renewable energy. Very few earth-abundant catalysts have shown CO2 to CH4 reactivity, and significant opportunities exist to improve catalyst durability. Through the strategic design of a novel, redox-active bipyridyl-N-heterocyClic carbene macrocyClic ligand complexed with nickel, CO2 is converted into the energy-rich solar fuel, CH4, photocatalytically with a photosensitizer in the presence of water. Up to 19 000 turnovers of CH4 from CO2 are observed. An exceptional turnover number of 570 000 for CH4 production via a photodriven formal hydrogenation of CO to CH4 was also found. This unique reactivity from a tunable, highly durable macrocyClic framework was studied via a series of photocatalytic and electrocatalytic reactions varying the atmospheric composition, as well as by isotopic labeling experiments and quantum yield calculations to evaluate the effect of ligand structure on product generation.Durable Solar-Powered Systems with Ni-Catalysts for Conversion of CO2 or CO to CH448201935#N/ATRUE
1342
jacs.8b1130310.1021/jacs.8b11303FALSEhttps://doi.org/10.1021/jacs.8b11303Sun, SHJ. Am. Chem. Soc.We report a new strategy of controlling catalytic activity and selectivity of Cu nanopartiCles (NPs) for the ammonia borane initiated hydrogenation reaction. Cu NPs are active and selective for chemoselective reduction of nitrostyrene to Vinylaniline under ambient conditions. Their activity, selectivity, and more importantly, stability are greatly enhanced by their anchoring on WO2.72 nanorods, providing a room-temperature full conversion of nitrostyrene selectively to Vinylaniline (>99% yield). Compared with all other catalysts developed thus far, our new Cu/WO2.72 catalyst shows much enhanced hydrogenation selectivity and stability without the use of pressured hydrogen. The synthetic approach demonstrated here can be extended to prepare various M/WO2.72 catalysts (M = Fe, Co, Ni), with M being stabilized for many chemical reactions.Room-Temperature Chemoselective Reduction of 3-Nitrostyrene to 3-Vinylaniline by Ammonia Borane over Cu NanopartiClesx33201838#N/AFALSE
1343
jacs.8b1126210.1021/jacs.8b11262FALSEhttps://doi.org/10.1021/jacs.8b11262Nocera, DGJ. Am. Chem. Soc.A reaction cyCle for redox-mediated, Ni-catalyzed Aryl etherification is proposed under both photoredox and electrochemically mediated conditions. We demonstrate that a self-sustained Ni(I/III) cyCle is operative in both cases by chemically synthesizing and characterizing a common paramagnetic Ni intermediate and establishing its catalytic activity. Furthermore, deleterious pathways leading to off-cyCle Ni(II) species have been identified, allowing us to discover optimized conditions for achieving self-sustained reactivity at a,15 fold increase in the quantum yield and a 3-fold increase in the faradaic yield. These results highlight the importance of leveraging insight of complete reaction cyCles for increasing the efficiency of redox-mediated reactions.Elucidation of a Redox-Mediated Reaction CyCle for Nickel-Catalyzed Cross Couplingx41201921#N/AFALSE
1344
jacs.8b1370110.1021/jacs.8b13701FALSEhttps://doi.org/10.1021/ol0495063Huang, HTValence Engineering via Selective Atomic Substitution on Tetrahedral Sites in Spinel Oxide for Highly Enhanced Oxygen Evolution Catalysis2019#N/ATRUE
1345
jacs.8b1115910.1021/jacs.8b11159FALSEhttps://doi.org/10.1021/jacs.8b11159Murakami, MJ. Am. Chem. Soc.A convenient method for the synthesis of 1,3-dienes from readily available compounds is reported. 2-Aryoxy-1,3-dienes are produced stereoselectively by a nickel-catalyzed reaction of propargyl carbonates with phenols. Functional group tolerance is broad to allow iodo, Carbonyl, and boryl groups. The resulting 1,3-dienes are of much synthetic value because they can participate in a wide variety of reactions, inCluding the Diels Alder reaction.Synthesis of 2-Aryloxy-1,3-dienes from Phenols and Propargyl Carbonatesx9201945#N/AFALSE
1346
jacs.8b1353410.1021/jacs.8b13534FALSEhttps://doi.org/10.1021/jacs.8b13534Cornella, JJ. Am. Chem. Soc.Herein we present a Ni-catalyzed Alkylation of C-SMe with Alkyl bromides for the decoration of heterocyClic frameworks. The protocol, reminiscent to the Liebeskind-Srogl coupling, makes use of simple C(sp(2))-SMe to be engaged in a reductive coupling. The reaction is suitable for a preponderance of highly valuable heterocyClic motifs. In addition to cyClic bromides, noncyClic Alkyl bromides are well accommodated with exquisite levels of retention over isomerization. The protocol is scalable and permits orthogonal couplings in the presence of other functionalization handles.Ni-Catalyzed Reductive Liebeskind-Srogl Alkylation of HeterocyCles20201968#N/ATRUE
1347
jacs.8b0944910.1021/jacs.8b09449https://doi.org/10.1021/jacs.8b09449Boettcher, SWJ. Am. Chem. Soc.Solar water splitting provides a mechanism to convert and store solar energy in the form of stable chemical bonds. Water-splitting systems often inClude semiconductor photoanodes, such as n-Fe2O3 and n-BiVO4, which use photogenerated holes to oxidize water. These photoanodes often exhibit improved performance when coated with metal-oxide/(oxy)hydroxide overlayers that are catalytic for the water-oxidation reaction. The mechanism for this improvement, however, remains a controversial topic. This is, in part, due to a lack of experimental techniques that are able to directly track the flow of photogenerated holes in such multicomponent systems. In this Perspective, we illustrate how this issue can be addressed by using a second working electrode to make direct current/voltage measurements on the catalytic overlayer during operation in a photoelectrochemical cell. We discuss examples where the second working electrode is a thin metallic film deposited on the catalyst layer, as well as where it is the tip of a conducting atomic-force-microscopy probe. In applying these techniques to multiple semiconductors (Fe2O3, BiVO4, Si) paired with various metal-(oxy)hydroxide overlayers (e.g., Ni(Fe)OxHy and CoOxHy)) we found in all cases investigated that the overlayers collect photogenerated holes from the semiconductor, charging to potentials sufficient to drive water oxidation. The overlayers studied thus form charge-separating heterojunctions with the semiconductor as well as serve as water-oxidation catalysts.Metal Oxide/(oxy)hydroxide Overlayers as Hole Collectors and Oxygen-Evolution Catalysts on Water-Splitting PhotoanodesPhotocatalyst68201984#N/AFALSE
1348
jacs.8b1316910.1021/jacs.8b13169FALSEhttps://doi.org/10.1021/jacs.8b13169Shinokubo, HJ. Am. Chem. Soc.Ni(II) 10-Phosphacorrole, a porphyrinoid containing phosphorus at the meso position, was synthesized from a bis(alpha,alpha'-dibromodipyrrin) Ni(II) complex and a phosphine anion via the palladium-catalyzed formation of a C-C and two C-P bonds. The optoelectronic properties of Ni(II) 10-phosphacorrole can be modulated effectively by oxidation or coordination of a metal to the phosphorus center. While Ni(II) 10-phosphacorrole exhibits a distinctly aromatic character due to the cyClic conjugation of 18 pi-electrons, its oxide exhibited weak antiaromaticity, which was confirmed experimentally and theoretically.Ni(II) 10-Phosphacorrole: A Porphyrin Analogue Containing Phosphorus at the Meso Position12201970#N/ATRUE
1349
jacs.8b0910810.1021/jacs.8b09108FALSEhttps://doi.org/10.1021/jacs.8b09108Switzer, JAJ. Am. Chem. Soc.Surfaces of achiral materials exhibit two dimensional chirality if they lack mirror symmetry. An example is the (643) surface of face-centered-cubic metals such as Au. The (643) and ((643) over bar) surfaces are non-superimposable mirror images of each other. Chiral surfaces offer the possibility of serving as heterogeneous catalysts for chiral synthesis or providing a platform for chiral separation or crystallization. Here, we show the symmetry requirements for surface chirality, and we demonstrate that chiral surfaces can be produced by electrochemically depositing epitaxial films of Au onto commercially available Si(643) wafers. Au(643) is deposited onto one side of the wafer, and its enantiomer Au((643) over bar) is deposited on the other side of the wafer. In addition to the (643) orientation, the (8 14 17) orientation of Au is produced on the Si(643) wafers. The (8 14 17) orientation has a similar kinked surface to the (643) surface, but it has staggered kinks. Other metal films inCluding Pt, Ni, Cu, and Ag that are electrodeposited onto the Au films exhibit strong in-plane and out-of-plane order. Hence, the method provides a pathway for producing chiral surfaces of a wide range of materials, and it obviates the need to work with expensive single crystals. The Ag/Au/Si(643) surface showed a preference for the electrochemical oxidation of D-glucose, whereas the Ag/Au/Si((643) over bar) surface showed preference for the oxidation of L-glucose.Epitaxial Electrodeposition of Chiral Metal Surfaces on Silicon(643)x14201844#N/AFALSE
1350
jacs.8b0882210.1021/jacs.8b08822https://doi.org/10.1021/jacs.8b08822Wang, ZXJ. Am. Chem. Soc.In this invited Perspective, recent developments and possible future directions of research on photoactive coordination compounds made from nonprecious transition metal elements will be discussed. The focus is on conceptually new, structurally well-characterized complexes with excited-state lifetimes between 10 ps and 1 ms in fluid solution for possible applications in photosensitizing, light-harvesting, luminescence and catalysis. The key metal elements considered herein are Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W and Ce in various oxidation states equipped with diverse ligands, giving access to long-lived excited states via a range of fundamentally different types of electronic transitions. Research performed in this area over the past five years demonstrated that a much broader spectrum of metal complexes than what was long considered relevant exhibits useful photophysics and photochemistry.Photoactive Complexes with Earth-Abundant MetalsPhotocatalyst1432018119#N/AFALSE
1351
jacs.8b1278410.1021/jacs.8b12784FALSEhttps://doi.org/10.1021/jacs.8b12784Hosono, HJ. Am. Chem. Soc.LnNiSi (Ln = La-Nd) comprising a three-dimensional NiSi framework has electrons in the crystallographic cavity space. In the temperature region 473-773 K, it accepts the insertion/de-insertion of hydrogen topotactically without a change in unitcell volume. The insertion of hydrogens into the cavity space is accompanied by a redox reaction with the orbitals of atoms constituting the cavity wall. Having small work functions, such intermetallic electrides exhibit metallic electrical and magnetic properties. Owing to a high electron-donating power and reversible exchange between hydrogen and the electrons, Ru5wt%-loaded LaNiSi powder worked as an efficient catalyst for ammonia synthesis under ambient pressure.Zeolitic Intermetallics: LnNiSi (Ln = La-Nd)9201921#N/ATRUE
1352
jacs.8b1254810.1021/jacs.8b12548FALSEhttps://doi.org/10.1021/jacs.8b12548Leigh, DACoordination Chemistry of a Molecular Pentafoil Knot2019#N/ATRUE
1353
jacs.8b1238610.1021/jacs.8b12386FALSEhttps://doi.org/10.1021/jacs.8b12386Carter, EAJ. Am. Chem. Soc.The active site for electrocatalytic water oxidation on the highly active iron(Fe)-doped beta-nickel oxyhydroxide (beta-NiOOH) electrocatalyst is hotly debated. Here we characterize the oxygen evolution reaction (OER) activity of an unexplored facet of this material with first-principles quantum mechanics. We show that molecular-like 4-fold-lattice-oxygen coordinated metal sites on the ((1) over bar2 (1) over bar1) surface may very well be the key active sites in the electrocatalysis. The predicted OER overpotential (eta(OER)) for a Fe-centered pathway is reduced by 0.34 V relative to a Ni-centered one, consistent with experiments. We further predict unprecedented, near quantitative lower bounds for the eta(OER), of 0.48 and 0.14 V for pure and Fe doped beta-NiOOH((1) over bar2 (1) over bar1), respectively. Our hybrid density functional theory calculations favor a heretofore unpredicted pathway involving an iron(W)-oxo species, Fe4+=0. We posit that an iron(IV)-oxo intermediate that stably forms under a low coordination environment and the favorable discharge of Ni3+ to Ni2+ are key to beta-NiOOH's OER activity.Unraveling Oxygen Evolution on Iron-Doped beta-Nickel Oxyhydroxide: The Key Role of Highly Active Molecular-like Sites74201979#N/ATRUE
1354
jacs.8b1210110.1021/jacs.8b12101FALSEhttps://doi.org/10.1021/jacs.8b12101Schmidt, TJJ. Am. Chem. Soc.Perovskite oxides have been at the forefront among catalysts for the oxygen evolution reaction (OER) in alkaline media offering a higher degree of freedom in cation arrangement. Several highly OER active Co-based perovskites have been known to show extraordinary activities and stabilities when the B-site is partially occupied by Fe. At the current stage, the role of Fe in enhancing the OER activity and stability is still unClear. In order to elucidate the roles of Co and Fe in the OER mechanism of cubic perovskites, two prospective perovskite oxides, La0.2Sr0.8Co1-xFexO3-delta and Ba0.5Sr0.3Co1-xFexO3-delta with x = 0 and 0.2, were prepared by flame spray synthesis as nanopartiCles. This study highlights the importance of Fe in order to achieve high OER activity and stability by drawing relations between their physicochemical and electrochemical properties. Ex situ and operando X-ray absorption spectroscopy (XAS) was used to study the local electronic and geometric structure under oxygen evolving conditions. In parallel, density function theory computational studies were conducted to provide theoretical insights into our findings. Our findings show that the incorporation of Fe into Co-based perovskite oxides alters intrinsic properties rendering efficient OER activity and prolonged stability.Functional Role of Fe-Doping in Co-Based Perovskite Oxide Catalysts for Oxygen Evolution Reaction98201977#N/ATRUE
1355
jacs.8b1172910.1021/jacs.8b11729FALSEhttps://doi.org/10.1021/jacs.8b11729Frei, ENi Single Atom Catalysts for CO2 Activation2019#N/ATRUE
1356
jacs.8b1160510.1021/jacs.8b11605FALSEhttps://doi.org/10.1021/jacs.8b11605Driess, MJ. Am. Chem. Soc.The first zerovalent germanium complex (germylone) 3, [Si-II(Xant)Si-II]Ge-0, stabilized by a chelating bis(N-heterocyClic silylene)xanthene donor ligand 1 was successfully synthesized via the dechlorination of the corresponding {[Si-II(Xant)Si-II]GeCl}Cl-+(-) complex 2 with KC8; it was structurally and spectroscopically characterized, and also studied by density functional theory (DFT) calculations. Natural bond orbital (NBO) analysis of 3 unambiguously exhibits two lone pairs of electrons (one sigma-type lone-pair and one 3p(Ge) lone-pair) on the zerovalent Ge atom. This is why the Ge atom can form the corresponding mono- and bis-AlBr3 Ge -> Al Lewis adducts [Si-II(Xant)Si-II]Ge(AlBr3) 4 and [Si-II(Xant)Si-II]Ge(AlBr3)(2) 5, respectively. Due to the electron-rich character of the Ge-0 atom, the germylone 3 displayed quite unusual reactivities. Thus, the reaction of 3 with 9-borabicyClo[3.3.1]nonane (9-BBN) as a potential Lewis acid furnished the first boryl(silyl)germylene complex 6, possessing a heteroallylic B center dot center dot center dot Ge center dot center dot center dot Si pi-conjugation. When 3 was allowed to react with Ni(cod)(2) (cod = 1,5-cyClooctadiene), the unique {[Si-II(Xant)Si-II]Ge-I}(2)Ni-II complex with a three-membered ring Ge2Ni-metallacyCle was obtained via reductive coupling of two Ge-0 atoms on the Ni center. Moreover, 3 was suitable to form a frustrated Lewis pair (FLP) with BPh3, which was capable of heterolytic H-2 Cleavage at 1 atm and room temperature, representing, for the first time, that a metallylone could be applied in FLP chemistry.An Isolable Bis(silylene)-Stabilized Germylone and Its Reactivity19201996#N/ATRUE
1357
jacs.8b0740510.1021/jacs.8b07405TRUEhttps://doi.org/10.1021/jacs.8b07405Martin, RJ. Am. Chem. Soc.Triplet ketone sensitizers are of central importance within the realm of photochemical transformations. Although the radical-type character of triplet excited states of diAryl ketones suggests the viability for triggering hydrogen-atom transfer (HAT) and single-electron transfer (SET) processes, among others, their use as multifaceted catalysts in C-C bond-formation via sp(3) C-H functionalization of alkane feedstocks still remains rather unexplored. Herein, we unlock a modular photochemical platform for forging C(sp(3))-C(sp(2)) and C(sp(3))-C(sp(3)) linkages from abundant alkane sp(3) C-H bonds as functional handles using the synergy between nickel catalysts and simple, cheap and modular diAryl ketones. This method is distinguished by its wide scope that is obtained from cheap catalysts and starting precursors, thus complementing existing inner-sphere C-H functionalization protocols or recent photoredox scenarios based on iridium polypyridyl complexes. Additionally, such a platform provides a new strategy for streamlining the synthesis of complex molecules with high levels of predictable site selectivity and preparative utility. Mechanistic experiments suggest that sp(3) C-H abstraction occurs via HAT from the ketone triplet excited state. We believe this study will contribute to a more systematic utilization of triplet excited ketones as catalysts in metallaphotoredox scenarios.sp(3) C-H Arylation and Alkylation Enabled by the Synergy of Triplet Excited Ketones and Nickel CatalystsPhotocatalystCsp3-Csp2_arHBrAlkylIonic-CO31052018976/1/2022FALSE
1358
jacs.8b0727110.1021/jacs.8b07271https://doi.org/10.1021/jacs.8b07271Zhang, JJ. Am. Chem. Soc.Triplet triplet energy transfer (EnT) is a fundamental Activation pathway in photocatalysis. In this work, we report the mechanistic origins of the triplet excited state of carbazole-cyanobenzene donor-acceptor (D-A) fluorophores in EnT-based photocatalytic reactions and demonstrate the key factors that control the accessibility of the (LE)-L-3 (locally excited triplet state) and (CT)-C-3 (charge-transfer triplet state) via a combined photochemical and transient absorption spectroscopic study. We found that the energy order between (CT)-C-1 (charge transfer singlet state) and (LE)-L-3 dictates the accessibility of (LE)-L-3/(CT)-C-3 for EnT, which can be effectively engineered by varying solvent polarity and D-A character to depopulate (LE)-L-3 and facilitate EnT from the chemically more tunable (CT)-C-3 state for photosensitization. Following the above design principle, a new D-A fluorophore with strong D-A character and weak redox potential is identified, which exhibits high efficiency for Ni(II)-catalyzed cross coupling of Carbonylic acids and Aryl halides with a wide substrate scope and high selectivity. Our results not only provide key fundamental insight on the EnT mechanism of D-A fluorophores but also establish its wide utility in EnT-mediated photocatalytic reactions.Donor-Acceptor Fluorophores for Energy-Transfer-Mediated PhotocatalysisPhotocatalyst67201851#N/AFALSE
1359
jacs.8b0690110.1021/jacs.8b06901FALSEhttps://doi.org/10.1021/jacs.8b06901Lescop, CJ. Am. Chem. Soc.A thermally activated delayed fluorescence (TADF) tetrametallic Cu(I) metallacyCle A behaves as a conformationally adaptive preorganized precursor to afford, through straightforward and rational coordination-driven supramolecular processes, a variety of room-temperature solid-state luminescent polymetallic assemblies. Reacting various cyano-based building blocks with A, a homometallic Cu(I) 1D-helical coordination polymer C and Cu8M discrete circular heterobimetallic assemblies D-M (M = Ni, Pd, Pt) are obtained. Their luminescence behaviors are studied, revealing notably the crucial impact of the spin-orbit coupling offered by the central M metal center on the photophysical properties of the heterobimetallic D-M derivatives.Adaptive Coordination-Driven Supramolecular Syntheses toward New Polymetallic Cu(I) Luminescent Assembliesx40201821#N/AFALSE
1360
jacs.8b0684210.1021/jacs.8b06842FALSEhttps://doi.org/10.1021/jacs.8b06842Itami, KJ. Am. Chem. Soc.The synthesis and X-ray crystal structure of the first member of the carbon nanobelt family is reported. [12] Carbon nanobelt ([12]CNB) was originally obtained from a nickel-mediated reductive coupling reaction of a dodecabrominated macrocyClic precursor, albeit only in 1% yield. The present artiCle reports on the development of this synthetic strategy and its extension to the preparation of the [16] and [24] CNB analogues. In particular, our extensive investigations on the final belt-forming, nickel-mediated reaction led to the development of a new ligand system that provides [12]CNB in up to 7% yield, contributing to the commercialization of [12]CNB. The belt structures of [12], [16], and [24]CNB were characterized by NMR, UV-vis, and Raman spectroscopy as well as mass spectrometry and X-ray crystallography. The fluorescence of the CNBs in solution displayed a remarkable dependence on the ring size, ranging from a broad red emission ([12]CNB) to a narrow-band blue emission ([24]CNB), while both features are observed for [16]CNB.Synthesis and Size-Dependent Properties of [12], [16], and [24]Carbon Nanobeltsx69201873#N/AFALSE
1361
jacs.8b0681710.1021/jacs.8b06817FALSEhttps://doi.org/10.1021/jacs.8b06817Musaev, DGJ. Am. Chem. Soc.Using computation, we examine the generality and strength of beta-effects from transition metal centers on beta-elimination. In particular, we find that a beta-Pd(II) substituent imparts over twice the stabilization to a carbocation as a Si substituent, representative of the well-known beta-silicon effect. We established efficient and practical computational parameters to investigate the sigma sigma conjugation in an experimentally relevant system: N,N-picolinamide Vinyl metalacyCles with fisubstituents that can undergo elimination. We have found that the beta-Pd effect depends on the nature of the C-beta substituent (X): This effect is negligible for X = H, Me, OH, and F, but is significant for X = Cl, Br, and I. We have also extended these studies to the beta-effect in N,N-picolinamide Vinyl metalacyCles with beta-substituents of other transition metals-Fe(II), Ru(II), Os(II), Co(III), Rh(III), Ir(III), Ni(II), Pd(II), Pt(II), Cu(III), Ag(III), and Au(III). We found that the electronegativity of the metals correlates reasonably well with the relative beta-effects, with first-row transition metals exerting the strongest influence. Overall, it is our anticipation that a more profound appreciation of transition metal beta effects will facilitate the design of novel reactions, inCluding new variants of transition metal catalyzed C-H functionalization.Generality and Strength of Transition Metal beta-Effectsx9201866#N/AFALSE
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jacs.8b1139310.1021/jacs.8b11393FALSEhttps://doi.org/10.1021/jacs.8b11393Driess, MJ. Am. Chem. Soc.The first hypercoordinated disilene with the longest Si=Si distance (2.623(1) angstrom) reported to date, the 5,6-bis(amidinato silylenyl)acenaphtene (amidinato = PhC((NBu)-Bu-t)(2)) (1), is presented. It results from a spatially compelled double dative interaction between the two singlet silylene moieties, due to their Close proximity. The dynamic behavior of the Si=Si bond contraction and elongation in 1 predicted by quantum chemical calculations could be confirmed experimentally by variable temperature NMR spectroscopy. Compound 1 exhibits an ambivalent reactivity, reacting as disilene with ethylene, diphenylacetylene and benzophenone to give [2+2] cyCloaddition products, but as bis(silylene) toward Ni(cod)(2) (cod = cyCloocta-1,4-diene) to form the corresponding bis(silylene)Ni-0(eta(4)-cod) complex.Geometrically Compelled Disilene with lambda(4)-Coordinate Si-II Atoms9201862#N/ATRUE
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jacs.8b0651110.1021/jacs.8b06511FALSEhttps://doi.org/10.1021/jacs.8b06511Astruc, DJ. Am. Chem. Soc.Ammonia borane hydrolysis is considered as a potential means of safe and fast method of H-2 production if it is efficiently catalyzed. Here a series of nearly monodispersed alloyed bimetallic nanopartiCle catalysts are introduced, optimized among transition metals, and found to be extremely efficient and highly selective with sharp positive synergy between 2/3 Ni and 1/3 Pt embedded inside a zeolitic imidazolate framework (ZIF-8) support. These catalysts are much more efficient for H-2 release than either Ni or Pt analogues alone on this support, and for instance the best catalyst Ni2Pt@ZiF-8 achieves a TOF of 600 mol(H2).mol(catal)(-1). min(-1) and 2222 mol(H2).mol(pt)(-1)min(-1) under ambient conditions, which overtakes performances of previous Pt-base catalysts. The presence of NaOH boosts H-2 evolution that becomes 87 times faster than in its absence with Ni2Pt@ZiF-8, whereas NaOH decreases H-2 evolution on the related Pt@ZiF-8 catalyst. The ZIF-8 support appears outstanding and much more efficient than other supports inCluding graphene oxide, active carbon and SBA-15 with these nanopartiCles. Mechanistic studies especially involving kinetic isotope effects using D2O show that Cleavage by oxidative addition of an O-H bond of water onto the catalyst surface is the rate-determining step of this reaction. The remarkable catalyst activity of Ni2Pt@ZiF-8 has been exploited for successful tandem catalytic hydrogenation reactions using ammonia borane as H-2 source. In conClusion the selective and remarkable synergy disClosed here together with the mechanistic results should allow significant progress in catalyst design toward convenient H2 generation from hydrogen-rich substrates in the Close future.Highly Selective and Sharp Volcano-type Synergistic Ni2Pt@ZIF-8-Catalyzed Hydrogen Evolution from Ammonia Borane Hydrolysisx136201877#N/AFALSE
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jacs.8b1125710.1021/jacs.8b11257FALSEhttps://doi.org/10.1021/jacs.8b11257Mirica, KAJ. Am. Chem. Soc.This paper describes the first demonstration of using a series of isoreticular nickel phthalocyanine- and nickel naphthalocyanine-based bimetallic conductive two-dimensional (2D) metal-organic frameworks (MOFs) as active materials in chemiresistive sensing of gases. Devices achieve exceptional sensitivity at sub-part-per-million (ppm) to part-per-billion (ppb) detection limits toward NH3 (0.31-0.33 ppm), H2S (19-32 ppb), and NO (1.0-1.1 ppb) at low driving voltages (0.01-1.0 V) within 1.5 min of exposure. The devices maintain their performance in the presence of humidity (5000 ppm of H2O). The isoreticular analogs enable modular control over selectivity and sensitivity in gas sensing through different combinations of linkers and metal nodes. Electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy studies suggest that the chemiresistive response of the MOFs involves charge transfer interactions triggered by the analytes adsorbed on MOFs.Welding Metallophthalocyanines into Bimetallic Molecular Meshes for Ultrasensitive, Low-Power Chemiresistive Detection of Gases83201991#N/ATRUE
1365
jacs.8b0610810.1021/jacs.8b06108FALSEhttps://doi.org/10.1021/jacs.8b06108Xie, YJ. Am. Chem. Soc.Perovskites are prototype electrocatalyts benefiting from their high terrestrial availability and high stability. Electronic state regulation plays a key role in promising higher electrocatalytic efficiencies. Herein, we highlighted a vibronic superexchange in double perovskite to synergistically optimize e(g) electron filling state and increase the formation of active species on the surface of catalysts. Vibronic superexchange of Ni3+-O-Mn3+ in La2NiMnO6 nanopartiCles brings the optimal e(g) electron filling state of Mn and Ni ions toward unity. Moreover, a vibronic superexchange interaction of Ni3+-O-Mn3+ induces strong Jahn-Teller distortion of MnO6 and NiO6 octahedra, elongating metal-O bonds, which helps to form the active species of Mn/Ni hydroxide/oxide on the surface of catalysts. Surprisingly, La2NiMnO6 nano partiCles exhibit superior oxygen evolution reaction (OER) catalytic performance with higher current density and lower Tafel slope than its bulk counterpart. Our finding will be a promising pathway to develop advanced precious-metal-free catalysts.Vibronic Superexchange in Double Perovskite Electrocatalyst for Efficient Electrocatalytic Oxygen Evolution
Electrocatalytic
64201840#N/AFALSE
1366
jacs.8b1091010.1021/jacs.8b10910FALSEhttps://doi.org/10.1021/jacs.8b10910Hu, PJJ. Am. Chem. Soc.Heterogeneous catalysis performs on specific sites of a catalyst surface even if specific sites of many catalysts during catalysis could not be identified readily. Design of a catalyst by managing catalytic sites on an atomic scale is significant for tuning catalytic performance and offering high activity and selectivity at a relatively low temperature. Here, we report a synergy effect of two sets of single-atom sites (Ni-1 and Ru-1) anchored on the surface of a CeO2 nanorod, Ce0.95Ni0.025Ru0.025O2. The surface of this catalyst, Ce0.95Ni0.025Ru0.025O2, consists of two sets of single-atom sites which are highly active for reforming CH4 using CO2 with a turnover rate of producing 73.6 H-2 molecules on each site per second at 560 degrees C. Selectivity for producing H-2 at this temperature is 98.5%. The single-atom sites Ni-1 and Ru-1 anchored on the CeO2 surface of Ce0.95Ni0.025Ru0.025O2 remain singly dispersed and in a cationic state during catalysis up to 600 degrees C. The two sets of single-atom sites play a synergistic role, evidenced by lower apparent Activation barrier and higher turnover rate for production of H-2 and CO on Ce0.95Ni0.025Ru0.025O2 in contrast to Ce0.95Ni0.05O2 with only Ni-1 single-atom sites and Ce0.95Ru0.05O2 with only Ru-1 single-atom sites. Computational studies suggest a molecular mechanism for the observed synergy effects, which originate at (1) the different roles of Ni-1 and Ru-1 sites in terms of Activations of CH4 to form CO on a Ni-1 site and dissociation of CO2 to CO on a Ru-1 site, respectively and (2) the sequential role in terms of first forming H atoms through Activation of CH4 on a Ni-1 site and then coupling of H atoms to form H-2 on a Ru-1 site. These synergistic effects of the two sets of single-atom sites on the same surface demonstrated a new method for designing a catalyst with high activity and selectivity at a relatively low temperature.Synergy of Single-Atom Ni-1 and Ru-1 Sites on CeO2 for Dry Reforming of CH459201949#N/ATRUE
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jacs.8b0934610.1021/jacs.8b09346FALSEhttps://doi.org/10.1021/jacs.8b09346Zhou, QLJ. Am. Chem. Soc.We developed a highly regioselective addition of 1,3-dienes with simple ketones by nickel-hydride catalyst bearing DTBM-SegPhos ligand. A wide range of aromatic and aliphatic ketones directly coupled with 1,3-dienes, providing synthetically useful y,delta-unsaturated ketones in high yield and regioselectivity. The asymmetric version of the reaction was also realized in high enantioselectivity by using novel chiral ligand DTBM-HO-BIPHEP. The utility of this hydroAlkylation was demonstrated by facile product modification and enantioselective synthesis of (R)-flobufen.Nickel(0)-Catalyzed HydroAlkylation of 1,3-Dienes with Simple Ketones48201842#N/ATRUE
1368
jacs.8b0565010.1021/jacs.8b05650https://doi.org/10.1021/jacs.8b05650Doyle, AGJ. Am. Chem. Soc.Nickel -Catalyzed Enantioselective Reductive Cross-Coupling of Styrenyl Aziridines (vol 139, pg 5688, 2017)Correaction of jacs.7b03448220181#N/AFALSE
1369
jacs.8b0874410.1021/jacs.8b08744FALSEhttps://doi.org/10.1021/jacs.8b08744Li, YDJ. Am. Chem. Soc.Metal-organic frameworks (MOF) have recently emerged as versatile precursors to fabricate functional MOF derivatives for oxygen evolution reactions (OER). Herein, we developed a controlled partial pyrolysis strategy to construct robust NiCo/Fe3O4 heteropartiCles within MOF-74 for efficient OER using trimetallic NiCoFe-MOF-74 as precursor. The partial pyrolysis method preserves the framework structure of MOF for effective substrates diffusion while producing highly active nanopartiCles. The as-prepared NiCo/Fe3O4/MOF-74 delivered remarkably stable OER current with an overpotential as low as 238 mV at 10.0 mA cm(-2) and an Tafel slop of 29 mV/dec, outperforming those of pristine NiCoFe-MOF-74, totally decomposed MOF derivatives, and most reported non-noble metal based electrocatalysts. The key for the formation of NiCo/Fe3O4/MOF-74 nanostructures is that the metals can be decomposed from NiCoFe-MOF-74 in the order of Ni, Co, and Fe under controlled heat treatment. Density functional theory calculations reveals that the underlying NiCo promotes the OER activity of Fe3O4 through exchange stabilization of active oxygen species.Constructing NiCo/Fe3O4 HeteropartiCles within MOF-74 for Efficient Oxygen Evolution Reactions174201837#N/ATRUE
1370
jacs.8b0829610.1021/jacs.8b08296FALSEhttps://doi.org/10.1021/jacs.8b08296Uyeda, CJ. Am. Chem. Soc.CyClic structures are highly represented in organic molecules, motivating a wealth of catalytic methods targeting their synthesis. Among the various ring-forming processes, cyClooligomerization reactions possess several attractive features but require addressing a unique challenge associated with controlling ring-size selectivity. Here we describe the catalytic reductive cocyClooligomerization of an enone and three carbene equivalents to generate a cyClopentane, a process that constitutes a formal [2 + 1 + 1 + 1]-cyCloaddition. The reaction is promoted by a (quinox)Ni catalyst and uses CH2Cl2/Zn as the C-1 component. Mechanistic studies are consistent with a metallacyCle-based pathway, featuring sequential migratory insertions of multiple carbene equivalents to yield cyCloalkanes larger than cyClopropanes.Catalytic CyClooligomerization of Enones with Three Methylene Equivalents6201837#N/ATRUE
1371
jacs.8b0529410.1021/jacs.8b05294FALSEhttps://doi.org/10.1021/jacs.8b05294Zhang, SJ. Am. Chem. Soc.Developing highly efficient oxygen evolution reaction (OER) catalysts and understanding their activity are pivotal for electrochemical conversion technologies. Here, we report NiFe Prussian blue analogue (PBA) as a promising electrocatalyst for OER in alkaline conditions. This material has an impressively low overpotential of 258 mV that reaches a current density of 10 mA cm(-2). Post-mortem characterization showed that the as-prepared catalyst is entirely transformed into amorphous nickel hydroxide after the electrochemical treatment, and Ni(OH)(2) acts as the active species. Operando X-ray spectroscopic studies further found that this in situ generated Ni(OH)(2) displays an unique feature that allows deprotonation under applied potential creating NiOOH2-x that contains Ni4+ ions. The deprotonation reaction is reversible and potential-dependent, i.e., the amount of Ni4+ increases with increasing applied potential. Theoretical calculations were used to show that the role of Ni4+ is to trigger oxidized oxygen ions as electrophilic centers with the subsequent Activation of anion redox reactions for OER.Operando Spectroscopic Identification of Active Sites in NiFe Prussian Blue Analogues as Electrocatalysts: Activation of Oxygen Atoms for Oxygen Evolution Reactionx149201849#N/AFALSE
1372
jacs.8b0819010.1021/jacs.8b08190FALSEhttps://doi.org/10.1021/jacs.8b08190Kong, WQJ. Am. Chem. Soc.A Ni-catalyzed enantioselective reductive diArylation of activated alkenes by domino cyClizative/ cross-coupling of two Aryl bromides is developed. This reaction proceeds under very mild conditions and shows broad substrate scope, without requiring the use of preformed organometallic reagents. Moreover, this approach provides direct access to various bis-heterocyCles bearing all-carbon quaternary centers in synthetically useful yields (up to 81%) with excellent enantioselectivity (>30 examples, 90-99% ee).Ni-Catalyzed Enantioselective Reductive DiArylation of Activated Alkenes by Domino CyClization/Cross-Coupling104201884#N/ATRUE
1373
jacs.8b0812410.1021/jacs.8b08124FALSEhttps://doi.org/10.1021/jacs.8b08124Duan, XFJ. Am. Chem. Soc.Two-dimensional (2D) layered materials have stimulated extensive research interest for their unique thickness-dependent electronic and optical properties. However, the layer-number-dependent studies on 2D materials date are largely limited to exfoliated flakes with relatively small lateral size and poor yield. The direct synthesis of 2D materials with a precise control of the number of atomic layers remains a substantial synthetic challenge. Here we report a systematic study of chemical vapor deposition synthesis of large-area atomically thin 2D nickel telluride (NiTe2) single crystals and investigate the thickness dependent electronic properties. By controlling the growth temperature, we show that the highly uniform NiTe2 single crystals can be synthesized with precisely tunable thickness varying from 1, 2, 3,... to multilayers with a standard deviation (similar to 0.3 nm) of less than the thickness of a monolayer layer NiTe2. Our studies further reveal a systematic evolution of single crystal domain size and nuCleation density with the largest lateral domain size up to similar to 440 mu m. X-ray diffraction, transmission electron microscopy, and high resolution scanning transmission electron microscope studies demonstrate that the resulting 2D crystals are high quality single crystals and adopt hexagonal 1T phase. Electrical transport studies reveal that the 2D NiTe2 single crystals show a strong thickness-tunable electrical properties, with an excellent conductivity up to 7.8 X 10(5) S m(-1) and extraordinary breakdown current density up to 4.7 X 10(7) A/cm(2). The systematic study and robust synthesis of NiTe2 nanosheets defines a reliable chemical route to 2D single crystals with precisely tailored thickness and could enable the design of new device architectures based on thickness-tunable electrical properties.Synthetic Control of Two-Dimensional NiTe2 Single Crystals with Highly Uniform Thickness Distributions50201847#N/ATRUE
1374
jacs.8b0786810.1021/jacs.8b07868FALSEhttps://doi.org/10.1021/jacs.8b07868Ledendecker, MJ. Am. Chem. Soc.Increasing the catalyst's stability and activity are one of the main quests in catalysis. Tailoring crystal surfaces to a specific reaction has demonstrated to be a very effective way in increasing the catalyst's specific activity. Shape controlled nanopartiCles with specific crystal facets are usually grown kinetically and are highly susceptible to morphological changes during the reaction due to agglomeration, metal dissolution, or Ostwald ripening. A strong interaction of the catalytic material to the support is thus crucial for successful stabilization. Taken both points into account, a general catalyst design is proposed, combining the enhanced activity of shape-controlled nanopartiCles with a pore-confinement approach for high stability. Hollow graphitic spheres with narrow and uniform bimodal mesopores serve as model system and were used as support material. As catalyst, different kinds of partiCles, such as pure platinum (Pt), platinum/nickel (Pt3Ni) and Pt3Ni doped with molybdenum (Pt3Ni-Mo), have exemplarily been synthesized. The advantages, limits and challenges of the proposed concept are discussed and elaborated by means of time-resolved, in and ex situ measurements. It will be shown that during catalysis, the potential boundaries are crucial especially for the proposed catalyst design, resulting in either retention of the initial activity or drastic loss in shape, size and elemental composition. The synthesis and catalyst design can be adapted to a wide range of catalytic reactions where stabilization of shape-controlled partiCles is a focus.Shape-Controlled NanopartiCles in Pore-Confined Space19201832#N/ATRUE
1375
jacs.8b0479810.1021/jacs.8b04798FALSEhttps://doi.org/10.1021/jacs.8b04798Armstrong, FAJ. Am. Chem. Soc.Catalytic long-range proton transfer in [NiFe]-hydrogenases has long been associated with a highly conserved glutamate (E) situated within 4 angstrom of the active site. Substituting for glutamine (Q) in the O-2-tolerant [NiFe]-hydrogenase-1 from Escherichia coli produces a variant (E28Q) with unique properties that have been investigated using protein film electrochemistry, protein film infrared electrochemistry, and X-ray crystallography. At pH 7 and moderate potential, E28Q displays approximately 1% of the activity of the native enzyme, high enough to allow detailed infrared measurements under steady-state conditions. Atomic level crystal structures reveal partial displacement of the amide side chain by a hydroxide ion, the occupancy of which increases with pH or under oxidizing conditions supporting formation of the superoxidized state of the unusual proximal [4Fe-3S] Cluster located nearby. Under these special conditions, the essential exit pathway for at least one of the H+ ions produced by H-2 oxidation, and assumed to be blocked in the E28Q variant, is partially repaired. During steady-state H-2 oxidation at neutral pH (i.e., when the barrier to H+ exit via Q28 is almost totally Closed), the catalytic cyCle is dominated by the reduced states Ni-a-R and Ni-a-C, even under highly oxidizing conditions. Hence, E28 is not involved in the initial Activation/deprotonation of H-2, but facilitates H+ exit later in the catalytic cyCle to regenerate the initial oxidized active state, assumed to be Ni-a-SI. Accordingly, the oxidized inactive resting state, Ni-B, is not produced by E28Q in the presence of H-2 at high potential because Ni-a-SI (the precursor for Ni-B) cannot accumulate. The results have important implications for understanding the catalytic mechanism of [NiFe]-hydrogenases and the control of long-range proton-coupled electron transfer in hydrogenases and other enzymes.Mechanistic Exploitation of a Self-Repairing, Blocked Proton Transfer Pathway in an O-2-Tolerant [NiFe]-Hydrogenasex17201872#N/AFALSE
1376
jacs.8b0470310.1021/jacs.8b04703FALSEhttps://doi.org/10.1021/jacs.8b04703Zhou, QLJ. Am. Chem. Soc.A highly enantioselective nickel-catalyzed intramolecular hydroalkenylation of N- or O-tethered 1,6-dienes was developed by using monodentate chiral spiro phosphoramidite ligands. The reaction provides an efficient and straightforward method for preparing very useful six-membered N- and O-heterocyCles with high regioselectivity as well as excellent stereoselectivity from easily accessible starting materials under mild reaction conditions. The chiral spiro nickel catalyst developed in this study represents one of the few catalysts for highly enantioselective cyClization of unconjugated dienes.Highly Enantioselective Nickel-Catalyzed Intramolecular Hydroalkenylation of N- and O-Tethered 1,6-Dienes To Form Six-Membered HeterocyClesx25201833#N/AFALSE
1377
jacs.8b0468110.1021/jacs.8b04681FALSEhttps://doi.org/10.1021/jacs.8b04681Cosa, GJ. Am. Chem. Soc.The photostability of fluorescent labels comprises one of the main limitations in single-molecule fluorescence (SMF) and super-resolution imaging. An attractive strategy to increase the photostability of organic fluorophores relies on their coupling to photostabilizers, e.g., triplet excited state quenchers, rendering self-healing dyes. Herein we report the self-healing properties of trisNTA-Alexa647 fluorophores (NTA, N-nitrilotriacetic acid). Primarily designed to specifically label biomolecules containing an oligohistidine tag, we hypothesized that the increased effective concentration of Ni(II) triplet state quenchers would lead to their improved photostability. We evaluated photon output, survival time, and photon count rate of different Alexa647-labeled trisNTA constructs differing in the length and rigidity of the fluorophore-trisNTA linker. Maximum photon output enhancements of 25-fold versus Alexa647-DNA were recorded for a short tetraproline linker, superseding the solution based photostabilization by Ni(II). Steady-state and time-resolved studies illustrate that trisNTA self-healing role is associated with a dynamic excited triplet state quenching by Ni(II). Here improved photophysical/photochemical properties require for a judicious choice of linker length and rigidity, and in turn a balance between rapid dynamic triplet excited state quenching versus dynamic/static singlet excited state quenching. TrisNTA fluorophores offer superior properties for SMF allowing specific labeling and increased photostability, making them ideal candidates for extended single-molecule imaging techniques.Tris-N-Nitrilotriacetic Acid Fluorophore as a Self-Healing Dye for Single-Molecule Fluorescence Imagingx10201837#N/AFALSE
1378
jacs.8b0780610.1021/jacs.8b07806FALSEhttps://doi.org/10.1021/jacs.8b07806Kong, JJ. Am. Chem. Soc.Lateral heterostructures with planar integrity form the basis of two-dimensional (2D) electronics and optoelectronics. Here we report that, through a two-step chemical vapor deposition (CVD) process, high-quality lateral heterostructures can be constructed between metallic and semiconducting transition metal disulfide (TMD) layers. Instead of edge epitaxy, polycrystalline monolayer MoS2 in such junctions was revealed to nuCleate from the vertices of multilayered VS2 crystals, creating one-dimensional junctions with ultralow contact resistance (0.5 k Omega.mu m). This lateral contact contributes to 6-fold improved field-effect mobility for monolayer MoS2, compared to the conventional on-top nickel contacts. The all-CVD strategy presented here hence opens up a new avenue for all-2D-based synthetic electronics.Synthetic Lateral Metal-Semiconductor Heterostructures of Transition Metal Disulfides50201831#N/ATRUE
1379
jacs.8b0380910.1021/jacs.8b03809FALSEhttps://doi.org/10.1021/jacs.8b03809Rodriguez, JAJ. Am. Chem. Soc.The transformation of methane into methanol or higher alcohols at moderate temperature and pressure conditions is of great environmental interest and remains a challenge despite many efforts. Extended surfaces of metallic nickel are inactive for a direct CH4 -> CH3OH conversion. This experimental and computational study provides Clear evidence that low Ni loadings on a CeO2(111) support can perform a direct catalytic cyCle for the generation of methanol at low temperature using oxygen and water as reactants, with a higher selectivity than ever reported for ceria-based catalysts. On the basis of ambient pressure X-ray photoemission spectroscopy and density functional theory calculations, we demonstrate that water plays a crucial role in blocking catalyst sites where methyl species could fully decompose, an essential factor for diminishing the production of CO and CO2, and in generating sites on which methoxy species and ultimately methanol can form. In addition to water-site blocking, one needs the effects of metal-support interactions to bind and activate methane and water. These findings should be considered when designing metal/oxide catalysts for converting methane to value-added chemicals and fuels.Direct Conversion of Methane to Methanol on Ni-Ceria Surfaces: Metal-Support Interactions and Water-Enabled Catalytic Conversion by Site Blockingx52201835#N/AFALSE
1380
jacs.8b0374410.1021/jacs.8b03744https://doi.org/10.1021/jacs.8b03744Miyake, GMJ. Am. Chem. Soc.C-N cross-coupling is an important Class of reactions with far-reaching impacts across chemistry, materials science, biology, and medicine. Transition metal complexes can elegantly orchestrate diverse aminations but typically require demanding reaction conditions, precious metal catalysts, or oxygen-sensitive procedures. Here, we introduce a mild nickel-catalyzed C-N cross-coupling methodology that operates at room temperature using an inexpensive nickel source (NiBr2 center dot 3H(2)O), is oxygen tolerant, and proceeds through direct irradiation of the nickel-amine complex. This operationally robust process was employed for the synthesis of diverse C-N-coupled products (40 examples) by irradiating a solution containing an amine, an Aryl halide, and a catalytic amount of NiBr2 center dot 3H(2)O with a commercially available 365 nm LED at room temperature without added photoredox catalyst and the amine substrate serving additional roles as the ligands and base. Density functional theory calculations and kinetic isotope effect experiments were performed to elucidate the observed C-N cross-coupling reactivity.C-N Cross-Coupling via Photoexcitation of Nickel-Amine ComplexesPhotocatalyst81201851#N/AFALSE
1381
jacs.8b0666610.1021/jacs.8b06666FALSEhttps://doi.org/10.1021/jacs.8b06666Bao, ZAJ. Am. Chem. Soc.Conductive metal-organic frameworks (c-MOFs) have shown outstanding performance in energy storage and electrocatalysis. Varying the bridging metal species and the coordinating atom are versatile approaches to tune their intrinsic electronic properties in c-MOFs. Herein we report the first synthesis of the oxygen analog of M-3(C6X6)(2) (X = NH, S) family using Cu(II) and hexahydroxybenzene (HHB), namely Cu-HHB [Cu-3(C6O6)(2)], through a kinetically controlled approach with a competing coordination reagent. We also successfully demonstrate an economical synthetic approach using tetrahydroxyquinone as the starting material. Cu-HHB was found to have a partially eClipsed packing between adjacent 2D layers and a bandgap of approximately 1 eV. The addition of Cu-HHB to the family of synthetically realized M-3(C6X6)(2) c-MOFs will enable greater understanding of the influence of the organic linkers and metals, and further broadens the range of applications for these materials.Synthetic Routes for a 2D Semiconductive Copper Hexahydroxybenzene Metal-Organic Framework79201833#N/ATRUE
1382
jacs.8b0322310.1021/jacs.8b03223https://doi.org/10.1021/jacs.8b03223Mecking, SJ. Am. Chem. Soc.Novel complexes based on 2,4,8-triArylnaphthylamine [[(2,4-{3,5-(CF3)(2)C6H3}(2)-8-(3,5-R2C6H3)-C10H4)-N=C(H)-{3-(9-anthryl)-2-O-C6H3}-kappa(2)-N,O]Ni(CH3)(pyridine)] (4-Py, R = Me; 5-Py, R = CF3) were synthesized from 8-Arylnaphthylamines which can be generated via selective lithiation, borylation, and coupling in a one-pot procedure. Due to their living characteristics in ethylene polymerization and the particularly low propensity of 5-Py for beta-H elimination as reflected by a high linearity even at elevated polymerization temperatures of 60 degrees C, ultrahigh molecular weight polyethylene (UHMWPE) is formed in polar organic solvents (THF, diethyl ether) as a reaction medium in a controlled polymerization (M-w/M-n = 1.2 at M-n = 1.1 x 10(6) g mol(-1)).Controlled Polymerization in Polar Solvents to Ultrahigh Molecular Weight Polyethylenex45201835#N/AFALSE
1383
jacs.8b0316310.1021/jacs.8b03163FALSEhttps://doi.org/10.1021/jacs.8b03163Giri, RJ. Am. Chem. Soc.We disClose a [(PhO)(3)P]/NiBr2-catalyzed regioselective beta,delta-diArylation of unactivated olefins in ketimines with Aryl halides and Arylzinc reagents. This diArylation proceeds at remote locations to the Carbonyl group to afford, after simple H+ workup, diversely substituted beta,delta-diArylketones that are otherwise difficult to access readily with existing methods. Deuterium labeling and crossover experiments indicate that diArylation proceeds by ligand-enabled contraction of transient nickellacyCles.Ni-Catalyzed Regioselective beta,delta-DiArylation of Unactivated Olefins in Ketimines via Ligand-Enabled Contraction of Transient NickellacyCles: Rapid Access to Remotely DiArylated Ketonesx64201886#N/AFALSE
1384
jacs.8b0645810.1021/jacs.8b06458FALSEhttps://doi.org/10.1021/jacs.8b06458Shenvi, RAJ. Am. Chem. Soc.Cobalt/nickel-dual catalyzed hydroArylation of terminal olefins with iodoarenes builds complexity from readily available starting materials, with a high preference for the Markovnikov (branched) product. Here, we advance a mechanistic model of this reaction through the use of reaction progress kinetic analysis (RPKA), radical Clock experiments, and stoichiometric studies. Through exClusion of competing hypotheses, we conClude that the reaction proceeds through an unprecedented Alkylcobalt to nickel direct transmetalation. Demonstration of catalytic alkene prefunctionalization, via spectroscopic observation of an organocobalt species, distinguishes this Csp(2)-Csp(3) cross-coupling method from a conventional transmetalation process, which employs a stoichiometric organometallic nuCleophile, and from a bimetallic oxidative addition of an organohalide across nickel, described by radical scission and subsequent Alkyl radical capture at a second nickel center. A refined understanding of the reaction leads to an optimized hydroArylation procedure that exCludes exogenous oxidant, demonstrating that the transmetalation is net redox neutral. Catalytic alkene prefunctionalization by cobalt and engagement with nickel catalytic cyCles through direct transmetalation provides a new platform to merge these two rich areas of chemistry in preparatively useful ways.Mechanistic Interrogation of Co/Ni-Dual Catalyzed HydroArylation762018136#N/ATRUE
1385
jacs.8b0602010.1021/jacs.8b06020FALSEhttps://doi.org/10.1021/jacs.8b06020Bao, ZAJ. Am. Chem. Soc.Redox-active organic materials have gained growing attention as electrodes of rechargeable batteries. However, their key limitations are the low electronic conductivity and limited chemical and structural stability under redox conditions. Herein, we report a new cobalt-based ;2D conductive metal-organic framework (MOF), Co-HAB, having stable, accessible, dense active sites for high-power energy storage device through conjugative coordination between a redox-active linker, hexaaminobenzene (HAB), and a Co(II) center. Given the exceptional capability of Co-HAB for stabilizing reactive HAB, a reversible three-electron redox reaction per HAB was successfully demonstrated for the first time, thereby presenting a promising new electrode material for sodium-ion storage. Specifically, through synthetic tunability of Co-HAB, the bulk electrical conductivity of 1.57 S cm(-1) was achieved, enabling an extremely high rate capability, delivering 214 mAh g(-1) within 7 min or 152 mAh g(-1) in 45 s. Meanwhile, an almost linear increase of the areal capacity upon increasing active mass loading up to 9.6 mg cm(-2) was obtained, demonstrating 2.6 mAh cm(-2) with a trace amount of conducting agent.Stabilization of Hexaaminobenzene in a 2D Conductive Metal-Organic Framework for High Power Sodium Storage154201862#N/ATRUE
1386
jacs.8b0271010.1021/jacs.8b02710FALSEhttps://doi.org/10.1021/jacs.8b02710Zhou, HCJ. Am. Chem. Soc.The predesignable porous structures in metal-organic frameworks (MOFs) render them quite attractive as a host-guest platform to address a variety of important issues at the frontiers of science. In this work, a perfluorophenylene functionalized metalloporphyrinic MOF, namely, PCN-624, has been rationally designed, synthesized, and structurally characterized. PCN-624 is constructed by 12-connected [Ni-8(OH)(4)(H2O)(2)Pz(12)] (Pz = pyrazolide) nodes and fluorinated 5,10,15,20-tetrakis-(2,3,5,6-tetrafluoro-4-(1H-pyrazol-4-yOphenyl)-porphyrin (TTFPPP) linker with an ftw-a topological net. Notably, PCN-624 exhibits extinguished robustness under different conditions, inCluding organic solvents, strong acid, and base aqueous solutions. The pore surface of PCN-624 is decorated with pendant perfluorophenylene groups. These moieties fabricate densely fluorinated nanocages resulting in the selective guest capture of the material. More importantly, PCN-624 can be employed as an efficient heterogeneous catalyst for the selective synthesis of fullerene-anthracene bisadduct. Owing to the high chemical robustness of PCN-624, it can be recyCled over five times without significant loss of its catalytic activity. All of these results demonstrate that MOFs can serve as a powerful platform with great flexibility for functional design to solve various synthetic problems.Tailor-Made Pyrazolide-Based Metal-Organic Frameworks for Selective Catalysisx78201875#N/AFALSE
1387
jacs.8b0600610.1021/jacs.8b06006FALSEhttps://doi.org/10.1021/jacs.8b06006Hupp, JTJ. Am. Chem. Soc.To modify its steric and electronic properties as a support for heterogeneous catalysts, electron withdrawing and electron-donating ligands, hexafluoroacetylacetonate (Facac(-)) and acetylacetonate (Acac(-)), were introduced to the metal-organic framework (MOF), NU-1000, via a process akin to atomic layer deposition (ALD). In the absence of Facac(-) or Acac(-), NU-1000-supported, AIM-installed Ni(II) sites yield a mixture of C4, C6, C8, and polymeric products in ethylene oligomerization. (AIM = (A) under bar LD-like deposition in (M) under bar OFs). In contrast, both Ni-Facac-AIM-NU-1000 and Ni-Acac-AIM-NU-1000 exhibit quantitative catalytic selectivity for C4 species. Experimental findings are supported by density functional theory calculations, which show increases in the Activation barrier for the C-C coupling step, due mainly to rearrangement of the siting of Facac(-) or Acac(-) to partially ligate added nickel. The results illustrate the important role of structure tuning support modifiers in controlling the activity of MOF-sited heterogeneous catalysts and in engendering catalytic selectivity. The results also illustrate the ease with which crystallographically well-defined modifications of the catalyst support can be introduced when the node coordinating molecular modifier is delivered via the vapor phase.Beyond the Active Site: Tuning the Activity and Selectivity of a Metal-Organic Framework-Supported Ni Catalyst for Ethylene Dimerization57201840#N/ATRUE
1388
jacs.8b0568010.1021/jacs.8b05680FALSEhttps://doi.org/10.1021/jacs.8b05680Brown, MKJ. Am. Chem. Soc.A three-component coupling of Aryl bromides, Arylboron reagents, and alkenylarenes is presented. The method tolerates a variety of substitution patterns on all of the components. In particular, 1,2-disubstituted alkenylarenes are suitable and undergo highly diastereoselective diArylation.Nickel-Catalyzed Stereoselective DiArylation of Alkenylarenes64201833#N/ATRUE
1389
jacs.8b0564410.1021/jacs.8b05644FALSEhttps://doi.org/10.1021/jacs.8b05644Humphrey, SMOrganoarsine Metal-Organic Framework with cis-Diarsine Pockets for the Installation of Uniquely Confined Metal Complexes2018#N/ATRUE
1390
jacs.8b0214410.1021/jacs.8b02144FALSEhttps://doi.org/10.1021/jacs.8b02144Guo, XGJ. Am. Chem. Soc.Development of high-performance unipolar n-type organic semiconductors still remains as a great challenge. In this work, all-acceptor bithiophene imide-based ladder-type small molecules BTIn and semiladder-type homopolymers PBTIn (n = 1-5) were synthesized, and their structure-property correlations were studied in depth. It was found that Pd-catalyzed Stille coupling is superior to Ni-mediated Yamamoto coupling to produce polymers with higher molecular weight and improved polymer quality, thus leading to greatly increased electron mobility (mu(e)). Due to their all-acceptor backbone, these polymers all exhibit unipolar n-type transport in organic thin-film transistors, accompanied by low off-currents (10(-10)-10(-9) A), large on/off current ratios (10(6)), and small threshold voltages (similar to 15-25 V). The highest kte, up to 3.71 cm(2) V-1 s(-1), is attained from PBTI1 with the shortest monomer unit. As the monomer size is extended, the mu(e) drops by 2 orders to 0.014 cm(2) for PBTIS. This monotonic decrease of ye was also observed in their homologous BTIn small molecules. This trend of mobility decrease is in good agreement with the evolvement of disordered phases within the film, as revealed by Raman spectroscopy and X-ray diffraction measurements. The extension of the ladder-type building blocks appears to have a large impact on the motion freedom of the building blocks and the polymer chains during film formation, thus negatively affecting film morphology and charge carrier mobility. The result indicates that synthesizing building blocks with more extended ladder-type backbone does not necessarily lead to improved mobilities. This study marks a significant advance in the performance of all-acceptor-type polymers as unipolar electron transporting materials and provides useful guidelines for further development of (semi)ladder-type molecular and polymeric semiconductors for applications in organic electronics.(Semi)ladder-Type Bithiophene Imide-Based All-Acceptor Semiconductors: Synthesis, Structure-Property Correlations, and Unipolar n-Type Transistor Performancex98201895#N/AFALSE
1391
jacs.8b0537410.1021/jacs.8b05374FALSEhttps://doi.org/10.1021/jacs.8b05374Giri, RJ. Am. Chem. Soc.We report a Ni-catalyzed regioselective AlkylArylation of Vinylarenes with Alkyl halides and Arylzinc reagents to generate 1,1-diArylalkanes. The reaction proceeds well with primary, secondary and tertiary Alkyl halides, and electronically diverse Arylzinc reagents. Mechanistic investigations by radical probes, competition studies and quantitative kinetics reveal that the current reaction proceeds via a Ni(0)/Ni(I)/Ni(II) catalytic cyCle by a rate-limiting direct halogen atom abstraction via single electron transfer to Alkyl halides by a Ni(0)-catalyst.Ni-Catalyzed Regioselective AlkylArylation of Vinylarenes via C(sp(3))-C(sp(3))/C(sp(3))-C(sp(2)) Bond Formation and Mechanistic Studies88201868#N/ATRUE
1392
jacs.8b0154810.1021/jacs.8b01548FALSEhttps://doi.org/10.1021/jacs.8b01548Yu, GHJ. Am. Chem. Soc.Seeking earth-abundant electrocatalysts with high efficiency and durability has become the frontier of energy conversion research. Mixed-transition-metal (MTM)-based electrocatalysts, owing to the desirable electrical conductivity, synergistic effect of bimetal atoms, and structural stability, have recently emerged as new-generation hydrogen evolution reaction (HER) electrocatalysts. However, the correlation between anion species and their intrinsic electrocatalytic properties in MTM-based electrocatalysts is still not well understood. Here we present a novel approach to tuning the 30 anion-dependent electrocatalytic characteristics in MTM-based catalyst for HER, using holey Ni/Co-based phosphides/selenides/oxides (Ni-Co-A, A = P, Se, O) as the model materials. The electrochemical results, combined with the electrical conductivity measurement and DFT calculation, reveal that P substitution could modulate the electron configuration, lower the hydrogen adsorption energy, and facilitate the desorption of hydrogen on the active sites in Ni-Co-A holey nanostructures, resulting in superior HER catalytic activity. Accordingly we fabricate the NCP holey nanosheet electrocatalyst for HER with an ultralow onset overpotential of nearly zero, an overpotential of 58 mV, and long-term durability, along with an applied potential of 1.56 V to boost overall water splitting at 10 mA cm(-2), among the best electrocatalysts reported for non noble-metal catalysts to date. This work not only presents a deeper understanding of the intrinsic HER electrocatalytic properties for MTM-based electrocatalyst with various anion species but also offers new insights to better design efficient and durable water splitting electrocatalysts.Dual Tuning of Ni-Co-A (A = P, Se, O) Nanosheets by Anion Substitution and Holey Engineering for Efficient Hydrogen Evolutionx270201831#N/AFALSE
1393
jacs.8b0146810.1021/jacs.8b01468FALSEhttps://doi.org/10.1021/jacs.8b01468Meyer, FJ. Am. Chem. Soc.Dioxygen Activation at nickel complexes is much less studied than for the biologically more relevant iron or copper systems but promises new reactivity patterns because of the distinct coordination chemistry of nickel. Here we report that a pyrazolate-based dinickel(II) dihydride complex [KL(Ni-H)(2)] (1a) smoothly reacts with O-2 via reductive H-2 elimination to give the mu-1,2-peroxo dinickel(II) complex [KLNi2(O-2)] (2a) and, after treatment with dibenzo[18]-crown-6, the separated ion pair [K(DB18C6)][LNi2(O-2)] (2b); these are the first mu-1,2-peroxo dinickel intermediates to be characterized by X-ray diffraction. In 2a, the K+ is found side-on associated with the peroxo unit, revealing a pronounced weaking of the O-O bond: d(O-O) = 1.482(2) angstrom in 2a versus 1.465(2) in 2b; (nu) over bar (O-O) = 720 cm(-1) in 2a versus 755 cm(-1) in 2b. Reaction of la (or 2a/2b) with an excess of O-2 Cleanly leads to [LNi2(O-2)] (3), which was shown by X-ray crystallography (d(O-O) = 1.326(2) angstrom), electron paramagnetic resonance and Raman spectroscopy ((nu) over bar (O-O) = 1007 cm(-1)), magnetic measurements, and density functional theory calculations to feature two low-spin d(8) nickel(II) ions and a genuine mu-1,2-superoxo ligand with the unpaired electron in the out-of-plane pi*(o-o) orbital. These mu-1,2-superoxo and mu-1,2-peroxo species, all containing the O-2-derived unit within the Cleft of the dinickel(II) core, can be reversibly interconverted chemically and also electrochemically at very low potential (E-1/2 = -1.22 V vs Fc/Fc(+)). Initial reactivity studies indicate that protonation of 2a, or reaction of 3 with TEMPO-H, ultimately gives the mu-hydroxo dinickel(II) complex [LNi2(mu-OH)] (4). This work provides an entire new series of Closely related and unusually rugged Ni-2/O-2 intermediates, avoiding the use of unstable nickel(I) precursors but storing the redox equivalents for reductive O-2-binding in nickel(II) hydride bonds.Reductive O-2 Binding at a Dihydride Complex Leading to Redox Interconvertible mu-1,2-Peroxo and mu-1,2-Superoxo Dinickel(II) Intermediatesx25201884#N/AFALSE
1394
jacs.8b0094710.1021/jacs.8b00947FALSEhttps://doi.org/10.1021/jacs.8b00947Rappe, AMJ. Am. Chem. Soc.The activity of Ni2P catalysts for the hydrogen evolution reaction (HER) is currently limited by strong H adsorption at the Ni3-hollow site. We investigate the effect of surface nonmetal doping on the HER activity of the Ni3P2 termination of Ni2P(0001), which is stable at modest electrochemical conditions. Using density functional theory (DFT) calculations, we find that both 2p nonmetals and heavier chalcogens provide nearly thermoneutral H adsorption at moderate surface doping concentrations. We also find, however, that only chalcogen substitution for surface P is exergonic. For intermediate surface concentrations of S, the free energy of H adsorption at the Ni3-hollow site is 0.11 eV, which is significantly more thermoneutral than the undoped surface (-0.45 eV). We use the regularized random forest machine learning algorithm to discover the relative importance of structure and charge descriptors, extracted from the DFT calculations, in determining the HER activity of Ni2P(0001) under different doping concentrations. We discover that the Ni Ni bond length is the most important descriptor of HER activity, which suggests that the nonmetal dopants induce a chemical pressure-like effect on the Ni3-hollow site, changing its reactivity through compression and expansion.Chemical Pressure-Driven Enhancement of the Hydrogen Evolving Activity of Ni2P from Nonmetal Surface Doping Interpreted via Machine Learningx56201838#N/AFALSE
1395
jacs.8b0524710.1021/jacs.8b05247FALSEhttps://doi.org/10.1021/jacs.8b05247Reisman, SEJ. Am. Chem. Soc.Nickel-Catalyzed Asymmetric Reductive Cross Coupling To Access 1,1-DiArylalkanes (vol 139, pg 5684, 2017)120181#N/ATRUE
1396
jacs.8b0519410.1021/jacs.8b05194FALSEhttps://doi.org/10.1021/jacs.8b05194Shafaat, HSJ. Am. Chem. Soc.Well-defined molecular systems for catalytic hydrogen production that are robust, easily generated, and active under mild aqueous conditions remain underdeveloped. Nickel-substituted rubredoxin (NiRd) is one such system, featuring a tetrathiolate coordination environment around the nickel center that is identical to the native [NiFe] hydrogenases and demonstrating hydrogenase-like proton reduction activity. However, until now, the catalytic mechanism has remained elusive. In this work, we have combined quantitative protein film electrochemistry with optical and vibrational spectroscopy, density functional theory calculations, and molecular dynamics simulations to interrogate the mechanism of H-2 evolution by NiRd. Proton-coupled electron transfer is found to be essential for catalysis. The coordinating thiolate ligands serve as the sites of protonation, a role that remains debated in the native [NiFe] hydrogenases, with reduction occurring at the nickel center following protonation. The rate-determining step is suggested to be intramolecular proton transfer via thiol inversion to generate a Ni-III-hydride species. NiRd catalysis is found to be completely insensitive to the presence of oxygen, another advantage over the native [NiFe] hydrogenase enzymes, with potential implications for membrane-less fuel cells and aerobic hydrogen evolution. Targeted mutations around the metal center are seen to increase the activity and perturb the rate determining process, highlighting the importance of the outer coordination sphere. Collectively, these results indicate that NiRd evolves H-2 through a mechanism similar to that of the [NiFe] hydrogenases, suggesting a role for thiolate protonation in the native enzyme and guiding rational optimization of the NiRd system.Going beyond Structure: Nickel-Substituted Rubredoxin as a Mechanistic Model for the [NiFe] Hydrogenases242018126#N/ATRUE
1397
jacs.8b0050310.1021/jacs.8b00503FALSEhttps://doi.org/10.1021/jacs.8b00503Uyeda, CJ. Am. Chem. Soc.Azoarenes are valuable chromophores that have been extensively incorporated as photoswitchable elements in molecular machines and biologically active compounds. Here, we report a catalytic nitrene dimerization reaction that provides access to structurally and electronically diverse azoarenes. The reaction utilizes Aryl azides as nitrene precursors and generates only gaseous N-2 as a byproduct. By circumventing the use of a stoichiometric redox reagent, a broad range of organic functional groups are tolerated, and common byproducts of current methods are avoided. A catalyst featuring a Ni-Ni bond is found to be uniquely effective relative to those containing only a single Ni center. The mechanistic origins of this nuClearity effect are described.Catalytic Azoarene Synthesis from Aryl Azides Enabled by a DinuClear Ni Complexx372018102#N/AFALSE
1398
jacs.8b0027110.1021/jacs.8b00271https://doi.org/10.1021/jacs.8b00271Frei, HJ. Am. Chem. Soc.Monitoring of visible light sensitized reduction of CO2 at Cu nanopartiCles in aqueous solution by rapid-scan ATR FT-IR spectroscopy on the time scale of seconds allowed structural identification of a one-electron intermediate and demonstrated its kinetic relevancy for the first time. Isotopic labeling (C-12: 1632, 1358, 1346 cm(-1); C-13: 1588, 1326, 1316 cm(-1)) revealed a species of carbon dioxide dimer radical anion structure, most likely bound to the catalyst surface through carbon. Intermediacy of Cu-C(=O)OCO2- surface species is in agreement with a recently proposed mechanism for electrocatalytic CO2 reduction at Cu metal nanopartiCles based on Tafel slope analysis. Spontaneous decrease of the intermediate after termination of the photosensitization pulse (Sn porphyrin excited at 405 nm) was accompanied by the growth of HCO3-. CO was produced as well, but sensitive detection required photolysis for tens of minutes. A direct kinetic link between a C2O4- surface intermediate and the CO product was also demonstrated for photocatalyzed CO2 reduction at aqueous CdSe nanopartiCles, where first order growth of a Cd-C(=O)OCO2- species was accompanied by rise of CO (monitored by a fast Ni complex trap) and HCO3- showing a distinct induction period. The detection of the one-electron surface intermediate and confirmation of its catalytic relevancy was enabled by the delivery of electrons one-by-one by the photosensitization method. The observation of carbon dioxide dimer radical anion points to approaches for rate enhancements of heterogeneous CO2 reduction by creating catalytic environments that favor formation of this intermediate.Carbon Dioxide Dimer Radical Anion as Surface Intermediate of Photoinduced CO2 Reduction at Aqueous Cu and CdSe NanopartiCle Catalysts by Rapid-Scan FT-IR SpectroscopyPhotocatalystx43201862#N/AFALSE
1399
jacs.8b0513410.1021/jacs.8b05134FALSEhttps://doi.org/10.1021/jacs.8b05134Ramakrishna, SJ. Am. Chem. Soc.The durability and reactivity of catalysts can be effectively and precisely controlled through the careful design and engineering of their surface structures and morphologies. Herein, we develop a novel adsorption-calcination-reduction strategy to synthesize spinel transitional metal oxides with a unique necklace-like multishelled hollow structure exploiting sacrificial templates of carbonaceous microspheres, inCluding NiCo2O4 (NCO), CoMn2O4, and NiMn2O4. Importantly, benefiting from the unique structures and reduction treatment to offer rich oxygen vacancies, the unique reduced NCO (R-NCO) as a bifunctional electrocatalyst exhibits the dual characteristics of good stability as well as high electrocatalytic activity for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). At 1.61 V cell voltage, a 10 mA cm(-2) water splitting current density is obtained from the dual-electrode, alkaline water electrolyzer. Calculations based on density functional theory (DFT) reveal a mechanism for the promotion of the catalytic reactions based on a decrease in the energy barrier for the formation of intermediates resulting from the introduction of oxygen vacancies through the reduction process. This method could prove to be an effective general strategy for the preparation of complex, hollow structures and functionalities.Necklace-like Multishelled Hollow Spinel Oxides with Oxygen Vacancies for Efficient Water Electrolysis195201859#N/ATRUE
1400
jacs.8b0001510.1021/jacs.8b00015https://doi.org/10.1021/jacs.8b00015Mayer, JMJ. Am. Chem. Soc.Tandem dye-sensitized photoelectrosynthesis cells are promising architectures for the production of solar fuels and commodity chemicals. A key bottleneck in the development of these architectures is the low efficiency of the photocathodes, leading to small current densities. Herein, we report a new design principle for highly active photocathodes that relies on the outer-sphere reduction of a substrate from the dye, generating an unstable radical that proceeds to the desired product. We show that the direct reduction of dioxygen from dye-sensitized nickel oxide (NiO) leads to the production of H2O2. In the presence of oxygen and visible light, NiO photocathodes sensitized with commercially available porphyrin, coumarin, and ruthenium dyes exhibit large photocurrents (up to 400 mu A/cm(2)) near the thermodynamic potential for O-2/H2O2 in near-neutral water. Bulk photoelectrolysis of porphyrin-sensitized NiO over 24 h results in millimolar concentrations of H2O2 with essentially 100% faradaic efficiency. To our knowledge, these are among the most active NiO photocathodes reported for multiproton/multielectron transformations. The photoelectrosynthesis proceeds by initial formation of superoxide, which disproportionates to H2O2. This disproportionation-driven charge separation circumvents the inherent challenges in separating electron-hole pairs for photocathodes tethered to inner sphere electrocatalysts and enables new applications for photoelectrosynthesis cells.Highly Active NiO Photocathodes for H2O2 Production Enabled via Outer-Sphere Electron TransferPhotocatalyst33201840#N/AFALSE
1401
jacs.8b0405310.1021/jacs.8b04053FALSEhttps://doi.org/10.1021/jacs.8b04053Smith, ABJ. Am. Chem. Soc.A unified synthetic strategy leading to the total synthesis of (-)-nodulisporic acids D, C, and B is described. Key synthetic transformations inClude a nickel-chromium-mediated cyClization, an aromatic ring functionalization employing a novel copper-promoted Alkylation, a palladium-catalyzed cross-coupling cascade/indole ring construction, and a palladium-mediated regio- and diastereoselective allylic substitution/cyClization reaction, the latter to construct ring D.Total Synthesis of (-)-Nodulisporic Acids D, C, and B: Evolution of a Unified Synthetic Strategy11201886#N/ATRUE
1402
jacs.7b1344810.1021/jacs.7b13448FALSEKonig, BLigand-Controlled Regioselective HydroCarbonylation of Styrenes with CO2 by Combining Visible Light and Nickel Catalysisx2018#N/AFALSE
1403
jacs.7b1328110.1021/jacs.7b13281https://doi.org/10.1021/jacs.7b13281Doyle, AGJ. Am. Chem. Soc.Here we investigate the photophysics and photochemistry of Ni(II) Aryl halide complexes common to cross-coupling and Ni/photoredox reactions. Computational and ultrafast spectroscopic studies reveal that these complexes feature long-lived (MLCT)-M-3 excited states, implicating Ni as an underexplored alternative to precious metal photocatalysts. Moreover, we show that (MLCT)-M-3 Ni(II) engages in bimolecular electron transfer with ground-state Ni(II), which enables access to Ni(III) in the absence of external oxidants or photoredox catalysts. As such, it is possible to facilitate Ni-catalyzed C-O bond formation solely by visible light irradiation, thus representing an alternative strategy for catalyst Activation in Ni cross-coupling reactions.Long-Lived Charge-Transfer States of Nickel(II) Aryl Halide Complexes Facilitate Bimolecular Photoinduced Electron TransferPhotocatalyst87201836#N/AFALSE
1404
jacs.8b0354910.1021/jacs.8b03549FALSEhttps://doi.org/10.1021/jacs.8b03549RajanBabu, TVJ. Am. Chem. Soc.A stereogenic center, placed at an exocyClic location next to a chiral carbon in a ring to which it is attached, is a ubiquitous structural motif seen in many bioactive natural products, inCluding di and triterpenes and steroids. Installation of these centers has been a long-standing problem in organic chemistry. Few Classes of compounds illustrate this problem better than serrulatanes and amphilectanes, which carry multiple methyl-bearing exocyClic chiral centers. Nickel-catalyzed asymmetric hydroVinylation (AHV) of Vinylarenes and 1,3-dienes such as 1-VinylcyCloalkenes provides an exceptionally facile way of introducing these chiral centers. This ArtiCle documents our efforts to demonstrate the generality of AHV to access not only the natural products but also their various diastereoisomeric derivatives. Key to success here is the availability of highly tunable phosphoramidite Ni(II) complexes useful for overcoming the inherent selectivity of the chiral intermediates. The yields for hydroVinylation (HV) reactions are excellent, and selectivities are in the range of 92-99% for the desired isomers. Discovery of novel, configurationally fluxional, yet sterically less demanding 2,2'-biphenol-derived phosphoramidite Ni complexes (fully characterized by X-ray) turned out to be critical for success in several HV reactions. We also report a less spectacular yet equally important role of solvents in a metal ammonia reduction for the installation of a key Benzylic chiral center. Starting with simple oxygenated styrene derivatives, we iteratively install the various exocyClic chiral centers present in typical serrulatane [e.g., a (+)-p-benzoquinone natural product, elisabethadione, nor-elisabethadione, helioporin D, a known advanced intermediate for the synthesis of colombiasin and elisapterosin] and amphilectane [e.g., A-F, G-J, and K,L pseudopterosins] derivatives. A concise table showing various synthetic approaches to these molecules is inCluded in the Supporting Information. Our attempts to synthesize a hitherto elusive target, elisabethin A, led to a stereoselective, biomimetic route to pseudopterosin A F aglycones.Broadly Applicable Stereoselective Syntheses of Serrulatane, Amphilectane Diterpenes, and Their Diastereoisomeric Congeners Using Asymmetric HydroVinylation for Absolute Stereochemical Control15201896#N/ATRUE
1405
jacs.8b0311710.1021/jacs.8b03117FALSEhttps://doi.org/10.1021/jacs.8b03117Wei, MJ. Am. Chem. Soc.The mechanism on interfacial synergistic catalysis for supported metal catalysts has long been explored and investigated in several important heterogeneous catalytic processes (e.g., water-gas shift (WGS) reaction). The modulation of metal-support interactions imposes a substantial influence on activity and selectivity of catalytic reaction, as a result of the geometric/electronic structure of interfacial sites. Although great efforts have validated the key role of interfacial sites in WGS over metal catalysts supported on reducible oxides, direct evidence at the atomic level is lacking and the mechanism of interfacial synergistic catalysis is still ambiguous. Herein, Ni nanopartiCles supported on TiO2-x (denoted as Ni@TiO2-x) were fabricated via a structure topotactic transformation of NiTi-layered double hydroxide (NiTi-LDHs) precursor, which showed excellent catalytic performance for WGS reaction. In situ microscopy was carried out to reveal the partially encapsulated structure of Ni@TiO2, catalyst. A combination study inCluding in situ and operando EXAFS, in situ DRIFTS spectra combined with TPSR measurements substantiates a new redox mechanism based on interfacial synergistic catalysis. Notably, interfacial Ni species (electron -enriched Ni delta- site) participates in the dissociation of H2O molecule to generate H-2, accompanied by the oxidation of Ni delta--O-v-Ti3+ (O-v: oxygen vacancy) to Ni delta+-O-Ti4+ structure. Density functional theory calculations further verify that the interfacial sites of Ni@ TiO2-x catalyst serve as the optimal active site with the lowest Activation energy barrier (similar to 0.35 eV) for water dissociation. This work provides a fundamental understanding on interfacial synergistic catalysis toward WGS reaction, which is constructive for the rational design and fabrication of high activity heterogeneous catalysts.Insights into Interfacial Synergistic Catalysis over Ni@TiO2-x Catalyst toward Water-Gas Shift Reaction86201854#N/ATRUE
1406
jacs.7b1261510.1021/jacs.7b12615FALSEhttps://doi.org/10.1021/jacs.7b12615Dai, ZHJ. Am. Chem. Soc.The construction of highly efficient and stable Pt-free catalysts for electrochemical hydrogen generation is highly desirable. Herein, we demonstrate the first metal-phosphides-metal system consisting of Ru, Ni2P, and Ni, which forms unique multiheterogeneous Ni@Ni2P-Ru nanorods. Interestingly, a Ru modulation effects that promotes the desorption of H-2 to achieve a moderate hydrogen adsorption energy (Delta G(H)), and enables the formation of Ni@Ni2P nanorods via Ru-Ni coordination to enhance the conductivity was discovered. Due to its optimal Delta G(H), improved conductivity and rodlike morphology, this catalyst shows superior electrocatalytic HER performances in both acidic and alkaline conditions, which are superior to those of some recently reported phosphides and Close to that of commercial 20% Pt/C. Such a design strategy is not limited to Ni2P and Ru but also may be extended to other similar phosphides and noble metals, providing a new promising approach and an alternative to Pt catalysts for electrocatalytic applications.Ru Modulation Effects in the Synthesis of Unique Rod-like Ni@Ni2P-Ru Heterostructures and Their Remarkable Electrocatalytic Hydrogen Evolution Performance
Electrocatalytic
160201821#N/AFALSE
1407
jacs.7b1221310.1021/jacs.7b12213FALSEhttps://doi.org/10.1021/jacs.7b12213Malcolmson, SJJ. Am. Chem. Soc.We introduce a new strategy for synthesis of chiral amines: couplings of alpha-aminoAlkyl nuCleophiles generated by enantioselective migratory insertion of 2-azadienes to a Cu-H. In this report, we demonstrate its application in catalytic reductive coupling of 2-azadienes and ketones to furnish 1,2-amino tertiary alcohols with vicinal stereogenic centers.2-Azadienes as Reagents for Preparing Chiral Amines: Synthesis of 1,2-Amino Tertiary Alcohols by Cu-Catalyzed Enantioselective Reductive Couplings with Ketonesx39201868#N/AFALSE
1408
jacs.8b0296310.1021/jacs.8b02963FALSEhttps://doi.org/10.1021/jacs.8b02963Coates, GWJ. Am. Chem. Soc.We report the discovery of C-2-symmetric nickel catalysts capable of the regio- and isoselective polymerization of 1-butene to produce isotactic 4,2-poly(1-butene), a new semi-crystalline polyolefin. The catalyst exhibits enantioface selectivities as high as 84% and the resulting polymers display melting temperatures up to 86 degrees C. This system marks a rare example of preserving stereochemistry through a chain walking polymerization process.Synthesis of Semicrystalline Polyolefin Materials: Precision Methyl Branching via Stereoretentive Chain Walking32201841#N/ATRUE
1409
jacs.8b0254210.1021/jacs.8b02542FALSEhttps://doi.org/10.1021/jacs.8b02542Liu, YHJ. Am. Chem. Soc.The first efficient and general nickel-catalyzed hydrocyanation of terminal alkynes with Zn(CN)(2) in the presence of water has been developed. The reaction provides a regioselective protocol for the synthesis of functionalized Vinyl nitriles with a range of structural diversity under mild reaction conditions while obviating use of the volatile and hazardous reagent of HCN. Deuterium-labeling experiments confirmed the role of water as the hydrogen source in this hydrocyanation reaction.Nickel-Catalyzed Highly Regioselective Hydrocyanation of Terminal Alkynes with Zn(CN)(2) Using Water as the Hydrogen Source42201845#N/ATRUE
1410
jacs.7b1195310.1021/jacs.7b11953FALSEhttps://doi.org/10.1021/jacs.7b11953McDonald, ARJ. Am. Chem. Soc.Oxo-metal-halide moieties have often been implicated as C-H bond activating oxidants with the terminal oxo-metal entity identified as the electrophilic oxidant. The electrophilic reactivity of metal-halide species has not been investigated. We have prepared a high-valent nickel-halide complex [Ni-III(Cl)(L)] (2, L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamide) by one-electron oxidation of a [Ni-II(Cl)(L)](-) precursor. 2 was characterized using electronic absorption, electron paramagnetic resonance, and X-ray absorption spectroscopies and mass spectrometry. 2 reacted readily with substrates containing either phenolic O-H or hydrocarbon C-H bonds. Analysis of the Hammett, Evans-Polanyi, and Marcus relationships between the determined rate constants and substrate pK(a), X-H bond dissociation energy, and oxidation potential, respectively, was performed. Through this analysis, we found that 2 reacted by a hydrogen atom transfer (HAT) mechanism. Our findings shine light on enzymatic high-valent oxo-metal-halide oxidants and open new avenues for oxidative halogenation catalyst design.Hydrogen Atom Transfer by a High-Valent Nickel-Chloride Complexx192018100#N/AFALSE
1411
jacs.8b0250810.1021/jacs.8b02508FALSEhttps://doi.org/10.1021/jacs.8b02508Murray, LJJ. Am. Chem. Soc.One-electron reduction of Cu3EL (L3- = tris(beta-diketiminate)cyClophane, and E = S, Se) affords [Cu3EL](-), which reacts with CO2 to yield exClusively C2O42- (95% yield, TON = 24) and regenerate Cu3EL. Stopped-flow UV/visible data support an A -> B mechanism under pseudo-first-order conditions (k(obs), (298K) = 115(2) s(-1)), which is 10(6) larger than those for reported copper complexes. The k(obs) values are dependent on the countercation and solvent (e.g., k(obs) is greater for [K(18-crown-6)](+) vs (Ph3P)(2)N+, and there is a 20-fold decrease in k(obs) in THF vs DMF). Our results suggest a mechanism in which cations and solvent influence the stability of the transition state.Countercations and Solvent Influence CO2 Reduction to Oxalate by Chalcogen-Bridged Tricopper CyClophanates21201886#N/ATRUE
1412
jacs.8b0222510.1021/jacs.8b02225FALSEhttps://doi.org/10.1021/jacs.8b02225Goddard, WAJ. Am. Chem. Soc.The oxygen evolution reaction (OER) is critical to efficient water splitting to produce the H-2 fuel for sustainable energy production. Currently, the best non noble metal OER electrocatalyst in base conditions is the Fe-doped NiOOH (N1-xFexOOH), with an overpotential of eta = 0.4, but much lower values are desired. We use density functional theory to determine the overall mechanism for the OER of N1-xFexOOH, conCluding that promoting radical character on the metal-oxo bond is critical to efficient OER Then we consider replacing Fe with 17 other transition metals of the Fe, Ru, and Os rows, where we find 3 new promising candidates: Co, Rh, and Ir, which we estimate to have eta = 0.27, 0.15, and 0.02, respectively, all very much improved performance compared to Fe, making all three systems excellent candidates for experimental testing.In Silico Discovery of New Dopants for Fe-Doped Ni Oxyhydroxide (N1-xFexOOH) Catalysts for Oxygen Evolution Reaction143201818#N/ATRUE
1413
jacs.8b0172610.1021/jacs.8b01726FALSEhttps://doi.org/10.1021/jacs.8b01726Sarlah, DJ. Am. Chem. Soc.We describe the development of an arenophile-mediated, nickel-catalyzed dearomative trans-1,2-carboamination protocol. A range of readily available aromatic compounds was converted to the corresponding dienes using Grignard reagents as nuCleophiles. This strategy provided products with exClusive trans-selectivity and high enantioselectivity was observed in case of benzene and naphthalene. The utility of this methodology was showcased by controlled and stereoselective preparation of small, functionalized molecules.Nickel-Catalyzed Dearomative trans-1,2-Carboamination42201875#N/ATRUE
1414
jacs.8b0075210.1021/jacs.8b00752FALSEhttps://doi.org/10.1021/jacs.8b00752Zhang, BJ. Am. Chem. Soc.A fundamental understanding of the origin of oxygen evolution reaction (OER) activity of transition metal-based electrocatalysts, especially for single precious metal atoms supported on layered double hydroxides (LDHs), is highly required for the design of efficient electrocatalysts toward further energy conversion technologies. Here, we aim toward single-atom Au supported on NiFe LDH (Au-s/NiFe LDH) to Clarify the activity origin of LDHs system and a 6-fold OER activity enhancement by 0.4 wt % Au-s decoration. Combining with theoretical calculations, the active behavior of NiFe LDH results from the in situ generated NiFe oxyhydroxide from LDH during the OER process. With the presence of Au-s, Au-s/NiFe LDH possesses an overpotential of 0.21 V in contrast to the calculated result (0.18 V). We ascribe the excellent OER activity of sAu/NiFe LDH to the charge redistribution of active Fe as well as its surrounding atoms causing by the neighboring Au-s on NiFe oxyhydroxide stabilized by interfacial CO32- and H2O interfacing with LDH.Single-Atom Au/NiFe Layered Double Hydroxide Electrocatalyst: Probing the Origin of Activity for Oxygen Evolution Reaction399201845#N/ATRUE
1415
jacs.7b1104210.1021/jacs.7b11042FALSEhttps://doi.org/10.1021/jacs.7b11042Clerac, RJ. Am. Chem. Soc.An iron(II) pyridyl-benzohydrazonate-based complex decorated with long Alkyl chains is reported as a rare spin-crossover compound displaying a wide thermal hysteresis spanning room temperature. On heating, this compound exhibits a spin transition between a LS ground state and an ordered HS-LS phase with symmetry breaking from monoClinic P2(1)/n into orthorhombic P2(1)2(1)2 space groups. During cooling, the compound first transits into a magnetically distinguishable HS-LS phase with monoClinic P2(1) symmetry before returning into the LS phase. Interconversion between the two distinct HS-LS phases is the result of subtle structural changes in the Alkyl chains and produces a second minor thermal hysteresis that superposes to the large one. This unprecedented result shows that the combination of a conventional cooperative spin transition and ligand-driven magnetic changes can promote magnetic tristability at room temperature.Multistability at Room Temperature in a Bent-Shaped Spin-Crossover Complex Decorated with Long Alkyl Chainsx43201842#N/AFALSE
1416
jacs.8b0060510.1021/jacs.8b00605FALSEhttps://doi.org/10.1021/jacs.8b00605Farha, OKJ. Am. Chem. Soc.Nickel(IV) bis(dicarbollide) is incorporated in a zirconium-based metal organic framework (MOF), NU-1000, to create an electrically conductive MOF with mesoporosity. All the nickel bis(dicarbollide) units are located as guest molecules in the microporous channels of NU-1000, which permits the further incorporation of other active species in the remaining mesopores. For demonstration, manganese oxide is installed on the nodes of the electrically conductive MOF. The electrochemically addressable fraction and specific capacitance of the manganese oxide in the conductive framework are more than 10 times higher than those of the manganese oxide in the parent MOF.Increased Electrical Conductivity in a Mesoporous Metal-Organic Framework Featuring Metallacarboranes Guests98201866#N/ATRUE
1417
jacs.8b0013110.1021/jacs.8b00131FALSEhttps://doi.org/10.1021/jacs.8b00131Krische, MJJ. Am. Chem. Soc.p-Bromo-terminated oligo(p-phenylenevi-nylenes) emanating from a 1,3,S-benzene core are dihydroxylated and subjected to ruthenium catalyzed diol-diene benzannulation to form tripodal oligo(phenylenes). Copper- or nickel-mediated 3-fold reductive biAryl homocoupling delivers a series of triple-stranded phenylene cages of helical rod-like topology bearing 14, 17, and 20 benzene rings.Helical Rod-like Phenylene Cages via Ruthenium Catalyzed Diol-Diene Benzannulation: A Cord of Three Strands17201873#N/ATRUE
1418
jacs.7b1064310.1021/jacs.7b10643FALSEhttps://doi.org/10.1021/jacs.7b10643Morris, AJJ. Am. Chem. Soc.Metal-organic frameworks (MOFs) have shown great promise in catalysis, mainly due to their high content of active centers, large internal surface areas, tunable pore size, and versatile chemical functionalities. However, it is a challenge to rationally design and construct MOFs that can serve as highly stable and reusable heterogeneous catalysts. Here two new robust 3D porous metal-cyClam-based zirconium MOFs, denoted VPI-100 (Cu) and VPI-100 (Ni), have been prepared by a modulated synthetic strategy. The frameworks are assembled by eight-connected Zr-6 Clusters and metallocyClams as organic linkers. Importantly, the cyClam core has accessible axial coordination sites for guest interactions and maintains the electronic properties exhibited by the parent cyClam ring. The VPI-100 MOFs exhibit excellent chemical stability in various organic and aqueous solvents over a wide pH range and show high CO2 uptake capacity (up to similar to 9.83 wt% adsorption at 273 K under 1 atm). Moreover, VPI-100 MOFs demonstrate some of the highest reported catalytic activity values (turnover frequency and conversion efficiency) among Zr-based MOFs for the chemical fixation of CO2 with epoxides, inCluding sterically hindered epoxides. The MOFs, which bear dual catalytic sites (Zr and Cu/Ni), enable chemistry not possible with the cyClam ligand under the same conditions and can be used as recoverable stable heterogeneous catalysts without losing performance.A New Class of Metal-CyClam-Based Zirconium Metal-Organic Frameworks for CO2 Adsorption and Chemical Fixationx120201876#N/AFALSE
1419
jacs.7b1053710.1021/jacs.7b10537FALSEhttps://doi.org/10.1021/jacs.7b10537Hartwig, JFJ. Am. Chem. Soc.Recent interest in the valorization of lignin has led to reactions involving the Cleavage of strong aromatic C-O bonds. However, few experimental mechanistic studies of these reactions have been published. We report detailed mechanistic analysis of the hydrogenolysis of diAryl ethers catalyzed by the combination of Ni(COD)(2) (COD = 1,5-cyClooctadiene) and an N-heterocyClic carbene (NHC). Experiments on the catalytic reaction indicated that NaOt-Bu was necessary for catalysis, but kinetic analysis showed that the base is not involved in the rate-limiting C-O bond Cleavage. The resting state of the catalyst is an NHC-Ni(eta(6)-arene) complex. Substitution of the coordinated solvent with diAryl ether allowed isolation of a diAryl ether-bound Ni complex. Rate-limiting C-O bond Cleavage occurs to generate a three-coordinate product of oxidative addition, a metallacyClic version of which has been prepared independently. Stoichiometric studies show that arene and phenol products are released following reaction with H-2. NaOt-Bu was found to deprotonate the phenol product and to prevent formation of inactive Ni-I dimers.Mechanistic Investigations of the Hydrogenolysis of Diary! Ethers Catalyzed by Nickel Complexes of N-HeterocyClic Carbene Ligandsxy39201747#N/AFALSE
1420
jacs.7b1353610.1021/jacs.7b13536FALSEhttps://doi.org/10.1021/jacs.7b13536Muller, TJ. Am. Chem. Soc.2,5-Disilylsubstituted germole dianions 1 react with hafnocene dichloride to give hafnocene-based bicyClo[2.1.1]hexene germylenes 3. Their formation proceeds via hafnocene-germylene complexes 2 that were identified by NMR and UV spectroscopy. Germylenes 3 are stabilized by homoconjugation between the empty 4p(Ge) orbital and the pi-bond of the innercyClic C-2=C-3 double bond. This interaction can be understood as sigma(2), pi-coordination of the butadiene part to the dicoordinated germanium atom that leaves the 16e(-) hafnocene moiety electronically unsaturated. We demonstrate that this new Class of germylenes might serve as ligand to a variety of low-valent transition-metal complexes. The structure of the germylene ligand in complexes with Fe(0), Ni(0), and Au(I) and in reaction products with N-heterocyClic carbenes showed an intriguing structural flexibility that allows to accommodate different electronic situations at the ligating germanium atom. The origin of this structural adaptability is the interplay between the topological flexible unsaturated germanium ring and the hafnocene group.Hafnocene-based BicyClo[2.1.1]hexene Germylenes - Formation, Reactivity, and Structural Flexibility20201851#N/ATRUE
1421
jacs.7b1322010.1021/jacs.7b13220FALSEhttps://doi.org/10.1021/jacs.7b13220Martin, RJ. Am. Chem. Soc.A site-selective catalytic incorporation of multiple CO2 molecules into 1,3-dienes en route to adipic acids is described. This protocol is characterized by its mild conditions, excellent chemo- and regioselectivity and ease of execution under CO2 (1 atm), inCluding the use of bulk butadiene and/or isoprene feedstocks.Ni-Catalyzed Site-Selective DiCarbonylation of 1,3-Dienes with CO256201857#N/ATRUE
1422
jacs.7b1028110.1021/jacs.7b10281https://doi.org/10.1021/jacs.7b10281Brookhart, MJ. Am. Chem. Soc.Copolymerizations of ethylene with Vinyltrialkoxysilanes using cationic (alpha-diimine)Ni(Me)(CH3CN)(+) complexes 4a,b/B(C6F5)(3) yield high molecular weight copolymers exhibiting highly branched to nearly linear backbones depending on reaction conditions and catalyst choice. Polymerizations are first-order in ethylene pressure and inverse-order in silane concentration. Microstructural analysis of the copolymers reveals both in-chain and chain-end incorporation of -Si(OR)(3) groups whose ratios depend on temperature and ethylene pressure. Detailed low-temperature NMR spectroscopic investigations show that well-defined complex 3b (alpha-diimine)Ni(Me)(OEt2)(+) reacts rapidly at -60 degrees C with Vinyltrialkoxysilanes via both 2,1 and 1,2 insertion pathways to yield 4- and 5-membered chelates, respectively. Such chelates are the major catalyst resting states but are in rapid equilibrium with ethylene-opened chelates, (alpha-diimine)Ni(R)-(C2H4)(+) complexes, the species responsible for chain growth. Chelate rearrangement via beta-silyl elimination accounts for formation of chain-end -Si(OR)(3) groups and constitutes a chain-transfer mechanism. Chelate formation and coordination of the Ni center to the ether moiety, R-O-Si, of the Vinylsilane somewhat decreases the turnover frequency (TOF) relative to ethylene homopolymerization, but still remarkably high TOFs of up to 4.5 x 10(5) h(-1) and overall productivities can be achieved. Activation of readily available (alpha-diimine)NiBr2 complexes 2 with a combination of AlMe3/B(C6F5)(3)/[Ph3C][B(C6F5)(4)] yields a highly active and productive catalyst system for the convenient synthesis of the copolymer, a cross-linkable PE. For example, copolymers containing 0.23 mol % silane can be generated at 60 degrees C, 600 psig ethylene over 4 h with a productivity of 560 kg copolymer/g Ni. This method offers an alternative route to these materials, normally prepared via radical routes, which are precursors to the commercial cross-linked polyethylene, PEX-b.Nickel-Catalyzed Copolymerization of Ethylene and Vinyltrialkoxysilanes: Catalytic Production of Cross-Linkable Polyethylene and Elucidation of the Chain-Growth Mechanismx56201777#N/AFALSE
1423
jacs.7b0991410.1021/jacs.7b09914FALSEhttps://doi.org/10.1021/jacs.7b09914Schatz, GCJ. Am. Chem. Soc.We present a combined theoretical and experimental study of CO hydrogenation on a Ni(110) surface, inCluding studies of the role of gas-phase atomic hydrogen, surface hydrogen, and subsurface hydrogen reacting with adsorbed CO. Reaction mechanisms leading both to methane and methanol are considered. In the reaction involving surface or subsurface hydrogen, we investigate four possible pathways, using density functional theory to characterize the relative energetics of each intermediate, inCluding the importance of further hydrogenation versus C-O bond breaking, where the latter may lead to methane production. The most energetically favorable outcome is the production of methanol along a pathway involving the sequential hydrogenation of CO to a H3CO* intermediate, followed by a final hydrogenation to give methanol. In addition, we find that subsurface hydrogen noticeably alters reaction barriers, both passively and through the energy released by diffusion to the surface. Indeed, the effective reaction barriers are even lower than for CO methanolation on Cu(211) and Cu(111) than for Ni(110). In studies of gas-phase H atoms impinging on a CO-adsorbed Ni(110) surface, Born-Oppenheimer molecular dynamics simulations show that direct impact of H is unlikely to result in hydrogenation of CO. This means that Eley-Rideal or hot-atom mechanisms are not important; thus, thermal reactions involving subsurface hydrogen are the primary reaction mechanisms leading to methanol. Finally, we demonstrate experimentally for the first time the production of methanol and formaldehyde from CO hydrogenation on Ni(110) and confirm the role of subsurface hydrogen in the mechanism of this reaction.Hydrogenation of CO to Methanol on Ni(110) through Subsurface Hydrogenx26201746#N/AFALSE
1424
jacs.7b1319310.1021/jacs.7b13193FALSEhttps://doi.org/10.1021/jacs.7b13193Chen, WJ. Am. Chem. Soc.Catalyst plays a very important role in the exploration of new energy. To obtain a highly efficient electrocatalyst for the glucose oxidation and tiny metal nanoCluster catalysts, a calixarene-based {Ni-18} coordination wheel with sulfur atoms on the cavity surface was designed, synthesized, and used as the porous template. Contributing from the active sites of nickel cations, the as-synthesized coordination wheels can efficiently catalyze the electrochemical oxidation of glucose with the onset and peak potentials of 0.3 and 0.46 V in alkaline medium, and the catalysis does not depend on the atmosphere (N-2, air, or O-2), which indicates that the coordination wheel will be a promising electrocatalyst candidate for the compartmentless glucose-air fuel cell. Meanwhile, benefiting from its confined cavity and inner sulfur surface, such a coordination wheel can serve as a general template for the fabrication and encapsulation of tiny metal nanoClusters of Au, Pd, Ir, Ru, Rh, Pt, and AuPd. In electrochemical examinations, the bimetallic AuPd Clusters confined in the coordination wheel show higher current density than commercial Pt/C toward hydrogen evolution reaction (HER). The present study shows that the designed coordination wheel can be used as not only a type of novel catalyst itself but also a Class of templates for metal Cluster catalysts.Calixarene-Based {Ni-18} Coordination Wheel: Highly Efficient Electrocatalyst for the Glucose Oxidation and Template for the Homogenous Cluster Fabrication43201880#N/ATRUE
1425
jacs.7b0948210.1021/jacs.7b09482https://doi.org/10.1021/jacs.7b09482Hong, XJ. Am. Chem. Soc.N-Glutarimide amides have recently emerged as an exceptional group of compounds with unusually high reactivity in amide C-N bond Activation. To understand the key factors that control the remarkable reactivity of these resonance destabilized amides, we explored the Ni-catalyzed deCarbonylative and nondeCarbonylative Suzuki-Miyaura coupling with N-glutarimide amides, through density functional theory calculations. Two leading effects are responsible for the C-N Cleavage activity of N-glutarimide amides, the coordinating N-substituents and the geometric twisting. The Carbonyl substituent of the N-glutarimide amides provides crucial nickel-oxygen interaction, which essentially acts as a directing group to facilitate the formation of the reactive intermediate for the amide C-N bond Cleavage. The geometric twisting weakens the resonance stability by removing the acyl-nitrogen conjugation, which lowers the energy penalty for the C-N bond stretch during oxidative addition. For the chemoselectivity of deCarbonylation versus Carbonyl retention, we found that the C-C reductive elimination for ketone formation is kinetically faster than that for biAryl formation, while ketone is thermodynamically less stable with respect to the deCarbonylated biAryls. The computations also suggest that the nickel catalyst is able to promote the deCarbonylation of biAryl ketones via an unexpected C-C bond Activation.Factors Controlling the Reactivity and Chemoselectivity of Resonance Destabilized Amides in Ni-Catalyzed DeCarbonylative and NondeCarbonylative Suzuki-Miyaura Couplingx612017905/11/2022FALSE
1426
jacs.7b0934310.1021/jacs.7b09343FALSEhttps://doi.org/10.1021/jacs.7b09343Cavazza, CJ. Am. Chem. Soc.Designing systems that merge the advantages of heterogeneous catalysis, enzymology, and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, and molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial nonheme iron oxygenase crystals, we filled this gap by developing biobased heterogeneous catalysts capable of oxidizing carbon-carbon double bonds. First, reductive O-2 Activation induces selective oxidative Cleavage, revealing the indestructible character of the solid catalyst (at least 30 000 turnover numbers without any loss of activity). Second, the use of 2-electron oxidants allows selective and high-efficiency hydroxychlorination with thousands of turnover numbers. This new technology by far outperforms catalysis using the inorganic complexes alone, or even the artificial enzymes in solution. The combination of easy catalyst synthesis, the improvement of omic technologies, and automation of protein crystallization makes this strategy a real opportunity for the future of (bio)catalysis.Cross-Linked Artificial Enzyme Crystals as Heterogeneous Catalysts for Oxidation Reactionsx17201760#N/AFALSE
1427
jacs.7b0918610.1021/jacs.7b09186FALSEhttps://doi.org/10.1021/jacs.7b09186Li, AJ. Am. Chem. Soc.The first and asymmetric total synthesis of longeracinphyllin A, a hexacydic Daphniphyllum alkaloid, has been accomplished. A tetracyClic intermediate was prepared through silver-catalyzed alkyne cyClization and Luche radical cyClization. A phosphine-promoted [3 + 2] cyCloaddition reaction was exploited to construct the sterically congested E ring bearing vicinal tertiary and quaternary centers. The cyClopentenone motif was assembled by using intramolecular Horner-Wadsworth-Emmons olefination. Raney Ni reduction delivered the tertiary amine from a thioamide precursor at a late stage.Total Synthesis of Longeracinphyllin Ax63201741#N/AFALSE
1428
jacs.7b1216010.1021/jacs.7b12160FALSEhttps://doi.org/10.1021/jacs.7b12160Brown, MKJ. Am. Chem. Soc.A Ni-catalyzed method for Arylboration is disClosed. The method allows for highly stereoselective Arylboration of unactivated alkenes. The reactions utilize a simple Ni-catalyst and work with a broad range of alkenes and Aryl bromides. The products represent useful intermediates for chemical synthesis due to the versatility of the C-B bond. Preliminary mechanistic details of the method are also disClosed.Nickel-Catalyzed Stereoselective Arylboration of Unactivated Alkenes69201854#N/ATRUE
1429
jacs.7b1200710.1021/jacs.7b12007FALSEhttps://doi.org/10.1021/jacs.7b12007Ogoshi, SJ. Am. Chem. Soc.In the presence of a catalytic amount of Ni(cod)(2) (cod = 1,5-cyClooctadiene) and PCy3 (Cy = cyClohexyl), the cross-tetramerization of tetrafluoroethylene (TFE), alkynes, and ethylene occurred in a highly selective manner to afford a variety of 1,3-dienes with a 3,3,4,4-tetrafluorobutyl chain. In addition, a Ni(0)-catalyzed cross-tetramerization of TFE, alkynes, ethylene, and styrenes was developed. These catalytic reactions might proceed via partially fluorinated five- and seven-membered nickelacyCle key intermediates.Nickel-Catalyzed Formation of 1,3-Dienes via a Highly Selective Cross-Tetramerization of Tetrafluoroethylene, Styrenes, Alkynes, and Ethylene14201755#N/ATRUE
1430
jacs.7b0865710.1021/jacs.7b08657FALSEhttps://doi.org/10.1021/jacs.7b08657Sun, YJJ. Am. Chem. Soc.Photocatalytic upgrading of crucial biomass -derived intermediate chemicals (i.e., furfural alcohol,5-hydroxymethylfurfural (HMF)) to value-added products (aldehydes and acids) was carried out on ultrathin CdS nanosheets (thickness similar to 1 nm) decorated with nickel (Ni/CdS). More importantly, simultaneous H-2 production was realized upon visible light irradiation under ambient conditions utilizing these biomass intermediates as proton sources. The remarkable difference in the rates of transformation of furfural alcohol and HMF to their corresponding aldehydes in neutral water was observed and investigated. Aided by theoretical computation, it was rationalized that the slightly stronger binding affinity of the aldehyde group in HMF to Ni/CdS resulted in the lower transformation of HMF to 2,5-diCarbonylfuran compared to that of furfural alcohol to furfural. Nevertheless, photo catalytic oxidation of furfural alcohol and HMF under alkaline conditions led to complete transformation to the respective Carbonylates with concomitant production of H-2.Visible-Light-Driven Valorization of Biomass Intermediates Integrated with H-2 Production Catalyzed by Ultrathin Ni/CdS Nanosheetsx199201739#N/AFALSE
1431
jacs.7b0864310.1021/jacs.7b08643FALSEhttps://doi.org/10.1021/jacs.7b08643Sun, SHJ. Am. Chem. Soc.Stabilizing a 3d-transition metal component M from an MPd alloy structure in an acidic environment is key to the enhancement of MPd catalysis for various reactions. Here we demonstrate a strategy to stabilize Cu in S nm CuPd nanopartiCles (NPs) by coupling the CuPd NPs with perovskite-type WO2.72 nanorods (NRs). The CuPd NPs are prepared by controlled diffusion of Cu into Pd NPs, and the coupled CuPd/WO2.72 are synthesized by growing WO2.72 NRs in the presence of CuPd NPs. The CuPd/WO2.72 can stabilize Cu in 0.1 M HClO4 solution and, as a result, they show Cu, Pd composition dependent activity for the electrochemical oxidation of formic acid in 0.1 M HClO4 + 0.1 M HCOOH. Among three different CuPd/WO2.72 studied, the Cu(4)sPd(52)/WO2.72 is the most efficient catalyst, with its mass activity reaching 2086 mA/mgpd in a broad potential range of 0.40 to 0.80 V (vs RHE) and staying at this value after the 12 h chronoamperometry test at 0.40 V. The synthesis can be extended to obtain other MPd/ WO2.72 (M = Fe, Co, Ni), making it possible to study MPd-WO2.72 interactions and MPd stabilization on enhancing MPd catalysis for various chemical reactions.Stabilizing CuPd NanopartiCles via CuPd Coupling to WO2.72 Nanorods in Electrochemical Oxidation of Formic Acidx76201735#N/AFALSE
1432
jacs.7b0862910.1021/jacs.7b08629FALSEhttps://doi.org/10.1021/jacs.7b08629Meyer, FJ. Am. Chem. Soc.A compartmental ligand scaffold HL with two beta-diketiminato binding sites spanned by a pyrazolate bridge gave a series of dinuClear nickel(II) dihydride complexes M[LNi2(H)2], M = Na (Na center dot 2) and K (K center dot 2), which were isolated after reacting the precursor complex [LNi2(mu-Br)] (1) with MHBEt3 (M = Na and K). Crystallographic characterization showed the two hydride ligands to be directed into the bimetallic pocket, Closely interacting with the alkali metal cation. Treatment of K center dot 2 with dibenzo(18-crown-6) led to the separated ion pair [LNi2(H)(2)]-[K(DB18C6)] (2[K(DB18C6)]). Reaction of Na center dot 2 or K center dot 2 with D-2 was investigated by a suite of H-1 and H-2 NMR experiments, revealing an unusual pairwise H-2/D-2 exchange process that synchronously involves both Ni-H moieties without H/D scrambling. A mechanistic picture was provided by DFT calculations which suggested facile recombination of the two terminal hydrides within the bimetallic Cleft, with a moderate enthalpic barrier of similar to 62 kJ/mol, to give H-2 and an antiferromagnetically coupled [LNi2I](-) species. This was confirmed by SQUID monitoring during H-2 release from solid 2[K(DB18C6)]. Interaction with the Lewis acid cation (Na+ or K+) significantly stabilizes the dihydride core. Kinetic data for the M[L(Ni-H)(2)] -> H-2 transition derived from 2D H-1 EXSY spectra confirmed first-order dependence of H-2 release on M center dot 2 concentration and a strong effect of the alkali metal cation M. Treating [LNi2(D)(2)](-) with phenylacetylene led to D-2 and dinickel(II) complex 3(-) with a twice reduced styrene-1,2-diyl bridging unit in the bimetallic pocket. Complexes [LNi2II(H)(2)](-) having two adjacent terminal hydrides thus represent a masked version of a highly reactive dinickel(I) core. Storing two reducing equivalents in adjacent metal hydrides that evolve H-2 upon substrate binding is reminiscent of the proposed N-2 binding step at the FeMo cofactor of nitrogenase, suggesting the use of the present bimetallic scaffold for reductive bioinspired Activation of a range of inert small molecules.Pairwise H-2/D-2 Exchange and H-2 Substitution at a Bimetallic Dinickel(II) Complex Featuring Two Terminal Hydridesx24201765#N/AFALSE
1433
jacs.7b0852110.1021/jacs.7b08521FALSEhttps://doi.org/10.1021/jacs.7b08521Li, GRJ. Am. Chem. Soc.Low-cost transition-metal dichalcogenides (MS2) have attracted great interest as alternative catalysts for hydrogen evolution. However, a significant challenge is the formation;of sulfur-hydrogen bonds on MS2 (S-H-ads), which will severely suppress hydrogen evolution reaction (HER). Here we report Cu nanodots (NDs)-decorated Ni3S2 nanotubes (NTs) supported on carbon fibers (CFs) (Cu NDs/Ni3S2 NTs-CFs) as efficient electrocatalysts for HER in alkaline media. The electronic interactions between Cu and Ni3S2 result in Cu NDs that are positively charged arid can promote water adsorption and Activation. Meanwhile, Ni3S2 NTs are negatively charged and can weaken S-H-ads bonds formed on catalyst surfaces. Therefore, the Cu/Ni3S2 hybrids can optimize H adsorption and desorption on electrocatalysts and can promote both Volmer and Heyrovsky steps of HER The strong interactions between Cu and Ni3S2 cause the Cu NDs/Ni3S2 NTs-CFs electrocatalysts to exhibit the outstanding HER catalytic performance with low onset potential, high catalytic activity, and excellent stability.Efficient Hydrogen Evolution on Cu Nanodots-Decorated Ni3S2 Nanotubes by Optimizing Atomic Hydrogen Adsorption and Desorptionx334201847#N/AFALSE
1434
jacs.7b0846110.1021/jacs.7b08461FALSEhttps://doi.org/10.1021/jacs.7b08461McCloskey, BDJ. Am. Chem. Soc.The role of residual lithium carbonate in the electrochemistry and outgassing of lithium transition-metal oxides (TMOs) has been largely overlooked. By combining in situ gas analysis, isotopic labeling, and a surface carbonate titration, we show that the presence of residual lithium carbonate (Li2CO3) on the surface of both Ni-rich Li-stoichiometric (specifically LiNi0.6Mn0.2Co0.2O2) and Li-rich (Li1.2Ni0.15Co0.1Mn0.55O2) TMOs has a direct correlation with the amount of CO2 and CO evolved and has a relationship with O-2 evolved from the TMO lattice on the first charge. By selectively isotopically labeling the residual surface Li2CO3, which remains in small quantities (similar to 0.1 wt %) after synthesis, and not the carbonate electrolyte, we further show that, up to 4.8 V vs Li/Li+ on the first charge, carbonate electrolyte degradation negligibly contributes to gas evolution. These key conClusions warrant a reassessment of our notion of oxidative decomposition of carbonate electrolytes on TMO surfaces and, more generally, the reactivity of TMO surfaces. For the battery research community, our results highlight the importance of quantification of the surface contaminants and suggest that further research is needed to fully understand the long-term effects of trace surface Li2CO3.Residual Lithium Carbonate Predominantly Accounts for First CyCle CO2 and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxidesx150201742#N/AFALSE
1435
jacs.7b0845610.1021/jacs.7b08456FALSEhttps://doi.org/10.1021/jacs.7b08456Evans, WJJ. Am. Chem. Soc.The first (N=N)(2-) complex of a rare-earth metal with an end-on dinitrogen bridge, {K-(crypt)}(2)-([(R2N)(3)Sc](2)[mu-eta(1):eta(1)-N-2]} (crypt = 2.2.2-crypt- and, R = SiMe3), has been isolated from the reduction of Sc(NR2)(3) under dinitrogen at -35 degrees C and characterized by X-ray crystallography. The structure differs from the characteristic side-on structures previously observed for over 40 crystallographically characterized rare-earth metal (N=N)(2-) complexes of formula [A(2)Ln(THF)(x)](2)[mu-eta(2):eta(2)-N-2] (Ln = Sc, Y, and lanthanides; x = 0, 1; A = anionic ligand such as amide, cyClopentadienide, and Aryloxide). The 1.221(3) angstrom N-N distance and the 1644 cm(-1) Raman stretch are consistent with the presence of an (N=N)(2-) bridge. The observed paramagnetism of the complex by Evans method measurements is consistent with DFT calculations that suggest a triplet ((3)A(2)) ground state in D-3 symmetry involving two degenerate Sc-N-2-Sc bonding orbitals. Upon brief exposure of the orange Sc3+ bridging dinitrogen complex to UV-light, photolysis to form the monomeric Sc2+ complex, [K(crypt)(2)][Sc(NR2)(3)], was observed. Conversion of the Sc2+ complex to the Sc3+ dinitrogen complex was not observed with this crypt system, but it did occur with the 18-crown-6 (crown) analog which formed {K(crown)}(2){[(R2N)(3)Sc](2)[mu-eta(1):eta(1)-N-2]. This suggests the importance of the alkali metal chelating agent in the reversibility of dinitrogen binding in this scandium system.End-On Bridging Dinitrogen Complex of Scandiumx15201749#N/AFALSE
1436
jacs.7b0815810.1021/jacs.7b08158https://doi.org/10.1021/jacs.7b08158Wu, JJ. Am. Chem. Soc.A direct hydroAlkylation of disubstituted alkynes with unfunctionalized ethers and amides was achieved in an atom-efficient and additive-free manner through the synergistic combination of photoredox and nickel catalysis. The protocol was effective with a wide range of internal alkynes, providing products in a highly selective fashion. Notably, the observed regioselectivity is complementary to conventional radical addition processes. Mechanistic investigations suggest that the photoexcited iridium catalyst facilitated the nickel Activation via single-electron transfer.Photoinduced Nickel-Catalyzed Chemo- and Regioselective HydroAlkylation of Internal Alkynes with Ether and Amide alpha-Hetero C(sp(3))-H BondsPhotocatalyst73201763#N/AFALSE
1437
jacs.7b0810210.1021/jacs.7b08102FALSEhttps://doi.org/10.1021/jacs.7b08102Mirica, KAJ. Am. Chem. Soc.This Communication describes the use of porous coordination polymers (PCP) with integrated metal bis(dithiolene) units to achieve electrochemically controlled capture and release of ethylene in the solid state. Applying positive potential (+2.0 V) to these PCPs promotes ethylene capture, and subsequent dose of negative potential (-2.0 V) induces the release. These materials are resistant to poisoning by small reactive gases (CO and H2S) that may interact with embedded metallic sites.Porous Scaffolds for Electrochemically Controlled Reversible Capture and Release of Ethylenex28201749#N/AFALSE
1438
jacs.7b0788010.1021/jacs.7b07880FALSEhttps://doi.org/10.1021/jacs.9b12005Ribas, XCarbonylate-Assisted Formation of Aryl-Co(III) Masked-Carbenes in Cobalt-Catalyzed C-H Functionalization with Diazo Estersx2017#N/AFALSE
1439
jacs.7b1126710.1021/jacs.7b11267FALSEhttps://doi.org/10.1021/jacs.7b11267Koper, MTMJ. Am. Chem. Soc.This work provides insights to understand the selectivity during the reduction of CO2 with metalloporphyrin (MP) catalysts. The attack of a nuCleophile on the carbon of the CO, appears as an important event that triggers the catalytic reaction, and the nature of this nuCleophile determines the selectivity between CO (or further reduced species) and HCOOH/HCOO-. For MP, the possible electrogenerated nuCleophiles are the reduced metal-center and the hydride donor species, metal-hydride and phlorin-hydride ligand. The reduced metal-center activates the CO2 with the formation of the metal carbon bond, which then gives rise to the formation of CO. The hydride donor species trigger the CO2 reduction by the attack of the hydride on the carbon of the CO2 (formation of a C-H bond), which results in the formation of HCOOH/HCOO- (formation of the metal-bonded formate intermediate is not involved). The MP with the metals Ni, Cu, Zn, Pd, Ag, Cd, Ga, In, and Sn are predicted to only form the phlorin-hydride intermediate and are thus suitable to produce HCOOH/HCOO-. This agrees well with the available experimental results. The MP with the metals Fe, Co, and Rh can form both the reduced-metal center and the hydride donor species (metal-hydride and phlorin-hydride), and thus are able to form both CO and HCOOH/HCOO-. The production of CO for Fe and Co is indeed observed experimentally, but not for Rh, probably due to the presence of axial ligands that may hinder the formation of the metal-bonded intermediates and thus drive the CO2RR to HCOOH/HCOO- via the phlorin intermediate.Determinant Role of Electrogenerated Reactive NuCleophilic Species on Selectivity during Reduction of CO2 Catalyzed by Metalloporphyrins39201853#N/ATRUE
1440
jacs.7b0762210.1021/jacs.7b07622FALSEhttps://doi.org/10.1021/jacs.7b07622Gingras, MJ. Am. Chem. Soc.A one-step synthesis of a nanographene propeller with a D-3-symmetry was obtained starting from 7,8-dibromo[5]helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported.Chiral Nanographene Propeller Embedding Six Enantiomerically Stable [5]Helicene Unitsx73201747#N/AFALSE
1441
jacs.7b1107410.1021/jacs.7b11074FALSEhttps://doi.org/10.1021/jacs.7b11074Lee, YJ. Am. Chem. Soc.Addition of CO, to a low-valent nickel species has been explored with a newly designed (PNP)-P-acri pincer ligand ((PNP-)-P-acri = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide). This is a crucial step in understanding biological CO2 conversion to CO found in carbon monoxide dehydrogenase (CODH). A four-coordinate nickel(0) state was reliably accessed in the presence of a CO ligand, which can be prepared from a stepwise reduction of a cationic {((PNP)-P-acri)Ni(II)-CO}(+) species. All three Ni(II), Ni(I), and Ni(0) monoCarbonyl species were Cleanly isolated and spectroscopically characterized. Addition of electrons to the nickel(II) species significantly alters its geometry from square planar toward tetrahedral because of the filling of the d(x)(-y)(2)(2) orbital. Accordingly, the CO ligand position changes from equatorial to axial, angle N-Ni-C of 176.2(2)degrees to 129.1(4)degrees, allowing opening of a CO, binding site. Upon addition of CO2 to a nickel(0) CO species, a nickel(II) Carbonylate species with a Ni(eta(1)-CO2-KC) moiety was formed and isolated (75%). This reaction occurs with the concomitant expulsion of CO(g). This is a unique result markedly different from our previous report involving the flexible analogous PNP ligand, which revealed the formation of multiple products inCluding a tetrameric Cluster from the reaction with CO2. Finally, the carbon dioxide conversion to CO at a single nickel center is modeled by the successful isolation of all relevant intermediates, such as Ni-CO2, Ni-COOH, and Ni-CO.Direct CO2 Addition to a Ni(0)-CO Species Allows the Selective Generation of a Nickel(II) Carbonylate with Expulsion of CO31201874#N/ATRUE
1442
jacs.7b0736110.1021/jacs.7b07361FALSEhttps://doi.org/10.1021/jacs.7b07361Patzke, GRJ. Am. Chem. Soc.The future of artificial photosynthesis depends on economic and robust water oxidation catalysts (WOCs). Cobalt-based WOCs are especially promising for knowledge transfer between homogeneous and heterogeneous catalyst design. We introduce the active and stable {(Co4O4)-O-II} cubane [Co-4(II)(dpy{OH}O)(4)(OAc)(2)(H2O)(2)] (ClO4)(2) (Co4O4-dpk) as the first molecular WOC with the characteristic {H2O-Co-2(OR)(2)-OH2} edge-site motif representing the sine qua non moiety of the most efficient heterogeneous Co-oxide WOCs. DFT-MD modelings as well as in situ EXAFS measurements indicate the stability of the cubane cage in solution. The stability of Co4O4-dpk under photocatalytic conditions ([Ru(bpy)(3)](2+)/S2O82+) was underscored with a wide range of further analytical methods and recyCling tests. FT-IR monitoring and HR-ESI-MS spectra point to a stable coordination of the acetate ligands, and DFT-MD simulations along with H-1/H-2 exchange experiments highlight a favorable intramolecular base functionality of the dpy{OH}O ligands. All three ligand types enhance proton mobility at the edge site through a unique bioinspired environment with multiple hydrogen-bonding interactions. In situ XANES experiments under photocatalytic conditions show that the {(Co4O4)-O-II} core undergoes oxidation to Co(III) or higher valent states, which recover rather slowly to Co(II). Complementary ex situ chemical oxidation experiments with [Ru(bpy)(3)](3+) furthermore indicate that the oxidation of all Co(II) centers of Co4O4-dpk to Co(III) is not a mandatory prerequisite for oxygen evolution. Moreover, we present the [Co-x(II) Ni4-x,(dpy{OH}O)(4)(OAc)(2)(H2O)(2)] (ClO4)(2) (CoxNi4-x,O-4-dpk) series as the first mixed Co/Ni-cubane WOCs. They newly bridge homogeneous and heterogeneous catalyst design through fine-tuned edge-site environments of the Co centers.{Co4O4} and {Co,Ni-4,O-4} Cubane Water Oxidation Catalysts as Surface Cut-Outs of Cobalt Oxidesx572017114#N/AFALSE
1443
jacs.7b0721610.1021/jacs.7b07216https://doi.org/10.1021/jacs.7b07216Meyer, TJJ. Am. Chem. Soc.In a dye sensitized photoelectrosynthesis cell (DSPEC), the relative orientation of the catalyst and chromophore plays an important role in determining the device efficiency. Here we introduce a new; robust atomic layer deposition (ALD) procedure for the preparation of molecular chromophore-catalyst assemblies,on wide bandgap semiconductors. In this procedure, solution deposited, phosphonate derivatized metal complexes on metal oxide surfaces are treated with reactive metal reagents in the gas phase by ALD to form an outer metal, on bridging group, which can bind a second: phosphonate containing species from solution to establish a R-1-PO2-O-M-O-PO2-R-2 type surface assembly. With the ALD procedure, assemblies bridged by Al(III), Sn(W), Ti(IV), or Zr(W) metal oxide units have been prepared. To evaluate the performance of this new type of surface assembly, intra-assembly electron transfer was investigated by transient absorption spectroscopy, and light-driven water splitting experiments under steady-state illumination were conducted. A SnO2 bridged assembly on SnO2/TiO2 core/shell electrodes undergoes light-driven water oxidation with an incident photon to current efficiency (IPCE) of 17.1% at 440 nm. Light-driven water reduction with a ruthenium trisbipyridine Chromophore and molecular Ni(II) catalyst on NiO films was also used to produce H-2. Compared to conventional solution-based procedures, the ALD approach offers significant advantages in scope and flexibility for the preparation of stable surface structures.Layer-by-Layer Molecular Assemblies for Dye-Sensitized Photoelectrosynthesis Cells Prepared by Atomic Layer DepositionPhotocatalystx40201751#N/AFALSE
1444
jacs.7b1100510.1021/jacs.7b11005FALSEhttps://doi.org/10.1021/jacs.7b11005Hawker, CJControl of Amphiphile Self-Assembly via Bioinspired Metal Ion Coordination2018#N/ATRUE
1445
jacs.7b0684610.1021/jacs.7b06846FALSEhttps://doi.org/10.1021/jacs.7b06846Strasser, PTuning the Electrocatalytic Oxygen Reduction Reaction Activity and Stability of Shape-Controlled Pt-Ni NanopartiCles by Thermal Annealing Elucidating the Surface Atomic Structural and Compositional Changesx2017#N/AFALSE
1446
jacs.7b1085510.1021/jacs.7b10855FALSEhttps://doi.org/10.1021/jacs.7b10855Crudden, CMJ. Am. Chem. Soc.We describe the development of a nickel-catalyzed Suzuki-Miyaura cross-coupling of tertiary Benzylic and allylic sulfones with Arylboroxines. A variety of tertiary sulfones, which can easily be prepared via a deprotonation-Alkylation route, were reacted to afford symmetric and unsymmetric quaternary products in good yields. We highlight the use of either BrettPhos or Doyle's phosphines as effective ligands for these challenging desulfonative coupling reactions. The utility of this methodology was demonstrated in the concise synthesis of a vitamin D receptor modulator analogue.Preparation of Quaternary Centers via Nickel-Catalyzed Suzuki-Miyaura Cross-Coupling of Tertiary Sulfones65201843#N/ATRUE
1447
jacs.7b0674510.1021/jacs.7b06745https://doi.org/10.1021/jacs.7b06745Mecking, SJ. Am. Chem. Soc.Highly electron-withdrawing pentafluorosulfanyl groups were probed as substituents in an organometallic catalyst. In Ni(II) salicylaldiminato complexes as an example case, these highly electron-withdrawing substituents allow for polymerization of ethylene to higher molecular weights with reduced branching due to significant reductions in beta-hydrogen elimination. Combined with the excellent functional group tolerance of neutral Ni(II) complexes, this suppression of beta-hydrogen elimination allows for the direct polynierizatiori of ethylene in water to nanocrystal dispersions of disentangled, ultrahigh-molecular-weight linear polyethylene.Pentafluorosulfanyl Substituents in Polymerization Catalysisx43201735#N/AFALSE
1448
jacs.7b1051910.1021/jacs.7b10519FALSEhttps://doi.org/10.1021/jacs.7b10519Morken, JPJ. Am. Chem. Soc.The catalytic enantioselective conjunctive coupling of C(sp(3)) electrophiles can be accomplished with Ni catalysis. The enantioselectivity of the reaction is dependent on reaction mechanism with many substrates able to engage in an asymmetric process with Pybox-Ni complexes, whereas other substrates provide racemic product mixtures. The link between substrate structure and selectivity is addressed.Ni-Catalyzed Enantioselective Conjunctive Coupling with C(sp(3)) Electrophiles: A Radical-Ionic Mechanistic Dichotomy61201731#N/ATRUE
1449
jacs.7b1036510.1021/jacs.7b10365FALSEhttps://doi.org/10.1021/jacs.7b10365Shi, ZZJ. Am. Chem. Soc.An efficient enantioselective protocol has been reported to build highly oxygenated and densely substituted bicyClo[m.n.1] skeletons through intramolecular asymmetric alpha-Arylative desymmetrization of 1,3-diketones. Employing Pd catalyst and FOXAP ligand, various bicyClo[m.n.1] skeleton with different size can be accessed with high enantio- and diastereoselectivities. Utilizing the present method as a key step, formal asymmetric total synthesis of the (-)-parvifoline has been demonstrated.Enantioselective Palladium-Catalyzed Intramolecular alpha-Arylative Desymmetrization of 1,3-Diketones40201749#N/ATRUE
1450
jacs.7b0956910.1021/jacs.7b09569FALSEFigueroa, JSCrystalline Coordination Networks of Zero-Valent Metal Centers: Formation of a 3-Dimensional Ni(0) Framework with m-Terphenyl Diisocyanides2017#N/ATRUE
1451
jacs.7b0643410.1021/jacs.7b06434FALSEhttps://doi.org/10.1021/jacs.7b06434Sun, YJJ. Am. Chem. Soc.The development of low-cost hybrid water splitting biosynthetic systems that mimic natural photosynthesis to achieve solar-to chemical conversion is of great promise for future energy demands, but often limited by the kinetically sluggish hydrogen evolution reaction (HER) on the surface, of nonprecious transition metal catalysts in neutral media. It is thus highly desirable to rationally tailor the reaction interface to boost the neutral HER catalytic kinetics. Herein, we report a general surface nitrogen modification of diverse transition metals (e.g., iron, cobalt, nickel, copper, and nickel cobalt alloy), accomplished by a facile low-temperature ammonium carbonate treatment, for significantly improved hydrogen generation from neutral water. Various physicochemical characterization techniques inCluding synchrotron X-ray absorption spectroscopy (XAS) and theory modeling demonstrate that the surface nitrogen modification does not change the chemical composition of the underlying transition metals. Notably, the resulting nitrogen-modified nickel framework (N-Ni) exhibits an extremely low overpotential of 64 mV at 10 mA cm(-2), which is, to our knowledge, the best among those nonprecious electrocatalysts reported for hydrogen evolution at pH 7. Our combined experimental results and density functional theory (DFT) calculations reveal that the surface electron-rich nitrogen simultaneously facilitates the initial adsorption of water via the electron-deficient H atom and the subsequent dissociation of the electron-rich HO-H bond via H transfer to N on the nickel surface, beneficial to the overall hydrogen evolution process.Universal Surface Engineering of Transition Metals for Superior Electrocatalytic Hydrogen Evolution in Neutral Water
Electrocatalytic
x124201738#N/AFALSE
1452
jacs.7b0639710.1021/jacs.7b06397FALSEhttps://doi.org/10.1021/jacs.7b06397Long, JRJ. Am. Chem. Soc.The metal-organic frameworks M-2(m-dobdc) (M = Mn, Fe, Co, Ni; m-dobdc(4-) = 4,6-dioxido-1,3-benzenediCarbonylate) were evaluated as adsorbents for separating olefins from paraffins. Using single-component and multicomponent equilibrium gas adsorption measurements, we show that the coordinatively unsaturated M2+ sites in these materials lead to superior performance for the physisorptive separation of ethylene from ethane and propylene from propane relative to any known adsorbent, inCluding para-functionalized structural isomers of the type M-2(p-dobdc)(p-dobdc(4-) = 2,5-dioxido-1,4-benzenediCarbonylate). Notably, the M-2(m-dobdc) frameworks all exhibit an increased affinity for olefins over paraffins relative to their corresponding structural isomers, with the Fe, Co, and Ni variants showing more than double the selectivity. Among these frameworks, Fe-2(m-dobdc) displays the highest ethylene/ethane (>25 ) and propylene/propane (>55) selectivity under relevant conditions, together with olefin capacities exceeding 7 mmol/g. Differential enthalpy calculations in conjunction with structural characterization of ethylene binding in Co-2(m-dobdc) and Co-2(p-dobdc) via in situ single-crystal X-ray diffraction reveal that the vast improvement in selectivity arises from enhanced metal-olefin interactions induced by increased charge density at the metal site. Moderate olefin binding enthalpies, below 55 and 70 kJ/mol for ethylene and propylene, respectively, indicate that these adsorbents maintain sufficient reversibility under mild regeneration conditions. Additionally, transient adsorption experiments show fast kinetics, with more than 90% of ethylene adsorption occurring within 30 s after dosing. Breakthrough measurements further indicate that Co-2(m-dobdc) can produce high purity olefins without a temperature swing, an important test of process applicability. The excellent olefin/paraffin selectivity, high olefin capacity, rapid adsorption kinetics, and low raw materials cost make the M-2(m-dobdc) frameworks the materials of choice for adsorptive olefin/paraffin separations.M2(&ITm&IT-dobdc) (M = Mn, Fe, Co, Ni) Metal-Organic Frameworks as Highly Selective, High-Capacity Adsorbents for Olefin/Paraffin Separationsx92201750#N/AFALSE
1453
jacs.7b0626010.1021/jacs.7b06260FALSEhttps://doi.org/10.1021/jacs.7b06260Cargnello, MJ. Am. Chem. Soc.Promoters enhance the performance of catalytic active phases by increasing rates, stability, and/or selectivity. The process of identifying promoters is in most cases empirical and relies on testing a broad range of catalysts prepared with the random deposition of active and promoter phases, typically with no fine control over their localization. This issue is particularly relevant in supported bimetallic systems, where two metals are codeposited onto high-surface area materials. We here report the use of colloidal bimetallic nanocrystals to produce catalysts where the active and promoter phases are colocalized to a fine extent. This strategy enables a systematic approach to study the promotional effects of several transition metals on palladium catalysts for methane oxidation. In order to achieve these goals, we demonstrate a single synthetic protocol to obtain uniform palladium-based bimetallic nanocrystals (PdM, M = V, Mn, Fe, Co, Ni, Zn, Sn, and potentially extendable to other metal combinations) with a wide variety of compositions and sizes based on high temperature thermal decomposition of readily available precursors. Once the nanocrystals are supported onto oxide materials, thermal treatments in air cause segregation of the base metal oxide phase in Close proximity to the Pd phase. We demonstrate that some metals (Fe, Co, and Sn) inhibit the sintering of the active Pd metal phase, while others (Ni and Zn) increase its intrinsic activity compared to a monometallic Pd catalyst. This procedure can be generalized to systematically investigate the promotional effects of metal and metal oxide phases for a variety of active metal-promoter combinations and catalytic reactions.Systematic Identification of Promoters for Methane Oxidation Catalysts Using Size- and Composition-Controlled Pd-Based Bimetallic Nanocrystalsx72201755#N/AFALSE
1454
jacs.7b0907410.1021/jacs.7b09074FALSEhttps://doi.org/10.1021/jacs.7b09074Xie, YJ. Am. Chem. Soc.Electrochemical reduction of carbon dioxide (CO2) to value-added carbon products is a promising approach to reduce CO2 levels and mitigate the energy crisis. However, poor product selectivity is still a major obstaCle to the development of CO2 reduction. Here we demonstrate exClusive Ni-N-4 sites through a topochemical transformation strategy, bringing unprecedentedly high activity and selectivity for CO2 reduction. Topochemical transformation by carbon layer coating successfully ensures preservation of the Ni-N4 structure to a maximum extent and avoids the agglomeration of Ni atoms to partiCles, providing abundant active sites for the catalytic reaction. The Ni-N4 structure exhibits excellent activity for electrochemical reduction of CO2 with particularly high selectivity, achieving high faradaic efficiency over 90% for CO in the potential range from -0.5 to -0.9 V and gives a maximum faradaic efficiency of 99% at -0.81 V with a current density of 28.6 mA cm(-2). We anticipate exClusive catalytic sites will shed new light on the designExClusive Ni-N-4 Sites Realize Near-Unity CO Selectivity for Electrochemical CO2 Reduction382201729#N/ATRUE
1455
jacs.7b0537210.1021/jacs.7b05372FALSEhttps://doi.org/10.1021/jacs.7b05372Li, YDJ. Am. Chem. Soc.Preparing metal single-atom materials is currently attracting tremendous attention and remains a significant challenge. Herein, we report a novel core-shell strategy to synthesize single-atom materials. In this strategy, metal hydroxides or oxides are coated with polymers, followed by high-temperature pyrolysis and acid leaching, metal single atoms are anchored on the inner wall of hollow nitrogen-doped carbon (CN) materials. By changing metal precursors or polymers, we demonstrate the successful synthesis of different metal single atoms dispersed on CN materials (SA-M/CN, M = Fe, Co, Ni, Mn, FeCo, FeNi, etc.). Interestingly, the obtained SA-Fe/CN exhibits much higher catalytic activity for hydroxylation of benzene to phenol than Fe nanopartiCles/CN (45% vs 5% benzene conversion). First-principle calculations further reveal that the high reactivity originates from the easier formation of activated oxygen species at the single Fe site. Our methodology provides a convenient route to prepare a variety of metal single-atom materials representing a new Class of catalysts.Metal (Hydr)oxides@Polymer Core-Shell Strategy to Metal Single-Atom Materialsx146201730#N/AFALSE
1456
jacs.7b0898410.1021/jacs.7b08984FALSEhttps://doi.org/10.1021/jacs.7b08984Comas-Vives, AJ. Am. Chem. Soc.Transition metal nanopartiCles (NPs) are typically supported on oxides to ensure their stability, which may result in modification of the original NP catalyst reactivity. In a number of cases, this is related to the formation of NP/support interface sites that play a role in catalysis. The metal/support interface effect verified experimentally is commonly ascribed to stronger reactants adsorption or their facile Activation on such sites compared to bare NPs, as indicated by DFT-derived potential energy surfaces (PESs). However, the relevance of specific reaction elementary steps to the overall reaction rate depends on the preferred reaction pathways at reaction conditions, which usually cannot be inferred based solely on PES. Hereby, we use a multiscale (DFT/microkinetic) modeling approach and experiments to investigate the reactivity of the Ni/Al2O3 interface toward water-gas shift (WGS) and dry reforming of methane (DRM), two key industrial reactions with common elementary steps and intermediates, but held at significantly different temperatures: 300 vs 650 degrees C, respectively. Our model shows that despite the more energetically favorable reaction pathways provided by the Ni/Al2O3 interface, such sites may or may not impact the overall reaction rate depending on reaction conditions: the metal/support interface provides the active site for WGS reaction, acting as a reservoir for oxygenated species, while all Ni surface atoms are active for DRM. This is in contrast to what PESs alone indicate. The different active site requirement for WGS and DRM is confirmed by the experimental evaluation of the activity of a series of Al2O3-supported Ni NP catalysts with different NP sizes (2-16 nm) toward both reactions.Contrasting the Role of Ni/Al2O3 Interfaces in Water-Gas Shift and Dry Reforming of Methane80201765#N/ATRUE
1457
jacs.7b0869110.1021/jacs.7b08691FALSEhttps://doi.org/10.1021/jacs.9b13572Uyeda, CCatalytic Carbonylative Rearrangement of Norbornadiene via DinuClear Carbon-Carbon Oxidative Addition2017#N/ATRUE
1458
jacs.7b0436310.1021/jacs.7b04363https://doi.org/10.1021/jacs.7b04363Meggers, EJ. Am. Chem. Soc.A reaction design is reported in which a substrate-bound chiral Lewis acid complex absorbs visible light and generates an excited state that directly reacts with, a cosubstrate in a highly stereocontrolled fashion. Specifically, a chiral rhodium complex catalyzes visible, light-activated intermolecular [2+2] cyCloadditions, providing a wide range of cyClobutanes with up to >99% ee and up to >20:1 d.r. Noteworthy is the ability to create vicinal all-carbon-quaternary stereocenters inCluding spiro centers in an intermolecular fashion.Direct Visible-Light-Excited Asymmetric Lewis Acid Catalysis of Intermolecular [2+2] PhotocyCloadditionsPhotocatalyst99201741#N/AFALSE
1459
jacs.7b0806410.1021/jacs.7b08064FALSEhttps://doi.org/10.1021/jacs.7b08064Zhu, SLJ. Am. Chem. Soc.A highly efficient strategy for remote reductive cross-electrophile coupling has been developed through the ligand-controlled nickel migration/Arylation. This general protocol allows the use of abundant and bench-stable Alkyl bromides and Aryl bromides for the synthesis of a wide range of structurally diverse 1,1-diArylalkanes in excellent yields and high regioselectivities under mild conditions. We also demonstrated that Alkyl bromide could be replaced by the proposed olefin intermediate while using n-propyl bromide/Mn-0 as a potential hydride source.Remote Migratory Cross-Electrophile Coupling and Olefin HydroArylation Reactions Enabled by in Situ Generation of NiH108201791#N/ATRUE
1460
jacs.7b0766710.1021/jacs.7b07667FALSEhttps://doi.org/10.1021/jacs.7b07667Murakami, MJ. Am. Chem. Soc.A palladium-isocyanide complex opens the two four-membered rings of benzocyClobutenone and silacyClobutane to merge them into an eight-membered ring skeleton. The present reaction provides a unique example of an intermolecular cross metathesis-type reaction between covalent sigma-bonds of low polarity.Palladium-Catalyzed Intermolecular Exchange between C-C and C-Si sigma-Bonds47201779#N/ATRUE
1461
jacs.7b0738810.1021/jacs.7b07388FALSEhttps://doi.org/10.1021/jacs.7b07388Yang, ZJ. Am. Chem. Soc.The enantioselective synthesis of (-)-pavidolide B (1) was achieved in a linear sequence of 10 steps. The key steps are (a) an enantioselective organocatalytic cyClopropanation; (b) a radical-based cascade annulation for the regio- and diastereo-selective synthesis of the highly functionalized lactone 3 bearing the characteristic tricyClic core and seven contiguous stereocenters; (c) a sequential ring-Closing metathesis reaction and a RhCl3-catalyzed double bond isomerization to form the seven-membered D ring of (-)-pavidolide B.Enantioselective Total Synthesis of (-)-Pavidolide B30201741#N/ATRUE
1462
jacs.7b0711710.1021/jacs.7b07117FALSEhttps://doi.org/10.1021/jacs.7b07117Boettcher, SWJ. Am. Chem. Soc.Fe is a critical component of record-activity Ni/Fe (oxy)hydroxide (Ni(Fe)OxHy) oxygen evolution reaction (OER) catalysts, yet its precise role remains unClear. We report evidence for different types of Fe species within Ni(Fe)OxHy- those that are rapidly incorporated into the Ni oxyhydroxide from Fe cations in solution (and that are likely at edges or defects) and are responsible for the enhanced OER activity, and those substituting for bulk Ni that modulate the observed Ni voltammetry. These results suggest that the exceptional OER activity of Ni(Fe)OxHy does not depend on Fe in the bulk or on average electrochemical properties of the Ni cations measured by voltammetry, and instead emphasize the role of the local structure.Reactive Fe-Sites in Ni/Fe (Oxy)hydroxide Are Responsible for Exceptional Oxygen Electrocatalysis Activity280201724#N/ATRUE
1463
jacs.7b0350710.1021/jacs.7b03507FALSEhttps://doi.org/10.1021/jacs.7b03507Hu, JSJ. Am. Chem. Soc.Developing bifunctional efficient and durable non-noble electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desirable and challenging for overall water splitting. Herein, Co-Mn carbonate hydroxide (CoMnCH) nanosheet arrays with controllable morphology and composition were developed on nickel foam (NF) as such a bifunctional electrocatalyst. It is discovered that Mn doping in CoCH can simultaneously modulate the nanosheet morphology to significantly increase the electrochemical active surface area for exposing more accessible active sites and tune the electronic structure of Co center to effectively boost its intrinsic activity. As a result, the optimized Co1Mn1CH/NF electrode exhibits unprecedented OER activity with an ultralow overpotential of 294 mV at 30 mA cm(-2), compared with all reported metal carbonate hydroxides. Benefited from 3D open nanosheet array topographic structure with tight contact between nanosheets and NF, it is able to deliver a high and stable current density of 1000 mA cm(-2) at only an overpotential of 462 mV with no interference from high-flux oxygen evolution. Despite no reports about effective HER on metal carbonate hydroxides yet, the small overpotential of 180 mV at 10 mA cm(-2) for HER can be also achieved on Co1Mn1CH/NF by the dual modulation of Mn doping. This offers a two-electrode electrolyzer using bifunctional Co1Mn1CH/NF as both anode and cathode to perform stable overall water splitting with a cell voltage of only 1.68 V at 10 mA cm(-2). These findings may open up opportunities to explore other multimetal carbonate hydroxides as practical bifunctional electrocatalysts for scale-up water electrolysis.Electronic and Morphological Dual Modulation of Cobalt Carbonate Hydroxides by Mn Doping toward Highly Efficient and Stable Bifunctional Electrocatalysts for Overall Water Splittingx450201774#N/AFALSE
1464
jacs.7b0678510.1021/jacs.7b06785FALSEhttps://doi.org/10.1021/jacs.7b06785Wang, DHJ. Am. Chem. Soc.A Cu(II)-catalyzed ortho-selective functionalization of free phenols with trifluorB(OH)2rates to afford C-sp2-C-sp3 coupling products under mild conditions has been developed. A variety of functional groups on the phenol and the potassium aminomethyltrifluorB(OH)2rate substrates were found compatible, furnishing the corresponding products in moderate to excellent yields. A single-electron transfer radical coupling mechanism involving a six-membered transition state is proposed to rationalize the high levels of ortho-selectivity in the reaction. This protocol provides straightforward access to ortho-aminomethyl-substituted phenols, unnatural amino acids and other bioactive small molecules.Cu(II)-Catalyzed ortho-Selective Aminomethylation of Phenols40201774#N/ATRUE
1465
jacs.7b0664410.1021/jacs.7b06644FALSEhttps://doi.org/10.1021/jacs.7b06644Vargas, AMonomeric 16-Electron pi-Diborene Complexes of Zn(II) and Cd(II)2017#N/ATRUE
1466
jacs.7b0656710.1021/jacs.7b06567FALSEhttps://doi.org/10.1021/jacs.7b06567Engle, KMJ. Am. Chem. Soc.A nickel-catalyzed conjunctive cross-coupling between non-conjugated alkenes, Aryl iodides, and Alkylzinc reagents is reported. Excellent regiocontrol is achieved utilizing an 8-aminoquinoline directing group that can be readily Cleaved to unmask net beta,gamma-dicarbofunctionalized Carbonylic acid products. Under optimized conditions, both terminal and internal alkene substrates provided the corresponding Alkyl/Aryl difunctionalized products in moderate to excellent yields. The methodology developed herein represents the first three-component 1,2-dicarbofunctionalization of non-conjugated alkenes involving a C(sp(3))-C(sp(3)) reductive elimination step.Nickel-Catalyzed beta,gamma-Dicarbofunctionalization of Alkenyl Carbonyl Compounds via Conjunctive Cross-Coupling129201748#N/ATRUE
1467
jacs.7b0273610.1021/jacs.7b02736FALSEhttps://doi.org/10.1021/jacs.7b02736Li, YDJ. Am. Chem. Soc.Single-atom catalysts often exhibit unexpected catalytic activity for many important chemical reactions because of their unique electronic and geometric structures with respect to their bulk counterparts. Herein we adopt metal-organic frameworks (MOFs) to assist the preparation of a catalyst containing single Ni sites for efficient electroreduction of CO2. The synthesis is based on ionic exchange between Zn nodes and adsorbed Ni ions within the cavities of the MOF. This single-atom catalyst exhibited an excellent turnover, frequency for electroreduction of CO2 (5273 h(-1)), with a Faradaic efficiency for CO production of over 71.9% and a current density of 10.48 mA cm(-2) at an overpotential of 0.89 V. Our findings present some guidelines for the rational design and accurate modulation of nanostructured catalysts at the atomic scale.Ionic Exchange of Metal Organic Frameworks to Access Single Nickel Sites for Efficient Electroreduction of CO2x632201730#N/AFALSE
1468
jacs.7b0238710.1021/jacs.7b02387FALSEhttps://doi.org/10.1021/jacs.7b02387Sanford, MSJ. Am. Chem. Soc.This communication describes a series of oxidatively induced intramolecular arene C-H Activation reactions of Ni-II model complexes to yield Ni-IV sigma-Aryl products. These reactions proceed within to min at room temperature, which represents among the mildest conditions reported for C-H Cleavage at a Ni center. A combination of density functional theory and preliminary experimental mechanistic studies implicate a pathway involving initial 2e(-) oxidation of the Ni-II starting materials by the transfer reagent N-fluoro-2,4,6-trimethylpyr-idinium triflate followed by triflate-assisted C-H Cleavage at Ni-IV to yield the products.Oxidatively Induced C-H Activation at High Valent NickelDFTxx36201756#N/AFALSE
1469
jacs.7b0646910.1021/jacs.7b06469FALSEhttps://doi.org/10.1021/jacs.7b06469Fu, YJ. Am. Chem. Soc.Herein, we described a nickel-catalyzed monofluoroalkenylation through defluorinative reductive cross-coupling of gem-difluoroalkenes with Alkyl halides. Key to the success of this strategy is the combination of C- F Cleavage with Alkyl halides Activation. This reaction enables the convenient synthesis of a large variety of functionalized monofluoroalkenes under mild reaction conditions with broad functional group compatibility and excellent Z-selectivity. The combination of Ni catalysis with (Bpin)(2)/K3PO4 as terminal reductant promoted the efficient C(sp(2))-C(sp(3)) formation especially the generation of all-carbon quatemary centers with high chemoselectivity.Nickel-Catalyzed Defluorinative Reductive Cross-Coupling of gem-Difluoroalkenes with Unactivated Secondary and Tertiary Alkyl Halides100201766#N/ATRUE
1470
jacs.7b0195610.1021/jacs.7b01956https://doi.org/10.1021/jacs.7b01956Kojima, TJ. Am. Chem. Soc.A Ni(II) complex bearing an S2N2-type tetradentate ligand inspired by the active site of carbon monoxide dehydrogenase was found to selectively catalyze CO2 reduction to produce CO in a photocatalytic system using [Ru(bpy)(3)](2+) (bpy = 2,2'-bipyridine) as a photo sensitizer and 1,3-dimethy1-2-pheny1-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. The Ni(II) complex shows a high turnover number over 700 with high CO selectivity of >99% and quantum yield of 1.42% in the photocatalytic system.Visible-Light-Driven Photocatalytic CO2 Reduction by a Ni(II) Complex Bearing a Bioinspired Tetradentate Ligand for Selective CO ProductionPhotocatalyst115201735#N/AFALSE
1471
jacs.7b0590110.1021/jacs.7b05901FALSEhttps://doi.org/10.1021/jacs.7b05901Uyeda, CJ. Am. Chem. Soc.MethylenecyClopropanes are important synthetic intermediates that possess strain energies exceeding those of saturated cyClopropanes by >10 kcal/mol. This report describes a catalytic reductive methylenecyClopropanation reaction of simple olefins, utilizing 1,1-dichloroalkenes as Vinylidene precursors. The reaction is promoted by a dinuClear Ni catalyst, which is proposed to access Ni-2(Vinylidenoid) intermediates via C-Cl oxidative addition.Catalytic Reductive Vinylidene Transfer Reactions31201748#N/ATRUE
1472
jacs.7b0163210.1021/jacs.7b01632FALSEhttps://doi.org/10.1021/jacs.7b01632Chin, YHCConsequences of Surface Oxophilicity of Ni, Ni-Co, and Co Clusters on Methane Activationx2017#N/AFALSE
1473
jacs.7b0162510.1021/jacs.7b01625FALSEhttps://doi.org/10.1021/jacs.7b01625Coperet, CJ. Am. Chem. Soc.Syngas production via the dry reforming of methane (DRM) is a highly endothermic process conducted under harsh conditions; hence, the main difficulty resides in generating stable catalysts. This can, in principle, be achieved by reducing coke formation, sintering, and loss of metal through diffusion in the support. [{Ni(mu(2)-OCHO)(OCHO)(tmeda)}(2)(mu(2)-2OH(2))] (tmeda = tetramethylethylenediamine), readily synthesized and soluble in a broad range of solvents, was developed as a molecular precursor to form 2 nm Ni(0) nanopartiCles on alumina, the commonly used support in DRM. While such small nanopartiCles prevent coke deposition and increase the initial activity, operando X-ray Absorption Near-Edge Structure (XANES) spectroscopy confirms that deActivation largely occurs through the migration of Ni into the support. However, we show that Ni loss into the support can be mitigated through the Mg-doping of alumina, thereby increasing significantly the stability for DRM. The superior performance of our catalytic system is a direct consequence of the molecular design of the metal precursor and the support, resulting in a maximization of the amount of accessible metallic nickel in the form of small nanopartiCles while preventing coke deposition.Molecularly Tailored Nickel Precursor and Support Yield a Stable Methane Dry Reforming Catalyst with Superior Metal Utilizationx67201748#N/AFALSE
1474
jacs.7b0533210.1021/jacs.7b05332FALSEhttps://doi.org/10.1021/jacs.7b05332Osuka, AJ. Am. Chem. Soc.Porphyrin tapes possessing meso-meso beta-beta beta-beta triple direct linkages have been targets of extensive studies because of their fully conjugated characteristic pi-electronic networks. In this paper, we report porphyrin arch tapes that bear additional Carbonyl group(s) or methylene group(s) inserted between one of the beta-beta linkage(s) of the porphyrin tapes. The Carbonyl-inserted porphyrin arch-tapes were efficiently synthesized by double fusion reactions of beta-to-beta Carbonyl-bridged porphyrin oligomers with DDQ and Sc(OTf)(3), and were converted to the methylene-bridged porphyrin arch-tapes via Luche reduction with NaBH4 and CeCl3 followed by ionic hydrogenation with HBF4 center dot OEt2 and BH3 center dot NEt3. While the conventional porphyrin tapes display rigid and planar structures and low solubilities, these porphyrin arch-tapes show remarkably contorted structures, flexible conformations, and improved solubilities because of the presence of the incorporated seven-membered ring(s). Interestingly, the methylene inserted arch-tapes exhibited conjugative electronic interactions that were comparable to those of porphyrin tapes probably owing to through-space interaction in the contorted conformations. The Carbonyl-inserted arch-tapes displayed distinctly larger conjugative interactions owing to an active involvement of the Carbonyl group(s) in the electronic conjugation. A similar trend was observed in the nonlinear optical properties, as evidenced by their two-photon absorption cross sections. Furthermore, as a benefit of the contorted structures, these porphyrin arch-tapes can catch C-60 fullerene effectively. Naturally, the electron-rich methylene-bridged arch-tapes exhibited larger association constants than the electron-deficient Carbonyl-bridged arch-tapes. Among these arch-tapes, a methylene-bridged syn-Ni(II) porphyrin trimer recorded the largest association constant of (1.5 +/- 0.4) X 10(7) M-1 in toluene at 25 degrees C.Porphyrin Arch-Tapes: Synthesis, Contorted Structures, and Full Conjugation40201794#N/ATRUE
1475
jacs.7b0146210.1021/jacs.7b01462https://doi.org/10.1021/jacs.7b01462Tong, RJ. Am. Chem. Soc.Poly(alpha-hydroxy acids) are important biodegradable polymers with wide applications. Attempts to synthesize them from O-carboxyanhydrides with pendant functional groups by various methods, inCluding methods involving organocatalysts or organometallics, have been plagued by uncontrolled polymerization, inCluding epimerization for some monomers, which hampers the preparation of stereoregular high-molecular-weight polymers. Herein we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring opening polymerization, allowing for the synthesis of isotactic polyesters with expected molecular weights (>140 kDa) and narrow molecular weight distributions (M-w/M-n < 1.1). Mechanistic studies indicate that the use of a low temperature (-20 degrees C) and photoredox Ni/Ir catalysis synergistically accelerates ring-opening and deCarbonylation of the monomer for chain propagation while avoiding the formation of the undesired Ni-Carbonyl complex.Controlled Photoredox Ring-Opening Polymerization of O-CarboxyanhydridesPhotocatalyst39201750#N/AFALSE
1476
jacs.7b0458310.1021/jacs.7b04583FALSEhttps://doi.org/10.1021/jacs.7b04583Montgomery, JJ. Am. Chem. Soc.An exceptionally hindered Class of enantiopure NHC ligands has been developed. While racemic forms had previously been utilized, a scalable and practical route to the enantiopure form of this ligand Class is described utilizing a Buchwald-Hartwig N,N-diArylation in a highly sterically demanding environment. Using this newly accessible ligand Class, nickel-catalyzed enantioselective reductive coupling reactions of aldehydes and alkynes have been developed. These studies illustrate that the newly available NHC ligands are well suited for simultaneous control of regio- and enantioselectivity, even in cases with internal alkynes possessing only very subtle steric differences between two aliphatic substituents. The steric demand of the new ligand Class enables a complementary regiochemical outcome compared with previously described enantioselective processes. Using this method, a number of allylic alcohol derivatives were efficiently obtained with high regioselectivity (up to >95:5) and high enantioselectivity (up to 94% ee). The reaction conditions can also be extended to the reaction of aldehydes and allenes, providing silyl-protected allylic alcohol derivatives possessing a terminal methylene substituent. Computational studies have explained the origin of the exceptional steric demand of this ligand Class, the basis for enantioselectivity, and the cooperative relationship of the aldehyde, alkyne, and ligand in influencing enantioselectivity.NHC Ligands Tailored for Simultaneous Regio- and Enantiocontrol in Nickel-Catalyzed Reductive Couplings36201784#N/ATRUE
1477
jacs.7b0415810.1021/jacs.7b04158FALSEhttps://doi.org/10.1021/jacs.7b04158Browne, WRJ. Am. Chem. Soc.A reactive high-valent dinuClear nickel(IV) oxido bridged complex is reported that can be formed at room temperature by reaction of [(L)(2)Ni(II)(2)(mu-X)(3)]X (X = Cl or Br) with NaOCl in methanol or acetonitrile (where L = 1,4,7 - trimethyl-1,4,7-triazacyClononane). The unusual Ni(IV) oxido species is stabilized within a dinuClear tris-mu-oxido-bridged structure as [(L)(2)Ni(IV)(2)(mu-O)(3)](2+). Its structure and its reactivity with organic substrates are demonstrated through a combination of UV-vis absorption, resonance Raman, H-1 NMR, EPR, and X-ray absorption (near-edge) spectroscopy, ESI mass spectrometry, and DFT methods, The identification. of a Ni(IV)-O species opens opportunities to control the reactivity of NaOCl for selective oxidations.Transient Formation and Reactivity of a High-Valent Nickel(IV) Oxido Complex31201745#N/ATRUE
1478
jacs.7b0120210.1021/jacs.7b01202FALSEhttps://doi.org/10.1021/jacs.7b01202Tezcan, FAJ. Am. Chem. Soc.Previously, we adopted the construction principles of metal-organic frameworks (MOFs) to design a 3D crystalline protein lattice in which pseudospherical ferritin nodes decorated on their C-3 symmetric vertices with Zn coordination sites were connected via a ditopic benzene-dihydroxamate linker. In this work, we have systematically varied both the metal ions presented at the vertices of the ferritin nodes (Zn(II), Ni(II), and Co(II)) and the synthetic dihydroxamate linkers, which yielded an expanded library of 15 ferritin MOFs with the expected body-centered (cubic or tetragonal) lattice arrangements. Crystallographic and small-angle X-ray scattering (SAXS) analyses indicate that lattice symmetries and dimensions of ferritin-MOFs can be dictated by both the metal and linker components. SAXS measurements on bulk crystalline samples reveal that some ferritin-MOFs can adopt multiple lattice conformations, suggesting dynamic behavior. This work establishes that the self-assembly of ferritin-MOFs is highly robust and that the synthetic modularity that underlies the structural diversity of conventional MOFs can also be applied to the self-assembly of protein-based crystalline materials.Synthetic Modularity of Protein-Metal-Organic Frameworksx51201757#N/AFALSE
1479
jacs.7b0068310.1021/jacs.7b00683FALSEhttps://doi.org/10.1021/jacs.7b00683Zhu, SLJ. Am. Chem. Soc.Mild and Regioselective Benzylic C-H Functionalization: Ni-Catalyzed Reductive Arylation of Remote and Proximal Olefins (vol 139, pg 1061, 2017)x1201723#N/AFALSE
1480
jacs.7b0036910.1021/jacs.7b00369https://doi.org/10.1021/jacs.7b00369Reisner, EJ. Am. Chem. Soc.Photocatalytic conversion of CO2 into carbonaceous feedstock chemicals is a promising strategy to mitigate greenhouse gas emissions and simultaneously store solar energy in chemical form. Photocatalysts for this transformation are typically based on precious metals and operate in nonaqueous solvents to suppress competing H-2 generation. In this work, we demonstrate selective visible-light-driven CO2 reduction in water using a synthetic photocatalyst system that is entirely free of precious metals. We present a series of self-assembled nickel terpyridine complexes as electrocatalysts for the reduction of CO2 to CO in organic media. Immobilization on CdS quantum dots allows these catalysts to be active in purely aqueous solution and photocatalytically reduce CO2 with >90% selectivity under UV-filtered simulated solar light irradiation (AM 1.5G, 100 mW cm(-2), lambda > 400 nm, pH 6.7, 25 degrees C). Correlation between catalyst immobilization efficiency and product selectivity shows that anchoring the molecular catalyst on the semiconductor surface is key in controlling the selectivity for CO2 reduction over H-2 evolution in aqueous solutionSelective Photocatalytic CO2 Reduction in Water through Anchoring of a Molecular Ni Catalyst on CdS NanocrystalsPhotocatalystx244201788#N/AFALSE
1481
jacs.7b0389210.1021/jacs.7b03892FALSEhttps://doi.org/10.1021/jacs.7b03892Shafaat, HSJ. Am. Chem. Soc.The acetyl coenzyme A synthase (ACS) enzyme plays a central-role in the metabolism of anaerobic bacteria and archaea, catalyzing the reversible synthesis of acetyl-CoA from CO and a methyl group through a series of nickel-based organometallic intermediates. Owing to the extreme complexity of the native enzyme systems, the mechanism by which this catalysis occurs remains poorly understood. In this work, we have developed a protein-based model for the Ni-p center of acetyl coenzyme A synthase using a nickel-substituted azurin protein (NiAz). NiAz is the first model nickel protein system capable of accessing three (Ni-I/Ni-II/Ni-III) distinct oxidation states within a physiological potential range in aqueous solution, a critical feature for achieving organometallic ACS activity, and binds CO and -CH3 groups with biologically relevant affinity. Characterization of the Ni-I-CO species through spectroscopic and computational techniques reveals fundamentally similar features between the model NiAz system and the native ACS enzyme, highlighting the potential for related reactivity in this model protein. This work provides insight into the enzymatic process, with implications toward engineering biological catalysts for organometallic processes.Multielectron Chemistry within a Model Nickel Metalloprotein: Mechanistic Implications for Acetyl-CoA Synthase13201764#N/ATRUE
1482
jacs.7b0379410.1021/jacs.7b03794FALSEhttps://doi.org/10.1021/jacs.7b03794Robinson, GHJ. Am. Chem. Soc.Sulfurization of anionic N-heterocyClic dicarbene, [:C{[N(2,6-(Pr2C6H3)-C-i)](2)CHCli}(n) (2), with elemental sulfur (in a 1:2 ratio) in Et2O at low temperature gives 3 by inserting two sulfur atoms into the Li-C (i.e., C2 and C4) bonds in polymeric 2. Further reaction of 3 with 2 equiv of elemental sulfur in THF affords 4(center dot) via unexpected C-H bond Activation, which represents the first anionic dithiolene radical to be structurally characterized in the solid state. Alternatively, 4(center dot) may also be synthesized directly by reaction of 1 with sulfur (in a 1:4 ratio) in THF. Reaction of 4(center dot) with GeCl2-dioxane gives an anionic germanium(W)-bis(dithiolene) complex (5). The nature of the bonding in 4(center dot) and 5 was probed by experimental and theoretical methods.A Stable Anionic Dithiolene Radical24201746#N/ATRUE
1483
jacs.7b0351010.1021/jacs.7b03510FALSEhttps://doi.org/10.1021/jacs.7b03510Huang, XQJ. Am. Chem. Soc.Although explosive studies on pursuing high-performance Pt-based nanomaterials for fuel cell reactions have been carried out, the combined controls of surface composition, exposed facet, and interior structure of the catalyst remains a formidable challenge. We demonstrate herein a facile chemical approach to realize a new Class of intermetallic Pt-Pb-Ni octahedra for the first time. Those nanostructures with unique intermetallic core, active surface composition, and the exposed facet enhance oxygen reduction electrocatalysis with the optimized PtPb1.12Ni0.14 octahedra exhibiting superior specific and mass activities (5.16 mA/cm(2) and 1.92 A/mg(Pt)) for oxygen reduction reaction (ORR) that are similar to 20 and similar to 11 times higher than the commercial Pt/C, respectively. Moreover, the PtPb1.12Ni0.14 octahedra can endure at least 15 000 cyCles with negligible activity decay, showing a new Class of Pt-based electrocatalysts with enhanced performance for fuel cells and beyond.PtPb/PtNi Intermetallic Core/Atomic Layer Shell Octahedra for Efficient Oxygen Reduction Electrocatalysis131201744#N/ATRUE
1484
jacs.7b0004910.1021/jacs.7b00049FALSEhttps://doi.org/10.1021/jacs.7b00049Yamaguchi, JJ. Am. Chem. Soc.Because diAryl ethers are present as an important motif in pharmaceuticals and natural products, extensive studies for the development of novel methods have been conducted. A conventional method for the construction of the diAryl ether moiety is the intermolecular cross-coupling reaction of Aryl halides and phenols with a copper or palladium catalyst. We developed a catalytic deCarbonylative etherification of aromatic esters using a palladium or nickel catalyst with our enabling diphosphine ligand to give the corresponding diAryl ethers. The present reaction can be conducted on grain scale in excellent yield. This reaction not only functions in an intramolecular setting but also allows for a crossetherification using other phenols.DeCarbonylative DiAryl Ether Synthesis by Pd and Ni Catalysisx84201773#N/AFALSE
1485
jacs.6b1310010.1021/jacs.6b13100FALSEhttps://doi.org/10.1021/jacs.6b13100Qiao, SZJ. Am. Chem. Soc.Organometallic complexes with metal nitrogen/carbon (M-N/C) coordination are the most important alternatives to precious metal catalysts for oxygen reduction and evolution reactions (ORR and OER) in energy conversion devices. Here, we designed and developed a range of molecule -level graphitic carbon nitride (g-C3N4) coordinated transition metals (M-C3N4) as a new generation of M-N/C catalysts for these oxygen electrode reactions. As a proof-of-concept example, we conducted theoretical evaluation and experimental validation on a cobalt C3N4 catalyst with a desired molecular configuration, which possesses comparable electrocatalytic activity to that of precious metal benchmarks for the ORR and OER in alkaline media. The correlation of experimental and computational results confirms that this high activity originates from the precise M-N-2, coordination in the g-C3N4 matrix. Moreover, the reversible ORR/OER activity trend for a wide variety of M C3N4 complexes has been constructed to provide guidance for the molecular design of this promising Class of catalysts.Molecule-Level g-C3N4 Coordinated Transition Metals as a New Class of Electrocatalysts for Oxygen Electrode Reactionsx695201724#N/AFALSE
1486
jacs.7b0337110.1021/jacs.7b03371FALSEhttps://doi.org/10.1021/jacs.7b03371Krische, MJJ. Am. Chem. Soc.Under the conditions of nickel(0) catalysis, enantiomerically enriched Vinyl dioxanones engage boroxines or B-2(pin)(2) in stereospecific cross-coupling to form diverse tetrasubstituted cyClopropanes bearing all-carbon quaternary stereocenters. The collective data corrB(OH)2rate a mechanism involving nickel(0)-mediated Benzylic oxidative addition with inversion of stereochemistry followed by reversible olefin insertion to form a (cyClopropylcarbinyl)nickel complex, which upon reductive elimination releases the cyClopropane.Nickel-Catalyzed Cross-Coupling of Vinyl Dioxanones to Form Enantiomerically Enriched CyClopropanes13201745#N/ATRUE
1487
jacs.7b0319510.1021/jacs.7b03195FALSEhttps://doi.org/10.1021/jacs.7b03195Nevado, CJ. Am. Chem. Soc.An intermolecular, three-component reductive dicarbofunctionalization of alkenes is presented here. The combination of Ni catalysis with TDAE as final reductant enables the direct formation of Csp(3)-Csp(3) and Csp(3)-Csp(2) bonds across a variety of pi-systems using two different electrophiles that are sequentially activated with exquisite selectivity under mild reaction conditions.Nickel-Catalyzed Reductive Dicarbofunctionalization of Alkenes167201749#N/ATRUE
1488
jacs.7b0287010.1021/jacs.7b02870FALSEhttps://doi.org/10.1021/jacs.7b02870Lu, CCJ. Am. Chem. Soc.A triad of d(10) cobalt dihydrogen complexes was synthesized by utilizing Lewis acidic group 13 metalloligands, M[N((o-C6H4)(NCH2PPr2)-Pr-i)(3)], where M = Al, Ga, and In. These coinplexes have formal Co(-I) oxidation states, representing the only coordination complexes in which dihydrogen is bound to a subvalent transition metal center. Single-crystal X-ray diffraction and NMR studies support the assignment of these complexes as nonClassical dihydrogen adducts of Co(-I).Stable Dihydrogen Complexes of Cobalt(-I) Suggest an Inverse trans-Influence of Lewis Acidic Group 13 Metalloligands36201757#N/ATRUE
1489
jacs.7b0232310.1021/jacs.7b02323FALSEhttps://doi.org/10.1021/jacs.7b02323Khalifah, PGJ. Am. Chem. Soc.Motivated by predictions made using a bond valence sum difference map (BVS-DM) analysis, the novel Li-ion conductor Li2Mg2P3O9N was synthesized by ion exchange from a Na2Mg2P3O9N precursor. Impedance spectroscopy measurements indicate that Li2Mg2P3O9N has a room temperature Li-ion conductivity of about 10(-6) S/cm (comparable to UPON), which is 6 orders of magnitude higher than the extrapolated Na-ion conductivity of Na2Mg2P3O9N at this temperature. The structure of Li2Mg2P3O9N was determined from ex situ synchrotron and time-of-flight neutron diffraction data to retain the P2(1)3 space group, though with a cubic lattice parameter of a = 9.11176(8) A that is significantly smaller than the a = 9.2439(1) angstrom of Na2Mg2P3O9N. The two Li-ion sites are found to be very substantially displaced (similar to 0.5 angstrom) relative to the analogous Na sites in the precursor phase. The non-molten salt ion exchange method used to prepare Li2Mg2P3O9N produces a minimal background in powder diffraction experiments, and was therefore exploited for the first time to follow a Li+/Na+ ion exchange reaction using in situ powder neutron diffraction. Lattice parameter changes during ion exchange suggest that the reaction proceeds through a Na2-xLixMg2P3O9N solid solution (stage 1) followed by a two-phase reaction (stage 2) to form Li2Mg2P3O9N. However, full Rietveld refinements of the in situ neutron diffraction data indicate that the actual transformation mechanism is more complex and instead involves two thermodynamically distinct solid solutions in which the Li exClusively occupies the Li1 site at low Li contents (stage 1a) and then migrates to the Li3 site at higher Li contents (stage 1b), a crossover driven by the different signs of the local volume change at these sites. In addition to highlighting the importance of obtaining full structural data in situ throughout the ion exchange process, these results provide insights into the general question of what constitutes a thermodynamic phase.In Situ Neutron Diffraction Studies of the Ion Exchange Synthesis Mechanism of Li2Mg2P3O9N: Evidence for a Hidden Phase Transition12201741#N/ATRUE
1490
jacs.6b1240410.1021/jacs.6b12404FALSEhttps://doi.org/10.1021/jacs.6b12404Cook, TRJ. Am. Chem. Soc.Herein we report the first study of the oxygen reduction reaction (ORR) catalyzed by a cofacial porphyrin scaffold accessed in high yield (overall 53%) using coordination-driven self-assembly with no chromatographic purification steps. The ORR activity was investigated using chemical and electrochemical techniques on monomeric cobalt(II) tetra(meso-4-pyridyl)-porphyrinate (CoTPyP) and its cofacial analogue [Ru-8(eta(6)-iPrC(6)H(4)Me)(8)(dhbq)(4)(CoTPyP)(2)][OTf](8) (Co Prism) (dhbq = 2,5-dihydroxy-1,4-benzoquinato, OTf = triflate) as homogeneous oxygen reduction catalysts. Co Prism is obtained in one self-assembly step that organizes six total building blocks, two CoTPyP units and four arene-Ru Clips, into a cofacial motif previously demonstrated with free-base, Zn(II), and Ni(II) porphyrins. Turnover frequencies (TOFs) from chemical reduction (66 vs 6 h(-1)) and rate constants of overall homogeneous catalysis (kappa(obs)) determined from rotating ring disk experiments (1.1 vs 0.05 h(-1)) establish a cofacial enhancement upon comparison of the activities of Co Prism and CoTPyP, respectively. CyClic voltammetry was used to initially probe the electrochemical catalytic behavior. Rotating ring disk electrode studies were completed to probe the Faradaic efficiency and obtain an estimate of the rate constant associated with the ORR.A Self-Assembled Cofacial Cobalt Porphyrin Prism for Oxygen Reduction Catalysisx97201738#N/AFALSE
1491
jacs.6b1232910.1021/jacs.6b12329FALSEhttps://doi.org/10.1021/jacs.6b12329Newman, SGJ. Am. Chem. Soc.The Suzuki-Miyaura coupling is among the most important C-C bond-forming reactions available due to its reliability, chemoselectivity, and diversity. Aryl halides and pseudohalides such as iodides, bromides, and triflates are traditionally used as the electrophilic coupling partner. The expansion of the reaction scope to nontraditional electrophiles is an ongoing challenge to enable an even greater number of useful products to be made from simple starting materials. Herein, we present how an NHC-based Pd catalyst can enable Suzuki-Miyaura coupling where the C(acyl)-O bond of Aryl esters takes on the role of electrophile, allowing the synthesis of various ketone-containing products. This contrasts known reactions of similar esters that provide biAryls via nickel catalysis. The underlying cause of this mechanistic divergence is investigated by DFT calculations, and the robustness of esters compared to more electrophilic acylative coupling partners is analyzed.Palladium-Catalyzed Suzuki-Miyaura Coupling of Aryl Estersx143201789#N/AFALSE
1492
jacs.7b0168210.1021/jacs.7b01682FALSEhttps://doi.org/10.1021/jacs.7b01682Zaworotko, MJJ. Am. Chem. Soc.We report water vapor sorption studies on four primitive cubic, pcu, pillared square grid materials: SIFSIX-1-Cu, SIFSIX-2-Cu-i, SIFSIX-3-Ni, and SIFSIX-14-Cu-i. SIFSIX-1-Cu, SIFSIX-3-Ni, and SIFSIX-14-Cu-i were observed to exhibit negative water vapor adsorption at ca. 40-50% relative humidity (RH). The negative adsorption is attributed to a water-induced phase transformation from a porous pcu topology to nonporous sql and sql-c* topologies. Whereas the phase transformation of SIFSIX-1-Cu was found to be irreversible, SIFSIX-3-Ni could be regenerated by heating and can therefore be recyCled. In contrast, SIFSIX-2-Cu-i, which is isostructural with SIFSIX-14-Cu-i, exhibited a type V isotherm and no phase change. SIFSIX-2-Cu-i was observed to retain both structure and gas sorption properties after prolonged exposure to heat and humidity. The hydrolytic stability of SIFSIX-2-Cu-i in comparison to its structural counterparts is attributed to structural features and therefore offers insight into the design of hydrolytically stable porous materials.Water Vapor Sorption in Hybrid Pillared Square Grid Materials57201748#N/ATRUE
1493
jacs.6b1225010.1021/jacs.6b12250FALSEhttps://doi.org/10.1021/jacs.6b12250Strasser, PJ. Am. Chem. Soc.Ni-Fe oxyhydroxides are the most active known electrocatalysts for the oxygen evolution reaction (OER) in alkaline electrolytes and are therefore of great scientific and technological importance in the context of electrochemical energy conversion. Here we uncover, investigate, and discuss previously unaddressed effects of conductive supports and the electrolyte pH on the Ni-Fe(OOH) catalyst redox behavior and catalytic OER activity, combining in situ UV-vis spectro-electrochemistry, operando electrochemical mass spectrometry (DEMS), and in situ cryo X-ray absorption spectroscopy (XAS). Supports and pH > 13 strongly enhanced the precatalytic voltammetric charge of the Ni-Fe oxyhydroxide redox peak couple, shifted them more cathodically, and caused a 2-3-fold increase in the catalytic OER activity. Analysis of DEMS-based faradaic oxygen efficiency and electrochemical UV-vis traces consistently confirmed our voltammetric observations, evidencing both a more cathodic O-2 release and a more cathodic onset of Ni oxidation at higher pH. Using UV-vis, which can monitor the amount of oxidized Ni+3/+4 in situ, confirmed an earlier onset of the redox process at high electrolyte pH and further provided evidence of a smaller fraction of Ni+3/+4 in mixed Ni-Fe centers, confirming the unresolved paradox of a reduced metal redox activity with increasing Fe content. A nonmonotonic super-Nernstian pH dependence of the redox peaks with increasing Fe content-displaying Pourbaix slopes as steep as -120 mV/pH-suggested a two proton-one electron transfer. We explain and discuss the experimental pH effects using refined coupled (PCET) and decoupled proton transfer-electron transfer (PT/ET) schemes involving negatively charged oxygenate ligands generated at Fe centers. Together, we offer new insight into the catalytic reaction dynamics and associated catalyst redox chemistry of the most important Class of alkaline OER catalysts.Tracking Catalyst Redox States and Reaction Dynamics in Ni-Fe Oxyhydroxide Oxygen Evolution Reaction Electrocatalysts: The Role of Catalyst Support and Electrolyte pHx281201753#N/AFALSE
1494
jacs.7b0153810.1021/jacs.7b01538FALSEhttps://doi.org/10.1021/jacs.7b01538Schatz, GCJ. Am. Chem. Soc.Mechanistic details of catalytic reactions are critical to the development of improved catalysts. Here, we perform high quality Born-Oppenheimer molecular dynamics simulations of the reaction mechanisms associated with hydrogen-assisted CO2 reduction on Ni(110). The simulation results show direct theoretical evidence for both associative and redox mechanisms in the reaction of atomic hydrogen with CO2. Because H-2 is dissociatively chemisorbed on Ni(110) with nearly unit probability, the mechanisms we find are also relevant to the reverse water-gas shift reaction (H-2 with adsorbed CO2). Furthermore, we provide the first real-time demonstration of both Eley-Rideal (ER) and hot atom (HA) mechanisms when H impinges on adsorbed CO2, and we show that both occur even for low kinetic energies. The trade-off between ER or HA mechanisms is found to be strongly dependent on CO2 coverage. The results are compared with recent gas/surface measurements.Mechanisms of Hydrogen-Assisted CO2 Reduction on Nickel38201725#N/ATRUE
1495
jacs.7b0137610.1021/jacs.7b01376FALSEhttps://doi.org/10.1021/jacs.7b01376Li, YDJ. Am. Chem. Soc.The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts. The atomic structure of the Rh2P NCs was directly observed by annular dark-field scanning transmission electron microscopy, which revealed a phosphorus-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorus plays a crucial role in determining the robust catalyst properties.High-Performance Rh2P Electrocatalyst for Efficient Water Splitting215201740#N/ATRUE
1496
jacs.6b1141810.1021/jacs.6b11418https://doi.org/10.1021/jacs.6b11418Xiao, WJJ. Am. Chem. Soc.A novel visible-light-responsive chiral ligand has been developed by grafting a triplet state photo sensitizer to chiral bisoxazoline ligands. Complexation of this ligand with Ni(acac)(2) results in a powerful catalyst for the asymmetric oxidation reaction of beta-ketoesters, which uses oxygen or air as the green oxidant and visible light or sunlight as the ideal driving force. Using this protocol, products containing the alpha-hydroxy-beta-diCarbonyl motif are produced in high yields and with excellent enantiopurities.Bifunctional Photocatalysts for Enantioselective Aerobic Oxidation of beta-KetoestersPhotocatalyst129201776#N/AFALSE
1497
jacs.6b1121810.1021/jacs.6b11218FALSEhttps://doi.org/10.1021/jacs.6b11218Chen, WJ. Am. Chem. Soc.To obtain stable and ultrafine Pt nano Clusters, a trigonal prismatic coordination cage with the sulfur atoms on the edges was solvothermally synthesized to confine them. In the structure of {Ni-24(TC4A-SO2)(6)(TD C)(12) (H2O)(6)} (H(4)TC4A-SO2 = p-tert-butylsulfonylcalix[4]arene; H2TDC = 2,5-thiophenediCarbonylic acid), three Ni-4-(TC4A-SO2) SBUs are bridged by three TDC ligands into a triangle and two such triangles are pillared by three pairs of TDC ligands to form a trigonal prism. The cage cavity has 12 sulfur atoms on the surface. Because of the porous structure and strong covalent interaction between metal and sulfur, ultrafine Pt nanoClusters composed of less than similar to 18 Pt atoms can be facilely confined in the present trigonal prismatic cage (Pt@CIAC-121). The as-synthesized Pt NCs exhibit higher electrocatalytic activity than commercial Pt/C toward hydrogen evolution reaction.Ultrafine Pt NanoClusters Confined in a Calixarene-Based {Ni-24} Coordination Cage for High-Efficient Hydrogen Evolution Reactionx103201644#N/AFALSE
1498
jacs.6b1046210.1021/jacs.6b10462https://doi.org/10.1021/jacs.6b10462Brookhart, MJ. Am. Chem. Soc.Copolymerizations of ethylene with Vinyltrialkoxysilanes are reported using both a traditional cationic Pd(II) Aryldiimine catalyst, t-1 (Aryl = 2,6-diisopropylphenyl), and a sandwich-type Aryldiimine catalyst, s-2 (Aryl = 8-tolylnaphthyl). Incorporation levels of Vinyltrialkoxysilanes between 0.25 and 2.0 mol % were achieved with remarkably little rate retardation relative to ethylene homopolymerizations. In the case of the traditional catalyst system, molecular weights decrease as the level of comonomer increases and only one trialkoxysilyl group is incorporated per chain. Molecular weight distributions of ca. 2 are observed. For the sandwich catalyst, higher molecular weights are observed with many more trialkoxysilyl groups incorporated per chain. Polymers with molecular weight distributions of ca. 1.2-1.4 are obtained. Detailed NMR mechanistic studies have revealed the formation of intermediate pi-complexes of the type (diimine)Pd(Alkyl)-(Vinyltrialkoxysilane)(+). 1,2-Migratory insertions of these complexes occur with rates similar to ethylene insertion and result in formation of observable five-membered chelate intermediates. These chelates are rapidly opened with ethylene forming Alkyl ethylene complexes, a requirement for chain growth. An unusual beta-silyl elimination mechanism was shown to be responsible for chain transfer and formation of low molecular weight copolymers in the traditional catalyst system, t-1. This chain transfer process is retarded in the sandwich system. Relative binding affinities of ethylene and Vinyltrialkoxysilanes to the cationic palladium center have been determined. The quantitative mechanistic studies reported fully explain the features of the bulk polymerization results.Mechanistic Studies of Pd(II)-Catalyzed Copolymerization of Ethylene and Vinylalkoxysilanes: Evidence for a beta-Silyl Elimination Chain Transfer Mechanismx72201663#N/AFALSE
1499
jacs.7b0121210.1021/jacs.7b01212FALSENolan, EMNickel Sequestration by the Host-Defense Protein Human Calprotectin2017#N/ATRUE
1500
jacs.7b0027910.1021/jacs.7b00279FALSEhttps://doi.org/10.1021/jacs.7b00279Bard, AJJ. Am. Chem. Soc.The hydrogen evolution reaction (HER) on Ni in alkaline media was investigated by scanning electrochemical microscopy under two operating modes. First, the substrate generation/tip collection mode was employed to extract the true cathodic current associated with the HER from the total current in the polarization curve. Compared to metallic Ni, the electrocatalytic activity of the HER is improved in the presence of the low-valence-state oxide of Ni. This result is in agreement with a previous Claim that the dissociative adsorption of water can be-enhanced at the Ni/Ni oxide interface. Second, the surface interrogation scanning electrochemical microscopy (SI-SECM) mode was used to directly measure the coverage of the adsorbed hydrogen on Ni at given potentials. Simulation indicates that the hydrogen coverage follows a Frumkin isotherm with respect to the applied potential. On the basis of the combined analysis of the Tafel slope and surface hydrogen coverage, the rate determining step is suggested to be the adsorption of hydrogen (Volmer step) in the investigated potential window.A Study of the Mechanism of the Hydrogen Evolution Reaction on Nickel by Surface Interrogation Scanning Electrochemical Microscopy56201729#N/ATRUE
1501
jacs.7b0026810.1021/jacs.7b00268FALSEhttps://doi.org/10.1021/jacs.7b00268Wagner, MJ. Am. Chem. Soc.A two-step synthesis sequence furnishes quadruply annulated borepins in high yields. The first step involves a nuCleophilic substitution reaction between Aryl-BF3K salts (Aryl = mesityl, phenyl) and lithiated bromonapthalene derivatives LiNaph(Br,R) (HNaph(Br,R) = 8-bromonaphthalene (a), 5-bromoacenaphthene (b), 5-bromoacenaphthylene (c)). In the second step, the resulting heteroleptic triArylboranes Aryl-B(Naph(Br,R)), (3a-c) are subjected to an intramolecular Ni-mediated Yamamoto reaction to Close the seven-membered rings and create the borepins 4a-c. Only in the case of 3b is the Yamamoto reaction accompanied by a C-H Activation reaction furnishing the 7-hydro-7-borabenzo[de]anthracene derivative 5. The product ratio 4b/5 can be influenced by control of the local Ni(0) concentration. The borepins 4a-c are benchtop stable and highly soluble even in hexane. Compounds 4a-c undergo reversible one-electron reduction; 4c is also able to accept a second electron in a reversible manner and already at moderate potential values (E-1/2 = -1.49 V and -1.84 V (vs FcH/FcH(+))). 4a, 4b, and 5 show photoluminescence in the blue-green region of the spectrum, while 4c is nonfluorescent, which is likely attributable to an intramolecular charge-transfer transition.Facile Route to Quadruply Annulated Borepins52201779#N/ATRUE
1502
jacs.7b0016410.1021/jacs.7b00164FALSEhttps://doi.org/10.1021/jacs.7b00164Meng, YSJ. Am. Chem. Soc.Large-scale electric energy storage is fundamental to the use of renewable energy. Recently, research and development efforts on room-temperature sodium-ion batteries (NIBs) have been revitalized, as NIBs are considered promising, low-cost alternatives to the current Li-ion battery technology for large-scale applications. Herein, we introduce a novel layered oxide cathode material, Na0.78Ni0.23Mn0.69O2. This new compound provides a high reversible capacity of 138 mAh g(-1) and an average potential of 3.25 V vs Na+/Na with a single smooth voltage profile. Its remarkable rate and cyCling performances are attributed to the elimination of the P2-O2 phase transition upon cyCling to 4.5 V. The first charge process yields an abnormally excess capacity, which has yet to be observed in other P2 layered oxides. Metal K-edge XANES results show that the major charge compensation at the metal site during Na-ion deintercalation is achieved via the oxidation of nickel (Ni2+) ions, whereas, to a large extent, manganese (Mn) ions remain in their Mn4+ state. Interestingly, electron energy loss spectroscopy (EELS) and soft X-ray absorption spectroscopy (sXAS) results reveal differences in electronic structures in the bulk and at the surface of electrochemically cyCled partiCles. At the surface, transition metal ions (TM ions) are in a lower valence state than in the bulk, and the 0 K-edge prepeak disappears. On the basis of previous reports on related Li-excess LIB cathodes, it is proposed that part of the charge compensation mechanism during the first cyCle takes place at the lattice oxygen site, resulting in a surface to bulk transition metal gradient. We believe that by optimizing and controlling oxygen activity, Na layered oxide materials with higher capacities can be designed.Exploring Oxygen Activity in the High Energy P2-Type Na0.78Ni0.23Mn0.69O2 Cathode Material for Na-Ion Batteries210201761#N/ATRUE
1503
jacs.6b1308510.1021/jacs.6b13085FALSEhttps://doi.org/10.1021/jacs.6b13085Schubertt, HJ. Am. Chem. Soc.Transition-metal complexes of radical ligands can exhibit low-energy electronic transitions in the near-infrared (NIR) spectral region. NIR band energy and intensity sensitively depend on the degree of electronic coupling of the chromophore. Using the example of open-shell complexes derived from platinum and a 1,4-terphenyldithiophenol, we present a novel approach toward spectroscopically distinct MR dyes for which the degree of electronic coupling correlates with the relative orientation of radical ligand and metal orbitals. Ligand/metal orbital alignment is modulated by auxiliary phosphine donors and selectively results in electron localized Class II-III or delocalized Class III structures that display distinct MR transitions at 6500 and 4000 cm(-1).Controlling Near-Infrared Chromophore Electronic Properties through Metal-Ligand Orbital Alignment14201762#N/ATRUE
1504
jacs.6b1305110.1021/jacs.6b13051https://doi.org/10.1021/jacs.6b13051Shimizu, FJ. Am. Chem. Soc.Ni(II) complexes bearing an o-bis(Aryl)phosphinophenolate ligand were synthesized as catalysts for copolymerization of ethylene and Alkyl acrylates. When the P-bound Aryl group was 2,6-dimethoxyphenyl group, one of the oxygen atoms in the methoxy groups coordinated to the nickel center on its apical position. This complex was a highly active catalyst without any activators to give highly linear and high molecular weight copolymers. The structures of the copolymers were determined by H-1 and C-13 NMR to Clarify that the Alkyl acrylate comonomers were incorporated in the main chain and that the structures of the copolymers were significantly influenced by the structure of the Aryl group in the ligand.Nickel Catalyzed Copolymerization of Ethylene and Alkyl Acrylates88201744#N/ATRUE
1505
jacs.6b0946310.1021/jacs.6b09463FALSEhttps://doi.org/10.1021/jacs.6b09463Zhou, HCJ. Am. Chem. Soc.A base-resistant porphyrin metal organic framework (MOF), namely PCN-602 has been constructed with 12-connected [Ni-8(OH)(4)(H2O)(2)Pz(12)] (Pz = pyrazolate) Cluster and a newly designed pyrazolate-based porphyrin ligand, 5,10,15,20-tetralds (4- (pyrazolate-4-yl)phenyl)porphyrin under the guidance of the reticular synthesis strategy. Besides its robustness in hydroxide solution, PCN-602 also shows excellent stability in aqueous solutions of F-, CO32-, and PO43- ions. Interestingly, the Mn3+-porph-yrinic PCN-602, as a recyClable MOF catalyst, presents high catalytic activity for the C-H bond halogenation reaction in a basic system, significantly outperforming its homogeneous counterpart. For the first time, a porphyrinic MOF was thus used as an efficient catalyst in a basic solution with coordinating anions, to the best of our knowledge.A Base-Resistant Metalloporphyrin Metal-Organic Framework for C-H Bond Halogenationx161201743#N/AFALSE
1506
jacs.6b0935110.1021/jacs.6b09351FALSEhttps://doi.org/10.1021/jacs.6b09351Sun, SHJ. Am. Chem. Soc.We report a facile nitrogenation/exfoliation process to prepare hybrid Ni-C-N nanosheets. These nanosheets are <2 nm thin, chemically stable, and metallically conductive. They serve as a robust catalyst for the hydrogen evolution reaction in 0.5 M H2SO4, or 1.0 M KOH or 1.0 M PBS (pH = 7). For example, they catalyze the hydrogen evolution reaction in 0.5 M 112504 at an onset potential of 34.7 mV, an overpotential of 60.9 mV (at j = 10 mA cm(-2)) and with remarkable long-term stability (similar to 10% current drop after 70 h testing period). They are promising as a non-Pt catalyst for practical hydrogen evolution reaction.Ni-C-N Nanosheets as Catalyst for Hydrogen Evolution Reactionx298201650#N/AFALSE
1507
jacs.6b0880310.1021/jacs.6b08803FALSEhttps://doi.org/10.1021/jacs.6b08803
Mendoza-Cortes, JL
J. Am. Chem. Soc.Physisorption is an effective route to meet hydrogen gas (H-2) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H-2 which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H-2 binding enthalpy of 5 linkers which were chelated with 11 different transition metals (Tm), inCluding abundant first-row Tm (Sc through Cu), totaling 60 molecular compounds with more than 4 configurations related to the different number of H-2 that interact with the molecular compound. It was found that first-row Tm gave similar and sometimes superior van der Waals interactions with H-2 than precious Tm. Based on these linkers, 30 new covalent organic frameworks (COFs) were constructed. The H-2 uptakes of these new COFs were determined using quantum mechanics (QM)-based force fields and grand canonical Monte Carlo (GCMC) simulations. For the first time, the range for the adsorption pressure was explored for 0-700 bar and 298 K. It was determined that Co-, Ni-, and Fe-based COFs can give high H-2 uptake and delivery when compared to bulk H-2 on this unexplored range of pressure.Design Principles for High H-2 Storage Using Chelation of Abundant Transition Metals in Covalent Organic Frameworks for 0-700 bar at 298 Kx67201625#N/AFALSE
1508
jacs.6b1260710.1021/jacs.6b12607FALSEhttps://doi.org/10.1021/jacs.6b12607Baker, RTJ. Am. Chem. Soc.Treatment of Ni(0) complexes 1a-e with sub-atmospheric pressures of trifluoroethylene (TrFE) affords hydrofluoronickelacyClopentanes L2Ni(C4F6H2) 2a-e (L = PPh3, P(O-o-tol)(3), PPh2Me, Ptoluene2, PMe3). Fluorine NMR analysis of 2a-e demonstrates predominant formation of three (of the possible six) isomers upon oxidative cyCloaddition of TrFE: the cis and trans head tail isomers and the trans head head isomer, where the CHF group is defined as the TrFE head. The respective ratios of L2Ni(C4F6H2) isomers are influenced by the nature of L, with smaller phosphines favoring the thermodynamically preferred (from DFT calculations) trans head head isomer (cf. 50% with PMe3) and the largest affording small amounts of the tail tail isomers. Lewis and Bronsted acids induce a surprising double C-F bond Activation in 2c-d, affording small functionalized hydrofluoroalkenes. Interestingly, varying the acid employed dictates the organic product obtained from the head tail isomers: BF3 center dot OEt2 is selective for 1,1,2,3-tetrafluorocyClobutene, whereas Me3SiOTf and N,N-dimethylanilinium bromide yield (Z,E)-1,1,3,4-tetrafluorobutadiene as the major fluorinated product. Reaction intermediates were isolated, and possible pathways are discussed.Generation of HydrofluoronickelacyCles from Trifluoroethylene and Ni(0): Ligand Effects on Regio-/Stereoselectivity and Reactivity9201756#N/ATRUE
1509
jacs.6b0840610.1021/jacs.6b08406FALSEhttps://doi.org/10.1021/jacs.6b08406McDonald, ARJ. Am. Chem. Soc.Two metastable Ni-III complexes, [Ni-III(OAc)(L)] and [Ni-III(ONO2)(L)] (L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate, OAc = acetate), were prepared, adding to the previously prepared [Ni-III(OCO2H)(L)], with the purpose of probing the properties of terminal late-transition metal oxidants. These high-valent oxidants were prepared by the one-electron oxidation of their Ni-II precursors ([Ni-II(OAc)(L)]- and [Ni-II(ONO2)(L)]-) with tris(4-bromophenyl)ammoniumyl hexachloroantimonate. Fascinatingly, the reaction between any [Ni-II(X)(L)]- and NaOCl/acetic acid (AcOH) or cerium ammonium nitrate ((NH4)(2)[Ce-IV(NO3)(6)], CAN), yielded [Ni-III(OAc)(L)] and [Ni-III(ONO2)(L)], respectively. An array of spectroscopic characterizations (electronic absorption, electron paramagnetic resonance, X-ray absorption spectroscopies), electrochemical methods, and computational predictions (density functional theory) have been used to determine the structural, electronic, and magnetic properties of these highly reactive metastable oxidants. The Ni-III-oxidants proved competent in the oxidation of phenols (weak O-H bonds) and a series of hydrocarbon substrates (some with strong CH bonds). Kinetic investigation of the reactions with di-tert-butylphenols showed a 15-fold enhanced reaction rate for [Ni-III(ONO2)(L)] compared to [Ni-III(OCO2H)(L)] and [Ni-III(OAc)(L)], demonstrating the effect of electron-deficiency of the O-ligand on oxidizing power. The oxidation of a series of hydrocarbons by [Ni-III(OAc)(L)] was further examined. A linear correlation between the rate constant and the bond dissociation energy of the C-H bonds in the substrates was indicative of a hydrogen atom transfer mechanism. The reaction rate with dihydroanthracene (k(2) = 8.1 M-1 s(-1)) compared favorably with the most reactive high-valent metal-oxidants, and showcases the exceptional reactivity of late transition metaloxygen adducts.Tuning the Reactivity of Terminal Nickel(III)-Oxygen Adducts for C-H Bond Activationx36201673#N/AFALSE
1510
jacs.6b0839710.1021/jacs.6b08397TRUEhttps://doi.org/10.1021/jacs.6b08397Doyle, AGJ. Am. Chem. Soc.Here we report the development of a C(sp(3))-H cross-coupling platform enabled by the catalytic generation of Chlorine radicals by nickel and photoredox catalysis. Aryl chlorides serve as both cross-coupling partners and the chlorine radical source for the alpha-oxy C(sp(3))-H Arylation of cyClic and acyClic ethers. Mechanistic studies suggest that photolysis of a Ni(III) Aryl chloride intermediate, generated by photoredox-mediated single-electron oxidation, leads to elimination of a chlorine radical in what amounts to the sequential capture of two photons. Arylations of a Benzylic C(sp(3))-H bond of toluene and a completely unactivated C(sp(3))-H bond of cyClohexane demonstrate the broad implications of this manifold for accomplishing numerous C(sp(3))-H bond functionalizations under exceptionally mild conditions.Direct C(sp(3))-H Cross Coupling Enabled by Catalytic Generation of Chlorine RadicalsPhotocatalystCsp3-Csp2_arHClAlkylIonic-PO42382016276/1/2022FALSE
1511
jacs.6b1243410.1021/jacs.6b12434FALSEhttps://doi.org/10.1021/jacs.6b12434Limberg, CJ. Am. Chem. Soc.The Activation and selective transformation of virtually inexhaustible or easy-to-generate chemicals like N-2, O-2, CO2, CO, Hy or methane gas to value-added products is a lively area of current research, because of its economic relevance as well as its huge ecological impact. Biologists and chemists have put forth a lot of effort toward understanding and modeling the mechanisms of biological small-molecule Activation, and in several catalytic cyCles proposed for nickel-containing enzymes, nickel(I) plays a key role. In recent years also in synthetic chemistry the huge potential of complex nickel(I) units for the Activation and transformation of small molecules has been discovered and exploited. This Perspective highlights some representative examples of nickel(I)-based small-molecule Activation, intending to establish awareness of the competencies and scope of nickel(I) compounds.Activation of Small Molecules at Nickel(I) Moieties602017151#N/ATRUE
1512
jacs.6b0778910.1021/jacs.6b07789FALSEhttps://doi.org/10.1021/jacs.6b07789Dyer, RBJ. Am. Chem. Soc.[NiFe] hydrogenases are metalloenzymes that catalyze the reversible oxidation of H-2. While electron transfer to and from the active site is understood to occur through iron sulfur Clusters, the mechanism of proton transfer is still debated. Two mechanisms for proton exchange with the active site have been proposed that involve distinct and conserved ionizable amino acid residues, one a glutamate, and the other an arginine. To examine the potential role of the conserved glutamate on active site acid base chemistry, we mutated the putative proton donor E-17 to Q in the soluble hydrogenase I from Pyrococcus furiosus using site directed mutagenesis. FTIR spectroscopy, sensitive to the CO and CN ligands of the active site, reveals catalytically active species generated upon reduction with H-2, inCluding absorption features consistent with the Ni-a-C intermediate. Time-resolved IR spectroscopy, which probes active site dynamics after hydride photolysis from Nia-C, indicates the E(17)Q mutation does not interfere with the hydride photolysis process generating known intermediates Ni-a-I-1 and Ni-a-I-2. Strikingly, the E-17 Q mutation disrupts obligatory proton-coupled electron transfer from the 'Ni-a-I-1 state, thereby preventing formation of Ni-a-S. These results directly establish E-17 as a proton donor/acceptor in the Ni-a-S <-> Ni-a-C equilibrium.Glutamate Gated Proton-Coupled Electron Transfer Activity of a [NiFe]-Hydrogenasex31201690#N/AFALSE
1513
jacs.6b0773310.1021/jacs.6b07733FALSEhttps://doi.org/10.1021/jacs.6b07733Wu, JJ. Am. Chem. Soc.[4]Rotaxanes featuring three axles threaded through a single ring have been prepared through active metal template synthesis. Nickel-catalyzed sp(3)-sp(3) hornocouplings of Alkyl bromide half-threads through 37- and 38-membered 2,2':6',2-terpyridyl macrocyCles generate triply threaded [4]rotaxanes in up to 11% yield. An analogous 39-membered macrocyCle produced no rotaxane products under similar conditions. The constitutions of the [4]rotaxanes were determined by NMR spectroscopy and mass spectrometry. Doubly threaded [3]rotaxanes were also obtained from the reactions but no [2]rotaxanes were isolated, suggesting that upon demetalation the axle of a singly threaded rotaxane can slip through a macrocyCle that is sufficiently large to accommodate three threads.Triply Threaded [4]Rotaxanesx28201639#N/AFALSE
1514
jacs.6b1229310.1021/jacs.6b12293FALSEhttps://doi.org/10.1021/jacs.6b12293Chatani, NJ. Am. Chem. Soc.Despite advances in methods for the deCarbonylation of aldehydes, the deCarbonylation of ketones has been met with limited success because this process requires the Activation of two inert carbon carbon bonds. All of the deCarbonylation reactions of simple unstrained ketones reported to date require the addition of a stoichiometric rhodium complex. We report herein the nickel/N-heterocyClic carbene-mediated deCarbonylation of simple diAryl ketones. This reaction shows unique acceleration effects based on the presence of both electron donating and electron-withdrawing groups.Nickel-Mediated DeCarbonylation of Simple Unstrained Ketones through the Cleavage of Carbon-Carbon Bonds60201754#N/ATRUE
1515
jacs.6b1210910.1021/jacs.6b12109FALSEhttps://doi.org/10.1021/jacs.9b05230Eichhorn, BSb@Ni-12@Sb-20(-/+) and Sb@Pd-12@Sb-20(n) Cluster Anions, Where n =+1,-1,-3,-4: Multi-Oxidation-State Clusters of Interpenetrating Platonic Solids2017#N/ATRUE
1516
jacs.6b1148710.1021/jacs.6b11487FALSEhttps://doi.org/10.1021/jacs.6b11487Muller, CJ. Am. Chem. Soc.The dry reforming of methane (DRM), i.e., the reaction of methane and CO2 to form a synthesis gas, converts two major greenhouse gases into a useful chemical feedstock. In this work, we probe the effect and role of Fe in bimetallic NiFe dry reforming catalysts. To this end, monometallic Ni, Fe, and bimetallic Ni-Fe catalysts supported on a MgxAlyOz matrix derived via a hydrotalcite-like precursor were synthesized. Importantly, the textural features of the catalysts, i.e., the specific surface area (172-178 m(2)/g(cat)), pore volume (0.51-0.66 cm(3)/g(cat)), and partiCle size (5.4-5.8 nm) were kept constant. Bimetallic, Ni4Fe1 with Ni/ (Ni + Fe) = 0.8, showed the highest activity and stability, whereas rapid deActivation and a low catalytic activity were observed for monometallic Ni and Fe catalysts, respectively. XRD, Raman, TPO, and TEM analysis confirmed that the deActivation of monometallic Ni catalysts was in large due to the formation of graphitic carbon. The promoting effect of Fe in bimetallic Ni-Fe was elucidated by combining operando XRD and XAS analyses and energy -dispersive X-ray spectroscopy complemented with density functional theory calculations. Under dry reforming conditions, Fe is oxidized partially to FeO leading to a partial dealloying and formation of a Ni-richer NiFe alloy. Fe migrates leading to the formation of FeO preferentially at the surface. Experiments in an inert helium atmosphere confirm that FeO reacts via a redox mechanism with carbon deposits forming CO, whereby the reduced Fe restores the original Ni-Fe alloy. Owing to the high activity of the material and the absence of any XRD signature of FeO, it is very likely that FeO is formed as small domains of a few atom layer thickness covering a fraction of the surface of the Ni-rich partiCles, ensuring a Close proximity of the carbon removal (FeO) and methane Activation (Ni) sites.Cooperativity and Dynamics Increase the Performance of NiFe Dry Reforming Catalysts165201777#N/ATRUE
1517
jacs.6b0712710.1021/jacs.6b07127FALSEhttps://doi.org/10.1021/jacs.6b07127Sun, YJJ. Am. Chem. Soc.Conventional water electrolyzers produce H-2 and O-2 simultaneously, such that additional gas separation steps are needed to prevent H-2/O-2 mixing. The sluggish anodic O-2 evolution reaction (OER) always results in low overall energy conversion efficiency and the product of OER, O-2, is not of significant value. In addition, the potential formation of reactive oxygen species (ROS) may lead to degradation of cell membranes and thus premature device failure. Herein we report a general concept of integrating oxidative biomass upgrading reactions with decoupled H-2 generation from water splitting. Five representative biomass substrates, ethanol, Benzyl alcohol, furfural, furfuryl alcohol, and S-hydroxymethylfurfural (HMF), were selected for oxidative upgrading catalyzed by a hierarchically porous Ni3S2/Ni foam bifunctional electrocatalyst (Ni3S2/NF). All the five organics can be oxidized to value-added liquid products at much lower overpotentials than that of OER. In particular, the electrocatalytic oxidation of HMF to the value-added 2,5-furandiCarbonylic acid (FDCA) was further studied in detail. Benefiting from the more favorable thermodynamics of HMF oxidation than that of OER, the cell voltage for integrated H-2 production and HMF oxidation was significantly reduced by-100 mV relative to pure water splitting to achieve 100 mA cm(-2), while the oxidation product (FDCA) at the anode was much more valuable than O-2. When utilized as electrocatalysts for both cathode and anode, Ni3S2/NF demonstrated outstanding durability and nearly unity Faradaic efficiencies for both H-2 and FDCA production. Overall, such an integration of oxidative biomass valorization and HER via earth-abundant electrocatalysts not only avoids the generation of explosive H-2/O-2 mixture and ROS, but also yields products of high value at both electrodes with lower voltage input, maximizing the energy conversion efficiency.A General Strategy for Decoupled Hydrogen Production from Water Splitting by Integrating Oxidative Biomass Valorizationx267201668#N/AFALSE
1518
jacs.6b1037510.1021/jacs.6b10375FALSEhttps://doi.org/10.1021/jacs.6b10375Ma, DJ. Am. Chem. Soc.Ruthenium is a promising low-temperature catalyst for Fischer-Tropsch synthesis (FTS). However, its scarcity and modest specific activity limit its widespread industrialization. We demonstrate here a strategy for tuning the crystal phase of catalysts to expose denser and active sites for a higher mass-specific activity. Density functional theory calculations show that upon CO dissociation there are a number of open facets with modest barrier available on the face-centered cubic (fcc) Ru but only a few step edges with a lower barrier on conventional hexagonal-Closest packed (hcp) Ru. Guided by theoretical calculations, water-dispersible fcc Ru catalysts containing abundant open facets were synthesized and showed an unprecedented mass-specific activity in the aqueous-phase FTS, 37.8 mol(CO).mol(Ru)(-1).h(-1) at 433 K. The mass-specific activity of the fcc Ru catalysts with an average size of 6.8 nm is about three times larger than the previous best hcp catalyst with a smaller size of 1.9 nm and a higher specific surface area. The origin of the higher mass-specific activity of the fcc Ru catalysts is identified experimentally from the 2 orders of magnitude higher density of the active sites, despite its slightly higher apparent barrier. Experimental results are in excellent agreement with prediction of theory. The great influence of the crystal phases on site distribution and their intrinsic activities revealed here provides a rationale design of catalysts for higher mass-specific activity without decrease of the partiCle size.Chemical Insights into the Design and Development of Face Centered Cubic Ruthenium Catalysts for Fischer Tropsch Synthesis85201788#N/ATRUE
1519
jacs.6b0686010.1021/jacs.6b06860https://doi.org/10.1021/jacs.6b06860Xu, DSJ. Am. Chem. Soc.Splitting of alcohols into-hydrogen and corresponding Carbonyl compounds has potential applications in hydrogen production and chemical industry. Herein, we report that a heterogeneous photocatalyst, (Nimodified CdS nanopartiCles) could efficiently split alcohols into hydrogen and corresponding aldehydes or ketones in a stoichiometric manner under visible light irradiation. Optimized apparent quantum yields of 38%, 46%, and 48% were obtained at 447 nm for dehydrogenation of methanol, ethanol, and 2-propanol, respectively. In the case of dehydrogenation of 2-propanol, a turnover number of greater than. 44 000 was achieved. To our knowledge, these are unprecedented values for photkatalytic splitting of liquid alcohols under visible light to date. Besides, the current catalyst system, functions well with other aliphatic and aromatic alcohols, affording the corresponding Carbonyl Compounds with good to excellent conversion and outstanding selectivity. Moreover, mechanistic investigations suggest that an interface between Ni nanocrystal and CdS plays a key role in the reaction mechanismof the photocatalytic splitting of alcohol.Efficient Visible Light-Driven Splitting of Alcohols into Hydrogen and Corresponding Carbonyl Compounds over a Ni-Modified CdS PhotocatalystPhotocatalyst171201633#N/AFALSE
1520
jacs.6b0673610.1021/jacs.6b06736FALSEhttps://doi.org/10.1021/jacs.6b06736Telfer, SGJ. Am. Chem. Soc.We report a new methodology for producing monometallic or bimetallic nanopartiCles confined within hollow nitrogen-doped porous carbon capsules. The capsules are derived from metal organic framework (MOB) crystals that are coated with a shell of a secondary material, comprising either a metal tannic acid coordination polymer or a resorcinol formaldehyde polymer. Platinum,nanopartiCles are optionally sandwiched between the MOF and the shell. Pyrolysis of the MOF shell composites produces hollow capsules of porous nitrogen-doped carbon that: bear either monometallic (Pt, Co, and Ni) or alloyed (PtCo and PtNi) metal nanopartiCles. The Co and Ni components of the bimetallic nanopartiCles are derived from the shell surrounding the MOF crystals. The hollow capsules prevent sintering and detachment of the nanopartiCles, and their porous walls allow for efficient mass transport. Alloyed PtCo nanopartiCles embedded in the capsule walls are highly active, selective, and recyClable catalysts for the hydrogenation of nitroarenes to anilines.Catalytically Active Bimetallic NanopartiCles Supported on Porous Carbon Capsules Derived From Metal-Organic Framework Compositesx150201678#N/AFALSE
1521
jacs.6b1031610.1021/jacs.6b10316FALSEhttps://doi.org/10.1021/jacs.6b10316McGrier, PLJ. Am. Chem. Soc.Constructing metalated three-dimensional (3D) covalent organic frameworks is a challenging synthetic task. Herein, we report the synthesis and characterization of a highly porous (SA(BET) = 5083 m(2) g(-1)) 3D COF with a record low density (0.13 g cm(-3)) containing, pi-electron conjugated dehydrobenzoannulene (DBA) units. Metalation of DBA-3D-COF 1 with Ni to produce Ni-DBA-3D-COF results in a minimal reduction in the surface area (SA(BET) = 4763 m(2) g(-1)) of the material due to the incorporation of the metal within the cavity of the DBA units, and retention of crystallinity. Both 3D DBA-COFs also display great uptake capacities for ethane and ethylene gas.Metalation of a Mesoporous Three-Dimensional Covalent Organic Framework161201646#N/ATRUE
1522
jacs.6b0585110.1021/jacs.6b05851FALSEhttps://doi.org/10.1021/jacs.6b05851Yang, JYJ. Am. Chem. Soc.Electrocatalytic activity of a water-soluble nickel complex, [Ni(DHMPE)(2)](2+) (DHMPE = 2-bis(di(hydroxymethyl)phosphino)ethane), for the hydrogen evolution reaction (HER) at pH 1 is reported. The catalyst functions at a rate of similar to 10(3) s(-1) (kobs). with high Faradaic efficiency. Quantification of the complex before and after 18+ hours of electrolysis reveals negligible decomposition under catalytic conditions. Although highly acidic conditions are common in electrolytic cells, this is a rare example of a homogeneous catalyst for HER that functions with high stability at low pH. The stability of the compound and proposed catalytic intermediates enabled detailed mechanistic studies. The thermodynamic parameters governing electron and proton transfer were used to determine the appropriate reductants and acids to access the catalytic cyCle in a stepwise fashion, permitting direct spectroscopic identification of intermediates. These studies support 4 mechanism for proton reduction that proceeds through two-electron reduction of the nickel(II) complex, protonation to generate [HNi(DHMPE)(2)](+), and further protonation to initiate hydrogen bond formation.Electrocatalytic Hydrogen Evolution under Acidic Aqueous Conditions and Mechanistic Studies of a Highly Stable Molecular Catalyst
Electrocatalytic
61201646#N/AFALSE
1523
jacs.6b1030410.1021/jacs.6b10304FALSEhttps://doi.org/10.1021/jacs.6b10304Simonov, ANJ. Am. Chem. Soc.Detection and quantification of redox transformations involved in water oxidation electrocatalysis is often not possible using conventional techniques. Herein, use of large amplitude Fourier transformed ac voltammetry and comprehensive analysis of the higher harmonics has enabled us to access the redox processes responsible for catalysis. An examination of the voltammetric data for water oxidation in borate buffered solutions (pH 9.2) at electrodes functionalized with systematically varied low loadings of cobalt (CoOx), manganese (MnOx), and nickel oxides (NiOx) has been undertaken, and extensive experiment-simulation comparisons have been introduced for the first time. Analysis shows that a single redox process controls the rate of catalysis for Co and Mn oxides, while two electron transfer events contribute in the Ni case. We apply a molecular catalysis model that couples a redox transformation of a surface-confined species (effective reversible potential, E-eff(0)) to a catalytic reaction with a substrate in solution (pseudo-first-order rate constant, k(1)(f)), accounts for the important role of a Bronsted base, and mimics the experimental behavior. The analysis revealed that E-eff(0) values for CoOx, MnOx, ;and NiOx lie within the range 1.9-2.1 V vs reversible hydrogen electrode, and k(1)(f) varies from 2 x 10(3) to 4 x 10(4) s(-1). The k(1)(f) values are much higher than reported for any water electrooxidation catalyst before. The E-eff(0) values provide a guide for in situ spectroscopic characterization of the active states involved in catalysis by metal oxides.Parameterization of Water Electrooxidation Catalyzed by Metal Oxides Using Fourier Transformed Alternating Current Voltammetry21201673#N/ATRUE
1524
jacs.6b0519610.1021/jacs.6b05196FALSEhttps://doi.org/10.1021/jacs.6b05196Hu, XLJ. Am. Chem. Soc.The electrolysis of water to produce hydrogen and oxygen is a simple and attractive approach to store renewable energies in the form of chemical fuels. The oxygen evolution reaction (OER) is a complex four-electron process that constitutes the most energy-inefficient step in water electrolysis. Here we describe a novel electrochemical method for the deposition of a family of thin-film transition metal (oxy)hydroxides as OER catalysts. The thin films have nanodomains of crystallinity with lattice spacing similar to those of double-layered hydroxides. The loadings of these thin-film catalysts were accurately determined with a resolution of below 1 mu g cm(-2) using an electrochemical quartz microcrystal balance. The loading-activity relations for various catalysts were established using voltammetry and impedance spectroscopy. The thin-film catalysts have up to four types of loading-activity dependence due to film nuCleation and growth as well as the resistance of the films. A zone of intrinsic activity has been identified for all of the catalysts where the mass-averaged activity remains constant while the loading is increased. According to their intrinsic activities, the metal oxides can be Classified into three categories: NiOx, MnOx, and FeOx belong to category I, which is the least active; CoOx and CoNiOx belong to category II, which has medium activity; and FeNiOx, CoFeOx, and CoFeNiOx belong to category III, which is the most active. The high turnover frequencies of CoFeOx and CoFeNiOx at low overpotentials and the simple deposition method allow the fabrication of high-performance anode electrodes coated with these catalysts. In 1 M KOH and with the most active electrode, overpotentials as low as 240 and 270 mV are required to reach 10 and 100 mA cm(-2), respectively.Oxidatively Electrodeposited Thin-Film Transition Metal (Oxy)hydroxides as Oxygen Evolution Catalystsx243201646#N/AFALSE
1525
jacs.6b0519010.1021/jacs.6b05190FALSEhttps://doi.org/10.1021/jacs.6b05190Ye, JHJ. Am. Chem. Soc.Water splitting represents a promising technology for renewable energy conversion and storage, but it is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). Here, using Au-nanopartiCle-decorated Ni(OH)(2) nanosheets [Ni(OH)(2)-Au] as catalysts, we demonstrate that the photon-induced surface plasmon resonance (SPR) excitation on Au nanopartiCles could significantly activate the OER catalysis, specifically achieving a more than 4 fold enhanced activity and meanwhile affording a markedly decreased over potential of 270 mV at the current density of 10 mA cm(-2) and a small Tafel slope of 35 mV dec(-1) (no iR-correction), which is much better than those of the benchmark IrO2 and RuO2, as well as most Ni-based OER catalysts reported to date. The synergy of the enhanced generation of Ni-III/IV active species and the improved charge transfer, both induced by hot-electron excitation on Au nanopartiCles, is proposed to account for such a markedly increased activity. The SPR-enhanced OER catalysis could also be observed over cobalt oxide (CoO) Au and iron oxy-hydroxide (FeOOH) Au catalysts, suggesting the generality of this strategy. These findings highlight the possibility of activating OER catalysis by plasmonic excitation and could open new avenues toward the design of more-energy-efficient catalytic water oxidation systems with the assistance of light energy.Promoting Active Species Generation by Plasmon-Induced Hot-Electron Excitation for Efficient Electrocatalytic Oxygen Evolution
Electrocatalytic
212201679#N/AFALSE
1526
jacs.6b1030310.1021/jacs.6b10303FALSEhttps://doi.org/10.1021/jacs.6b10303Mirica, LMJ. Am. Chem. Soc.The use of the tridentate ligand 1,4,7-trimethyl-1,4,7-triazacyClononane (Me(3)tacn) and the cyClic Alkyl/Aryl C-donor ligand -CH2CMe2-o-C6H4- (cyCloneophyl) allows for the synthesis of isolable organometallic Ni-II, Ni-III, and Ni-IV complexes. Surprisingly, the five-coordinate Ni-III, complex is stable both in solution and the solid state, and exhibits limited C-C bond formation reactivity. Oxidation by one electron of this Ni-III species generates a six-coordinate Ni-IV complex, with an acetonitrile molecule bound to Ni. Interestingly, illumination of the Ni-IV complex with blue LEDs results in rapid formation of the cyClic C-C product at room temperature. This reactivity has important implications for the recently developed dual Ni/photoredox catalytic systems proposed to involve high-valent organometallic Ni intermediates. Additional reactivity studies show the corresponding Ni-II species undergoes oxidative addition with Alkyl halides, as well as rapid oxidation by O-2, to generate detectable Niln and/or Ni-IV intermediates and followed by C-C bond formation.Oxidative C-C Bond Formation Reactivity of Organometallic Ni(II), Ni(III), and Ni(IV) Complexes38201757#N/ATRUE
1527
jacs.6b0478910.1021/jacs.6b04789https://doi.org/10.1021/jacs.6b04789Molander, GAJ. Am. Chem. Soc.An iridium photocatalyst and visible light facilitate a room temperature, nickel-catalyzed coupling of (hetero)Aryl bromides with activated alpha-heterosubstituted or Benzylic C(sp(3))-H bonds. Mechanistic investigations on this unprecedented transformation have uncovered the possibility of an unexpected mechanism hypothesized to involve a Ni-Br homolysis event from an excited-state nickel complex. The resultant bromine radical is thought to abstract weak C(sp(3))-H bonds to generate reactive Alkyl radicals that can be engaged in Ni-catalyzed Arylation. Evidence suggests that the iridium photocatalyst facilitates nickel excitation and bromine radical generation via triplet-triplet energy transfer.Photochemical Nickel-Catalyzed C-H Arylation: Synthetic Scope and Mechanistic InvestigationsPhotocatalyst2112016416/1/2022FALSE
1528
jacs.6b0457910.1021/jacs.6b04579FALSEhttps://doi.org/10.1021/jacs.6b04579Rauchfuss, TBJ. Am. Chem. Soc.The intermediacy of a reduced nickel-iron hydride in hydrogen evolution catalyzed by Ni-Fe complexes was verified experimentally and computationally. In addition to catalyzing hydrogen evolution, the highly basic and bulky (dppv)Ni(mu-pdt)Fe(CO)(dppv) ([1](0); dppv = cis-C2H2(PPh2)(2)) and its hydride derivatives have yielded to detailed characterization in terms of spectroscopy, bonding, and reactivity. The protonation of [1](0) initially produces unsym-[H1](+), which converts by a first-order pathway to sym-[H1](+). These species have (unsym) and C-s (sym) symmetries, respectively, depending on the stereochemistry of the octahedral Fe site. Both experimental and computational studies show that [H1](+) protonates at sulfur. The S = 1/2 hydride [H1](0) was generated by reduction of [H1](+) with Cp*Co-2. Density functional theory (DFT) calculations indicate that [H1](0) is best described as a Ni(I)-Fe(II) derivative with significant spin density on Ni and some delocalization on S and Fe. EPR spectroscopy reveals both kinetic and thermodynamic isomers of [H1](0). Whereas [H1](+) does not evolve H-2 upon protonation, treatment of [H1](0) with acids gives H-2. The redox state of the remote metal (Ni) modulates the hydridic character of the Fe(II)-H center. As supported by DFT calculations, H-2 evolution proceeds either directly from [H1](0) and external acid or from protonation of the Fe-H bond in [H1](0) to give a labile dihydrogen complex. Stoichiometric tests indicate that protonation-induced hydrogen evolution from [H1](0) initially produces [1](+), which is reduced by [H1](0). Our results reconcile the required reductive Activation of a metal hydride and the resistance of metal hydrides toward reduction. This dichotomy is resolved by reduction of the remote (non-hydride) metal of the bimetallic unit.Mechanism of H-2 Production by Models for the [NiFe]-Hydrogenases: Role of Reduced HydridesX41201658#N/AFALSE
1529
jacs.6b0432510.1021/jacs.6b04325FALSEhttps://doi.org/10.1021/jacs.6b04325Reisner, EJ. Am. Chem. Soc.Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O-2. Herein, we demonstrate an alternative approach and couple solar H-2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride ((CNx)-C-NCN) and a molecular nickel(II) bis(diphosphine) H-2-evolution catalyst (NiP) enabled the production of H-2 with concomitant selective oxidation of Benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The (CNx)-C-NCN-NiP system showed an activity of 763 mu mol (g CNx)(-1) h(-1) toward H-2 and aldehyde production, a Ni-based turnover frequency of 76 h(-1), and an external quantum efficiency of 15% (lambda = 360 +/- 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of (CNx)-C-NCN is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon type carbon nitride. Photoexcited (CNx)-C-NCN in the presence of an organic substrate can accumulate ultralong-lived trapped electrons, which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a Closed redox cyCle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel.Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride-Molecular Ni Catalyst Systemx153201664#N/AFALSE
1530
jacs.6b1030010.1021/jacs.6b10300FALSEhttps://doi.org/10.1021/jacs.6b10300Dinca, MJ. Am. Chem. Soc.A recently developed metal organic framework (MOP) catalyst for the dimerization of ethylene has a combination of selectivity and activity that surpasses that of commercial homogeneous catalysts, which have dominated this important industrial process for nearly 50 years. The uniform catalytic sites available in MOFs provide a unique opportunity to directly study reaction mechanisms in heterogeneous catalysts, a problem typically intractable due to the multiplicity of coordination environments found in many solid catalysts. In this work, we use a combination of isotopic labeling studies, mechanistic, probes, and DFT calculations to demonstrate that Ni-MFU-4l operates via the Cossee-Arlman mechanism, which has also been implicated in homogeneous late transition metal catalysts. These studies demonstrate that metal nodes in MOFs mimic homogeneous catalysts not just functionally, but also mechanistically. They provide a blueprint for the development of advanced heterogeneous catalysts with similar degrees of tunability to their homogeneous counterparts.Mechanism of Single-Site Molecule-Like Catalytic Ethylene Dimerization in Ni-MFU-4l77201763#N/ATRUE
1531
jacs.6b0968110.1021/jacs.6b09681FALSELim, MHMechanistic Insights into Tunable Metal-Mediated Hydrolysis of Amyloid-beta Peptides2017#N/ATRUE
1532
jacs.6b0850710.1021/jacs.6b08507FALSEhttps://doi.org/10.1021/jacs.6b08507Shenvi, RAJ. Am. Chem. Soc.A combination of cobalt and nickel catalytic cyCles enables a highly branch-selective (Markovnikov) olefin hydroArylation. Radical cyClization and ring scission experiments are consistent with hydrogen atom transfer (HAT) generation of a carbon-centered radical that leads to engagement of a nickel cyCle.Branch-Selective HydroArylation: Iodoarene-Olefin Cross-Coupling125201674#N/ATRUE
1533
jacs.6b0808410.1021/jacs.6b08084FALSEhttps://doi.org/10.1021/jacs.6b08084Hayton, TWJ. Am. Chem. Soc.The reactivity of the masked terminal nickel sulfide complex, [K(18-crown-6)][(L-tBu)Ni-II(S)] (L-tBu = {(2,6-(Pr2C6H3)-Pr-i)NC(Bu-t)}(2)CH), with the biologically important small molecules CO and NO, was surveyed. [K(18-crown-6)][(L-tBu)Ni-II(S)] reacts with carbon monoxide (CO) via addition across the Ni-S bond to give a Carbonyl sulfide complex, [K(18-crown-6)][(L-tBu)Ni-II(S,C:eta(2)-COS)] (1). Additionally, [K(18-crown-6)][(LtBu)NiII(S)] reacts with nitric oxide (NO) to yield a nickel nitrosyl, [(L-tBu)Ni(NO)] (2), and a perthionitrite anion, [K(18-crown-6)][SSNO] (3). The isolation of 3 from this reaction confirms, for the first time, that transition metal sulfides can react with NO to form the biologically important [SSNO](-) anion.Reactivity of a Nickel Sulfide with Carbon Monoxide and Nitric Oxide18201637#N/ATRUE
1534
jacs.6b0313410.1021/jacs.6b03134FALSEhttps://doi.org/10.1021/jacs.6b03134Yang, PDJ. Am. Chem. Soc.Here, we demonstrate the successful syn.= thesis of brightly emitting colloidal cesium lead halide (CspbX3, X = Cl, Br, I) nanowires (NWs) with uniform diameters and tunable compositions. By using highly monodisperse CspbBr3 NWs as templates, the NW composition can be independently controlled through anion-exchange reactions. CspbX3 alloy NWs with a wide range of alloy compositions can be achieved with wellpreserved morphology and crystal structure. The NI/Vs are highly luminescent with photoluminescence quantum yields (PLQY) ranging from 20% to 80%. The bright photoluminescence can be tuned over nearly the entire visible spectrum. The high PLQYs together with charge transport measurements exemplify the efficient alloying of the anionic sublattice in a one-dimensional CspbX3 system. The wires increased functionality in the form of fast photoresponse rates and the low defect density suggest CspbX3 NWs as prospective materials for,optoelectronic applications.Synthesis of Composition Tunable and Highly Luminescent Cesium Lead Halide Nanowires through Anion-Exchange Reactionsx282201628#N/AFALSE
1535
jacs.6b0756710.1021/jacs.6b07567FALSEhttps://doi.org/10.1021/jacs.6b07567Jarvo, ERJ. Am. Chem. Soc.The stereospecific reductive cross-electrophile coupling reaction of 2-Vinyl-4-halotetrahydropyrans for VinylcyClopropane synthesis is reported. The nickel-catalyzed reaction occurs with both Alkyl fluorides and Alkyl chlorides. To the best of our knowledge, this is the first reported cross-electrophile coupling reaction of an Alkyl fluoride. Ring contraction proceeds with high stereospecificity, providing selective synthesis of either diastereomer of di- and trisubstituted cyClopropanes. The utility of this methodology is demonstrated by several synthetic applications inCluding the synthesis of the natural product dictyopterene A. 2-Vinyl-4-fluorotetrahydrofurans also undergo stereospecific ring contractions, providing access to synthetically useful hydroxymethyl cyClopropanes.Nickel-Catalyzed Cross-Electrophile Coupling of Alkyl Fluorides: Stereospecific Synthesis of VinylcyClopropanes36201651#N/ATRUE
1536
jacs.6b0240510.1021/jacs.6b02405FALSEhttps://doi.org/10.1021/jacs.6b02405Mirica, LMJ. Am. Chem. Soc.Herein we report an atom- and step economic aromatic cyanoAlkylation reaction that employs nitriles as building blocks and proceeds through C-sp(2)-H and C-sp(3)-H bond Activation steps mediated by Ni-III. In addition to cyanomethylation with MeCN, regioselective alpha-cyanoAlkylation was observed with various nitrile substrates to generate secondary and tertiary nitriles. Importantly, to the best of our knowledge these are the first examples of C-H bond Activation reactions occurring at a Ni-III center, which may exhibit different reactivity and selectivity profiles than those corresponding to analogous Ni-II centers. These studies provide guiding principles to design catalytic C-H Activation and functionalization reactions involving high-valent Ni species.Aromatic CyanoAlkylation through Double C-H Activation Mediated by Ni(III)X45201655#N/AFALSE
1537
jacs.6b0217610.1021/jacs.6b02176FALSEhttps://doi.org/10.1021/jacs.6b02176Chen, LXJ. Am. Chem. Soc.Photoexcited Nickel(II) tetramesitylporphyrin (NiTMP), like many open-shell metalloporphyrins, relaxes rapidly through multiple electronic states following an initial porphyrin-based excitation, some involving metal centered electronic configuration changes that could be harnessed catalytically before excited state relaxation. While a NiTMP excited state present at 100 ps was previously identified by X-ray transient absorption (XTA) spectroscopy at a synchrotron source as a relaxed (d,d) state, the lowest energy excited state (J. Am. Chem. Soc., 2007, 129, 9616 and Chem. Sci., 2010, 1, 642), structural dynamics before thermalization were not resolved due to the similar to 100 ps duration of the available X-ray probe pulse. Using the femtosecond (fs) X-ray pulses of the Linac Coherent Light Source (LClS), the Ni center electronic configuration from the initial excited state to the relaxed (d,d) state has been obtained via ultrafast Ni K-edge XANES (X-ray absorption near edge structure) on a time scale from hundreds of femtoseconds to 100 ps. This enabled the identification of a short-lived Ni(I) species aided by time-dependent density functional theory (TDDFT) methods. Computed electronic and nuClear structure for critical excited electronic states in the relaxation pathway characterize the dependence of the complex's geometry on the electron occupation of the 3d orbitals. Calculated XANES transitions for these excited states assign a short-lived transient signal to the spectroscopic signature of the Ni(I) species, resulting from intramolecular charge transfer on a time scale that has eluded previous synchrotron studies. These combined results enable us to examine the excited state structural dynamics of NiTMP prior to thermal relaxation and to capture intermediates of potential photocatalytic significance.Ultrafast Excited State Relaxation of a Metalloporphyrin Revealed by Femtosecond X-ray Absorption Spectroscopyx55201688#N/AFALSE
1538
jacs.6b0754410.1021/jacs.6b07544FALSEhttps://doi.org/10.1021/jacs.6b07544Company, AJ. Am. Chem. Soc.Terminal high-valent metal-oxygen species are key reaction intermediates in the catalytic cyCle of both enzymes (e.g., oxygenases) and synthetic oxidation catalysts. While tremendous efforts have been directed toward the characterization of the biologically relevant terminal manganese oxygen and iron-oxygen species, the corresponding analogues based on late-transition metals such as cobalt, nickel or copper are relatively scarce. This scarcity is in part related to the Oxo Wall concept, which predicts that late transition metals cannot support a terminal oxido ligand in a tetragonal environment. Here, the nickel(II) complex (1) of the tetradentate macrocyClic ligand bearing a 2,6-pyridinedicarboxamidate unit is shown to be an effective catalyst in the chlorination and oxidation of C-H bonds with sodium hypochlorite as terminal oxidant in the presence of acetic acid (AcOH). Insight into the active species responsible for the observed reactivity was gained through the study of the reaction of 1 with CIO- at low temperature by UV-vis absorption, resonance Raman, EPR, ESI-MS, and XAS analyses. DFT calculations aided the assignment of the trapped chromophoric species (3) as a nickel-hypochlorite species. Despite the fact that the formal oxidation state of the nickel in 3 is +4, experimental and computational analysis indicate that 3 is best fon-nulated as a Ni-III complex with one unpaired electron delocalized in the ligands surrounding the metal center. Most remarkably, 3 reacts rapidly with a-range of substrates inCluding those with strong aliphatic C-H bonds, indicating the direct involvement of 3 in the oxidation/chlorination reactions observed in the 1/CIO-/AcOH catalytic system.Rapid Hydrogen and Oxygen Atom Transfer by a High-Valent Nickel-Oxygen Species34201674#N/ATRUE
1539
jacs.6b0741110.1021/jacs.6b07411FALSEhttps://doi.org/10.1021/jacs.6b07411Lei, AWJ. Am. Chem. Soc.Oxygenation of alkenes is one of the most straightforward routes for the construction of Carbonyl compounds. Wacker oxidation provides a broadly useful strategy to convert the mineral oil into higher value-added Carbonyl chemicals. However, the conventional Wacker chemistry remains problematic, such as the poor activity for internal alkenes, the lack of anti-Markovnikov regioselectivity, and the high cost and chemical waste resulted from noble metal catalysts and stoichiometric oxidant. Here, we describe an unprecedented dehydrogenative oxygenation of beta-Alkyl styrenes and their derivatives with water under external-oxidant-free conditions by utilizing the synergistic effect of photo catalysis and proton-reduction catalysis that can address these challenges. This dual catalytic system possesses the single anti-Markovnikov selectivity due to the property of the visible-light-induced alkene radical cation intermediate.Anti-Markovnikov Oxidation of beta-Alkyl Styrenes with H2O as the Terminal Oxidant85201666#N/ATRUE
1540
jacs.6b0160610.1021/jacs.6b01606FALSEhttps://doi.org/10.1021/jacs.6b01606Zhang, TRJ. Am. Chem. Soc.Faceted NiO nanopartiCles preferentially exposing high surface energy planes demand attention due to their excellent electrocatalytic properties. However, the activity of faceted NiO nanopartiCles generally remains suboptimal due to their large lateral size and thickness, which severely limits the availability of coordinatively unsaturated active reactive edge and corner sites. Here, ultrafine NiO nanosheets with a platelet size of similar to 4.0 nm and thickness (similar to 1.1 nm) stabilized by TiO2 were successfully prepared by calcination of a monolayer layered double hydroxide precursor. The ultrafine NiO nanosheets displayed outstanding performance in electrochemical water oxidation due to a high proportion of reactive NiO {110} facets, intrinsic Ni3+ and Ti3+ sites, and abundant interfaces, which act synergistically to promote H2O adsorption and facilitate charge-transfer.Ultrafine NiO Nanosheets Stabilized by TiO2 from Monolayer NiTi-LDH Precursors: An Active Water Oxidation Electrocatalystx381201657#N/AFALSE
1541
jacs.6b0686210.1021/jacs.6b06862FALSEhttps://doi.org/10.1021/jacs.6b06862Mirica, LMJ. Am. Chem. Soc.Nickel-catalyzed cross-coupling reactions are experiencing a dramatic resurgence in recent years given their ability to employ a wider range of electrophiles as well as promote stereospecific or stereoselective transformations. In contrast to the extensively studied Pd catalysts that generally employ diamagnetic intermediates, Ni systems can more easily access various oxidation states inCluding odd-electron configurations. For example, organometallic Ni-III intermediates with Aryl and/or Alkyl ligands are commonly proposed as the active intermediates in cross-coupling reactions. Herein, we report the first isolated Ni-III-diAlkyl complex and show that this species is involved in stoichiometric and catalytic C-C bond formation reactions. Interestingly, the rate of C-C bond formation from a Ni-III center is enhanced in the presence of an oxidant, suggesting the involvement of transient Ni-IV species. Indeed, such a Ni-IV species was observed and characterized spectroscopically for a nickelacyCle system. Overall, these studies suggest that both Ni-III and Ni-IV species could play an important role in a range of Ni-catalyzed cross-coupling reactions, especially those involving Alkyl substrates.Isolated Organometallic Nickel(III) and Nickel(IV) Complexes Relevant to Carbon-Carbon Bond Formation Reactions54201678#N/ATRUE
1542
jacs.6b0053810.1021/jacs.6b00538FALSEhttps://doi.org/10.1021/jacs.6b00538Merner, BLJ. Am. Chem. Soc.A series of p-terphenyl-based macrocyCles, containing highly distorted p-phenylene units, have been synthesized. BiAryl bonds of the nonplanar p-terphenyl nuClei were constructed in the absence of Pd-catalyzed or Ni-mediated cross-coupling reactions, using 1,4-diketones as surrogates to strained arene units. A streamlined synthetic protocol for the synthesis of 1,4-diketo macrocyCles has been developed, using only 2.5 mol % of the Hoveyda Grubbs second-generation catalyst in both metathesis and transfer hydrogenation reactions. Under protic acid-mediated dehydrative aromatiza-BENT tion conditions, the central and most strained benzene ring of the p-terphenyl systems was susceptible to rearrangement reactions. To overcome this, a dehydrative aromatization reactions. To overcome this, a dehydrative aromatization protocol using the Burgess reagent was developed. Under these conditions, no strain-induced rearrangement reactions occur, delivering p-phenylene units with up to 28.4 kcal/mol strain energy and deformation angles that sum up to 40 degrees.Overcoming Strain-Induced Rearrangement Reactions: A Mild Dehydrative Aromatization Protocol for Synthesis of Highly Distorted p-Phenylenesx19201629#N/AFALSE
1543
jacs.6b0628510.1021/jacs.6b06285FALSEhttps://doi.org/10.1021/jacs.6b06285Tang, WJJ. Am. Chem. Soc.We herein report a transition-metal-free cross-coupling between secondary Alkyl halides/mesylates and Aryl/alkenylboronic acid, providing expedited access to a series of nonchiral/chiral coupling products in moderate to good yields. Stereospecific S(N)2-type coupling is developed for the first time with alkenylboronic adds as pure nuCleophiles, offering an attractive alternative to the stereospecific transition-metal-catalyzed C(sp(2))-C(sp(3)) cross-coupling.Transition-Metal-Free Stereospecific Cross-Coupling with Alkenylboronic Acids as NuCleophiles33201671#N/ATRUE
1544
jacs.6b0534510.1021/jacs.6b05345FALSEhttps://doi.org/10.1021/jacs.6b05345Eddaoudi, MJ. Am. Chem. Soc.The development of functional solid-state materials for carbon capture at low carbon dioxide (CO2) concentrations, namely, from confined spaces (<0.5%) and in particular from air (400 ppm), is of prime importance with respect to energy and environment sustainability. Herein, we report the deliberate construction of a hydrolytically stable fluorinated metal organic framework (MOF), NbOFFIVE-1-Ni, with the appropriate pore system (size, shape, and functionality), ideal for the effective and energy-efficient removal of trace carbon dioxide. Markedly, the CO2-selective NbOFFIVE-1-Ni exhibits the highest CO2 gravimetric and volumetric uptake (ca. 1.3 mmol/g and 51.4 cm(3) (STP) cm(-3)) for a physical adsorbent at 400 ppm of CO2 and 298 K. Practically, NbOFFIVE-1-Ni offers the complete CO2 desorption at 328 K under vacuum with an associated moderate energy input of 54 kJ/mol, typical for the full CO2 desorption in conventional physical adsorbents but considerably lower than chemical sorbents. Noticeably, the contracted square-like channels, affording the Close proximity of the fluorine centers, permitted the enhancement of the CO2 framework interactions and subsequently the attainment of an unprecedented CO2 selectivity at very low CO2 concentrations. The precise localization of the adsorbed CO2 at the vicinity of the periodically aligned fluorine centers, promoting the selective adsorption of CO2, is evidenced by the single-crystal X-ray diffraction study on NbOFFIVE-1-Ni hosting CO2 molecules. CyClic CO2/N-2 mixed-gas column breakthrough experiments under dry and humid conditions corrB(OH)2rate the excellent CO2 selectivity under practical carbon capture conditions. Pertinently, the notable hydrolytic stability positions NbOFFIVE-1-Ni as the new benchmark adsorbent for direct air capture and CO2 removal from confined spaces.A Fine-Tuned Fluorinated MOF Addresses the Needs for Trace CO2 Removal and Air Capture Using Physisorption172201640#N/ATRUE
1545
jacs.6b0511110.1021/jacs.6b05111FALSEhttps://doi.org/10.1021/jacs.6b05111Bruce, PGJ. Am. Chem. Soc.Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn3+/4+ in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O-2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li+/Li. The capacity at 4.5 V is dominated by oxidation of the O-2(-) anions accounting for similar to 0.43 e(-)/formula unit, with an additional 0.06 e(-)/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, similar to 0.08 e(-)/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn4+/Li+). The results have been obtained by combining operando electrochemical mass spec on 180 labeled Li[Li0.2Ni0.2Mn0.6]O-2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal oxygen interaction on anion redox in lithium rich cathode materials.Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O-2173201641#N/ATRUE
1546
jacs.6b0346510.1021/jacs.6b03465FALSEhttps://doi.org/10.1021/jacs.6b03465Fu, GCJ. Am. Chem. Soc.A wide array of cross-coupling methods for the formation of C-C bonds from unactivated Alkyl electrophiles have been described in recent years. In contrast, progress in the development of methods for the construction of C-heteroatom bonds has lagged; for example, there have been no reports of metal-catalyzed cross-couplings of unactivated secondary or tertiary Alkyl halides with silicon nuCleophiles to form C-Si bonds. In this study, we address this challenge, establishing that a simple, commercially available nickel catalyst (NiBr2 center dot diglyme) can achieve couplings of Alkyl bromides with nuCleophilic silicon reagents under unusually mild conditions (e.g., -20 degrees C); especially noteworthy is our ability to employ unactivated tertiary Alkyl halides as electrophilic coupling partners, which is still relatively uncommon in the field of cross-coupling chemistry. Stereochemical, relative reactivity, and radical-trap studies are consistent with a homolytic pathway for C-X bond Cleavage.Silicon-Carbon Bond Formation via Nickel-Catalyzed Cross-Coupling of Silicon NuCleophiles with Unactivated Secondary and Tertiary Alkyl Electrophiles49201640#N/ATRUE
1547
jacs.6b0338410.1021/jacs.6b03384FALSEhttps://doi.org/10.1021/jacs.6b03384Morken, JPJ. Am. Chem. Soc.Nickel-catalyzed enantioselective cross-couplings between symmetric cyClic sulfates and aromatic Grignard reagents are described. These reactions are effective with a broad range of substituted cyClic sulfates and deliver products with asymmetric tertiary carbon centers. Mechanistic experiments point to a stereoinvertive S(N)2-like oxidative addition of a nickel complex to the electrophilic substrate.Nickel-Catalyzed Asymmetric Kumada Cross-Coupling of Symmetric CyClic Sulfates25201676#N/ATRUE
1548
jacs.5b1333110.1021/jacs.5b13331https://doi.org/10.1021/jacs.5b13331Imrie, CTJ. Am. Chem. Soc.The liquid crystal nonsymmetric dimer, 1-(4-butoxyazobenzene-4'-yloxy)-6-(4-cyanobipheny1-4'-yl) hexane (CB6OABOBu), shows enantiotropic twist bend nematic, N-TB, and nematic, N, phases. The N-TB phase has been confirmed using polarized light microscopy, freeze fracture transmission electron microscopy, and X-ray diffraction. The helicoidal pitch in the N-TB phase is 18 nm. The N-TB-N (T-NTBN) and N-I (T-NI) transition temperatures are reduced upon UV light irradiation, with the reduction in T-NTBN being much larger than that in T-NI. An isothermal, reversible N-TB-N transition may be driven photochemically. These observations are attributed to a trans-cis photoisomerization of the azobenzene fragment on UV irradiation, with the cis isomers stabilizing the standard nematic phase and the trans isomers stabilizing the N-TB phase. The dramatic changes in T-NTBN provide evidence that the transition between the normal nematic and twist bend nematic with spontaneous breaking of chiral symmetry is crucially dependent on the shape of molecular dimers, which changes greatly during the trans cis isomerization.Reversible Isothermal Twist-Bend Nematic-Nematic Phase Transition Driven by the Photoisomerization of an Azobenzene-Based Nonsymmetric Liquid Crystal DinnerPhotocatalystx111201632#N/AFALSE
1549
jacs.5b1292810.1021/jacs.5b12928FALSEhttps://doi.org/10.1021/jacs.5b12928Agapie, TJ. Am. Chem. Soc.A novel p-terphenyl diphosphine ligand was synthesized with a noninnocent hydroquinone moiety as the central arene (1-H). Pseudo-tetrahedral 4-coordinate Ni-0 and Pd-0-quinone (2 and 3, respectively) complexes proved accessible by metalating 1-H with the corresponding M(OAc)(2) precursors. O-2 does not react with the Pd-0-quinone species (3) and protonation occurs at the quinone moiety indicating that the coordinated oxidized quinonoid moiety prevents reactivity at the metal. A 2-coordinate Pd hydroquinone complex (4-H) was prepared using a one-pot metalation with Pd followed by reduction. The reduced quinonoid moiety in 4-H shows metal-coupled reactivity with small molecules. 4-H was capable of reducing a variety of substrates inCluding dioxygen, nitric oxide, nitrous oxide, 1-azido adamantane, trimethylamine n-oxide, and 1,4-benzoquinone quantitatively producing 3 as the Pd-0-containing reaction product. Mechanistic investigations of dioxygen reduction revealed that the reaction proceeds through a eta(2)-peroxo intermediate (Int1) at low temperatures followed by subsequent ligand oxidation at higher temperatures in a reaction that consumed half an equivalent of O-2 and produced water as a final oxygenic byproduct. Control compounds with methyl protected phenolic moieties (4-Me), displaying a Ag-I center incapable of O-2 binding (7-H) or a cationic Pd-H motif (6-H) allowed for the independent examination of potential reaction pathways. The reaction of 4-Me with dioxygen at low temperature produces a species (8-Me) analogous to Intl demonstrating that initial dioxygen Activation is an inner sphere Pd-based process where the hydroquinone moiety only subsequently participates in the reduction of O-2, at higher temperatures, by H+/e(-) transfers.Dioxygen Reduction by a Pd(0)-Hydroquinone Diphosphine Complexx252016104#N/AFALSE
1550
jacs.6b0334210.1021/jacs.6b03342FALSEhttps://doi.org/10.1021/jacs.6b03342Avarvari, NJ. Am. Chem. Soc.The first examples of chiral single component conductors are reported. Both (S,S) and (R,R) enantiomers of 5,6-dimethy1-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm=dddt) ligand have been used to prepare anionic metal bis(dithiOlene) complexes formulated as ([(n-Bu)(4)N][M(dm-dddt)(2)] (M = Au, Ni), which are isostructural according to single crystal X-ray analysis. Single crystal transport measurements indicate semiconducting behavior for the anionic radical Ni complexes, with low room temperature conductivity values and high Activation energies. Electrocrystallization experiments provided neutral [M(dm-dddt)(2)] (M = Au, Ni) complexes. The neutral radical gold compounds Show intermolecular S center dot center dot center dot S interactions in the solid state giving rise to layers interconnected through Weak C-H center dot center dot center dot S hydrogen bonds. The most peculiar structural feature concerns a dissymmetry between the two dithiolene moieties, while the nickel counterpart is symmetric. Single crystal resistivity measurements show thermally activated behavior for the open-shell gold complexes, with room temperature conductivity values of 0.02-0:04 S.cm-' and Activation energies strongly influenced by hydrostatic pressure. A thorough thebretical study on nickel anion radical and gold neutral radiCal bis(dithiolene) complexes applied to the chiral complexes [M(dm-dddt)(2)] (M = Ail, Ni-) and to a series of previously reported compounds addressed, the issue of symmetry versus asymmetry from an electronic coupling perspective between the two dithiolene ligands. It results that neutral gold complexes with dithiolene ligands without extended delocalization are Class II mixed-valent compounds in the Robin and Day Classification, presenting an inherent tendency toward asymmetric structures,, which can be however modulated by the intermolecular organization in the solid state.Localization versus Delocalization in Chiral Single Component Conductors of Gold Bis(dithiolene) Complexes36201675#N/ATRUE
1551
jacs.5b1258210.1021/jacs.5b12582FALSEhttps://doi.org/10.1021/jacs.5b12582Betley, TAJ. Am. Chem. Soc.A sterically accessible tert-butyl-substituted dipyrrinato di-iron(II) complex [(L-tBu)FeCl](2) possessing two bridging chloride atoms was synthesized from the previously reported solvento adduct. Upon treatment with Aryl azides, the formation of high-spin Feu' species was confirmed by Fe-57 Mossbauer spectroscopy. Crystallographic characterization revealed two possible oxidation products: (1) a terminal iron iminyl from Aryl azides bearing ortho isopropyl substituents, (L-tBu)FeCl(center dot NC6H3-2,6-Pr-i(2)); or (2) a bridging di-iron imido arising from reaction with 3,S-bis(trifluoromethyl)Aryl azide, [(L-tBu)FeCl](2)(mu-NC6H3-3,5-(CF3)(2)). Similar to the previously reported (L-Ar)FeCl((NC6H4)-N-center dot-4-Bu-t), the monomeric iron imido is best described as a high-spin Fein antiferromagnetically coupled to an iminyl radical, affording an S = 2 spin state as confirmed by SQUID magnetometry. The di-iron imido possesses an S = 0 ground state, arising from two high-spin F-III centers weakly antiferromagnetically coupled through the bridging imido ligand. The terminal iron iminyl complex undergoes facile decomposition via intra- or intermolecular hydrogen atom abstraction (HAA) from an imido Aryl ortho isopropyl group, or from 1,4-cyClohexadiene, respectively. The bridging di-iron imido is a competent N-group transfer reagent to cyClic internal olefins as well as styrene. Although solid-state magnetometry indicates an antiferromagnetic interaction between the two iron centers (J = -108.7 cm(-1)) in [((tBu))FeCl](2)(mu-NC6H3-3,5-(CF3)(2)), we demonstrate that in solution the bridging imido can facilitate HAA as well as dissociate into a terminal iminyl species, which then can promote HAA. In situ monitoring reveals the di-iron bridging imido is a catalytically competent intermediate, one of several iron complexes observed in the amination of C-H bond substrates or styrene aziridination.Characterization of Iron-In-Imido Species Relevant for N-Group Transfer Chemistryx94201679#N/AFALSE
1552
jacs.6b0320210.1021/jacs.6b03202FALSEhttps://doi.org/10.1021/jacs.6b03202Bard, AJJ. Am. Chem. Soc.We report the electrochemical detection of femtomolar amounts of cobalt, iridium, nickel, and iron ions in solution by electrocatalyst formation and amplification. The metal oxides of these ions can be formed electrochemically and can catalyze the oxidation of water. Alternatively, the reduction of metal ions to metals, such as the reduction of IrCl63- to iridium, is capable of electrocatalytically reducing protons to molecular hydrogen, as shown previously with Pt. These events, which manifest themselves in amperometry, correspond to the formation of electrocatalytic nuClei on the electrode surface, capable of electrocatalytically oxidizing water or reducing protons. An analysis of the frequency of anodic blips compared to theory implies that the requirement for water oxidation is 10 +/- 1 ions of cobalt, 13 +/- 4 ions of iridium, and 11 +/- 3 ions of nickel. A similar analysis for iridium reduction and the corresponding catalytic reduction of protons implies that 6 +/- 2 ions of iridium are required for proton reduction. These numbers are confirmed in an analysis of the time of first nuCleation event, i.e. the time at which the first blip on the amperometric i-t experiment occurs. We further show that the anodic blips in detecting nickel increase in intensity upon increasing amounts of iron ions in solution to a ratio of Ni/Fe of similar to 5, surprisingly Close to that for bulk electrocatalysts of Ni-Fe.Toward the Digital Electrochemical Recognition of Cobalt, Iridium, Nickel, and Iron Ion Collisions by Catalytic Amplification23201613#N/ATRUE
1553
jacs.5b1198610.1021/jacs.5b11986https://doi.org/10.1021/jacs.8b06817Zou, JJHollow Cobalt-Based Bimetallic Sulfide Polyhedra for Efficient All-pH-Value Electrochemical and Photocatalytic Hydrogen EvolutionPhotocatalystx2016#N/AFALSE
1554
jacs.5b1162510.1021/jacs.5b11625FALSEhttps://doi.org/10.1021/jacs.5b11625Zhu, JPJ. Am. Chem. Soc.Intrarmolecular asymmetric carbopalladation of N-Aryl acrylamides followed by intermolecular trapping of the resulting sigma-C(sp(3))-Pd complex by azoles afforded 3,3-disubstituted oxindoles in good yields with excellent enantioselectivities. Two C-C bonds were created with concurrent formation of an all-carbon quaternary stereocenter. Oxadiazole substituted oxindoles were subsequently converted to pyrroloindolines by an unprecedented reductive cyClization protocol. The utility of this chemistry was illustrated by an enantioselective synthesis of (+)-esermethole.Palladium-Catalyzed Enantioselective Domino Heck/Intermolecular C-H Bond Functionalization: Development and Application to the Synthesis of (+)-Esermetholex105201571#N/AFALSE
1555
jacs.6b0272110.1021/jacs.6b02721FALSEhttps://doi.org/10.1021/jacs.6b02721Kawamoto, TJ. Am. Chem. Soc.Prussian blue is a historical pigment synthesized for the first time at the beginning of 18th century. Here we demonstrate that the historical pigment exhibits surprising adsorption properties of gaseous ammonia. Prussian blue shows 12.5 mmol/g of ammonia capacity at 0.1 MPa, whereas standard ammonia adsorbents show only 5.08-11.3 mmol/g. Dense adsorption was also observed for trace contamination in atmosphere. Results also show higher adsorption by Prussian blue analogues with the optimization of chemical composition. The respective capacities of cobalt hexacyanocobaltate (CoHCC) and copper hexacyanoferrate (CuHCF) were raised to 21.9 and 20.2 mmol/g, the highest value among the recyClable adsorbents. Also, CoHCC showed repeated adsorption in vacuum. CuHCF showed regeneration by acid washing. The chemical state of the adsorbed ammonia depends on the presence of the water in atmosphere: NH3, which was stored as in the dehydrated case, was converted into NH4+ in the hydrated case.Historical Pigment Exhibiting Ammonia Gas Capture beyond Standard Adsorbents with Adsorption Sites of Two Kinds63201650#N/ATRUE
1556
jacs.5b1131910.1021/jacs.5b11319FALSEhttps://doi.org/10.1021/jacs.5b11319Tucker, JHRJ. Am. Chem. Soc.The direct incorporation of macrocyClic cyClidene complexes into DNA via automated synthesis results in a new family of metal-functionalized DNA derivatives that readily demonstrate their utility through the ability of one redox-active copper(II)-containing strand to distinguish electrochemically between all four canonical DNA nuCleobases at a single site within a target sequence of DNA.MacrocyClic Metal Complex-DNA Conjugates for Electrochemical Sensing of Single NuCleobase Changes in DNAx29201641#N/AFALSE
1557
jacs.5b1124410.1021/jacs.5b11244https://doi.org/10.1021/jacs.5b11244Johannes, JWJ. Am. Chem. Soc.Ni-catalyzed cross-couplings of Aryl, Benzyl, and Alkyl thiols with Aryl and heteroAryl iodides were accomplished in the presence of an Ir-photoredox catalyst. Highly chemoselective C-S cross-coupling was achieved versus competitive C-O and C-N cross-couplings. This C-S cross-coupling method exhibits remarkable functional group tolerance, and the reactions can be carried out in the presence of molecular oxygen. Mechanistic investigations indicated that the reaction proceeded through transient Ni(I)-species and thiyl radicals. Distinct from nickel-catalyzed cross-coupling reactions involving carbon-centered radicals, control experiments and spectroscopic studies suggest that this C-S cross-coupling reaction does not involve a Ni(0)-species.Photoredox Mediated Nickel Catalyzed Cross-Coupling of Thiols With Aryl and HeteroAryl Iodides via Thiyl RadicalsPhotocatalyst215201651#N/AFALSE
1558
jacs.5b1123010.1021/jacs.5b11230FALSEhttps://doi.org/10.1021/jacs.5b11230Mallouk, TEJ. Am. Chem. Soc.Interfacial interactions between late transition metal/metal oxide nanopartiCles and oxide supports impact catalytic activity and stability. Here, we report the use of isothermal titration calorimetry (ITC), electron microscopy and density functional theory (DFT) to explore periodic trends in the heats of nanopartiCle-support interactions for late transition metal and metal oxide nanopartiCles on layered niobate and silicate supports. Data for Co(OH)(2), hydroxyiridate-capped IrOx center dot nH(2)O, Ni(OH)(2), CuO, and Ag2O nanopartiCles were added to previously reported data for Rh(OH)3 grown on nanosheets of TBA(0.24)H(0.76)Ca(2)Nb(3)O(10) and a layered silicate. ITC measurements showed stronger bonding energies in the order Ag < Cu approximate to Ni approximate to Co < Rh < Ir on the niobate support, as expected from trends in M-O bond energies. NanopartiCles with exothermic heats of interaction were stabilized against sintering. In contrast, ITC measurements showed endothermic interactions of Cu, Ni, and Rh oxide/hydroxide nanopartiCles with the silicate and poor resistance to sintering. These trends in interfacial energies were corrB(OH)2rated by DFT calculations using single-atom and four-atom Cluster models of metal/metal oxide nanopartiCles. Density of states and charge density difference calculations reveal that strongly bonded metals (Rh, Ir) transfer d-electron density from the adsorbed Cluster to niobium atoms in the support; this mixing is absent in weakly binding metals, such as Ag and Au, and in all metals on the layered silicate support. The large differences between the behavior of nanopartiCles on niobate and silicate supports highlight the importance of d-orbital interactions between the nanopartiCle and support in controlling the nanopartiCles' stability.Charge Transfer Stabilization of Late Transition Metal Oxide NanopartiCles on a Layered Niobate Supportx43201547#N/AFALSE
1559
jacs.6b0212010.1021/jacs.6b02120FALSEhttps://doi.org/10.1021/jacs.6b02120Stoltz, BMJ. Am. Chem. Soc.A new strategy for catalytic enantioselective C-acylation to generate alpha-quaternary-substituted lactams is reported. Ni-catalyzed three-component coupling of lactam enolates, benzonitriles, and Aryl halides produces beta-imino lactams that then afford beta-keto lactams by acid hydrolysis. Use of a readily available Mandyphos-type ligand and addition of LiBr enable the construction of quaternary stereocenters on alpha-substituted lactams to form beta-keto lactams in up to 94% ee.Ni-Catalyzed Enantioselective C-Acylation of alpha-Substituted Lactams18201648#N/ATRUE
1560
jacs.5b1097710.1021/jacs.5b10977FALSEhttps://doi.org/10.1021/jacs.5b10977Bard, AJJ. Am. Chem. Soc.Nickel-iron mixed metal oxyhydroxides have attracted significant attention as an oxygen evolution reaction (OER) catalyst for solar fuel renewable energy applications. Here, we performed surface-selective and time-dependent redox titrations to directly measure the surface OER kinetics of Ni-IV and Fe-IV in NiOOH, FeOOH, and Ni1-xFexOOH (0 < x < 0.27) electrodes. Most importantly, two types of surface sites exhibiting fast and slow kinetics were found, where the fraction of fast sites in Ni1-xFexOOH matched the iron atom content in the film. This finding provides experimental support to the theory-proposed model of active sites in Ni1-xFexOOH. The OER rate constant of the fast site was 1.70 s(-1) per atom.Surface Interrogation Scanning Electrochemical Microscopy of Ni1-xFexOOH (0 < x < 0.27) Oxygen Evolving Catalyst: Kinetics of the fast Iron Sitesx168201629#N/AFALSE
1561
jacs.5b1096310.1021/jacs.5b10963https://doi.org/10.1021/jacs.5b10963Molander, GAJ. Am. Chem. Soc.Single-electron transmetalation is recognized as an enabling technology for the mild transfer of Alkyl groups to transition metal catalysts in cross-coupling reactions. Hypercoordinate silicates represent a new and improved Class of radical precursors because of their low oxidation potentials and the innocuous byproducts generated upon oxidation. Herein, we report the cross-coupling of secondary and primary ammonium Alkylsilicates with (hetero)Aryl bromides in good to excellent yields. The base-free conditions have exceptional protic group tolerance on both partners, permitting the cross-coupling of unprotected primary and secondary amines.Base-Free Photoredox/Nickel Dual-Catalytic Cross-Coupling of Ammonium AlkylsilicatesPhotocatalyst165201647#N/AFALSE
1562
jacs.5b1085310.1021/jacs.5b10853FALSEhttps://doi.org/10.1021/jacs.5b10853Helm, MLJ. Am. Chem. Soc.The hydrogen production electrocatalyst Ni(P(Ph)2N(2)(Ph))(2)(2+) (1) is capable of traversing multiple electrocatalytic pathways. When using dimethylformamidium, DMF(H)(+), the mechanism of H-2 formation by 1 changes from an ECEC to an EECC mechanism as the potential approaches the Ni(I/0) couple. Two electrochemical methods, current-potential analysis and foot-of-the-wave analysis (FOWA), were performed on 1 to measure detailed kinetics of the competing ECEC and EECC pathways. A sensitivity analysis was performed on the methods using digital simulations to understand their strengths and limitations. Chemical rate constants were significantly underestimated when not accounting for electron-transfer kinetics, even when electron transfer was fast enough to afford a reversible noncatalytic wave. The EECC pathway of 1 was faster than the ECEC pathway under all conditions studied. Buffered DMF:DMF(H)(+) mixtures afforded an increase in the catalytic rate constant (k(obs)) of the EECC pathway, but k(obs) for the ECEC pathway did not change when using buffered acid. Further kinetic analysis of the ECEC path revealed that base increases the rate of isomerization from exo-protonated Ni(0) isomers to the catalytically active endo-isomers, but decreases the rate of protonation of Ni(I). FOWA did not provide accurate rate constants, but FOWA was used to estimate the reduction potential of the previously undetected exo-protonated Ni(I) intermediate. Comparison of catalytic Tafel plots for 1 under different conditions reveals substantial inaccuracies in the turnover frequency at zero overpotential when the kinetic and thermodynamic effects of the conjugate base are not accounted for properly.Kinetic Analysis of Competitive Electrocatalytic Pathways: New Insights into Hydrogen Production with Nickel Electrocatalysts
Electrocatalytic
34201669#N/AFALSE
1563
jacs.6b0165610.1021/jacs.6b01656FALSEhttps://doi.org/10.1021/jacs.6b01656Ishida, NPotential of Metal-Catalyzed C-C Single Bond Cleavage for Organic Synthesis2016#N/ATRUE
1564
jacs.5b1069910.1021/jacs.5b10699FALSEhttps://doi.org/10.1021/jacs.5b10699Stahl, SSJ. Am. Chem. Soc.Nickel-iron oxides/hydroxides are among the most active electrocatalysts for the oxygen evolution reaction. In an effort to gain insight into the role of Fe in these catalysts, we have performed operando Mossbauer spectroscopic studies of a 3:1 Ni:Fe layered hydroxide and a hydrous Fe oxide electrocatalyst. The catalysts were prepared by a hydrothermal precipitation method that enabled catalyst growth directly on carbon paper electrodes. Fe4+ species were detected in the NiFe hydroxide catalyst during steady-state water oxidation, accounting for up to 21% of the total Fe. In contrast, no Fe's was detected in the Fe oxide catalyst. The observed Fe4+ species are not kinetically competent to serve as the active site in water oxidation; however, their presence has important implications for the role of Fe in NiFe oxide electrocatalysts.Operando Analysis of NiFe and Fe Oxyhydroxide Electrocatalysts for Water Oxidation: Detection of Fe4+ by Mossbauer Spectroscopyx396201547#N/AFALSE
1565
jacs.5b1069810.1021/jacs.5b10698FALSEArnold, PLMetal-Metal Bonding in Uranium-Group 10 Complexesx2016#N/AFALSE
1566
jacs.5b1035110.1021/jacs.5b10351https://doi.org/10.1021/jacs.5b10351Do, LHJ. Am. Chem. Soc.To gain a better understanding of the influence of cationic additives on coordination-insertion polymerization and to leverage this knowledge in the construction of enhanced olefin polymerization catalysts, we have synthesized a new family of nickel phenoxyimine-polyethylene glycol complexes (NiL0, NiL2-NiL4) that form discrete molecular species with alkali metal ions (M+ = Li+, Na+, K+). Metal binding titration studies and structural characterization by X-ray crystallography provide evidence for the self-assembly of both 1:1 and 2:1 NiL:M+ species in solution, except for NiL4/Na+ which form only the 1:1 complex. It was found that upon treatment with a phosphine scavenger, these NiL complexes are active catalysts for ethylene polymerization. We demonstrate that the addition of M+ to NiL can result in up to a 20-fold increase in catalytic efficiency as well as enhancement in polymer molecular weight and branching frequency compared to the use of NiL without coadditives. To the best of our knowledge, this work provides the first systematic study of the effect of secondary metal ions on metal-catalyzed polymerization processes and offers a new general design strategy for developing the next generation of high performance olefin polymerization catalysts.Fine-Tuning Nickel Phenoxyimine Olefin Polymerization Catalysts: Performance Boosting by Alkali Cationsx53201560#N/AFALSE
1567
jacs.6b0054110.1021/jacs.6b00541FALSEhttps://doi.org/10.1021/jacs.6b00541Overman, LEJ. Am. Chem. Soc.The first total synthesis of a chromodorolide diterpenoid is described. The synthesis features a bimolecular radical addition/cyClization/fragmentation cascade that unites butenolide and trans-hydrindane fragments while fashioning two C-C bonds and stereo selectively forming three of the ten contiguous stereo centers of chromodorolide B.Total Synthesis of (-)-Chromodorolide B29201636#N/ATRUE
1568
jacs.5b1021510.1021/jacs.5b10215https://doi.org/10.1021/jacs.5b10215Patzke, GRJ. Am. Chem. Soc.The development of economic water oxidation catalysts is a key step toward large-scale water splitting. However, their current exploration remains empirical to a large extent. Elucidating the correlations between electronic properties and catalytic activity is crucial for deriving general and straightforward catalyst design principles. Herein, strongly correlated electronic systems with abundant and easily tunable electronic properties, namely La1-xSrxBO3 perovskites and La2-xSrxBO4 layered perovskites (B = Fe, Co, Ni, or Mn), were employed as model systems to identify favorable electronic structures for water oxidation. We established a direct correlation between the enhancement of catalytic activity and the insulator to metal transition through tuning the electronic properties of the target perovskite families via the La3+/Sr2+ ratio. Their improved photochemical water oxidation performance was Clearly linked to the increasingly metallic character. These electronic structure-activity relations provide a promising guideline for constructing efficient water oxidation catalysts.Promoting Photochemical Water Oxidation with Metallic Band StructuresPhotocatalyst21201662#N/AFALSE
1569
jacs.5b1006610.1021/jacs.5b10066FALSEhttps://doi.org/10.1021/jacs.5b10066Zargarian, DJ. Am. Chem. Soc.This contribution presents evidence for new pathways manifested in the reactions of the phenylhydrosilanes PhnSiH4-n with the pincer complexes (POCsp2OP)Ni(OSiMe3), 1-OSiMe3, and (POCsp3OP)Ni(OSiMe3), 2-OSiMe3 (POCsp3OP = 2,6-(i-Pr2PO)(2)C6H3; POCsp3OP = (i-Pr2POCH2)(2)CH). Excess PhSiH3 or Ph2SiH2 reacted with 1-OSiMe3 to eliminate the disilyl ethers PhnH3-nSiOSiMe3 (n = 1 or 2) and generate the nickel hydride species 1-H. Subsequent reaction of the latter with more substrate formed corresponding nickel silyl species 1-SiPhH2 or 1-SiPh2H and generated multiple Si-containing products, inCluding disilanes and redistribution products. The reaction of 1-OSiMe3 with excess Ph2SiH2/Ph2SiD2 revealed a net KIE of ca. 1.3-1.4 at room temperature. Treating 1-OSiMe3 with excess Ph3SiH also gave 1-H and the corresponding disilyl ether Ph3SiOSiMe3, but this reaction also generated the new siloxide 1-OSiPh3 apparently via an unconventional sigma-bond metathesis pathway in which the Ni center is not involved directly. The reaction of excess PhSiH3 and 2-OSiMe3 gave polysilanes of varying solubilities and molecular weights; NMR investigations showed that these polymers arise from Ni(0) species generated in situ from the reductive elimination of the highly reactive hydride intermediate, 2-H. The stoichiometric reactions of 2-OSiMe3 with Ph2SiH2 and Ph3SiH gave, respectively, siloxides 2-OSiPh2(OSiMe3) and 2-OSiPh3. Together, these results demonstrate the strong influence of pincer backbone and hydrosilane sterics on the different reactivities of 1-OSiMe3 and 2-OSiMe3 toward PhnSiH4-n (dimerization, polymerization, and redistribution vs formation of new siloxides). The mechanisms of the reactions that lead to the observed Si-O, Si-C, and Si-Si bond formations are discussed in terms of Classical and unconventional sigma-bond metathesis pathways.Reactions of Phenylhydrosilanes with Pincer-Nickel Complexes: Evidence for New Si-O and Si-C Bond Formation Pathwaysx332015155#N/AFALSE
1570
jacs.5b1002710.1021/jacs.5b10027https://doi.org/10.1021/jacs.5b10027Stupp, SIJ. Am. Chem. Soc.Light harvesting supramolecular assemblies are potentially useful structures as components of solar-to-fuel conversion materials. The development of these functional constructs requires an understanding of optimal packing modes for chromophores. We investigated here assembly in water and the photocatalytic function of perylene monoimide chromophore amphiphiles with different Alkyl linker lengths separating their hydrophobic core and the hydrophilic Carbonylate headgroup. We found that these chromophore amphiphiles (CAs) self-assemble into charged nanostructures of increasing aspect ratio as the linker length is increased. The addition of salt to screen the charged nanostructures induced the formation of hydrogels and led to internal crystallization within some of the nanostructures. For linker lengths up to seven methylenes, the CAs were found to pack into 2D crystalline unit cells within ribbon-shaped nanostructures, whereas the nine methylene CAs assembled into long nanofibers without crystalline molecular packing. At the same time, the different molecular packing arrangements after charge screening led to different absorbance spectra, despite the identical electronic properties of all PMI amphiphiles. While the crystalline CAs formed electronically coupled H-aggregates, only CAs with intermediate linker lengths showed evidence of high intermolecular orbital overlap. Photocatalytic hydrogen production using a nickel-based catalyst was observed in all hydrogels, with the highest turnovers observed for CA gels having intermediate linker lengths. We conClude that the improved photocatalytic performance of the hydrogels formed by supramolecular assemblies of the intermediate linker CA molecules likely arises from improved exciton splitting efficiencies due to their higher orbital overlap.Supramolecular Packing Controls H-2 Photocatalysis in Chromophore Amphiphile HydrogelsPhotocatalyst74201537#N/AFALSE
1571
jacs.5b0979010.1021/jacs.5b09790FALSEhttps://doi.org/10.1021/jacs.5b09790Yang, HQJ. Am. Chem. Soc.Despite their wide utility in laboratory synthesis and industrial fabrication, gas water solid multiphase catalysis reactions often suffer from low reaction efficiency because of the low solubility of gases in water. Using a surface-modification protocol, interface-active silica nanopartiCles were synthesized. Such nanopartiCles can assemble at the gas water interface, stabilizing micrometer-sized gas bubbles in water, and disassemble by tuning of the aqueous phase pH. The ability to stabilize gas microbubbles can be finely tuned through variation of the surface-modification protocol. As NI proof of this concept, Pd and Au were deposited on these silica nanopartides, leading to interface-active catalysts for aqueous hydrogenation and oxidation, respectively. With such catalysts, conventional gas water solid multiphase reactions can be transformed to H-2 or O-2 microbubble reaction systems. The resultant microbubble reaction systems exhibit significant catalysis efficiency enhancement effects compared with conventional multiphase reactions. The significant improvement is attributed to the pronounced increase in reaction interface area that allows for the direct contact of gas, water, and solid phases. At the end of reaction, the microbubbles can be removed from the reaction systems through changing the pH, allowing product separation and catalyst recyCling. Interestingly, the alcohol oxidation Activation energy for the microbubble systems is much lower than that for the conventional multiphase reaction, also indicating that the developed microbubble system may be a valuable platform to design innovative multiphase catalysis reactions.pH-Responsive Gas-Water-Solid Interface for Multiphase Catalysisx63201562#N/AFALSE
1572
jacs.5b0963910.1021/jacs.5b09639FALSEhttps://doi.org/10.1021/jacs.5b09639Yang, PDJ. Am. Chem. Soc.Understanding the atomic structure of a catalyst is crucial to exposing the source of its performance characteristics. It is highly unlikely that a catalyst remains the same under reaction conditions when compared to as-synthesized. Hence, the ideal experiment to study the catalyst structure should be performed in situ. Here, we use X-ray absorption spectroscopy (XAS) as an in situ technique to study Pt3Ni nanoframe partiCles which have been proven to be an excellent electro catalyst for the oxygen reduction reaction (ORR). The surface characteristics of the nanoframes were probed through electrochemical hydrogen underpotential deposition and carbon monoxide electrooxidation, which showed that nanoframe surfaces with different structure exhibit varying levels of binding strength to adsorbate molecules. It is well-known that Pt-skin formation on Pt-Ni catalysts will enhance ORR activity by weakening the binding energy between the surface and adsorbates. Ex situ and in situ XAS results reveal that nanoframes which bind adsorbates more strongly have a rougher Pt surface caused by insufficient segregation of Pt to the surface and consequent Ni dissolution. In contrast, nanoframes which exhibit extremely high ORR activity simultaneously demonstrate more significant segregation of Pt over Ni-rich subsurface layers, allowing better formation of the critical Pt-skin. This work demonstrates that the high ORR activity of the Pt3Ni hollow nanoframes depends on successful formation of the Pt-skin surface structure.Atomic Structure of Pt3Ni Nanoframe Electrocatalysts by in Situ X-ray Absorption Spectroscopyx145201551#N/AFALSE
1573
jacs.6b0033210.1021/jacs.6b00332FALSEhttps://doi.org/10.1021/jacs.6b00332Strasser, PJ. Am. Chem. Soc.Mixed Ni-Fe oxides are attractive anode catalysts for efficient water splitting in solar fuels reactors. Because of conflicting past reports, the catalytically active metal redox state of the catalyst has remained under debate. Here, we report an in operando quantitative deconvolution of the charge injected into the nanostructured Ni-Fe oxyhydroxide OER catalysts or into reaction product molecules. To achieve this, we explore the oxygen evolution reaction dynamics and the individual faradaic charge efficiencies using operando differential electrochemical mass spectrometry (DEMS). We further use X-ray absorption spectroscopy (XAS) under OER conditions at the Ni and Fe K-edges of the electrocatalysts to evaluate oxidation states and local atomic structure motifs. DEMS and XAS data consistently reveal that up to 75% of the Ni centers increase their oxidation state from +2 to +3, while up to 25% arrive in the +4 state for the NiOOH catalyst under OER catalysis. The Fe centers consistently remain in the +3 state, regardless of potential and composition. For mixed Ni100-xFex catalysts, where x exceeds 9 atomic %, the faradaic efficiency of O-2 sharply increases from similar to 30% to 90%, suggesting that Ni atoms largely remain in the oxidation state +2 under catalytic conditions. To reconcile the apparent low level of oxidized Ni in mixed Ni-Fe catalysts, we hypothesize that a kinetic competition between the (i) metal oxidation process and the (ii) metal reduction step during O-2 release may account for an insignificant accumulation of detectable high-valent metal states if the reaction rate of process (ii) outweighs that of (i). We conClude that a discussion of the superior catalytic OER activity of Ni-FeOOH electrocatalysts in terms of surface catalysis and redox-inactive metal sites likely represents an oversimplification that fails to capture essential aspects of the synergisms at highly active Ni-Fe sites.Oxygen Evolution Reaction Dynamics, Faradaic Charge Efficiency, and the Active Metal Redox States of Ni-Fe Oxide Water Splitting Electrocatalysts541201691#N/ATRUE
1574
jacs.5b0862110.1021/jacs.5b08621FALSEhttps://doi.org/10.1021/jacs.5b08621Zeng, XMJ. Am. Chem. Soc.Acting as an environmentally benign synthetic tool, the cross-coupling reactions with Aryl ethers via CO bond Activation have attracted broad interest. However, the functionalizations of CO bonds are mainly limited to nickel catalysis, and selectivity has long been a prominent challenge when several CO bonds are present in the one molecule. We report here the first chromium-catalyzed selective cross-coupling reactions of Aryl ethers with Grignard reagents by the Cleavage of CO(Alkyl) bonds. Diverse transformations were achieved using simple, inexpensive chromium(II) precatalyst combining imino auxiliary at room temperature. It offers a new avenue for buildup functionalized aromatic aldehydes with high efficiency and selectivity.Regio- and Chemoselective Kumada Tamao Corriu Reaction of Aryl Alkyl Ethers Catalyzed by Chromium Under Mild Conditionsx76201571#N/AFALSE
1575
jacs.5b0861210.1021/jacs.5b08612https://doi.org/10.1021/jacs.5b08612Mecking, SJ. Am. Chem. Soc.To date, an inconClusive and partially contradictive picture exists on the behavior of neutral Ni(II) insertion polymerization catalysts toward methyl methacrylate (MMA). We shed light on this issue by a combination of comprehensive mechanistic NMR and EPR studies, isolation of a key Ni(I) intermediate, and pressure reactor studies with ethylene and MMA, followed by detailed polymer analysis. An interlocking mechanistic picture of an insertion and a free radical polymerization is revealed. Both polymerizations run simultaneously (25 bar ethylene, neat MMA, 70 C); however, the chain growth cyCles are independent of each other, and therefore exClusively a physical mixture of homo-PE and homo-PMMA is obtained. A NiC bond Cleavage was exCluded as a free radical source. Rather a homolytic PC bond Cleavage in the labile Aryl phosphine ligand and the reaction of low-valent Ni(0/I) species with specific iodo substituted NO (ArI) ligands were shown to initiate radical MMA polymerizations. Several reductive elimination decomposition pathways of catalyst precursor or active intermediates were shown to form low-valent Ni species. One of those pathways is a bimolecular reductive coupling via intermediate (NO)Ni(I) formation. These intermediate Ni(I) species can be prevented from ultimate decomposition by capturing with organic radical sources, forming insertion polymerization active [(NO)Ni(II)R] species and prolonging the ethylene polymerization activity.Role of Radical Species in Salicylaldiminato Ni(II) Mediated Polymer Chain Growth: A Case Study for the Migratory Insertion Polymerization of Ethylene in the Presence of Methyl Methacrylatex33201560#N/AFALSE
1576
jacs.6b0005310.1021/jacs.6b00053FALSEhttps://doi.org/10.1021/jacs.6b00053Vicic, DAJ. Am. Chem. Soc.A stable and isolable difluoromethyl zinc reagent has been prepared through the reaction of ICF2H with diethyl zinc and DMPU. This new zinc reagent is a free-flowing solid and can be used in combination with a nickel catalyst to difluoromethylate Aryl iodides, bromides, and triflates at room temperature. Such mild conditions for the catalytic difluoromethylation of these substrates are unprecedented.Direct Difluoromethylation of Aryl Halides via Base Metal Catalysis at Room Temperature109201626#N/ATRUE
1577
jacs.6b0003610.1021/jacs.6b00036FALSEhttps://doi.org/10.1021/jacs.6b00036Shul, YGJ. Am. Chem. Soc.Establishment of a sustainable energy society has been strong driving force to develop cost-effective and highly active catalysts for energy conversion and storage devices such as metal-air batteries and electrochemical water splitting systems. This is because the oxygen evolution reaction (OER), a vital reaction for the operation, is substantially sluggish even with precious metals-based catalysts. Here, we show for the first time that a hexagonal perovskite, BaNiO3, can be a highly functional catalyst for OER in alkaline media. We demonstrate that the BaNiO3 performs OER activity at least an order of magnitude higher than an IrO2 catalyst. Using integrated density functional theory calculations and experimental validations, we unveil that the underlying mechanism originates from structural transformation from BaNiO3 to BaNi0.83O2.5 (Ba6Ni5O15) over the OER cyCling process.A New Family of Perovskite Catalysts for Oxygen-Evolution Reaction in Alkaline Media: BaNiO3 and BaNi0.83O2.5146201642#N/ATRUE
1578
jacs.5b0829710.1021/jacs.5b08297FALSEhttps://doi.org/10.1021/jacs.5b08297Dempsey, JLJ. Am. Chem. Soc.A detailed mechanistic analysis is presented for the hydrogen evolution catalyst [Ni((P2N2Ph)-N-Ph)(2)(CH2CN)][BF4](2) in acetonitrile ((P2N2Ph)-N-Ph = 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyClooctane). This complex has a Ni-II/I redox couple at -0.83 V and a Ni-I/0 redox couple at -1.03 V versus Fe+/0. These two Closely spaced redox events both promote proton reduction catalysis, each via a distinct mechanism: an electrochemical ECEC pathway and an EECC route. The EECC mechanism, operative at more negative potentials, was isolated through use of a weak acid (anilinium, pK(a) = 10.6 in CH3CN) to avert protonation of the singly reduced species. Electroanalytical methods and time-resolved spectroscopy were used to analyze the kinetics of the elementary steps of hydrogen evolution catalysis. The rate constant for the formation of a nickel(II)-hydride intermediate was determined via measurements of peak shift (k(1) = 1.2 X 10(6) s(-1)) and through foot-of-the-wave analysis (k(1) = 6.5 x 10(6) M-1 s(-1)). Reactivity of the isolated hydride with acid to release hydrogen and regenerate the nickel(II) complex was monitored by stopped-flow spectroscopy. Kinetics obtained from stopped-flow measurements are corrB(OH)2rated by current plateau analysis of the catalytic cyClic voltammograms. These kinetic data suggest the presence of an off-cyCle intermediate in the reaction.Potential-Dependent Electrocatalytic Pathways: Controlling Reactivity with pK(a) for Mechanistic Investigation of a Nickel-Based Hydrogen Evolution Catalyst
Electrocatalytic
49201543#N/AFALSE
1579
jacs.5b0818610.1021/jacs.5b08186FALSEhttps://doi.org/10.1021/jacs.5b08186Zou, XXJ. Am. Chem. Soc.Elaborate design of highly active and stable catalysts from Earth-abundant elements has great potential to produce materials that can replace the noble-metal-based catalysts commonly used in a range of useful (electro)chemical processes. Here we report, for the first time, a synthetic method that leads to in situ growth of {210} high-index faceted Ni3S2 nanosheet arrays on nickel foam (NF). We show that the resulting material, denoted Ni3S2/NF, can serve as a highly active, binder-free, bifunctional electro catalyst for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Ni3S2/NF is found to give similar to 100% Faradaic yield toward both HER and OER and to show remarkable catalytic stability (for >200 h). Experimental results and theoretical calculations indicate that Ni3S2/NF's excellent catalytic activity is mainly due to the synergistic catalytic effects produced in it by its nanosheet arrays and exposed {210} high-index facets.High-Index Faceted Ni3S2 Nanosheet Arrays as Highly Active and Ultrastable Electrocatalysts for Water Splittingx1133201520#N/AFALSE
1580
jacs.5b0813910.1021/jacs.5b08139FALSEhttps://doi.org/10.1021/jacs.5b08139Symes, MDJ. Am. Chem. Soc.Electrolytic water oxidation using earth-abundant elements is a key challenge in the quest to develop cheap, large surface area arrays for solar-to-hydrogen conversion. There have been numerous studies in this area in recent years, but there remains an imperative to demonstrate that the current densities reported are indeed due to the species under consideration and not due to the presence of adventitious (yet possibly highly active) contaminants at low levels. Herein, we show that adventitious nickel at concentrations as low as 17 nM can act as a water oxidation catalyst in mildly basic aqueous solutions, achieving stable (tens of hours) current densities of 1 mA cm(-2) at overpotentials as low as 540 mV at pH 9.2 and 400 mV at pH 13. This nickel was not added to the electrolysis baths deliberately, but it was found to be present in the electrolytes as an impurity by ICP-MS. The presence of nickel on anodes from extended-time bulk electrolysis experiments was confirmed by XPS. In showing that such low levels of nickel can perform water oxidation at overpotentials comparable to many recently reported water oxidation catalysts, this work serves to raise the burden of proof required of new materials in this field: contamination by adventitious metal ions at trace loadings must be exCluded as a possible cause of any observed water oxidation activity.Efficient Electrocatalytic Water Oxidation at Neutral and High pH by Adventitious Nickel at Nanomolar Concentrationsx68201586#N/AFALSE
1581
jacs.6b0002410.1021/jacs.6b00024FALSEhttps://doi.org/10.1021/jacs.6b00024Zhou, QLJ. Am. Chem. Soc.The first nickel-catalyzed intermolecular hydroacylation reaction of alkenes with simple aldehydes has been developed. This reaction offers a new approach to the selective preparation of branched ketones in high yields (up to 99%) and branched selectivities (up to 99:1). Experimental data provide evidence for reversible formation of Aryl-nickel-Alkyl intermediate, and DFT calculations show that the aldehyde C-H bond transfer to a coordinated alkene without oxidative addition is involved. The origin of the reactivity and regioselectivity of this reaction was also investigated computationally, which are consistent with experimental observations.Nickel-Catalyzed Hydroacylation of Styrenes with Simple Aldehydes: Reaction Development and Mechanistic Insights81201658#N/ATRUE
1582
jacs.5b0792410.1021/jacs.5b07924FALSEhttps://doi.org/10.1021/jacs.5b07924Wang, YJ. Am. Chem. Soc.Despite being promising substitutes for noble metal catalysts used in hydrogen evolution reaction (HER), the nonprecious metal catalysts (NPMCs) based on inexpensive and earth-abundant 3d transition metals (TMs) are still practically unfeasible due mainly to unsatisfactory activity and durability. Herein, a highly active and stable catalyst for HER has been developed on the basis of molybdenum-carbide-modified N-doped carbon vesiCle encapsulating Ni nanopartiCles (MoxC-Ni@NCV). This MoxC-Ni@NCV material was synthesized simply by the solid-state thermolysis of melamine-related composites of oxalate and molybdate with uniform Ni ions doping (Ni@MOM-com). Notably, the prepared MoxC-Ni@NCV was almost the most efficient NPMCs for HER in acidic electrolyte to date. Besides good long-term stability, MoxC-Ni@NCV exhibited a quiet low overpotential that was comparable to Pt/C. Thus, this work opens a new avenue toward the development of highly efficient, inexpensive HER catalysts.Molybdenum-Carbide-Modified Nitrogen-Doped Carbon VesiCle Encapsulating Nickel NanopartiCles: A Highly Efficient, Low-Cost Catalyst for Hydrogen Evolution Reactionx311201554#N/AFALSE
1583
jacs.660408810.1021/jacs.6604088FALSEhttps://doi.org/10.1021/jacs.6604088Martin, RJ. Am. Chem. Soc.A catalytic Carbonylation of unactivated primary, secondary, and tertiary Alkyl chlorides with CO, at atmospheric pressure is described. This protocol represents the first intermolecular cross-electrophile coupling of unactivated Alkyl chlorides, thus leading to new knowledge in the cross-coupling arena.Ni-Catalyzed Carbonylation of Unactivated Alkyl Chlorides with CO2106201655#N/ATRUE
1584
jacs.5b1282710.1021/jacs.5b12827FALSEhttps://doi.org/10.1021/jacs.5b12827Fout, ARJ. Am. Chem. Soc.This communication describes the two electron oxidation of ((CCC)-C-DIPP)NiX ((CCC)-C-DIPP = bis-(diisopropylphenyl-benzimidazol-2-ylidene)phenyl); X = Cl or Br) with halogen and halogen surrogates to form ((CCC)-C-DIPP)NiX3. These complexes represent a rare oxidation state of nickel, as well as an unprecedented reaction pathway to access these species through Br-2 and halogen surrogate (Benzyltrimethylammonium tribromide). The Ni-IV complexes have been characterized by a suite of spectroscopic techniques and can readily reduce to the Ni-II counterpart, allowing for cyCling between the Ni-II/Ni-IV oxidation states.Accessing Pincer Bis(carbene) Ni(IV) Complexes from Ni(II) via Halogen and Halogen Surrogates46201626#N/ATRUE
1585
jacs.5b1251510.1021/jacs.5b12515FALSEhttps://doi.org/10.1021/jacs.5b12515Farha, OKJ. Am. Chem. Soc.Developing supported single-site catalysts is an important goal in heterogeneous catalysis since the well-defined active sites afford opportunities for detailed mechanistic studies, thereby facilitating the design of improved catalysts. We present herein a method for installing Ni ions uniformly and precisely on the node of a Zr-based metal-organic framework (MOF), NU-1000, in high density and large quantity (denoted as Ni-AIM) using atomic layer deposition (ALD) in a MOF (AIM). Ni-AIM is demonstrated to be an efficient gas-phase hydrogenation catalyst upon Activation. The structure of the active sites in Ni-AIM is proposed, revealing its single-site nature. More importantly, due to the organic linker used to construct the MOF support, the Ni ions stay isolated throughout the hydrogenation catalysis, in accord with its long-term stability. A quantum chemical characterization of the catalyst and the catalytic process complements the experimental results. With validation of computational modeling protocols, we further targeted ethylene oligomerization catalysis by Ni-AIM guided by theoretical prediction. Given the generality of the AIM methodology, this emerging Class of materials should prove ripe for the discovery of new catalysts for the transformation of volatile substrates.Sintering-Resistant Single-Site Nickel Catalyst Supported by Metal Organic Framework211201633#N/ATRUE
1586
jacs.5b0777910.1021/jacs.5b07779FALSEhttps://doi.org/10.1021/jacs.5b07779van Santen, RAJ. Am. Chem. Soc.Quantum chemical calculations and simulated kinetics were used to examine the structure sensitivity of the oxygen evolution reaction on several surface terminations of Co3O4. Active sites consisting of two adjacent Co(IV) cations connected by bridging oxos were identified on both the (001) and (311) surfaces. Formation of the OO bond proceeds on these sites by nuCleophilic attack of water on a bridging oxo. It was found that the relative turnover frequencies for the different sites are highly dependent on the overpotential, with the dual-Co site on the (311) surface being most active at medium overpotentials (0.46-0.77 V), where OO bond formation by water addition is rate limiting. A similar dual-Co site on the (001) surface is most active at low overpotentials (<0.46 V), where O-2 release is rate limiting, and a single-Co site on the (110) surface is most active at overpotentials that are high enough (>0.77 V) to form a significant concentration of highly reactive terminal Co(V)=O species. Two overpotential-dependent Sabatier relationships were identified based on the Bronsted basicity and redox potential of the active site, explaining the change in the active site with overpotential. The (311) dual-Co site that is most active in the medium overpotential range is consistent with recent experimental observations suggesting that a defect site is responsible for the observed oxygen evolution activity and that a modest concentration of superoxo intermediates is present on the surface. Importantly, we find that it is essential to consider the kinetics of the water addition and O-2 release steps rather than only the thermodynamics.Structure Sensitivity of the Oxygen Evolution Reaction Catalyzed by Cobalt(II,III) Oxidex90201553#N/AFALSE
1587
jacs.5b0777010.1021/jacs.5b07770https://doi.org/10.1021/jacs.5b07770Nicewicz, DAJ. Am. Chem. Soc.A direct, catalytic hydrodeCarbonylation of primary, secondary, and tertiary Carbonylic acids is reported. The catalytic system consists of a Fukuzumi acridinium photooxidant with phenyldisulfide acting as a redox-active cocatalyst. Substoichiometric quantities of Hunig's base are used to reveal the Carbonylate. Use of trifluoroethanol as a solvent allowed for significant improvements in substrate compatibilities, as the method reported is not limited to Carbonylic acids bearing alpha heteroatoms or phenyl substitution. This method has been applied to the direct double deCarbonylation of malonic acid derivatives, which allows for the convenient use of dimethyl malonate as a methylene synthon. Kinetic analysis of the reaction is presented showing a lack of a kinetic isotope effect when generating deuterothiophenol in situ as a hydrogen atom donor. Further kinetic analysis demonstrated first-order kinetics with respect to the Carbonylate, while the reaction is zero-order in acridinium catalyst, consistent with another finding suggesting the reaction is light limiting and Carbonylate oxidation is likely turnover limiting. Stern-Volmer analysis was carried out in order to determine the efficiency for the Carbonylates to quench the acridinium excited state.HydrodeCarbonylation of Carbonylic and Malonic Acid Derivatives via Organic Photoredox Catalysis: Substrate Scope and Mechanistic InsightPhotocatalyst170201574#N/AFALSE
1588
jacs.5b0772810.1021/jacs.5b07728FALSEhttps://doi.org/10.1021/jacs.5b07728Yang, SHJ. Am. Chem. Soc.We report on the synthesis of iron-nickel sulfide (INS) ultrathin nanosheets by topotactic conversion from a hydroxide precursor. The INS nanosheets exhibit excellent activity and stability in strong acidic solutions as a hydrogen evolution reaction (HER) catalyst, lending an attractive alternative to the Pt catalyst. The metallic alpha-INS nanosheets show an even lower overpotential of 105 mV at 10 mA/cm(2) and a smaller Tafel slope of 40 mV/dec. With the help of DFT calculations, the high specific surface area, facile ion transport and charge transfer, abundant electrochemical active sites, suitable H+ adsorption, and H-2 formation kinetics and energetics are proposed to contribute to the high activity of the INS ultrathin nanosheets toward HER.Metallic Iron-Nickel Sulfide Ultrathin Nanosheets As a Highly Active Electrocatalyst for Hydrogen Evolution Reaction in Acidic Mediax475201541#N/AFALSE
1589
jacs.5b0750910.1021/jacs.5b07509FALSEhttps://doi.org/10.1021/jacs.5b07509Perutz, RNJ. Am. Chem. Soc.The association constants and enthalpies for the binding of hydrogen bond donors to group 10 transition metal complexes featuring a single fluoride ligand (trans-[Ni(F)(2-C5NF4)(PR3)(2)], R = Et la, Cy lb, trans-[Pd(F) (4-C5NF4) (PCy3)(2)](2), trans-[Pt(F){2-C5NF2H(CF3)}-(PCy3)(2)] 3 and of group 4 difluorides (Cp2MF2, M = Ti 4a, Zr 5a, Hf 6a; Cp*2MF2, M = Ti 4b, Zr 5b, Hf 6b) are reported. These measurements allow placement of these fluoride ligands on the scales of organic H-bond acceptor strength. The H-bond acceptor capability beta (Hunter scale) for the group 10 metal fluorides is far greater (la 12.1, lb 9.7, 2 11.6, 3 11.0) than that for group 4 metal fluorides (4a 5.8, Sa 4.7, 6a 4.7, 4b 6.9, Sb 5.6, 6b 5.4), demonstrating that the group 10 fluorides are comparable to the strongest organic H-bond acceptors, such as Me3NO, whereas group 4 fluorides fall in the same range as N-bases aniline through pyridine. Additionally, the measurement of the binding enthalpy of 4-fluorophenol to la in carbon tetrachloride (-23.5 +/- 0.3 kJ mol(-1)) interlocks our study with Laurence's scale of H-bond basicity of organic molecules. The much greater polarity of group 10 metal fluorides than that of the group 4 metal fluorides is consistent with the importance of p pi-d pi- bonding in the latter. The polarity of the group 10 metal fluorides indicates their potential as building blocks for hydrogen-bonded assemblies. The synthesis of trans-[Ni(F){2-C5NF3(NH2)}(PEt3)(2)], which exhibits an extended chain structure assembled by hydrogen bonds between the amine and metal-fluoride groups, confirms this hypothesis.The Contrasting Character of Early and Late Transition Metal Fluorides as Hydrogen Bond Acceptorsx192015134#N/AFALSE
1590
jacs.5b1136410.1021/jacs.5b11364FALSEhttps://doi.org/10.1021/jacs.5b11364Adzic, RRJ. Am. Chem. Soc.The main challenges to the commercial viability of polymer electrolyte membrane fuel cells are (i) the high cost associated with using large amounts of Pt in fuel cell cathodes to compensate for the sluggish kinetics of the oxygen reduction reaction, (ii) catalyst degradation, and (iii) carbon-support corrosion. To address these obstaCles, our group has focused on robust, carbon-free transition metal nitride materials with low Pt content that exhibit tunable physical and catalytic properties. Here, we report on the high performance of a novel catalyst with low Pt content, prepared by placing several layers of Pt atoms on nanopartiCles of titanium nickel binary nitride. For the ORR, the catalyst exhibited a more than 400% and 200% increase in mass activity and specific activity, respectively, compared with the commercial Pt/C catalyst. It also showed excellent stability/durability, experiencing only a slight performance loss after 10 000 potential cyCles, while TEM results showed its structure had remained intact. The catalyst's outstanding performance may have resulted from the ultrahigh dispersion of Pt (several atomic layers coated on the nitride nanopartiCles), and the excellent stability/durability may have been due to the good stability of nitride and synergetic effects between ultrathin Pt layer and the robust TiNiN support.Transition Metal Nitride Coated with Atomic Layers of Pt as a Low-Cost, Highly Stable Electrocatalyst for the Oxygen Reduction Reaction229201664#N/ATRUE
1591
jacs.5b1122310.1021/jacs.5b11223FALSEhttps://doi.org/10.1021/jacs.5b11223Osuka, AJ. Am. Chem. Soc.5-Hydroxy-10,15,20-triArylporphyrin (oxophlorin) and its Ni(II) and Zn(II) complexes were oxidized with PbO2 to give the corresponding porphyrin meso-oxy radicals as remarkably stable species. These radicals were fully characterized with X-ray diffraction analysis, UV/vis/NIR absorption and ESR spectroscopies, magnetic susceptibility measurement, electrochemical studies, and theoretical calculations. Free-base radical and its Ni(II) complex have been shown to exist as a monoradical in solution, while the Zn(II) complex exists in an equilibrium between monomer (doublet monoradical) and dimer (a non-Kekule singlet biradicaloid) with a dimerization constant of K-D = 3.0 x 10(5) M-1 in noncoordinating CH2Cl2 but becomes a pyridine-coordinated monoradical upon addition of pyridine. Variable temperature magnetic susceptibility measurements of these radicals revealed different magnetic interactions in the solid-states, which has been interpreted in terms of their different packing structures in a microscopic sense. These radicals undergo one-electron oxidation and reduction in a reversible manner within narrow potential windows of 0.57-0.82 V. Finally, one-electron oxidation of Ni(II) and Zn(II) porphyrin meso-oxy radicals with tris(4-bromophenyl)aminium hexachloroantimonate furnished oxophlorin pi-cations, which displayed nonaromatic Closed-shell character, NIR absorption, and significant double bond character of the C-O bond.TriArylporphyrin meso-Oxy Radicals: Remarkable Chemical Stabilities and Oxidation to Oxophlorin pi-Cations46201551#N/ATRUE
1592
jacs.5b1072810.1021/jacs.5b10728FALSEhttps://doi.org/10.1021/jacs.5b10728Berlinguette, CPJ. Am. Chem. Soc.The dynamic behavior of the anodic peak for amorphous nickel oxy/hydroxide (a-NiOx) films in basic media was investigated. Chronocoulometry of films with known nickel concentrations reveals that a total of four electrons per nickel site comprise the signature anodic peak at 1.32 V during the first oxidative scan, and two electrons are passed through the associated cathodic peak on the reverse scan. The anodic and cathodic signals each contain two electrons on the successive scans. Catalytic oxygen evolution reaction (OER) was detected within the anodic peak, which is at a lower potential than is widely assumed. In order to rationalize these experimental results, we propose that the four-electron oxidation event is the conversion of the film from nickel(II) hydroxide ([Ni-II-OH](-)) to a higher valent nickel peroxide species (e.g., Ni-IV-OO or Ni-III-OO.). The subsequent reduction of the nickel peroxide species is confined by a chemical step resulting in the accumulation of [Ni-II-OOH](-), which is then oxidized by two electrons to form Ni-IV-OO during the subsequent oxidative scan on the time scale of a cyClic voltammetric experiment. Our proposed mechanism and the experimental determination that each nickel site is oxidized by four electrons helps link the myriad of seemingly disparate literature data related to OER catalysis by nickel electrodes. The faster catalysis that occurs at higher oxidative potentials is derived from a minority species and is not elaborated here.Accounting for the Dynamic Oxidative Behavior of Nickel Anodes58201647#N/ATRUE
1593
jacs.5b1025710.1021/jacs.5b10257FALSEhttps://doi.org/10.1021/jacs.5b10257Jones, WDJ. Am. Chem. Soc.A highly selective (>99%) tandem catalytic system for the conversion of ethanol (up to 37%) to n-butanol, through the Guerbet process, has been developed using a bifunctional iridium catalyst coupled with bulky nickel or copper hydroxides. These sterically crowded nickel and copper hydroxides catalyze the key aldol coupling reaction of acetaldehyde to exClusively yield the C-4 coupling product, crotonaldehyde. Iridium-mediated dehydrogenation of ethanol to acetaldehyde has led to the development of an ethanol-to-butanol process operated at a lower temperature.Highly Selective Formation of n-Butanol from Ethanol through the Guerbet Process: A Tandem Catalytic Approach91201531#N/ATRUE
1594
jacs.5b0930910.1021/jacs.5b09309FALSEhttps://doi.org/10.1021/jacs.5b09309Hall, MBJ. Am. Chem. Soc.The spectroscopically observable tris(thiolate) complex [Ru(dppbt)(3)](+)(1(+)) (dppbt = diphenyl-phosphinobenzenethiolate) is reported to have chemistry based on thiyl-radical character. High-level ab initio methods predict the ground-state electronic structure of 1(+) to be an open-shell diradical singlet state with antiferromagnetic coupling between (S = 1/2) Ru(III) and (S = 1/2) S p(z), rather the previous description based on a diradical state involving two S p orbitals. These new results provide an improved understanding of the experimental chemistry of 1(+) and related species.Understanding the Radical Nature of an Oxidized Ruthenium Tris(thiolate) Complex and Its Role in the Chemistry13201540#N/ATRUE
1595
jacs.5b0656210.1021/jacs.5b06562FALSEhttps://doi.org/10.1021/jacs.5b06562Gladysz, JAJ. Am. Chem. Soc.The nickel salicylaldiminato phosphine complexes [1,2,3-C6H3(9-anthracenyl) O (CH=N(2,6-C6H3(iPr)(2))]Ni(Me)[P(4-C6H4R)(3)] (4; R = a, (CH2)(2)R-f8; b, (CH2)(3)R-f8; c, H (R-f8 = (CF2)(7)CF3)) are prepared from the corresponding phosphines 3a c and nickel NCMe adduct (46-68%). These are applied as catalysts for ethylene polymerization in toluene and fluorous/toluene liquid/liquid biphasic mixtures. Under the latter conditions, the fluorous phosphines 3a,b that must dissociate to generate the active catalyst migrate to the fluorous phase (partition coefficients 97.5:2.5 and 66.6:33.4 vs < 0.5:> 99.5 for 4a,b). Catalysts 4a,b show marked accelerations under biphasic conditions, but 4c (which has a lipophilic phosphine ligand) does not. Under all conditions, 4a,b are faster catalysts than the Ni(Ph)-(PPh3) analogue, a previously reported benchmark.Activation of Single-Component Nickel(II) Polyethylene Catalysts via Phase Transfer of Fluorous Phosphine Ligandsx15201532#N/AFALSE
1596
jacs.5b0844810.1021/jacs.5b08448FALSEhttps://doi.org/10.1021/jacs.5b08448Montgomery, JJ. Am. Chem. Soc.The nickel-catalyzed coupling of enones or enals with alkynes in the presence of slime and titanium alkoxide reductants provides direct access to skipped diene products. The process involves a net four-electron reductive coupling and proceeds with deoxygenation of the starting enone or enal. A new Class of well-defined nickel(0) precatalysts bearing an unhindered N-hetero-cyClic carbene ligand, which was developed in optimization of the process, is essential for the efficiency of the transformation. The strategy allows the high reactivity of alpha,beta-unsaturated Carbonyl substrates to be utilized in couplings with simultaneous extrusion of the oxygen atom, thus enabling a traceless strategy for alkene installation.Deoxygenative C-C Bond-Forming Processes via a Net Four-Electron Reductive Coupling37201571#N/ATRUE
1597
jacs.5b0572410.1021/jacs.5b05724https://doi.org/10.1021/jacs.5b05724Sivula, KJ. Am. Chem. Soc.A conjugated polymer known for high stability (poly[benzimidazobenzophenanthroline], coded as BBL) is examined as a photoanode for direct solar water oxidation. In aqueous electrolyte with a sacrificial hole acceptor (SO32-), photoelectrodes show a morphology-dependent performance. Films prepared by a dispersion-spray method with a nanostructured surface (feature size of similar to 20 nm) gave photocurrents up to 0.23 +/- 0.02 mA cm(-2) at 1.23 V-RHE under standard simulated solar illumination. Electrochemical impedance spectroscopy reveals a constant flat-band potential over a wide pH range at +0.31 V-NHE. The solar water oxidation photocurrent with bare BBL electrodes is found to increase with increasing pH, and no evidence of semiconductor oxidation was observed over a 30 min testing time. Characterization of the photo-oxidation reaction suggests H2O2 or center dot OH production with the bare film, while functionalization of the interface with 1 nm of TiO2 followed by a nickel-cobalt catalyst gave solar photocurrents of 20-30 mu A cm(-2), corresponding with 02 evolution. Limitations to photocurrent production are discussed.Direct Light-Driven Water Oxidation by a Ladder-Type Conjugated Polymer PhotoanodePhotocatalystx65201542#N/AFALSE
1598
jacs.5b0559710.1021/jacs.5b05597https://doi.org/10.1021/jacs.5b05597Jamison, TFJ. Am. Chem. Soc.Nickel/photoredox catalysis is used to Synthesize indolines in one step from iodoacetanilides and alkenes. Very high regioselectivity for 3-substituted indoline products is obtained for both aliphatic and styrenyl olefins. Mechanistic investigations indicate that oxidation to Ni(III) is necessary to perform the difficult C-N bond-forming reductive elimination, producing a Ni(I) complex, which in turn is reduced to Ni(0). This process serves to further demonstrate the utility of photoredox catalysts as controlled single electron transfer agents in multioxidation state nickel catalysis.Highly Regioselective Indoline Synthesis under Nickel/Photoredox Dual CatalysisPhotocatalyst116201535#N/AFALSE
1599
jacs.5b0831310.1021/jacs.5b08313FALSEhttps://doi.org/10.1021/jacs.5b08313Lu, CCJ. Am. Chem. Soc.A series of bimetallic complexes pairing zero-valent nickel with group 13 M(III) ions is reported. Stronger Ni -> M(III) dative bonds that render Ni more electron-deficient are seen for larger ions (In > Ga > Al). The larger Ga and In ions stabilize rare, nonClassical Ni-H-2 adducts that catalyze olefin hydrogenation. In contrast, neither the Ni-Al complex nor a single nickel center enables H-2 binding or olefin hydrogenation. By comparison of the structures, redox properties, and catalytic activities of the Ni-M series, the electronic and steric effects of the supporting metal ion are elucidated.Tuning Nickel with Lewis Acidic Group 13 Metalloligands for Catalytic Olefin Hydrogenation138201538#N/ATRUE
1600
jacs.5b0804410.1021/jacs.5b08044FALSEhttps://doi.org/10.1021/jacs.5b08044O'Hair, RAJJ. Am. Chem. Soc.Gas-phase studies utilizing ion-molecule reactions, supported by computational chemistry, demonstrate that the reaction of the enolate complexes [(CH2CO2-C,O)M(CH3)](-) (M = Ni (5a), Pd (5b)) with allyl acetate proceed via oxidative addition to give MIV species [(CH2CO2-C,O)M(CH3)(eta(1)-CH2-CH=CH2)(O2CCH3-O,O')](-) (6) that reductively eliminate 1-butene, to form [(CH2CO2-C,O)M(O2CCH3-O,O'](-) (4). The mechanism contrasts with the MR-mediated pathway for the analogous reaction of [(phen)M(CH3)](+) (1a,b) (phen = 1,10-phenanthroline). The different pathways demonstrate the marked effect of electron-rich metal centers in enabling higher oxidation state pathways. Due to the presence of two Alkyl groups, the metal-occupied d orbitals (particularly d(z)(2)) in 5 are considerably destabilized, resulting in more facile oxidative addition; the electron transfer from d(z)(2) to the C=C pi* orbital is the key interaction leading to oxidative addition of allyl acetate to M-II. Upon collision-induced dissociation, 4 undergoes deCarbonylation to form 5. These results provide support for the current exploration of roles for Ni-IV and Pd-IV in organic synthesis.Gas-Phase and Computational Study of Identical Nickel- and Palladium-Mediated Organic Transformations Where Mechanisms Proceeding via M-II or M-IV Oxidation States Are Determined by Ancillary Ligands6201535#N/ATRUE
1601
jacs.5b0517410.1021/jacs.5b05174FALSEhttps://doi.org/10.1021/jacs.5b05174Guidoni, LJ. Am. Chem. Soc.Amorphous transition-metal (hydr)oxides are considered as the most promising catalysts that promote the oxidation of water to molecular oxygen, protons, and energized electrons, and, in turn, as fundamental parts of artificial leaves that can be exploited for large scale generation of chemical fuels (e.g., hydrogen) directly from sunlight. We present here a joint theoretical experimental investigation of electrodeposited amorphous manganese oxides with different catalytic activities toward water oxidation (MnCats). Combining the information content of X-ray absorption fine structure (XAFS) measurements with the predictive power of ab initio calculations based on density functional theory, we have been able to identify the essential structural and electronic properties of MnCats. We have elucidated (i) the localization and structural connection of Mn(II), Mn(III), and Mn(IV) ions in such amorphous oxides and (ii) the distribution of protons at the MnCat/water interface. Our calculations result in realistic 3D models of the MnCat atomistic texture, formed by the interconnection of small planar Mn-oxo sheets cross-linked through different kinds of defective Mn atoms, isolated or arranged in Closed cubane-like units. Essential for the catalytic activity is the presence of undercoordinated Mn(III)O-5 units located at the boundary of the amorphous network, where they are ready to act as hole traps that trigger the oxidation of neighboring water molecules when the catalyst is exposed to an external positive potential. The present validation of a sound 3D model of MnCat improves the accuracy of XAFS fits and opens the way for the development of mechanistic schemes of its functioning beyond a speculative level.Atomistic Texture of Amorphous Manganese Oxides for Electrochemical Water Splitting Revealed by Ab Initio Calculations Combined with X-ray Spectroscopyx29201578#N/AFALSE
1602
jacs.5b0789510.1021/jacs.5b07895FALSESchmidt, RRAn Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst: Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts2015#N/ATRUE
1603
jacs.5b0489210.1021/jacs.5b04892https://doi.org/10.1021/jacs.5b04892Sanford, MSJ. Am. Chem. Soc.This communication describes the synthesis and reactivity of Ni-IV(Aryl)(CF3)(2) complexes supported by trispyrazolylborate and 4,4'-di-tert-butylbipyridine ligands. We demonstrate that isolable Ni-IV complexes can be accessed under mild conditions via the oxidation of Ni-II precursors with S-(trifluoromethyl)dibenzothiophenium triflate as well as with diAryliodonium and Aryl diazonium reagents. The Ni-IV intermediates undergo high yielding Aryl-CF3 bond-forming reductive elimination. These studies support the potential viability of Ni-IV intermediates in nickel-catalyzed coupling reactions involving diAryliodonium and Aryldiazonium electrophiles.Oxidation of Ni(II) to Ni(IV) with Aryl Electrophiles Enables Ni-Mediated Aryl-CF3 Couplingx81201543#N/AFALSE
1604
jacs.5b0472610.1021/jacs.5b04726FALSEhttps://doi.org/10.1021/jacs.5b04726Roke, DJ. Am. Chem. Soc.We report on the active template synthesis of a [2]rotaxane through a Goldberg, copper-catalyzed C-N bend forming reaction. A C-2-symmetric cyClohexyldiamine macrocyCle directs the assembly of the rotaxane, which can subsequently serve as a ligand for enantioselective nickel-catalyzed :conjugate addition reactions. Rotaxanes are a previously unexplored ligand: architecture for asymmetric. catalysis. We find that the rotaxane gives improved enantioselectivity compared to a noninterlocked ligand, at the expense of longer reaction times.Goldberg Active Template Synthesis of a [2]Rotaxane Ligand for Asymmetric Transition-Metal Catalysisx76201542#N/AFALSE
1605
jacs.5b0425610.1021/jacs.5b04256FALSEhttps://doi.org/10.1021/jacs.5b04256Iwasawa, YJ. Am. Chem. Soc.We have achieved significant improvements for the oxygen reduction reaction activity and durability with new SnO2-nanoislands/Pt3Co/C catalysts in 0.1 M HClO4, which were regulated by a strategic fabrication using a new selective electrochemical Sn deposition method. The nano-SnO2/Pt3Co/C catalysts with Pt/Sn = 4/1, 9/1, 11/1, and 15/1 were characterized by STEM-EDS, XRD, XRF, XPS, in situ XAFS, and electrochemical measurements to have a Pt3Co core/Pt skeleton-skin structure decorated with SnO2 nanoislands at the compressive Pt surface with the defects and dislocations. The high performances of nano-SnO2/Pt3Co/C originate from efficient electronic modification of the Pt skin surface (site 1) by both the Co of the Pt3Co core and surface nano-SnO2 and and more from the unique property of the periphery sites of the SnO2 nanoislands at the compressive Pt skeleton-skin surface (more active site 2), which were much more active than expected from the d-band center values. The white line peak intensity of the nano-SnO2/Pt3Co/C revealed no hysteresis in the potential up down operations between 0.4 and 1.0 V versus RHE, unlike the cases of Pt/C and Pt3Co/C, resulting in the high ORR performance. Here we report development of a new Class of cathode catalysts with two different active sites for next-generation polymer electrolyte fuel cells.Surface-Regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by a Selective Electrochemical Sn Deposition Methodx36201562#N/AFALSE
1606
jacs.5b0782710.1021/jacs.5b07827FALSEhttps://doi.org/10.1021/jacs.5b07827Ogoshi, SJ. Am. Chem. Soc.A highly enantioselective synthesis of 3-Aryl-, Vinyl-, and alkynyl-2,1-benzoxasiloles (up to 99.9% ee and 99% yield) was achieved via the sequential Activation of an aldehyde and a silane by nickel(0). This strategy was applied to a simultaneous generation of carbon- and silicon-stereogenic centers with excellent selectivity (dr = 99:1) via diastereotopic Aryl transfer. Initial mechanistic studies revealed the complete switching of an Aryl-transfer process from an intermolecular (racemic synthesis in the presence of IPr) to an intramolecular (enantioselective synthesis using chiral NHC, L5) fashion. A plausible rationale for the switching of the Aryl-transfer process is given by a preliminary DFT calculation, which suggests that the coordination of 1 to the nickel(0)/L5 fragment in an eta(2)-arene:eta(2)-aldehyde fashion would be a key to the intramolecular process, while the formation of the corresponding intermediate is not possible in the presence of IPr. Owing to the chemically labile nature of its C-Si and O-Si bonds, enantioenriched benzoxasiloles are utilized for the synthesis of chiral building blocks and antihistaminic and anticholinergic drug molecules such as (R)-orphenadrine and (S)-neobenodine with no erosion of the enantiomeric excess.Nickel(0)-Catalyzed Enantio- and Diastereoselective Synthesis of Benzoxasiloles: Ligand-Controlled Switching from Inter- to Intramolecular Aryl-Transfer Process47201584#N/ATRUE
1607
jacs.5b0778810.1021/jacs.5b07788FALSEhttps://doi.org/10.1021/jacs.8b00752Strasser, PMolecular Insight in Structure and Activity of Highly Efficient, Low-Ir Ir-Ni Oxide Catalysts for Electrochemical Water Splitting (OER)2015#N/ATRUE
1608
jacs.5b0362910.1021/jacs.5b03629FALSEhttps://doi.org/10.1021/jacs.5b03629Maroney, MJJ. Am. Chem. Soc.Computational investigations have implicated the amidate ligand in nickel, superoxide dismutase (NiSOD) in stabilizing Ni-centered redox catalysis and in preventing cysteine thiolate ligand oxidation. To test these predictions, we have used an experimental approach utilizing a semisynthetic scheme that employs native chemical ligation of a pentapeptide (HCDLP) to recombinant S. coelicolor NiSOD lacking these N-terminal residues, N Delta 5-NiSOD. Wild-type enzyme produced in this manner exhibits the characteristic spectral properties of recombinant WT-NiSOD and is as catalytically active. The semisynthetic scheme was also employed to construct a variant where, the amidate ligand was converted to a secondary amine, H1*-NiSOD, a novel strategy that retains a backbone N-donor atom. The H1*-NiSOD variant was found to have only similar to 1% of the catalytic activity of the recombinant wild-type enzyme, and had altered Spectroscopic properties. X-ray absorption spectroscopy reveals a four-coordinate planar site with N2S2-donor ligands, consistent with electronic absorption spectroscopic results indicating that the Ni center in H1*-NiSOD is mostly reduced in the as-isolated sample, as opposed to 50:50 Ni(II)/Ni(III) mixture that is typical for the recombinant wild-type enzyme. The EPR spectrum of as-isolated H1*-NiSOD accounts for similar to 11% of the Ni in the sample and is similar to WT-NiSOD, but more axial, with g(z) < g(x,y). N-14-hyperfine is observed on gz, confirming the addition of the apical histidine ligand in the Ni(III) complex. The altered electronic properties and implications for redox catalysis are discussed in light of prediction based on synthetic and computational models.A Semisynthetic Strategy Leads to Alteration of the Backbone Amidate Ligand in the NiSOD Active Sitex14201555#N/AFALSE
1609
jacs.5b0681410.1021/jacs.5b06814FALSEhttps://doi.org/10.1021/jacs.5b06814Smith, WAJ. Am. Chem. Soc.Ni-based oxygen evolution catalysts (OECs) are cost-effective and very active materials that can be potentially used for efficient solar-to-fuel conversion process toward sustainable energy generation. We present a systematic spectroelectrochemical characterization of two Fe-containing Ni-based OECs, namely nickel borate (Ni(Fe)-Bi) and nickel oxyhydroxide (Ni(Fe)OOH). Our Raman and X-ray absorption spectroscopy results show that both OECs are chemically similar, and that the borate anions do not play an apparent role in the catalytic process at pH 13. Furthermore, we show spectroscopic evidence for the generation of negatively charged sites in both , OECs (NiOO-), which can be described as adsorbed active oxygen. Our data conClusively links the OER activity of the Ni-based OECs with the generation of those sites on the surface of the OECs. The OER activity of both OECs is strongly pH dependent, which can be attributed to a deprotonation process of the Ni-based OECs, leading to the formation of the negatively charged surface sites that act as OER precursors. This work emphasizes the relevance of the electrolyte effect to obtain catalytically active phases in Ni-based OECs, in addition to the key role of the Fe impurities. This effect should be carefully considered in the development of Ni-based compounds meant to catalyze the OER at moderate pHs. Complementarily, UV-vis spectroscopy measurements show strong darkening of those catalysts in the catalytically active state. This coloration effect is directly related to the oxidation of nickel and can be an important factor limiting the efficiency of solar-driven devices utilizing Ni-based OECs.In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity252201558#N/ATRUE
1610
jacs.5b0674510.1021/jacs.5b06745FALSEhttps://doi.org/10.1021/jacs.8b00131Hoveyda, AHMechanism of NHC-Catalyzed Conjugate Additions of Diboron and Borosilane Reagents to alpha,beta-Unsaturated Carbonyl Compounds2015#N/ATRUE
1611
jacs.5b0349910.1021/jacs.5b03499FALSEhttps://doi.org/10.1021/jacs.5b03499Kishi, YJ. Am. Chem. Soc.A unified synthesis of the C1-C19 building blocks 8-10 of halichondrins A-C was developed from the common synthetic intermediates 26a,b. Acetylenic ketones 26a,b were in With synthesized via selective Activation/coupling of polyhalogenated nudeophiles 23a,b with aldehyde 11 in a (Ni)/Cr-mediated coupling reaction. Compared with Ni/Cr-mediated couplings Of Vinyl iodides and aldehydes, this (Ni)/Cr-mediated coupling exhibited two unique features: First, the coupling was found to proceed with a trace amount or no added Ni-catalyst. Second, TES-Cl, a dissociating agent to regenerate the Cr-catalyst, was found to give a better yield than Zr(Cp)(2)Cl-2. An adjustment of the oxidation state was required to transform acetylenic ketones 26a,13 into C1-C19 building blocks 8 and 9 of halichondrins A and B, respectively. In the halichondrin B series, a hydroxyl-directed (Me)(4)NBH(OAc)(3) reduction of E- and Z-beta-alkoxy-enones 30 was found Cleanly to achieve the required transformation, whereas a DMDO oxidation of E-Vinylogous ester 21 allowed to introduce the C13 hydroxyl group with a high stereoselectivity in the halichondrin A series. In the halichondrin C series, Hf(OTf)(4) was used to convert the double oxy-Michael product 28 into C1-C19 building block 10.Unified Synthesis of C1-C19 Building Blocks of Halichondrins via Selective Activation/Coupling of Polyhalogenated NuCleophiles in (Ni)/Cr-Mediated Reactionsx7201556#N/AFALSE
1612
jacs.5b0349810.1021/jacs.5b03498FALSEhttps://doi.org/10.1021/jacs.5b03498Kishi, YJ. Am. Chem. Soc.The C1-C19 building block 46 of halichondrin Bs was synthesized via a selective Activation/coupling of beta-bromoenone 34 with aldehyde 35 in a Ni/Cr-mediated reaction. The first phase of study was a method development to effect a coupling of a naked Vinylogous anion with an aldehyde. The study with the coupling of 9 + 10 -> 11 revealed: (1) beta-bromoenone 9b is a better nuCleophile than the corresponding beta-iodo- and beta-chloroenones 9a,c; (2) (Me)(2)Phen(OMe)(2)center dot NiCl2 13b is a better Ni-catalyst than (Me)(2)Phen(H)(2)center dot NiCl2 13a; and (3) a low Ni-catalyst loading, for example, 0.05-0.1 mol % Ni-catalyst against 10 mol % Cr-catalyst, is crucial for an effective coupling. The second phase of study was a method development to realize a selective Activation/coupling of polyhalogenated nuCleophiles such as 34. The competition experiment of 10 + 9b over 10 + 31a-c revealed: (1) (Me)(2)Phen(OMe)(2)center dot NiCl2 13b is more effective than (Me)(2)Phen(H)(2)center dot NiCl2 13a for the required selective Activation/coupling; (2) a low Ni-catalyst loading, for example, 0.05-0.1 mol % Ni-catalyst against 10 mol % Cr-catalyst, is crucial for discriminating beta-bromoenone 9b from the three types of Vinyl iodides 31a-c. The third phase of study was an application of the developed method to execute the proposed coupling of 34 + 35 -> 36. For this application, a polyether-type Ni-catalyst 37c, readily soluble in the reaction medium, was introduced to achieve the selective Activation/coupling with higher efficiency. With use of ion-exchange resin-based device, the coupling product 36 was transformed to the C1-C19 building block 46 of halichondrin Bs without purification/separation of the intermediates.Selective Activation/Coupling of Polyhalogenated NuCleophiles in Ni/Cr-Mediated Reactions: Synthesis of C1-C19 Building Block of Halichondrin Bsx13201553#N/AFALSE
1613
jacs.5b0673510.1021/jacs.5b06735FALSEhttps://doi.org/10.1021/jacs.5b06735Love, JAJ. Am. Chem. Soc.2-Nickelaoxetanes have been frequently invoked as reactive intermediates in catalytic reactions of epoxides using nickel, but have never been isolated or experimentally observed in these transformations. Herein, we report the preparation of a series of well-defined nickelaoxetanes formed -via the oxidative addition of nickel(0) with epoxides featuring ketones. The stereochemistry of the products is retained, which has not yet been reported for nickelaoxetanes. Theoretical calculations support a bimetallic ring-opening/Closing pathway over a concerted oxidative addition. Initial reactivity studies of a nickelaoxetane demonstrated protonolysis, oxidatively induced reductive elimination, deoxygenation, and elimination reactions when treated with the appropriate reagents.Synthesis of 2-Nickela(II)oxetanes from Nickel(0) and Epoxides: Structure, Reactivity, and a New Mechanism of Formation28201533#N/ATRUE
1614
jacs.5b0671610.1021/jacs.5b06716FALSEhttps://doi.org/10.1021/jacs.5b06716Kyritsis, PJ. Am. Chem. Soc.The high-spin (S = 1) tetrahedral Ni-II complex [Ni{(Pr2P)-Pr-i(Se)NP-(Se)Pr-i(2)}(2)] was investigated by magnetometry, spectroscopic, and quantum chemical methods. Angle-resolved magnetometry studies revealed the orientation of the magnetization principal axes. The very large zero-field splitting (zfs), D = 45.40(2) cm(-1) E = 1.91(2) cm(-1), of the complex was accurately determined by far-infrared magnetic spectroscopy, directly observing transitions between the spin sublevels of the triplet ground state. These are the largest zfs values ever determined directly for a high-spin Ni-II complex. Ab initio calculations further probed the electronic structure of the system, elucidating the factors controlling the sign and magnitude of D. The latter is dominated by spin orbit coupling contributions of the Ni ions, whereas the corresponding effects of the Se atoms are remarkably smaller.Direct Observation of Very Large Zero-Field Splitting in a Tetrahedral (NiSe4)-Se-II Coordination Complex33201572#N/ATRUE
1615
jacs.5b0319210.1021/jacs.5b03192https://doi.org/10.1021/jacs.5b03192Nocera, DGTrap-Free Halogen Photoelimination from MononuClear Ni(III) ComplexesPhotocatalyst2015#N/AFALSE
1616
jacs.5b0318210.1021/jacs.5b03182FALSEhttps://doi.org/10.1021/jacs.5b03182Armstrong, FAJ. Am. Chem. Soc.Despite extensive studies on [NiFe]-hydrogenases, the mechanism by which these enzymes produce and activate H-2 so efficiently remains unClear. A well-known EPR-active state produced under H-2 and known as Ni-C is assigned as a Ni-III-Fe-II species with a hydrido ligand in the bridging position between the two metals. It has long been known that low-temperature photolysis of Ni-C yields distinctive EPR-active states, collectively termed Ni-L, that are attributed to migration of the bridging-H species as a proton; however, Ni-L has mainly been regarded as an artifact with no mechanistic relevance. It is now demonstrated, based on EPR and infrared spectroscopic studies, that the Ni-C to Ni-L interconversion in Hydrogenase-1 (Hyd-1) from Escherichia coli is a pH-dependent process that proceeds readily in the dark proton migration from Ni-C being favored as the pH is increased. The persistence of Ni-L in Hyd-1 must relate to unassigned differences in proton affinities of metal and adjacent amino acid sites, although the unusually high reduction potentials of the adjacent Fe-S centers in this O-2-tolerant hydrogenase might also be a contributory factor, impeding elementary electron transfer off the [NiFe] site after proton departure. The results provide compelling evidence that Ni-L is a true, albeit elusive, catalytic intermediate of [NiFe]-hydrogenases.Discovery of Dark pH-Dependent H+ Migration in a [NiFe]-Hydrogenase and Its Mechanistic Relevance: Mobilizing the Hydrido Ligand of the Ni-C IntermediateX51201543#N/AFALSE
1617
jacs.5b0311310.1021/jacs.5b03113FALSEhttps://doi.org/10.1021/jacs.5b03113Yokozawa, TJ. Am. Chem. Soc.Intramolecular transfer of (Bu3PPd)-Bu-t(0) on a carbon carbon double bond (C=C) was investigated by using Suzuki-Miyaura coupling reaction of dibromostilbenes with Aryl boronic acid or boronic acid esters in the presence of various additives containing C=C as a model. Substituent groups at the ortho position of C=C of stilbenes are critical for selective intramolecular catalyst transfer and may serve to suppress formation of the bimolecular C=C-Pd-C=C complex that leads to intermolecular transfer of (Bu3PPd)-Bu-t(0).Structural Requirements for Palladium Catalyst Transfer on a Carbon-Carbon Double Bondx30201521#N/AFALSE
1618
jacs.5b0662710.1021/jacs.5b06627FALSEhttps://doi.org/10.1021/jacs.5b06627Mountford, PJ. Am. Chem. Soc.Reaction of Ti((N2N)-N-iPr)(NNPh2)(py) with Ph(R)SiH2 (R = H, Ph) or 9-BBN gave reductive Cleavage of the N-alpha-Ni-beta bond and formation of new silyl- or boryl-amido ligands. The corresponding reactions of Cp*Ti-{MeC((NPr)-Pr-i)(2)}(NNR2) (R = Me or Ph) with HBPin or 9-BBN gave borylhydrazido-hydride or borylimido products, respectively. N-alpha and N-beta atom transfer and dehydrogenative coupling reactions are also reported.Reactions of Titanium Hydrazides with Silanes and Boranes: N-N Bond Cleavage and N Atom Functionalization14201540#N/ATRUE
1619
jacs.5b0646610.1021/jacs.5b06466FALSEhttps://doi.org/10.1021/jacs.5b06466Reisman, SEJ. Am. Chem. Soc.A Ni-catalyzed asymmetric reductive cross-coupling of heteroAryl iodides and alpha-chloronitriles has been developed. This method furnishes enantioenriched alpha,alpha-disubstituted nitriles from simple organohalide building blocks. The reaction tolerates a variety of heterocyClic coupling partners, inCluding pyridines, pyrimidines, quinolines, thiophenes, and piperidines. The reaction proceeds under mild conditions at room temperature and preCludes the need to pregenerate organometallic nuCleophiles.Nickel-Catalyzed Asymmetric Reductive Cross-Coupling between HeteroAryl Iodides and alpha-Chloronitriles108201534#N/ATRUE
1620
jacs.5b0250410.1021/jacs.5b02504FALSEhttps://doi.org/10.1021/jacs.5b02504Tilley, TDJ. Am. Chem. Soc.The synthesis of the first heteroleptic, two-coordinate Fe-I complex IPr-Fe-N(SiMe3)DIPP (1) (IPr = , 1,3-2bis(2,6-diisopropylphenyl)imidazol-2-ylidene; DIPP = 2,6-Pr-i(2)-C6H3) is reported. Protonation of the Fe-II bis(amido) complex Fe[N(SiMe3)DIPP](2) followed by addition of IPr and reduction by potassium graphite in a one-pot reaction results in good yields of 1. The redox activity of 1 and comparison between 1 and its reduction ptoduct by Fe-57 Mossbauer spectroscopy are discussed, and the :reduction. was found to be metal,based lather than ligand-based. The activity of 1 toward the catalytic cyClotrimerization of terminal and internal alkynes is described.Synthesis, Characterization, and Alkyne Trimerization Catalysis of a Heteroleptic Two-Coordinate Fe-I Complexx54201556#N/AFALSE
1621
jacs.5b0228310.1021/jacs.5b02283FALSEhttps://doi.org/10.1021/jacs.5b02283Samori, PJ. Am. Chem. Soc.The self-assembly of multiple molecular components into complex supramolecular architectures is ubiquitous in nature and constitutes one of the most powerful strategies to fabricate multifunctional nanomaterials making use of the bottom-up approach. When spatial confinement in two dimensions on a solid substrate is employed, this approach can be exploited to generate periodically ordered structures from suitably designed molecular tectons. In this study we demonstrate that physisorbed directional periodic arrays of monometallic or heterobimetallic coordination polymers can be generated on a highly oriented pyrolitic graphite surface by combinations of a suitably designed directional organic tecton or metallatecton based on a porphyrin or nickel(II) metalloporphyrin backbone bearing both a pyridyl unit and a terpyridyl unit acting as coordinating sites for CoCl2. The periodic. architectures were visualized at the solid/liquid interface with a submolecular resolution by scanning tunneling microscopy and corrB(OH)2rated by combined density functional and time-dependent density functional theory calculations. The capacity to nanopattern the surface for the first time with two distinct metallic centers exhibiting different electronic and optical properties is a key step toward the bottom-up construction of robust multicomponent and, thus, multifunctional molecular nanostructures and nano devices.Nanopatterning of Surfaces with Monometallic and Heterobimetallic 1D Coordination Polymers: A Molecular Tectonics Approach at the Solid/Liquid Interfacex252015106#N/AFALSE
1622
jacs.5b0227710.1021/jacs.5b02277FALSEhttps://doi.org/10.1021/jacs.5b02277Nakamura, MJ. Am. Chem. Soc.The first iron-catalyzed enantioselective cross-coupling reaction between an organometallic compound and an organic electrophile is reported. Synthetically versatile racemic alpha-chloro- and alpha-bromoalkanoates were coupled with Aryl Grignard reagents in the presence of catalytic amounts of an iron salt and a chiral bisphosphine ligand, giving the products in high yields with acceptable and synthetically Useful enantioselectivities (er up to 91:9): The produced alpha-Arylalkanoates were readily converted to the corresponding alpha-Arylalkanoic acids with high optical enrichment (er up to >99:1) via simple deprotections/recrystallizations. The results of radical probe experiments are consistent with a methanism that involves the formation of an Alkyl radical intermediate, which undergoes subsequent enantioconvergent Arylation in an intermolecular manner. The developed asymmetric coupling offers not only facile. and practical access to various chiral alpha-Arylalkanoic acid derivatives, which are of significant pharmaceutical importance, but also a basis Of controlling enantioselectivity in an iron-catalyzed organometallic transformation.Iron-Catalyzed Enantioselective Cross-Coupling Reactions of alpha-Chloroesters with Aryl Grignard Reagentsx124201577#N/AFALSE
1623
jacs.5b0181410.1021/jacs.5b01814FALSEhttps://doi.org/10.1021/jacs.5b01814Itoh, SJ. Am. Chem. Soc.Selective hydroxylation of benzene to phenol has been achieved using H2O2 in the presence Of a catalytic amount of the nickel complex [Ni-II(tepa)](2+) (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60 degrees C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H2O2. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When (H2O2)-O-18 was utilized as the oxidant, O-18-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.Direct Hydroxylation of Benzene to Phenol Using Hydrogen Peroxide Catalyzed by Nickel Complexes Supported by PyridylAlkylamine Ligandsx98201544#N/AFALSE
1624
jacs.5b0179110.1021/jacs.5b01791FALSEhttps://doi.org/10.1021/jacs.5b01791Dyer, RBJ. Am. Chem. Soc.The movement of protons and electrons is common to the synthesis of all chemical fuels such as H-2. Hydrogenases, which catalyze the reversible reduction of protons, necessitate transport and reactivity between protons and electrons, but a detailed mechanism has thus far been elusive. Here, we use a phototriggered chemical potential jump method to rapidly initiate the proton reduction activity of a [NiFe] hydrogenase. Coupling the photochemical initiation approach to nanosecond transient infrared and visible absorbance spectroscopy afforded direct observation of interfacial electron transfer and active site chemistry. Tuning of intramolecular proton transport by pH and isotopic substitution revealed distinct concerted and stepwise proton-coupled electron transfer mechanisms in catalysis. The observed heterogeneity in the two sequential proton-associated reduction processes suggests a highly engineered protein environment modulating catalysis and implicates three new reaction intermediates; Ni-a-I, Ni-a-D, and Ni-a-SR-. The results establish an elementary mechanistic understanding of catalysis in a [NiFe] hydrogenase with implications in enzymatic proton-coupled electron transfer and biomimetic catalyst design.Proton-Coupled Electron Transfer Dynamics in the Catalytic Mechanism of a [NiFe]-HydrogenaseX61201565#N/AFALSE
1625
jacs.5b0554410.1021/jacs.5b05544FALSEhttps://doi.org/10.1021/jacs.7b08643Hu, XLAn Optically Transparent Iron Nickel Oxide Catalyst for Solar Water Splitting2015#N/ATRUE
1626
jacs.5b0132910.1021/jacs.5b01329FALSEhttps://doi.org/10.1021/jacs.5b01329Wang, EBJ. Am. Chem. Soc.Three new polyoxometalate(POM)-based polynuClear nickel Clusters, Na-24[Ni-12(OH)(9)(CO3)(3)(PO4)(SiW9O34)(3)] 56H(2)O (1), Na-25[Ni-13(H2O)(3)(OH)(9)(PO4)(4)(SiW9O34)(3)] 50H(2)O (2), and Na-50[Ni-25(H2O)(2)OH)(18)(CO3)(2)(PO4)(6)(SiW9O34)(6)] 85H(2)O (3) were synthesized and structurally characterized. Compounds 1-3 contain {Ni-12}, {Ni-13} and {Ni-25} core, respectively, connected by the inorganic {OH}, {PO4} and/or {CO3} linkers and encapsulated by the lacunary A-alpha-{SiW9O34} POM units. Compound 3 represents the currently largest POM-based Ni Clusters. All three compounds contain {Ni3O3} quasi-cubane or {Ni4O4} cubane units, which are similar to the natural oxygen-evolving center {Mn4O5Ca} in photosystem II (PSII). Visible light-driven water oxidation experiments with compounds 1-3 as the homogeneous catalysts indicate that all three compounds show good photocatalytic activities. The O2 evolution amount corresponds to a high TON of 128.2 for 1, 147.6 for 2, and 204.5 for 3, respectively. Multiple experiments inCluding dynamic light-scattering, UV-vis absorption, catalysts aged experiments, tetra-n-heptylammonium nitrate (THpANO(3)) toluene extraction, and capillary electrophoretic measurements results confirm that compounds 1-3 are dominant active catalysts but not Ni2+ ions(aq) or nickel oxide under the photocatalytic conditions. The above research results indicate a new and all-inorganic polynuClear Ni-based structural model as the visible light-driven water oxidation catalysts.Polyoxometalate-Based Nickel Clusters as Visible Light-Driven Water Oxidation Catalystsx259201568#N/AFALSE
1627
jacs.5b0110010.1021/jacs.5b01100FALSEhttps://doi.org/10.1021/jacs.7b08629Sun, SHA New Core/Shell NiAu/Au NanopartiCle Catalyst with Pt-like Activity for Hydrogen Evolution Reactionx2015#N/AFALSE
1628
jacs.5b0551310.1021/jacs.5b05513FALSEhttps://doi.org/10.1021/jacs.5b05513Martin, RJ. Am. Chem. Soc.A mild and user-friendly Ni-catalyzed regioselective hydroCarbonylation of alkynes with CO2 (1 bar) is described. This protocol is characterized by a wide scope While obviating the need for sensitive organometallic, species and by an unprecedented regioselectivity pattern using simple alcohols as proton sources.Ni-Catalyzed Regioselective HydroCarbonylation of Alkynes with CO2 by Using Simple Alcohols as Proton Sources125201565#N/ATRUE
1629
jacs.5b0499010.1021/jacs.5b04990FALSEhttps://doi.org/10.1021/jacs.5b04990Uyeda, CJ. Am. Chem. Soc.An evaluation of catalyst nuClearity effects in Ni-catalyzed alkyne oligomerization reactions is presented. A dinuClear complex, featuring a Ni-Ni bond supported by a naphthyridine-diimine (NDI) ligand, promotes rapid and selective cyClotrimerization to form 1,2,4-substituted arene products. Mononickel congeners bearing related N-donor chelates (2-iminopyridines, 2,2'-bipyridines, or 1,4,-diazadienes) are significantly less active and yield complex product mixtures. Stoichiometric reactions of the dinickel catalyst with hindered silyl acetylenes enable characterization of the alkyne complex and the metallacyCle that are implicated as catalytic intermediates. Based on these experiments and supporting DFT calculations, the role of the dinuClear active site in promoting regioselective alkyne coupling is discussed. Together, these results demonstrate the utility of exploring nuClearity as a parameter for catalyst optimization.Evaluating the Effect of Catalyst NuClearity in Ni-Catalyzed Alkyne CyClotrimerizations67201550#N/ATRUE
1630
jacs.5b0010410.1021/jacs.5b00104FALSEhttps://doi.org/10.1021/jacs.5b00104Ge, HBJ. Am. Chem. Soc.Nickel-Catalyzed Site-Selective Alkylation of Unactivated C(sp(3))-H Bonds (vol 136, pg 1789, 2014)X020151#N/AFALSE
1631
jacs.1c0658310.1021/jacs.1c06583FALSEhttps://doi.org/10.1021/jacs.1c06583Deng, LJ. Am. Chem. Soc.Metal-catalyzed hydrosilylation of alkynes is an ideal atom-economic method to prepare Vinylsilanes that are useful reagents in the organic synthesis and silicone industry. Although great success has been made in the preparation of beta-Vinylsilanes by metal-catalyzed hydrosilylation reactions of alkynes, reported metal-catalyzed reactions for the synthesis of alpha-Vinylsilanes suffer from narrow substrate scope and/or poor selectivity. Herein, we present selective Markovnikov hydrosilylation reactions of terminal alkynes with tertiary silanes using a dicobalt Carbonyl N-heterocyClic carbene (NHC) complex [(IPr)(2)Co-2(CO)(6)] (IPr = 1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) as catalyst. This cobalt catalyst effects the hydrosilylation of both Alkyl- and Aryl-substituted terminal alkynes with a variety of tertiary silanes with good functional group compatibility, furnishing a-Vinylsilanes with high yields and high alpha/beta selectivity. Mechanistic study revealed that the stoichiometric reactions of [(IPr)(2)Co-2(CO)(6)] with PhC equivalent to CH and HSiEt3 can furnish the dinuClear cobalt alkyne and mononuClear cobalt silyl complexes [(IPr)(CO)(2)Co(mu-eta(2):eta(2)-HCCPh)Co(CO)(3)], [(IPr)(CO)(2)Co(mu-eta(2):eta(2)-HCCPh)Co(CO)(2)(IPr)], and [(IPr) Co(CO)(3)(SiEt3)], respectively. Both dicobalt bridging alkyne complexes can react with HSiEt3 to yield alpha-triethylsilyl styrene and effect the catalytic Markovnikov hydrosilylation reaction. However, the mono(NHC) dicobalt complex [(IPr)(CO)(2)Co(mu-eta(2):eta(2)-HCCPh)Co(CO)(3)] exhibits higher catalytic activity over the di(NHC)-dicobalt complexes. The cobalt silyl complex [(IPr)Co(CO)(3)(SiEt3)] is ineffective in catalyzing the hydrosilylation reaction. Deuterium labeling experiments with Ph equivalent to CCD and DSiEt3 indicates the synaddition nature of the hydrosilylation reaction. The absence of deuterium scrambling in the hydrosilylation products formed from the catalytic reaction of PhC equivalent to CH with a mixture of DSiEt3 and HSi(OEt)(3) hints that mononuClear cobalt species are less likely the in-cyCle species. These observations, in addition to the evident of nonsymmetric Co2C2-butterfly core in the structure of [(IPr)(CO)(2)Co(mu-eta(2):eta(2)-HCCPh)Co(CO)(3)], point out that mono(IPr)-dicobalt species are the genuine catalysts for the cobaltcatalyzed hydrosilylation reaction and that the high a selectivity of the catalytic system originates from the joint play of the dicobalt Carbonyl species to coordinate alkynes in the Co(mu-eta(2):eta(2)-HCCR')Co mode and the steric demanding nature of IPr ligand.Markovnikov Hydrosilylation of Alkynes with Tertiary Silanes Catalyzed by DinuClear Cobalt Carbonyl Complexes with NHC Ligationx0202149#N/AFALSE
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jacs.5b0414210.1021/jacs.5b04142FALSEhttps://doi.org/10.1021/jacs.5b04142Sun, SHStable Cobalt NanopartiCles and Their Monolayer Array as an Efficient Electrocatalyst for Oxygen Evolution Reaction2015#N/ATRUE
1633
jacs.1c0575410.1021/jacs.1c05754FALSEhttps://doi.org/10.1021/jacs.1c05754Yao, TJ. Am. Chem. Soc.The development of atomically precise dinuClear heterogeneous catalysts is promising to achieve efficient catalytic performance and is also helpful to the atomic-level understanding on the synergy mechanism under reaction conditions. Here, we report a Ni-2(dppm)(2)Cl-3 dinuClear-Cluster-derived strategy to a uniform atomically precise Ni-2 site, consisting of two Ni-1-N-4 moieties shared with two nitrogen atoms, anchored on a N-doped carbon. By using operando synchrotron X-ray absorption spectroscopy, we identify the dynamically catalytic dinuClear Ni-2 structure under electrochemical CO2 reduction reaction, revealing an oxygen-bridge adsorption on the Ni-2-N-6 site to form an O-Ni-2-N-6 structure with enhanced Ni-Ni interaction. Theoretical simulations demonstrate that the key O-Ni-2-N-6 structure can significantly lower the energy barrier for CO2 Activation. As a result, the dinuClear Ni2 catalyst exhibits >94% Faradaic efficiency for efficient carbon monoxide production. This work provides bottom-up target synthesis approaches and evidences the identity of dinuClear sites active toward catalytic reactions.Atomically Precise DinuClear Site Active toward Electrocatalytic CO2 Reduction
Electrocatalytic
x0202135#N/AFALSE
1634
jacs.5b0408210.1021/jacs.5b04082FALSEhttps://doi.org/10.1021/jacs.5b04082Mirica, LMJ. Am. Chem. Soc.Herein we report the synthesis and reactivity of several organometallic Ni-III complexes stabilized by a modified tetradentate pyridinophane ligand containing one phenyl group: A room temperature stable dicationic Ni-III-disolvento complex was also isolated, and the presence of two available cis coordination sites in this complex offers an opportunity to probe the C-heteroatom bond formation reactivity of high-valent Ni centers. Interestingly, the Ni-III-dihydroxide and Ni-III-dimethoxide species can be synthesized and they undergo Aryl methoxylation and hydroxylation that is favored by addition of oxidant, which also limits the beta-hydride elimination side reaction. Overall, these results provide strong evidence for the involvement of high-valent organometallic Ni species, possibly both Ni-III and Ni-IV species, in oxidatively induced C-heteroatom bond formation reactions.Aromatic Methoxylation and Hydroxylation by Organometallic High-Valent Nickel Complexes44201535#N/ATRUE
1635
jacs.1c0556710.1021/jacs.1c05567https://doi.org/10.1021/jacs.1c05567Goddard-Borger, EDJ. Am. Chem. Soc.The biological functions of tryptophan C-mannosylation are poorly understood, in part, due to a dearth of methods for preparing pure glycopeptides and glycoproteins with this modification. To address this issue, efficient and scalable methods are required for installing this protein modification. Here, we describe unique Ni-catalyzed cross-coupling conditions that utilize photocatalysis or a Hantzsch ester photoreductant to couple glycosyl halides with (hetero)Aryl bromides, thereby enabling the alpha-C-mannosylation of 2-bromo-tryptophan, peptides thereof, and (hetero)Aryl bromides more generally. We also report that 2-(alpha-D-mannopyranosyl)-L-tryptophan undergoes facile anomerization in the presence of acid: something that must be considered when preparing and handling peptides with this modification. These developments enabled the first automated solid-phase peptide syntheses of C-mannosylated glycopeptides, which we used to map the epitope of an antibody, as well as providing the first verified synthesis of Carmo-HrTH-I, a C-mannosylated insect hormone. To complement this approach, we also performed late-stage tryptophan C-mannosylation on a diverse array of peptides, demonstrating the broad scope and utility of this methodology for preparing glycopeptides.Synthesis of C-Mannosylated Glycopeptides Enabled by Ni-Catalyzed Photoreductive Cross-Coupling ReactionsPhotocatalyst0202147#N/AFALSE
1636
jacs.1c0543910.1021/jacs.1c05439FALSEhttps://doi.org/10.1021/jacs.1c05439Swager, TMJ. Am. Chem. Soc.We report the synthesis of new carbon-nanomaterial-based metal chelates that enable effective electronic coupling to electrocatalytic transition metals. In particular, multiwalled carbon nanotubes (MWCNTs) and few-layered graphene (FLG) were covalently functionalized by a microwave-assisted cyClo-addition with nitrile oxides to form metal-binding isoxazoline functional groups with high densities. The covalent attachment was evidenced by Raman spectroscopy, and the chemical identity of the surface functional groups was confirmed by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The functional carbon nanomaterials effectively chelate precious metals Ir(III), Pt(II), and Ru(III), as well as earth-abundant metals such as Ni(II), to afford materials with metal contents as high as 3.0 atom %. The molecularly dispersed nature of the catalysts was confirmed by X-ray absorption spectroscopy (XAS) and energy-dispersive X-ray spectroscopy (STEM-EDS) elemental mapping. The interplay between the chelate structure on the graphene surface and its metal binding ability has also been investigated by a combination of experimental and computational studies. The defined ligands on the graphene surfaces enable the formation of structurally precise heterogeneous molecular catalysts. The direct attachment of the isoxazoline functional group on the graphene surfaces provides strong electronic coupling between the chelated metal species and the conductive carbon nanomaterial support. We demonstrate that the metal-chelated carbon nanomaterials are effective heterogeneous catalysts in the oxygen evolution reaction with low overpotentials and tunable catalytic activity.Electrocatalytic Isoxazoline-Nanocarbon Metal Complexesx02021112#N/AFALSE
1637
jacs.5b0358710.1021/jacs.5b03587FALSEhttps://doi.org/10.1021/jacs.5b03587Ogoshi, SJ. Am. Chem. Soc.In the presence of a catalytic amount of Ni(cod)(2) and IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), a cross-trimerization reaction of tetrafluoro-ethylene (TFE), ethylene, and aldehydes proceeded in a selective manner to afford a variety of 4,4,5,5-tetrafluoro-1-pentanone derivatives in good to excellent yields. The present system involves a five-membered nickelacyCle key intermediate generated via the oxidative cyClization of TFE and ethylene.Nickel-Catalyzed Formation of Fluorine-Containing Ketones via the Selective Cross-Trimerization Reaction of Tetrafluoroethylene, Ethylene, and Aldehydes38201549#N/ATRUE
1638
jacs.1c0503210.1021/jacs.1c05032https://doi.org/10.1021/jacs.1c05032Jiang, HLModulating Coordination Environment of Single-Atom Catalysts and Their Proximity to Photosensitive Units for Boosting MOF PhotocatalysisPhotocatalyst2021#N/AFALSE
1639
jacs.1c0494610.1021/jacs.1c04946https://doi.org/10.1021/jacs.1c04946Bai, JFJ. Am. Chem. Soc.Reticular chemistry and methane storage materials have been predominately focused on finite metal-Cluster-based metal-organic frameworks (MOFs). In contrast, MOFs constructed from infinite rod secondary building units (SBUs), i.e., rod MOFs, are less developed, and the existing ones are typically built from simple one-way helical, zigzag, or (mixed)polyhedron SBUs. Herein, inspired by a recent unveiled structure of Zn-6(H2O)(3)(BTP)(4) and by means of an amide-functionalized preliminary single triCarbonylate, a subsequent mixed triCarbonylate, and diCarbonylate linkers, an intricate three-way rod MOF and the next three isoreticular three-way rod MOFs have been successfully realized, namely, 3W-ROD-1 and 3W-ROD-2-X (X = -OH, -F, and -CH3), respectively. The structural analyses disClosed that the four compounds were constructed from unprecedented three-way invariant nonintersecting trigonal rod-packing SBUs cross-linked via the noncovalent-interaction-driven self-assembly of pseudo hexaCarbonylates with the original triCarbonylate or different functional ditopic linkers, resulting in cage-like pore geometries accessible via ultramicroporous apertures concomitant with the complex topology transitivity, namely, 18 42 and 18 44. Sorption studies show that the apparent surface areas of these materials are among the most highly porous materials for rod MOFs. Due to the presence of favorable pocket sites created by X, ketone, and proximal amide groups as revealed by Monte Carlo molecular dynamics (MCMD) computational calculations, the MOFs exhibit impressive methane storage working capacities, outperforming the well-known rod Ni-MOF-74 and representing the highest values among rigid rod MOFs.New Reticular Chemistry of the Rod Secondary Building Unit: Synthesis, Structure, and Natural Gas Storage of a Series of Three-Way Rod Amide-Functionalized Metal-Organic Frameworksx0202143#N/AFALSE
1640
jacs.1c0465210.1021/jacs.1c04652FALSEhttps://doi.org/10.1021/jacs.1c04652Bird, MJJ. Am. Chem. Soc.Here we report the use of pulse radiolysis and spectroelectrochemistry to generate low-valent nickel intermediates relevant to synthetically important Ni-catalyzed cross-coupling reactions and interrogate their reactivities toward comproportio-nation and oxidative addition processes. Pulse radiolysis provided a direct means to generate singly reduced [(dtbbpy)NiBr], enabling the identification of a rapid Ni(0)/Ni(II) comproportionation process taking place under synthetically relevant electrolysis conditions. This approach also permitted the direct measurement of Ni(I) oxidative addition rates with electronically differentiated Aryl iodide electrophiles (k(OA) = 1.3 x 10(4)-2.4 x 10(5) M-1 s(-1)), an elementary organometallic step often proposed in nickel-catalyzed cross-coupling reactions. Together, these results hold implications for a number of Ni-catalyzed cross-coupling processes.The Application of Pulse Radiolysis to the Study of Ni(I) Intermediates in Ni-Catalyzed Cross-Coupling Reactionsx0202146#N/AFALSE
1641
jacs.5b0353610.1021/jacs.5b03536FALSEhttps://doi.org/10.1021/jacs.5b03536Ager, JWJ. Am. Chem. Soc.Achieving stable operation of photoanodes used as components of solar water splitting devices is critical to realizing the promise of this renewable energy technology. It is shown that p-type transparent conducting oxides (p-TCOs) can function both as a selective hole contact and corrosion protection layer for photoanodes used in light-driven water oxidation. Using NiCo2O4 as the p-TCO and n-type Si as a prototypical light absorber, a rectifying heterojunction capable of light driven water oxidation was created. By placing the charge separating junction in the Si using a np(+) structure and by incorporating a highly active heterogeneous Ni-Fe oxygen evolution catalyst, efficient light-driven water oxidation can be achieved. In this structure, oxygen evolution under AM1.5G illumination occurs at 0.95 V vs RHE, and the current density at the reversible potential for water oxidation (1.23 V vs RHE) is >25 mA cm(-2). Stable operation was confirmed by observing a constant current density over 72 h and by sensitive measurements of corrosion products in the electrolyte. In situ Raman spectroscopy was employed to investigate structural transformation of NiCo2O4 during electrochemical oxidation. The interface between the light absorber and p-TCO is crucial to produce selective hole conduction to the surface under illumination. For example, annealing to produce more crystalline NiCo2O4 produces only small changes in its hole conductivity, while a thicker SiOx layer is formed at the n-Si/p-NiCo2O4 interface, greatly reducing the PEC performance. The generality of the p-TCO protection approach is demonstrated by multihour, stable, water oxidation with n-InP/p-NiCo2O4 heterojunction photoanodes.p-Type Transparent Conducting Oxide/n-Type Semiconductor Heterojunctions for Efficient and Stable Solar Water Oxidation90201560#N/ATRUE
1642
jacs.1c0434810.1021/jacs.1c04348FALSEhttps://doi.org/10.1021/jacs.1c04348Shinokubo, HJ. Am. Chem. Soc.Three-dimensional aromaticity arising from the Close stacking of two antiaromatic pi-conjugated macrocyCles has recently received considerable attention. Here, a cyClophane consisting of two antiaromatic Ni(II) norcorrole units tethered with two flexible Alkyl chains was synthesized. The norcorrole cyClophane showed crystal polymorphism providing three different solid-state structures. Surprisingly, one of them adopted an aligned face-to-face stacking arrangement with negligible displacement along the slipping axis. Although the exchange repulsion between two pi-Clouds should be maximized in this orientation, the pi-pi distance is remarkably Close (3.258 angstrom). Three-dimensional aromaticity in this conformation has been supported experimentally and theoretically as evidenced by small bond length alternations as well as the presence of a diatropic ring current. An analogous cyClophane with two aromatic Ni(II) porphyrin units was prepared for comparison. The porphyrin cyClophane exhibited a slipped-stacking conformation with a larger displacement (2.9 angstrom) and a larger interplanar distance (3.402 angstrom) without noticeable change of the aromaticity of each porphyrin unit. In solution, the norcorrole cyClophane forms a twist stacking arrangement with effective interplanar orbital overlap and exists in an equilibrium between stacked and nonstacked structures. Thermodynamic parameters of the stacking process were estimated, revealing an inherently large attractive interaction operating between two norcorrole units, which has been further supported by energy decomposition analysis.Determinant Factors of Three-Dimensional Aromaticity in Antiaromatic CyClophanesx0202152#N/AFALSE
1643
jacs.5b0342610.1021/jacs.5b03426FALSESurendranath, YHeazlewoodite, Ni3S2: A Potent Catalyst for Oxygen Reduction to Water under Benign Conditions2015#N/ATRUE
1644
jacs.5b0334010.1021/jacs.5b03340FALSEhttps://doi.org/10.1021/jacs.5b03340Martin, RJ. Am. Chem. Soc.A user-friendly Ni-catalyzed reductive cyClization/Carbonylation of unactivated Alkyl halides with. CO2 is described: The protocol operates under mild conditions with, an excellent chemoselectivity profile and a divergent syn/anti selectivity pattern that can be easily modulated by the Substrate utilized.Ni-Catalyzed Divergent CyClization/Carbonylation of Unactivated Primary and Secondary Alkyl Halides with CO2106201575#N/ATRUE
1645
jacs.5b0309210.1021/jacs.5b03092FALSEhttps://doi.org/10.1021/jacs.5b03092Uyeda, CJ. Am. Chem. Soc.An electron rich Ni(I)-Ni(I) bond supported by a douhly reduced naphthyridine diimine (NDI) ligand reacts rapidly and reversibly with Ph2SiH2 and Et2SiH2 to form stable adducts. The solid-state structures of these complexes reveal binding modes in which the silanes symmetrically span the Ni Ni bond and exhibit highly distorted H-Si-H angles and elongated Si-H bonds. This process is facilitated by the release Of electron density stored in the pi-system of the NDI ligand. Based on this dinuClear mode of Activation, [NDI]Ni-2 complexes are shown to catalyze the high-yielding hydrosilylation of alkenes, dienes, alkynes, aldehydes, ketones, enones, and amides. In comparative Studies of alkyne hydrosilylations, the [NDI]Ni-2 catalyst is found to be significantly more active than its mononuClear counterparts for Aryl-substituted substrates.Reversible Substrate Activation and Catalysis at an Intact Metal-Metal Bond Using a Redox-Active Supporting Ligand113201580#N/ATRUE
1646
jacs.5b0294510.1021/jacs.5b02945TRUEhttps://doi.org/10.1021/jacs.5b02945Helquist, PJ. Am. Chem. Soc.A procedure for Ni-catalyzed cross-coupling of ketone enolates with alkenyl halides has been developed. Intermolecular coupling of aromatic and aliphatic ketone lithium enolates with a variety of alkenyl halides is achieved in the presence of Ni(cod)(2) catalyst (5 mol %), an N-heterocyClic carbene (NHC) ligand, and LiI (10 mol %) at 6-22 degrees C for 0.5-12 h with yields of up to 90%. During the initial development of this reaction, a misleading result with respect to the actual active catalyst was obtained using commercially available Q:Phos ligand, which was found to contain a trace of Pd metal contaminant sufficient to catalyze the reaction. However, under the final conditions optimized for Ni(cod)(2) in the presence of an NHC ligand, Pd was incompetent as a catalyst.Ni-Catalyzed Alkenylation of Ketone Enolates under Mild Conditions: Catalyst Identification and OptimizationCsp3-Csp2E-NuHHBrAlkylIonicNitrogen(neutral)382015422/28/2022TRUE
1647
jacs.1c0390110.1021/jacs.1c03901FALSEhttps://doi.org/10.1021/jacs.1c03901Farha, OKJ. Am. Chem. Soc.Organophosphorus nerve agents, a Class of extremely toxic chemical warfare agents (CWAs), have remained a threat to humanity because of their continued use against civilian populations. To date, Zr(IV)-based metal organic framework (MOFs) are the most prevalent nerve agent hydrolysis catalysts, and relatively few reports disClose MOFs containing nodes with other Lewis acidic transition metals. In this work, we leveraged this synthetic tunability to explore how the identity of the transition metal node in the M-MFU-4l series of MOFs (M = Zn, Cu, Ni, Co) influences the catalytic performance toward the hydrolysis of the nerve agent simulant dimethyl (4-nitrophenyl)phosphate (DMNP). Experimental studies reveal that Cu-MFU-4l exhibits the best performance in this series with a half-life for hydrolysis of similar to 2 min under these conditions. In contrast, both Ni- and Co-MFU-4l demonstrate significantly slower reactivity toward DMNP, as they both fail to surpass 30% conversion of DMNP after 1 h under analogous conditions. Further modification of the active site within Cu-MFU-4l is possible, and we found that although the identity of the anion coordinated to the Cu(II)-X (X = Cl-, HCOO-, ClO4-, NO3-) active site has little influence on the catalytic performance, reduction of the Cu(II) sites yields nodes that contain Cu(I) ions in a trigonal geometry with open metal sites, leading to remarkable catalytic activity with a half-life for hydrolysis less than 2 min. Computational studies indicate the Cu(I) sites exhibit stronger binding affinities than Cu(II) to both water and DMNP, which corrB(OH)2rates the experimental results.Insights into Catalytic Hydrolysis of Organophosphonates at M-OH Sites of Azolate-Based Metal Organic Frameworksx0202148#N/AFALSE
1648
jacs.5b0165010.1021/jacs.5b01650FALSEhttps://doi.org/10.1021/jacs.5b01650Reisner, EJ. Am. Chem. Soc.Carbon quantum dots (CQDs) are established as excellent photosensitizers in combination with a molecular catalyst for solar light driven hydrogen production in aqueous solution. The inexpensive CQDs an be prepared, by straightforward thermolysis of citric acid in a simple one-pot,, multigram synthesis and are therefore scalable. The CQDs produced reducing equivalents under solar irradiation in a homogeneous photocatalytic system: with a Ni-bis-(diphosphine) catalyst, giving: an activity of 398 mu mol(H2) (g(CQD))(-1) h(-1) and a per Ni catalyst turnover frequency of 41 h(-1). The CQDs displayed activity in the visible region beyond lambda > 4:55 Am and maintained their full photocatalytic, activity for at least 1 day under full Solar spectrum irradiation. A high quantum efficiency of 1.4% was recorded for the noble- and toxic-metal free photocatalytic system. Thus, CQDs are shown to be a highly sustainable light absorbing material for photocatalytic schemes, which are not limited by cost, toxicity, or lack of scalability. The photocatalytic hybrid system was limited by the lifetime of the molecular catalyst, and intriguingly, no photo catalytic activity Was observed using the CQDs and 3d transition metal salts or platinum precursors: This observation highlights the advantage of using a molecular catalyst over commonly used:heterogeneous catalysts in this photocatalytic system.Solar Hydrogen Production Using Carbon Quantum Dots and a Molecular Nickel Catalyst350201559#N/ATRUE
1649
jacs.1c0376310.1021/jacs.1c03763FALSEhttps://doi.org/10.1021/jacs.1c03763Morandi, BJ. Am. Chem. Soc.The past 20 years have seen an extensive implementation of nickel in homogeneous catalysis through the development of unique reactivity not easily achievable by using noble transition metals. Many catalytic cyCles propose Ni(I) complexes as potential reactive intermediates, yet the scarcity of nickel(I) precursors and the lack of a general, non-ligand-specific protocol for their synthesis have hampered progress in this field of research. This has in turn also limited the access to novel, well-defined Ni(I) species for the development of new catalytic reactions. Herein, we report a simple, general route to access a wide variety of Ni(I)-phenolate complexes via an unusual example of an olefinic Ni(I) complex, [Ni(COD)(OPh*)] (COD = 1,5-cyClooctadiene, OPh* = O(tBu)(3)C6H2). This route has proven to be highly efficient for several coordination numbers and ligand Classes enabling access to the following complexes: [Ni(IPr)(OPh*)] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), [Ni(dcype)(OPh*)] (dcype = 1,2-bis(dicyClohexylphosphino)ethane), [Ni(dppe)(OPh*)] (dppe = 1,2-bis(diphenylphosphino)ethane), and [Ni(terpy)(OPh*)] (terpy = 2,2':6',2 ''-terpyridine). Moreover, reacting [Ni(dcype)(OPh*)] with trimethylsilyl triflate has led to the isolation of a unique example of a cationic binuClear Ni(I)-arene complex. All these complexes have been characterized by single-crystal X-ray, DFT, and EPR analyses, thus providing crucial experimental and theoretical information about their coordination environment and confirming a d(9) electronic structure for all complexes involved. Overall, this new synthetic approach offers exciting opportunities for the discovery of new stoichiometric and catalytic reactivity as well as the mechanistic elucidation of Ni-based catalytic cyCles.One to Find Them All: A General Route to Ni(I)-Phenolate Speciesx0202166#N/AFALSE
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jacs.5b0053810.1021/jacs.5b00538FALSEhttps://doi.org/10.1021/jacs.5b00538Schoenebeck, FJ. Am. Chem. Soc.A catalytic protocol to convert Aryl and heteroAryl chlorides to the corresponding trifluoromethyl sulfides is reported herein. It relies on a relatively inexpensive Ni(cod)(2)/dppf (cod = 1,5-cyClooctadiene; dppf = 1,1'-bis(diphenylphosphino)ferrocene) catalyst system and the readily accessible coupling reagent (Me4N)SCF3. Our computational and experimental mechanistic data are consistent with a Ni-(0)/Ni-(II) cyCle and inconsistent with Ni-(I) as the reactive species. The relevant intermediates were prepared, characterized by X-ray crystallography, and tested for their catalytic competence. This revealed that a monomeric tricoordinate Ni-(I) complex is favored for dppf and Cl whose role was unambiguously assigned as being an off-cyCle catalyst deActivation product. Only bidentate ligands with wide bite angles (e.g., dppf) are effective. These bulky ligands render the catalyst resting state as [(P-P)Ni(cod)]. The latter is more reactive than Ni(P-P)(2), which was found to be the resting state for ligands with smaller bite angles and suffers from an initial high-energy dissociation of one ligand prior to oxidative addition, rendering the system unreactive. The key to effective catalysis is hence the presence of a labile auxiliary ligand in the catalyst resting state. For more challenging substrates, high conversions were achieved via the employment of MeCN as a traceless additive. Mechanistic data suggest that its beneficial role lies in decreasing the energetic span, therefore accelerating product formation. Finally, the methodology has been applied to synthetic targets of pharmaceutical relevance.Fundamental Studies and Development of Nickel-Catalyzed Trifluoromethylthiolation of Aryl Chlorides: Active Catalytic Species and Key Roles of Ligand and Traceless MeCN Additive Revealed1652015127#N/ATRUE
1651
jacs.1c0333810.1021/jacs.1c03338https://doi.org/10.1021/jacs.1c03338Kramer, JRJ. Am. Chem. Soc.Polyproline (PP) based polypeptides have broad applications as protein mimics, ordered materials, hydrogels, and surface coatings. However, a lack of rapid and efficient preparatory methods has challenged synthesis of well-defined high molecular weight materials. Here, we report facile and high-yielding methods for preparation and polymerization of Pro and trans-4-acetoxy-Pro N-carboxyanhdrides (NCAs). For decades, transition metal initiators of NCA polymerization were assumed to be nonstarters with Pro due to the lack of an amide NH proton. We carefully considered the known steps in the initiation mechanism and applied a Ni initiator that intercepts an intermediate and does not require an NH group. This initiator efficiently catalyzes controlled, living polymerization of Pro NCAs, revealing that routes alternate to the previously proposed mechanism must be at play. We also found Co species can catalyze Pro NCA polymerization, and we improved the synthetic methods to prepare the NCA monomers. Our methods are high-yielding and rapid and give tunable, end-functional PP-based homo, statistical, and block polypeptides. We characterized the conformation of PP and trans-4-hydroxy-PP by CD and confirmed the time scale for quantitative conversion from PPI to PPII helices. Overall, our data shed light on the general propagation mechanism of transition metal catalyzed NCA polymerization and have opened the door for efficient preparation of a desirable Class of biomaterials.Rethinking Transition Metal Catalyzed N-Carboxyanhydride Polymerization: Polymerization of Pro and AcOPro N-Carboxyanhydridesx0202159#N/AFALSE
1652
jacs.1c0303910.1021/jacs.1c03039FALSEhttps://doi.org/10.1021/jacs.1c03039Feng, XLJ. Am. Chem. Soc.Advanced supercapacitor electrodes require the development of materials with dense redox sites embedded into conductive and porous skeletons. Two-dimensional (2D) conjugated metal-organic frameworks (c-MOFs) are attractive supercapacitor electrode materials due to their high intrinsic electrical conductivities, large specific surface areas, and quasi-one-dimensional aligned pore arrays. However, the reported 2D c-MOFs still suffer from unsatisfying specific capacitances and narrow potential windows because large and redox- inactive building blocks lead to low redox-site densities of 2D c-MOFs. Herein, we demonstrate the dual-redox-site 2D c-MOFs with copper phthalocyanine building blocks linked by metal-bis(iminobenzosemiquinoid) (M-2[CuPc(NH)(8)], M = Ni or Cu), which depict both large specific capacitances and wide potential windows. Experimental results accompanied by theoretical calculations verify that phthalocyanine monomers and metalbis(iminobenzosemiquinoid) linkages serve as respective redox sites for pseudocapacitive cation (Na+) and anion (SO42-) storage, enabling the continuous Faradaic reactions of M-2[CuPc(NH)(8)] occurring in a large potential window of -0.8 to 0.8 V vs Ag/AgCl (3 M KCl). The decent conductivity (0.8 S m(-1)) and high active-site density further endow the Ni-2[CuPc(NH)(8)] with a remarkable specific capacitance (400 F g(-1) at 0.5 A g(-1)) and excellent rate capability (183 F g(-1) at 20 A g(-1)). Quasi-solid-state symmetric supercapacitors are further assembled to demonstrate the practical application of Ni-2[CuPc(NH)(8)] electrode, which deliver a stateof-the-art energy density of 51.6 Wh kg(-1) and a peak power density of 32.1 kW kg(-1).Dual-Redox-Sites Enable Two-Dimensional Conjugated Metal-Organic Frameworks with Large Pseudocapacitance and Wide Potential Windowx0202156#N/AFALSE
1653
jacs.1c0300710.1021/jacs.1c03007FALSEhttps://doi.org/10.1021/jacs.1c03007Baran, PSJ. Am. Chem. Soc.One of the most oft-employed methods for C-C bond formation involving the coupling of Vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki-Hiyama-Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process, those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate Classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyClic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.Electrochemical Nozaki-Hiyama-Kishi Coupling: Scope, Applications, and Mechanismx0202170#N/AFALSE
1654
jacs.1c0288910.1021/jacs.1c02889FALSEhttps://doi.org/10.1021/jacs.1c02889Mashima, KJ. Am. Chem. Soc.Recent advances in the catalytic application of cerium complexes were achieved through controlling the Ce(IV/III) redox couple. Although Ce(IV) complexes have been extensively investigated as stoichiometric oxidants in organic synthesis on the basis of their highly positive redox potentials, these complexes can be used as catalysts, not only by introducing supporting ligands around the coordination sphere of cerium, but also by taking advantage of the photoresponsive properties of Ce(IV) and Ce(III) species. Cerium is highly abundant, comparable to that of some first-row transition metals such as copper, nickel, and zinc. Cerium complexes are new and promising homogeneous catalyst candidates for a variety of organic transformations under mild reaction conditions. They are typically used to activate dioxygen to oxidize organic compounds and applied for organic radical generation using the photoresponsive character of Ce(IV) Carbonylates and alkoxides as well as electronic transition of Ce(III), in which homolysis of Ce(IV)-ligand covalent bonds is an important step for the overall catalytic cyCle. In this Perspective, we first review the early discovery of Ce(OAc)(4)-mediated oxidative transformations to emphasize the importance of Ce(IV)-OAc bond homolysis in various C-C bond-forming reactions and its relation to recent developments. We then focus on the fundamental importance of Ce(IV) reactivity involving thermal and photoassisted homolysis of the Ce(IV)-ligand covalent bond and the developments regarding Ce(IV/III) redox changes in catalytic reactions together with our recent findings on cerium-based catalysis.Renaissance of Homogeneous Cerium Catalysts with Unique Ce(IV/III) Couple: Redox-Mediated Organic Transformations Involving Homolysis of Ce(IV)-Ligand Covalent Bondsx02021115#N/AFALSE
1655
jacs.1c0227210.1021/jacs.1c02272FALSEhttps://doi.org/10.1021/jacs.1c02272Han, YJ. Am. Chem. Soc.The production of 1-butene by ethylene dimerization is an important chemical industrial process currently implemented using homogeneous catalysts. Here, we describe a highly active heterogeneous catalyst (Ni-ZIF-8) for ethylene dimerization, which consists of isolating Ni-active sites selectively located on the crystal surface of a zeolitic imidazolate framework. Ni-ZIF-8 can be easily prepared by a simple one-pot synthesis method in which site-specific anchoring of Ni is achieved spontaneously because of the incompatibility between the cr electronic configuration of Ni2+ and the three-dimensional framework of ZIF-8. The full exposure and square-planar coordination of the Ni sites accounts for the high catalytic activity of Ni-ZIF-8. It exhibits an average ethylene turnover frequency greater than 1 000 000 h(-1) (1-butene selectivity >85%) at 35 degrees C and 50 bar, far exceeding the activities of previously reported heterogeneous catalysts and many homogeneous catalysts under similar conditions. Moreover, compared to molecular Ni complexes used as homogeneous catalysts for ethylene dimerization, Ni-ZIF-8 has significantly higher stability and shows constant activity during 4 h of continuous reaction. Isotopic labeling experiments indicate that ethylene dimerization over Ni-ZIF-8 follows the Cossee-Arlman mechanism, and detailed characterizations combined with density functional theory calculations rationalize this observed high activity.Highly Active Heterogeneous Catalyst for Ethylene Dimerization Prepared by Selectively Doping Ni on the Surface of a Zeolitic Imidazolate Frameworkx1202161#N/AFALSE
1656
jacs.1c0192310.1021/jacs.1c01923FALSEhttps://doi.org/10.1021/jacs.1c01923Audisio, DJ. Am. Chem. Soc.The incorporation of carbon-14 allows tracking of organic molecules and provides vital knowledge on their fate. This information is critical in pharmaceutical development, crop science, and human food safety evaluation. Herein, a transition-metal-catalyzed procedure enabling carbon isotope exchange on aromatic nitriles is described. By utilizing the radiolabeled precursor Zn([C-14]CN)(2), this protocol allows the insertion of the desired carbon tag without the need for structural modifications, in a single step. By reducing synthetic costs and limiting the generation of radioactive waste, this procedure will facilitate the labeling of nitrile containing drugs and accelerate C-14-based ADME studies supporting drug development.Direct Carbon Isotope Exchange of Pharmaceuticals via Reversible Decyanationx0202155#N/AFALSE
1657
jacs.5b0028110.1021/jacs.5b00281FALSEhttps://doi.org/10.1021/jacs.5b00281Boettcher, SWJ. Am. Chem. Soc.Cobalt oxides and (oxy)hydroxides have been widely studied as electrocatalysts for the oxygen evolution reaction (OER). For related Ni-based materials, the addition of Fe dramatically enhances OER activity. The role of Fe in Co-based materials is not well-documented. We show that the intrinsic OER activity of Co1-xFex(OOH) is similar to 100-fold higher for x approximate to 0.6-0.7 than for x = 0 on a per-metal turnover frequency basis. Fe-free CoOOH absorbs Fe from electrolyte impurities if the electrolyte is not rigorously purified. Fe incorporation and increased activity correlate with an anodic shift in the nominally Co2+/3+ redox wave, indicating strong electronic interactions between the two elements and likely substitutional doping of Fe for Co. In situ electrical measurements show that Co1-xFex(OOH) is conductive under OER conditions (similar to 0.7-4 mS cm(-1) at similar to 300 mV overpotential), but that FeOOH is an insulator with measurable conductivity (2.2 x 10(-2) mS cm(-1)) only at high overpotentials >400 mV. The apparent OER activity of FeOOH is thus limited by low conductivity. Microbalance measurements show that films with x >= 0.54 (i.e., Fe-rich) dissolve in 1 M KOH electrolyte under OER conditions. For x < 0.54, the films appear chemically stable, but the OER activity decreases by 16-62% over 2 h, likely due to conversion into denser, oxide-like phases. We thus hypothesize that Fe is the most-active site in the catalyst, while CoOOH primarily provides a conductive, high-surface area, chemically stabilizing host. These results are important as Fe-containing Co- and Ni-(oxy)hydroxides are the fastest OER catalysts known.Cobalt-Iron (Oxy)hydroxide Oxygen Evolution Electrocatalysts: The Role of Structure and Composition on Activity, Stability, and Mechanism1036201590#N/ATRUE
1658
jacs.1c0164210.1021/jacs.1c01642FALSEhttps://doi.org/10.1021/jacs.1c01642Miao, QJ. Am. Chem. Soc.This study explores a bottom-up approach toward negatively curved carbon allotropes from octabenzo[8]circulene, a negatively curved nanographene. Stepwise chemical reduction reactions of octabenzo[8]circulene with alkali metals lead to a unique highly reduced hydrocarbon pentaanion, which is revealed by X-ray crystallography suggesting a local view for the reduction and alkali metal intercalation processes of negatively curved carbon allotropes. Polymerization of the tetrabromo derivative of octabenzo[8]circulene by the nickel-mediated Yamamoto coupling reaction results in a new type of porous carbon-rich material, which consists of a covalent network of negatively curved nanographenes. It has a specific surface area of 732 m(2) g(-1) and functions as anode material for lithium ion batteries exhibiting a maximum capacity of 830 mAh.g(-1) at a current density of 100 mA.g(-1). These results indicate that this covalent network presents the key structural and functional features of negatively curved carbon allotropes.Charging a Negatively Curved Nanographene and Its Covalent Networkx0202161#N/AFALSE
1659
jacs.1c0657410.1021/jacs.1c06574FALSEhttps://doi.org/10.1021/jacs.1c06574Giri, RJ. Am. Chem. Soc.Ni-Catalyzed Regioselective 1,2-DiAlkylation of Alkenes Enabled by the Formation of Two C(sp(3))-C(sp(3)) Bonds (vol 142, pg 20930, 2020)020211#N/ATRUE
1660
jacs.1c0564910.1021/jacs.1c05649FALSEhttps://doi.org/10.1021/jacs.1c05649Zhang, QWJ. Am. Chem. Soc.The practical synthesis of P-stereogenic tertiary phosphines, which have wide applications in asymmetric catalysis, materials, and pharmaceutical chemistry, represents a significant challenge. A regio- and enantioselective hydrophosphination using cheap and ubiquitous alkynes catalyzed by a nickel complex was designed, in which the toxic and air-sensitive secondary phosphines were prepared in situ from bench-stable secondary phosphine oxides. This methodology has been demonstrated with unprecedented substrate scope and functional group compatibility to afford electronically and structurally diversified P(III) compounds. The products could be easily converted into various precursors of bidentate ligands and organocatalysts, as well as a variety of transitionmetal complexes containing both P- and metal-stereogenic centers.Ni-Catalyzed Asymmetric Hydrophosphination of Unactivated Alkynes0202192#N/ATRUE
1661
jacs.1c0528110.1021/jacs.1c05281FALSEhttps://doi.org/10.1021/jacs.1c05281Rousseaux, SALJ. Am. Chem. Soc.The design of new ligands for cross-coupling is essential for developing new catalytic reactions that access valuable products such as pharmaceuticals. In this report, we exploit the reactivity of nitrile-containing additives in Ni catalysis to design a benzonitrile-containing ligand for cross-coupling involving tertiary nuCleophiles. Kinetic and Hammett studies are used to elucidate the role of the optimized ligand, which demonstrate that the benzonitrile moiety acts as an electron-acceptor to promote reductive elimination over beta-hydride elimination and stabilize low-valent Ni. With these conditions, a protocol for decyanation-metalation and Ni-catalyzed Arylation is conducted, enabling access to quaternary alpha-Arylnitriles from disubstituted malononitriles.Design of an Electron-Withdrawing Benzonitrile Ligand for Ni-Catalyzed Cross-Coupling Involving Tertiary NuCleophiles0202164#N/ATRUE
1662
jacs.1c0108610.1021/jacs.1c01086FALSEhttps://doi.org/10.1021/jacs.1c01086Ragsdale, SWJ. Am. Chem. Soc.Methyl-coenzyme M reductase (MCR) catalyzes both the synthesis and the anaerobic oxidation of methane (AOM). Its catalytic site contains Ni at the core of cofactor F-430. The Ni ion, in its low-valent Ni(I) state, lights the fuse leading to homolysis of the C-S bond of methylcoenzyme M (methyl-SCoM) to generate a methyl radical, which abstracts a hydrogen atom from coenzyme B (HSCoB) to generate methane and the mixed disulfide CoMSSCoB. Direct reversal of this reaction activates methane to initiate anaerobic methane oxidation. On the basis of the crystal structures, which reveal a Ni-thiol interaction between Ni(II)-MCR and inhibitor CoMSH, a Ni(I)-thioether complex with substrate methyl-SCoM has been transposed to canonical MCR mechanisms. Similarly, a Ni(I)-disulfide with CoMSSCoB is proposed for the reverse reaction. However, this Ni(I)-sulfur interaction poses a conundrum for the proposed hydrogenatom abstraction reaction because the >6 A distance between the thiol group of SCoB and the thiol of SCoM observed in the structures appears to be too long for such a reaction. The spectroscopic, kinetic, structural, and computational studies described here establish that both methyl-SCoM and CoMSSCoB bind to the active Ni(I) state of MCR through their sulfonate groups, forming a hexacoordinate Ni(I)-N/O complex, not Ni(I)-S. These studies rule out direct Ni(I)-sulfur interactions in both substrate-bound states. As a solution to the mechanistic conundrum, we propose that both the forward and the reverse MCR reactions emanate through long-range electron transfer from the Ni(I)-sulfonate complexes with methyl-SCoM and CoMSSCoB, respectively.Nickel-Sulfonate Mode of Substrate Binding for Forward and Reverse Reactions of Methyl-SCoM Reductase Suggest a Radical Mechanism Involving Long-Range Electron Transferx0202166#N/AFALSE
1663
jacs.1c0066610.1021/jacs.1c00666FALSEhttps://doi.org/10.1021/jacs.1c00666Zhang, TJ. Am. Chem. Soc.Electrically activated soft actuators capable of large deformation are powerful and broadly applicable in multiple fields. However, designing soft actuators that can withstand a high strain, provide a large actuation displacement, and exhibit stable reversibility are still the main challenges toward their practical application. Here, for the first time, we report a two-dimensional (2D) conductive metal-organic framework (MOF) based electrochemical actuator, which consists of vertically oriented and hierarchical Ni-CAT NWAs/CNF electrodes through the use of a facile one-step in situ hydrothermal growth method. The soft actuator prepared in this study demonstrated improvements in actuation performance and benefits from both the intrinsically ordered porous architecture and efficient transfer pathways for fast ion and electron transport; furthermore, this actuator facilitated a considerably high diffusion rate and low interfacial resistance. In particular, the actuator demonstrated a rapid response (<19 s) at a 3 V DC input, large actuation displacement (12.1 mm), and a correspondingly high strain of 0.36% under a square-wave AC voltage of +/- 3 V. Specifically, the actuator achieved a broad-band frequency response (0.1-20 Hz) and long-term cyClability in air (10000 cyCles) with a negligible degradation in actuation performance. Our work demonstrates new opportunities for bioinspired artificial actuators and overcomes current limitations in electrode materials for soft rB(OH)2tics and bionics.Soft Electrochemical Actuators with a Two-Dimensional Conductive Metal-Organic Framework Nanowire Arrayx1202159#N/AFALSE
1664
jacs.1c0065910.1021/jacs.1c00659FALSEhttps://doi.org/10.1021/jacs.1c00659Gryko, DJ. Am. Chem. Soc.Ring-opening of epoxides furnishing either linear or branched products belongs to the group of Classic transformations in organic synthesis. However, the regioselective cross-electrophile coupling of Aryl epoxides with Aryl halides still represents a key challenge. Herein, we report that the vitamin B-12/Ni dual-catalytic system allows for the selective synthesis of linear products under blue-light irradiation, thus complementing methodologies that give access to branched alcohols. Experimental and theoretical studies corrB(OH)2rate the proposed mechanism involving Alkylcobalamin as an intermediate in this reaction.Cobalt Catalyst Determines Regioselectivity in Ring Opening of Epoxides with Aryl Halidesx0202154#N/AFALSE
1665
jacs.1c0061810.1021/jacs.1c00618https://doi.org/10.1021/jacs.1c00618Zuo, ZWJ. Am. Chem. Soc.Under mild reaction conditions with inexpensive cerium and nickel catalysts, easily accessible free alcohols can now be utilized as operationally simple and robust carbon pronuCleophiles in selective C(sp(3))-C(sp(2)) cross-couplings. Facilitated by automated high-throughput experimentation, sterically encumbered benzoate ligands have been identified for robust cerium complexes, enabling the synergistic cooperation of cerium catalysis in the emerging metallaphotoredox catalysis. A broad range of free alcohols and aromatic halides can be facilely employed in this transformation, representing a new paradigm for the C(sp(3))-C(sp(2)) bond construction between free alcohols and Aryl halides with the extrusion of formaldehyde. Moreover, mechanistic investigations have been conducted, leading to the identification of a tribenzoate cerium(III) complex as a viable intermediate.Photocatalytic Dehydroxymethylative Arylation by Synergistic Cerium and Nickel CatalysisPhotocatalyst5202171#N/AFALSE
1666
jacs.1c0056610.1021/jacs.1c00566https://doi.org/10.1021/jacs.1c00566Agapie, TJ. Am. Chem. Soc.The efficient copolymerization of acrylates with ethylene using Ni catalysts remains a challenge. Herein, we report two neutral Ni(II) catalysts (POP-Ni-py (1) and PONap-Ni-py (2)) that exhibit high thermal stability and significantly higher incorporation of polar monomer (for 1) or improved resistance to tert-butylacrylate (tBA)-induced chain transfer (for 2), in comparison to previously reported catalysts. Nickel Alkyl complexes generated after tBA insertion, POP-Ni-CCO(py) (3) and PONap-Ni-CCO(py) (4), were isolated and, for the first time, characterized by crystallography. Weakened lutidine vs pyridine coordination in 2-lut facilitated the isolation of a N-donor-free adduct after acrylate insertion PONap-Ni-CCO (5) which represents a novel example of a four-membered chelate relevant to acrylate polymerization catalysis. Experimental kinetic studies of six cases of monomer insertion with aforementioned nickel complexes indicate that pyridine dissociation and monomer coordination are fast relative to monomer migratory insertion and that monomer enchainment after tBA insertion is the rate limiting step of copolymerization. Further evaluation of monomer insertion using density functional theory studies identified a cis-trans isomerization via Berry-pseudorotation involving one of the pendant ether groups as the rate-limiting step for propagation, in the absence of a polar group at the chain end. The energy profiles for ethylene and tBA enchainments are in qualitative agreement with experimental measurements.Efficient Copolymerization of Acrylate and Ethylene with Neutral P, O-Chelated Nickel Catalysts: Mechanistic Investigations of Monomer Insertion and Chelate Formationx1202166#N/AFALSE
1667
jacs.1c0052910.1021/jacs.1c00529FALSEhttps://doi.org/10.1021/jacs.1c00529Morandi, BJ. Am. Chem. Soc.We describe a new functional group metathesis between Aryl nitrites and Aryl thioethers. The catalytic system nickel/ dcype is essential to achieve this fully reversible transformation in good to excellent yields. Furthermore, the cyanide- and thiol-free reaction shows high functional group tolerance and great efficiency for the late-stage derivatization of commercial molecules. Finally, synthetic applications demonstrate its versatility and utility in multistep synthesis.Nickel-Catalyzed Reversible Functional Group Metathesis between Aryl Nitriles and Aryl Thioethersx3202159#N/AFALSE
1668
jacs.1c0441910.1021/jacs.1c04419FALSEhttps://doi.org/10.1021/jacs.1c04419Scheschkewitz, DTransition-Metal Complexes of Heavier CyClopropenes: Non-Dewar-Chatt-Duncanson Coordination and Facile Si = Ge Functionalization2021#N/ATRUE
1669
jacs.1c0433910.1021/jacs.1c04339FALSEhttps://doi.org/10.1021/jacs.1c04339Yang, YJ. Am. Chem. Soc.Fine-tuning the exposed active sites of platinum group metal (PGM)-based materials is an efficient way to improve their electrocatalytic performance toward large-scale applications in renewable energy devices such as Zn-air batteries (ZABs). However, traditional synthetic methods trade off durability for the high activity of PGM-based catalysts. Herein, a novel dynamic CO2-bubble template (DCBT) approach was established to electrochemically fine-tuning the exposed Pt active sites in PtFeNi (PFN) porous films (PFs). Particularly, CO2 bubbles were intentionally generated as gas-phase templates by methanol electrooxidation. The generation, adsorption, residing, and desorption of CO2 bubbles on the surface of PFN alloys were explored and controlled by adjusting the frequency of applied triangular-wave voltage. Thereby, the surface morphology and Pt exposure of PFN PFs were controllably regulated by tuning the surface coverage of CO2 bubbles. Consequently, the Pt1.1%Fe8.8%Ni PF with homogeneous nanoporous structure and sufficiently exposed Pt active sites was obtained, showing preeminent activities with a half-wave potential (E-1/2) of 0.87 V and onset overpotential (eta(onset)) of 288 mV at 10 mA cm(-2) for oxygen reduction and evolution reactions (ORR and OER), respectively, at an ultralow Pt loading of 0.01 mg cm(-2). When tested in ZABs, a high power density of 175.0 mW cm(-2) and a narrow voltage gap of 0.64 V were achieved for the long cyCling tests over 500 h (750 cyCles), indicating that the proposed approach can efficiently improve the activity of PGM catalysts by fine-tuning the microstructure without compromising the durability.CO2 Bubble-Assisted Pt Exposure in PtFeNi Porous Film for High-Performance Zinc-Air Battery0202139#N/ATRUE
1670
jacs.0c1342710.1021/jacs.0c13427FALSEhttps://doi.org/10.1021/jacs.0c13427Dai, HJJ. Am. Chem. Soc.Reducing CO2 to value-added multicarbon (C2+) fuels and chemicals using renewable energy is a viable way to circumvent CO2 buildup in the atmosphere and facilitate Closing the carbon cyCle. To date it remains a challenge to achieve high product selectivity and long-term stability of electrocatalytic carbon dioxide reduction reaction (CO2RR) especially at practically relevant high current levels >100 mA cm(-2). Here, we report a simple electrodeposited Cu electrocatalyst on a hydrophobic porous gas-diffusion layer (GDL) electrode affording stable and selective CO2RR to C2+ products in nearneutral KCI electrolytes. By directing the CO, stream to fully submerged hydrophobic GDLs in a H-cell, high C2+ partial current densities near 100 mA cm(-2) were achieved. In a flow-cell setup, the Cu/GDL cathode in 2 M KCl afforded stable CO2RR superior to that in widely used KOH electrolytes. We found that Cu etching/corrosion associated with trace oxygen played a role in the catalyst instability in alkaline media under cathodic CO2 RR conditions, a problem largely suppressed in near-neutral electrolyte. A two-electrode CO2 electrolyzer was constructed with a Cu/GDL cathode in KCI catholyte and an anode comprised of nickel-iron hydroxide on nickel foam (NiFe/NF) in a KOH anolyte separated by Nafion membrane. By periodically adding HCl to the KCl catholyte to compensate the increasing pH and remove accumulated (bi)carbonates, we observed little decay over similar to 30 h in flow-cell CO2RR activity and selectivity at 150 mA cm(-2) with a high Faradaic efficiency (FE) of similar to 75% and energy efficiency of 40% for C2+ products.Selective and High Current CO2 Electro-Reduction to Multicarbon Products in Near-Neutral KCl Electrolytesx2202173#N/AFALSE
1671
jacs.0c1309310.1021/jacs.0c13093TRUEhttps://doi.org/10.1021/jacs.0c13093Li, CJ. Am. Chem. Soc.As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C-C bonds. Here, we demonstrate that the combination of anodic preparation of the alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive crosscoupling provides an efficient method to construct C(sp(2))-C(sp(3)) bonds, in which free alcohols and Aryl bromides-both readily available chemicals.can be directly used as coupling partners. This nickel-catalyzed paired electrolysis reaction features a broad substrate scope bearing a wide gamut of functionalities, which was illustrated by the late-stage Arylation of several structurally complex natural products and pharmaceuticals.Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl HalidesElectrochemistryCsp3-Csp2_arOHBrAlkyl#N/ANo Base520211023/10/2022FALSE
1672
jacs.0c1307710.1021/jacs.0c13077https://doi.org/10.1021/jacs.0c13077Molander, GAJ. Am. Chem. Soc.Alkenes, ethers, and alcohols account for a significant percentage of bulk reagents available to the chemistry community. The petrochemical, pharmaceutical, and agrochemical industries each consume gigagrams of these materials as fuels and solvents each year. However, the utilization of such materials as building blocks for the construction of complex small molecules is limited by the necessity of prefunctionalization to achieve chemoselective reactivity. Herein, we report the implementation of efficient, sustainable, diAryl ketone hydrogen-atom transfer (HAT) catalysis to activate native C-H bonds for multicomponent dicarbofunctionalization of alkenes. The ability to forge new carbon-carbon bonds between reagents typically viewed as commodity solvents provides a new, more atom-economic outlook for organic synthesis. Through detailed experimental and computational investigation, the critical effect of hydrogen bonding on the reactivity of this transformation was uncovered.Photochemical C-H Activation Enables Nickel-Catalyzed Olefin DicarbofunctionalizationPhotocatalyst4202148#N/AFALSE
1673
jacs.1c0426910.1021/jacs.1c04269FALSEhttps://doi.org/10.1021/jacs.1c04269Chapman, KWJ. Am. Chem. Soc.Understanding and controlling nanomaterial structure, chemistry, and defects represents a synthetic and characterization challenge. Metal-organic frameworks (MOFs) have recently been explored as unconventional precursors from which to prepare nanomaterials. Here we use in situ X-ray pair distribution function analysis to probe the mechanism through which MOFs transform into nanomaterials during pyrolysis. By comparing a series of bimetallic MOFs with trimeric node different compositions (Fe-3, Fe2Co, and Fe2Ni) linked by Carbonylate ligands in a PCN-250 lattice, we demonstrate that the resulting nanopartiCle structure, chemistry, and defect concentration depend on the node chemistry of the original MOF. These results suggest that the preorganized structure and chemistry of the MOF offer new potential control over the nanomaterial synthesis under mild reaction conditions. In the case of Fe2Ni-PCN-250, selective extraction of one Ni ion from each node without collapsing the framework (i.e., node-ligand connectivity) leaves a metal-deficient MOF state that may provide a new route to post-synthetically tune the chemistry the MOF and subsequent nanomaterials.Mechanistic Insights into NanopartiCle Formation from Bimetallic Metal-Organic Frameworks0202126#N/ATRUE
1674
jacs.0c1275510.1021/jacs.0c12755FALSEhttps://doi.org/10.1021/jacs.0c12755Li, JFJ. Am. Chem. Soc.PtNi alloy catalysts have excellent catalytic activity and are considered some of the most promising electrocatalysts capable of replacing pure Pt for the oxygen reduction reaction (ORR). For PtNi alloys, Ni-doping can improve performance by changing the electronic and structural properties of the catalyst surface and its interaction with reaction intermediates. However, to date there is no direct spectral evidence detecting or identifying the effect of Ni on the ORR in PtNi alloy catalysts. Herein, we introduce a surface-enhanced Raman spectroscopic (SERS) borrowing strategy for investigating ORR processes catalyzed by Au@PtNi nanopartiCles (NPs). The bond vibration of adsorbed peroxide intermediate species (*OOH) was obtained, and the effect of Ni on the interaction between surface Pt and *OOH was studied by varying the Ni content in the alloy. The frequency of the *OOH spectral band has an obvious red-shift with increasing Ni content. Combined with density functional theory (DFT) calculations, we show that Ni-doping can optimize *OOH surface binding on the Pt surface, achieving more efficient electron transfer, thus improving the ORR rate. Notably, these results evidence the SERS borrowing strategy as an effective technique for in situ observations of catalytic processes.Molecular Insight of the Critical Role of Ni in Pt-Based Nanocatalysts for Improving the Oxygen Reduction Reaction Probed Using an In Situ SERS Borrowing Strategyx3202125#N/AFALSE
1675
jacs.1c0407710.1021/jacs.1c04077FALSEhttps://doi.org/10.1021/jacs.1c04077Nie, ZRA Practice of Reticular Chemistry: Construction of a Robust Mesoporous Palladium Metal-Organic Framework via Metal Metathesis2021#N/ATRUE
1676
jacs.0c1251610.1021/jacs.0c12516FALSEhttps://doi.org/10.1021/jacs.0c12516Singleton, JControlling Magnetic Anisotropy in a Zero-Dimensional S=1 Magnet Using Isotropic Cation Substitutionx2021#N/AFALSE
1677
jacs.0c1244910.1021/jacs.0c12449FALSEhttps://doi.org/10.1021/jacs.0c12449Wei, QSelf-Luminescent Lanthanide Metal-Organic Frameworks as Signal Probes in Electrochemiluminescence Immunoassayx2021#N/AFALSE
1678
jacs.1c0390310.1021/jacs.1c03903FALSEhttps://doi.org/10.1021/jacs.1c03903Fu, GCJ. Am. Chem. Soc.Interest in unnatural alpha-amino acids has increased rapidly in recent years in areas ranging from protein design to medicinal chemistry to materials science. Consequently, the development of efficient, versatile, and straightforward methods for their enantioselective synthesis is an important objective in reaction development. In this report, we establish that a chiral catalyst based on nickel, an earth-abundant metal, can achieve the enantioconvergent coupling of readily available racemic Alkyl electrophiles with a wide variety of Alkylzinc reagents (1:1.1 ratio) to afford protected unnatural alpha-amino acids in good yield and ee. This cross-coupling, which proceeds under mild conditions and is tolerant of air, moisture, and a broad array of functional groups, complements earlier approaches to the catalytic asymmetric synthesis of this valuable family of molecules. We have applied our new method to the generation of several enantioenriched unnatural alpha-amino acids that have previously been shown to serve as useful intermediates in the synthesis of bioactive compounds.Asymmetric Synthesis of Protected Unnatural alpha-Amino Acids via Enantioconvergent Nickel-Catalyzed Cross-Coupling0202135#N/ATRUE
1679
jacs.0c1193710.1021/jacs.0c11937https://doi.org/10.1021/jacs.0c11937Nocera, DGJ. Am. Chem. Soc.Photoredox-mediated nickel-catalyzed cross-couplings have evolved as a new effective strategy to forge carbon- heteroatom bonds that are difficult to access with traditional methods. Experimental mechanistic studies are challenging because these reactions involve multiple highly reactive intermediates and perplexing reaction pathways, engendering competing, but unverified, proposals for substrate conversions. Here, we report a comprehensive mechanistic study of photoredox nickel-catalyzed C-S cross-coupling based on time-resolved transient absorption spectroscopy, Stern-Volmer quenching, and quantum yield measurements. We have (i) discovered a self-sustained productive Ni(I/III) cyCle leading to a quantum yield Phi > 1; (ii) found that pyridinium iodide, formed in situ, serves as the dominant quencher for the excited state photocatalyst and a critical redox mediator to facilitate the formation of the active Ni(I) catalyst; and (iii) observed critical intermediates and determined the rate constants associated with their reactivity. Not only do the findings reveal a complete reaction cyCle for C-S cross-coupling, but the mechanistic insights have also allowed for the reaction efficiency to be optimized and the substrate scope to be expanded from Aryl iodides to inClude Aryl bromides, thus broadening the applicability of photoredox C-S cross-coupling chemistry.Photoredox Nickel-Catalyzed C-S Cross-Coupling: Mechanism, Kinetics, and GeneralizationPhotocatalyst5202164#N/AFALSE
1680
jacs.0c1189410.1021/jacs.0c11894FALSEhttps://doi.org/10.1021/jacs.0c11894de Alaniz, JRJ. Am. Chem. Soc.Self-healing polymer electrolytes are reported with light-switchable conductivity based on dynamic N-donor ligand-containing diArylethene (DAE) and multivalent Ni2+ metal-ion coordination. Specifically, a polystyrene polymer grafted with poly(ethylene glycol-r-DAE)acrylate copolymer side chains was effectively cross-linked with nickel(II) bis(trifluoromethanesulfonimide) (Ni(TFSI)(2)) salts to form a dynamic network capable of self-healing with fast exchange kinetics under mild conditions. Furthermore, as a photoswitching compound, the DAE undergoes a reversible structural and electronic rearrangement that changes the binding strength of the DAE-Ni2+ complex under irradiation. This can be observed in the DAE-containing polymer electrolyte where irradiation with UV light triggers an increase in the resistance of solid films, which can be recovered with subsequent visible light irradiation. The increase in resistance under UV light irradiation indicates a decrease in ion mobility after photoswitching, which is consistent with the stronger binding strength of ring-Closed DAE isomers with Ni2+. H-1-N-15 heteronuClear multiple-bond correlation nuClear magnetic resonance (HMBC NMR) spectroscopy, continuous wave electron paramagnetic resonance (cw EPR) spectroscopy, and density functional theory (DFT) calculations confirm the increase in binding strength between ring-Closed DAE with metals. Rheological and in situ ion conductivity measurements show that these polymer electrolytes efficiently heal to recover their mechanical properties and ion conductivity after damage, illustrating potential applications in smart electronics.Light-Switchable and Self-Healable Polymer Electrolytes Based on Dynamic DiArylethene and Metal-Ion Coordinationx2202150#N/AFALSE
1681
jacs.0c1130710.1021/jacs.0c11307FALSEhttps://doi.org/10.1021/jacs.0c11307Gong, MJ. Am. Chem. Soc.NiFe oxyhydroxide is one of the most promising oxygen evolution reaction (OER) catalysts for renewable hydrogen production, and deciphering the identity and reactivity of the oxygen intermediates on its surface is a key challenge but is critical to the catalyst design for improving the energy efficiency. Here, we screened and utilized in situ reactive probes that can selectively target specific oxygen intermediates with high rates to investigate the OER intermediates and pathway on NiFe oxyhydroxide. Most importantly, the oxygen atom transfer (OAT) probes (e.g., 4-(diphenylphosphino) benzoic acid) could efficiently inhibit the OER kinetics by scavenging the OER intermediates, exhibiting lower OER currents, larger Tafel slopes, and larger kinetic isotope effect (KIE) values, while probes with other reactivities demonstrated much smaller effects. Combining the OAT reactivity with electrochemical kinetic and operando Raman spectroscopic techniques, we identified a resting Fe=O intermediate in the Ni-O scaffold and a rate-limiting O-O chemical coupling step between a Fe=O moiety and a vicinal bridging O. DFT calculation further revealed a longer Fe=O bond formed on the surface and a large kinetic energy barrier of the O-O chemical coupling step, corrB(OH)2rating the experimental results. These results point to a new direction of liberating lattice O and expediting O-O coupling for optimizing NiFe-based OER electrocatalyst.Recognition of Surface Oxygen Intermediates on NiFe Oxyhydroxide Oxygen-Evolving Catalysts by Homogeneous Oxidation Reactivityx3202148#N/AFALSE
1682
jacs.1c0382710.1021/jacs.1c03827FALSEhttps://doi.org/10.1021/jacs.1c03827Kong, WQJ. Am. Chem. Soc.Transition-metal-catalyzed dicarbofunctionalization of alkenes involving intramolecular Heck cyClization followed by intermolecular cross-coupling has emerged as a powerful engine for building heterocyCles with sterically congested quaternary carbon centers. However, only exo-cyClization/cross-coupling products can be obtained; endo-selective cyClization/cross-coupling has not been reported yet and still poses a formidable challenge. We herein report the first example of catalyst-controlled dicarbofunctionalization of alkenes for the regiodivergent synthesis of five- and six-membered benzo-fused lactams bearing all-carbon quaternary centers. Using a chiral Pyrox- or Phox-type bidentate ligand, 5-exo cyClization/cross-couplings proceed favorably to produce indole-2-ones in good yields with excellent regioselectivity and enantioselectivities (up to 98% ee). When C6-Carbonylic acid-modified 2,2'-bipyridine was used as the ligand, 3,4-dihydroquinolin-2-ones were obtained in good yields through 6-endo-selective cyClization/cross-coupling processes. This transformation is modular and tolerant of a variety of functional groups. The ligand rather than the substrate structures precisely dictates the regioselectivity pattern. Moreover, the synthetic value of this regiodivergent protocol was demonstrated by the preparation of biologically relevant molecules and structural scaffolds.Ni-Catalyzed Ligand-Controlled Regiodivergent Reductive Dicarbofunctionalization of Alkenes0202192#N/ATRUE
1683
jacs.1c0356310.1021/jacs.1c03563FALSEhttps://doi.org/10.1021/jacs.1c03563Ngai, MYJ. Am. Chem. Soc.Nickel catalysis offers exciting opportunities to address unmet challenges in organic synthesis. Herein we report the first nickel-catalyzed radical migratory cross-coupling reaction for the direct preparation of 2-Aryl-2-deoxyglycosides from readily available 1-bromosugars and Arylboronic acids. The reaction features a broad substrate scope and tolerates a wide range of functional groups and complex molecular architectures. Preliminary experimental and computational studies suggest a concerted 1,2-acyloxy rearrangement via a cyClic five-membered-ring transition state followed by nickel-catalyzed carbon-carbon bond formation. The novel reactivity provides an efficient route to valuable C-2-Arylated carbohydrate mimics and building blocks, allows for new strategic bond disconnections, and expands the reactivity profile of nickel catalysis.Nickel-Catalyzed Radical Migratory Coupling Enables C-2 Arylation of Carbohydrates0202177#N/ATRUE
1684
jacs.0c1116110.1021/jacs.0c11161FALSEhttps://doi.org/10.1021/jacs.0c11161Radosevich, ATJ. Am. Chem. Soc.Insertion of a tricoordinate phosphorus ligand into late metal-carbon bonds is reported. Metalation of a P<^>P-chelating ligand (L1), composed of a nontrigonal phosphorous (i.e., P(III)) triamide moiety, P(N(o-N(Ar)C6H4)(2), tethered by a phenylene linker to a -PiPr(2) anchor, with group 10 complexes L2M(Me)Cl (M = Ni, Pd) results in insertion of the nontrigonal phosphorus site into the metal-methyl bond. The stable methylmetallophosphorane compounds thus formed are characterized spectroscopically and crystallographically. Metalation of L1 with (cod)Pt-II(Me)(Cl) does not lead to a metallophosphorane but rather to the standard bisphosphine chelate (kappa(2) -L1)Pt(Me)(Cl). These divergent reactivities within group 10 are rationalized by reference to periodic variation in M-C bond enthalpies.Enthalpy-Controlled Insertion of a Nonspectator Tricoordinate Phosphorus Ligand into Group 10 Transition Metal-Carbon Bondsx1202099#N/AFALSE
1685
jacs.1c0181010.1021/jacs.1c01810FALSEhttps://doi.org/10.1021/jacs.1c01810Gunnoe, TBJ. Am. Chem. Soc.On a large scale, the dominant method to produce Alkyl arenes has been arene Alkylation from arenes and olefins using acid-based catalysis. The addition of arene C-H bonds across olefin C=C bonds catalyzed by transition-metal complexes through C-H Activation and olefin insertion into metal-Aryl bonds provides an alternative approach with potential advantages. This Perspective presents recent developments of olefin hydroArylation and oxidative olefin hydroArylation catalyzed by molecular complexes based on group 10 transition metals (Ni, Pd, Pt). Emphasis is placed on comparisons between Pt catalysts and other group 10 metal catalysts as well as Ru, Ir, and Rh catalysts.Advances in Group 10 Transition-Metal-Catalyzed Arene Alkylation and Alkenylation32021108#N/ATRUE
1686
jacs.1c0145410.1021/jacs.1c01454FALSEhttps://doi.org/10.1021/jacs.1c01454Strotman, NAJ. Am. Chem. Soc.A facile one-pot strategy for (CN)-C-13 and (CN)-C-14 exchange with Aryl, heteroAryl, and alkenyl nitriles using a Ni phosphine catalyst and BPh3 is described. This late-stage carbon isotope exchange (CIE) strategy employs labeled Zn(CN)(2) to facilitate enrichment using the nonlabeled parent compound as the starting material, eliminating de novo synthesis for precursor development. A broad substrate scope encompassing multiple pharmaceuticals is disClosed, inCluding the preparation of [C-14] belzutifan to illustrate the exceptional functional group tolerance and utility of this labeling approach. Preliminary experimental and computational studies suggest the Lewis acid BPh3 is not critical for the oxidative addition step and instead plays a role in facilitating CN exchange on Ni. This CIE method dramatically reduces the synthetic steps and radioactive waste involved in preparation of C-14 labeled tracers for Clinical development.Late-Stage Carbon Isotope Exchange of Aryl Nitriles through Ni-Catalyzed C-CN Bond Activation0202138#N/ATRUE
1687
jacs.0c1092410.1021/jacs.0c10924FALSEhttps://doi.org/10.1021/jacs.0c10924Choi, KSJ. Am. Chem. Soc.Selective oxidation of alcohols to their corresponding aldehyde or Carbonylic acid is one of the most important Classes of organic synthesis reactions. In addition, electrochemical alcohol oxidation is considered a viable anode reaction that can be paired with H-2 evolution or other reductive fuel production reactions in electrochemical and photoelectrochemical cells. NiOOH, a material that has been extensively studied as an oxygen evolution catalyst, is among the most promising electrocatalysts for selective alcohol oxidation. Electrochemical alcohol oxidation by NiOOH has been understood since the 1970s to proceed through a hydrogen atom transfer to NiOOH. In this study, we establish that there is a second, more dominant general alcohol oxidation pathway on NiOOH enabled at more positive potentials. Using a three-step electrochemical procedure we developed, we deconvoluted the currents corresponding to these two pathways for various alcohols and aldehydes. The results show that alcohols and aldehydes have a distinct difference in their respective preferences for the two oxidation pathways. Our three-step electrochemical procedure also allowed us to evaluate the Ni valence involved with the different oxidation pathways to elucidate their mechanistic differences. Using these experimental results coupled with a computational investigation, we propose that the new pathway entails hydride transfer from the substrate to Ni4+ sites in NiOOH. This study offers an essential foundation to understand various oxidative electrochemical dehydrogenation reactions on oxide and hydroxide-based catalytic electrodes.Unraveling Two Pathways for Electrochemical Alcohol and Aldehyde Oxidation on NiOOHx5202038#N/AFALSE
1688
jacs.0c1088210.1021/jacs.0c10882https://doi.org/10.1021/jacs.0c10882Wang, JYJ. Am. Chem. Soc.Devising artificial photoenzymes for abiological bond-forming reactions is of high synthetic value but also a tremendous challenge. DisClosed herein is the first photobiocatalytic cross-coupling of Aryl halides enabled by a designer artificial dehalogenase, which features a genetically encoded benzophenone chromophore and site-specifically modified synthetic Ni-II(bpy) cofactor with tunable proximity to streamline the dual catalysis. Transient absorption studies suggest the likelihood of energy transfer Activation in the elementary organometallic event. This design strategy is viable to significantly expand the catalytic repertoire of artificial photoenzymes for useful organic transformations.Biocatalytic Cross-Coupling of Aryl Halides with a Genetically Engineered Photosensitizer Artificial DehalogenasePhotocatalyst0202165#N/AFALSE
1689
jacs.1c0113810.1021/jacs.1c01138FALSEhttps://doi.org/10.1021/jacs.1c01138Chang, SMerging NiH Catalysis and Inner-Sphere Metal-Nitrenoid Transfer for Hydroamidation of Alkynes2021#N/ATRUE
1690
jacs.0c1066110.1021/jacs.0c10661FALSEhttps://doi.org/10.1021/jacs.0c10661Kim, JKJ. Am. Chem. Soc.Developing efficient and inexpensive electrocatalysts for the hydrogen evolution reaction (HER) in alkaline water electrolysis plays a key role for renewable hydrogen energy technology. The slow reaction kinetics of HER in alkaline solutions, however, has hampered advances in high-performance hydrogen production. Herein, we investigated the trends in HER activity with respect to the binding energies of Ni-based thin film catalysts by incorporating a series of oxophilic transition metal atoms. It was found that the doping of oxophilic atoms enables the modulation of binding abilities of hydrogen and hydroxyl ions on the Ni surfaces, leading to the first establishment of a volcano relation between OH-binding energies and alkaline HER activities. In particular, Cr-incorporated Ni catalyst shows optimized OH-binding as well as H-binding energies for facilitating water dissociation and improving HER activity in alkaline media. Further enhancement of catalytic performance was achieved by introducing an array of three-dimensional (3D) Ni nanohelixes (NHs) that provide abundant surface active sites and effective channels for charge transfer and mass transport. The Cr dopants incorporated into the Ni NHs accelerate the dissociative adsorption process of water, resulting in remarkably enhanced catalytic activities in alkaline medium. Our approach can provide a rational design strategy and experimental methodology toward efficient bimetallic electrocatalysts for alkaline HER using earth-abundant elements.Tailoring Binding Abilities by Incorporating Oxophilic Transition Metals on 3D Nanostructured Ni Arrays for Accelerated Alkaline Hydrogen Evolution Reactionx4202187#N/AFALSE
1691
jacs.1c0109710.1021/jacs.1c01097FALSEhttps://doi.org/10.1021/jacs.1c01097Tsang, SCEJ. Am. Chem. Soc.Transition metal doped chalcogenides are one of the most important Classes of catalysts that have been attracting increasing attention for petrochemical and energy related chemical transformations due to their unique physiochemical properties. For practical applications, achieving maximum atom utilization by homogeneous dispersion of metals on the surface of chalcogenides is essential. Herein, we report a detailed study of a deposition method using thiourea coordinated transition metal complexes. This method allows the preparation of a library of a wide range of single atoms inCluding both noble and non-noble transition metals (Fe, Co, Ni, Cu, Pt, Pd, Ru) with a metal loading as high as 10 wt % on various ultrathin 2D chalcogenides (MoS2, MoSe2, WS2 and WSe2). As demonstrated by the state-of-the-art characterization, the doped single transition metal atoms interact strongly with surface anions and anion vacancies in the exfoliated 2D materials, leading to high metal dispersion in the absence of agglomeration. Taking Fe on MoS2 as a benchmark, it has been found that Fe is atomically dispersed until 10 wt %, and beyond this loading, formation of coplanar Fe Clusters is evident. Atomic Fe, with a high electron density at its conduction band, exhibits a superior intrinsic activity and stability in CO2 hydrogenation to CO per Fe compared to corresponding surface Fe Clusters and other Fe catalysts reported for reverse water-gas-shift reactions.High Loading of Transition Metal Single Atoms on Chalcogenide Catalysts2202157#N/ATRUE
1692
jacs.1c0044010.1021/jacs.1c00440FALSEhttps://doi.org/10.1021/jacs.1c00440Diao, TNJ. Am. Chem. Soc.Low-valent organonickel radical complexes are common intermediates in cross-coupling reactions and metalloenzyme-mediated processes. The electronic structures of N-ligand supported nickel complexes appear to vary depending on the actor ligands and the coordination number. The reduction products of a series of divalent (pyrox)Ni complexes establish the redox activity of pyrox in stabilizing electron-rich Ni(II)-Alkyl and -Aryl complexes by adopting a ligand-centered radical configuration. The reduced pyrox imparts an enhanced trans-influence. In contrast, such redox activity was not observed in a (pyrox)Ni(I)-bromide species. The excellent capability of pyrox in stabilizing electron-rich Ni species resonates with its proClivity in promoting the reductive Activation of C(sp(3)) electrophiles in cross-coupling reactions.Redox Activity of Pyridine-Oxazoline Ligands in the Stabilization of Low-Valent Organonickel Radical Complexes2202147#N/ATRUE
1693
jacs.1c0037710.1021/jacs.1c00377FALSEhttps://doi.org/10.1021/jacs.1c00377Goddard, WAJ. Am. Chem. Soc.Electrochemical conversion of light alkanes to high-value oxygenates provides an attractive avenue for eco-friendly utilization of these hydrocarbons. However, such conversion under ambient conditions remains exceptionally challenging due to the high energy barrier of C-H bond Cleavage. Herein, we investigated theoretically the partial oxidation of propane on a series of single atom alloys by using active intermediates generated during water oxidation as the oxidant. We show that by controlling the potential and pH, stable surface oxygen atoms can be maintained under water oxidation conditions. The free energy barrier for C-H bond Cleavage by the surface oxygen can be as small as 0.54 eV, which can be surmounted easily at room temperature. Our calculations identified three promising surfaces as effective propane oxidation catalysts. Our complementary experiments demonstrated the partial oxidation of propane to acetone on Ni-doped Au surfaces. We also investigated computationally the steps leading to acetone formation. These studies show that the concept of exploiting intermediates generated in water oxidation as oxidants provides a fruitful strategy for electrocatalyst design to efficiently convert hydrocarbons into value-added chemicals.Selective Activation of Propane Using Intermediates Generated during Water Oxidation0202164#N/ATRUE
1694
jacs.0c1001510.1021/jacs.0c10015FALSEhttps://doi.org/10.1021/jacs.0c10015Marks, TJJ. Am. Chem. Soc.A family of metal dichloride complexes having a bis-ferrocenyl-substituted pyridinediimine ligand was systematically synthesized ((Fc(2)PDI)MCl2, M = Mg, Zn, Fe, and Co) and characterized crystallographically, spectroscopically, electrochemically, and computationally. Electronic coupling between the ligand ferrocene units is switched on upon binding to a MCl2 fragment, as evidenced by both sequential oxidation of the ferrocenes in cyClic voltammetry (Delta E-ox approximate to 200 mV) and by Inter-Valence Charge Transfer electronic excitations in the near IR. Additionally, UV-vis spectra are used to directly observe orbital mixing between the ferrocenyl units and the imine pi system since breaking of the orbital symmetry results in allowed transitions (c = 2800 M-1 cm(-1) vs c approximate to 200 M-1 cm(-1) in free ferrocene) as well as broadening and red-shifting of the ferrocenyl transitions-indicating organic character in formerly pure metal-centered transitions. DFT analysis reveals that interaction between the ferrocenes and the MCl2 fragment is small and suggests that communication is mediated by better energy matching between the ferrocene and organic pi* orbitals upon coordination, allowing superexchange coupling through the LUMO. Furthermore, single crystal diffraction data obtained from oxidation of one and both ferrocenes show distortions, introducing the empty d(xy)/d(x2-y2) orbitals into the secondary coordination sphere of the MCl2 fragment. Such structural rearrangements are infrequent in ferrocenyl mixedvalent compounds, and implications for catalysis as well as electronic communication are discussed.Bis-Ferrocenyl-Pyridinediimine TrinuClear Mixed-Valent Complexes with Metal-Binding Dependent Electronic Coupling: Synthesis, Structures, and Redox-Spectroscopic Characterizationx32020126#N/AFALSE
1695
jacs.0c1284310.1021/jacs.0c12843FALSEhttps://doi.org/10.1021/jacs.0c12843Watson, DAJ. Am. Chem. Soc.We report an asymmetric homocoupling of ortho-(iodo)Arylphosphine oxides and ortho-(iodo)Arylphosphonates resulting in highly enantioenriched axially chiral bisphosphine oxides and bisphosphonates. These products are readily converted to enantioenriched biAryl bisphosphines without need for chiral auxiliaries or optical resolution. This provides a practical route for the development of previously uninvestigated atroposelective biAryl bisphosphine ligands. The conditions have also proven effective for asymmetric dimerization of other, non-phosphorus-containing Aryl halides.Synthesis of Axially Chiral 2,2 '-Bisphosphobiarenes via a Nickel-Catalyzed Asymmetric Ullmann Coupling: General Access to Privileged Chiral Ligands without Optical Resolution3202157#N/ATRUE
1696
jacs.0c0983910.1021/jacs.0c09839FALSEhttps://doi.org/10.1021/jacs.0c09839Betley, TAJ. Am. Chem. Soc.The trityl-substituted bisoxazoline ((box)-B-TrH) was prepared as a chiral analogue to a previously reported nickel dipyrrin system capable of ring-Closing amination catalysis. Ligand metalation with divalent NiI2(py)(4) followed by potassium graphite reduction afforded the monovalent ((box)-B-TrH)Ni(py) (4). Slow addition of 1.4 equiv of a benzene solution of 1-adamantylazide to 4 generated the tetrazido ((box)-B-TrH)Ni (kappa(2)-N(4)Ad(2)) (5) and terminal iminyl adduct ((box)-B-TrH)Ni(NAd) (6). Investigation of 6 via single-crystal X-ray crystallography, NMR and EPR spectroscopies, and computations revealed a Ni(II)-iminyl radical formulation, similar to its dipyrrinato congener. Complex 4 exhibits enantioselective intramolecular C-H bond amination to afford N-heterocyClic products from 4-Aryl-2-methyl-2-azidopentanes. Catalytic C-H amination occurs under mild conditions (5 mol % catalyst, 60 degrees C) and provides pyrrolidine products in decent yield (29%-87%) with moderate ee (up to 73%). Substrates with a 3,5-diAlkyl substitution on the 4-Aryl position maximized the observed enantioselectivity. Kinetic studies to probe the reaction mechanism were conducted using H-1 and F-19 NMR spectroscopies. A small, intermolecular kinetic isotope effect (1.35 +/- 0.03) suggests an H-atom abstraction step with an asymmetric transition state while the reaction rate is measured to be first order in catalyst and zeroth order in substrate concentrations. Enantiospecific deuterium labeling studies show that the enantioselectivity is dictated by both the H-atom abstraction and radical recombination steps due to the comparable rate between radical rotation and C-N bond formation. Furthermore, the competing elements of the two-step reaction where H-removal from the pro-R configuration is preferred while the preferential radical capture occurs with the Si face of the carboradical likely lead to the diminished ee observed, as corrB(OH)2rated by theoretical calculations. Based on these enantio-determining steps, catalytic enantioselective synthesis of 2,5-bis-tertiary pyrrolidines is demonstrated with good yield (50-78%) and moderate ee ( up to 79%).Enantioselective C-H Amination Catalyzed by Nickel Iminyl Complexes Supported by Anionic Bisoxazoline (box) Ligandsx4202192#N/AFALSE
1697
jacs.0c1256810.1021/jacs.0c12568FALSEhttps://doi.org/10.1021/jacs.0c12568Weber, BJ. Am. Chem. Soc.The response of the spin state to in situ variation of the coordination number (CISSS) is a promising and viable approach to smart sensor materials, yet it suffers to date from insensitive detection. Herein, we present the synthetic access to a family of planar nickel(II) complexes, whose CISSS is sensitively followed by means of fluorescence detection. For this purpose, nickel(II) complexes with four phenazine-based Schiff base-like ligands were synthesized and characterized through solution-phase spectroscopy (NMR and UV-vis), solid-state structure analysis (single-crystal XRD), and extended theoretical modeling. All of them reveal CISSS in solution through axial ligating a range of N- and O-donors. CISSS correlates nicely with the basicity of the axial ligand and the substitution-dependent acidity of the nickel(II) coordination site. Remarkably, three out of the four nickel(II) complexes are fluorescent in noncoordinating solvents but are fluorescence-silent in the presence of axial ligands such as pyridine. As these complexes are rare examples of fluorescent nickel(II) complexes, the photophysical properties with a coordination number of 4 were studied in detail, inCluding temperature-dependent lifetime and quantum yield determinations. Most importantly, fluorescence quenching upon adding axial ligands allows a black or white, i.e. digital, sensoring of spin state alternation. Our studies of fluorescence-detected CISSS (FD-CISSS) revealed that absorption-based CISSS and FD-CISSS are super proportional with respect to the pyridine concentration: FD-CISSS features a higher sensitivity. Overall, our findings indicate a favored ligation of these nickel(II) complexes in the excited state in comparison to the ground state.A Fluorescence-Detected Coordination-Induced Spin State Switch6202161#N/ATRUE
1698
jacs.0c1228210.1021/jacs.0c12282FALSEhttps://doi.org/10.1021/jacs.0c12282Zeng, JJ. Am. Chem. Soc.Hollow frame structures are of special interest in the realm of catalysis since they hold only ridges and hollow interiors, enabling the accessibility of active sites to the most extent. Herein, we prepared Pd-Pt hollow frame structures composed of double-shell cubes linked by body diagonals as an efficient catalyst toward the oxygen reduction reaction (ORR), inspired by the 4D analogue of a cube, denoted as a tesseract. The etching process involves the selective removal of Pd atoms and the subsequent rearrangement of the remaining Pd and Pt atoms. The successful preparation of Pd-Pt tesseracts via etching lies in the selection of Pd/Pt ratio in the initial Pd-Pt nanocubes. With various ratios of Pd-Pt nanocubes as templates, we obtained Pd-Pt octapods, tesseracts, and nanoframes, respectively. During the ORR, Pd-Pt tesseracts exhibited the highest mass activity of 1.86 A mg(Pt)(-1), among these Pd-Pt nanocrystals. On the basis of mechanistic studies, the high activity of Pd-Pt tesseracts derived from the optimal oxygen adsorption energy due to the facet effect and composition effect.Pd-Pt Tesseracts for the Oxygen Reduction Reaction6202124#N/ATRUE
1699
jacs.0c1128510.1021/jacs.0c11285FALSEhttps://doi.org/10.1021/jacs.0c11285Ma, DJ. Am. Chem. Soc.We report the syntheses of highly dispersed CoNi bimetallic catalysts on the surface of alpha-MoC based on the strong metal support interaction (SMSI) effect. The interaction between the nearly atomically dispersed Co and Ni atoms was observed for the first time by the real-space chemical mapping at the atomic level. Combined with the ability of alpha-MoC to split water at low temperatures, the as-synthesized CoNi/alpha-MoC catalysts exhibited robust and synergistic performance for the hydrogen production from hydrolysis of ammonia borane. The metal-normalized activity of the bimetallic 1.5Co1.5Ni/alpha-MoC catalyst reached 321.1 mol(H2).mol(-1) (CoNi).min(-1) at 298 K, which surpasses all the noble metal-free catalysts ever reported and is four times higher than that of the commercial Pt/C catalyst.Maximizing the Synergistic Effect of CoNi Catalyst on alpha-MoC for Robust Hydrogen Production9202133#N/ATRUE
1700
jacs.0c1119510.1021/jacs.0c11195FALSEhttps://doi.org/10.1021/jacs.0c11195Mathey, FJ. Am. Chem. Soc.[1 + 2] cyCloaddition is a Classical reaction between the electrophilic phosphinidene and an alkene. However, a spatial constraint blocks this well-known reaction and enables an unprecedented chemoselective C(sp(2))-Ar sigma-bond insertion of the alkene. The theoretical calculations demonstrate that this C-C bond Cleavage is energetically feasible and thermodynamically favored through an electrophilic rearrangement and concomitant 1,9-Aryl migration without involving any strained intermediate.Cleavage of the Inert C(sp(2))-Ar sigma-Bond of Alkenes by a Spatial Constrained Interaction with Phosphinidene1202089#N/ATRUE
1701
jacs.0c0900910.1021/jacs.0c09009FALSEhttps://doi.org/10.1021/jacs.0c09009Zuo, JLJ. Am. Chem. Soc.Functionalizing the redox-active tetrathiafulvalene (TTF) core with groups capable of coordination to metals provides new perspectives on the modulation of architectures and electronic properties of organic-inorganic hybrid materials. With a view to extending this concept, we have now synthesized nickel bis(dithiolene-dibenzoic acid), [Ni(C2S2(C6H4COOH)(2))(2)], which can be considered as the inorganic analogue of the organic tetrathiafulvalene-tetrabenzoic acid (H4TTFTB). Likewise, [Ni(C2S2(C6H4COOH)(2))(2)] is a redox-active linker for new functional metal-organic frameworks, as demonstrated here with the synthesis of [Mn-2{Ni(C2S2(C6H4COO)(2))(2)}(H2O)(2)]center dot 2DMF, (1, DMF = N,N-dimethylformamide). 1 is isomorphic to the reported [Mn-2(TTFTB)(H2O)(2)] (2) but is a better electrochemical glucose sensor due to the multiple oxidation-reduction states of the [NiS4] core, which allow glucose to be oxidized to glucolactone by the high oxidation state [NiS4] center. As a non-enzymatic glucose sensor, 1 on Cu foam (CF), 1-CF, was synthesized by a one-step hydrothermal method and exhibited an excellent electrochemical performance. The fabricated 1-CF electrode offers a high sensitivity of 27.9 A M-1 cm(-2), with a wide linear detection range from 2.0 X 10(-6) to 2.0 X 10(-3) M, a low detection limit of 1.0 X 10(-7) M (signal/noise = 3), and satisfactory stability and reproducibility.A Metal-Organic Framework Based on a Nickel Bis(dithiolene) Connector: Synthesis, Crystal Structure, and Application as an Electrochemical Glucose Sensorx6202041#N/AFALSE
1702
jacs.0c1100810.1021/jacs.0c11008FALSEhttps://doi.org/10.1021/jacs.0c11008Choi, CHJ. Am. Chem. Soc.Electrocatalytic conversion of CO2 into value-added products offers a new paradigm for a sustainable carbon economy. For active CO2 electrolysis, the single-atom Ni catalyst has been proposed as promising from experiments, but an idealized Ni-N-4 site shows an unfavorable energetics from theory, leading to many debates on the chemical nature responsible for high activity. To resolve this conundrum, here we investigated CO2 electrolysis of Ni sites with well-defined coordination, tetraphenylporphyrin (N-4-TPP) and 21-oxatetraphenylporphyrin (N3O-TPP). Advanced spectroscopic and computational studies revealed that the broken ligand-field symmetry is the key for active CO2 electrolysis, which subordinates an increase in the Ni redox potential yielding Ni-I. Along with their importance in activity, ligand-field symmetry and strength are directly related to the stability of the Ni center. This suggests the next quest for an activity-stability map in the domain of ligand-field strength, toward a rational ligand-field engineering of single-atom Ni catalysts for efficient CO2 electrolysis.Identification of Single-Atom Ni Site Active toward Electrochemical CO2 Conversion to CO5202153#N/ATRUE
1703
jacs.0c0888610.1021/jacs.0c08886FALSEhttps://doi.org/10.1021/jacs.0c08886Tian, HNJ. Am. Chem. Soc.Surface states of mesoporous NiO semiconductor films have particular properties differing from the bulk and are able to dramatically influence the interfacial electron transfer and adsorption of chemical species. To achieve a better performance of NiO-based p-type dye-sensitized solar cells (p-DSCs), the function of the surface states has to be understood. In this paper, we applied a modified atomic layer deposition procedure that is able to passivate 72% of the surface states on NiO by depositing a monolayer of Al2O3. This provides us with representative control samples to study the functions of the surface states on NiO films. A main conClusion is that surface states, rather than the bulk, are mainly responsible for the conductivity in mesoporous NiO films. Furthermore, surface states significantly affect dye regeneration (with as redox couple) and hole transport in NiO-based p-DSCs. A new dye regeneration mechanism is proposed in which electrons are transferred from reduced dye molecules to intra-bandgap states, and then to I-3(-) species. The intrabandgap states here act as catalysts to assist I-3(-) reduction. A more complete mechanism is suggested to understand the particular hole transport behavior in p-DSCs, in which the hole transport time is independent of light intensity. This is ascribed to the percolation hole hopping on the surface states. When the concentration of surface states was significantly reduced, the light-independent charge transport behavior in pristine NiO-based p-DSCs transformed into having an exponential dependence on light intensity, similar to that observed in TiO2-based n-type DSCs. These conClusions on the function of surface states provide new insight into the electronic properties of mesoporous NiO films.Understanding the Role of Surface States on Mesoporous NiO Filmsx2202071#N/AFALSE
1704
jacs.0c1095810.1021/jacs.0c10958FALSEhttps://doi.org/10.1021/jacs.0c10958Anderson, JSJ. Am. Chem. Soc.High-valent transition metal-oxo, -peroxo, and -superoxo complexes are crucial intermediates in both biological and synthetic oxidation of organic substrates, water oxidation, and oxygen reduction. While high-valent oxygenated complexes of Mn, Fe, Co, and Cu are increasingly well-known, high-valent oxygenated Ni complexes are comparatively rarer. Herein we report the isolation of such an unusual high-valent species in a thermally unstable Ni-2(III)(mu-1,2-peroxo) complex, which has been characterized using single-crystal X-ray diffraction and X-ray absorption, NMR, and UV-vis spectroscopies. Reactivity studies show that this complex is stable toward dissociation of oxygen but reacts with simple nuCleophiles and electrophiles.Generation and Reactivity of a Ni-2(III)(mu-1,2-peroxo) Complex5202071#N/ATRUE
1705
jacs.0c1077610.1021/jacs.0c10776FALSEhttps://doi.org/10.1021/jacs.0c10776Ma, DJ. Am. Chem. Soc.Methanol-water reforming is a promising solution for H-2 production/transportation in stationary and mobile hydrogen applications. Developing inexpensive catalysts with sufficiently high activity, selectivity, and stability remains challenging. In this paper, nickel-supported over face-centered cubic (fcc) phase alpha-MoC has been discovered to exhibit extraordinary hydrogen production activity in the aqueous-phase methanol reforming reaction. Under optimized condition, the hydrogen production rate of 2% Ni/alpha-MoC is about 6 times higher than that of conventional noble metal 2% Pt/Al2O3 catalyst. We demonstrate that Ni is atomically dispersed over alpha-MoC via carbon bridge bonds, forming a Ni-1-C-x motif on the carbide surface. Such Ni-1-C-x motifs can effectively stabilize the isolated Ni-1 sites over the alpha-MoC substrate, rendering maximized active site density and high structural stability. In addition, the synergy between Ni-1-C-x motif and alpha-MoC produces an active interfacial structure for water dissociation, methanol Activation, and successive reforming processes with compatible activity.Atomically Dispersed Ni/alpha-MoC Catalyst for Hydrogen Production from Methanol/Water12202131#N/ATRUE
1706
jacs.0c0864110.1021/jacs.0c08641FALSEhttps://doi.org/10.1021/jacs.0c08641Delferro, MJ. Am. Chem. Soc.Various metal oxide Clusters upward of 8 atoms (Cu, Cd, Co, Fe, Ga, Mn, Mo, Ni, Sn, W, Zn, In, and Al) were incorporated into the pores of the metal-organic framework (MOF) NU-1000 via atomic layer deposition (ALD) and tested via high-throughput screening for catalytic isomerization and selective hydrogenation of propyne. Cu and Co were found to be the most active for propyne hydrogenation to propylene, and synergistic bimetallic combinations of Co and Zn, along with standalone Zn and Cd, were established as the most active for conversion to the isomerized product, propadiene. The combination of Co and Zn in NU-1000 diminished the propensity for full hydrogenation to propane as well as coking compared to its individual components. This study highlights the potential for high-throughput screening to survey monometallic and bimetallic Cluster combinations that best affect the efficient transformation of small molecules, while discerning mechanistic differences in isomerization and hydrogenation by different metals.Isomerization and Selective Hydrogenation of Propyne: Screening of Metal-Organic Frameworks Modified by Atomic Layer Depositionx1202045#N/AFALSE
1707
jacs.0c0846010.1021/jacs.0c08460FALSEhttps://doi.org/10.1021/jacs.0c08460Long, JRJ. Am. Chem. Soc.We present an extensive study of tetranuClear transition-metal Cluster compounds M-4((NPBu3)-Bu-t)(4) and [M-4((NPBu3)-Bu-t)(4)] [B(C6F5)(4)] (M = Ni, Cu; Bu-t = tert-butyl), which feature low-coordinate metal centers and direct metal-metal orbital overlap. X-ray diffraction, electrochemical, magnetic, spectroscopic, and computational analysis elucidate the nature of the bonding interactions in these Clusters and the impact of these interactions on the electronic and magnetic properties. Direct orbital overlap results in strongly coupled, large-spin ground states in the [Ni-4((NPBu3)-Bu-t)(4)](+/0) Clusters and fully delocalized, spincorrelated electrons. Correlated electronic structure calculations confirm the presence of ferromagnetic ground states that arise from direct exchange between magnetic orbitals, and, in the case of the neutral Cluster, itinerant electron magnetism similar to that in metallic ferromagnets. The cationic nickel Cluster also possesses large magnetic anisotropy exemplified by a large, positive axial zero- field splitting parameter of D = +7.95 or +9.2 cm(-1), as determined by magnetometry or electron paramagnetic resonance spectroscopy, respectively. The [Ni-4((NPBu3)-Bu-t)(4)](+) Cluster is also the first molecule with easy-plane magnetic anisotropy to exhibit zero-field slow magnetic relaxation, and under a small applied field, it exhibits relaxation exClusively through an Orbach mechanism with a spin relaxation barrier of 16 cm(-1). The S = 1/2 complex [Cu-4((NPBu3)-Bu-t)(4)](+) exhibits slow magnetic relaxation via a Raman process on the millisecond time scale, supporting the presence of slow relaxation via an Orbach process in the nickel analogue. Overall, this work highlights the unique electronic and magnetic properties that can be realized in metal Clusters featuring direct metal-metal orbital interactions between low-coordinate metal centers.Strong Electronic and Magnetic Coupling in M-4 (M = Ni, Cu) Clusters via Direct Orbital Interactions between Low-Coordinate Metal Centersx5202038#N/AFALSE
1708
jacs.0c0843610.1021/jacs.0c08436FALSEhttps://doi.org/10.1021/jacs.0c08436Zhao, YLJ. Am. Chem. Soc.Covalent organic frameworks (COFs) are an emerging Class of crystalline porous polymers with tailor-made structures and functionalities. To facilitate their utilization for advanced applications, it is crucial to develop a systematic approach to control the properties of COFs, inCluding the crystallinity, stability, and functionalities. However, such an integrated design is challenging to achieve. Herein, we report supramolecular strategy-based linkage engineering to fabricate a versatile 2D hydrazone-linked COF platform for the coordination of different transition metal ions. Intra- and intermolecular hydrogen bonding as well as electrostatic interactions in the antiparallel stacking mode were first utilized to obtain two isoreticular COFs, namely COF-DB and COF-DT. On account of suitable nitrogen sites in COF-DB, the further metalation of COF-DB was accomplished upon the complexation with seven divalent transition metal ions M(II) (M = Mn, Co, Ni, Cu, Zn, Pd, and Cd) under mild conditions. The resultant M/COF-DB exhibited extended p-conjugation, improved crystallinity, enhanced stability, and additional functionalities as compared to the parent COF-DB. Furthermore, the dynamic nature of the coordination bonding in M/COF-DB allows for the easy replacement of metal ions through a postsynthetic exchange. In particular, the coordination mode in Pd/COF-DB endows it with excellent catalytic activity and cyClic stability as a heterogeneous catalyst for the Suzuki-Miyaura cross-coupling reaction, outperforming its amorphous counterparts and Pd/COF-DT. This strategy provides an opportunity for the construction of 2D COFs with designable functions and opens an avenue to create COFs as multifunctional systems.Linkage Engineering by Harnessing Supramolecular Interactions to Fabricate 2D Hydrazone-Linked Covalent Organic Framework Platforms toward Advanced Catalysisx9202064#N/AFALSE
1709
jacs.0c0831910.1021/jacs.0c08319FALSEhttps://doi.org/10.1021/jacs.0c08319Mazet, CJ. Am. Chem. Soc.Two complementary regiodivergent [(P,N)Ni]-catalyzed hydroAlkylations of branched dienes are reported. When amides are employed as unstabilized C(sp(3)) nuCleophiles, a highly regioselective 1,4-addition process is favored. The addition products are obtained in high yield and with excellent stereocontrol of the internal olefin. With use of a chiral ligand and imides as carbon nuCleophiles, a 3,4-addition protocol was developed, enabling construction of two contiguous tertiary stereocenters in a single step with moderate to high levels of diastereocontrol and excellent enantiocontrol. Both methods operate under mild reaction conditions, display a broad scope, and show excellent functional group tolerance. The synthetic potential of the 3,4-hydroAlkylation reaction was established via a series of postcatalytic modifications.Ni-Catalyzed Regiodivergent and Stereoselective HydroAlkylation of AcyClic Branched Dienes with Unstabilized C(sp(3)) NuCleophilesx10202063#N/AFALSE
1710
jacs.0c1058810.1021/jacs.0c10588https://doi.org/10.1021/jacs.0c10588Harth, EJ. Am. Chem. Soc.This work explores the mechanism whereby a cationic diimine Pd(II) complex combines coordination insertion and radical polymerization to form polyolefin-polar block copolymers. The initial requirement involves the insertion of a single acrylate monomer into the Pd(II)-polyolefin intermediates, which generate a stable polymeric chelate through a chain-walking mechanism. This thermodynamically stable chelate was also found to be photochemically inactive, and a unique mechanism was discovered which allows for radical polymerization. Rate-determining opening of the chelate by an ancillary ligand followed by additional chain walking allows the metal to migrate to the alpha-carbon of the acrylate moiety. Ultimately, the molecular parameters necessary for blue-light-triggered Pd-C bond homolysis from this alpha-carbon to form a carbon-centered macroradical species were established. This intermediate is understood to initiate free radical polymerization of acrylic monomers, thereby facilitating block copolymer synthesis from a single Pd(II) complex. Key intermediates were isolated and comprehensively characterized through exhaustive analytical methods which detail the mechanism while confirming the structural integrity of the polyolefin-polar blocks. Chain walking combined with blue-light irradiation functions as the mechanistic switch from coordination insertion to radical polymerization. On the basis of these discoveries, robust di- and triblock copolymer syntheses have been demonstrated with olefins (ethylene and 1-hexene) which produce amorphous or crystalline blocks and acrylics (methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate) in broad molecular weight ranges and compositions, yielding AB diblocks and BAB triblocks.Dual Polymerization Pathway for Polyolefin-Polar Block Copolymer Synthesis via MILRad: Mechanism and Scope1202064#N/ATRUE
1711
jacs.0c0814510.1021/jacs.0c08145https://doi.org/10.1021/jacs.0c08145Kim, JJ. Am. Chem. Soc.The efficient and selective light-driven conversion of carbon dioxide to formate is a scientific challenge for green chemistry and energy science, especially utilizing visible-light energy and earth-abundant catalytic materials. In this report, two mononuClear Ni(II) complexes of pyridylbenzimidazole (pbi) and pyridylbenzothiazole (pbt), such as Ni(pbt)(pyS)(2) (1) and Ni(pbi)(pyS)(2) (2) (pyS = pyridine-2-thiolate), were prepared and their reactivities studied. The two Ni complexes were examined for CO2 conversion using eosin Y as a photosensitizer upon visible-light irradiation in a H2O/ethanol solvent. The photoreaction of CO2 catalyzed by complexes 1 and 2 selectively affords formate with a high efficiency (14000 turnover number) and a high catalytic selectivity of -99%. Undesirable proton reduction pathways were completely suppressed in the photocatalytic reactions with these sulfur-rich Ni catalysts under CO2. Hydrogen photoproduction was also studied under argon. Their kinetic isotope effects and influence of solution pH for formate and H-2 production in the photocatalytic reactions are described in relation to the reaction mechanisms. These bioinspired Ni(II) catalysts with N/S ligation in relation to [NiFe]-hydrogenases are the first examples of early transition metal complexes affording such high selectivity and efficiencies, providing a future path to design solar-to-fuel processes for artificial photosynthesis.Visible-Light Photocatalytic Conversion of Carbon Dioxide by Ni(II) Complexes with N4S2 Coordination: Highly Efficient and Selective Production of FormatePhotocatalyst7202037#N/AFALSE
1712
jacs.0c0813910.1021/jacs.0c08139FALSEhttps://doi.org/10.1021/jacs.0c08139Bao, XHJ. Am. Chem. Soc.Encapsulation of metal nanocatalysts by support-derived materials is well known as a Classical strong metal-support interaction (SMSI) effect that occurs almost exClusively with active oxide supports and often blocks metal-catalyzed surface reactions. In the present work this Classical SMSI process has been surprisingly observed between metal nanopartiCles, e.g., Ni, Fe, Co, and Ru, and inert hexagonal boron nitride (h-BN) nanosheets. We find that weak oxidizing gases such as CO2 and H2O induce the encapsulation of nickel (Ni) nanopartiCles by ultrathin boron oxide (box) overlayers derived from the h-BN support (Ni@box/h-BN) during the dry reforming of methane (DRM) reaction. In-situ surface characterization and theory calculations reveal that surface B-O and B-OH sites in the formed box encapsulation overlayers work synergistically with surface Ni sites to promote the DRM process rather than blocking the surface reactions.Reaction-Induced Strong Metal-Support Interactions between Metals and Inert Boron Nitride Nanosheetsx14202062#N/AFALSE
1713
jacs.0c0800010.1021/jacs.0c08000FALSEhttps://doi.org/10.1021/jacs.0c08000Morris, RHJ. Am. Chem. Soc.Understanding the thermodynamics of paramag- netic transition metal hydride complexes, especially of the abundant 3d metals, is important in the design of electrocatalysts and organometallic catalysts. The pK(a)(MeCN)([MHLn](+)/[MLn) of paramagnetic hydrides in MeCN are estimated for the first time using the ligand acidity constant (LAC) equation where contributions to the pK(a)(MeCN) from each ligand are simply added together, with the sum corrected for effects of charge and Sd metals. The pK(a)(LAC-MeCN)([MHLn](+)/[MLn) of over 200 hydride complexes MHLn are used, along with their electrochemical potentials from the literature, in an uncommonly applied thermochemical cyCle in order to reveal systematic trends in the redox couples M-III/II and M-V/IV (M = Cr, Mo, W), Mn-II/I, Re-VI/V and Re-IV/III, M-III/II and M-IV/III (M = Fe, Ru, Os), and M-II/I and M-II/I (M = Co, Rh, and Ir) and allow the estimation of the bond dissociation free energies BDFE(MH) of the unoxidized hydrides MHLn and the prediction of the electrochemical potential for their oxidation. Density functional theory (DFT) calculations are used to validate the pK(a) values of hydrides of Ru-III, Co-II, and Ni-III. When a pk(a)(LAC-MeCN) is less than zero for a given complex [MHLn](+), the oxidation of MHL n is irreversible due to proton loss from the oxidized complex to the solvent. When pk(a)(LAC-MeCN) >> 0, the oxidation is reversible when there is no gross change in the coordination geometry upon a change in the redox state. Twenty paramagnetic hydrides prepared in bulk all have pK(a)(LAC-MeCN) > 8.Systematic Trends in the Electrochemical Properties of Transition Metal Hydride Complexes Discovered by Using the Ligand Acidity Constant Equationx22020152#N/AFALSE
1714
jacs.0c0749210.1021/jacs.0c07492FALSEhttps://doi.org/10.1021/jacs.0c07492Shu, XZJ. Am. Chem. Soc.Deoxygenative radical C-C bond-forming reactions of alcohols are a long-standing challenge in synthetic chemistry, and the current methods rely on multistep procedures. Herein, we report a direct dehydroxylative radical Alkylation reaction of tertiary alcohols. This new protocol shows the feasibility of generating tertiary carbon radicals from alcohols and offers an approach for the facile and precise construction of all-carbon quaternary centers. The reaction proceeds with a broad substrate scope of alcohols and activated alkenes. It can tolerate a wide range of electrophilic coupling partners, inCluding allylic Carbonylates, Aryl and Vinyl electrophiles, and primary Alkyl chlorides/bromides, making the method complementary to the cross-coupling procedures. The method is highly selective for the Alkylation of tertiary alcohols, leaving secondary/primary alcohols (Benzyl alcohols inCluded) and phenols intact. The synthetic utility of the method is highlighted by its 10-g-scale reaction and the late-stage modification of complex molecules. A combination of experiments and density functional theory calculations establishes a plausible mechanism implicating a tertiary carbon radical generated via Ti-catalyzed homolysis of the C-OH bond.Radical Dehydroxylative Alkylation of Tertiary Alcohols by Ti Catalysisx10202053#N/AFALSE
1715
jacs.0c0739010.1021/jacs.0c07390FALSEhttps://doi.org/10.1021/jacs.0c07390Kishi, YJ. Am. Chem. Soc.The first total synthesis of halistatins 1 and 2 has been completed using Cr-mediated coupling reactions for the C11/C12, C17/C18, and C19/C20 bond formation. For the C11/C12 bond formation, a stoichiometric Ni/Cr-mediated reaction is used to couple an alpha-quaternary aldehyde with a Vinyl iodide. The solubilized Cr-reagent, prepared from CrCl2 and a sulfonamide ligand, allows one to perform the coupling with similar to 1 equiv of Cr-reagent. Catalytic, asymmetric Co/Cr-mediated iodoallylation is adopted to incorporate the requisite C17-C19 functionality in a stereoselective manner. Asymmetric Ni/Cr-mediated coupling is used to form the C19/C20 bond effectively. Through this study, it has been found that the stereoselectivity of [5,5]-spiroketalization dramatically depends on solvents; p-toluenesulfonic acid (PTSA) in 1:1 methanol-water gave a >20:1 stereoselectivity favoring the natural series. This condition is also effective to isomerize C38-epi-halichondrins into C38 natural halichondrins.Total Synthesis of Halistatins 1 and 2x2202042#N/AFALSE
1716
jacs.0c1045810.1021/jacs.0c10458FALSEhttps://doi.org/10.1021/jacs.0c10458Goldberg, KIMetal/Ligand Proton Tautomerism Facilitates DinuClear H-2 Reductive Elimination2020#N/ATRUE
1717
jacs.0c0704110.1021/jacs.0c07041FALSEhttps://doi.org/10.1021/jacs.0c07041Mirica, KAJ. Am. Chem. Soc.The use of reticular materials in the electrochemical reduction of carbon dioxide to value-added products has the potential to enable tunable control of the catalytic performance through the modulation of chemical and structural features of framework materials with atomic precision. However, the tunable functional performance of such systems is still largely hampered by their poor electrical conductivities. This work demonstrates the use of four systematic structural analogs of conductive two-dimensional (2D) metal-organic frameworks (MOFs) made of metallophthalocyanine (MPc) ligands linked by Cu nodes with electrical conductivities of 2.73 x 10(-3) to 1.04 x 10(-1) S cm(-1) for the electrochemical reduction of CO2 to CO. The catalytic performance of the MOFs, inCluding the activity and selectivity, is found to be hierarchically governed by two important structural factors: the metal within the MPc (M = Co vs Ni) catalytic subunit and the identity of the heteroatomic cross-linkers between these subunits (X = O vs NH). The activity and selectivity are dominated by the choice of metal within MPcs and are further modulated by the heteroatomic linkages. Among these MOFs, CoPc-Cu-O exhibited the highest selectivity toward CO product (Faradaic efficiency FECO = 85%) with high current densities up to -17.3 mA cm-2 as a composite with carbon black at 1:1 mass ratio) at a low overpotential of -0.63 V. Without using any conductive additives, the use of CoPc-Cu-O directly as an electrode material was able to achieve a current density of -9.5 mA cm(-2) with a FECO of 79%. Mechanistic studies by comparison tests with metal-free phthalocyanine MOF analogs supported the dominant catalytic role of the central metal of the phthalocyanine over Cu nodes. Density-functional theory calculations further suggested that, compared with the NiPc-based and NH-linked analogs, CoPc-based and O-linked MOFs have lower Activation energies in the formation of Carbonyl intermediate, in line with their higher activities and selectivity. The results of this study indicate that the use of 2D MPc-based conductive framework materials holds great promise for achieving efficient CO2 reduction through strategic ligand engineering with multiple levels of tunability.Hierarchical Tuning of the Performance of Electrochemical Carbon Dioxide Reduction Using Conductive Two-Dimensional Metallophthalocyanine Based Metal-Organic Frameworksx82020119#N/AFALSE
1718
jacs.0c0696010.1021/jacs.0c06960FALSEhttps://doi.org/10.1021/jacs.0c06960Noveron, JCTuning of Trifunctional NiCu Bimetallic NanopartiCles Confined in a Porous Carbon Network with Surface Composition and Local Structural Distortions for the Electrocatalytic Oxygen Reduction, Oxygen and Hydrogen Evolution Reactionsx2020#N/AFALSE
1719
jacs.0c0690910.1021/jacs.0c06909FALSEhttps://doi.org/10.1021/jacs.0c06909Freedman, DEJ. Am. Chem. Soc.The inherent atomic level structural control of synthetic chemistry enables the creation of qubits, the base units of a quantum information science system, designed for a target application. For quantum sensing applications, enabling optical read-out of spin in tunable molecular systems, akin to defect-based systems, would be transformative. This approach would bring together molecular tunability with optical read-out technology. In theory, nickel ions in octahedral symmetry meet all the criteria for optical readout of spin. Yet, to the best of our knowledge, there are no pulse EPR studies on Ni2+ molecules. We identified two compounds featuring highly symmetric Ni2+ centers, thereby engendering weak zero-field splitting to enable EPR addressability: [Ni(phen)(3)](BF4)(2) (1) and [Ni(pyr(3))(2)](BF4)(2) (2) (phen = 1,10-phenanthroline; pyr(3) = tris-2-pyridyl-methane). Crucially, these complexes feature the requisite strong field ligands to enable emission for optical addressability. We extracted axial zero-field splitting parameters of D = +0.9 cm(-1) and +2.7 cm(-1) for 1 and 2, respectively, enabling pulse EPR measurements. Both compounds produce emission at lambda(max) = 938-944 nm. The aggregate of these results expands the catalogue of qubit materials to Ni2+-based compounds and offers a future pathway for optical readout of these molecules.Nickel(II) Metal Complexes as Optically Addressable Qubit Candidatesx9202048#N/AFALSE
1720
jacs.0c1005510.1021/jacs.0c10055FALSEhttps://doi.org/10.1021/jacs.0c10055Kong, WQJ. Am. Chem. Soc.SpirocyCles play an important role in drug discovery and development owing to their inherent three-dimensionality and structural novelty. Despite the recent significant progress, the straightforward catalytic asymmetric assembly of spirocyClic scaffolds with multiple stereocenters from readily available starting materials remains a formidable challenge. Herein, we develop an unprecedented nickel-catalyzed one-pot synthesis of enantioenriched spiroindanones from easily available 1,6-enynes and o-CarbonylArylboronic acids. The reaction proceeds smoothly under redox-neutral conditions, without the need for an additional hydrogen donor, and features a broad substrate scope and excellent regio-, enantio-, and diastereoselectivity.Diastereo- and Enantioselective Construction of SpirocyCles by Nickel-Catalyzed Cascade Borrowing Hydrogen CyClization8202173#N/ATRUE
1721
jacs.0c0662410.1021/jacs.0c06624FALSEhttps://doi.org/10.1021/jacs.0c06624Hosono, HJ. Am. Chem. Soc.Ammonia is one of the most important feedstocks for the production of fertilizer and as a potential energy carrier. Nitride compounds such as LaN have recently attracted considerable attention due to their nitrogen vacancy sites that can activate N-2 for ammonia synthesis. Here, we propose a general rule for the design of nitride-based catalysts for ammonia synthesis, in which the nitrogen vacancy formation energy (E-NV) dominates the catalytic performance. The relatively low E-NV (ca. 1.3 eV) of CeN means it can serve as an efficient and stable catalyst upon Ni loading. The catalytic activity of Ni/CeN reached 6.5 mmol.g(-1).h(-1) with an effluent NH3 concentration (E-NH3) of 0.45 vol %, reaching the thermodynamic equilibrium (E-NH3 = 0.45 vol %) at 400 degrees C and 0.1 MPa, thereby circumventing the bottleneck for N-2 Activation on Ni metal with an extremely weak nitrogen binding energy. The activity far exceeds those for other Co- and Ni-based catalysts, and is even comparable to those for Ru-based catalysts. It was determined that CeN itself can produce ammonia without Ni-loading at almost the same Activation energy. Kinetic analysis and isotope experiments combined with density functional theory (DFT) calculations indicate that the nitrogen vacancies in CeN can activate both N-2 and H-2 during the reaction, which accounts for the much higher catalytic performance than other reported nonloaded catalysts for ammonia synthesis.Contribution of Nitrogen Vacancies to Ammonia Synthesis over Metal Nitride Catalystsx10202047#N/AFALSE
1722
jacs.0c0641210.1021/jacs.0c06412FALSEhttps://doi.org/10.1021/jacs.0c06412Yoshikai, NJ. Am. Chem. Soc.A catalytic system comprising a cobalt-diphosphine complex and a Lewis acid (LA) such as AIMe(3) has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines and related azines, imidazo[1,2-a]pyridines, and azole derivatives through site-selective C-H Activation. Compared with known Ni/LA catalytic systems for analogous transformations, the present catalytic systems not only feature convenient setup using inexpensive and bench-stable precatalyst and ligand such as Co(acac)(3) and 1,3-bis(diphenylphosphino)-propane (dppp) but also display distinct site-selectivity toward C-H Activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Meanwhile, the present catalytic system proved to promote exClusively C5-selective alkenylation of imidazo[1,2-a]pyridine derivatives. Mechanistic studies inCluding DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves Cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkenyl(carbamoyl)cobalt intermediate.Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C-H ActivationX7202079#N/AFALSE
1723
jacs.0c0600710.1021/jacs.0c06007FALSEhttps://doi.org/10.1021/jacs.0c06007Itami, KJ. Am. Chem. Soc.The synthesis, structure, and properties of methylene-bridged [6]cyCloparaphenylene ([6]CPP), a nonalternant aromatic belt, are described. This belt-shaped methylene-bridged [6]CPP, in which each phenylene unit is tethered to its neighbors by methylene bridges, was constructed through 6-fold intramolecular nickel-mediated Aryl-Aryl coupling of triflate-functionalized pillar[6]arene in 18% isolated yield. As compared to the analogous [6]CPP, the methylene bridges coplanarize neighboring paraphenylene units and enhance the degree of pi-conjugation, which results in a significant decrease in energy gap. Moreover, the incorporation of small molecules in the defined pocket of methylene-bridged [6]CPP makes it an attractive supramolecular architecture. Methylene-bridged [6]CPP is characterized by high internal strain energy reaching 110.2 kcal mol(-1), attributed to its restricted structure. This work not only exhibits an efficient strategy to construct a new family of aromatic belt, but also showcases their properties, which combine the merits of CPPs and pillararenes.A Nonalternant Aromatic Belt: Methylene-Bridged [6]CyCloparaphenylene Synthesized from Pillar[6]arenex19202062#N/AFALSE
1724
jacs.0c0595010.1021/jacs.0c05950FALSEhttps://doi.org/10.1021/jacs.0c05950Hoffman, BMJ. Am. Chem. Soc.EPR and Electron NuClear Double Resonance spectroscopies here characterize CO binding to the active-site A Cluster of wild-type (WT) Acetyl-CoA Synthase (ACS) and two variants, F229W and F229A. The A-Cluster binds CO to a proximal Ni (Ni-p) that bridges a [4Fe-4S] Cluster and a distal Ni-d. An alcove seen in the ACS crystal structure near the A-Cluster, defined by hydrophobic residues inCluding F229, forms a cage surrounding a Xe mimic of CO. Previously, we only knew WT ACS bound a single CO to form the A(red)-CO intermediate, containing Ni-p(I)-CO with CO located on the axis of the d(z)(2) odd-electron orbital (g(perpendicular to) > g(parallel to) similar to 2). Here, the two-dimensional field-frequency pattern of 2K-35 GHz C-13-ENDOR spectra collected across the Ared-CO EPR envelope reveals a second CO bound in the d(z)(2) orbital's equatorial plane. This WT A-Cluster conformer dominates the nearly conservative F229W variant, but C-13-ENDOR reveals a minority A conformation with (g(parallel to) > g(vertical bar) similar to 2) characteristic of a Cloverleaf (e.g., d(x)(2) - (2)(y)) odd-electron orbital, with Nip binding two, apparently in-plane CO. Disruption of the alcove through introduction of the smaller alanine residue in the F229A variant diminishes conversion to Ni(I) similar to 10-fold and introduces extensive Cluster flexibility. C-13-ENDOR shows the F229A Cluster is mostly (60%) in the A conformation but with similar to 20% each of the WT conformer and an O state in which d(z)(2) Ni-p(I) (g(perpendicular to) > g(parallel to) similar to 2) surprisingly lacks CO. This paper thus demonstrates the importance of an intact alcove in forming and stabilizing the Ni(I)-CO intermediate in the Wood-Ljungdahl pathway of anaerobic CO and CO2 fixation.C-13 Electron NuClear Double Resonance Spectroscopy Shows Acetyl-CoA Synthase Binds Two Substrate CO in Multiple Binding Modes and Reveals the Importance of a CO-Binding Alcovex1202039#N/AFALSE
1725
jacs.0c0590110.1021/jacs.0c05901https://doi.org/10.1021/jacs.0c05901MacMillan, DWCJ. Am. Chem. Soc.The combined use of reaction kinetic analysis, ultrafast spectroscopy, and stoichiometric organometallic studies has enabled the elucidation of the mechanistic underpinnings to a photocatalytic C-N cross-coupling reaction. Steady-state and ultrafast spectroscopic techniques were used to track the excited-state evolution of the employed iridium photocatalyst, determine the resting states of both iridium and nickel catalysts, and uncover the photochemical mechanism for reductive Activation of the nickel cocatalyst. Stoichiometric organometallic studies along with a comprehensive kinetic study of the reaction, inCluding rate-driving force analysis, unveiled the crucial role of photocatalysis in both initiating and sustaining a Ni(I)/Ni(III) cross-coupling mechanism. The insights gleaned from this study further enabled the discovery of a new photocatalyst providing a >30-fold rate increase.Mechanistic Analysis of Metallaphotoredox C-N Coupling: Photocatalysis Initiates and Perpetuates Ni(I)/Ni(III) Coupling ActivityPhotocatalyst21202043#N/AFALSE
1726
jacs.0c0994910.1021/jacs.0c09949FALSEhttps://doi.org/10.1021/jacs.0c09949Ye, MCJ. Am. Chem. Soc.A carbamoyl fluoride-enabled enantioselective Ni-catalyzed carbocarbamoylation of unactivated alkenes was developed, providing a broad range of chiral gamma-lactams bearing an all-carbon quaternary center in 45-96% yield and 38-97% ee.Carbamoyl Fluoride-Enabled Enantioselective Ni-Catalyzed Carbocarbamoylation of Unactivated Alkenes7202091#N/ATRUE
1727
jacs.0c0977810.1021/jacs.0c09778FALSEhttps://doi.org/10.1021/jacs.0c09778Giri, RJ. Am. Chem. Soc.We disClose a Ni-catalyzed vicinal difunctionalization of alkenes with Benzyl halides and Alkylzinc reagents, which produces products with two new Alkyl-Alkyl bonds. This alkene diAlkylation is effective in combining secondary Benzyl halides and secondary Alkylzinc reagents with internal alkenes, which furnishes products with three contiguous all-carbon secondary stereocenters. The products can be readily elaborated to access complex tetralene, benzosuberene, and bicyClodecene cores. The reaction also features as the most efficient alkene difunctionalization process to date with catalyst loadings down to 500 ppm and the catalytic turnover number (TON) and turnover frequency (TOF) registering up to 2 x 10(3) and 165 h(-1) at rt, respectively.Ni-Catalyzed Regioselective 1,2-DiAlkylation of Alkenes Enabled by the Formation of Two C(sp(3))-C(sp(3)) Bonds8202072#N/ATRUE
1728
jacs.0c0510410.1021/jacs.0c05104https://doi.org/10.1021/jacs.0c05104Kojima, TJ. Am. Chem. Soc.Efficient Photocatalytic CO2 Reduction by a Ni(II) Complex Having Pyridine Pendants through Capturing a Mg2+ Ion as a Lewis-Acid Cocatalyst (vol 141, pg 20309, 2019)Photocatalyst220201#N/AFALSE
1729
jacs.0c0507410.1021/jacs.0c05074FALSEhttps://doi.org/10.1021/jacs.0c05074Li, JRJ. Am. Chem. Soc.The application scope of metal-organic frameworks (MOFs) is severely restricted by their weak chemical stability and limited pore size. A robust MOF with large mesopores is highly desired, yet poses a great synthetic challenge. Herein, two chemically stable Ni(II)-pyrazolate MOFs, BUT-32 and -33, were constructed from a conformation-matched elongated pyrazolate ligand through the isoreticular expansion. The two MOFs share the same sodalite-type net, but have different pore sizes due to the network interpenetration in BUT-32. Controlled syntheses of the two MOFs have been achieved through precisely tuning reaction conditions, where the microporous BUT-32 was demonstrated to be a thermodynamically stable product while the mesoporous BUT-33 is kinetically favored. To date, BUT-32 represents the first example of Ni-4-pyrazolate MOF whose structure was unambiguously determined by single-crystal X-ray diffraction. Interestingly, the kinetic product BUT-33 integrates 2.6 nm large mesopores with accessible Ni(II) active sites and remarkable chemical stability even in 4 M NaOH aqueous solution and 1 M Grignard reagent. This MOF thus demonstrated an excellent catalytic performance in carbon-carbon coupling reactions, superior to other Ni(II)-MOFs inCluding BUT-32. These findings highlight the importance of kinetic control in the reticular synthesis of mesoporous MOFs, as well as their superiority in heterogeneous catalysis.Kinetically Controlled Reticular Assembly of a Chemically Stable Mesoporous Ni(II)-Pyrazolate Metal-Organic Frameworkx20202060#N/AFALSE
1730
jacs.0c0501010.1021/jacs.0c05010https://doi.org/10.1021/jacs.0c05010Cavallo, LJ. Am. Chem. Soc.We report here a comprehensive computational analysis of the mechanisms of the photoredox-nickel-HAT (HAT: hydrogen atom transfer) catalyzed Arylation and Alkylation of alpha-amino C-sp3-H bonds developed by MacMillan and co-workers. Different alternatives for the three catalytic cyCles were tested to identify unambiguously the operative reaction mechanism. Our analysis indicated that the Ir-III photoredox catalyst, upon irradiation with visible light, can be either reduced or oxidized by the HAT and nickel catalysts, respectively, indicating that both reductive and oxidative quenching catalytic cyCles can be operative, although the reductive cyCle is favored. Our analysis of the HAT cyCle indicated that Activation of a alpha-amino C-sp3-H bond of the substrate is facile and selective relative to Activation of a beta-amino C-sp3-H bond. Finally, our analysis of the nickel cyCle indicated that both Arylation and Alkylation of alpha-amino Csp3-H bonds occurs via the sequence of nickel oxidation states Ni-I-Ni-II-Ni-I-Ni-III and of elementary steps: radical addition-SET-oxidative addition-reductive elimination.Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of alpha-Amino C-sp3-H BondsPhotocatalyst8202059#N/AFALSE
1731
jacs.0c0963910.1021/jacs.0c09639FALSEhttps://doi.org/10.1021/jacs.0c09639Ogoshi, SJ. Am. Chem. Soc.The first example of the oxidative addition of a C(sp(3))-F bond in trifluoromethylarenes to a nickel(0) complex is described. A nickel(0) complex that bears two N-heterocyClic carbene (NHC) ligands of low steric demand is able to Cleave C(sp(3))-F bonds of trifluoromethylarenes to afford the corresponding trans-difluoroBenzyl nickel(H) fluoride complexes. Isolation and characterization studies suggested that the Cleavage of the C(sp(3))-F bond proceeds via an eta(2)-arene nickel(0) complex. Taking advantage of the reactivity of these nickel(II) fluoride complexes, we developed a catalytic hydrodefluorination of trifluoromethylarenes using hydrosilanes. A computational study indicated that the electron-rich nickel(0) center supported by two relatively small NHC ligands Cleaves the C(sp(3))-F bond via a syn S(N)2' mechanism.Cleavage of C(sp(3))-F Bonds in Trifluoromethylarenes Using a Bis(NHC)nickel(0) Complex12202065#N/ATRUE
1732
jacs.0c0951010.1021/jacs.0c09510FALSEhttps://doi.org/10.1021/jacs.0c09510Wang, QJ. Am. Chem. Soc.Electrolytic water splitting is an effective approach for H-2 mass production. A conventional water electrolyzer concurrently generates H-2 and O-2 in neighboring electrode compartments separated by a membrane, which brings about compromised purity, energy efficiency, and system durability. On the basis of distinct redox electrochemistry, here, we report a system that enables the decoupling of both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) from the electrodes to two spatially separated catalyst bed reactors in alkaline solutions. Through a pair of Close-loop electrochemical-chemical cyCles, the system operates upon 7,8-dihydroxy-2-phenazinesulfonic acid (DHPS) and ferricyanide-mediated HER and OER, respectively, on Pt/Ni(OH)(2) and NiFe(OH)(2) catalysts. Near unity faradaic efficiency and sustained production of hydrogen has been demonstrated at a current density up to 100 mA/cm(2). The superior reaction kinetics, particularly the HER reaction mechanism of DHPS as a robust electrolyte-borne electron and proton carriers, were scrutinized both computationally and experimentally. We anticipate the system demonstrated here would provide an intriguing alternative to the conventional water electrolytic hydrogen production.Decoupled Redox Catalytic Hydrogen Production with a Robust Electrolyte-Borne Electron and Proton Carrier3202142#N/ATRUE
1733
jacs.0c0922210.1021/jacs.0c09222FALSEhttps://doi.org/10.1021/jacs.0c09222Mirkin, CAJ. Am. Chem. Soc.Semiconductor nanowires (NWs) capped with metal nanopartiCles (NPs) show multifunctional and synergistic properties, which are important for applications in the fields of catalysis, photonics, and electronics. Conventional colloidal syntheses of this Class of hybrid structures require complex sequential seeded growth, where each section requires its own set of growth conditions, and methods for preparing such wires are not universal. Here, we report a new and general method for synthesizing metal-semiconductor nanohybrids based on partiCle catalysts, prepared by scanning probe block copolymer lithography, and chemical vapor deposition. In this process, metallic heterodimer NPs were used as catalysts for NW growth to form semiconductor NWs capped with metallic partiCles (Au, Ag, Co, Ni). Interestingly, the growth processes for NWs on NPs are regioselective and controlled by the chemical composition of the metallic heterodimer used. Using a systematic experimental approach, paired with density functional theory calculations, we were able to postulate three different growth modes, one without precedent.Synthesis of Metal-Capped Semiconductor Nanowires from Heterodimer NanopartiCle Catalysts0202051#N/ATRUE
1734
jacs.0c0896210.1021/jacs.0c08962FALSESun, SHAnisotropic Strain Tuning of L1(0) Ternary NanopartiCles for Oxygen Reduction2020#N/ATRUE
1735
jacs.0c0878510.1021/jacs.0c08785FALSEhttps://doi.org/10.1021/jacs.0c08785Dey, AJ. Am. Chem. Soc.Activation and reduction of N-2 have been a major challenge to chemists and the focus since now has mostly been on the synthesis of NH3. Alternatively, reduction of N-2 to hydrazine is desirable because hydrazine is an excellent energy vector that can release the stored energy very conveniently without the need for catalysts. To date, only one molecular catalyst has been reported to be able to reduce N-2 to hydrazine chemically. A trinuClear T-shaped nickel thiolate molecular complex has been designed to activate dinitrogen. The electrochemically generated all Ni(I) state of this molecule can reduce N-2 in the presence of PhOH as a proton donor. Hydrazine is detected as the only nitrogen-containing product of the reaction, along with gaseous H-2. The complex reported here is selective for the 4e(-)/4H(+) reduction of nitrogen to hydrazine with a minor overpotential of similar to 300 mV.Electrocatalytic Reduction of Nitrogen to Hydrazine Using a TrinuClear Nickel Complex3202062#N/ATRUE
1736
jacs.0c0870810.1021/jacs.0c08708FALSEhttps://doi.org/10.1021/jacs.0c08708Zhang, XGJ. Am. Chem. Soc.Transition-metal-catalyzed Carbonylation is one of the most straightforward strategies to prepare Carbonyl compounds. However, compared to well-established noble-metal-catalyzed Carbonylation reactions, analogue coupling via base-metal, nickel catalysis has received less attention because of the easy formation of highly toxic and unreactive Ni(CO)(4) species between Ni(0) and CO. To date, the use of inexpensive and widely available carbon monoxide (CO) gas for nickel-catalyzed Carbonylation reaction remains challenging, and nickel-catalyzed four-component Carbonylative reaction has not been reported yet. Here, we report a highly selective nickel-catalyzed four-component carboCarbonylation of alkenes under 1 atm (1 atm) of CO gas to efficiently achieve an array of complex Carbonyl compounds, inCluding fluorinated amino acids and oligopeptides of great interest in medicinal chemistry and chemical biology. This reaction relies on a nickel-catalyzed one-pot cascade process to assemble CO, Arylboronic acids, and difluoroAlkyl electrophiles across the carbon-carbon double bond of alkenes, paving a new way for base-metal-catalyzed Carbonylative cascade reaction.YNickel-Catalyzed Four-Component CarboCarbonylation of Alkenes under 1 atm of CO10202058#N/ATRUE
1737
jacs.0c0825410.1021/jacs.0c08254https://doi.org/10.1021/jacs.0c08254Leibfarth, FAMechanistic Insight into the Stereoselective Cationic Polymerization of Vinyl Ethers2020#N/ATRUE
1738
jacs.0c0727410.1021/jacs.0c07274FALSEhttps://doi.org/10.1021/jacs.0c07274Zhao, DYJ. Am. Chem. Soc.Water-soluble doped quantum dots have unique photophysical properties and functionalities as optical labels for bioimaging and chemo-/biosensing. However, doping in quantum dots is not easy due to the dopant-ion size mismatch and self-purification effect. Here, we demonstrate a successful preparation of Mn-, Cu-, and Ni-doped CdS quantum dots with bimetallic Clusters instead of ions as building blocks under mild aqueous conditions up to gram scale. The representative Mn-doped quantum dots have uniform size, about 3.2 +/- 0.5 nm, and emit at 620 nm. The doping concentration can be adjusted in the range 6.4%-25.7%. On the premise of good water solubility, they are stable and nontoxic so as to be directly used for cell imaging. Copper and nickel doping have similar results. Because of the Close sizes of bimetallic Clusters and the low reaction temperature, the challenges posed by dopant size mismatch and ion diffusion are ignored. X-ray absorption fine structure analysis proves that dopants are inside the quantum dots rather than on the surface, indicating that the self-purification effect can be effectively overcome. Furthermore, codoped ZnS quantum dots with adjustable emission are achieved, which validates the versatility of our new approach.An Aqueous Route Synthesis of Transition-Metal-Ions-Doped Quantum Dots by Bimetallic Cluster Building Blocks2202042#N/ATRUE
1739
jacs.0c0437910.1021/jacs.0c04379FALSEhttps://doi.org/10.1021/jacs.6b05111Seferos, DSIsolation of Living Conjugated Polymer Chainsx2020#N/AFALSE
1740
jacs.0c0423110.1021/jacs.0c04231FALSEhttps://doi.org/10.1021/jacs.0c04231Liu, QHJ. Am. Chem. Soc.The structural dynamics of the solid-liquid interfaces (SLEIs) determines the chemistry in all electrochemical processes. Here, by combining multiple operando synchrotron spectroscopies, we identify at the atomic level a general evolution of single-atom Ni at SLEIs into a near-free atom state in the electrochemical oxygen reduction reaction (ORR). We uncover that the single-atom Ni at SLEIs tends to be dynamically released from the nitrogen-carbon substrate and then forms a near-free, isolated-zigzag active site (Ni1(2-delta)+N2) during the reaction. This isolated-zigzag Ni1(2-delta)+N2 active site facilitates the adsorption and dissociation of O-2 into a crucial *O intermediate within the electrical double layers, realizing a highly efficient single-atom catalyst with the best ORR performance in alkaline solutions reported thus far. These findings may pave a general way for dissecting other important structural dynamic processes at SLEIs, such as hydrogen evolution, oxygen evolution, and CO2 reduction reactions.Dynamic Evolution of Solid-Liquid Electrochemical Interfaces over Single-Atom Active Sitesx13202030#N/AFALSE
1741
jacs.0c0690410.1021/jacs.0c06904TRUEhttps://doi.org/10.1021/jacs.0c06904Rousseaux, SALJ. Am. Chem. Soc.The ability to understand and predict reactivity is essential for the development of new reactions. In the context of Ni-catalyzed C(sp(3))-O functionalization, we have developed a unique strategy employing activated cyClopropanols to aid the design and optimization of a redox-active leaving group for C(sp(3))-O Arylation. In this chemistry, the cyClopropane ring acts as a reporter of leaving-group reactivity, since the ring-opened product is obtained under polar (2e) conditions, and the ringClosed product is obtained under radical (1e) conditions. Mechanistic studies demonstrate that the optimal leaving group is redox-active and are consistent with a Ni(I)/Ni(III) catalytic cyCle. The optimized reaction conditions are also used to synthesize a number of ArylcyClopropanes, which are valuable pharmaceutical motifs.The CyClopropane Ring as a Reporter of Radical Leaving-Group Reactivity for Ni-Catalyzed C(sp(3))-O ArylationCsp3-Csp2_arE-NuO
OC(S)N(Ph)Bz
ZnXAlkyl#N/ANo Base920201033/15/2022TRUE
1742
jacs.0c0584510.1021/jacs.0c05845FALSEhttps://doi.org/10.1021/jacs.5b13331Wu, XLConstructing Asymmetrical Ni-Centered {NiN2O4} Octahedra in Layered Metal-Organic Structures for Near-Room-Temperature Single-Phase Magnetoelectricity2020#N/ATRUE
1743
jacs.0c0329810.1021/jacs.0c03298https://doi.org/10.1021/jacs.0c03298Walczak, MAJ. Am. Chem. Soc.Carbohydrates, one of the three primary macromolecules of living organisms, play significant roles in various biological processes such as intercellular communication, cell recognition, and immune activity. While the majority of established methods for the installation of carbohydrates through the anomeric carbon rely on nuCleophilic displacement, anomeric radicals represent an attractive alternative because of their functional group compatibility and high anomeric selectivities. Herein, we demonstrate that anomeric nuCleophiles such as C1 stannanes can be converted into anomeric radicals by merging Cu(I) catalysis with blue light irradiation to achieve highly stereoselective C(sp(3))-S cross-coupling reactions. Mechanistic studies and DFT calculations revealed that the C-S bond-forming step occurs via the transfer of the anomeric radical directly to a sulfur electrophile bound to Cu(II) species. This pathway complements a radical chain observed for photochemical metal-free conditions where a disulfide initiator can be activated by a Lewis base additive. Both strategies utilize anomeric nuCleophiles as efficient radical donors and achieve a switch from an ionic to a radical pathway. Taken together, the stability of glycosyl nuCleophiles, a broad substrate scope, and high anomeric selectivities observed for the thermal and photochemical protocols make this novel C-S cross coupling a practical tool for late-stage glycodiversification of bioactive natural products and drug candidates.Catalytic and Photochemical Strategies to Stabilized Radicals Based on Anomeric NuCleophilesPhotocatalyst13202080#N/AFALSE
1744
jacs.0c0324410.1021/jacs.0c03244FALSEhttps://doi.org/10.1021/jacs.0c03244Anderson, JSJ. Am. Chem. Soc.Metal ligand cooperativity is a powerful strategy in transition metal chemistry. This type of mechanism for the Activation of O-2 is best exemplified by heme centers in biological systems. While aerobic oxidations with Fe and Cu are well precedented, Ni-based oxidations are frequently less common due to less-accessible metal-based redox couples. Some Ni enzymes utilize special ligand environments for tuning the Ni(II)/(III) redox couple such as strongly donating thiolates in Ni superoxide dismutase. A recently characterized example of a Ni-containing protein, however, suggests an alternative strategy for mediating redox chemistry with Ni by utilizing ligand-based reducing equivalents to enable oxygen binding. While this mechanism has little synthetic precedent, we show here that Ni complexes of the redox-active ligand (DHP)-D-tBu,Tol ((DHP)-D-tBu,Tol = 2,5-bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole) activate O-2 to generate a Ni(II) superoxo complex via ligand-based electron transfer. This superoxo complex is competent for stoichiometric oxidation chemistry with alcohols and hydrocarbons. This work demonstrates that coupling ligand-based redox chemistry with functionally redox-inactive Ni centers enables oxidative transformations more commonly mediated by metals such as Fe and Cu.Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocencex5202077#N/AFALSE
1745
jacs.0c0514010.1021/jacs.0c05140FALSEhttps://doi.org/10.1021/jacs.0c05140Hyeon, TDirect Synthesis of Intermetallic Platinum-Alloy NanopartiCles Highly Loaded on Carbon Supports for Efficient Electrocatalysis2020#N/ATRUE
1746
jacs.0c0284810.1021/jacs.0c02848https://doi.org/10.1021/jacs.0c02848Seeberger, PHJ. Am. Chem. Soc.Dual photocatalysis and nickel catalysis can effect cross-coupling under mild conditions, but little is known about the in situ kinetics of this Class of reactions. We report a comprehensive kinetic examination of a model Carbonylate O-Arylation, comparing a state-of-the-art homogeneous photocatalyst (Ir(ppy)(3)) with a competitive heterogeneous photocatalyst (graphitic carbon nitride). Experimental conditions were adjusted such that the nickel catalytic cyCle is saturated with excited photocatalyst. This approach was designed to remove the role of the photocatalyst, by which only the intrinsic behaviors of the nickel catalytic cyCles are observed. The two reactions did not display identical kinetics. Ir(ppy)(3) deactivates the nickel catalytic cyCle and creates more dehalogenated side product. Kinetic data for the reaction using Ir(ppy)(3) supports a turnover-limiting reductive elimination. Graphitic carbon nitride gave higher selectivity, even at high photocatalyst-to-nickel ratios. The heterogeneous reaction also showed a rate dependence on Aryl halide, indicating that oxidative addition plays a role in rate against the current mechanistic hypothesis, which states that the photocatalyst is only involved determination. The results argue to trigger reductive elimination.Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carbonylate O-ArylationsPhotocatalyst7202046#N/AFALSE
1747
jacs.0c0280510.1021/jacs.0c02805https://doi.org/10.1021/jacs.0c02805Doyle, AGJ. Am. Chem. Soc.Methylation of organohalides represents a valuable transformation, but typically requires harsh reaction conditions or reagents. We report a radical approach for the methylation of (hetero)Aryl chlorides using nickel/photoredox catalysis wherein trimethyl orthoformate, a common laboratory solvent, serves as a methyl source. This method permits methylation of (hetero)Aryl chlorides and acyl chlorides at an early and late stage with broad functional group compatibility. Mechanistic investigations indicate that trimethyl orthoformate serves as a source of methyl radical via beta-scission from a tertiary radical generated upon chlorine-mediated hydrogen atom transfer.Nickel/Photoredox-Catalyzed Methylation of (Hetero)Aryl Chlorides Using Trimethyl Orthoformate as a Methyl Radical SourcePhotocatalyst212020416/15/2022FALSE
1748
jacs.0c0493710.1021/jacs.0c04937FALSEhttps://doi.org/10.1021/jacs.0c04937Lu, CCJ. Am. Chem. Soc.A homogeneous rhodium-indium catalyst hydrodefluorinates substrates bearing strong Aryl C-F bonds, inCluding difluoro- and fluorobenzene, using 1 atm of H-2, alkoxide bases, and moderate temperatures (70-90 degrees C). Characterization of catalytic intermediates establishes a formal Rh-I/Rh-I redox cyCle. The Rh -> In interaction is proposed to enable catalysis by stabilizing the reactive Rh--(I) species, which is responsible for Cleaving the Ar-F bond and is ultimately regenerated using H-2 and base.Catalytic Hydrogenolysis of Aryl C-F Bonds Using a Bimetallic Rhodium-Indium Complex13202069#N/ATRUE
1749
jacs.0c0258410.1021/jacs.0c02584FALSEhttps://doi.org/10.1021/jacs.0c02584Zhang, SJ. Am. Chem. Soc.Generalized synthetic strategies for nanostructures with well-defined physical dimensions and broad-range chemical compositions are at the frontier of advanced nanomaterials design, functionalization, and application. Here, we report a composition-programmable synthesis of multimetallic phosphide CoMPx nanorods (NRs) wherein M can be controlled to be Fe, Ni, Mn, Cu, and their binary combinations. Forming Co2P/MPx core/shell NRs and subsequently converting them into CoMPx solid-solution NRs through thermal post-treatment are essential to overcome the obstaCle of morphology/structure inconsistency faced in conventional synthesis of CoMP(x)with the different M compositions. The resultant CoMPx with uniform one-dimensional (1-D) structure provides us a platform to unambiguously screen the M synergistic effects in improving the electrocatalytic activity, as exemplified by the oxygen evolution reaction. This new approach mediated by core/shell nanostructure formation and conversion can be extended to other multicomponent nanocrystal systems (metal alloy, mixed oxide, and chalcogenide, etc.) for diverse applications.Programmable Synthesis of Multimetallic Phosphide Nanorods Mediated by Core/Shell Structure Formation and Conversionx21202053#N/AFALSE
1750
jacs.0c0490510.1021/jacs.0c04905FALSEhttps://doi.org/10.1021/jacs.0c04905Nakao, YJ. Am. Chem. Soc.We report the magnesiation of Aryl fluorides catalyzed by an Al-Rh heterobimetallic complex. We show that the complex is highly reactive to Cleave the C-F bonds across the polarized Al-Rh bond under mild conditions. The reaction allows the use of an easy-to-handle magnesium powder to generate a range of Arylmagnesium reagents from Aryl fluorides, which are conventionally inert to such metalation compared with other Aryl halides.Magnesiation of Aryl Fluorides Catalyzed by a Rhodium-Aluminum Complex14202074#N/ATRUE
1751
jacs.0c0235510.1021/jacs.0c02355https://doi.org/10.1021/jacs.0c02355Gutierrez, OJ. Am. Chem. Soc.The merger of photoredox and nickel catalysis has enabled the construction of quaternary centers. However, the mechanism, role of the ligand, and effect of the spin state for this transformation and related Ni-catalyzed cross-couplings involving tertiary Alkyl radicals in combination with bipyridine and diketonate ligands remain unknown. Several mechanisms have been proposed, all invoking a key Ni(III) species prior to undergoing irreversible inner-sphere reductive elimination. In this work, we have used open-shell dispersion-corrected DFT calculations, quasi-Classical dynamics calculations, and experiments to study in detail the mechanism of carbon-carbon bond formation in Ni bipyridine- and diketonate-based catalytic systems. These calculations revealed that access to high spin states (e.g., triplet spin state tetrahedral Ni(II) species) is critical for effective radical cross-coupling of tertiary Alkyl radicals. Further, these calculations revealed a disparate mechanism for the C-C bond formation. Specifically, contrary to the neutral Ni-bipyridyl system, diketonate ligands lead directly to the corresponding tertiary radical cross-coupling products via an outer-sphere reductive elimination step via triplet spin state from the Ni(III) intermediates. Implications to related Ni-catalyzed radical cross-couplings and the design of new transformations are discussed.On the Nature of C(sp(3))-C(sp(2)) Bond Formation in Nickel-Catalyzed Tertiary Radical Cross-Couplings: A Case Study of Ni/Photoredox Catalytic Cross-Coupling of Alkyl Radicals and Aryl HalidesPhotocatalyst29202046#N/AFALSE
1752
jacs.0c0486710.1021/jacs.0c04867FALSEhttps://doi.org/10.1021/jacs.0c04867Hu, XLJ. Am. Chem. Soc.The oxygen evolution reaction (OER) is the performance-limiting half reaction of water splitting, which can be used to produce hydrogen fuel using renewable energies. Whereas a number of transition metal oxides and oxyhydroxides have been developed as promising OER catalysts in alkaline medium, the mechanisms of OER onco these catalysts are not well understood. Here we combine electrochemical and in situ spectroscopic methods, particularly operando X-ray absorption and Raman spectroscopy, to study the mechanism of OER on cobalt oxyhydroxide (CoOOH), an archetypical unary OER catalyst. We find the dominating resting state of the catalyst as a Co(IV) species CoO2. Through oxygen isotope exchange experiments, we discover a cobalt superoxide species as an active intermediate in the OER. This intermediate is formed concurrently to the oxidation of CoOOH to CoO2. Combing spectroscopic and electrokinetic data, we identify the rate-determining step of the OER as the release of dioxygen from the superoxide intermediate. The work provides important experimental fingerprints and new mechanistic perspectives for OER catalysts.Mechanism of Oxygen Evolution Catalyzed by Cobalt Oxyhydroxide: Cobalt Superoxide Species as a Key Intermediate and Dioxygen Release as a Rate-Determining Step46202086#N/ATRUE
1753
jacs.0c0469510.1021/jacs.0c04695FALSEhttps://doi.org/10.1021/jacs.0c04695Martin, RJ. Am. Chem. Soc.Although the catalytic Carbonylation of unactivated Alkyl electrophiles has reached remarkable levels of sophistication, the intermediacy of (phenanthroline)Ni(I)-Alkyl species-complexes proposed in numerous Ni-catalyzed reductive cross-coupling reactions-has been subject to speculation. Herein we report the synthesis of such elusive (phenanthroline)Ni(I) species and their reactivity with CO2, allowing us to address a long-standing question related to Ni-catalyzed Carbonylation reactions.Ni(I)-Alkyl Complexes Bearing Phenanthroline Ligands: Experimental Evidence for CO2 Insertion at Ni(I) Centers14202059#N/ATRUE
1754
jacs.0c0217210.1021/jacs.0c02172FALSEhttps://doi.org/10.1021/jacs.0c02172Yam, VWWJ. Am. Chem. Soc.A series of cyClometalating tridentate N<^>C<^>N and tetradentate N<^>C<^>N<^>O ligand-containing complexes of earth-abundant nickel(II) has been designed and synthesized. Among them, the carbazolylnickel(II) complex demonstrates, for the first time, an orange color room-temperature luminescence. Such a complex is also found to exhibit intense luminescence with excited state lifetimes in the submicrosecond regime at 77 K, suggesting the triplet nature of the emissive state. Meanwhile, the self-assembly property of the tetradentate ligand-containing nickel(II) complex in solution has been investigated. Owing to its nearly perfect square planar geometry, as evidenced by X-ray crystal structure determination, it is found to exhibit self-assembly properties with the aid of pi-pi interactions and possibly weak Ni center dot center dot center dot Ni interactions, which have been supported by DFT calculations and NCI plot. Indeed, the ground-state aggregation behavior of this complex has been confirmed by concentration-dependent UV-vis absorption spectroscopy. Moreover, in the solution-induced aggregation studies, upon the addition of nonsolubilizing solvents, the emergence of low-energy absorption bands has been realized, and such a complex is found to demonstrate interesting self-assembly behaviors to offer well-defined and highly ordered supramolecular architectures.Toward the Design of Phosphorescent Emitters of CyClometalated Earth-Abundant Nickel(II) and Their Supramolecular Studyx12202050#N/AFALSE
1755
jacs.0c0469010.1021/jacs.0c04690FALSEhttps://doi.org/10.1021/jacs.0c04690Bourissou, DJ. Am. Chem. Soc.A new mode of bond Activation involving M -> Z interactions is disClosed. Coordination to transition metals as sigma-acceptor ligands was found to enable the Activation of fluorosilanes, opening the way to the first transition-metal-catalyzed Si-F bond Activation. Using phosphines as directing groups, sila-Negishi couplings were developed by combining Pd and Ni complexes with external Lewis acids such as MgX2. Several key catalytic intermediates have been authenticated spectroscopically and crystallographically. Combined with DFT calculations, all data support cooperative Activation of the fluorosilane via Pd/Ni -> Si-F -> Lewis acid interaction with conversion of the Z-type fluorosilane ligand into an X-type silyl moiety.Fluorosilane Activation by Pd/Ni -> Si-F -> Lewis Acid Interaction: An Entry to Catalytic Sila-Negishi Coupling6202050#N/ATRUE
1756
jacs.0c0446210.1021/jacs.0c04462FALSEhttps://doi.org/10.1021/jacs.0c04462Zhang, XGJ. Am. Chem. Soc.Efficient construction of optically pure molecules from readily available starting materials in a simple manner is an ongoing goal in asymmetric synthesis. As a straightforward route, transition-metal-catalyzed enantioconvergent coupling between widely available secondary Alkyl electrophiles and organometallic nuCleophiles has emerged as a powerful strategy to construct chiral center(s). However, the scope of racemic secondary Alkylmetallic nuCleophiles for this coupling remains limited in specific substrates because of the difficulties in stereoselective formation of the key Alkylmetal intermediates. Here, we report an enantiodivergent strategy to efficiently achieve an array of synthetically useful chiral cyClopropanes, inCluding chiral fluoroAlkylated cyClopropanes and enantiomerically enriched cyClopropanes with chiral side chains, from racemic cyClopropylzinc reagents. This strategy relies on a one-pot, two-step enantiodivergent relay coupling process of the racemic cis-cyClopropylzinc reagents with two different electrophiles, which involves kinetic resolution of racemic cis-cyClopropylzinc reagents through a nickel-catalyzed enantioselective coupling with Alkyl electrophiles, followed by a stereospecific relay coupling of the remaining enantiomeric cyClopropylzinc reagent with various electrophiles, to produce two types of functionalized chiral cyClopropanes with opposite configurations on the cyClopropane ring. These chiral cyClopropanes are versatile synthons for diverse transformations, rendering this strategy effective for obtaining structurally diversified molecules of medicinal interest.Stereoselective Functionalization of Racemic CyClopropylzinc Reagents via Enantiodivergent Relay Coupling8202061#N/ATRUE
1757
jacs.0c0204510.1021/jacs.0c02045https://doi.org/10.1021/jacs.0c02045Daugulis, OJ. Am. Chem. Soc.New neutral nickel and palladium ethylene polymerization catalysts have been prepared that incorporate an anionic (N,O) chelating ligand. Extensive axial shielding is provided by two 3,5-dichloroAryl moieties in a sandwich orientation. Such shielding results in an exceptionally slow rate of chain transfer relative to migratory insertion in the nickel catalyst, and thus highly controlled polymerization of ethylene is observed, leading to lightly branched ultra-high molecular weight polyethylene with M n values up to 4.1 X 10(6) g/mol. The analogous palladium catalysts provide the means for a detailed mechanistic study of chain propagation in an electronically asymmetric neutral palladium catalyst. Both isomers of the methyl ethylene complex can be generated and observed at low temperatures allowing experimental elucidation of mechanistic details of chain propagation probed in other electronically asymmetric systems only through DFT studies or by examination of model studies. The barrier to migratory insertion in these complexes is ca. 19.2 kcal/mol. Investigation of the equilibration of the methyl ethylene isomers in the presence of excess ethylene showed the isomerization rate is dependent on ethylene concentration. This is the first direct proof that isomerization in these Alkyl ethylene intermediates is catalyzed by ethylene. Furthermore, isomer equilibration is much faster than migratory insertion so that the barriers for insertion of individual isomers cannot be determined.New Neutral Nickel and Palladium Sandwich Catalysts: Synthesis of Ultra-High Molecular Weight Polyethylene (UHMWPE) via Highly Controlled Polymerization and Mechanistic Studies of Chain Propagationx23202047#N/AFALSE
1758
jacs.0c0172410.1021/jacs.0c01724https://doi.org/10.1021/jacs.0c01724Doyle, AGJ. Am. Chem. Soc.A photoassisted Ni-catalyzed reductive cross-coupling between tosyl-protected Alkyl aziridines and commercially available (hetero)Aryl iodides is reported. This mild and modular method proceeds in the absence of stoichiometric heterogeneous reductants and uses an inexpensive organic photocatalyst to access medicinally valuable beta-phenethylamine derivatives. Unprecedented reactivity was achieved with the Activation of cyClic aziridines. Mechanistic studies suggest that the regioselectivity and reactivity observed under these conditions are a result of nuCleophilic iodide ring opening of the aziridine to generate an iodoamine as the active electrophile. This strategy also enables cross-coupling with Boc-protected aziridines.Synthesis of beta-Phenethylamines via Ni/Photoredox Cross-Electrophile Coupling of Aliphatic Aziridines and Aryl IodidesPhotocatalyst172020656/21/2022FALSE
1759
jacs.0c0171810.1021/jacs.0c01718FALSEhttps://doi.org/10.1021/jacs.0c01718Szymczak, NKJ. Am. Chem. Soc.We present the development of ligands featuring the unconventional hydrogen bond donor, -CF2H, within a metal's secondary coordination sphere. When metalated with palladium, o-CF2H-functionalized 1,10-phenanthroline provides highly directed H-bonding interactions with Pd-coordinated substrates. Spectroscopic and computational analyses with a series of X-type ligand acceptors (-F, -Cl, -Br, -OR) establish the H-bonding interaction strength for the -CF2H group (similar to 3 kcal/mol). The synthesis of Pd-0/Ni-0 complexes and subsequent coupling (Ni) highlight the unique reductive and base compatibility of the -CF2H hydrogen bond donor group.Reductively Stable Hydrogen-Bonding Ligands Featuring Appended CF2-H UnitsX6202072#N/AFALSE
1760
jacs.0c0445810.1021/jacs.0c04458FALSEhttps://doi.org/10.1021/jacs.0c04458Dinca, MJ. Am. Chem. Soc.We report on the continuous fine-scale tuning of band gaps over 0.4 eV and of the electrical conductivity of over 4 orders of magnitude in a series of highly crystalline binary alloys of two-dimensional electrically conducting metal-organic frameworks M-3(HITP)(2) (M = Co, Ni, Cu; HITP = 2,3,6,7,10,11-hexaiminotriphenylene). The isostructurality in the M-3(HITP)(2) series permits the direct synthesis of binary alloys (MxM'(3-x))(HITP) 2 (MM' = CuNi, CoNi, and CoCu) with metal compositions precisely controlled by precursor ratios. We attribute the continuous tuning of both band gaps and electrical conductivity to changes in free-carrier concentrations and to subtle differences in the interlayer displacement or spacing, both of which are defined by metal substitution. The Activation energy of (CoxNi3-x)(HITP)(2) alloys scales inversely with an increasing Ni percentage, confirming thermally activated bulk transport.Continuous Electrical Conductivity Variation in M-3(Hexaiminotriphenylene)(2) (M = Co, Ni, Cu) MOF Alloys33202046#N/ATRUE
1761
jacs.0c0445610.1021/jacs.0c04456FALSEhttps://doi.org/10.1021/jacs.0c04456Ohmiya, HJ. Am. Chem. Soc.The generation of tertiary, secondary, and primary Alkyl radicals has been achieved by the direct visible-light excitation of a boracene-based Alkylborate. This system is based on the photophysical properties of the organB(OH)2ron molecule. The protocol is applicable to decyanoAlkylation, Giese addition, and nickel-catalyzed carbon-carbon bond formations such as Alkyl-Aryl cross-coupling or vicinal AlkylArylation of alkenes, enabling the introduction of various C(sp(3)) fragments to organic molecules.Generation of Alkyl Radical through Direct Excitation of Boracene-Based Alkylborate18202049#N/ATRUE
1762
jacs.0c0382110.1021/jacs.0c03821FALSEhttps://doi.org/10.1021/jacs.0c03821Qi, XBJ. Am. Chem. Soc.The direct and chemoselective conversion of the carbon-metal bond of gem-dimetallic reagents enables rapid and sequential formation of multiple carbon-carbon and carbon-heteroatom bonds, thus representing a powerful method for efficiently increasing structural complexity. Herein, we report a visible-light-induced, nickel-catalyzed, chemoselective cross-coupling reaction between gem-borazirconocene alkanes and diverse Aryl halides, affording a wide range of Alkyl Bpin derivatives in high yields with excellent regioselectivity. This practical method features attractively simple reaction conditions and a broad substrate scope. Additionally, we systematically investigated a Bpin-directed chain walking process underlying the regioselectivity of Alkylzirconocenes, thus uncovering the mechanism of the remote functionalization of internal olefins achieved with our method. Finally, DFT calculations indicate that the high regioselectivity of this reaction originates from the directing effect of the Bpin group.Chemoselective Cross-Coupling of gem-Borazirconocene Alkanes with Aryl Halides72020103#N/ATRUE
1763
jacs.0c0370810.1021/jacs.0c03708FALSEhttps://doi.org/10.1021/jacs.0c03708Chu, LLJ. Am. Chem. Soc.A nickel-catalyzed, enantioselective, three-component fluoroAlkylArylation of unactivated alkenes with Aryl halides and perfluoroAlkyl iodides has been described. This cross-electrophile coupling protocol utilizes a chiral nickel/BiOx system as well as a pendant chelating group to facilitate the challenging three-component, asymmetric difunctionalization of unactivated alkenes, providing direct access to valuable chiral beta-fluoroAlkyl Arylalkanes with high efficiency and excellent enantioselectivity. The mild conditions allow for a broad substrate scope as well as good functional group toleration.Enantioselective Three-Component FluoroAlkylArylation of Unactivated Olefins through Nickel-Catalyzed Cross-Electrophile Coupling40202082#N/ATRUE
1764
jacs.0c0285910.1021/jacs.0c02859FALSEhttps://doi.org/10.1021/jacs.0c02859McCloskey, BJ. Am. Chem. Soc.Layered Li-rich Ni, Mn, Co (NMC) oxide cathodes in Li-ion batteries provide high specific capacities (>250 mAh/g) via O-redox at high voltages. However, associated high-voltage interfacial degradation processes require strategies for effective electrode surface passivation. Here, we show that an acidic surface treatment of a Li-rich NMC layered oxide cathode material leads to a substantial suppression of CO2 and O-2 evolution, similar to 90% and similar to 100% respectively, during the first charge up to 4.8 V vs Li+/0. CO2 suppression is related to Li(2)CO(3 )removal as well as effective surface passivation against electrolyte degradation. This treatment does not result in any loss of discharge capacity and provides superior long-term cyCling and rate performance in comparison to as-received, untreated materials. We also quantify the extent of lattice oxygen participation in charge compensation (O-redox) during Li+ removal by a novel ex situ acid titration. Our results indicate that the peroxo-like species resulting from O-redox originate on the surface at least 300 mV earlier than the Activation plateau region at around 4.5 V. X-ray photoelectron spectra and Mn L-edge X-ray absorption spectra of the cathode powders reveal a Li+ deficiency and a partial reduction of Mn ions on the surface of the acid-treated material. More interestingly, although the irreversible oxygen evolution is greatly suppressed through the surface treatment, O K-edge resonant inelastic X-ray scattering shows that the lattice O-redox behavior is largely sustained. The acidic treatment, therefore, only optimizes the surface of the Li-rich material and almost eliminates the irreversible gas evolution, leading to improved cyCling and rate performance. This work therefore presents a simple yet effective approach to passivate cathode surfaces against interfacial instabilities during high-voltage battery operation.Extended Interfacial Stability through Simple Acid Rinsing in a Li-Rich Oxide Cathode Material21202046#N/ATRUE
1765
jacs.0c0078110.1021/jacs.0c00781https://doi.org/10.1021/jacs.0c00781Doyle, AGJ. Am. Chem. Soc.Synthetic organic chemistry has seen major advances due to the merger of nickel and photoredox catalysis. A growing number of Ni-photoredox reactions are proposed to involve generation of excited nickel species, sometimes even in the absence of a photoredox catalyst. To gain insights about these excited states, two of our groups previously studied the photophysics of Ni((t-Bu)bpy)(o-Tol)Cl, which is representative of proposed intermediates in many Ni-photoredox reactions. This complex was found to have a long-lived excited state (tau = 4 ns), which was computationally assigned as a metal-to-ligand charge transfer (MLCT) state with an energy of 1.6 eV (38 kcal/mol). This work evaluates the computational assignment experimentally using a series of related complexes. Ultrafast UV-Vis and mid-IR transient absorption data suggest that a MLCT state is generated initially upon excitation but decays to a long-lived state that is (3)d-d rather than (MLCT)-M-3 in character. Dynamic cis,trans-isomerization of the square planar complexes was observed in the dark using H-1 NMR techniques, supporting that this (3)d-d state is tetrahedral and accessible at ambient temperature. Through a combination of transient absorption and NMR studies, the (3)d-d state was determined to lie similar to 0.5 eV (12 kcal/mol) above the ground state. Because the (3)d-d state features a weak Ni-Aryl bond, the excited Ni(II) complexes can undergo Ni homolysis to generate Aryl radicals and Ni(I), both of which are supported experimentally. Thus, photoinduced Ni-Aryl homolysis offers a novel mechanism of initiating catalysis by Ni(I).(3)d-d Excited States of Ni(II) Complexes Relevant to Photoredox Catalysis: Spectroscopic Identification and Mechanistic ImplicationsPhotocatalyst35202058#N/AFALSE
1766
jacs.0c0075810.1021/jacs.0c00758FALSEhttps://doi.org/10.1021/jacs.0c00758Meyer, FJ. Am. Chem. Soc.Nickel(I) metalloradicals bear great potential for the reductive Activation of challenging substrates but are often too unstable to be isolated. Similar chemistry may be enabled by nickel(II) hydrides that store the reducing equivalents in hydride bonds and reductively eliminate H-2 upon substrate binding. Here we present a pyrazolate-based bis(beta-diketiminato) ligand [L-Ph](3-) with bulky m-terphenyl substituents that can host two Ni-H units in Close proximity. Complexes [L-Ph(Ni-II-H)(2)](-) (3) are prone to intramolecular reductive H-2 elimination, and an equilibrium between 3 and orthometalated dinickel(II) monohydride complexes 2 is evidenced. 2 is shown to form via intramolecular metal-metal cooperative phenyl group C(sp(2))-H oxidative addition to the dinickel(I) intermediate [(LNi2I)-Ni-Ph]- (4). While Ni-I species have been implicated in catalytic C-H functionalization, discrete Activation of C-H bonds at Ni-I complexes has rarely been described. The reversible H-2 and C-H reductive elimination/oxidative addition equilibrium smoothly unmasks the powerful 2-electron reductant 4 from either 2 or 3, which is demonstrated by reaction with benzaldehyde. A dramatic cation effect is observed for the rate of interconversion of 2 and 3 and also for subsequent thermally driven formation of a twice orthometalated dinickel(II) complex 6. X-ray crystallographic and NMR titration studies indicate distinct interaction of the Lewis acidic cation with 2 and 3. The present system allows for the unmasking of a highly reactive [(LNi2I)-Ni-Ph]-intermediate 4 either via elimination of H-2 from dihydride 3 or via reductive C-H elimination from monohydride 2. The latter does not release any H-2 byproduct and adds a distinct platform for metal-metal cooperative two-electron substrate reductions while circumventing the isolation of any unstable superreduced form of the bimetallic scaffold.Competing H-2 versus Intramolecular C-H Activation at a DinuClear Nickel Complex via Metal-Metal Cooperative Oxidative Additionx5202043#N/AFALSE
1767
jacs.0c0267310.1021/jacs.0c02673FALSEhttps://doi.org/10.1021/jacs.0c02673Weix, DJJ. Am. Chem. Soc.Alkyl chlorides and Aryl chlorides are among the most abundant and stable carbon electrophiles. Although their coupling with carbon nuCleophiles is well developed, the cross-electrophile coupling of Aryl chlorides with Alkyl chlorides has remained a challenge. We report here the first general approach to this transformation. The key to productive, selective cross-coupling is the use of a small amount of iodide or bromide along with a recently reported ligand, pyridine-2,6-bis(N-cyanocarboxamidine) (PyBCam(CN)). The scope of the reaction is demonstrated with 35 examples (63 +/- 16% average yield), and we show that the Br- and I- additives act as cocatalysts, generating a low, steady-state concentration of more-reactive Alkyl bromide/iodide.Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Chlorides with Primary Alkyl Chlorides19202072#N/ATRUE
1768
jacs.0c0028310.1021/jacs.0c00283FALSEhttps://doi.org/10.1021/jacs.0c00283Zeng, XMJ. Am. Chem. Soc.We report here the first example of cross-coupling between two different and unactivated C(Aryl)-O bonds with chromium catalysis. The combination of a low-cost Cr(II) salt, 4,4'-di-tart-butyl-2,2'-dipyridyl (dtbpy) as the ligand, and magnesium as the reductant shows high reactivity in promoting the reductive cross-coupling of Aryl methyl ether derivatives with Aryl esters by Cleavage and coupling of two different C(Aryl)-O bonds under mild conditions. The formation of active low-valent Cr species by reduction of CrCl2 with Mg can be considered, which prefers to initially activate the C(Aryl)-O bond of phenyl methyl ether with the chelation help of dtbpy and an o-imine auxiliary. The subsequent consecutive reduction, second C(Aryl)-O Activation, and reductive elimination allow for the achievement of selective cross-coupling of C(Aryl)-O/C(Aryl)-O bonds.Chemoselective Cross-Coupling between Two Different and Unactivated C(Aryl)-O Bonds Enabled by Chromium Catalysisx23202060#N/AFALSE
1769
jacs.0c0238410.1021/jacs.0c02384FALSEhttps://doi.org/10.1021/jacs.0c02384Solomon, EIJ. Am. Chem. Soc.The multicopper oxidases (MCOs) couple four 1e(-) oxidations of substrate to the 4e(-) reduction of O-2 to H2O. These divide into two groups: those that oxidize organic substrates with high turnover frequencies (TOFs) up to 560 s(-1) and those that oxidize metal ions with low TOFs, similar to 1 s(-1) or less. The catalytic mechanism of the organic oxidases has been elucidated, and the high TOF is achieved through rapid intramolecular electron transfer (IET) to the native intermediate (NI), which only slowly decays to the resting form. Here, we uncover the factors that govern the low TOF in Fet3p, a prototypical metallooxidase, in the context of the MCO mechanism. We determine that the NI decays rapidly under optimal turnover conditions, and the mechanism thereby becomes rate-limited by slow IET to the resting enzyme. Development of a catalytic model leads to the important conClusions that proton delivery to the NI controls the mechanism and enables the slow turnover in Fet3p that is functionally significant in Fe metabolism enabling efficient ferroxidase activity while avoiding ROS generation.Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled Fe-II Oxidation for Efficient Metabolism1202064#N/ATRUE
1770
jacs.0c0223710.1021/jacs.0c02237https://doi.org/10.1021/jacs.0c02237Doyle, AGJ. Am. Chem. Soc.We previously reported the development of an electron-deficient olefin (EDO) ligand, Fro-DO, that promotes the generation of quaternary carbon centers via Ni-catalyzed Csp(3)-Csp(3) cross-coupling with aziridines. By contrast, electronically and structurally similar EDO ligands such as dimethyl fumarate and electron-deficient styrenes afford primarily beta-hydride elimination side reactivity. Only a few catalyst systems have been identified that promote the formation of quaternary carbons via Ni-catalyzed Csp(3)-Csp(3) cross-coupling. Although Fro-DO represents a promising ligand in this regard, the basis for its superior performance is not well understood. Here we describe a detailed mechanistic study of the aziridine cross-coupling reaction and the role of EDO ligands in facilitating Csp(3)-Csp(3) bond formation. This analysis reveals that cross-coupling proceeds by a Ni-0/II cyCle with a Ni-II azametallacyClobutane catalyst resting state. Turnover-limiting C-C reductive elimination occurs from a spectroscopically observable Ni-II-diAlkyl intermediate bound to the EDO. Computational analysis shows that Fro-DO accelerates turnover limiting reductive elimination via LUMO lowering. However, it is no more effective than dimethyl fumarate at reducing the barrier to Csp(3)-Csp(3) reductive elimination. Instead, Fro-DO's unique reactivity arises from its ability to associate favorably to Ni-II intermediates. Natural bond order second-order perturbation theory analysis of the catalytically relevant Ni-II intermediate indicates that Fro-DO binds to Ni-II through an additional stabilizing donor-acceptor interaction between its sulfonyl group and Ni-II. Design of new ligands to evaluate this proposal supports this model and has led to the development of a new and tunable ligand framework.Role of Electron-Deficient Olefin Ligands in a Ni-Catalyzed Aziridine Cross-Coupling To Generate Quaternary Carbons8202048#N/ATRUE
1771
jacs.0c0024110.1021/jacs.0c00241FALSEhttps://doi.org/10.1021/jacs.0c00241Cheng, YWJ. Am. Chem. Soc.The low-cost hydrogen production from water electrolysis is crucial to the deployment of sustainable hydrogen economy but is currently constrained by the lack of active and robust electrocatalysts from earth-abundant materials. We describe here an unconventional heterostructure composed of strongly coupled Ni-deficient LixNiO nanoClusters and polycrystalline Ni nanocrystals and its exceptional activities toward the hydrogen evolution reaction (HER) in aqueous electrolytes. The presence of lattice oxygen species with strong Brensted basicity is a significant feature in such heterostructure, which spontaneously split water molecules for accelerated Volmer H-OH dissociation in neutral and alkaline HER. In combination with the intimate LixNiO and Ni interfacial junctions that generate localized hotspots for promoted hydride coupling and hydrogen desorption, the catalysts produce hydrogen at a current density of 10 mA cm(-2) under overpotentials of only 20, 50, and 36 mV in acidic, neutral, and alkaline electrolytes, respectively, making them among the most active Pt-free catalysts developed thus far. In addition, such heterostructures also exhibited superior activity toward the hydrogen oxidation reaction in alkaline electrolytes.LixNiO/Ni Heterostructure with Strong Basic Lattice Oxygen Enables Electrocatalytic Hydrogen Evolution with Pt-like Activity
Electrocatalytic
16202051#N/AFALSE
1772
jacs.0c0014710.1021/jacs.0c00147https://doi.org/10.1021/jacs.0c00147Tambar, UKJ. Am. Chem. Soc.Endergonic isomerizations are thermodynamically unfavored processes that are difficult to realize under thermal conditions. We report a photocatalytic and diastereoselective isomerization of acyClic cinnamyl chlorides to strained cyClopropanes. Quantum mechanical calculations (uM06-2X and DLPNO), inCluding TD-DFT calculations, and experimental studies provide evidence for the energy transfer from an iridium photocatalyst to the allylic chloride substrate followed by C-Cl homolytic Cleavage. Subsequent Cl-center dot radical migration forms a localized triplet 1,3-diradical intermediate that, after intersystem crossing, undergoes ring-Closing to form the desired product. The mild reaction conditions are compatible with a broad range of functional groups to generate chlorocyClopropanes in high yields and diastereoselectivities. A more efficient process is developed by addition of a catalytic amount of a nickel complex, and we propose a novel role for this cocatalyst to recyCle an allyl chloride byproduct generated in the course of the reaction. The reaction is also shown to be stereoconvergent, as an E/Z mixture of cinnamyl chlorides furnish the anti-chlorocyClopropane product in high diastereoselectivity. We anticipate that the use of a visible light activated photocatalyst to transform substrates in combination with a transition metal catalyst to recyCle byproducts back into the catalytic cyCle will provide unique opportunities for the discovery of new reactivity.Photocatalyzed Diastereoselective Isomerization of Cinnamyl Chlorides to CyClopropanesPhotocatalyst15202080#N/AFALSE
1773
jacs.0c0218810.1021/jacs.0c02188FALSEhttps://doi.org/10.1021/jacs.0c02188Chen, JJ. Am. Chem. Soc.Exploring isotropic negative thermal expansion (NTE) compounds is interesting, but remains challenging. Here, a new concept of average atomic volume is proposed to find new NTE open-framework materials. According to this guidance, two NTE compounds, AgB(CN)(4) and CuB(CN)(4), have been discovered, of which AgB(CN)(4) exhibits a large NTE over a wide temperature range (alpha(v) = -40 X 10(-6) K-1, 100-600 K). The analysis by extended X-ray absorption fine structure spectroscopy and first-principles calculation indicate that (i) the NTE driving force comes from the transverse vibrations of bridge chain atoms of C and N, corresponding to the low-frequency phonon modes; and (ii) the same transverse vibration direction of C and N atoms is a key factor for the occurrence of strong NTE in AgB(CN)(4). The present concept of average atomic volume can be a simple parameter to explore new NTE compounds especially in those open-framework materials.Discovering Large Isotropic Negative Thermal Expansion in Framework Compound AgB(CN)(4) via the Concept of Average Atomic Volume20202037#N/ATRUE
1774
ja994281q10.1021/ja994281qFALSEhttps://doi.org/10.1021/ja994281qCurtin, SAJ. Am. Chem. Soc.In the presence of certain ligands and solvents, nickel- and cobalt-mediated living polymerizations of alpha-amino acid-N-carboxyanhydrides (NCAs) produce polymers with molecular weights several times greater than predicted by initial molar ratios of monomer to initiator. Such molecular weight inflation could result either from competitive formation of catalytic intermediates of reduced activity or from incomplete formation of a single catalytically active species. Evidence is presented here supporting the latter possibility. Specifically, evidence is given that the concentration of the key amido-amidate metallacyClic active species is reduced in situ by (1) complexation of metal(0) preinitiator by CO liberated upon addition of an NCA monomer to another molecule of preinitiator, (2) incomplete ring contraction of a six-membered amido-AlkylmetallacyClic intermediate due to inefficient proton migration, and (3) dimerization of the amido-amidate active species to give catalytically inactive complexes.Chain initiation efficiency in cobalt- and nickel-mediated polypeptide synthesisx91200029#N/AFALSE
1775
jacs.0c0214310.1021/jacs.0c02143FALSEhttps://doi.org/10.1021/jacs.0c02143Yang, ZJ. Am. Chem. Soc.The asymmetric total synthesis of (+)-waihoensene, which has a cis-fused [6,5,5,5] tetracyClic core bearing an angular triquinane, a cis-fused six-membered ring, and four contiguous quaternary carbon atoms, was achieved through a sequence of chemical reactions in a stereochemically well-defined manner. The total synthesis features the following: (1) Cu-catalyzed asymmetric conjugated 1,4-addition; (2) diastereoselective Conia-ene type reaction; (3) diastereoselective intramolecular Pauson-Khand reaction; (4) Ni-catalyzed diastereoselective conjugated 1,4-addition; and (5) radical-initiated intramolecular hydrogen atom transfer (HAT). Control experiments and density functional theory calculations support the proposed HAT process.Asymmetric Total Synthesis of (+)-Waihoensene19202062#N/ATRUE
1776
jacs.0c0207510.1021/jacs.0c02075FALSEhttps://doi.org/10.1021/jacs.0c02075Liu, WBJ. Am. Chem. Soc.Chiral nitriles are valuable molecules in modern organic synthesis and drug discovery. Selectively differentiating the two nitrile groups of widely available malononitrile derivatives is a straightforward yet underdeveloped route to construct enantioenriched nitriles. Here we report an enantioselective nickel-catalyzed desymmetrization of malononitriles for the generation of nitrile-containing all-carbon quaternary stereocenters. This protocol involves a nickel-catalyzed addition of Aryl boronic acids to alkynes, followed by a selective nitrile insertion, providing unprecedented access to enantioenriched 5-7-membered alpha-cyanocyCloenones with a fully substituted olefin from a broad range of substrates. The synthetic utility of these nitrile products is demonstrated by gram-scale synthesis and conversion to several useful functional groups.Enantioselective Assembly of CyCloenones with a Nitrile-Containing All-Carbon Quaternary Center from Malononitriles Enabled by Ni Catalysis12202062#N/ATRUE
1777
ja993761e10.1021/ja993761eFALSEhttps://doi.org/10.1021/ja993761eScherz, AJ. Am. Chem. Soc.The relation between electronegativity and the electronic chemical potential provides new avenues for investigating chemical entities and their dynamics. One particular application concerns the tuning of biological redox centers consisting of metals and different ligands, where the effective charge at the metal center and the association and dissociation of the ligands play a key role. To quantify these factors we have recently synthesized a set of metal-substituted bacteriochlorophylls ([M]-BChls), whereby the caged metal can bind various axial ligands of biological significance and the BChl pi-system is used as a molecular potentiometer to estimate the metal's effective charge. Here, we have concentrated on modifying this charge by axial ligation. We specifically selected [Ni]-BChl because (I) it forms three states of coordination with nitrogenous ligands, (2) Ni(II) has biological significance. and (3) [Ni]-porphyrins are extensively used for modeling [Fe]-porphyrins. The pure spectrum of each state of coordination and the equilibrium constants for monoligation (K-1 = 5.6 +/- 0.2 and 29.6 =/- 1.1 M-1) and biligation (K-2 = 35.1 +/- 0.9 and 26.8 +/- 0.9 M-1) of pyridine (Py) and imidazole (Im), respectively, were determined by factor analysis. Following the principle of electronegativity equalization and the model described in our previous paper (Noy, D.; Fiedor, L.; Hartwich, G.; Scheer, H.; Scherz, A. J. Am. Chan. Sec. 1998, 120, 3684-3693), we estimated that 0.30 and 0.27 electron charge units migrated from imidazole and pyridine, respectively, into the [Ni]-BChl central core upon monoligation. An additional, similar amount was transferred with the second ligation. High-level hybrid density functional theory (HDFT) calculations performed for [Ni]-BChl and [Ni]-BChl Im in the gas phase were in very good agreement with the empirical results, suggesting that the [Ni]-BChl central core is enriched by 0.21 electron charge units upon ligation to a single Im molecule. Moreover, the Ni(II) covalent radius expanded by 0.07 and 0.09 Angstrom upon monoligation acid by 0.13 and 0.18 Angstrom upon biligation with pyridine and imidazole, respectively. These results are in good agreement with X-ray data for ligated [Ni]-porphyrins (Jia, S. L.; Jentzen, W.; Shang, M.; Song, X. Z.; Ma, J. G.; Scheidt, W. R,; Shelnutt, J. A. Inorg. Chem. 1998, 37, 4402-4412) and our HDFT calculations (0.085 Angstrom expansion upon Im monoligation). Line shape analyses of the Q(y) bands indicated that the initial excited-state lifetimes of [Ni]-BChl were 75; 153, and 184 fs when ligated with zero, one, or two molecules of imidazole. The lifetimes for the analogous complexes with pyridine were 50% longer. Excitation of [Ni]-BChl . Py-2 caused dissociation of the ligands (in similar to 100 ps), which recovered after a much longer time.Optical absorption and computational studies of [Ni]-bacteriochlorophyll-a. New insight into charge distribution between metal and ligandsx38200061#N/AFALSE
1778
ja993546y10.1021/ja993546yFALSEhttps://doi.org/10.1021/ja993546yObata, KJ. Am. Chem. Soc.The introduction of a thiol group into a chiral alcohol reagent for asymmetric Meerwein-Ponndorf-Verley (MPV) reductions allows asymmetric reduction of alpha,beta-unsaturated ketones to secondary alcohols and allylic alcohols via a novel tandem Michael addition/MPV reduction. The reaction of acyClic alpha,beta-unsaturated ketones 1 and an optically active 1,3-mercapto alcohol (-)-2 using dimethylaluminum chloride afforded the MPV reduction products 3 diastereoselectively in very high yields (up to 96%). Mechanistic studies elucidated (1) the structure of the chelation complex D with (-)-2 and Me2AlCl, (2) an asymmetric 1,7-hydride shift (intramolecular MPV reduction), and (3) dynamic kinetic resolution via reversible Michael addition. Subsequent reductive desulfurization of the MPV products 3 with a modified Raney nickel system led to the highly enantioselective reduction of alpha,beta-unsaturated ketones to saturated secondary alcohols in 96-98% ee. beta-Elimination of the corresponding sulfoxides gave the allylic alcohols in 86-98% ee. Applications to the asymmetric reduction of a synthetic intermediate 1m of prostaglandins and to a new asymmetric synthesis of the (+)-Rove beetle pheromone 11 are described.A novel tandem Michael addition/Meerwein-Ponndorf-Verley reduction: Asymmetric reduction of acyClic alpha,beta-unsaturated ketones using a chiral mercapto alcoholx88200075#N/AFALSE
1779
ja993483j10.1021/ja993483jFALSEhttps://doi.org/10.1021/ja993483jHoffmann, RJ. Am. Chem. Soc.Chemisorbed hydrogen and various intermediate hydrocarbon fragments play an important role in the important reaction of ethylene hydrogenation to ethane, which is catalyzed by Pt(lll). As a first step toward building a theoretical mechanism of the ethylene hydrogenation process, binding site preferences and geometries of chemisorbed hydrogen, methyl, and ethyl on the Pt(lll) surface are presented and rationalized. State-of-the-art Pseudopotential Planewave Density Functional Theory is employed for calculating accurate binding energies and geometries for the adsorbates. A comprehensive theory of hydrogen and methyl chemisorption on Pt(lll) is developed with the help of Crystal Orbital Hamilton Population formalism within the extended Huckel molecular orbital theory. The symmetry properties of the surface Pt orbitals as well as the mixing of Pt s, p, and d orbitals in pure Pt is shown to be crucial in determining the strength of subsequent interaction with an adsorbate. It is suggested that hydrogen moves freely on the Pt(lll) surface while the methyl and ethyl groups are essentially pinned on the atop position. Strong agostic interactions between C-H bonds and surface Pt are proposed for methyl and ethyl on higher symmetry sites. The different nature of chemisorption on Pt and Ni surfaces is speculated. Theoretical results presented in this paper are generally consistent with the available experimental data.A comparative theoretical study of the hydrogen, methyl, and ethyl chemisorption on the Pt(111) surfacex170200065#N/AFALSE
1780
jacs.0c0170010.1021/jacs.0c01700FALSEhttps://doi.org/10.1021/jacs.0c01700Furstner, AJ. Am. Chem. Soc.The marine macrolide chagosensine is supposedly distinguished by a (Z,Z)-configured 1,3-chlorodiene contained within a highly strained 16-membered lactone ring, which also incorporates two trans-2,5-disubstituted tetrahydrofuran (THF) rings; this array is unique. After our initial synthesis campaign had shown that the originally proposed structure is incorrect, the published data set was critically revisited to identify potential mis-assignments. The northern THF ring and the anti-configured diol in the southern sector both seemed to be sites of concern, thus making it plausible that a panel of eight diastereomeric chagosensine-like compounds would allow the puzzle to be solved. To meet the challenge, the preparation of the required building blocks was optimized, and a convergent strategy for their assembly was developed. A key role was played by the cobalt-catalyzed oxidative cyClization of alken-5-ol derivatives (Mukaiyama cyClization), which is shown to be exquisitely chemoselective for terminal alkenes, leaving even terminal alkynes (and other sites of unsaturation) untouched. Likewise, a palladium-catalyzed alkyne alkoxyCarbonylation reaction with formation of an alpha-methylene-gamma-lactone proved instrumental, which had not found application in natural product synthesis before. Further enabling steps were a nickel-catalyzed Tamaru-type homocrotylation, stereodivergent aldehyde homologations, radical hydroindation, and palladium-catalyzed alkyne-1,2-bis-stannation. The different building blocks were assembled in a serial fashion to give the idiosyncratic chlorodienes by an unprecedented siteselective Stille coupling followed by copper-mediated tin/chlorine exchange. The macrolactones were Closed under forcing Yamaguchi conditions, and the resulting products were elaborated into the targeted compound library. Yet, only one of the eight diastereomers turned out to be stable in the solvent mixture that had been used to analyze the natural product; all other isomers were prone to ring opening and/or ring expansion. In addition to this stability issue, our self-consistent data set suggests that chagosensine has almost certainly little to do with the structure originally proposed by the isolation team.Chagosensine: A Riddle Wrapped in a Mystery Inside an Enigma122020140#N/ATRUE
1781
ja993210o10.1021/ja993210oFALSEhttps://doi.org/10.1021/ja993210oVerdaguer, MJ. Am. Chem. Soc.A S=7 ground spin-state Cluster built from three shells of different spin carriers ferromagnetically coupled, transition-metal ions and nitroxide free radicalsx201200017#N/AFALSE
1782
ja993132510.1021/ja9931325FALSEhttps://doi.org/10.1021/ja9931325Lippert, BJ. Am. Chem. Soc.The molecular triangle [{enPt(bpz-N4,N4')}(3)](6+) (en = ethylenediamine; bpz = 2,2'-bipyrazine) has been crystallized as a C-2-symmetric species (1), as a compound of approximate C-3 symmetry, and as a mixture of both forms (Ib). The two triangles differ in their topologies, their Pt-Pt distances, and their anion binding properties. While for the C-2 form insertion of a single PF6- anion in the central cavity is seen in Ib, the C-3 forms of 1a and 1b incorporate either two different anions simultaneously, NO3- and ClO4- (la), or only a single PF6- (1b). Anion inClusion also occurs in solution as detected by H-1 NMR spectroscopy. The molecular triangles l-lb are the kinetic reaction products of enPt(II) and bpz. The thermodynamic product is the chelate [enPt(bpz-N1,N1')](2+) (2a) that is obtained from 1 upon prolonged heating in water. The all-cia geometry of the bpz ligands in the triangle (Cg form) can be locked by chelation of three enPd(II) to the NI,N1' sites. HexanuClear [{enPt(N4,N4'-bpz-N1,N1')Pden}(3)](12+) (3) has been reported by us before. Now the Pt-6 analogue 4, the Pd-6 analogue 5, and the isomer of 3 with the two sorts of metals inverted (6) have been isolated and structurally characterized. All four compounds (3-6), which crystallize as mixed NO3-, PF6- salts, have two different anions embedded in the cavity of the cations of +12 charge. Molecular triangles of the C-3 type can be fused by Ag+ cations via N1,N1' positions to afford the higher-nuClearity compounds Pt6Ag2 (7) and Pt6-Ag3 (8). The latter encapsulates an additional Ag+ and five NO3- anions in its interior (8a). X-ray crystal structures for la, Ib, 2a, 3, 5, 6, 7, and 8a are reported.Molecular architecture based on metal triangles derived from 2,2 '-bipyrazine (Bpz) and EnM(II) (M = Pt, Pd)x135200068#N/AFALSE
1783
jacs.0c0147510.1021/jacs.0c01475TRUEhttps://doi.org/10.1021/jacs.0c01475Sevov, CSJ. Am. Chem. Soc.Cross-electrophile coupling (XEC) of Alkyl and Aryl halides promoted by electrochemistry represents an attractive alternative to conventional methods that require stoichiometric quantities of high-energy reductants. Most importantly, electroreduction can readily exceed the reducing potentials of chemical reductants to activate catalysts with improved reactivities and selectivities over conventional systems. This work details the mechanistically-driven development of an electrochemical methodology for XEC that utilizes redox-active shuttles developed by the energy-storage community to protect reactive coupling catalysts from overreduction. The resulting electrocatalytic system is practical, scalable, and broadly applicable to the reductive coupling of a wide range of Aryl, heteroAryl, or Vinyl bromides with primary or secondary Alkyl bromides. The impact of overcharge protection as a strategy for electrosynthetic methodologies is underscored by the dramatic differences in yields from coupling reactions with added redox shuttles (generally >80%) and those without (generally <20%). In addition to excellent yields for a wide range of substrates, reactions protected from overreduction can be performed at high currents and on multigram scales.General C(sp(2))-C(sp(3)) Cross-Electrophile Coupling Reactions Enabled by Overcharge Protection of Homogeneous ElectrocatalystsCsp2_ar-Csp3XXXArylNo baseNo Base232020847/28/2022TRUE
1784
jacs.0c0113510.1021/jacs.0c01135FALSEhttps://doi.org/10.1021/jacs.0c01135Muller, CRJ. Am. Chem. Soc.Ruthenium pyrochlores, that is, oxides of composition A(2)Ru(2)O(7-delta), have emerged recently as state-of-the-art catalysts for the oxygen evolution reaction (OER) in acidic conditions. Here, we demonstrate that the A-site substituent in yttrium ruthenium pyrochlores Y1.8M0.2Ru2O7-delta (M = Cu, Co, Ni, Fe, Y) controls the concentration of surface oxygen vacancies (V-O) in these materials whereby an increased concentration of V-O sites correlates with a superior OER activity. DFT calculations rationalize these experimental trends demonstrating that the higher OER activity and V-O surface density originate from a weakened strength of the M-O bond, scaling with the formation enthalpy of the respective MOx phases and the coupling between the M d states and O 2p states. Our work introduces a novel catalyst with improved OER performance, Y1.8M0.2Ru2O7-delta, and provides general guidelines for the design of active electrocatalysts.Tailoring Lattice Oxygen Binding in Ruthenium Pyrochlores to Enhance Oxygen Evolution Activity44202042#N/ATRUE
1785
jacs.0c0090510.1021/jacs.0c00905FALSEhttps://doi.org/10.1021/jacs.0c00905Lu, CCJ. Am. Chem. Soc.Bimetallic catalysts of nickel(0) with a trivalent rare-earth ion or Ga(III), NiML3 (where L is [(Pr2PCH2NPh)-Pr-i](-), and M is Sc, Y, La, Lu, or Ga), were investigated for the selective hydrogenation of diphenylacetylene (DPA) to (E)-stilbene. Each bimetallic complex features a relatively short Ni-M bond length, ranging from 2.3395(8) angstrom (Ni-Ga) to 2.5732(4) angstrom (Ni-La). The anodic peak potentials of the NiML3 complexes vary from -0.48 V to -1.23 V, where the potentials are negatively correlated with the Lewis acidity of the M(III) ion. Three catalysts, Ni-Y, Ni-Lu, and Ni-Ga, showed nearly quantitative conversions in the semi-hydrogenation of DPA, with NiYL3 giving the highest selectivity for (E)-stilbene. Initial rate studies were performed on the two tandem catalytic reactions: DPA hydrogenation and (Z)-stilbene isomerization. The catalytic activity in DPA hydrogenation follows the order Ni-Ga > Ni-La > Ni-Y > Ni-Lu > Ni-Sc. The ranking of catalysts by (Z)-stilbene isomerization initial rates is Ni-Ga >> Ni-Sc > Ni-Lu > Ni-Y > Ni-La. In operando P-31 and H-1 NMR studies revealed that in the presence of DPA, the Ni bimetallic complexes supported by Y, Lu, and La form the Ni(eta(2)-alkyne) intermediate, (eta(2)-PhC CPh)Ni(iPr(2)PCH(2)NPh) M-2(kappa(2)-(Pr2PCH2NPh)-Pr-i). In contrast, the Ni-Ga resting state is the Ni(eta(2)-H-2) species, and Ni-Sc showed no detectable binding of either substrate. Hence, the mechanism of Ni-catalyzed diphenylacetylene semihydrogenation adheres to two different kinetics: an autotandem pathway (Ni-Ga, Ni-Sc) versus temporally separated tandem reactions (Ni-Y, Ni-Lu, Ni-La). Collectively, the experimental results demonstrate that modulating a base-metal center via a covalently appended Lewis acidic support is viable for promoting selective alkyne semihydrogenation.Rare-Earth Supported Nickel Catalysts for Alkyne Semihydrogenation: Chemo- and Regioselectivity Impacted by the Lewis Acidity and Size of the Support22202084#N/ATRUE
1786
ja992332d10.1021/ja992332dKelly, LAPhotoprocesses of naphthalene imide and diimide derivatives in aqueous solutions of DNAPhotocatalyst2000#N/AFALSE
1787
jacs.0c0071210.1021/jacs.0c00712FALSEhttps://doi.org/10.1021/jacs.0c00712Peters, JCJ. Am. Chem. Soc.Terminal Ni-III hydrides are proposed intermediates in proton reduction catalyzed by both molecular electrocatalysts and metalloenzymes, but well-defined examples of paramagnetic nickel hydride complexes are largely limited to bridging hydrides. Herein, we report the synthesis of an S = 1/2, terminally bound thiolate-Ni-III-H complex. This species and its terminal hydride ligand in particular have been thoroughly characterized by vibrational and EPR techniques, inCluding pulse EPR studies. Corresponding DFT calculations suggest appreciable spin leakage onto the thiolate ligand. The hyperfine coupling to the terminal hydride ligand of the thiolate-Ni-III-H species is comparable to that of the hydride ligand proposed for the Ni-C hydrogenase intermediate (Ni-III-H-Fe-II). Upon warming, the featured thiolate-Ni-III-H species undergoes bimolecular reductive elimination of H-2. Associated kinetic studies are discussed and compared with a structurally related Fe-III-H species that has also recently been reported to undergo bimolecular H-H coupling.H-2 Evolution from a Thiolate-Bound Ni(III) Hydride9202083#N/ATRUE
1788
jacs.0c0025710.1021/jacs.0c00257FALSEhttps://doi.org/10.1021/jacs.0c00257Wang, SYJ. Am. Chem. Soc.The exact role of a defect structure on transition metal compounds for electrocatalytic oxygen evolution reaction (OER), which is a very dynamic process, remains unClear. Studying the structure-activity relationship of defective electrocatalysts under operando conditions is crucial for understanding their intrinsic reaction mechanism and dynamic behavior of defect sites. Co3O4 with rich oxygen vacancy (V-O) has been reported to efficiently catalyze OER. Herein, we constructed pure spinel Co3O4 and V-O-rich Co3O4 as catalyst models to study the defect mechanism and investigate the dynamic behavior of defect sites during the electrocatalytic OER process by various operando characterizations. Operando electrochemical impedance spectroscopy (EIS) and cyClic voltammetry (CV) implied that the V-O could facilitate the pre-oxidation of the low-valence Co (Co2+, part of which was induced by the V-O to balance the charge) at a relatively lower applied potential. This observation confirmed that the V-O could initialize the surface reconstruction of V-O-Co3O4 prior to the occurrence of the OER process. The quasi-operando X-ray photoelectron spectroscopy (XPS) and operando X-ray absorption fine structure (XAFS) results further demonstrated the oxygen vacancies were filled with OH center dot first for V-O-Co3O4 and facilitated pre-oxidation of low-valence Co and promoted reconstruction/deprotonation of intermediate Co-OOH center dot. This work provides insight into the defect mechanism in Co3O4 for OER in a dynamic way by observing the surface dynamic evolution process of defective electrocatalysts and identifying the real active sites during the electrocatalysis process. The current finding would motivate the community to focus more on the dynamic behavior of defect electrocatalysts.Operando Identification of the Dynamic Behavior of Oxygen Vacancy-Rich Co3O4 for Oxygen Evolution Reaction89202079#N/ATRUE
1789
ja991931h10.1021/ja991931hhttps://doi.org/10.1021/ja991931hBrookhart, MJ. Am. Chem. Soc.Low-temperature spectroscopic observation of chain growth and migratory insertion barriers in (alpha-diimine)Ni(II) olefin polymerization catalystsx238199932#N/AFALSE
1790
jacs.0c0024510.1021/jacs.0c00245FALSEhttps://doi.org/10.1021/jacs.0c00245Gryko, DJ. Am. Chem. Soc.Strain-release-driven methodology is a powerful tool for accessing structural motifs, highly desirable by the pharmaceutical industry. The reactivity of spring-loaded cyClic reagents is dominated by transformations relying on their inherent electrophilic reactivity. Herein, we present a polarity-reversal strategy based on light-driven cobalt catalysis, which enables the generation of nuCleophilic radicals through strain release. The applicability of this methodology is demonstrated by the design of two distinct types of reactions: Giese-type addition and Co/Ni-catalyzed cross-coupling. Moreover, a series of electrochemical, spectroscopic, and kinetic experiments as well as X-ray structural analysis of the intermediate Alkylcobalt(III) complex give deeper insight into the mechanism of the reaction.Polarity-Reversal Strategy for the Functionalization of Electrophilic Strained Molecules via Light-Driven Cobalt Catalysis17202046#N/ATRUE
1791
ja994324310.1021/ja9943243FALSEhttps://doi.org/10.1021/ja9943243Parusel, ABJJ. Am. Chem. Soc.Using regular nonlocal density functional theory (DFT) as well as combined DFT and configuration interaction calculations, we have carried out a first theoretical study of the electronic structure of metallocorroles. The valence orbital energy spectra and the calculated electronic absorption spectrum of (Cor)Ga (Cor(3-) = corrolato), a prototype non-transition-metal carrole, are qualitatively similar to those of a metalloporphyrin such as zinc porphyrin. The four-orbital model holds well for corroles. The a(2) and b(1) KOMOs of (Cor)Ga are crude analogues of the well-known a(1u) and a(2u) porphyrin HOMOs, respectively. Thus, as in the case of porphyrins, there are two nearly equienergetic pi-cation radical states for corroles. DFT also appears to provide a good description of the stabilization of high-valent transition-metal centers and of Ligand noninnocence, two intertwined and central themes in metallocorrole chemistry. The calculated ground state of (Cor)Cu is a diamagnetic d(8) Cu(III) state, with Cu(II) pi-cation radical states only slightly higher in energy, which faithfully mirrors the experimental scenario. In contrast, there are no known Cu(UT) porphyrin complexes. For (Cor)Ni, low-spin Ni(II) x-cation radical states are significantly lower in energy than a Ni(III) state, again consistent with experiment, reflecting the favorable energetics of d(8) square planar complexes. The various optimized geometries reveal significant, characteristic structural changes accompanying the formation of A(2)- and B-1-type corrole pi-cation radicals. We predict that the resonance Raman spectra of metallocorroles should reflect these structural features and, thereby, assist in the assignment of valence tautomeric states of transition-metal corrole complexes.Electronic structure of gallium, copper, and nickel complexes of corrole. High-valent transition metal centers versus noninnocent ligands162200036#N/ATRUE
1792
ja994059l10.1021/ja994059lFALSEhttps://doi.org/10.1021/ja994059lMori, MJ. Am. Chem. Soc.A novel asymmetric cyClization of omega-Carbonyl-1,3-dienes catalyzed by a zerovalent nickel complex in the presence of silanes63200028#N/ATRUE
1793
ja993861k10.1021/ja993861kFALSEhttps://doi.org/10.1021/ja993861kYamamoto, YJ. Am. Chem. Soc.Nickel(0)-catalyzed unprecendented zipper annulation of certain conjugated enynes27200010#N/ATRUE
1794
ja991285m10.1021/ja991285mFALSEhttps://doi.org/10.1021/ja991285mSwager, TMJ. Am. Chem. Soc.The synthesis, electrochemistry, and spectroscopic behavior of tetradentate bis(salicylidenimine) transition metal complexes 5-9 are reported. Appending these complexes with 3,4-ethylenedioxythiophene (EDOT) moieties allows for electrochemical polymerization at much lower potentials than the parent salen complexes. The resulting polymers display well-defined organic-based electrochemistry at potentials <0.5 V vs Fc/Fc(+). The EDOT-modified N,N'-ethylene bis(salicylidene), N,N'-o-phenylene bis(salicylidene), and N,N'-trans-cyClohexylene bis(salicylidene) complexes 5a-b, 6a-b, and 8a-b display cyClic voltammograms with four organic-based redox waves. Increasing the interchain separation through the use of nonplanar bis(salicylidene) ligands results in only two redox waves. The conductivity of the copper-based polymers decreases with increasing interchain spacing, with the maximum conductivity being 92 S cm(-1) for poly(5a) and 16 S cm(-1) for poly(7a). The nickel complexes were less sensitive to increased interchain separation and showed conductivities greater than 48 S cm(-1) regardless of the interchain spacing and near 100 S cm(-1) in the case of poly(6b). In situ spectroelectrochemistry was consistent with the segmented electronic nature of these polymers. CyClic voltammetry of an analogous uranyl complex. 5c, revealed that two electrons per repeat unit were removed during oxidation. Consideration of our collective investigations, which also inCluded in situ EPR spectroscopic studies, led to a postulation that pi-aggregation processes are occurring in those polymers which are allowed to have Close interchain spacing.Polythiophene hybrids of transition-metal bis(salicylidenimine)s: Correlation between structure and electronic propertiesx106199950#N/AFALSE
1795
ja993306i10.1021/ja993306iFALSEhttps://doi.org/10.1021/ja993306iMallouk, TEJ. Am. Chem. Soc.A topochemical route to nondefect, three-dimensional perovskites from lamellar Dion-Jacobson and Ruddlesden-Popper precursors was demonstrated. The method involves reduction of one of the ions (in this case Eu3+) in the precursor phase and concomitant loss of oxygen. CsEu2Ti2NbO10, a three-layer Dion-Jacobson compound, was ion-exchanged to AEu(2)Ti(2)NbO(10) (A = Na, Li) and reduced in hydrogen to form the SrTiO3-type perovskites AEu(2)Ti(2)NbO(9). Similarly, K2Eu2Ti3O10, a three-layer Ruddlesden-Popper compound, underwent divalent ion exchange to form the Dion-Jacobson compounds A(II)Eu(2)Ti(3)O(10) (A(II) = Ca, Sr) and (MEu2Ti3O10)-Eu-II (MII = Ni, CU, Zn), which were reduced in hydrogen to perovskite-type A(II)Eu(2)Ti(3)O(9) and M-II- Eu2Ti3O9, respectively. The A(II) and Eu2+ ions of A(II)Eu(2)Ti(3)O(9) remain ordered, while A-site disordering occurs in the other perovskites. In all cases, the anisotropic texture of the layered precursors is retained in the product perovskite phase.Topochemical synthesis of three-dimensional perovskites from lamellar precursors72200057#N/ATRUE
1796
ja992944y10.1021/ja992944yFALSEhttps://doi.org/10.1021/ja992944yMcBreen, PHJ. Am. Chem. Soc.The molecular orientation and conformation of methyl pyruvate on Ni(lll) was studied in the temperature range 105-220 K. The full monolayer formed at 105 K was found to be almost exClusively in the bidentate cis-conformation, with the molecular plane oriented perpendicular to the surface, in contrast, the low coverage layer at 105 K was found to be composed of a mixture of trans- and cis-methyl pyruvate. However, direct exposure at 200-220 K yielded exClusively cis-bidentate adsorption at all coverages. The observation of the preferred cis-bidentate species is at odds with the adsorption geometry and conformation usually assumed in rationalizations of the enantioselective hydrogenation of methyl pyruvate on chiral-compound modified platinum metal partiCle catalysts.Orientation and conformation of methyl pyruvate on Ni(111)35200066#N/ATRUE
1797
ja990618c10.1021/ja990618cFALSEhttps://doi.org/10.1021/ja990618cBalch, ALJ. Am. Chem. Soc.Solutions of C-60, C60O, or C-70 and metal complexes of octaethylporphyrin (OEPH2) yield crystals that contain both the fullerene and the porphyrin. The structures of C-60. 2Co(II)(OEP). CHCl3, C-60. 2Zn(II)(OEP). CHCl3, and C60O . 2Co(II)(OEP). CHCl3 are isomorphous and contain an ordered C-60 cage surrounded by two M-II(OEP) units. Although there is no covalent bond between the fullerene and porphyrin components, the separation between these units is shorter than normal van der Waals contact. Crystals of C-70. Co-II(OEP). C6H6. CHCl3, C-70. Ni-II(OEP). C6H6. CHCl3, and C-70. Cu-II(OEP). C6H6. CHCl3 are also isomorphous with an ordered fullerene, but have only one porphyrin/fullerene contact. Crystalline C-60. ClFeIII(OEP). CHCl3 lacks the Close face-to-face porphyrin/porphyrin contact that is common to all of the other structures reported here but retains the intimate contact between the porphyrin and the fullerene. In (C120O). Co-II(OEP). 0.6C(6)H(6). 0.4CHCl(3) the fullerene dimer is enClosed by two Con(OEP) moieties. Unfortunately disorder in the fullerene portion obscures details of the geometry of the bridging region between the fullerenes.Interaction of curved and flat molecular surfaces. The structures of crystalline compounds composed of fullerene (C-60, C60O, C-70, and C120O) and metal octaethylporphyrin unitsx331199961#N/AFALSE
1798
ja990449w10.1021/ja990449whttps://doi.org/10.1021/ja990449wWilliams, DJJ. Am. Chem. Soc.The synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMXn (M = Fe, X = Cl, n = 2, 3, X = Br, n = 2; M = Co, X = CI, n = 2), bearing chelating 2,6-bis(imino)pyridyl ligands L [L = 2,6-(ArNCR1)(2)C5H3N] is reported. X-ray diffraction studies show the geometry at the metal centers to be either distorted square pyramidal or distorted trigonal bipyramidal. Treatment of the complexes LMXn with methylaluminoxane (MAO) leads to highly active ethylene polymerization catalysts converting ethylene to highly linear polyethylene (PE). LFeX2 precatalysts with ketimine ligands (R-1 = Me) an approximately an order of magnitude more active than precatalysts with aldimine ligands (R-1 = H). Catalyst productivities in the range 3750-20600 g/mmol.h.bar are observed for Fe-based ketimine catalysts, while Co ketimine systems display activities of 450- 1740 g/mmol.h.bar. Molecular weights (M-w) of the polymers produced are in the range 14000-611000. Changing reaction conditions also affects productivity and molecular weight; in some systems, a bimodal molecular weight distribution is observed. On the basis of evidence gathered to date, the lower molecular weight fraction is a result of chain transfer to aluminum while the higher molecular weight fraction is produced by a combination of mainly beta-H transfer and some chain transfer to aluminum.Iron and cobalt ethylene polymerization catalysts bearing 2,6-bis(imino)pyridyl ligands: Synthesis, structures, and polymerization studiesx1000199965#N/AFALSE
1799
ja990432d10.1021/ja990432dFALSEhttps://doi.org/10.1021/ja990432dBlomgren, PAJ. Am. Chem. Soc.Nickel on charcoal (Ni/C): An expedient and inexpensive heterogeneous catalyst for cross-couplings between Aryl chlorides and organometallics. I. Functionalized organozinc reagentsx100199932#N/AFALSE
1800
ja990397a10.1021/ja990397aFALSEhttps://doi.org/10.1021/ja990397aLudden, PWJ. Am. Chem. Soc.The carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum was examined at several potentials. The electron paramagnetic resonance (EPR) spectrum of CODH poised at approximately -295 mV exhibits a species (referred to as C-red1) that was previously attributed to [Fe4S4](C)(1+) (S = 1/2) weakly exchange-coupling with Ni2+ (S = 1) to yield apparent g-values of (g(z,y,x) = 2.03, 1.88, 1.71). UV-visible absorption spectroscopy showed only one [Fe4S4] Cluster to be reduced at -295 mV. Based upon our assignment of S = 1/2 resonances in indigo carmine-poised C531A CODH (see Part 1: Staples, C. R.; Heo, J.; Spangler, N. J.; Kerby, R. L.; Roberts, G. P.; Ludden, P. W. J. Am. Chem. Sec. In press) to a [(COL)Fe3+-Ni2+-H-](4+) Cluster, a careful search for similar resonances in the EPR spectrum of the enzyme state of wild-type CODH producing C-red1 was undertaken. Coupled putative [(COL)Fe3+-Ni2+-H-](4+) signals were observed in low intensity, which, in conjunction with the other assignments, prompted a reinterpretation of the redox state of the enzyme producing C-red1 Instead of coupling with Ni2+ (S = 1), we propose [Fe4S4]c(1+) (S = 1/2) couples with [(COL)Fe3+-Ni2+-H-](4+) (S 1/2). Th, putative [FeNi] signals were heterogeneous, but this heterogeneity could be removed by preincubation with CO prior to subsequent poising. We propose that an unreactive CO molecule (COL) is bound to the [FeNi] Cluster, possibly modulating the reduction potential and activating the [FeNi] Cluster for catalysis of a substrate CO molecule (COs). Either Zn2+ or Co2+ was incorporated into purified, Ni-deficient CODH. The EPR spectra of reduced Zn-CODH and Co-CODH contain resonances in the g = 1.73-1.76 region (which we call C-red2A), and an upfield wing (shoulder) near g = 2.09. That these features are observed without a paramagnetic heterometal present indicates that they are derived solely from the [Fe4S4](1+) Clusters. These resonances are attributed in fully reduced CODH to spin-spin coupling between [Fe4S4](C)(1+) (S = 1/2) and [Fe4S4](B)(1+) (S = 1/2) When CODH was poised at a calculated potential of -326 mV, the UV-visible absorption spectrum indicated that only one of the [Fe4S4] Clusters was reduced. However, the EPR spectrum was much different than that observed at ca. -295 mV. The EPR spectrum of CODH at -326mV exhibited resonances arising from a slow-relaxing [Fe4S4](1+) (S = 1/2) Cluster (g,,, = 2.04, 1.93, 1.89) and a very minor amount of a fast-relaxing [Fe4S4](1+) (S = 1/2) Cluster. None of the C-red1 coupling signal was present. The fast-relaxing Cluster is assigned to [Fe4S4](B)(1+), while the slow-relaxing Cluster is assigned to uncoupled [Fe4S4](C)(1+). The observation of uncoupled [Fe4S4](C)(1+) at slightly lower potentials suggests the reduction of [(COL)Fe3+-Ni2+-H-](4+) (S 1/2) to [(COL)Fe2+-Ni2+-H-](3+) (S = 0). Treatment of CODH with its physiological product (CO2) while poised at -326mV with 99% reduced phenosafranin results in accumulation of oxidized dye, the production of CO, and the appearance of a new species with g(x) = 1.75. This species has relaxation properties unlike C-red2A. Based upon the method of generation and the relaxation properties of the species, the g = 1.75 feature is assigned to [Fe4S4](C)(1+) (S = 1/2) spin-coupling with [Fe2+-Ni2+](4+) (S = 1) (and is referred to as C-red2B). Based on the data presented in this and Part 1, a mechanism for the oxidation of CO to CO2 by R. rubrum CODH is proposed.Rhodospirillum rubrum CO-dehydrogenase. Part 2. Spectroscopic investigation and assignment of spin - Spin coupling signalsx21199933#N/AFALSE
1801
ja990396i10.1021/ja990396iFALSEhttps://doi.org/10.1021/ja990396iLudden, PWJ. Am. Chem. Soc.A variant of the carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum was constructed by site-directed mutagenesis of the cooS gene to yield a CODH with ala in place of cys-531. This variant form of CODH (C531A) has a metal content identical to that of wild-type CODH but has an extremely slow turnover rate. Cys-531 is not essential for construction of the [Fe4S4] Clusters or for incorporation of nickel. The K-m for methyl viologen is identical to that of wild-type CODH, but the K-m for CO is approximately 30% that of wild-type CODH. The data suggest that in C531A CODH a rate-limiting step has been introduced at the point of electron transfer from the Ni site to an associated [Fe4S4](C) Cluster. Examination of indigo carmine-poised, CO-pretreated C531A CODH revealed the presence of a paramagnetic species (g = 2.33, 2.10, 2.03; g(ave) = 2.16), which was also observed in dithionite-treated samples. This species was shown to represent as much as 0.90 +/- 0.10 spins/molecule, yet production of the species from fully oxidized C531A CODH did not involve a concurrent decrease in the molar extinction coefficient at 420 nm, indicating that the [Fe4S4] Clusters remained in the 2+ oxidation state. Ni-61-substituted CO-pretreated C531A CODH, when poised with indigo carmine, showed no broadening of the resonances, indicating that no detectable spin density resides upon Ni. Comparisons of the EPR spectrum of the g,,, = 2.16 species to Ni-C(CO) and Ni-C of Alcaligenes eutrophus [NiFe] hydrogenase are presented. On the basis of these comparisons and on the lack of Ni-61 broadening, the g(ave) = 2.16 resonance is interpreted as arising from a [(COL)Fe3+-Ni2+-H-](4+) (S = 1/2) system, where COL is an activating nonsubstrate CO ligand. On the basis of the absence of spectroscopic features present in wild-type CODH, and representing coupled forms of the putative [FeNi] Cluster with a [Fe4S4], cys-531 is proposed to be directly involved in the coupling of the putative [FeNi] site with the associated [Fe4S4] Cluster.Rhodospirillum rubrum CO-dehydrogenase. Part 1. Spectroscopic studies of CODH variant C531A indicate the presence of a binuClear [FeNi] Clusterx26199944#N/AFALSE
1802
ja992689h10.1021/ja992689hFALSEhttps://doi.org/10.1021/ja992689hTogni, AJ. Am. Chem. Soc.The catalytic hydroamination of alkenes via alkene Activation and subsequent nuCleophilic attack has been investigated with Car-Parrinello ab initio molecular-dynamics calculations using the projector-augmented wave method. The complete cyCle inCluding all intermediates and transition stales was studied with d(8) transition-metal complexes of the type {MCl(PH3)(2)}(z+) (M = Co, Ph, Ir [z = 0] and Ni, Pd, Pt [z = 1] as catalysts, comparing the different metals for their suitability. For group 9, nuCleophilic attack was identified as the rate-determining step, while the Cleavage of the M-C bond is rate-determining for group 10. Overall, group 10 is more favorable than group 9. In particular, nickel complexes were found to be the best-suited potential catalysts with an Activation barrier for the rate-determining step of 108 kJ mol(-1). beta-Hydride elimination as a competing side reaction was found to be kinetically competitive, but thermodynamically disfavored.Toward an alkene hydroamination catalyst: Static and dynamic ab initio DFT studies157200064#N/ATRUE
1803
ja992447h10.1021/ja992447hhttps://doi.org/10.1021/ja992447hLippard, SJJ. Am. Chem. Soc.A series of dinuClear nickel complexes, [Ni-2(H2O)(4)(bdptz)](OTs)(4), [Ni-2(OH)(H2O)(3)(bdptz)](OTs)(3), and [Ni-2(H2O)(OH)(2)(bdptz)](2)(OTs)(4), where bdptz is the dinuCleating ligand 1,4-bis(2,2'-dipyridylmethyl)phthalazine and OTs is p-toluenesulfonate, were prepared as models for urease. Potentiometric titration of [Ni-2(H2O)(4)(bdptz)](OTs)(4) revealed two deproronation constants with pK(a) values of 4.38 +/- 0.02 and 8.51 +/- 0.02. The product of the first deprotonation, [Ni-2(OH)(H2O)(3)(bdptz)](OTs)(3), effected the stoichiometric hydrolysis of picolinamide in ethanol, a heretofore unprecedented transformation in a dinuClear metallohydrolase model complex. Picolinamide hydrolysis by [Ni-2(H2O)(4)(bdptz)](OTs)(4) or [Ni(teTpy)(H2O)(3)](OTs)(2) (terpy = 2,2':6',2 -terpyridine) under the same conditions was not observed. This amide hydrolysis mimics the hydrolysis of urea by the metalloenzyme urease in that a hydroxide nuCleophile is produced by the dinuClear metal center and the amide is activated for nuCleophilic attack by coordination to the dinuClear nickel center.Amide hydrolysis effected by a hydroxo-bridged dinickel(II) complex: Insights into the mechanism of urease96199959#N/ATRUE
1804
ja990197z10.1021/ja990197zFALSEhttps://doi.org/10.1021/ja990197zZolliker, MJ. Am. Chem. Soc.The ground-state properties of the tetranuClear Ni2+ Cluster [Ni-4(H2O)2(PW9O34)(2)](10-) were investigated by combining magnetic susceptibility and magnetization measurements with a detailed inelastic neutron scattering (INS) study on a fully deuterated sample of K6Na4[Ni-4(H2O)(2)(PW9O34)(2)]. 24H(2)O. The temperature dependence of the magnetic susceptibility indicates a ferromagnetic coupling of the four constituent Ni2+ ions (s = 1), and a low-temperature magnetization study provides the magnitude of the S = 4 ground-multiplet splitting due to the single-ion anisotropy of the Ni2+ ions. Besides a more direct and precise determination of the anisotropic S = 4 ground-multiplet splitting, INS enabled the determination of excited spin multiplets. The best fit to the experimental energy level diagram was obtained by an isotropic Spin Hamiltonian with the inClusion of axial single-ion anisotropy: H=-2J(S1S3 + S1S4 + S2S3 + S2S4)-2J' S1S2 + D(S-z1(2) + S-z2(2)), where J = 0.83 meV, J' = 0.39 meV, D = 0.47 meV, and D' = 0.60 meV. Within this model the experimental intensities of the magnetic Cluster excitations, their characteristic dependence on the scattering vector (Q) over right arrow, as well as the temperature dependence of the magnetic susceptibility and the magnetization properties are reproduced.Magnetic excitations in polyoxometalate Clusters observed by inelastic neutron scattering: Evidence for ferromagnetic exchange interactions and spin anisotropy in the tetrameric nickel(II) Cluster [Ni-4(H2O)(2)(PW9O34)(2)](10-) and comparison with the magnetic propertiesx80199932#N/AFALSE
1805
ja992375u10.1021/ja992375uFALSEhttps://doi.org/10.1021/ja992375uJenkins, HDBJ. Am. Chem. Soc.We develop a powerful new limiting relation between lattice potential energy, U-POT, and unit cell volume, V (hence, also, density), applicable to some of the most complex ionic solids known (inCluding minerals, and superconductive and even disordered, amorphous or molten materials). Our equation (which has a correlation coefficient, R = 0.998) possesses no empirical constants whatsoever, and takes the following form: U-POT = AI(2I/V-m)(1/3). It is capable of estimating Lattice energies in the range 5000 < U-POT/kJ mol(-1) less than or equal to 70 000 and extending toward 100 MJ mol(-1). The relation relies only on the following: (i) an ionic strength related term, I (defined as 1/2 Sigma n(i)z(i)(2) where ni is the number of ions of type i per formula unit, each bearing the charge z(i), with the summation extending over all ions of the formula unit); (ii) a standard electrostatic conversion term, A/kJ mol(-1) nm = 121.39 (the normal Madelung and electrostatic factor as found in the Kapustinskii equation, for example); and (iii) V-m the volume of the formula unit (the molar or molecular volume). The equation provides estimates of U-POT to certainly within +/-7%; in most cases, estimates are significantly better than this. Examples are provided to illustrate the uses of the equation in predicting lattice energies and densities; the calculations require minimal data and can be performed easily and rapidly, even on a pocket calculator. In the lower lattice energy range (i.e., U-POT/kJ mol(-1) < 5000, corresponding to the simpler compounds and to many inorganic salts possessing complex ions), our recently published linear correlation is more accurate. The linear equation, though empirically developed, is consistent with and can be rationalized following the approach developed here.Lattice energies and unit cell volumes of complex ionic solids154200021#N/ATRUE
1806
ja984129910.1021/ja9841299FALSEhttps://doi.org/10.1021/ja9841299Kelly, LAJ. Am. Chem. Soc.The rate constants for electron transfer from guanosine 5'-monophosphate (GMP), adenosine 5'-monophosphate (AMP), cytidine 5'-monophosphate (CMP), and thymidine 5'-monophosphate (TMP) to the triplet excited states of N-(3-propanol)-1,8-naphthalimide (NI), N,N'-(3-propanol)-1,4,5,8-naphthaldiimide (NDI), and N,N'-(3-propanol)-3,3',4,4'-benzophenone (BPDI) have been determined in 1:1 H2O/CH3CN solution. Upon 355-nm (8 ns laser flash excitation of each of the imide or diimides in solution, the triplet sates decayed by first-order kinetics under conditions of low excitation energy. Photoinduced electron transfer to the lowest electronically excited tripler stare of N-(3-propanol)-1,8-naphthalimide from GMP occurred with a rate constant of 2.0 x 10(7) M-1 s(-1) Electron-transfer quenching by the other nuCleotides was almost 2 orders of magnitude slower. In the case of BPDI, photooxidation rate constants ranged from 2.3 x 10(8) M-1 s(-1) for quenching by CMP to 1.1 x 10(9) M-1 s(-1) by GMP. In all cases, the imide radical anion was observed by laser flash photolysis, and the yields were quantified. From these investigations, nuCleotide oxidation by the triplet state of a series of redox-active photosensitizers has been demonstrated. The results represent a systematic study of nuCleotide oxidation by the triplet states of a series of structurally related organic photosensitizers in which the reduction potential can be tuned by ca. 800 mV. The greater than 100-fold variation in bimolecular rate constants for oxidation of base monophosphates by these photosensitizers offers the-prospect of kinetic selectivity of oxidative damage in random-sequence DNA.NuCleic acid oxidation mediated by naphthalene and benzophenone imide and diimide derivatives: Consequences for DNA redox chemistryx139199932#N/AFALSE
1807
ja992300q10.1021/ja992300qFALSEhttps://doi.org/10.1021/ja992300qPeng, SMJ. Am. Chem. Soc.The pentacoordinate, 16-electronFe(11) complex [PPN][Fe(CO)(2)(CN)(S,NH-C6H5)] (1), stabilized by strong S. N pi-donation of chelating [S,NH-C6H4](2-) ligand, was prepared by the reaction of 2-aminophenyl disulfide and [PPN][Fe(CO)(4)(CN)]. Protonation of complex 1 by electrophiles (2-mercaptopyrimidine and 2-aminophenylthiol) yielded hexacoordinate iron(II)-thiolate cyanoCarbonyl complexes [PPN][Fe(CO)(CN)(S-C4H3N2)(2)] (5) and [PPN][Fe(CO)(2)(CN)(S-C6H4NH2)(S,NH2-C6H4)] (3) respectively. The IR spectrum of complex 5 in the aprotic solvent CH3CN displayed a weak nu(CN) band at 2090 cm(-1) and a strong nu(CO) band at 1945 cm(-1). Chemical oxidation of complex 5 in CH3CN at - 20 degrees C with [Cp2Fe][PF6] displayed absorption bands at 2096 and 1962 cm(-1) which were assigned to the nu(CN) and nu(CO) vibrational frequencies respectively of the thermally unstable neutral Fe-III(CO)(CN)(S-C4H3N2)(2). Complex 5 was reobtained upon addition of [PPN][BH4] to Fe-III(CO)(CN)(S-C4H3N2)(2) in CH3CN at -20 degrees C. The first dinuClear Fe(II)-thiolate cyanoCarbonyl compound [PPN](2)[(CN)(CO)(2)Fe(mu-S,S-C6H4)](2) (4), the promising structural and functional model compound of the dinuClear iron active sites of [Fe]-only hydrogenases isolated from D. desulfuricans and C. pasteurianum, was prepared by reacting 1,2-benzenedithiol with complex 1 in THF at -10 degrees C. The X-ray structural analysis shows that complex 4 possesses crystallographically imposed centrosymmetry. Two six-coordinate Fe(II) centers are connected via two thiolate bridges, and both CN- ligands point into the antiparallel direction. The IR spectrum of complex 4 in the aprotic solvent CH2Cl2 revealed a weak absorption band for the CN- ligands at 2101 cm(-1), and two strong absorption bands fur the CO groups at 2013 and 1960 cm(-1). When the CH2Cl2 solution of complex 4 was exposed to (CO)-C-13 at 0 degrees C, absorbances at 1968 and 1915 cm(-1) appeared within 10 min. Reappearance of the 2013 and 1960 cm-l bands on the removal of the (CO)-C-13 and replacement with (CO)-C-12 atmosphere demonstrated reversibility of the CO ligand lability of complex 4. The vibrational spectroscopies of the Fe(CO)(2)(CN) and Fe(CO)(CN) fragments (nu(CN) ranges from 2094 to 2105 cm(-1), nu(CO) ranges from 1928 to 2013 cm(-1)) found in complexes 1, 3, 4, and 5 may be regarded as spectroscopic references of [Fe] hydrogenases in the various enzymatic states.DinuClear and mononuClear iron(II)-thiolate complexes with mixed CO/CN- ligands: Synthetic advances for iron sites of [Fe]-only hydrogenases84200044#N/ATRUE
1808
ja992164p10.1021/ja992164pFALSEhttps://doi.org/10.1021/jacs.5b03192Stevens, KLA convergent approach to coenzyme Q1999#N/ATRUE
1809
ja991888y10.1021/ja991888yFALSEhttps://doi.org/10.1021/ja991888yDuBois, DLJ. Am. Chem. Soc.A series of [M(diphosphine)(2)]X-2, [HM(diphosphine)(2)]X, and M(diphosphine)(2) complexes have been prepared for the purpose of determining the relative thermodynamic hydricities of the [HM(diphosphine)(2)]X complexes (M = Ni, Pt; X = BF4, PF6; diphosphine = bis(diphenylphosphino)ethane (dppe), bis(diethylphosphino)ethane (depe), bis(dimethylphosphino)ethane (dmpe), bis(dimethylphosphino)propane (dmpp)). Measurements of the half-wave potentials (E-1/2) for the M(II) and M(O) complexes and pK(a) measurements for the metal hydride complexes have been used in a thermochemical cyCle to obtain quantitative thermodynamic information on the relative hydride donor abilities of the metal-hydride complexes. The hydride donor strengths vary by 23 kcal/mol and are influenced by the metal, the ligand substituents, and the size of the chelate bite of the diphosphine Ligand. The best hydride donor of the complexes prepared is [HPt(dmpe)(z)](PF6), a third-row transition metal with basic substituents and a diphosphine ligand with a small chelate bite. The best hydride accepters have the opposite characteristics. X-ray diffraction studies were carried out on eight complexes: [Ni(dmpe)(2)](BF4)(2), [Ni(depe)(2)](BF4)(2), [Ni(dmpp)(2)](BF4)(2), [Pt(dmpp)(2)](PF6)(2), [Ni(dmpe)(2)(CH3CN)] (BF4)(2), [Ni(dmpp)(2)(CH3CN)](BF4)(2), Ni(dmpp)(2), and Pt(dmpp)(2). The cations [Ni(dmpp)(2)](2+) and [Pt(dmpp)(2)](2+) exhibit significant tetrahedral distortions from a square-planar geometry arising from the larger chelate bite of dmpp compared to that of dmpe. This tetrahedral distortion produces a decrease in the energy of the lowest unoccupied molecular orbital of the [M(dmpp)(2)](2+) complexes, stabilizes the +1 oxidation state, and makes the [HM(dmpp)(2)](+) complexes poorer hydride donors than their dmpe analogues. Another interesting structural feature is the shortening of the M-P bond upon reduction from M(II) to M(O).Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine)(2)]PF6 complexes (M = Pt, Ni)188199993#N/ATRUE
1810
ja991703n10.1021/ja991703nFALSEhttps://doi.org/10.1021/ja991703nNolan, SPJ. Am. Chem. Soc.Efficient cross-coupling of Aryl chlorides with Aryl grignard reagents (Kumada reaction) mediated by a palladium/imidazolium chloride system367199955#N/ATRUE
1811
ja991573i10.1021/ja991573iFALSEhttps://doi.org/10.1021/ja991573iSloan, JJ. Am. Chem. Soc.The capability of sodium hydride as a reducing agent in oxide deintercalation reactions is explored. The Ni(III) perovskite LaNiO3 can be reduced topotactically to LaNiO2, isostructural with the infinite layer cuprates, using solid sodium hydride in a sealed evacuated tube at 190 less than or equal to T/degrees C less than or equal to 210, and a similar infinite layer phase is prepared by reduction of NdNiO3. Structural characterization indicates the coexistence of incompletely reduced regions, with five-coordinate Ni centers due to the introduction of oxide anions between the NiO23- sheets, giving samples with a refined stoichiometry of LaNiO2.025(3). Neutron powder diffraction and magnetization measurements indicate that the lamellar Ni(I) phase does not show the long-range antiferromagnetic ordering characteristic of isoelectronic Cu(II) oxides. This may be due either to the influence of the interlamellar oxide defect regions or to the reduced covalent mixing of Ni 3d and O 2p levels.Sodium hydride as a powerful reducing agent for topotactic oxide deintercalation: Synthesis and characterization of the nickel(I) oxide LaNiO2218199945#N/ATRUE
1812
ja991310o10.1021/ja991310oFALSEhttps://doi.org/10.1021/jacs.5b06466Siegel, JSSynthesis of corannulene and Alkyl derivatives of corannulene1999#N/ATRUE
1813
ja990997+10.1021/ja990997+FALSEhttps://doi.org/10.1021/ja990997+Montgomery, JJ. Am. Chem. Soc.Nickel catalysis in the stereoselective preparation of quinolizidine, pyrrolizidine, and indolizidine alkaloids: Total synthesis of (+)-allopumiliotoxin 267A121199926#N/ATRUE
1814
ja990827x10.1021/ja990827xFALSEVerani, GNew [M(R,R ' timdt)(2)] metal-dithiolenes and related compounds (M = Ni, Pd, Pt; R,R ' timdt = monoanion of disubstituted imidazolidine-2,4,5-trithiones): An experimental and theoretical investigation1999#N/ATRUE
1815
ja983303q10.1021/ja983303qFALSEhttps://doi.org/10.1021/ja983303qWeaver, DFJ. Am. Chem. Soc.Selective effects of transition metal cations (MR+) on biological activities of nerve growth factor (NGF) have recently been described. It has been suggested that four residues in NGF (His(4), His(8), His(84'), and Asp(105')) form a distorted square base pyramidal coordination complex [M(N . His)(3)((-O2Cgamma). Asp)], thereby inducing a conformational transition within the NGF amino terminus (residues Ser(1)-Phe(12)), which constitutes a critical part of the receptor binding determinant. In this report, we provide theoretical and experimental data validating this structure and suggest a model for the selectivity of the M(II)-NGF interaction. The structures of the model complexes [M(NH3)(3)(-O2CCH3)] and [M(HNCH2)(3)(-O2CCH3)] (mimicking the M(II)-NGF coordination site) with first- and second-row divalent transition metal cations Co(II), Ni(II), Cu(II), Zn(II), Rh(II), Pd(II), and Cd(II) were studied by fully optimized ab initio molecular orbital calculations. Regardless of the chemical nature of the neutral ligands, these cations split into three groups: (i) Ni(II), Cu(II), and Pd(II) (d(8) and d(9) metals), which prefer a square pyramidal coordination; (ii) Co(II), Rh(II) (d(7) metals), and Zn(II) (the d(10) first-row transition metal), which prefer a triangular bipyramidal environment; and (iii) Cd(II) (the d(10) second-row transition metal), which has no intrinsic stereochemical preference. It should be noted, however, that stereochemical preferences of Cu(II) and Zn(II) are minor. Molecular mechanics calculations demonstrate that particular geometric features of the M(II)-NGF coordination sire are most suitable for metal cations of intermediate sizes. Taken together with the intrinsic stereochemical preference of transition metal cations, three ions (Zn(II), Cu(II) and Pd(II)) are expected to be specific NGF antagonists, which is consistent with the effects of these ions on the conformation and biological activities of NGF.Theoretical and biochemical studies on the selectivity of nerve growth factor for transition metal cationsx21199983#N/AFALSE
1816
ja983270e10.1021/ja983270eFALSEhttps://doi.org/10.1021/ja983270eBazan, GCJ. Am. Chem. Soc.Addition of primary and secondary alcohols to C5H5B-PMe3 (2) affords 1-alkoxyboracyClohexa-2,4-dienes hn high yields. Deprotonation of these;boracyClohexadienes, using NaH or lithium diisopropylamide, followed by the reaction with ZrCl4 allows for the coordination of alkoxyboratabenzene ligands to zirconium; Thus, complexes of the type [C5H5B-OR](2)ZrCl2 (R = Et,1; Cy, 3; Ph, 4; and CH2Ph, 5) can be produced in 45-65% overall yield. The crystallographically determined molecular structure of 4 shows evidence for B-O pi orbital overlap. The linked diols 1,2-trans-cyClohexandiol and binaphthol can be used to generate ansa-type zirconium complexes 7 and 9, respectively. When 1, 3, 4, or 5 react with (AlMe3)(2) the organometallic produce is [C5H5B-Me](2)ZrCl2 (10). Cp*[C5H5B-OEt]ZrCl2 (11, Cp* = C5Me5) and (AlMe3)(2) give Cp*[C5H5B-Me]ZrCl2 (13). The complex Cp*[C5H5B(OEt)(AlMe3)]ZrCl2 (12) appears to be an intermediate in the conversion of 11 to 13. A comparison of the molecular structures of 11 and 12 shows that the B-O interaction weakens and the Zr-B distance contracts upon adduct formation. Complexes 1, 3, 4, 9, 10, and [C5H5B-Ph](2)ZrCl2 (14) react with excess methylaluminoxane (MAO) and ethylene (1 atm) to give a Flory-Shultz distribution of olefins. For 7/MAO, ethylene addition results in the formation of polyethylene. The overall activity toward monomer and selectivity for linear 1-alkenes of the catalyst solutions are determined by the exocyClic group of the alkoxyboratabenzene zirconium precursor.Alkoxy- and Aryloxyboratabenzene complexes of zirconiumx45199950#N/AFALSE
1817
ja983247t10.1021/ja983247tFALSEhttps://doi.org/10.1021/ja983247tYoung, DMJ. Am. Chem. Soc.The six-coordinate coordination complex trans-[Ni(cyan-kappa N)(2)(NH3)(4)] has been characterized in the solid state by X-ray and neutron diffraction at temperatures ranging from ii to 298 K, by electronic spectroscopy over the temperature range 14-297 K, and by magnetic susceptibility measurements from 1.8 to 300 K. At room temperature the observed space group is Fmmm, although then is reason to believe that at a finer level of distinction it is really Cmcm approximating Fmmm. The nickel center lies on a site of apparent point symmetry mmm. At lower temperatures, the space group is unambiguously Cmcm without appreciable change in the unit cell parameters. and the molecule lies at a site of m2m symmetry. The shape of the molecule changes smoothly with temperature variations from room temperature down to about 140 K, in a behavior characteristic of second-order phase transformations. The molecular shape varies, but by lesser amounts, below 140 K. Possible causes of this phenomenon are discussed. The increase in intensity on cooling of some of the bands observed in the polarized crystal spectrum of the complex is consistent with the change in the molecular structure. Bonding parameters derived from the transition energies indicate that the cyanurate produces a very weak ligand field, which is consistent with the long metal-ligand bond to this ligand. The magnetic properties of the solid display Curie-Weiss behavior through the temperature range of the most pronounced molecular shape changes, but antiferromagnetic interactions become significant below 50 K, with antiferromagnetic ordering at 2.61 K. The propagation pathways for the magnetic interactions are inferred.Tunable molecular distortion in a nickel complex coupled to a reversible phase transition in the crystalline statex20199933#N/AFALSE
1818
ja990385p10.1021/ja990385pFALSEhttps://doi.org/10.1021/ja990385pYamamoto, YJ. Am. Chem. Soc.Lewis acid-catalyzed stereoselective intramolecular trans-Vinylsilylation of unactivated alkynes32199932#N/ATRUE
1819
ja990311d10.1021/ja990311dFALSEhttps://doi.org/10.1021/ja990311dMoro-oka, YJ. Am. Chem. Soc.Synthesis, structures, and properties of bis-(mu-oxo)nickel(III) and bis(mu-superoxo)nickel(II) complexes: an unusual conversion of a Ni-2(III)(mu-O)(2) core into a Ni-2(II)(mu-OO)(2) core by H2O2 and oxygenation of ligand112200050#N/ATRUE
1820
ja982768d10.1021/ja982768dFALSEhttps://doi.org/10.1021/ja982768dTanaka, TMetal ion induced self-assembly of a designed peptide into a triple-stranded alpha-helical bundle: A novel metal binding site in the hydrophobic coreX1998#N/AFALSE
1821
ja982705v10.1021/ja982705vFALSEhttps://doi.org/10.1021/ja982705vHong, SHJ. Am. Chem. Soc.To enhance the catalytic activity of metal-terpyridyl complexes toward transesterification :of an RNA model [(2-hydroxypropyl)-p-nitrophenyl phosphate, HPNPP], the conformation of terpyridyl moieties assembled on poly(ethylenimine) (PEI) is optimized by attaching the Ni(II) complex of a terpyridyl derivative ((NiTP)-T-II) and lauryl (Lau) group to PEI in random combinations. The catalytic activity per Ni(II) center for transesterification of HPNPP varies by up to several thousand times depending on pH as the content of (NiTP)-T-II or Lau is changed. The best catalyst obtained is [(NiTP)-T-II](5)Lau(12)PEI, in which the contents of (NiTP)-T-II and Lau are 5 and 12 residue mol %, respectively. The catalytic activity of [(NiTP)-T-II](5)Lau(12)PEI expressed in terms of k(cat) is much higher than those of previously reported binuClear metal complexes whose structures were designed through deliberate planning. In the PEI derivatives containing (NiTP)-T-II and Lau, several (NiTP)-T-II groups can be positioned in proximity in the hydrophobic Clusters formed on the polymer. When the (NiTP)-T-II groups take productive positions, the two phosphoryl-oxygen bonds and the hydroxyl group of HPNPP can be effectively activated Thus, artificial active sites comprising multiple catalytic groups are obtained by self-assembly of the catalytic groups. Moreover, cooperative action among the catalytic groups is optimized through combinatorial approach.Catalytic activity of Ni(II)-terpyridine complex in phosphodiester transesterification remarkably enhanced by self-assembly of terpyridines on poly(ethylenimine)x54199866#N/AFALSE
1822
ja982637c10.1021/ja982637cFALSEhttps://doi.org/10.1021/ja982637cDahl, LFJ. Am. Chem. Soc.Efforts to obtain large trimetallic Au-Pd-Ni Carbonyl Clusters have given rise to the first reported high-nuClearity trimetallic Carbonyl Cluster [Au6Pd6(Pd6-xNix)Ni-20(CO)(44)](6-) (1). The centrosymmetric architecture of its 38-atom core ideally consists of the hcp stacking of two inner Au3M3Ni6 and two outer Pd-3 layers along with two Pds-capped and six AuNi2-capped Ni atoms. The resulting octahedral-like Aug kernel is antiprismatically capped on opposite triangular faces by the two Pd3 triangles. The microscopic nature of its nonstoichiometric composition was unequivocally established from complete X-ray diffraction analyses via a SMART CCD system of seven crystals of its [PPh4](+) Salt from different samples. A substitutional Pd/Ni crystal disorder was found at only six specific nonadjacent atomic M sites (three crystallographically independent); for the composite six-site crystal disorder of the (6-x) Pd/x Ni atoms, x was determined for the seven crystals to range from 2.1 (65% Pd, 35% Ni) to 5.5 (8% Pd, 92% Ni). The overall geometry of 1 inCluding the 44 CO ligands (in the crystal-averaged unit cell) ideally has trigonal D-3d((3) over bar 2/m) symmetry. A structure/bonding analysis as to why this particular Pd/Ni substitutional crystal disorder is found in 1 provides a striking illustration that the occurrence of a bimetallic substitutional crystal disorder at only certain crystallographic sites (coloring problem) in a heterometallic Carbonyl Cluster is critically dependent upon the extent of dissimilarity in the composite relative bond-energy effects of metal-metal/metal-CO interactions. 1 was obtained as a major product (35-40% yields) from reactions of [Ni-6(CO)(12)](2-) With Pd(OAc)(2)/Au(PPh3)Cl mixtures in DMSO. Our desire to obtain the hypothetical isostructural [Au6Ni32(CO)(44)](6-) (2), in which all Pd atoms are replaced with Ni ones, led to the designed synthesis and structural determination of 2, which in turn provided an operational test of our coloring-problem analysis of 1. The maximum metal-core diameters in 1 and 2 are ca. 1.1 nm parallel and 0.8 nm perpendicular to the principal 3-fold axis.Isostructural [Au6Pd6(Pd6-xNix)Ni-20(CO)(44)](6-) and [Au6Ni32(CO)(44)](6-) Clusters containing corresponding nonstoichiometric Au6Pd6(Pd6-xNix)Ni-20 and stoichiometric Au6Ni32 nanosized cores: Substitutional Pd Ni crystal disorder (coloring problem) at only six specific nonadjacent pseudoequivalent metal sites in the 38-atom trimetallic Close-packed frameworkx341999100#N/AFALSE
1823
ja982520o10.1021/ja982520oFALSEhttps://doi.org/10.1021/ja982520oKnochel, PJ. Am. Chem. Soc.Ni(II)-catalyzed cross-coupling between polyfunctional Arylzinc derivatives and primary Alkyl iodidesx114199813#N/AFALSE
1824
ja984423110.1021/ja9844231FALSEhttps://doi.org/10.1021/ja9844231Sato, YJ. Am. Chem. Soc.Nickel-catalyzed asymmetric multiple-component tandem coupling. Effects of simple monodentate oxazolines as chiral ligands58199922#N/ATRUE
1825
ja982500m10.1021/ja982500mhttps://doi.org/10.1021/ja982500mSuginome, MJ. Am. Chem. Soc.Aromatizing polymerization of 1,2-diisocyanobenzene derivatives was mediated by optically active organopalladium(II) complexes bearing 1,1'-binaphth-2-yl groups to give optically active poly(quinoxaline-2,3-diyl)s with varying screw-sense selectivities, which crucially depended upon the substituents on the binaphthyl groups. The most effective catalyst, which has 7'-methoxy-1,1'-binaphthyl group, induced the formation of a single screw-sense. Isolation and structural analyses (single-crystal X-ray diffraction and H-1 NMR spectroscopy) of intermediary [oligo(quinoxalinyl)]palladium complexes revealed that the screw-sense selection in the polymerization may be decisively governed by the diastereomeric ratios of the (terquinoxalinyl)-palladium(II) complex intermediate.Asymmetric synthesis of helical poly(quinoxaline-2,3-diyl)s by palladium-mediated polymerization of 1,2-diisocyanobenzenes: Effective control of the screw-sense by a binaphthyl group at the chain-endx112199827#N/AFALSE
1826
ja982277t10.1021/ja982277thttps://doi.org/10.1021/ja982277tCheng, CHJ. Am. Chem. Soc.A novel method for the construction of a fused cyClohexadiene ring on C-60 based on a nickel-promoted [2+2+2] cyCloaddition of 1,6-diynes is described. Treatment of C-60 With terminal 1,6-diynes(HC equivalent to CCH2)(2)X) in the presence of NiCl2(PPh3)(2), Zn, and PPh3 at 90 OC:in toluene afforded [2+2+2] bicyClic hexadiene derivatives (X = C(CO2Me)(2) (2a), C(CO2Et)(2) (2b), C(COMe)(2) (2c), CH2 (2d), O (2e), NSO2-p-C6H5CH3 (2f), C(SO2Ph)(2) (2g), and CC(O)CH2C(CH3)(2)CH2C(O) (2h) in good yields. Spectral data for products 2a-h indicated that the cyCloaddition of diynes to C-60 occurs across a 6,6-ring junction on the fullerene. On the basis of the established chemistry of metal-mediated [2+2+2] cyCloaddition, a mechanism is proposed to account for the present nickel-mediated reaction. All the hexadiene derivatives 2a-h in solution are readily oxidized by molecular oxygen in the presence of Light at ambient temperature. The oxidation process of compound 2a in chloroform-d was monitored by H-1 NMR spectroscopy, and the results showed that 2a first reacted with molecular oxygen to form peroxide 3 and was subsequently converted to dialdehyde 4 and C-60- containing polymeric material. Photochemical properties of some cyClohexadiene derivatives were then investigated. Upon irradiation (350 nm), compounds 2a-c, 2f, and 2h readily underwent [4+4] cyCloaddition to give the corresponding bisfulleroids 5a-c, 5f, and 5h in excellent yields.Nickel-promoted first ene-diyne cyCloaddition reaction on C-60: Synthesis and photochemistry of the fullerene derivativesPhotocatalyst71199858#N/AFALSE
1827
ja982194c10.1021/ja982194cFALSEhttps://doi.org/10.1021/ja982194cToniolo, CDestabilization of the 3(10)-helix in peptides based on C-alpha-tetrasubstituted alpha-amino acids by main-chain to side-chain hydrogen bondsX1998#N/AFALSE
1828
ja984122r10.1021/ja984122rFALSEhttps://doi.org/10.1021/ja984122rDrago, RSJ. Am. Chem. Soc.Adsorption isotherms are reported for Wa-mordenite and H-mordenite at several temperatures with a series of gas adsorptives above their critical temperature. The data sets are analyzed with the multiple equilibrium analysis (MEA) method [Drago, R. S.; et al. J. Am. Chem. Sec. 1998, 120, 538-547. Drago, R. S.; et al. J. Phys. Chem. B 1997, 101, 7548-7555], which produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, Delta H-i, and entropies, Delta S-i) of adsorption for each process. The limited pore size distribution present in the zeolite mordenite presents an interesting comparison to the amorphous carbons studied previously by MEA [Drago,:R. S.; et al. J. Phys. Chem. B 1997, 101, 7548-7555]. The results of the MEA description of the adsorption data gathered for the interaction of an adsorbate (particularly, N-2, CO, and Xe) with Na-mordenite and H-mordenite are compared to other literature reports (inCluding infrared spectroscopic studies and Monte Carlo simulations), and good agreement is found. In general, for adsorbates that can access the small channel (small adsorbates), three processes are required to describe adsorption. Two processes are required to describe adsorption for the larger adsorbates into the large (main) channel. The smaller total micropore volumes of Na- and H-mordenite for these adsorptives result in decreased capacity compared to that of the amorphous carbons. The process capacities from MEA (mol g(-1)) are converted to pore volumes using the calculated molar volume of the adsorbate, and the accessible surface area for a given process is converted with the exCluded molecular area of the adsorbate. The results show that MEA provides a more detailed and accurate assessment of the interaction of admolecules with microporous solids, which addresses a matter of fundamental importance to researchers and practitioners-the interactions between gas-phase molecules and a surface of a condensed phase. This analysis leads to an increased understanding of this behavior in gas adsorption and catalysis.Multiple equilibrium analysis description of adsorption on Na-mordenite and H-mordenite51199953#N/ATRUE
1829
ja982174a10.1021/ja982174aFALSEhttps://doi.org/10.1021/ja982174aHrbek, JJ. Am. Chem. Soc.The surface chemistry of SO2 on polycrystalline Sn, Pt(lll), and a (root 3 x root 3)R30 degrees-Sn/Pt(lll) surface alloy has been investigated using synchrotron-based high-resolution photoemission and ab initio self-consistent field calculations. Metallic tin has a large chemical affinity for SO2. At 100-150 K, SO2 disproportionates on polycrystalline tin forming multilayers of SO3 (2SO(2,a) --> SOgas + SO3,a). At these low temperatures, the full dissociation of SO2 (SO2,a --> S-a + 2O(a)) is minimal. As the temperature is raised to 300 K, the SO3 decomposes, yielding SO4, S, and O on the surface. Pure tin exhibits a much higher reactivity toward SO2 than late transition metals (Ni, Pd, Pt, Cu, Ag, Au) In contrast, tin atoms in contact with Pt(111) interact weakly with SO2. A (root 3 x root 3)R30 degrees-Sn/Pt(111) alloy is much less reactive toward SO2 than polycrystalline tin or Clean Pt(lll). At 100 K, SO2 adsorbs molecularly on (root 3 x root 3)R30 degrees-Sn/Pt( ill). Most of the adsorbed SO2 desorbs intact from the surface (250-300K), whereas a small fraction dissociates into S and O. The drastic drop in reactivity when going from pure tin to the (root 3 x root 3)R30 degrees-Sn/Pt(111) alloy can be attributed to a combination of ensemble and electronic effects. On the other hand, the low reactivity of the Pt sites in (root 3 x root 3)R30 degrees-Sn/Pt(lll) with respect to P(111) is a consequence of electronic effects. The Pt-Sn bond is complex, involving a Sn(5s,5p)--> Pt(6s,6p) charge transfer and a Pt(5d)--> Pt(6s,6p) rehybridization that localize electrons in the region between the metal centers. These phenomena reduce the electron donor ability of Pt and Sn, and both metals are not able to respond in an effective way to the presence of SO2. The Sn/Pt system illustrates how a redistribution of electrons that occurs in bimetallic bonding can be useful for the design of catalysts that have a remarkably low reactivity toward SO2 and for controlling sulfur poisoning.Surface chemistry of SO2 on Sn and Sn/Pt(111) alloys: Effects of metal-metal bonding on reactivity toward sulfurx80199872#N/AFALSE
1830
ja982136r10.1021/ja982136rFALSEhttps://doi.org/10.1021/ja982136rKadish, KMJ. Am. Chem. Soc.Homogeneous electron-transfer kinetics for the oxidation of seven different iron(III) porphyrins using three different oxidants were examined in deaerated acetonitrile, and the resulting data were evaluated in light of the Marcus theory of electron transfer to determine reorganization energies of the rate-determining oxidation of iron(III) to iron(IV). The investigated compounds are represented as (P)Fe(R), where P = the dianion of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin (OETPP) and R = C6H5, 3,5-C6F2H3, 2,4,6-C6F3H2, or C6F5 Or P = the dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) and R = C6H5, 2,4,6-C6F3H2, or 2,3,5,6-C6F4H. The first one-electron transfer from (P)Fe(R) to [RU(bpy)(3)](3+) (bpy = 2,2'-bipyridine) leads to an Fe(IV) sigma-bonded complex, [(P)Fe-IV(R)](+), and occurs at a rate which is much slower than the second one-electron transfer from [(P)Fe-IV(R)](+) to [Ru(bpy)(3)](3+) to give [(P)Fe-IV(R)](. 2+). The one- or two-electron oxidation of each (OETPP)Fe(R) or (OEP)Fe(R) derivative was also attained by using [Fe(phen)(3)](3+) (phen = 1,10-phenanthroline) or [Fe(4,7-Me(2)phen)(3)](3+) (Me(2)phen = 4,7-dimethyl-1,10-phenanthroline) as an electron-transfer oxidant. The reorganization energies (kcal mol(-1)) for the metal-centered oxidation of (P)Fe-III(R) to [(P)Fe-IV(R)](+) increase in the order (OEP)Fe(R) (83 +/- 4) much less than (OETPP)Fe(C6F5)(99 +/- 2) < (OETPP)Fe(2,4,6-C6F3H2) (107 +/- 2) < (OETPP)Fe(3,5-C6F2H3) (109 +/- 3) < (OETPP)Fe(C6H5) (113 +/- 3). Each value is significantly larger than the reorganization energies determined for the porphyrin-centered oxidations involving the same two series of compounds, i.e., the second electron transfer of (P)Fe(R). In each case, the first metal-centered oxidation is the rate-determining step for generation of the iron(IV) porphyrin pi radical cation. Coordination of pyridine to (OETPP)Fe(C6F5) as a sixth axial ligand enhances significantly the rate of electron-transfer oxidation.Electron-transfer kinetics for generation of organoiron(IV) porphyrins and the iron(IV) porphyrin pi radical cationsx51199949#N/AFALSE
1831
ja983971b10.1021/ja983971bFALSEhttps://doi.org/10.1021/ja983971bField, MJJ. Am. Chem. Soc.We have investigated using theoretical methods some of the redox states of the active site of Desulfovibrio gigas NiFe hydrogenase, which is a metalloprotein that catalyzes the reversible reaction H-2 <--(-->) 2H(+) + 2 e(-). A hybrid potential that combines ab initio density functional theory and a molecular mechanics energy function was employed. Starting from the X-ray structure of the oxidized form refined at 2.54 Angstrom resolution, we have optimized the structures of the active site redox states, believed to be involved in the Activation and the catalytic cyCle of the enzyme, and compared them with the available X-ray data. We have also tested various hypotheses concerning the oxidation states of the Ni-Fe bimetallic center and the protonation states of the active site by comparing calculated spin densities and vibrational frequencies with EPR and IR spectroscopic data. The good agreement we have obtained with experiment allows us to identify more precisely those structures that are likely to be important in the enzymatic reaction mechanism.A hybrid density functional theory molecular mechanics study of nickel-iron hydrogenase: Investigation of the active site redox states127199954#N/ATRUE
1832
ja983939h10.1021/ja983939hFALSEhttps://doi.org/10.1021/ja983939hPorschke, KR1,6-diene complexes of palladium(0) and platinum(0): Highly reactive sources for the naked metals and [L-M-0] fragments1999#N/ATRUE
1833
ja983931810.1021/ja9839318FALSEhttps://doi.org/10.1021/ja9839318Yamabe, TJ. Am. Chem. Soc.The inversion of methane bound to first-row transition-metal ions from Sc+ to Cu+ is systematically investigated using the B3LYP method, a hybrid density-functional-theory method of Becke and Lee, Yang, and Parr. The computed transition states for the methane inversion on the M+(CH4) complexes have a C-s structure in which one pair of C-H bonds is about 1.2 Angstrom in length and the other pair is about 1.1 Angstrom. The barrier height for the methane inversion is significantly decreased from 109 kcal/mol for free methane to 43-48 kcal/mol on the late transition-metal complexes, Fe+(CH4), Co+(CH4), Ni+(CH4), and Cu+(CH4). Since each Activation energy involves the binding energy of the complex (16 kcal/mol on the average), the actual barrier height should be lower by this quantity if measured from the dissociation limit. The inversion of methane can therefore occur at the transition-metal active center of catalysts or enzymes under ambient conditions through a thermally accessible transition state, and it would reasonably lead to inversion of stereochemistry at a carbon atom in catalytic reactions of hydrocarbons. We propose that a radical mechanism based on a planar carbon species may not be the sole source of the observed loss of stereochemistry in transition-metal-catalyzed hydrocarbon hydroxylations and other related reactions.Inversion of methane on transition-metal complexes: A possible mechanism for inversion of stereochemistry331999118#N/ATRUE
1834
ja981457010.1021/ja9814570FALSEhttps://doi.org/10.1021/ja9814570Vogel, EJ. Am. Chem. Soc.The electrochemistry of (OEC)M where M Mn, Co, Ni, or Cu and OEC is the trianion of 2,3,7,8, 12,13,17,18-octaethylcorrole was investigated in dichloromethane, benzonitrile, or pyridine, and the oxidized compounds were characterized by UV-visible and/or ESR spectroscopy. The first two oxidations of the Co, Ni, and Cu corroles involve the reversible stepwise abstraction of 1.0 electron per two (OEC)M units and lead to [(OEC)M](2)(+) and [(OEC)M](2)(2+), which are assigned as pi-pi dimers containing oxidized corrole macrocyCles and divalent central-metal ions on the basis of the electrochemical and spectroscopic data. The ESR spectrum of [(OEC)Cu](2)(+) suggests the presence of one ESR-active Cu(II) center in the singly oxidized dimer. Further bulk electrooxidation of [(OEC)Cu](2)(+) at potentials positive of the second oxidation results in the abstraction of a second electron from the dimeric unit and leads to a triplet ESR spectrum typical of a copper(II) dimer, from which a Cu-Cu distance of 3.88 Angstrom is calculated. The ESR spectrum of [(OEC)Co](2)(+) in frozen CH2Cl2 at 77 K has a major line at g(perpendicular to) = 2.40 with a weak signal at g(parallel to) = 1.89 and is typical of a Co(II) ion. The doubly oxidized dimer, [(OEC)Co](2)(2+), is ESR silent in CH2Cl2 or PhCN, thus suggesting that the two unpaired electrons of the two Co(II) ions in [(OEC)Co](2)(2+) are coupled. The absolute potential difference between E-1/2 for generation of [(OEC)M](2)(+) and [(OEC)M](2)(+) can be related to the degree of interaction between the two (OEC)M units of the dimer and follows the order Co (Delta E-1/2 = 460 mV) > Ni (Delta E-1/2 = 260 mV) > Cu (Delta E-1/2 =; 140 mV). No evidence is seen for dimerization of (OEC)Mn after oxidation to its Mn(IV) form in the first electron-transfer step, and the occurrence of this metal-centered reaction may be the reason for the absence of dimerization.Electrogeneration of oxidized corrole dimers. Electrochemistry of (OEC)M where M = Mn, Co, Ni, or Cu and OEC is the trianion of 2,3,7,8,12,13,17,18-octaethylcorrolex94199851#N/AFALSE
1835
ja983521j10.1021/ja983521jFALSEhttps://doi.org/10.1021/jacs.1c04348Verdaguer, MSoft X-ray magnetic circular dichroism in paramagnetic systems: Element-specific magnetization of two heptanuClear Cr-III M-6(II) high-spin molecules1999#N/ATRUE
1836
ja983469r10.1021/ja983469rFALSEhttps://doi.org/10.1021/ja983469rHall, MBJ. Am. Chem. Soc.The catalytic cyCle for H-2 oxidation in [NiFe] D. gigas hydrogenase has been investigated through density functional theory (DFT) calculations on a wide variety of redox and protonated structures of the active site model, (CO)(CN)(2)Fe(mu-SMe)(2)Ni(SMe)(2). DFT calculations on a series of known LFe(CO)(CN)(L')(n-) (L = Cp or Cp*, L' = CN, CO, CNCH3; n = 0, 1, 2) complexes are used to calibrate the calculated CO bond distances with the measured IR stretching frequency. By combining this calibration curve with the energy and CO bond distance of the DFT calculations on the active site model and the experimental IR frequencies on the enzyme, the redox states and structures of active site species have been determined: Ni-B is a Ni(III)-Fe(II) species, Ni-SI(a) is a Ni(LI)-Fe(II) species, Ni-SI(b) has a protonated terminal sulfur (Ni bound), Ni-R is a Ni(II)-Fe(II) dihydrogen complex with H-2 bound at Fe, and Ni-C is a Ni(III)-Fe(II) species with an Fe-H-Ni bridge. The latter species returns to W-SI through a Ni(I)-Fe(II) intermediate, which is potentially observable. Protonation of the Ni bound terminal sulfur results in a folding of the Fe(mu-S)(2)Ni framework. Dihydrogen Activation is more exothermic on the Ni(III) species than on the corresponding Ni(II) or Ni(I) species. Our final set of proposed structures are consistent with IR, EPRI ENDOR,and XAS measurements for these species, and the correlation coefficient between the measured CO frequency in the enzyme and the CO distance calculated for the model species is 0.905.Theoretical characterization, of the reaction intermediates in a model of the nickel-iron hydrogenase of Desulfovibrio gigas176199944#N/ATRUE
1837
ja983400j10.1021/ja983400jFALSEhttps://doi.org/10.1021/ja983400jBoese, RJ. Am. Chem. Soc.Metal atom synthesis of (eta(6)-toluene)(eta(2)-ethene)iron(sigma(1)-stannandiyls): Unusual iron(0) complexes20199924#N/ATRUE
1838
ja983348r10.1021/ja983348rFALSEhttps://doi.org/10.1021/ja983348rSato, YJ. Am. Chem. Soc.Enones 1 reacted with two molecules of alkynes 2 (R = R' in eq 1) in the presence of a nickel(0) and aluminum catalytic system to give cyClotrimerization adducts regioselectively. Aluminum phenoxide (MenAl(OPh)(3-n) (n = 0-3)) functions as a Lewis acid cocatalyst and activates 1. Stoichiometric experiments suggest that the cyCloaddition of 1 and 2 proceeds via nickelacyClopentadiene intermediates, which are formed by the oxidative coupling of Ni(0) species with 2. In addition, the selective cyClotrimerization of 1 and two different alkynes 2 and 2' (R not equal R' in eq 1) was also accomplished in the presence of a binary metal catalytic system. The reaction occurs effectively when an Alkyl- or Aryl-substituted alkyne (alkyne B, 1 equiv vs 1) is added slowly to a mixture of 1 and a bulkier alkyne (alkyne A, 1 equiv vs 1) such as tert-butylacetylene (2f) or (trimethylsilyl)acetylene (2g).Selective cyClotrimerization of enones and alkynes by a nickel and aluminum catalytic system74199927#N/ATRUE
1839
ja983081w10.1021/ja983081wFALSEhttps://doi.org/10.1021/ja983081wMontgomery, JJ. Am. Chem. Soc.Novel chemoselectivity and stereochemical aspects of nickel-catalyzed [2+2+2] cyCloadditions79199915#N/ATRUE
1840
ja982851110.1021/ja9828511FALSEhttps://doi.org/10.1021/ja9828511Nuzzo, RGJ. Am. Chem. Soc.We have investigated the growth, morphology, and phase evolution of Pt-Si intermetallic thin films using scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). These materials were formed through an inverted CVD deposition process that involves the exposure of a Pt(100) crystal to silane (SiH4) followed by flash annealing treatments. Structural studies performed as a function of the annealing temperature reveal a complicated phase behavior that involves the sequential formation of four atomically ordered phases with multilevel character. The nature of this process is analyzed to obtain information about the primary structure-determining interactions responsible for the phase transformations seen in this system. We describe the structure-determining influences seen on the Pt(100) surface and provide a comparison with earlier results obtained on Pt(111) and Ni surfaces. The substrate effects are marked and the differences between the results obtained on Pt(100) and Pt(111) are discussed in detail. A model is presented that relates the structure of the phases obtained on the Pt(100) surface to known bulk Pt silicide phases. Of particular interest is the finding that inverted CVD via the thermolytic decomposition of SiH4 on the Pt(100) substrate yields, upon suitable thermal treatment, a(root 17 x root 17)R14.0 degrees overlayer structure exhibiting two chiral surface domains. This multilayer structure is well described by a termination of the bulk Pt-Si intermetallic phase that is isomorphic with the well-known Ni12P5 structure.Thermal phase evolution of Pt-Si intermetallic thin films prepared by the activated adsorption of SiH4 on Pt(100) and comparison to known structural models9199941#N/ATRUE
1841
ja982515k10.1021/ja982515kFALSEhttps://doi.org/10.1021/ja982515kDidillon, BJ. Am. Chem. Soc.To understand the mechanism of Pt deposition during the synthesis of supported catalysts, liquid phase Pt-195 NMR spectroscopy was applied first to study the speciation of platinum complexes in aqueous solutions of H2PtCl6 as a function of pH and time of hydrolysis and second to follow the adsorption of platinum complexes on gamma-alumina from these solutions. Five of the six Pt complexes that can exist in hydrolyzed Hz PtCl6 solutions are identified by their Pt-195 chemical shift(delta(Pt)): [PtCl6](2-), [PtCl5(H2O)](-), [PtCl5(OH)](2-), [PtCl4(H2O)(2)], and [PtC4(OH)(2)](2-). For [PtCl4(OH)(H2O)](-), which cannot be directly detected in NMR spectra due to fast proton exchange. delta(Pt), is calculated from the best fit of the delta(Pt) = f(pH) dependence to the experimental data. The acid dissociation constants (pK(a),) for aquaplatinates are also determined and discussed in comparison to literature data. For H2PtCl6 solution-Al2O3 mixtures, NMR signals of [PtCl6](2-) and [PtCl5(OH)](2-) at the interface were observed for the first time. The [PtCl6](2-) signal has a small negative delta(Pt) relative to that in H2PtCl6 solutions, which indicates a slight perturbation of the Pt atom coordination sphere by the alumina surface. It is suggested that adsorbed [PtCl5(OH)](2-) results from fast deprotonation of the water molecule ligand in [PtCl5(H2O)](-) by alumina basic hydroxyls. Most likely, the platinum anions are held on the positively charged alumina surface by electrostatic interaction. The fraction of adsorbed [PtCl5(OH)(2-) rises with increasing initial pH of H2PtCl6 solutions and becomes dominant at higher pH. The [PtCl6](2-) and [PtCl5(OH)(2-) signals disappear after removal of physisorbed water from alumina powder at room temperature and reappear almost unchanged upon subsequent rewetting of the solid. In contrast, after drying at 90 degrees C for 1.5 h, no NMR signal can be detected for the dried samples, and much weaker signals than those in the original solid are observed for the rewetted sample. The disappearance of the NMR signals is supposed to be due to formation of lower symmetry grafted Pt complexes with a higher chemical shift anisotropy. The likely mechanisms of platinum deposition from acidic H2PtCl6 solutions on positively charged alumina surface are discussed.Application of NMR to interfacial coordination chemistry: A Pt-195 NMR study of the interaction of hexachloroplatinic acid aqueous solutions with alumina72199948#N/ATRUE
1842
ja982178f10.1021/ja982178fFALSEhttps://doi.org/10.1021/ja982178fRizzoli, CJ. Am. Chem. Soc.This report deals with the different transition metal- and alkali cation-assisted oxidation pathways of the meso-octaethylporphyrinogen tetraanion [Et8N4](4-). The two-electron oxidation of [Et8N4Mn{Na(thf)(2)}(2)], 4, with Cp2FeBPh4 led to the corresponding monocyClopropane derivative [Et8N4(Delta)Mn], 6, [Delta = cyClopropane], while the one-electron oxidation with CuCl2 or O-2 led to the Mn(III)-porphyrinogen [Et8N4Mn][Li(thf)(4)], 5, which can be further oxidized by an excess of CuCl2 to [Et8N4(Delta)(2)Mn-Cl](+)[Cu9Cl11](0.5), 7. The formation of 7 does not follow the expected sequence Mn(II) --> Mn(III) --> Mn(II)-monocyClopropane --> Mn(II) - biscyClopropane-porphyrinogen. In the case of iron(II)-porphyrinogen, [Et8N4Fe{Li(thf)(2)}(2)], 9, the oxidation led in a preliminary stage to the iron(III) derivative [Et8N4Fe][Li(thf)(4)], 10, then to the metalated form of the biscyClopropane-porphyrinogen [Et8N4(Delta)(2)Fe-Cl]{mu-Cu4Cl5}], 11. The supposed stabilization of the biscyClopropane by the copper(I) Cluster was ruled out by carrying the oxidation of [Cy4N4Fe{Li(thf)(2)}(2)], 11, to [Cy4N4(Delta)(2)Fe-Cl][Cu2Cl4], 14. The stepwise oxidation of [Et8N4M(thf)(4)] [M = Li, 1; M = Na, 2] with Cp2FeBPh4 led to [Et8N4(Delta)Li(2)thf(2)], 15, [Et8N4(Delta)Li]BPh4, 16, and [Et8N4(Delta)Na]BPh4, 17. The reaction of 1 with 16 leading to 15 showed how the C-C moiety in cyClopropane can be engaged in an intermolecular electron transfer. The reaction of 17 with 18-crown-6 allowed the release of biscyClopropane-porphyrinogen [Et8N4(Delta(2))] Particularly interesting is the thermal rearrangement of 15 to 19 occurring via intra- and intermolecular electron transfers with the transposition of the C-C bond of the cyClopropane to a C-C bridge across the beta position of two adjacent pyrroles. In the case of metals, such as Ni(II), which do not undergo oxidation state changes, the primary oxidation product of a metalla-meso-octaAlkylporphyrinogen is the monocyClopropane derivative, which reacting with the starting material masks an overall one-electron oxidation. In fact, the reaction of [Et8N4Ni{Li(thf)(2)}(2)], 20, with 2 equiv of Cp2FeBPh4 led to the expected [Et8N4(Delta)Ni], 21, while the reaction of 20 with 1 equiv of Cp2FeBPh4 led to the dimer [(beta-beta)(Et8N4)(2)Ni-2], 22, which forms equally well from the reaction of 20 and 21. Complex 22 is a quite unique metallaporphyrinogen dimer, where the two monomeric units are joined via a C-C bond in the beta position of a pyrrole. Such a reaction shows that the methodology can accede to oligomeric forms of metallaporphyrinogens.One- and two-electron oxidative pathways leading to cyClopropane-containing oxidized porphyrinogens and C-C-coupled porphyrinogens from alkali cation and transition metal meso-octaethylporphyrinogen complexes31199946#N/ATRUE
1843
ja982064410.1021/ja9820644FALSEhttps://doi.org/10.1021/ja9820644Andrews, LJ. Am. Chem. Soc.Laser-ablated Ni atoms and electrons react with CO in excess argon during condensation to form the Ni(CO)(1-4) complexes and Ni(CO)(1-3)(-) anions. Matrix infrared spectra of the neutral complexes with (CO)-C-12-O-16, (CO)-C-13-O-16 and (CO)-C-12-O-18 substitution are in agreement with earlier reports with thermal Ni atoms. In addition, new absorptions at 1847.0, 1801.7, and 1858.8 cm(-1) exhibit isotopic spectra in excellent agreement with DFT calculations for the Ni(CO)(1-3)(-) anions. An experiment doped with the CCl4 electron-trapping molecule gave the same Ni(CO)(1-4) spectrum without the corresponding anions, which strongly supports this identification of the molecular anions.Matrix infrared spectra and density functional calculations of Ni(CO)(x)(-), x = 1-381199836#N/ATRUE
1844
ja981837l10.1021/ja981837lFALSEhttps://doi.org/10.1021/ja981837lMoro-Oka, YJ. Am. Chem. Soc.First synthesis and structural characterization of dinuClear M(III) bis(mu-oxo) complexes of nickel and cobalt with hydrotris(pyrazolyl)borate ligand127199846#N/ATRUE
1845
ja981661n10.1021/ja981661nFALSEAlemany, PMagnetic coupling in end-on azido-bridged transition metal complexes: A density functional study1998#N/ATRUE
1846
ja980504l10.1021/ja980504lFALSEhttps://doi.org/10.1021/ja980504lSuh, MPJ. Am. Chem. Soc.Novel multidimensional supramolecular networks with brick wall and honeycomb structures, [Ni(C12H30N6O2)](3)[C6H3(COO)(3)](2). 18H(2)O (1) and [Ni(C12H30N6O2)](3)[C6H3(COO)(3)](2). 14H(2)O . 2C(5)H(5)N (2), respectively, have been constructed by the self-assembly of S = 0 Ni(II) macrocyClic complex containing hydroxyl pendent chains and I,3,5-benzenetriCarbonylate (BTC3-). The host structures assembled are greatly affected even by the partial change of the guests. X-ray crystal structures indicate that each Ni(II) macrocyCle binds two BTC3- in the trans position and each BTC3- coordinates three NI(II) macrocyClic units via C-1 symmetry in 1 and C-3 symmetry in 2. The simplest cyClic motif of the two-dimensional (2-D) networks in 1 and 2 is a large ring consisting of six Ni(TI) macrocyClic complexes and six BTC3- anions. The rings are extended to form a 2-D layer. The layers are stacked in parallel, separated by 8.850 Angstrom in 1 and 8.973 Angstrom in 2. They are interconnected by the hydrogen-bonding interactions between the hydroxyl pendants of the macrocyCle in a layer and the secondary amines of the macrocyCle located in the neighboring layers, which gives rise to the three-dimensional structures. The effective cavity size of 1 is ca. 6.7 x 13 Angstrom and that of 2 ca. 11.4 x 11.4 Angstrom. The cavities are filled with guest molecules. In 2, the pyridine guest experiences pi-pi interaction with the benzene ring of BTC3-. Variable-temperature (2-300 K) magnetic susceptibility measurements indicate chat both 1 and 2 exhibit weak anti-ferromagnetic interactions between the S = 1 Ni(II) paramagnetic centers.Self-assembly of molecular brick wall and molecular honeycomb from nickel(II) macrocyCle and 1,3,5-benzenetriCarbonylate: Guest-dependent host structuresx370199846#N/AFALSE
1847
ja980409c10.1021/ja980409chttps://doi.org/10.1021/ja980409cWasielewski, MRJ. Am. Chem. Soc.We report the results of time-resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of biomimetic supramolecular compounds dissolved in oriented liquid crystal solvents. The molecules contain a chlorophyll-like (zinc 9-desoxomethylpyropheophorbide a) electron donor, D (ZC), and two electron accepters with different reduction potentials, i.e., pyromellitimide, A(1) (PI), and 1,8:4,5-naphthalenediimide, A(2) (NI). The compounds investigated are ZCPI, ZCNI, and ZCPINI, and they have small but well-defined differences of their ion-pair energies. Temperature-dependent TREPR studies on this series of compounds permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low-temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal. As the temperature is increased, the radical pair with the lowest energy is the first to exhibit triplet-initiated charge separation as the solvent reorganization energy increases in the liquid crystal. The energy levels of the radical pairs and the solvent reorganization energy are determined by using the known singlet: and triplet excited state energy levels of ZC, the electrochemically determined relative energies between the radical ion pairs in polar isotropic solvents, and the TREPR data. All these yield information about the ordering of the radical ion pair energy levels relative to the excited-state energy levels of ZC.Determination of the energy levels of radical pair states in photosynthetic models oriented in liquid crystals with time-resolved electron paramagnetic resonancePhotocatalystx56199830#N/AFALSE
1848
ja980313i10.1021/ja980313iFALSEhttps://doi.org/10.1021/ja980313iWang, ZXJ. Am. Chem. Soc.Amino acid derived nickelacyCles: Intermediates in nickel-mediated polypeptide synthesisx101199816#N/AFALSE
1849
ja981431910.1021/ja9814319FALSEhttps://doi.org/10.1021/jacs.1c01923Leary, JAMechanistic studies of diastereomeric nickel(II) N-glycoside complexes using tandem mass spectrometry1998#N/ATRUE
1850
ja974101h10.1021/ja974101hhttps://doi.org/10.1021/ja974101hHolten, DJ. Am. Chem. Soc.The lifetime of the (d(z)(2),d(x -y)(2)) metal excited state of nickel(II) 5,10,15,20-tetra-tert-butylporphyrin (NiT(t-Bu)P) exhibits an extraordinary dependence on solvent dielectric properties and temperature. At room temperature, the excited-state deActivation time varies from 2 ps in highly polar solvents to about 50 ns in nonpolar media. The lifetimes increase to several microseconds in both polar and nonpolar solvents near 80 K. In contrast, the (d,d) lifetimes of nominally planar nickel porphyrins such as nickel tetraphenylporphyrin (NiTPP) vary only weakly with solvent dielectric properties and temperature, and typically fall in the range of 100 to 300 ps. All available evidence indicates that NiT(t-Bu)P in solution is highly ruffled (nonplanar) in the ground electronic state. It is proposed that the photoinduced conformational changes that occur in NiT(t-Bu)P in order to accommodate the excited-state electronic distribution are limited by the severe steric constraints imposed by the bulky meso tert-butyl substituents, and result in molecular and electronic asymmetry and thus a polar excited state. Solvent dielectric properties and temperature modulate these conformational excursions and thus the electronic deActivation rates by affecting the excited-state energies, porphyrin/solvent reorganizations, and the populations of low-frequency out-of-plane vibrations of the macrocyCle. The novel findings for this nonplanar nickel porphyrin demonstrate the intimate connectivity that exists between the static and dynamic molecular structures of porphyrins and their ground- and excited-state electronic properties. Furthermore, the results obtained provide insights into the interactions between tetrapyrrole chromophores and their host proteins, and suggest the potential use of nonplanar porphyrins as building blocks for molecular photonics applications.Picosecond to microsecond photodynamics of a nonplanar nickel porphyrin: Solvent dielectric and temperature effectsPhotocatalyst132199870#N/AFALSE
1851
ja974073310.1021/ja9740733FALSEhttps://doi.org/10.1021/ja9740733Reber, CJ. Am. Chem. Soc.The absorption spectra of Ni(H2O)6(2+), trans-NiCl2(H2O)(4), and NiCl64- show an unusual band shape for the (3)A(2g) --> T-3(1g), E-1(g) (O-h labels) electronic transitions in the near-infrared to visible wavelength range. A barely resolved broad band and an intense vibronic progression with a spacing larger than the totally symmetric ground-state metal-ligand vibrational frequency are superposed. Low-temperature polarized spectra are analyzed with a quantitative model and both the large interval and the band intensities are shown to arise from efficient intersystem crossings between the two excited states. Alternative assignments proposed in the literature are examined.Coupled excited states in nickel(II) complexes probed by polarized absorption spectroscopyx46199846#N/AFALSE
1852
ja973873a10.1021/ja973873aFALSEhttps://doi.org/10.1021/ja973873aMatsuda, HJ. Am. Chem. Soc.Stacking of poly(3-Alkylthiophene)s P3RThs and poly(4-Alkylthiazole)s P4RTzs has been studied. Light scattering analysis indicates that head-to-tail (HT) type HT-P3HexTh (R = n-C6H13) gives a degree of depolarization (rho(v)) of 0.26 in CHCl3, which reveals that HT-P3HexTh takes a stiff structure even in the good solvent. Addition of CH3OH to CHCl3 solutions of HT-P3HexTh and head-to-head (HH) type HH-P4HepTz (R = n-C7H15) leads to pi-stacking of the polymer molecules to form stable colloidal partiCles. The light scattering analysis of the colloidal solution of HT-P3HexTh in a 2:1 solution of CHCl3 and CH3OH reveals that HT-P3HexTh is aggregated in a parallel style. Results of filtration experiments using membranes with 0.20 and 0.02 mu m pores agree with the degree of the aggregation. P3HexThs with irregular structures (P3HexTh (Fe) and P3HexTh (Ni) with HT/HH ratios of about 7/3 and 1/2, respectively) show a weaker trend to aggregate; however, P3HexTh (Fe) is considered to stack in a surface region of a stretched poly(ethylene terephthalate) PET film. A dichroism observed with the stretched PET film indicates that the pi-pi* absorption as well as photoluminescence of the stacked P3HexTh molecules have a transition moment along the direction of the polymer main chain. X-ray diffraction analysis of HT-P3RThs and HH-P4RTzs reveals that they take a face-to-face stacked structure with an end-to-end packing mode, except for HT-P3MeTh (R = Me). HT-P3MeTh forms a face-centered lattice with an interlayer distance of 3.51 Angstrom. An alternative copolymer of bithiazole and 4,4'-dibutylbithiazole is packed in an interdigitation mode. At temperatures below 0 degrees C, the HT-P3HexTh molecules are pi-stacked in CHCl3, and the H-1 NMR spectrum shows a severe magnetic effect on the thiophene ring. Solid C-13 NMR data are also consistent with the pi-stacking.Extensive studies on pi-stacking of poly(3-Alkylthiophene-2,5-diyl)s and poly(4-Alkylthiazole-2,5-diyl)s by optical spectroscopy, NMR analysis, light scattering analysis, and X-ray crystallographyx5151998110#N/AFALSE
1853
ja973856l10.1021/ja973856lFALSEhttps://doi.org/10.1021/jacs.1c05649Triki, SHybrid molecular materials based upon magnetic polyoxometalates and organic pi-electron donors: Syntheses, structures, and properties of bis(ethylenedithio)tetrathiafulvalene radical salts with monosubstituted Keggin polyoxoanionsx1998#N/AFALSE
1854
ja981417w10.1021/ja981417wFALSEhttps://doi.org/10.1021/ja981417wDolphin, DJ. Am. Chem. Soc.A novel stepwise degradation of porphyrins. Synthesis and structural characterization of meso-tetraphenylchlorophinato nickel(II) and meso-tetraphenylsecochlorinato nickel(II)51199933#N/ATRUE
1855
ja981317q10.1021/ja981317qFALSEhttps://doi.org/10.1021/ja981317qBrookhart, MJ. Am. Chem. Soc.Iron-based catalysts with exceptionally high activities and selectivities for oligomerization of ethylene to linear alpha-olefins716199819#N/ATRUE
1856
ja973834z10.1021/ja973834zFALSEhttps://doi.org/10.1021/ja973834zArmentrout, PBJ. Am. Chem. Soc.Complexes of the first-row transition-metal cations (Ti+-Cu+) with one and two ethene molecules are studied by guided ion beam mass spectrometry. Thermalized complexes are formed in a flow tube source and examined by energy-resolved collision-induced dissociation with Xe. The energy dependence of the CID cross sections is analyzed with consideration of multiple collisions, internal energy of the reactants, and lifetime effects. First, D-0(M+-C2H4), and second, D-0(C2H4M+-C2H4), adiabatic metal ion ethene bond energies, in eV, obtained in this study are 1.51 +/- 0.11 for Ti (first bond only), 1.29 +/- 0.08 and 1.32 +/- 0.14 for V, 0.99 +/- 0.11 and 1.12 +/- 0.11 for Cr, 0.94 +/- 0.12 and 0.91 +/- 0.15 for Mn, 1.50 +/- 0.11 and 1.57 +/- 0.16 for Fe, 1.93 +/- 0.09 and 1.58 +/- 0.14 for Co, 1.84 +/- 0.11 and 1.79 +/- 0.15 for Ni, and 1.82 +/- 0.14 and 1.80 +/- 0.13 for Cu, respectively. These values inClude corrections for diabatic dissociation in the cases of Fe+(C2H4) and Mn+(C2H4)(2), a point that is discussed in detail. Previous work obtained from theory and experiment is then compared with values determined in this study. Periodic trends observed for the mono-and bis-ethene complexes cations are also discussed and compared with the isobaric metal mono-and diCarbonyl cation complexes.Transition-metal ethene bonds: Thermochemistry of M+(C2H4)(n) (M=Ti-Cu, n=1 and 2) complexesx103199880#N/AFALSE
1857
ja981266x10.1021/ja981266xFALSEhttps://doi.org/10.1021/ja981266xHillhouse, GLJ. Am. Chem. Soc.Sulfur-atom transfer from elemental sulfur to nickel-carbon bonds as a new route to reactive nickel(II) thiolates38199839#N/ATRUE
1858
ja981257o10.1021/ja981257oFALSEhttps://doi.org/10.1021/ja981257oKishi, YJ. Am. Chem. Soc.Total synthesis of pinnatoxin A159199820#N/ATRUE
1859
ja981217k10.1021/ja981217kFALSEhttps://doi.org/10.1021/ja981217kBurgess, KDesign and optimization of new phosphine oxazoline ligands via high-throughput catalyst screening1998#N/ATRUE
1860
ja973148010.1021/ja9731480FALSEhttps://doi.org/10.1021/ja9731480Hoffman, BMJ. Am. Chem. Soc.The C-Cluster of carbon monoxide dehydrogenase (CODH) catalyzes the reversible oxidation of CO to form CO2. This study reports electron nuClear double resonance (ENDOR) spectroscopy of the one-electron reduced (C-red1), the CN--inhibited, and the CO (or dithionite)-reduced (C-red2) forms of the C-Cluster from Clostridium thermoaceticum CODH (CODHCt). The observed hyperfine interactions of H-1,H-2,N-14, C-13, and Fe-57 support and extend the current Ni-X-[Fe4S4] C-Cluster model in which a [Fe4S4] center is linked to a Ni ion through a unique iron, FCII. The unpaired electron spin apparently is localized on the [Fe4S4] component of the Cluster, and thus the hyperfine interactions observed by ENDOR most probably reflect species associated with that component. A solvent-exchangeable proton with a maximum hyperfine coupling of A(H-1) = 16 MHz is detected in the C-red1 form, but not in the CN--inhibited or C-red2 forms. The exchangeable proton is assigned to a probable solvent-derived (HxO, x = 1, 2) ligand to FCII of the C-red1 [Fe4S4](1+) center and is predicted to be a substrate in CO/CO2 catalysis. For both C-red1 and C-red2, We find ENDOR features in the region expected for a nitrogen-donor ligand which likely arise from a histidine ligand to the [Fe4S4] center. Fe-57 ENDOR detects at least two Classes of Fe in C-red1 that most likely arise from the (Fe2.5+)(2) mixed-valence pair. Their large maximum couplings of A(Fe-57) > 40 MHz support the unusual nature of the Cluster; these do not change dramatically between the C-red1 and C-red2 forms of the enzyme. C-red2 formed by reduction with (CO)-C-13 reveals no new C-13 features, strongly suggesting that neither CO nor its oxidized products are bound to the [Fe4S4] center in C-red2 Taken together, these ENDOR assignments suggest that in the C-red1 state, the unique Fe ion of the CODH C-Cluster has an available coordination site that stably binds HxO or CN- and that reduction of the C-Cluster results in rearrangement at that site, causing loss of the bound aqueous ligand.A multinuClear ENDOR study of the C-Cluster in CO dehydrogenase from Clostridium thermoaceticum: Evidence for HxO and histidine coordination to the [Fe4S4] centerx65199862#N/AFALSE
1861
ja981181w10.1021/ja981181wFALSEhttps://doi.org/10.1021/ja981181wSchneider, WDJ. Am. Chem. Soc.PartiCles of nanometer size (nanopartiCles) supported on well-characterized oxide surfaces are of particular interest to model the high complexity of real catalysts to answer questions such as the rule of intrinsic size effects and the influence of the support.(1,2) Model systems so far consisted of size-distributed nanopartiCles deposited on oxide substrates,(3-5) which do not allow an unambiguous determination of the Cluster's chemical nature. Here, we report on the size-dependent chemical reactivity of nickel Clusters, size selected and deposited with low energy (0.2 eV/atom) on thin MgO(100) films; Monodispersed Ni-30 Clusters show a higher reactivity for CO dissociation than Ni-11 and Ni-20. In particular, Ni-30 Clusters are extremely reactive and dissociate up to 10 CO molecules at temperatures below 280 K. Our results demonstrate that such small, supported Clusters are unique for catalytic reactions not only due to their high surface-to-volume ratio but essentially because of the distinctive properties of different Cluster sizes.Size-dependent molecular dissociation on mass-selected, supported metal Clusters123199833#N/ATRUE
1862
ja973088y10.1021/ja973088yFALSEhttps://doi.org/10.1021/ja973088yBalch, ALJ. Am. Chem. Soc.Carbonylbiliverdin and related chlorophyll-derived molecules are possible products of heme catabolism and other biologically important oxidative processes and are likely to be initially formed as metal complexes. To explore the properties of the Carbonylbiliverdin moiety bound to transition metal ions, complexes of octaethylCarbonylbiliverdin (H2OEFB) with Cu(II), Ni(II), and Co(II) have been prepared, since attempts to prepare an iron complex have produced only an unstable material. Transmetalation of Mg-II(OEFB), made by photooxidation of Mg-II(octaethyl-porphyrin), with a metal(II) acetate yields the low-spin complexes: Cu-II(OEFB), Ni-II(OEFB), and Co-II(OEFB). Single-crystal X-ray diffraction of Cu-II(OEFB) reveals that it consists of a four-coordinate copper(II) center which is bound to the four nitrogen atoms in distorted planar coordination. The tetrapyrrole ligand has a helical geometry. The structure of the solid is complicated by the existence of three molecules in the asymmetric unit and C-H ... O hydrogen bonding between pairs of these in the tab/slot arrangement seen in complexes of octaethylbiliverdin. Both Cu-II(OEFB) and Co-II(OEFB) can be converted to the verdoheme analogues, [Cu-II(OEOP)](+) and [Co-II(OEOP)](+), where OEOP is the anion of octaethyl-5-oxaporphyrin, by the addition of hydrogen peroxide. Additionally, [Cu-II(OEOP)](+) can be produced by heating a toluene solution Cu-II(OEFB) in the presence of trifluoroacetic acid under dioxygen. Carbon monoxide is produced when Cu-II(OEFB) is converted to [Cu-II(OEOP)](+) by either method. [Cu-II(OEOP)](PF6) has been characterized by single-crystal X-ray diffraction which shows that the cation has a planar, porphyrin-like structure. The room-temperature EPR spectrum of this complex shows that the copper is four-coordinate with four nitrogen based ligands, but frozen solutions of [Cu-II(OEOP)](+) show a triplet EPR spectrum indicative of a dimeric species much like that in the X-ray crystal structure. The H-1 NMR spectrum of diamagnetic Ni-II(OEFB) has been shown to be consistent with the helical structure through the use of lanthanide and chiral lanthanide shift reagents. The EPR spectra of Co-II(OEFB) show that it forms a low-spin adduct with pyridine and that this adduct acts as a reversible dioxygen carrier. The geometric and electronic structural properties of these complexes of Carbonylbiliverdin are compared to those of analogous compounds of biliverdin and of porphyrins.Possible intermediates in biological metalloporphyrin oxidative degradation. Nickel, copper, and cobalt complexes of octaethylformybiliverdin and their conversion to a verdohemex52199846#N/AFALSE
1863
ja972833410.1021/ja9728334https://doi.org/10.1021/ja9728334Morokuma, KJ. Am. Chem. Soc.The integrated molecular orbital-molecular mechanics (IMOMM) method adopting the B3LYP:MM3 combination has been used to study the full catalysts in the diimine-M (M = Ni, Pd) catalyzed ethylene polymerization reaction. These results have been compared with previous molecular orbital calculations on model systems (model). There is a lowering of the migratory insertion Activation barriers when inCluding substituent effects from 9.9 (model) to 3.8 (IMOMM) kcal/mol for nickel and from 16.2 (model) to 14.1 (IMOMM) kcal/mol for palladium. Steric interactions decrease the complexation energy which leads to a lowering of the barrier. The beta-H transfer process which involves the reaction n-propyl beta-agostic --> olefin hydride --> isopropyl beta-agostic is the likely mechanism leading to branching of polyethylenes. In the nickel system, the olefin-hydride intermediate lies 13.6 (model) or 14.5 (IMOMM) kcal/mol above the n-propyl beta-agostic species, indicating that this pathway is unlikely for unsubstituted or substituted nickel diimine catalysts. For palladium, where the olefin-hydride intermediate resided 5.4 kcal/mol above the beta-agostic species in model B3LYP predictions, IMOMM reduces this difference to almost zero, suggesting branching to be more prominent with bulky substituents. Although beta-H transfer is more likely for substituted palladium, the formation of the 5-coordinate intermediate is not possible due to steric effects and thus an associative chain termination process is not possible for substituted palladium while it likely can occur for unsubstituted Pd catalysts.Theoretical study of substituent effects in the diimine-M(II) catalyzed ethylene polymerization reaction using the IMOMM methodx143199848#N/AFALSE
1864
ja981040u10.1021/ja981040uFALSEhttps://doi.org/10.1021/ja981040uYoungs, WJJ. Am. Chem. Soc.Synthesis of neutral tetranuClear and octanuClear macrocyClic platinum-butadiyne heterocyClynes102199851#N/ATRUE
1865
ja972556110.1021/ja9725561FALSEhttps://doi.org/10.1021/ja9725561Michalowicz, AJ. Am. Chem. Soc.The influence of the Ni deposition mode on the dispersion of Ni2+ precursors was investigated in the preparation of Ni/SiO2 catalysts. The coordination sphere of Ni complexes was mainly studied by XAFS spectroscopy in the initial step (dried samples) and after a vacuum activating treatment at 700 degrees C. Four modes of deposition were compared, two leading to supported silicate phases (exchange with ammine ligands and deposition-precipitation) and the other ones using the ethanediamine ligand (exchange and impregnation modes) which produced isolated Ni2+ precursors in electrostatic interaction with the silica support. In this work, EXAFS spectroscopy has been found to be a suitable technique to probe metal-support interactions in the first step of the preparation (dried samples). For samples activated at 700 OC, this spectroscopy showed the presence of several categories of atoms in the first (oxygen backscatterers) and second (Ni and. Si backscatterers) shells. A distribution of long (d approximate to 2.04 Angstrom) and short (d approximate to 1.75 Angstrom) Ni-O distances was found, corresponding to hexacoordinated (Ni-6c(2+)) and isolated tricoordinated (Ni-3c(2+)) ions, respectively. Modeling of the structure of the Ni-3c(2+). Site indicated a distorted site with two short and one long Ni-O distance. The exchange mode with ethanediamine ligand led to isolated Ni-3c(2+) ions which could then be photoreduced into Ni-3c(+) ions with the highest yield. Impregnation with ethanediamine Ni nitrate was also found advantageous as it led after thermal Activation at 700 degrees C to NiO partiCles smaller than those produced from impregnation with Ni nitrate and therefore to smaller Ni partiCles after the subsequent reduction step.Control of dispersion of Ni2+ ions via chelate ligands in the preparation of Ni/SiO2 materials. A XAFS studyx80199872#N/AFALSE
1866
ja972524d10.1021/ja972524dFALSEhttps://doi.org/10.1021/ja972524dLippard, SJJ. Am. Chem. Soc.The dinuClear complex [Co-2(mu-OH)(mu-XDK)(bpy)(2)(EtOH)](NO3), where XDK is the dinuCleating diCarbonylate Ligand m-xylylenediamine bis(Kemp's triacid imide) and bpy = 2, 2'-bipyridine, was prepared as a functional model for arginase. The substrate aminoguanidinium nitrate was hydrolyzed to urea in ethanol by the complex but not by free hydroxide ion under the same conditions. The amino group of the substrate binds to cobalt, as demonstrated by W-vis spectroscopic studies. The syntheses of related dinuClear cobalt(II) complexes [Co-2(mu-XDK)(NO3)(2)(CH3OH)(2)(H2O)], [Co-2(mu-Cl)(mu-XDK)(bpy)(2)(EtOH)(2)](NO3), and [Co-2(mu-XDK)(py)(3)(NO3)(2)] are described. MononuClear complexes [Co(XDK)(bpy)(H2O)] and [Zn(XDK)(bpy)(H2O)] were also prepared and characterized. The former catalytically hydrolyzes aminoguanidinium nitrate to urea in basic 1:1 methanol/water solutions, whereas the latter does not promote this reaction. Hydrolysis of aminoguanidinium ion is effected by [Co(CH3COO)(2)] and [Cu(CH3COO)(2)] in the presence of bpy, but not by [Zn(CH3COO)(2)], [Ni(CH3COO)(2)], or [Mn(CH3COO)(2)] in the presence of bpy in 1:1 methanol/water solution. In all cases, coordination of the amino group of the substrate to the metal center under the reaction conditions may activate the leaving group and orient the guanidinium moiety Close to the attacking nuCleophile, metal-bound hydroxide ion, to promote the hydrolysis reaction.Aminoguanidinium hydrolysis effected by a hydroxo-bridged dicobalt(II) complex as a functional model for arginase and catalyzed by mononuClear cobalt(II) complexesx48199840#N/AFALSE
1867
ja980961210.1021/ja9809612FALSEhttps://doi.org/10.1021/ja9809612Milstein, DJ. Am. Chem. Soc.Metal-mediated generation, stabilization, and controlled release of a biologically relevant, simple para quinone methide: BHT-QM29199845#N/ATRUE
1868
ja972191k10.1021/ja972191kFALSEhttps://doi.org/10.1021/ja972191kHoveyda, AHJ. Am. Chem. Soc.The first enantioselective total synthesis of antifungal agent Sch 38516, also known as fluvirucin B-1, is described. The synthesis inCludes a convergent asymmetric preparation of amine 17 and acid 18, which are then united to afford diene 62. Metal-catalyzed transformations play a crucial role in the synthesis of the latter moiety. Of particular note are the diastereo-and enantioselective Zr-catalyzed Alkylations, a tandem Ti-and Ni-catalyzed process that constitutes a hydroVinylation reaction, and a Ru-catalyzed alcohol oxidation to afford Carbonylic acid 18. The requisite carbohydrate 38 is synthesized in a highly diastereo-and enantioselective fashion. Optical purity of the carbohydrate moiety arises from the use of the asymmetric dihydroxylation method of Sharpless; diastereochemical control is achieved through a selective dipolar [3 + 2] cyCloaddition with a readily available amine serving as the chiral auxiliary. Union of the appropriately outfitted carbohydrate 71 and diene 62 through an efficient and diastereoselective glycosylation is followed by a remarkably efficient Mo-catalyzed macrocyClization that proceeds readily at room temperature.Applications of Zr-catalyzed carbomagnesation and Mo-catalyzed macrocyClic ring Closing metathesis in asymmetric synthesis. Enantioselective total synthesis of Sch 38516 (fluvirucin B-1)x128199791#N/AFALSE
1869
ja972178010.1021/ja9721780FALSEhttps://doi.org/10.1021/ja9721780Hyeon, CJ. Am. Chem. Soc.One-pot template synthesis and properties of a molecular bowl: Dodecaaza macrotetracyCle with mu(3)-oxo and mu(3)-hydroxo tricopper(II) coresX79199822#N/AFALSE
1870
ja972021810.1021/ja9720218FALSEhttps://doi.org/10.1021/ja9720218Long, ECJ. Am. Chem. Soc.Ni(II) chelated peptides of the form NH2-Xaa-Xaa-His-CONH2 (Ni(II). Xaa-Xaa-His) mediate deoxyribose damage through C4'-H abstraction of a targeted nuCleotide when activated with KHSO5 (oxone), MMPP (magnesium monoperoxyphthalate), or H2O2 The products released and identified in comparison to the authentic C4'-H oxidant Fe(II) bleomycin inCluded fragmented DNA terminating in 5'-phosphates, 3'-phosphates, and 3'-phosphoglycolates; upon treatment of Ni(II). Xaa-Xaa-His Cleavage reactions with NaOH or NH2NH2, fragmented DNA 3'-termini were released consistent with the intermediate formation of ketoaldehyde abasic (alkaline-labile) sites. In addition, nuCleobases and nuCleobase propenals were detected in proportions consistent with abasic site and 3'-phosphoglycolate termini formation, respectively. These results indicate that Ni(II). Xaa-Xaa-His metallopeptides, like Fe(II). bleomycin, degrade DNA through two pathways resulting from an initial C4'-H modification. Importantly, the partitioning between these two pathways appears to be dependent on the structure of the Ni(II). Xaa-Xaa-His metallopeptide employed in the Cleavage reaction and the nuCleotide sequence targeted. Further studies also indicate that metallopeptide Activation with KHSO5, MMPP, or H2O2 yields identical reaction products and sequence-selective DNA Cleavage suggesting the formation of a common activated metallopeptide responsible for C4'-H deoxyribose damage, quite possibly a metal-bound hydroxyl radical. These studies also demonstrate that metallopeptide Activation with KHSO5 is condition-dependent resulting in (1) C4'-H damage in common with MMPP or H2O2 under relatively low ionic strength conditions (10 mM Na-cacodylate, pH 7.5, equimolar KHSO5/metallopeptide) or (2) guanine nuCleobase oxidation under higher ionic strength conditions (100 mM NaCl, 10 mM phosphate, pH 7.0, excess KHSO5).Ni(II)center dot Xaa-Xaa-His induced DNA Cleavage: Deoxyribose modification by a common activated intermediate derived from KHSO5, MMPP, or H2O2x76199856#N/AFALSE
1871
ja971993c10.1021/ja971993chttps://doi.org/10.1021/ja971993cRedmond, RWPhotochemical mechanisms responsible for the versatile application of naphthalimides and naphthaldiimides in biological systemsPhotocatalyst1997#N/AFALSE
1872
ja980762i10.1021/ja980762iFALSEhttps://doi.org/10.1021/ja980762iMoloy, KGJ. Am. Chem. Soc.Kinetic study of reductive elimination from the complexes (diphosphine)Pd(R)(CN)115199834#N/ATRUE
1873
ja971681+10.1021/ja971681+FALSEhttps://doi.org/10.1021/ja971681+Crabtree, RHJ. Am. Chem. Soc.DFT quantum chemical methods are used to probe the mechanism of the nickel-iron hydrogenases. Starting from the experimental X-ray structure, all plausible oxidation states and spin states were investigated, The structure and reactivity pattern of the NiFe Cluster are best reproduced by assuming a NiFe(II,III) oxidation state assignment of the resting state of the Cluster. In our proposed mechanism of H(2) oxidation by the enzyme, H(2) first binds to Fe in the form of a molecular hydrogen complex, which then undergoes heterolytic splitting. This process is spin-dependent and does not occur for the high-spin sextet state. In the key step, hydride transfer to iron and proton transfer to the adjacent cysteinethiolate ligand is accompanied by decoordination of the protonated cysteinethiol from Ni while remaining bound to iron. Simultaneously, the cyanide ligand on iron binds with the nickel atom in a rare bridging binding mode. After the H(2) dissociation, the hydride bound to Fe can then be transferred to Ni which should be a necessary preliminary for subsequent hydrogen atom or electron transport. The transition state for hydrogen splitting was located, and the resulting calculated energy barrier is in remarkably good agreement with the experimental value.Mechanism of H-H Activation by nickel-iron hydrogenaseX138199849#N/AFALSE
1874
ja980604r10.1021/ja980604rFALSEhttps://doi.org/10.1021/ja980604rRossi, IJ. Am. Chem. Soc.In this paper we have studied the [2+2] cyCloaddition of two olefins catalyzed by Ni(O) complexes using a hybrid DFT/B3LYP computational approach with the pseudopotential LANL2DZ basis set. Two model systems have been used to emulate the catalytic process: the ethylene-nickel complex Ni(PH3)(2)C2H4 and the bis(ethylene)-nickel complex Ni(PH3)(2)(C2H4)(2), both reacting-with an ethylene;molecule, For both these complexes we have investigated in detail the first steps of the catalytic process,corresponding to the formation of nickelacyClopentane, which has been experimentally demonstrated to produce the cyClobutane product by reductive elimination. We have found that the incoming ethylene molecule reacts with both complexes not at the metal center but at one ligand ethylene. This attack affords an anti I,fi-biradical intermediate that can lead to nickelacyClopentane and where the two unpaired electrons are mainly localized on the nickel atom and on the terminal methylene. While for the attack of the ethylene molecule on Ni(PH3)(2)C2H4 no catalytic effect is observed (the Activation energy is almost identical to-that found for the noncatalyzed process, i.e., about 40 kcal mol(-1)), a catalytic effect, even if not very large, is found for the Ni(PH3)(2)(C2H4)(2) complex (the barrier decreases to 35.80 kcal mol(-1)). A diabatic analysis has pointed out that the factors which are responsible for the catalytic effect of the Ni(PH3)(2)(C2H4)(2) complex are the energy gap between the singlet ground state and the first triplet state in the complex and the stability of the biradical intermediate.A DFT investigation of ethylene dimerization catalyzed by Ni(0) complexes44199832#N/ATRUE
1875
ja980222l10.1021/ja980222lFALSEhttps://doi.org/10.1021/ja980222lKocovsky, PJ. Am. Chem. Soc.The steric course of the first step of Pd(0)-catalyzed allylic substitution with stabilized C-nuCleophiles can be completely reversed by a suitably positioned coordinating Ph2P group, resulting in an overall inversion (1 --> 4 --> 5), as opposed to the normally observed retention (1 --> 2 --> 3). Thus, on reaction with NaCH-(CO2Me)(2), the allylic acetate 10, containing a phosphinous amide moiety, gives 24 as a result of ret.-inv. pathway, whereas 9, lacking the coordinating group, affords the normal inv.-inv. product 23. The intermediate eta(3)-complex 32; generated in the former reaction, has been characterized by H-1 and P-31 NMR spectroscopy. While this stereochemical control is highly successful with cyClic substrates, it does not operate in acyClic series, as documented by the reactivity of the anti-configured 1,4-functionalized hexenes 14 and 15, which both give the product of inv. -inv. pathway, i.e., 35 and 36, respectively. The syn-configured allylic substrates 21 and 22 exhibit the same pattern, irrespective of the presence of the coordinating neighboring group. The lack of overriding control in the latter instances has been attributed to a rotation about the C-C bond connecting the coordinating group to the allylic system, which allows the precoordinated Pd(0) to approach the allylic moiety from the face opposite to the leaving group (15 --> 41 --> 42). Precoordination of the catalyst to the Ph2P group is evidenced by substantial acceleration of the reaction in all cases studied. For the Ni(0)-catalyzed reaction of the allylic methoxy derivatives with MeMgX, precoordination proved to be the prerequisite for the reaction to occur (50 --> 51 --> 52); ret.-ret. pathway was observed.The stereochemical dichotomy in palladium(0)- and nickel(0)-catalyzed allylic substitution55199884#N/ATRUE
1876
ja971349y10.1021/ja971349yFALSEMarks, TJSynthesis, characterization, optical spectroscopic, electronic structure, and second-order nonlinear optical (NLO) properties of a novel Class of donor-acceptor bis(salicylaldiminato)nickel(II) Schiff base NLO chromophoresx1997#N/AFALSE
1877
ja971037v10.1021/ja971037vFALSEhttps://doi.org/10.1021/ja971037vPorschke, KRJ. Am. Chem. Soc.The two N donor atoms in the tertiary diamine N,N'-dimethyl-3,7-diazabicyClo[3.3.1]nonane (dabn, C9H18N2) are ideally positioned in the bicyClic structure for chelation to a metal center. This feature was utilized to synthesize unusual diamine nickel(0)-ethene and -ethyne complexes, which represent limiting cases of the Pearson hard-soft acid-base concept. Thus, the reaction of Ni(C2H4)(3) With dabn affords yellow TP-3 (C9H18N2)Ni(C2H4) (1) (dec. 0 degrees C) in which the ethene ligand displays extreme high-field NMR shifts at delta(H) 0.27 and delta(C) 20.4 and an exceptionally small coupling constant (1)J(CH) = 142 Hz. Reaction of 1 with butadiene yields the red mononuClear T-4 complex (C9H18N2)Ni(eta(2)-C4H6)(2) (2a) in solution, from which the dinuClear derivative {(C9H18N2)Ni(eta(2)-C4H6)}(2)(mu-eta(2),eta(2)-C4H6) (2) (dec. 20 degrees C) is isolated. Complexes 2 and 2a are more soluble than 1 and thus better suited for further reactions. When ethyne is added to a solution of 2 or 2a at -78 degrees C, the yellow TP-3 complex (C9H18N2)Ni(C2H2) (3) (dec. -30 degrees C) is obtained. The ethyne ligand of 3 exhibits the lowest IR C=C stretching frequency (1560 cm(-1)) and by far the smallest NMR coupling constant (1)J(CH) = 178 Hz yet reported for a mononuClear nickel(0)-ethyne complex. In addition, Ni(CO)(4) reacts with dabn to yield orange T-4 (C9H18N2)Ni(CO)(2) (4) The results demonstrate that tertiary diamines, which are hard Lewis bases and which a priori are expected to coordinate poorly to the soft Lewis acid Ni(0), may be supported in such a coordination by the stabilizing principle of preorganization and consequently act as very powerful donor ligands.Applying the macrocyClic effect to smaller ring structures. N,N'-dimethyl-3,7-diazabicyClo[3.3.1]nonane Nickel(0) complexesx31199796#N/AFALSE
1878
ja973847c10.1021/ja973847cFALSEhttps://doi.org/10.1021/ja973847cTamaru, YJ. Am. Chem. Soc.Novel and highly regio- and stereoselective nickel-catalyzed homoallylation of benzaldehyde with 1,3-dienes152199825#N/ATRUE
1879
ja970882a10.1021/ja970882aFALSEhttps://doi.org/10.1021/ja970882aMansuy, DJ. Am. Chem. Soc.New metalloporphyrins with extremely altered redox properties: Synthesis, structure, and facile reduction to air-stable pi-anion radicals of zinc and nickel beta-heptanitroporphyrinsx54199727#N/AFALSE
1880
ja970834q10.1021/ja970834qFALSEhttps://doi.org/10.1021/ja970834qPilato, RSJ. Am. Chem. Soc.Luminescence and excited-state electron-transfer reactions of (dppe)Pt{S2C2(2-pyridine)(H)} and (dppe)-Pt{S2C2(4-pyridine)(H)} (dppe = diphenyldiphosphinoethane) are enabled by protonation of the appended pyridine, thus serving as a novel means of electronic switching. The neutral complexes have low-lying d-to-d transitions that lead to rapid decay of excited states by nonradiative processes. However, upon protonation, a 1,2-enedithiolate-to-heterocyCle pi* intraligand charge-transfer transition (ILCT) becomes lower in energy than the d-to-d transition, thus giving rise to emissive (ILCT)-I-1* and (ILCT)-I-3* excited states for [(dppe)Pt{S2C2(2-pyridinium)(H)}][BF4] and [(dppe)-Pt{S2C2(4-pyridinium)(H)}][BF4]. The assignment of these excited states was based on their energies and lifetimes (tau) which range from tau = 3 to 4 ns for the singlet and from tau = 2000 to 7500 ns for the triplet, respectively. Emission quantum yields (phi) increase with solvent polarity and range from phi = 0.0006 to 0.003 for the singlet and from phi = 0.001 to 0.03 for the triplet. The electron accepters p-dinitrobenzene and tetracyanoquinodimethane quench the 3ILCT* with k(q) values of 4 x 10(9) and 9 x 10(9) M-1 s(-1), respectively. The k(q) values are nearly identical for the 2- and 4-pyridinium complexes, reflecting the similarity in the thermodynamic driving forces for electron transfer from these complexes. The ability to employ a simple and reversible ground-state reaction (ligand protonation) to control access to reactive excited states should prove useful in numerous applications.Protonation-state-dependent luminescence and excited-state electron-transfer reactions of 2- and 4-pyridine (-ium)-substituted metallo-1,2-enedithiolatesx31199752#N/AFALSE
1881
ja973844010.1021/ja9738440FALSEhttps://doi.org/10.1021/ja9738440Venanzi, LMJ. Am. Chem. Soc.Synthesis and characterization of the first mononuClear Ni-II phosphorane imino complex22199816#N/ATRUE
1882
ja973519c10.1021/ja973519cFALSEhttps://doi.org/10.1021/ja973519cCurran, DPJ. Am. Chem. Soc.Cationic aqua complexes are prepared from a trans-chelating tridentate ligand, (R,R)-4,6-dibenzofurandiyl-2,2'-bis(4-phenyloxazoline) (DBFOX/Ph), and various transition-metal(II) perchlorates. These complexes are effective catalysts in the Diels-Alder reactions of cyClopentadiene with 3-alkenoyl-2-oxazolidinone dienophiles and show excellent enantioselectivities. The active catalyst complex prepared from nickel(II) perchlorate hexahydrate has an octahedral structure with three aqua ligands, and it can be isolated and stored for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. The absolute configuration induced in the reaction can be readily predicted on the basis of the C-2-symmetric structure of the complexes as well as the simple structure of the substrate complex. The aqua complex prepared from Ni(II) or Zn(II) perchlorate results in highly effective chiral amplification in the Diels-Alder reaction. Use of the DBFOX/Ph ligand of a low enantio purity of 20% ee leads to a 96% ee for the endo cyCloadduct. Two mechanisms for amplification are involved in this remarkable chiral amplification: (1) precipitation of an S-4-symmetric meso 2:1 complex between DBFOX/Ph and Ni(II) ion and (2) associative formation of 1:1 heterochiral complexes by the aid of hydrogen bonds based on aqua ligands to produce stable meso oligomers.Transition-metal aqua complexes of 4,6-dibenzofurandiyl-2,2 '-bis(4-phenyloxazoline). Effective catalysis in Diels-Alder reactions showing excellent enantioselectivity, extreme chiral amplification, and high tolerance to water, alcohols, amines, and acids211199882#N/ATRUE
1883
ja973410510.1021/ja9734105FALSEhttps://doi.org/10.1021/ja9734105Youngs, WJJ. Am. Chem. Soc.Synthesis of titanium cyClynes Cp2Ti(OBET) and Cp*Ti-2(OBET) and the unusual stability of the bimetallic complex Ni[Cp2Ti(OBET)] to CO and O-215199827#N/ATRUE
1884
ja970347a10.1021/ja970347aFALSEBosch, JA general synthetic entry to Strychnos alkaloids of the curan type via a common 3a-(2-nitrophenyl)hexahydroindol-4-one intermediate. Total syntheses of (+/-)- and (-)-tubifolidine, (+/-)-akuammicine, (+/-)-19,20-dihydroakuammicine, (+/-)-norfluorocurarine, (+/-)-echitamidine, and (+/-)-20-epilochneridinex1997#N/AFALSE
1885
ja970297+10.1021/ja970297+FALSEhttps://doi.org/10.1021/ja970297+Urriolabeitia, EPJ. Am. Chem. Soc.A series of nine coordination compounds is described, in which a common supramolecular structure, a ribbon of cyanurates, persists across variations in the metal center, coordination geometry, coordination environment, and crystal type. The syntheses and solid-state structures, as determined by single-crystal X-ray diffraction, are described for six of the complexes, trans-[Cu(cyan-kappa N)(2)(H2O)(2)]. 2Na(cyan). 4H(2)O (1), trans-[Cu(cyan-kappa N)(2)(NH3)(2)] (5), trans-[Cu(cyan-kappa N)(2)(NH3)(2)]trans-[Cu(cyan-kappa O-2)(2)(NH3)(4)] (6), trans-[Ni(cyan-kappa N)(2)(NH3)(4)] (7), (OC-6-33)-[Ni(cyan-kappa N)(2)(NH3)(2)(H2O)(2)] (8), and [Cu(cyan-kappa N)(PPh3)(2)]. 2CDCl(3) (9). The results are discussed together with the previously reported structures of the other three complexes, [M(cyan-kappa N)(H2O)(5)](cyan). 2H(2)O (M = Mn (2), Co (3), Ni (4)). In all cases, the ribbon of cyanurates is propagated through a recognition interaction involving a pair of hydrogen bonds between adjacent cyanurates, with a topological pattern of the type R-2(2)(8). In eight of the nine cases, the ribbon is linear, but for compound 5, which is the first product of the reaction from which compound 6 is derived, the ribbon is crenelled. An unsuccessful attempt to synthesize a product without the cyanurate ribbon in the solid state is described. The possibility that the cyanurate ribbon represents a traditional self-assembly in some of these systems but not in others is discussed. It is conCluded that the formation of the cyanurate ribbon is a determinative factor in the solid-state structural coordination chemistry of the cyanurates of metals of the first transition series.The cyanurate ribbon in structural coordination chemistry: An aggregate structure that persists across different coordination environments and structural typesx40199753#N/AFALSE
1886
ja970226a10.1021/ja970226ahttps://doi.org/10.1021/ja970226aZiegler, TJ. Am. Chem. Soc.The role of the bulky ligands in Ni(II) diimine catalyzed ethylene polymerization has been examined with a combined density functional theory quantum mechanics and molecular mechanics (QM/MM) model. Specifically, we have examined the catalytic center of the type (ArN=C(R)-C(R)=NAr)Ni-II-R'(+), where R = Me and Ar = 2,6-C6H3(i-Pr)(2). The Ar and R groups were treated by a molecular mechanics force field while density functional theory was applied to the remainder of the system. The chain propagation, chain branching, and chain termination processes have been investigated with the hybrid method and found to have barriers of Delta H-double dagger = 11.8, 15.3, and 18.4 kcal/mol, respectively, which is in excellent agreement with experiment in both absolute and relative terms. This is in stark contrast to the pure QM model in which the influence of the bulky Ar and R groups was neglected and the established order of the barriers is not even reproduced. The role played by the bulky substituents is dual in nature. First, the Ar and R groups act to sterically hinder the axial coordination sites of the Ni center. This has the most dramatic destabilizing effect on the resting state and termination transition states, in which both axial positions are occupied. In addition to the steric factor, we find that the electronic preference for the Aryl rings to orient themselves in a coplanar fashion with the diimine ring results in a stabilization of the insertion transition state relative to the resting state. These two factors act to both lower the propagation barrier and increase the termination barrier compared to the ''naked'' pure QM model system.The role of bulky substituents in Brookhart-type Ni(II) diimine catalyzed olefin polymerization: A combined density functional theory and molecular mechanics studyx328199750#N/AFALSE
1887
ja973186j10.1021/ja973186jFALSEhttps://doi.org/10.1021/ja973186jSzczepura, LFJ. Am. Chem. Soc.The properties of the carbon sulfide C6S8 (1) as well as its dioxo analogue C6S6O2 (2) have been studied in the fully oxidized and fully reduced forms, i.e., 1(0), 1,(2-) 2(0), 2(2-). A crystallographic study shows that compound 2 is a tricyClic species with a twisted 1,2-dithiin (unsaturated C4S2 ring) core. Reduction of 1 with 2 equiv of LiBHEt3 gave C6S82- (1(2-)), which was isolated as its PP4+ salt. A crystallographic study of this salt shows that reduction has resulted in Cleavage of the S-S bond and that, in the solid state, the dihedral angle between the two rings is 180 degrees. Both 1(2-) and 2(2-) undergo two sequential and reversible 1e(-) oxidations near 0 V (vs Ag/AgCl), thus establishing that 1(0) and 2(0) are good oxidants relative to other disulfides. Treatment of (PPh4)(2)[C6S8] with [Ni(H2O)(6)]Cl-2 afforded the dark red (PPh4)(2)[Ni(C6S8)(2)] (3). The analogous Pt complex (4) was also prepared. Crystallographic analysis of 3 shows that the nickel center is square planar, comprising two seven-membered NiS2C4 rings. The paramagnetism observed for solutions of 3 are attributed to the formation of a tetrahedral isomer.Studies on the electroactive heterocyCles C6S80/2- and C6S6O20/2- and related metal complexes22199853#N/ATRUE
1888
ja964319o10.1021/ja964319oFALSEhttps://doi.org/10.1021/ja964319oSchneider, HJJ. Am. Chem. Soc.Complexes between cobalt(III) and eight different 1,4,7,10-tetraazacyClododecane (cyClen) as well as two tris(3-aminopropyl)amine (trpn) derivatives are reported with varying numbers and structures of perAlkylammonium groups in side chains of the ligands. The presence of additional positive charges has small effects on hydrolysis rates of nitrophenyl- and bis(nitrophenyl)phosphate esters but leads to substantially enhanced Cleavage of plasmid DNA. Increasing the number of the charged side groups and/or their distance to the metal ion center provides for better binding to the DNA groove, as shown also by affinity measurements with calf-thymus DNA. In line with this, saturation kinetics of plasmid DNA Cleavage yield a corresponding increase of efficiency in Michaelis-Menten-type K-M values, with rather constant k(cat) parameters. A binuClear cobalt complex with two cyClen centers separated by a -(CH2)(6)-N+(CH3)(2)-(CH2)(6)-N+(CH3)(2)-(CH2)(6)- spacer shows, with only 5 x 10(-5) M catalyst concentration, the largest known rate enhancement factor of >10(7) (corresponding to >10(11) at 1 M) against DNA; incubation with 0.05 mM at 37 degrees C for only 2 h leads to almost complete Cleavage without appearance of products typical for redox Cleavage. These results are in contrast to experiments with corresponding copper(II) complexes with added hydrogen peroxide, which has no effect with corresponding Co, Zn, Cd, or Ni complexes.Cobalt(III) polyamine complexes as catalysts for the hydrolysis of phosphate esters and of DNA. A measurable 10 million-fold rate increasex241199758#N/AFALSE
1889
ja973112810.1021/ja9731128FALSEhttps://doi.org/10.1021/ja9731128Sen, AJ. Am. Chem. Soc.Novel nickel(II)- and palladium(II)-based catalytic systems for the synthesis of hyperbranched polymers from ethene52199818#N/ATRUE
1890
ja964187z10.1021/ja964187zFALSEhttps://doi.org/10.1021/ja964187zDarensbourg, MYJ. Am. Chem. Soc.The synthesis, structural characterization, and electrochemical properties of N3S2-ligated metal complexes of the ligand 4,10-dithia-1,7,13-triazabicyClo[11.3.3] are described. Complexes of Ni-II, Co-II, and Rh-III have been characterized by X-ray crystallography as six-coordinate complexes of the pentadentate ligand with Cl-anions occupying the position trans to the secondary amine donor. In addition, the chelation of the N3S2 donor ligand to the reactor-produced radionuClide Rh-105 was shown to give a single product in high yield (>98% at pH 5). The ligand is prepared by the template reaction of (N,N-bis(2-mercaptoethyl)-1,5-diazacyClooctane)nickel(II), Ni-1, with bis(2-chloroethyl)amine, yielding (S,S'-(3-aza-1,5 -pentanediyl)-N,N'-bis(2-mercaptoethyl)-1,5-diazacyClooctane N,N',N'',S,S')nickel(II) chloride, [Ni(amine)Cl]Cl. Removal of nickel from [Ni(amine)Cl]Cl and subsequent reaction of the ligand with CoCl2 or RhCl3.xH(2)O afforded (S,S'-(3-aza-1,5-pentanediyl)-N,N'-bis(2-diazacyClooctane-N,N'N'',S,S)cobalt(II) chloride, [Co(amine)Cl]Cl, C14H29N3S2CoCl2.1.75MeOH, and (S,S'-(3-aza-1 ,5-pentanediyl)-N,N'-bis (2-mercaptoethyl)-1,5-diazacyClooctane-N,N',N'',S,S')rhodium(III) chloride, [Rh(amine)Cl]Cl-2, C14H29N3S2RhCl3, respectively. The blue complex [Ni(amine)Cl]Cl, C14H29N3S2NiCl2.MeOH, contains nickel in an octahedral environment of N3S2Cl donors and crystallizes in the monoClinic space group P2(1)/c with a = 13.278(3) Angstrom, b = 11.976(4) Angstrom, c = 12.928(4) Angstrom, beta = 102.17(2)degrees, and Z = 4. The complex [Co(amine)Cl]Cl is fuchsia and crystallizes in the monoClinic space group P2(1)/n with a = 10.321(2) Angstrom, b = 7.892(1) Angstrom, c = 27.684(3) Angstrom, beta = 96.91(1)degrees, and Z = 4. Yellow crystals of [Rh(amine)Cl]Cl-2, C14H29N3S2RhCl3, were determined to be in the monoClinic space group ClCl with a = 9.655(2) Angstrom, b = 16.805(4) Angstrom, c = 11.756(3) Angstrom, beta = 96.29(2)degrees, and Z = 4.A new macrocyClic N3S2 ligand and its nickel(II), cobalt(II), rhodium(III)-103, and rhodium(III)-105 complexesx18199749#N/AFALSE
1891
ja972692610.1021/ja9726926FALSEhttps://doi.org/10.1021/ja9726926Liebeskind, LSJ. Am. Chem. Soc.Sulfonium salts. Participants par Excellence in metal-catalyzed carbon-carbon bond-forming reactions187199732#N/ATRUE
1892
ja972210q10.1021/ja972210qFALSEhttps://doi.org/10.1021/ja972210qHaymond, GSJ. Am. Chem. Soc.The free-base and Zn(II) complexes of N-methyl-beta-octaethyl- and meso-tetratolylchlorin and isobacteriochlorin were synthesized and characterized. Direct methylation of free-base hydroporphyrin compounds was unexpectedly selective. Only one of the several possible regioisomers that could result from Alkylation of the. inequivalent N atoms was produced for each hydroporphyrin free-base. This result was independent of the electropilic reagent [(MeSPh2][BF4] for meso-tetraAryl compounds and methyl trifluoromethanesulfonate for beta-octaethyl compounds) or the peripheral substituents on the hydroporphyrin. However, the greater basicity of the beta-oetaethyl substituted compounds resulted in their isolation as protonated cations. Methylation occurred at a pyrrole ring rather than a pyrroline ring. In chlorins, the pyrrole ring across the macrocyCle from the pyrroline ring was methylated to afford the symmetric N-methyl chlorins H(s-N23-MeTTC) and H-2(s-N23-MeOEC)(+). The selectivity is a result of kinetic rather than thermodynamic factors. Slow air oxidation of H(N-MeTTiBC) affords the unsymmetric N-methyl chlorin H(u-N22-MeTTC). The bacteriochlorins H-2(TTBC) and H-2(OEBC) were unreactive toward all electrophilic reagents investigated. An alternative synthetic approach, reduction of H(N-MeTTP), appears to have a selectivity complementary to direct methylation. It afforded a complex mixture of compounds that contained H(u-N22-MeTTC) and one other yet unidentified N-methyl hydroporphyrin. Free-base N-methyl hydroporphyrins react rapidly and quantitatively with zinc salts to afford Zn(II) complexes. The H-1 NMR spectra were characterized by N-methyl group resonances that have shifts between 0 and 4 ppm upfield of TMS and decreased ring current effects as the saturation of the macrocyCle increases. The inequivalence of the two faces of the macrocyCle owing to the N-methyl group revealed that the meso-Aryl groups undergo restricted rotational motion. The barriers to rotation vary with saturation and metalation but are substantially smaller than in metallo-TTP compounds. Both the oxidations and reductions of free-base N-methyl hydroporphyrin compounds are markedly irreversible. However, the zinc complexes have reversible reductions.The synthesis, properties, and reactivities of free-base- and Zn(II)-N-methyl hydroporphyrin compounds. The unexpected selectivity of the direct methylation of free-base hydroporphyrin compounds31199779#N/ATRUE
1893
ja963701y10.1021/ja963701yFALSEhttps://doi.org/10.1021/ja963701yBurrows, CJJ. Am. Chem. Soc.Guanine-specific modification of both single- and double-stranded oligodeoxynuCleotides via the autoxidation of sulfite is shown to be catalyzed by [NiCR](2+) (where CR = 2,12-dimethyl-3,7,11,17-tetraazabicyClo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene) and [NiKGH-NH2](+) (where KGH = lysylglycylhistidine). In the latter case, the nickel complex is proposed to act as a catalyst in three separate steps of sulfur oxide chemistry. Oxidative damage of guanines led to strand scission after piperidine treatment. The observed reactivity represents the first demonstration of DNA damage by sulfite and nickel(IT) complexes. Importantly, these reactions were conducted using sulfite concentrations relevant to levels known to be cytotoxic. Mechanistic studies suggest the importance of both monoperoxysulfate and sulfate radical anion in the observed DNA damage. Evidence for formation of guanine radical cation as the initial product of DNA oxidation was found by comparison of the sequence dependence of guanine reactivity in a duplex restriction fragment. These studies underscore a role for sulfite in nickel toxicity and suggest a new method of site-specific oxidation with bioconjugates using sulfite rather than highly reactive oxidants such as monoperoxysulfate.DNA damage from sulfite autoxidation catalyzed by a nickel(II) peptidex163199760#N/AFALSE
1894
ja963693l10.1021/ja963693lFALSEhttps://doi.org/10.1021/ja963693lSchaad, OJ. Am. Chem. Soc.The lability of the mononuClear octahedral complex tris(5-methyl-2-(1'-methylbenzimidazol-2-yl)-pyridine)-cobalt(II), [Co(2)(3)](2+), is compared with the dinuClear triple-helical complex tris[bis[1-methyl-2-(5'-methylpyrid-2'-yl]benzimidazol-5-yl]methane]dicobalt(II), [Co-2(1a)(3)](4+).[Co(2)(3)](2+) undergoes rapid isomerization between mer and fac forms (k(298)(mer-fac) = 1.6 +/- 0.2 s(-1)) in acetonitrile while the racemization of (-)(589)-[Co-2(1a)(3)](4+) is roughly 10(5) times slower (k(298) = 1.4 +/- 2 10(-5) s(-1)). The pressure dependence of the isomerization of [Co(2)(3)](2+) suggests a dissociatively activated process. The racemization of (-)(589)-[Co-2(1a)(3)](4+) is found to be independent of pH above pH 4, and is not affected by added cobalt(II) or a change of solvent. Ligand exchange between [Co-2(1b)(3)](4+) (1b = bis[1-ethyl-2-(5'-methylpyrid-2'-yl)benzimidazol-5-yl]methane) and free la may be followed by electrospray mass spectrocopy and establishes the mechanism of formation of the triple helix to be initial formation of mononuClear [Co(1a)(3)](2+) followed by capping by a second cobalt to give [Co-2(1a)(3)](4+). The slow racemization of (-)(589)-[Co-2-(1a)(3)](4+) is attributed to the very slow dissociation of a cobalt ion from the triple helix: This inertness is attributed to the rigidity of the ligand and the tight pitch of the helix.A comparison of the lability of mononuClear octahedral and dinuClear triple-helical complexes of cobalt(II)x71199742#N/AFALSE
1895
ja971705c10.1021/ja971705cFALSEhttps://doi.org/10.1021/ja971705cPeng, SMJ. Am. Chem. Soc.Distorted square planar Ni(II)-chalcogenolate Carbonyl complexes [Ni(CO)(SPh)(n)(SePh)(3-n)](-) (n=0, 1, 2): Relevance to the nickel site in CO dehydrogenases and [NiFeSe] hydrogenase46199736#N/ATRUE
1896
ja963200c10.1021/ja963200chttps://doi.org/10.1021/ja963200cFreiser, BSJ. Am. Chem. Soc.The infrared multiphoton dissociation (IRMPD) of the two isomers, M(1,3-butadiene)(+) and M(C2H2)-(C2H4)(+) (M = Fe, Co, or Ni), was investigated. For the butadiene system, FeC4H6+ was observed to give three products, CoC4H6+ four products, and NiC4H6+ Only one product. The observation of four products has not been previously seen in IRMPD studies of ions and suggests a fortuitous balance of several factors. Interestingly, the IRMPD of M(butadiene-1,1,4,4-d(4))(+) was observed not only to give one product for M = Fe, Co, or Ni but also to proceed with a decreased photodissociation rate. For the M(C2H2)(C2H4)(+) system, IRMPD suggests that D-o(Co+-C2H2) similar to D-o(CO+-C2H4) Also, SORI and/or competitive CID indicate that D-o(M(+)-C2H2) > D-o(M(+)-C2H4) by 0.5-2 kcal/mol for M = Fe or Ni. On the basis of these observations, we assign D-o(Fe+-C2H2) = 6 +/- 2 kcal/mol, D-o(Co+-C2H2) = 43 +/- 2 kcal/mol, and D-o(Ni+-C2H2) = 45 +/- 2 kcal/mol. These results are compared to recent theoretical and experimental findings.Infrared multiphoton dissociation of MC(4)H(6)(+) [M=Fe, Co, or Ni; C4H6=1,3-butadiene or (C2H2)(C2H4)]Photocatalyst16199767#N/AFALSE
1897
ja971621410.1021/ja9716214FALSEhttps://doi.org/10.1021/ja9716214Scheidt, WRJ. Am. Chem. Soc.The crystal structures of three porphyrin diacid species, [H4OEP](ClO4)(2), [H(4)Tpp](ClO4)(2), and [H4TMP]-(ClO4)(2), have been determined from low-temperature X-ray diffraction data to delineate how the peripheral substituents of the porphyrin affect the overall molecular flexibility. [H4OEP](ClO4)(2) (\Cb\ = 0.67 Angstrom), [H4TMP](ClO4)(2) (\Cb\ = molecule 1), and [H4TPP](ClO4)(2) (\Cb\ = 0.93 Angstrom) show increasingly saddled core conformations with effective D-2d symmetry. The mean porphyrin-Aryl group dihedral angles in [H4TPP](ClO4)(2) and [H4TMP](ClO4)(2) (molecule 1) are 27(2)degrees and 63(13)degrees, respectively. The steric bulk of the mesityl substituents in [H4TMP](2+) limits the range of observed porphyrin-Aryl group dihedral angles to >50 degrees and, consequently, the magnitude of the core distortion. [H4TMP](2+) is therefore less flexible than [H4TPP](2+). Molecular mechanics calculations, using a modified version of MM2(87) and a newly developed force field for porphyrin diacids, correctly predict that the flexibility of mesotetraAryl porphyrin diacids decreases as the steric bulk of the peripheral substituents increases: [H4TPyP](2+) approximate to [H4TPP](2+) > [H4T-2,6-(OH)(2)PP](2+) approximate to [H4T-2,6-F2PP](2+) > [H4T-2,6-Cl2PP](2+) approximate to [H4TMP](2+). Grid searches of conformational space for [H(4)porphine](2+), [H4OEP](2+), [H4TPP](2+), and [H4T-2,6-Cl2PP](2+) located pairs of inversion-related minima with D-2d -saddled and C-2h,-stepped core conformations. The in vacuo strain energy barrier to inversion of the lowest-energy D-2d-saddled conformation increases from 0.45 kcal/mol in [H(4)porphine](2+) to 1.9 kcal/mol in [H4T-2,6-Cl2PP](2+). The calculations indicate that the relative stability and magnitude of distortion of the D-2d isomer increases as the steric bulk of the peripheral substituents increases; [H4OEP](2+) is therefore calculated to be less distorted than [H4TPP](2+), in agreement with the X-ray structures of these species.An analysis of porphyrin molecular flexibility - Use of porphyrin diacids160199787#N/ATRUE
1898
ja971619c10.1021/ja971619cFALSEhttps://doi.org/10.1021/ja971619cSpiro, TGJ. Am. Chem. Soc.Ferrochelatase catalyzes Fe2+ insertion into porphyrins, and is inhibited by Hg2+. Resonance Raman spectra of mesoporphyrin IX show that binding to ferrochelatase restricts the conformation of the propionate sidechains, but does not perturb the ring conformation. However, a pronounced perturbation is seen in the ternary complex with Hg2+. Several additional RR bands are activated, inCluding some arising from IR-active vibrations, establishing loss of an effective symmetry Center. Out-of-plane modes appear in the low frequency region. The strongest of these bands, gamma(5) and gamma(6), correspond to pyrrole tilting vibrations, which are in the same symmetry Class as a doming distortion of the porphyrin. All four pyrrole N atoms are pointing toward the same side of the porphyrin plane, a geometry expected to facilitate Fe2+ insertion. This distortion is proposed to result from occupation of a metal-binding site, proximate to the porphyrin which promotes insertion of Fe2+, while occupation by Hg2+ is inhibitory.Resonance Raman spectra of ferrochelatase reveal porphyrin distortion upon metal binding43199747#N/ATRUE
1899
ja971025+10.1021/ja971025+FALSEhttps://doi.org/10.1021/ja971025+Munck, EJ. Am. Chem. Soc.The A-center of carbon monoxide dehydrogenase (CODH) resides in the enzyme's alpha-subunit and is responsible for the acetyl-CoA synthase activity. The center comprises a Ni site and an iron-sulfur Cluster. We have isolated the alpha-subunit using both continuous and discontinuous electrophoresis methods. When incubated with CO, samples prepared using continuous gels attain the A(red)-CO state that exhibits an S = 1/2 EPR feature (g = 2.048, 2.046, 2.021) similar to the so-called NiFeC signal of native CODH. Both signals consistently quantify to <0.4 spin/alpha. In order to elucidate the structure of the A-Cluster and to understand the cause of the substoichiometric spin intensities, we have studied the alpha-subunit with Mossbauer and EPR spectroscopy. As found for CODH, populations of isolated alpha are heterogeneous: they contain two major A-Cluster forms designated nonlabile and Ni-labile. In native CODH, only the Ni-labile form develops the NiFeC signal and exhibits catalytic activity. Oxidized samples of alpha exhibit Mossbauer spectra (S = 0, Delta E-Q = 1.08 mm/s, delta = 0.45 mm/s) typical of [Fe4S4](2+) Clusters. Upon reduction with dithionite, the Fe4S4 Cluster of nonlabile A-Clusters exhibits Mossbauer (average Delta E-Q = 1.0 mm/s, delta = 0.54 mm/s) and EPR properties similar to those of S = 3/2 [Fe4S4](+) cubanes; in contrast, Ni-labile Clusters are not reducible by dithionite. Treatment with CO yielded a sample for which 40% of the Fe was associated with A(red)-CO, while 47% of the Clusters (the nonlabile form) remained oxidized. Thus, the presence of nonlabile A-Clusters is largely responsible for the low spin intensities of the NiFeC signal. Upon formation of A(red)-CO, the Fe4S4 portion of the A-Cluster exhibits Fe-57 magnetic hyperfine interactions; the Cluster sites divide into equivalent pairs with (isotropic) A(A) = A(B) = -34.2 MHz and A(C) = A(D) = +26.8 MHz. However, the values of Delta E-Q and delta show that the Cluster has remained in the [Fe4S4](2+) state. We explain these observations with an electronic model that considers a Ni+-X-[Fe4S4](2+) assembly for which the Ni+ is exchange-coupled with one Fe site of the cube through a bridging ligand (X). The coupling was found to be substantial, namely \j\ approximate to 100 cm(-1) (H-NiFe = jS(Ni).S-Fe). The Mossbauer spectra provide no evidence that CO is bound ro the Fe4S4 Cluster in the state A(red)-CO, as has been conCluded from resonance Raman studies [Qiu, D.; Kumar, M.; Ragsdale, S. W.; Spiro, T. G. Science 1994, 264, 817-819]. We could not determine if the two metal centers are linked in the oxidized state (for either the Ni-labile or nonlabile form), but if they are, the Ni2+ must be low-spin (S-Ni = 0).Mossbauer and EPR study of the Ni-activated alpha-subunit of carbon monoxide dehydrogenase from Clostridium thermoaceticum80199754#N/ATRUE
1900
ja962831410.1021/ja9628314https://doi.org/10.1021/ja9628314Morokuma, KJ. Am. Chem. Soc.The mechanism of diimine-Ni-catalyzed ethylene polymerization reaction has been studied theoretically using the B3LYP density functional method. The chain initiation reaction proceeds with the coordination of ethylene to the model active catalyst [L(2)NiCH(3)](+), L(2) = (HNCH)(2), followed by ethylene insertion into the metal-Alkyl bond with a rate-determining 11.7 kcal/mol free energy barrier to form a gamma-agostic intermediate, which with a small barrier rearranges to a more stable beta-agostic intermediate and then forms an olefin Alkyl complex upon coordination of the next ethylene. Linear polymer propagation takes place from this olefin Alkyl complex, the resting state in the catalytic cyCle, via the same insertion, rearrangement, and coordination pathway. An alternative pathway from the olefin Alkyl complex passes over a 14-15 kcal/mol barrier for beta-hydride elimination and reinsertion for branched polymer propagation. These energetics suggest that the Ni(II)-catalyzed reaction is expected to produce more linear than methyl-branched polymers, and that higher temperature increases and higher ethylene pressure decreases the branching. Hydrogenolysis is an energetically favorable termination pathway, proceeding via coordination of a hydrogen molecule to the metal center, followed by H-H Activation through a four-centered ''metathesis-like'' transition state and reductive elimination of alkane. A comparison with zirconocene-catalyzed ethylene polymerization shows that the Ni(II)catalyzed polymerization should be slightly slower and should give more branching.A density functional study of the mechanism of the diimine-nickel-catalyzed ethylene polymerization reactionx161199750#N/AFALSE
1901
ja962805610.1021/ja9628056FALSEhttps://doi.org/10.1021/ja9628056Tjandra, SThe thermal chemistry of neopentyl iodide on Ni(100) surfaces: Selectivity between alpha-C-H and gamma-C-H and between C-H and C-C bond-scission steps in chemisorbed neopentyl moietiesx1996#N/AFALSE
1902
ja970551y10.1021/ja970551yFALSEhttps://doi.org/10.1021/ja970551yBalaram, PJ. Am. Chem. Soc.The Schellman motif is a widely observed, helix terminating structural motif in proteins, which is achieved by the adoption of a left-handed helical (at) conformation by a C-terminus residue. The resulting hydrogen bonding pattern involves an intramolecular 6-->1 interaction. This helix terminating motif is readily mimicked in synthetic helical peptides by placing an achiral residue at the penultimate position of the helix. The crystal structure of the heptapeptide Boc-Leu-Aib-Val-Gly-Leu-Aib-Val-OMe (1) reveals a 3(10)-helix terminated by a Schellman motif with Aib(6) adopting an alpha(L) - conformation. The crystals are in the space group P2(1) with a=9.958(3) Angstrom, b=20.447(3)A, c=11.723 (2) Angstrom, beta=99.74(2)degrees, and Z = 2. The final R-1 and wR(2) values are 7.2% and 18.9%, respectively, for 1731 observed reflections [I greater than or equal to 2 sigma(1)]. A 6-->1 hydrogen bond between Aib(2)CO----Val(7)NH and a 5-->2 hydrogen bond between Val(3)CO----Aib(6)NH are observed. An analysis of several alpha(L) terminated helical peptides in crystals suggests that the medium range (CiH)-H-alpha----Ni+3H [d(alpha N)(i,i+3)] and (CiH)-H-alpha----Ni+4H [d(alpha)(i,i+4)] interproton distances are indeed characteristic of the Schellman motif. NMR studies in CDCl3 establish retention of the 3(10)-helical conformation with key NOEs demonstrating the persistence of the conformation determined in crystals. The present study demonstrates the identification of the Schellman motif in solution in a synthetic helical peptide.Characterization of helix terminating Schellman motifs in peptides. Crystal structure and nuClear overhauser effect analysis of a synthetic heptapeptide helix28199748#N/ATRUE
1903
ja970449110.1021/ja9704491FALSEhttps://doi.org/10.1021/ja9704491Sato, YJ. Am. Chem. Soc.Regioselective cyClic cotrimerization of alpha,beta-enones and alkynes by a nickel-aluminum catalyst system70199718#N/ATRUE
1904
ja962671w10.1021/ja962671wFALSEhttps://doi.org/10.1021/ja962671wNorth, JTJ. Am. Chem. Soc.Xestospongin A [also known as araguspongine D (1)], a C-2-symmetric macrocyClic alkaloid isolated from the sponge Xestospongia exigua (Xestospongia sp.), and its C(9) epimer xestospongin C [also known as araguspongine E (2)] have been synthesized. The route capitalizes on the facile condensation between 5-halovaleraldehydes and 19-aminoalcohols to produce an oxaquinolizidine ring system in which all proper relative stereochemical relationships are controlled by equilibration. A linchpin synthesis was used to construct one key monomeric precursor-a 2,5-disubstituted thiophene derivative 26 [N=CCH2CH(OH)-2-Th-5-CH2CH2CH(CH(OMe)(2))CH2CH2CH2Cl]. A second precursor lacking the thiophene ring 38 [N=CCH2CH(OH)(CH2)(6)CH(CH(OMe)(2))CH2CH2CH2Cl] was assembled in a similar fashion. The carbinol center in each of these precursors was efficiently resolved enzymatically; lipase (PS-30) hydrolysis of the racemic acetate derivative of the thiophenemethanol derivative 26 and SP-435-catalyzed esterification of the beta-hydroxynitrile 38 proved effective. The initial macrocyClization strategy involved (i) hydrolysis of a portion of monomer (+)-26 to the corresponding aldehyde, (ii) reduction of the nitrile to a 1,3-aminoalcohol derivative with a second portion of the monomer, (iii) condensation of these two, end-differentiated monomers to give the ''half-cyClized'' oxaquinolizidine 30 that bears pendant nitrile and acetal groups, (iv) sequential reduction and acid-catalyzed hydrolysis to give the corresponding aldehyde ammonium ion 31, and v) dilution and elevation of pH leading to the macrocyClic bis-thiophene (-)-32. Final reductive removal of both thiophenes with Raney nickel proceeded smoothly to give (+)-xestospongin A/(+)-araguspongine D (1). The impact of pH-control, concentration effects, and monomer rigidity on the macrocyClic dimerization event are discussed. A more direct strategy involved sequential nitrile reduction and acetal hydrolysis within (+)-26 and direct, two-stage macrocyClic dimerization to (-)-32. Control of pH is important to the success of this cyClization. In an analogous fashion the non-thiophene monomer (-)-38 was converted to the ammonium ion/aldehyde S-41. This could be used to probe the effect of substrate rigidity on the efficiency of macrocyCle formation. Substrate S-41 spontaneously dimerized to produce a mixture of xestospongin A (1) and xestospongin C (2) with similar efficiency to the thiophene-containing 33.Synthesis of the C-2-symmetric, macrocyClic alkaloid, (+)-xestospongin A and its C(9)-epimer, (-)-xestospongin C: Impact of substrate rigidity and reaction conditions on the efficiency of the macrocyClic dimerization reactionx20199616#N/AFALSE
1905
ja962625w10.1021/ja962625wFALSEhttps://doi.org/10.1021/ja962625wGarg, NKJ. Am. Chem. Soc.Transition metal-amine initiators for preparation of well-defined poly(gamma-Benzyl L-glutamate)x57199724#N/AFALSE
1906
ja962533710.1021/ja9625337FALSEhttps://doi.org/10.1021/ja9625337Hoffman, BMJ. Am. Chem. Soc.The terminal step in methane generation by the archaeon Methanobacterium thermoautotrophicum is catalyzed by the enzyme S-methyl coenzyme M reductase (methylreductase). This enzyme contains a Ni(II) tetrapyrrole cofactor, F-430, at the active site in the resting state. A Ni(I) state ((NiF430)-F-I) has been proposed as the active form of the cofactor. Nickel isobacteriochlorins have been used to model F-430. We have investigated both (NiF430)-F-I and Ni(I)OEiBC using CW and pulsed EPR and ENDOR spectroscopy at X-band and Q-band microwave frequencies. In agreement with a previous X-band EPR and ESEEM study, at Q-band, the g tensor of (NiF430)-F-I appears axial and H-1,H-2 ENDOR of (NiF430)-F-I in H2O versus D2O solvent shows no evidence for strongly coupled, solvent-exchangeable hydrogens, and this indicates that there is no water axially coordinated to Ni(I) in contrast to the Ni(LI) resting state. Both (NiF430)-F-I and Ni(I)OEiBC give N-14 ENDOR signals arising from the four pyrrole nitrogen ligands to Ni(I). Previous EXAFS studies of Ni(I)OEiBC and Ni(I)F(430)Me(5) showed two sets of NL(I)-N distances differing by similar to 8, and in agreement with this, the N-14 ENDOR signals for both Ni(I)OEiBC and (NiF430)-F-I can be analyzed in terms of superimposed signals from two distinct types of nitrogen ligand. The difference in bond lengths determined by EXAFS is reflected in different hyperfine and quadrupole coupling constants as determined by ENDOR. Comparison of these magnetic parameters for Ni(I) complexes with those for related species, such as (CuTPP)-T-II, shows that one Set of nitrogen ligands resembles porphyrin pyrrole, while the other set is distinctively different.Investigation by EPR and ENDOR spectroscopy of the nickel(I) form of cofactor F-430 of Methanobacterium thermoautotrophicum and of nickel(I) octaethylisobacteriochlorinx35199774#N/AFALSE
1907
ja962516h10.1021/ja962516hhttps://doi.org/10.1021/ja962516hBrookhart, MLiving polymerization of alpha-olefins using Ni-II-alpha-diimine catalysts. Synthesis of new block polymers based on alpha-olefinsx1996#N/AFALSE
1908
ja970418610.1021/ja9704186FALSEhttps://doi.org/10.1021/ja9704186Holm, RHJ. Am. Chem. Soc.The frequent occurrence of the cuboidal Cluster [Fe3S4(S . Cys)(3)] in a variety of proteins has prompted extensive investigation of its chemical and biological properties. The biological function remains in question, but the Cluster is known to sustain two reactions: (i) electron transfer, and (ii) heterometal ion incorporation The recent preparation of [Fe3S4(LS3)](3-) (3) [Zhou, J.; Hu, Z.; Miinck, E.; Helm, R. H. J. Am. Chem. Sec. 1996, 118, 1966] has permitted detailed structural, electronic, and reactivity characterization of the cuboidal [Fe3S4](0) oxidation state (LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-). Redox properties (i) have been reported previously: here reaction type (ii), resulting in the formation of cubane-type MFe3S4 Clusters, has been investigated. Reaction of 3 with [M(PPh3)4](1+) affords [(Ph3P)MFe3S4(LS3)](2-) (M = Cu (6), Ag (8)) while [(NC)M(PPh3)(3)] leads to [(NC)MFe3S4(LS3)](3-) (M = Cu (7), Ag (9)). Treatment of 3 with Tl(O3SCF3) yields [TlFe3S4(LS3)](2-) (10). The fragment formalism {M1+ + [Fe3S4](0)} applies to 6-10, which retain the S = 2 ground state of 3. Reaction of 3 with [M(PPh3)(3)Cl] yields [(Ph3P>MFe3S4(LS3)](2-) (M = Co (12), Ni (14)) in inner-sphere redox reactions. Clusters 12 (S = 1) and 14 (S = 3/2) are formulated as {M2+ + [Fe3S4](1-)}; antiferromagnetic coupling of fragment spins gives rise to the indicated spin ground states. The reactions (ii) are metal-ion incorporation processes, a new reaction type in Fe-S chemistry. Previously, all cubane-type MFe3S4 Clusters had been synthesized by spontaneous self-assembly or reductive rearrangement reactions. Cluster 7 exhibits reversible oxidation and reduction reactions; it is the only Cluster that forms a stable oxidized product containing the [Fe3S4](1+) fragment. All other Clusters show a reversible reduction and an irreversible or quasireversible oxidation. Potentials of the synthetic Clusters are considered intrinsic to the various core units, being less influenced by environmental factors than are those in proteins. At parity of Cluster charge and terminal ligation, the potential order is M = Fe < Co < Ni and Co < Ni < Cu < Ag ( Tl for the [MFe3S4](2+,1+) and [MFe3S4](1+,0) core redox reactions. These orders are compared with those determined in proteins.Metal ion incorporation reactions of the Cluster [Fe3S4(LS3)](3-), containing the cuboidal [Fe3S4](0) core54199761#N/ATRUE
1909
ja962429p10.1021/ja962429pFALSEhttps://doi.org/10.1021/ja962429pMaroney, MJJ. Am. Chem. Soc.Structural information obtained from the analysis of nickel K-edge X-ray absorption spectroscopic data of [NiFe]hydrogenases from Desulfovibrio gigas, Thiocapsa roseopersicina, Desulfovibrio desulfuricans (ATCC 27774), Escherichia coli (hydrogenase-1), Chromatium vinosum, and Alcaligenes eutrophus H16 (NAD(+)-reducing, soluble hydrogenase), poised in different redox states, is reported. The data allow the active-site structures of enzymes from several species to be compared, and allow the effects of redox poise on the structure of the nickel sites to be examined. In addition, the structure of the nickel site obtained from recent crystallographic studies of the D. gigas enzyme (Volbeda, A.; Charon, M.-H.; Piras, C.; Hatchikian, E. C.; Frey, M.; Fontecilla-Camps, J. C. Nature 1995, 373, 580-587) is compared with the structural features obtained from the analysis of XAS data from the same enzyme. The nickel sites of all but the oxidized (as isolated) sample of A. eutrophus hydrogenase are quite similar. The nickel K-edge energies shift 0.9-1.5 eV to lower energy upon reduction from oxidized (forms A and B) to fully reduced forms. This value is comparable with no more than a one-electron metal-centered oxidation state change. With the exception of T. roseopersicina hydrogenase, most of the edge energy shift (-0.8 eV) occurs upon reduction of the oxidized enzymes to the EPR-silent intermediate redox level (SI). Analysis of the XANES features assigned to 1s-->3d electronic transitions indicates that the shift in energy that occurs for reduction of the enzymes to the SI level may be attributed at least in part to an increase in the coordination number from five to six. The smallest edge energy shift is observed for the T. roseopersicina enzyme, where the XANES data indicate that the nickel center is always six-coordinate. With the exception of the oxidized sample of A. eutrophus hydrogenase, the EXAFS data are dominated by scattering from S-donor ligands at similar to 2.2 Angstrom. The enzyme obtained from T. roseopersicina also shows evidence for the presence of O,N-donor ligands. The data from A. eutrophus hydrogenase are unique in that they indicate that a significant structural change occurs upon reduction of the enzyme. EXAFS data obtained from the oxidized (as isolated) A. eutrophus enzyme indicate that the EXAFS is dominated by scattering from 3-4 N,O-donor atoms at 2.06(2) Angstrom, with contributions from 2-3 S-donor ligands at 2.35(2) Angstrom. This changes upon reduction to a more typical nickel site composed of similar to 4 S-donor ligands at a Ni-S distance of 2.19(2) Angstrom. Evidence for the presence of atoms in the 2.4-2.9 Angstrom distance range is found in most samples, particularly the reduced enzymes (SI, form C, and R). The analysis of these data is complicated by the fact that it is difficult to distinguish between S and Fe scattering atoms at this distance, and by the potential presence of both S and another metal atom at similar distances. The results of EXAFS analysis are shown to be in general agreement with the published crystal structure of the D. gigas enzyme.Structure of the Ni sites in hydrogenases by X-ray absorption spectroscopy. Species variation and the effects of redox poisex103199639#N/AFALSE
1910
ja970194r10.1021/ja970194rFALSEhttps://doi.org/10.1021/ja970194rPohl, SJ. Am. Chem. Soc.[Ni(EtN2S2)] (1) (EtN2S2 = N,N'-diethyl-3,7-diazanonane-1,9-dithiolate) and [Ni(S-4)] (2) (S-4 = 3,7-dithianonane-1,9-dithiolate) react with [Fe4S4I4](2-) to afford the neutral Clusters [{Ni(EtN2S2)}(2)Fe4S4I2] (3) and [{Ni(S-4)}(2)Fe4S4I2] (4), respectively. Metathesis with potassium arenethiolates yields the Clusters [{Ni(EtN2S2))(2)Fe4S4(Stip)(2)] (5) and [{Ni(S-4))(2)Fe4S4(Stip)(2)] (6) (tip = 2,4,6-triisopropylbenzene). Alternatively, the latter compounds can be synthesized by action of the corresponding Ni complexes on [Fe4S4(Stip)(2)L-2] (L = 2,3-dimethyl-1-phenyl-3-pyrazoline-5-thione), where the neutral ligands are displaced by the Ni complexes. As elucidated by single-crystal X-ray crystallography, 3, 5, and 6 are composed of an [Fe4S4](2+) unit and two Ni(II) complexes and the Ni and Fe centers are bridged via one and two mu(2)-sulfur atoms from either the EtN2S2 or the S-4 ligands. In 3 and 5 two N and two 5 (thiolate) atoms serve as donors for a square planar coordinated Ni(II) ion, whereas 6 contains two Ni(II) ions in a square planar S-2 (thioether) S-2 (thiolate) environment. The structures of the NiFe heterometallic Clusters are discussed and related to the structures of the active sites of Ni containing CO dehydrogenases/acetyl-CoA synthases. As demonstrated by H-1-NMR spectroscopy, 3, 5, and 6 retain their bridged structures in solution. However, the spectra of 5 and 6 can be interpreted in terms of a symmetrical bidentate coordination of both Fe4S4-bound Ni complex fragments, which would be in contrast to the unidentate (5) or unsymmetrically bidentate (6) binding observed in the solid state. The redox properties of Clusters 3, 5, and 6 were determined by cyClic voltammetry. In dichloromethane solution 5 exhibits two quasi-reversible oxidation processes at 0 and +485 mV and one quasireversible reduction wave at -1050 mV (vs SCE).Unidentate and bidentate binding of Nickel(II) complexes to an Fe4S4 Cluster via bridging thiolates: Synthesis, crystal structures, and electrochemical properties of model compounds for the active sites of nickel containing CO dehydrogenase acetyl-CoA synthase48199763#N/ATRUE
1911
ja962198m10.1021/ja962198mFALSEhttps://doi.org/10.1021/ja962198mHashimoto, YJ. Am. Chem. Soc.Cyanide-bridged bimetallic assemblies [Ni(pn)(2)](2)[Fe(CN)(6)]X . catnH(2)O (X = ClO4- and n = 2 (1); X = BF4- and n = 2 (2); X = PF6- and n = 2 (3)) and [Ni(1,1-dmen)(2)](2)[Fe(CN)(6)]X . nH(2)O (X = ClO4- and n = 2 (4); x = BF4- and n = 3 (5); X = PF6- and n = 2 (6); X = CF3SO3- and n = 2 (7); X = BzO(-) and n = 6 (8); X = I- and n = 4 (9); X = N-3(-) and n = 4 (10); X = NCS- and n = 1 (11); X = NO3- and n = 4 (12)) have been prepared (pn = 1,2-propanediamine, 1,1-dmen = 1,1-dimethylethylenediamine). 7 crystallizes in a monoClinic space group P2(1)/m (no. 11), with a = 10.300(6), b = 20.632(4), c = 10.352(7) Angstrom, beta = 109.45(4)degrees, V = 2074(1) Angstrom(3) for Z = 4. 8 crystallizes in a triClinic space group P (1) over bar (no. 2), a = 10.413(6), b = 22.060(6), c = 10.377(3) Angstrom, alpha = 101.78(2), beta = 95.71(4), gamma = 77.29(3)degrees, V = 2272(1) Angstrom(3) for Z = 2. 10 crystallizes in triClinic space group P (1) over bar (no. 2), a = 10.314(1), b = 10.374(1), c = 10.233(1) Angstrom, alpha = 93.23(1), beta = 106.15(1), gamma = 86.37(1)degrees, V = 1045.0(2) Angstrom(3) for Z = 2. In each compounds [Fe(CN)(6)](3-) coordinates to four [Ni(1,1-dmen)(2)](2+) cations through four cyano nitrogens on a plane, providing a 2-D sheet of a square structure extended by Fe-CN-Ni linkages. The square with four Fe(III) ions at the corners and four trans Ni(II) on the edges shows a slight distortion to a rhombus. A ferromagnetic interaction operates within the sheet in all the compounds. The overall magnetic property is governed by the intersheet separation: a small intersheet separation provides metamagnets (1, 2, 3, 4, 6, 11) owing to intersheet antiferromagnetic interaction, whereas a large intersheet separation (>10 Angstrom) provides ferromagnets (5, 7, 8, 9, 10, 12). The ferromagnets became metamagnets on dehydration owing to shortening of the intersheet separation.Bimetallic magnetic material [Ni(diamine)(2)](2)[Fe(CN)(6)]X with two-dimensional network extended by Fe(III)-CN-Ni(II) linkagesx212199725#N/AFALSE
1912
ja964210g10.1021/ja964210gFALSEhttps://doi.org/10.1021/ja964210gSeevogel, KNovel Ni(0)-COT complexes, displaying semiaromatic planar COT ligands with alternating C-C and C=C bonds1997#N/ATRUE
1913
ja961911510.1021/ja9619115FALSEhttps://doi.org/10.1021/ja9619115Hoffman, BMJ. Am. Chem. Soc.We have developed the synthesis of unsymmetrical metalloporphyrazines of the form M[pz(A:B-3)], where A and B refer to two different types of peripheral functionality, and have used it to prepare new bi- and trimetallic solitaire-porphyrazines in which A represents a mono- or bimetallic moiety. The macrocyClic complexes described are based on the binuCleating ligand, [M(norphthalocyanine-2,3-dithiolate)](2-), [M(norpc)](2-). This can be thought of as a metalloporphyrazine when B is a fused benzo ring; A represents two thiolates fused at the beta-pyrrole positions to form a dithiolene moiety that can bind a transition-metal ion in addition to one within the macrocyClic cavity. solitaire-Porphyrazines have been synthesized by chelation of [(L-L)M'](2+) to the [M(norpc)](2-) ligand where M = ''2H'', Ni, Cu, or Mn-CI, L-L is a bis(diphosphino) or bis(diamino) group and M' = Ni, Pd, or Pt. Crystal structures have been obtained for 11b, where the [H-2(norpc)](2-) ligand coordinates the diphosphinopalladium moiety, [Pd-(dppf)](2+), by the two thiolate sulfur atoms at its periphery, and for 11h, with the diaminoplatinum moiety, [Pt-(teeda)](2+), bound to the periphery of the [Ni(norpc)](2-) ligand. In crystals of 11b and 11h, the molecules appear as face-to-face dimers. However, the dimer of 11b and the two crystallographically independent dimers of 11h each shows a distinctly different degree of overlap. The electronic absorption spectra of a series of porphyrazines in which the two peripheral sulfur atoms form thioether moieties with a modified Benzyl-protecting group (6-10) show that the peripheral asymmetry of the macrocyClic framework causes a strong splitting of the (pi-pi*) Q-band. In contrast, when the peripheral sulfurs bind a metal ion to form solitaire-porphyrazines 11a-h, the optical spectra Closely resemble that of the symmetrical pc, with unsplit Q band. The EPR spectrum of solitaire lid, where M = Cu, L-L = a bis(diphosphino) cap, M' = Pd, has features consistent with other square-planar copper(II) porphyrins and phthalocyanines. CyClic voltammograms of compound 11b shows two reversible ring reductions at potentials similar to those of H-2(pc) as well as a reversible oxidation associated with the ferrocene portion of the Pd(dppf) moiety.solitaire-porphyrazines: Synthetic, structural, and spectroscopic investigation of complexes of the novel binuCleating norphthalocyanine-2,3-dithiolato ligandx93199662#N/AFALSE
1914
ja961695010.1021/ja9616950FALSEhttps://doi.org/10.1021/ja9616950Scheidt, WRJ. Am. Chem. Soc.Solution equilibria and optical spectra of several metallooctaethylporphyrin pi-cation radicals have been examined in methylene chloride solution. The several pi-cation radical species, [M(OEP(.))]Y (M = Cu, Ni, Zn, Pd, or VO; Y = ClO4- or SbCl6-), are found to dimerize to form [M(OEP(.))](2)(2+). These dimeric species are characterized by the appearance of a new, strongly concentration-dependent near-infrared absorption band. This band is found in the region of 900-960 nm for all compounds except for the vanadyl complex which absorbs farther to the red at 1375 nm. The equilibrium constants for the dimerization reaction (2[M(OEP(.))](+) (K-D) [M(OEP(.))](2)(2+)) have been evaluated from multiple-wavelength concentration-dependent absorption data. Equimolar solutions of these pi-cation radicals and their analogous neutral M(OEP) derivatives react to form new binuClear species, [M(OEP(./2))](2)(+), in which the single radical electron is delocalized over both porphyrin rings. These new species, for which we suggest the term ''mixed-valence'' pi-cation radical and which bear a formal relationship to the oxidized special pair of photosynthetic reaction centers, also display a near-infrared absorption band. The near-IR band is however distinctly different from that of the pi-cation radical dimers. Equilibrium constants for the formation of these new species (M(OEP) + [M(OEP(.))](+) (K-MV) [M(OEP(./2))](2)(+)), have also been determined. The values of K-MV are 10-100-fold larger than the analogous dimerization constant K-D. Values of Delta H and Delta S have been obtained for both equilibrium processes. The variations in K-MV and K-D values are largely the consequence of entropy differences that probably result from a much stronger solvation of the pi-cation radical compared to the neutral porphyrin.Metalloporphyrin mixed-valence pi-cation radicals: Solution stability and propertiesx38199773#N/AFALSE
1915
ja964004910.1021/ja9640049FALSEhttps://doi.org/10.1021/ja9640049Jordan, RBJ. Am. Chem. Soc.The kinetic influence of an alkyne ligand, hexafluorobut-2-yne (HFB), has been investigated by studying the reactions of phosphines (PR3) with the complexes M(CO)(4)(eta(2)-HFB) (M = Fe, Ru, Os). The rate of production of M(CO)(3)(PR3)(eta(2)-HFB) is independent of the nature and concentration of the phosphine in all cases, indicating that the rate-controlling step is CO dissociation. The kinetic parameters, k(1) (s(-1), 25 degrees C), Delta H* (kJ mol(-1)), and Delta S* (cal mol(-1) K-1) are: 9.5, 88.2 +/- 2.3, 70 +/- 10 (Fe); 1.25 x 10(-2), 103.6 +/- 2.4, 66 +/- 8.6 (Ru); 3.5 x 10(-3), 99.5 +/- 0.8, 21 +/- 2.7 (Os). When the rate constants at 25 degrees C for M(CO)(4)(eta(2)-HFB) are compared to those of the parent M(CO)(5), the ratios are similar to 3 x 10(13), 1.8 x 10(2) and 1 x 10(7) for M = Fe, Ru, and Os, respectively. Clearly the alkyne increases the substitution lability, and the effect is spectacular with Fe, very large with Os, and substantial but relatively more modest with Ru, The increased lability results mainly from a reduced Delta H* of similar to 80, 10, and 33 kJ mol(-1) for Fe, Ru, and Os, respectively, and this is attributed largely to stabilization of the transition state by 4-electron donation from the alkyne ligand. Also reported are kinetics of formation of some trans M(CO)(2)(PR3)(2)(eta(2)-HFB) complexes and an extension of earlier work on the Os(CO)(5)/PPh3 system.Alkyne ligand enhancement of the substitution lability of mononuClear osmium, ruthenium, and iron Carbonyls32199869#N/ATRUE
1916
ja961550t10.1021/ja961550tFALSEhttps://doi.org/10.1021/ja961550tSasaki, SJ. Am. Chem. Soc.Various pi-conjugated copolymers constituted of pi-excessive thiophene, selenophene, or furan units (Ar) and pi-deficient pyridine or quinoxaline (Ar') units have been prepared in high yields by the following organometallic polycondensation methods: (i) n X-Ar-Ar'-X + n Ni(0)Lm --> (Ar-Ar')(n) (X = halogen, Ni(0)-Lm = zerovlent nickel complex), (ii) n X-Ar-X + n Me(3)Sn-Ar'-SnMe(3) --> (Ar-Ar')(n) (palladium catalyzed), and (iii) a X-Ar-X + b X-Ar'-X + (a + b)Ni(0)Lm --> (Ar)(x)(Ar')(y). Powder X-ray diffraction analysis confirms an alternative structure of a polymer prepared by the method ii. The copolymers have a molecular weight of 5.4 x 10(3) to 3.3 x 10(5) and an [eta] value of 0.37 to 4.4 dL g(-1). pi-pi* absorption bands of the copolymers generally show red shifts from those of the corresponding homopolymers, (Ar)(n), and (Ar')(n), and the red shifts are accounted for by charge-transferred CT structures of the copolymers. For example, an alternative copolymer of thiophene and 2,3-diphenylquinoxaline gives rise to an absorption band at lambda(max) = 603 nm, whereas homopolymers of thiophene and 2,3-diphenylquinoxaline exhibit absorption peaks at about 460 and 440 nm, respectively. The CT copolymers are electrochemically active in both oxidation and reduction regions, showing oxidation (or p-doping) peaks in a range of 0.39 to 1.32 V vs Ag/Ag+ and reduction (or n-doping) peaks in a range of -1.80 to -2.22 V vs Ag/Ag+, respectively. Copolymers of pyridine give unique cyClic voltammograms exhibiting p-undoping peaks at potentials much different (about 2-3 V lower) from the corresponding p-doping potentials, and this large difference between p-doping and p-undoping potentials is explained by an EC mechanism. They are converted into semiconductors by chemical and electrochemical oxidation and reduction. Copolymers of thiophene with pyridine and quinoxaline show the third-order nonlinear optical susceptibility chi((3)) of about 5 x 10(-11) esu at the three-photon resonant wavelength, which is 5-7 times larger than those of the corresponding homopolymers and related to the CT structure in the copolymers.pi-conjugated donor-acceptor copolymers constituted of pi-excessive and pi-deficient Arylene units. Optical and electrochemical properties in relation to CT structure of the polymerx361199678#N/AFALSE
1917
ja963982+10.1021/ja963982+FALSEhttps://doi.org/10.1021/ja963982+Suzuki, SJ. Am. Chem. Soc.Structures and catalytic activities of Carbonylate-bridged dinickel(II) complexes as models for the metal center of urease83199716#N/ATRUE
1918
ja961408s10.1021/ja961408sFALSEhttps://doi.org/10.1021/ja961408sWang, ZXJ. Am. Chem. Soc.Nickel-catalyzed reaction of highly fluorinated epoxides with halogensx21199649#N/AFALSE
1919
ja963595010.1021/ja9635950FALSEhttps://doi.org/10.1021/ja9635950Chen, HMechanism of water exchange for the di- and trivalent metal hexaaqua ions of the first transition series1997#N/ATRUE
1920
ja963061z10.1021/ja963061zFALSEhttps://doi.org/10.1021/ja963061zNorton, JRKinetics and mechanism of Alkyl transfer from organocobalt(III) to nickel(I): Implications for the synthesis of acetyl coenzyme A by CO dehydrogenase1997#N/ATRUE
1921
ja963060710.1021/ja9630607FALSEhttps://doi.org/10.1021/ja9630607Corbett, JDJ. Am. Chem. Soc.A family of compounds has been discovered in which pairs of octahedral rare-earth-metal Clusters, each centered by a late transition metal Z, share a common edge. These R(10)Z(2) units, sheathed and interbridged by iodine atoms, occur in the quaternary phases Rb2La10I17Co2, CS(2)La(10)I(17)Z(2) (Z = CO, Ni, Ru, Os), CS2Ce10I17Os2, and Cs(2)Pr(10)I(17)Z(2) (Z = CO, RU, Os) and in the ternary La10I15Os2. All are obtained as black, air-sensitive crystals from reactions of RI(3), R, Z, and RbI or CsI as appropriate in welded Nh containers at 800-850 degrees C. The structure of Cs2Ce10I17Os2 has been refined by single-crystal X-ray diffraction methods for comparison with the isotypic Cs2La10I17Co2 (monoClinic, C2/m, Z = 2, R(F)/R(w) = 4.0/4.4%), and the structure of a unique ternary La10I15Os2 has been defined (triClinic, P (1) over bar, Z = 1, R/R(w) = 5.0/5.1%). These new bioctahedral Clusters may be regarded as the missing links between discrete Clusters and infinite chains of condensed octahedral Clusters among rare-earth-metal Cluster halides that are stabilized by interstitial transition metals. The biClusters in both structures are extensively interconnected into three-dimensional arrays through bridging iodine atoms. The structural interconversion between Cs2La10I17Os2 and La10I15Os2 + 2CsI may be easily visualized in terms of changes in iodide bridging modes and accommodation of cesium cations. All the biClusters contain an odd number of Cluster-bonding electrons, and this feature has been confirmed by magnetic susceptibility studies. EHMO Cluster and band calculations on biClusters and their structures are in agreement with the localized bonding properties and ranges of electron counts.Two Closely related structure types with unprecedented bioctahedral rare-earth-metal Clusters centered by transition metals: A(2)R(10)I(17)Z(2) (A=Rb,Cs; R=La,Ce,Pr; Z=Co,Ni,Ru,Os) and La10I15Os226199729#N/ATRUE
1922
ja960435f10.1021/ja960435fFALSEhttps://doi.org/10.1021/ja960435fSpiro, TGJ. Am. Chem. Soc.Clostridium thermoaceticum and other autotrophic anaerobic bacteria contain a bifunctional enzyme, carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS), that catalyzes two reactions of CO at two separate Ni-FeS Clusters. Oxidation of CO to CO2 is catalyzed by Cluster C, while incorporation of CO into acetyl-CoA occurs at Cluster A. In this study, resonance Raman [RR] and infrared [IR] spectroscopy are applied to the adduct of Cluster C with cyanide, a selective inhibitor of CO oxidation. The RR spectra reveal that CN- binds simultaneously to Fe and Ni, because bands whose C-13 and N-15 shifts identify them as cyanide-metal stretching and bending modes are sensitive to incorporation of both Fe-54 and Ni-64 into the enzyme. The IR spectrum reveals a low frequency, 2037 cm(-1), for the C-N stretch, indicative of Fe-II binding via the C end. Vibrational modeling of the frequencies and isotope shifts indicates a bent Fe-CN-Ni bridging geometry, with a similar to 140 degrees C-N-Ni angle. This geometry of the inhibitory adduct suggests that CO oxidation involves a bimetallic mechanism. It is proposed that pre-organization of the metal ions by the enzyme promotes CO oxidation by Ni-II-OH- attack on Fe-II-CO, followed by Ni-FeS reduction as CO2 is released. This chemistry is analogous to the metal-catalyzed water-gas shift reaction.Raman and infrared spectroscopy of cyanide-inhibited CO dehydrogenase/acetyl-CoA synthase from Clostridium thermoaceticum: Evidence for bimetallic enzymatic CO oxidationx13199659#N/AFALSE
1923
ja962860e10.1021/ja962860ehttps://doi.org/10.1021/ja962860eZiegler, TJ. Am. Chem. Soc.We have applied a nonlocal density functional method to the study of ethylene polymerization with a Ni(II) catalytic center coordinated to diimine (HN=CH-CH=NH). We have investigated chain initialization, chain propagation, as well as chain isomerization and chain termination. Chain initialization proceeds in a stepwise fashion, with an overall Activation barrier of 11.1 kcal/mol. Chain propagation can proceed via two different pathways, which have similar Activation energies (16.8 and 17.5 kcal/mol, respectively). In contrast to behavior observed for metallocene catalysts, none of the insertion transition states show agostic stabilization. The Activation energy for chain isomerization is 12.8 kcal/mol, which proceeds via a concerted mechanism, rotating the chain and simultaneously abstracting the beta-agostic hydrogen. Chain termination occurs via a stable hydride intermediate, which is formed with a barrier of 9.7 kcal/mol and decays into the termination product with a small Activation energy of 1.7 kcal/mol. Production of experimentally observed high molecular weight polymers can only be explained by suppression of the chain termination transition state due to sterically demanding substituents on the diimine ligand.A density functional study of Nickel(II) diimide catalyzed polymerization of ethylene190199737#N/ATRUE
1924
ja954269810.1021/ja9542698FALSEhttps://doi.org/10.1021/ja9542698Chen, CTJ. Am. Chem. Soc.X-ray absorption spectroscopy at the L(2,3) edges of 3d transition metals has been used to study the electronic structure of molecular-based magnets with Curie temperatures ranging from 66 to 315 K. These magnets are bimetallic cyanides of the Prussian blue family, constructed by a three-dimensional assembling of -NC-Cr-III-CN-A(II)-units. The chemical selectivity of X-ray absorption spectroscopy allows information to be extracted on each of the two different metal transition ions that carry the spin moments. Using Ligand Field Multiplet calculations, where hybridization is mainly taken into account through configuration interaction, we have been able to reproduce nicely all the features of the divalent 3d ion L(2,3) edges. From the knowledge of the exact ground state, we have determined its electronic structure and relevant parameters, such as the crystal field strength and the spin-orbit coupling. We have separated covalence and charge transfer effects occurring in the bond between the 3d ions and the cyano ligand. From the L(2,3) edges of A(II) divalent ions, we found that the A(II)-NC bond has a weak covalent character with a 10% charge transfer. From the Lr-2,Lr-3 edges of Cr-III, where Cr ions are bonded to the carbon atom of the cyano ligand, we have shown that the Ligand Field Multiplet model is still fully applicable for strongly hybridized bonds. In this case it is essential to separate between covalence and charge transfer and to take the charge transfer into account through pi back-bonding. The precise knowledge of these parameters is essential for the determination of macroscopic characters like magnetic properties.Characterization of chemical bonds in bimetallic cyanides using X-ray absorption spectroscopy at L(2,3) edgesx59199643#N/AFALSE
1925
ja954173d10.1021/ja954173dFALSEhttps://doi.org/10.1021/ja954173dKanbara, TJ. Am. Chem. Soc.Dehalogenation polycondensation of 5,8-dibromoquinoxaline derivatives and 2,6-dibromoquinoxaline with zerovalent nickel complex affords a series of n-conjugated polyquinoxalines with a molecular weight of 6 x 10(3) to 260 x 10(3). The polymers are electrochemically reduced (or n-doped) with an E degrees value of -1.75 to -2.35 V vs Ag/Ag+ and converted into electrically conducting materials with a conductivity of 1 x 10(-4) to 7 x 10(-3) S cm(-1) by chemical reduction. Poly(quinoxaline-5,8-diyl)s with aromatic substituents give strong fluorescence with emission peaks at 450-520 nm in solutions as well as in cast films, A light-emitting diode (LED), ITO/polymer/Mg(Ag) (polymer = poly(2,3-diphenylquinoxaline-5,8-diyl)), emits blue-green light (lambda(max) at about 500 nm). Introduction of hole-transporting layers such as vacuum-deposited or spin-coated thin layers of poly(thiophene-2,5-diyl), poly(p-phenylene), and poly(N-Vinylcarbazole) between ITO and the light-emitting layer enhances electroluminescence efficiency by about 2 orders of magnitude. Polyquinoxalines have an ionization potential of 5.83 +/- 0.11 eV and a band gap of 2.56 +/- 0.26 eV.Preparation of new electron-accepting pi-conjugated polyquinoxalines. Chemical and electrochemical reduction, electrically conducting properties, and use in light-emitting diodesx224199659#N/AFALSE
1926
ja962748g10.1021/ja962748gFALSEhttps://doi.org/10.1021/ja962748gGong, XPCatalytic palladium-mediated bisdiene carbocyClizations: Bisdiene to enediene cyCloisomerizations1997#N/ATRUE
1927
ja962699810.1021/ja9626998FALSEhttps://doi.org/10.1021/ja9626998Pilato, RSExcited state properties of quinoxaline-substituted platinum 1,2-enedithiolates1997#N/ATRUE
1928
ja953963k10.1021/ja953963kFALSEhttps://doi.org/10.1021/ja953963kEichhorn, BWJ. Am. Chem. Soc.Synthesis and characterization of [eta(4)-P7Ni(CO)](3-), [eta(4)-HP7Ni(CO)](2-), and [eta(2)-P7PtH(PPh(3))](2-): Two electronically equivalent protonated zintl ion complexes with markedly different structuresx42199624#N/AFALSE
1929
ja953873f10.1021/ja953873fFALSEhttps://doi.org/10.1021/ja953873fAndersen, RAMe(5)C(5)Ni(acac): A monomeric, paramagnetic, 18-electron, spin-equilibrium moleculex1996#N/AFALSE
1930
ja962447710.1021/ja9624477FALSEhttps://doi.org/10.1021/ja9624477Clase, HJJ. Am. Chem. Soc.A major advance has been made in the incremental molecular design of long-lived cobalt(II) dioxygen carriers. Preceding mechanistic studies revealed that ionizable methyl groups trigger the autoxidation of the O-2 adduct of the cobalt(rr) cyClidene. Two members of a new family of unsubstituted (no methyl groups) lacunar cyClidene dioxygen carriers have been prepared in an eight-step synthesis, and a complex with a hexamethylene bridge has been structurally characterized. in contrast to previously studied cyClidenes, these materials bear no substituents on the chelated macrocyClic platform. As anticipated, the rates of autoxidation of these unsubstituted cyClidene complexes were found to be 5-8 times slower than those for the most stable previously known cyClidene derivatives. Because of the absence of Me-Me vicinal repulsion, the CG bridge assumes a zig-zag conformation directly across the cavity. The accompanying, relatively low, dioxygen affinity is explained on the basis of electronic and steric factors. The rates of dioxygen binding to these newly prepared cobalt(II) unsubstituted cyClidenes are fast and approximately equal to the corresponding values for their Me-substituted analogs. Consequently, differences in dissociation rates are responsible for the differences in O-2 affinities. This isa Clear example of an unusual steric effect for O-2 adducts.Unsubstituted cyClidenes - A novel family of lacunar dioxygen carriers with enhanced stability toward autoxidation: Synthesis, characterization, and a representative X-ray structure27199749#N/ATRUE
1931
ja953484l10.1021/ja953484lFALSEhttps://doi.org/10.1021/ja953484lMadix, RJJ. Am. Chem. Soc.The bonding and reactivity of ethylene on hydrogen presaturated Fe(100) has been investigated using temperature programmed reaction spectroscopy (TPRS) and electron energy loss spectroscopy (EELS). Hydrogen preadsorbed on Fe(100) limits the extent of electron back-donation to coadsorbed ethylene, resulting in weak rehybridization relative to adsorption on Clean Fe(100). Adsorption at 100 K leads to rehybridization intermediate between the sp(2) gas phase species and the nearly sp(3) di-sigma bound ethylene on Clean Fe(100), as indicated by pi sigma parameters of 0.58 (0.53 for C2D4). Migratory insertion of coadsorbed hydrogen into this adsorbed ethylene occurs below 170 K; vibrational spectroscopy positively identifies the intermediate formed as surface ethyl groups.Hydrogenation of weakly rehybridized ethylene on Fe(100)-H: Ethyl group formationx23199654#N/AFALSE
1932
ja962296810.1021/ja9622968FALSEhttps://doi.org/10.1021/ja9622968Pecoraro, VLJ. Am. Chem. Soc.Facile preparation of face differentiated, chiral 15-metallacrown-5 complexes103199627#N/ATRUE
1933
ja961968r10.1021/ja961968rFALSEhttps://doi.org/10.1021/ja961968rMunck, EJ. Am. Chem. Soc.Nickel(II) thiolate complex with carbon monoxide and its Fe(II) analog: Synthetic models for CO adducts of nickel-iron-containing enzymes67199627#N/ATRUE
1934
ja953247i10.1021/ja953247ihttps://doi.org/10.1021/ja953247iBrookhart, MJ. Am. Chem. Soc.Copolymerization of ethylene and propylene with functionalized Vinyl monomers by palladium(II) catalystsx1227199622#N/AFALSE
1935
ja953106g10.1021/ja953106ghttps://doi.org/10.1021/ja953106gBae, YYJ. Am. Chem. Soc.A five-coordinate Ni(I) macrocyClic complex, (R,S,R,S)-[Ni(L)(NHC(OH)CH3)]ClO4, where L is 1,3,6,8, 12,15-hexaazatricyClo[13.3.1.1(8,12)]icosane has been prepared by the reduction of Ni(II) complex (R,R,S,S)-[Ni(L)]-(ClO4)(2) . 1/2H(2)O With Na(Hg) in MeCN under a nitrogen atmosphere. In the formation of the complex, the solvent MeCN was hydrated to acetamide and coordinated to the Ni(I) ion. The complex shows rhombic EPR spectra with the powder sample or in the frozen MeCN solution. It equilibrates with four-coordinate (R,R,S,S)-[Ni(L)](+) in MeCN. [Ni(L)(NHC(OH)CH3)]ClO4 (NiC16H35N7O5Cl) crystallizes in the orthorhombic space group Pbca with a = 10.053(5) Angstrom, b = 14.120(3) Angstrom, c = 31.005(3) Angstrom, and Z = 8. The structure was solved by the direct method and refined to R values of R(1) = 0.0500 and omega R(2) = 0.0983 for 2153 unique reflections measured with Mo Ka radiation on a CAD-4 diffractometer. The Ni(I) ion of the complex has square-pyramidal geometry with an acetamide coordinating in the iminol form at the apical position. The complex shows two sets of Ni-N(macrocyCle) bond distances: 2.092(3) Angstrom (av) for Ni-N(sec) and 2.135(3) Angstrom (av) for Ni-N(tert), which are significantly longer than those of the square-planar Ni(I) complex (R,R,S,S)-[Ni(L)]ClO4. The Ni-N(iminol) bond distance is 1.969(5) Angstrom. The three bonds of Ni-N-C-O involving an iminol group have multiple bonding character.Acetamide coordination in a nickel(I) macrocyClic complex: Synthesis, properties, and X-ray crystal structure of a five-coordinate nickel(I) iminol complex of 1,3,6,8,12,15-hexaazatricyClo[13.3.1.1(8,12)]icosanex60199672#N/AFALSE
1936
ja961676q10.1021/ja961676qFALSEhttps://doi.org/10.1021/ja961676qShelnutt, JAJ. Am. Chem. Soc.The influence of substituents with increasing steric demands on the structure of nickel(II) 5,15-disubstituted porphyrins has been investigated with X-ray crystallography, UV-visible absorption spectroscopy, resonance Raman spectroscopy, molecular energy optimization calculations, and INDO/s molecular orbital calculations. Nickel 5,15-diphenylporphyrin is predicted by molecular mechanics calculations to be a mixture of planar and nonplanar conformers. All of the nickel diAlkylporphyrins (where the Alkyl group is propyl, isopropyl, and tert-butyl) are calculated to be in a predominantly gabled (gab) conformation resulting from an alpha alpha orientation of the substituents with respect to the macrocyCle. This nonplanar gab distortion is made up of a linear combination of distortions along the lowest-frequency out-of-plane macrocyCle normal coordinates of A(2u) (doming) and B-1u (ruffling) symmetry types. A higher energy stable ap conformer is also predicted for diAlkylporphyrins, and its nonplanar structure can be represented as an equal combination of distortions along the x- and y-components of the lowest-frequency E(g) (waving) normal coordinate. The nonplanar structures calculated by using molecular mechanics have been structurally decomposed into the displacements alone the lowest-frequency normal coordinate of each symmetry type, and the contributions of each type to the total distortion in the calculated structures agree well with contributions obtained from structural decompositions of the available X-ray crystal structures. The predicted gab distortion is confirmed most convincingly by the X-ray crystal structure of [5,15-di-tert-butylporphinato]nickel(II) which is found to be in a gab alpha alpha conformation. Finally, INDO/s calculations show that the red shifts in the absorption spectra of the nickel disubstituted porphyrins are caused by the increasing nonplanarity resulting from increasing steric crowding within the series.Representation of nonplanar structures of nickel(II) 5,15-disubstituted porphyrins in terms of displacements along the lowest-frequency normal coordinates of the macrocyCle101199667#N/ATRUE
1937
ja961498110.1021/ja9614981FALSEhttps://doi.org/10.1021/ja9614981Bergman, RGJ. Am. Chem. Soc.Synthesis, structure, and reactivity studies of an eta(2)-N-2-titanium diazoalkane complex. Generation and trapping of a carbene complex intermediate37199625#N/ATRUE
1938
ja961305+10.1021/ja961305+FALSEhttps://doi.org/10.1021/ja961305+Trautwein, AXJ. Am. Chem. Soc.A series of homo- and heterotrinuClear complexes containing three face-sharing octahedra has been synthesized by using the pendent arm macrocyClic ligands 1,4,7-tris(3,5-dimethyl-2-hydroxyBenzyl)Clononane, L(0)H(3), and 1,4,7-tris(4-tert-butyl-2-mercaptoBenzyl)-1,4,7-triazacyClononane, LH(3): [{L(0)Ni(II)}Ni-2(II)](1) and [{LCo(III)}Co-2(III)](PF6)(3) (2); [{LCo(III)}Ni-2](n+) (n = 2 (3), 3 (4), 4 (5)); [{LNi}Co-2(III)](n+) (n = 1 (6), 2 (7), 3 (8)) and its linkage isomers [{LNi}Ni{Co(III)L}](n+) (n = 1 (9), 2 (10), 3 (11)) and, finally, the complexes [{LNi}Ni-2](n+) (n = 0 (12), 1 (13), 2 (14), 3 (15)). In complex 1 three octahedral Ni-II ions form a linear array with two terminal [L(0)Ni(II)](-) moieties in a facial N3O3 donor set and a central Ni-II ion which is connected to the terminal ions via six phenolate bridging pendent arms of L(0). In complexes 2-15 the three metal ions are always in the same ligand matrix yielding an N(3)M(mu-S)(3)M(mu-S)(3)MN(3) first-coordination sphere regardless of the nature of the metal ions (nickel or cobalt) or their formal oxidation states. From temperature dependent magnetic susceptibility measurements it has been determined that 1 has an S = 3 ground state whereas in 12 it is 5 = 1. In order to understand this difference in exchange coupling (ferromagnetic in 1 and antiferromagnetic in 12) in two apparently very similar complexes the magnetic properties of 2-15 have been investigated. Complex 3 has an S = 1 and 4 an S = 1/2, and 5 is diamagnetic (S 0) as is its isoelectronic counterpart 2. This indicates the availability of the oxidation states II, III, and IV of the central NiS6 unit. In the isostructural complexes 6, 7, and 8, two terminal nickel ions are bridged by a central diamagnetic CoIII. The exchange coupling between two terminal paramagnetic nickel ions was studied as a function of their formal oxidation state. In 6 the two Ni-II ions are ferromagnetically coupled (5 = 2); the mixed-valent (NiNiIII)-Ni-II species 7 has an S = 3/2 ground state and in 8 most probably two Ni-III ions (d(7) low spin) give rise to an 5 = 1 ground state. In contrast, in the series 9, 10, and 11 where two nickel ions are in a position adjacent to each other 9 has an S = 0 (antiferromagnetic coupling), but in the mixed-valent complex 10 an S = 3/2 ground state (ferromagnetic coupling) is observed. In fl an S = I ground state prevails which may be achieved by ferromagnetic coupling between two Ni-III ions. For the trinuClear nickel complexes 12-15 an S = 1 ground state has been determined for 12, an S = 3/2 for the mixed valent complex 13, and an S = 2 for 14, and 15 exhibits an S = 3/2 ground state. The Goodenough-Kanamori rules do not provide a consistent explanation for the observed ground states in all cases. The concept of double exchange, originally introduced by Zener in 1951, appears to provide a more appropriate description for the mixed-valent species 7, 10, 13, 14, and 15. This picture is corrB(OH)2rated by the electrochemistry and EPR spectroscopy of complexes.Exchange and double-exchange phenomena in linear homo- and heterotrinuClear nickel(II,III,IV) complexes containing six mu(2)-phenolato or mu(2)-thiophenolato bridging ligands93199667#N/ATRUE
1939
ja960964j10.1021/ja960964jFALSEhttps://doi.org/10.1021/ja960964jKasdorf, KTotal synthesis of the pentacyClopropane antifungal agent FR-9008481996#N/ATRUE
1940
ja952702810.1021/ja9527028FALSEhttps://doi.org/10.1021/ja9527028Glowiak, TJ. Am. Chem. Soc.The methylation of a nickel(II) complex (CTPP)Ni-II of 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin (CTPPH2) with the mild methylating agent methyl iodide yields novel stable organonickel(II) complexes: diamagnetic (21-CH3TPP)Ni-II and two scarce paramagnetic species (2-NH-21-CH3CTPP)Ni(II)X and (2-NCH3-21-CH3CTPP)Ni(II)X (X = Cl, I). The demetalation procedure resulted in isolation of two 21-carbaporphyrin derivatives, methylated at the internal C(21) carbon atom, i.e., 2-aza-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (21-CH3-CTPPH2) and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (2-NCH3-21-CH3CTPPH). The methylation mechanism involves the oxidative addition of the methyl cation to the carbaporphyrin C(21) activated due to Ni-C coordination. These C-methylated macrocyCles preserve their coordinating properties as the remetalation processes have been carried out. The reversible concerted addition of HX converts the diamagnetic (21-CH3TPP)Ni-II into the paramagnetic (2-NH-21-CH3CTPP)Ni(II)X. The axial coordination step is accompanied by a protonation of the peripheral nitrogen. The structures of (21-CH3CTPP)NIII (monoClinic, P2(1)/c; a = 15.055(3) Angstrom, b = 15.795(3) Angstrom, c = 17.069(3) Angstrom, beta = 115.00(3)degrees, Z = 4, least-square refinement of 476 parameters using 3622 reflections, R = 0.069) and (2-NCH3-21- CH3CTPP)(NiI)-I-II (monoClinic, P2(1)/n; a = 12.946(3) Angstrom, b = 23.519(5) Angstrom, c = 13.945 Angstrom; beta = 93.2(3)degrees, Z = 4, the least-square refinement of 502 parameters using 3257 reflections, R = 0.0559) have been determined by X-raji diffraction. In the first case the nickel(II) is four-coordinate with bonds to three pyrrole nitrogen atoms (Ni-N distances 1.948(5); 1.955(5); 1.938(5) Angstrom) and the pyrrole carbon (Ni-C 2.005(6) Angstrom). The nickel lies in the plane of the three nitrogens, while the methylated pyrrole is sharply tilted out of the plane with dihedral angle between the plane of three nitrogens and the methylated pyrrole plane being -42.2 degrees. The methylated pyrrole is bound to nickel via a pyramidal carbon in the eta(1)-fashion. The first structurally characterized paramagnetic organonickel(II) complex (2-NCH3-21-CH3CTPP)(NiI)-I-II presents unique features related to its electronic structure. The nickel(II) is five-coordinate with bonds to three pyrrole nitrogen atoms (Ni-N distances 2.032(8); 2.057(8); 1.979(8) Angstrom) and to the pyrrole C(21) carbon (Ni-C 2.406(9) Angstrom). The nickel is moved out from the plane of the three nitrogen plane toward the iodide ligand. The 21-CH3 group and iodide are located on the opposite sides of the macrocyCle. The substituted pyrrole is sharply tilted out of the plane with the dihedral angle between the three nitrogen plane and the methylated pyrrole plane being -55.3 degrees. The methylated pyrrole is bound to nickel in the eta(1)-fashion but the coordinating C(21) atom preserves features related to trigonal sp(2) hybridization. The angle between the inverted pyrrole plane and the Ni-C bond increases from 42.8 degrees to 70.1 degrees on moving from the diamagnetic to paramagnetic species. The H-1 NMR and H-2 NMR spectra of paramagnetic (2-NH-21-CH3CTPP)Ni(II)X and (2-NCH3-21-CH3CTPP)Ni(II)X complexes have been examined. Functional group assignments have been made with use of selective deuteration and 2D COSY experiments. The characteristic patterns of six downfield shifted pyrrole resonances accompanied by upfield shifted 3-H and 2-NH resonances are diagnostic of C-methylation. The 21-CH3 resonance appears in a characteristic 90-110 ppm region.Reactions of nickel(II) 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin with methyl iodide. The first structural characterization of a paramagnetic organometallic nickel(II) complexx155199675#N/AFALSE
1941
ja960746q10.1021/ja960746qFALSEhttps://doi.org/10.1021/ja960746qGroy, TLJ. Am. Chem. Soc.The reaction of M(II) acetate hydrate (M = Co, Ni, and Zn) with 1,3,5-benzenetriCarbonylic (BTC) acid yields a material formulated as M(3)(BTC)(2) . 12H(2)O. These compounds are isostructural as revealed by their XRPD patterns and a single crystal structure analysis performed on the cobalt containing solid [monoClinic, space group C2, a = 17.482 (6) Angstrom, b = 12.963 (5) Angstrom, c = 6.559 (2) Angstrom, beta = 112.04 degrees, V = 1377.8 (8) Angstrom, Z = 4]. This solid is composed of zigzag chains of tetra-aqua cobalt(II) benzenetriCarbonylate that are hydrogen-bonded to yield a tightly held 3-D network. Upon liberating 11 water ligands per formula unit a porous solid results, M(3)(BTC)(2) . H2O, which was found to reversibly and repeatedly bind water without destruction of the framework. The proposed 1-D channels of the monohydrate have a pore diameter of 4 x 5 Angstrom, which is typical of those observed in zeolites and molecular sieves. The successful inClusion of ammonia into the porous solid was demonstrated. Larger molecules and others without a reactive lone pair are disallowed from entering the channels.Construction of porous solids from hydrogen-bonded metal complexes of 1,3,5-benzenetriCarbonylic acid769199655#N/ATRUE
1942
ja952520d10.1021/ja952520dhttps://doi.org/10.1021/ja952520dGhosh, SJ. Am. Chem. Soc.Ni(II), Cu(II), and Zn(II) cryptate-enhanced fluorescence of a trianthrylcryptand: A potential molecular photonic OR operatorPhotocatalyst267199634#N/AFALSE
1943
ja952518m10.1021/ja952518mFALSEhttps://doi.org/10.1021/ja952518mBurrows, CJJ. Am. Chem. Soc.Reaction of a single-stranded oligodeoxynuCleotide or a 17-base hairpin-forming oligodeoxynuCleotide with CoCl2 and KHSO5 produced guanine-specific Cleavage after piperidine treatment. The observed reactivity is shown to be nearly twice that obtained for NiCR (CR=2,12-dimethyl-3,7,11,17-tetraazabicyClo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene) under equivalent conditions, although NiCR displays a slightly higher degree of selectivity for unpaired guanine residues. Cobalt-induced DNA modification was catalytic with respect to the,metal complex and was observed at temperatures up to 80 degrees C, conditions under which NiCR was ineffective. Mechanistic studies of the cobalt-mediated reaction suggest that SO4.- is responsible for guanine oxidation. Reaction with tRNA(Phe) induced aniline . HOAc-labile (pH 4.5) lesions also at accessible guanine sites. The high reactivities of G20 acid G34 are consistent with attack of SO4.- on the rr face of the guanine heterocyCle as opposed to recognition of G N7 as proposed for NiCR. CoCl2 should become an extremely attractive probe of nuCleic acid structure since it induces base-specific and conformation-specific Cleavage of DNA under a much wider variety of experimental conditions than NiCR, acts with a different mode of guanine selectivity than do nickel complexes, and is commercially available.DNA and RNA modification promoted by [Co(H2O)(6)]Cl-2 and KHSO5: Guanine selectivity, temperature dependence, and mechanismx113199651#N/AFALSE
1944
ja960184a10.1021/ja960184aFALSEhttps://doi.org/10.1021/ja960184aRueping, MJ. Am. Chem. Soc.The structures of the transition states and intermediates formed in the water-exchange of hexaaqua complexes of the first row transition elements have been computed with ab initio methods at the Hartree-Fock or CAS-SCF level. As an approximation, water molecules in the second coordination sphere except one, bulk water, and anions have been neglected. For each of the three types of Activation, namely associative, concerted, and dissociative mechanism, a representative transition metal complex has been studied, viz. Ti(OH2)(6)(3+), V(OH2)(6)(2+), and Ni(OH2)(6)(2+). Each type of mechanism proceeds via a characteristic transition state. For the A and D mechanisms, respectively, hepta- or pentacoordinated intermediates are formed, and their lifetimes were estimated based on the energy difference between that of the transition state and the corresponding intermediate. The computed Activation energies are in agreement with the experimental values and are independent of the mechanism or the charge on the metal center. The bond length changes occurring during the Activation agree with the corresponding experimental Delta V-double dagger values. In a recent artiCle, Akesson et al. (J. Am. Chem. Sac. 1994, 116, 8705) proposed an interpretation of the experimental Delta V-double dagger values that differs from that commonly applied (Merbach, A. E. Pure Appl. Chem. 1987, 59, 161). In particular, they Claimed a dissociative Activation for the water-exchange of the hexaaqua ions of V-II and Mn-II in spite of their negative volumes of Activation. The present computational results on V-II are in perfect agreement with the I-a mechanism attributed on the basis of its Delta V-double dagger: value. It should be noted that in principle, the D mechanism is possible for al the hexaaqua ions of the first transition series, but in many cases, the associative or concerted pathway is preferred, For a given complex, all the possible mechanisms must be analyzed, before the most favorable pathway can be determined. The presently studied case of V-II, where equal energies of Activation have been computed for the I-a and D mechanism, illustrates this point. The attribution of the mechanism was only possible by comparison with the experimental volume of Activation. Computed energies of Activation alone may not suffice to identify the mechanism; a safe attribution can only be made if the structural changes agree with the volume of Activation.Structure of the transition states and intermediates formed in the water-exchange of metal hexaaqua ions of the first transition series124199630#N/ATRUE
1945
ja954113810.1021/ja9541138FALSEhttps://doi.org/10.1021/ja9541138Smith, KMJ. Am. Chem. Soc.The stepwise syntheses and characterization of a series of symmetrical and unsymmetrical bisporphyrins, bischlorins, and biscorroles, and of porphyrin-chlorin and porphyrin-corrole dyads possessing ethylene, phenyl, and stilbene linking units are described. The methodology for synthesis of 10-substituted corroles 2 and their cobalt complexes 9 via a,c-biladiene salts 1 was first developed, and then extended to provide biscorroles (e.g., 4 and 5) linked through the 10-positions with phenyl linker units. Using a similar methodology, phenyl-linked corrole-porphyrin dyads 28 and 30 were also prepared. By way of intermediate phenyl-linked unsymmetrical bisdipyrromethanes, a completely unsymmetrical heterobimetallic bisporphyrin system, 45, was synthesized. Low-valent titanium coupling (McMurry) reactions were used to prepared stilbene-linked bisdipyrromethanes (e.g., 46) which were subsequently transformed into stilbene-linked bisporphyrins (e.g., 48). McMurry cross-coupling reactions of porphyrins bearing p-Carbonylphenyl substituents also afforded an unsymmetrically substituted bisporphyrinylstilbene, 60, as well as the corresponding homodimers 56 and 59. Likewise, McMurry cross-coupling of a p-Carbonylphenyl-substituted porphyrin, 62, with a Carbonylchlorin, 63, afforded a stilbene-linked bisporphyrin, 64, a bischlorin, 66, and a novel porphyrin-chlorin heterodimer, 65. All novel products were characterized by H-1 NMR, IV-vis, and mass spectroscopy and elemental analysis. X-ray structural information was also obtained for the zinc/nickel bisporphyrin 45 and for the bis-nickel porphyrin-chlorin 65.Stepwise syntheses of bisporphyrins, bischlorins, and biscorroles, and of porphyrin-chlorin and porphyrin-corrole heterodimers98199675#N/ATRUE
1946
ja943960s10.1021/ja943960sFALSEhttps://doi.org/10.1021/jacs.0c02172Reedijk, JNovel hybrid spin systems of 7,7',8,8'-tetracyanoquinodimethane (TCNQ) radical anions and 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt). Crystal structure of [Fe(abpt)(2)(TCNQ)(2)] at 298 and 100 K, Mossbauer spectroscopy, magnetic properties, and infrared spectroscopy of the series [M(II)(abpt)(2)(TCNQ)(2)] (M=Mn, Fe, Co, Ni, Cu, Zn)x1996#N/AFALSE
1947
ja910963x10.1021/ja910963xFALSEhttps://doi.org/10.1021/ja910963xLong, JRJ. Am. Chem. Soc.An S = 3/2, high-anisotropy building unit, trans-[ReCl4(CN)(2)](2-), representing the first paramagnetic complex with a mixture of just cyanide and halide ligands, has been synthesized through the reaction of (Bu4N)CN with ReCl4(THF)(2). This species is characterized in detail and employed in directing the formation of a series of one-dimensional coordination solids of formula (DMF)(4)MReCl4(CN)(2) (M = Mn (2), Fe (3), Cc (4), Ni (5)). Variable-temperature dc magnetic susceptibility measurements demonstrate the presence of intrachain antiferromagnetic (2) and ferromagnetic (3-5) exchange coupling within these solids. In addition, probing the ac magnetic susceptibility as a function of both temperature and frequency reveals that all of the chain compounds exhibit slow relaxation of the magnetization. The relaxation time is shown to be thermally activated, with energy barriers to relaxation of A, = 31, 56, 17, and 20 cm(-1) for 2-5, respectively. Notably, the field-dependent magnetization of the iron congener exhibits a significant hysteresis effect at low temperature, with a coercive field of H-C = 1.0 T, thus demonstrating magnetlike behavior in this one-dimensional system. Finally, the magnetization dynamics of all solids occur within the finite-size regime, where the magnetic domain growth is limited due to physical defects along the chains within the crystals.[ReCl4(CN)(2)](2-): A High Magnetic Anisotropy Building Unit Giving Rise to the Single-Chain Magnets (DMF)(4)MReCl4(CN)(2) (M = Mn, Fe, Co, Ni)x180201063#N/AFALSE
1948
ja953988j10.1021/ja953988jFALSEhttps://doi.org/10.1021/ja953988jTucker, AJ. Am. Chem. Soc.Axial hydrophobic fence in highly-stable Ni(II) complex of des-angiotensinogen N-terminal peptide70199623#N/ATRUE
1949
ja953686h10.1021/ja953686hFALSEhttps://doi.org/10.1021/ja953686hDarensbourg, MYJ. Am. Chem. Soc.The molecular structure of a nickel(0) complex with P,S-donor atom ligands has been characterized by X-ray crystallography. Complex 1, (Ph(2)P(o-C6H4)SCH3)(2)Ni-0, prepared by Na/Hg amalgam reduction of the Ni-II complex [(Ph(2)P(o-C6H4)SCH3)(2)Ni](BF4)(2) ([2](BF4)(2)), degrades photochemically with loss of CH3 radicals to yield complex 3, (Ph(2)P(o-C6H4)S)(2)Ni-II. Crystallographic parameters for the three compounds are as follows: 1, monoClinic space group C2/c with a = 11.467(2) Angstrom, b = 17.613(3) Angstrom, c = 15.733(2) Angstrom, beta = 96.450(10)degrees, V = 3157.5(9) Angstrom(3), and Z = 4; [2](BF4)(2), monoClinic space group P2(1)/c with a = 9.417(4) Angstrom, b = 14.822(9) Angstrom, c = 13.773(2) Angstrom, beta = 98.55(3)degrees, V = 9101(14) Angstrom(3), and Z = 2; and 3, monoClinic space group P2(1)/c with a 9.651(2) Angstrom, b = 12.971(8) Angstrom, c = 12.540(2) Angstrom, beta = 110.46(2)degrees, V = 1470.7(11) Angstrom(3), and Z = 2. While complex 1 has a distorted tetrahedral geometry, complexes [2](BF4)(2) and 3 are square planar with trans stereochemistry. The cyClic voltammogram of [2](BF4)(2) in CH3CN shows two redox events assigned to Ni-II/I and Ni-I/0, whereas the thiolate 3 reveals only one reversible wave assigned to Ni-II/III. The chemical reduction of [2](BF4)(2) with Cp(2)Co provided a Ni-I species, [(Ph(2)P(o-C6H4)SCH3)(2)Ni-I](+), characterized at 100 K by an axial EPR signal with g(x) = g(y) = 2.10 and g(z) = 1.96. Hyperfine spectral features resulting from coupling to two P-31 nuClei suggests a retention of substantially square planar geometry. In contrast the isotropic character of the EPR signal of [(Ph(2)P(o-C6H4)SCH3)(Ph(2)P(o-C6H4)S)Ni-I], presumed to be the first product of the photochemical demethylation of 1 ultimately yielding the doubly demethylated complex 3, suggested the intervening thioether/thiolate Ni-I species to be pseudotetrahedral. Protonation of the nickel(0) species 1 produced a five-coordinate nickel hydride complex, [(H)(arom-PSMe)(2)Ni]BF4, 4.Characteristics of nickel(0), nickel(I), and nickel(II) in phosphino thioether complexes: Molecular structure and S-deAlkylation of (Ph(2)P(o-C6H4)SCH3)(2)Ni-067199665#N/ATRUE
1950
ja910504t10.1021/ja910504tFALSEhttps://doi.org/10.1021/ja910504tMing, LJJ. Am. Chem. Soc.The peptidyl antibiotic bacitracin (Bc) is one of the most widely used antibiotics which can bind divalent transition metal ions, inCluding Mn(II), Co(II), Ni(II), Cu(II), and Zn(II). The metal binding is essential for its antimicrobial activity. Previous analysis of the hyperfine-shifted H-1 NMR signals of Co(II)-Bc A(1) revealed the structure of the metal binding environment and a potential hydrophobic site important for the bioactivity of this antibiotic. Co(II)-Bc in DMSO shows relatively sharper hyperfine-shifted H-1 NMR signals compared with the spectrum acquired in an aqueous solution, allowing more thorough analysis of the signals with 1D and 2D NMR methods. Pyrophosphate and derivatives bind to Co(II)-Bc to form kinetically inert ternary complexes. The coordinated D-Glu-4 is found detached from the metal center of metallobacitracin upon trimetaphosphate binding, implying its role in the antibiotic activity of Bc. We further demonstrate in this report the structure-function relationship on desamido-Bc of low antibiotic activity by the use of NMR, wherein D-Glu-4 is suggested to be important for the bioactivity of Bc. The interaction of the phosphomoiety with Bc is also reflected by DNA binding, wherein metal-free Bc does not bind DNA, whereas various metal complexes of Bc do. Cu(II)-Bc was further demonstrated to bind and oxidatively Cleave DNA under reduction conditions in the air. It also exhibited a significant oxidative activity toward catechol oxidation, showing enzyme-like saturation kinetics with k(cat) = 7.0 x 10(-3) s(-1) and k(cat)/K-m = 2.1 M-1 s(-1) aerobically and k(cat) = 0.38 s(-1) and k(cat)/K-m = 14.7 M-1 s(-1) in the presence of 32 mM of H2O2. The binding of pyrophosphate moiety to metallobacitracin, the detachment of D-Glu-4, and the significant oxidative activity of Cu(II) Bc provide further insights into the bioactivity of this metallopeptide and Cu-oxygen chemistry.H-1 NMR, Mechanism, and MononuClear Oxidative Activity of the Antibiotic Metallopeptide Bacitracin: The Role of D-Glu-4, Interaction with Pyrophosphate Moiety, DNA Binding and Cleavage, and Bioactivityx22201058#N/AFALSE
1951
ja953446210.1021/ja9534462FALSEhttps://doi.org/10.1021/ja9534462Saveant, JMJ. Am. Chem. Soc.Addition of weak Bronsted acids such as 1-propanol, 2-pyrrolidone, and CF3CH2OH triggers a considerable improvement of the catalysis of CO2 reduction by iron(0) tetraphenylporphyrins. Both the catalytic currents and the life time of the catalyst increase without significant formation of hydrogen. Unprecedented values of the turnover numbers per hour can thus be reached. Carbon monoxide is the main product, while formic acid is formed to a lesser extent. The yield of formic acid counterintuitively decreases as the acidity of the acid synergist increases, becoming negligible with CF3CH2OH. Analysis of the reaction kinetics suggests that the action of the acid synergist is to stabilize the initial (FeCO22-)-C-II carbenoid complex by hydrogen bonding. The formation of a doubly hydrogen-bonded complex opens the route to the Cleavage of one of the two C-O bonds resulting in the formation of CO within the iron coordination sphere. The formation of formic acid involves a reaction pathway where the iron-CO2 interactions are weaker. The effect of the acid synergist is an example of electrophilic assistance in a two-electron push-pull mechanism where pulling the electron pair out of the substrate by means of the synergist is as important as pushing electrons from the catalyst into the substrate. With CF3CH2OH, the production of CO is so fast that it commences to inhibit the catalytic reaction. This self-inhibition phenomenon can be satisfactorily modeled under the assumption that product adsorption on the electrode surface obeys a Langmuir equilibrium and that the covered portions of the surface are totally inactive toward reduction of the catalyst.Catalysis of the electrochemical reduction of carbon dioxide by iron(O) porphyrins: Synergystic effect of weak Bronsted acids248199659#N/ATRUE
1952
ja910122r10.1021/ja910122rFALSEhttps://doi.org/10.1021/ja910122rOshio, HJ. Am. Chem. Soc.The multicomponent system of [Fe(dpp)(2)][Ni(mnt)(2)](2)center dot MeNO2 (1; dpp = 2,6-bis(pyrazol-1-yl)pyridine and mnt = maleonitriledithiolate) was prepared by the reaction of [Fe(dpp)(2)](BF4)(2) with (Bu4N)[Ni(mnt)(2)] in MeNO2. Variable-temperature X-ray structural analyses, magnetic susceptibility, and heat capacity measurements confirmed that 1 undergoes multiple spin-state conversions in both the cationic and anionic components. The asymmetric unit in the crystal contains one [Fe(dpp)(2)](2+) cation, two [Ni(mnt)(2)](-) anions ([Ni1](-) and [Ni2](-)), and one solvent molecule. Magnetic susceptibility measurements revealed that a paramagnetic state in the high-temperature region (HT phase) was abruptly converted to a diamagnetic low-temperature (LT) phase below 180 K as the temperature was lowered from 270 K. As the temperature was raised from 125 to 270 K, successive phase transitions occurred to the HT phase via intermediate phases (IM1, IM2, and IM3) at 175.5, 186.5, 194.0, and 244.0K, respectively. In the HT phase [Fe(dpp)(2)](2+) is in the high-spin state, and each [Ni1](-) and [Ni2](-) moiety is arranged in monomeric form with an S = 1/2 spin ground state. In the LT phase [Fe(dpp)(2)](2+) is in the low-spin state and the nickel moieties are dimerized and diamagnetic. In the IM1 and IM2 phases the iron(II) sites are partially in the HS state and both [Ni](-) moieties are dimeric, as suggested by Fe-57 Mossbauer measurements. In the IM3 phase, [Fe(dpp)(2)](2+) is in the HS state and the anions exist in both their monomeric ([Ni1](-)) and dimeric ([Ni2](-)) forms. Rapid thermal quenching from 300 to 5 K yielded a metastable HS phase, which relaxed to the LT phase via the IM1 phase as the temperature was raised to 150 K. A partial light induced spin transition on the iron site was observed at 5 K.Multiple Bistability and Tristability with Dual Spin-State Conversions in [Fe(dpp)(2)][Ni(mnt)(2)](2)center dot MeNO2x107201079#N/AFALSE
1953
ja953308c10.1021/ja953308cFALSEhttps://doi.org/10.1021/ja953308cSugimori, AJ. Am. Chem. Soc.Electrophilic and radical substitution of 1,2,5-cobaltadithiolenes49199619#N/ATRUE
1954
ja953010m10.1021/ja953010mFALSEhttps://doi.org/10.1021/ja953010mKubiak, PJ. Am. Chem. Soc.The dihalide capped trinuClear nickel Clusters Ni-3(mu(3)-X)(2)(mu(2)-dppm)(3) (X = I (1a), Br (1b); dppm = Ph(2)PCH(2)PPh(2)) were synthesized and converted to their respective monocations [Ni-3(mu(3)-X)(2)(mu(2)-dppm)(3)](+) (X = I (1a(+)), Br (1b(+))) via a single electron oxidation. Clusters 1a and 1a(+) were characterized by X-ray crystallography. Displacement of a triply-bridging iodide ligand in Ni-3(mu(3)-I)(2)(mu(2)-dppm)(3) (1a) by pi-acceptor ligands produces a Class of 48-electron trinuClear nickel Clusters of the general formula [Ni-3(mu(3)-L)(mu(3)-I)(mu(2)-dppm)(3)](+) (L = CO (2a); CNR, R = CH3 (3a), 2,6-(CH3)(2)C6H3 (4a), i-C3H7 (5), C6H11 (6), t-C4H9 (7), CH2C6H5 (8), C6H5 (9), p-C6H4I (10), p-C6H4Br (11), p-C6H4Cl (12), p-C6H4F (13), p-C6H4CH3 (14), p-C6H4CF3 (15), p-C6H4OCH3 (16), and p-C6H4CN (17)). A similar but less extensive study was conducted with the dibromide capped Cluster 1b. The X-ray crystal structure of Cluster 2a, as the PF6- salt, was also obtained. Clusters 2-17 possess strikingly similar spectroscopic and electrochemical properties. This is ascribed to the lack of interaction between the a(2) LUMO of Clusters 2-17 and the molecular orbitals of the capping pi-acceptor ligands. The unexpected appearance of two nu(C=N) bands in the FT-IR spectra of Clusters 3-17 was demonstrated to be the result of a Fermi resonance involving the nu(C=N) fundamental and the first overtone of the nu(N-C(Alkyl)) fundamental of the capping isocyanide. In addition, molecular orbital calculations on 1-17 provide insights into the differences in the physical properties and reactivities of Clusters of this Class capped by pi-donor (1) or pi-acceptor ligands (2-17).A Class of halide-supported trinuClear nickel Clusters [Ni-3(mu(3)-L)(mu(3)-X)(mu(2)-dppm)(3)](n+) (L=I-, Br-, CO, CNR; X=I-, Br-; n=0, 1; dppm=Ph(2)PCH(2)PPh(2)): Novel physical properties and the Fermi resonance of symmetric mu(3)-eta(1) bound isocyanide ligands34199666#N/ATRUE
1955
ja909243z10.1021/ja909243zFALSEhttps://doi.org/10.1021/ja909243zSun, SSJ. Am. Chem. Soc.Monodisperse nickel nanopartiCles are prepared from the reduction of Ni(acac)(2) with borane tributylamine in the presence of oleylamine and oleic acid. Without any special treatment to remove the surfactants, the as-synthesized Ni nanopartiCles supported on the Ketjen carbon support exhibit high catalytic activity in hydrogen generation from the hydrolysis of the ammonia-borane (H3NBH3) complex with a total turnover frequency value of 8.8 mol of H-2 center dot(mol of Ni)(-1).min(-1). Such catalysis based on Ni nanopartiCles represents a promising step toward the practical development of the H3NBH3 complex as a feasible hydrogen storage medium for fuel cell applications.Monodisperse Nickel NanopartiCles; and Their Catalysis in Hydrolytic Dehydrogenation of Ammonia Boranex414201035#N/AFALSE
1956
ja952915x10.1021/ja952915xFALSEhttps://doi.org/10.1021/ja952915xLeary, JAJ. Am. Chem. Soc.Differentiation of diastereomeric nickel(II) N-glycoside complexes using tandem mass spectrometry and kinetic energy release measurements58199615#N/ATRUE
1957
ja952882l10.1021/ja952882lFALSEhttps://doi.org/10.1021/ja952882lBergman, RGJ. Am. Chem. Soc.The first cyClopentadienylnickel amido complexes have been isolated and characterized as [(eta-C(5)Me(4)R')Ni(mu-NHR)](2) (R = Ph, p-tol, 2,6-xyl, (t)Bu; R' = Me, Et). These complexes are dimers in solution and in the solid state, as shown by the synthesis of mixed amido complexes, by NMR spectroscopy, and by crystallographic studies on cis-[Cp(Et)Ni(mu-NH(p-tol))](2) (cis-1'), trans-[Cp(Et)Ni(mu-NH(2,6-xylyl))](2) (trans-3'), and cis-[Cp(Et)Ni(mu-NH(t)Bu)](2) (4') (Cp(Et) = eta-C(5)Me(4)Et). Resonances in the H-1 NMR spectra of these diamagnetic dimers display unusual chemical shifts that are explained on the basis of ring-current anisotropy and inductive effects. The dimers undergo reversible cis/trans isomerization at elevated temperatures; mechanistic studies indicate that this process proceeds through Cleavage of one dative nitrogen-nickel bond, rate-limiting rotation of the amido group, and recoordination to regenerate the bridge. Dimethylzirconocene was essential as a scavenger for trace water in these studies. The dimer [Cp*Ni(mu-NH(p-tol))](2) (1) reacts with CO and with (t)BuNC to give the insertion products Cp*Ni(CO)(C(O)NH(p-tol)) (6) and Cp*Ni(CN(t)Bu)(C(N(t)Bu)NH(p-tol)) (7), respectively, and with PMe(3) to give the unstable monomeric amido complex Cp*Ni(PMe(3))(NH(p-tol)) (5).Synthesis, characterization, isomerization, and reactivity of dimeric cyClopentadienylnickel amido complexes50199686#N/ATRUE
1958
ja908674x10.1021/ja908674xFALSEhttps://doi.org/10.1021/ja908674xCaulton, KGJ. Am. Chem. Soc.Collision of H-2 with the unusual nickel complex, (PNP)Ni+, where PNP = ((Bu2PCH2SiMe2)-Bu-t)(2)N, forms a rare dihydrogen complex of the d(8) configuration which then rearranges to heterolytically Cleave the H-H bond Experimental studies support a short H/H distance in the coordinated diatomic, and DFF calculations show that the transition state for heterolysis, in spite of the fact that tills Involves an amide nitrogen located trans to the H-2, has the H/H bond fully split, and has all the geometric features of Ni(IV), but this is a local maximum, not a minimum.Mechanism of Heterolysis of H-2 by an Unsaturated d(8) Nickel Center: via Tetravalent Nickel?x59201026#N/AFALSE
1959
ja952838610.1021/ja9528386FALSEhttps://doi.org/10.1021/ja9528386Munch, ENature of the C-Cluster in Ni-containing carbon monoxide dehydrogenases1996#N/ATRUE
1960
ja908176510.1021/ja9081765FALSEhttps://doi.org/10.1021/ja9081765Zamble, DBJ. Am. Chem. Soc.Metallochaperones are essential for the safe and targeted delivery of necessary yet toxic metal cofactors to their respective protein partners. In this study we examine the nickel-binding properties of the Escherichia coli protein SlyD, a factor that contributes to optimal nickel accumulation in this organism. This protein is also required for E. coli energy metabolism because it participates in the nickel insertion step during [Ni-Fe]-hydrogenase metallocenter assembly. Our study demonstrates that SlyD is a multiple nickel ion binding protein. The analysis of noncovalent metal-protein complexes via electrospray ionization mass spectrometry revealed that SlyD binds up to seven nickel ions in a noncooperative manner with submicromolar affinity (<2 mu M, upper limit) and that the protein exists in a dynamic mixture of metalloforms that is dependent on the availability of nickel ions in solution. Structural analysis indicates that this metallochaperone undergoes small but distinct changes in the structure upon metal binding and that the nickel-binding sites are assembled through beta-turn formation. Although the C-terminal metal-binding domain is primarily responsible for metal chelation, we find that metal binding also perturbs the structure of the N-terminal domains. An investigation of the nickel sites by using X-ray absorption spectroscopy shows that SlyD binds nickel ions by adapting several different geometries and coordination numbers. Finally, the characterization of SlyD mutants demonstrates that the cysteine residues in the C-terminal domain confer tighter affinity as well as increased binding capacity to SlyD. On the basis of the presented data a model for nickel binding to SlylD as well as its role in nickel homeostasis is discussed.The Ni(II)-Binding Properties of the Metallochaperone SlyDx31200982#N/AFALSE
1961
ja907882n10.1021/ja907882nFALSEhttps://doi.org/10.1021/ja907882nPercec, VJ. Am. Chem. Soc.The synthesis of 4'-hydroxy-4-biphenylpropionic, 3',4'-dihydroxy-4-biphenylpropionic, 3',5'-dihydroxy-4-biphenylpropionic, and 3',4',5'-trihydroxy-4-biphenylpropionic methyl esters via three efficient and modular strategies inCluding one based on Ni-catalyzed borylation and sequential cross-coupling is reported. These building blocks were employed in a convergent iterative approach to the synthesis of one library of 3,4,5-trisubstituted and two libraries of constitutional isomeric 3,4- and 3,5-disubstituted biphenylpropyl ether dendrons. Structural and retrostructural analysis of supramolecular dendrimers revealed that biphenylpropyl ether dendrons self-assemble and self-organize into the same periodic lattices and quasi-periodic arrays observed in previously reported libraries, but with larger dimensions, different mechanisms of self-assembly, and improved solubility, thermal, acidic, and oxidative stability. The different mechanisms of self-assembly led to the discovery of two new supramolecular structures. The first represents a new banana-like lamellar crystal with a four layer repeat. The second is a giant vesicular sphere self-assembled from 770 dendrons that exhibits an ultrahigh molar mass of 1.73 x 10(6) g/mol. Thus, the enhanced size of the self-assembled structures constructed from biphenylpropyl ether dendrons permitted for the first time discrimination of various molecular mechanisms of spherical self-assembly and elaborated a continuum between small filled spheres and very large hollow spheres that is dictated by the primary structure of the dendron. The comparative analysis of libraries of biphenylpropyl ether dendrons with the previously reported libraries of Benzyl-, phenylpropyl-, and biphenyl-4-methyl ether dendrons demonstrated biomimetic self-assembly wherein the primary structure of the dendron and to a lesser extent the structure of its repeat unit determines the supramolecular tertiary structure. A nanoperiodic table of self-assembling dendrons and supramolecular dendrimers that allows the prediction of the general features of tertiary structures from primary structures was elaborated.Predicting the Structure of Supramolecular Dendrimers via the Analysis of Libraries of AB(3) and Constitutional Isomeric AB(2) Biphenylpropyl Ether Self-Assembling Dendronsx121200989#N/AFALSE
1962
ja907625k10.1021/ja907625kFALSEhttps://doi.org/10.1021/ja907625kWasielewski, MRJ. Am. Chem. Soc.A series of donor-bridge-acceptor (D-B-A) triads have been synthesized in which the donor, 3,5-dimethyl-4-(9-anthracenyl)julolidine (DMJ-An), and the acceptor, naphthalene-1,8:4,5-bis(dicarboximide) (NI), are linked by p-oligophenylene (Ph-n) bridging units (n = 1-5). Photoexcitation of DMJ-An produces DMJ(+center dot)-An(-center dot) quantitatively, so that An(-center dot) acts as a high potential electron donor, which rapidly transfers an electron to NI yielding a long-lived spin-coherent radical ion pair (DMJ(+center dot)-An-Ph-n-NI-center dot). The charge transfer properties of 1-5 have been studied using transient absorption spectroscopy, magnetic field effects (MFEs) on radical pair and triplet yields, and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The charge separation (CS) and recombination (CR) reactions exhibit exponential distance dependencies with damping coefficients of beta = 0.35 angstrom(-1) and 0.34 angstrom(-1), respectively. Based on these data, a change in mechanism from superexchange to hopping was not observed for either process in this system. However, the CR reaction is spin-selective and produces the singlet ground state and both (3)*An and (3)*NI. A kinetic analysis of the MFE data shows that superexchange dominates both pathways with beta = 0.48 angstrom(-1) for the singlet CR pathway and beta = 0.35 angstrom(-1) for the triplet CR pathway. MFEs and TREPR experiments were used to measure the spin-spin exchange interaction, 2J, which is directly related to the electronic coupling matrix element for CR, V-CR(2). The magnitude of 2J also shows an exponential distance dependence with a damping coefficient alpha = 0.36 angstrom(-1), which agrees with the P values obtained from the distance dependence for triplet CR. These results were analyzed in terms of the bridge molecular orbitals that participate in the charge transport mechanism.Spin-Selective Charge Transport Pathways through p-Oligophenylene-Linked Donor-Bridge-Acceptor Moleculesx662009106#N/AFALSE
1963
ja907567r10.1021/ja907567rFALSEhttps://doi.org/10.1021/ja907567rBal, WJ. Am. Chem. Soc.Previously we demonstrated for several examples that peptides having a general internal sequence R-N-Yaa-Ser/Thr-Xaa-His-Zaa-R-C (Yaa = Glu or Ala, Xaa = Ala or His, Zaa = Lys, R-N and R-C = any N- and C-terminal amino acid sequence) were hydrolyzed specifically at the Yaa-Ser/Thr peptide bond in the presence of Ni(II) ions at alkaline pH (Krezel, A.; Mylonas, M.; Kopera, E.; Bal, E. Acta Biochim. Polon. 2006, 53, 721-727 and references therein). Hereby we report the synthesis of a combinatorial library of CH3CO-Gly-Ala-(Ser/Thr)-Xaa-His-Zaa-Lys-Phe-Leu-NH2 peptides, where Xaa residues inCluded 17 common alpha-amino acids (except Asp, Glu, and Cys) and Zaa residues inCluded 19 common alpha-amino acids (except Cys). The Ni(II)-dependent hydrolysis at 37 and 45 degrees C of batches of combinatorial peptide mixtures randomized at Zaa was monitored by MALDI-TOF mass spectrometry. The correctness of library-based predictions was confirmed by accurate measurements of hydrolysis rates of seven selected peptides using HPLC. The hydrolysis was strictly limited to the Ala-Ser/Thr bond in all library and individual peptide experiments. The effects of individual residues on hydrolysis rates were quantified and correlated with physical properties of their side chains according to a model of independent contributions of Xaa and Zaa residues. The principal component analysis calculations demonstrated partial molar side chain volume and the free energy of amino acid vaporization for both Xaa and Zaa residues and the amine pK(a) for Zaa residues to be the most significant empirical parameters influencing the hydrolysis rate. Therefore, efficient hydrolysis required bulky and hydrophobic residues at both variable positions Xaa and Zaa, which contributed independently to the hydrolysis rate. This relationship between the peptide sequence and the hydrolysis rate provides a basis for further research, aimed at the elucidation of the reaction mechanism and biotechnological applications of Ni(II)-dependent peptide bond hydrolysis.Sequence-Specific Ni(II)-Dependent Peptide Bond Hydrolysis for Protein Engineering. Combinatorial Library Determination of Optimal Sequencesx48201053#N/AFALSE
1964
ja952598u10.1021/ja952598uFALSEhttps://doi.org/10.1021/ja952598uMoll, MJ. Am. Chem. Soc.In quest of nickel complexes with sulfur ligation that model the acetyl-CoA synthase function of CO dehydrogenase (CODH), [Ni('S(4)C(3)Me(2)')] (1, 'S(4)C(3)Me(2)'(2-) = 1,3-bis(2-mercaptophenylthio)-2,2-dimethyl-propane-(2-)) was synthesized by template Alkylation of Na-2[Ni('S-2')(2)] ('S-2'(2-) = benzene-1,2-dithiolate(2-)) with CMe(2)(CH2Br)(2). Acidic hydrolysis of 1 yielded the thiol ''S(4)C(3)Me(2)''-H-2 (2). Reduction of 1 with Na/Hg resulted in Cleavage of the 'S(4)C(3)Me(2)'(2-)ligand and formation of the thermally stable trinuClear nickel(II) Alkyl thiolato complex [Ni('mu-S(2)C(3)Me(2)')](3) (3, 'S(2)C(3)Me(2)'(2-) = 1-(2-mercaptophenylthio)-2,2-dimethylpropyl(2-)). Treatment of 3 with L = Py, THF, or PMe(3) afforded the mononuClear compounds [Ni('S(2)C(3)Me(2)')(L)] (4, L = Py; 5, L = PMe(3)). The stoichiometric reaction of [Ni('S(2)C(3)Me(2)')(L)] with CO led to the cyClic thioester 'S(2)C(3)Me(2)CO' (6, 'S(2)C(3)Me(2)CO' = 2,3-benzo-6,6-dimethyl-8-oxo-1,4-dithia-cyClooctane) and Ni(CO)(4). In the analogous reaction of 5 with CO the intermediate nickel(II) acyl thiolato complex [Ni('S(2)C(3)Me(2)CO')(PMe(3))] (7 'S(2)C(3)Me(2)CO'(2-) = 1-(2-mercaptophenylthio)-2,2-dimethyl-3-oxobutyl(2-)) could be intercepted and fully characterized. The reaction of Ni(CO)(4) with the thiol 2 yielded the starting Ni(II) complex 1 and allowed to Close the reaction cyCle that comprises the CODH sequence: [Ni] --> [Ni-Alkyl] --> [Ni-acyl] --> [Ni] + thioester. The net reaction can be formulated as 'S(4)C(3)Me(2)'-H-2 (2) + CO --> 'S(2)C(3)Me(2)CO' (6) + 'S-2'-H-2 and represents the first example of nickel mediated thioester formation in a complete reaction cyCle. X-ray structure determinations of complexes 1, 3, 4, and 7 revealed approximately square planar coordination geometry for al Ni centers.Transition metal complexes with sulfur ligands .117. A reaction cyCle for nickel mediated thioester formation from Alkyl, CO, and thiolate groups modeling the acetyl-coenzyme A synthase function of CO dehydrogenase56199652#N/ATRUE
1965
ja907329j10.1021/ja907329jFALSEhttps://doi.org/10.1021/ja907329jWeckhuysen, BMJ. Am. Chem. Soc.Tomographic energy dispersive diffraction imaging (TEDDI) is a recently developed synchrotron-based characterization technique used to obtain spatially resolved X-ray diffraction and fluorescence information in a noninvasive manner. With the use of a synchrotron beam, three-dimensional (3D) information can be conveniently obtained on the elemental composition and related crystalline phases of the interior of a material. In this work, we show for the first time its application to characterize the structure of a heterogeneous catalyst body in situ during thermal treatment. Ni/gamma-Al2O3 hydrogenation catalyst bodies have been chosen as the system of study. As a first example, the heat treatment in N-2 of a [Ni(en)(3)](NO3)(2)/gamma-Al2O3 catalyst body has been studied. In this case, the crystalline [Ni(en)(3)](NO3)(2) precursor was detected in an egg-shell distribution, and its decomposition to form metallic Ni crystallites of around 5 nm was imaged. In the second example, the heat treatment in N-2 of a [Ni(en)(H2O)(4)]Cl-2/gamma-Al2O3 catalyst body was followed. The initial [Ni(en)(H2O)(4)]Cl-2 precursor was uniformly distributed within the catalyst body as an amorphous material and was decomposed to form metallic Ni crystallites of around 30 nm with a uniform distribution. TEDDI also revealed that the decomposition of [Ni(en)(H2O)(4)]Cl-2 takes place via two intermediate crystalline structures. The first one, which appears at around 180 degrees C, is related to the restructuring of the Ni precursor on the alumina surface; the second one, assigned to the formation of a limited amount of Ni3C, is observed at 290 degrees C.Tomographic Energy Dispersive Diffraction Imaging To Study the Genesis of Ni NanopartiCles in 3D within gamma-Al2O3 Catalyst Bodiesx48200939#N/AFALSE
1966
ja952515+10.1021/ja952515+FALSEhttps://doi.org/10.1021/ja952515+Pope, MTJ. Am. Chem. Soc.H-1 NMR spectra of pyridine and alpha-, beta-, and gamma-picoline coordinated to the paramagnetic heteropolyanion [HmSiW9O37Cu3]((10-m)-) (SiW9Cu3) are reported. NMR lines are assigned to [HmSiW9O37Cu3(ptl)(n)]((10-m)-) (n = 1, 2 or 3; m = 0, 1 or 2; ptl = pyridine-type ligands) on the basis of their pH and [SiW9Cu3]/[ptl] dependence. The isotropic NMR shifts come mainly from the contact shifts, which for some protons exceed 70% of those in analogous nickel complexes. The nuClear longitudinal relaxation times are 0.006, 0.06, and 0.1 s for alpha-, beta-, and gamma-H in pyridine coordinated to SiW9Cu3. The electronic correlation time calculated from the T-1 values is in the order of 10(-11) or 10(-12) s, which is two or three orders of magnitude smaller than those of ordinary copper complexes. It is suggested that spin frustration causes rapid electronic relaxation in these complexes in which the three Cu2+ ions form an equilateral triangle.Trimetallo derivatives of lacunary 9-tungstosilicate heteropolyanions .2. Isotropic NMR shifts in pyridine-type ligands coordinated to the paramagnetic 9-tungsto-3-cuprio(II)silicate anion28199633#N/ATRUE
1967
ja907038b10.1021/ja907038bFALSEhttps://doi.org/10.1021/ja907038bJarvo, ERJ. Am. Chem. Soc.N,N-DiAlkyl-N-chloroamines are an effective source of electrophilic nitrogen for nickel-catalyzed coupling with diArylzinc reagents. A variety of N-chloroamines as well as organozinc reagents react smoothly under the reaction conditions. A one-pot procedure that circumvents the need to isolate the N-chloroamines is described.Umpolung Amination: Nickel-Catalyzed Coupling Reactions of N,N-DiAlkyl-N-chloroamines with Diorganozinc Reagentsx141200930#N/AFALSE
1968
ja950744q10.1021/ja950744qFALSEhttps://doi.org/10.1021/ja950744qOertling, WAJ. Am. Chem. Soc.When CO(g) is added to solutions of the cobaltous porphyrin pi cation radical [Co(II)OEP(.)]ClO4, prepared by oxidation of CoOEP by AgClO4 in anhydrous CH2Cl2, room temperature binding of CO to the metal center occurs. Two distinct products result, [(CO)Co(III)OEP]ClO4 and [(CO)(2)Co(III)OEP]ClO4. These compounds exhibit Soret maxima at 366 and 414 nm, respectively. Resonance Raman (RR) spectra measured before the addition of CO are used to characterize the cobaltous porphyrin pi cation radical, and, after the addition of CO, RR spectra obtained by using 363.8 nm excitation confirm the occurrence of the five-coordinate Co(III) porphyrin complex. This complex, along with halide ligated analogs, displays some structure-sensitive vibrational frequencies which suggest that an unusual distortion of the porphyrin core occurs in CH2Cl2 solution. RR spectra obtained by using 413.1 nm excitation after the addition of CO are used to identify the second product as a typical six-coordinate cobaltic porphyrin. Titrations with CO reveal that the five- and six-coordinate complexes, [(CO)Co(III)OEP]ClO4 and [(CO)2Co(III)OEP]ClO4, form with P-1/2 values of 36 +/- 3 and 4000 +/- 300 Torr of CO, respectively. Isosbestic points in the UV-vis spectra occur at 368 nm for binding of the first CO and at 385 nm during binding of the second CO ligand. FTIR and RR spectra of [(CO)Co(III)OEP]ClO4 reveal vibrations at 2110 and 441 cm(-1) which shift upon substitution of (CO)-C-13 or (CO)-O-18 for the natural abundance CO. Isotope sensitive vibrations of [(CO)2Co(III)OEP]ClO4 were measured at 2137 and 468 cm(-1). In each case the modes above 2100 cm(-1) correspond to C=O stretching frequencies, while the lower frequency features are assigned to Co-C stretching motions. The resonance Raman enhancement of these isotope sensitive frequencies confirm CO binding to the metal center. The selective presence of these features in the Raman and FTIR data is consistent with that expected from symmetry based selection rules for five- and six-coordinate CO complexes. The relatively high C=O stretching frequencies observed are suggestive of weak metal d pi --> ligand pi* backbonding that results from the oxidation of Co(II) to Co(III).Room temperature binding of CO to cobaltous porphyrin pi cation radical: Spectroscopic characterization of mono and bis CO complexes with cobaltic porphyrin22199676#N/ATRUE
1969
ja910874x10.1021/ja910874xFALSEhttps://doi.org/10.1021/ja910874xChen, YJ. Am. Chem. Soc.The vapor-liquid-solid (VLS) growth model has been widely used to direct the growth of one-dimensional (1D) nanomaterials, but the origin of the proposed process has not been experimentally confirmed. Here we report the experimental evidence of the origin of VLS growth. Al69Ni31 alloyed partiCles are used as catalysts for growing AIN nanowires by nitridation reaction in N-2-NH3 at different temperatures. The nanowire growth occurs following the emergence of the catalyst droplets as revealed by in situ X-ray diffraction and thermal analysis. The physicochemical process involved has been elucidated by quantitative analysis on the evolution of the lattice parameters and relative contents of the nitridation products. These direct experimental results reveal that VLS growth of AIN nanowires is dominated by the phase equilibrium of the Al-Ni alloy catalyst. The in-depth insight into the VLS mechanism indicates the general validity of this growth model and may facilitate the rational design and controllable growth of 1D nanomaterials according to the corresponding phase diagrams.Phase-Equilibrium-Dominated Vapor-Liquid-Solid Growth Mechanism20201024#N/ATRUE
1970
ja906367h10.1021/ja906367hFALSEhttps://doi.org/10.1021/ja906367hHarmer, JJ. Am. Chem. Soc.Methyl-coenzyme M reductase (MCR) is the key enzyme in methane formation by methanogenic Archaea. It converts the thioether methyl-coenzyme M and the thiol coenzyme B into methane and the heterodisulfide of coenzyme M and coenzyme B. The catalytic mechanism of MCR and the role of its prosthetic group, the nickel hydrocorphin coenzyme F-430, is still disputed, and no intermediates have, been observed so far by fast spectroscopic techniques when the enzyme was incubated with the natural substrates. In the presence of the competitive inhibitor coenzyme M instead of methyl-coenzyme M, addition of coenzyme B to the active Ni(I) state MCRred1 induces two new species called MCRred2a and MCRred2r which have been characterized by pulse EPR spectroscopy. Here we show that the two MCRred2 signals can also be induced by the S-methyl- and the S-trifluoromethyl analogs of coenzyme B. F-19-ENDOR data for MCRred2a and MCRred2r induced by S-CF3-coenzyme B show that, upon binding of the coenzyme B analog, the end of the 7-thioheptanoyl chain of coenzyme B moves Closer to the nickel center of F-430 by more than 2 angstrom as compared to its position in both, the Ni(l) MCRred1 form and the X-ray structure of the inactive Ni(II) MCRox1-silent form. The finding that the protein is able to undergo a conformational change upon binding of the second substrate helps to explain the dramatic change in the coordination environment induced in the transition from MCRred1 to MCRred2 forms and opens the possibility that nickel coordination geometries other than square planar, tetragonal pyramidal, or elongated octahedral might occur in intermediates of the catalytic cyCle.Binding of Coenzyme B Induces a Major Conformational Change in the Active Site of Methyl-Coenzyme M Reductasex31201048#N/AFALSE
1971
ja906340u10.1021/ja906340uFALSEhttps://doi.org/10.1021/ja906340uRonnebro, EJ. Am. Chem. Soc.Magnesium hydride (MgH2) is an attractive candidate for solid-state hydrogen storage applications. To improve the kinetics and thermodynamic properties of MgH2 during dehydrogenation-rehydrogenation cyCles, a nanostructured MgH2-0.1TiH(2) material system prepared by ultrahigh-energy-high-pressure mechanical milling was investigated. High-resolution transmission electron microscope (TEM) and scanning TEM analysis showed that the grain size of the milled MgH2-0.1TiH(2) powder is approximately 5-10 nm with uniform distributions of TiH2 among MgH2 PartiCles. Pressure-composition-temperature (PCT) analysis demonstrated that both the nanosize and the addition of TiH2 contributed to the significant improvement of the kinetics of dehydrogenation and hydrogenation compared to commercial MgH2. More importantly, PCT cyCle analysis demonstrated that the MgH2-0.1 TiH2 material system showed excellent cyCle stability. The results also showed that the Delta H value for the dehydrogenation of nanostructured MgH2-0.1TiH(2) is significantly lower than that of commercial MgH2. However, the AS value of the reaction was also lower, which results in minimum net effects of the nanosize and the addition of TiH2 on the equilibrium pressure of dehydrogenation reaction of MgH2.Hydrogen Storage Properties of Nanosized MgH2-0.1TiH(2) Prepared by Ultrahigh-Energy-High-Pressure Millingx216200953#N/AFALSE
1972
ja910838d10.1021/ja910838dFALSEhttps://doi.org/10.1021/ja910838dLubitz, WJ. Am. Chem. Soc.The membrane-bound hydrogenase (Hase I) of the hyperthermophilic bacterium Aquifex aeolicus belongs to an intriguing Class of redox enzymes that show enhanced thermostability and oxygen tolerance. Protein film electrochemistry is employed here to portray the interaction of Hase I with molecular oxygen and obtain an overall picture of the catalytic activity. Fourier transform infrared (FTIR) spectroscopy integrated with in situ electrochemistry is used to identify structural details of the [NiFe] site and the intermediate states involved in its redox chemistry. We found that the active site coordination is similar to that of standard hydrogenases, with a conserved Fe(CN)(2)CO moiety. However, only four catalytic intermediates could be detected; these correspond structurally to the Ni-B, Ni-Sl(a), Ni-C, and Ni-R states of standard hydrogenases. The Ni-Sl/Ni-C and Ni-C/Ni-R midpoint potentials are approximately 100 mV more positive than those observed in mesophilic hydrogenases, which may be the reason that A. aeolicus Hase I is more suitable as a catalyst for H-2 oxidation than production. Protein film electrochemistry shows that oxygen inhibits the enzyme by reacting at the active site to form a single species (Ni-B); the same inactive state is obtained under oxidizing, anaerobic conditions. The mechanism of anaerobic inActivation and reActivation in A. aeolicus Hase I is similar to that in standard hydrogenases. However, the reActivation of the former is more than 2 orders of magnitude faster despite the fact that reduction of Ni-B is not thermodynamically more favorable. A scheme for the enzymatic mechanism of A. aeolicus Hase I is presented, and the results are discussed in relation to the proposed models of oxygen tolerance.Membrane-Bound Hydrogenase I from the Hyperthermophilic Bacterium Aquifex aeolicus: Enzyme Activation, Redox Intermediates and Oxygen Tolerance116201078#N/ATRUE
1973
ja910199710.1021/ja9101997FALSEhttps://doi.org/10.1021/ja9101997Perez-Ramirez, JJ. Am. Chem. Soc.A new generation of heterogeneous Cu-Ni-Fe catalysts with appropriate metal ratios displayed outstanding alkene selectivity in the gas-phase hydrogenation of propyne (S(C3H6) up to 100%) and ethyne (S(C2H4) up to 80%). The design was accomplished by orchestrating key functions in the catalyst: copper is the base hydrogenation metal, nickel increases the hydrogen coverage to minimize oligomerization, and iron acts as structural promoter. In addition to the largely improved alkene selectivity compared to that of the commonly applied Pd catalysts, the ternary Cu-Ni-Fe catalysts promise substantial process advantages, since they do not require CO feeding as selectivity enhancer and they yield high alkene selectivity in a broad window of H-2/alkyne ratios. The ternary system requires higher operating temperatures compared to those for palladium.Cooperative Effects in Ternary Cu-Ni-Fe Catalysts Lead to Enhanced Alkene Selectivity in Alkyne Hydrogenation110201037#N/ATRUE
1974
ja905497710.1021/ja9054977FALSEhttps://doi.org/10.1021/ja9054977Luscombe, CKExternally Initiated Regioregular P3HT with Controlled Molecular Weight and Narrow Polydispersityx2009#N/AFALSE
1975
ja905338x10.1021/ja905338xFALSEhttps://doi.org/10.1021/ja905338xFigueroa, JSJ. Am. Chem. Soc.Mg metal reduction of the divalent precursor PdCl2(CNArDipp2)(2) (Dipp = 2,6-diisopropylphenyl) provides the isolable, two-coordinate Pd(0) bis-isocyanide, Pd(CNArDipp2)(2), which is the first stable monomeric isocyanide complex of zerovalent palladium. Variable temperature H-1 NMR and FTIR studies on Pd(CNArDipp2)(2) in the presence of added CNArDipp2 revealed that free and coordinated isocyanide undergo rapid exchange, but the components do not form a stable tris-isocyanide complex. Bis-isocyanide Pd(CNArDipp2)(2) is active for oxidative addition reactions and readily reacts with Benzyl chloride and mesityl bromide to form Pd(Cl)(Bz)(CNArDipp2)(2) and Pd(Br)(Mes)(CNArDipp2)(2), respectively. Room-temperature Suzuki-Miyaura cross-coupling reactions are mediated by Pd(CNArDipp2)(2). Coordinatively and electronically unsaturated substrates also react with Pd(CNArDipp2)(2). Addition of thallium(I) triflate (TlOTf) to Pd(CNArDipp2)(2) results in the salt [TlPd(CNArDipp2)(2)]OTf, while addition of O-2 results in the peroxo complex (eta(2)-O)Pd(CNArDipp2)(2). Most remarkably, 2 equiv of nitrosobenzene react with Pd(CNArDipp2)(2) to form the square planar complex (kappa(1)-N-PhNO)(2) Pd(CNArDipp2)(2), the geometry of which strongly suggests the formation of a divalent Pd center. With the aid of density functional theory calculations, this valence change is rationalized in terms of a formal reduction of the bond order-in each NO unit to 1.5.Bond Activation, Substrate Addition and Catalysis by an Isolable Two-Coordinate Pd(0) Bis-Isocyanide Monomerx64200926#N/AFALSE
1976
ja909820h10.1021/ja909820hFALSEhttps://doi.org/10.1021/ja909820hIshihara, TJ. Am. Chem. Soc.We have investigated in situ the crystal structure, oxygen diffusion path, oxygen permeation rate, and electrical conductivity of a doped praseodymium nickel oxide, Pr2NiO4-based mixed conductor, (Pr0.9La0.1)(2)(Ni0.74Cu0.21Ga0.05)O4+delta (PLNCG) in air between 27 degrees C and 1015 6 degrees C The PLNCG has a tetragonal I4/mmm K2NiF4-type structure which consists of a (Pr0.9La0.1)(Ni0.74Cu0.21Ga0.05)O-3 perovskite unit and a (Pr0.9La0.1)O rock salt unit in the whole temperature range Both experimental and theoretical electron density maps indicated two-dimensional networks of (Ni0.74Cu0.2Ga0.05)-O covalent bonds in PLNCG Highest occupied molecular orbitals (HOMO) in PLNCG demonstrate that the electron-hole conduction occurs via Ni and Cu atoms in the (Ni0.74Cu0.21Ga0.05)-O layer The bulk oxygen permeation rate was high (137 mu mol cm(-2) min(-1) at 1000 degrees C), and its Activation energy was low (51 kJ mol(-1) at 950 degrees C) The Rietveld method, maximum-entropy method (MEM), and MEM-based pattern fitting analyses of neutron and synchrotron diffraction data indicate a large anisotropic thermal motion of the apical O2 oxygen at the 4e site (0, 0, z, z approximate to 0 2) in the (Pr0.9La0.1)(Ni0.74Cu0.21Ga0.05)O-3 perovskite unit Neutron and synchrotron diffraction data and theoretical structural optimization show the interstitial oxygen (O3) atom at (x, 0, z) (x approximate to 0.6 and z approximate to 0.2). The nuClear density analysis indicates that the bulk oxide-ion diffusion, which is responsible for the high oxygen permeation rate, occurs through the interstitial O3 and anisotropic apical O2 sites The nuClear density at the bottleneck on the oxygen diffusion path increases with temperature and with the oxygen permeation rate The Activation energy from the nuClear density at the bottleneck decreases with temperature, which is consistent with the decrease of the Activation energy from oxygen permeation rate The extremely low Activation energy (12 kJ mol(-1) at 900 degrees C) from the nuClear density at the bottleneck indicates possible higher bulk oxygen permeation rates in quality single crystals and epitaxial thin films.Crystal Structure, Diffusion Path, and Oxygen Permeability of a Pr2NiO4-Based Mixed Conductor (Pr0.9La0.1)(2)(Ni0.74Cu0.21Ga0.05)O4+delta95201040#N/ATRUE
1977
ja904885w10.1021/ja904885wFALSEhttps://doi.org/10.1021/ja904885wKiriy, AJ. Am. Chem. Soc.Herein, we present a new paradigm in the engineering of nanostructured hybrids between conjugated polymer and inorganic materials via a chain-growth surface-initiated Kumada catalyst-transfer, polycondensation (SI-KCTP) from partiCles. Poly(3-hexylthiophene), P3HT, a benchmark material for organic electronics, was selectively grown by SI-KCTP from (nano)partiCles bearing surface-immobilized Ni catalysts supported by bidentate phosphorus ligands, that resulted in hairy (nano)partiCles with end-tethered P3HT chains. Densely grafted P3HT chains exhibit strongly altered optical properties compared to the untethered counterparts (red shift and vibronic fine structure in absorption and fluorescence spectra), as a result of efficient planarization and chain-aggregation. These effects are observed in solvents that are normally recognized as good solvents for P3HT (e.g., tetrahydrofurane). We attribute this to strong interchain interactions within densely grafted P3HT chains, which can be tuned by changing the surface curvature (or size) of the supporting partiCle. The hairy P3HT nanopartiCles were successfully applied in bulk heterojunction solar cells.Hairy Poly(3-hexylthiophene) PartiCles Prepared via Surface-Initiated Kumada Catalyst-Transfer Polycondensationx134200950#N/AFALSE
1978
ja909562y10.1021/ja909562yFALSEhttps://doi.org/10.1021/ja909562yHouk, KNJ. Am. Chem. Soc.The origins of reactivity and regioselectivity in nickel-catalyzed reductive coupling reactions of alkynes and aldehydes were investigated with density functional calculations. The regioselectivities of reactions of simple alkynes are controlled by steric effects, while conjugated enynes and diynes are predicted to have increased reactivity and very high regioselectivities, placing alkenyl or alkynyl groups distal to the forming C-C bond The reactions of enynes and diynes involve 1,4-attack of the Ni-Carbonyl complex on the conjugated enyne or diyne The consequences of these conClusions on reaction design are discussed.Origins of Regioselectivity and Alkene-Directing Effects in Nickel-Catalyzed Reductive Couplings of Alkynes and Aldehydes92201085#N/ATRUE
1979
ja909136h10.1021/ja909136hFALSEhttps://doi.org/10.1021/ja909136hZamble, DBJ. Am. Chem. Soc.The Escherichia coli NikR transcription factor is a Ni(II)-dependent repressor that regulates the production of a nickel ion transporter. The X-ray crystal structure of the Ni(II)-NikR-DNA bound complex revealed a K+-binding site positioned at the interface of the metal- and DNA-binding domains, but the significance of the potassium was unClear. Mutation of one of the K+ ligands impairs the affinity and specificity of DNA binding in the presence of either stoichiometric or excess Ni(II). Removal of K+ abrogates Ni(II)-responsive DNA binding completely while the addition of K+ restores this activity. Furthermore, the observed K+ dependence can be relieved by replacing the K+ ligand Asp34 with an arginine. These mutagenesis and cation exchange experiments reveal that K+ is a critical structural component for the Activation of Ni(II)-responsive DNA binding by NikR.Potassium Is Critical for the Ni(II)-Responsive DNA-Binding Activity of Escherichia coli NikR10201025#N/ATRUE
1980
ja908721t10.1021/ja908721tFALSEhttps://doi.org/10.1021/ja908721tMaspoch, DJ. Am. Chem. Soc.Long chiral metal-organic nanofibers can be grown using conventional coordination chemistry and biologically derived components in a diffusion controlled growth procedure.Amino Acid Based Metal-Organic Nanofibers106200926#N/ATRUE
1981
ja904197q10.1021/ja904197qhttps://doi.org/10.1021/ja904197qMcNeil, AJJ. Am. Chem. Soc.The mechanisms for Ni(dppe)Cl-2-catalyzod chain-growth polymerization of 4-bromo-2,5-bis(hexyloxy)phenyl magnesium chloride and 5-bromo-4-hexylthiophen-2-ylmagnesium chloride were investigated. Rate studies utilizing IR spectroscopy and gas chromatography revealed that both polymerizations exhibit a first-order dependence on the catalyst concentration but a zeroth-order dependence on the monomer concentration. P-31 NMR spectroscopic studies of the reactive organometallic intermediates suggest that the resting states are unsymmetrical Ni-II-biAryl and Ni-II-bithiophene complexes. In combination, the data implicate reductive elimination as the rate-determining step for both monomers. Additionally, LiCl was found to have no effect on the rate-determining step or molecular weight distribution in the arene polymerization.Mechanistic Studies on Ni(dppe)Cl-2-Catalyzed Chain-Growth Polymerizations: Evidence for Rate-Determining Reductive Eliminationx1562009124#N/AFALSE
1982
ja904150w10.1021/ja904150whttps://doi.org/10.1021/ja904150wOsakada, KJ. Am. Chem. Soc.Isomerization polymerization of 4-AlkylcyClopentenes catalyzed by Pd-diimine complexes produces the polymers with trans-1,3-disubstituted cyClopentane rings located regularly along the polymer chain. The polymers with isotactic structure formed by using a C-2-symmetric catalyst exhibited liquid-crystalline properties.Isomerization Polymerization of 4-AlkylcyClopentenes Catalyzed by Pd Complexes: Hydrocarbon Polymers with Isotactic-Type Stereochemistry and Liquid-Crystalline Propertiesx36200922#N/AFALSE
1983
ja904128d10.1021/ja904128dFALSEhttps://doi.org/10.1021/ja904128dYashima, EJ. Am. Chem. Soc.An optically inactive poly(4-carboxyphenyl isocyanide) (poly-1-H) changed its structure into the prevailing, one-handed helical structure upon complexation with optically active amines in dimethylsulfoxide (DMSO) and water, and the complexes show a characteristic induced circular dichroism in the polymer backbone region. Moreover, the macromolecular helicity induced in water and aqueous organic solutions containing more than 50 vol % water could be memorized even after complete removal of the chiral amines (h-poly-1b-H), while that induced in DMSO and DMSO-water mixtures containing less than 30 vol % water could not maintain the optical activity after removal of the chiral amines (poly-1a-H). We now report fully detailed studies of the helix induction mechanism with chiral amines and the memory of the macromolecular helicity in water and a DMSO-water mixture by various spectroscopic measurements, theoretical calculations, and persistence length measurements together with X-ray diffraction (XRD) measurements. From the spectroscopic results, such as circular dichroism (CD), absorption, IR, vibrational CID, and NMR of poly-1a-H, h-poly-1b-H, and original poly-1-H, we conCluded that the specific configurational isomerization around the C=N double bonds occurs during the helicity induction process in each solvent. In order to obtain the structural information, XRD measurements were done on the uniaxially oriented films of the corresponding methyl esters (poly-1-Me, poly-1a-Me, and h-poly-1b-Me) prepared from their liquid crystalline polymer solutions. On the basis of the XRD analyses, the most plausible helical structure of poly-la-Me was proposed to be a 9-unit/5-turn helix with two monomer units as a repeating unit, and that of h-poly-1b-Me was proposed to be a 10-unit/3-turn helix consisting of one repeating monomer unit. The density functional theory calculations of poly(phenyl isocyanide), a model polymer of h-poly-1b-Me, afforded a 7-unit/2-turn helix as the most possible helical structure, which is in good agreement with the XRD results. Furthermore, the persistence length measurements revealed that these structural changes accompany a significant change in the main-chain stiffness. The mechanism of helix induction in poly-1-H and the memory of the macromolecular helicity are discussed on the basis of these results.Mechanism of Helix Induction in Poly(4-carboxyphenyl isocyanide) with Chiral Amines and Memory of the Macromolecular Helicity and Its Helical Structuresx762009123#N/AFALSE
1984
ja904045n10.1021/ja904045nFALSEhttps://doi.org/10.1021/ja904045nAnslyn, EVJ. Am. Chem. Soc.The design of a sensor array that uses a single entity as both the host and the indicator (squaraine dye, SO) to differentiate a series of metal ions and a series of thiols is reported. The metal ions and thiols act as both analytes and modulators of the squaraine response allowing pattern-based discrimination. Mercury(II), palladium(II), copper(II), iron(II), and nickel(II) can be discriminated when combining SO with five thiols: propane thiol (PT), 3-mercaptopropionic acid (MPA), naphthalene-2-thiol (NT), 2,3-dimercaptopropanol (DMP), and 2-acetylamino-3-mercaptopropionic acid methyl ester (ACM). Likewise, the five thiols can be discriminated using SO and the five metals. For example, SO in combination with 2-acetylamino-3-mercaptopropionic acid methyl ester (ACM) afforded very good differentiation of all five metal ions. However, propanethiol, 3-mercaptopropionic acid, and naphthalene-2-thiol produced very similar differentiation of the considered metal ions. On the other hand, all metal ions considered in this study are able to discriminate 2,3-dimercaptopropanol (DMP) and 2-acetylamino-3-mercaptopropionic acid methyl ester (ACM) Clearly and completely, both from one another and from the other three thiols (PT, NT, MPA). Importantly, mercury(II) is the only metal ion able to effect the discrimination of naphthalenethiol (NT) from PT and MPA, thus giving the best discrimination overall. The study shows that complex discrimination of widely diverse Classes, metal ions and thiols, can be achieved via a single receptor/indicator.Pattern-Based Recognition of Thiols and Metals Using a Single Squaraine Indicatorx162200930#N/AFALSE
1985
ja903997a10.1021/ja903997aFALSEhttps://doi.org/10.1021/ja903997aBetley, TAJ. Am. Chem. Soc.Transition metal complexes (Mn -> Zn) of the dipyrromethane ligand, 1,9-dimesityl-5,5-dimethyldipyrromethane (dpm), have been prepared. Arylation of the dpm ligand alpha to the pyrrolic nitrogen donors limits the accessibility of the pyrrole pi-electrons for transition metal coordination, instead forcing eta(1),eta(1) coordination to the divalent metal series as revealed by X-ray diffraction studies. Structural and magnetic characterization (SQUID, EPR) of the bis-pyridine adducts of (dpm)Mn-II(py)(2), (dpm)Fe-II(py)(2), and (dpm)Co-II(py)(2) reveal each divalent ion to be high-spin and pseuClotetrahedral in the solid state, whereas the (dpm)Ni-II(py)(2) is low-spin and adopts a square-planar geometry. Differential pulse voltammetry on the (dpm)M-II(py)(2) series reveals a common two-electron oxidation pathway that is entirely ligand-based, invariant to the divalent metal-bound, its geometry or spin state within the dpm framework. This latter observation indicates that fully populated ligand-based orbitals from the dpm construct fie above partially filled metal 3d orbitals without intramolecular redox chemistry or spin-state tautomerism occurring. DFT analysis on this family of complexes corrB(OH)2rates this electronic structure assignment, revealing that the highest lying molecular orbitals are completely ligand-based. Chemical oxidation of the deprotonated dpm framework results in the four-electron oxidation of the dipyrrolide framework, although this oxidation product was not observed either in the electrochemical or chemical oxidation of the (dpm)M-II(py)(2) complexes.Unusual Electronic Structure of First Row Transition Metal Complexes Featuring Redox-Active Dipyrromethane Ligandsx36200931#N/AFALSE
1986
ja908360710.1021/ja9083607FALSEhttps://doi.org/10.1021/ja9083607Montgomery, JJ. Am. Chem. Soc.Strategies for the reductive coupling of enones or enals with alkynes have been developed. The reducing agents employed inClude organozincs, organB(OH)2ranes, organosilanes, and methanol. The latter of these strategies is simple, cost-effective, and tolerant of many functional groups. Isotopic labeling strategies have provided supporting evidence for the mechanistic proposals.Evolution of Efficient Strategies for Enone-Alkyne and Enal-Alkyne Reductive Couplings47200954#N/ATRUE
1987
ja907448t10.1021/ja907448tFALSEhttps://doi.org/10.1021/ja907448tLiu, LJ. Am. Chem. Soc.Transition-metal-catalyzed deCarbonylative coupling presents a new and important direction in synthetic chemistry. Mechanistic studies on deCarbonylative coupling not only improve the understanding of the newly discovered transformations, but also may have valuable implications for the development of more effective catalyst systems. In this work, a comprehensive theoretical study was conducted on the mechanism of Myers' Pd-catalyzed deCarbonylative Heck reaction. The catalytic cyCle was found to comprise four steps: deCarbonylation, Clef in insertion, beta-hydride elimination, and catalyst regeneration. DeCarbonylation was the rate-limiting step, and it proceeded through a dissociative pathway in which Pd(II) mediated the extrusion of CO2 from an aromatic Carbonylic acid to form a Pd(II)-Aryl intermediate. Further analysis was conducted on the factors that might control the efficiency of Myers' deCarbonylative Heck reaction. These factors inCluded Pd salts, ligands, acid substrates, and metals. (1) Regarding Pd salts, PdCl2 and PdBr2 were worse catalysts than Pd(TFA)(2), because the exchange of Cl or Br by a Carbonylate from Pd was thermodynamically unfavorable. (2) Regarding ligands, DMSO provided the best compromise between Carbonyl exchange and deCarbonylation. Phosphines and N-heterocarbenes disfavored deCarbonylation because of their electron richness, whereas pyridine ligands disfavored Carbonyl exchange. (3) Regarding acid substrates, a good correlation was observed between the energy barrier of R-COOH deCarbonylation and the R-H acidity. Substituted benzoic acids showed deviation from the correlation because of the involvement of pi(substituent)-sigma(C-ipso-Pd) interaction. (4) Regarding metals, Ni and Pt were worse catalysts than Pd because of the less favorable Carbonyl exchange and/or DMSO removal steps in Ni and Pt catalysis.Theoretical Analysis of Factors Controlling Pd-Catalyzed DeCarbonylative Coupling of Carbonylic Acids with Olefins197201068#N/ATRUE
1988
ja907214t10.1021/ja907214tFALSEhttps://doi.org/10.1021/ja907214tHiyama, TJ. Am. Chem. Soc.Regioselective alkenylation and Alkylation of 2-pyridone derivatives are achieved through inter- and intramolecular insertion of alkynes, 1,3-dienes, and alkenes into the C(6)-H bond by nickel/AlMe3 catalysis. Coordination of the heterocyCles to the Lewis acid cocatalyst through their basic Carbonyl oxygen is considered to be responsible for the regioselective Activation of the C-H bonds, probably through oxidative addition to nickel(0).Direct Alkenylation and Alkylation of Pyridone Derivatives by Ni/AlMe3 Catalysis158200915#N/ATRUE
1989
ja906594310.1021/ja9065943FALSEhttps://doi.org/10.1021/ja9065943Rohde, JUJ. Am. Chem. Soc.Bis(imino)pyridine complex [Ni{2,6-(ArN=CMe)(2)C5H3N}Cl] (where Ar 2,6-(Pr2C6H3)-Pr-i) was synthesized by reduction of the corresponding dichloride complex and characterized as a Ligand-radical complex of Ni-II. Reaction of this complex with O-2 caused intraligand C-C bond Cleavage to afford the Ni complex of the new iminoethylpyridylcarboxamidato ligand, which also was isolated as the corresponding carboxamide, 6-(ArN=CMe)C5H3N-2-C(O)NHAr. This reaction serves as an example of small-molecule Activation effected directly at the redox-active bis(imino)pyridine ligand without an overall oxidation state change at the Ni center.Reaction of a Redox-Active Ligand Complex of Nickel with Dioxygen Probes Ligand-Radical Character39200929#N/ATRUE
1990
ja902093f10.1021/ja902093fFALSEhttps://doi.org/10.1021/ja902093fBaik, MHJ. Am. Chem. Soc.The electronic structures of the low and high-spin states of the cationic complex [Ni(H)(OH)](+) that was previously found to be highly reactive toward CH4 and O-2 were examined. Earlier computational work suggested that the low-spin doublet state D-0 of the Ni-III-d(7) system is significantly lower in energy than its high-spin quartet analogue Q(1). Recent DFT-studies indicated, however, that Q(1) is the reactive species requiring Q(1) to have a sufficiently long lifetime for undergoing thermal reactions with the small molecule reactants under single collision conditions in the gas phase. These observations raise the question as to why Q(1) does not spontaneously undergo intersystem crossing. Our work based on DFT, coupled-Cluster and MCSCF calculations suggests that the hydroxyl ligand behaves as a redox noninnocent ligand and becomes oxidized to formally afford an electronic structure that is consistent with a Ni-II-(OH)center dot species. As a result, the doublet and quartet ground states are not related by a single electron spin flip and the intersystem crossing becomes inhibited, as indicated by unexpectedly small spin-orbit coupling constants. After extensive sampling of the potential energy surfaces, we conCluded that there is no direct way of converting Q(1) to the ground state doublet D-0 Alternative multistep pathways for the Q(1) -> D-0 decay involving doublet excited states were also evaluated and found to be energetically not accessible under the experimental conditions.A Redox Non-Innocent Ligand Controls the Life Time of a Reactive Quartet Excited State - An MCSCF Study of [Ni(H)(OH)](+)x27200994#N/AFALSE
1991
ja906550h10.1021/ja906550hFALSEhttps://doi.org/10.1021/ja906550hCummins, CCJ. Am. Chem. Soc.While P-4 is the stable molecular form of phosphorus, a recent study illustrated the possibility of P-2 generation for reactions in organic media under mild conditions. The heavier group 15 element arsenic can exist as As-4 molecules, but As-4 cannot be stored as a pure substance because it is both light-sensitive and reverts thermally to its stable, metallic gray form. Herein we report As-4 Activation giving rise to a mu-As-2 diniobium complex, serving in turn as precursor to a terminal arsenide anion complex of niobium. Functionalization of the latter provides the new AsPNMes(star) ligand, which when complexed with tungsten pentaCarbonyl elicits extrusion of the (AsP)W(CO)(5) molecule as a reactive intermediate. Trapping reactions of the latter with organic dienes are found to furnish double Diels-Alder adducts in which the ASP unit is embedded in a polycyClic organic framework. Thermal generation of (AsP)W(CO)(5) in the presence of the neutral terminal phosphide complex P Mo(N[Pr-i]Ar)(3) leads to the cyClo-AsP2 complex (OC)(5)W(cyClo-AsP2)Mo(N[Pr-i]Ar)(3). The (AsP)W(CO)(5) trapping products were crystallized and characterized by X-ray diffraction methods, and computational methods were applied for analysis of the As-As and As-P bonds in the complexes.Triple-Bond Reactivity of an AsP Complex Intermediate: Synthesis Stemming from Molecular Arsenic, As-444200977#N/ATRUE
1992
ja906040t10.1021/ja906040tFALSEhttps://doi.org/10.1021/ja906040tZhou, QLJ. Am. Chem. Soc.Highly enantioselective hydroVinylation of alpha-Alkyl Vinylarenes. An approach to the construction of all-carbon quaternary stereocenters87200628#N/ATRUE
1993
ja905847510.1021/ja9058475FALSEhttps://doi.org/10.1021/ja9058475Kishi, YJ. Am. Chem. Soc.With sequential use of catalytic asymmetric Cr-mediated coupling reactions, E7389 C14-C35 and halichondrin C14-C38 building blocks have been stereoselectively synthesized. The C19-C20 bond is first formed via the catalytic asymmetric Ni/Cr-mediated coupling, i.e., 8 + 9 -> 10 (90%; dr = 22:1), in which Vinyl iodide 8 is used as the limiting substrate. The C23-C24 bond is then formed via the catalytic asymmetric Co/Cr-mediated coupling, i.e., 13 + 14 -> 4 (82%; or = 22:1), in which the Alkyl-iodide bond in 14 is selectively activated over the Vinyl-iodide bond. The catalytic asymmetric Ni/Cr-mediated reaction is employed to couple C14-C26 segment 19 with E7389 C27-C35 segment 20 (91%; dr = >55:1). In this synthesis, the C23-0 bond is stereoselectively constructed via a double-inversion process, i.e., 21 -> 22, to furnish E7389 C14-C35 building block 22 in 84% yield. The same synthetic sequence has been employed to synthesize halichondrin C14-C38 building block 18b, i.e., 16a + 19 -> 18b.New Syntheses of E7389 C14-C35 and Halichondrin C14-C38 Building Blocks: Double-Inversion Approach56200936#N/ATRUE
1994
ja901346g10.1021/ja901346gFALSEhttps://doi.org/10.1021/ja901346gGreen, JCJ. Am. Chem. Soc.Oxidative addition of the tridentate N-heterocyClic carbene (NHC) diphosphine ligand precursor ([PCP]H)PF6 (1) {[PCP] = o-(Pr2PC6H4)-Pr-i(NC3H4N)o-(C6H4PPr2)-Pr-i} to Ni(COD)(2) results in the formation of the nickel(II) hydride complex ([PCP]NiH)PF6 (2). This hydride undergoes a rapid reaction with ethylene to generate a nickel(O) complex in which an ethyl group has been transferred to the carbene carbon of the original NHC-diphosphine ligand. If the first intermediate is the anticipated square-planar nickel(II) ethyl species, then the formation of the product would require a process that involves a trans C-C coupling of the NHC carbon and a presumed Ni-ethyl intermediate. Deuterium-labeling studies provide evidence for migratory insertion of the added ethylene into the Ni-H bond rather than into the Ni-catene linkage; this is based on the observed deuterium scrambling, which requires reversible P-elimination, alkene rotation, and hydride readdition. However, density functional theory studies suggest that a key intermediate is an agostic ethyl species that has the Ni-C bond cis to the NHC unit. A possible transition state containing two cis-disposed carbon moieties was also identified. Such a process represents a new pathway for catalyst deActivation involving NHC-based metal complexes.Noninnocent Behavior of Ancillary Ligands: Apparent Trans Coupling of a Saturated N-HeterocyClic Carbene Unit with an Ethyl Ligand Mediated by Nickelx65200926#N/AFALSE
1995
ja901267210.1021/ja9012672https://doi.org/10.1021/ja9012672Meisel, MWJ. Am. Chem. Soc.Tuning the composition of the ternary transition-metal Prussian blue analogue Na alpha Ni1-xCox-[Fe(CN)(6)](beta)center dot nH(2)O allows the sign of the photoinduced change in magnetization to be controlled. The parent cobalt hexacyanoferrate material is well-known to display photoinduced and thermal charge-transfer-induced spin transitions (CTISTs). Upon partial replacement of Co ion sites with Ni-II, irradiation with halogen light can cause either an increase or a decrease in magnetization, depending upon the extent of Ni-II substitution, the applied field, and the temperature. For all compositions with x > 0, photoexcitation generates new moments according to the same mechanism observed for the parent x = 1 compound. However, the presence of Ni-II introduces a superexchange of opposite sign, providing a mechanism for controlling the sign of the change in magnetization with applied light. Additionally, dilution of the spin-crossover material reduces the magnitude and hysteresis of the thermal CTIST effect. These effects can be qualitatively explained by simple mean-field models.Tuning the Sign of Photoinduced Changes in Magnetization: Spin Transitions in the Ternary Metal Prussian Blue Analogue Na alpha Ni1-xCox[Fe(CN)(6)](beta)center dot nH(2)OPhotocatalyst21200982#N/AFALSE
1996
ja900909u10.1021/ja900909uFALSEhttps://doi.org/10.1021/ja900909uMiller, JSJ. Am. Chem. Soc.DinuClear [(TPyA)M-II(DBQ(2-))M-II(TPyA)](BF4)(2) [TPyA = tris(2-pyridylmethyl)amine; DBQ(2-) = 2,5-di-tert-butyl-3,6-dihydroxy-1,4-benzoquinonate; M = Co (1(2+)), Fe (2(2+)), Ni (3(2+))] complexes have been prepared by the reaction of M2+, TPyA, H(2)DBQ, and triethylamine in MeOH solution. Their monooxidized form [(TPyA)M-III(DBQ(center dot 3))M-III(TPyA)](3+) [Co = (1(3+)), Fe (2(3+))] has been synthesized by using ferrocenium tetrafluorB(OH)2rate, and the dioxidized form of 1(2+), [(TPyA)Co-III(DBQ(2-))Co-III(TPyA)](4+) (1(4+)), has been obtained by using thianthrinium tetrafluorB(OH)2rate. These dinuClear compounds were characterized by X-ray crystallography, electrochemistry, magnetism, and EPR spectroscopy. Valence ambiguous 1(3+) forms via redox-induced electron transfer, whereby the one-electron oxidation of the [Co-II(DBQ(2-))Co-II](2+) core forms [Co-III(DBQ(center dot 3-))Co-III](3+), and it also exhibits spin crossover behavior to the core [Co-III(DBQ(2-))Co-II](3+) above room temperature. The M ions in 1 and 2 have a distorted octahedral geometry by coordination with four nitrogens of a TPyA, two oxygens of a DBQ(2-/center dot 3-). Due to the interdimer offset face-to-face pi-pi and/or herringbone interactions, 1(2+), 1(3+), and 2(2+) show extended 1-D and/or 2-D supramolecular structures. The existence of DBQ(center dot 3-) in 1(3+) is confirmed from both solid-state magnetic and solution EPR data. Co- and Ni-based 1(2+) and 3(2+) show weak antiferromagnetic interactions [1(2+): g = 2.44, J/k(B) = -3.20 K (-2.22 cm(-1)); 3(2+): g = 2.13, J/k(B) = -3.22 K (-2.24 cm(-1)), H = -2JS(1)center dot S-2 for 1(2+) and 3(2+)], while Fe-based 2(2+) exhibits strong spin crossover behavior above room temperature. 1(2+) has three reversible one-electron transfer waves at E-1/2 (vs SCE in MeCN) = -1.121, 0.007, and 0.329 V, and a fourth wave at -1.741 V that exhibits a slight chemical irreversibility. The first three correspond to [Co(II)DBQ(2-)Co(II)](2+) reduction to [Co(II)DBQ(center dot 3-)Co(II)](+), and oxidation to [Co(III)DBQ(center dot 3-)Co(III)](3+) and [Co(III)DBQ(2-)Co(III)](4+), respectively. The mechanism of the multielectron transfer oxidation from [Co(II)DBQ(2-)Co(II)](2+) to [Co(III)DBQ(center dot 3-)Co(III)](3+) is unknown; the energy of stabilization for oxidizing the Co-II centers in the presence of DBQ(center dot 3-), relative to oxidizing the Coll centers in the presence of DBQ(2-) is Computed to be 1.45 eV. 2(2+) also has three reversible one-electron transfer waves at 0.802, 0.281, and -1.007 V that correspond to two successive one-electron oxidations (2(2+)/2(3+) and 2(3+)/2(4+)), and a one-electron reduction (2(2+)/2(+)). 2(2+) has the [Fe-hs(II)(DBQ(2))Fe-hs(II)](2+) eectronic structure that becomes [Fe-hs(III)(DBQ(center dot 3))Fe-hs(III)](3+) upon oxidation. The latter undergoes spin crossover above room temperature to populate the [Fe-hs(III)(DBQ(2-))Fe-hs(II)](3+) excited state.Observation of Redox-Induced Electron Transfer and Spin Crossover for DinuClear Cobalt and Iron Complexes with the 2,5-Di-tert-butyl-3,6-dihydroxy-1,4-benzoquinonate Bridging Ligandx86200945#N/AFALSE
1997
ja905065j10.1021/ja905065jFALSEhttps://doi.org/10.1021/ja990197zRovis, TEnantioselective Rhodium-Catalyzed [2+2+2] CyCloadditions of Terminal Alkynes and Alkenyl Isocyanates: Mechanistic Insights Lead to a Unified Model that Rationalizes Product Selectivity2009#N/ATRUE
1998
ja904689410.1021/ja9046894FALSEhttps://doi.org/10.1021/ja9046894Suginome, MJ. Am. Chem. Soc.A nickel-catalyzed intermolecular hydroacylation of methylenecyClopropanes (MCPs) has been developed. The reaction proceeds with stereospecific Cleavage of the proximal C-C bond of the cyClopropane ring to give gamma,delta-unsaturated ketones with high diastereoselectivities. A nickel catalyst generated in situ from Ni(cod)(2) and P(n-Bu)(3) with a P/Ni ratio of 1:1 is effective for the hydroacylation, in which benzaldehyde derivatives, heteroAryl aldehydes, and aliphatic aldehydes react with MCPs at 60-100 degrees C to afford the corresponding ketones in high yields,Nickel-Catalyzed Ring-Opening Hydroacylation of MethylenecyClopropanes: Synthesis of gamma,delta-Unsaturated Ketones from Aldehydes65200929#N/ATRUE
1999
ja904647610.1021/ja9046476FALSEhttps://doi.org/10.1021/ja9046476Dobbek, HJ. Am. Chem. Soc.Carbon monoxide dehydrogenases (CODHs) catalyze the reversible oxidation of carbon monoxide with water to carbon dioxide, two protons, and two electrons. The CODHs of anaerobic microorganisms harbor a complex Ni/Fe/S-containing metal center called a C-Cluster in their active site, which activates the substrates water and carbon monoxide, stabilizes an intermediary metal-Carbonylate, and transiently stores the two electrons generated in the reaction. Several small molecules have been reported to inhibit carbon monoxide oxidation by CONS, among which the cyanide anion acts as a slow binding inhibitor. Cyanide is isoelectronic to the substrate carbon monoxide, and its binding to the C-Cluster has been reported to involve nickel, nickel and iron, or only iron. We report the crystal structure of CODH-II from Carboxydothermus hydrogenoformans in complex with cyanide at 1.36 angstrom resolution. The structure reveals that cyanide binds to the C-Cluster at an open coordination site completing the square-planar coordination geometry of the nickel ion. White active CON has a water/hydroxo-ligand bound to an iron ion near nickel, in the cyanide complex the water/hydroxo-ligand is lost and iron occupies a position more Close to the nickel ion. Based on the structure, we suggest that the competitive inhibitory character of cyanide originates from it obstruction of carbon monoxide binding to the nickel ion while the slow binding inhibition is due to a conformational change of the protein during which the water/hydroxo-ligand bound to iron is lost.Structural Basis of Cyanide Inhibition of Ni, Fe-Containing Carbon Monoxide Dehydrogenase39200917#N/ATRUE
2000
ja900483x10.1021/ja900483xFALSEhttps://doi.org/10.1021/ja900483xDuBois, DLJ. Am. Chem. Soc.The mixed-ligand complex [Ni(dppp)(p(2)(Ph)N(2)(Bz))](BF4)(2), 3, (whem (P2N2Bz)-N-Ph is 1,5-diBenzyl-3,7-diplienyl-1,5-diaza-3,7-diphosphacyClooctane and dppp is 1, 3-bis(diphenylphosphino)propane) has been synthesized. Treatment of this complex with H-2 and triethylamine results in the formation of the NO complex, Ni(dppp)((P2N2Bz)-N-Ph), 4, whose structure has been determined by a single-crystal X-ray diffraction study. Heterolytic Cleavage of H-2 by 3 at room temperature forms [HNi(dppp)((P2NBz)-N-Ph(mu-H)N-Bz)](BF4)(2), 5a, in which one proton interacts with two nitrogen atoms of the cyClic diphosphine ligand and a hydride ligand is bound to nickel. Two intermediates are observed for this reaction using low-temperature NMR spectroscopy. One species is a dihydride, [(H)(2)Ni(dppp)((P2N2Bz)-N-Ph)](BF4)(2), 5b, and the other is [Ni(dppp) ((P2N2H2)-N-Ph-H-Bz)](BF4)(2), 5c, in which both protons are bound to the N atoms in an endo geometry with respect to nickel. These two species interconvert via a rapid and reversible intramolecular proton exchange between nickel and the nitrogen atoms of the diphosphine ligand. Complex 3 is a catalyst for the electrochemical oxidation of H-2 in Vie presence of base, and new insights into the mechanism derived from low-temperature NMR and thermodynamic studies are presented. A comparison of the rate and thermodynamics of H-2 addition for this complex to related catalysts studied previously indicates that for Ni-II complexes containing two diphosphine ligands, the Activation of H-2 is favored by the presence of two positioned pendant bases.Mechanistic Insights into Catalytic H-2 Oxidation by Ni Complexes Containing a Diphosphine Ligand with a Positioned Amine Basex135200949#N/AFALSE
2001
ja900346k10.1021/ja900346kFALSEhttps://doi.org/10.1021/ja900346kWeckhuysen, BMJ. Am. Chem. Soc.Magnetic resonance imaging (MRI) was used to study the impregnation step during the preparation of Ni/gamma-Al2O3 hydrogenation catalysts with Ni2+ metal ion present in different coordinations. The precursor complexes were [Ni(H2O)(6)](2+) and [Ni(edtaH(x))]((2-x)-) (where x = 0, 1, 2 and edta = ethylenediaminetetraacetic acid), representing a nonshielded and a shielded paramagnetic complex, respectively. Due to this shielding effect of the ligands, the dynamics of [Ni(H2O)(6)](2+) or [Ni(edtaH(X))]((2-x)-) were visualized applying T-2 or T-1 image contrast, respectively. MRI was applied in a quantitative manner to calculate the [Ni(H2O)(6)](2+) concentration distribution after impregnation when it was present alone in the impregnation solution, or together with the [Ni(edtaH(x))]((2-x)-) species. Moreover, the combination of MRI with UV-vis microspectroscopy allowed the visualization of both species with complementary information on the dynamics and adsorption/desorption phenomena within gamma-Al2O3 catalyst bodies. These phenomena yielded nonuniform Ni distributions after impregnation, which are interesting for certain industrial applications.Magnetic Resonance Imaging Studies on Catalyst Impregnation Processes: Discriminating Metal Ion Complexes within Millimeter-Sized gamma-Al2O3 Catalyst Bodiesx34200946#N/AFALSE
2002
ja904301f10.1021/ja904301fFALSEhttps://doi.org/10.1021/ja904301fSiegbahn, PEMJ. Am. Chem. Soc.The formation of methyl-Ni(F-430) species in methyl-coenzyme M reductase (MCR) has been investigated using the B3LYP hybrid density functional method and an active-site model built on the basis of X-ray crystal structure. CH3-I, CH3-Br, CH3-Cl, and CH3-S-CH3 were chosen as the substrates, the last one regarded as a model of the native substrate (methyl-coenzyme M, CH3-SCoM). The calculations indicate that the formation of CH3-Ni(F-430) in MCR is dependent on the acidity of the substrate leaving group. A CH3-Ni(F-430) species has been observed with methyl halides as substrates, while the formation of CH3-Ni(F-430) from the native substrate is demonstrated to be inaccessible energetically. These results agree well with the current experiments.Is There a Ni-Methyl Intermediate in the Mechanism of Methyl-Coenzyme M Reductase?25200917#N/ATRUE
2003
ja903927c10.1021/ja903927cFALSEhttps://doi.org/10.1021/ja903927cOzerov, OVJ. Am. Chem. Soc.DiAlkylalumenium cation equivalents coupled with the hexabromocarborane anion function as efficient and long-lived catalysts for Alkylation of aliphatic C-F bonds (Alkylative defluorination or AlkDF) by Alkylaluminum compounds. Only C(sp(3))-F bonds undergo AlkDF; C(sp(2))-F bonds are unaffected. Examples of compounds undergoing AlkDF inClude monofluoroalkanes, gem-difluorocyClopentane, and compounds containing a CF3 group attached to either an Aryl or an Alkyl substituent. Conversion of C-F bonds to C-Me bonds is accomplished with high fidelity using Me3Al as the stoichiometric reagent. In reactions with Et3Al, hydrodefluorination of the C-F bonds is competitive with Alkylation, indicative presumably of competitive hydride vs Alkyl transfer from Et3Al. In a triAlkylaluminum reagent, 1.1-1.4 Alkyl groups per Al can be used to replace C-F bonds. Organoaluminum compounds efficiently remove water from the reaction mixture, obviating the need for rigorously dry solvents. Some organoaluminum compounds, especially methylaluminoxane, are capable of AlkDF with more reactive substrates, but catalysis by alumenium offers an advantage over the uncatalyzed C-F Activation in terms of both increased rate and, in some cases, a dramatically increased selectivity.Carbon-Carbon Coupling of C(sp(3))-F Bonds Using Alumenium Catalysis111200940#N/ATRUE
2004
ja903550n10.1021/ja903550nFALSEhttps://doi.org/10.1021/ja903550nWarren, THJ. Am. Chem. Soc.Monovalent nickel and copper beta-diketiminato complexes react with ArN=O (Ar = 3,5-Me2C6H3, Ph) to give C-nitroso adducts that exhibit three different modes of bonding with varying degrees of N-O bond Activation. The addition of ArNO to 2 equiv of [Me2NN]Ni(2,4-lutidine) {[Me2NN](-) = 2,4-bis(2,6-dimethylphenylimido)pentyl} gives {[Me2NN]Ni}(2)(mu-eta(2):eta(2)-ONAr) (1a and 1b), which exhibit symmetrical bonding of the ArN=O moiety between two [Me2NN]Ni fragments, with a N-O bond distance of 1.440(4) angstrom in 1a that is significantly longer than those in free C-organonitroso compounds (1.13-1.29 angstrom). [Me2NN]Cu(NCMe) reacts with 0.5 equiv of ArNO in ether to give the dinuClear adducts {[Me2NN]Cu}(2)(mu-eta(2):eta(1)-ONAr) (2a and 2b), which exhibit eta(2) and eta(1) bonding of the ArN=O moiety with separate [Me2NN]Cu fragments possessing N-O distances of 1.375(6) angstrom (2a) and 1.368(2) angstrom (2b). In arene solvents, one beta-diketiminatocopper(I) fragment dissociates from 2 to give [Me2NN]Cu(eta(2)-ONAr) (3a and 3b), which may be isolated by the addition of 1 equiv of ArNO to [Me2NN]Cu(NCMe). The X-ray structures of 3a and 3b are similar to those of related Cu(I) alkene adducts, with N-O distances in the narrow range 1.333(4)-1.338(5) angstrom. IR spectra of the nitrosobenzene, adducts 1b, 2b, and 3b exhibit nu(NO) stretching frequencies at 915, 1040, and 1113 cm(-1), respectively, following the decreasing degree of N=O Activation observed in the X-ray structures of species 1, 2, and 3. Both la and 3a react with anaerobic NO(g) to give the corresponding N-Aryl-N-nitrosohydroxylaminato complexes [Me2NN]M(kappa(2)-O2N2Ar) [M = Ni (4), Cu (5)]. In the reaction of dinuClear 1a with NO, one [Me2NN]Ni fragment is trapped as the nickel nitrosyl [Me2NN]Ni(NO). Reaction of the monovalent complex [Me2NN]Cu(eta(2)-ONAr) with NO(g) to give divalent [Me2NN]Cu(kappa(2)-O2N2Ar) represents an example of oxidative nitrosylation.Nitric Oxide Oxidatively Nitrosylates Ni(I) and Cu(I) C-Organonitroso Adducts47200961#N/ATRUE
2005
ja902968610.1021/ja9029686FALSEhttps://doi.org/10.1021/ja9029686Guldi, DMJ. Am. Chem. Soc.Coordinating different transition metals-manganese(III), iron(III), nickel(II), and copper(II)-by a dendronized porphyrin afforded a new family of redox-active metalloporphyrins to which C-60 was attached as a ground-state electron acceptor. Such a strategy introduced an additional center of redoxactivity, that is, a change of the oxidation state of the metal. CyClic voltammetry and absorption/fluorescence measurements provided support for mutual interactions between the redox-active constituents in the ground state. In particular, slightly anodic shifted reduction potentials/cathodic shifted oxidation potentials and the occurrence of new charge transfer features in the 700-900 nm range prompt to sizable electronic coupling in the range of 300 cm(-1). Photophysical means-steady-state/time-resolved fluorescence and transient absorption measurements-shed light on the excited-state interactions. To this end, we have added pulse radiolytic investigations to characterize the radical cation (i.e., metalloporphyrins) and radical anion (i.e., fullerene) characteristics. pi-pi stacking of the excited state electron donor and the electron acceptor is key to overcome the intrinsically fast deActivation of the excited states in these metalloporphyrins and to power an exothermic charge transfer. The lifetimes of the rapidly and efficiently generated radical ion pair states, which range from 15 to >3000 ps, revealed several important trends. First, they were found to depend on the solvent polarity. Second, the nature of the transition metal plays a similarly decisive role. It is important that the product of charge recombination, namely tripmultiplet excited states versus ground state, had a great impact. Finally, a correlation between the charge transfer rate (i.e., charge separation and charge recombination) and the free energy change for the underlying reaction reveals a parabolic dependence with parameters of the reorganization energy (0.84 eV) and electronic coupling (70 cm(-1)) Closely resembling that seen for the zinc(II) and free base analogues.trans-2 Addition Pattern to Power Charge Transfer in Dendronized Metalloporphyrin C-60 Conjugates34200987#N/ATRUE
2006
ja809552p10.1021/ja809552pFALSEhttps://doi.org/10.1021/ja809552pBaik, MHJ. Am. Chem. Soc.The role of spin state equilibria on the thermodynamics of electron transfer in [M(tacn)(2)](3+/2+) complexes (tacn = 1,4,7-triazacyClononane; M = Cr, Mn, Fe, Co, Ni) was examined using density functional theory at the B3LYP*/cc-pVTZ(-f) level coupled to a continuum solvation model to afford excellent agreement between computed and experimental redox properties. An intuitive explanation of the previously observed nonperiodic trend in reduction potentials, which display a sawtooth pattern along the first-row transition metal series, is offered utilizing a novel diagrammatic illustration of the relationship between spin state energetics and reduction potentials. This representation leads to a generalized proposal for analyzing and designing nearly isoenergetic spin states of transition metals in a given ligand environment. A new ligand specific parameter a that allows for quantifying the differential reduction potential as a function of the metal identity is introduced, and a novel protocol is presented that divides the ligand-metal interactions into primary and secondary characteristics, which we anticipate will be useful for rationally designing the electronics of transition metal complexes in general,Spin Crossover-Coupled Electron Transfer of [M(tacn)(2)](3+/2+) Complexes (tacn=1,4,7-TriazacyClononane; M = Cr, Mn, Fe, Co, Ni)x37200996#N/AFALSE
2007
ja902672710.1021/ja9026727FALSEhttps://doi.org/10.1021/ja9026727Driess, MJ. Am. Chem. Soc.The first silicon(II) hydroxide and related electronically tunable NHSi ligands have been synthesized in the coordination sphere of a [Ni(CO)(3)] moiety through facile addition of water and other electrophiles to the corresponding NHSi-triCarbonylnickel complex. The latter modified silicon (11) ligands are unique and exhibit striking donor/acceptor capabilities depending on their substitution pattern. While strong Lewis acids [H+ or B(C6F5)(3)] lead to modified silicon(II) ligands in the coordination sphere of nickel with an increased pi-acceptor and decreased sigma-donor character (PF3-like), by contrast, addition of water or trifluoromethanesulfonic acid furnishes the corresponding donor-stabilized silicon (II)-nickel complexes with a inverse donor/acceptor strength similar to those of triorganophosphines and NHCs.Diketiminate Silicon(II) and Related NHSi Ligands Generated in the Coordination Sphere of Nickel(0)76200915#N/ATRUE
2008
ja809457s10.1021/ja809457sFALSEhttps://doi.org/10.1021/ja809457sGarcia, JJJ. Am. Chem. Soc.The reactivity of the nickel(I) dimer [(dippe)(2)Ni(mu-H)](2) (1) with biphenyl-2-thiol was explored with the aim of Clarifying the key step of sulfur extrusion during the hydrodesulfurization process using dibenzothiophene (DBT). These reactions were monitored by variable temperature NMR experiments which allowed the complete characterization and isolation of [(dippe)(2)Ni-2(mu-H)(mu-S-2-biphenyl)] (3). The latter compound evolves to the terminal nickel-hydride [(dippe)Ni (eta(1)-C-2-biphenyl)(H)] (4) and transient [(dippe)NiS] (5), to ultimately yield [(dippe)(2)Ni-2(mu-S)] (2) and biphenyl as the resulting HDS products. The reactivity of 1 and biphenyl-2-thiol was examined using different ratios of reactants, which allowed preparation of [(dippe)Ni(eta(1)-S-biphenyl-2-thiolate)(2)] (6) when using an excess of this substrate. The reactivity of 6 with 1 was addressed, yielding compound 2 and an equivalent amount of biphenyl.Mechanistic Insights on the Hydrodesulfurization of Biphenyl-2-thiol with Nickel Compoundsx37200939#N/AFALSE
2009
ja901640m10.1021/ja901640mFALSEhttps://doi.org/10.1021/ja901640mPerutz, RNJ. Am. Chem. Soc.DFT calculations are reported of the energetics of C-H oxidative addition of benzene and fluorinated benzenes, (ArH)-H-F (Ar-F = C6FnH5-n, n = 0-5) at ZrCp2 (Cp = eta(5)-C5H5), TaCp2H, TaCp2Cl, WCp2, ReCp(CO)(2), ReCp(CO)(PH3), ReCp(PH3)(2), RhCp(PH3), RhCp(CO), IrCp(PH3), IrCp(CO), Ni(H2PCH2CH2PH2), Pt(H2PCH2CH2PH2). The change in M-C bond energy of the products fits a linear function of the number of fluorine substituents, with different coefficients corresponding to ortho-, meta-, and para-fluorine. The values of the ortho-coefficient range from 20 to 32 kJ mol(-1), greatly exceeding the values for the meta- and para-coefficients (2.0-4.5 kJ mol(-1)). Similarly, the H-C bond energies of (ArH)-H-F yield ortho- and para-coefficients of 10.4 and 3.4 kJ mol(-1), respectively, and a negligible meta-coefficient. These results indicate a large increase in the M-C bond energy with ortho-fluorine substitution on the Aryl ring. Plots of D(M-C) vs D(H-C) yield slopes RM-C/H-C that vary from 1.93 to 3.05 with metal fragment, all in excess of values of 1.1-1.3 reported with other hydrocarbyl groups. Replacement of PH3 by CO decreases RM-C/H-C significantly. For a given ligand set and metals in the same group of the periodic table, the value of RM-C/H-C does not increase with the strength of the M-C bond. Calculations of the charge on the Aryl ring show that variations in ionicity of the M-C bonds correlate with variations in M-C bond energy. This strengthening of metal-Aryl bonds accounts for numerous experimental results that indicate a preference for ortho-fluorine substituents.Exceptional Sensitivity of Metal-Aryl Bond Energies to ortho-Fluorine Substituents: Influence of the Metal, the Coordination Sphere, and the Spectator Ligands on M-C/H-C Bond Energy Correlations136200980#N/ATRUE
2010
ja809067t10.1021/ja809067tFALSEhttps://doi.org/10.1021/ja809067tPalinkas, GJ. Am. Chem. Soc.We synthesized and structurally characterized the first cyanoaurate-based organotin polymer Me3Sn[Au(CN)(2)] (1), which exhibits unusual ion-exchange properties. In the structure of 1, the void space of the 2D grids formed via Au center dot center dot center dot Au bonding is filled by arrays of zigzag chains joined by weak Au center dot center dot center dot Au interactions. Interestingly, the practically insoluble polymer I shows unusual ion-exchange properties. The polymer Me2Sn[Au(CN)(2)](2) (2) was obtained in the metathesis reaction of 1 with Me2SnCl2. Compound 2 displays cyanide-bridged uninodal four-connected 3D nets with 6(5).8 topology corresponding to the CdSO4 prototype. Interestingly, 2 can be converted back into 1 by metathesis with Me3SnCl. Moreover, we performed a series of metal.-exchange experiments in which I was soaked in aqueous solutions of bivalent transition-meta[ cations M2+ (M = Co, Ni, Cu, Zn). As a result, 1 was completely converted into transition-metal cyanoaurates. To our knowledge, this represents the first study revealing the metal-exchange properties of a cyanoaurate-based heterometallic polymer.Synthesis and Structure of a Cyanoaurate-Based Organotin Polymer Exhibiting Unusual Ion-Exchange Propertiesx36200935#N/AFALSE
2011
ja901522a10.1021/ja901522aFALSEhttps://doi.org/10.1021/ja901522aIllas, FJ. Am. Chem. Soc.Photoemission and first-principles DF calculations were used to study the interaction of thiophene with TiC(001) and Au/TiC(001) surfaces. The adsorption strength of thiophene on TiC(001) is weak, and the molecule desorbs at temperatures below 200 K. The molecule binds to Ti centers of TiC(001) through its sulfur atom with negligible structural perturbations. In spite of the very poor desulfurization performance of TiC(001) or Au(111), a Au/TiC(001) system displays a hydrodesulfurization activity higher than that of conventional Ni/MoS(x) catalysts. The Au <-> TiC(001) interactions induce a polarization of electron density around Au which substantially increases the chemical reactivity of this metal. Au nanopartiCles drastically increase the hydrodesulfurization activity of TiC(001) by enhancing the bonding energy of thiophene and by helping in the dissociation of H(2) to produce the hydrogen necessary for the hydrogenolysis of C-S bonds and the removal of sulfur. H(2) spontaneously dissociates on small two-dimensional Clusters of gold in contact with TiC(001). On these systems, the adsorption energy of thiophene is 0.45-0.65 eV larger than that on TiC(001) or Au(111). Thiophene binds in a eta(5) configuration with a large elongation (similar to 0.2 angstrom) of the C-S bonds.Desulfurization of Thiophene on Au/TiC(001): Au-C Interactions and Charge Polarization67200978#N/ATRUE
2012
ja808974710.1021/ja8089747FALSEhttps://doi.org/10.1021/ja8089747Cundari, TRJ. Am. Chem. Soc.Application of the dipyridylazaallyl ligand (2-py)CHNCH(2-py) (smif) to a series of first-row transition metals afforded (smif)(2)M-n [n = 0, M = Fe (1), Co (2), Ni (3); n = +1, M = CO (2+)] and {(TMS)(2)NFe}(2)(smif)(2) (4(2)) via metathetical procedures. The Mossbauer spectrum of 1 (S = 0) and TDDFT calculations, inCluding a UV-vis spectral. simulation, reveal it to be a covalent, strong-field system with Delta(o) estimated as similar to 18000 cm(-1) and B = 470 cm(-1). (smif)(2)Co (2) has S = 1/2 according to SQUID data at 10 K. DFT calculations suggest that the odd electron is localized in a smif Pi* orbital, i.e., smif is redox-active. EPR-silent (smif)(2)Ni (3) has S = 1 (SQUID), and calculations show that the unpaired spins reside in the d(z)(2) and d(x)(-y)(2)(2) orbitals. X-ray structural parameters suggest that low-spin d(6) 1 and 2+ are relatively symmetric D-2d species, but 2 and 3 manifest a distortion in which one smif is canted in the plane perpendicular to the other. (smif)FeN(TMS)(2) (4) is principally monomeric in solution, but reversibly dimerizes (K-eq approximate to 10(-4) M-1) via C-C bond formation in the azaallyl, backbone to crystallize as {(TMS)(2)NFe}(2)(smif)(2) (4(2)). The azaallyl compounds possess extraordinary UV-vis absorptivities (epsilon = 18000-52000) at 580 +/- 15 nm and 406(25) nm that have been identified as intraligand bands with C-nb -> smif Pi* character.Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)(2)M [M = Fe, Co, Co+, Ni; smif = {(2-py)CH}(2)N] and [(TMS)(2)NFe](2)(smif)(2)x59200914#N/AFALSE
2013
ja808964e10.1021/ja808964eFALSEhttps://doi.org/10.1021/ja808964eProsser, RSJ. Am. Chem. Soc.Oxygen and Ni(II) are ideal paramagnetic species for NMR studies of immersion depth since they establish prominent concentration gradients across the membrane-water interface of either bilayers or micelles. Corresponding gradients of paramagnetic shifts and relaxation rates are observed by NMR for membrane embedded amphiphiles. Specifically, Upon dissolution of oxygen at a partial pressure of 20 bar or more, C-13 NMR spectra of membrane embedded amphiphiles reveal chemical shift perturbations which depend sensitively on average immersion depth in the membrane. Similarly, depth-dependent enhancements of spin-lattice relaxation rates can be detected by H-1 NMR. Generally, such paramagnetic effects depend both on steric or accessibility factors and on the local concentration of the paramagnet. The steric terms can be factored out by combining paramagnetic rates arising from O-2 and Ni, in the form of a ratio, R-1P(O-2)/R-1P(Ni). The natural logarithm of this ratio is shown to depend linearly on immersion depth in a micelle. The analysis is verified using molecular dynamics simulations of dodecylphosphocholine in a detergent micelle, while thorough consideration of the paramagnetic rate data also allows for the determination of the orientation of imipramine in the micelle. Thus, a complete picture of topology arises from this approach which is readily applicable to studies of drugs and amphiphiles in fast-tumbling bicelles, small unilamellar vesiCles, and micelles.A Solution NMR Approach to the Measurement of Amphiphile Immersion Depth and Orientation in Membrane Model Systemsx26200955#N/AFALSE
2014
ja808855v10.1021/ja808855vhttps://doi.org/10.1021/ja808855vMecking, SJ. Am. Chem. Soc.The novel dimethyl sulfoxide (DMSO)-coordinated complex [(N,O)Ni(CH3)(DMSO)] {1-DMSO; (N,O) = kappa(2)-N,O(2,6-(3,5-(F3C)(2)C6H3)(2)C6H3)-N=CH-(3,5-l(2)-2-OC6H2)} was found to be a well-defined, very reactive precursor that enables direct observation of the Activation and deActivation of neutral Ni(II) catalysts. Preparative reaction with ethylene afforded the ethyl complex [(N,O)Ni((CH2CH3)-C-alpha-C-beta)(DMSO)] (2-DMSO). 2-DMSO is subject to interconversion of the C-alpha and C-beta moieties via an intermediate [(N,O)Ni(II)H(ethylene)] complex (this process is slow on the NMR time scale). Exposure of 1-DMSO to ethylene in DMSO solution at 55 degrees C results in partial reaction to form propylene (pseudo-first-order rate constant k(ins,Me) = 6.8 +/- 0.3 x 10(-4) s(-1) at an ethylene concentration of 0.15 M) and conversion to 2-DMSO, which catalyzes the conversion of ethylene to butenes. A relevant decomposition route of the catalyst precusor is the bimolecular elimination of ethane [Delta H-double dagger = (57 +/- 1) kJ mol(-1) and Delta S-double dagger = -(129 +/- 2) J mol(-1) K-1 over the temperature range 55-80 degrees C). This reaction is specific to the Ni(II)-Me complex; corresponding homocoupling of the higher Ni(II)-Alkyls of the propagating species in catalytic C-C linkage of ethylene was not observed, but Ni(II)-Me reacted with Ni(II)-Et to form propane, as conCluded from studies with 2-DMSO and its analogue that is perdeuterated in the Ni(II)-Et moiety. Under the reaction conditions of the aforementioned catalytic C-C linkage of ethylene, additional ethane evolves from the reaction of intermediate Ni(II)-Et with Ni(II)-H. This is independently supported by reaction of 2-DIMSO with the separately prepared hydride complex [(N,O)NiH(PMe3)] (3-PMe3) to afford ethane. Kinetic studies show this reaction to be bimolecular [Delta H-double dagger = (47 +/- 6) W mol(-1) and Delta S-double dagger = -(117 +/- 15) J mol(-1) K-1 over the temperature range 6-35 degrees C]. In contrast to these reactions identified as decomposition routes, hydrolysis of Ni(II)-Alkyls by added water (D2O; H2O) occurred only to a minor extent for the Ni(II)-Me catalyst precursor, and no Clear evidence of hydrolysis was observed for higher Ni(II)-Alkyls. The rate of the aforementioned insertion of ethylene in 1-DMSO and the rate of catalytic ethylene dimerization are not affected by the presence of water, indicating that water also does not compete significantly with the substrate for binding sites.DeActivation Pathways of Neutral Ni(II) Polymerization Catalystsx82200972#N/AFALSE
2015
ja808784s10.1021/ja808784sFALSEhttps://doi.org/10.1021/ja808784sYang, SHHydrazine-Linked Convergent Self-Assembly of Sophisticated Concave Polyhedrons of beta-Ni(OH)(2) and NiO from Nanoplate Building Blocksx2009#N/AFALSE
2016
ja808648310.1021/ja8086483FALSEhttps://doi.org/10.1021/ja8086483Mashuta, MSJ. Am. Chem. Soc.The influence of oxidation state on the reversibility of carbon-sulfur bond forming reactions between ethylene and [Re(DPPBT)(3)](n+) (n = 0, +1, +2; DPPBT = 2-diphenylphosphinobenzenethiolate) has been investigated. For the neutral complex [Re(DPPBT)(3)], no reaction with ethylene is spectroscopically detectable consistent with the determined equilibrium constant, K(1), of (1.9 +/- 0.4) x 10(-11) M(-1). Oxidation by one electron to [Re(DPPBT)(3)](+) yields a stable complex that rapidly and reversibly binds ethylene with electrochemically determined constants of k(f) = (1.2 +/- 0.2) x 10(-1) M(-1) s(-1), k(r) = (3.0 +/- 0.4) x 10(-2) s(-1), and K(2) = 4.0 +/- 0.8 M(-1). C-S bond formation/Cleavage can be regulated by ethylene concentration, and the system is stable to multiple cyCles of nitrogen/ethylene purges. Further oxidation to the dication in the presence of ethylene by chemical or electrochemical methods stabilizes the C-S bond, K(3) = (2.5 +/- 0.9) x 10(9) M(-1), and the dithioether product has been characterized by X-ray crystallography. The large differences in K as a function of charge permit the controlled binding and release of ethylene as a function of applied potential.Redox-Regulated Ethylene Binding to a Rhenium-Thiolate Complexx31200922#N/AFALSE
2017
ja901360b10.1021/ja901360bhttps://doi.org/10.1021/ja901360bMecking, SJ. Am. Chem. Soc.The Ni(II) complexes [(N boolean AND O)Ni(H)(PMe3)] (1) and [(N boolean AND O)Ni(CH2CH3)(dmso)] (3) (N boolean AND O = kappa(2)-{(2,6-(3,5-(F3C)(2)C6H3)(2)C6H3)-N=C(H)-(3,5-l(2)-2-O-C6H2)}) were found to be well-defined model compounds to study the reactivity of polymerization active neutral Ni(II) species toward polar Vinyl monomers. Methyl acrylate (MA) insertion into the Ni(II)-hydride bond of 1 was monitored at T >= -40 degrees C by NMR spectroscopy. 2,1-Insertion yields the functionalized Ni(II) Alkyl complex [(N boolean AND O)Ni(C alpha H(CH3)C-beta(O)OCH3)(PMe3)] (4). Low-temperature 2D ROESY data indicate a weak Ni(II)center dot center dot center dot O=C-beta interaction in 4. This is supported by ab initio calculations at the gradient-corrected DFT (BP86/LACPV*) level of theory. Exposure of 1 to equal amounts of MA and ethylene afforded 4 and the Ni(II) ethyl complex 7 in a 9:1 ratio, which indicates that MA and ethylene effectively compete with each other for coordination and insertion. NMR spectroscopic monitoring revealed that 4 is stable in the absence of residual 1 at low temperatures but is subject to rapid bimolecular elimination of the functionalized Alkyl moiety in the presence of free Ni(II) hydride species even at T = -40 degrees C. Isomerization into the 1,2-MA-insertion product was observed at T = 25 degrees C but occurred slowly compared to decomposition, which occurs at 0 degrees C by reaction of 4 with Ni(II) hydride formed by beta-elimination from 4 itself at this temperature. Exposure of the higher Ni(II) Alkyl complex 3 to MA in the presence of excess ethylene results in the immediate formation of methyl pentanoate as the ultimate decomposition product. Functionalized Ni(II) Alkyl species formed from 2,1-insertion of MA into the metal-carbon bond of higher Ni(II) Alkyls are subject to rapid hydrolysis in the presence of trace amounts of water in. the reaction medium, which contrasts the stability of nonfunctionalized Ni(II) Alkyls toward water. Exposure of 1 to Vinyl acetate (VA) affords the kinetic 1,2-insertion product [(N boolean AND O)Ni(CH2CH2OC gamma'(O)CH3)(PMe3)] (5) at temperatures T >= -10 degrees C, which rearranges into the thermodynamically favored 2,1-insertion product [(N boolean AND O)Ni(CH(CH3)OC(O)CH3)(PMe3)] (6). NMR data and ab initio calculations suggest a Ni(II)center dot center dot center dot O=C-gamma' interaction in 6. 5 decomposes via beta-acetate elimination to yield ethylene and Ni(II) acetate species. Notably, VA does not undergo observable nickel-carbon bond insertion with 3, but reacted with Ni(II) hydride species in equilibrium with 3 to yield 5* which is subject to rapid decomposition via beta-acetate elimination.Mechanistic Insights on the Copolymerization of Polar Vinyl Monomers with Neutral Ni(II) Catalysts50200977#N/ATRUE
2018
ja808149k10.1021/ja808149kFALSEhttps://doi.org/10.1021/ja808149kWieghardt, KJ. Am. Chem. Soc.The four-coordinate heteroleptic complex [Fe-III((F)pda(2-))((F)dad(*-))] (1) and its homoleptic analogue [Fe-II((F)dad(*-))2] (2), where (F)pda(2-) is the Closed-shell ligand N,N'-bis(pentafluorophenyl)-o-phenylenediamide(2-) and (F)dad(*-) is the singly reduced N,N'-bis(pentafluorophenyl)-2,3-dimethyl-1,4-diazabutadiene pi-radical anion, have been synthesized. X-ray crystallographic studies reveal a twisted tetrahedral geometry of the FeN4 coordination polyhedron in both 1 and 2. The electronic structures of 1 and 2 were probed by magnetic susceptibility measurements, Fe-57 Mossbauer and electronic spectroscopy, and density functional theory (DFT) calculations. In spite of their similar geometries and a common triplet ground state (S-t = 1), the electronic structures of 1, 2, and the previously reported homoleptic analogue [Fe-III((F)pda(2-))((F)pda(*-))] (3), where (F)pda(*-) is a one-electron-oxidized form of (F)pda(2-), differ. The electronic structure of 2 consists of two (F)dad(*-) radicals coupled antiferromagnetically to a high-spin Fe-II center, whereas in 3, only one (F)pda(*-)radical is coupled antiferromagnetically to an intermediate-spin Fe-III ion. This ligand mixed-valent species exhibits Class-III behavior. Heteroleptic 1 contains a single (F)dad(*-) radical coupled antiferromagnetically to an intermediate-spin Fe-III center but behaves as a Class-II ligand mixed-valent species. The observed diversity in the electronic structures of 1-3 is ascribed to the difference in the redox potentials of the ligands. Analysis of reduced orbital charges and spin densities obtained from DFT calculations also suggests that the electronic structures of 1-3 are best described as either a high-spin Fe-II ion coordinated to two radical monoanions (2) or as an intermediate-spin Fe-III ion coordinated to one radical monoanion and one Closed-shell dianion (1, 3).Tuning the Oxidation Level, the Spin State, and the Degree of Electron Delocalization in Homo- and Heteroleptic Bis(alpha-diimine)iron Complexesx812009119#N/AFALSE
2019
ja808139510.1021/ja8081395FALSEhttps://doi.org/10.1021/ja8081395Saliba, MJ. Am. Chem. Soc.The reaction of (PEt(3))(2)Ni(eta(2)-C(14)H(10)), a source of the reactive Ni(PEt(3))(2) moiety, with 1,2,4,5-F(4)C(6)H(2) yields a mixture of three C-F bond Activation products that inClude the unexpected products (PEt(3))(2)NiF-2,3,5,6-F(4)C(6)H and (PEt(3))(2)NiF-2,3,5-F(3)C(6)H(2). Monitoring the reaction mixture via (19)F and (1)H NMR also reveals the presence of the C-H bond Activation product, (PEt(3))(2)NiH-2,3,5,6-F(4)C(6)H which is produced in a rapid equilibrium reaction, This observation provides insight into the steps necessary to modify nickel complexes for selective C-F bond Activation in a variety of polyfluorinated aromatic substrates, but also expands the potential of simple nickel compounds for C-H bond Activation and functionalization reactions.Unexpected Intermediates and Products in the C-F Bond Activation of Tetrafluorobenzenes with a Bis(triethylphosphine)Nickel Synthon: Direct Evidence of a Rapid and Reversible C-H Bond Activation by Ni(0)x94200840#N/AFALSE
2020
ja900876w10.1021/ja900876wFALSEhttps://doi.org/10.1021/ja900876wSuginome, MJ. Am. Chem. Soc.The C-H bond of triisopropylsilylacetylene adds to the C=C bond of substituted methylenecyClopropanes in a regio- and stereoselective manner at room temperature in the presence of nickel catalysts bearing PMePh2. The C-C bond formation takes place at the internal sp(2) carbon atom with high regioselectivity from the pi face opposite the substituents located in the three-membered rings.Nickel-Catalyzed, Regio- and Stereoselective Hydroalkynylation of MethylenecyClopropanes with Retention of the CyClopropane Ring, Leading to the Synthesis of 1-Methyl-1-AlkynylcyClopropanes63200925#N/ATRUE
2021
ja900805y10.1021/ja900805yFALSEhttps://doi.org/10.1021/ja900805yMatsubara, SJ. Am. Chem. Soc.An intermolecular nickel-catalyzed addition reaction in which isatoic anhydrides react with alkynes to afford substituted quinolones has been developed. A mechanistic rationale is proposed, implying oxidative addition of Ni(0) to a carbamate, which allows intermolecular addition to alkynes via deCarbonylation.Nickel-Catalyzed DeCarbonylative Carboamination of Alkynes with Isatoic Anhydrides112200930#N/ATRUE
2022
ja900701g10.1021/ja900701gFALSEhttps://doi.org/10.1021/ja900701gHouk, KNJ. Am. Chem. Soc.The mechanism of nickel-catalyzed reductive alkyne-aldehyde coupling reactions has been investigated using density functional theory. The preferred mechanism involves oxidative cyClization to form the nickeladihydrofuran intermediate followed by transmetalation and reductive elimination. The rate- and selectivity-determining oxidative cyClization transition state is analyzed in detail. The d -> Pi*(perpendicular to) back-donation stabilizes the transition state and leads to higher reactivity for alkynes than alkenes. Strong Lewis acids accelerate the couplings with both alkynes and alkenes by coordinating with the aldehyde oxygen in the transition state.Mechanism and Transition-State Structures for Nickel-Catalyzed Reductive Alkyne-Aldehyde Coupling Reactions76200931#N/ATRUE
2023
ja900257k10.1021/ja900257khttps://doi.org/10.1021/ja900257kMarks, TJJ. Am. Chem. Soc.The synthesis and characterization of the bimetallic 2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato group 10 metal polymerization catalysts {[Ni(CH3)](2)[1,8-(O)(2)C10H4-2,7-[CH=N(2,6-(Pr2C6H3)-Pr-i)](PMe3)(2)} and {[Ni(1-naphthyl)](2)[1,8-(O)(2)C10H4-2,7-[CH=N(2,6-(Pr2C6H3)-Pr-i)](PPh3)(2)} [FI2-Ni-2(PR3)(2)] are presented, along with the synthesis and characterization of the mononuClear analogues [Ni(CH3)[3-Bu-t-2-(O)C6H3CH=N(2,6-(Pr2C6H3)-Pr-i)](PMe)(3)} and (Ni(1-naphthyl)[3-Bu-t-2-(O)C6H3CH=N(2,6-(Pr2C6H3)-Pr-i)](PPh)(3)} [FI-Ni (PR3)]. Monometallic Ni catalysts were also prepared by functionalizing one ligation center of the bimetallic ligand with a trimethylsilyl group (TMS), yielding {Ni(CH3)[1,8-(O)(TMSO)C10H4-2,7-[CH=N(2,6-(Pr2C6H3)-Pr-i)](PMe3)} [TMS-FI2-Ni(PMe3)]. The FI2-Ni-2 catalysts exhibit significant increases in ethylene homopolymerization activity versus the monometallic analogues, as well as increased branching and methyl branch selectivity, even in the absence of a Ni(cod)(2) cocatalyst. Increasing ethylene concentrations significantly suppress branching and alter branch morphology. FI2-Ni-2-mediated copolymerizations with ethylene + polar-functionalized norbornenes exhibit a 4-fold increase in comonomer incorporation versus FI-Ni, yielding copolymers with up to 10% norbornene copolymer incorporation. FI2-Ni-2-catalyzed copolymerizations with ethylene + methylacrylate or methyl methacrylate incorporate up to 11% acrylate comonomer, while the corresponding mononuClear FI-Ni catalysts incorporate negligible amounts. Furthermore, the FI2-Ni-2-mediated polymerizations exhibit appreciable polar solvent tolerance, turning over in the presence of ethyl ether, acetone, and even water. The mechanism by which the present cooperative effects take place is investigated, as is the nature of the copolymer microstructures; produced.RETRACTED: Bimetallic Effects for Enhanced Polar Comonomer Enchainment Selectivity in Catalytic Ethylene Polymerization (Retracted artiCle. See vol. 135, pg. 17651, 2013)1012009114#N/ATRUE
2024
ja900146u10.1021/ja900146uFALSEhttps://doi.org/10.1021/ja900146uFukuzawa, SJ. Am. Chem. Soc.The first highly selective 1:2 cross-trimerization between triisopropylsilytacetylene and 2 equiv of internal alkynes, leading to 1,3-diene-5-yne compounds, was achieved using the Ni(cod)(2)/(PPr3)-Pr-n catalyst. Various symmetrical and asymmetrical internal alkynes could be used for the cross-trimerization reaction with high regio- and stereoselectivity.Nickel-Catalyzed Highly Regio- and Stereoselective Cross-Trimerization between Triisopropylsilylacetylene and Internal Alkynes Leading to 1,3-Diene-5-ynes40200923#N/ATRUE
2025
ja807000a10.1021/ja807000aFALSEhttps://doi.org/10.1021/ja807000aNakamura, EJ. Am. Chem. Soc.Mechanistic studies of the Ni-catalyzed cross-coupling reaction of Grignard reagents through analysis of kinetic isotope effects and theoretical calculations indicated that the product-to-substrate ligand exchange process is the first irreversible step and affects the turnover efficiency and selectivity of the reaction. On the other hand, the oxidative addition step is the first irreversible step in Pd catalysis. This finding has useful implications for the development of efficient Ni catalysis and also illustrates the importance of the catalyst turnover step that has so far received less attention than subsequent catalytic steps.Ligand Exchange as the First Irreversible Step in the Nickel-Catalyzed Cross-Coupling Reaction of Grignard Reagentsx94200817#N/AFALSE
2026
ja806660f10.1021/ja806660fFALSEhttps://doi.org/10.1021/ja806660fGirolami, GSJ. Am. Chem. Soc.Mossbauer, EPR, magnetic susceptibility, and DFT studies of the unusual two-coordinate iron(II) amide Fe[N(t-Bu)(2)](2) show that it retains a linear N-Fe-N framework due to the nonbonding delta nature of the (xy, x(2)-y(2)) orbitals. The resulting near-degenerate ground state gives rise to a large magnetic moment and a remarkably large internal hyperfine field. The results confirm that extraordinary orbital magnetic effects can arise in linear transition metal complexes in which orbital degeneracies are not broken by Jahn-Teller or Renner-Teller distortions.Consequences of a Linear Two-Coordinate Geometry for the Orbital Magnetism and Jahn-Teller Distortion Behavior of the High Spin Iron(II) Complex Fe[N(t-Bu)(2)](2)x73200925#N/AFALSE
2027
ja900069510.1021/ja9000695FALSEhttps://doi.org/10.1021/ja9000695Tezcan, FAJ. Am. Chem. Soc.We previously devised a strategy (metal-directed protein self-assembly, MDPSA) that utilizes the simultaneous stability, lability, and directionality of metal-ligand bonds to drive protein-protein interactions. Here we show that both the structural and functional scopes of MDPSA can be broadened by incorporation of non-natural metal-chelating ligands onto protein surfaces. A cytochrome cb(562) variant, MBP-Phen1, which features a covalently attached phenanthroline (Phen) group on its surface, self-assembles into an unusual triangular architecture (Ni-3:MBP-Phen1(3)) upon binding Ni as a result of specific Phen-protein interactions. The crystal structure of Ni-3:MBP-Phen1(3) reveals that the Phen group is buried in a small pocket on the protein surface, which results in an unsaturated Ni coordination environment.A Superprotein Triangle Driven by Nickel(II) Coordination: Exploiting Non-Natural Metal Ligands in Protein Self-Assembly51200911#N/ATRUE
2028
ja809580b10.1021/ja809580bFALSEhttps://doi.org/10.1021/ja809580bDeGrado, WFJ. Am. Chem. Soc.The de novo design of molecular switching peptiCles is of increasing interest because it tests and extends our fundamental understanding of this process while laying the groundwork for the creation of new chemical and biological sensors. Here, an alpha-helical amphiphilic cell-lytic peptide, mastoparan X, was engineered to bind divalent cations. Binding of Zn(II) or Ni(II) to the designed peptide Mst-HH stabilizes the lytic amphiphilic structure and increases the activity of the peptide. Although both Zn(II) and Ni(II) activate Mst-HH for membrane lysis, they appear to do so via different mechanisms. Additionally, a series of metal binding-site mutants were synthesized to assess the relationship of charge and helical propensity to the toxicity and switchability. Additionally, by changing the characteristics of the metal-binding ligands, we can vary the selectivity of the site.Metal-Binding Dependent Disruption of Membranes by Designed Helices26200935#N/ATRUE
2029
ja809542r10.1021/ja809542rFALSEhttps://doi.org/10.1021/ja809542rAmorelli, BJ. Am. Chem. Soc.A total synthesis of the mitochondrial complex I inhibitor piericidin A1 is described. It features a unique strategy for the key disconnection, highlighting a modified Negishi carboalumination/Ni-catalyzed cross-coupling on a polyenyne precursor.Total Synthesis of Piericidin A1. Application of a Modified Negishi Carboalumination-Nickel-Catalyzed Cross-Coupling52200919#N/ATRUE
2030
ja809291e10.1021/ja809291eFALSEhttps://doi.org/10.1021/ja809291eLinic, SJ. Am. Chem. Soc.Identifying structure-performance relationships is critical for the discovery and optimization of heterogeneous catalysts. Recent theoretical contributions have led to the development of Cl-band theory, which relates the calculated electronic structure of a metal to its chemical and catalytic activity. While there are many contributions where quantum-chemical calculations have been utilized to validate the Cl-band theory, experimental examples relating the electronic structures of commercially relevant nonmodel catalysts to their performance are lacking. We show that even small changes in the near-Fermi-level electronic structures of, nonmodel supported catalysts, induced by the formation of surface alloys, can be measured and related to the chemical and catalytic performance of these materials. We demonstrate that critical shifts in the Cl-band center in alloys are related to the formation of new electronic states in response to alloying rather than to charge redistribution among constitutive alloy elements, i.e., the number of d holes and d electrons localized on the constitutive alloy elements is constant. On the basis of the presented results, we provide a simple, physically transparent framework for predicting shifts in the Cl-band center in response to alloying and relating these shifts to the chemical characteristics of the alloys.Measuring and Relating the Electronic Structures of Nonmodel Supported Catalytic Materials to Their Performance82200936#N/ATRUE
2031
ja808989410.1021/ja8089894FALSEhttps://doi.org/10.1021/ja8089894Fujita, MJ. Am. Chem. Soc.Encapsulation by synthetic hosts can transform the spin states of square planar Ni(II)(acen) and Co(II)(tap) complexes. Upon encapsulation, the red Ni(II) diamagnetic state was converted into a green paramagnetic state, whereas the Co(II) low spin (S = 1/2) state was changed into a coupled (S = 1/2 and S = 3/2) state. The host cages are noninnocent and host-guest interactions within the confined cavity influence the resultant properties of the enClathrated metal complexes.Spin Crossover by Encapsulation107200916#N/ATRUE
2032
ja808430210.1021/ja8084302FALSEhttps://doi.org/10.1021/ja8084302Erker, GJ. Am. Chem. Soc.Treatment of the bis-acetyliCle zirconocene complexes (RCP)(2)Zr(C C-SiMe3)(2) (8a, R = CH3; 8b, R = tert-butyl) with HB(C6F5)(2) results in the formation of the five-membered organometallic zirconacyCloallenoid products (9a, 9b). Both were characterized by X-ray diffraction, and the special bonding features of 9a were studied by DFT calculation. The overall reaction was followed by NMR experiments at variable temperature. Starting from 8a the reaction proceeds by alkynyl abstraction to give a zwitterionic [(MeCP)(2)ZrC C-SiMe3](+)[eta-(Ar2B)-B-F(H)C C-SiMe3](-) intermediate (12a), single crystals of which were obtained at -30 degrees C for characterization by X-ray diffraction, followed by a 1,1-hydrB(OH)2ration/sigma-ligand coupling sequence to give the new five-membered zirconacyCloallenoid product 9a.Five-Membered ZirconacyCloallenoids: Synthesis and Characterization of Members of a Unique Class of Internally Metal-Stabilized Bent Allenoid Compounds662009213#N/ATRUE
2033
ja805296k10.1021/ja805296kFALSEhttps://doi.org/10.1021/ja805296kZhou, QLJ. Am. Chem. Soc.A highly efficient nickel-catalyzed asymmetric Alkylative coupling of alkynes, aldehydes, and dimethylzinc has been realized by using bulky spirobiindane phosphoramidite ligands, affording allylic alcohols with a tetrasubstituted olefin functionality in high yields, high regioselectivities, and excellent enantioselectivities.Nickel-Catalyzed Enantioselective Alkylative Coupling of Alkynes and Aldehydes: Synthesis of Chiral Allylic Alcohols with Tetrasubstituted Olefinsx84200827#N/AFALSE
2034
ja805276p10.1021/ja805276pFALSEhttps://doi.org/10.1021/ja805276pLee, JLJ. Am. Chem. Soc.We report the room-temperature ferromagnetism in transition metals (Co, Ni)-doped 8-hydroxy-quinoline aluminum (Alq(3)) by thermal coevaporation of high purity metal and Alq(3) powders. For 5% Co-doped Alq(3), a maximum magnetization of similar to 0.33 mu(B)/Co at 10 K was obtained and ferromagnetic behavior was observed up to 300 K. The Co atoms interact chemically with 0 atoms and provide electrons to Alq(3), forming new states acting as electron trap sites. From this, it is suggested that ferromagnetism may be associated with the strong chemical interaction of Co atoms and Alq(3) molecules.Electronic structure and magnetism in transition metals doped 8-hydroxy-ouinoline aluminumx26200820#N/AFALSE
2035
ja808099u10.1021/ja808099uFALSEhttps://doi.org/10.1021/ja808099uPurrello, RJ. Am. Chem. Soc.The anionic nickel(II) porphyrin NiTPPS is able to selectively sense the spermine induced left-handed Z-form of DNA while it is completely silent in the presence of right-handed B-DNA. Interactions between the DNA and the porphyrin can be easily modulated by pH and temperature. The resulting Z-DNA-porphyrin-spermine complex behaves as a supramolecular reversible information storage system and as a reversible AND logic gate.Interactions of a Tetraanionic Porphyrin with DNA: from a Z-DNA Sensor to a Versatile Supramolecular Device97200923#N/ATRUE
2036
ja805094j10.1021/ja805094jFALSEhttps://doi.org/10.1021/ja805094jJacobsen, ENJ. Am. Chem. Soc.The enantioselective, intramolecular Arylcyanation of unactivated olefins via C-CN bond Activation has been accomplished using a Ni (0) catalyst and BPh3 co-catalyst. High enantioselectivities are achieved using TangPHOS as a chiral ligand. This method allows the generation of two new C-C bonds and one new quaternary carbon stereogenic center in a single synthetic step, converting readily available benzonitrile substrates into 1,1-disubstituted indanes in 49-85% yield and 92-97% ee.Asymmetric intramolecular Arylcyanation of unactivated Olefins via C-CN bond Activationx163200825#N/AFALSE
2037
ja808023y10.1021/ja808023yFALSEhttps://doi.org/10.1021/ja808023yFeng, XMJ. Am. Chem. Soc.Highly enantioselective Carbonyl-ene reaction of glyoxal derivatives and glyoxylate with various alkenes was accomplished using a novel nickel (II)-N,N'-dioxide complex under mild conditions, which facilitated the asymmetric synthesis of biologically interesting a-hydroxy Carbonyl compounds. Various aromatic, aliphatic, and Het glyoxal derivatives, as well as glyoxylate, could be tolerated in this system and afforded the corresponding adducts in excellent enantioselectivities (97->99% ee) with high yields. Moreover, the catalyst loading could even be decreased to 1 mol%, while the enantioselectivity was basically maintained.Asymmetric Carbonyl-Ene Reaction Catalyzed by Chiral N,N '-Dioxide-Nickel(II) Complex: Remarkably Broad Substrate Scope104200844#N/ATRUE
2038
ja804999610.1021/ja8049996FALSEhttps://doi.org/10.1021/ja8049996Yamaguchi, MJ. Am. Chem. Soc.In the presence of a catalytic amount of RhH(PPh3)(4) and 1,2-bis (diphenylphosphino)benzene, an aromatic fluoride, an organic disulfide (0.5 equiv), and triphenylphosphine (0.5 equiv) reacted in refluxing chlorobenzene to give an Aryl sulfide in high yield. Since triphenylphosphine trapped fluoride atoms forming phosphine difluoride, both organothio groups of the disulfide reacted effectively, and the fluoride substituent reacted more readily than the chloride and bromide. The reaction of hexafluorobenzene and a diAryl disulfide gave 1,4-diArylthio-2,3,5,6-tetrafluorobenzene, 1,2,4,5-tetraArylthio-3,6-difluorobenzene, and hexaArylthiobenzene in a stepwise manner; pentafluorobenzene gave 1-arthio-2,3,5,6-tetrafluorobenzene; 1,2,3,4-tetrafluorobenzene gave 1,2-diArylthio-3,6-difluorobenzene; and 1,2,4,5-tetrafluorobenzene gave 1,4-diArylthio-2-5-difluorobenzene. The polyArylthiolation reaction of polyfluorobenzenes exhibited a strong tendency to form 1,4-difiuorobenzenes.Rhodium-catalyzed substitution reaction of Aryl fluorides with disulfides: p-orientation in the polyArylthiolation of polyfluorobenzenesx162200836#N/AFALSE
2039
ja804685u10.1021/ja804685uFALSEhttps://doi.org/10.1021/ja804685uKurmoo, MJ. Am. Chem. Soc.The magnetic properties and magnetic structures from neutron diffraction of two synthetic natrochalcites, NaM2II(H3O2)(MoO4)(2), M = CO (1Co) or Ni (2Ni), are reported. They are isostructural (monoClinic C2/m) and consist of chains of edge-shared MO6 octahedra connected by mu-O from H3O2- and MoO42-. These chains form a three-dimensional network with O-H-O, O-Mo-O, and O-Na-O bridging 4, 3, and 4 metal ions, respectively. Both compounds behave as canted antiferromagnets but differ in their behaviors, 1Co showing a broad maximum (28 K) above the Neel transition (21 K) and the canting taking place at 13 K, some 8 K below T-N, while for 2Ni the canting takes place at T-N (28 K). Analyses of the neutron powder diffraction data shed some light on the geometry of D3O2- and suggest antiferromagnetism with a propagation vector k = (0,0,0) with the moments within each chain being parallel but antiparallel to those in neighboring chains. The difference between 1Co and 2Ni is in the orientation of the moments; they are parallel to the chain axis (b-axis) for 1Co and perpendicular to it for 2Ni with a major component along the c-axis and a small one along the a-axis. The heat capacity data peak at 20.9(3) K (1Co) and 25.1 (1) K (2Ni). The derived magnetic entropies, following correction of the lattice contribution using the measured data for the nonmagnetic Zn analogue, suggest S = 1/2 for 1Co but is lower than that expected for 2Ni (S = 1). In both cases, only ca. 60% of the entropy is found below the magnetic ordering temperature, suggesting considerable short-range correlations at higher temperatures. While the temperature at which the magnetic diffraction becomes observable coincides with that of at the peak in heat capacity, it is lower than TN observed by magnetization measurements in both cases, and there is evidence of short-range ordering in a narrow range of temperature (T-N +/- 5 K).Magnetic properties and magnetic structures of synthetic natrochalcites, NaM2II(D3O2)(MoO4)(2), M = Co or Nix24200883#N/AFALSE
2040
ja804339m10.1021/ja804339mFALSEhttps://doi.org/10.1021/ja804339mStack, TDPJ. Am. Chem. Soc.The geometric and electronic structure of an oxidized Cu complex ([CuSal](+); Sal = N,N-bis(3,5-di-tert-butylsalicylidene)-1,2-cyClohexane-(1R,2R)-diamine) with a non-innocent salen ligand has been investigated both in the solid state and in solution. Integration of information from UV-vis-NIR spectroscopy, magnetic susceptibility, electrochemistry, resonance Raman spectroscopy, X-ray crystallography, X-ray absorption spectroscopy, and density functional theory calculations provides critical insights into the nature of the localization/delocalization of the oxidation locus. In contrast to the analogous Ni derivative [NiSal](+) (Storr, T.; et al. Angew. Chem., Int. Ed. 2007, 46, 5198), which exists solely in the Ni(II) ligand-radical form, the locus of oxidation is metal-based for [CuSal](+), affording exClusively a Cu(III) species in the solid state (4-300 K). Variable-temperature solution studies suggest that [CuSal](+) exists in a reversible spin-equilibrium between a ligand-radical species [Cu(II)Sal(center dot)](+) (S = 1) and the high-valent metal form [Cu(III)Sal](+) (S = 0), indicative of nearly isoenergetic species. It is surprising that a bis-imine-bis-phenolate ligation stabilizes the Cu(III) oxidation state, and even more surprising that in solution a spin equilibrium occurs without a change in coordination number. The oxidized tetrahydrosalen analogue [CuSal(red)](+) (Sal red = N,N-bis(3,5-di-tert-butylhydroxyBenzyl)-1,2-cyClohexane-(1 R,2R)-diamine) exists as a temperature-invariant Cu(II)-ligand-radical complex in solution, demonstrating that ostensibly simple variations of the ligand structure affect the locus of oxidation in Cu-bis-phenoxide complexes.Defining the Electronic and Geometric Structure of One-Electron Oxidized Copper-Bis-phenoxide Complexesx1392008144#N/AFALSE
2041
ja807742g10.1021/ja807742gFALSEhttps://doi.org/10.1021/ja807742gImahori, HJ. Am. Chem. Soc.Core-modified isophlorin-metal complexes were successfully prepared by redox-coupled complexation of P,S,N(2)-hybrid porphyrin with zerovalent palladium, nickel, and platinum. In this transformation, the core-phosphorus atom plays crucial roles in enhancing the electron-accepting ability of the 18(Pi) porphyrin ring and stabilizing the 20(Pi) isophlorin ring owing to high P-M affinity. The isolated Pd and Pt complexes are chemically stable under ambient conditions. The Pd-P,S,N(2) isophlorin complex was structurally characterized by X-ray crystallography, which revealed a distorted 20(Pi) plane with a square planar palladium(II) center, Experimental ((1)H, UV-vis, and X-ray) and theoretical (density functional theory calculations) results suggest that the P,S,N(2)-isophlorin-metal complexes possess nonaromaticity in terms of both magnetic and geometrical criteria.Redox-Coupled Complexation of 23-Phospha-21-thiaporphyrin with Group 10 Metals: A Convenient Access to Stable Core-Modified Isophlorin-Metal Complexes57200824#N/ATRUE
2042
ja807735a10.1021/ja807735aFALSERiordan, CGSynthesis and Spectroscopic Identification of a mu-1,2-Disulfidodinickel Complex2009#N/ATRUE
2043
ja807724e10.1021/ja807724eFALSEhttps://doi.org/10.1021/ja807724eDubertret, BJ. Am. Chem. Soc.Well documented procedures to grow zero-dimensional systems, dots, and one-dimensional systems, wires and tubes, as colloidal partiCles in solution have been reported. In contrast, there are no methods of preparation that yield optically active two-dimensional soluble partiCles. Yet, ultrathin films (quantum wells) of II-VI and III-V semiconductors epitaxially grown on substrates by molecular beam epitaxy for example have proven extremely useful. for both fundamental. studies and a wealth of applications in optoelectronics. We show that II-VI cadmium selenide platelets, with thicknesses tuned at the atomic level, can be synthesized in solution. We describe the method for the preparation of these new colloidal. nanocrystals and characterize them structurally and optically. We identified three platelets populations with emission maximums at 462, 513, and 550 nm with corresponding thicknesses estimated at 1.9, 2.2, and 2.5 nm, respectively. Despite the fact that the platelet aspect ratio within a population can range from 4 to several. hundreds, the emission spectra full width half-maximum of each population is < 10 nm at room temperature with quantum yields that can reach 30%. The platelets we have synthesized are an extension of the quantum wells epitaxially grown on substrates, with the advantages that they can be easily synthesized in solution at low cost and used as building blocks for more advanced structures and have a uniform thickness that can be tuned within one CdSe monolayer and finite lateral dimensions ranging from 10 nm to a few 100 nm.Quasi 2D Colloidal CdSe Platelets with Thicknesses Controlled at the Atomic Level488200817#N/ATRUE
2044
ja802842q10.1021/ja802842qFALSEhttps://doi.org/10.1021/ja802842qvan Eldik, RJ. Am. Chem. Soc.Paramagnetic effects on the relaxation rate and shift difference of the O-17 nuCleus of bulk water enable the study of water exchange mechanisms on transition metal complexes by variable temperature and variable pressure NMR. The water exchange kinetics of [Mn-II(edta)(H2O)](2-) (CN 7, hexacoordinated edta) was reinvestigated and complemented by variable pressure NMR data. The results revealed a rapid water exchange reaction for the [Mn-II(edta)(H2O)](2-) complex with a rate constant of k(ex) = (4.1 +/- 0.4) x 10(8) s(-1) at 298.2 K and ambient pressure. The Activation parameters Delta H double dagger, Delta S double dagger, and Delta V double dagger are 36.6 +/- 0.8 kJ mol(-1), +43 +/- 3 J K-1 mol(-1), and +3.4 +/- 0.2 cm(3) mol(-1), which are in line with a dissociatively activated interchange (l(d)) mechanism. To analyze the structural influence of the chelate, the investigation was complemented by studies on complexes of the edta-related tmdta (trimethylenediaminetetraacetate) chelate. The kinetic parameters for [Fe-II(tmdta)(H2O)](2-) are k(ex) = (5.5 +/- 0.5) x 10(6) s(-1) at 298.2 K, Delta H double dagger = 43 +/- 3 kJ mol(-1), Delta S double dagger = +30 +/- 13 J K-1 mol(-1), and Delta V double dagger = +15.7 +/- 1.5 cm(3) mol(-1), and those for [Mn-II(tmdta)(H2O)](2-) are k(ex) = (1.3 +/- 0.1) x 10(8) s(-1) at 298.2 K, Delta H double dagger = 37.2 +/- 0.8 kJ mol(-1), Delta S double dagger = +35 3 J K-1 mol(-1), and Delta V double dagger +8.7 +/- 0.6 cm(3) mol(-1). The water containing species, [Fe-III(tmdta)(H2O)](-) with a fraction of 0.2, is in equilibrium with the water-free hexa-coordinate form, [Fe-III(tmdta)](-). The kinetic parameters for [Fe-III(tmdta)(H2O)](-) are k(ex) = (1.9 +/- 0.8) x 10(7) s(-1) at 298.2 K, Delta H double dagger = 42 +/- 3 kJ mol(-1), Delta S double dagger = +36 +/- 10 J K-1 mol(-1), and Delta V double dagger = +7.2 +/- 2.7 cm(3) mol(-1). The data for the mentioned tmdta complexes indicate a dissociatively activated exchange mechanism in all cases with a Clear relationship between the sterical hindrance that arises from the ligand architecture and mechanistic details of the exchange process for seven-coordinate complexes. The unexpected kinetic and mechanistic behavior of [Ni-II(edta')(H2O)](2-) and [Ni-II(tmdta')(H2O)](2-) is accounted for in terms of the different coordination number due to the strong preference for an octahedral coordination environment and thus a coordination equilibrium between the water-free, hexaClentate [M(L)](n+) and the aqua-pentadentate forms [M(L')(H2O)](n+) of the Ni-II-edta complex, which was studied in detail by variable temperature and pressure UV-vis experiments. For [Ni(II)edta')(H2O)](2-) (CN 6, pentacoordinated edta) a water substitution rate constant of (2.6 +/- 0.2) x 10(5) s(-1) at 298. 2 K and ambient pressure was measured, and the Activation parameters Delta H double dagger, Delta S double dagger, and Delta V dagger were found to be 34 +/- 1 kJ mol(-1), -27 +/- 2 J K-1 mol(-1), and +1.8 +/- 0.1 cm(3) mol(-1), respectively. For [Ni-II(tmdta')(H2O)](2-), we found k = (6.4 +/- 1.4) x 10(5) s(-1) at 298.2 K, Delta H double dagger = 22 +/- 4 kJ mol(-1), and Delta S double dagger = -59 +/- 5 J K-1 mol(-1). The process is referred to as a water substitution instead of a water exchange reaction, since these observations refer to the intramolecular displacement of coordinated water by the Carbonylate moiety in a ring-Closure reaction.Triggering Water Exchange Mechanisms via Chelate Architecture. Shielding of Transition Metal Centers by AminopolyCarbonylate Spectator Ligandsx50200873#N/AFALSE
2045
ja802726310.1021/ja8027263FALSEhttps://doi.org/10.1021/ja8027263Challis, GLJ. Am. Chem. Soc.Putrebactin is a dihydroxamate iron chelator produced by the metabolically versatile marine bacterium Shewanella putrefaciens. It is a macrocyClic dimer of N-hydroxy-N-succinyl-putrescine (HSP) and is structurally related to desferrioxamine E, which is a macrocyClic trimer of N-hydroxy-N-succinyl-cadaverine (HSC), We recently showed that DesD, a member of the NIS synthetase superfamily, catalyzes the key step in desferrioxamine E biosynthesis: ATP-dependent trimerisation and macrocylization of HSC. Here we report identification of a conserved gene Cluster in the sequenced genomes of several Shewanella species, inCluding Shewanella putrefaciens, which is hypothesized to direct putrebactin biosynthesis from putrescine, succinyl-CoA and molecular oxygen, The pubC gene within this gene Cluster encodes a protein with similar to 65% similarity to DesD. We overexpressed pubC from Shewanella species MR-4 and MR-7 in E. coli. The resulting His(6)-PubC fusion proteins were purified by Ni-NTA affinity and gel filtration chromatography. The recombinant proteins were shown to catalyze ATP-dependent cyClodimerization of HSP to form putrebactin. The uncyClized dimer of HSP pre-putrebactin was shown to be an intermediate in the conversion of two molecules of HSP to putrebactin. The data indicate that pre-putrebactin is converted to putrebactin via PubC-catalyzed Activation of the Carbonyl group by adenylation, followed by PubC-catalyzed nuCleophilic attack of the amino group on the Carbonyl carbon of the acyl adenylate. This mechanism for macrocyCle formation is very different from the mechanism involved in the biosynthesis of many other macrocyClic natural products, where already-activated acyl thioesters are converted by thioesterase domains of polyketide synthases and nonribosomal peptide synthetases to macrocyCles via covalent enzyme bound intermediates. The results of this study demonstrate that two Closely related enzymes, PubC and DesD, catalyze specific cyClodimerization and cyClotrimerization reactions, respectively, of structurally similar substrates, raising intriguing questions regarding the molecular mechanism of specificity.Identification of a gene Cluster that directs putrebactin biosynthesis in Shewanella species: PubC catalyzes cyClodimerization of N-hydroxy-N-succinyiputrescinex43200810#N/AFALSE
2046
ja802593810.1021/ja8025938FALSEhttps://doi.org/10.1021/ja8025938Hu, XLJ. Am. Chem. Soc.A new pincer-type bis(amino)amine (NN(2)) ligand and its lithium and nickel complexes, inCluding Ni(II) methyl, ethyl, and phenyl complexes, were synthesized. The Ni(II) Alkyl complexes react Cleanly with Alkyl halides. More interestingly, the Ni(II) Alkyls undergo unprecedented reactions with CH(2)Cl(2) and CHCl(3) to Cleave all the C-Cl bonds and replace them with C-C bonds. The reactions are highly selective and lead to the first efficient catalytic coupling of CHCl(2) with Alkyl Grignards. A conversion of 82% and a turnover number of 47 are achieved within minutes. Coupling of CD(2)Cl(2) and 1,1-dichloro-3,3-dimethylbutane with (n)BuMgX is also realized. Preliminary mechanistic study suggests a radical initiated process for these reactions.Nickel complexes of a pincer NN(2) ligand: Multiple carbon-chloride Activation of CH(2)Cl(2) and CHCl(3) leads to selective carbon-carbon bond formationx151200825#N/AFALSE
2047
ja806298t10.1021/ja806298tFALSEhttps://doi.org/10.1021/ja806298tMarti-Gastaldo, CJ. Am. Chem. Soc.The anionic oxalate-bridged bimetallic chain [Co(H2O)(2)Cr(ox)(3)](-) shows slow relaxation of the magnetization, typical of the so-called single-chain magnets, when crystallized in segregated layers in a mixed salt with the supramolecular cations [C12H24O6K](+) and [(C12H24O6)(FC6H4NH3)](+). This is the first time that such phenomenon has been observed in an oxalate-bridge material. In view of the wide synthetic versatility exhibited by the oxalate ligand, it opens the door for the realization of a complete family of SCM materials whose physical properties might be tuned by the suitable replacement of M3+ ions within the chain. The information extracted from the systematic study of these compounds should provide important information concerning the main parameters that affect the slow-relaxation phenomena in this sort of 1D nanomagnets.Single Chain Magnets Based on the Oxalate Ligand118200832#N/ATRUE
2048
ja802417d10.1021/ja802417dFALSEhttps://doi.org/10.1021/ja802417dDorn, HCJ. Am. Chem. Soc.Y-2@C79N and Tb-2@C79N have been prepared by conducting the Kratschmer-Huffman electric-arc process under 20 Torr of N-2 and 280 Torr of He with metal oxide-doped graphite rods. These new heterofullerenes were separated from the resulting mixture of empty cage fullerenes and endohedral fullerenes by chemical separation and a two-stage chromatographic process. Crystallographic data for Tb-2@C79N-Ni(OEP)center dot 2C(6)H(6) demonstrate the presence of an 80-atom cage with idealized I-h symmetry and two, widely separated Tb atoms inside with a Tb-Tb separation of 3.9020(10) A for the major terbium sites. The EPR spectrum of the odd-electron Y-2@C79N indicates that the spin density largely resides on the two equivalent yttrium ions. Computational studies on Y-2@C79N suggest that the nitrogen atom resides at a 665 ring junction in the equator on the fullerene cage and that the unpaired electron is localized in a bonding orbital between the two yttrium ions of this stable radical. Thus, the Tb-Tb bond length of the single-electron bond is an exceedingly long metal-metal bond.M-2@C79N (M = Y, Tb): Isolation and characterization of stable endohedral metallofullerenes exhibiting M-M bonding interactions inside aza[80]fullerene cagesx114200850#N/AFALSE
2049
ja806136910.1021/ja8061369FALSEhttps://doi.org/10.1021/ja8061369Anderson, HLJ. Am. Chem. Soc.Amphiphilic donor-acceptor meso-ethynyl porphyrins with polar pyridinium electron-acceptor head groups and hydrophobic diAlkyl-aniline electron donors have high molecular hyperpolarizabilities (as measured by hyper-Rayleigh scattering) and high affinities for biological membranes. When bound to water droplets in dodecane, or to the plasma membranes of living cells, they can be used for second harmonic generation (SHG) microscopy; an incident light of wavelength 840 nm generates a strong frequency-doubled signal at 420 nm. Copper(II) and nickel(II) porphyrin complexes give similar SHG signals to those of the free-base porphyrins, while exhibiting no detectable two-photon excited fluorescence.Amphiphilic Porphyrins for Second Harmonic Generation Imaging110200921#N/ATRUE
2050
ja806101h10.1021/ja806101hFALSEhttps://doi.org/10.1021/ja806101hDriess, MJ. Am. Chem. Soc.The first isolable 'side-on' supersulfidonickel(II) complex 1(1) with the elusive S2(-center dot) ligand has been synthesized by facile oxidation of the corresponding nickel(I) precursor [LNi] with elemental sulfur. Remarkably, paramagnetic 1(1) associates voluntarily to give the diamagnetic dimer 1(2) with a four-sulfur two-electron bond as proven by X-ray diffraction analysis, spectroscopic measurements (H-1 NMR, EPR, SQUID), and DFT calculations. Gentle sulfur transfer of 1(1) to Ph3P or its reaction with [LNi] affords solely the genuine disuffide complex 3 having a Ni-2(mu-mu(2):mu(2)-S-2) core.From a paramagnetic, mononuClear supersulfidonickel(II) complex to a diamagnetic dimer with a four-sulfur two-electron bond39200824#N/ATRUE
2051
ja805804s10.1021/ja805804sFALSEhttps://doi.org/10.1021/ja805804sHillhouse, GLTwo-coordinate d(9) complexes. Synthesis and oxidation of NHC nickel(I) amides2008#N/ATRUE
2052
ja801784710.1021/ja8017847https://doi.org/10.1021/ja8017847Guan, ZBJ. Am. Chem. Soc.An alpha-diimine ligand (1) containing an axial donating pyridine group is developed for late metal polymerization catalysis. Despite having no substitution on the bottom face of the ligand, the nickel and palladium complexes of 1 are highly active for ethylene polymerization, producing linear high molecular weight polymers. For example, 1-NiBr(2) (3) forms PR with a M(n) of up to 109 224 g/mol with 1.4 branches/1000 C's. Similarly, 1-PdMeCl (5) forms PE with a M(n) of up to 880 379 g/mol with 5.1 branches/1000 C's. In sharp contrast, catalysts containing the control ligand (2) consisting of a noncoordinating phenyl group gave only low molecular weight branched oligomers. It is observed that AlMe(2)Cl plays a specific role in generating the active species for the pyridine-based complexes. Presumably, the pyridine group may interact with AlMe(2)Cl to form a bimetallic species which suppresses the beta-hydride elimination process, hence resulting in reduced chain transfer and more linear structure.Axial donating ligands: A new strategy for late transition metal olefin polymerization catalysisx93200822#N/AFALSE
2053
ja805713810.1021/ja8057138FALSEhttps://doi.org/10.1021/ja8057138O'Hare, DJ. Am. Chem. Soc.The synthesis of the bimetallic permethylpentalene complexes Pn*M-2(2) (M = V, Cr, Mn, Co, Ni; Pn* = C8Me6) has been accomplished, and all of the complexes have been structurally characterized in the solid state by single-crystal X-ray diffraction. Pn*V-2(2) (1) and Pn*Mn-2(2) (3) show very short intermetallic distances that are consistent with metal-metal bonding, while the cobalt centers in Pn*2CO2 (4) exhibit differential bonding to each side of the Pn* ligand that is consistent with an 175:17 3 formulation. The Pn* ligands in Pn*Ni-2(2) (5) are best described as eta(3):eta(3)-bonded to the metal centers. H-1 NMR studies indicate that all of the Pn*M-2(2) species exhibit D-2h molecular symmetry in the solution phase; the temperature variation of the chemical shifts for the resonances of Pn*Cr-2(2) (2) indicates that the molecule has an S = 0 ground state and a thermally populated S = 1 excited state and can be successfully modeled using a Boltzmann distribution (Delta H degrees = 14.9 kJ mol(-1) and Delta S degrees = 26.5 J K-1 mol(-1)). The solid-state molar magnetic susceptibility of 3 obeys the Curie-Weiss law with mu(eff) = 2.78 mu(B) and theta = -1.0 K; the complex is best described as having an S = 1 electronic ground state over the temperature range 4-300 K. Paradoxically, attempts to isolate the double ferrocene equivalent, Pn*Fe-2(2), led only to the isolation of the permethylpentalene dimer Pn*(2) (6). Solution electrochemical studies were performed on all of the organometallic compounds; 2-5 exhibit multiple quasi-reversible redox processes. Density functional theory calculations were performed on this series of complexes in order to rationalize the observed structural and spectroscopic data and provide estimates of the M-M bond orders.Homoleptic Permethylpentalene Complexes: Double Metallocenes of the First-Row Transition Metals732008123#N/ATRUE
2054
ja801412b10.1021/ja801412bFALSEhttps://doi.org/10.1021/ja801412bRay, PCJ. Am. Chem. Soc.Contamination of the environment with heavy metal ions has been an important concern throughout the world for decades. Driven by the need to detect trace amounts of mercury in environmental samples, this artiCle demonstrates for the first time that nonlinear optical (NLO) properties of MPA-HCys-PDCA-modified gold nanopartiCles can be used for rapid, easy and reliable screening of Hg(II) ions in aqueous solution, with high sensitivity (5 ppb) and selectivity over competing analytes. The hyper Rayleigh scattering (HRS) intensity increases 10 times after the addition of 20 ppm Hg(2+) ions to modified gold nanopartiCle solution. The mechanism for HRS intensity change has been discussed in detail using partiCle size-dependent NLO properties as well as a two-state model. Our results show that the HRS assay for monitoring Hg(II) ions using MPA-HCys-PDCA-modified gold nanopartiCles has excellent selectivity over alkali, alkaline earth (Li(+), Na(+), K(+), Mg(2+), Ca(2+)), and transition heavy metal ions (Pb(2+), Pb(+), Mn(2+), Fe(2+), Cu(2+), Ni(2+), Zn(2+), Cd(2+)).Selective detection of mercury (II) ion using nonlinear optical properties of gold nanopartiClesx375200830#N/AFALSE
2055
ja805304p10.1021/ja805304phttps://doi.org/10.1021/ja805304pMecking, SJ. Am. Chem. Soc.With a new titanium imineenolato complex, ethylene is polymerized in an unprecedented living fashion affording a polymer with a high molecular weight (M-n > 10(5) g mol(-1)) and an extremely narrow distribution (M-w/M-n 1.01) at the time; the living character is also retained even at an elevated temperature of 75 degrees C, and blockcopolymers are accessible.Extremely narrow-dispersed high molecular weight polyethylene from living polymerization at elevated temperatures with o-F substituted Ti enolatoimines75200829#N/ATRUE
2056
ja800959g10.1021/ja800959gFALSEhttps://doi.org/10.1021/ja800959gCalvino, JJJ. Am. Chem. Soc.It is generally accepted that good hydrogenation noble and nonnoble metal catalysts such as Pt, Ru, or Ni are not chemoselective for hydrogenation of nitro groups in substituted aromatic molecules. We have found that it is possible to transform nonchemoselective into highly chemoselective metal catalysts by controlling the coordination of metal surface atoms while introducing a cooperative effect between the metal and a properly selected support. Thus, highly chemoselective and general hydrogenation Pt, Ru, and Ni catalysts can be prepared by generating nanosized crystals of the metals on the surface of a TiO2 support and decorating the exposed (111) and (100) crystal faces by means of a simple catalyst Activation procedure. By doing this, it has been possible to change the relative rate for hydrogenating competitive groups present in the molecule by almost 2 orders of magnitude, increasing the chemoselectivity from less than 1% to more than 95%.Transforming nonselective into chemoselective metal catalysts for the hydrogenation of substituted nitroaromaticsx391200834#N/AFALSE
2057
ja800955510.1021/ja8009555FALSEhttps://doi.org/10.1021/ja8009555Shionoya, MJ. Am. Chem. Soc.Metal-mediated self-assembly of bioinspired molecular building blocks shows promise as an excellent strategy to provide well-defined metal arrays and nanoscopic metallo-architectures in a programmable way. Herein, we report Ni(II)-mediated self-assembly of artificial beta-dipeptides (1) which were prepared from a newly designed P-amino acid bearing a propanediamine ligand as the side chain. The P-dipeptide (1) has thus two sets of ligands, that is, each building block serves as a tridentate ligand with a bidentate propanediamine unit and an amide Carbonyl group. Both C- and N-terminal tridentate ligands in 1 bind to two Ni(II) ions independently, and consequently, four beta-dipeptides are circularly arranged in a head-to-tail fashion to form a macrocyClic tetranuClear Ni(II) complex, Ni(4)1(4)(Clo(4))(8)(H2O)(10). The cyClic structure was determined by X-ray analysis and ESI-TOF mass spectrometry. The resulting unique twisted-boat structure allows the formation of isolated spaces for in-line hydrogen-bonded arrangement of water and anion molecules within a hole and two grooves rich in hydrogen bonding groups.Ni(II)-Mediated self-assembly of artificial beta-dipeptides forming a macrocyClic tetranuClear complex with interior spaces for in-line molecular arrangementx16200832#N/AFALSE
2058
ja805165y10.1021/ja805165yFALSEhttps://doi.org/10.1021/ja805165yFu, GCJ. Am. Chem. Soc.A stereoconvergent method for the catalytic asymmetric Negishi cross-coupling of racemic secondary propargylic halides with Arylzinc reagents has been developed. Neither family of compounds has previously been shown to be a suitable partner in such coupling processes. From a practical point of view, it is noteworthy that the catalyst components (NiCl2 glyme and pybox ligand 1) are commercially available.Nickel-catalyzed asymmetric cross-couplings of racemic propargylic halides with Arylzinc reagents139200823#N/ATRUE
2059
ja805088r10.1021/ja805088rFALSEhttps://doi.org/10.1021/ja805088rOgoshi, SJ. Am. Chem. Soc.A catalyst system derived from nickel and cocatalytic AlMe2Cl effects the intramolecular Arylcyanation of alkenes. The reaction takes place in an exClusive exo-dig manner to give a wide range of nitrites having a Benzylic quaternary carbon in good yields. Detailed investigations are described on the scope and mechanism as well as preliminary results on the asymmetric version of the reaction to provide novel access to chiral quaternary stereocenters.Intramolecular Arylcyanation of alkenes catalyzed by nickel/AlMe2CI192200818#N/ATRUE
2060
ja803774s10.1021/ja803774sFALSEhttps://doi.org/10.1021/ja803774sMontgomery, JJ. Am. Chem. Soc.The nickel-catalyzed coupling of aldehydes, alkynes, and diAlkylsilanes results in an unusual dehydrogenative cyClocondensation process to afford five-membered silacyClic products. The process allows diAlkylsilanes to serve as a silylene synthetic equivalent. A mechanistic pathway for the process involving the formation of an aldehyde/alkyne-derived nickel metallacyCle followed by sequential sigma-bond metathesis processes involving the two Si-H bonds has been proposed.Dehydrogenative cyClocondensation of aldehydes, alkynes, and diAlkylsilanes44200831#N/ATRUE
2061
ja800234210.1021/ja8002342FALSEhttps://doi.org/10.1021/ja8002342Bowers, MTJ. Am. Chem. Soc.The interaction of the cyClic nonapeptide oxytocin (OT) with a number of alkaline earth and divalent transition metal ions (X2+) was examined employing mass spectrometry (MS) and ion mobility spectrometry (IMS) techniques in combination with molecular dynamics (MD) and density functional theory (DFT) calculations. Under acidic conditions it was found that OT exhibits an exceptionally strong affinity for all divalent metal ions resulting in strong [OT + X](2+) peaks in the mass spectrum. Under basic conditions only Cu2+ and Ni2+-OT complexes were detected and these were singly, doubly, triply, or quadruply deprotonated. Collision-induced dissociation of the [OT - 3H + Cu](-) complex yielded exClusively C-terminal Cu2+-containing fragments (Cu(2+)fragment(3-)), suggesting that the Cu2+ ligation site inCludes deprotonated C-terminal backbone amide nitrogen atoms and the N-terminal amino nitrogen atom in [OT - 3H + Cu](-). MD and DFT calculations indicate a square-planar complex is consistent with these observations and with experimental collision cross sections. MID and DFT calculations also indicate either an octahedral or trigonal-bipyramidal complex between Zn2+ and OT is lowest in energy with Carbonyl oxygens being the primary ligation sites. Both complexes yield cross sections in agreement with experiment. The biological impact of the structural changes induced in OT by divalent metal ion coodination is discussed.Interactions of the hormone oxytocin with divalent metal ionsx65200859#N/AFALSE
2062
ja800233b10.1021/ja800233bFALSEhttps://doi.org/10.1021/ja800233bBarron, ARJ. Am. Chem. Soc.Carbon nanotubes (CNTs) have been grown using Fe, Co, Ni, and Co/Fe spin-on-catalyst (SOC) systems, involving the metal salt dispersed with a spin-on-glass precursor. During initial growth runs (CH4/H-2/900 degrees C), the CNT yield followed the order Co-SOC > Fe-SOC >> Ni-SOC. The Fe catalysts produced the longest nanotubes at the expense of a larger average CNT diameter and broader diameter distribution than the Co-SOC system. A series of Co/Fe-SOCs were prepared where as the atomic percentage of Co is increased nuCleation of CNT increases but the CNT length decreases. The linear relationship between the diameter and length of CNTs grown from the Co/Fe-SOC suggests that slow growth is beneficial with respect to control over CNT diameter. After initial CNT growth, the original samples were subjected to additional growth runs. Four individual reactions were observed in the Fe-SOC and binary Co/Fe-SOC: regrowth (amplification), double growth (a second CNT growing from a previously active catalyst), CNT etching, and nuCleation from initially inactive catalysts (new growth). CNT etching was observed for the mixed catalyst systems (Co/Fe-SOC) but not for either Fe-SOC or Co-SOC. During the regrowth experiments, CNTs were observed that were not present after the initial growth run (and were not as a result of amplification or double growth). Thus, catalysts, which were initially inactive toward nuCleation of CNTs in the original growth run, are capable of becoming activated when placed back into the furnace and submitted to regrowth under identical conditions.Growth, new growth, and amplification of carbon nanotubes as a function of catalyst compositionx41200817#N/AFALSE
2063
ja803435w10.1021/ja803435wFALSEhttps://doi.org/10.1021/ja803435wDong, VMJ. Am. Chem. Soc.Organozinc reagents are widely used in organic synthesis due primarily to their high functional group compatibility. However, under mild conditions, these organometallic reagents do not react directly with CO2, the ideal C1 source for organic synthesis. Herein, we report that both Ni and Pd complexes can catalyze the addition of organozinc reagents to CO2 under mild conditions (1 atm CO2, 0 degrees C). This transformation represents an important extension of the Negishi cross-coupling and is believed to occur via a novel mechanism involving Aresta's complex and/or its corresponding Pd analogue.Beyond Aresta's complex: Ni- and Pd-catalyzed organozinc coupling with CO2233200832#N/ATRUE
2064
ja803226310.1021/ja8032263FALSEhttps://doi.org/10.1021/ja8032263Balch, ALJ. Am. Chem. Soc.The structure of Gd3N@C-s(39663)-C-82 has been determined through single crystal X-ray diffraction on Gd3N@C-s (39663)-C-82-Ni-II(OEP)center dot 2(C6H6) The carbon cage has a distinct egg shape because of the presence of a single pair of fused pentagons at one apex of the molecule. Although 9 IPR structures are available to the C-82 Gage, one of the 39709 isomeric structures that do not conform to the IPR was found in Gd3N@C-S(39663)-C-82. The egg-shaped structure of Gd3N@C-s(39663)-C-82 is similar to that observed previously for M3N@C-s(51365)-C-84 (M = Gd, Tm, Tb). As noted for other non-IPR endohedral fullerenes, one Gd atom in Gd3N@C-s(39663)-C-82 is nestled within the fold of the fused pentagons.Is the isolated pentagon rule merely a suggestion for endohedral fullerenes? The structure of a second egg-shaped endohedral fullerene-Gd3N @ C-s(39663)-C-8294200826#N/ATRUE
2065
ja711322g10.1021/ja711322gFALSEhttps://doi.org/10.1021/ja711322gMullen, KJ. Am. Chem. Soc.Fluorescent probes are essential for the exploration of protein function, detection of molecular interactions, and conformational changes. The nitrilotriacetic acid derivatives of different chromophores were successfully used for site-selective noncovalent fluorescence labeling of histidine-tagged proteins. All of them, however, suffer from the same drawback-loss of the fluorescence upon binding of the nickel ions. Herein we present the solution and solid phase synthesis of water-soluble perylene(dicarboximide) functionalized with a nitrilotriacetic acid moiety (PDI-NTA). The photophysical properties of PDI-NTA revealed an exceptional photostability and fluorescence quantum yield that remained unchanged upon addition of nickel ions. The F(1) complex of F(0)F(1)-ATP synthase from Escherichia coli, containing three hexahistidine tags, was labeled and the suitability for site-specific labeling of the new chromophore demonstrated using fluorescence correlation spectroscopy.Exploiting the nitrilotriacetic acid moiety for biolabeling with ultrastable perylene dyesx94200821#N/AFALSE
2066
ja802474b10.1021/ja802474bFALSEhttps://doi.org/10.1021/ja802474bBockrath, BJ. Am. Chem. Soc.Rare hysteretic adsorption/desorption isotherms are reported for CO2 and N-2 on a pillared Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)(4)] compound (NiBpeneNiCN). The hysteresis occurs under moderate pressure and at temperatures above the critical temperatures of the respective gases. Powder X-ray diffraction measurements indicate that the material is an extended three-dimensional analogue of the well-known Hofmann Clathrates which is formed through axial bridging of the in-plane octahedral Ni sites by the bidentate 1,2-bis(4-pyridyl) ethylene. The hysteretic behavior toward guest adsorption and desorption is attributed to a structural phase transition in the material resulting from a variation in the tilt angle of the 1,2-bis(4-pyridyl)ethylene pillars. Kinetics studies on the desorption of acetone from the material show two first-order processes with two rate constants yielding Activation energies of 68 and 55 kJ/mol when loadings are greater than 1 equiv of acetone per formula unit. The CO2 adsorption/desorption isotherms on the series of structurally similar Ni(L)[Ni(CN)(4)] compounds, where L = pyrazine, 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethane, and dipyridylacetylene, are also reported. In contrast to NiBpeneNiCN, the rigid members of this series show normal type I isotherms with no measureable hysteresis and no significant structural changes during the adsorption/desorption cyCle, while the flexible 1,2-bis(4-pyridyl)ethane-bridged sample collapses in the guest-free state and shows no significant adsorption of CO2.Hysteresis in the physisorption of CO2 and N-2 in a flexible pillared layer nickel cyanide107200837#N/ATRUE
2067
ja801981h10.1021/ja801981hFALSEhttps://doi.org/10.1021/ja801981hMunck, EJ. Am. Chem. Soc.The active site A-Cluster in the a subunit of the title enzyme consists of an Fe(4)S(4) Cluster coordinated to a [Ni(p) Ni(d)] subcomponent, The Cluster must be activated for catalysis using low-potential reductants such as Ti(III) citrate. Relative to the inactive {[Fe(4)S(4))(2+) Ni(p)(2+) Ni(d)(2+)} state, the activated state appears to be 2-electrons more reduced, but the location of these electrons within the A-Cluster is uncertain, with {[Fe(4)S(4)](2+) Ni(p)(2+) Ni(d)(2+)} and {[Fe(4)S(4)](1+) Ni(p)(1+) Ni(d)(2+)) configurations proposed. Recombinant apo-alpha subunits oligomerize after Activation with NiCl(2). The dimer fraction, upon reduction with excess Ti(III)citrate, exhibited Mossbauer spectra consisting of two quadrupole doublets representing 51% and 21% of the Fe, with parameters indicating [Fe(4)S(4)](1+) states. Spectra recorded in strong magnetic fields were typical of diamagnetic systems, indicating an exchange-coupled S = 0 {[Fe(4)S(4)](1+) Ni(p)(1+)) state. Additional treatment with CO altered the doublet Mossbauer parameters, suggesting an interaction with CO, but maintaining the Cluster in the {[Fe(4)S(4)](1+) Ni(p)(1+)) state. Reduction with substoichiometric equivalents of Ti(III) citrate afforded an EPR signal typical of Ni(1+) ions, with g. = 2.10 and g(perpendicular to) = 2.02. Addition of more Ti caused the signal intensity to deCline, suggesting that it arises from the semireduced {[Fe(4)S(4)](2+) Nip(1+)} state.Mossbauer evidence for an exchange-coupled {[Fe(4)S(4)](1+) Ni(p)(1+)} A-Cluster in isolated alpha Subunits of acetyl-coenzyme a synthase/carbon monoxide dehydrogenase21200817#N/ATRUE
2068
ja801941r10.1021/ja801941rFALSEhttps://doi.org/10.1021/ja801941rBowler, BEJ. Am. Chem. Soc.The effect of global stability on the kinetics of interconversion between the native (N) and a compact, partially unfolded form (I) of iso-1-cytochrome c stabilized by His73-heme ligation is investigated using a novel conformationally gated ET method. For the K73H variant and the 2-fold less stable AcH73 variant, the N and I conformers are of nearly equal stability at pH 7.5. The pH jump kinetic data yield k(obs) = k(NI) + k(IN) of 35-40 s(-1) at final pH values from 6 to 8 for the AcH73 variant, about 3-fold faster than for the more stable K73H variant. Gated ET measurements give k(NI) = 28 s(-1) and k(IN) = 13 s(-1) for the AcH73 variant, 10- and 2- fold greater than that for the more stable K73H variant. Thus, funneled landscape have evolved such that loss of global stability lowers barriers at the bottom of a folding funnel, still allowing for efficient folding.Probing the bottom of a folding funnel using conformationally gated electron transfer reactions22200820#N/ATRUE
2069
ja801865c10.1021/ja801865cFALSEhttps://doi.org/10.1021/ja801865cGrubbs, RHJ. Am. Chem. Soc.Dehydrogenation of the dihydride (PNP)IrH2 with norbornylene in the presence of t-butyl methyl ether leads to formation of an iridium(I) Fischer carbene complex, (PNP)Ir C(H)(OBu)-Bu-t, by double C-H Activation and loss of H-2. The square planar pincer-type carbene effects quantitative oxygen-atom transfer from CO2 (1 atm) at ambient temperature to generate t-butyl formate and (PNP)Ir-CO. The iridium carbene reacts similarly with Carbonyl sulfide and phenyl isocyanate, causing sulfur-atom and nitrene-group transfer, respectively. In the absence of a hydrogen acceptor, thermolysis of (PNP)IrH2 in t-butyl methyl ether under an atmosphere of CO2 also results in the formation of (PNP)Ir -CO and oxidation of f-butyl methyl ether to t-butyl formate via an iridium carbene. Preliminary mechanistic studies indicate that these reactions proceed through an intermediate four-membered metallalactone.Oxygen-atom transfer from carbon dioxide to a Fischer carbene at (PNP)Ir73200841#N/ATRUE
2070
ja710067d10.1021/ja710067dFALSEhttps://doi.org/10.1021/ja710067dChivers, PTJ. Am. Chem. Soc.Escherichia coli RcnR and Mycobacterium tuberculosis CsoR are the founding members of a recently identified, large family of bacterial metal-responsive DNA-binding proteins. RcnR controls the expression of the metal efflux protein RcnA only in response to Ni(II) and Co(II) ions. Here, the interaction of Ni(II) and Co(II) with wild-type and mutant RcnR proteins is examined to understand how these metals function as allosteric effectors. Both metals bind to RcnR with nanomolar affinity and stabilize the protein to denaturation. X-ray absorption and electron paramagnetic resonance spectroscopies reveal six-coordinate high-spin sites for each metal that contains a thiolate ligand. Experimental data support a tripartite N-terminal coordination motif (NH2-Xaa-NH-His) that is common for both metals. However, the Ni(II)- and Co(II)-RcnR complexes are shown to differ in the remaining coordination environment. Each metal coordinates a conserved Cys ligand but with distinct M-S distances. Co(II)-thiolate coordination has not been observed previously in Ni(II)-/Co(II)-responsive metalloregulators. The ability of RcnR to recruit ligands from the N-terminal region of the protein distinguishes it from CsoR, which uses a lower coordination geometry to bind Cu(I). These studies facilitate comparisons between Ni(II)-RcnR and NikR, the other Ni(II)-responsive transcriptional regulator in E coli, to provide a better understanding how different nickel levels are sensed in E coli. The characterization of the Ni(II)- and Co(II)-binding sites in RcnR, in combination with bioinformatics analysis of all RcnR/CsoR family members, identified a four amino acid fingerprint that likely defines ligand-binding specificity, leading to an emerging picture of the similarities and differences between different Classes of RcnR/CsoR proteins.Ni(II) and Co(II) sensing by Escherichia coli RcnRx99200881#N/AFALSE
2071
ja801607610.1021/ja8016076FALSEHall, DGCatalytic enantioselective allyl- and crotylboration of aldehydes using chiral diol center dot SnCl4 complexes. Optimization, substrate scope and mechanistic investigations2008#N/ATRUE
2072
ja801367710.1021/ja8013677FALSEhttps://doi.org/10.1021/ja8013677Fu, GCJ. Am. Chem. Soc.The first effective method for asymmetric cross-couplings of unactivated Alkyl electrophiles has been developed, specifically, a nickel-based catalyst for stereoconvergent Suzuki reactions of homoBenzylic bromides with Alkylboranes. To the best of our knowledge, there are no previous examples of enantioselective Suzuki couplings of Alkyl electrophiles (activated or unactivated). Both of the catalyst components are commercially available.Enantioselective Alkyl-Alkyl suzuki cross-couplings of unactivated homoBenzylic halides187200816#N/ATRUE
2073
ja513102m10.1021/ja513102mFALSEhttps://doi.org/10.1021/ja513102mOsuka, AJ. Am. Chem. Soc.beta-to-beta Directly linked cyClic Ni(II) porphyrin trimer, tetramer, and pentamer ([3]CP, [4]CP, and [5]CP) have been synthesized by reaction of a 2,12-diborylated Ni(II) porphyrin with Pt(cod)Cl-2 followed by reductive elimination. The structures of these cyClic porphyrin arrays have been revealed by X-ray diffraction analysis. The strain energies of these cyClic oligomers are calculated to be 77, 57, and 47 kcal/mol for [3]CP, [4]CP, and [5]CP, respectively. Intramolecular excitation energy hopping was observed between the (3)(d,d) states of the Ni(II) porphyrins with rates of 3.0, 4.4, and 4.6 ps for [3]CP, [4]CP, and [5]CP, respectively, reflecting the Close proximity of the Ni(II) centers.CyClic 2,12-Porphyrinylene Nanorings as a Porphyrin Analogue of CyCloparaphenylenesx66201545#N/AFALSE
2074
ja513079r10.1021/ja513079rhttps://doi.org/10.1021/ja513079rKozlowski, MCJ. Am. Chem. Soc.The cross-coupling of sp(3)-hybridized organB(OH)2ron reagents via photoredox/nickel dual catalysis represents a new paradigm of reactivity for engaging Alkylmetallic reagents in transition-metal-catalyzed processes. Reported here is an investigation into the mechanistic details of this important transformation using density functional theory. Calculations bring to light a new reaction pathway involving an Alkylnickel(I) complex generated by addition of an Alkyl radical to Ni(0) that is likely to operate simultaneously with the previously proposed mechanism. Analysis of the enantioselective variant of the transformation reveals an unexpected manifold for stereoinduction involving dynamic kinetic resolution (DKR) of a Ni(III) intermediate wherein the stereodetermining step is reductive elimination. Furthermore, calculations suggest that the DKR-based stereoinduction manifold may be responsible for stereoselectivity observed in numerous other stereoconvergent Ni-catalyzed cross-couplings and reductive couplings.Nickel-Catalyzed Cross-Coupling of Photoredox-Generated Radicals: Uncovering a General Manifold for Stereoconvergence in Nickel-Catalyzed Cross-CouplingsPhotocatalyst308201534#N/AFALSE
2075
ja800878f10.1021/ja800878fFALSEhttps://doi.org/10.1021/ja800878fBousseksou, AJ. Am. Chem. Soc.Single crystals of the {Fe-II(pyrazine)[Pt(CN)(4)]} spin crossover complex were synthesized by a slow diffusion method, The crystals exhibit a thermal spin transition around room temperature (298 K), which is accompanied by a 14 K wide hysteresis loop. X-ray single-crystal analysis confirms that this compound crystallizes in the tetragonal P4/mmm space group in both spin states. Within the thermal hysteresis region a complete bidirectional photoconversion was induced between the two phases (high spin low spin) when a short single laser pulse (4 ns, 532 nm) was shined on the sample.Single-laser-shot-induced complete bidirectional spin transition at room temperature in single crystals of (Fe-II(pyrazine)(Pt(CN)(4)))159200833#N/ATRUE
2076
ja800691c10.1021/ja800691cFALSEhttps://doi.org/10.1021/ja800691cSuffert, JJ. Am. Chem. Soc.Fenestranes are regarded as a particularly challenging synthetic targets, and only few syntheses have been reported in the recent past. These rare compounds of synthetic and theoretical interest are a Class of tetracyClic skeletons, defined as doubly a,a'-bridged spiroalkanes. The reported results are focused on the synthesis of new and original [4.6.4.6]fenestradienes 3a-f and [4.6.4.6]fenestrenes 4a-e. Our approach implies the formation of this tetracyClic structure by a reaction cascade, based on consecutive transformations starting from the trienyne 1a-f: an initial soft hydrogenation using a P-2 Nickel catalyst at room temperature, followed by a conrotatory 8p electrocyClization and a disrotatory 6p electrocyClization and a final oxidation. Several examples of this type of new compounds are described in this Communication.Synthesis of [4.6.4.6]fenestradienes and [4.6.4.6]fenestrenes based on an 8 pi-6 pi-cyClization-oxidation cascade44200836#N/ATRUE
2077
ja512915410.1021/ja5129154FALSEhttps://doi.org/10.1021/ja5129154Dai, ZHJ. Am. Chem. Soc.The synthesis of highly active oxygen reduction reaction (ORR) catalysts with good durability and low cost is highly desirable but still remains a significant challenge. In this work, we present the synthesis of five-fold twinned Pd2NiAg nanocrystals (NCs) with a Ni-terminal surface which exhibit excellent electrocatalytic performance for ORR in alkaline media, even better than the performance of the commercial Pt/C catalyst. Using high-angle annular-dark-field imaging together with density functional theory calculations, it is found that the surfaces of the five-fold twinned Pd2NiAg NCs exhibit an unusual valence electron density. The maximum catalytic activity originates from the increased availability of surface Ni sites in five-fold twinned Pd2NiAg NCs and the features of twinned structural defects. This study provides an explanation of the enhanced ORR from the special structure of this novel material, which opens up new avenues for the design of novel Classes of electrocatalysts for fuel cells and metal-air batteries.Five-Fold Twinned Pd2NiAg Nanocrystals with Increased Surface Ni Site Availability to Improve Oxygen Reduction Activityx80201534#N/AFALSE
2078
ja512575v10.1021/ja512575vFALSEhttps://doi.org/10.1021/ja512575vKubiak, CPJ. Am. Chem. Soc.The homogeneous electrochemical reduction of CO2 by the molecular catalyst [Ni(cyClam)](2+) is studied by electrochemistry and infrared spectroelectrochemistry. The electrochemical kinetics are probed by varying CO2 substrate and proton concentrations. Products of CO2 reduction are observed in infrared spectra obtained from spectroelectrochemical experiments. The two major species observed are a Ni(I) Carbonyl, [Ni(cyClam)(CO)](+), and a Ni(II) coordinated bicarbonate, [Ni(cyClam)(CO2OH)](+). The rate-limiting step during electrocatalysis is determined to be CO loss from the deactivated species, [Ni(cyClam)(CO)](+), to produce the active catalyst, [Ni(cyClam)](+). Another macrocyClic complex, [Ni(TMC)](+), is deployed as a CO scavenger in order to inhibit the deActivation of [Ni(cyClam)](+) by CO. Addition of the CO scavenger is shown to dramatically increase the catalytic current observed for CO2 reduction. Evidence for the [Ni(TMC)](+) acting as a CO scavenger inCludes the observation of [Ni(TMC)(CO)](+) by IR. Density functional theory (DFT) calculations probing the optimized geometry of the [Ni(cyClam)(CO)](+) species are also presented.The Homogeneous Reduction of CO2 by [Ni(cyClam)(+): Increased Catalytic Rates with the Addition of a CO Scavengerx145201538#N/AFALSE
2079
ja800541c10.1021/ja800541cFALSEhttps://doi.org/10.1021/ja800541cBlumel, JJ. Am. Chem. Soc.Di- and tetraphosphines with rigid phenyl-, bilphenyl-, and tetraphenylstannane, -silane, and -methane scaffolds, and various substituents F, have been synthesized and immobilized via triethoxysilane-propagated formation of one or two surface-bound phosphonium moieties. The remaining phosphine groups can be coordinated to metal complexes. All the detective work and proof is done by solid-state NMR spectroscopy.Easily immobilized di- and tetraphosphine linkers: Rigid scaffolds that prevent interactions of metal complexes with oxide supports41200824#N/ATRUE
2080
ja511951x10.1021/ja511951xFALSEhttps://doi.org/10.1021/ja511951xStepien, MJ. Am. Chem. Soc.NonClassical nanotube end-caps have been constructed from strain-free heterocyClic precursors using a one-step synthetic procedure, involving multiple nickel-mediated Ullmann couplings. These systems consist of tubular macrocyClic sections that are tightly capped on one side with a bridging benzene ring, forming deep, chemically accessible cavities. The end-caps are characterized by exceptionally high internal strain energies reaching 144 kcal/mol. The optical absorption and emission properties of these molecules show a marked dependence on conjugation length and geometrical factors. The mechanism of end-cap formation, investigated using DFT calculations, relies on precise timing of transmetalation and reductive elimination events.Highly Strained NonClassical Nanotube End-caps. A Single-Step Solution Synthesis from Strain-Free, Non-MacrocyClic Precursorsx42201563#N/AFALSE
2081
ja511949510.1021/ja5119495FALSEhttps://doi.org/10.1021/ja5119495Xie, YJ. Am. Chem. Soc.Exploring efficient and inexpensive oxygen evolution reaction (OER) electrocatalysts is of great importance for various electrochemical energy storage and conversion technologies. Ni-based electrocatalysts have been actively pursued because of their promising activity and earth abundance. However, the OER efficiency for most of the developed Ni-based electrocatalysts has been intrinsically limited due to their low electrical conductivity and poor active site exposure yield. Herein, we report metallic Ni3N nanosheets as an efficient OER electrocatalyst for the first time. The first-principles calculations and electrical transport property measurements unravel that the Ni3N is intrinsically metallic, and the carrier concentration can be remarkably improved with dimensional confinement. The EXAFS spectra provide solid evidence that the Ni3N nanosheets have disordered structure resultant of dimensional reduction, which then could provide more active sites for OER. Benefiting from enhanced electrical conductivity with metallic behavior and atomically disordered structure, the Ni3N nanosheets realize intrinsically improved OER activity compared with bulk Ni3N and NiO nanosheets. Our finding suggests that metallic nitride nanosheets could serve as a new group of OER electrocatalysts with excellent property.Metallic Nickel Nitride Nanosheets Realizing Enhanced Electrochemical Water Oxidationx739201547#N/AFALSE
2082
ja511858c10.1021/ja511858cFALSEhttps://doi.org/10.1021/ja511858cKwon, SJJ. Am. Chem. Soc.Collisions of electrocatalytic platinum (Pt) single nanopartiCles (NPs) with a less electrocatalytic nickel (Ni) ultramicroelectrode (UME) surface were detected by amplification of the current by electrocatalysis of NPs. Two typical types of current responses, a current staircase or blip (or spike), in single NP collision experiments were observed at a time with a new system consisting of Pt NP/Ni UME/hydrazine oxidation. The staircase current response was obtained when the collided NPs were attached to the electrode and continued to produce electrocatalytic current. On the other hand, the blip current response was believed to be obtained when the NP attached but was deactivated. The different current responses depend on the different electrocatalytic reaction mechanism, characteristics of the NP, or the electrode material. How the deActivation of the electrocatalytic process affects on the current response of NP collision was investigated using the Ni UME. The current response of a single Pt NP collision is controllable from staircase to blip by changing the applied potential. The current response of the Pt NP was observed as a staircase response with 0 V (vs Ag/AgCl) and as a blip response with 0.1 V (vs Ag/AgCl) applied to the Ni UME.Potential-Controlled Current Responses from Staircase to Blip in Single Pt NanopartiCle Collisions on a Ni Ultramicroelectrodex38201533#N/AFALSE
2083
ja800103z10.1021/ja800103zFALSEhttps://doi.org/10.1021/ja800103zFu, GCJ. Am. Chem. Soc.Complementing previous advances in allylation chemistry, an effective nickel/Pybox catalyst for regioselective asymmetric Negishi cross-couplings of racemic secondary allylic chlorides with readily available organozinc halides has been developed. The method has been applied in two key steps of a formal total synthesis of fluvirucinine A(1).Nickel-catalyzed asymmetric Negishi cross-couplings of secondary allylic chlorides with Alkylzincs176200818#N/ATRUE
2084
ja511669810.1021/ja5116698FALSEhttps://doi.org/10.1021/ja5116698Kostecki, RThe Formation Mechanism of Fluorescent Metal Complexes at the LixNi0.5Mn1.5O4-delta/Carbonate Ester Electrolyte Interfacex2015#N/AFALSE
2085
ja511645210.1021/ja5116452FALSEhttps://doi.org/10.1021/ja9726926Ellman, JACobalt(III)-Catalyzed Synthesis of Indazoles and Furans by C-H Bond Functionalization/Addition/CyClization Cascadesx2015#N/AFALSE
2086
ja711475f10.1021/ja711475fFALSEhttps://doi.org/10.1021/ja972210qRajanBabu, TVLigand tuning in asymmetric hydroVinylation of 1,3-dienes: A stereoselective route to either steroid-C(20) (S) or -C(20) (R) derivatives2008#N/ATRUE
2087
ja511596c10.1021/ja511596cFALSEhttps://doi.org/10.1021/ja511596cZeng, JOctahedral Pd@Pt1.8Ni Core-Shell Nanocrystals with Ultrathin PtNi Alloy Shells as Active Catalysts for Oxygen Reduction Reactionx2015#N/AFALSE
2088
ja511559d10.1021/ja511559dFALSEhttps://doi.org/10.1021/ja963693lBell, ATIdentification of Highly Active Fe Sites in (Ni,Fe)OOH for Electrocatalytic Water Splitting
Electrocatalytic
2015#N/AFALSE
2089
ja711050910.1021/ja7110509FALSEhttps://doi.org/10.1021/ja971705cMito, MPressure response of three-dimensional cyanide-bridged bimetallic magnets2008#N/ATRUE
2090
ja710949e10.1021/ja710949eFALSEhttps://doi.org/10.1021/ja710949eJaun, BJ. Am. Chem. Soc.Methanogenic archaea utilize a specific pathway in their metabolism, converting C, substrates (i.e., CO2) or acetate to methane and thereby providing energy for the cell. Methyl-coenzyme M reductase (MCR) catalyzes the key step in the process, namely methyl-coenzyme M (CH3-S-COM) plus coenzyme B (HS-CoB) to methane and CoM-S-S-CoB. The active site of MCR contains the nickel porphinoid F-430. We report here on the coordinated ligands of the two paramagnetic MCRred2 states, induced when HS-CoM (a reversible competitive inhibitor) and the second substrate HS-CoB or its analogue CH3-S-CoB are added to the enzyme in the active MCRred1 state ((NiF430)-F-I). Continuous wave and pulse EPR spectroscopy are used to show that the MCRred2a state exhibits a very large proton hyperfine interaction with principal values A(H-1) = [-43,-42,-5] MHz and thus represents formally a (NiF430)-F-III hydride complex formed by oxidative addition to Nil. In view of the known ability of nickel hydrides to activate methane, and the growing body of evidence for the involvement of MCR in reverse methanogenesis (anaerobic oxidation of methane), we believe that the nickel hydride complex reported here could play a key role in helping to understand both the mechanism of reverse and forward methanogenesis.A nickel hydride complex in the active site of methyl-coenzyme M reductase: Implications for the catalytic cyCle48200872#N/ATRUE
2091
ja510908410.1021/ja5109084FALSEhttps://doi.org/10.1021/ja5109084Walsh, PJJ. Am. Chem. Soc.The first cobalt-catalyzed asymmetric Kumada cross-coupling with high enantioselectivity has been developed. The reaction affords a unique strategy for the enantioselective Arylation of alpha-bromo esters catalyzed by a cobalt-bisoxazoline complex. A variety of chiral alpha-Arylalkanoic esters were prepared in excellent enantioselectivity and yield (up to 97% ee and 96% yield). The Arylated products were transformed into alpha-ArylCarbonylic acids and primary alcohols without erosion of ee. The new enantioenriched alpha-Arylpropionic esters synthesized herein are potentially useful in the development of nonsteroidal anti-inflammatory drugs. This method was conducted on gram-scale and applied to the synthesis of highly enantioenriched (S)-fenoprofen and (S)-ar-turmerone.Cobalt-Bisoxazoline-Catalyzed Asymmetric Kumada Cross-Coupling of Racemic alpha-Bromo Esters with Aryl Grignard Reagentsx872014147#N/AFALSE
2092
ja710848610.1021/ja7108486FALSEhttps://doi.org/10.1021/ja971619cMindiola, DJStructural, spectroscopic, and theoretical elucidation of a redox-active pincer-type ancillary applied in catalysis2008#N/ATRUE
2093
ja710663n10.1021/ja710663nFALSEhttps://doi.org/10.1021/ja710663nWieghardt, KJ. Am. Chem. Soc.A series of bis(alpha-iminopyridine)metal complexes featuring the first-row transition ions (Cr, Mn, Fe, Co, Ni, and Zn) is presented. It is shown that these ligands are redox noninnocent and their paramagnetic T radical monoanionic forms can exist in coordination complexes. Based on spectroscopic and structural characterizations, the neutral complexes are best described as possessing a divalent metal center and two monoanionic pi radicals of the alpha-iminopyridine. The neutral M(L-center dot)(2) compounds undergo ligand-centered, one-electron oxidations generating a second series, [(L-x)(2)M(THF)][B(Ar-F)(4)] [where L-x represents either the neutral alpha-iminopyridine (L)(0) and/or its reduced pi radical anion (L-center dot)(-)]. The cationic series comprise mostly mixed-valent complexes, wherein the two ligands have formally different redox states, (L)(0) and (L-center dot)(-), and the two ligands may be electronically linked by the bridging metal atom. Experimentally, the cationic Fe and Co complexes exhibit Robin-Day Class III behavior (fully delocalized), whereas the cationic Zn, Cr, and Mn complexes belong to Class I (localized) as shown by X-ray crystallography and UV-vis spectroscopy. The delocalization versus localization of the ligand radical is determined only by the nature of the metal linker. The cationic nickel complex is exceptional in this series in that it does not exhibit any ligand mixed valency. Instead, its electronic structure is consistent with two neutral ligands (L)(0) and a monovalent metal center or [(L)(2)Ni(THF)][B(Ar-F)(4)]. Finally, an unusual spin equilibrium for Fe(II), between high spin and intermediate spin (S-Fe = 2 <-> S-Fe = 1), is described for the complex [(L-center dot)(L)Fe(THF)][B(Ar-F)(4)], which consequently is characterized by the overall spin equilibrium (S-tot = 3/2 <-> S-tot = 1/2). The two different spin states for Fe(II) have been characterized using variable temperature X-ray crystallography, EPR spectroscopy, zero-field and applied-field Mossbauer spectroscopy, and magnetic susceptibility measurements. Complementary DFT studies of all the complexes have been performed, and the calculations support the proposed electronic structures.Neutral bis(alpha-iminopyridine)metal complexes of the first-row transition ions (Cr, Mn, Fe, Co, Ni, Zn) and their, monocationic analogues: Mixed valency involving a redox noninnocent ligand system222200867#N/ATRUE
2094
ja509906610.1021/ja5099066FALSEhttps://doi.org/10.1021/ja5099066Murray, CBJ. Am. Chem. Soc.We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanopartiCles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (approximate to 1 nm) FePt shell and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allows the optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2/0.8 nm core/shell Ni/FePt after acetic acid wash reach 1.95 mA/cm(2) and 490 mA/mg(pt) at 0.9 V (vs reversible hydrogen electrode), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm(2) and 92 mA/mg(pt) at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with nonprecious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.Monodisperse Core/Shell Ni/FePt NanopartiCles and Their Conversion to Ni/Pt to Catalyze Oxygen Reductionx135201447#N/AFALSE
2095
ja513166w10.1021/ja513166wFALSEhttps://doi.org/10.1021/ja513166wHayashi, TJ. Am. Chem. Soc.Three-component reaction of Aryl Grignard reagerits, alkynes, and Aryl halides in the presence of 1 mol % of NiCl2 proceeded sequentially through carbomagnesiation of the alkyne followed by cross-coupling of the resulting alkenyl Grignard reagent with Aryl halide to give tetrasubstituted alkene in high yields.Nickel-Catalyzed Three-Component Domino Reactions of Aryl Grignard Reagents, Alkynes, and Aryl Halides Producing Tetrasubstituted Alkenes80201559#N/ATRUE
2096
ja509214d10.1021/ja509214dFALSEhttps://doi.org/10.1021/ja509214dShao-Horn, YJ. Am. Chem. Soc.We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanopartiCles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M3+ and M2+) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M3+ and M2+ in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu3+, as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu3+ is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts.Structure, Bonding, and Catalytic Activity of Monodisperse, Transition-Metal-Substituted CeO2 NanopartiClesx101201452#N/AFALSE
2097
ja509150j10.1021/ja509150jFALSEhttps://doi.org/10.1021/ja509150jSolomon, EIJ. Am. Chem. Soc.The multicopper oxidases (MCOs) are the family of enzymes that catalyze the 4-electron reduction of O-2 to H2O coupled to the four 1-electron oxidations of substrate. In the catalytic cyCle electrons are transferred intramolecularly over similar to 13 angstrom from a Type 1 (T1) Cu site that accepts electrons from substrate to a trinuClear Cu Cluster (TNC) where O-2 is reduced to H2O at rapid rates consistent with turnover (560 s(-1)). The oxygen reduction mechanism for the MCOs is well-characterized, whereas the rereduction is less understood. Our initial study of Rhus vernicifera Laccase (Heppner et al. J. Am. Chem. Soc. 2013, 135, 12212) experimentally established that the native intermediate (NI), the species formed upon O-O bond Cleavage, is reduced with an IET rate >700 s(-1) and is the catalytically relevant fully oxidized form of the enzyme, rather than the resting state. In this report, we present kinetic and spectroscopic results coupled to DFT calculations that evaluate the mechanism of the 3 e(-)/3 H+ reduction of NI, where all three catalytically relevant intramolecular electron transfer (IET) steps are rapid and involve three different structural changes. These three rapid IET processes reflect the sophisticated mechanistic control of the TNC to enable rapid turnover. All three IET processes are fast due to the associated protonation of the bridging oxo and hydroxo ligands, generated by O-O Cleavage, to form water products that are extruded from the TNC upon full reduction, thereby defining a unifying mechanism for oxygen reduction and rapid IET by the TNC in the catalytic cyCle of the MCOs.Mechanism of the Reduction of the Native Intermediate in the Multicopper Oxidases: Insights into Rapid Intramolecular Electron Transfer in Turnoverx30201459#N/AFALSE
2098
ja513112r10.1021/ja513112rFALSEhttps://doi.org/10.1021/ja513112rLee, YJ. Am. Chem. Soc.Reversible transformations are observed between a phosphide-nickel(II) alkoxide and a phosphinite-nickel(0) species via a P-O bond formation coupled with a 2-e(-) redox change at the nickel center. In the forward reaction, the nickel(0) dinitrogen species ((PPP)-P-OMe)Ni(N-2) (2) and {((PPP)-P-OMe)Ni}(2)(mu-N-2) (3) were formed from the reaction of (PPP)NiCl (1) with a methoxy anion. In the backward reaction, a (PPP)Ni(II) moiety was regenerated from the CO2 reaction of 3 with the concomitant formation of a methyl carbonate ligand in (PPP)Ni(OCOOMe) (7). Thus, unanticipated metal-ligand cooperation involving a phosphide based ligand is reported.Phosphinite-Ni(0) Mediated Formation of a Phosphide-Ni(II)-OCOOMe Species via Uncommon Metal-Ligand Cooperation33201549#N/ATRUE
2099
ja513003410.1021/ja5130034FALSEhttps://doi.org/10.1021/ja5130034Osuka, Ameso-meso Linked Porphyrin-[26]Hexaphyrin-Porphyrin Hybrid Arrays and Their Triply Linked Tapes Exhibiting Strong Absorption Bands in the NIR Region2015#N/ATRUE
2100
ja508407810.1021/ja5084078https://doi.org/10.1021/ja5084078Hill, ClJ. Am. Chem. Soc.A tetra-nickel-containing polyoxotungstate, Na6K4[Ni-4(H2O)(2)(PW9O34)(2)]center dot 32H(2)O (Na6K4-Ni4P2), has been synthesized in high yield and systematically characterized. The X-ray crystal structure confirms that a tetra-nickel Cluster core [Ni4O14] is sandwiched by two trivacant, heptadentate [PW9O34]9--POM ligands. When coupled with (4,4'-di-tert-butyl-2,2'-dipyridyl)-bis(2-phenylpyridine(1H))-iridium(III) hexafluorophosphate [Ir(ppy)(2)(dtbbpy)][PF6] as photosensitizer and triethanolamine (TEOA) as sacrificial electron donor, the noble-metal-free complex Ni4P(2) works as an efficient and robust molecular catalyst for H-2 production upon visible light irradiation. Under minimally optimized conditions, Ni4P2 catalyzes H-2 production over 1 week and achieves a turnover number (TON) of as high as 6500 with almost no loss in activity. Mechanistic studies (emission quenching, time-resolved fluorescence decay, and transient absorption spectroscopy) confirm that, under visible light irradiation, the excited state [Ir(ppy)(2)(dtbbpy)](+)* can be both oxidatively and reductively quenched by Ni4P2 and TEOA, respectively. Extensive stability studies (e.g., UV-vis absorption, FT-IR, mercury-poison test, dynamic light scattering (DLS) and transmission electron microscopy (TEM)) provide very strong evidence that Ni4P2 catalyst remains homogeneous and intact under turnover conditions.A Noble-Metal-Free, Tetra-nickel Polyoxotungstate Catalyst for Efficient Photocatalytic Hydrogen EvolutionPhotocatalyst140201473#N/AFALSE
2101
ja512946e10.1021/ja512946eFALSEhttps://doi.org/10.1021/ja512946eMolander, GAJ. Am. Chem. Soc.Single-electron-mediated Alkyl transfer affords a novel mechanism for transmetalation, enabling cross-coupling under mild conditions. Here, general conditions are reported for cross-coupling of secondary AlkyltrifluorB(OH)2rates with an array of Aryl bromides mediated by an Ir photoredox catalyst and a Ni cross-coupling catalyst.Single-Electron Transmetalation: An Enabling Technology for Secondary Alkylboron Cross-Coupling209201545#N/ATRUE
2102
ja512040c10.1021/ja512040cFALSEhttps://doi.org/10.1021/ja512040cTsuji, YJ. Am. Chem. Soc.A regiodivergent silaCarbonylation of allenes under a CO2 atmosphere with toluene2Si-B(pin) as a silicon source in the presence of a copper catalyst at 70 degrees C has been developed. The regioselectivity of the reaction is successfully reversed by the proper choice of ligand; Carbonylated Vinylsilanes are obtained with rac-Me-DuPhos as the ligand, whereas the use of PCy3 affords Carbonylated allylsilanes. Thus, two different Carbonylated silanes can be selectively and regiodivergently synthesized from a single allene substrate.Copper-Catalyzed Regiodivergent SilaCarbonylation of Allenes with Carbon Dioxide and a Silylborane85201472#N/ATRUE
2103
ja507619d10.1021/ja507619dFALSEhttps://doi.org/10.1021/ja507619dNishihara, HJ. Am. Chem. Soc.A bulk material comprising stacked nanosheets of nickel bis(dithiolene) complexes is investigated. The average oxidation number is -3/4 for each complex unit in the as-prepared sample; oxidation or reduction respectively can change this to 0 or -1. Refined electrical conductivity measurement, involving a single microflake sample being subjected to the van der Pauw method under scanning electron microscopy control, reveals a conductivity of 1.6 x 10 (2) S cm(1), which is remarkably high for a coordination polymeric material. Conductivity is also noted to modulate with the change of oxidation state. Theoretical calculation and photoelectron emission spectroscopy reveal the stacked nanosheets to have a metallic nature. This work provides a foothold for the development of the first organic-based two-dimensional topological insulator, which will require the precise control of the oxidation state in the single-layer nickel bisdithiolene complex nanosheet (cf. Liu, F. et al. Nano Lett. 2013, 13, 2842).Redox Control and High Conductivity of Nickel Bis(dithiolene) Complex pi-Nanosheet: A Potential Organic Two-Dimensional Topological Insulatorx266201445#N/AFALSE
2104
ja507297p10.1021/ja507297phttps://doi.org/10.1021/ja507297pKanatzidis, MGJ. Am. Chem. Soc.Naturally abundant enzymes often feature active sites comprising transition metal Cluster units that catalyze chemical processes and reduce small molecules as well as protons. We introduce a family of new chalcogenide aerogels (chalcogels), aiming to model the function of active sites and the structural features of a larger protective framework. New metal incorporated iron sulfur tin sulfide chalcogels referred to as ternary chalcogels and specifically the chalcogels M-ITS-cg3, fully integrate biological redox-active Fe4S4 Clusters into a semiconducting porous framework by bridging them with Sn4S10 linking units. In the M-ITS-cg3 system we can tailor the electro- and photocatalytic properties of chalcogels through the control of spatial distance of redox-active Fe4S4 centers using additional linking metal ions, M2+ (Pt, Zn, Co, Ni, Sn). The presence of a third metal does not change the structural properties of the biomimetic chalcogels but modifies and even enhances their functional performance. M-ITS-cg3s exhibit electrocatalytic activity in proton reduction that arises from the Fe4S4 Clusters but is tuned inductively by M2+. The metal ions alter the reduction potential of Fe4S4 in a favorable manner for photochemical hydrogen production. The Pt incorporated ITS-cg3 shows the greatest improvement in the overall hydrogen yield compared to the binary ITS-cg3. The ability to manipulate the properties of biomimetic chalcogels through synthetic control of the composition, while retaining both structural and functional properties, illustrates the chalcogels' flexibility and potential in carrying out useful electrochemical and photochemical reactions.Enhanced Photochemical Hydrogen Evolution from Fe4S4-Based Biomimetic Chalcogels Containing M2+ (M = Pt, Zn, Co, Ni, Sn) CentersPhotocatalyst34201457#N/AFALSE
2105
ja511778a10.1021/ja511778aFALSEhttps://doi.org/10.1021/ja511778aMontgomery, JJ. Am. Chem. Soc.Combinations of ligand, reducing agent, and reaction conditions have been identified that allow alteration in the rate- and regioselectivity-determining step of nickel-catalyzed aldehyde-alkyne reductive couplings. Whereas previously developed protocols involve metallacyCle-forming oxidative cyClization as the rate-determining step, this study illustrates that the combination of large ligands, large silanes, and elevated reaction temperature alters the rate- and regiochemistry-determining step for one of the two possible product regioisomers. These modifications render metallacyCle formation reversible for the minor isomer pathway, and sigma-bond metathesis of the metallacyCle Ni-O bond with the silane reductant becomes rate limiting. The ability to tune regiocontrol via this alteration in reversibility of a key step allows highly regioselective outcomes that were not possible using previously developed methods.Regiocontrol in Catalytic Reductive Couplings through Alterations of Silane Rate Dependence35201551#N/ATRUE
2106
ja506230r10.1021/ja506230rFALSEhttps://doi.org/10.1021/ja506230rLong, JRJ. Am. Chem. Soc.The well-known frameworks of the type M-2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenediCarbonylate) have numerous potential applications in gas storage and separations, owing to their exceptionally high concentration of coordinatively unsaturated metal surface sites, which can interact strongly with small gas molecules such as H-2 center dot Employing a related meta-functionalized linker that is readily obtained from resorcinol, we now report a family of structural isomers of this framework, M-2(m-dobdc) (M = Mg, Mn, Fe, Co, Ni; m-dobdc(4-) = 4,6-dioxido-1,3-benzenediCarbonylate), featuring exposed M-2 cation sites with a higher apparent charge density. The regioisomeric linker alters the symmetry of the ligand field at the metal sites, leading to increases of 0.4-1.5 kJ/mol in the H-2 binding enthalpies relative to M-2(dobdc). A variety of techniques, inCluding powder X-ray and neutron diffraction, inelastic neutron scattering, infrared spectroscopy, and first-principles electronic structure calculations, are applied in elucidating how these subtle structural and electronic differences give rise to such increases. Importantly, similar enhancements can be anticipated for the gas storage and separation properties of this new family of robust and potentially inexpensive metal-organic frameworks.M-2(m-dobdc) (M = Mg, Mn, Fe, Co, Ni) Metal-Organic Frameworks Exhibiting Increased Charge Density and Enhanced H-2 Binding at the Open Metal Sitesx131201495#N/AFALSE
2107
ja506087h10.1021/ja506087hFALSEhttps://doi.org/10.1021/ja506087hMuller, AMJ. Am. Chem. Soc.Surfactant-free mixed-metal hydroxide water oxidation nanocatalysts were synthesized by pulsed-laser ablation in liquids. In a series of [Ni-Fe]-layered double hydroxides with intercalated nitrate and water, [Ni1-xFex(OH)(2)](NO3)(y)(OH)(x-y)center dot nH(2)O, higher activity was observed as the amount of Fe decreased to 22%. Addition of Ti4+ and La3+ ions further enhanced electrocatalysis, with a lowest overpotential of 260 mV at 10 mA cm(-2). Electrocatalytic water oxidation activity increased with the relative proportion of a 405.1 eV N 1s (XPS binding energy) species in the nanosheets.Highly Active Mixed-Metal Nanosheet Water Oxidation Catalysts Made by Pulsed-Laser Ablation in Liquidsx217201451#N/AFALSE
2108
ja505858y10.1021/ja505858yFALSEhttps://doi.org/10.1021/ja505858yLu, XJ. Am. Chem. Soc.The endohedral fullerene once erroneously identified as Sc-3@C-82 was recently shown to be Sc3C2@I-h-C-80, the first example of an open-shell Cluster metallofullerene. We herein report that Benzyl bromide (1) reacts with Sc3C2@ I-h-C-80 via a regioselective radical addition that affords only one isomer of the adduct Sc3C2@I-h-C-80(CH2C6H5) (2) in high yield. An X-ray crystallographic study of 2 demonstrated that the Benzyl moiety is singly bonded to the fullerene cage, which eliminates the paramagnetism of the endohedral in agreement with the ESR results. Interestingly, X-ray results further reveal that the 3-fold disordered Sc3C2 Cluster adopts two different configurations inside the cage. These configurations represent the so-called planar form and the computationally predicted, but not crystallographically characterized, trifoliate form. It is noteworthy that this is the first crystallographic observation of the trifoliate form for the Sc3C2 Cluster. In contrast, crystallographic investigation of a Sc3C2@I-h-C-80/Ni(OEP) cocrystal, in which the endohedral persists in an open-shell structure with paramagnetism, indicates that only the former form occurs in pristine Sc3C2@ I-h-C-80. These results demonstrate that the Cluster configuration in EMFs is highly sensitive to the electronic structure, which is tunable by exohedral modification. In addition, the electrochemical behavior of Sc3C2@I-h-C-80 has been markedly changed by the radical addition, but the absorption spectra of the pristine and the derivative are both featureless. These results suggest that the unpaired electron of Sc3C2@I-h-C-80 is buried in the Sc3C2 Cluster and does not affect the electronic configuration of the cage.Regioselective Benzyl Radical Addition to an Open-Shell Cluster Metallofullerene. Crystallographic Studies of Cocrystallized Sc3C2@I-h-C-80 and Its Singly Bonded Derivativex26201432#N/AFALSE
2109
ja505853210.1021/ja5058532FALSELi, YDSophisticated Construction of Au Islands on Pt-Ni: An Ideal Trimetallic Nanoframe Catalystx2014#N/AFALSE
2110
ja505791r10.1021/ja505791rFALSEhttps://doi.org/10.1021/ja505791rJaramillo, TFJ. Am. Chem. Soc.Fuels and industrial chemicals that are conventionally derived from fossil resources could potentially be produced in a renewable, sustainable manner by an electrochemical process that operates at room temperature and atmospheric pressure, using only water, CO2, and electricity as inputs. To enable this technology, improved catalysts must be developed. Herein, we report trends in the electrocatalytic conversion of CO2 on a broad group of seven transition metal surfaces: Au, Ag, Zn, Cu, Ni, Pt, and Fe. Contrary to conventional knowledge in the field, all metals studied are capable of producing methane or methanol. We quantify reaction rates for these two products and describe catalyst activity and selectivity in the framework of CO binding energies for the different metals. While selectivity toward methane or methanol is low for most of these metals, the fact that they are all capable of producing these products, even at a low rate, is important new knowledge. This study reveals a richer surface chemistry for transition metals than previously known and provides new insights to guide the development of improved CO2 conversion catalysts.Electrocatalytic Conversion of Carbon Dioxide to Methane and Methanol on Transition Metal Surfaces
Electrocatalytic
800201436#N/AFALSE
2111
ja511607j10.1021/ja511607jFALSEhttps://doi.org/10.1021/ja511607jBerry, JFElectronic Structure of Ni2E2 Complexes (E = S, Se, Te) and a Global Analysis of M2E2 Compounds: A Case for Quantized E-2(n-) Oxidation Levels with n=2, 3, or 42015#N/ATRUE
2112
ja505454v10.1021/ja505454vFALSEhttps://doi.org/10.1021/ja505454vHofmann, SJ. Am. Chem. Soc.The dynamics of the graphene-catalyst interaction during chemical vapor deposition are investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy, and complementary grand canonical Monte Carlo simulations coupled to a tight-binding model. We thereby reveal the interdependency of the distribution of carbon Close to the catalyst surface and the strength of the graphene-catalyst interaction. The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon Close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10(-6)-10(-3) mbar). A further hydrocarbon pressure increase (to similar to 10(-1) mbar) leads to weakening of the graphene-Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We show that growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. The key implications of these results for graphene growth control and their relevance to carbon nanotube growth are highlighted in the context of existing literature.Interdependency of Subsurface Carbon Distribution and Graphene-Catalyst Interactionx72201471#N/AFALSE
2113
ja505318p10.1021/ja505318pFALSEhttps://doi.org/10.1021/ja505318pLong, JRJ. Am. Chem. Soc.Six metal organic frameworks of the M-2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobdc(4-) = 2,5-dioxido-1,4-benzenedicarbox-ylate) structure type are demonstrated to bind carbon monoxide reversibly and at high capacity. Infrared spectra indicate that, upon coordination of CO to the divalent metal cations lining the pores within these frameworks, the C-O stretching frequency is blue-shifted, consistent with nonClassical metal-CO interactions. Structure determinations reveal M-CO distances ranging from 2.09(2) angstrom for M = Ni to 2.49(1) angstrom for M = Zn and M-C-O angles ranging from 161.2(7)degrees for M = Mg to 176.9(6) for M = Fe. Electronic structure calculations employing density functional theory (DFT) resulted in good agreement with the trends apparent in the infrared spectra and crystal structures. These results represent the first crystallographically characterized magnesium and zinc Carbonyl compounds and the first high-spin manganese(II), iron(II), cobalt(II), and nickel(II) Carbonyl species. Adsorption isotherms indicate reversible adsorption, with capacities for the Fe, Co, and Ni frameworks approaching one CO per metal cation site at 1 bar, corresponding to loadings as high as 6.0 mmol/g and 157 cm(3)/cm(3). The six frameworks display (negative) isosteric heats of CO adsorption ranging from 52.7 to 27.2 kJ/mol along the series Ni > Co > Fe > Mg > Mn > Zn, following the Irving Williams stability order. The reversible CO binding suggests that these frameworks may be of utility for the separation of CO from various industrial gas mixtures, inCluding CO/H-2 and CO/N-2. Selectivities determined from gas adsorption isotherm data using ideal adsorbed solution theory (IAST) over a range of gas compositions at 1 bar and 298 K indicate that all six M-2(dobdc) frameworks could potentially be used as solid adsorbents to replace current cryogenic distillation technologies, with the choice of M dictating adsorbent regeneration energy and the level of purity of the resulting gases.Reversible CO Binding Enables Tunable CO/H-2 and CO/N-2 Separations in Metal-Organic Frameworks with Exposed Divalent Metal Cationsx136201495#N/AFALSE
2114
ja505119q10.1021/ja505119qFALSEhttps://doi.org/10.1021/ja505119qZebger, IJ. Am. Chem. Soc.[NiFe] hydrogenases catalyze the reversible Cleavage of hydrogen and, thus, represent model systems for the investigation and exploitation of emission-free energy conversion processes. Valuable information on the underlying molecular mechanisms can be obtained by spectroscopic techniques that monitor individual catalytic intermediates. Here, we employed resonance Raman spectroscopy and extended it to the entire binuClear active site of an oxygen-tolerant [NiFe] hydrogenase by probing the metal-ligand modes of both the Fe and, for the first time, the Ni ion. Supported by theoretical methods, this approach allowed for monitoring H-transfer from the active site and revealed novel insights into the so far unknown structure and electronic configuration of the hydrogen-binding intermediate of the catalytic cyCle, thereby providing key information about catalytic intermediates and reactions of biological hydrogen Activation.Resonance Raman Spectroscopy on [NiFe] Hydrogenase Provides Structural Insights into Catalytic Intermediates and Reactionsx40201411#N/AFALSE
2115
ja504942h10.1021/ja504942hFALSEhttps://doi.org/10.1021/ja504942hArmstrong, FAJ. Am. Chem. Soc.Cyanide reacts rapidly with [NiFe]-hydrogenases (hydrogenase-1 and hydrogenase-2 from Escherichia coli) under mild oxidizing conditions, inhibiting the electrocatalytic oxidation of hydrogen as recorded by protein film electrochemistry. Electrochemical, EPR, and FTIR measurements show that the final enzyme product, formed within a second (even under 100% H-2), is the resting state known as Ni-B, which contains a hydroxido-bridged species, Ni-III-mu(OH)-Fe-II, at the active site. Cyanide inhibition is easily reversed because it is simply the reductive Activation of Ni-B. This paper brings back into focus an observation originally made in the 1940s that cyanide inhibits microbial H-2 oxidation and addresses the interesting mechanism by which cyanide promotes the formation of Ni-B. As a much stronger nuCleophile than hydroxide, cyanide binds more rapidly and promotes oxidation of Ni-II to Ni-III; however, it is quickly replaced by hydroxide which is a far superior bridging ligand.Unusual Reaction of [NiFe]-Hydrogenases with Cyanidex8201443#N/AFALSE
2116
ja504744510.1021/ja5047445FALSEhttps://doi.org/10.1021/ja5047445Winpenny, REPJ. Am. Chem. Soc.Compounds of general formula [Cr7MF3(Etglu)-((O2CBu)-Bu-t)(15)(Phpy)] [H(5)Etglu = N-ethyl-n-glucamine; Phpy = 4-phenylpyridine; M = Zn (1), Mn (2), Ni (3)] have been prepared. The structures contain an irregular octagon of metal sites formed around the penta-deprotonated Etglu(5-) ligand; the chirality of N-ethyl-n-glucamine is retained in the final product. The seven Cr-III sites have a range of coordination environments, and the divalent metal site is crystallographically identified and has a Phpy ligand attached to it. By using complementary experimental techniques, inCluding magnetization and specific heat measurements, inelastic neutron scattering, and electron paramagnetic resonance spectroscopy, we have investigated the magnetic features of this family of {Cr7M} rings. Microscopic parameters of the spin Hamiltonian have been determined as a result of best fits of the different experimental data, allowing a direct comparison with corresponding parameters found in the parent compounds. We examine whether these parameters can be transferred between compounds and compare them with those of an earlier family of heterometallic rings.A Detailed Study of the Magnetism of Chiral {Cr7M} Rings: An Investigation into Parametrization and Transferability of Parametersx15201436#N/AFALSE
2117
ja504667f10.1021/ja504667fFALSEhttps://doi.org/10.1021/ja504667fPeters, JCJ. Am. Chem. Soc.New approaches toward the generation of late first-row metal catalysts that efficiently facilitate two-electron reductive transformations (e.g., hydrogenation) more typical of noble-metal catalysts is an important goal. Herein we describe the synthesis of a structurally unusual S = 1 bimetallic Co complex, [((PBP)-P-Cy)CoH](2) (1), supported by bis(phosphino)boryl and bis(phosphino)hydridB(OH)2rane ligands. This complex reacts reversibly with a second equivalent of H-2 (1 atm) and serves as an olefin hydrogenation catalyst under mild conditions (room temperature, 1 atm H-2). A bimetallic Co species is invoked in the rate-determining step of the catalysis according to kinetic studies. A structurally related (NiNiI)-Ni-I dimer, [((PBP)-P-Ph)Ni](2) (3), has also been prepared. Like Co catalyst 1, Ni complex 3 displays reversible reactivity toward H-2, affording the bimetallic complex [((PBHP)-P-Ph)NiH](2) (4). This reversible behavior is unprecedented for NiI species and is attributed to the presence of a borylNi bond. Lastly, a series of monomeric ((PBP)-P-tBu)NiX complexes (X = Cl (5), OTf (6), H (7), OC(H)O (8)) have been prepared. The complex ((PBP)-P-tBu)NiH (7) shows enhanced catalytic olefin hydrogenation activity when directly compared with its isoelectronic/isostructural analogues where the boryl unit is substituted by a phenyl or amine donor, a phenomenon that we posit is related to the strong trans influence exerted by the boryl ligand.Boryl-Metal Bonds Facilitate Cobalt/Nickel-Catalyzed Olefin Hydrogenationx1402014130#N/AFALSE
2118
ja511503d10.1021/ja511503dFALSEhttps://doi.org/10.1021/ja511503dWeckhuysen, BMJ. Am. Chem. Soc.Full-field transmission X-ray microscopy has been used to determine the 3D structure of a whole individual fluid catalytic cracking (FCC) partiCle at high spatial resolution and in a fast, noninvasive manner, maintaining the full integrity of the partiCle. Using X-ray absorption mosaic imaging to combine multiple fields of view, computed tomography was performed to visualize the macropore structure of the catalyst and its availability for mass transport. We mapped the relative spatial distributions of Ni and Fe using multiple-energy tomography at the respective X-ray absorption K-edges and correlated these distributions with porosity and permeability of an equilibrated catalyst (E-cat) partiCle. Both metals were found to accumulate in outer layers of the partiCle, effectively decreasing porosity by Clogging of pores and eventually restricting access into the FCC partiCle.Mapping Metals Incorporation of a Whole Single Catalyst PartiCle Using Element Specific X-ray Nanotomography59201515#N/ATRUE
2119
ja504283610.1021/ja5042836FALSEJones, MOHydrogen Production from Ammonia Using Sodium Amidex2014#N/AFALSE
2120
ja504282w10.1021/ja504282wFALSEhttps://doi.org/10.1021/ja504282wAllen, JPJ. Am. Chem. Soc.The utilization of solar energy requires an efficient means for its storage as chemical energy. In bioinspired artificial photosynthesis, light energy can be used to drive water oxidation, but catalysts that produce molecular oxygen from water are needed to avoid excessive driving potentials. In this paper, we demonstrate the utility of a novel complex utilizing earth-abundant Ni in combination with glycine as an efficient catalyst with a modest overpotential of 0.475 +/- 0.005 V at a current density of 1 mA/cm(2) at pH 11. Catalysis requires the presence of the amine moiety with the glycine most likely coordinating the Ni in a 4:1 molar ratio. The production of molecular oxygen at a high potential is verified by measurement of the change in oxygen concentration, yielding a Faradaic efficiency of 60 +/- 5%. The catalytic species is most likely a heterogeneous Ni-hydroxide formed by electrochemical oxidation. This Ni species can achieve a current density of 4 mA/cm2 that persists for at least 10 h. Based upon the observed pH dependence of the current amplitude and oxidation/reduction peaks, the catalytic mechanism is an electron proton coupled process.Water Oxidation by a Nickel-Glycine Catalystx69201421#N/AFALSE
2121
ja511299y10.1021/ja511299yFALSEhttps://doi.org/10.1021/ja511299yKey, BJ. Am. Chem. Soc.Direct observations of structure-electrochemical activity relationships continue to be a key challenge in secondary battery research. Li-6 magic angle spinning (MAS) nuClear magnetic resonance (NMR) spectroscopy is the only structural probe currently available that can quantitatively characterize local lithium environments on the subnanometer scale that dominates the free energy for site occupation in lithium-ion (Li-ion) intercalation materials. In the present study, we use this local probe to gain new insights into the complex electrochemical behavior of activated (0).(5Li2MnO3)-Li-6.(0).(5LiMn0)-Li-6.Ni-5(0).O-5(2), lithium- and manganese-rich transition-metal (TM) oxide intercalation electrodes. We show direct evidence of path-dependent lithium site occupation, correlated to structural reorganization of the metal oxide and the electrochemical hysteresis, during lithium insertion and extraction. We report new Li-6 resonances centered at 1600 ppm that are assigned to LiMn6-TMtet sites, specifically, a hyperfine shift related to a small fraction of re-entrant tetrahedral TMs (Mn-tet), located above or below lithium layers, coordinated to LiMn6 units. The intensity of the TM layer lithium sites correlated with tetrahedral TMs loses intensity after cyCling, indicating limited reversibility of TM migrations upon cyCling. These findings reveal that defect sites, even in dilute concentrations, can have a profound effect on the overall electrochemical behavior.Re-entrant Lithium Local Environments and Defect Driven Electrochemistry of Li- and Mn-Rich Li-Ion Battery Cathodes121201543#N/ATRUE
2122
ja503541v10.1021/ja503541vFALSEhttps://doi.org/10.1021/ja503541vSpiro, TGJ. Am. Chem. Soc.The recently developed technique of femtosecond stimulated Raman spectroscopy, and its variant, femtosecond Raman-induced Kerr effect spectroscopy (FRIKES), offer access to ultrafast excited-state dynamics via structurally specific vibrational spectra. We have used FRIKES to study the photoexcitation dynamics of nickel(11) phthalocyanine with eight butoxy substituents, NiPc(OBu)(8). NiPc(OBu)(8) is reported to have a relatively long-lived ligand-to-metal charge-transfer (LMCT) state, an essential characteristic for efficient electron transfer in photocatalysis. Following photoexcitation, vibrational transitions in the FRIKES spectra, assignable to phthalocyanine ring modes, evolve on the femtosecond to picosecond time scales. Correlation of ring core size with the frequency of the nu(10) (asymmetric C-N stretching) mode confirms the identity of the LMCT state, which has a similar to 500 ps lifetime, as well as that of a precursor d-d excited state. An even earlier (similar to 0.2 ps) transient is observed and tentatively assigned to a higher-lying Jahn-Teller-active LMCT state. This study illustrates the power of FRIKES spectroscopy in elucidating ultrafast molecular dynamics.Ultrafast Charge Transfer in Nickel Phthalocyanine Probed by Femtosecond Raman-Induced Kerr Effect Spectroscopyx12201489#N/AFALSE
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ja510442p10.1021/ja510442pFALSEhttps://doi.org/10.1021/ja510442pJaramillo, TFJ. Am. Chem. Soc.Objective comparisons of electrocatalyst activity and stability using standard methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, we use a standard protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochemically active surface area (ECSA) of 18 electrocatalysts for the hydrogen evolution reaction (HER) and 26 electrocatalysts for the oxygen evolution reaction (OER) under conditions relevant to an integrated solar water-splitting device in aqueous acidic or alkaline solution. Our primary figure of merit is the overpotential necessary to achieve a magnitude current density of 10 mA cm(-2) per geometric area, the approximate current density expected for a 10% efficient solar-to-fuels conversion device under 1 sun illumination. The specific activity per ECSA of each material is also reported. Among HER catalysts, several could operate at 10 mA cm(-2) with overpotentials <0.1 V in acidic and/or alkaline solutions. Among OER catalysts in acidic solution, no non-noble metal based materials showed promising activity and stability, whereas in alkaline solution many OER catalysts performed with similar activity achieving 10 mA cm(-2) current densities at overpotentials of similar to 0.33-0.5 V. Most OER catalysts showed comparable or better specific activity per ECSA when compared to Ir and Ru catalysts in alkaline solutions, while most HER catalysts showed much lower specific activity than Pt in both acidic and alkaline solutions. For select catalysts, additional secondary screening measurements were conducted inCluding Faradaic efficiency and extended stability measurements.Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices19932015116#N/ATRUE
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ja503107h10.1021/ja503107hFALSEhttps://doi.org/10.1021/ja503107hRomesberg, FEJ. Am. Chem. Soc.Many residues within proteins adopt conformations that appear to be stabilized by interactions between an amide NH and the amide N of the previous residue. To explore whether these interactions constitute hydrogen bonds, we characterized the IR stretching frequencies of deuterated variants of proline and the corresponding carbamate, as well as the four proline residues of an Src homology 3 domain protein. The C delta D2 stretching frequencies are shifted to lower energies due to hyperconjugation with N-i electron density, and engaging this density via protonation or the formation of the Ni+1H center dot center dot center dot N-i interaction ablates this hyperconjugation and thus induces an otherwise difficult to explain blue shift in the CD absorptions. Along with density functional theory calculations, the data reveal that the Ni+1H center dot center dot center dot N-i interactions constitute H-bonds and suggest that they may play an important and previously underappreciated role in protein folding, structure, and function.Evidence of an Unusual N-H center dot center dot center dot N Hydrogen Bond in Proteinsx33201431#N/AFALSE
2125
ja509993510.1021/ja5099935FALSEhttps://doi.org/10.1021/ja5099935Houk, KNJ. Am. Chem. Soc.The distortion/interaction model has been used to explain and predict reactivity in a variety of reactions where more common explanations, such as steric and electronic factors, do not suffice. This model has also provided new fundamental insight into regioselectivity trends in reactions of unsymmetrical arynes, which in turn has fueled advances in aryne methodology and natural product synthesis. This artiCle describes a systematic experimental and computational study of one particularly important Class of arynes, 3-halobenzynes. 3-Halobenzynes are useful synthetic building blocks whose regioselectivities have been explained by several different models over the past few decades. Our efforts show that aryne distortion, rather than steric factors or charge distribution, are responsible for the regioselectivities observed in 3-haloaryne trapping experiments. We also demonstrate the synthetic utility of 3-halobenzynes for the efficient synthesis of functionalized heterocyCles, using a tandem aryne-trapping/cross-coupling sequence involving 3-chlorobenzyne.The Role of Aryne Distortions, Steric Effects, and Charges in Regioselectivities of Aryne Reactions1792014104#N/ATRUE
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ja502674410.1021/ja5026744FALSEhttps://doi.org/10.1021/ja5026744Zhong, CJAtomic-Structural Synergy for Catalytic CO Oxidation over Palladium-Nickel Nanoalloysx2014#N/AFALSE
2127
ja509779q10.1021/ja509779qFALSEhttps://doi.org/10.1021/ja509779qJones, AKJ. Am. Chem. Soc.Here we report the electrocatalytic reduction of protons to hydrogen by a novel S2P2 coordinated nickel complex, [Ni(bdt)(dppf)] (bdt = 1,2-benzenedithiolate, dppf = 1,1'-bis(diphenylphosphino)ferrocene). The catalysis is fast and efficient with a turnover frequency of 1240 s(-1) and an overpotential of only 265 mV for half activity at low acid concentrations. Furthermore, catalysis is possible using a weak acid, and the complex is stable for at least 4 h in acidic solution. Calculations of the system carried out at the density functional level of theory (DFT) are consistent with a mechanism for catalysis in which both protonations take place at the nickel center.A Nickel Phosphine Complex as a Fast and Efficient Hydrogen Production Catalyst105201577#N/ATRUE
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ja502474910.1021/ja5024749FALSEhttps://doi.org/10.1021/ja5024749Mirica, LMJ. Am. Chem. Soc.Nickel complexes have been widely employed as catalysts in C-C and C heteroatom bond formation reactions. In addition to Ni(0) and Ni(II) intermediates, several Ni-catalyzed reactions are proposed to also involve odd-electron Ni(I) and Ni(III) oxidation states. We report herein the isolation, structural and spectroscopic characterization, and organometallic reactivity of Ni(III) complexes containing Aryl and Alkyl ligands. These Ni(III) species undergo transmetalation and/or reductive elimination reactions to form new C-C or C heteroatom bonds and are also competent catalysts for Kumada and Negishi cross-coupling reactions. Overall, these results provide strong evidence for the direct involvement of organometallic Ni(111) species in cross-coupling reactions and oxidatively induced C-heteroatom bond formation reactions.Organometallic Nickel(III) Complexes Relevant to Cross-Coupling and Carbon-Heteroatom Bond Formation Reactionsx109201469#N/AFALSE
2129
ja509077a10.1021/ja509077aFALSEhttps://doi.org/10.1021/ja509077aMartin, RJ. Am. Chem. Soc.A novel Ni-catalyzed regiodivergent reductive Carbonylation of allyl esters with CO2 has been developed. This mild, user-friendly, and operationally simple method is characterized by an exquisite selectivity profile that is dictated by the ligand backbone.Ligand-Controlled Regiodivergent Ni-Catalyzed Reductive Carbonylation of Allyl Esters with CO2120201450#N/ATRUE
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ja508909u10.1021/ja508909uFALSEhttps://doi.org/10.1021/ja508909uMontgomery, JJ. Am. Chem. Soc.The mechanism of nickel(0)-catalyzed reductive coupling of aldehydes and alkynes has been studied. Extensive double-labeling crossover studies have been conducted. While previous studies illustrated that phosphine- and N-heterocyClic carbene-derived catalysts exhibited differing behavior, the origin of these effects has now been evaluated in detail. Many variables, inCluding ligand Class, sterics of the ligand and alkyne, temperature, and ring size being formed in intramolecular versions, all influence the extent of crossover observed. A computational evaluation of these effects suggests that dimerization of a key metallacyClic intermediate provides the origin of crossover. Protocols that proceed with crossover are typically less efficient than those without crossover given the thermodynamic stability and low reactivity of the dimeric metallacyCles involved in crossover pathways.Dimer Involvement and Origin of Crossover in Nickel-Catalyzed Aldehyde-Alkyne Reductive Couplings28201459#N/ATRUE
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ja502128j10.1021/ja502128jFALSEhttps://doi.org/10.1021/ja502128jYan, YSJ. Am. Chem. Soc.Electrochemical water splitting is a Clean technology that can store the intermittent renewable wind and solar energy in H-2 fuels. However, large-scale H-2 production is greatly hindered by the sluggish oxygen evolution reaction (OER) kinetics at the anode of a water electrolyzer. Although many OER electrocatalysts have been developed to negotiate this difficult reaction, substantial progresses in the design of cheap, robust, and efficient catalysts are still required and have been considered a huge challenge. Herein, we report the simple synthesis and use of alpha-Ni(OH)(2) nanocrystals as a remarkably active and stable OER catalyst in alkaline media. We found the highly nanostructured alpha-Ni(OH)(2) catalyst afforded a current density of 10 mA cm(-2) at a small overpotential of a mere 0.331 V and a small Tafel slope of similar to 42 mV/decade, comparing favorably with the state-of-the-art RuO2 catalyst. This alpha-Ni(OH)(2) catalyst also presents outstanding durability under harsh OER cyCling conditions, and its stability is much better than that of RuO2. Additionally, by comparing the performance of alpha-Ni(OH)(2) with two kinds of beta-Ni(OH)(2), all synthesized in the same system, we experimentally demonstrate that alpha-Ni(OH)(2) effects more efficient OER catalysis. These results suggest the possibility for the development of effective and robust OER electrocatalysts by using cheap and easily prepared alpha-Ni(OH)(2) to replace the expensive commercial catalysts such as RuO2 or IrO2.Efficient Water Oxidation Using Nanostructured alpha-Nickel-Hydroxide as an Electrocatalystx903201453#N/AFALSE
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ja508067c10.1021/ja508067cFALSEhttps://doi.org/10.1021/ja508067cReisman, SEJ. Am. Chem. Soc.A Ni-catalyzed asymmetric reductive cross-coupling between Vinyl bromides and Benzyl chlorides has been developed. This method provides direct access to enantioenriched products bearing Aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope is achieved under mild reaction conditions that preClude the pregeneration of organometallic reagents and the regioselectivity issues commonly associated with asymmetric allylic ArylationNickel-Catalyzed Asymmetric Reductive Cross-Coupling Between Vinyl and Benzyl Electrophiles121201457#N/ATRUE
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ja501497n10.1021/ja501497nFALSEhttps://doi.org/10.1021/ja501497nCui, YJ. Am. Chem. Soc.Development of a non-noble-metal hydrogen-producing catalyst is essential to the development of solar water-splitting devices. Improving both the activity and the stability of the catalyst remains a key challenge. In this Communication, we describe a two-step reaction for preparing three-dimensional electrodes composed of CoSe2 nanopartiCles grown on carbon fiber paper. The electrode exhibits excellent catalytic activity for a hydrogen evolution reaction in an acidic electrolyte (100 mA/cm(2) at an overpotential of similar to 180 mV). Stability tests though long-term potential cyCles and extended electrolysis confirm the exceptional durability of the catalyst. This development offers an attractive catalyst material for large-scale water-splitting technology.CoSe2 NanopartiCles Grown on Carbon Fiber Paper: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reactionx1043201448#N/AFALSE
2134
ja501293x10.1021/ja501293xFALSEhttps://doi.org/10.1021/ja501293xPeng, ZMJ. Am. Chem. Soc.Although octahedral Pt-Ni alloy nanopartiCles possess an excelling property in oxygen reduction reaction (ORR) and are of great potential as an electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs), mass production of the materials at low cost remains a big challenge. By combining the advantages of both solid-state chemistry and wet synthetic chemistry, we developed one scalable, surfactant-free, and cost-effective method for producing octahedral Pt-Ni alloy nanopartiCles on carbon support. The octahedral Pt-Ni samples were prepared with different compositions and studied for the ORR property. They exhibit a much improved reaction activity compared to the commercial catalyst. The experiments demonstrate an innovative strategy for preparing shaped metal nanopartiCles and make significant progress in the ORR catalyst research.Solid-State Chemistry-Enabled Scalable Production of Octahedral Pt-Ni Alloy Electrocatalyst for Oxygen Reduction Reactionx166201434#N/AFALSE
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ja507951410.1021/ja5079514FALSEhttps://doi.org/10.1021/ja5079514Neupane, KPJ. Am. Chem. Soc.Nickel-containing superoxide dismutase (NiSOD) is a mononuClear cysteinate-ligated nickel metalloenzyme that catalyzes the disproportionation of superoxide into dioxygen and hydrogen peroxide by cyCling between Ni-II and Ni-III oxidation states. All of the ligating residues to nickel are found within the first six residues from the N-terminus, which has prompted several research groups to generate NiSOD metallopeptide-based mimics derived from the first several residues of the NiSOD sequence. To assess the viability of using these metallopeptide-based mimics (NiSOD maquettes) to probe the mechanism of SOD catalysis facilitated by NiSOD, we computationally explored the initial step of the O-2(-) reduction mechanism catalyzed by the NiSOD maquette {Ni-II(SODm1)} (SODm1 = HCDLP CGVYD PA). Herein we use spectroscopic (S K-edge X-ray absorption spectroscopy, electronic absorption spectroscopy, and circular dichroism spectroscopy) and computational techniques to derive the detailed active-site structure of {Ni-II(SODm1)}. These studies suggest that the {Ni-II(SODm1)} active-site possesses a Ni-II-S(H+)-Cys(6) moiety and at least one associated water molecule contained in a hydrogen-bonding interaction to the coordinated Cys(2) and Cys(6) sulfur atoms. A computationally derived mechanism for O-2(-) reduction using the formulated active-site structure of {Ni-II(SODm1)} suggests that O-2(-) reduction takes place through an apparent initial outersphere hydrogen atom transfer (HAT) from the Ni-II-S(H+)-Cys(6) moiety to the O-2(-) molecule. It is proposed that the water molecule aids in driving the reaction forward by lowering the Ni-II-S(H+)-Cys(6) pK(a). Such a mechanism is not possible in NiSOD itself for structural reasons. These results therefore strongly suggest that maquettes derived from the primary sequence of NiSOD are mechanistically distinct from NiSOD itself despite the similarities in the structure and physical properties of the metalloenzyme vs the NiSOD metallopeptide-based models.Cysteinate Protonation and Water Hydrogen Bonding at the Active-Site of a Nickel Superoxide Dismutase Metallopeptide-Based Mimic: Implications for the Mechanism of Superoxide Reduction12201451#N/ATRUE
2136
ja507269n10.1021/ja507269nFALSEhttps://doi.org/10.1021/ja507269nZhou, HCJ. Am. Chem. Soc.A series of mesoporous metalloporphyrin Fe-MOFs, namely PCN-600(M) (M = Mn, Fe, Co, Ni, Cu), have been synthesized using the preassembled [Fe3O(OOCCH3)(6)] building block. PCN-600 exhibits a one-dimensional channel as large as 3.1 nm and the highest experimental pore volume of 1.80 cm(3) g(-1) among all the reported porphyrinic MOFs. It also shows very high stability in aqueous solutions with pH values ranging from 2-11 and is to our knowledge the only mesoporous porphyrinic MOF stable under basic aqueous conditions. PCN-600(Fe) has been demonstrated as an effective peroxidase mimic to catalyze the co-oxidation reaction.A Series of Highly Stable Mesoporous Metalloporphyrin Fe-MOFs238201447#N/ATRUE
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ja505783z10.1021/ja505783zFALSEhttps://doi.org/10.1021/ja505783zRauchfuss, TBJ. Am. Chem. Soc.Theory and experiment indicate that the protonation of reduced NiFe dithiolates proceeds via a previously undetected isomer with enhanced basicity. In particular, it is proposed that protonation of (OC)(3)Fe(pdt)-Ni(dppe) (I; pdt(2-) = S-(CH2)(3)S-; dppe = Ph2P(CH2)(2)PPh2) occurs at the Fe site of the two-electron mixed-valence Fe(0)Ni(II) species, not the Fe(I)-Ni(I) bond for the homovalence isomer of 1. The new pathway, which may have implications for protonation of other complexes and Clusters, was uncovered through studies on the homologous series L(OC)(2)Fe(pdt)M(dppe), where M = Ni, Pd (2), and Pt (3) and L = CO, PCy3. Similar to 1, complexes 2 and 3 undergo both protonation and 1e(-) oxidation to afford well-characterized hydrides ([2H](+) and [3H](+)) and mixed-valence derivatives ([2](+) and [3](+)), respectively. Whereas the Pd site is tetrahedral in 2, the Pt site is square-planar in 3, indicating that this complex is best described as Fe(0)Pt(II). In view of the results on 2 and 3, the potential energy surface of 1 was reinvestigated with density functional theory. These calculations revealed the existence of an energetically accessible and more basic Fe(0)Ni(II) isomer with a square-planar Ni site.Protonation of Nickel-Iron Hydrogenase Models Proceeds after Isomerization at Nickel23201465#N/ATRUE
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ja504289p10.1021/ja504289pFALSEhttps://doi.org/10.1021/ja504289pTalham, DRLight-Induced Magnetization Changes in a Coordination Polymer Heterostructure of a Prussian Blue Analogue and a Hofmann-like Fe(II) Spin Crossover Compound2014#N/ATRUE
2139
ja504150e10.1021/ja504150eFALSEhttps://doi.org/10.1021/ja504150eWang, JJ. Am. Chem. Soc.The use of an ultrasound (US) field for rapid and reversible control of the movement of bubble-propelled chemically powered PEDOT/Ni/Pt microengines is demonstrated. Such operation reflects the US-induced disruption of normal bubble evolution and ejection, essential for efficient propulsion of catalytic microtubular engines. It offers precise speed control, with sharp increases and decreases of the speed at low and high US powers, respectively. A wide range of speeds can thus be generated by tuning the US power. Extremely fast changes in the motor speed (<0.1 s) and reproducible On/Off' Activations are observed, indicating distinct advantages compared to motion control methods based on other external stimuli. Such effective control of the propulsion of chemically powered microengines, inCluding remarkable braking ability, holds considerable promise for diverse applications.Ultrasound-Modulated Bubble Propulsion of Chemically Powered Microengines124201450#N/ATRUE
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ja503489b10.1021/ja503489bFALSEhttps://doi.org/10.1021/ja943960sXie, ZWTransition-Metal-Mediated Three-Component Cascade CyClization: Selective Cage B-C(sp(2)) Coupling of Carborane with Aromatics and Synthesis of Carborane-Fused TricyClics2014#N/ATRUE
2141
ja412317s10.1021/ja412317sFALSEhttps://doi.org/10.1021/ja412317sYang, JLJ. Am. Chem. Soc.Exploring half-metallic materials with high Curie temperature, wide half-metallic gap, and large magnetic anisotropy energy is one of the effective solutions to develop high-performance spintronic devices. Using first-principles calculations, we design a practicable half-metal based on a layered La(Mn0.5Zn0.5)AsO alloy via element substitutions. At its ground state, the pristine La(Mn0.5Zn0.5)AsO alloy is an antiferromagnetic semiconductor. Either hole doping via (Ca2+/Sr2+,La3+) substitutions or electron doping via (H-/F-,O2-) substitutions in the [LaO](+) layer induce half-metallicity in the La(Mn0.5Zn0.5)AsO alloy. The half-metallic gap is as large as 0.74 eV. Monte Carlo simulations based on the Ising model predict a Curie temperature of 475 K for 25% Ca doping and 600 K for 50% H doping, respectively. Moreover, the quasi two-dimensional structure endows the doped La(Mn,Zn)AsO alloy a sizable magnetic anisotropy energy with the magnitude of at least one order larger than those of Fe, Co, and Ni bulks.Room-Temperature Half-Metallicity in La(Mn,Zn)AsO Alloy via Element Substitutionsx74201446#N/AFALSE
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ja502839b10.1021/ja502839bFALSEhttps://doi.org/10.1021/ja502839bWang, ZQSynthetic Supercontainers Exhibit Distinct Solution versus Solid State Guest-Binding Behavior2014#N/ATRUE
2143
ja502601g10.1021/ja502601gFALSEhttps://doi.org/10.1021/ja502601gMurakami, MJ. Am. Chem. Soc.C-C and C-Si sigma-bonds are Cleaved to undergo bond exchange when substrates equipped with cyClobutanone and silacyClobutane moieties are treated with a palladium(0) catalyst. The skeletal exchange results in construction of silabicyClo[5.2.1]decanes in a diastereoselective manner.Cleavage of C-C and C-Si sigma-Bonds and Their Intramolecular Exchange77201459#N/ATRUE
2144
ja411945n10.1021/ja411945nFALSEhttps://doi.org/10.1021/ja411945nMecking, SJ. Am. Chem. Soc.The neutral kappa N-2,O-salicylaldiminato Ni(II) complexes [kappa N-2,O-{(2,6-(3',5'-R2C6H3)(2)C6H3-N=C(H)-(3,5-I-2-2-O-C6H2)}]NiCH3(pyridine)] (1a-pyr, R = Me; 1b-pyr, R = Et; 1c-pyr, R = iPr) convert ethylene to hyperbranched low-molecular-weight oligomers (M-n ca. 1000 g mol(-1)) with high productivities. While all three catalysts are capable of generating hyperbranched structures, branching densities decrease significantly with the nature of the remote substituent along Me > Et > iPr and oligomer molecular weights increase. Consequently, only 1a-pyr forms hyperbranched structures over a wide range of reaction conditions (ethylene pressure 5-30 atm and 20-70 degrees C). An in situ catalyst system achieves similar activities and identical highly branched oligomer microstructures, eliminating the bottleneck given by the preparation and isolation of Ni Me catalyst precursor species. Selective introduction of one primary Carbonylic acid ester functional group per highly branched oligoethylene molecule was achieved by isomerizing ethoxyCarbonylation and alternatively cross metathesis with ethyl acrylate followed by hydrogenation. The latter approach results in complete functionalization and no essential loss of branched oligomer material and molecular weight, as the reacting double bonds are Close to a chain end. Reduction yielded a monoalcohol-functionalized oligomer. Introduction of one reactive epoxide group per branched oligomer occurs completely and selectively under mild conditions. All reaction steps involved in oligomerization and monofunctionalization are efficient and readily scalable.Monofunctional Hyperbranched Ethylene Oligomersx89201452#N/AFALSE
2145
ja411941210.1021/ja4119412FALSEEsposito, DTitanium Nitride-Nickel Nanocomposite as Heterogeneous Catalyst for the Hydrogenolysis of Aryl Ethersx2014#N/AFALSE
2146
ja410822p10.1021/ja410822pFALSEhttps://doi.org/10.1021/ja410822pSola, EJ. Am. Chem. Soc.The five-coordinate carbene complexes [Ru{kappa P,P,Si-Si(Me)(C6H4-2-PiPr(2))(2)}Cl(=CHR)] (2, R = Ph; 3, R = SiMe3), analogues of the Grubbs catalyst, were prepared from the dimer [Ru(mu-Cl){kappa P,Si-Si(Me)(C6H4-2-PiPr(2))(2)}](2) (1) and the corresponding diazoalkane N2CHR. The particular structural features that result from the presence of a strongly trans directing silyl group at the pincer ligand of these complexes are discussed on the basis of NMR information and the crystal structure of the Vinylidene analogue [Ru{kappa P,P,Si-Si(Me)(C6H4-2-PiPr(2))(2)}Cl(=C=CHPh)] (4), which was also obtained from 1 and phenylacetylene. The reactions of 3 with reagents such as P(OMe)(3), CO, NCMe, and K(acac) illustrate that the first response of these carbene complexes to an increase of the coordination number around ruthenium is the insertion of the carbene ligand into the Ru-Si bond. These reactions also indicate that the insertion process is reversible and allows typical transformations of carbene ligands such as C-H functionalizations via carbene insertion (in the acac ligand) or the formation of ketene from CO. In addition, the reactions of 3 with terminal alkynes such as phenylacetylene or 3,3-dimethyl-1-butyne show that the inserted carbenes can also undergo reactions typical of metal-bound Alkyls such as alkyne insertion and C-H reductive elimination.Reversible Insertion of Carbenes into Ruthenium-Silicon Bondsx34201384#N/AFALSE
2147
ja410592d10.1021/ja410592dhttps://doi.org/10.1021/ja410592dReisner, EJ. Am. Chem. Soc.The generation of renewable. H-2 through an efficient photochemical route requires photoinduced electron transfer (ET) from a light harvester to an efficient electrocatalyst in water. Here, we report on a molecular H-2 evolution catalyst (NiP) with a DuBois-type [Ni(P-2(R)'N-2(R)'')(2)](2+) core (P-2(R)'N-2(R)'' = bis(1,5-R'-diphospha-3,7-R ''-diazacyClooctane), which contains an outer coordination sphere with phosphonic acid groups. The latter functionality allows for good solubility in water and immobilization on metal oxide semiconductors. Electrochemical studies confirm that NiP is a highly active electrocatalyst in aqueous electrolyte solution (overpotential of approximately 200 mV at pH 4.5 with a Faradaic yield of 85 +/- 4%). Photocatalytic experiments and investigations on the ET kinetics were carried out in combination with a phosphonated Ru(II) tris(bipyridine) dye (RuP) in homogeneous and heterogeneous environments. Time-resolved luminescence and transient absorption spectroscopy studies confirmed that directed ET from RuP to NiP occurs efficiently in all systems on the nano- to microsecond time scale, through three distinct routes: reductive quenching of RuP in solution or on the surface of ZrO2 (on partiCle system) or oxidative quenching of RuP when the compounds were immobilized on TiO2 (through partiCle system). Our studies show that NiP can be used in a purely aqueous solution and on a semiconductor surface with a high degree of versatility. A high TOF of 460 +/- 60 h(-1) with a TON of 723 +/- 171 for photocatalytic H-2 generation with a molecular Ni catalyst in water and a photon-to-H-2 quantum yield of approximately 10% were achieved for the homogeneous system.Versatile Photocatalytic Systems for H-2 Generation in Water Based on an Efficient DuBois-Type Nickel CatalystPhotocatalyst183201496#N/AFALSE
2148
ja410528y10.1021/ja410528yFALSEhttps://doi.org/10.1021/ja410528yEisenhut, CJ. Am. Chem. Soc.Through the use of an N-heterocyClic carbene (NHC) and the super-silyl group (tBu(3)Si), the novel silylene hydride 2 could be synthesized and isolated in 41% yield. The reaction of 2 with bis(1,5-cyClooctadiene)nickel(0) afforded complex 3, which represents the first example of a dihydrodisilene transition metal complex. Compounds 2 and 3 were fully characterized, inCluding single-crystal X-ray diffraction analysis. The reaction mechanism for the formation of 3 from 2 was investigated by density functional theory calculations, which showed that migration of the NHC from silicon to nickel takes place in this reaction.A Dihydrodisilene Transition Metal Complex from an N-HeterocyClic Carbene-Stabilized Silylene Monohydridex77201364#N/AFALSE
2149
ja502379c10.1021/ja502379cFALSEhttps://doi.org/10.1021/ja502379cBoettcher, SWJ. Am. Chem. Soc.Fe plays a critical, but not yet understood, role in enhancing the activity of the Ni-based oxygen evolution reaction (OER) electrocatalysts. We report electrochemical, in situ electrical, photoelectron spectroscopy, and X-ray diffraction measurements on Ni1-xFex(OH)(2)/Ni1-xFexOOH thin films to investigate the changes in electronic properties, OER activity, and structure as a result of Fe inClusion. We developed a simple method for purification of KOH electrolyte that uses precipitated bulk Ni(OH)(2) to absorb Fe impurities. CyClic voltammetry on rigorously Fe-free Ni(OH)(2)/NiOOH reveals new Ni redox features and no significant OER current until >400 mV overpotential, different from previous reports which were likely affected by Fe impurities. We show through controlled crystallization that beta-NiOOH is less active for OER than the disordered gamma-NiOOH starting material and that previous reports of increased activity for beta-NiOOH are due to incorporation of Fe-impurities during the crystallization process. Through-film in situ conductivity measurements show a >30-fold increase in film conductivity with Fe addition, but this change in conductivity is not sufficient to explain the observed changes in activity. Measurements of activity as a function of film thickness on Au and glassy carbon substrates are consistent with the hypothesis that Fe exerts a partial-charge-transfer Activation effect on Ni, similar to that observed for noble-metal electrode surfaces. These results have significant implications for the design and study of Ni1-xFexOOH OER electrocatalysts, which are the fastest measured OER catalysts under basic conditions.Nickel-Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation1697201483#N/ATRUE
2150
ja410137s10.1021/ja410137sFALSEhttps://doi.org/10.1021/ja410137sHwang, BJJ. Am. Chem. Soc.High-capacity layered, lithium-rich oxide cathodes show great promise for use as positive electrode materials for rechargeable lithium ion batteries. Understanding the effects of oxygen activating reactions on the cathode's surface during electrochemical cyCling can lead to improvements in stability and performance. We used in situ surfaced-enhanced Raman spectroscopy (SERS) to observe the oxygen-related surface reactions that occur during electrochemical cyCling on lithium-rich cathodes. Here, we demonstrate the direct observation of Li2O formation during the extended plateau and discuss the consequences of its formation on the cathode and anode. The formation of Li2O on the cathode leads to the formation of species related to the generation of H2O together with LiOH and to changes within the electrolyte, which eventually result in diminished performance. Protection from, or mitigation of, such devastating surface reactions on both electrodes will be necessary to help realize the potential of high-capacity cathode materials (270 mAhg(-1) versus 140 mAhg(-1) for LiCoO2) for practical applications.Direct In situ Observation of Li2O Evolution on Li-Rich High-Capacity Cathode Material, Li[NixLi(1-2x)/3Mn(2-x)/3]O-2 (0 <= x <= 0.5)x303201449#N/AFALSE
2151
ja409803x10.1021/ja409803xC-O activation theorerical studyFALSEhttps://pubs.acs.org/doi/10.1021/ja409803xItami, KIsolation, Structure, and Reactivity of an Arylnickel(II) Pivalate Complex in Catalytic C-H/C-O BiAryl Coupling2013#N/ATRUE
2152
ja502130w10.1021/ja502130wFALSEhttps://doi.org/10.1021/ja502130wCoates, GWJ. Am. Chem. Soc.While traditional polymerization of linear alpha-olefins (LAOs) typically provides amorphous, low T-g polymers, chain-straightening polymerization represents a route to semicrystalline materials. A series of alpha-diimine nickel catalysts were tested for the polymerization of various LAOs. Although known systems yielded amorphous or low-melting polymers, the sandwich alpha-diimines 3-6 yielded semicrystalline polyethylene comprised primarily of unbranched repeat units via a combination of uncommon regioselective 2,1-insertion and precision chain-walking events.Secondary Alkene Insertion and Precision Chain-Walking: A New Route to Semicrystalline Polyethylene from alpha-Olefins by Combining Two Rare Catalytic Events109201431#N/ATRUE
2153
ja501900j10.1021/ja501900jFALSEhttps://doi.org/10.1021/ja501900jHillhouse, GLThree-Coordinate Nickel Carbene Complexes and Their One-Electron Oxidation Products2014#N/ATRUE
2154
ja409476410.1021/ja4094764https://doi.org/10.1021/ja4094764Chang, CJJ. Am. Chem. Soc.A cobalt-sulfide (Co-S) film prepared via electrochemical deposition on conductive substrates is shown to behave as an efficient and robust catalyst for electrochemical and photoelectrochemical hydrogen generation from neutral pH water. Electrochemical experiments demonstrate that the film exhibits a low catalytic onset overpotential (eta) of 43 mV, a Tafel slope of 93 mV/dec, and near 100% Faradaic efficiency in pH 7 phosphate buffer. Catalytic current densities can approach 50 mA/cm(2) and activity is maintained for at least 40 h. The catalyst can also be electrochemically coated on silicon, rendering a water-compatible photoelectrochemical system for hydrogen production under simulated 1 sun illumination. The facile preparation of this Co-S film, along with its low overpotential, high activity, and long-term aqueous stability, offer promising features for potential use in solar energy applications.Electrodeposited Cobalt-Sulfide Catalyst for Electrochemical and Photoelectrochemical Hydrogen Generation from WaterPhotocatalyst424201376#N/AFALSE
2155
ja501257d10.1021/ja501257dFALSEhttps://doi.org/10.1021/ja501257dThummel, RPVisible Light-Driven Hydrogen Evolution from Water Catalyzed by A Molecular Cobalt Complex2014#N/ATRUE
2156
ja409298410.1021/ja4092984FALSEhttps://doi.org/10.1021/ja4092984Li, DJ. Am. Chem. Soc.A series of neutral cubic nickel(II)-imidazolate Ni8L12X4 cages were prepared by rational choices of substituents and anions with solvothermal subcomponent self-assembly technology. Both substituents and halide anions play a critical role in the formation and stabilization of cubic cages. Changing one of the factors in the reaction will switch the final structure to a Ni14L24 rhombic dodecahedral cage. The cubic cage can transform to a large rhombic dodecahedral cage in the presence of methylamine at room temperature accompanied by a color change from purple to light yellow.Polyhedral Metal-Imidazolate Cages: Control of Self-Assembly and Cage to Cage Transformationx96201340#N/AFALSE
2157
ja408905t10.1021/ja408905thttps://doi.org/10.1021/ja408905tLong, BKJ. Am. Chem. Soc.Sterically demanding Ni-II alpha-diimine precatalysts were synthesized utilizing 2,6-bis(diphenylmethyl)-4-methyl aniline. When activated with methylaluminoxane, the catalyst NiBr2(ArN=C(Me)-C(Me)=NAr) (Ar = 2,6 bis(diphenylmethyl)-4-methylbenzene) was highly active, produced well-defined polyethylene at temperatures up to 100 degrees C (M-w/M-n = 1.09-1.46), and demonstrated remarkable thermal stability at temperatures appropriate for industrially used gas-phase polymerizations (80-100 degrees C).A Robust Ni(II) alpha-Diimine Catalyst for High Temperature Ethylene Polymerizationx200201332#N/AFALSE
2158
ja408787k10.1021/ja408787khttps://doi.org/10.1021/ja408787kNocera, DGJ. Am. Chem. Soc.Photochemical HX splitting requires the management of two protons and the execution of multielectron photoreactions. Herein, we report a photoinduced two-electron reduction of a polypyridyl Ni(II) chloride complex that provides a route to H-2 evolution from HCl. The excited states of Ni complexes are too short to participate directly in HX Activation, and hence, the excited state of a photoredox mediator is exploited for the Activation of HX at the Ni(II) center. Nanosecond transient absorption (TA) spectroscopy has revealed that the excited state of the polypyridine results in a photoreduced radical that is capable of mediating HX Activation by producing a Ni(I) center by halogen-atom abstraction. Disproportionation of the photogenerated Ni(I) intermediate affords Ni(II) and Ni(0) complexes. The Ni(0) center is capable of reacting with HX to produce H-2 and the polypyridyl Ni(II) dichloride, Closing the photocyCle for H-2 generation from HCl.Two-Electron HCl to H-2 PhotocyCle Promoted by Ni(II) Polypyridyl Halide ComplexesPhotocatalystx33201362#N/AFALSE
2159
ja408780c10.1021/ja408780cFALSEhttps://doi.org/10.1021/ja408780cHayashi, HJ. Am. Chem. Soc.Threonine synthase catalyzes the most complex reaction among the pyridoxal-5'-phosphate (PLP)-dependent enzymes. The important step is the addition of a water molecule to the C beta-C alpha double bond of the PLP aminocrotonate aldimine intermediate. Transaldimination of this intermediate with Lys61 as a side reaction to form alpha-ketobutyrate competes with the normal addition reaction. We previously found that the phosphate ion released from the O-phospho-L-homoserine substrate plays a critical role in specifically promoting the normal reaction. In order to elucidate the detailed mechanism of this product-assisted catalysis, we performed comparative QM/MM calculations with an exhaustive search for the lowest-energy-barrier reaction pathways starting from PLP-alpha-aminocrotonate aldimine intermediate. Satisfactory agreements with the experiment were obtained for the free energy profile and the UV/vis spectra when the PLP pyridine NI was unprotonated and the phosphate ion was monoprotonated. Contrary to an earlier proposal, the base that abstracts a proton from the attacking water was the epsilon-amino group of Lys6I rather than the phosphate ion. Nevertheless, the phosphate ion is important for stabilizing the transition state of the normal transaldimination to form L-threonine by making a hydrogen bond with the hydroxy group of the L-threonine moiety. The absence of this interaction may account for the higher energy barrier of the side reaction, and explains the mechanism of the reaction specificity afforded by the phosphate ion product. Additionally, a new mechanism, in which a proton temporarily resides at the phenolate O3' of PLP, was proposed for the transaldimination process, a prerequisite step for the catalysis of all the PLP enzymes.A QM/MM Study of the L-Threonine Formation Reaction of Threonine Synthase: Implications into the Mechanism of the Reaction Specificityx15201428#N/AFALSE
2160
ja501204q10.1021/ja501204qFALSEhttps://doi.org/10.1021/ja501204qGambardella, PSpin Tuning of Electron-Doped Metal-Phthalocyanine Layers2014#N/ATRUE
2161
ja408511y10.1021/ja408511yFALSEhttps://doi.org/10.1021/ja408511yDe Gioia, LJ. Am. Chem. Soc.A comparative analysis of a series of DFT models of [NiFe]-hydrogenases, ranging from minimal NiFe Clusters to very large systems inCluding both the first and second coordination sphere of the bimetallic cofactor, was carried out with the aim of unraveling which stereoelectronic properties of the active site of [NiFe]-hydrogenases are crucial for efficient H-2 binding and Cleavage. H-2 binding to the Ni-SIa redox state is energetically favored (by 4.0 kcal mol(-1)) only when H-2 binds to Ni, the NiFe metal Cluster is in a low spin state, and the Ni cysteine ligands have a peculiar seesaw coordination geometry, which in the enzyme is stabilized by the protein environment. The influence of the Ni coordination geometry on the H-2 binding affinity was then quantitatively evaluated and rationalized analyzing frontier molecular orbitals and populations. Several plausible reaction pathways leading to H-2 Cleavage were also studied. It turned out that a two-step pathway, where H-2 Cleavage takes place on the Ni-SIa redox state of the enzyme, is characterized by very low reaction barriers and favorable reaction energies. More importantly, the seesaw coordination geometry of Ni was found to be a key feature for facile H-2 Cleavage. The discovery of the crucial influence of the Ni coordination geometry on H-2 binding and Activation in the active site of [NiFe]-hydrogenases could be exploited in the design of novel biomimetic synthetic catalysts.DisClosure of Key Stereoelectronic Factors for Efficient H-2 Binding and Cleavage in the Active Site of [NiFe]-Hydrogenasesx45201476#N/AFALSE
2162
ja408397v10.1021/ja408397vFALSEhttps://doi.org/10.1021/ja408397vPeters, JCJ. Am. Chem. Soc.We describe the synthesis of a cobalt(I)-N-2 complex (2) supported by a meridional bis-phosphinB(OH)2ryl (PBP) ligand. Complex 2 undergoes a Clean reaction with 2 equiv of dihydrogen to afford a dihydridB(OH)2rato-cobalt dihydride (3). The ability of boron to switch between a boryl and a dihydridB(OH)2rate conformation makes possible the reversible conversion of 2 and 3. Complex 3 reacts with HMe2N-BH3 to give a hydridB(OH)2rane cobalt tetrahydridB(OH)2rate complex. We explore this boryl-cobalt system in the context of catalytic olefin hydrogenation as well as amine-borane dehydrogenation/transfer hydrogenation.Boryl-Mediated Reversible H-2 Activation at Cobalt: Catalytic Hydrogenation, Dehydrogenation, and Transfer Hydrogenationx159201350#N/AFALSE
2163
ja500859610.1021/ja5008596FALSERitter, T1,2-Selective Hydrosilylation of Conjugated Dienes2014#N/ATRUE
2164
ja500319710.1021/ja5003197FALSECronin, LLow pH Electrolytic Water Splitting Using Earth-Abundant Metastable Catalysts That Self-Assemble in Situ2014#N/ATRUE
2165
ja412725r10.1021/ja412725rFALSEhttps://doi.org/10.1021/ja412725rzur Loye, HCJ. Am. Chem. Soc.A family of rare U(IV)-containing quaternary fluorides, Na4MU6F30 (M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+), was synthesized in single crystal form via a mild hydrothermal technique utilizing an in situ U(VI) to U(IV) reduction step. The modified hydrothermal route is described, and the conditions to obtain single crystals in high yield are detailed. The crystal structures were determined by single crystal X-ray diffraction. The isostructural fluorides crystallize in a new structure type in the trigonal space group P (3) over bar c1. They exhibit a complex three-dimensional crystal structure consisting of corner- and edge-shared UF9 and MF6 polyhedra. The main building block, a U6F306- group, is arranged to create two distinct hexagonal channels, inside which MF6 octahedra and Na+ cations are located. The copper-containing member of the series, Na4CuU6F30, is unusual in that the Cu2+ cation exhibits a rare symmetrical coordination environment consisting of six identical Cu-F bond distances, indicating the lack of the expected Jahn-Teller distortion. Magnetic susceptibility measurements of Na4ZnU6F30 yielded an effective magnetic moment of 3.42 mu(B) for the U4+ (f(2)) cation in the structure. Measurements of the other members containing magnetic transition-metal cations in addition to U4+, Na4MU6F30 (M = Mn2+, Co2+, Ni2+, and Cu2+) yielded total effective magnetic moments of 10.2, 9.84, 8.87, and 8.52 mu(B) for the Mn-, Co-, Ni-, and Cu-containing materials, respectively. No evidence for long-range magnetic ordering was found down to 2 K. Measurements of the magnetization as a function of applied magnetic field at 2 K for Na4MnU6F30 confirmed that the U4+ magnetic cation exhibits a nonmagnetic singlet ground state at low temperature. Thermal stability measurements and UV-vis diffuse reflectance spectroscopy are also reported.Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na4MU6F30 (M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) Crystal Growth, Structures, and Magnetic Properties51201470#N/ATRUE
2166
ja408105610.1021/ja4081056FALSEhttps://doi.org/10.1021/ja4081056Khalifah, PGJ. Am. Chem. Soc.A two-step solid-state reaction for preparing cobalt molybdenum nitride with a nanoscale morphology has been used to produce a highly active and stable electrocatalyst for the hydrogen evolution reaction (HER) under acidic conditions that achieves an iR-corrected current density of 10 mA cm(-2) at -0.20 V vs RHE at low catalyst loadings of 0.24 mg/cm(2) in rotating disk experiments under a H-2 atmosphere. Neutron powder diffraction and pair distribution function (PDF) studies have been used to overcome the insensitivity of X-ray diffraction data to different transition-metal nitride structural polytypes and show that this cobalt molybdenum nitride crystallizes in space group P6(3)/mmc with lattice parameters of a = 2.85176(2) angstrom and c = 10.9862(3) angstrom and a formula of Co0.6Mo1.4N2. This space group results from the four-layered stacking sequence of a mixed Close-packed structure with alternating layers of transition metals in octahedral and trigonal prismatic coordination and is a structure type for which HER activity has not previously been reported. Based on the accurate bond distances obtained from time-of-flight neutron diffraction data, it is determined that the octahedral sites contain a mixture of divalent Co and trivalent Mo, while the trigonal prismatic sites contain Mo in a higher oxidation state. X-ray photoelectron spectroscopy (XPS) studies confirm that at the sample surface nitrogen is present and N-H moieties are abundant.Mixed Close-Packed Cobalt Molybdenum Nitrides as Non-noble Metal Electrocatalysts for the Hydrogen Evolution Reactionx698201324#N/AFALSE
2167
ja407995r10.1021/ja407995rFALSEhttps://doi.org/10.1021/ja407995rYap, GPAJ. Am. Chem. Soc.Addition of selenium to the nickel(l) complex, [Ni(Me-4[12]aneN(4))(CO)]PF6, effects a redox reaction leading to the diselenido dinickel(II) complex, {[(Ni(Me-4[12]aneN(4))](2)(Se-2)}(PF6)(2), in 70% crystalline yield. The product's structure features a mu-eta(2):eta(2)-Se-2 ligand with Se-Se bond length of 2.379(13) angstrom. Upon mild heating, {[(Ni(Me-4[12]aneN(4))](2)(mu-eta(2):eta(2)-Se-2)}(PF6)(2) oxidizes 9,10-dihydroanthracene or 1,4-cyClohexadiene forming the terminal hydroselenide, [Ni(Me-4[12]aneN(4))(SeH)PF6, and anthracene or benzene, respectively. [Ni(Me-4[12]aneN(4))(SeH)]PF6 Cleanly converts back to the diselenido dinickel(II) adduct upon addition of a phenoxy radical.C-H Activation by a Diselenido Dinickel(II) Complexx13201330#N/AFALSE
2168
ja407826d10.1021/ja407826dFALSEhttps://doi.org/10.1021/ja407826dShaw, WJJ. Am. Chem. Soc.Hydrogenase enzymes use first-row transition metals to interconvert H-2 with protons and electrons, reactions that are important for the storage and recovery of energy from intermittent sources such as solar, hydroelectric, and wind. Here we present Ni((P2N2Gly)-N-Cy)(2), a water-soluble molecular electrocatalyst with the amino acid glycine built into the diphosphine ligand framework. Proton transfer between the outer coordination sphere Carbonylates and the second coordination sphere pendant amines is rapid, as observed by cyClic voltammetry and FTIR spectroscopy, indicating that the Carbonylate groups may participate in proton transfer during catalysis. This complex oxidizes H-2 (1-33 s(-1)) at low overpotentials (150-365 mV) over a range of pH values (0.1-9.0) and produces H-2 under identical solution conditions (>2400 s(-1) at pH 0.5). Enzymes employ proton channels for the controlled movement of protons over long distances-the results presented here demonstrate the effects of a simple two-component proton channel in a synthetic molecular electrocatalyst.Minimal Proton Channel Enables H-2 Oxidation and Production with a Water-Soluble Nickel-Based Catalystx94201345#N/AFALSE
2169
ja412471u10.1021/ja412471uFALSEhttps://doi.org/10.1021/ja412471uShafirovich, VJ. Am. Chem. Soc.The mechanistic aspects of hydration of guanine radical cations, G(center dot+) in double- and single-stranded oligonuCleotides were investigated by direct time-resolved spectroscopic monitoring methods. The G(center dot+) radical one-electron oxidation products were generated by SO4 center dot- radical anions derived from the photolysis of S2O82- anions by 308 nm laser pulses. In neutral aqueous solutions (pH 7.0), after the complete decay of SO4 center dot- radicals (similar to 5 mu s after the actinic laser flash) the transient absorbance of neutral guanine radicals, G(-H)(center dot) with maximum at 312 nm, is dominant. The kinetics of decay of G(-H)(center dot) radicals depend strongly on the DNA secondary structure. In double-stranded DNA, the G(-H)(center dot) decay is biphasic with one component decaying with a lifetime of similar to 2.2 ms and the other with a lifetime of similar to 0.18 s. By contrast, in single-stranded DNA the G(-H)(center dot) radicals decay monophasically with a similar to 0.28 s lifetime. The ms decay component in double-stranded DNA is correlated with the enhancement of 8-oxo-7,8-dihydroguanine (8-oxoG) yields which are similar to 7 greater than in single-stranded DNA. In double-stranded DNA, it is proposed that the G(-H)(center dot) radicals retain radical cation character by sharing the NI-proton with the N3-site of C in the [G(center dot+):C] base pair. This [G(-H)(center dot):H+C reversible arrow G(center dot+):C] equilibrium allows for the hydration of G(center dot+) followed by formation of 8-oxoG. By contrast, in single-stranded DNA, deprotonation of G(center dot+) and the irreversible escape of the proton into the aqueous phase competes more effectively with the hydration mechanism, thus diminishing the yield of 8-oxoG, as observed experimentally.Mechanistic Aspects of Hydration of Guanine Radical Cations in DNA67201462#N/ATRUE
2170
ja407400310.1021/ja4074003https://doi.org/10.1021/ja4074003Chang, CJJ. Am. Chem. Soc.The solar-driven reduction of carbon dioxide to value-added chemical fuels is a longstanding challenge in the fields of catalysis, energy science, and green chemistry. In order to develop effective CO2 fixation, several key considerations must be balanced, inCluding (1) catalyst selectivity for promoting CO2 reduction over competing hydrogen generation from proton reduction, (2) visible-light harvesting that matches the solar spectrum, and (3) the use of cheap and earth-abundant catalytic components. In this report, we present the synthesis and characterization of a new family of earth-abundant nickel complexes supported by N-heterocyClic carbene-amine ligands that exhibit high selectivity and activity for the electrocatalytic and photocatalytic conversion of CO2 to CO. Systematic changes in the carbene and amine donors of the ligand have been surveyed, and [Ni((Pr)bimiq1)](2+) (1c, where (Pr)bimiq1 = bis(3-(imidazolyl)isoquinolinyl)propane) emerges as a catalyst for electrochemical reduction of CO2 with the lowest cathodic onset potential (E-cat = -1.2 V vs SCE). Using this earth-abundant catalyst with Ir(ppy)(3) (where ppy = 2-phenylpyridine) and an electron donor, we have developed a visible-light photoredox system for the catalytic conversion of CO2 to CO that proceeds with high selectivity and activity and achieves turnover numbers and turnover frequencies reaching 98,000 and 3.9 s(-1), respectively. Further studies reveal that the overall efficiency of this solar-to-fuel cyCle may be limited by the formation of the active Ni catalyst and/or the chemical reduction of CO2 to CO at the reduced nickel center and provide a starting point for improved photoredox systems for sustainable carbon-neutral energy conversion.Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-HeterocyClic Carbene-Isoquinoline ComplexPhotocatalyst2262013112#N/AFALSE
2171
ja412268y10.1021/ja412268yFALSEhttps://doi.org/10.1021/ja412268yGarcia, JJOn the Catalytic Hydrodefluorination of Fluoroaromatics Using Nickel Complexes: The True Role of the Phosphine2014#N/ATRUE
2172
ja407390410.1021/ja4073904FALSEhttps://doi.org/10.1021/ja4073904Seferos, DSJ. Am. Chem. Soc.Electron-deficient pi-conjugated polymers are important for organic electronics, yet the ability to polymerize electron-deficient monomers in a controlled manner is challenging. Here we show that Ni(II)diimine catalysts are well suited for the controlled polymerization of electron-deficient heterocyCles. The relative stability of the calculated catalyst monomer (or catalyst-chain end) complex directly influences the polymerization. When the complex is predicted to be most stable (139.2 kJ/mol), these catalysts display rapid reaction kinetics, leading to relatively low polydispersities (similar to 1.5) chain lengths that are controlled by monomer:catalyst ratio, controlled monomer consumption up to 60% conversion, linear chain length growth up to 40% conversion, and 'living' chain ends that can be readily extended by adding more monomer. These are desirable features that highlight the importance of catalyst design for the synthesis of new conjugated polymers.Designing and Refining Ni(II)diimine Catalysts Toward the Controlled Synthesis of Electron-Deficient Conjugated Polymersx76201368#N/AFALSE
2173
ja412263210.1021/ja4122632FALSEhttps://doi.org/10.1021/ja4122632Nakao, YJ. Am. Chem. Soc.A cooperative palladium/triorganB(OH)2ron catalyst to accomplish the intramolecular aminocyanation of alkenes through the Cleavage of N-CN bonds is reported. 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) is found to be crucial as a ligand for palladium to effectively catalyze the transformation with high chemo- and regioselectivity. A range of substituted indolines and pyrrolidines with both tetra- or trisubstituted carbon and cyano functionalities are readily furnished by the newly developed cyanofunctionalization reaction. A preliminary example of enantioselective aminocyanation is also described.Intramolecular Aminocyanation of Alkenes by Cooperative Palladium/Boron Catalysis83201444#N/ATRUE
2174
ja407115p10.1021/ja407115pFALSEhttps://doi.org/10.1021/ja407115pJaramillo, TFJ. Am. Chem. Soc.Objective evaluation of the activity of electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion technologies inCluding integrated solar water-splitting devices, water electrolyzers, and Li-air batteries. However, current methods employed to evaluate oxygen-evolving catalysts are not standardized, making it difficult to compare the activity and stability of these materials. We report a protocol for evaluating the activity, stability, and Faradaic efficiency of electro-deposited oxygen-evolving electrocatalysts. In particular, we focus on methods for determining electrochemically active surface area and measuring electrocatalytic activity and stability under conditions relevant to an integrated solar water-splitting device. Our primary figure of merit is the overpotential required to achieve a current density of 10 mA cm(-2) per geometric area, approximately the current density expected for a 10% efficient solar-to-fuels conversion device. Utilizing the aforementioned surface area measurements, one can determine electrocatalyst turnover frequencies. The reported protocol was used to examine the oxygen-evolution activity of the following systems in acidic and alkaline solutions: CoOx, CoPi, CoFeOx, NiOx, NiCeOx, NiCoOx, NiCuOx, NiFeOx, and NiLaOx. The oxygen-evolving activity of an electrodeposited IrOx catalyst was also investigated for comparison. Two general observations are made from comparing the catalytic performance of the OER catalysts investigated: (1) in alkaline solution, every non-noble metal system achieved 10 mA cm(-2) current densities at similar operating overpotentials between 0.35 and 0.43 V, and (2) every system but IrOx was unstable under oxidative conditions in acidic solutions.Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reactionx3304201380#N/AFALSE
2175
ja407004y10.1021/ja407004yFALSEhttps://doi.org/10.1021/ja407004yWhittlesey, MKSynthesis, Electronic Structure, and Magnetism of [Ni(6-Mes)(2)](+): A Two-Coordinate Nickel(I) Complex Stabilized by Bulky N-HeterocyClic Carbenesx2013#N/AFALSE
2176
ja406961310.1021/ja4069613FALSEhttps://doi.org/10.1021/ja4069613Hawthorne, MFJ. Am. Chem. Soc.Effective utilization of [Closo-B12H12](2-) derivatives in targeted drug delivery applications depends upon an efficient strategy to differentiate at least one of the 12 vertices on the B-12(2-) core. Precursor molecules must also be able to withstand the initial harsh hydrogen peroxide treatment necessary for hydroxylation of the B-H vertices. We report here a method for preparation of the ammonio derivative [Closo-B-12(OH)(11)NH3](-) and also demonstrate its utility in construction of a targeted drug delivery scaffold. Treatment of the precursor [Closo-B12H11NH3]- with hydrogen peroxide gives the corresponding nitro derivative [Closo-B-12(OH)(11)NO2](2-) in good yield. The nitro group is easily reduced with hydrogen over a Raney nickel catalyst to produce [Closo-B-12(OH)(11)NH3](-). The 11 hydroxyl groups can then be readily converted to carbonates or carbamates. As a proof-of-principle of its utility as a drug delivery system, we used the resulting vertex-differentiated ammonio derivative to construct a platinated pro-drug possessing 11 copies of a carboplatin analogue conjugated to the B-12(2-) core via carbamate linkage and a fluorescein molecule attached at the remaining vertex by an amide linkage. In vitro cytotoxicity assays demonstrated that activity of an untagged analog was similar to carboplatin against platinum-sensitive A459 cells and higher than carboplatin against platinum-resistant SK-OV-3 cells. Further fluorescence microscopy revealed that the fluorescein-tagged pro-drug localizes to the nuClei of A459 cells.Synthesis of [Closo-B-12(OH)(11)NH3](-): A New Heterobifunctional Dodecaborane Scaffold for Drug Delivery Applicationsx17201348#N/AFALSE
2177
ja410233e10.1021/ja410233eFALSEhttps://doi.org/10.1021/ja410233eXie, ZWJ. Am. Chem. Soc.A three-component [2+2+1] cross-cyClotrimerization of carboryne, alkene, and trimethylsilylalkyne has been achieved under the cooperative action of zirconium and nickel, leading to the synthesis of a series of dihydrofulvenocarboranes. The bulkiness of the alkyne and phosphine ligand plays a key role in the selective formation of the products.Three-Component [2+2+1] Cross-cyClotrimerization of Carboryne, Unactivated Alkene, and Trimethylsilylalkyne Co-mediated by Zr and Ni26201355#N/ATRUE
2178
ja406806310.1021/ja4068063FALSEhttps://doi.org/10.1021/ja4068063Li, YDJ. Am. Chem. Soc.Here we present a shape recovery phenomenon of Pt-Ni bimetallic nanocrystals that is unequivocally attributed to the defect effects. High-resolution electron microscopy revealed the overall process of conversion from concave octahedral Pt3Ni to regular octahedral Pt3Ni@Ni upon Ni deposition. Further experiments and theoretical investigations indicated that the intrinsic defect-dominated growth mechanism allows the site-selective nuCleation of a third metal around the defects to achieve the sophisticated design of trimetallic Pt3Ni@M core shell structures (M = Au, Ag, Cu, Rh). Consideration of geometrical and electronic effects indicated that trimetallic atomic steps in Pt3Ni@M could serve as reactive sites to significantly improve the catalytic performance, and this was corrB(OH)2rated by several model reactions. The synthesis strategy based on our work paves the way for the atomic-level design of trimetallic catalysts.Defect-Dominated Shape Recovery of Nanocrystals: A New Strategy for Trimetallic Catalystsx84201325#N/AFALSE
2179
ja409720c10.1021/ja409720cFALSEhttps://doi.org/10.1021/ja409720cInoue, SJ. Am. Chem. Soc.The reactivity of ylide-like phosphasilene 1 [LSi(TMS)=P(TMS), L = PhC(NtBu)(2)] with group 10 d(10) transition metals is reported. For the first time, a reaction of a phosphasilene with a transition metal that actually involves the silicon-phosphorus double bond was found. In the reaction of 1 with ethylene bis(triphenylphosphine) platinum(0), a complete silicon-phosphorus bond breakage occurs, yielding the unprecedented dinuClear platinum complex 3 [LSi{Pt(PPh3)}(2)P(TMS)(2)]. Spectroscopic, structural, and theoretical analysis of complex 3 revealed the cationic silylene (silyliumylidene) character of the silicon unit in complex 3. Similarly, formation of the analogous dinuClear palladium complex 4 [LSi{Pd(PPh3)}(2)P(TMS)(2)] from tetrakis(triphenylphosphine) palladium(0) was observed. On the other hand, in the case of bis(cyClooctadiene) nickel(0) as starting material, a distinctively different product, the bis(silylene) nickel complex 5 [{(LSi)(2)P(TMS)}Ni(COD)], was obtained. Complex 5 was fully characterized inCluding X-ray diffraction analysis. Density functional theory calculations of the reaction mechanisms showed that the migration of the TMS group in the case of platinum and palladium was induced by the oxidative addition of the transition metal into the silicon-silicon bond. The respective platinum intermediate 2 [LSi{Pt(TMS)(PPh3)}P(TMS)] was also experimentally observed. This is contrasted by the reaction of nickel, in which the equilibrium of phosphasilene 1 and the phosphinosilylene 6 [LSiP(TMS)(2)] was utilized for a better coordination of the silicon(II) moiety in comparison with phosphorus to the transition metal center.From a Zwitterionic Phosphasilene to Base Stabilized Silyliumylidene-Phosphide and Bis(silylene) Complexes47201365#N/ATRUE
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ja409523610.1021/ja4095236FALSEhttps://doi.org/10.1021/ja4095236Hillhouse, GLJ. Am. Chem. Soc.Reaction of [(IPr)Ni(mu-Cl)](2) (1-Cl; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with ClMg{CH(SiMe3)(2)}center dot Et2O affords (IPr)Ni{CH(SiMe3)(2)} (2), a two-coordinate Ni(I) Alkyl complex. An analogous two-coordinate Aryl derivative, (IPr)Ni(dmp) (dmp = 2,6-dimesitylphenyl), can be similarly prepared from Li(dmp) and 1-Cl. Reaction of 2 with Alkyl bromides gives the three-coordinate Ni(II) Alkyl halide complex (IPr)Ni{CH(SiMe3)(2)}Br. Evidence for a radical mechanism is presented to explain the reaction of 2 with Alkyl halides.Synthesis and Reactivity of Two-Coordinate Ni(I) Alkyl and Aryl Complexes57201360#N/ATRUE
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ja406374t10.1021/ja406374thttps://doi.org/10.1021/ja406374tMori, AJ. Am. Chem. Soc.Revisiting Murahashi coupling, we found that it effectively allows polymerization of lithiated (hetero)arenes by nickel(II)-catalyzed polycondensation. Deprotonative polymerization of 2-chloro-3-substituted thiophene with n-butyllithium gave head-to-tail-type poly(3-substituted thiophene). Poly(1,4-Arylene)s were obtained by the reaction of the corresponding dibromides through lithium bromine exchange. A lithiated thiophene derivative obtained via deprotonative halogen dance also underwent polymerization to afford a bromo-substituted polythiophene.Murahashi Coupling Polymerization: Nickel(II)-N-HeterocyClic Carbene Complex-Catalyzed Polycondensation of Organolithium Species of (Hetero)arenesx59201337#N/AFALSE
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ja409320k10.1021/ja409320kFALSEhttps://doi.org/10.1021/ja409320kRosenthal, UJ. Am. Chem. Soc.A study of the coordination chemistry of bis(diphenylphosphino)acetylene, Ph2P-C=C-PPh2, with selected group 4 metallocenes is presented. By substitution of the alkyne in complexes of the type Cp'M-2(L)(eta(2)-Me3SiC2SiMe3) (M = Ti, no L; M = Zr, L = pyridine; Cp' = substituted or unsubstituted bridged or unbridged eta(5)-cyClopentadienyl), the expected mononuClear complexes Cp-2*Ti(eta(2)-Ph2PC2PPh2) (4Ti), (rac-ebthi)Ti(eta(2)-Ph2PC2PPh2) (5Ti), and (rac-ebthi)Zr(eta(2)-Ph2PC2PPh2) (5Zr) [ebthi = ethylenebis(tetrahydroindenyl)] were obtained. When [Cp2Zr] was used in the reaction of Cp2Zr(py)(eta(2)-Me3SiC2SiMe3) with Ph2P-C C-PPh2, the dinuClear complex [Cp2Zr(eta(2)-Ph2PC2PPh2)](2) (6) was formed and isolated in the solid state. In solution, this complex is in equilibrium with the very spectacular structure of complex 7b as the first example of such a highly strained four-membered heterometallacyCle of a group 4 metal, involving the rare R2PCCR' fragment in the cyClic unit. Both the stability and reactivity of heterodisubstituted alkynes X-C C-X (X = NR2, PR2, SR, SiR3, etc.) themselves and also of their complexes are of general interest. Complex 6 did not react with a second [Cp2Zr] fragment to form a homobimetallic complex. In contrast, for (rac-ebthi)Zr(eta(2)-Ph2PC2PPh2) (5Zr) this reaction occurs. In the reaction of complex 4Ti with the Ni(0) complex (Cy3P)(2)Ni(eta(2)-C2H4) (Cy = cyClohexyl), C-P bond Cleavage of the alkyne ligand resulted in the formation of the isolated complex [(Cy3P)Ni(mu-PPh2)](2) (11). The structure and bonding of the complexes were investigated by DFT analysis to compare the different possible coordination modes of the R2P-C C-PR2 ligand. For compound 7h, a flip-flop coordination of the phosphorus atoms was proposed. Complexes 4Ti, 5Ti, 5Zr, 6, and 11 were characterized by X-ray crystallography.Synthesis, Characterization and Reactivity of Group 4 Metallocene Bis(diphenylphosphino)acetylene Complexes-A Reactivity and Bonding Study30201345#N/ATRUE
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ja406074w10.1021/ja406074whttps://doi.org/10.1021/ja406074wMacDonnell, FMPhotochemical Reduction of Carbon Dioxide to Methanol and Formate in a Homogeneous System with Pyridinium CatalystsPhotocatalyst2013#N/AFALSE
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ja408283a10.1021/ja408283aFALSEhttps://doi.org/10.1021/ja408283aPicozzi, SJ. Am. Chem. Soc.We perform density functional theory calculations on a recently synthesized metal-organic framework (MOP) with a perovskite-like topology ABX(3), i.e., [CH3CH2NH3]Mn(HCOO)(3), and predict a multiferroic behavior, i.e., a coexistence of ferroelectricity and ferromagnetism. A peculiar canted ordering of the organic A-cation dipole moments gives rise to a ferroelectric polarization of similar to 2 mu C/cm(2). Starting from these findings, we show that by choosing different organic A cations, it is possible to tune the ferroelectric polarization and increase it up. to 6 mu C/cm(2). The possibility of changing the magnitude and/or the canting of the organic molecular dipole opens new routes toward engineering ferroelectric polarization in the new Class of multiferroic metal-organic frameworks.Tuning the Ferroelectric Polarization in a Multiferroic Metal-Organic Framework203201352#N/ATRUE
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ja405874t10.1021/ja405874tFALSEhttps://doi.org/10.1021/ja405874tSojka, ZJ. Am. Chem. Soc.Interaction of tetracoordinated nickel(I) centers generated inside the channels of ZSM-5 zeolite with carbon monoxide ((CO)-C-12,13, p(CO) < 1 Torr) led to the formation of T-shaped, top-on monoCarbonyl adducts with a unique trigonal nickel core, supported by two oxygen donor ligands. The mechanism of the formation of the {Ni-I-CO}ZSM-5 species was accounted for by a quantitative molecular orbital correlation diagram of CO ligation. Detailed electronic and magnetic structure of this adduct was obtained from comprehensive DFT calculations, validated by quantitative reproduction of its continuous wave electron paramagnetic resonance (CW-EPR), hyperfine sublevel correlation (HYSCORE), and IR fingerprints, using relativistic Pauli and ZORA-SOMF/B3LYP methods. Molecular analysis of the stretching frequency, nu(CO) = 2109 cm(-1), g and A(C-13) tensors (g(xx) = 2.018, g(yy) = 2.380, g(zz) = 2.436, A(xx) = +1.0 +/- 0.3 MHz, A(yy) = -3.6 +/- 0.9 MHz, A(zz) = -1.6 +/- 0.3 MHz) and Q(Al-27) parameters (e(2)Qq/h = -13 MHz and eta = 0.8) supported by quantum chemical modeling revealed that the Ni-CO bond results from the pi overlap between the low-laying pi(2p) CO states with the 3d(zz) and 3d(yz) orbitals, with a small sigma contribution due to the overlap of sigma(2p+2s) orbital and a protruding lobe of the in-plane 3d(xz) orbital. Two types of orbital channels (associated with the sigma and pi overlap) of the electron and spin density flows within the {Ni-I-CO} unit were identified. A bathochromic shift of the nu(CO) stretching vibration was accounted for by resolving quantitatively the separate contributions due to the sigma donation and pi back-donation, whereas the C-13 hyperfine coupling was rationalized by incongruent alpha and beta spin flows via the sigma and nu channels. As a result the very nature of the carbon-metal bond in the Ni-I-CO adduct and the molecular backbone of the corresponding spectroscopic parameters were revealed with unprecedented accuracy.Intimate Binding Mechanism and Structure of Trigonal Nickel(I) MonoCarbonyl Adducts in ZSM-5 Zeolite-Spectroscopic Continuous Wave EPR, HYSCORE, and IR Studies Refined with DFT Quantification of Disentangled Electron and Spin Density Redistributions along sigma and pi Channelsx16201367#N/AFALSE
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ja408151h10.1021/ja408151hFALSEhttps://doi.org/10.1021/ja408151hTilley, TDJ. Am. Chem. Soc.A structurally persistent bis-amido ligand framework capable of supporting nickel compounds in three different oxidation states has been identified. A highly unusual, isolable Ni(III) Alkyl species has been prepared and characterized via a rare example of a two-electron oxidative addition of MeI to Ni(I).A Structurally Rigid Bis(amido) Ligand Framework in Low-Coordinate Ni(I), Ni(II), and Ni(III) Analogues Provides Access to a Ni(III) Methyl Complex via Oxidative Addition74201329#N/ATRUE
2187
ja405277g10.1021/ja405277ghttps://doi.org/10.1021/ja405277gUtschig, LMJ. Am. Chem. Soc.The direct conversion of sunlight into fuel is a promising means for the production of storable renewable energy. Herein, we use Nature's specialized photosynthetic machinery found in the Photosystem I (PSI) protein to drive solar fuel production from a nickel diphosphine molecular catalyst. Upon exposure to visible light, a self-assembled PSI-[Ni((P2N2Ph)-N-Ph)(2)](BF4)(2) hybrid generates H-2 at a rate 2 orders of magnitude greater than rates reported for photosensitizer/[Ni((P2N2Ph)-N-Ph)(2)](BF4)(2) systems. The protein environment enables photocatalysis at pH 6.3 in completely aqueous conditions. In addition, we have developed a strategy for incorporating the Ni molecular catalyst with the native acceptor protein of PSI, flavodoxin. Photocatalysis experiments with this modified flavodoxin demonstrate a new mechanism for biohybrid creation that involves protein-directed delivery of a molecular catalyst to the reducing side of Photosystem I for light-driven catalysis. This work further establishes strategies for constructing functional, inexpensive, earth-abundant solar fuel-producing PSI hybrids that use light to rapidly produce hydrogen directly from water.Protein Delivery of a Ni Catalyst to Photosystem I for Light-Driven Hydrogen ProductionPhotocatalyst64201331#N/AFALSE
2188
ja405257s10.1021/ja405257sFALSEhttps://doi.org/10.1021/ja405257sEisenberg, RJ. Am. Chem. Soc.A series of mononuClear nickel(II) thiolate complexes (Et4N)Ni(X-pyS)(3) (Et4N = tetraethylammonium; X = 5-H (1a), 5-Cl (1b), 5-CF3 (1c), 6-CH3 (1d); pyS = pyridine-2-thiolate), Ni(pySH)(4)(NO3)(2) (2), (Et4N)Ni(4,6-Y-2-pymS)(3) (Y = H (3a), CH3 (3b); pymS = pyrimidine-2-thiolate), and Ni(4,4'-Z-2,2'-bpy)(pyS)(2) (Z = H (4a), CH3 (4b), OCH3 (4c); bpy = bipyridine) have been synthesized in high yield and characterized. X-ray diffraction studies show that 2 is square planar, while the other complexes possess tris-chelated distorted-octahedral geometries. All of the complexes are active catalysts for both the photocatalytic and electrocatalytic production of hydrogen in 1/1 EtOH/H2O. When coupled with fluorescein (El) as the photosensitizer (PS) and triethylamine (TEA) as the sacrificial electron donor, these complexes exhibit activity for light-driven hydrogen generation that correlates with ligand electron donor ability. Complex 4c achieves over 7300 turnovers of H-2 in 30 h, which is among the highest reported for a molecular noble metal-free system. The initial photochemical step is reductive quenching of Fl* by TEA because of the latter's greater concentration. When system concentrations are modified so that oxidative quenching of Fl* by catalyst becomes more dominant, system durability increases, with a system lifetime of over 60 h. System variations and cyClic voltammetry experiments are consistent with a CECE mechanism that is common to electrocatalytic and photocatalytic hydrogen production. This mechanism involves initial protonation of the catalyst followed by reduction and then additional protonation and reduction steps to give a key Ni-H-/N-H+ intermediate that forms the H-H bond in the turnover-limiting step of the catalytic cyCle. A key to the activity of these catalysts is the reversible dechelation and protonation of the pyridine N atoms, which enable an internal heterocoupling of a metal hydride and an N-bound proton to produce H-2.Nickel Pyridinethiolate Complexes as Catalysts for the Light-Driven Production of Hydrogen from Aqueous Solutions in Noble-Metal-Free SystemsPhotocatalyst186201356#N/AFALSE
2189
ja405233410.1021/ja4052334FALSEhttps://doi.org/10.1021/ja4052334Mecking, SJ. Am. Chem. Soc.The water-soluble catalyst precursor [[(2,4,6-(3,5-(CF3)(2)C6H3)(3)-C6H2)-N=C(H)-(3-(9-anthry1)-2-O-C61-13)-kappa(2)-N,0]Ni(CH3)(TPPTS)] (TPPTS = tri-(sodiumphenylsulfonate)phosphine) polymerizes ethylene to aqueous dispersions of highly ordered nanoscale crystals (crystallinity chi(DSC) >= 9096) of strictly linear polyethylene (<0.7 methyl-branches/1000 carbon atoms, Mu = 4.2 x 105 g mol(-1)). SAXS in combination with cryo-TEM confirms this unusually high degree of order (chi(SAXS) = 82%) and shows the nanopartiCles to possess a very thin amorphous layer on the crystalline lamella, just sufficient to accommodate a loop, but likely no entanglements. This ideal chain-folded structure is corrB(OH)2rated by annealing studies on the aqueous-dispersed nanopartiCles, which show that the chain can move through the crystal as evidenced by lamella thickening without disturbing the crystalline order as conCluded from an unaltered low thickness of the amorphous layers. These ideal chain-folded polyethylene nanocrystals arise from the crystallization in the confined environment of a nanopartiCle and a deposition of the growing polymer chain on the crystal growth front as the chain is formed by the catalyst.Ideal Polyethylene Nanocrystalsx54201322#N/AFALSE
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ja408137t10.1021/ja408137tFALSEhttps://doi.org/10.1021/ja408137tHartwig, JFJ. Am. Chem. Soc.The first [ECE]Ni(II) pincer complexes with E = Si-II and E = Ge-II metallylene donor arms were synthesized via C-X (X = H, Br) oxidative addition, starting from the corresponding [EC(X)E] ligands. These novel complexes were fully characterized (NMR, MS, and XRD) and used as catalyst for Ni-catalyzed Sonogashira reactions. These catalysts allowed detailed information on the elementary steps of this catalytic reaction (transmetalation -> oxidative addition -> reductive elimination), resulting in the isolation and characterization of an unexpected intermediate in the transmetalation step. This complex, {[ECE]Ni acetylide -> CuBr} contains both nickel and copper, with the copper bound to the alkyne pi-system. Consistent with these unusual structural features, DFT calculations of the {[ECE]Ni acetylide -> CuBr} intermediates revealed an unusual E-Cu-Ni three-center two-electron bonding scheme. The results reveal a general reaction mechanism for the Ni-based Sonogashira coupling and broaden the application of metallylenes as strong a-donor ligands for catalytic transformations.From Bis(silylene) and Bis(germylene) Pincer-Type Nickel(II) Complexes to Isolable Intermediates of the Nickel-Catalyzed Sonogashira Cross-Coupling Reaction160201365#N/ATRUE
2191
ja407589e10.1021/ja407589eFALSEhttps://doi.org/10.1021/ja407589eWeix, DJJ. Am. Chem. Soc.The direct cross-coupling of two different electrophiles, such as an Aryl halide with an Alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nuCleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of Aryl halides with Alkyl halides and demonstrate that the selectivity arises from an unusual catalytic cyCle that combines both polar and radical steps to form the new C-C bond.Mechanism and Selectivity in Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Halides with Alkyl Halides330201379#N/ATRUE
2192
ja404580r10.1021/ja404580rFALSEhttps://doi.org/10.1021/ja404580rRauchfuss, TBJ. Am. Chem. Soc.Described are experiments demonstrating incorporation of cyanide cofactors and hydride substrate into [NiFe]-hydrogenase (H(2)ase) active site models. Complexes of the type (CO)(2)(CN)(2)Fe(pdt)Ni(dxpe) (dxpe = dppe, 1; dxpe = dcpe, 2) bind the Lewis acid B(C6F5)(3) (BAr3F) to give the adducts (CO)(2)(CNBAr3F)(2)Fe(pdt)Ni(dxpe), (1(BAr3F)(2), 2(BAr3F)(2)). Upon deCarbonylation using amine oxides, these adducts react with H-2 to give hydrido derivatives [(CO)(CNBAr3F)(2)Fe(H)(pdt)Ni-(dxpe)](-) (dxpe = dppe, [H3(BAr3F)(2)](-); dxpe = dcpe, [H4(BAr3F)(2)](-)). Crystallographic analysis shows that Et4N[H3(BAr3F)(2)] generally resembles the active site of the enzyme in the reduced, hydride-containing states (Ni-C/R). The Fe-H center dot center dot center dot Ni center is unsymmetrical with r(Fe-H) = 1.51(3) angstrom and r(Ni-H) = 1.71(3) angstrom. Both crystallographic and F-19 NMR analyses show that the CNBAr3F- ligands occupy basal and apical sites. Unlike cationic Ni-Fe hydrides, [H3(BAr3F)(2)](-) and [H4(BAr3F)(2)](-) oxidize at mild potentials, near the Fc(+/0) couple. Electrochemical measurements indicate that in the presence of base, [H3(BAr3F)(2)](-) catalyzes the oxidation of H-2. NMR evidence indicates dihydrogen bonding between these anionic hydrides and R3NH+ salts, which is relevant to the mechanism of hydrogenogenesis. In the case of Et4N[H3(BAr3F)(2)], strong acids such as HCl induce H-2 release to give the chloride Et4N[(CO)(CNBAr3F)(2)Fe(Cl)(pdt)Ni-(dppe)].Hydrogen Activation by Biomimetic [NiFe]-Hydrogenase Model Containing Protected Cyanide Cofactorsx70201341#N/AFALSE
2193
ja404528910.1021/ja4045289FALSEhttps://doi.org/10.1021/ja4045289Yildirim, TJ. Am. Chem. Soc.We have examined the methane uptake properties of six of the most promising metal organic framework (MOF) materials: PCN-14, UTSA-20, HKUST-1, Ni-MOF-74 (Ni-CPO-27), NU-111, and NU-125. We discovered that HKUST-1, a material that is commercially available in gram scale, exhibits a room-temperature volumetric methane uptake that exceeds any value reported to date. The total uptake is about 230 cc(STP)/cc at 35 bar and 270 cc(STP)/cc at 65 bar, which meets the new volumetric target recently set by the Department of Energy (DOE) if the packing efficiency loss is ignored. We emphasize that MOFs with high surface areas and pore volumes perform better overall. NU-111, for example, reaches similar to 75% of both the gravimetric and the volumetric targets. We find that values for gravimetric uptake, pore volume, and inverse density of the MOFs we studied scale essentially linearly with surface area. From this linear dependence, we estimate that a MOF with surface area 7500 m(2)/g and pore volume 3.2 cc/g could reach the current DOE gravimetric target of 0.5 g/g while simultaneously exhibiting around similar to 200 cc/cc volumetric uptake. We note that while values for volumetric uptake are based on ideal single crystal densities, in reality the packing densities of MOFs are much lower. Finally, we show that compacting HKUST-1 into wafer shapes partially collapses the framework, decreasing both volumetric and gravimetric uptake significantly. Hence, one of the important challenges going forward is to find ways to pack MOFs efficiently without serious damage or to synthesize MOFs that can withstand substantial mechanical pressure.Methane Storage in Metal-Organic Frameworks: Current Records, Surprise Findings, and Challengesx621201359#N/AFALSE
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ja407394q10.1021/ja407394qFALSEhttps://doi.org/10.1021/ja407394qBard, AJJ. Am. Chem. Soc.Here we demonstrate the use of a previously reported pattern recognition algorithm to evaluate correlations between 50 different materials properties of the elements and their kinetics for the hydrogen evolution reaction in acid. We determined that the melting point and bulk modulus of the elements quantitatively gave the highest correlations of all materials properties investigated. We also showed that the melting point and bulk modulus correlations held true for a popular hydrogen evolution catalysts alloy, NiMo, and a previously untested material, MoSi2. In addition, we quantified the previously known relationship between the d-band center of an element and its kinetics for hydrogen evolution, and found that the melting point and bulk modulus correlations have correlations that are similar to but slightly stronger than those of the d-band center.Pattern Recognition Correlating Materials Properties of the Elements to Their Kinetics for the Hydrogen Evolution Reaction25201343#N/ATRUE
2195
ja407147d10.1021/ja407147dFALSEhttps://doi.org/10.1021/ja407147dNolan, EMJ. Am. Chem. Soc.Human calprotectin (CP) is an antimicrobial protein that coordinates Mn(II) with high affinity in a Ca(II)dependent manner at an unusual histidine-rich site (site 2) formed at the S100A8/S100A9 dimer interface. We present a 16-member CP mutant family where mutations in the S100A9 C-terminal tail (residues 96-114) are employed to evaluate the contributions of this region, which houses three histidines and four acidic residues, to Mn(II) coordination at site 2. The results from analytical size-exClusion chromatography, Mn(II) competition titrations, and electron paramagnetic resonance spectroscopy establish that the C-terminal tail is essential for high-affinity Mn(II) coordination by CP in solution. The studies indicate that His103 and His105 (HXH motif) of the tail complete the Mn(II) coordination sphere in solution, affording an unprecedented biological His(6) site. These solution studies are in agreement with a Mn(II)-CP crystal structure reported recently (Damo, S. M.; et al. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 3841). Remarkably high-affinity Mn(II) binding is retained when either H103 or H105 are mutated to Ala, when the HXH motif is shifted from positions 103-105 to 104-106, and when the human tail is substituted by the C-terminal tail of murine S100A9. Nevertheless, antibacterial activity assays employing human CP mutants reveal that the native disposition of His residues is important for conferring growth inhibition against Escherichia coli and Staphylococcus aureus. Within the S100 family, the S100A8/S100A9 heterooligomer is essential for providing high-affinity Mn(10 binding; the S100A7, S100A9(C3S), S100A12, and S100B homodimers do not exhibit such Mn(II)-binding capacity.Contributions of the S100A9 C-Terminal Tail to High-Affinity Mn(II) Chelation by the Host-Defense Protein Human Calprotectin482013107#N/ATRUE
2196
ja406846810.1021/ja4068468FALSEhttps://doi.org/10.1021/ja4068468Uchiyama, MJ. Am. Chem. Soc.A density functional theory (DFT) study was performed to elucidate the mechanism of the Ni-catalyzed [3 + 2 + 2] CyClization reaction of cyClo-propylideneacetate with two alkynes. A systematic search showed that the nature of the alkynes determines the choice between two reaction pathways and hence the regioselectivity. Strongly electron-deficient acetylenes preferentially afford 2,5-disubstituted products via nickel-acyClopentadienes generated by [2 + 2] cocyClization, whereas normal alkynes afford 3,4 or 3,5-products via an unprecedented pathway involving a [3 + 2] nickelacyCle intermediate.Mechanistic Origin of Chemo- and Regioselectivity of Nickel-Catalyzed [3+2+2] CyClization Reaction38201352#N/ATRUE
2197
ja404267510.1021/ja4042675FALSEhttps://doi.org/10.1021/ja4042675Armstrong, FAJ. Am. Chem. Soc.The most efficient catalysts for solar fuel production should operate Close to reversible potentials, yet possess a bias for the fuel-forming direction. Protein film electrochemical studies of Ni-containing carbon monoxide dehydrogenase and [NiFeSe]-hydrogenase, each a reversible electrocatalyst, show that the electronic state of the electrode strongly biases the direction of electrocatalysis of CO2/CO and H+/H-2 interconversions. Attached to graphite electrodes, these enzymes show high activities for both oxidation and reduction, but there is a marked shift in bias, in favor of CO2 or H+ reduction, when the respective enzymes are attached instead to n-type semiconductor electrodes constructed from CdS and TiO2 nanopartiCles. This catalytic rectification effect can arise for a reversible electrocatalyst attached to a semiconductor electrode if the electrode transforms between semiconductor- and metallic-like behavior across the same narrow potential range (<0.25 V) that the electrocatalytic current switches between oxidation and reduction.How Light-Harvesting Semiconductors Can Alter the Bias of Reversible Electrocatalysts in Favor of H-2 Production and CO2 Reductionx53201335#N/AFALSE
2198
ja404006w10.1021/ja404006wFALSEhttps://doi.org/10.1021/ja404006wKobayashi, SJ. Am. Chem. Soc.We have developed heterogeneous polymer-incarcerated nickel nanopartiCles (NPs), which catalyze cross-coupling reactions. The matrix structure of these catalysts incorporates both N-heterocyClic carbenes (NHCs) as ligands and Ni-NPs, thanks to a new design of cross-linking agents in polymer supports. These embedded NHCs were detected by field gradient swollen-resin magic angle spinning NMR analysis. They were successfully applied to Corriu-Kumada-Tamao reactions with a broad substrate scope inCluding functional group tolerance, and the catalyst could be recovered and reused several times without loss of activity.Copolymer-Incarcerated Nickel NanopartiCles with N-HeterocyClic Carbene Precursors as Active Cross-Linking Agents for Corriu-Kumada-Tamao Reactionx57201355#N/AFALSE
2199
ja403440e10.1021/ja403440eFALSEhttps://doi.org/10.1021/ja403440eSchaak, REJ. Am. Chem. Soc.NanopartiCles of nickel phosphide (Ni2P) have been investigated for electrocatalytic activity and stability for the hydrogen evolution reaction (HER) in acidic solutions, under which proton exchange membrane-based electrolysis is operational. The catalytically active Ni2P nanopartiCles were hollow and faceted to expose a high density of the Ni2P(001) surface, which has previously been predicted based on theory to be an active HER catalyst. The Ni2P nanopartiCles had among the highest HER activity of any non-noble metal electrocatalyst reported to date, producing H-2(g) with nearly quantitative faradaic yield, while also affording stability in aqueous acidic media.Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reactionx2082201331#N/AFALSE
2200
ja403102j10.1021/ja403102jFALSEhttps://doi.org/10.1021/ja403102jBerlinguette, CPJ. Am. Chem. Soc.Photochemical metal organic deposition (PMOD) was used to prepare amorphous metal oxide films containing specific concentrations of iron, cobalt, and nickel to study how metal composition affects heterogeneous electrocatalytic water oxidation. Characterization of the films by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed excellent stoichiometric control of each of the 21 complex metal oxide films investigated. In studying the electrochemical oxidation of water catalyzed by the respective films, it was found that small concentrations of iron produced a significant improvement in Tafel slopes and that cobalt or nickel were critical in lowering the voltage at which catalysis commences. The best catalytic parameters of the series were obtained for the film of composition a-Fe20Ni80. An extrapolation of the electrochemical and XPS data indicates the optimal behavior of this binary film to be a manifestation of iron stabilizing nickel in a higher oxidation level. This work represents the first mechanistic study of amorphous phases of binary and ternary metal oxides for use as water oxidation catalysts, and provides the foundation for the broad exploration of other mixed-metal oxide combinations.Water Oxidation Catalysis: Electrocatalytic Response to Metal Stoichiometry in Amorphous Metal Oxide Films Containing Iron, Cobalt, and Nickel
Electrocatalytic
637201337#N/AFALSE
2201
ja406742n10.1021/ja406742nFALSEhttps://doi.org/10.1021/ja406742nParvez, MJ. Am. Chem. Soc.Nickel complexes of a PCcarbeneP pincer ligand framework are described. Dehydrobromination of the precursor (PCsp3P)NiBr in the presence of a donor (PPh3 or (NCBu)-Bu-t) leads to the title complexes, which feature a rare nickel-carbene linkage as the pincer ligand anchor point. This strongly donating, nuCleophilic carbene center engages in a variety of E-H bond Activations (E = H, C, N, O), some of which are reversible. This represents a new mode of bond Activation by ligand cooperativity in nickel pincer complexes.Activation of Water, Ammonia, and Other Small Molecules by PCcarbeneP Nickel Pincer Complexes161201344#N/ATRUE
2202
ja403041g10.1021/ja403041gFALSEhttps://doi.org/10.1021/ja809457sSun, SHSynthetic Control of FePtM Nanorods (M = Cu, Ni) To Enhance the Oxygen Reduction Reactionx2013#N/AFALSE
2203
ja406485z10.1021/ja406485zFALSEhttps://doi.org/10.1021/ja406485zJaun, BMethyl-Coenzyme M Reductase from Methanogenic Archaea: Isotope Effects on the Formation and Anaerobic Oxidation of Methane2013#N/ATRUE
2204
ja402103u10.1021/ja402103uFALSEhttps://doi.org/10.1021/ja402103uMason, JAJ. Am. Chem. Soc.The quantum sieving effect between D-2 and H-2 is examined for a series of metal-organic frameworks (MOFs) over the temperature range 77-150 K. Isothermal adsorption measurements demonstrate a consistently larger isosteric heat of adsorption for D-2 vs H-2, with the largest difference being 1.4 kJ/mol in the case of Ni-MOF-74. This leads to a low-pressure selectivity for this material that increases from 1.5 at 150 K to 5.0 at 77 K. Idealized adsorption solution theory indicates that the selectivity decreases with increasing pressure, but remains well above unity at ambient pressure. Infrared measurements on different MOF materials show a strong correlation between selectivity and the frequency of the adsorbed H-2 translational band. This confirms that the separation is predominantly due to the difference in the zero-point energies of the adsorbed isotopologues.Highly Selective Quantum Sieving of D-2 from H-2 by a Metal-Organic Framework As Determined by Gas Manometry and Infrared Spectroscopyx75201365#N/AFALSE
2205
ja406112u10.1021/ja406112uFALSEhttps://doi.org/10.1021/ja406112uAndrada, DMJ. Am. Chem. Soc.The cyClic Alkyl(amino) carbene (cAAC:)-stabilized acyClic germylones (Me-2-cAAC:)(2)Ge (1) and (Cy-2-cAAC:)(2)Ge (2) were prepared utilizing a one-pot synthesis of GeCl2(dioxane), cAAC:, and KC8 in a 1:2:2.1 molar ratio. Dark green crystals of compounds 1 and 2 were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of 1 and 2 feature the C-Ge-C bent backbone, which possesses a three-center two-electron pi-bond system. Compounds 1 and 2 are the first acyClic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds 1 and 2 confirmed the singlet spin ground state. DFT calculations on 1/2 revealed that the singlet ground state is more stable by similar to 16 to 18 kcal mol(-1) than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (1)/267.1 (2) and 180.4 (1)/183.8 (2) kcal mol(-1), respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of 1 and 2. The TD-DFT calculations exhibit an absorption band at similar to 655 nm in n-hexane solution that originates from the diradicaloid character of germylones 1 and 2.AcyClic Germylones: Congeners of Allenes with a Central Germanium Atom105201373#N/ATRUE
2206
ja401758c10.1021/ja401758cFALSEhttps://doi.org/10.1021/ja401758cDuan, CYJ. Am. Chem. Soc.Chiral metal-organic frameworks (MOFs) with porous and tunable natures have made them feasible for performing a variety of chemical reactions as heterogeneous asymmetric catalysts. By incorporating the oxidation catalyst [BW12O40](5-) and the chiral group, L- or D-pyrrolidin-2-ylimidazole (PYI), into one single framework, the two enantiomorphs Ni-PYI1 and Ni-PYI2 were obtained via self-assembly, respectively. The channels of Ni-PYIs were enlarged through a guest exchange reaction to remove the cationic chiral templates and were well modulated with hydrophilic/hydrophobic properties to allow molecules of both H2O2 and olefin ingress and egress. The coexistence of both the chiral directors and the oxidants within a confined space provided a special environment for the formation of reaction intermediates in a stereoselective fashion with high selectivity. The resulting MOP acted as an amphipathic catalyst to prompt the asymmetric dihydroxylation of Aryl olefins with excellent stereoselectivity.Engineering Chiral Polyoxometalate Hybrid Metal-Organic Frameworks for Asymmetric Dihydroxylation of Olefinsx285201339#N/AFALSE
2207
ja406027x10.1021/ja406027xFALSEhttps://doi.org/10.1021/ja406027xDias, HVRJ. Am. Chem. Soc.Organoazides and their nitrogen expulsion chemistry have attracted the attention of many scientists because they serve as a useful source of nitrene fragments and interesting nitrene rearrangement products. Gold-mediated reactions are also of significant current interest. This manuscript describes several important discoveries based at the intersection of these fields. In particular, we report the first isolable gold organoazides ([(SIPr)AuN(1-Ad)NN][SbF6], [(SIPr)AuN(2-Ad)NN][SbF6] and [(SIPr)AuN(1-Ad)NN]-[SbF6]; [SbF6]; SIPr = a N-heterocyClic carbene; 1-AdNNN = 1-azidoadamantane; 2-AdNNN = 2-azidoadamantane; CyNNN = azidocyClohexane), and their gold-mediated nitrogen expulsion chemistry, and the isolation of formal nitrene rearrangement products of 1-AdN, 2-AdN and CyN (inCluding the elusive 4-azahomoadamant-3-ene) as their gold complexes. We have also performed a computational study to understand and explain the observed structure of gold-coordinated 1-AdNNN and 2-AdNNN and their nitrogen elimination pathways, which implies that the conversion of the organoazide complex to the imine is a concerted process without a nitrene/nitrenoid intermediate. Kinetic studies of [(SIPr)AuN(2-Ad)NNN][SbF6] from 30 to 50 degrees C indicate that nitrogen elimination is a first-order process. The experimentally determined Activation parameters are in good agreement with the calculated values.Gold-Mediated Expulsion of Dinitrogen from Organic Azides17201356#N/ATRUE
2208
ja401555y10.1021/ja401555yFALSEhttps://doi.org/10.1021/ja401555yHuang, DJNickel(II) Dithiocarbamate Complexes Containing Sulforhodamine B as Fluorescent Probes for Selective Detection of Nitrogen Dioxidex2013#N/AFALSE
2209
ja405997s10.1021/ja405997sFALSEhttps://doi.org/10.1021/ja405997sBell, ATJ. Am. Chem. Soc.The presence of layered cobalt oxides has been identified experimentally in Co-based anodes under oxygen-evolving conditions. In this work, we report the results of theoretical investigations of the relative stability of layered and spinel bulk phases of Co oxides, as well as the stability of selected surfaces as a function of applied potential and pH. We then study the oxygen evolution reaction (OER) on these surfaces and obtain activity trends at experimentally relevant electro-chemical conditions. Our calculated volume Pourbaix diagram shows that beta-CoOOH is the active phase where the OER occurs in alkaline media. We calculate relative surface stabilities and adsorbate coverages of the most stable low-index surfaces of beta-CoOOH: (0001), (01 (1) over bar2), and (10 (1) over bar4). We find that at low applied potentials, the (10 (1) over bar4) surface is the most stable, while the (01 (1) over bar2) surface is the more stable at higher potentials. Next, we compare the theoretical overpotentials for all three surfaces and find that the (10 (1) over bar4) surface is the most active one as characterized by an overpotential of eta = 0.48 V. The high activity of the (10 (1) over bar4) surface can be attributed to the observation that the resting state of Co in the active site is Co3+ during the OER, whereas Co is in the Co4+ state in the less active surfaces. Lastly, we demonstrate that the overpotential of the (10 (1) over bar4) surface can be lowered further by surface substitution of Co by Ni. This finding could explain the experimentally observed enhancement in the OER activity of NiyCo1-yOx thin films with increasing Ni content. All energetics in this work were obtained from density functional theory using the Hubbard-U correction.Theoretical Investigation of the Activity of Cobalt Oxides for the Electrochemical Oxidation of Water694201362#N/ATRUE
2210
ja401466y10.1021/ja401466yFALSEAckermann, Lmeta-Selective C-H Bond Alkylation with Secondary Alkyl Halidesx2013#N/AFALSE
2211
ja401146v10.1021/ja401146vFALSEhttps://doi.org/10.1021/ja401146vKnochel, PJ. Am. Chem. Soc.A formal regioselective cross-coupling of various pyridines with Alkyl and Aryl groups can be achieved by a BF3 center dot OEt2-mediated addition of Grignard or organozinc reagents to pyridines bearing various substituents (chloro, bromo, cyano, Vinyl, phenyl, carbethoxy, nitro, etc.) followed by an oxidative aromatization mediated by chloranil. Good regioselectivity and wide functional group tolerance make this method very versatile for the preparation of polyfunctional pyridines. No transition-metal catalyst is required in these coupling reactions.Transition-Metal-Free BF3-Mediated Regioselective Direct Alkylation and Arylation of Functionalized Pyridines Using Grignard or Organozinc Reagentsx95201375#N/AFALSE
2212
ja400705a10.1021/ja400705aFALSEhttps://doi.org/10.1021/ja400705aBullock, RMJ. Am. Chem. Soc.A nickel bis(diphosphine) complex containing pendant amines in the second coordination sphere, [Ni-((P2N2t-Bu)-N-Cy)(2)](BF4)(2) ((P2N2t-Bu)-N-Cy = 1,5-di(tert-butyl)-3,7-dicyClohexyl-1,5-diaza-3,7-diphosphacyClooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni-II complex gives three isomers of the doubly protonated Ni-0 complex [Ni((P2N2t-BuH)-N-Cy)(2)](BF4)(2). Using the pK(a) values and Ni-II/I and Ni-1/0 redox potentials in a thermochemical cyCle, the free energy of hydrogen addition to [Ni((P2N2t-Bu)-N-Cy)(2)](2+) was determined to be -7.9 kcal mol(-1). The catalytic rate observed in dry acetonitrile for the oxidation of H-2 depends on base size, with larger bases (NEt3, t-BuNH2) resulting in much slower catalysis than n-BuNH2. The addition of water accelerates the rate of catalysis by facilitating deprotonation of the hydrogen addition product before oxidation, especially for the larger bases NEt3 and t-BuNH2. This catalytic pathway, where deprotonation occurs prior to oxidation, leads to an overpotential that is 0.38 V lower compared to the pathway where oxidation precedes proton movement. Under the optimal conditions of 1.0 atm H-2 using n-BuNH2 as a base and with added water, a turnover frequency of 58 s(-1) is observed at 23 degrees C.Two Pathways for Electrocatalytic Oxidation of Hydrogen by a Nickel Bis(diphosphine) Complex with Pendant Amines in the Second Coordination Sphere
Electrocatalytic
89201388#N/AFALSE
2213
ja405351s10.1021/ja405351sFALSEhttps://doi.org/10.1021/ja405351sBell, ATJ. Am. Chem. Soc.A detailed investigation has been carried out of the structure and electrochemical activity of electrodeposited Ni-Fe films for the oxygen evolution reaction (OER) in alkaline electrolytes. Ni-Fe films with a bulk and surface composition of 40% Fe exhibit OER activities that are roughly 2 orders of magnitude higher than that of a freshly deposited Ni film and about 3 orders of magnitude higher than that of an Fe film. The freshly deposited Ni film increases in activity by as much as 20-fold during exposure to the electrolyte (KOH); however, all films containing Fe are stable as deposited. The oxidation of Ni(OH)(2) to NiOOH in Ni films occurs at potentials below the onset of the OER. Incorporation of Fe into the film increases the potential at which Ni(OH)(2)/NiOOH redox occurs and decreases the average oxidation state of Ni in NiOOH. The Tafel slope (40 mV dec(-1)) and reaction order in OH- (1) for the mixed Ni-Fe films (containing up to 95% Fe) are the same as those for aged Ni films. In situ Raman spectra acquired in 0.1 M KOH at OER potentials show two bands characteristic of NiOOH. The relative intensities of these bands vary with Fe content, indicating a change in the local environment of Ni-O. Similar changes in the relative intensities of the bands and an increase in OER activity are observed when pure Ni films are aged. These observations suggest that the OER is catalyzed by Ni in Ni-Fe films and that the presence of Fe alters the redox properties of Ni, causing a positive shift in the potential at which Ni(OH)(2)/NiOOH redox occurs, a decrease in the average oxidation state of the Ni sites, and a concurrent increase in the activity of Ni cations for the OER.An Investigation of Thin-Film Ni-Fe Oxide Catalysts for the Electrochemical Evolution of Oxygen1367201347#N/ATRUE
2214
ja405223t10.1021/ja405223tFALSEhttps://doi.org/10.1021/ja405223tLu, XJ. Am. Chem. Soc.Endohedral metallofullerenes (EMFs) encapsulating divalent metal ions have received limited attention because of their low production yields. Here, we report the results of structural determination and chemical functionalization of a typical divalent metallofullerene, Yb@C-84(II). Single-crystal X-ray crystallographic studies of Yb@C-84/Ni-II(OEP) cocrystals (OEP is the dianion of octaethylporphyrin) unambiguously established the chiral C-2(13)-C-84 cage structure and revealed multiple sites for Yb2+, indicating a moving metal ion inside the cage. The chemical property of Yb@C-2(13)-C-84 was probed with the electrophillic adamantylidene carbene (1). Three monoadduct isomers were isolated and characterized. Crystallographic results of the major isomer (2b) revealed that, although the cyCloaddition breaks a [5,6]-bond on the cage, Yb2+ is localized under a hexagonal ring distant from the sites of addition. Thus, it is proved that the dynamic motion of the divalent metal ion in Yb@C-84 has been effectively halted by exohedral functionalization. Spectroscopic results show that the electronic property of Yb@C-2(13)-C-84 is pertained in the derivatives, although the addend exerts a mild reduction effect on the electrochemical behavior of the EMF. Computational works demonstrated that addition of 1 to Yb@C-2(13)-C-84 is mainly driven by releasing the local strains of cage carbons rather than charge recombination, which is always prominent to the affinity of typical trivalent EMFs such as M@C-2 nu(9)-C-82 (M = Sc, Y, La, Ce, Gd) toward 1. Accordingly, it is speculated that the chemical behaviors of divalent EMFs more likely resemble those of empty fullerenes because both are dosed-shell compounds, but they differ from those of trivalent EMFs, which have open-shell electronic configurations instead.Molecular Structure and Chemical Property of a Divalent Metallofullerene Yb@C-2(13)-C-8418201347#N/ATRUE
2215
ja405192310.1021/ja4051923FALSEhttps://doi.org/10.1021/ja4051923Hu, XLJ. Am. Chem. Soc.Many nickel-based catalysts have been reported for cross-coupling reactions of nonactivated Alkyl halides. The mechanistic understanding of these reactions is still primitive. Here we report a mechanistic study of Alkyl-Alkyl Kumada coupling catalyzed by a preformed nickel(II) pincer complex ([(N2N)Ni-Cl]). The coupling proceeds through a radical process, involving two nickel centers for the oxidative addition of Alkyl halide. The catalysis is second-order in Grignard reagent, first-order in catalyst, and zero-order in Alkyl halide. A transient species, [(N2N)Ni-Alkyl(2)] (Alkyl(2)-MgX), is identified as the key intermediate responsible for the Activation of Alkyl halide, the formation of which is the turnover-determining step of the catalysis.Bimetallic Oxidative Addition Involving Radical Intermediates in Nickel-Catalyzed Alkyl-Alkyl Kumada Coupling Reactions170201367#N/ATRUE
2216
ja400253p10.1021/ja400253pFALSEhttps://doi.org/10.1021/ja400253pKotting, CJ. Am. Chem. Soc.Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy allows a detailed analysis of surface attached molecules, inCluding their secondary structure, orientation, and interaction with small molecules in the case of proteins. Here, we present a universal immobilization technique on germanium for all oligo-histidine-tagged proteins. For this purpose, new triethoxysilane derivates were developed: we synthesized a linker-silane with a succinimidyl ester as amine-reactive headgroup and a matrix-silane with an unreactive ethylene glycol group. A new methodology for the attachment of triethoicysilanes on germanium was established, and the surface was characterized by ATR-FTIR and X-ray photoelectron spectroscopy. In the next step, the succinimidyl ester was reacted with aminonitrilotriacetic acid. Subsequently, Ni2+ was coordinated to form Ni-nitrilotriacetic acid for His-tag binding. The capability of the functionalized surface was demonstrated by experiments using the small GTPase Ras and photosystem I (PS I). The native binding of the proteins was proven by difference spectroscopy, which probes protein function. The function of Ras as molecular switch was demonstrated by a beryllium trifluoride anion titration assay, which allows observation of the on and off switching of Ras at atomic resolution. Furthermore, the activity of immobilized PS I was proven by light-induced difference spectroscopy. Subsequent treatment with imidazole removes attached proteins, enabling repeated binding. This universal technique allows specific attachment of His-tagged proteins and a detailed study of their function at the atomic level using FTIR difference spectroscopy.Universal Method for Protein Immobilization on Chemically Functionalized Germanium Investigated by ATR-FTIR Difference Spectroscopyx46201334#N/AFALSE
2217
ja400181a10.1021/ja400181aFALSEhttps://doi.org/10.1021/ja400181aHelm, MLJ. Am. Chem. Soc.A series of Ni-based electrocatalysts, [Ni(7P(2)(Ph)N(C6H4X))(2)](BF4)(2), featuring seven-membered cyClic diphosphine ligands incorporating a single amine base, 1-para-X-phenyl-3,6-triphenyl-1-aza-3,6-diphosphacyCloheptane (7P(2)(Ph)N(C6H4X), where X = OMe, Me, Br, Cl, or CF3), have been synthesized and characterized. X-ray diffraction studies have established that the [Ni(7P(2)(Ph)N(C6H4X))(2)](2+) complexes have a square planar geometry, with bonds to four phosphorus atoms of the two bidentate diphosphine ligands. Each of the complexes is an efficient electrocatalyst for hydrogen production at the potential of the Ni(II/I) couple, with turnover frequencies ranging from 2400 to 27 000 s(-1) with [(DMF)H](+) in acetonitrile. Addition of water (up to 1.0 M) accelerates the catalysis, giving turnover frequencies ranging from 4100 to 96 000 s(-1). Computational studies carried out on the [Ni(7P(2)(Ph)N(C6H4X))(2)](2+) family indicate the catalytic rates reach a maximum when the electron-donating character of X results in the pK(a) of the Ni(I) protonated pendant amine matching that of the acid used for proton delivery. Additionally, the fast catalytic rates for hydrogen production by the [Ni(7P(2)(Ph)NC(6H4X))(2)](2+) family relative to the analogous [Ni((P2N2C6H4X)-N-Ph)(2)](2+) family are attributed to preferred formation of endo protonated isomers with respect to the metal center in the former, which is essential to attain suitable proximity to the reduced metal center to generate H-2. The results of this work highlight the importance of precise pK(a) matching with the acid for proton delivery to obtain optimal rates of catalysis.High Catalytic Rates for Hydrogen Production Using Nickel Electrocatalysts with Seven-Membered CyClic Diphosphine Ligands Containing One Pendant Aminex104201381#N/AFALSE
2218
ja404523s10.1021/ja404523sFALSEhttps://doi.org/10.1021/ja404523sJin, SJ. Am. Chem. Soc.Promising catalytic activity from molybdenum disulfide (MoS2) in the hydrogen evolution reaction (HER) is attributed to active sites located along the edges of its two-dimensional layered crystal structure, but its performance is currently limited by the density and reactivity of active sites, poor electrical transport, and inefficient electrical contact to the catalyst. Here we report dramatically enhanced HER catalysis (an electrocatalytic current density of 10 mA/cm(2) at a low overpotential of 187 mV vs RHE and a Tafel slope of 43 mV/decade) from metallic nanosheets of 1T-MoS2 chemically exfoliated via lithium intercalation from semiconducting 2H-MoS2 nanostructures grown directly on graphite. Structural characterization and electrochemical studies confirmed that the nanosheets of the metallic MoS2 polymorph exhibit facile electrode kinetics and low-loss electrical transport and possess a proliferated density of catalytic active sites. These distinct and previously unexploited features of 1T-MoS2 make these metallic nanosheets a highly competitive earth-abundant HER catalyst.Enhanced Hydrogen Evolution Catalysis from Chemically Exfoliated Metallic MoS2 Nanosheets2314201334#N/ATRUE
2219
ja312643210.1021/ja3126432FALSEhttps://doi.org/10.1021/ja3126432Nocera, DGJ. Am. Chem. Soc.A critical determinant of solar-driven water splitting efficiency is the kinetic profile of the O-2 evolving catalyst (OEC). We now report the kinetic profiles of water splitting by a self-assembled nickel-borate (NiBi) OEC. Mechanistic studies of anodized films of NiBi exhibit the low Tafel slope of 2.3 X RT/2F (30 mV/decade at 25 degrees C). This Tafel slope together with an inverse third order rate dependence on H+ activity establishes NiBi as an ideal catalyst to be used in the construction of photoelectrochemical devices for water splitting. In contrast, nonanodized NiBi films display significantly poorer activity relative to their anodized congeners that we attribute to a more sluggish electron transfer from the catalyst resting state. Borate is shown to play two ostensibly antagonistic roles in OEC activity: as a promulgator of catalyst activity by enabling proton-coupled electron transfer (PCET) and as an inhibitor in its role as an adsorbate of active sites. By defining the nature of the PCET pre-equilibrium that occurs during turnover, trends in catalyst activity may be completely reversed at intermediate pH as compared to those at pH extremes. These results highlight the critical role of PCET pre-equilibria in catalyst self-assembly and turnover, and accordingly suggest a reassessment in how OEC activities of different catalysts are compared and rationalized.Mechanistic Studies of the Oxygen Evolution Reaction Mediated by a Nickel-Borate Thin Film Electrocatalystx315201389#N/AFALSE
2220
ja312549210.1021/ja3125492FALSEhttps://doi.org/10.1021/ja9000695Tarascon, JMPreparation, Structure, and Electrochemistry of Layered Polyanionic Hydroxysulfates: LiMSO4OH (M = Fe, Co, Mn) Electrodes for Li-Ion Batteriesx2013#N/AFALSE
2221
ja404285b10.1021/ja404285bFALSEhttps://doi.org/10.1021/ja404285bKambe, NJ. Am. Chem. Soc.The cobalt-catalyzed cross-coupling of Alkyl (pseudo)halides with Alkyl Grignard reagents in the presence of 1,3-butadiene as a ligand precursor and LiI is described. Sterically congested quaternary carbon centers could be constructed by using tertiary Alkyl Grignard reagents. This reaction proceeds via an ionic mechanism with inversion of stereochemistry at the reacting site of the Alkyl halide and is compatible with various functional groups. The use of both 1,3-butadiene and LiI was essential for achieving high yields and high selectivities.Co-Catalyzed Cross-Coupling of Alkyl Halides with Tertiary Alkyl Grignard Reagents Using a 1,3-Butadiene Additive78201353#N/ATRUE
2222
ja404273710.1021/ja4042737FALSEhttps://doi.org/10.1021/ja4042737Goodenough, JBJ. Am. Chem. Soc.Oxide ion electrolytes determine the temperature of operation of solid oxide fuel cells, oxygen separation membranes, and oxygen sensors. There is a strong incentive to lower their operating temperatures, in a solid oxide fuel cell, for example, from T-op > 800 degrees C to T-op approximate to 500 degrees C. The use of low-cost Na+ rather than K+ as the dopant in monoClinic SrSiO3 (C12/C1) is shown to provide a larger solid solution range (0 < x <= 0.45) in Sr1-xNaxSiO3-0.5x and to achieve an oxide ion conductivity sigma(o) >= 10(-2) S.cm(-1) by 525 degrees C as a result of lowering the temperature of a smooth transition to full disorder of the mobile oxide ions. The Sr1-xNaxSiO3-0.5x electrolytes are much less hygroscopic than Sr1-xNaxSiO3-0.5x and are stable with a nickel composite anode in 5% H-2/Ar as well as with cathodes such as La1-xSrxMnO3-delta and Sr0.7Y0.3CoO3-delta in air, which makes them candidate electrolytes for intermediate-temperature solid oxide fuel cells or for other applications of oxide ion electrolytes.MonoClinic Sr1-xNaxSiO3-0.5x: New Superior Oxide Ion Electrolytes63201328#N/ATRUE
2223
ja403046210.1021/ja4030462FALSEhttps://doi.org/10.1021/ja4030462Vicic, DAJ. Am. Chem. Soc.Mechanistic proposals for nickel-catalyzed coupling reactions often invoke five-coordinate Alkyl- or Aryl-bound Ni(II) and/or high-valent nickel(III) species, but because of their reactive nature, they have been difficult to study and fingerprint. In this work, we invoked the stabilizing properties of fluoroAlkyl ligands to access such nickel species bearing ligands that are commonplace in organic coupling reactions. We show that five-coordinate Ni(II) complexes containing nickel-carbon bonds can readily be prepared given the appropriate precursor, and we also present evidence for the formation of Ni(III) species upon chemical and electrochemical oxidation of the five-coordinate complexes.A Five-Coordinate Nickel(II) FluoroAlkyl Complex as a Precursor to a Spectroscopically Detectable Ni(III) Species85201355#N/ATRUE
2224
ja402771510.1021/ja4027715FALSEhttps://doi.org/10.1021/ja4027715Dai, HJJ. Am. Chem. Soc.Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, inCluding water splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel-iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.An Advanced Ni-Fe Layered Double Hydroxide Electrocatalyst for Water Oxidation1863201335#N/ATRUE
2225
ja402027710.1021/ja4020277FALSEhttps://doi.org/10.1021/ja4020277Hikichi, SJ. Am. Chem. Soc.The nickel(II)-acylperoxo complex [Ni(Tp(CF3Me)) (kappa(2)-mCPBA)] (1(CF3Me)) [Tp(CF3Me) = hydrotris(3-trifluoromethyl-5-methylpyrazolyl)borate, mCPBA = m-chloroperbenzoate] was isolated and fully characterized. The electrophilic oxygenation ability of 1(CF3Me) toward sulfides and olefins was confirmed. The Michaelis Menten-type behavior of thioanisole oxygenation indicates the existence of a pre-equilibrium of substrate association in the reaction. In addition, 1(CF3Me) retains H-atom abstraction ability for hydrocarbons with activated methylene C-H bonds (e.g., fluorene). The oxidations of styrenes and these readily oxidizable hydrocarbons follow second-order kinetics, first-order each with respect to 1(CF3Me) and substrate. The lack of Clear acceleration in the decay of 1(CF3Me) in the presence of substrates with high C-H bond dissociation energies (e.g., cyClohexane) suggests that another reaction pathway contributes through the O-O-Cleaved intermediate.Structural Characterization and Oxidation Reactivity of a Nickel(II) Acylperoxo Complex44201325#N/ATRUE
2226
ja401579x10.1021/ja401579xFALSEhttps://doi.org/10.1021/ja401579xStryker, JMJ. Am. Chem. Soc.A structurally unique Class of hydrocarbon-soluble, ancillary-ligand-free, tetrametallic Co(I) and Ni(I) Clusters is reported. The highly unsaturated complexes are supported by simple, sterically bulky phosphoranimide ligands, one per metal. The electron-rich nitrogen centers are strongly bridging but sterically limited to bimetallic interactions. The hydrocarbon-soluble Clusters consist of four coplanar metal centers, mutually bridged by single nitrogen atoms. Each metal center is monovalent, rigorously linear, and two-coordinate. The Clusters are in essence two-dimensional atomic-scale molecular squares, a structural motif adapted from supramolecular chemistry. Both Clusters exhibit high solution-phase magnetic susceptibility at room temperature, suggesting the potential for applications in molecular electronics. Designed to be catalyst precursors, both Clusters exhibit high activity for catalytic hydrogenation of unsaturated hydrocarbons at low pressure and temperature.Hydrocarbon-Soluble Nanocatalysts with No Bulk Phase: Coplanar, Two-Coordinate Arrays of the Base Metals27201346#N/ATRUE
2227
ja311589910.1021/ja3115899FALSEhttps://doi.org/10.1021/ja3115899Neese, FA Metal-Metal Bond in the Light-Induced State of [NiFe] Hydrogenases with Relevance to Hydrogen Evolutionx2013#N/AFALSE
2228
ja401548d10.1021/ja401548dFALSEhttps://doi.org/10.1021/ja401548dMuller, TJ. Am. Chem. Soc.The coordination behavior of disilylated stannylenes toward zerovalent group 10 transition metal complexes was studied. This was accomplished by reactions of PEt3 adducts of disilylated stannylenes with zerovalent group 10 transition metal complexes. The thus obtained products differed between the first row example nickel and its heavier congeners While with nickel stannylene complex formation was observed, coordination of the stannylenes to palladium and platinum compounds led to unusual silastannene complexes of these metals A computational model study indicated that in each case metal stannylene complexes were formed first and that the disilylstannylene/silastannene rearrangement occurs only after complexation to the group 10 metal. The isomerization is a two-step process with relatively small barriers, suggesting a thermodynamic control of product formation. In addition, the results of the computational investigation revealed a subtle balance of steric and electronic effects, which determines the relative stability of the metalastannylene complex relative to its silastannene isomer. In the case of cyClic disilylstannylenes, the Pd(0) and Pt(0) silastannene complexes are found to be more stable, while with acyClic disilylstannylenes the Ni(0) stannylene complex is formed preferentially.Coordination Chemistry of Disilylated Stannylenes with Group 10 d(10) Transition Metals: Silastannene vs Stannylene Complexation30201349#N/ATRUE
2229
ja400481610.1021/ja4004816Agapie, TBimetallic Coordination Insertion Polymerization of Unprotected Polar Monomers: Copolymerization of Amino Olefins and Ethylene by Dinickel Bisphenoxyiminato Catalysts2013#N/ATRUE
2230
ja311055d10.1021/ja311055dFALSEhttps://doi.org/10.1021/ja311055dArmstrong, FAJ. Am. Chem. Soc.Hyd-1, produced by Escherichia coli, exemplifies a special Class of [NiFe]-hydrogenase that can sustain high catalytic H-2 oxidation activity in the presence of O-2-an intruder that normally incapacitates the sulfur- and electron-rich active site. The mechanism of O-2 tolerance involves a critical role for the Fe-S Clusters of the electron relay, which is to ensure the availability for immediate transfer back to the active site-of all of the electrons required to reduce an attacking O-2 molecule completely to harmless H2O. The unique [4Fe-3S] Cluster proximal to the active site is crucial because it can rapidly transfer two of the electrons needed. Here we investigate and establish the equally crucial role of the high potential medial [3Fe-4S] Cluster, located >20 angstrom from the active site. A variant, P242C, in which the medial [3Fe-4S] Cluster is replaced by a [4Fe-4S] Cluster, is unable to sustain steady-state H-2 oxidation activity in 1% O-2. The [3Fe-4S] Cluster is essential only for the first stage of complete O-2 reduction, ensuring the supply of all three electrons needed to form the oxidized inactive state Ni-B or Ready (Ni(III)-OH). Potentiometric titrations show that Ni-B is easily reduced (E-m approximate to +0.1 V at pH 6.0); this final stage of the O-2-tolerance mechanism regenerates active enzyme, effectively completing a competitive four-electron oxidase cyCle and is fast regardless of alterations at the proximal or medial Clusters. As a consequence of all these factors, the enzyme's response to O-2, viewed by its electrocatalytic activity in protein film electrochemistry (PFE) experiments, is merely to exhibit attenuated steady-state H-2 oxidation activity; thus, O-2 behaves like a reversible inhibitor rather than an agent that effectively causes irreversible inActivation. The data consolidate a rich picture of the versatile role of Fe-S Clusters in electron relays and suggest that Hyd-1 can function as a proficient hydrogen oxidase.Principles of Sustained Enzymatic Hydrogen Oxidation in the Presence of Oxygen - The Crucial Influence of High Potential Fe-S Clusters in the Electron Relay of [NiFe]-Hydrogenasesx76201370#N/AFALSE
2231
ja400426p10.1021/ja400426pFALSEhttps://doi.org/10.1021/ja400426pThieuleux, CNickel-Silicide Colloid Prepared under Mild Conditions as a Versatile Ni Precursor for More Efficient CO2 Reforming of CH4 Catalysts (vol 134, pg 20624, 2012)2013#N/ATRUE
2232
ja309915e10.1021/ja309915eFALSEhttps://doi.org/10.1021/ja309915eLercher, JAJ. Am. Chem. Soc.A novel Ni/SiO2-catalyzed route for selective Cleavage of ether bonds of (lignin-derived) aromatic ethers and hydrogenation of the oxygen-containing intermediates at 120 degrees C in presence of 6 bar H-2 in the aqueous phase is reported. The C-O bonds of alpha-O-4 and beta-O-4 linkages are Cleaved by hydrogenolysis on Ni, while the C-O bond of the 4-O-5 linkage is Cleaved via parallel hydrogenolysis and hydrolysis. The difference is attributed to the fact that the C fragments generated from hydrolysis of alpha-O-4 and beta-O-4 linkages can undergo further hydrogenolysis, while phenol (produced by hydrolysis of the 4-O-S linkage) is hydrogenated to produce cyClohexanol under conditions investigated. The apparent Activation energies, Ea(alpha-O-4) <E-3(beta-O-4) < E-a(4-O-5), vary proportionally with the bond dissociation energies. In the conversion of beta-O-4 and 4-O-5 ether bonds, C-O bond Cleavage is the rate-determining step, with the reactants competing with hydrogen for active sites, leading to a maximum reaction rate as a function of the H-2 pressure. For the very fast C-O bond Cleavage of the a-O-4 linkage, increasing the H-2 pressure increases the rate-determining product desorption under the conditions tested.Ni-Catalyzed Cleavage of Aryl Ethers in the Aqueous Phasex314201233#N/AFALSE
2233
ja309873z10.1021/ja309873zFALSEhttps://doi.org/10.1021/ja309873zHouk, KNJ. Am. Chem. Soc.The mechanism and origins of selectivities in [Ni(NHC)]-catalyzed intramolecular (5 + 2) cyCloadditions and homo-ene reactions of VinylcyClopropanes (VCPs) and alkynes have been studied using density functional theory. The preferred mechanism involves oxidative alkyne-alkene cyClization to form a metallacyClopentene intermediate, in contrast to a cyClopropane Cleavage pathway in the reaction with Rh(I) catalysts. The selectivity between the (5 + 2) and homo-ene products is determined in the subsequent competing reductive elimination and beta-hydride elimination steps. Two similar-sized N-heterocyClic carbene (NHC) ligands, SIPr and ItBu, yielded reversed product selectivity, favoring the (5 + 2) and homo-ene products respectively. This is attributed to the anisotropic steric environment of these NHC ligands, which positions the bulky substituents on the ligand toward different directions and leads to distinct steric control in the reductive elimination and beta-hydride elimination transition states.Mechanism and Origins of Ligand-Controlled Selectivities in [Ni(NHC)]-Catalyzed Intramolecular (5+2) CyCloadditions and Homo-Ene Reactions: A Theoretical Studyx64201389#N/AFALSE
2234
ja309771h10.1021/ja309771hhttps://doi.org/10.1021/ja309771hFukuzumi, SJ. Am. Chem. Soc.Single or mixed oxides of iron and nickel have been examined as catalysts in photocatalytic water oxidation using [Ru(bpy)(3)](2+) as a photosensitizer and S2O82- as a sacrificial oxidant. The catalytic activity of nickel ferrite (NiFe2O4) is comparable to that of a catalyst containing Ir, Ru, or Co in terms of O-2 yield and O-2 evolution rate under ambient reaction conditions. NiFe2O4 also possesses robustness and ferromagnetic properties, which are beneficial for easy recovery from the solution after reaction. Water oxidation catalysis achieved by a composite of earth-abundant elements will contribute to a new approach to the design of catalysts for artificial photosynthesis.Catalysis of Nickel Ferrite for Photocatalytic Water Oxidation Using [Ru(bpy)(3)](2+) and S2O82-Photocatalyst204201245#N/AFALSE
2235
ja308950d10.1021/ja308950dFALSEhttps://doi.org/10.1021/ja308950dXi, ZFJ. Am. Chem. Soc.An efficient Pd-catalyzed Cleavage of C(sp(3))-N bonds in secondary amines and a consequent C(sp(2))-N and C(sp(3))-N coupling process was developed. Various secondary amines could be used to react with alkenyl or Aryl dibromides, affording pyrroles and indoles in high yields. CyClopentadiene-phosphine ligands, a new type of P-olefin ligand, were found to be able to promote the efficiency of this Pd-catalyzed process remarkably. A reactive Pd complex coordinated with a cyClopentadiene-phosphine ligand was successfully isolated and structurally characterized.CyClopentadiene-Phosphine/Palladium-Catalyzed Cleavage of C-N Bonds in Secondary Amines: Synthesis of Pyrrole and Indole Derivatives from Secondary Amines and Alkenyl or Aryl Dibromidesx862012113#N/AFALSE
2236
ja308746710.1021/ja3087467https://doi.org/10.1021/ja3087467Lescouezec, RJ. Am. Chem. Soc.A repeatable bidirectional paramagnetic <-> diamagnetic photomagnetic effect has been observed in the cyanide-bridged Fe-Co square complex {[Fe{B(pz)(4)}-(CN)(3)](2)[Co(bik)(2)](2)}(ClO4)(2)center dot 3H(2)O [B(pz)(4) = tetrapyrazolylborate, bik = bis(1-methylimidazol-2-yl)ketone]. Magnetic measurements and low-temperature single-crystal X-ray diffraction experiments have shown that a complete electron transfer from the diamagnetic Fe-II -Co (III) state to the paramagnetic Fe-III -Co (II) metastable state is induced by 808 nm laser light irradiation, whereas the diamagnetic state is recovered in an almost quantitative yield under irradiation at 532 nm.On/Off Photoswitching in a Cyanide-Bridged {Fe2Co2} Magnetic Molecular SquarePhotocatalystx97201329#N/AFALSE
2237
ja400367h10.1021/ja400367hFALSEMashima, KEnzyme-Like Catalysis via Ternary Complex Mechanism: Alkoxy-Bridged DinuClear Cobalt Complex Mediates Chemoselective O-Esterification over N-Amidation2013#N/ATRUE
2238
ja308591210.1021/ja3085912FALSEhttps://doi.org/10.1021/ja3085912Hartwig, JFJ. Am. Chem. Soc.A heterogeneous nickel catalyst for the selective hydrogenolysis of Aryl ethers to arenes and alcohols generated without an added dative ligand is described. The catalyst is formed in situ from the well-defined soluble nickel precursor Ni(COD)(2) or Ni(CH2TMS)(2)(TMEDA) in the presence of a base additive, such as BuONa. The catalyst selectively Cleaves C-Ar-O bonds in Aryl ether models of lignin without hydrogenation of aromatic rings, and it operates at loadings down to 0.25 mol % at 1 bar of H-2 pressure. The selectivity of this catalyst for electronically varied Aryl ethers differs from that of the homogeneous catalyst reported previously, implying that the two catalysts are distinct from each other.A Heterogeneous Nickel Catalyst for the Hydrogenolysis of Aryl Ethers without Arene Hydrogenationx222201218#N/AFALSE
2239
ja308493k10.1021/ja308493kFALSEhttps://doi.org/10.1021/ja308493kArmstrong, FAJ. Am. Chem. Soc.Several small molecules and ions, notably carbon monoxide, cyanide, cyanate, and hydrogen sulfide, are potent inhibitors of Ni-containing carbon monoxide dehydrogenases (Ni-CODH) that catalyze very rapid, efficient redox interconversions of CO2 and CO. Protein film electrochemistry, which probes the dependence of steady-state catalytic rate over a wide potential range, reveals how these inhibitors target particular oxidation levels of Ni-CODH relating to intermediates (C-ox, C-red1, and C-red2) that have been established for the active site. The following properties are thus established: (1) CO suppresses CO2 reduction (CO is a product inhibitor), but its binding affinity decreases as the potential becomes more negative. (2) Cyanide totally inhibits CO oxidation, but its effect on CO2 reduction is limited to a narrow potential region (between -0.5 and -0.6 V), below which CO2 reduction activity is restored. (3) Cyanate is a strong inhibitor of CO2 reduction but inhibits CO oxidation only within a narrow potential range just above the CO2/CO thermodynamic potential-EPR spectra confirm that cyanate binds selectively to C-red2. (4) Hydrogen sulfide (H2S/HS-) inhibits CO oxidation but not CO2 reduction-the complex on/off characteristics are consistent with it binding at the same oxidation level as C-ox and forming a modified version of this inactive state rather than reacting directly with C-red1. The results provide a new perspective on the properties of different catalytic intermediates of Ni-CODH-uniting and Clarifying many previous investigations.A Unified Electrocatalytic Description of the Action of Inhibitors of Nickel Carbon Monoxide Dehydrogenase
Electrocatalytic
44201343#N/AFALSE
2240
ja312687a10.1021/ja312687aFALSEhttps://doi.org/10.1021/ja312687aDing, FJ. Am. Chem. Soc.The formation and kinetics of single and double vacancies in graphene chemical vapor deposition (CVD) growth on Cu(111), Ni(111), and Co(0001) surfaces are investigated by the first principles calculation. It is found that the vacancies in graphene on the metal surfaces are dramatically different from those in free-standing graphene. The interaction between the vacancies and the metal surface and the involvement of a metal atom in the vacancy structure greatly reduce their formation energies and significantly change their diffusion barriers. Furthermore, the kinetic process of forming vacancies and the potential route of their healing during graphene CVD growth on Cu(111) and Ni(111) surfaces are explored. The results indicate that Cu is a better catalyst than Ni for the synthesis of high-quality graphene because the defects in graphene on Cu are formed in a lower concentration and can be more efficiently healed at the typical experimental temperature. This study leads to a deep insight into the atomic process of graphene growth, and the mechanism revealed in this study can be used for the experimental design of high-quality graphene synthesis.Formation and Healing of Vacancies in Graphene Chemical Vapor Deposition (CVD) Growth71201364#N/ATRUE
2241
ja308146e10.1021/ja308146eFALSEhttps://doi.org/10.1021/ja308146eGuihery, NJ. Am. Chem. Soc.This paper reports the experimental and theoretical investigations of two trigonal bipyramidal Ni(II) complexes, [Ni(Me(6)tren)Cl](ClO4) (1) and [Ni(Me(6)tren)Br](Br) (2). High-field, high-frequency electron paramagnetic resonance spectroscopy performed on a single crystal of 1 shows a giant uniaxial magnetic anisotropy with an experimental D-expt value (energy difference between the M-s = +/- 1 and M-s = 0 components of the ground spin state S = 1) estimated to be between -120 and -180 cm(-1). The theoretical study shows that, for an ideally trigonal Ni(II) complex, the orbital degeneracy leads to a first-order spin-orbit coupling that results in a splitting of the M-s = +/- 1 and M-s = 0 components of approximately -600 cm(-1). Despite the Jahn-Teller distortion that removes the ground term degeneracy and reduces the effects of the first-order spin orbit interaction, the D value remains very large. A good agreement between theoretical and experimental results (theoretical D-theor, between -100 and -200 cm(-1)) is obtained.Giant Ising-Type Magnetic Anisotropy in Trigonal Bipyramidal Ni(II) Complexes: Experiment and Theoryx110201391#N/AFALSE
2242
ja307951y10.1021/ja307951yFALSEhttps://doi.org/10.1021/ja307951yYoo, SJJ. Am. Chem. Soc.The design of electrocatalysts for polymer electrolyte membrane fuel cells must satsify two equally important fundamental principles: optimization of electrocatalytic activity and long-term stability in acid media (pH <1) at high potential (0.8 V). We report here a solution-based approach to the preparation of Pt-based alloy with early transition metals and realistic parameters for the stability and activity of Pt3M (M = Y, Zr, Ti, Ni, and Co) nanocatalysts for oxygen reduction reaction (ORR). The enhanced stability and activity of Pt-based alloy nanocatalysts in ORR and the relationship between electronic structure modification and stability were studied by experiment and DFT calculations. Stability correlates with the d-band fillings and the heat of alloy formation of Pt3M alloys, which in turn depends on the degree of the electronic perturbation due to alloying. This concept provides realistic parameters for rational catalyst design in Pt-based alloy systems.Role of Electronic Perturbation in Stability and Activity of Pt-Based Alloy Nanocatalysts for Oxygen Reductionx153201253#N/AFALSE
2243
ja307909x10.1021/ja307909xFALSEhttps://doi.org/10.1021/ja307909xMorrow, JRJ. Am. Chem. Soc.Paramagnetic Ni(II) complexes are shown here to form paraCEST MRI contrast agents (paraCEST = paramagnetic: chemical exchange saturation transfer; NICEST = Ni(II) based CEST agents). Three azamacro-cyCles with amide pendent groups bind Ni(II) to form stable NiCEST contrast agents inCluding 1,4,7-tris-(carbamoylmethyl)-1,4,7-triazacyClononane. (L1), 1,4,8,11-tetrakis(carbamoylmethyl)-1,4,8,11-tetraazacyClo-tetradecane (L2), and 7,13-bis(carbamoylmethyl)-1,4,10-trioxa-7,13-diazacyClopentadecane (L3). [Ni(L3)](2+), [Ni(L1)](2+), and [Ni(L2)](2+) have CEST peaks attributed to amide protons that are shifted 72, 76, and 76 ppm from the bulk water resonance, respectively. Both CEST MR images and CEST spectroscopy show that [Ni(L3)](2+) has the largest CEST effect in 100 mM NaCl, 20 mM HEPES pH 7.4 at 37 degrees C. This larger CEST effect is attributed to the sharper proton resonances of the complex which arise from a rigid structure and low relaxivity.The NiCEST Approach: Nickel(II) ParaCEST MRI Contrast Agentsx67201215#N/AFALSE
2244
ja307699u10.1021/ja307699uFALSEhttps://doi.org/10.1021/ja307699uBetley, TAJ. Am. Chem. Soc.The reaction of (L-Ar)Co(py) with (BuN3)-Bu-t afforded the isolable three-coordinate Co-imido complex (L-Ar)Co((NBu)-Bu-t), which is paramagnetic at room temperature. Variable-temperature (VT) H-1 NMR spectroscopy, VT crystallography, and magnetic susceptibility measurements revealed that (L-Ar)Co((NBu)-Bu-t) undergoes a thermally induced spin crossover from an S = 0 ground state to a quintet (S = 2) state. The reaction of (L-Ar)Co(py) with mesityl azide yielded an isolable S = 1 terminal imido complex that was converted into the metallacyCloindoline (L-Ar)Co(kappa(2)-NHC6H2-2,4-Me-2-6-CH2) via Benzylic C-H Activation.Co(III) Imidos Exhibiting Spin Crossover and C-H Bond Activationx106201251#N/AFALSE
2245
ja312458f10.1021/ja312458fFALSEhttps://doi.org/10.1021/ja312458fStein, MJ. Am. Chem. Soc.The mixed-valence diiron hydrido complex (mu H)Fe-2(pdt)(CO)(2)(dppv)(2) ([H1](0), where pdt =1,3-propanedithiolate and dppv = cis-1,2-C2H2(PPh2)(2)), was generated by reduction of the differous hydride [H1](+) using decamethylcobaltocene. Crystallographic analysis shows that [H1](0) retains the stereochemistry of its precursor, where one dppv ligand spans two basal sites and the other spans apical and basal positions. The Fe-Fe bond elongates to 2.80 from 2.66 angstrom, but the Fe-P bonds only change subtly. Although the Fe-H distances are indistinguishable in the precursor, they differ by 0.2 angstrom in [H1](0). The X-band electron paramagnetic resonance (EPR) spectrum reveals the presence of two stereoisomers, the one characterized crystallographically and a contribution of about 10% from a second symmetrical (sym) isomer wherein both dppv ligands occupy apical-basal sites. The unsymmetrical (unsym) arrangement of the dppv ligands is reflected in the values of A(P-31), which range from 31 MHz for the basal phosphines to 284 MHz for the apical phosphine. Density functional theory calculations were employed to rationalize the electronic structure of [H1](0) and to facilitate spectral simulation and assignment of EPR parameters inCluding H-1 and P-31 hyperfine couplings. The EPR spectra of [HI](0) and [D1](0) demonstrate that the singly occupied molecular orbital is primarily localized on the Fe center with the longer bond to H, that is, Fe-II-H center dot center dot center dot Fe-I. The coupling to the hydride is A(H-1) = 55 and 74 MHz for unsym- amd sym[H1](0), respectively. Treatment of [H1](0) with H+ gives 0.5 equiv of H-2 and [H1](+). Reduction of D+ affords D-2, leaving the hydride ligand intact. These experiments demonstrate that the bridging hydride ligand in this complex is a spectator in the hydrogen evolution reaction.Isolation of a Mixed Valence Diiron Hydride: Evidence for a Spectator Hydride in Hydrogen Evolution Catalysis51201350#N/ATRUE
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ja307504910.1021/ja3075049FALSEhttps://doi.org/10.1021/ja3075049Krische, MJJ. Am. Chem. Soc.The ruthenium catalyst generated in situ from Ru-3(CO)(12) and tricyClohexylphosphine, PCy3, promotes the redox-neutral C-C coupling of Aryl-substituted alpha-hydroxy esters to isoprene and myrcene at the diene C4-position, resulting in direct carbinol C-H prenylation and geranylation, respectively. This process enables direct conversion of secondary to tertiary alcohols in the absence of stoichiometric byproducts or premetalated reagents, and is the first example of C4-regioselectivity in catalytic C-C couplings of 2-substituted dienes to Carbonyl partners. Mechanistic studies corrB(OH)2rate a catalytic cyCle involving diene-Carbonyl oxidative coupling.Direct, Redox-Neutral Prenylation and Geranylation of Secondary Carbinol C-H Bonds: C4-Regioselectivity in Ruthenium-Catalyzed C-C Couplings of Dienes to alpha-Hydroxy Estersx68201281#N/AFALSE
2247
ja307413x10.1021/ja307413xFALSEhttps://doi.org/10.1021/ja307413xBullock, RMJ. Am. Chem. Soc.To examine the role of proton delivery and removal in the electrocatalytic oxidation and production of hydrogen by Ni((P2N2R)-N-R')(2))(2+) (where (P2N22R')-N-R is 1,5-R'-3,7-R-1,5-diaza-3,7-diphosphacyClooctane); we report experimental and theoretical studies of the intermolecular proton exchange reactions underlying the isomerization of [Ni((P2N2H)-N-Cy-H-Bn)(2)](2+)(Cy - cyClohexyl, Bn = Benzyl) species formed during the oxidation of H-2 by [Ni-II((P2N2Bn)-N-Cy)(2)](2+) or the protonation of [Ni-0((P2N2Bn)-N-Cy)(2)]. Three... protonated isomers are formed-(endo/endo, endo/exo, or exo/exo) which differ in position Of the to nickel. The endo/endo isomer is most productive isomer dne to the two protons being sufficiently Close to the nickel proceed readily to the transition state to form/Cleave H-2. Therefore, the rate of the (endo/endo, endo/exo, or exo/exo), isomers to generate the endoterido isomer can have an important impact on catalytic rates. We have found that the rate of isomenzation is limited by proton removal from, or delivery,to, the complex. In particular, the endo position is more-stencally. : hindered than the exo position, therefore, protonation exo to the metal is kinetically favOred over endoprotonation which leads to less catalytically productive pathway. In hydrogen oxidation, deprotonation of the sterically hindered endo position in external base may lead to slow catalytic turnover For hydrogen production catalysts, the limited accessibility of the endb.position: can result in the preferential formation of the exo protonated isomerS, which may undergo one or more isomerization.steps to generate the catalytically productive end protonafed isoMer. The results of these studies highlight the importance of precise proton delivery, and the Mechanistic details described herein will be used to -future catalyst design.Proton Delivery and Removal in [Ni((P2N2R)-N-R ')](2) Hydrogen Production and Oxidation Catalystsx100201255#N/AFALSE
2248
ja312380b10.1021/ja312380bFALSEhttps://doi.org/10.1021/ja312380bNishihara, HJ. Am. Chem. Soc.A pi-conjugated nanosheet comprising planar nickel bis(dithiolene) complexes was synthesized by a bottom-up method. A liquid-liquid interfacial reaction using benzenehexathiol in the organic phase and nickel(II) acetate in the aqueous phase produced a semiconducting bulk material with a thickness of several micrometers. Powder X-ray diffraction analysis revealed that the crystalline portion of the bulk material comprised a staggered stack of nanosheets. A single-layer nanosheet was successfully realized using a gas-liquid interfacial reaction. Atomic force microscopy and scanning tunneling microscopy confirmed that the pi-conjugated nanosheet was single-layered. Modulation of the oxidation state of the nanosheet was possible using chemical redox reactions.pi-Conjugated Nickel Bis(dithiolene) Complex Nanosheet494201337#N/ATRUE
2249
ja306329310.1021/ja3063293FALSEhttps://doi.org/10.1021/ja3063293Blanchette, CDJ. Am. Chem. Soc.Subunit antigen-based vaccines can provide a number of important benefits over traditional vaccine candidates, such as overall safety. However, because of the inherently low immunogenicity of these antigens, methods for colocalized delivery of antigen and immunostimulatory molecules (i.e., adjuvants) are needed. Here we report a robust nanolipoprotein partiCle (NLP)-based vaccine delivery platform that facilitates the codelivery of both subunit antigens and adjuvants. Ni-chelating NLPs (NiNLPs) were assembled to incorporate the amphipathic adjuvants monophosphoryl lipid A and cholesterol-modified CpG oligodeoxynuCleotides, which can bind His-tagged protein antigens. Colocalization of antigen and adjuvant delivery using the NiNLP platform resulted in elevated antibody production against His-tagged influenza hemagglutinin 5 and Yersinia pestis LcrV antigens. Antibody titers in mice immunized with the adjuvanted NLPs were 5-10 times higher than those observed with coadministration formulations and nonadjuvanted NiNLPs. Colocalized delivery of adjuvant and antigen provides significantly greater immune stimulation in mice than coadministered formulations.Colocalized Delivery of Adjuvant and Antigen Using Nanolipoprotein PartiCles Enhances the Immune Response to Recombinant Antigensx51201318#N/AFALSE
2250
ja306260b10.1021/ja306260bhttps://doi.org/10.1021/ja306260bInoue, KMolecular Photoconductor with Simultaneously Photocontrollable Localized SpinsPhotocatalyst2012#N/AFALSE
2251
ja306003510.1021/ja3060035FALSEhttps://doi.org/10.1021/ja3060035Zhong, CJJ. Am. Chem. Soc.The understanding of the atomic-scale structural and chemical ordering in supported nanosized alloy partiCles is fundamental for achieving active catalysts by design. This report shows how such knowledge can be obtained by a combination of techniques inCluding X-ray photoelectron spectroscopy and synchrotron radiation based X-ray fine structure absorption spectroscopy and high-energy X-ray diffraction coupled to atomic pair distribution function analysis, and how the support-nanoalloy interaction influences the catalytic activity of ternary nanoalloy (platinum-nickel-cobalt) partiCles on three different supports: carbon, silica, and titania. The reaction of carbon monoxide with oxygen is employed as a probe to the catalytic activity. The thermochemical processing of this ternary composition, in combination with the different support materials, is demonstrated to be capable of fine-tuning the catalytic activity and stability. The support-nanoalloy interaction is shown to influence structural and chemical ordering in the nanopartiCles, leading to support-tunable active sites on the nanoalloys for oxygen Activation in the catalytic oxidation of carbon monoxide. A nickel/cobalt-tuned catalytic site on the surface of nanoalloy is revealed for oxygen Activation, which differs from the traditional oxygen-Activation sites known for oxide-supported noble metal catalysts. The discovery of such support-nanoalloy interaction-enabled oxygen-Activation sites introduces a very promising strategy for designing active catalysts in heterogeneous catalysis.Role of Support-Nanoalloy Interactions in the Atomic-Scale Structural and Chemical Ordering for Tuning Catalytic Sitesx66201271#N/AFALSE
2252
ja312120x10.1021/ja312120xFALSEhttps://doi.org/10.1021/ja312120xFarrusseng, DJ. Am. Chem. Soc.The one-pot postfunctionalization allows anchoring a molecular nickel complex into a mesoporous metal-organic framework (Ni@(Fe)MIL-101). It is generating a very active and reusable catalyst for the liquid-phase ethylene dimerization to selectively form 1-butene. Higher selectivity for 1-butene is found using the Ni@(Fe)MIL-101 catalyst than reported for molecular nickel diimino complexes.MOF-Supported Selective Ethylene Dimerization Single-Site Catalysts through One-Pot Postsynthetic Modification189201362#N/ATRUE
2253
ja304475710.1021/ja3044757FALSEhttps://doi.org/10.1021/ja3044757Kobayashi, HJ. Am. Chem. Soc.Crystals of the single-component molecular conductor [Cu(dmdt)(2)] (dmdt = dimethyltetrathiafulvalenedithiolate) were prepared as a molecular system, with three-dimensionally arranged magnetic moments embedded in sea of pi conduction electrons. [Cu(dmdt)(2)] had fairly large room-temperature conductivity (110 S cm(-1)) and exhibited weakly metallic behavior near room temperature. Below 265 K, the resistivity (R) increased very slowly with decreasing temperature and then increased rapidly, indicating a transition from a highly conducting state to an insulating state near 95 K. The magnetic susceptibility showed Curie Weiss behavior at 100-300 K (C = 0.375 emu/mol, Theta = 180 K). The Curie constant and the high-temperature resistivity behavior indicate that conduction electrons and three-dimensionally arranged magnetic moments coexist in the crystal. The ESR intensity increased down to about 95 K. The ESR signal was broadened and decreased abruptly near 95 K, suggesting that electric and antiferromagnetic transitions occurred simultaneously near 95 K. The crystal structure was determined down to 13 K. To examine the stability of the twisted conformation of Cu complex with dithiolate ligands, the dihedral angle dependence of the conformational energy of an isolated M(L)(2)(n-) molecule was calculated, which revealed the dihedral angle dependence on the ligand (L) and the oxidation state of the molecule (n). High-pressure four-probe resistivity measurements were performed at 3.3-9.3 GPa using a diamond anvil cell. The small resistivity increase observed at 3.3 GPa below 60 K suggested that the insulating transition observed at ambient pressure near 95 K was essentially suppressed at 3.3 GPa. The intermolecular magnetic interactions were examined on the basis of simple mean field theory of antiferromagnetic transition and the calculated intermolecular overlap integrals of the singly occupied molecular orbital (SOMO) of Cu(dmdt)(2).Single-Component Molecular Conductor [Cu(dmdt)(2)] with Three-Dimensionally Arranged Magnetic Moments Exhibiting a Coupled Electric and Magnetic Transitionx34201236#N/AFALSE
2254
ja304228c10.1021/ja304228chttps://doi.org/10.1021/ja304228cAwaga, KJ. Am. Chem. Soc.Photodetection based on bis-(4-dimethylaminodithiobenzil)-Ni(II) (BDN), a representative and well-studied metal dithiolene that shows strong absorption in the near-infrared region of the electromagnetic spectrum, has been investigated. By adopting a metal/insulator/semiconductor/metal (MISM) structure, the peak photocurrent response to an oscillating light chain is increased by up to SO times, compared to devices without an insulating layer. The transient form of the MISM photoresponse, while unsuitable for steady-state photodetection, can be used to detect periodic light signals of frequencies up to 1 MHz, and is thus applicable for optical communication. Further improvements have been realized by nanostructuring carbon black into the dithiolene layer, improving charge collection, and yielding detectivity of up to 1.6 x 10(11) Jones at wavelengths beyond the scope of silicon photodiodes. Such an architecture may allow the favorable absorption properties of other such metal dithiolenes to be harnessed, where their low charge carrier mobilities and short excitation lifetimes have previously limited their applicability to this field.Utilizing Photocurrent Transients for Dithiolene-Based Photodetection: Stepwise Improvements at Communications Relevant WavelengthsPhotocatalyst39201243#N/AFALSE
2255
ja304204q10.1021/ja304204qFALSEhttps://doi.org/10.1021/ja304204qHayton, TWJ. Am. Chem. Soc.Addition of 2,2'-bipyridine (bipy) to [Ni(NO)(bipy)][PF6] (1) results in formation of a rare five-coordinate nickel nitrosyl [Ni(NO)(bipy)(2)][PF6] (2). This complex exhibits a bent NO- ligand in the solid state. On standing in acetonitrile, 2 furnishes the NO coupled product, [Ni(kappa(2)-O2N2)(bipy)] (8) in moderate yield. Subsequent addition of 2 equiv of acetylacetone (H(acac)) to 8 results in formation of [Ni(acac)(2)(bipy)], N2O, and H2O. Preliminary mechanistic studies suggest that the N-N bond is formed via a bimetallic coupling reaction of two NO- ligands.Formation of N2O from a Nickel Nitrosyl: Isolation of the cis-[N2O2](2-) Intermediatex40201259#N/AFALSE
2256
ja311796n10.1021/ja311796nFALSEhttps://doi.org/10.1021/ja311796nPrakash, GKSJ. Am. Chem. Soc.A catalyst based on nickel oxide on magnesium oxide (NiO/MgO) thermally activated under hydrogen is effective for the bi-reforming with steam and CO2 (combined steam and dry reforming) of methane as well as natural gas in a tubular flow reactor at elevated pressures (5-30 atm) and temperatures (800-950 degrees C). By adjusting the CO2-to-steam ratio in the gas feed, the H-2/CO ratio in the produced syn-gas could be easily adjusted in a single step to the desired value of 2 for methanol and hydrocarbon synthesis.Bi-reforming of Methane from Any Source with Steam and Carbon Dioxide ExClusively to Metgas (CO-2H(2)) for Methanol and Hydrocarbon Synthesis156201320#N/ATRUE
2257
ja303950v10.1021/ja303950vFALSEhttps://doi.org/10.1021/ja303950vYang, HJ. Am. Chem. Soc.This communication describes the synthesis of Pt-M (M = Au, Ni, Pd) icosahedral nanocrystals based on the gas reducing agent in liquid solution method. Both CO gas and organic surface capping agents play critical roles in stabilizing the icosahedral shape with {111} surfaces. Among the Pt-M alloy icosahedral nanocrystals generated, Pt3Ni had an impressive ORR specific activity of 1.83 mA/cm(Pt)(2) and 0.62 A/mg(Pt). Our results further show that the area-specific activity, of icosahedral Pt3Ni catalysts was about 50% higher than that of the octahedral Pt,Ni catalysts (1.26 mA/cm(Pt)(2)), even though both shapes are bound by {111} facets. Density functional theory calculations and molecular dynamics simulations indicate that this improvement may arise from strain-induced electronic effects.Icosahedral Platinum Alloy Nanocrystals with Enhanced Electrocatalytic Activitiesx390201265#N/AFALSE
2258
ja303728c10.1021/ja303728cFALSEhttps://doi.org/10.1021/ja303728cWu, CDJ. Am. Chem. Soc.We incorporate metal 5,10,15,20-tetrakis(3,5-bisCarbonylphenyl)porphyrin (M-H8OCPP), for the first time, into porous metal organic frameworks. The self-assembled porous metalloporphyrinic frameworks [Mn5Cl2(MnCl-OCPP)-(DMF)(4)(H2O)(4)]center dot 2DMF center dot 8CH(3)COOH center dot 14H(2)O (ZJU-18; ZJU = Zhejiang University), [Mn5Cl2(Ni-OCPP)(H2O)(8)]center dot 7DMF center dot 6CH(3)COOH center dot 11H(2)O (ZJU-19), and [Cd5Cl2(MnCl-OCPP)-(H2O)(6)]center dot 13DMF center dot 2CH(3)COOH center dot 9H(2)O (ZJU-20) are isostructural as revealed by their single X-ray crystal structures. The metalloporphyrin octaCarbonylates (M-OCPP) (M = (MnCl)-Cl-III for ZJU-18 and ZJU-20, M = Ni-II for ZJU-19) are bridged by binuClear and trinuClear metal Carbonylate secondary building units to form a 3-periodic, binodal, edge-transitive net with Reticular Chemistry Structure Resource symbol tbo with pore windows of about 11.5 angstrom and pore cages about 21.3 angstrom in diameter. The porous nature of these metalloporphyrinic frameworks is further established by sorption studies in which different substrates such as ethanol, acetonitrile, acetone, cyClohexane, benzene, toluene, ethylbenzene, and acetophenone can readily have access to the pores. Their catalytic activities for the oxidation of Alkylbenzenes were examined at 65 degrees C using tert-butyl hydroperoxide as the oxidant. The results indicate that ZJU-18 is much superior to ZJU-19, ZJU-20, and homogeneous molecular MnCl-Me8OCPP, exhibiting highly efficient and selective oxidation of ethylbenzene to acetophenone in quantitative >99% yield and a turnover number of 8076 after 48 h.Porous Metalloporphyrinic Frameworks Constructed from Metal 5,10,15,20-Tetrakis(3,5-bisCarbonylphenyl)porphyrin for Highly Efficient and Selective Catalytic Oxidation of Alkylbenzenesx2402012133#N/AFALSE
2259
ja311671810.1021/ja3116718FALSEhttps://doi.org/10.1021/ja3116718Jamison, TFJ. Am. Chem. Soc.The synthesis and characterization of the air-stable nickel(II) complex trans-(PCy2Ph)(2)Ni(o-tolyl)Cl is described in conjunction with an investigation of its use for the Mizoroki-Heck-type, room temperature, internally selective coupling of substituted Benzyl chlorides with terminal alkenes. This reaction, which employs a terminal alkene as an alkenylmetal equivalent, provides rapid, convergent access to substituted allylbenzene derivatives in high yield and with regioselectivity greater than 95:5 in nearly all cases. The reaction is operationally simple, can be carried out on the benchtop with no purification or degassing of solvents or reagents, and requires no exClusion of air or water during setup. Synthesis of the precatalyst is accomplished through a straightforward procedure that employs inexpensive, commercially available reagents, requires no purification steps, and proceeds in high yield.Simplifying Nickel(0) Catalysis: An Air-Stable Nickel Precatalyst for the Internally Selective Benzylation of Terminal Alkenes120201371#N/ATRUE
2260
ja311669p10.1021/ja311669pFALSEhttps://doi.org/10.1021/ja311669pFu, GCJ. Am. Chem. Soc.The first Suzuki cross-couplings of unactivated tertiary Alkyl electrophiles are described. The method employs a readily accessible catalyst (NiBr2 center dot diglyme/4,4'-di-tert-butyl-2,2'-bipyridine, both commercially available) and represents the initial example of the use of a group 10 catalyst to cross-couple unactivated tertiary electrophiles to form C-C bonds. This approach to the synthesis of all-carbon quaternary carbon centers does not suffer from isomerization of the, Alkyl group, in contrast with the umpolung strategy for this bond construction (cross-coupling of a tertiary Alkylmetal with an Aryl electrophile). Preliminary mechanistic studies are consistent with the generation of a radical intermediate along the reaction pathway.Nickel-Catalyzed Carbon-Carbon Bond-Forming Reactions of Unactivated Tertiary Alkyl Halides: Suzuki Arylations220201330#N/ATRUE
2261
ja311179710.1021/ja3111797FALSEhttps://doi.org/10.1021/ja3111797Thieuleux, CJ. Am. Chem. Soc.Preparing highly active and stable non-noble-metal-based dry reforming catalysts remains a challenge today. In this context, supported nickel nanopartiCles with sizes of 1.3 +/- 0.2 and 2.1 +/- 0.2 nm were synthesized on silica and ceria, respectively, via a two-step colloidal approach. First, 2-nm nickel silicide colloids were synthesized from Ni(COD)(2) and octylsilane at low temperature; they were subsequently dispersed onto supports prior to reduction under H-2. The resulting catalysts display high activity in dry reforming compared to their analogues prepared using conventional approaches, ceria providing greatly improved catalyst stability.Nickel-Silicide Colloid Prepared under Mild Conditions as a Versatile Ni Precursor for More Efficient CO2 Reforming of CH4 Catalysts66201225#N/ATRUE
2262
ja311092c10.1021/ja311092cFALSESchneider, SThe Mechanism of Borane-Amine Dehydrocoupling with Bifunctional Ruthenium Catalysts2013#N/ATRUE
2263
ja302606d10.1021/ja302606dFALSEhttps://doi.org/10.1021/ja302606dLi, YDSyntheses of Water-Soluble Octahedral, Truncated Octahedral, and Cubic Pt-Ni Nanocrystals and Their Structure-Activity Study in Model Hydrogenation Reactionsx2012#N/AFALSE
2264
ja302436q10.1021/ja302436qFALSEhttps://doi.org/10.1021/ja302436qLercher, JAJ. Am. Chem. Soc.A new route to convert crude microalgae oils using ZrO2-promoted Ni catalysts into diesel-range alkanes in a cascade reaction is presented. Ni nanopartiCles catalyze the selective Cleavage of the C-O of fatty acid esters, leading to the hydrogenolysis of triglycerides. Hydrogenation of the resulting fatty acids to aldehydes (rate-determining step) is uniquely catalyzed via two parallel pathways, one via aldehyde formation on metallic Ni and the second via a synergistic action by Ni and ZrO2 through adsorbing the Carbonylic groups at the oxygen vacancies of ZrO2 to form Carbonylates and subsequently abstracting the alpha-hydrogen atom to produce ketene, which is in turn hydrogenated to aldehydes and deCarbonylated on Ni nanopartiCles.Stabilizing Catalytic Pathways via Redundancy: Selective Reduction of Microalgae Oil to Alkanesx233201218#N/AFALSE
2265
ja302340b10.1021/ja302340bFALSEhttps://doi.org/10.1021/ja302340bCui, YJ. Am. Chem. Soc.Chiral nanoporous metal organic frameworks are constructed by using diCarbonyl-functionalized chiral Ni(salen) and Co(salen) ligands. The Co(salen)based framework is shown to be an efficient and recyClable heterogeneous catalyst for hydrolytic kinetic resolution (HKR) of racemic epoxides with up to 99.5% ee. The MOF structure brings Co(salen) units into a highly dense arrangement and Close proximity that enhances bimetallic cooperative interactions, leading to improved catalytic activity and enantioselectivity in HKR compared with its homogeneous analogues, especially at low catalyst/substrate ratios.Chiral Nanoporous Metal-Metallosalen Frameworks for Hydrolytic Kinetic Resolution of Epoxidesx226201253#N/AFALSE
2266
ja311045f10.1021/ja311045fFALSEhttps://doi.org/10.1021/ja311045fMartin, RJ. Am. Chem. Soc.A novel Ni-catalyzed Carbonylation of Benzyl halides with CO2 has been developed. The described Carbonylation reaction proceeds under mild conditions (atmospheric CO, pressure) at room temperature. Unlike other routes for similar means, our method does not require well-defined and sensitive organometallic reagents and thus is a user-friendly and operationally simple protocol for assembling phenylacetic acids.Ni-Catalyzed Direct Carbonylation of Benzyl Halides with CO2209201350#N/ATRUE
2267
ja302149k10.1021/ja302149kFALSEhttps://doi.org/10.1021/ja302149kWarren, THJ. Am. Chem. Soc.We report bifunctional reactivity of the beta-diketiminato Ni(III)-imide [Me3NN]Ni=NAd (1), which undergoes H-atom abstraction (HAA) reactions with Benzylic substrates R-H (indane, ethylbenzene, toluene). Nickel imide 1 competes with the nickel-amide HAA product [Me3NN]Ni-NHAd (2) for the resulting hydrocarbyl radical R. to give the nickel amide [Me3NN]Ni-N(CHMePh)Ad (3) (R-H = ethylbenzene) or aminoAlkyl tautomer [Me3NN]Ni(eta(2)-CH(Ph)NHAd) (4) (R-H = toluene). A significant amount of functionalized amine R-NHAd is observed in the reaction of 1 with indane along with the dinickel imide {[Me3NN]Ni}(2)(mu-NAd) (5). Kinetic and DFT analyses point to rate-limiting HAA from R-H by 1 to give R*, which may add to either imide 1 or amide 2, each featuring significant N-based radical character. Thus, these studies illustrate a fundamental competition possible in C-H amination systems that proceed via a HAA/radical rebound mechanism.C-H Functionalization Reactivity of a Nickel-Imidex92201262#N/AFALSE
2268
ja308706d10.1021/ja308706dFALSEhttps://doi.org/10.1021/ja308706dAkasaka, TJ. Am. Chem. Soc.Single crystals of three soluble :Yb@C-82 isomers, namely,,Yb@C-2(5)-C-(82,) Yb@C-5(6)-C-82 and Yb@ C-2v(9)-C-82, cocrystallized with Ni-II(octaethylporphyrin); allowed accurate crystallographic elucidation of their molecular, structures in terms of both cage symmetry and metal location. Multiple metal positions were found in all these isomers, but the major metal sites were found in some specific regions within these cages. Specifically, the Yb2+ ion prefers to reside Close to a hexagonal ring in Yb@C-2(5)-C-82 and Yb@C-2v(9)-C-82 but a [5,6,6] junction carbon atom in Yb@C-5(6)-C-82. Theoretical calculations at the B3LYP level revealed: that these metal 'positions all correspond to energy minima from the electrostatic potential maps and give rise to the most stable configurations of these Yb@C-82 isomers. Furthermore, it is noteworthy that this is the first report on X-ray crystallographic studies of such-metallofullerenes, with the popular C-2v(9)-C-82 encapsulating a divalent inefat ion, described as M2+@[C-2v(9)-C-82](2-).Single-Crystal X-ray Diffraction Study of Three Yb@C-82 Isomers Cocrystallized with Ni-II(octaethylporphyrin)52201245#N/ATRUE
2269
ja301879710.1021/ja3018797FALSEhttps://doi.org/10.1021/ja3018797Eichhorn, BJ. Am. Chem. Soc.K4Sn9 dissolves in ethylenediamine (en) to give equilibrium mixtures of the diamagnetic HSn93- ion along with KxSn9(4-x)- ion pairs, where x = 0, 1, 2, 3. The HSn93- Cluster is formed from the deprotonation of the en solvent and is the conjugate acid of Sn-9(4-). DFT studies show that the structure is quite similar to the known isoelectronic RSn93- ions (e.g., R = i-Pr). The hydrogen atom of HSn93- (delta = 6.18 ppm) rapidly migrates among all nine Sn atoms in an intramolecular fashion; the Sn-9 core is also highly dynamic on the NMR time scale. The HSn93- Cluster reacts with Ni(cod)(2) to give the Ni@HSn93- ion containing a hydridic hydrogen (delta = 28.3 ppm) that also scrambles across the Sn-9 Cluster. The Sn-9(4-) ion competes effectively with 2,2,2-crypt for binding K+ in en solutions, and the pK(a) of HSn93- is similar to that of en (i.e., Sn-9(4-) is a very strong Bronsted base with a pK(b) comparable to that of the NH2CH2CH2NH- anion). Competition studies show that the HSn93- reversible arrow Sn-9(4-) + H+ equilibrium is fully reversible. The HSn93- anion is present in significant concentrations in en solutions containing 2,2,2-crypt, yet it has gone undetected for over 30 years.Surprising Acid/Base and Ion-Sequestration Chemistry of Sn-9(4-): HSn93-, Ni@HSn93-, and the Sn-9(3-) Ion Revisitedx32201247#N/AFALSE
2270
ja308479710.1021/ja3084797FALSEhttps://doi.org/10.1021/ja3084797Ritter, TJ. Am. Chem. Soc.A one-step oxidative fluorination for carbon-fluorine bond formation from well-defined nickel complexes with oxidant and aqueous fluoride is presented, which enables a straightforward and practical F-18 late-stage fluorination of complex small molecules with potential for PET imaging.Nickel-Mediated Oxidative Fluorination for PET with Aqueous [F-18] Fluoride208201223#N/ATRUE
2271
ja307507a10.1021/ja307507aFALSEhttps://doi.org/10.1021/ja307507aBoettcher, SWSolution-Cast Metal Oxide Thin Film Electrocatalysts for Oxygen Evolution2012#N/ATRUE
2272
ja301586m10.1021/ja301586mFALSEhttps://doi.org/10.1021/ja301586mLee, YHJ. Am. Chem. Soc.Coexistence of both edge plane and basal plane in graphite often hinders the understanding of lithium ion diffusion mechanism. In this report, two types of graphene samples were prepared by chemical vapor deposition (CVD): (i) well-defined basal plane graphene grown on Cu foil and (ii) edge plane-enriched graphene layers grown on Ni film. Electrochemical performance of the graphene electrode can be split into two regimes depending on the number of graphene layers: (i) the corrosion-dominant regime and (ii) the lithiation-dominant regime. Li ion diffusion perpendicular to the basal plane of graphene is facilitated by defects, whereas diffusion parallel to the plane is limited by the steric hindrance that originates from aggregated Li ions adsorbed on the abundant defect sites. The critical layer thickness (l(c)) to effectively prohibit substrate reaction using CVD-grown graphene layers was predicted to be similar to 6 layers, independent of defect population. Our density functional theory calculations demonstrate that divacancies and higher order defects have reasonable diffusion barrier heights allowing lithium diffusion through the basal plane but neither monovacancies nor Stone-Wales defect.Diffusion Mechanism of Lithium Ion through Basal Plane of Layered Graphenex210201251#N/AFALSE
2273
ja301567f10.1021/ja301567fFALSEhttps://doi.org/10.1021/ja301567fCarter, EAJ. Am. Chem. Soc.In photoelectrochemical cells, sunlight may be converted into chemical energy by splitting water into hydrogen and oxygen molecules. Hematite (alpha-Fe2O3) is a promising photoanode material for the water oxidation component of this process. Numerous research groups have attempted to improve hematite's photocatalytic efficiency despite a lack of foundational knowledge regarding its surface reaction kinetics. To elucidate detailed reaction mechanisms and energetics, we performed periodic density functional theory + U calculations for the water oxidation reaction on the fully hydroxylated hematite (0001) surface. We investigate two different concentrations of surface reactive sites. Our best model involves calculating water oxidation mechanisms on a pure (1x1) hydroxylated hematite slab (corresponding to 1/3 ML of reactive sites) with an additional overlayer of water molecules to model solvation effects. This yields an overpotential of 0.77 V, a value only slightly above the 0.5-0.6 V experimental range. To explore whether doped hematite can exhibit an even lower overpotential, we consider cation doping by substitution of Fe by Ti, Mn, Co, Ni, or Si and F anion doping by replacing O on the fully hydroxylated surface. The reaction energetic; on pure or doped hematite surfaces are described using a volcano plot. The relative stabilities of holes on the active O anions are identified as the underlying cause for trends in energetics predicted for different dopants. We show that moderately charged O anions give rise to smaller overpotentials. Co- or Ni-doped hematite surfaces give the most thermodynamically favored reaction pathway (lowest minimum overpotential) among all dopants considered. Very recent measurements (Electrochim. Acta 2012, 59, 121-127) reported improved reactivity with Ni doping, further validating our predictions.Water Oxidation on Pure and Doped Hematite (0001) Surfaces: Prediction of Co and Ni as Effective Dopants for Electrocatalysisx361201288#N/AFALSE
2274
ja307179q10.1021/ja307179qFALSEhttps://doi.org/10.1021/ja307179qHecht, SMJ. Am. Chem. Soc.Because of the lack of sensitivity to small changes in distance by available FRET pairs (a constraint imposed by the dimensions of the enzyme), a DHFR containing two pyrene moieties was prepared to enable the observation of excimer formation. Pyren-I-ylalanine was introduced into DHFR positions 16 and 49 using an in vitro expression system in the presence of pyren-l-ylalanyl-tRNA(CUA). Excimer formation (lambda(ex) 342 nm; lambda(em) 481 nm) was observed in the modified DHFR, which retained its catalytic competence and was studied under multiple and single turnover conditions. The excimer appeared to follow a protein conformational change after the H transfer involving the relative position and orientation of the pyrene moieties and is likely associated with product dissociation.Two Pyrenylalanines in Dihydrofolate Reductase Form an Excimer Enabling the Study of Protein Dynamics29201231#N/ATRUE
2275
ja300834b10.1021/ja300834bFALSEhttps://doi.org/10.1021/ja300834bMaroney, MJJ. Am. Chem. Soc.RcnR (resistance to cobalt and nickel regulator) is a 40-kDa homotetrameric protein and metalloregulator that controls the transcription of the Co(II) and Ni(II) exporter, RcnAB, by binding to DNA as an apoprotein and releasing DNA in response to specifically binding Co(II) and Ni(II) ions. Using X-ray absorption spectroscopy (XAS) to examine the structure of metals bound and lacZ reporter assays of the transcription of RcnA in response to metal binding, in WT and mutant proteins, the roles of coordination number, ligand selection, and residues in the N-terminus of the protein were examined as determinants in metal ion recognition. The studies show that the cognate metal ions, Co(II) and Ni(II), which bind in (N/O)(5)S six-coordinate sites, are distinguished from non-cognate metal ions (Cu(I) and Zn(II)), which bind only three protein ligands and one anion from the buffer, by coordination number and ligand selection. Using mutations of residues near the N-terminus, the N-terminal amine is shown to be a ligand of the cognate metal ions that is missing in the complexes with non-cognate metal ions. The side chain of His3 is also shown to play an important role in distinguishing metal ions. The imidazole group is shown to be a ligand in the Co(II) RcnR complex, but not in the Zn(II) complex. Further, His3 does not appear to bind to Ni(II), providing a structural basis for the differential regulation of RcnAB by the two cognate ions. The Zn(II) complexes change coordination number in response to the residue in position three. In H3C-RcnR, the Zn(II) complex is five-coordinate, and in H3E-RcnR the Zn(II) ion is bound to six protein ligands. The metric parameters of this unusual Zn(II) structure resemble those of the WT-Ni(II) complex, and the mutant protein is able to regulate expression of RcnAB in response to binding the non-cognate ion. The results are discussed within a protein allosteric model for gene regulation by metalloregulators.Role of the N-terminus in Determining Metal-Specific Responses in the E. coli Ni- and Co-Responsive Metalloregulator, RcnRx33201264#N/AFALSE
2276
ja300756y10.1021/ja300756yFALSEhttps://doi.org/10.1021/ja300756yTessema, MMJ. Am. Chem. Soc.Platinum alloy nanopartiCles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanopartiCles (NPs), with a particular focus on Pt-Ni alloys. Well-faceted alloy nanocrystals were generated with this method, inCluding predominantly cubic and cuboctahedral nanocrystals of Pt3Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanopartiCles were measured with a rotating disk electrode (RDE) technique. While some Pt3Ni alloy nanopartiCle catalysts showed specific activities greater than 1000 mu A/cm(P nu)(2) alloy catalysts prepared with a nominal composition of PtNi displayed activities Close to 3000 mu A/cm(P nu)(2) or almost 15 times that of a state-of-the-art Pt/carbon catalyst. XRD and EDS confirmed the presence of two NP compositions in this catalyst. HAADF-STEM examination of the PtNi nanopartiCle catalyst after RDE testing revealed the development of hollows in a number of the nanopartiCles due to nickel dissolution. Continued voltage cyCling caused further nickel dissolution and void formation, but significant activity remained even after 20 000 cyCles.Solvothermal Synthesis of Platinum Alloy NanopartiCles for Oxygen Reduction Electrocatalysisx316201230#N/AFALSE
2277
ja304867j10.1021/ja304867jFALSEBalch, ALX-ray Crystallographic Characterization of New Soluble Endohedral Fullerenes Utilizing the Popular C-82 Bucky Cage. Isolation and Structural Characterization of Sm@C-3v(7)-C-82, Sm@C-s(6)-C-82, and Sm@C-2(5)-C-822012#N/ATRUE
2278
ja304068t10.1021/ja304068tFALSEhttps://doi.org/10.1021/ja304068tFu, GCJ. Am. Chem. Soc.Through the use of a catalyst formed in situ from NiBr2 center dot diglyme and a pybox ligand (both of which are commercially available), we have achieved our first examples of coupling reactions of unactivated tertiary Alkyl electrophiles, as well as our first success with nickel-catalyzed couplings that generate bonds other than C C bonds. Specifically, we have determined that this catalyst accomplishes Miyaura-type borylations of unactivated tertiary, secondary, and primary Alkyl halides with diboron reagents to furnish Alkylboronates, a family of compounds with substantial (and expanding) utility, under mild conditions; indeed, the umpolung borylation of a tertiary Alkyl bromide can be achieved at a temperature as low as -10 degrees C. The method exhibits good functional-group compatibility and is regiospecific, both of which can be issues with traditional approaches to the synthesis of Alkylboronates. In contrast to seemingly related nickel-catalyzed C-C bond-forming processes, tertiary halides are more reactive than secondary or primary halides in this nickel-catalyzed C-B bond-forming reaction; this divergence is particularly noteworthy in view of the likelihood that both transformations follow an inner-sphere electron-transfer pathway for oxidative addition.Nickel-Catalyzed Coupling Reactions of Alkyl Electrophiles, InCluding Unactivated Tertiary Halides, To Generate Carbon-Boron Bonds205201238#N/ATRUE
2279
ja211864w10.1021/ja211864wFALSEPirngruber, GDComparison of the Behavior of Metal-Organic Frameworks and Zeolites for Hydrocarbon Separationsx2012#N/AFALSE
2280
ja303514b10.1021/ja303514bFALSEhttps://doi.org/10.1021/ja303514bTsuji, YJ. Am. Chem. Soc.Nickel-catalyzed Carbonylation of Aryl and Vinyl chlorides employing carbon dioxide has been developed. The reactions proceeded under a CO2 pressure of 1 atm at room temperature in the presence of nickel catalysts and Mn powder as a reducing agent. Various Aryl chlorides could be converted to the corresponding Carbonylic acid in good to high yields. Furthermore, Vinyl chlorides were successfully Carbonylated with CO2. Mechanistic study suggests that Ni(I) species is involved in the catalytic cyCle.Nickel-Catalyzed Carbonylation of Aryl and Vinyl Chlorides Employing Carbon Dioxide218201239#N/ATRUE
2281
ja211594m10.1021/ja211594mFALSEhttps://doi.org/10.1021/ja211594mShima, SJ. Am. Chem. Soc.[Fe]-hydrogenase catalyzes the reversible hydride transfer from H-2 to methenyltetrahydromethanoptherin, which is an intermediate in methane formation from H-2 and CO2 in methanogenic archaea. The enzyme harbors a unique active site iron-guanylylpyridinol (FeGP) cofactor, in which a low-spin Fell is coordinated by a pyridinol-N, an acyl group, two carbon monoxide, and the sulfur of the enzyme's cysteine. Here, we studied the biosynthesis of the FeGP cofactor by following the incorporation of C-13 and H-2 from labeled precursors into the cofactor in growing methanogenic archaea and by subsequent NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), electrospray ionization Fourier transform ion cyClotron resonance mass spectrometry (ESI-FT-ICR-MS) and IR analysis of the isolated cofactor and reference compounds. The pyridinol moiety of the cofactor was found to be synthesized from three C-1 of acetate, two C-2 of acetate, two C-1 of pyruvate, one carbon from the methyl group of L-methionine, and one carbon directly from CO2. The metabolic origin of the two CO-ligands was CO2 rather than C-1 or C-2 of acetate or pyruvate exCluding that the two CO are derived from dehydroglycine as has previously been shown for the CO-ligands in [FeFe]-hydrogenases. A formation of CO from CO2 via direct reduction catalyzed by a nickel-dependent CO dehydrogenase or from formate could also be exCluded. When the cells were grown in the presence of (CO)-C-13, the two CO-ligands and the acyl group became C-13-labeled, indicating either that free CO is an intermediate in their synthesis or that free CO can exchange with these iron-bound ligands. Based on these findings, we propose pathways for how the FeGP cofactor might be synthesized.Biosynthesis of the Iron-Guanylylpyridinol Cofactor of [Fe]-Hydrogenase in Methanogenic Archaea as Elucidated by Stable-Isotope Labelingx28201256#N/AFALSE
2282
ja303370j10.1021/ja303370jFALSEhttps://doi.org/10.1021/ja303370jLatturner, SEJ. Am. Chem. Soc.R33Fe14-xAlx+yB25-yC34 (R = La or Ce; x <= 0.9; y <= 0.2) and R33Fe13-xAlxB18C34 (R = Ce or Pr; x < 0.1) were synthesized from reactions of iron with boron, carbon, and aluminum in R-T eutectic fluxes (T = Fe, Co, or Ni). These phases crystallize in the cubic space group Im<(3)over bar>m (a = 14.617(1) angstrom, Z = 2, R-1 = 0.0155 for Ce33Fe13.1Al11B24.8C34, and a = 14.246(8) angstrom, Z = 2, R-1 = 0.0142 for R33Fe13B18C34 ). Their structures can be described as body-centered cubic arrays of large Fe-13 or Fe, Clusters which are capped by borocarbide chains and surrounded by rare earth cations. The magnetic behavior of the cerium-containing analogs is complicated by the possibility of two valence states for cerium and possible presence of magnetic moments on the iron sites. Temperature-dependent magnetic susceptibility measurements and Mossbauer data show that the boron-centered Fe-14 Clusters in Ce33Fe14-xAlx+yB25-yC34 are not magnetic. X-ray photoelectron spectroscopy data. indicate that the cerium is trivalent at room temperature, but the temperature dependence of the resistivity and the magnetic susceptibility data suggest Ce3+/4+ valence fluctuation beginning at 120 K. Bond length analysis and XPS studies of Ce33Fe13B18C34 indicate the cerium in this phase is tetravalent, and the observed magnetic ordering at T-c = 180 K is due to magnetic, moments on the Fen Clusters.A Tale of Two Metals: New Cerium Iron Borocarbide Intermetallics Grown from Rare-Earth/Transition Metal Eutectic Fluxes16201252#N/ATRUE
2283
ja302859r10.1021/ja302859rFALSEhttps://doi.org/10.1021/ja302859rBalch, ALJ. Am. Chem. Soc.Two isomers of Sm@C-92 and four isomers of Sm@C-94 were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm2O3. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni-II(octaethylporphyrin) reveals the identities of two of the Sm@C-92 isomers: Sm@C-92(I), which is the more abundant isomer, is Sm@C-1(42)-C-92, and Sm@C-92(II) is Sm@C-s(24)-C-92. The structure of the most abundant form of the four isomers of Sm@C-94, Sm@C-94(1), is Sm@C-3v(134)-C-94, which utilizes the same cage isomer as the previously known Ca@C-3v(134)-C-94 and Tm@C-3v(134)-C-94. All of the structurally characterized isomers obey the isolated pentagon rule. While the four Sm@C-90 and five isomers of Sm@C-84 belong to common isomerization maps that allow these isomers to be interconverted through Stone-Wales transformations, Sm@C-1(42)-C-92 and Sm@C-s(24)-C-92 are not related to each other by any set of Stone-Wales transformations. UV-vis-NIR spectroscopy and computational studies indicate that Sm@C-1(42)-C-92 is more stable than Sm@C-s(24)-C-92 but possesses a smaller HOMO-LUMO gap. While the electronic structures of these endohedrals can be formally described as Sm2+@C-2n(2-), the net charge transferred to the cage is less than two due to some back-donation of electrons from pi orbitals of the cage to the metal ion.Single Samarium Atoms in Large Fullerene Cages. Characterization of Two Isomers of Sm@C-92 and Four Isomers of Sm@C-94 with the X-ray Crystallographic Identification of Sm@C-1(42)-C-92, Sm@C-s(24)-C-92, and Sm@C-3v(134)-C-9439201261#N/ATRUE
2284
ja302851n10.1021/ja302851nFALSEhttps://doi.org/10.1021/ja302851nRuiz, EJ. Am. Chem. Soc.PolynuClear 3d transition metal-Gd complexes are good candidates to present large magnetocaloric effect. This effect is favored by the presence of weak ferromagnetic exchange interactions that have been investigated using methods based on Density Functional Theory. The first part of the study is devoted to dinuClear complexes, focusing on the nature and mechanism of such exchange interactions. The presence of two bridging ligands is found more favorable for ferromagnetic coupling than a triple-bridged assembly, especially for complexes with small M-O center dot center dot center dot O-Gd hinge angles. Our results show the crucial role of the Gd 5d orbitals in the exchange interaction while the 6s orbital seems to have a negligible participation. The analysis of the atomic and orbital spin populations reveals that the presence of spin density in the Gd 5d orbital is mainly due to a spin polarization effect, while a delocalization mechanism from the 3d orbitals of the transition metal can be ruled out. We propose a numerical DFT approach using pseudopotentials to calculate the exchange coupling constants in four polynuClear first-row transition metal-Gd complexes. Despite the complexity of the studied systems, the numerical approach gives coupling constants in excellent agreement with the available experimental data and, in conjunction with exact diagonalization methods (or Monte Carlo simulations), it makes it possible to obtain theoretical estimates of the entropy change due to the magnetization/demagnetization process of the molecule.Theoretical Study of Exchange Coupling in 3d-Gd Complexes: Large Magnetocaloric Effect Systems133201282#N/ATRUE
2285
ja302177z10.1021/ja302177zFALSEhttps://doi.org/10.1021/ja302177zKishi, YJ. Am. Chem. Soc.The importance of the Ni catalyst in achieving catalytic asymmetric Ni/Cr-mediated coupling reactions effectively is demonstrated. Six phenanthroline-NiCl2 complexes 1a-c and 2a-c and five types of alkenyl iodides A-E were chosen for the study, thereby demonstrating that these Ni catalysts display a wide range of overall reactivity profiles in terms of the degree of asymmetric induction, geometrical isomerization, and coupling rate. For three types of alkenyl iodides A-C, a satisfactory Ni catalyst(s) was found within 1a-c and 2a-c. For disubstituted (Z)-alkenyl iodide D, 2c was identified as an acceptable Ni catalyst: in terms of the absence of Z --> E isomerization and the degree of asymmetric induction but not in terms of the coupling rate. Two phosphine-based Ni catalysts, [(Me)(3)P](2)center dot NiCl2 and [(cy)(3)P](2)center dot NiCl2, were found to meet all three criteria for D. The bond-forming reaction at the C16-C17 position of palytoxin was used to demonstrate the usefulness of the Ni catalysts thus identified.On Ni Catalysts for Catalytic, Asymmetric Ni/Cr-Mediated Coupling Reactions23201243#N/ATRUE
2286
ja301949810.1021/ja3019498FALSEhttps://doi.org/10.1021/ja3019498Erlebacher, JJ. Am. Chem. Soc.We present a comprehensive experimental study of the formation and activity of dealloyed nanoporous Ni/Pt alloy nanopartiCles for the cathodic oxygen reduction reaction. By addressing the kinetics of nuCleation during solvothermal synthesis we developed a method to control the size and composition of Ni/Pt alloy nanopartiCles over a broad range while maintaining an adequate size distribution. Electrochemical dealloying of these size-controlled nanopartiCles was used to explore conditions in which hierarchical nanoporosity within nanopartiCles can evolve. Our results show that in order to evolve fully formed porosity, partiCles must have a minimum diameter of similar to 15 nm, a result consistent with the surface kinetic processes occurring during dealloying. Nanoporous nanopartiCles possess ligaments and voids with diameters of approximately 2 nm, high surface area/mass ratios usually associated with much smaller partiCles, and a composition consistent with a Pt-skeleton covering a Ni/Pt alloy core. Electrochemical measurements show that the mass activity for the oxygen reduction reaction using carbon-supported nanoporous Ni/Pt nanopartiCles is nearly four times that of commercial Pt/C catalyst and even exceeds that of comparable nonporous Pt-skeleton Ni/Pt alloy nanopartiCles.Structure/Processing/Properties Relationships in Nanoporous NanopartiCles As Applied to Catalysis of the Cathodic Oxygen Reduction Reaction215201287#N/ATRUE
2287
ja301769r10.1021/ja301769rTRUEhttps://doi.org/10.1021/ja301769rWeix, DJJ. Am. Chem. Soc.A general method is presented for the synthesis of Alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of Aryl and Vinyl bromides are reductively coupled with Alkyl bromides in high yields. Under similar conditions, activated Aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exClude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stile, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nuCleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nuCleophilic carbon (R-[M]) for organB(OH)2ron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of sigma and sigma(-) parameters with the relative rate of reaction of substituted Aryl bromides with bromoalkanes. The small rho values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of Alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon Aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.Replacing Conventional Carbon NuCleophiles with Electrophiles: Nickel-Catalyzed Reductive Alkylation of Aryl Bromides and ChloridesCsp2_ar-Csp3XBrBrArylNo baseNo Base22420121527/28/2022TRUE
2288
ja210871j10.1021/ja210871jFALSEhttps://doi.org/10.1021/ja513166wSommer, MOn the Role of Single Regiodefects and Polydispersity in Regioregular Poly(3-hexylthiophene): Defect Distribution, Synthesis of Defect-Free Chains, and a Simple Model for the Determination of Crystallinityx2012#N/AFALSE
2289
ja301640e10.1021/ja301640eFALSEhttps://doi.org/10.1021/ja301640eRajanBabu, TVJ. Am. Chem. Soc.1-VinylcyCloalkenes undergo highly regio- and enantioselective (>98% ee) 1,4-hydroVinylation (HV) when treated with ethylene (1 aim) at room temperature in the presence of [(S,S)-2,4-bis-diphenylphosphinopentane (BDPP)]CoCl2 (0.05 equiv) and methylaluminoxane. The minor 1,2-HV products, seen only in 1-VinylcyClohexene (similar to 15%) and 1-VinylcyCloheptene (2%), are formed as racemic mixtures. The corresponding Ni(II)-catalyzed HV reactions of these substrates give mostly the 1,2-adducts. Racemic 4-tert-butyl-1-VinylcyClohexene, when treated with Co[(S,S)-(BDPP)]Cl-2 and ethylene, undergoes a rare enantiodivergent reaction giving two diastereomers each in >98% cc.Asymmetric HydroVinylation of 1-VinylcyCloalkenes. Reagent Control of Regio- and Stereoselectivity53201227#N/ATRUE
2290
ja301018q10.1021/ja301018qFALSEhttps://doi.org/10.1021/ja301018qNocera, DGJ. Am. Chem. Soc.An oxygen evolution catalyst that forms as a thin film from Ni(aq)(2+) solutions containing borate electrolyte (Ni-B-i) has been studied by in situ X-ray absorption spectroscopy. A dramatic increase in catalytic rate, induced by anodic Activation of the electrodeposited films, is accompanied by structure and oxidation state changes. Coulometric measurements correlated with X-ray absorption near-edge structure spectra of the active catalyst show that the nickel centers in activated films possess an average oxidation state of +3.6, indicating that a substantial proportion of nickel centers exist in a formal oxidation state of Ni(IV). In contrast, nickel centers in nonactivated films exist predominantly as Ni(III). Extended X-ray absorption fine structure reveals that activated catalyst films comprise bis-oxo/hydroxo-bridged nickel centers organized into sheets of edge-sharing NiO6 octahedra. Diminished long-range ordering in catalyst films is due to their ostensibly amorphous nature. Nonactivated films display a similar oxidic nature but exhibit a distortion in the local coordination geometry about nickel centers, characteristic of Jahn-Teller distorted Ni(III) centers. Our findings indicate that the increase in catalytic activity of films is accompanied by changes in oxidation state and structure that are reminiscent of those observed for conversion of beta-NiOOH to gamma-NiOOH and consequently challenge the long-held notion that the beta-NiOOH phase is a more efficient oxygen-evolving catalyst.Structure-Activity Correlations in a Nickel-Borate Oxygen Evolution Catalyst462201257#N/ATRUE
2291
ja300641c10.1021/ja300641cFALSEhttps://doi.org/10.1021/ja300641cGagne, MRJ. Am. Chem. Soc.Diastereoselective Ni-Catalyzed Negishi Cross-Coupling Approach to Saturated, Fully Oxygenated C-Alkyl and C-Aryl Glycosides (vol 130, pg 12177, 2008)020121#N/ATRUE
2292
ja212206m10.1021/ja212206mFALSEhttps://doi.org/10.1021/ja212206mTong, YXJ. Am. Chem. Soc.Porous Pt-Ni-P composite nanotube arrays (NTAs) on a conductive substrate in good solid contact are successfully synthesized via template-assisted electrodeposition and show high electrochemical activity and long-term stability for methanol electrooxidation. Hollow nanotubular structures, porous nanostructures, and synergistic electronic effects of various elements contribute to the high electrocatalytic performance of porous Pt-Ni-P composite NTA electrocatalysts.Porous Pt-Ni-P Composite Nanotube Arrays: Highly Electroactive and Durable Catalysts for Methanol Electrooxidation334201266#N/ATRUE
2293
ja209631710.1021/ja2096317FALSEhttps://doi.org/10.1021/ja2096317Bogaerts, AJ. Am. Chem. Soc.Carbon nanotubes (CNTs) are nowadays routinely grown in a thermal CVD setup. State-of-the-art plasma-enhanced CVD (PECVD) growth, however, offers advantages over thermal CVD. A lower growth temperature and the growth of aligned freestanding single-walled CNTs (SWNTs) makes the technique very attractive. The atomic scale growth mechanisms of PECVD CNT growth, however, remain currently entirely unexplored. In this contribution, we employed molecular dynamics simulations to focus on the effect of applying an electric field on the SWNT growth process, as one of the effects coming into play in PECVD. Using sufficiently strong fields results in (a) alignment of the growing SWNTs, (b) a better ordering of the carbon network, and (c) a higher growth rate relative to thermal growth rate. We suggest that these effects are due to the small charge transfer occurring in the Ni/C system. These simulations constitute the first study of PECVD growth of SWNTs on the atomic level.Insights in the Plasma-Assisted Growth of Carbon Nanotubes through Atomic Scale Simulations: Effect of Electric Fieldx63201240#N/AFALSE
2294
ja211785u10.1021/ja211785uFALSEhttps://doi.org/10.1021/ja211785uBalch, ALIsolation of Three Isomers of Sm@C-84 and X-ray Crystallographic Characterization of Sm@D-3d(19)-C-84 and Sm@C-2(13)-C-842012#N/ATRUE
2295
ja208791f10.1021/ja208791fFALSEhttps://doi.org/10.1021/ja208791fCowan, JAJ. Am. Chem. Soc.A series of compounds that target reactive enzyme (sACE-1) have been synthesized. Half-maximal transition-metal chelates to somatic angiotensin converting inhibitory concentrations (IC50) and rate constants for both inActivation and Cleavage of full-length sACE-1 have been determined and evaluated in terms of metal chelate size, charge, reduction potential, coordination unsaturation, and coreactant selectivity. Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), 1,4,7,10-tetraazacyClododecane-1,4,7,10-tetraacetic acid (DOTA), and tripeptide GGH were linked to the lysine side chain of lisinopril by 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride/N-hydroxysuccinimide coupling. The resulting amide-linked chelate-lisinopril (EDTA-lisinopril, NTA-lisinopril, DOTA-lisinopril, and GGH-lisinopril) conjugates were used to form coordination complexes with iron, cobalt, nickel, and copper, such that lisinopril could mediate localization of the reactive metal chelates to sACE-1. ACE activity was assayed by monitoring Cleavage of the fluorogenic substrate Mca-RPPGFSAFK(Dnp)-OH, a derivative of bradykinin, following preincubation with metal chelate-lisinopril compounds. Concentration-dependent inhibition of sACE-1 by metal chelate-lisinopril complexes revealed IC50 values ranging from 44 to 4500 nM for Ni-NTA-lisinopril and Ni-DOTA-lisinopril, respectively, versus 1.9 nM for lisinopril. Stronger inhibition was correlated with smaller size and lower negative charge of the attached metal chelates. Time-dependent inActivation of sACE-1 by metal chelate-lisinopril complexes revealed a remarkable range of catalytic activities, with second-order rate constants as high as 150 000 M-1 min(-1) (Cu-GGH-lisinopril), while catalyst-mediated Cleavage of sACE-1 typically occurred at much lower rates, indicating that inActivation arose primarily from side chain modification. Optimal inActivation of sACE-1 was observed when the reduction potential for the metal center was poised near 1000 mV, reflecting the difficulty of protein oxidation. This Class of metal chelate-lisinopril complexes possesses a range of high-affinity binding to ACE, introduces the advantage of irreversible catalytic turnover, and marks an important step toward the development of multiple-turnover drugs for selective inActivation of sACE-1.Targeted Catalytic InActivation of Angiotensin Converting Enzyme by Lisinopril-Coupled Transition-Metal Chelatesx37201258#N/AFALSE
2296
ja211485t10.1021/ja211485tFALSEhttps://doi.org/10.1021/ja211485tXie, ZWJ. Am. Chem. Soc.Reactions of Cp2Zr(mu-Cl)(mu-C2B10H10)Li(OEt2)(2) with alkynes (RC)-C-1 CR2 gave as insertion products zirconacyClopentenes incorporating a carboranyl unit, 1,2-[Cp2ZrC(R-1)=C(R-2)]-1,2-C2B10H10 (1). Treatment of 1 with another type of alkyne (RC)-C-3 CR4 in the presence of stoichiometric amounts of NiCl2 and FeCl3 or a catalytic amount of NiCl2 afforded symmetric or unsymmetric benzocarboranes. The regioselectivity was dominated by the polarity of the corresponding alkynes. These reactions could also be carried out in one pot, leading to the equivalent of a three-component [2 + 2 + 2] cyCloaddition of carboryne and two different alkynes promoted by transition metals. A reaction mechanism was proposed after the isolation and structural characterization of the key intermediate nickelacyCle. These results show that nickel complexes are more reactive than the iron ones toward the insertion of alkynes but that the latter do not initiate the trimerization of alkynes, making the insertion of activated alkynes possible. This work also demonstrates that a catalytic amount of nickel works as well as a stoichiometric amount of nickel in the presence of excess FeCl3 for the reactions. Such a catalytic reaction may shed some light on the development of zirconocene-based catalytic reactions.Transition-Metal-Promoted or -Catalyzed ExocyClic Alkyne Insertion via ZirconacyClopentene with Carborane Auxiliary: Formation of Symmetric or Unsymmetric Benzocarboranes312012105#N/ATRUE
2297
ja208710x10.1021/ja208710xhttps://doi.org/10.1021/ja208710xKiriy, AJ. Am. Chem. Soc.Strongly electron-deficient (n-type) main-chain g-conjugated polymers are commonly prepared via well-established step-growth polycondensation protocols which enable limited control over polymerization. Here we demonstrate that activated Zn and electron-deficient brominated thiophene-naphthalene diimide oligomers form anion-radical complexes instead of conventional Zn-organic derivatives. These highly unusual zinc complexes undergo Ni-catalyzed chain-growth polymerization leading to n-type conjugated polymers with controlled molecular weight, relatively narrow polydispersities, and specific end-functions.Chain-Growth Polymerization of Unusual Anion-Radical Monomers Based on Naphthalene Diimide: A New Route to Well-Defined n-Type Conjugated Copolymersx118201138#N/AFALSE
2298
ja211419t10.1021/ja211419tFALSEhttps://doi.org/10.1021/ja211419tPeters, JCJ. Am. Chem. Soc.We report the synthesis and characterization of a series of nickel complexes of the chelating diphosphine-borane ligands ArB(o-Ph2PC6H4)(2) ([(DPBPh)-D-Ar]; Ar = Ph, Mes). The [(DPBPh)-D-Ar] framework supports pseudo-tetrahedral nickel complexes featuring eta(2)-B,C coordination from the ligand backbone. For the B-phenyl derivative, the adduct [(DPBPh)-D-Ph]Ni(THF) has been characterized by X-ray diffraction and features a very short interaction between nickel and the eta(2)-B,C ligand. For the B-mesityl derivative, the reduced nickel complex [(DPBPh)-D-Mes]Ni is isolated as a pseudo-three-coordinate naked species that undergoes reversible, nearly thermoneutral oxidative addition of dihydrogen to give a borohydrido-hydride complex of nickel(II) which has been characterized in solution by multinuClear NMR Furthermore, [(DPBPh)-D-Mes]Ni is an efficient catalyst for the hydrogenation of olefin substrates under mild conditions.Reversible H-2 Addition across a Nickel-Borane Unit as a Promising Strategy for Catalysis211201231#N/ATRUE
2299
ja208475y10.1021/ja208475yFALSEhttps://doi.org/10.1021/ja208475yXu, QJ. Am. Chem. Soc.Noble-metal-free nickel iron alloy nanopartides exhibit excellent catalytic performance for the complete decomposition of hydrous hydrazine, for which the NiFe nanocatalyst, with equimolar compositions of Ni and Fe, shows 100% hydrogen selectivity in basic solution (0.5 M NaOH) at 343 K. The development of low-cost and high-performance catalysts may encourage the effective application of hydrous hydrazine as a promising hydrogen storage material.Noble-Metal-Free Bimetallic NanopartiCle-Catalyzed Selective Hydrogen Generation from Hydrous Hydrazine for Chemical Hydrogen Storagex267201142#N/AFALSE
2300
ja208469n10.1021/ja208469nFALSEhttps://doi.org/10.1021/ja208469nLi, DJ. Am. Chem. Soc.The gyroid is ubiquitous for underlying the construction of natural substance and artificial zeolites, but it has been, surprisingly, overlooked by chemists who work in the field of metal-organic frameworks (MOFs). In this work, a series of gyroidal MOFs with gie topology, constructed from 1,2-bis((5H-imidazol-4-yl)methylene)hydrazine and octahedral metal ions, such as Zn-II, Mn-II, Cu-II, and Ni-II, have been synthesized. The Zn-II analogue, named as STU-1, shows exceptional thermal and chemical stabilities, and exhibits permanent porosity and CO2 capture ability.Gyroidal Metal-Organic Frameworksx62201226#N/AFALSE
2301
ja208387q10.1021/ja208387qFALSEhttps://doi.org/10.1021/ja208387qSojka, ZJ. Am. Chem. Soc.This artiCle reports on the Activation of dioxygen on nickel(I) dispersed inside the nanopores of the ZSM-5 zeolite, which can be regarded as a heterogeneous mimetic system (zeozyme) for Ni-bearing enzymes. The side-on eta 2-coordination of the resulting nickel-bound superoxo adduct was ascer16O2 species supported by computer simulations of the spectra tamed by detailed analysis of the EPR spectra of both 16O2 and 17O2 species supported by computer simulations of the spectra and relativistic DFT calculations of the EPR signatures. Molecular analysis of the g and A(17O) tensors (gxx = 2.0635, gyy = 20.884, gzz = 2.1675; vertical bar Axx vertical bar approximate to 1.0 mT, vertical bar Ayy vertical bar = 5.67 mT, vertical bar A(zz)vertical bar approximate to 1.3 mT 1.3 mT) and quantum chemical modeling revealed an unusual electronic and magnetic structure of the observed adduct (with g(zz)(g(max)) > g(yy)(g(mid)) > g(xx)(g(min)) and the largest O-17 hyperfine splitting along the g(mid) direction) in comparison to the known homogeneous and enzymatic nickel-superoxo systems. It is best described as a mixed metalloradical with two supporting oxygen donor-ligands and even triangular spin-density redistribution within the)eta 2(-){NiO2}(11) magnetophore. The semioccupied molecular orbital (SOMO) is constituted by highly covalent 6 overlap between the out-of-plane 2p(pi(g)*) MO of dioxygen and the 3d(x2-y2) MO nickel. By means of the extended transition state-natural orbitals for the chemical valence approach (ETS-NOCV), three distinct orbital channels (associated with a, pi, and delta overlap) of congruent and incongruent charge and spin density flows within the eta(2)-{NiO2}(11) unit, contributing jointly to Activation of the attached dioxygen, were identified. Their individual energetic relevance was quantified, which allowed for explaining the oxygen binding mechanism with unprecedented accuracy. The nature and structure sensitivity of the g tensor was rationalized in terms of the contributions due to the magnetic field-induced couplings of the relevant molecular orbitals that control the g-tensor anisotropy. The calculated O-17 hyperfine coupling constants correspond well with the experimental parameters, supporting assignment of the adduct. To the best of our knowledge, the eta(2)-{NiO2}(11) superoxo adducts have not been observed yet for digonal mononuClear nickel(I) centers supported by oxygen donor ligands.Heterogeneous Binding of Dioxygen: EPR and DFT Evidence for Side-On Nickel(II)-Superoxo Adduct with Unprecedented Magnetic Structure Hosted in MFI Zeolitex31201167#N/AFALSE
2302
ja208324n10.1021/ja208324nFALSEhttps://doi.org/10.1021/ja208324nDatye, AKJ. Am. Chem. Soc.Sintering of nanopartiCles (NPs) of Ni supported on MgAl2O4 was monitored in situ using transmission electron microscopy (TEM) during exposure to an equimolar mixture of H-2 and H2O at a pressure of 3.6 mbar at 750 degrees C, conditions relevant to methane steam reforming. The TEM images revealed an increase in the mean partiCle size due to disappearance of smaller, immobile NPs and the resultant growth of the larger NPs. A new approach for predicting the long-term sintering of NPs is presented wherein microscopic observations of the ripening of individual NPs (over a span of a few seconds) are used to extract energetic parameters that allow a description of the collective behavior of the entire population of NPs (over several tens of minutes).Relating Rates of Catalyst Sintering to the Disappearance of Individual NanopartiCles during Ostwald Ripeningx176201135#N/AFALSE
2303
ja211247f10.1021/ja211247fFALSEhttps://doi.org/10.1021/ja211247fStack, TDPJ. Am. Chem. Soc.Nonsymmetric substitution of salen (1(R1,R2)) and reduced salen (2(R1,R2)) Cu-II-phenoxyl complexes with a combination of -Bu-t, -(SPr)-Pr-i, and -OMe substituents leads to dramatic differences in their redox and spectroscopic properties, providing insight into the influence of the cysteine-modified tyrosine cofactor in the enzyme galactose oxidase (GO). Using a modified Marcus-Hush analysis, the oxidized copper complexes are characterized as Class II mixed-valent due to the electronic differentiation between the two substituted phenolates. Sulfur K-edge X-ray absorption spectroscopy (XAS) assesses the degree of radical delocalization onto the single sulfur atom of nonsymmetric [1(tBu,SMe)](+) at 7%, consistent with other spectroscopic and electrochemical results that suggest preferential oxidation of the -SMe bearing phenolate. Estimates of the thermodynamic free energy difference between the two localized states (Delta G degrees) and reorganizational energies (lambda(R1R2)) of [1(R1,R2)](+) and [2(R1,R2)](+) lead to accurate predictions of the spectroscopically observed IVCT transition energies. Application of the modified Marcus-Hush analysis to GO using parameters determined for [2(R1,R2)](+) predicts a nu(max) of similar to 43600 cm(-1), well within the energy range of the broad Vis-NIR band displayed by the enzyme.Electrochemical and Spectroscopic Effects of Mixed Substituents in Bis(phenolate)-Copper(II) Galactose Oxidase Model Complexes72201255#N/ATRUE
2304
ja210990t10.1021/ja210990tAgapie, TBimetallic Effects on Ethylene Polymerization in the Presence of Amines: Inhibition of the DeActivation by Lewis Bases2012#N/ATRUE
2305
ja208008610.1021/ja2080086https://doi.org/10.1021/ja2080086Kobayashi, SJ. Am. Chem. Soc.Considering the importance of the development of powerful green catalysts and the omnipresence of amide bonds in natural and synthetic compounds, we report here on reactions between alcohols and amines for amide bond formation in which heterogeneous gold and gold/iron, -nickel, or -cobalt nanopartides are used as catalysts and molecular oxygen is used as terminal oxidant. Two catalysts show excellent activity and selectivity, depending on the type of alcohols used. A wide variety of alcohols and amines, inCluding aqueous ammonia and amino acids, can be used for the amide synthesis. Furthermore, the catalysts can be recovered and reused several times without loss of activity.Powerful Amide Synthesis from Alcohols and Amines under Aerobic Conditions Catalyzed by Gold or Gold/Iron, -Nickel or -Cobalt NanopartiClesx226201146#N/AFALSE
2306
ja210984k10.1021/ja210984kFALSEhttps://doi.org/10.1021/ja210984kPoeppelmeier, KRJ. Am. Chem. Soc.A methodology for the design of polar, inorganic structures is demonstrated here with the packing of lambda (Lambda)-shaped basic building units (BBUs). Noncentrosymmetric (NCS) solids with interesting physical properties can be created with BBUs that lack an inversion center and are likely to pack into a polar configuration; previous methods to construct these solids have used NCS octahedra as BBUs. Using this methodology to synthesize NCS solids, one must increase the coordination of the NCS octahedra with maintenance of the noncentrosymmetry of the bulk. The first step in this progression from an NCS octahedron to an inorganic NCS solid is the formation of a bimetallic BBU. This step is exemplified with the compound CuVOF4(H2O)(7): this compound, presented here, crystallizes in an NCS structure with ordered, isolated [Cu(H2O)(5)](2+) cations and [VOF4(H2O)](2-) anions into Lambda-shaped, bimetallic BBUs to form CuVOF4(H2O)(6)center dot H2O, owing to the Jahn-Teller distortion of Cu2+. Conversely, the centrosymmetric heterotypes with the same formula MVOF4(H2O)(2) (M-II = Co, Ni, and Zn) exhibit ordered, isolated [VOF4(H2O)](2-) and [M(H2O)(6)](2+) ionic species in a hydrogen bond network CuVOF4(H2O)(7) exhibits a net polar moment while the heterotypes do not; this demonstrates that Lambda-shaped BBUs give a greater probability for and, in this case, lead to NCS structures.The Role of Polar, Lamdba (Lambda)-Shaped Building Units in Noncentrosymmetric Inorganic Structures91201278#N/ATRUE
2307
ja210899210.1021/ja2108992FALSEhttps://doi.org/10.1021/ja2108992Willis, MCJ. Am. Chem. Soc.A Rh(I)-catalyzed method for the efficient functionalization of arenes is reported. Aryl methyl sulfides are combined with terminal alkynes to deliver products of carbothiolation. The overall process results in reincorporation of the original arene functional group, a methyl sulfide, into the products as an alkenyl sulfide. The carbothiolation process can be combined with an initial Rh(I)-catalyzed alkene or alkyne hydroacylation reaction in three-component cascade sequences. The utility of the alkenyl sulfide products is also demonstrated in simple carbo- and heterocyCle-forming processes. We also provide mechanistic evidence for the course of this new process.Aryl Methyl Sulfides as Substrates for Rhodium-Catalyzed Alkyne Carbothiolation: Arene Functionalization with Activating Group RecyCling105201237#N/ATRUE
2308
ja207461t10.1021/ja207461tFALSEhttps://doi.org/10.1021/ja207461tMoore, TAJ. Am. Chem. Soc.Hydrogenases catalyze the interconversion of protons and hydrogen according to the reversible reaction: 2H(+) + 2e(-) reversible arrow H-2 while using only the earthabundant metals nickel and/or iron for catalysis. Due to their high activity for proton reduction and the technological significance of the H+/H-2 half reaction, it is important to characterize the catalytic activity of [FeFe]-hydrogenases using both biochemical and electrochemical techniques. Following a detailed electrochemical and photoelectrochemical study of an [FeFe]-hydrogenase from Clostridium acetobutylicum (CaHydA), we now report electrochemical and single-molecule imaging studies carried out on a catalytically active hydrogenase preparation. The enzyme CaHydA, a homologue (70% identity) of the [FeFe]-hydrogenase from Clostridium pasteurianum, CpI, was adsorbed to a negatively charged, self-assembled monolayer (SAM) for investigation by electrochemical scanning tunneling microscopy (EC-STM) techniques and macroscopic electrochemical measurements. The EC-STM imaging revealed uniform surface coverage with sufficient stability to undergo repeated scanning with a STM tip as well as other electrochemical investigations. CyClic voltammetry yielded a characteristic cathodic hydrogen production signal when the potential was scanned sufficiently negative. The direct observation of the single enzyme distribution on the Au-SAM surface coupled with macroscopic electrochemical measurements obtained from the same electrode allowed the evaluation of a turnover frequency (TOF) as a function of potential for single [FeFe]-hydrogenase molecules.Catalytic Turnover of [FeFe]-Hydrogenase Based on Single-Molecule Imagingx123201247#N/AFALSE
2309
ja207293410.1021/ja2072934FALSEhttps://doi.org/10.1021/ja2072934Bertozzi, CRJ. Am. Chem. Soc.New additions to the bioorthogonal chemistry compendium can advance biological research by enabling multiplexed analysis of biomolecules in complex systems. Here we introduce the quadricyClane ligation, a new bioorthogonal reaction between the highly strained hydrocarbon quadricyClane and Ni bis(dithiolene) reagents. This reaction has a second-order rate constant of 0.25 M-1 s(-1), on par with fast bioorthogonal reactions of azides, and proceeds readily in aqueous environments. Ni bis(dithiolene) probes selectively labeled quadricyClane-modified bovine serum albumin, even in the presence of cell lysate. We have demonstrated that the quadricyClane ligation is compatible with, and orthogonal to, strain-promoted azide-alkyne cyCloaddition and oxime ligation chemistries by performing all three reactions in one pot on differentially functionalized protein substrates. The quadricyClane ligation joins a small but growing list of tools for the selective covalent modification of biomolecules.A Bioorthogonal QuadricyClane Ligationx50201142#N/AFALSE
2310
ja207138410.1021/ja2071384FALSEhttps://doi.org/10.1021/ja2071384Rowsell, JLCJ. Am. Chem. Soc.Diffuse reflectance infrared (IR) spectroscopy performed over a wide temperature range (35-298 K) is used to study the dynamics of H-2 adsorbed within the isostructural metal organic frameworks M2L (M = Mg, Mn, Co, Ni and Zn; L = 2,5-dioxidobenzene-1,4-diCarbonylate) referred to as MOF-74 and CPO-27. Spectra collected at H-2 concentrations ranging from 0.1 to 3.0 H-2 per metal cation reveal that strongly red-shifted vibrational modes arise from isolated H-2 bound to the available metal coordination site. The red shift of the bands associated with this site correlate with reported isosteric enthalpies of adsorption (at small surface coverage), which in turn depend on the identity of M. In contrast, the bands assigned to H-2 adsorbed at positions >3 angstrom from the metal site exhibit only minor differences among the five materials. Our results are consistent with previous models based on neutron diffraction data and independent IR studies, but they do not support a recently proposed adsorption mechanism that invokes strong H-2 center dot center dot center dot H-2 interactions (Nijem et al. J. Am. Chem. Soc. 2010, 132, 14834-14848). Room temperature IR spectra comparable to those on which the recently proposed adsorption mechanism was based were only reproduced after contaminating the adsorbent with ambient air. Our interpretation that the uncontaminated spectral features result from stepwise adsorption at discrete framework sites is reinforced by systematic red shifts of adsorbed H-2 isotopologues and consistencies among overtone bands that are well-described by the Buckingham model of molecular interactions in vibrational spectroscopy.Metal-Specific Interactions of H-2 Adsorbed within Isostructural Metal-Organic Frameworksx61201158#N/AFALSE
2311
ja206812f10.1021/ja206812fhttps://doi.org/10.1021/ja206812fHerges, RJ. Am. Chem. Soc.Magnetic bistability in spin-crossover materials generally is a collective phenomenon that arises from the cooperative interaction of a large number of microscopic magnetic moments within the crystal lattice in the solid state. We now report on individual molecules in homogeneous solution that are switched between the diamagnetic and paramagnetic states at room temperature by light-driven coordination-induced spin-state switching (LD-CISSS). Switching of the coordination number (and concurrently of the spin state) was achieved by using Ni-porphyrin as a square-planar platform and azopyridines as photodissociable axial ligands. The square-planar Ni-porphyrin is diamagnetic (low-spin, S = 0), and all complexes with axial ligands are paramagnetic (high-spin, S = 1). Association constants were determined for all conceivable 1:1 and 1:2 porphyrin/azopyriCline complexes. The binding constants of the trans azopyridines are larger than those of the corresponding cis isomers. Thus, upon irradiation with UV light (365 nm, trans -> cis) and visible light (455 nm, cis -> trans), switching of the magnetic properties was achieved. Upon substitution of the azopyridines at the 4- and 4'-positions with larger substituents, the difference in trans and cis association constants, and thus the switching efficiency, was increased. A photoinduced, reversible switching between 20 and 68% paramagnetic Ni species in solution was achieved with isopropyl substituents at room temperature.Light-Induced Spin Change by Photodissociable External Ligands: A New Principle for Magnetic Switching of MoleculesPhotocatalystx109201143#N/AFALSE
2312
ja210796510.1021/ja2107965FALSEHall, MBThe Mechanism of Alkene Addition to a Nickel Bis(dithiolene) Complex: The Role of the Reduced Metal Complex2012#N/ATRUE
2313
ja206244w10.1021/ja206244wFALSEhttps://doi.org/10.1021/ja206244wBalch, ALJ. Am. Chem. Soc.The carbon soot obtained by electric arc vaporization of carbon rods doped with Sm2O3 contains a series of monometallic endohedral fullerenes, Sm@C-2n, along with smaller quantities of the dimetallic endohedrals Sm-2@C-2n with n = 44, 45, 46, and the previously described Sm-2@D-3d(822)-C-104. The compounds Sm-2@C-2n with n = 44, 45, 46 were purified by high pressure liquid chromatography on several different columns. For endohedral fullerenes that contain two metal atoms, there are two structural possibilities: a normal dimetallofullerene, M-2@C-2n, or a metal carbide, M-2(mu-C-2)@C2n-2. For structural analysis, the individual Sm-2@C-2n endohedral fullerenes were cocrystallized with Ni-(octaethylporphyrin), and the products were examined by single-crystal X-ray diffraction. These data identified the three new endohedrals as normal dimetallofullerenes and not as carbides: Sm-2@D-2(35)-C-88, Sm-2@C-1(21)-C-90, and Sm-2@D-3(85)-C-92. All four of the known Sm-2@C-2n endohedral fullerenes have cages that obey the isolated pentagon rule (IPR). As the cage size expands in this series, so do the distances between the variously disordered samarium atoms. Since the UV/vis/NIR spectra of Sm-2@D-2(35)-C-88 and Sm-2@C-1(21)-C-90 are very similar to those of Gd2C90 and Gd2C92, we conClude that Gd2C90 and Gd2C92 are the carbides Gd-2(mu-C-2)@D-2(35)-C-88 and Gd-2(mu-C-2)@C-1(21)-C-90, respectively.Large Endohedral Fullerenes Containing Two Metal Ions, Sm-2@D-2(35)-C-88, Sm-2@C-1(21)-C-90, and Sm-2@D-3(85)-C-92, and Their Relationship to Endohedral Fullerenes Containing Two Gadolinium Ionsx46201149#N/AFALSE
2314
ja206042k10.1021/ja206042kFALSEhttps://doi.org/10.1021/ja206042kWieghardt, KJ. Am. Chem. Soc.Multiple spectroscopic and computational methods were used to characterize the ground-state electronic structure of the novel {CoNO}(9) species Tp*Co(NO) (Tp* = hydro-tris (3,5-Me-2-pyrazolyl)borate). The metric parameters about the metal center and the pre-edge region of the Co K-edge X-ray absorption spectrum were reproduced by density functional theory (DFT), providing a qualitative description of the Co-NO bonding interaction as a Co(II) (S-Co = 3/2) metal center, antiferromagnetically coupled to a triplet NO- anion (S-NO = 1), an interpretation of the electronic structure that was validated by ab initio multireference methods (CASSCF/MRCI). Electron paramagnetic resonance (EPR) spectroscopy revealed significant g-anisotropy in the S = 1/2, ground state, but the linear-response DFT performed poorly at calculating the g-values. Instead, CASSCF/MRCI computational studies in conjunction with quasi-degenerate perturbation theory with respect to spin orbit coupling were required for obtaining accurate modeling of the molecular g-tensor. The computational portion of this work was extended to the diamagnetic Ni analogue of the Co complex, Tp*Ni(NO), which was found to consist of a Ni(II) (S-Ni = 1) metal center antiferromagnetically coupled to an S-NO = 1 NO-. The similarity between the Co and Ni complexes contrasts with the previously studied Cu analogues, for which a Cu(I) bound to NO0 formulation has been described. This discrepancy will be discussed along with a comparison of the DFT and ab initio computational methods for their ability to predict various spectroscopicA Step beyond the Feltham-Enennark Notation: Spectroscopic and Correlated ab lnitio Computational Support for an Antiferromagnetically Coupled M(II)-(NO)(-) Description of Tp*M(NO) (M = Co, Ni)x68201197#N/AFALSE
2315
ja205981v10.1021/ja205981vFALSEhttps://doi.org/10.1021/ja205981vKanatzidis, MGJ. Am. Chem. Soc.Enzymes that catalytically transform small molecules such as CO, formate, or protons are naturally composed of transition metal Cluster units bound into a larger superstructure. Artificial biomimetic catalysts are often modeled after the active sites but are typically molecular in nature. We present here a series of fully integrated porous materials containing Fe4S4 Clusters, dubbed biomimetic chalcogels. We examine the effect of third metal cations on the electrochemical and electrocatalytic properties of the chalcogels. We find that ternary biomimetic chalcogels containing Ni or Co show increased effectiveness in transformations of carbon dioxide and can be thought of as solid-state analogues of NiFe or NiFeS reaction centers in enzymes.Enhanced Electrocatalytic Reduction of CO2 with Ternary Ni-Fe4S4 and Co-Fe4S4-Based Biomimetic Chalcogels
Electrocatalytic
43201130#N/AFALSE
2316
ja210364r10.1021/ja210364rFALSEhttps://doi.org/10.1021/ja210364rVicic, DAJ. Am. Chem. Soc.Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of Aryl iodides and Aryl bromides at room temperature using the convenient [NMe4][SCF3] reagent.Nickel-Catalyzed Synthesis of Aryl Trifluoromethyl Sulfides at Room Temperature278201212#N/ATRUE
2317
ja205913q10.1021/ja205913qhttps://doi.org/10.1021/ja205913qWasielewski, MRJ. Am. Chem. Soc.Donor-bridge-acceptor (D-B-A) systems in which a 3,5-dimethyl-4-(9-anthracenyl)julolidine (DMJ-An) chromophore and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor are linked by oligomeric 2,7-fluorenone (FNn) bridges (n = 1-3) have been synthesized. Selective photoexcitation of DMJ-An quantitatively produces DMJ(+center dot)-An(-center dot), and An(-center dot)acts as a high-potential electron donor. Femtosecond transient absorption spectroscopy in the visible and mid-IR regions showed that electron transfer occurs quantitatively in the sequence: DMJ(+center dot)-An(-center dot)-FNn-NI -> DMJ(+center dot)-An-FNn-center dot-NI -> DMJ(+center dot)-An-FNn-NI-center dot. The charge-shift reaction from An(-center dot) to NI-center dot exhibits an exponential distance dependence in the nonpolar solvent toluene with an attenuation factor (beta) of 0.34 angstrom(-1), which would normally be attributed to electron tunneling by the superexchange mechanism. However, the FNn-center dot radical anion was directly observed spectroscopically as an intermediate in the charge-separation mechanism, thereby demonstrating conClusively that the overall charge separation involves the incoherent hopping (stepwise) mechanism. Kinetic modeling of the data showed that the observed exponential distance dependence is largely due to electron injection onto the first FN unit followed by charge hopping between the FN units of the bridge biased by the distance-dependent electrostatic attraction of the two charges in D+center dot-B-center dot-A. This work shows that wirelike behavior does not necessarily result from building a stepwise, energetically downhill redox gradient into a D-B-A molecule.Exponential Distance Dependence of Photoinitiated Stepwise Electron Transfer in Donor-Bridge-Acceptor Molecules: Implications for Wirelike BehaviorPhotocatalyst44201251#N/AFALSE
2318
ja205259910.1021/ja2052599FALSEhttps://doi.org/10.1021/ja2052599Cowan, JAJ. Am. Chem. Soc.A library of complexes that inCluded iron, cobalt, nickel, and copper chelates of cyClam, cyClen, DOTA, DTPA, EDTA, tripeptide GGH, tetrapeptide KGHK, NTA, and TACN was evaluated for DNA nuClease activity, ascorbate consumption, superoxide and hydroxyl radical generation, and reduction potential under physiologically relevant conditions. Plasmid DNA Cleavage rates demonstrated by combinations of each complex and biological co-reactants were quantified by gel electrophoresis, yielding second-order rate constants for DNA(supercoiled) to DNA(nicked) conversion up to 2.5 x 10(6) M-1 min(-1), and for DNA(nicked) to DNA(linear) up to 7 x 10(5) M-1 min(-1). Relative rates of radical generation and characterization of radical species were determined by reaction with the fluorescent radical probes TEMPO-9-AC and rhodamine B. Ascorbate turnover rate constants ranging from 3 x 10(-4) to 0.13 min(-1) were determined, although many complexes demonstrated no measurable activity. Inhibition and Freifelder-Trumbo analysis of DNA Cleavage supported concerted Cleavage of dsDNA by a metal-associated reactive oxygen species (ROS) in the case of Cu2+(aq), Cu-KGHK, Co-KGHK, and Cu-NTA and stepwise Cleavage for Fe2+(aq), Cu-cyClam, Cu-cyClen, Co-cyClen, Cu-EDTA, Ni-EDTA, Co-EDTA, Cu-GGH, and Co-NTA. Reduction potentials varied over the range from -362 to +1111 mV versus NHE, and complexes demonstrated optimal catalytic activity in the range of the physiological redox co-reactants ascorbate and peroxide (-66 to +380 mV).Factors Influencing the DNA NuClease Activity of Iron, Cobalt, Nickel, and Copper Chelatesx100201164#N/AFALSE
2319
ja210277810.1021/ja2102778FALSEhttps://doi.org/10.1021/ja2102778Gunnoe, TBJ. Am. Chem. Soc.Metal-mediated formation of C-O bonds is an important transformation that can occur by a variety of mechanisms. Recent studies suggest that oxygen-atom insertion into metal-hydrocarbyl bonds in a reaction that resembles the Baeyer-Villiger transformation is a viable process. In an effort to identify promising new systems, this study is designed to assess the impact of metal identity on such O-atom insertions for the reaction [(bpy)(x)M(Me)(OOH)](n) --> [(bpy)(x)M(OMe)(OH)](n) (x = 1 or 2; bpy = 2,2'-bipyridyl; n is varied to maintain the d-electron count at d(6) or d(8)). Six d(8)-square-planar complexes (M = Pt-II, Pd-II, Ni-II, Ir-II, Rh-I, and Co-I) and eight d(6)-octahedral systems (M = Ir-III, Rh-III, Co-III, Fe-III Ru-II, Os-II, Mn-I, and Tc-I) are studied. Using density functional theory calculations, the structures and energies of ground-state and transition-state species are elucidated. This study shows Clear trends in calculated Delta G double dagger's for the 0-atom insertions. The organometallic Baeyer-Villiger insertions are favored by lower coordination numbers (x = 1 versus x = 2), earlier transition metals, and first-row (3d) transition metals.Carbon-Oxygen Bond Formation via Organometallic Baeyer-Villiger Transformations: A Computational Study on the Impact of Metal Identity32201262#N/ATRUE
2320
ja209974410.1021/ja2099744FALSEhttps://doi.org/10.1021/ja2099744Lu, CCJ. Am. Chem. Soc.Coordination complexes that pair a zero-valent transition metal (Ni, Co, Fe) and an aluminum(III) center have been prepared. They add to the few examples of structurally characterized metal alanes and are the first reported metallalumatranes. To understand the M-Al interaction and gauge the effect of varying the late metal, the complexes were characterized by X-ray crystallography, electrochemistry, UV-Vis-NIR and NMR spectroscopies, and theoretical calculations. The M-Al bond strength decreases with varying M in the order Ni > Co > Fe.Metal-Alane Adducts with Zero-Valent Nickel, Cobalt, and Iron113201133#N/ATRUE
2321
ja208786f10.1021/ja208786fFALSEhttps://doi.org/10.1021/ja208786fChen, JGGJ. Am. Chem. Soc.Controlling the activity and selectivity of converting biomass derivatives to syngas (H(2) and CO) is critical for the utilization of biomass feedstocks as renewable sources for chemicals and fuels. One key chemistry in the conversion is the selective bond scission of the C-OH and C=O functionalities, which are present in many biomass derivatives. Because of the high molecular weight and low vapor pressure, it is relatively difficult to perform fundamental surface science studies of C6 sugars, such as glucose and fructose, using ultrahigh vacuum techniques. Glycolaldehyde (HOCH(2)CH=O) is the smallest molecule that contains both the C-OH and CO functional groups, as well as the same C/O ratio as C6 sugars, and thus is selected as a probe molecule in the current study to determine how the presence of the C=O bond affects the reaction mechanism. Using a combination of density functional theory calculations and experimental measurements, our results indicate that the reaction pathway of glycolaldehyde to produce syngas can be enhanced by supporting monolayer Ni on a Pt substrate, which shows higher activity than either of the parent metals. Furthermore, the Pt substrate can be replaced by tungsten monocarbide to achieve similar activity and selectivity, indicating the possibility of using Ni/WC to replace Ni/Pt as active and selective catalysts with higher stability and lower cost.Glycolaldehyde as a Probe Molecule for Biomass Derivatives: Reaction of C-OH and C=O Functional Groups on Monolayer Ni Surfaces39201131#N/ATRUE
2322
ja204518x10.1021/ja204518xFALSEhttps://doi.org/10.1021/ja204518xAdzic, RRJ. Am. Chem. Soc.Core-shell nanopartiCles increasingly are found to be effective in enhancing catalytic performance through the favorable influence of the core materials on the active components at the surface. Yet, sustaining high activities under operating conditions often has proven challenging. Here we explain how differences in the components' diffusivity affect the formation and stability of the core-shell and hollow nanostructures, which we ascribe to the Kirkendall effect. Using Ni nanopartiCles as the templates, we fabricated compact and smooth Pt hollow nanocrystals that exhibit a sustained enhancement in Pt mass activity for oxygen reduction in acid fuel cells. This is achieved by the hollow-induced lattice contraction, high surface area per mass, and oxidation-resistant surface morphology-a new route for enhancing both the catalysts' activity and durability. The results indicate challenges and opportunities brought by the nanoscale Kirkendall effect for designing, at the atomic level, nanostructures with a wide range of novel properties.Kirkendall Effect and Lattice Contraction in Nanocatalysts: A New Strategy to Enhance Sustainable Activityx216201148#N/AFALSE
2323
ja204489e10.1021/ja204489eFALSEhttps://doi.org/10.1021/ja204489eKubiak, CPJ. Am. Chem. Soc.[Ni((PRN2R')-N-2)(2)(CH3CN)](2+) complexes with R. = Ph, R'= 4-MeOPh or R = Cy, R' = Ph, and a mixed-ligand [Ni(p(2)(R)N(2)(R'))(p(R):NwTR2) (rw IN (CN)-C-13)](2+) with R = Cy, R' = Ph, R = Ph, have been synthesized and characterized by single-crystal X-ray crystallography. These and previously reported complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO2, protons, and electrons, with rates that are first-order in catalyst and formate at formate concentrations below similar to 0.04 M (34 equiv). At concentrations above similar to 0.06 M formate (52 equiv), catalytic rates become nearly independent of formate concentration. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 to 15.8 s(-1) at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. These catalysts are the only base-metal electrocatalysts as well as the only homogeneous electrocatalysts reported to date for the oxidation of formate. An acetate complex demonstrating an eta(1)-OC(O)CH3 binding mode to nickel has also been synthesized and characterized by single-crystal X-ray crystallography. Based on this structure and the electrochemical and spectroscopic data, a mechanistic scheme for electrocatalytic formate oxidation is proposed which involves formate binding followed by a rate-limiting proton and two-electron transfer step accompanied by CO2 liberation. The pendant amines have been demonstrated to be essential for electrocatalysis, as no activity toward formate oxidation was observed for the similar [Ni(depe)(2)](2+) (depe = 1,2-bis(diethylphosphino)ethane) complex.Electrocatalytic Oxidation of Formate by [Ni((P2N2R ')-N-R)(2)(CH3CN)](2+) Complexes
Electrocatalytic
87201143#N/AFALSE
2324
ja204396810.1021/ja2043968https://doi.org/10.1021/ja2043968Garg, NKPrecise Isomerization Polymerization of AlkenylcyClohexanes: Stereoregular Polymers Containing Six-Membered Rings along the Polymer Chainx2011#N/AFALSE
2325
ja208555h10.1021/ja208555hFALSEhttps://doi.org/10.1021/ja208555hXu, RJ. Am. Chem. Soc.We report the use of a simple complex assembled from Ni(II) salt and 2-mecaptoethanol in one step in water as the efficient catalyst in a molecular hydrogen system which can be sensitized by a low-cost xanthene dye, Erythrosin B. An excellent quantum efficiency of 24.5% is attained at 460 nm. This simple system is expected to contribute toward the development of economical and environmentally benign solar hydrogen production systems.Nickel-Thiolate Complex Catalyst Assembled in One Step in Water for Solar H-2 Production226201131#N/ATRUE
2326
ja204256x10.1021/ja204256xFALSEhttps://doi.org/10.1021/ja204256xEspinet, PJ. Am. Chem. Soc.The complexity of the transmetalation step in a Pd-catalyzed Negishi reaction has been investigated by combining experiment and theoretical calculations. The reaction between trans-[PdMeCl(PMePh2)(2)] and ZnMe2 in THF as solvent was analyzed. The results reveal some unexpected and relevant mechanistic aspects not observed for ZnMeCl as nuCleophile. The operative reaction mechanism is not the same when the reaction is carried out in the presence or in the absence of an excess of phosphine in the medium. In the absence of added phosphine an ionic intermediate with THF as ligand ([PdMe(PMePh2)(2)(THF)(+)) opens ionic transmetalation pathways. In contrast, an excess of phosphine retards the reaction because of the formation of a very stable cationic complex with three phosphines ([PdMe(PMePh2)(3)](+)) that sequesters the catalyst. These ionic intermediates had never been observed or proposed in palladium Negishi systems and warn on the possible detrimental effect of an excess of good ligand (as PMePh2) for the process. In contrast, the ionic pathways via cationic complexes with one solvent (or a weak ligand) can be noticeably faster and provide a more rapid reaction than the concerted pathways via neutral intermediates. Theoretical calculations on the real molecules reproduce well the experimental rate trends observed for the different mechanistic pathways.Cationic Intermediates in the Pd-Catalyzed Negishi Coupling. Kinetic and Density Functional Theory Study of Alternative Transmetalation Pathways in the Me-Me Coupling of ZnMe2 and trans-[PdMeCl(PMePh2)(2)]x56201146#N/AFALSE
2327
ja204023c10.1021/ja204023cFALSEhttps://doi.org/10.1021/ja204023cBogaerts, AJ. Am. Chem. Soc.The growth mechanism and chirality formation of a single-walled carbon nanotube (SWNT) on a surface-bound nickel nanoCluster are investigated by hybrid reactive molecular dynamics/force-biased Monte Carlo simulations. The validity of the interatomic potential used, the so-called ReaxFF potential, for simulating catalytic SWNT growth is demonstrated. The SWNT growth process was found to be in agreement with previous studies and observed to proceed through a number of distinct steps, viz., the dissolution of carbon in the metallic partiCle, the surface segregation of carbon with the formation of aggregated carbon Clusters on the surface, the formation of graphitic islands that grow into SWNT caps, and finally continued growth of the SWNT. Moreover, it is Clearly illustrated in the present study that during the growth process, the carbon network is continuously restructured by a metal-mediated process, thereby healing many topological defects. It is also found that a cap can nuCleate and disappear again, which was not observed in previous simulations. Encapsulation of the nanopartiCle is observed to be prevented by the carbon network migrating as a whole over the Cluster surface. Finally, for the first time, the chirality of the growing SWNT cap is observed to change from (11,0) over (9,3) to (7,7). It is demonstrated that this change in chirality is due to the metal-mediated restructuring process.Changing Chirality during Single-Walled Carbon Nanotube Growth: A Reactive Molecular Dynamics/Monte Carlo Studyx118201153#N/AFALSE
2328
ja203376y10.1021/ja203376yFALSEhttps://doi.org/10.1021/ja203376yJones, AKJ. Am. Chem. Soc.Protein film electrochemistry (PFE) was utilized to characterize the catalytic activity and oxidative inActivation of a bidirectional [NiFe]-hydrogenase (HoxEFUYH) from the cyanobacterium Synechocystis sp. PCC 6803. PFE provides precise control of the redox potential of the adsorbed enzyme so that its activity can be monitored under changing experimental conditions as current. The properties of HoxEFUYH are different from those of both the standard uptake and the oxygen-tolerant [NiFe] -hydrogenases. First, HoxEFUYH is biased toward proton reduction as opposed to hydrogen oxidation. Second, despite being expressed under aerobic conditions in vivo, HoxEFUYH is Clearly not oxygen-tolerant. Aerobic inActivation of catalytic hydrogen oxidation by HoxEFUYH is total and nearly instantaneous, producing two inactive states. However, unlike the Ni-A and Ni-B inactive states of standard [NiFe]-hydrogenases, both of these states are quickly (<90 s) reactivated by removal of oxygen and exposure to reducing conditions. Third, proton reduction continues at 25-50% of the maximal rate in the presence of 1% oxygen. Whereas most previously characterized [NiFe]-hydrogenases seem to be preferential hydrogen oxidizing catalysts, the cyanobacterial enzyme works effectively in both directions. This unusual catalytic bias as well as the ability to be quickly reactivated may be essential to fulfilling the physiological role in cyanobacteria, organisms expected to experience swings in cellular reduction potential as they switch between aerobic conditions in the light and dark anaerobic conditions. Our results suggest that the uptake [NiFe] -hydrogenases alone are not representative of the catalytic diversity of [NiFe]-hydrogenases, and the bidirectional heteromultimeric enzymes may serve as valuable models to understand the diverse mechanisms of tuning the reactivity of the hydrogen activating site.The [NiFe]-Hydrogenase of the Cyanobacterium Synechocystis sp PCC 6803 Works Bidirectionally with a Bias to H-2 Productionx63201181#N/AFALSE
2329
ja203057z10.1021/ja203057zFALSEhttps://doi.org/10.1021/ja203057zCowan, JAJ. Am. Chem. Soc.A series of compounds that target reactive metal chelates to the HIV-1 Rev response element (RRE) mRNA have been synthesized. Dissociation constants and chemical reactivity toward HIV RRE RNA have been determined and evaluated in terms of reduction potential, coordination unsaturation, and overall charge associated with the metal-chelate-Rev complex Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), dithylenetriaminepentaacetic acid (DTPA), and 1,4,7,10-tetraazacyClododecane-1,4,7,10-tetraacetic acid (DOTA) were linked to a lysine side chain of a Rev-derived peptide by either EDC/NHS or isothiocyanate coupling. The resulting chelate-Rev (EDTA-Rev, DTPA-Rev, NTA-Rev, and DOTA-Rev) conjugates were used to form coordination complexes with Fe(2+), Co(2+), Ni(2+), and Cu(2+) such that the arginine-rich Rev peptide could mediate localization of the metal chelates to the Rev peptide's high-affinity mRNA binding partner, RRE stem loop JIB. Metal complexes of the extended peptides GGH-Rev and KGHK-Rev, which also contain N-terminal peptidic chelators (ATCUN motifs), were studied for comparison. A fluorescence titration assay revealed high-affinity RRE RNA binding by all 22 metal-chelate-Rev species, with K(D) values ranging from similar to 0.2 to 16 nM, indicating little to no loss of RNA affinity due to the coupling of the metal chelates to the Rev peptide. Dissociation constants for binding at a previously unobserved low-affinity site are also reported. Rates of RNA modification by each metal-chelate-Rev species were determined and varied from similar to 0.28 to 4.9 nM/min but were optimal for Cu(2+)-NTA-Rev. Metal-chelate reduction potentials were determined and varied from -228 to +1111 mV vs NHE under similar solution conditions, allowing direct comparison of reactivity with redox thermodynamics. Optimal activity was observed when the reduction potential for the metal center was poised between those of the two principal co-reagents for metal-promoted formation of reactive oxygen species: E degrees(ascorbate/ascorbyl radical) = -66 mV and E degrees (H2O2 /hydroxyl radical) = 380 mV. Given variety of oxidative activities of these metal complexes and their high-affinity binding to the targeted RRE mRNA following coupling to the Rev peptide, this Class of metal-chelate-Rev derivatives constitutes a promising step toward development of multiple-turnover reagents for selective eradication of HIV-1 RRE mRNA.Targeted Cleavage of HIV RRE RNA by Rev-Coupled Transition Metal Chelatesx42201141#N/AFALSE
2330
ja202877q10.1021/ja202877qFALSEBazan, GCDesign and Synthesis of Monofunctionalized, Water-Soluble Conjugated Polymers for Biosensing and Imaging Applicationsx2011#N/AFALSE
2331
ja202499310.1021/ja2024993FALSEhttps://doi.org/10.1021/ja2024993Hillhouse, GLJ. Am. Chem. Soc.A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. Oxidation of nickel(II) complexes led to the formation of both Aryl- and Alkyl-substituted nickel(III)-imides, and examples of both types have been isolated and fully characterized. The Aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two Ni(III)-imide compounds showed different variable-temperature magnetic properties but analogous EPR spectra at low temperatures. To account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the Alkyl-substituted Ni(III)-imide complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the unpaired electron is mostly localized on the imide nitrogen for the Ni(III) complexes. The results of reactions carried out in the presence of hydrogen donors supported the findings from DFT calculations that the adamantyl substituent was a significantly more reactive hydrogen-atom abstractor. Interestingly, the steric properties of the 2,6-dimesitylphenyl substituent are important not only in protecting the Ni=N core but also in favoring one rotamer of the resulting Ni(III)-imide, by locking the phenyl ring in a perpendicular orientation with respect to the NiPP plane.Synthesis and Characterization of Three-Coordinate Ni(III)-Imide Complexesx88201144#N/AFALSE
2332
ja208256u10.1021/ja208256uFALSEhttps://doi.org/10.1021/ja208256uZaworotko, MJJ. Am. Chem. Soc.meso-Tetra(N-methyl-4-pyridyl)porphine tetratosylate (TMPyP) templates the synthesis of six new metal-organic materials by the reaction of benzene-1,3,5-triCarbonylate with transition metals, five of which exhibit HKUST-1 or tbo topology (M = Fe, Mn, Co, Ni, Mg). The resulting materials, porph@MOMs, selectively encapsulate the corresponding metalloporphyrins in octahemioctahedral cages and can serve as size-selective heterogeneous catalysts for oxidation of olefins.Template-Directed Synthesis of Nets Based upon Octahemioctahedral Cages That Encapsulate Catalytically Active Metalloporphyrins134201249#N/ATRUE
2333
ja202022910.1021/ja2020229FALSEhttps://doi.org/10.1021/ja2020229Suginome, MJ. Am. Chem. Soc.The addition of silylboronic esters to pyridine takes place in toluene at 50 degrees C in the presence of a palladium catalyst to give N-boryl-4-silyl-1,4-dihydropyridines in high yield. The regioselective 1,4-silaboration also proceeds in the reaction of 2-picoline and 3-substituted pyridines, whereas 4-substituted pyridines undergo 1,2-silaboration to give N-boryl-2-silyl-1,2-dihydropyridines regioselectively.Palladium-Catalyzed Regioselective Silaboration of Pyridines Leading to the Synthesis of Silylated Dihydropyridinesx74201160#N/AFALSE
2334
ja202007s10.1021/ja202007sFALSEhttps://doi.org/10.1021/ja202007sHouk, KNJ. Am. Chem. Soc.The regioselectivities of N-heterocyClic carbene (NHC) ligands in Ni-catalyzed alkyne-aldehyde reductive coupling reactions with silane reducing agents are investigated using density functional theory. Reversal of regioselectivity can be achieved by varying the steric bulldness of the ligand. The steric influences of NHC ligands are highly anisotropic. Regioselectivity is primarily controlled by the steric hindrance at the region of the ligand dose to the alkyne. Analysis of 2D contour maps of the NHC ligands indicates that the regioselectivities are directly affected by the shape and orientation of the N-substituents on the ligand.Ligand Steric Contours To Understand the Effects of N-HeterocyClic Carbene Ligands on the Reversal of Regioselectivity in Ni-Catalyzed Reductive Couplings of Alkynes and Aldehydesx83201138#N/AFALSE
2335
ja201951t10.1021/ja201951tFALSEhttps://doi.org/10.1021/ja201951tBrunner, EJ. Am. Chem. Soc.Recently, we have described the metal-organic framework Ni-2(2,6-ndc)(2)(dabco), denoted as DUT-8(Ni)(1) (DUT = Dresden University of Technology, 2,6-ndc = 2,6-naphthalenediCarbonylate, dabco = 1,4-diazabicyClo [2.2.2]octane). Upon adsorption of molecules such as nitrogen and xenon, this material exhibits a pronounced gate-pressure effect which is accompanied by a large change of the specific volume. Here, we describe the use of high-pressure in situ Xe-129 NMR spectroscopy, i.e., the NMR spectroscopic measurements of xenon adsorption/desorption isotherms and isobars, to characterize this effect. It appears that the pore system of DUT-8(Ni) takes up xenon until a liquid-like state is reached. Deeper insight into the interactions between the host DUT-8(Ni) and the guest atom xenon is gained from ab initio molecular dynamics (MD) simulations. van der Waals interactions are inCluded for the first time in these calculations on a metal organic framework compound. MD simulations allow the identification of preferred adsorption sites for xenon as well as insight into the breathing effect at a molecular scale. Grand canonical Monte Carlo (GCMC) simulations have been performed in order to simulate adsorption isotherms. Furthermore, the favorable influence of a sample pretreatment using solvent exchange and drying with supercritical CO2 as well as the influence of repeated pore opening/Closure processes, i.e., the aging behavior of the compound, can be visualized by Xe-129 NMR spectroscopy.High-Pressure in Situ Xe-129 NMR Spectroscopy and Computer Simulations of Breathing Transitions in the Metal-Organic Framework Ni-2(2,6-ndc)(2)(dabco) (DUT-8(Ni))x93201188#N/AFALSE
2336
ja201838x10.1021/ja201838xFALSEhttps://doi.org/10.1021/ja201838xBullock, RMJ. Am. Chem. Soc.Proton transport is ubiquitous in chemical and biological processes, inCluding the reduction of dioxygen to water, the reduction of CO2 to formate, and the production/oxidation of hydrogen. In this work we describe intramolecular proton transfer between Ni and positioned pendant amines for the hydrogen oxidation electrocatalyst [Ni((P2N2H)-N-Cy-H-Bn)(2)](2+) ((P2Ni2Bn)-Ni-Cy = 1,5-diBenzyl-3,7-dicyClohexyl-1,5-diaza-3,7-diphosphacyClooctane). Rate constants are determined by variable-temperature one-dimensional NMR techniques and two-dimensional EXSY experiments. Computational studies provide insight into the details of the proton movement and energetics of these complexes. Intramolecular proton exchange processes are observed for two of the three experimentally observable isomers of the doubly protonated Ni(0) complex, [Ni((P2N2H)-N-Cy-H-Bn)(2)](2+), which have N-H bonds but no Ni-H bonds. For these two isomers, with pendant amines positioned endo to the Ni, the rate constants for proton exchange range from 10(4) to 10(5) s(-1) at 25 degrees C, depending on isomer and solvent. No exchange is observed for protons on pendant amines positioned exo to the Ni. Analysis of the exchange as a function of temperature provides a barrier for proton exchange of Delta G(double dagger) = 11-12 kcal/mol for both isomers, with little dependence on solvent. Density functional theory calculations and molecular dynamics simulations support the experimental observations, suggesting metal-mediated intramolecular proton transfers between nitrogen atoms, with chair-to-boat isomerizations as the rate-limiting steps. Because of the fast rate of proton movement, this catalyst may be considered a metal center surrounded by a Cloud of exchanging protons. The high intramolecular proton mobility provides information directly pertinent to the ability of pendant amines to accelerate proton transfers during catalysis of hydrogen oxidation. These results may also have broader implications for proton movement in homogeneous catalysts and enzymes in general, with specific implications for the proton channel in the Ni-Fe hydrogenase enzyme.Moving Protons with Pendant Amines: Proton Mobility in a Nickel Catalyst for Oxidation of Hydrogenx121201161#N/AFALSE
2337
ja201801t10.1021/ja201801tFALSEhttps://doi.org/10.1021/ja201801tVlachos, DGJ. Am. Chem. Soc.Understanding and controlling bond-breaking sequences of oxygenates on transition metal catalysts can greatly impact the utilization of biomass feedstocks for fuels and chemicals. The decomposition of ethylene glycol, as the simplest representative of biomass-derived polyols, was studied via density functional theory (DFT) calculations to identify the differences in reaction pathways between Pt and the more active Ni/Pt bimetallic catalyst. Comparison of the computed transition states indicated three potentially feasible paths from ethylene glycol to C1 oxygenated adsorbates on Pt. While not important on Pt, the pathway to 1,2-dioxyethylene (OCH2CH2O) is favored energetically on the Ni/Pt catalyst. Temperature-programmed desorption (TPD) experiments were conducted with deuterated ethylene glycols for comparison with DFT results. These experiments confirmed that decomposition of ethylene glycol on Pt proceeds via initial O-H bond Cleavage, followed by C-H and the second O-H bond Cleavages, whereas on the Ni/Pt surface, both O-H bonds are Cleaved initially. The results are consistent with vibrational spectra and indicate that tuning of the catalyst surface can selectively control bond breaking. Finally, the significant mechanistic differences in decomposition of polyols compared to that of monoalcohols and hydrocarbons serve to identify general trends in bond scission sequences.Differentiation of O-H and C-H Bond Scission Mechanisms of Ethylene Glycol on Pt and Ni/Pt Using Theory and Isotopic Labeling Experimentsx94201138#N/AFALSE
2338
ja207838j10.1021/ja207838jFALSEhttps://doi.org/10.1021/ja207838jScott, SLJ. Am. Chem. Soc.A supported, single-site Lewis acid, SiOB(C6F5)(2), was prepared by water-catalyzed grafting of B(C6F5)(3) onto the surface of amorphous silica, and its subsequent use as a cocatalyst for heterogeneous olefin polymerization was explored. Although B(C6F5)(3) has been reported to be unreactive toward silica in the absence of a Bronsted base, we find that it can be grafted even at room temperature, albeit slowly. The mechanism was investigated by H-1 and F-19 NMR, in both the solution and solid states. In the presence of a trace amount of H2O, either added intentionally or formed in situ by borane-induced dehydration of silanol pairs, the adduct (C6F5)(3)B center dot OH2 hydrolyzes to afford C6F5H and (C6F5)(2)BOH. The latter reacts with the surface hydroxyl groups of silica to yield SiOB(C6F5)(2) sites and regenerate H2O. When B(C6F5)(3) is present in excess, the resulting grafted boranes appear to be completely dry, due to the eventual formation of [(C6F5)(2)B](2)O. The immobilized, tri-coordinate Lewis acid sites were characterized by solid-state B-11 and F-19 NMR, IR, elemental analysis, and C5H5N-TPD. Their ability to activate two molecular C2H4 polymerization catalysts, Cp2ZrMe2 and an (alpha-iminocarboxamidato)nickel(II) complex, was explored.Borane-Induced Dehydration of Silica and the Ensuing Water-Catalyzed Grafting of B(C6F5)(3) To Give a Supported, Single-Site Lewis Acid, SiOB(C6F5)(2)27201270#N/ATRUE
2339
ja207801510.1021/ja2078015FALSEhttps://doi.org/10.1021/ja2078015Gray, HBJ. Am. Chem. Soc.A cobalt bis(iminopyridine) complex is a highly active electrocatalyst for water reduction, with an estimated apparent second order rate constant k(app) <= 10(7) M-1 s(-1) over a range of buffer/salt concentrations. Scan rate dependence data are consistent with freely diffusing electro-active species over pH 4-9 at room temperature for each of two catalytic reduction events, one of which is believed to be ligand based. Faradaic H-2 yields up to 87 +/- 10% measured in constant potential electrolyses (-1.4 V vs SCE) confirm high reactivity and high fidelity in a catalyst supported by the noninnocent bis(iminopyridine) ligand. A mechanism involving initial reduction of Co2+ and subsequent protonation is proposed.Rapid Water Reduction to H-2 Catalyzed by a Cobalt Bis(iminopyridine) Complex202201148#N/ATRUE
2340
ja200909r10.1021/ja200909rFALSEhttps://doi.org/10.1021/ja200909rMiller, GJJ. Am. Chem. Soc.The electronic structures of Ti9-nFe2+nRu18B8 (n = 0, 0.5, 1, 2, 3), in connection to the recently synthesized Ti9-nFe2+nRu18B8 = 1, 2), have been investigated and analyzed using LSDA tight-binding calculations to elucidate the distribution of Fe and Ti, to determine the maximum Fe content, and to explore possible magnetic structures to interpret experimental magnetization results. Through a combination of calculations on specific models and using the rigid band approximation, which is validated by the DOS curves for Ti9-nFe2+nRu18B8 (n = 0, 0.5, 1, 2, 3), mixing of Fe and Ti is anticipated at both the 2b- and 4h-chain sites. The model Ti8.5Fe2.5Ru18B8 (n = 0.5) revealed that both Brewer-type Ti-Ru interactions as well as ligand field splitting of the Fe 3d orbitals regulated the observed valence electron counts between 220 and 228 electrons/formula unit. Finally, models of magnetic structures were created using Ti6Fe5Ru18B8 (n = 3). A rigid band analysis of the LSDA DOS curves conCluded preferred ferromagnetic ordering at low Fe content (n <= 0.75) and ferrimagnetic ordering at higher Fe content (n > 0.75). Ferrimagnetism arises from antiferromagnetic exchange coupling in the scaffold of Fel-ladder and 4h-chain sites.Scaffolding, Ladders, Chains, and Rare Ferrimagnetism in Intermetallic Borides: Electronic Structure Calculations and Magnetic Orderingx20201124#N/AFALSE
2341
ja206722t10.1021/ja206722tFALSEhttps://doi.org/10.1021/ja206722tMontgomery, JJ. Am. Chem. Soc.Strategies for the reductive cyCloaddition of enals or enoates with alkynes have been developed. The enal-alkyne cyCloaddition directly affords cyClopentenols, whereas the enoate-alkyne cyCloaddition affords the analogous cyClopentenones. The mechanism of these processes likely involves formation and protonation of a metallacyClic intermediate. The general strategy provides a straightforward entry to five-membered ring products from simple, stable pi-systems.Synthesis of CyClopentenols and CyClopentenones via Nickel-Catalyzed Reductive CyCloaddition43201165#N/ATRUE
2342
ja200669a10.1021/ja200669aFALSEhttps://doi.org/10.1021/ja200669aOsuka, AJ. Am. Chem. Soc.Subbacteriochlorins, which were prepared via hydrogenation of subporphyrins with Raney nickel, are modestly aromatic due to 14 pi-diazaannulenic circuit and exhibit characteristic blue-shifted Soret-like bands, intensified fluorescence spectra, and high oxidation potentials.Synthesis and Properties of Boron(III)-Coordinated Subbacteriochlorinsx27201129#N/AFALSE
2343
ja205953g10.1021/ja205953gFALSEhttps://doi.org/10.1021/ja205953gMori, AJ. Am. Chem. Soc.Iterative growth of thiophene oligomers by single-step extensions has been realized by regioselective metalation of 3-substituted thiophenes with the Knochel-Hauser base (TMPMgX center dot LiCl) and coupling with bromothiophene using a nickel catalyst. Treatment of 3-hexylthiophene with TMPMgX center dot LiCl induces metalation at the 5-position selectively. Subsequent addition of 2-bromo-3-hexylthiophene and a nickel catalyst leads to the corresponding bithiophene. The obtained bithiophene is converted to the terthiophene and then to the quaterthiophene by repeating the similar protocol. A concise synthesis of MK-1 and MK-2, which are organic dye molecules bearing an oligothiophene moiety that are used in photovoltaic cells, has been achieved.Synthesis of Well-Defined Head-to-Tail-Type Oligothiophenes by Regioselective Deprotonation of 3-Substituted Thiophenes and Nickel-Catalyzed Cross-Coupling Reaction76201163#N/ATRUE
2344
ja111479j10.1021/ja111479jFALSEhttps://doi.org/10.1021/ja111479jRosenthal, UJ. Am. Chem. Soc.The reaction of the low-valent metallocene(II) sources Cp2Ti(eta(2)-Me3SiC2SiMe3) (7) and Cp2Zr(py)(eta(2)-Me3SiC2SiMe3) (11, Cp = eta(5)-cyClopentadienyl, py = pyridine) with carbodiimides RN=C=NR (R = Cy, i-Pr, p-Tol) leads to the formation of five membered hetero-metallacyCloallenes Cp2M{Me3SiC=C=C[N(SiMe3)(R)]-N(R)} (9M-R) (M = Ti, R = i-Pr; M = Zr, R = Cy, i-Pr, p-Tol). Elimination of the alkyne (as the hitherto known reactivity of titanocene and zirconocene alkyne complexes would suggest) was not observed. The molecular structures of the obtained complexes were confirmed by X-ray studies. Moreover, the structure and bonding of the complexes 9Zr-Cy and 9Zr-p-Tol was investigated by DFT calculations.Reactions of Group 4 Metallocene Alkyne Complexes with Carbodiimides: Experimental and Theoretical Studies of the Structure and Bonding of Five-Membered Hetero-MetallacyCloallenesx55201175#N/AFALSE
2345
ja205167e10.1021/ja205167eFALSEhttps://doi.org/10.1021/ja205167eWu, JJ. Am. Chem. Soc.We report that a 2,2':6',2-terpyridylmacrocyCle-Ni complex can efficiently mediate the threading of two Alkyl chains with bulky end groups in an active metal template sp(3)-carbon-to-sp(3)-carbon homocoupling reaction, resulting in a rare example of a doubly threaded [3]rotaxane in up to 51% yield. The unusual architecture is confirmed by X-ray crystallography (the first time that a one-ring-two-thread [3]rotaxane has been characterized in the solid state) and is found to be stable with respect to dethreading despite the large ring size of the macrocyCle. Through such active template reactions, in principle, a macrocyCle should be able to assemble as many axles in its cavity as the size of the ring and the stoppers will allow. A general method for threading multiple axles through a macrocyCle adds significantly to the tools available for the synthesis of different types of rotaxane architectures.En Route to a Molecular Sheaf: Active Metal Template Synthesis of a [3]Rotaxane with Two Axles Threaded through One Ring53201187#N/ATRUE
2346
ja111160r10.1021/ja111160rFALSEhttps://doi.org/10.1021/ja111160rStrasser, PJ. Am. Chem. Soc.We report the discovery of a highly active Ni-Co alloy electrocatalyst for the oxidation of hydrazine (N2H4) and provide evidence for competing electrochemical (faradaic) and chemical (nonfaradaic) reaction pathways. The electrochemical conversion of hydrazine on catalytic surfaces in fuel cells is of great scientific and technological interest, because it offers multiple redox states, complex reaction pathways, and significantly more favorable energy and power densities compared to hydrogen fuel. Structure reactivity relations of a Ni60Co40 alloy electrocatalyst are presented with a 6-fold increase in catalytic N2H4 oxidation activity over today's benchmark catalysts. We further study the mechanistic pathways of the catalytic N2H4 conversion as function of the applied electrode potential using differentially pumped electrochemical mass spectrometry (DEMS). At positive overpotentials, N2H4 is electrooxidized into nitrogen consuming hydroxide ions, which is the fuel cell-relevant faradaic reaction pathway. In parallel, N2H4 decomposes chemically into molecular nitrogen and hydrogen over a broad range of electrode potentials. The electroless chemical decomposition rate was controlled by the electrode potential, suggesting a rare example of a liquid-phase electrochemical promotion effect of a chemical catalytic reaction (EPOC). The coexisting electrocatalytic (faradaic) and heterogeneous catalytic (electroless, nonfaradaic) reaction pathways have important implications for the efficiency of hydrazine fuel cells.Noble Metal-Free Hydrazine Fuel Cell Catalysts: EPOC Effect in Competing Chemical and Electrochemical Reaction Pathwaysx216201164#N/AFALSE
2347
ja110910y10.1021/ja110910yFALSEhttps://doi.org/10.1021/ja110910yHeld, GJ. Am. Chem. Soc.The coadsorption of water with organic molecules under near-ambient pressure and temperature conditions opens up new reaction pathways on model catalyst surfaces that are not accessible in conventional ultrahigh-vacuum surface-science experiments. The surface chemistry of glycine and alanine at the water-exposed Cu{110} interface was studied in situ using ambient-pressure photoemission and X-ray absorption spectroscopy techniques. At water pressures above 10(-5) Torr a significant pressure-dependent decrease in the temperature for dissociative desorption was observed for both amino acids, accompanied by the appearance of a new CN intermediate, which is not observed for lower pressures. The most likely reaction mechanisms involve dehydrogenation induced by O and/or OH surface species resulting from the dissociative adsorption of water. The linear relationship between the inverse decomposition temperature and the logarithm of water pressure enables determination of the Activation energy for the surface reaction, between 213 and 232 kJ/mol, and a prediction of the decomposition temperature at the solid-liquid interface by extrapolating toward the equilibrium vapor pressure. Such experiments near the equilibrium vapor pressure provide important information about elementary surface processes at the solid-liquid interface, which can be retrieved neither under ultrahigh vacuum conditions nor from interfaces immersed in a solution.A Step toward the Wet Surface Chemistry of Glycine and Alanine on Cu{110}: Destabilization and Decomposition in the Presence of Near-Ambient Water Vaporx24201170#N/AFALSE
2348
ja110890v10.1021/ja110890vFALSEhttps://doi.org/10.1021/ja110890vJensen, MPJ. Am. Chem. Soc.The complex Tp(Ph,Me)NiS(2)CNMe(2) [Tp(Ph,Me) = hydrotris(3-phenyl-5-methyl- 1 -pyrazolyl)borate] features a bioinspired N3S2 ligand set supporting a five-coordinate, trigonally distorted square-pyramidal geometry in the solid state. Spin crossover of Ni(II) was demonstrated by temperature-dependent X-ray crystallography and magnetic susceptibility measurements. The crystal lattice contains two independent molecules (i.e., Nil and Ni2). At 293 K, the observed bond lengths and susceptibility are consistent with high-spin (S = 1) Ni(II), and both molecules exhibit relatively short axial Ni-N bonds and long Ni-N and Ni-S equatorial bonds. At 123 K, the Nil complex remains high-spin, but the Ni2 molecule substantially crosses to a structurally distinct diamagnetic (S = 0) state with significant elongation of the axial Ni-N bond and offsetting contraction of the equatorial bonds. The temperature-dependent susceptibility data were fit to a spin equilibrium at Ni2 [Delta H degrees = 1.13(2) kcal/mol and Delta S degrees = +7.3(1) cal mor(-1) K-1] consistent with weak coupling to lattice effects. Cooling below 100 K results in crossover of the Nil complex.Solid-State Spin Crossover of Ni(II) in a Bioinspired N3S2 Ligand Fieldx30201135#N/AFALSE
2349
ja204851x10.1021/ja204851xFALSEhttps://doi.org/10.1021/ja204851xBrookhart, MJ. Am. Chem. Soc.Syntheses of the olefin hydride complexes [(POCOP)M(H) (olefin)] [BAr4f] (6a-M, M = Ir or Rh, olefin = C2H4; 6b-M, M = Ir or Rh, olefin = C3H6; POCOP = 2,6-bis-(di-tert-burylphosphinito)benzene; Bar(t) = tetrakis(3,5-trifluoromethylphenyl)borate) are reported. A single-crystal X-ray structure determination of 6b-Ir shows a square-pyramidal coordination geometry for Ir, with the hydride ligand occupying the apical position. Dynamic NMR techniques were used to characterize these complexes. The rates of site exchange between the hydride and the olefinic hydrogens yielded Delta G(double dagger) = 15.6 (6a-Ir), 16.8 (6b-Ir), 12.0 (6a-Rh), and 13.7 (6b-Rh) kcal/mol. The NMR exchange data also established that hydride migration in the propylene complexes yields exClusively the primary Alkyl intermediate arising from 1,2-insertion. Unexpectedly, no averaging of the top and bottom faces of the square-pyramidal complexes is observed in the NMR spectra at high temperatures, indicating that the barrier for facial equilibration is >20 kcal/mol for both the Ir and Rh complexes. A DFT computational study was used to characterize the free energy surface for the hydride migration reactions. The Classical terminal hydride complexes, [M(POCOP)(olefin)Hr, are calculated to be the global minima for both Rh and Ir, in accord with experimental results. In both the Rh ethylene and propylene complexes, the transition state for hydride migration (TS1) to form the agostic species is higher on the energy surface than the transition state for in-place rotation of the coordinated C H bond (TS2), while for Ir, TS2 is the high point on the energy surface. Therefore, only for the case of the Rh complexes is the NMR exchange rate a direct measure of the hydride migration barrier. The trends in the experimental barriers as a function of M and olefin are in good agreement with the trends in the calculated exchange barriers. The calculated barriers for the hydride migration reaction in the Rh complexes are 2 kcal/mol higher than for the Ir complexes, despite the fact that the energy difference between the olefin hydride ground state and the agostic Alkyl structure is similar to 4 kcal/mol larger for Ir than for Rh. This feature, together with the high barrier for interchange of the top and bottom faces of the complexes, is proposed to arise from the unique coordination geometry of the agostic complexes and the strong preference for a cis-divacant octahedral geometry in four-coordinate intermediates.Role of Coordination Geometry in Dictating the Barrier to Hydride Migration in d(6) Square-Pyramidal Iridium and Rhodium Pincer Complexes21201152#N/ATRUE
2350
ja110492p10.1021/ja110492pFALSEhttps://doi.org/10.1021/ja110492pWilmot, CMJ. Am. Chem. Soc.We present the 1.2 angstrom resolution X-ray crystal structure of a Ni-methyl species that is a proposed catalytic intermediate in methyl-coenzyme M reductase (MCR), the enzyme that catalyzes the biological formation of methane. The methyl group is situated 2.1 angstrom proximal of the Ni atom of the MCR coenzyme F(430). A rearrangement of the substrate channel has been posited to bring together substrate species, but Ni(III)-methyl formation alone does not lead to any observable structural changes in the channel.Structural Analysis of a Ni-Methyl Species in Methyl-Coenzyme M Reductase from Methanothermobacter marburgensisx31201120#N/AFALSE
2351
ja109926k10.1021/ja109926kFALSEhttps://doi.org/10.1021/ja109926kSchanze, KSJ. Am. Chem. Soc.A set of two donor acceptor-type conjugated polymers with Carbonylic acid side groups have been synthesized and utilized as active materials for dye-sensitized solar cells (DSSCs). The polymers feature a pi-conjugated backbone consisting of an electron-poor 2,1,3-benzothiadiazole (BTD, acceptor) unit, alternating with either a thiophene-fluorene-thiophene triad (2a) or a terthiophene (3a) segment as the donor. The donor-acceptor polymers absorb broadly throughout the visible region, with terthiophene-BTD polymer 3a exhibiting an absorption onset at approximately 625 nm corresponding to a similar to 1.9 eV bandgap. The polymers adsorb onto the surface of nanostructured TiO2 due to interaction of the polar Carbonylic acid units with the metal oxide surface. The resulting films absorb visible light strongly, and their spectra approximately mirror the polymers' solution absorption. Interestingly, a series of samples of 3a with different molecular weight (M-n) adsorb to TiO2 to an extent that varies inversely with M-n. DSSCs that utilize the donor acceptor polymers as sensitizers were tested using an I-/I-3(-) electrolyte. Importantly, for the set of polymer sensitizers 3a with varying M, the DSSC efficiency varies inversely with NI, a result that reflects the difference in adsorption efficiency observed in the film absorption experiments. The best DSSC cell tested is based on a sample of 3a with M-n similar to 4000, and it exhibits a similar to 65% peak IPCE with J(sc) similar to 12.6 mA cm-2 under AM 1.5 illumination and an overall power conversion efficiency of similar to 3%.Low-Bandgap Donor-Acceptor Conjugated Polymer Sensitizers for Dye-Sensitized Solar Cellsx89201131#N/AFALSE
2352
ja204653z10.1021/ja204653zFALSEhttps://doi.org/10.1021/ja204653zAkasaka, TJ. Am. Chem. Soc.Single crystal X-ray diffraction studies of Yb@C-2v(3)-C-80 center dot Ni-II(OEP) center dot CS2 center dot 1.5C(6)H(6) (OEP = octa-ethylporphinate) reveal that a relatively flat region of the fullerene interacts with the Ni-II(OEP) molecule, featuring shape-matching interactions. Surprisingly, it is found that the internal metal is located under a hexagonal carbon ring apart from the 2-fold axis of the C-2v(3)-C-80 cage, presenting the first example of metallofullerenes with an asymmetrically positioned metal. Such an anomalous location of Yb2+ is associated with its strong ability to pursue a large coordination number and the lack of hexagon along the C-2 axis of C-2v(3)-C-80. It is accordingly assumed that a suitable cage hexagon is most likely to be preferred by the single rare earth metal to stay behind inside a medium-sized fullerene, such as C-80 and C-82.Crystallographic X-ray Analyses of Yb@C-2v(3)-C-80 Reveal a Feasible Rule That Governs the Location of a Rare Earth Metal inside a Medium-Sized Fullerene41201151#N/ATRUE
2353
ja204575u10.1021/ja204575uFALSEhttps://doi.org/10.1021/ja204575uHicks, RGJ. Am. Chem. Soc.The electronic structures of (Vd)Ru(LX)(2) complexes (Vd = 1,5-diisopropyl-3-(2-pyridyl)-6-oxoverdazyl radical; LX = acac or hfac) as neutral, cationic, and anionic species have been investigated experimentally and computationally to probe the interplay between the ruthenium ion and the redox-active verdazyl ligand. The cationic complexes were prepared by oxidation of the corresponding neutral species with silver(I) salts. The hfac-based anionic complex was synthesized by reduction of the neutral species with cobaltocene, but the anionic acac analogue could not be prepared. Experimental (X-ray structures, electronic spectra) and computational (TD-DFT (PCM)) studies reveal that the expression of redox activity of the ligand and metal moieties is highly sensitive to the nature of the ancillary ligands on ruthenium. In the hfac series, the cationic, neutral, and anionic complexes can, respectively, be adequately described as Ru(II) complexes of a coordinated verdazyl cation, neutral radical, and anion. However, the more electron-donating acac coligands facilitate a stronger interaction between ruthenium and verdazyl-via Ru(d) to Vd(pi*) backbonding which is dependent on the overall charge of the complex and has the net effect of creating a high degree of metal-ligand covalency. Studies on the two cationic complexes reveal further distinctions between the acac- and hfac-containing systems: whereas the former has a significant open-shell singlet contribution to the complex ground state, this open-shell formulation is a minor component of the latter.Electronic Structure Investigations of Neutral and Charged Ruthenium Bis(beta-diketonate) Complexes of Redox-Active Verdazyl Radicals242011150#N/ATRUE
2354
ja204287n10.1021/ja204287nFALSEhttps://doi.org/10.1021/ja204287nFlowers, RAJ. Am. Chem. Soc.The addition of catalytic amounts of Ni(II) salts provide enhanced reactivity and selectivity in numerous reactions of SmI2, but the mechanistic basis for their effect is unknown. We report spectroscopic and kinetic studies on the mechanistic role of catalytic Ni(II) in the samarium Barbier reaction. The mechanistic studies presented herein show that the samarium Barbier reaction containing catalytic amounts of Ni(II) salts is driven solely by the reduction of Ni(11) to Ni(0) in a rate-limiting step. Once formed, Ni(0) inserts into the,Alkyl halide bond through oxidative addition to produce an organonickel species. During the reaction, the formation of colloidal Ni(0) occurs concomitantly with Ni(0) oxidative addition as an unproductive process. Overall, this study shows that a reaction thought to be driven by the unique features of SmI2 is in fact a result of known Ni(0) chemistry.Catalytic Ni(II) in Reactions of SmI2: Sm(II)- or Ni(0)-Based Chemistry?29201136#N/ATRUE
2355
ja202451t10.1021/ja202451tFALSEBringmann, GHelimeric Porphyrinoids: Stereostructure and Chiral Resolution of meso-TetraArylmorpholinochlorins2011#N/ATRUE
2356
ja201960h10.1021/ja201960hFALSEhttps://doi.org/10.1021/ja201960hHupp, JTNi(III)/(IV) Bis(dicarbollide) as a Fast, Noncorrosive Redox Shuttle for Dye-Sensitized Solar Cells (vol 132, pg 4580, 2010)2011#N/ATRUE
2357
ja109624m10.1021/ja109624mFALSEhttps://doi.org/10.1021/ja109624mMirkin, CAJ. Am. Chem. Soc.A series of homoligated Ni(II) complexes formed from two phosphino thioether (P,S) chelating ligands has been synthesized and characterized. Interestingly, this inCluded octahedral Ni(II) complexes which, unlike previously characterized d(8) Rh(I), Pt(II), and Pd(II) analogues, exhibit in situ exchange processes centered around chloride ligand dissociation. This was verified and studied through the controlled abstraction from and introduction of chloride ions to this system, which showed that these processes proceed through complexes with square pyramidal, tetrahedral, and square planar geometries. These complexes were studied with a variety of characterization methods, induding single-crystal X-ray diffraction studies, solution P-31 {H-1) NMR spectroscopy, UV-vis spectroscopy, and DFT calculations. A general set of synthetic procedures that involve the use of coordinating and noncoordinating counteranions, as well as different hemilabile ligands, to mediate geometry transformations are presented.Plasticity of the Nickel(II) Coordination Environment in Complexes with Hemilabile Phosphino Thioether Ligandsx12201171#N/AFALSE
2358
ja109483a10.1021/ja109483aFALSEhttps://doi.org/10.1021/ja109483aBao, XHJ. Am. Chem. Soc.Various well-defined Ni-Pt(111) model catalysts are constructed at atomic-level precision under ultra-high-vacuum conditions and characterized by X-ray photoelectron spectroscopy and scanning tunneling microscopy. Subsequent studies of CO oxidation over the surfaces show that a sandwich surface (NiO(1-x)/Pt/Ni/Pt(111)) consisting of both surface Ni oxide nanoislands and subsurface Ni atoms at a Pt(111) surface presents the highest reactivity. A similar sandwich structure has been obtained in supported Pt-Ni nanopartiCles via Activation in H(2) at an intermediate temperature and established by techniques inCluding acid leaching, inductively coupled plasma, and X-ray adsorption near-edge structure. Among the supported Pt-Ni catalysts studied, the sandwich bimetallic catalysts demonstrate the highest activity to CO oxidation, where 100% CO conversion occurs near room temperature. Both surface science studies of model catalysts and catalytic reaction experiments on supported catalysts illustrate the synergetic effect of the surface and subsurface Ni species on the CO oxidation, in which the surface Ni oxide nanoislands activate O(2), producing atomic O species, while the subsurface Ni atoms further enhance the elementary reaction of CO oxidation with O.Synergetic Effect of Surface and Subsurface Ni Species at Pt-Ni Bimetallic Catalysts for CO Oxidationx224201184#N/AFALSE
2359
ja109399f10.1021/ja109399fFALSEhttps://doi.org/10.1021/ja109399fNakashima, NJ. Am. Chem. Soc.Single-walled carbon nanotubes (SWNTs) have remarkable and unique electronic, mechanical, and thermal properties, which are Closely related to their chiralities; thus, the chirality-selective recognition/extraction of the SWNTs is one of the central issues in nanotube science. However, any rational materials design enabling one to efficiently extract/solubilize pure SWNT with a desired chirality has yet not been demonstrated. Herein we report that certain chiral polyfluorene copolymers can well-recognize SWNTs with a certain chirality preferentially, leading to solubilization of specific chiral SWNTs. The chiral copolymers were prepared by the Ni-0-catalyzed Yamamoto coupling reaction of 2,7-dibromo-9,9-di-n-decylfluorene and 2,7-dibromo-9,9-bis[(S)-(+)-2-methylbutyl]fluorene comonomers. The selectivity of the SWNT chirality was mainly determined by the relative fraction of the achiral and chiral side groups. By a molecular mechanics simulation, the cooperative interaction between the fluorene moiety, Alkyl side chain, and graphene wall were responsible for the recognition/dissolution ability of SWNT chirality. This is a first example describing the rational design and synthesis of novel fluorene-based copolymers toward the ::recognition/extraction of targeted (n, m) chirality of the SWNTs.Rational Concept To Recognize/Extract Single-Walled Carbon Nanotubes with a Specific Chiralityx106201133#N/AFALSE
2360
ja109018h10.1021/ja109018hFALSEhttps://doi.org/10.1021/ja109018hMorokuma, KJ. Am. Chem. Soc.Since the discovery of single-walled carbon nanotubes (SWNTs) in the early 1990s, the most commonly accepted model of SWNT growth on traditional catalysts (i.e., transition metals inCluding Fe, Co, Ni, etc.) is the vapor-liquid-solid (VLS) mechanism. In more recent years, the synthesis of SWNTs on nontraditional catalysts, such as SiO2, has also been reported. The precise atomistic mechanism explaining SWNT growth on nontraditional catalysts, however, remains unknown. In this work, CH4 chemical vapor deposition (CVD) and single-walled carbon nanotube (SWNT) nuCleation on SiO2 nanopartiCles have been investigated using quantum-chemical molecular dynamics (QM/MD) methods. Upon supply of CHx species to the surface of a model SiO2 nanopartiCle, CO was produced as the main chemical product of the CH4 CVD process, in agreement with a recent experimental investigation [Bachmatiuk et al., ACS Nano 2009, 3, 4098]. The production of CO occurred simultaneously with the carbothermal reduction of the SiO2 nanopartiCle. However, this reduction, and the formation of amorphous SiC, was restricted to the nanopartiCle surface, with the core of the SiO2 nanopartiCle remaining oxygen-rich. In cases of high carbon concentration, SWNT nuCleation then followed, and was driven by the formation of isolated sp(2)-carbon networks via the gradual coalescence of adjacent polyyne chains. These simulations indicate that the carbon saturation of the SiO2 surface was a necessary prerequisite for SWNT nuCleation. These simulations also indicate that a vapor-solid-solid mechanism, rather than a VLS mechanism, is responsible for SWNT nuCleation on SiO2. Fundamental differences between SWNT nuCleation on nontraditional and traditional catalysts are therefore observed.SWNT NuCleation from Carbon-Coated SiO2 NanopartiCles via a Vapor-Solid-Solid Mechanismx51201150#N/AFALSE
2361
ja201681310.1021/ja2016813FALSEhttps://doi.org/10.1021/ja2016813Fujii, HJ. Am. Chem. Soc.Ligand radicals from salen complexes are unique mixed-valence compounds in which a phenoxyl radical is electronically linked to a remote phenolate via a neighboring redox-active metal ion, providing an opportunity to study electron transfer from a phenolate to a phenoxyl radical mediated by a redox-active metal ion as a bridge. We herein synthesize one-electron-oxidized products from electronically diverse manganese(III) salen complexes in which the locus of oxidation is shown to be ligand-centered, not metal-centered, affording manganese(III) phenoxyl radical species. The key point in the present study is an unambiguous assignment of intervalence charge transfer bands by using nonsymmetrical salen complexes, which enables us to obtain otherwise inaccessible insight into the mixed-valence property. A d(4) high-spin manganese (III) ion forms a Robin Day Class II mixed-valence system, in which electron transfer is occurring between the localized phenoxyl radical and the phenolate. This is in Clear contrast to a d(8) low-spin nickel(II) ion with the same salen ligand, which induces a delocalized radical (Robin Day Class III) over the two phenolate rings, as previously reported by others. The present findings point to a fascinating possibility that electron transfer could be drastically modulated by exchanging the metal ion that bridges the two redox centers.One-Electron Oxidation of Electronically Diverse Manganese(III) and Nickel(II) Salen Complexes: Transition from Localized to Delocalized Mixed-Valence Ligand Radicals95201162#N/ATRUE
2362
ja108740c10.1021/ja108740cFALSEhttps://doi.org/10.1021/ja108740cMeyer, FJ. Am. Chem. Soc.First members of a new family of heterometallic Mn/Ni complexes [Mn2Ni3X2L4(LH)(2)(H2O)(2)] (X = Cl: 1; X = Br: 2) with the new ligand 2-{3-(2-hydroxyphenyl)-1H-pyrazol-1-yl}ethanol (H2L) have been synthesized, and single crystals obtained from CH2Cl2 solutions have been characterized crystallographically. The molecular structures feature a quasilinear Mn-III-Ni-II-Ni-II-Ni-II-Mn-III core with six-coordinate metal ions, where elongated axes of all the distorted octahedral coordination polyhedra are aligned parallel and are fixed with respect to each other by intramolecular hydrogen bonds. 1 and 2 exhibit quite strong ferromagnetic exchange interactions throughout (J(Mn-Ni) approximate to 40 K (1) or 42 K (2); J(Ni-Ni) approximate to 22 K (1) or 18 K (2)) that lead to an S-tot = 7 ground state, and a sizable uniaxial magnetoanisotropy with D-mol values -0.55 K (1) and -0.45 K (2). These values are directly derived also from frequency- and temperature-dependent high-field EPR spectra. Slow relaxation of the magnetization at low temperatures and single-molecule magnet (SMM) behavior are evident from frequency-dependent peaks in the out-of-phase ac susceptibilities and magnetization versus dc field measurements, with significant energy barriers to spin reversal U-eff = 27 K (1) and 22 K (2). Pronounced quantum tunnelling steps are observed in the hysteresis loops of the temperature- and scan rate-dependent magnetization data, but with the first relaxation step shifted above (1) or below (2) the zero crossing of the magnetic field, despite the very similar molecular structures. The different behavior of 1 and 2 is interpreted in terms of antiferromagnetic (1) or ferromagnetic (2) intermolecular interactions, which are discussed in view of the subtle differences of intermolecular contacts within the crystal lattice.A New Family of 1D Exchange Biased Heterometal Single-Molecule Magnets: Observation of Pronounced Quantum Tunneling Steps in the Hysteresis Loops of Quasi-Linear {Mn2Ni3} Clustersx65201176#N/AFALSE
2363
ja108588y10.1021/ja108588yFALSEhttps://doi.org/10.1021/ja108588yKomaba, SJ. Am. Chem. Soc.Lithium-excess manganese layered oxides, which are commonly described by the chemical formula zLi(2)MnO(3)-(1 - z)LiMeO2 (Me = Co, Ni, Mn, etc.), are of great importance as positive electrode materials for rechargeable lithium batteries. In this ArtiCle, LixCo0.13Ni0.13Mn0.54O2-delta samples are prepared from Li1.2Ni0.13Co0.13Mn0.54O2 (or 0.5Li(2)MnO(3)-0.5LiCo(1/3)Ni(1/3)Mn(1/3)O(2)) by an electrochemical oxidation/reduction process in an electrochemical cell to study a reaction mechanism in detail before and after charging across a voltage plateau at 4.5 V vs Li/Li+ Changes of the bulk and surface structures are examined by synchrotron X-ray diffraction (SXRD), X-ray absorption spectroscopy ()CAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (SIMS). SXRD data show that simultaneous oxygen and lithium removal at the voltage plateau upon initial charge causes the structural rearrangement, inCluding a cation migration process from metal to lithium layers, which is also supported by XAS. This is consistent with the mechanism proposed in the literature related to the Li-excess manganese layered oxides. Oxygen removal associated with the initial charge on the high voltage plateau causes oxygen molecule generation in the electrochemical cells. The oxygen molecules in the cell are electrochemically reduced in the subsequent discharge below 3.0 V, leading to the extra capacity. Surface analysis confirms the formation of the oxygen containing species, such as lithium carbonate, which accumulates on the electrode surface. The oxygen containing species are electrochemically decomposed upon second charge above 4.0 V. The results suggest that, in addition to the conventional transition metal redox reactions, at least some of the reversible capacity for the Li-excess manganese layered oxides originates from the electrochemical redox reaction of the oxygen molecules at the electrode surface.Detailed Studies of a High-Capacity Electrode Material for Rechargeable Batteries, Li2MnO3-LiCo1/3Ni1/3Mn1/3O2x937201171#N/AFALSE
2364
ja201004810.1021/ja2010048FALSEhttps://doi.org/10.1021/ja2010048Balbach, JJ. Am. Chem. Soc.Slow protein folding processes during which kinetic folding intermediates occur for an extended time can lead to aggregation and dysfunction in living cells. Therefore, protein folding helpers have evolved, which prevent proteins from aggregation and/or speed up folding processes. In this study, we present the structural characterization of a long-living transient folding intermediate of RNase T1 (S54G/P55N) by time-resolved NMR spectroscopy. NMR resonances of this kinetic folding intermediate could be assigned mainly by a real-time 3D BEST-HNCA. These assignments were the basis to investigate the interaction sites between the protein folding helper enzyme SlyD(1-165) (SlyD*) from Escherichia coli (E. coli) and this kinetic intermediate at a residue resolution. Thus, we investigated the Michaelis-Menten complex of this enzyme reaction, because the NMR data acquisition was performed during the actual catalysis. The interaction surface of the transient folding intermediate is restricted to a region around the peptidyl-prolyl bond (Y38-P39), whose isomerization is catalyzed by SlyD*. The interaction surface regarding SlyD* extends from specific amino acids of the FKBP domain forming the peptidyl-prolyl cis/transisomerase active site to almost the entire IF domain. This illustrates an effective interplay between the two functional domains of SlyD* to facilitate protein folding catalysis.Transient Enzyme-Substrate Recognition Monitored by Real-Time NMR15201188#N/ATRUE
2365
ja108050810.1021/ja1080508FALSEhttps://doi.org/10.1021/ja1080508de Jong, KPJ. Am. Chem. Soc.We explored melt infiltration of mesoporous silica supports to prepare supported metal catalysts with high loadings and controllable partiCle sizes. Melting of Co(NO3)(2)center dot 6H(2)O in the presence of silica supports was studied in situ with differential scanning calorimetry. The melting point depression of the intraporous phase was used to quantify the degree of pore loading after infiltration. Maximum pore-fillings corresponded to 70-80% of filled pore volume, if the intraporous phase was considered to be crystalline Co(NO3)(2)center dot 6H(2)O. However, diffraction was absent in XRD both from the ordered mesopores at low scattering angles and from crystalline cobalt nitrate phases at high angles. Hence, an amorphous, lower density, intraporous Co(NO3)(2)center dot 6H(2)O phase was proposed to fill the pores completely. Equilibration at 60 degrees C in a Closed vessel was essential for successful melt infiltration. In an open crucible, dehydration of the precursor prior to infiltration inhibited homogeneous filling of support partiCles. The dispersion and distribution of Co3O4 after calcination could be controlled using the same toolbox as for preparation via solution impregnation: confinement and the calcination gas atmosphere. Using ordered mesoporous silica supports as well as an industrial silica gel support, catalysts with Co metal loadings in the range of 10-22 wt% were prepared. The Co3O4 crystallite sizes ranged from 4 to 10 nm and scaled with the support pore diameters. By calcination in N-2, pluglike nanopartiCles were obtained that formed aggregates over several pore widths, while calcination in 1% NO/N-2 led to the formation of smaller individual nanopartiCles. After reduction, the Co/SiO2 catalysts showed high activity for the Fischer-Tropsch synthesis, illustrating the applicability of melt infiltration for supported catalyst preparation.Fundamentals of Melt Infiltration for the Preparation of Supported Metal Catalysts. The Case of Co/SiO2 for Fischer-Tropsch Synthesisx80201057#N/AFALSE
2366
ja107703n10.1021/ja107703nFALSEhttps://doi.org/10.1021/ja107703nMurphy, JAJ. Am. Chem. Soc.The first crown-tetracarbene complex of Ni(II) has been prepared, and its crystal structure determined. The complex can be reduced by Na/Hg, with an uptake of two electrons. The reduced complex reductively Cleaves arenesulfonamides, inCluding those derived from secondary aliphatic amines, and effects Birch reduction of anthracenes as well as reductive Cleavage of stilbene oxides. Computational studies show that the orbital that receives electrons upon reduction of the complex 2 is predominantly based on the crown carbene ligand and also that the HOMO of the parent complex 2 is based on the ligand.Reductions of Challenging Organic Substrates by a Nickel Complex of a Noninnocent Crown Carbene Ligandx49201037#N/AFALSE
2367
ja107403p10.1021/ja107403pFALSEhttps://doi.org/10.1021/ja107403pWard, MDJ. Am. Chem. Soc.The bis-bidentate bridging ligand L {alpha,alpha'-bis-[3-(2-pyridyl)pyrazol-1-yl]-1,4-dimethylbenzene}, which contains two chelating pyrazolyl-pyridine units connected to a 1,4-phenylene spacer via flexible methylene units, reacts with transition metal dications to form a range of polyhedral coordination cages based on a 2M:3 L ratio in which a metal ion occupies each vertex of a polyhedron, a bridging ligand lies along every edge, and all metal ions are octahedrally coordinated. Whereas the Ni(II) complex [Ni8L12]-(BF4)(12)(SiF6)(2) is an octanuClear cubic cage of a type we have seen before, the Cu(II), Zn(II), and Cd(II) complexes form new structural types. [Cu6L9](BF4)(12) is an unusual example of a trigonal prismatic cage, and both Zn(II) and Cd(II) form unprecedented hexadecanuClear cages [M16L24]X-32(X = ClO4 or BF4) whose core is a skewed tetracapped truncated tetrahedron. Both Cu6L9 and M16L24 cages are based on a cyClic helical M3L3 subunit that can be considered as a triangular panel, with the cages being constructed by interconnection of these (homochiral) panels with additional bridging ligands in different ways. Whereas [Cu6L9](BF4)(12) is stable in solution (by electrospray mass spectrometry, ES-MS) and is rapidly formed by combination of Cu(BF4)(2) and L in the correct proportions in solution, the hexadecanuClear cage [Cd16L24](BF4)(32) formed on crystallization slowly rearranges in solution over a period of several weeks to the trigonal prism [Cd6L9](BF4)(12), which was unequivocally identified on the basis of its H-1 NMR spectrum. Similarly, combination of Cd(BF4)(2) and L in a 2:3 ratio generates a mixture whose main component is the trigonal prism [Cd6L9](BF4)(12). Thus the hexanuClear trigonal prism is the thermodynamic product arising from combination of Cd(II) and L in a 2:3 ratio in solution, and arises from both assembly of metal and ligand (minutes) and rearrangement of the Cd-16 cage (weeks); the large cage [Cd16L24](BF4)(32) is present as a minor component of a mixture of species in solution but crystallizes preferentially.Structures and Dynamic Behavior of Large Polyhedral Coordination Cages: An Unusual Cage-to-Cage Interconversionx138201145#N/AFALSE
2368
ja200762710.1021/ja2007627FALSEhttps://doi.org/10.1021/ja2007627Louie, JJ. Am. Chem. Soc.Ni-phosphine complexes were used as catalysts for the cyCloaddition of various ketenes and diynes. In general, 2,4-cyClohexadienones were formed instead of products arising from deCarbonylation of the ketenes.Ni-Catalyzed Ketene CyCloaddition: A System That Resists the Formation of DeCarbonylation Side Products45201155#N/ATRUE
2369
ja106999q10.1021/ja106999qhttps://doi.org/10.1021/ja106999qBielawski, CWJ. Am. Chem. Soc.Block copolymers of poly(3-hexylthiophene) and a poly(Arylisocyanide) were synthesized in a single pot via the addition of 2-bromo-3-hexyl-5-chloromagnesiothiophene followed by n-decyl 4-isocyanobenzoate to a solution of Ni(1,3-bis(diphenylphosphino)propane)Cl-2. The respective mechanistically distinct polymerizations proceeded in a controlled fashion and afforded well-defined block copolymers with tunable molecular weights and compositions. The block copolymers exhibited microphase separation characteristics in the solid state.Synthesis of Poly(3-Alkylthiophene)-block-poly(Arylisocyanide): Two Sequential, Mechanistically Distinct Polymerizations Using a Single Catalystx96201025#N/AFALSE
2370
ja200289w10.1021/ja200289wFALSEhttps://doi.org/10.1021/ja200289wBalch, ALJ. Am. Chem. Soc.Single-crystal X-ray diffraction studies of Sc-2(mu(2)-S)@C-s(6)-C-82 center dot Ni-II(OEP)center dot 2C(6)H(6) and Sc-2(mu(2)-S)@C-3v(8)-C-82 center dot Ni-II(OEP)center dot 2C(6)H(6) reveal that both contain fully ordered fullerene cages. The crystallographic data for Sc-2(mu(2)-S)@C-s(6)-C-82 center dot Ni-II(OEP)center dot 2C(6)H(6) show two remarkable features: the presence of two slightly different cage sites and a fully ordered molecule Sc-2(mu(2)-S)@C-s(6)-C-82 in one of these sites. The Sc-S-Sc angles in Sc-2(mu(2)-S)@C-s(6)-C-82 (113.84(3)degrees) and Sc-2(mu(2)-S)@C-3v(8)-C-82 differ (97.34(13)degrees). This is the first case where the nature and structure of the fullerene cage isomer exerts a demonstrable effect on the geometry of the Cluster contained within. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule for C-82, the cage stability changes markedly between 0 and 250 K, but the C-s(6)-C-82 cage is preferred at temperatures >= 250 degrees C when using the energies obtained with the free encapsulated model (FEM). However, the C-3v(8)-C-82 cage is preferred at temperatures >= 250 degrees C using the energies obtained by rigid rotor-harmonic oscillator (RRHO) approximation. These results corrB(OH)2rate the fact that both cages are observed and likely to trap the Sc-2(mu(2)-S) Cluster, whereas earlier FEM and RRHO calculations predicted only the C-s(6)-C-82 cage is likely to trap the Sc-2(mu(2)-O) Cluster. We also compare the recently published electrochemistry of the sulfide-containing Sc-2(mu(2)-S)@C-s(6)-C-82 to that of corresponding oxide-containing Sc-2(mu(2)-O)@C-s(6)-C-82.The Shape of the Sc-2(mu(2)-S) Unit Trapped in C-82: Crystallographic, Computational, and Electrochemical Studies of the Isomers, Sc-2(mu(2)-S)@C-s(6)-C-82 and Sc-2(mu(2)-S)@C-3v(8)-C-8296201141#N/ATRUE
2371
ja106814p10.1021/ja106814pFALSEhttps://doi.org/10.1021/ja106814pYoshikai, NJ. Am. Chem. Soc.Ternary catalytic systems consisting of cobalt salts, phosphine ligands, and Grignard reagents promote addition of Arylpyridines and imines to unactivated internal alkynes with high regio- and stereoselectivities. Deuterium-labeling experiments suggest that the reaction involves chelation-assisted oxidative addition of the Aryl C-H bond to the cobalt center and insertion of the C-C triple bond into the Co-H bond, followed by reductive elimination of the resulting diorganocobalt species.Cobalt-Catalyzed HydroArylation of Alkynes through Chelation-Assisted C-H Bond Activationx229201039#N/AFALSE
2372
ja111465n10.1021/ja111465nFALSEhttps://doi.org/10.1021/ja111465nBalch, ALJ. Am. Chem. Soc.Four isomers with the composition SmC90 were obtained from carbon soot produced by electric arc vaporization of carbon rods doped with Sm2O3. These were labeled Sm@C-90(I), Sm@C-90(II), Sm@C-90(III), and Sm@C-90(IV) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni(octaethylporphyrin) reveals the identities of the individual isomers as follows: I, Sm@C-2(40)-C-90; II, Sm@C-2(42)-C-90; III, Sm@C-2v(46)-C-90 and IV, Sm@C-2(45)-C-90. This is the most extensive series of isomers of any endohedral fullerene to have their individual structures determined by single-crystal X-ray diffraction. The cage structures of these four isomers can be related pairwise to one another in a formal sense through sequential Stone-Wales transformations.Isolation and Crystallographic Identification of Four Isomers of Sm@C-9040201140#N/ATRUE
2373
ja106387310.1021/ja1063873FALSEhttps://doi.org/10.1021/ja1063873Adzic, RRJ. Am. Chem. Soc.We describe a simple method for preparing multimetallic nanopartiCles by in situ decomposition of the corresponding Prussian blue analogue, which is adsorbed on carbon black. The example involves the AuNi0.5Fe core of the Pt-ML/Au1Ni0.5Fe core-shell electrocatalyst for the oxygen reduction reaction. The core contains 3-5 surface atomic layers of Au, which play an essential role in determining the activity and stability of the catalyst. The Pt-ML/AuNi0.5Fe electrocatalyst exhibited Pt mass and specific activities of 1.38 A/mg(Pt) and 1.12 x 10(-3) A/cm(Pt)(2), respectively, both of which are several times higher than those of commercial Pt/C catalysts. Its all-noble-metal mass activity (0.18 A/mg(Pt,Au)) is higher than or comparable to those of commercial samples. Stability tests showed an insignificant loss in activity after 15 000 triangular-potential cyCles. We ascribe the high activity and stability of the Pt-ML/AuNi0.5Fe electrocatalyst to its hierarchical structural properties, the Pt-core interaction, and the high electrochemical stability of the gold shell that preCludes exposure to the electrolyte of the relatively active inner-core materials.Platinum-Monolayer Shell on AuNi0.5Fe NanopartiCle Core Electrocatalyst with High Activity and Stability for the Oxygen Reduction Reactionx169201017#N/AFALSE
2374
ja110522x10.1021/ja110522xFALSEhttps://doi.org/10.1021/ja110522xScrosati, BJ. Am. Chem. Soc.In this paper we report the study of a high capacity Sn-C nanostructured anode and of a high rate, high voltage Li[Ni(0.45)Co(0.1)Mn(1.45)]O(4) spinel cathode. We have combined these anode and cathode materials in an advanced lithium ion battery that, by exploiting this new chemistry, offers excellent performances in terms of cyCling life, i.e., ca. 100 high rate cyCles, of rate capability, operating at 5C and still keeping more than 85% of the initial capacity, and of energy density, expected to be of the order of 170 Wh kg(-1). These unique features make the battery a very promising energy storage for powering low or zero emission HEV or EV vehiCles.An Advanced Lithium Ion Battery Based on High Performance Electrode Materials341201119#N/ATRUE
2375
ja106264q10.1021/ja106264qFALSEhttps://doi.org/10.1021/ja106264qMorokuma, KJ. Am. Chem. Soc.The mechanism and kinetics of single-walled carbon nanotube (SWNT) nuCleation from Fe- and Ni-carbide nanopartiCle precursors have been investigated using quantum chemical molecular dynamics (QM/MD) methods. The dependence of the nuCleation mechanism and its kinetics on environmental factors, inCluding temperature and metal-carbide carbon concentration, has also been elucidated. It was observed that SWNT nuCleation occurred via three distinct stages, viz, the precipitation of the carbon from the metal-carbide, the formation of a surface/subsurface carbide intermediate species, and finally the formation of a nascent sp(2)-hybidrized carbon structure supported by the metal catalyst. The SWNT cap nuCleation mechanism itself was unaffected by carbon concentration and/or temperature. However, the kinetics of SWNT nuCleation exhibited distinct dependences on these same factors. In particular, SWNT nuCleation from NixCy nanopartiCles proceeded more favorably compared to nuCleation from FexCy nanopartiCles. Although SWNT nuCleation from FexCy and NixCy nanopartiCle precursors occurred via an identical route, the ultimate outcomes of these processes also differed substantially. Explicitly, the Ni-x-supported sp(2)-hybridized carbon structures tended to encapsulate the catalyst partiCle itself, whereas the Fe-x-supported structures tended to form isolated SWNT cap structures on the catalyst surface. These differences in SWNT nuCleation kinetics were attributed directly to the relative strengths of the metal-carbon interaction, which also dictates the precipitation of carbon from the nanopartiCle bulk and the longevity of the resultant surface/subsurface carbide species. The stability of the surface/subsurface carbide was also influenced by the phase of the nanopartiCle itself. The observations agree well with experimentally available data for SWNT growth on iron and nickel catalyst partiCles.QM/MD Simulation of SWNT NuCleation on Transition-Metal Carbide NanopartiClesx85201042#N/AFALSE
2376
ja106064310.1021/ja1060643FALSEhttps://doi.org/10.1021/ja1060643Hawker, CJJ. Am. Chem. Soc.The functionalization and cross-linking of polyethylene is synthetically challenging, commonly relying on highly optimized radical based postpolymerization strategies. To address these difficulties, a norbornene monomer containing Meldrum's acid is shown to be effectively copolymerized with polyethylene using a nickel alpha-iminocarbaxamidato complex, providing high-melting, semicrystalline polymers with a tunable incorporation of the functional comonomer. Upon heating the copolymer to common polyethylene processing temperatures, the thermolysis of Meldrum's acid to ketene provides the desired reactive group. This simple and versatile methodology does not require small molecule radical sources or catalysts, and the dimerization of the in situ generated ketenes is shown to provide tunable cross-linking densities in polyethylene. Subsequent rheological and tensile experiments illustrate the ability to tune cross-linked polyethylene properties by comonomer incorporation and elucidate valuable structure/property relationships in these materials. This study illustrates the power of well-defined and synthetically accessible functional groups in polyolefin synthesis and functionalization.Ketene Functionalized Polyethylene: Control of Cross-Link Density and Material Propertiesx55201032#N/AFALSE
2377
ja105693810.1021/ja1056938FALSEhttps://doi.org/10.1021/ja1056938Bazan, GCJ. Am. Chem. Soc.Novel binuClear complexes, 4,4'-bis{[N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-propanamidato-kappa(2)-N,O-(trimethylphosphine)nickel(II)]methyl}-1,1'-biphenyl (2a) and 4,4'-bis{[N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-4-methylpentamidato-kappa(2)-N,O-(trimethylphosphine)nickel(II)]methyl}-1,1'-biphenyl (2b), were synthesized by linking two nickel centers through a bis(Benzyl) fragment. When activated with nickel bis(1,5-cyClooctadiene) (Ni(COD)(2)), 2a and 2b are capable of polymerizing ethylene in a quasi-living fashion, producing polymers with approximately twice the molecular weights relative to those obtained by using a structurally related mononuClear system. In addition, 2b/Ni(COD)(2) was utilized to synthesize a series of pseudo-triblock polyethylene (PE) macroinitiating copolymers, bearing atom-transfer radical polymerization (ATRP) initiators. Pseudo-pentablock copolymers were also prepared by taking advantage of a pressure-pulsing technique, wherein the ethylene pressure was increased from 100 to 500 psi in order to produce semicrystalline ethylene-rich end-blocks. Copolymers with elastomeric properties were synthesized by grafting n-butyl acrylate from the PE macroinitiators via ATRP. Examination using monotonic and step-cyClic stress strain tests demonstrates that the materials exhibit large strains at break (1600-2000%) and excellent elastic recoveries at large strains (similar to 80%). That materials with such desirable properties could not be attained using a mononuClear initiator demonstrates the Clear advantage of growing the polymer via a telechelic mechanism.BinuClear Initiators for the Telechelic Synthesis of Elastomeric Polyolefinsx20201050#N/AFALSE
2378
ja105511t10.1021/ja105511thttps://doi.org/10.1021/ja105511tSztaray, BJ. Am. Chem. Soc.Metallocene ions (Cp2M+, M = Cr, Co, Ni) were studied by threshold photoelectron photoion coincidence spectroscopy (TPEPICO) to investigate the mechanism, energetics, and kinetics of the ionic dissociation processes. The examined energy-selected Cp2M(+) ions fragment by losing the neutral cyClopentadienyl ligand. In addition, CH and C2H2 losses appear as minor channels, while the cobaltocene ion also loses an H atom. A possible isomerization pathway has also been observed for Cp2Ni+, yielding a complex with pentafulvalene (C10H8) with a loss of H-2. In order to determine the 0 K appearance energies for the CpM+ fragment ions, the asymmetric time-of-flight peak shapes and the breakdown diagrams of the energy-selected metallocene ions were modeled by both the rigid activated complex (RAC) Rice-Ramsperger-Kassel-Marcus (RRKM) theory and the simplified statistical adiabatic channel model (SSACM). The following appearance energies were obtained with SSACM, which is more reliable for loose transition states: 10.57 +/- 0.14, 11.01 +/- 0.13, and 10.18 +/- 0.13 eV for M = Cr, Co, and Ni, respectively. These values combined with the corresponding adiabatic ionization energies yield M-Cp bond dissociation energies in Cp2M+ ions of 5.04 +/- 0.16, 5.77 +/- 0.15, and 3.96 +/- 0.15 eV. Density functional calculations at the B3LYP/6-311G(d,p) level of theory were used to determine the structures of these complexes and to provide parameters necessary for the analysis of the experimental data. The trends in the M-Cp bond energies can be related to the electronic structures of the metallocene ions based on a simple molecular orbital picture.Binding Energies and Isomerization in Metallocene Ions from Threshold Photoelectron Photoion Coincidence SpectroscopyPhotocatalystx14201070#N/AFALSE
2379
ja109911p10.1021/ja109911pFALSEhttps://doi.org/10.1021/ja109911pOgoshi, SJ. Am. Chem. Soc.Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond Activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with Arylzinc reagents in the presence of lithium iodide, giving alpha,beta,beta-trifluorostyrene derivatives in excellent yields.Palladium-Catalyzed Coupling Reactions of Tetrafluoroethylene with Arylzinc Compounds118201173#N/ATRUE
2380
ja105368p10.1021/ja105368pFALSEhttps://doi.org/10.1021/ja105368pVeiros, LFJ. Am. Chem. Soc.Nickel joins the fairly exClusive list of metals that can activate nitrile C-H bonds. We report the first example of the C-H Activation of an acetonitrile ligand on a nickel center. The acetonitrile ligand formally loses a proton and undergoes a sharp flip to give a cyanomethyl ligand that is coordinated to the nickel atom. Structures of an initial N-bound acetonitrile-nickel complex and of a final cyanomethyl-nickel complex are both presented.C-H Activation of Acetonitrile at Nickel: Ligand Flip and Conversion of N-Bound Acetonitrile into a C-Bound Cyanomethyl Ligandx51201039#N/AFALSE
2381
ja105312p10.1021/ja105312pFALSEhttps://doi.org/10.1021/ja105312pRauchfuss, TBJ. Am. Chem. Soc.The [NiFe]-hydrogenase model complex NiFe(pdt)(dppe)(CO)(3) (1) (pdt = 1,3-propanedithiolate) has been efficiently synthesized and found to be robust. This neutral complex sustains protonation to give the first nickel-iron hydride [1H]BF4. One CO ligand in [1H]BF4 is readily substituted by organophosphorus ligands to afford the substituted derivatives [HNiFe(pdt)(dppe)(PR3)(CO)(2)]BF4, where PR3 = P(OPh)(3) ([2H]BF4); PPh3 ([3H]BF4); PPh2Py ([4H]BF4, where Py = 2-pyridyl). Variable temperature NMR measurements show that the neutral and protonated derivatives are dynamic on the NMR time scale, which partially symmetrizes the phosphine complex. The proposed stereodynamics involve twisting of the Ni(dppe) center, not rotation at the Fe(CO)(2)(PR3) center. In MeCN solution, 3, which can be prepared by deprotonation of [3H]BF4 with NaOMe, is about 10(4) stronger base than is 1. X-ray crystallographic analysis of [3H]BF4 revealed a highly unsymmetrical bridging hydride, the Fe-H bond being 0.40 angstrom shorter than the Ni-H distance. Complexes [2H]BF4, [3H]BF4, and [4H]BF4 undergo reductions near -1.46 V vs Fc(0/+). For [2H]BF4, this reduction process is reversible, and we assign it as a one-electron process. In the presence of trifluoroacetic acid, proton reduction catalysis coincides with this reductive event. The dependence of i(c)/i(p) on the concentration of the acid indicates that H-2 evolution entails protonation of a reduced hydride. For [2H](+), [3H](+), and [4H](+), the acid-independent rate constants are 50-75 s(-1). For [2H](+) and [3H](+), the overpotentials for H-2 evolution are estimated to be 430 mV, whereas the overpotential for the N-protonated pyridinium complex [4H(2)](2+) is estimated to be 260 mV. The mechanism of H-2 evolution is proposed to follow an ECEC sequence, where E and C correspond to one-electron reductions and protonations, respectively. On the basis of their values for its pK(a) and redox potentials, the room temperature values of Delta G(H center dot) and Delta G(H center dot) are estimated as respectively as 57 and 79 kcal/mol for [1H](+).Hydride-Containing Models for the Active Site of the Nickel-Iron Hydrogenasesx179201067#N/AFALSE
2382
ja105232910.1021/ja1052329FALSEhttps://doi.org/10.1021/ja1052329Hillhouse, GLJ. Am. Chem. Soc.Reaction of the dimeric Ni(I) chloride complex [(dtbpe)-NiCl](2) (1) with dimesitylsilyl potassium affords the three-coordinate Ni(I) silyl complex (dtbpe)Ni(SiHMes(2)) (2). Alternatively, 2 can be prepared by an oxidative-addition reaction of Mes(2)Si(H)OTf (Tf = CF3SO3) with the nickel(0) complex [(dtbpe)Ni](2)(mu-C6H6) (3), with (dtbpe)Ni(OTf) (4) formed as an easily separable byproduct. The one-electron oxidation of 2 by ferrocenium affords diamagnetic [(dtbpe)Ni(mu-H)SiMes(2)][BAr4F] (5), a Ni(II) complex formed by partial 1,2-H migration from silicon to nickel and featuring an unusual 3-center, 2-electron bonding motif between Ni, Si, and the bridging H. Complex 5 was also obtained from Mes(2)SiH(2) Activation by the neopentyl complex salt [(dtbpe)Ni(CH2CMe3)]-[BAr4F] (6) with elimination of neopentane.Arrested 1,2-Hydrogen Migration from Silicon to Nickel upon Oxidation of a Three-Coordinate Ni(I) Silyl Complexx62201046#N/AFALSE
2383
ja109799510.1021/ja1097995FALSEhttps://doi.org/10.1021/ja1097995Wright, PAJ. Am. Chem. Soc.Crystalline microporous cobalt and nickel bisphosphonates with a hexagonal array of one-dimensional channels 1.8 nm in diameter have been prepared hydrothermally and provide the first example of the use of isoreticular chemistry in the synthesis of phosphonate metal-organic frameworks. The materials contain both physisorbed and coordinating water molecules in the as-prepared form, but these can be removed to give permanent extra-large microporosity, with pore volumes of up to 0.68 cm(3) g(-1), coordinatively unsaturated sites, with concentrations up to 4.25 mmol g(-1).Extending the Pore Size of Crystalline Metal Phosphonates toward the Mesoporous Regime by Isoreticular Synthesis113201127#N/ATRUE
2384
ja109755f10.1021/ja109755fFALSEhttps://doi.org/10.1021/ja109755fDuBois, DLJ. Am. Chem. Soc.A series of mononuClear nickel(II) bis(diphosphine) complexes [Ni((P2N2C6H4X)-N-Ph)(2)](BF4)(2) ((P2N2C6H4X)-N-Ph = 1,5-di(para-X-phenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyClooctane; X = OMe, Me, CH2P(O)(OEt)(2), Br, and CF3) have been synthesized and characterized. X-ray diffraction studies reveal that [Ni((P2N2C6H4Me)-N-Ph)(2)](BF4)(2) and [Ni((P2N2C6H4OMe)-N-Ph)(2)] (BF4)(2) are tetracoordinate with distorted square planar geometries. The Ni(II/I) and Ni(I/0) redox couples of each complex are electrochemically reversible in acetonitrile with potentials that are increasingly cathodic as the electron-donating character of X is increased. Each of these complexes is an efficient electrocatalyst for hydrogen production at the potential of the Ni(II/I) couple. The catalytic rates generally increase as the electron-donating character of X is decreased, and this electronic effect results in the favorable but unusual situation of obtaining higher catalytic rates as overpotentials are decreased. Catalytic studies using acids with a range of plc values reveal that turnover frequencies do not correlate with substrate acid plc values but are highly dependent on the acid structure, with this effect being related to substrate size. Addition of water is shown to dramatically increase catalytic rates for all catalysts. With [Ni((P2NC6H4CH2P(O))-N-Ph)((OEt)2)(2))(2)](BF4)(2) using [(DMF)H]+OTf- as the acid and with added water, a turnover frequency of 1850 s(-1) was obtained.[Ni((P2N2C6H4X)-N-Ph)(2)](2+) Complexes as Electrocatalysts for H-2 Production: Effect of Substituents, Acids, and Water on Catalytic Rates289201170#N/ATRUE
2385
ja109686v10.1021/ja109686vFALSEhttps://doi.org/10.1021/ja109686vJohnson, JBJ. Am. Chem. Soc.The rhodium-catalyzed intramolecular carboacylation of quinolinyl ketones serves as an ideal subject for the mechanistic study of carbon-carbon bond Activation. Combined kinetic and NMR studies of this reaction allowed the identification of the catalytic resting state and determination of the rate law, C-12/C-13 kinetic isotope effects, and Activation parameters. These results have identified the Activation of a ketone-arene carbon-carbon single bond as the turnover-limiting step of catalysis and provided quantitative detail into this process.Rhodium-Catalyzed Acylation with Quinolinyl Ketones: Carbon-Carbon Single Bond Activation as the Turnover-Limiting Step of Catalysis47201138#N/ATRUE
2386
ja104505t10.1021/ja104505tFALSEhttps://doi.org/10.1021/ja104505tZhou, QLJ. Am. Chem. Soc.The nickel-catalyzed reductive coupling of alkynes and imines with Et2Zn as a reductant by using electron-rich phosphine ligands has been developed, affording various allylic amines with high yields and excellent chemoselectivities. Chiral induction was also achieved in this reductive coupling reaction when a nickel catalyst containing a chiral spiro phosphine ligand was used.Enantioselective Nickel-Catalyzed Reductive Coupling of Alkynes and Iminesx69201023#N/AFALSE
2387
ja109671f10.1021/ja109671fFALSEhttps://doi.org/10.1021/ja109671fAnderson, HLA Porphyrin Fused to Four Anthracenes2011#N/ATRUE
2388
ja108787s10.1021/ja108787sFALSEhttps://doi.org/10.1021/ja108787sDementin, SJ. Am. Chem. Soc.Hydrogenases are efficient biological catalysts of H-2 oxidation and production. Most of them are inhibited by O-2, and a prerequisite for their use in biotechnological applications under air is to improve their oxygen tolerance. We have previously shown that exchanging the residue at position 74 in the large subunit of the oxygen-sensitive [NiFe] hydrogenase from Desulfovibrio fructosovorans could impact the reaction of the enzyme with O-2 (Dementin, S.; et al. J. Am. Chem. Soc. 2009, 131, 10156-10164; Liebgott, P. P.; et al. Nat. Chem. Biol. 2010, 6, 63-70). This residue, a valine in the wild-type enzyme, located at the bottleneck of the gas channel near the active site, has here been exchanged with a cysteine. A thorough characterization using a combination of kinetic, spectroscopic (EPR, FTIR), and electrochemical studies demonstrates that the V74C mutant has features of the naturally occurring oxygen-tolerant membrane-bound hydrogenases (MBH). The mutant is functional during several minutes under O-2, has impaired H-2-production activity, and has a weaker affinity for CO than the WT. Upon exposure to O-2, it is converted into the more easily reactivatable inactive form, Ni-B, and this inactive state reactivates about 20 times faster than in the WT enzyme. Control experiments carried out with the V74S and V74N mutants indicate that protonation of the position 74 residue is not the reason the mutants reactivate faster than the WT enzyme. The electrochemical behavior of the V74C mutant toward O-2 is intermediate between that of the WT enzyme from D. fructosovorans and the oxygen-tolerant MBH from Aquifex aeolicus.Original Design of an Oxygen-Tolerant [NiFe] Hydrogenase: Major Effect of a Valine-to-Cysteine Mutation near the Active Site73201158#N/ATRUE
2389
ja108426f10.1021/ja108426fFALSEhttps://doi.org/10.1021/ja108426fCaulton, KGThree-Coordinate Ni-II: Tracing the Origin of an Unusual, Facile Si-C(sp(3)) Bond Cleavage in [((Bu2PCH2SiMe2)-Bu-t)(2)N]Ni+2011#N/ATRUE
2390
ja107115q10.1021/ja107115qFALSEHillhouse, GLHydrogen-Atom Abstraction from Ni(I) Phosphido and Amido Complexes Gives Phosphinidene and Imide Ligands2010#N/ATRUE
2391
ja103367e10.1021/ja103367eFALSEhttps://doi.org/10.1021/ja103367eManners, IJ. Am. Chem. Soc.The group 10 bis(phosphine)metalla[1]ferrocenophanes, [{Fe(eta(5)-C5H4)(2)}M(Pn-Bu-3)(2)] [M = Ni (4a), Pd (4b), and Pt (4c)], have been prepared by the reaction of Li-2[Fe(eta(5)-C5H4)(2)].tmeda (5, tmeda = N,N,N',N'-tetramethylethylenediamine) with trans-[MCl2(Pn-Bu-3)(2)] [M = Ni (trans-6a) and Pd (trans-6b)] and cis-[PtCl2(Pn-Bu-3)(2)] (cis-6c), respectively. Single crystal X-ray diffraction revealed highly tilted, strained structures as characterized by a angles of 28.4 degrees (4a), 24.5 degrees (4b), and 25.2 degrees (4c) and a distorted square planar environment for the group 10 metal center. UV/visible spectroscopy and cyClic voltammetry indicated that all three compounds had smaller HOMO-LUMO gaps and were more electron-rich in nature than ferrocene and other comparable [1]ferrocenophanes. DFT calculations suggested that these differences were principally due to the electron-releasing nature of the M(Pn-Bu3)2 metal-ligand fragments. Attempts to induce thermal or anionic ring-opening polymerization of 4a- c were unsuccessful and were complicated by, for example, competing ligand dissociation processes or unfavorable chain propagation. In contrast, these species all reacted rapidly with acids effecting Clean extrusion of the bis(phosphine)metal fragment. Carbon monoxide inserted Cleanly into one of the palladium-carbon bonds of 4b to afford the ring-expanded, acylated product [{Fe(eta(5)-C5H4)(eta(5)-C5H4)(CO))Pd(Pn-Bu-3)(2)] (10). The nickel analogue 4a, however, afforded [Ni(CO)(2)(Pn-Bu-3)(2)] whereas the platinum-bridged complex 4c was inert. Remarkably, all compounds 4a-c were readily oxidized by elemental sulfur to afford the [5,5']bicyClopentadienylidene (pentafulvalene) complexes [{eta(4):eta(0)-C5H4(C5H4)M(Pn-Bu-3)(2)] [M = Ni (11a)] and [(eta(2)-C10H8)M(pn-Bu-3)(2)] [M = pd (11b) and Pt (11c)] by a formal 4-electron oxidation of the carbocyClic ligands. Compounds 11b and 11c represent the first examples of [5,5']bicyClopentadienylidene as a neutral eta(2)-ligand. The relative energies of eta(2)-coordination with respect to that of eta(4):eta(0) bonding were investigated for 11a -c by DFT calculations.Synthesis, Electronic Structure, and Reactivity of Strained Nickel-, Palladium-, and Platinum-Bridged [1]Ferrocenophanesx272010113#N/AFALSE
2392
ja106829k10.1021/ja106829kFALSEhttps://doi.org/10.1021/ja106829kHoveyda, AHJ. Am. Chem. Soc.Catalytic enantioselective allylic substitution (EAS) reactions, which involve the use of Alkyl- or Aryl-substituted Vinylaluminum reagents and afford 1,4-dienes containing a quaternary carbon stereogenic center at their C-3 site, are disClosed. The C-C bond-forming transformations are promoted by 0.5-2.5 mol % of sulfonate bearing chiral bidentate N-heterocyClic carbene (NHC) complexes, furnishing the desired products efficiently (66-97% yield of isolated products) and in high site (>98% S(N)2')- and enantioselectivity [up to 99:1 enantiomer ratio (er)]. To the best of our knowledge, the present report puts forward the first cases of allylic substitution reactions that result in the generation of all-carbon quaternary stereogenic centers through the addition of a Vinyl unit. The Aryl- and Vinyl-substituted Vinylaluminum reagents, which cannot be prepared in high efficiency through direct reaction with diisobutylaluminum hydride, are accessed through a recently introduced Ni-catalyzed reaction of the corresponding terminal alkynes with the same inexpensive metal-hydride agent. Sequential Ni-catalyzed hydrometalations and Cu-catalyzed C-C bond-forming reactions allow for efficient and selective synthesis of a range of enantiomerically enriched EAS products, which cannot be accessed by previously disClosed strategies (due to inefficient Vinylmetal synthesis or low reactivity and/or selectivity with Si-substituted derivatives). The utility of the protocols developed is demonstrated through a concise enantioselective synthesis of natural product bakuchiol.Synthesis of Quaternary Carbon Stereogenic Centers through Enantioselective Cu-Catalyzed Allylic Substitutions with Vinylaluminum Reagents127201058#N/ATRUE
2393
ja103196c10.1021/ja103196cFALSEhttps://doi.org/10.1021/ja103196cClarke, SJJ. Am. Chem. Soc.The response of the superconducting state and crystal structure of LiFeAs to chemical substitutions on both the Li and the Fe sites has been probed using high-resolution X-ray and neutron diffraction measurements, magnetometry, and muon-spin rotation spectroscopy. The superconductivity is extremely sensitive to composition: Li-deficient materials (Li1-yFe1+yAs with Fe substituting for Li) show a very rapid suppression of the superconducting state, which is destroyed when y exceeds 0.02, echoing the behavior of the Fe1+ySe system. Substitution of Fe by small amounts of Co or Ni results in monotonic lowering of the superconducting transition temperature, T-c, and the superfluid stiffness, rho(s), as the electron count increases. T-c is lowered monotonically at a rate of 10 K per 0.1 electrons added per formula unit irrespective of whether the dopant is Co and Ni, and at higher doping levels superconductivity is completely suppressed. These results and the demonstration that the superfluid stiffness in these LiFeAs-derived compounds is higher than in all of the iron pnictide materials underlines the unique position that LiFeAs occupies in this Class.Compositional Control of the Superconducting Properties of LiFeAsx57201041#N/AFALSE
2394
ja102862j10.1021/ja102862jFALSEhttps://doi.org/10.1021/ja102862jBordiga, SJ. Am. Chem. Soc.Two highly porous coordination polymers, containing rare octanuClear hydroxo-nickel Clusters and long bis-pyrazolyl spacers, are shown to possess, after mild thermal treatment, lattice cavities up to 72% of the total crystal volume.Cubic OctanuClear Ni(II) Clusters in Highly Porous Polypyrazolyl-Based Materialsx116201028#N/AFALSE
2395
ja102686u10.1021/ja102686uFALSEhttps://doi.org/10.1021/ja102686uBielawski, CWJ. Am. Chem. Soc.Optimized syntheses for 1,3-dimesitylnaphthoquinimidazolium chloride [1H]Cl and the corresponding silver NHC complex [AgCl(1)] (2) were developed, enabling access to this versatile reagent in near-quantitative yield. Transmetalation from 2 to [NiCl2(PPh3)(2)], trans-[PdCl2(PhCN)(2)], or trans-[PtCl2(PhCN)(2)] afforded the Group 10 complexes trans-[MCl2(1)(2)] (3a-c, M = Ni, Pd, and Pt, respectively) in excellent overall yield (>95%) after three steps from commercially available starting materials. Electrochemical measurements indicated that the E-1/2 and Delta E-1/2 values for the quinone reduction couples were independent of the identity of the bridging transition metal in these complexes. Whereas attempts to isolate the reduced complexes were unsuccessful, UV/vis spectroelectrochemical analysis confirmed that electrochemical reduction of 3a-c in situ afforded optical difference spectra consistent with the formation of the expected reduced species. Complex 3a was found to catalyze the Kumada cross-coupling reaction between PhMgX and a range of bromoarenes at room temperature. Addition of 2 equiv of cobaltocene (with respect to 3a) to the coupling reaction with bromotoluene caused a decrease in catalytic activity (from 4.7 x 10(-5) to 2.7 x 10(-6) s(-1)), which was attributed to the conversion of 3a to an arrested state. Subsequent introduction of ferrocenium tetrafluorB(OH)2rate (2 equiv with respect to 3a) restored a significant degree of catalytic activity (k(obs) = 1.2 x 10(-5) s(-1)). Redox-switching experiments performed over different time scales revealed that the catalyst was stable in the reduced/inactive state and that extended durations in this state did not impede catalytic reActivation upon subsequent oxidation.Arrested Catalysis: Controlling Kumada Coupling Activity via a Redox-Active N-HeterocyClic CarbeneX 1042010119#N/AFALSE
2396
ja106458p10.1021/ja106458pFALSEhttps://doi.org/10.1021/ja106458pDriess, MAn Isolable Bis-Silylene Oxide (Disilylenoxane) and Its Metal Coordination2010#N/ATRUE
2397
ja106266v10.1021/ja106266vFALSEhttps://doi.org/10.1021/ja106266vStosser, RJ. Am. Chem. Soc.An investigation concerning the stepwise reduction of the beta-diketiminato nickel(11) hydride dimer [LNi(mu-H)(2)NiL], 1 (L = [HC(CMeNC6H3(Pr)(2))(2)](-)), has been carried out. While the reaction with one equivalent of potassium graphite, KC8, led to the mixed valent Ni-l/Ni-11 complex K[LNi(mu-H)(2)NiL], 3, treatment of 1 with two equivalents of KC8 surprisingly yielded in the trinuClear complex K-2[LNi(mu-H)(2)Ni(mu-H)(2)NiL], 4, in good yields. The Ni3H4 core contains one Ni-11 and two Ni-1 centers, which are antiferromagnetically coupled so that a singlet ground state results. 4 represents the first structurally characterized molecular compound with three nickel atoms bridged by hydride ligands, and it shows a very interesting chemical behavior: Single-electron oxidation yields in the (Ni2Ni1)-Ni-11 compound K[LNi(mu-H)(2)Ni(mu-H)2NiL), 5, and treatment with CO leads to the elimination of H-2 with formation of the Carbonyl complex K-2[LNi(CO)](2), 6. Beyond that, it could be shown that 4 undergoes HID exchange with deuterated solvents and the deuteride-compound 4-D-4 reacts with H-2 to give back 4. The crystal structures of the novel compounds 3-6 have been determined, and their electronic structures have been investigated by EPA and NMR spectroscopy, magnetic measurements, and DFT calculations.A Reduced beta-Diketiminato-Ligated Ni3H4 Unit Catalyzing H/D Exchange462010124#N/ATRUE
2398
ja102210r10.1021/ja102210rFALSEhttps://doi.org/10.1021/ja102210rKiriy, AJ. Am. Chem. Soc.A walking process of Ni catalysts during Kumada catalyst-transfer polycondensation along polymerizing poly(3-hexylthiophene), P3HT, chains was investigated. To simplify polymer end group identifications, a compound Br-C6H4-Ni(dppe)-Br was prepared and used as an externally addable initiator. Normally, Aryl moieties present in initiators incorporate into the structure of the resulting P3HT as the starting groups. We demonstrate that due to the presence of the C-Br group located in the para-position to the Ni substituent of the initiator, two different polymeric products are formed. One of them is the normal product, that is, P3HT with a para-bromophenyl end group, whereas another one has the phenyl ring inside the P3HT chain. The content of the product with the internal phenyl ring increases with the increase of the polymerization degree. Control experiments demonstrated that no intermolecular catalyst transfer takes place in the conditions used. Such results suggest that catalytic Ni(0) species are able to walk along the polymerizing chain containing many tens of thienyl rings up to the opposite end and can initiate polymerization there. Numerical analysis of a random hopping model was undertaken, which revealed that a combination of a random catalyst walking along the chain and a sticking effect at the end groups is operative in Kumada catalyst-transfer polycondensation.Random Catalyst Walking along Polymerized Poly(3-hexylthlophene) Chains in Kumada Catalyst-Transfer Polycondensationx173201037#N/AFALSE
2399
ja102163d10.1021/ja102163dFALSEhttps://doi.org/10.1021/ja102163dIshida, TJ. Am. Chem. Soc.Two novel copper(II) complexes with tert-butyl 2-pyridyl nitroxide (2pyNO(center dot)), [Cu2+(2pyNO(-))(2PyNO(center dot))](2)(BF4-)(2)(1 center dot BF4) and [Cu2+(2pyNO(-))(2pyNO(center dot))](2)(ClO4-)(2)(1 center dot ClO4), were prepared and structurally characterized. They contained mixed-valent ligands from 2pyNO, whose oxygen atoms were located at equatorial positions of the copper ion. The [Cu2+(2pyNO(-))(2pyNO(center dot))] unit was dimerized by mu-oxo bridges of the anion ligand, giving a zigzag linear spin system involving four paramagnetic S = 1/2 centers. The two compounds are isomorphous in an orthorhombic Pbca space group. Magnetic study revealed that 1 center dot ClO4 showed ferromagnetic copper-radical coupling in all temperature ranges investigated here. On the other hand, 1 center dot BF4 exhibited a structural phase transition at 64 K, where the magnetic susceptibility was drastically dropped on cooling. The copper-radical magnetic couplings were characterized as ferro- and antiferromagnetic for the high- and low-temperature phases, respectively. The crystallographic analysis Clarified that the nitroxide oxygen atom remained at the equatorial position throughout the single-crystal-to-single-crystal phase transition, while the previously known spin-transition-like copper-radical compounds showed conversion of the roles of equatorial and axial positions. The orthogonal arrangement between the copper d sigma and nitroxide pi(star) orbitals is essential for the ferromagnetic coupling, and a slight dislocation of the radical oxygen atom from the chelate plane leads to violation of the orthogonal orbital arrangement, giving a practically diamagnetic low-temperature phase.Ferro- and Antiferromagnetic Coupling Switch Accompanied by Twist Deformation around the Copper(II) and Nitroxide Coordination Bondx58201089#N/AFALSE
2400
ja105408a10.1021/ja105408aFALSEhttps://doi.org/10.1021/ja105408aSlavicek, PJ. Am. Chem. Soc.Electrospray ionization of an aqueous solution of nickel(II) sulfate provides direct experimental evidence for the formation of triple ions of the type [Ni-2(SO4)(H2O)(n)](2+) and [Ni(SO4)(2)](2-), whose existence in aqueous solution has previously been proposed based on relaxation spectroscopy [Chen et al. J. Sol. Chem. 2005, 34, 1045]. Formally, these triple ions are formed by aggregation of the solvated ions Ni2+ and SO42-, respectively, with the neutral ion pair NiSO4. In addition, also higher adducts are observed, e.g. the pentuple ions [Ni-3(SO4)(2)(H2O)(n)](2+) (n = 7-9) and [Ni-2(SO4)(3)](2-), of which the dicationic is extensively hydrated, whereas the anionic is not. The structures of the dinuClear nickel Clusters are derived from ab initio calculations and their infrared spectra are compared with experimental data obtained for the gaseous ions [Ni2SO4(H2O)(5)](2+) and [Ni-2(SO4)(3)](2-), respectively. The calculations show that the structures are crucially controlled by the degree of solvation of nickel ion. Explicit consideration of solvating water molecules within the first coordination sphere suggest that the dicationic triple ion [Ni2SO4](aq)(2+) is bent and thus bears a permanent dipole moment, whereas the [Ni(SO4)(2)](aq)(2-) dianion tends to be quasi-linear. The experimental and theoretical data for the gaseous ions thus support the elegant, but indirect, deductions previously made based on solution-phase studies.Direct Observation of Triple Ions in Aqueous Solutions of Nickel(II) Sulfate: A Molecular Link Between the Gas Phase and Bulk Behavior38201186#N/ATRUE
2401
ja101699a10.1021/ja101699aFALSEhttps://doi.org/10.1021/ja101699aAgapie, TJ. Am. Chem. Soc.Mono- and bimetallic complexes of nickel supported by a terphenyl diphosphine have been synthesized. The reported complexes show diverse metal-arene interactions in the solid state. Reactions of an o,o'-biphenyldiyl dinickel complex with CO and dichloroalkanes lead to fluorene derivatives, indicating the formation of carbon-carbon bonds at a bimetallic moiety.Synthesis and C-C Coupling Reactivity of a DinuClear Ni-I-Ni-I Complex Supported by a Terphenyl Diphosphinex106201024#N/AFALSE
2402
ja101599e10.1021/ja101599eFALSEhttps://doi.org/10.1021/ja101599eStack, TDPFacile C-H Bond Cleavage via a Proton-Coupled Electron Transfer Involving a C-H center dot center dot center dot Cu-II InteractionX2010#N/AFALSE
2403
ja104896b10.1021/ja104896bFALSEhttps://doi.org/10.1021/ja104896bHoveyda, AHJ. Am. Chem. Soc.A method for Ni-catalyzed hydroalumination of terminal alkynes, leading to the formation of alpha-Vinylaluminum isomers efficiently (>98% cony in 2-12 h) and with high selectivity (95% to >98% alpha), is described. Catalytic alpha-selective hydroalumination reactions proceed in the presence of a reagent (diisobutylaluminum hydride; dibal-H) and 3.0 mol % metal complex (Ni(dppp)Cl(2)) that are commercially available and inexpensive. Under the same conditions, but with Ni(PPh(3))(2)Cl(2), hydroalumination becomes highly beta-selective, and, unlike uncatalyzed transformations with dibal-H, generates little or no alkynylaluminum byproducts. All hydrometalation reactions are reliable, operationally simple, and practical and afford an assortment of Vinylaluminums that are otherwise not easily accessible. The derived alpha-Vinyl halides and boronates can be synthesized through direct treatment with the appropriate electrophiles [e.g., Br(2) and methoxy(pinacolato)boron, respectively]. Ni-catalyzed hydroaluminations can be performed with as little as 0.1 mol % catalyst and on gram scale with equally high efficiency and selectivity.alpha-Selective Ni-Catalyzed Hydroalumination of Aryl- and Alkyl-Substituted Terminal Alkynes: Practical Syntheses of Internal Vinyl Aluminums, Halides, or Boronates137201038#N/ATRUE
2404
ja104796a10.1021/ja104796aFALSEhttps://doi.org/10.1021/ja400705aFurster, AProtecting-Group-Free and Catalysis-Based Total Synthesis of the Ecklonialactones2010#N/ATRUE
2405
ja104529610.1021/ja1045296FALSEhttps://doi.org/10.1021/ja1045296Lei, AWJ. Am. Chem. Soc.Transmetalation is the rate-limiting step! The transmetalation between Arylzinc reagents and (ArNiR)-R-II was confirmed as the rate-limiting step in the nickel-catalyzed oxidative coupling reactions. It was proved to be an excellent model allowing the first quantitative measurement of the kinetic rate constants of transmetalation from a live catalytic system. Rate constants from 0.04 to 0.31 M-1 s(-1) were obtained for different Arylzinc reagents under the conditions, and the Activation enthalpy Delta H double dagger was 14.6 kcal/mol for PhZnX. The substituent effect on the transmetalation was also gained for the first time from the catalytic reaction.Transmetalation is the Rate-Limiting Step: Quantitative Kinetic Investigation of Nickel-Catalyzed Oxidative Coupling of Arylzinc Reagents29201020#N/ATRUE
2406
ja100605m10.1021/ja100605mFALSEhttps://doi.org/10.1021/ja100605mOzerov, OVJ. Am. Chem. Soc.TriAlkylsilylium cation equivalents partnered with halogenated carborane anions (such as Et3Si[HCB11H5Cl6]) function as efficient and long-lived catalysts for hydrodehalogenation of C-F, C-Cl, and C-Br bonds with triAlkylsilanes as stoichiometric reagents. Only C(sp(3))-halogen bonds undergo this reaction. The range of C-F bond-containing substrates that participate in this reaction is quite broad and inCludes simple Alkyl fluorides, benzotrifluorides, and compounds with perfluoroAlkyl groups attached to an aliphatic chain. However, CF4 has proven immune to this reaction. Hydrodechlorination was carried out with a series of Alkyl chlorides and benzotrichlorides, and hydrodebromination was studied only with primary Alkyl bromide substrates. Competitive experiments established a pronounced kinetic preference of the catalytic system for Activation of a carbon halogen bond of a lighter halide in primary Alkyl halides. On the contrary, hydrodechlorination of C6F5CCl3 proceeded much faster than hydrodefluorination of C6F5CF3 in one-pot experiments. A solid-state structure of Et3Si[HCB11H5Cl6] was determined by X-ray diffraction methods.Hydrodefluorination and Other Hydrodehalogenation of Aliphatic Carbon-Halogen Bonds Using Silylium CatalysisX151201071#N/AFALSE
2407
ja104158h10.1021/ja104158hFALSEhttps://doi.org/10.1021/ja104158hJones, WDJ. Am. Chem. Soc.The processes of C C and C S bond Cleavage have been studied with the homogeneous organometallic compound [Ni(dippe)H](2) (1). When 1 is reacted with 2-cyanothiophene at room temperature, Cleavage of the nitrile-substituted C S bond occurs, forming the Ni-metallacyCle complex (dippe)Ni(kappa(2)-S,C-SCH=CHCH=C(CN)) (2a), which has been fully characterized by NMR spectroscopy and X-ray diffraction. 2a was converted to the C CN Cleavage product (dippe)Ni(CN)(2-thiophenyl) (3) when heated in solution. On Closer inspection, four other intermediates were observed by P-31 NMR spectroscopy at low temperature. Structures for the intermediates were elucidated through a combination of independent synthesis, theoretical calculations, chemical characterization, and experimental precedent. A kinetic product (dippe)Ni(kappa(2)-S,C-SC(CN)=CHCH=CH) (2b) was formed from Cleavage of the nonsubstituted C S bond, as well as a Ni(0) eta(2)-nitrile intermediate, (dippe)Ni(eta(2)-C,N-2-cyanothiophene) (4), and a dinuClear mixed Ni(0) Ni(II) product (6b). A complete DFT analysis of this system has been carried out to reveal comparative details about the two bond Cleavage transition states.Competitive Carbon-Sulfur vs Carbon-Carbon Bond Activation of 2-Cyanothiophene with [Ni(dippe)H](2)51201055#N/ATRUE
2408
ja104155f10.1021/ja104155fFALSEhttps://doi.org/10.1021/ja104155fNakamura, MJ. Am. Chem. Soc.A novel cross-coupling reaction of Alkyl Aryl sulfides with Aryl Grignard reagents has been achieved to produce the alkenyl-Aryl coupling products in high yields by using catalytic Ni(cod)(2) and a bulky N-heterocyClic carbene ligand, SIPr.Nickel-Catalyzed Alkenylative Cross-Coupling Reaction of Alkyl Sulfides31201025#N/ATRUE
2409
ja104118r10.1021/ja104118rFALSEhttps://doi.org/10.1021/ja104118rMichel, SLJJ. Am. Chem. Soc.The metalloregulatory protein NikR from Helicobacter pylori (HpNikR) is a master regulator of gene expression which both activates and represses specific genes in response to nickel availability. Here, we report the first crystal structure (at 2.37 angstrom resolution) of Ni(II)HpNikR prepared directly from the holo protein. The protein contains four nickel ions located in two distinct coordination environments. Two nickel ions are bound to sites in a four-coordinate square-planar geometry as predicted on the basis of the structures of NikR from Escherichia coli and Pyrococcus horikoshii. The remaining two nickel ions are bound to sites with unexpected 5- or 6-coordination geometries which were previously thought to be involved in nickel incorporation into the protein. The nickel with 5-/6-coordination geometry utilizes three histidines from two separate monomeric HpNikR units along with two or three water molecules as ligands. The spatial location of the nickel in the 5-/6-coordinate site is within approximately 5 angstrom of the expected site if a 4-coordinate square-planar geometry occurred. Two of the histidines that participate as ligands in the 5-/ 6-coordinate site would also participate as ligands if the 4-coordinate site was occupied, making it impossible for both sites to be occupied simultaneously. DFT calculations show that the 5-/6-coordinate geometries are energetically favorable when the local protein environment is inCluded in the calculations. The presence of two distinct coordination environments in HpNikR is suggested to be related to the specificity and binding affinity of this transcription factor for DNA.Holo-Ni(II)HpNikR Is an Asymmetric Tetramer Containing Two Different Nickel-Binding Sites27201063#N/ATRUE
2410
ja103982t10.1021/ja103982tFALSEhttps://doi.org/10.1021/ja103982tGuan, HRJ. Am. Chem. Soc.Nickel hydride with a diphosphinite-based ligand catalyzes the highly efficient reduction of CO(2) with catecholborane, and the hydrolysis of the resulting methoxyboryl species produces CH(3)OH in good yield. The mechanism involves a nickel formate, formaldehyde, and a nickel methoxide as different reduced stages for CO(2). The reaction may also be catalyzed by an air-stable nickel formate.An Efficient Nickel Catalyst for the Reduction of Carbon Dioxide with a Borane304201023#N/ATRUE
2411
ja103296g10.1021/ja103296gFALSEhttps://doi.org/10.1021/ja103296gRoussel, CRidge-Tile-like Chiral Topology: Synthesis, Resolution, and Complete Chiroptical Characterization of Enantiomers of Edge-Sharing BinuClear Square Planar Complexes of Ni(II) Bearing Achiral Ligands2010#N/ATRUE
2412
ja102430d10.1021/ja102430dFALSEhttps://doi.org/10.1021/ja102430dLee, GHJ. Am. Chem. Soc.MononuClear, distorted trigonal bipyramidal [PPN][Ni-III(R)-(P(C6H3-3-SiMe3-2-S)(3))] (R = Me (1); R = Et (2)) were prepared by reaction of [PPN][(NiCl)-Cl-III(P(C6H3-3-SiMe3-2-S)(3))] and CH3MgX/C2H5MgX, individually. EPR, SQUID studies as well as DFT computations reveal that the Ni-III in 1 has a low-spin d(7) electronic configuration in a distorted trigonal bipyramidal ligand field. The Ni-C bond lengths of 1.994(3) angstrom in 1 and 2.015(3) angstrom in 2 are comparable to that in the Ni-III-methyl state of MCR (similar to 2.04 angstrom) (Sarangi, R.; Dey, M.; Ragsdale, S. W. Biochemistry 2009, 48, 3146). Under a CO atmosphere, CO triggers homolytic Cleavage of the Ni-III-CH3 bond in 1 to produce Ni-II-thiolate Carbonyl [PPN][Ni-II(CO)(P(C6H3-3-SiMe3-2-S)(3))] (3). Additionally, protonation of 1 with phenylthiol generates Ni-III-thiolate [PPN][Ni-III(SPh)-(P(C6H3-3-SiMe3-2-S)(3))] (4).MononuClear Ni-III-Alkyl Complexes (Alkyl = Me and Et): Relevance to the Acetyl-CoA Synthase and Methyl-CoM Reductase33201034#N/ATRUE
2413
ja100312510.1021/ja1003125FALSEhttps://doi.org/10.1021/ja1003125Holm, RHJ. Am. Chem. Soc.A singular feature of the catalytic C-Cluster of carbon monoxide dehydrogenase is a sulfide-bridged Ni center dot center dot center dot Fe locus where substrate is bound and transformed in the reversible reaction CO + H2O = CO2 + 2H(+) + 2e(-). A similar structure has been sought in this work. MononuClear planar Ni-II complexes [Ni(pyN(2)(Me2))L](1-) (pyN(2)(Me2) = bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-)) derived from a NNN pincer ligand have been prepared inCluding L = OH- (1) and CN- (7). Complex 1 reacts with ethyl formate and CO2 to form unidentate L = HCO2- (5) and HCO3- (6) products. A binuCleating macrocyCle was prepared which specifically binds Ni-II at a NNN pincer site and five-coordinate Fe-II at a triamine site. The Ni-II macrocyle forms hydroxo (14) and cyanide complexes (15) analogous to 1 and 7. Reaction of 14 with FeCl2 alone and with ethyl formate and 15 with FeCl2 affords molecules with the Ni-II-L-Fe-II bridge unit in which L = mu(2):eta(1)-OH- (17) and mu(2):eta(2)-HCO2- (18) and -CN- (19). All bridges are nonlinear (17, 140.0 degrees; 18, M-O-C 135.9 degrees (Ni), 120.2 degrees (Fe); 19, Ni-C-N 170.3 degrees, Fe-N-C 141.8 degrees) with Ni center dot center dot center dot Fe separations of 3.7-4.8 angstrom. The (NiFeII)-Fe-II complexes, lacking appropriate Ni-Fe-S Cluster structures, are not site analogues, but their synthesis and reactivity provide the first demonstration that molecular Ni-II center dot center dot center dot Fe-II sites and bridges can be attained, a necessity in the biomimetic chemistry of C-Clusters.Reactions of the Terminal Ni-II-OH Group in Substitution and Electrophilic Reactions with Carbon Dioxide and Other Substrates: Structural Definition of Binding Modes in an Intramolecular Ni-II center dot center dot center dot Fe-II Bridged Sitex110201048#N/AFALSE
2414
ja100261z10.1021/ja100261zFALSEhttps://doi.org/10.1021/ja100261zCavallini, MJ. Am. Chem. Soc.Here we describe the synthesis and magnetic characterization of a family of 2D polymetallic oxalate-bridged polymeric networks with general formula [M-II(H2O)(2)](3)[M-III(ox)(3)](2)(18-crown-6)(2) (M-III = Cr, Fe; = Mn, Fe, Co, Ni; 18-crown-6 = C12H24O6). Depending on the nature of the trivalent metal ion, they exhibit ferro- (Cr3+) or ferrimagnetic (Fe3+) ordering in the 3.6-20 K interval. In contrast with most of the oxalate-bridged CPs reported so far, these complexes do not need any additional templating cation for their assembly and represent the first series of oxalate-based polymeric networks which can be considered intrinsically neutral. As previously observed for other crown ether containing oxalate-based coordination polymers, these compounds are soluble in water, whereas they remain nonsoluble in other organic solvents. Furthermore, when these molecular precursors are subjected to a thermally controlled decomposition process, pure phases of mixed oxides with spinel-like structures can be conveniently generated. Among the resulting materials, the (Mn,Co,Fe)304 derivative is particularly remarkable, since it behaves as a magnet at room temperature. Finally, taking advantage of the solubility of these molecular precursors, this room-temperature magnetic oxide has been successfully nanostructured onto a Si(110) substrate via the lithographically controlled wetting (LCW) technique.Polymetallic Oxalate-Based 2D Magnets: Soluble Molecular Precursors for the Nanostructuration of Magnetic Oxidesx52201090#N/AFALSE
2415
ja078298h10.1021/ja078298hFALSEhttps://doi.org/10.1021/ja078298hRoe, DCJ. Am. Chem. Soc.Reaction paths leading to palladium catalyst deActivation during cyanation of haloarenes (eq 1) have been identified and studied. Each key step of the catalytic loop (Scheme 1) can be disrupted by excess cyanide, inCluding ArX oxidative addition, X/CN exchange, and ArCN reductive elimination. The catalytic reaction is terminated via the facile formation of inactive [(CN)(4)Pd](2-), [(CN)(3)PdH](2-), and [(CN)(3)PdAr](2-). Moisture is particularly harmful to the catalysis because of facile CN- hydrolysis to HCN that is highly reactive toward Pd(0). Depending on conditions, the reaction of [(Ph3P)(4)Pd] with HCN in the presence of extra CN- can give rise to [(CN)(4)Pd](2-) and/or the remarkably stable new hydride [(CN)(3)PdH](2-) (NMR, X-ray). The X/CN exchange and reductive elimination steps are vulnerable to excess CN- because of facile phosphine displacement leading to stable [(CN)(3)PdAr](2-) that can undergo ArCN reductive elimination only in the absence of extra CN-. When a quaternary ammonium cation such as [Bu4N](+) is used as a phase-transfer agent for the cyanation reaction, C-N bond Cleavage in the cation can occur via two different processes. In the presence of trace water, CN- hydrolysis yields HCN that reacts with Pd(0) to give [(CN)(3)PdH)(2-). This also releases highly active OH- that causes Hofmann elimination of [Bu4N](+) to give Bu3N, 1-butene, and water. This decomposition mode is therefore catalytic in H2O. Under anhydrous conditions, the formation of a new species, [(CN)(3)PdBu](2-), is observed, and experimental studies suggest that electron-rich mixed cyano phosphine Pd(0) species are responsible for this unusual reaction. A combination of experimental (kinetics, labeling) and computational studies demonstrate that in this case C-N Activation occurs via an S(N)2-type displacement of amine and rule out alternative 3-center C-N oxidative addition or Hofmann elimination processes.Mechanisms of catalyst poisoning in palladium-catalyzed cyanation of haloarenes. Remarkably facile C-N bond Activation in the [(Ph3P)(4)Pd]/[Bu4N](+) CN- systemx1042008124#N/AFALSE
2416
ja078202j10.1021/ja078202jFALSEhttps://doi.org/10.1021/ja078202jHelliwellt, MJ. Am. Chem. Soc.Nickel phosphide, nickel selenide thin films and their heterostructure (Ni0.85Se/Ni2P) were deposited from a newly synthesized single source precursor {Ni[(Pr2P)-Pr-i(S)NP(Se)Pr-i(2)](2)} just by altering the deposition temperature using CVD.The chemical vapor deposition of nickel phosphide or selenide thin films from a single precursorx166200826#N/AFALSE
2417
ja078184610.1021/ja0781846FALSEhttps://doi.org/10.1021/ja0781846Montgomery, JJ. Am. Chem. Soc.Two distinct nickel-catalyzed fully intermolecular three-component couplings are described. The catalytic addition of enals, alkynes, and alcohols provided gamma,delta-unsaturated esters, whereas the catalytic addition of enones, alkynes, and aldehydes provides stereodefined, unsymmetrical 2-allyl-1,3-diketones. An internal redox process allows the reactions to proceed in the absence of reducing agents. On the basis of deuterium-labeling studies, a likely mechanistic pathway is proposed.Fully intermolecular nickel-catalyzed three-component couplings via internal redoxx62200851#N/AFALSE
2418
ja102262v10.1021/ja102262vFALSEhttps://doi.org/10.1021/ja102262vMontgomery, JJ. Am. Chem. Soc.A strategy for catalyst-controlled regioselectivity in aldehyde-alkyne reductive couplings has been developed. This strategy is the first where either regiochemical outcome may be selected for a broad range of couplings, without relying on substrate biases or directing effects. The complementary use of small cyClopropenylidene carbene ligands or highly hindered N-heterocyClic carbene ligands allows the regiochemical reversal with unbiased internal alkynes, aromatic internal alkynes, conjugated enynes, or terminal alkynes.A General Strategy for Regiocontrol in Nickel-Catalyzed Reductive Couplings of Aldehydes and Alkynes119201035#N/ATRUE
2419
ja101704610.1021/ja1017046FALSEhttps://doi.org/10.1021/ja1017046Fu, GCJ. Am. Chem. Soc.A new family of organometallic compounds, organozirconium reagents, are shown to serve as suitable partners in cross-coupling reactions of (activated) secondary Alkyl electrophiles. Thus, the first catalytic method for coupling secondary alpha-bromoketones with alkenylmetal reagents has been developed, specifically, a mild, versatile, and stereoconvergent carbon-carbon bond-forming process that generates potentially labile beta,gamma-unsaturated ketones with good enantioselectivity.Enantioselective Alkenylation via Nickel-Catalyzed Cross-Coupling with Organozirconium Reagents98201015#N/ATRUE
2420
ja101334410.1021/ja1013344FALSEhttps://doi.org/10.1021/ja1013344Britt, RDEPR Evidence for Co(IV) Species Produced During Water Oxidation at Neutral pH2010#N/ATRUE
2421
ja077386z10.1021/ja077386zFALSEhttps://doi.org/10.1021/ja077386zWasielewski, MRJ. Am. Chem. Soc.Understanding how the electronic structures of electron donor-bridge-acceptor (D-B-A) molecules influence the lifetimes of radical ion pairs (RPs) photogenerated within them (D+ center dot-B-A-center dot) is critical to designing and developing molecular systems for solar energy conversion. A general question that often arises is whether the HOMOs or LUMOs of D, B, and A within D+ center dot -B-A-center dot are primarily involved in charge recombination. We have developed a new series of D-B-A molecules consisting of a 3,5-dimetho4-(9-anthracenyl)julolidine (DMJ-An) electron donor linked to a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor via a series of Ph-n oligomers, where n = 1.4, to give DMJ-An-Ph-n-NI. The photoexcited charge transfer state of DMJ-An acts as a high-potential photoreductant to rapidly and nearly quantitatively transfer an electron across the Ph-n bridge to produce a spin-coherent singlet RP (1)(DWJ(+) center dot-An-Ph-n-NI-center dot 0). Subsequent radical pair intersystem crossing yields 3(DMJ(+) center dot-An-Ph-n-NI-center dot). Charge recombination within the triplet RP then gives the neutral triplet state. Time-resolved EPR spectroscopy shows directly that charge recombination of the RP initially produces a spin-polarized triplet state, DMJ-An-Ph-n-3(+)NI, that can only be produced by hole transfer involving the HOMOs of D, B, and A within the D-B-A system. After the initial formation of DMJ-An-Ph-n-3(+)NI, triplet-triplet energy transfer occurs to produce DMJ-3(+)An-Ph-n-NI with rate constants that show a distance dependence consistent with those determined for charge separation and recombination.Direct observation of the preference of hole transfer over electron transfer for radical ion pair recombination in donor-bridge-acceptor moleculesx61200824#N/AFALSE
2422
ja077337m10.1021/ja077337mFALSEhttps://doi.org/10.1021/ja077337mHeyduk, AFJ. Am. Chem. Soc.The new complex, [Zr(pda)(2)](n) (1, pda(2-) = N,N-'-bis(neo-pentyl)-ortho-phenylenediamide, n = 1 or 2), prepared by the reaction of 2 equiv of pdaLi(2) with ZrCl4, reacts rapidly with halogen oxidants to afford the new product ZrX2(disq)(2) (3, X = Cl, Br, I; disq(-) = NAr-bis(neo-pentyl)-ortho-diiminosemiquinonate) in which each redox-active ligand has been oxidized by one electron. The oxidation products 3a-c have been structurally characterized and display an unusual parallel stacked arrangement of the disq(-) ligands in the solid state, with a separation of similar to 3 angstrom. Density functional calculations show a bonding-type interaction between the SOMOs of the disq- ligands to form a unique HOMO while the antibonCling linear combination forms a unique LUMO. This orbital configuration leads to a Closed-shell-singlet ground-state electron configuration (S = 0). Temperature-dependent magnetism measurements indicate a low-lying triplet excited state at similar to 750 cm(-1). In solution, 3a-c show strong disq(-)-based absorption bands that are invariant across the halide series. Taken together these spectroscopic measurements provide experimental values for the one- and two-electron energies that characterize the pi-stacked bonding interaction between the two disqligands.pi(radical)-pi(radical) bonding interactions generated by halogen oxidation of zirconium(IV) redox-active ligand complexesx77200884#N/AFALSE
2423
ja077328d10.1021/ja077328dFALSEDuBois, MRThe role of the second coordination sphere of [Ni((P2N2Bz)-N-Cy)(2)](BF4)(2) in reversible carbon monoxide bindingx2008#N/AFALSE
2424
ja101121j10.1021/ja101121jFALSEhttps://doi.org/10.1021/ja101121jSlawin, AMZJ. Am. Chem. Soc.We report on an unusual Ni-/Cu-mediated alkyne homocoupling reaction, directed through the cavity of a bidentate macrocyClic ligand by chelated metal ions to furnish [2]rotaxanes in excellent (up to 95%) yields. This is the first active metal template reaction to employ an octahedral coordination geometry metal ion, Ni(II), and the study provides some interesting mechanistic insights into the mixed bimetallic reaction mechanism. The mixed-metal catalyst system was discovered serendipitously when Cu(I) was added to a Ni(II)-catalyzed alkyne homocoupling reaction in an attempt to facilitate chloride-acetylide ligand exchange. The role of Cu(I) in the reaction is, in fact, quite different from that originally intended. The effectiveness of having both nickel and copper present can be rationalized by the nature of a pi-activated, sigma-bonded, bimetallic intermediate in which the substitution of Ni(II) for one Cu(I) ion in the Classic bimetallic Glaser reaction mechanism apparently aids reductive elimination of the acetylide ligands. The system may prove useful for the development of general mixed-metal protocols for catalytic alkyne coupling reactions as well as being a highly effective route to rotaxanes with bis-acetylene threads, which are potentially useful for materials applications (insulated molecular wires) and in molecular machines (rigid, nonfolding axles).An Unusual Nickel-Copper-Mediated Alkyne Homocoupling Reaction for the Active-Template Synthesis of [2]Rotaxanes105201092#N/ATRUE
2425
ja076842g10.1021/ja076842gFALSEhttps://doi.org/10.1021/ja076842gChang, CJJ. Am. Chem. Soc.We report the design, syntheses, and oxidation reactivity of a new family of non-heme iron pyrrole complexes. The most reactive congener is capable of activating N2O, an appealing yet challenging oxidant, for oxygen atom transfer. The first generation tpa(Ph)Fe complex reacts with oxygen atom donors to generate a ligand hydroxylated species by intramolecular C-H Activation and oxygenation. The second-generation tpa(Mes)Fe system expands on this reactivity to intermolecular hydrogen atom abstraction chemistry through N2O Activation. The observation of arene C-H hydroxylation and the consumption of external hydrogen atom donors implicates a potent metal-centered oxidant, likely an iron(IV)-oxo species, along these reaction pathways. This work establishes a new coordination platform for high-valent iron reactivity.N2O Activation and oxidation reactivity from a non-heme iron pyrrold platformX79200742#N/AFALSE
2426
ja100962910.1021/ja1009629FALSEhttps://doi.org/10.1021/ja1009629Sun, SHJ. Am. Chem. Soc.We report the structure-controlled synthesis of FePt/MgO NPs and their catalysis for oxygen reduction reaction (ORR) in 0.5 M H2SO4 solution. The synthesis yields fcc-FePt/MgO and fct-FePt/MgO NPs with the MgO coating being readily removed for catalytic studies. The fct-FePt NPs show higher activity and durability than the fcc-FePt in the ORR condition. The results indicate that the fully ordered fct-FePt could serve as a practical Pt-based catalyst for fuel cell applications.Structurally Ordered FePt NanopartiCles and Their Enhanced Catalysis for Oxygen Reduction Reaction359201021#N/ATRUE
2427
ja076333e10.1021/ja076333eFALSEhttps://doi.org/10.1021/ja076333eHainfeld, JFJ. Am. Chem. Soc.We developed a method in preparing size-controllable gold nanopartiCles (Au NPs, 2-6 nm) capped with glutathione by varying the pH (between 5.5 and 8.0) of the solution before reduction. This method is based on the formation of polymeric nanopartiCle precursors, Au(I)-glutathione polymers, which change size and density depending on the pH. Dynamic light scattering, size exClusion chromatography, and UV-vis spectroscopy results suggest that lower pH values favor larger and denser polymeric precursors and higher pH values favor smaller and less dense precursors. Consequently, the larger precursors led to the formation of larger Au NPs, whereas smaller precursors led to the formation of smaller Au NPs. Using this strategy, Au NPs functionalized with nickel(II) nitriloacetate (Ni-NTA) group were prepared by a mixed-ligand approach. These Ni-NTA functionalized Au NPs exhibited specific binding to 6x-histidine-tagged Adenovirus serotype 12 knob proteins, demonstrating their utility in biomolecular labeling applications.Gold nanopartiCle size controlled by polymeric Au(I) thiolate precursor sizex177200843#N/AFALSE
2428
ja100573d10.1021/ja100573dFALSEhttps://doi.org/10.1021/ja100573dNomura, KJ. Am. Chem. Soc.(Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl(2)[2-ArNCH(2)(C(5)H(4)N)] (R = 1-adamantyl (Ad), cyClohexyl (Cy), phenyl), exhibit remarkably high catalytic activities (e.g. TOF = 2 730 000 h(-1) (758 s(-1)) by V(NAd)Cl(2)[2-(2,6-Me(2)C(6)H(3))NCH(2)(C(5)H(4)N)) for ethylene dimerization in the presence of MAO, affording 1-butane exClusively (selectivity 90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity (polymerization vs dimerization), and the electronic nature directly affects the catalytic activity (activity: R = Ad > Cy > Ph).Highly Efficient Dimerization of Ethylene by (Imido)vanadium Complexes Containing (2-Anilidomethyl)pyridine Ligands: Notable Ligand Effect toward Activity and Selectivity62201051#N/ATRUE
2429
ja100572410.1021/ja1005724FALSEMaroney, MJCommunication between the Zinc and Nickel Sites in Dimeric HypA: Metal Recognition and pH Sensing2010#N/ATRUE
2430
ja100564b10.1021/ja100564bFALSEhttps://doi.org/10.1021/ja100564bWeix, DJJ. Am. Chem. Soc.Nickel-Catalyzed Reductive Cross-Coupling of Aryl Halides with Alkyl Halides (vol 132, pg 920, 2010)520103#N/ATRUE
2431
ja100521m10.1021/ja100521mFALSE
van Leeuwen, PWNM
Efficient Bulky Phosphines for the Selective Telomerization of 1,3-Butadiene with Methanol2010#N/ATRUE
2432
ja074834u10.1021/ja074834uFALSEhttps://doi.org/10.1021/ja074834uHe, HJ. Am. Chem. Soc.Zeolite analcime with a core-shell and hollow icositetrahedron architecture was prepared by a one-pot hydrothermal route in the presence of ethylamine and Raney Ni. Detailed investigations on samples at different preparation stages revealed that the growth of the complex single crystalline geometrical structure did not follow the Classic crystal growth route, i.e., a crystal with a highly symmetric morphology (such as polyhedra) is normally developed by attachment of atoms or ions to a nuCleus. A reversed crystal growth process through oriented aggregation of nanocrystallites and surface recrystallization was observed. The whole process can be described by the following four successive steps. (1) Primary analcime nanoplatelets undergo oriented aggregation to yield discus-shaped partiCles. (2) These disci further assemble into polycrystalline microspheres. (3) The relatively large platelets grow into nanorods by consuming the smaller ones, and meanwhile, the surface of the microspheres recrystallizes into a thin single crystalline icositetrahedral shell via Ostwald ripening. (4) Recrystallization continues from the surface to the core at the expense of the nanorods, and the thickness of the monocrystalline shell keeps on increasing until all the nanorods are consumed, leading to hollow single crystalline analcime icositetrahedra. The present work adds new useful information for the understanding of the principles of zeolite growth.Self-construction of core-shell and hollow zeolite analcime icositetrahedra: A reversed crystal growth process via oriented aggregation of nanocrystallites and recrystallization from surface to corex164200748#N/AFALSE
2433
ja100470310.1021/ja1004703FALSEhttps://doi.org/10.1021/ja1004703RajanBabu, TVJ. Am. Chem. Soc.Monosubstituted acyClic (E)-1,3-dienes undergo efficient hydroVinylation giving (Z)-3-Alkylhexa-1,4-dienes upon treatment with catalytic amounts of bidentate phosphine-CoCl2 complexes {[P similar to](CoCl2)} and Me3Al in an atmosphere of ethylene. The regioselectivity Utile reaction (i.e., 1,4- or 1,2-addition) depends on the nature of the ligand and temperature at which the reaction is carried out. Complexes derived from (RR)-DIOP and (SS)-BDDP at 45 C give very high enantioselectivities for several prototypical 1,3-dienes. In sharp contrast to the corresponding Ni(II)-catalyzed hydroVinylation, I-Aryl-substituted 1,3-dienes give almost exClusively achiral linear 1,4-addition products, unless the 2-position is also substituted. Solid-state structures of the precatalysts are presented.Asymmetric HydroVinylation of Unactivated Linear 1,3-Dienes102201042#N/ATRUE
2434
ja100396n10.1021/ja100396nFALSEhttps://doi.org/10.1021/ja100396nHupp, JTJ. Am. Chem. Soc.Nickel bis(dicarbollide) is used as a fast, one-electron outer sphere redox couple in dye-sensitized solar cells. Device performances with this anionic shuttle are investigated with different electrolyte concentrations and additives, using only 0.030 M of the Ni(III) bis(dicarbollide) to efficiently regenerate the ruthenium dye. Atomic layer deposition of Al2O3 on the nanoparticulate TiO2 photoanodes is further used to improve device performances, increasing current densities almost 2-fold and attaining power conversion efficiencies similar to 10x greater than its metallocene analogue, ferrocene/ferrocenium. Open-circuit voltage decay is used to probe the kinetics of the Ni(III)/(IV) bis(dicarbollide) redox couple, and electron interception is found to be similar to 10(3)x slower than ferrocene/ferrocenium, explaining the large discrepancy in open-circuit voltage potentials between these two redox shuttles.Ni(III)/(IV) Bis(dicarbollide) as a Fast, Noncorrosive Redox Shuttle for Dye-Sensitized Solar Cells165201054#N/ATRUE
2435
ja074556z10.1021/ja074556zFALSEhttps://doi.org/10.1021/ja074556zHoffman, BMJ. Am. Chem. Soc.The enzyme methyl coenzyme M reductase (MCR) catalyzes the final step of methane production by methanogenic organisms. The active site contains a Ni-macrocyClic complex, F-430, in which the Ni is in the 1+ oxidation state in the active form, MCRred1. We describe the preparation and spectroscopic characterization of a Ni-methyl species, denoted MCRMe, generated from MCRred1, by reaction with CH3I. EPR and C-13,1,2H pulsed ENDOR spectra of methyl isotopologues (CH3, CD3, (CH3)-C-13) umambiguously establish the presence of CH3-Ni(III)(M) moiety. They explain why both MCRred1, and MCRMe have d(x), (2)-y 2 odd-electrons although formally having Ni(I) in the former and Ni(M) in the latter. The simple MO description further gives a simple explanation to the small transfer of spin density (similar to 1%) from Ni to methyl. The MCRMe species undergoes conversion to methane and to methyl-SCoM, indicating its catalytic competence as an intermediate in methanogenesis.Biochemical and spectroscopic studies of the electronic structure and reactivity of a methyl-ni species formed on methyl-coenzyme M reductasex51200724#N/AFALSE
2436
ja074125g10.1021/ja074125gFALSEhttps://doi.org/10.1021/ja074125gGunnoe, TBJ. Am. Chem. Soc.Recent reports of 1,2-addition of C-H bonds across Ru-X (X = amido, hydroxo) bonds of TpRu-(PMe3)X fragments {Tp = hydridotris(pyrazolyl)borate suggest opportunities for the development of new catalytic cyCles for hydrocarbon functionalization. In order to enhance understanding of these transformations, computational examinations of the efficacy of model d(6) transition metal complexes of the form [(Tab)M-(PH3)(2) X](q) (Tab = tris-azo-borate; X = OH, NH2; q = -1 to +2; M = Tc-I, Re-I, Ru-II, Co-III, Ni-IV, Nt(IV), Pt-IV) for the Activation of benzene C-H bonds, as well as the potential for their incorporation into catalytic functionalization cyCles, are presented. For the benzene C-H Activation reaction steps, kite-shaped transition states were located and found to have relatively little metal-hydrogen interaction. the C-H Activation process is best described as a metal-mediated proton transfer in which the metal center and ligand X function as an activating electrophile and intramolecular base, respectively. While the metal plays a primary role in controlling the kinetics and thermodynamics of the reaction coordinate for C-H Activation/ functionalization, the ligand X also influences the energetics. On the basis of three thermodynamic criteria characterizing salient energetic aspects of the proposed catalytic cyCle and the detailed computational studies reported herein, late transition metal complexes (e.g., Pt, Co, etc.) in the d(6) electron configuration {especially the TabCo(PH3)(2)(OH)(+) complex and related Co(Ill) systems} are predicted to be the most promising for further catalyst investigation.Activation of carbon-hydrogen bonds via 1,2-addition across M-X (X = OH or NH2) bonds of d(6) transition metals as a potential key step in hydrocarbon functionalization: A computational studyx712007133#N/AFALSE
2437
ja073947a10.1021/ja073947aFALSEhttps://doi.org/10.1021/ja073947aSolomon, EIJ. Am. Chem. Soc.The multicopper oxidases (MCOs) utilize a blue type 1 (T1) copper site and a trinuClear Cu Cluster composed of a type 2 T2) and a binuClear type 3 T3) site that together catalyze the four-electron reduction of O-2 to H2O. Reaction of the fully reduced enzyme with O-2 proceeds via two sequential two-electron steps generating the peroxy intermediate (PI) and the native intermediate (NI). While a detailed description of the geometric and electronic structure of NI has been developed, this has been more elusive for PI largely due to the diamagnetic nature of its ground state. Density functional theory (DFT) calculations have been used to correlate to spectroscopic data to generate a description of the geometric and electronic structure of PI. A highly conserved Carbonylate residue near the T2 site is found to play a critical role in stabilizing the PI structure, which induces oxidation of the T2 and one T3 Cu center and strong superexchange stabilization via the peroxide bridge, allowing irreversible binding of O-2 at the trinuClear Cu site. Correlation of PI to NI is achieved using a two-dimensional potential energy surface generated to describe the catalytic two-electron reduction of the peroxide O-O bond by the MCOs. It is found that the reaction is thermodynamically driven by the relative stability of NI and the involvement of the simultaneous two-electron-transfer process. A low Activation barrier (calculated similar to 5-6 kcal/mol and experimental similar to 3-5 kcal/mol) is produced by the triangular topology of the trinuClear Cu Cluster site, as this symmetry provides good donor-acceptor frontier molecular orbital (FMO) overlap. Finally, the O-O bond Cleavage in the trinuClear Cu Cluster can be achieved via either a proton-assisted or a proton-unassisted process, allowing the MCOs to function over a wide range of pH. It is found that while the proton helps to stabilize the acceptor O2(2)-sigma* orbital in the proton-assisted process for better donor-acceptor FMO overlap, the third oxidized Cu center in the trinuClear site assumes the role as a Lewis acid in the proton-unassisted process for similarly efficient O-O bond Cleavage.Electronic structure of the peroxy intermediate and its correlation to the native intermediate in the multicopper oxidases: Insights into the reductive Cleavage of the O-O bondx56200760#N/AFALSE
2438
ja073900p10.1021/ja073900pFALSEhttps://doi.org/10.1021/ja073900pFox, JMTrans-cyClohexane-1,2-diamine is a weak director of absolute helicity in chiral Nickel-Salen complexesx2007#N/AFALSE
2439
ja073643o10.1021/ja073643oFALSEhttps://doi.org/10.1021/ja073643oArmstrong, FAJ. Am. Chem. Soc.The Ni-containing carbon monoxide dehydrogenase I from Carboxydothermus hydrogenoformans adsorbed on a pyrolytic graphite edge electrode catalyzes rapid CO2/CO interconversions at the thermodynamic potential.Rapid and efficient electrocatalytic CO2/CO interconversions by Carboxydothermus hydrogenoformans CO dehydrogenase I on an electrode
Electrocatalytic
124200717#N/AFALSE
2440
ja077976x10.1021/ja077976xFALSEhttps://doi.org/10.1021/ja077976xLubitz, WJ. Am. Chem. Soc.Electron double resonance-detected NMR (EDNMR) is introduced as a powerful technique to directly measure metal hyperfine interactions in the active sites of metalloproteins. Measurement of these quantities by electron nuClear double resonance is usually difficult because of fast relaxation times and large anisotropic (dipolar) hyperfine couplings. In EDNMR, electron paramagnetic resonance (EPR) 'forbidden' transitions are excited, which become EPR allowed to some extent because of the presence of a large dipolar hyperfine and possibly quadrupole interaction. The usefulness of EDNMR is demonstrated with measurements on Ni-61-enriched hydrogenase of D. vulgaris Miyazaki F in the Ni-B state.Electron-electron double resonance-detected NMR to measure metal hyperfine interactions: Ni-61 in the Ni-B state of the [NiFe] hydrogenase of Desulfovibrio vulgaris Miyazaki F24200824#N/ATRUE
2441
ja073565510.1021/ja0735655Kim, DPhotophysics of meso-beta doubly linked Ni(II) porphyrin arrays: Large two-photon absorption cross-section and fast energy relaxation dynamicsPhotocatalyst2007#N/AFALSE
2442
ja077762f10.1021/ja077762fFALSERosseinsky, MJModular construction of oxide structures-compositional control of transition metal coordination environments2008#N/ATRUE
2443
ja077501610.1021/ja0775016FALSEhttps://doi.org/10.1021/ja306260bConticello, VPDesign of a selective metal ion switch for self-assembly of peptide-based fibrils2008#N/ATRUE
2444
ja072619810.1021/ja0726198FALSEhttps://doi.org/10.1021/ja0726198Zheng, LSJ. Am. Chem. Soc.A structurally fascinating Keplerate magnetic Cluster featuring an icosidodecahedron of Ni(II) ions encapsulating a dodecahedron of La(III) ions was assembled under hydrothermal conditions starting with La(NO3)(3), Ni(NO3)(2), and iminodiacetic acid. The cage-like arrangement of the two distinct sets of metal ions manifests the beauty of symmetry as both ideally possess icosahedral (I-h) symmetry, the highest possible symmetry for molecules. The Cluster constitutes a framework of Ni(II) centers with an unusual spin topology. Interesting ferromagnetic interactions between the Ni(II) ions upon lowering the temperature from 300 to 2 K were revealed.A keplerate magnetic Cluster featuring an icosidodecahedron of Ni(II) ions encapsulating a dodecahedron of La(III) ionsx175200728#N/AFALSE
2445
ja072580710.1021/ja0725807FALSEhttps://doi.org/10.1021/ja0725807van Slageren, JJ. Am. Chem. Soc.Spin Hamiltonian parameters for a ferromagnetically coupled dinuClear Ni(II) complex [Ni-2(en)(4)Cl-2]Cl-2: J = +9.66 cm(-1), g = 2.242, D-A = -4.78 cm(-1), D-AB = -0.64 cm(-1) and zj = -0.402 cm(-1) were reliably determined from a powder sample by simultaneously fitting them to magnetic data and tunable-frequency high-field EPR resonances. The importance of employing both techniques is underscored in view of the weak-exchange limit in this particular system. The parameters and the novel methodology developed in obtaining them will serve to better understand magnetic properties of more complicated transition metal Clusters.Definitive determination of zero-field splitting and exchange interactions in a Ni(II) dimer: Investigation of [Ni-2(en)(4)Cl-2]Cl-2 using magnetization and tunable-frequency high-field electron paramagnetic resonancex50200710#N/AFALSE
2446
ja072504410.1021/ja0725044FALSEhttps://doi.org/10.1021/ja0725044Long, JRJ. Am. Chem. Soc.The homoleptic dimer complex [U(Me(2)PZ)(4)](2) (Me(2)PZ- = 3,5-dimethylpyrazolate) was obtained upon reacting UCl4 with KMe(2)PZ in THF, followed by extraction into toluene. The structure of the dimer consists of two U-IV centers, each coordinated in a pseudo trigonal bipyramidal geometry, connected through two bridging Me(2)Pz(-) ligands. Bases are capable of Cleaving the dimer; for example, reaction with THF affords the mononuClear complex (Me(2)PZ)(4)U(THF). More importantly, the dimer can be Cleaved via insertion of terminal chloride ligands, such that reactions with (cyClam)MCl2 (M = Ni, Cu, Zn; cyClam = 1,4,8,11-tetraazacyClotetradecane) in dichloromethane generate the linear, chloride-bridged Clusters (cyClam)M[((sic)Cl-L)U(Me(2)Pz)(4)](2). variable temperature magnetic susceptibility data were collected for all three Clusters to probe any possible magnetic exchange coupling. The data for the Cluster centered by an S = 0 Zn-II ion exhibit behavior typical of UIV complexes, with chi T-M decreasing steadily as the temperature drops. Data for the CuU2 Cluster show a parallel variance with temperature, indicating the absence of any magnetic exchange coupling. In contrast, subtracting the ZnU2 data from the NiU2 data exposes a rise in chi T-M with decreasing temperature, suggesting weak ferromagnetic coupling between the Ni-II (S = 1) and U-IV centers. Employing a simple spin-only exchange model, a lower bound for the coupling constant was estimated at J = 2.3 cm(-1). Consistent with a simple superexchange mechanism for the coupling, density functional theory calculations performed on a [(Me(2)Pz)(4)UCl](-) fragment of the Cluster show the spin to reside in 5f(xyz) and 5f(Z) (x 2(-y) (2)) orbitals, exhibiting delta symmetry with respect to the U-Cl bond. Low-temperature magnetization data collected for NiU2 suggest the presence of a large axial zero-field splitting; however, ac magnetic susceptibility experiments gave no indication of single-molecule magnet behavior.Magnetic exchange coupling in chloride-bridged 5f-3d heterometallic complexes generated via insertion into a Uranium(IV) dimethylpyrazolate dimerx58200744#N/AFALSE
2447
ja077141m10.1021/ja077141mFALSEhttps://doi.org/10.1021/ja077141mHancock, RDEnhanced metal ion selectivity of 2,9-di-(pyrid-2-yl)-1,10-phenanthroline and its use as a fluorescent sensor for cadmium(II)2008#N/ATRUE
2448
ja071744g10.1021/ja071744gFALSEhttps://doi.org/10.1021/ja071744gTolman, WBJ. Am. Chem. Soc.Heterobimetallic CuPd and CuPt bis(mu-oxo) complexes have been prepared by the reaction of (PPh3)(2)MO2 (M = Pd, Pt) with LCu(I) precursors (L = beta-diketiminate and di- and triamine ligands) and characterized by low-temperature UV-vis, resonance Raman, and H-1 and P-31{H-1} NMR spectroscopy in conjunction with DFT calculations. The complexes decompose upon warming to yield OPPh3, and in one case this was shown to occur by an intramolecular process through crossover experiments using double-labeling (oxo and phosphine). The reactivity of one of the complexes, (LCu)-Cu-Me2(mu-O)(2)Pt(PPh3)(2) (L-Me2 = beta-diketiminate), with a variety of reagents inCluding CO2, 2,4-di-tert-butylphenol, 2,4-di-tert-butylphenolate, [NH4][PF6], and dihydroanthracene, was compared to that of homometallic Pt-2 and Cu-2 counterparts. Unlike typical [Cu-2(mu-O)(2)](2+) cores which have electrophilic oxo groups, the oxo groups in the [Cu(mu-O)(2)Pt](+) core behave as bases and nuCleophiles, similar to previously described Pt-2 compounds. In addition, however, the [Cu(mu-O)(2)Pt](+) core is capable of oxidatively coupling 2,4-di-tert-butylphenol and 2,4-di-tert-butylphenolate. Theoretical evaluation of the electron affinities, basicities, and H-atom transfer kinetics and thermodynamics of the Cu-2 and CuM (M = Pd, Pt) cores showed that the latter are more basic and form stronger O-H bonds.Heterobimetallic dioxygen Activation: Synthesis and reactivity of mixed Cu-Pd and Cu-Pt bis(mu-oxo) complexesx48200794#N/AFALSE
2449
ja071706x10.1021/ja071706xFALSEhttps://doi.org/10.1021/ja071706xMcQuade, DTJ. Am. Chem. Soc.In this paper, we describe the development and application of a multistep one-pot reaction that is made possible by the site isolation of two otherwise incompatible catalysts. We prepared a microencapsulated amine catalyst by interfacial polymerization and used it in conjunction with a nickel-based catalyst for the transformation of an aldehyde to a Michael adduct via a nitroalkene intermediate. The amine-catalyzed conversion of an aldehyde to a nitroalkene was found to proceed through an imine rather than a nitroalcohol. Kinetic studies indicated that the reaction is first order in both the nickel catalyst and the shell of the encapsulated amine catalyst. Furthermore, we provide evidence against interaction between amine and nickel catalysts and present kinetic data that demonstrates that there is a rate enhancement of the Michael addition due to the urea groups on the surface of the microencapsulated catalyst. We applied our one-pot reaction to the development of a new synthetic route for pregabalin that proceeds with an overall yield of 74%.Mechanism and application of a microcapsule enabled multicatalyst reactionx103200720#N/AFALSE
2450
ja071343110.1021/ja0713431FALSEhttps://doi.org/10.1021/ja0713431Kakiuchi, FJ. Am. Chem. Soc.The RuH2(CO)(PPh3)(3)-catalyzed reaction of 2-amino-6-methylacetophenone with phenylboronic acid 2,2-dimethyl-1,3-propanediol ester in refluxing toluene gave the corresponding phenylation product in 83% yield via Aryl carbon-nitrogen bond Cleavage. This reaction involves two notable features: (1) the coupling proceeds via the oxidative addition of an Aryl carbon-nitrogen bond in anilines to the ruthenium complex, and (2) C-C bond formation takes place via transmetalation between the Ru-NR2 species and organB(OH)2ronates.Ruthenium-catalyzed carbon-carbon bond formation via the Cleavage of an unreactive Aryl carbon-nitrogen bond in aniline derivatives with organB(OH)2ronatesx151200728#N/AFALSE
2451
ja071201710.1021/ja0712017FALSEhttps://doi.org/10.1021/ja0712017Rajca, SJ. Am. Chem. Soc.Nitroxide diradicals, in which nitroxides are annelated to m-phenylene forming tricyClic benzobisoxazine-like structures, have been synthesized and characterized by X-ray crystallography, magnetic resonance (EPR and H-1 NMR) spectroscopy, as well as magnetic studies in solution and in solid state. For the octamethyl derivative of benzobisoxazine nitroxide diradical, the conformationally constrained nitroxide moieties are coplanar with the m-phenylene, leading to large values of 2J (2J/k > 200 K in solution and 2J/k > 300 K in the solid state). For the diradical, in which all ortho and para positions of the m-phenylene are sterically shielded, distortion of the nitroxide moieties from coplanarity is moderate, such that the singlet-triplet gaps remain large in both solution (2J/k > 200 K) and the solid state (2J/k approximate to 400-800 K), though an onset of thermal depopulation of the triplet ground state is detectable near room temperature. These diradicals have robust triplet ground states with strong ferromagnetic coupling and good stability at ambient conditions. Magnetic behavior of the nitroxide diradicals at low temperature is best fit to the model of one-dimensional S = 1 Heisenberg chains with intrachain antiferromagnetic coupling. The antiferromagnetic coupling between the S = 1 diradicals may be associated with the methyl nitroxide C-H- - -O contacts, inCluding nonClassical hydrogen bonds. These unprecedented organic S = 1 antiferromagnetic chains are highly isotropic, compared to those of the extensively studied Ni(II)-based chains.Conformationally constrained, stable, triplet ground state (S=1) nitroxide diradicals. Antiferromagnetic chains of S=1 diradicalsx63200774#N/AFALSE
2452
ja071086010.1021/ja0710860FALSEhttps://doi.org/10.1021/ja0710860Power, PPJ. Am. Chem. Soc.Monomeric, two-coordinate, univalent, Aryl chromium(I) species [(3,5-Pr-i(2)-Ar*)Cr(L)] (L = THF, PMe3) have been synthesized with use of a very bulky terphenyl ligand which prevents Cr-Cr bond formation.Monomeric, two-coordinate, univalent chromium(I) compounds: Steric prevention of metal-metal bond formationx51200723#N/AFALSE
2453
ja071076z10.1021/ja071076zFALSEhttps://doi.org/10.1021/ja071076zWengel, JJ. Am. Chem. Soc.Herein we describe the reversible changing of DNA duplex thermal stability by exploiting transition metal complexation phenomena. A terpyridine ligand was conjugated to the N2'-atoms of 2'-amino-2'-deoxyuridine and its locked counterpart 2'-amino-LNA, and these metal-complexing monomers were incorporated into oligodeoxyribonuCleotides. Upon addition of varying amounts of transition metal ions, the thermal stability of DNA duplexes containing these terpyridine-functionalized units in different constitutions was affected to different degrees (Delta T-m values = -15.5 to +49.0 degrees C, relative to the unmodified duplex). The most pronounced effects were observed when two complexing monomers were positioned in opposite strands. Addition of 1 equiv of Ni2+ to such a system induced extraordinary duplex stabilization. Molecular modeling studies suggest, as an explanation for this phenomenon, formation of nickel-mediated interstrand linkages in the minor groove. Addition of an excess of metal ions resulted in largely decreased T-m values. Alternating addition of metal ions and EDTA demonstrated reversibility of metal ion-induced changes in hybridization strength, proving that the described approach provides an efficient method for duplex stability modulation.Effective modulation of DNA duplex stability by reversible transition metal complex formation in the minor groovex53200766#N/AFALSE
2454
ja071030610.1021/ja0710306FALSEhttps://doi.org/10.1021/ja0710306Kiriy, AJ. Am. Chem. Soc.We describe a new method to grow conductive polymer (CP) brushes of regioregular head-to-tail poly(3-Alkylthiophenes) (P3AT) via surface-initiated polycondensation of 2-bromo-5-chloromagnesio-3-Alkylthiophene. A simple procedure for the preparation of the Ni(II) macroinitiator by the reaction of Ni(PPh3)(4) with photocross-linked poly-4-bromostyrene films was developed. Exposure of the initiator layers to the monomer solution leads to selective chain growth polycondensation of the monomer from the surface, resulting in P3AT brushes in a very economical way. In contrast to the P3AT films prepared by traditional solvent casting methods, our approach leads to mechanically robust CP films, stable against delamination. We believe that our approach will be helpful in the fabrication of all-plastic devices.Conductive polymer brushes of regioregular head-to-tail poly(3-Alkylthiophenes) via catalyst-transfer surface-initiated polycondensationx164200729#N/AFALSE
2455
ja076762c10.1021/ja076762cFALSEhttps://doi.org/10.1021/ja076762cChristensen, CHIndirect, reversible high-density hydrogen storage in compact metal ammine salts2008#N/ATRUE
2456
ja070759b10.1021/ja070759bFALSEhttps://doi.org/10.1021/ja070759bCrossley, MJJ. Am. Chem. Soc.Porphyrin-2,3-diones and porphyrin-2,3,7,8- and porphyrin-2,3,12,13-tetraones were shown to have a redox-active unit that can function independently of the macrocyCle at large. Electroreduction of 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin-2,3-diones [(P-dione)M] and the corresponding -2,3,12,13-tetraones [L-(P-tetraone)M] and -2,3,7,8-tetraones [C-(P-tetraone)M], where M = 2H, Cu-II, Zn-II, Ni-II, and Pd-II was investigated and the products were characterized by ESR and thin-layer UV-visible spectroelectrochemistry. Electrochemical and spectroelectrochemical data show that the first two reductions of the porphyrin-diones and the first three reductions of the porphyrin-tetraones occur at the dione units. This was confirmed by ESR spectra of first reduction products which show that the electron spin is totally localized on a semidione unit, independent of the central metal ion and of the number and location of dione units. ESR spectra of the radical anions derived from free-base porphyrin-2,3-dione [(P-dione)2H] and porphyrin-2,3,12,13-tetraone [L-(P-tetraone)2H] confirm the trans-arrangement of the two inner protons and their location on nonsubstituted pyrrolic rings, thereby maintaining an 18-atom 18-pi electron bacteriochlorin-like aromatic delocalization pathway. The redox unit is not similarly isolated in the corner free-base porphyrin-2,3,7,8-tetraone [C-(P-tetraone)2H]. A one-electron reduction of C-(P-tetraone)2H leads to the formation of a tautomer with trans inner hydrogens with one residing on the N of the ring with the reduced unit as the only detectable product. This process is favorable because it creates a more delocalized 18-atom 18-pi electron aromatic pathway. This result is consistent with the measured redox potentials which show the first reduction of C-(P-tetraone)2H to be substantially easier than (P-dione)2H or L-(P-tetraone)2H.Porphyrin-diones and porphyrin-tetraones: Reversible redox units being localized within the porphyrin macrocyCle and their effect on tautomerismx22200776#N/AFALSE
2457
ja076304410.1021/ja0763044FALSEhttps://doi.org/10.1021/ja0763044Christy, JPJ. Am. Chem. Soc.The Ni(0)-catalyzed [2 + 2 + 2 + 2] cyCloadditions of 1,6- and 1,7-diynes are shown to provide an efficient and selective method for the preparation of 1,2,5,6-tetrasubstituted cyClooctatetraenes; (COTs). Catalysts and conditions are described that favor in all cases COT formation over competing [2 + 2 + 2) cyCloadditions. A hitherto unexplored crossed reaction is also described, providing access to non-symmetrical COTs.Nickel(0)-catalyzed [2+2+2+2] cyCloadditions of terminal diynes for the synthesis of substituted cyClooctatetraenes53200734#N/ATRUE
2458
ja070508310.1021/ja0705083FALSEhttps://doi.org/10.1021/ja0705083Cowan, JAJ. Am. Chem. Soc.The DNA Cleavage chemistry of a series of metallopeptides based on the amino-terminal Cu and Ni (ATCUN) binding motif of proteins has been studied. Specifically, the impact of the positioning of charged Lys side chains and their stereochemistry on metal reduction potentials and DNA Cleavage reactivity have been quantitatively evaluated. Both Cu and Ni metallopeptides show a general increase in reactivity toward DNA with an increasing number of Lys residues, while a corresponding decrease in complex reduction potential reflects the enhanced sigma-donor character of the Lys side chain relative to that of Gly. Placement of Lys at the first position in the tripeptide ligand sequence resulted in a greater increase in DNA Cleavage reactivity, relative to placement at the second position, while a switch from an L-Lys to a D-Lys typically resulted in enhanced reactivity, as well as perturbations of reduction potential. In the case of Cu peptides, reactivity was enhanced with both increasing positive charge density on the peptide and stabilization of the Cu3+ state. However, for Ni peptides, while the general trends are the same, the correlation with redox behavior was less pronounced. Most likely these differences in specific trends for the Cu and Ni complexes reflect the distinct coordination preferences for Cu3+/2+ and Ni3+/2+ oxidation states, and the consequent distinct positioning of metal-associated reactive oxygen species, as well as the orientation of the DNA-associated complex. Thus, the amino acid composition and stereochemistry of ATCUN metallopeptides can tune the intrinsic reactivities of these systems (their ability to promote formation and activity of metal-associated ROS) as well as their overall structural features, and both of these aspects appear to influence their reactivity and efficiency of DNA strand scission.Influence of stereochemistry and redox potentials on the single- and double-strand DNA Cleavage efficiency of Cu(II)center dot and Ni(II)center dot Lys-Gly-His-derived ATCUN metallopeptidesx118200749#N/AFALSE
2459
ja075630g10.1021/ja075630gFALSEhttps://doi.org/10.1021/ja075630gSadighi, JPJ. Am. Chem. Soc.The treatment of [(IPr)Ni(mu-Cl)](2) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with NaOt -Bu and then pinB-Bpin (bis (pinacolato)diboron) gives rise to a mono-NHC-Ni(0) complex, which dimerizes upon crystallization. The same product is prepared by the treatment of [(IPr)Ni(mu-Cl)](2) with Li(BEt)(3)H, or with NaOt -Bu and then HSi(OEt)(3). The treatment of [(IPr)Ni](2) or its monomer with CO2 reduces CO2 to CO generating [(IPr)Ni](2)(mu-CO)(mu eta(2),eta(2)-CO2). This compound represents an unprecedented symmetric double-bridging mode Of CO2.Generation of a doubly bridging CO2 ligand and deoxygenation of CO2 by an (NHC)Ni(O) complex104200737#N/ATRUE
2460
ja070264m10.1021/ja070264mFALSEhttps://doi.org/10.1021/ja070264mChen, JGJ. Am. Chem. Soc.In the current study we have performed experimental studies and density functional theory (DFT) modeling to investigate the selective hydrogenation of the CO bond in acrolein on two bimetallic surface structures, the subsurface Pt-Ni-Pt(111) and surface Ni-Pt-Pt(111). We have observed for the first time the production of the desirable unsaturated alcohol (2-propenol) on Pt-Ni-Pt(111) under ultra-high vacuum conditions. Furthermore, our DFT modeling revealed a general trend in the binding energy and bonding configuration of acrolein with the surface d-band center of Pt-Ni-Pt(111), Ni-Pt-Pt(111), and Pt(111), suggesting the possibility of using the value of the surface d-band center as a parameter to predict other bimetallic surfaces for the selective hydrogenation of acrolein.Selective hydrogenation of the CO bond in acrolein through the architecture of bimetallic surface structuresx105200724#N/AFALSE
2461
ja075106+10.1021/ja075106+FALSEhttps://doi.org/10.1021/ja075106+Tomas, MJ. Am. Chem. Soc.A broad range of substituted 2-cyClopentenone derivatives 3-6 are synthesized by the nickel-(0)-mediated [3 + 2] cyClization reaction of chromium alkenyl(methoxy)carbene complexes 1 and internal alkynes 2. The reaction takes place with complete regioselectivity with both unactivated alkynes and activated alkynes (electron-withdrawing and electron-donating substituted alkynes). Representative cyCloadducts containing boron and tin substituents are further demonstrated to be active partners in Classical Pd-catalyzed C-C coupling processes to allow the production of 2-Aryl- and 2-alkynyl-substituted cyClopentenones 9-13.A general and regioselective synthesis of cyClopentenone derivatives through nickel(0)-mediated [3+2] cyClization of alkenyl Fischer carbene complexes and internal alkynes43200749#N/ATRUE
2462
ja074922e10.1021/ja074922eFALSEhttps://doi.org/10.1021/ja074922eVogt, DJ. Am. Chem. Soc.A triptycene-based diphosphine ligand was synthesized in good yield following a new route. The corresponding Pt(II)- and Ni(0)complexes were characterized. In butadiene hydrocyanation the tript-PPh2Ni(cod) catalyst leads to exceptionally high selectivities for the linear product 3-pentenenitrile, combining high activity for both hydrocyanation and isomerization. This one-step procedure could be the key toward process intensification.Highly selective hydrocyanation of butadiene toward 3-pentenenitrile81200726#N/ATRUE
2463
ja069166b10.1021/ja069166bFALSEhttps://doi.org/10.1021/ja069166bKitagawa, SReversible water-induced magnetic and structural conversion of a flexible microporous Ni(II)Fe(III) ferromagnetx2007#N/AFALSE
2464
ja074706610.1021/ja0747066FALSEhttps://doi.org/10.1021/ja0747066Cano, JJ. Am. Chem. Soc.Self-assembly of the ligands N,N'-1,5-naphthalenebis(oxamate) (1,5-naba) and N,N'-2,6'-anthracenebis(oxamate) (2,6-anba) by Cu-II ions affords the two new dicopper(II) metal lacyClophanes 2a and 3b, whereby the metal centers are connected by double naphthalene- and anthracenediamidate bridges with alpha,alpha' and beta,beta' substitution patterns, respectively. Despite the largely different intermetallic distances of 8.3 angstrom (2a) and 12.3 angstrom (3b), magnetic susceptibility measurements show a moderately strong antiferromagnetic coupling with rather similar J values in the range from -20.5 to -20.7 (2a) and from -21.2 to -23.0 (3b) cm(-1) (H= -J S-1 center dot S-2; S-1 = S-2 =1/2). Density functional theory calculations on the two series of dicopper(II) metal lacyClophanes 1a-10a and 1b-10b with linear alpha,alpha'- and beta,beta'-disubstituted oligoacenediamidate bridges, respectively, confirm the better efficiency of the latter substitution pattern on long-range magnetic coupling. More importantly, they predict a unprecedented wirelike magnetic behavior for the longest members of the series with octacene through decacene spacers (J values up to +3.0 cm(-1) for intermetallic distances reaching 28.8 angstrom).Structure and magnetism of dinuClear Copper(II) metallacyClophanes with oligoacenebis(oxamate) bridging ligands: Theoretical predictions on wirelike magnetic coupling58200872#N/ATRUE
2465
ja068782510.1021/ja0687825FALSEhttps://doi.org/10.1021/ja0687825Kato, RJ. Am. Chem. Soc.The supramolecular conductor (Me-3,5-DIP)[Ni(dmit)(2)](2), which was prepared by electrochemical oxidation, consists of two crystallographically independent layers of Ni(dmit)(2) anions (Layers I and II). The tight-binding band calculation suggests that Layer I is in a Mott insulating state to inClude localized spins, and Layer II displays two-dimensional metallic conduction. The coexistence of the two contrastive molecular pi-electrons of Ni(dmit)(2) anions is evidenced by electrical resistivity and magnetic susceptibility measurements.Coexistence of conducting and magnetic electrons based on molecular pi-electrons in the supramolecular conductor (Me-3,5-DIP)[Ni(dmit)(2)](2)x64200719#N/AFALSE
2466
ja068505y10.1021/ja068505yFALSEhttps://doi.org/10.1021/ja068505yMaroney, MJJ. Am. Chem. Soc.Studies of the transcriptional repression of the Ni-specific permease encoded by the P-nik operon by Escherichia coli NikR using a LacZ reporter assay establish that the NikR response is specific to nickel in vivo. Toward understanding this metal ion-specific response, X-ray absorption spectroscopy (XAS) analysis of various M-NikR complexes (M = Co(II), Ni(II), Cu(II), Cu(I), and Zn(II)) was used to show that each high-affinity binding site metal adopts a unique structure, with Ni(II) and Cu(II) being the only two metal ions to feature planar four-coordinate complexes. The results are consistent with an allosteric mechanism whereby the geometry and ligand selection of the metal present in the high-affinity site induce a unique conformation in NikR that subsequently influences DNA binding. The influence of the high-affinity metal on protein structure was examined using hydrogen/deuterium (H/D) exchange detected by liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). Each NikR complex gives rise to differing amounts of H/D exchange; Zn(II)- and Co(II)-NikR are most like apo-NikR, while the exchange time course is substantially different for Ni(II) and to a lesser extent for Cu(II). In addition to the high-affinity metal binding site, E. coli NikR has a low-affinity metal-binding site that affects DNA binding affinity. We have characterized this low-affinity site using XAS in heterobimetallic complexes of NikR. When Cu(II) occupies the high-affinity site and Ni(II) occupies the low-affinity site, the Ni K-edge XAS spectra show that the Ni site is composed of six N/O-donors. A similar low-affinity site structure is found for the NikR complex when Co(II) occupies the low-affinity site and Ni(II) occupies the high-affinity site, except that one of the Co(II) ligands is a chloride derived from the buffer.Nickel-specific response in the transcriptional regulator, Escherichia coli NikRx64200757#N/AFALSE
2467
ja074640e10.1021/ja074640eFALSEhttps://doi.org/10.1021/ja074640eMix, AJ. Am. Chem. Soc.The reaction of [Ni-2((i)Pr(2)Im)(4)(COD)] 1a or [Ni((i)Pr(2)Im)(2) (eta(2)-C2H4)] 1b with different fluorinated arenes is reported. These reactions occur with a high chemo- and regioselectivity. In the case of polyfluorinated aromatics of the type C6F5X such as hexafluorobenzene (X = F) octafluorotoluene (X = CF3) trimethyl(pentafluorophenyl)silane (X = SiMe3) or decafluorobiphenyl (X = C6F5) the C-F Activation regioselectively takes place at the C-F bond in the para position to the X group to afford the complexes trans-[Ni((i)Pr(2)Im)(2)(F)(C6F5)] 2, trans-[Ni((i)Pr(2)Im)(2)(F)(4-(CF3)C6F4)] 3, trans-[Ni((i)Pr(2)Im)(2)(F)(4-(CF3)C6F5)] 4, and trans-[Ni((i)Pr(2)Im)(2)(F)(4-(CF3)C6F5)] 5. Complex 5 was structurally characterized by X-ray diffraction. The reaction of 1a with partially fluorinated aromatic substrates C6HxFy leads to the products of a C-F Activation trans-[Ni((i)Pr(2)Im)(2)(F)(2-(C6F4)] 7, trans-[Ni((i)Pr(2)Im)(2)(F)(3,5-(C6F2H3)] 8, trans-[Ni((i)Pr(2)Im)(2)(F)(2,3-(C6F2H3)]9a and trans-[Ni((i)Pr(2)Im)(2)(F)(2,6-(C6F2H3)] 9b, trans-[Ni((i)Pr(2)Im)(2)(F)(2,5-(C6F2H3)] 10, and trans-[Ni((i)Pr(2)Im)(2)(F)(2,3,5,6-(C6F4H)] 11. The reaction of 1a with octafluoronaphthalene yields exClusively trans-[Ni((i)Pr(2)Im)(2)(F)(1,3,45,6,7,8-(C10F7)] 6a, the product of an insertion into the C-F bond in the 2-position, whereas for the reaction of 1b with octafluoronaphthalene the two isomers trans-[Ni((i)Pr(2)Im)(2)(F)(1,3,4,5,6,7,8-C10F7)] 6a and trans-[Ni((i)Pr(2)Im)(2)(F)(2,3,4,5,6,7,8-C10F7)] 6b are formed in a ratio of 11:1. The reaction of 1a or of 1b with pentafluoropyridine at low temperatures affords trans[Ni((i)Pr(2)Im)(2)(F)(4-C5NF4)] 12a as the sole product, whereas the reaction of 1b performed at room temperature leads to the generation of trans-[Ni((i)Pr(2)Im)(2)(F)(4-(C5NF4)] 12a and trans-[Ni((i)Pr(2)Im)(2)(F)(2-C5NF4)] 12b in a ratio of approximately 1:2. The detection of intermediates as well as kinetic studies gives some insight into the mechanistic details for the Activation of an aromatic carbon-fluorine bond at the {Ni((i)Pr(2)Im)(2)} complex fragment. The intermediates of the reaction of 1b with hexafluorobenzene and octafluoronaphthalene, [Ni((i)Pr(2)Im)(2)(eta(2)-(C6F6)] 13 and [Ni((i)Pr(2)Im)(2)(eta(2)-C10F8)] 14, have been detected in solution. They convert into the C-F Activation products. Complex 14 was structurally characterizd by X-ray diffraction. The rates for the loss of 14 at different temperatures for the C-F Activation of the coordinated naphthalene are first order and the estimated Activation enthalpy Delta H double dagger for this process was determined to be Delta H double dagger = 116 +/- 8 kJ mol(-1) (Delta S double dagger = 37 +/- 25 J K-1 mol(-1)). Furthermore, density functional theory calculations on the reaction of la with hexafluorobenzene, octafluoronaphthalene, octafluorotoluene, 1,2,4-trifluorobenzene, and 1,2,3-trifluorobenzene are presented.Activation of fluorinated arenes using NHC-stabilized nickel(0) complexes: Selectivity and mechanistic investigations1912008124#N/ATRUE
2468
ja068328110.1021/ja0683281FALSEhttps://doi.org/10.1021/ja0683281Dunbar, KRJ. Am. Chem. Soc.A series of structurally related pseudocubic metal cyanide Clusters of Re(II) and 3d metal ions [{MX}(4){Re(triphos)(CN)(3)}(4)] (M = Mn, Fe, Co, Ni, Zn; X = Cl, I, -OCH3) have been prepared, and their magnetic and electrochemical properties have been probed to evaluate the effect of changing the identity of the 3d metal ion. Electrochemistry of the Clusters reveals several rhenium-based oxidation and reduction processes, some of which result in Cluster fragmentation. The richest electrochemistry was observed for the iron congener, which exists as the Re(I)/Fe(III) Cluster at the resting potential and exhibits six Clear one-electron reversible redox couples and two, Closely spaced one-electron quasi-reversible processes. The [{(MnCl)-Cl-II}(4){Re-II(triphos)(CN)(3)}(4)] complex exhibits single molecule magnetism with a fast tunneling relaxation process observed at H = 0 determined by micro-SQUID magnetization measurements. A comparative evaluation of the magnetic properties across the series reveals that the compounds exhibit antiferromagnetic coupling between the metal ions, except for [{(NiCl)-Cl-II}(4){Re-II(triphos)(CN)(3)}(4)] that shows ferromagnetic behavior. Despite the large ground-state spin value of [{(NiCl)-Cl-II}(4){Re-II(triphos)(CN)(3)}(4)] (S = 6), only manganese congeners exhibit SMM behavior to 1.8 K.A family of mixed-metal cyanide cubes with alternating octahedral and tetrahedral corners exhibiting a variety of magnetic behaviors inCluding single molecule magnetismx149200766#N/AFALSE
2469
ja073604c10.1021/ja073604cFALSEhttps://doi.org/10.1021/ja073604cCheng, CHJ. Am. Chem. Soc.Cobalt complex/Zn systems effectively catalyze the reductive coupling of activated alkenes with alkynes in the presence of water to give substituted alkenes with very high regio- and stereoselectivity in excellent yields. While the intermolecular reaction of acrylates, acrylonitriles, and Vinyl sulfones with alkynes takes place in the presence Of COl(2)(PPh3)(2)/Zn, the reaction of enones and enals with alkynes requires the use of the Col(2)(dppe)/Zn/Znl(2) system. The intramolecular reductive coupling of activated alkenes (enones, enals, acrylates, and acrylonitriles) with alkynes also works efficiently. Further a variety of cyClic lactones and lactams were prepared using this methodology. Possible mechanistic pathways are proposed based on a deuterium-labeling experiment carried out in the presence of D2O.Cobalt-catalyzed reductive coupling of activated alkenes with alkynes75200776#N/ATRUE
2470
ja073450110.1021/ja0734501FALSEhttps://doi.org/10.1021/ja0734501Duin, ECJ. Am. Chem. Soc.An organometallic methyl-nickel species was detected in the enzyme methyl-coenzyme M reductase (MCR). This is the key enzyme in microbial methane production and is probably also involved in anaerobic methane oxidation. Incubation of MCR with C-13-bromomethane results in the formation of an electron paramagnetic resonance (EPR) active nickel-methyl species in the active site of this enzyme. High-resolution pulse electron nuClear double resonance and hyperfine sublevel correlation investigations showed the presence of C-13 hyperfine couplings of 18-44 MHz that are associated with the nickel-based EPR signal. The large C-13 hyperfine interaction shows unambiguously that the methyl group from bromomethane is directly coordinated to the nickel ion. The EPR structure and parameters are fully supported by density functional theory calculations.Formation of a nickel-methyl species in methyl-coenzyme M reductase, an enzyme catalyzing methane formation58200721#N/ATRUE
2471
ja073162510.1021/ja0731625FALSEhttps://doi.org/10.1021/ja0731625Shearer, JJ. Am. Chem. Soc.Nickel superoxide dismutase (NiSOD) is a bacterial metalloenzyme that possesses a mononuClear Ni-center and catalyzes the disproportionation Of O2(center dot-) by cyCling between Ni-II and Ni-III oxidation states. Herein we present evidence from several SOD active metallopeptide maquettes ([Ni((SODH)-H-M2(1)X)]; (SODH)-H-M2(1)X = H2N-XCDLPCG-COOH; X = H, D, or A) that the Ni-center of NiSOD most likely remains five-coordinate during SOD catalysis using thin-film voltammetry. N-3- and CN- titration studies suggest that O-2(center dot-) disproportionation by [Ni(SODM2 H(1)X)] proceeds via an outersphere mechanism. Computationally derived values for the nuClear reorganization energy of the [Ni-II(SODM2)]/[Ni-III(SODM2)] self-exchange reaction combined with the experimentally determined value for k(o) (similar to 450 s(-1)) suggest that axial ligation enhances the O-2(center dot-) disproportionation reaction in [Ni(SODM2)] (and NiSOD by analogy) by optimizing the Ni-II/Ni-III redox couple such that it is Close to the midpoint of the O-2(center dot-) reduction and oxidation couples.Probing variable axial ligation in nickel superoxide dismutase utilizing metal lopeptide-based models: Insight into the superoxide disproportionation mechanism55200768#N/ATRUE
2472
ja067112w10.1021/ja067112wFALSEhttps://doi.org/10.1021/ja067112wJohnson, SAJ. Am. Chem. Soc.The known aryne complex (PEt3)(2)Ni(eta(2)-C6H2-4,5-F-2) (1a) reacts with a catalytic amount of Br2Ni(PEt3)(2) over 1% Na/Hg to afford the dinuClear Ni(I) biArylyl complex [(PEt3)(2)Ni](2)(mu-eta(1):eta(1)-3,4-F2C6H2-3',4'-F2C6H2) (2a), which results from a combination of C-C bond formation and C-H bond rearrangement. The dinuClear benzyne [(PEt3)(2)Ni](2)(mu-eta(2):eta(2)-C6H2-4,5-F-2) (3) was obtained by the reaction of 1a with a stoichiometric amount of Br2Ni(PEt3)(2) over excess 1% Na/Hg, and 3 was found to catalyze the conversion of 1a to 2a. The reaction of 1a with B(C6F5)(3) produced the trinuClear complex (PEt3)(3)Ni-3(mu(3):eta(1):eta(1):eta(2)-4,5-F2C6H2)(mu(3):eta(1):eta(1):eta(2)-4,5-F2C6H2-4',5'-F2C6H2) (6). The addition of PEt3 to 6 produced 1 equiv of 1a and 1 equiv of [(PEt3)(2)Ni](2)(mu-eta(1):eta(1)-4,5-F2C6H2-4',5'-F2C6H2) (7a). Both 6 and 7a were identified as intermediates in the conversion of 1a to 2a. The analogue [(PEt3)(PMe3)Ni](2)(mu-eta(1):eta(1)-4,5-F2C6H2-4',5'-F2C6H2) (7b) was prepared by the addition of PMe3 to 6 and was structurally characterized. NMR spectroscopic evidence identified the additional asymmetric biArylyl [(PEt3)(2)Ni](2)(mu-eta(1):eta(1)-4,5-F2C6H2-3',4'-F2C6H2) (8a) during the conversion of 1a to 2a. The initial observation of 2 equiv of 8a for every equivalent of 2a produced from solutions of 7a suggests that 8a and 2a are formed from a common intermediate. A crossover labeling experiment shows that the C-H bond rearrangement steps in the conversion of 1a to 2a occur with the intermolecular scrambling of hydrogen and deuterium labels. The evidence collected suggests that Ni(I) complexes are capable of activating aromatic C-H bonds.1,4-shifts in a dinuClear Ni(I) biArylyl complex: A mechanistic study of C-H bond Activation by monovalent nickelX60200785#N/AFALSE
2473
ja067107s10.1021/ja067107shttps://doi.org/10.1021/ja067107sYokozawa, TJ. Am. Chem. Soc.Catalyst-transfer polycondensation for the synthesis of poly(p-phenylene) with controlled molecular weight and low polydispersityx187200623#N/AFALSE
2474
ja067022r10.1021/ja067022rFALSEhttps://doi.org/10.1021/ja067022rYamauchi, OJ. Am. Chem. Soc.Group 10 metal(II) complexes of H(2)tbu-salen (H(2)tbu-salen = N,N'-bis(3',5'-di-tert-butylsalicylidene)ethylenediamine) and H(2)tbu-salcn (H(2)tbu-salcn = N,N'-bis(3',5'-di-tert-butylsalicylidene)-1,2-cyClohexanediamine) containing two 2,4-di(tert-butyl)phenol moieties, [Ni(tbu-salen)] (1a), [Ni(tbu-salcn)] (1b), [Pd(tbu-salen)] (2a), [Pd(tbu-salcn)] (2b), and [Pt(tbu-salen)] (3), were prepared and structurally characterized by X-ray diffraction, and the electronic structures of their one-electron-oxidized species were established by spectroscopic and electrochemical methods. All the complexes have a mononuClear structure with two phenolate oxygens coordinated in a very similar square-planar geometry. These complexes exhibited similar absorption spectra in CH2Cl2, indicating that they all have a similar structure in solution. CyClic voltammograms of the complexes showed a quasi-reversible redox wave at E-1/2 = 0.82-1.05 V (vs Ag/AgCl), corresponding to formation of the relatively stable one-electron-oxidized species. The electrochemically oxidized or Ce(IV)-oxidized species of 1a, 2a, and 3 displayed a first-order decay with a half-life of 83, 20, and 148 min at -20 degrees C, respectively. Ni(II) complexes 1a and 1b were converted to the phenoxyl radicals upon one-electron oxidation in CH2Cl2 above -80 degrees C and to the Ni(III)-phenolate species below -120 degrees C. The temperature-dependent conversion was reversible with the Ni(III)-phenolate ground state and was found to be a valence tautomerism governed by the solvent. One-electron-oxidized 1b was isolated as [Ni(tbu-salcn)]NO3 (4) having the Ni(II)-phenoxyl radical ground state. One-electron-oxidized species of the Pd(II) complexes 2a and 2b were different from those of the Ni(II) complexes, the Pd(II)-phenoxyl radical species being the ground state in CH2Cl2 in the range 5-300 K. The one-electron-oxidized form of 2b, [Pd(tbu-salcn)]NO3 (5), which was isolated as a dark green powder, was found to be a Pd(II)-phenoxyl radical complex. On the other hand, the ESR spectrum of the one-electron-oxidized species of Pt(II) complex 3 exhibited a temperature-independent large g anisotropy in CH2Cl2 below -80 degrees C, while its resonance Raman spectrum at -60 degrees C displayed nu(8a) of the phenoxyl radical band at 1600 cm(-1). These results indicated that the ground state of the Pt(II)-phenoxyl radical species has a large distribution of the radical electron spin at the Pt center. One-electron oxidation of 3 gave [Pt(tbu-salen)]NO3 (6) as a solid, where the oxidation state of the Pt center was determined to be ca. +2.5 from the XPS and XANES measurements.Syntheses and electronic structures of one-electron-oxidized group 10 metal(II)-(disalicylidene)diamine complexes (Metal = Ni, Pd, Pt)x135200779#N/AFALSE
2475
ja072063o10.1021/ja072063oFALSERiordan, CGMethyl transfer from methylcobaloxime to (Triphos)Ni(PPh3): Relevance to the mechanism of acetyl coenzyme A synthase2007#N/ATRUE
2476
ja066814i10.1021/ja066814iFALSEhttps://doi.org/10.1021/ja066814iDunsch, LJ. Am. Chem. Soc.The high-yield synthesis of Dy3N@C-80 (I) opens the possibility of characterizing its molecular and vibrational structures. We report on the structure determination of Dy3N@C-80 (I) by X-ray crystallographic study of single crystal of Dy3N@C-80 center dot Ni(OEP)center dot 2C(6)H(6), revealing a nearly planar Dy3N Cluster encapsulated in an I-h-C-80 cage. The vibrational structure of Dy3N@C-80 (I) is studied by Fourier transform infrared (FTIR) and Raman spectroscopy in combination with force-field calculations. A correlation was found between the antisymmetric metal-nitrogen stretching vibration and the structure of the M3N Cluster of M3N@C-80 (I) (M = Y, Gd, Tb, Dy, Ho, Er, Tm). Moreover, a stronger interaction between the encaged nitride Cluster and the C-80 carbon cage was found in the Class II M3N@C-80 (I) (M = Y, Gd, Tb, Dy, Ho, Er, Tm) than in Sc3N@C-80 (I). This study demonstrates that the Cluster size plays the dominating role in the structure of the M3N Cluster in M3N@C-80 (I).Deviation from the planarity - a large Dy3N Cluster encapsulated in an I-h-C-80 cage: An X-ray crystallographic and vibrational spectroscopic studyx105200633#N/AFALSE
2477
ja066594910.1021/ja0665949FALSESolomon, EISulfur K-edge X-ray absorption spectroscopy as a probe of ligand-metal bond covalency: Metal vs ligand oxidation in copper and nickel dithiolene complexesx2007#N/AFALSE
2478
ja066437+10.1021/ja066437+FALSEhttps://doi.org/10.1021/ja066437+Balch, ALJ. Am. Chem. Soc.The recent finding that isomer 2 of Tb3N@C-84 uses one of the 51 568 possible nonisolated pentagon rule (non-IPR) structures for the C-84 cage rather than one of the 24 cage isomers that do obey the IPR suggests that further experimental work on the structure of larger endohedrals is needed to observe the utility of the IPR rule in this uncharted territory. The structures of the newly synthesized endohedral fullerenesTb(3)N@C-88, Tb3N@C-86, and the I-h and D-5h isomers of Tb3N@C-80 have been determined by single-crystal X-ray diffraction on samples cocrystallized with Ni-II(octaethylporphyrin). In contrast to the situation for isomer 2 of Tb3N@C-84, the structures of Tb3N@C-88 and Tb3N@C-86 do conform to the IPR. Both Tb3N@C-88 and Tb3N@C-86 have chiral structures with D-2 symmetry for Tb3N@C-88 and D-3 symmetry for Tb3N@C-86. Within this group of endohedrals, the size of the carbon cage affects the Tb-N and Tb-C distances, the orientations of the carbon cage with respect to the porphyrin plane, the locations of the metal ions and their orientations relative to the porphyrin plane, and the degree of pyramidalization of the Tb3N unit.Isolation and structural characterization of a family of endohedral fullerenes inCluding the large, chiral cage fullerenes Tb3N@C-88 and Tb3N@C-86 as well as the I-h and D-5h isomers of Tb3N@C-80X137200731#N/AFALSE
2479
ja066140b10.1021/ja066140bFALSEhttps://doi.org/10.1021/ja066140bOhba, MJ. Am. Chem. Soc.Chirality plays a key role for exhibiting specific physical properties in functional materials. Molecule-based magnets can strategically introduce the chirality in their frameworks as a molecular property of co-ligand, and magnetic frameworks providing local magnetic anisotropy and oncentrosymmetric structure are expected to form a genuine chiral magnetic structure.Chiral cyanide-bridged (MnMnIII)-Mn-II ferrimagnets, [Mn-II(HL)(H2O)][Mn-III(CN)(6)]center dot 2H(2)O (L = S- or R-1,2-diaminopropane): Syntheses, structures, and magnetic behaviorsx144200722#N/AFALSE
2480
ja070855c10.1021/ja070855cFALSEhttps://doi.org/10.1021/ja070855cChen, QYJ. Am. Chem. Soc.The 20 pi-electron nonaromatic isophlorin 2 had been successfully isolated and thoroughly characterized and was formed by reduction of Cu(II) beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin (Cu1) with activated zinc powder. However, the reaction utilizing Ni(II) beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin (Ni1) as a substrate and Na2S2O4 as a reductant at 100 degrees C resulted in the formation of a porphydimethene 5. Subsequent N-methylation of the isophlorin 2 led to N-dimethylated isophlorin 3 or N-tetramethylated isophlorin 4 depending on the choice of the base used.Synthesis and reactions of 20 pi-electron beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrins88200737#N/ATRUE
2481
ja065623c10.1021/ja065623cFALSEhttps://doi.org/10.1021/ja065623cIshida, TJ. Am. Chem. Soc.Strong ferromagnetic exchange couplings in copper(II) and nickel(II) complexes with a paramagnetic tridentate chelate ligand, 2,2 '-bipyridin-6-yl tert-butyl nitroxidex69200628#N/AFALSE
2482
ja070733k10.1021/ja070733kFALSEhttps://doi.org/10.1021/ja070733kWang, SLJ. Am. Chem. Soc.The first 26R channel structure, NTHU-5, built up with two types of helical metal phosphite chains has been synthesized under mild hydrothermal conditions; this novel open framework is composed of both octahedral Al3+ and tetrahedral Zn2+ centers and represents the first example with participation of aluminum in a pore size over 20R; the 26R channel is truly a stack of 26-membered rings instead of just an opening; this study has successfully demonstrated that two differently charged metal ions can form M-O-P-O-M' bonded structure with ring size larger than any other existing inorganic open frameworks; in addition, varied metal analogues can be prepared using the same approach; the system of NTHU-5 has provided an intriguingly new chemical synthesis for inorganic microporous materials with interesting reaction conditions.26-ring-channel structure constructed from bimetal phosphite helical chains125200727#N/ATRUE
2483
ja065505p10.1021/ja065505pFALSEhttps://doi.org/10.1021/ja065505pHuang, YLJ. Am. Chem. Soc.Intermolecular arene C-H Activation by nickel(II)X95200637#N/AFALSE
2484
ja065384t10.1021/ja065384thttps://doi.org/10.1021/ja212206mBrannen, ClDonor-acceptor biradicals as ground state analogues of photoinduced charge separated statesPhotocatalyst2007#N/AFALSE
2485
ja064921710.1021/ja0649217FALSEhttps://doi.org/10.1021/ja0649217Cheetham, AKJ. Am. Chem. Soc.A porous hybrid inorganic/organic material, NaNi3(OH)(SIP)(2) [SIP = 5-sulfoisophthalate] [1], is shown to strongly bind molecular hydrogen at coordinatively unsaturated metal sites. A combination of H-2 sorption isotherms, temperature programmed desorption, and inelastic neutron scattering spectroscopy show the existence of a considerable number of such strong binding sites in [1] along with other sites where hydrogen is more weakly physisorbed. The overall capacity for hydrogen of this material as well as the much stronger binding of hydrogen than in typical porous material represent an important step toward a possible utilization of porous media for hydrogen storage.Adsorption of molecular hydrogen on coordinatively unsaturated Ni(II) sites in a nanoporous hybrid materialx172200630#N/AFALSE
2486
ja070364s10.1021/ja070364shttps://doi.org/10.1021/ja070364sBrookhart, MJ. Am. Chem. Soc.The polymerization of 1,3-dienes has been well-studied using an array of metal-containing complexes. Although a variety of (pi-allyl) Ni(II) catalysts have been shown to be active for diene polymerization, details concerning the mechanism of chain growth are largely speculative and supported primarily by DFT calculations. The observation by low-temperature NMR spectroscopy of the key intermediates and the catalyst resting states in the chain growth are described here and provide a more complete and detailed mechanism of butadiene polymerization.The mechanism of polymerization of butadiene by ligand-free nickel(II) complexes37200716#N/ATRUE
2487
ja070224i10.1021/ja070224iFALSEhttps://doi.org/10.1021/ja070224iRieger, BJ. Am. Chem. Soc.Starting from differently substituted boronic acids as versatile building block, new ortho-Aryl alpha-diimine ligands a-h were synthesized in an easy, high-yielding route. Reaction of the complex precursor diacetylacetonato-nickel(II) with a trityl salt, like [CPh3] [B(C6F5)(4)] or [CPh3] [SbCl6], in the presence of the diimine ligands afford the monocationic, square planar complexes 2a-g in almost quantitative yields. Suitable crystals (2d',e,f,g) were submitted for X-ray diffraction analysis. A geometry model was developed to describe the orientation of ligand fragments around the nickel(II) center that influence the polymer microstructure. At elevated reaction temperature and pressure, and in the presence of hydrogen, 2a-e catalyze the homopolymerization of ethylene to give branched PE products ranging from HD- to LLD-PE grades. The polymerization results indicate the possibility of precise microstructure control depending on the particular complex substitution. Preliminary investigations on material density and mechanical behavior by uniaxial stretching until failure point toward new material properties that can result from the simple ethylene monomer by catalyst design.New Nickel(II) diimine complexes and the control of polyethylene microstructure by catalyst design182200759#N/ATRUE
2488
ja064151z10.1021/ja064151zFALSEhttps://doi.org/10.1021/ja064151zZhu, ZPJ. Am. Chem. Soc.The synthesis of carbon nanotubes (CNTs) has been proved to be greatly promoted by vapor metal catalysts, but the fast reaction feature and the required high-temperature environment involved in CNT evolution usually make it difficult for an insight into the evolution mechanism. Here, we successfully freeze the synthetic reaction at intermediary stages and observe the detailed morphologies and structures of the obtained intermediates and various objects related to carbon nanotubes. It is unveiled that there is a kindred evolution linkage among carbon nanopartiCles, nanowires, and nanotubes in the vapor catalyst-involved synthetic processes: tiny carbon nanopartiCles first form from a condensation of gaseous carbon species and then self-assemble into nanowires driven by an anisotropic interaction, and the nanowires finally develop into nanotubes, as a consequence of partiCle coalescence and structural crystallization. The function of metals is to promote the anisotropic interactions between the nanopartiCles and the structural crystallization. An annealing transformation of carbon nanopartiCles into nanotubes is also achieved, which gives further evidence for the evolution mechanism.PartiCle-wire-tube mechanism for carbon nanotube evolutionx48200659#N/AFALSE
2489
ja070181610.1021/ja0701816FALSEhttps://doi.org/10.1021/ja0701816Huang, SDJ. Am. Chem. Soc.Hydrothermal reaction of (S)-1,1'1' '-2,4,6-trimethylbenzene-1,3,5-triyl-tris(methylene)-tris-pyrrolidine-2-Carbonylic acid (TBPLA) with Ni(ClO4)(2)center dot 6H(2)O gave pale green block crystals of 1. X-ray crystal structure analysis showed the complex to be a trinuClear descrete homochiral molecule with each Ni center sitting in distorted octahedron geometries. Anisotropic permittivity measurements reveal that 1 exhibits huge dielectric anisotropy along its three different crystal axes that is ca. 3.5 times of epsilon(r) (E//c)/epsilon(r) (E//b) with temperature and frequency independence.Dielectric anisotropy of a homochiral trinuClear nickel(II) complex174200717#N/ATRUE
2490
ja063770510.1021/ja0637705FALSEhttps://doi.org/10.1021/ja0637705Huskens, JJ. Am. Chem. Soc.The multivalent binding of a supramolecular complex at a multivalent host surface by combining the orthogonal beta-cyClodextrin (CD) host-guest and metal ion-ethylenediamine coordination motifs is described. As a heterotropic, divalent linker, an adamantyl-functionalized ethylenediamine derivative was used. This was complexed with Cu(II) or Ni(II). The binding of the complexes to a CD self-assembled monolayer (SAM) was studied as a function of pH by means of surface plasmon resonance (SPR) spectroscopy. A heterotropic, multivalent binding model at interfaces was used to quantify the multivalent enhancement at the surface. The Cu(II) complex showed divalent binding to the CD surface with an enhancement factor higher than 100 relative to the formation of the corresponding divalent complex in solution. Similar behavior was observed for the Ni(II) system. Although the Ni(II) system could potentially be trivalent, only divalent binding was observed at the CD SAMs, which was confirmed by desorption experiments.Expression of a supramolecular complex at a multivalent interfacex35200652#N/AFALSE
2491
ja068993+10.1021/ja068993+FALSEhttps://doi.org/10.1021/ja068993+Levy, LMBiAryl synthesis via Pd-catalyzed deCarbonylative coupling of aromatic Carbonylates with Aryl halides2007#N/ATRUE
2492
ja063334i10.1021/ja063334iFALSEhttps://doi.org/10.1021/ja063334iVicic, DAJ. Am. Chem. Soc.The ability of the terpyridine ligand to stabilize Alkyl complexes of nickel has been central in obtaining a fundamental understanding of the key processes involved in Alkyl-Alkyl cross-coupling reactions. Here, mechanistic studies using isotopically labeled (TMEDA)NiMe2 (TMEDA = N,N,N',N'-tetramethyleth-ylenediamine) have shown that an important catalyst in Alkyl-Alkyl cross-coupling reactions, (tpy')NiMe (2b, tpy' = 4,4',4 ''-tri-tert-butylterpyridine), is not produced via a mechanism that involves the formation of methyl radicals. Instead, it is proposed that (terpyridine) NiMe complexes arise via a comproportionation reaction between a Ni(II)-dimethyl species and a Ni(0) fragment in solution upon addition of a terpyridine ligand to (TMEDA)NiMe2. EPR and DFT studies on the paramagnetic (terpyridine) NiMe (2a) both suggest that the unpaired electron resides heavily on the terpyridine ligand and that the proper electronic description of this nickel complex is a Ni(II)-methyl cation bound to a reduced terpyridine ligand. Thus, an important consequence of these results is that Alkyl halide reduction by (terpyridine)NiRAlkyl complexes appears to be substantially ligand based. A comprehensive survey investigating the catalytic reactivity of related ligand derivatives suggests that electronic factors only moderately influence reactivity in the terpyridine-based catalysis and that the most dramatic effects arise from steric and solubility factors.Ligand redox effects in the synthesis, electronic structure, and reactivity of an Alkyl-Alkyl cross-coupling catalystx356200660#N/AFALSE
2493
ja068488c10.1021/ja068488cFALSEhttps://doi.org/10.1021/ja068488cHayashi, TJ. Am. Chem. Soc.Asymmetric homo-cyClodimerization of oxabicyClic alkenes proceeded with high efficiency in the presence of a cationic rhodium/(R)-binap catalyst to give high yields of chiral tetrahydrofurans of up to 99% ee. The cationic rhodium complex also catalyzed the asymmetric cross-cyClodimerization between oxabicyClic alkenes and dimethyl 2-butynedioate, which gave dihydrofurans as [3+2] cyCloadducts with high enantioselectivity (99% ee).Rhodium-catalyzed asymmetric cyClodimerization of oxa- and azabicyClic alkenes40200728#N/ATRUE
2494
ja062430g10.1021/ja062430gFALSEhttps://doi.org/10.1021/ja062430gNocera, DGJ. Am. Chem. Soc.A homologous set of porphyrin derivatives possessing an isocyClic five-membered ring appended with an amidinium functionality has been used to examine proton-coupled electron transfer (PCET) through well-characterized amidine-Carbonylic acid interfaces. Conjugation between the porphyrin chromophore and the amidinium interface can be altered by selective reduction of the isocyClic ring of an amidinium-purpurin to produce an amidinium-chlorin. The highly conjugated amidinium-purpurin displays large spectral shifts in the visible region upon alteration of the amidinium/amidine protonation state; no such change is observed for the chlorin homologue. Analysis of the UV-vis absorption and emission profiles of the amidinium-purpurin upon deprotonation allows for the measurement of the porphyrinic-amidinium acidity constant for the ground state (pK(a) = 9.55 +/- 0.1 in CH3CN) and excited state (pK(a)* = 10.40 +/- 0.1 in CH3CN). The absorption spectrum of the purpurin also provides a convenient handle for determining the protonation state of assembled interfaces. In this way, the purpurin macrocyCle provides a general tool for PCET studies because it can be used to determine the location of a proton within PCET interfaces formed from Carbonylic acid electron acceptors inCluding dinitrobenzenes (DNBs) and naphthalenediimide (NI), which have been used extensively in previous PCET studies. An amidine-Carbonylic acid interface is observed for electron-rich acceptors, whereas the ionized amidinium- Carbonylate interface is observed for electron-poor acceptors. The PCET kinetics for purpurin/chlorin associated to NI are consistent with an amidine-Carbonylic acid interface, which is also verified spectrally.Spectroscopic determination of proton position in the proton-coupled electron transfer pathways of donor-acceptor supramolecule assembliesx78200667#N/AFALSE
2495
ja062051n10.1021/ja062051nFALSEhttps://doi.org/10.1021/ja062051nBominaar, ELJ. Am. Chem. Soc.This work reports Mossbauer and DFT studies of the diiron-N-2 complex (LFeNNFeLMe)-Fe-Me (L = beta-diketiminate), 1a. Complex 1a, formally diiron(1), has a system spin S = 3 with an isolated M-S = +/- 3 quasi-doublet as a ground state; the M-S = +/- 2 doublet is > 100 cm(-1) higher in energy. Complex 1a exhibits at 4.2 K a large, positive magnetic hyperfine field, B-int = + 68.1 T, and an effective g value of 16 +/- 2 along the easy magnetization axis of the ground doublet; this value is significantly larger than the spin- only value ( g) 12). These results have been rationalized by DFT calculations, which show that each Fe site donates significant electron density into the pi* orbitals of dinitrogen, resulting in a configuration best described as two high-spin Fe-II (S-a = S-b = 2) bridged by triplet N-2(2-) (S-c = 1). In this description the minority spin electron of each iron is accommodated by two nonbonding, Closely spaced 3d orbitals, z(2) and yz(z is perpendicular to the diketiminate planes, x is along the Fe center dot center dot center dot Fe vector). Spin-orbit coupling between these orbital states generates a large unquenched orbital momentum along the iron-iron vector. The S = 3 ground state of 1a results from strong antiferromagnetic direct exchange couplings of the Fe spins (S-a = S-b = 2) to the N-2(2-) spin (S-c = 1) and can be formulated as vertical bar((S-a,S-b)S-ab = 4, S-c = 1), S = 3); H = J(S-a+ S-b)center dot S-c with J approximate to 3500 cm(-1).Mossbauer and computational study of an N-2-bridged diiron diketiminate complex: Parallel alignment of the iron spins by direct antiferromagnetic exchange with activated dinitrogenx68200644#N/AFALSE
2496
ja061996210.1021/ja0619962https://doi.org/10.1021/ja0619962Mecking, SJ. Am. Chem. Soc.Water-soluble salicylaldiminato Ni(II)-methyl complexes: Enhanced dissociative Activation for ethylene polymerization with unprecedented nanopartiCle formationx91200621#N/AFALSE
2497
ja061911x10.1021/ja061911xFALSEhttps://doi.org/10.1021/ja061911xSutter, JPEvidence for increased exchange interactions with 5d compared to 4d metal ions. Experimental and theoretical insights into the ferromagnetic interactions of a series of trinuClear [{M(CN)(8)}(3-)/Ni-II] compounds (M = Mo-V or W-V)x2006#N/AFALSE
2498
ja068118o10.1021/ja068118oFALSEhttps://doi.org/10.1021/ja068118oTempleton, JLMechanistic studies of platinum(II)-catalyzed ethylene dimerization: Determination of barriers to migratory insertion in diimine Pt(II) hydrido ethylene and ethyl ethylene intermediates2007#N/ATRUE
2499
ja061842m10.1021/ja061842mFALSEhttps://doi.org/10.1021/ja061842mEichhorn, BJ. Am. Chem. Soc.Ethylenediamine (en) solutions of K4Pb9 react with toluene solutions of ML4 (M = Pt, Pd, L = PPh3; M = Ni, L-2 = COD) and 2,2,2-crypt to give M@Pb-12(2-) Cluster anions (M = Pt (1), Pd (2), Ni (3)) as the [K(2,2,2-crypt)](+) salts in low (Ni) to good (Pt) yields. The ions have near perfect I-h point symmetry and have been characterized by X-ray diffraction, Pb-207 NMR and LDI-TOF mass spectrometry studies. For M = Ni, the primary product formed is the D-4d Ni@Pb-10(2-) Cluster that has also been structurally characterized. The M@Pb-10(2-) Clusters (M = Pd, Pt) and the new Zintl ions Closo-Pb-10(2-) and Closo-Pb-12(2-) were formed in the gas phase but have not been detected in solution or the solid state. The structural trends of these series of Clusters have been investigated through DFT calculations. The Ni@Pb-10(2-) Cluster is dynamic on the Pb-207 NMR time scale at -45 degrees C and 104.7 MHz. The M@Pb-12(2-) ions show unusually deshielded Pb-207 NMR chemical shifts that presumably arise from sigma-aromatic effects associated with their high symmetries. In the solid state, the salts form superlattices of cations and anions (e.g. the AlB2 lattice of [ K( 2,2,2-crypt)](2)[Pt@Pb-12]) and are prototypes for assembled Cluster materials.The Pb-12(2-) and Pb-10(2-) zintl ions and the M@Pb-12(2-) and M@Pb-10(2-) Cluster series where M = Ni, Pd, Ptx171200658#N/AFALSE
2500
ja061633210.1021/ja0616332FALSEhttps://doi.org/10.1021/ja0616332Tamaru, YJ. Am. Chem. Soc.Nickel-catalyzed multicomponent connection of dimethylzinc, alkynes, 1,3-butadiene, aldehydes, and aminesx33200625#N/AFALSE
2501
ja061557310.1021/ja0615573FALSEhttps://doi.org/10.1021/ja0615573Dorn, HCJ. Am. Chem. Soc.In this paper we report enhanced reactivity of the D 5 h isomers in comparison with the more common I-h isomers of Sc3N@C-80 and Lu3N@C-80 toward Diels-Alder and 1,3-dipolar tritylazomethine ylide cyCloaddition reactions. Also, the structure of the D-5h isomer of Sc3N@C-80 has been determined through single-crystal X-ray diffraction on D-5h-Sc3N@(C80Ni)-Ni-.(OEP), 2benzene (OEP) octaethylporphyrin). The Sc3N portion of D-5h-Sc3N@C-80 is strictly planar, but the plane of these four atoms is tipped out of the noncrystallographic, horizontal mirror plane of the fullerene by 30 degrees. The combination of short bond length and high degree of pyramidization for the central carbon atoms of the pyracylene sites situated along a belt that is perpendicular to the C-5 axis suggests that these are the sites of greatest reactivity in the D-5h isomer of Sc3N@C-80. Consistent with the observation of higher reactivity observed for the D-5h isomers, cyClic voltammetry and molecular orbital (MO) calculations demonstrate that the D-5h isomers have slightly smaller energy gaps than those of the I-h isomers. The first mono- and bis-adducts of D-5h Sc3N@C-80 have been synthesized via 1,3-dipolar cyCloaddition of tritylazomethine ylide. The NMR spectrum for the monoadduct 2b is consistent with reaction at the 6,6-ring juncture in the pyracylene unit of the D-5h Sc3N@C-80 cage and is the thermodynamically stable isomer. On the other hand, monoadduct 2a undergoes thermal conversion to other isomeric monoadducts, and three possible structures are proposed.Structure and enhanced reactivity rates of the D-5h Sc3N@C-80 and Lu3N@ C-80 metallofullerene isomers: The importance of the pyracylene motifx142200669#N/AFALSE
2502
ja067364x10.1021/ja067364xFALSEhttps://doi.org/10.1021/ja067364xHiyama, TJ. Am. Chem. Soc.Lewis-acid catalysts such as AlMe3, AlMe2Cl, and BPh3 significantly improve the efficiency of the nickel-catalyzed Arylcyanation of alkynes. Electron-rich Aryl cyanides, which exhibit poor reactivity in the absence of Lewis acids, readily undergo the Arylcyanation reaction under the newly disClosed conditions. Excellent chemoselectivity is observed for Aryl cyanides having a chloro and bromo group, allowing a single-step preparation of the synthetic intermediate of P-3622, a squalene synthetase inhibitor. Moreover, the first examples of alkenyl- and Alkylcyanation of alkynes have been achieved by the nickel-Lewis acid dual catalyst.A dramatic effect of Lewis-acid catalysts on nickel-catalyzed carbocyanation of alkynes233200719#N/ATRUE
2503
ja067121510.1021/ja0671215FALSEhttps://doi.org/10.1021/ja0671215Ueki, HJ. Am. Chem. Soc.The first example of design and synthesis of helical molecules using a ridge-tile-like topological mode of nonplanarity is reported. The modular nature of the design of the starting glycine derivatives renders this approach general for the preparation of structurally varied and functionalized derivatives of this type of bended molecules with inherent helical chirality.Design, synthesis, and characterization of binuClear Ni(II) complexes with inherent helical chirality37200730#N/ATRUE
2504
ja061104y10.1021/ja061104yFALSEhttps://doi.org/10.1021/ja061104yLambert, RMJ. Am. Chem. Soc.We have studied the proline-directed, Pd-catalyzed enantioselective hydrogenation of isophorone in the liquid state using a variety of methods. Our results unambiguously reveal the true reaction pathway and demonstrate that all earlier mechanistic hypotheses are wrong: although a proline/isophorone condensation product is formed, it is merely a spectator and not a key reaction intermediate in subsequent heterogeneous hydrogenation. Enantioselectivity is the result of kinetic resolution-a process that occurs homogeneously in solution and not at the metal surface. Racemic 3,3,5-trimethylcyClohexanone (TMCH) is produced by initial heterogeneous hydrogenation of isophorone; proline then reacts homogeneously, preferentially with one enantiomer of TMCH, leaving an excess of the other. Thus in complete contrast to the case of ketoester asymmetric hydrogenation, the metal surface is not involved in the crucial enantio-differentiation step. The mechanism we propose also explains why the maximum attainable yield of enantiopure TMCH cannot exceed 50%.Heterogeneously catalyzed asymmetric C = C hydrogenation: Origin of enantioselectivity in the proline-directed Pd/isophorone systemx49200623#N/AFALSE
2505
ja060982t10.1021/ja060982tFALSEhttps://doi.org/10.1021/ja060982tBeer, PDJ. Am. Chem. Soc.Polymetallic nanodimensional assemblies have been prepared via metal directed assembly of dithiocarbamate functionalized cavitand structural frameworks with late transition metals (Ni, Pd, Cu, Au, Zn, and Cd). The coordination geometry about the metal centers is shown to dictate the architecture adopted. X-ray crystallographic studies confirm that square planar coordination geometries result in cagelike octanuClear complexes, whereas square-based pyramidal metal geometries favor hexanuClear molecular loop structures. Both Classes of complex are sterically and electronically complementary to the fullerenes (C-60 and C-70). The strong binding of these guests occurred via favorable interactions with the sulfur atoms of multiple dithiocarbamate moieties of the hosts. In the case of the tetrameric copper(II) complexes, the lability of the copper(II)-dithiocarbamate bond enabled the fullerene guests to be encapsulated in the electron-rich cavity of the host, over time. The examination of the binding of fullerenes has been undertaken using spectroscopic and electrochemical methods, electrospray mass spectrometry, and molecular modeling.Nanosized polymetallic resorcinarene-based host assemblies that strongly bind fullerenesx75200696#N/AFALSE
2506
ja066817v10.1021/ja066817vFALSEhttps://doi.org/10.1021/ja066817vVerdaguer, MJ. Am. Chem. Soc.Tris(bipyridine)ruthenium(II) is used as a templating agent to insert palladium(II) into three-dimensional oxalate-based networks. The templated-assembly of [Ru(bpy)(3)][Pd-2(ox)(3)] (Pd2) and [Ru(bpy)(3)][PdMn(ox)(3)] (PdMn) is described. The latter compound is structurally characterized by powder X-ray diffraction and X-ray absorption spectroscopy. These techniques reveal an unusual 6-fold oxygen environment around the Pd(II) atoms with two short (2.02 A) and four long (2.17 angstrom) Pd-O distances. As stated by magnetometry, this environment is associated with a triplet ground state (S = 1) of the palladium(II) ion: when the temperature is decreased, the chi T-M product shows a monotonous decrease from 5.54 cm(3) K mol(-1) at 300 K, a value which is slightly lower than the one expected for independent paramagnetic Pd(II) (S = 1, g = 2) and Mn(II) (S = (5)/(2), g = 2) ions. This thermal variation is due to antiferromagnetic exchange interactions between the two spin bearers. Nevertheless, no long-range magnetic order is detected down to 2 K. These results are confirmed by an analysis of the [M-II(C2O4)(3)](4-) (M = Ni, Pd, Pt) complex and of a [Pd-II{mu-(C2O4)Mn-II(OH2)(4)}(3)](2+) tetranuClear model using density functional theory.Six-fold oxygen-coordinated triplet (S=1) palladium(II) moieties templated by tris(bipyridine)ruthenium(II) ions24200761#N/ATRUE
2507
ja065789d10.1021/ja065789dFALSEhttps://doi.org/10.1021/ja206042kHinds, BJMolecular electrodes at the exposed edge of metal/insulator/metal trilayer structures2007#N/ATRUE
2508
ja065524z10.1021/ja065524zFALSEhttps://doi.org/10.1021/ja065524zPeters, JCJ. Am. Chem. Soc.Fe(I)-mediated reductive Cleavage and coupling of CO2: An Fe-II(mu-O,mu-CO)Fe-II core119200722#N/ATRUE
2509
ja060580l10.1021/ja060580lFALSEhttps://doi.org/10.1021/ja060580lKurosawa, HJ. Am. Chem. Soc.The reversible oxidative cyClization of dienes and aldehydes with nickel(0) proceeded to give eta(3):eta(1)-allylalkoxynickel complexes. The treatment of these complexes with carbon monoxide led to the formation of the corresponding lactone and/or the regeneration of a butadiene and an aldehyde concomitant with the formation of Ni(CO)(3)(PCy3). The scission of the nickel-oxygen bond of the allylalkoxy complexes with ZnMe2 leading to eta(3)-allyl(methyl) nickel was very efficient to suppress the reverse reaction of the oxidative cyClization. The methylated eta(3)-allylnickel compound underwent the reductive elimination. The Carbonylative coupling reaction of the eta(3)-allyl(methyl) nickel proceeded as well under a carbon monoxide atmosphere. Similarly, the addition of Me3SiCl to eta(3):eta(1)-allylalkoxynickel complexes was also efficient for the inhibition of the reverse reaction. The resulting eta(3)-1-siloxyethylallylnickel complex was treated with carbon monoxides followed by the addition of MeOH to give the expected hydroxyester. This method is efficient as well even for the eta(3):eta(1)-allyl(alkoxy) nickel complex containing acetone as a component, which was so prone to undergo the reverse reaction hampering its isolation. The isolation of the eta(3):eta(1)-allylalkoxynickel complex containing ketone as a component was made easier by the use of heavier butadiene and ketone, such as 2,3-diBenzyl-1,3-butadiene and benzophenone or by the use of cyClobutanone. The reaction with styrene oxide gave the eta(3):eta(1)-allylalkoxynickel containing phenylacetoaldehyde, an isomer of styrene oxide.Reversible carbon-carbon bond formation between 1,3-dienes and aldehyde or ketone on nickel(0)x99200628#N/AFALSE
2510
ja064725010.1021/ja0647250FALSEhttps://doi.org/10.1021/ja0647250Kawaguchi, HJ. Am. Chem. Soc.From carbon dioxide to methane: Homogeneous reduction of carbon dioxide with hydrosilanes catalyzed by zirconium-borane complexes183200632#N/ATRUE
2511
ja064378u10.1021/ja064378uFALSEhttps://doi.org/10.1021/ja064378uVogt, DJ. Am. Chem. Soc.The enantioselective step in the nickel-catalyzed hydrocyanation of 1,3-cyClohexadiene42200623#N/ATRUE
2512
ja060133610.1021/ja0601336https://doi.org/10.1021/ja0601336Berreau, LMJ. Am. Chem. Soc.The synthesis, characterization, and hemithioacetal isomerization reactivity of a mononuClear Ni(II) deprotonated amide complex, [(bppppa(-))Ni]CIO4 center dot CH3OH (1, bppppa(-) = monoanion of N,N-bis-[(6-phenyl-2-pyridyl) methyl]-N-[(6-pivaloylamido-2-pyridyl) methyl]amine), are reported. Complex 1 was characterized by X-ray crystallography, H-1 NMR, UV-vis, FTIR, and elemental analysis. Treatment of 1 with an equimolar amount of the hemithioacetal PhC(O)CH(OH)SCD3 in dry acetonitrile results in the production of the thioester PhCH(OH)C(O)SCD3 in similar to 60% yield. This reaction is conveniently monitored via H-2 NMR spectroscopy. A protonated analogue of 1, [(bppppa)Ni](ClO4)(2) (2), is unreactive with the hemithioacetal, thus indicating the requirement of the anionic chelate ligand in 1 for hemithioacetal isomerization reactivity. Complex 1 is unreactive with the thioester product, PhCH(OH)C(O)SCD3, which indicates that the pK(a) value for the PhCH(OH)C(O)SCD3 proton of the thioester must be significantly higher than the pK(a) value of the C-H proton of the hemithioacetal (PhC(O)CH(OH)SCD3). Complex 1 is the first well-characterized Ni(II) coordination complex to exhibit reactivity relevant to Ni(II)-containing E. coli glyoxalase I. Treatment of NiBr2 center dot 2H(2)O with PhC(O)CH(OH)SCD3 in the presence of 1-methylpyrrolidine also yields thioester product, albeit the reaction is slower and involves the formation of multiple -SCD3 labeled species, as detected by H-2 NMR spectroscopy. The results of this study provide the first insight into hemithioacetal isomerization promoted by a synthetic Ni(II) coordination complex versus a simple Ni(II) ion.Glyoxalase I-type hemithioacetal isomerization reactivity of a mononuClear Ni(II) deprotonated amide complexx14200625#N/AFALSE
2513
ja060047610.1021/ja0600476FALSEhttps://doi.org/10.1021/ja0600476Markovic, NMJ. Am. Chem. Soc.The surface properties of PtM (M) Co, Ni, Fe) polycrystalline alloys are studied by utilizing Auger electron spectroscopy, low energy ion scattering spectroscopy, and ultraviolet photoemission spectroscopy. For each alloy initial surface characterization was done in an ultrahigh vacuum (UHV) system, and depending on preparation procedure it was possible to form surfaces with two different compositions. Due to surface segregation thermodynamics, annealed alloy surfaces form the outermost Pt-skin surface layer, which consists only platinum atoms, while the sputtered surfaces have the bulk ratio of alloying components. The measured valence band density of state spectra Clearly shows the differences in electronic structures between Pt-skin and sputtered surfaces. Well-defined surfaces were hereafter transferred out from UHV and exposed to the acidic (electro) chemical environment. The electrochemical and post-electrochemical UHV surface characterizations revealed that Pt-skin surfaces are stable during and after immersion to an electrolyte. In contrast all sputtered surfaces formed Pt-skeleton outermost layers due to dissolution of transition metal atoms. Therefore, these three different near-surface compositions (Pt-skin, Pt-skeleton, and pure polycrystalline Pt) all having pure-Pt outermost layers are found to have different electronic structures, which originates from different arrangements of subsurface atoms of the alloying component. Modification in Pt electronic properties alters adsorption/catalytic properties of the corresponding bimetallic alloy. The most active systems for the electrochemical oxygen reduction reaction are established to be the Pt-skin near-surface composition, which also have the most shifted metallic d-band center position versus Fermi level.Effect of surface composition on electronic structure, stability, and electrocatalytic properties of Pt-transition metal alloys: Pt-skin versus Pt-skeleton surfaces
Electrocatalytic
x754200634#N/AFALSE
2514
ja063829810.1021/ja0638298FALSEhttps://doi.org/10.1021/ja0638298Linic, SJ. Am. Chem. Soc.Controlling carbon surface chemistry by alloying: Carbon tolerant reforming catalyst147200618#N/ATRUE
2515
ja063357x10.1021/ja063357xFALSEhttps://doi.org/10.1021/ja063357xKociok-Kohn, GJ. Am. Chem. Soc.Observation of intramolecular paramagnetic T-1 spin decoupling in the C-13 NMR spectra of triazacyClohexane complexes of Ni(II)520067#N/ATRUE
2516
ja062770210.1021/ja0627702FALSEhttps://doi.org/10.1021/ja0627702Lindahl, PAJ. Am. Chem. Soc.Acetyl-CoA synthase/carbon monoxide dehydrogenase is a Ni-Fe-S-containing enzyme that catalyzes the synthesis of acetyl-CoA from CO, CoA, and a methyl group. The methyl group is transferred onto the enzyme from a corrinoid-iron-sulfur protein (CoFeSP). The kinetics of two steps within the catalytic mechanism were studied using the stopped-flow method, inCluding the insertion of CO into a putative Ni-2+-CH3 bond and the transfer of the resulting acetyl group to CoA. Neither step had been studied previously. Reactions were monitored indirectly, starting with the methylated intermediate form of the enzyme. Resulting traces were analyzed by constructing a simple kinetic model describing the catalytic mechanism under reducing conditions. Besides methyl group transfer, CO insertion, and acetyl group transfer, fitting to experimental traces required the inClusion of an inhibitory step in which CO reversibly bound to the form of the enzyme obtained immediately after product release. Global simulation of the reported datasets afforded a consistent set of kinetic parameters. The equilibrium constant for the overall synthesis of acetyl-CoA was estimated and compared to the product of the individual equilibrium constants. Simulations obtained with the model duplicated the essential behavior of the enzyme, in terms of the variation of activity with [CO], and the time-dependent decay of the NiFeC EPR signal upon reaction with CoFeSP. Under standard assay conditions, the model suggests that the vast majority of active enzyme molecules in a population should be in the methylated form, suggesting that the subsequent catalytic step, namely CO insertion, is rate limiting. This conClusion is further supported by a sensitivity analysis showing that the rate is most sensitively affected by a change in the rate coefficient associated with the CO insertion step.Kinetics of CO insertion and acetyl group transfer steps, and a model of the acetyl-CoA synthase catalytic mechanism35200635#N/ATRUE
2517
ja058454p10.1021/ja058454pFALSEhttps://doi.org/10.1021/ja058454pYamamoto, HJ. Am. Chem. Soc.Catalytic enantioselective Nozaki-Hiyama allylation reaction with tethered bis(8-quinolinolato) (Tbox) chromium complexx68200630#N/AFALSE
2518
ja058265710.1021/ja0582657FALSEhttps://doi.org/10.1021/ja0582657Iwasa, YJ. Am. Chem. Soc.We report on the first synthesis of Li-intercalated manganese-phthalocyanine (MnPc) in the bulk form and on the evolution of the structural and magnetic properties as a function of Li concentration, x. We find that solid beta-MnPc, which comprises rodlike assemblies of individual planar molecules, is best described as a glassy one-dimensional ferromagnet without three-dimensional ordering and that it can be quasi-continuously intercalated with Li up to x= 4, forming an isosymmetrical series of Li-x[MnPc] phases. Inserted Li+ ions strongly bond to pyrrole-bridging nitrogen atoms of the PC rings, thereby disrupting the ferromagnetic Mn-(NaMn)-Mn-... superexchange pathways. This gradually induces a crossover of the intrachain exchange interactions from ferromagnetic to antiferromagnetic as the doping level, x, increases coupled with a spin-state transition of the Mn2+ ions from intermediate spin, S = 3/2, to high spin, S = 5/2.Synthesis, structure, and magnetic properties of Li-doped manganese-phthalocyanine, Li-x[MnPc] (0 <= x <= 4)x54200630#N/AFALSE
2519
ja058183i10.1021/ja058183ihttps://doi.org/10.1021/ja058183iCoates, GWJ. Am. Chem. Soc.Living polymerization of alpha-olefins with an alpha-diimine Ni(II) catalyst: Formation of well-defined ethylene-propylene copolymers through controlled chain-walkingx143200623#N/AFALSE
2520
ja058171x10.1021/ja058171xFALSEhttps://doi.org/10.1021/ja058171xGeiger, WEJ. Am. Chem. Soc.An integrated approach to the control of Delta E-1/2 values, and therefore comproportionation equilibria, through medium effects was delineated for multi-step redox reactions involving cationic products. Delta E-1/2 values (defined as E-1/2(2+/1+) - E-1/2(1+/0)) of the two one-electron oxidations of bis(fulvalene)dinickel, 1, were measured under 45 different conditions of solvent and supporting electrolyte. The smallest value, 212 mV, was found in anisole/0.1 M [NBU4]Cl and the largest, 850 mV, in CH2Cl2/0.02 M Na[B(C6H3(CF3)(2))(4)]. By systematically changing the solvent properties, the degree of ion-pairing strengths of the supporting electrolyte ions, and the concentration of the electrolytes, a set of ideal properties was found for maximizing Delta E-1/2 values involving positively charged electrode products. Most importantly (i) the solvent must be of lower polarity and low donor strength and (ii) the supporting electrolyte must have a weakly coordinating anion (WCA). The contrast in ion-pairing tendencies of 1(2+) with WCAs (on the weak side) and halides (on the strong side) mimics that of dianions in THF, where longer chain tetraAlkylammonium ions (weak ion pairing) contrast with alkali metal ions (strong ion pairing). The broad picture of medium effects is that of a mirror image of solvent and electrolyte properties that influence the tuning of Delta E-1/2 values for multi-electron systems. Application was made both to the four-step oxidation process and to the two-step reduction process of the tetraferrocentyl complex Ni(S2C2FC2)(2), Fc = Fe(C5H5)(C5H4), 2. The two-electron process 2(0/2-) is observed either as a single two-electron voltammetric wave or as two well-separated one-electron waves, depending on the medium. The consequences of the present model for the interpretation of Delta E-1/2 values in mixed-valence chemistry are discussed.Use of weakly coordinating anions to develop an integrated approach to the tuning of Delta E-1/2 values by medium effectsx425200694#N/AFALSE
2521
ja061864910.1021/ja0618649FALSEhttps://doi.org/10.1021/ja0618649Fernandez, COJ. Am. Chem. Soc.The aggregation of alpha-synuClein (AS) is characteristic of Parkinson's disease and other neurodegenerative synuCleinopathies. Interactions with metal ions affect dramatically the kinetics of fibrillation of AS in vitro and are proposed to play a potential role in vivo. We recently showed that Cu(II) binds at the N-terminus of AS with high affinity (K(d) similar to 0.1 mu M) and accelerates its fibrillation. In this work we investigated the binding features of the divalent metal ions Fe(II), Mn(II), Co(II), and Ni(II), and their effects on AS aggregation. By exploiting the different paramagnetic properties of these metal ions, NMR spectroscopy provides detailed information about the protein-metal interactions at the atomic level. The divalent metal ions bind preferentially and with low affinity (millimolar) to the C-terminus of AS, the primary binding site being the (119)DPDNEA(124) motif, in which Asp121 acts as the main anchoring residue. Combined with backbone residual dipolar coupling measurements, these results suggest that metal binding is not driven exClusively by electrostatic interactions but is mostly determined by the residual structure of the C-terminus of AS. A comparative analysis with Cu(II) revealed a hierarchal effect of AS-metal(II) interactions on AS aggregation kinetics, dictated by structural factors corresponding to different protein domains. These findings reveal a strong link between the specificity of AS-metal(II) interactions and the enhancement of aggregation of AS in vitro. The elucidation of the structural basis of AS metal binding specificity is then required to elucidate the mechanism and Clarify the role of metal-protein interactions in the etiology of Parkinson's disease.Interaction of alpha-synuClein with divalent metal ions reveals key differences: A link between structure, binding specificity and fibrillation enhancement237200668#N/ATRUE
2522
ja057845110.1021/ja0578451FALSEhttps://doi.org/10.1021/ja0578451Neese, FJ. Am. Chem. Soc.Transition metal complexes involving the benzene-1,2-dithiol (L (2-)) and Sellmann's 3,5-di-tert-butylbenzene-1,2-dithiol(LBu 2-) ligands have been studied by UV-vis, infrared (IR), and resonance Raman (rR) spectroscopies. Raman spectra were obtained in resonance with the intervalence charge transfer (IVCT) bands in the near-infrared region and ligand-to-metal charge transfer (LMCT) bands in the near-UV region. Geometry optimization and frequency calculations using density functional theory (DFT) have been performed for [M(L)(2)](z) and [M(L-Bu)(2)](z) species (M = Ni, Pd, Pt, Co, Cu, Au, z = -1; M = Au, z = 0). On the basis of frequency calculations and normal-mode analysis, we have assigned the most important totally symmetric vibrations as well as corresponding overtone and combination bands that appear in rR spectra of compounds [Ni(L)(2)](1-), [M(L-Bu)(2)](1-) (M = Ni, Pt, Co, Cu). Experimental values of dimensionless normal coordinate displacements in excited states have been determined by fitting of rR spectra together with the absorption band shape, based on the time-dependent theory of Heller. Time-dependent density functional theory (TD-DFT) and multireference post-Hartree-Fock ab initio calculations, using the difference dedicated configuration interaction (MR-DDCI) method, were carried out to evaluate dimensionless normal coordinate displacements quantum chemically. The calculations show encouraging agreement with the experimental values. The large distortions along several normal modes led to significant vibronic broadening of lVCT and LMCT bands, and the broadening was accounted for in the deconvolution of the absorption spectra. The presence of an intense rR band around similar to 1100 cm(-1) was found to be a reliable marker for the presence of sulfur-based radicals.Vibrational markers for the open-shell character of transition metal bis-dithiolenes: An infrared, resonance Raman, and quantum chemical studyx892006110#N/AFALSE
2523
ja057255310.1021/ja0572553FALSEhttps://doi.org/10.1021/ja0572553Johnson, SAJ. Am. Chem. Soc.Nickel(0)-catalyzed isomerization of an aryne complex: Formation of a dinuClear Ni(I) complex via C-H rather than C-F bond Activationx46200623#N/AFALSE
2524
ja057117d10.1021/ja057117dFALSEhttps://doi.org/10.1021/ja057117dGossauer, AJ. Am. Chem. Soc.Taking into consideration the model geometry of the macrocyClic hexaporphyrin 1 as a host molecule, the structure of a benzene-centered porphyrin trimer bearing pyridine rings at the apical positions has been designed with the aim to use the latter as a template for the synthesis of its own host. Indeed, in the presence of the porphyrin trimer 5, the yield of the cyClization of a linear porphyrin hexamer, as a precursor of 1, could be improved from 8 to 30% (variable yield) to 50% (reproducible yield). Even the condensation of equimolecular amounts of porphyrin monomers 20b and 21b in the presence of 5 led-probably through a loose preorganized complex between the latter and the Zn(II) chelate 20b-to the formation of I in only five steps from 19, as compared with 13 steps of the synthesis via linear porphyrin hexamer in the absence of template. As evidenced by H-1 NMR spectroscopic analysis of the supramolecular complex between 5 and an analogue of 1b in which all H-atoms at the pyrrole rings have been replaced by deuterium, in the presence of unlabeled 1b, a rapid dissociation and recombination of the host and guest molecules forming the supramolecular complex takes place even at low temperature (-40 degrees C). As at 55 degrees C all six Zn(II) porphyrinate rings of the complex 1b + 5 become magnetically equivalent in the 500 MHz H-1 NMR time scale, approximate kinetic data for the ligand exchange process could be obtained.One-step template-directed synthesis of a macrocyClic tetraArylporphyrin hexamer based on supramolecular interactions with a C-3-symmetric tetraArylporphyrin trimerx472006107#N/AFALSE
2525
ja056975710.1021/ja0569757FALSEhttps://doi.org/10.1021/ja0569757Long, ECJ. Am. Chem. Soc.Site-selective DNA Cleavage by diastereoisomers; of Ni(II)center dot Gly-Gly-His-derived metallopeptides was investigated through high-resolution gel analyses and molecular dynamics simulations. Ni(II)center dot L-Arg-Gly-His and Ni(II)center dot D-Arg-Gly-His (and their respective Lys analogues) targeted A/T-rich regions; however, the L-isomers consistently modified a subset of available nuCleotides within a given minor groove site, while the D-isomers differed in both their sites of preference and their ability to target individual nuCleotides within some sites. In comparison, Ni(II)center dot L-Pro-Gly-His and Ni(II)center dot D-Pro-Gly-His were unable to exhibit a similar diastereoselectivity. Simulations of the above systems, along with Ni(II)center dot Gly-Gly-His, indicated that the stereochemistry of the amino-terminal amino acid produces either an isohelical metallopeptide that associates stably at individual DNA sites (L-Arg or L-Lys) or, with D-Arg and D-Lys, a noncomplementary metallopeptide structure that cannot fully employ its side chain nor amino-terminal amine as positional stabilizing moieties. In contrast, amino-terminal Pro-containing metallopeptides of either stereochemistry, lacking an extended side chain directed toward the minor groove, did not exhibit a similar diastereoselectivity. While the identity and stereochemistry of amino acids located in the amino-terminal peptide position influenced DNA Cleavage, metallopeptide diastereoisomers containing L- and D-Arg (or Lys) within the second peptide position did not exhibit diastereoselective DNA Cleavage patterns; simulations indicated that a positively charged amino acid in this location alters the interaction of the metallopeptide equatorial plane and the minor groove leading to an interaction similar to Ni(II)center dot Gly-Gly-His.Diastereoselective DNA Cleavage recognition by Ni(II)center dot Gly-Gly-His-derived metallopeptidesx26200644#N/AFALSE
2526
ja056963l10.1021/ja056963lFALSEhttps://doi.org/10.1021/ja056963lJang, SYJ. Am. Chem. Soc.A two-dimensional (2D) square-grid coordination polymer, {[Ni(cyClam)](2)[BPTC]}(n)-2nH(2)O (1), has been assembled from [Ni(cyClam)](CIO4)(2) (cyClam = 1,4,8,11 -tetraazacyClotetradecane) and H4BPTC (H4BPTC = 1,1'-biphenyl-2,2',6,6'-tetraCarbonylic acid) in H2O/MeOH (2.51, v/v) in the presence of triethylamine. When solid 1 was immersed in the EtOH solutions of AgNO3 (1.3 x 10(-1) M) and NaAuCl4 center dot 2H(2)O (3.4 x 10(-2) M), respectively, for 5 min at room temperature, solids inCluding Ag (3.7 +/- 0.4 nm, diameter) and Au (2 nm, diameter) nanopartiCles were formed by the redox reactions between Ni(II) ions incorporated in I and metal ions, as evidenced by HRTEM images, EPR, and XPS spectra. When single-crystal 1 was heated at 180 degrees C under 10(-5) Torr for 24 h, it was transformed to dehydrated compound {[Ni(cyClam)](2)[BPTC]}(n) (2) in the single-crystal-to-single-crystal manner. The X-ray crystal structure of 2 reveals extensive dynamic motions of the molecular components in response to guest removal, involving rotation of the Carbonylate and macrocyCle, swing of the biphenyl, and bending of the macrocyClic coordination plane toward the Carbonylate plane, which reduces the interlayer distance.A redox-active two-dimensional coordination polymer: Preparation of silver and gold nanopartiCles and crystal dynamics on guest removalx227200657#N/AFALSE
2527
ja056532310.1021/ja0565323FALSEhttps://doi.org/10.1021/ja0565323Akiyama, TJ. Am. Chem. Soc.Low-valent niobium-mediated double Activation of C-F/C-H bonds: Fluorene synthesis from o-Arylated alpha,alpha,alpha-trifluorotoluene derivativesx144200642#N/AFALSE
2528
ja061536910.1021/ja0615369FALSEhttps://doi.org/10.1021/ja0615369Elsegood, MRJJ. Am. Chem. Soc.An unprecedented alpha-olefin distribution arising from a homogeneous ethylene oligomerization catalyst84200620#N/ATRUE
2529
ja061471+10.1021/ja061471+FALSEhttps://doi.org/10.1021/ja061471+Jamison, TFJ. Am. Chem. Soc.Nickel-catalyzed, Carbonyl-ene-type reactions: Selective for alpha olefins and more efficient with electron-rich aldehydes39200624#N/ATRUE
2530
ja060916r10.1021/ja060916rFALSEhttps://doi.org/10.1021/ja060916rKepert, CJJ. Am. Chem. Soc.The effect of M-II substitution on the magnitude of the negative thermal expansion (NTE) behavior within a series of Prussian Blue analogues, (MPtIV)-Pt-II(CN)(6) for M-II = Mn, Fe, Co, Ni, Cu, Zn, Cd, has been investigated using variable-temperature powder X-ray diffraction (100-400 K). The NTE behavior varies widely with MII substitution, from near zero thermal expansion in NiPt(CN)(6) (alpha = dIII dT = -1.02(11) x 10(-6) K-1) up to a maximum in CdPt(CN)(6) (alpha = -10.02(11) x 10(-6) K-1). The trend in the magnitude of the NTE behavior, with increasing atomic number (Z) of the M-II ion, follows the order Mn-II > Fe-II > Co-II > Ni-II < Cu-II > Zn-II > Cd-II, which correlates with the trends for MII cation size, the lattice parameter, and structural flexibility as indicated by the temperature-dependent structural refinements and Raman spectroscopy. Analysis of the temperature dependence of the average structures suggests that the differences in the thermal expansion are due principally to the different strengths of the metal-cyanide binding interaction and, accordingly, the different energies of transverse vibration of the cyanide bridge, with enhanced NTE behavior for more flexible lattices.Compositional dependence of negative thermal expansion in the Prussian blue analogues (MPtIV)-Pt-II(CN)(6) (M = Mn, Fe, Co, Ni, Cu, Zn, Cd)174200646#N/ATRUE
2531
ja056342s10.1021/ja056342shttps://doi.org/10.1021/ja056342sWang, LSJ. Am. Chem. Soc.A detailed understanding of the electronic structure of transition metal bis(dithiolene) complexes is important because of their interesting redox, magnetic, optical, and conducting properties and their relevance to enzymes containing molybdenum and tungsten bis(dithiolene) centers. The electronic structures of the bis(dithiolene) anions [M(mnt)(2)](n-) (M = Ni, Pd, Pt; mnt = 1,2-S2C2(CN)(2); n = 0-2) were examined by a combination of photodetachment photoelectron spectroscopy (PES) and density functional theory calculations. The combined experimental and theoretical data provide insight into the molecular orbital energy levels of [M(mnt)(2)](2-) and the ground and excited states of [M(mnt)(2)](1-) and [M(mnt)(2)]. Detachment features from ligand-based orbitals of [M(mnt)(2)](2-) occur at similar energies for each species, independent of the metal center, while those arising from metal-based orbitals occur at higher energies for the heavier congeners. Electronic excitation energies inferred for [M(mnt)(2)](1-) from the PES experiments agree well with those obtained in optical absorption experiments in solution, with the PES experiments providing additional insight into the changes in energy of these transitions as a function of metal. The singly charged anions [M(mnt)(2)](1-) were also prepared and studied independently. Electron detachment from the ground states of these doublet anions accessed the lowest singlet and triplet states of neutral [M(mnt)(2)], thereby providing a direct experimental measure of their singlet-triplet splitting.Probing the intrinsic electronic structure of the bis(dithiolene) anions [M(mnt)(2)](2-) and [M(mnt)(2)](1-) (M = Ni, Pd, Pt; mnt=1,2-S2C2(CN)(2)) in the gas phase by photoelectron spectroscopyPhotocatalystx26200664#N/AFALSE
2532
ja060876r10.1021/ja060876rFALSEhttps://doi.org/10.1021/ja060876rDarensbourg, MYJ. Am. Chem. Soc.sThe molecular structure of the acetyl CoA synthase enzyme has Clarified the role of individual nickel atoms in the dinickel active site which mediates C-C and C-S coupling reactions. The NiN2S2 portion of the biocatalyst (N2S2 a cysteine-glycine-cysteine or CGC(4-) tripeptide ligand) serves as an S-donor ligand comparable to Classical bidentate ligands operative in organometallic chemistry, ligating the second nickel which is redox and catalytically active. Inspired by this biological catalyst, the synthesis of NiN2S2 metalloligands, inCluding the solid-phase synthesis of resin-bound Ni(CGC)(2-), and sulfur-based derivatization with W(CO)(5) and Rh(CO)(2+) have been carried out. Through comparison to analogous well-characterized, solution-phase complexes, Attenuated Total Reflectance FTIR spectroscopy establishes the presence of unique heterobimetallic complexes, of the form [Ni(CGC)] M(CO)(x), both in solution and immobilized on resin beads. This work provides the initial step toward exploitation of such an evolutionarily optimized nickel peptide as a solid support anchor for hybrid bioinorganic-organometallic catalysts.A nickel tripeptide as a metallodithiolate ligand anchor for resin-bound organometallics30200632#N/ATRUE
2533
ja060747a10.1021/ja060747aFALSEhttps://doi.org/10.1021/ja060747aZargarian, DJ. Am. Chem. Soc.Reaction of the dimeric species [(eta(3)-Ind) Pd(A-Cl)] 2 (1) (Ind) indenyl) with NEt3 gives the complex (eta(3-5)-Ind) Pd(NEt3) Cl (3), whereas the analogous reactions with BnNH2 (Bn) PhCH2) or pyridine (py) afford the complexes trans-L2Pd(eta(1)-Ind) Cl ( L) BnNH2 ( 4), py ( 5)). Similarly, the one-pot reaction of 1 with a mixture of BnNH2 and the phosphine ligands PR3' gives the mixed-ligand, amino and phosphine species (PR3)( BnNH2) Pd(eta(1)-Ind) Cl (R = Cy (6a), Ph (6b)); the latter complexes can also be prepared by addition of BnNH2 to (A(3-5)-Ind) Pd(PR3) Cl (R) Cy (2a), Ph (2b)). Complexes 6 undergo a gradual decomposition in solution to generate the dinuClear Pd-I compounds (mu,eta(3)-Ind)(mu-Cl) Pd-2(PR3)(2) (R = Cy (7a), Ph (7b)) and the Pd-II compounds (BnNH2)(PR3) PdCl2 (R) Cy (8a), Ph (8b)), along with 1,1'-biindene. The formation of 7 is proposed to proceed by a comproportionation reaction between in situ-generated Pd-II and Pd-0 intermediates. Interestingly, the reverse of this reaction, disproportionation, also occurs spontaneously to give 2. All new compounds have been characterized by NMR spectroscopy and, in the case of 3, 4, 5, 6a, 7a, 7b, and 8a, by X-ray crystallography.New palladium(II)-(eta(3/5)- or eta(1)-indenyl) and dipalladium(I)-(mu,eta(3)-indenyl) complexes24200682#N/ATRUE
2534
ja060519g10.1021/ja060519gFALSEhttps://doi.org/10.1021/ja060519gHiyama, TJ. Am. Chem. Soc.Allylcyanation of alkynes: Regio- and stereoselective access to functionalized di- or trisubstituted acrylonitriles104200635#N/ATRUE
2535
ja055688010.1021/ja0556880https://doi.org/10.1021/ja0556880Yokozawa, TJ. Am. Chem. Soc.We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio3-hexylthiophene (1) with Ni(dppp)Cl-2 [dppp = 1,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the M-n is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with Aryl Grignard reagent gave HT-P3HT with Aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the H-1 NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl-2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism catalyst-transfer polycondensation.Catalyst-transfer polycondensation. Mechanism of Ni-catalyzed chain-growth polymerization leading to well-defined poly(3-hexylthiophene)x486200524#N/AFALSE
2536
ja060220y10.1021/ja060220yFALSEhttps://doi.org/10.1021/ja060220yKurosawa, HJ. Am. Chem. Soc.Formation of nickeladihydropyran by oxidative addition of cyClopropyl ketone. Key intermediate in nickel-catalyzed cyCloaddition99200622#N/ATRUE
2537
ja059911510.1021/ja0599115FALSEhttps://doi.org/10.1021/ja0599115Tamaru, YJ. Am. Chem. Soc.Highly stereo- and regioselective Ni-catalyzed homoallylation of aldimines with conjugated dienes promoted by diethylzinc (vol 126, pg 14360, 2004)620051#N/ATRUE
2538
ja058626i10.1021/ja058626iFALSEhttps://doi.org/10.1021/ja058626iHolmes, SMJ. Am. Chem. Soc.An S=6 cyanide-bridged octanuClear (Fe4Ni4II)-Ni-III complex that exhibits slow relaxation of the magnetization194200616#N/ATRUE
2539
ja058509n10.1021/ja058509nFALSEhttps://doi.org/10.1021/ja058509nVilar, RJ. Am. Chem. Soc.Stabilization of G-quadruplex DNA and inhibition of telomerase activity by square-planar nickel(II) complexes286200625#N/ATRUE
2540
ja054994a10.1021/ja054994aFALSEhttps://doi.org/10.1021/ja054994aWang, YJ. Am. Chem. Soc.The cationic complex {[Ru]=C=CHCPh2CH2CH CH2}BF4 (3a, [Ru] = (eta(5)-C5H5)(PPh3)(2)Ru) in solution transforms to {[Ru]=C=CHCH2CPh2CH=CH2}BF4 (4a) via a new metathesis process of the terminal Vinyl group with the C C of the Vinylidene group which is confirmed by C-13 labeling studies. This transformation is irreversible as revealed by deuteration and decomplexation studies. The cationic complex {[Ru]=C=CHCPh2CH2CMe=CH2}BF4 (3b) undergoes a cyClization process yielding 6b containing a eta(2)-cyClic allene ligand which is fully characterized by single-crystal X-ray diffraction analysis. Analogous complexes 4a' and 6b' ([Ru] = (eta(5)-C5H5)(dppe)Ru) containing dppe ligands were similarly obtained from protonation of the corresponding acetylide complexes via formation of Vinylidene intermediate. Protonation of the acetylide complex containing a terminal alkynyl group [Ru]-C CCPh2CH2C CH (2c) generates the Vinylidene complex {[Ru]=C=CHCPh2CH2C CH}BF4 (3c) which again undergoes an irreversible transformation to give {[Ru] C=CHCH2CPh2C CH}BF4 (4c) possibly via a g-coordinated alkynyl complex followed by hydrogen and metal migration. No similar transformation is observed for the analogous dppe complex 3c'. With an extra methylene group, complex {[Ru]=C=CHCPh2CH2CH2CH=CH2}BF4 (3d) and complex {[Ru]=C=CHCPh2CH2Ph}BF4 (3e) are stable. The presence of a gem-diphenylmethylene moiety at the Vinylidene ligand with the appropriate terminal Vinyl or alkynyl group along with the correct steric environment implements such a novel reactivity in the ruthenium Vinylidene complexes.Intramolecular metathesis of a Vinyl group with Vinylidene C=C double bond in Ru complexesx28200592#N/AFALSE
2541
ja057941210.1021/ja0579412FALSEhttps://doi.org/10.1021/ja0579412Seshadri, RJ. Am. Chem. Soc.Macroporous manganese oxides with regenerative mesopores69200617#N/ATRUE
2542
ja056448n10.1021/ja056448nFALSEhttps://doi.org/10.1021/ja056448nLi, MElectrochemical growth of highly oriented organic-inorganic superlattices using solid-supported multilamellar membranes as templates2006#N/ATRUE
2543
ja054590i10.1021/ja054590iFALSEhttps://doi.org/10.1021/ja054590iMontgomery, JJ. Am. Chem. Soc.Access to macrocyClic endocyClic and exocyClic allylic alcohols by nickel-catalyzed reductive cyClization of ynalsx73200537#N/AFALSE
2544
ja056442y10.1021/ja056442yFALSEhttps://doi.org/10.1021/ja056442yDuBois, DLJ. Am. Chem. Soc.Highly efficient electrocatalysts for both hydrogen evolution and hydrogen oxidation have been designed, synthesized, and characterized. The catalysts in their resting states are air-stable, mononuClear nickel(I I) complexes containing cyClic diphosphine ligands with nitrogen bases incorporated into the ligand backbone. X-ray diffraction studies have established that the cation of [Ni((P2N2Ph)-N-Ph)(2)(CH3CN)](BF4)(2), 6a, (where p(2)(Ph)N(2)(Ph) is 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyClooctane) is a trigonal bipyramid with bonds to four phosphorus atoms of the two bidentate diphosphine ligands and the nitrogen atom of an acetonitrile molecule. Two of the six-membered rings formed by the diphosphine ligands and Ni have boat conformations with an average (NiN)-N-... distance to the two pendant bases of 3.4 angstrom. The cation of [Ni((P2N2Bz)-N-Cy)(2)](BF4)(2), 6b, (where Cy = cyClohexyl and Bz = Benzyl) is a distorted square planar complex. For 6b, all four six-membered rings formed upon coordination of the diphosphine ligands to the metal are in the boat form. In this case, the average (NiN)-N-... distance to the pendant base is 3.3 angstrom. Complex 6a is an electrocatalyst for hydrogen production in acidic acetonitrile solutions, and compound 6b is an electrocatalyst for hydrogen oxidation in basic acetonitrile solutions. It is demonstrated that the high catalytic rates observed with these complexes are a result of the positioning of the nitrogen base so that it plays an important role in the formation and Cleavage of the H-H bond.Hydrogen oxidation and production using nickel-based molecular catalysts with positioned proton relays422200645#N/ATRUE
2545
ja054144V10.1021/ja054144VFALSEhttps://doi.org/10.1021/ja054144VKang, YJJ. Am. Chem. Soc.A novel tandem Pd-catalyzed cross-coupling and [4 + 4] cyCloaddition sequence allows the rapid synthesis of eight-membered carbocyCles starting from alpha-bromoVinyl arenes and propargyl bromides in one reaction vessel. It is noteworthy that four components are assembled into one molecule via this procedure. In contrast to alpha-bromoVinyl arenes, alpha-bromoVinyl alkanes afforded tandem cross-coupling and homo 14 + 21 cyCloaddition products. Subjecting an equimolar mixture of alpha-bromostyrene and 2-bromo-1-octene to propargyl bromides furnished the tandem Pd-catalyzed cross-coupling and hetero [4 + 2] cyCloaddition product. Exposure of equimolar mixtures of alpha-bromoVinyl arenes to allenylindium resulted in tandem a Pd-catalyzed cross-coupling and hetero [4 + 4] cyCloaddition products. Synthesis of Vinylallene from the reaction of Vinyl triflate with allenylindium followed by Pd-catalyzed carbon monoxide insertion reaction gave the corresponding 3,7-nonadienone product via tandem Pd-catalyzed cross-coupling and [4 + 4 + 1] annulation. Tandem Pd-catalyzed cross-coupling, [4 + 4] cyCloaddition, and [4 + 2] cyCloaddition provided the rapid synthesis of bicyClo[6.4.0]dodecene derivatives starting from (x-bromoVinyl arenes, propargyl bromides, and dienophiles in one operation, in which five components were integrated into one molecule.In situ generation of Vinyl allenes and its applications to one-pot assembly of cyClohexene, cyClooctadiene, 3,7-nonadienone, and bicyClo[6.4.0]dodecene derivatives with palladium-catalyzed multicomponent reactionsx97200659#N/AFALSE
2546
ja054002110.1021/ja0540021FALSEhttps://doi.org/10.1021/ja0540021Coates, GWJ. Am. Chem. Soc.A C-2-symmetric, living alpha-diimine Ni(II) catalyst: Regioblock copolymers from propylenex183200519#N/AFALSE
2547
ja054001910.1021/ja0540019FALSEhttps://doi.org/10.1021/ja204575uRodriguez, JACatalysts for hydrogen evolution from the [NiFe] hydrogenase to the Ni2P(001) surface: The importance of ensemble effectx2005#N/AFALSE
2548
ja053866j10.1021/ja053866jFALSEhttps://doi.org/10.1021/ja053866jCeyer, STJ. Am. Chem. Soc.Catalyzed CO oxidation at 70 K on an extended Au/Ni surface alloyx56200628#N/AFALSE
2549
ja053820q10.1021/ja053820qFALSEhttps://doi.org/10.1021/ja053820qFranco, FJ. Am. Chem. Soc.Ni(II) Tol-BINAP-catalyzed enantioselective Michael reactions of beta-ketoesters and unsaturated N-acylthiazolidinethionesx57200522#N/AFALSE
2550
ja056346x10.1021/ja056346xFALSEhttps://doi.org/10.1021/ja056346xBerreau, LMJ. Am. Chem. Soc.Aliphatic carbon-carbon bond Cleavage reactivity of a mononuClear Ni(II) cis-beta-keto-enolate complex in the presence of base and O-2: A model reaction for acireductone dioxygenase (ARD)43200524#N/ATRUE
2551
ja056327n10.1021/ja056327nFALSEhttps://doi.org/10.1021/ja056327nNakamura, EJ. Am. Chem. Soc.Nickel-catalyzed cross-coupling reaction of Aryl fluorides and chlorides with Grignard reagents under nickel/magnesium bimetallic cooperation200200534#N/ATRUE
2552
ja056229210.1021/ja0562292FALSEhttps://doi.org/10.1021/ja0562292Goldberg, KIJ. Am. Chem. Soc.Insertion of molecular oxygen into a palladium(II) hydride bond150200626#N/ATRUE
2553
ja056000m10.1021/ja056000mFALSEhttps://doi.org/10.1021/ja056000mGarcia, JJJ. Am. Chem. Soc.The reactions of the complexes [(dcype)NiH](2), 1, [(dippe)NiH](2), 2, and [(dtbpe)NiH](2), 3, with a mixture of BEt3 and Super-Hydride (LiHBEt3) afforded sigma-borane nickel(O) compounds of the type [(dcype)Ni(sigma-HBEt2)], 4, [(dippe)Ni(sigma-HBEt2)], 5, [(dtbpe)Ni(sigma-HBEt2)], 6, respectively, with the concomitant formation in each case of [(dcype)(2)Ni-2(H)(3)][BEt4], 7, [(dippe)(2)Ni-2(H)(3)][BEt4], 8 and [(dtbpe)(2)Ni-2(H)(3)][BEt4], 9, respectively. X-ray crystal structures are reported for 4 and 8. The reaction of BEt3 and LiHBEt3 was also reviewed in detail.sigma-Borane coordinated to nickel(0) and some related nickel(II) trihydride complexes61200563#N/ATRUE
2554
ja055396z10.1021/ja055396zFALSEhttps://doi.org/10.1021/ja055396zSuginome, MJ. Am. Chem. Soc.Nickel-catalyzed trans-alkynylboration of alkynes via Activation of a boron-chlorine bond95200525#N/ATRUE
2555
ja053556110.1021/ja0535561FALSEhttps://doi.org/10.1021/ja0535561Hruby, VJJ. Am. Chem. Soc.This paper describes a systematic study of addition reactions between the chiral Ni(II) complex of the Schiff base of glycine with (S)-o-[N-(N-Benzylprolyl)amino]benzophenone and (S)- or (R)-3-[(E)enoyl]-4-phenyl-1,3-oxazolidin-2-ones as a general and synthetically efficient approach to beta-substituted pyroglutamic acids and relevant compounds. These reactions were shown to occur at room temperature in the presence of nonchelating organic bases and, most notably, with very high (>98% diastereomeric excess (de)) stereoselectivity at both newly formed stereogenic centers. The stereochemical outcome of the reactions was found to be overwhelmingly controlled by the stereochemical preferences of the Michael acceptors, and the chirality of the glycine complex influenced only the reaction rate. Thus, in the reactions of both the (S)-configured Ni(II) complex and the Michael acceptors, the reaction rates were exceptionally high, allowing preparation of the corresponding products with virtually quantitative (>98%) chemical and stereochemical yields. In contrast, reactions of the (S)-configured Ni(II) complex and (R)-configured Michael acceptors proceeded at noticeably lower rates, but the addition products were obtained in high diastereo-and enantiomeric purity. To rationalize the remarkably high and robust stereoselectivity observed in these reactions, we consider an enzyme-substrate-like mode of interaction involing a topographical match or mismatch of two geometric figures. Excellent chemical and stereochemical yields, combined with the simplicity and operational convenience of the experimental procedures, render the present method of immediate use for preparing various beta-substituted pyroglutamic acids and related compounds.Michael addition reactions between chiral equivalents of a nuCleophilic glycine and (S)- or (R)-3-[(E)-Enoyl]-4-phenyl-1,3-oxazolidin-2-ones as a general method for efficient preparation of beta-substituted pyroglutamic acids. Case of topographically controlled stereoselectivityx87200558#N/AFALSE
2556
ja053386s10.1021/ja053386sFALSEhttps://doi.org/10.1021/ja053386sThomson, RJJ. Am. Chem. Soc.Ni(II) Tol-BINAP-catalyzed enantioselective orthoester Alkylations of N-acylthiazolidinethionesx56200518#N/AFALSE
2557
ja055363j10.1021/ja055363jFALSEhttps://doi.org/10.1021/ja055363jJamison, TFJ. Am. Chem. Soc.Simple alkenes as substitutes for organometallic reagents: Nickel-catalyzed, intermolecular coupling of aldehydes, silyl triflates, and alpha olefins60200529#N/ATRUE
2558
ja055289510.1021/ja0552895FALSEhttps://doi.org/10.1021/ja0552895Matsuda, TJ. Am. Chem. Soc.Eight-membered ring construction by [4+2+2] annulation involving beta-carbon elimination142200618#N/ATRUE
2559
ja053038q10.1021/ja053038qFALSEhttps://doi.org/10.1021/ja053038qde Jong, KPJ. Am. Chem. Soc.Deposition precipitation of nickel hydroxide onto modified carbon nanofibers has been studied and compared to deposition onto silica. The carbon nanofiber support materials consisted of graphite-like material of the fishbone-type with a diameter of 20-50 nm and a specific surface area of 150 m(2)/g. Modification involved surface oxidation (CNF-O) optionally followed by partial reduction (CNF-OR) or thermal treatment (CNF-OT). Titration of the support materials showed the presence of 0.17 and 0.03 mmol/g Carbonylic acid groups for CNF-O and CNF-OR, respectively. For the CNF-OT only basic groups were present. The deposition precipitation of 20 wt % nickel onto these supports has been studied by time dependent pH and nickel loading studies. With silica, nickel ion adsorption did not occur prior to nuCleation of the nickel hydroxide phase at pH = 5.6. With CNF-O, nickel ion adsorption took place right from the start of the deposition process at pH = 3.5, and at pH = 5.6 already 4 wt % nickel was adsorbed. NuCleation of nickel hydroxide onto adsorbed nickel ion Clusters proceeded subsequently. Characterization of the dried Ni/CNF-O samples with TEM and XRD showed well dispersed and thin (5 nm) platelets of nickel hydroxide adhering to the carbon nanofibers. After reduction at 773 K in hydrogen the Ni/CNF-O contained metallic nickel partiCles of 8 nm homogeneously distributed over the fibers. With CNF-OR and CNF-OT, precipitation of large platelets (> 500 nm) separate from the support took place. Clearly, the presence of Carbonylic acid groups is essential to successfully deposit nickel hydroxide onto modified carbon nanofibers.Deposition precipitation for the preparation of carbon nanofiber supported nickel catalystsx166200552#N/AFALSE
2560
ja052953910.1021/ja0529539FALSEhttps://doi.org/10.1021/ja0529539Blackburn, NJJ. Am. Chem. Soc.Sco1 is a mitochondrial membrane protein involved in the assembly of the CUA site of cytochrome c oxidase. The Bacillus subtilis genome contains a homologue of yeast Sco(1), YpmQ (hereafter termed BSco), deletion of which leads to a phenotype lacking in caa(3) (CUA-containing) oxidase activity but expressing normal levels of aa(3) (quinol) oxidase activity. Here, we report the characterization of the metal binding site of BSco in its Cu(I)-, Cu(II)-, Zn(II)-, and Ni(II)-bound forms. Apo BSco was found to bind Cu(II), Zn(II), and Ni(II) at a 1:1 protein/metal ratio. The Cu(l) protein could be prepared by either dithionite reduction of the Cu(II) derivative or by reconstitution of the apo protein with Cu(I). X-ray absorption (XAS) spectroscopy showed that Cu(I) was coordinated by two cysteines at 2.22 +/- 0.01 angstrom and by a weakly bound low-Zscatterer at 1.95 +/- 0.03 angstrom. The Cu(II) derivative was reddish-orange and exhibited a strong type-2 thiolate to Cu(II) transition around 350 nm. Multifrequency electron paramagnetic resonance (EPR), electron-nuClear double resonance (ENDOR), and electron spin-echo envelope modulation (ESEEM) studies on the Cu(II) derivative provided evidence of one strongly coupled histidine residue, at least one strongly coupled cysteine, and coupling to an exchangeable proton. XAS spectroscopy indicated two cysteine ligands at 2.21 angstrom and two O/N donor ligands at 1.95 A, at least one of which is derived from a coordinated histidine. The Zn(II) and Ni(II) derivatives were 4-coordinate with MS2N(His)X coordination. These results provide evidence that a copper chaperone can engage in redox chemistry at the metal center and may suggest interesting redox-based mechanisms for metalation of the mixed-valence CUA center of cytochrome c oxidase.Spectroscopic studies of metal binding and metal selectivity in Bacillus subtilis BSco, a homologue of the yeast mitochondrial protein scolpx49200586#N/AFALSE
2561
ja052951o10.1021/ja052951oFALSEhttps://doi.org/10.1021/ja052951oEklund, PCJ. Am. Chem. Soc.IR and Raman spectroscopy has been used to study the evolution of the vibrational spectrum of bundled single-walled carbon nanotubes (SWNTs) during the purification process needed to remove metal catalyst and amorphous carbon present in arc-derived SWNT soot. We have carried out a systematic study to define the different outcomes stemming from the purification protocol (e.g., DO, DO/HCl, DO/HNO3, H2O2, H2O2/HCl), where dry oxidation (DO) or refluxing in H2O2 was used in a first purification step to remove amorphous carbon. The second step involves acid reflux (HCl or HNO3) to remove the residual growth catalyst (Ni-Y). During strong chemical processing, it appears possible to create additional defects where carbon atoms are eliminated, the ring structure is now open, localized C C bonds are created, and O-containing groups can be added to this defect to stabilize the structure. Evolution of SWNT skeletal disorder obtained via chemical processing was studied by Raman scattering. Higher intensity ratios of Rand G-band (I-R/I-G) are more typically found in SWNT materials with low D-band intensity and narrow G-band components. Using IR transmission through thin films of nanotubes, we can resolve the structure due to functional groups that were present in the starting material or added through chemical processing. After high-temperature vacuum annealing of the purified material at 1100 degrees C, IR spectroscopy shows that most of the added functional groups can be removed and that the structure that remains is assigned to the one- and two-phonon modes of SWNTs.Raman and IR spectroscopy of chemically processed single-walled carbon nanotubesx485200546#N/AFALSE
2562
ja055051g10.1021/ja055051gFALSEhttps://doi.org/10.1021/ja055051gDarensbourg, MYJ. Am. Chem. Soc.The physical properties and structures of a series of six complexes of the type (NiN2S2)W(CO)(4) have been used to establish electronic and steric parameters for square planar NiN2S2 complexes as bidentate, S-donor ligands. According to the nu(CO) stretching frequencies and associated computed Cotton-Kraihanzel force constants of the tungsten Carbonyl adducts, there is little difference in donor abilities of the five neutral NiN2S2 metallodithiolate ligands in the series. The dianionic Ni(ema)(2-) (ema = N,N-ethylenebis(2-mercaptoacetamide)) complex transfers more electron density onto the W(CO)(4) moiety. A ranking of donor abilities and a comparison with Classical bidentate ligands is as follows: Ni(ema)(=) > {[NiN2S2)](0)} > bipy approximate to phen > Ph2PCH2CH2PPh2 > Ph2PCH2PPh2. Electrochemical data from cyClic voltammetry find that the reduction event in the (NiN2S2)W(CO)(4) derivatives is shifted to more positive potentials by ca. 0.5 V compared to the ca. -2 V Ni-II/I redox event in the free NiN2S2 ligand, consistent with the electron drain from the nickel-dithiolate ligands by the W(CO)(4) acceptor. Differences in Ni-II/I Delta E-1/2 values appear to have a ligand dependence which is related to a structural feature of the hinge angle imposed by the (mu-SR)(2) bridges. Thus the angle formed by the intersection of NiN2S2/WS2C2 planes has been established by X-ray diffraction analyses as a unique orientational feature of the nickel-dithiolate ligands in contrast to Classical diphosphine or diimine ligands and ranges in value from 136 to 107 degrees. Variable-temperature C-13 NMR studies show that the spatial orientations of the ligands remained fixed with respect to the W(CO)(4) moiety to temperatures of 100 degrees C.Characterization of steric and electronic properties of NiN2S2 complexes as S-donor metallodithiolate ligands46200557#N/ATRUE
2563
ja054926o10.1021/ja054926oFALSEhttps://doi.org/10.1021/ja054926oMarchon, JCJ. Am. Chem. Soc.Circular dichroism (CD) spectra and density functional theory (DFT) calculations are reported for a series of conformationally bistable chiroporphyrins with 8-methylene bridles MBCP-8, which can display either an alpha alpha alpha alpha or an alpha beta alpha beta orientation of their meso substituents. From DFT geometry optimizations, the most stable form of ZnBCP-8 is found to be the alpha alpha alpha alpha conformer. By passing to NiBCP-8, there is a strong stabilization of the alpha beta alpha beta conformation with respect to the alpha alpha alpha alpha conformation, consistent with the X-ray structures of alpha alpha alpha alpha-ZnBCP-8 and alpha beta alpha beta- NiBCP-8. A correlation between the sign of the CD signal in the Soret region and the conformation of the BCP-8 compounds is reported: the alpha alpha alpha alpha conformers H2BCP-8 and ZnBCP-8 show a positive CD signal, whereas the alpha beta alpha beta conformers NiBCP-8 and CuBCP-8 exhibit a negative signal. The possible contributions to the rotational strengths of alpha beta alpha beta-NiBCP-8 and alpha alpha alpha-ZnBCP8, calculated on the basis of their crystal structures, have been analyzed. The CD signals are found to result from a combination of both the inherent chirality of the porphyrin and of extrinsic contributions due to the chiral bridles. These results may have a broad significance for understanding the chiroptical properties of chiral porphyrins and hemoproteins and for monitoring stimuli-responsive, conformationally bistable chiroporphyrin compounds.Chiroptical and computational studies of a bridled chiroporphyrin and of its nickel(II), copper(II), and zinc(II) complexes19200654#N/ATRUE
2564
ja052515210.1021/ja0525152FALSEhttps://doi.org/10.1021/ja200289wSolomon, EIVariable-temperature, variable-field magnetic circular dichroism studies of tris-hydroxy- and mu(3)-oxo-bridged trinuClear Cu(II) complexes: Evaluation of proposed structures of the native intermediate of the multicopper oxidasesx2005#N/AFALSE
2565
ja054690o10.1021/ja054690oFALSEhttps://doi.org/10.1021/ja054690oBrunold, TCJ. Am. Chem. Soc.Methyl transfer reactions are important in a number of biochemical pathways. An important Class of methyltransferases uses the cobalt cofactor cobalamin, which receives a methyl group from an appropriate methyl donor protein to form an intermediate organometallic methyl-Co bond that subsequently is Cleaved by a methyl acceptor. Control of the axial ligation state of cobalamin influences both the mode (i.e., homolytic vs heterolytic) and the rate of Co-C bond Cleavage. Here we have studied the axial ligation of a corrinoid iron-sulfur protein (CFeSP) that plays a key role in energy generation and cell carbon synthesis by anaerobic microbes, such as methanogenic archaea and acetogenic bacteria. This protein accepts a methyl group from methyltetrahydrofolate forming Me-Co3+CFeSP that then donates a methyl cation (Me) from MeCo3+CFeSP to a nickel site on acetyl-CoA synthase. To unambiguously establish the binding scheme of the corrinoid cofactor in the CFeSP, we have combined resonance Raman, magnetic circular dichroism, and EPR spectroscopic methods with computational chemistry. Our results Clearly demonstrate that the Me-Co3+ and Co2+ states of the CFeSP have an axial water ligand like the free MeCbi(+) and Co2+ Cbi(+) cofactors; however, the Co-OH2 bond length is lengthened by about 0.2 angstrom for the protein-bound cofactor. Elongation of the Co-OH2 bond of the CFeSP-bound cofactor is proposed to make the cobalt center more Co1+-like, a requirement to facilitate heterolytic Co-C bond Cleavage.Spectroscopic studies of the corrinoid/iron-sulfur protein from Moorella thermoacetica38200681#N/ATRUE
2566
ja052350x10.1021/ja052350xhttps://doi.org/10.1021/ja052350xZiegler, TJ. Am. Chem. Soc.Calculations utilizing anionic substituted derivates of the cationic N <^> N Ni(II) and Pd(II) diimine Brookhart complex have been carried out on the barriers of ethylene and acrylonitrile insertion into a M- methyl, propyl and CH(CN)Et bond for M = Ni, Pd. The possibility of side reactions such as chelate formation with the polar functionality and oligomerization of the active species after acrylonitrile insertion are explored. The diimine ring system N <^> N = -NRCR1CR2NR with R = 2,6-C6H3(i-Pr)(2) and R-1,R-2 = Me was functionalized by adding one or two anionic groups (BF3-, etc.) in place of i-Pr on the Aryl rings or by replacing one Me diimine backbone group (R-1) with BH3-. The objective of this investigation is computationally to design catalysts for ethylene/acrylonitrile copolymerization that have activities that are comparable to that of the cationic Ni(II) diimine or at least the Pd(II) diimine Brookhart system for ethylene homopolymerization. Complexes that might meet this objective are discussed.Copolymerization of ethylene with polar monomers: Chain propagation and side reactions. A DFT theoretical study using zwitterionic Ni(II) and Pd(II) catalystsx18200570#N/AFALSE
2567
ja052333810.1021/ja0523338FALSEhttps://doi.org/10.1021/ja0523338Sasaki, TJ. Am. Chem. Soc.We report on the controlled synthesis of single-crystal platelets of alpha- and beta-Co(OH)(2) via homogeneous precipitation using hexamethylenetetramine as a hydrolysis agent. The alpha- and beta-Co(OH)(2) hexagonal platelets of several micrometers in width and about 15 nm in thickness were reproducibly yielded in rather dilute CoCl2 solutions in the presence and absence of NaCl at 90 degrees C, respectively. The phase and size control of the products were achieved by varying both CoCl2 and NaCl concentrations. Polarized optical microscope observations revealed Clear liquid crystallinity of colloidal suspensions of these high aspect-ratio platelets. The as-prepared alpha-Co(OH)(2) containing interlayer chloride ions was intercalated with various inorganic or organic anions, keeping its high crystallinity and hexagonal platelike morphology.Selective and controlled synthesis of alpha- and beta-cobalt hydroxides in highly developed hexagonal plateletsx483200551#N/AFALSE
2568
ja054248610.1021/ja0542486FALSEhttps://doi.org/10.1021/ja0542486Kurosawa, HAlMe3-promoted oxidative cyClization of eta(2)-alkene and eta(2)-ketone on nickel(0). Observation of intermediate in methyl transfer process2005#N/ATRUE
2569
ja053794w10.1021/ja053794wFALSEhttps://doi.org/10.1021/ja053794wSchweiger, AJ. Am. Chem. Soc.Methyl-coenzyme M reductase (MCR) catalyses the reduction of methyl-coenzyme M (CH3-S-CoM) with coenzyme B (H-S-CoB) to CH4 and CoM-S-S-CoB in methanogenic archaea. Here we present a pulse EPR study of the ready form MCRox1, providing a detailed description of the spin density and the coordination of coenzyme M (CoM) to the Ni cofactor F-430. To achieve this, MCR was purified from cells grown in a Ni-61 enriched medium and samples were prepared in D2O with the substrate analogue CoM either deuterated in the P-position or with S-33 in the thiol group. To obtain the magnetic parameters ENDOR and HYSCORE measurements were done at X- and Q-band, and CW EPR, at X- and W-band. The hyperfine couplings of the P-protons of CoM indicate that the nickel to beta-proton distances in MCRox1 are very similar to those in Ni(II)-MCRox1-silent, and thus the position of CoM relative to F-430 is very similar in both species. Our thiolate sulfur and nickel EPR data prove a Ni-S coordination, with an unpaired spin density on the sulfur of 7 +/- 3%. These results highlight the redox-active or noninnocent nature of the sulfur ligand on the oxidation state. Assuming that MCRox1 is oxidized relative to the Ni(II) species, the complex is formally best described as a Ni(III) (d(7)) thiolate in resonance with a thiyl radical/high-spin Ni(II) complex, Ni-III--SR <-> Ni-II-(SR)-S-..Spin density and coenzyme M coordination geometry of the ox1 form of methyl-coenzyme M reductase: A pulse EPR study41200553#N/ATRUE
2570
ja053723x10.1021/ja053723xFALSEhttps://doi.org/10.1021/ja053723xLatos-Grazynski, LJ. Am. Chem. Soc.Dithiadiazuliporphyrin: Facile generation of carbaporphyrinoid cation radical and dication54200530#N/ATRUE
2571
ja053715g10.1021/ja053715gFALSEhttps://doi.org/10.1021/ja053715gYamashita, MJ. Am. Chem. Soc.Direct observation of the disorder of the methyl group of (R)-1,2-diaminopropane ligand in the quasi-1D bromo-bridged Ni(III) complex by STM7200522#N/ATRUE
2572
ja050923010.1021/ja0509230FALSEhttps://doi.org/10.1021/ja0509230Rayner, DMJ. Am. Chem. Soc.We report on the interaction of carbon monoxide with cationic gold Clusters in the gas phase. Successive adsorption of CO molecules on the Au-n(+) Clusters proceeds until a Cluster size specific saturation coverage is reached. Structural information for the bare gold Clusters is obtained by comparing the saturation stoichiometry with the number of available equivalent sites presented by candidate structures of Au-n(+). Our findings are in agreement with the planar structures of the Au-n(+) Cluster cations with n <= 7 that are suggested by ion mobility experiments [Gilb, S.; Weis, P.; Furche, F.; Ahlrichs, R.; Kappes, M. M. J. Chem. Phys. 2001, 116, 4094]. By inference we also establish the structure of the saturated Au-n(CO)(m)(+) complexes. In certain cases we find evidence suggesting that successive adsorption of CO can distort the metal Cluster framework. In addition, the vibrational spectra of the Au-n(CO)(m)(+) complexes in both the CO stretching region and in the region of the Au-C stretch and the Au-C-O bend are measured using infrared photodepletion spectroscopy. The spectra further aid in the structure determination of Au-n(+), provide information on the structure of the Au-n(+)-CO complexes, and can be compared with spectra of CO adsorbates on deposited Clusters or surfaces.Gold Cluster Carbonyls: Saturated adsorption of CO on gold Cluster cations, vibrational spectroscopy, and implications for their structuresx150200548#N/AFALSE
2573
ja053675g10.1021/ja053675gFALSEhttps://doi.org/10.1021/ja053675gAmine, KJ. Am. Chem. Soc.The high capacity of Ni-rich Li[Ni1-xMx]O-2 (M = Co, Mn) is very attractive, if the structural instability and thermal properties are improved. Li[Ni0.5Mn0.5]O-2 has good thermal and structural stabilities, but it has a low capacity and rate capability relative to the Ni-rich Li[Ni1-xMx]O-2. We synthesized a spherical coreshell structure with a high capacity (from the Li[Ni0.8Co0.1Mn0.1]O-2 core) and a good thermal stability (from the Li[Ni0.5Mn0.5]O-2 shell). This report is about the microscale spherical core-shell structure, that is, Li[Ni0.8Co0.1Mn0.1]O-2 as the core and a Li[Ni0.5Mn0.5]O-2 as the shell. A high capacity was delivered from the Li[Ni0.8Co0.1Mn0.1]O-2 core, and a high thermal stability was achieved by the Li[Ni(0.5)Nn(0.5)]O-2 shell. The core-shell structured Li[(Ni0.8Co0.1Mn0.1)(0.8)(Ni0.5Mn0.5)(0.2)]O-2/carbon cell had a superior cyClability and thermal stability relative to the Li[Ni0.8Co0.1Mn0.1]O-2 at the 1 C rate for 500 cyCles. The core-shell structured Li[(Ni0.8Co0.1Mn0.1)(0.8)(Ni0.5Mn0.5)(0.2)]O-2 as a new positive electrode material is a significant breakthrough in the development of high-capacity lithium batteries.Synthesis and characterization of Li[(Ni0.8Co0.1Mn0.1)(0.8)(Ni0.5Mn0.5)(0.2)]O-2 with the microscale core-shell structure as the positive electrode material for lithium batteries356200532#N/ATRUE
2574
ja050886c10.1021/ja050886cFALSEhttps://doi.org/10.1021/ja050886cFox, JMJ. Am. Chem. Soc.Described are the design, synthesis, and study of nonbiological molecules based on salophen and salen ligands that fold into single-stranded helices in the presence of either Ni(II) or Cu(II). X-ray diffraction studies show that the materials fold into helical structures in the solid state, and a series of NMR studies provide strong evidence that the folded structures are conserved in solution. Metal coordination is required for folding, as NMR and X-ray show that the free ligands do not adopt helical structures. Two of the racemic metallofoldamers spontaneously resolve during crystallization from CHCl3/acetonitrile, and CD spectroscopy and optical rotation show that the resolved, crystalline materials racemize quickly when dissolved at 5 C. This shows that the secondary structures can reorganize easily and can, therefore, provide the basis for responsive materials. By comparison, an analogue from enantiomerically pure (R,R)(-)-trans-cyClohexanediamine showed a strong CD signal and a large specific rotation. Electrochemical experiments show that a structural reorganization occurs upon metal-centered reduction of a Cu(II)-containing foldamer. When the reduction is carried out in the presence of coordinating ligands, it is proposed that apical binding of those ligands gives square pyramidal complexes. Semiempirical (AM1) calculations support that the helical structure would be disrupted by the reduction to Cu(I) with concomitant reorganization to a square pyramidal complex.Abiotic metallofoldamers as electrochemically responsive moleculesElectrochemistry80200580#N/AFALSE
2575
ja053665f10.1021/ja053665fFALSEhttps://doi.org/10.1021/ja053665fSiegbahn, PEMJ. Am. Chem. Soc.The reaction mechanism for the disproportionation of the toxic superoxide radical to molecular oxygen and hydrogen peroxide by the nickel-dependent superoxide dismutase ( NiSOD) has been studied using the B3LYP hybrid DFT method. Based on the recent X-ray structures of the enzyme in the resting oxidized Ni( III) and X-ray-reduced Ni( II) states, the model investigated inCludes the backbone spacer of six residues ( sequence numbers 1-6) as a structural framework. The side chains of residues His1, Cys2, and Cys6, which are essential for nickel binding and catalysis, were modeled explicitly. The catalytic cyCle consists of two half-reactions, each initiated by the successive substrate approach to the metal center. The two protons necessary for the dismutation are postulated to be delivered concertedly with the superoxide radical anions. The first ( reductive) phase involves Ni( III) reduction to Ni( II), and the second ( oxidative) phase involves the metal reoxidation back to its resting state. The Cys2 thiolate sulfur serves as a transient protonation site in the interim between the two half-reactions, allowing for the dioxygen and hydrogen peroxide molecules to be released in the reductive and oxidative phases, respectively. The His1 side chain nitrogen and backbone amides of the active site channel are shown to be less favorable transient proton locations, as compared to the Cys2 sulfur. Comparisons are made to the Cu- and Zn-dependent SOD, studied previously using similar models.Nickel superoxide dismutase reaction mechanism studied by hybrid density functional methods64200665#N/ATRUE
2576
ja053318610.1021/ja0533186FALSEhttps://doi.org/10.1021/ja1052329Warren, THA terminal Ni(III)-imide with diverse reactivity pathways2005#N/ATRUE
2577
ja053084q10.1021/ja053084qFALSEhttps://doi.org/10.1021/ja053084qRheingold, ALJ. Am. Chem. Soc.The molecule 4,4-di-n-octyl-p-quaterphenyl was synthesized in one step by a nickel-catalyzed cross-coupling reaction. Powder X-ray diffraction shows that it crystallizes in a layered structure with the long axis of the molecule nearly perpendicular to the layer plane. Differential scanning calorimetry indicates a transition to a liquid-crystalline phase at 81 degrees C. Reaction of 4,4'-bis(4-pyridyl)biphenyl with 1-bromooctane yields the dication 2(2+)2Br(-), an extended viologen isostructural with 4,4-di-n-octyl-p-quaterphenyl. Reduction of 2(2+)2Br(-) with sodium amalgam in DMF yields 2, the first neutral extended viologen to be isolated. The molecule 2 is, to the best of our knowledge, the most reducing neutral organic molecule that has, been synthesized. Single-crystal X-ray diffraction shows that a diradical form, either singlet or triplet, makes an important contribution to the electronic structure of 2. The broadened H-1 NMR spectrum of 2 indicates the presence of a triplet, but it has not been possible to observe the triplet by ESR spectroscopy. The electronic structure of 2 appears to be Closely related to that of a Classic molecule, Chichibabin's hydrocarbon.Synthesis and characterization of a highly reducing neutral extended viologen and the isostructural hydrocarbon 4,4 ''''-Di-n-octyl-p-quaterphenyl122200536#N/ATRUE
2578
ja052663s10.1021/ja052663sFALSEhttps://doi.org/10.1021/ja052663sNakamura, TJ. Am. Chem. Soc.Metal-organic thin-film transistor (MOTfT) based on bis(o-diiminobenzosemiquinonate) nickel(II) complex46200533#N/ATRUE
2579
ja050631z10.1021/ja050631zFALSEhttps://doi.org/10.1021/ja050631zMeng, QJJ. Am. Chem. Soc.Magnetic switchable maleonitriledithiolate (mnt) complexes were studied by density functional theory. The calculations were performed for anion dimers of [RBzPyR'][Ni(mnt)21 (RBzPyR' = derivatives of Benzylpyridinium) to elucidate magnetostructural correlations and the nature of the weak intermolecular chemical bonding. The calculated results showed that the spin delocalization, favored by the eClipsed stacking and the shorter interlayer distance, was responsible for the diamagnetic character of [1-Benzyl-4-aminopyridinium)[Ni(mnt)(2)] at low temperature. The weak antiferromagnetic and ferromagnetic interactions were also reproduced for [1-Benzyl-4-aminopyridinium][Ni(mnt)(2)] and [1-(4'-fluoroBenzyl)pyridinium][Ni(mnt)(2)] at high temperature, respectively. The natural bond orbital analysis suggested that the cooperative effect of the weak intermolecular bondings may be the intrinsic driving force resulting in the switchable property, which is essentially similar to those in organic radicals exhibiting magnetic bistability. Further investigations with varying interlayer distance d, the extent of slippage (slipping distance rand deviation angle alpha), and rotational angle theta suggested that the extent of slippage played an important role in magnetic interactions. Therefore, the abrupt modulation of the extent of slippage in the [Ni(mnt)(2)](-) complexes by external perturbations provided new possibilities for the design of molecular magnetic switching devices.Theoretical studies on the magnetic switching controlled by stacking patterns of bis(maleonitriledithiolato) nickelate(III) dimersx1322005105#N/AFALSE
2580
ja052571310.1021/ja0525713FALSEhttps://doi.org/10.1021/ja0525713Moreto, JMJ. Am. Chem. Soc.The Ni-mediated cyCloCarbonylation of allyl halides and alkynes made catalytic. Evidence supporting the involvement of pseudoradical Ni-1 species in the mechanism25200524#N/ATRUE
2581
ja049875u10.1021/ja049875uFALSEhttps://doi.org/10.1021/ja049875uLong, ECJ. Am. Chem. Soc.A study of the minor-groove recognition of A/T-rich DNA sites by Ni(II)-(L)-Arg-Gly-His and Ni(II)-(D)-Arg-Gly-His was carried out with a fluorescence-based binding assay, one- and two-dimensional (1 D and 2D) NMR methodologies, and molecular simulations. Fluorescence displacement titrations revealed that Ni(II)(.)(L)-Arg-Gly-His binds to A/T-rich sequences better than the (D)-Arg diastereomer, while NMR investigations revealed that both metallopeptides bind to the minor groove of an AATT core region as evidenced by an intermolecular nuClear Overhauser effect (NOE) between each metallopeptide His imidazole C4 proton and the C2 proton of adenine. Results from molecular dynamics simulations of these systems were consistent with the experimental data and indicated that the His imidazole N-H, the N-terminal peptide amine, and Arg side chains of each metallopeptide are major determinants of minor-groove recognition by functioning as H-bond donors to the O2 of thymine residues or N3 of adenine residues.Ni(II)center dot Arg-Gly-His - DNA interactions: Investigation into the basis for minor-groove binding and recognitionx54200458#N/AFALSE
2582
ja052381s10.1021/ja052381sFALSEhttps://doi.org/10.1021/ja052381sHolm, RHJ. Am. Chem. Soc.Synthesis of an analogue of the C-Cluster of C. hydrogenoformans carbon monoxide dehydrogenase requires formation of a planar Ni-II site and attachment of an exo iron atom in the core unit NiFe4S5. The first objective has been achieved by two reactions: (i) displacement of Ph3P or (BuNC)-N-t at tetrahedral Ni-II sites of cubane-type [NiFe3S4](+) Clusters with chelating diphosphines, and (ii) metal atom incorporation into a cuboidal [Fe3S4](0) Cluster with a M-0 reactant in the presence of bis(1,2-dimethylphosphino)ethane (dmpe). The isolated product Clusters [(dmpe)MFe3S4(LS3)](2-) (M = Ni-II (9), Pd-II (12), Pt-II (13); LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-)) contain the cores [MFe3(mu(2)-S*)(mu(3)-S)(3)](+) having planar (MP2S2)-P-II sites and variable nonbonding M center dot center dot center dot S* distances of 2.6-3.4 angstrom. Reaction (i) involves a tetrahedral -> planar Ni-II structural change between isomeric cubane and cubanoid [NiFe3S4](+) cores. Based on the magnetic properties of 12 and earlier considerations, the S = 5/2 ground state of the cubanoid Cluster arises from the [Fe3S4](-) fragment, whereas the S = 3/2 ground state of the cubane Cluster is a consequence of antiferromagnetic coupling between the spins of Ni2+ (S = 1) and [Fe3S4](-). Other substitution reactions of [NiFe3S4](+) Clusters and 1:3 site-differentiated [Fe4S4](2+) Clusters are described, as are the structures of 12, 13, [(Me3P)NiFe3S4(LS3)](2-), and [Fe4S4(LS3)L'](2-) (L' = Me2NC2H4S-, Ph2P(O)C2H4S-). This work significantly expands our initial report of Cluster 9 (Panda et al. J. Am. Chem. Soc. 2004, 126, 6448-6459) and further demonstrates that a planar M-II site can be stabilized within a cubanoid [NiFe3S4](+) core.Synthesis of MFe3S4 Clusters containing a planar M-II site (M = Ni, Pd, Pt), a structural element in the C-Cluster of carbon monoxide dehydrogenase26200557#N/ATRUE
2583
ja052183110.1021/ja0521831FALSEhttps://doi.org/10.1021/ja0521831Jamison, TFJ. Am. Chem. Soc.Highly enantioselective and regioselective nickel-catalyzed coupling of allenes, aldehydes, and silanes99200540#N/ATRUE
2584
ja052108q10.1021/ja052108qFALSEhttps://doi.org/10.1021/ja052108qDunbar, KRJ. Am. Chem. Soc.Reactions of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with solvated first-row transition metals M(II) (M(II) = Ni, Zn, Mn, Fe, Cu) have been explored with emphasis on the factors that influence the identity of the resulting cyClic products for Ni(II) and Zn(II). The relatively small anions, namely [ClO4](-) and [BF4](-), lead to the formation of molecular squares [{M-4(bptz)(4)(CH3CN)(8})subset of X][X](7), (M = Zn(II), Ni(II); X = [BF4](-), [ClO4](-)), whereas the larger anion [SbF6](-) favors the molecular pentagon [{Ni-5(bPtz)(5-)(CH3CN)(10})subset of SbF6][SbF6](9). The molecular pentagon easily converts to the square in the presence of excess [BF4](-), [ClO4](-), and [I]- anions, whereas the Ni(II) square can be partially converted to the less stable pentagon under more forcing conditions in the presence of excess [SbF6](-) ions. No evidence for the molecular square being in equilibrium with the pentagon was observed in the ESI-MS spectra of the individual square and pentagon samples. Anion-exchange reactions of the encapsulated ion in [{Ni-4(bPtz)(4)(CH3CN)(8)}subset of ClO4][subset of ClO4](7) reveal that a larger anion such as [104]- cannot replace [ClO4](-) inside the cavity, but that the linear [Br-3](-) anion is capable of doing so. ESI-MS studies of the reaction between [Ni(CH3CN)(6)][NO3](2) and bptz indicate that the product is trinuClear. Mass spectral studies of the bptz reactions with Mn(II), Fe(II), and Cu(II), in the presence of [ClO4](-) anions, support the presence of molecular squares. The formation of the various metallacyClophanes is discussed in light of the factors that influence these self-assembly reactions, such as choice of metal ion, anion, and solvent.Anion template effect on the self-assembly and interconversion of metallacyClophanes303200597#N/ATRUE
2585
ja052081a10.1021/ja052081aFALSEhttps://doi.org/10.1021/ja052081aSteed, JWJ. Am. Chem. Soc.Four isomorphous complexes of formula [M(L)(4)(H2O)(2)]SO4 center dot 2H(2)O (M = CO, 1a; Ni, 1b; Cu, 1c; Zn, 1d) have been isolated and characterized by single-crystal X-ray diffraction and neutron diffraction using the quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin as well as by thermogravimetric analysis. The structures contain a discrete, strongly hydrogen-bonded water tetramer which causes a significant distortion of the metal coordination sphere in each case. Partial atomic charges and hardness analysis (PACHA) calculations reveal that the shortest hydrogen bonds are not the strongest in this constrained, cyClic solid-state structure and show that the distortion at the metal center is caused by the drive to maintain the integrity of the water tetramer. The system undergoes a disorder-order transition on slow cooling that provides insight into the nature of communication between water squares.Cooperative hydrogen-bonding effects in a water square: A single-crystal neutron and partial atomic charges and hardness analysis study60200561#N/ATRUE
2586
ja048911m10.1021/ja048911mFALSEhttps://doi.org/10.1021/ja048911mZargarian, DJ. Am. Chem. Soc.The role of methylaluminoxane (MAO) in the Ni-catalyzed dehydrogenative homologation of PhSiH3 has been investigated with a view to designing new cocatalysts possessing well-defined chemical compositions and structures. These studies show that species such as the bifunctional reagent (Me2PCH2AlMe2)(2), 3, should act as co-catalyst for the Si-Si bond formation reactions. Thus, it was found that the combination of (1-Me-indenyl)Ni(PPh3)Me, 2a, and 3 (Ni/Al ratio of 1:1) converts PhSiH3 to cyClic oligomers (PhSiH)(n) with a turnover frequency (TOF) of >500 h(-1), 50 times faster than with 2a alone. Detailed NMR studies have indicated that this acceleration is due to the formation of the intermediate (1-Me-indenyl)Ni(Me)(Me2PCH2AlMe2), 4. Coordination of the PMe2 moiety in this complex to the Ni center allows the tethered AlMe2 moiety to interact with the Ni-Me moiety in such a way that promotes fairly slow Al-Me/Ni-CD3 exchange (t(1/2) ca. 12 h) but accelerates the Si-H bond Activation and Si-Si bond formation reactions. The catalysis promoted by 2a/3 proceeds even faster in the presence of NEt3 or THF (TOF > 1600 h(-1)), because these Lewis bases favor the monomeric form of 3, which in turn favors the formation of 4. On the other hand, the much more nuCleophilic base quinuClidine suppresses the catalysis (TOF < 300 h(-1)) by hindering the Ni...R...Al interactions. These observations point to an emerging strategy for using bifunctional reagents such as 3 to place geometrically constrained Lewis acid moieties adjacent to metal centers, thereby activating certain metal-ligand bonds.Me2AlCH2PMe2: A new, bifunctional cocatalyst for the Ni(II)-catalyzed oligomerization of PhSiH3x91200478#N/AFALSE
2587
ja051662x10.1021/ja051662xFALSEhttps://doi.org/10.1021/ja051662xOsuka, AAromatic and antiaromatic gold(III) hexaphyrins with multiple gold-carbon bonds2005#N/ATRUE
2588
ja048568l10.1021/ja048568lFALSEhttps://doi.org/10.1021/ja048568lLiaw, WFJ. Am. Chem. Soc.MononuClear, distorted square planar [Ni-II(ER)(P(o-C6H4S)(2)(o-C6H4SH))](-) (ER = SePh (1), 2-S-C4H3S (2)) with a S-H proton directly interacting with both nickel and sulfur atoms were prepared by reaction of [Ni(CO)(SePh)(3)](-)/[Ni(CO)(2-S-C4H3S)(3)](-) and P(o-C6H4SH)(3), individually. The presence of combinations of intramolecular [Ni-S...H-SR]/[Ni...H-SR] interactions was verified in the solid state by the observation of an IR v(SH) stretching band (2273 and 2283 cm(-1) (KBr) for complexes 1 and 2, individually) and H-1 NMR spectra (delta 8.079 (d) (CD2Cl2) and 8.39 (d) (C4D8O) ppm (-SH) for complexes 1 and 2, respectively) and subsequently confirmed by X-ray diffraction study. The exo-thiol proton (o-C6H4SH) in complexes 1 and 2 was identified as a D2O exchangeable proton from NMR and IR studies and was quantitatively removed by Lewis base Et3N to yield Ni(II) dinner [Ni-II(P(o-C6H4S)(3))](2)(2-) (5). Instead of the ligand-based oxidation to form dinuClear Ni(II) complexes and dichalcogenide, oxidation of THF-CH3CN solution of complexes 1 and 2 by O-2 resulted in the formation of the mononuClear, distorted trigonal bipyramidal [Ni-III(ER)(P(o-C6H4S)(3))](-) (ER = SePh (3), 2-S-C4H3S (4)) accompanied by byproduct H2O identified by H-1 NMR, respectively. The 4.2 K EPR spectra of complexes 3 and 4 exhibiting high rhombicities with three principal g values of 2.304, 2.091, and 2.0 are consonant with Ni(III) with the odd electron in the d(z)(2) orbital. Complex 3 undergoes a reversible Ni-III/II process at E-1/2 = -0.67 V vs Ag/AgCl in MeCN.MononuClear nickel(III) and nickel(II) thiolate complexes with intramolecular S-H proton interacting with both sulfur and nickel: Relevance to the [NiFe]/[NiFeSe] hydrogenasesx40200458#N/AFALSE
2589
ja048556010.1021/ja0485560FALSEhttps://doi.org/10.1021/ja0485560van Meurs, MJ. Am. Chem. Soc.The bis(imino)pyridine iron complex, [{2,6-(MeC=N-2,6-(Pr2C6H3)-Pr-i)(2)C5H3N}FeCl2] (1), in combination with MAO and ZnEt2 (> 500 equiv.), is shown to catalyze polyethylene chain growth on zinc. The catalyzed chain growth process is characterized by an exceptionally fast and reversible exchange of the growing polymer chains between the iron and zinc centers. Upon hydrolysis of the resultant ZnR2 product, a Poisson distribution of linear alkanes is obtained; linear alpha-olefins with a Poisson distribution can be generated via a nickel-catalyzed displacement reaction. Other diAlkylzinc reagents such as ZnMe2 and (ZnPr2)-Pr-i also show catalyzed chain growth; in the case of ZnMe2 a slight broadening of the product distribution is observed. The products obtained from Zn(CH2Ph)(2) show evidence for chain transfer but not catalyzed chain growth, whereas ZnPh2 shows no evidence for chain transfer. The Group 13 metal Alkyl reagents AlR3 (R = Me, Et, octyl, Bu-i) and GaR3 (R = Et, Bu-n) act as highly efficient chain transfer agents, whereas GaMe3 exhibits behavior Close to catalyzed chain growth. (LiBu)-Bu-n, (MgBu2)-Bu-n and BEt3 result in very low activity catalyst systems. SnMe4 and PbEt4 give active catalysts, but with very little chain transfer to Sn or Pb. The remarkably efficient iron catalyzed chain growth reaction for ZnEt2 compared to other metal Alkyls can be rationalized on the basis of: (1) relatively low steric hindrance around the zinc center, (2) their monomeric nature in solution, (3) the relatively weak Zn-C bond, and (4) a reasonably Close match in Zn-C and Fe-C bond strengths.Iron catalyzed polyethylene chain growth on zinc: A study of the factors delineating chain transfer versus catalyzed chain growth in zinc and related metal Alkyl systemsx2122004117#N/AFALSE
2590
ja050893110.1021/ja0508931FALSEhttps://doi.org/10.1021/ja0508931Louie, JJ. Am. Chem. Soc.A nickel-catalyzed route to pyridines195200529#N/ATRUE
2591
ja048289y10.1021/ja048289yFALSEhttps://doi.org/10.1021/ja048289yKing, DAJ. Am. Chem. Soc.The self-organized (2root3 x 2root3) coadsorbed phases of C6H6 with 0 and with CO are investigated within first-principles density functional theory. The main driving force for formation of the C6H6/ 20 phase is found to be the reduction of O adatom repulsive interactions, while for the C6H6/2CO phase it is the interspecies attractive interactions and benzene-benzene repulsive interactions which are most important.Driving forces for self-organized coadsorption: C-6-H-6/2O and C-6-H-6/2CO on Ni{111}x12200432#N/AFALSE
2592
ja050842410.1021/ja0508424FALSEhttps://doi.org/10.1021/ja0508424De Gioia, LJ. Am. Chem. Soc.Density functional theory has been used to investigate the reaction between H-2 and [Ni(NHPnPr(3))('S3')] or [Pd(NHPnPr(3))('S3')], where 'S3' = bis(2-sulfanylphenyl)sulfide(2-), which are among the few synthetic complexes featuring a metal coordination environment similar to that observed in the [NiFe] hydrogenase active site and capable of catalyzing H-2 heterolytic Cleavage. Results allowed us to unravel the reaction mechanism, which is consistent with an oxidative addition-hydrogen migration pathway for [Ni(NHPnPr(3))('S3')], whereas metathesis is also possible with [Pd(NHPnPr(3))('S3')]. Unexpectedly, H-2 binding and Activation implies structural reorganization of the metal coordination environment. It turns out that the structural rearrangement in [Ni(NHPnPr(3))('S3')] and [Pd(NHPnPr(3))('S3')] can take place due to the peculiar structural features of the Ni and Pd ligands, explaining the remarkable catalytic properties. However, the structural reorganization is the most unfavorable step along the H-2 Cleavage pathway (Delta G > 100 kJ mol(-1)), an observation that is relevant for the design and synthesis of novel biomimetic catalysts.DFT investigation of H-2 Activation by [M(NHPnPr(3))(' S3 ')] (M = Ni, Pd). Insight into key factors relevant to the design of hydrogenase functional models262005102#N/ATRUE
2593
ja047945r10.1021/ja047945rFALSEhttps://doi.org/10.1021/ja102163dShirakawa, MTwo-metal ion, Ni(II) and Cu(II), binding alpha-helical coiled coil peptidex2004#N/AFALSE
2594
ja047722110.1021/ja0477221FALSEhttps://doi.org/10.1021/ja0477221Strassner, TJ. Am. Chem. Soc.Addition of BF3.OEt2 to ethereal solutions of the Ni(II) beta-diketiminates [Me2NN]Ni(R)(2,4-lutidine) (R = Et (1), Pr (2)) allows the isolation of the neutral beta-H agostic monoAlkyls [Me2NN]Ni(R) (R = Et (3), Pr (4)). X-ray studies of primary Alkyls 3 and 4a reveal acute Ni-C-alpha-C-beta angles with short Ni-C-beta distances, indicating structures along the beta-H elimination pathway. Positional disorder of the Alkyl group in the X-ray structure of 4 corresponds to partial (22%) occupancy by the secondary Alkyl [Me2NN]Ni(CHMe2) (4b). Variable-temperature NMR spectra of 3 and 4 reveal fluxional behavior that result from beta-H elimination, in-plane rotation of the beta-CH3 group, and a tetrahedral triplet structure for 3 that were investigated by density functional theory calculations at the Becke3LYP/6-31G* level of theory without simplifications on the beta-diketiminate ancillary ligand. Calculations support low temperature NMR studies that identify the linear beta-H agostic propyl isomer 4a as the ground state with the branched beta-H agostic isomer 4b slightly higher in energy. NMR studies and calculations show that the beta-agostic 3 reluctantly coordinates ethene and that 3 is the ground state for this ethylene oligomerization catalyst. The thermodynamic isotope effect K-H/K-D = 1.3(2) measured for the loss of 2,4-lutidine from 1 to form beta-agostic 3 was also examined by DFT calculations.Structure and dynamics of neutral beta-h agostic nickel Alkyls: A combined experimental and theoretical studyx74200478#N/AFALSE
2595
ja050697u10.1021/ja050697uFALSEhttps://doi.org/10.1021/ja050697uGrey, CPJ. Am. Chem. Soc.The local environments and short-range ordering of LiNi(0.5)Nn(0.5)O(2), a potential Li-ion battery positive electrode material, were investigated by using a combination of X-ray and neutron diffraction and isotopic substitution (NDIS) techniques, Li-6 Magic Angle Spinning (MAS) NMR spectroscopy, and for the first time, X-ray and neutron Pair Distribution Function (PDF) analysis, associated with Reverse Monte Carlo (RMC) calculations. Three samples were studied: Li-6(NiMn)(0.5)O-2, Li-7(NiMn)(0.5)O-2, and Li-7(NiMn)(0.5)O-2 enriched with Ni-62 (denoted as (LiNi0.5Mn0.5O2)-Li-7-Ni-ZERO), so that the resulting scattering length of Ni atoms is null. LiNi0.5Mn0.5O2 adopts the LiCoO2 structure (space group R3m) and comprises separate lithium layers, transition metal layers (Ni, Mn), and oxygen layers. NMR experiments and Rietveld refinements show that there is approximately 10% of Ni/Li site exchange between the Li and transition metal layers. PDF analysis of the neutron data revealed considerable local distortions in the layers that were not captured in the Rietveld refinements performed using the Bragg diffraction data and the LiCoO2 structure, resulting in different M-O bond lengths of 1.93 and 2.07 angstrom for Mn-O and Ni/Li-O, respectively. Large Clusters of 2400-3456 atoms were built to investigate cation ordering. The RMC method was then used to improve the fit between the calculated model and experimental PDF data. Both NMR and RMC results were consistent with a nonrandom distribution of Ni, Mn, and Li cations in the transition metal layers; both the Ni and Li atoms are, on average, Close to more Mn ions than predicted based on a random distribution of these ions in the transition metal layers. Constraints from both experimental methods showed the presence of short-range order in the transition metal layers comprising LiMn6 and LiMn5Ni Clusters combined with Ni and Mn contacts resembling those found in the so-called flower structure or structures derived from ordered honeycomb arrays.Short- and long-range order in the positive electrode material, Li(NiMn)(0.5)O-2: A joint X-ray and neutron diffraction, pair distribution function analysis and NMR study148200533#N/ATRUE
2596
ja050674f10.1021/ja050674fFALSEhttps://doi.org/10.1021/ja050674fMatsuda, TJ. Am. Chem. Soc.Nickel-catalyzed intermolecular alkyne insertion into cyClobutanones144200524#N/ATRUE
2597
ja0506458610.1021/ja05064586FALSEhttps://doi.org/10.1021/ja05064586Martin, RJ. Am. Chem. Soc.A Ni-catalyzed Carbonylation of unactivated primary Alkyl bromides and sulfonates with CO2 at atmospheric pressure is described. The method is characterized by its mild conditions and remarkably wide scope without the need for air- or moisture-sensitive reagents, which make it a user-friendly and operationally simple protocol en route to Carbonylic acids.Ni-Catalyzed Carbonylation of Unactivated Primary Alkyl Bromides and Sulfonates with CO2134201450#N/ATRUE
2598
ja046818s10.1021/ja046818sFALSEhttps://doi.org/10.1021/ja046818sAlbracht, SPJJ. Am. Chem. Soc.The iron-sulfur-Cluster-free hydrogenase Hmd (H-2-forming methylenetetrahydromethanopterin dehydrogenase) from methanogenic archaea has recently been found to contain one iron associated tightly with an extractable cofactor of yet unknown structure. We report here that Hmd contains intrinsic CO bound to the Fe. Chemical analysis of Hmd revealed the presence of 2.4 +/- 0.2 mol of CO/mol of iron. Fourier transform infrared spectra of the native enzyme showed two bands of almost equal intensity at 2011 and 1944 cm(-1), interpreted as the stretching frequencies of two CO molecules bound to the same iron in an angle of 90degrees. We also report on the effect of extrinsic (CO)-C-12, (CO)-C-13, (CN-)-C-12, and (CN-)-C-13 on the IR spectrum of Hmd.Carbon monoxide as an intrinsic ligand to iron in the active site of the iron-sulfur-Cluster-free hydrogenase H-2-Forming methylenetetrahydromethanopterin dehydrogenase as revealed by infrared spectroscopyx160200435#N/AFALSE
2599
ja046671510.1021/ja0466715FALSEhttps://doi.org/10.1021/ja0466715Suh, MPJ. Am. Chem. Soc.A metal-organic pillared bilayer open framework having 3D channels, [Ni-2(C26H52N10)](3)[BTC](4)-6C(5)H(5)N.36H(2)O (BOF-1, 1), has been assembled from bismacrocyClic nickel(II) complex [Ni-2(C26H52N10)(Cl)4].H2O and sodium 1,3,5-benzenetriCarbonylate (Na3BTC). The channels are occupied by pyriCline and water guest molecules. When the single crystal of 1 was dried in air and then heated at 75degreesC for 1.5 h, respectively, [Ni-2(C26H52N10)]3[BTC](4).30H(2)O (1') and [Ni-2(C26H52N10)](3)[BTC](4).4H(2)O (2) resulted with retention of the single crystallinity. The X-ray structures reveal spongelike dynamic behavior of the bilayer framework that reduces the interlayer distance in response to the amount of guest molecules. Solid 2 differentiates various alcohols. When 1 was immersed in pyriCline and benzene, guest molecules were exchanged with retention of the single-crystal nature to give rise to [Ni-2(C26H52N10)](3)[BTC](4).20pyridine-6H2O (3) and [Ni-2(C26H52N10)](3)[BTC](4)-14benzene- 19H(2)O (4), respectively. Furthermore, crystal 1 reacted with 12 via single-crystal -to-single-crystal transformation to produce [Ni2(C26H52N10)](3)[C9H3O6](4)(l(3))(4).nl(2).17H(2)O (5) that consists of positively charged framework incorporating nickel(III) and nickel(II) ions and the channels inCluding 13 and 12.Dynamic and redox active pillared bilayer open framework: Single-crystal-to-single-crystal transformations upon guest removal, guest exchange, and framework oxidationx318200446#N/AFALSE
2600
ja050160g10.1021/ja050160gFALSEhttps://doi.org/10.1021/ja050160gZakharov, LJ. Am. Chem. Soc.Sulfoxide carbon-sulfur bond Activation21200527#N/ATRUE
2601
ja046192610.1021/ja0461926FALSEhttps://doi.org/10.1021/ja0461926Haumann, MJ. Am. Chem. Soc.Structure and oxidation state of the Ni-Fe cofactor of the NAD-reducing soluble hydrogenase (SH) from Ralstonia eutropha were studied employing X-ray absorption spectroscopy (XAS) at the Ni K-edge, EPR, and FTIR spectroscopy. The SH comprises a nonstandard (CN)Ni-Fe(CN)(3)(CO) site; its hydrogen-Cleavage reaction is resistant against inhibition by dioxygen and carbon monoxide. Simulations of the XANES and EXAFS regions of XAS spectra revealed that, in the oxidized SH, the Ni-II is six-coordinated ((CN)-O3S2); only two of the four conserved cysteines, which bind the Ni in standard Ni-Fe hydrogenases, provide thiol ligands to the Ni. Upon the exceptionally rapid reductive Activation of the SH by NADH, an oxygen species is detached from the Ni; hydrogen may subsequently bind to the vacant coordination site. Prolonged reducing conditions cause the two thiols that are remote from the Ni in the native SH to become direct Ni ligands, creating a standardlike Ni-II(CysS)(4) site, which could be further reduced to form the Ni-C (Ni-III-H-) state. The Ni-C state does not seem to be involved in hydrogen Cleavage. Two site-directed mutants (HoxH-164A, HoxH-L1 18F) revealed structural changes at their Ni sites and were employed to further dissect the role of the extra CN ligand at the Ni. It is proposed that the predominant coordination by (CN),O ligands stabilizes the Ni-II oxidation state throughout the catalytic cyCle and is a prerequisite for the rapid Activation of the SH in the presence of oxygen.Structural and oxidation-state changes at its nonstandard Ni-Fe site during Activation of the NAD-reducing hydrogenase from Ralstonia eutropha detected by X-ray absorption, EPR, and FTIR spectroscopyx632005115#N/AFALSE
2602
ja049644n10.1021/ja049644nFALSEhttps://doi.org/10.1021/ja049644nMontgomery, JJ. Am. Chem. Soc.Ligand-dependent scope and divergent mechanistic behavior in nickel-catalyzed reductive couplings of aldehydes and alkynes201200426#N/ATRUE
2603
ja049506y10.1021/ja049506yFALSEhttps://doi.org/10.1021/ja049506yMori, MJ. Am. Chem. Soc.Highly enantioselective catalytic carbon dioxide incorporation reaction: Nickel-catalyzed asymmetric Carbonylative cyClization of bis-1,3-dienes161200420#N/ATRUE
2604
ja045560310.1021/ja0455603FALSEhttps://doi.org/10.1021/ja0455603Sayre, LMJ. Am. Chem. Soc.The consensus mechanism for biogenesis of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor in copper amine oxidases involves a key water addition to the dopaquinone intermediate. Although hydration of o-quinones seems straightforward and was implicated previously in aqueous autoxidation of catechols to give ultimately hydroxyquinones, a recent study (Mandal, S.; Lee, Y.; Purdy, M. M.; Sayre, L. M. J. Am. Chem. Soc. 2000, 122, 3574-3584) showed that the observed hydroxyquinones arise not from hydration, but from addition to the o-quinones of H(2)O(2) generated during autoxidation of the catechols. In the enzyme case, hydration of dopaquinone is proposed to be mediated by the active site Cu(II). To establish precedent for this mechanism, we engineered a catechol tethered to a Cu(II)-coordinating unit, such that the corresponding o-quinone could be generated in situ by oxidation with periodate (to avoid generation of H(2)O(2)). Thus, coordination of 4-((2-(bis(2-pyridylmethyl)amino)ethylamino)methyl)-1,2-benzenediol (1) to Cu(II) and subsequent addition of periodate resulted in rapid formation of the TPQ-like corresponding hydroxyquinone. Hydroxyquinone formation was seen also using Zn(II) and Ni(II), but not in the absence of M(II). Under the same conditions, periodate oxidation of the simple catechol 4-test-butylcatechol does not give hydroxyquinone in the presence or absence of Cu(II). M(II)OH(2) pKa data for the Cu(II), Zn(II), and Ni(II) complexes with the pendant tetradentate ligand in the masked (dimethyl ether) catechol form, and kinetic pH-rate profiles of the metal-dependent hydroxyquinone formation from periodate oxidation of catechol 1, suggested a rate-limiting addition step of the ligand-coordinated M(II)OH to the o-quinone intermediate. This study represents the first chemical demonstration of a true o-quinone hydration, which occurs in cofactor biogenesis in copper amine oxidases.A dopaquinone model that mimics the water addition step of cofactor biogenesis in copper amine oxidasesx20200549#N/AFALSE
2605
ja045557j10.1021/ja045557jFALSEhttps://doi.org/10.1021/ja045557jKishi, YJ. Am. Chem. Soc.Fe/Cr- and Co/Cr-mediated catalytic asymmetric 2-haloallylations of aldehydesx82200414#N/AFALSE
2606
ja049430610.1021/ja0494306FALSEhttps://doi.org/10.1021/ja0494306Komagawa, SJ. Am. Chem. Soc.Nickel-catalyzed intermolecular [3+2+2] cocyClization of ethyl cyClopropylideneacetate and alkynes110200439#N/ATRUE
2607
ja049173510.1021/ja0491735FALSEhttps://doi.org/10.1021/ja0491735Jamison, TFJ. Am. Chem. Soc.Alkene-directed, nickel-catalyzed alkyne coupling reactions124200445#N/ATRUE
2608
ja048811g10.1021/ja048811gFALSEhttps://doi.org/10.1021/ja048811gLindahl, PAJ. Am. Chem. Soc.The structure of the active-site C-Cluster in CO dehydrogenase from Carboxydothermus hydrogenoformans inCludes a mu(2)-sulfide ion bridged to the Ni and unique Fe, whereas the same Cluster in enzymes from Rhodospirillum rubrum (CODHRr) and Moorella thermoacetica (CODHMt) lack this ion. This difference was investigated by exploring the effects of sodium sulfide on activity and spectral properties. Sulfide partially inhibited the CO oxidation activity of CODHRr and generated a lag prior to steady-state. CODHMt was inhibited similarly but without a lag. Adding sulfide to CODHMt in the C-red1 state caused the g(av) = 1.82 EPR signal to deCline and new features to appear, inCluding one with g = 1.95, 1.85 and (1.70 or 1.62). Removing sulfide caused the g(av) = 1.82 signal to reappear and activity to recover. Sulfide did not affect the g(av) = 1.86 signal from the C-red2 state. A model was developed in which sulfide binds reversibly to C-red1, inhibiting catalysis. Reducing this adduct causes sulfide to dissociate, C-red2 to develop, and activity to recover. Using this model, apparent K-I values are 40 +/- 10 nM for CODHRr and 60 +/- 30 muM for CODHMt. Effects of sulfide are analogous to those of other anions, inCluding the substrate hydroxyl group, suggesting that these ions also bridge the Ni and unique Fe. This proposed arrangement raises the possibility that CO binding labilizes the bridging hydroxyl and increases its nuCleophilic tendency toward attacking Ni-bound Carbonyl.Effect of sodium sulfide on Ni-containing carbon monoxide dehydrogenases29200421#N/ATRUE
2609
ja048390310.1021/ja0483903FALSEhttps://doi.org/10.1021/ja0483903Vicic, DAJ. Am. Chem. Soc.Evidence for a Ni-I active species in the catalytic cross-coupling of Alkyl electrophiles210200421#N/ATRUE
2610
ja048131d10.1021/ja048131dFALSEhttps://doi.org/10.1021/ja048131dTakagi, KJ. Am. Chem. Soc.Iridium complex-catalyzed highly enantio- and diastereoselective [2+2+2] cyCloaddition for the synthesis of axially chiral terAryl compounds170200425#N/ATRUE
2611
ja047433c10.1021/ja047433cFALSEhttps://doi.org/10.1021/ja047433cFu, GCJ. Am. Chem. Soc.Nickel-catalyzed cross-couplings of organosillicon reagents with unactivated secondary Alkyl bromides151200433#N/ATRUE
2612
ja047052z10.1021/ja047052zFALSEhttps://doi.org/10.1021/ja047052zHillhouse, GLJ. Am. Chem. Soc.Preparation of stable Alkyl complexes of Ni(I) and their one-electron oxidation to Ni(II) complex cations83200435#N/ATRUE
2613
ja046901f10.1021/ja046901fFALSEhttps://doi.org/10.1021/ja046901f
van Leeuwen, PWNM
J. Am. Chem. Soc.Dendrimers, specifically suited to construct site-isolated groups due to their well-defined hyperbranched structure, have been used as a ligand design element for the construction of nickel catalysts for ethylene oligomerization. The dendritic P,O ligand indeed suppresses the formation of inactive bis(P,O)Ni complexes in toluene, as is evident from NMR studies, and, as a consequence, outperforms the parent ligand in catalysis in this solvent. The dendritic effect observed in methanol is more subtle because both the dendritic ligand 1 and the parent 2 form bis(P,O)nickel complexes in solution according to NMR spectroscopy. Unlike the parent complex 8, the dendritic bis(P,O)Ni complex 7 derived from dendrimer ligand 1 is able to dissociate to a mono-ligated species under catalytic conditions, that is, 40 bar ethylene and 80 degreesC, which can enter the catalytic cyCle. Indeed, dendritic ligand 1 gives much more active nickel catalysts for the oligomerization in methanol than does 2.Site-isolation effects in a dendritic nickel catalyst for the oligomerization of ethylene99200447#N/ATRUE
2614
ja046328010.1021/ja0463280FALSEhttps://doi.org/10.1021/ja0463280Ogura, KJ. Am. Chem. Soc.The synthesis, crystal structures, inClusion ability, and structural robustness of novel crystalline inClusion compounds of [Ni(SCN)(2)(isoH)(2)].xG (isoH = isonicotinic acid; G = aromatic guest) are described. The inClusion compounds are constructed by stacking identical 2D host layers that consist of SCN-, isoH, and Ni2+ with van der Waals contact separation. In the layer, two types of rectangular cavities (A-type and B-type) are formed, and the guests are inCluded in the former cavity. The inClusion compounds were categorized into four stacking modes according to the difference in the stacking mode of the layers. A systematic investigation of the crystal structures of the 21 inClusion compounds Clarified the Close relationship between the molecular structure of the guest and the resultant stacking mode of the layers.Crystalline inClusion compounds constructed through self-assembly of isonicotinic acid and thiocyanato coordination bridges50200448#N/ATRUE
2615
ja046071610.1021/ja0460716FALSEhttps://doi.org/10.1021/ja0460716Kurosawa, HJ. Am. Chem. Soc.Direct observation of oxidative CyClization of eta(2)-alkene and eta(2)-aldehyde on Ni(0) center. Significant acceleration by addition of Me3SiOTf121200421#N/ATRUE
2616
ja045969s10.1021/ja045969shttps://doi.org/10.1021/ja045969sBrookhart, MReactions of Vinyl acetate and Vinyl trifluoroacetate with cationic diimine Pd(II) and Ni(II) Alkyl complexes: Identification of problems connected with copolymerizations of these monomers with ethylene2005#N/ATRUE
2617
ja044119+10.1021/ja044119+FALSEhttps://doi.org/10.1021/ja044119+Benet-Buchholz, JJ. Am. Chem. Soc.The reactions of a series of Pd(II) methyl compounds of general formula LPd(NCCH3)CH3, where L is a bulky phenoxydiazene or phenoxyaldimine ligand with the polar olefin acrylonitrile (AN), are reported. The compounds react with an excess of AN to give the products of 2,11 insertion into the Pd-Me bond, yielding dinners and/or trimers which feature bridging a-cyano groups. The reactions were studied by low temperature H-1 NMR spectroscopy, revealing an initial formation of compounds featuring N-bound AN, which isomerized to an (unobserved) pi-bound species that rapidly underwent 2,11 insertion into the Pd-Me bond. Intermediate oligomeric complexes retaining a Pd-Me function were observed at low [AN] in these reactions. Under pseudo first-order conditions, k(obs) values of 8.5 x 10(-5) to 2.68 x 10(-3) M-1 (-22 degreesC to 10 degreesC, 100 equiv of AN) and Activation parameters of DeltaH(#) = 14.4(5) kcal mol(-1) and DeltaS(#) = -19(5) eu were obtained in one case. Comparison of the overall rates of insertion between two LPd(NCCH3)CH3, differing in the overall charge on the supporting ligand L, showed that the complex bearing a negatively charged ligand reacts with AN twice as fast as one with no anionic charge. The rates of insertion in both of these complexes are significantly faster than reported rates for analogous reactions in cationic Pd(II) derivatives, indicating that increasing the negative charge on the complex enhances the rate of AN insertion. These results provide fundamental mechanistic insights into a crucial reaction for incorporation of polar comonomers into alpha olefins via a coordination polymerization mechanism.Insertion of acrylonitrile into palladium methyl bonds in neutral and anionic Pd(II) complexesx62200592#N/AFALSE
2618
ja045309n10.1021/ja045309nFALSEhttps://doi.org/10.1021/ja045309nShelnutt, JAJ. Am. Chem. Soc.The effects of ruffling on the axial ligation properties of a series of nickel(II) tetra(Alkyl)porphyrins have been investigated with UV-visible absorption spectroscopy, resonance Raman spectroscopy, X-ray crystallography, Classical molecular mechanics calculations, and normal-coordinate structural decomposition analysis. For the modestly nonplanar porphyrins, porphyrin ruffling is found to cause a decrease in binding affinity for pyrrolidine and piperidine, mainly caused by a decrease in the binding constant for addition of the first axial ligand; ligand binding is completely inhibited for the more nonplanar porphyrins. The lowered affinity, resulting from the large energies required to expand the core and flatten the porphyrin to accommodate the large high-spin nickel(II) ion, has implications for nickel porphyrin-based molecular devices and the function of heme proteins and methyl-coenzyme M reductase.Energetics and structural consequences of axial ligand coordination in nonplanar nickel porphyrins86200569#N/ATRUE
2619
ja043882110.1021/ja0438821FALSEhttps://doi.org/10.1021/ja0438821Nolan, SPJ. Am. Chem. Soc.N-heterocyClic carbene ligands IMes (1), SIMes (2), IPr (3), SIPr (4), and lCy (5) react with Ni(CO)(4) to give the saturated triCarbonyl complexes Ni(CO)(3)(IMes) (8), Ni(CO)(3)(SIMes) (9), Ni(CO)(3)(IPr) (10), Ni(CO)(3)(SIPr) (11), and Ni(CO)(3)(ICy) (12), respectively. The electronic properties of these complexes have been compared to their phosphine analogues of general formula Ni(CO)(3)(PR3) by recording their v(CO) stretching frequencies. While all of these NHCs are better donors than tertiary phosphines, the differences in donor properties between ligands 1-5 are surprisingly small. Novel, unsaturated Ni(CO)(2)(IAd) (13) and Ni(CO)(2)((IBu)-Bu-t) (14) compounds are obtained from the reaction of Ni(CO)(4) with IAd (6) and (IBu)-Bu-t (7). Complexes 13 and 14 are highly active toward substitution of the NHC as well as the Carbonyl ligands. This has allowed the determination of Ni-C(NHC) bond dissociation energies and the synthesis of various unsaturated Ni(0) and Ni(II) complexes. Computational studies on compounds 8-14 are in line with the experimental findings and show that IAd (6) and (IBu)-Bu-t (7) are more bulky than IMes (1), SIMes (2), IPr (3), SIPr (4), and lCy (5). Furthermore, a method based on %V-bur values has been developed for the direct comparison of steric requirements of NHCs and tertiary phosphines. Complexes 8-14, as well as NiCl(C3H5)((IBu)-Bu-t) (16) and NiBr(C3H5)((IBu)-Bu-t) (17), have been characterized by X-ray crystallography.Steric and electronic properties of N-heterocyClic carbenes (NHC): A detailed study on their interaction with Ni(CO)(4)x479200564#N/AFALSE
2620
ja045284s10.1021/ja045284sFALSEhttps://doi.org/10.1021/ja045284sMascharak, PKJ. Am. Chem. Soc.Structural models of the bimetallic subunit at the A-Cluster of acetyl coenzyme A synthase/CO dehydrogenase: BinuClear sulfur-bridged Ni-Cu and Ni-Ni complexes and their reactions with CO42200423#N/ATRUE
2621
ja045035410.1021/ja0450354FALSEhttps://doi.org/10.1021/ja0450354Tamaru, YJ. Am. Chem. Soc.Highly stereo- and regioselective Ni-catalyzed homoallylation of aldimines with conjugated dienes promoted by diethylzinc52200421#N/ATRUE
2622
ja043335f10.1021/ja043335fFALSEhttps://doi.org/10.1021/ja043335fFunck, ESJ. Am. Chem. Soc.Intermetallic compounds and alloys are traditionally synthesized by heating mixtures of metal powders to high temperatures for long periods of time. A low-temperature solution-based alternative has been developed, and this strategy exploits the enhanced reactivity of nanopartiCles and the nanometer diffusion distances afforded by binary nanocomposite precursors. Prereduced metal nanopartiCles are combined in known ratios, and they form nanomodulated composites that rapidly transform into intermetallics and alloys upon heating at low temperatures. The approach is general in terms of accessible compositions, structures, and morphologies. Multiple compounds in the same binary system can be readily accessed; e.g., AuCu, AuCu3, Au3Cu, and the AuCu-II superlattice are all accessible in the Au-Cu system. This concept can be extended to other binary systems, inCluding the intermetallics FePt3, CoPt, CuPt, and Cu-3-Pt and the alloys Ag-Pt, Au-Pd, and Ni-Pt. The ternary intermetallic Ag2Pd3S can also be rapidly synthesized at low temperatures from a nanocomposite precursor comprised of Ag2S and Pd nanopartiCles. Using this low-temperature solution-based approach, a variety of morphologically diverse nanomaterials are accessible: surface-confined thin films (planar and nonplanar supports), free-standing monoliths, nanomesh materials, inverse opals, and dense gram-scale nanocrystalline powders of intermetallic AuCu. Importantly, the multimetallic materials synthesized using this approach are functional, yielding a room-temperature Fe-Pt ferromagnet, a superconducting sample of Ag2Pd3S (T-C = 1.10 K), and a AuPd4 alloy that selectively catalyzes the formation of H2O2 from H-2 and O-2. Such flexibility in the synthesis and processing of functional intermetallic and alloy materials is unprecedented.Metallurgy in a beaker: NanopartiCle toolkit for the rapid low-temperature solution synthesis of functional multimetallic solid-state materialsx134200572#N/AFALSE
2623
ja044957410.1021/ja0449574FALSEhttps://doi.org/10.1021/ja0449574Togni, AJ. Am. Chem. Soc.Nickel(II)-catalyzed highly enantioselective hydrophosphination of methacrylonitrile127200422#N/ATRUE
2624
ja044950m10.1021/ja044950mFALSEhttps://doi.org/10.1021/ja044950mBohme, DKJ. Am. Chem. Soc.Atomic cations (26), M+, have been shown to lie within a thermodynamic window for O-atom transport catalysis of the reduction of N2O by CO and have been checked for catalytic activity at room temperature with kinetic measurements using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. Only 10 of these 26 atomic cations were seen to be catalytic: Ca+, Fe+, Ge+, Sr+, Ba+, Os+, Ir+, Pt+, Eu+, and Yb+. The remaining 16 cations that lie in the thermodynamic window (Cr+, Mn+, Co+, Ni+, Cu+, Se+, Mo+, Ru+, Rh+, Sn+, Te+, Re+, Pb+, Bi+, Tm+, and Lu+) react too slowly at room temperature either in the formation of MO+ or in its reduction by CO. Many of these reactions are known to be spin forbidden and a few actually may lie outside the thermodynamic window. A new measure of efficiency is introduced for catalytic cyCles that allows the discrimination between catalytic cations on the basis of the efficiencies of the two legs of the catalytic cyCle. Also, a potential-energy landscape is computed for the reduction of N2O by CO catalyzed by Fe+(D-6) that vividly illustrates the operation of an ionic catalyst.O-atom transport catalysis by atomic cations in the gas phase: Reduction of N2O by CO127200526#N/ATRUE
2625
ja043061w10.1021/ja043061wFALSEhttps://doi.org/10.1021/ja043061wHaddon, RCJ. Am. Chem. Soc.We compare popular analytical techniques, inCluding scanning and transmission electron microscopy (SEM and TEM), thermogravimetric analysis (TGA), and Raman and near-infrared (NIR) spectroscopy, for the evaluation of the purity of bulk quantities of single-walled carbon nanotubes (SWNTs). Despite their importance as imaging techniques, SEM and TEM are not capable of quantitatively evaluating the purity of typical inhomogeneous bulk SWNT samples because the image frame visualizes less than 1 pg of SWNT material; furthermore, there is no published algorithm to convert such images into numerical data. The TGA technique is capable of measuring the amount of metal catalyst in an SWNT sample, but does not provide an unambiguous separation between the content of SWNTs and carbonaceous impurities. We discuss the utilization of solution-phase near-infrared spectroscopy and solution-phase Raman spectroscopy to quantitatively compare arbitrary samples of bulk SWNT materials of different purities. The primary goal of this paper is to provide the chemical community with a realistic evaluation of current analytical tools for the purity evaluation of a bulk sample of SWNTs. The secondary goal is to draw attention to the growing crisis in the SWNT industry as a result of the lack of quality control and the misleading advertising by suppliers of this material.Comparison of analytical techniques for purity evaluation of single-walled carbon nanotubesx287200560#N/AFALSE
2626
ja044872310.1021/ja0448723FALSEhttps://doi.org/10.1021/ja0448723Hiyama, TJ. Am. Chem. Soc.Nickel-catalyzed Arylcyanation of alkynes194200425#N/ATRUE
2627
ja044805910.1021/ja0448059FALSEhttps://doi.org/10.1021/ja0448059Rodgers, MAJJ. Am. Chem. Soc.Two-pump-one-probe femtosecond studies of Ni(II) porphyrins excited states26200419#N/ATRUE
2628
ja042936410.1021/ja0429364FALSEhttps://doi.org/10.1021/ja0429364Matyjaszewski, KJ. Am. Chem. Soc.A new initiating/catalytic system for atom transfer radical polymerization (ATRP) is reported. This system starts with Alkyl halides as initiators and transition metal complexes in their oxidatively stable state (e.g., (CuBr2)-Br-II/ligand) as catalysts. The activators are generated by electron transfer (AGET) without involvement of initiating organic radicals. AGET ATRP has a significant advantage over simultaneous reverse and normal initiation (SR&NI) ATRP, because it provides a simple route for synthesizing pure polymers with complex architectures such as star copolymers, block copolymers, etc. Furthermore, AGET ATRP can be also successfully carried out in miniemulsion. Homopolymers and pure block copolymers were successfully synthesized via ATRP in miniemulsion using AGET ATRP. The final products were analyzed via two-dimensional chromatography, which combines high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). The resulting chromatograms showed that pure linear block copolymers and star block copolymers were prepared without the presence of any homopolymers.Preparation of homopolymers and block copolymers in miniemulsion by ATRP using activators generated by electron transfer (AGET)x439200533#N/AFALSE
2629
ja042749610.1021/ja0427496FALSEhttps://doi.org/10.1021/ja0427496Hyeon, TJ. Am. Chem. Soc.We synthesized uniform-sized nanorods of transition metal phosphides from the thermal decomposition of continuously delivered metal-phosphine complexes using a syringe pump. MnP nanorods with dimensions of 8 nm x 16 nm and 6 nm x 22 nm sized were synthesized by the thermal decomposition of Mn-TOP complex, which was prepared from the reaction of Mn-2(CO)(10) and tri-n-octylphosphine (TOP), using a syringe pump with constant injection rates of 10 and 20 mL/h, respectively. When Co-TOP complex, which was prepared from the reaction of cobalt acetylacetonate and TOP, was reacted in a mixture solvent composed of octyl ether and hexadecylamine at 300 degrees C using a syringe pump, uniform 2.5 nm x 20 nm sized Co2P nanorods were generated. When cobaltocene was employed as a precursor, uniform Co2P nanorods with 5 nm x 15 nm were obtained. When Fe-TOP complex was added to trioctylphosphine oxide (TOPO) at 360 degrees C using a syringe pump and then allowed to age at 360 degrees C for 30 min, uniform-sized FeP nanorods with an average dimension of 12 nm x 500 nm were produced. Nickel phosphide (Ni2P) nanorods with 4 nm x 8 nm were synthesized successfully by thermally decomposing the Ni-TOP complex, which was synthesized by reacting acetylacetonate [Ni(acac)(2)] and TOP, We measured the magnetic properties of these nanorods, and some of the nanorods exhibited different magnetic characteristics compared to the bulk counterparts.Generalized synthesis of metal phosphide nanorods via thermal decomposition of continuously delivered metal-phosphine complexes using a syringe pumpx256200569#N/AFALSE
2630
ja044797w10.1021/ja044797wFALSEhttps://doi.org/10.1021/ja044797wPoeppellmeier, KRJ. Am. Chem. Soc.The related parameters of cation size and valence that control the crystallization of Sr3CaRu2O9 into a 1:2 B-site-ordered perovskite structure were explored by cationic substitution at the strontium and calcium sites and by the application of high pressure. At ambient pressures, Sr3MRu2O9 stoichiometries yield multiphasic mixtures for M = Ni2+, Mg2+, and Y3+, whereas pseudocubic perovskites result lot M = Cu2+ and Zn2+. For A-site substitutions, an ordered perovskite structure results for Sr3-xCaxCaRu2O9, with 0 less than or equal to x less than or equal to 1.5. In contrast, Ba2+ substitution for Sr2+ is accompanied by a phase change to a hexagonal BaTiO3 structure type. At high pressures and temperatures, a 1:2 B-site-ordered perovskite structure is stabilized for Sr3-xBaxCaRu2O9, with 0 less than or equal to x less than or equal to 3. The scarcity of B-site-ordered perovskite ruthenates at ambient pressure and the metastable nature of the high-pressure phases underscore the strict size and valence requirements that must be met by the constituent cations to achieve these uncommon ordered structures.Effect of explicit cationic size and valence constraints on the phase stability of 1 : 2 B-Site-ordered perovskite ruthenates15200530#N/ATRUE
2631
ja042493410.1021/ja0424934FALSEhttps://doi.org/10.1021/ja0424934Armstrong, FAJ. Am. Chem. Soc.Activation of the oxidized inactive state (termed Unready or Ni-u*) of the [NiFe]-hydrogenase from Allochromatium vinosum requires removal of an unidentified oxidizing entity [0], produced by partial reduction Of O-2. Dynamic electrochemical kinetic studies, subjecting enzyme molecules on an electrode to sequences of potential steps and gas injections, establish the order of events in an otherwise complex sequence of reactions that involves more than one intermediate retaining [0] or its redox equivalent; fast and reversible electron transfer precedes the rate-determining step which is followed by a reaction with H-2, or the inhibitor GO, that renders the reductive Activation process irreversible.The mechanism of Activation of a [NiFe]-hydrogenase by electrons, hydrogen, and carbon monoxidex73200560#N/AFALSE
2632
ja042222t10.1021/ja042222thttps://doi.org/10.1021/ja042222tChen, XMJ. Am. Chem. Soc.One-pot solvothermal treatments of organonitriles, ammonia, and Cu-II salts yielded Cu-II and 3,5-disubstituted 1,2,4-triazolates. The organic triazolate components were derived from copper-mediated oxidative cyCloaddition of nitriles and ammonia, in which a key intermediate 1,3,5-triazapentadienate was isolated as [Cu-II(4-pytap)(2)] (4-Hpytap = 2,4-di(4-pyridyl)-1,3,5-triazapentadiene) via controlled solvothermal conditions. This intermediate could also be synthesized by Ni-II-mediated reactions; however, the final triazoles were obtained only when Cu-II was employed. Therefore, the reaction mechanism of these reactions was elucidated as follows: nitrile was first attacked by ammonia to form the amidine, which further reacted with another nitrile or self-condensed to yield 1,3,5.-triazapentadiene, which was coordinated to two Cu-II ions in its deprotonated form. A two-electron oxidation of the 1,3,5-triazapentadienate mediated by two Cu-II ions gave one triazolate and Cu-I cations. Other in situ ligand reactions, such as C-C bond Cleavage and hydrolysis, were also found for the nitriles under these solvothermal conditions. Another remarkable feature of these crystalline Cu-I triazolates is their simple, typical 3- or 4-connected network topologies. The self-assembly of these nets is presumably controlled by steric hindrance, which is subsequently applied to the rational design of the Close-packed 2D networks [Cu-I(tz)](infinity) and [Ag-I(tz)](infinity) (Htz = 1,2,4-triazole), as well as the porous 3D network [Cu-I(etz)](infinity) (Hetz = 3,5-diethyl-1,2,4-triazole). The interesting photoluminescence properties of these coinage d(10) metal complexes were also investigated.Copper(I) 1,2,4-triazolates and related complexes: Studies of the solvothermal ligand reactions, network topologies, and photoluminescence propertiesPhotocatalyst536200570#N/AFALSE
2633
ja044394w10.1021/ja044394wFALSEhttps://doi.org/10.1021/ja044394wMontgomery, JJ. Am. Chem. Soc.Ligand-dependent scope and divergent mechanistic behavior in nickel-catalyzed reductive couplings of aldehydes and alkynes (vol 126, pg 3698, 2004)220041#N/ATRUE
2634
ja044308s10.1021/ja044308sFALSEhttps://doi.org/10.1021/ja044308sBrennessel, WWTrimethylsilylated allyl complexes of nickel the stabilized bis(pi-allyl)nickel complex [eta(3)-1,3,(SiMe3)(2)C3H3](2)Ni and its mono(pi-allyl)NiX (X = Br, I) derivatives2005#N/ATRUE
2635
ja040222n10.1021/ja040222nFALSEhttps://doi.org/10.1021/ja040222nHolm, RHJ. Am. Chem. Soc.The construction of a synthetic analogue of the A-Cluster of carbon monoxide dehydrogenase/acetylcoenzyme synthase, the site of acetylcoenzyme A formation, requires as a final step the formation of an unsupported [Fe4S4]-(mu(2)-SR)-Ni-parallel to bridge to a preformed Cluster. Our previous results (Rao, P. V.; Bhaduri, S.; Jiang, J.; Holm, R. H. Inorg. Chem. 2004, 43, 5833) and the work of others have addressed synthesis of dinuClear complexes relevant to the A-Cluster. This investigation concentrates on reactions pertinent to bridge formation by examining systems containing dinuClear and mononuClear Ni-parallel to complexes and the 3:1 site-differentiated Clusters [Fe4S4(LS3)L'](2-) (L' = TfO- (14), SEt (15)). The system 14/[{Ni(Lo-S2N2)}M(SCH2CH2PPh2)](+) results in Cleavage of the dinuClear complex and formation of [{Ni(Lo-S2N2)}-Fe-4(LS3)](-) (18), in which the Ni-parallel to complex binds at the unique Cluster site with formation of a Ni(mu(2)-SR)(2)Fe bridge rhomb. Cluster 18 and the related species [{Ni(phma)}Fe4S4(LS3)](3-) (19) are obtainable by direct reaction of the corresponding cis-planar Ni-parallel to-S2N2 complexes with 14. The mononuClear complexes [M(pdmt)(SEt)](-) (M = Ni-parallel to, Pd-parallel to) with 14 in acetonitrile or Me2SO solution react by thiolate transfer to give 15 and [M-2(pdmt)(2)]. However, in dichloromethane the Ni-parallel to reaction product is interpreted as [{Ni(pdmt)(mu(2-)SEt)} Fe4S4(LS3)](2-) (20). Reaction of Et3NH+ and 15 affords the double cubane [{Fe4S4(LS3)}(2)(mu(2)-SEt)](3-) (21). Cluster 18 contains two mutually supportive Fe-(mu(2)-SR)-Ni-parallel to bridges, 19 exhibits one strong and one weaker bridge, 20 has one unsupported bridge (inferred from the H-1 NMR spectrum), and 21 has one unsupported Fe-(mu(2)-SR)-Fe bridge. Bridges in 18, 19, and 21 were established by X-ray structures. This work demonstrates that a bridge of the type found in the enzyme A-Clusters is achievable by synthesis and implies that more stable, unsupported single thiolate bridges may require reinforcement by an additional covalent linkage between the Fe4S4 and nickel-containing components. (LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio) benzene (3-); Lo-S2N2 = N,N'-diethyl-3,7-diazanonane-1,9-dithiolate(2-); pdmt = pyridine-2,6-methanedithiolate(2-); phma N,N'-1,2-phenylenebis(2-acetylthio)-acetamidate(4-); TfO = triflate.)On [Fe4S4](2+)-(mu(2)-SR)-M-II bridge formation in the synthesis of an A-Cluster analogue of carbon monoxide dehydrogenase/acetyl coenzyme A synthasex47200558#N/AFALSE
2636
ja039882310.1021/ja0398823FALSEhttps://doi.org/10.1021/ja0398823Mullen, KJ. Am. Chem. Soc.A new route to ladder-type pentaphenylenes has been developed in which both good hole-accepting p-type and electron-accepting n-type materials can be prepared from a common intermediate. This key intermediate is a pentaphenylene diester 5 obtained in high yield by Suzuki coupling of 2 equiv of fluorene boronates with 2,5-dibromoterephthalate. Addition of Aryllithium followed by ring Closure with boron trifluoride produced a blue-emitting ladder-type pentaphenylene. Bromination followed by reductive polymerization with nickel(O) gave new high molecular mass polymers, which show efficient blue emission with a very small Stokes shift. These polymers bridge the gap in emission between polyfluorenes and fully ladder-type polyphenylenes. An alternative ring Closure of the dibromopentaphenylene diester 14 with acid made a diketone that is a good electron-accepting material, as it displays a reversible two-electron reduction. The reduction onset potential of -0.875 V against Ag/Ag+ corresponds to a lowest unoccupied molecular orbital (LUMO) energy level of 3.53 eV, comparable to the work function of magnesium, suggesting that this unit could be used to greatly increase the injection of electrons into polymers containing it in a light-emitting diode (LED) or solar cell. A red-emitting material was prepared by Suzuki coupling of the dibromopentaphenylene 10b with a perylene dye, thus offering the prospect of tuning the emission from pentaphenylene materials over the whole visible range by attachment of suitable dyes. Unoptimized single-layer organic LEDs that used 11b showed stable pure-blue emission with brightnesses of over 200 cd/m(2) at 7 V, with moderate efficiencies.Ladder-type pentaphenylenes and their polymers: Efficient blue-light emitters and electron-accepting materials via a common intermediatex211200438#N/AFALSE
2637
ja039757r10.1021/ja039757rFALSEhttps://doi.org/10.1021/ja039757rHyeon, TJ. Am. Chem. Soc.Designed synthesis of atom-economical Pd/Ni bimetallic nanopartiCle-based catalysts for sonogashira coupling reactionsx444200428#N/AFALSE
2638
ja039588a10.1021/ja039588aFALSEhttps://doi.org/10.1021/ja039588aEklund, PCJ. Am. Chem. Soc.Wet chemical methods involving ultrasound and amide solvents were used to purify and separate large bundles of single-walled carbon nanotubes (SWNTs) into individual nanotubes that could then be transported to silicon or mica substrates. The SWNTs studied were produced by the arc-discharge process. Dry oxidation was used in an initial step to remove amorphous carbon. Subsequently, two acid purification schemes were investigated (HCl- and HNO3-reflux) to remove the metal growth catalyst (Ni-Y). Finally, ultrasonic dispersion of isolated tubes into either N,N-dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP) was carried out. Raman scattering, atomic force microscopy (AFM), and electron microscopy were used to study the evolution of the products. Raman scattering was used to probe possible wail damage during the chemical processing. We found that both HCl and HNO3 could be used to successfully remove the Ni-Y below similar to1 wt %. However, the HNO3-reflux produced significant wall damage (that could be reversed by vacuum annealing at 1000 degreesC). In the dispersion step, both amide solvents (DMF and NMP) produced a high degree of isolated tubes in the final product, and no damage during this dispersion step was observed. HNO3-refluxed tubes were found to disperse the best into the amide solvents, perhaps because of significant wall functionalization. AFM was used to study the filament diameter and length distributions in the final product, and interesting differences in these distributions were observed, depending on the chemical processing route.Debundling and dissolution of single-walled carbon nanotubes in amide solventsx374200446#N/AFALSE
2639
ja044271b10.1021/ja044271bFALSEhttps://doi.org/10.1021/ja044271bMeyer, KJ. Am. Chem. Soc.Terminal cobalt(III) imido complexes supported by tris(carbene) ligands: Imido insertion into the cobalt-carbene bond156200418#N/ATRUE
2640
ja043922110.1021/ja0439221FALSEhttps://doi.org/10.1021/ja0439221Field, MJJ. Am. Chem. Soc.Recent experimental and theoretical studies have focused on the mechanism of the A-Cluster active site of acetyl-CoA synthase that produces acetyl-CoA from a methyl group, carbon monoxide, and CoA. Several proposals have been made concerning the redox states of the (Ni-Ni) bimetallic center and the iron-sulfur Cluster connected to one of the metals. Using hybrid density functional theory, we have investigated putative intermediate states from the catalytic cyCle. Among our conClusions are the following: (i) the zerovalent state proposed for the proximal metal is unlikely if the charge on the iron-sulfur Cluster is +2; (ii) a mononuClear mechanism in which both CO and CH3 bind the proximal nickel is favored over the binuClear mechanism in which CO and CH3 bind the proximal and distal nickel ions, respectively; (iii) the formation of a disulfide bond in the active site could provide the two electrons necessary for the reaction but only if methylation occurs simultaneously; and (iv) the crystallographic Closed form of the active site needs to open to accommodate ligands in the equatorial site.A quantum chemical study of the reaction mechanism of acetyl-coenzyme A synthase38200530#N/ATRUE
2641
ja043781310.1021/ja0437813FALSEhttps://doi.org/10.1021/ja0437813Finke, RGIridium(0) nanoCluster, acid-assisted catalysis of neat acetone hydrogenation at room temperature: Exceptional activity, catalyst lifetime, and selectivity at complete conversion2005#N/ATRUE
2642
ja043701v10.1021/ja043701vFALSEhttps://doi.org/10.1021/ja043701vLindahl, PAJ. Am. Chem. Soc.The effect of [CO] on acetyl-CoA synthesis activity of the isolated alpha subunit of acetyl-coenzyme A synthase/carbon monoxide dehydrogenase from Moorella thermoacetica was determined. In contrast to the complete alpha(2)beta(2) enzyme where multiple CO molecules exhibit strong cooperative inhibition, alpha was weakly inhibited, apparently by a single CO with K-I = 1.5 +/- 0.5 mM; other parameters inClude k(cat) = 11 +/- 1 min(-1) and K-M = 30 +/- 10 mu M. The alpha subunit lacked the previously described majority activity of the complete enzyme but possessed its residual activity. The site affording cooperative inhibition may be absent or inoperative in isolated alpha subunits. Ni-activated alpha rapidly and reversibly accepted a methyl group from CH3- Co3+FeSP affording the equilibrium constant K-MT = 10 +/- 4, demonstrating the superior nuCleophilicity of alpha(red) relative to Co1+FeSP. CO inhibited this reaction weakly (K-I = 540 +/- 190 mu M). NiFeC EPR intensity of a developed in accordance with an apparent K-d = 30 mu M, suggesting that the state exhibiting this signal is not responsible for inhibiting catalysis or methyl group transfer and that it may be a catalytic intermediate. At higher [CO], signal intensity deClined slightly. Attenuation of catalysis, methyl group transfer, and the NiFeC signal might reflect the same weak CO binding process. Three mutant alpha(2)beta(2) proteins designed to block the tunnel between the A- and C-Clusters exhibited little/no activity with CO2 as a substrate and no evidence of cooperative CO inhibition. This suggests that the tunnel was blocked by these mutations and that cooperative CO inhibition is related to tunnel operation. Numerous CO molecules might bind cooperatively to some region associated with the tunnel and institute a conformational change that abolishes the majority activity. Alternatively, crowding of CO in the tunnel may control flow through the tunnel and deliver CO to the A-Cluster at the appropriate step of catalysis. Residual activity may involve CO from the solvent binding directly to the A-Cluster.The tunnel of acetyl-coenzyme a synthase/carbon monoxide dehydrogenase regulates delivery of CO to the active site42200533#N/ATRUE
2643
ja039244k10.1021/ja039244kFALSESaigo, KReaction of [2-(SiH3)C6H4](2)SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)(2): Characterization of eta(2)(Si-H)Ni and Ni-IV-H complexesx2004#N/AFALSE
2644
ja043253r10.1021/ja043253rFALSEhttps://doi.org/10.1021/ja043253rLouie, JJ. Am. Chem. Soc.Selectivity in nickel-catalyzed rearrangements of cyClopropylenynes100200520#N/ATRUE
2645
ja043162u10.1021/ja043162uFALSEhttps://doi.org/10.1021/ja0712017Dunbar, KRA charge-transfer-induced spin transition in a discrete complex: The role of extrinsic factors in stabilizing three electronic isomeric forms of a cyanide-bridged Co/Fe Cluster2005#N/ATRUE
2646
ja042958q10.1021/ja042958qFALSEhttps://doi.org/10.1021/ja042958qPower, PPJ. Am. Chem. Soc.A sequence of first row transition metal(II) dithiolates M(SAr*)(2) (M = Cr(1), Mn(2), Fe(3), Co(4), Ni(5) and Zn(6); Ar* = C6H3-2,6-(C6H2-2,4,6-Pr-3(i))2) has been synthesized and characterized. Compounds 1-5 were obtained by the reaction of two equiv of LiSAr* with a metal dihalide, whereas 6 was obtained by treatment of ZnMe2 with 2 equiv of HSAr*. They were characterized by spectroscopy, magnetic measurements, and X-ray crystallography. The dithiolates 1, 2, and 4-6 possess linear or nearly linear SMS units with further interactions between M and two ipso carbons from C6H2-2,4,6-Pr-3(i) rings. The iron species 3, however, has a bent geometry, two different Fe-S distances, and an interaction between iron and one ipso carbon of a flanking ring. The secondary M-C interactions vary in strength in the sequence Cr2+ approximate to Fe2+ > Co2+ approximate to Ni2+ > Mn2+ approximate to Zn2+ Sue h that the manganese and zinc compounds have essentially two coordination but the chromium and iron complexes are quasi four and three coordinate, respectively. The geometric distortions in the iron species 3 suggested that the structure represents the initial stage of a rearrangement into a sandwich structure involving metal-Aryl ring coordination. The bent structure of 3 probably also preCludes the observation of free ion magnetism of Fe2+ recently reported for Fe{C(SiMe3)(3)}(2). DFT calculations on the model compounds M(SPh)(2) (M = Cr-Ni) support the higher tendency of the iron species to distort its geometry.Synthesis and characterization of quasi-two-coordinate transition metal dithiolates M(SAr*)(2) (M = Cr, Mn, Fe, Co, Ni, Zn; Ar* = C6H3-2,6(C6H2-2,4,6-Pr-3(i))(2)83200559#N/ATRUE
2647
ja037862v10.1021/ja037862vFALSEhttps://doi.org/10.1021/ja037862vJaun, BJ. Am. Chem. Soc.The UV-visible and electron paramagnetic resonance (EPR) spectra of MCRred1, the catalytically active state of methyl-coenzyme M reductase, are almost identical to those observed when free coenzyme F430 or its pentamethyl ester (F430M) are reduced to the Ni(I) valence state. Investigations and proposals concerning the catalytic mechanism of MCR were therefore based on MCRred1 containing Ni(I)F430 until, in a recent report, Tang et al. (J. Am. Chem. Soc. 2002, 124, 13242) interpreted their resonance Raman data and titration experiments as indicating that, in MCRred1, coenzyme F430 is not only reduced at the nickel center but at one of the C=N double bonds of the hydrocorphinoid macrocyCle as well. To resolve this contradiction, we have investigated the stoichiometry of the reduction of coenzyme F430 pentamethyl ester (F430M) by three independent methods. Spectroelectrochemistry showed Clean reduction to a single product that exhibits the UV-vis spectrum typical for MCRred1. In three bulk electrolysis experiments, 0.96 +/- 0.1 F/mol was required to generate the reduced species. Reduction with decamethylcobaltocene in tetrahydrofuran (THF) consumed 1 mol of (Cp*)(2)Co/mol of F430M, and the stoichiometry of the reoxidation of the reduced form with the two-electron oxidant methylene blue was 0.46 +/- 0.05 mol of methylene blue/mol of reduced F430M. These experiments demonstrate that the reduction of coenzyme F430M to the species having almost identical UV-vis and EPR spectra as MCRred1 is a one-electron process and therefore inconsistent with a reduction of the macrocyCle chromophore.Direct determination of the number of electrons needed to reduce coenzyme F430 pentamethyl ester to the Ni(I) species exhibiting the electron paramagnetic resonance and ultraviolet-visible spectra characteristic for the MCRred1 state of methyl-coenzyme M reductasex30200333#N/AFALSE
2648
ja042938o10.1021/ja042938oFALSEhttps://doi.org/10.1021/ja042938oCoucouvanis, DJ. Am. Chem. Soc.Systematic synthesis of heterometallic Ni/Fe/S and Cu/Fe/S Clusters with a pentlandite-like M8S6 core10200520#N/ATRUE
2649
ja042565r10.1021/ja042565rFALSEhttps://doi.org/10.1021/ja042565rKambe, NJ. Am. Chem. Soc.Ni-catalyzed Alkylative dimerization of Vinyl Grignard reagents using Alkyl fluorides65200517#N/ATRUE
2650
ja037537810.1021/ja0375378FALSEhttps://doi.org/10.1021/ja0375378Harrison, MDJ. Am. Chem. Soc.The type 1 copper sites of cupredoxins typically have a HiS(2)Cys equatorial ligand set with a weakly interacting axial Met, giving a distorted tetrahedral geometry. Natural variations to this coordination environment are known, and we have utilized paramagnetic H-1 NMR spectroscopy to study the active-site structure of umecyanin (UMC), a stellacyanin with an axial Gin ligand. The assigned spectra of the Cu(II) UMC and its Ni(II) derivative [Ni(II) UMC] demonstrate that this protein has the typical HiS(2)Cys equatorial coordination observed in other structurally characterized cupredoxins. The NMR spectrum of the Cu(II) protein does not exhibit any paramagnetically shifted resonances from the axial ligand, showing that this residue does not contribute to the singly occupied molecular orbital (SOMO) in Cu(II) UMC. The assigned paramagnetic H-1 NMR spectrum of Ni(II) UMC demonstrates that the axial Gln ligand coordinates in a monodentate fashion via its side-chain amide oxygen atom. The alkaline transition, a feature common to stellacyanins, influences all of the ligating residues but does not alter the coordination mode of the axial Gin ligand in UMC. The structural features which result in Cu(II) UMC possessing a Classic type 1 site as compared to the perturbed type 1 center observed for other stellacyanins do not have a significant influence on the paramagnetic H-1 NMR spectra of the Cu(II) or Ni(II) proteins.The active-site structure of umecyanin, the stellacyanin from horseradish rootsx19200453#N/AFALSE
2651
ja037444q10.1021/ja037444qFALSEhttps://doi.org/10.1021/ja037444qLong, JRJ. Am. Chem. Soc.The first face-capped octahedral Clusters with 25 metal-based valence electrons are shown to provide versatile building units capable of engaging in magnetic exchange coupling. Reactions of [Re5OsSe8Cl6](3-) and [Re4Os2Se8Cl6](2-) with NaCN in a melt of NaNO3 or KCF3SO3 afford the 24-electron Clusters [Re5OsSe8(CN)(6)](3-) and [Re4Os2Se8(CN)(6)](2-). The C-13 NMR spectrum of a C-13-labeled version of the latter species indicates a 1:2 mixture of cis and trans isomers. CyClic voltammograms of the Clusters in acetonitrile display reversible [Re5OsSe8(CN)(6)](3-/4-), cis-[Re4Os2Se8(CN)(6)](2-/3-), and trans-[ Re4Os2Se8-(CN)(6)](2-/3-) couples at E-1/2 = -1.843, -0.760, and -1.031 V vs FeCp20/+, respectively, in addition to other redox processes. Accordingly, reduction of [Re5OsSe8(CN)(6)](3-) with sodium amalgam and [Re4Os2Se8(CN)(6)](2-) with cobaltocene produces the 25-electron Clusters [Re5OsSe8(CN)(6)](4-) and [Re4Os2Se8(CN)(6)](3-). EPR spectra of these S = (1)/(2) species in frozen DMF solutions exhibit isotropic signals with g = 1.46 for the monoosmium Cluster and g = 1.74 and 1.09 for the respective cis and trans isomers of the diosmium Cluster. In each case, results from DFT calculations show the unpaired spin to delocalize to some extent into the pi* orbitals of the cyanide ligands, suggesting the possibility of magnetic superexchange. Reaction of [Re5OsSe8(CN)(6)](3-) with [Ni(H2O)(6)](2+) in aqueous solution generates the porous Prussian blue analogue Ni-3[Re5OsSe8(CN)(6)](2). 32H(2)O; however, the tendency of the 25-electron Clusters to oxidize in water prohibits their use in reactions of this type. Instead, a series of cyano-bridged assemblies, {Re6-nOsnSe8[CNCu(Me(6)tren)](6)}(9+) (n = 0, 1, 2; Me6tren = tris(2-(dimethylamino)ethyl)amine), were synthesized to permit comparison of the exchange coupling abilities of Clusters with 23-25 electrons. As expected, the results of magnetic susceptibility measurements show no evidence for exchange coupling in the assemblies containing the 23- and 24-electron Clusters, but reveal the presence of weak ferromagnetic coupling in {Re4Os2Se8[CNCu(Me(6)tren)](6})(9+). Assuming all Cluster-Cull exchange interactions to be equivalent, the data were fit to give an estimated coupling strength of J = 0.4 cm(-1). To our knowledge, the ability of such Clusters to participate in magnetic exchange coupling has never previously been demonstrated.Cluster-to-metal magnetic coupling: Synthesis and characterization of 25-electron [Re6-nOsnSe8(CN)(6)]((5-n)-) (n=1, 2) Clusters and {Re6-nOSnSe8[CNCu(Me(6)tren)](6)}(9+) (n=0, 1, 2) assembliesx632003108#N/AFALSE
2652
ja037424o10.1021/ja037424oFALSEhttps://doi.org/10.1021/ja037424oMClaughlin, LWJ. Am. Chem. Soc.The development of a multiarm metal-centered DNA building block as a precursor for the construction of supramolecular assemblies has relied upon the preparation of a Ni(II)-1,4,8,11-tetrazacyClotetradecane ligand (cyClam) functionalized with four linkers. This complex can be incorporated into a support-bound DNA sequence and the remaining three linkers can then be elongated by DNA synthesis. The result is a Ni(II)-cyClam complex tethering four 20-mer DNA strands. This building block, designed to be tetrahedral in nature, can in principle be used to form tetrahedral assemblies. These assemblies can be designed to be of known size and composition or permitted to grow into complexes of essentially infinite size, ideally the macroscopic version of a crystal.Four-arm oligonuCleotide Ni(II)-cyClam-centered complexes as precursors for the generation of supramolecular periodic assembliesx78200440#N/AFALSE
2653
ja042217p10.1021/ja042217pFALSEhttps://doi.org/10.1021/ja042217pAkatsu, MJ. Am. Chem. Soc.A heterometal single-molecule magnet of [(Mn2Ni2Cl2)-Ni-III-Cl-II(salpa)(2)]111200524#N/ATRUE
2654
ja037002e10.1021/ja037002eFALSEhttps://doi.org/10.1021/ja037002eJones, WDJ. Am. Chem. Soc.Reaction of [(dippe)Ni(mu-H)](2) With allyl cyanide at low temperature quantitatively generates the eta(2)-olefin complex (dippe)Ni(CH2=CHCH2CN) (1). At ambient temperature or above, the olefin complex is converted to a mixture of C-CN Cleavage product (dippe)Ni(eta(3) -allyl)(CN) (3) and the olefin-isomerization products (dippe)Ni(eta(2) -crotonitrile) (cis- and trans-2), which form via C-H Activation. The latter are the exClusive products at longer reaction times, indicating that C-CN Cleavage is reversible and the crotononitrile complexes 2 are more thermodynamically stable than eta(3)-allyl species 3. The kinetics of this reaction have been followed as a function of temperature, and rate constants have been extracted by modeling of the reaction. The rate constants for C-CN bond formation (the reverse of C-CN Cleavage) show a stronger temperature dependence than those for C-CN and C-H Activation, making the observed distribution of C-H versus C-CN Cleavage products strongly temperature-dependent. The Activation parameters for the C-CN formation step are also quite distinct from those of the C-CN and C-H Cleavage steps (larger DeltaH(not equal) and positive DeltaS(not equal)). Addition of the Lewis acid BPh3 to 1 at low temperature yields exClusively the C-CN Activation product (dippe)Ni(eta(3)-allyl)(CNBPh3) (4). Independently prepared (dippe)Ni(crotononitrile-BPh3) (cis- and trans-7) does not interconvert with 4, indicating that 4 is the kinetic product of the BPh3-mediated reaction. On standing in solution at ambient temperature, 4 decomposes slowly to complex 5, with structure [(dippe)Ni(eta(3) -allyl)(NdropC-BPh3) while addition of a second equivalent of BPh3 immediately produces [(dippe)Ni(eta(3)-allyl)](+)[Ph(3)BCdropNBPh(3)](-) (6). Comparison of the barriers to pi-sigma allyl interconversion (determined via dynamic H-1 NMR spectroscopy) for all of the eta(3)-allyl complexes reveals that axial cyanide ligands facilitate eta-sigma interconversion by moving into the P2Ni square plane when the allyl group is a-bound.Kinetics, thermodynamics, and effect of BPh3 on competitive C-C and C-H bond Activation reactions in the interconversion of allyl cyanide by [Ni(dippe)]x164200453#N/AFALSE
2655
ja036792p10.1021/ja036792phttps://doi.org/10.1021/ja036792pHartwig, JFJ. Am. Chem. Soc.Palladium-catalyzed alpha-Arylation of esters and amides under more neutral conditionsx187200324#N/AFALSE
2656
ja040237l10.1021/ja040237lFALSEhttps://doi.org/10.1021/ja040237lWieghardt, KJ. Am. Chem. Soc.The electronic structures of complexes of iron containing two S,S'-coordinated benzene-1,2-dithiolate, (L)(2-), or 3,5-di-tert-butyl-1,2-benzenedithiolate, (L-Bu)(2-), ligands have been elucidated in depth by electronic absorption, infrared, X-band EPR, and Mossbauer spectroscopies. It is conClusively shown that, in contrast to earlier reports, high-valent iron(IV) (d(4), S = 1) is not accessible in this chemistry. Instead, the S,S'-coordinated radical monoanions (L-center dot)(1-) and/or (L-Bu center dot)(1-) prevail. Thus, five-coordinate [Fe(L)(2)(PMe3)] has an electronic structure which is best described as [Fe-III] (L)(L-center dot)(PMe3)] where the observed triplet ground state of the molecule is attained via intramolecular, strong antiferromagnetic spin coupling between an intermediate spin ferric ion (S-Fe = 3/2) and a ligand radical (L-center dot)(1-) (S-rad = 1/2). The following complexes containing only benzene-1 2-dithiolate(2-) ligands have been synthesized, and their electronic structures have been studied in detail: [NH(C2H5)(3)](2)[Fe-II](L)(2)] (1), [N(n-Bu)(4)](2)[Fe-2(III)(L)(4)] (2), [N(n-Bu)(4)](2)[Fe-2(III)(L-Bu)(4)] (3); [P(CH3)Ph-3][Fe-III(L)(2)(t-Bu-py)] (4) where t-Bu-py is 4-tert-butylpyridine. Complexes containing an Fe-2(III))(L-center dot)- or Fe-III(L-Bu)(L-Bu center dot)-moiety are [N(n-Bu)(4)][FeIII2(L-Bu center dot)(3)](3(ox)), [Fe-III(L)(L-center dot)(t-Bu-py)] (4(ox)), [Fe-III(L-Bu)(L-Bu center dot)-(PMe3)] (7), [Fe-III(L-Bu) (L-Bu center dot)(PMe3)(2)] (8), and [Fe-III(L-Bu)(L-Bu center dot)(PPr3)] (9), where Pr represents the n-propyl substituent. Complexes 2, 3(ox), 4, [Fe-III(L)(L-center dot)PMe3)(2)] (6), and 9 have been structurally characterized by X-ray crystallography.Redox-noninnocence of the S,S'-coordinated ligands in bis(benzene-1,2-dithiolato)iron complexes97200546#N/ATRUE
2657
ja039545u10.1021/ja039545uFALSEhttps://doi.org/10.1021/ja039545uBaldridge, KKJ. Am. Chem. Soc.The remarkable advances accomplished in the past two decades in theoretical and computational capabilities have made the in silico study of complex chemical systems feasible. However, this progress is in strong contrast to the lag in experimental capabilities relating to the measurement of fundamental chemical quantities within convoluted environments such as solvents or protein milieu. As a result, many works rely extensively on predictions provided by ab initio methodologies without having independent experimental support. Such a proliferation of theory and computational approaches without being substantiated by appropriate experimental data is undesirable. The feasibility of using nickel-bacteriochlorophyll as a molecular potentiometer was recently demonstrated for the systematic evaluation of fragmental charge density transfer for metal complexes in solution, thus providing an experimental assay with high accuracy and sensitivity (better than +/-0.005 e(-); Yerushalmi, R.; Baldridge, K. K.; Scherz, A. J. Am. Chem. Soc. 2003, 125, 12706-12707). Here the experimentally determined fragmental charge density transfer values measured by the molecular potentiometer for metal complexes in solvent are used to provide, for the first time, an independent and critical experimental evaluation of theoretical approaches commonly used in determining atomic charges and fragmental charge density transfer among interacting molecular systems. Importantly, these findings indicate that the natural population analysis (NPA) charge analysis is highly robust and well-suited for determining charge transfer processes involving donor-acceptor coordination interactions. The majority of computational charge schemes fail to provide an accurate chemical picture for the whole range of systems considered here. In cases where the role of electronic correlation varies significantly among chemically related structures, as with mono- and biligated complexes, the widely used electrostatic potential fit-based methods for evaluating atomic charges may prove to be problematic for predictive studies. In such cases, alternative methods that do not rely on the net dipole moment or other higher multipoles of the system for determining charges should be employed.Direct experimental evaluation of charge scheme performance by a molecular charge-meter24200456#N/ATRUE
2658
ja036603310.1021/ja0366033FALSEhttps://doi.org/10.1021/ja0366033Cramer, SPJ. Am. Chem. Soc.The 5-subunit-containing acetyl-CoA deCarbonylase/synthase (ACDS) complex plays an important role in methanogenic Archaea that convert acetate to methane, by catalyzing the central reaction of acetate C-C bond Cleavage in which acetyl-CoA serves as the acetyl donor substrate reacting at the ACDS beta subunit active site. The properties of Ni in the active site A-Cluster in the ACDS beta subunit from Methanosarcina thermophila were investigated. A recombinant, C-terminally truncated form of the beta subunit was employed, which mimics the native subunit previously isolated from the ACDS complex, and contains an A-Cluster composed of an [Fe4S4] center bridged to a binuClear Ni-Ni site. The electronic structures of these two Ni were studied using L-edge absorption and X-ray magnetic circular dichroism (XMCD) spectroscopy. The L-edge absorption data provided evidence for two distinct Ni species in the as-isolated enzyme, one with low-spin Ni(II) and the other with high-spin Ni(I). XMCD spectroscopy confirmed that the species producing the high-spin signal was paramagnetic. Upon treatment with Ti3+ citrate, an additional Ni species emerged, which was assigned to Ni(I). By contrast, CO treatment of the reduced enzyme converted nearly all of the Ni in the sample to low-spin Ni(I). The results implicate reaction of a high-spin tetrahedral Ni site with CO to form an enzyme-CO adduct transformed to a low-spin Ni(II) state. These findings are discussed in relation to the mechanism of C-C bond Activation, in connection with the model of the beta subunit A-Cluster developed from companion Ni and Fe K edge, XANES, and EXAFS studies.Chemically distinct Ni sites in the A-Cluster in subunit beta of the Acetyl-CoA deCarbonylase/synthase complex from Methanosarcina thermophila: Ni L-edge absorption and x-ray magnetic circular dichroism analysesx53200434#N/AFALSE
2659
ja039524010.1021/ja0395240FALSEhttps://doi.org/10.1021/ja0395240DuBois, DLJ. Am. Chem. Soc.A series of [Pd(diphosphine)(2)](BF4)(2) and Pd(diphosphine)(2) complexes have been prepared for which the natural bite angle of the diphosphine ligand varies from 78degrees to 111degrees. Structural studies have been completed for 7 of the 10 new complexes described. These structural studies indicate that the dihedral angle between the two planes formed by the two phosphorus atoms of the diphosphine ligands and palladium increases by over 500 as the natural bite angle increases for the [Pd(diphosphine)21(BF4)2 complexes. The dihedral angle for the Pd(diphosphine)(2) complexes varies less than 10degrees for the same range of natural bite angles. Equilibrium reactions of the Pd(diphosphine)2 complexes with protonated bases to form the corresponding [HPd(diphosphine)(2)](+) complexes were used to determine the pK(a) values of the corresponding hydrides. CyClic voltammetry studies of the [Pd(diphosphine)21(BF4)2 complexes were used to determine the half-wave potentials of the Pd(ll/l) and Pd(l/0) couples. Thermochemical cyCles, half-wave potentials, and measured pK(a) values were used to determine both the homolytic ([HPd(diphosphine)(2)](+) --> [Pd(diphosphine)(2)](+) + H-.) and the heterolytic ([HPd(diphosphine)(2)](+) --> [Pd(diphosphine)(2)](2+) + H-) bond-dissociation free energies, DeltaG(H)(O)(.) and DeltaG(H)(O)-, respectively. Linear free-energy relationships are observed between pK(a) H and the Pd(1/0) Couple and between DeltaG(H)(o)- and the Pd(ll/l) couple. The measured values for DeltaG(H)(o)(.) were all 57 kcal/mol, whereas the values of DeltaG(H)(o)- ranged from 43 kcal/mol for [HPd(depe)(2)](+) (where depe is bis- (diethylphosphino)ethane) to 70 kcal/mol for [HPd(EtXantphOS)(2)1](+) (where EtXantphos is 9,9-dimethyl-4,5bis(diethylphosphino)xanthene). It is estimated that the natural bite angle of the ligand contributes approximately 20 kcal/mol to the observed difference of 27 kcal/mol for DeltaG(H)(o)-.Using ligand bite angles to control the hydricity of palladium diphosphine complexes112200433#N/ATRUE
2660
ja039419q10.1021/ja039419qFALSEhttps://doi.org/10.1021/ja039419qHalfen, JAElectronic structure control of the nuCleophilicity of transition metal-thiolate complexes: An experimental and theoretical study2004#N/ATRUE
2661
ja036173g10.1021/ja036173gFALSEhttps://doi.org/10.1021/ja036173gSingh, AJ. Am. Chem. Soc.We describe the fabrication of metallic Cu spiral/helical nanostructures prepared via selective electroless metallization of a phospholipid microtubule template. The metallization template is created through selective, sequential adsorption of the oppositely charged polyelectrolytes, sodium poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI), onto nanoscale seams naturally occurring on the microtubule surface. A negatively charged Pd(II) nanopartiCle catalyst is bound to the terminal cationic PEI layer of the multilayer film and initiates selective template metallization to form the helical Cu nanostructures. Details of the process are presented, and a mechanism and factors affecting the control of the feature critical dimensions are discussed.Fabrication of nanoscale metallic spirals using phospholipid microtubule organizational templatesx66200327#N/AFALSE
2662
ja035981510.1021/ja0359815FALSEhttps://doi.org/10.1021/ja0359815Bard, AJJ. Am. Chem. Soc.The electrical properties of self-assembled monolayers (SAMS) on a gold surface have been explored to address the relation between the conductance of a molecule and its electronic structure. We probe interfacial electron transfer processes, particularly those involving electroactive groups, of SAMS of thiolates on Au by using shear force-based scanning probe microscopy (SPM) combined with current-voltage (i-V) and current-distance (i-d) measurements. Peak-shaped i-V curves were obtained for the nitro- and amino-based SAMS studied here. Peak-shaped cathodic i-V curves for nitro-based SAMS were observed at negative potentials in both forward and reverse scans and were used to define the threshold tip bias, V-TH, for electric conduction. For a SAM of 2',5'-dinitro-4,4'-bis(phenylethynyl)-1-benzenethiolate, VIII, V-TH was nearly independent of the tip material [Ir, Pt, Ir-Pt (20-80%), Pd, Ni, Au, Ag, In]. For all of the SAMS studied, the current decreased exponentially with increasing distance, d, between tip and substrate. The exponential attenuation factors (beta values) were lower for the nitro-based SAMS studied here, as compared with Alkylthiol-based SAMS. Both V-TH and beta of the nitro-based SAMS also depended strongly on the molecular headgroup on the end benzene ring addressed by the tip. Finally, we confirmed the memory effect observed for nitro-based SAMS. For mixed SAMS of VII and hexaClecanethiol, 1, the fraction of the charge collected in the negative tip bias region that can be read out at a positive tip bias on reverse scan (up to 38%) depended on the film composition and decreased with an increasing fraction of 1, suggesting that lateral electron hopping among molecules of VII occurs in the vicinity of the tip.Structure-dependent charge transport and storage in self-assembled monolayers of compounds of interest in molecular electronics: Effects of tip material, headgroup, and surface concentrationx122200458#N/AFALSE
2663
ja039384u10.1021/ja039384uFALSEhttps://doi.org/10.1021/ja039384uLatajka, ZJ. Am. Chem. Soc.Weak metal-arene interactions have been investigated in Zn, Cd, Hg, and Ni complexes of meso-tetraAryl m- and p-benziporphyrin (1 and 2) and of the new compound, m-benziporphodimethene (3). Compounds 1-3 incorporate the phenylene moiety into a macrocyClic structure so as to facilitate the interaction between the arene and coordinated metal ion. X-ray studies performed on Cd(II) and Ni(II) complexes show that the arene fragment approaches the ion at a distance much shorter than the sum of van der Waals radii. In chloronickel(II) m-benziporphyrin, a weak agostic bond is actually formed. In the NMR spectra of the Cd(II) and Hg(II) species, unusual H-1-M and C-13-M scalar couplings have been observed that are transmitted directly between the metal and the arene. DFT calculations performed for two Cd(II) species and subsequent AIM analysis show that the accumulation of electron density between the metal and arene necessary to induce these couplings is fairly small and the interaction is steric in nature. In the paramagnetic Ni(II) complexes of 1 and 3, the agostic proton of the m-phenylene exhibits large downfield H-1 NMR shifts (386 and 208 ppm at 298 K, respectively). An agostic mechanism of spin density transfer is proposed to explain these shifts as resulting from electron donation from the CH bond to the metal. In chloronickel(II) p-benziporphyrin, the inner protons of the p-phenylene have a contrastingly small shift (0.0 ppm at 298 K), indicating that in this case the agostic interaction is inefficient, in agreement with the X-ray, data.Cadmium(II) and nickel(II) complexes of benziporphyrins. A study of weak intramolecular metal-arene interactions141200489#N/ATRUE
2664
ja035806o10.1021/ja035806oFALSEhttps://doi.org/10.1021/ja035806oYamauchi, OJ. Am. Chem. Soc.One-electron oxidized nickel(II)-(disalicylidene)diamine complex: Temperature-dependent tautomerism between Ni(III)-phenolate and Ni(II)-phenoxyl radical statesx160200328#N/AFALSE
2665
ja035737d10.1021/ja035737dFALSEhttps://doi.org/10.1021/ja035737dBlower, PJJ. Am. Chem. Soc.The first copper bis(selenosemicarbazone) complexes have been synthesized, using the ligands glyoxal bis(selenosemicarbazone), pyruvaldehyde bis(selenosemicarbazone), and 2,3-butanedione bis(selenosemicarbazone). Their spectroscopic properties indicate that they are structurally analogous to their well-known square-planar sulfur-containing counterparts, the copper bis(thiosemicarbazone) complexes. Spectroscopic comparison of the sulfur- and selenium-containing complexes provides insight into their electronic structure. The effects on spectroscopic and redox properties of replacing sulfur with selenium, and of successive addition of methyl groups to the ligand backbone, are rationalized in terms of their electronic structure using spin-unrestricted density functional calculations. These suggest that, like the sulfur analogues, the complexes have a very low-lying empty ligand-based pi-orbital immediately above the LUMO, while the LUMO itself has d(x2-y2) character (i.e., is the spin partner of the HOMO). Replacement of S by Se shifts the oxidation potentials much more than the reduction potentials, whereas Alkylation of the ligand backbone shifts the reduction potentials more than the oxidation potentials. This suggests that oxidation and reduction involve spatially different orbitals, with the additional electron in the reduced species occupying the ligand-based pi-orbital rather than d(x2-y2). Density functional calculations on the putative singlet Cu(I)reduced species suggest that this ligand pi-character could be brought about by distortion away from planarity during reduction, allowing the low-lying ligand pi-LUMO to mix into the d(x2-y2)-based HOMO. The analogy in the structure and reduction behavior between the sulfur- and selenium-containing complexes suggests that labeled with positron emitting isotopes of copper (Cu-60, Cu-62, Cu-64), the complexes warrant biological evaluation as radiopharmaceuticals for imaging of tissue perfusion and hypoxia.Hypoxia-targeting copper bis(selenosemicarbazone) complexes: Comparison with their sulfur analoguesx37200356#N/AFALSE
2666
ja035532510.1021/ja0355325FALSEhttps://doi.org/10.1021/ja0355325Zhou, ZYJ. Am. Chem. Soc.X-ray structural and spectroscopic properties of a series of heterodinuClear d(8)-d(10) metal complexes [M'M(mu-dcpM)(2)(CN)(2)](+) containing d(8) Pt(II), Pd(II), or Ni(II) and d(10) Au(I), Ag(I), or Cu(I) ions with a dcpm bridging ligand have been studied (dcpm = bis(dicyClohexylphosphino)methane; M' = Pt, M = Au 4, Ag 5, Cu, 6; M = Au, M' = Pd 7, Ni 8). X-ray crystal analyses showed that the metal(...)metal distances in these heteronuClear metal complexes are shorter than the sum of van der Waals radii of the M' and M atoms. The UV-vis absorption spectra of 4-6 display red-shifted intense absorption bands from the absorption spectra of the mononuClear trans-[Pt(phosphine)(2)(CN)(2)] and [M(phosphine)(2)] counterparts, attributable to metal-metal interactions. The resonance Raman spectra confirmed assignments of (1)[nd(sigma)*-->(n + 1)p(sigma)] electronic transitions to the absorption bands at 317 and 331 nm in 4 and 6, respectively. The results of theoretical calculations at the MP2 level reveal an attractive interaction energy curve for the skewed [trans- Pt(PH3)(2)(CN)(2)-Au(PH3)(2)(+)] dimer. The interaction energy of Pt(II)-Au(I) was calculated to be ca. 0.45 ev.Metal-metal interactions in heterobimetallic d(8)-d(10) complexes. Structures and spectroscopic investigation of [M ' M ''(mu-dcpm)(2)(CN)(2)](+) (M ' = Pt, Pd; M '' = Cu, Ag, Au) and related complexes by UV-vis absorption and resonance Raman spectroscopy and ab initio calculationsx96200370#N/AFALSE
2667
ja038936610.1021/ja0389366FALSEhttps://doi.org/10.1021/ja0389366Fu, GCJ. Am. Chem. Soc.Cross-couplings of unactivated secondary Alkyl halides: Room-temperature nickel-catalyzed Negishi reactions of Alkyl bromides and iodides252200324#N/ATRUE
2668
ja035296y10.1021/ja035296yFALSEhttps://doi.org/10.1021/ja035296yArmstrong, FAJ. Am. Chem. Soc.The cyCling between active and inactive states of the catalytic center of [NiFe]-hydrogenase from Allochromatium vinosum has been investigated by dynamic electrochemical techniques. Adsorbed on a rotating disk pyrolytic graphite edge electrode, the enzyme is highly electroactive: this allows precise manipulations of the complex redox chemistry and facilitates quantitative measurements of the interconversions between active catalytic states and the inactive oxidized form Ni-r* (also called Ni-B or ready) as functions of pH, H-2 partial pressure, temperature, and electrode potential. CyClic voltammograms for catalytic H-2 oxidation (current is directly related to turnover rate) are highly asymmetric (except at pH > 8 and high temperature) due to inActivation being much slower than Activation. Controlled potential-step experiments show that the rate of oxidative inActivation increases at high pH but is independent of potential, whereas the rate of reductive Activation increases as the potential becomes more negative. Indeed, at 45 degreesC, Activation takes just a few seconds at -288 mV. The cyClic asymmetry arises because interconversion is a two-stage reaction, as expected if the reduced inactive Ni-r-S state is an intermediate. The rate of inActivation depends on a chemical process (rearrangement and uptake of a ligand) that is independent of potential, but sensitive to pH, while Activation is driven by an electron-transfer process, Ni(III) to Ni(II), that responds directly to the driving force. The potentials at which fast Activation occurs under different conditions have been analyzed to yield the potential-pH dependence and the corresponding entropies and enthalpies. The reduced (active) enzyme shows a pK of 7.6; thus, when a one-electron process is assumed, reductive Activation at pH < 7 involves a net uptake of one proton (or release of one hydroxide), whereas, at pH > 8, there is no net exchange of protons with solvent. Activation is favored by a large positive entropy, consistent with the release of a ligand and/or relaxation of the structure around the active site.Enzyme electrokinetics: Electrochemical studies of the anaerobic interconversions between active and inactive states of Allochromatium vinosum [NiFe]-hydrogenasex138200352#N/AFALSE
2669
ja034919510.1021/ja0349195FALSEhttps://doi.org/10.1021/ja0349195Murakami, MJ. Am. Chem. Soc.Palladium- and nickel-catalyzed intramolecular cyanB(OH)2ration of alkynesx152200317#N/AFALSE
2670
ja038886510.1021/ja0388865FALSEhttps://doi.org/10.1021/ja0388865Zhang, GSJ. Am. Chem. Soc.A detailed theoretical investigation of the mechanism for the [Ni-0]-catalyzed co-oligomerization of 1,3-butadiene and ethylene to afford linear and cyClic C-10-olefins is presented. Crucial elementary processes have been carefully explored for a tentative catalytic cyCle, employing a gradient-corrected density functional theory (DFT) method, The favorable route for oxidative coupling starts from the prevalent [Ni-0-(eta(2)-butadiene)(2)(ethylene)] form of the active catalyst through oxidative coupling between the two eta(2)-butadienes. The initial eta(3),eta(1)(C-1)-octadienediyl-Ni-II product is the active precursor for ethylene insertion, which preferably takes place into the syn-eta(3)-allyl-Ni-II bond of the prevalent eta(3)-syn,eta(1)(C-1),Delta-cis isomer. The insertion is driven by a strong thermodynamic force, giving rise entirely to eta(3),eta(1), Delta-trans-decatrienyl-Ni forms, with the eta(3)-anti,eta(1),Delta-trans isomer almost exClusively generated. Occurrence of allyl,eta(1),Delta-cis isomers, however, is preCluded on both kinetic and thermodynamic grounds, thereby rationalizing the observation that cis-DT and cis,cis-CDD are never formed. Linear and cyClic C-10-olefins are generated in a highly stereoselective fashion, with trans-DT and cis,trans-CDD as the only isomers, along competing routes of stepwise transition-metal-assisted H-transfer (DT) and reductive CC elimination under ring Closure (CDD), respectively, that start from the prevalent eta(3)-anti,eta(1),Delta-trans-decatrienyl-Ni species. The role of allylic conversion in the octadienediyl-Ni-II and decatrienyl-Ni-II complexes has been analyzed. As a result of the detailed exploration of all important elementary steps, a theoretically verified, refined catalytic cyCle is proposed and the regulation of the selectivity for formation of linear and cyClic C-10-olefins is elucidated.[Ni-0]-catalyzed co-oligomerization of 1,3-butadiene and ethylene: A theoretical mechanistic investigation of competing routes for generation of linear and cyClic C-10-olefins16200445#N/ATRUE
2671
ja038154c10.1021/ja038154cFALSEhttps://doi.org/10.1021/ja038154cSautet, PJ. Am. Chem. Soc.The catalytic activity of a 4 monolayer deposit of Pd on a Ni(110) surface toward the hydrogenation of ethylene is investigated by using gradient-corrected periodic density functional calculations. The Pd/ Ni(l 10) surface is strongly nanostructured, due to the anisotropic stress induced by the Ni(110) substrate on the Pd layer. A kinetic analysis, based on the investigation of the optimal reaction pathway for the hydrogenation of ethylene to ethane, is presented, allowing a comparison between Pd/Ni(110) and pure Pd(110) surfaces. The calculated Activation energies allow one to reproduce the experimental result, which shows that the Pd/Ni(110) surface is about 30 times more active than the pure Pd(110) surface. This marked increase of the catalytic activity is a consequence of the specific nanostructure of the Pd/Ni(110) surface. By examining the structure of the adsorbed species and of the transition states and by analyzing the electronic properties, we show that this rate increase can be associated to the fact that the ethylene adsorption energy in the first hydrogenation step and the ethyl-hydrogen coadsorption energy in the second step are both much lower on Pd/Ni(110) than on pure Pd(110).Understanding the high activity of a nanostructured catalyst obtained by a deposit of Pd on Ni: First principle calculations27200424#N/ATRUE
2672
ja037776v10.1021/ja037776vFALSEhttps://doi.org/10.1021/ja037776vMeyer, OJ. Am. Chem. Soc.During the past two years, crystal structures of Cu- and Mo-containing carbon monoxide dehydrogenases (CODHs) and Ni- and Fe-containing CODHs have been reported. The active site of CODHs from anaerobic bacteria (Cluster C) is composed of Ni, Fe, and S for which crystallographic studies of the enzymes from Carboxydothermus hydrogenoformans, Rhodospirillum rubrum, and Moorella thermoacetica revealed structural similarities in the overall protein fold but showed substantial differences in the essential Ni coordination environment. The [Ni-4Fe-5S] Cluster C in the fully catalytically competent dithionite-reduced CODH II from C. hydrogenoformans (CODHIICh) at 1.6 Angstrom resolution contains a characteristic mu(2) -sulfido ligand between Ni and Fe1, resulting in a square-planar ligand arrangement with four S-ligands at the Ni ion. In contrast, the [Ni-4Fe-4S] Clusters C in CO-treated CODH from R. rubrum resolved at 2.8 A and in CO-treated acetyl-CoA synthase/CODH complex from M. thermoacetica at 2.2 and 1.9 Angstrom resolution, respectively, do not contain the mu(2)-Sulfido ligand between Ni and Fe1 and display dissimilar geometries at the Ni ion. The [Ni-4Fe-4S] Cluster is composed of a cubane [Ni-3Fe-4S] Cluster linked to a mononuClear Fe site. The described coordination geometries of the Ni ion in the [Ni-4Fe-4S] Cluster of R. rubrum and M. thermoacetica deviate from the square-planar ligand geometry in the [Ni-4Fe-5S) Cluster C of CODHIICh. In addition, the latter was converted into a [Ni-4Fe-4S] Cluster under specific conditions. The objective of this study was to elucidate the relationship between the structure of Cluster C in CODHIICh and the functionality of the protein. We have determined the CO oxidation activity of CODHIICh under different conditions of crystallization, prepared crystals of the enzyme in the presence of dithiothreitol or dithionite as reducing agents under an atmosphere of N-2 or CO, and solved the corresponding structures at 1.1 to 1.6 A resolutions. Fully active CODHIIch obtained after incubation of the enzyme with dithionite under N2 revealed the [Ni-4Fe-5S] Cluster. Short treatment of the enzyme with CO in the presence of dithiothreitol resulted in a catalytically competent CODHIICh with a CO-reduced [Ni-4Fe-5S] Cluster, but a prolonged treatment with CO caused the loss of CO-oxidizing activity and revealed a [Ni-4Fe-4S] Cluster, which did not contain a mu(2)-S. These data suggest that the [Ni-4Fe-4S] Cluster of CODHIICh is an inactivated decomposition product originating from the [Ni-4Fe-5S] Cluster.Carbon monoxide induced decomposition of the active site [Ni-4Fe-5S] Cluster of CO dehydrogenase74200425#N/ATRUE
2673
ja034143810.1021/ja0341438FALSEhttps://doi.org/10.1021/ja0341438Schroder, MJ. Am. Chem. Soc.The tetradentate imino-Carbonylate ligand [L](2-) chelates the equatorial sites of Ni-II to give the complex [Ni(L)(MeOH)(2)] in which a Ni-II center is bound in an octahedral coordination environment with MeOH ligands occupying the axial sites. Lanthanide (Ln) and Group 11 metal ions (M) template the aggregation of six [Ni(L)] fragments into the octahedral cage aggregates {M[Ni(L)](6)}(x+) (1: M = Sr-II; x= 2, 2: M = Ball; x = 2, 3: M = La-III; x = 3, 4: M = Ce-III; x = 3, 5: M = Pr-III; x = 3, and 6: M = Nd-III; x = 3). In the presence of Group I cations, however, aggregates composed of the alkali metal-oxide cations template various cage compounds. Thus, Na+ forms the trigonal bipyramidal [Na5O](3+) core within a tricapped trigonal prismatic [Ni(L)](9) aggregate to give {(Na5O)subset of[Ni(L)](9)(MeOH)(3)}(BF4)(2)(OHCH3OH)-O-.-C-., 7. Li+ and Na+ together form a mixed Li+/Na+ core comprising distorted trigonal bipyramidal [Na3Li2O](3+) within an approximately anti-square prismatic [Ni(L)](8) cage in {(Na3Li2O)subset of[Ni(L)](8)(CH3OH)(1.3)(BF4)(0.7)}(BF4)(2.3.)(CH3OH)(2.75)(.)(C4H10O)(0.5), 8, while in the presence of Li+, a tetrahedral [Li4O](2+) core within a hexanuClear open cage [Ni(L)](6) in {(Li4O)subset of[Ni(L)](6)(CH3OH)(3)}2ClO(4).1.85CH(3)OH, 9, is produced. In the presence of H2O, the Cs+ cation induces the aggregation of the [Ni(L)(H2O)(2)] monomer to give the Cluster Cs-2[Ni(L)(H2O)(2)](6).2l-4CH(3)OH.5.25H(2)O, 10. Analysis by electronic spectroscopy and mass spectrometry indicates that in solution the trend in stability follows the order 1-6 > 7 > 8 similar to 9. Magnetic susceptibility data indicate that there is net antiferromagnetic exchange between magnetic centers within the cages.Cationic assembly of metal complex aggregates: Structural diversity, solution stability, and magnetic propertiesx70200345#N/AFALSE
2674
ja037718+10.1021/ja037718+FALSEhttps://doi.org/10.1021/ja037718+Cheng, CHJ. Am. Chem. Soc.Nickel-catalyzed highly regio- and stereoselective three-component assembly of allenes, Aryl iodides, and alkenylzirconium reagents32200329#N/ATRUE
2675
ja037370i10.1021/ja037370iFALSEhttps://doi.org/10.1021/ja037370iKim, YJ. Am. Chem. Soc.Highly selective electrocatalytic conversion of CO2 to CO at -0.57V (NHE) by carbon monoxide dehydrogenase from Moorella thermoacetica67200341#N/ATRUE
2676
ja036700w10.1021/ja036700wFALSEhttps://doi.org/10.1021/ja036700wMcBreen, PHJ. Am. Chem. Soc.Adsorption states and modifier-substrate interactions on Pt(111) relevant to the enantioselective hydrogenation of Alkyl pyruvates in the Orito reaction61200320#N/ATRUE
2677
ja036684310.1021/ja0366843FALSEhttps://doi.org/10.1021/ja0366843Gorski, WJ. Am. Chem. Soc.The ionic interactions were studied in aqueous solutions of Na(3)lrCl(6) + Pb(NO3)(2) in order to develop a facilitated electrosynthesis of iridium-based catalytic surfaces. Spectroscopic studies indicated that ion pair charge-transfer complexes [IrCl63-]-Pb(II) (K = 6 x 10(3)) and [Ir(H2O) Cl-5(2-)]-Pb(II) (K = 2 x 10(3)) were formed in fresh and aged solutions, respectively. Electrochemical studies showed that interactions between the Ir(H2O)Cl-5(2-) and Pb(II) species lead to synergistic lowering of the overpotential that was necessary for nuCleation and growth of mixed metal oxide PbIrOx on the surface of glassy carbon electrodes. The Ir:Pb stoichiometry of the PbIrOx surface films was the same (1:1) as that of the high-temperature phase of Pb-Ir-O pyrochlore. Compared to IrOx, the PbIrOx films displayed enhanced catalytic activity toward the electrooxidation of carbohydrates. This was ascribed to synergism that involved retention of carbohydrate molecules at the Pb(II) sites of a PbIrOx film and oxidation at the adjacent Ir(IV) sites. The synergistic electroplating utilizing interactions between the partially aquated transition metal complex and posttransition metal ion represents a new synthetic route to highly homogeneous and reactive films of mixed metal oxides.Synergistic effects in multicomponent electrocatalysts: The Pb-Ir-O system13200346#N/ATRUE
2678
ja030634g10.1021/ja030634ghttps://doi.org/10.1021/ja030634gBrookhart, MJ. Am. Chem. Soc.An extensive mechanistic investigation has been carried out on ethylene polymerizations catalyzed by neutral Ni(II) catalysts derived from bulky anilinotropone ligands. Complexes and precatalysts prepared inClude Aryl derivatives [(2,6-i-Pr2C6H3)NC7H4O(7-Aryl)Ni(Ph)(PPh3)] (9, Aryl = phenyl(a), 1-naphthyl(b), p-methoxyphenyl(c), p-trifluoromethylphenyl(d)), Alkyl derivatives [[(2,6-(Pr2C6H3)-Pr-i)NC7H5O]Ni(R)(2,4-lutidine)] (16, R = Et (a), n-Pr (b)) and [[(2,6-iPr(2)C(6)H(3))NC7H5O]Ni(R)(PPh3)] (17, R = Et (a), n-Pr (b), n-hexyl (c), i-Pr (d)), and the nickel hydride complex [[(2,6-(Pr2C6H3)-Pr-i)NC7H5O]Ni(H)(PPh3)], 20. Branched polyethylenes are produced at 40-80 degreesC in toluene with M-n values in the 100-200K range and molecular weight distributions of ca. 1.4-2.2. Branching ranges from 15 to 64 branches/1000 carbons depending on temperature and ethylene pressure. The electron-withdrawing -CF3 substituent on the 7-Aryl group increases activity but has little effect on branching and molecular weight. NMR experiments establish that in the case of the PPh3-substituted systems, the catalyst rests as an equilibrating mixture of the Alkyl phosphine and the Alkyl ethylene complexes. At high ethylene pressures, the turnover frequency saturates, indicating that the equilibrium has shifted nearly completely to the Alkyl olefin complex. Under these conditions, the barriers to migratory insertion were determined to be ca. 16-17 kcal/mol for 9a, 9c, 9d, and 16a. Extraction of 2,6-lutidine from complexes 16a,b yields highly dynamic beta-agostic Alkyl complexes [[(2,6-i-Pr2C6H3)NC7H5O]-Ni(Et)] 21 and [[(2,6-i-Pr2C6H3)NC7H5O]Ni(i-Pr)] 22. Free energy barriers to nickel-carbon bond rotation and beta-hydride elimination of 11.1 and ca. 17 kcal/mol, respectively, were determined for 22. Themolysis of 17c at 50 degreesC generates hydride 20 and hexene and occurs by two pathways, one independent of [PPh3] and one retarded by PPh3. At much slower rates, hydride 20 reductively eliminates free ligand, which ultimately generates a bis-ligand complex, 25. Catalyst decay under polymerization conditions was shown to occur by a similar process to generate free ligand and a bis-ligand complex formed by reaction of free ligand with an active catalyst species. The major chain transfer route is a simple beta-elimination process, not chain transfer to monomer.A mechanistic investigation of the polymerization of ethylene catalyzed by neutral Ni(II) complexes derived from bulky anilinotropone ligandsx133200451#N/AFALSE
2679
ja036602a10.1021/ja036602aFALSEhttps://doi.org/10.1021/ja036602aGrahame, DAJ. Am. Chem. Soc.The acetyl-CoA deCarbonylase/synthase (ACDS) complex catalyzes the Cleavage of acetyl-CoA in methanogens that metabolize acetate to CO2 and CH4, and also carries out acetyl-CoA synthesis during growth on one-carbon substrates. The ACDS complex contains five subunits, among which beta possesses an Ni-Fe-S active-site metal Cluster, the A-Cluster, at which reaction with acetyl-CoA takes place, generating an acetyl-enzyme species poised for C-C bond Cleavage. We have used Ni and Fe K fluorescence XANES and EXAFS analyses to characterize these metals in the ACDS beta subunit, expressed as a C-terminally shortened form. Fe XANES and EXAFS confirmed the presence of an [Fe4S4] Cluster, with typical Fe-S and Fe-Fe distances of 2.3 and 2.7 Angstrom respectively. An Fe:Ni ratio of similar to2:1 was found by Kalphabeta fluorescence analysis, indicating 2 Ni per [Fe4S4]. Ni XANES simulations were consistent with two distinct Ni sites in Cluster A, and the observed spectrum could be modeled as the sum of separate square planar and tetrahedral Ni sites. Treatment of the beta subunit with Ti3+ citrate resulted in shifts to lower energy, implying significant reduction of the [Fe4S4] center, along with conversion of a smaller fraction of Ni(II) to Ni(I). Reaction with CO in the presence of Ti3+ citrate generated a unique Ni XANES spectrum, while effects on the Fe-edge were not very different from the reaction with Ti3+ alone. Ni EXAFS revealed an average Ni coordination of 2.5 S at 2.19 Angstrom and 1.5 N/O at 1.89 Angstrom. A distinct feature at similar to2.95 Angstrom most likely results from Ni-Ni interaction. The methanogen beta subunit A-Cluster is proposed to consist of an [Fe4S4] Cluster bridged to an Ni-Ni center with one Ni in square planar geometry coordinated by 2 S + 2 N and the other approximately tetrahedral with 3 S + 1 N/O ligands. The electronic consequences of two distinct Ni geometries are discussed.The a-Cluster in subunit beta of the acetyl-CoA deCarbonylase/synthase complex from Methanosarcina thermophila: Ni and FeK-Edge XANES and EXAFS analyses37200347#N/ATRUE
2680
ja030611210.1021/ja0306112FALSEhttps://doi.org/10.1021/ja0306112de Dios, ACJ. Am. Chem. Soc.Different potassium salts and zinc(II) and nickel(II) O,O'-diAlkyldithiophosphate complexes were studied by solid-state P-31 CP/MAS and static NMR and ab initio quantum mechanical calculations. Spectra were obtained at different spinning frequencies, and the intensities of the spinning sidebands were used to estimate the chemical shift anisotropy parameters. Useful correlations between the shapes of the P-31 chemical shift tensor and the type of ligand were found: terminal ligands have negative values of the skew kappa, while bridging and ionic ligands have positive values for this parameter. The experimental results were compared with known X-ray diffraction structures for some of these complexes as well as with ab initio quantum mechanical calculations, and a useful correlation between the delta(22) component of the P-31 chemical shift tensor and the S-P-S bond angle in the O,O'-diAlkyldithiophoshate zinc(II) and nickel(II) complexes was found: delta(22) increases more than 50 ppm with the increase of S-P-S bond angle from ca. 100degrees to 1201, while the other two principal values of the tensor, delta(11), and delta(33), are almost conserved. This eventually leads to the change in sign for kappa in the bridging type of ligand, which generally has a larger S-P-S bond angle than the terminally bound O,O'-diAlkyldithiophoshate group forming chelating four-membered P<(S)(S)>Me heterocyCles.Correlations between P-31 chemical shift anisotropy and molecular structure in polycrystalline O,O '-diAlkyldithiophosphate zinc(II) and nickel(II) complexes: P-31 CP/MAS NMR and Ab initio quantum mechanical calculation studiesx49200545#N/AFALSE
2681
ja030221f10.1021/ja030221fFALSEhttps://doi.org/10.1021/ja030221fBalch, ALJ. Am. Chem. Soc.The powder and single-crystal EPR spectra of Co-II(OEP) (OEP is the dianion of octaethylporphyrin) doped into a range of diamagnetic crystals inCluding simple four-coordinate hosts, H-2(OEP), the triClinic B form of Ni-II(OEP), the tetragonal form of Ni-II(OEP) and Zn-II(OEP); five-coordinate hosts, (mu-dioxane)-{Zn-II(OEP)}(2) and (py)Zn-II(OEP); six-coordinate hosts, (py)(2)Zn-II(OEP) and (py)(2)Mg-II(OEP); and hosts containing fullerenes, C-60.2Zn(II)(OEP).CHCl3, C-70.Ni-II(OEP).C6H6.CHCl3, and C-60.Ni-II(OEP).2C(6)H(6) have been obtained and analyzed. Spectra were simulated using a program that employed the exact diagonalization of the 16 x 16 complex spin Hamiltonian matrix. The EPR spectra of these doped samples are very sensitive to the environment within each crystal with the crystallographic site symmetry determining whether axial or rhombic resonance patterns are observed. For Co-II(OEP) doped into tetragonal Ni-II(OEP) (which displays a very large g(perpendicular to) of 3.405 and a very small g(parallel to) of 1.544) and several other crystals containing four-coordinate metal sites, the g components could not be fit using existing theory with the assumption of the usual z(2) ground state. However, reasonable agreement of the observed EPR parameters could be obtained by assuming that the unpaired electron resides in an xy orbital in the four-coordinate complexes.Crystal environments probed by EPR spectroscopy. Variations in the EPR spectra of Co-II(octaethylporphyrin) doped in crystalline diamagnetic hosts and a reassessment of the electronic structure of four-coordinate cobalt(II)x61200346#N/AFALSE
2682
ja036218d10.1021/ja036218dFALSEhttps://doi.org/10.1021/ja036218dCramer, SPJ. Am. Chem. Soc.We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L-3-centroid energy is 853.1 (1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character.X-ray magnetic circular dichroism of Pseudomonas aeruginosa nickel(II) azurin11200467#N/ATRUE
2683
ja035837j10.1021/ja035837jFALSEhttps://doi.org/10.1021/ja035837jStack, TDPJ. Am. Chem. Soc.Intramolecular charge transfer and biomimetic reaction kinetics in galactose oxidase model complexes115200326#N/ATRUE
2684
ja035509j10.1021/ja035509jFALSEhttps://doi.org/10.1021/ja035509jHubbs, JLNi(II) bis(oxazoline)-catalyzed enantioselective syn aldol reactions of N-propionylthiazolidinethiones in the presence of silyl triflates2003#N/ATRUE
2685
ja030123u10.1021/ja030123uFALSEhttps://doi.org/10.1021/ja030123uWieghardt, KJ. Am. Chem. Soc.Two series of square planar, diamagnetic, neutral complexes of nickel(II), palladium(II), and platinum(II) containing two N,N-coordinated o-diiminobenzosemiquinonate(1-) pi radical ligands have been synthesized and characterized by UV-vis and H-1 NMR spectroscopy: [M-II(L-2(ISQ))(2)], M = Ni (1), Pd (2), Pt (3), and [M-II(L-3(ISQ))(2)] M = Ni (4), Pd (5), Pt (6). H-2[L-2(PDI)] represents 3,5-di-tert-butyl-o-phenylenediamine and H-2[L-3(PDI)] is N-phenyl-o-phenylenediamine; (L-ISQ)(1-) is the o-diiminobenzosemiquinonate pi radical anion, and (L-IBQ)(0) is the o-diiminobenzoquinone form of these ligands. The structures of complexes 1, 4, 5, and 6 have been (re)determined by X-ray crystallography at 100 K. CyClic voltammetry established that the complete electron-transfer series consisting of a dianion, monoanion, neutral complex, a mono- and a dication exists: [M(L)(2)](z) = -2, -1, 0, 1+, 2+. Each species has been electrochemically generated in solution and their X-band EPR and UV-vis spectra have been recorded. The oxidations and reductions are invariably ligand centered. Two o-diiminobenzoquinones(0) and two fully reduced o-diiminocatecholate-(2-) ligands are present in the dication and dianion, respectively, whereas the monocations and monoanions are delocalized mixed valent Class III species [M-II(L-ISQ)(L-IBQ)](+) and [M-II(L-ISQ)(L-PDI)](-), respectively. One-electron oxidations of 1 and trans-6 yield the diamagnetic dications {cis-[Ni-II(L-2(ISQ))(L-2(IBQ))](2)}Cl-2 (7) and {trans[pt(II)(L-3(ISQ))(L-3(IBQ))](2)}(CF3SO3)(2) (8), respectively, which have been characterized by X-ray crystallography; both complexes possess a weak M...M bond and the ligands adopt an eClipsed configuration due to weak bonding interactions via pi stacking.Molecular and electronic structures of bis-(o-diiminobenzosemiquinonato)metal(II) complexes (Ni, Pd, Pt), their monocations and -anions, and of dimeric dications containing weak metal-metal bondsx203200342#N/AFALSE
2686
ja034468o10.1021/ja034468oFALSEhttps://doi.org/10.1021/ja034468oBrookhart, MJ. Am. Chem. Soc.Cationic Rh(III) complex [Cp*(PMe3)Rh(SiPh3)(CH2Cl2)]BAr4' (1) activates the carbon-carbon bond of Aryl and Alkyl cyanides (R-CN, where R = Ph, (4-(CF3)C6H4), (4-(OMOC6H4), Me, Pr-i, Bu-t) to produce complexes of the general formula [Cp*(PMe3)Rh(R)(CNSiPh3)]BAr4'. With the exception of the (BuCN)-Bu-t case, every reaction proceeds at room temperature (t(1/2) < 1 h for Aryl cyanides, t(1/2) < 14 h for Alkyl cyanides). A general mechanism is presented on the basis of (1) an X-ray crystal structure determination of an intermediate isolated from the reaction involving 4-methoxybenzonitrile and (2) kinetic studies performed on the C-C bond Cleavage of para-substituted Aryl cyanides. Initial formation of an n(1)-nitrile species is observed, followed by conversion to an eta(2)-iminoacyl intermediate, which was observed to undergo migration of R (Aryl or Alkyl) to rhodium to form the product [Cp*(PMe3)Rh(R)(CNSiPh3)]BAr4'.A mechanistic investigation of the carbon-carbon bond Cleavage of Aryl and Alkyl cyanides using a cationic Rh(III) silyl complex121200330#N/ATRUE
2687
ja034431410.1021/ja0344314FALSEhttps://doi.org/10.1021/ja0344314Schweiger, AJ. Am. Chem. Soc.Coenzyme B induced coordination of coenzyme M via its thiol group to Ni(I) of F-430 in active methyl-coenzyme M reductase46200315#N/ATRUE
2688
ja034201p10.1021/ja034201pFALSEhttps://doi.org/10.1021/ja034201pKambe, NJ. Am. Chem. Soc.Ni- or Cu-catalyzed cross-coupling reaction of Alkyl fluorides with Grignard reagents216200325#N/ATRUE
2689
ja029806k10.1021/ja029806kFALSEhttps://doi.org/10.1021/ja029806kSolomon, EIJ. Am. Chem. Soc.The pterin-dithiolene cofactor is an essential component of the catalytic sites of all molybdoenzymes except nitrogenase. Understanding its bonding to transition metals allows for development of electronic structure/function correlations in catalysis. The electronic structure description for a series of bis(dithiolene) complexes ([NiL2](z), L = 1,2-Me2C2S2; Z = 2-, 1 -, 0) using sulfur XAS provides the basis for extension to the biologically relevant metal-containing dithiolenes. The transition dipole integral has been developed for the dithiolene sulfur through correlation of XAS pre-edge energy positions of sulfide-, thiolate-, and enedithiolate-S. The ground state wave functions of all three NiL2 complexes have more than 50% S character experimentally demonstrating the noninnocent behavior of the dithiolene ligand. The S K-edge experimental results are correlated with spin-unrestricted, broken-symmetry density functional calculations. These show only limited spin polarization in the neutral complex and delocalized, ligand based ground states for the mono- and dianionic complexes. These XAS and DFT results are correlated with other spectroscopic features and provide insight into reactivity.Description of the ground state wave functions of Ni dithiolenes using sulfur K-edge X-ray absorption spectroscopyx158200379#N/AFALSE
2690
ja034129v10.1021/ja034129vFALSEhttps://doi.org/10.1021/ja034129vYan, CHJ. Am. Chem. Soc.Two-dimensional homochiral manganese(II)-azido frameworks incorporating an achiral ligand: Partial spontaneous resolution and weak ferromagnetism264200327#N/ATRUE
2691
ja029481810.1021/ja0294818FALSEhttps://doi.org/10.1021/ja0294818Ferey, GJ. Am. Chem. Soc.A new mixed zinc-aluminum phosphate Zn3Al6(PO4)(12), 4tren, 17H(2)O (MIL-74) has been hydrothermally synthesized with the tris(2-aminoethyl)amine (tren) as a structure-directing agent (453 K, 36 h, autogenous pressure). The solid was characterized by a nonClassical method combining single-crystal X-ray diffraction and several solid-state NMR experiments, RFDR, C7 double quantum (P-31), and 3QMAS (Al-27). Its crystal structure is cubic, a = 16.7942(1) Angstrom, but the choice of the space group does not follow usual routes of structure determination, due to some disorder between Zn and Al. It can be assigned as well to I-43m or to P-43n. The open-framework is built up from an enneameric unit (T = Zn, Al) containing five TO4 and four PO4 tetrahedra (one of the P-O bonds is terminal). A central TO4 tetrahedral unit shares all of the corners with four phosphates groups. Two phosphate groups are connected to two other peripheral TO4 units. It results in the formation of a pseudo planar building block T5P4 consisting of four square 4-rings. The connection of the T5P4 units generates a three-dimensional framework, which defines a super-soClalite topology. The resulting cavities (diameter of 10 Angstrom) are bound by 12-ring windows in which are located the tren species in interaction with the phosphate groups (mainly terminal P-O bonds) through hydrogen bonds. A Cluster of 17 water molecules occupies the center of the super-soClalite cage. The cationic (Zn, Al) occupancy is discussed for this specific topology.Order-disorder in the super-sodalite Zn3Al6(PO4)(12), 4tren, 17H(2)O (MIL-74): A combined XRD-NMR assessmentx81200355#N/AFALSE
2692
ja029062a10.1021/ja029062aFALSEhttps://doi.org/10.1021/ja029062aWasielewski, MRJ. Am. Chem. Soc.The spin-spin exchange interaction, 2J, in a radical ion pair produced by a photoinduced electron transfer reaction can provide a direct measure of the electronic coupling matrix element, V, for the subsequent charge recombination reaction. We have developed a series of dyad and triad donor-acceptor molecules in which 2J is measured directly as a function of incremental changes in their structures. In the dyads the chromophoric electron donors 4-(N-pyrrolidinyl)- and 4-(N-piperidinyl)naphthalene-1,8-dicarboximide, 5ANI and 6ANI, respectively, and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor are linked to the meta positions of a phenyl spacer to yield 5ANI-Ph-NI and 6ANI-Ph-NI. In the triads the same structure is used, except that the piperidine in 6ANI is replaced by a piperazine in which a para-X-phenyl, where X = H, F, Cl, MeO, and Me2N, is attached to the N' nitrogen to form a para-X-aniline (XAn) donor to give XAn-6ANI-Ph-NI. Photoexcitation yields the respective 5ANI(+)-Ph-NI-, 6ANI(+)-Ph-NI-, and XAn(+)-6ANI-Ph-NI- singlet radical ion pair states, which undergo subsequent radical pair intersystem crossing followed by charge recombination to yield (NI)-N-3*. The radical ion pair distances within the dyads are about 11-12 Angstrom, whereas those in the triads are about similar to16-19 Angstrom. The degree of delocalization of charge (and spin) density onto the aniline, and therefore the average distance between the radical ion pairs, is modulated by the para substituent. The (NI)-N-3* yields monitored spectroscopically exhibit resonances as a function of magnetic field, which directly yield 2J for the radical ion pairs. A plot of In 2J versus r(DA), the distance between the centroids of the spin distributions of the two radicals that comprise the pair, yields a slope of -0.5 +/- 0.1. Since both 2J and k(CR), the rate of radical ion pair recombination, are directly proportional to V-2, the observed distance dependence of 2J shows directly that the recombination rates in these molecules obey an exponential distance dependence with beta = 0.5 +/- 0.1 Angstrom(-1). This technique is very sensitive to small changes in the electronic interaction between the two radicals and can be used to probe subtle structural differences between radical ion pairs produced from photoinduced electron transfer reactions.Mapping the influence of molecular structure on rates of electron transfer using direct measurements of the electron spin-spin exchange interactionx73200350#N/AFALSE
2693
ja028687610.1021/ja0286876FALSEhttps://doi.org/10.1021/ja0286876Sigman, MSJ. Am. Chem. Soc.Unusual reactivity of molecular oxygen with pi-allylnickel(N-heterocyClic carbene) chloride complexesx79200333#N/AFALSE
2694
ja028525+10.1021/ja028525+FALSEhttps://doi.org/10.1021/ja028525+Ragsdale, SWJ. Am. Chem. Soc.Methyl-coenzyme M reductase (MCR) from Methanothermobacter marburgensis (Mtm), catalyses the final step in methane synthesis in all methanogenic organisms. Methane is produced by coenzyme B-dependent two-electron reduction of methyl-coenzyme M. At the active site of MCR is the corphin cofactor F-430, which provides four-coordination through the pyrrole nitrogens to a central Ni ion in all states of the enzyme. The important MCRox1 (ready) and MCRred1 (active) states contain six-coordinate Ni(l) and differ in their upper axial ligands; furthermore, red1 appears to be two-electrons more reduced than in ox1 and other Ni(11) states that have been studied. On the basis of the reactivity of MCRred1 and MCRox1 with a substrate analogue and inhibitor (3-bromopropanesulfonate) and other small molecules (chloroform, dichloromethane, mercaptoethanol, and nitric oxide), we present evidence that the six-coordinate Ni(l) centers in the MCRred1 and MCRox1 states exhibit markedly different inherent reactivities. MCRred1 reacts faster with chloroform (2100-fold or 35000-fold when corrected for temperature effects), nitric oxide (90-fold), and 3-bromopropanesulfonate (10(6)-fold) than MCRox1. MCRred1 reacts with chloroform and dichloromethane and, like F-430, can catalyze dehalogenation reactions and produce lower halogenated products. We conClude that the enhanced reactivity of MCRred1 is due to the replacement of a relatively exchange-inert thiol ligand in MCRox1 with a weakly coordinating upper axial ligand in red1 that can be easily replaced by incoming ligands.Rapid ligand exchange in the MCRred1 form of methyl-coenzyme m reductasex10200339#N/AFALSE
2695
ja028355110.1021/ja0283551FALSEhttps://doi.org/10.1021/ja0283551Bazan, GCJ. Am. Chem. Soc.Tandem catalysis in a single medium presents challenges and opportunities for creating novel synthetic protocols. Thus far, only two homogeneous catalysts have been used in tandem. Herein, we report that it is possible to coordinate the action of three well-defined homogeneous catalysts to produce a wide range of branched polyethylenes from a single monomer. Thus, {[(eta(5)-C5Me4)SiMe2(eta(1)-NCMe3)]-TiMe}{MeB(C6F5)(3)} (1). [(C6H5)(2)PC6H4C(OB(C6H5)(3))O-kappa(2)P,O]Ni(eta(3)-CH2C6H5) (2), and {(H3C)C[N(C6H5)C-[O-B(C6F5)(3)][N(C6H5)]-kappa(2)N,N}Ni(eta(3)-CH2C6H5) (3) react with ethylene to produce branched polyethylene with structures that cannot be obtained using a single- or a two-component Catalyst combination. The properties of the polyethylene depend on the ratio of the three catalysts. High-throughput screening techniques proved essential for optimizing reaction conditions and for probing how the catalyst composition influences the polymer properties.Triple tandem catalyst mixtures for the synthesis of polyethylenes with varying structuresx128200241#N/AFALSE
2696
ja028341v10.1021/ja028341vFALSEhttps://doi.org/10.1021/ja028341vCheetham, AKJ. Am. Chem. Soc.Hydrogen sorption in the nanoporous nickel phosphates VSB-1 and VSB-5 has been studied with a combination of BET, temperature programmed desorption (TPD), and inelastic neutron scattering (INS) measurements. H-2 BET isotherms for VSB-1 are similar to those seen in nanoporous zeolites, while VSB-5 adsorbs substantially more hydrogen due to a steep initial uptake at low partial pressures. TPD data show that hydrogen interacts strongly with VSB-5, with desorption peaks at 109 and 149 K in a nitrogen flow, whereas the absence of similar peaks for VSB-1 suggests a weaker interaction. INS spectra of the rotational tunnel transition of the adsorbed H-2 also reveal a strong interaction with the VSB-5 host. These data strongly suggest the existence of coordinatively unsaturated Ni2+ sites accessible to H-2 molecules in the pores of VSB-5.Hydrogen adsorption in nanoporous Nickel(II) phosphatesx231200322#N/AFALSE
2697
ja028337j10.1021/ja028337jFALSEhttps://doi.org/10.1021/ja028337jBeauchamp, JLJ. Am. Chem. Soc.Copper(l) and silver(l) Fischer carbenes are synthesized in the gas phase. Various diazomalonate-based compounds with an attached metal ion are introduced into the gas phase by electrospray ionization and subjected to collisional Activation. Loss of N-2 generates a metastable Fischer carbene, which subsequently undergoes Wolff rearrangement and loss of CO. Further excitation leads to the loss of another CO molecule and the generation of a stable Fischer carbene. Isotopically labeled compounds are utilized to confirm the assignment of the products resulting from this process. DFT calculations are used to evaluate various mechanistic possibilities and to quantitatively assess the energetics of reactants and products. Silver(l) is shown to be more effective in facilitating Wolff rearrangement than copper(l), although both are more effective when compared to spectator charges such as sodium or a fixed quaternary nitrogen. Carbenes are not produced when copper(II), nickel(II), or a proton is used to form a quasi-molecular ion from the diazomalonate carbene precursor. Finally, trapping of the Fischer carbene by various functional groups attached through the open coordination site of the metal is investigated.Gas-phase synthesis of charged copper and silver Fischer carbenes from diazomalonates: Mechanistic and conformational considerations in metal-mediated Wolff rearrangementsx53200344#N/AFALSE
2698
ja034050q10.1021/ja034050qFALSEhttps://doi.org/10.1021/ja034050qLau, CPDihydrogen-bond-promoted catalysis: Catalytic hydration of nitriles with the indenylruthenium hydride complex (eta(5)-C9H7)Ru(dppm)H (dppm = bis(diphenylphosphino)methane)2003#N/ATRUE
2699
ja028093310.1021/ja0280933FALSEhttps://doi.org/10.1021/ja0280933Shelnutt, JAJ. Am. Chem. Soc.The view that the large red shifts seen in the UV-visible absorption bands of peripherally crowded nonplanar porphyrins are the result of nonplanar deformations of the macrocyCle has recently been challenged by the suggestion that the red shifts arise from substituent-induced changes in the macrocyCle bond lengths and bond angles, termed in-plane nuClear reorganization (IPNR). We have analyzed the contributions to the UV-visible band shifts in a series of nickel or zinc meso-tetraAlkylporphyrins to establish the origins of the red shifts in these ruffled porphyrins. Structures were obtained using a molecular mechanics force field optimized for porphyrins, and the nonplanar deformations were quantified by using normal-coordinate structural decomposition (NSD). Transition energies were calculated by the INDO/S semiempirical method. These computational studies demonstrate conClusively that the large Soret band red shifts (similar to40 nm) seen for very nonplanar meso-tetra(tert-butyl)porphyrin compared to meso-tetra(methyl)porphyrin are primarily the result of nonplanar deformations and not IPNR. Strikingly, nonplanar deformations along the high-frequency 2B(1u) and 3B(1u) normal coordinates of the macrocyCle are shown to contribute significantly to the observed red shifts, even though these deformations are an order of magnitude smaller than the observed ruffling (1B(1u)) deformation. Other structural and electronic influences on the UV-visible band shifts are discussed and problems with the recent studies are examined (e.g., the systematic underestimation of the 2B(1u) and 3B(1u) modes in artificially constrained porphyrin structures that leads to a mistaken attribution of the red shift to IPNR). The effect of nonplanar deformations on the UV-visible absorption bands is then probed experimentally with a series of novel bridled nickel chiroporphyrins. In these compounds, the substituent effect is essentially invariant and the amount of nonplanar deformation decreases as the length of the straps connecting adjacent meso-cyClopropyl substituents decreases (the opposite of the effect observed for conventional strapped porphyrins). Several spectroscopic markers for nonplanarity (UV-visible bands, resonance Raman lines, and H-1 NMR resonances) are found to correlate with time-averaged deformations obtained from an NSD analysis of molecular dynamics snapshot structures. These results suggest that UV-visible band shifts of tetrapyrroles in proteins are potentially useful indicators of changes in nonplanarity provided other structural and electronic factors can be eliminated.Origin of the red shifts in the optical absorption bands of nonplanar tetraAlkylporphyrinsx231200366#N/AFALSE
2700
ja028080p10.1021/ja028080phttps://doi.org/10.1021/ja028080pNishihara, HSynthesis of azo-conjugated metal ladithiolenes and their photo- and proton-responsive isomerization reactionsPhotocatalyst2003#N/AFALSE
2701
ja027966q10.1021/ja027966qFALSEGatteschi, DTheoretical study of the magnetic behavior of hexanuClear Cu(II) and Ni(II) polysiloxanolato complexesx2003#N/AFALSE
2702
ja034039q10.1021/ja034039qFALSEhttps://doi.org/10.1021/ja034039qWei, QJ. Am. Chem. Soc.A highly regio- and stereoselective halohydroxylation of 1,2-allenyl sulfoxides with X+ and water was developed. The reaction shows E-stereoselectivity. In the iodohydroxylation reaction, 12 was used to introduce the iodine atom. For bromohalohydroxylation, CuBr2, NBS, or Br-2 can be used. When using 12, NBS, or Br2, the addition of LiOAc.2H(2)O is necessary for high yields of the halohydroxylation products. The chlorohydroxylation reaction was preformed by milling 1,2-allenyl sulfoxides and CuCl2.2H(2)O with silica gel. Under the catalysis of a Pd(0) complex, the halohydroxylation products, that is, E-2-halo-1-phenylsulfinyl-1-alken-3-ols, can undergo Sonogashira, Suzuki, and Negishi cross-coupling reactions leading to Z-2-substituted-1-phenyisulfonyl-1-alken-3-ols. The C-S bond of the coupling product may undergo a further coupling reaction with organozincs under the catalysis of an Ni catalyst. Here, the presence of a hydroxyl group is important for a smooth coupling involving the C-S bond. Thus, optically active stereodefined multisubstituted allylic alcohols can be prepared by the reaction of the easily available optically active propargylic alcohols with sulfinyl chloride followed by E-halohydroxylation and a selective Pd- or Ni-coupling reaction.Highly regio- and stereoselective halohydroxylation reaction of 1,2-allenyl phenyl sulfoxides. Reaction scope, mechanism, and the corresponding Pd- or Ni-catalyzed selective coupling reactions92200375#N/ATRUE
2703
ja027719m10.1021/ja027719mFALSEhttps://doi.org/10.1021/ja027719mSadler, PJJ. Am. Chem. Soc.We have investigated the recognition of nuCleic acid derivatives by organometallic ruthenium(II) arene anticancer complexes of the type [(eta(6)-arene)Ru(II)(en)X] where en = ethylenediamine, arene = biphenyl (Bip), tetrahydroanthracene (THA), dihydroanthracene (DHA), p-cymene (Cym) or benzene (Ben), X = Cl- or H2O using H-1, P-31 and N-15 (N-15-en) NMR spectroscopy. For mononuCleosides, {(eta(6)-Bip)Ru(en)}(2+) binds only to N7 of guanosine, to N7 and N1 of inosine, and to N3 of thymidine. Binding to N3 of cytidine was weak, and almost no binding to adenosine was observed. The reactivity of the various binding sites of nuCleobases toward Ru at neutral pH decreased in the order G(N7) > I(N7) > I(NI), T(N3) > C(N3) > A(N7), A(N1). Therefore, pseudo-octahedral diamino Ru(II) arene complexes are much more highly discriminatory between G and A bases than square-planar Pt(II) complexes. Such site-selectivity appears to be controlled by the en NH2 groups, which H-bond with exocyClic oxygens but are nonbonding and repulsive toward exocyClic amino groups of the nuCleobases. For reactions with mononuCleotides, the same pattern of site selectivity was observed, but, in addition, significant amounts of the 5'-phosphate-bound species (40-60%) were present at equilibrium for 5'-TMP, 5'-CMP and 5'-AMP. In contrast, no binding to the phosphodiester groups of 3', 5'-cyClic-GMP (cGMP) or CAMP was detected. Reactions with nuCleotides proceeded via aquation of [(eta(6)-arene)Ru(en)Cl](+), followed by rapid binding to the 5'-phosphate, and then rearrangement to give N7, N1, or N3-bound products. Small amounts of the dinuClear species, e.g., Ru-O(PO3)GMPN7-Ru, Ru-O(PO3)IMPN1-Ru, Ru-O(PO3)TMP N3-Ru, Ru-N7IMP N1-Ru, and Ru-N7InoN1-Ru were also detected. In competitive binding experiments for [(eta(6) -Bip)Ru(en)Cl](+) with 5'-GMP versus 5'-AMP or 5'-CMP or 5'-TMP, the only final adduct was [(eta(6)-Bip)Ru(en)(N7-GMP)]. Ru-H2O species were more reactive than Ru-OH species. The presence of Cl- or phosphate in neutral solution significantly decreased the rates of Ru-N7 binding through competitive coordination to Ru. In kinetic studies (pH 7.0, 298 K, 100 mM NaClO4), the rates of reaction of cGMP with {(eta(6)-arene)Ru(II)(en)X}(n+) (X = Cl- or H2O) decreased in the order: THA > Bip > DHA >> Cym > Ben, suggesting that N7-binding is promoted by favorable arene-purine hydrophobic interactions in the associative transition state. These findings have revealed that the diamine NH2 groups, the hydrophobic arene, and the chloride leaving group have important roles in the novel mechanism of recognition of nuCleic acids by Ru arene complexes, and will aid the design of more effective anticancer complexes, as well as new site-specific DNA reagents.Highly selective binding of organometallic ruthenium ethylenediamine complexes to nuCleic acids: Novel recognition mechanismsx337200377#N/AFALSE
2704
ja031656610.1021/ja0316566FALSEhttps://doi.org/10.1021/ja0316566Krische, MJHydrogen-mediated C-C bond formation: Catalytic regio- and stereoselective reductive condensation of alpha-keto aldehydes and 1,3-enynes2004#N/ATRUE
2705
ja030627s10.1021/ja030627sFALSEhttps://doi.org/10.1021/ja030627sHolm, RHJ. Am. Chem. Soc.A method has been devised that creates a planar Ni-II site from a tetrahedral site in a NiFe3S4 cubane-type Cluster. Reaction of [(Ph3P)NiFe3S4(LS3)](2-) (2) with 1,2-bis(dimethylphosphino)ethane affords [(dmpe)NiFe3S4(LS3)](2-) (3), isolated in ca. 45% yield as (Et4N)(2)[3a]-2.5MeCN and (Et4N)(2)[3b](.)0.25MeCN, both of which occur in triClinic space group P (1) over bar. Each crystalline form contains two crystallographically inequivalent Clusters with the same overall structure but slightly different dimensions. The Cluster is bound by three thiolate terminal ligands to semirigid cavitand ligand LS3. The NiFe3S4 core contains three tetrahedral sites, one Fe(mu(3)-S)(3)(SR) and two Fe(mu(3)-S)(2)(mu(2)-S)(SR) with normal metric features, and one distorted square planar Ni(mu(3)-S)(2)P-2 site in a Ni(mu(3)-S)(2)Fe face with mean bond lengths Ni-P = 2.147(9) Angstrom and Ni-S = 2.29(2) Angstrom. The opposite Fe-2(mu(3)-S)(mu(2)-S) face places the mu(2)-S atom at nonbonding and variable distances (2.60-2.90 Angstrom) above the nickel atom. Binding of the strong-field ligand dmpe results in a planar Ni-II site and deconstruction of the full cubane geometry. The structure approximates that established crystallographically in the C-Cluster of C. hydrogenoformans carbon monoxide dehydrogenase whose NiFe4S4 core contains a planar NiS4 site and three tetrahedral FeS4 sites in a fragment that is bridged by sulfide atoms to an exo iron atom. Mossbauer studies of polycrystalline samples containing both Clusters 3a and 3b reveal the presence of at least two Cluster types. The spectroscopically best defined Cluster accounts for ca. 54% of total iron and exhibits hyperfine interactions quite similar to those reported for the S = (5)/(2) state of the protein-bound cubane-type Cluster [ZnFe3S4](1+), whose Mossbauer spectrum revealed the presence of a high-spin Fe2+ site and a delocalized Fe2.5+Fe2.5+ pair. Development of reactions leading to a planar nickel and a sulfide-bridged iron atom is requisite to attainment of a synthetic analogue of this complex protein-bound Cluster. This work demonstrates a tetrahedral (2) --> planar (3) Ni-II stereochemical conversion can be effected by binding of ligands that generate a sufficiently strong in-plane ligand field (dmpe = 1,2-bis(dimethylphosphino)ethane, LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-)).Initial structure modification of tetrahedral to planar Nickel(II) in a nickel-iron-sulfur Cluster related to the c-Cluster of carbon monoxide dehydrogenase29200463#N/ATRUE
2706
ja027049k10.1021/ja027049kFALSEhttps://doi.org/10.1021/ja027049kBrunold, TJ. Am. Chem. Soc.Spectroscopic and density functional theory (DFT) electronic structure computational studies on a binuClear bis-mu-oxo bridged (Ni3+)(2) complex, [(PhTt(tBu))(2)Ni-2(mu-O)(2)] (1), where (PhTt(tBu)) represents phenyltris((tert-butylthio)methyl) borate, are presented and discussed. These studies afford a detailed description of the Ni2O2 core electronic structure in bis-mu-oxo (Ni3+)(2) dimers and provide insight into the possible role of the (PhTtBu) thioether ligand in the formation of 1 from a Ni1+ precursor by O-2 Activation. From a normal coordinate analysis of resonance Raman data, a value of k(NI-O) = 2.64 mdyn/Angstrom is obtained for the Ni-O stretch force constant for 1. This value is smaller than k(cu-O) = 2.82-2.90 mdyn/Angstrom obtained for bis-mu-oxo (Cu3+)(2) dimers possessing nitrogen donor ligands, indicating a reduced metal-oxo bond strength in 1. Electronic absorption and magnetic circular dichroism spectroscopic techniques permit identification of several O-->Ni and S-->Ni charge transfer (CT) transitions that are assigned on the basis of DFT calculations. The dominant O-Ni CT transition of 1 occurs at 17 700 cm(-1), red-shifted by similar to7000 cm-1 relative to the corresponding transition in bis-mu-oxo (Ni3+)(2) dimers with nitrogen donor ligands. This red-shift along with the relatively low value of k(Ni-O) are due primarily to the presence of the thioether ligands in 1 that greatly affect the compositions of the Ni2O2 core MOs. This unique property of the thioether ligand likely contributes to the reactivity of the Ni center in the precursor [(PhTtBu)Ni1+CO] toward O-2. DFT computations reveal that conversion of a hypothetical side-on peroxo (Ni2+)(2) dimer, [(PhTtBu)(2)Ni-2(mu-eta(2):eta(2)-O-2)], to the bis-mu-oxo (Ni3+)(2) dimer 1 is energetically favorable by 32 kcal/mol and occurs without a significant Activation energy barrier (DeltaH(double dagger) = 2 kcal/mol).Spectroscopic and computational studies on [(PhTt(tBu))(2)Ni-2(mu-O)(2)]: Nature of the bis-mu-oxo (Ni3+)(2) diamond corex46200285#N/AFALSE
2707
ja030196d10.1021/ja030196dFALSEhttps://doi.org/10.1021/ja0600476Chan, MKRuffling-induced chirality: Synthesis, metalation, and optical resolution of highly nonplanar, cyClic, benzimidazole-based ligands2004#N/ATRUE
2708
ja026753y10.1021/ja026753yFALSEhttps://doi.org/10.1021/ja026753yCaudle, MTJ. Am. Chem. Soc.The N-carboxyimidazolidone anion, 2(-), was prepared as an analogue for N-1-carboxybiotin, and the kinetics of its CO2-dependent chemistry were studied in polar aprotic media The objective was to assess the viability of unimolecular CO2 elimination from N-1-carboxybiotin as a microscopic step in biotin-dependent Carbonyl transfer enzymes. The anionic 2(-) was prepared as its lithium salt by first deprotonating 2-imidazolidone with phenyllithium, followed by direct reaction with carbon dioxide This procedure also permitted isolation of the C-13 enriched derivative 2(-){C-13} by reaction with (CO2)-C-13 Proton and C-13 NMR and isotope-dependent FTIR measurements confirmed that Carbonylation had occurred at the nitrogen atom of 2-imidazolidone to give 2(-). Time-dependent FTIR spectroscopy showed that Li2 undergoes Carbonyl exchange with free carbon dioxide, with kinetics indicative of rate-limiting unmolecular dissociation of the N-CO2 bond Under these conditions, the weak Lewis acid Mg2+ catalyses the exchange of 2(-) with free CO2, which appears to be related to the ability of the metal ion to coordinate to 2(-). Reaction of Li2 with Carbonylic acids in DMSO results in acid-dependent deCarbonylation of 2(-) with a rate that is dependent on the concentration of the acid and its pK(a). A common mechanistic framework is presented for both Lewis acid catalyzed Carbonyl exchange and acid-dependent deCarbonylation that involves initial interaction at the Carbonyl oxygen and which has the effect of polarizing the nitrogen lone pair toward the imidazolidone ring rather than the Carbonyl group. Lewis acid interaction with the Carbonyl oxygen thus weakens the N-CO2- bond and functions as a trigger for dissociation of CO2-. In the context of biotin-dependent enzymes, this suggests a means by which the kinetically stable N-1-carboxybiotin cofactor intermediate might be triggered for dissociation of CO2-.Kinetics and mechanism for CO2 scrambling in a N-carboxyimidazolidone analogue for N-1-carboxybiotinx8200248#N/AFALSE
2709
ja030145g10.1021/ja030145gFALSEhttps://doi.org/10.1021/ja030145gMerz, KMJ. Am. Chem. Soc.Herein, we present results from a computational study of dinickel complexes that are relevant to the catalytic hydrolysis of urea exerted by the urease enzymes. The B3LYP density functional is used to characterize the equilibrium geometry, electronic and magnetic properties, and energies for a series of realistic complexes modeling the active site of ureases. The analysis of the theoretical results gives new insight into the structure, substrate binding, and catalytic mechanism. The water bridge between the two Ni(II) ions observed in the crystallographic structures of the ureases was assigned to a hydroxide bridge in agreement with the observed small antiferromagnetic coupling. Both monodentate and bidentate urea-bound complexes, in which urea had favorable orientations for catalysis, were characterized. Finally, two reaction mechanisms were investigated starting from the monodetante and bidentate urea-bound complexes, respectively, Both a Ni1...Ni2 bridging hydroxide and a Ni2-bound water molecule play crucial roles in the two mechanisms.Ureases: Quantum chemical calculations on Cluster models49200336#N/ATRUE
2710
ja030124m10.1021/ja030124mFALSEhttps://doi.org/10.1021/ja030124mNeese, FJ. Am. Chem. Soc.This paper reports a detailed theoretical study of the interaction between a central low-spin d(8) nickel ion and two N,N-coordinating diiminobenzosemiquinonate(1-) ligands in a square planar arrangement. Such complexes have recently attracted much attention due to their unusual bonding patterns, structures, optical, and magnetic properties. Geometry optimizations using various levels of density functional theory (DFT) result in excellent agreement with the experimentally determined structure and in particular reproduce the quinoidal distortions in the aromatic rings well. A detailed analysis of the orbital structure reveals that the complex features essentially two strongly interacting ligand radicals which interact with each other via an efficient superexchange mechanism that is mediated by a back-bonding interaction to the central metal. An analysis of the broken symmetry DFT wave function is presented and a new index for the diradical character is proposed which shows that [Ni(L-ISQ)(2)] has a diradical character of similar to77%. These results are in full agreement with elaborate multireference post-Hartree-Fock ab initio calculations for [Ni(L-ISQ)(2)] using the difference dedicated configuration interaction (DDCI) method as well as second-order multireference Moller-Plesset (MR-MP2) theory, which give diradical characters of 65-80%. On the basis of these calculations our best estimate for the singlet-triplet gap in this system is 3096 cm(-1). This very large value results from an efficient mixing of the ionic configurations into the mainly singlet diradical ground state which is feasible because the semiquinonate SOMOs are delocalized and, therefore, have moderate on-site Coulomb repulsion parameters. As pointed out in the discussion, this represents an interesting difference to the case of magnetically interacting transition metal ions which typically show much smaller magnetic exchange couplings.Analysis and interpretation of metal-radical coupling in a series of square planar nickel complexes: Correlated ab initio and density functional investigation of [Ni(L-ISQ)(2)] (L-ISQ=3,5-di-tert-butyl-o-diiminobenzosemiquinonate(1-))2632003110#N/ATRUE
2711
ja030100f10.1021/ja030100fFALSEhttps://doi.org/10.1021/ja030100fPrat-Resina, XJ. Am. Chem. Soc.A theoretical investigation at the DFT(B3LYP) level on the Carbonylation reaction of allyl bromide catalyzed by nickel tetra-Carbonyl Ni(CO)(4) is discussed. The computational results show the following: (i) Three main steps characterize the catalytic cyCle: (a) an oxidative addition step, (b) a Carbonylation step, and (c) a reductive elimination step where the acyl product is obtained and the catalyst is regenerated. (ii) Both Ni(CO)(3) and Ni(CO)(4) complexes can behave as active catalytic species. (iii) The oxidative addition leads to the formation of either eta(3) or eta(1)-allyl nickel complexes, which are involved in a fast equilibrium. (iv) The Carbonylation occurs much more easily on the eta(1) than on the eta(3) intermediates.DFT computational study of the mechanism of allyl halides Carbonylation catalyzed by nickel tetraCarbonyl16200342#N/ATRUE
2712
ja030038m10.1021/ja030038mFALSETorres, TDonor-acceptor phthalocyanine nanoaggregates2003#N/ATRUE
2713
ja029823+10.1021/ja029823+https://doi.org/10.1021/ja029823+Jordan, RFJ. Am. Chem. Soc.The reactions of Vinyl chloride (VC) with representative late metal, single-site olefin dimerization and polymerization catalysts have been investigated. VC coordinates more weakly than ethylene or propylene to the simple catalyst (Me(2)bipy)PdMe+ (Me(2)bipy = 4,4'-Me-2-2,2'-bipyridine). Insertion rates of (Me(2)bipy)Pd(Me)(olefin)(+) species vary in the order VC > ethylene > propylene. The VC complexes (Me-2-bipy)Pd(Me)(VC)(+) and (alpha-diimine)Pd(Me)(VC)(+) (alpha-diimine = (2,6-'Pr-2-C6H3)N=CMeCMe=N(2,6-'Pr-2-C6H3)) undergo net 1,2 VC insertion and beta-Cl elimination to yield Pd-Cl species and propylene. Analogous chemistry occurs for (pyridine-bisimine)MCl2/MAO catalysts (M = Fe, Co; pyridine-bisimine = 2,6-{(2,6-'Pr-2-C6H3)N=CMe}(2)-pyridine) and for neutral (sal)Ni(Ph)PPh3 and (P-O)Ni(Ph)PPh3 catalysts (sal = 2-{C-(H)=N(2,6-'Pr-2-C6H3)}-6-Ph-phenoxide; P-O = {Ph2PC(SO3Na)=C(p-tol)O}), although the initial metal Alkyl VC adducts were not detected in these cases. These results show that the LnMCH2CHClR species formed by VC insertion into the active species of late metal olefin polymerization catalysts undergo rapid beta-Cl elimination which preCludes VC polymerization. Termination of chain growth by beta-Cl elimination is the most significant obstaCle to metal-catalyzed insertion polymerization of VC.Reaction of Vinyl chloride with late transition metal olefin polymerization catalysts102200393#N/ATRUE
2714
ja029560j10.1021/ja029560jhttps://doi.org/10.1021/ja029560jFujita, TJ. Am. Chem. Soc.The propylene polymerization behavior of a series of Ti complexes featuring fluorine-containing phenoxy-imine chelate ligands is reported. The Ti complexes combined with methylalumoxane (MAO) can be catalysts for living and, at the same time, stereospecific polymerization of propylene at room temperature or above. DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a beta-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization. Although the Ti complexes possess C-2 symmetry, they are capable of producing highly syndiotactic polypropylenes. C-13 NMR is used to demonstrate that the syndiotacticity is governed by a chain-end control mechanism and that the polymerization is initiated exClusively via 1,2-insertion followed by 2,1-insertion as the principal mode of polymerization. C-13 NMR spectroscopy also elucidated that the polypropylenes produced with the Ti complexes possess regio-block structures. Substitutions on the phenoxy-imine ligands have profound effects on catalytic behavior of the Ti complexes. The steric bulk of the substituent ortho to the phenoxy oxygen plays a decisive role in achieving high syndioselectivity for the chain-end controlled polymerization. Over a temperature range of 0-50 degreesC, Ti complex having a trimethylsilyl group ortho to the phenoxy oxygen forms highly syndiotactic, nearly monodisperse polypropylenes (94-90% rr) with extremely high peak melting temperatures (T-m = 156149 degreesC). The polymerization behavior of the Ti complexes can be explained well by the recently proposed site-inversion mechanism for the formation of syndiotactic polypropylene by a Ti complex having a pair of fluorine-containing phenoxy-imine ligands.Syndiospecific living propylene polymerization catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands2662003124#N/ATRUE
2715
ja026211g10.1021/ja026211gFALSEhttps://doi.org/10.1021/ja026211gInabe, TJ. Am. Chem. Soc.Hydrogen-bonded supramolecular cation assemblies of (NH4+/NH2-NH3+)(crown ether), where the crown ether is [12]crown-4, [15]crown-5, or [18]crown-6, were incorporated into electrically conducting [Ni(dmit)(2)] salts (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate). (NH4+)([12]crown-4)[Ni(dmit)(2)](3)(CH3CN)(2) had a pyramidal shape, while ionic channels were observed in (NH4+)0.88([15]crown-5)[Ni(dmit)(2)](2) and (NH4+)(0.70)- ([18]crown-6)[Ni(dmit)(2)](2). Both (NH4+)(0.88)([15]crown-5) and (NH4+)(0.70)([18]crown-6) contained regularly spaced [Ni(dMit)(2)] stacks formed by N-(HO)-O-... hydrogen bonding between the oxygen atoms in crown ethers and the NH4+ ion. NH4+ occurred nonstoichiometrically; there were vacant ionic sites in the ionic channels. The ionic radius of NH4+ is larger than the cavity radius of [15]crown-5 and [18]crown-6. Therefore, NH4+ ions could not pass through the cavity and were distributed randomly in the ionic channels. The static disorder caused the conduction electrons to be randomly localized to the [Ni(dMit)(2)] stacks. Hydrazinium (NH2NH3+) formed the supramolecular cations in (NH2-NH3+)([12]crown-4)(2)[Ni(dmit)(2)](4) and (NH2-NH3+)(2)([15]crown-5)(3)[Ni(dmit)(2)](6), possessing a sandwich and Club-sandwich structure, respectively. To the best of our knowledge, these represent the first hydrazinium-crown ether assemblies to be identified in the solid. In the supramolecular cations, hydrogen bonding was detected between the ammonium or the amino protons of NH2-NH3+ and the oxygen atoms of crown ethers. The sandwich-type cations coexisted with the [Ni(dmit)(2)] dimer stacks. Although the assemblies were typically semiconducting, ferromagnetic interaction (Weiss temperature = +1 K) was detected in the case of (NH2-NH3+)(2)([15]crown-5)(3)[Ni(dmit)(2)](6). The (NH2- NH3+)(0.8)([18]crown-6)[Ni(dmit)(2)](2) and (NH4+)(0.76)([18]crown-6)[Ni(dmit)(2)](2) crystals were isomorphous. The large and flexible [18]crown-6 allowed for maintaining the same ionic channel structure through replacement of the NH4+ cation by NH2-NH3+.Supramolecular cation assemblies of hydrogen-bonded (NH4+/NH2NH3+)(crown ether) in [Ni(dmit)(2)]-based molecular conductors and magnetsx71200234#N/AFALSE
2716
ja026072310.1021/ja0260723FALSEhttps://doi.org/10.1021/ja0260723Sadler, PJJ. Am. Chem. Soc.As platforms for the design of metal-based therapeutic and diagnostic agents, macrocyCles are rigid enough to provide strong metal binding sites and orient functional groups stereoselectively, yet flexible enough to accommodate structural changes required for induced-fit recognition of biological targets. We consider the recognition of the Zn(II) complex of the bis-tetraazamacrocyCle xylyl-bicyClam, a potent anti-HIV agent, by the coreceptor CXCR4, a G-protein-coupled receptor used by HIV for membrane fusion and cell entry. NMR studies show that the macrocyCles of Zn(11)2-xylyl-bicyClam perchlorate exist in aqueous solution as two major configurations, trans-I (nitrogen chirality R,S,R,S), and trans-III (S,S,R,R). Acetate addition induced a major structural change. X-ray crystallography shows that the acetate complex contains the unusual cis-V cyClam configuration (R,R,R,R and folded) with bidentate coordination of acetate to Zn(II) plus second-coordination-sphere double H-bond formation between diagonal NH protons on the opposite cyClam face and acetate Carbonylate oxygens. Detailed 1D and 2D NMR studies show that the major configuration of Zn(11)2-xylyl-bicyClam acetate in aqueous solution is cis-V/trans-I. Molecular modeling shows that an analogous cis-V site can be formed when Zn(11)(2)-xylyl-bicyClam binds to CXCR4, involving the Carbonylate groups of Asp262 (Zn(II) coordination) and Glu288 (double H-bonding). The second cyClam can adopt the trans-I (or trans-III) configuration with Zn(II) binding to Asp-171. These interactions are consistent with the known structure-activity relationships for bicyClam anti-HIV activity and receptor mutation. Consideration of the anti-HIV activity of xylyl-bicyClam complexes of other metal ions suggests that affinity for Carbonylates, configurational flexibility, and kinetic factors may all play roles in receptor recognition. For example, Pd(II) cyClam complexes interact only weakly with axial ligands and are inflexible and inactive, whereas Co(Ill) cyClams bind Carbonylates strongly, are configurationally flexible, and yet have low activity. Our findings should aid the design of new generations of active macrocyCles inCluding highly specific chemokine receptor antagonists.Structure and dynamics of metallomacrocyCles: Recognition of zinc xylyl-bicyClam by an HIV coreceptorx125200264#N/AFALSE
2717
ja026028n10.1021/ja026028nFALSECramer, SPElectronic structure of Ni complexes by X-ray resonance Raman spectroscopy (resonant inelastic X-ray scattering)x2002#N/AFALSE
2718
ja028258810.1021/ja0282588FALSEhttps://doi.org/10.1021/ja0282588Hayashi, TJ. Am. Chem. Soc.Nickel-catalyzed asymmetric Grignard cross-coupling of dinaphthothiophene giving axially chiral 1,1 '-binaphthyls74200229#N/ATRUE
2719
ja027762+10.1021/ja027762+FALSEhttps://doi.org/10.1021/ja056963lMacMillan, DWCPd(0) mechanism of palladium-catalyzed cyClopropanation of alkenes by CH2N2: A DFT study2002#N/ATRUE
2720
ja025749j10.1021/ja025749jFALSEhttps://doi.org/10.1021/ja025749jYeo, BSJ. Am. Chem. Soc.Isolation and identification of surface-bound acetone enolate on Ni(111)x25200231#N/AFALSE
2721
ja027522u10.1021/ja027522uFALSELubitz, WSingle crystal EPR studies of the reduced active site of [NiFe] hydrogenase from Desulfiovibrio vulgaris Miyazaki F2003#N/ATRUE
2722
ja025653p10.1021/ja025653pFALSEhttps://doi.org/10.1021/ja061471+Komiyama, MMetal ion-induced site-selective RNA hydrolysis by use of acridine-bearing oligonuCleotide as cofactorx2002#N/AFALSE
2723
ja027148y10.1021/ja027148yFALSEhttps://doi.org/10.1021/ja027148yMontgomery, JJ. Am. Chem. Soc.Enantioselective total synthesis of (+)-testudinariol A using a new nickel-catalyzed allenyl aldehyde cyClization32200220#N/ATRUE
2724
ja026918310.1021/ja0269183FALSEhttps://doi.org/10.1021/ja0269183Hillhouse, GLJ. Am. Chem. Soc.Synthesis, structure, and reactions of a three-coordinate nickel-carbene complex, {1,2-bis(di-tert-butylphosphino)ethane}Ni=CPh2136200229#N/ATRUE
2725
ja021071w10.1021/ja021071whttps://doi.org/10.1021/ja021071wBrookhart, MJ. Am. Chem. Soc.The synthesis of a series of (alpha-diimine)NiR2 (R = Et, Pr-n) complexes via Grignard Alkylation of the corresponding (alpha-diimine)NiBr2 precursors is presented. Protonation of these species by the oxonium acid [H(OEt2)(2)](+)[BAr'(4)](-) at low temperatures yields cationic Ni(II) beta-agostic Alkyl complexes which model relevant intermediates present in nickel-catalyzed olefin polymerization reactions. The highly dynamic nature of these agostic Alkyl cations is quantitatively addressed using NMR line broadening techniques. Trapping of these complexes with ethylene provides cationic Ni Alkyl ethylene species, which are used to determine rates of ethylene insertion into primary and secondary carbon centers. The Ni agostic Alkyl cations are also trapped by CH3CN and Me2S to yield Ni(R)(L)(+) (L = CH3CN, Me2S) complexes, and the dynamic behavior of these species in the presence of varied [L] is discussed. The kinetic data obtained from these experiments are used to present an overall picture of the ethylene polymerization mechanism for (a-diimine)Ni catalysts, inCluding effects of reaction temperature and ethylene pressure on catalyst activity, polyethylene branching, and polymer architecture. Detailed comparisons of these systems to the previously presented analogous palladium catalysts are made.Mechanistic studies of nickel(II) Alkyl agostic cations and Alkyl ethylene complexes: Investigations of chain propagation and isomerization in (alpha-diimine)Ni(II)-catalyzed ethylene polymerizationx252200352#N/AFALSE
2726
ja020715x10.1021/ja020715xFALSEhttps://doi.org/10.1021/ja020715xKampf, JWJ. Am. Chem. Soc.We report molecular structures and temperature-dependent magnetic susceptibility data for several new metal complexes of heterospin triplet ground-state biradical ligands. The ligands are comprised of both nitronyl-nitroxide (NN) and serniquinone (SQ) spin carriers. Five compounds are five-coordinate M-11 complexes (M = Mn, Co, Ni, Cu, and Zn), and one is a six-coordinate Ni-11 complex. Five compounds were structurally characterized. During copper complex formation a reaction with methanol occurs to form a unique methoxy-substituted SQ ring. Variable-temperature magnetic susceptibility studies are consistent with strong intraligand (NN-SQ and NN-PhSQ) ferromagnetic exchange coupling. For the five-coordinate Mn, Co, and Ni complexes, the S = I ligand is antiferromagnetically coupled to the metal. For both the five-coordinate Cu complex and the six-coordinate Ni complex, the ligand is ferromagnetically coupled to the metal spins in accordance with orbital symmetry arguments. Despite the low molecular symmetries, the predicted trend in metal-ligand exchange interactions is supported by spin dimer analysis based on extended Huckel calculations. For (NN-SQ)NiTp(Cum,Me) (Tp(Cum,Me) = hydro-tris(3-cumenyl-5-methylpyrazolyl)borate), an antisymmetric exchange term was required for the best fit of the magnetic susceptibility data. Antisymmetric exchange was less important for the other complexes due to inherently smaller Deltag. Finally, it is shown that intraligand exchange coupling is of paramount importance in stabilizing high-spin states of mixed metal-biradical complexes.Trends in metal-biradical exchange interaction for first-row M-II(nitronyl nitroxide-semiquinone) complexesx70200378#N/AFALSE
2727
ja020611m10.1021/ja020611mhttps://doi.org/10.1021/ja020611mHolten, DJ. Am. Chem. Soc.The ground- and excited-state metal-ligand dynamics of nonplanar nickel(II) 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin (NiDPP) and two fluorinated analogues (NiF20D,PP and NiF28DPP) have been investigated using static and time-resolved absorption spectroscopy in toluene and in ligating media that differ in basicity, aromaticity, and steric encumbrance. Because of the electronic and steric consequences of nonplanarity, NiDPP does not bind axial ligands in the ground state, but metal coordination does occur after photoexcitation with multistep dynamics that depend on the properties of the ligand. Following the structural relaxations that occur in all nickel porphyrins within similar to10 ps, ligand binding to photoexcited NiDPP is progressively longer in pyridine, piperidine, and 3,5-lutidine (25-100 ps) but does not occur at all in 2,6-lutidine in which the ligating nitrogen is sterically encumbered. The transient intermediate that is formed, which nominally could be either a five- or six-coordinate species, also has a ligand-dependent lifetime (200-550 ps). Decay of this intermediate occurs partially via ligand release to re-form the uncoordinated species, in competition with binding of the second axial ligand and/or conformational/electronic relaxations (of a six-coordinate intermediate) to give the ground state of the bisligated photoproduct. The finding that the photoproduct channel principally depends on ligand characteristics along with the time-evolving spectra suggests that the transient intermediate may involve a five-coordinate species. In contrast to NiDPP, the fluorinated analogues NiF20DPP and NiF28DPP do coordinate axial ligands in the ground state but eject them after photoexcitation. Collectively, these results demonstrate the sensitivity with which the electronic and structural characteristics of the macrocyCle' substituents, and solvent (ligands) can govern the photophysical and photochemical properties of nonplanar porphyrins and open new avenues for exploring photoinduced ligand association and dissociation behavior.Photoinduced axial ligation and deligation dynamics of nonplanar nickel dodecaArylporphyrinsPhotocatalyst57200372#N/AFALSE
2728
ja026735g10.1021/ja026735gFALSECrabtree, RHAbnormal ligand binding and reversible ring hydrogenation in the reaction of imidazolium salts with IrH5(PPh3)(2)2002#N/ATRUE
2729
ja020431c10.1021/ja020431cFALSEhttps://doi.org/10.1021/ja020431cCase, MAJ. Am. Chem. Soc.A helical peptide designed to present an all-leucine core upon folding has been shown to exhibit concentration-dependent helicity and to exist as an ill-defined equilibrium population of oligomers. In marked contrast, an identical peptide covalently modified with a 2,2'-bipyridyl group at the N terminus forms a stable three-stranded parallel coiled coil in the presence of transition metal ions. We have employed paramagnetic Ni2+ and Co2+ ions to stabilize the trimeric assembly and to exploit their shift and relaxation properties in NMR structural studies. We find that metal-ion binding and helix-bundle folding are tightly coupled. Surprisingly, the three-helix bundle exhibits a dynamic N-terminal region, and a well-structured C-terminal half. The spectra indicate the presence of a dual conformation for the bundle extending from the N terminus to residue 12. The structure of the two isomeric forms has been ascertained from interpretation of NOES in the Ni(II) complex and H-1 pseudocontact shifts in the Co(II) complex. Two different facial isomers with distinct susceptibility tensors were identified. The bulky leucine side chain at position 3 in the peptide chain appears to play a role in the conformational variation at the N terminus.Structural characterization of a paramagnetic metal-ion-assembled three-stranded alpha-helical coiled coilx31200234#N/AFALSE
2730
ja026620c10.1021/ja026620cFALSEhttps://doi.org/10.1021/ja026620cMori, MJ. Am. Chem. Soc.Novel catalytic CO2 incorporation reaction: Nickel-catalyzed regio- and stereoselective ring-Closing Carbonylation of bis-1,3-dienes150200235#N/ATRUE
2731
ja020314h10.1021/ja020314hFALSEhttps://doi.org/10.1021/ja020314hBocian, DFJ. Am. Chem. Soc.Methyl-coenzyme M reductase (MCR) catalyzes methane formation from methyl-coenzyme M (methyl-SCoM) and N-7-mercaptoheptanoylthreonine phosphate (CoBSH). MCR contains a nickel hydro-corphin cofactor at its active site, called cofactor F-430. Here we present evidence that the macrocyClic ligand participates in the redox chemistry involved in catalysis. The active form of MCR, the red1 state, is generated by reducing another spectroscopically distinct form called ox1 with titanium(III) citrate. Previous electron paramagnetic resonance (EPR) and N-14 electron nuClear double resonance (ENDOR) studies indicate that both the ox1 and red1 states are best described as formally Ni(I) species on the basis of the character of the orbital containing the spin in the two EPR-active species. Herein, X-ray absorption spectroscopic (XAS) and resonance Raman (FIR) studies are reported for the inactive (EPR-silent) forms and the red1 and ox1 states of MCR. FIR spectra are also reported for isolated cofactor F430 in the reduced, resting, and oxidized states; selected FIR data are reported for the N-15 and Ni-64 isotopomers of the cofactor, both in the intact enzyme and in solution. Small Ni K-edge energy shifts indicate that minimal electron density changes occur at the Ni center during redox cyCling of the enzyme. Titrations with Ti(III) indicate a 3-electron reduction of free cofactor F430 to generate a stable Ni(I) state and a 2-electron reduction of Ni(I)-ox1 to Ni(I)-red1. Analyses of the XANES and EXAFS data reveal that both the ox1 and red1 forms are best described as hexacoordinate and that the main difference between ox1 and red1 is the absence of an axial thiolate ligand in the red1 state. The FIR data indicate that cofactor F430 undergoes a significant conformational change when it binds to MCR. Furthermore, the vibrational characteristics of the ox1 state and red1 states are significantly different, especially in hydrocorphin ring modes with appreciable C=N stretching character. It is proposed that these differences arise from a 2-electron reduction of the hydrocorphin ring upon conversion to the red1 form. Presumably, the ring-reduction and ligand-exchange reactions reported herein underlie the enhanced activity of MCRred1, the only form of MCR that can react productively with the methyl group of methyl-SCoM.X-ray absorption and resonance Raman studies of methyl-coenzyme M reductase indicating that ligand exchange and macrocyCle reduction accompany reductive Activationx39200249#N/AFALSE
2732
ja026584h10.1021/ja026584hFALSEhttps://doi.org/10.1021/ja026584hHartwig, JFJ. Am. Chem. Soc.Synthesis, characterization, and reactivity of Arylpalladium cyanoAlkyl complexes: Selection of catalysts for the alpha-Arylation of nitriles136200228#N/ATRUE
2733
ja026433e10.1021/ja026433eFALSEhttps://doi.org/10.1021/ja026433ePeters, JCJ. Am. Chem. Soc.We have prepared a series of divalent cobalt(II) complexes supported by the [PhBP3] ligand [PhBP3] = (PhB(CH2PPh2)(3)-) to probe certain structural and electronic phenomena that arise from this strong field, anionic tris(phosphine) donor ligand. The solid-state structure of the complex [PhBP3] Col (1), accompanied by SQUID, EPR, and optical data, indicates that it is a pseudotetrahedral cobalt(II) species with a doublet ground state-the first of its type. To our knowledge, all previous examples of 4-coordinate cobalt(II) complexes with doublet ground states have adopted square planar structure types. Complex 1 provided a useful precursor to the corresponding bromide and chloride complexes, {[PhBP3]Co(mu-Br)}2, (2), and {[PhBP3]Co(mu-Cl)}2, (3). These complexes were similarly characterized and shown to be dimeric in the solid-state. In solution, however, the monomeric low spin form of 2 and 3 dominates at 25 degrees C. There is spectroscopic evidence for a temperature-dependent monomer/dimer equilibrium in solution for complex 3. Furthermore, the dimers 2 and 3 did not display appreciable antiferromagnetic coupling that is typical of halide and oxo-bridged copper(II) and cobalt(II) dimers. Rather, the EPR and SQUID data for solid samples of 2 and 3 suggest that they have triplet ground states. Complexes 1, 2, and 3 are extremely oxygen sensitive. Thus, stoichiometric oxidation of 1 by dioxygen produced the 4-coordinate, high spin complex (PhB(CH2P(O)PhO2)(CH2PPh2)) Col (4), in which the [PhBP3] ligand had undergone a 4-electron oxidation. Reaction of 1 With TIOAr (Ar = 2,6-Me2Ph) afforded an example of a 4-coordinate, high spin complex, [PhBP3]Co(0-2,6-Me2Ph) (5), with an intact [PhBP3] ligand, The latter two complexes were spectroscopically and structurally characterized for comparison to complexes 1, 2, and 3. Our data for these complexes collectively suggest that the [PhBP3] ligand provides an unusually strong ligand-field to these divalent cobalt complexes that is chemically distinct from typical tris(phosphine) donor ligand sets, and distinct from tridentate borato ligands that have been previously studied. Coupling this strong ligand-field with a pronounced axial distortion away from tetrahedral symmetry, a geometric consequence that is enforced by the [PhBP3] ligand, provides access to monomeric [PhBP3]CoX complexes with doublet rather than quartet ground states.Elucidation of a low spin cobalt(II) system in a distorted tetrahedral geometry108200272#N/ATRUE
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ja020188h10.1021/ja020188hFALSEhttps://doi.org/10.1021/ja020188hKahn, OJ. Am. Chem. Soc.The spin population distribution in the ferromagnetically coupled hetero-bimetallic chain compound [MnNi(NO2)(4)(en)(2)] (en = 1,2-ethanediamine) has been investigated by means of polarized neutron diffraction experiments, and the results compared with those from theoretical estimates obtained via calculations based on density functional theory on dinuClear molecular models of the chain. The spin distributions obtained from experiment and from theory are consistent and reflect a larger spin delocalization from the Ni atom due to the more covalent character of the Ni-N bonds compared to the Mn-O ones. Also a nearly isotropic spin distribution is observed for the more ionic d(5) Mn2+ ion and a Clearly anisotropic distribution for the d(8) Ni2+ ion. The use of dinuClear molecular models for the calculation of the exchange coupling constant between Ni and Mn provide upper and lower limits (+17.6 and -4.2 cm(-1)) for the experimentally determined value (+1.3 cm(-1)), depending on how the missing part of the chain is simulated, but yield essentially the same spin distribution. The Mn(II)-Ni(11) weak ferromagnetic coupling in the chain is interpreted in a spin delocalization mechanism as resulting from the weakness of the overlap between the magnetic orbitals centered on nickel and those centered on manganese which are only weakly delocalized on the ligands.Spin densities in a ferromagnetic bimetallic chain compound: Polarized neutron diffraction and DFT calculationsx36200258#N/AFALSE
2735
ja026409110.1021/ja0264091FALSEhttps://doi.org/10.1021/ja0264091Wenger, EJ. Am. Chem. Soc.A series of nickel(II) and palladium(II) Aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr{o-C6H4B(pin)}L-2] (M = Ni, L-2 = 2PPh(3) (2a), 2PCy(3) (2b), 2PEt(3) (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L-2 = 2PPh(3) (3a), 2PCy(3) (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with (KOBu)-Bu-t to form the corresponding benzyne complexes [M(eta(2)-C6H4)L-2] (M = Ni, L-2 = 2PPh(3) (4a), 2PCy(3) (4b), 2PEt(3) (4c), dcpe (4d); M = Pd, L-2 = 2PCy(3) (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with (KOBu)-Bu-t, but in this case disproportionation of the initially formed eta(2)-C6H4 complex (5d) leads to a 1:1 mixture of a novel dinuClear palladium(l) complex, [(dcpe)Pd(mu(2)-C6H4)Pd(dcpe)] (6), and a 2,2'-biphenyldiyl complex, [Pd(2,2'-C6H4C6H4)-(dcpe)] (7d). Complexes 2a. 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species.Preparation of benzyne complexes of group 10 metals by intramolecular suzuki coupling of ortho-metalated phenylboronic esters: Molecular structure of the first benzyne-palladium(0) complex982002107#N/ATRUE
2736
ja017899k10.1021/ja017899kFALSEhttps://doi.org/10.1021/ja054590iMure, MRole of copper ion in bacterial copper amine oxidase: Spectroscopic and crystallographic studies of metal-substituted enzymesx2003#N/AFALSE
2737
ja017888r10.1021/ja017888rFALSEhttps://doi.org/10.1021/ja017888rOsakada, KJ. Am. Chem. Soc.Structure of 4-sila-3-platinacyClobutene and its formation via Pt-promoted gamma-Si-H bond Activation of 3-sila-1-propenyiplatinum precursorx22200232#N/AFALSE
2738
ja026234v10.1021/ja026234vFALSEhttps://doi.org/10.1021/ja026234vGuillon, DJ. Am. Chem. Soc.Tetradental cis-enaminoketone Ni (II) complexes with different molecular shape have been synthesized. Intramolecular hydrogen bonds, which stiffen the mesogenic core and restrict rotation of some molecular parts, have been introduced in these compounds. In the case of molecules with two hydrogen bonds and alkoxy terminal chains filling the inner molecular space, the uncommon phase sequence Iso-D-h-Iso(re)-SmA (series III-3) was detected. For the first time, it was observed that the isotropic re-entrant (Iso(re)) phase (short-range order) is separating the columnar (D) (high-temperature) and the lamellar (SmA) (low-temperature) phases, both revealing long-range ordered structures.Re-entrant isotropic phase between lamellar and columnar mesophases41200218#N/ATRUE
2739
ja025958410.1021/ja0259584FALSEhttps://doi.org/10.1021/ja0259584Fiedler, PJ. Am. Chem. Soc.An original approach to helicene frameworks exploiting atom economic isomerization of appropriate energy-rich aromatic cis,cis-dienetriynes has been developed. The new paradigm provides nonphotochemical syntheses of helicenes based on the easy, convergent, and modular assembly of key cis,cis-dienetriynes and their nickel(0)-catalyzed [2+2+2] cyCloisomerization. The potential of the methodology is underlined by the syntheses of the parent [5]helicene (2), 7,8-dibutyl[5]helicene (23), [6]helicene (24), and [7]helicene (25). The approach can be adapted to prepare functionalized helicenes as exemplified by the eight-step synthesis of 7,8-dibutyl-2,3-dimethoxy[6]helicene (34). Density functional theory (DFT) calculations showed that bis[2-((1Z)-1-buten-3-ynyl)phenyl]acetylene (1) and isomeric [5]helicene (2) differ enormously in the Gibbs energy content (DeltaG = -136.6 kcal.mol(-1)) to favor highly the devised intramolecular simultaneous construction of three aromatic rings.Synthesis of [5]-, [6]-, and [7]helicene via Ni(0)- or Co(I)-catalyzed isomerization of aromatic cis,cis-dienetriynes1292002110#N/ATRUE
2740
ja025924w10.1021/ja025924wFALSEhttps://doi.org/10.1021/ja025924wLindahl, PAJ. Am. Chem. Soc.In this study, a genetics-based method is used to truncate acetyl-coenzyme A synthase from Clostridium thermoaceticum (ACS), an alpha(2)beta(2) tetrameric 310 kDa bifunctional enzyme. ACS catalyzes the reversible reduction of CO2 to CO and the synthesis of acetyl-CoA from CO (or CO2 in the presence of low-potential reductants), CoA, and a methyl group bound to a corrinoid-iron sulfur protein (CoFeSP). ACS contains seven metal-sulfur Clusters of four different types called A, B, C, and D. The B, C, and D Clusters are located in the 72 kDa beta subunit, while the A-Cluster, a Ni-X-Fe4S4 Cluster that serves as the active site for acetyl-CoA synthase activity, is located in the 82 kDa a subunit. The extent to which the essential properties of the Cluster, inCluding catalytic, redox, spectroscopic, and substrate-binding properties, were retained as ACS was progressively truncated was determined. Acetyl-CoA synthase catalytic activity remained when the entire P subunit was removed, as long as CO, rather than CO2 and a low-potential reductant, was used as a substrate. Truncating an similar to30 kDa region from the N-terminus of the a subunit yielded a 49 kDa protein that lacked catalytic activity but exhibited A-Cluster-like spectroscopic, redox, and CO-binding properties. Further truncation afforded a 23 kDa protein that lacked recognizable A-Cluster properties except for UV-vis spectra typical of [Fe4S4](2+) Clusters. Two chimeric proteins were constructed by fusing the gene encoding a ferredoxin from Chromatium vinosum to genes encoding the 49 and 82 kDa fragments of the cc subunit. The chimeric proteins exhibited EPR signals that were not the simple sum of the signals from the separate proteins, suggesting magnetic interactions between Clusters. This study highlights the potential for using genetics to simplify the study of complex multicentered metalloenzymes and to generate new complex metalloenzymes with interesting properties.Genetic construction of truncated and chimeric metalloproteins derived from the alpha subunit of acetyl-CoA synthase from Clostridium thermoaceticum23200254#N/ATRUE
2741
ja025673r10.1021/ja025673rFALSEhttps://doi.org/10.1021/ja025673rBredas, JLJ. Am. Chem. Soc.In organics-based (opto) electronic devices, the interface dipoles formed at the organic/metal interfaces play a key role in determining the barrier for charge (hole or electron) injection between the metal electrodes and the active organic layers. The origin of this dipole is rationalized here from the results of a joint experimental and theoretical study based on the interaction between acrylonitrile, a pi-conjugated molecule, and transition metal surfaces (Cu, Ni, and Fe). The adsorption of acrylonitrile on these surfaces is investigated experimentally by photoelectron spectroscopies, while quantum mechanical methods based on density functional theory are used to study the systems theoretically. It appears that the interface dipole formed at an organic/metal interface can be divided into two contributions: (i) the first corresponds to the chemical dipole induced by a partial charge transfer between the organic layers and the metal upon chemisorption of the organic molecules on the metal surface, and (ii) the second relates to the change in metal surface dipole because of the modification of the metal electron density tail that is induced by the presence of the adsorbed organic molecules. Our analysis shows that the charge injection barrier in devices can be tuned by modulating various parameters: the chemical potential of the bare metal (given by its work function), the metal surface dipole, and the ionization potential and electron affinity of the organic layer.Characterization of the interface dipole at organic/metal interfaces432200284#N/ATRUE
2742
ja025583m10.1021/ja025583mFALSEhttps://doi.org/10.1021/ja025583mLachicotte, RJJ. Am. Chem. Soc.Three-coordinate organometallic complexes are rare, especially with the prototypical methyl ligand. Using a hindered, rigid bidentate ligand (L), it is possible to create 12-electron methyliron(II) and 13-electron m ethyl cobalt(l 1) complexes. These complexes are thermally stable, and H-1 NMR spectra suggest that the low coordination number is maintained in solution. Attempts to create the 14-electron LNiCH3 led instead to the three-coordinate nickel(l) complex LNi(THF). Single crystals of LMCH3 are isomorphous with the new three-coordinate chloride complexes LNiCl and LCoCl. Along with the recently reported LFeCl (Smith, J.M.; Lachicotte, R.J.; Holland, P. L. Chem. Commun. 2001, 1542), these are the only examples of three-coordinate iron(II), cobalt(II), and nickel(II) complexes with terminal chloride ligands, enabling the systematic evaluation of the effect of coordination number and metal identity on M-Cl bond lengths. Electronic structure calculations predict the ground states of the trigonal complexes.Electronically unsaturated three-coordinate chloride and methyl complexes of iron, cobalt, and nickel198200286#N/ATRUE
2743
ja021123h10.1021/ja021123hFALSEhttps://doi.org/10.1021/ja021123hWieghardt, KJ. Am. Chem. Soc.The electronic structure of the known iron complexes [Fe(gma)](2) (S-t = 0) (1)(6) and [Fe(gma)(py)].py (S-t = 1) (2)(7) where H-2(gma) represents glyoxal-bis(2-mercaptoanil) has been shown by X-ray crystallography, Mossbauer spectroscopy, and density functional theory calculations to be best described as ferric (S-Fe = 3/2) complexes containing a coordinated open-shell pi radical trianion (gma(.))(3-) and not as previously reported(6,7) as ferrous species with a coordinated Closed-shell dianion (gma)(2-). Compound 1 (or 2) can be oxidized by I-2 yielding [Fe-III(gma)l] (S-t = 1/2) (3). With cyanide anions, complex 1 forms the adduct [(n-Bu)(4)N][Fe-III(gma(.))(CN)] (S-t = 1) (4), which can be one-electron oxidized with iodine yielding the neutral species [Fe-III(gma)(CN)] (S-t = 1/2) (5). With phosphines complex 1 also forms adducts(7) of which [Fe-III(gma(.))(P(n-propyl)(3))] (S-t = 1) (6) has been isolated and characterized by X-ray crystallography. [Fe-II-(gma(.))(P(n-propyl)(3))(2)] (S-t = 0) (7) represents the only genuine ferrous species of the series. Density functional theory (DFT) calculations at the BP86 and B3LYP levels were applied to calculate the structural as well as the EPR and Mossbauer spectroscopic parameters of the title compounds as well as of the known complexes [Zn(gma)](0/-) and [Ni(gma)](0/-). Overall, the calculations give excellent agreement with the available spectroscopic information, thus lending support to the following electronic structure descriptions: The gma ligand features an unusually low lying LUMO, which readily accepts an electron to give (gma(.))(3-). The one-electron reduction of [Zn(gma)] and [Ni(gma)] is strictly ligand centered and differences in the physical properties of [Zn(gma(.))](-) and [Ni(gma(.))](-) are readily accounted for in terms of a model that features enhanced back-bonding from the metal to the gma LUMO in the case of [Ni(gma(.))](-). In the case of [Fe(gma)(PH3)], [Fe(gma)(py)], and [Fe(gma)(CN)](-) an electron transfer from the iron to the gma LUMO takes place to give strong antiferromagnetic coupling between an intermediate spin Fe(III) (S-Fe = 3/2) and (gma(.))(3-) (S-gma = 1/2), yielding a total spin S-t = 1. Broken symmetry DFT calculations take properly account of this experimentally calibrated electronic structure description. By contrast, the complexes [Fe(gma)(PH3)(2)] and [Fe(PhBMA)] feature Closed-shell ligands with a low-spin Fe(II) (S-Fe = S = 0) and an intermediate spin central Fe(II) (S-Fe = S-1 = 1), respectively. The most interesting case is provided by the one-electron oxidized species [Fe(gma)(py)](+), [Fe(gma)l], and [Fe(gma)(CN)]. Here the combination of theory and experiment suggests the coupling of an intermediate spin Fe(III) (S-Fe = 3/2) to the dianionic ligand (gma)(2-) formally in its first excited triplet state (S-gma = 1) to give a resulting 5 = 1/2. All physical properties are in accord with this interpretation. It is suggested that this unique excited state coordination is energetically driven by the strong antiferromagnetic exchange interaction between the metal and tNoninnocence of the ligand glyoxal-bis(2-mercaptoanil). The electronic structures of [Fe(gma)](2), [Fe(gma)(py)]center dot py, [Fe(gma)(CN)](1-/0), [Fe(gma)l], and [Fe(gma)(PR3)n] (n = 1, 2). Experimental and theoretical evidence for excited state coordination90200375#N/ATRUE
2744
ja020493310.1021/ja0204933FALSEhttps://doi.org/10.1021/ja0204933Jones, WDJ. Am. Chem. Soc.The nickel(0) fragment [(dippe)Ni] has been found to react with a variety of aromatic nitriles. Initial pi-coordination to the C=C and CdropN bonds of 2-cyanoquinoline is found to lead ultimately to C-CN oxidative addition. 3-Cyanoquinoline reacts similarly, although no eta(2)-CN complex is observed. 2-, 3-, And 4-cyanopyridines react initially to give eta(2)-nitrile complexes that then lead to quantitative formation of C-CN oxidative addition products. Benzonitrile reacts similarly but undergoes reversible insertion into the Ph-CN bond to give an equilibrium mixture of Ni(II) and Ni(0) adducts. A series of para-substituted benzonitriles has been studied in terms of both the position of the equilibrium between (dippe)Ni(eta(2)-Arylnitrile) reversible arrow (dippe)-Ni(CN)(Aryl) and the rate of approach to equilibrium, and the Hammett plots indicate a buildup of negative charge at the ipso carbon both in the transition state and the Ni(II) product. Terephthalonitrile gives both eta(2)-nitrile and oxidative addition adducts, as well as dimetalated products. No C-C or C-N Cleavage of the aromatic ring is seen with quinoline or acridine; only eta(2)-arene complexes are formed. The structures of many of these compounds are supported by X-ray data.Cleavage of carbon-carbon bonds in aromatic nitriles using nickel(0)219200237#N/ATRUE
2745
ja016747m10.1021/ja016747mFALSEhttps://doi.org/10.1021/ja016747mBakac, AJ. Am. Chem. Soc.The rapid (kgreater than or equal to10(6) M-1 s(-1)) reaction between NO and L-2(H2O)RhOO2+ (L-2 = meso-Me-6-[14]-ane-N-4) generates two strongly oxidizing, scavengeable intermediates, believed to be NO2 and L-2(H2O)-RhO2+. A mechanism is proposed whereby a peroxynitrito complex L-2(H2O)RhOONO2+ is formed first. The homolysis of O-O bond produces NO2 and L-2(H2O)Rho(2+) which were trapped with ABTS(2-) and Ni([14]aneN(4))(2+). In the absence of scavengers, the decomposition of L-2(H2O)RhOONO2+ produces both free NO3- and a rhodium nitrato complex L-2(H2O)RhONO22+, which releases NO3- in an inverse acid-dependent process. The total yield of L-2(H2O)RhONO22+ is 70%. In a minor, parallel path, NO and L-2(H2O)RhOO2+ react to give nitrite and the hydroperoxo complex L-2(H2O)RhOOH2+.Reaction of nitrogen monoxide with a macrocyClic superoxorhodium(III) complex produces an observable nitratorhodium intermediatex26200243#N/AFALSE
2746
ja020423w10.1021/ja020423wFALSEhttps://doi.org/10.1021/ja020423wZiegler, TJ. Am. Chem. Soc.We present a comprehensive theoretical investigation of the influence of the ligand L on the regulation of the product selectivity for the [(NiL)-L-0]-catalyzed cyClodimerization of 1,3-butadiene. The investigation was based on density functional theory (DFT) and a combined DFT and molecular mechanics (QM/MM) approach for the real [bis(butadiene)(NiL)-L-0] catalysts with L = PMe3, I; PPh3, II; P(Pr-i)(3), III; and P(OPh)(3), IV. The role of electronic and steric effects has been elucidated for all crucial elementary steps of the entire catalytic cyCle. Allylic isomerization, allylic enantioface conversion. as well as oxidative coupling are shown to be influenced to a minor extent by electronic and steric effects. In contrast, the ligand's properties have a distinct influence on the preestablished equilibrium between the eta(3),eta(1)(C-1) and biS-eta(3) forms 2 and 4, respectively, of the [(octadienediyl)(NiL)-L-II] complex and on the rate-determining reductive elimination following competing routes for generation of either VCH, cis-1,2-DVCB, or cis,cis-COD. Electronic factors are shown to predominantly determine the position of the kinetically mobile 2 4 equilibrium. 4 is the prevailing species for ligands L that are pi-acceptors (L = P(OPh)(3)) or weak sigma-donors (L = PPh3) while stronger sigma-donors (L = PMe3, P(Pr-i)(3)) displace the equilibrium to the left. Steric bulk on the ligand as well as its pi-acceptor ability act to facilitate the reductive elimination, while sigma-donor abilities serve to retard this process. Electronic and steric factors are found to not influence uniformly the reductive elimination routes with either 2 or 4 involved. The regulation of the product selectivity is elucidated on the basis of both thermodynamic and kinetic considerations.[(NiL)-L-0]-catalyzed cyClodimerization of 1,3-butadiene: A density functional investigation of the influence of electronic and steric factors on the regulation of the selectivity28200267#N/ATRUE
2747
ja016209+10.1021/ja016209+FALSEhttps://doi.org/10.1021/ja016209+Riordan, CGDioxygen Activation by a nickel thioether complex: Characterization of a Ni-2(III)(mu-O)(2) corex2001#N/AFALSE
2748
ja020311510.1021/ja0203115FALSEhttps://doi.org/10.1021/ja0203115Coulon, CJ. Am. Chem. Soc.We herein present the synthesis, crystal structure, and magnetic properties of a new heterometallic chain of Mn-III and Ni-II ions, [Mn-2(saltmen)(2)Ni(pao)(2)(py)(2)](ClO4)(2) (1) (saltmen(2-) = N,N'-(1,1,2,2-tetramethylethylene) bis(salicylideneiminate) and pao(-) = pyridine-2-aldoximate). The crystal structure of 1 was investigated by X-ray crystallographic analysis: compound 1 crystallized in monoClinic, space group C2/c (No. 15) with a = 21.140(3) Angstrom, b = 15.975(1) Angstrom, c = 18.6212(4) Angstrom, beta = 98.0586(4)degrees, V = 6226.5(7) Angstrom(3), and Z = 4. This compound consists of two fragments, the out-of-plane dinner [Mn-2(saltmen)(2)](2+) as a coordination acceptor building block and the neutral mononuClear unit [Ni(pao)(2)(py)(2)] as a coordination donor building block, forming an alternating chain having the repeating unit [-Mn-(O)(2)-Mn-ON-Ni-NO-](n). In the crystal structure, each chain is well separated with a minimum intermetallic distance between Mn and Ni ions of 10.39 Angstrom and with the absence of interchain pi overlaps between organic ligands. These features ensure a good magnetic isolation of the chains. The dc and ac magnetic measurements were performed on both the polycrystalline sample and the aligned single crystals of 1. Above 30 K, the magnetic susceptibility of this one-dimensional compound was successfully described in a mean field approximation as an assembly of trimers ((MnNiMn)-Ni-...-Mn-...) with a (NiMnIII)-Mn-II... antiferromagnetic interaction (J = -21 K) connected through a ferromagnetic (MnMnIII)-Mn-III... interaction (J). However, the mean field theory fails to describe the magnetic behavior below 30 K emphasizing the one-dimensional magnetic character of the title compound. Between 5 and 15 K, the susceptibility in the chain direction was fitted to a one-dimensional Ising model leading to the same value of J. Hysteresis loops are observed below 3.5 K, indicating a magnet-type behavior. In the same range of temperature, combined ac and dc measurements show a slow relaxation of the magnetization. This result indicates the presence of a metastable state without magnetic long-range order. This material is the first experimental design of a heterometallic chain with S-T = 3 magnetic units showing a single-chain magnet behavior predicted in 1963 by R. J. Glauber for an Ising one-dimensional system. This work opens new perspectives for one-dimensional systems to obtain high temperature metastable magnets by combining high spin magnetic units, strong interunit interactions, and uniaxial anisotropy.Evidence for single-chain magnet behavior in a Mn-III-Ni-II chain designed with high spin magnetic units: A route to high temperature metastable magnets760200244#N/ATRUE
2749
ja020223k10.1021/ja020223kFALSEhttps://doi.org/10.1021/ja020223kKrische, MJJ. Am. Chem. Soc.In the presence of phenylsilane and 5 mol % cobalt(II) bis(2,2,6,6-tetramethylheptane-3,5-dionate), Aryl-substituted monoenone monoaldehydes and bis(enones) undergo reductive cyClization to afford synaldol and anti-Michael products, respectively. For both aldol and Michael cyCloreductions, five- and six-membered ring formation occurs in good yield with high levels of diastereoselectivity. CyCloreduction of monoenone monoaldehyde is in the presence of d(3)-phenylsilane reveals incorporation of a single deuterium at the enone beta-position as an equimolar mixture of epimers, inferring rapid isomerization of the kinetically formed cobalt enolate prior to cyClization. The deuterated product was characterized by single-crystal neutron diffraction analysis. For bis(enone) substrates, modulation of the silane source enables partitioning of the competitive Michael cyCloreduction and [2 + 2] cyCloaddition manifolds. A study of para-substituted acetophenone-derived bis(enones) reveals that substrate electronic features also direct partitioning of cyCloreduction and cyCloaddition manifolds. Further mechanistic insight is obtained through examination of the effects of enone geometry on product stereochemistry and electrochemical studies involving cathodic reduction of bis(enone) substrates. The collective experiments reveal competitive enone reduction pathways. Enone hydrometalation produces metallo-enolates en route to aldol and Michael cyCloreduction products, that is, products derived from coupling at the a-position of the enone. Electron-transfer-mediated enone reduction produces metallo-oxy-pi-allyls en route to [2 + 2] cyCloadducts and, under Ni catalysis, homoaldol cyCloreduction products, that is, products derived from coupling at the beta-position of the enone. The convergent outcome of the metal-catalyzed and electrochemically induced transformations suggests the proposed oxy-pi-allyl intermediates embody character consistent with the mesomeric metal-complexed anion radicals.Diastereoselective cyCloreductions and cyCloadditions catalyzed by co(dpm)(2)-silane (dpm=2,2,6,6-tetramethylheptane-3,5-dionate): mechanism and partitioning of hydrometallative versus anion radical pathways125200277#N/ATRUE
2750
ja015732l10.1021/ja015732lhttps://doi.org/10.1021/ja015732lHartwig, JFC-C bond-forming reductive elimination of ketones, esters, and amides from isolated Arylpalladium(II) enolatesx2001#N/AFALSE
2751
ja020037e10.1021/ja020037eFALSEhttps://doi.org/10.1021/ja020037eKermarec, MJ. Am. Chem. Soc.This work reports on the reactivity of coordination vacancies of Ni-II ions grafted onto the tridentate silica support (Ni-3c(II) ions) with respect to CO used as a probe molecule. The adsorption of CO at 77 K in the 0.3 to 3.5 Pa CO pressure range is studied by FTIR on two samples differing in the dispersion of nickel. Quantum chemical calculations by the DFT method are performed to investigate, using a Cluster approach, the binding of Ni to silica and, after CO adsorption, the geometry of the resulting Carbonyl Ni complexes. Silica is modeled by using Clusters composed of three types of monodentate ligands, SiO-, SiOSi and/or SiOH, found on the surface of silica. This work is devoted to the monoCarbonyl complexes, Whatever the sample, only one type of monoCarbonyl is formed from Ni-3c(II) ions. It is shown that the charge of the silica Cluster is the major parameter influencing the CO IR frequency whereas the nature and the size of the silica Cluster do not affect the CO bond length, confirming that local electrostatic interactions predominate. Only the 1 - charged silica Cluster Si5O3-, composed of SiO-, 2SiOSi fragments, respectively, reproduces the Ni-O distances derived from EXAFS for the Ni-3c(II) grafted site and gives CO frequencies in good agreement with the experimental values. It is shown that CO is stabilized by a magnetic transition from the Ni-3(2+) triplet to the Ni-1(2+) singlet state occurring upon adsorption.IR and theoretical studies of monoCarbonyl Ni complexes formed by adsorption of CO at low pressure on silica-supported Ni-II ions32200279#N/ATRUE
2752
ja017652n10.1021/ja017652nFALSEhttps://doi.org/10.1021/ja017652nHillhouse, GLJ. Am. Chem. Soc.Interactions of aziridines with nickel complexes: Oxidative-addition and reductive-elimination reactions that break and make C-N bonds159200230#N/ATRUE
2753
ja012595j10.1021/ja012595jFALSEhttps://doi.org/10.1021/ja012595jZeng, HCJ. Am. Chem. Soc.A synthesis of beta-Co(OH)(2) nanocrystalline materials has been investigated with the assistance of chelating agent ethylenedlamine. By controlling precipitation processes, various forms of beta-Co(OH)(2) crystallites can be prepared at different stages. The crystallite morphologies inClude two-dimensional hexagonal sheet platelets, one-dimensional nanorods, and butterfly-like nanocrystallite intermediates. In particular, a triangular construction unit for beta-Co(OH)(2) crystallites has been revealed with the ethylenediamine mediation in the synthesis. With the successful arrest of these butterfly-like intermediate crystallites, especially of linearly aligned butterflies, the formation mechanism of one-dimensional nanorods or nanoribbons has been experimentally explained. The chemical composition of solution precursors and resultant beta-Co(OH)(2) crystallites has been analyzed with UV-vis/FFIR/CHN /XRD/TGA/TEM/SAED methods. The relationships among various observed crystallite morphologies have also been discussed on the basis of the experimental findings.Arresting butterfly-like intermediate nanocrystals of ss-Co(OH)(2) via ethylenediamine-mediated synthesisx185200263#N/AFALSE
2754
ja017584510.1021/ja0175845FALSEhttps://doi.org/10.1021/ja0175845Montgomery, JJ. Am. Chem. Soc.A new two-step four-component synthesis of highly functionalized cyClohexenols by sequential nickel-catalyzed couplings44200218#N/ATRUE
2755
ja012259310.1021/ja0122593FALSEhttps://doi.org/10.1021/ja0122593Coates, GWJ. Am. Chem. Soc.A highly regioselective secondary enchainment of propylene in a group IV catalyst system is reported. End-group analysis of polypropylene formed using the phenoxyimine-based titanium catalysts revealed a reversal in the regioselectivity of insertion for this Class of catalysts. To the best of our knowledge, bis(phenoxyimine)-based titanium complexes are the only known group IV catalysts that insert propylene with exClusive 2,1-regiochemistry. Insertion of propylene into the initiating titanium hydride occurs with high 1,2-regiochemistry. Subsequent insertions into primary titanium Alkyls are regiorandom, while insertions into secondary titanium Alkyls proceed with high 2,1-regioselectivity. CyClopolymerization and ethylene/ propylene copolymerization strategies are employed to support this proposal.Mechanism of propylene insertion using bis(phenoxyimine)-based titanium catalysts: An unusual secondary insertion of propylene in a group IV catalyst systemx191200258#N/AFALSE
2756
ja017545t10.1021/ja017545tFALSEhttps://doi.org/10.1021/ja017545tBuchwald, SLJ. Am. Chem. Soc.Nickel-BINAP catalyzed enantioselective alpha-Arylation of alpha-substituted gamma-butyrolactones156200221#N/ATRUE
2757
ja012107810.1021/ja0121078FALSEhttps://doi.org/10.1021/ja0121078Scherz, AJ. Am. Chem. Soc.Modification of the metal's electronic environment by ligand association and dissociation in metalloenzymes is considered cardinal to their catalytic activity. We have recently presented a novel system that utilizes the bacteriochlorophyll (BChl) macrocyCle as a ligand and reporter. This system allows for charge mobilization in the equatorial plane and experimental estimate of changes in the electronic charge density around the metal with no modification of the metal's chemical environment. The unique spectroscopy, electrochemistry and coordination chemistry of [Ni]-bacteriochlorophyll ([Ni]-BChl) enable us to follow directly fine details and steps involved in the function of the metal redox center. This approach is utilized here whereby electro-chemical reduction of [Ni]-BChl to the monoanion [Ni]-BChl(-) results in reversible dissociation of biologically relevant axial ligands. Similar ligand dissociation was previously detected upon photoexcitation of [Ni]-BChl (Musewald, C.; Hartwich, G.; Lossau, H.; Gilch, P.; Pollinger-Dammer, F.; Scheer, H.; Michel-Beyerle, M. E. J. Phys. Chem. 9 1999, 103, 7055-7060 and Noy, D.; Yerushalmi, R.; Brumfeld, V.; Ashur, I.; Baldridge, K. K.; Scheer, H.; Scherz, A. J. Am. Chem. Soc. 2000, 122, 3937-3944). The electrochemical measurements and quantum mechanical (QM) calculations performed here for the neutral, singly reduced, monoligated, and singly reduced, monoligated [Ni]-BChl suggest the following: (a) Electroreduction, although resulting in pi anion [Ni]-BChl(-) radical, causes electron density migration to the [Ni]-BChl core. (b) Reduction of nonligated [Ni]-BChl does riot change the macrocyCle conformation, whereas axial ligation results in a dramatic expansion of the metal core and a flattening of the highly ruffled macrocyCle conformation. (c) In both the monoanion and singly excited [Ni]-BChl ([Ni]-BChl*), the frontier singly occupied molecular orbital (SOMO) has a small but nonnegligible metal character. Finally, (d) computationally, we found that a reduction of [Ni]-BChl-imidazole results in a weaker metal-axial ligand bond. Yet, it remains weakly bound in the gas phase. The experimentally observed ligand dissociation is accounted for computationally when solvation is considered. On the basis of the experimental observations and QM calculations, we propose a mechanism whereby alterations in the equatorial,T system and modulation of sigma bonding between the axial ligands and the metal core are mutually correlated. Such a mechanism highlights the dynamic role of axial ligands in regulating the activity of metal centers such as factor F430 (F430), a nickel-based coenzyme that is essential in methanogenic archea.Mutual control of axial and equatorial ligands: Model studies with [Ni]-bacteriochlorophyll-ax17200262#N/AFALSE
2758
ja017436e10.1021/ja017436eFALSEhttps://doi.org/10.1021/ja017436eIshii, YJ. Am. Chem. Soc.Syntheses and skeletal transformations of NCNH- and NCN-bridged tetrairidium(III) cages28200239#N/ATRUE
2759
ja012021e10.1021/ja012021eFALSEhttps://doi.org/10.1021/ja012021eRaval, RJ. Am. Chem. Soc.The chiral molecule (R,R)-tartaric acid adsorbed on nickel surfaces creates highly enantioselective heterogeneous catalysts, but the nature of chiral modification remains unknown. Here, we report on the behavior of this chiral molecule with a defined Ni(110) surface. A combination of reflection absorption infrared spectroscopy, scanning tunneling microscopy, and periodic density functional theory calculations reveals a new mode of chiral induction. At room temperatures and low coverages, (R,R)-tartaric acid is adsorbed in its bitartrate form with two-point bonding to the surface via both Carbonylate groups. The molecule is preferentially located above the 4-fold hollow site with each Carbonylate functionality adsorbed at the short bridge site via 0 atoms placed above adjacent Ni atoms. However, repulsive interactions between the chiral OH groups of the molecule and the metal atoms lead to severely strained adsorption on the bulk-truncation Ni(l 10) surface. As a result, the most stable adsorption structure is one in which this adsorption-induced stress is alleviated by significant relaxation of surface metal atoms so that a long distance of 7.47 A between pairs of Ni atoms can be accommodated at the surface. Interestingly, this leads the bonding Ni atoms to describe a chiral footprint at the surface for which all local mirror symmetry planes are destroyed. Calculations show only one chiral footprint to be favored by the (R,R)-tartaric acid, with the mirror adsorption site being unstable by 6 kJ mol(-1). This energy difference is sufficient to enable the same local chiral reconstruction and motif to be sustained over 90% of the system, leading to an overall highly chiral metal surface.From local adsorption stresses to chiral surfaces: (R,R)-tartaric acid on Ni(110)x173200257#N/AFALSE
2760
ja017390p10.1021/ja017390pFALSEhttps://doi.org/10.1021/ja017390pCheng, CHJ. Am. Chem. Soc.Synthesis of seven-membered lactones via nickel- and zinc-catalyzed highly regio- and stereoselective cyClization of 2-iodoBenzyl alcohols with propiolates32200241#N/ATRUE
2761
ja011861q10.1021/ja011861qFALSEhttps://doi.org/10.1021/ja011861qHodgson, KOJ. Am. Chem. Soc.In earlier work, de novo designed peptides with a helix-loop-helix motif and 63 residues have been synthesized as potential scaffolds for stabilization of the [Ni-II-X-Fe4S4] bridged assembly that is the spectroscopically deduced structure of the A-Cluster in Clostridial carbon monoxide dehydrogenase. The 63mers contain a consensus tricysteinyl ferredoxin domain in the loop for binding an Fe4S4 Cluster and Cys and His residues proximate to the loop for binding Ni(II), with one Cys residue designed as the bridge X. The metallopeptides HC4H2-[Fe4S4]-Ni and HC5H-[Fe4S4]-M, containing three His and one Cys residue for Ni(II) coordination and two His and two Cys residues for binding M = Ni(II) and Co(II), have been examined by Fe-, Ni-, and Co-K edge spectroscopy and EXAFS. All peptides bind an [Fe4S4](2+) cubane-type Cluster. Interpretation of the Ni and Co data is complicated by the presence of a minority population of six-coordinate species with low Z ligands, designated for simplicity as [M(OH2)6]2+. Best fits of the data were obtained with ca. 20% [M(OH2)(6)](2+) and ca. 80% M(II) with mixed N/S coordination. The collective XAS results for HC4H2-[Fe4S4]-Ni and HC5H-[Fe4S4]-M demonstrate the presence of an Fe4S4 Cluster and support the existence of the distorted square-planar coordination units [Ni-II(S.Cys)(N.HiS)(3)] and [Ni-II(S.Cys)(2).(N.His)(2)] in the HC4H2 and HC5H metallopeptides, respectively. In the HC5H metallopeptide, tetrahedral [Co-II(S-Cys)(2)(N.HiS)(2)] is present. We conClude that the designed scaffolded binding sites, inCluding Ni-(mu(2)-Cys)-Fe bridges, have been achieved. This is the first XAS study of a de novo designed metallopeptide intended to stabilize a bridged biological assembly, and one of a few XAS analyses of metal derivatives of designed peptides. The scaffolding concept should be extendable to other bridged metal assemblies.Structural characterization of metallopeptides designed as scaffolds for the stabilization of nickel(II)-Fe4S4 bridged assemblies by X-ray absorption spectroscopyx25200248#N/AFALSE
2762
ja017131010.1021/ja0171310FALSEhttps://doi.org/10.1021/ja0171310Hall, MBHigh-spin Ni(II), a surprisingly good structural model for [NiFe] hydrogenase2002#N/ATRUE
2763
ja016996a10.1021/ja016996aFALSEhttps://doi.org/10.1021/ja016996aO'Keeffe, MJ. Am. Chem. Soc.A flexible germanate structure containing 24-ring channels and with very low framework density151200124#N/ATRUE
2764
ja016676r10.1021/ja016676rFALSEhttps://doi.org/10.1021/ja016676rLindahl, PAJ. Am. Chem. Soc.Kinetics of methyl group transfer between the Ni-Fe-S-containing acetyl-CoA synthase (ACS) and the corrinoid protein (CoFeSP) from Clostridium thermoaceticum were investigated using the stopped-flow method at 390 nm. Rates of the reaction CH3-Co3+FeSP + ACS(red);= Co1+FeSP + CH3-ACS(ox)., in both forward and reverse directions were determined using various protein and reductant concentrations. Tl3+-citrate, dithionite, and CO were used to reductively activate ACS (forming ACS(red)). The simplest mechanism that adequately fit the data involved formation of a [CH3-Co3+FeSP]:[ACS(red)] complex, methyl group transfer (forming [Co1+FeSP]:[CH3-ACS(ox)]), product dissociation (forming Co1+FeSP + CH3-ACS(ox)), and CO binding yielding a nonproductive enzyme state (ACS(red) -4- CO = ACS(red)-CO). Best-fit rate constants were obtained. CO inhibited methyl group transfer by binding ACS(red) in accordance with K-D = 180 +/- 90 muM. Fits were unimproved when > 1 CO was assumed to bind. Tl(3+)citrate and dithionite inhibited the reverse methyl group transfer reaction, probably by reducing the D-site of CH3-ACS(ox). This redox site is oxidized by 2e(-) when the methyl cation is transferred from CH3-Co3+FeSP to ACS(red), and is reduced during the reverse reaction. Best-fit K-D values for pre- and post-methyl-transfer complexes were 0.12 +/- 0.06 and 0.3 +/- 0.2 muM, respectively. Intracomplex methyl group transfer was reversible with K-eq = 2.3 +/- 0.9 (k(f)/k(f) = 6.9 s(-1)/3.0 s(-1)). The nuCleophilicity of the {Ni2+Dred} unit appears comparable to that of Co1+ cobalamins. Reduction of the D-site may cause the Ni2+ of the A-Cluster to behave like the Ni of an organometallic Ni-o complex.Stopped-flow kinetics of methyl group transfer between the corrinoid-iron-sulfur protein and acetyl-coenzyme A synthase form Clostridium thermoaceticum44200241#N/ATRUE
2765
ja016089610.1021/ja0160896FALSEBrookhart, MFour- and five-coordinate CO insertion mechanisms in d(8)-nickel(III) complexes2001#N/ATRUE
2766
ja011278+10.1021/ja011278+FALSEhttps://doi.org/10.1021/ja011278+Armentrout, PBJ. Am. Chem. Soc.Threshold collision-induced dissociation of M+(adenine) with xenon is studied using guided ion beam mass spectrometry. M+ inCludes all 10 first-row transition metal ions: Sc+, Ti+, V+, Cr+, Mn+, Fe+, Co+, Ni+, Cu+, and Zn+. For the systems involving the late metal ions, Cr+ through Cu+, the primary product corresponds to enClothermic loss of the intact adenine molecule, whereas for Zn+, this process occurs but to form Zn + adenine(+). For the complexes to the early metal ions, Sc+, Ti+, and V+, intact ligand loss competes with endothermic elimination of purine and of HCN to form MNH+ and M+(C4H4N4), respectively, as the primary ionic products, For Sc+, loss of ammonia is also a prominent process at low energies. Several minor channels corresponding to formation of M+(CxHxNx), x = 1-3, are also observed for these three systems at elevated energies. The energy-dependent collision-induced dissociation cross sections for M+(adenine), where M+ = V+ through Zn+, are modeled to yield thresholds that are directly related to 0 and 298 K bond dissociation energies for M+-adenine after accounting for the effects of multiple ion-molecule collisions, kinetic and internal energy distributions of the reactants, and dissociation lifetimes. The measured bond energies are compared to those previously studied for simple nitrogen donor ligands, NH3 and pyrimidine, and to results for alkali metal cations bound to adenine. Trends in these results and theoretical calculations on Cu+(adenine) suggest distinct differences in the binding site propensities of adenine to the alkali vs transition metal ions, a consequence of s-dsigma hybridization on the latter.Influence of d orbital occupation on the binding of metal ions to adeninex82200286#N/AFALSE
2767
ja015930c10.1021/ja015930cFALSEhttps://doi.org/10.1021/ja015930cJacobs, PAJ. Am. Chem. Soc.Tungstate, exchanged on a (Ni,Al) layered double hydroxide, is applied as a heterogeneous catalyst in the oxidation of bromide with H2O2 and the ensuing electrophilic bromination of olefins. The high halogenation activity of the catalyst in essentially neutral conditions mimicks the activity of V-bromoperoxidase enzymes. In water, aromatic and aliphatic olefins are selectively converted to bromohydrins; in methanol, methoxybromides are produced. In appropriate solvent conditions, the bromohydroxylation of geminally di-, tri-, and tetrasubstituted olefins proceeds via dehydrobromination to the epoxide. Evidence for this mechanism is provided by kinetic and labeling experiments. This one-pot alternative for the two-step halohydrin epoxidation process is enabled by the mild pH conditions: bromide is effective in substoichiometric, catalytic amounts. All new catalytic procedures are characterized by a high oxidative stability of the catalyst, high productivity of the catalyst on weight basis, high W turnover frequencies in ambient conditions (up to 50 mol of product per W per h), and high chemo-, regio-, and stereoselectivities.Use of WO42- on layered double hydroxides for mild oxidative bromination and bromide-assisted epoxidation with H2O2118200170#N/ATRUE
2768
ja012747a10.1021/ja012747aFALSEhttps://doi.org/10.1021/ja012747aSessler, JLJ. Am. Chem. Soc.The preparation of first-row transition-metal complexes of texaphyrin, a porphyrin-like, monoanionic penta-aza macrocyClic ligand, is reported. Specifically, the synthesis of organic-soluble Mn(II) (1), Co(II) (2), Ni(II) (3), Zn(II) (4), and F-e(III) (5) texaphyrin derivatives and their water-soluble counterparts (6-10) from appropriate metal-free, nonaromatic macrocyClic precursors is described. It was found that metal cations of sufficient reduction potential could act to oxidize the nonaromatic macrocyClic precursor in the course of metal insertion. Complexes were characterized by X-ray diffraction analysis, electrochemistry, flash photolysis, and EPR spectroscopy. The structural and electronic properties of these expanded porphyrin complexes are compared with those of analogous porphyrins. Notably, the texaphyrin ligand is found to support the complexation of cations in a lower valence and a higher spin state than do porphyrins. Interactions between the coordinated cation and the ligand pi system appear to contribute to the overall bonding. Texaphyrin complexes of Mn(II), Co(II), and Fe(III) in particular may possess sufficient aqueous stability to permit their use in pharmaceutical applications.Late first-row transition-metal complexes of texaphyrin52200268#N/ATRUE
2769
ja011055j10.1021/ja011055jFALSEhttps://doi.org/10.1021/ja011055jBrookhart, MJ. Am. Chem. Soc.A series of stable diAlkyl complexes of Pd, (a-diimine)PdR2 (alpha -diimine = Aryl-substituted diimine, R = n-Pr, n-Bu, i-Bu), have been prepared via Grignard Alkylation of the corresponding (alpha -diimine)PdCl2 complexes. Protonation of these diAlkyl species at low temperature results in loss of alkane and formation of cationic Pd beta -agostic Alkyl complexes, which have been observed as intermediates in the polymerization of ethylene and propylene by these Pd catalysts. Studies of the structure and dynamic behavior of these Alkyl complexes are presented. along with the results of trapping reactions of these species with ligands such as NCMe, CO, and C2H4. Trapping with ethylene results in formation of cationic Alkyl ethylene complexes which model the catalyst resting state in these systems. These complexes have been used to obtain mechanistic details and kinetic parameters of several processes, inCluding isomerization of the Alkyl ethylene complexes, associative and dissociative exchange with free ethylene, and migratory insertion rates of both primary and secondary Alkyl ethylene species. These studies indicate that the overall branching observed in polyethylenes produced by these Pd catalysts is governed both by the kinetics of migratory insertion and by the equilibria involving the Alkyl ethylene complexes.Palladium(II) beta-agostic Alkyl cations and Alkyl ethylene complexes: Investigation of polymer chain isomerization mechanismsx183200154#N/AFALSE
2770
ja012735p10.1021/ja012735pFALSEhttps://doi.org/10.1021/ja012735pHolm, RHJ. Am. Chem. Soc.The recent development of structural and functional analogues of the DMSO reductase family of isoenzymes allows mechanistic examination of the minimal oxygen atom transfer paradigm M-IV + QO --> (MO)-O-VI + Q with the biological metals M = Mo and W. Systematic variation of the electronic environment at the W-IV center of desoxo bis(dithiolene) complexes is enabled by introduction of para-substituted phenyl groups in the equatorial (eq) dithiolene ligand and the axial (ax) phenolate ligand, The compounds [W(CO)(2)-(S2C2(C6H4-rho-X)(2))(2)] (54-60%) have been prepared by ligand transfer from [Ni(S2C2(C6H4-p-X)(2))(2)] to [W(CO)(3)-(MeCN)(3)]. A series of 25 complexes [W-IV(OC6H4-p-X')(S2C2(C6H4-p-X)(2))(2)](1-) ([X4X'], X = Br, F, H, Me, OMe; X' = CN, Br, H, Me, NH2; 41-53%) has been obtained by ligand substitution of five diCarbonyl complexes with five phenolate ligands. Linear free energy relationships between E-1/2 and Hammett constant sigma(p) for the electron-transfer series [Ni(S2C2(C6H4-p-X)(2))(2)](0.1-.2-) and [W(CO)(2)(S2C2(C6H4-p-X)(2))(2)](0.1-.2-) demonstrate a substituent influence on electron density distribution at the metal center. The reactions [W-IV(OC6H4-p-X')-(S2C2(C6H4-p-X)(2))(2)](1-) + (CH2)4(S)O --> [(WO)-O-VI(OC6H4-p-X')(S2C2(C6H4-p-X)(2))(2)](1) + (CH2)(4)S with constant substrate are second order with large negative Activation entropies indicative of an associative transition state. Rate constants at 298 K adhere to the Hammett equations log(k((X4,X')/k(X4,H))) = rho(ax)sigma(p) and log(k((X4,X')/lJ4.X'))) = 4(rhoeq)sigma(p). Electron-withdrawing groups (EWG) and electron-donating groups (EDG) have opposite effects on the rate such that k(EWG) > k(EDG). The effects of X' on reactivity are found to be similar to5 times greater than that of X (rho(ax) = 2.1, rho(eq) = 0.44) in the Hammett equation. Using these and other findings, a stepwise oxo transfer reaction pathway is proposed in which an early transition state, of primary W-IV-O(substrate) bond-making character, is rate-limiting. This is followed by a six-coordinate substrate complex and a second transition state proposed to involve atom and electron transfer leading to the development of the W-VI = O group. This work is the most detailed mechanistic investigation of oxo transfer mediated by a biological metal.Functional analogue reaction systems of the DMSO reductase isoenzyme family: Probable mechanism of S-oxide reduction in oxo transfer reactions mediated by bis(dithiolene)-tungsten(IV,VI) complexes56200237#N/ATRUE
2771
ja010851m10.1021/ja010851mFALSEhttps://doi.org/10.1021/ja010851mHolm, RHHelix-loop-helix peptides as scaffolds for the construction of bridged metal assemblies in proteins: The spectroscopic A-Cluster structure in carbon monoxide dehydrogenaseX2001#N/AFALSE
2772
ja010825o10.1021/ja010825oFALSEhttps://doi.org/10.1021/ja010825oYaghi, OMJ. Am. Chem. Soc.The secondary building unit (SBU) has been identified as a useful tool in the analysis of complex metal-organic frameworks (MOFs). We illustrate its applicability to rationalizing MOF crystal structures by analysis of nine new MOFs which have been characterized by single-crystal X-ray diffraction. Tetrahedral SBUs in Zn(ADC)(2)(.)(HTEA)(2) (MOF-31), Cd(ATC)(.)[Cd(H2O)(6)](H2O)(5) (MOF-32), and Zn-2(ATB)(H2O)(.) (H2O)(3)(DMF)(3) (MOF-33) are linked into diamond networks, while those of Ni-2(ATC)(H2O)(4)(.)(H2O)(4) (MOF-34) have the structure of the Al network in SrAl2. Frameworks constructed from less symmetric tetrahedral SBUs have the Ga network of CaGa2O4 as illustrated by Zn-2(ATC)(.)(C2H5OH)(2)(H2O)(2) (MOF-35) structure. Squares and tetrahedral SBUs in Zn-2(MTB)(H2O)(2)(.)(DMF)(6)(H2O)(5) (MOF-36) are linked into the PtS network, which is the simplest structure type known for the assembly of these shapes. The octahedral SBUs found in Zn-2(NDC)(3)(.)[(HTEA)(DEF)(ClBz)](2) (MOF-37) form the most common structure for linking octahedral shapes, namely, the boron network in CaB6. New structure types for linking triangular and trigonal prismatic SBUs are found in Zn3O(BTC)(2)(.)(HTEA)(2) (MOF-38) and Zn3O(HBTB)(2)(H2O)(.)(DMF)(0.5)(H2O)(3) (MOF-39). The synthesis, crystal structure, and structure analysis using the SBU approach are presented for each MOF.Assembly of metal-organic frameworks from large organic and inorganic secondary building units: New examples and simplifying principles for complex structuresx788200141#N/AFALSE
2773
ja010647z10.1021/ja010647zFALSEhttps://doi.org/10.1021/ja010647zBalch, ALJ. Am. Chem. Soc.Pd-4(OEB)(2), in which a [Pd-2](2+) unit is bound in pi -fashion to olefinic sites that are exocyClic, to pyrrole rings of the octaethylbilindione ligand, undergoes an unprecedented sequence of reactions that results, in the rearrangement of the framework of the bilindione ligand and the formation of trans-Pd(py)(2)I-2. This process of bilindione. rearrangement and oxidation occurs as a direct consequence of the pi -coordination of the palladium. The reaction results in the migration of a nitrogen atom from a pyrrole carbon atom to what was formerly a meso carbon atom to transform a former pyrrole ring into a six-membered ring. This process also involves Cleavage of the Pd-Pd and Pd-C bonds, oxidation of palladium, and introduction of an oxygen atom (from water) not necessarily in this particular sequence.A remarkable skeletal rearrangement of a coordinated tetrapyrrole: Chemical consequences of palladium pi-coordination to a bilindionex13200131#N/AFALSE
2774
ja010628p10.1021/ja010628pFALSEhttps://doi.org/10.1021/ja010628pWhite, AHJ. Am. Chem. Soc.Oxidative addition of different imidazolium cations to zerovalent group 10 metals, to afford heterocyClic carbene complexes, has been investigated by both density functional theory (DFT) and experimental studies. The theoretical analysis shows that addition of imidazoliums to Pt-0 and Ni-0 is more exothermic than to Pdl, and Nil is predicted to react with a much lower barrier than either Pt-0 or Pd-0. Strongly basic supporting ligands on the metal, as well as cis-chelating ligands, increase the exothermicity of the reaction and also lower the Activation barrier. The addition of 2-H imidazoliums is easier and more exothermic than addition of 2-Alkylimidazoliums, and a halo-imidazolium is expected to further lower the barrier to oxidative addition and increase the exothermicity. The DFT results show that all three of the metals should be able to oxidatively add imidazolium cations under appropriate conditions. Experimental studies confirmed that oxidative addition is possible, and a number of Pt- and Pd-carbene complexes were prepared via oxidative addition of imidazolium salts to MO precursors. Most significantly, oxidative addition of 2-H azolium salts was found to readily occur, and the reaction of 1,3-dimethylimidazolium tetrafluorB(OH)2rate with Pt(PPh3)(2) and Pt(PCy3)2 affords [PtH(dmiy)(PPh3)(2)]BF4 (10) and [PtH(dmiy)(PCy3)(2)]BF4 (11), while reaction between 3,4-dimethylthiazolium tetrafluorB(OH)2rate and Pt(PCy3)(2) yields [PtH(dmty)(PCy3)(2)]BF4 (12) (dmiy = 1,3-dimethylimidazolin-2-ylidene, dmty = 3,4-dimethylthiazolin-2-ylidene). Addition of 2-iodo-1,3,4,5-tetramethylimidazolium tetrafluorB(OH)2rate to Pt(PPh3)(4) or Pd(dcype)(dba) yields [PtI(tmiy)(PPh3)(2)]BF4 (9) and [PdI(tmiy)(dcype)]BF4 (14), respectively (tmiy = 1,3,4,5-tetramethylimidazolin-2-ylidene, dcype = 1,3-bis(dicyClohexylphosphino)ethane)). X-ray crystal structures are reported for complexes 9 and 11 (cis and trans). These studies Clearly show for the first time that oxidative addition of imidazolium and thiazolium cations is possible, and the results are discussed in terms of the ramifications for catalysis in imidazolium-based ionic liquids with both carbene-based and non-carbene-based complexes.Oxidative addition of the imidazolium cation to zerovalent Ni, Pd, and Pt: A combined density functional and experimental studyx217200180#N/AFALSE
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ja012372t10.1021/ja012372tFALSEhttps://doi.org/10.1021/ja012372tZiegler, TJ. Am. Chem. Soc.We present a comprehensive theoretical investigation of the mechanism for cyClodimerization of butadiene by the generic [bis(butadiene)(NiPH3)-P-0] catalyst employing a gradient-corrected DFT method. We have explored all critical elementary steps of the whole catalytic cyCle, namely, oxidative coupling of two butadienes, reductive elimination under ring Closure, and allylic isomerization. Oxidative coupling of two butadienes in the [bis(butadiene)(NiL)-L-0] complex and reductive elimination in the [(bis(eta(3))-octadienediyl)(NiL)-L-II] species take place under different stereocontrol, which makes isomerization indispensable. Commencing from a preestablished equilibrium between several configurations of the [(octadienediyl)(NiL)-L-II] complex, the major cyClodimer products, namely, VCH, cis-1,2-DVCB, and cis,cis-COD, are formed along competing reaction paths via reductive elimination, which is found to be the overall rate-determining step. Careful exploration of different possible conceivable routes revealed that bis(eta(1)) species are not involved as critical intermediates either in reductive elimination or in isomerization along the most feasible pathway. The regulation of the selectivity of the cyClodimer formation based on both thermodynamic and kinetic considerations is outlined.[(NiL)-L-0]-catalyzed cyClodimerization of 1,3-butadiene: A comprehensive density functional investigation based on the generic [(C4H6)(2)(NiPH3)-P-0] catalyst20200255#N/ATRUE
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ja010428d10.1021/ja010428dFALSEhttps://doi.org/10.1021/ja010428dHoffman, BMJ. Am. Chem. Soc.Methyl-coenzyme M reductase (MCR) catalyzes the formation of methyl-coenzyme M (CH3S-CH2CH2SO3) from methane. The active site is a nickel tetrahydrocorphinoid cofactor, factor 430, which in inactive form contains EPR-silent Ni(II). Two such forms, denoted MCRsilent and MCRox1-silent, were previously structurally characterized by X-ray crystallography. We describe here the cryoreduction of both of these MCR forms by gamma -irradiation at 77 K, which yields reduced protein maintaining the structure of the oxidized starting material. Cryoreduction of MCRsilent yields an EPR signal that strongly resembles that of MCRred1, the active form of MCR; and stepwise annealing to 260-270 K leads to formation of MCRred1. Cryoreduction of MCRox1-silent solutions shows that our preparative method for this state yields enzyme that contains two major forms. One behaves similarly to MCRsilent, as shown by the observation that both of these forms give essentially the same redlike EPR signals upon cryoreduction, both of which give MCRred1 upon annealing. The other form is assigned to the crystallographically characterized MCRox1-silent and directly gives MCRox1 upon cryoreduction. X-band spectra of these cryoreduced samples, and of conventionally prepared MCRred1 and MCRox1, all show resolved hyperfine splitting from four equivalent nitrogen ligands with coupling constants in agreement with those determined in previous EPR studies and from N-14 ENDOR of MCRred1 and MCRox1. These experiments have confirmed that all EPR-visible forms of MCR contain Ni(I) and for the first time generated in vitro the EPR-visible, enzymatically active MCRred1 and the activate-able ready MCRox1 from silent precursors. Because the solution Ni(II) species we assign as MCRox1-silent gives as its primary cryoreduction product the Ni(I) state MCRox1, previous crystallographic data on MCRox1-silent allow us to identify the exogenous axial ligand in MCRox1 as the thiolate from CoM; the cryoreduction experiments further allow us to propose possible axial ligands in MCRred1 The availability of model compounds for MCRred1 and MCRox1 also is discussed.Cryoreduction of methyl-coenzyme M reductase: EPR characterization of forms, MCRox1 and MCRred1x48200146#N/AFALSE
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ja012108010.1021/ja0121080FALSEhttps://doi.org/10.1021/ja0121080Perez, MJ. Am. Chem. Soc.Reduction of an oxide in hydrogen is a method frequently employed in the preparation of active catalysts and electronic devices, Synchrotron-based time-resolved X-ray diffraction (XRD), X-ray absorption fine structure (NEXAFS/EXAFS), photoemission, and first-principles density-functional (DF) slab calculations were used to study the reaction of H-2 with nickel oxide. In experiments with a NiO(100) crystal and NiO powders, oxide reduction is observed at atmospheric pressures and elevated temperatures (250-350degreesC), but only after an induction period. The results of in situ time-resolved XRD and NEXAFS/EXAFS show a direct NiO-->Ni transformation without accumulation of any intermediate phase, During the induction period, surface defect sites are created that provide a high efficiency for the dissociation of H-2. A perfect NiO(100) surface, the most common face of nickel oxide, exhibits a negligible reactivity toward H-2. The presence of O vacancies leads to an increase in the adsorption energy of H-2 and substantially lowers the energy barrier associated with the Cleavage of the H-H bond. At the same time, adsorbed hydrogen can induce the migration of O vacancies from the bulk to the surface of the oxide. A correlation is observed between the concentration of vacancies in the NiO lattice and the rate of oxide reduction, These results illustrate the complex role played by O vacancies in the mechanism for reduction of an oxide. The kinetic models frequently used to explain the existence of an induction time during the reduction process can be important, but a more relevant aspect is the initial production of active sites for the rapid dissociation of H-2.Experimental and theoretical studies on the reaction of H-2 with NiO: Role of O vacancies and mechanism for oxide reduction289200279#N/ATRUE
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ja012099v10.1021/ja012099vFALSEhttps://doi.org/10.1021/ja012099vLeitner, WJ. Am. Chem. Soc.Highly enantioselective nickel-catalyzed hydroVinylation with chiral phosphoramidite ligands123200226#N/ATRUE
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ja010342k10.1021/ja010342kFALSEhttps://doi.org/10.1021/ja010342kLe Pape, LJ. Am. Chem. Soc.New dissymmetric tertiary amines (N3SR) with varying N/S donor sets have been synthesized to provide mono- and dinuClear complexes. Acetate ions are used to complete the octahedral coordination sphere around nickel(II) atom(s). The facile conversion of mononuClear to dinuClear systems can be controlled to produce either mono- or dinuClear complexes from the same ligand. The dinuClear complex a(BPh4)(2) ([Ni-2(N-3-SSN3)(OAc)(2)](BPh4)(2)) has been characterized in the solid state by X-ray diffraction techniques as solvate: a(BPh4)(2). (1)/(2)[5(CH3OH). (CH3CN). (CH3CH2OH)]. The two Ni atoms are six-coordinated and bridged by a disulfide group and two bidentate acetates. Magnetic susceptibility reveals a weak ferromagnetic exchange interaction between the two Ni atoms with J = 2.5(7) cm(-1). UV-vis studies suggest that the six-coordinated structure persists in solution. The H-1 NMR spectrum of a(BPh4)(2) exhibits sharp significantly hyperfine shifted ligand signals. A complete assignment of resonances is accomplished by a combination of methods: 2D-COSY experiments, selective chemical substitution, and analysis of proton relaxation data. Proton isotropic hyperfine shifts are shown to originate mainly from contact interactions and to intrinsically contain a small J-magnetic coupling and/or zero-field splitting contribution. A temperature dependence study of longitudinal relaxation times indicates that a very unusual paramagnetic Curie dipolar mechanism is the dominant relaxation pathway in these weakly ferromagnetically spin-coupled dinickel(II) centers. The mononuClear nickel(II) analogue exhibits extremely broader H-1 NMR signals and only partial analysis could be performed. These data are consistent with a shortening of electronic relaxation times in homodinuClear compounds with respect to the corresponding mononuClear species.Paramagnetic NMR investigations of high-spin nickel(II) complexes. Controlled synthesis, structural, electronic, and magnetic properties of dinuClear vs mononuClear speciesx35200160#N/AFALSE
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ja011869010.1021/ja0118690FALSEhttps://doi.org/10.1021/ja0118690Hu, PJ. Am. Chem. Soc.We have carried out extensive density functional theory (DFT) calculations for possible redox states of the active center in Fe-only hydrogenases. The active center is modeled by [(H(CH3)S)(CO)(CN-)Fe-p(mu-DTN)(mu-CO)Fe-d(CO)(CN-)(L)](z) (z is the net charge in the complex; Fe-p= the proximal Fe, Fe-d = the distal Fe, DTN = (-SCH2NHCH2S-), L is the ligand that bonds with the Fed at the trans position to the bridging CO). Structures of possible redox states are optimized, and CO stretching frequencies are calculated. By a detailed comparison of all the calculated structures and the vibrational frequencies with the available experimental data, we find that (i) the fully oxidized, inactive state is an Fe(II)-Fe(II) state with a hydroxyl (OH-) group bonded at the Fe-d, (ii) the oxidized, active state is an Fe(II)-Fe(l) complex which is consistent with the assignment of Cao and Hall (J. Am. Chem. Soc. 2001, 123, 3734), and (iii) the fully reduced state is a mixture with the major component being a protonated Fe(l)-Fe(l) complex and the other component being its self-arranged form, Fe(II)-Fe(II) hydride, Our calculations also show that the exogenous CO can strongly bond with the Fe(II)-Fe(l) species, but cannot bond with the Fe(l)-Fe(l) complex. This result is consistent with experiments that CO tends to inhibit the oxidized, active state, but not the fully reduced state. The electronic structures of all the redox states have been analyzed. It is found that a frontier orbital which is a mixing state between the e(g) of Fe and the 2pi of the bridging CO plays a key role concerning the reactivity of Fe-only hydrogenases: (1) it is unoccupied in the fully oxidized, inactive state, half-occupied in the oxidized, active state, and fully occupied in the fully reduced state; (ii) the e(g)-2pi orbital is a bonding state, and this is the key reason for stability of the low oxidation states, such as Fe(l)-Fe(l) complexes; and (iii) in the e(g)-2pi orbital more charge accumulates between the bridging CO and the Fe-d than between the bridging CO and the Fe-p, and the occupation increase in this orbital will enhance the bonding between the bridging CO and the Fe-d, leading to the bridging-CO shift toward the Fe-d.A density functional theory study on the active center of Fe-only hydrogenase: Characterization and electronic structure of the redox states160200250#N/ATRUE
2781
ja010072610.1021/ja0100726https://doi.org/10.1021/ja051662xHipps, KWScanning tunneling microscopy, orbital-mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vaporPhotocatalystx2001#N/AFALSE
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ja011664r10.1021/ja011664rFALSEhttps://doi.org/10.1021/ja011664rCrabtree, RHJ. Am. Chem. Soc.The mechanism for methane formation in methyl-coenzyme M reductase (MCR) has been investigated using the B3LYP hybrid density functional method and chemical models consisting of 107 atoms. The experimental X-ray crystal structure of the enzyme in the inactive MCRox1-silent state was used to set up the initial model structure. The calculations suggest a mechanism not previously proposed, in which the most remarkable feature is the formation of an essentially free methyl radical at the transition state. The reaction cyCle suggested starts from a Michaelis complex with CoB and methyl-CoM coenzymes bound and with a squareplanar coordination of the Ni(I) center in the tetrapyrrole F-430 prosthetic group. In the rate-limiting step the methyl radical is released from methyl-CoM, induced by the attack of Ni(l) on the methyl-CoM thioether sulfur. In this step, the metal center is oxidized from Ni(I) to Ni(II). The resulting methyl radical is rapidly quenched by hydrogen-atom transfer from the COB thiol group, yielding the methane molecule and the COS radical. The estimated Activation energy is around 20 kcal/mol, which inCludes a significant contribution from entropy due to the formation of the free methyl. The mechanism implies an inversion of configuration at the reactive carbon. The size of the inversion barrier is used to explain the fact that CF3-S-COM is an inactive substrate. Heterodisulfide CoB-S-S-CoM formation is proposed in the final step in which nickel is reduced back to Ni(I), The suggested mechanism agrees well with experimental observations.A mechanism from quantum chemical studies for methane formation in methanogenesis92200234#N/ATRUE
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ja011645h10.1021/ja011645hFALSEhttps://doi.org/10.1021/ja011645hLong, JRJ. Am. Chem. Soc.The substitution of Mo-III for Cr-III in metal-cyanide Clusters is demonstrated as an effective means of increasing the strength of the magnetic exchange coupling and introducing magnetic anisotropy. Synthesis of the octahedral complex [(Me(3)tacn)Mo(CN)(3)] (Me(3)tacn = N,N'N-trimethyl-1,4,7-triazacyClononane) is accomplished with the addition of precisely 3 equiv of LiCN to a solution of [(Me(3)tacn)Mo(CF3SO3)(3)] in DMF. An excess of LiCN prompts formation of a seven-coordinate complex, [(Me(3)tacn)Mo(CN)(4)](1-), whereas less LiCN produces multinuClear species such as [(Me(3)tacn)(2)Mo-2(CN)(5)](1+). In Close parallel to reactions previously performed with [(Me(3)tacn)Cr(CN)(3)], assembly reactions between [(Me(3)tacn)Mo(CN)(3)] and [Ni(H2O)(6)](2+) or [(cyClam)Ni(H2O)(2)](2+) (cyClam = 1,4,8,11-tetraazacyClotetradecane) afford face-centered cubic [(Me(3)taCn)(8)Mo8Ni6(CN)(24)](12+) and linear [(Me(3)tacn)(2)(cyClam)NiMo2(CN)(6)](2+) Clusters, respectively. Generation of the former involves a thermally induced cyanide linkage isomerization, which rapidly leads to a low-spin form of the Cluster containing diamagnetic Ni-II centers. The cyClic voltammagram of this species in DMF reveals a sequence of six successive reduction waves spaced approximately 130 mV apart, suggesting Class II mixed-valence behavior upon reduction. The magnetic properties of the aforementioned linear Cluster are consistent with the expected ferromagnetic coupling and an S = 4 ground state, but otherwise vary slightly with the specific conformation adopted (as influenced by the packing of associated counteranions and solvate molecules in the crystal). Magnetization data indicate an axial zero-field splitting parameter with a magnitude falling in the range \D\ = 0.44-0.72 cm(-1), and fits to the magnetic susceptibility data yield exchange coupling constants in the range J = 17.0-17.6 cm(-1). These values represent significant increases over those displayed by the analogous Cr-III-containing Cluster. When perchlorate is used as a counteranion, [(Me(3)tacn)(2)(cyClam)NiMo2(CN)(6)](2+) crystallizes from water in a dimeric form with pairs of the linear Clusters directly linked via hydrogen bonding. In this case, fitting the magnetic susceptibility data requires use of two coupling constants: one intramolecular with J = 14.9 cm(-1) and another intermolecular with J = -1.9 cm(-1). Reacting [(Me(3)tacn)Mo(CN)(3)] with a large excess of [(cyClam)Ni(H2O)(2)](2+) produces a [(Me(3)tacn)(2)(cyClam)(3)(H2O)(2)Ni3Mo2(CN)(6)](6+) Cluster possessing a zigzag structure that is a simple extension of the linear Cluster geometry. Its magnetic behavior is consistent with weaker ferromagnetic coupling and an S = 6 ground state. Similar reactions employing an equimolar ratio of reactants afford related one-dimensional chains of formula [(Me(3)tacn)(cyClam)NiMo(CN)(3)](2+). Once again, the ensuing structure depends on the associated counteranions, and the magnetic behavior indicates ferromagnetic coupling. It is hoped that substitutions of the type exemplified here will be of utility in the design of new single-molecule magnets.Nickel(II)-molybdenum(III)-cyanide Clusters: Synthesis and magnetic behavior of species incorporating [(Me(3)tacn)Mo(CN)(3)]312200289#N/ATRUE
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ja011634o10.1021/ja011634oFALSEhttps://doi.org/10.1021/ja011634oPayen, EJ. Am. Chem. Soc.Hydrogen adsorption on Mo-S, Co-Mo-S, and Ni-Mo-S (10 (1) over bar0) surfaces has been modeled by means of periodic DFT calculations taking into account the gaseous surrounding of these catalysts in working conditions. On the stable Mo-S surface, only six-fold coordinated Mo cations are present, whereas substitution by Co or Ni leads to the creation of stable coordinatively unsaturated sites. On the stable MoS2 surface, hydrogen dissociation is always endothermic and presents a high Activation barrier. On Co-Mo-S surfaces, the ability to dissociate H-2 depends on the nature of the metal atom and the sulfur coordination environment. As an adsorption center, Co strongly favors molecular hydrogen Activation as compared to the Mo atoms. Co also increases the ability of its sulfur atom ligands to bind hydrogen. Investigation of surface acidity using ammonia as a probe molecule confirms the crucial role of sulfur basicity on hydrogen Activation on these surfaces. As a result, Co-Mo-S surfaces present Co-S sites for which the dissociation of hydrogen is exothermic and weakly activated. On Ni-Mo-S surfaces, Ni-S pairs are not stable and do not provide for an efficient way for hydrogen Activation. These theoretical results are in good agreement with recent experimental studies of H-2-D-2 exchange reactions.Hydrogen Activation on Mo-based sulfide catalysts, a periodic DFT study156200265#N/ATRUE
2785
ja00854a01910.1021/ja00854a019FALSEhttps://doi.org/10.1021/ja00854a019JENNY, CJJ. Am. Chem. Soc.Singly hydrogen-bridged borane anions derived from the hydrB(OH)2ration products of 1,3-butadiene. X-ray structure determination of tetrabutylammonium .mu.-hydro-1,2-dihydro-1,2:1,2-bis(tetramethylene)diboratex422014Added by Yizhou#N/AFALSE
2786
ja011504f10.1021/ja011504fFALSEhttps://doi.org/10.1021/ja011504fLee, GHJ. Am. Chem. Soc.The dicyanodiCarbonyliron(II) thiolate complexes trans, cis-[(CN)(2)(CO)(2)Fe(S, S-C-R)](-) (R = OEt (2), N(Et)(2) (3)) were prepared by the reaction of [Na][S-C(S)-R] and [Fe(CN)(2)(CO)(3)(Br)](-) (1). Complex 1 was obtained from oxidative addition of cyanogen bromide to [Fe(CN)(CO)(4)](-). In a similar fashion, reaction of complex 1 with [Na][S,O-C5H4N], and [Na][S,N-C5H4] produced the six-coordinate trans, cis-[(CN)(2)(CO)(2)Fe(S,O-C5H4N)](-) (6) and trans, cis-[(CN)(2)(CO)(2)Fe(S,N-C5H4)](-) (7) individually. Photolysis of tetrahydrofuran (THF) solution of complexes 2, 3, and 7 under CO led to formation of the coordinatively unsaturated iron(II) dicyanoCarbonyl thiolate compounds [(CN)(2)(CO)Fe(S,S-C-R)](-) (R = OEt (4), N(Et)(2) (5)) and [(CN)(2)(CO)Fe(S,N-C5H4)](-) (8), respectively. The IR nu(CN) stretching frequencies and patterns of complexes 4, 5, and 8 have unambiguously identified two CN- ligands occupying cis positions. In addition, density functional theory calculations suggest that the architecture of five-coordinate complexes 4, 5, and 8 with a vacant site trans to the CO ligand and two CN- ligands occupying cis positions serves as a conformational preference. Complexes 2, 3, and 7 were reobtained when the THF solution of complexes 4, 5, and 8 were exposed to CO atmosphere at 25degreesC individually. Obviously, CO ligand can be reversibly bound to the Fe-II site in these model compounds. Isotopic shift experiments demonstrated the lability of Carbonyl ligands of complexes 2, 3, 4, 5, 7, and 8. Complexes [(CN)(2)(CO)Fe(S,S-C-R)](-) and NiA/NiC states [NiFe] hydrogenases from D. gigas exhibit a similar one-band pattern in the nu(CO) region and two-band pattern in the nu(CN) region individually, but in different positions, which may be accounted for by the distinct electronic effects between [S,S-C-R](-) and cysteine ligands. Also, the facile formations of five-coordinate complexes 4, 5, and 8 imply that the strong sigma-donor, weak pipi-acceptor CN- ligands play a key role in creating/stabilizing five-coordinate iron(II) [(CN)(2)(CO)Fe(S,S-C-R)](-) complexes with a vacant coordination site trans to the CO ligand.Six-coordinate and five-coordinate Fe-II(CN)(2)(CO)(x) thiolate complexes (x=1, 2): Synthetic advances for iron sites of [NiFe] hydrogenases43200261#N/ATRUE
2787
ja00852a05410.1021/ja00852a054FALSEhttps://doi.org/10.1021/ja00852a054STOPPIONI, PJ. Am. Chem. Soc.SYNTHESIS, CHARACTERIZATION, AND X-RAY STRUCTURE OF A TETRAHYDROFURAN ADDUCT OF MU-IODO-BIS[TRIS(2-DIPHENYLARSINOETHYL)AMINE]NICKEL(I) TETRAPHENYLBORATEx719758#N/AFALSE
2788
ja011155p10.1021/ja011155pFALSEhttps://doi.org/10.1021/ja011155pWieghardt, KJ. Am. Chem. Soc.The ligand 2-mercapto-3,5-di-tert-butylaniline, H[L-AP], an o-aminothiophenol, reacts with metal(II) salts of Ni and Pd in CH3CN or C2H5OH in the presence of NEt3 under strictly anaerobic conditions with formation of beige to yellow cis-[M-II(L-AP)(2)] (M = Ni (1), Pd (2)) where (L-AP)(1-) represents the o-aminothiophenolate(1-) form. The crystal structure of cis-[Pd-II(L-AP)(2)] [HN(C2H5)(3)][CH3CO2] has been determined by X-ray crystallography. In the presence of air the same reaction produces dark blue solutions from which mixtures of the neutral complexes trans/cis-[M-II(L-ISQ)(2)] (M = Ni (1a/1b), Pd (2a/2b), and Pt (3a/3b)) have been isolated as dark blue-black solid materials. By using HPLC the mixture of 3a/3b has been separated into pure samples of 3a and 3b, respectively; (L-ISQ)(1-) represents the o-iminothionebenzosemiquinonate(1-) pi -radical. The structures of 1a.dmf and 3a.CH2Cl2 have also been determined. All compounds are square-planar and diamagnetic. H-1 NMR spectroscopy established the cis reversible arrow trans equilibrium of 1a/1b, 2a/2b, and 3a/3b in CH2Cl2 solution where the isomerization rate is very fast for the Ni, intermediate for the Pd, and very slow for the Pt species. It is shown that the electronic structures of 1a/1b, 2a/2b, 3a, and 3b are best described as diradicals with a singlet ground state. The spectro- and electrochemistries of all complexes display the usual full electron transfer series where the monocation, the neutral species, the mono- and dianions have been spectroscopically characterized. X-band EPR spectra of the monocations [1a/1b](+) and [3a](+) support the assignment of an oxidation-state distribution as predominantly [M-II(L-ISQ)(L-IBQ)](+) where (L-IBQ)(0) represents the o-iminothionequinone level. In contrast, the EPR spectra of the monoanions [1a/1b]- and [3a](-) indicate an [M-II(L-ISQ)(L-AP-H)](-) distribution but with a significant contribution of the [M-I(L-ISQ)(2)](-) resonance hybrid; (L-AP-H)(2-) represents the o-imidothiophenolato(2-) oxidation level. Analysis of the geometric features of 120 published structures of complexes containing ligands of the o-aminothiophenolate type show that high precision X-ray crystallography allows to discern the differing protonation and oxidation levels of these ligands. o-Amino-thiophenolates are unequivocally shown to be noninnocent ligands; the (L-ISQ)(1-) radical form is quite prevalent in coordination compounds and the electronic structure of a number of published complexes must be reconsidered.Experimental evidence for the noninnocence of o-aminothiophenolates: Coordination chemistry of o-iminothionebenzosemiquinonate(1-) pi-radicals with Ni(II), Pd(II), Pt(II)150200192#N/ATRUE
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ja00848a01510.1021/ja00848a015FALSEhttps://doi.org/10.1021/ja00848a015MOCELLA, MTJ. Am. Chem. Soc.MECHANISM OF BASE PROMOTED REDUCTION OF NICKEL(III) COMPLEXES OF MACROCYClIC AMINES - COORDINATED LIGAND RADICAL INTERMEDIATEx113197542#N/AFALSE
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ja00842a03410.1021/ja00842a034https://doi.org/10.1021/ja00842a034WILSON, JJ. Am. Chem. Soc.PHOTOCHEMICAL PERTURBATION AND CHEMICAL RELAXATION OF PLANAR - TETRAHEDRAL EQUILIBRIUM IN A DI(TERTIARY PHOSPHINE) COMPLEX OF NICKEL(II)Photocatalyst22197514#N/AFALSE
2791
ja011093310.1021/ja0110933FALSEhttps://doi.org/10.1021/ja0110933Osuka, AJ. Am. Chem. Soc.Directly fused diporphyrins display the extensive pi conjugation as evinced by highly perturbed electronic absorption spectra as well as lowered and largely split first oxidation potentials. Such diporphyrins prepared inClude meso-beta doubly linked diporphyrins 7, meso-meso beta-beta beta-beta triply linked diporphyrins 8, and meso-meso beta-beta doubly linked diporphyrins 9. Oxidation of 5,15-diAryl-substituted and 5,10,15-triAryl-substituted Ni-II-, Cu-II-, and Pd-II-porphyrins with tris(4-bromophenyl)aminium hexachloroantimonate (BAHA) in CHCl3 afforded 7, and triply linked Cu-II- diporphyrins 8a and 8g were respectively prepared by the oxidation of meso-meso singly linked Cu-II-diporphyrins 5c and 5f with BAHA. Meso-meso beta-beta doubly linked Ni-II-diporphyrin 9a was isolated along with triply linked Ni-II-diporphyrin 8e from the similar oxidation of meso-meso singly linked N-II-diporphyrin 5a. Doubly linked diporphyrins 7 and 9a both exhibit significantly perturbed electronic absorption spectra, in which the Soret-like bands are largely split at around 405-418 and 500-616 am and the Q-bandlike absorption bands are substantially intensified and red-shifted at 748-820 nm, probably as a consequence of symmetry lowering. Triply linked diporphyrins 8 display more strongly perturbed electronic absorption spectra with split Soret-like bands at 408-419 and 567-582 nm and Q-bandlike absorption bands reaching far-infrared region. Structures of three types of fused diporphyrins 7b and 7c, 8g and 8j, and 9a have been unambiguously determined by X-ray crystallography to be nearly coplanar. Both the triply linked diporphyrins 8g and 8j exhibit very flat structures, whereas the doubly linked diporphyrins 7b and 7c exhibit ruffled structures. The doubly linked diporphyrin 9a shows a helically twisted conformation with larger ruffling toward the opposite directions and has been actually separated into two enantiomers, which display strong Cotton effects in the CD spectra. The first oxidation potentials (E-oxl) decrease in the order of 5 > 7 greater than or equal to 9 > 8, indicating lift-up of HOMO orbital in this order, and split potential differences DeltaE = E-ox1 - E-ox2, in turn, increase in the reverse order of 5 < 7 <less than or equal to> 9 < 8. The H-1 NMR spectra have indicated that the aromatic porphyrin ring current becomes weakened in the order of 5 > 7 > 8. Collectively, the electronic interactions between the diporphyrins have been conCluded to increase in the other of 5 << 7 less than or equal to 9 < 8.Syntheses, structural characterizations, and optical and electrochemical properties of directly fused diporphyrins216200198#N/ATRUE
2792
ja010853710.1021/ja0108537FALSEhttps://doi.org/10.1021/ja0108537Wozniak, KJ. Am. Chem. Soc.[2]Catenane systems containing copper(II) and nickel(II) as metal centers have been self-assembled using tetraazamacrocyClic complexes and benzo-24-crown-8 as building blocks. A variety of methods, inCluding X-ray crystallography, ESI mass spectrometry, C-13 and H-1 NMR, and electrochemistry, were applied to characterize these new face-to-face bismacrocyClic systems. Weak pi...pi interactions introduced by interlocking transition metal complexes with benzocrown moieties were shown to increase the communication (cooperativity) of metal centers. Introduction of the benzocrown increases the stability of the mixed valence state of the macrocyClic complex, which is reflected in high values of conproportionation constants. Moreover, this effect was found to be stronger than that obtained by shortening the length of the spacer between the two tetraazamacrocyClic subunits in the parent bismacrocyCles. The extent of communication is larger for the nickel catenane than for the copper one.Novel [2]catenane structures introducing communication between transition metal centers via pi center dot center dot center dot pi interactions70200138#N/ATRUE
2793
ja010516y10.1021/ja010516yFALSEhttps://doi.org/10.1021/ja010516ySuslick, KSJ. Am. Chem. Soc.Sonochemical preparation of Co and Ni promoted MoS2 Supported on alumina was achieved by high-intensity ultrasonic irradiation of isodurene solutions containing molybdenum Carbonyl, dicobalt octaCarbonyl, elemental sulfur, and Al2O3 or Ni-Al2O3 under Ar flow. The sonochemically prepared catalysts were characterized by elemental analysis, XPS, SEM, TEM, and XEDS, and hydrodesulfurization (HDS) activity evaluated for thiophene and dibenzothiophene substrates. The TEM studies on the sonochemically prepared catalysts indicate the formation of layered hexagonal MoS2 (lattice fringes similar to6.2 Angstrom) on the alumina support. The sonochemically prepared Co-Mo-S/Al2O3, Ni-Mo-S/Al2O3, and Co-Ni-Mo-S/Al2O3 are extremely active catalysts for the HDS of thiophene and dibenzothiophene, with activities severalfold those of comparable commercial catalysts under identical conditions. The layered structure Of MoS2 remained intact after 120 h of HDS, and the catalyst is reusable.Sonochemical preparation of supported hydrodesulfurization catalysts81200165#N/ATRUE
2794
ja00839a02410.1021/ja00839a024FALSEhttps://doi.org/10.1021/ja00839a024WEISS, RJ. Am. Chem. Soc.NEW HOMOPORPHYRIN SYSTEM - 21-ETHOXYCarbonyl-5,10,15,20-TETRAPHENYL-21H-21-HOMOPORPHINE - CRYSTAL-STRUCTURE AND MOLECULAR STEREOCHEMISTRY OF NICKEL(II) COMPLEXX22197529#N/AFALSE
2795
ja010409410.1021/ja0104094FALSEhttps://doi.org/10.1021/ja049644nFukuzumi, SFormation, characterization, and reactivity of bis(mu-oxo)dinickel(III) complexes supported by a series of bis[2-(2-pyridyl)ethyl]amine ligands2001#N/ATRUE
2796
ja00836a01210.1021/ja00836a012FALSEhttps://doi.org/10.1021/ja00836a012BAILAR, JCJ. Am. Chem. Soc.NOVEL OCTAHEDRAL COMPLEXES OF NICKEL(II) WITH THIOETHER DERIVATIVES OF CYSTEINE ETHYL-ESTERx7197533#N/AFALSE
2797
ja010358a10.1021/ja010358aFALSEhttps://doi.org/10.1021/ja010358aHillhouse, GLJ. Am. Chem. Soc.Terminal amido and imido complexes of three-coordinate nickel218200129#N/ATRUE
2798
ja00834a00610.1021/ja00834a006FALSEhttps://doi.org/10.1021/ja00834a006GRAY, HBJ. Am. Chem. Soc.ELECTRONIC SPECTRAL AND MAGNETIC-SUSCEPTIBILITY STUDIES OF NICKEL(II) AND COBALT(II) CARboxYPEPTIDASE A COMPLEXESx122197552#N/AFALSE
2799
ja010204v10.1021/ja010204vFALSEhttps://doi.org/10.1021/ja010204vHoffman, BMJ. Am. Chem. Soc.Crystallographic studies of the hydrogenases (Hases) from Desulfovibrio gigas (Dg) and Desulfovibrio vulgaris Miyazaki (DvM) have revealed heterodinuClear nickel-iron active centers in both enzymes. The structures, which represent the as-isolated (unready) Ni-A (S = 1/2) enzyme state, disClose a nonprotein ligand (labeled as X) bridging the two metals. The bridging atom was suggested to be an oxygenic (O2- or OH-) species in Dg Hase and an inorganic sulfide in DvM Hase. To determine the nature and chemical characteristics of the Ni-X-Fe bridging ligand in Dg Hase, we have performed 35 GHz CW O-17 ENDOR measurements on the Ni-A form of the enzyme, exchanged into (H2O)-O-17, on the active Ni-C (S = 1/2) form prepared by H-2-reduction of Ni-A in (H2O)-O-17, and also on Ni-A formed by reoxidation of Ni-C in (H2O)-O-17. In the native state of the protein (Ni-A), the bridging ligand does not exchange with the (H2O)-O-17 solvent. However, after a reduction/reoxidation cyCle (Ni-A up arrow Ni-C --> Ni-A), an O-17 label is introduced at the active site, as seen by ENDOR, Detailed analysis of a 2-D field-frequency plot of ENDOR spectra taken across the EPR envelope of Ni-A(O-17) shows that the incorporated O-17 has a roughly axial hyperfine tensor, A(O-17) approximate to [5, 7, 20] MHz, disCloses its orientation relative to the g tensor, and also yields an estimate of the quadrupole tensor, The substantial isotropic component (a(iso)(O-17) approximate to 11 MHz) of the hyperfine interaction indicates that a solvent-derived O-17 is indeed a ligand to Ni and thus that the bridging ligand X in the Ni-A state of Dg Hase is indeed an oxygenic (O2- or OH-) species; comparison with earlier EPR results by others indicates that the same holds for Ni-B. The small Fe-57 hyperfine coupling seen previously for Ni-A (A(Fe-57) approximate to 0.9 MHz) is now shown to persist in Ni-C, A(Fe-57) similar to 0.8 MHz. However, the O-17 signal is lost upon reductive Activation to the Ni-C state; reoxidation to Ni-A leads to the reappearance of the signal. Consideration of the electronic structure of the EPR-active states of the dinuClear center leads us to suggest that the oxygenic bridge in NI-A(B) is lost in Ni-C and is re-formed from solvent upon reoxidation to Ni-A. This implies that the reductive Activation to Ni-C opens Ni/Fe coordination sites which may play a central role in the enzyme's activity.O-17 ENDOR detection of a solvent-derived Ni-(OHx)-Fe bridge that is lost upon Activation of the hydrogenase from Desulfovibrio gigas106200231#N/ATRUE
2800
ja010056910.1021/ja0100569FALSEhttps://doi.org/10.1021/ja0100569Richeson, DSJ. Am. Chem. Soc.A novel mononuClear germylene, Ge[1,8-((PrN)-Pr-i)(2)C10H6] (1), was isolated as a stable crystalline solid by the reaction of Li-2[1,8-((PrN)-Pr-i)(2)C10H6] with GeCl2(dioxane). Structural examination of I shows that this compound possesses a planar six-membered heterocyClic ring system with a Ge(II) center and that the steric impact of the substituents on the nitrogen centers is greater than that for the related five-membered metalloheterocyCles. Compound 1 is readily oxidized with elemental S and Se and the structural details for the dinuClear product [[1,8-((PrN)-Pr-i)(2)C10H6]Ge(mu -S)](2) are reported. Furthermore, the lone pair of electrons on the Ge(II) center in I allows this species to function as a novel ligand for the preparation of the unique tetrakis(germylene) complex Ni{Ge[((PrN)-Pr-i)(2)C10H6]}(4) (4). The structural features of 4 are reported and show that the germylene ligand, when coordinated to the Ni(O) center, now exhibited a twisted (nonplanar) heterometallocyCle and a cone angle of 145 degrees.Synthesis and properties of a germanium(II) metalloheterocyCle derived from 1,8-di(isopropylamino)naphthalene. A novel ligand leading to formation of Ni{Ge[((PrN)-Pr-i)(2)C10H6]}(4)76200136#N/ATRUE
2801
ja00858a01110.1021/ja00858a011FALSEhttps://doi.org/10.1021/ja00858a011KOCHI, JKJ. Am. Chem. Soc.MECHANISTIC STUDIES OF NICKEL CATALYSIS IN CROSS COUPLING OF Aryl HALIDES WITH AlkylMETALS - ROLE OF ArylAlkylNICKEL(II) SPECIES AS INTERMEDIATES196197559#N/ATRUE
2802
ja00542a03210.1021/ja00542a032FALSEhttps://doi.org/10.1021/ja00542a032MEEK, DWJ. Am. Chem. Soc.1ST SYNTHESIS, CHARACTERIZATION, AND X-RAY STRUCTURAL DETERMINATION OF THE MACROCYClIC PHOSPHINEAMINE COMPLEX [NI(ME2[16]DIENEN2P2)](PF6)2.0.5H2Ox20198015#N/AFALSE
2803
ja00854a03910.1021/ja00854a039FALSEhttps://doi.org/10.1021/ja00854a039SCHAEFFER, EJ. Am. Chem. Soc.ACID-CATALYZED ISOMERIZATION AND THERMAL REARRANGEMENT OF NICKEL HOMOPORPHYRINS1819757#N/ATRUE
2804
ja00853a06410.1021/ja00853a064FALSEhttps://doi.org/10.1021/ja00853a064THORSETT, EJ. Am. Chem. Soc.TOTAL SYNTHESIS OF NICKEL(II) OCTAMETHYLCORPHIN2319756#N/ATRUE
2805
ja00848a05010.1021/ja00848a050FALSEhttps://doi.org/10.1021/ja00848a050KUMADA, MJ. Am. Chem. Soc.ONE-STEP PREPARATION OF METACYClOPHANES AND (2,6)PYRIDINOPHANES BY NICKEL-CATALYZED GRIGNARD CYClOCOUPLING75197521#N/ATRUE
2806
ja00842a01410.1021/ja00842a014FALSEhttps://doi.org/10.1021/ja00842a014WALKER, JMELECTRONIC EFFECTS IN TRANSITION-METAL PORPHYRINS .1. REACTION OF PIPERIDINE WITH A SERIES OF PARA-SUBSTITUTED AND META-SUBSTITUTED NICKEL(II) AND VANADIUM(IV) TETRAPHENYLPORPHYRINS1975#N/ATRUE
2807
ja00842a01310.1021/ja00842a013FALSEhttps://doi.org/10.1021/ja00842a013JORDAN, RBJ. Am. Chem. Soc.COMPLEXING OF NICKEL(II) BY CYSTEINE, TYROSINE, AND RELATED LIGANDS AND EVIDENCE FOR ZWITTERION REACTIVITY28197531#N/ATRUE
2808
ja00841a04910.1021/ja00841a049FALSEhttps://doi.org/10.1021/ja00841a049MOODY, WEJ. Am. Chem. Soc.NUClEAR MAGNETIC-RESONANCE STUDIES OF METAL-COMPLEXES USING LANTHANIDE SHIFT-REAGENTS - LANTHANIDE INDUCED SHIFTS IN SPECTRA OF OXYGEN-DONOR LIGANDS COORDINATED TO NICKEL(II)19197514#N/ATRUE
2809
ja00837a02210.1021/ja00837a022FALSEhttps://doi.org/10.1021/ja00837a022TAKAYA, HJ. Am. Chem. Soc.NICKEL-CATALYZED REACTIONS INVOLVING STRAINED BONDS .12. NICKEL(0)-CATALYZED REACTION OF QUADRICYClANE WITH ELECTRON-DEFICIENT OLEFINS80197589#N/ATRUE
2810
ja00835a01910.1021/ja00835a019FALSEhttps://doi.org/10.1021/ja00835a019SMITH, LRJ. Am. Chem. Soc.SELECTIVE, HIGH-YIELD, LINEAR DIMERIZATION OF 1,3-BUTADIENE CATALYZED BY (PPH3)2NIBR2 AND NABH4 AND ITS POLYMER-BOUND NI(O) ANALOG44197530#N/ATRUE
2811
ja005622z10.1021/ja005622zFALSEhttps://doi.org/10.1021/ja005622zBuchwald, SLJ. Am. Chem. Soc.A catalytic asymmetric Suzuki coupling for the synthesis of axially chiral biAryl compounds389200030#N/ATRUE
2812
ja00504a02610.1021/ja00504a026FALSEhttps://doi.org/10.1021/ja00504a026STEWART, RPOXYGEN ATOM TRANSFER PROCESSES - REACTION OF TRANS-DINITROBIS(TRIETHYLPHOSPHINE)NICKEL(II), NI(NO2)2(PET3)2, WITH CARBON-MONOXIDEx1979#N/AFALSE
2813
ja00547a04010.1021/ja00547a040FALSEhttps://doi.org/10.1021/ja00547a040YOSHIKAWA, SJ. Am. Chem. Soc.REACTIONS OF METAL-COMPLEXES WITH CARBOHYDRATES .1. SYNTHESIS AND CHARACTERIZATION OF NOVEL BLUE PARAMAGNETIC NICKEL(II) COMPLEXES CONTAINING N-GLYCOSIDES5019804#N/ATRUE
2814
ja00500a06310.1021/ja00500a063https://doi.org/10.1021/ja00500a063MARGERUM, DWJ. Am. Chem. Soc.THERMALLY STABLE COPPER(III)-TRIPEPTIDE AND NICKEL(III)-TRIPEPTIDE COMPLEXES AND THEIR PHOTO-CHEMICAL DECOMPOSITION IN ACID-SOLUTIONPhotocatalyst72197925#N/AFALSE
2815
ja00500a01810.1021/ja00500a018FALSEhttps://doi.org/10.1021/ja00500a018MERBACH, AEJ. Am. Chem. Soc.HIGH-PRESSURE NUClEAR MAGNETIC-RESONANCE KINETICS .3. PROTON NUClEAR MAGNETIC-RESONANCE STUDY OF THE EFFECT OF TEMPERATURE AND PRESSURE ON THE EXCHANGE OF ACETONITRILE ON NICKEL(II)x70197930#N/AFALSE
2816
ja00542a03410.1021/ja00542a034FALSEhttps://doi.org/10.1021/ja00542a034IBERS, JAJ. Am. Chem. Soc.FACILE SYNTHESES OF TETRAAlkylCHLORIN AND TETRAAlkylPORPHYRIN COMPLEXES AND COMPARISON OF THE STRUCTURES OF THE TETRAMETHYLCHLORIN AND TETRAMETHYLPORPHYRIN COMPLEXES OF NICKEL(II)61198017#N/ATRUE
2817
ja00538a03610.1021/ja00538a036FALSEhttps://doi.org/10.1021/ja00538a036GRAY, HBJ. Am. Chem. Soc.A BINUClEAR NICKEL(II) ENCAPSULATING AGENT FOR CHLORIDE AND BROMIDE IONS19198016#N/ATRUE
2818
ja00538a02010.1021/ja00538a020FALSEhttps://doi.org/10.1021/ja00538a020ZANCHINI, CJ. Am. Chem. Soc.EXCHANGE INTERACTIONS IN COPPER(II)-NICKEL(II) AND NICKEL(II)-NICKEL(II) PAIRS IN TETRA(MU-BENZOATO-0,0')BIS(QUINOLINE)DIMETAL(II) COMPLEXES30198048#N/ATRUE
2819
ja00535a02310.1021/ja00535a023FALSEhttps://doi.org/10.1021/ja00535a023KLABUNDE, KJJ. Am. Chem. Soc.PI-ARENE COMPLEXES OF NICKEL(II) - SYNTHESIS (FROM METAL ATOMS) OF (PI-ARENE)BIS(PENTAFLUOROPHENYL)NICKEL(II) - PROPERTIES, PI-ARENE LABILITY, AND CHEMISTRY46198053#N/ATRUE
2820
ja00531a06310.1021/ja00531a063FALSEhttps://doi.org/10.1021/ja00531a063SCHWARTZ, JJ. Am. Chem. Soc.ELECTRON-TRANSFER IN NICKEL-CATALYZED ADDITION-REACTIONS33198010#N/ATRUE
2821
ja00524a04910.1021/ja00524a049FALSEhttps://doi.org/10.1021/ja00524a049INGLE, DMJ. Am. Chem. Soc.INTRAMOLECULAR ELECTRON-TRANSFER AND VALENCE ISOMERIZATION IN MONONUClEAR NICKEL-MACROCYClIC LIGAND COMPLEXES - FORMATION OF PARAMAGNETIC NICKEL(I)-Carbonyl COMPLEXES63198014#N/ATRUE
2822
ja00515a02810.1021/ja00515a028FALSEhttps://doi.org/10.1021/ja00515a028KOCHI, JKJ. Am. Chem. Soc.MECHANISM OF OXIDATIVE ADDITION - REACTION OF NICKEL(0) COMPLEXES WITH AROMATIC HALIDES3591979100#N/ATRUE
2823
ja00513a02710.1021/ja00513a027FALSEhttps://doi.org/10.1021/ja00513a027JACOBSON, SEJ. Am. Chem. Soc.SYNTHESIS AND P-31 NMR-STUDIES OF UNSYMMETRICAL CIS-DIPHOSPHINOALKENES AND THEIR COMPLEXES WITH NICKEL(II), PALLADIUM(II), AND PLATINUM(II)73197954#N/ATRUE
2824
ja00512a05710.1021/ja00512a057FALSEhttps://doi.org/10.1021/ja00512a057RUF, FJ. Am. Chem. Soc.BARRIERS AGAINST CONFIGURATIONAL ISOMERIZATION AT TETRAHEDRAL NICKEL(II)12197910#N/ATRUE
2825
ja00459a05110.1021/ja00459a051https://doi.org/10.1021/ja00459a051MCGARVEY, JJJ. Am. Chem. Soc.OBSERVATION OF A RAPID IONIC PHOTOASSOCIATION REACTION IN Q-SWITCHED LASER PHOTOLYSIS OF A PLANAR COMPLEX OF NICKEL(II) IN SOLUTIONPhotocatalyst5197710#N/AFALSE
2826
ja00508a07510.1021/ja00508a075FALSEhttps://doi.org/10.1021/ja00508a075SMITH, RJJ. Am. Chem. Soc.MACROCYClIC RING-SIZE CONTROL OF KINETIC LABILITY - KINETICS OF DISSOCIATION OF A RANGE OF NICKEL(II) COMPLEXES OF O2N2-DONOR MACROCYClES IN ACID16197923#N/ATRUE
2827
ja00456a05510.1021/ja00456a055FALSEhttps://doi.org/10.1021/ja00456a055RATHKE, MWJ. Am. Chem. Soc.NICKEL-CATALYST FOR ArylATION AND VinylATION OF LITHIUM ESTER ENOLATESx116197718#N/AFALSE
2828
ja00503a01010.1021/ja00503a010FALSEhttps://doi.org/10.1021/ja00503a010MCMILLIN, DRJ. Am. Chem. Soc.DETAILED ANALYSIS OF THE CHARGE-TRANSFER BANDS OF A BLUE COPPER PROTEIN - STUDIES OF THE NICKEL(II), MANGANESE(II), AND COBALT(II) DERIVATIVES OF AZURIN116197939#N/ATRUE
2829
ja00490a05110.1021/ja00490a051FALSEhttps://doi.org/10.1021/ja00490a051JACOBSON, RAJ. Am. Chem. Soc.UNUSUAL COORDINATION OF ALPHA-DIOXIME LIGAND IN BIS(CAMPHORQUINONE DIOXIMATO)NICKEL(II)22197821#N/ATRUE
2830
ja00477a02610.1021/ja00477a026FALSEhttps://doi.org/10.1021/ja00477a026OSTERYOUNG, RAJ. Am. Chem. Soc.ELECTROCHEMISTRY OF NI(II) AND BEHAVIOR OF OXIDE IONS IN CHLOROALUMINATE MELTS35197819#N/ATRUE
2831
ja00474a05310.1021/ja00474a053FALSEhttps://doi.org/10.1021/ja00474a053COUCOUVANIS, DJ. Am. Chem. Soc.TETRAHEDRAL MERCAPTIDE COMPLEXES - CRYSTAL AND MOLECULAR-STRUCTURES OF [(C6H5)4P]2M(SC6H5)4 COMPLEXES (M=CD(II), ZN(II), NI(II), CO(II), AND MN(II)245197823#N/ATRUE
2832
ja00472a01310.1021/ja00472a013FALSEhttps://doi.org/10.1021/ja00472a013GRIMMELMANN, EKJ. Am. Chem. Soc.THEORETICAL STUDIES OF KINETICS OF PLANAR-TETRAHEDRAL EQUILIBRATION IN NICKEL(II) COMPLEXES .2. REACTION PROBABILITIES AND RATE CONSTANTS9197833#N/ATRUE
2833
ja00472a01210.1021/ja00472a012FALSEhttps://doi.org/10.1021/ja00472a012Wang, ZXJ. Am. Chem. Soc.THEORETICAL STUDIES OF KINETICS OF PLANAR-TETRAHEDRAL EQUILIBRATION IN NICKEL(II) COMPLEXES .1. REACTION COORDINATES AND POTENTIAL-ENERGY SURFACES16197849#N/ATRUE
2834
ja00469a02410.1021/ja00469a024FALSEhttps://doi.org/10.1021/ja00469a024STUEHR, JEJ. Am. Chem. Soc.INTERACTIONS OF DIVALENT METAL-IONS WITH INORGANIC AND NUClEOSIDE PHOSPHATES .6. THERMODYNAMIC AND KINETIC STUDY OF NICKEL(II)-ADENOSINE 5'-TRIPHOSPHATE AND NICKEL(II)ADENOSINE 5'-DIPHOSPHATE SYSTEMS29197829#N/ATRUE
2835
ja00445a01610.1021/ja00445a016FALSEhttps://doi.org/10.1021/ja00445a016DAVIS, PHJ. Am. Chem. Soc.ELECTRONIC-STRUCTURE OF 3-COORDINATE NICKEL (I) - ELECTRON-PARAMAGNETIC RESONANCE OF NICKEL-DOPED HALOBIS(TRIPHENYLPHOSPHINE)COPPER(I)x49197725#N/AFALSE
2836
ja00469a02310.1021/ja00469a023FALSEhttps://doi.org/10.1021/ja00469a023STUEHR, JEJ. Am. Chem. Soc.INTERACTIONS OF DIVALENT METAL-IONS WITH INORGANIC AND NUClEOSIDE PHOSPHATES .5. KINETICS OF NICKEL(II) WITH HP3O104-, CYTIDINE 5'-TRIPHOSPHATE, HP2O73-, AND CYTIDINE 5'-DIPHOSPHATE15197813#N/ATRUE
2837
ja00463a07210.1021/ja00463a072FALSEhttps://doi.org/10.1021/ja00463a072STEPHENSON, LMJ. Am. Chem. Soc.MECHANISM OF NICKEL(0)-CATALYZED DIMERIZATION OF 1,3-BUTADIENE26197717#N/ATRUE
2838
ja00460a00110.1021/ja00460a001FALSEhttps://doi.org/10.1021/ja00460a001GRANT, DMJ. Am. Chem. Soc.C-13 RELAXATION IN PARAMAGNETIC-COMPLEXES OF AMINO-ACIDS - STRUCTURAL AND DYNAMICAL INFORMATION ON NICKEL(II) COMPLEXES OF HISTIDINE48197781#N/ATRUE
2839
ja00457a05310.1021/ja00457a053FALSEhttps://doi.org/10.1021/ja00457a053KLEIN, HFNICKEL PHOSPHINE COMPLEXES - CRYSTAL AND MOLECULAR-STRUCTURE OF A NEW NICKEL(I) COMPLEX - [NI(P(CH3)3)4]B(C6H5)41977#N/ATRUE
2840
ja004336k10.1021/ja004336kFALSEhttps://doi.org/10.1021/ja004336kSautet, PJ. Am. Chem. Soc.In the present work the interaction of different bitartrate isomers on the Cu(110) surface has been investigated systematically by using the Vienna Ab-initio Simulation Package (VASP), which performs periodical density functional theory (DFT) calculations. Among all bitartrate isomers the R,R-configuration is the most stable under the (3 1, 1 2) domain on the Cu surface. Its optical isomer, the S,S-bitartrate, is 10 kJ mol(-1) less stable in the same domain. This energy difference is sufficient to produce the distinct chiral assemblies observed after the adsorption of each optical isomer on the Cu surface. The calculations also showed that these domains are not formed due to intermolecular H-bonds, in contrast with the previous proposal by Raval et al.(Nature 2000, 23, 376). In fact, there is a formation of optimal intramolecular H-bonds in the chemisorption structures. A favorable packing orientation is also needed for the respective chiral domains. For instance, the S,S-configuration suffers from a destabilizing packing energy of 21 kJ mol(-1) under the same domain, due to a short contact between the H atoms of the hydroxy groups. These intramolecular H-bonds cause also some distortions on the bitartrate molecule, which appear to be dependent on the relative position of the a-hydroxy groups. The stability of the extended asymmetric domains, when the surface is modified by a chiral additive, might have important consequences for understanding and optimizing the properties of enantioselective heterogeneous catalysts.Stability of chiral domains produced by adsorption of tartaric acid isomers on the Cu(110) surface: A periodic density functional theory studyx105200131#N/AFALSE
2841
ja00451a05510.1021/ja00451a055FALSEhttps://doi.org/10.1021/ja00451a055VANHORN, DEJ. Am. Chem. Soc.SELECTIVE CARBON-CARBON BOND FORMATION VIA TRANSITION-METAL CATALYSIS .4. NOVEL-APPROACH TO CROSS-COUPLING EXEMPLIFIED BY NICKEL-CATALYZED REACTION OF ALKENYLZIRCONIUM DERIVATIVES WITH Aryl HALIDES166197710#N/ATRUE
2842
ja00451a04610.1021/ja00451a046FALSEhttps://doi.org/10.1021/ja00451a046SIGEL, HJ. Am. Chem. Soc.TERNARY COMPLEXES IN SOLUTION .26. STACKING INTERACTIONS IN MIXED-LIGAND COMPLEXES FORMED BY ADENOSINE OR INOSINE 5'-TRIPHOSPHATE, 2,2'-BIPYRIDYL, AND COBALT(II), NICKEL(II), COPPER(II), OR ZINC(II) - EVIDENCE FOR PHOSPHATE-PROTONATED COMPLEXES93197765#N/ATRUE
2843
ja00451a02010.1021/ja00451a020FALSEhttps://doi.org/10.1021/ja00451a020BUSCH, DHJ. Am. Chem. Soc.SPECTROCHEMICAL PROPERTIES OF TETRAGONAL COMPLEXES OF HIGH-SPIN NICKEL(II) CONTAINING MACROCYClIC LIGANDS249197748#N/ATRUE
2844
ja00449a01610.1021/ja00449a016FALSEhttps://doi.org/10.1021/ja00449a016IBERS, JAJ. Am. Chem. Soc.CYClOPROPANATION REACTIONS OF DIAZOALKANES WITH SUBSTITUTED OLEFINS IN PRESENCE AND ABSENCE OF NICKEL(0) AND PALLADIUM(0) CATALYSTS - STRUCTURE OF (DIAZOFLUORENE)BIS(TERT-BUTYL ISOCYANIDE)NICKEL(0) - COMPLEX CONTAINING A PI-BONDED DIAZOFLUORENE MOLECULE122197787#N/ATRUE
2845
ja00447a05010.1021/ja00447a050FALSEhttps://doi.org/10.1021/ja00447a050MARTELL, AEJ. Am. Chem. Soc.CONFORMATION AND SOLUTION EQUILIBRIA OF DIASTEREOISOMERIC DIPEPTIDES AND THEIR COPPER(II) AND NICKEL(II) COMPLEXES29197736#N/ATRUE
2846
ja00447a04910.1021/ja00447a049FALSEhttps://doi.org/10.1021/ja00447a049HIRAYAMA, YJ. Am. Chem. Soc.COPPER(II) AND NICKEL(II) COMPLEXES OF SULFHYDRYL AND IMIDAZOLE CONTAINING PEPTIDES - CHARACTERIZATION AND A MODEL FOR BLUE COPPER SITES59197725#N/ATRUE
2847
ja00422a07110.1021/ja00422a071FALSEhttps://doi.org/10.1021/ja00422a071BAREFIELD, EKJ. Am. Chem. Soc.PARAMAGNETIC, SQUARE-PYRAMIDAL NICKEL(II) Alkyl COMPLEXx4119766#N/AFALSE
2848
ja00446a01710.1021/ja00446a017FALSEhttps://doi.org/10.1021/ja00446a017NAKON, RJ. Am. Chem. Soc.KINETICS AND MECHANISM OF TETRADENTATE NICKEL(II) CHELATE AND METAL NITRILOTRIACETATE PROMOTED HYDROLYSIS OF METHYL GLYCINATE - ISOKINETIC RELATIONSHIP19197720#N/ATRUE
2849
ja00445a01510.1021/ja00445a015FALSEhttps://doi.org/10.1021/ja00445a015GRIFFITHS, CHJ. Am. Chem. Soc.HALOGEN OXIDATION OF BIS(DIPHENYLGLYOXIMATO) COMPLEXES OF NICKEL(II) AND PALLADIUM(II) - STOICHIOMETRY, STRUCTURE, AND THERMAL-STABILITY34197741#N/ATRUE
2850
ja00438a03310.1021/ja00438a033FALSEhttps://doi.org/10.1021/ja00438a033LEGG, JIJ. Am. Chem. Soc.5-COORDINATE AMINO-ACID COMPLEXES - SYNTHESIS AND CHARACTERIZATION OF NICKEL(II), COPPER(II), AND ZINC(II) COMPLEXES OF 1,5-DIAZACYClOOCTANE-N-MONOACETIC ACID19197629#N/ATRUE
2851
ja00438a03010.1021/ja00438a030FALSEhttps://doi.org/10.1021/ja00438a030JORDAN, RBJ. Am. Chem. Soc.RATE CONTROLLING PROTON-TRANSFER IN COMPLEXING OF COPPER(II) AND NICKEL(II) BY 2-AMINOMETHYLPYRIDINE13197633#N/ATRUE
2852
ja00437a06710.1021/ja00437a067FALSEhttps://doi.org/10.1021/ja00437a067NEGISHI, EJ. Am. Chem. Soc.NOVEL STEREOSPECIFIC ALKENYL-ALKENYL CROSS-COUPLING BY A PALLADIUM-CATALYZED OR NICKEL-CATALYZED REACTION OF ALKENYLALANES WITH ALKENYL HALIDES303197613#N/ATRUE
2853
ja004050f10.1021/ja004050fFALSEhttps://doi.org/10.1021/ja004050fMoiroux, JJ. Am. Chem. Soc.Molecular monolayers of immunoglobulins bearing terminally attached ferrocene poly(ethylene glycol) chains (IgG-PEG-Fc) were self-assembled at an electrode surface in a step-by-step manner involving antigen-antibody recognition reactions. The total number N of assembled IgG-PEG-Fc monolayers and the number of spacers ni separating two successive IgG-PEG-Fc monolayers were controlled and varied. Electron transport through the protein assembly involves the dynamics of the terminally attached PEG chains and isotopic electron exchange between ferrocene heads belonging to successive IgG-PEG-Fc monolayers. The model of elastic bounded diffusion enabled us to analyze quantitatively the dependence of the rate of electron transport on N, n(i), and the rate constant (k(e)) of isotopic electron exchange. Wiring of a molecular monolayer of redox enzyme is also quantitatively characterized.Elastic bounded diffusion and electron propagation: Dynamics of the wiring of a self-assembly of immunoglobulins bearing terminally attached ferrocene poly(ethylene glycol) chains according to a spatially controlled organizationx22200137#N/AFALSE
2854
ja004324z10.1021/ja004324zFALSEhttps://doi.org/10.1021/ja004324zHubbard, JLJ. Am. Chem. Soc.Using a series of Ir(I) and Rh(I) ketene complexes, conClusions about the structure and bonding of complexes of the fundamentally important ketene ligand Class are reached. In a unique comparison of X-ray structures of the same metal fragment to ketenes in both the eta (2)-(C,C) and the eta (2)-(C,O) binding mode, the Ir-Cl bond distances in complexes of trans-Cl(Ir)[P(i-Pr)(3)](2) to phenylketene [4, eta (2)-(C,C)] and diphenylketene [2a, eta (2)-(C,O)] are 2.371(3) and 2.285(2) Angstrom, respectively. This would be consistent with greater trans influence of a ketene ligand bound to a metal through its C double bondC bond than one connected by its C double bondO bond. Back-bonding of Ir(I) and Rh(I) to diphenylketene was assessed using trans-CI(M)[P(i-Pr)(3)](2)[eta (2)-(C,O)-diphenylketene] (2a and 2d). Most bond lengths and angles are identical, but slightly greater back-bonding by Ir(l) is suggested by the somewhat greater deformation of the ketene C double bondC double bondO system [C-C-O angles are 136.6(4) and 138.9(4) in the Ir and Rh cases 2a and 2d, respectively]. Syntheses of new labeled ketenes Ph2C double bond C-13 double bondO and Ph2C double bondC double bond O-18 and their Ir(I) and Rh(I) complexes are reported, along with the generation of an Ir(l) complex of PhCH double bond C-13 double bondO. The effects of isotopic substitution on infrared absorption data for ketene complexes are presented for the first time. Preliminary normal coordinate mode analysis allowed definitive assignment of absorptions ascribed to the C-O stretching frequencies of coordinated ketenes, which are near the absorptions for aromatic ring systems commonly found as substituents on ketenes. For free diphenylketene and four of its complexes and a phenylketene complex characterized by X-ray diffraction, the magnitude of the C-13-C-13 coupling between the two ketene carbons is correlated to carbon-carbon bond distance.First direct structural comparison of complexes of the same metal fragment to ketenes in both C,C- and C,O-bonding modes45200185#N/ATRUE
2855
ja00430a01810.1021/ja00430a018FALSEhttps://doi.org/10.1021/ja00430a018HECK, RFJ. Am. Chem. Soc.MECHANISM OF CarbonylATION OF HALO(BIS LIGAND )ORGANOPLATINUM(II), PALLADIUM(II), AND NICKEL(II) COMPLEXES270197621#N/ATRUE
2856
ja00428a06110.1021/ja00428a061FALSEhttps://doi.org/10.1021/ja00428a061KUMADA, MJ. Am. Chem. Soc.HIGH STEREOSELECTIVITY IN ASYMMETRIC GRIGNARD CROSS-COUPLING CATALYZED BY NICKEL-COMPLEXES OF CHIRAL(AMINOAlkylFERROCENYL)PHOSPHINES143197619#N/ATRUE
2857
ja00397a04810.1021/ja00397a048FALSEhttps://doi.org/10.1021/ja00397a048PICCOLO, OJ. Am. Chem. Soc.STEREOCHEMICAL ASPECTS OF THE NICKEL-CATALYZED AlkylATION OF ALLYLIC ALCOHOLSx4519819#N/AFALSE
2858
ja00428a02010.1021/ja00428a020FALSEhttps://doi.org/10.1021/ja00428a020WHIMP, POJ. Am. Chem. Soc.HYDROGEN ABSTRACTIONS FROM AN OLEFINIC DI(TERTIARY PHOSPHINE) PROMOTED BY COMPLEXES OF DIVALENT NICKEL, PALLADIUM, AND PLATINUM - CHELATE ETA-3-ALLYL, ETA-1-ALLYL, AND ETA-1-ALKENYL COMPLEXES AND CRYSTAL AND MOLECULAR-STRUCTURE OF A CHELATE ETA-1-ALLYLPALLADIUM(II) COMPLEX31197651#N/ATRUE
2859
ja003954y10.1021/ja003954yFALSEhttps://doi.org/10.1021/ja003954yFu, GCJ. Am. Chem. Soc.With a single protocol, commercially available Pd(P(t-Bu)(3))(2) can effect the Negishi cross-coupling of a wide range of Aryl and Vinyl chlorides with Aryl- and Alkylzinc reagents. The process tolerates nitro groups, and it efficiently generates sterically hindered biAryls. In addition, a high turnover number (>3000) can be achieved.The first general method for palladium-catalyzed Negishi cross-coupling of Aryl and Vinyl chlorides: Use of commercially available Pd(P(t-BU)(3))(2) as a catalystx385200151#N/AFALSE
2860
ja00426a05110.1021/ja00426a051FALSEWEISS, RUNUSUAL METALLOPORPHYRIN DERIVATIVE - INSERTION OF AN ETHOXYCarbonylCARBENE FRAGMENT INTO A NI-N BOND OF NICKEL(II) MESO-TETRAPHENYLPORPHINE - CRYSTAL AND MOLECULAR-STRUCTURE OF COMPLEX1976#N/ATRUE
2861
ja00390a02810.1021/ja00390a028FALSEhttps://doi.org/10.1021/ja00390a028PRESTON, KFJ. Am. Chem. Soc.SINGLE-CRYSTAL ELECTRON-PARAMAGNETIC-RES SPECTRA OF 2 NI(III) TETRAAZAMACROCYClE COMPLEXESx7198220#N/AFALSE
2862
ja00424a02710.1021/ja00424a027FALSEhttps://doi.org/10.1021/ja00424a027JORDAN, RBJ. Am. Chem. Soc.RATE CONTROLLING CHELATE RING ClOSING IN COMPLEXING OF NICKEL(II) BY PICOLINIC AND FUSARIC ACIDS11197612#N/ATRUE
2863
ja003831d10.1021/ja003831dFALSEhttps://doi.org/10.1021/ja003831dWieghardt, KJ. Am. Chem. Soc.The ligand 2-anilino-4,6-di-tert-butylphenol and its 2-(3,5-dichloroanilino)-4,6-di-tert-butylphenol analogue react in CH3CN or CH3OH solutions with divalent transition metal ions in the presence of air and triethylamine. Depending on the metal:ligand ratio (1:1, 1:2, or 1:3) and the presence (or absence) of the cyClic amine 1,4-dimethyl-1,4,7-triazacyClononane (dmtacn), the following complexes have been isolated as crystalline solids: [Co-III(L-ISQ)(3)] (1); [Cu-II(dmtacn)(L-ISQ)]PF6 (2); [Cu-II(L-ISQ)(2)] (3); [Ni-II(L-ISQ)(2)] (4a); [Ni-II(L-Cl(ISQ))(2)] (4b); [Pd-II(L-ISQ)(2)] (5). (L-ISQ)(-) represents the monoanionic o-iminobenzosemiquinonate radical (S-rad = 1/2). Compounds 1-5 have been characterized by single-crystal X-ray crystallography at 100(2) K. For all complexes it is unambiguously established that the O,N-coordinated o-iminobenzosemiquinonato(1-) ligand is present. Complexes 3, 4b, and 5 are square planar molecules which possess an S-t = 1/2, 0, and 0 ground state, respectively, as was established by H-1 NMR and EPR spectroscopies and variable-temperature magnetic susceptibility measurements. Complex 2 possesses an S-t = 1 ground state which is attained via strong intramolecular ferromagnetic coupling (J = +195 cm(-1)) between the d(x2-y2) magnetic orbital of the Cu-II ion and the pi -orbital of the ligand radical. Complex 1 contains three mutually orthogonal (L-ISQ)(-.) ligands and has an S-t = 3/2 ground state. It is shown that the electronic structure of 4a and 5 is adequately described as singlet diradical containing a divalent, diamagnetic d(8) configurated central metal ion and two strongly antiferromagnetically coupled (L-ISQ)(-) radical ligands. It is conCluded that the same electronic structure prevails in the Classic bis(o-diiminobenzosemiquinonato)- and bis(o-benzosemiquinonato)metal complexes of Ni-II, Pd-II, and Pt-II. The electrochemistry of all complexes has been investigated in detail. For 3, la, and 5 a series of reversible one-electron-transfer waves leads to the formation of the anions and cations [M(L)(2)](2-,1-,1+,2+) which have been characterized spectroelectrochemically. All redox processes are shown to be ligand-based.Electronic structure of bis(o-iminobenzosemiquinonato)metal complexes (Cu, Ni, Pd). The art of establishing physical oxidation states in transition-metal complexes containing radical ligandsx488200133#N/AFALSE
2864
ja00422a03310.1021/ja00422a033FALSEhttps://doi.org/10.1021/ja00422a033TAKAYA, HJ. Am. Chem. Soc.NICKEL-CATALYZED REACTIONS INVOLVES STRAINED BONDS .13. PERISELECTIVITIES AND REGIOSELECTIVITIES OF NICKEL(O)-CATALYZED VALENCE ISOMERIZATION OF 1,8-BISHOMOCUBANE SYSTEM - MOLECULAR-ORBITAL CONSIDERATION10197672#N/ATRUE
2865
ja004191h10.1021/ja004191hhttps://doi.org/10.1021/ja004191hBu, XHJ. Am. Chem. Soc.alpha-Iminocarboxamidato-Nickel(II) ethylene polymerization catalysts168200126#N/ATRUE
2866
ja00379a03910.1021/ja00379a039FALSEhttps://doi.org/10.1021/ja00379a039KODAMA, MJ. Am. Chem. Soc.NOVEL NICKEL(II) COMPLEXES WITH DOUBLY DEPROTONATED DIOXOPENTAAMINE MACROCYClIC LIGANDS FOR UPTAKE AND Activation OF MOLECULAR-OXYGENx117198220#N/AFALSE
2867
ja00410a04410.1021/ja00410a044FALSEhttps://doi.org/10.1021/ja00410a044WILLIAMSON, ANJ. Am. Chem. Soc.CYClOPENTADIENYLBIS(LIGAND)NICKEL(I) - SYNTHESIS AND CHARACTERIZATION, INClUDING THE X-RAY STRUCTURE OF ETA-5-CYClOPENTADIENYL-1,1'-BIPYRIDYLNICKEL(I) - OBSERVATIONS ON THE MECHANISM OF SUBSTITUTION OF NICKELOCENE46198126#N/ATRUE
2868
ja00373a01310.1021/ja00373a013FALSEhttps://doi.org/10.1021/ja00373a013PELLACANI, GCJ. Am. Chem. Soc.COORDINATION BEHAVIOR OF L-ASPARTIC ACID - TERNARY NICKEL(II) COMPLEXES WITH IMIDAZOLES - CRYSTAL AND MOLECULAR-STRUCTURE OF (L-ASPARTATE)TRIS(IMIDAZOLE)NICKEL(II)x42198234#N/AFALSE
2869
ja003719f10.1021/ja003719fFALSEhttps://doi.org/10.1021/ja003719fMcBreen, PHJ. Am. Chem. Soc.Selective C-C bond Activation of methyl pyruvate on Ni(111) to yield surface methoxyCarbonylx13200136#N/AFALSE
2870
ja00407a02710.1021/ja00407a027FALSEhttps://doi.org/10.1021/ja00407a027SCHAMMEL, WPJ. Am. Chem. Soc.SYNTHESIS AND CHARACTERIZATION OF A NOVEL FAMILY OF DIMERIC NICKEL(II) COMPLEXES - BIMETALLIC SPECIES SEPARATED BY A PERSISTENT VOID39198127#N/ATRUE
2871
ja00405a02910.1021/ja00405a029FALSEhttps://doi.org/10.1021/ja00405a029SCHWARTZ, JJ. Am. Chem. Soc.ELECTRON-TRANSFER IN NICKEL-CATALYZED ADDITION-REACTIONS OF ORGANOZIRCONIUM COMPOUNDS TO UNSATURATED-KETONES49198148#N/ATRUE
2872
ja00402a06710.1021/ja00402a067FALSEhttps://doi.org/10.1021/ja00402a067MACNEIL, PAJ. Am. Chem. Soc.HYBRID MULTI-DENTATE LIGANDS - TRIDENTATE AMIDOPHOSPHINE COMPLEXES OF NICKEL(II) AND PALLADIUM(II)75198114#N/ATRUE
2873
ja004004f10.1021/ja004004fFALSEhttps://doi.org/10.1021/ja004004fMori, MJ. Am. Chem. Soc.Cross-coupling reaction of oxo-pi-allylnickel complex generated from 1,3-diene under an atmosphere of carbon dioxide98200129#N/ATRUE
2874
ja00398a01110.1021/ja00398a011FALSEhttps://doi.org/10.1021/ja00398a011DAHL, LFJ. Am. Chem. Soc.SYNTHESIS AND STEREOCHEMICAL ANALYSIS OF THE TRIANGULAR COBALT-DINICKEL ClUSTERS (ETA-5-C5H5-NMEN)CONI2(ETA-5-C5H5)2(MU3-CO)2 (WHERE N= 0, 1, 5) - DIRECT EVIDENCE FOR THE ANTI-BONDING TRIMETAL CHARACTER OF THE UNPAIRED ELECTRON IN THE FISCHER-PALM NI3(ETA-5-C5H5)3(MU-3-CO)2 AND RESULTING GEOMETRICAL EFFECTS UPON FORMAL OXIDATION BY REPLACEMENT OF A NICKEL WITH A COBALT ATOM58198142#N/ATRUE
2875
ja00362a00910.1021/ja00362a009FALSEhttps://doi.org/10.1021/ja00362a009ENDICOTT, JFJ. Am. Chem. Soc.OXIDATION-REDUCTION REACTIONS WITH MACROCYClIC LIGANDS - DEPENDENCE OF THE RATE ADVANTAGE FOR THE INNER-SPHERE ELECTRON-TRANSFER PATHWAY ON ELECTRONIC-STRUCTURE FOR LOW-SPIN CO-III,CO-II,NI-III,NI-II, AND CU-III,CU-II COUPLESx381983121#N/AFALSE
2876
ja003576x10.1021/ja003576xFALSEhttps://doi.org/10.1021/ja003576xHu, PJ. Am. Chem. Soc.The study of catalytic behavior begins with one seemingly simple process, namely the hydrogenation of O to H2O on platinum. Despite the apparent simplicity its mechanism has been much debated. We have used density functional theory with,gradient corrections to examine microscopic reaction pathways for several elementary steps implicated in this fundamental catalytic process. We find that H2O formation from chemisorbed O and H atoms is a highly activated process. The largest barrier along this route, with a value of similar to1 eV, is the addition of the first H to O to produce OH. Once formed, however, OH groups are easily hydrogenated to H2O with a barrier of similar to0.2 eV. Disproportionation reactions with 1:1 and 2:1 stoichiometries of H2O and O have been examined as alternative routes for OH formation. Both stoichiometries of reaction produce OH groups with barriers that are much lower than that associated with the O + H reaction. H2O, therefore, acts as an autocatalyst in the overall H O formation process. Disproportionation with a 2:1 stoichiometry is thermodynamically and kinetically favored over disproportionation with a l:I stoichiometry. This highlights an additional (promotional) role of the second H2O molecule in this process. In support of our previous suggestion that the key intermediate in the low-temperature H2O formation reaction is a mixed OH and H2O overlayer we find that then is a very large barrier for the dissociation of the second H2O molecule in the 2:1 disproportionation process. We suggest that the proposed intermediate is then hydrogenated to H2O through a very facile proton transfer mechanism.Catalytic water formation on platinum: A first-principles studyx272200151#N/AFALSE
2877
ja00356a02110.1021/ja00356a021FALSEhttps://doi.org/10.1021/ja00356a021Szostak, MJ. Am. Chem. Soc.REDUCTION OF DELTA-2-ISOXAZOLINES .3. RANEY-NICKEL CATALYZED FORMATION OF BETA-HYDROXY KETONESX308198392#N/AFALSE
2878
ja00352a02110.1021/ja00352a021FALSEhttps://doi.org/10.1021/ja00352a021WHITE, AHJ. Am. Chem. Soc.LIGAND DESIGN AND METAL-ION RECOGNITION - INTERACTION OF NICKEL(II) WITH 17-MEMBERED TO 19-MEMBERED MACROCYClES CONTAINING O2N3 AND O3N2 DONOR SETS AND THE X-RAY STRUCTURE OF THE PARENT 17-MEMBERED MACROCYClIC LIGANDx126198325#N/AFALSE
2879
ja00349a08010.1021/ja00349a080FALSEhttps://doi.org/10.1021/ja00349a080COOPER, SRJ. Am. Chem. Soc.CROWN THIOETHER CHEMISTRY - THE NICKEL(II) COMPLEX OF 1,4,7,10,13,16-HEXATHIACYClOOCTADECANE, THE HEXATHIA ANALOG OF 18-CROWN-6x58198319#N/AFALSE
2880
ja00396a03010.1021/ja00396a030FALSEhttps://doi.org/10.1021/ja00396a030MOCAK, JJ. Am. Chem. Soc.MOLECULAR-SPECIES CONTAINING PERSISTENT VOIDS - TEMPLATE SYNTHESIS AND CHARACTERIZATION OF A SERIES OF LACUNAR-NICKEL(II) COMPLEXES AND THE CORRESPONDING FREE LIGANDS53198127#N/ATRUE
2881
ja00394a05010.1021/ja00394a050FALSEhttps://doi.org/10.1021/ja00394a050GRAY, GMJ. Am. Chem. Soc.SYNTHESIS AND STRUCTURE OF TRANS-[[[CIS-TETRACarbonylBIS(N-((2-DIPHENYLPHOSPHINAMIDO)ETHYL)SALICYLALDIMINO-P)]MOLYBDENUM(0)]-N,N',O,O']NICKEL(II), A NOVEL BIMETAL TRANS-LIGATING TETRADENTATE SCHIFF-BASE COMPLEX WITH A FLY-OVER CHAIN CONTAINING A METAL ATOM34198124#N/ATRUE
2882
ja003861g10.1021/ja003861gFALSEhttps://doi.org/10.1021/ja003861gCavell, KJKinetic and density functional studies on Alkyl-carbene elimination from Pd-II heterocylic carbene complexes: A new type of reductive elimination with Clear implications for catalysis2001#N/ATRUE
2883
ja00380a00510.1021/ja00380a005FALSEhttps://doi.org/10.1021/ja00380a005SMITH, KMJ. Am. Chem. Soc.Vinyl INFLUENCES ON PROTOHEME RESONANCE RAMAN-SPECTRA - NICKEL(II) PROTOPORPHYRIN-IX WITH DEUTERATED Vinyl GROUPS168198229#N/ATRUE
2884
ja00338a01810.1021/ja00338a018FALSEhttps://doi.org/10.1021/ja00338a018BUIST, RJJ. Am. Chem. Soc.NMR-STUDIES OF NICKEL HYDRIDES - THE INTRAMOLECULAR REARRANGEMENT OF THE HYDRIDOTRIS(TRI-PARA-TOLYL PHOSPHITE)NICKEL(II) IONx8198436#N/AFALSE
2885
ja00379a05310.1021/ja00379a053FALSEhttps://doi.org/10.1021/ja00379a053DAHL, LFJ. Am. Chem. Soc.TRANSITION-METAL-PROMOTED CARBON CARBON BOND FORMATION BY REDUCTIVE DIMERIZATION OF CARBON-DISULFIDE - DIRECT SYNTHESIS OF THE BIS(1,2-DITHIOLENE-LIKE) TETRATHIOOXALATO (C2S4) LIGAND FROM CARBON-DISULFIDE BY REACTION WITH THE DIMERIC NICKEL(I) COMPLEXES NI2(ETA-5-C5R5)2(MU-CO)2(R=H,ME)57198220#N/ATRUE
2886
ja00379a01010.1021/ja00379a010FALSEhttps://doi.org/10.1021/ja00379a010SIGEL, HJ. Am. Chem. Soc.TERNARY COMPLEXES IN SOLUTION .41. AS MODELS FOR ENZYME METAL-ION SUBSTRATE COMPLEXES - COMPARISON OF THE COORDINATION TENDENCY OF IMIDAZOLE AND AMMONIA TOWARD THE BINARY COMPLEXES OF MN(II), CO(II), NI(II), CU(II), ZN(II), OR CD(II) AND URIDINE 5'-TRIPHOSPHATE OR ADENOSINE 5'-TRIPHOSPHATE71198244#N/ATRUE
2887
ja00331a01810.1021/ja00331a018FALSEhttps://doi.org/10.1021/ja00331a018KODAMA, MJ. Am. Chem. Soc.MACROCYClIC DIOXO PENTAAMINES - NOVEL LIGANDS FOR 1-1 NI(II)-O2 ADDUCT FORMATIONx97198446#N/AFALSE
2888
ja00370a01110.1021/ja00370a011FALSEhttps://doi.org/10.1021/ja00370a011STROMMEN, DPJ. Am. Chem. Soc.RESONANCE RAMAN-SPECTRA AND VIBRATIONAL ASSIGNMENTS OF RED AND BLACK FORMS OF POTASSIUM BIS(DITHIOOXALATO)NICKEL(II)16198223#N/ATRUE
2889
ja00328a05010.1021/ja00328a050FALSEhttps://doi.org/10.1021/ja00328a050VEIDIS, MJ. Am. Chem. Soc.TRANSMETALATION REACTIONS OF TETRANUClEAR COPPER(II) COMPLEXES .2. STOICHIOMETRY AND PRODUCTS OF REACTION OF [(DENC)CUCl]4O2, [(DENC)CUCl]4(CO3)2, [(DENC)CUCl]4Cl4, AND (DENC)4CU4Cl6O COMPLEXES (DENC = N,N-DIETHYLNICOTINAMIDE) WITH NI(NS)2 COMPLEXES (NS IS AN S-METHYL HYDRAZINECARBODITHIOATE SCHIFF-BASE), THE KINETICS OF PRODUCT ISOMERIZATION IN APROTIC-SOLVENTS, AND INHIBITION OF COPPER-CATALYZED PHENOLIC OXIDATIVE COUPLING BY DIOXYGEN THROUGH TRANSMETALATIONSCx79198441#N/AFALSE
2890
ja00366a04010.1021/ja00366a040FALSEhttps://doi.org/10.1021/ja00366a040ZERNER, BJ. Am. Chem. Soc.NICKEL(II)-PROMOTED ETHANOLYSIS AND HYDROLYSIS OF N-(2-PYRIDYLMETHYL)UREA - A MODEL FOR UREASE91198226#N/ATRUE
2891
ja00366a01110.1021/ja00366a011FALSEWASYLISHEN, RESTUDIES OF PHOSPHORUS(III) LIGANDS AND THEIR COMPLEXES OF NI(II), PD(II), AND PT(II) IMMOBILIZED ON INSOLUBLE SUPPORTS BY HIGH-RESOLUTION SOLID-STATE P-31 NMR USING MAGIC-ANGLE SPINNING TECHNIQUES1982#N/ATRUE
2892
ja00315a02610.1021/ja00315a026FALSEhttps://doi.org/10.1021/ja00315a026UENO, AJ. Am. Chem. Soc.CATALYST PREPARATION PROCEDURE PROBED BY EXAFS SPECTROSCOPY .1. NICKEL ON SILICAx114198413#N/AFALSE
2893
ja00365a03310.1021/ja00365a033FALSEhttps://doi.org/10.1021/ja00365a033KUMADA, MJ. Am. Chem. Soc.ASYMMETRIC-SYNTHESIS CATALYZED BY CHIRAL FERROCENYLPHOSPHINE TRANSITION-METAL COMPLEXES .2. NICKEL-CATALYZED AND PALLADIUM-CATALYZED ASYMMETRIC GRIGNARD CROSS-COUPLING266198276#N/ATRUE
2894
ja00365a01810.1021/ja00365a018FALSEhttps://doi.org/10.1021/ja00365a018IBERS, JAJ. Am. Chem. Soc.(TETRABENZOPORPHYRINATO)NICKEL(II) IODIDE - A DOUBLY MIXED-VALENCE MOLECULAR CONDUCTOR122198292#N/ATRUE
2895
ja00348a01210.1021/ja00348a012FALSEhttps://doi.org/10.1021/ja00348a012IBERS, JAJ. Am. Chem. Soc.CHARGE-DENSITY AND BONDING IN (5,10,15,20-TETRAMETHYLPORPHYRINATO)NICKEL(II) - A COMBINED EXPERIMENTAL AND THEORETICAL-STUDY55198347#N/ATRUE
2896
ja00347a01610.1021/ja00347a016FALSEhttps://doi.org/10.1021/ja00347a016IBERS, JAJ. Am. Chem. Soc.CONDUCTIVE MOLECULAR-CRYSTALS - STRUCTURAL, MAGNETIC, AND CHARGE-TRANSPORT PROPERTIES OF (5,10,15,20-TETRAMETHYLPORPHYRINATO)NICKEL(II) IODIDE62198384#N/ATRUE
2897
ja00343a05610.1021/ja00343a056FALSEhttps://doi.org/10.1021/ja00343a056WELCH, AJUNIQUE STABLE ORGANOMETALLIC NICKEL(III) COMPLEXES - SYNTHESES AND THE MOLECULAR-STRUCTURE OF NI[C6H3(CH2NME2)2-ORTHO,ORTHO']I21983#N/ATRUE
2898
ja00340a02610.1021/ja00340a026FALSEhttps://doi.org/10.1021/ja00340a026REDDY, GSEFFECT OF NICKEL(II) AND COBALT(III) AND OTHER METAL-IONS ON THE RACEMIZATION OF FREE AND BOUND L-ALANINE1983#N/ATRUE
2899
ja00337a04010.1021/ja00337a040FALSEhttps://doi.org/10.1021/ja00337a040
TRZCINSKABANCROFT, B
HIEBER AND BRUCK REVISITED - THE X-RAY MOLECULAR-STRUCTURE AND PROPERTIES OF THE ANIONIC PRECURSOR TO HIEBERS NICKEL(IV) DITHIOLATE, [K(2,2,2-CRYPT)][NI(S2CC6H5)3]1984#N/ATRUE
2900
ja00334a08410.1021/ja00334a084FALSEhttps://doi.org/10.1021/ja027049kSPRINGER, JPTOTAL SYNTHESIS OF THE UNIQUE MYCOTOXIN ALPHA-CYClOPIAZONIC ACID (ALPHA-CA) - AN UNUSUAL DIMETHYLZINC-MEDIATED REPLACEMENT OF A PHENYLTHIO SUBSTITUENT BY A METHYL-GROUP AND A CONTRATHERMODYNAMIC RANEY-NICKEL DESULFURIZATION REACTION1984#N/ATRUE
2901
ja00330a02110.1021/ja00330a021FALSEhttps://doi.org/10.1021/ja00330a021IBERS, JAJ. Am. Chem. Soc.DIRECT PREPARATION OF A SIROHEME MODEL-COMPOUND - SYNTHESIS AND STRUCTURE OF (5,10,15,20-TETRAMETHYLISOBACTERIOCHLORINATO)NICKEL(II)74198459#N/ATRUE
2902
ja00284a02710.1021/ja00284a027https://doi.org/10.1021/ja00284a027SCAIANO, JCJ. Am. Chem. Soc.SENSITIZED PHOTOREDUCTION OF BIS(ACETYLACETONATO)NICKEL(II) BY TRIPLET-STATE AROMATIC KETONESPhotocatalyst38198660#N/AFALSE
2903
ja00323a02110.1021/ja00323a021FALSEhttps://doi.org/10.1021/ja00323a021MCDOWELL, CAJ. Am. Chem. Soc.A SOLID-STATE HIGH-RESOLUTION C-13 NMR-STUDY OF OCTAETHYLPORPHYRIN AND ITS ZINC(II) AND NICKEL(II) METAL-COMPLEXES USING CP-MAS TECHNIQUES22198443#N/ATRUE
2904
ja00316a00810.1021/ja00316a008FALSEhttps://doi.org/10.1021/ja00316a008BOCIAN, DFJ. Am. Chem. Soc.RESONANCE RAMAN-SPECTRA OF NICKEL(II) ACETYL AND Carbonyl DEUTEROPORPHYRINS - EFFECTS OF SELECTIVE 2 VS 4 SUBSTITUTION AND ALTERED ELECTRON-WITHDRAWING CAPABILITY OF CONJUGATING GROUPS26198450#N/ATRUE
2905
ja00314a05710.1021/ja00314a057FALSEhttps://doi.org/10.1021/ja00314a057LIPSCOMB, WNJ. Am. Chem. Soc.STRUCTURES OF NICKEL(II) AND COBALT(II) CARboxYPEPTIDASE-A53198412#N/ATRUE
2906
ja003137y10.1021/ja003137yFALSEhttps://doi.org/10.1021/ja003137yDiMagno, SGJ. Am. Chem. Soc.In the first part of this paper, the syntheses, structural characterization, molecular modeling, and electronic spectra for planar and nonplanar perfluoroatkylated porphyrins, (R-f)(4)P's, are reported. These studies demonstrate that the intrinsic substituent effect of the perfluoroAlkyl group on the long-wavelength electronic spectrum of porphyrins is substantial, and similar tin magnitude) to that of a phenyl ring, Moreover, it is shown that out-of-plane distortion of (R-f)(4)P'S has a negligible impact on their electronic spectra. These data bolster the findings of our earlier work and demonstrate that nonplanarity of (R-f)(4)P'S does not result in a red-shift in their optical spectra. In the second part of this paper, time-dependent density functional spectral calculations (B3LYP/6-311G*/TD) for porphine, 5,10,15,20-tetrakis(trifluoromethyl)porphrin and 5,10,15, 20-tetramethylporphyrin in a variety of ruffled conformations are reported. The results of these studies indicate that (1) substantial ruffling of porphyrins has a negligible effect upon their electronic spectra, (2) similarly small effects upon electronic spectra are predicted if electron-withdrawing or electron-releasing groups decorate the porphyrin periphery, (3) for sterically encumbered porphyrins, ruffling can actually result in hypsochromic shifts in various absorption bands, and (4) the bulk of the red-shift commonly thought to be due to nonplanar distortion actually arises from other substituent effects. These results pose serious challenges to previous theoretical and empirical studies that have sought to find a cause-and-effect relationship between nonplanarity and electronic spectra in porphyrins.On the negligible impact of ruffling on the electronic spectra of porphine, tehramethylporphyrin, and perfluoroAlkylporphyrins96200129#N/ATRUE
2907
ja00275a08510.1021/ja00275a085FALSEhttps://doi.org/10.1021/ja00275a085IHLE, NCJ. Am. Chem. Soc.NICKEL-CATALYZED INTRAMOLECULAR [4 + 4] CYClOADDITIONS - A NEW METHOD FOR THE SYNTHESIS OF POLYCYClES CONTAINING 8-MEMBERED RINGSx181198629#N/AFALSE
2908
ja00309a01510.1021/ja00309a015FALSEhttps://doi.org/10.1021/ja029823+OLMSTEAD, MMA COMPLEX CONTAINING A NI-O UNIT AT THE CENTER OF A PORPHYRIN - THE X-RAY CRYSTAL AND MOLECULAR-STRUCTURE OF THE NICKEL(II) COMPLEX OF OCTAETHYLPORPHYRIN N-OXIDE DIANION1985#N/ATRUE
2909
ja00308a06210.1021/ja00308a062FALSEhttps://doi.org/10.1021/ja00308a062WHITTLESEY, BRJ. Am. Chem. Soc.REACTIONS OF COORDINATED LIGANDS - COUPLING OF 2 DIPHOSPHENES (P=P) AT A METAL CENTER TO GIVE A COORDINATED PHOSPHAMETALLOCYClOPENTANE - SYNTHESIS AND X-RAY STRUCTURE OF (TERT-BUPP-TERT-BU)NI(TERT-BUP-TERT-BUP-TERT-BUP-TERT-BUP) - A SQUARE-PLANAR NI(II) GEOMETRY IMPARTED BY STERICALLY DEMANDING LIGANDS39198554#N/ATRUE
2910
ja00303a02210.1021/ja00303a022FALSEhttps://doi.org/10.1021/ja00303a022GOFF, DAJ. Am. Chem. Soc.SYNTHESIS OF NICKEL(II) ISOBACTERIOCHLORINS FROM NICKEL(II) COMPLEXES OF CHLOROPHYLL DERIVATIVES32198522#N/ATRUE
2911
ja00265a01610.1021/ja00265a016FALSEhttps://doi.org/10.1021/ja00265a016WING, RMJ. Am. Chem. Soc.REDOX CHEMISTRY AND SPECTROSCOPY OF toluene-3,4-DITHIOL (TDTH2) AND OF ITS M(TDT)22-/- COMPLEXES WITH ZINC(II), COPPER(II), NICKEL(II), COBALT(II), IRON(II), AND MANGANESE(II) - FORMATION OF A STABLE DN-(.SR) BOND UPON OXIDATION BY ONE ELECTRONx76198650#N/AFALSE
2912
ja00299a01810.1021/ja00299a018FALSEhttps://doi.org/10.1021/ja00299a018LIPPARD, SJJ. Am. Chem. Soc.STEREOCHEMICAL AND ELECTRONIC SPIN STATE TUNING OF THE METAL CENTER IN THE NICKEL(II) TROPOCORONANDS53198527#N/ATRUE
2913
ja00264a02310.1021/ja00264a023FALSEhttps://doi.org/10.1021/ja00264a023ESPENSON, JHJ. Am. Chem. Soc.KINETICS AND MECHANISM OF THE AlkylNICKEL FORMATION IN ONE-ELECTRON REDUCTIONS OF Alkyl-HALIDES AND HYDROPEROXIDES BY A MACROCYClIC NICKEL(I) COMPLEXx147198664#N/AFALSE
2914
ja002638g10.1021/ja002638gFALSEhttps://doi.org/10.1021/ja002638gRheingold, ALJ. Am. Chem. Soc.Organometallic cobalt(II) and nickel(II) complexes supported by thioether ligation: Unexpected nickel Alkylation by the borato ligand phenyltris ((tert-butylthio)methyl)boratex67200113#N/AFALSE
2915
ja00297a02210.1021/ja00297a022FALSEhttps://doi.org/10.1021/ja00297a022EIGENBROT, CWJ. Am. Chem. Soc.STUDY OF THE REACTIONS OF SUBSTITUTED ALLENES WITH TRIS(TRIPHENYLPHOSPHINE)NICKEL(0) - AN ANALYSIS OF THE FACTORS AFFECTING THE REGIOCHEMISTRY AND STEREOCHEMISTRY OF PI-COMPLEX FORMATION AND COUPLING TO FORM NICKELACYClOPENTANE COMPLEXES48198523#N/ATRUE
2916
ja00294a03310.1021/ja00294a033FALSEhttps://doi.org/10.1021/ja00294a033RENNER, MWJ. Am. Chem. Soc.STRUCTURE OF OCTAETHYLPORPHYRIN N-OXIDE AND THE CHARACTERIZATION OF ITS NICKEL(II) AND COPPER(II) COMPLEXES47198515#N/ATRUE
2917
ja00251a03610.1021/ja00251a036FALSEhttps://doi.org/10.1021/ja00251a036TOUR, JMJ. Am. Chem. Soc.A NOVEL NICKEL-CHROMIUM CATALYST SYSTEM FOR CYClIZATION VIA INTRAMOLECULAR CARBAMETALATIONx113198721#N/AFALSE
2918
ja00251a01610.1021/ja00251a016FALSEhttps://doi.org/10.1021/ja00251a016FABBRIZZI, LJ. Am. Chem. Soc.N-(AMINOETHYL)CYClAM - A TETRAAZA MACROCYClE WITH A COORDINATING TAIL (SCORPIAND) - ACIDITY CONTROLLED COORDINATION OF THE SIDE-CHAIN TO NICKEL(II) AND NICKEL(III) CATIONSx139198718#N/AFALSE
2919
ja00244a06510.1021/ja00244a065FALSEhttps://doi.org/10.1021/ja00244a065WALSH, CTJ. Am. Chem. Soc.NICKEL-CONTAINING CO DEHYDROGENASE CATALYZES REVERSIBLE DECarbonylATION OF ACETYL COA WITH RETENTION OF STEREOCHEMISTRY AT THE METHYL-GROUPx26198720#N/AFALSE
2920
ja00289a03810.1021/ja00289a038FALSEhttps://doi.org/10.1021/ja00289a038POWER, PPJ. Am. Chem. Soc.SYNTHESES AND X-RAY STRUCTURES OF [LI(THF)4][NI(NPH2)3].0.5C7H8, [(NI(NPH2)2)2], AND [(CO(NPH2)2)2] - STRUCTURAL CHARACTERIZATION OF 3-COORDINATE 1ST-ROW D7 AND D8 COMPLEXES88198520#N/ATRUE
2921
ja002820h10.1021/ja002820hhttps://doi.org/10.1021/ja002820hBochmann, MJ. Am. Chem. Soc.The formation of adducts of tris(pentafluorophenyl)borane with strongly coordinating anions such as CN- and [M(CN)(4)](2-) (M = Ni, Pd) is a synthetically facile route to the bulky, very weakly coordinating anions [CN{B(C6F5)(3)}(2)](-) and [M{CNB(C6F5)(3)}(4)](2-) which are isolated as stable NHMe2Ph+ and CPh3+ salts. The crystal structures of [CPh3][CN{B(C6F5)(3)}(2)] (1), [CPh3][ClB(C6F5)(3)] (2), [NHMe2Ph](2)[Ni{CNB(C6F5)(3)}(4)]. 2Me(2)CO (4b . 2Me(2)CO), [CPh3](2)[Ni{CNB(C6F5)(3)}(4)]. 2CH(2)Cl(2) (4c . 2CH(2)Cl(2)), and [CPh3](2)[Pd{CNB(C6F5)(3)}(4)]. 2CH(2)Cl(2) (5c . 2CH(2)Cl(2)) are reported. The CN stretching frequencies in 4 and 5 are shifted by similar to 110 cm(-1) to higher wavenumbers compared to the parent tetracyano complexes in aqueous solution, although the M-C and C-N distances show no significant change on B(C6F5)(3) coordination. Zirconocene dimethyl complexes L2ZrMe2 [L-2 = Cp-2, SBI = rac-Me2Si(Ind)(2)] react with 1, 4c or 5c in benzene solution at 20 degreesC to give the salts of binuClear methyl-bridged cations, [(L2ZrMe)(2)(mu -Me)] [CN{B(C6F5)(3)}(2)] and [(L2ZrMe)(2)(mu -Me)](2)[M{CNB-(C6F5)(3)}(4)] The reactivity of these species in solution was studied in comparison with the known [{(SBI)ZrMe}(2)(mu -Me)][B(C6F5)(4)]. While the latter reacts with excess [CPh3][B(C6F5)(4)] in benzene to give the mononuClear ion pair [(SBI)ZrMe+. . .B(C6F5)(4)(-)] in a pseudo-first-order reaction, k = 3 x 10(-4) s(-1), [(L2- ZrMe)(2)(mu -Me)][CN{B(C6F5)(3)}(2)] reacts to give a mixture of L2ZrMe(mu -Me)B (C6F5)(3) and L2ZrMe(mu -NC)B(C6F5)(4)] Recrystallization of [CpZr-2(mu -Me)(2)AlMe2] [CN{B(C6F5)(3)}(2)] affords Cp2ZrMe(mu -NC)B(C6F5)(3) 6, the X-ray structure of which is reported. The stability of [L2ZrMe)(2)(mu -Me)]X-+(-) decreases in the order X [B(C6F5)(4)] > [M{CNB(C6F5)(3)}(4)] > [CN{B(C6F5)(3)}(2)] and increases strongly with the steric bulk of L-2 Cp-2 << SBI. Activation of (SBI)ZrMe2 by 1 in the presence of AlBu3i gives extremely active ethene polymerization catalysts. Polymerization studies at 1-7 bar monomer pressure suggest that these, and by implication most other highly active ethene polymerization catalysts, are strongly mass-transport limited. By contrast, monitoring propene polymerization activities with the systems (SBI)ZrMe2/1/AlBu3i and CGCTiMe(2)/ 1/AlBu3i at 20 degreesC as a function of catalyst concentration demonstrates that in these cases mass-transport limitation is absent up to [metal] approximate to 2 x 10(-5) mol L-1. Propene polymerization activities decrease in the order [CN{B(C6F5)(3)}(2)](-) > [B(C6F5)(4)](-) > [M{CNB(C6F5)(3)}(4)](2-) >> [MeB(C6F5)(3)](-), with differences in Activation barriers relative to [CN{B(C6F5)(3)}(2)](-) of Delta DeltaG double dagger = 1.1 (B(C6F5)(4)(-)), 4.1 (Ni{CNB(C6F5)(3)}(4)(2-)) and 10.7-12.8 kJ mol(-1) (MeB(C6F5)(3)(-)). The data suggest that even in the case of very bulky anions with delocalized negative charge the displacement of the anion by the monomer must be involved in the rate-limiting step.Synthesis, structures, and reactivity of weakly coordinating anions with delocalized berate structure: The assessment of anion effects in metallocene polymerization catalysts206200194#N/ATRUE
2922
ja002792310.1021/ja0027923FALSEhttps://doi.org/10.1021/ja0027923Amunugama, RJ. Am. Chem. Soc.Threshold collision-induced dissociation of M+(pyridine) with xenon is studied using guided ion beam mass spectrometry. M+ inClude the following metal ions: Mg+, Al+, Sc+: Ti+, V+, Cr+, Mn+, Fe+, Co+, Ni+, Cu+, and Zn+. In all cases, the primary product corresponds to endothermic loss of the intact pyridine molecule, with minor production of MXe+ formed by ligand exchange. In the Cr+(pyridine) system, an additional minor reaction pathway involving a ring-opening reaction with small neutral molecule loss is also observed. The cross-section thresholds are interpreted to yield 0 and 298 K bond dissociation energies for M+-pyridine after accounting for the effects of multiple ion-molecule collisions, internal energy of the reactant ions, and dissociation lifetimes. Density functional calculations at the B3LYP/6-31G(d,p) level of theory are used to determine the structures of these complexes and provide molecular constants necessary for the thermodynamic analysis of the experimental data. Theoretical bond dissociation energies at this level of theory are unreliable as even the trends in the calculated values do not parallel measured values. Measured M+-pyridine bond dissociation energies compare favorably to the four values previously determined by kinetic method or photodissociation experiments.Periodic trends in the binding of metal ions to pyridine studied by threshold collision-induced dissociation and density functional theory91200066#N/ATRUE
2923
ja00278a05710.1021/ja00278a057FALSEhttps://doi.org/10.1021/ja00278a057KISHI, YJ. Am. Chem. Soc.CATALYTIC EFFECT OF NICKEL(II) CHLORIDE AND PALLADIUM(II) ACETATE ON CHROMIUM(II)-MEDIATED COUPLING REACTION OF IODO OLEFINS WITH ALDEHYDES498198623#N/ATRUE
2924
ja00278a01710.1021/ja00278a017FALSEhttps://doi.org/10.1021/ja00278a017VOLLHARDT, KPCJ. Am. Chem. Soc.ON THE MECHANISM OF THE CYClOOCTATETRAENE SYNTHESIS FROM ETHYNE EMPLOYING NICKEL-CATALYSTS371986147#N/ATRUE
2925
ja00272a02510.1021/ja00272a025FALSEhttps://doi.org/10.1021/ja00272a025BANCI, LJ. Am. Chem. Soc.NMR PROTON RELAXATION IN BIMETALLIC COMPLEXES OF ZINC(II), NICKEL(II), AND COPPER(II)31198622#N/ATRUE
2926
ja00266a04210.1021/ja00266a042FALSEhttps://doi.org/10.1021/ja00266a042VANNICE, MAJ. Am. Chem. Soc.DIRECT SIMS OBSERVATION OF METHYLIDYNE, METHYLENE, AND METHYL INTERMEDIATES ON A NI(111) METHANATION CATALYST121198615#N/ATRUE
2927
ja00228a06110.1021/ja00228a061https://doi.org/10.1021/ja00228a061KUBIAK, CPJ. Am. Chem. Soc.PHOTOCHEMICAL Activation OF CO2 - TRANSIENT ABSORBANCE KINETIC-STUDIES OF THE ADDITION OF CO2 TO A METAL-TO-BRIDGING LIGAND CHARGE-TRANSFER STATE OF A BINUClEAR NI(0) COMPLEXPhotocatalyst33198823#N/AFALSE
2928
ja002661210.1021/ja0026612FALSEhttps://doi.org/10.1021/ja0026612van Koten, GJ. Am. Chem. Soc.Transmetalation of polylithiated, carbosilane (CS) dendrimers functionalized with the potentially terdentate ligand [C6H2(CH2NMe2)(2)-2,6-R-4](-) ( NCN) with NiCl2(PEt3)(2) produced a series of nickel-containing dendrimers [GO]-N-4 (4), [G1]-Ni-12 (5), and [G2]-Ni-36 (7) in moderate to good yields. The metallodendrimers 4, 5, and 7 are catalytically active in the atom-transfer radical addition (ATRA) reaction (Kharasch addition reaction), viz. the 1:1 addition of CCl4 to methyl methacrylate (MMA). The catalytic data were compared to those obtained for the respective mononuClear compound [NiCl(C6H2{CH2NMe2}(2)-2,6-SiMe3-4)] (2). This comparison indicates a fast deActivation for the dendrimer catalysts beyond generation [GO]. The deActivation of [G1]-Ni-12 (5) and [G2]-Ni-36 (7) is caused by irreversible formation of catalytically inactive Ni(III) sites on the periphery of these dendrimers. This hypothesis is supported by results of model studies as well as ESR spectroscopic investigations. Interestingly, the use of two alternative nickelated [G1] dendrimers [G1]*-Ni-12 (11) and [G1]-Ni-8 (15), respectively, in which the distance between the Ni sites is increased, leads to significantly improved catalytic efficiencies which approximate those of the parent derivative 2 and [GO]-Ni-4 (4). Preliminary membrane catalysis experiments with [GO]-Ni-4 (4) and [G1]-Ni-12 (5) show that 5 can be efficiently retained in a membrane reactor system. The X-ray crystal structure of the Ni(III) complex [NiCl2(C6H2{CH2NMe2}(2)-2,6-SiMe3-4)] (16), obtained from the reaction of 2 with CCl4, is also reported.A dendritic effect in homogeneous catalysis with carbosilane-supported Arylnickel(II) catalysts: Observation of active-site proximity effects in atom-transfer radical addition203200065#N/ATRUE
2929
ja00228a03510.1021/ja00228a035https://doi.org/10.1021/ja00228a035DRENTH, WJ. Am. Chem. Soc.SCREW SENSE SELECTIVE POLYMERIZATION OF ACHIRAL ISOCYANIDES CATALYZED BY OPTICALLY-ACTIVE NICKEL(II) COMPLEXESx188198857#N/AFALSE
2930
ja00264a04010.1021/ja00264a040FALSEhttps://doi.org/10.1021/ja00264a040STUEHR, JJ. Am. Chem. Soc.THERMODYNAMIC AND KINETIC-STUDY OF THE INTERACTIONS OF NI(II) WITH FMN AND FAD12198629#N/ATRUE
2931
ja00225a05510.1021/ja00225a055FALSEhttps://doi.org/10.1021/ja00225a055CORREIA, CRDJ. Am. Chem. Soc.NICKEL-CATALYZED INTRAMOLECULAR [4 + 4] CYClO-ADDITIONS .4. ENANTIOSELECTIVE TOTAL SYNTHESIS OF (+)-ASTERISCANOLIDEx154198835#N/AFALSE
2932
ja00224a02610.1021/ja00224a026FALSEhttps://doi.org/10.1021/ja00224a026STERSHIC, MTJ. Am. Chem. Soc.REACTIONS OF THE NICKEL(I) OCTAETHYLISOBACTERIOCHLORIN ANION WITH Alkyl-HALIDESx78198872#N/AFALSE
2933
ja00256a07510.1021/ja00256a075FALSEhttps://doi.org/10.1021/ja00256a075BAKAC, AJ. Am. Chem. Soc.ETHYLENE FORMATION IN THE REDUCTION OF 1,4-DIHALOALKANES WITH A NICKEL(I) MACROCYClE27198718#N/ATRUE
2934
ja00256a02010.1021/ja00256a020FALSEhttps://doi.org/10.1021/ja00256a020TAYLOR, RWJ. Am. Chem. Soc.FORMATION AND DISSOCIATION KINETICS OF NICKEL(II) WITH IONOPHORE-A23187 IN 80-PERCENT METHANOL WATER9198748#N/ATRUE
2935
ja00215a01810.1021/ja00215a018FALSEhttps://doi.org/10.1021/ja00215a018BIRD, PHA NICKEL(0) DIMER MONOMER SYSTEM WITH FACILE AND REVERSIBLE CARBON-MONOXIDE UPTAKE - NI2(CO)3(DPPM)2, NI2(CO)4(DPPM)2 AND NI(CO)3(ETA-1-DPPM)x1988#N/AFALSE
2936
ja00214a02410.1021/ja00214a024FALSEhttps://doi.org/10.1021/ja00214a024SAYERS, DJ. Am. Chem. Soc.INTRAZEOLITE CHEMISTRY OF NICKEL(0) COMPLEXES AND NI(0,II) ClUSTERS STUDIED BY EXAFS, SOLID-STATE NMR, AND FT IR SPECTROSCOPYx44198826#N/AFALSE
2937
ja00242a02410.1021/ja00242a024FALSEhttps://doi.org/10.1021/ja00242a024OKUKADO, NJ. Am. Chem. Soc.NICKEL-CATALYZED OR PALLADIUM-CATALYZED CROSS COUPLING .31. PALLADIUM-CATALYZED OR NICKEL-CATALYZED REACTIONS OF ALKENYLMETALS WITH UNSATURATED ORGANIC HALIDES AS A SELECTIVE ROUTE TO ArylATED ALKENES AND CONJUGATED DIENES - SCOPE, LIMITATIONS, AND MECHANISM286198752#N/ATRUE
2938
ja00242a00910.1021/ja00242a009FALSEhttps://doi.org/10.1021/ja00242a009BOCIAN, DFJ. Am. Chem. Soc.CHLOROPHYLL MODEL COMPOUNDS - EFFECTS OF LOW SYMMETRY ON THE RESONANCE RAMAN-SPECTRA AND NORMAL MODE DESCRIPTIONS OF NICKEL(II) DIHYDROPORPHYRINS108198783#N/ATRUE
2939
ja00209a00110.1021/ja00209a001FALSE
https://www.koreascience.or.kr/artiCle/JAKO201013343110902.pub?orgId=chemical
BOWERS, MTKINETIC-ENERGY RELEASE DISTRIBUTIONS AS A PROBE OF TRANSITION-METAL-MEDIATED H-H, C-H, AND C-C BOND FORMATION PROCESSES - REACTIONS OF COBALT AND NICKEL IONS WITH ALKANESx1988#N/AFALSE
2940
ja00240a06010.1021/ja00240a060FALSEhttps://doi.org/10.1021/ja00240a060SCHUGAR, HJNEARLY TETRAHEDRAL 1-2 COMPLEXES OF COPPER(I), COPPER(II), NICKEL(II), COBALT(II), AND ZINC(II) WITH 2,2'-BIS(2-IMIDAZOLYL)BIPHENYL1987#N/ATRUE
2941
ja00237a02010.1021/ja00237a020FALSEhttps://doi.org/10.1021/ja00237a020KUBIAK, CPJ. Am. Chem. Soc.CARBON-DIOXIDE CHEMISTRY AND ELECTROCHEMISTRY OF A BINUClEAR CRADLE COMPLEX OF NI(0), NI2(MU-CNME)(CNME)2(PPH2CH2PPH2)283198723#N/ATRUE
2942
ja00233a05710.1021/ja00233a057FALSEhttps://doi.org/10.1021/ja00233a057SAEGUSA, TJ. Am. Chem. Soc.NICKEL(0)-CATALYZED REACTION OF DIYNES WITH ALDEHYDES85198815#N/ATRUE
2943
ja00233a02810.1021/ja00233a028FALSEhttps://doi.org/10.1021/ja00233a028ODA, MJ. Am. Chem. Soc.A NEW APPROACH TO THE CONSTRUCTION OF RADIALENES BY THE NICKEL-CATALYZED CYClOOLIGOMERIZATION OF [3]CUMULENES (BUTATRIENES)81198890#N/ATRUE
2944
ja00200a02810.1021/ja00200a028FALSEhttps://doi.org/10.1021/ja020223kIBERS, JADESIGNED SYNTHESIS OF A RADICAL CATION SALT OF NI(TMP) - STRUCTURAL, MAGNETIC, AND CHARGE-TRANSPORT PROPERTIES OF BIS[5,10,15,20-TETRAMETHYLPORPHYRINATO)NICKEL(II)] HEXAFLUOROPHOSPHATEx1989#N/AFALSE
2945
ja00199a02110.1021/ja00199a021FALSEhttps://doi.org/10.1021/ja00199a021HOFFMAN, BMJ. Am. Chem. Soc.2-CHANNEL CONDUCTIVITY AND CARRIER CROSSOVER IN COXNI1-X(PC)I, ALLOYS OF THE MOLECULAR CONDUCTORS (PHTHALOCYANINATO)NICKEL IODIDE AND (PHTHALOCYANINATO)COBALT IODIDEx14198928#N/AFALSE
2946
ja00232a03010.1021/ja00232a030FALSEhttps://doi.org/10.1021/ja00232a030ITO, YJ. Am. Chem. Soc.ASYMMETRIC-SYNTHESIS CATALYZED BY CHIRAL FERROCENYLPHOSPHINE TRANSITION-METAL COMPLEXES .6. PRACTICAL ASYMMETRIC-SYNTHESIS OF 1,1'-BINAPHTHYLS VIA ASYMMETRIC CROSS-COUPLING WITH A CHIRAL [(ALKOXYAlkyl)FERROCENYL]MONOPHOSPHINE NICKEL-CATALYST275198843#N/ATRUE
2947
ja00228a05610.1021/ja00228a056FALSEhttps://doi.org/10.1021/ja00228a056PARDI, LJ. Am. Chem. Soc.INTERNAL ELECTRON-TRANSFER IN A QUINONE ADDUCT OF A NICKEL(II)-CATECHOLATE COMPLEX21198820#N/ATRUE
2948
ja00198a07110.1021/ja00198a071FALSEhttps://doi.org/10.1021/ja00198a071JENKINS, TEJ. Am. Chem. Soc.NICKEL-CATALYZED INTRAMOLECULAR [4 + 2] DIENYNE CYClO-ADDITIONS - AN EFFICIENT NEW METHOD FOR THE SYNTHESIS OF POLYCYClES CONTAINING CYClOHEXA-1,4-DIENESx151198929#N/AFALSE
2949
ja00226a02910.1021/ja00226a029FALSEhttps://doi.org/10.1021/ja00226a029BURROWS, CJJ. Am. Chem. Soc.MECHANISTIC STUDIES OF ALKENE EPOXIDATION CATALYZED BY NICKEL(II) CYClAM COMPLEXES - O-18 LABELING AND SUBSTITUENT EFFECTS129198868#N/ATRUE
2950
ja002241c10.1021/ja002241cFALSEhttps://doi.org/10.1021/ja002241cYamamoto, YJ. Am. Chem. Soc.The nickel-catalyzed [2 + 2] annulations of electron-deficient allenes proceed efficiently in a highly regioselective manner under very mild conditions to give the head-to-head cyClodimerization products, bismethylenecyClobutanes, as single isomers in good to fair yields. We also carried out the stoichiometric reaction of these allenes in the presence of Ni(0) complexes and elucidated the mechanism of this highly selective reaction.Nickel(0)-catalyzed [2+2] annulation of electron-deficient allenes. Highly regioselective synthesis of cyClobutanes63200035#N/ATRUE
2951
ja00189a00810.1021/ja00189a008FALSEhttps://doi.org/10.1021/ja00189a008FABBRIZZI, LDESIGN OF REDOX SYSTEMS FOR THE SELECTIVE TRANSPORT OF ELECTRONS ACROSS LIQUID MEMBRANES - NICKEL(II,III) TETRAAZA MACROCYClIC COMPLEXESx1989#N/AFALSE
2952
ja00220a03310.1021/ja00220a033FALSEhttps://doi.org/10.1021/ja00220a033SHELNUTT, JAJ. Am. Chem. Soc.NEW CRYSTALLINE PHASE OF (OCTAETHYLPORPHINATO)NICKEL(II) - EFFECTS OF PI-PI-INTERACTIONS ON MOLECULAR-STRUCTURE AND RESONANCE RAMAN-SPECTRA181198838#N/ATRUE
2953
ja00212a04510.1021/ja00212a045FALSEhttps://doi.org/10.1021/ja00212a045ITO, YJ. Am. Chem. Soc.NICKEL(0)-PROMOTED CYClIZATION OF ENYNES WITH ISOCYANIDES - A NEW ROUTE TO POLYCYClIC CYClOPENTENONE SKELETONS128198833#N/ATRUE
2954
ja002125+10.1021/ja002125+FALSEhttps://doi.org/10.1021/ja002125+Le Floch, PJ. Am. Chem. Soc.The radical anion (tmbp)(.-), where tmbp = 4,4',5,5'-tetramethyl-2,2'-biphosphinine was generated by reduction of tmbp on a potassium mirror. EPR/ENDOR spectra and DFT calculations show that, in contrast to the neutral species, this anion is planar and that the unpaired electron is mainly delocalized on the PCCP fragment with a large participation of the phosphorus p(pi) orbitals. This planar structure was confirmed by the first crystal structure of an anionic biphosphinine: [tmbp][Li(2.2.1)]. Reduction of [Ni(tmbp)(2)] led to the 19-electron complex whose g and P-31 hyperfine tensors were obtained from EPR in liquid and frozen solutions. These results, together with DFT calculations on [Ni(bp)(2)] and [Ni(bp)(2)](.-), indicate that, by accepting an extra electron, the neutral nickel complex distorts toward a mon planar geometry and that the dihedral angle between the two phosphinine rings of each ligand slightly increases. In the reduced Ni complex, the unpaired electron is mainly delocalized on the ligands, in a molecular orbital which retains the characteristics of the SOMO found for the reduced isolated ligand. A charge decomposition analysis (CDA) shows that, in [Ni(bp)(2)], metal-ligand back-donation strongly contributes to the metal-ligand bonding.One-electron reduction product of a biphosphinine derivative and of its Ni-(0) complex: Crystal structure, EPR/ENDOR, and DFT investigations on (tmbp)(center dot-) and [Ni(tmbp)2](center dot-)32200035#N/ATRUE
2955
ja00207a02910.1021/ja00207a029FALSEhttps://doi.org/10.1021/ja00207a029LUH, TYJ. Am. Chem. Soc.TRANSITION-METAL PROMOTED REACTIONS .30. CYClOPROPYL ANION AS AN ALLYL ANION SYNTHON - NOVEL SYNTHESIS OF BUTADIENES BY NICKEL-CATALYZED COUPLING OF CYClOPROPYL GRIGNARD-REAGENTS WITH DITHIOACETALS23198929#N/ATRUE
2956
ja00205a04310.1021/ja00205a043FALSEhttps://doi.org/10.1021/ja00205a043CEYER, STJ. Am. Chem. Soc.SYNTHESIS OF BENZENE FROM METHANE OVER A NI(111) CATALYST64198910#N/ATRUE
2957
ja00205a01010.1021/ja00205a010FALSEhttps://doi.org/10.1021/ja00205a010FAJER, JJ. Am. Chem. Soc.ELECTROCHEMICAL, THEORETICAL, AND ESR CHARACTERIZATIONS OF PORPHYCENES - THE PI-ANION RADICAL OF NICKEL(II) PORPHYCENE72198934#N/ATRUE
2958
ja002042t10.1021/ja002042tFALSEhttps://doi.org/10.1021/ja016676rBazan, GCSynthesis, characterization, and ethylene oligomerization action of [(C6H5)(2)PC6H4C(O-B(C6F5)(3))O-k(2)P,O]Ni(eta(3)-CH2C6H5)2000#N/ATRUE
2959
ja001991j10.1021/ja001991jFALSEhttps://doi.org/10.1021/ja001991jLong, JRJ. Am. Chem. Soc.The synthesis of high-nuClearity metal-cyanide Clusters presents a possible means of controlling magnetic properties in the design of new single-molecule magnets. Previous work employed tridentate blocking ligands in directing the assembly of a cubic [(tacn)(8)Co-8(CN)(12)](12+) (tacn = 1,4,7-triazacyClononane) Cluster; an improved crystal structure now confirms the lack of a guest water molecule inside the Cluster cage. The ability to generate larger Clusters by using a blocking ligand on only one of the mononuClear reaction components is demonstrated with the synthesis of a fourteen-metal [(Me(3)tacn)(8)Cr8Ni6(CN)(24)](12+) Cluster. The geometry of this Cluster consists of a cube of eight Me(3)tacn-ligated Cr-III ions connected via bridging cyanide ligands to six square-planar Ni-II ions situated just above the center of each cube face. Surprisingly, no guest species are evident within the 283 Angstrom (3) cavity defined by the rigid metal-cyanide cage. Assembly of the Cluster in boiling aqueous solution involves a linkage isomerization wherein the carbon end of each cyanide ligand reorients from binding a Cr-III center in the reactant to binding the softer Ni-II center in the product. Consequently, the Ni-II ions become diamagnetic, resulting in magnetic behavior at high temperatures that is consistent with eight isolated Cr-III (S = 3/2) ions per Cluster. However, below 30 K, a drop in the chi T-M is attributed to weak antiferromagnetic coupling between Cr-III ions through the LUMO orbitals of the [Ni(CN)(4)](2-) like units centering each Cluster face. Carrying out the assembly reaction in methanol at -40 degreesC forestalls the Linkage isomerization, yielding a high-spin green form of the Cluster. Reaction of [(Me(3)tacn)(8)Cr8Ni6(CN)(24)](12+) with [Ni(CN)(4)](2-) affords an aggregate species with a tetracyanonickelate ion capping each face of the Cluster through a mean Ni Ni contact of 3.00(1) Angstrom, an interaction that destroys the long-range antiferromagnetic coupling between Cr-III ions, Efforts to construct a larger Cluster with an edge-bridged cubic geometry produced a linear [(Me(3-)tacn)(2)(cyClam)NiCr2(CN)(6)](2+) (cyClam = 1,4,8,11-tetraazacyClotetradecane) fragment exhibiting an S = 4 ground state. The weak ferromagnetic coupling (J = 10.9 cm(-1)) within this Cluster leads to a more rapid decrease in the magnetization with increasing temperature at higher magnetic fields as a result of the Zeeman splitting and population of low-lying excited states.High-nuClearity metal-cyanide Clusters: Assembly of a Cr8Ni6(CN)(24) cage with a face-centered cubic geometry176200060#N/ATRUE
2960
ja00179a02110.1021/ja00179a021FALSEhttps://doi.org/10.1021/ja00179a021FRANZEN, MMJ. Am. Chem. Soc.SYNTHESES AND SPECTROSCOPIC CHARACTERIZATION OF (T(PARA-ME2N)F4PP)H2 AND (T(PARA-ME2N)F4PP)M WHERE T(PARA-ME2N)F4PP IS THE DIANION OF MESO-TETRAKIS(ORTHO,ORTHO,META,META-TETRAFLUORO-PARA-(DIMETHYLAMINO)PHENYL)-PORPHYRIN AND M = CO(II), CU(II), OR NI(II) - STRUCTURES OF (T(PARA-ME2N)F4PP)CO AND (MESO-TETRAKIS(PENTAFLUOROPHENYL)PORPHINATO)COBALT(II), (TF5PP)COx145199024#N/AFALSE
2961
ja00198a10010.1021/ja00198a100FALSEhttps://doi.org/10.1021/ja00198a100ITO, YNICKEL(0)-CATALYZED CYClIZATION OF 1,7-DIYNES VIA HYDROSILATION - ONE-STEP SYNTHESIS OF 1,2-DIAlkylIDENECYClOHEXANES WITH A (Z)-VinylSILANE MOIETY1989#N/ATRUE
2962
ja00177a02410.1021/ja00177a024FALSEhttps://doi.org/10.1021/ja00177a024MUNCK, EMODELS FOR IRON OXO PROTEINS - MOSSBAUER AND EPR STUDY OF AN ANTIFERROMAGNETICALLY COUPLED FE-III NI-II COMPLEXx1990#N/AFALSE
2963
ja00194a05410.1021/ja00194a054FALSEhttps://doi.org/10.1021/ja00194a054HENDRICKSON, DNJ. Am. Chem. Soc.ACTIVE-SITE MODEL OF UREASE - SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES OF A BINUClEAR NI(II) COMPLEX CONTAINING A POLYIMIDAZOLE LIGAND91198943#N/ATRUE
2964
ja00169a07610.1021/ja00169a076FALSEhttps://doi.org/10.1021/ja00169a076HOLM, RHREACTION SEQUENCE RELATED TO THAT OF CARBON-MONOXIDE DEHYDROGENASE (ACETYL COENZYME A SYNTHASE) - THIOESTER FORMATION MEDIATED AT STRUCTURALLY DEFINED NICKEL CENTERSx1990#N/AFALSE
2965
ja00167a10210.1021/ja00167a102FALSEhttps://doi.org/10.1021/ja00167a102DERVAN, PBJ. Am. Chem. Soc.NICKEL-MEDIATED SEQUENCE-SPECIFIC OXIDATIVE ClEAVAGE OF DNA BY A DESIGNED METALLOPROTEINx119199020#N/AFALSE
2966
ja00192a05110.1021/ja00192a051FALSEhttps://doi.org/10.1021/ja00192a051ODA, MJ. Am. Chem. Soc.NICKEL-CATALYZED CYClO-DIMERIZATION OF [5]CUMULENE (HEXAPENTAENE) - SYNTHESIS OF A NOVEL [4]RADIALENE SYSTEM32198929#N/ATRUE
2967
ja00188a02010.1021/ja00188a020FALSEhttps://doi.org/10.1021/ja00188a020SHELNUTT, JAJ. Am. Chem. Soc.RUFFLING OF NICKEL(II) OCTAETHYLPORPHYRIN IN SOLUTION120198928#N/ATRUE
2968
ja001870j10.1021/ja001870jFALSEhttps://doi.org/10.1021/ja001870jGhosh, AJ. Am. Chem. Soc.Theoretical modeling of putative Ni(III)-F-430 intermediates of methylcoenzyme M reductase40200114#N/ATRUE
2969
ja00160a05610.1021/ja00160a056FALSEhttps://doi.org/10.1021/ja00160a056FAJER, JJ. Am. Chem. Soc.STRUCTURAL CONSEQUENCES OF NICKEL VERSUS MACROCYClE REDUCTIONS IN F430 MODELS - EXAFS STUDIES OF A NI(I) ANION AND NI(II) PI-ANION RADICALSx119199032#N/AFALSE
2970
ja00185a05110.1021/ja00185a051FALSEhttps://doi.org/10.1021/ja00185a051GAIS, HJJ. Am. Chem. Soc.NICKEL-CATALYZED CROSS-COUPLINGS OF ALKENYL AND ALPHA-METALATED ALKENYL SULFOXIMINES WITH ORGANOMETALLICS - STEREOSELECTIVE SYNTHESIS OF CARBACYClINS61198934#N/ATRUE
2971
ja00185a02210.1021/ja00185a022FALSEhttps://doi.org/10.1021/ja00185a022ALPER, HJ. Am. Chem. Soc.LANTHANIDE-PROMOTED AND NICKEL CYANIDE CATALYZED CarbonylATION REACTIONS UNDER PHASE-TRANSFER CONDITIONS33198918#N/ATRUE
2972
ja00154a02310.1021/ja00154a023FALSEhttps://doi.org/10.1021/ja00154a023GRIMES, RNJ. Am. Chem. Soc.Triple-decker and tetradecker sandwich complexes having planar C2B3 or pyramidal C2B4 carborane ligands at one or both ends, the first examples of this genre, were prepared and characterized. A 3-way reaction of the Cp*Co(2,3-Et(2)C(2)B(3)H(2)-5-Me)(2-) and 2,3-Et(2)C(2)B(4)H(4)(2-) dianions with CoCl2 gave the diamagnetic 30 ve (valence electron) triple-decker Cp*Co(Et(2)C(2)B(3)H(2)Me)CoH(Et(2)C(2)B(4)H(4)) (2) and the paramagnetic 29 ve triple-decker Cp*Co(Et(2)C(2)B(3)H(2)Me)Co(Et(2)C(2)B(4)H(4)) (3) Decapitation of these species gave diamagnetic Cp*Co(Et(2)C(2)B(3)H(2)Me)CoH(Et(2)C(2)B(3)H(5)) (4), whose triple-decker geometry was confirmed by an X-ray structure determination that established the location of the hydrogen atom capping a CoB2 triangular face. Removal of the CoH proton in 4 followed by oxidation of the anion in air gave paramagnetic Cp*Co(Et(2)B(3)H(2)Me)Co(Et(2)C(2)B(3)H(5)) (5) Treatment of neutral 4 and 5 with n-bromosuccinimide afforded the mono- and dibromo derivatives 6-8. The 30 ve triple-decker Cp*Co(Et(2)C(2)B(3)Me(3))Ni(Et(2)C(2)B(4)H(4)?) (10) was prepared from the perAlkylated synthon Cp*Co(2,3-Et(2)C(2)B(3)Me(3))(2-), Et(2)C(2)B(4)H(4)(2-), and NiBr2. A similar approach employing the cymeneruthenacarborane dianion (CHMe(2)C(6)H(4)Me)Ru(Et(2)C(2)B(3)H(2)Me)(2-) gave the paramagnetic triple-decker (CHMe(2)C(6)H(4)Me)Ru(Et(2)C(2)B(3)H(2)Me)Co(Et(2)C(2)B(4)H(4)) (12), which was decapitated to yield diamagnetic (CHMe(2)C(6)H(4)Me)Ru(Et(2)C(2)B(3)H(2)Me)CoH(Et(2)C(2)B(3)H(5)) (13); the latter species was air-oxidized to afford 29 ve (CHMe(2)C(6)H(4)Me)Ru(Et(2)C(2)B(3)H(2)Me)Co(Et(2)C(2)B(3)H(5)) (14). Stacking reactions of the nido, Close dianion (Et(2)C(2)B(3)H(4)Me)Co(Et(2)C(2)B(4)H(4))(2-) (15(2-)) with CO2+ or Ni2+ ions gave the paramagnetic carborane-bicapped tetradecker sandwiches M[(Et(2)C(2)B(3)H(2)Me)Co(Et(2)C(2)B(4)H(4))](2) (16, M = CO. 41 ve; 17, M = NiH, 43 ve). Reactions of the 15(3-) trianion with Cp*Co(2,3-Et(2)C(2)B(3)H(2)Me)(2-) ion and Co2+ or Ni2+ gave the carborane-monocapped tetradeckers Cp*Co(Et(2)C(2)B(3)H(2)Me)M(Et(2)C(2)B(3)H(2)Me)COH(Et(2)C(2)B(4)H(4) (18, M = Co, 41 ve; 19, M = Ni, 42 ve, diamagnetic). Decapitation of 18 gave paramagnetic 41 ve Cp*Co(Et(2)C(2)B(3)H(2)Me)Co(Et(2)C(2)B(3)H(2)Me)CoH(Et(2)C(2)B(3)H(5)) (20), a 41 ve tetradecker sandwich having an open carborane end ligand. The new compounds were characterized via UV-visible and mass spectra, H-1 and B-11 NMR spectra (for diamagnetic species), and ESR spectra (for paramagnetic complexes). Features of the spectroscopic data are discussed and related to the electronic structures of these systems. Crystal data for 4: space group P2(1)/a; a = 9.312(3) Angstrom, b = 28.25(1) Angstrom, 10.234(4) Angstrom, beta = 95.56(3)degrees; Z = 4; R = 0.048 for 3834 independent reflections having I > 3 sigma(I).ORGANOTRANSITION-METAL METALLACARBORANES .43. DIRECTED SYNTHESIS OF CARBORANE-ENDCAPPED MULTIDECKER SANDWICHESx21199543#N/AFALSE
2973
ja00182a00810.1021/ja00182a008FALSEhttps://doi.org/10.1021/ja00182a008BABCOCK, GTJ. Am. Chem. Soc.The resonance Raman (RR) and infrared (IR) spectra of the Zn, Cu, and Ni complexes of trans-octaethylchlorin (OEC) reveal significant differences in the vibrational-mode properties of metallochlorins and metalloporphyrins. Modes with a contribution from the C(a)C(m) stretching coordinate are distinguished by their sensitivity to metal substitution and to selective d2 and d4 methine deuteration. Comparison of the resonance Raman spectrum of CuOEC with that of CuECI (ECI = etiochlorin I) identifies those modes with a contribution from C(b)C(b) and C(b)C(a) stretching and C(b)C(s) bending coordinates. The results obtained show that there is substantial mixing of C(a)C(m) and C(b)C(b) stretching character in the high-frequency modes of MOEC. The suggestion21 that the symmetry reduction that occurs in metallochlorins relative to metalloporphyrins produces vibrations-mode localization to specific hemispheres or quandrants of the macrocyCle has been tested and confirmed by specific d2 deuteration at the methine carbons. Resonance Raman spectra of CuOEP-d2 (OEP = octaethylporphyrin) and CuOEP-d4 establish that, for a delocalized mode, methine d2 deuteration can be expected to produce half the d4 shift. For CuOEC, selective deuteration at the alpha,beta and gamma,delta methine positions causes different patterns of frequency shifts that indicate the extent of mode localization. Analysis of these data shows that the normal modes of the MOEC Class of compounds have varying degrees of localization; moreover, it identifies those modes that retain delocalized, porphyrin-like behavior, albeit with altered potential energy distributions relative to the MOEP situation. In agreement with the analysis by Boldt et al., however, we find that, in general, it is not possible to assign the vibrational modes of metallochlorins by direct analogy with metalloporphyrins. An exception to this occurs for several modes below 1350 cm-1 that are localized in the alpha,beta positions away from the reduced pyrole ring, but modes that are gamma,delta localized in this frequency region have no porphyrin counterparts.NORMAL-MODE CHARACTERISTICS OF CHLOROPHYLL MODELS - VIBRATIONAL ANALYSIS OF METALLOOCTAETHYLCHLORINES AND THEIR SELECTIVELY DEUTERATED ANALOGS24199072#N/ATRUE
2974
ja00181a06310.1021/ja00181a063FALSEhttps://doi.org/10.1021/ja00181a063MARTELL, AEJ. Am. Chem. Soc.OXYGEN INSERTION IN THE NI(II) COMPLEXES OF DIOXOPENTAAZA MACROCYClIC LIGANDS3519909#N/ATRUE
2975
ja00149a02110.1021/ja00149a021FALSEhttps://doi.org/10.1021/ja00149a021BOWERS, MTJ. Am. Chem. Soc.Product kinetic energy release distributions (KERDs) for reactions of Fe+, Co+, and Ni+ with acetone to eliminate C2H6 and CO have been measured. These distributions are statistical and are very sensitive to the energy of the rate-limiting transition state, We argue this transition state is most likely due to initial C-C bond insertion. The rate-limiting transition state acts to restrict high angular momentum reactant collision complexes from going on to products, thereby reducing the average kinetic energy released. By modeling the experimental KERDs, the rate-limiting transition state was determined to lie in the range of 9 +/- 3 kcal/mol below the energy of the M(+) + acetone reactants for all three metal ions. Bond energies for M(+)-CO and M(+)-C2H6 have also been determined:D-0(o)(Co+-CO) 39.1 +/- 3 kcal/mol, D-0(o)(Fe+-C2H6) = 17.9 +/- 3 kcal/mol, and D-0(o)(Ni+-C2H6) = 28.7 +/- 3 kcal/mol. In addition, modeling the experimental KERDs indicates that the MC(2)H(6)(+) product formed in the reaction of M(+) with acetone is nearly exClusively an ethane adduct, with a maximum 10-15% of the dimethyl complex being formed. Finally, arguments relating the initial rate-limiting transition state to the C-H bond Activation transition state in propane are made and suggest that the C-C bond Activation transition state in small alkanes is 6 +/- 5 kcal/mol higher in energy than C-H bond Activation.DETAILS OF POTENTIAL-ENERGY SURFACES INVOLVING C-C BOND Activation - REACTIONS OF FE+, CO+, AND NI+ WITH ACETONEx51199565#N/AFALSE
2976
ja00181a04310.1021/ja00181a043FALSEhttps://doi.org/10.1021/ja00181a043LUH, TYJ. Am. Chem. Soc.TRANSITION-METAL PROMOTED REACTIONS .34. UNIFIED SYNTHESIS OF VinylSILANES AND SILYLATED BUTADIENES - NICKEL-CATALYZED OLEFINATION AND SILYLOLEFINATION OF DITHIOACETALS59199090#N/ATRUE
2977
ja00146a00910.1021/ja00146a009FALSEhttps://doi.org/10.1021/ja00146a009BLECKMAN, TJ. Am. Chem. Soc.The second generation strategy for the total synthesis of brevetoxin B (1) is presented. According to this strategy, the heptacyClic [ABCDEFG] phosphonium iodide 4 and the tricyClic [IJK] aldehyde 3 were defined as the precursors for the brevetoxin B skeleton. The Yamaguchi lactonization was successfully applied for the formation of the [EFG] and [DEFG] lactones (15 --> 7) and (29 --> 6), respectively. The required appendage on ring [E] was efficiently introduced via a Mural coupling, involving addition of a higher order organocuprate derived from iodide 20 to the lactone-derived enol triflate 16 (16 --> 25). The minor epimer of the resulting product 6 beta was then converted to the desired isomer 6 alpha via hydrogenation using an Ir(I) catalyst. A number of approaches were considered for further elaboration of lactone 6. Among them a convienient Cr/Ni-promoted coupling reaction was developed and applied to the introduction of the side chain on ring D. The scope and generality df this reaction was examined with a variety of aldehydes (e.g., 39, 59, and 62). Construction of 38 was thus achieved from Vinyl triflate 36 and the ring B aldehyde 39. However, the projected intramolecular Michael addition (41 --> 42) and reductive hydroxy ketone cyClization (47 --> 48) failed to yield ring C. Fetizon cyClization afforded the pentacyClic lactone [CDEFG] (51 --> 52), which resisted further useful functionalization. Using the more elaborate aldehyde 62, the Cr/Ni coupling reaction afforded allylic alcohol 64, which then served as a precursor to the pentacyClic lactol 80. The latter compound also resisted advancement to more elaborate intermediates, leading to abandonment of this approach and the formulation of a new strategy.TOTAL SYNTHESIS OF BREVETOXIN-B .2. 2ND GENERATION STRATEGIES AND CONSTRUCTION OF THE DIOXEPANE REGION [DEFG]x88199534#N/AFALSE
2978
ja00180a05810.1021/ja00180a058FALSEhttps://doi.org/10.1021/ja00180a058FAJER, JJ. Am. Chem. Soc.EXAFS STUDIES OF NICKEL(II) AND NICKEL(I) FACTOR-430M - CONFORMATIONAL FLEXIBILITY OF THE F430 SKELETON101199019#N/ATRUE
2979
ja00144a01010.1021/ja00144a010FALSEhttps://doi.org/10.1021/ja00144a010ANSON, FCJ. Am. Chem. Soc.In acidic solutions, the chemical or slow electrochemical reduction of the organic ligand-oxidant 1,10-phenanthroline-5,6-dione consumes two electrons and two protons. However, when the electrochemical reduction is examined on shorter time scales using cyClic or rotating disk voltammetry, fewer than two electrons are consumed in the reduction. The magnitude of the electron deficit depends upon pH and the deficit is eliminated at pH values where the pyridine nitrogen sites on the molecule are not protonated. Complexation of metal cations, e.g., Os(II) or Ni(II), to the 1,10-phenanthroline portion of the molecule also produces an electron deficit in electrochemical reductions of the dione. A proton- or metal ion-induced addition of H2O to the quinone Carbonyl groups is shown to be responsible for the observed behavior. Rate and equilibrium constants for the hydration-dehydration equilibrium were evaluated by fitting experimental and calculated parameters in a digital simulation. The possible consequences of the results to studies in which the dione is used to oxidize amines and other organic reductants are pointed out.HYDRATION OF THE Carbonyl GROUPS IN 1,10-PHENANTHROLINE-5,6-DIONE INDUCED BY BINDING PROTONS OR METAL-CATIONS TO THE PYRIDINE NITROGEN SITESx34199518#N/AFALSE
2980
ja00177a06210.1021/ja00177a062FALSEhttps://doi.org/10.1021/ja00177a062Watson, MPJ. Am. Chem. Soc.CAN CO2 COORDINATE TO A NI(I) COMPLEX - AN ABINITIO MO/SD-CI STUDY37199034#N/ATRUE
2981
ja00143a01910.1021/ja00143a019FALSEhttps://doi.org/10.1021/ja00143a019ZAERA, FJ. Am. Chem. Soc.The chemistry of 1-iodopropane, 1-iodobutane, 2-iodobutane, 1-iodo-2-methylpropane, 2-iodo-2-methylpropane, 1-iodopentane, and 1-iodohexane on Ni(100) surfaces has been studied by using temperature-programmed desorption and X-ray photoelectron spectroscopy. Below 100 K all the compounds adsorb molecularly through the iodine atom. The hydrocarbon chain orients parallel to the surface at first, but flips as the coverage increases, and becomes perpendicular to the surface at saturation. The C-I bond dissociates between 120 and 180 K to yield the corresponding Alkyl fragment on the surface. At higher temperatures the Alkyl groups decompose further, directly to carbon and hydrogen at low coverages (below half-saturation), but mainly to a mixture of alkanes and alkenes at saturation. The change in the ratio between alkane and alkene production was examined with respect to both the degree of substitution and the length of the carbon chain. It was found that the beta-hydride elimination that yields the alkenes is favored over the reductive elimination responsible for the alkane formation in Alkyl species with a large number of beta-hydrogens, even in the presence of coadsorbed hydrogen on the surface. On the other hand, the hydrogenation steps were seen to dominate in the coadsorbed systems for Alkyl species with a small number of beta-hydrogen atoms. An increase in chain length has the effect of decreasing the alkene-to-alkane ratio further.THERMAL-REACTIONS OF Alkyl IODIDES ON NI(100) SINGLE-CRYSTAL SURFACESx63199533#N/AFALSE
2982
ja00143a00210.1021/ja00143a002FALSEhttps://doi.org/10.1021/ja00143a002LONG, ECJ. Am. Chem. Soc.DNA Cleavage by synthetic tripeptides of the form NH2-Xaa-Xaa-His-CONH2 was investigated in the presence of Ni(II) and the oxygen activating agent oxone. Studies with Ni(II). Gly-Gly-His, Ni(II). Lys-Gly-His, and Ni(II). Arg-Gly-His indicated that each metallopeptide is capable of inducing strand scission via a non-diffusible oxidant at mixed A/T-rich regions, albeit with an avoidance of homopolymeric A/T sites, in a reaction that can be inhibited by the minor groove binding drug distamycin. Additional metallopeptides containing substitutions of D-His for L-His and neutral metallopeptides containing Asn residues demonstrate the ability to alter site-selectivity through subtle structural changes; the metallopeptide Ni(II). Gly-D-Asn-His displayed a selectivity for 5'-CCT sites while other substitutions varied with respect to their levels of site discrimination in comparison to Ni(II). Gly-Gly-His. These observations indicate that the metallopeptides in question are sensitive to DNA structure and are capable of interacting selectively with the minor groove, suggesting the possibility of exploiting the chemical diversity and chirality of peptides in the further design of site-selective DNA binding and modifying agents.METALLOPEPTIDE DNA INTERACTIONS - SITE-SELECTIVITY BASED ON AMINO-ACID-COMPOSITION AND CHIRALITYx64199535#N/AFALSE
2983
ja00173a02810.1021/ja00173a028FALSEhttps://doi.org/10.1021/ja00173a028VALENTINE, JSJ. Am. Chem. Soc.NMR-STUDIES OF NICKEL(II)-SUBSTITUTED DERIVATIVES OF BOVINE COPPER-ZINC SUPEROXIDE-DISMUTASE WITH NICKEL(II) BOUND IN THE COPPER SITE24199047#N/ATRUE
2984
ja00140a02310.1021/ja00140a023FALSEhttps://doi.org/10.1021/ja00140a023GELLMAN, AJJ. Am. Chem. Soc.We have investigated fluorine substitution effects on the rate of coupling of adsorbed Alkyl groups on a Ag(111) surface. Alkyl groups are formed by thermal dissociation of the C-I bond in adsorbed Alkyl iodides. Variable heating rate temperature programmed reaction (TPR) studies were used to determine the kinetic parameters for the coupling of ethyl groups and propyl groups. They are E(a) = 15.1 +/- 0.6 kcal/mol, nu = 10(16.7+/-0.8) s(-1), and E(a) 16.9 +/- 0.4 kcal/mol, nu = 10(17.1+/-0.4) s(-1), respectively. Substitution of fluorine for hydrogen in the adsorbed Alkyl groups systematically raises the coupling reaction temperature. For example, trifluoropropyl groups self-couple at temperatures similar to 70 K higher than propyl groups on Ag(111). Coadsorbed propyl and trifluoropropyl groups cross; couple at temperatures similar to 10 K higher than the propyl self-coupling reaction. The kinetic parameters evaluated from the results of this study and from results of earlier studies by X.-L. Zhou, J. M. White, and co-workers [Surf. Sci. 1989, 219, 294; Catal. Lett. 1989, 2, 375; J. Phys. Chem. 1991, 95, 5575] are used to plot linear free energy relationships (LFER) which provide insight into the electronic nature of the reaction center. The implication of the LFER plots for the surface Alkyl coupling reaction is that the reaction center in the transition state is electron deficient with respect to the initial state.FLUORINE SUBSTITUTION EFFECTS ON THE Alkyl COUPLING REACTION ON A AG(111) SURFACEx17199552#N/AFALSE
2985
ja00137a01410.1021/ja00137a014FALSEhttps://doi.org/10.1021/ja00137a014GILBERT, PJJ. Am. Chem. Soc.An electronic energy term for transition metals has been constructed for extending Molecular Mechanics (MM) to open-shell, Werner-type coordination compounds. The d-orbital energies from a generalized ligand field calculation are used to compute the Cellular Ligand Field Stabilization Energy (ClFSE). The ClFSE models the geometrical effects of the stereochemical activity of d electrons and can be computed for any coordination number, molecular symmetry, and ligand type. In conjunction with ligand-ligand nonbonding and metal-ligand bond stretch terms, ClFSEs provide a general framework for incorporating transition metals into MM. An explicit angle-bend term is not required. After describing the theoretical basis of ClFSEs, the method is illustrated using a range of six-coordinate high-spin and four-coordinate low-spin Ni-II amine complexes plus four-, five- and six-coordinate Cu-II amine systems. For the nickel complexes, the spin-state change is modeled simply by changing the d-orbital occupancies. A single set of force field and ClF parameters simultaneously reproduces the metal coordination for all ten nickel complexes with overall root-mean-square errors of 0.010 Angstrom in Ni-N bond lengths and 0.621 degrees in N-Ni-N angles. For the copper compounds, the (slightly modified) force field automatically models the Jahn-Teller distorted structures of six-coordinate species, the planar coordination in the four-coordinate compounds, and the distorted geometries of five-coordinate systems. The root-mean-square errors in bond lengths and angles for all 15 Cu molecules are higher (0.024 Angstrom and 0.897 degrees, respectively) due to the inherent variability of the structural data. Copper complexes, especially pentacoordinate ones, are intrinsically flexible or ''plastic'' which, with the added influence of the Jahn-Teller effect, can result in large geometrical changes from relatively minor crystal packing effects.MOLECULAR MECHANICS FOR COORDINATION-COMPLEXES - THE IMPACT OF ADDING D-ELECTRON STABILIZATION ENERGIESx94199573#N/AFALSE
2986
ja00137a00810.1021/ja00137a008FALSEhttps://doi.org/10.1021/ja00137a008MEYERSTEIN, DJ. Am. Chem. Soc.The electrochemical reduction of the Cu(II) complexes with the ligands 2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane, 2,5,9,12-tetramethyl-2,5,9,12-tetraazatridecan and 2,6,9,13-tetramethyl-2,6,9,13-tetraazatetradecane in deaerated aqueous solutions yields the corresponding thermodynamically stable copper(I) complexes. The same complexes are obtained also via the comproportionation reaction of CuL(i) (2+) and Cu-0 in the presence of excess ligand. Delta S-0 values of the reduction processes were determined. The basicity constants of L(i) and the stability constants of their Cu(II) complexes were determined potentiometrically. The ESR spectra of CuL(i) (2+) point out that these complexes are not significantly tetrahedrally distorted. The binding constants of axial singly charged anions to the CuL(i) (2+) complexes were determined. Analysis of the data points out that the thermodynamic stabilization of the monovalent copper complexes via N-methylation is mainly due to the destabilization of the CuL(i) (2+) complexes. It is conCluded that a major factor contributing to the observed effects is the hydrophobic nature of the tertiary-amine ligands.USE OF HYDROPHOBIC LIGANDS FOR THE STABILIZATION OF LOW-VALENT TRANSITION-METAL COMPLEXES .1. THE EFFECT OF N-METHYLATION OF LINEAR TETRAAZAALKANE LIGANDS ON THE PROPERTIES OF THEIR COPPER-COMPLEXESx101199544#N/AFALSE
2987
ja00167a07810.1021/ja00167a078FALSEhttps://doi.org/10.1021/ja00167a078BURROWS, CJJ. Am. Chem. Soc.HIGH TURNOVER RATES IN PH-DEPENDENT ALKENE EPOXIDATION USING NAOCl AND SQUARE-PLANAR NICKEL(II) CATALYSTS117199024#N/ATRUE
2988
ja00134a02510.1021/ja00134a025FALSEhttps://doi.org/10.1021/ja00134a025MANTELE, WJ. Am. Chem. Soc.The monoanions (the terms monoanions (anions) and monocations (cations) used in this paper refer to pi-monoanion radical and pi-monocation radical, respectively) and monocations of transmetalated bacteriochlorophyll a [M]-BChla (M = Mn, Zn, Cd, Co, Ni, Cu, Pd) and the corresponding 13(2)-hydroxy derivatives [M]-OH-BChla were investigated by a combination of Fourier transform infrared (FTIR) spectroscopy and electrochemistry between 1800 and 1200 cm(-1). [M]-BChla undergoing only ring-centered redox processes (M = Zn, Cd, Ni, Cu, and Pd) exhibit FTIR difference spectra typical for the monoanions [M]-BChla(.-) and for the monocations [M]-BChla(.+). The exceptions are the Ni derivatives and the monocations of the Co derivatives. They are attributed to a deformation of the bacteriochlorin macrocyCle from a planar toward a nonplanar conformer. [M]-BChla undergoing metal centered redox processes (M = Mn, Co) resemble the FTIR difference spectra of the [M]-BChla undergoing ring-centered redox processes in the Carbonyl frequency region and below 1400 cm(-1), where the main contributions arise from C-N and C-C modes. The skeletal modes between 1400 and 1600 cm(-1) are strongly influenced by the metal-centered redox reactions. The 13(2)-ester absorption and difference band is proposed as a marker band for distortions of the planar macrocyCle toward a nonplanar conformer.FOURIER-TRANSFORM INFRARED-SPECTROSCOPY OF ELECTROGENERATED ANIONS AND CATIONS OF METAL-SUBSTITUTED BACTERIOCHLOROPHYLL-ALPHAx23199560#N/AFALSE
2989
ja00134a02410.1021/ja00134a024FALSEhttps://doi.org/10.1021/ja00134a024HEINZE, JJ. Am. Chem. Soc.A series of transmetalated bacteriochlorophyll a, [M]-BChla (M = Mn, Zn, Cd, Co, Ni, Cu, Pd), and the corresponding 13(2)-hydroxy derivatives, [M]-OH-BChla, were investigated by low-temperature cyClic voltammetry and by spectroelectrochemistry in the vis/near-IR range. This is the first systematical investigation of bacteriochlorin macrocyCles with electrochemical methods. In the cyClic voltammetry measurements, we were able to generate the dianions and dications of all species. Furthermore, we have observed the trianions for the Ni and Cu derivatives as well as the tetraanions of the Co derivatives. With the exception of the tri- and tetraanions, the redox potentials exhibit a linear relationship with the E(N)/r(i) values (E(N) = electronegativities, r(i) = radius of the divalent metal ion). Deviations are observed for the Ni, Co, and Cd derivatives and are interpreted in terms of structural deformations. Kinetic electrochemical measurements show that the native BChla has the highest rate constant for the heterogeneous charge transfer. Using VIS/near-IR spectroelectrochemistry, we were able to distinguish between metal-centered and ring-centered redox processes. For the Co and Mn derivatives, metal-centered redox reactions are observed. A ''pi-anion-state-marker'' band positioned between 927 and 974 nm is proposed.AN ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL INVESTIGATION OF METAL-SUBSTITUTED BACTERIOCHLOROPHYLL-ALPHAx38199569#N/AFALSE
2990
ja00132a00410.1021/ja00132a004FALSEhttps://doi.org/10.1021/ja00132a004LINDAHL, PAJ. Am. Chem. Soc.The alpha metallosubunit of carbon monoxide dehydrogenase from Clostridium thermoaceticum was isolated by subjecting native enzyme to low concentrations of the detergent sodium dodecyl sulfate, followed by anaerobic preparative native polyacrylamide gel electrophoresis. The isolated alpha subunit absorbs in the 400 nm region and contains one Ni and four Fe ions. The irons are organized into an [Fe4S4](2+/1+) Cluster, the reduced form of which exhibits EPR features between g = 6 and 3, and a weak (0.1 spin/alpha) g(av) = 1.94 signal. The reduced Cluster appears to exist in an S = 3/2 : S = 1/2 spin-state mixture and to be predominantly S = 3/2 at 10 K. The Ni center is EPR silent and presumably Ni(II). X-ray absorption edge and EXAFS spectra reveal that the Ni center has a distorted square-planar geometry with two S donors at 2.19 degrees and two N/O donors at 1.89 Angstrom. Comparison of the Ni edge spectrum with those of structurally characterized Ni(II)N2S2 model compounds suggests a D-2d distortion with a dihedral angle of about 20-30 degrees. The Ni center does not appear to be incorporated into the Cluster, and it may or may not be bridged to the Cluster. These centers may be decompositional relatives of the A-Cluster, the active site for acetyl-coenzyme A synthesis.EXAFS, EPR, AND ELECTRONIC ABSORPTION SPECTROSCOPIC STUDY OF THE ALPHA-METALLOSUBUNIT OF CO DEHYDROGENASE FROM ClOSTRIDIUM-THERMOACETICUMx61199547#N/AFALSE
2991
ja00165a03210.1021/ja00165a032FALSEhttps://doi.org/10.1021/ja010358aSCHUGAR, HJPREPARATION, STRUCTURE, AND PROPERTIES OF PSEUDOTETRAHEDRAL, D2D COMPLEXES OF CU(II), NI(II), CO(II), CU(I), AND ZN(II) WITH THE GEOMETRICALLY CONSTRAINING BIDENTATE LIGAND 2,2'-BIS(2-IMIDAZOLYL)BIPHENYL - EXAMINATION OF ELECTRON SELF-EXCHANGE FOR THE CU(I) CU(II) PAIR1990#N/ATRUE
2992
ja001316+10.1021/ja001316+FALSEhttps://doi.org/10.1021/ja001316+Smith, KMJ. Am. Chem. Soc.A novel trimeric porphyrin array in which the macrocyCles are directly fused through their beta -pyrrolic carbons has been prepared and investigated. These molecules feature a 7,8,17,18-tetraethylporphyrin moiety flanked on opposite sides by two tetraphenylporphyrin (TPP) moieties. The 2,3 and 12,13 beta -carbon positions of the tetraethylporphyrin substructure also function as the beta -carbons in the 2 and 3 positions of the two TPP macrocyCles. This framework was prepared via the reaction of 2,5-bis[(N,N,N-trimethylammonium)methyl] 3,4-diethylpyrrole diiodide with the nickel(II) complex of pyrrolo[3,4-b]-5,10,15,20-tetraphenylporphyrin, which afforded a 62-pi -electron 72-atom macrocyCle (2) with a central free-base tetraethylporphyrin and two terminal nickel(II) TPP functionalities. The tri-free-base complex (1) was obtained by treatment of the dinickel(II) complex with sulfuric acid followed by neutralization. Crystallographic characterization of 1 (as its tetracation salt) and 2 (as its dication salt) revealed that this type of molecule bears a considerable degree of macrocyClic flexibility. Luminescence spectra of 1 displayed an intense band around 800 nm, making these types of macrocyCles promising candidates as chromophores for labels and sensors in biological media. Both 1 and 2 exhibited complex optical spectra, each of which displayed an intensely red shifted Q-band [1, lambda (max) (nm) 369 II (epsilon 36 400), 416 (49 700), 488 (71 200), 562 (16 500), 650 (15 700), 744 (42 300); 2, lambda (max) nm 361 (epsilon 87 200), 408 (107 000), 486 (189 000), 558 (27 700), 650 (28 200), 682 (31 100), 716 (175 500)]. Selective protonation of 1 with TFA afforded a green tetracationic species [(H-4-H-2-H-4)(4+).1] with an even more red-shifted Q-band (848 nm) while addition of excess TFA yielded a red hexaprotonated species [(H-4-H-4-H-4)(6+).1]. Optical analyses of 1, using the INDO/SCI and orbital localization techniques, were performed to obtain information with regard to the degree of macrocyClic pi -electron delocalization. These studies showed that the optical properties of 1 cannot be described within the excitonic model of weakly interacting macrocyCles (alpha > 60%), and that pi -electron delocalization over the 72-atom macrocyCle is not complete. Even though resonance structures for the 72-atom macrocyCle imply a fully conjugated aromatic system, our data indicated that the three constituent porphyrin macrocyCles behave somewhat more like discrete aromatic systems.beta-fused oligoporphyrins: A novel approach to a new type of extended aromatic systemx65200051#N/AFALSE
2993
ja00130a00910.1021/ja00130a009https://doi.org/10.1021/ja00130a009FUJITA, EJ. Am. Chem. Soc.Cobalt macrocyCles mediate electron transfer in the photoreduction of CO2 with p-terphenyl as a photosensitizer and a tertiary amine as a sacrificial electron donor in a 5:1 acetonitrile/methanol mixture. The mechanism and kinetics of this system have been studied by continuous and flash photolysis techniques. Transient spectra provide evidence for the sequential formation of the p-terphenyl radical anion, the Co(I)L(+) complex, the [Co(I)L-CO2](+) complex, and the [S-Co(III)L-(CO22-)](+) complex (L = HMD = 5,7,7,12,14,14-hexamethyl-1,4,8,11- tetraazacyClotetradeca-4,11-diene; S = solvent) in the catalytic system. The electron-transfer rate constant for the reaction of p-terphenyl radical anion with Co(II)L(2+) is 1.1 x 10(10) M(-1) s(-1) and probably diffusion controlled because of the large driving force (similar to+1.1 V). Flash photolysis studies yield a rate constant 1.7 x 10(8) M(-1) s(-1) and an equilibrium constant 1.1 x 10(4) M(-1) for the binding of CO2 to Co(I)L(+) in the catalytic system. These are consistent with those previously obtained by conventional methods in acetonitrile. Studies of catalytic systems with varying cobalt macrocyCles highlight some of the factors controlling the kinetics of the photoreduction of CO2. Steric hindrance and reduction potentials are important factors in the catalytic activity for photochemical CO2 reduction.MECHANISTIC AND KINETIC-STUDIES OF COBALT MACROCYClES IN A PHOTOCHEMICAL CO2 REDUCTION SYSTEM - EVIDENCE OF CO-CO2 ADDUCTS AS INTERMEDIATESPhotocatalyst137199561#N/AFALSE
2994
ja00129a01110.1021/ja00129a011FALSEhttps://doi.org/10.1021/ja00129a011HOLM, RHJ. Am. Chem. Soc.Current mechanistic proposals for the acetyl synthase activity of nickel-containing carbon monoxide dehydrogenases (CH3-THF + CoA . SH --> CoA . SCOCH3 + THF; THF = tetrahydrofolate, CoA . SH = coenzyme A) implicate a Ni catalytic center and the steps [Ni-CH3] --> [Ni-COCH3] --> CoA . SCOCH3. The second step presumably involves attack by the sulfur nuCleophile of coenzyme A at the acyl carbon atom in the overall reaction [Ni-II-COCH3] + RS(H) --> RSCOCH(3) + Ni-II (+ H+) + 2e(-). We have previously demonstrated these steps in Ni(II) complexes with physiological-type ligation. In this work, it is shown that the reaction of acyl and thiolate ligands coordinated to Ni(II) affords thioesters in high yield, The complex [Ni(bpy)(CH3)(2)], established to be planar by an X-ray structure determination, reacts with 1 equiv of arenethiol to afford diamagnetic planar [Ni(bpy)(CH3)(SR)] (8) with R = p-C6H4CH3, 2,6-C6H3(CH3)2 (8b), mesityl (8c), 2,4,6-C(6)H(2)iPr(3), and 2,6-C6H3Cl2 (8e) (bpy = 2,2'-bipyridyl). An analogous reaction gives [Ni(bpy)(C2H5)(S-mesityl)] (12) from [Ni(bpy)(C2H5)(2)]. Planar structures of 8c,e were confirmed by X-ray analysis. Complexes 12 and 8 with different R substituents undergo thiolate ligand exchange in THF with K-eq approximate to 1. Reaction of 8e with 1 equiv of carbon monoxide yields the acyl complex [Ni(bpy)(COCH3)(S-2,6-C6H3Cl2)] (9a), whose planar coordination unit was confirmed by X-ray methods. Treatment of the complexes 8 in THF with more than 3 equiv of carbon monoxide yields [Ni(bpy)(CO)(2)] and the thioesters RSCOCH(3) in 96-100% yield in situ. A solution initially containing 8b and 12 gave under the same conditions four thioesters in equal amounts, consistent with four complexes in the equilibrated solution prior to reaction with carbon monoxide. Reaction of 9a in THF with carbon monoxide produced 2,6-dichlorophenyl thioacetate quantitatively, indicating that Ni(II)-acyl-thiolate complexes are intermediates in thioester formation. The overall reaction is [Ni(bpy)(R')(SR)] + 3CO --> RSCOR' + [Ni(bpy)(CO)2] (R' = CH3, C2H5); the two electrons in the generalized reaction are captured by the metal as Ni(0). A related and necessarily intramolecular reaction of [Ni(bpy)(SCH2CH2CH2)] was confirmed and shown to produce gamma-thiobutyrolactone in quantitative yield in situ. Evidence supporting an analogous intramolecular path for reaction systems based on 8 is summarized. This investigation provides the first examples of Ni-mediated acyClic thioester synthesis and demonstrates a possible means of enzymatic thioester formation should coenzyme A(-) and an acetyl group coordinate to the Ni(II) catalytic center.NICKEL-MEDIATED FORMATION OF THIOESTERS FROM BOUND METHYL, THIOLS, AND CARBON-MONOXIDE - A POSSIBLE REACTION PATHWAY OF ACETYL-COENZYME A SYNTHASE ACTIVITY IN NICKEL-CONTAINING CARBON-MONOXIDE DEHYDROGENASESx81199554#N/AFALSE
2995
ja00128a05410.1021/ja00128a054https://doi.org/10.1021/ja00128a054BROOKHART, MJ. Am. Chem. Soc.NEW PD(II)-BASED AND NI(II)-BASED CATALYSTS FOR POLYMERIZATION OF ETHYLENE AND ALPHA-OLEFINSx2461199519#N/AFALSE
2996
ja00165a02710.1021/ja00165a027FALSEhttps://doi.org/10.1021/ja00165a027LEWIS, NSJ. Am. Chem. Soc.EFFECTS OF REDOX POTENTIAL, STERIC CONFIGURATION, SOLVENT, AND ALKALI-METAL CATIONS ON THE BINDING OF CARBON-DIOXIDE TO COBALT(I) AND NICKEL(I) MACROCYClES88199075#N/ATRUE
2997
ja001254n10.1021/ja001254nFALSEhttps://doi.org/10.1021/ja001254nJager, EGJ. Am. Chem. Soc.The macrocyClic nickel complexes shown in Figure 1 are able to catalyze the electrochemical reduction of CO2 to oxalate. In the case of the complexes with R-2 = COOEt or COMe, the overall reaction can be interpreted in terms of an outer-sphere electron-transfer reaction (6) followed by a dimerization of the CO2.- radical anions (7), but the variation of the electron-transfer rate constants with the standard potentials points to a coordinative interaction between the complexes and the CO2 molecule. Complexes without COOEt or COMe substitution in the R-2 position undergo a fast deActivation reaction (first order with respect to [CO2]) that is even visible in the time scale of the cyClic voltammetric experiments. The results of the cyClic voltammetric investigations could be confirmed in preparative-scale electrolyses where the complex Ni-Etn(Me/COOEt)-Etn proved to be the most active and persistent redox catalyst for the electrochemical reduction of CO2 to oxalate that has been described so far.MacrocyClic [N-4(2-)] coordinated nickel complexes as catalysts for the formation of oxalate by electrochemical reduction of carbon dioxidex82200032#N/AFALSE
2998
ja00159a08610.1021/ja00159a086FALSEhttps://doi.org/10.1021/ja00159a086PETIT, FJ. Am. Chem. Soc.REGIOCONTROLLED AND STEREOCONTROLLED C-C BOND FORMATION VIA LINEAR DIMERIZATION OF CONJUGATED DIENES CATALYZED BY NICKEL-AMINOPHOSPHINITE COMPLEXES2319909#N/ATRUE
2999
ja00158a03010.1021/ja00158a030FALSEhttps://doi.org/10.1021/ja00158a030SHELNUTT, JAJ. Am. Chem. Soc.INFLUENCES OF PI-PI-COMPLEX FORMATION, DIMERIZATION, AND BINDING TO HEMOGLOBIN ON THE PLANARITY OF NICKEL(II) PORPHYRINS95199044#N/ATRUE
3000
ja00153a01510.1021/ja00153a015FALSEhttps://doi.org/10.1021/ja00153a015SCHULTZ, FAJ. Am. Chem. Soc.M(tacn)(2)(3+/2+) redox couples (M = Fe, Ni, Co; tacn = 1,4,7-triazacyClononane) exhibit different extents of M-N bond lengthening upon electrochemical reduction and standard heterogeneous rate constants (k(s,h)) that decrease systematically in accord with this structural feature. Inner-shell enthalpies of Activation (Delta H double dagger(is)) obtained from temperature-dependent measurements of k(s,h) [Crawford, P. W,; Schultz, F. A. Inorg. Chem. 1991, 33, 4344] equal 1.7, 1.9, and 13.2 kcal mol(-1) for M = Fe, Ni, and Co, respectively, in contrast with values of 0.2, 2.2, and 6.0 kcal mol(-1) calculated by the harmonic oscillator model of M-N bond elongation. In an attempt to resolve this discrepancy we have carried out molecular mechanics calculation of Delta H double dagger(is) for M(tacn)(2)(3+/2+) couples using MMX and CHARMM force fields. The procedure for doing so involves intersecting potential energy curves of oxidized and reduced reactants generated from the force field parameters required to optimize the ground state structure of each oxidation state. MMX barrier heights estimated in this way are in Close correspondence with the harmonic oscillator approximation widely used in Marcus theory calculation of inner-shell reorganization energies. The vibrational entropies of the molecules are calculated, and differences in these quantities correlate with the half-reaction entropy (Delta S degrees(rc)) of the M(tacn)(2)(3+/2+) couples. Non-zero, metal-dependent values of Delta S degrees(rc) for these complexes are thought to arise from changes in M-N frequencies upon reduction [Richardson, D. E.; Sharpe, P. Inorg. Chern, 1991, 30, 1412]. Poor correspondence between measured and calculated Activation enthalpies remains in cases where the electrode reaction exhibits a large half-reaction entropy. The molecular mechanics force fields are used to partition the energy of the molecules into component terms, and it is found that the majority of the inner-shell barrier derives from M-N bond stretching.MOLECULAR MECHANICS CALCULATION OF INNER-SHELL Activation BARRIERS TO HETEROGENEOUS ELECTRON-TRANSFER IN M(TACN)(2)(3+/2+) REDOX COUPLES (M=FE, CO, NI, TACN=1,4,7-TRIAZACYClONONANE)20199541#N/ATRUE
3001
ja00121a00110.1021/ja00121a001FALSEhttps://doi.org/10.1021/ja00121a001TOUR, JMJ. Am. Chem. Soc.Described are the polymerizations of three new dibrominated Carbonyl-stabilized ylide monomers using copper-bronze in DME to afford polymers that are soluble in common solvents and have unique optical and electronic properties. The first monomer is a zwitterionic N-butylpyrrolinium oxide derivative which, upon polymerization, gives a polymer that has a strong optical absorbance at 520 nm in CCl4. An interunit ionic interaction is proposed to explain this large red-shifted band. Bronsted bases and Lewis bases induce a reversible structural change in the polymer to give bathochromic shifts from the visible to the near-IR spectral region. Upon mild reduction of the zwitterionic polymer with Pd/C and H-2 (1 atm), some of the extended conjugation is lost, but a polymer forms that has an enormous optical absorption maximum range from the near-UV (290 nm) to the near-IR (886 nm) depending on the solvent or hydroxide Concentration. A sample of the reduced polymer can be dispersed in platicized poly-(Vinyl chloride), The flexible polymer composite reversibly changes from dark blue-brown in aqueous sodium hydroxide to bright yellow-orange in aqueous HCl. The second monomer, a zwitterionic N-dodecylpyrrolinium oxide derivative, was also synthesized in three steps from pyrrole and, upon polymerization, gives rise to a polymer which also responds reversibly toward Bronsted and Lewis bases, This polymer can be solution cast into flexible free-standing films. The third monomer is a zwitterionic N-[oligo(ethylene glycol) monomethyl ether]pyrrolinium oxide derivative which, upon polymerization, affords a polymer that not only responds reversibly toward Bronsted and Lewis bases but also is water soluble and optically sensitive toward the addition of specific salts. The presence of the oligoethylene substituents is critical for the dramatic ionochromic response. Additionally, Pd-catalyzed cross-coupling methodology can be used for the incorporation of the N-butylpyrrolinium oxide monomer unit into an AB-type oligomeric system where the B component is a 1,4-phenylene moiety.SYNTHESIS AND PROPERTIES OF LOW-BANDGAP ZWITTERIONIC AND PLANAR CONJUGATED PYRROLE-DERIVED POLYMERIC SENSORS - REVERSIBLE OPTICAL-ABSORPTION MAXIMA FROM THE UV TO THE NEAR-IRx71199548#N/AFALSE
3002
ja00150a00810.1021/ja00150a008FALSEhttps://doi.org/10.1021/ja00150a008SHELNUTT, JAJ. Am. Chem. Soc.Metalloporphyrins undergo remarkable nonplanar distortions of the macrocyCle that perturb the chemical and photochemical properties of these important protein cofactors. Further, the tertiary structure of the surrounding protein can manipulate these distortions as a means of regulating biological function. For cytochromes c, for example, an energetically unfavorable, conserved nonplanar distortion of the heme exists and likely plays a role in its electron-transfer function. The heme distortion is primarily of the ruffling (run type (corresponding to the lowest frequency B-1u-symmetry normal mode) in which the pyrroles are twisted about the metal-N-pyrrole bond. This B-1u-symmetry nonplanar distortion is commonly observed in metalloporphyrin crystal structures, as are the saddling (sad) B-2n-symmetry distortion, waving (wav) E(g)-symmetry distortions, and doming (dom) A(2u)-symmetry distortion. Each of these nonplanar distortions is expected to result in unique alterations of the chemical and physical properties of the nominally planar porphyrin macrocyCle. Symmetrical porphyrin substitution with tetrahedrally bonded atoms at the four meso bridging carbons generally results in the B-1u ruffling distortion; therefore, we investigated a series of meso-tetrasubstituted porphyrins for which the substituents vary in size (methyl, ethyl, propyl, pentyl, isopropyl, cyClopropyl derivative 11a, cyClohexyl, apopinenyl (10), tert-butyl, adamantyl), increasing the steric crowding at the periphery. Molecular mechanics calculations show increasing degree of ruffling (CalphaNNCalpha angle for opposite pyrroles varies from 0 to 57 degrees) for this series of porphyrins, generally agreeing with the X-ray structures that are available. In addition, the frequencies of the structure-sensitive Raman lines decrease nonlinearly with increasing ruffling angle. The localization of the B-1u nonplanar distortion in only the C(a)lpha-C-m bond torsion (not the case for the B-2u sad distortion) suggests a means by which the B-1u distortion might be distinguished from other types of nonplanar distortion by using resonance Raman spectroscopy. Also, the size of the red shifts in the pi-->pi* absorption bands depends on C(a)lpha-C-m torsion angle in a nonlinear fashion and the shift is accurately predicted by INDO/s molecular orbital calculations when the nonplanar structures obtained from molecular mechanics are used.RUFFLING IN A SERIES OF NICKEL(II) MESO-TETRASUBSTITUTED PORPHYRINS AS A MODEL FOR THE CONSERVED RUFFLING OF THE HEME OF CYTOCHROMES-C278199573#N/ATRUE
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ja00146a01210.1021/ja00146a012FALSEhttps://doi.org/10.1021/ja00146a012LOUGH, AJJ. Am. Chem. Soc.Active catalysts which promote the homo-Diels-Alder (HDA) cyCloaddition with a variety of electron-deficient olefins with bicyClo[2.2.1]hepta-2,5-diene (norbornadiene, NBD) have been developed. The nickel complex and the additives (e.g., Ligands, reducing agents) influence the activity of the catalyst. Dienophiles which participate in this cyCloaddition inClude acyClic and cyClic enones, lactones, sulfones, and sulfoxides. The dienophile substituent, the catalyst, and the temperature affected the exo/endo selectivity in the HDA reaction. A diastereoselective reaction with an optically enriched Vinyl sulfoxide led to the synthesis of an optically active deltacyClane. The regio- and stereoselectivity of the HDA reaction between 2-substituted norbornadienes and electron-deficient dienophiles has also been studied. The substituents on the diene and dienophile as well as the ligands were found to exert a dramatic effect on the selectivity. With very reactive dienophiles, an alternative [2 pi+2 pi] cyCloaddition was discovered for 2-substituted norbornadienes. In some cases, the [2 pi+2 pi] cyCloaddition can occur with high chemo- and regioselectivity and moderate levels of stereoselectivity.NICKEL-CATALYZED [2-PI+2-PI+2-PI] (HOMO-DIELS-ALDER) AND [2-PI+2-PI] CYClOADDITIONS OF BICYClO[2.2.1]HEPTA-2,5-DIENES561995109#N/ATRUE
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ja00119a01610.1021/ja00119a016FALSEhttps://doi.org/10.1021/ja00119a016ANDERSEN, RAJ. Am. Chem. Soc.Several platinum cis-dihydride phosphine complexes, (diphos)PtH2 [4, diphos = iPr(2)P(CH2)(2)PiPr(2) (dippe); 5, diphos = Cy(2)P(CH2)(2)PCy(2) (dcype); and 6, diphos = tBu(2)P(CH2)(2)PtBu(2) (dtbpe)], have been found to be unstable in solution, reversibly losing H-2 and forming binuClear complexes of the general formula [(P-P)PtH](2). The extent of dimerization in solution is directly related to the steric size of the phosphine ligand, larger phosphines imparting kinetic stability to the cis-dihydride monomers. The dimeric complexes possess terminal hydride ligands on the basis of their IR spectra; however, the room-temperature H-1, P-31{H-1} and Pt-195{H-1} NMR spectra show equivalence within the sets of H, Pt, and P nuClei, indicating that the dimers are fluxional in solution. This fluxional process can be stopped at low temperature for the (dippe) and (dcype) derivatives, 1 and 2, but not for the (dtbpe) derivative, 3. The complex 1 crystallizes in the orthorhombic space group P2(1)2(1)2(1) in a cell of dimensions a = 9.245(2) Angstrom, b = 16.966(2) Angstrom, c = 22.690(6) Angstrom, and Z = 4. The structure shows square planar geometry about each Pt(I) center, the coordination sphere being composed of one bidentate phosphine ligand, a terminal hydride, and a direct, unbridged bond to the other Pt center. The angle between the two square planes is 93.2(1)degrees, and the Pt-Pt distance is 2.5777(5) Angstrom. The complex 3 crystallizes as a toluene solvate in the triClinic space group P (1) over bar with a = 11.552(3) Angstrom, b = 13.123(3) Angstrom, c = 17.694(4) Angstrom, alpha = 81,20(2)degrees, beta = 89.20(2)degrees, gamma = 66.55(2)degrees, and Z = 2. The structure is similar to that of 1; however, there are several distortions resulting from steric crowding caused by the larger tert-butyl groups (Pt-Pt distance = 2.6094(6) Angstrom). The spectral and structural details, the solution properties, and the nature of the fluxional process are discussed.REVERSIBLE FORMATION OF [P2PTH](2) PLATINUM(I) COMPLEXES FROM CIS-P2PTH2 COMPLEXES, WHERE P-2 IS A CHELATING PHOSPHINEx49199545#N/AFALSE
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ja00145a01310.1021/ja00145a013FALSEhttps://doi.org/10.1021/ja00145a013BARTLETT, NJ. Am. Chem. Soc.F- accepters (BF3, AsF5, SbF5, or BiF5) added to solutions of NiF62- salts in anhydrous hydrogen fluoride (aHF) below -65 degrees C precipitate the tan solid NiF4. This solid, preserved at less than or equal to-65 degrees C, is quantitatively converted, by 2 equiv of F- donor (XeF6 or KF) in aHF, to dissolved NiF62-. Dry NiF4 loses F-2 above -60 degrees C, the decomposition to nearly black NiF3 becoming rapid at similar to 0 degrees C. When the dry NiF4 is prepared from K2NiF6, inClusion of some K+ leads, on thermolysis at 0 degrees C, to a pyrochlore form of NiF3 (P-NiF3). P-NiF3 contains K+ in the open channels, with KxNiF3, x approximate to 0.1. The nearly cubic P-NiF3 unit cell is rhombohedral: a(0) = 9.933(3) Angstrom, alpha = 91.01(3)degrees, V = 980 Angstrom(3), z = 16, with absent reflections coincident with those of the cubic space group O-h(7)-Fd3m, appropriate for pyrochlore. Decomposition of NiF4 in aHF begins at -65 degrees C and is rapid at 0 degrees C, giving black rhombohedral NiF3 (R-NiF3) with a(0) = 5.168(2) Angstrom, alpha = 55.46(3)degrees, V = 87.3 Angstrom(3), z = 2. When the NiF4 is made and decomposed at similar to 20 degrees C, with Kf present, a hexagonal tungsten bronze form of NiF3 is precipated (H-NiF3), with a(0) = 7.074(6) Angstrom, c(0) = 7.193(6) Angstrom, V = 312 Angstrom(3), z = 6. R- and H-NiF3 can also be made by mixing solutions of Ni2+ salts [e.g., Ni(AsF6)(2)] With NiF62- salts (e.g. K2NiF6) in aHF. All forms of the trifluoride (R, H, and P) lose F-2 on warming (R > 39 degrees, H > 72 degrees and P > 138 degrees C) to yield NiF2, but an intermediate red-brown phase is observed for R-NiF3. R-NiF3 at similar to 20 degrees C, oxidizes Xe to Xe(VI), perfluoropropene, C3F6, to perfluoropropane, C3F8, and solid LiCl with incandescence. H-NiF3 and P-NiF3 interact similarly but less energetically.THERMODYNAMICALLY UNSTABLE FLUORIDES OF NICKEL - NIF4 AND NIF3 SYNTHESES AND SOME PROPERTIES54199547#N/ATRUE
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ja00118a00810.1021/ja00118a008FALSEhttps://doi.org/10.1021/ja00118a008KINOSHITA, MJ. Am. Chem. Soc.The highly efficient syntheses of the erythromycin A (1) from its aglycon, (9S)-9-dihydroerythronolide A (4), and the C-D-E trisaccharide 3 of olivomycin A have been accomplished by the successful application of stereocontrolled glycosidations using 2,6-anhydro-2-thio sugars. The former synthesis inCludes the highly alpha-stereoselective glycosidation of the C5 desosaminated lactone 12 with phenyl 2,6-anhydro-4-O-Benzyl-3-C-methyl-3-O-methyl-1 ,2-dithio-L-altropyranoside (10), which was achieved by using NIS-TfOH. The latter synthesis involves both the highly beta-stereoselective glycosidation of 1,3-di-O-acetyl-2,6-anhydro-4-O-Benzyl-2-thio-beta-D-altropy (23), which was realized by employing TMSOTf, and the highly alpha-stereoselective glycosidation of phenyl 2,6-anhydro-3-O-(diethylisopropylsilyl) -4-O-isobutyryl-3-C-methyl-1,2-dithio-L-manno-pyranoside (24), which succeeded by utilizing NBS. Hydrogenolyses using Raney Ni as a catalyst and selective deprotections of the key glyco substances 17 and 22 led to the total syntheses of erythromycin A (1) and the C-D-E trisaccharide 3 of olivomycin A, respectively.APPLICATION OF HIGHLY STEREOCONTROLLED GLYCOSIDATIONS EMPLOYING 2,6-ANHYDRO-2-THIO SUGARS TO THE SYNTHESES OF ERYTHROMYCIN-A AND OLIVOMYCIN-A TRISACCHARIDEx451995114#N/AFALSE
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ja00117a00710.1021/ja00117a007https://doi.org/10.1021/ja00117a007HEGEDUS, LSJ. Am. Chem. Soc.Bis-chromium alkoxycarbene complexes, bridged via the alkoxy groups, underwent photochemical cyCloaddition to protected imidazolines to give protected bis-azapenams. Deprotection followed by treatment with acid produced bis-dioxocyClams bridged top and bottom with four-, five-, six-, and twelve-atom alpha,omega-diol linkages. These bis-dioxocyClam ligands formed mono- and bis-nickel(II) complexes. The five-atom bridged system (-O(CH2)(3)O-) was characterized by X-ray crystallography and had a number of unusual features.SYNTHESIS AND METAL COMPLEXATION REACTIONS OF BIS-DIOXOCYClAMS FROM PHOTOCHEMICAL-REACTION OF BIS-CHROMIUM ALKOXYCARBENE COMPLEXES WITH IMIDAZOLINESPhotocatalyst40199538#N/AFALSE
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ja00114a03210.1021/ja00114a032FALSESPIRO, TGFREEZE QUENCH RESONANCE RAMAN-SPECTROSCOPIC EVIDENCE FOR AN FE-CO ADDUCT DURING ACETYL-COA SYNTHESIS AND NI INVOLVEMENT IN CO OXIDATION BY CARBON-MONOXIDE DEHYDROGENASE FROM ClOSTRIDIUM-THERMOACETICUMx1995#N/AFALSE
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ja00143a03010.1021/ja00143a030FALSEhttps://doi.org/10.1021/ja00143a030FACKLER, JPJ. Am. Chem. Soc.SYNTHESES AND STRUCTURAL CHARACTERIZATIONS OF 2 NEW CU-S ClUSTERS OF DIAlkyl DITHIOPHOSPHATES - A SULFIDE-CENTERED CU-8(I) CUBE,(CU-8[S2P((OPR)-PR-I)(2)](6)(MU(8)-S)) AND A DISTORTED OCTAHEDRAL (CU-6[S2P(OET)(2)](6)CENTER-DOT-2H(2)O) ClUSTER85199548#N/ATRUE
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ja00142a01410.1021/ja00142a014FALSEhttps://doi.org/10.1021/ja00142a014MARKS, TJROLE OF METAL ELECTRONIC-PROPERTIES IN TUNING THE 2ND-ORDER NONLINEAR-OPTICAL RESPONSE OF COORDINATION-COMPLEXES - A COMBINED EXPERIMENTAL AND THEORETICAL INVESTIGATION OF A HOMOLOGOUS SERIES OF (N,N'-DISALICYLIDENE-1,2-PHENYLENEDIAMINATO)M(II) (M=CO, NI, CU) COMPLEXES1995#N/ATRUE
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ja00136a03410.1021/ja00136a034FALSEhttps://doi.org/10.1021/ja00136a034AKIBA, KJ. Am. Chem. Soc.SYNTHESIS AND STRUCTURE OF PHOSPHORUS(V) OCTAETHYLPORPHYRINS THAT CONTAIN A SIGMA-BONDED ELEMENT-CARBON BOND - CHARACTERIZATION OF A PORPHYRIN BEARING AN R-P=O BOND AND RELATION OF THE RUFFLING OF THE PORPHYRIN CORE WITH THE ELECTRONEGATIVITY OF THE AXIAL LIGANDS55199529#N/ATRUE
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ja00131a00810.1021/ja00131a008FALSEhttps://doi.org/10.1021/ja00131a008SMITH, ACJ. Am. Chem. Soc.The scope of the cobalt-catalyzed [2 pi + 2 pi + 2 pi] (home Diels-Alder, HDA) and [2 pi + 2 pi + 4 pi] cyCloaddition reactions with norbornadienes has been investigated. Cobalt acetylacetonate, Co(acac)(3) or Co(acac)(2), upon reduction by diethylaluminum chloride (Et(2)AlCl) in the presence of 1,2-bis(diphenylphosphino)ethane (dppe), is very effective in promoting the HDA reaction between norbornadiene and a variety of unactivated acetylenes to yield deltacyClenes. Azeotropic drying of the cobalt compound before use is found to increase the reactivity of the catalyst. Moderate to excellent enantioselectivity of these [2 pi + 2 pi + 2 pi] (up to 91% ee) and [2 pi + 2 pi + 4 pi] (up to 79% ee) cyCloadditions can be achieved by the use of a chiral phosphine. 7-Substituted norbornadienes are also found to be reactive in the cobalt-catalyzed HDA reactions, affording the corresponding deltacyClenes in good yields. However, low anti/syn selectivities are observed, in contrast with the corresponding nickel-catalyzed HDA reaction with electron-deficient dienophiles. 2-Substituted norbornadienes are found to be less reactive in the cobalt-catalyzed HDA reactions, and the regio- and stereoselectivities are only moderate. The intramolecular versions of these [2 pi + 2 pi + 2 pi] and [2 pi + 2 pi + 4 pi] cyCloadditions have also been investigated and provide efficient methods for the construction of highly strained pentacyClic frameworks from norbornadiene.COBALT-CATALYZED [2-PI+2-PI+2-PI] (HOMO DIELS-ALDER) AND [2-PI+2-PI+4-PI] CYClOADDITIONS OF BICYClO[2.2.1]HEPTA-2,5-DIENES1061995133#N/ATRUE
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ja00113a00710.1021/ja00113a007FALSEhttps://doi.org/10.1021/ja00113a007MAITLIS, PMJ. Am. Chem. Soc.The thiaplatinacyCles, [(PtSC12H8)(PEt(3))(2)], 1, [(PtSC8H6)(PEt(3))(2)], 2, and [(PtSC4H4)(PEt(3))(2)], 3, in which Pt(PEt(3))(2) has inserted into one C-S bond of dibenzothiophene (DBT), benzothiophene (BT), and thiophene (T), respectively, are formed by the reversible reaction of tris(triethylphosphine)platinum(O) with the thiophene. The structure of complex [(PtSC8H6)(PEt(3))(2)] (2) was confirmed by an X-ray determination that showed a square-planar Pt(II) bound to two cis PEt(3) ligands, and to the S and the CH=, in a six-membered Pt-S-C-C-C-C ring [Pt-S(1), 2.315(5) Angstrom; Pt-C(4), 2.035(19) Angstrom; Pt-P(1), 2.301(5) Angstrom, trans to S(1); and Pt-P(2), 2.386(5) Angstrom, trans to C(4); P(1)-Pt-P(2), 97.6(2)degrees; S(1)-Pt-P(2), 87.0(2)degrees; S(1)-Pt-C(4), 88.6(6)degrees; P(1)-Pt-C(4), 86.8(6)degrees]. The adducts 1 and 3, derived from DBT and T, have been shown to have similar structures spectroscopically. The free thiophenes and Pt(PEt(3))(3) are regenerated on heating complexes 1-3 with Et(3)P; [(PtSCaHb)(PEt(3))(2)] + Et(3)P reversible arrow [Pt(Et(3)P)(3)] + SCaHb. K-eqm = [Pt(Et(3)P)(3)] [SCaHb]/[PtSCaHb)(PEt(3))(2)] [Et(3)P] and is 10 for 1 (DBT) and 3 (T) and 1 for 2 (BT) at 100 degrees C. The complexes 1-3 undergo a variety of Cleavage reactions; thus, the Pt-C bond in 1 is Cleaved by HCl to give 2-phenylthiophenol and [Pt(PEt(3))(2)Cl-2], and all three complexes are degraded by hydride reagents to give the completely desulfurized hydrocarbons: biphenyl from 1, styrene and ethylbenzene from 2, and butadiene and butenes from 3. When the reactions are carried out with Et(3)SiH as reducer, the complex [Pt(SH)(H)(PEt(3))(2)] is identified among the products, together with [Pt(Et(3)Si)(H)(PEt(3))(2)]. The former is a coproduct of the desulfurization, while the latter arises from addition of Et(3)SiH to [Pt(PEt(3))(2)] (from reversal of the formation of [(PtSCaHb)(PEt(3))(2)]) and is accompanied by the formation of the free thiophene. Under comparable conditions, the amount of desulfurization decreases in the order BT complex 2 (73%) > DBT complex 1 (50%), T complex 3 (ca. 4%). These hydride reactions show the novel feature that the C-S bond is Cleaved as well as the Pt-C bond; possible mechanisms for the platinum and for the known nickel- and hydride-promoted hydrodesulfurization (HDS) reactions are discussed.EQUILIBRIA OF THE THIAMETALLACYClES WITH TRIS(TRIETHYLPHOSPHINE)PLATINUM(0) AND DIBENZOTHIOPHENE, BENZOTHIOPHENE, OR THIOPHENE - THE HYDRODESULFURIZATION REACTIONx134199549#N/AFALSE
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ja00113a00210.1021/ja00113a002FALSEhttps://doi.org/10.1021/ja00113a002BARTLETT, PAJ. Am. Chem. Soc.Three enzymes of the shikimic acid pathway, isochorismate synthase (IS), anthranilate synthase (AS), and p-aminobenzoate synthase (PABS), exhibit significant sequence homology and may be related mechanistically. Compounds 1, 2, and 3 were designed to mimic, in their all-axial conformations, the putative transition state for these enzymes. The inhibitors were prepared in racemic form starting from Diels-Alder addition of a propiolate ester to a protected 1-oxy- or 1-amino-1,3-butadiene in 14%, 4%, and 9%, overall yields, respectively. All three compounds are competitive inhibitors of the three enzymes, binding IS and AS strongly and PABS weakly. For both IS and AS, the affinity of the 6-amino-4-hydroxy isomer 2 is ca. 10-fold that of the 4-amino-6-hydroxy isomer 3, a difference that is largely due to their conformational equilibria; 2 is 25 +/- 2% axial and 3 is 6 +/- 3% axial, as determined by the temperature dependence of their NI?IR spectra. The similarity between IS and AS was extended by the finding that IS, like AS, catalyzes formation of 2-amino-2-deoxyisochorismate (ADIC) in the presence of ammonia. These observations are consistent with direct 1,5-substitution mechanisms for both IS and AS; the weak inhibition of PABS by these inhibitors suggests that it operates by a significantly different mechanism.CHORISMATE-UTILIZING ENZYMES ISOCHORISMATE SYNTHASE, ANTHRANILATE SYNTHASE, AND P-AMINOBENZOATE SYNTHASE - MECHANISTIC INSIGHT THROUGH INHIBITOR DESIGNx61199558#N/AFALSE
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ja00112a01410.1021/ja00112a014FALSEhttps://doi.org/10.1021/ja00112a014LOUIS, CJ. Am. Chem. Soc.A new method of preparation of silica-supported nickel materials makes possible the control of the partiCle size of metallic nickel in the range 20-60 Angstrom and in particular the obtention of decreasing partiCle size for increasing metal content. The preparation involves a two-step procedure: nickel in strong interaction with the support is deposited first, then nickel in weak interaction. After temperature-programmed reduction up to 700 degrees C, metal nickel partiCles are obtained whose size depends on the respective amounts of nickel deposited at each step of preparation. The average partiCle size is always smaller and the size distribution narrower than those of samples prepared by Classical impregnation. This preparation method involves an easy to carry out procedure: (i) nickel in strong interaction is obtained by impregnation of nickel nitrate followed by water-washing or by ion-exchange followed by calcination; (ii) nickel in weak interaction is obtained by impregnation. It is shown that a mechanism of partiCle growth on the nickel nuClei is responsible for the changes in partiCle size. It takes place after impregnation during the drying step at 90 degrees C via condensation reactions between the two types of nickel. Nickel in strong interaction, identified as phyllosilicates or as grafted nickel depending on the preparation conditions, acts as nuCleation sites for the partiCle growth arising from nickel in weak interaction. During drying in air at 90 degrees C, impregnated nickel nitrate transforms into a basic nitrate whose OH groups can react either with those in phyllosilicates or with H2O in the coordination sphere of grafted nickel.NUClEATION AND PARTIClE GROWTH-PROCESSES INVOLVED IN THE PREPARATION OF SILICA-SUPPORTED NICKEL MATERIALS BY A 2-STEP PROCEDUREx105199580#N/AFALSE
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ja00110a01310.1021/ja00110a013FALSEhttps://doi.org/10.1021/ja00110a013MASCHARAK, PKJ. Am. Chem. Soc.The reaction of [Ni(terpy)Cl-2] with similar to 2 equiv of 2,4,6-(Me)(3)C6H2Se- in 3:1 acetonitrile/ethanol affords [Ni(terpy)(2,4,6-(Me)3C(6)H(2)Se)(2)] (7), while [Ni(DAPA)Cl-2] (DAPA = 2,6-bis[1-(phenylimino)ethyl]pyridine) reacts with similar to 2 equiv of PhSe(-) and PhSe(-) in neat ethanol or acetonitrile to yield [Ni(DAPA)(SPh)(2)] (8) and [Ni(DAPA)-(SePh)(2)] (9), respectively. All three complexes contain the distorted trigonal bipyramidal (TBP) NiN(3)E(2) (E = S, Se) chromophore. Previous X-ray absorption spectroscopic data have indicated a distorted TBP NiN3S2 coordination for the nickel site of the hydrogenase (H(2)ase) from Thiocapsa roseopersicina. Complex 7 crystallizes in the monoClinic space group P2(1)/n with a = 13.170(6) Angstrom, b = 16.091(5) A, c = 15.111(8) Angstrom, beta = 114.42(2)degrees, V = 2916(2) Angstrom(3), and Z = 4. The structure of 7 was refined to R = 4.78% on the basis of 2730 reflections (I > 4 sigma(I). Complex 8.CH3-CN crystallizes in the monoClinic space group P2(1)/c with a = 23.012(7) Angstrom, b = 17.814(5) Angstrom, c = 15.698(4) Angstrom, beta = 108.52(2)degrees, V = 6099(5) Angstrom(3), and Z = 8. The structure of 8.CH3CN was refined to R = 6.46% on the basis of 6133 reflections (I > 4 sigma(I)). Complex 9.CH3CN also crystallizes in the monoClinic space group P(2)1/c with a = 23.209(2) Angstrom, b = 17.960(1) Angstrom, c = 15.749(1) Angstrom, beta = 108.482(6)degrees, V = 6225 Angstrom(3) and Z = 8, The structure of 9.CH3CN was refined to 3.90% on the basis of 5808 reflections (I > 4 sigma(I)). Reduction of the terpy analogue 7 with aqueous dithionite gives rise to the corresponding Ni(I) complex which binds CO (reversibly) and H-. The EPR parameters of the CO and hydride adducts resemble the Ni-CO and Ni-C signal of the H(2)ases. Much like the other terpy analogues reported previously by this group, oxidation of 7 affords unstable Ni(III) products in low yields. The two DAPA analogues (8 and 9), on the other hand, are readily oxidized and reduced by biologically relevant oxidants and reductants, and the transformation Ni(III) <-- Ni(II)) --> Ni(I) is reversible. The Ni(III) species (10 and 13) derived from 8 and 9 via oxidation with [Fe(CN)(6)](3-) are comparatively stable and do not bind CO (or H-). The single electron in both 10 and 13 resides in the d(z2) orbital. Upon reduction with aqueous dithionite, 8 and 9 produce the corresponding Ni(I) species 11 and 14 with the single electron in the d(x2-y2) orbital. These Ni(I) complexes are quite stable at low temperatures but slowly lose thiolates/selenolates at room temperature to give [Ni(DAPA)(solv)(2)](+). Both 11 and 14 bind CO reversibly. The affinity of the Ni(I) (but not the Ni(III)) model complexes toward CO strongly suggests the presence of Ni(I) in the C form of the H(2)ases since the enzymes bind CO only in the Ni-C form. Reaction of NaBH4 with 8 and 9 results in the hydride adducts 19 and 20. These hydride adducts are stable under basic conditions. The absence of any detectable proton hyperfine coupling indicates that the H- ligand is located at the basal plane of the Ni(I) center. The EPR parameters of the CO and hydride adducts are quite similar to those of the Ni-CO and Ni-C signals of the H(2)ases. Under basic conditions, both 8 and 9 react with dihydrogen at ambient temperature and pressure to afford the hydride adducts 19 and 20 in significant yields. This reaction is quite remarkable since the model complexes mimic the reductive Activation step of the biological nickel site in such a reaction to ultimately produce Ni-C-like signals. Taken together, the present results strongly suggest a Ni(I)-H- formalism for the nickel site in the C form of the H(2)ases. In addition, enhancement of the intensities of the EPR signals of the hydride adducts in the presence of a base indicates heterolytic Cleavage of H (coordinated or not) at the Ni(I) site of the model complexes and probably also at the enzyme active sites.TOWARD FUNCTIONAL MODELS OF THE NICKEL SITES IN [FENI] AND [FENISE] HYDROGENASES - SYNTHESES, STRUCTURES, AND REACTIVITIES OF NICKEL(II) COMPLEXES CONTAINING [NIN3S2] AND [NIN3SE2] CHROMOPHORESx104199559#N/AFALSE
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ja00128a00410.1021/ja00128a004FALSEMILLER, JSSTRUCTURAL-PROPERTIES AND PHYSICAL-PROPERTIES OF DELOCALIZED MIXED-VALENT [CP-ASTERISK-M(PENTALENE)M'CP-ASTERISK](N+) AND [CP-ASTERISK-M(INDACENE)M'CP-ASTERISK](N+) (M, M'=FE, CO, NI, N=0, 1, 2) COMPLEXES1995#N/ATRUE
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ja00108a01310.1021/ja00108a013FALSEhttps://doi.org/10.1021/ja00108a013DARENSBOURG, MYJ. Am. Chem. Soc.A series of nickel(II) complexes containing sulfinate and sulfenate S-donor sites has been prepared from systematic oxygenations of the dithiolate complex [1,5-bis(2-mercapto-2-methylpropyl)-1,5-diazacyClooctanato(2-)]nickel(II) ((bme*-daco)Ni, 1*) and the whole series characterized by mass spectrometry: and X-ray crystallography. The dithiolate complex reacts in organic solvents with molecular oxygen to produce sulfinate (NiS(O)(2)R) complexes, while reactions with hydrogen peroxide have, in addition,permitted the isolation of sulfenate (NiS(O)R) products. The X-ray crystal structures of the complexes [1-(2-mercapto-2-methylpropyl)-5-(2-sulfino-2-methylpropyl)-1,5-diazacyClooctanato(2-)]nickel(II) (2*), [1,5-bis(2-sulfino-2-methylpropyl)-1,5-diazacyClootanato-(2-)]nickel(II)) (3*), [1,5-bis(2-sulfeno-2-methylpropyl)-1,5-diazacyClooctanato(2-)]nickel(II) (5*), and [1-(2-sulfeno-2-methylpropyl)-5-(2-sulfino-2-methylpropyl)-1,5-diazacyClooctanato(2-)]nickel(II) (6*) were determined and metric data compared with previously characterized 1* and 4*, [1-(2-mercapto-2-methylpropyl)-5-(2-sulfeno-2-methylpropyl)-1,5-diazacyClooctanato(2-)]nickel(II). Analysis of the Ni-S-(av) bond distances for homoleptic complexes reveals that the bond distances are in the order Ni-S(O)R (2.167(5)) > Ni-SR (2.159(3)) > Ni-S(O)(2)R (2.127(3)). The average nickel sulfinate S-O distance at 1.459 Angstrom is ca. 0.1 Angstrom shorter than the average nickel sulfenate S-O distance at 1.545 Angstrom. These bond dimensions correlated well with spectroscopic and reactivity data. Electrochemical studies find the Ni-II/I reversible couple to be stabilized by ca. 100 mV with conversion of thiolate-S to sulfenate-S donor, while conversion of a sulfenate to a sulfinate stabilized the Ni-I state by an additional 200 mV. Mass spectrometry delineated O-atom loss pathways to dominate initial fragmentation patterns from the parent ions in the protic matrix thioglycerol; however, SO2 extrusion also occurs and is prominent in a nitroBenzyl alcohol (NBA) matrix. The sulfenate complexes are unexpectedly stable and do not undergo either inter- or intramolecular disproportionation reactions to thiolate and sulfinate, nor do they transfer oxygen to triphenyl- or tributylphosphine. Sulfur dioxide removed oxygen from the sulfenates, yielding thiolates and SO3, whereas no reaction occurred with the sulfinate complexes. Complexes that represent partial oxidation of the sulfurs further reacted with hydrogen peroxide to produce higher oxygenates and also reacted with electrophiles such as Alkylhalides to produce S-bound sulfoxide ligands.STUDY OF SULFINATE AND SULFENATE COMPLEXES DERIVED FROM THE OXYGENATION OF THIOLATE SULFUR IN [1,5-BIS(2-MERCAPTO-2 METHYLPROPYL)-1,5-DIAZACYClOOCTANATO(2-)]NICKEL(II)x138199540#N/AFALSE
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ja00124a05510.1021/ja00124a055FALSEhttps://doi.org/10.1021/ja00124a055DARENSBOURG, MYJ. Am. Chem. Soc.STUDY OF SULFINATE AND SULFENATE COMPLEXES DERIVED FROM THE OXYGENATION OF THIOLATE SULFUR IN [1,5-BIS(2-MERCAPTO-2-METHYLPROPYL)-1,5-DIAZATYClOOCTANATO(2-)]NICKEL(II) (VOL 117, PG 963, 1995)719951#N/ATRUE
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ja00122a02610.1021/ja00122a026FALSEhttps://doi.org/10.1021/ja00122a026SAILLARD, JYJ. Am. Chem. Soc.The bonding in metal-centered M(9)(mu(4)-E)(6)L(8) cubic Clusters is analyzed by means of extended Huckel and self-consistent field-multiple scattering-X alpha calculations. Different electron counts are allowed depending on the magnitude of the interaction of the interstitial metal atom (M(c)) with its metallic cubic host (M(s)) and the nature of the capping E ligands (either bare or substituted). In all cases, a strong interaction is observed between the s and p AOs of the encapsulated atom and metallic MOs of the cube. Significant additional M(c)-M(s) bonding is obtained if strong interactions occur between the five d AOs and corresponding metallic MOs. This still hypothetical situation, which leads to a count of 120 metallic valence electrons (MVEs). is favored for long M(s)-M(s) and short M(c)-E contacts. Another Closed-shell configuration, corresponding to 124 MVEs, is obtained if the interaction of the M(c) t(2g) d AOs with the metallic cube is large and the e(g) one weak. This is the case for Ni-9(mu(4)-GeEt)(6)(CO)(8). Electron counts corresponding to open-shell ground-state configurations can occur when the capping E ligands are strong donors and/or when the MVE count is larger than 120. In such cases, the levels which may be partly populated an of e(g), t(2g), and (for large electron counts) t(1g) symmetry. For example, the ground-state electron distribution of the 124-MVE Clusters Pd-9(mu(4)-E)(6)(PPh(3))(8) (E = As, Sb) corresponds to (t(2g))(4)(e(g))(0)(t(1g))(0), while it is found to be (e(g))(4)(t(1g))(4)(t(2g))(2) for the 150-MVE Cluster Ni-9(mu(4)-Te)(6)(PEt(3))(8). The various possibilities for the electron distribution in these levels are discussed for various MVE counts, in relation to the M-M and M-E bond distances and the nature of E. The possibility of incorporating main-group elements at the center of the metallic cube is also discussed.BONDING ANALYSIS IN INORGANIC TRANSITION-METAL CUBIC ClUSTERS .2. METAL-CENTERED HEXACAPPED M(9)(MU(4)-E)(6)L(8) SPECIES25199537#N/ATRUE
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ja00122a02310.1021/ja00122a023FALSEhttps://doi.org/10.1021/ja00122a023RODGERS, MAJJ. Am. Chem. Soc.Pulse radiolysis and laser flash photolysis have been used to generate and characterize Ni(cyClam)(+), where cyClam is 1,4,8,11-tetraazacyClotetradecane, in aqueous solution. Reduction of Ni(cyClam)(2+) was carried out at ambient temperature (22 +/- 2 degrees C) by solvated electrons, e(aq)(-), hydrogen atoms, H-., and carbon dioxide radical anions, CO2.-. Reduction by e(aq)(-) occurs with a rate constant of (4.1 +/- 0.2) x 10(10) M(-1) s(-1) (I less than or equal to 2 x 10(-4) M). Reduction by CO2.- and H-. proceeds via an inner-sphere mechanism to yield [Ni(cyClam)(CO2)](+) and [Ni(cyClam)(H)](2+), with rate constants of(6.7 +/- 0.2) x 10(9) and (5 +/- 2) x 10(9) M(-1) s(-1), respectively. Decomposition of the adducts, to yield Ni(cyClam)(+) and Co-2 or H+, proceeds with rate constants of (2.0 +/- 0.2) x 10(6) and (5.3 +/- 0.7) x 10(5) s(-1), respectively. Carbon dioxide and proton dissociation constants for [Ni(cyClam)(Co-2)](+) and [Ni(cyClam)(H)](2+) were found to be (6.2 +/- 0.3) x 10(-2) and (1.6 +/- 0.4) x 10(-2) M, respectively. The rate constants for the addition of CO2 and H+ to Ni(cyClam)(+) were calculated to be (3.2 +/- 0.4) x 10(7) and (3 +/- 1) x 10(7) M(-1) s(-1), respectively. The selective reduction of CO2 by Ni(cyClam)(+) in the presence of protons at pH 4 is rationalized.THE THERMODYNAMICS AND KINETICS OF CO2 AND H+ BINDING TO NI(CYClAM)(+) IN AQUEOUS-SOLUTION60199563#N/ATRUE
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ja001205a10.1021/ja001205aFALSEhttps://doi.org/10.1021/ja001205aYamamoto, YJ. Am. Chem. Soc.2-Trimethylsilylphenyl trifluoromethanesulfonate la, a benzyne precursor, reacted with the allylic chlorides 2a-f in the presence of CsF (2.0 equiv) and Pd-2(dba)(3). CHCl3 (2.5 mol %)-dppf (5 mol %) in a 1:1 mixed solvent of CH3CN and THF to produce the phenanthrene derivatives 3 along with their minor regioisomers 4 in good yields (i) and the reaction of la with 2a and the internal alkynes 15a,c-e afforded the naphthalene derivatives 16 in moderate yields (ii). The reaction of benzyne precursor la with the alkynes 15a-c,f-h in the presence of Pd(OAc)(2) (5 mol %)-(o-tolyl)(3)P (5 mol %) catalyst and CsF (2.0 equiv) in CH3CN gave the phenanthrene derivatives 17 (iii), whereas the reaction of la with the alkynes 15a,b,i in the presence of the same catalysts and CsF in CH3CN-toluene gave the indene derivatives 18 in good yields (iv). Detailed mechanistic investigation revealed that the former two reactions i and ii proceed through carbopalladation to free benzyne, while the latter two reactions iii and iv proceed through the nonfree benzyne mechanism, in which the initial step of the catalytic cyCle begins with Pd(0) insertion to the Ar-OTf bond of 1.Palladium-catalyzed controlled carbopalladation of benzyne194200033#N/ATRUE
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ja00106a03210.1021/ja00106a032FALSEhttps://doi.org/10.1021/ja00106a032STOLZENBERG, AMJ. Am. Chem. Soc.The structural properties of nickel and copper complexes of octaethylisobacteriochlorin (OEiBC) are investigated as part of an effort to understand the chemistry of factor 430 (F430), the nickel hydrocorphinoid cofactor of methyl coenzyme-M reductase. Both Ni-II and Cu-II(OEiBC) undergo one-electron reductions to yield metal(I) complexes. The nature of the starting materials, the anionic metal(I) reduction products, and their ligand-binding properties are probed with electron paramagnetic resonance (EPR) and X-ray absorption techniques. Comparison between the structures of the isoelectronic Ni-I and Cu-II complexes reveals that the marked distortions observed in the Ni-I-macrocyCle core environment, which has two Ni-N distances of 1.91(2) Angstrom and two Ni-N distances of 2.07(2) Angstrom, are not apparent for Cu-II, which has four Cu-N distances of 2.00(2) Angstrom. Thus, the distortion of the Ni-I environment does not result from an electronic configuration effect such as a Jahn-Teller distortion. X-ray absorption near-edge studies of OEiBC complexes at reduced temperatures demonstrate for the first time that Ni-I hydroporphyrins can bind a single axial ligand. Optical and EPR spectra are found to be insensitive to the axial binding for these cases. Chemical reduction of Cu-II(OEiBC), using sodium amalgam, affords a Cu-I complex that has unchanged Cu-N distances and two sodium ions coordinated on opposite sides of the OEiBC ring at Cu-Na distances of 2.89(4) Angstrom. The sodium ions can be sequestered using the crown ether 18-crown-6. Direct comparison of Cu-II and the non-ion-paired Cu-I complexes, which have the same geometry and coordination environment, establishes that the average Cu-N distance increases 0.06 Angstrom upon reduction. The structural differences between the Ni-I and Cu-I complexes may account for their different reactivities toward Alkyl halides and oxygen.EFFECTS OF METAL-CENTERED REDUCTION ON THE STRUCTURAL, ELECTRONIC, AND COORDINATION PROPERTIES OF NICKEL AND COPPER OCTAETHYLISOBACTERIOCHLORINSx18199566#N/AFALSE
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ja00106a02710.1021/ja00106a027FALSEhttps://doi.org/10.1021/ja00106a027RIEKE, RDJ. Am. Chem. Soc.A systematically regiocontrolled synthesis of poly(3-Alkylthiophenes) (P3AT) mediated by Rieke zinc is reported. Rieke zinc undergoes oxidative addition to 2,5-dibromo-3-Alkylthiophene or 2-bromo-5-iodo-3-Alkylthiophene regioselectively to afford 2-bromo-5-(bromozincio)-3-Alkylthiophene (2) or 2-bromo-5-(iodozincio)-3-Alkylthiophene (10). The intermediate 2 or 10 can be polymerized catalytically to a series of regiospecific poly(3-Alkylthiophenes) using different catalysts. The regioregularity of the polymer chain is solely controlled by the structure of the catalyst. An almost completely regioregular head-to-tail (HT) P3AT (4) is obtained by using Ni(DPPE)Cl-2 ([1,2-bis-(diphenylphosphino)ethane]nickel(II) chloride). Use of Pd(DPPE)Cl-2 leads to a reduction in the regioregularity (70:30 HT/HH), while using Ni(PPh(3))(4) also leads to a much reduced regioregular P3AT (63:35 HT/HH). A totally regiorandom (50:50 HT/HH) P3AT (5) is afforded by using Pd(PPh(3))(4). The poly(3-butylthiophene) 4a is a 97% HT regioregular polymer. Other poly(3-Alkylthiophenes) (Alkyl = hexyl (4b), octyl (4c), decyl (4d), dodecyl (4e), and tetradecyl (4f)) are regioregular P3ATs with the HT linkage larger than 98.5% based on NMR analysis. Electronic absorption, X-ray diffraction, and crossed polarizing micrograph studies show that the cast films of the regioregular P3ATs (4) are self-organized, crystalline, flexible, and bronze-colored films with a metallic luster, while that of the regiorandom P3ATs (5) are amorphous and orange-colored films. The regioregular P3ATs exhibit a small bandgap (1.7 eV) which is 0.4 eV lower than that of regiorandom P3ATs (2.1 eV). Regioregular HT P3ATs have considerably improved electroconductivity and other physical properties over regiorandom P3ATs.REGIOCONTROLLED SYNTHESIS OF POLY(3-AlkylTHIOPHENES) MEDIATED BY RIEKE ZINC - THEIR CHARACTERIZATION AND SOLID-STATE PROPERTIESx1486199581#N/AFALSE
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ja00119a02310.1021/ja00119a023FALSEhttps://doi.org/10.1021/ja00119a023ARMENTROUT, PBJ. Am. Chem. Soc.The sequential bond energies of Cu(CO)(x)(+) and Ag(CO)(x)(+) (x = 1-4) are determined by collision-induced dissociation in a guided ion beam tandem mass spectrometer. Values (in eV) for the 0 K (COCu+-CO bond energies are found to be 1.54 +/- 0.07, 1.78 +/- 0.03, 0.78 +/- 0.04, and 0.55 +/- 0.03 for x = 1-4, respectively, while those for (COAg+-CO are determined to be 0.92 +/- 0.05, 1.13 +/- 0.04, 0.57 +/- 0.08, and 0.47(-0.04)(+0.19) for x = 1-4, respectively. The energies for loss of one CO from the mono- and diCarbonyls of both metal ions disagree with one set of theoretical values, but those for Ag(CO)(x)(+) (x = 1-3) are in excellent agreement with more recent theoretical predictions and help verify the trends in stability found for these complexes in recent synthetic studies. Trends in bond dissociation energies with increasing ligation are discussed for both systems and compared to those for isoelectronic Ni(CO)(x) and Co(CO)(x)(-) complexes.SEQUENTIAL BOND-ENERGIES OF CU(CO)(X)(+) AND AG(CO)(X)(+) (X=1-4)149199554#N/ATRUE
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ja00119a01410.1021/ja00119a014FALSEhttps://doi.org/10.1021/ja00119a014CRABTREE, RHJ. Am. Chem. Soc.In a functional model study of carbon monoxide dehydrogenase (CODH), a homologous series of Ni(II) complexes with a biologically relevant O, N, S ligand set has been synthesized and characterized. In aqueous solution at room temperature, they are active for CO oxidation by methylviologen (= mv(2+)) to produce CO2. The key features of the reaction are pseudo-first-order dependence on catalyst, CO, H2O, and mv(2+), a sigmoidal rate-pH profile with an inflection point at pH 7.6, and the absence of any H-2 as a product, although H-2 is the exClusive product of the related water gas shift reaction. The proposed mechanism, involving deCarbonylation of a Ni-COO- intermediate by mv(2+) in the key step, accounts for all these features. As in CODH itself, CO oxidation is inhibited by both CN- and MeI. O-2 is also a competent electron acceptor in this system because reduced mv(+) is air-sensitive.A FUNCTIONAL-MODELING STUDY OF THE CO OXIDATION SITE OF NICKEL CO DEHYDROGENASE27199541#N/ATRUE
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ja00103a00810.1021/ja00103a008https://doi.org/10.1021/ja00103a008GRUBBS, RHJ. Am. Chem. Soc.The molecular weight and structural regularity of the polyphenylene produced from thermal conversion of two precursor polymers based on the acetyl derivative of 5,6-dihydroxy-1,3-cyClohexadiene depend on the stereochemistry of the precursor and the presence of aromatization catalysts. Two competing reactions occur during the bulk thermal conversion of these precursors: (1) thermal chain fracturing of the polymer and (2) thermally-induced acid elimination (aromatization) resulting in polyphenylene formation. The relative rates of these two processes ultimately determine the molecular weight of the final product and depend heavily upon the stereochemistry of the polymer backbone. For a 1,4-linked stereoregular precursor polymer made by nickel-catalyzed polymerization, the onset of chain degradation occurs before the onset of aromatization during heating. Consequently, this precursor only affords low-quality polyphenylene oligomers, despite having a regular stereochemistry that is ideal for facile cis pyrolytic acid elimination. On the other hand, the reverse relationships are true for its radically polymerized analog containing 10% 1,2-linkages. Although chain degradation still occurs during the pyrolysis of this atactic precursor, the relative amount of backbone fracturing is less than that of aromatization. The problems associated with the limited thermal stability of the precursor polymers can be overcome through the use of Bronsted and Lewis acid catalysts during bulk pyrolysis. Acids lower the onset temperature of aromatization to a regime well below that at which thermal chain scission can occur by selectively catalyzing the acid elimination reaction in both precursor polymers. However, characterization of the resulting polyphenylenes made from both polymers indicates that the structural regularity of the polyphenylene produced by the acid-catalyzed aromatization process depends entirely on the regiochemistry of the initial precursor. High molecular weight, structurally regular poly(p-phenylene) is produced only by the acid-catalyzed bulk aromatization of the 1,4-linked stereoregular polymer. Acid-catalyzed bulk pyrolysis of the radically polymerized analog only affords polyphenylene containing substantial amounts of 1,2-linkages.STEREOREGULAR PRECURSORS TO POLY(P-PHENYLENE) VIA TRANSITION-METAL-CATALYZED POLYMERIZATION .2. THE EFFECTS OF POLYMER STEREOCHEMISTRY AND ACID CATALYSTS ON PRECURSOR AROMATIZATION - A CHARACTERIZATION STUDYx43199438#N/AFALSE
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ja00102a01810.1021/ja00102a018https://doi.org/10.1021/ja00102a018GRUBBS, RHSTEREOREGULAR PRECURSORS TO POLY(P-PHENYLENE) VIA TRANSITION-METAL-CATALYZED POLYMERIZATION .1. PRECURSOR DESIGN AND SYNTHESISx1994#N/AFALSE
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ja00114a02010.1021/ja00114a020FALSEhttps://doi.org/10.1021/ja00114a020LINDAHL, PAJ. Am. Chem. Soc.The NiFe hydrogenase from Desulfovibrio gigas contains one [Fe3S4](1+/0) Cluster, two [Fe4S4](2+/1+) Clusters, and one active-site Ni center that can be stabilized in four magnetic states (designated Ni-AB, Ni-SI, Ni-C, and Ni-R). Ni-AB and Ni-SI almost certainly correspond to Ni3+ and Ni2+ electronic states, respectively, while the electronic designations of Ni-C and Ni-R are uncertain. Ni-C arises from a species containing a photolabile hydrogenic species (H+, H-, or H-2). Stoichiometric reductive titrations of thionin-oxidized Hase were performed, using the reductant H-2. Titrations were monitored at 310 nm and by EPR. The resulting titration curves were simulated using two models. Each assumed that the enzyme contains the redox centers mentioned above, but they differed as to the number of electrons assumed to separate Ni-C from Ni-AB. One model assumed Ni-C was two electrons more reduced than Ni-AB, the other that it was four electrons more reduced. The former model fit the data substantially better than the latter. This restricts possible Ni-C designations to either a protonated Ni1+ species, a Ni3+ hydride, a Ni3+(n(2)-H-2) complex, or a Ni2+ species with a ligand radical. An argument is expanded in support of a Ni1+ dithiol designation of Ni-C. Partially reduced enzyme also exhibits an unusually complex EPR signal (the g = 2.21 signal) that has been proposed to originate from magnetic coupling between Ni-C and one of the reduced [Fe4S4](1+) Clusters. The analysis presented indicates that the interacting Cluster is the one with the more negative redox potential, designated Fe-4b. This Cluster is almost certainly located nearest to the Ni center. The Ni-C/Ni-R and [Fe-4b](2+/1+) couples are both in odor equilibrium with H-2. A mechanism of catalysis based on the spatial proximity and odor properties of the Ni center and Fe-4b is discussed.STOICHIOMETRIC REDUCTIVE TITRATIONS OF DESULFOVIBRIO-GIGAS HYDROGENASE75199548#N/ATRUE
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ja00113a03810.1021/ja00113a038FALSEhttps://doi.org/10.1021/ja00113a038ISHII, YJ. Am. Chem. Soc.UNUSUALLY STRONG-INTERACTIONS MEDIATED BY BOTH PI-PI STACKING AND CH-PI INTERACTIONS PRESENT IN THE DIMER OF NICKEL(II) COMPLEX COORDINATED WITH N-BUTYL-SUBSTITUTED SALEN6919957#N/ATRUE
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ja00100a04310.1021/ja00100a043FALSEhttps://doi.org/10.1021/ja00100a043GODDARD, WAJ. Am. Chem. Soc.We report here spectroscopic and theoretical (AM1) studies on zinc(II) octa-beta-halotetrakis(pentafluorophenyl)-porphyrins (ZnTFPPX(8); X = Cl, Br) that show a red shift in the Soret and Q absorption bands attributable to substituent-induced saddling of the macrocyCle. The electronic effect of the halogens is to reduce the energies of both the HOMOs and LUMOs; however, this stabilization of orbital energies is counteracted by the distortion of the macrocyCle, which results in a large destabilization of the porphyrin HOMOs and a smaller destabilization of the LUMOs. The net result is a slight increase in stability of the HOMOs and a greater stabilization of the LUMOs. Lowering the energies of the porphyrin HOMOs is an important factor to consider in the development of robust porphyrin catalysts.ELECTRONIC-STRUCTURES OF HALOGENATED PORPHYRINS - SPECTROSCOPIC PROPERTIES OF ZNTFPPX(8) (TFPPX(8)=OCTA-BETA-HALOTETRAKIS(PENTAFLUOROPHENYL)PORPHYRIN X=Cl, BR)x111199426#N/AFALSE
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ja00100a01910.1021/ja00100a019https://doi.org/10.1021/ja00463a072TAN, KHVARIABLE-ENERGY PHOTOELECTRON-SPECTROSCOPY OF M(ETA(3)-C3H5)(2) (M=NI, PD, AND PT) - MOLECULAR, ORBITAL ASSIGNMENTSPhotocatalystx1994#N/AFALSE
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ja00100a01610.1021/ja00100a016FALSEhttps://doi.org/10.1021/ja00100a016GUTLICH, PJ. Am. Chem. Soc.The tris-chelated [M(II)(bpy)(3)](2+) cations, where M(II) is a divalent transition metal and bpy is 2,2'-bipyridine, cause a remarkable crystallization of anionic three-dimensional (3D) coordination polymers of oxalate-bridged metal complexes [M(2)(ox)(3)](2n-)(n). With these cations, which are appropriate in charge, size, and symmetry, two types of stoichiometric units of the anionic 3D networks, with metals in different valence states, can be distinguished: [M(2)(II)(ox)(3)](2-) and [M(I)M(III)(ox)(3)](2-). Results of a structural analysis of compounds within each of the two isomorphous series are discussed: [Ni-II(bpy)(3)][Mn-2(II)(ox)(3)] (3), cubic, merohedrically twinned, P4(1)32/P4(3)32, a = 15.579(2) Angstrom, Z = 4; [Fe-II(bpy)(3)] [NaFeIII(ox)(3)] (4), cubic, P2(1)3, a = 15.507(3) Angstrom, Z = 4; [Fe-II(bpy)(3)][LiCrIII(ox)(3)] (5), cubic, P2(1)3, a = 15.262(4) Angstrom, Z = 4. The Mossbauer spectra of the iron-containing compounds [Fe-II(bpy)(3)][Fe-2(II)(ox)(3)] (1) and [Fe-II(bpy)(3)][Mn-2(II)(ox)(3)] (2) and type 4 but LiFeIII are consistent with the stoichiometric formula and the corresponding iron valence states. The straightforward synthetic approach and easy crystallization behavior, as well as the variety of metal combinations within the 3D networks, fender these systems valuable candidates for studies in the field of molecular-based magnets. They fulfill the requirements of three-dimensional connectivity as well as accessibility to detailed structural characterization. The magnetic susceptibility data in the temperature range 2-300 K of 1, 2 and type 4 but LiFeIII are presented and the results should be taken as a starting point for more extended systematical studies. 1 and 2 reveal antiferromagnetic ordering behavior, indicated by a negative Weiss constant theta of -28 and -33 K, whereas the LiFeIII compound exhibits the expected behavior of single iron(III) ions. Further extensions to possible networks of the types [M(II)M(III)(ox)(3)](1n-)(n) and [M(I)M(II)(ox)(3)](3n-)(n) are discussed.A CONCEPT FOR THE SYNTHESIS OF 3-DIMENSIONAL HOMOMETALLIC AND BIMETALLIC OXALATE-BRIDGED NETWORKS [M(2)(OX)(3)](N) - STRUCTURAL, MOSSBAUER, AND MAGNETIC STUDIES IN THE FIELD OF MOLECULAR-BASED MAGNETSx405199449#N/AFALSE
3034
ja00099a02210.1021/ja00099a022FALSEhttps://doi.org/10.1021/ja00099a022TATSUTA, KJ. Am. Chem. Soc.Powerful and highly stereocontrolled O-glycosidation methods using several kinds of 2,6-anhydro-2-thio sugars as glycosyl donors have been developed for the synthesis of both 2,6-dideoxy-alpha- and -beta-glycosides which frequently occur in biologically important natural products. Both glycosidations of phenyl 3,4-di-O-acetyl-2,6-anhydro-1,2-dithio-D-altropyranoside (2) and 3,4-di-O-acetyl-2,6-anhydro-1-fluoro-2-thio-D-altropyranoside (3) with alcohols exClusively gave the corresponding 2,6-anhydro-2-thio-alpha-glycosides. In contrast, the glycosidations of 1,3,4-tri-O-acetyl-2,6-anhydro-2-thio-D-altropyranos (4) with alcohols afforded the corresponding 2,6-anhydro-2-thio-beta-glycosides with high stereocontrol. Furthermore, a novel method for the controlled block synthesis of 2,6-dideoxy oligosaccharides by the combined use of the activated 2,6-anhydro-2-thio sugar 23 and the deactivated 2,6-anhydro-2-sulfinyl sugar 24, both of which have the same thiophenyl leaving group at the anomeric positions, has been demonstrated. The 2,6-anhydro-2-thio-alpha- and -beta-glycosides obtained by the present methods were effectively converted into the corresponding 2,6-dideoxy-alpha- and -beta-glycosides by both hydrogenolysis using Raney-Ni as a catalyst and reductive desulfurization using Bu(3)SnH and AIBN.NOVEL GLYCOSIDATION METHOD USING 2,6-ANHYDRO-2-THIO SUGARS FOR STEREOCONTROLLED SYNTHESIS OF 2,6-DIDEOXY-ALPHA-GLYCOSIDES AND 2,6-DIDEOXY-BETA-GLYCOSIDESx33199485#N/AFALSE
3035
ja00098a01910.1021/ja00098a019FALSEhttps://doi.org/10.1021/ja00098a019FAJER, JJ. Am. Chem. Soc.Crystal structures are reported for the sterically crowded porphyrin Copper(II) 2,3,7,8,12,13, 17,18-octaethyl-5,10,15,20-tetraphenylporphyrin (Cu(OETPP), 1) and its pi cation radical Cu(OETPP)(ClO4-)-Cl-.+ (2). 1 was chosen to assess the consequences of oxidation in a nonplanar porphyrin on the expectation that its multiple peripheral substituents not only induce an S4 saddle conformation on the macrocyCle but should also prevent the dimerizations in the solid that have complicated several previous crystallographic studies of porphyrin pi cation radicals. Interest in the consequences of oxidation arises from the presence of nonplanar bacteriochlorophylls in photosynthetic reaction centers in which the chromophores lie van der Waals contact so that even small structural changes induced by electron transfer would alter the electronic coupling between the pi cation and anion radicals generated by the primary photochemical charge separation. Oxidation of 1 does indeed result in further conformational changes in 2: an additional ruffling is imposed on the original saddle shape of 1 in which the pyrrole rings twist, the meso carbons move alternately up and down out of the porphyrin plane by similar to 0.2 Angstrom, and the phenyl groups rotate further into that plane by more than 10 degrees. The additional distortions are attributed to changes in electronic configuration due to the oxidation and to the low-energy barriers between nonplanar conformers with different degrees of nonplanarity predicted by previous molecular mechanics calculations. OETPPs retain their saddle conformations in solution because of the steric crowding of the multiple substituents. 2 thus provides a test of the proposal by Reed, Scheidt, and co-workers (e.g., J. Am. Chem. Soc. 1987, 109, 2644) that the conformations of porphyrin pi cation radicals comprised of paramagnetic metals control magnetic coupling with the metals and that nonplanar macrocyCles exhibit antiferromagnetic coupling. 2 displays optical and FT-IR spectral signatures diagnostic of a pi cation radical in solution, but it is EPR-silent, and its NMR spectrum Clearly indicates a diamagnetic species. The Cu(II) and the nonplanar pi radical spins in 2 are thus indeed antiferromagnetically coupled, in accord with the above proposal. The saddle conformation of 1 destabilizes the pi system of the macrocyCle and causes the molecule to be readily oxidized with molecular iodine, a mild oxidizing agent. Unexpectedly, the radical crystallized in the presence of excess I-2 carries a discrete I-7(-) counterion. We report here the first example and structure of such a large polyiodide union to be stabilized by a porphyrin cation: Cu(OETPP)I-.+(7-) (3). Crystallographic data. CuN4C60H60 (1): triClinic space group <P(1)over bar>, a = 13.888(4) Angstrom, b = 16.820(3) Angstrom, c = 13.222(3) Angstrom, alpha = 97.33(2)degrees, beta = 107.97(2)degrees, gamma = 103.52(2)degrees, V = 2843.3 Angstrom(3), Z = 2, R(F) = 0.057 and R(wF) = 0.086 based on 7391 reflections with F-o > 3 sigma F-o, T = 298 K. (CuN4C60H60ClO)-Cl-.+(-)(4).CH2Cl2 (2): monoClinic space group P2(1)/n, a = 11.896(1) Angstrom, b = 24.242(5) Angstrom, c = 19.090(3) Angstrom, beta = 100.73(1)degrees, V = 5408.8 Angstrom(3), Z = 4, R(F) = 0.048 and R(wF) = 0.049 based on 4570 reflections with F-o > 3 sigma F-o, T = 298 K. (BBCuN4C60H60I7-)-I-.+ (3): monoClinic space group P2(1), a = 13.108(17) Angstrom, b = 18.332(14) Angstrom, c = 13.683(10) Angstrom, beta = 107.88(8)degrees, V = 3129.2 Angstrom(3), Z = 2, R(F) = 0.101 and R(wF) = 0.117 based on 2269 reflections with F-o > 4 sigma F-o, T = 200 K.CONSEQUENCES OF OXIDATION IN NONPLANAR PORPHYRINS - MOLECULAR-STRUCTURE AND DIAMAGNETISM OF THE PI-CATION-RADICAL OF COPPER(II) OCTAETHYLTETRAPHENYLPORPHYRINx147199497#N/AFALSE
3036
ja00113a01510.1021/ja00113a015FALSEhttps://doi.org/10.1021/ja00113a015SOLOMON, EILIGAND K-EDGE X-RAY-ABSORPTION SPECTROSCOPIC STUDIES - METAL-LIGAND COVALENCY IN A SERIES OF TRANSITION-METAL TETRACHLORIDES1995#N/ATRUE
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ja00113a01410.1021/ja00113a014FALSEhttps://doi.org/10.1021/ja00113a014BERNARDINELLI, GJ. Am. Chem. Soc.The new diphosphaalkene 1,3-bis[2-(2,4,6-tri-tert-butylphenyl)phosphanediylmethyl]benzeneL has been synthesized. Due to the presence of two P double bond C bonds three isomers (EE, EZ, ZZ) were observed by P-31 NMR, and the crystal structures of two of them could be determined (EE, ZZ). The electrochemical behavior of L has been studied by cyClic voltametry: a quasi-reversible reduction occurs at -1.89 V/SCE and corresponds to the formation of a radical anion which has been studied by ESR at variable temperature. The experimental P-31 and H-1 hyperfine constants are consistent with free rotation about the P double bond C and C-phosphaalkene-C-benzene bonds at room temperature and agree with ab initio predictions. One of the isomers of L forms complexes with palladium(II) and platinum(III) ions. The crystal structures show that L is orthometalated and acts as a terdentate Ligand by coordinating the metal with each phosphorus atom. These complexes are electrochemically reduced between -0.92 and -1.29 V, and the resulting paramagnetic species are studied by ESR in liquid and frozen solutions. This reduction process was shown to be a ligand-centered process, an appreciable part of the unpaired electron is localized on each of the phosphaalkene carbons (20%) and phosphorus atoms (5%).THE BENZODIPHOSPHAALKENE LIGAND AND ITS PD-II AND PT-II COMPLEXES - THEIR SYNTHESIS, STRUCTURE, AND AN ESR STUDY OF THEIR REDUCTION PRODUCTS64199545#N/ATRUE
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ja00095a04610.1021/ja00095a046https://doi.org/10.1021/ja00095a046HOLTEN, DJ. Am. Chem. Soc.Time-resolved and steady-state optical data are presented for a series of substituted free-base porphyrins. The porphyrins are grouped into ''normal'' and ''perturbed'' categories based on observed photophysical behavior, and the distinctions between the two Classes correlate well with the conformations of the molecules. Normal porphyrins qualitatively and quantitatively follow the deActivation pathways traditionally reported for planar metal-free porphyrins. In contrast, the out-of-plane distortion in a series of sterically-crowded porphyrins results in unusual optical properties and enhanced radiationless decay of the (1)(pi,pi*) excited state. In particular, macrocyCle distortions increase the rates of both the internal conversion and intersystem crossing decay pathways, Enhanced internal conversion of (1)(pi,pi*) to the ground state in the perturbed porphyrins is interpreted as arising from an enhanced Franck-Condon factor associated with a structural reorganization in the excited state. Enhanced intersystem crossing from (1)(pi,pi>*) most likely arises from increased spin-orbit coupling caused by the nonplanarity of the macrocyCle. These results demonstrate that structural perturbations of porphyrin macrocyCles, imposed by peripheral substitution in vitro or the protein environment in vivo, can result in significant changes in electronic properties, inCluding the rates and yields of the fundamental excited state deActivation processes.PHOTOPHYSICAL PROPERTIES OF CONFORMATIONALLY DISTORTED METAL-FREE PORPHYRINS - INVESTIGATION INTO THE DEActivation MECHANISMS OF THE LOWEST EXCITED SINGLET-STATEPhotocatalyst214199447#N/AFALSE
3039
ja000946910.1021/ja0009469FALSEhttps://doi.org/10.1021/ja0009469Cramer, SPJ. Am. Chem. Soc.Carbon monoxide dehydrogenase from Clostridium thermoaceticum (Ct-CODH) is a nickel-containing enzyme that catalyzes acetyl-CoA synthesis and CO oxidation at two separate Ni sites, the A-Cluster and C-Cluster, respectively. Carbon monoxide dehydrogenase from Rhodospirillum rubrum (Rr-CODH) contains only a C-type Cluster and catalyzes only Ca oxidation. We have used L-edge X-ray absorption spectroscopy to study the Ni electronic structure of these two enzymes. The spectra indicate that most of the Ni in as-isolated Ct-CODH is low-spin Ni(II). Upon CO treatment, a fraction of the nickel is converted either to high-spin Ni(II) and/or to Ni(I). Ni in dithionite-reduced Rr-CODH also exhibits a Clear low spin Ni(II) component, again mixed with either high-spin Ni(II) or Ni(I). The spectrum of Rr-CODH shifts to higher energy upon indigo carmine oxidation, suggesting either that most of the high-spin Ni(II) is converted to low-spin Ni(II) and/or that some Ni is oxidized between these two forms; These results are;discussed and compared with recent L-edge spectra for the Ni site in hydrogenase.Characterization of heterogeneous nickel sites in CO dehydrogenases from Clostridium thermoaceticum and Rhodospirillum rubrum by nickel L-edge X-ray spectroscopyx53200078#N/AFALSE
3040
ja000945g10.1021/ja000945gFALSEhttps://doi.org/10.1021/ja000945gCramer, SPJ. Am. Chem. Soc.L-edge X-ray absorption spectroscopy has been used to study, under a variety of conditions, the electronic structure of Ni in the Ni-Fe hydrogenases from Desulfovibrio gigas, Desulfovibrio baculatus, and Pyrococcus furiosus. The status of the enzyme films used for these measurements was monitored by FT-IR spectroscopy. The L-edge spectra were interpreted by ligand field multiplet simulations and by comparison with data for Ni model complexes. The spectrum for Ni in D. gigas enzyme form A is consistent with a covalent Ni(III) species. In contrast, all of the reduced enzyme samples exhibited high spin Ni(II) spectra. The significance of the Ni(II) spin state for the structure of the hydrogenase active site is discussed.Nickel L-edge soft X-ray spectroscopy of nickel-iron hydrogenases and model compounds - Evidence for high-spin nickel(II) in the active enzymex110200077#N/AFALSE
3041
ja00108a01810.1021/ja00108a018FALSEhttps://doi.org/10.1021/ja00108a018FLANK, AMJ. Am. Chem. Soc.The pseudooctahedral Fe-II(phen)(2)(NCS)(2) (where phen = 1,10-phenanthroline) complex is well-known for its changing spin state under external perturbations like temperature. In this paper, a detailed X-ray absorption study of the thermally induced spin transition at the iron K and L(2,3) edges is presented. The XANES features at both edges are extremely sensitive to the spin state. But insofar as the spin transition is associated simultaneously with a change in the magnetic state, S = 2 reversible arrow S = 0, and a modification of the atomic arrangement, the attribution of strong changes in XANES spectra is not obvious. In order to sort out the nature of these modifications, we have performed calculations of the X-ray absorption cross sections at both edges. In the framework of the multiple scattering theory, we have calculated the iron K edge spectra of both spin states, and by using the multiplet picture in the intermediate crystal field framework, we have simulated the iron L(2,3) edge spectra of both spin states. We show that the main XANES changes at the K edge are related to the structural modifications around the iron, whereas those at the L(2,3) edges are due to the change of the occupancy of the 3d levels split by the pseudooctahedral crystal field. Furthermore, we show that multiplet calculations give precise information about the ground state of iron(II) in O-h symmetry. We have determined the 10Dq crystal field strengths in both spin states and compared them with those determined by optical spectroscopy. In the low-spin state, both visible and X-ray spectroscopies give comparable values, but we observe a large discrepancy in the high-spin state. Analyzing the LS terms of the ground state and their energies for both spin states, we discuss, in the case of the 3d(6) iron ion, the effect of the 10Dq values introduced in the multiplet calculations in reproducing experimental spectra and explaining the discrepancy between 10Dq values extracted from the two spectroscopies for the high-spin state.FULL MULTIPLE-SCATTERING AND CRYSTAL-FIELD MULTIPLET CALCULATIONS PERFORMED ON THE SPIN TRANSITION FE-II(PHEN)(2)(NCS)(2) COMPLEX AT THE IRON K(2,3) AND L(2,3) X-RAY-ABSORPTION EDGES77199571#N/ATRUE
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ja00092a04010.1021/ja00092a040FALSEhttps://doi.org/10.1021/ja00092a040MCBREEN, PJ. Am. Chem. Soc.The thermal chemistry of methyl formate, ethyl formate, and methyl acetate on Ni(111) was studied using infrared reflection absorption spectroscopy and temperature programmed desorption. The principal molecular decomposition products in each case were CO and H-2. Methane and acetaldehyde were also formed from ethyl formate. For each of the three molecules, adsorption occurred through the interaction of the Carbonyl lone pair with the metal. The orientation of the molecular plane, in each case, was approximately perpendicular to the surface. The molecular surface decomposition species were detected by RAIRS. Methoxy species were formed from methyl formate and methyl acetate. Ethoxy was produced by ethyl formate. Evidence was obtained for the formation of a stable acetyl species during the decomposition of methyl acetate. The decomposition of methyl acetate occurred above 170 K whereas the other two esters began to decompose at approximately 140 K. This study shows that the adsorption induced shifts in the infrared spectra of esters are similar to those which occur on the formation of ester-Lewis acid adducts.RAIRS AND TPD STUDY OF METHYL FORMATE, ETHYL FORMATE, AND METHYL ACETATE ON NI(111)x46199463#N/AFALSE
3043
ja00107a02010.1021/ja00107a020FALSEhttps://doi.org/10.1021/ja00107a020ARMENTROUT, PBJ. Am. Chem. Soc.Guided ion beam techniques are used to measure cross sections as a function of kinetic energy for the reaction of SiH4 with M(+) = Fe+, Co+, and Ni+. Ionic products inClude MSiH(x)(+) (x = 0-3), as well as MH(+) and SiH3+. No structural information concerning the MSiH(x)(+) species is obtained in the present results. The major low-energy process in all three systems is formation of MSiH(2)(+) + H-2, while at higher energies, formation of MH(+) + SiH3 (M = Fe and Co) or SiH3+ + MH (M = Ni) dominates the reactivity. Variation of source conditions allows the effect of electronic excitation on the reactivity of Fe+ to be studied in detail. The a(4)F first excited state of Fe+ is more reactive by approximately an order of magnitude than the a(6)D ground state and has a different product distribution. The reactivity of Fe+ (a(4)F) is found to Closely resemble that of ground state Co+ (a(3)F), which is approximately half as reactive as ground state Ni+ (a(2)D). The reactivity of these systems may be understood in terms of simple molecular orbital and spin conservation arguments. The thresholds for Fe+, Co+, and Ni+ reactions are evaluated to yield 0 K bond dissociation energies (BDEs) for M(+)-Si, M(+)-SiH, M(+)-SiH2, and M(+)-SiH3 of 2.87 +/- 0.09, 2.63 +/- 0.13, 1.88 +/- 0.09, and 1.90 +/- 0.09 eV, respectively, for M = Fe; 3.25 +/- 0.07, 3.03 +/- 0.16, 2.25 +/- 0.08, and 1.96 +/- 0.13 eV, respectively, for M = Co; and 3.34 +/- 0.07, 3.38 +/- 0.15, greater than or equal to 2.39 +/- 0.07, and 1.91 +/- 0.12 eV, respectively, for M = Ni. Evaluation of thresholds for SiH3+ + MH formation (M = Fe, Co, and Ni) is combined with previous studies in our laboratories to yield 0 K BDEs for Fe-H of 1.52 +/- 0.05 eV, for Co-H of 1.95 +/- 0.05 eV, and for Ni-H of 2.56 +/- O.11 eV.REACTIONS OF FE+, CO+, AND NI+ WITH SILANE - ELECTRONIC-STATE EFFECTS, COMPARISON TO REACTIONS WITH METHANE, AND M(+)-SIHX (X=0-3) BOND-ENERGIES77199568#N/ATRUE
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ja00090a03110.1021/ja00090a031FALSEhttps://doi.org/10.1021/ja00090a031KUBOTA, KJ. Am. Chem. Soc.Dehalogenation polycondensation of corresponding dihalo compounds with a zerovalent nickel complex gives pi-conjugated polymers constituted of pyridine units and 2,2'-bipyridine units in high yields. Poly(pyridine-2,5-diyl) (PPy), poly(2,2'-bipyridine-5,5'-diyl) (PBpy), 3-, 4-, and 6-methylated poly(pyridine-2,5-diyl)s (PMePy's), poly(6-hexylpyridine-2,5-diyl) (P6HexPy), poly(3,3'-dimethyl-2,2'-bipyridine-5,5'-diyl) (P3MeBpy), and poly(6,6'-dihexyl-2,2'-bipyridine-5,5'-diyl) (P6HexBpy) are constituted of 42-300 pi-conjugated pyridine rings as measured by light-scattering methods. PPy and PBpy have a rigidly linear rodlike structure as revealed by their showing a theoretically limiting rho(Y) (degree of depolarization) value of 0.33, and they exhibit a large refractive index increment (Delta n/Delta c = 0.59 cm(3) g(-1)) and a large refractive index of n(D) = 2.2. Stretching of poly(Vinyl alcohol) film containing the PPy or PBpy molecules in its surface region affords a polarizer which shows a dichroic ratio of 45. The PBpy molecules stand upright on a carbon substrate in a PBpy film vacuum deposited on the carbon substrate as revealed by electron diffractometry. On the other hand, PBpy molecules in a film vacuum deposited on a glass substrate are oriented in parallel with the surface of the glass substrate as revealed by analysis of optical second-harmonic generation from the PBpy film, which shows alignment of all the PBpy molecules attached to the glass substrate (1 x 1 cm) in a same direction: coordination of a PBpy molecule to the Si-O-H group is proposed to explain such orientation of the PBpy molecules. PPy exhibits fluorescence with a peak at 440 nm in a dilute solution (2 x 10(-6) M monomer unit), whereas PPy shows an additional excimer-like emission at 550 nm in a saturated solution (0.5 M monomer unit) and PPy and PBpy films emit only the excimer-like emission at 550 nm. Picosecond time-resolved fluorescence also supports the excimer-like fluorescence. PPy, PBpy, and their Alkyl derivatives are electrochemically reduced or n-doped more easily than poly(p-phenylene) and poly(thiophene-2,5-diyl), reflecting pi-electron-deficient nature of the pyridine ring, and E(0) values of -2.2 through -2.5 v vs ag/ag(+) are observed for the polymers; the n-doping and its reverse reaction (n-undoping) are accompanied by a color change (e.g., yellow in the n-undoped state and blue in the n-doped state for PPy and PBpy). Chemically n-doped PPy and PBpy with sodium naphthalide have electrical conductivities of 1.1 X 10(-1) and 1.6 X 10(-1) S cm(-1), respectively, as measured with compressed powder. On the contrary, PPy, PBpy, and their Alkyl derivatives undergo p-doping neither electrochemically nor chemically (e.g., by treatment with AsF5), reflecting the pi-deficient nature of the pyridine ring. PBpy and P6HexBpy form complexes with Ru(II), Ni(II), Ni(0), and Fe(III) species, and cyClic voltammetry of the PBpy-Ru complex reveals electron exchange between the coordinated Ru species, which is considered to occur through the pi-conjugation system of the conjugated polymer ligand. The complexes are active for photoevolution of H-2 from aqueous media as well as for reduction of CO2.PI-CONJUGATED POLY(PYRIDINE-2,5-DIYL), POLY(2,2'-BIPYRIDINE-5,5'-DIYL), AND THEIR Alkyl DERIVATIVES - PREPARATION, LINEAR STRUCTURE, FUNCTION AS A LIGAND TO FORM THEIR TRANSITION-METAL COMPLEXES, CATALYTIC REACTIONS, N-TYPE ELECTRICALLY CONDUCTING PROPERTIES, OPTICAL-PROPERTIES, AND ALIGNMENT ON SUBSTRATESx4921994113#N/AFALSE
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ja00106a06210.1021/ja00106a062FALSEhttps://doi.org/10.1021/ja00106a062ROVIS, TJ. Am. Chem. Soc.NICKEL-CATALYZED HYDROALUMINATION OF OXABICYClIC ALKENES - LIGAND EFFECTS ON THE REGIOSELECTIVITY AND ENANTIOSELECTIVITY88199544#N/ATRUE
3046
ja00089a02910.1021/ja00089a029FALSEhttps://doi.org/10.1021/ja00089a029DAVIDSON, FJ. Am. Chem. Soc.The syntheses and characterizations of 2-coordinate homoleptic bis(carbene) adducts of 14-electron Ni(0) and Pt(0) are described. These carbene adducts are available directly from the reaction of the stable nuCleophilic carbene 1,3-dimesitylimidazol-2-ylidene and the corresponding metal bis(cyClooctadiene) complexes. NMR data are consistent with the bis(carbene)-metal structures and suggest a higher degree of d pi-p pi back-donation from the metal relative to Closely related Cu(I), Ag(I), and Au(I) complexes. The X-ray crystal structures of both the nickel-carbene and platinum-carbene adducts are reported. The metals exhibit an essentially linear 2-coordinate geometry with the imidazole rings twisted 53 degrees (Ni) and 51 degrees (Pt) relative to one another.LOW-COORDINATE CARBENE COMPLEXES OF NICKEL(0) AND PLATINUM(0)x231199433#N/AFALSE
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ja00106a05610.1021/ja00106a056FALSEhttps://doi.org/10.1021/ja00106a056ZIEGLER, TJ. Am. Chem. Soc.A nonlocal, quasirelativistic density functional (DF) method, NL-SCF+QR, has been applied to the calculation of M-CO bond lengths and the first bond dissociation energy (FBDE) in the binary transition metal Carbonyls M(CO)(4) (M = Ni, Pd, Pd), M(CO)(5) (M = Fe, Ru, Os), and M(CO)(6) (M = Cr, Mo, W). The calculated M-CO bond lengths are in good agreement with available experimental data with an error typically smaller than 0.01 Angstrom. The calculated FBDE's are 29.9 (Ni), 12.3 (Pd), 15.7 (Pt), 45.7 (Fe), 33.0 (Ru), 34.7 (Os), 46.2 (Cr), 39.7 (Mo), and 43.7 ON) kcal/mol, respectively. These values compare well with the available experimental estimates of 25 (Ni), 42 (Fe), 28 (Ru), 31 (Os), 37 (Cr), 41 (Mo), and 46 (W), respectively. Calculations have also been carried out on the CO association energy, AE, corresponding to the following process: M(CO)(6) + CO (M = Cr, Mo, W) --> M(CO)(7) + AE. The calculated AE's are 47.0 (Cr), 40.4 (Mo), and 35.8 (W) kcal/mol. These calculations underline that CO substitution in M(CO)(6) (M = Cr, Mo, W) can proceed by CO dissociation as well as CO association. The relativistic effects are found to contract M-CO bonds by between 0.07 and 0.16 Angstrom and strengthen the FBDE's by 5-11 kcal/mol for third-row compounds. The relativistic stabilization of the FBDE's among the 5d elements makes in general the M-CO bond of the 4d element the weakest within a triad. The way in which relativity enhances the M-CO bond is analyzed by an energy decomposition scheme based on the Extended Transition State (ETS) method.A REASSESSMENT OF THE FIRST METAL-Carbonyl DISSOCIATION-ENERGY IN M(CO)(4) (M=NI, PD, PT), M(CO)(5) (M=FE, RU, OS), AND M(CO)(6) (M=CR, MO, W) BY A QUASI-RELATIVISTIC DENSITY-FUNCTIONAL METHOD4281995102#N/ATRUE
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ja00106a05010.1021/ja00106a050FALSEhttps://doi.org/10.1021/ja00106a050THIEL, PAJ. Am. Chem. Soc.We have investigated the thermally-induced and electron-impact-induced chemistry of CF3I on Ni(100) following adsorption at 100 K. The data support a model for the thermally-induced chemistry, in which CF3I dissociates to CF3 and I, either upon adsorption or at slightly-elevated temperatures. Most CF3 decomposes to adsorbed C and F. Above 75% saturation of the first layer, the availability of surface sites for decomposition decreases to a level where some adsorbed CF3 remains intact and desorbs as such. Bombardment of multilayer CF3I by low-energy electrons introduces new chemistry. Electron-induced decomposition (EID) of the parent molecule occurs through both C-I and C-F bond scission, with a measured cross section of 1.5 x 10(-16) cm(2) (upper limit). Thermally-induced desorption from the electron-bombarded surface indicates a number of EID fragment reactions, most notably carbon-carbon bond formation, as evidenced by C2F3I+, C2F4+, C2F5+, C3F5+, and C4F7+. To our knowledge, this is the first report of C-C bond formation in small. fluorocarbons adsorbed on metal surfaces.THERMALLY-INDUCED AND ELECTRON-INDUCED CHEMISTRY OF CF3I ON NI(100)23199536#N/ATRUE
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ja00088a01410.1021/ja00088a014FALSEhttps://doi.org/10.1021/ja00088a014ARMENTROUT, PBJ. Am. Chem. Soc.Reactions of Fe+ and Ni+ with propane, propane-2-d(1), propane-2,2-d(2), propane-1,1,1-d(3), propane-1,1,1,3,3,3-d(6) and propane-d(8) are examined to gain insight into the mechanism and energetics for the H-2 and CH4 elimination channels. The questions of C-H and/or C-C bond Activation and the relative contributions from primary and secondary C-H bond Activation are addressed. Total cross section measurements indicate that ground-state Ni+(D-2) and Fe+(D-6) react with propane inefficiently, 13% and 7.5% of the Langevin collision cross section, respectively, with CH4 loss favored over H-2 loss by a factor of 4.0 for Ni+ and 2.8 for Fe+. For reactions with C3D8, the total cross sections decrease by factors of 3.8 for Ni+ and 4.4 for Fe+ relative to C3H8, with the dehydrogenation channel enhanced over demethanation for both Ni+ and Fe+. Kinetic energy release distributions (KERDs) from nascent metastable Ni(propane)(+) and Fe(propane)(+) complexes were measured for H-2 loss and CH4 loss. For H-2 loss, the distribution is bimodal. Studies using propane-2,2,d(2) and propane-1,1,1,3,3,3-d(6) indicate that both primary and secondary C-H insertions are involved as initial steps. Initial secondary C-H insertion is responsible for the high-energy component in the bimodal KERD, which is much broader than predicted from statistical theory, indicating that a tight transition state leads to the final products. The low-energy component for H-2 loss involves initial primary C-H insertion and appears to be statistical, suggesting little or no reverse Activation barrier as the system separates to products. The kinetic energy distribution for demethanation is statistical and is very sensitive to the energy of the rate-limiting C-H insertion transition state. A lower limit for the energy of this transition state is obtained by modeling the experimental kinetic energy release distribution for demethanation using statistical phase space theory. The barrier reduces the contribution of high angular momentum states to the final products, thus reducing the high-energy portion of the product kinetic energy distribution. Modeling the cross section, the isitope effect, and the KERD for CH4 loss using statistical phase space theory indicates that the barrier for C-H bond insertion is located 0.10 +/- 0.03 eV below the Ni+/C3H8 asymptotic energy and 0.075 +/- 0.03 eV below the Fe+/C3H8 ground-state asymptotic energy. All data can be explained by initial C-H insertion, without the need to invoke initial C-C bond Activation for ground-state Fe+ and Ni+ reacting with propane at low kinetic energy.RELATIVE ENERGETICS OF C-H AND C-C BOND Activation OF ALKANES - REACTIONS OF NI+ AND FE+ WITH PROPANE ON THE LOWEST ENERGY (ADIABATIC) POTENTIAL-ENERGY SURFACESx85199479#N/AFALSE
3050
ja00104a04610.1021/ja00104a046FALSEhttps://doi.org/10.1021/ja00104a046LATOUR, JMJ. Am. Chem. Soc.A NEW BIMETALLIC FERROMAGNET, [NI(EN)(2)](3)[FE(CN)(6)](2)CENTER-DOT-2H(2)O, WITH A RARE ROPE-LADDER CHAIN STRUCTURE241199437#N/ATRUE
3051
ja00103a01810.1021/ja00103a018FALSEhttps://doi.org/10.1021/ja00103a018OYOUNG, ClJ. Am. Chem. Soc.Five hydrated inorganic divalent cations, Mg2+, Co2+, Ni2+, CU2+ and Zn2+, have successfully been used as templates for the synthesis of manganese oxide octahedral molecular sieves (OMS-1) having the todorokite structure. The OMS-1 samples have been well characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy/energy dispersive X-ray studies, inductively coupled plasma analysis, electron paramagnetic resonance, Fourier transform infrared spectroscopy, thiosulfate titration, and cyClohexane sorption. Catalytic CO oxidation and 2-propanol decomposition were carried out. Results show that these OMS-1 samples with a tunnel size of about 6.9 Angstrom are crystalline and chemically pure. They have the following formulas: Mg3.17Mn5.05O12.4.52H(2)O, Co1.84Mn5.59O12.3.45H(2)O, Ni1.64Mn5.75O12.4.19H(2)O, CU3.50Mn4.45O12.5.33H(2)O, and Zn3.55Mn4.47O12.2.59H(2)O. Their thermal stability largely depends on the nature of the cations: Mg-OMS-1 is thermally stable in air up to 600 degrees C; Co-OMS-1 and Ni-OMS-1 are stable to 500 degrees C, and Cu-OMS-1 and Zn-OMS-1 are stable to 300 degrees C. The crystal morphologies of the OMS-1 samples can be plates, needles, or fibrous shapes, depending on the nature of the cations. The cations also have profound effects on acidity: Mg-OMS-1, Co-OMS-1, and Ni-OMS-1 have intermediate strength Bronsted and Lewis acid sites, while Cu-OMS-1 and Zn-OMS-1 have no Bronsted acid sites and weak Lewis acid sites. All the OMS-1 samples have six hyperfine electron paramagnetic resonance lines for Mn2+ located in an octahedral environment.EFFECTS OF INORGANIC CATION TEMPLATES ON OCTAHEDRAL MOLECULAR-SIEVES OF MANGANESE OXIDE183199452#N/ATRUE
3052
ja00101a00710.1021/ja00101a007FALSEhttps://doi.org/10.1021/ja00101a007WARREN, THJ. Am. Chem. Soc.The enantioselectivity of the nickel-catalyzed, asymmetric hydrocyanation of Vinylarenes using glucose-derived, chiral phosphinite ligands, L, increases dramatically when the ligands contain electron-withdrawing P-Aryl substituents. The substrate and solvent also strongly influence the enantioselectivity, with the highest ee's (85-91% for 6-methoxy-2-Vinylnaphthalene (MVN)) obtained for the hydrocyanation of electron-rich Vinylarenes in a nonpolar solvent such as hexane. Mechanistic studies suggest the catalytic cyCle consists of an initial HCN oxidative addition or Vinylarene coordination to ''NiL'', followed by insertion to form an (eta(3)-Benzyl)nickel cyanide complex, and irreversible reductive elimination of the nitrile. A kinetic analysis of the NiL(a)(COD) (L(a), P-Aryl = 3,5-(CF3)(2)C6H3) catalyzed hydrocyanation of MVN indicates that as the HCN concentration is increased the catalyst resting state shifts from NiL(a)(COD) to a complex containing both MVN and HCN, presumably the (eta(3)-Benzyl)nickel cyanide intermediate NiL(a)(eta(3)-CH3CHC10H6OCH3)CN. A P-31 NMR analysis of the intermediate NiL(a)(MVN) shows little ground state differentiation of the MVN enantiofaces and suggests that the enantioselectivity is determined later in the mechanism. Deuterium labeling studies suggest that electron-withdrawing P-Aryl substituents increase the rate of reductive elimination of the product nitrile from the (eta(3)-Benzyl)nickel cyanide intermediate and, on this basis, a rationale for the ligand electronic effect is proposed.LIGAND ELECTRONIC EFFECTS IN ASYMMETRIC CATALYSIS - ENHANCED ENANTIOSELECTIVITY IN THE ASYMMETRIC HYDROCYANATION OF VinylARENES256199481#N/ATRUE
3053
ja00087a01110.1021/ja00087a011FALSEhttps://doi.org/10.1021/ja00087a011SHELNUTT, JASTRUCTURAL HETEROGENEITY AND COORDINATION CHEMISTRY OF NICKEL(II) OCTAETHYL-MESO-NITROPORPHYRINSx1994#N/AFALSE
3054
ja00100a06110.1021/ja00100a061FALSEhttps://doi.org/10.1021/ja00100a061MORI, MJ. Am. Chem. Soc.NOVEL STEREOSELECTIVE CYClIZATION VIA PI-ALLYLNICKEL COMPLEX GENERATED FROM 1,3-DIENE AND HYDRIDE NICKEL-COMPLEX107199426#N/ATRUE
3055
ja00085a01610.1021/ja00085a016https://doi.org/10.1021/ja00085a016ZILLER, JWJ. Am. Chem. Soc.A bifunctional nickel initiator, bis(mu-trifluoroacetato)(eta3:eta3-2,2'-biallyl)dinickel(II), IV, was synthesized to promote the living polymerization of butadiene to high cis-1,4-content polymer with both chain ends active. Other potential initiator, [1,4-phenylenebis(eta3-1-allyl)nickel trifluoroacetate)]n, II, and [1,4-cyClohexanediylbis((eta3-1-allyl)-nickel trifluoroacetate)]n, III, were found to be completely ineffective due to intermolecular Carbonylate bridges which gave the complexes polymeric structures. The intramolecular bridges in IV and its molecularity were confirmed by X-ray crystallography. IV cocrystallizes in space group P1BAR with 0.5 equiv of 2,3-bis((trifluoroacetoxy)methyl)-1,3-butadiene in the unit cell with constants of a = 9.5600(8) angstrom, b = 9.6554(9) angstrom, c = 11.7615(10) angstrom; alpha = 73.711(7)degrees, beta = 73.537(7)degrees, gamma = 71.938(7)degrees; V= 967.50(15) angstrom3; and Z = 2. Refinement of the model, which contained a disordered C6H8 unit, led to convergence with R(F) = 5.8%, R(wF) = 6.9%, and GOF = 2.21 for 276 variables refined against those 2852 data with \F(o)\>3.0sigma/(\F(o)\)). The living polybutadiene samples were successfully used to prepare triblock copolymers of the structure poly(1-phenylethyl isocyanide-b-butadiene-b-1-phenylethyl isocyanide), which have been characterized using gel permeation chromatography, differential scanning calorimetry, C-13 NMR, elemental analysis, and transmission electron microscopy. The bifunctional living polybutadiene was also successfully end-capped with p-(trifluoromethyl)benzaldehyde to afford a telechelic polymer with hydroxy functionalities at both chain ends.LIVING POLYMERIZATION OF BUTADIENE AT BOTH CHAIN-ENDS VIA A BIMETALLIC NICKEL INITIATOR - PREPARATION OF HYDROXYTELECHELIC POLY(BUTADIENE) AND SYMMETRICAL POLY(ISOCYANIDE-B-BUTADIENE-B-ISOCYANIDE) ELASTOMERIC TRIBLOCK COPOLYMERSx55199436#N/AFALSE
3056
ja00097a03010.1021/ja00097a030FALSEhttps://doi.org/10.1021/ja00097a030BERNSTEIN, JJ. Am. Chem. Soc.A crystal orbital displacement function (COD) is defined as the variation of the contribution of an atomic orbital (or atom, fragment, or fragment molecular orbital) to the density of states (DOS) on going from a sublattice to the complete crystal lattice, within the one-electron approximation of tight-binding band calculations. This simple definition allows one to abstract relevant information on weak interactions in solids, by discarding the large amount of noninteracting levels and the strong (covalent or metallic) interactions present in complex systems. The degree of charge transfer between donor and acceptor sublattices can be obtained as the integral of a COD function (ICOD) up to the Fermi level, Omega(i)(epsilon(F)). The general shapes of the COD curves are described, and simple examples of interpretation of the COD and ICOD diagrams to well-known chemical systems are presented. Extended Huckel tight binding (EHTB) band calculations and the derived COD and ICOD curves are applied to the study of host-guest interaction in the Hofmann Clathrate Ni(NH3)(2)Ni(CN)(4).2C(6)H(6), and the role of the different building blocks of the host lattice in the host...guest interaction is discussed. The calculated barrier for the rotation of benzene around the molecular 6-fold axis, the predicted orientations of the guest molecules, changes in bond distances of the host and guest sublattices produced by enClathration, and variations of vibrational frequencies produced by enClathration are in agreement with a wealth of experimental data.CRYSTAL ORBITAL DISPLACEMENT ANALYSIS OF INTERACTIONS IN THE SOLID-STATE - APPLICATION TO THE STUDY OF HOST-GUEST INTERACTIONS IN THE HOFMANN ClATHRATES501994123#N/ATRUE
3057
ja00083a01510.1021/ja00083a015https://doi.org/10.1021/ja00083a015STILLMAN, MJJ. Am. Chem. Soc.An extensive analysis of the optical absorption and magnetic circular dichroism (MCD) spectra of the anion radical of zinc phthalocyanine ([(ZnPc(-3)](-)) is described. Novel photochemical formation of the ring-reduced [ZnPc(-3)](-) from (hydrazine)Zn(II)Pc(-2) is reported for reactions carried out at room temperature using visible-wavelength light and hydrazine as the electron donor. Absorption and MCD spectra of the radical anion species have been obtained at both room and cryogenic temperatures. Phosphorescence and fluorescence life:time studies of ZnPc(-2) show that the photoexcited (hydrazine)ZnPc(-2) complex reacts via the triplet state to form the ring reduced anion radical, [ZnPc(3)](-). The complete lack of temperature dependence assignable to orbital degeneracies in the low-temperature MCD spectrum shows conClusively that the (2)Eg, ground state of [ZnPc(-3)](-) is split into nondegenerate components at least 800 cm(-1) apart. The ground and excited states are completely nondegenerate. It is proposed that the coupled effects of the loss of aromaticity with the addition of the 19th pi-electron, Jahn-Teller distortion, and nonsymmetric solvation of the ring lead to a change in molecular geometry from D-4h of ZnPc(-2) to C-2D, for [ZnPc(-3)](-). The first complete assignment of the optical spectrum of any porphyrin or phthalocyanine a nion radical is proposed on the basis of a B-2(1) ground state and supported by results from extensive deconvolution calculations. Comparison between the absorption and MCD spectral data indicated that a significant fraction of the spectral intensity observed at room temperature can be assigned as ''hot'' bands. The hot bands, which are much more pronounced in the spectral data of [ZnPc(-3)](-) than in the spectral data of the parent ZnPc(-2), are associated with interactions between the solvent, the Pc(-3) ring, and vibronic bands associated with the split ground state. A detailed study of the temperature dependence of the absorption and MCD spectra showed that meaningful spectral deconvolution,n calculations could only he carried out on spectra obtained from vitrified solutions of [ZnPc(-3)](-) at cryogenic temperatures eratures. Bandwidths calculated to fit the absorption spectrum increase in magnitude as a function of the transition energy from 10 000 to 33 000 cm(-1), which allows the Classification of sets of bands to one of five major electronic tran;sitions, namely, Q between 750 and 1000 nm, n-->pi(*) between 580 and 750 nm pi(*) --> pi(*) between 430 and 650 nm, B1 and B2 between 300 and 450 nm.PHOTOCHEMICAL FORMATION OF THE ANION-RADICAL OF ZINC PHTHALOCYANINE AND ANALYSIS OF THE ABSORPTION AND MAGNETIC CIRCULAR-DICHROISM SPECTRAL DATA - ASSIGNMENT OF THE OPTICAL-SPECTRUM OF [ZNPC(-3)](-)Photocatalyst1521994101#N/AFALSE
3058
ja00096a04510.1021/ja00096a045FALSEhttps://doi.org/10.1021/ja00096a045ZHAO, HJ. Am. Chem. Soc.The gas-phase binding chemistry between Ca2+, Co2+, and Ni2+ and 33 tri- through decapeptides is evaluated with respect to aqueous-phase and theoretical chemistry. Metastable ion decompositions of tetrapeptide and larger peptide complexes that contain either hydrocarbon amino acid side chains or Pro reveal the intrinsic binding preferences. Tripeptide complexes do not. Interactions with the Ca2+-specific binding sequence in staphylococcal nuClease and with the Asp side chain in the third position from the N-terminus are also presented. For Co2+ and Ni2+, aqueous-phase chemistry is reflected in the gas-phase results. Mass spectrometry detects some weakly abundant, less favorable complexes, species that aqueous-phase studies do not detect. Gas-phase complexes of Ca2+ are not seen in solution because aqueous equilibria favor precipitation of Ca(OH)(2). Solution-phase binding interactions between Co2+ and Ni2+, however, are intrinsic, independent of solvation. Metastable ion decomposition mass spectrometry has a future in the direct elucidation of important metal ion binding sites in peptides and proteins.INTRINSIC (GAS-PHASE) BINDING OF CO2+ AND NI2+ BY PEPTIDES - A DIRECT REFLECTION OF AQUEOUS-PHASE CHEMISTRY74199443#N/ATRUE
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ja00092a06110.1021/ja00092a061FALSEhttps://doi.org/10.1021/ja00092a061SATO, YJ. Am. Chem. Soc.SYNTHESIS OF STEREODEFINED ENYNES BY THE NICKEL-CATALYZED COUPLING REACTION OF ALKYNYLTINS, ALKYNES, AND ENONES104199422#N/ATRUE
3060
ja00079a01510.1021/ja00079a015FALSEhttps://doi.org/10.1021/ja00079a015SHELNUTT, JAPLANAR NONPLANAR CONFORMATIONAL EQUILIBRIUM IN METAL DERIVATIVES OF OCTAETHYLPORPHYRIN AND MESO-NITROOCTAETHYLPORPHYRINx1993#N/AFALSE
3061
ja00092a02110.1021/ja00092a021FALSEhttps://doi.org/10.1021/ja00092a021RIZZOLI, CJ. Am. Chem. Soc.We report here a two-electron oxidation of a porphyrinogen tetraanion and its conversion into a dianionic form containing a cyClopropane unit [abbreviated as (Delta)]. The dianionic porphyrinogen form was structurally identified in nickel(II) and copper(II) derivatives. The redox chemistry of meso-octaethylporphyrinogen copper(II) helped to Clarify the stepwise process leading to the oxidized form of porphyrinogen. The Ni(II)-meso-octaethylporphyrinogen complex [Et(8)N(4)NiLi(2)(THF)(4)] (1) can be converted into the oxidized form [Et(8)N(4)(Delta)Ni] (3) by reaction with excess of p-benzoquinone. Complex 3 contains the oxidized form of porphyrinogen which can be reduced, by lithium metal, back to complex 1. The structural features of the oxidized form have been elucidated by X-ray crystal analysis of 2. In contrast to the case of Ni(II), the oxidation of [Et(8)N(4)CuLi(2)(THF)(4)] (2) is a stepwise process initially leading to the formation of a diamagnetic square planar copper(III) derivative, [Et(8)N(4)Cu][Li(THF)(4)] (5). Further oxidation of 5, with CuCl2, led to the monocyClopropane form of porphyrinogen in [Et(8)N(4)(Delta)Cu] (4). There is an interesting redox relationship between 2, 4, and 5. The copper(III) derivative (5), disproportionates into 2, containing copper(II), and 4 containing formally a copper(IV), the cyClopropane counting for a +2 oxidation state. This reaction occurs in benzene, and it can be reversed in coordinating solvents such as THF. Such a finding emphasizes the inter- and intramolecular electron-transfer processes which can occur in such systems. The best way to prepare the monocyClopropane form of porphyrinogen is, however, via the oxidation of 2 with p-benzoquinone. The X-ray analysis carried out on 2, 4, and 5 allows description of the major conformational changes of the porphyrinogen skeleton during the oxidation process. Crystallographic details: 2 is monoClinic, space group C2/c, a = 20.808(2) Angstrom, b = 10.946(1) Angstrom, c = 22.811(2) Angstrom, alpha = gamma = 90 degrees, beta 104.57(2)degrees, Z = 4, and R = 0.056. 3 is orthorhombic, space group P2(1)2(1)2(1), a 11.526(1) Angstrom, b = 15.132(1) Angstrom, c = 21.098(2) Angstrom, alpha = beta = gamma = 90 degrees, Z = 4, and R = 0.057. 4 is orthorhombic, space group P2(1)2(1)2(1), a = 14.880(2) Angstrom, b = 22.050(2) Angstrom, c = 11.436(2) Angstrom, alpha = beta = gamma = 90 degrees, Z = 4, and R = 0.043. 5 is hexagonal, space group P3(1)21, a = b = 11.329(1) Angstrom, c = 34.939(2) Angstrom, alpha = beta = 90 degrees, gamma = 120 degrees, Z = 3, and R = 0.062.OXIDATION OF METAL-MESO-OCTAETHYLPORPHYRINOGEN COMPLEXES LEADING TO NOVEL OXIDIZED FORMS OF PORPHYRINOGEN OTHER THAN PORPHYRINS .1. THE REDOX CHEMISTRY OF NICKEL(II)- AND COPPER(II)-MESO-OCTAETHYLPORPHYRINOGEN COMPLEXES OCCURRING WITH THE FORMATION AND ClEAVAGE OF A CYClOPROPANE UNIT45199462#N/ATRUE
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ja00089a03410.1021/ja00089a034FALSEhttps://doi.org/10.1021/ja00089a034VANSANTEN, RAJ. Am. Chem. Soc.Elementary reaction steps for the catalytic cyCle of thiophene desulfurization on Ni3Sy and Ni4Sy Clusters are investigated using density functional quantum chemical calculations. The Ni3S2 Cluster is active while the Ni4Sy Cluster is relatively inactive for HDS catalysis. Adsorption and overall reaction energies are computed on complete geometry-optimized Cluster-adsorbate systems. The nickel-sulfide Cluster is found to significantly reorganize upon interaction with adsorbates. Sulfur readily rearranges between 3-fold and 2-fold binding sites. Hydrogen adsorbs molecularly and dissociates heterolytically over Ni3S2 to form both adsorbed sulfhydryl (SH) and hydryl (MH) species. The presence of coadsorbed hydrogen affects both the heat of adsorption and the coordination of thiophene. On the ''bare'' Ni3S2 Cluster thiophene binds eta(4)-coordinated, while in the presence of coadsorbed hydrogen thiophene prefers the eta(1) site. 2,5-Dihydrothiophene (DHT) adsorbs somewhat stronger than thiophene on the Ni3S2 Cluster. In the preferred eta(3) configuration, the ethylene moiety of the DHT adsorbs at one nickel atom site while its sulfur adsorbs at the neighboring nickel atom site. For the HDS cyCles initiated by eta(1) or eta(4) thiophene adsorption, the energy change associated with the carbon-sulfur bond scission step of adsorbed dihydrothiophene and that for the removal of sulfur via H2S are the most endothermic steps and are speculated to be rate limiting. Their comparable values indicate that the two steps compete. The cyCle which is initiated by the removal of sulfur from Ni3S2 is energetically unfavorable.THEORY OF CARBON-SULFUR BOND Activation BY SMALL METAL SULFIDE PARTIClES111199475#N/ATRUE
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ja00077a07110.1021/ja00077a071FALSEhttps://doi.org/10.1021/ja00077a071ClAUSE, OJ. Am. Chem. Soc.SURFACE COPRECIPITATION OF CO(II), NI(II), OR ZN(II) WITH AL(III) IONS DURING IMPREGNATION OF GAMMA-ALUMINA AT NEUTRAL PHx77199311#N/AFALSE
3064
ja00077a04410.1021/ja00077a044FALSEhttps://doi.org/10.1021/ja00077a044KIBAYASHI, CJ. Am. Chem. Soc.Remarkably high regio- and stereoselective approaches for the syntheses of dendrobatid alkaloids (+)-allopumiliotoxin 267A and 339A have been developed. As a model study for the syntheses of these alkaloids, we initially undertook intramolecular chromium(II)-mediated cyClization of the racemic N-(iodoalkenyl)piperidine 8, which smoothly proceeded by treatment with CrCl2 (5 equiv) and catalytic NiCl2 (2.5 mol %) in DMF to form a 1.3:1 epimeric mixture of 2-hydroxy-3(E)-Alkylidene-trans-quinolizidines 33a and 33b. When the alternative chiral N-(iodoalkenyl)piperidine 9 was subjected to the identical cyClization conditions, the 3(E)-Alkylidene-trans-quinolizidine 35a with the axially oriented 2-hydroxy group was formed as a single isomer. Based on these model studies, we then undertook the enantioselective total synthesis of (+)-allopumiliotoxin 267A (1). For the synthesis of (+)-allopumiliotoxin 267A (1), coupling of the two segments, (E)-Vinyl iodide 45, obtained via stereospecific palladium-catalyzed hydrostannation, and the pyrrolidine derivative 54, gave the N-(iodoalkenyl)pyrrolidine 56, which underwent intramolecular chromium(II)-mediated cyClization, exClusively providing 58 with complete retention of the required (E)-alkenyl geometry. Subsequent Cleavage of the Benzyl group furnished 1. Synthesis of allopumiliotoxin 339A (2) was next investigated by employing the strategy developed for 1. The side-chain segment, (E)-Vinyl iodide 74, was prepared via high-degree stereo- and regioselective reactions involving Evans Alkylation and palladium-catalyzed hydrostannation. Intramolecular nickel(II)/chromium(II)-mediated cyClization of the N-(iodoalkenyl)pyrrolidine 82, available via coupling 74 with pyrrolidine derivative 79, led to exClusive formation of 83, which was deprotected to afford 2.HIGHLY STEREOSELECTIVE TOTAL SYNTHESES OF (+)-ALLOPUMILIOTOXIN-267A AND (+)-ALLOPUMILIOTOXIN-339A VIA INTRAMOLECULAR NICKEL(II) CHROMIUM(II)-MEDIATED CYClIZATIONx63199361#N/AFALSE
3065
ja000893v10.1021/ja000893vhttps://doi.org/10.1021/ja00407a027Brookhart, MMechanistic studies of Pd(II)-alpha-diimine-catalyzed olefin polymerizations2000#N/ATRUE
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ja00076a01410.1021/ja00076a014FALSEhttps://doi.org/10.1021/ja00076a014STOLZENBERG, AMJ. Am. Chem. Soc.Stability constants and thermodynamic data are reported for coordination of piperidine, pyridine, and substituted pyridines to the cobalt(II) and zinc(II) complexes of octaethylporphyrin (OEP), t-octaethylchlorin (OEC) and the tct- and ttt-isomers of octaethylisobacteriochlorin (OEiBC) in toluene, cyClohexane, and chloroform solution at 25.0-degrees-C. Under the conditions of the study, only 1:1 complexes are formed. With the exception of the case of 2-substituted pyridines, the stability constants, log K, correlate roughly with the base strength of the nitrogenous ligand but correlate Closely with the log K for coordination of the base to Zn(OEP). A cis-influence of the macrocyCle saturation level on the stability constants is observed. Stability constants for coordination of a given ligand to OEiBC complexes are typically 4 times greater than those for coordination to OEP complexes and 1.8 times greater than those for coordination to OEC complexes. The stability constants of both Co- and Zn(OEiBC) complexes were unaffected by the stereochemistry (tct vs ttt) of the ethyl substituents, unlike the case for nickel. DELTAH and DELTAS vary between -8 and -12 kcal/mol and -12 and -24 cal K-1 mol-1, respectively, and correlate linearly with each other. They do not correlate directly with either log K or the saturation level of the macrocyCle. For most bases, log K is greater for the zinc complexes than for the cobalt complexes. However, for 3,5-dichloropyridine, log K is greater for the cobalt complexes. The acid dissociation constants for the free-base compounds H2(OEP), H2(OEC), and H2(OEiBC) were measured in THF/n-butanol solution. All three compounds ionize to dianions by simultaneous loss of two protons. OEP and OEiBC have pK(a) = 15.9. OEC is a weaker acid with pK(a) = 16.6. The increase in log K with macrocyCle saturation level does not correlate with the acidity of the respective free bases, but the latter is not necessarily representative of the sigma-donor strength of the macrocyCle dianion. Solvation and pi-effects are not responsible for either the dependence of log K on macrocyCle saturation level or the reversal for weak bases of the relative Lewis acid strengths of the cobalt and zinc complexes. The latter is attributed to a relief of strain due to core expansion that occurs upon ligand coordination to cobalt complexes. Cobalt complexes are more sensitive than zinc complexes to steric interactions with the ortho-substituents of a pyridine ligand owing to the much smaller out-of-plane displacement of the cobalt atom compared to the zinc atom in five-coordinate complexes.THE CIS-INFLUENCE OF HYDROPORPHYRIN MACROCYClES ON THE AXIAL LIGATION EQUILIBRIA OF COBALT(II) AND ZINC(II) PORPHYRIN COMPLEXESx261993113#N/AFALSE
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ja00075a01610.1021/ja00075a016FALSEhttps://doi.org/10.1021/ja00075a016HOFFMAN, BMJ. Am. Chem. Soc.We have synthesized new pentametallic macrocyClic complexes based on the polynuCleating ligand, porphyrazine-2,3,7,8,12,13,17,18-octathiolate, (pzot)8-. This ligand can be thought of as a porphyrazine (tetraazaporphyrin) bearing four dithiolene moieties peripherally at the beta-pyrrole positions, and we show that a transition-metal ion can be chelated to each of the four peripheral dithiolene moieties. The complexes [(P-P)Ni]4[Ni(pzot)] (2a, P-P = dppe; 2b, P-P = dppy; 2c, P-P = dppb; 2d, P-P = dcpe) have been synthesized and characterized. Complex 2a crystallizes in the orthorhombic space group Cmc2(1) (No. 36) with 4 macrocyCles and 16 solvent molecules (N,N-dimethylformamide) in a unit cell of dimensions a = 24.630(5) angstrom, b = 20.607(4) angstrom, c = 30.675(6) angstrom. The [Ni(pzot)]8- ligand in 2a coordinates four Ni(P-P) moieties around its periphery with the two thiolate sulfur atoms of each pyrrole binding a nickel ion in a bidentate (S-S) coordination mode. This is in contrast to the reaction of [Ni(pzot)]8- with SnR2X2, which yielded Ni(pzot)(SnR2)4 (1), where each tin is coordinated in the tridentate (S-N-S) mode, with the thiolate sulfur atoms from two pyrroles and one m-nitrogen atom as ligands from the macrocyCle (Velazquez, C. S.; Fox, G. A.; Broderick, W. E.; Andersen, K; Anderson, O. P.; Barrett, A. G. M.; Hoffman, B. M. J. Am. Chem. Soc. 1992, 114, 7416-7424). Comparison of the crystal structures of 1,2a, and aquo(octakis(methylthio)porphyrazinato)magnesium(II) (Mg(omtp)), a structurally unconstrained reference compound with eight peripheral methylthio groups, shows that [Ni(pzot)]8- adjusts to accommodate either the (S-S) or (S-N-S) modes of coordinating the metal ions at the periphery by a swing of the C(beta)-S bond. H-1 and P-31 NMR studies have been used to determine the nature of the coordination of the Ni(P-P) units to the [Ni(pzot)]8- macrocyCle in solution. Model compounds were synthesized as structural references to mimic both possible coordination sites of the [Ni(pzot)]8- ligand. The H-1 and P-31 NMR chemical shifts of macrocyCles 2a-d and their respective bidentate model complexes Clearly indicate that the macrocyCle in solution also binds the Ni(P-P) units in a bidentate fashion. The electronic absorption spectra of complexes 2a-d show a red-shift of the absorbance in the Q-band region due to interaction of the porphyrazine pi-system with the four peripheral metal ions.STAR PORPHYRAZINES - PERIPHERAL CHELATION OF PORPHYRAZINEOCTATHIOLATE BY DIPHOSPHINONICKEL IONSx57199383#N/AFALSE
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ja000749+10.1021/ja000749+FALSEhttps://doi.org/10.1021/ja000749+Bruckner, CJ. Am. Chem. Soc.This paper presents the first electrochemical study of Ni(II) secochlorins, chlorophin, and homoporphyrins and demonstrates the influence of macrocyCle-rigidity on the site of electroreduction. Oxidations and reductions were investigated by cyClic voltammetry. The measured electrode potentials were found to be dependent on the nature of the substituents attached to the porphyrinic moiety and on the ring flexiblitiy. The voltammetric behavior of these molecules when employed as catalysts for the electrochemical catalytic debromination of trans-1,2-dibromocyClohexane was used to determine whether reduction peaks were due to a metal-based (formation of catalytically active Ni(I) complexes) or ligand-based (formation of catalytically less active pi-anion radical) reduction. The results showed that the homoporphyrins formed ligand-based reduction products. The homoporphyrins are locked into a nonplanar conformation stabilizing the small Ni(II) ion which results in their inability to accommodate the larger Ni(I) ion. In contrast, the electronically quite similar but conformationally flexible chlorin and secochlorin complexes formed Ni(I) complexes upon electrochemical reduction. Our findings shed further light on the structural features required of porphyrinic cofactors such as factor F-430 to undergo metal-centered reduction events in their catalytic cyCles. The results also provide a blue-print for synthetic porphyrinic NL(II) complexes to be utilized for electrochemical catalysis.Nickel(II) meso-tetraphenyl-homoporphyrins, -secochlorins, and -chlorophin: Control of redox chemistry by macrocyCle rigidityx58200061#N/AFALSE
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ja00073a02810.1021/ja00073a028https://doi.org/10.1021/ja00073a028NOVAK, BMJ. Am. Chem. Soc.All mechanistic aspects of nickel-mediated isocyanide polymerizations have been examined experimentally. Chain initiation has been studied by C-13{H-1} NMR at low temperature using a living polymerization system. Chain propagation has been examined by cyClic voltammetry, ESR spectroscopy, magnetic susceptibility measurements, temperature dependent kinetic studies, and substituent effect analysis. The chain-propagation studies were performed on both living and Classical heterogeneous systems and were found to be invariant with respect to the type of nickel initiator used. Finally, chain-transfer reactions were studied by NMR, kinetic studies, substituent effect analyses, and chemical studies. Comprehensive mechanistic schemes have been derived from the experimental data and are presented as the most probable reaction pathways.MECHANISTIC STUDIES ON THE NICKEL-CATALYZED POLYMERIZATION OF ISOCYANIDESx88199368#N/AFALSE
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ja00088a01710.1021/ja00088a017FALSEhttps://doi.org/10.1021/ja00088a017RETTIG, SJJ. Am. Chem. Soc.The reaction of Pd(dippp)Cl-2 (dippp = 1,3-bis(diisopropylphosphino)propane) with a 1:1 mixture of LiBEt(2)H(2) and LiBEt(4) in THF generates the binuClear hydride derivative [(dippp)Pd](2)(mu-H)(2).LiBEt(4) (1) in which the LiBEt(4) is bound to the palladium hydride core. The bare palladium hydride dimer [(dippp)Pd](2)(mu-H)(2) (2) was prepared by reaction of 2 equiv of KBEt(3)H in toluene with Pd(dippp)I-2. Addition of LiBEt(4) to the bare palladium dimer 2 generates the LiBEt(4) adduct 1; this approach has been extended to the preparation of [(dippp)Pd](2)(mu-H)2.NaBEt(4) (3) and [(dippp)Pd](2)(mu-H)(2).LiAlEt(4) (4) by the addition of NaBEt(4) and LiAlEt(4) respectively to 2. On the basis of NMR spectroscopy, there is no evidence for dissociation of the lithium of sodium berate or aluminate salts from the hydride dimer but the ME'Et(4) (M = Li, Na; E' = B, Al) units are labile on the basis of exchange studies and variable temperature NMR data. Crystals of [(dippp)Pd](2)(mu-H)(2).LiBEt(4)0.5(C6H14) (1) are monoClinic, a = 11.537(2) Angstrom, b = 19.114(2) Angstrom, c = 24.020(1) Angstrom, beta = 98.674(9)degrees, Z = 4, space group P2(1)/n; those of [(dippp)Pd](2)(mu-H)(2) (2) are monoClinic, a = 13.128(1) Angstrom, b = 14.362(4) Angstrom, c = 20.353(1) Angstrom, beta = 99.593(6)degrees, Z = 4, space group P2(1)/n; and those of [(dippp)-Pd](2)(mu-H)(2).NaBEt(4) (3) are monoClinic, a = 20.099(2) Angstrom, b = 11.457(5) Angstrom, c = 21.600(3) Angstrom, beta = 92.87(1)degrees, Z = 4, space group P2(1)/c. The structures were solved by the Patterson method and were refined by full-matrix least-squares procedures to R = 0.033, 0.052, and 0.033 (R(W) = 0.029, 0.054, and 0.028) for 5954, 4560, and 5018 reflections with I greater than or equal to 3 sigma(I), respectively. In the solid-state structure of 1, there are three C-H...Li interactions from the ethyl groups attached to boron whereas in the solid-state structure of 3 there are four such C-H...Na interactions.BINUClEAR PALLADIUM COMPLEXES WITH BRIDGING HYDRIDES - UNUSUAL COORDINATION BEHAVIOR OF LIBET(4) AND NABET(4)62199449#N/ATRUE
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ja00067a09610.1021/ja00067a096https://doi.org/10.1021/ja00067a096KUBIAK, CPJ. Am. Chem. Soc.PHOTOREDUCTION OF CARBON-DIOXIDE TO ITS RADICAL-ANION BY [NI3(MU-3-I)2(DPPM)3] - FORMATION OF 2 CARBON-CARBON BONDS VIA ADDITION OF CO2(.-) TO CYClOHEXENEPhotocatalyst62199358#N/AFALSE
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ja00087a08910.1021/ja00087a089FALSEhttps://doi.org/10.1021/ja00087a089HILLHOUSE, GLJ. Am. Chem. Soc.REACTIONS OF ORGANOAZIDES WITH NICKEL AlkylS - SYNTHESES AND REACTIONS OF NICKEL(II) AMIDO COMPLEXES46199425#N/ATRUE
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ja00066a03410.1021/ja00066a034FALSEhttps://doi.org/10.1021/ja00066a034HAGEN, WRJ. Am. Chem. Soc.The nickel(II) ion in factor F430 pentaCarbonylic acid, both in the native form and in the 12,13-di-epimer, in aqueous solution can be reversibily reduced in a one-electron step to the monovalent state by the action of titanium(III) citrate. The 3d9 Ni(I) is quantitatively detected by EPR spectroscopy as a tetragonally distorted octahedral system with the hole in the d(x2 - y2) orbital resulting in an S = 1/2 spin with g(parallel-to) = 2.244, g(perpendicular-to) = 2.06 1, (g(parallel-to) = 2.238, g(perpendicular-to) = 2.057 for the di-epimer), subject to isotropic superhyperfine interaction from the four in-plane nitrogen ligands with A = 1.0 mT. The UV-visible spectrum of the reduced native F430 has peaks (extinction coefficients in mM-1 cm-1) at 268 (24.0), 378 (34.7), and 715 nm (2.3). In the reduced di-epimer these values are 265 (23.7), 376 (27.6), and 710 nm (1.6). Complete reduction is achieved only at alkaline pH; the process has an apparent pK of 8.9 (native) or 9.4 (di-epimer). The Ni(II)/Ni(I) couple in F430 has a reduction potential E(m,10.4) = -0.65 (native) or -0.62 V (diepimer). Three-pulse stimulated ESEEM spectroscopy on the reduced complexes reveals a single, near isotropic proton resonance at almost-equal-to 13 MHz. In (H2O)-H-2 solution this line is replaced by a quadrupole-split deuterium resonance around almost-equal-to 2 MHz, indicating that the Ni(I) in both native and 12,13-di-epimeric F430 is weakly coordinated by water. The absence of a strong axial bond with water would leave the ability of the d(z2) pair for nuCleophilic attack on substrate carbon largely intact.A SPECTROELECTROCHEMICAL STUDY OF FACTOR F430 NICKEL(II/I) FROM METHANOGENIC BACTERIA IN AQUEOUS-SOLUTIONx70199335#N/AFALSE
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ja00066a02110.1021/ja00066a021FALSEhttps://doi.org/10.1021/ja00066a021LINDAHL, PAJ. Am. Chem. Soc.Carbon monoxide dehydrogenase from Clostridium thermoaceticum has an (alphabeta)3 quaternary protein structure and contains a novel Ni-and-Fe-containing complex (the NiFe complex) that exhibits an EPR signal (the NiFeC signal) of unusually low spin intensity. The Ni in the NiFe complex can be removed by reaction with 1,10-phenanthroline, yielding enzyme devoid of CO/acetyl-CoA exchange activity and unable to exhibit the NiFeC signal. On average, each CODH alphabeta dimer was found to react rapidly and stoichiometrically with as few as 1.0 +/- 0.2 phenanthrolines. Metal analyses of the enzyme before and after phenanthroline treatment, and of the phenanthroline-containing products of the reaction, revealed that only approximately 0.3 Ni per alphabeta were removed. Incubation of phenanthroline-treated enzyme with radioactive Ni-63(2+) followed by chromatographic separation of the Ni-63-containing enzyme from unreacted Ni-63(2+) demonstrated that only 0.3 Ni per alphabeta could be reinserted into the empty labile sites. These results indicate that the enzyme is heterogeneous; 30% of the alphabeta protein subunits contain a labile Ni ion while the remaining 70% do not. Only those alphabeta subunits with labile Ni ions can exhibit the NiFeC EPR signal and contain the NiFe complex in the form commonly recognized as such. Enzyme solutions lacking labile Ni are completely devoid of CO/acetyl-CoA exchange activity, suggesting that only alphabeta subunits with labile Ni ions are capable of catalyzing CO/acetyl-CoA exchange. However, this activity may only be afforded to (alphabeta)3 molecular assemblies that inClude both types of subunits, thereby preCluding assignment of activity to a particular type of subunit. This analysis explains the low-spin intensity of the NiFeC signal and suggests that the NiFe complex contains significantly more irons than previously thought. The unusually mild conditions required for removal of the labile Ni suggests that this Ni may be coordinatively unsaturated.HETEROGENEOUS NICKEL ENVIRONMENTS IN CARBON-MONOXIDE DEHYDROGENASE FROM ClOSTRIDIUM-THERMOACETICUMx54199333#N/AFALSE
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ja00066a01810.1021/ja00066a018FALSEhttps://doi.org/10.1021/ja00066a018MOROOKA, YJ. Am. Chem. Soc.By using the hindered tris(pyrazolyl)borate ligand HB(3,5-iPr2pz)3, (hydrotris(3,5-diisopropyl-1-pyrazolyl)-borate), a series of hydroxo complexes of first-row divalent metal ions (Mn (1), Fe (2), Co (3), Ni (4), Cu (5), Zn (6)) was synthesized. X-ray crystallography was applied to 1-5, establishing that all these hydroxo complexes have a dinuClear structure solely bridged with a bis(hydroxo) unit. The structure of 6 was characterized by spectroscopy, which indicates that 6 is monomeric. All these hydroxo complexes were found to react with CO2, even atmospheric CO2, to afford mu-carbonato dinuClear complexes of Mn (7), Fe (8), Co (9), Ni (10), Cu (11), and Zn (12). The molecular structures of the complexes 8-12 were determined. A variety of coordination modes of the carbonate group was seen. In 10 and 11, the carbonate group is bound to both metal centers bidentately in a symmetric fashion, while in 8 and 9, the carbonate coordination modes are described as an unsymmetric bidentate. The carbonate group in 12 is coordinated to one zinc ion bidentately, but it is bound to the other zinc ion unidentately. From IR data, the coordination mode of the carbonate group in 7 was suggested to be similar to those found in 8 and 9. Thus, the order of the coordination distortions of the carbonate groups in this series of mu-carbonato dinuClear complexes is as follows: Zn > Mn almost-equal-to Fe almost-equal-to Co > Ni almost-equal-to Cu. On the other hand, the reactivities of the hydroxo complexes toward CO2 fixation were found to be ordered Zn > Cu > Ni almost-equal-to Co > Mn > Fe. It is noteworthy that the order of the CO2 fixation capabilities of the hydroxo complexes does not fit with the order of activities known for metal-substituted carbonic anhydrases. The order of activities for CO2 hydration by the carbonic anhydrases is Zn > Co >> Ni almost-equal-to Mn > Cu almost-equal-to 0. Thus, the order is correlated mostly with the coordination distortions of the carbonate group in the mu-carbonate complexes but not the reactivities of the hydroxo complexes toward CO2.FIXATION OF ATMOSPHERIC CO2 BY A SERIES OF HYDROXO COMPLEXES OF DIVALENT METAL-IONS AND THE IMPLICATION FOR THE CATALYTIC ROLE OF METAL-ION IN CARBONIC-ANHYDRASE - SYNTHESIS, CHARACTERIZATION, AND MOLECULAR-STRUCTURE OF [LM(OH)]N (N = 1 OR 2) AND LM(MU-CO3)ML (M(II) = MN, FE, CO, NI, CU, ZN L = HB(3,5-IPR2PZ)3)x309199372#N/AFALSE
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ja000662o10.1021/ja000662oFALSEhttps://doi.org/10.1021/ja000662oLevanon, HJ. Am. Chem. Soc.We report on a series of electron donor-acceptor (D-A) dyads that undergo singlet-initiated charge separation to produce a strongly spin coupled radical ion pair that subsequently undergoes charge recombination to produce a triplet state with unusual spin polarization. The molecules consist of either a 4-(N-piperidinyl)naphthalene-1,8-imide (6P) or 4-(N-pyrrolidinyl)-naphthalene-1,8-imide (5P) donor and a 1,8:4,5-naphthalenediimide (NI) or pyromellitimide (PI) acceptor. Selective photoexcitation of D within D--A produces the radical ion pair (1)[D-.+-A(.-)] quantitatively. This is followed by the formation of 3[D.+-A(.-)] via singlet-triplet mixing within the radical pair. Radical pair intersystem crossing (RP-ISC) leads to charge recombination to yield [D-(3*)A] or [3(*)D-A]. Time-resolved optical absorption and emission spectroscopy is coupled with EPR spectroscopy to characterize the mechanism of the nearly quantitative initial charge separation, reaction and the subsequent radical ion pair recombination reaction leading to the unusually spin polarized triplet state. These radical pairs also possess charge transfer emission bands that aid in the data analysis. The small number of previously reported covalent donor-acceptor systems that yield a triplet state from radical ion pair recombination use multistep charge separation reactions to achieve a greater than or equal to 20 Angstrom spacing between the oxidized donor and reduced acceptor. These examples have small exchange couplings, J, within the radical pair, so that S-To mixing between the radical pair energy levels occurs. In the strongly coupled systems described here, we show that the triplet states are formed by means of both S-T-0 and S-T-1 mixing, producing novel spin-polarized EPR spectra characterized by anisotropic spin lattice relaxation.Novel mechanism for triplet state formation in short distance covalently linked radical ion pairsx77200027#N/AFALSE
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ja00064a03010.1021/ja00064a030FALSEhttps://doi.org/10.1021/ja00064a030DARENSBOURG, MYJ. Am. Chem. Soc.CyClic voltammetry has been used to examine Ni(II/I) and Ni(II/III) redox potential data for a structurally characterized homologous series of six NiN2S2 complexes, in which the sulfur sites are systematically varied in donor ability: thiolate (RS-), thioether (RSR), sulfinate (RSO2-), and mixtures of these. These inClude [N,N'-bis(mercaptoethyl)-1,5-diazacyClooctanato]nickel(II) ((bme-daco)Ni(II), 1), [N-(mercaptoethyl)-N'-(sulfinoethyl)-1,5-diazacyClooctanato]nickel(II) ((mese-daco)Ni(II), 2), [N,N'-bis(sulfinoethyl)-1,5-diazacyClooctanato]nickel(II) ((bse-daco)Ni(II), 3), [N-(mercaptoethyl)-N'-(3-thiabutyl)-1,5-diazacyClooctanato]nickel(II) iodide ([(metb-daco)Ni][I], 4), [N-(sulfinoethyl)-N'-(3-thiabutyl)-1,5-diazacyClooctanato]nickel(II) iodide ([(setb-daco)Ni][I], 5), and [N,N'-bis(3-thiabutyl)-1,5-diazacyClooctane]nickel(II) diiodide ([(btb-daco)Ni][I]2, 6). X-ray crystallography has established that all complexes are largely square planar with distortions toward tetrahedral ranging from 1-degrees (strictly square planar) to 18.3-degrees. Throughout the series, the differences in Ni-S bond distances vary <0.08 angstrom, with the shortest distance at 2.133(3) angstrom for Ni-SO2R in 3 and the longest distance at 2.211(3) angstrom for Ni-SR2 in 6. All complexes show reversible reduction waves in CH3CN, assigned to the Ni(II/I) couple in complexes 2-6 by EPR of chemically reduced solutions. The Ni(II/I) potentials vary over a ca. 1.5-V range. Within the series the Ni(I) state is most accessible (-482 mV vs NHE in CH3CN) for the dithioether complex (6) and least for the dithiolate (1). Changes in the donor character of the sulfur ligands have a consistent and additive effect on the redox potentials: in CH3CN each methylation of the nickel-bound bound thiolates results in stabilization of Ni(I) by ca. 700 mV whereas each oxygenation stabilizes the Ni(II/I) couple ca. 300 mV. Potential measurements in water demonstrate large hydrogen-bonding effects for the complexes with thiolate and sulfinate donor sites. Reversible Ni(II/III) couples are observed only for complexes 3 and 6. For all complexes the separation between reduction and oxidation events is ca. 2 V. The crystal structure is given of previously reported (bse-daco)Ni(II) (3), which crystallizes in the orthorhombic P2(1)2(1)2 (No. 18) space group with a = 8.696(4) angstrom, b = 9.993(5) angstrom, c = 8.015(4) angstrom, V = 696.5(5) angstrom3, and Z = 2. The synthesis and structure of two new compounds are given: [(metb-daco)Ni(II)][I] (4) crystallizes in the triClinic P1BAR (No. 2) space group with a = 7.558(5) angstrom, b = 8.922(7) angstrom, c = 12.559(9) angstrom, alpha = 102.79(6)degrees, beta = 95.05(6)degrees, gamma = 107.23(6)degrees, V = 778.0(10) angstrom3, and Z = 2; and [(setb)-daco)Ni(II)] [I] (5) crystallizes in the monoClinic P2(1)/n (No. 14) space group with a = 9.012(2) angstrom, b = 12.891(3) angstrom, c = 14.055(3) angstrom, beta = 99.42(2)degrees, V = 1610.8(6) angstrom3, and Z = 4.EFFECTS OF SULFUR SITE MODIFICATION ON THE REDOX POTENTIALS OF DERIVATIVES OF [N,N'-BIS(2-MERCAPTOETHYL)-1,5-DIAZACYClOOCTANATO]NICKEL(II)x116199355#N/AFALSE
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ja00087a03310.1021/ja00087a033FALSEhttps://doi.org/10.1021/ja00087a033LINDAHL, PAJ. Am. Chem. Soc.The Ni-C state of the NiFe hydrogenase from Desulfovibrio gigas was found to be stable for over 40 h at pH 8.0 in the strict absence of H-2. This demonstrates that Ni-C is unable to spontaneously reduce protons to H-2 under these conditions, a result that is contrary to earlier reports. The form of the nickel that spontaneously reduces protons is probably Ni-R, the EPR-silent state that appears to be one electron more reduced than Ni-C, The stability of Ni-C permitted, for the first time, stoichiometric oxidative titrations of the H-2-free, reduced enzyme. Four such titrations were performed, using the oxidant thionin and monitoring the progress of the titrations by electronic absorption (at 410 nm) and EPR spectroscopies. Redox changes in the enzyme's two Fe4S4 Clusters were readily followed by changes at 410 nm, while those of the Ni were observed by EPR. Redox changes of the Fe3S4 Cluster were monitored by both spectroscopic methods. At the start of the titrations, the Ni center was in the Ni-C state and the Fe-S Clusters were partially oxidized. Adding thionin caused disappearance of Ni-C, development of the EPR-silent intermediate state, and eventually the appearance of Ni-B. The Fe-S Clusters oxidized gradually throughout every stage of the titrations. An average of 4.2 oxidizing equiv/mol of thionin was consumed overall. After the number of equiv/mol consumed by the Fe-S Clusters and the EPR-active Ni ions were substracted, an average of 1.2 oxidizing equiv/mol remained unassigned. The activity of the enzyme appears to be correlated to the ability of the Ni site to undergo redox chemistry.STABILITY OF THE NI-C STATE AND OXIDATIVE TITRATIONS OF DESULFOVIBRIO-GIGAS HYDROGENASE MONITORED BY EPR AND ELECTRONIC ABSORPTION SPECTROSCOPIES46199436#N/ATRUE
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ja00087a03210.1021/ja00087a032FALSEhttps://doi.org/10.1021/ja00087a032KITAGAWA, TJ. Am. Chem. Soc.Resonance Raman (RR) spectra are reported for iron(III) tetramesityl porphyrin (TMP) N-oxide and its O-18 and N-15 derivatives, The RR bands assignable to the Fe-O stretching, O-N stretching, and Fe-O-N bending vibrations were observed at 506, 1122, and 743 and 708 cm(-1), respectively. This confirms that the complex has the Fe-O-N bridged structure. The RR bands of the macrocyCle such as the CbetaCbeta and CalphaN stretching modes were split into doublets due to lowering of symmetry. The RR band arising from the C-m-phenyl stretching band exhibited a downshift by 4 cm(-1) upon formation of the N-oxide, suggesting considerable distortion of the macrocyCle.RESONANCE RAMAN CHARACTERIZATION OF IRON(III) PORPHYRIN N-OXIDE - EVIDENCE FOR AN FE-O-N BRIDGED STRUCTURE16199435#N/ATRUE
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ja00062a02910.1021/ja00062a029FALSEhttps://doi.org/10.1021/ja00062a029FAJER, JJ. Am. Chem. Soc.A series of Ni(II) tetraphenylporphyrins with varying beta substituents was examined by X-ray crystallography and EXAFS to assess peripheral steric effects on the conformations of the macrocyCles. The compounds are the low-spin Ni(II) derivatives of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin (1), 2,3,7,8,12,13,17-18-octapropyl-5,10,15,20-tetrapbenylporphyrin (2), 2,3,7,8,12,13,17,18-tetracyClohexenyl-5,10,15,20-tetraphenylporphyrin (3), 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin (4), 2,3,7,8,12,13,17,18-tetracyClopentenyl-5,10,15,20-tetraphenylprophyrin (5), and 2,3,7,8,12,13,17,18-tetracyClopentenyl-5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl)porphyrin (6). X-ray structures of 1, 2, and 3 reveal that the molecules are severely nonplanar and assume saddle shapes in which the pyrrole rings lie alternately above and below the porphyrin planes with beta carbon displacements of more than 1 angstrom while the meso carbons remain in plane. 1 crystallizes with three methanols of solvation per porphyrin that form an unusual infinite hydrogen-bonded methanol network that transverses one axis of the crystal. Advantage is taken of the fact that short and long Ni-N distances are diagnostic of ruffled and planar Ni macrocyCles, respectively, to establish the conformations of the molecules in solution and in the amorphous state by EXAFS. Within the precision of the EXAFS data (0.02 angstrom), the Ni-N distances in 1, 2, and 3 are the same in solution and in amorphous powders as in the crystals and establish therefore that the distorted conformations of the compounds are maintained in all three phases. EXAFS data for 4, whose structure is unknown, indicate an equally distorted geometry in solution and in the powder. In contrast to 1-4, EXAFS results for 5 and 6 as powders, and for 6 in solution, Clearly signal planar conformations for the two tetracyClopentenyl derivatives. Further evidence that 6 is not sterically constrained derives from the observation that it can be converted to a high-spin hexacoordinated Ni(II) complex in pyridine (5 is insoluble). The conformations and Ni-N distances obtained crystallographically or by EXAFS for 1-6 agree well with previous molecular mechanics calculations. The macrocyCle distortions induce optical red shifts attributed to a smaller gap between the HOMOs and LUMOs of the porphyrins. In particular, the first optical transition, which is principally a HOMO to LUMO excitation, is correctly predicted by INDO/s calculations based on the crystal coordinates for 1, 2, and 3 reported here. An additional assessment of the effects of the substituents and macrocyCle conformations on the frontier orbitals of the molecules is obtained from cyClic voltammetry measurements of oxidation and reduction potentials which provide an experimental probe of the migration of the HOMOs and LUMOs; the electrochemically determined differences in redox potentials mirror the first optical transitions. Crystallographic data: NiN4C60H60.3CH3OH (1): triClinic space group P1BAR, a = 13.739(1) angstrom, b = 17.055(4) angstrom, c = 12.938(2) angstrom, alpha = 96.89(1)degrees, beta = 107.66(1)degrees, gamma = 104.58(2)degrees, V = 2731.7 angstrom3, Z = 2, R(F) =0.066 and R(wF) = 0.091 based on 8077 reflections with F(o) > 6sigmaF(o). NiN4C68H76 (2): monoClinic space group P2(1)/n, a = 15.195(8) angstrom, b = 19.577(9) angstrom, c = 19.137(5) angstrom, beta = 98. 77(3)degrees, V = 5626.2 angstrom3, Z = 4, R(F) = 0.054 and R(wF) = 0.060 based on 5716 reflections with F(o) > 3sigmaF(o). NiN4C60H52.CH2Cl2 (3): tetragonal space group I4BAR, a = b = 32.111(11) angstrom, c = 9.876(8) angstrom, V = 10183 angstrom3, Z = 8, R(F) = 0.081 and R(wF) = 0.108 based on 3161 reflections with F(o) > 2sigmaF(o). T = 200 K.CRYSTALLOGRAPHIC AND EXAFS STUDIES OF CONFORMATIONALLY DESIGNED NONPLANAR NICKEL(II) PORPHYRINSx208199360#N/AFALSE
3081
ja00086a02610.1021/ja00086a026FALSEhttps://doi.org/10.1021/ja00086a026BROWN, GEJ. Am. Chem. Soc.Quantitative determination of local atomic structure in complex materials using extended X-ray absorption fine structure (EXAFS) analysis was tested on eight inorganic compounds of known structure, inCluding natural and synthetic crystalline solids, at ambient conditions. Our aim was to test the accuracy of experimental and theoretical EXAFS standard functions in determining the number of backscattering atoms (N) at a distance (R) beyond the ligating shell of the central absorber atom where effects from disorder, multiple-scattering, and overlapping shells of atoms may significantly influence the EXAFS spectra. These compounds have complicated structures compared to metals and contain Fe, Co, or Ni as the central absorbing atom and mixtures of second-row (C, O, F), third-row (Si, Cl), and fourth-row (Ca, Fe, Co, Ni) atoms as backscatterers. Comparison of results using both experimental phase-shift and amplitude functions (derived from the EXAFS spectra of the compounds) and those calculated from ab initio theory (using the computer code FEFF 5) shows that interatomic distances for single-scattering paths among metal atoms can be determined to within 0.02 Angstrom of values determined independently by X-ray diffraction up to a distance of 4 Angstrom from the central absorber by either method. Theoretical standards calculated using FEFF 5, however, eliminate several drawbacks associated with using experimental standards, such as isolating individual shells of backscattering atoms, obtaining appropriate compounds of high purity and crystallinity, and errors introduced in background subtraction of experimental spectra. Because of the high degree of correlation between N and the Debye-Waller factor (sigma(2)) in the EXAFS function; the ability to determine N for backscatterers of different Z beyond the first shell is limited by incomplete knowledge of sigma(2) for individual absorber-backscatterer paths. For a particular set of backscatterers, N can be determined to better than +/-1 if values for sigma(2) (+/-20-30%) can be estimated. For atoms with a small amount of static disorder, estimation methods inClude using sigma(2) values from reference compounds, averaging atomic root-mean-square displacements from X-ray diffraction, or using a correlated Debye model. Static disorder, however, can eliminate completely backscattering amplitudes at ambient temperatures for some absorber-backscatterer pairs and is not necessarily predictable in unknown systems. Multiple-scattering (MS) (for k = 3-12 Angstrom(-1)) was found to contribute significant amplitude to EXAFS only if focusing occurred among metal atoms. Nonfocused MS, especially for paths involving oxygen atoms, contributed insignificant amplitude to the EXAFS of these compounds for the k-range analyzed.EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE (EXAFS) ANALYSIS OF DISORDER AND MULTIPLE-SCATTERING IN COMPLEX CRYSTALLINE SOLIDS273199451#N/ATRUE
3082
ja00062a02210.1021/ja00062a022FALSEhttps://doi.org/10.1021/ja00062a022MARONEY, MJJ. Am. Chem. Soc.The results of X-ray absorption spectroscopic studies of Thiocapsa roseopersicina hydrogenase poised in three forms exhibiting EPR signals due to the Ni center (A, B, and C) and two states that are epr silent with respect to the Ni center are reported. These spectra are used to examine the structural changes that occur during the reduction of the enzyme. Analyses of Ni K-edge spectra reveal the presence of weak features at ca. 8332 eV in the spectra obtained from forms A and B and the silent intermediate (SI) that are assigned to 1s --> 3d transitions. The lack of a significant pre-edge peak in the active form of the enzyme and low peak areas in other forms, coupled with the absence of edge features associated with planar four-coordinate Ni complexes, indicate that the Ni site in all states of the enzyme is five- or six-coordinate. No observable shift in edge energy occurs upon reduction of the enzyme to any level. This demonstrates that no significant change in the electron density of the Ni site occurs during reduction. Analyses of the EXAFS spectra obtained from scattering atoms in the first coordination sphere of Ni in all rive states of the enzyme that are defined by Ni EPR signals (or lack thereof) are consistent with a Ni site composed of 3 +/- 1 N(O)-donors at 2.00 +/- 0.06 angstrom and 2 +/- 1 S-donors at 2.23 +/- 0.03 angstrom. These results are discussed in light of various models for the structure and function of the Ni site in the enzyme. No evidence to support a redox role for Ni in hydrogenase is found in the XAS data.AN X-RAY-ABSORPTION SPECTROSCOPIC STUDY OF NICKEL REDOX CHEMISTRY IN HYDROGENASEx95199390#N/AFALSE
3083
ja00084a01110.1021/ja00084a011FALSEhttps://doi.org/10.1021/ja00084a011ClAUSE, OJ. Am. Chem. Soc.The structure of the Al promoted magnesium and nickel oxides obtained by calcination of hydrotalcite-type coprecipitates was investigated by X-ray diffraction, Al-27 MAS-NMR, EXAFS, and alkaline leachings. In addition to the reflections of the MgO rock-salt type structure, the diffraction patterns of the Al modified MgO exhibited an additional, well-defined reflection at d = 0.253 nm, attributable to cations on tetrahedral sites. The tetrahedrally coordinated cations were likely to belong to a nonstoichiometric spinel-type phase inCluding an excess of magnesium. The same behavior was observed when Ga(III) were substituted for Al(III) ions in the materials. Furthermore, in the Ga promoted magnesium oxides, EXAFS indicated that only a minor part of the Ga(III) ions was substitutionally dissolved in MgO. The nature of the phases present at the surface of the Al-modified magnesium and nickel oxides was investigated employing alkaline leachings with aqueous sodium hydroxide solutions on Al-doped NiO and with sodium ethoxide in anhydrous ethanol solutions on Al-doped MgO systems. In both cases, the selective dissolution of aluminum-rich phases at the surface of the mixed oxides was observed. Al-27 MAS-NMR before and after leachings confirmed that the surface of the Al modified MgO was enriched in tetrahedrally coordinated aluminum. The presence of an alumina phase at the surface of the Al promoted NiO was also suggested in view of the crystallization of boehmite upon hydrothermal treatments under moderate temperature and pressure, whereas more severe hydrothermal conditions led to hydrotalcite-like structure reconstitution. The aluminum distribution in the magnesium and nickel oxides is not homogeneous and the local composition of the mixed oxides fluctuates between magnesium (or nickel) and aluminum-rich phases. The Al-doped MgO or NiO partiCles can also be viewed as ''decorated'' by aluminate-type patches, which are thought to be responsible for their surface properties and for their resistance to sintering.DECORATION OF NICKEL AND MAGNESIUM-OXIDE CRYSTALLITES WITH SPINEL-TYPE PHASES125199470#N/ATRUE
3084
ja00080a03810.1021/ja00080a038FALSEhttps://doi.org/10.1021/ja00080a038HOUK, KNJ. Am. Chem. Soc.A fully flexible, quantitative model based on Allinger's MM2 force field has been developed to predict diastereoinduction in intramolecular nickel-catalyzed [4 + 4] cyCloadditions. The position of all atoms are optimized with a force field consisting of MM2 parameters for normal atoms and new parameters for atoms attached to the metal. The new parameters for MM2 were derived from crystallographic data augmented by ab initio calculations where experimental data were lacking. Application of this new force field to a number of test complexes demonstrates that the method can be used to predict molecular structures for these systems and that the pi-allyl parameters are transferable to other square-planar metal complexes. Initial modeling studies on the conformational preferences of species relevant to nickel-catalyzed cyClodimerizations are presented. Molecular mechanics calculations on various proposed organonickel species suggest that stereoselectivity can be reproduced by consideration of the energies of stereoisomeric anti-eta1,eta3-bis-allylic nickel phosphine complexes. Predictions of new stereoselectivities are made for several systems.STEREOSELECTIVE ORGANOMETALLIC REACTIONS - A FORCE-FIELD STUDY OF PI-ALLYL INTERMEDIATES IN NICKEL(0)-CATALYZED CYClOADDITIONS23199472#N/ATRUE
3085
ja00079a01810.1021/ja00079a018FALSEhttps://doi.org/10.1021/ja00079a018SPIRO, TGJ. Am. Chem. Soc.Resonance Raman (RR) and FT-IR spectra are reported for nickel(II) 1,5-dihydroxy-1,5-dimethyloctaethylbacteriochlorin [Ni(HOEBC)] and its meso-d4 isotopomer. All the in-plane skeletal RR-active modes and most IR-active modes are assigned with the aid of a normal mode analysis by using a force field developed for nickel(II) octaethylporphyrin and by scaling the bond stretch force constants to bond lengths revealed in the crystal structure of nickel(II) octaethylbacteriochlorin. The calculated eigenvectors provide insight into the essential vibrational characteristics of metallobacteriochlorins. The RR spectra of Ni(HOEBC) were acquired with a variety of excitation wavelengths, near resonance with the B(x),Q(x), and Q(y) transitions. The enhancement pattern of the observed RR intensities reveals that the B(x)- and near-Q(y)-resonant spectra are dominated by Franck-Condon-active modes while the Q(x)-resonant spectrum is dominated by vibronically active modes. The B(x)-resonant spectrum also shows significant vibronic scattering, via coupling between the B(x)- and B(y)-excited states. Frequencies correlate well among Ni(II) complexes of octaethylporphine (OEP) and hydroporphyrins for modes containing similar local mode contributions, when allowance is made for C(beta)-C(beta) bond order reduction and the effects of symmetry lowering. Assignments are proposed for the existing RR data on bacteriochlorophyll a.SYNTHESIS, VIBRATIONAL-SPECTRA, AND NORMAL-MODE ANALYSIS OF NICKEL(II) 1,5-DIHYDROXY-1,5-DIMETHYLOCTAETHYLBACTERIOCHLORIN - A MODEL FOR BACTERIOCHLOROPHYLLS21199392#N/ATRUE
3086
ja00078a01710.1021/ja00078a017FALSEhttps://doi.org/10.1021/ja00078a017MORISHIMA, IJ. Am. Chem. Soc.A dication complex of (meso-tetramesitylporphynato)iron(III) (Fe(III)TMP) has been prepared by the reaction of Fe(III)TMP N-oxide with trifluoroacetic acid in toluene at low temperature. The electronic structure of the complex is characterized to be ferric high spin with rhombic symmetry on the basis of iodometric titration and UV-vis, H-2 NMR, and EPR spectroscopies. A value of E/D, which shows rhombicity of the heme environment, was estimated to be 0.29 by EPR measurement. An unusually high E/D value indicates that the symmetry of the ligand field around the iron is rather similar to those of nonheme ferric complexes, and the porphyrin ring could exhibit large nonplanarity. While tetraphenylporphyrin dication complexes of Zn, Mg, and Ni are known to react with methanol to afford the corresponding isoporphyrins, the dication complex of Fe(III)TMP was found to react with methanol to yield Fe(III)TMP N-methoxide, possibly due to the sterric barrier of the o-methyl groups of mesitylene. The Fe(III)TMP dication is not thermally stable and is readily reduced to the Fe(III)TMP pi-cation radical even at -25-degrees-C in toluene. The dication complex of (meso-tetrakis(2,6-dichlorophenyl)porphynato)iron(III) (Fe(III)TDCPP) was also prepared by the same reaction. The preparation of the dication complex of Fe(III) porphyrin demonstrates possible manipulation of the two-electron-oxidized equivalent in various forms by Fe porphyrin, i.e., the O=Fe(IV) porphyrin pi-cation radical, O=Fe(V) porphyrin, Fe(III) porphyrin N-oxide, and the Fe(III) porphyrin dication.PREPARATION, CHARACTERIZATION, AND REACTIONS OF NOVEL IRON(III) PORPHYRIN DICATION COMPLEXES26199336#N/ATRUE
3087
ja00058a02310.1021/ja00058a023FALSEhttps://doi.org/10.1021/ja00058a023VALENTINE, JSJ. Am. Chem. Soc.We have measured the extent of O-18 incorporation into the products of metal complex-catalyzed oxygenations of organic compounds when H-2 O-18 is added to the reaction mixture. The oxidants studied were hydrogen peroxide, tert-butyl hydroperoxide, m-chloroperbenzoic acid (MCPBA), and iodosylbenzene, and the reactions were carried out in organic solvents. In reactions of hydrogen peroxide, tert-butyl hydroperoxide, and MCPBA, no or at most a small amount of O-18 was incorporated into the products in either olefin epoxidation or alkane hydroxylation reactions catalyzed by (meso-tetrakis(2,6-dichlorophenyl)porphinato)iron(III) chloride (Fe(TDCPP)Cl), (meso-tetrakis(2,6-dichlorophenyl)porphinato)manganese(III) chloride (Mn(TDCPP)Cl) with imidazole added, iron(II) cyClam (cyClam = 1,4,8,11-tetraazacyClotetradecane), manganese(II) cyClam, and nickel(II) cyClam. Assuming that high-valent metal oxo intermediates are generated in all of the reactions of iron and manganese porphyrin complexes with the oxidants PhIO, H2O2, tert-butyl hydroperoxide, and MCPBA, we conClude that the high-valent iron oxo and manganese oxo intermediates do not exchange or slowly exchange with labeled H-2 O-18 during the course of these catalytic oxygenation reactions under our reaction conditions. Several different iron(III) and manganese(III) porphyrin complexes such as Fe(TDCPP)Cl, (meso-tetraphenylporphinato)iron(III) chloride (Fe(TPP)Cl), (meso-tetra-mesitylporphinato)iron(III) chloride (Fe(TMP)Cl), and Mn(TDCPP)Cl were used to catalyze cyClohexene epoxidation by MCPBA at low temperature (-78-degrees-C) in the presence of H-2 O-18. The epoxide obtained in the epoxidation of cyClohexene catalyzed by Fe(TDCPP)Cl, Fe(TPP)Cl, Fe(TMP)Cl, and Mn(TDCPP)Cl contained 0%, 4%, 22%, and 0% O-18, respectively. By contrast, in the iodosylbenzene reactions, oxygen from labeled (H2O)-O-18 was fully incorporated into products in aprotic and protic solvents in olefin epoxidation and alkane hydroxylation reactions catalyzed by either iron(III) porphyrin, manganese(III) porphyrin, or metallocyClam (M = Fe, Mn, Ni) complexes. Labeled oxygen from H-2 O-18 was also fully incorporated into cyClohexene oxide in the epoxidation of cyClohexene catalyzed by a zinc complex which is not able to form a high-valent zinc oxo species as an intermediate. We conClude from these results that, in the case of iodosylbenzene, the mechanism for oxygen exchange does not involve metal oxo intermediates and that the observation of incorporation of labeled oxygen from H-2 O-18 into products does not provide evidence for the intermediacy of metal oxo complexes in iodosylbenzene reactions. In the case of oxidants other than iodosylbenzene, our results also suggest that reactions of high-valent metal oxo complexes with organic substrates in catalytic oxygenation reactions are often comparable in rate to or faster than the reactions with isotopically labeled water that lead to oxygen exchange.REEVALUATION OF THE SIGNIFICANCE OF O-18 INCORPORATION IN METAL COMPLEX-CATALYZED OXYGENATION REACTIONS CARRIED OUT IN THE PRESENCE OF (H2O)-O-18)x142199365#N/AFALSE
3088
ja00077a09310.1021/ja00077a093FALSEhttps://doi.org/10.1021/ja00077a093RAGSDALE, SWJ. Am. Chem. Soc.KINETIC EVIDENCE THAT CARBON-MONOXIDE DEHYDROGENASE CATALYZES THE OXIDATION OF CARBON-MONOXIDE AND THE SYNTHESIS OF ACETYL-COA AT SEPARATE METAL CENTERS73199318#N/ATRUE
3089
ja00077a02810.1021/ja00077a028FALSEhttps://doi.org/10.1021/ja00348a012CHU, MMIXED-VALENCE COINAGE METAL-ClUSTERS WITH 1,1-THIOPERTHIO LIGANDS - SYNTHESES AND MOLECULAR-STRUCTURES OF THE [CU4L3]2-, [CU5L4]-, AND [AUCU4L4]- ANIONS (L = 1,1-DICARBO-TERT-BUTOXYETHYLENE-2,2-THIOPERTHIOLATE) - A GEOMETRICALLY-LOCKED, CHARGE-SEPARATED VALENCE STATE IN THE [CU5L4]- ANION1993#N/ATRUE
3090
ja00056a04010.1021/ja00056a040FALSEhttps://doi.org/10.1021/ja00056a040BATISTA, JJ. Am. Chem. Soc.A variety of magnetic resonance experiments were performed to investigate the local environment of Mn in MnAPSO-44. MnAPSO-44 is a member of the aluminophosphate molecular sieves family and has a chabazite-like structure. Two samples with different Mn contents (Mn/(P + Al + Si) = 0.9 and 0.07 atom %) in their as-synthesized, calcined hydrated and dehydrated forms were studied. The P-31, Si-29, and Al-27 MAS NMR spectra are similar to those of the corresponding SAPO-44 samples showing only one type of TO4 tetrahedra. In the hydrated sample an Al-27 signal at -13 ppm, characteristic of octahedral Al, appears as well due to water coordination. EPR spectra were measured at X- and Q-band. The Mn(II) in the as-synthesized and calcined samples showed hyperfine splittings of 85 and 93 G, respectively, the latter being characteristic of octahedral environment. Dehydration at 400-degrees-C reduced the hyperfine constant to 65 G, indicating a change to tetrahedral coordination upon water removal. The nuClei in the immediate surrounding of the Mn were probed by the electron spin echo envelope modulation (ESEEM) technique. Both P-31 and Al-27 modulations were observed. The EPR and ESEEM results are interpreted in terms of Mn incorporation into tetrahedral framework sites for the sample with the low Mn content. The spatial distribution of the Mn throughout the sample was investigated by the ''2 + 1'' electron spin echo (ESE) experiment. It was found that only about 15% of the Mn(II) is homogeneously distributed and contributes to the echo signal.MAGNETIC-RESONANCE STUDIES OF SAPO-44 AND MNAPSO-44x28199342#N/AFALSE
3091
ja00055a03210.1021/ja00055a032https://doi.org/10.1021/ja00055a032YANAGIDA, SEFFICIENT AND SELECTIVE ELECTRON MEDIATION OF COBALT COMPLEXES WITH CYClAM AND RELATED MACROCYClES IN THE P-TERPHENYL-CATALYZED PHOTOREDUCTION OF CO2Photocatalyst1993#N/AFALSE
3092
ja00070a02510.1021/ja00070a025FALSEhttps://doi.org/10.1021/ja00070a025CANNON, RDELECTRONIC INTERACTIONS IN MIXED-VALENCE AND MIXED-METAL ION ClUSTERS - INELASTIC NEUTRON-SCATTERING SPECTRA OF THE COMPLEXES [FE(III)2M(II)O(OOCME)6(PY)3](PY), WHERE M = MN, NI1993#N/ATRUE
3093
ja00067a03310.1021/ja00067a033FALSEhttps://doi.org/10.1021/ja00067a033GRIMES, RNJ. Am. Chem. Soc.Bis(cobaltacarborane) complexes bridged by fulvalene or 1,4-bis(tetramethylcyClopentadienyl)benzene ligands, and containing reactive carborane C2B3 end rings, are effective synthons for the stepwise construction of air-stable multisandwich oligomers and polymers that are soluble in organic solvents. Bridge deprotonation of the end rings followed by coordination of two such units to a central transition metal (Ni(IV), Co(IV), Co(III)H) formed multilevel species having a central tetradecker sandwich linked to double-decker end units. The latter groups have exposed C2B3 rings on which the same reaction sequence can be repeated to generate progressively larger oligomers. Products having 5-17 metal atoms have been isolated via chromatography on silica and representative complexes characterized via H-1 and B-11 NMR, UV-visible, and FAB mass spectra. X-ray diffraction studies established the structures of a 5-cobalt complex, [(Et2C2B3H5)Co(C5Me4)C6H4(C5Me4)Co(Et2C2B3H-4,5-Cl2)]2Co (4b), containing a central Co-Co-Co tetradecker sandwich, and a fulvalene-bridged dimer, [(Et2C2B3H2-4,6-Br2-5-Me)Co(C5H4)]2 (2c). Crystal data for 4b: M = 1632.0; monoClinic, space group C2/c; Z = 4; a = 33.57(1) angstrom, b = 8.720(3) angstrom, c = 29.412(5) angstrom; beta = 109.95(2)degrees; V = 8093(4) angstrom3; R = 0.083 for 3250 reflections having I > 3.5sigma(I). Crystal data for 2c: M = 828.9; monoClinic, space group P2(1)/n; Z = 2; a = 9.956(4) angstrom, b = 13.439(5) angstrom, c = 11.327(4) angstrom; beta = 103.87(2)degrees; V = 1471(2) angstrom3; R = 0.038 for 1477 reflections having I > 2sigma(I).ORGANOTRANSITION-METAL METALLACARBORANES .31. METALLACARBORANE STAIRCASE OLIGOMERS - STEPWISE ASSEMBLY VIA TETRADECKER STACKING REACTIONS68199356#N/ATRUE
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ja000648b10.1021/ja000648bFALSEhttps://doi.org/10.1021/ja000648bGhosh, AJ. Am. Chem. Soc.Nonlocal density functional theory calculations, with full geometry optimization, are reported for the Ni(I) and low-spin Ni(II) forms of high-fidelity models of coenzyme F-430, the nickel tetracorphinoid cofactor of methylcoenzyme M reductase (MCR), and its 12,13-diepimer. The diepimer appears to exhibit the conformational characteristics of a typical hydroporphyrin in terms of a strong tendency to adopt highly ruffled conformations and short Ni(II)-N bond distances. In contrast, for native F-430, the steric effects of peripheral substituents impose a potent planarizing influence on the ring system. The relative inability to ruffle implies that the N-4 core of F-430 cannot contract sufficiently to optimally coordinate a small low-spin Ni(II) ion. This appears to be the key factor that results in the stabilization of the larger Ni(I) and high-spin Ni(II) ions by the F-430 ligand environment. The optimized Ni-N bond distances for the Ni(I)-F-430 model compound are 198, 200, 203, and 214 pm and span an extremely wide range of 16 pm, which qualitatively reproduces the central feature of the experimental EXAFS results. Understandably, these bond distances are similar to those found in a crystallographic study of a six-coordinate NI(II) form of MCR. The relatively long Ni-N distances in the optimized geometry of the low-spin Ni(II) form of the F-430 model compound provide a natural explanation for the enhanced axial ligand affinity of F-430 and its greater tendency to switch to the high-spin Ni(II) form, relative to its diepimer. Consistent with experiment, the calculations also predict that Ni(II)-diepi-F-430 is thermodynamically more stable than native Ni(II)-F-430 However, for the Ni(Ij oxidation level, the two epimers ale predicted to be equienergetic. In qualitative agreement with electrochemical measurements, the adiabatic ionization potential of Ni(I)-F-430 is about 0.2 eV higher than that of Ni(I)-diepi-F-430, again reflecting a unique destabilization of low-spin Ni(II) by the F-430 ligand. Finally, the nickel center in Ni(I)-F-430 is truly Ni(I): it carries approximately 82% of the molecular unpaired spin, compared to a nickel spin population of only 56% for Ni(I)-diepi-F-430.A first-principles quantum chemical study of coenzyme F-430: Interplay of skeletal stereoisomerism and conformation in the stabilization of Nickel(I)29200044#N/ATRUE
3095
ja00052a04210.1021/ja00052a042FALSEhttps://doi.org/10.1021/ja00052a042RORABACHER, DBJ. Am. Chem. Soc.The kinetics of electron-transfer reactions involving CuII/I([14]aneS4) reacting with a series of selected counterreagents have been measured in aqueous solution at 25-degrees-C, mu = 0.10 M (ClO4-). The reagents utilized inClude four oxidants [Ru(NH3)4bpy3+, Ni([14]aneN4)3+, Ru(NH3)2(bpy)23+, and Fe(4,7-Me2phen)3(3+)] and four reductants [Co(Me4[14]tetraeneN4)2+, Ru(NH3)4bpy2+, Ru(NH3)5isn2+, and Ru(NH3)5py2+], which were selected to provide a variety of reagent self-exchange rate constants and overall reaction potentials, thereby yielding a range of cross reaction rate constant values. Application of the Marcus equation to the cross reaction rate constants for the four reduction studies yielded consistent self-exchange rate constant values of log k11(red) = 3.78 (+/-0.26) for CuII/I([14]aneS4). By contrast, the two oxidation kinetic studies having the largest reaction potentials [i.e., using Ru(NH3)2(bpy)23+ and Fe(4,7-Me2phen)3(3+) as oxidants] yielded log k11(ox) almost-equal-to 0 (+/-0.26), while the oxidation reactions with smaller reaction potentials [i.e., using Ru(NH3)4bpy3+ and Ni([14]aneN4)3+ as oxidants] yielded an apparent value of log k11(ox) almost-equal-to 2.5 for CuII/I([14]aneS4) when relatively small concentrations of the counteroxidant were used. Upon an increase in the Ni([14]aneN4)3+ Concentration, however, k11(ox) appeared to decrease until, at relatively high concentrations of the Ni(III) reagent, limiting first-order kinetic behavior was observed. In an independent study, NMR line-broadening measurements were made on CuI([14]aneS4) solutions containing variable amounts of CuII([14]aneS4) to obtain a direct measurement of log k11(ex) almost-equal-to 3.88 +/- 0.09 at 25-degrees-C (DELTAH(double dagger) = 20.7 +/- 4.5 kJ mol-1; DELTAS(double dagger) = -101 +/- 13 J K-1 mol-1). This is in direct agreement with the values calculated from the reduction reactions. The patterns in the kinetic behavior of CuII/I([14]aneS4) are shown to be consistent with a dual-pathway square scheme, as characterized by rapid-scan cyClic voltammetry. For Cu(I)L oxidation reactions, the conformational change to form a metastable Cu(I)L species becomes rate-limiting under specific conditions, resulting in the appearance of ''gated'' electron-transfer kinetics; ultimately, the oxidation reaction switches to the alternate reaction pathway.GATED ELECTRON-TRANSFER BEHAVIOR IN COPPER(II/I) SYSTEMS - COMPARISON OF THE KINETICS FOR HOMOGENEOUS CROSS REACTIONS, NMR SELF-EXCHANGE RELAXATION, AND ELECTROCHEMICAL DATA FOR A COPPER MACROCYClIC TETRATHIOETHER COMPLEX IN AQUEOUS-SOLUTIONx69199246#N/AFALSE
3096
ja00063a03510.1021/ja00063a035FALSEhttps://doi.org/10.1021/ja00063a035JACOBSON, AJNICKEL K-EDGE X-RAY-ABSORPTION FINE-STRUCTURE OF LITHIUM NICKEL OXIDES1993#N/ATRUE
3097
ja00062a02810.1021/ja00062a028FALSEhttps://doi.org/10.1021/ja00062a028BUSCH, DHJ. Am. Chem. Soc.The rates of autoxidation of iron(II) cyClidenes have been studied as functions of dioxygen pressure and with variations in the size of the cavity within which the O2 molecules must reside in order to bind to the iron atom. As the cavity is opened up, first O2 and then solvent species can enter and bind to iron, and this is accompanied by changes in the algebraic form of the rate law for autoxidation. Analysis strongly suggests that the molecule of O2 that oxidizes the iron(II) is not bound, there by implicating an electron-transfer mechanism for the autoxidation process. The peculiar nature of the O2 dependences of myoglobin and hemoglobin autoxidations indicates that the same mechanism applies.THE ELECTRON-TRANSFER MECHANISM OF AUTOXIDATION FOR HEMOGLOBIN, MYOGLOBIN, AND THEIR IRON(II) CYClIDENE MODELS38199338#N/ATRUE
3098
ja00060a02210.1021/ja00060a022FALSEhttps://doi.org/10.1021/ja00060a022ZANOBINI, FA FAMILY OF STABLE IRON(I) SIGMA-ALKYNYL COMPLEXES - SYNTHESIS, CHARACTERIZATION, STRUCTURE, AND ELECTRON-TRANSFER CHEMISTRY1993#N/ATRUE
3099
ja00059a07110.1021/ja00059a071FALSEhttps://doi.org/10.1021/ja00059a071ZOVINKA, EPJ. Am. Chem. Soc.CARBON CARBON BOND FORMATION IN THE DIMERIZATION OF (OCTAETHYLOXOPHLORIN RADICAL)NICKEL(II)27199316#N/ATRUE
3100
ja00059a02810.1021/ja00059a028FALSEhttps://doi.org/10.1021/ja00059a028MEVS, JMJ. Am. Chem. Soc.The preparation and electrochemical reduction of a series of metal-cyClooctatetraene complexes is described. (eta6-C6Me6)Co(1,3-C8H8)+ was prepared through the reaction of (eta6-C6Me6)2Co+ with C8H8. The nickel group complexes (C5R5)Ni(C8H8)+ R = H, Me, were prepared by reaction of C8H8 with a 33e- dinuClear complex, respectively either Cp2Ni2(mu-C2Ph2)+ or Cp*2Ni2(mu-CO)2+. The Pd complex (eta-C5Ph5)Pd(C8H8)+ was formed in the reaction of C8H8 with (C5Ph5)2Pd2(mu-C2Ph2)+. The cyClooctatetraene ring adopted the chair-like 1,3-conformation in the Co complex and the tub-like (1,5-) conformation in the Ni and Pd complexes. One-electron reduction proceeded with retention of isomeric structure. The retention of the 1,5-conformation in the Ni and Pd complexes contrasts with formally isoelectronic CpCo(C8H8), which undergoes rapid isomerization to the 1,3-isomer in the 19e- species. Electron spin resonance studies are able to rationalize the differences in rearrangement tendencies on the basis that the LUMOs of the Co complexes are largely ligand (C8H8)-based, whereas those of the Ni and Pd complexes are largely metal-based. The SOMO for the 19e- Co complexes is assigned as 4a', highly delocalized onto the cyClooctatetraene ring, with about 40% metal (d(xy)) character for CpCo(1,3-C8H8)- and 50% metal character for (C6Me6)Co(C8H8). The SOMO of the 19e- Ni and Pd complexes is assigned as 2b2, about 70% metal (d(yz)) in character.STRUCTURAL CONSEQUENCES OF ELECTRON-TRANSFER REACTIONS .25. ELECTRON-TRANSFER-INDUCED ISOMERIZATIONS OF CO-CYClOOCTATETRAENE, NI-CYClOOCTATETRAENE, AND PD-CYClOOCTATETRAENE COMPLEXES - THE ROLE PLAYED BY THE LIGAND VS METAL COMPOSITION OF THE REDOX ORBITAL251993103#N/ATRUE
3101
ja000593d10.1021/ja000593dFALSEhttps://doi.org/10.1021/ja000593dLong, JRJ. Am. Chem. Soc.A technique for increasing the porosity in solid structures by replacing octahedral metal ions with hexanuClear Cluster cores is extended with the expansion of the ion-exchange material Na2Zn3[Fe(CN)(6)](2). 9H(2)O. At high relative Cluster concentrations, the reaction between [Zn(H2O)(6)](2+) and Na-4[Re6Se8(CN)(6)] produces Na2Zn3[Re6Se8(CN)(6)](2). 24H(2)O (1), a compound exhibiting a porous three-dimensional framework isotypic with that of Na2Zn3[Fe(CN)(6)](2). 9H(2)O. Its framework is characterized by hexagonal bipyramidal cages, each enClosing two Na+ ions and 24 water molecules in a volume of 1340 Angstrom(3)-more than triple the volume of the cages in the original structure. The expanded cavities and framework openings in compound 1 are shown to facilitate absorption of larger cationic complexes, specifically [M(H2O)(6)](n+) (M = Mg2+, Cr3+, Mn2+, Ni2+, Zn2+) and [Cr(en)(3)](3+), via exchange for the Na+ ions. Indeed, when the preparation of 1 is attempted using a slight excess of the zinc reactant, [Zn(H2O)(6)](2+) incorporates instead of Na+, leading to direct formation of the ion exchanged compound [Zn(H2O)(6)]Zn-3[Re6Se8(CN)(6)](2). 18H(2)O (2). The crystal structure Of 2 reveals the [Zn(H2O)(6)](2+) complexes to reside at the exact center of the hexagonal bipyramidal cages. With prolonged exposure to air, compound 1 and its ion-exchanged variants undergo a color change from orange to green, which is attributed to the one-electron oxidation of the [Re6Se8](2+) Cluster cores in the solid framework. In a further: parallel with ferrocyanide chemistry, the reaction between [Zn(H2O)(6)](2+) and Na-4[Re6Se8(CN)(6)] at low relative Cluster concentrations is found to yield [Zn(H2O)](2)[Re6Se8CN)(6)]. 13H(2)O (3), a phase exhibiting a two-dimensional framework structure isotypic with that of [Zn(H2O)](2)[Fe(CN6)]. 0.5H(2)O.Expansion of the porous solid Na2Zn3[Fe(CN)(6)](2)center dot 9H(2)O: Enhanced ion-exchange capacity in Na2Zn3[Re6Se8(CN)(6)](2)center dot 24H(2)O134200059#N/ATRUE
3102
ja00049a07810.1021/ja00049a078FALSEhttps://doi.org/10.1021/ja00049a078VEILLET, PHIGH-TC MOLECULAR-BASED MAGNETS - A FERROMAGNETIC BIMETALLIC CHROMIUM(III) NICKEL(II) CYANIDE WITH TC = 90-Kx1992#N/AFALSE
3103
ja00049a03510.1021/ja00049a035FALSEhttps://doi.org/10.1021/ja00049a035HAWTHORNE, MFJ. Am. Chem. Soc.The synthesis and characterization of a family of pyrazole-bridged metallacarborane Clusters is described. These species serve as nonradioactive models for the corresponding radio-transition-metal carriers which are potentially useful for the antibody-mediated gamma-imaging or beta-therapy of tumors (Venus flytrap Clusters). Both monofunctional and bifunctional chelate precursors were prepared from the reactions of the anions of pyrazole and 4-carbomethoxypyrazole, respectively, with 2 equiv of Closo-1,8-C2B9H11. In each instance, meso- and dl-isomers of the pyrazole-bridged nido-carboranes were obtained. The diastereomers were then converted, in the presence of stoichiometric amounts of aqueous base, to the formal 7,9-bis(dicarbollide) anions. The metal ions Co3+, Ni3+, Cu3+, and Fe3+ were incorporated into the unsubstituted pyrazole derivative in aqueous media at pH 12-14, resulting in the mixed meso- and dl-metallacarborane derivatives of 7, 8, 9, and 10, respectively. The carbomethoxy pyrazole dicarbollide derivative was complexed with Co3+ and Co-57(3+) in a similar manner to produce mixed meso- and dl-cobaltacarborane derivatives of 11 and 12, respectively. All diastereomeric metallacarborane derivatives were separated by column chromatography or HPLC techniques and characterized by spectroscopic and electrochemical techniques. The molecular structures of dl-Co3+ (7a), dl-Ni3+ (8a), meso-Ni3+ (8b), meso-Cu3+ (9b), dl-Fe3+ (10a), and meso-Co3+ (11b) have been determined from single-crystal X-ray diffraction experiments, and the structures of the diastereomeric complexes are correlated with H-1 and B-11 FT NMR spectra. dl-7a crystallizes in the monoClinic space group P2(1)/c with a = 10.618 (1) angstrom, b = 13.366 (1) angstrom, c = 14.326 (2) angstrom, beta = 109.925 (3)-degrees, V = 1901 angstrom3, and Z = 4. dl-8a crystallizes in the orthorhombic space group Pnma with a = 13.6874 (7) angstrom, b = 15.8587 (8) angstrom, c = 11.2429 (6) angstrom, V = 2447 angstrom3, and Z = 4. meso-8b crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 7.2139 (5) angstrom, b = 13.404 (1) angstrom, c = 19.768 (2) angstrom, V = 1908 angstrom3, and Z = 4. meso-% crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 7.1854 (8) angstrom, b = 13.434 (2) angstrom, c = 19.980 (2) angstrom, V = 1925 angstrom3, and Z = 4. dl-10a crystallizes in the monoClinic space group P1(1)/c with a = 10.6926 (5) angstrom, b = 13.3320 (7) angstrom, c = 14.3288 (7) angstrom, beta = 110.081 (1)-degrees, V = 1952 angstrom3, and Z = 4. meso-11b crystallizes in the triClinic space group P1BAR with a = 9.966 (2) angstrom, b = 10.475 (2) angstrom, c = 17.134 (3) angstrom, alpha = 79.957 (7)-degrees, beta = 77.882 (7)-degrees, gamma = 74.732 (7)-degrees, V = 1674 angstrom3, and Z = 2. Spectroscopic and structural data for the bridged complexes are compared with those for the corresponding unsubstituted metallacarborane derivatives.SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF PYRAZOLE-BRIDGED METALLA-BIS(DICARBOLLIDE) DERIVATIVES OF COBALT, NICKEL, COPPER, AND IRON - MODELS FOR VENUS FLYTRAP ClUSTER REAGENTSx43199235#N/AFALSE
3104
ja00057a02710.1021/ja00057a027FALSEhttps://doi.org/10.1021/ja00057a027SAFARI, NJ. Am. Chem. Soc.The verdohemes are shown to contain the planar, tetradentate oxoporphyrin structure. Structural studies of paramagnetic {(OEOP)FeIIICl2}, where OEOP is the monoanion of octaethyloxoporphyrin, by H-1 NMR spectroscopy and X-ray crystallography reveal that the iron is six-coordinate and high-spin (S = 5/2). The iron resides in the plane of the oxoporphyrin and is coordinated by two equivalent axial chloride ligands. Paramagnetic {(OEOP)Fe(II)Cl} contains a five-coordinate iron which is also high-spin (S = 2). The iron is 0.69 angstrom out of the porphyrin plane and bound to a single axial chloride. The average Fe-N distance increases from 1.964 angstrom in the iron(III) complex to 2.094 angstrom in the iron(II) complex. {(OEOP)FeIIICl2} was obtained by treatment of (OEP)Fe(py)2 (OEP is the dianion of octaethylporphyrin) with dioxygen in the presence of ascorbic acid to form the verdohemochrome [(OEOP)FeII(PY)2]Cl, which was subsequently reacted with hydrogen chloride in air. Reduction of {(OEOP)FeIIICl2} with sodium dithionite yields air-sensitive {(OEOP)Fe(II)Cl}. When {(OEOP)Fe(II)Cl} is dissolved in pyridine, [(OEOP)FeII(py)2]Cl is reformed.STRUCTURAL CHARACTERIZATION OF VERDOHEME ANALOGS - IRON COMPLEXES OF OCTAETHYLOXOPORPHYRIN88199341#N/ATRUE
3105
ja00048a02110.1021/ja00048a021FALSEhttps://doi.org/10.1021/ja00048a021CASTRO, CENICKEL(I) OCTAETHYLISOBACTERIOCHLORIN ANION - AN EXCEPTIONAL NUClEOPHILE - REDUCTION AND COUPLING OF Alkyl-HALIDES BY ANIONIC AND RADICAL PROCESSES - A MODEL FOR FACTOR-F-430x1992#N/AFALSE
3106
ja00046a05710.1021/ja00046a057https://doi.org/10.1021/ja00046a057NOVAK, BMJ. Am. Chem. Soc.ENANTIOSELECTIVE POLYMERIZATIONS OF ACHIRAL ISOCYANIDES - PREPARATION OF OPTICALLY-ACTIVE HELICAL POLYMERS USING CHIRAL NICKEL-CATALYSTSx105199225#N/AFALSE
3107
ja00056a04510.1021/ja00056a045FALSEhttps://doi.org/10.1021/ja00056a045DAHL, LFJ. Am. Chem. Soc.A NEW FAMILY OF ICOSAHEDRAL CAGES WITH TRANSITION-METAL AND MAIN GROUP-IV (14)-ATOMS - SYNTHESIS AND STRUCTURAL-BONDING ANALYSIS OF THE [NI11(SNR)2(CO)18]2- DIANIONS (R = N-BU, ME) CONTAINING NI-CENTERED ICOSAHEDRAL NI10SN2 CAGES AND OF THEIR UNUSUAL [NI(SNRCl2)4(CO)]2- PRECURSORS CONTAINING A TRIGONAL-BIPYRAMIDAL D8 NICKEL(II) CONFIGURATION33199336#N/ATRUE
3108
ja00045a01310.1021/ja00045a013FALSEhttps://doi.org/10.1021/ja00045a013HOFFMAN, BMSTAR-PORPHYRAZINES - SYNTHETIC, STRUCTURAL, AND SPECTRAL INVESTIGATION OF COMPLEXES OF THE POLYNUClEATING PORPHYRAZINEOCTATHIOLATO LIGANDx1992#N/AFALSE
3109
ja00055a03010.1021/ja00055a030FALSEhttps://doi.org/10.1021/ja00055a030SHELNUTT, JAMETAL DEPENDENCE OF THE NONPLANAR DISTORTION OF OCTAAlkylTETRAPHENYLPORPHYRINS1993#N/ATRUE
3110
ja00053a02110.1021/ja00053a021FALSEhttps://doi.org/10.1021/ja00053a021HOLM, RHJ. Am. Chem. Soc.The heterometal cubane-type Clusters [CoFe3S4(Smes)4]2- (7, 80%) and [NiFe3S4(PPh3)(SMes)3]2- (12, 57-71%) have been prepared in good yield as Et4N+ salts by reductive rearrangement reactions of the linear Cluster [Fe3S4(Smes)4]3-(4, Smes = mesitylthiolate(1-)) with Co(I) and Ni(0) reactants, respectively. (Et4N)2[7] crystallizes in orthorhombic space group Pbcn with a = 20.673 (3) angstrom, b = 16.600 (3) angstrom, c = 17.259 (2) angstrom, and Z = 4. (Et4N)2[NiFe3S4(PPh3)(SMes)3].2MeCN was obtained in triClinic space group P1BAR with a = 13.138 (3) angstrom, b = 15.461 (4) angstrom, c = 19.622 (4) angstrom, alpha = 107.12 (2)-degrees, beta = 94.54 (2)-degrees, gamma = 108.47 (2)-degrees, and Z = 2. The crystal structures confirm the cubane-type structures and tetrahedral coordination at the M = Fe, Co, and Ni subsites of the [MFe3S4]z+ cores. In 7, the Co and Fe subsites are disordered and in 12 the phosphine ligand is bound to the Ni subsite. The Clusters [NiFe3S4(SMes)4]3- (10) and [Fe4S4(Smes)4]2- (6) were obtained as an ca. 1:1 mixture by the reaction of Ni(AsPh3)4 and 4. Potential and actual synthetic routes to [MFe3S4]z+ Clusters are outlined. The species 6, 7, 10 form a comparative set with equivalent structures and identical terminal ligands. These species and 12 are best distinguished by their H-1 NMR spectra which manifest contact-shifted resonances that are oppositely signed for substituents at the Fe and M = Co/Ni subsites. In 7, the Fe subsites appear to be more reactive to ligand substitution by thiol than is the Co subsite; both subsites are substituted in the ligand redistribution system 5/7. The three-member electron transfer series [CoFe3S4]3+/2+/1+ and [NiFe3S4]2+/1+/0 have been established. For the reversible couples [MFe3S4(SMes)4]2-/3- the order of potentials is M = Fe < Co (0.18 V) < Ni (0.30 V), with the indicated potential differences vs M = Fe. Mossbauer spectroscopy reveals that 7 and the protein-bound [CoFe3S4]2+ Cluster of D. gigas ferredoxin II have equivalent electronic structures at 4.2 K. As judged by isomer shifts at 1.5 K, the [NiFe3S4]1+ core of polycrystalline 12 contains three equivalent iron sites. However, the 4.2 K Mossbauer spectra obtained in strong applied magnetic fields show Clearly that the three sites are magnetically distinct. Interestingly, the room temperature solution H-1 NMR data of 7 and 12 indicate equivalent sites. Isomer shifts imply the fragment formulations Co2+ (S = 3/2) + [Fe3S4]0 (S = 2) and Ni2+ (S = 1) + [Fe3S4]1- (S = 5/2), with antiparallel spin coupling affording the observed S = 1/2 and 3/2 ground states, respectively. Comparison of the isomer shifts of the [NiFe3S4]1+ core with those of other [MFe3S4]1+ cubanes (M = Fe, Zn, Cd) suggests a shifted electron density from the [Fe3S4]1- fragment to the nickel site. The Close correspondence of Mossbauer and EPR parameters of synthetic Clusters (7, 12) with those of protein [CoFe3S4]2+ and [NiFe3S4]1+Clusters indicates that the latter contain the tightly bound cubane-type structures established by X-ray diffraction for the synthetic species.SYNTHESIS AND COMPARATIVE REACTIVITY AND ELECTRONIC STRUCTURAL FEATURES OF [MFE3S4]Z+ CUBANE-TYPE ClUSTERS (M = FE, CO, NI)69199266#N/ATRUE
3111
ja00044a03810.1021/ja00044a038FALSEhttps://doi.org/10.1021/ja00044a038WADE, PWJ. Am. Chem. Soc.Molecular mechanics techniques using a modified version of the program MM2(87) were used to analyze the ruffling of metalloporphyrins as a function of metal ion size, orientation of axial ligands, and orientation of substituents on the porphyrin periphery. The structures chosen for the parametrization, [P(TPP)(OH)2]+, the planar and ruffled forms of low-spin (S = 0) [Ni(OEP)], (S = 1) [Fe(TPP)], [Zn(TPP)], and [Pb(TPrP)], contain metal ions of very different sizes and hence extents of porphyrin core ruffling. The planar and moderately ruffled structures could be satisfactorily reproduced by developing new parameters involving the metal ion and using the parameters built into the program for the porphyrin core. The total strain energy in a planar metalloporphyrin was investigated as a function of metal ion size. The principal components which contribute to the total strain energy are nonbonded van der Waals repulsion, bond angle deformation, and bond length deformation. A minimum in the strain energy curve occurs at 2.035 angstrom which is the best-fit metal ion size in the planar macrocyCle cavity. In the case of the very small ion, P(V), only a ruffled conformer is possible, but for intermediate size metal ions (Ni(II) and Fe(II)) both planar and ruffled forms of the metalloporphyrins were found (in accord with the experimental observation of the two forms of [Ni(OEP)] in solution and in the solid state), As ruffling increases, there is a balance between a decrease in bond length deformation and angle bending strain, and an increase in torsional strain, such that the energy difference between the two forms is small with the planar structure 1-1.5 kcal.mol-1 more stable. For the larger ion, Zn(II), only the planar form was found, and for the very large ion, Pb(II), a domed structure results in which the coordination geometry is best described as square pyramidal. The flexibility of the porphyrin core was further demonstrated by showing that at the expense of a modest 1.3 kcal.mol-1 (arising principally from an increase in angle bending strain) the porphyrin ring can undergo a cavity expansion of 0.15 angstrom and accommodate a change in the spin state of Fe(II) from low spin to high spin without requiring the metal ion to be extruded out of the mean plane. The ruffling of a metalloporphyrin is normally either of the sad or ruf variety, and the sense and extent of the ruffling is demonstrated to be controlled by the specific orientations of phenyl groups in TPP complexes and by the orientation of ligands such as 2-methylimidazole coordinated to the axial sites of the metal ion. Some examples of the ruffling of porphyrins in hemoproteins in response to their environment are considered.MOLECULAR MECHANICS STUDY OF THE RUFFLING OF METALLOPORPHYRINSx1081992110#N/AFALSE
3112
ja00052a05110.1021/ja00052a051FALSEhttps://doi.org/10.1021/ja00052a051MAXWELL, KAJ. Am. Chem. Soc.Electron-transfer equilibrium (ETE) methods have been used to establish the gas-phase ionization and electron attachment energetics for nickelocene and several Alkylated derivatives, (RCp)(R'Cp)Ni (R, R' = H, Me, Et, t-Bu). The nickelocene derivatives were highly purified by reversed-phase HPLC, and ETE studies were performed on a Fourier transform ion cyClotron resonance mass spectrometer. The results are summarized as free energies of ionization (DELTAG(i)-degrees) and free energies of electron attachment (DELTAG(a)-degrees) at 350 K for the (RCp)(R'Cp)Ni0/+ and (RCp)(R'Cp)Ni0/- couples, respectively. The order of ionization energies follows the expected trend, with more and larger Alkyl substituents leading to decreasing values of DELTAG(i)-degrees. The DELTAG(a)-degrees values become more endoergic as methyl groups are substituted, but larger Alkyl groups lead to more exoergic electron attachment as the size of the Alkyl substituents increases. Alkyl substituent effects cannot be described as uniformly ''electron donating'' in these redox processes and must be rationalized on the basis of more detailed models. As an example, a model based on a combination of inductive and polarization effects is used to analyze the data. Alternative single-parameter correlations with published substituent parameters are also considered. The average differential solvation free energy for the Cp2Ni+/0 and Cp2Ni0/- couples in THF is estimated from the gas-phase data and the difference in the solution electrode potentials (DELTADELTAG(solv,av)-degrees = -39 +/- 3 kcal mol-1).Alkyl SUBSTITUENT EFFECTS IN CYClOPENTADIENYL METAL-COMPLEXES - TRENDS IN GAS-PHASE IONIZATION AND ELECTRON-ATTACHMENT ENERGETICS OF AlkylNICKELOCENES20199261#N/ATRUE
3113
ja00044a00410.1021/ja00044a004FALSEhttps://doi.org/10.1021/ja00044a004OKAWA, HJ. Am. Chem. Soc.The reaction of K3[Cr(ox)3].3H2O, a metal(II) salt, and tetra(n-butyl)ammonium bromide in the molar ratio of 1:1:1.5 in water at room temperature afforded a series of mixed-metal assemblies with the formula {NBU4[MCr(OX)3]}x (M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (5), Zn2+ (6)). These compounds are designed so as to assume a three-dimensional structure consisting of alternately arrayed Cr(III) and M(II) ions due to the D3 symmetry of the building block [Cr(ox)3]3-. The magnetic susceptibility data of 1-5 above ca. 20 K obey the Curie-Weiss law with positive Weiss constants, and upon lowering the temperature, the effective magnetic moments increase gradually in the 300-20 K range and abruptly below ca. 20 K. The temperature dependences of magnetizations studied under a weak applied field (1 G) showed a magnetic phase transition at T(c) = 6, 12, 10, 14, and 7 K for 1, 2, 3, 4, and 5, respectively. Field dependences of the magnetization up to 7.5 T have been studied at 4.2 K using a pulsed magnet and the saturation magnetization values per formula M(S) were compatible with M(S) = Ng-beta(S(Cr) + S(M)) (M(S)/N-beta = 7.74, 6.71, 5.94, 4.94, 3.83, and 2.79 for 1, 2, 3, 4, 5, and 6, respectively). Hysteresis loops have been obtained at 5 K, where the remnant magnetizations are 1500, 4100, 3000, 1200, and 1500 cm3 mol-1 G and the coercive fields are 20, 320, 80, 160, and 30 G for 1, 2, 3, 4, and 5, respectively.DESIGN OF METAL-COMPLEX MAGNETS - SYNTHESES AND MAGNETIC-PROPERTIES OF MIXED-METAL ASSEMBLIES (NBU4[MCR(OX)3])X (NBU4+=TETRA(NORMAL-BUTYL)AMMONIUM ION OX(2-)= OXALATE ION M=MN2+,FE2+,CO2+,NI2+,CU2+,ZN2+)x758199256#N/AFALSE
3114
ja00043a03810.1021/ja00043a038FALSEhttps://doi.org/10.1021/ja00043a038SUMMERS, MFJ. Am. Chem. Soc.Two-dimensional nuClear magnetic resonance (2D NMR) spectroscopic methods have been employed in combination with distance geometry and Overhauser effect back-calculation computational methods to determine the solution-state structure of the 12,13-diepimeric form of coenzyme F430 (12,13-diepimeric F430). NMR signal assignments were made for all non-exchangeable protons using double quantum filtered correlated (DQF-COSY), homonuClear Hartmann-Hahn (HOHAHA), nuClear Overhauser effect (NOESY), and rotating frame Overhauser effect (ROESY) H-1-H-1 correlated spectroscopies. Assignments were made for most carbon atoms via heteronuClear multiple quantum coherence (HMQC) and heteronuClear multiple bond (HMBC) H-1-C-13 correlated spectroscopies. The three-dimensional structure of 12,13-diepimeric F430 was determined with an approach developed originally for studies of biopolymers that inCludes back-calculation of 2D nuClear Overhauer effect spectra for model structures generated by DG/SA computations. As a first step, primary restraints were derived that allowed for maximum conformational flexibility in the absence of NOE-derived distance information. Structures generated subsequently with loose NOE-derived distance restraints (2.0-2.5, 2.0-3.5, and 2.0-4.5 angstrom for strong, medium, and weak NOE cross peak intensities, respectively) converged to a unique conformation, with pairwise root-mean-square deviation (RMSD) values for the macrocyCle atoms in the range 0.019 to 0.153 angstrom. Except for some side-chain atoms, the back-calculated NOESY spectra of the DG/SA structures were consistent with the experimental NOESY spectrum. Most of the side-chain groups did not converge to unique conformations, and pairwise RMSD values for all atoms were in the range 0.67 to 1.25 angstrom. The NMR structure is compared with the recently determined X-ray structure of the pentamethylated ester derivative, 12,13-diepimeric F430M. Both structures exhibit a very similar corphin ring conformation that is characterized by an extreme saddle-shaped deformation. The average RMS difference between the 24 corphin ring atoms of the X-ray structure and the NMR structures is 0.28 angstrom. Larger differences are observed only for atoms of the flexible side chains. The similarity of the NMR and X-ray structures provides grounds for optimism that the NMR approach may be extendable in a general way to studies of smaller molecules that have proven difficult to crystallize, inCluding the native form of coenzme F430.STRUCTURAL MODELING OF SMALL MOLECULES BY NMR - SOLUTION-STATE STRUCTURE OF 12,13-DIEPIMERIC COENZYME-F430 AND COMPARISON WITH THE X-RAY STRUCTURE OF THE PENTAMETHYL ESTER DERIVATIVEx17199250#N/AFALSE
3115
ja00052a03710.1021/ja00052a037FALSEhttps://doi.org/10.1021/ja00052a037DAHL, LFJ. Am. Chem. Soc.Reactions of [Ni6(CO)12]2- (1) with MePCl2 have led to the isolation of [Ni10(PMe)2(CO)18]2- (2), [Ni9(PMe)3(CO)15]2-(3), and [Ni8(PMe)4(CO)12]2- (4) which contain noncentered Ni12-xPx icosahedral cages (x = 2, 3, 4). The three members of this unparalleled series are related by the formal substitution of isolobal PMe fragments for Ni(CO)3 fragments; they, like the regular noncentered [B12H12]2- icosahedron, possess 13 skeletal electron pairs. The Closely related 2, 3, and 4 dianions were separated by column chromatography on silica gel as were two side products-[Ni9(PMe)3(CO)14(mu2-PMe2)]- (5) and [Ni10(mu5-PMe)2(mu4-PMe)5(CO)10]2- (6). The electronically equivalent 5 contains a dimethylphosphido ligand in place of one doubly bridging Carbonyl ligand and one negative charge in 3. The structurally unprecedented pseudo-D5h Ni10P7 cage in 6 contains a completely bonding electron-precise pentagonal prism of nickel atoms with its two pentagonal and five rectangular faces capped by methylphosphinidene ligands. X-ray crystallographic studies of 2, 3, and 4 revealed a geometric change from the squashed cylindrical 1,12-Ni10P2 icosahedral cage in 2 toward the more spherical 1,2,12-Ni9P3 cage in 3 and 1,2,9,12-Ni8P4 cage in 4; this geometrical alteration is evidenced by a convergence of the (icosahedral center)-to-(cage atom) distances on going from the pseudo-D5d Ni10P2 cage in 2 to the pseudo-C(S) Ni9P3 cage in 3 and then to the pseudo-D2h Ni8P4 cage in 4. Other trends among these three icosahedral dianions are as follows: (1) IR spectra exhibiting a linear decrease in terminal Carbonyl frequency, presumably due to enhanced Ni(dpi)-CO(pi*) backbonding; (2) cyClic voltammograms displaying irreversible or quasireversible oxidations indicating that it is hardest to oxidize 2 and easiest to oxidize 4; and (3) P-31{H-1} NMR spectra showing a general upfield shift. These trends are consistent with the homolog containing the greater number of PMe fragments being more electron-rich such that the electron-density surface charge on the Ni12-xPx icosahedral cage (x = 2, 3, 4) is largest for 4 (x = 4) and smallest for 2 (x = 2). The P-31{H-1} NMR solution spectra of Ni10P2 2 and Ni8P4 4 give no insight concerning possible nonrigidity of their cage frameworks in solution. Fluxional behavior of the Ni12-xPx cages on the NMR time scale is exCluded on the basis of virtually identical P-31{H-1} NMR spectra of Ni9P3 3 al 22 and 50-degrees-C exhibiting three well-resolved phosphorus signals with an ABX pattern that conforms to the solid-state structure. The following salient structural features emerge from the single-crystal X-ray diffraction studies: (1) 2 possesses crystallographic C(i)-1BAR site symmetry and an experimentally equivalent configuration in each of its three salts; the same Carbonyl arrangement of 10 terminal, four doubly bridging, and two triply bridging Carbonyl ligands markedly affects the Ni-Ni bond lengths such that the pseudosymmetry of the centrosymmetric Ni10P2 cage is reduced from D5d to C2h-2/m. (2) 3 has crystallographic C(l)-1 site symmetry and an overall pseudo-C(S) symmetry in each of its two salts. Although the overall disposition of nine terminal and six bridging Carbonyl ligands is the same, there are marked differences in the Ni-CO(bridging) distances for the bridging Carbonyl ligands. This alteration in bridging Carbonyl linkage to the Ni9P3 icosahedra of 3 in the two salts is attributed to dissimilar crystallographic packing interactions. (3) 4 in the [PPh3Me]+ salt has crystallographic C(i)-1BAR site symmetry and approximately conforms to D2h-mmm symmetry with eight terminal and four asymmetrically-coordinated triply-bridging Carbonyl ligands.SYNTHESIS, CHROMATOGRAPHIC-SEPARATION, AND STEREOPHYSICAL ANALYSIS OF THE HOMOLOGOUS [NI12-X(PME)X(CO)24-3X]2- SERIES (X = 2, 3, 4) CONTAINING NONCENTERED NI12-XPX ICOSAHEDRAL CAGES AND THE [NI10(MU-5-PME)2(MU-4-PME)5(CO)10]2- DIANION CONTAINING A STRUCTURALLY UNPRECEDENTED HEPTACAPPED PENTAGONAL PRISMATIC METAL CAGE - STRUCTURAL, SPECTROSCOPIC, AND ELECTROCHEMICAL CONSEQUENCES DUE TO REPLACEMENT OF NI(CO)3 FRAGMENTS WITH ELECTRONICALLY EQUIVALENT (ISOLOBAL) PME FRAGMENTS37199296#N/ATRUE
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ja00042a01710.1021/ja00042a017FALSEhttps://doi.org/10.1021/ja00042a017BURROWS, CJJ. Am. Chem. Soc.Nickel(II)-promoted oxidation of accessible guanine residues in deoxyoligonuCleotides using KHSO5 as oxidant was found to be highly dependent upon the macrocyClic ligand employed. Systematic structural variations of the ligands Me2[14]py-dieneN4 (CR) and [14]aneN4 (cyClam) have provided information about the importance of ring size, degree of unsaturation, steric bulk, redox potential, in-plane ligand field strength, and conformational flexibility in determining DNA reactivity with a 17-base hairpin oligonuCleotide Reactions were monitored by analyzing DNA fragments produced after alkaline-induced strand scission. Certain nickel(II) complexes, such as NiTMPP4+ (TMPP = tetra(N-methylpyridyl)porphyrin), Ni(phen)3(2+), and Ni(phen)2(2+), were unreactive. TetraazamacrocyCles providing strong in-plane coordination by amine, imine, or pyridine donors gave the optimum characteristics for DNA reactivity as long as the complex was sufficiently flexible to adapt to DNA binding. These features now define the important criteria for design of nickel-based reagents as structural probes of nuCleic acids.LIGAND EFFECTS ASSOCIATED WITH THE INTRINSIC SELECTIVITY OF DNA OXIDATION PROMOTED BY NICKEL(II) MACROCYClIC COMPLEXESx92199255#N/AFALSE
3117
ja00051a01910.1021/ja00051a019FALSEhttps://doi.org/10.1021/ja00051a019SHELNUTT, JAJ. Am. Chem. Soc.The syntheses, structures, and spectroscopic properties of some novel dodecaphenyl- and dodecaAlkylporphyrins have been investigated with the aim of designing model compounds to aid in evaluating theoretical models of porphyrin nonplanarity. It was found that dodecaphenylporphyrin (3) and the dodecaAlkylporphyrins 4a-c could be prepared using standard synthetic procedures and that these porphyrins adopted very distorted nonplanar structures in the crystalline state. In the crystal structure of 3 the pyrrole rings were tilted with respect to the mean plane of the porphyrin to give a saddle conformation, whereas in the crystal structure of the nickel(II) complex of 4c (Ni4c) the pyrrole rings were twisted with respect to the mean plane to give a ruffled conformation. Nonplanar conformations with the same distortion modes were obtained as minimum energy structures for Ni3 and Ni4c using a molecular mechanics force field, which showed that the observed nonplanar conformations were due to steric repulsions between the peripheral substituents. Low-temperature NMR spectra indicated that the solution conformations of 3 and Ni4c were consistent with those found in the crystal structures. Several conformations of Ni4b and Ni4c with different quasi-axial and quasi-equatorial orientations of the Alkyl chains were observed in solution, and saddle and ruffled distortion modes were Clearly differentiated for the dications and nickel(II) complexes of porphyrins 4b and 4c. Finally, an attempt was made to synthesize the dodecaAlkylporphyrin 5 using the same conditions applied to porphyrins 4a-c. This gave only the 5,15-dihydroporphyrin 6, presumably because the more spatially demanding six-membered ring prevented the oxidation of 6 to porphyrin 5 using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.NONPLANAR DISTORTION MODES FOR HIGHLY SUBSTITUTED PORPHYRINS360199250#N/ATRUE
3118
ja00041a03610.1021/ja00041a036FALSEhttps://doi.org/10.1021/ja00041a036YOUNG, NAJ. Am. Chem. Soc.The isolation of the dichlorides of Ca, Cr, Mn, Fe, Co, Ni, and Zn in argon matrices doped with ca. 1% carbon monoxide results in a nu(CO) feature shifted to high frequency of free CO. In two cases (Cr and Fe) annealing caused the formation of Carbonyl halides with nu(CO) at 2096 and 2110 cm-1, respectively. When the dichlorides were isolated in pure CO matrices (or argon matrices which were highly enriched in CO), in all cases except Ca (d0), Mn (d5), and Zn (d10), Carbonyl halides were formed. This was demonstrated by the use of isotopic substitution and infrared spectroscopy to identify delta(MCO) and (in several cases) nu(M-C) modes. The use of isotopic and partial isotopic substitution ((CO)-C-13; (CO)-O-18) enabled the complete identification of trans-[Fe(CO)4Cl2]. EXAFS data are fully in agreement with the formulation and give the following distances: Fe-C, 1.85 (3) angstrom; Fe-0, 2.96 (4) angstrom; Fe-Cl, 2.25 (3) angstrom. On the basis of combined infrared and EXAFS data, trans-[Cr(CO)4Cl2] is also characterized. The following bond lengths were obtained: Cr-C, 2.00 (3) angstrom; Cr-O, 3.11 (5) angstrom; Cr-Cl, 2.27 (3) angstrom. For CoCl2 and NiCl2, the spectra are complicated by the presence of more than one species in the matrix, so that EXAFS data were not of assistance. In both cases, metal Carbonyl halides were formed and isotopic substitution coupled with nu(M-Cl) frequencies led to the suggestion that the major species are trans-[Ni(CO)2Cl2] and trans-[CO(CO)4Cl2].CHARACTERIZATION OF SOME NOVEL 1ST ROW TRANSITION-METAL Carbonyl CHLORIDES BY INFRARED AND EXAFS SPECTROSCOPY OF MATRIX-ISOLATED SPECIESx19199264#N/AFALSE
3119
ja00050a09410.1021/ja00050a094FALSEhttps://doi.org/10.1021/ja00050a094LINDAHL, PAJ. Am. Chem. Soc.DISCOVERY OF A LABILE NICKEL ION REQUIRED FOR CO ACETYL-COA EXCHANGE ACTIVITY IN THE NIFE COMPLEX OF CARBON-MONOXIDE DEHYDROGENASE FROM ClOSTRIDIUM-THERMOACETICUM57199228#N/ATRUE
3120
ja00039a02710.1021/ja00039a027FALSEhttps://doi.org/10.1021/ja00266a042HWANG, BKCOMPARABLE RATES FOR ClEAVAGE OF AMIDE AND ESTER BONDS THROUGH NUClEOPHILIC-ATTACK BY CarbonylATE ANION AND GENERAL ACID CATALYSIS BY METAL-BOUND WATER IN A CARboxYPEPTIDASE-A MODELx1992#N/AFALSE
3121
ja00039a01010.1021/ja00039a010https://doi.org/10.1021/ja00039a010HEGEDUS, LSJ. Am. Chem. Soc.Photolysis of chromium alkoxycarbene complexes with N-(BenzyloxyCarbonyl)imidazolines produced protected azapenams. Hydrogenolysis gave free azapenams which were stable, one of which was characterized by X-ray crystallography. Hydrogenolysis under acidic conditions produced hexahydro-1,4-diazepin-5-ones. Treatment of the free azapenams with camphorsulfonic acid produced unsaturated 14-membered tetraazamacrocyCles in excellent yield. These were reduced to dioxocyClams.SYNTHESIS OF AZAPENAMS, DIAZEPINONES, AND DIOXOCYClAMS VIA THE PHOTOLYTIC REACTION OF CHROMIUM ALKOXYCARBENE COMPLEXES WITH IMIDAZOLINESPhotocatalyst71199266#N/AFALSE
3122
ja00050a06110.1021/ja00050a061FALSEhttps://doi.org/10.1021/ja00050a061MASCHARAK, PKJ. Am. Chem. Soc.A MONONUClEAR NICKEL(II) COMPLEX WITH [NIN3S2] CHROMOPHORE THAT READILY AFFORDS THE NI(I) AND NI(III) ANALOGS - PROBE INTO THE REDOX BEHAVIOR OF THE NICKEL SITE IN [FENI] HYDROGENASES55199232#N/ATRUE
3123
ja00050a02510.1021/ja00050a025FALSEhttps://doi.org/10.1021/ja00050a025MATHEY, FJ. Am. Chem. Soc.The Insertion of NiL2 (L = phosphine) into the P-P bond of 1,2,3,4-tetraphenyl-1,2-dihydro-1,2-diphosphete has been achieved via two methods. In the first, the P-P bond is initially Cleaved with lithium and the derivatized dianion allowed to react with [NiCl2L2]. This yields primarily a nickeladiphospholene with a distorted square-planar geometry at the metal in which the chelating ligand acts as a (1 + 1) electron donor, and the metal is formally in the +2 oxidation state. The second route involves the direct insertion of a [NiL2] fragment into the P-P bond at low temperature. In this case the results suggest the formation of a 1,4-diphosphadiene complex of nickel(0) in which the ligand acts as a (2 + 2) electron donor and the geometry at the metal is tetrahedral. Although both forms can be isolated for some coligands, only one form is observed in several cases and isomerization between the two forms has been observed in the other cases. The second route has also been transposed to platinum. The crystal structures of the Ni(Ph2PCH2CH2PPh2) and Pt(PPh3)2 complexes have been studied and a distortion from planarity observed in each case as shown by interplane LML/PMP angles of 38-degrees and 57-degrees, respectively. The phosphorus atoms are Closer to planarity and the ring C=C bond lengths longer in the platinum complex than in the nickel. The platinum complex can be seen as lying halfway between a 1,4-diphospholene platinum(II) and a 1,4-diphosphadiene platinum(0) complex. This work suggests that with an adequate choice of coligand and substitution pattern it would be possible to achieve an electronic delocalization similar to that observed in metal-dithiolenes.INSERTION OF TRANSITION-METALS INTO THE PHOSPHORUS-PHOSPHORUS BOND OF 1,2-DIHYDRO-1,2-DIPHOSPHETES - TOWARD THE PHOSPHORUS ANALOGS OF METAL DITHIOLENE COMPLEXES20199210#N/ATRUE
3124
ja00037a05610.1021/ja00037a056https://doi.org/10.1021/ja00037a056NOVAK, BMJ. Am. Chem. Soc.LIVING POLYMERIZATIONS AS MECHANISTIC PROBES - STEREOSELECTION IN THE NICKEL-CATALYZED POLYMERIZATION OF CHIRAL ISOCYANIDESx34199239#N/AFALSE
3125
ja00050a00610.1021/ja00050a006FALSEhttps://doi.org/10.1021/ja00050a006MCCOMB, SJ. Am. Chem. Soc.Enediynes 7 and 9 were designed for their potential to act as radical-generating species upon oxidation to the corresponding quinone. Their synthesis entailed a chromium-nickel-mediated ring Closure of iodo aldehyde 6. Investigations with these molecules and their derivatives 8 and 10 demonstrated the anticipated acceleration of the Bergman cyCloaromatization of the oxidized species as compared to the reduced compounds and potent DNA-Cleaving and antitumor properties.REDOX-CONTROLLED BERGMAN CYClOAROMATIZATIONS - DESIGNED ENEDIYNES WITH DNA-ClEAVING PROPERTIES AND ANTITUMOR-ACTIVITY103199212#N/ATRUE
3126
ja00036a03110.1021/ja00036a031FALSEhttps://doi.org/10.1021/ja00036a031SPIRO, TGJ. Am. Chem. Soc.The responsiveness of metalloporphyrin skeletal mode vibrational frequencies to changes in the core size and in the planarity of the macrocyCle have been investigated, using normal mode analysis with the recently developed empirical force field for NiOEP (nickel octaethylporphyrin) and NiTPP (meso-tetraphenylporphyrin). Crystallographic data for OEP and TPP show correlations of structure parameters with core size: as the core expands, so do the C(alpha)C(m) bridge bonds, the pyrrole C(alpha)C(beta) and C(beta)C(beta) bonds, and the C(alpha)C(m)C(alpha) bridge angles, while the C(alpha)N bonds contract. These empirical correlations were used to define a structural model of core expansion in order to calculate the vibrational frequency dependence. The kinematic consequences of core expansion are negligible, but when the bond stretching force constants were scaled to the bond distances, using the empirical equation of Burgi and Dunitz, the frequency correlations were calculated nearly quantitatively. Core size effects were also examined with QCFF/Pi semiempirical calculations on a metallo-OEP model at a series of metal-nitrogen distances. The trends in geometry were in reasonable agreement with the crystallographic data except that C(beta)C(beta) was calculated to decrease strongly with core size, contrary to the observed trend. Consequently, the calculated frequency dependencies had slopes differing in sign from the observed slopes for modes having major C(BETA)C(BETA) contributions, nu-3 and nu-11. The kinematics of porphyrin ruffling and doming were calculated to produce appreciable downshifts in the nu-10 and nu-19 modes, involving out-of-phase stretching of the C(alpha)C(m) bridge bonds, due to out-of-plane displacements of the C(m) atoms. MNDO/3 calculations, carried out on zinc(II) porphine with dihedral angles artificially constrained to produce ruffled and domed structures, showed the ring bond distances to be essentially unaffected by the out-of-plane distortions. Consequently, the changes in frequency should be calculable from kinematics alone if the distortion is imposed externally, e.g. by crystal packing or by steric forces in proteins. Some ruffled or domed metalloporphyrins show additional deviations from expectations based on core size, however, probably because of electronic influences. Thus, the ruffled form of NiOEP shows downshifts of nu-2 and nu-11, relative to the planar form, which are calculable by bond distance scaling, since the C(beta)C(beta) distance is observed to lengthen. Five-coordinate complexes of Fe(II), Co(II), and Mn(II) show depressed nu-4 frequencies; this effect is suggested to arise from interaction of the d(z)2 electrons with the filled a2u pi-orbitals, an interaction permitted in these C4-upsilon complexes, and which is made effective by the low valency of the metal ions.CORE EXPANSION, RUFFLING, AND DOMING EFFECTS ON METALLOPORPHYRIN VIBRATIONAL FREQUENCIESx79199264#N/AFALSE
3127
ja00036a00710.1021/ja00036a007FALSEhttps://doi.org/10.1021/ja00036a007TANAKA, KJ. Am. Chem. Soc.A controlled potential electrolysis at -1.55 V versus SCE of CO2-saturated CH3CN containing (Et4N)3[Mo2Fe6S8(SEt)9], CH3C(O)SEt, Bu4NBF4, and Molecular Sieve 3A as a desiccant produced CH3C(O)COO- with a current efficiency of 27%. Similar electrolysis using C2H5C(O)SEt and C6H5C(O)SEt also catalytically afforded C2H5C(O)COO- and C6H5C(O)COO-with current efficiencies of 49 and 13%, respectively. These reactions are strongly inhibited by the presence of not only H2O but also excess EtS-. Strong acylating agents such as acetyl chloride, acetic anhydride, acetyl-sulfide, and acetylimidazole in place of CH3C(O)SEt caused decomposition of [Mo2Fe6S8(SEt)9]3-, and no CH3C(O)COO- was formed under the same electrolysis conditions.ELECTROCHEMICAL CARBON-DIOXIDE FIXATION TO THIOESTERS CATALYZED BY [MO2FE6S8(SET)9]3-Electrochemica;25199266#N/AFALSE
3128
ja00035a01710.1021/ja00035a017FALSEhttps://doi.org/10.1021/ja00035a017STERNHELL, SJ. Am. Chem. Soc.The allylic interproton spin-spin coupling constant, 4J(CH3C = CH) (4J(Me,H)), which has previously been established as a sensitive probe of bond order, was measured in a range of free-base porphyrins and metallo-2-methylporphyrins. The measured room temperature 4J(Me,H) values in a range of substituted porphyrins ((1.02-1.45) +/- 0.03 Hz) were correlated to the pi-bond order of the four beta-beta pyrrolic linkages of the porphyrins. In 2-methyl-5,10,15,20-tetraphenylporphyrin (2) (average 4J(Me,H) 1.19 +/- 0.03 Hz), the bond order across the two beta-beta' pyrrolic bonds involved in the aromatic delocalization pathway in each of the isolated tautomers, 2a and 2b, is considerably higher than the bond order in toluene and pyrrole and corresponds to a Pauling bond order of ca. 0.76 or a self-consistent field (SCF) bond order of ca. 0.66. The bond order across the two beta-beta' pyrrolic bonds not involved in the delocalization pathway is similar to that found in pure double bonds, and these bonds may be regarded as essentially fully localized carbon-carbon double bonds. The room-temperature 4J(Me,H) values in methylnitroporphyrins 5-10 ranged from 1.12 to 1.45 Hz and reflect the relative tautomer populations. Ground-state structural information about bond delocalization between the beta- and beta'-pyrrolic positions of metalloporphyrins was similarly obtained from measurement of the 4J(Me,H) values for a series of 2-methylporphyrins (15-18) (M = Mg, Zn, Pd, Ni). The 4J(Me,H) values lie in the range 1.14-1.21 Hz, i.e., a Pauling bond order of ca. 0.76 which Clearly rules out the possibility of a 16-atom dianion structure with localized double bonds at the four beta-beta' pyrrolic positions as has been previously been proposed for a magnesium(II) porphyrin (Spangler, D.; Maggiora, G. M.; Shipman, L. L.; Christoffersen, R. E. J. Am. Chem. Soc. 1977, 99, 7470). Bond orders were determined on two free-base methylnitroporphyrins and their corresponding zinc(II) chelates. In the free-base methylnitroporphyrins 8 and 9, the nitro group causes bond fixation such that one 18-pi tautomer predominates over the other tautomeric form. In contrast, no such bond fixation was detected in the zinc chelates, 19 and 20, respectively. These findings indicate that the bond order at all beta-beta' pyrrolic positions in metalloporphyrins is intermediate between that of aromatic and localized bonds.USE OF NMR-SPECTROSCOPY TO DETERMINE BOND ORDERS BETWEEN BETA-PYRROLIC AND BETA'-PYRROLIC POSITIONS OF PORPHYRINS - STRUCTURAL DIFFERENCES BETWEEN FREE-BASE PORPHYRINS AND METALLOPORPHYRINSx40199250#N/AFALSE
3129
ja00048a04010.1021/ja00048a040FALSEhttps://doi.org/10.1021/ja00048a040RICHARDSON, DEJ. Am. Chem. Soc.Free energies of ionization for Cp2V, Cp2Mn, Cp2Fe, Cp2Ni, Cp2Ru, Cp2OS (Cp = eta2-cyClopentadienyl), and a series of ferrocene derivatives have been determined through gas-phase electron-transfer equilibrium (ETE) reactions by using Fourier transform ion cyClotron resonance mass spectrometry. Temperature dependence studies involving ETE of ferrocene with N,N-diethyltoluidine lead to a value of the enthalpy of ionization, DELTAH(i)-degrees, for ferrocene of 6.82 +/- 0.08 eV. Experimental and statistical mechanical analyses indicate that the one-electron oxidation of ferrocene is accompanied by a positive entropy of ionization, DELTAS(i)-degrees, most of which is associated with changes in the electronic and vibrational contributions to the partition functions of ferrocene and the ferrocenium ion. Ionization energies of Alkylferrocene derivatives are correlated with Alkyl Taft parameters. Thermochemical cyCles are used to derive estimates of average homolytic and heterolytic bond disruption enthalpies (DELTAH(hom)-degrees and DELTAH(het)-degrees) for selected metallocenium ions. For Cp2M+, the following mean M-Cp bond disruption enthalpies (kcal mol-1) are derived: DELTAH(hom)-degrees (M+-Cp) = 95 +/- 3 (V), 74 +/- 4 (Mn), 91 +/- 3 (Fe), 83 +/- 3 (Ni); DELTAH(het)-degrees (M+3-Cp) = 563 +/- 4 (V), 604 +/- 5 (Mn), 593 +/- 4 (Fe), 659 +/- 4 (Ni). Differential solvation free energies (DELTADELTAG(solv)-degrees) for several metallocene/metallocenium redox couples are derived. With the exception of Cp2V+/0, most of the first transition row metallocene/metallocenium redox couples are estimated to have DELTADELTAG(solv)-degrees values of 38 +/- 5 kcal mol-1, which is consistent with the Born approximation for predicting ion solvation energies. These assessments of bonding and solvation energetics based on gas-phase adiabatic ionization energies lead to a complete thermochemical interpretation of observed solution electrode potentials for the metallocene redox couples studied.ADIABATIC IONIZATION ENERGIES, BOND DISRUPTION ENTHALPIES, AND SOLVATION FREE-ENERGIES FOR GAS-PHASE METALLOCENES AND METALLOCENIUM IONS97199268#N/ATRUE
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ja00034a00110.1021/ja00034a001FALSEhttps://doi.org/10.1021/ja00034a001RIDGE, DPJ. Am. Chem. Soc.Rate constants and product distributions for reactions of the title anions with 15 organic electrophiles as measured by Fourier transform ion cyClotron resonance techniques are reported. The electrophiles are all aromatic or olefinic compounds with electronegative substituents. The reaction efficiencies defined as the overall rate constant divided by the collision rate (k/k(c)) vary from unity to unmeasurable (upper limit 10(-3) or less). For each anion reactivity drops rapidly as the electron affinity (EA) of the electrophile drops below some critical range values. The critical range (eV) is 0.62-0.91, 1.01-1.29, and 1.29-1.44 for Ni(CO)3-, Cr(CO)5-, and Fe(CO)4-, respectively. Eight cases were examined where the EA of the electrophile was below the critical range, and no reactivity was observed for any of those cases. Twenty-four cases were examined where the EA of the electrophile is above the critical range, and in all of those cases reaction was efficient (k/k(c) > 0.10). Reactivity was observed for the four cases where the EA of the electrophile was in the critical range, but the efficiency was lower (k/k(c) < 0.05). In most cases where any reaction was observed displacement of one or more CO ligands was the dominant process. Exothermic charge transfer competes with ligand substitution in the Ni(CO)3- reactions, but only with tetracyanoethylene is charge transfer a significant product for Cr(CO)5- and Fe(CO)4-. These results are interpreted in terms of a mechanism for ligand substitution involving incipient charge transfer within a collision complex to produce a 16-electron metal center which then undergoes substitution. The ligand substitution results are compared to previous results on the reactions of the title ions both in the gas phase and in solution. Products of subsequent reactions of the initial products are described. It is suggested that oxidative addition to the metal of carbon-halogen and in one case carbon-carbon bonds (i.e., the deCarbonylation of benzophenone) plays a role in this chemistry. One sequence of reactions is described that appears to involve formation of a carbon-carbon bond (i.e., the coupling of two 4-nitrophenyl groups in reactions of 1-bromo-4-nitrobenzene).GAS-PHASE REACTIONS OF CR(CO)5(-), FE(CO)4(-), AND NI(CO)3(-) WITH ORGANIC ELECTROPHILESx16199247#N/AFALSE
3131
ja00046a02910.1021/ja00046a029FALSEhttps://doi.org/10.1021/ja00046a029FAGAN, PJJ. Am. Chem. Soc.The electrochemical properties of the complexes (Ph3P)2Pt(eta-2-C60), (Et3P)2M(eta-2-C60), [(Et3P)2M]6C60 (M = Ni, Pd, Pt; Et = ethyl, Ph = phenyl), and [(Et3P)2Pt]nC60 (n = 2-4) have been investigated. In the case of the monosubstituted complexes (Ph3P)2Pt(eta-2-C60) and (Et3P)2 M(eta-2-C60), three to four sequential one-electron reduction waves are observed shifted to more negative potentials relative to C60. Reduction is accompanied by loss of the metal fragment (R3P)2M. The rate of metal dissociation upon reduction is dependent on the identity of the phosphine ligand ((Ph3P)2Pt(eta-2-C60)2- > (Et3P)2Pt(eta-2-C60)2-), the metal (Ni > Pd > Pt), and the extent of reduction ((Et3P)2PtC603- > (Et3P)2PtC602- > (Et3P)2PtC60-). The cyClic voltammograms have been simulated to obtain kinetic and thermodynamic information regarding these processes. The reduction events in the metal complexes are C60-centered, whereas the irreversible oxidation waves observed for these complexes are proposed to be metal-centered from comparison with the model complexes (Et3P)2M(eta-2-CH2=CHCO2CH3) (M = Ni, Pd, Pt). The results lead to the conClusion that there is negligible extension of d-orbital backbonding density beyond the carbon-carbon double bond where the metal is attached. Coordination of one of these metals to C60 is proposed to lower the electron affinity of the carbon Cluster by effectively removing one of the C60 carbon-carbon double bonds from conjugation and inductively adding electron density to the a bond framework. Addition of more metals continues to lower the electron affinity of the C60 core, with the reversible potentials for [(Et3P)2Pt]nC60 shifting 0.36 V in the negative direction with each metal added for n = 0-4.ELECTROCHEMICAL STUDIES ON METAL DERIVATIVES OF BUCKMINSTERFULLERENE (C-60)121199255#N/ATRUE
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ja00030a06510.1021/ja00030a065https://doi.org/10.1021/ja00030a065KITAIKE, YJ. Am. Chem. Soc.NICKEL(0)-CATALYZED ALTERNATING COPOLYMERIZATION OF CARBON-DIOXIDE WITH DIYNES TO POLY(2-PYRONES)x5219929#N/AFALSE
3133
ja00044a06010.1021/ja00044a060FALSEhttps://doi.org/10.1021/ja00044a060LUH, TYJ. Am. Chem. Soc.A CHELATION APPROACH TOWARD Activation OF C(SP3)-S BONDS - NICKEL-CATALYZED SELECTIVE CROSS COUPLING OF BISDITHIOACETALS WITH GRIGNARD-REAGENTS23199212#N/ATRUE
3134
ja00027a04110.1021/ja00027a041FALSEhttps://doi.org/10.1021/ja00027a041ROKITA, SEJ. Am. Chem. Soc.DNA oxidation promoted by a square-planar complex of nickel(II) (1) in conjunction with KHSO5 provided an excellent method for selectively detecting guanine residues that did not adopt a standard Watson-Crick duplex structure. Sites of modification were indicated by a diagnostic strand scission of DNA induced by subsequent treatment with piperidine. The specificity and, consequently, the utility of this nickel-based reagent were demonstrated through the use of defined oligonuCleotide targets. All guanine residues of a random coil reacted readily under the described conditions while the other residues, adenosine, cytidine, and thymidine, remained inert. Most importantly, guanine residues were protected from modification when held within a duplex of complementary paired and stacked bases. This property then allowed for the reliable identification of mispaired, bulged, looped, and terminal guanines from otherwise helical regions of DNA. In addition, the predicted asymmetry of base stacking in a loop structure was confirmed by preferential derivatization of specific guanine residues.CONFORMATION-SPECIFIC DETECTION OF GUANINE IN DNA - ENDS, MISMATCHES, BULGES, AND LOOPSx90199247#N/AFALSE
3135
ja00044a04210.1021/ja00044a042FALSEhttps://doi.org/10.1021/ja00044a042BOSNICH, BMOLECULAR MECHANICS FORCE-FIELDS FOR LINEAR METALLOCENES1992#N/ATRUE
3136
ja000261910.1021/ja0002619FALSEhttps://doi.org/10.1021/ja0002619Nakatani, KJ. Am. Chem. Soc.A series of 35 layered compounds A[(MCrIII)-Cr-II(C2O4)(3)].n solvent has been synthesized with five different metals (M = Mn, Fe, Co, Ni, Cu) and seven hyperpolarizable stilbazolium-shaped A chromophores: (4-[4-(dimethylamino)-alpha-styryl]-N-Alkylpyridinium), Alkyl = methyl, ethyl, isopropyl (DAMS, DAES, DAPS respectively); (4-[4-methoxy-alpha-styryl-N-Alkylpyridinium), Alkyl = isopentyl, heptyl (MIPS, MHS); DAZOP and CINDAMS are DAMS analogues, where the central [C=C] core has replaced by azo or butadiene cores, respectively]. These compounds have been designed as possible multiproperty materials associating ferromagnetism and second-order optical nonlinearity. Two-third of these compounds exhibit second harmonic generation (with efficiency up to 100 times that of urea at 1.9 mu m), the others being inactive. All of them order ferromagnetically below Curie temperatures that range from 6 to 13 K. The structures of DAPS[Mn-II- Cr-III(C2O4)(3)].CH3CN and MIPS[(MnCrIII)-Cr-II(C2O4)(3)] have been resolved. Both of them belong to the centrosymmetric P2(1)/c space group, which accounts for their NLO inactivity. The long axes of the chromophores in a given layer are parallel, but the dipolar moments are antiparallel. Two successive chromophore layers along the stacking direction have approximately orthogonal orientations, giving rise to a doubling of the c parameter. X-ray powder diffraction shows that the high crystalline compounds of the series possess the same monoClinic unit cell as A[(MnCrIII)-Cr-II(C2O4)(3)] (A = DAPS, MIPS). A search for structure-property correlation emphasizes the relationship between a short interlayer distance and the alignment of the chromophore dipoles.Structure and NLO properties of layered bimetallic oxalato-bridged ferromagnetic networks containing stilbazolium-shaped chromophoresx188200038#N/AFALSE
3137
ja00044a01810.1021/ja00044a018FALSEhttps://doi.org/10.1021/ja00044a018NIELSEN, MFJ. Am. Chem. Soc.The reduction of Aryl halides in the presence of stoichiometric amounts of carbon dioxide and catalytic amounts of Pd(II)Cl2(PPh3)2 has been previously reported to result in the formation of the corresponding Carbonylic acids. It is shown here that the mechanism proceeds via a catalytic cyCle initiated by the one-step, two-electron reduction of the divalent palladium complex followed by oxidative addition of the Aryl halide to the resulting poorly ligated zerovalent palladium center Pd0(PPh3)2, to afford the corresponding sigma-Arylpalladium(II) intermediate. One-step, two-electron reduction of the latter yields an anionic sigma-Arylpalladium(0), ArPd0(PPh3)2-, which reversibly dissociates to restore the low-ligated zerovalent palladium complex, Pd0(PPh3)2, while producing a free sigma-Aryl anion, Ar-. NuCleophilic attack of carbon dioxide by the latter yields the Carbonylate derivative, ArCO2-, while oxidative addition of the Aryl halide to Pd0(PPh3)2 completes the catalytic cyCle. It is thus conCluded that the palladium-catalyzed Carbonylation proceeds only through the involvement of diamagnetic palladium-centered intermediates, in contradiction with what has been established previously for the nickel catalysis of the same reaction.CARBON-DIOXIDE AS A C1 BUILDING BLOCK - MECHANISM OF PALLADIUM-CATALYZED CarbonylATION OF AROMATIC HALIDES89199272#N/ATRUE
3138
ja00042a06510.1021/ja00042a065FALSEhttps://doi.org/10.1021/ja00042a065MILLAR, MJ. Am. Chem. Soc.SYNTHESIS, STRUCTURE, AND CHARACTERIZATION OF A MIXED-VALENCE [NI(II)NI(III)] THIOLATE DIMER61199221#N/ATRUE
3139
ja00023a01310.1021/ja00023a013FALSEhttps://doi.org/10.1021/ja00023a013COOPER, SRJ. Am. Chem. Soc.The conformational and Ni(II)-binding properties of 1,4,8,11-tetrathiocyClotetradecane (1) and derivatives bearing gem-dimethyl pairs at the 6- or at the 6- and 13-positions (2 and 3, respectively) are compared. The syntheses and crystal structures of 2, 3, and their Ni(ClO4)2 complexes are reported; analogous data for 1 and its Ni(BF4)2 complex have been in the literature for some time. All three Ni(II) complexes show very similar 14-membered ring conformations, but the metal-free macrocyCles display different conformations, in the solid state. These structural data suggest that each gem-dimethyl pair progressively biases the macrocyCle toward the chelating conformation. We have examined the relative Ni(II) affinities of 1-3 in CD3NO2 by means of competition experiments monitored by H-1 NMR. Tetrathioether 2 binds Ni(II) approximately 7.3 times more tightly than does 1 at room temperature, and 3 binds Ni(II) approximately 49 times more tightly than does 1. Thus, each gem-dimethyl pair leads to a 1.1 kcal/mol improvement in Ni(II) binding free energy under these conditions. We suggest that the incremental improvement in binding strength across the series 1-3 is correlated to the incremental changes in macrocyCle conformation observed in the crystal structures of the metal-free thioethers.ENHANCED NICKEL(II) CHELATION BY GEM-DIMETHYL-SUBSTITUTED MACROCYClIC TETRATHIOETHERSx55199149#N/AFALSE
3140
ja00041a04010.1021/ja00041a040FALSEhttps://doi.org/10.1021/ja00041a040SCHWARZ, HJ. Am. Chem. Soc.The reactions of the first-row transition-metal ions from Ti+ to Zn+ with several secondary and tertiary isocyanates are studied using a Fourier transform ion cyClotron resonance (FTICR) spectrometer. The late transition-metal ions Cr+-Zn+ react with i-PrNCO (1), s-BuNCO (2), t-BuNCO (3), and t-PentNCO (4) via an ion/dipole mechanism to form mainly M(HNCO)+ and M(alkene)+ by loss of an alkene or HNCO, respectively. In contrast, the early transition-metal ions Ti+ and V+ show a pronouncedly different behavior. Among a plethora of small products, the most prominent pathways in the case of the secondary isocyanates 1 and 2 afford nitrile complexes by initial deCarbonylation and subsequent 1,1-elimination of an alkane. For tertiary isocyanates this process is absent, revealing an inability to break two C-C bonds in the course of the alkane elimination. The results are discussed in connection with a surface-catalyzed process that generates acetonitrile from 1 and HNCO/isobutene from 3. Some secondary reactions of Cr+-Zn+ are also presented. While for M+ = Cr+, Mn+, and Zn+ the primary M(HNCO)+ and M(alkene)+ products react with the secondary isocyanates to form M(RNCO)+ adduct complexes by simple ligand exchange, for Fe+-Cu+ isomeric M(HNCO)(alkene)+ ions are obtained. In the case of tertiary isocyanates, Cr+ behaves like Fe+-Cu+ and only Mn+ and Zn+ react by simple ligand exchange.GAS-PHASE REACTIONS OF SECONDARY AND TERTIARY ISOCYANATES WITH TI+ TO ZN+ - MODEL STUDIES FOR CATALYTIC PROCESSES101992187#N/ATRUE
3141
ja00022a04110.1021/ja00022a041FALSEhttps://doi.org/10.1021/ja00022a041HOLM, RHJ. Am. Chem. Soc.A series of nickel complexes [Ni(NS3R)L]+ derived from the tripodal ligand NS3R = N(CH2CH2SR)3 (R = i-Pr, t-Bu) has been prepared in order to investigate the stabilities and reactions of certain species potentially relevant to the nickel sites in carbon monoxide dehydrogenase (CODH). Reaction of [Ni(NS3R)Cl]+ with MeMgX affords [Ni(NS3R)Me]+, which with CO yields [Ni(NS3R)COMe]+. Reaction of [Ni(NS3tBu)Cl]+ with NaBH4 gives [Ni(NS3tBu)H]+ and the Ni(I) species [Ni(NS3tBu)]+. The hydride complex was obtained with minimal Ni(I) contamination by removal of ethylene from the equilibrium system [Ni(NS3tBu)Et]+/[Ni(NS3tBu)H]+/C2H4. Reaction of [Ni(NS3tBu)]+ with CO affords [Ni(NS3tBu)CO]+, whereas [Ni(NS3tBu)H]+ under the same conditions gives Ni(CO)4 and protonated ligand. All reactions were performed in THF, and all complexes were isolated as BPh4-salts. This series inCludes rare examples of the stabilization of Ni-methyl, -acyl, -hydride, and -Carbonyl ligands in the absence of nonphysiological (C/P/As) coligands. Trigonal-bipyramidal stereochemistry has been demonstrated for five complexes with L = Cl, Me, COMe, H, and CO by X-ray crystallography. The methyl/acyl transformations with carbon monoxide and the formation in high yield of the thioesters R'SCOMe (R' = Et, CH2Ph, Ph) upon reaction of [Ni(NS3R)COMe]+ with thiols in THF are two previously undocumented processes mediated at Ni(II) sites lacking non-physiological (C/P/As) ligation. These are relevant to current views of the catalytic reaction cyCle of Clostridium thermoaceticum CODH, which is presented. The Ni(II)-H and Ni(I)-CO species may be pertinent to the CO/CO2 activity of CODH. Full details of all preparations, other reactions, and structures are presented. This work is an initial attempt to place the reaction chemistry of CODH on a rational basis, and provides some viability for the present reaction cyCle of the enzyme.STRUCTURAL AND REACTION CHEMISTRY OF NICKEL-COMPLEXES IN RELATION TO CARBON-MONOXIDE DEHYDROGENASE - A REACTION SYSTEM SIMULATING ACETYL-COENZYME-A SYNTHASE ACTIVITYx100199158#N/AFALSE
3142
ja00039a06310.1021/ja00039a063FALSEhttps://doi.org/10.1021/ja00039a063HOLM, RHSYNTHETIC NICKEL-CONTAINING HETEROMETAL CUBANE-TYPE ClUSTERS WITH NIFE3Q4 CORES (Q = S, SE)1992#N/ATRUE
3143
ja00022a02610.1021/ja00022a026FALSEhttps://doi.org/10.1021/ja00022a026JUTAND, AJ. Am. Chem. Soc.The role and effect of chloride and bromide ions on the intimate mechanisms and rates of oxidative addition of iodobenzene to electrogenerated low-ligated zerovalent palladium complex Pd0(PPh3)2 are examined and discussed on the basis of P-31 NMR and transient electrochemistry. It is shown that Pd0(PPh3)2 actually consists of a mixture of three anionic species, [Pd0(PPh3)2Cl]2(2-) (A), Pd0(PPh3)2Cl- (B), and Pd0(PPh3)2Cl2(2-) (C), which are in rapid equilibrium within the time scale of their oxidative addition by iodobenzene. This stabilization of low-ligated zerovalent palladium by chloride ions occurs also during the oxidative addition of iodobenzenes to the ubiquitous Pd0(PPh3)4. This shows that the results of this study may be transposed to more Classical procedures of generation of the active zerovalent palladium complex Pd0(PPh3)2, and also affords a tentative explanation of the effect of chloride ions in palladium-catalyzed nuCleophilic substitutions or in the Heck reaction.ROLE AND EFFECTS OF HALIDE-IONS ON THE RATES AND MECHANISMS OF OXIDATIVE ADDITION OF IODOBENZENE TO LOW-LIGATED ZEROVALENT PALLADIUM COMPLEXES PD0(PPH3)2x270199198#N/AFALSE
3144
ja00021a01910.1021/ja00021a019FALSEhttps://doi.org/10.1021/ja00021a019BURRIEL, RJ. Am. Chem. Soc.We report on the magnetic behavior of the compounds M(t)M(M'EDTA)2.4H2O (in short [M(t)MM']) in the very low temperature range. The structure of these compounds can be formally regarded as ordered bimetallic layers of alternating chelated and hydrated octahedral sites M and M', with tetrahedral sites M(t) connecting different MM' layers. We have obtained the compounds [ZnZnNi], [ZnNiNi], [CoNiNi], [CoCoNi], and [CoCoCo]. While the compound [ZnNiNi] may support a 2-D magnetic lattice of Ni(II), since Zn(II) occupies tetrahedral sites, in the compounds without Zn the layers are connected through Co(II), increasing the dimensionality of the lattice to 3-D. A leveling of the magnetic susceptibility has been observed in [ZnNiNi], which has been attributed to zero-field splitting effects of the chelated Ni(II) ions. On the other hand, as expected on the basis of the structure, the substitution of Zn(II) by Co(II) in the tetrahedral site leads to the appearance of 3-D ferrimagnetic interactions in the compounds [CoNiNi], [CoCoNi], and [CoCoCo]. This is Clearly noticeable from the sharp transition temperatures in the first two compounds at T(c) = 0.44 and 0.10 K, respectively, with an out-of-phase susceptibility signal below T(c). In [CoCoNi], there is a rounded maximum in the chi(m)T plot at T = 0.40 K. The magnetic data in the low-dimensional region have been analyzed for the compounds [CoCoCo] and [CoCoNi] by means of an anisotropic (Ising-type) model that assumes three different magnetic sublattices exchange-coupled by two magnetic interactions, as well as the local anisotropies of tetrahedral Co(II) and chelated Ni(II) ions.FROM 1-D TO 3-D FERRIMAGNETS IN THE EDTA FAMILY - MAGNETIC CHARACTERIZATION OF THE TETRAHYDRATE SERIES M(T)M(M'EDTA)2.4H2O [M(T), M, M' = CO(II), NI(II), ZN(II)]x26199123#N/AFALSE
3145
ja00038a03810.1021/ja00038a038FALSEhttps://doi.org/10.1021/ja00038a038CHE, MJ. Am. Chem. Soc.The adsorption on silica of various amminenickel(II) complexes has been investigated as a function of the preparation procedure, i.e., the composition of the impregnating solution and the washing and drying steps. Quite different adsorption modes can be distinguished by EXAFS, XANES, and infrared spectroscopies depending on the pH of the impregnating solution: [Ni(NH3)6]2+ weakly adsorbs (electrostatic adsorption) while [Ni(H2O)6-n(NH3)n]2+ (n < 6) complexes strongly interact with the carrier, giving rise to the formation of layered nickel silicate structures. A Classification of the bonding of cations on supports, the latter acting as dispersing agents, macroanions, or chemical reagents, is proposed. The EXAFS technique is shown to be a powerful tool for the determination of the ion-support interaction during the first steps of the preparation of silica-supported nickel materials.NICKEL(II) ION SUPPORT INTERACTIONS AS A FUNCTION OF PREPARATION METHOD OF SILICA-SUPPORTED NICKEL MATERIALS134199257#N/ATRUE
3146
ja000202v10.1021/ja000202vFALSEhttps://doi.org/10.1021/ja000202vLippard, SJJ. Am. Chem. Soc.A hydroxide-bridged dinuClear nickel complex with a urea molecule linking the two metal ions through its Carbonyl oxygen atom has been prepared as a model for the metalloenzyme urease. This complex, [Ni-2(mu-OH)(mu-urea)(bdptz)(urea) (CH3CN)](ClO4)(3), where bdptz is the dinuCleating ligand 1,4-bis(2,2'-dipyridylmethyl)phthalazine, effects the hydrolysis of urea upon heating in a two-step reaction. In the first step, a molecule of ammonia is eliminated from urea with concomitant production of cyanate, the first-order rate constant in acetonitrile being (7.7 +/- 0.5) x 10(-4) h(-1). This reaction is at least 500 times faster than the spontaneous decomposition of urea under the same conditions. When the cyanate-containing product is further heated in the presence of water, the cyanate is hydrolyzed with a second-order rate constant of (9.5 +/- 1) x 10(-4) M-1 h(-1). Reaction of [Ni-2(mu-OH)(mu-urea)(bdptz)(urea)(CH3CN)](ClO4)(3) in 50% aqueous acetonitrile afforded ammonia with no appreciable buildup of the cyanate-containing species. A possible analogue of the cyanate-containing product, [Ni-2(mu-OH)(mu-H2O)(bdptz)(mu-OCN)](2)(OTs)(4) was independently synthesized and structurally characterized. These results establish the precedence for hydrolysis of urea via a cyanate intermediate as an alternative mechanism for the urease-catalyzed hydrolysis of urea.Interaction of urea with a hydroxide-bridged dinuClear nickel center: An alternative model for the mechanism of ureasex120200037#N/AFALSE
3147
ja00018a02710.1021/ja00018a027FALSEhttps://doi.org/10.1021/ja00018a027FAJER, JJ. Am. Chem. Soc.The reductive chemistry of a series of progressively more saturated Ni(II) porphyrins, derived from anhydromesorhodochlorin XV methyl ester, has been examined as models of F430. CyClic voltammetry, spectroelectrochemistry, electron paramagnetic resonance, and X-ray absorption studies are used to characterize the parent compounds and their reduction products. Within the Ni(II) porphyrin, chlorin, isobacteriochlorin (iBC), and hexa- and octahydro porphyrin series, only the iBCs are reduced to Ni(I). The other compounds yield pi-anion radicals or pi-radicals with some metal character. The structure of one of the iBCs in the series has been determined by single-crystal X-ray diffraction and used to validate EXAFS results. Crystallographic data for Ni(II) anhydromesorhodoisobacteriochlorin methyl ester with rings C and D reduced, 3, are the following: space group P2(1), a = 13.688 (1) angstrom, b = 8.124 (1) angstrom, c = 14.178 (1) angstrom, beta = 111.83 (1)degrees, V = 1463.6 angstrom3, and Z = 2. The structure was refined against 1226 data points to R(F) = 0.058 and R(wF) = 0.056. Saturation of the macrocyCles affects their electronic configurations as evidenced by changes in redox and optical properties as well as sites of reduction. In addition, structural factors emerge as significant determinants of the chemistry of the Ni compounds. Their ability to form Ni(I) or hexacoordinate high-spin Ni(II) requires that the macrocyCles be flexible enough to accommodate the conformational changes that accompany reduction to Ni(I) or axial ligation of square-planar Ni(II). Thus, interdependent electronic and structural factors control the reactivity of the models considered here and, by analogy, that of F430 as well.MODELS OF FACTOR-430 - STRUCTURAL AND SPECTROSCOPIC STUDIES OF NI(II) AND NI(I) HYDROPORPHYRINSx97199181#N/AFALSE
3148
ja00018a01910.1021/ja00018a019FALSEhttps://doi.org/10.1021/ja00018a019GIBBS, EJJ. Am. Chem. Soc.Binding of ethidium to DNA increases the fluorescence efficiency of the molecular ion by about 1 order of magnitude. Quenching of the fluorescence of such an ethidium.DNA complex by tetrakis(4-N-methylpyridyl)porphine (H2T4), and its nickel(II) and zinc(II) derivatives (NiT4 and ZnT4), was investigated in the present study. Results of absorbance and fluorescence measurements obtained for these systems are consistent with a mechanism for quenching that does not involve appreciable displacement of ethidium from the nuCleic acid. Sten-Volmer-type plots are nonlinear and can be fit satisfactorily by an equation of the form [GRAPHICS] in which [Q] is the concentration of the porphyrin quencher and sigma is the minimum number of base pairs between ethidium (E+) and the porphyrin required to permit the excited fluorophore to emit a photon. It can be conCluded from these studies that, in the presence of DNA, porphyrins are capable of efficiently quenching the fluorescence of an excited ethidium ion at a distance of 25-30 angstrom.LONG-RANGE FLUORESCENCE QUENCHING OF ETHIDIUM ION BY CATIONIC PORPHYRINS IN THE PRESENCE OF DNAx209199139#N/AFALSE
3149
ja00038a02310.1021/ja00038a023FALSEhttps://doi.org/10.1021/ja00038a023DARENSBOURG, MYJ. Am. Chem. Soc.Discrete compounds resulting from thc oxidation and oxygenation of nickel thiolate complexes have been isolated, separated, and characterized. Molecular oxygen or hydrogen peroxide reacted with [NN'-bis(mercaptoethyl)-1,5-diazacyClooctane]nickel(II), (BME-DACO)Ni(II) (1), to produce two oxygenates, [(mercaptoethyl)(sulfinatoethyl)diazacyClooctane]nickel(II), (MESE-DACO)Ni(II) (2), and [bis(sulfinatoethyl)diazacyClooctane]nickel(II), (BSE-DACO)Ni(II) (3), as well as a trimetallic, [(BME-DACO)Ni]2Ni2+ (4). Matrix-assisted laser desorption (MALD) ionization was used to obtain Fourier transform ion cyClotron resonance (FT-ICR) mass spectra on isotopomers of 2 and 3. Isotopic labeling experiments (O-18(2)/O-16(2) mixtures) demonstrated that both oxygens in the sulfinate ligand of 1 were derived from the same dioxygen molecule. The molecular structures of 2 and 4 were determined by X-ray crystallography. Crystallographic data are given as a, b, c; beta; space group, Z, 2-theta range, unique observed reflections, R(R(w)) (%). (MESE-DACON)Ni(II): 8.306 (3), 12.258 (3), 12.773 (4) angstrom; 101.36 (3)-degrees, P2(1)/n, 4, 4.0-degrees/50.0-degrees, 2047 (I > 2.0-sigma(I)), 2.85 (3.61). {[(BME-DACO)Ni]2Ni}Br2: 7.144 (2), 10.931 (2), 17.296 (3) angstrom; 91.72 (2)-degrees, P2(1)/c, 4, 4.0-degrees/50.0-degrees, 2053 (I > 2.0-sigma(I), 4.46 (4.84). The pseudo-square-planar NiN2S2 complex 2 has cis sulfur donor atoms and a tetrahedral twist of 18.4-degrees. The Ni-S(sulfinato) distance of 2.140 (1) angstrom is significantly shorter than the Ni-S(thiolate) distance, 2.163 (1) angstrom. The trimetallic 4 contains a staircaselike structure where two molecules of 1 serve as metallothiolate ligands to the central Ni2+ creating an NiS4 square plane (dihedral angle between best square planes = 103.4-degrees).ISOTOPIC LABELING INVESTIGATION OF THE OXYGENATION OF NICKEL-BOUND THIOLATES BY MOLECULAR-OXYGEN132199223#N/ATRUE
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ja000372810.1021/ja0003728FALSEhttps://doi.org/10.1021/ja0003728Caminiti, RJ. Am. Chem. Soc.Local structure of Fe(III), Cr(LU), and Zn(II) cations has been determined on the amorphous sample by means of the difference method used for liquid systems. We recorded energy-dispersive X-ray diffraction spectra of a chelating resin (Chelex 100), containing paired iminodiacetate ions coupled to a styrene-diVinylbenzene support, in several ionic forms. Coordination geometry of Fe(III), Cr(III), and Zn(LI) metal cations with Chelex 100 resin ligand sites, and conformation of the ligand groups have been determined.Structural characterization of complexes between iminodiacetate blocked on styrene-diVinylbenzene matrix (Chelex 100 resin) and Fe(III), Cr(III), and Zn(II) in solid phase by energy-dispersive X-ray diffraction59200129#N/ATRUE
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ja00034a06010.1021/ja00034a060FALSEhttps://doi.org/10.1021/ja00034a060DAHL, LFJ. Am. Chem. Soc.A NEW FAMILY OF 14-VERTEX HEXACAPPED METAL CUBES WITH MAIN GROUP-IV (14) ATOMS - SYNTHESIS AND STRUCTURAL-BONDING ANALYSIS OF NI9(MU-4-GEET)6(CO)8 CONTAINING A NICKEL-CENTERED NI8(MU-4-GE)6 CUBIC CAGE WITH AN UNUSUAL ELECTRON COUNT33199229#N/ATRUE
3152
ja00032a01910.1021/ja00032a019FALSEhttps://doi.org/10.1021/ja00032a019Pan, YJ. Am. Chem. Soc.Ab initio MO/SD-CI calculations of several Ni(I)- and Ni(II)-CO2 complexes indicate that CO2 can coordinate to Ni(I)F(NH3)4, yielding a stable eta-1-CO2 complex, but cannot to [Ni(II)F(NH3)4]+, [Ni(I)(NH3)4]+, and [Ni(I)(NH3)5]+. The HOMO of Ni(I)F(NH3)4(eta-1-CO2) is largely contributed from the O p(pi) orbital and lies higher in energy than the HOMO (nonbonding pi-orbital) of the uncomplexed CO2. At the same time, the electron density increases around the O atom upon CO2 coordination. As a result, the coordinated CO2 in Ni(I)F(NH3)4(eta-1-CO2) is activated to electrophilic attack and is expected to undergo facile protonation. MO calculations show that the second one-electron reduction can easily occur in the protonated species [NiF(NH3)4(CO2H)]+, yielding the triplet state of [NiF(NH3)4(CO2H)], but cannot in the unprotonated species NiF(NH3)4(CO2). The second reduction significantly weakens the C-OH bond, which suggests that OH- easily dissociates from [NiF(NH3)4(CO2H)], yielding the triplet state of [Ni(II)F(NH3)4(CO)]+. The CO coordinate bond to Ni(II) is calculated to be weak, which suggests that CO easily dissociates from Ni(II). All these results support Sauvage's reaction mechanism of electrocatalytic reduction of CO2 by NiCl2(cyClam).AN ABINITIO MO/SD-CI STUDY OF MODEL COMPLEXES OF INTERMEDIATES IN ELECTROCHEMICAL REDUCTION OF CO2 CATALYZED BY NICl2(CYClAM)50199257#N/ATRUE
3153
ja00016a07610.1021/ja00016a076FALSEhttps://doi.org/10.1021/ja00016a076VOGL, OJ. Am. Chem. Soc.HALOALDEHYDE POLYMERS. 51. HELIX-SENSE REVERSAL OF ISOTACTIC CHLORAL OLIGOMERS IN SOLUTIONx101199121#N/AFALSE
3154
ja00016a03710.1021/ja00016a037FALSEhttps://doi.org/10.1021/ja00016a037SABAT, MJ. Am. Chem. Soc.A direct method for the conversion of conjugated enals and enones into [1-[(triAlkylsilyl)oxy]allyl]nickel(II) chloride complexes is described. Reaction of R1CH = CR2CHO (R1 = H, Me, Ph; R2 = H and R1 = H; R2 = Me) with Ni(COD)2 (COD = 1,5-cyClooctadiene) and ClSiMe2R3 (R3 = Me or t-Bu) affords bis[[1,2,3-eta-3-1-[(triAlkylsilyl)oxy]-2-propenyl](mu-chloro)nickel(II)] complexes 1a-f as burgundy-red crystalline solids in high to excellent yields (86-98%). The X-ray crystal structure of 1c confirms the eta-3-bonding mode for the allyl ligand and provides evidence of significant overlap of oxygen lone pair electron density with the allyl pi-system. Reaction of 3-buten-2-one with Ni(COD)2 and Me3SiCl similarly affords bis[[1,2,3-eta-3-1-methyl-1-[(trimethylsilyl)oxy]-2-propenyl](mu-chloro)nickel(II)] (1g) in 72% yield, while the corresponding 2-cyClopentenone reaction fails, giving rise to a nickel metal mirror. The latter reaction does, however, succeed when conducted in the presence of pyridine, giving bis(pyridine)(chloro)[1,2,3-eta-3-1-[(tert-butyldimethylsilyl)oxy]-2-cyClopentenyl]nickel(II) complex (1h) in 95% yield. Irradiation of 1e (R1 = R2 = H; R3 = t-Bu) in the presence of 2-iodopropane affords tert-butyldimethylsilyl (E)-enol ether 2a in 78% yield (E:Z = 10:1). Similar results are observed with [1-(triAlkylsilyl)oxy]allyl]nickel(II) chloride complexes generated in situ from propenal, 2-methylpropenal, 2-butenal, 2-methyl-2-butenal, hexenal, and 3-buten-2-one, in coupling reactions with 1-iodobutane, 2-iodopropane, 1-bromoethene, 2-bromopropene, bromobenzene, o-bromobenzaldehyde, and isobutyryl chloride, affording the corresponding silyl (E)-enol ethers in 60-78% isolated, purified yield, based on Ni(1,5-COD)2. High C(3) regioselectivities (> 20:1) are observed for all of the C(3)-unsubstituted enals, while lower regioselectivities, in the range of 4-6:1 before purification, are observed for the C(3)-substituted enals; regioisomerically pure materials are obtained upon chromatography. Moderate to high E:Z stereoselectivities (E:Z = 4-15:1 before purification; E:Z = 20-50:1 after chromatography) are observed in all cases, save the reaction of isobutyryl chloride with 1e and the reaction of the 3-buten-2-one-derived allylnickel complex with 2-bromopropene, both of which give 1:1 E:Z ratios. In a more convenient, economical, and general variant, Ni(COD)2 is generated in situ via the sodium metal reduction of NiCl2(pyridine)4 (in turn prepared from NiCl2(H2O)6) in the presence of cyClooctadiene and reacted with the enal or enone in the presence of ClSiMe2R3 to afford the [1-[(triAlkylsilyl)oxy]allyl](chloro)(pyridine)nickel(II) complex, which is treated with the halocarbon and irradiated to afford the usual silyl enol ether products. Yields of 63-84%, based on enal or enone, were observed in reactions with propenal, (E)-2-hexenal, 2-cyClopentenone, and 2-cyClohexenone in reactions with bromoethene, bromobenzene, and 1-iodobutane using this procedure.A PRACTICAL REVERSED-POLARITY ALTERNATIVE TO ORGANOCUPRATE CONJUGATE ADDITION CHEMISTRY - HALOCARBON COUPLING REACTIONS OF ENAL-DERIVED AND ENONE-DERIVED ALLYLNICKEL REAGENTSx67199139#N/AFALSE
3155
ja00030a01710.1021/ja00030a017FALSEhttps://doi.org/10.1021/ja00030a017THIEL, PAJ. Am. Chem. Soc.We have studied the adsorption of HCOOH on Pt(111) at 80-100 K and its conversion to formate with increasing surface temperature. The techniques employed are thermal desorption spectroscopy and high-resolution electron energy loss spectroscopy. At very low exposures (< 0.2 langmuir), we Posit that HCOOH exists molecularly as monomers or discrete dimer pairs. As exposure increases, there is evidence for hydrogen-bonded chains with the molecular plane of HCOOH nearly parallel to the surface, At an exposure of 0.2 L, these chains resemble the solid-phase beta-polymorph as indicated by the vibrational frequencies of the OH out-of-plane bending vibration. Heating this surface causes the chains to break apart into discrete dimer pairs, followed by deprotonation to a bridging formate adspecies. The formate decomposes between 210 K and 280 K, causing CO2 desorption and leaving hydrogen adatoms. Increasing the exposure above 0.6 L causes the chains to adopt a structure similar to the denser alpha-polymorph. Heating this surface causes molecular desorption in two states. One is centered at 160 K and is dominated by gaseous HCOOH dimers. Desorption in this state leaves bridging formate and beta-polymorphic HCOOH coexistent on the surface. The other is centered at 200 K and is primarily gaseous monomers. Desorption in this state leaves only the formate adspecies. Its decomposition then proceeds as on the surface exposed to 0.2 L HCOOH.THE TEMPERATURE AND COVERAGE DEPENDENCES OF ADSORBED FORMIC-ACID AND ITS CONVERSION TO FORMATE ON PT(111)87199238#N/ATRUE
3156
ja00026a01710.1021/ja00026a017FALSEhttps://doi.org/10.1021/ja00026a017SCOTT, RAJ. Am. Chem. Soc.We have used molecular mechanics calculations to investigate the effect of macrocyCle reduction on core-hole size and flexibility of a series of metallo(hydro)porphyrin molecules. MacrocyCle reduction at beta-pyrrole positions results in an increase in core size, whereas reduction at methine positions results in a decrease in core size. The tetrapyrroles are found to become significantly more flexible (susceptibile to S4 ruffling) only when reduction occurs at methine positions. These results are used to explain the unique ligand-binding ability of the nickel-tetrapyrrole F430 cofactor of the S-methyl coenzyme M reductase enzyme of methanogenic bacteria. Molecular mechanics also predicts the increased axial-ligand affinity of the native F430 isomer compared to the 12,13-diepimer, as a result of the increase in macrocyCle torsional strain in the 4-coordinate native isomer.CORE SIZE AND FLEXIBILITY OF METALLOHYDROPORPHYRIN MACROCYClES - IMPLICATIONS FOR F430 COORDINATION CHEMISTRY33199125#N/ATRUE
3157
ja000253s10.1021/ja000253sFALSEhttps://doi.org/10.1021/ja000253sRe, NThe porphyrinogen-porphodimethene relationship leading to novel synthetic methodologies focused on the modification and functionalization of the porphyrinogen and porphodimethene skeletons2000#N/ATRUE
3158
ja00013a02210.1021/ja00013a022https://doi.org/10.1021/ja00013a022SHIRO, MJ. Am. Chem. Soc.A novel tetradentate, dithia diamide 9 (6,6-dimethyl-5,7-dioxo-1,11-dithia-4,8-diazacyClotetradecane, ''dioxo-[14]aneN2S2'') and a pentadentate, trithia diamide macrocyClic ligand 10 (12,12-dimethyl-11,13-dioxo-1,4,7-trithia-10,14-diazacyClohexadecane, ''dioxo[16]aneN2S3'') have been synthesized and their ligand properties examined. They smoothly encapsulate only divalent noble metal ions Pt(II) (to 17 and 19, respectively) and Pd(II) (to 18 and 20, respectively) but not other typical transition-metal ions, Cu(II), Ni(II), or Co(II). Moreover, 9 and 10 can effectively remove Pt(II) from cis-[Pt(II)(NH3)2Cl2] to yield Pt(II)-in complexes 17 and 19, respectively. Pt(II) complex 19 possesses a four-coordinated, square-planar geometry with (N-)2S2 donors (N- denotes a deprotonated amide anion), where the central S(4) atom is not coordinated, as shown by the X-ray crystal structure resolved by the heavy-atom method with 2543 unique reflections with (F(o)) > 4-sigma(F(o)). Final R and R(w) were 0.040 and 0.060, respectively: monoClinic, space group P2(1)/c with a = 11.753 (6) angstrom, b = 9.574 (3) angstrom, and c = 19.183 (9) angstrom, beta = 126.78 (3) degrees, and V = 1729 (1) angstrom 3; rho-c = 2.096 g cm-3 for Z = 4, and formula weight 545.62. The cyClic voltammetry of 19 in dimethyl formamide (DMF) displays a 2e- oxidation at +0.81 V vs SCE (Pt(II) --> Pt(IV)) and a 2e- reduction at +0.32 V (Pt(IV) --> Pt(II)), implying that the Pt(II) state is stabilized by the square-planar (N-)2S2 coordination and that the electrochemically oxidized Pt(IV) state requires additional axial S(4) and DMF donors for stabilization. The two amide anions in Pt(II)-in complexes 17 and 19 are reversibly protonated to Pt(II)-out complexes 27 and 28. Treatment of 28 with an equimolar amount of 10 yields 2:1 macrocyCle-Pt(II) complex 29. In 9 and 10 discriminating functions are endowed by the combination of the characteristic S donors and amide groups in the macrocyClic skeleton to concertedly work only on Pt(II) and Pd(II) ions.DESIGN OF DISCRIMINATING HOSTS FOR NOBLE-METAL IONS WITH DOUBLE FUNCTIONS OF THIA AND AMIDE DONORS IN MACROCYClIC STRUCTURESx27199137#N/AFALSE
3159
ja00023a02310.1021/ja00023a023FALSEhttps://doi.org/10.1021/ja00023a023HALTIWANGER, RCELECTROCHEMICAL REDUCTION OF CO2 CATALYZED BY [PD(TRIPHOSPHINE)(SOLVENT)](BF4)2 COMPLEXES - SYNTHETIC AND MECHANISTIC STUDIES1991#N/ATRUE
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ja00022a04710.1021/ja00022a047FALSEhttps://doi.org/10.1021/ja00022a047Shi, ZZJ. Am. Chem. Soc.C2-SYMMETRICAL BIS(PHOSPHOLANES) AND THEIR USE IN HIGHLY ENANTIOSELECTIVE HYDROGENATION REACTIONS413199122#N/ATRUE
3161
ja00022a03710.1021/ja00022a037FALSEhttps://doi.org/10.1021/ja00022a037PERICHON, JJ. Am. Chem. Soc.The incorporation of carbon dioxide into nonactivated alkynes catalyzed by electrogenerated nickel-bipyridine complexes affords alpha,beta-unsaturated acids in moderate to good yields. The electroCarbonylation reaction was undertaken on a preparative scale in the presence of a sacrificial magnesium anode: the formation of acids from alkynes is stoichiometric with respect to the nickel complex if performed in a two-compartment cell but can be made catalytic in a single-compartment cell. An intermediate nickelacyCle was isolated from the reaction with 4-octyne. The Cleavage of this metallacyCle by magnesium ions is the key step to explain catalysis.FROM STOICHIOMETRY TO CATALYSIS - ELECTROREDUCTIVE COUPLING OF ALKYNES AND CARBON-DIOXIDE WITH NICKEL BIPYRIDINE COMPLEXES - MAGNESIUM-IONS AS THE KEY FOR CATALYSIS127199159#N/ATRUE
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ja000116v10.1021/ja000116vFALSEhttps://doi.org/10.1021/ja000116vHall, MBJ. Am. Chem. Soc.Optimized structures for the redox species of the diiron active site in [Fe]-hydrogenase as observed by FTLR and for species in the catalytic cyCle for the reversible H(2) oxidation have been determined by density- functiona' calculations on the active site model, [(L)(CO)(CN)Fe(mu -PDT)(mu -CO)Fe(CO)(CN)(L ')](q) (L = H(2)O, CO, H(2), H(-) PDT = SCH(2)CH(2)CH(2)S, L ' = CH(3)S(-), CH(3)SH; q = 0, 1-, 2-, 3-). Analyticai DFT frequencies on model complexes (mu -PDT)Fe(2)(CO)(6) and [(mu -PDT)Fe(2)(CO)(4)(CN)(2)](2-) are used to talibrate the calculated CN(-) and CO frequencies against the measured FTIR bands in these model compounds. By comparing the predicted CN(-) and CO frequencies from DFT frequency calculations on the active site model with the observed bands of D. vulgaris [Fe]-hydrogenase under various conditions, the oxidation states and structures for the diiron active site are proposed. The fully oxidized, EPR-silent form is an Fe(II)-Fe(II) species. Coordination of H(2)O to the empty site in the enzyme's diiron active center results in an oxidized inactive form (H(2)O)Fe(II))-Fe(II). The calculations show that reduction of this inactive form releases the H(2)O to provide an open coordination site for H(2). The partially oxidized active state, which has an S = 1/2 EPR Signal, is an; Fe(I)-Fe(II) species. Fe(I)-Fe(I) species with and without bridging CO account for the fully reduced, EPR-silent state. For this fully reduced state.;the species without the bridging CO is slightly more stable than the structure with the bridging CO,The correlation coefficient between the predicted CN- and CO frequencies forth; proposed! model species and the measured CN- and CO frequencies in the enzyme is 0.964. The proposed species are so consistent with the EPR, ENDOR, and Mossbauer spectroscopies for the enzyme states.' Our results preClude the presence of Fe(III)-Fe(II) or Fe(III)-Fe(III) states among those observed by FTIR. A proposed reaction mechanism (catalytic cyCle) based on the DFT calculations shows that heterolytic Cleavage of H(2) can occur from (eta (2)-H(2))Fe(II)-Fe(II) via a proton transfer to spectator ligands. Proton transfer to a CN(-) ligand is thermodynamically favored bur kinetically unfavorable over proton transfer to the: bridging S of the PDT. Proton mi,oration from a metal hydride to a base (S, CN, or basic protein site) results in a two-electron reduction at the metals and explains in part the active site's dimetal requirement and ligand framework which supports low-oxidation-state metals. The calculations also suggest that species with a protonated Fe-Fe bond could be involved if the protein could accommodate such species.Modeling the active sites in metalloenzymes. 3. Density functional calculations on models for [Fe]-hydrogenase: Structures and vibrational frequencies of the observed redox forms and the reaction mechanism at the diiron active centerx156200153#N/AFALSE
3163
ja00020a02010.1021/ja00020a020FALSEhttps://doi.org/10.1021/ja00020a020ESPENSON, JHJ. Am. Chem. Soc.The reactions of Ni(1,4,8,11-tetraazacyClotetradecane)2+ with Alkyl radicals were studied. Data were collected for the R,R,S,S (or beta) and R,R,R,R (or alpha) isomers. The reactions form sigma-bonded organometallic cations, as in the equation NiL2+ + R. + H2O reversible RNiL(H2O)2+. The values of the rate constants for the forward (colligation) and reverse (homolysis) reactions were measured separately by laser flash photolysis techniques with a kinetic probe. The values of k(col) lie in the order CH3 >> primary >> secondary, and just the reverse order applies to k(hom). Thus the equilibrium constants for formation of RNiL(H2O)2+, given by k(col)/k(hom), are most favorable for methyl and least favorable for secondary Alkyls. These nickel-Alkyl bonds are much weaker than those in corresponding cobalt and chromium complexes. For that reason, values of k(col) vary widely with the nature of R.. Values of k(col) are considerably higher for alpha-Ni(cyClam)2+ than for the beta-isomer, and the reverse order applies to k(hom). Also, the alpha-isomer has the highest equilibrium constant for the formation equilibrium. The kinetic and thermodynamic trends can be rationalized by structural effects.FORMATION AND HOMOLYSIS OF ORGANONICKEL(III) COMPLEXES36199124#N/ATRUE
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ja00010a00810.1021/ja00010a008FALSEhttps://doi.org/10.1021/ja00010a008JANDA, KCJ. Am. Chem. Soc.Laser induced thermal desorption measurements are used to measure the kinetics of isotope exchange between CO molecules chemisorbed on a potassium-promoted Ni(111) surface: (CO)-C-13-O-16 + (CO)-C-12-O-18 arrow pointing right over arrow pointing left (CO)-C-13-O-18 + (CO)-C-12-O-16. The efficiency of the reaction is maximized for a 1:1 K:CO stoichiometry and a 0.3 adspecies/Ni ratio for both K and CO. Over the temperature range 400-525 K the isotope exchange reaction has an apparent Activation energy of only 72 +/- 4 kJ/mol. Even for long reaction times and high surface temperature, however, the reaction proceeds to only 50% of the statistical limit. To explain these phenomena, we propose that the reaction proceeds via a K2C2O2 etherate intermediate adsorbed on Ni(111). This species may be of importance in the promoter action of potassium on CO chemistry on transition-metal surfaces.RATE LAW AND Activation-ENERGY OF ISOTOPE MIXING BETWEEN CHEMISORBED CO MOLECULES ON A K-PROMOTED NI(111) SURFACEx8199122#N/AFALSE
3165
ja00017a01310.1021/ja00017a013FALSEhttps://doi.org/10.1021/ja00017a013WHITTEN, JLJ. Am. Chem. Soc.The adsorption of methyl on the (111) surface of nickel is treated by using a many-electron embedding theory to describe bonding, modeling the lattice as a 28-atom, three-layer Cluster. Ab initio valence orbital configuration interaction (multiple parent) calculations carried out on a local surface region permit an accurate description of bonding at the surface. Calculated adsorption energies for CH3 on the Ni(111) surface are 39 kcal/mol at the 3-fold sites and 36 and 34 kcal/mol at the bridge and the atop atom sites with the equilibrium Ni-C distances of 2.35, 2.34, and 2.03 angstrom, respectively. Calculated CH3-(Ni surface) perpendicular stretching frequencies are 369, 296, and 416 cm-1 for the 3-fold, bridge, and atop sites. In the equilibrium geometry methyl hydrogens are in a plane parallel to the surface with a nearly tetrahedral structure. A low C-H vibrational frequency is calculated at 2627 cm-1 if one of the hydrogens is tilted to give a C-H bond parallel to the surface, and CH3 is shifted away from the 3-fold center by 0.67 au, which puts one of the hydrogens directly above a Ni atom. This geometry is only 1.6 kcal/mol higher in energy than the calculated equilibrium geometry for which normal C-H vibrational frequencies of around 3000 cm-1 are calculated. The reaction of chemisorbed CH2(ads) + H(ads) = CH3(ads) on the surface is 13 kcal/mol exothermic. An energy barrier occurs when CH2 and H are moved from infinite separation to form CH3. A combination of covalent s and d bonding characterizes the bonding of CH3 to the nickel surface.ABINITIO CHEMISORPTION STUDIES OF CH3 ON NI(111)86199146#N/ATRUE
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ja00008a03910.1021/ja00008a039FALSEhttps://doi.org/10.1021/ja00008a039SIEBERT, WJ. Am. Chem. Soc.Thermal displacement of the cyClooctatriene ligand in (eta-6-C8H10)Fe(II)(Et2C2B4H4) by indene at 180-degrees-C afforded orange air-stable (eta-6-C9H8)Fe(II)(Et2C2B4H4) (1) in high yield together with a minor product (2), which is evidently a dimer of 1. The eta-6-coordination of indene to iron in 1 was confirmed by X-ray diffraction. Treatment of 1 with tetramethylethylenediamine (TMEDA) gave the yellow decapitated product (eta-6-C9H8)Fe(II)(Et2C2B3H5) (3). Deprotonation of 1 at -78-degrees-C gave a violet anionic intermediate; reaction of that species with dry HCl at -78-degrees-C regenerated 1. However, when the anion was warmed to 0-degrees-C or higher, proton NMR data indicated that a haptotropic rearrangement occurred to produce the (eta-5-C9H7)Fe(Et2C2B4H4)- anion 4-. Treatment of the latter species with HCl.Et2O gave the Fe-protonated complex (eta-5-C9H7)FeH(Et2C2B4H4) (5), which on reaction with NaH regenerated 4-. Exposure of 4- or 5 to oxygen gave magenta, paramagnetic (eta-5-C9H7)Fe(III)(Et2C2B4H4) (4), whose ESR spectrum supports the assignment of an Fe(III) oxidation state; reduction of 4 with potassium metal afforded 4- quantitatively. The reaction of the 4- anion with LiCp*/NiBr2, and with the cobalt-diborole complex CpCo(Et2MeC3B2Et2)- and NiBr2, generated, respectively, the compounds (eta-5-C9H7)Fe-(Et2C2B4H4)NiCp* (6) and (eta-5-C9H7)Fe(Et2C2B4H4)Ni(Et2MeC3B2Et2)CoCp (7). An X-ray diffraction study of 6 established that these species incorporate eight-vertex FeNiC2B4 Clusters, representing the first Clear examples of cage expansion of a seven-vertex metallacarborane via metal insertion. In 7, the nickel atom also participates in a seven-vertex NiCoC3B2 Cluster. In an analogous reaction, Cp*Fe(Et2C2B4H4)- (8-, a C5Me5 counterpart of 4-) and LiCp*/NiBr2 gave Cp*Fe(Et2C2B4H4)NiCp* (9), which was assigned an FeNiC2B4 Cluster geometry corresponding to that of 6. A similar reaction of 8- with the cobalt-diborole complex CpCo(Et2HC3B2Me2)- produced Cp*Fe(Et2C2B4H4)Ni(Et2HC3B2Me2)CoCp (10), whose proposed structure is analogous to that of 7. The new compounds were isolated via column and/or plate chromatography on silica and characterized from their H-1, B-11, and (in some cases) C-13 NMR spectra; infrared and mass spectra; ESR spectra on 4; and crystallographic studies on 1 and 6. In addition, cyClic voltammetry was conducted on the compounds 1, 3, 4, 5, and 7. The electrochemical behavior of most species examined was complex, with oxidation and/or reduction leading in several cases to chemical reactions whose products generate further signals during cyClic voltammetry. Crystal data for 1: mol wt 301.4; space group P2(1)/c; Z = 4; a = 8.267 (3), b = 14.459 (6), c = 13.512 (5) angstrom; beta = 103.04 (3)-degrees; V = 1574 angstrom-3; R = 0.041 for 2081 reflections having F(o)2 > 2.0-sigma(F(o)2). Crystal data for 6: mol wt 494.3; space group P2(1)/a; Z = 4; a = 14.529 (8), b = 8.507 (5), c = 20.374 (12) angstrom; beta = 93.09 (4)-degrees; V = 2514 angstrom-3; R = 0.038 for 3754 reflections having F(o)2 > 2.0-sigma(F(o)2).ORGANOTRANSITION-METAL METALLACARBORANES .19. INDENYLIRON(II) AND INDENYLIRON(III) COMPLEXES AND RELATED SPECIES - ETA-6-]ETA-5 HAPTOTROPIC REARRANGEMENT, ELECTROCHEMISTRY, AND POLYHEDRAL EXPANSION OF (ARENE)FE(ET2C2B4H4) ClUSTERSx35199151#N/AFALSE
3167
ja00017a01010.1021/ja00017a010FALSEhttps://doi.org/10.1021/ja00017a010CHAMPENEY, DCJ. Am. Chem. Soc.The method of isotopic substitution in neutron diffraction is applied to study the coordination environment of the Ni2+ ion in a 0.956 m solution of Ni(CF3SO3)2 in fully deuterated ethylene glycol (EG). It is shown that EG molecules do not act as monodentate ligands but that Ni(EG)3(2+) tris-chelate complexes are formed. There is no evidence of inner-sphere complexing by the CF3SO3- anion, but the data are consistent with a spatially well defined hydrogen bond between EG ligands in the first and second coordination shells of the cation. If this bond is assumed to be linear, then it is of length approximately 1.8 (1) angstrom. The number of second-shell EG molecules that participate in this hydrogen-bond process is estimated at six, Furthermore, there is evidence for weak ordering of the Ni2+ correlations on a length scale of 10 less-than-or-similar-to r (angstrom) less-than-or-similar-to 16. The stability of the Ni(EG)3(2+) complex is briefly discussed.STRUCTURE OF NI2+ SOLUTIONS IN ETHYLENE-GLYCOL BY NEUTRON-DIFFRACTION - AN OBSERVED HYDROGEN-BOND BETWEEN THE SOLVENT LIGANDS IN THE 1ST AND 2ND CATION COORDINATION SHELLS18199156#N/ATRUE
3168
ja00017a00910.1021/ja00017a009FALSEhttps://doi.org/10.1021/ja00017a009GOODMAN, DWIRAS OBSERVATIONS OF PHASE-TRANSITIONS AT NI/MO(110) AND CO/MO(110) INTERFACES1991#N/ATRUE
3169
ja00005a03410.1021/ja00005a034FALSEhttps://doi.org/10.1021/ja00005a034JUTAND, AJ. Am. Chem. Soc.Electrochemical reduction of Pd(II)Cl2(PPh3)2 affords a low-ligated zerovalent palladium complex which is shown to undergo a facile oxidative addition by (Z)- or (E)-1,2-dichloroethylene. In each case, the reaction is shown to proceed rapidly and quantitatively to the corresponding cis-sigma-Vinylpalladium(II) complex. The formation of the cis intermediate occurs via two reversible steps: (i) a rapid and exergonic coordination of the dihaloalkene to the low-ligated palladium(0) is followed by (ii) an inner-shell oxidative addition step. For the E isomer an additional step then involves the reversible and exergonic coordination of a second molecule of dichloroethylene to the cis-sigma-Vinylpalladium(II) complex. On a much longer time scale, the cis-sigma-Vinylpalladium(II) complexes isomerize to the more stable trans-sigma-Vinylpalladium(II) ones. The consequences of the rates and of the reversibility of the overall oxidative addition process for palladium-catalyzed nuCleophilic substitutions or cross-coupling reactions involving carbon-halogen Vinylic bonds are discussed.RATES AND MECHANISM OF THE REVERSIBLE OXIDATIVE ADDITION OF (Z)-1,2-DICHLOROETHYLENE AND (E)-1,2-DICHLOROETHYLENE TO LOW-LIGATED ZERO-VALENT PALLADIUMx58199167#N/AFALSE
3170
ja00016a08210.1021/ja00016a082FALSEhttps://doi.org/10.1021/ja00016a082CHENG, CHFACILE Aryl Aryl EXCHANGE BETWEEN THE PALLADIUM CENTER AND PHOSPHINE-LIGANDS IN PALLADIUM(II) COMPLEXES1991#N/ATRUE
3171
ja00003a06110.1021/ja00003a061FALSEhttps://doi.org/10.1021/ja00003a061PARVEZ, MJ. Am. Chem. Soc.COMPLEXATION THROUGH NITROGEN IN COPPER AND NICKEL-COMPLEXES OF SUBSTITUTED UREASx64199145#N/AFALSE
3172
ja00003a02310.1021/ja00003a023FALSEhttps://doi.org/10.1021/ja00003a023FUJITA, EJ. Am. Chem. Soc.Nickel(II) complexes of tetraazamacrocyCles undergo one-electron reduction to produce either a nickel(I) complex or a nickel(II) anion radical. Both reduced species react with CO. The nature of the parent Ni(II) complexes, the reduced species, and the Ni(I)-CO complexes were studied in CH3CN by means of EXAFS and UV-vis spectroscopy to characterize structural differences as a function of oxidation state and axial ligation of the metal in solution. The EXAFS results reveal that the reduction of Ni(II) to Ni(I) results not only in an expansion of the macrocyCle core (0.1 angstrom change in Ni-N bond distance) but also a distortion. On the other hand, the Ni(II) to Ni(II) anion radical reduction leaves the geometry around the nickel atom unchanged. The anion radical of Ni(II) tetraene+ (NiL3+, L3 = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyClotetradeca-1,3,8,10-tetraene) dimerizes in solution forming diamagnetic adducts. The monomer-dimer equilibrium constant was determined to be K1 = (5.5 +/- 1.0) x 10(4) M-1 from the electronic spectra. EXAFS data on CO adducts of Ni(I)L1,-L2, and -L3 (L1 = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyClotetradeca-4,11-diene, L2 = 5,7,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyClotetradeca-4,14-diene) Clearly indicate that these are five-coordinate complexes with a short Ni-C bond. Both Ni-N(imine) and Ni-N(amine) distances in the CO adducts of the Ni(I) complexes increase quite dramatically compared to those in the parent Ni(II) and Ni(I) complexes. The structure of the nickel(I) complex has been determined from single-crystal X-ray diffraction data collected by using Mo K-alpha radiation. Crystallographic data are as follows: space group P2/n with a = 15.717 (6) angstrom, b = 8.196 (2) angstrom, c = 16.049 (6) angstrom, beta = 100.67 (3) degrees, V = 2031 (2) angstrom3, Z = 4. The two square-planar nickel atoms in the asymmetric unit are situated on crystallographic inversion centers. The Ni-N(imine) are 1.988 (7) and 1.979 (7) angstrom and Ni-N(amine) distances are 2.063 (6) and 2.068 (6) angstrom, which are in good agreement with the EXAFS data.EXAFS STUDIES OF NI(II), NI(I), AND NI(I)-CO, TETRAAZAMACROCYClES AND THE CRYSTAL-STRUCTURE OF (5,7,7,12,14,14-HEXAMETHYL-1,4,8,11-TETRAAZACYClOTETRADECA-4,11-DIENE)NICKEL(I) PERCHLORATEx74199197#N/AFALSE
3173
ja00015a06510.1021/ja00015a065FALSEhttps://doi.org/10.1021/ja00015a065BURROWS, CJJ. Am. Chem. Soc.DNA MODIFICATION - INTRINSIC SELECTIVITY OF NICKEL(II) COMPLEXES91199127#N/ATRUE
3174
ja00001a04810.1021/ja00001a048FALSEhttps://doi.org/10.1021/ja00001a048SZALDA, DJJ. Am. Chem. Soc.The cobalt(I) complexes of several 14-membered tetraazamacrocyCles were prepared in CH3CN by either electrochemical or sodium amalgam reduction. The electronic absorption spectra and other physical properties of the Co(I), Co(I)-CO2 and CO(I)-CO complexes are reported. The CO2 and CO binding constants were determined by spectroscopic and/or electromechanical methods. The binding constants range from 5 x 10(4) to greater-than-or-equal-to 3 x 10(8) M-1 for CO and from less-than-or-equal-to 0.5 to > 10(6) M-1 for CO2 at 25-degrees-C. Both binding constants increase as the CoL2+/+ reduction potentials (which range from -0.34 to -1.65 V vs SCE in CH3CN) become more negative. Thus charge transfer from Co(1) to CO2 or CO is an important factor in stabilizing these adducts. However, hydrogen-bonding interactions between the bound CO2 and amine macrocyCle N-H protons may serve to additionally stabilize the adduct in some cases, while steric repulsion by the macrocyCle methyl groups may destabilize the adducts, depending upon the complex. The equilibrium ratios of N-meso and N-rac isomers of (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyClotetradeca-4,11-diene cobalt(I) and -(II) complexes were determined by H-1 NMR; the N-rac isomers of both predominate in CD3CN at room temperature. The crystal and molecular structure of the perchlorate sale of (3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyClotetradeca-4,11-diene cobalt(I) was determined from single-crystal X-ray diffraction data collected with use of Mo K-alpha-radiation. Crystallographic data: space group Pl with a = 8.433 (2) angstrom, b = 18.333 (4) angstrom, c = 7.257 (2) angstrom, alpha = 100.22 (2)-degrees, beta = 91.29 (2)-degrees, gamma = 87.68 (2)-degrees, V = 1103 (1) angstrom 3, Z = 2 (R = 0.085, R(w) = 0.105). The two square-planar cobalt atoms in the asymmetric unit are situated on crystallographic inversion centers.CARBON-DIOXIDE Activation BY COBALT(I) MACROCYClES - FACTORS AFFECTING CO2 AND CO BINDINGx1431991105#N/AFALSE
3175
ja00014a00210.1021/ja00014a002FALSEhttps://doi.org/10.1021/ja00014a002WILLETT, GDJ. Am. Chem. Soc.Laser (Nd/YAG, 1064 nm) ablation of Ni3S2 or NiS, monitored by Fourier transform ion cyClotron resonance mass spectrometry, yields at least 28 [Ni(x)S(y)]- ions, ranging from [NiS]- to [Ni15S10]-. The x,y combinations are 1,1; 1,2; 1,3; 2,2; 2,3; 3,2; 3,3; 4,4; 4,5; 5,4; 6,4; 6,5; 7,5; 7,6; 8,5; 8,6; 8,7; 9,6; 9,7; 10,7; 10,8; 11,7; 11,8; 12,7; 12,8; 12,11; 13,8; 15,10. [Ni2S2]- and [Ni5S4]- are unaffected by collisions with argon at 2 x 10(-7) mbar, while the ions [NiS2]-, [Ni3S3]-, and [Ni4S4]- decompose in ca 0.05 s under the same conditions. Evidence for isomeric ions with differing reactivities could be obtained for [Ni3S3]-, but sensitivity limitations preCluded reactivity measurements for larger ions. Geometrical structures are postulated for all ions, based on established structural principles, and correspond in many cases to the structures of condensed phase Clusters, devoid of terminal ligands.LASER-ABLATION FTICR MASS-SPECTROMETRY OF METAL SULFIDES - GASEOUS ANIONIC [NIXSY] ClUSTERS40199186#N/ATRUE
3176
d1sc03087f10.1039/d1sc03087fFALSEhttps://doi.org/10.1039/d1sc03087fLi, WXChem. Sci.Atomically dispersed metal catalysts with high atomic utilization and selectivity have been widely studied for acetylene semi-hydrogenation in excess ethylene among others. Further improvements of activity and selectivity, in addition to stability and loading, remain elusive due to competitive adsorption and desorption between reactants and products, hydrogen Activation, partial hydrogenation etc. on limited site available. Herein, comprehensive density functional theory calculations have been used to explore the new strategy by introducing an appropriate ligand to stabilize the active single atom, improving the activity and selectivity on oxide supports. We find that the hydroxyl group can stabilize Ni single atoms significantly by forming Ni-1(OH)(2) complexes on anatase TiO2(101), whose unique electronic and geometric properties enable high performance in acetylene semi-hydrogenation. Specifically, Ni-1(OH)(2)/TiO2(101) shows favorable acetylene adsorption and promotes the heterolytic dissociation of H-2 achieving high catalytic activity, and it simultaneously weakens the ethylene bonding to facilitate subsequent desorption showing high ethylene selectivity. Hydroxyl stabilization of single metal atoms on oxide supports and promotion of the catalytic activity are sensitive to transition metal and the oxide supports. Compared to Co, Rh, Ir, Pd, Pt, Cu, Ag and Au, and anatase ZrO2, IrO2 and NbO2 surfaces, the optimum interactions between Ni, O and Ti and resulted high activity, selectivity and stability make Ni-1(OH)(2)/TiO2(101) a promising catalyst in acetylene hydrogenation. Our work provides valuable guidelines for utilization of ligands in the rational design of stable and efficient atomically dispersed catalysts.Hydroxyl improving the activity, selectivity and stability of supported Ni single atoms for selective semi-hydrogenationx0202176#N/AFALSE
3177
ja00013a02810.1021/ja00013a028FALSEhttps://doi.org/10.1021/ja00173a028SCOTT, WJPALLADIUM-CATALYZED OXYHEXATRIENE CYClIZATION - A NOVEL-APPROACH TO CYClOHEXENONE ANNULATION1991#N/ATRUE
3178
d1sc02547c10.1039/d1sc02547chttps://doi.org/10.1039/d1sc02547cMolander, GAChem. Sci.Alkene 1,2-dicarbofunctionalizations are highly sought-after transformations as they enable a rapid increase of molecular complexity in one synthetic step. Traditionally, these conjunctive couplings proceed through the intermediacy of Alkylmetal species susceptible to deleterious pathways inCluding beta-hydride elimination and protodemetalation. Herein, an intermolecular 1,2-dicarbofunctionalization using Alkyl N-(acyloxy)phthalimide redox-active esters as radical progenitors and organotrifluorB(OH)2rates as carbon-centered nuCleophiles is reported. This redox-neutral, multicomponent reaction is postulated to proceed through photochemical radical/polar crossover to afford a key carbocation species that undergoes subsequent trapping with organB(OH)2ron nuCleophiles to accomplish the carboallylation, carboalkenylation, carboalkynylation, and carboArylation of alkenes with regio- and chemoselective control. The mechanistic intricacies of this difunctionalization were elucidated through Stern-Volmer quenching studies, photochemical quantum yield measurements, and trapping experiments of radical and ionic intermediates.Photoinduced 1,2-dicarbofunctionalization of alkenes with organotrifluorB(OH)2rate nuCleophiles via radical/polar crossoverPhotocatalyst02021104#N/AFALSE
3179
ja00012a06410.1021/ja00012a064FALSEhttps://doi.org/10.1021/ja00012a064UFFELMAN, ESJ. Am. Chem. Soc.A SQUARE-PLANAR NICKEL(III) COMPLEX OF AN INNOCENT LIGAND SYSTEM96199126#N/ATRUE
3180
ja00012a04210.1021/ja00012a042FALSEhttps://doi.org/10.1021/ja00012a042MENU, MJJ. Am. Chem. Soc.NOVEL IMIDO-NICKEL(II) AND PHOSPHORANE-IMIDO-NICKEL(II) COMPLEXES - CRYSTAL AND MOLECULAR-STRUCTURE OF (MU-3-NH)(MU-3-NPME3)(NIClPME3)327199116#N/ATRUE
3181
ja00011a00410.1021/ja00011a004FALSEhttps://doi.org/10.1021/ja00011a004SMITH, KMJ. Am. Chem. Soc.Molecular mechanics calculations, based on a force field derived from a previously published normal coordinate analysis for NiOEP (1) and the X-ray structure of NiOEP B triClinic form, have been used to predict the structures of NiTPP (2), NiP(3), and several recently synthesized nickel porphyrins which bear Alkyl or phenyl groups at all 12 peripheral positions (4-10). These calculations predict that porphyrins 4 (NiOMTPP),5 (NiOETPP), 6 (NiOPTPP), 7 (NiDPP),9 (NiTC6TPP), and 10 (NiTC7TPP) adopt a saddle conformation with varying degrees of nonplanarity of the macrocyCle. To evaluate the accuracy of these calculations, a single-crystal X-ray structure of the porphyrin with the most nonplanar calculated structure (NiOPTPP) was determined. The agreement between observed and calculated structures is good, both in terms of the general molecular conformation and more subtle structural differences such as a decrease in core size and increase in the C-alpha-NC-alpha bond angle compared to planar nickel porphyrins. The structural parameters obtained from these calculations were then used to investigate the relationship between core size and the frequency of the structure-sensitive Raman lines (nu-4, nu-3, nu-2, and nu-19). The linear relationship between core size and Raman frequency has a positive slope, in contrast to the negative slope exhibited by the usual core size-Raman frequency relationship. Thus it is not the core size that determines the frequencies of the structure-sensitive Raman lines. On the other hand, the linear correlation between the C-alpha-NC-alpha angle and Raman frequency has a negative slope for both the nickel porphyrins used in this study and the metalloporphyrins of the conventional core-size relationship, suggesting a more direct relationship between this angle and the marker line frequencies.RELATIONSHIPS BETWEEN STRUCTURAL PARAMETERS AND RAMAN FREQUENCIES FOR SOME PLANAR AND NONPLANAR NICKEL(II) PORPHYRINS323199168#N/ATRUE
3182
d1sc00943e10.1039/d1sc00943ehttps://doi.org/10.1039/d1sc00943eMolander, GAChem. Sci.A dual photochemical/nickel-mediated deCarbonylative strategy for the assembly of C(sp(3))-C(sp(2)) linkages is disClosed. Under light irradiation at 390 nm, commercially available and inexpensive Hantzsch ester (HE) functions as a potent organic photoreductant to deliver catalytically active Ni(0) species through single-electron transfer (SET) manifolds. As part of its dual role, the Hantzsch ester effects a deCarbonylative-based radical generation through electron donor-acceptor (EDA) complex Activation. This homogeneous, net-reductive platform bypasses the need for exogenous photocatalysts, stoichiometric metal reductants, and additives. Under this cross-electrophile paradigm, the coupling of diverse C(sp(3))-centered radical architectures (inCluding primary, secondary, stabilized Benzylic, alpha -oxy, and alpha -amino systems) with (hetero)Aryl bromides has been accomplished. The protocol proceeds under mild reaction conditions in the presence of sensitive functional groups and pharmaceutically relevant cores.Photoactive electron donor-acceptor complex platform for Ni-mediated C(sp(3))-C(sp(2)) bond formationPhotocatalyst52021105#N/AFALSE
3183
d1sc00647a10.1039/d1sc00647aFALSEhttps://doi.org/10.1039/d1sc00647aBrechin, EKExploiting host-guest chemistry to manipulate magnetic interactions in metallosupramolecular M4L6 tetrahedral cagesx2021#N/AFALSE
3184
d1sc00573a10.1039/d1sc00573aFALSEhttps://doi.org/10.1039/d1sc00573aKornienko, NChem. Sci.The allure of metal-organic frameworks (MOFs) in heterogeneous electrocatalysis is that catalytically active sites may be designed a priori with an unparalleled degree of control. An emerging strategy to generate coordinatively-unsaturated active sites is through the use of organic linkers that lack a functional group that would usually bind with the metal nodes. To execute this strategy, we synthesize a model MOF, Ni-MOF-74 and incorporate a fraction of 2-hydroxyterephthalic acid in place of 2,5-dihydroxyterephthalic acid. The defective MOF, Ni-MOF-74D, is evaluated vs. the nominally defect-free Ni-MOF-74 with a host of ex situ and in situ spectroscopic and electroanalytical techniques, using the oxidation of hydroxymethylfurtural (HMF) as a model reaction. The data indicates that Ni-MOF-74D features a set of 4-coordinate Ni-O-4 sites that exhibit unique vibrational signatures, redox potentials, binding motifs to HMF, and consequently superior electrocatalytic activity relative to the original Ni-MOF-74 MOF, being able to convert HMF to the desired 2,5-furandiCarbonylic acid at 95% yield and 80% faradaic efficiency. Furthermore, having such rationally well-defined catalytic sites coupled with in situ Raman and infrared spectroelectrochemical measurements enabled the deduction of the reaction mechanism in which co-adsorbed *OH functions as a proton acceptor in the alcohol oxidation step and carries implications for catalyst design for heterogeneous electrosynthetic reactions en route to the electrification of the chemical industry.Rational incorporation of defects within metal-organic frameworks generates highly active electrocatalytic sites
Electrocatalytic
x0202175#N/AFALSE
3185
ja00010a04410.1021/ja00010a044FALSEhttps://doi.org/10.1021/ja00010a044MASCHARAK, PKJ. Am. Chem. Soc.The results of the analysis of Ni K-edge EXAFS data from the Ni site in Thiocapsa roseopersicina hydrogenase poised in form C are presented. Form C represents a single, reduced, active form of the enzyme. The results obtained from the analysis are consistent with a Ni ligand environment composed of 3 +/- 1 N,O donors at 2.06 angstrom and 2 +/- 1 S donors at 2.21 angstrom. These results are compared with structural data from EXAFS and crystallographic studies of a number of Ni complexes with mixed ligand environments and with the results of EXAFS analyses of the Ni sites of other hydrogenases. The latter comparisons reveal a strong similarity between the data from T. roseopersicina and the data from the Fe,Ni,Se enzyme from Desulfovibrio baculatus. Data from scattering atoms in the second and third coordination spheres indicate that the Ni center in the enzyme is near to, but not part of, an Fe,S Cluster. The data are consistent with Ni-Fe distances of 4.3 and 6.2 angstrom. Although scattering from S atoms at distances greater than 4 angstrom makes a negligible contribution to the overall EXAFS spectrum, the fits of Fourier-filtered second coordination sphere EXAFS are improved by the addition of S-scattering atoms at 4.2 angstrom. These data indicate that Ni-containing hydrogenases contain a novel Fe,S,Ni Cluster.EXAFS INVESTIGATIONS OF THE NI SITE IN THIOCAPSA-ROSEOPERSICINA HYDROGENASE - EVIDENCE FOR A NOVEL NI,FE,S ClUSTER64199180#N/ATRUE
3186
ja00009a02010.1021/ja00009a020FALSEhttps://doi.org/10.1021/ja00009a020LINDOY, LFCOMPARATIVE MOLECULAR MECHANICS STUDY OF THE LOW-SPIN NICKEL(II) COMPLEXES OF AN EXTENDED SERIES OF TETRAAZA MACROCYClES1991#N/ATRUE
3187
ja00008a00310.1021/ja00008a003FALSEhttps://doi.org/10.1021/ja00008a003JUTAND, AJ. Am. Chem. Soc.In the presence of stoichiometric amounts of carbon dioxide, and catalytic amounts of Ni(II)(dppe)Cl2, electrolysis of bromobenzene results in the nearly quantitative formation of benzoic acid with negligible production of benzene or biphenyl. The mechanism of the nickel-catalyzed electroCarbonylation is shown to proceed through a chain reaction involving Ni(0), Ni(I), Ni(II), and Ni(III) intermediates, very reminiscent of that previously established for the nickel-catalyzed coupling of bromobenzene. Based on a detailed kinetic analysis of the propagation of this catalytic chain and of its competition with the biphenyl chain, all the key steps of the catalytic chain are identified and their rate constants determined.Activation OF CARBON-DIOXIDE BY ELECTRON-TRANSFER AND TRANSITION-METALS - MECHANISM OF NICKEL-CATALYZED ELECTROCarbonylATION OF AROMATIC HALIDES971991117#N/ATRUE
3188
d0sc07099h10.1039/d0sc07099hFALSEhttps://doi.org/10.1039/d0sc07099hGlorius, FChem. Sci.Carbenes, a Class of low-valent group 14 ligand, have shifted the paradigm in our understanding of the effects of supporting ligands in transition-metal reactivity and catalysis. We now seek to move towards utilizing the heavier group 14 elements in effective ligand systems, which can potentially surpass carbon in their ability to operate via 'non-innocent' bond Activation processes. Herein we describe our initial results towards the development of scalable acyClic chelating germylene ligands (viz.1a/b), and their utilization in the stabilization of Ni-0 complexes (viz.4a/b), which can readily and reversibly undergo metathesis with ammonia with no net change of oxidation state at the Ge-II and Ni-0 centres, through ammonia bonding at the germylene ligand as opposed to the Ni-0 centre. The DFT-derived metathesis mechanism, which surprisingly demonstrates the need for three molecules of ammonia to achieve N-H bond Activation, supports reversible ammonia binding at Ge-II, as well as the observed reversibility in the overall reaction.Reversible metathesis of ammonia in an acyClic germylene-Ni-0 complexx1202153#N/AFALSE
3189
d0sc07093a10.1039/d0sc07093ahttps://doi.org/10.1039/d0sc07093aShen, SHChem. Sci.Polymeric carbon nitride (PCN) has been widely used as a metal-free photocatalyst for solar hydrogen generation from water. However, rapid charge carrier recombination and sluggish water catalysis kinetics have greatly limited its photocatalytic performance for overall water splitting. Herein, a single-atom Ni terminating agent was introduced to coordinate with the heptazine units of PCN to create new hybrid orbitals. Both theoretical calculation and experimental evidence revealed that the new hybrid orbitals synergistically broadened visible light absorption via a metal-to-ligand charge transfer (MLCT) process, and accelerated the separation and transfer of photoexcited electrons and holes. The obtained single-atom Ni terminated PCN (PCNNi), without an additional cocatalyst loading, realized efficient photocatalytic overall water splitting into easily-separated gas-product H-2 and liquid-product H2O2 under visible light, with evolution rates reaching 26.6 and 24.0 mu mol g(-1) h(-1), respectively. It was indicated that single-atom Ni and the neighboring C atom served as water oxidation and reduction active sites, respectively, for overall water splitting via a two-electron reaction pathway.Single-atom nickel terminating sp(2) and sp(3) nitride in polymeric carbon nitride for visible-light photocatalytic overall water splittingPhotocatalyst3202148#N/AFALSE
3190
ja00007a07210.1021/ja00007a072FALSEhttps://doi.org/10.1021/ja00007a072LIEBESKIND, LSJ. Am. Chem. Soc.NICKEL(0)-CATALYZED SYNTHESIS OF SUBSTITUTED PHENOLS FROM CYClOBUTENONES AND ALKYNES126199121#N/ATRUE
3191
d0sc06429g10.1039/d0sc06429ghttps://doi.org/10.1039/d0sc06429gDurrant, JRWater oxidation kinetics of nanoporous BiVO4 photoanodes functionalised with nickel/iron oxyhydroxide electrocatalystsPhotocatalystx2021#N/AFALSE
3192
d0sc06096h10.1039/d0sc06096hhttps://doi.org/10.1039/d0sc06096hHess, CRChem. Sci.Photoredox catalysts are integral components of artificial photosystems, and have recently emerged as powerful tools for catalysing numerous organic reactions. However, the development of inexpensive and efficient earth-abundant photoredox catalysts remains a challenge. We here present the photochemical and photophysical properties of a Ni-Mabiq catalyst ([Ni-II(Mabiq)]OTf (1); Mabiq = 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N-6)-and of a Zn-containing analogue ([Zn-II(Mabiq)OTf] (2))-using steady state and time resolved optical spectroscopy, time-dependent density functional theory (TDDFT) calculations, and reactivity studies. The Ni and Zn complexes exhibit similar absorption spectra, but markedly different photochemical properties. These differences arise because the excited states of 2 are ligand-localized, whereas metal-centered states account for the photoactivity of 1. The distinct properties of the Ni and Zn complexes are manifest in their behavior in the photo-driven aza-Henry reaction and oxidative coupling of methoxyBenzylamine.The central role of the metal ion for photoactivity: Zn- vs. Ni-MabiqPhotocatalyst0202156#N/AFALSE
3193
d0sc06014c10.1039/d0sc06014cFALSEhttps://doi.org/10.1039/d0sc06014cRodriguez, AChem. Sci.The concept of metal-ligand cooperation opens new avenues for the design of catalytic systems that may offer alternative reactivity patterns to the existing ones. Investigations of this concept with ligands bearing a boron center in their skeleton established mechanistic pathways for the Activation of small molecules in which the boron atom usually performs as an electrophile. Here, we show how this electrophilic behavior can be modified by the ligand trans to the boron center, evincing its ambiphilic nature. Treatment of diphosphinB(OH)2ryl (PBP) nickel-methyl complex 1 with bis(catecholato)diboron (B(2)Cat(2)) allows for the synthesis of nickel(ii) bis-boryl complex 3 that promotes the Clean and reversible heterolytic Cleavage of dihydrogen leading to the formation of dihydrB(OH)2rate nickel complex 4. Density functional theory analysis of this reaction revealed that the heterolytic Activation of H-2 is facilitated by the cooperation of both boryl moieties and the metal atom in a concerted mechanism that involves a Ni(ii)/Ni(0)/Ni(ii) process. Contrary to 1, the boron atom from the PBP ligand in 3 behaves as a nuCleophile, accepting a formally protic hydrogen, whereas the catecholboryl moiety acts as an electrophile, receiving the attack from the hydride-like fragment. This manifests the dramatic change in the electronic properties of a ligand by tuning the substituent trans to it and constitutes an unprecedented cooperative mechanism that involves two boryl ligands in the same molecule operating differently, one as a Lewis acid and the other one as a Lewis base, in cooperation with the metal. In addition, reactivity towards different nuCleophiles such as amines or ammonia confirmed the electrophilic nature of the Bcat moiety, allowing the formation of aminB(OH)2ranes.Ambiphilic boryl groups in a neutral Ni(ii) complex: a new Activation mode of H-2x1202197#N/AFALSE
3194
ja00005a00110.1021/ja00005a001FALSEhttps://doi.org/10.1021/ja00005a001MADIX, RJJ. Am. Chem. Soc.When C2H4 alone is adsorbed on a hydrogen-presaturated Fe(100) surface (Fe(100)-H) without coadsorbed CO, reversible formation of ethyl groups (C2H5) occurs, and no ethane is observed. Remarkably, the coadsorption of CO with ethylene on Fe(100)-H induces the facile formation of ethane at 170 K. The coadsorption of CO weakens Fe-H bonds and appears to induce ethane formation by reducing the Activation barrier for the reductive elimination reaction between H adatoms and adsorbed ethyl groups. The observed Activation barrier for this reaction is approximately 5-6 kcal/mol. When CO is adsorbed onto Fe(100)-H before C2H4 adsorption, the maximum ethane yield is achieved with a CO coverage of 0.2 ML. At a CO saturation coverage of 0.5 ML no ethylene will adsorb, and thus no ethane is formed. When CO is adsorbed onto Fe(100)-H after C2H4, the ethane yield is reduced at high CO exposures due to displacement of ethylene by CO. Similarly, high exposures of CO onto an Fe(100)-H surface covered with ethyl groups led to the displacement of ethane. Ethane formation at H precoverages below saturation requires a threshold CO coverage governed by the relationship 4-THETA-CO + THETA-H greater-than-or-equal-to 1. CO adsorbed at coverages below the threshold coverage appears to compress H adatoms into regions of locally higher concentration. Apparently CO must bind within surface regions locally concentrated with H in order to induce ethane formation.CO-INDUCED ETHANE FORMATION FROM ETHYLENE AND HYDROGEN ON FE(100) - EFFECTS OF LIGANDS IN SURFACE-REACTIONS39199144#N/ATRUE
3195
ja00002a01910.1021/ja00002a019FALSEhttps://doi.org/10.1021/ja00002a019SAZOU, DJ. Am. Chem. Soc.The effect of temperature, porphyrin macrocyCle, and solvent on the electroreduction of (P)NiII where P is the dianion of meso-tetrakis(p-(diethylamino)phenyl)porphyrin (T(p-Et2N)PP) or meso-tetrakis(o,o,m,m-tetrafluoro-p-(dimethyl-amino)phenyl)porphyrin (T(p-Me2N)F4PP) is reported. Both compounds were reduced by controlled potential electrolysis and characterized by ESR and UV-visible spectroscopy. The site of electron transfer varied as a function of experimental conditions and the stable electrogenerated products were assigned as Ni(I) porphyrins, Ni(II) porphyrin pi-anion radicals, or Ni(II) porphyrin pi-anion radicals with some Ni(I) character. Ni(I) ESR spectra were obtained for [(T(p-Et2N)PP)Ni]- and [(T(p-Me2N)F4PP)Ni]- at low temperature in THF under a CO atmosphere as well as in DMF or pyridine under N2. In contrast, ESR spectra of Ni(II) porphyrin pi-anion radicals or Ni(II) porphyrin pi-anion radicals with some Ni(I) character were obtained in THF under N2 at room and low temperature, respectively. [(T(p-Et2N)PP)Ni]- catalytically reduces CH3I at room temperature, consistent with the presence of some Ni(I) character in the reactive species. [(T(p-Me2N)F4PP)Ni]- also reacts with CH3I, but this reaction is not catalytic at room temperature and one or more beta pyrrole methylated nickel chlorins are formed as stable products. These species were characterized by UV-visible spectroscopy, H-1 NMR spectroscopy, and mass spectrometry and give data which suggests a high electron density on the porphyrin macrocyCle of [(T(p-Me2N)F4PP)N]-.FACTORS DETERMINING THE SITE OF ELECTROREDUCTION IN NICKEL METALLOPORPHYRINS - SPECTRAL CHARACTERIZATION OF NI(I) PORPHYRINS, NI(II) PORPHYRIN PI-ANION RADICALS, AND NI(II) PORPHYRIN PI-ANION RADICALS WITH SOME NI(I) CHARACTER61199129#N/ATRUE
3196
d0sc04578k10.1039/d0sc04578khttps://doi.org/10.1039/d0sc04578kAckermann, LChem. Sci.The 3d transition metal-catalyzed enantioselective C-H functionalization provides a sustainable strategy for the construction of chiral molecules. A better understanding of the catalytic nature of the reactions and the factors controlling the enantioselectivity is important for rational design of more efficient systems. Herein, the mechanisms of Ni-catalyzed enantioselective C-H cyClization of imidazoles are investigated by density functional theory (DFT) calculations. Both the pi-allyl nickel(II)-promoted sigma-complex-assisted metathesis (sigma-CAM) and the nickel(0)-catalyzed oxidative addition (OA) mechanisms are disfavored. In addition to the typically proposed ligand-to-ligand hydrogen transfer (LLHT) mechanism, the reaction can also proceed via an unconventional sigma-CAM mechanism that involves hydrogen transfer from the JoSPOphos ligand to the alkene through P-H oxidative addition/migratory insertion, C(sp(2))-H Activation via sigma-CAM, and C-C reductive elimination. Importantly, computational results based on this new mechanism can indeed reproduce the experimentally observed enantioselectivities. Further, the catalytic activity of the pi-allyl nickel(II) complex can be rationalized by the regeneration of the active nickel(0) catalyst via a stepwise hydrogen transfer, which was confirmed by experimental studies. The calculations reveal several significant roles of the secondary phosphine oxide (SPO) unit in JoSPOphos during the reaction. The improved mechanistic understanding will enable design of novel enantioselective C-H transformations.Understanding the unique reactivity patterns of nickel/JoSPOphos manifold in the nickel-catalyzed enantioselective C-H cyClization of imidazolesxyy0202163#N/AFALSE
3197
d0sc04512h10.1039/d0sc04512hFALSEhttps://doi.org/10.1021/ja00145a013Queen, WLA metal-organic framework/polymer derived catalyst containing single-atom nickel species for electrocatalysisx2020#N/AFALSE
3198
d0sc04384b10.1039/d0sc04384bFALSEhttps://doi.org/10.1039/d0sc04384bDriess, MChem. Sci.An unprecedented molecular 2Fe-2As precursor complex was synthesized and transformed under soft reaction conditions to produce an active and long-term stable nanocrystalline FeAs material for electrocatalytic water oxidation in alkaline media. The 2Fe2As-centred beta-diketiminato complex, having an unusual planar Fe2As2 core structure, results from the salt-metathesis reaction of the corresponding beta-diketiminato (FeCl)-Cl-II complex and the AsCO- (arsaethynolate) anion as the monoanionic As- source. The as-prepared FeAs phase produced from the precursor has been electrophoretically deposited on conductive electrode substrates and shown to act as a electro(pre)catalyst for the oxygen evolution reaction (OER). The deposited FeAs undergoes corrosion under the severe anodic alkaline conditions which causes extensive dissolution of As into the electrolyte forming finally an active two-line ferrihydrite phase (Fe2O3(H2O)(x)). Importantly, the dissolved As in the electrolyte can be fully recaptured (electro-deposited) at the counter electrode making the complete process eco-conscious. The results represent a new and facile entry to unexplored nanostructured transition-metal arsenides and their utilization for high-performance OER electrocatalysis, which are also known to be magnificent high-temperature superconductors.A soft molecular 2Fe-2As precursor approach to the synthesis of nanostructured FeAs for efficient electrocatalytic water oxidationx42020106#N/AFALSE
3199
ja00001a02010.1021/ja00001a020FALSEhttps://doi.org/10.1021/ja00001a020CHANG, CKJ. Am. Chem. Soc.The newly synthesized metalloporphycenes represent a Class of molecules that are structural isomers of metalloporphyrins. In particular, the Ni(II) and Cu(II) complexes of 2,7,12,17-tetrapropylporphycene (NiPPC and CuPPC) display UV-visible absorption and resonance Raman (RR) spectra superficially like those of analogous complexes of octaethylporphyrin (OEP). However, Close examination of absorption band positions and spectral shifts caused by metal substitution and ring bromination, as well as relative oscillator strengths, suggest that, unlike those of metalloporphyrins, the pi --> pi* states of NiPPC and CuPPC are adequately defined by one-electron wave functions. Thus, the pi-electron configuration interaction that gives rise to Gouterman's Q and B metalloporphyrin excited states is weak in metalloporphycenes. Rather, these novel complexes appear to be a near-perfect example of Platt's long-field molecules (Platt, J. R. J. Chem. Phys. 1950, 18, 1168-1173). Raman spectra in resonance with the major absorptions of CuPPC show little evidence of Jahn-Teller or Herzberg-Teller coupling. Thus, the rich vibronic coupling present in metalloporphyrins giving rise to the celebrated anomalously polarized scattering (Spiro, T. G; Strekas, T. C. Proc. Natl. Acad. Sci. U.S.A. 1972, 69, 2622-2626) most likely does not complicate the spectra of metalloporphycenes. Vibrational analyses of RR spectra of specifically deuterated derivatives of NiPPC give some insight into the normal mode compositions. Metal substitution reveals structure-sensitive vibrations and suggests that frequency-structure correlations will be possible when more X-ray crystal data are available. Similarly to hemes, both UV-visible and RR spectra of FePPC derivatives demonstrate sensitivity to iron spin and oxidation state that suggests overlap of the iron d(xz) and d(yz) and the porphycene pi-orbitals. Once properly calibrated by comparison to results from magnetic-based techniques, the RR frequencies of the macrocyCle will be a reliable probe of the metal electronic state in iron porphycenes.OPTICAL ABSORPTIONS AND RAMAN-SCATTERING OF METALLOPORPHYCENES REVEAL ELECTRONIC AND VIBRONIC PROPERTIES DISTINCT FROM THOSE OF METALLOPORPHYRINS37199173#N/ATRUE
3200
d0sc04237d10.1039/d0sc04237dFALSEhttps://doi.org/10.1039/d0sc04237dRadius, UChem. Sci.The reaction of [Ni(Mes(2)Im)(2)] (1) (Mes(2)Im = 1,3-dimesityl-imidazolin-2-ylidene) with polyfluorinated arenes as well as mechanistic investigations concerning the insertion of1and [Ni((i)Pr(2)Im)(2)] (1(ipr)) ((i)Pr(2)Im = 1,3-diisopropyl-imidazolin-2-ylidene) into the C-F bond of C(6)F(6)is reported. The reaction of1with different fluoroaromatics leads to formation of the nickel fluoroAryl fluoride complexestrans-[Ni(Mes(2)Im)(2)(F)(Ar-F)] (Ar-F= 4-CF3-C(6)F(4)2, C(6)F(5)3, 2,3,5,6-C(6)F(4)N4, 2,3,5,6-C(6)F(4)H5, 2,3,5-C(6)F(3)H(2)6, 3,5-C(6)F(2)H(3)7) in fair to good yields with the exception of the formation of the pentafluorophenyl complex3(less than 20%). Radical species and other diamagnetic side products were detected for the reaction of1with C6F6, in line with a radical pathway for the C-F bond Activation step using1. The difluoride complextrans-[Ni(Mes(2)Im)(2)(F)(2)] (9), the bis(Aryl) complextrans-[Ni(Mes(2)Im)(2)(C6F5)(2)] (15), the structurally characterized nickel(i) complextrans-[Ni-I(Mes(2)Im)(2)(C6F5)] (11) and the metal radicaltrans-[Ni-I(Mes(2)Im)(2)(F)] (12) were identified. Complex11, and related [Ni-I(Mes(2)Im)(2)(2,3,5,6-C6F4H)] (13) and [Ni-I(Mes(2)Im)(2)(2,3,5-C6F3H2)] (14), were synthesized independently by reaction oftrans-[Ni(Mes(2)Im)(2)(F)(Ar-F)] with PhSiH3. Simple electron transfer from1to C(6)F(6)was exCluded, as the redox potentials of the reaction partners do not match and [Ni(Mes(2)Im)(2)](+), which was prepared independently, was not detected. DFT calculations were performed on the insertion of [Ni((i)Pr(2)Im)(2)] (1(ipr)) and [Ni(Mes(2)Im)(2)] (1) into the C-F bond of C6F6. For1(ipr), concerted and NHC-assisted pathways were identified as having the lowest kinetic barriers, whereas for1, a radical mechanism with fluoride abstraction and an NHC-assisted pathway are both associated with almost the same kinetic barrier.Coligand role in the NHC nickel catalyzed C-F bond Activation: investigations on the insertion of bis(NHC) nickel into the C-F bond of hexafluorobenzenex62020106#N/AFALSE
3201
d1sc02948g10.1039/d1sc02948gFALSEhttps://doi.org/10.1039/d1sc02948gWolf, RChem. Sci.Oxidative addition of the P-P single bond of an ortho-carborane-derived 1,2-diphosphetane (1,2-C-2(PMes)(2)B10H10) (Mes = 2,4,6-Me3C6H2) to cobalt(-i) and nickel(0) sources affords the first heteroleptic complexes of a carborane-bridged bis(phosphanido) ligand. The complexes also incorporate labile ligands suitable for further functionalisation. Thus, the cobalt(i) complex [K([18]crown-6)][Co{1,2-(PMes)(2)C2B10H10}(cod)] (cod = 1,5-cyClooctadiene) bearing a labile cyClooctadiene ligand undergoes facile ligand exchange reactions with isonitriles and tert-butyl phosphaalkyne with retention of the bis(phosphanido) ligand. However, in the reaction with one equivalent of P-4, the electron-rich bis(phosphanido) moiety abstracts a single phosphorus atom with formation of a new P-3 chain, while the remaining three P atoms derived from P-4 form an eta(3)-coordinating cyClo-P-3 ligand. In contrast, when the same reaction is performed with two equivalents of the cobalt(i) complex, a dinuClear product is formed which features an unusual P-4 chain in its molecular structure.Synthesis of a carborane-substituted bis(phosphanido) cobaltate(i), ligand substitution, and unusual P-4 fragmentation065#N/ATRUE
3202
d0sc04098c10.1039/d0sc04098cFALSEhttps://doi.org/10.1039/d0sc04098cMeyer, DChem. Sci.In contrast to the Classical method where a single molecule is designed to extract metal cations under specific conditions, dynamic covalent chemistry provides an approach based on the implementation of an adaptive dynamic covalent library for inducing the generation of the extractant species. This approach has been applied to the liquid-liquid extraction of copper(ii) nitrate based on a dynamic library of acylhydrazones constituents that self-build and distribute through the interface of a biphasic system. The addition of copper(ii) cations to this library triggers a modification of its composition and the up-regulation of the ligand molecules driven by coordination to the metal cations. Among these, one species has proven to be sufficiently lipophilic to play the role of carrier agent and its formation by component exchange enables the partial extraction of the copper(ii). The study of different pathways to generate the dynamic covalent library demonstrates the complete reversibility and the adaptability of the system. The detailed analytical investigation of the system provides a means to assess the mechanism of the dynamic extraction process.Phase transfer of metal cations by induced dynamic carrier agents: biphasic extraction based on dynamic covalent chemistryx1202079#N/AFALSE
3203
d0sc03917a10.1039/d0sc03917aFALSEhttps://doi.org/10.1039/d0sc03917aLuo, WChem. Sci.Ni3B/Ni heterostructures have been constructed, which exhibit exceptional catalytic performance toward the hydrogen oxidation reaction (HOR) under alkaline media, with the mass activity being about 10 times greater than that of Ni3B and Ni, respectively, ranking among the most active platinum-group-metal-free electrocatalysts. Experimental results and theoretical calculations confirm electron transfer from Ni3B to Ni at the Ni3B/Ni interface, resulting in inter-regulated d-band centers of these two components. This inter-regulation gives rise to optimized binding energies of intermediates, which together contribute to enhanced alkaline HOR activity.Inter-regulated d-band centers of the Ni3B/Ni heterostructure for boosting hydrogen electrooxidation in alkaline mediax4202048#N/AFALSE
3204
d0sc03776a10.1039/d0sc03776aFALSEhttps://doi.org/10.1039/d0sc03776aFeng, XMChem. Sci.A catalytic asymmetric conjugate addition/Schmidt-type rearrangement of Vinyl azides and (E)-alkenyloxindoles was realized. It afforded a variety of optically active 3,2 '-pyrrolinyl spirooxindoles with high yields (up to 98%), and excellent diastereo- and enantioselectivities (up to 98% ee, >19 : 1 dr), even at the gram-scale in the presence of a chiral N,N '-dioxide-nickel(ii) complex. In addition, a possible catalytic cyCle and transition state model were proposed to rationalize the stereoselectivity.Catalytic asymmetric synthesis of 3,2 '-pyrrolinyl spirooxindoles via conjugate addition/Schmidt-type rearrangement of Vinyl azides and (E)-alkenyloxindolesx1202052#N/AFALSE
3205
d0sc03616a10.1039/d0sc03616aFALSEhttps://doi.org/10.1039/d0sc03616aSen Gupta, SOxoiron(v) mediated selective electrochemical oxygenation of unactivated C-H and Cxe001;C bonds using water as the oxygen sourcex2020#N/AFALSE
3206
d0sc03280h10.1039/d0sc03280hFALSEhttps://doi.org/10.1039/d0sc03280hStrasser, PChem. Sci.Pyrolyzed iron-based platinum group metal (PGM)-free nitrogen-doped single site carbon catalysts (Fe-NC) are possible alternatives to platinum-based carbon catalysts for the oxygen reduction reaction (ORR). Bimetallic PGM-free M1M2-NC catalysts and their active sites, however, have been poorly studied to date. The present study explores the active accessible sites of mono- and bimetallic Fe-NC and FeNi-NC catalysts. Combining CO cryo chemisorption, X-ray absorption and Fe-57 Mossbauer spectroscopy, we evaluate the number and chemical state of metal sites at the surface of the catalysts along with an estimate of their dispersion and utilization. Fe L-3,L-2-edge X-ray adsorption spectra, Mossbauer spectra and CO desorption all suggested an essentially identical nature of Fe sites in both monometallic Fe-NC and bimetallic FeNi-NC; however, Ni blocks the formation of active sites during the pyrolysis and thus causes a sharp reduction in the accessible metal site density, while with only a minor direct participation as a catalytic site in the final catalyst. We also use the site density utilization factor, phi(SDsurface/bulk), as a measure of the metal site dispersion in PGM-free ORR catalysts. phi(SDsurface/bulk) enables a quantitative evaluation and comparison of distinct catalyst synthesis routes in terms of their ratio of accessible metal sites. It gives guidance for further optimization of the accessible site density of M-NC catalysts.Surface site density and utilization of platinum group metal (PGM)-free Fe-NC and FeNi-NC electrocatalysts for the oxygen reduction reactionx0202181#N/AFALSE
3207
d1sc02260a10.1039/d1sc02260aFALSEhttps://doi.org/10.1039/d1sc02260aMaeda, HChem. Sci.In this study, charged pi-electronic species are observed to develop stacking structures based on electrostatic and dispersion forces. (i)pi-(i)pi Interaction, defined herein, functions for the stacking structures consisting of charged pi-electronic species and is in contrast to conventional pi-pi interaction, which mainly exhibits dispersion force, for electronically neutral pi-electronic species. Establishing the concept of (i)pi-(i)pi interaction requires the evaluation of interionic interactions for pi-electronic ion pairs. Free base (metal-free) and diamagnetic metal complexes of 5-hydroxy-10,15,20-tris(pentafluorophenyl)porphyrin were synthesized, producing pi-electronic anions upon the deprotonation of the hydroxy unit. Coexisting cations in the ion pairs with porphyrin anions were introduced as the counter species of the hydroxy anion as a base for commercially available cations and as ion-exchanged species, via Na+ in the intermediate ion pairs, for synthesized pi-electronic cations. Solid-state ion-pairing assemblies were constructed for the porphyrin anions in combination with aliphatic tetrabutylammonium (TBA(+)) and pi-electronic 4,8,12-tripropyl-4,8,12-triazatriangulenium (TATA(+)) cations. The ordered arrangements of charged species, with the contributions of the charge-by-charge and charge-segregated modes, were observed according to the constituent charged building units. The energy decomposition analysis (EDA) of single-crystal packing structures revealed that electrostatic and dispersion forces are important factors in stabilizing the stacking of pi-electronic ions. Furthermore, crystal-state absorption spectra of the ion pairs were correlated with the assembling modes. Transient absorption spectroscopy of the single crystals revealed the occurrence of photoinduced electron transfer from the pi-electronic anion in the charge-segregated mode.Ion-pairing pi-electronic systems: ordered arrangement and noncovalent interactions of negatively charged porphyrins0202173#N/ATRUE
3208
d0sc03078c10.1039/d0sc03078cFALSEhttps://doi.org/10.1039/d0sc03078cLong, JRSemiquinone radical-bridged M-2(M = Fe, Co, Ni) complexes with strong magnetic exchange giving rise to slow magnetic relaxationx2020#N/AFALSE
3209
d0sc02986f10.1039/d0sc02986fhttps://doi.org/10.1039/d0sc02986fTang, JWChem. Sci.The covalent attachment of molecules to 2D materials is an emerging area as strong covalent chemistry offers new hybrid properties and greater mechanical stability compared with nanopartiCles. A nickel bis-aminothiophenol catalyst was grafted onto a range of 2D carbon nitrides (C3NxHy) to form noble metal-free photocatalysts for H(2)production. The hybrids produce H(2)beyond 8 days with turnover numbers reaching 1360 based on nickel, a more than 3 fold higher durability than reported molecular catalyst-carbon nitride mixtures, and under longer wavelengths (>475 nm). Time-resolved spectroscopy reveals sub-microsecond electron transfer to the grafted catalyst, six orders of magnitude faster compared with similar reports of non-grafted catalysts. The photoelectrons on the catalyst have aca.1000 times longer half-time (7 ms) compared with bare carbon nitride (10 mu s). The grafting strategy operates across a range of molecular catalyst-carbon nitride combinations, thus paving the way for robust efficient photocatalysts based on low-cost tunable components.Covalent grafting of molecular catalysts on C(3)N(x)H(y)as robust, efficient and well-defined photocatalysts for solar fuel synthesisPhotocatalyst2202035#N/AFALSE
3210
d0sc02859b10.1039/d0sc02859bhttps://doi.org/10.1039/d0sc02859bAbate, AChem. Sci.The power conversion efficiency (PCE) of NiO based perovskite solar cells has recently hit a record 22.1% with a hybrid organic-inorganic perovskite composition and a PCE above 15% in a fully inorganic configuration was achieved. Moreover, NiO processing is a mature technology, with different industrially attractive processes demonstrated in the last few years. These considerations, along with the excellent stabilities reported, Clearly point towards NiO as the most efficient inorganic hole selective layer for lead halide perovskite photovoltaics, which is the topic of this review. NiO optoelectronics is discussed by analysing the different doping mechanisms, with a focus on the case of alkaline and transition metal cation dopants. Doping allows tuning the conductivity and the energy levels of NiO, improving the overall performance and adapting the material to a variety of perovskite compositions. Furthermore, we summarise the main investigations on the NiO/perovskite interface stability. In fact, the surface of NiO is commonly oxidised and reactive with perovskite, also under the effect of light, thermal and electrical stress. Interface engineering strategies should be considered aiming at long term stability and the highest efficiency. Finally, we present the main achievements in flexible, fully printed and lead-free perovskite photovoltaics which employ NiO as a layer and provide our perspective to accelerate the improvement of these technologies. Overall, we show that adequately doped and passivated NiO might be an ideal hole selective layer in every possible application of perovskite solar cells.Progress, highlights and perspectives on NiO in perovskite photovoltaicsPhotocatalyst142020182#N/AFALSE
3211
d1sc01458g10.1039/d1sc01458gFALSEhttps://doi.org/10.1039/d1sc01458gBrooker, SCorrelations between ligand field Delta(o), spin crossover T-1/2 and redox potential E-pa in a family of five dinuClear helicates2021#N/ATRUE
3212
d0sc02592e10.1039/d0sc02592eFALSEhttps://doi.org/10.1039/d0sc02592eDempsey, JLChem. Sci.The solubility of molecular transition metal complexes can vary widely across different redox states, leaving these compounds vulnerable to electron transfer-initiated heterogenization processes in which oxidation or reduction of the soluble form of the redox couple generates insoluble molecular deposits. These insoluble species can precipitate as suspended nanopartiCles in solution or, under electrochemical conditions, as an electrode-adsorbed material. While this electrochemically-driven solubility cyCling is technically reversible, the reverse electron transfer to regenerate the soluble redox couple state is a practical challenge if sluggish electron transfer kinetics result in a loss of electronic communication between the molecular deposits and the electrode. In this work, we present an example of this electrochemically-driven solubility cyCling, report a novel strategy for catalytically enhancing the oxidation of the insoluble material using homogeneous redox mediators, and develop the theoretical framework for analysing and digitally simulating the action of a homogeneous catalyst on a heterogeneous substrateviacyClic voltammetry. First, a mix of electrochemical and spectroscopic methods are used to characterize an example of this electrochemically-driven solubility cyCling which is based on the two-electron reduction of homogeneous [Ni((P2N2Ph)-N-Ph)(2)(CH3CN)](2+)((P2N2Ph)-N-Ph= 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyClooctane). The limited solubility of the doubly-reduced product in acetonitrile leads to precipitation and deposition of molecular [Ni((P2N2Ph)-N-Ph)(2)]. While direct oxidation of this heterogeneous [Ni((P2N2Ph)-N-Ph)(2)] at the electrode surface is possible, this electron transfer is kinetically limited. We demonstrate how a freely diffusing redox mediator (ferrocene) - which shuttles electrons between the electrode and the molecular material - can be used to overcome these slow electron transfer kinetics, enabling catalytic regeneration of soluble [Ni((P2N2Ph)-N-Ph)(2)](2+). Finally, mathematical models are developed that describe the current-potential response for a generic EC ' mechanism involving a homogeneous catalyst and surface-adsorbed substrate. This novel strategy has the potential to enable reversible redox chemistry for heterogeneous, molecular deposits that are adsorbed on the electrode or suspended as nanopartiCles in solution.Redox mediators accelerate electrochemically-driven solubility cyCling of molecular transition metal complexesElectrochemistry1202046#N/AFALSE
3213
d1sc01018b10.1039/d1sc01018bFALSEhttps://doi.org/10.1021/ja00122a023Wang, HFTowards the object-oriented design of active hydrogen evolution catalysts on single-atom alloys2021#N/ATRUE
3214
d0sc02452j10.1039/d0sc02452jFALSEhttps://doi.org/10.1039/d0sc02452jAmaya, TChem. Sci.Chiral cyClic [n]spirobifluorenylenes consisting of helically arranged quaterphenyl rods, illustrating partial units of woven patterns, were designed and synthesized as a new family of carbon nanorings. The synthesis was accomplished by the Ni(0)-mediated Yamamoto-coupling of chiral spirobifluorene building blocks. The structures of the cyClic 3-, 4-, and 5-mers were determined by X-ray crystallographic analysis. These carbon nanorings exhibited a strong violet colored emission with high quantum yields in solution (95%, 93%, and 94% for 3-, 4-, and 5-mer, respectively). Other spectroscopic properties, inCluding their chiroptical properties, were also investigated. Theg-values for circularly polarized luminescence were found to be in the order of 10(-3). Characteristic spiroconjugation induced by multiple (>= 3) bifluorenyl units, for example the even-odd effect of the number of units in the matching of the signs of the orbitals, was also indicated by DFT calculations.Chiral cyClic [n]spirobifluorenylenes: carbon nanorings consisting of helically arranged quaterphenyl rods illustrating partial units of woven patternsx2202060#N/AFALSE
3215
d0sc02190c10.1039/d0sc02190cFALSEhttps://doi.org/10.1039/d0sc02190cSteed, JWChem. Sci.Spatially resolved soft materials, such as vesiCles and microgels, have shown promise as selective adsorbents and microscale reaction vessels. However, spatiotemporal control of aggregation can be difficult to achieve. In this study, nickel(ii) chloride and a dipyridyl oligo(urea) ligand were combined in a vapour-diffusion setup to produce a localised spheroidal aggregate at the liquid-vapour interface. This aggregate formsviathe self-assembly and fusion of monodisperse colloids and grows until its weight is no longer counterbalanced by surface tension. A simple physical model reveals that this process, termed lilypad aggregation, is possible only for surface energies that favour neither bulk aggregation nor the growth of an interfacial film. These surface energies dictate the final size and shape of the aggregate and may be estimated through visual monitoring of its changing morphology. Lilypad aggregates sequester metal from the surrounding sol and can be collected manually from the surface of the liquid.Lilypad aggregation: localised self-assembly and metal sequestration at a liquid-vapour interfacex1202081#N/AFALSE
3216
d0sc01747g10.1039/d0sc01747ghttps://doi.org/10.1039/d0sc01747gZou, ZGChem. Sci.Selective photoreduction of CO(2)into a given product is a great challenge but desirable. Inspired by natural photosynthesis occurring in hierarchical networks over non-precious molecular metal catalysts, we demonstrate an integration of single Ni sites into the hexagonal pores of polyimide covalent organic frameworks (PI-COFs) for selective photoreduction of CO(2)to CO. The single Ni sites in the hexagonal pores of the COFs serve as active sites for CO(2)Activation and conversion, while the PI-COFs not only act as a photosensitizer to generate charge carriers but also exert a promoting effect on the selectivity. The optimized PI-COF with a triazine ring exhibits excellent activity and selectivity. A possible intra- and inter-molecular charge-transfer mechanism was proposed, in which the photogenerated electrons in PI-COFs are efficiently separated from the central ring to the diimide linkage, and then transferred to the single Ni active sites, as evidenced by theoretical calculations.Integrating single Ni sites into biomimetic networks of covalent organic frameworks for selective photoreduction of CO2Photocatalystx14202060#N/AFALSE
3217
d0sc01585g10.1039/d0sc01585ghttps://doi.org/10.1039/d0sc01585gZeng, HYChem. Sci.The use of photochemical reactions that do not require expensive photocatalysts or transition metals is an environmentally friendly strategy for accomplishing a variety of structural transformations. Herein, we report a protocol for photoinduced transition-metal- and external-photocatalyst-free intramolecular heteroAryl/Aryl rearrangement reactions of 2-heteroAryl/Aryloxybenzaldehydes. The protocol was compatible with a variety of functionalities, inCluding methyl, methoxy, cyano, ester, trifluoromethyl, halogen, and Het rings. Control experiments suggested that the reaction proceededviaa photoinduced intramolecular heteroAryl/Aryl rearrangement process involving photoexcitation of the aldehyde Carbonyl group, radical addition, C-C bond formation and C(Ar)-O bond Cleavage.Photoinduced transition-metal- and external-photosensitizer-free intramolecular Aryl rearrangement via C(Ar)-O bond CleavagePhotocatalyst11202072#N/AFALSE
3218
d0sc01532f10.1039/d0sc01532fFALSEhttps://doi.org/10.1039/d0sc01532fChen, JChem. Sci.Electrochemical water splitting is a promising technology for hydrogen production and sustainable energy conversion, but the electrolyzers that are currently available do not have anodic electrodes that are robust enough and highly active for the oxygen evolution reaction (OER). Electrodeposition provides a feasible route for preparing freestanding OER electrodes with high active site utilization, fast mass transport and a simple fabrication process, which is highly attractive from both academic and commercial points of view. This minireview focuses on the recent electrodeposition strategies for metal (hydro)oxide design and water oxidation applications. First, the intrinsic advantages of electrodeposition in comparison with traditional technologies are introduced. Then, the unique properties and underlying principles of electrodeposited metal (hydro)oxides in the OER are unveiled. In parallel, illustrative examples of the latest advances in materials structural design, controllable synthesis, and mechanism understanding through the electrochemical synthesis of (hydro)oxides are presented. Finally, the latest representative OER mechanism and electrodeposition routes for OER catalysts are briefly overviewed. Such observations provide new insights into freestanding (hydro)oxides electrodes preparedviaelectrodeposition, which show significant practical application potential in water splitting devices. We hope that this review will provide inspiration for researchers and stimulate the development of water splitting technology.Electrodeposition of (hydro)oxides for an oxygen evolution electrodex122020115#N/AFALSE
3219
d0sc01471k10.1039/d0sc01471kFALSEhttps://doi.org/10.1039/d0sc01471kChu, LLChem. Sci.A selective, sequential C-O deCarbonylative Vinylation/C-H Arylation of cyClic alcohol derivatives enabled by visible-light photoredox/nickel dual catalysis is described. This protocol utilizes a multicomponent radical cascade process, i.e. deCarbonylative Vinylation/1,5-HAT/Aryl cross-coupling, to achieve efficient, site-selective dual-functionalization of saturated cyClic hydrocarbons in one single operation. This synergistic protocol provides straightforward access to sp(3)-enriched scaffolds and an alternative retrosynthetic disconnection to diversely functionalized saturated ring systems from the simple starting materials.Sequential C-O deCarbonylative Vinylation/C-H Arylation of cyClic oxalates via a nickel-catalyzed multicomponent radical cascadePhotocatalyst13202091#N/AFALSE
3220
d0sc01445a10.1039/d0sc01445aTRUEhttps://doi.org/10.1039/d0sc01445aHu, XLChem. Sci.Convergent paired electrosynthesis is an energy-efficient approach in organic synthesis; however, it is limited by the difficulty to match the innate redox properties of reaction partners. Here we use nickel catalysis to cross-couple the two intermediates generated at the two opposite electrodes of an electrochemical cell, achieving direct Arylation of Benzylic C-H bonds. This method yields a diverse set of diArylmethanes, which are important structural motifs in medicinal and materials chemistry. Preliminary mechanistic study suggests oxidation of a Benzylic C-H bond, Ni-catalyzed C-C coupling, and reduction of a Ni intermediate as key elements of the catalytic cyCle.Nickel catalysis enables convergent paired electrolysis for direct Arylation of Benzylic C-H bondsxCsp2_ar-Csp3-ring(s)HBrAryl192020566/9/2022FALSE
3221
d0sc01408g10.1039/d0sc01408gFALSEhttps://doi.org/10.1039/d0sc01408gFeng, XLChem. Sci.Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have recently emerged for potential applications in (opto-)electronics, chemiresistive sensing, and energy storage and conversion, due to their excellent electrical conductivity, abundant active sites, and intrinsic porous structures. However, developing ultrathin 2D c-MOF nanosheets (NSs) for facile solution processing and integration into devices remains a great challenge, mostly due to unscalable synthesis, low yield, limited lateral size and low crystallinity. Here, we report a surfactant-assisted solution synthesis toward ultrathin 2D c-MOF NSs, inCluding HHB-Cu (HHB = hexahydroxybenzene), HHB-Ni and HHTP-Cu (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene). For the first time, we achieve single-crystalline HHB-Cu(Ni) NSs featured with a thickness of 4-5 nm (similar to 8-10 layers) and a lateral size of 0.25-0.65 mu m(2), as well as single-crystalline HHTP-Cu NSs with a thickness of similar to 5.1 +/- 2.6 nm (similar to 10 layers) and a lateral size of 0.002-0.02 mu m(2). Benefiting from the ultrathin feature, the synthetic NSs allow fast ion diffusion and high utilization of active sites. As a proof of concept, when serving as a cathode material for Li-ion storage, HHB-Cu NSs deliver a remarkable rate capability (charge within 3 min) and long-term cyCling stability (90% capacity retention after 1000 cyCles), superior to the corresponding bulk materials and other reported MOF cathodes.Ultrathin two-dimensional conjugated metal-organic framework single-crystalline nanosheets enabled by surfactant-assisted synthesisx18202036#N/AFALSE
3222
d0sc01348j10.1039/d0sc01348jFALSEhttps://doi.org/10.1039/d0sc01348jXie, WZChem. Sci.Solving challenges for the scaling-up, high metal loadings and low turnover frequency (TOF, defined as mol O2 per mol metal per second), of FeNi catalysts in water electrolysis, we report the first discovery of pH tunable tannic acid single molecular layer formed on nano-sized carbons (NCs), which promotes the gram-production of pseudo-atomic-scale FeNi oxyhydroxide nanoClusters well-dispersed on NCs. It results in ultra-low metal loading (0.42 mu g cm(-2)) and remarkably large TOF of 14.03 s(-1)for the oxygen evolution reaction, which is three orders of magnitude higher than that of state-of-the-art FeNi catalysts. A volcano-shaped activity trend in specific activity and TOF was found to depend on the Fe content in FeNi oxyhydroxide. The micro-morphologies from the atomic-level exposure of active sites and surface spectra analyses confirm the model of synergism between Ni and Fe centers.Pseudo-atomic-scale metals well-dispersed on nano-carbons as ultra-low metal loading oxygen-evolving electrocatalystsx1202049#N/AFALSE
3223
d1sc00450f10.1039/d1sc00450fFALSEhttps://doi.org/10.1039/d1sc00450fHadlington, TJChem. Sci.Carbenes, a Class of low-valent group 14 ligand, have shifted the paradigm in our understanding of the effects of supporting ligands in transition-metal reactivity and catalysis. We now seek to move towards utilizing the heavier group 14 elements in effective ligand systems, which can potentially surpass carbon in their ability to operate via 'non-innocent' bond Activation processes. Herein we describe our initial results towards the development of scalable acyClic chelating germylene ligands (viz.1a/b), and their utilization in the stabilization of Ni-0 complexes (viz.4a/b), which can readily and reversibly undergo metathesis with ammonia with no net change of oxidation state at the Ge-II and Ni-0 centres, through ammonia bonding at the germylene ligand as opposed to the Ni-0 centre. The DFT-derived metathesis mechanism, which surprisingly demonstrates the need for three molecules of ammonia to achieve N-H bond Activation, supports reversible ammonia binding at Ge-II, as well as the observed reversibility in the overall reaction.Reversible metathesis of ammonia in an acyClic germylene-Ni-0 complex1202153#N/ATRUE
3224
d0sc01084g10.1039/d0sc01084gFALSEhttps://doi.org/10.1039/d0sc01084gJagadeesh, RVChem. Sci.The development of base metal catalysts for industrially relevant amination and hydrogenation reactions by applying abundant and atom economical reagents continues to be important for the cost-effective and sustainable synthesis of amines which represent highly essential chemicals. In particular, the synthesis of primary amines is of central importance because these compounds serve as key precursors and central intermediates to produce value-added fine and bulk chemicals as well as pharmaceuticals, agrochemicals and materials. Here we report a Ni-triphos complex as the first Ni-based homogeneous catalyst for both reductive amination of Carbonyl compounds with ammonia and hydrogenation of nitroarenes to prepare all kinds of primary amines. Remarkably, this Ni-complex enabled the synthesis of functionalized and structurally diverse Benzylic, heterocyClic and aliphatic linear and branched primary amines as well as aromatic primary amines starting from inexpensive and easily accessible Carbonyl compounds (aldehydes and ketones) and nitroarenes using ammonia and molecular hydrogen. This Ni-catalyzed reductive amination methodology has been applied for the amination of more complex pharmaceuticals and steroid derivatives. Detailed DFT computations have been performed for the Nitriphos based reductive amination reaction, and they revealed that the overall reaction has an innersphere mechanism with H-2 metathesis as the rate-determining step.General and selective synthesis of primary amines using Ni-based homogeneous catalystsx6202084#N/AFALSE
3225
d1sc00283j10.1039/d1sc00283jFALSEhttps://doi.org/10.1039/d1sc00283jGong, HGChem. Sci.We report an asymmetric Ni-catalyzed reductive cross-coupling of Aryl/heteroAryl halides with racemic alpha -chlorosulfones to afford enantioenriched sulfones. The reaction tolerates a variety of functional groups under mild reaction conditions, which complements the current methods. The utility of this work was demonstrated by facile late-stage functionalization of commercial drugs.Nickel-catalyzed asymmetric reductive Arylation of alpha-chlorosulfones with Aryl halides0202158#N/ATRUE
3226
d0sc00712a10.1039/d0sc00712ahttps://doi.org/10.1039/d0sc00712aRueping, MRecent advances in photoredox and nickel dual-catalyzed cascade reactions: pushing the boundaries of complexityPhotocatalyst2020#N/AFALSE
3227
d1cc01526e10.1039/d1cc01526eFALSEOhba, MGuest-selective and reversible magnetic phase switching in a pseudo-pillared-layer porous magnet2021#N/ATRUE
3228
d0sc06716d10.1039/d0sc06716dFALSEhttps://doi.org/10.1039/d0sc06716dGao, FChem. Sci.NiFe alloy catalysts have received increasing attention due to their low cost, easy availability, and excellent oxygen evolution reaction (OER) catalytic activity. Although it is considered that the co-existence of Ni and Fe is essential for the high catalytic activity, the identification of active sites and the mechanism of OER in NiFe alloy catalysts have been controversial for a long time. This review focuses on the catalytic centers of NiFe alloys and the related mechanism in the alkaline water oxidation process from the perspective of crystal structure/composition modulation and structural design. Briefly, amorphous structures, metastable phases, heteroatom doping and in situ formation of oxyhydroxides are encouraged to optimize the chemical configurations of active sites toward intrinsically boosted OER kinetics. Furthermore, the construction of dual-metal single atoms, specific nanostructures, carbon material supports and composite structures are introduced to increase the abundance of active sites and promote mass transportation. Finally, a perspective on the future development of NiFe alloy electrocatalysts is offered. The overall aim of this review is to shed light on the exploration of novel electrocatalysts in the field of energy.Intrinsic activity modulation and structural design of NiFe alloy catalysts for an efficient oxygen evolution reaction12021103#N/ATRUE
3229
d0sc05856d10.1039/d0sc05856dFALSEhttps://doi.org/10.1039/d0sc05856dLuis, FChem. Sci.We report the existence of a sizeable quantum tunnelling splitting between the two lowest electronic spin levels of mononuClear Ni complexes. The level anti-crossing, or magnetic Clock transition, associated with this gap has been directly monitored by heat capacity experiments. The comparison of these results with those obtained for a Co derivative, for which tunnelling is forbidden by symmetry, shows that the Clock transition leads to an effective suppression of intermolecular spin-spin interactions. In addition, we show that the quantum tunnelling splitting admits a chemical tuning via the modification of the ligand shell that determines the crystal field and the magnetic anisotropy. These properties are crucial to realize model spin qubits that combine the necessary resilience against decoherence, a proper interfacing with other qubits and with the control circuitry and the ability to initialize them by cooling.Chemical tuning of spin Clock transitions in molecular monomers based on nuClear spin-free Ni(ii)1202155#N/ATRUE
3230
d0sc00404a10.1039/d0sc00404aFALSEhttps://doi.org/10.1039/d0sc00404aCheng, YJChem. Sci.Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new Class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s-PSSe, PSTe, and PSeTe-through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)-from a thiophene unit via a selenophene unit to a tellurophene unit-to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes.Synthesis of side-chain regioregular and main-chain alternating poly(bichalcogenophene)s and an ABC-type periodic poly(terchalcogenophene)x2202071#N/AFALSE
3231
d0sc00136h10.1039/d0sc00136hFALSEhttps://doi.org/10.1039/d0sc00136hKornienko, NChem. Sci.The electrochemical oxidation of biomass platforms such as 5-hydroxymethylfurfural (HMF) to value-added chemicals is an emerging Clean energy technology. However, mechanistic knowledge of this reaction in an electrochemical context is still lacking and operando studies are even more rare. In this work, we utilize core-shell gold-metal oxide nanostructures which enable operando surface-enhanced Raman spectroelectrochemical studies to simultaneously visualize catalyst material transformation and surface reaction intermediates under an applied voltage. As a case study, we show how the transformation of NiOOH from similar to 1-2 nm amorphous Ni layers facilitates the onset of HMF oxidation to 2,5-furandiCarbonylic acid (FDCA), which is attained with 99% faradaic efficiency in 1 M KOH. In contrast to the case in 1 M KOH, NiOOH formation is suppressed, and consequently HMF oxidation is sluggish in 10 mM KOH, even at highly oxidizing potentials. Operando Raman experiments elucidate how surface adsorption and interaction dictates product selectivity and how the surface intermediates evolve with applied potential. We further extend our methodology to investigate NiFe, Co, Fe, and CoFe catalysts and demonstrate that high water oxidation activity is not necessarily correlated with excellent HMF oxidation performance and highlight catalytic factors important for this reaction such as reactant-surface interactions and the catalysts' physical and electronic structure. The insights extracted are expected to pave the way for a deepened understanding of a wide array of electrochemical systems such as for organic transformations and CO2 fixation.Electrochemical biomass valorization on gold-metal oxide nanoscale heterojunctions enables investigation of both catalyst and reaction dynamics with operando surface-enhanced Raman spectroscopyx17202039#N/AFALSE
3232
d0sc05439a10.1039/d0sc05439aFALSEhttps://doi.org/10.1039/d0sc05439aOgawa, SChem. Sci.The Class II chelatase CfbA catalyzes Ni2+ insertion into sirohydrochlorin (SHC) to yield the product nickel-sirohydrochlorin (Ni-SHC) during coenzyme F430 biosynthesis. CfbA is an important ancestor of all the Class II chelatase family of enzymes, inCluding SirB and CbiK/CbiX, functioning not only as a nickel-chelatase, but also as a cobalt-chelatase in vitro. Thus, CfbA is a key enzyme in terms of diversity and evolution of the chelatases catalyzing formation of metal-SHC-type of cofactors. However, the reaction mechanism of CfbA with Ni2+ and Co2+ remains elusive. To understand the structural basis of the underlying mechanisms and evolutionary aspects of the Class II chelatases, X-ray crystal structures of Methanocaldococcus jannaschii wild-type CfbA with various ligands, inCluding SHC, Ni2+, Ni-SHC, and Co2+ were determined. Further, X-ray crystallographic snapshot analysis captured a unique Ni2+-SHC-His intermediate complex and Co-SHC-bound CfbA, which resulted from a more rapid chelatase reaction for Co2+ than Ni2+. Meanwhile, an in vitro activity assay confirmed the different reaction rates for Ni2+ and Co2+ by CfbA. Based on these structural and functional analyses, the following substrate-SHC-assisted Ni2+ insertion catalytic mechanism was proposed: Ni2+ insertion to SHC is promoted by the support of an acetate side chain of SHC.The nickel-sirohydrochlorin formation mechanism of the ancestral Class II chelatase CfbA in coenzyme F430 biosynthesis0202130#N/ATRUE
3233
d0sc04326e10.1039/d0sc04326eFALSEhttps://doi.org/10.1039/d0sc04326eWei, HChem. Sci.We report here cobalt-N-heterocyClic carbene catalytic systems for the intramolecular deCarbonylative coupling through the chelation-assisted C-C bond Cleavage of acylindoles and diArylketones. The reaction tolerates a wide range of functional groups such as Alkyl, Aryl, and heteroAryl groups, giving the deCarbonylative products in moderate to excellent yields. This transformation involves the Cleavage of two C-C bonds and formation of a new C-C bond without the use of noble metals, thus reinforcing the potential application of deCarbonylation as an effective tool for C-C bond formation.Cobalt-catalyzed intramolecular deCarbonylative coupling of acylindoles and diArylketones through the Cleavage of C-C bonds4202075#N/ATRUE
3234
d0sc04173d10.1039/d0sc04173dFALSEhttps://doi.org/10.1039/d0sc04173dKong, WQChem. Sci.The reductive coupling of alkynes represents a powerful strategy for the rapid synthesis of highly substituted 1,3-dienes. This method has the advantages of high atom and step economy, and readily available substrates. Unfortunately, the intermolecular coupling of unsymmetrical internal alkynes remains extremely challenging due to the difficulty in controlling self-dimerization and cross-coupling, as well as stereo- and regioselectivity. Previous reports are still limited to intramolecular processes or the use of stoichiometric amounts of metal catalyst. Herein, we report that nickel-catalyzed reductive coupling of two unsymmetrical internal alkynes can overcome the above-mentioned limitations by using a hemilabile directing group strategy to control the regioselectivity. A series of synthetically challenging penta-substituted 1,3-dienes are obtained in good yields with high regio- and enantioselectivity (mostly > 20/1 rr, >90% ee).Stereoselective synthesis of pentasubstituted 1,3-dienes via Ni-catalyzed reductive coupling of unsymmetrical internal alkynes8202088#N/ATRUE
3235
d0cc03230a10.1039/d0cc03230ahttps://doi.org/10.1021/ja00092a040Xu, LDual aminoquinolate diArylboron and nickel catalysed metallaphotoredox platform for carbon-oxygen bond constructionPhotocatalyst2020#N/AFALSE
3236
d0sc03217d10.1039/d0sc03217dFALSEhttps://doi.org/10.1039/d0sc03217dYin, GYChem. Sci.The selective cross-coupling of activated electrophiles with unactivated ones has been regarded as a challenging task in cross-electrophile couplings. Herein we describe a migratory cross-coupling strategy, which can overcome this obstaCle to access the desired cross-coupling products. Accordingly, a selective migratory cross-coupling of two Alkyl electrophiles has been accomplished by nickel catalysis. Remarkably, this Alkyl-Alkyl cross-coupling reaction provides a platform to prepare 2 degrees-2 degrees carbon-carbon bonds from 1 degrees and 2 degrees carbon coupling partners. Preliminary mechanistic studies suggest that chain-walking occurs at both Alkyl halides in this reaction, thus a catalytic cyCle with the key step involving two Alkylnickel(ii) species is proposed for this transformation.Nickel-catalyzed migratory Alkyl-Alkyl cross-coupling reaction3202043#N/ATRUE
3237
d0sc02812f10.1039/d0sc02812fFALSEhttps://doi.org/10.1039/d0sc02812fBerben, LAChem. Sci.Ligand-based mixed valent (MV) complexes of Al(III) incorporating electron donating (ED) and electron withdrawing (EW) substituents on bis(imino)pyridine ligands (I2P) have been prepared. The MV states containing EW groups are both assigned as Class II/III, and those with ED functional groups are Class III and Class II/III in the (I2P-)(I2P2-)Al and [(I2P2-)(I2P3-)Al](2-) charge states, respectively. No abrupt changes in delocalization are observed with ED and EW groups and from this we infer that ligand and metal valence porbitals are well-matched in energy and the absence of LMCT and MLCT bands supports the delocalized electronic structures. The MV ligand charge states (I2P-)(I2P2-)Al and [(I2P2-)(I2P3-)Al](2-) show intervalence charge transfer (IVCT) transitions in the regions 6850-7740 and 7410-9780 cm(-1), respectively. Alkali metal cations in solution had no effect on the IVCT bands of [(I2P2-)(I2P3-)Al](2-) complexes containing -PhNMe2 or -PhF5 substituents. Minor localization of charge in [(I2P2-)(I2P3-)Al](2-) was observed when -PhOMe substituents are inCluded.Delocalization tunable by ligand substitution in [L2Al](n-) complexes highlights a mechanism for strong electronic coupling0202159#N/ATRUE
3238
d0cc02132f10.1039/d0cc02132fFALSEhttps://doi.org/10.1039/d0cc02132fLiu, EHTrimetallic NiCoMo/graphene multifunctional electrocatalysts with moderate structural/electronic effects for highly efficient alkaline urea oxidation reactionx2020#N/AFALSE
3239
d0sc02584d10.1039/d0sc02584dFALSEhttps://doi.org/10.1039/d0sc02584dDarensbourg, MYChem. Sci.At some point, all HER (Hydrogen Evolution Reaction) catalysts, important in sustainable H2O splitting technology, will encounter O(2)and O-2-damage. The [NiFeSe]-H(2)ases and some of the [NiFeS]-H(2)ases, biocatalysts for reversible H(2)production from protons and electrons, are exemplars of oxygen tolerant HER catalysts in nature. In the hydrogenase active sites oxygen damage may be extensive (irreversible) as it is for the [FeFe]-H(2)ase or moderate (reversible) for the [NiFe]-H(2)ases. The affinity of oxygen for sulfur, in [NiFeS]-H(2)ase, and selenium, in [NiFeSe]-H(2)ase, yielding oxygenated chalcogens results in maintenance of the core NiFe unit, and myriad observable but inactive states, which can be reductively repaired. In contrast, the [FeFe]-H(2)ase active site has less possibilities for chalcogen-oxygen uptake and a greater chance for O-2-attack on iron. Exposure to O(2)typically leads to irreversible damage. Despite the evidence of S/Se-oxygenation in the active sites of hydrogenases, there are limited reported synthetic models. This perspective will give an overview of the studies of O(2)reactions with the hydrogenases and biomimetics with focus on our recent studies that compare sulfur and selenium containing synthetic analogues of the [NiFe]-H(2)ase active sites.The roles of chalcogenides in O-2 protection of H(2)ase active sites1202061#N/ATRUE
3240
d0sc01246g10.1039/d0sc01246gFALSEhttps://doi.org/10.1039/d0sc01246gGrey, CPChem. Sci.We report the structures of six new divalent transition metal hexathiocyanatobismuthate frameworks with the generic formula , M = Mn, Co, Ni and Zn. These frameworks are defective analogues of the perovskite-derived trivalent transition metal hexathiocyanatobismuthates M-III[Bi(SCN)(6)]. The defects in these new thiocyanate frameworks order and produce complex superstructures due to the low symmetry of the parent structure, in contrast to the related and more well-studied cyanide Prussian Blue analogues. Despite the Close similarities in the chemistries of these four transition metal cations, we find that each framework contains a different mechanism for accommodating the lowered transition metal charge, making use of some combination of Bi(SCN)(6)(3-) vacancies, M-Bi antisite defects, water substitution for thiocyanate, adventitious extra-framework cations and reduced metal coordination number. These materials provide an unusually Clear view of defects in molecular framework materials and their variety suggests that similar richness may be waiting to be uncovered in other hybrid perovskite frameworks.The structures of ordered defects in thiocyanate analogues of Prussian Blue3202040#N/ATRUE
3241
d0sc00997k10.1039/d0sc00997kFALSEhttps://doi.org/10.1039/d0sc00997kTilley, TDChem. Sci.A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl](+), is a precursor to efficient catalysts for the hydrosilation of alkenes with a variety of hydrosilanes under mild conditions and low catalyst loadings. DFT studies reveal the presence of two coupled catalytic cyCles based on [(NPN)NiH](+) and [(NPN)NiSiR3](+) active species, with the latter being more efficient for producing the product. The preferred silyl-based catalysis is not due to a more facile insertion of alkene into the Ni-Si (vs. Ni-H) bond, but by consistent and efficient conversions of the hydride to the silyl complex.Efficient alkene hydrosilation with bis(8-quinolyl)phosphine (NPN) nickel catalysts. The dominant role of silyl-over hydrido-nickel catalytic intermediates1202085#N/ATRUE
3242
cs502132y10.1021/cs502132yFALSEhttps://doi.org/10.1021/cs502132yHelm, MLACS Catal.A new Ni(II) complex, [N-i(7P(2)(Ph)N(H))(2)H](3+) (7P(2)(Ph)N(HH) = 3,6-diphenyl-1-aza-3,6-diphosphacyCloheptane), has been synthesized, and its electrochemical properties have been reported. The 7P(2)(Ph)N(HH) ligand features an NH, ensuring properly positioned protonated amine groups (NH+) for electrocatalysis, regardless of whether protonation occurs exo or endo to the metal center. The compound is an electrocatalyst for H-2 production in the presence of organic acids (pK(a) range 1013 in CH3CN), with turnover frequencies ranging from 160 to 780 s(1) at overpotentials between 320 and 470 mV, as measured at the potential of the catalytic wave. In stark contrast to [Ni((P2N2R')-N-Ph)(2)](2+) ((P2N2R')-N-Ph = 3,7-diphenyl-1,5-diaza-3,7-diphosphacyClooctane) and other [Ni(7P(2)(Ph)N(R'))(2)](2+) complexes, catalytic turnover frequencies for H-2 production by [Ni(7P(2)(Ph)N(H))(2)](2+) do not show catalytic rate enhancement upon the addition of H2O. This finding supports the assertion that [Ni(7P(2)(Ph)N(H'))(2)](2+) eliminates the distinction between the endo- and exo-protonation isomers.Electrocatalytic Hydrogen Production by [Ni(7P(2)(Ph)N(H))(2)](2+): Removing the Distinction Between Endo- and Exo-Protonation Siteshydrogen production; electrocatalysis; proton relays; pendant amines; nickel complexes; nickel phosphine complexes
Electrocatalytic
14201537#N/AFALSE
3243
d0sc00676a10.1039/d0sc00676aFALSEhttps://doi.org/10.1039/d0sc00676aKovnir, KChem. Sci.How the crystal structures of ordered transition-metal phosphide catalysts affect the hydrogen-evolution reaction (HER) is investigated by measuring the anisotropic catalytic activities of selected crystallographic facets on large (mm-sized) single crystals of iron-phosphide (FeP) and monoClinic nickel-diphosphide (m-NiP2). We find that different crystallographic facets exhibit distinct HER activities, in contrast to a commonly held assumption of severe surface restructuring during catalytic activity. Moreover, density-functional-theory-based computational studies show that the observed facet activity correlates well with the H-binding energy to P atoms on specific surface terminations. Direction dependent catalytic properties of two different phosphides with different transition metals, crystal structures, and electronic properties (FeP is a metal, while m-NiP2 is a semiconductor) suggests that the anisotropy of catalytic properties is a common trend for HER phosphide catalysts. This realization opens an additional rational design for highly efficient HER phosphide catalysts, through the growth of nanocrystals with specific exposed facets. Furthermore, the agreement between theory and experimental trends indicates that screening using DFT methods can accelerate the identification of desirable facets, especially for ternary or multinary compounds. The large single-crystal nature of the phosphide electrodes with well-defined surfaces allows for determination of the catalytically important double-layer capacitance of a flat surface, C-dl = 39(2) mu F cm(-2) for FeP, useful for an accurate calculation of the turnover frequency (TOF). X-ray photoelectron spectroscopy (XPS) studies of the catalytic crystals that were used show the formation of a thin oxide/phosphate overlayer, presumably ex situ due to air-exposure. This layer is easily removed for FeP, revealing a surface of pristine metal phosphide.Crystallographic facet selective HER catalysis: exemplified in FeP and NiP2 single crystals11202050#N/ATRUE
3244
cs502103510.1021/cs5021035https://doi.org/10.1021/cs5021035Eisenberg, RACS Catal.The present study reports photelectrochemical H-2 evolution using a water-solubilized S-3-cap-CdSe quantum dot-sensitized NiO as the photocathode and either [Co(bdt)(2)](-) (bdt =1,2-benzenedithiolate) or Ni(DHLA)(x) (DHLA= the anion of dihydrolipoic acid) complex as the H-2-forming catalyst. The NiO-S-3-cap-CdSe/[Co(bdt)(2)](-) system produces H-2 with a turnover frequency of 3000 per CdSe mol.h. Faradaic efficiency for this system is essentially quantitative. Both systems are stable for more than 16 h.Photoelectrochemical Generation of Hydrogen from Water Using a CdSe Quantum Dot-Sensitized Photocathodephotoelectrochemistry; photocathodes; quantum dots; hydrogen; solar energy; molecular catalystPhotocatalyst46201538#N/AFALSE
3245
d0sc00628a10.1039/d0sc00628aFALSEhttps://doi.org/10.1039/d0sc00628aDyer, RBChem. Sci.Metal-ligand cooperativity is an essential feature of bioinorganic catalysis. The design principles of such cooperativity in metalloenzymes are underexplored, but are critical to understand for developing efficient catalysts designed with earth abundant metals for small molecule Activation. The simple substrate requirements of reversible proton reduction by the [NiFe]-hydrogenases make them a model bioinorganic system. A highly conserved arginine residue (R355) directly above the exogenous ligand binding position of the [NiFe]-catalytic core is known to be essential for optimal function because mutation to a lysine results in lower catalytic rates. To expand on our studies of soluble hydrogenase-1 fromPyrococcus furiosus(PfSH1), we investigated the role of R355 by site-directed-mutagenesis to a lysine (R355K) using infrared and electron paramagnetic resonance spectroscopic probes sensitive to active site redox and protonation events. It was found the mutation resulted in an altered ligand binding environment at the [NiFe] centre. A key observation was destabilization of the Ni-a(3+)-C state, which contains a bridging hydride. Instead, the tautomeric Ni-a(+)-L states were observed. Overall, the results provided insight into complex metal-ligand cooperativity between the active site and protein scaffold that modulates the bridging hydride stability and the proton inventory, which should prove valuable to design principles for efficient bioinspired catalysts.Metal-ligand cooperativity in the soluble hydrogenase-1 fromPyrococcus furiosus1202076#N/ATRUE
3246
d0sc00534g10.1039/d0sc00534gFALSEhttps://doi.org/10.1039/d0sc00534gCalle-Vallejo, FChem. Sci.Reactivity trends on transition metals can generally be understood through the d-band model, but no analogous theory exists for transition metal oxides. This limits the generality of analyses in oxide-based catalysis and surface chemistry and has motivated the appearance of numerous descriptors. Here we show that oxygen vacancy formation energy (Delta E-Vac) is an inexpensive yet accurate and general descriptor for trends in transition-state energies, which are usually difficult to assess. For rutile-type oxides (MO2 with M = 3d metals from Ti to Ni), we show that Delta E-Vac captures the trends in C-O and N-O bond scission of CO2, CH3OH, N2O, and NH2OH at oxygen vacancies. The proportionality between Delta E-Vac and transition-state energies is rationalized by analyzing the oxygen-metal bonds, which change from ionic to covalent from TiO2 to NiO2. Delta E-Vac may be used to design oxide catalysts, in particular those where lattice oxygen and/or oxygen vacancies participate in the catalytic cyCles.Trends in C-O and N-O bond scission on rutile oxides described using oxygen vacancy formation energies3202061#N/ATRUE
3247
d0cc07372e10.1039/d0cc07372eFALSEWang, PFree-standing Pt-Ni nanowires catalyst for H-2 generation from hydrous hydrazine2021#N/ATRUE
3248
d0cc05874b10.1039/d0cc05874bFALSEZhou, XGBi-reforming of methane with steam and CO2 under pressurized conditions on a durable Ir-Ni/MgAl2O4 catalyst2020#N/ATRUE
3249
cs501894e10.1021/cs501894eFALSEhttps://doi.org/10.1021/cs501894eMurzin, DYACS Catal.The influence of substrate chirality was studied in the aqueous phase reforming (APR) over Pt/Al2O3 in a continuous fixed-bed reactor at 225 degrees C. Two epimeric sugar alcohols, namely sorbitol and galactitol, were used for performance comparison. For the very first time galactitol was used in the APR process. The reliability of the liquid-phase product analysis was considerably improved due to application of a spiking technique for qualitative analysis and subsequent peak fitting for quantification. A detailed analysis of the gas and liquid phases showed almost the same behavior of both polyols, apart from the formation of several intermediate oxygenates. This implies that industrially relevant feedstocks with different chiralities can be efficiently processed in APR, since the chirality of the initial substance does not affect the reaction rate and selectivity to the final products. However, the observed difference in the liquid phase composition should be considered, because the catalyst should be active in the conversion of both polyols and oxygenates. Finally, possible reaction pathways were proposed and discussed from a thermodynamic point of view.Aqueous Phase Reforming of Industrially Relevant Sugar Alcohols with Different Chiralitiesaqueous phase reforming; sorbitol; galactitol; Pt/Al2O3; thermodynamicsx27201588#N/AFALSE
3250
cs501835c10.1021/cs501835cFALSEhttps://doi.org/10.1021/cs501835cJin, JACS Catal.Hydrogen is considered by many to be a promising energy currency, particularly for the transportation sector and for mobile devices. To realize a hydrogen-based fuel economy, hydrogen must be produced in an efficient and sustainable manner. In this artiCle, single-layer nickel hydroxide (Ni(OH)(2))-nanosheet-assisted Pt/C catalysis for the hydrogen evolution reaction (HER) in an alkaline environment was investigated. The HER activity trajectories of the hybrid catalysts in correlation with the composition and morphology of Ni(OH)(2) were explored in depth. By optimizing the Volmer step through addition of single-layer Ni(OH)(2) into Pt/C catalysis, this hybrid catalyst manifests a 110% increase of the HER activity by using only 20 wt % single-layer Ni(OH)(2) with a lithium ion additive as compared to the state-of-the-art Pt/C catalyst. Density functional theory calculations revealed that the single layer Ni(OH)(2) behaves superior in adsorption ability of OH- when compared with multilayer Ni(OH)(2). The single layer Ni(OH)(2) contributes to dual improvement on both the Volmer step and the adsorption of OW during HER.Optimizing the Volmer Step by Single-Layer Nickel Hydroxide Nanosheets in Hydrogen Evolution Reaction of Platinumhydrogen evolution reaction; single-layer Ni(OH)(2); the Volmer step; density functional theory; Ni(OH)(2)/Pt compositex88201544#N/AFALSE
3251
d0cc04174b10.1039/d0cc04174bFALSEhttps://doi.org/10.1039/d0cc04174bHardre, RHydrogen evolution reaction mediated by an all-sulfur trinuClear nickel complex2020#N/ATRUE
3252
d0cc03077e10.1039/d0cc03077eFALSEhttps://doi.org/10.1039/d0cc03077eDyer, PWAdditives boosting the performance of tungsten imido-mediated ethylene dimerization systems for industrial application2020#N/ATRUE
3253
cs501534h10.1021/cs501534hhttps://doi.org/10.1021/cs501534hLau, TCACS Catal.A series of nickel(II) complexes bearing tetradentate macrocyClic N-4, N3S, and N3P ligands were synthesized, and their photocatalytic activity toward proton reduction has been investigated by using [Ir(dF(CF3)ppy)2(dmbpy)]PF6 (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine and dmbpy = 4,4'-dimethyl-2,2'-dipyridyl) as the photosensitizer and triethylamine (TEA) as the sacrificial reductant. The complex [Ni(L4)](2+) (L4 = 2,12-dimethyl-7-phenyl-3,11,17-triaza-7-phospha-bicyClo[11,3,1]heptadeca-1(17),13,15-triene), which bears a phosphorus donor atom, shows the highest efficiency with TON up to 5000 under optimized conditions, while the tetraaza macrocyClic nickel complexes [Ni(L1)](2+) and [Ni(L2)](2+) (L1 = 2,12-dimethyl-3,7,11,17-tetra-azabicyClo[11.3.l]heptadeca-1(17),2,11,13,15-pentaene; L2 = 2,12-dimethyl-3,7,11,17-tetra-azabicyClo[11.3.l]heptadeca-1(17),13,15-triene) show lower photocatalytic activities. Transient UVvis absorption and spectroelectrochemical experiments show that Ni(II) is reduced to Ni(I) under photocatalytic conditions. However, dynamic light scattering and mercury poisoning experiments suggest that the Ni(I) is further reduced to Ni(0) nanopartiCles which are the real catalysts for H-2 production. Electrocatalytic proton reduction by [Ni(L4)](2+) has also been investigated. In this case, the electrochemical behavior is consistent with a homogeneous pathway, and no Ni nanopartiCles were observed on the electrode surface during the first few hours of electrolysis. However, on prolonged electrolysis for >17 h, nickel-based nanopartiCles were observed on the electrode surface, which are active catalysts for H-2 production.Dual Homogeneous and Heterogeneous Pathways in Photo- and Electrocatalytic Hydrogen Evolution with Nickel(II) Catalysts Bearing Tetradentate MacrocyClic Ligandshydrogen evolution; nickel catalyst; macrocyClic ligands; electrochemical catalysis; photocatalysis
Electrocatalytic
57201565#N/AFALSE
3254
cs501515710.1021/cs5015157https://doi.org/10.1021/cs5015157Spiccia, LACS Catal.Current energy resources largely rely on fossil fuels that are expected to be depleted in 50-200 years. On a global scale, the intensive use of this energy source has resulted in highly detrimental effects to the environment. Hydrogen production by water splitting, with sunlight as the main energy source, is a promising way to augment the production of renewable energy; however, the development of an efficient and stable water-oxidizing catalyst remains a key task before a technological breakthrough based on water splitting can be realized. A main issue hampering the development of commercially viable, non-precious-metal-based catalysts is their susceptibility to degradation. To efficiently address this major drawback, self-healing catalysts that can repair their structure without human intervention will be necessary. In this review, we focus on water oxidation by natural and artificial Mn-, Co-, and Ni-based catalysts and then discuss the self-healing properties that contribute to sustaining their catalytic activity.Damage Management in Water-Oxidizing Catalysts: From Photosystem II to Nanosized Metal Oxideswater oxidation catalysts; self-healing catalysts; photosystem II; manganese; cobalt; nickelPhotocatalystx432015140#N/AFALSE
3255
d0cc02163f10.1039/d0cc02163fFALSEhttps://doi.org/10.1039/d0cc02163fXu, JSustainable synthesis of 1,2,3,4-cyClohexanetetraCarbonylate from sugar-derived Carbonylic acids2020#N/ATRUE
3256
cs501447d10.1021/cs501447dhttps://doi.org/10.1021/cs501447dTonks, IAACS Catal.The ability of various group 10 alpha-diimine and salicylaldimine polymerization catalysts to undergo chain transfer with main group metal Alkyls during ethylene polymerization has been investigated in depth. The catalyst systems with the most efficient chain transfer were found to be cationic (alpha-diimine)Ni catalysts paired with diAlkyl zinc chain-transfer reagents, in which all growing polymeryl chains were transferred to Zn on the basis of C-13 NMR analysis. In these systems, chain transfer was found to be dependent on the sterics of both the catalyst and the chain-transfer reagent (CTR). When less sterically encumbered catalysts or CTRs were utilized, the relative rate of bimetallic chain transfer to chain propagation was increased; however, in cases where chain termination via beta-H elimination was extremely rapid, chain transfer to Zn was kinetically not viable. Importantly, chain transfer from (alpha-diimine)Ni catalysts to Zn Alkyls is also very sensitive to the strength of the ZnC bond: ZnMe2 (186 kJ/mol) is a significantly poorer chain-transfer reagent than ZnEt2 (157 kJ/mol), despite being less sterically encumbered. Finally, the nature of the catalyst counteranion (MAO or B(ArF)(4) ArF = 3,5-(CF3)(2)C6H3) does not have a significant impact on the rate of chain transfer to ZnR2 relative to propagation, indicating that the same factors that determine propagation rates also determine bimetallic chain-transfer rates.Analysis of Polymeryl Chain Transfer Between Group 10 Metals and Main Group Alkyls during Ethylene Polymerizationpolymerization catalysis; chain transfer; polyethylene; group 10; metal Alkyls; kineticsx23201463#N/AFALSE
3257
cs501372m10.1021/cs501372mFALSEhttps://doi.org/10.1021/cs501372mZhang, TACS Catal.Using cellulosic biomass to synthesize bulk quantities of high-value chemicals is of great interest for developing a sustainable biobased society. Especially, direct catalytic conversion of cellulose to glycols, important building blocks for polymers, remains a grand challenge. Herein, we report the development of a versatile binary nickel-lanthanum(III) catalyst for the conversion of cellulose to both ethylene glycol (EG) and propylene glycol (1,2-PG) in a yield of 63.7%, which is one of the best performances reported for this catalytic reaction. Especially, lanthanum(III) exhibited a high level of activity toward the degradation of cellulose (TON = 339) at a very low concentration (0.2 mmol/L). On the basis of density functional theory calculations and experimental analyses, we addressed a dual route for this catalytic mechanism: a major route involving the selective cracking of sugars into C-2 molecules and a minor route involving the hydrogenolysis of sugar alcohols. Lanthanum(III) catalyzes the Cleavage of the C-2-C-3 bond in glucose via sequential epimerization and 2,3-hydride shift reactions to form glycolaldehyde, the precursor of EG.Versatile Nickel-Lanthanum(III) Catalyst for Direct Conversion of Cellulose to Glycolscellulose; ethylene glycol; propylene glycol; nickel-lanthanum catalyst; dual route; theoretical calculationx62201554#N/A
3258
d0cc01345e10.1039/d0cc01345eFALSELiu, XHCH4 conversion over Ni/HZSM-5 catalyst in the absence of oxygen: decomposition or dehydroaromatization?2020#N/ATRUE
3259
d0cc00449a10.1039/d0cc00449aFALSEGee, ADCarbon-11 Carbonylation of trialkoxysilane and trimethylsilane derivatives using [C-11]CO22020#N/ATRUE
3260
cs501356h10.1021/cs501356hFALSEhttps://doi.org/10.1021/cs501356hWan, YACS Catal.In this study, heterogeneous palladium catalysts supported on ordered mesoporous cobalt oxide-carbon nanocomposites were applied to the water-mediated Suzuki coupling reaction of chlorobenzene and phenylboronic acid and exhibited a high yield of biphenyl (49%) under mild reaction conditions free of phase-transfer agents and ligands. Product yields in the reaction of Aryl chlorides containing electron-withdrawing groups attached to their benzene ring can reach approximately 90%. Thiol-functionalized mesoporous silica, which can trap soluble Pd species, was used to confirm the negligible leaching in solution and therefore heterogeneous reaction. This heterogeneous catalyst is stable, showing unobvious activity loss after 10 catalytic runs. Characterization by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption fine structure analysis, and N-2 sorption techniques revealed intercalated CoO nanopartiCles inside a carbon matrix with uniform mesopore sizes (similar to 3 nm), high surface area (similar to 504 m(2)/g), and large pore volumes (similar to 0.38 cm(3)/g). Additionally, very small Pd Clusters consisting of approximately three atoms and Pd-O bonds formed on the interface between CoO and Pd nanopartiCles. The unsaturated coordinative Pd may be responsible for the Activation of chlorobenzene in the absence of any additives or ligands. Uniform mesopores and the hydrophobic nature of the carbon support may also facilitate the mass transfer of the reactant molecules and enrichment inside pores. For comparison, the catalytic activities of Pd catalysts supported on pristine mesoporous carbon and carbon embedded with nickel oxide nanopartiCles were also tested.Activation of Aryl Chlorides in Water under Phase-Transfer Agent-Free and Ligand-Free Suzuki Coupling by Heterogeneous Palladium Supported on Hybrid Mesoporous CarbonPd Cluster; hybrid mesoporous carbon; Aryl chloride; Suzuki coupling; water; TBAB-free; ligand-freex45201593#N/AFALSE
3261
d0cc00361a10.1039/d0cc00361aFALSEFeng, SHHigh-efficiency methanol oxidation electrocatalysts realized by ultrathin PtRuM-O (M = Ni, Fe, Co) nanosheets2020#N/ATRUE
3262
cs502112g10.1021/cs502112gFALSEhttps://doi.org/10.1021/cs502112gPeng, ZMACS Catal.Development of a highly active and stable electrocatalyst is of great significance in the oxygen reduction reaction (ORR) research. Although octahedral Pt-Ni nanopartide catalysts have attracted much interest because of their high activity, their poor stability raises a severe issue for real applications. We achieve both outstanding ORR. activity and much improved catalyst stability by preparing octahedral Pt2CuNi alloy nanopartiCles with uniform element distribution, with the activity far exceeding the DOE target and the stability comparable to that of state-of-the-art Pt/C. The improved stability is attributed to uniform elemental distribution within the ternary partiCles, which helps with formation of intact Pt surface layers and good retention of the octahedral morphology.Octahedral Pt2CuNi Uniform Alloy NanopartiCle Catalyst with High Activity and Promising Stability for Oxygen Reduction Reactionoxygen reduction reaction; electrocatalyst; octahedral nanopartiCle; activity; stability92201538#N/ATRUE
3263
cs501273410.1021/cs5012734FALSEhttps://doi.org/10.1021/cs5012734Chen, JGACS Catal.Bond scission of C-O/C=O, C-C, and C-H from oxygenates on Mo(110), Ni/Mo(110), and Co/Mo(110) has been investigated via density functional theory (DFT) calculations, temperature-programmed desorption (TPD), and high-resolution electron energy loss spectroscopy (HREELS). Propanal and 1-propanol are used as probe molecules for biomass-derived oxygenates due to their relatively high vapor pressures, allowing their easy introduction into UHV systems. DFT results predict that the binding energy trend of propanal and 1-propanol is Mo(110) > Co/Mo(110) > Ni/Mo(110), which suggests that binding energies are reduced by the modification of Mo(110) with Ni and Co admetals. TPD and HREELS results show that bond scission activity and selectivity can be tuned upon admetal modification of Mo(110). For both molecules, Mo(110) shows a highly selective deoxygenation pathway toward C-O/C=O bond scission to produce propene, while bimetallic surfaces instead exhibit a higher activity for C-C and C-H bond scission. Among the three surfaces, Ni modification leads to the highest selectivity for deCarbonylation to produce ethylene and Co modification results in the highest selectivity for reforming to produce syngas.Understanding the Role of Metal-Modified Mo(110) Bimetallic Surfaces for C-O/C=O and C-C Bond Scission in C3 Oxygenatespropanal; 1-propanol; deoxygenation; reforming; deCarbonylation; nonprecious bimetallic surfacesx8201551#N/AFALSE
3264
cs501202t10.1021/cs501202tFALSEhttps://doi.org/10.1021/cs501202tSchlaf, MACS Catal.The complexes [(4'-Ph-terpy)Ru(H2O)(3)](OTf)(2) and [(4'-Ph-terpy)Ir(OTf)(3)] have been evaluated as catalysts for the conversion of 2,5-hexanedione and 2,5-dimethylfuran to hydrodeoxygenated products in aqueous acidic medium at elevated temperature (150-225 degrees C) under hydrogen gas (5.5 MPa). These two substrates form part of a value chain leading from C6 sugars to 2,5-hexanediol, 2,5-dimethyltetrahydrofuran, and hexane, which can be generated by the homogeneously acting ruthenium catalyst in up to 69%, 80%, and 10% yield, respectively, while at T > 175 degrees C the iridium system decomposes to a highly active but heterogeneously acting coating in the reactor defeating the premise of a homogeneous catalyst system. The deActivation and decomposition pathway of both catalysts leads to the formation of a series of isostructural complexes [M(4'-Ph-terpy)2](n)+ (M = Fe, Ni, Ru, Ir; n = 2, 3) characterized by ESI-MS and single crystal X-ray crystallography, in which the source of the Fe and Ni is the 316SS reactor body.Hydrodeoxygenation of 2,5-Hexanedione and 2,5-Dimethylfuran by Water-, Air-, and Acid-Stable Homogeneous Ruthenium and Iridium Catalystshomogeneous catalysis; aqueous media; hydrogenation; hydrodeoxygenation; biomass conversion; catalyst decompositionx28201455#N/AFALSE
3265
cs501119d10.1021/cs501119dFALSEhttps://doi.org/10.1021/cs501119dYamashita, HACS Catal.An acidic resin bearing -SO3 functional groups within its macroreticular structure acts as an efficient support for in situ formation of a noble-metal-free Ni-based catalyst responsible for visible-light-driven H-2 production from water. Characterization by means of XAFS revealed that simple ion-exchange of the resin with a trinuClear Ni complex, Ni(NiL2)(2)C(l)2 (L = beta-mercaptoethylamine), affords monomeric Ni(II) species involving beta-mercaptoethylamine and aqua ligands in an octahedral coordination geometry, which is easily transformed into real active species containing a TEOA ligand during the initial induction period of the photocatalytic reaction. Such in situ-generated Ni species offer a simple and efficient photocatalytic system whose activity is five times greater than that of its homogeneous counterpart, enabling efficient H-2 production when xanthene dye is employed as a visible-light-responsive photosensitizer. The acidity of the resins as well as beta-mercaptoethylamine and the TEOA ligands were found to be key factors in achieving efficient catalytic performance. Moreover, leaching and agglomeration of the active Ni species were not observed, and the recovered catalyst could be recyCled without significant loss of activity.Creation of Nickel-Based Active Species within a Macroreticular Acidic Resin: A Noble-Metal-Free Heterogeneous Catalyst for Visible-Light-Driven H-2 Evolution from Wateracidic resin; Ni complex; H-2 production; photocatalysis; visible-light; noble-metal-freex22201442#N/AFALSE
3266
cs501081a10.1021/cs501081ahttps://doi.org/10.1021/cs501081aWu, QACS Catal.1-Hexene polymerizations were carried out with amine imine nickel complexes [(ArN=C(R-1)-((RR3)-R-2)CNHAr)-NiBr2, 1a, R-1 = R-2 = R-3 = Me, Ar = 2,6-(iPr)(2)C6H3; 1b, R-1 = R-2 = R-3 = Me, Ar = 2,6-(Me)(2)C6H3; 2a, R-1 = Me, R-2 = R-3 = H, Ar = 2,6-(iPr)(2)C6H3; 3a, R-1 = Me, R-2 = tBu, R-3 = H, Ar = 2,6-(iPr)(2)C6H3] in the presence of MMAO or Et2AlCl. The ligand-directed regioselectivity involving insertion fashion and chain walking in amine imine nickel-catalyzed 1-hexene polymerization is Clearly observed. Catalyst la with two methyl substituents on the bridging carbon can polymerize 1-hexene to afford semicrystalline polyethylene with long methylene sequence (-(CH2)(n)-, n = 40-74) via a combination of 90% selectivity of 2,1-insertion fashion and precise chain walking, whereas catalyst 3a with a tert-butyl on the bridging carbon can polymerize 1-hexene in 80% selectivity of 1,2-insertion to produce amorphous polyolefin with predominant methyl branches through 2,6-enchainment.Ligand-Directed Regioselectivity in Amine-Imine Nickel-Catalyzed 1-Hexene Polymerization1-hexene; nickel; chain walking; regioselectivityx56201558#N/AFALSE
3267
cs500934g10.1021/cs500934gFALSEhttps://doi.org/10.1021/cs500934gAnanikov, VPNoninnocent Nature of Carbon Support in Metal/Carbon Catalysts: Etching/Pitting vs Nanotube Growth under Microwave Irradiationx2014#N/AFALSE
3268
cs500918c10.1021/cs500918cFALSEhttps://doi.org/10.1021/cs500918cKleitz, FACS Catal.Dry reforming of methane is gaining great interest owing to the fact that this process efficiently converts two greenhouse gases (CH4 and CO2) into synthesis gas (CO + H-2), which can be further processed into liquid fuels and chemicals. Herein, a perovskite-derived nanostructured Ni/La2O3 material is reported as an efficient and stable catalyst for this reaction. High-surface-area LaNiO3 perovskite precursor is first synthesized by the method of nanocasting using ordered mesoporous silica SBA-15 as a hard template. The resulting nanostructured perovskite was found to possess high specific surface area as obtained from the BET method (150 m(2) g(-1)). The reduction behavior of the nanocast perovskite was monitored by performing the temperature-programmed reduction of hydrogen (TPR-H-2). It has been found that the complete destruction of perovskite structure occurs below 700 degrees C, leading to the formation of highly dispersed Ni-0 in La(2)O3, as observed in the XRD pattern of the material after reduction. Similar behavior was observed for the LaNiO3 perovskite synthesized using the conventional citrate process. However, the specific surface area of the former material was found to be much higher than that of the latter (50 m(2) g(-1)), which obviously resulted from the mesoporous architecture of the nanocast LaNiO3. It was found that the nanostructured Ni/La2O3 obtained from the reduction of the nanocast LaNiO3 exhibited high activity for the conversion of the reactant gases (CH4 and CO2) compared to the catalyst obtained from conventional perovskite, under the reaction conditions used in the present study. Particularly, no coke formation was observed for the mesoporous catalyst under the present conditions of operation, which in turn reflects the enhanced stability of the catalyst obtained from the nanocast LaNiO3. The improved performance of the nanostructured catalyst is attributed to the accessibility of the active sites resulting from the high specific surface area and the confinement effect leading to the stabilization of Ni nanopartiCles.Nanocast LaNiO3 Perovskites as Precursors for the Preparation of Coke-Resistant Dry Reforming Catalystsdry reforming; nanocasting; perovskites; coke resistance; high surface area; synthesis gas; mesoporousx115201459#N/AFALSE
3269
cs502075510.1021/cs5020755FALSEhttps://doi.org/10.1021/cs5020755Bueno, JMCACS Catal.Steam reforming of ethanol (SRE) is a strategic reaction for H-2 production. However, despite considerable work, several aspects of the mechanism and catalytic system for this reaction are not fully understood. There have been many efforts to improve the understanding of the catalysts' behavior during SRE, using both theoretical studies and experimental investigations based on operando characterization techniques. Even though cobalt and nickel are considered the most promising catalytically active metals for industrial SRE, acquiring further knowledge on the reaction mechanism, metal support interactions, and catalyst deActivation (due to carbon accumulation, sintering, or metal oxidation) will enable the successful design of new and stable catalysts. In this review, we analyze the reaction pathways for metal-catalyzed SRE and discuss the available experimental and theoretical data to suggest alternatives to address three major issues: (i) the impact of partiCle size and metal oxidation state in the SRE performance; (ii) the importance of metal surface electronic properties to obtain a balanced and stable catalyst; and (iii) the influence of support on the catalyst selectivity and stability. Clarification of these issues is a key point for understanding the SRE reaction and for the development of new high performance catalysts.Toward Understanding Metal-Catalyzed Ethanol Reformingethanol reforming; hydrogen production; reaction mechanism; metal catalyst; heterogeneous catalysis; biomass conversion; ethanol decomposition1272015229#N/ATRUE
3270
cs500853f10.1021/cs500853fFALSEhttps://doi.org/10.1021/cs500853fAppel, AMACS Catal.Nickel complexes were prepared with diphosphine ligands that contain pendant amines, and these complexes catalytically oxidize primary and secondary alcohols to their respective aldehydes and ketones. Kinetic and mechanistic studies of these prospective electrocatalysts were performed to understand what influences the catalytic activity. For the oxidation of diphenylmethanol, the catalytic rates were determined to be dependent on the concentration of both the catalyst and the alcohol and independent of the concentration of base and oxidant. The incorporation of pendant amines to the phosphine ligand results in substantial increases in the rate of alcohol oxidation with more electron-donating substituents on the pendant amine exhibiting the fastest rates.Catalytic Oxidation of Alcohol via Nickel Phosphine Complexes with Pendant Aminesalcohol oxidation; nickel; electrochemistry; catalysis; proton relayx41201457#N/AFALSE
3271
cs500809w10.1021/cs500809wFALSEhttps://doi.org/10.1021/cs500809wMedlin, JWACS Catal.To inhibit sintering of similar to 5 nm supported Ni partiCles during dry reforming of methane (DRM), catalysts were stabilized with porous alumina grown by ABC alucone molecular layer deposition (MLD). The uncoated catalyst continuously deactivated during DRM at 973 K In contrast, the DRM rates for the MLD-coated catalysts initially increased before stabilizing, consistent with an increase in the exposed nickel surface area with exposure to high temperatures. Post-reaction partiCles were smaller for the MLD-coated catalysts. Catalysts with only 5 MLD layers had higher DRM rates than the uncoated catalyst, and a sample with 10 MLD layers remained stable for 108 h.Stabilizing Ni Catalysts by Molecular Layer Deposition for Harsh, Dry Reforming Conditionsdry reforming of methane; heterogeneous catalysis; molecular layer deposition; thin films; catalyst stabilityx121201424#N/AFALSE
3272
cs500757k10.1021/cs500757kFALSEhttps://doi.org/10.1021/cs500757kShimizu, KACS Catal.Supported platinum catalysts have been studied for the reductive amination of levulinic acid (LA) by H-2 to N-Alkyl-5-methyl-2-pyrrolidones under solvent-free conditions. The activity depends on the type of metal (Pt, Re, Pd, Rh, Ru, Cu, Ni), support material, and coloaded oxides of transition metals (V, Cr, Mo, W, Re). In 24 kinds of catalyst tested, Pt and MoOx (molybdenum oxide) coloaded TiO2 (Pt-MoOx/TiO2) shows the highest activity. Pt-MoOx/TiO2 is effective for reductive amination of LA with wide varieties of amines under mild conditions (3 bar of H-2, 100 degrees C, solvent-free) to give high isolated yield of pyrrolidinones and shows higher turnover number (TON) than previously reported catalysts for reductive amination of LA with an aliphatic amine. The catalyst can be separated from the reaction mixture by filtration, and the recovered catalyst can be reused. This is the first general and reusable heterogeneous catalytic system for the reductive amination of LA. On the basis of mechanistic studies, high activity of Pt-MoOx/TiO2 can be attributed to acid-base interaction between the add sites of Pt-MoOx/TiO2 and Carbonyl groups in LA and an intermediate.Heterogeneous Pt Catalysts for Reductive Amination of Levulinic Acid to Pyrrolidonesbiomass; levulinic acid; reductive amination; amines; supported platinum catalystsx88201420#N/AFALSE
3273
cs500744x10.1021/cs500744xFALSEhttps://doi.org/10.1021/cs500744xHuang, PYACS Catal.In this work, the effects of the addition of transition metals (Mn, Fe, Co, Ni, Cu) on the structure and performance of the doped carbon catalysts M-PANI/C-Mela are investigated. The results show that the doping of various transition metals affected structures and performances of the catalysts significantly. Doping with Fe and Mn leads to a catalyst with a graphene-like structure, and doping with Co, Ni, and Cu leads to a disordered or nanosheet structure. The doping of transition metals can enhance the performance of the catalysts, and their ORR activity follows the order of Fe > Co > Cu > Mn > Ni, which is consistent with the order of their active N contents. We suggest that the various performance enhancements of the transition metals may be the result of the joint effect of the following three aspects: the N content/active N content, metal residue, and the surface area and pore structure, but not the effect of any single factor.Effect of Transition Metals on the Structure and Performance of the Doped Carbon Catalysts Derived From Polyaniline and Melamine for ORR Applicationdoped carbon; effect; oxygen reduction reaction; performance; structure; transition metalsx229201453#N/AFALSE
3274
cs500737p10.1021/cs500737pFALSEhttps://doi.org/10.1021/cs500737pMavrikakis, MACS Catal.We present a first-principles, self-consistent periodic density functional theory (PW91-GGA) study of formic acid (HCOOH) decomposition on model (111) and (100) facets of eight fcc metals (Au, Ag, Cu, Pt, Pd, Ni, Ir, and Rh) and (0001) facets of four hcp (Co, Os, Ru, and Re) metals. The calculated binding energies of key formic acid decomposition intermediates inCluding formate (HCOO), Carbonyl (COOH), carbon monoxide (CO), water (H2O), carbon dioxide (CO2), hydroxyl (OH), carbon (C), oxygen (O), and hydrogen (H; H-2) are presented. Using these energetics, we develop thermochemical potential energy diagrams for both the Carbonyl-mediated and the formate-mediated dehydrogenation mechanisms on each surface. We evaluate the relative stability of COOH, HCOO, and other isomeric intermediates (i.e., CO + OH, CO2 + H, CO + O + H) on these surfaces. These results provide insights into formic acid decomposition selectivity (dehydrogenation versus dehydration), and in conjunction with calculated vibrational frequency modes, the results can assist with the experimental search for the elusive Carbonyl (COOH) surface intermediate. Results are compared against experimental reports in the literature.Trends in Formic Acid Decomposition on Model Transition Metal Surfaces: A Density Functional Theory studyformic acid; density functional theory; structure sensitivity; dehydrogenation; thermochemistry; selectivityx136201485#N/AFALSE
3275
cs500694m10.1021/cs500694mhttps://doi.org/10.1021/cs500694mLong, BKACS Catal.Sterically demanding 2,6-bis(diphenylmethyl)-4-methylaniline was condensed onto acenaphthenequinone via an aminoalane intermediate and metalated using nickel(II) dibromide dimethoxyethane adduct to yield bis[(2,6-dibenzhydry1-4-methylimino) acenaphthene]dibromo nickel(II). This alpha-diimine precatalyst was examined for high-temperature ethylene polymerization and proved to be thermally robust at temperatures as high as 90 degrees C, demonstrating enhanced activity as compared with related catalysts. Furthermore, the resultant polymers displayed increased melting transitions as compared with those produced using catalysts with identical N-Aryl moieties appended to nonacenaphthenequinone-derived ligand backbones.Enhancing alpha-Diimine Catalysts for High-Temperature Ethylene Polymerizationpolyethylene; nickel; alpha-diimine; catalysis; high temperature; coordination polymerizationx125201437#N/AFALSE
3276
cs501952410.1021/cs5019524FALSEhttps://doi.org/10.1021/cs5019524Na, CZACS Catal.Metal-catalyzed hydrolysis is an important reaction for releasing hydrogen stored in ammonia borane, a promising fuel form for the future hydrogen economy, under ambient conditions. A variety of catalysts made of different transition metals have been investigated to improve the efficiency of hydrogen generation; however, little attention has been given to the possible influence of the compensation effect on catalyst design. Using face-centered cubic (FCC) packed ruthenium (Ru) nanopartiCles supported on layered double oxide nanodisks, we show that the compensation effect produces an isokinetic temperature at Ti = 17.5(+/-1.6) degrees C within the operational range of hydrogen generation. We further show that the turnover frequency (TOF) of the reaction can be maximized for operations performed below Ti by reducing the size of Ru-FCC nanopartiCles, which increases the fraction of edge and corner atoms and lowers the Activation energy. At 15 degrees C, TOF can reach more than 90% of the theoretical maximum (0.72 mol m(-2) h(-1)) using Ru nanopartiCles having an average diameter of 2 nm and giving an Activation energy of 17.7(+/-0.7) kJ mol(-1). To generate hydrogen above Ti, TOF is maximized by using enlarged Ru nanopartiCles with a diameter of 3.8 nm, giving an Activation energy of 87.3(+/-5.8) kJ mol(-1). At 25 degrees C, these nanopartiCles produce a TOF of 1.8(+/-0.3) mol m(-2) h(-1), representing at least an 81% increase in comparison to the highest TOF reported for elemental catalysts. Our results suggest that controlling the reaction Activation energy by adjusting nanopartiCle size represents a viable strategy for designing catalysts that can maximize TOF for ammonia borane hydrolysis operated both below and above the isokinetic temperature.Isokinetic Temperature and Size-Controlled Activation of Ruthenium-Catalyzed Ammonia Borane Hydrolysiscompensation effect; isokinetic temperature; metal hydride; hydrogen storage and production; nanopartiCle nuCleation; supported and stabilized nanocatalyst; layered double hydroxide derivative76201597#N/ATRUE
3277
cs500562u10.1021/cs500562uFALSEhttps://doi.org/10.1021/cs500562uSavage, PEACS Catal.Herein, we report on the development of supported Ni and Raney Ni catalysts doped with Cu for the hydrothermal hydrodeoxygenation (HDO) of o-cresol. Raney Ni catalysts doped with >10 wt % Cu show a significant reduction in gasification activity and produce a higher yield of liquid products than the unmodified Raney Ni catalyst. Adding Cu did not, however, increase the yield of the desired HDO products, liquid hydrocarbons. The addition of acid sites to the catalysts, by supporting Ni and NiCu on Al2O3 and by calcining the Raney Ni to produce Al2O3 within the catalyst, however, did significantly increase the HDO activity of the catalysts such that yields of liquid hydrocarbons exceeded 60%. Two catalysts, a novel calcined 5% Raney NiCu catalyst and a NiCu/Al2O3 catalyst, produced the highest liquid hydrocarbon yields to date (similar to 70%) for stable, non-noble metal, hydrothermal HDO catalysts.Development of NiCu Catalysts for Aqueous-Phase Hydrodeoxygenationhydrodeoxygenation; hydrothermal; Raney Ni; o-cresol; aqueous phase; NiCu catalysts; alumina; biomassx32201445#N/AFALSE
3278
cs500523k10.1021/cs500523kFALSEhttps://doi.org/10.1021/cs500523kDing, WPACS Catal.A nanocomposite able to function as a hydrogenation catalyst under strongly acidic conditions without the presence of noble metals is synthesized and thoroughly studied. This specially designed catalyst possesses a unique structure composed of carbon nitride (CN) with underlying nickel, in which the nickel endows the CN with new active sites for hydrogen adsorption and Activation while it itself is physically isolated from the reactive environment and protected from poisoning or loss. The CN is inert for hydrogenation without the help of nickel. The catalyst shows good performance for hydrogenation of nitro compounds under strong acidic conditions, inCluding the one-step hydrogenation of nitrobenzene in 1.5 M H2SO4 to produce p-amoniophenol, for which the acid in the reaction system has restricted the catalyst only to noble metals in previous studies. Further characterization has demonstrated that the nickel in the catalyst is in an electron-deficient state because some of its electron has been donated to CN (HRTEM, PES); thus, the hydrogen can be directly adsorbed and activated by the CN (HD exchange, in situ IR and NMR). With this structure, the active nickel is protected by inert CN from the corrosion of acid, and the inert CN is activated by the nickel for catalytic hydrogenation. The assembly of them gives a new catalyst that is effective and stable for hydrogenation even under a strongly acidic environment.Acid-Resistant Catalysis without Use of Noble Metals: Carbon Nitride with Underlying Nickelhydrogenation; corrosion-resistance; carbon nitride; hetero junction; noble metal freex99201456#N/AFALSE
3279
cs501948d10.1021/cs501948dFALSEhttps://doi.org/10.1021/cs501948dBrookhart, MACS Catal.Neutral nickel methyl complexes incorporating 2,8-diArylnaphthyl groups have been synthesized and characterized. Salicylaldiminato nickel systems 1a,b are exceptionally active neutral nickel single component catalysts for the polymerization of ethylene capable of producing lightly branched ultrahigh-molecular-weight polyethylene (UHMWPE). In addition, complex la shows a quasi-living polymerization behavior.Synthesis of Branched Ultrahigh-Molecular-Weight Polyethylene Using Highly Active Neutral, Single-Component Ni(II) Catalystsnickel catalysts; polymerization; UHMWPE; salicyaldimine; branched polyethylene67201576#N/ATRUE
3280
cs501911r10.1021/cs501911rFALSEhttps://doi.org/10.1021/cs501911rSingh, AKACS Catal.Late-transition-metal-doped Pt Clusters are prevalent in CO oxidation catalysis, as they exhibit better catalytic activity than pure Pt, while reducing the effective cost and poisoning However, completely eliminating the critical problem of Pt poisoning still poses a big challenge. Here, we report for the first time that, among the bimetallic Clusters ((Pt3M where M = Co, Ni, and Cu)/MgO(100)), the CO adsorption site inverts for Pt3Co/MgO(100) from Pt to Co, due to the complete uptake of Pt d-states by lattice oxygen. While this resolves the problem of Pt poisoning, good reaction kinetics are predicted through low barriers for Langmuir-Hinshelwood and Mars van Krevelen (MvK) mechanisms of CO oxidation for Pt3Co/MgO(100) and Li-doped MgO(100), respectively. Li doping in MgO(100) compensates for the charge imbalance caused by a spontaneous oxygen vacancy formation. Pt-3 Co/Li-doped MgO(100) stands out as an exceptional CO oxidation catalyst, giving an MvK reaction barrier as low as 0.11 eV. We thereby propose a novel design strategy of d-band center inversion for CO oxidation catalysts with no Pt poisoning and excellent reaction kinetics.Pt-Poisoning-Free Efficient CO Oxidation on Pt3Co Supported on MgO(100): An Ab Initio Studybimetallic Clusters; CO oxidation; catalysis; Pt poisoning free; density functional theory15201557#N/ATRUE
3281
cs500412u10.1021/cs500412uFALSEhttps://doi.org/10.1021/cs500412uLewis, NSACS Catal.The catalytically inactive components of a film have been converted, through an operando method of synthesis, to produce a catalyst for the reaction that the film is catalyzing. Specifically, thin films of molybdenum diselenide have been synthesized using a two-step wet-chemical method, in which excess sodium selenide was first added to a solution of ammonium heptamolydbate in aqueous sulfuric acid, resulting in the spontaneous formation of a black precipitate that contained molybdenum triselenide (MoSe3), molybdenum trioxide (MoO3), and elemental selenium. After purification and after the film had been drop cast onto a glassy carbon electrode, a reductive potential was applied to the precipitate-coated electrode. Hydrogen evolution occurred within the range of potentials applied to the electrode, but during the initial voltammetric cyCle, an overpotential of similar to 400 mV was required to drive the hydrogen-evolution reaction at a benchmark current density of -10 mA cm(-2). The overpotential required to evolve hydrogen at the benchmark rate progressively decreased with subsequent voltammetry cyCles, until a steady state was reached at which only similar to 250 mV of overpotential was required to pass -10 mA cm(-2) of current density. During the electrocatalysis, the catalytically inactive components in the as-prepared film were (reductively) converted to MoSe2 through an operando method of synthesis of the hydrogen-evolution catalyst. The initial film prepared from the precipitate was smooth, but the converted film was completely covered with pores similar to 200 nm in diameter. The porous MoSe2 film was stable while being assessed by cyClic voltammetry for 48 h, and the overpotential required to sustain 10 mA cm(-2) of hydrogen evolution increased by <50 mV over this period of operation.Operand Synthesis of Macroporous Molybdenum Diselenide Films for Electrocatalysis of the Hydrogen-Evolution Reactionhydrogen-evolution reaction; synthesis of molybdenum diselenide; wet-chemical synthesis of layered electrocatalysts; mesoporous catalysts; synthesis of group VI dichalcogenidesx106201461#N/AFALSE
3282
cs500337a10.1021/cs500337aFALSEhttps://doi.org/10.1021/cs500337aRossi, LMACS Catal.The preparation of bimetallic nanopartiCles with controlled size, shape, and composition remains a difficult task, and reproducible methods are highly desired. Here, we report the codecomposition of Ni(cod)(2) and Pd-2(dba)(3) organometallic precursors in the presence of hexadecylamine (HDA) and hydrogen as an efficient approach to get size-controlled bimetallic nickel palladium nanopartiCles. Presynthesized nickel palladium nanopartiCles of different Ni/Pd ratios were further used for the preparation of supported catalysts by the sol-immobilization method onto a magnetic silica. The obtained supported catalysts were investigated in the hydrogenation of cyClohexene and compared to Ni and Pd monometallic catalysts. The catalysts prepared with a 1:9 Ni/Pd molar ratio achieved the highest initial turnover frequency > 50000 h(-1), providing higher activity than the pure Pd monometallic counterpart. This represents an important saving of noble metal. Moreover, the magnetic separation allows excellent separation of the catalyst from the liquid products without metal leaching and exposure to air, leading to an efficient recyCling.Organometallic Preparation of Ni, Pd, and NiPd NanopartiCles for the Design of Supported Nanocatalystsorganometallic synthesis; bimetallic nanopartiCles; monometallic nanopartiCles nickel; palladium; hydrogenation; magnetic separationx34201468#N/AFALSE
3283
cs500328c10.1021/cs500328cFALSEhttps://doi.org/10.1021/cs500328cRossmeisl, JACS Catal.One of the main challenges associated with the electrochemical CO or CO2 reduction is poor selectivity toward energetically rich products. In order to promote selectivity toward hydrocarbons and alcohols, most notably, the hydrogen evolution reaction (HER) should be suppressed. To achieve this goal, we studied intermetallic compounds consisting of transition metal (TM) elements that can reduce CO (Ru, Co, Rh, Ir, Ni, Pd, Pt, and Cu) separated by TM and post transition metal elements (Ag, Au, Cd, Zn, Hg, In, Sn, Pb, Sb, and Bi) that are very poor HER catalysts. In total, 34 different stable binary bulk alloys forming from these elements have been investigated using density functional theory calculations. The electronic and geometric properties of the catalyst surface can be tuned by varying the size of the active centers and the elements forming them. We have identified six different potentially selective intermetallic surfaces on which CO can be reduced to methanol at potentials comparable to or even slightly positive than those for CO/CO2 reduction to methane on Cu. Common features shared by most of the selective alloys are single TM sites. The role of single sites is to block parasitic HER and thereby promote CO reduction.Intermetallic Alloys as CO Electroreduction Catalysts-Role of Isolated Active Sitesalloys; intermetallics; CO2 reduction; CO reduction; density functional theory; single sitesx69201452#N/AFALSE
3284
cs500228810.1021/cs5002288FALSEhttps://doi.org/10.1021/cs5002288Ruoff, RSACS Catal.We present first-principles modeling of water oxidation over various graphene systems, such as nitrogen-doped graphene; graphene monolayers on iron, nickel, and copper surfaces; and bi- and trilayer graphene on copper surfaces. It is shown that nitrogen-doped graphene and graphene over copper are better for this reaction than those over platinum at temperatures below 100 degrees C. Bi- and trilayer graphene on copper have catalytic properties similar to those of a monolayer on copper.Water Splitting over Graphene-Based Catalysts: Ab Initio Calculationsgraphene; water splitting; oxidation; carbocatalysis; DFT; modelingx43201462#N/AFALSE
3285
cs501826s10.1021/cs501826sFALSEhttps://doi.org/10.1021/ja00067a033Stubbs, ECCopper-in-Charcoal Revisited: Delineating the Nature of the Copper Species and Its Role in Catalysis2015#N/ATRUE
3286
cs500167k10.1021/cs500167kFALSEhttps://doi.org/10.1021/cs500167kSun, SHACS Catal.We report a facile synthesis of monodisperse NiPd alloy nanopartiCles (NPs) and their assembly on graphene (G) to catalyze the tandem dehydrogenation of ammonia borane (AB) and hydrogenation of R-NO2 and/or R-CN to R-NH2 in aqueous methanol solutions at room temperature. The 3.4 nm NiPd alloy NPs were prepared by coreduction of nickel(II) acetate and palladium(H) acetlyacetonate by borane-tert-butylamine in oleylamine and deposition on G via a solution phase self-assembly process. G-NiPd showed composition-dependent catalysis on the tandem reaction with G-Ni30Pd70 being the most active. A variety of R-NO2 and/or R-CN derivatives were reduced selectively into R-NH2 via G-Ni30Pd70 catalyzed tandem reaction in 5-30 mm reaction time with the conversion yields reaching up to 100%. Our study demonstrates a new approach to G-NiPd-catalyzed dehydrogenation of AB and hydrogenation of R-NO2 and R-CN. The G-NiPd NP catalyst is efficient and reusable, and the reaction can be performed in an environment-friendly process with short reaction times and high yields.Tandem Dehydrogenation of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds Catalyzed by Graphene-Supported NiPd Alloy NanopartiClesalloy nanopartiCles; tandem reaction; dehydrogenation; hydrogenation; nitro/nitrile compounds; primary aminesx170201452#N/AFALSE
3287
cs500162510.1021/cs5001625FALSEhttps://doi.org/10.1021/cs5001625Zhang, YWACS Catal.Delicate elaboration of the nanostructures of multimetal catalytic materials with well-defined shapes and compositions to reveal their potential use as heterogeneous nanocatalysts for organic synthetic reactions with the combined merits of heterogeneous and homogeneous catalysis is both scientifically and technologically important, but this type of investigation has remained rarely pursued. In this work, we demonstrated a facile hydrothermal approach toward the one-pot shape-selective syntheses of Pd-Rh nanocrystals with tunable compositions and morphologies, inCluding hollow nanocubes (NCs), nanoicosahedrons (NIs), and nanotruncated octahedrons (NTOs), using poly(Vinylpyrrolidone) as both reductant and capping agent and halide anions (Br-/I-) as shape control agents. The formation of Pd-Rh hollow NCs was induced by an iodine adsorbate-induced reconstruction mechanism with KI, whereas the formation of Pd-Rh NIs and NTOs were realized by controlling the selective nuCleation of twinned seeds or single crystal seeds and their relative growth rates along different facets (e.g., (111) and (100) facets) through finely adjusting the Pd/Rh ratio and the amount of KBr added in the absence of KI. Due to the great significance of Pd-catalyzed organic reactions, the catalytic performances of Pd-Rh nanocrystals for Suzuki cross-coupling reactions with different reactants were evaluated. The measured turnover frequencies (TOFs) suggested that Pd-Rh hollow NCs held considerably enhanced catalytic activities (at least 3 times) than other Pd-based solid nanocrystals inCluding Pd-Rh NIs, Pd-Rh NTOs, Pd-Rh NCs, Pd-NCs, and commercial Pd/C, with iodobenzene as the reactant. In addition, even for more inert reactants such as bromobenzene or 4-bromotoluene, the catalytic activities of Pd-Rh hollow NCs were still impressive (showing similar TOFs to those of other shapes for reactions with iodobenzene as the reactant), indicating the promising application of Pd-based nanocatalysts for other powerful Pd-catalyzed organic synthesis reactions. Meanwhile, Pd-based solid NCs, enClosed with (100) facets only, showed better catalytic performance than NIs as well as NTOs, which had a larger fraction of (111) facets other than (100) ones, further suggesting that morphology differences were vitally significant to tune the catalytic performances of bimetallic nanocatalysts.Pd-Rh Nanocrystals with Tunable Morphologies and Compositions as Efficient Catalysts toward Suzuki Cross-Coupling ReactionsPd-Rh nanocrystals; bimetallic alloys; shape control; nanocatalysis; Suzuki cross-coupling reaction; heterogeneous catalystx57201463#N/AFALSE
3288
cs500125y10.1021/cs500125yFALSEhttps://doi.org/10.1021/cs500125yWong, SSACS Catal.An ambient, surfactant-based synthetic means was used to prepare ultrathin binary (d similar to 2 nm) Pd-Ni nanowires, which were subsequently purified using a novel butylamine-based surfactant-exchange process coupled with an electrochemical CO adsorption and stripping treatment to expose active surface sites. We were able to systematically vary the chemical composition of as-prepared Pd-Ni nanowires from pure elemental Pd to Pd0.50Ni0.50 (atomic ratio), as verified using EDS analysis. The overall morphology of samples possessing >60 atom % Pd consisted of individual, discrete one-dimensional nanowires. The electrocatalytic performances of elemental Pd, Pd0.90Ni0.10, Pd0.83Ni0.17, and Pd0.75Ni0.25 nanowires in particular were examined. Our results highlight a volcano-type relationship between chemical composition and corresponding ORR activities with Pd0.90Ni0.10, yielding the highest activity (i.e., 1.96 mA/cm(2) at 0.8 V) among all nanowires tested. Moreover, the Pd0.90Ni0.10 sample exhibited outstanding methanol tolerance ability. In essence, there was only a relatively minimal 15% loss in the specific activity in the presence of 4 mM methanol, which was significantly better than analogous data on Pt nanopartiCles and Pt nanowires. In addition, we also studied ultrathin, core-shell Pt similar to Pd0.90Ni0.10 nanowires, which exhibited a specific activity of 0.62 mA/cm(2) and a corresponding mass activity of 1.44 A/mg(Pt), at 0.9 V. Moreover, our as-prepared core shell electrocatalysts maintained excellent electrochemical durability. We postulate that one-dimensional Pd-Ni nanostructures represent a particularly promising platform for designing ORR catalysts with high performance.Probing Ultrathin One-Dimensional Pd-Ni Nanostructures As Oxygen Reduction Reaction CatalystsPd-Ni; binary electrocatalyst; ORR; methanol tolerance; core-shell structurex94201450#N/AFALSE
3289
cs501602910.1021/cs5016029https://doi.org/10.1021/cs5016029Brookhart, MACS Catal.Cationic Pd(II) catalysts incorporating bulky 8-p-tolylnaphthyl substituted diimine ligands have been synthesized and investigated for ethylene polymerization and ethylene/methyl acrylate copolymerization. Homopolymerization of ethylene at room temperature resulted in branched polyethylene with narrow M-w/M-n values (ca. 1.1), indicative of a living polymerization. A mechanistic study revealed that the catalyst resting state was an Alkyl olefin complex and that the turnover-limiting step was migratory insertion, thus the turnover frequency is independent of ethylene concentration. Copolymerization of ethylene and methyl acrylate (MA) was also achieved. MA incorporation was found to increase linearly with MA concentration, and copolymers with up to 14 mol % MA were prepared. Mechanistic studies revealed that acrylate insertion into a PdCH3 bond occurs at -70 degrees C to yield a four-membered chelate, which isomerizes first to a five-membered chelate and then to a six-membered chelate. Barriers to migratory insertion of both the (diimine)PdCH3(C2H4)(+) (19.2 kcal/mol) and (diimine)PdCH3(eta(2)-C2H3CO2Me)(+) (15.2 kcal/mol) were measured by low-temperature NMR kinetics.Living Polymerization of Ethylene and Copolymerization of Ethylene/Methyl Acrylate Using Sandwich Diimine Palladium Catalystspalladium; diimine; ethylene; living polymerization; methyl aaylate109201542#N/ATRUE
3290
cs500114b10.1021/cs500114bhttps://doi.org/10.1021/cs500114bMarks, TJACS Catal.The synthesis, structural characterization, and ethylene polymerization properties of two neutrally charged Ni(II) phenoxyiminato catalysts are compared and contrasted. Complex FI-SO2-Ni features a -SO2- group embedded in the ligand skeleton, whereas control FI-CH2-Ni has the -SO2- replaced by a -CH2- functionality. In comparison with FI-CH2-Ni, at 25 degrees C, FI-SO2-Ni is 18 times more active, produces polyethylene with 3.2 times greater M-W and 1.5 times branch content, and is significantly more thermally stable. The FI-SO2-Ni-derived polymer is a hyperbranched polyethylene (148 branches 1000 C-1, M-W = 3500g mol(-1)) versus that from FI-CH2-Ni (98 branches 1000 C-1, M-W = 1100g mol(-1)). DFT calculations argue that the distinctive FI-SO2-Ni catalytic behavior versus that of FI-CH2-Ni is associated with nonnegligible OSO center dot center dot center dot Ni interactions involving the activated catalyst.Ni(II) Phenoxyiminato Olefin Polymerization Catalysis: Striking Coordinative Modulation of Hyperbranched Polymer Microstructure and Stability by a Proximate Sulfonyl Grouphemilabile ligand; sulfonyl group; nickel; hyperbranched polyethylene; DFT calculationsx79201445#N/AFALSE
3291
cs500103a10.1021/cs500103aFALSEhttps://doi.org/10.1021/cs500103aJeon, SACS Catal.A series of graphene (G)-supported NixPd100-x binary alloyed catalysts (BACs) were prepared with variation of Ni and Pd metal loading through a facile chemical reduction method and were used as an anode catalyst for ethanol oxidation reaction (EOR), which is superior fuels for direct ethanol fuel cells (DEFCs). The X-ray diffraction (XRD) data reveals that the NixPd100-x/G catalysts were homogeneously alloyed, and Ni was present with the oxidized form. The transmission electron microscopy (TEM) images also suggest the alloyed formation with different shapes of metal nanopartiCles (NPs). The electrochemical properties of the catalysts were evaluated using cyClic voltammetry (CV) and chronoamperometry (CA) in 1 M KOH electrolyte. The higher catalytic activity for EOR was increased in the order Ni75Pd25/G > Ni0Pd100/G > Ni25Pd75/G > Ni50Pd50/G. Among NixPd100-x/G BACs, the Ni50Pd50/G catalyst showed the highest onset potential (-0.8 V) on CV and long-term stability on amperometric measurements. The overall parameters of EOR study were determined that the Ni50Pd50/G was more favorable in various ethanol (EtOH) concentrations and scan rate.Highly Active Graphene-Supported NixPd100-x Binary Alloyed Catalysts for Electro-Oxidation of Ethanol in an Alkaline MediaNi-Pd; binary alloyed catalysts; ethanol oxidation reaction; electrocatalyst; direct ethanol fuel cellx152201451#N/AFALSE
3292
cs501480s10.1021/cs501480sFALSEhttps://doi.org/10.1021/cs501480sDu, PWACS Catal.The production of hydrogen through water splitting via electrolysis/photocatalysis seems a promising and appealing pathway for Clean energy conversion and storage. Herein we report for the first time that a series of water-soluble copper complexes can be used as catalyst precursors to generate the copper-based bifunctional catalyst composite for both hydrogen production and water oxidation reactions. Under an applied cathodic potential, a thin catalyst film was grown on a fluorine-doped tin oxide (FTO) electrode, accompanied by the production of a large amount of hydrogen gas bubbles. Scanning electron microscopy shows the presence of nanoparticulate material on the FTO. Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated that the materials consist of amorphous cuprous oxide mixed copper hydroxide (H-2-CuCat), which can catalyze water reduction in a copper-free aqueous solution (pH = 9.2) under a low overpotential. Remarkably, under an applied anodic potential, the material can also efficiently catalyze water oxidation to evolve oxygen. The present robust, bifunctional, switchable, and noble-metal-free catalytic material has potential applications in solar water-splitting devices.Earth-Abundant Copper-Based Bifunctional Electrocatalyst for Both Catalytic Hydrogen Production and Water Oxidationelectrocatalysis; noble-metal-free electrocatalyst; copper; water oxidation; hydrogen production; bifunctional120201579#N/ATRUE
3293
cs500034d10.1021/cs500034dFALSEhttps://doi.org/10.1021/cs500034dLercher, JAACS Catal.MoS2 and Ni-promoted MoS2 catalysts supported on gamma-Al2O3, siliceous SBA-15, and Zr- and Ti-modified SBA-15 were explored for the simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of o-propylaniline (OPA). In all cases, OPA reacted preferentially via initial hydrogenation, and DBT was converted through direct sulfur removal. HDN and HDS activities of MoS2 catalysts are determined by the dispersion of the sulfide phase. Ni promotion increased its dispersion and activity for DBT HDS and also increased the rate of HDN via enhancing the rate of hydrogenation. On nonpromoted MoS2 catalysts, HDS was strongly inhibited by NH3, and the addition of Ni dramatically reduced this inhibiting effect. The conClusion is that HDS is proportional to the concentration of Mo and Ni on the edges of sulfide partiCles. In contrast, the direct hydrodenitrogenation of OPA occurs only on accessible Mo cations and, hence, decreases with increasing Ni substitution. The nature of the support influences the dispersion of the nonpromoted catalysts as well as the decoration degree of Ni on the edges of the Ni Mo S phase. Furthermore, the acidity of the support influences the acidity of the supported sulfide phase, which may play an important role in HDN.Effects of the Support on the Performance and Promotion of (Ni)MoS2 Catalysts for Simultaneous Hydrodenitrogenation and HydrodesulfurizationHDS; HDN; SBA-15; MoS2; Ni promotion; support effectx1212014100#N/AFALSE
3294
cs401245q10.1021/cs401245qFALSEhttps://doi.org/10.1021/cs401245qSelloni, AACS Catal.Mixed nickel iron oxides have recently emerged as promising electrocatalysts for water oxidation because of their low cost and high activity, but the composition and structure of the catalyst's active phase under working conditions are not yet fully established. We present here density functional theory calculations with on-site Coulomb repulsion of the energetics of the oxygen evolution reaction (OER) on selected surfaces of pure and mixed Ni-Fe oxides that are possible candidates for the catalyst's active phase. The investigated surfaces are pure beta-NiOOH(01 (1) over bar5) and gamma-NiOOH(101), Fe-doped beta-NiOOH(01 (1) over bar5) and gamma-NiOOH(101), NiFe2O4(001), and Fe3O4(001). We find that Fe-doped beta-NiOOH(01 (1) over bar5) has by far the lowest overpotential (eta = 0.26 V), followed by NiFe2O4(001) (eta = 0.42 V). Our results indicate that Fe-doped beta-NiOOH and, to a lesser extent, NiFe2O4 could be the phases responsible for the enhanced OER activity of NiOx when it is doped with Fe.Mechanism and Activity of Water Oxidation on Selected Surfaces of Pure and Fe-Doped NiOxwater oxidation; electrocatalysis; DFT; mixed Ni-Fe oxides; active phasesx282201450#N/AFALSE
3295
cs401189a10.1021/cs401189aFALSEhttps://doi.org/10.1021/cs401189aBell, ATACS Catal.Two Ni2+-containing metal-organic frameworks, Ni-2(dobdc) and Ni-2(dobpdc), are shown to be active for the oligomerization of propene in the gas phase. The metal-organic frameworks exhibit activity comparable to Ni2+-exchanged aluminosilicates but maintain high selectivity for linear oligomers. Thus, these frameworks should enable the high yielding synthesis of linear propene oligomers for use in detergent and diesel fuel applications.Selective Propene Oligomerization with Nickel(II)-Based Metal-Organic Frameworksmetal-organic frameworks; catalysis; oligomerization; propene; nickelx71201430#N/AFALSE
3296
cs401141k10.1021/cs401141kFALSEhttps://doi.org/10.1021/cs401141kChen, HACS Catal.The strategy using N,N-bidentate directing groups is a promising way to achieve selective C(sp(2))-H Activation inaccessible by that of monodentate directing groups. Herein, through theoretical calculations, we present a rationale behind this strategy, which deciphers its key roles in C-H Activation promoted by Ni, Pd, Ru, and Cu. The calculations reveal two key points: (a) Between the two coordination sites of the N,N-bidentate directing group, the proximal one influences more the C-H Activation barrier Delta G(double dagger), whereas the distal site affects more the free energy change Delta G relevant to the substrate coordination. (b) Enlarging/shrinking the chelation ring can exert different effects on the reactivity, depending on the metal identity and the ring size. Importantly, our computational results are in full agreement with previous experimental findings concerning reactivity. Furthermore, a prediction about the unprecedented reactivity from our theory is confirmed by our experiments, lending more credence to the rationale and insights gained in this study.Origins of Selective C(sp(2))-H Activation Using Transition Metal Complexes with N,N-Bidentate Directing Groups: A Combined Theoretical-Experimental StudyN,N-bidentate directing group; C(sp(2))-H Activation; transition metal; coordination free energy; reaction barrier; density firnctional theoryx452014108#N/AFALSE
3297
cs401140g10.1021/cs401140gFALSEhttps://doi.org/10.1021/cs401140gBron, MRapid Microwave-Assisted Polyol Reduction for the Preparation of Highly Active PtNi/CNT Electrocatalysts for Methanol Oxidationx2014#N/AFALSE
3298
cs401135g10.1021/cs401135gFALSEhttps://doi.org/10.1021/cs401135gGeng, BYACS Catal.Density functional calculations were performed to investigate the role of Au in graphene growth on the Ni(111) step. It was shown that armchair (AC) and zigzag (ZZ) graphene edge growths have nuCleation selectivity, depending on the curvature of the stepped surface. The AC and ZZ pristine graphene edges are energetically more favorable than the Ni-terminated one, and the stabilities of Au-passivated graphene edges strongly depend on the Au concentration. Au modification on the Ni terrace lowers the energy barrier of C incorporation onto the AC/ZZ graphene edge process, in agreement with the experimental observation that graphene can be produced at the low temperature of similar to 723 K with Au alloying. The growth rate of the AC graphene edge is always faster than the ZZ, leading to the ZZ edge's dominating the circumference of the growing graphene islands. With a decrease in the temperature, the increase in the AC graphene edge growth ratio greatly exceeds that of ZZ, driving the edges to incorporate a zigzag geometry. The overwhelming domination of ZZ edge rationalizes the experimental observation that Au modification can dramatically increase the quality of the graphene films at the lower temperature. On the basis of these results, we suggest that to obtain a high-quality graphene sheet on a Ni surface, the presence of a step should be necessary, and a promoter such as Au should be added to the Ni surface after graphene nuCleation at the step edge site. Furthermore, this work not only provides implications on how to synthesize a high-quality graphene by a CVD approach but also guides inhibition of the undesirable graphene formation in some instances. This work represents the first attempt to investigate the graphene growth mechanism on a surface alloy by theoretical means, which will stimulate further experimental efforts to synthesize high-quality graphene by using a surface alloy as the substrate, especially the choice of an alloyed metal with low cost.Role of Au in Graphene Growth on a Ni SurfaceAu/Ni alloy; high-quality graphene; density functional theory; carbon deposits; zigzag edge; growth mechanismx5201451#N/AFALSE
3299
cs401104w10.1021/cs401104wFALSEhttps://doi.org/10.1021/cs401104wRaugei, SACS Catal.A general strategy is reported for the computational exploration of catalytic pathways of molecular catalysts. Our results are based on a set of linear free energy relationships derived from extensive electronic structure calculations that permit predicting the thermodynamics of intermediates, with accuracy comparable to experimental data. The approach is exemplified with the catalytic oxidation and production of H-2 by [Ni(diphosphine)(2)](2+) electrocatalysts with pendant amines incorporated in the second coordination sphere of the metal center. The analysis focuses upon prediction of thermodynamic properties inCluding reduction potentials, hydride donor abilities, and pK(a) values of both the protonated Ni center and the pendant amine. It is shown that all of these chemical properties can be estimated from the knowledge of only the two redox potentials for the Ni(II)/Ni(I) and Ni(O/Ni(0) couples of the nonprotonated complex, and the pK(a) of the parent primary aminium ion. These three quantities are easily accessible either experimentally or theoretically. The proposed correlations reveal intimate details about the nature of the catalytic mechanism and its dependence on chemical structure and thermodynamic conditions such as applied external voltage and species concentration. This computational methodology is applied to the exploration of possible catalytic pathways, identifying low and high-energy intermediates and, consequently, possibly avoiding bottlenecks associated with undesirable intermediates in the catalytic reactions. We discuss how to optimize some of the critical reaction steps to favor catalytically more efficient intermediates. The results of this study highlight the substantial interplay between the various parameters characterizing the catalytic activity, and form the basis needed to optimize the performance of this Class of catalysts.Computing Free Energy Landscapes: Application to Ni-based Electrocatalysts with Pendant Amines for H-2 Production and Oxidationmolecular electrocatalysis; thermodynamics; Ni complexes; computational chemistry; hydrogen oxidation and production; catalyst optimizationx55201463#N/AFALSE
3300
cs401081w10.1021/cs401081wFALSEhttps://doi.org/10.1021/cs401081wPivovar, BSACS Catal.Platinum (Pt)-coated nickel (Ni) nanowires (PtNiNWs) are synthesized by the partial spontaneous galvanic displacement of NiNWs, with a diameter of 150-250 nm and a length of 100-200 mu m. PtNiNWs are electrochemically characterized for oxygen reduction (ORR) in rotating disk electrode half-cells with an acidic electrolyte and compared to carbon-supported Pt (Pt/HSC) and a polycrystalline Pt electrode. Like other extended surface catalysts, the nanowire morphology yields significant gains in ORR specific activity compared to Pt/HSC. Unlike other extended surface approaches, the resultant materials have yielded exceptionally high surface areas, greater than 90 m(2) g(Pt)(-1). These studies have found that reducing the level of Pt displacement increases Pt surface area and ORR mass activity. PtNiNWs produce a peak mass activity of 917 mA mg(Pt)(-1), 3.0 times greater than Pt/HSC and 2.1 times greater than the U.S. Department of Energy target for proton-exchange membrane fuel cell activity.Platinum-Coated Nickel Nanowires as Oxygen-Reducing Electrocatalystsoxygen reduction reaction; fuel cells; electrochemistry; galvanic displacement; electrocatalysisx68201435#N/AFALSE
3301
cs501371q10.1021/cs501371qhttps://doi.org/10.1021/cs501371qDhepe, PLACS Catal.It is imperative to develop an efficient and environmentally benign pathway to valorize profusely available lignin, a component of nonedible lignocellulosic materials, into value-added aromatic monomers, which can be used as fuel additives and platform chemicals. To convert lignin, earlier studies used mineral bases (NaOH, CsOH) or supported metal catalysts (Pt, Ru, Pd, Ni on C, SiO2, Al2O3, etc.) under a hydrogen atmosphere, but these methods face several drawbacks such as corrosion, difficulty in catalyst recovery, sintering of metals, loss of activity, etc. Here we show that under an inert atmosphere various solid acid catalysts can efficiently convert six different types of lignins into value-added aromatic monomers. In particular, the SiO2Al2O3 catalyst gave exceptionally high yields of ca. 60% for organic solvent soluble extracted products with 95 +/- 10% mass balance in the depolymerization of dealkaline lignin, bagasse lignin, and ORG and EORG lignins at 250 degrees C within 30 min. GC, GC-MS, HPLC, LC-MS, and GPC analysis of organic solvent soluble extracted products confirmed the formation of aromatic monomers with ca. 90% selectivity. In the products, confirmation of retention of aromatic nature as present in lignin and the appearance of several functional groups has been carried out by FT-IR and H-1 and C-13 NMR studies. Further, isolation of major products by column chromatography was carried out to obtain aromatic monomers in pure form and their characterization by NMR is presented. A detailed characterization of six different types of lignins obtained from various sources helped in substantiating the catalytic results obtained in these reactions. A meticulous study on fresh and spent catalysts revealed that the amorphous catalysts are preferred to obtain reproducible catalytic results.Lignin Depolymerization into Aromatic Monomers over Solid Acid Catalystsbiomass; lignin; solid acid catalysts; depolymerization; aromatic monomers; column chromatography185201585#N/ATRUE
3302
cs401027p10.1021/cs401027pFALSEhttps://doi.org/10.1021/cs401027pKawi, SACS Catal.The CO2 (dry) reforming of methane (DRM) reaction is an environmentally benign process to convert two major greenhouse gases into synthesis gas for chemical and fuel production. A great challenge for this process involves developing catalysts with high carbon resistance abilities. Herein we synthesize, for the first time, a yolk satellite shell structured Ni-yolk@Ni@SiO2 nanocomposite for the DRM reaction by varying the shell thickness of Ni@SiO2 core shell nanopartiCles. The formation of Ni-yolk@Ni@SiO2 is proved to be shell thickness dependent. Compared with Ni@SiO2, Ni-yolk@Ni@SiO2 with 11.2 rim silica shell thickness shows stable and near equilibrium conversion for CH4 and CO2 for 90 h at 800 C with negligible carbon deposition. The dual effects of formation of small satellite Ni partiCles due to strong Ni-SiO4 interactions and yolk shell structures contribute to its high activity and stability. These findings shed light on the design of other metal yolk silica shell nanocomposites to be utilized in renewable energy transfer processes such as DRM reactions driven by solar energy.Yolk-Satellite-Shell Structured Ni-Yolk@Ni@SiO2 Nanocomposite: Superb Catalyst toward Methane CO2 Reforming ReactionNi-yolk@Ni@SiO2; satellite Ni; nanocomposite; superb catalyst; methane CO2 reformingx290201464#N/AFALSE
3303
cs501365y10.1021/cs501365yFALSEhttps://doi.org/10.1021/cs501365yOuyang, JYACS Catal.This artiCle presents a facile one-pot synthetic method to prepare ternary NiAuPt nanopartiCles on reduced graphene oxide (rGO) nanosheets (NiAuPt-NGs) through the simultaneous chemical reduction of metal precursors and GO in solution and an investigation of NiAuPt-NGs as electrocatalysts toward ethanol oxidation reaction (EOR). The NiAuPt nanopartiCles grow on the rGO sheets after the chemical reduction of their precursors. They consist of tightly coupled nanostructures of Ni, Au, and Pt, which have neither an alloy nor a core-shell structure, as revealed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. As indicated by the Raman spectra, GO is reduced to rGO more completely in the presence of the metal precursors than in the absence of the metal precursors. The electrocatalysis of NiAuPt-NGs toward EOR in alkaline medium was investigated by cyClic voltammetry, chronoamperometry, and impedance spectroscopy. NiAuPt-NGs can effectively catalyze EOR The ternary NiAuPt-NGs give rise to a high peak current density for EOR, which is more than 8 times higher than that on the monometallic Pt-NGs, 4 times higher than that on the bimetallic NiPt-NGs, and almost 2 times higher than that on the bimetallic AuPt-NGs. In addition, NiAuPt-NGs substantially lower the onset potential for EOR It is -803 mV vs SHE, which suggests the excellent tolerance of NiAuPt-NGs against the residues of EOR. The high electrocatalytic activity of NiAuPt-NGs is attributed to the synergetic effect of the three nanostructured metals for EOR.Ternary NiAuPt NanopartiCles on Reduced Graphene Oxide as Catalysts toward the Electrochemical Oxidation Reaction of Ethanolelectrocatalysis; ethanol oxidation reaction; ternary nanopartiCles; NiAuPt; durability76201574#N/ATRUE
3304
cs400991v10.1021/cs400991vhttps://doi.org/10.1021/cs400991vDutta, PKACS Catal.A synthesis method that results in similar to 180 nm plate-like crystallites of beta-(Co(OH)(2) anchored on the surface of zeolite Y partiCles is reported. These crystals of beta-Co(OH)(2) are transformed to Co3O4 by thermal treatment without a change in morphology. Characterization of the cobalt phases and the transformation was carried out by powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and electron microscopy. These cobalt-based materials provide an opportunity to contrast their photocatalytic activity. Using the Ru(bpy)(3)(2+) persulfate system, the oxidation of water to oxygen was measured. The most active catalyst was beta-(Co(OH)(2), and with transformation to Co3O4, the catalytic activity deClined, suggesting that beta-Co(OH)(2) is a better photocatalyst than Co3O4. The photocatalytic activity of the beta-(Co(OH)(2)/zeolite decreased during a second photocatalytic cyCle, due to surface transformation to Co3O4, though the bulk of the catalyst still maintains the brucite-like beta-Co(OH)(2) structure. This is the first report on how catalytic activity is altered in the cobalt oxide system by phase transformation, keeping morphological features unchanged.Topotactic Transformation of Zeolite Supported Cobalt(II) Hydroxide to Oxide and Comparison of Photocatalytic Oxygen Evolutionwater oxidation; zeolite Y; transition metal photocatalysis; metal hydroxides; cobalt ClustersPhotocatalyst15201429#N/AFALSE
3305
cs501354b10.1021/cs501354bFALSEhttps://doi.org/10.1021/cs501354bLiu, PACS Catal.We report the methanol synthesis from CO2 and H-2 on metal (M = K, Ti, Co, Rh, Ni, and Cu)-modified model Mo6S8 catalyst using density functional theory (DFT). The results show that the catalytic behavior of a Mo6S8 Cluster is changed significantly due to the modifiers, via the electron transfer from M to Mo6S8 and therefore the reduction of the Mo cation (ligand effect) and the direct participation of M in the reaction (ensemble effect) to promote some elementary steps. With the most positively charged modifier, the ligand effect in the case of K-Mo6S8 is the most obvious among the systems studied; however, it cannot compete with the ensemble effect, which plays a dominate role in determining activity via the electrostatic attraction in particular to stabilize the CHxOy species adsorbed at the Mo sites of Mo6S8. In comparison, the ligand effect is weaker and the ensemble effect is more important when the other modifiers are used. In addition, the modifiers also vary the optimal reaction pathway for methanol synthesis on Mo6S8, ranging from the reverse water-gas shift (RWGS) + CO hydrogenation as that of Mo6S8 to the formate pathway. Finally, K is able to accelerate the methanol synthesis on Mo6S8 the most, whereas the promotion by Rh is relatively small. Using the modifiers like Ti, Co, Ni, and Cu, the activity of Mo6S8 is decreased instead. The relative stability between *HCOO and *HOCO is identified as a descriptor to capture the variation in mechanism and scales well with the estimated activity. Our study not only provides better understanding of the reaction mechanism and actives on the modified Mo6S8 but also predicts some possible candidates, which can be used as a promoter to facilitate the CH3OH synthesis on Mo sulfides.Mechanistic Study of Methanol Synthesis from CO2 and H-2 on a Modified Model Mo6S8 ClusterCO2 Activation; methanol; modified molybdenum sulfide; alkali metal; DFT50201542#N/ATRUE
3306
cs400759u10.1021/cs400759uFALSEhttps://doi.org/10.1021/cs400759uMyers, DJACS Catal.Vertically aligned platinum nickel (Pt-Ni) alloy nanorod arrays were grown on glassy carbon electrodes using a magnetron sputtering glancing angle deposition (GLAD) technique. X-ray diffraction and electron microscopy results show that the as-deposited nanorods are alloys and that the alloy composition and geometric properties of Pt-Ni nanorods can be changed by controlling the GLAD deposition parameters. The GLAD Pt-Ni nanorod electrodes were investigated as potential electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) using cyClic voltammetry (CV) and rotating-disk electrode (RDE) techniques in aqueous perchloric acid electrolyte. The electrochemically active surface area (ECA), determined from the charge for hydrogen adsorption and desorption in the CVs, was estimated to be a factor of 3 or more larger than the geometric surface area of the nanorods. The ORR mass-specific activity of the Pt-Ni nanorods was found to be a factor of 2.3-3.5 higher than that of pure Pt nanorods of the same dimensions and increase with increasing Ni content, whereas ORR area-specific activity enhancement was only observed for the nanorods with the highest Pt content. In addition, the Pt-Ni nanorods were found to have higher stability against loss of ECA during potential cyCling than Pt nanorods and conventional high-surface-area-carbon-supported Pt nanopartiCles.GLAD Pt-Ni Alloy Nanorods for Oxygen Reduction Reactionglancing angle deposition (GLAD); Pt-Ni nanorods; oxygen reduction reaction (ORR); nanostructured electrocatalysts; Pt-Ni alloy catalyst; polymer electrolyte fuel cellsx51201358#N/AFALSE
3307
cs400735h10.1021/cs400735hFALSEhttps://doi.org/10.1021/cs400735hKasai, HACS Catal.Recent theoretical and experimental findings have motivated the use of 3d transition metals as alloying elements to improve the performance of Au for the electro-oxidation of borohydride. In this paper, we provide mechanistic insights into the electrochemical oxidation of borohydride on pure Au and Au-3d alloys (Au3M with M = Cr, Mn, Fe, Co, Ni) using first principles calculations. We found that the initial oxidative adsorption of borohydride is the least exothermic among the elementary reactions considered for the complete eight-electron oxidation process. Interestingly, Au-3d metal alloy surfaces promote this oxidation step at a lower electrode potential compared to pure Au due the enhanced stability of borohydride on these alloy surfaces. The most negative borohydride oxidation potential is achieved by M = Co, followed by Fe, Ni, Mn, and Cr in order of increasing electrode potential. Subsequent to the initial oxidative adsorption of borohydride, the dehydrogenations of BH3*, BH2OH*, and BH(OH)(2)* are endothermic on pure Au at very low potentials. However, these activated and possibly limiting elementary reaction steps are more exothermic on Au-3d alloys than on pure Au. Following the adsorption of borohydride on the surface, all elementary reaction steps for the complete electro-oxidation process proceed downhill in energy at a lower electrode potential on Au-3d alloys than on pure Au.Mechanistic Insight into the Au-3d Metal Alloy-Catalyzed Borohydride Electro-Oxidation: From Electronic Properties to Thermodynamicsborohydride oxidation; Au alloys; 3d transition metals; electrochemical modeling; density functional theoryx20201354#N/AFALSE
3308
cs400705p10.1021/cs400705phttps://doi.org/10.1021/cs400705pShan, HHACS Catal.Ni/MgAl2O4 catalysts with high NiO loadings were highly active for isobutane cracking, which led to abundant formation of methane, hydrogen and coke. The results of activity testing and XRD characterization jointly revealed that large ensembles of metallic nickel species formed during reaction notably catalyzed cracking instead of dehydrogenation. However, after introduction of sulfur into Nil MgAl2O4 catalyst through impregnation with ammonium sulfate, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene increased remarkably. Totally, up to similar to 42 wt % isobutene could be obtained at 560 degrees C in a single pass after the modification. From the characterization results, it was also conCluded that, after sulfur introduction, NiO partiCles became much smaller and better dispersed on the catalyst surface. NiS species, formed during the induction period of the reaction, not only facilitated isobutene desorption from the catalyst, but also constituted the active sites for isobutane dehydrogenation. In addition, due to the appearance of NiS species, Ni/MgAl2O4 catalyst after H2S/H-2 sulfuration exhibited a high initial activity without experiencing an induction period, further confirming the crucial role that introduced sulfur played.Promoting Effect of Sulfur Addition on the Catalytic Performance of Ni/MgAl2O4 Catalysts for Isobutane Dehydrogenationisobutane; dehydrogenation; Ni/MgAl2O4 catalysts; sulfur addition; NiSx46201352#N/AFALSE
3309
cs400675u10.1021/cs400675uFALSEhttps://doi.org/10.1021/cs400675uRoberts, JASACS Catal.Films electrodeposited onto glassy carbon electrodes from acidic acetonitrile solutions of [Bu4N][Ni(bdt)(2)] (bdt = 1,2-benzenedithiolate) are active toward electrocatalytic hydrogen production at potentials 0.2-0.4 V positive of untreated electrodes. This activity is preserved when the electrode is rinsed and transferred to a fresh acid solution. X-ray photoelectron spectra indicate that the deposited material contains Ni and S, and time-of-flight secondary ion mass spectrometry shows that electro-deposition decomposes the Ni(bdt)(2) assembly. Correlations between voltammetric and spectroscopic results indicate that the deposited material is active, i.e., that catalysis is heterogeneous rather than homogeneous. Control experiments establish that obtaining the observed catalytic response requires both Ni and the 1,2-benzenedithiolate ligand to be present during deposition.Electrodeposition from Acidic Solutions of Nickel Bis(benzenedithiolate) Produces a Hydrogen-Evolving Ni-S Film on Glassy Carbonhydrogen; electrocatalysis; electrodeposition; nickel thiolate; electrode modificationx50201451#N/AFALSE
3310
cs400638f10.1021/cs400638fFALSEhttps://doi.org/10.1021/cs400638fHelm, MLACS Catal.A Ni-based electrocatalyst for H-2 production, [Ni(8P(2)(Ph)N(C6H4Br))(2)](BF4)(2), featuring eight-membered cyClic diphosphine ligands incorporating a single amine base, 1-para-bromophenyl-3,7-triphenyl-1-aza-3,7-diphosphacyCloheptane (8P(2)(Ph)N(C6H4Br)) has been synthesized and characterized. X-ray diffraction studies reveal that the cation of [Ni(8P(2)(Ph)N(C6H4Br))(2)](CH3CN)(BF4)(2) has a distorted trigonal bipyramidal geometry. In CH3CN, [Ni(8P(2)(Ph)N(C6H4Br))(2)](2+) is an electrocatalyst for reduction of protons, and it has a maximum turnover frequency for H-2 production of 800 s(-1) with a 700 mV overpotential (at E-cat/2) when using [(DMF)H]OTf as the acid. Addition of H2O to acidic CH3CN solutions of [Ni(8P(2)(Ph)N(C6H4Br))(2)](2+) results in an increase in the turnover frequency for H-2 production to a maximum of 3300 s(-1) with an overpotential of 760 mV at E-cat/2. Computational studies carried out on [Ni(8P(2)(Ph)N(C6H4Br))(2)](2+) indicate the observed catalytic rate is limited by formation of nonproductive protonated isomers, diverting active catalyst from the catalytic cyCle. The results of this research show that proton delivery from the exogenous acid to the correct position on the proton relay of the metal complex is essential for fast H-2 production.Hydrogen Production Using Nickel Electrocatalysts with Pendant Amines: Ligand Effects on Rates and Overpotentialshydrogen production; electrocatalysis; nickel phosphine complexes; pendant amines; proton relay; proton reductionx48201380#N/AFALSE
3311
cs400621p10.1021/cs400621pFALSEhttps://doi.org/10.1021/cs400621pKawi, SACS Catal.Iron-alumina-supported nickel-iron alloy catalysts were tested in a fixed-bed reactor for steam reforming of toluene as a biomass tar model compound. The influence of the calcination temperature of the iron-alumina support was also explored for the steam reforming reaction. Ni supported on an Fe2O3-Al2O3 support calcined at 500 degrees C [NFA(500)] gave superior catalytic performance in terms of activity and stability over other catalysts. NFA(500) gave a toluene conversion of more than 90% for a period of 26 h with a H-2/CO value of 4.5. According to XRD analysis, the Ni-Fe alloys were formed and stable throughout the reforming reaction. It was observed from XPS results that the surface of the reduced NFA(500) catalyst was enriched with Fe species, where the other catalysts were enriched with Ni species. These surface Fe species play the role of cocatalysts by increasing the coverage of oxygen species during the reforming reaction to enhance the reaction of toluene and suppresses coke formation. The presence of oxygen species in the reduced catalysts was confirmed by temperature-programmed surface reaction (TPSR) with toluene and water over NFA catalysts. A temperature-programmed oxidation (TPO) study on spent catalysts revealed that the NFA(500) and NFA(700) catalysts have an additional low-temperature oxidation peak at around 525 and 535 degrees C, respectively, suggesting the presence of a higher amount of amorphous carbon compared with the NFA(900) catalyst. The presence of a low-temperature oxidation peak at 525 degrees C for the NFA(500) catalyst is one of the reasons for its stable catalytic performance compared with other catalysts.Nickel-Iron Alloy Supported over Iron-Alumina Catalysts for Steam Reforming of Biomass Tar Model Compoundhydrogen production; nickel-iron alloy; biomass; toluene steam reforming; iron-aluminax175201444#N/AFALSE
3312
cs501313z10.1021/cs501313zFALSEhttps://doi.org/10.1021/cs501313zDavis, MEACS Catal.Two nickel-containing zincosilicates (Ni-CIT-6 and NiZn-MCM-41) and two nickel-containing aluminosilicates (Ni-HiAl-BEA and Ni-USY) are synthesized and used as catalysts to oligomerize propylene into C(3)n (C-6 and C-9) products. Both Ni-CIT-6 and Ni-HiAl-BEA have the *BEA topology and are investigated to assess the effects of framework zinc versus aluminum because the former gives two framework charges per atom, whereas the latter, only one. Ni-CIT-6 and NiZn-MCM-41 enable the comparison of a microporous to a mesoporous zincosilicate. Ni2+ ion-exchanged into zeolite Y has been previously reported to oligomerize propylene and is used here for comparison. Reaction data are obtained at 180 and 250 degrees C, atmospheric pressure, and WHSV = 1.0 h(-1) in a feed stream of 85 mol % propylene (in inert). At these conditions, all catalysts are capable of oligomerizing propylene with steady-state conversions ranging from 3 to 16%. With the exception of Ni-HiAl-BEA, all catalysts have higher propylene conversions at 250 degrees C than at 180 degrees C. Both *BEA materials exhibit similar propylene conversions at each temperature, but Ni-HiAl-BEA is not as selective to C(3)n products as Ni-CIT-6. Zincosilicates demonstrate higher average selectivities to C3n products than the aluminosilicates at both reaction temperatures tested. Hexene products other than those expected by simple oligomerization are present, likely formed by double-bond isomerization catalyzed at acid sites. Additionally, both of the aluminosilicate materials catalyzed cracking reactions, forming non-C3n products. The reduced acidity of the zincosilicates relative to the aluminosilicates likely accounts for higher C3n product selectivity of the zincosilicates. Zincosilicates also exhibited higher linear-to-branched hexene isomer ratios (typically 1.01.5) when compared with the aluminosilicates, which had ratios on the order of 0.3. The mesoporous zincosilicate shows the best reaction behavior (inCluding C3n product selectivity: 99% at both temperatures for NiZn-MCM-41) of the catalytic materials tested here.Nickel-Exchanged Zincosilicate Catalysts for the Oligomerization of Propylenepropylene; oligomerization; nickel; zincosilicate *BEA30201427#N/ATRUE
3313
cs400516610.1021/cs4005166FALSEhttps://doi.org/10.1021/cs4005166Vlachos, DGACS Catal.Heteroepitaxial bimetallic catalytic materials have, been attracting considerable interest because of their unique properties and applications in energy, chemicals, and fuel sectors. Optimizing the activity of bimetallic catalysts requires the ability to understand and precisely manipulate the nanostructure (loading and dispersion of an admetal on a host metal). Ammonia decomposition catalyzed by Ni on Pt(111) [Ni/Pt(111)] is a prototype structure sensitive reaction for this purpose, in which both N-H bond breaking and N-N bond formation can be rate-limiting steps. Here, a first-principles kinetic Monte Carlo simulation framework reveals the bifunctional role of Ni Clusters on Pt(111) in NH3 decomposition: dehydrogenation on Ni terrace and N-2 desorption near Ni steps on Pt. We show that the dynamic interplay between surface nitrogen diffusion and association near the steps of Ni dusters and Pt terraces is responsible for the lower than expected nitrogen desorption temperature found in experiments. Our results illustrate the significance of metal loading and microstructure on macroscopic performance. A model is introduced with the aim of optimizing the bimetallic surface at nanoscale for improved reactivity. This simulation framework can be employed to understand and eventually tune bimetallic catalytic materials for arbitrarily complex chemistries.Design Principles of Heteroepitaxial Bimetallic Catalystsbifunctional; bimetallic catalyst; nanostructure; Ni/Pt; ammonia decomposition; multiscalex23201364#N/AFALSE
3314
cs500915p10.1021/cs500915pFALSEhttps://doi.org/10.1021/cs500915pKawi, SACS Catal.The effect of Na loading on the water gas shift (WGS) activity of Ni/xNa/Ce02 (with x = 0, 0.5, 1, 2, 5, and 10 wt %) catalysts has been investigated. Ni/2Na/Ce02 exhibited the highest performance in terms of WGS activity and methane suppression. Through H-2-TPR and XRD, the solubility limit of Na+ in Ce02 was found to be 2 wt %. At low loadings of Na (0.5 to 2 wt 96), Na+ was incorporated into the Ce02 lattice, generating a lattice strain and activating the lattice 02, thereby increasing the reducibility of the catalyst. However, beyond the solubility limit of 2 wt %, Na deposited on the Ce02 surface, retarding the reducibility of the catalyst. XPS spectra reveal greater surface concentration of adsorbed oxygen species with the introduction of Na. This can be attributed to the generation of more oxide vacancies for oxygen adsorption due to Na substitution into the ceria lattice. By in situ DRIFTS, methanation was found to be inhibited by the interaction between Na and Ni, leading to the absence of subCarbonyl species which are responsible for this undesirable side reaction. KEYWORDS: water gas shift, nickel catalyst, ceria, sodium, DRIFTSHighly Active Ni/xNa/CeO2 Catalyst for the Water Gas Shift Reaction: Effect of Sodium on Methane Suppressionwater gas shift; nickel catalyst; ceria; sodium; DRIFTS95201470#N/ATRUE
3315
cs400408410.1021/cs4004084FALSEhttps://doi.org/10.1021/cs4004084Ishida, HAerobic Oxidative Esterification of Aldehydes with Alcohols by Gold-Nickel Oxide NanopartiCle Catalysts with a Core-Shell Structurex2013#N/AFALSE
3316
cs500684410.1021/cs5006844FALSEhttps://doi.org/10.1021/cs5006844Lu, GXACS Catal.In this work, a highly active H-2 evolution NiSx catalyst decorated on graphene (NiSx/G) nanohybrid was prepared by an in situ chemical deposition method, in which nickel ion was first adsorbed onto graphene and subsequently reacted with sulfide ion to yield the NiSx/G nanohybrid. The NiSx/G catalyst exhibited activity for hydrogen generation 2-fold higher than that of pristine NiSx under visible light irradiation. The highest quantum efficiency of 32.5% was reached at 430 nm when Eosin Y was used as a photo-sensitizer. In this system, graphene not only provided a large area and two-dimensional substrate for the confined growth of NiSx but also greatly enhanced the transfer of photoelectrons from excited Eosin Y to the NiSx cocatalyst because of its promotion of charge separation, leading to the great enhancement of photocatalytic hydrogen evolution.Dye-Sensitized NiSx Catalyst Decorated on Graphene for Highly Efficient Reduction of Water to Hydrogen under Visible Light IrradiationNiSx; graphene; dye; photocatalyst; visible light; hydrogen generation; sensitized139201455#N/ATRUE
3317
cs500462z10.1021/cs500462zFALSEhttps://doi.org/10.1021/cs500462zChu, DACS Catal.A Class of Pd-Ni-P electrocatalysts are prepared for the ethanol electrooxidation reaction (EOR). X-ray diffraction and transmission electron microscope reveal that the synthesized Pd-Ni-P catalyst possesses a more amorphous structure with smaller partiCle sizes when compared with a Pd-Ni sample without P and a control Pd black (Pd-blk) sample. The Pd-Ni-P catalyst contains double the number of electrocatalytically active sites (12.03%) compared with the Pd-Ni (6.04%) and Pd-blk (5.12%) samples. For the EOR, the Pd-Ni-P catalyst has the lowest onset potential (-0.88 V vs SCE), the most negative peak potential (-0.27 V vs SCE), and the highest EOR activity in 0.1 M KOH solution. Moreover, a 110 mV decrease in overpotential is observed for the EOR on the Pd-Ni-P catalyst compared with the Pd-blk catalyst. A Tafel slope of 60 mV/dec at low polarization potentials (<-0.76 V vs SCE) was obtained for EOR at a Pd-Ni-P-coated electrode with a reaction rate constant of 2.8 x 10(-4) cm.S-1.M-1 at -0.3 V vs SCE in KOH media. Finally, we find that the electrooxidation of ethanol on the Pd-Ni-P catalyst undergoes a 4-electron process to acetate.A Class of (Pd-Ni-P) Electrocatalysts for the Ethanol Oxidation Reaction in Alkaline MediaPd-Ni-P catalyst; ethanol electrooxidation; direct ethanol fuel cells; kinetics and mechanisms of EOR; substitutional/interstitial alloy124201445#N/ATRUE
3318
cs500436f10.1021/cs500436fFALSEhttps://doi.org/10.1021/cs500436fKhodakov, AYACS Catal.Stability and deActivation phenomena are of utmost importance for metal nanocatalysts from both fundamental and industrial points of view. The presence of small amounts of sulfur at ppm and ppb levels in the synthesis gas produced from fossil and renewable sources (e.g., biomass, coal) is a major reason for deActivation of nickel catalysts for carbon monoxide hydrogenation. This paper addresses reaction pathways and deActivation mechanisms of alumina-supported nickel catalysts for methane synthesis from pure syngas and syngas containing small amounts of sulfur. A combination of SSITKA and operando FTIR is indicative of both reversible molecular and irreversible dissociative carbon monoxide adsorption on nickel nanopartiCles under the reaction conditions. Methanation reaction involves irreversible carbon monoxide adsorption, dissociation, and hydrogenation on nanopartiCle steps and edges. Hydrogenation of adsorbed carbon species leading to methane seems to be the reaction kinetically relevant step. Molecular forms of carbon monoxide reversibly adsorbed on nickel terraces are likely not to be involved in carbon monoxide hydrogenation. The results suggest a competition between sulfur and carbon monoxide for nickel surface sites. During methanation, sulfur preferentially adsorbs on the sites of reversible molecular carbon monoxide adsorption, whereas the low-coordinated nickel sites responsible for carbon monoxide dissociation and hydrogenation are affected to a lesser extent by sulfur poisoning. The active sites of carbon monoxide hydrogenation are poisoned much more rapidly by sulfur, when the catalyst has been exposed to small amounts of H2S in the absence of methanation.Impact and Detailed Action of Sulfur in Syngas on Methane Synthesis on Ni/gamma-Al2O3 Catalystmethanation; nickel; deActivation; structure sensitivity; SSITKA; sulfur31201445#N/ATRUE
3319
cs500168t10.1021/cs500168tFALSEhttps://doi.org/10.1021/cs500168tCrooks, RMACS Catal.Here, we report the development of a parallel electrocatalyst screening platform for the hydrogen evolution reaction (HER) using bipolar electrodes (BPEs). Electrocatalyst candidates are subjected to screening in a N-2-purged bipolar electrochemical cell where a pair of driving electrodes produce an electric field in the electrolyte solution. The HER occurring at the BPE cathodes is electrically coupled to the electrodissolution of an array of Cr microbands present at the BPE anodes. The readout of this device is simple, where the species that dissolve the most Cr microbands are identified as the most promising electrocatalyst candidates for further evaluation. We demonstrate the utility of this technique by comparing several bi- and trimetallic systems involving Co, Fe, Ni, Mo, and W, which are compared directly with pure Pt. Of all the compositions tested, Ni-8-Mo-2 is demonstrated to be the most active for the HER in a neutral electrolyte solution.Evaluating Electrocatalysts for the Hydrogen Evolution Reaction Using Bipolar Electrode Arrays: Bi- and Trimetallic Combinations of Co, Fe, Ni, Mo, and Welectrochemistry; electrocatalysis; high-throughput screening63201455#N/ATRUE
3320
cs400266e10.1021/cs400266eFALSEhttps://doi.org/10.1021/cs400266eJensen, ADACS Catal.Four groups of catalysts have been tested for hydrodeoxygenation (HDO) of phenol as a model compound of bio-oil, inCluding oxide catalysts, methanol synthesis catalysts, reduced noble metal catalysts, and reduced non-noble metal catalysts. In total, 23 different catalysts were tested at 100 bar H-2 and 275 degrees C in a batch reactor. The experiments showed that none of the tested oxides or methanol synthesis catalysts had any significant activity for phenol HDO under the given conditions, which were linked to their inability to hydrogenate the aromatic ring of phenol. HDO of phenol over reduced metal catalysts could effectively be described by a kinetic model involving a two-step reaction in which phenol initially was hydrogenated to cyClohexanol and then subsequently deoxygenated to cyClohexane. Among reduced noble metal catalysts, ruthenium, palladium, and platinum were all found to be active, with activity decreasing in that order. Nickel was the only active non-noble metal catalyst. For nickel, the effect of support was also investigated and ZrO2 was found to perform best. Pt/C, Ni/CeO2, and Ni/CeO2-ZrO2 were the most active catalysts for the initial hydrogenation of phenol to cyClohexanol but were not very active for the subsequent deoxygenation step. Overall, the order of activity of the best performing HDO catalysts was as follows: Ni/ZrO2 > Ni-V2O5/ZrO2 > Ni-V2O5/SiO2 > Ru/C > Ni/Al2O3 > Ni/SiO2 >> Pd/C > Pt/C. The choice of support influenced the activity significantly. Nickel was found to be practically inactive for HDO of phenol on a carbon support but more active than the carbon-supported noble metal catalysts when supported on ZrO2. This observation indicates that the nickel-based catalysts require a metal oxide as a carrier on which the Activation of the phenol for the hydrogenation can take place through heterolytic dissociation of the O-H bond to facilitate the reaction.Screening of Catalysts for Hydrodeoxygenation of Phenol as a Model Compound for Bio-oilbio-oil; catalyst screening; hydrodeoxygenation; noble metals; phenol; oxides; reduced metalsx259201359#N/AFALSE
3321
cs500124n10.1021/cs500124nFALSEhttps://doi.org/10.1021/cs500124nChen, JGGACS Catal.Designing catalysts with high activity and selectivity for biomass conversion to fuels and chemicals requires the understanding and controlling of the bond scission mechanism in biomass derivatives. In the current study, ethylene glycol, the smallest polyol from cellulose with the same atomic C/O ratio as CS and C6 sugars, is employed as a surrogate molecule for controlling the bond scission sequence of O-H, C-H, C-O, and C-C bonds. A promising methodology for catalyst design is established in this work by constructing a microkinetic model to predict the activity and selectivity for ethylene glycol transformation reactions on molybdenum carbide (Mo2C) and metalmodified Mo2C surfaces, followed by supplementing the theoretical prediction with temperature program desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) experiments on model surfaces. The fundamental insights from the theoretical approach and experimental results thus helps to guide the catalyst design and reduce the number of catalyst candidates in future experiments.Theoretical and Experimental Studies of C-C versus C-O Bond Scission of Ethylene Glycol Reaction Pathways via Metal-Modified Molybdenum Carbidescatalyst design; microkinetic model; temperature program desorption (TPD); metal (Ni, Au, Cu, and Pt)-modified Mo2C surfaces; biomass derivatives; ethylene glycol35201441#N/ATRUE
3322
cs500094410.1021/cs5000944FALSEhttps://doi.org/10.1021/cs5000944Shan, HHACS Catal.Metal sulfide catalysts were highly efficient in the Activation of C-H bond for isobutane dehydrogenation, and the dehydrogenation performance was better than that of the commercial catalysts Cr2O3/Al2O3 and Pt-Sn/Al2O3, providing a Class of environmentally friendly and economical alternative catalysts for industrial application.Highly Efficient Metal Sulfide Catalysts for Selective Dehydrogenation of Isobutane to Isobutene61201432#N/ATRUE
3323
cs400197t10.1021/cs400197tFALSEhttps://doi.org/10.1021/cs400197tBao, XHACS Catal.Supported Au-Ni nanocatalysts consisting of Au nanoparticies decorated with Ni/NiO nanostructures were synthesized using a two-step method and characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. The structural characterization indicates that a small part of surface Ni atoms can diffuse into Au cores upon reduction at 600 degrees C, while the alloyed Ni atoms segregate onto the Au nanopartiCle surfaces when oxidizing at a similar temperature. The inward and outward diffusion of Ni atoms at Au surfaces are reversible with response to cyCled reduction and oxidation treatments. CO oxidation reactions over the Au-Ni catalysts suggest that Au nanopartiCles decorated with highly dispersed NiO nanopatches are the active surface architecture. Optimum activity has been observed by maximizing the density of boundaries between NiO patches and Au surfaces, which can be achieved through suitable redox pretreatments of the Au-Ni catalysts. NiO surface structures in the NiO-on-Au inverse catalysts not only enhance Au-catalyzed CO oxidation performance but also prevent sintering of Au nanopartiCles at elevated temperatures. Similar high activity for the CO oxidation has been observed in the CoOx-on-Au and FeOx-on-Au inverse catalysts.A Highly Active NiO-on-Au Surface Architecture for CO Oxidationinverse catalysts; Au catalysis; CO oxidation; NiO; redox treatmentx55201375#N/AFALSE
3324
cs401030u10.1021/cs401030uFALSEhttps://doi.org/10.1021/cs401030uLi, FWACS Catal.Bimetallic catalysts are of great importance due to their unique catalytic properties. However, their conventional synthesis requires tedious multistep procedures and prolonged synthetic time, and the resulting bimetallics usually disperse unevenly and show poor stability. It is challenging to develop a facile and step-economic synthetic methodology for highly efficient bimetallic catalysts. In this study, we report an elegant metal complex-involved multicomponent assembly route to highly efficient Ru-Ni bimetallics in ordered mesoporous carbons (OMC). The fabrication of composition-tuned Ru Ni bimetallics in OMC (RuxNi1-x-OMC, x = 0.5-0.9) was facilely realized via in situ construction of CTAB-directed cubic Ia3d chitosan-ruthenium nickel silica mesophase before pyrolysis and silica removal. The resulting RuxNi1-x-OMC materials are in-depth characterized with X-ray diffraction, N2 adsorption desorption, transmission electron microscopy, infrared spectrum, and X-ray absorption fine structure. This facile fabrication method renders homogeneously dispersed Ru Ni bimetallics embedded in the mesoporous carbonaceous framework and creates a highly active and stable Ru0.9Ni01-OMC catalyst for the hydrogenation of levulinic acid (LA) to prepare gamma-valerolactone (GVL), a biomass-derived platform molecule with wide application in the preparation of renewable chemicals and liquid transportation fuels. A high TOF (>2000 h(-1) was obtained, and the Ru0.9Ni0.1-OMC catalyst could be used at least 15 times without obvious loss of its catalytic performance.Facile Fabrication of Composition-Tuned Ru-Ni Bimetallics in Ordered Mesoporous Carbon for Levulinic Acid Hydrogenationembedded bimetallics; ordered mesoporous carbon; pyrolysis; self-assembly; levulinic acid hydrogenation; high stability105201451#N/ATRUE
3325
cs400994610.1021/cs4009946FALSEhttps://doi.org/10.1021/cs4009946Zou, GACS Catal.A highly efficient nickel/triArylphosphine catalyst system, Ni[P(4-MeOPh)(3)](2)Cl-2/2P(4-MeOPh)(3), has been developed for cross-coupling of diArylborinic acids with a wide range of Aryl chlorides. A variety of unsymmetrical biAryl and heterobiAryl compounds with various functional groups and steric hindrance could be obtained in good to excellent yields using 0.5-2 mol % catalyst loadings in the presence of K3PO4 center dot 3H(2)O in toluene. The high atom economy of diArylborinic acids and cost-effectiveness of the nickel/phosphine catalyst system make the cross-coupling truly practical in the production of biAryl fine chemicals. Usefulness of the nickel/phosphine catalyzed cross-coupling of diArylborinic acids with Aryl chlorides has been demonstrated in the development of a scalable and economical process for synthesis of 4'-methyl-2-cyanobiphenyl, Sartan biphenyl.Nickel-Catalyzed Cross-Coupling of DiArylborinic Acids with Aryl Chloridesnickel; phosphine; cross coupling; diArylborinic acid; Aryl chloride242014110#N/ATRUE
3326
cs400126710.1021/cs4001267https://doi.org/10.1021/cs4001267Satsuma, AACS Catal.Nickel nanopartiCles loaded onto various supports (Ni/MOx) have been prepared and studied for the N-Alkylation of amines with alcohols. Among the catalysts, Ni/theta-Al2O3 prepared by in situ H-2-reduction of Ni/theta-Al2O3 shows the highest activity, and it acts as reusable heterogeneous catalyst for the Alkylation of anilines and aliphatic amines with Various alcohols (Benzyl and aliphatic alcohols) under additive free conditions. Primary amines are converted into secondary amines and secondary amines into tertiary amines. For the reaction of with, an aliphatic alcohol the catalyst shows higher turnover number (TON) than precious metal-based state-of-the-art catalysts. Mechanistic studies suggest that the reaction proceeds through hydrogen-borrowing mechanism. The activity of Ni catalysts depends on the nature of support materials; acid-base bifunctional supports give higher activity than basic or acidic supports, indicating that acid-base sites on supports are necessary. The presence of basic (pyridine) or acidic (acetic acid) additive in the solution decreased the activity of Ni/theta-Al2O3, which suggests the cooperation of the acid base site of theta-Al2O3. For a series of Ni/theta-Al2O3 catalysis with different partiCle size, the turnover frequency, (TOF) per surface Ni increases with decreasing Ni mean partiCle size, inClicating that low-coordinated Ni species and/or metal-support interface are active sites. From these results, we propose that the site for this reaction is metal-support interface, where low-coordinated. atoms adjacent to the acid-base sites of alumina.Heterogeneous Ni Catalysts for N-Alkylation of Amines with Alcoholsalcohols; amines; heterogeneous catalysis; nickel; nanopartiClesx143201344#N/AFALSE
3327
cs400096910.1021/cs4000969FALSEhttps://doi.org/10.1021/cs4000969Rodriguez, JAACS Catal.The steam reforming of ethanol on a Ni-based CeO2-supported catalyst was studied using in situ X-ray diffraction (XRD), operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and mass spectroscopy (MS) with a focus on the structural characterization of the catalysts, Chemical-identification of the reaction pathway, and understanding of the interaction between Ni and the CeO2 support. Ethoxy, acetate, carbonate, and hydroxyl species are identified by DRIFTS as surface intermediates that appear during the reaction process. The oxidation of ethoxy to acetate and the decomposition of acetate are two key steps in the steam reforming process. The CeO2 support facilitates the oxidation of ethoxy to acetate below 350 degrees C. Above 350 degrees C, the Ni metal catalyzes dissociation of the C-C bond in acetate to form carbonate and methyl, something that the CeO2 support is not able to do. The Ce(III) sites produced by the reduction of ceria in ethanol help to dissociate water forming the surface hydroxyl groups, which react with the methyl groups to produce CO2 and inhibited the methyl groups progress to CH4 Post-reaction transmission electron microscopy (TEM) images of the Ni/CeO2 catalyst reveal two types of carbon configurations: encapsulating carbon and filamentous carbon . A water-rich atmosphere favors formation of carbon filaments, which do not deactivate two catalyst.Steam Reforming of Ethanol on Ni/CeO2: Reaction Pathway and Interaction between Ni and the CeO2 Supportethanol; steam reforming; nickel; hydrogen production; ceriax154201367#N/AFALSE
3328
cs400077r10.1021/cs400077rFALSEhttps://doi.org/10.1021/cs400077rLi, FWACS Catal.In this work, we report a novel and facile procedure for a one-pot preparation of palladium nanopartiCle catalysts supported on porous N-doped carbon (Pd@CNT) by direct carbonization of palladium-N-heterocyClic carbene coordination polymer (P-Pd-NHC). This method could be conveniently extended to the synthesis of the Ni and alloy (PdxNiy) nanopartiCle catalysts (Ni@CN800 PdxNy@OCN800) The treatment temperature played an important role, on the growth and properties of the resultant M@CNT wherein M@CN800 carbonized at 800 degrees C showed well-monodispersed metal nanopartiCles (MNPs), graphene-like layers of the N-doped carbon supports, and strong interaction between MNPs and the support. Pd@CN800 displayed high efficiency and stable recyClability toward the demino Carbonylative synthesis of pyrazole derivatives. Interestingly, its catalytic performance has been even higher than that of the representative PdCl2(PPh3)(2) within six runs.One-Pot Synthesis of Pd NanopartiCle Catalysts Supported on N-Doped Carbon and Application in the Domino CarbonylationN-doped carbon; N-heterocyClic carbenes; supported catalysts; nanopartiCles; Carbonylationx98201366#N/AFALSE
3329
cs400780910.1021/cs4007809FALSEhttps://doi.org/10.1021/cs4007809Bell, ATACS Catal.A series of alkali metal- and nickel-exchanged Al-MCM-41 catalysts were prepared via aqueous ion exchange and then investigated for gas-phase oligomerization of propene at 453 K and near ambient pressures. All catalysts were active and produced oligomers with >98% selectivity. The highest activities per Ni2+ cation were observed when the cations were highly dispersed as a consequence of either lowering the Ni loading for a fixed MCM-41 Si/Al ratio or by decreasing the concentration of exchangeable sites within the material by increasing the MCM-41 Si/Al ratio at a fixed Ni loading. The identity of the alkali metal cation had no significant effect on the catalytic activity or degree of dimer branching, except for the sample containing Cs+ cations, where the decreased pore volume resulted in a lower catalyst activity and slightly more linear dimer products. Comparison of Ni-MCM-41 prepared with and without Na+ cations showed that a higher yield of oligomers could be achieved when Na+ cations are present because of partial removal of strong Bronsted acid sites. For the same reaction conditions, Ni-Na-MCM-41 was more than twice as active as smaller-pored Ni-Na-X zeolites, demonstrating that the activity of Ni2+ cations increases with the increasing free volume near the site. This effect of free volume on the activity of Ni2+ cations was further confirmed by comparing the activities of Ni-Na-X, Ni-Na-MCM-41, Ni-Na-MCM-48, and Ni-Na-SBA-15 with respect to pore size.Propene Oligomerization using Alkali Metal- and Nickel-Exchanged Mesoporous Aluminosilicate Catalystsoligomerization; propene; MCM-41; nickel; alkali metal28201419#N/ATRUE
3330
cs300747310.1021/cs3007473FALSEhttps://doi.org/10.1021/cs3007473Kondo, JNACS Catal.This paper reports the synthesis of primary amines from alcohols and NH3 by an Al2O3-supported Ni nanopartiCle catalyst as the first example of heterogeneous and noble-metal-free catalytic system for this reaction without additional hydrogen sources under relatively mild conditions. Various aliphatic alcohols are tolerated, and turnover numbers were higher than those of Ru-based homogeneous catalysts. The catalyst was recoverable and was reused. The effects of the Ni oxidation states and the acid-base nature of support oxides on the catalytic activity are studied. It is Clarified that the surface metallic Ni sites are the catalytically active species, and the copresence of acidic and basic sites on the support surface is also indispensable for this catalytic system.Heterogeneous Ni Catalyst for Direct Synthesis of Primary Amines from Alcohols and Ammoniaalcohols; amines; ammonia; heterogeneous catalysis; nickelx136201335#N/AFALSE
3331
cs300707y10.1021/cs300707yFALSEhttps://doi.org/10.1021/cs300707yLi, YDACS Catal.It is highly challenging but desirable to develop efficient catalysts for the Activation of oxygen under mild conditions. Here, we report that various monodispersed metal nanopartiCles (Ag, Pt, Co, Cu, Ni, Pd, and Au) efficiently activated molecular oxygen under mild conditions, illustrated by the aerobic oxidation of anilines to form either symmetric or asymmetric aromatic azo compounds. This discovery indicates that exploiting the catalytic power of nanopartiCles could enable sustainable chemistry suitable for important oxidation reactions.Room Temperature Activation of Oxygen by Monodispersed Metal NanopartiCles: Oxidative Dehydrogenative Coupling of Anilines for Azobenzene SynthesesnanopartiCle; oxygen Activation; oxidation coupling; azobenzenex93201351#N/AFALSE
3332
cs300691m10.1021/cs300691mFALSEhttps://doi.org/10.1021/cs300691mGray, HBNi-Mo Nanopowders for Efficient Electrochemical Hydrogen Evolutionx2013#N/AFALSE
3333
cs300605t10.1021/cs300605tFALSEhttps://doi.org/10.1021/cs300605tNieminen, RMACS Catal.Because of its high specific surface area and unique electronic properties, graphene with substitutional impurity metal atoms and Clusters attached to defects in the graphene sheet is attractive for use in hydrogen fuel cells for oxygen reduction at the cathode. In an attempt to find a cheap yet efficient catalyst for the reaction, we use density-functional theory calculations to study the structure and properties of transition-metal-vacancy complexes in graphene. We calculate formation energies of the complexes, which are directly related to their stability, along with oxygen and water adsorption energies. In addition to metals, we also consider nonmetal impurities like B, P, and Si, which form strong bonds with under-coordinated carbon atoms at defects in graphene. Our results indicate that single Ni, Pd, Pt, Sn, and P atoms embedded into divacancies in graphene are promising candidates for the use in fuel cell cathodes for oxygen reduction reaction (ORR). We further discuss how ion irradiation of graphene combined with metal sputtering and codeposition can be used to make an efficient and relatively inexpensive graphene-based material for hydrogen fuel cells.Doped Graphene as a Material for Oxygen Reduction Reaction in Hydrogen Fuel Cells: A Computational Studygraphene; DFT; oxygen reduction reaction; irradiation; impurity; vacancyx86201347#N/AFALSE
3334
cs300530h10.1021/cs300530hFALSEhttps://doi.org/10.1021/cs300530hAlmeida-Gaschet, TACS Catal.For the first time, bimetallic copper-thorium (Cu-Th-O), nickel-thorium (Ni-Th-O), and nickel uranium (Ni-U-O) oxides were tested for the conversion of methane using N2O as oxidant. The behavior of the uranium and thorium catalysts is very different: at 10% methane isoconversion (700 degrees C), the production of C2 hydrocarbons is high over the uranium catalyst (approximate to 180%), but the formation of oxidation products (CO2, CO) prevails over the thorium-based catalysts (approximate to 85 and approximate to 15% selectivity to COx and C2). At higher temperature (750 degrees C), the formation of C2 hydrocarbons remains high over the uranium catalysts (conversion CH4 approximate to 20%, selectivity to C2 approximate to 60%), but the production of syngas is now very high over the thorium-based catalysts (conversion CH4 approximate to 50%, selectivity to CO and H-2 approximate to 90% at 750 degrees C over Ni-Th-O) without formation of C2). This distinct behavior could not be assigned to the catalytic behavior of pure metal oxides or mechanical mixtures of single metal oxides, which is very different from that of the bimetallic oxides and was explained by the differences on the accessibility and acidity of the catalysts surface. The catalytic behavior seems to depend on the actinide element, and the catalyst can be selected accordingly with the products that we want to achieve. To our knowledge, this is the first time that the conversion of methane using N2O as oxidant is reported over 5f block element-based catalysts.Conversion of Methane over Bimetallic Copper and Nickel Actinide Oxides (Th, U) Using Nitrous Oxide As Oxidantintermetallic; bimetallic actinide oxides; methane; nitrous oxide; syngas; C2 hydrocarbonsx16201261#N/AFALSE
3335
cs300472p10.1021/cs300472pFALSEhttps://doi.org/10.1021/cs300472pLi, HACS Catal.Control of the size and morphology of metallic nanomaterials enables mastery of their properties to enhance their catalytic performances. In this work, uniform Co-B amorphous alloy nanopartiCles were synthesized by a simple chemical reduction of [CoX4](-) with BH4- in the presence of Bu4P+. With the characterization of X-ray diffraction, selective area electronic diffraction, X-ray photoelectron spectroscopy, differential scanning calorimetry, and transmission electron microscopy, the resulting Co-B spherical nanopartiCles were identified to be amorphous alloys in an average partiCle size around 55 nm. The synergistic effect of the halide anion and Bu4P+ cation is essential for the formation of monodisperse and uniform spherical nanopartiCles. During the Heck-type carbon-carbon coupling reactions and the hydrogenation of butyraldehyde to n-butanol, the as-synthesized Co-B catalyst was extremely active compared with the conventional Co-B obtained via the direct reduction of cobalt ions with BH4- in aqueous solution. In addition, the as-prepared Co-B amorphous alloy also exhibited recyClability during the hydrogenation of butyraldehyde due to better thermal stability, which was related to the higher surface B content and the uniform partiCle size.Facile Synthesis of Co-B Amorphous Alloy in Uniform Spherical NanopartiCles with Enhanced Catalytic PropertiesCo-B; amorphous alloy; Heck reaction; hydrogenation; high stabilityx64201233#N/AFALSE
3336
cs400541910.1021/cs4005419FALSENorskov, JKNi-Fe-S Cubanesin CO2 Reduction Electrocatalysis: A DFT Study2013#N/ATRUE
3337
cs300396310.1021/cs3003963FALSEhttps://doi.org/10.1021/cs3003963Thomas, AACS Catal.Silica supported nanopartiCles of nickel manganese oxide, Ni0.2Mn0.8O, were prepared in a one-pot approach, combining co-precipitation and sot-gel chemistry. This approach enables the preparation of small ternary oxide crystallites evenly dispersed on porous silica. The resulting materials were used as catalyst for dry reforming of methane (DRM), and show a much higher activity as the reference bulk material prepared from conventional co-precipitation. Notably, the catalyst shows a remarkable activity even at low temperatures for DRM, thus nearly reaching thermodynamic equilibrium at 500 degrees C.One-Pot Synthesis of Supported, Nanocrystalline Nickel Manganese Oxide for Dry Reforming of Methanedry reforming; methane; carbon dioxide; Activation; heterogeneous catalysis; metal oxide catalystx57201334#N/AFALSE
3338
cs300376u10.1021/cs300376uFALSEhttps://doi.org/10.1021/cs300376uShimizu, KACS Catal.To confirm whether the activity trends in multistep organic reactions can be understood in terms of the Hammer-Norskov d-band model in combination with the linear energy relations, we studied correlations between the reaction rates for dehydrogenation and hydrogenation reactions and the position of the d-band center (epsilon(d)) relative to the Fermi energy (E-F), the epsilon(d) - E-F value, of various metal catalysts. SiO2-supported metal (M = Ag, Cu, Pt, Ir, Pd, Rh, Ru, Ni, and Co) catalysts with the same metal loading (5 wt %) and similar metal partiCle size (8.9-11.7 nm) were prepared. The dehydrogenation of adsorbed 2-propanol in a flow of He and the hydrogenation of adsorbed nitrobenzene in a flow of H-2 were tested as model reactions of organic reactions on the metal surface. As a test reaction of H-2 dissociation on the surface, SiOH/SiOD exchange on the M/SiO2 catalysts in a flow of D-2 is carried out. The liquid phase hydrogenation of nitrobenzene under 3.0 MPa of H-2 is adopted as an organic reaction under realistic conditions. Generally, the activities show volcano-type dependences on the epsilon(d) - E-F value, indicating that the epsilon(d) - E-F value is useful as a qualitative activity descriptor in heterogeneous catalysis of metal nanopartiCles for multistep organic reactions.Volcano-Curves for Dehydrogenation of 2-Propanol and Hydrogenation of Nitrobenzene by SiO2-Supported Metal NanopartiCles Catalysts As Described in Terms of a d-Band Modeltransition metals; trend in catalytic activity; d-band centerx49201230#N/AFALSE
3339
cs400441u10.1021/cs400441uFALSEhttps://doi.org/10.1021/cs400441uHu, XLACS Catal.Amorphous molybdenum sulfide films, prepared by electrodeposition, are a Class of highly active catalysts for hydrogen evolution. The growth mechanism of the films and the true active species were unClear. Herein, we report a study of the growth and Activation of these films using Electrochemical Quartz Crystal Microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS). Three processes, inCluding oxidative deposition, reductive corrosion, and reductive deposition, are occurring during the growth of a molybdenum sulfide film. Deposition method, precursor concentration, and potential window are among the factors influencing the film growth. Regardless of deposition methods, all films exhibit similar catalytic activity on a per mass base. Potentiostatic oxidation (anodic electrolysis) is the method for fastest film growth; it produces a MoS3 film precatalyst which can be electrochemically activated. The activity of the MoS3 precatalyst scales with catalyst loading; at a loading of 0.2 mg/cm(2), the current density is 20 mA/cm(2) at an overpotential of 170 mV. Films differently deposited have different initial compositions, but the active catalysts in all films are the same MoS2+x species, whose XPS characteristics are distinct from those of crystalline MoS2. The Activation process of a MoS3 film precatalyst involves a reductive removal of slightly less than one equivalent of sulfide to form MoS2+x.Growth and Activation of an Amorphous Molybdenum Sulfide Hydrogen Evolving Catalysthydrogen evolution; molybdenum sulfide; electrocatalysis; electrochemical quartz crystal microbalance; X-ray photoelectron spectroscopy; thin films206201341#N/ATRUE
3340
cs300211y10.1021/cs300211yFALSEhttps://doi.org/10.1021/cs300211ySun, SHMethanolysis of Ammonia Borane by CoPd NanopartiClesx2012#N/AFALSE
3341
cs400327y10.1021/cs400327yFALSEhttps://doi.org/10.1021/cs400327yPeressi, MSteering the Chemistry of Carbon Oxides on a NiCu Catalyst2013#N/ATRUE
3342
cs300147c10.1021/cs300147chttps://doi.org/10.1021/cs300147cJordan, RFACS Catal.Binding of B(C6F5)(3) to a sulfonate oxygen of (orthophosphino-arenesulfonate)PdR catalysts results in a 3-4 fold increase in the rate of chain growth and a larger increase in the rate of chain transfer. The reaction of (PO-Et)PdMe(py) (1a, [PO-Et](-) = ortho-{(2-Et-Ph)(2)P}-para-toluenesulfonate) with 1 equiv of B(C6F5)(3) yields the base-free dimer {(PO-Et)PdMe}(2) (2a), in which the (PO-Et)PdMe units are linked through an eight-membered [PdSO2](2) ring. The reaction of ((PO-3,5-'Bu-2)PdMe}(2)(TMEDA) (4b; [PO-3,5-Bu-t(2)](-) = ortho-{(3,5-(Bu2-Ph)-Bu-t)(2)P}-para-toluenesulfonate, TMEDA = N,N,N',N'-tetramethylethylenediamine) with BF3.Et2O yields the soluble base-free dimer {(PO-3,5-Bu-t(2))PdMe}(2) (2b), in which the (PO-3,5-Bu-t(2))PdMe units are linked through a four-membered Pd2O2 ring. 2b reacts with 2 equiv of B(C6F5)(3) to yield {[PO.B(C6F5)(3)-3,5-Bu-t(2)]PdMe}(2) (5b, [PO.B(C6F5)(3)-3,5-Bu-t(2)](-) = [2-{(3,5-Bu-t(2)-Ph)(2)P}-4-Me-C6H3SO2OB(C6F5)(3)](-)), which crystallizes from Et2O as the monomeric complex [POB(C6F5)(3)-3,5-Bu-t(2)]PdMe(Et2O) (6b). In both 5b and 6h, the B(C6F5)(3) binds to a sulfonate oxygen. In toluene solution at 60 degrees C, 2h polymerizes ethylene (80 psi) to linear polyethylene with M-n = 3,000, while the B(C6F5)(3) adducts 5b and 6h yield ethylene oligomers (M-n = 160-170). 5b and 6h are 3-4 times more active than 2h. Similarly, la polymerizes ethylene to linear polyethylene with M-n = 29,300 (toluene, 80 degrees C, 435 psi), while la-4 B(C6F5)(3) yields polymer with M-n = 2,520 with a 4 fold increase in activity. 2b reacts with ethylene at 7 degrees C to form the ethylene adduct (PO-3,5-Bu-t(2))PdMe(CH2=CH2) (7b) followed by multiple insertions to generate (PO-3,5-Bu-t(2))Pd(CH2CH2)(n)CH3 species. In contrast, 5b reacts with ethylene to form [POB(C6F5)(3)-3,5-Bu-t(2)]PdMe(CH2=CH2) (8b) followed by insertion and, beta-H transfer to yield propene with subsequent catalytic formation of 1-butene and higher olefins. The rate of ethylene insertion of 8b is 3 times greater than that of 7b, consistent with the batch polymerization results. The polymer yield and molecular weight data show that binding of B(C6F5)(3) to 2b and la increases the chain transfer rates by a factor of 80 and 42, respectively.Enhancement of Chain Growth and Chain Transfer Rates in Ethylene Polymerization by (Phosphine-sulfonate)PdMe Catalysts by Binding of B(C6F5)(3) to the Sulfonate Groupethylene polymerization; ethylene oligomerization; (phosphine-sulfonate)Pd catalyst; Lewis acid; remote bindingx56201247#N/AFALSE
3343
cs400311310.1021/cs4003113FALSEhttps://doi.org/10.1021/cs4003113Chu, WACS Catal.A series Of ordered mesoporous Ni-Ce-Al composite oxides with various cerium contents were synthesized via a one-pot route: evaporation-induced self-assembly (EISA) strategy and tested in methane dry reforming for hydrogen and synthesis gas production. Using, this method, the hydrophobic nickel precursor was directly incorporated into the hydrophobic cores of surfactant micelles,, and thus, the highly dispersed Ni nanopartiCles were Stabilized inside the mesopore Channels' of an alumina matrix. For comparison, Ni-based catalysts were also prepared by a traditional impregnation method. The characterization results confirmed that the ordered mesostructiires were well maintained in all of the cerium-incorporated Ni-Al materials (Ce/(Ce + Al) molar ratio <= 3%). The catalyst with a Ce/(Ce + Al) ratio of 1% exhibited the highest catalytic activity (with CO2 and CH4 initial conversions being 70% and 68% at 700 degrees C, respectively) and remained stable in a methane dry reforming reaction. This improved activity can be attributed to the large surface area and high dispersion and reducibility of Ni nanopartiCles,which were Stable because of the stable alumina framework and high oxygen mobility in these Cerium-containing samples. Resistance to carbon deposition was found over the Ni-Ce-Al Catalyst, whereas amounts of graphitic carbon species were found over the Ni-impregnated catalysts, which was responsible for deActivation.Facile Route for Synthesizing Ordered Mesoporous Ni-Ce-Al Oxide Materials and Their Catalytic Performance for Methane Dry Reforming to Hydrogen and SyngasOne-pot synthesis; Ordered mesopores; Confinement effect; Methane dry reforming; Hydrogen247201365#N/ATRUE
3344
cs300048u10.1021/cs300048uFALSEhttps://doi.org/10.1021/cs300048uXu, LYACS Catal.One-step transformation of isobutyl alcohol to aromatics (benzene, toluene, and xylene) has been studied in a gas phase, fixed-bed reactor system over several purely acidic zeolites and zeolite-supported metal catalysts. ZSM-5 zeolites give higher aromatics yields (similar to 42 wt %) among the evaluated zeolites, and the Si! Al ratios (Si/Al = 13-43) of ZSM-5 slightly influence their catalytic performances. During the transformation of isobutyl alcohol, large amounts of short alkanes (mainly propane and butane isomers) are also generated on the acidic ZSM-S. To improve the conversion to aromatics, several metal species (Zn, Ga, Mo, La, Ni, Ag, and Pt) are supported on the ZSM-5. The enhancements in aromatics yields (similar to 60wt %) are observed only on the Zn/ZSM-5 catalysts. The incorporation of Zn species preferentially decreases the strong-strength Bronsted acidity and, thus, suppresses the cracking to C-3 fragments. Moreover, mainly the Zn species at the exchange sites facilitate the recombinative desorption of H-2 and, hence, enhance the reactions toward aromatics. Through these effects, Zn/ZSM-5 catalysts exhibit the remarkably promoted formation of toluene and xylene and inhibit the generation of undesired alkanes products.Transformation of Isobutyl Alcohol to Aromatics over Zeolite-Based Catalystsisobutyl alcohol; zeolites; aromatization; zinc speciesx67201232#N/AFALSE
3345
cs300019h10.1021/cs300019hFALSEhttps://doi.org/10.1021/cs300019hBullock, RMACS Catal.A nickel(II) bis(diphosphine) complex, [Ni((P2N2Ph)-N-Me)(2)](BF4)(2) ((P2N2Ph)-N-Me = 1,5-diphenyl-3,7-dimethyl-1,5-diaza-3,7-diphosphacyClooctane), has been synthesized and characterized. This complex, which contains pendant amines in the diphosphine ligand, is an electrocatalyst for hydrogen production by proton reduction. Using [(DMF)H]OTf as the acid, a turnover frequency of 1,540 s(-1) was obtained with no added water, and a turnover frequency of 6,700 s(-1) was found with 1.0 M water added. Thermochemical studies show that the hydride donor ability of [HNi((P2N2Ph)-N-Me)(2)](BF4) is Delta G degrees(H)-= 54.0 kcal/mol, and we estimate a driving force for H-2 elimination of 13.8 kcal/mol. [Ni((P2N2Ph)-N-Me)(2)](BF4)(2) is the fastest H-2 production catalyst in the [Ni((P2N2R')-N-R)(2)](BF4)(2) complexes.[Ni((P2N2Ph)-N-Me)(2)](BF4)(2) as an Electrocatalyst for H-2 Productionhydrogen; electrocatalysis; proton relay; pendant amine; proton reduction; nickelx75201279#N/AFALSE
3346
cs400306310.1021/cs4003063FALSEhttps://doi.org/10.1021/cs4003063Lercher, JAACS Catal.Reforming of acetic acid was investigated on Rh supported on CeO2-ZrO2 modified with 3 wt % La. The active catalyst converted acetic acid to H-2-rich gas and hardly formed coke. The low rate of coke formation is conCluded to be related to the presence of redox-active oxygen limiting the concentration of coke precursors. Temperature-programmed O-18(2)) isotope exchange measurements showed that the La2O3 and Rh enhanced the mobility of lattice oxygen compared with that of the parent CeO2-ZrO2. Ketonization and deCarbonylation of acetic acid are the dominating reactions over the latter up to 600 degrees C, whereas above 600 degrees C, steam reforming and water gas shift also contribute. Over 0.5 wt % Rh on La2O3/CeO2-ZrO2, reforming and water gas shift reactions dominate, even below 300 degrees C, producing mostly H-2 and CO2. Using isotope labeling, it is shown that acetic acid adsorbs dissociatively on Rh, forming acetates, which sequentially deCarbonylate and form surface methyl groups. The latter are in turn converted to CO, CO2, and H-2.Acetic Acid Reforming over Rh Supported on La2O3/CeO2-ZrO2: Catalytic Performance and Reaction Pathway Analysishydrogen production; steam reforming; acetic acid; La2O3/CeO2-ZrO2; supported Rh56201362#N/ATRUE
3347
cs400293b10.1021/cs400293bFALSECaballero, APromotional Effect of the Base Metal on Bimetallic Au-Ni/CeO2 Catalysts Prepared from Core-Shell NanopartiCles2013#N/ATRUE
3348
cs200659r10.1021/cs200659rFALSEhttps://doi.org/10.1021/cs200659rSerrano, DPACS Catal.A novel hydrodeoxygenation catalytic system, Ni2P/SBA-15, has been synthesized by temperature-programmed reduction of a nickel phosphate precursor impregnated in the mesostructured silica support. The formation of this active phase was, verified by X-ray diffraction, whereas the study by transmission electron microscopy revealed that the catalyst is mainly constituted of nickel phosphide partiCles of relatively uniform size dispersed within the SBA-15 channels. Both Ni2P/SBA-15 and a reference Ni/SBA-15 catalyst were tested for the hydrodeoxygenation of methyl oleate (C17H33-COO-CH3) in a fixed-bed continuous flow reactor. This compound was used as a convenient surrogate of triglyceride molecules present M vegetable oils that following catalytic hydrotreating yields n-alkanes as the main products. In the whole range of pressure studied (3-40 bar) and for temperatures higher than 290 degrees C, both systems achieve more than 80% ester conversion at 20 h(-1) WHSV, although the Ni/SBA-15 catalyst presents a slightly higher activity. Overall, higher pressure and lower temperature and space velocity favors the formation of C-18 hydrocarbon, which is the preferred product in terms of carbon atom economy. Nevertheless, under all the assayed conditions, the n-C-18/n-C-17 ratio was remarkably higher for Ni2P/SBA-15 than for Ni/SBA-15 catalysts. On the basis of these results, it can be conCluded that both deoxygenation and deCarbonylation occur simultaneously over the Ni2P catalyst, whereas deCarbonylation and cracking are the prevailing processes over the Ni catalyst. Owing to these high yields of long-chain paraffins, Ni2P/SBA-15 can be considered as a very promising catalyst for the production of green diesel.Ni2P/SBA-15 As a Hydrodeoxygenation Catalyst with Enhanced Selectivity for the Conversion of Methyl Oleate Into n-Octadecanehydrodeoxygenation; nickel phosphide; SBA-15; green diesel; biofuels; methyl oleate; triglyceridesx139201220#N/AFALSE
3349
cs200658610.1021/cs2006586FALSEhttps://doi.org/10.1021/cs2006586Weststrate, CJACS Catal.Density functional theory (DFT) calculations and temperature programmed desorption (TPD) experiments were performed to study the adsorption of hydrogen on the Co(111) and Co(100) surfaces. On the Co(111) surface, hydrogen adsorption is coverage dependent and the calculated adsorption energies are very similar to those on the Co(0001) surface. The experimental adsorption saturation coverage on the Co(111)/(0001) surface is theta(max) approximate to 0.5 ML, although DFT predicts theta(max) approximate to 1.0 ML. DFT calculations indicate that preadsorbed hydrogen will kinetically impede the adsorption process as the coverage approaches theta = 0.5 ML, giving rise to this difference. Adsorption on Co(100) is coverage independent up to theta = 1.00 ML, contrasting observations on the Ni(100) surface. Hydrogen atoms have low barriers of diffusion on both the Co(111) and Co(100) surfaces. A microkinetic analysis of desorption, simulating the expected TPD experiments, indicated that on the Co(111) surface two TPD peaks are expected, while on the Co(100) only one peak is expected. Low coverage adsorption energies of between 0.97 and 1.1 eV are obtained from the TPD experiment on a smooth single crystal of Co(0001), in line with the DFT results. Defects play a important role in the adsorption process. Further calculations on the Co(211) and Co(221) surfaces have been performed to model the effects of step and defect sites, indicating that steps and defects will expose a broad range of adsorption sites with varying (mostly less favorable) adsorption energies. The effect of defects has been studied by TPD by sputtering of the Co crystal surface. Defects accelerate the adsorption of hydrogen by providing alternative, almost barrierless pathways, making it possible to increase the coverage on the Co(111)/(0001) surface to above theta = 0.50 ML. The presence of defects at a high concentration will give rise to adsorption sites with much lower desorption Activation energies, resulting in broad low temperature TPD features.Hydrogen Adsorption on Co Surfaces: A Density Functional Theory and Temperature Programmed Desorption StudyDFT; TPD; hydrogen adsorption; microkinetic analysis; cobaltx80201240#N/AFALSE
3350
cs400245m10.1021/cs400245mFALSEhttps://doi.org/10.1021/ja00013a022Lee, JSBarium Substituted Lanthanum Manganite Perovskite for CO2 Reforming of Methane2013#N/ATRUE
3351
cs200593c10.1021/cs200593chttps://doi.org/10.1021/cs200593cWu, QACS Catal.A series of pyridine-amine nickel complexes with various substituents were synthesized and used to evaluate substituent effects of catalyst precursors on the reactivity of ethylene polymerization. Substituent effects, inCluding the steric effect of the pyridine moiety, steric effect of the bridge carbon, and steric and electronic effects of the amine moiety, were investigated systematically. Introduction of bulky Aryls onto the pyridine moiety on amine pyridine nickel leads to a significant decrease in the activity and molecular weight of polyethylene, whereas an increase in bulk of substituents on the bridge carbon causes an increase in the polymerization activity and molecular weight of polyethylene. For the amine moiety, increasing the steric hindrance results in decreasing activity and affords a higher molecular weight polyethylene with a narrow polydispersity, and introduction of an electron-donating group on the amine moiety leads to formation of a high molecular weight polyethylene with enhanced activity. By optimizing ligand frameworks and reaction conditions, two bulky pyridine-amine, nickel complexes are also developed successfully as catalyst precursors for living polymerization of ethylene.Substituent Effects of Pyridine-amine Nickel Catalyst Precursors on Ethylene Polymerizationpyridine-amine; nickel complex; ethylene; living polymerizationx60201253#N/AFALSE
3352
cs200530e10.1021/cs200530eFALSEhttps://doi.org/10.1021/cs200530eQuadrelli, EAACS Catal.The Metal-Organic Framework, [Ni-2(dhtp)] (H(4)dhtp = 2,5-dihydroxyterephthalic acid) was modified by gas-phase grafting of Mo(CO)(6) at the gram-scale via a post-synthesis modification approach. A highly dispersed well-defined bimetallic material containing the [Ni-2(dhtp)Mo(CO)(3)] fragment either in the staggered or in the eClipsed conformation was obtained, with a maximum coverage of 506,61, as shown by inultitechnique characterization: IR (diagnostic v(CO) = 1996, 1972, 1926, 1885, and 1797 cm-(1)), N-2 adsorption (Brunauer-Emmett-Teller (BET) surface area = 172 m(2) g(-1) pore volume 0.1 cm(3)/g), elemental analyses (Ni = 21.6%(wt), Mo = 9.6%(wt)), mass balanced analyses of evolved gases (3.0 +/- 0.2 mols of CO evolved/mol of grafted Mo(CO)(6) high-resolution transmission electron microscopy (HRTEM). The staggered conformer is stabilized by an intermolecular Ni center dot center dot center dot(OC)Mo interaction with the framework open Ni(II) site, which causes the markedly blue-shifted stretching band observed at v(CO) = 1797 cm(-1). Upon decomposition in dihydrogen-hydrogen sulfide at 350 degrees C (to p(H2) = 50 bar), the resulting bulk material is a heterogeneous catalyst for hydrodesulfurization (HDS). The HDS activity of the catalyst was based on the average measured conversion of dibenzothiophene to biphenyl (BP) or cyClohexylbenzene (CHB) by online calibrated GC-MS analyses under steady state conditions and converted to the corresponding relative pseudo first-order rate constants [k(HDS) = k(BP) + k(CHB)]. The activity of the MOF-generated material is markedly superior to the reference bulk unsupported HDS catalysts NiMoO4 (pseudo first-order rate k(HDS) = 30 vs 14 h(-1)) while containing 4 time less molybdenum (wt % = 10 vs 44). Activities on hydrodenitrogenation (HDN) and hydrogenation (HYD) are also reported. Analysis by HRTEM and X-ray diffraction (XRD) of the spent catalyst and comparison with model systems revealed well-formed MoS2 nanopartides (average sheet thickness 25 A, corresponding to about 4 stacked layers of MoS2 sheets, the MoS2 (011) interlayer distance being 6.15 angstrom). The presence of Ni in the MoS2 partiCles was inferred by the lack of HDS activity of the nickel-free material obtained from analogous chemisorption of Mo(CO)(6) in isostructural Zn analogue followed by the same in situ sulfidation procedure.Bulk Hydrodesulfurization Catalyst Obtained by Mo(CO)(6) Grafting on the Metal-Organic Framework Ni-2(2,5-dihydroxoterephthalate)HDS; heterogeneous catalysts; MOF; CPO-27-Ni; Ni-MOF-74; molybdenum; nickelx19201242#N/AFALSE
3353
cs200385y10.1021/cs200385yFALSEhttps://doi.org/10.1021/cs200385yShanthi, KACS Catal.Mesoporous Al-SBA-15 with different Si/Al molar ratio (10, 20, 30, and 40) was synthesized hydrothermally, and Mo-Ni catalysts were prepared by incipient wet impregnation method and characterized by different techniques. An impressive catalytic performance was observed on Mo-Ni/Al-SBA-15(10) for MethylcyClohexylamine conversion to hydrocarbons. The observed trend of activity is correlated with the aluminum content, and it is conCluded that the variation in Si/Al ratio remarkably affects the hydro-denitrogenation ability of Al-SBA-15 supported Mo-Ni catalysts.Mo-Ni/Al-SBA-15 (Sulfide) Catalysts for Hydrodenitrogenation: Effect of Si/Al Ratio on Catalytic Activityhydrodenitrogenation; methylcyClohexylamine; SBA-15; Al-SBA-15; Mo-Ni catalystsx48201226#N/AFALSE
3354
cs400199b10.1021/cs400199bFALSEhttps://doi.org/10.1021/cs400199bInamoto, SACS Catal.Adding Cr to heat-tolerant Co0.054Ni0.018Mg0.93O solid-solution catalysts for CH4/CO2/H2O reforming at 2.1 M.Pa allowed us to control the key properties determining the behavior of the supported catalysts, such as the reduction degree of the metal, metal partiCle size, and amount of exposed zerovalent metals. A small load of Cr [Cr/(Co + Ni) = 0.11 mol %] efficiently catalyzed Co2+ and Ni2+ reduction. This catalyst, which had abundant small alloy partiCles on the support material, resisted coking and oxidative deActivation, even under accelerated deterioration conditions: X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, extended X-ray absorption fine structure, and scanning transmission electron microscopy energy-dispersive X-ray measurements indicated that Cr existed as a trivalent cation in a CrxCo0.054Ni0.018Mg0.93O1+1.5x solid solution, leading to the formation of a divalent cation vacancy and that Cr3+ was abundant on the surface of the catalyst partiCles after calcination at 1373 K. The Cr3+ destabilized Co2+ and Ni2+ in the solid solution, especially on the surface of the catalyst partiCles and, thus, promoted Co2+ and Ni2+ reduction. However, excess Cr3+ induced sintering of the catalyst partiCles, resulting in aggregation of alloy partiCles and, thus, in an increased risk of coking.Cr3+-Co0.054Ni0.018Mg0.93O Solid-Solution Catalysts for High-Pressure Syngas Production: Effect of Chromium on the Reduction and Catalysistailoring catalyst; solid-solution; chromium; methane; reforming; syngas production8201340#N/ATRUE
3355
cs200336r10.1021/cs200336rFALSEhttps://doi.org/10.1021/cs200336rWang, ZXACS Catal.The production of fuels and chemicals from biomass requires heterogeneous catalysts that facilitate selective reactions of highly functional oxygenates. Although designing catalysts for high selectivity is a universal challenge in heterogeneous catalysis research, the problem is particularly acute for highly functional molecules, which contain two or more functional groups that may react over metal surfaces. This perspective artiCle focuses on recent efforts to develop structure-property relations on metal surfaces and catalysts for two Classes of highly functional molecules: multifunctional oxygenates such. as alpha,beta-unsaturated aldehydes and furanic compounds, and polyfunaional oxygenates such as glycerol and otherpolyols. Recent results from comparative reaction studies over a variety of catalysts, surface science experiments, and computational investigations suggest an array of approaches for producing more selective catalysts, many relying on the addition of multiple metals or other surface modifiers. General strategies that appear to show promise in the selective reactions of unsaturated oxygenates and of polyols are discussed in detail.Understanding and Controlling Reactivity of Unsaturated Oxygenates and Polyols on Metal Catalystscellulosic biomass; biorefinery; alcohol oxidation; aldehyde hydrogenation; platinum; gold; palladium; rutheniumx862011177#N/AFALSE
3356
cs400159w10.1021/cs400159wFALSEhttps://doi.org/10.1021/cs400159wTada, MACS Catal.Ni-ceria nanopartiCles (Ni/Ce = 1/1) in the cage-like pores of SBA-16 were prepared and evaluated in methane dry reforming reactions. Coexistence of ceria in NiCe/SBA-16 resulted in forming uniformly sized Ni partiCles (ay. 5.7 nm) within the mesopores of SBA-16, because of the confinement effect from the framework of SBA-16 and the strong interaction between Ni and ceria. Ceria addition facilitated the reduction of NiCe/SBA-16 compared with Ni/SBA-16, and Ce3+ was the dominant species in both fresh and used NiCe/SBA-16 catalysts, as determined by Ce L-III-edge X-ray absorption near-edge structure (XANES). The methane conversion was much more stable on NiCe/SBA-16 than on Ni/CeO2 and Ni/SBA-16 in the methane dry reforming at 973 K during a 100 h reaction period; the deActivation of the Ni catalyst and the collapse of the SBA-16 framework were preferably suppressed for NiCe/SBA-16 under the reaction conditions. The remarkable effect of ceria on the structural stability of both the active Ni partiCles and the SBA-16 framework led to the consistent catalytic performance of NiCe/SBA-16 in methane dry reforming.Ceria-Doped Ni/SBA-16 Catalysts for Dry Reforming of Methanemethane dry reforming; nickel catalyst; mesoporous support; SBA-16; ceria; XAFS214201378#N/ATRUE
3357
cs200308b10.1021/cs200308bhttps://doi.org/10.1021/cs200308bRedshaw, CACS Catal.The series of N-(5,6,7-trihydroquinolin-8-ylidene)nitroArylamine ligands (L1-L4) was prepared and used to synthesize the chloro-bridged dinickel complexes (Ni1-Ni4) and the bis-ligated mononickel(II) complex (Ni5) in good yield. Molecular structures of Ni1, Ni2, Ni4, and Ni5 were confirmed by single-crystal X-ray diffraction analysis, revealing a pseudosquare-pyramidal geometry around nickel in the chloro-bridged complexes (Nil, Ni2, and Ni4) and a distorted octahedral geometry at the nickel atom in the bis-ligated complex (Ni5). Upon treatment with ethylaluminum sesquichloride (EASC, Et3Al2Cl3) or methylaluminoxane (MAO), all nickel complexes exhibited high activities (up to 4.05 x 10(6) g (PE) mol(-1) h(-1)) for ethylene polymerization. Moreover, heterocyClic impurities such as tetrahydrofuran (THF) and pyridine, often detected in common solvents, were added to the catalytic system of precatalyst Ni2 under controlled conditions and were found to have a negative influence on the catalytic behavior during ethylene polymerization.Synthesis, Characterization, and Ethylene Polymerization Behavior of 8-(NitroArylamino)-5,6,7-trihydroquinolylnickel Dichlorides: Influence of the Nitro Group and Impurities on Catalytic Activityethylene polymerization; nickel precatalyst; 2-nitroArylimino-5,6,7-trihydroquinoline; branching polyethylene; X-ray diffractionx63201155#N/AFALSE
3358
cs400135k10.1021/cs400135kFALSEhttps://doi.org/10.1021/ja00008a039Chen, MWGeometrically Controlled Nanoporous PdAu Bimetallic Catalysts with Tunable Pd/Au Ratio for Direct Ethanol Fuel Cells2013#N/ATRUE
3359
cs400059n10.1021/cs400059nFALSEhttps://doi.org/10.1021/cs400059nLi, HACS Catal.In this paper, uniform Co-B amorphous alloy nanospheres with an average partiCle size of 50 nm were synthesized by chemical reduction of cobalt ion with borohydride in aqueous solution containing Bu4PBr and KCl. Then, Pd was introduced into this system by galvanic replacement reaction (GRR) between Co and Na2PdCl4, Pd/Co-B catalysts with different Pd content could be obtained via adjusting the amount of Na2PdCl4 in reaction mixture. The crystal structure, morphology, and surface electronic state of as-prepared catalysts were characterized by XRD, TEM, XPS, and H-2-TPD. During the liquid-phase hydrogenation of 2-ethyl-2-hexenaldehyde, the as-prepared Pd/Co-B catalysts exhibited extremely active and more selectivity to 2-ethyl-1-hexanol than the monometallic Pd and Co-B amorphous alloy, showing potential application in industry. The enhanced performances could be attributed to the highly dispersed Pd on the surface of Co-B prepared by GRR and the synergetic effect between Pd and Co.Highly Dispersed Pd on Co-B Amorphous Alloy: Facile Synthesis via Galvanic Replacement Reaction and Synergetic Effect between Pd and CoPd/Co-B; bimetallic catalyst; galvanic replacement reaction; hydrogenation; 2-ethyl-2-hexenaldehyde; 2-ethyl-1-hexanol23201338#N/ATRUE
3360
cs200057y10.1021/cs200057yFALSEhttps://doi.org/10.1021/cs200057yChen, JGACS Catal.Selective reforming of biomass-derived oxygenates to produce hydrogen or syngas (H-2 + CO) offers an attractive route for biomass utilization. As reported previously, the Ni/Pt(111) bimetallic surface, with one monolayer of Ni residing on top of Pt(111), showed enhanced activity in oxygenate reforming. However, the Ni/Pt(111) structure is not stable at high temperatures because of diffusion of Ni into bulk Pt. In the current study we explore the possibility of replacing the Pt substrate with tungsten monocarbide (WC) to prevent the diffusion of monolayer Ni into the bulk. We report a combined study using density functional theory (DFT), temperature programmed desorption (TPD), and high resolution electron energy loss spectroscopy (HREELS) to compare the reforming reaction of ethanol on Ni/Pt and Ni/WC surfaces. Strong similarities are observed in the reaction pathways of ethanol on monolayer Ni/Pt and Ni/WC, demonstrating the feasibility to replace Pt with WC and to use monolayer Ni/WC as active and less expensive reforming catalysts.Replacing Platinum with Tungsten Carbide (WC) for Reforming Reactions: Similarities in Ethanol Decomposition on Ni/Pt and Ni/WC Surfacesethanol; reforming reaction; Ni/Pt; Ni/WC; bimetallic surfacesx39201130#N/AFALSE
3361
cs200047210.1021/cs2000472FALSEhttps://doi.org/10.1021/cs2000472Song, CSACS Catal.Supported nickel catalysts are widely used in hydrocarbon steam reforming for producing hydrogen. Carbon deposition is a major cause of Ni catalyst deActivation. In this work, supported Ni and Ni/Rh catalysts were synthesized and tested for liquid hydrocarbon steam reforming. Carbon analysis on the spent catalysts illustrates that the carbon deposition is significantly reduced with inClusion of Rh. Extended X-ray Absorption Fine Structure (EXAFS) analysis indicates Close interactions between Ni and Rh atoms. Density functional theory (DFT) results show that a Ni/Rh alloy is thermodynamically more stable than Ni and Rh alone at the synthesis and reaction temperatures. Adsorption, diffusion, and oxidation of carbon atoms over Ni and Ni/Rh alloy surfaces were examined by DFT calculations. Alloying with Rh reduces the stability of deposited carbon atoms an Clusters over both terraces and steps: of the catalyst Moreover, Rh addition enhances the competition of oxidation reactions against carbon deposition by altering the relative diffusion rates and bond formation rates of the two processes.Improving the Carbon Resistance of Ni-Based Steam Reforming Catalyst by Alloying with Rh: A Computational Study Coupled with Reforming Experiments and EXAFS Characterizationsteam reforming; deActivation; coking; nickel; rhodium; Ni-Rh; catalyst; DFT; stepped surfaces; reforming; EXAFSx46201165#N/AFALSE
3362
cs300422710.1021/cs3004227FALSEChen, JGGCorrelating Ethylene Glycol Reforming Activity with In Situ EXAFS Detection of Ni Segregation in Supported NiPt Bimetallic Catalysts2012#N/ATRUE
3363
cs300247g10.1021/cs300247gFALSEhttps://doi.org/10.1021/cs300247gMuller, CRACS Catal.A bifunctional catalyst for the sorbent-enhanced steam methane reforming (SE-SMR) reaction was derived from a hydrotalcite-based precursor synthesized via a coprecipitation technique. The material contained both the Ni reforming catalyst and the Ca-based CO2 sorbent and was characterized using X-ray diffraction, H-2 chemisorption, N-2 physisorption, transmission electron microscopy, and temperature-programmed reduction. Reduction of the calcined hydrotalcite converted the (Al:Ca:Mg:Ni)O-x mixed oxide into nickel and CaO partiCles supported on an (Al:Mg)O-x matrix with a surface area of 54 m(2)g(-1). The high CO2 absorption capacity and its stability with carbonation cyCles was attributed to the high dispersion of CaO on the porous and thermally stable (Al:Mg)O-x network, whereas for naturally occurring limestone, a rapid decay in the CO2 absorption capacity was observed. Under SE-SMR conditions, the recorded mole fraction of hydrogen in the effluent stream was 99 vol % (dry and without inert component); that is, thermodynamic equilibrium calculated to be 99 vol % (without inert component) was reached. The CO2 uptake of the bifunctional material averaged 0.074 g CO2/g sorbent over 10 cyCles. After approximately seven cyCles, the CO2 capture capacity stabilized, resulting in an average decay rate of only 0.3% per cyCle over the last three cyCles. The bifunctional material developed here produced a larger amount of high-purity H, than limestone mixed with Ni-SiO2 or a Ca-free, nickel hydrotalcite-derived catalyst, making the new material an interesting candidate for the SE-SMR process.Sorbent-Enhanced Methane Reforming over a Ni-Ca-Based, Bifunctional Catalyst Sorbentsorbent-enhanced steam methane reforming; bifunctional catalyst; CO2 capture; hydrogen; nickel catalyst; calcium oxide87201275#N/ATRUE
3364
cs300154510.1021/cs3001545FALSEhttps://doi.org/10.1021/cs3001545Kuhn, JNACS Catal.Sulfur K-edge XANES identified transformation of sulfides to sulfates during combined steam and air regeneration on a Ni/Mg/K/Al2O3 catalyst used to condition biomass derived syngas. This catalyst was tested over multiple reaction/regeneration/reduction cyCles. Postreaction catalysts showed the presence of sulfides on H2S-poisoned sites. Although H2S was observed to leave the catalyst bed during regeneration, sulfur remained on the catalyst, and a transformation from sulfides to sulfates was observed. Following the oxidative regeneration, the subsequent H-2 reduction led W.:a partial reduction of sulfates back to sulfides, indicating the difficulty and sensitivity in achieving complete sulfur removal during regeneration for biomass-conditioning catalysts.Transformation of Sulfur Species during Steam/Air Regeneration on a Ni Biomass Conditioning CatalystXANES; nickel; biomass; sulfates; sulfides; regeneration18201218#N/ATRUE
3365
cs300107210.1021/cs3001072FALSEhttps://doi.org/10.1021/cs3001072Chou, LJACS Catal.Ordered mesoporous tricompound NiOCaO-Al2O3 composite oxides with various Ca content were first designed and facilely synthesized via a one pot, evaporation induced, self assembly (EISA) strategy. The obtained mesoporous materials with advantageous textural properties and superior thermal stabilities were investigated as the catalysts for the carbon dioxide reforming of methane reaction. These mesoporous catalysts entirely showed high catalytic activities as well as king catalytic stabilities toward this reaction. The improved catalytic activities were suggested to be Closely associated with the advantageous structural properties, such as large specific surface areas; big pore volumes; and uniform pore sizes, which could provide sufficient accessible active centers for the gaseous reactants. In addition, the confinement effect of the mesoporous matrixes contributed to stabilizing the Ni active sites during the processes of reduction and reaction, accounting for the long lifetime stabilities of these mesoporous catalysts. The modification of Ca played dual roles in promoting the catalytic activities and suppressing the carbon deposition by enhancing the chemisorption of the CO2. Generally, the ordered mesoporous NiO-CaO-Al2O3 composite oxides could be considered as promising catalysts for the carbon dioxide reforming of methane reaction.One-Pot Synthesis of Ordered Mesoporous NiO-CaO-Al2O3 Composite Oxides for Catalyzing CO2 Reforming of CH4one pot ordered mesopores; confinement effect; NiO-CaO-Al2O3; carbon dioxide reforming; methane169201266#N/ATRUE
3366
cs200695t10.1021/cs200695tFALSESong, CSComparative Study on the Sulfur Tolerance and Carbon Resistance of Supported Noble Metal Catalysts in Steam Reforming of Liquid Hydrocarbon Fuel2012#N/ATRUE
3367
cs200678910.1021/cs2006789FALSEhttps://doi.org/10.1021/cs2006789Hu, PACS Catal.Activity and selectivity are both important issues in heterogeneous catalysis and recent experimental results have shown that Ni catalysts doped by gold exhibit high activity for the hydrogenation of acetylene with good selectivity of ethylene formation. To unravel the underlying mechanism for this observation, the general trend of activity and selectivity of Ni surfaces doped by Au, Ag, and Cu has been investigated using density functional theory calculations. Complete energy profiles from C2H2 to C2H4 on Ni(111), Au/Ni(111), Ag/Ni(111) and Cu/Ni(111) are obtained and their turnover frequencies (TOFs) are computed. The results show that acetylene adsorption on Ni catalyst is strong which leads to the low activity while the doping of Au, Ag, and Cu on the Ni catalyst weakens the acetylene adsorption, giving rise to the increase of activity. The selectivity of ethylene formation is also quantified by using the energy difference between the hydrogenation barriers and the absolute value of the adsorption energies of ethylene. It is found that the selectivity of ethylene formation increases by doping Au and Ag, while those of Cu/Ni and Ni are similar.Origin of the Increase of Activity and Selectivity of Nickel Doped by Au, Ag, and Cu for Acetylene HydrogenationDFT; selective hydrogenation; activity; selectivity; acetylene; ethylene; Ni; Au; Ag; Cu125201242#N/ATRUE
3368
chem.20200426710.1002/chem.202004267FALSEhttps://doi.org/10.1002/chem.202004267Wang, LRational Design and Controlled Synthesis of V-Doped Ni3S2/NixPy Heterostructured Nanosheets for the Hydrogen Evolution Reactionx2021#N/AFALSE
3369
cs200609e10.1021/cs200609eFALSEhttps://doi.org/10.1021/cs200609eRossi, LMACS Catal.The synthesis of nickel catalysts for industrial applications is relatively simple; however, nickel oxidation is usually difficult to avoid, which makes it challenging to optimize catalytic activities, metal loadings, and high-temperature Activation steps. A robust, oxidation-resistant and very active nickel catalyst was prepared by controlled decomposition of the organometallic precursor [bis(1,5-cyClooctadiene)nickel(0)], Ni(COD)(2), over silica-coated magnetite (Fe3O4@SiO2). The sample is mostly Ni(0), and surface oxidized species formed after exposure to air are easily reduced in situ during hydrogenation of cyClohexene under mild conditions recovering the initial activity. This unique behavior may benefit several other reactions that are likely to proceed via Ni heterogeneous catalysis.Direct Access to Oxidation-Resistant Nickel Catalysts through an Organometallic Precursornickel nanopartiCles; organometallic; Ni(COD)(2); hydrogenation; magnetic separation18201237#N/ATRUE
3370
chem.20200322010.1002/chem.202003220FALSEhttps://doi.org/10.1039/d1sc02547cYao, YDUltrathin Mn Doped Ni-MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitorx2020#N/AFALSE
3371
cs200359310.1021/cs2003593FALSEhttps://doi.org/10.1021/cs2003593Vlachos, DGACS Catal.Knowledge of the underlying mechanisms controlling oxygenate catalytic decomposition to synthesis gas can lead to the design of better catalysts and reactors, enabling the utilization of biomass feedstock for fuels and chemicals. This work studies the decomposition of ethylene glycol, as a simple surrogate to biomass-derived polyols, through the analysis of two catalytic kinetic models. First, a density functional theory (DFT) and statistical mechanical parametrized model of 81 reversible, elementary like reactions is used to predict and understand ethylene glycol decomposition on Pt Reaction path analysis indicates that while the majority of decomposition occurs through initial O-H bond breaking, initial C-H bond breaking is active at temperatures around 500 K. Further, sensitivity analysis shows that early dehydrogenation reactions (specifically HOCH2CH2O* -> HOCH2CHO* + H*) are kinetically important reactions, rather than C-C bond breaking. We show that steady state reactor conditions open up new reaction pathways not seen in surface science (temperature programmed desorption) experiments. The second model, parametrized based on semiempirical linear scaling and linear free energy relationships, consists of 250 reversible, elementary-like reactions and maps the dependence of ethylene glycol decomposition rate and selectivity to various products versus atomic binding energy descriptors. The results show that an optimal catalyst that maximizes the H-2 production rate should have binding energies of 58, 116, and 145 kcal/mol for atomic hydrogen, oxygen, and carbon, respectively. These models can be used to guide future experimental efforts in developing catalysts for polyol reforming.Kinetic Modeling of Pt Catalyzed and Computation-Driven Catalyst Discovery for Ethylene Glycol Decompositionethylene glycol; dehydrogenation; decomposition; Pt; Ni/Pt; rational catalyst design; microkinetic model; linear scaling relationships; Bronsted-Evans-Polanyi relationships; catalysis66201171#N/ATRUE
3372
cs200328z10.1021/cs200328zFALSEhttps://doi.org/10.1021/cs200328zStamenkovic, VRACS Catal.Alloying has shown enormous potential for tailoring the atomic and electronic structures, and improving the performance of catalytic materials. Systematic studies of alloy catalysts are, however, often compromised by inhomogeneous distribution of alloying components. Here we introduce a general approach for the synthesis of monodispersed and highly homogeneous Pt-bimetallic alloy nanocatalysts. Pt3M (where M = Fe, Ni, or Co) nanopartiCles were prepared by an organic solvothermal method and then supported on high surface area carbon. These catalysts attained a homogeneous distribution of elements, as demonstrated by atomic-scale elemental analysis using scanning transmission electron microscopy. They also exhibited high catalytic activities for the oxygen reduction reaction (ORR), with improvement factors of 2-3 versus conventional Pt/carbon catalysts. The measured ORR catalytic activities for Pt3M nanocatalysts validated the volcano curve established on extended surfaces, with Pt3Co being the most active alloy.Synthesis of Homogeneous Pt-Bimetallic NanopartiCles as Highly Efficient Electrocatalystshomogeneous alloy nanopartiCles; Pt-bimetallic catalysts; oxygen reduction reaction; fuel cells; scanning electron microscopy99201137#N/ATRUE
3373
cs200254810.1021/cs2002548FALSEhttps://doi.org/10.1021/cs2002548Shan, HHACS Catal.Desulfurization of thiophene and its hydrogenated derivatives on Pt(111) are studied using self-consistent periodic density functional theory (DFT), and the hydrodesulfurization network is mapped out. On Pt(111), thiophene has two types of adsorption configurations (parallel cross-bridge and partially tilted bridge-hollow), and for its hydrogenated derivates, the molecule is gradually lifted up from the surface with the addition of hydrogen atoms. In all the adsorbed thiophenic compounds, the S atom is always sp(3) hybridized; the C atom in the methylene group is always sp(3) hybridized, whereas it is either sp(2) or sp(3) hybridized in the methyne group depending on how the group interacts with the surface Pt atoms. On the basis of the thermodynamic and kinetic analysis of the elementary steps, a direct desulfurization pathway is proposed for the hydrodesulfurization of thiophene on Pt(111). In contrast to the common thought that hydrogenation toward aromatic organosulfur compounds would make desulfurization easier, the present work Clearly demonstrates that hydrogenations of thiophene on Pt(111) do not reduce the energy barrier for the C-S bond Cleavage.Density Functional Theory Study of the Adsorption and Desulfurization of Thiophene and Its Hydrogenated Derivatives on Pt(111): Implication for the Mechanism of Hydrodesulfurization over Noble Metal Catalystsdesulfurization; thiophene; hydrodesulfurization on Pt(111); organosulfur compounds; C-S bond; hydrogenation43201162#N/ATRUE
3374
cs200093910.1021/cs2000939FALSEhttps://doi.org/10.1021/cs2000939Bullock, RMACS Catal.[(NiP2N22BN)-N-Ph)(2) (CH3CN)](2+) (where (P2N2BN)-N-Ph is 1,5-dilienzy1-3,7-diphenyl-1,5-diaza-3,7-diphosphacydooctane), has been studied as an electrocatalyst for the production of hydrogen in acetonitrile. Strong acids, such as p-cyanoanilinium, protonate [Ni((P2N22BN)-N-Ph)(2)(CH3CN)](2+) prior to reduction under catalytic conditions, and an effective plc of 6.7 +/- 0.4 was determined for the protonation product. Through multinuClear NMR spectroscopy studies, the nickel(II) complex was found to be doubly protonated without any observed singly protonated species. In the doubly protonated complex, both protons are positioned exo with respect to the metal center and are stabilized by an N-H-N hydrogen bond. The formation of exo protonated isomers is proposed to hunt the rate of hydrogen production because the protons are unable to gain suitable proximity to the reduced metal center to generate H-2: Preprotonation of [Ni((P2N2BN2)-N-Ph)(2)(CH3CN)](2+) has been found to shift the catalytic operating potential to more positive potentials by up to 440 mV, depending upon the conditions. The half-wave potential for the catalytic production of H2 depends linearly on the pH of the solution and indicates a proton-coupled electron transfer reaction. The overpotential remains low and nearly constant at 74 +/- 44 mV over the pH range of 6.2-11.9. The catalytic rate was found to increase by an order of magnitude by increasing the, solution pH or through the addition of water.[Ni((P2N22BN)-N-Ph)(2)(CH3CN)](2+) as an Electrocatalyst for H-2 Production: Dependence on Add Strength and Isomer Distributionelectrocatalysis; catalyst; hydrogen production; pendant amine; PCET; potential90201132#N/ATRUE
3375
cs200022s10.1021/cs200022sFALSEhttps://doi.org/10.1021/cs200022sZhong, CJACS Catal.This paper describes the results of an investigation of the synthesis of PtIrCo nanopartiCles (2-3 nm) for electrocatalytic oxygen reduction reaction. The carbon supported PtIrCo catalysts (PtIrCo/C) were thermally treated at temperatures ranging from 400 to 900 degrees C. The size, composition, and atomic-scale structures of the PtIrCo/C catalysts were characterized for establishing their correlation with the electrocatalytic activity toward. oxygen reduction reaction. The specific activity was found to increase by a factor of 3-5 for the PtIrCo/C catalysts in comparison with Pt/C catalysts. A correlation was identified between the specific activity and the nanopartiCle's fcc-type lattice parameter. The specific activity increases whereas the fcc-type lattice parameter decreases with the thermal treatment temperature. This correlation was further substantiated by analyzing the interatomic spatial parameters in the trimetallic nanopartiCles based on X-ray absorption fine structure spectroscopic and high-energy XRD experiments. Implications of these findings, along with the durability of the catalysts, to the design of active electrocatalysts were also discussed.Structural and Electrocatalytic Properties of PtIrCo/C Catalysts for Oxygen Reduction Reaction48201150#N/ATRUE
3376
chem.20200121810.1002/chem.202001218FALSEhttps://doi.org/10.1021/ja00010a044Schurko, RWOctaboraneyl Complexes of Nickel: Monomers for Redox-Active Coordination Polymersx2020#N/AFALSE
3377
chem.20200086710.1002/chem.202000867FALSEhttps://doi.org/10.1002/chem.202000867Stride, JAMagnetic Phase Transitions in a Ni4O4-Cubane-Based Metal-Organic Frameworkx2020#N/AFALSE
3378
cs200014j10.1021/cs200014jFALSEhttps://doi.org/10.1021/cs200014jWang, YACS Catal.The catalytic roles of Co-0 and Co2+ during steam reforming of ethanol Were investigated over Co/MgO catalysts. Catalysts with different Co-0/(Co-0 + Co2+) fraction were prepared through calcination and/or reduction at different temperatures, and the Co-0 fraction was quantified by temperature programmed reduction (TPR) and in situ X-ray photoelectron spectroscopy (XPS). Higher temperature calcination of Co/MgO allowed us to prepare catalysts with more nonreducible Co2+ incorporated in the MgO lattice, while lower calcination tempratures allowed for the preparation of catalysts with higher Co-0/(Co-0 + Co2+) fractions. The catalytic tests on Co-0, nonreducible Co2+, and reducible Co2+ indicated that Co-0 is much more active than either reducible or nonreducible Co2+ for C-C Cleavage and water gas shift reaction. In addition, catalysts with a higher Co-0 surface fraction exhibited a lower selectivity to CH4.Catalytic Roles of Co-0 and Co2+ during Steam Reforming of Ethanol on Co/MgO Catalysts74201142#N/ATRUE
3379
cs100151510.1021/cs1001515FALSEhttps://doi.org/10.1021/ja00008a003Sievers, CStructural Changes of gamma-Al2O3-Supported Catalysts in Hot Liquid Water2011#N/ATRUE
3380
cs100141p10.1021/cs100141pFALSEhttps://doi.org/10.1039/d0sc07099hJose-Yacaman, MDirect Imaging and Identification of Individual Dopant Atoms in MoS2 and WS2 Catalysts by Aberration Corrected Scanning Transmission Electron Microscopy2011#N/ATRUE
3381
cs100116m10.1021/cs100116mFALSEhttps://doi.org/10.1021/cs100116mCaballero, AACS Catal.The effect of a reduction process with CO or H-2 on the Size of nickel partiCles in Ni/ZrO2 dry methane reforming catalysts have been studied by means of in situ X-ray Spectroscopy (XAS) and Diffuse Reflectance FTIR Spectroscopy (DRIFTS). Our results Clearly indicate that a high temperature treatment with CO increases the dispersion of the nickel metallic phase. XAS results have shown a lower coordination number of Ni in the sample treated with CO than that reduced with H-2. From the DRIFTS results, it can he established that, under the CO treatment, the formation of Ni(CO)(4) complexes corrodes the nickel partiCles, decreasing their size. The formation of these gas molecules occurs without measurable losses of nickel from the catalyst which maintains the same nickel content after the hydrogen or the CO treatment at high temperature:Therefore, this airborne nickel compound, by colliding with the zirconia surface, must deposit the nickel metal metal atoms around onto the support. This behavior is evidence of an important interaction b etween nickel and zirconia surface as unlike other supports there is no losses of nickel during the dispersion process on zirconia. Although different effects of CO on nickel catalysts have been previously described, we have found for the first time several experimental evidences demonstrating the whole redispersion phenomenon.Modifying the Size of Nickel Metallic PartiCles by H-2/CO Treatment in Ni/ZrO2 Methane Dry Reforming Catalystsnickel catalysts; XAS; FTIR; DRIFTS; dispersion; dry methane reforming; reduction with CO105201137#N/ATRUE
3382
chem.20210082110.1002/chem.202100821FALSEhttps://doi.org/10.1002/chem.202100821Navarro, JARImpact of Pore Size and Defects on the Selective Adsorption of Acetylene in Alkyne-Functionalized Nickel(II)-Pyrazolate-Based MOFs2021#N/ATRUE
3383
chem.20190362510.1002/chem.201903625FALSEhttps://doi.org/10.1002/chem.201903625Iwasawa, NDevelopment of N-Phosphinomethyl-Substituted NHC-Nickel(0) Complexes as Robust Catalysts for Acrylate Salt Synthesis from Ethylene and CO2xy2019#N/AFALSE
3384
chem.20200394910.1002/chem.202003949FALSEhttps://doi.org/10.1002/chem.202003949Hureau, CImpact of N-Truncated A beta Peptides on Cu- and Cu(A beta)-Generated ROS: Cu-I Matters!2021#N/ATRUE
3385
chem.20200240310.1002/chem.202002403FALSEhttps://doi.org/10.1002/chem.202002403Nyman, MBuilding [U-70(IV)(OH)(36)(O)(64)](4-)OxoCluster Frameworks with Sulfate, Transition Metals, and U-V2020#N/ATRUE
3386
chem.20200215710.1002/chem.202002157FALSEhttps://doi.org/10.1002/chem.202002157Osuka, APropeller-Shaped Semi-fused Porphyrin Trimers: Molecular-Symmetry-Dependent Chiroptical Response2020#N/ATRUE
3387
chem.20200207210.1002/chem.202002072FALSELi, CMRu-Doping Enhanced Electrocatalysis of Metal-Organic Framework Nanosheets toward Overall Water Splitting2020#N/ATRUE
3388
chem.20190227410.1002/chem.201902274FALSEhttps://doi.org/10.1002/chem.201902274Biradha, KIsostructural Ni-II Metal-Organic Frameworks (MOFs) for Efficient Electrocatalysis of Oxygen Evolution Reaction and for Gas Sorption Propertiesx2019#N/AFALSE
3389
chem.20190209510.1002/chem.201902095https://doi.org/10.1002/chem.201902095Martin, RSite-Selective, Remote sp(3) C-H Carbonylation Enabled by the Merger of Photoredox and Nickel CatalysisPhotocatalyst2019#N/AFALSE
3390
chem.20190109510.1002/chem.201901095FALSEhttps://doi.org/10.1002/chem.201901095Maeda, HPeripheral Modifications of meso-Hydroxyporphyrins: Formation of pi-Electronic Anions and Ion-Pairing Assembliesx2019#N/AFALSE
3391
chem.20200194410.1002/chem.202001944FALSEhttps://doi.org/10.1002/chem.202001944Jobbgy, MUnveiling the Occurrence of Co(III) in NiCo Layered Electroactive Hydroxides: The Role of Distorted Environments2020#N/ATRUE
3392
chem.20200128910.1002/chem.202001289FALSEhttps://doi.org/10.1002/chem.202001289Apfel, UPEnhancing the CO(2)Electroreduction of Fe/Ni-Pentlandite Catalysts by S/Se Exchange2020#N/ATRUE
3393
chem.20190462010.1002/chem.201904620FALSEhttps://doi.org/10.1002/chem.201904620Ahn, HSStoichiometry-Controlled Synthesis of Nanoparticulate Mixed-Metal Oxyhydroxide Oxygen Evolving Catalysts by Electrochemistry in Aqueous Nanodroplets2020#N/ATRUE
3394
chem.20180452410.1002/chem.201804524FALSEhttps://doi.org/10.1002/chem.201804524Ghadwal, RSDiradical Character Enhancement by Spacing: N-HeterocyClic Carbene Analogues of Muller's Hydrocarbonx2018#N/AFALSE
3395
chem.20190458310.1002/chem.201904583FALSEhttps://doi.org/10.1002/chem.201904583Revaprasadu, NFlexible Molecular Precursors for Selective Decomposition to Nickel Sulfide or Nickel Phosphide for Water Splitting and Supercapacitance2020#N/ATRUE
3396
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3397
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3399
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3403
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3413
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3425
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chem.20030570510.1002/chem.200305705FALSEhttps://doi.org/10.1021/cs501354bKersting, BRealization of unusual ligand binding motifs in metalated container molecules: Synthesis, structures, and magnetic properties of the complexes [(L-Me)Ni-2(mu-L ')(n+) with L ' = NO3-, NO2-, N-3(-), N2H4, pyridazine, phthalazine, pyrazolate, and benzoatex2004#N/AFALSE
3498
chem.20070147810.1002/chem.200701478FALSEhttps://doi.org/10.1002/chem.200701478Huskens, JAnchoring of histidine-tagged proteins to molecular printboards: Self-assembly, thermodynamic modeling, and patterning2008#N/ATRUE
3499
chem.20070084810.1002/chem.200700848FALSEhttps://doi.org/10.1002/chem.200700848Hannon, MJSupramolecular circular helicates formed by destabilisation of supramolecular dimers2007#N/ATRUE
3500
chem.20060135710.1002/chem.200601357FALSEhttps://doi.org/10.1021/cs400705pMonge, AConjugate additions of cyClic oxygen-bound nickel enolates to alpha,beta-unsaturated ketones2007#N/ATRUE
3501
cc996000212110.1039/cc9960002121FALSEhttps://doi.org/10.1021/cs400705pKushi, YFormation of a nickel(II) complex with a new N2S2 macrocyClic ligand by C-Cl bond Cleavage and C-S bond formationx1996#N/AFALSE
3502
chem.20060119410.1002/chem.200601194FALSEGatteschi, DEffects of 3d-4f magnetic exchange interactions on the dynamics of the magnetization of Dy-III-M-II-Dy-III trinuClear Clusters2007#N/ATRUE
3503
cc996000005910.1039/cc9960000059FALSEYao, XKNovel structure of a macrocyClic dioxotetraamine copper(II) complexx1996#N/AFALSE
3504
chem.20060031910.1002/chem.200600319FALSEMota, AEthylene oligomerisation and polymerisation with nickel phosphanylenolates bearing electron-withdrawing substituents: Structure-reactivity relationships2006#N/ATRUE
3505
chem.20050068610.1002/chem.200500686FALSEKniep, RBa-2[Ni3N2]: A low-valent nitridonickelate - Synthesis, crystal structure, and physical properties2006#N/ATRUE
3506
chem.20050038710.1002/chem.200500387FALSEhttps://doi.org/10.1002/chem.200500387Brooker, SSynthesis and some first-row transition-metal complexes of the 1,2,4-triazole-based bis(terdentate) ligands TsPMAT and PMAT2005#N/ATRUE
3507
c9sc05636j10.1039/c9sc05636jFALSEhttps://doi.org/10.1039/c9sc05636jYamauchi, YGeneral synthesis of hierarchical sheet/plate-like M-BDC (M = Cu, Mn, Ni, and Zr) metal-organic frameworks for electrochemical non-enzymatic glucose sensingx2020#N/AFALSE
3508
chem.20050028310.1002/chem.200500283FALSEhttps://doi.org/10.1002/chem.200500283Braunstein, PTunable charge delocalization in dinickel quinonoid complexes2005#N/ATRUE
3509
c9sc05246a10.1039/c9sc05246aFALSEhttps://doi.org/10.1039/c9sc05246aLam, HWChem. Sci.The enantioselective nickel-catalyzed reaction of tethered allene-ketones with (hetero)Arylboronic acids or potassium VinyltrifluorB(OH)2rate is described. Carbonickelation of the allene gives allylnickel species, which undergo cyClization by 1,2-allylation to produce chiral tertiary-alcohol-containing aza- and carbocyCles in high diastereo- and enantioselectivities.Enantioselective nickel-catalyzed Arylative and alkenylative intramolecular 1,2-allylations of tethered allene-ketonesx4202064#N/AFALSE
3510
chem.20050009710.1002/chem.200500097FALSEhttps://doi.org/10.1002/chem.200500097Coropceanu, VHomo-/heterotrinuClear mixed-valent oxo-centered iron/nickel Clusters - Mossbauer studies on internal electron-exchange processes2005#N/ATRUE
3511
chem.20040092810.1002/chem.200400928FALSEhttps://doi.org/10.1002/chem.200400928Furstner, ADiaminocarbene- and Fischer-carbene complexes of palladium and nickel by oxidative insertion: Preparation, structure, and catalytic activity2005#N/ATRUE
3512
c9sc04879k10.1039/c9sc04879kFALSEhttps://doi.org/10.1039/c9sc04879kBetley, TAChem. Sci.Metalation of the deprotonated dipyrrin (L-AdF)Li with NiCl2(py)(2) afforded the divalent Ni product (L-AdF)NiCl(py)(2) (1) (L-AdF: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine). To generate a reactive synthon on which to explore oxidative group transfer, we used potassium graphite to reduce 1, affording the monovalent Ni synthon (L-AdF)Ni(py) (2) and concomitant production of a stoichiometric equivalent of KCl and pyridine. Slow addition of mesityl- or 1-adamantylazide in benzene to 2 afforded the oxidized Ni complexes (L-AdF)Ni(NMes) (3) and (L-AdF)Ni(NAd) (4), respectively. Both 3 and 4 were characterized by multinuClear NMR, EPR, magnetometry, single-crystal X-ray crystallography, theoretical calculations, and X-ray absorption spectroscopies to provide a detailed electronic structure picture of the nitrenoid adducts. X-ray absorption near edge spectroscopy (XANES) on the Ni reveals higher energy Ni 1s -> 3d transitions (3: 8333.2 eV; 4: 8333.4 eV) than Ni-I or unambiguous Ni-II analogues. N K-edge X-ray absorption spectroscopy performed on 3 and 4 reveals a common low-energy absorption present only for 3 and 4 (395.4 eV) that was assigned via TDDFT as an N 1s promotion into a predominantly N-localized, singly occupied orbital, akin to metal-supported iminyl complexes reported for iron. On the continuum of imido (i.e., NR2-) to iminyl (i.e., (NR-)-N-2) formulations, the complexes are best described as Ni-II-bound iminyl species given the N K-edge and TDDFT results. Given the open-shell configuration (S = 1/2) of the iminyl adducts, we then examined their propensity to undergo nitrenoid-group transfer to organic substrates. The adamantyl complex 4 readily consumes 1,4-cyClohexadiene (CHD) via H-atom abstraction to afford the amide (L-AdF)Ni(NHAd) (5), whereas no reaction was observed upon treatment of the mesityl variant 3 with excess amount of CHD over 3 hours. toluene can be functionalized by 4 at room temperature, exClusively affording the N-1-adamantyl-Benzylidene (6). Slow addition of the organoazide substrate (4-azidobutyl)benzene (7) with 2 exClusively forms 4-phenylbutanenitrile (8) as opposed to an intramolecular cyClized pyrrolidine, resulting from facile beta-H elimination outcompeting H-atom abstraction from the Benzylic position, followed by rapid H-2-elimination from the intermediate Ni hydride ketimide intermediate.Synthesis, characterization and C-H amination reactivity of nickel iminyl complexesx13202059#N/AFALSE
3513
chem.20040054510.1002/chem.200400545FALSEhttps://doi.org/10.1002/chem.200400545Oshima, KCobalt-catalyzed cross-coupling reactions of Alkyl halides with allylic and Benzylic grignard reagents and their application to tandem radical cyClization/cross-coupling reactions2004#N/ATRUE
3514
c9sc04381k10.1039/c9sc04381kFALSEhttps://doi.org/10.1039/c9sc04381kAnderson, JSChem. Sci.Here we report that capping the molecule TTFtt (TTFtt = tetrathiafulvalene-2,3,6,7-tetrathiolate) with diAlkyl tin groups enables the isolation of a stable series of redox congeners and facile transmetalation to Ni and Pd. TTFtt has been proposed as an attractive building block for molecular materials for two decades as it combines the redox chemistry of TTF and dithiolene units. TTFttH(4), however, is inherently unstable and the incorporation of TTFtt units into complexes or materials typically proceeds through the in situ generation of the tetraanion TTFtt(4-). Capping of TTFtt(4-) with Bu2Sn2+ units dramatically improves the stability of the TTFtt moiety and furthermore enables the isolation of a redox series where the TTF core carries the formal charges of 0, +1, and +2. All of these redox congeners show efficient and Clean transmetalation to Ni and Pd resulting in an analogous series of bimetallic complexes capped by 1,2-bis(diphenylphosphino)ethane (dppe) ligands. Furthermore, by using the same transmetalation method, we synthesized analogous palladium complexes capped by 1,1 '-bis(diphenylphosphino)ferrocene (dppf) which had been previously reported. All of these species have been thoroughly characterized through a systematic survey of chemical and electronic properties by techniques inCluding cyClic voltammetry (CV), ultraviolet-visible-near infrared spectroscopy (UV-vis-NIR), electron paramagnetic resonance spectroscopy (EPR), nuClear magnetic resonance spectroscopy (NMR) and X-ray diffraction (XRD). These detailed synthetic and spectroscopic studies highlight important differences between the transmetalation strategy presented here and previously reported synthetic methods for the installation of TTFtt. In addition, the utility of this stabilization strategy can be illustrated by the observation of unusual TTF radical-radical packing in the solid state and dimerization in the solution state. Theoretical calculations based on variational 2-electron reduced density matrix methods have been used to investigate these unusual interactions and illustrate fundamentally different levels of covalency and overlap depending on the orientations of the TTF cores. Taken together, this work demonstrates that tin-capped TTFtt units are ideal reagents for the installation of redox-tunable TTFtt ligands enabling the generation of entirely new geometric and electronic structures.Redox, transmetalation, and stacking properties of tetrathiafulvalene-2,3,6,7-tetrathiolate bridged tin, nickel, and palladium compoundsx102020132#N/AFALSE
3515
c9sc04371c10.1039/c9sc04371cFALSEhttps://doi.org/10.1021/cs5000944Teranishi, TPhase segregated Cu2-xSe/Ni3Se4 bimetallic selenide nanocrystals formed through the cation exchange reaction for active water oxidation precatalystsx2020#N/AFALSE
3516
c9sc04308j10.1039/c9sc04308jhttps://doi.org/10.1039/c9sc04308jChatani, NChem. Sci.Rhodium(ii)-catalyzed unusual branch-selective ortho-C-H Alkylation of Aryl sulfonamides with Vinylsilanes was achieved using an 8-aminoquinoline directing group. Notably, the para-substituted Aryl sulfonamides gave mono-(branched)Alkylated products exClusively without the formation of any double C-H Alkylated byproducts. The results of deuterium labeling experiments suggest that both hydrometalation and carbometalation pathways are involved in this conversion.Rh(ii)-catalyzed branch-selective C-H Alkylation of Aryl sulfonamides with Vinylsilanesx7202074#N/AFALSE
3517
chem.1997003020910.1002/chem.19970030209FALSEhttps://doi.org/10.1002/chem.19970030209Mullen, KTerrylenimides: New NIR fluorescent dyes1997#N/ATRUE
3518
c9sc03816g10.1039/c9sc03816gFALSEhttps://doi.org/10.1039/c9sc03816gSu, GChem. Sci.Inspired by the successful synthesis of Fe/Cu-5,5 '-bis(4-pyridyl)(2,2 '-bipirimidine) (PBP), a family of two-dimensional (2D) metal-organic frameworks (MOFs) with the Shastry-Sutherland lattice, i.e., transition metal (TM)-PBP (TM = Cr, Mn, Fe, Co, Ni, Cu, Zn) has been systematically investigated by means of first-principles density functional theory calculations and Monte Carlo simulations. Mn-PBP is discovered to be the first ferromagnetic 2D MOF with the Shastry-Sutherland lattice and the Curie temperature is predicted to be about 105 K, while Fe-PBP, TM-PBP (TM = Cr, Co, Ni) and TM-PBP (TM = Cu, Zn) are found to be stripe-order antiferromagnetic, magnetic-dimerized and nonmagnetic, respectively. The electronic structure calculations reveal that TM-PBP MOFs are semiconductors with band gaps ranging from 0.12 eV to 0.85 eV, which could be easily modulated by various methods. Particularly, Mn-PBP would exhibit half-metallic behavior under compressive strain or appropriate electron/hole doping and a Mn-PBP based spintronic device has been proposed. This study not only improves the understanding of the geometric, electronic and magnetic properties of the 2D TM-PBP MOF family, but also provides a novel spin lattice playground for the research of 2D magnetic systems, which has diverse modulating possibilities and rich potential applications.Two-dimensional magnetic metal-organic frameworks with the Shastry-Sutherland latticex7201953#N/AFALSE
3519
c9sc03758f10.1039/c9sc03758fFALSEhttps://doi.org/10.1039/c9sc03758fMirica, LMChem. Sci.Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. While Ni(0), Ni(i), and Ni(ii) intermediates are most relevant in these transformations, recently Ni(iii) and Ni(iv) species have also been proposed to play a role in catalysis. Reported herein is the synthesis, detailed characterization, and reactivity of a series of Ni(ii) and Ni(iii) metallacyCle complexes stabilized by tetradentate pyridinophane ligands with various N-substituents. Interestingly, while the oxidation of the Ni(ii) complexes with various other oxidants led to exClusive C-C bond formation in very good yields, the use of O-2 or H2O2 as oxidants led to formation of appreciable amounts of C-O bond formation products, especially for the Ni(ii) complex supported by an asymmetric pyridinophane ligand containing one tosyl N-substituent. Moreover, cryo-ESI-MS studies support the formation of several high-valent Ni species as key intermediates in this uncommon Ni-mediated oxygenase-type chemistry.Aerobic C-C and C-O bond formation reactions mediated by high-valent nickel speciesx5201960#N/AFALSE
3520
chem.1996002011410.1002/chem.19960020114FALSEhttps://doi.org/10.1002/chem.19960020114Sacchi, DFluorescent sensors for transition metals based on electron-transfer and energy-transfer mechanisms1996#N/ATRUE
3521
c9sc02905b10.1039/c9sc02905bFALSEhttps://doi.org/10.1039/c9sc02905bChen, MChem. Sci.Cu-catalyzed stereoselective synthesis of (E)-delta-silyl-anti-homoallylic alcohols from 1,3-dienylsilane was developed. Mechanistic studies revealed that the borocupration of dienylsilane proceeded through a 1,2-addition pathway to give an allylcopper intermediate with Cu distal to the silyl group. However, the subsequent aldehyde allylation proceeded via Curtin-Hammett control to give (E)-delta-silyl-anti-homoallylic alcohols with high diastereoselectivities. This method was applied to the synthesis of the C1-9 fragment of a polyketide natural product, mycinolide IV.alpha-Silicon effect assisted Curtin-Hammett allylation using allylcopper reagents derived from 1,3-dienylsilanesx182019117#N/AFALSE
3522
c9sc02870f10.1039/c9sc02870fFALSEhttps://doi.org/10.1039/c9sc02870fYang, JYChem. Sci.Local electric fields contribute to the high selectivity and catalytic activity in enzyme active sites and confined reaction centers in zeolites by modifying the relative energy of transition states, intermediates and/or products. Proximal charged functionalities can generate equivalent internal electric fields in molecular systems but the magnitude of their effect and impact on electronic structure has been minimally explored. To generate quantitative insight into installing internal fields in synthetic systems, we report an experimental and computational study using transition metal (M-1) Schiff base complexes functionalized with a crown ether unit containing a mono- or dicationic alkali or alkaline earth metal ion (M-2). The synthesis and characterization of the complexes M-1 = Ni(ii) and M-2 = Na+ or Ba2+ are reported. The electronic absorption spectra and density functional theory (DFT) calculations establish that the cations generate a robust electric field at the metal, which stabilizes the Ni-based molecular orbitals without significantly changing their relative energies. The stabilization is also reflected in the experimental Ni(ii/i) reduction potentials, which are shifted 0.12 V and 0.34 V positive for M-2 = Na+ and Ba2+, respectively, compared to a complex lacking a proximal cation. To compare with the cationic Ni complexes, we also synthesized a series of Ni(salen) complexes modified in the 5 ' position with electron-donating and -withdrawing functionalities (-CF3, -Cl, -H, -tBu, and -OCH3). Data from this series of compounds provides further evidence that the reduction potential shifts observed in the cationic complexes are not due to inductive ligand effects. DFT studies were also performed on the previously reported monocationic and dicatonic Fe(ii)(CH3CN) and Fe(iii)Cl analogues of this system to analyze the impact of an anionic chloride on the electrostatic potential and electronic structure of the Fe site.Installation of internal electric fields by non-redox active cations in transition metal complexesx16201948#N/AFALSE
3523
cc996000273110.1039/cc9960002731FALSEhttps://doi.org/10.1021/cs300707yGorecka, ENon-discoidal copper(II) and nickel(II) binuClear complexes forming columnar mesophases1996#N/ATRUE
3524
cc996000045710.1039/cc9960000457FALSEhttps://doi.org/10.1039/cc9960000457Schroder, MSchiff-base compartmental macrocyClic complexes1996#N/ATRUE
3525
c9sc06197e10.1039/c9sc06197eFALSEhttps://doi.org/10.1039/c9sc06197eXie, YSChem. Sci.Oxidative ring Closure of linear oligopyrroles is one of the synthetic approaches to novel porphyrinoids with dinuClear coordination sites and helical chirality. The spatial arrangement of the pyrrolic groups of octapyrrole (P8) affected the position of the intramolecular oxidative coupling of the pyrrolic units; tripyrrin-armed isosmaragdyrin analogue (1) containing a beta,beta-linked bipyrrole moiety was synthesized regioselectively in a high yield by using FeCl3. Ni-II-coordination at the armed tripyrrin site of 1 allowed the formation of diastereomeric helical twisted complexes (2A and 2B) and succeeding Cu-II-coordination at the macrocyClic core afforded heterodinuClear Ni-II/Cu-II-complexes (3A and 3B). Each of them comprised a pair of separable enantiomers, exhibiting P- and M-helices, respectively. Notably, diastereomeric interconversion from 2A to 2B was quantitatively achieved as a consequence of helical transformation under acidic conditions.Tripyrrin-armed isosmaragdyrins: synthesis, heterodinuClear coordination, and protonation-triggered helical inversion4202049#N/ATRUE
3526
c9sc02624j10.1039/c9sc02624jFALSEhttps://doi.org/10.1039/c9sc02624jManners, IChem. Sci.Ring-opening polymerisation (ROP) of strained [1]- and [2]metallocenophanes and related species is well-established, and the monomer ring-strain is manifest in a substantial tilting of the cyClopentadienyl ligands, giving alpha angles of similar to 14-32 degrees. Surprisingly, tetracarba[4]nickelocenophane [Ni(eta(5)-C5H4)(2)(CH2)(4)] (2) undergoes ROP (pyridine, 20 degrees C, 5 days) to give primarily insoluble poly(nickelocenylbutylene) [Ni(eta(5)-C5H4)(2)(CH2)(4)](n) (12), despite the lack of significant ring-tilt. The exoenthalpic nature of the ROP was confirmed by DFT calculations involving the cyClic precursor and model oligomers (Delta H0ROP = -14 +/- 2 kJ mol(-1)), and is proposed to be a consequence of torsional strain present in the ansa bridge of 2. The similarly untilted disila-2-oxa[3]nickelocenophanes [Ni(eta(5)-C5H4)(2)(SiMe2)(2)O] (13) and [Ni(eta(5)-C5H4)(2)(SiMePh)(2)O] (14) were found to lack similar torsional strain and to be resistant to ROP under the same conditions. In contrast, 1-methyltricarba[3]nickelocenophane {Ni(eta(5)-C5H4)(2)(CH2)(2)[CH(CH3)]} (15) with a significant tilt angle (alpha similar to 16 degrees) was found to undergo ROP to give soluble polymer {Ni(eta(5)-C5H4)(2)(CH2)(2)[CH(CH3)]}(n) (18). The reversibility of the process in this case allowed for the effects of temperature and reaction concentration on the monomer-polymer equilibrium to be explored and thereby thermodynamic data to be elucidated (Delta H0ROP = -8.9 kJ mol(-1), Delta G0ROP = -3.1 kJ mol(-1)). Compared to the previously described ROP of the unsubstituted analogue [Ni(eta(5)-C5H4)(2)(CH2)(3)] (1) (Delta H0ROP = -10 kJ mol(-1), Delta G0ROP = -4.0 kJ mol(-1)), the presence of the additional methyl substituent in the ansa bridge appears to marginally disfavour ROP and leads to a corresponding decrease in the equilibrium polymer yield.Role of torsional strain in the ring-opening polymerisation of low strain [n]nickelocenophanesx1201965#N/AFALSE
3527
c9sc02457c10.1039/c9sc02457cFALSEhttps://doi.org/10.1039/c9sc02457cTetlow, DJChem. Sci.The synthesis of unsymmetrical axle [2]rotaxanes through a recently developed Ni-catalyzed C(sp(3))-C(sp(3)) cross-coupling of redox-active esters (formed directly from Carbonylic acids) and organozinc reagents (derived from Alkyl bromides) is reported. The method also furnishes, as a minor product, the symmetrical axle [2]rotaxanes resulting from the homo-coupling of the organozinc half-thread. The rotaxanes are formed in up to 56% yield with the ratio of unsymmetrical rotaxane increasing with the cavity size of the macrocyCle. In the absence of the redox-active ester neither rotaxane is formed, even though the homo-coupling rotaxane product does not incorporate the redox-active ester building block. A Ni(iii) intermediate is consistent with these observations, providing support for the previously postulated mechanism of the Ni-catalyzed cross-coupling reaction.Active template rotaxane synthesis through the Ni-catalyzed cross-coupling of Alkylzinc reagents with redox-active estersx7201963#N/AFALSE
3528
c9sc02018g10.1039/c9sc02018gFALSEhttps://doi.org/10.1039/c9sc02018gLu, CCChem. Sci.Understanding H-2 binding and Activation is important in the context of designing transition metal catalysts for many processes, inCluding hydrogenation and the interconversion of H-2 with protons and electrons. This work reports the first thermodynamic and kinetic H-2 binding studies for an isostructural series of first-row metal complexes: NiML, where M = Al (1), Ga (2), and In (3), and L = [N(o-((NCH2PPr2)-Pr-i)C6H4)(3)](3-). Thermodynamic free energies (Delta G degrees) and free energies of Activation (Delta G(double dagger)) for binding equilibria were obtained via variable-temperature P-31 NMR studies and lineshape analysis. The supporting metal exerts a large influence on the thermodynamic favorability of both H-2 and N-2 binding to Ni, with Delta G degrees values for H-2 binding found to span nearly the entire range of previous reports. The non-Classical H-2 adduct, (eta(2)-H-2)NiInL (3-H-2), was structurally characterized by single-crystal neutron diffraction-the first such study for a Ni(eta(2)-H-2) complex or any d(10) M(eta(2)-H-2) complex. UV-Vis studies and TD-DFT calculations identified specific electronic structure perturbations of the supporting metal which poise NiML complexes for small-molecule binding. ETS-NOCV calculations indicate that H-2 binding primarily occurs via H-H sigma-donation to the Ni 4p(z)-based LUMO, which is proposed to become energetically accessible as the Ni(0)-> M(iii) dative interaction increases for the larger M(iii) ions. Linear free-energy relationships are discussed, with the Activation barrier for H-2 binding (Delta G(double dagger)) found to decrease proportionally for more thermodynamically favorable equilibria. The Delta G degrees values for H-2 and N-2 binding to NiML complexes were also found to be more exergonic for the larger M(iii) ions.Thermodynamic and kinetic studies of H-2 and N-2 binding to bimetallic nickel-group 13 complexes and neutron structure of a Ni(eta(2)-H-2) adductx14201991#N/AFALSE
3529
c9sc01902b10.1039/c9sc01902bFALSEhttps://doi.org/10.1039/c9sc01902bJiang, JXChem. Sci.The key challenges of aqueous Zn-based batteries (ZBBs) are their unsatisfactory energy density and poor lifespan, mainly arising from the low capacity and irreversibility of the cathode materials. Herein, a three-dimensional (3D) ordered mesoporous nanoarchitecture cobaltosic oxide (M-Co3O4) with rich oxygen vacancies (M-Co3O4-x) is reported as a new promising advanced cathode material for rechargeable ZBBs. The experimental results and DFT calculations reveal that the energy storage capacity is significantly enhanced by the synergistic effect of mesopores and oxygen vacancies. Benefiting from the merits of a substantially fast ion diffusion channel, high electrical conductivity, large active surface area, strong OH- adsorption capacity and stable structure, the fabricated M-Co3O4-x//Zn battery delivers a remarkable capacity of 384 mA h g(-1) at 1.0 A g(-1) which even rises up to 420 mA h g(-1) after cyCling Activation with an ultrahigh energy density of 722.4 W h kg(-1) (based on the weights of the cathode active material), which outperforms most of the previously reported aqueous ZBBs. More impressively, the M-Co3O4-x//Zn battery exhibits extraordinary cyCling stability, both at 1 A g(-1) and 10 A g(-1) without any decay of capacity after 6000 and 60 000 cyCles, respectively, and such high cyCling stability is reported for the first time in ZBBs. The ultrahigh energy and superlong lifespan of aqueous ZBBs could make it satisfy some practical energy demands.Structural and defect engineering of cobaltosic oxide nanoarchitectures as an ultrahigh energy density and super durable cathode for Zn-based batteriesx19201958#N/AFALSE
3530
c9sc01817d10.1039/c9sc01817dFALSEhttps://doi.org/10.1039/c9sc01817dKnochel, PChem. Sci.A cobalt-catalyzed acylation reaction of various primary, secondary and tertiary Alkyl, Benzyl and (hetero)Aryl S-pyridyl thioesters with (hetero)Arylzinc pivalates is reported. The thioesters were prepared directly from the corresponding Carbonylic acids under mild conditions, thus tolerating sensitive functional groups. Acylations of alpha-chiral S-pyridyl esters proceeded with very high stereoretention leading to optically enriched alpha-chiral ketones.Cobalt-catalyzed acylation-reactions of (hetero)Arylzinc pivalates with thiopyridyl ester derivativesx14201947#N/AFALSE
3531
c9sc06006e10.1039/c9sc06006eFALSEhttps://doi.org/10.1039/c9sc06006eEngle, KMChem. Sci.Nickel-catalyzed three-component alkene difunctionalization has rapidly emerged as a powerful tool for forging two C-C bonds in a single reaction. Building upon the powerful modes of bond construction in traditional two-component cross-coupling, various research groups have demonstrated the versatility of nickel in enabling catalytic 1,2-dicarbofunctionalization using a wide range of carbon-based electrophiles and nuCleophiles and in a fully intermolecular fashion. Though this area has emerged only recently, the last few years have witnessed a proliferation of publications on this topic, underscoring the potential of this strategy to develop into a general platform that offers high regio- and stereoselectivity. This minireview highlights the recent progress in the area of intermolecular 1,2-dicarbofunctionalization of alkenes via nickel catalysis and discusses lingering challenges within this reactivity paradigm.Recent developments in nickel-catalyzed intermolecular dicarbofunctionalization of alkenes53202057#N/ATRUE
3532
c9sc05669f10.1039/c9sc05669fFALSEhttps://doi.org/10.1039/c9sc05669fLopez, NChem. Sci.The oxygen evolution reaction (OER) is the major bottleneck to develop viable and cost-effective water electrolysis, a key process in the production of renewable fuels. Hematite, all iron alpha-Fe2O3, would be an ideal OER catalyst in alkaline media due to its abundance and easy processing. Despite its promising theoretical potential, it has demonstrated very poor OER activity under multiple experimental conditions, significantly worse than that of Co or Ni-based oxides. In the search for improving hematite performance, we have analysed the effect of doping with redox vs. non-redox active species (Ni or Zn). Our results indicate that Zn doping Clearly outperforms Ni, commonly accepted as a preferred dopant. Zn-doped hematite exhibits catalytic performances Close to the state-of-the-art for alkaline water splitting: reaching 10 mA cm(-2) at just 350 mV overpotential (eta) at pH 13, thus twenty times that of hematite. Such a catalytic enhancement can be traced back to a dramatic change in the reaction pathway. Incorporation of Ni, as previously suggested, decreases the energetic barrier for the OER on the available centres. In contrast, Zn facilitates the appearance of a dominant and faster alternative via a two-site reaction, where the four electron oxidation reaction starts on Fe, but is completed on Zn after thermodynamically favoured proton coupled electron transfer between adjacent metal centres. This unique behaviour is prompted by the non-redox character of Zn centres, which maintain the same charge during OER. Our results open an alternative role for dopants on oxide surfaces and provide a powerful approach for catalytic optimisation of oxides, inCluding but not limited to highly preferred all-iron oxides.Non-redox doping boosts oxygen evolution electrocatalysis on hematite8202069#N/ATRUE
3533
c9sc00717b10.1039/c9sc00717bFALSEhttps://doi.org/10.1021/cs400327yLee, YOne metal is enough: a nickel complex reduces nitrate anions to nitrogen gasx2019#N/AFALSE
3534
c9sc00694j10.1039/c9sc00694jhttps://doi.org/10.1039/c9sc00694jSciammetta, NChem. Sci.Ni/ photoredox (4DPAIPN) dual catalysis enabled challenging peptide C(sp2)-O coupling reactions. Successful cross-coupling reactions were demonstrated with highly functionalized alcohols inCluding side chains of amino acids (i. e., serine, threonine, tyrosine), trans-4-hydroxy-L-proline, Alkyl alcohols, alkynylated alcohols, and carbohydrates. Coupling reactions between bromobenzoyl-capped peptides containing various side chains and either a protected serine building block or a serine-containing dipeptide also proceeded efficiently. Chemoselective C-O coupling (over C-N) was achieved in intermolecular reactions in the presence of a C-terminal primary amide. Furthermore, by judicious structural design in combination with computational modeling, we demonstrated side chain-to-tail macrocyClization of peptides containing a b-turn motif via C-O coupling. The methodology developed in this work brings new opportunities for late-stage diversification of complex linear and macrocyClic peptides.<bold> </bold>Photoredox Ni-catalyzed peptide C(sp(2))-O cross-coupling: from intermolecular reactions to side chain-to-tail macrocyClizationPhotocatalyst18201952#N/AFALSE
3535
c9sc00691e10.1039/c9sc00691eFALSEhttps://doi.org/10.1039/c9sc00691eZhang, ZHChem. Sci.Selective hydrogenolysis of the C-Aryl-O bonds in lignin is a key strategy for the generation of fuels and chemical feedstocks from biomass. Currently, hydrogenolysis has been mainly conducted using hydrogen, which is flammable and not sustainable or economical. Herein, an external hydrogen-free process for Aryl ethers hydrogenolysis in lignin models and dioxasolv lignin over nickel nanopartiCles supported on Al2O3, is reported. Kinetic studies reveal that the transfer hydrogenolysis activity of the three model compounds decreased in the following order: Benzyl phenyl ether (a-O-4), 2-phenylethyl phenyl ether (b-O-4) and diphenyl ether (4-O-5), which linearly corresponds to their binding energies and the Activation energies. The main reaction route for the three model compounds was the Cleavage of the ether bonds to produce aromatic alkanes and phenol, and the latter was further reduced to cyClohexanol. Dioxasolv lignin depolymerization results exhibit a significant CAryl-O decrease over the Ni nanopartiCles supported on Al2O3 with iso-propanol as the hydrogen source through 2D-HSQC-NMR analysis, which confirmed the transfer hydrogenolysis conClusion in the model study. This work provides an economical and environmentally-friendly method for the selective Cleavage of lignin and lignin model compounds into value-added chemicals.Selective Cleavage of lignin and lignin model compounds without external hydrogen, catalyzed by heterogeneous nickel catalystsx57201946#N/AFALSE
3536
c9sc05565g10.1039/c9sc05565gFALSEhttps://doi.org/10.1039/c9sc05565gBrudvig, GWChem. Sci.The high-valent nickel(iii) complex Ni(pyalk)(2)(+) (2) was prepared by oxidation of a nickel(ii) complex, Ni(pyalk)(2) (1) (pyalk = 2-pyridyl-2-propanoate). 2 and derivatives were fully characterized by mass spectrometry and X-ray crystallography. Electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy confirm that the oxidation is metal-centered. 2 was found to react with a variety of phenolic and hydrocarbon substrates. A linear correlation between the measured rate constant and the substrate bond dissociation enthalpy (BDE) was found for both phenolic and hydrocarbon substrates. Large H/D kinetic isotope effects were also observed for both sets of substrates. These results suggest that 2 reacts through concerted proton-electron transfer (CPET). Analysis of measured thermodynamic parameters allows us to calculate a bond dissociation free energy (BDFE) of similar to 91 kcal mol(-1) for the O-H bond of the bound pyalk ligand. These findings may shed light onto CPET steps in oxidative catalysis and have implications for ligand design in catalytic systems.Concerted proton-electron transfer oxidation of phenols and hydrocarbons by a high-valent nickel complex4202049#N/ATRUE
3537
c9sc05018c10.1039/c9sc05018cFALSEhttps://doi.org/10.1039/c9sc05018cHu, JBChem. Sci.A highly efficient method for controllable double CF2-insertion into pentafluorophenylcopper species using TMSCF3 as difluoromethylene source has been developed. The newly generated fluoroAlkylcopper(i) species, C6F5CF2CF2Cu, shows good reactivity towards a myriad of structurally diverse Aryl, heteroAryl and alkenyl iodides. This protocol is easy to handle, ready to scale up and applicable for the synthesis of relative complex molecules, thus providing a convenient method for facile access to tetrafluoroethylene-bridged structures.Controllable double CF2-insertion into sp(2) C-Cu bond using TMSCF3: a facile access to tetrafluoroethylene-bridged structures11202033#N/ATRUE
3538
c9sc00174c10.1039/c9sc00174cFALSEhttps://doi.org/10.1039/c9sc00174cZhang, JChem. Sci.The electrocatalytic conversion of CO2 to CO using non-noble metal catalysts under mild conditions is of great importance. Achieving the combination of high activity, selectivity and current density by developing electrocatalysts with desirable compositions and structures is challenging. Here we prepared for the first time CuxNiy alloy nanopartiCles embedded in a nitrogen-carbon network. Such an electrocatalyst not only well overcomes the disadvantages of single Cu and Ni catalysts but has a high CO2 adsorption capacity. Outstandingly, the catalyst can effectively convert CO2 into CO with a maximum faradaic efficiency of 94.5% and current density of 18.8 mA cm(2) at a low applied potential of 0.60 V (versus reversible hydrogen electrode, RHE). Moreover, the catalyst is very stable during long-term electrolysis owing to the stabilization of the nitrogen-carbon network.CuxNiy alloy nanopartiCles embedded in a nitrogen-carbon network for efficient conversion of carbon dioxidex14201949#N/AFALSE
3539
c9sc05005a10.1039/c9sc05005aFALSEhttps://doi.org/10.1039/c9sc05005aLi, YDChem. Sci.Non-noble metal isolated single atom site (ISAS) catalysts have attracted much attention due to their low cost, ultimate atom efficiency and outstanding catalytic performance. Herein, atomically dispersed Fe atoms are prepared by a covalent organic framework (COF)-absorption-pyrolysis strategy. The obtained Fe ISASs anchored on COF-derived N-doped carbon nanospheres (Fe-ISAS/CN) served as a multi-functional catalyst in electro-catalysis and organic catalysis, exhibiting better catalytic performance than commercial Pt/C for the ORR with good stability and methanol tolerance. Besides electro-catalysis, the Fe-ISAS/CN also showed outstanding catalytic performance in organic reactions, such as the selective oxidation of ethylbenzene to acetophenone and dehydrogenation of 1,2,3,4-tetrahydroquinoline with excellent reactivity, selectivity, stability and recyClability. Co and Ni ISAS materials can also be prepared by this method, suggesting that it is a general strategy to obtain metal ISAS catalysts. This work will provide new insight into the design of COF-derived metal ISAS multi-functional catalysts for electro-catalysis and organic reactions using rationally designed synthetic routes and the optimized structure of substrates.Atomically dispersed Fe atoms anchored on COF-derived N-doped carbon nanospheres as efficient multi-functional catalysts29202037#N/ATRUE
3540
c9sc04603h10.1039/c9sc04603hFALSEhttps://doi.org/10.1039/c9sc04603hWei, ZDChem. Sci.Developing efficient and cheap electrocatalysts for the alkaline hydrogen evolution reaction is still a big challenge due to the sluggish water dissociation kinetics as well as poor M-H-ad energetics. Herein, hydroxide modification and element incorporation have been demonstrated to realize a synergistic modulation on a new Class of M(OH)(x)/M-MoPOx catalysts for accelerating water dissociation and hydrogen ad-desorption steps in the HER. Theoretical and experimental results disClosed that in situ modification with hydroxide endowed M(OH)(x)/M-MoPOx with a strong ability to dissociate water, and meanwhile, oxygen incorporation effectively optimized the M-H-ad energetics of the NiMoP catalyst. Moreover, the interaction between M(OH)(x) and M-MoPOx components in M(OH)(x)/M-MoPOx further enhances their ability to catalyze the two elementary steps in alkaline hydrogen evolution, providing a wide avenue for efficiently catalyzing hydrogen evolution. In general, the optimized Ni(OH)(2)/NiMoPOx catalyst exhibits excellent alkaline HER activity and durability, superior to the state-of-the-art Pt/C catalyst when the overpotential exceeds 65 mV.Accelerated alkaline hydrogen evolution on M(OH)(x)/M-MoPOx (M = Ni, Co, Fe, Mn) electrocatalysts by coupling water dissociation and hydrogen ad-desorption steps12202052#N/ATRUE
3541
c9cc05487a10.1039/c9cc05487aFALSEhttps://doi.org/10.1039/c9cc05487aGu, ZYUltrathin 2D nickel zeolitic imidazolate framework nanosheets for electrocatalytic reduction of CO2x2019#N/AFALSE
3542
c9cc04559g10.1039/c9cc04559gFALSEhttps://doi.org/10.1021/cs400245mGuo, ZHAnchoring carbon nanotubes and post-hydroxylation treatment enhanced Ni nanofiber catalysts towards efficient hydrous hydrazine decomposition for effective hydrogen generationx2019#N/AFALSE
3543
c9sc04199k10.1039/c9sc04199kFALSEhttps://doi.org/10.1039/c9sc04199kBrown, MKChem. Sci.Nickel-catalyzed 1,2-carbB(OH)2ration of alkenes is emerging as a useful method for chemical synthesis. Prior studies have been limited to only the incorporation of Aryl groups. In this manuscript, a method for the 1,2-Benzylboration of unactivated alkenes is presented. The reaction combines readily available alkenes, diboron reagents and Benzylchlorides to generate synthetically versatile products with control of stereochemistry. The utility of the products as well as the mechanistic details of the process are also presented.Ni-catalyzed 1,2-Benzylboration of 1,2-disubstituted unactivated alkenes10201922#N/ATRUE
3544
c9sc03115d10.1039/c9sc03115dFALSEhttps://doi.org/10.1039/c9sc03115dWagner, MChem. Sci.The well-known red emitter tetrabenzo[de,hi,op,st]pentacene (TBPA) has been transformed into a bright blue emitter (B-2-TBPA; lambda(em) = 472 nm; c-hexane) via substitutional doping with two boron atoms. In contrast to the electron-rich TBPA, which forms endo-peroxides with O-2 under daylight, the benchtop-stable B-2-TBPA is a good electron acceptor and undergoes reversible reduction at a moderate half-wave potential of E-1/2 = -1.73 V (vs. FcH/FcH(+); THF). Although the size of B-2-TBPA falls within the nanoscale, the helically twisted compound readily dissolves in c-hexane and does not require solubilizing substituents. The synthesis of B-2-TBPA is based on the nickel-mediated Yamamoto-type dehalogenation of tetrabrominated 9,10-di(naphth-1-yl)-9,10-dihydro-9,10-diboraanthracene. This intramolecular C-C heterocoupling reaction shows a remarkable solvent dependence: B-2-TBPA forms only in pyridine (79% yield), whereas an oxadiborepin is obtained from THF solutions (ODBE, 81%; the reaction mixture is quenched with air in both cases). Insight into the corresponding reaction mechanism was gained from the isolation of intermediates and an investigation of their chemical properties. ODBE is an interesting blue emitter in its own right. Furthermore, it can be ring-opened with excess BBr3 at the B-O-B moiety to afford a dimeric borabenzo[de]anthracene.Selective access to either a doubly boron-doped tetrabenzopentacene or an oxadiborepin from the same precursor11201981#N/ATRUE
3545
c9sc02806d10.1039/c9sc02806dFALSEhttps://doi.org/10.1039/c9sc02806dWang, XSChem. Sci.A nickel-catalyzed difluoroAlkylation of alpha-C-H bonds of Aryl ketones to furnish highly stereo-defined tetrasubstituted monofluoroalkenes or quaternary Alkyl difluorides from secondary or tertiary ketones, respectively, has been established. Mechanistic investigations indicated that these C-H fluoroAlkylations proceed via a Ni(i)/Ni(iii) catalytic cyCle. An obvious fluorine effect was observed in the reaction, and this reaction has demonstrated high stereoselectivity, mild conditions, and broad substrate scopes, thus enabling the late-stage fluoroAlkylation of bioactive molecules. This method offers a solution for expedient construction of monofluoroalkenes from readily available materials, and provides an efficient approach for the synthesis of bioactive fluorinated compounds for the discovery of lead compounds in medicinal chemistry.Highly stereoselective nickel-catalyzed difluoroAlkylation of Aryl ketones to tetrasubstituted monofluoroalkenes and quaternary Alkyl difluorides10201977#N/ATRUE
3546
c9sc02749a10.1039/c9sc02749aFALSEhttps://doi.org/10.1039/c9sc02749aSuero, MGChem. Sci.An operationally simple and broadly applicable novel cyClopropanation of styrenes using gem-diiodomethyl Carbonyl reagents has been developed. Visible-light triggered the photoinduced generation of iodomethyl Carbonyl radicals, able to cyClopropanate a wide array of styrenes with excellent chemoselectivity and functional group tolerance. To highlight the utility of our photocyClopropanation, we demonstrated the late-stage functionalization of biomolecule derivatives.A transition-metal-free & diazo-free styrene cyClopropanation5201979#N/ATRUE
3547
c8sc05677c10.1039/c8sc05677chttps://doi.org/10.1039/c8sc05677cKanai, MChem. Sci.We describe a hybrid system that realizes cooperativity between an organophotoredox acridinium catalyst and a chiral chromium complex catalyst, thereby enabling unprecedented exploitation of unactivated hydrocarbon alkenes as precursors to chiral allylchromium nuCleophiles for asymmetric allylation of aldehydes. The reaction proceeds under visible light irradiation at room temperature, affording the corresponding homoallylic alcohols with a diastereomeric ratio >20/1 and up to 99% ee. The addition of Mg(ClO4)(2) markedly enhanced both the reactivity and enantioselectivity.Catalytic asymmetric allylation of aldehydes with alkenes through allylic C(sp(3))-H functionalization mediated by organophotoredox and chiral chromium hybrid catalysisPhotocatalyst57201992#N/AFALSE
3548
c8sc05423a10.1039/c8sc05423aFALSEhttps://doi.org/10.1039/c8sc05423aLi, DQChem. Sci.The impregnation method is commonly employed to prepare supported multi-metallic catalysts but it is often difficult to achieve homogeneous and stable alloy structures. In this work, we revealed the dependence of alloying behavior on the support morphology by fabricating Ni-Cu over different shaped CeO2. Specifically, nanocube ceria favoured the formation of monometallic Cu and Ni-rich phases whereas polycrystalline and nanorod ceria induced the formation of a mixture of Cu-rich alloys with monometallic Ni. Surprisingly, nanopolyhedron (NP) ceria led to the generation of homogeneous Ni-Cu nanoalloys owing to the equivalent interactions of Ni and Cu species with CeO2 (111) facets which exposed relatively few coordinative unsaturated sites. More importantly, a strong interfacial effect was observed for Ni-Cu/CeO2-NP due to the presence of CeOx adjacent to metal sites at the interface, resulting in excellent stability of the alloy structure. With the aid of CeOx, NiCu nanoalloys showed outstanding catalytic behaviour in acetylene and hexyne hydrogenation reactions. This study provides valuable insights into how fully alloyed and stable catalysts may be prepared by tailoring the support morphology while still employing a universal impregnation method.Support morphology-dependent alloying behaviour and interfacial effects of bimetallic Ni-Cu/CeO2 catalystsx13201945#N/AFALSE
3549
c9sc02723h10.1039/c9sc02723hFALSEhttps://doi.org/10.1039/c9sc02723hYang, SHChem. Sci.Creating atomic defects in nanomaterials is an effective approach to promote the catalytic performance of a catalyst, but the defective catalysts are often prone to mechanical collapse if not properly synthesized. The uncontrollably formed defects also make it difficult to systematically investigate their effects on the catalytic performance. Herein, we report an efficient method of ionic reductive complexation extraction (IRCE) to fabricate atomic vacancies in a transition metal based nanomaterial without damaging its nanostructure, turning the otherwise catalytically inactive material to an advanced catalyst towards water oxidation in alkaline electrolyte. Here nickel based layered double hydroxide mixed with Cu(ii) is used to demonstrate the concept. With a tunable content and uniform dispersion of Cu(ii) on the brucite layer of the LDH, a suitable complexing agent could specifically combine with and remove the target Cu(ii), thereby creating the desired vacancies. The resulting vacancy rich TM LDH is found to be an excellent OER electrocatalyst with a low overpotential and small Tafel slope, due to the purposely modulated geometric and electronic structures of the active sites, and the greatly decreased charge transfer resistance.Dispersing transition metal vacancies in layered double hydroxides by ionic reductive complexation extraction for efficient water oxidation22201952#N/ATRUE
3550
c9sc01165j10.1039/c9sc01165jFALSEhttps://doi.org/10.1039/c9sc01165jKros, AChem. Sci.Designing peptides that fold and assemble in response to metal ions tests our understanding of how peptide folding and metal binding influence one another. Here, histidine residues are introduced into the hydrophobic core of a coiled-coil trimer, generating a peptide that self-assembles upon the addition of metal ions. HisAD, the resulting peptide, is unstructured in the absence of metal and folds selectively to form an alpha-helical construct upon complexation with Cu(ii) and Ni(ii) but not Co(ii) or Zn(ii). The structure, and metal-binding ability, of HisAD is probed using a combination of circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AUC), nuClear magnetic resonance (NMR) spectroscopy and X-ray crystallography. These show the peptide is trimeric and binds to both Cu(ii) and Ni(ii) in a 1 : 1 ratio with the histidine residues involved in the metal coordination, as designed. The X-ray crystal structure of the HisAD-Cu(ii) complex reveals the trimeric HisAD peptide coordinates three Cu(ii) ions; this is the first example of such a structure. Additionally, HisAD demonstrates an unprecedented discrimination between transition metal ions, the basis of which is likely to be related to the stability of the peptide-metal complexes formed.Selective coordination of three transition metal ions within a coiled-coil peptide scaffold6201960#N/ATRUE
3551
c8sc05085f10.1039/c8sc05085fFALSEhttps://doi.org/10.1039/c8sc05085fNitschke, JRChem. Sci.Metal-organic containers are readily prepared through self-assembly, but achieving solubility and stability in water remains challenging due to ligand insolubility and the reversible nature of the self-assembly process. Here we have developed conditions for preparing a broad range of architectures that are both soluble and kinetically stable in water through metal(II)-templated (M-II = Co-II, Ni-II, Zn-II, Cd-II) subcomponent self-assembly. Although these structures are composed of hydrophobic and poorlysoluble subcomponents, sulfate counterions render them water-soluble, and they remain intact indefinitely in aqueous solution. Two strategies are presented. Firstly, stability increased with metalligand bond strength, maximising when NiII was used as a template. Architectures that disassembled when Co-II, Zn-II and Cd-II templates were employed could be directly prepared from NiSO4 in water. Secondly, a higher density of connections between metals and ligands within a structure, considering both ligand topicity and degree of metal chelation, led to increased stability. When tritopic amines were used to build highly chelating ligands around Zn-II and Cd-II templates, cryptate-like water-soluble structures were formed using these labile ions. Our synthetic platform provides a unified understanding of the elements of aqueous stability, allowing predictions of the stability of metal-organic cages that have not yet been prepared.Waterproof architectures through subcomponent self-assemblyx292019117#N/AFALSE
3552
c8sc05020a10.1039/c8sc05020aFALSEhttps://doi.org/10.1039/c8sc05020aClever, GHChem. Sci.Four imidazoles, serving as metalloprotein-inspired ligands for complexing a range of transition metal cations, were incorporated into tetramolecular G-quadruplex DNA structures. Modified quadruplexes were found to complex Cu(II), Ni(II), Zn(II) and Co(II) in a 1 : 1 ratio with unprecedented strong thermal stabilizations of up to Delta T-1/2 = +51 degrees C. Furthermore, addition of Cu(II) was found to lead to extraordinarily fast G-quadruplex association rates with kon values being similar to 100 times higher compared to unmodified G-quadruplexes. This is ascribed to a template effect of Cu(II), preorganizing the four single strands via coordination, followed by rapid formation of hydrogen-bonded G-quartets. Native electrospray ionization mass spectrometry (ESI), coupled with trapped ion-mobility spectrometry (timsTOF), supports the proposed 1 : 1 G-quadruplex-metal complexes and could further disClose their ability to bind the iron-porphyrin complex hemin in a 1 : 1 stoichiometry. DNA sequence design allowed us to equip this G-quadruplex-hemin complex, known to function as a horseradish peroxidase mimic, with a metal-dependent trigger. A competitive screen of transition metals revealed a high selectivity for Cu(II), even in mixtures of several divalent metal cations. Once formed, the Cu(II)-carrying DNAzyme was shown to be preserved in the presence of EDTA, attributed to its remarkable kinetic stability. Stimuli-responsive G-quadruplexes promise application in DNAzymes with switchable activity, adaptive sensors and dynamic DNA origami constructs.Imidazole-modified G-quadruplex DNA as metal-triggered peroxidasex13201940#N/AFALSE
3553
c8sc04967j10.1039/c8sc04967jFALSEhttps://doi.org/10.1039/c8sc04967jLu, XHChem. Sci.The exploration of a stable and high-rate anode is of pivotal importance for achieving advanced aqueous rechargeable batteries. Owing to the beneficial properties of high conductivity, suitable negative working voltage, and three-electron redox, bismuth (Bi) is considered as a promising anode material, but it suffers from poor stability. Here, we successfully endow Bi nanoflakes (NFs) with prominent cyCling performance by a one-step surface oxidation approach to remarkably boost its reversibility. As a result, the partially oxidized Bi NFs (BiOx) show an admirable capacity (0.38 mA h cm(-2) at 2 mA cm(-2)), good rate capability and superior long-term stability (almost no capacity decay after 20000 cyCles). Furthermore, a durable aqueous Ni//Bi battery is constructed based on the optimized BiOx anode, which exhibits excellent durability with 96% capacity retention after 5000 cyCles. This study could open a new avenue for the rational design of efficient anodes for eco-friendly and reliable aqueous rechargeable batteries.Engineering high reversibility and fast kinetics of Bi nanoflakes by surface modulation for ultrastable nickel-bismuth batteriesx12201942#N/AFALSE
3554
c9sc01144g10.1039/c9sc01144gFALSEhttps://doi.org/10.1039/c9sc01144gNishihara, HChem. Sci.The construction of two-dimensional metal complex materials is fascinating because of the structural and functional diversity of these materials. Previously, we have reported the synthesis of electroconductive nickelladithiolene (NiDT) and palladadithiolene (PdDT) nanosheets using benzenehexathiol (BHT). Down the group from Ni, Pd to Pt, there is a distinct positive shift in the reduction potential; as a result, it becomes synthetically more challenging to stabilize Pt2+ than to form metallic Pt(0) in the presence of BHT as a reducing agent. Herein, a novel synthetic strategy for the preparation of platinadithiolene nanosheet (PtDT) using a dibutyltin-protected BHT ligand is reported, leading to transmetallation in the presence of dioxygen. Both free-standing stacked sheets and atomic layer sheets were obtained and characterized by microscopic techniques such as AFM, SEM, and TEM. To study the morphology of the sheets and determine their charge neutrality, X-ray photoelectron (XP) and infrared (IR) spectroscopic techniques were used. Powder X-ray diffraction analysis of the multilayer PtDT indicates a half-way slipped hexagonal configuration in the P (3) over bar 1m space group. The band structure of this PtDT exhibits a band gap at the Fermi level, which is different from that of NiDT in the staggered configuration, and a Dirac gap, indicating the possibility of 2D topological insulation at room temperature. PtDT is insulating but chemically activated by oxidation with I-2 to increase the conductivity by more than 10(6) folds up to 0.39 S cm(-1). The MDT sheets exhibit electrocatalytic activity for the hydrogen evolution reaction, and the activity order is NiDT < PdDT < PtDT.Interfacial transmetallation synthesis of a platinadithiolene nanosheet as a potential 2D topological insulator20201949#N/ATRUE
3555
c8sc04808h10.1039/c8sc04808hhttps://doi.org/10.1039/c8sc04808hSeferos, DSChem. Sci.Catalyst transfer polycondensation is the only method to prepare p-conjugated polymers in a chain-growth manner, yet several aspects that underlie this polymerization are not fully understood. Here, we investigate the nickel-catalyzed polymerization mechanisms of a series of thiophene monomers bearing different halogen functionalities (Cl, Br, I). We have discovered the significant role that halogens and magnesium salts play in this polymerization. More specifically, the catalyst resting state changes depending on the type of halogenated monomer. For chlorinated monomers a mixture of Ni(II)-dithienyl and dissociated Ni(phosphine) complexes are the resting states, which results in uncontrolled polymerization. For brominated monomers, a Ni(II)-dithienyl complex is the resting state, which leads to controlled polymerization. For iodinated monomers, a Ni(II)-thienyl iodide complex is the resting state, and notable inhibition by magnesium salt by-products is observed. The catalyst resting state changes to a Ni(II)dithienyl complex when a turbo Grignard reagent (i-PrMgX center dot LiCl) is used. These findings are used to guide the design of a new monomer, 2-bromo-3-(2-ethylhexyl)-5-iodotellurophene, which enables the first controlled polymerization of a tellurophene monomer containing a sterically encumbered 2-ethylhexyl side chain. These insights are crucial for deepening the mechanistic understanding of Kumada cross coupling reactions and the controlled synthesis of p-conjugated polymers.The role of halogens in the catalyst transfer polycondensation for pi-conjugated polymersx14201943#N/AFALSE
3556
c9sc00640k10.1039/c9sc00640kFALSEhttps://doi.org/10.1039/c9sc00640kLiu, TLChem. Sci.A direct nickel-catalyzed, high atom- and step-economical reaction of cyanohydrins with aldehydes or ketones via an unprecedented cyano-borrowing reaction has been developed. Cleavage of the C-CN bond of cyanohydrins followed by aldol condensation and conjugate addition of cyanide to alpha,beta-unsaturated ketones proceeded to deliver a range of racemic beta-cyano ketones with good to high yields. The practical procedure with the use of a commercial and less-toxic CN source bodes well for wide application of this protocol.Cyano-borrowing reaction: nickel-catalyzed direct conversion of cyanohydrins and aldehydes/ketones to beta-cyano ketone8201974#N/ATRUE
3557
c9sc00554d10.1039/c9sc00554dFALSEhttps://doi.org/10.1039/c9sc00554dVicic, DAChem. Sci.We report herein the exploitment of the partially fluorinated trifluoroethyl as precatalyst ligands in nickelcatalyzed Suzuki-type Alkylation and fluoroAlkylation coupling reactions. Compared with the [LnNiII(Aryl)(X)] precatalysts, the unique characters of bis-trifluoroethyl ligands imparted precatalyst [(bipy) Ni(CH2CF3) (2)] with bench-top stability, good solubilities in organic media and interesting catalytic activities. Preliminary mechanistic studies reveal that an eliminative extrusion of a Vinylidene difluoride (VDF, CH2] CF2) mask from [(bipy) Ni(CH2CF3) (2)] is a critical step for the initiation of a catalytic reaction.Exploiting the trifluoroethyl group as a precatalyst ligand in nickel-catalyzed Suzuki-type Alkylations62019107#N/ATRUE
3558
c9cc09249h10.1039/c9cc09249hFALSEhttps://doi.org/10.1021/cs2006789Anderson, JSNickel(ii)-methyl complexes adopting unusual seesaw geometries2020#N/ATRUE
3559
c9cc07389b10.1039/c9cc07389bFALSELu, YA Ni-foam-structured MoNi4-MoOx nanocomposite catalyst for hydrogenation of dimethyl oxalate to ethanol2020#N/ATRUE
3560
c8sc03732a10.1039/c8sc03732aFALSEhttps://doi.org/10.1039/c8sc03732aSun, ZYChem. Sci.The development of highly selective, low cost, and energy-efficient electrocatalysts is crucial for CO2 electrocatalysis to mitigate energy shortages and to lower the global carbon footprint. Herein, we first report that carbon-coated Ni nanopartiCles supported on N-doped carbon enable efficient electroreduction of CO2 to CO. In contrast to most previously reported Ni metal catalysts that resulted in severe hydrogen evolution during CO2 conversion, the Ni partiCle catalyst here presents an unprecedented CO faradaic efficiency of approximately 94% at an overpotential of 0.59 V, even comparable to that of the best single Ni sites. The catalyst also affords a high CO partial current density and a large CO turnover frequency, reaching 22.7 mA cm(-2) and 697 h(-1) at -1.1 V (versus the reversible hydrogen electrode), respectively. Experiments combined with density functional theory calculations showed that the carbon layer coated on Ni and N-dopants in carbon material both play important roles in improving catalytic activity for electrochemical CO2 reduction to CO by stabilizing *COOH without affecting the easy *CO desorption ability of the catalyst.Carbon-supported Ni nanopartiCles for efficient CO2 electroreductionx81201833#N/AFALSE
3561
c8sc03719a10.1039/c8sc03719aFALSEhttps://doi.org/10.1039/c8sc03719aAnderson, JSChem. Sci.A T-shaped Ni(II) complex [(DHPy)-D-Tol,Ph] Ni has been prepared and characterized. EPR spectra and DFT calculations of this complex suggest that the electronic structure is best described as a high-spin Ni(II) center antiferromagnetically coupled with a ligand-based radical. This complex reacts with water at room temperature to generate the dimeric complex [(DHPy)-D-Tol,Ph] Ni(mu-OH) Ni[(DHPyH)-D-Tol,Ph] which has been thoroughly characterized by SXRD, NMR, IR and deuterium-labeling experiments. Addition of simple ligands such as phosphines or pyridine displaces water and demonstrates the reversibility of water Activation in this system. The water Activation step has been examined by kinetic studies and DFT calculations which suggest an unusual homolytic reaction via a bimetallic mechanism. The Delta H-double dagger, Delta S-double dagger and KIE (k(H)/k(D)) of the reaction are 5.5 kcal mol(-1), - 23.8 cal mol(-1) K-1, and 2.4(1), respectively. In addition to the reversibility of water addition, this system is capable of activating water towards net O-atom transfer to substrates such as aromatic C-H bonds and phosphines. This reactivity is facilitated by the ability of the dihydrazonopyrrole ligand to accept H-atoms and illustrates the utility of metal ligand cooperation in activating O-H bonds with high bond dissociation energies.Reversible homolytic Activation of water via metal-ligand cooperativity in a T-shaped Ni(ii) complexx6201974#N/AFALSE
3562
c8sc03555e10.1039/c8sc03555eFALSEhttps://doi.org/10.1039/c8sc03555eApfel, UPChem. Sci.The electrocatalytic reduction of carbon dioxide (CO2RR) to valuable bulk chemicals is set to become a vital factor in the prevention of environmental pollution and the selective storage of sustainable energy. Inspired by structural analogues to the active site of the enzyme CODHNi, we envisioned that bulk Fe/Ni sulfides would enable the efficient reduction of CO2. By careful adjustment of the process conditions, we demonstrate that pentlandite ((Fe4.5Ni45S8)-S-.) electrodes, in addition to HER, also support the CO2RR reaching a peak faradaic efficiency of 87% and 13% for the formation of CO and methane, respectively at 3 mA cm(-2). The choice of solvent, the presence of water/protons and CO2 solubility are identified as key-properties to adjust the balance between HER and CO2RR in favour of the latter. Such experiments can thus serve as model reactions to elucidate a potential catalyst within gas diffusion electrodes.Bio-inspired design: bulk iron-nickel sulfide allows for efficient solvent-dependent CO2 reductionx27201952#N/AFALSE
3563
c8sc03407a10.1039/c8sc03407aFALSEhttps://doi.org/10.1039/c8sc03407aDriess, MChem. Sci.In large-scale, hydrogen production from water-splitting represents the most promising solution for a Clean, recyClable, and low-cost energy source. The realization of viable technological solutions requires suitable efficient electrochemical catalysts with low overpotentials and long-term stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) based on cheap and nontoxic materials. Herein, we present a unique molecular approach to monodispersed, ultra-small, and superiorly active iron phosphide (FeP) electrocatalysts for bifunctional OER, HER, and overall water-splitting. They result from transformation of a molecular iron phosphide precursor, containing a [Fe2P3] core with mixed-valence (FeFeIII)-Fe-II sites bridged by an asymmetric cyClo-P-(2+1)(3-) ligand. The as-synthesized FeP nanopartiCles act as long-lasting electrocatalysts for OER and HER with low overpotential and high current densities that render them one of the best-performing electrocatalysts hitherto known. The fabricated alkaline electrolyzer delivered low cell voltage with durability over weeks, representing an attractive catalyst for large-scale water-splitting technologies.From an Fe2P3 complex to FeP nanopartiCles as efficient electrocatalysts for water-splittingx56201857#N/AFALSE
3564
c9cc02902h10.1039/c9cc02902hFALSEhttps://doi.org/10.1021/cs2002548Rath, SPA counter ion triggers stabilization of two geometrical isomers of a Ni(ii) dication diradical porphyrin dimer: the role of anion-pi interactions2019#N/ATRUE
3565
c9cc01204d10.1039/c9cc01204dFALSEhttps://doi.org/10.1021/cs2000939Platas-Iglesias, CReinforced Ni(ii)-cyClam derivatives as dual H-1/F-19 MRI probes2019#N/ATRUE
3566
c8sc03297a10.1039/c8sc03297ahttps://doi.org/10.1039/c8sc03297aWang, DWChem. Sci.The energy conversion efficiency of a photoelectrochemical system is intimately connected to a number of processes, inCluding light absorption, charge excitation, separation and transfer processes. Of these processes, the charge transfer rate at the electrode|electrolyte interface is the slowest and, hence, the rate-limiting step causing charge accumulation. Such an understanding underpins efforts focused on applying highly active electrocatalysts, which may contribute to the overall performance by augmenting surface charge accumulation, prolonging charge lifetime or facilitating charge transfer. How the overall effect depends on these individual possible mechanisms has been difficult to study previously. Aiming at advancing knowledge about this important interface, we applied first-order serial reactions to elucidate the charge excitation, separation and recombination kinetics on the semiconductor|electrocatalyst interfaces in air. The study platform for the present work was prepared using a two-step Mo-doped BiVO4 film modified with an ultrathin Fe-doped NiO nanosheet, which was derived from an Fe-doped -Ni(OH)(2) nanosheet by a convenient precipitation and ion-exchange method. The simulation results of the transient surface photovoltage (TSPV) data showed that the surface charge accumulation was significantly enhanced, even at an extremely low coverage (0.12-120 ppm) using ultra-thin Fe-NiO nanosheets. Interestingly, no improvement in the charge separation rate constants or reduction of recombination rate constants was observed under our experimental conditions. Instead, the ultra-thin Fe-NiO nanosheets served as a charge storage layer to facilitate the catalytic process for enhanced performance.Ultrathin Fe-NiO nanosheets as catalytic charge reservoirs for a planar Mo-doped BiVO4 photoanodePhotocatalystx23201861#N/AFALSE
3567
c9cc00527g10.1039/c9cc00527gFALSELi, XGPlasma enabled non-thermal phosphorization for nickel phosphide hydrogen evolution catalysts2019#N/ATRUE
3568
c8sc03040e10.1039/c8sc03040eFALSEhttps://doi.org/10.1039/c8sc03040eSchalley, CAChem. Sci.Coordinative halogen bonds have recently gained interest for the assembly of supramolecular capsules. Ion mobility-mass spectrometry and theoretical calculations now reveal the well-defined gas-phase structures of dimeric and hexameric [NI+N] halogen-bonded capsules with counterions located inside their cavities as guests. The solution reactivity of the large hexameric capsule shows the intriguing solvent-dependent equilibrium between the hexamer and an unprecedented pentameric [NI+N] halogen-bonded capsule, when the solvent is changed from chloroform to dichloromethane. The intrinsic flexibility of the cavitands enables this novel structure to adopt a pseudo-trigonal bipyramidal geometry with nine [NI+N] bonds along the edges and two pyridine binding sites uncomplexed.Surprising solvent-induced structural rearrangements in large [N center dot center dot center dot I+center dot center dot center dot N] halogen-bonded supramolecular capsules: an ion mobility-mass spectrometry studyx21201860#N/AFALSE
3569
c8sc02868k10.1039/c8sc02868kFALSEhttps://doi.org/10.1039/c8sc02868kZhang, JMChem. Sci.Rechargeable lithium-ion batteries (LIBs) have been the dominating technology for electric vehiCles (EV) and grid storage in the current era, but they are still extensively demanded to further improve energy density, power density, and cyCle life. Herein, a novel 3D layered nanoarchitecture network of Ni(HCO3)(2)/rGO composites with highly uniform Ni(HCO3)(2) nanocubes (average diameter of 100 +/- 20 nm) wrapped in rGO films is facilely fabricated by a one-step hydrothermal self-assembly process based on the electrostatic interaction and coordination principle. Benefiting from the synergistic effects, the Ni(HCO3)(2)/rGO electrode delivers an ultrahigh capacity (2450 mA h g(-1) at 0.1 A g(-1)), ultrafast rate capability and ultralong cyCling stability (1535 mA h g(-1) for the 1000th cyCle at 5 A g(-1), 803 mA h g(-1) for the 2000th cyCle at 10 A g(-1)). The detailed electrochemical reaction mechanism investigated by in situ XRD further indicates that the 3D architecture of Ni(HCO3)(2)/rGO not only provides a good conductivity network and has a confinement effect on the rGO films, but also benefits from the reversible transfer from LiHCO3 to LixC2 (x = 0-2), further oxidation of nickel, and the formation of a stable/durable solid electrolyte interface (SEI) film (LiF and LiOH), which are responsible for the excellent storage performance of the Li-ions. This work could shed light on the design of high-capacity and low-cost anode materials for high energy storage in LIBs to meet the critical demands of EV and mobile information technology devices.Construction of 3D architectures with Ni(HCO3)(2) nanocubes wrapped by reduced graphene oxide for LIBs: ultrahigh capacity, ultrafast rate capability and ultralong cyCle stabilityx20201881#N/AFALSE
3570
c8sc02841a10.1039/c8sc02841ahttps://doi.org/10.1039/c8sc02841aPoluektov, OGChem. Sci.Nature's solar energy converters, the Photosystem I (PSI) and Photosystem II (PSII) reaction center proteins, flawlessly manage photon capture and conversion processes in plants, algae, and cyanobacteria to drive oxygenic water-splitting and carbon fixation. Herein, we utilize the native photosynthetic Z-scheme electron transport chain to drive hydrogen production from thylakoid membranes by directional electron transport to abiotic catalysts bound at the stromal end of PSI. Pt-nanopartiCles readily self-assemble with PSI in spinach and cyanobacterial membranes as evidenced by light-driven H-2 production in the presence of a mediating electron shuttle protein and the sacrificial electron donor sodium ascorbate. EPR characterization confirms placement of the Pt-nanopartiCles on the acceptor end of PSI. In the absence of sacrificial reductant, H-2 production at PSI occurs via coupling to light-induced PSII O-2 evolution as confirmed by correlation of catalytic activity to the presence or absence of the PSII inhibitor DCMU. To create a more sustainable system, first-row transition metal molecular cobaloxime and nickel diphosphine catalysts were found to perform photocatalysis when bound in situ to cyanobacterial thylakoid membranes. Thus, the self-assembly of abiotic catalysts with photosynthetic membranes demonstrates a tenable method for accomplishing solar overall water splitting to generate H2, a renewable and Clean fuel. This work benchmarks a significant advance toward improving photosynthetic efficiency for solar fuel production.Z-scheme solar water splitting via self-assembly of photosystem I-catalyst hybrids in thylakoid membranesPhotocatalyst10201853#N/AFALSE
3571
c8sc02820f10.1039/c8sc02820fFALSEhttps://doi.org/10.1039/c8sc02820fDunbar, KRChem. Sci.Geometric control in mononuClear complexes has come to the forefront in the field of molecular magnets due to its profound effects on relaxation pathways and blocking temperature in single molecule magnets (SMMs). Herein we report the synthesis and magnetic characterization of six trigonally symmetric, divalent Fe, Co, and Ni molecules, with the rigid geometry enforced via the use of the tris-anionic, tetradentate ligand MST (N,N,N-[2,2,2-nitrilotris-(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamide)). A systematic study on the effect of converting between trigonal monopyramidal complexes, (Me4N)[M(MST)], and trigonal bipyramidal complexes, (Me4N)[M(MST)(OH2)] was conducted experimentally and computationally. It was found that (Me4N)[Ni(MST)] exhibits a very large, near record zero-field splitting parameter (D) value of -434 cm(-1), owing to an extremely low lying first excited state. The trigonal monopyramidal cobalt and iron complexes exhibit slow magnetic relaxation under applied fields, resulting in barriers of 45 K and 63.9 K respectively. Coordination of a single water molecule in the open axial site of the trigonal monopyramidal complexes exerts drastic dampening effects on the D value as well as slow relaxation. Computations reveal that coordination of water rotates the D-zz axis away from the C-3 axis of symmetry resulting in a smaller D value. The aquo species (Me4N)[Co(MST)(OH2)] also exhibits magnetic relaxation under an applied field, but the barrier is reduced to 9.9 K. Water coordination totally quenches the magnetic behavior in the iron complex, and reduces the D value for nickel to -185 cm(-1). These results showcase the drastic effect that a small change in the coordination environment can have on magnetic behavior, as well as that trigonal monopyramidal geometry can lead to near record D values.Effects of coordination sphere on unusually large zero field splitting and slow magnetic relaxation in trigonally symmetric moleculesx20201841#N/AFALSE
3572
c8sc02575d10.1039/c8sc02575dhttps://doi.org/10.1039/c8sc02575dGibson, EAChem. Sci.A new approach to increasing the faradaic efficiency of dye-sensitised photocathodes for H-2 evolution from water, using integrated photocatalysts, furnished with ester groups on the peripheral ligands, [Ru(decb)(2)(bpt)PdCl(H2O)](PF6)(2) (1) and [Ru(decb)(2)(2,5-bpp)PtI(CH3CN)](PF6)(2) (2), (decb = 4,4-diethylcarboxy-2,2-bipyridine, bpp = 2,2':5,2-terpyridine, bpt = 3,5-bis(2-pyridyl)-1,2,4-triazole) is described. Overall, 1|NiO is superior to previously reported photocathodes, producing photocurrent densities of 30-35 A cm(-2) at an applied bias of -0.2 V vs. Ag/AgCl over 1 hour of continuous white light irradiation, resulting in the generation of 0.41 mol h(-1) cm(-2) of H-2 with faradaic efficiencies of up to 90%. Furthermore, surface analysis of the photocathodes before and after photoelectrocatalysis revealed that the ruthenium bipyridyl chromophore and Pd catalytic centre (1) were photochemically stable, highlighting the benefits of the approach towards robust, hybrid solar-to-fuel devices.Photoelectrocatalytic H2 evolution from integrated photocatalysts adsorbed on NiO
Electrocatalytic
17201971#N/AFALSE
3573
c9cc00159j10.1039/c9cc00159jFALSEhttps://doi.org/10.1039/c9cc00159jBall, ZTRapid nickel(ii)-promoted cysteine S-Arylation with Arylboronic acids2019#N/ATRUE
3574
c8sc05256e10.1039/c8sc05256eFALSEhttps://doi.org/10.1039/c8sc05256eReal, JADiscrimination between two memory channels by molecular alloying in a doubly bistable spin crossover material2019#N/ATRUE
3575
c8sc05247f10.1039/c8sc05247fFALSEhttps://doi.org/10.1039/c8sc05247fCao, RChem. Sci.Ga-III chloride tetrakis(pentafluorophenyl) porphyrin (1) was synthesized and shown to be a highly active and stable post-transition metal-based electrocatalyst for the hydrogen evolution reaction (HER). Electrochemical and spectroscopic studies indicate that both the first and second reduction events of 1 are ligand-centered. The 2e-reduced form 1(2-) reacts with a proton to give Ga-III-H species (1-H), which undergoes protonolysis with Bronsted acids to produce H-2. The identification of key intermediates 1(-), 1(2-), and 1-H leads to a catalytic cyCle, which is valuable for the fundamental understanding of the HER. This study presents a rare but highly active HER electrocatalyst with unusual features, inCluding ligand-centered electron transfer and formation of post-transition metal hydride.Electrocatalytic hydrogen evolution with gallium hydride and ligand-centered reduction28201980#N/ATRUE
3576
c8sc04965c10.1039/c8sc04965cFALSEhttps://doi.org/10.1039/c8sc04965cAbe, HChem. Sci.Methane reforming at low temperatures is of growing importance to mitigate the environmental impact of the production of synthesis gas, but it suffers from short catalyst lifetimes due to the severe deposition of carbon byproducts. Herein, we introduce a new Class of topology-tailored catalyst in which tens-of-nanometer-thick fibrous networks of Ni metal and oxygen-deficient Y2O3 are entangled with each other to form a rooted structure, i.e., Ni#Y2O3. We demonstrate that the rooted Ni#Y2O3 catalyst stably promotes the carbon-dioxide reforming of methane at 723 K for over 1000 h, where the performance of traditional supported catalysts such as Ni/Y2O3 diminishes within 100 h due to the preCluded mass transport by accumulated carbon byproducts. In situ TEM demonstrates that the supported Ni nanopartiCles are readily detached from the support surface in the reaction atmosphere, and migrate around to result in widespread accumulation of the carbon byproducts. The long-term stable methane reforming over the rooted catalyst is ultimately attributed to the topologically immobilized Ni catalysis centre and the synergistic function of the oxygen-deficient Y2O3 matrix, which successfully inhibits the accumulation of byproducts.Topologically immobilized catalysis centre for long-term stable carbon dioxide reforming of methane15201943#N/ATRUE
3577
c8sc04500c10.1039/c8sc04500cFALSEhttps://doi.org/10.1039/c8sc04500cSproules, SChem. Sci.A bis(dithiolene) gold complex is presented as a model for an organic molecular electron spin qubit attached to a metallic surface that acts as a conduit to electrically address the qubit. A two-membered electron transfer series is developed of the formula [Au-III(adt)(2)](1-/0), where adt is a redox-active dithiolene ligand that is sequentially oxidized as the series is traversed while the central metal ion remains Au-III and steadfastly square planar. One-electron oxidation of diamagnetic [Au-III(adt)(2)](1-) (1) produces an S = 1/2 charge-neutral complex, [Au-III(adt(2)(3-center dot) c)] (2) which is spectroscopically and theoretically characterized with a near negligible Au contribution to the ground state. A phase memory time (T-M) of 21 mu s is recorded in 4 : 1 CS2/CCl4 at 10 K, which is the longest ever reported for a coordination complex possessing a thirdrow transition metal ion. With increasing temperature, T-M dramatically decreases becoming unmeasurable above 80 K as a consequence of the diminishing spin-lattice (T-1) relaxation time fueled by spin-orbit coupling. These relaxation times are 1-2 orders of magnitude shorter for the solid dilution of 2 in isoelectronic [Ni(adt)(2)] because this material is a molecular semiconductor. Although the conducting properties of this material provide efficient pathways to dissipate the energy through the lattice, it can also be used to electrically address the paramagnetic dopant by tapping into the mild reduction potential to switch magnetism on and off in the gold complex without compromising the integrity of its structure. These results serve to highlight the need to consider all components of these spintronic assemblies.Enabling single qubit addressability in a molecular semiconductor comprising gold-supported organic radicals7201997#N/ATRUE
3578
c8sc01704b10.1039/c8sc01704bhttps://doi.org/10.1039/c8sc01704bDixon, DJChem. Sci.A visible light mediated iridium photocatalysed reverse polarity Povarov reaction of Aryl imines and electron deficient alkenes is described. Operating via a putative nuCleophilic alpha-amino radical, generated by a proton coupled electron transfer process, addition to a range of conjugated electron deficient alkene substrates affords substituted tetrahydroquinoline products in high yields and with typically good to excellent diastereoselectivity in favor of the trans diastereoisomer. Sub-stoichiometric quantities of Hantzsch ester were found to be key to initiate the overall redox-neutral, free radical cyClization cascade. This new reaction complements existing two electron Lewis acid mediated variants and expands the capabilities of imine umpolung chemistry to synthetically relevant cyClisation methodology.Photocatalytic reverse polarity Povarov reactionPhotocatalyst25201856#N/AFALSE
3579
c8sc04346a10.1039/c8sc04346aFALSEhttps://doi.org/10.1039/c8sc04346aWang, WGChem. Sci.The synergism of the electronic properties of nickel and cobalt enables bimetallic NiCo complexes to process H-2. The nickel-cobalt hydride [(dppe)Ni(pdt)(H)CoCp*](+) ([1H](+)) arising from protonation of the reduced state 1 was found to be an efficient electrocatalyst for H-2 evolution with Cl2CHCOOH, and the oxidized [Ni(II)Co(III)](2+) form is capable of activating H-2 to produce [1H](+). The features of stereodynamics, acid-base properties, redox chemistry and reactivity of these bimetallic NiCo complexes in processing H-2 are potentially related to the active site of [NiFe]-H(2)ases.Bimetallic nickel-cobalt hydrides in H-2 Activation and catalytic proton reduction12201982#N/ATRUE
3580
c8sc04162h10.1039/c8sc04162hFALSEhttps://doi.org/10.1039/c8sc04162hFeng, CChem. Sci.We describe a nickel-catalyzed highly regio- and stereoselective migratory fluoro-alkenylation of unactivated Alkyl bromides. A unique catalytic cyCle merging Alkyl nickel chain-walking and defluorinative coupling enables the introduction of a broad array of fluoroalkenyl moieties into carbon chains. Control experiments with other halogenated alkenes demonstrated the essential role of fluorine atoms in this reaction. Notably, the reaction proceeds under mild conditions and allows for the synthesis of a variety of valuable monofluoroalkenes.Ni-catalyzed migratory fluoro-alkenylation of unactivated Alkyl bromides with gem-difluoroalkenes43201965#N/ATRUE
3581
c8sc03877e10.1039/c8sc03877eFALSEhttps://doi.org/10.1039/c8sc03877ePeng, YChem. Sci.Water electrolysis for hydrogen production has long been regarded as an ideal tactic for renewable energy conversion and storage, but is impeded by the sluggish kinetics of both the hydrogen and oxygen evolution reactions, which are therefore in urgent need for high-performance but low-cost electrocatalysts. Herein, nanoframes of transition metal phosphides (TMPs) with the 3D framework carved open have been demonstrated as highly potent bifunctional catalysts for overall water splitting, reaching the benchmark performance of the Pt/CRuO2 couple, and are much superior to their nanocubic counterparts. This excellent water splitting behavior can be attributed to the enlarged active surface area, less obstructed electrolyte infiltration, promoted charge transfer, and facilitated gas release. Further through in-depth activity analysis and post-electrocatalysis characterization, special attention has been paid to the fate and role of phosphorus in the electrocatalytic process, suggesting that despite the chemical instability of the TMPs (especially under OER conditions), excellent electrocatalytic stability can still be achieved through the amorphous bimetallic hydroxides/oxides formed in situ.Carved nanoframes of cobalt-iron bimetal phosphide as a bifunctional electrocatalyst for efficient overall water splitting116201981#N/ATRUE
3582
c8sc01353e10.1039/c8sc01353eFALSEhttps://doi.org/10.1039/c8sc01353eAnanikov, VPChem. Sci.Numerous reactions are catalyzed by complexes of metals (M) with N-heterocyClic carbene (NHC) ligands, typically in the presence of oxygen bases, which significantly shape the performance. It is generally accepted that bases are required for either substrate Activation (exemplified by transmetallation in the Suzuki cross-coupling), or HX capture (e.g. in a variety of C-C and C-heteroatom couplings, the Heck reaction, C-H functionalization, heterocyClizations, etc.). This study gives insights into the behavior of M(II)/NHC (M = Pd, Pt, Ni) complexes in solution under the action of bases conventionally engaged in catalysis (KOH, NaOH, t-BuOK, Cs2CO3, K2CO3, etc.). A previously unaddressed transformation of M(II)/NHC complexes under conditions of typical base-mediated M/NHC catalyzed reactions is disClosed. Pd(II) and Pt(II) complexes widely used in catalysis react with the bases to give M(0) species and 2(5)-oxo-substituted azoles via an O-NHC coupling mechanism. Ni(NHC)(2)X-2 complexes hydrolyze in the presence of aqueous potassium hydroxide, and undergo the same O-NHC coupling to give azolones and metallic nickel under the action of t-BuOK under anhydrous conditions. The study reveals a new role of NHC ligands as intramolecular reducing agents for the transformation of M(II) into ligandless M(0) species. This demonstrates that the disClosed base-mediated O-NHC coupling reaction is integrated into the catalytic M/NHC systems and can define the mechanism of catalysis (molecular M/NHC vs. NHC-free cocktail-type catalysis). A proposed mechanism of the revealed transformation inCludes NHC-OR reductive elimination, as implied by a series of mechanistic studies inCluding O-18 labeling experiments.Revealing the unusual role of bases in Activation/deActivation of catalytic systems: O-NHC coupling in M/NHC catalysisx28201882#N/AFALSE
3583
c8sc01219a10.1039/c8sc01219ahttps://doi.org/10.1039/c8sc01219aGong, LA chiral nickel DBFOX complex as a bifunctional catalyst for visible-light-promoted asymmetric photoredox reactionsPhotocatalyst2018#N/AFALSE
3584
c8sc01209a10.1039/c8sc01209aFALSEhttps://doi.org/10.1039/c8sc01209aGhadwal, RSKekule diradicaloids derived from a Classical N-heterocyClic carbenex2018#N/AFALSE
3585
c8sc03385d10.1039/c8sc03385dFALSEhttps://doi.org/10.1039/c8sc03385dChen, JChem. Sci.Nickel-rich layered transition metal oxides are attractive cathode materials for rechargeable lithium-ion batteries but suffer from inherent structural and thermal instabilities that limit the deliverable capacity and cyCling performance on charging to a cutoff voltage above 4.3 V. Here we report LiNi0.90Co0.07Mg0.03O2 as a stable cathode material. The obtained LiNi0.90Co0.07Mg0.03O2 microspheres exhibit high capacity (228.3 mA h g(-1) at 0.1C) and remarkable cyClability (84.3% capacity retention after 300 cyCles). Combined X-ray diffraction and Cs-corrected microscopy reveal that Mg doping stabilizes the layered structure by suppressing Li/Ni cation mixing and Ni migration to interlayer Li slabs. Because of the pillar effect of Mg in Li sites, LiNi0.90Co0.07Mg0.03O2 shows decent thermal stability and small lattice variation until it is charged to 4.7 V, undergoing a H1-H2 phase transition without discernible formation of an unstable H3 phase. The results indicate that moderate Mg doping is a facile yet effective strategy to develop high-performance Ni-rich cathode materials.Stabilizing nickel-rich layered oxide cathodes by magnesium doping for rechargeable lithium-ion batteries77201955#N/ATRUE
3586
c8sc00990b10.1039/c8sc00990bhttps://doi.org/10.1039/c8sc00990bHammarstrom, LChem. Sci.Co-sensitization of molecular dyes and catalysts on semiconductor surfaces is a promising strategy to build photoelectrodes for solar fuel production. In such a photoelectrode, understanding the charge transfer reactions between the molecular dye, catalyst and semiconductor material is key to guide further improvement of their photocatalytic performance. Herein, femtosecond mid-infrared transient absorption spectroscopy is used, for the first time, to probe charge transfer reactions leading to catalyst reduction on co-sensitized nickel oxide (NiO) photocathodes. The NiO films were co-sensitized with a molecular dye and a proton reducing catalyst from the family of [FeFe](bdt)(CO)(6) (bdt = benzene-1,2-dithiolate) complexes. Two dyes were used: an organic push-pull dye denoted E2 with a triArylamine-oligothiophene-dicyanoVinyl structure and a coumarin 343 dye. Upon photo-excitation of the dye, a Clear spectroscopic signature of the reduced catalyst is observed a few picoseconds after excitation in all co-sensitized NiO films. However, kinetic analysis of the transient absorption signals of the dye and reduced catalyst reveal important mechanistic differences in the first reduction of the catalyst depending on the co-sensitized molecular dye (E2 or C343). While catalyst reduction is preceded by hole injection in NiO in C343-sensitized NiO films, the singly reduced catalyst is formed by direct electron transfer from the excited dye E2* to the catalyst in E2-sensitized NiO films. This change in mechanism also impacts the lifetime of the reduced catalyst, which is only ca. 50 ps in E2-sensitized NiO films but is >5 ns in C343-sensitized NiO films. Finally, the implication of this mechanistic study for the development of better co-sensitized photocathodes is discussed.Direct evidence of catalyst reduction on dye and catalyst co-sensitized NiO photocathodes by mid-infrared transient absorption spectroscopyPhotocatalystx18201827#N/AFALSE
3587
c8sc03321h10.1039/c8sc03321hFALSEhttps://doi.org/10.1039/c8sc03321hHarrop, TCChem. Sci.Nitric oxide (NO) is used as a substrate analogue/spectroscopic probe of metal sites that bind and activate oxygen and its derivatives. To assess the interaction of superoxide with the Ni center in Ni-containing superoxide dismutase (NiSOD), we studied the reaction of NO+ and NO with the model complex, Et4N [Ni(nmp)(SPh-o-NH2-p-CF3)] (1; nmp(2-) = dianion of N-(2-mercaptoethyl)picolinamide; -SPh-o-NH2-p-CF3 = 2-amino-4-(trifluoromethyl)benzenethiolate) and its oxidized analogue 1(ox), respectively. The ultimate products of these reactions are the disulfide of -SPh-o-NH2-p-CF3 and the S,S-bridged tetrameric complex [Ni-4(nmp)(4)], a result of S-based redox activity. However, introduction of NO to 1 affords the green dimeric {NiNO}(10) complex (Et4N)(2)[{Ni(kappa(2)-SPh-o-NNO-p-CF3)(NO)}(2)] (2) via NO-induced loss of nmp(2-) as the disulfide and N-nitrosation of the aromatic thiolate. Complex 2 was characterized by X-ray crystallography and several spectroscopies. These measurements are in-line with other tetrahedral complexes in the {NiNO}(10) Classification. In contrast to the established stability of this metal-nitrosyl Class, the Ni-NO bond of 2 is labile and release of NO from this unit was quantified by trapping the NO with a Co-II-porphyrin (70-80% yield). In the process, the Ni ends up coordinated by two o-nitrosaminobenzenethiolato ligands to result in the structurally characterized trans-(Et4N)(2)[Ni(SPh-o-NNO-p-CF3)(2)] (3), likely by a disproportionation mechanism. The isolation and characterization of 2 and 3 suggest that: (i) the strongly donating thiolates dominate the electronic structure of Ni-nitrosyls that result in less covalent Ni-NO bonds, and (ii) superoxide undergoes disproportionation via an outer-sphere mechanism in NiSOD as complexes in the {NiNO}(9/8) state have yet to be isolated.Simultaneous nitrosylation and N-nitrosation of a Ni-thiolate model complex of Ni-containing SOD2201885#N/ATRUE
3588
c8sc00833g10.1039/c8sc00833gFALSEhttps://doi.org/10.1039/c8sc00833gJia, DZChem. Sci.A novel single organic molecule-carborane conjugate, CAN, was synthesized in a high yield via a modified nickel-catalyzed cross-coupling reaction incorporating an anthracene unit and an o-carborane moiety. CAN exhibits multiple functions of tricolored mechanochromism and mechanically triggered thermochromism. The fluorescence could be switched from blue to bright yellow then to pink by grinding. The robust and reversible thermochromic process was triggered by the mechanical force. The locally excited (LE) state emission, intermolecular excimer formation and twisted intermolecular charge transfer (TICT) are the primary origins of this tricolor switching property. High temperature sensitivity of the heavily ground CAN powders contribute to the mechanical force induced TICT emission enhancement and color switching.Mechanically triggered reversible stepwise tricolor switching and thermochromism of anthracene-o-carborane dyadx73201852#N/AFALSE
3589
c8sc00742j10.1039/c8sc00742jFALSEhttps://doi.org/10.1039/c8sc00742jDyson, PJChem. Sci.Bimetallic Ru-Ni and Rh-Ni nanocatalysts coated with a phase transfer agent efficiently Cleave Aryl ether C-O linkages in water in the presence of hydrogen. For dimeric substrates with weaker C-O linkages, i.e. alpha-O-4 and beta-O-4 bonds, low loadings of the precious metal (Rh or Ru) in the nanocatalysts quantitatively afford monomers, whereas for the stronger 4-O-5 linkage higher amounts of the precious metal are required to achieve complete conversion. Under the optimized, relatively mild operating conditions, the C-O bonds in a range of substituted ether compounds are efficiently Cleaved, and mechanistic insights into the reaction pathways are provided. This work paves the way to sustainable approaches for the hydrogenolysis of C-O bonds.Efficient Cleavage of Aryl ether C-O linkages by Rh-Ni and Ru-Ni nanoscale catalysts operating in waterx32201869#N/AFALSE
3590
c8sc03193b10.1039/c8sc03193bFALSEhttps://doi.org/10.1039/c8sc03193bZheng, ZPMerohedral icosahedral M-48 (M = Co-II, Ni-II) cage Clusters supported by thiacalix[4]arene2018#N/ATRUE
3591
c8sc00420j10.1039/c8sc00420jhttps://doi.org/10.1039/c8sc00420jTeranishi, TChem. Sci.The high overpotential of the oxygen evolution reaction is a critical issue to be overcome to realize efficient overall water splitting and enable hydrogen generation powered by sunlight. Homogeneous and stable nanopartiCles (NPs) dispersed in solvents are useful as both electrocatalysts and cocatalysts of photocatalysts for the electro- and photo-catalytic oxygen evolution reaction, respectively, through their adsorption on various electrode substrates. Here, phase-segregated NiPx@FePyOz core@shell NPs are selectively synthesized by the reaction of Fe(CO)(5) with amorphous NiPx seed-NPs. The NiPx@FePyOz NPs on conductive substrates exhibit higher electrocatalytic activity in the oxygen evolution reaction than those of other metal phosphide-based catalysts. The NiPx@FePyOz NPs can also be used as a cocatalyst of an anodic BiVO4 photocatalyst to boost the photocatalytic water oxidation reaction. The excellent catalytic activity and high stability of the NiPx@FePyOz NPs without any post-treatments are derived from in situ Activation through both the structural transformation of NiPx@FePyOz into mixed hydroxide species, (Ni, Fe)OxHy, and the spontaneous removal of the insulating organic ligands from NPs to form a smooth and robust (Ni, Fe)OxHy/substrate heterointerface during the oxygen evolution reaction.Phase-segregated NiPx@FePyOz core@shell nanopartiCles: ready-to-use nanocatalysts for electro- and photo-catalytic water oxidation through in situ Activation by structural transformation and spontaneous ligand removalPhotocatalyst11201842#N/AFALSE
3592
c8sc00203g10.1039/c8sc00203gFALSEhttps://doi.org/10.1039/c8sc00203gGong, JLChem. Sci.La2O3 exhibits good performance for various catalytic applications, such as oxidative coupling of methane (OCM) and dry reforming of methane (DRM), during which coke formation may lead to the deActivation of catalysts. Typically, the reaction between CO2 adsorbed on La2O3 and coke is the rate-determining step of the coke elimination process. This paper describes the influence of Ce addition on the CO2 adsorption and Activation over La2O3. Combined with in situ and ex situ characterization and density functional theory (DFT) calculation, we show that Ce addition promotes the formation of bidentate carbonate on La2O3 via tuning CO2 adsorption energy. In addition, Ce addition adjusts the ratio of bidentate/monodentate carbonate, and affects the ratio of hexagonal/monoClinic La2O2CO3 on the binary oxides. DRM is used as a probe reaction to examine the coke elimination performance of Ce-La binary oxide. It is found that when the Ce/La ratio reaches the optimal value (0.15), Ce-La binary oxide has the highest CO2 adsorption energy and predominantly promotes the formation of bidentate carbonate, and hence possesses the highest basicity above 700 degrees C and finally exhibits the best coke elimination performance.On the role of Ce in CO2 adsorption and Activation over lanthanum speciesx21201871#N/AFALSE
3593
c8sc02536c10.1039/c8sc02536cFALSEhttps://doi.org/10.1039/c8sc02536cHayton, TWChem. Sci.The thiohyponitrite ([SNNO](2-)) complex, [K(18-crown-6)][(LNiII)-Ni-tBu(kappa(2)-SNNO)] (L-tBu = {(2,6-(Pr2C6H3)-Pr-i)NC(Bu-t)}(2)CH), extrudes N-2 under mild heating to yield [K(18-crown-6)][(LNiII)-Ni-tBu(eta(2)-SO)] (1), along with minor products [K(18-crown-6)][(LNiII)-Ni-tBu(eta(2)-OSSO)] (2) and [K(18-crown-6)][(LNiII)-Ni-tBu(eta(2)-S-2)] (3). Subsequent reaction of 1 with carbon monoxide (CO) results in the formation of [K(18-crown-6)][(LNiII)-Ni-tBu(eta(2)-SCO)] (4), [K(18-crown-6)][(LNiII)-Ni-tBu(S,O:kappa(2)-SCO2)] (5), [K(18-crown-6)][(LNiII)-Ni-tBu(kappa(2)-CO3)] (6), Carbonyl sulfide (COS) (7), and [K(18-crown-6)][(LNiII)-Ni-tBu(S2CO)] (8). To rationalize the formation of these products we propose that 1 first reacts with CO to form [K(18-crown-6)][(LNiII)-Ni-tBu(S)] (I) and CO2, via O-atom abstraction. Subsequently, complex I reacts with CO or CO2 to form 4 and 5, respectively. Similarly, the formation of complex 6 and COS can be rationalized by the reaction of 1 with CO2 to form a putative Ni(II) monothiopercarbonate, [K(18-crown-6)][(LNiII)-Ni-tBu(kappa(2)-SOCO2)] (11). The Ni(II) monothiopercarbonate subsequently transfers a S-atom to CO to form COS and [K(18-crown-6)][(LNiII)-Ni-tBu(kappa(2)-CO3)] (6). Finally, the formation of 8 can be rationalized by the reaction of COS with I. Critically, the observation of complexes 4 and 5 in the reaction mixture reveals the stepwise conversion of [K(18-crown-6)][(LNiII)-Ni-tBu(kappa(2)-SNNO)] to 1 and then I, which represents the formal reduction of N2O by CO.Synthesis and reactivity of a nickel(II) thioperoxide complex: demonstration of sulfide-mediated N2O reduction12201877#N/ATRUE
3594
c8sc02101e10.1039/c8sc02101eFALSEZhou, QLNickel(0)-catalyzed linear-selective hydroArylation of unactivated alkenes and styrenes with Aryl boronic acids2018#N/ATRUE
3595
c8sc02015a10.1039/c8sc02015aFALSEhttps://doi.org/10.1039/c8sc02015aLiu, ZPAccelerated active phase transformation of NiO powered by Pt single atoms for enhanced oxygen evolution reaction2018#N/ATRUE
3596
c8cc08511k10.1039/c8cc08511kFALSEhttps://doi.org/10.1039/c8cc08511kDing, YAmorphous Ni-Fe double hydroxide hollow nanocubes enriched with oxygen vacancies as efficient electrocatalytic water oxidation catalystsx2019#N/AFALSE
3597
c8cc08251k10.1039/c8cc08251kFALSEFeng, LGA comparative study of NiCo2O4 catalyst supported on Ni foam and from solution residuals fabricated by a hydrothermal approach for electrochemical oxygen evolution reactionx2018#N/AFALSE
3598
c8cc08146h10.1039/c8cc08146hhttps://doi.org/10.1039/c8cc08146hShen, MRA porous Ni-O/Ni/Si photoanode for stable and efficient photoelectrochemical water splittingPhotocatalyst2019#N/AFALSE
3599
c8sc01949e10.1039/c8sc01949eFALSEhttps://doi.org/10.1039/c8sc01949eCorminboeuf, CChem. Sci.The application of modern machine learning to challenges in atomistic simulation is gaining attraction. We present new machine learning models that can predict the energy of the oxidative addition process between a transition metal complex and a substrate for C-C cross-coupling reactions. In turn, this quantity can be used as a descriptor to estimate the activity of homogeneous catalysts using molecular volcano plots. The versatility of this approach is illustrated for vast libraries of organometallic catalysts based on Pt, Pd, Ni, Cu, Ag, and Au combined with 91 ligands. Out-of-sample machine learning predictions were made on a total of 18062 compounds leading to 557 catalyst candidates falling into the ideal thermodynamic window. This number was further refined by searching for candidates with an estimated price lower than 10 US$ per mmol. The 37 catalyst finalists are dominated by palladium phosphine ligand combinations but also inClude the earth abundant transition metal (Cu) with less common ligands. Our results indicate that modern statistical learning techniques can be applied to the computational discovery of readily available and promising catalyst candidates.Machine learning meets volcano plots: computational discovery of cross-coupling catalysts732018135#N/ATRUE
3600
c8sc01735b10.1039/c8sc01735bFALSEhttps://doi.org/10.1039/c8sc01735bEngle, KMChem. Sci.A nickel-catalyzed conjunctive cross-coupling of non-conjugated alkenes, Alkyl halides, and Alkylzinc reagents is reported. Regioselectivity is controlled by chelation of a removable bidentate 8-aminoquinoline directing group. Under optimized conditions, a wide range of 1,2-diAlkylated products can be accessed in moderate to excellent yields. To the best of our knowledge, this report represents the first example of three-component 1,2-diAlkylation of non-conjugated alkenes to introduce differentiated Alkyl fragments.Directed nickel-catalyzed 1,2-diAlkylation of alkenyl Carbonyl compounds74201846#N/ATRUE
3601
c8cc06099a10.1039/c8cc06099aFALSEhttps://doi.org/10.1002/chem.201900822Fu, HG2-D porous Ni3N-Co3N hybrids derived from ZIF-67/Ni(OH)(2) sheets as a magnetically separable catalyst for hydrogenation reactionsx2018#N/AFALSE
3602
c8cc03589j10.1039/c8cc03589jFALSEhttps://doi.org/10.1039/c8cc03589jXue, ZLUnusual rearrangement of an N-heterocyClic carbene via a ring-opening and ring-Closing processx2018#N/AFALSE
3603
c8sc01580e10.1039/c8sc01580eFALSEZare, RNPreparative microdroplet synthesis of Carbonylic acids from aerobic oxidation of aldehydes2018#N/ATRUE
3604
c8sc01533c10.1039/c8sc01533cFALSEhttps://doi.org/10.1039/c8sc01533cStock, NChem. Sci.The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H8TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr4+ and Hf4+. The compounds were thoroughly characterized regarding their sorption properties towards N-2 and H2O as well as thermal and chemical stability. During the synthesis optimization the reaction time could be substantially decreased under stirring from 24 to 3 h in glass vials. M-CAU-30, [M-2(Ni-H2TPPP)(OH/F)(2)]H2O (M = Zr, Hf) shows exceptionally high specific surface areas for metal phosphonates of a(BET) = 1070 and 1030 m(2) g(-1) for Zr- and Hf-CAU-30, respectively, which are very Close/correspond to the theoretical values of 1180 and 1030 m(2) g(-1). CAU-30 is always obtained as mixtures with one mol ZrO2/HfO2 per formula unit as proven by TEM, electron diffraction, TG and elemental analysis. Hence experimentally derived specific surface areas are 970 and 910 m(2) g(-1), respectively. M-CAU-30 is chemically stable in the pH range 0 to 12 in HCl/NaOH and thermally up to 420 degrees C in air as determined by variable-temperature powder X-ray diffraction (VT-PXRD). The crystal structure of M-CAU-30 was determined by combining electron diffraction tomography for structure solution and powder X-ray diffraction data for the structure refinement. The crystal structure consists of chains of corner sharing MO6 octahedra interconnected by the partly deprotonated linker molecules Ni-H2TPPP6-. Thus 1D channels with pore diameters of 1.3 x 2.0 nm are formed. The redox activity of Zr-CAU-30 was investigated by cyClic voltammetry resulting in a reversible redox process at a half-wave potential of E-1/2 = -0.649 V.Highly stable and porous porphyrin-based zirconium and hafnium phosphonates - electron crystallography as an important tool for structure elucidation44201875#N/ATRUE
3605
c8cc00271a10.1039/c8cc00271aFALSEhttps://doi.org/10.1039/c8cc00271aSzostak, MDeCarbonylative thioetherification by nickel catalysis using air- and moisture-stable nickel precatalystsx2018#N/AFALSE
3606
c8sc01358f10.1039/c8sc01358fFALSEhttps://doi.org/10.1039/c8sc01358fTseng, PKChem. Sci.Bimetallic Pt-Ni with Pt on the outermost layer and an innermost layer enriched in Ni, referred to as Pt3Ni(Pt-skin), is a promising configuration of an electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells. We prepare a core (Pd)/shell (Pt3Ni(Pt-skin)) catalyst (Pt3Ni(Pt-skin)/Pd/C) from Zn underpotential deposition (UPD) on a Ni UPD modified Pd/C catalyst, facilitating Pt atomic layer-by-layer growth on the Ni surface through the galvanic replacement process. Pt3Ni(Pt-skin)/Pd/C shows the best ORR performance, with a Pt specific activity of 16.7 mA cm(-2) and Pt mass activity of 14.2 A mg(Pt)(-1), which are 90- and 156- fold improvements over commercial Pt/C catalysts. The Pt3Ni(Pt-skin) structure effectively inhibits Ni leaching to improve the durability in two accelerated durability test modes mimicking the catalyst lifetime and start-up/shut-down cyCles.High performance layer-by-layer Pt3Ni(Pt-skin)-modified Pd/C for the oxygen reduction reaction15201865#N/ATRUE
3607
c7sc05395a10.1039/c7sc05395aFALSEhttps://doi.org/10.1039/c7sc05395aManners, IChem. Sci.Precatalysts active for the dehydropolymerisation of primary amine-boranes are generally based on mid or late transition metal. We have found that the activity of the precatalyst system formed from (Cp2TiCl2)-Ti-R and 2nBuLi towards the dehydrogenation of the secondary amine-borane Me2NH center dot BH3, to yield the cyClic diborazane [Me2N-BH2](2), increases dramatically with increasing electron-donating character of the cyClopentadienyl rings (Cp-R). Application of the most active precatalyst system (Cp-R = eta-C5Me5) to the primary amine-borane MeNH2 center dot BH3 enabled the first synthesis of high molar mass poly(N-methylaminB(OH)2rane), [MeNH-BH2](n), the BN analogue of polypropylene, by an early transition metal such as catalyst. Significantly, unlike other dehydropolymerization precatalysts for MeNH2 center dot BH3 such as [Ir(POCOP)H-2], skeletal nickel, and [Rh(COD)Cl](2), the Ti precatalyst system was also active towards a range of substrates inCluding BzNH(2)center dot BH3 (Bz = Benzyl) yielding high molar mass polymer. Moreover, in contrast to the late transition metal catalysed dehydropolymerisation of MeNH2 center dot BH3 and also the Ziegler-Natta polymerisation of olefins, studies indicate that the Ti-catalyzed dehydropolymerization reactions proceed by a step-growth rather than a chain-growth mechanism.Step-growth titanium-catalysed dehydropolymerisation of amine-boranesx19201876#N/AFALSE
3608
c7sc05320g10.1039/c7sc05320ghttps://doi.org/10.1039/c7sc05320gHess, CRChem. Sci.We present a late, first row transition metal photosensitizer that promotes photocatalytic C-C bond formation. The title compound, [Ni(Mabiq)] OTf, as well as its one-electron reduced form, Ni(Mabiq), were synthesized and molecular structures of both were obtained. The electronic structure of the reduced complex additionally was characterized by spectroscopic and DFT computational methods. Notably, [Ni-II(Mabiq)] OTf is photoactive: reduction of the compound was achieved photochemically upon irradiation at lambda = 457 nm and reductive quenching by NEt3. The performance of [Ni(Mabiq)] OTf as a photoredox catalyst was examined in the cyClization of a bromoAlkyl-substituted indole. In this reaction, the first-row transition metal compound is comparable if not superior to [Ru(bpy)3](2+) in terms of efficiency (turnover number) and chemoselectivity. Studies using a series of sacrificial donor amines indicate that the excited state redox potential of [Ni(Mabiq)]+* is >= 1.25 V vs. SCE. This value is similar to the excited state potential of commonly employed noble metal based photocatalysts. The Ni-Mabiq compound thus provides a rare example of an earth-abundant photoredox catalyst.Redox and photocatalytic properties of a Ni-II complex with a macrocyClic biquinazoline (Mabiq) ligandPhotocatalyst21201845#N/AFALSE
3609
c8sc01114a10.1039/c8sc01114aFALSEhttps://doi.org/10.1039/c8sc01114aTsang, SCEChem. Sci.Surface sites of extensively exposed basal planes of MoS2 monolayer nanosheets, prepared via BuLi exfoliation of MoS2, have been doped with transition metal atoms for the first time to produce 2D monolayer catalysts used for the electrochemical hydrogen evolution reaction (HER). Their HER activity is significantly higher than the corresponding thin and bulk MoS2 layers. HAADF-STEM images show direct proof that single transition metal atoms reside at the surface basal sites, which subtly modify the electro-catalytic activity of the monolayer MoS2, dependent on their electronic and stereospecific properties. It is found that these dopants play an important role in tuning the hydrogen adsorption enthalpies of the exposed surface S atoms and Mo atoms in HER. We report electrochemical testing, characterization and computational modelling and demonstrate that Co can significantly enhance the HER activity by the dominant Co-S interaction, whereas Ni substantially lowers the HER rate due to the Ni-Mo interaction at the same basal site. The two transition metal dopants show opposite doping behavior despite the fact that they are neighbors in the periodic table.Transition metal atom doping of the basal plane of MoS2 monolayer nanosheets for electrochemical hydrogen evolution92201840#N/ATRUE
3610
c8sc00890f10.1039/c8sc00890fFALSEhttps://doi.org/10.1039/c8sc00890fPerutz, RNChem. Sci.The syntheses of three series of complexes designed with self-complementary motifs for formation of halogen bonds between an iodotetrafluorophenyl ligand and a halide ligand at square-planar nickel are reported, allowing structural comparisons of halogen bonding between all four halides C6F4I center dot center dot center dot X-Ni (X = F, Cl, Br, I). In the series trans-[NiX(2,3,5,6-C6F4I)(PEt3)(2)] 1pX and trans-[NiX(2,3,4,5-C6F4I)(PEt3)(2)] (X = F, Cl, Br, I) 1oX, the iodine substituent on the benzene ring was positioned para and ortho to the metal, respectively. The phosphine substituents were varied in the series, trans-[NiX(2,3,5,6-C6F4I)(PEt2Ph)(2)] (X = F, I) 2pX. Crystal structures were obtained for the complete series 1pX, and for 1oF, 1oCl, 1oI and 2pI. All these complexes exhibited halogen bonds in the solid state, of which 1pF exhibited unique characteristics with a linear chain, the shortest halogen bond d(C6F4I center dot center dot center dot F-Ni) = 2.655(5) angstrom and the greatest reduction in halogen bond distance (I center dot center dot center dot F) compared to the sum of the Bondi van der Waals radii, 23%. The remaining complexes form zig-zag chains of halogen bonds with distances also reduced with respect to the sum of the van der Waals radii. The magnitude of the reductions follow the pattern F > Cl similar to Br > I, 1pX > 1oX, consistent with the halogen bond strength following the same order. The variation in the I center dot center dot center dot X-Ni angles is consistent with the anisotropic charge distribution of the halide ligand. The temperature dependence of the X-ray structure of 1pF revealed a reduction in halogen bond distance of 0.055(7) angstrom on cooling from 240 to 111 K. Comparison of three polymorphs of 1oI shows that the halogen bond geometry may be altered significantly by the crystalline environment. The effect of the halogen bond on the F-19 NMR chemical shift in the solid state is demonstrated by comparison of the magic-angle spinning NMR spectra of 1pF and 1oF with that of a complex incapable of halogen bond formation, trans-[NiF(C6F5)(PEt3)(2)] 3F. Halogen bonding causes deshielding of delta(iso) in the component of the tensor perpendicular to the nickel coordination plane. The results demonstrate the potential of fluoride ligands for formation of halogen bonds in supramolecular structures.Self-complementary nickel halides enable multifaceted comparisons of intermolecular halogen bonds: fluoride ligands vs. other halides21201877#N/ATRUE
3611
c8sc00604k10.1039/c8sc00604kFALSEhttps://doi.org/10.1039/c8sc00604kNakanishi, SChem. Sci.The electrochemical reduction of carbon dioxide (CO2) has attracted considerable attention as a means of maintaining the carbon cyCle. This process still suffers from poor performance, inCluding low faradaic efficiencies and high overpotential. Herein, we attempted to use coordination number as a control parameter to improve the electrocatalytic performance of metal species that have previously been thought to have no CO2 reduction activity. Covalent triazine frameworks (CTF) modified with coordinatively-unsaturated 3d metal atoms (Co, Ni or Cu) were developed for efficient electroreduction of CO2. Co-CTF and Ni-CTF materials effectively reduced CO2 to CO from -0.5 V versus RHE. The faradaic efficiency of the Ni-CTF during CO formation reached 90% at -0.8 V versus RHE. The performance of Ni-CTF is much higher than that of the corresponding metal-porphyrin (using tetraphenylporphyrin; TPP). First principles calculations demonstrated that the intermediate species (adsorbed COOH) was stabilized on the metal atoms in the CTF due to the low-coordination structure of this support. Thus, the free energy barriers for the formation of adsorbed COOH on the metal atoms in the CTF supports were lower than those on the TPP supports.Covalent triazine framework modified with coordinatively-unsaturated Co or Ni atoms for CO2 electrochemical reduction90201848#N/ATRUE
3612
c8sc00093j10.1039/c8sc00093jFALSEhttps://doi.org/10.1039/c8sc00093jVillagran, DChem. Sci.Free-base meso-tetra(pentafluorophenyl)porphyrin, 1, is electrocatalytically active for hydrogen gas generation in the presence of p-toluenesulfonic acid. The electrochemical potential of hydrogen evolution (-1.31 V vs. Fc/Fc(+) in THF) is comparable to those of metal containing electrocatalysts such as metallated porphyrins or other metallated macrocyCles. Combining experimental observations and DFT computations, we propose the most favorable hydrogen generation mechanism to be a (1) reduction, (2) protonation, (3) reduction, (4) protonation (E-P-E-P) pathway.Hydrogen gas generation using a metal-free fluorinated porphyrin20201850#N/ATRUE
3613
c8cc08929a10.1039/c8cc08929aFALSEhttps://doi.org/10.1039/c8cc08929aMazaki, YStereogenic cyClic oligonaphthalenes displaying ring size-dependent handedness of circularly polarized luminescence (CPL)2019#N/ATRUE
3614
c8cc08876d10.1039/c8cc08876dFALSEHayashi, TElectrochemical CO2 reduction by a cobalt bipyricorrole complex: decrease of an overpotential value derived from monoanionic ligand character of the porphyrinoid species2019#N/ATRUE
3615
c7sc04604a10.1039/c7sc04604aFALSEhttps://doi.org/10.1039/c7sc04604aMusaev, DGChem. Sci.The density functional theory method is used to elucidate the elementary steps of Ni(II)-catalyzed C(sp(2))-H iodination with I-2 and substrates bearing N, N'-bidentate directing centers, amide-oxazoline (AO) and 8-aminoquinoline (AQ). The relative stability of the lowest energy high-and low-spin electronic states of the catalyst and intermediates is found to be an important factor for all of the steps in the reaction. As a result, two-state reactivity for these systems is reported, where the reaction is initiated on the triplet surface and generates a high energy singlet nickelacyCle. It is shown that the addition of Na2CO3 base to the reaction mixture facilitates C-H Activation. The presence of I-2 in the reaction provides the much needed driving force for the C-H Activation and nickelacyCle formation and ultimately reacts to form a new C-I bond through either a redox neutral electrophilic Cleavage (EC) pathway or a one-electron reductive Cleavage (REC) pathway. The previously proposed Ni(II)/Ni(IV) and homolytic Cleavage pathways are found to be higher in energy. The nature of the substrate is found to have a large impact on the relative stability of the lowest electronic states and on the stability of the nickelacyCle resulting from C-H Activation.The mechanism of directed Ni(II)-catalyzed C-H iodination with molecular iodinex232018103#N/AFALSE
3616
c8cc07467d10.1039/c8cc07467dFALSEhttps://doi.org/10.1002/chem.201704027Sakai, KA family of molecular nickel hydrogen evolution catalysts providing tunable overpotentials using ligand-centered proton-coupled electron transfer paths2018#N/ATRUE
3617
c7sc04482h10.1039/c7sc04482hFALSEhttps://doi.org/10.1039/c7sc04482hShores, MPChem. Sci.Herein we report the first examples of single-molecule magnet (SMM) behaviour in S = 1/2 Ni(III) complexes. We find that low-spin 3d(7)trans-[Ni-III(cyClam)(X)(2)]Y complexes (cyClam = 1,4,8,11-tetraazacyClotetradecane; X and Y are singly charged anions) exhibit field-induced slow relaxation of magnetization for O-donor axial ligands (nitrate) but not for N-donor variants (isothiocyanate). Experimental and electronic structure computational investigations indicate that intrinsic spin polarisation of low-spin Ni(III) is modulated significantly by local coordination geometry and supramolecular interactions. Solid state dilution of Ni(III) with diamagnetic Co(III) ions forms a related complex salt, [NixCo1 (-x)(cyClam)(NO3)(2)](NO3)center dot 2HNO(3) (0.1 < x < 1), which preserves slow magnetic dynamics, thus supporting a molecular component to slow relaxation. An initial analysis of magnetic relaxation lifetime fits best to a combination of Raman and direct relaxation processes.Slow magnetic relaxation in octahedral low-spin Ni(III) complexesx20201852#N/AFALSE
3618
c7sc04476c10.1039/c7sc04476chttps://doi.org/10.1039/c7sc04476cReisner, EChem. Sci.Dye-sensitised photoelectrochemical (DSPEC) cells have emerged in recent years as a route to solar fuel production. However, fuel-forming photocathodes are presently limited by photo-corrodible narrow band gap semiconductors or the small range of available wide bandgap p-type semiconductors such as NiO that display low performance with dyes. Here, we introduce CuCrO2 as a suitable p-type semiconductor for visible light-driven H-2 generation upon co-immobilisation of a phosphonated diketopyrrolopyrrole dye with a Ni-bis(diphosphine) catalyst. The hybrid CuCrO2 photocathode displays an early photocurrent onset potential of +0.75 V vs. RHE and delivers a photocurrent of 15 mu A cm(-2) at 0.0 V vs. RHE in pH 3 aqueous electrolyte solution under UV-filtered simulated solar irradiation. Controlled potential photoelectrolysis at 0.0 V vs. RHE shows good stability and yields a Ni catalystbased turnover number of 126 +/- 13 towards H-2 after 2 h. This precious metal-free system outperforms an analogous NiO|dye/catalyst assembly and therefore highlights the benefits of using CuCrO2 as a novel material for DSPEC applications.Solar H-2 generation in water with a CuCrO2 photocathode modified with an organic dye and molecular Ni catalystPhotocatalyst37201891#N/AFALSE
3619
c7sc04460g10.1039/c7sc04460gFALSEhttps://doi.org/10.1039/c7sc04460gMurrie, MChem. Sci.Understanding and controlling magnetic anisotropy at the level of a single metal ion is vital if the miniaturisation of data storage is to continue to evolve into transformative technologies. Magnetic anisotropy is essential for a molecule-based magnetic memory as it pins the magnetic moment of a metal ion along the easy axis. Devices will require deposition of magnetic molecules on surfaces, where changes in molecular structure can significantly alter magnetic properties. Furthermore, if we are to use coordination complexes with high magnetic anisotropy as building blocks for larger systems we need to know how magnetic anisotropy is affected by structural distortions. Here we study a trigonal bipyramidal nickel(II) complex where a giant magnetic anisotropy of several hundred wavenumbers can be engineered. By using high pressure, we show how the magnetic anisotropy is strongly influenced by small structural distortions. Using a combination of high pressure X-ray diffraction, ab initio methods and high pressure magnetic measurements, we find that hydrostatic pressure lowers both the trigonal symmetry and axial anisotropy, while increasing the rhombic anisotropy. The ligand-metal-ligand angles in the equatorial plane are found to play a crucial role in tuning the energy separation between the d(x2-y2) and d(xy) orbitals, which is the determining factor that controls the magnitude of the axial anisotropy. These results demonstrate that the combination of high pressure techniques with ab initio studies is a powerful tool that gives a unique insight into the design of systems that show giant magnetic anisotropy.Probing the origin of the giant magnetic anisotropy in trigonal bipyramidal Ni(II) under high pressurex35201852#N/AFALSE
3620
c8cc06331a10.1039/c8cc06331aFALSELu, LMEnhanced electrocatalysis for alkaline hydrogen evolution by Mn doping in a Ni3S2 nanosheet array2018#N/ATRUE
3621
c7sc04292b10.1039/c7sc04292bhttps://doi.org/10.1039/c7sc04292bMolander, GAScalable thioArylation of unprotected peptides and biomolecules under Ni/photoredox catalysisPhotocatalyst2018#N/AFALSE
3622
c7sc03928j10.1039/c7sc03928jhttps://doi.org/10.1039/c7sc03928jPeng, ZJChem. Sci.Co-catalysis is regarded as a promising strategy to improve the hydrogen evolution performance of semiconductor-based photocatalysts. But developing a simple and effective technique to achieve the optimal synergy between co-catalysts and host photocatalysts has been a great challenge. Herein, hybrid photocatalysts consisting of beta-NiS modified CdS nanowires (NiS/CdS NWs) have been synthesized via a simple and green hydrothermal route using CdS NWs as the template from thiourea and nickel acetate in the presence of sodium hypophosphite. As a result, a metal Ni intermediate was formed via an electroless plating process assisted by H2PO2-, which facilitated the growth of highly conducting flake like beta-NiS nanostructures onto the surface of the CdS NWs. With the optimal loading amount of NiS, the obtained NiS/CdS NWs present a record-high photocatalytic activity for H-2 evolution in lactic acid aqueous solutions under visible light irradiation. At 25 degrees C, the rate of H-2 evolution was measured as 793.6 mu mol h(-1) (over a 5 mg photocatalyst sample), which is nearly 250-fold higher than that over pure CdS NWs, and the apparent quantum yield reached an exceptionally high value of 74.1% at 420 nm. The mechanism for the photocatalytic H-2 evolution over the present NiS/CdS NWs was also proposed. This strategy would provide new insight into the design and development of high-performance heterostructured photocatalysts.beta-NiS modified CdS nanowires for photocatalytic H-2 evolution with exceptionally high efficiencyPhotocatalystx66201845#N/AFALSE
3623
c8cc02487a10.1039/c8cc02487aFALSEhttps://doi.org/10.1039/c8cc02487aFarras, PProduction of solar chemicals: gaining selectivity with hybrid molecule/semiconductor assemblies2018#N/ATRUE
3624
c8cc01374h10.1039/c8cc01374hFALSEhttps://doi.org/10.1039/c8cc01374hLescouezec, RA [Fe-III(Tp)(CN)(3)](-) scorpionate-based complex as a building block for designing ion storage hosts (Tp: hydrotrispyrazolylborate)2018#N/ATRUE
3625
c7sc02692g10.1039/c7sc02692ghttps://doi.org/10.1039/c7sc02692gSzostak, MChem. Sci.The Suzuki-Miyaura cross-coupling has been widely recognized as one of the most important methods for the construction of C-C bonds. However, in contrast to traditional Aryl halide or pseudohalide electrophiles, coupling reactions with unactivated C-N and C-O electrophiles have proven significantly more challenging. Here we report the first general palladium-catalyzed Suzuki-Miyaura cross-coupling of both common amides and Aryl esters through the selective Cleavage of the C-N and C-O bonds under exceedingly mild conditions. Notably, for the first time we demonstrate selective C(acyl)-N and C(acyl)-O Cleavage/cross-coupling under the same reaction conditions. The reaction uses a commercially available, bench-stable and operationally-convenient (eta(3)-1-t-Bu-indenyl) Pd(IPr)(Cl) precatalyst. Furthermore, we demonstrate that the reactivity of generic amides and Aryl esters can be correlated with barriers to isomerization around the C(acyl)-X (X = N, O) bond, thus providing a blueprint for the development of a broad range of novel coupling reactions of ester and amide electrophiles by the selective Activation of C-O and C-N bonds.Suzuki-Miyaura cross-coupling of amides and esters at room temperature: correlation with barriers to rotation around C-N and C-O bondsx101201776#N/AFALSE
3626
c7sc02688a10.1039/c7sc02688aFALSEhttps://doi.org/10.1039/c7sc02688aNishihara, HChem. Sci.A pi-conjugated coordination nanosheet comprising bis(aminothiolato)nickel (NiAT) moieties was synthesized by the reaction of Ni(acac)(2) with 1,3,5-triaminobenzene-2,4,6-trithiol at liquid-liquid and gas-liquid interfaces. The sheet thickness could be controlled down to a single layer (0.6 nm). Selected area electron diffraction and grazing incidence X-ray diffraction analyses indicated the formation of a flat crystalline sheet with a kagome lattice stacked in a staggered alignment. NiAT was reversibly interconverted to a bis(iminothiolato) nickel (NiIT) nanosheet by the chemical 2H(+)-2e(-) reaction, which was accompanied by a drastic change in electrical conductivity from 3 x 10 (6) to 1 x 10 (1) S cm (1). This change in conductivity was explained by the difference in band structures between NiAT and NiIT. NiAT acted as an efficient electrocatalyst for the hydrogen evolution reaction, showing strong acid durability and an onset overpotential of -0.15 V.Bis(aminothiolato)nickel nanosheet as a redox switch for conductivity and an electrocatalyst for the hydrogen evolution reactionx76201774#N/AFALSE
3627
c7sc05452a10.1039/c7sc05452aFALSEhttps://doi.org/10.1039/c7sc05452aWang, XChem. Sci.Designing intricate structures and searching for functional materials has attracted wide interest in nanoscience. Herein we have fabricated (NiFe)S-2 pyrite mesocrystals in the form of nearly-single crystalline porous cubes, and studied their self-optimization to realize efficient activity toward water oxidation under electrochemical conditions. The growth mechanism of the mesocrystals was a non-Classical mechanism, which was initiated by the formation of a large quantity of small nickel sulfide Clusters, followed by the aggregation and transformation of these small Clusters in an oriented manner. When these mesocrystals were tested for water oxidation under electrocatalytic conditions, the materials served as pre-catalysts and immediately self-optimized to form amorphous S-doped metal (oxy) hydroxides, which are the real catalytically active materials. As a result, the observed overpotential to reach a current density of 10 mA cm(-2) on glassy carbon electrodes was less than 260 mV. The growth mechanism studied here may provide opportunities for constructing intricate sulfide structures, and the self-optimization process during water oxidation can inspire new thoughts on electrocatalysis.The formation of (NiFe)S-2 pyrite mesocrystals as efficient pre-catalysts for water oxidation35201839#N/ATRUE
3628
c7sc02516e10.1039/c7sc02516ehttps://doi.org/10.1039/c7sc02516eHong, SHChem. Sci.The first direct C(sp(3))-H thioCarbonylation reaction is achieved by visible light photoredox/Ni dual catalysis. The thioester group of thiobenzoate is transferred to the alpha-oxy carbon of various cyClic/acyClic ethers, which is the opposite to the commonly expected chemical reactivity involving acyl group transfer via the weaker C(acyl)-S Activation. Through mechanistic studies, we proposed that the reaction is initiated by photocatalytic reduction and fragmentation of the thioester into an acyl radical and a thiolate. A nickel complex binds to the thiolate and induces the deCarbonylation of the acyl radical to form an Aryl radical, which abstracts hydrogen from the alpha-oxy carbon of the ether. The resulting alpha-oxy C(sp(3)) centered radical re-binds to the (RS)(CO)Ni complex, which undergoes CO migratory insertion and reductive elimination to give the desired thioester product.Photoredox mediated nickel catalyzed C(sp(3))-H thioCarbonylation of ethersPhotocatalyst20201761#N/AFALSE
3629
c7sc01615h10.1039/c7sc01615hFALSEhttps://doi.org/10.1039/c7sc01615hBao, XHChem. Sci.The development of low-cost and high-performance electrocatalysts remains a challenge for the hydrogen oxidation reaction (HOR) in alkaline membrane fuel cells. Here, we have reported novel Ni@h-BN core-shell nanocatalysts consisting of nickel nanopartiCles encapsulated in few-layer h-BN shells. The Ni@hBN catalysts exhibit an improved HOR performance compared with the bare Ni nanopartiCles. In situ characterization experiments and density functional theory calculations indicate that the interactions of the O, H, and OH species with the Ni surface under the h-BN shell are weakened, which helps to maintain the active metallic Ni phase both in air and in the electrolyte and strengthen the HOR processes occurring at the h-BN/ Ni interfaces. These results suggest a new route for designing high-performance non-noble metal electrocatalysts with encapsulating two-dimensional material overlayers for HOR reactions.A nickel nanocatalyst within a h-BN shell for enhanced hydrogen oxidation reactionsx55201748#N/AFALSE
3630
c7sc01277b10.1039/c7sc01277bhttps://doi.org/10.1039/c7sc01277bReisner, EChem. Sci.The development of photoelectrodes capable of light-driven hydrogen evolution from water is an important approach for the storage of solar energy in the form of a chemical energy carrier. However, molecular catalyst-based photocathodes remain scarcely reported and typically suffer from low efficiencies and/or stabilities due to inadequate strategies for interfacing the molecular component with the light-harvesting material. In this study, we report the straightforward preparation of a p-silicon vertical bar mesoporous titania vertical bar molecular catalyst photocathode assembly that is active towards proton reduction in aqueous media with an onset potential of +0.4 V vs. RHE. The mesoporous TiO2 scaffold acts as an electron shuttle between the silicon and the catalyst, while also stabilising the silicon from passivation and enabling a high loading of molecular catalysts (>30 nmol (geometrical cm)(-2)). When a Ni bis(diphosphine)-based catalyst is anchored on the surface of the electrode, a high turnover number of similar to 1 x 10(3) was obtained from photoelectrolysis under UV-filtered simulated solar irradiation at 1 Sun after 24 h at pH 4.5. Notwithstanding its aptitude for molecular catalyst immobilisation, the p-Si vertical bar TiO2 photoelectrode showed great versatility towards different catalysts and pH conditions, with photoelectrocatalytic H-2 generation also being achieved with platinum and a hydrogenase as catalyst, highlighting the flexible platform it represents for many potential reductive catalysis transformations.Photoelectrocatalytic H-2 evolution in water with molecular catalysts immobilised on p-Si via a stabilising mesoporous TiO2 interlayer
Electrocatalytic
60201778#N/AFALSE
3631
c7sc05210c10.1039/c7sc05210cFALSEhttps://doi.org/10.1039/c7sc05210cOsuka, AChem. Sci.The non-innocent ligand nature of porphyrins was observed for compound I in enzymatic cyCles of cytochrome P450. Such porphyrin radicals were first regarded as reactive intermediates in catabolism, but recent studies have revealed that porphyrinoids, inCluding porphyrins, ring-contracted porphyrins, and ring-expanded porphyrins, display excellent radical-stabilizing abilities to the extent that radicals can be handled like usual Closed-shell organic molecules. This review surveys four types of stable porphyrinoid radical and covers their synthetic methods and properties such as excellent redox properties, NIR absorption, and magnetic properties. The radical-stabilizing abilities of porphyrinoids stem from their unique macrocyClic conjugated systems with high electronic and structural flexibilities.Porphyrinoids as a platform of stable radicals522018121#N/ATRUE
3632
c7sc05033j10.1039/c7sc05033jFALSEhttps://doi.org/10.1039/c7sc05033jLiu, LFChem. Sci.Transition metal phosphides (TMPs) have recently emerged as a new Class of pre-catalysts that can efficiently catalyze the oxygen evolution reaction (OER). However, how the OER activity of TMPs varies with the catalyst composition has not been systematically explored. Here, we report the alkaline OER electrolysis of a series of nanoparticulate phosphides containing different equimolar metal (M = Fe, Co, Ni) components. Notable trends in OER activity are observed, following the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP, which indicate that the introduction of a secondary metal(s) to a mono-metallic TMP substantially boosts the OER performance. We ascribe the promotional effect to the enhanced oxidizing power of bi-and tri-metallic TMPs that can facilitate the formation of MOH and chemical adsorption of OH- groups, which are the rate-limiting steps for these catalysts according to our Tafel analysis. Remarkably, the tri-metallic FeCoNiP pre-catalyst exhibits exceptionally high apparent and intrinsic OER activities, requiring only 200 mV to deliver 10 mA cm(-2) and showing a high turnover frequency (TOF) of >= 0.94 s(-1) at the overpotential of 350 mV.Trends in activity for the oxygen evolution reaction on transition metal (M = Fe, Co, Ni) phosphide precatalysts227201844#N/ATRUE
3633
c7sc00647k10.1039/c7sc00647kFALSEhttps://doi.org/10.1039/c7sc00647kDinca, MChem. Sci.Identifying the metal ions that optimize charge transport and charge density in metal-organic frameworks is critical for systematic improvements in the electrical conductivity in these materials. In this work, we measure the electrical conductivity and Activation energy for twenty different MOFs pertaining to four distinct structural families: M-2(DOBDC)(DMF)(2) (M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+); H4DOBDC = 2,5-dihydroxybenzene-1,4-diCarbonylic acid; DMF = N, N-dimethylformamide), M-2(DSBDC)(DMF)(2) (M = Mn2+, Fe2+; H4DSBDC = 2,5-disulfhydrylbenzene-1,4-diCarbonylic acid), M2Cl2(BTDD)(DMF)(2) (M = Mn2+, Fe2+, Co2+, Ni2+; H2BTDD = bis(1H-1,2,3-triazolo[4,5-b],[40,50-i]dibenzo[1,4]dioxin), and M(1,2,3-triazolate)(2) (M = Mg2+, Mn2+, Fe2+, Co2+, Cu2+, Zn2+, Cd2+). This comprehensive study allows us to single-out iron as the metal ion that leads to the best electrical properties. The iron-based MOFs exhibit at least five orders of magnitude higher electrical conductivity and significantly smaller charge Activation energies across all different MOF families studied here and stand out materials made from all other metal ions considered here. We attribute the unique electrical properties of iron-based MOFs to the high-energy valence electrons of Fe2+ and the Fe3+/2+ mixed valency. These results reveal that incorporating Fe2+ in the charge transport pathways of MOFs and introducing mixed valency are valuable strategies for improving electrical conductivity in this important Class of porous materials.Is iron unique in promoting electrical conductivity in MOFs?x89201744#N/AFALSE
3634
c7sc00499k10.1039/c7sc00499kFALSEhttps://doi.org/10.1039/c7sc00499kParkin, GChem. Sci.The tris[(1-isopropylbenzimidazol-2-yl) dimethylsilyl]methyl ligand, [Tism(PriBenz)], has been employed to form carbatrane compounds of both the main group metals and transition metals, namely [Tism(PriBenz)]Li, [Tism(PriBenz)]MgMe, [Tism(PriBenz)]Cu and [Tism(PriBenz)]NiBr. In addition to the formation of atranes, a zinc compound that exhibits kappa(3)-coordination, namely [kappa(3)-Tism(PriBenz)]ZnMe, has also been obtained. Furthermore, the [Tism(PriBenz)]ligand may undergo a thermally induced rearrangement to afford a novel tripodal tris(N-heterocyClic carbene) variant, as shown by the conversion of [Tism(PriBenz)]Cu to [kappa(4)-C-4-Tism(PriBenz)*]Cu. The transannular M-C bond lengths in the atrane compounds are 0.19-0.32 angstrom longer than the sum of the respective covalent radii, which is consistent with a bonding description that features a formally zwitterionic component. Interestingly, computational studies demonstrate that the Cu-Catrane interactions in [Tism(PriBenz)]Cu and [kappa(4)-C-4-Tism(PriBenz)*]Cu are characterized by an inverted ligand field, in which the occupied antibonding orbitals are localized more on carbon than on copper.Tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl]-methyl metal complexes, [Tism(PriBenz)]M: a new Class of metallacarbatranes, isomerization to a tris(N-heterocyClic carbene) derivative, and evidence for an inverted ligand fieldx172017178#N/AFALSE
3635
c7sc04851c10.1039/c7sc04851cFALSEhttps://doi.org/10.1039/c7sc04851cWei, ZDChem. Sci.The transition-metal compounds (MX) have gained wide attention as hydrogen evolution reaction (HER) electrocatalysts; however, the interaction between the non-metallic atom (X) and the metal atom (M) in MX, and the role of X in the enhanced catalytic activity of MX, are still ambiguous. In this work, we constructed a simple model [X/Ni(100)] to decipher the contribution of X towards enhancing the catalytic activity of NiX, which allows us to accurately predict the trend in HER catalytic activity of NiX based on the easily accessible physico-chemical characteristics of X. Theoretical calculations showed that the electronegativity (chi(X)) and the principle quantum number (n(X)) of X are two important descriptors for evaluating and predicting the HER catalytic activity of NiX catalysts effectively. X atoms in the VIA group can enhance the HER activity of X/Ni(100) more significantly than those in the second period due to the large chi(X) or n(X). At a relatively low X coverage, the S/Ni(100) possesses the best HER activity among all of the discussed X/Ni(100) models, and the optimum surface S : Ni atomic ratio is about 22-33%. Further experiments demonstrated that the Ni-Ni3S2 catalyst with a surface S : Ni atomic ratio of 28.9% exhibits the best catalytic activity and lowest charge transfer resistance. The trend in catalytic activity of NiX with differing X offers a new possible strategy to exploit MX materials and design new active catalysts rationally.Role of non-metallic atoms in enhancing the catalytic activity of nickel-based compounds for hydrogen evolution reaction26201850#N/ATRUE
3636
c7sc04849a10.1039/c7sc04849aFALSEhttps://doi.org/10.1039/c7sc04849aShen, YChem. Sci.It is highly desirable to develop efficient and low-cost catalysts to minimize the overpotential of the hydrogen evolution reaction (HER) for large-scale hydrogen production from electrochemical water splitting. Doping a foreign element into the host catalysts has been proposed as an effective approach to optimize the electronic characteristics of catalysts and thus improve their electrocatalytic performance. Herein we, for the first time, report vanadium-doped CoP on self-supported conductive carbon Cloth (V-CoP/CC) as a robust HER electrocatalyst, which achieves ultra-low overpotentials of 71, 123 and 47 mV to afford a current density of 10 mA cm(-2) in 1 M KOH, 1 M PBS and 0.5 M H2SO4 media, respectively. Meanwhile, the V-CoP/CC electrode exhibits a small Tafel slope and superior long-term stability over a wide pH range. Detailed characterizations reveal that the modulation of the electronic structure contributes to the superior HER performance of V-CoP/CC. We believe that doping engineering opens up new opportunities to improve the HER catalytic activity of transition metal phosphides through regulating their physicochemical and electrochemical properties.Electronic modulation of transition metal phosphide via doping as efficient and pH-universal electrocatalysts for hydrogen evolution reaction113201837#N/ATRUE
3637
c7cc09007b10.1039/c7cc09007bFALSEhttps://doi.org/10.1002/chem.201303995Yang, YCA self-supported amorphous Ni-P alloy on a CuO nanowire array: an efficient 3D electrode catalyst for water splitting in alkaline mediax2018#N/AFALSE
3638
c7sc04792d10.1039/c7sc04792dFALSEhttps://doi.org/10.1039/c7sc04792dDriess, MChem. Sci.For the first time, the reactivity of the metal- and N-heterocyClic carbene-supported monovalent hydrB(OH)2rylene is reported. Isocyanides react with the hydrB(OH)2rylene Ni-II complex [{cat(TMSL) Si}(Cl) Ni): <- BH(NHC)(2)] 1 (cat = ortho-C6H4O2; TMSL = N(SiMe3)(Dipp); Dipp = 2,6-(Pr2C6H3)-C-i; NHC = :C[(Pr-i) NC(Me)]2) to form the hydride-bridged hydrB(OH)2rylene-Ni-II complexes 2. The reaction of 1 with isoelectronic CO, however, is reversible and furnishes the related unprecedented hydride- and CO-bridged hydrB(OH)2rylene NiII complex 2-CO, which undergoes isomerisation through silyl/NHC exchange at ambient temperature to afford the corresponding hydro(silyl) boryl NiII complex 3. Markedly, 2 readily and quantitatively react with one further molar equiv. of isocyanide to give, under borylene liberation and H/Cl ligand exchange, boraketiminium species, which represent cationic B-I complexes. These latter compounds are highly reactive in solution, and can undergo quantitative transformation into previously unknown cyanB(OH)2renium cations.Striking transformations of the hydrB(OH)2rylene ligand in a HB:-> Ni-II complex with isocyanides and CO4201850#N/ATRUE
3639
c7cc07115a10.1039/c7cc07115aFALSELi, YDFacile synthesis of CoNix nanopartiCles embedded in nitrogen-carbon frameworks for highly efficient electrocatalytic oxygen evolutionx2017#N/AFALSE
3640
C7SC04675H10.1039/C7SC04675HFALSEhttps://doi.org/10.1039/C7SC04675HKambe, NChem. Sci.We describe the mechanism, substituent effects, and origins of the selectivity of the nickel-catalyzed four-component coupling reactions of Alkyl fluorides, Aryl Grignard reagents, and two molecules of 1,3-butadiene that affords a 1,6-octadiene carbon framework bearing Alkyl and Aryl groups at the 3- and 8-positions, respectively, and the competing cross-coupling reaction. Both the four-component coupling reaction and the cross-coupling reaction are triggered by the formation of anionic nickel complexes, which are generated by the oxidative dimerization of two molecules of 1,3-butadiene on Ni(0) and the subsequent complexation with the Aryl Grignard reagents. The C-C bond formation of the Alkyl fluorides with the gamma-carbon of the anionic nickel complexes leads to the four-component coupling product, whereas the cross-coupling product is yielded via nuCleophilic attack of the Ni center toward the Alkyl fluorides. These steps are found to be the rate-determining and selectivity-determining steps of the whole catalytic cyCle, in which the C-F bond of the Alkyl fluorides is activated by the Mg cation rather than a Li or Zn cation. ortho-Substituents of the Aryl Grignard reagents suppressed the cross-coupling reaction leading to the selective formation of the four-component products. Such steric effects of the ortho-substituents were Clearly demonstrated by crystal structure characterizations of ate complexes and DFT calculations. The electronic effects of the para-substituent of the Aryl Grignard reagents on both the selectivity and reaction rates are thoroughly discussed. The present mechanistic study offers new insight into anionic complexes, which are proposed as the key intermediates in catalytic transformations even though detailed mechanisms are not established in many cases, and demonstrates their synthetic utility as promising intermediates for C-C bond forming reactions, providing useful information for developing efficient and straightforward multicomponent reactions.Nickel-catalyzed coupling reaction of Alkyl halides with Aryl Grignard reagents in the presence of 1,3-butadiene: mechanistic studies of four-component coupling and competing cross-coupling reactions262018106#N/ATRUE
3641
c7cc05172g10.1039/c7cc05172gFALSECao, RFacile synthesis of sponge-like Ni3N/NC for electrocatalytic water oxidation
Electrocatalytic
2017#N/AFALSE
3642
c7cc04368f10.1039/c7cc04368fFALSEhttps://doi.org/10.1039/c7cc04368fZhao, HJHighly efficient electrocatalytic oxidation of urea on a Mn-incorporatedNi(OH)(2)/carbon fiber Cloth for energy-saving rechargeable Zn-air batteries
Electrocatalytic
2017#N/AFALSE
3643
c7cc03146g10.1039/c7cc03146gFALSEhttps://doi.org/10.1039/c7cc03146gSun, XPA NiCo2O4@Ni-Co-Ci core-shell nanowire array as an efficient electrocatalyst for water oxidation at near-neutral pHx2017#N/AFALSE
3644
c7sc04569g10.1039/c7sc04569gFALSEhttps://doi.org/10.1039/c7sc04569gLu, TBChem. Sci.The development of highly efficient, low-cost and stable electrocatalysts for overall water splitting is highly desirable for the storage of intermittent solar energy and wind energy sources. Herein, we show for the first time that nickel can be extracted from NiFe-layered double hydroxide (NiFe-LDH) to generate an Ni2P@FePOx heterostructure. The Ni2P@FePOx heterostructure was converted to an Ni2P@NiFe hydroxide heterostructure (P-NiFe) during water splitting, which displays high electrocatalytic performance for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, with an overpotential of 75 mV at 10 mA cm(-2) for HER, and overpotentials of 205, 230 and 430 mV at 10, 100 and 1000 mA cm(-2) for OER, respectively. Moreover, it could afford a stable current density of 10 mA cm(-2) for overall water splitting at 1.51 V in 1.0 M KOH with long-term durability (100 h). This cell voltage is among the best reported values for bifunctional electrocatalysts. The results of theoretical calculations demonstrate that P-NiFe displays optimized adsorption energies for both HER and OER intermediates at the nickel active sites, thus dramatically enhancing its electrocatalytic activity.Extraction of nickel from NiFe-LDH into Ni2P@NiFe hydroxide as a bifunctional electrocatalyst for efficient overall water splitting142201876#N/ATRUE
3645
c7sc04429a10.1039/c7sc04429aFALSEhttps://doi.org/10.1039/c7sc04429aReisner, EChem. Sci.A precious metal and Cd-free photocatalyst system for efficient CO2 reduction in water is reported. The hybrid assembly consists of ligand-free ZnSe quantum dots (QDs) as a visible-light photosensitiser combined with a phosphonic acid-functionalised Ni(cyClam) catalyst, NiCycP. This precious metal-free photocatalyst system shows a high activity for aqueous CO2 reduction to CO (Ni-based TONCO > 120), whereas an anchor-free catalyst, Ni(cyClam) Cl-2, produced three times less CO. Additional ZnSe surface modification with 2-(dimethylamino) ethanethiol (MEDA) partially suppresses H-2 generation and enhances the CO production allowing for a Ni-based TONCO of > 280 and more than 33% selectivity for CO2 reduction over H-2 evolution, after 20 h visible light irradiation (lambda > 400 nm, AM 1.5G, 1 sun). The external quantum efficiency of 3.4 +/- 0.3% at 400 nm is comparable to state-of-the-art precious metal photocatalysts. Transient absorption spectroscopy showed that band-gap excitation of ZnSe QDs is followed by rapid hole scavenging and very fast electron trapping in ZnSe. The trapped electrons transfer to NiCycP on the ps timescale, explaining the high performance for photocatalytic CO2 reduction. With this work we introduce ZnSe QDs as an inexpensive and efficient visible light-absorber for solar fuel generation.ZnSe quantum dots modified with a Ni(cyClam) catalyst for efficient visible-light driven CO2 reduction in water71201887#N/ATRUE
3646
C7CC01182B10.1039/C7CC01182BFALSEhttps://doi.org/10.1002/chem.201405777Mizuno, NA Ni-Mg-Al layered triple hydroxide-supported Pd catalyst for heterogeneous acceptorless dehydrogenative aromatizationx2017#N/AFALSE
3647
c7cc00678k10.1039/c7cc00678khttps://doi.org/10.1039/c7cc00678kIwasawa, NConstruction of a visible light-driven hydroCarbonylation cyCle of alkenes by the combined use of Rh(I) and photoredox catalystsPhotocatalystx2017#N/AFALSE
3648
c7sc03912c10.1039/c7sc03912cFALSEhttps://doi.org/10.1039/c7sc03912cSkrydstrup, TChem. Sci.A protocol for the Pd-catalysed cyanation of Aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of ex situ generated HCN in a Closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of Aryl and heteroAryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts. Cyanation was achieved employing the Pd(0) precatalyst, P(tBu)(3)-Pd-G3 and a weak base, potassium acetate, in a dioxane-water solvent mixture. The methodology was also suitable for the synthesis of C-13-labelled benzonitriles with ex situ generated C-13-hydrogen cyanide. Stoichiometric studies with the metal complexes were undertaken to delineate the mechanism for this catalytic transformation. Treatment of Pd(P(tBu)(3))(2) with (HCN)-C-13 in THF provided two Pd-hydride complexes, (P(tBu)(3))(2)Pd(H)((CN)-C-13), and [(P(tBu)(3)) Pd(H)](2)Pd((CN)-C-13)(4), both of which were isolated and characterised by NMR spectroscopy and X-ray crystal structure analysis. When the same reaction was performed in a THF : water mixture in the presence of KOAc, only (P(tBu)(3))(2)Pd(H)((CN)-C-13) was formed. Subjection of this cyano hydride metal complex with the oxidative addition complex (P(tBu)(3)) Pd(Ph)(Br) in a 1 : 1 ratio in THF led to a transmetallation step with the formation of (P(tBu)(3))(2)Pd(H)(Br) and C-13-benzonitrile from a reductive elimination step. These experiments suggest the possibility of a catalytic cyCle involving initially the formation of two Pd(II)-species from the oxidative addition of LnPd(0) into HCN and an Aryl bromide followed by a transmetallation step to LnPd(Ar)(CN) and LnPd(H)(Br), which both reductively eliminate, the latter in the presence of KOAc, to generate the benzonitrile and LnPd(0).Ex situ generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of Aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes222017114#N/ATRUE
3649
c6sc05473k10.1039/c6sc05473kFALSEhttps://doi.org/10.1039/c6sc05473kAbe, HChem. Sci.Catalytic remediation of automobile exhaust has relied on precious metals (PMs) inCluding platinum (Pt). Herein, we report that an intermetallic phase of Ni and niobium (Nb) (i.e., Ni3Nb) exhibits a significantly higher activity than that of Pt for the remediation of the most toxic gas in exhaust (i.e., nitrogen monoxide (NO)) in the presence of carbon monoxide (CO). When subjected to the exhaust-remediation atmosphere, Ni3Nb spontaneously evolves into a catalytically active nanophase-separated structure consisting of filamentous Ni networks (thickness < 10 nm) that are incorporated in a niobium oxide matrix (i.e., Nbox (x < 5/2)). The exposure of the filamentous Ni promotes NO dissociation, CO oxidation and N-2 generation, and the Nbox matrix absorbs excessive nitrogen adatoms to retain the active Ni-0 sites at the metal/oxide interface. Furthermore, the Nbox matrix immobilizes the filamentous Ni at elevated temperatures to produce long-term and stable catalytic performance over hundreds of hours.Nanophase-separated Ni3Nb as an automobile exhaust catalystx10201728#N/AFALSE
3650
c6sc05408k10.1039/c6sc05408kFALSEhttps://doi.org/10.1039/c6sc05408kDu, YPChem. Sci.Three dimensional (3D) N, O and S doped carbon foam (NOSCF) is prepared as a substrate for in situ vertically grown Ni(OH)(2) nanosheets. As designed Ni(OH)(2)/NOSCF possesses strong electrostatic interactions with OH- ions due to many C=O groups existing in NOSCF, which can facilitate the formation of crucial NiOOH intermediates during the OER process. CeO2 nanopartiCles (NPs) of similar to 3.3 nm in size are decorated on Ni(OH)2 nanosheets to design a highly efficient CeO2/Ni(OH)(2)/NOSCF electrocatalyst for the oxygen evolution reaction (OER). The CeO2 NP decorated Ni(OH) 2/NOSCF not only exhibits a remarkably improved OER performance with an onset potential of 240 mV, outperforming most reported non-noble metal based OER electrocatalysts, but also possesses a small Tafel slope of 57 mV dec(-1) and excellent stability under different overpotentials. The synergistic effect of producing more active species of Ni-III/IV and accelerating the charge transfer for Ni(OH)(2)/NOSCF by the introduction of CeO2 NPs is also investigated. These results demonstrate the possibility of designing energy efficient OER catalysts with the assistance of earth abundant CeO2-based catalysts.Regulating the active species of Ni(OH)2 using CeO2: 3D CeO2/Ni(OH)(2)/carbon foam as an efficient electrode for the oxygen evolution reactionx87201742#N/AFALSE
3651
c7sc03882h10.1039/c7sc03882hFALSEhttps://doi.org/10.1039/c7sc03882hOsuka, AChem. Sci.Organophosphorus(III) compounds usually take on stable pyramidal structures with a large inversion barrier of 30-35 kcal mol(-1). In contrast, diphenylphosphine-fused Ni(II) porphyrin, where the phosphorus atom is directly attached at the meso-position and embedded in a rigid skeleton, exhibits a considerably planarized phosphorus center. Here we report the synthesis of a mesityl-substituted Ni(II) porphyrin analogue, 6, which allowed an evaluation of the inversion barrier (Delta G(203)(double dagger)) by variable temperature H-1 NMR spectroscopy which showed it to be exceptionally small, at 14.0 kcal mol(-1). The observed small inversion barrier has been attributed to conformational constraint imposed by the fused structure. In addition, it was thought that the planar transition state is stabilized by the Ni(II) porphyrin network that allows the contribution of a 22 pi-aromatic circuit involving phosphorus lone-pair electrons. Along this postulate, we attempted to engineer diArylphosphine-fused porphyrins with smaller inversion barriers by replacing the fused benzene rings with five-membered heterocyClic rings such as thiophene, benzothiophene, benzofuran, indole, benzothiophene 1,1-dioxide, and thiophene 1,1-dioxide. In that order, the aromatic character of the heterocyCle decreases, which leads to increasing contribution of the 22p-aromatic circuit. Actually, the inversion barrier of the phosphorus center becomes smaller in this order and reaches 8.7 kcal mol(-1) for thiophene 1,1-dioxide-fused Ni(II) porphyrin 15, supporting the postulate.Effective stabilization of a planar phosphorus(III) center embedded in a porphyrin-based fused aromatic skeleton22201748#N/ATRUE
3652
c7sc02545a10.1039/c7sc02545aFALSEhttps://doi.org/10.1039/c7sc02545aUnwin, PRChem. Sci.Two dimensional (2D) semiconductor materials, such as molybdenum disulfide (MoS2) have attracted considerable interest in a range of chemical and electrochemical applications, for example, as an abundant and low-cost alternative electrocatalyst to platinum for the hydrogen evolution reaction (HER). While it has been proposed that the edge plane of MoS2 possesses high catalytic activity for the HER relative to the catalytically inert basal plane, this conClusion has been drawn mainly from macroscale electrochemical (voltammetric) measurements, which reflect the average electrocatalytic behavior of complex electrode ensembles. In this work, we report the first spatially-resolved measurements of HER activity on natural crystals of molybdenite, achieved using voltammetric scanning electrochemical cell microscopy (SECCM), whereby pixel-resolved linear-sweep voltammogram (LSV) measurements have allowed the HER to be visualized at multiple different potentials to construct electrochemical flux movies with nanoscale resolution. Key features of the SECCM technique are that characteristic surface sites can be targeted and analyzed in detail and, further, that the electrocatalyst area is known with good precision (in contrast to many macroscale measurements on supported catalysts). Through correlation of the local voltammetric response with information from scanning electron microscopy (SEM) and atomic force microscopy (AFM) in a multi-microscopy approach, it is demonstrated unequivocally that while the basal plane of bulk MoS2 (2H crystal phase) possesses significant activity, the HER is greatly facilitated at the edge plane (e.g., surface defects such as steps, edges or crevices). Semi-quantitative treatment of the voltammetric data reveals that the HER at the basal plane of MoS2 has a Tafel slope and exchange current density (J(0)) of 120 mV per decade and 2.5 x 10(-6) A cm(-2) (comparable to polycrystalline Co, Ni, Cu and Au), respectively, while the edge plane has a comparable Tafel slope and a J(0) that is estimated to be more than an order-of-magnitude larger (similar to 1 x 10(-4) A cm(-2)). Finally, by tracking the temporal evolution of water contact angle (WCA) after Cleavage, it is shown that cathodic polarization has a 'self-Cleaning' effect on the surface of MoS2, consistent with the time-independent (i.e., time after Cleavage) HER voltammetric response.Electrochemical maps and movies of the hydrogen evolution reaction on natural crystals of molybdenite (MoS2): basal vs. edge plane activity77201755#N/ATRUE
3653
c7sc01247k10.1039/c7sc01247kFALSEhttps://doi.org/10.1039/c7sc01247kKulik, HJChem. Sci.High-throughput computational screening has emerged as a critical component of materials discovery. Direct density functional theory (DFT) simulation of inorganic materials and molecular transition metal complexes is often used to describe subtle trends in inorganic bonding and spin-state ordering, but these calculations are computationally costly and properties are sensitive to the exchange-correlation functional employed. To begin to overcome these challenges, we trained artificial neural networks (ANNs) to predict quantum-mechanically-derived properties, inCluding spin-state ordering, sensitivity to Hartree-Fock exchange, and spin-state specific bond lengths in transition metal complexes. Our ANN is trained on a small set of inorganic-chemistry-appropriate empirical inputs that are both maximally transferable and do not require precise three-dimensional structural information for prediction. Using these descriptors, our ANN predicts spin-state splittings of single-site transition metal complexes (i.e., Cr-Ni) at arbitrary amounts of Hartree-Fock exchange to within 3 kcal mol(-1) accuracy of DFT calculations. Our exchange-sensitivity ANN enables improved predictions on a diverse test set of experimentally-characterized transition metal complexes by extrapolation from semi-local DFT to hybrid DFT. The ANN also outperforms other machine learning models (i.e., support vector regression and kernel ridge regression), demonstrating particularly improved performance in transferability, as measured by prediction errors on the diverse test set. We establish the value of new uncertainty quantification tools to estimate ANN prediction uncertainty in computational chemistry, and we provide additional heuristics for identification of when a compound of interest is likely to be poorly predicted by the ANN. The ANNs developed in this work provide a strategy for screening transition metal complexes both with direct ANN prediction and with improved structure generation for validation with first principles simulation.Predicting electronic structure properties of transition metal complexes with neural networks792017111#N/ATRUE
3654
c6sc05135a10.1039/c6sc05135ahttps://doi.org/10.1039/c6sc05135aTanaka, TChem. Sci.We found that plasmonic Au partiCles on titanium(IV) oxide (TiO2) act as a visible-light-driven photocatalyst for overall water splitting free from any additives. This is the first report showing that surface plasmon resonance (SPR) in a suspension system effectively induces overall water splitting. Modification with various types of metal nanopartiCles as co-catalysts enhanced the evolution of H-2 and O-2. Among these, Ni-modified Au/TiO2 exhibited 5-times higher rates of H-2 and O-2 evolution than those of Ni-free Au/TiO2. We succeeded in designing a novel solar energy conversion system inCluding three elemental technologies, charge separation with light harvest and an active site for O-2 evolution (plasmonic Au partiCles), charge transfer from Au to the active site for H-2 production (TiO2), and an active site for H-2 production (Ni cocatalyst), by taking advantage of a technique for fabricating size-controlled Au and Ni nanopartiCles. Water splitting occurred in aqueous suspensions of Ni-modified Au/TiO2 even under irradiation of light through an R-62 filter.Visible light-induced water splitting in an aqueous suspension of a plasmonic Au/TiO2 photocatalyst with metal co-catalystsPhotocatalyst83201738#N/AFALSE
3655
c7sc01239j10.1039/c7sc01239jFALSEhttps://doi.org/10.1039/c7sc01239jNocera, DGChem. Sci.Oxygen evolution reaction (OER) catalysts that are earth-abundant and are active and stable in acid are unknown. Active catalysts derived from Co and Ni oxides dissolve at low pH, whereas acid stable systems such as Mn oxides (MnOx) display poor OER activity. We now demonstrate a rational approach for the design of earth-abundant catalysts that are stable and active in acid by treating activity and stability as decoupled elements of mixed metal oxides. Manganese serves as a stabilizing structural element for catalytically active Co centers in CoMnOx films. In acidic solutions (pH 2.5), CoMnOx exhibits the OER activity of electrodeposited Co oxide (CoOx) with a Tafel slope of 70-80 mV per decade while also retaining the long-term acid stability of MnOx films for OER at 0.1 mA cm(-2). Driving OER at greater current densities in this system is not viable because at high anodic potentials, Mn oxides convert to and dissolve as permanganate. However, by exploiting the decoupled design of the catalyst, the stabilizing structural element may be optimized independently of the Co active sites. By screening potential-pH diagrams, we replaced Mn with Pb to prepare CoFePbox films that maintained the high OER activity of CoOx at pH 2.5 while exhibiting long-term acid stability at higher current densities (at 1 mA cm(-2) for over 50 h at pH 2.0). Under these acidic conditions, CoFePbox exhibits OER activity that approaches noble metal oxides, thus establishing the viability of decoupling functionality in mixed metal catalysts for designing active, acid-stable, and earth-abundant OER catalysts.Design of template-stabilized active and earth-abundant oxygen evolution catalysts in acid702017111#N/ATRUE
3656
c7cc09921e10.1039/c7cc09921eFALSEhttps://doi.org/10.1039/c7cc09921eParedes-Garcia, VRETRACTED: Ni-2[LnCl(6)] (Ln = Eu-II, Ce-II, Gd-II): the first Ln(II) compounds stabilized in a pure inorganic lattice (Retracted artiCle. See vol. 55, pg. 13183, 2019)2018#N/ATRUE
3657
c7cc09507d10.1039/c7cc09507dFALSEhttps://doi.org/10.1039/c7cc09507dPapish, ETNickel(II) pincer complexes demonstrate that the remote substituent controls catalytic carbon dioxide reduction2018#N/ATRUE
3658
c6sc03614g10.1039/c6sc03614gFALSEhttps://doi.org/10.1039/c6sc03614gCummins, CCChem. Sci.A family of cis-macrocyClic diphosphines was prepared in just three steps from white phosphorus and commercial materials using a modular synthetic approach. Alkylation of bicyClic diphosphane 3,4,8,9-tetramethyl-1,6-diphosphabicyClo(4.4.0) deca-3,8-diene, or P-2(dmb)(2), produced phosphinophosphonium salts [R-P-2(dmb)2]X, where R is methyl, Benzyl and isobutyl, in yields of 90-96%. Treatment of these salts with organolithium or Grignard reagents yielded symmetric and unsymmetric macrocyClic diphosphines of the form cis-1-R-6-R'-3,4,8,9-tetramethyl-2,5,7,10-tetrahydro-1,6DiPhospheCine, or R, R,R'-DPC, in which R' is methyl, cyClohexyl, phenyl or mesityl, in yields of 46-94%. Alternatively, symmetric diphosphine Cy2-DPC was synthesized in 74% yield from the dichlorodiphosphine Cl2P2(dmb) (2). As a first application, these cis-macrocyClic diphosphines were used as ligands in the nickel-catalyzed synthesis of acrylate from CO2 and ethylene, for which they showed promising catalytic activity.A family of cis-macrocyClic diphosphines: modular, stereoselective synthesis and application in catalytic CO2/ethylene couplingx19201759#N/AFALSE
3659
c6sc03356c10.1039/c6sc03356cFALSEhttps://doi.org/10.1039/c6sc03356cYu, SHChem. Sci.The development of active, stable and low-cost electrocatalysts towards both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for overall water splitting remains a big challenge. Herein, we report a new porous carbon-supported Ni/Mo2C (Ni/Mo2C-PC) composite catalyst derived by thermal treatment of nickel molybdate nanorods coated with polydopamine, which efficiently and robustly catalyses the HER and OER with striking kinetic metrics in alkaline electrolyte. The catalyst affords low onset potentials of -60 mV for the HER and 270 mV for the OER, as well as small overpotentials of 179 mV for the HER and 368 mV for the OER at a current density of 10 mA cm(-2). These results compare favorably to Mo2C-PC, Ni-PC, and most other documented Ni- and Mo-based catalysts. The high activity of Ni/Mo2C-PC is likely due to electron transfer from Ni to Mo2C, leading to a higher Ni valence and a lower Mo valence in the Ni/Mo2C-PC catalyst, as these are HER and OER active species and thus account for the enhanced activity. Remarkably, our home-made alkaline electrolyser, assembled with Ni/Mo2C-PC as a bifunctional catalyst, can enable a water-splitting current density of 10 mA cm(-2) to be achieved at a low cell voltage of 1.66 V.A one-dimensional porous carbon-supported Ni/Mo2C dual catalyst for efficient water splittingx256201753#N/AFALSE
3660
c6sc02895k10.1039/c6sc02895kFALSEhttps://doi.org/10.1039/c6sc02895kCampana, AGChem. Sci.Highly distorted polycyClic aromatic hydrocarbons (PAHs) are predicted to be attractive goals in nanoscience owing to the new properties they can exhibit. We have shown that a variety of functionalized distorted heptagon-containing nanographenes can be easily prepared from simple building blocks by a sequence of Co-catalyzed cyClotrimerization and cyClodehydrogenation reactions. The versatility of this strategy allows easy subsequent enlargement of these nanostructures by Ni-catalyzed cross-coupling and final cyClodehydrogenation reactions. Soluble extended distorted nanographenes 1 and 2 containing heptagon and an edge-shared pentagon-heptagon combination have been synthesized. High distortion of the polycyClic backbone of 2 caused by non-hexagonal rings and a helicene moiety was confirmed by X-ray crystallography. Experimental data reveal promising optical and electronic properties for distorted PAHs with long fluorescence lifetimes (up to 14.5 ns) and low band gaps (down to 2.27 eV). This straightforward and versatile synthetic strategy, the observed long fluorescence lifetimes and the small optical and electrochemical band gaps for the presented compounds may promote the future implementation of distorted graphene molecules in electronic devices.Versatile synthesis and enlargement of functionalized distorted heptagon-containing nanographenesx49201750#N/AFALSE
3661
c6sc02815b10.1039/c6sc02815bhttps://doi.org/10.1039/c6sc02815bDoyle, AGChem. Sci.We describe the functionalization of alpha-amino C-H bonds with Aryl halides using a combination of nickel and photoredox catalysis. This direct C-H, C-X coupling uses inexpensive and readily available starting materials to generate Benzylic amines, an important Class of bioactive molecules. Mechanistically, this method features the direct Arylation of alpha-amino radicals mediated by a nickel catalyst. This reactivity is demonstrated for a range of Aryl halides and N-Aryl amines, with orthogonal scope to existing C-H Activation and photoredox methodologies. We also report reactions with several complex Aryl halides, demonstrating the potential utility of this approach in late-stage functionalization.C-H functionalization of amines with Aryl halides by nickel-photoredox catalysisPhotocatalyst832016516/1/2022FALSE
3662
c6sc02721k10.1039/c6sc02721kFALSEhttps://doi.org/10.1039/c6sc02721kOsuka, AChem. Sci.Oxidative fusion reactions of meso-phenoxazino Ni(II) porphyrin were found to be temperature dependent, giving rise to either a doubly phenylene-fused product at room temperature or a singly phenoxazine-fused product at 70 degrees C. The latter was further oxidized to a doubly phenoxazine-fused Ni(II) porphyrin, which was subsequently converted to the corresponding free base porphyrin and Zn(II) porphyrin. Compared to previously reported diphenylamine-fused porphyrins that displayed a molecular twist, doubly phenoxazine-fused porphyrins exhibited distinctly different properties owing to their highly planar structures, such as larger fluorescence quantum yields, formation of an offset face-to-face dimer both in solution and the solid state, and the generation of a mixed-valence p-radical cation dimer upon electrochemical oxidation. One-electron oxidation of the phenoxazine-fused Ni(II) porphyrin with Magic Blue gave the corresponding radical cation, which was certainly stable and could be isolated by separation over a silica gel column but slowly chlorinated at the reactive beta-positions in the solid state. This finding led to us to examine beta, beta'-dichlorinated phenoxazine-fused and diphenylamine-fused Ni(II) porphyrins, which, upon treatment with Magic Blue, provided remarkably stable radical cations to an unprecedented level. It is actually possible to purify these radical cations by silica gel chromatography, and they can be stored for over 6 months without any sign of deterioration. Moreover, they exhibited no degradation even after the CH2Cl2 solution was washed with water. However, subtle structural differences (planar versus partly twisted) led to different crystal packing structures and solid-state magnetic properties.Highly planar diArylamine-fused porphyrins and their remarkably stable radical cationsx43201778#N/AFALSE
3663
c6sc02477g10.1039/c6sc02477ghttps://doi.org/10.1039/c6sc02477gWasielewski, MRChem. Sci.The design of efficient hydrogen-evolving photocathodes for dye-sensitized photoelectrochemical cells (DSPECs) requires the incorporation of molecular light absorbing chromophores that are capable of delivering reducing equivalents to molecular proton reduction catalysts at rates exceeding those of charge recombination events. Here, we report the functionalization and kinetic analysis of a nanostructured NiO electrode with a modified perylene-3,4-dicarboximide chromophore (PMI) that is stabilized against degradation by atomic layer deposition (ALD) of thick insulating Al2O3 layers. Following photoinduced charge injection into NiO in high yield, films with Al2O3 layers demonstrate longer charge separated lifetimes as characterized via femtosecond transient absorption spectroscopy and photoelectrochemical techniques. The photoelectrochemical behavior of the electrodes in the presence of Co(II) and Ni(II) molecular proton reduction catalysts is examined, revealing reduction of both catalysts. Under prolonged irradiation, evolved H-2 is directly observed by gas chromatography supporting the applicability of PMI embedded in Al2O3 as a photocathode architecture in DSPECs.Photodriven hydrogen evolution by molecular catalysts using Al2O3-protected perylene-3,4-dicarboximide on NiO electrodesPhotocatalyst57201772#N/AFALSE
3664
c6sc02456d10.1039/c6sc02456dFALSEhttps://doi.org/10.1039/c6sc02456dChen, PCovalent triazine framework supported non-noble metal nanopartiCles with superior activity for catalytic hydrolysis of ammonia borane: from mechanistic study to catalyst designx2017#N/AFALSE
3665
c7cc09003j10.1039/c7cc09003jFALSEhttps://doi.org/10.1039/c7cc09003jAgapie, TMild electrochemical synthesis of metal phosphides with dibenzo-7-phosphanorbornadiene derivatives: mechanistic insights and application to proton reduction in water2018#N/ATRUE
3666
c7cc06249d10.1039/c7cc06249dFALSEhttps://doi.org/10.1039/c7cc06249dWang, SDExplosive'' synthesis of metal-formate frameworks for methane capture: an experimental and computational study2017#N/ATRUE
3667
c6sc02083f10.1039/c6sc02083fFALSEhttps://doi.org/10.1039/c6sc02083fZhao, HJMolecular engineering of Ni-/Co-porphyrin multilayers on reduced graphene oxide sheets as bifunctional catalysts for oxygen evolution and oxygen reduction reactionsx2016#N/AFALSE
3668
c6sc01883a10.1039/c6sc01883aFALSEhttps://doi.org/10.1039/c6sc01883aSeitz, OChem. Sci.The total chemical synthesis of proteins is a tedious and time-consuming endeavour. The typical steps involve solid phase synthesis of peptide thioesters and cysteinyl peptides, native chemical ligation (NCl) in solution, desulfurization or removal of ligation auxiliaries in the case of extended NCl as well as many intermediary and final HPLC purification steps. With an aim to facilitate and improve the throughput of protein synthesis we developed the first method for the rapid chemical total on-resin synthesis of proteins that proceeds without a single HPLC-purification step. The method relies on the combination of three orthogonal protein tags that allow sequential immobilization (via the N-terminal and C-terminal ends), extended native chemical ligation and release reactions. The peptide fragments to be ligated are prepared by conventional solid phase synthesis and used as crude materials in the subsequent steps. An N-terminal His(6) unit permits selective immobilization of the full length peptide thioester onto Ni-NTA agarose beads. The C-terminal peptide fragment carries a C-terminal peptide hydrazide and an N-terminal 2-mercapto-2-phenyl-ethyl ligation auxiliary, which serves as a reactivity tag for the full length peptide. As a result, only full length peptides, not truncation products, react in the subsequent on-bead extended NCl. After auxiliary removal the ligation product is liberated into solution upon treatment with mild acid, and is concomitantly captured by an aldehyde-modified resin. This step allows the removal of the most frequently observed by-product in NCl chemistry, i. e. the hydrolysed peptide thioester (which does not contain a C-terminal peptide hydrazide). Finally, the target protein is released with diluted hydrazine or acid. We applied the method in the synthesis of 46 to 126 amino acid long MUC1 proteins comprising 2-6 copies of a 20mer tandem repeat sequence. Only three days were required for the parallel synthesis of 9 MUC1 proteins which were obtained in 8-33% overall yield with 90-98% purity despite the omission of HPLC purification.Total chemical synthesis of proteins without HPLC purificationx32201622#N/AFALSE
3669
c6sc01385f10.1039/c6sc01385fFALSEhttps://doi.org/10.1039/c6sc01385fZaworotko, MJChem. Sci.A new family of 2-fold interpenetrated primitive cubic (pcu) networks of formula [M(L)(2)(Cr2O7)](n)(M = Co2+, Ni2+, Cu2+ and Zn2+; L = 4,4'-azopyridine), DICRO-3-M-i, has been synthesised and their structures, permanent porosity and gas sorption properties were comprehensively characterised. Molecular simulations indicate that CO2 molecules occupy both of the two distinct ultramicropores that run through this isostructural series. The orientation of the Cr2O72- pillars is thought to contribute to high isosteric enthalpy of adsorption (Q(st)) towards CO2 and temperature programmed desorption experiments reveal that DICRO-3-Ni-i selectively adsorbs CO2 from gas mixtures that simulate flue gas. Performance in this context is among the highest for physisorbents measured to date and these materials are readily regenerated at 50 degrees C.Crystal engineering of a family of hybrid ultramicroporous materials based upon interpenetration and dichromate linkersx43201642#N/AFALSE
3670
c6sc00817h10.1039/c6sc00817hFALSEhttps://doi.org/10.1039/c6sc00817hKomatsu, TChem. Sci.Unprecedented molecular recognition ability governed by a simple bimetallic surface is reported. A series of Rh-based ordered alloys supported on silica gel (RhxMy/SiO2, where M is Bi, Fe, Ga, Ge, In, Ni, Pb, Sb, Sn, or Zn) were tested in the hydrogenation of nitrostyrene to form aminostyrene. RhIn/SiO2 showed remarkably high catalytic activity and good selectivity under 1 atm H-2 at room temperature. Moreover, various other nitroarenes containing Carbonyl, cyano, or halo moieties were selectively hydrogenated into the corresponding amino derivatives using RhIn/SiO2. Kinetic study and density functional theory (DFT) calculations revealed that the high selectivity originates from RhIn/SiO2 adsorbing nitro groups much more favorably than Vinyl groups. In addition, the DFT calculations indicated that the RhIn ordered alloy presents concave Rh rows and convex In rows on its surface, which are able to capture the nitro group with end-on geometry while effectively minimizing Vinyl-pi adsorption. Thus, the specific and highly ordered surface structure of RhIn enables the chemoselective molecular recognition of nitro groups over Vinyl groups through geometric and chemical effects.Well-structured bimetallic surface capable of molecular recognition for chemoselective nitroarene hydrogenationx44201642#N/AFALSE
3671
c6sc00715e10.1039/c6sc00715ehttps://doi.org/10.1039/c6sc00715eReisner, EChem. Sci.Capture and conversion of sunlight into the storable energy carrier H-2 can be achieved through photoelectrochemical water splitting using light-absorbing cathodes and anodes bearing H-2 and O-2 evolving catalysts. Here, we report on the development of a dye-sensitised p-type nickel oxide (NiO) photocathode with a hexaphosphonated Ru(2,2'-bipyridine)(3) based dye (RuP3) and a tetraphosphonated molecular [Ni(P2N2)(2)](2+) type proton reduction catalyst (NiP) for the photoreduction of aqueous protons to H-2. A layer-by-layer deposition approach was employed, using Zr4+ ions to link the phosphonate units in RuP3 and NiP in a supramolecular assembly on the NiO photocathode. This approach keeps the dye in Close proximity to the catalyst and semiconductor surface, but spatially separates NiP from NiO for advantageous electron transfer dynamics. The NiO vertical bar RuP3-Zr4+-NiP electrodes generate higher photocurrents and are more stable than photocathodes with RuP3 and NiP co-immobilised on the NiO surface in the absence of Zr4+ cations linking dye and catalyst. The generation of H-2 with the NiO vertical bar RuP3-Zr4+-NiP hybrid electrode in pH 3 aqueous electrolyte solution during irradiation with a UV-filtered solar light simulator (lambda > 400 nm, 100 mW cm(-2), AM1.5G) has been confirmed by gas chromatography at an underpotential of 300 mV (E-appl = +0.3 V vs. RHE), demonstrating the potential of these electrodes to store solar energy in the chemical bond of H-2.Photoelectrochemical hydrogen production in water using a layer-by-layer assembly of a Ru dye and Ni catalyst on NiOPhotocatalyst84201676#N/AFALSE
3672
C7CC01685A10.1039/C7CC01685AFALSEhttps://doi.org/10.1039/C7CC01685ABinnemans, KMetal extraction with a short-chain imidazolium nitrate ionic liquid2017#N/ATRUE
3673
c6cc09941f10.1039/c6cc09941fhttps://doi.org/10.1039/c6cc09941fFontecave, MRuthenium-cobalt dinuClear complexes as photocatalysts for CO2 reductionPhotocatalyst2017#N/AFALSE
3674
c6cc08505a10.1039/c6cc08505aFALSEhttps://doi.org/10.1002/chem.201102375Zhang, TOxygen surface groups of activated carbon steer the chemoselective hydrogenation of substituted nitroarenes over nickel nanopartiClesx2017#N/AFALSE
3675
c7cc01489a10.1039/c7cc01489aFALSEhttps://doi.org/10.1002/chem.201100604Nath, MCoNi2Se4 as an efficient bifunctional electrocatalyst for overall water splitting2017#N/ATRUE
3676
c6cc04400j10.1039/c6cc04400jFALSEhttps://doi.org/10.1039/c6cc04400jFedyanin, IVNi-based heterogeneous catalyst from a designed molecular precursor for the efficient electrochemical water oxidationx2016#N/AFALSE
3677
c6sc05556g10.1039/c6sc05556gFALSEhttps://doi.org/10.1039/c6sc05556gMankad, NPChem. Sci.Bimetallic catalysis represents an alternative paradigm for coupling chemistry that complements the more traditional single-site catalysis approach. In this perspective, recent advances in bimetallic systems for catalytic C-C and C-X coupling reactions are reviewed. Behavior which complements that of established single-site catalysts is highlighted. Two major reaction Classes are covered. First, generation of catalytic amounts of organometallic species of e.g. Cu,Au,or Ni capable of transmetallation to a Pd co- catalyst (or other traditional cross-coupling catalyst) has allowed important new C-C coupling technologies to emerge. Second, catalytic transformations involving binuClear bond-breaking and/epresent a frontier area for C-C and C-X coupling processes.Bimetallic catalysis for C-C and C-X coupling reactions1692017110#N/ATRUE
3678
c6sc05355f10.1039/c6sc05355fFALSEhttps://doi.org/10.1039/c6sc05355fAnderson, HLChem. Sci.Three different types of template-directed syntheses of linear porphyrin oligomers are presented. In the Classical approach the product has the same number of binding sites as the template, whereas in Vernier reactions the product has the lowest common multiple of the numbers of binding sites in the template and the building block. Mutual Vernier templating is like Vernier templating except that both strands of the Vernier complex undergo coupling simultaneously, so that it becomes impossible to say which is the 'template' and which is the 'building block'. The template-directed synthesis of monodisperse linear oligomers is more difficult than that of cyClic oligomers, because the products of linear templating have reactive ends. All three types of templating are demonstrated here, and used to prepare a nickel(II) porphyrin dodecamer with 4-pyridyl substituents on all twelve porphyrin units. The stabilities and cooperativities of the double-strand complexes involved in these reactions were investigated by UV-vis-NIR titration. The four-rung ladder duplex has a stability constant of about 2 x 10(18) M-1 in dichloromethane at 298 K.Template-directed synthesis of linear porphyrin oligomers: Classical, Vernier and mutual Vernier16201792#N/ATRUE
3679
c6cc02728h10.1039/c6cc02728hFALSEhttps://doi.org/10.1002/chem.201000220Zhao, JW[{beta-SiNi2W10O36(OH)(2)(H2O)}(4)](24-): a new robust visible light-driven water oxidation catalyst based on nickel-containing polyoxometalatex2016#N/AFALSE
3680
c6sc05219c10.1039/c6sc05219cFALSEhttps://doi.org/10.1039/c6sc05219cReisner, EChem. Sci.A series of diketopyrrolopyrrole (DPP) dyes with a terminal phosphonic acid group for attachment to metal oxide surfaces were synthesised and the effect of side chain modification on their properties investigated. The organic photosensitisers feature strong visible light absorption (lambda = 400 to 575 nm) and electrochemical and fluorescence studies revealed that the excited state of all dyes provides sufficient driving force for electron injection into the TiO2 conduction band. The performance of the DPP chromophores attached to TiO2 nanopartiCles for photocatalytic H-2 evolution with co-immobilised molecular Co and Ni catalysts was subsequently studied, resulting in solar fuel generation with a dye-sensitised semiconductor nanopartiCle system suspended in water without precious metal components. The performance of the DPP dyes in photocatalysis did not only depend on electronic parameters, but also on properties of the side chain such as polarity, steric hinderance and hydrophobicity as well as the specific experimental conditions and the nature of the sacrificial electron donor. In an aqueous pH 4.5 ascorbic acid solution with a phosphonated DuBois-type Ni catalyst, a DPP-based turnover number (TONDPP) of up to 205 was obtained during UV-free simulated solar light irradiation (100 mW cm(-2), AM 1.5G, lambda > 420 nm) after 1 day. DPP-sensitised TiO2 nanopartiCles were also successfully used in combination with a hydrogenase or platinum instead of the synthetic H-2 evolution catalysts and the platinum-based system achieved a TONDPP of up to 2660, which significantly outperforms an analogous system using a phosphonated Ru tris(bipyridine) dye (TONRu = 431). Finally, transient absorption spectroscopy was performed to study interfacial recombination and dye regeneration kinetics revealing that the different performances of the DPP dyes are most likely dictated by the different regeneration efficiencies of the oxidised chromophores.Solar H-2 evolution in water with modified diketopyrrolopyrrole dyes immobilised on molecular Co and Ni catalyst-TiO2 hybrids48201765#N/ATRUE
3681
c6cc00499g10.1039/c6cc00499gFALSEPrechtl, MHGSelective partial hydrogenation of alkynes to (Z)-alkenes with ionic liquid-doped nickel nanocatalysts at near ambient conditionsx2016#N/AFALSE
3682
c5sc04863j10.1039/c5sc04863jhttps://doi.org/10.1039/c5sc04863jReisner, EChem. Sci.Splitting water into hydrogen and oxygen with molecular catalysts and light has been a long-established challenge. Approaches in homogeneous systems have been met with little success and the integration of molecular catalysts in photoelectrochemical cells is challenging due to inaccessibility and incompatibility of functional hybrid molecule/material electrodes with long-term stability in aqueous solution. Here, we present the first example of light-driven water splitting achieved with precious-metal-free molecular catalysts driving both oxygen and hydrogen evolution reactions. Mesoporous TiO2 was employed as a low-cost scaffold with long-term stability for anchoring a phosphonic acid-modified nickel(II) bis-diphosphine catalyst (NiP) for electrocatalytic proton reduction. A turnover number of 600 mol H-2 per mol NiP was achieved after 8 h controlled-potential electrolysis at a modest overpotential of 250 mV. X-ray photoelectron, UV-vis and IR spectroscopies confirmed that the molecular structure of the Ni catalyst remains intact after prolonged hydrogen production, thereby reasserting the suitability of molecular catalysts in the development of effective, hydrogen-evolving materials. The relatively mild operating conditions of a pH 3 aqueous solution allowed this molecule-catalysed cathode to be combined with a molecular Fe(II) catalyst-modified WO3 photoanode in a photoelectrochemical cell. Water splitting into H-2 and O-2 was achieved under solar light illumination with an applied bias of >0.6 V, which is below the thermodynamic potential (1.23 V) for water splitting and therefore allowed the storage of solar energy in the fuel H-2.Precious-metal free photoelectrochemical water splitting with immobilised molecular Ni and Fe redox catalystsPhotocatalyst66201672#N/AFALSE
3683
c6sc05167g10.1039/c6sc05167gFALSEhttps://doi.org/10.1039/c6sc05167gLiu, LFChem. Sci.Electrochemical water splitting into hydrogen and oxygen is a promising technology for sustainable energy storage. The development of earth-abundant transition metal phosphides (TMPs) to catalyze the hydrogen evolution reaction (HER) and TMP-derived oxy-hydroxides to catalyze the oxygen evolution reaction (OER) has recently drawn considerable attention. However, most monolithically integrated metal phosphide electrodes are prepared by laborious multi-step methods and their operational stability at high current densities has been rarely studied. Herein, we report a novel vapor-solid synthesis of single-crystalline cobalt phosphide nanowires (CoP NWs) on a porous Co foam and demonstrate their use in overall water splitting. The CoP NWs grown on the entire surface of the porous Co foam ligaments have a large aspect ratio, and hence are able to provide a large catalytically accessible surface over a given geometrical area. Comprehensive investigation shows that under the OER conditions CoP NWs are progressively and conformally converted to CoOOH through electrochemical in situ oxidation/dephosphorization; the latter serving as an active species to catalyze the OER. The in situ oxidized electrode shows exceptional electrocatalytic performance for the OER in 1.0 M KOH, delivering 100 mA cm(-2) at an overpotential (eta) of merely 300 mV and a small Tafel slope of 78 mV dec(-1) as well as excellent stability at various current densities. Meanwhile, the CoP NW electrode exhibits superior catalytic activity for the HER in the same electrolyte, affording -100 mA cm(-2) at eta = 244 mV and showing outstanding stability. An alkaline electrolyzer composed of two symmetrical CoP NW electrodes can deliver 10 and 100 mA cm(-2) at low cell voltages of 1.56 and 1.78 V, respectively. The CoP NW electrolyzer demonstrates exceptional long-term stability for overall water splitting, capable of working at 20 and 100 mA cm(-2) for 1000 h without obvious degradation.Vapor-solid synthesis of monolithic single-crystalline CoP nanowire electrodes for efficient and robust water electrolysis103201751#N/ATRUE
3684
c6sc04819f10.1039/c6sc04819fFALSEhttps://doi.org/10.1039/c6sc04819fYang, HGChem. Sci.Water splitting is key to electrically-powered chemical fuel synthesis, but the slow kinetics of the oxygen evolution reaction (OER) hinder the wider promotion of such technology. Several first-row (3d) transition metal-based catalysts have been developed for the OER; however, these catalysts still require operating voltages that lie well above the fundamental thermodynamic potential. Here, we report high-valence metal molybdenum (Mo6+) modulated 3d metal (oxy) hydroxides. The obtained multimetal FeCoMo based OER catalysts require an overpotential of 277 mV to reach the current density of 10 mA cm(-2) on the glassy carbon electrode, and there was no evidence of degradation for about 40 hours of stability testing. The catalysts stay in their amorphous phases, potentially with atomically homogenous metal distribution. The in situ X-ray adsorption analysis unambiguously reveals the tuned electronic structures of the 3d metals owing to Mo6+, further demonstrating the modification effect of a high-valence metal for designing highly-efficient OER catalysts.Mo6+ activated multimetal oxygen-evolving catalysts70201737#N/ATRUE
3685
c5sc04644k10.1039/c5sc04644kFALSEhttps://doi.org/10.1039/c5sc04644kGade, LHChem. Sci.The study is aimed at a deeper understanding of the electronic structure of the T-shaped nickel(I) complex [Lig(iPr)(iso)Ni] (1b), bearing the iso-PyrrMebox (bis(oxazolinylmethylidene) pyrrolidinido) pincer ligand, and its CO adduct [Lig(iPr)(iso)Ni(CO)] (2b) as well as to provide insight into the mechanism of autoxidation of the different nickel peroxo species of this ligand type. CO was found to react reversibly with complex 1b resulting in the corresponding CO adduct 2b. The EPR data as well as the results of DFT modeling revealed significant differences in the electronic structure of 1b and 2b. Reaction of [Lig(Ph)(iso)Ni] and [Lig(iPr)(iso) Ni] (1a and b) with dioxygen yielded the 1,2-m-peroxo complexes [Lig(iso)NiO](2) 3a and b which reacted with hydrogen peroxide to give the hydroperoxo complexes [Lig(iso)NiOOH]5a and b. Thermal aerobic decomposition of the peroxo species 3a and 5a in the presence of O-2 led to a C-H Activation of the ligand at the Benzylic position of the oxazoline ring forming diastereomeric cyClic peroxo complexes 6 and 6'. For the 1,2-mu-peroxo complex 3b the autoxidation of the pincer in the absence of O-2 occurred at the tertiary C-H bond of the Pr-i-group and led to a selective formation of the terminal hydroxo complex [Lig(iPr)(iso)NiOH] 7b and the cyClic alkoxy complex 8 in equimolar quantities, while the corresponding cyClic peroxo species 9 was formed along with 7b in the presence of oxygen. Whether or not O-O bond Cleavage occurred in the generation of 9 was established upon performing labeling experiments which indicate that the transformation does not involve an initial O-O bond Cleaving step. Based on these observations and a series of stoichiometric transformations a tentative proposal for the processes involved in the anaerobic and aerobic decomposition of 3b has been put forward. Finally, the nickel(II) methyl complex [Lig(Ph)(iso)NiMe] 14 reacted with O-2 to give the methylperoxo complex [Lig(Ph)(iso)NiOOMe] 15 which slowly converted to a mixture of near equal amounts of the formato and the hydroxo complexes, [Lig(Ph)(iso)NiOOCH] 16 and [Lig(Ph)(iso)NiOH] 7a, along with half an equivalent of methanol. The formato complex 16 itself decomposed at elevated temperatures to CO2, dihydrogen as well as the nickel(I) species 1a.Electronic structure and reactivity of nickel(I) pincer complexes: their aerobic transformation to peroxo species and site selective C-H oxygenationx29201670#N/AFALSE
3686
c5sc04571a10.1039/c5sc04571aFALSEhttps://doi.org/10.1039/c5sc04571aBensch, WChem. Sci.Antimonato polyoxovanadate (POV) Cluster compounds {M(en)(3)}(3)[V15Sb6O42(H2O)(x)]center dot nH(2)O (M = Fe-II, Co-II, Ni-II and x = 0 or 1) obtained under solvothermal conditions exhibit unusual high water solubility making these compounds promising synthons for generation of new POV structure types. Electrospray ionization mass spectrometry provides evidence (i) for a water molecule encapsulated inside the cavity of a fraction of the spherical Cluster shells, (ii) for a post-functionalization in water, namely a slow exchange of VO against Sb2O, (iii) for the inner-phase reactivity of the encapsulated water that is capable of opening an oxo-bridge, and (iv) for a significant acceleration of the O-16/O-18 exchange reactions of oxygen atoms in the Cluster periphery with surrounding (H2O)-O-18, when encapsulated water is present. To the best of our knowledge, this is the first example in polyoxovanadate chemistry for the transduction of inner-phase reactivity of an encapsulated guest molecule into changes in the outer-phase reactivity of the Cluster. Magnetic susceptibility measurements reflect the individual contributions of the frustrated {V-15} spin polytope and the {M(en)(3)}(2+) complexes, with very weak coupling between these groups.Catalysis of outer-phase oxygen atom exchange reactions by encapsulated inner-phase water in {V15Sb6}-type polyoxovanadatesx302016105#N/AFALSE
3687
c6sc04048a10.1039/c6sc04048aFALSEhttps://doi.org/10.1002/chem.200800090Itami, KSynthesis and properties of [8]-, [10]-, [12]-, and [16] cyClo-1,4-naphthylenes2017#N/ATRUE
3688
c6sc03911a10.1039/c6sc03911aFALSEJung, YSingle-atom catalysts for CO2 electroreduction with significant activity and selectivity improvements2017#N/ATRUE
3689
c6sc02123a10.1039/c6sc02123aFALSEhttps://doi.org/10.1039/c6sc02123aGarcia-Lastra, JMChem. Sci.It is known that breaking the scaling relations between the adsorption energies of *O, *OH, and *OOH is paramount in catalyzing more efficiently the reduction of O-2 in fuel cells and its evolution in electrolyzers. Taking metalloporphyrins as a case study, we evaluate here the adsorption energies of those adsorbates on the metal centers Cr, Mn, Fe, Co, Ni and Cu, using H, F, OH, NH2, CH3, and BH2 as ring ligands. We show that covalence systematically breaks scaling relations under vacuum by strengthening certain M-OOH bonds. However, covalence modifies adsorbate solvation in solution depending on the degree of covalence of the metal-adsorbate bonds. The two effects have similar magnitudes and opposite signs, such that scaling relations are restored in solution. Thus, solvation is a crucial ingredient that must be taken into account in studies aimed at breaking scaling relations in solution. Our findings suggest that the choice of metal and ligand determines the catalytic activity within the limits imposed by scaling relations, whereas the choice of an appropriate solvent can drive such activity beyond those limits.How covalence breaks adsorption-energy scaling relations and solvation restores them87201739#N/ATRUE
3690
c5sc03361f10.1039/c5sc03361fFALSEhttps://doi.org/10.1002/chem.200701615Nozaki, KLigand-controlled insertion regioselectivity accelerates copolymerisation of ethylene with methyl acrylate by cationic bisphosphine monoxide-palladium catalystsx2016#N/AFALSE
3691
c6sc02106a10.1039/c6sc02106aFALSEhttps://doi.org/10.1039/c6sc02106aFischer, RAChem. Sci.The analogy between ZnR fragments and the hydrogen radical represents a fruitful concept in organometallic synthesis. The organozinc(II) and-zinc(I) sources ZnMe2 (Me = methyl) and [Zn2Cp*(2)] (Cp* = pentamethylcyClopentadienyl) provide one-electron fragments center dot ZnR (R = Me, Cp*), which can be trapped by transition metal complexes [LaM], yielding [L-b(ZnR)(n)]. The addition of the dizinc compound [Zn2Cp*(2)] to coordinatively unsaturated [LaM] by the homolytic Cleavage of the Zn-Zn bond can be compared to the Classic oxidative addition reaction of H-2, forming dihydride complexes [LaM(H)(2)]. It has also been widely shown that dihydrogen coordinates under preservation of the H-H bond in the case of certain electronic properties of the transition metal fragment. The sigma-aromatic triangular Clusters [Zn3Cp*(3)](+) and [Zn2CuCp*(3)] may be regarded as the first indication of this so far unknown, side-on coordination mode of [Zn2Cp*(2)]. With this background in mind the question arises if a series of complexes featuring the Zn2M structural motif can be prepared exhibiting a (more or less) intact Zn-Zn interaction, i.e. di-zinc complexes which are analogous to non-Classical dihydrogen complexes of the Kubas type. In order to probe this idea, a series of interrelated organozinc nickel and palladium complexes and Clusters were synthesized and characterized as model compounds: [Ni(ZnCp*)(ZnMe)(PMe3)(3)] (1), [Ni(ZnCp*)(2)(ZnMe)(2)(PMe3)(2)] (2), [{Ni((CNBu)-Bu-t)(2)(mu(2)-ZnCp*)(mu(2)-ZnMe)}(2)] (3), [Pd(ZnCp*)(4)((CNBu)-Bu-t)(2)] (4) and [Pd3Zn6(PCy3)(2)(Cp*)(4)] (5). The dependence of Zn center dot center dot center dot Zn interactions as a function of the ligand environments and the metal centers was studied. Experimental X-ray crystallographic structural data and DFT calculations support the analogy between dihydrogen and dizinc transition metal complexes.Zn center dot center dot center dot Zn interactions at nickel and palladium centers18201629#N/ATRUE
3692
c6sc00383d10.1039/c6sc00383dFALSEhttps://doi.org/10.1039/c6sc00383dShionoya, MChem. Sci.DNA three-way junctions (3WJs) are essential structural motifs for DNA nanoarchitectures and DNA-based materials. We report herein a metal-responsive structural transformation between DNA duplexes and 3WJs using artificial oligonuCleotides modified with a 2,2'-bipyridine (bpy) ligand. A mixture of bpy-modified DNA strands and natural complementary strands were self-assembled exClusively into duplexes without any transition metal ions, while they formed 3WJs in the presence of Ni-II ions. This transformation was induced by the formation of an interstrand Ni-II(bpy)(3) complex, which served as a template for the 3WJ assembly. Altering the amount and identity of the metal ion regulated the 3WJ induction efficiency. Removal of the metal using EDTA quantitatively regenerated the duplexes. The metal-dependent structural conversion shown here has many potential applications in the development of stimuli-responsive DNA materials.Metal-responsive structural transformation between artificial DNA duplexes and three-way junctions40201630#N/ATRUE
3693
c5sc03104d10.1039/c5sc03104dFALSEhttps://doi.org/10.1039/c5sc03104dFigueroa, JSChem. Sci.Complexes bearing electron rich transitionmetal centers, especially those displaying coordinative unsaturation, are well-suited to form reverse-dative s-interactions with Lewis acids. Herein we demonstrate the generality of zerovalent, group 10 m-terphenyl isocyanide complexes to form reverse-dative sigma-interactions to Tl(I) and Ag(I) centers. Structural and spectroscopic investigations of thesemetal-only Lewis pairs (MOLPs) has allowed insight into the electronic consequences of Lewis-acid ligation within the primary coordination sphere of a transition metal center. Treatment of the bis-isocyanide complex, Pt(CNArDipp2)(2) (Ar-Dipp2 = 2,6-(2,6-(i-Pr)(2)C6H3)(2)C6H3) with TlOTf (OTf = [O3SCF3](-)) yields the Pt/Tl MOLP [TlPt(CNArDipp2)(2)] OTf (1). H-1 NMR and IR spectroscopic studies on 1, and its Pd congener [TlPd(CNArDipp2)(2)] OTf (2), demonstrate that the M -> Tl interaction is labile in solution. However, treatment of complexes 1 and 2 with Na[BAr4F] (Ar-F = 3,5-(CF3)(2)C6H3) produces [TlPt(CNArDipp2)(2)] BAr4F (3) and [TlPd(CNArDipp2)(2)] BAr4F (4), in which Tl(I) binding is shown to be static by IR spectroscopy and, in the case of 3, Pt-195 NMR spectroscopy as well. This result provides strong evidence that the M -> Tl linkages can be attributed primarily to sigma-donation from the group 10 metal to Tl, as loss of ionic stabilization of Tl by the triflate anion is compensated for by increasing the degree of M -> Tl sigma-donation. In addition, X-ray Absorption Near-Edge Spectroscopy (XANES) on the Pd/Tl and Ni/Tl MOLPs, [TlPd(CNArDipp2)(2)]OTf (2) and [TlNi(CNArMes2)(3)]OTf, respectively, is used to illustrate that the formation of a reverse-dative sigma-interaction with Tl(I) does not alter the spectroscopic oxidation state of the group 10 metal. Also reported is the ability of M(CNArDipp2)(2) (M = Pt, Pd) to form MOLPs with Ag(I), yielding the complexes [AgM(CNArDipp2)(2)]OTf (5, M = Pt; 6, M = Pd). As was determined for the Tl-containing MOLPs 1-4, it is shown that the spectroscopic oxidation states of the group 10 metal in 5 and 6 are essentially unchanged compared to the zerovalent precursors M(CNArDipp2)(2). However, in the case of 5 and 6, the formation of a dative M -> Ag sigma-bonding interaction facilitates the binding of Lewis bases to the group 10 metal trans to Ag, illustrating the potential of acceptor fragments to open up new coordination sites on transition metal complexes without formal, two-electron oxidation.Metal-only Lewis pairs between group 10 metals and Tl(I) or Ag(I): insights into the electronic consequences of Z-type ligand bindingx26201590#N/AFALSE
3694
c5sc02854j10.1039/c5sc02854jFALSEhttps://doi.org/10.1039/c5sc02854jMurrie, MChem. Sci.Monometallic complexes based on 3d transition metal ions in certain axial coordination environments can exhibit appreciably enhanced magnetic anisotropy, important for memory applications, due to stabilisation of an unquenched orbital moment. For high-spin trigonal bipyramidal Ni(II), if competing structural distortions can be minimised, this may result in an axial anisotropy that is at least an order of magnitude stronger than found for orbitally non-degenerate octahedral complexes. Broadband, high-field EPR studies of [Ni(MDABCO)(2)Cl-3]ClO4 (1) confirm an unprecedented axial magnetic anisotropy, which pushes the limits of the familiar spin-only description. Crucially, compared to complexes with multidentate ligands that encapsulate the metal ion, we see only a very small degree of axial symmetry breaking. 1 displays field-induced slow magnetic relaxation, which is rare for monometallic Ni(II) complexes due to efficient spin-lattice and quantum tunnelling relaxation pathways.Pushing the limits of magnetic anisotropy in trigonal bipyramidal Ni(II)x103201523#N/AFALSE
3695
c6cc04951f10.1039/c6cc04951fFALSEYang, WSEnhancement of oxygen evolution performance through synergetic action between NiFe metal core and NiFeOx shell2016#N/ATRUE
3696
c5sc02611c10.1039/c5sc02611cFALSEhttps://doi.org/10.1039/c5sc02611cGao, SChem. Sci.The slow magnetic relaxation typical for single-ion magnets has been known for certain low-coordinate 3d metal complexes with d(6), d(7), and d(9) electronic configurations, but never for d(8) complexes. Herein, we report a study on two-coordinate d(8) cobalt(I)-N-heterocyClic carbene complexes, for which slow magnetic relaxation behavior was observed for [Co(IMes)(2)][BPh4] (IMes: 1,3-dimesitylimidazol-2-ylidene) under an applied dc field. The system represents the first d(8) single-ion magnet, and features a fitted energy barrier of U-eff = 21.3 cm(-1) and pre-exponential factor of tau(0) = 6.6 x 10(-6) s. The analog two-coordinate cobalt(I) complexes with different NHC ligands, [Co(sIMes)(2)][BPh4] (sIMes: 1,3-dimesitylimidazolin-2-ylidene) and [Co(IAd)(2)][BAr4F] (IAd: 1,3-dimesitylimidazol-2-ylidene; BAr4F: tetra(3,5-ditrifluoromethylphenyl)borate), do not show such single-ion magnet behaviour. Ab initio calculations imply that the dihedral angle between the two NHC planes and the degree of unsaturation of the NHC ligands can dramatically alter the D value of the two-coordinate cobalt(I)-NHC ions, possibly via changing of the Co-NHC pi-interactions, and hence affect the spin-orbit coupling splitting.Observation of the single-ion magnet behavior of d(8) ions on two-coordinate Co(I)-NHC complexesx82201554#N/AFALSE
3697
c5sc02544c10.1039/c5sc02544cFALSEhttps://doi.org/10.1039/cc9960000059Li, GRPt/Ni(OH)(2)-NiOOH/Pd multi-walled hollow nanorod arrays as superior electrocatalysts for formic acid electrooxidationx2015#N/AFALSE
3698
c5sc02417j10.1039/c5sc02417jFALSEhttps://doi.org/10.1039/c5sc02417jDuan, XChem. Sci.A new electrochemical synthesis route was developed for the fabrication of Fe-containing layered double hydroxide (MFe-LDHs, M = Ni, Co and Li) hierarchical nanoarrays, which exhibit highly-efficient electrocatalytic performances for the oxidation reactions of several small molecules (water, hydrazine, methanol and ethanol). Ultrathin MFe-LDH nanoplatelets (200-300 nm in lateral length; 8-12 nm in thickness) perpendicular to the substrate surface are directly prepared within hundreds of seconds (<300 s) under cathodic potential. The as-obtained NiFe-LDH nanoplatelet arrays display promising behavior in the oxygen evolution reaction (OER), giving rise to a rather low overpotential (0.224 V) at 10.0 mA cm(-2) with largely enhanced stability, much superior to previously reported electro-oxidation catalysts as well as the state-of-the-art Ir/C catalyst. Furthermore, the MFe-LDH nanoplatelet arrays can also efficiently catalyze several other fuel molecules' oxidation (e.g., hydrazine, methanol and ethanol), delivering a satisfactory electrocatalytic activity and a high operation stability. In particular, this preparation method of Fe-containing LDHs is amenable to fast, effective and large-scale production, and shows promising applications in water splitting, fuel cells and other Clean energy devices.Fast electrosynthesis of Fe-containing layered double hydroxide arrays toward highly efficient electrocatalytic oxidation reactions
Electrocatalytic
273201552#N/AFALSE
3699
c5sc02269j10.1039/c5sc02269jFALSEhttps://doi.org/10.1039/c5sc02269jDarensbourg, MYChem. Sci.The effect of S-acetylation in MN2S2 complexes on metal exchange reactivity was examined in a series of MN2S2O2 complexes. While Clean exchange processes do not occur for the MN2S2 derivatives where formation of S-bridged aggregates predominate, acetylation permits the metal exchange with hierarchy that follows the Irving-Williams series of stability for first row transition metals: Fe2+ < Co2+ < Ni2+ < Cu2+ > Zn2+. The rate determining step consistent with kinetic parameters depends on both M and M', supporting a mechanism of exchange that involves ligand unwrapping/rewrapping process as earlier defined by Margerum et al. for M(EDTA) systems. The enhanced metal exchange deriving from S-acetylation is of significance to probes and detection of cysteine-S metallo-proteins and metalloenzyme active sites, and highlights a new role for S-acetylation.The ligand unwrapping/rewrapping pathway that exchanges metals in S-acetylated, hexacoordinate N2S2O2 complexesx4201547#N/AFALSE
3700
c6cc03901d10.1039/c6cc03901dFALSEhttps://doi.org/10.1039/c6cc03901dShafaat, HSAn internal electron reservoir enhances catalytic CO2 reduction by a semisynthetic enzyme2016#N/ATRUE
3701
c5sc01349f10.1039/c5sc01349fhttps://doi.org/10.1039/c5sc01349fDurrant, JRChem. Sci.Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye (RuP) and a nickel bis(diphosphine) electrocatalyst (NiP) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H-2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP-NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH <4.5, the efficiency of the system is limited by the yield of RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP, which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP-NiP photocatalytic system, which can be widely applied to other photocatalytic systems.Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen productionPhotocatalyst30201546#N/AFALSE
3702
c5sc01137j10.1039/c5sc01137jFALSEhttps://doi.org/10.1039/c5sc01137jHong, SChem. Sci.The systematic investigation of substrate-bound alpha-amino acid auxiliaries has resulted in catalytic asymmetric C-H functionalization of cyClopropanes enabled by amino acid amides as chiral bidentate directing groups. The use of an Ile-NH2 auxiliary embedded in the substrate provided excellent levels of asymmetric induction (diastereomeric ratio of up to 72:1) in the Pd(II)-catalyzed beta-methylene C(sp(3))-H bond Activation of cyClopropanes and cross-coupling with Aryl iodides.Asymmetric C-H functionalization of cyClopropanes using an isoleucine-NH2 bidentate directing groupx56201574#N/AFALSE
3703
c6cc02911f10.1039/c6cc02911fFALSEhttps://doi.org/10.1039/c6cc02911fIwanaga, MEnantioselective construction of imidazolines having vicinal tetra-substituted stereocenters by direct Mannich reaction of alpha-substituted alpha-isocyanoacetates with ketimines2016#N/ATRUE
3704
c5sc00840a10.1039/c5sc00840aFALSEhttps://doi.org/10.1039/c5sc00840aJaramillo-Botero, AChem. Sci.Recently Debe et al. reported that Pt3Ni7 leads to extraordinary Oxygen Reduction Reaction (ORR) activity. However, several reports show that hardly any Ni remains in the layers of the catalysts Close to the surface (Pt-skin effect). This paradox that Ni is essential to the high catalytic activity with the peak ORR activity at Pt3Ni7 while little or no Ni remains Close to the surface is explained here using large-scale first-principles-based simulations. We make the radical assumption that processing Pt-Ni catalysts under ORR conditions would leach out all Ni accessible to the solvent. To simulate this process we use the ReaxFF reactive force field, starting with random alloy partiCles ranging from 50% Ni to 90% Ni and containing up to similar to 300 000 atoms, deleting the Ni atoms, and equilibrating the resulting structures. We find that the Pt3Ni7 case and a final partiCle radius around 7.5 nm lead to internal voids in communication with the exterior, doubling the external surface footprint, in fair agreement with experiment. Then we examine the surface character of these nanoporous systems and find that a prominent feature in the surface of the de-alloyed partiCles is a rhombic structure involving 4 surface atoms which is crystalline-like but under-coordinated. Using density-functional theory, we calculate the energy barriers of ORR steps on Pt nanoporous catalysts, focusing on the O-ad-hydration reaction (O-ad + H2Oad -> OHad + OHad) but inCluding the barriers of O-2 dissociation (O-2ad -> O-ad + O-ad) and water formation (O-Had + H-ad -> H-2Oad). We find that the reaction barrier for the Oad-hydration rate-determining-step is reduced significantly on the de-alloyed surface sites compared to Pt(111). Moreover we find that these active sites are prevalent on the surface of partiCles de-alloyed from a Pt-Ni 30 : 70 initial composition. These simulations explain the peak in surface reactivity at Pt3Ni7, and provide a rational guide to use for further optimization of improved catalytic and nanoporous materials.The atomistic origin of the extraordinary oxygen reduction activity of Pt3Ni7 fuel cell catalystsx40201549#N/AFALSE
3705
c6cc01510g10.1039/c6cc01510gFALSEhttps://doi.org/10.1039/c6cc01510gSteffen, AAn unexpected transmetalation intermediate: isolation and structural characterization of a solely CH3 bridged di-copper(I) complex2016#N/ATRUE
3706
c5sc00398a10.1039/c5sc00398aFALSEhttps://doi.org/10.1039/c5sc00398aHelm, MLChem. Sci.Oxidation of hydrogen (H-2) to protons and electrons for energy production in fuel cells is currently catalyzed by platinum, but its low abundance and high cost present drawbacks to widespread adoption. Precisely controlled proton removal from the active site is critical in hydrogenase enzymes in nature that catalyze H-2 oxidation using earth-abundant metals (iron and nickel). Here we report a synthetic iron complex, (Cp-C5F4N) Fe((PNPEt)-N-Et-P-(CH2)3NMe2)(Cl), that serves as a precatalyst for the oxidation of H-2, with turnover frequencies of 290 s(-1) in fluorobenzene, under 1 atm of H-2 using 1,4- diazabicyClo [2.2.2] octane (DABCO) as the exogenous base. The inClusion of a properly tuned outer coordination sphere proton relay results in a cooperative effect between the primary, secondary and outer coordination spheres for moving protons, increasing the rate of H-2 oxidation without increasing the overpotential when compared with the analogous complex featuring a single pendant base. This finding emphasizes the key role of pendant amines in mimicking the functionality of the proton pathway in the hydrogenase enzymes.Increasing the rate of hydrogen oxidation without increasing the overpotential: a bio-inspired iron molecular electrocatalyst with an outer coordination sphere proton relayx29201545#N/AFALSE
3707
c5sc04748j10.1039/c5sc04748jFALSEhttps://doi.org/10.1039/c5sc04748jOsuka, AChem. Sci.Oxidation of 10,15,20-triAryl Ni(II)-porphyrins bearing an electron-withdrawing substituent at the 5-position with DDQ and FeCl3 gave 10,12- and 18,20-doubly phenylene-fused Ni(II)-porphyrins regioselectively. A doubly phenylene-fused meso-chloro porphyrin thus prepared was reductively coupled to give a meso-meso linked dimer, which was further converted to a quadruply phenylene-fused meso-meso, beta-beta, beta-beta triply linked Zn(II)-diporphyrin via inner-metal exchange followed by oxidation with DDQ and Sc(OTf)(3). As compared to the usual meso-meso, beta-beta, beta-beta triply linked Zn(II)-diporphyrin, this pi-extended porphyrin dyad exhibits a smaller HOMO-LUMO gap and a larger two-photon absorption cross-section.Regioselective phenylene-fusion reactions of Ni(II)-porphyrins controlled by an electron-withdrawing meso-substituent19201659#N/ATRUE
3708
c5sc04652a10.1039/c5sc04652aFALSEhttps://doi.org/10.1039/c5sc04652aLiaw, WFChem. Sci.Carbon dioxide is expected to be employed as an inexpensive and potential feedstock of C-1 sources for the mass production of valuable chemicals and fuel. Versatile chemical transformations of CO2, i.e. insertion of CO2 producing bicarbonate/acetate/formate, Cleavage of CO2 yielding mu-CO/mu-oxo transition-metal complexes, and electrocatalytic reduction of CO2 affording CO/HCOOH/CH3OH/CH4/C2H4/oxalate were well documented. Herein, we report a novel pathway for the reductive Activation of CO2 by the [Ni-III(OMe)(P(C6H3-3-SiMe3-2-S)(3))](-) complex, yielding the [Ni-III(kappa(1)-OCOc(center dot-))(P(C6H3-3-SiMe3-2-S)(3))](-) complex. The formation of this unusual Ni-III(kappa(1)-OCOc(center dot-)) complex was characterized by single-crystal X-ray diffraction, EPR, IR, SQUID, Ni/S K-edge X-ray absorption spectroscopy, and Ni valence-to-core X-ray emission spectroscopy. The inertness of the analogous complexes [Ni-III(SPh)], [Ni-II(CO)], and [Ni-II(N2H4)] toward CO2, in contrast, demonstrates that the ionic [NiIII(OMe)] core attracts the binding of weak s-donor CO2 and triggers the subsequent reduction of CO2 by the nuCleophilic [OMe](-) in the immediate vicinity. This metal-ligand cooperative Activation of CO2 may open a novel pathway promoting the subsequent incorporation of CO2 in the buildup of functionalized products.[Ni-III(OMe)]-mediated reductive Activation of CO2 affording a Ni(kappa(1)-OCO) complex8201639#N/ATRUE
3709
c5cc05226b10.1039/c5cc05226bFALSEhttps://doi.org/10.1039/c5cc05226bKawi, SA highly active and stable Ni-Mg phyllosilicate nanotubular catalyst for ultrahigh temperature water-gas shift reactionx2015#N/AFALSE
3710
c5sc04486c10.1039/c5sc04486cFALSEhttps://doi.org/10.1039/c5sc04486cKoper, MTMThe importance of nickel oxyhydroxide deprotonation on its activity towards electrochemical water oxidation2016#N/ATRUE
3711
c5sc03663a10.1039/c5sc03663aFALSEhttps://doi.org/10.1039/c5sc03663aBroring, MChem. Sci.Cationic nickel(II) complexes of two ring-contracted porphyrinoid ligands distantly related to the corrins were prepared by metal templated macrocyClisation. The compounds show reversible electron transfer processes and were found to be the first porphyrinoid-based catalysts for C-C cross-coupling.Cationic nickel porphyrinoids with unexpected reactivity7201667#N/ATRUE
3712
c5sc03658e10.1039/c5sc03658eFALSEhttps://doi.org/10.1039/c5sc03658eFeng, XMNickel(II)-catalyzed enantioselective cyClopropanation of 3-alkenyl-oxindoles with phenyliodonium ylide via free carbene2016#N/ATRUE
3713
c5sc03225c10.1039/c5sc03225cFALSEhttps://doi.org/10.1039/c5sc03225cCowan, AJChem. Sci.The development of selective electrocatalysts for CO2 reduction in water offers a sustainable route to carbon based fuels and feedstocks. However, molecular catalysts are typically studied in non-aqueous solvents, in part to avoid competitive H-2 evolution. [Ni(cyClam)](2+) (1) is one of the few known electrocatalysts that operate in water and 30 years after its report its activity remains a rarely surpassed benchmark. Here we report that [Ni(cyClam-CO2H)](2+) (cyClam-CO2H = 1,4,8,11-tetraazacyClotetradecane-6-Carbonylic acid (2)) shows greatly enhanced activity versus 1 for CO production. At pHs < pK(a) of the pendant Carbonylic acid a large increase in catalytic activity occurs. Remarkably, despite the high proton concentration (pH 2), 2 maintains selectivity for CO2 reduction and is believed to be unique in operating selectively in such acidic aqueous solutions.A highly active nickel electrocatalyst shows excellent selectivity for CO2 reduction in acidic media51201638#N/ATRUE
3714
c4sc03946g10.1039/c4sc03946gFALSEhttps://doi.org/10.1039/c4sc03946gReisner, EChem. Sci.The catalyst [(CoBr)-Br-III((DO)(DOH)(4-BnPO3H2)(2-CH(2)py)pn)]Br, CoP3, has been synthesised to improve the stability and activity of cobalt catalysts immobilised on metal oxide surfaces. The CoP3 catalyst contains an equatorial diimine-dioxime ligand, (DOH)(2)pn = N-2, N-2'-propanediyl-bis(2,3-butanedione-2-imine-3-oxime), with a Benzylphosphonic acid (4-BnPO3H2) group and a methylpyridine (2-CH(2)py) ligand covalently linked to the bridgehead of the pseudo-macrocyClic diimine-dioxime ligand. The phosphonic acid functionality provides a robust anchoring group for immobilisation on metal oxides, whereas the pyridine is coordinated to the Co ion to enhance the catalytic activity of the catalyst. Electrochemical investigations in solution confirm that CoP3 shows electrocatalytic activity for the reduction of aqueous protons between pH 3 and 7. The metal oxide anchor provides the catalyst with a high affinity for mesostructured Sn-doped In2O3 electrodes (mesoITO; loading of approximately 22 nmol cm(-2)) and the electrostability of the attached CoP3 was confirmed by cyClic voltammetry. Finally, immobilisation of the catalyst on ruthenium-dye sensitised TiO2 nanopartiCles in aqueous solutions in the presence of a hole scavenger establishes the activity of the catalyst in this photocatalytic scheme. The advantages of the elaborate catalyst design in CoP3 in terms of stability and catalytic activity are shown by direct comparison with previously reported phosphonated Co catalysts. We therefore demonstrate that rational ligand design is a viable route for improving the performance of immobilised molecular catalysts.Enhancing H-2 evolution performance of an immobilised cobalt catalyst by rational ligand designx802015102#N/AFALSE
3715
c4sc03575e10.1039/c4sc03575eFALSEhttps://doi.org/10.1039/c4sc03575eClaverie, JPChem. Sci.The catalytic 1,2-insertion polymerization of polar norbornenes (NBEs) leads to the formation of functional rigid macromolecules with exceptional thermal, optical and mechanical properties. However, this remarkable reaction is plagued by the low reactivity of the polar monomers, and most notably of those bearing a functional group in endo position. We have examined the polymerization mechanism of NBEs bearing one or two CO2Me groups either in exo or endo position catalyzed by the so-called naked allyl Pd+ SbF6- catalyst (1). Although endo dimethyl ester of 5-norbornene-2,3-diCarbonylic acid (NBE(CO2Me)(2)) is polymerized by 1, two endo units are never inserted consecutively along the polymer chain. Indeed, 1 is a tandem catalyst which not only catalyzes the insertion of the monomer but also the isomerization of endo and exo isomers. Thus, the polymerization of endo monomers proceeds via a novel mechanism, coined rectification-insertion mechanism, whereby half of the endo monomers are rectified into exo ones prior insertion, leading to the formation of an alternating endo-exo copolymer using an endo only feedstock. With this mechanism, the lack of reactivity of endo norbornenes is bypassed, and the polymerization of predominantly endo polar NBEs bearing a variety of functionalities such as esters, imides, acids, aldehydes, alcohols, anhydrides, or Alkyl bromides proceeds with catalyst loadings as low as 0.002 mol%.Bypassing the lack of reactivity of endo-substituted norbornenes with the catalytic rectification-insertion mechanismx30201556#N/AFALSE
3716
c4sc03106g10.1039/c4sc03106gTRUEhttps://doi.org/10.1039/c4sc03106gWeix, DJChem. Sci.The nickel-catalyzed cross-coupling of Aryl halides with Alkyl radicals derived from Alkyl halides has recently been extended to couplings with carbon radicals generated by a co-catalyst. In this study, a new co-catalyst, cobalt phthalocyanine (Co(Pc)), is introduced and demonstrated to be effective for coupling substrates not prone to homolysis. This is because Co(Pc) reacts with electrophiles by an S(N)2 mechanism instead of by the electron-transfer or halogen abstraction mechanisms previously explored. Studies demonstrating the orthogonal reactivity of (bpy)Ni and Co(Pc), applying this selectivity to the coupling of Benzyl mesylates with Aryl halides, and the adaptation of these conditions to the less reactive Benzyl phosphate ester and an enantioconvergent reaction are presented.Cobalt co-catalysis for cross-electrophile coupling: diArylmethanes from Benzyl mesylates and Aryl halidesxCsp3-ring(s)-Csp2_ar
OP(O)(OEt)2
BrBenzylNo baseNo Base1152015554/15/2022FALSE
3717
c5sc03189c10.1039/c5sc03189cFALSEhttps://doi.org/10.1039/c5sc03189cJones, WDChem. Sci.A series of square-planar nickel hydride complexes supported by bis(phosphinite) pincer ligands with varying substituents (-OMe, -Me, and -But) on the pincer backbone have been synthesized and completely characterized by NMR spectroscopy, IR spectroscopy, elemental analysis, and X-ray crystallography. Their cyClic voltammograms show irreversible oxidation peaks (peak potentials from 101 to 316 mV vs. Fc(+)/Fc) with peak currents consistent with overall one-electron oxidations. Chemical oxidation by the one-electron oxidant Ce(NBu4)(2)(NO3)(6) was studied by NMR spectroscopy, which provided quantitative evidence for post-oxidative H-2 evolution leading to a solvent-coordinated nickel(II) species with the pincer backbone intact. Bulk electrolysis of the unsubstituted nickel hydride (3a) showed an overall one-electron stoichiometry and gas chromatographic analysis of the headspace gas after electrolysis further confirmed stoichiometric production of dihydrogen. Due to the extremely high rate of the post-oxidative chemical process, electrochemical simulations have been used to establish a lower limit of the bimolecular rate constant (k(f) > 10(7) M-1 s(-1)) for the H-2 evolution step. To the best of our knowledge, this is the fastest known oxidative H-2 evolution process observed in transition metal hydrides. Quantum chemical calculations based on DFT indicate that the one-electron oxidation of the nickel hydride complex provides a strong chemical driving force (90.3 kcal mol(-1)) for the production of H-2 at highly oxidizing potentials.Rapid oxidative hydrogen evolution from a family of square-planar nickel hydride complexes20201657#N/ATRUE
3718
c4sc02357a10.1039/c4sc02357ahttps://doi.org/10.1039/c4sc02357aNocera, DGChem. Sci.PhotoActivation of M-X bonds is a challenge for photochemical HX splitting, particularly with first-row transition metal complexes because of short intrinsic excited state lifetimes. Herein, we report a tandem H-2 photocyCle based on combination of a non-basic photoredox phosphine mediator and nickel metal catalyst. Synthetic studies and time-resolved photochemical studies have revealed that phosphines serve as photochemical H-atom donors to Ni(II) trihalide complexes to deliver a Ni(I) centre. The H-2 evolution catalytic cyCle is Closed by sequential disproportionation of Ni(I) to afford Ni(0) and Ni(II) and protolytic H-2 evolution from the Ni(0) intermediate. The results of these investigations suggest that H-2 photogeneration proceeds by two sequential catalytic cyCles: a photoredox cyCle catalyzed by phosphines and an H-2-evolution cyCle catalyzed by Ni complexes to circumvent challenges of photochemistry with first-row transition metal complexes.Tandem redox mediator/Ni(II) trihalide complex photocyCle for hydrogen evolution from HClPhotocatalyst11201546#N/AFALSE
3719
c4sc01231c10.1039/c4sc01231cFALSEhttps://doi.org/10.1039/c4sc01231cLemcoff, NGChem. Sci.A comprehensive methodology to prepare nanometric size organometallic partiCles (ONPs) containing rhodium(I), iridium(I) and nickel(0) with ROMP-derived polycyCloocta-1,5-diene (pCOD) by a controlled single chain collapse mechanism was developed. The polymeric complexes could be produced via direct exchange of the respective labile ligands of metal complexes by the 1,5-hexadiene elements in pCOD, or via in situ reduction of metal ions in the presence of the polymer. These well-defined p-bound polymeric complexes were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS) and size exClusion chromatography (SEC) measurements and the resulting polymer sizes were found to be inversely proportional to the amount of metal added due to concomitant single chain collapse. Moreover, these procedures were readily extended to the synthesis of organobimetallic nanopartiCles containing two metals; which could be added in commutative order and specific metal ratios. The embedded metal elements were found to be readily accessible for applications in catalysis, where the Close proximity of the catalytic centers led to distinctive reactivity compared to the isolated complexes.A general approach to mono- and bimetallic organometallic nanopartiClesx55201457#N/AFALSE
3720
c5sc02703a10.1039/c5sc02703aFALSEhttps://doi.org/10.1039/c5sc02703aHeyduk, AFNear-IR absorbing donor-acceptor ligand-to-ligand charge-transfer complexes of nickel(II)2016#N/ATRUE
3721
c5sc01441g10.1039/c5sc01441gFALSEhttps://doi.org/10.1039/c5sc01441gIluc, VMChem. Sci.A series of palladium(II) radical carbene complexes, [PC.(sp(2))P]PdI, [PC.(sp(2))P]PdBr, and [PC.(sp(2))P]PdCl (PC(sp(3))H2P = bis[2-(di-iso-propylphosphino)-phenyl]methane), is described. Compound [PC.(sp(2))P] PdI dimerizes to {[PC(sp(2))P]PdI}(2) in the solid state, akin to the formation of Gomberg's dimer. While the bromo and the iodo derivatives could be obtained from the oxidation of [PC.(sp(2))P]Pd(PMe3) by the respective dihalogens, a halogen transfer reaction from CH2Cl2 was used for the formation of [PC.(sp(2))P] PdCl. The halogen transfer from CH2X2 (X = Cl, Br, I) could be used to obtain all three radical carbene palladium complexes and also allowed the isolation of [PC(CH2)P]Pd(PMe3), which is the result of methylene group transfer from CH2X2. Compound [PC(CH2)P]Pd(PMe3) was independently synthesized from [PC(CH3)HP]PdCl2, which contains a supporting ligand analogous to that of the radical carbene complexes but has one of the hydrogen atoms replaced by a methyl group. All three carbene radical species abstract a hydrogen from 9,10-dihydroanthracene or (Bu3SnH)-Bu-n.Palladium carbene complexes as persistent radicals48201556#N/ATRUE
3722
c5sc00929d10.1039/c5sc00929dFALSEhttps://doi.org/10.1039/c5sc00929dRajanBabu, TVChem. Sci.In the presence of bidentate 1,n-bis-diphenylphosphinoalkane-CoCl2 complexes {Cl2Co[P similar to P]} and Me3Al or methylaluminoxane, acyClic (E)-1,3-dienes react with ethylene (1 atmosphere) to give excellent yields of hydroVinylation products. The regioselectivity (1,4- or 1,2-addition) and the alkene configuration (E- or Z-) of the resulting product depend on the nature of the ligand and temperature at which the reaction is carried out. Cobalt(II)-complexes of 1,1-diphenylphosphinomethane and similar ligands with narrow bite angles give mostly 1,2-addition, retaining the E-geometry of the original diene. Complexes of most other ligands at low temperature (-40 degrees C) give almost exClusively a single branched product, (Z)-3-Alkylhexa-1,4-diene, which arises from a 1,4-hydroVinylation reaction. A minor product is the linear adduct, a 6-Alkyl-hexa-1,4-diene, also arising from a 1,4-addition of ethylene. As the temperature is increased, a higher proportion of the major branched-1,4-adduct appears as the (E)-isomer. The unexpectedly high selectivity seen in the Cocatalysed reaction as compared to the corresponding Ni-catalysed reaction can be rationalized by invoking the intermediacy of an eta(4)-[(diene)[P similar to P]CoH](+)-complex and its subsequent reactions. The enhanced reactivity of terminal E-1,3-dienes over the corresponding Z-dienes can also be explained on the basis of the ease of formation of this eta(4)-complex in the former case. The lack of reactivity of the X2Co(dppb) (X = Cl, Br) complexes in the presence of Zn/ZnI2 makes the Me3Al-mediated reaction different from the previously reported hydroalkenylation of dienes. Electron-rich phospholanes, bis-oxazolines and N-heterocyClic carbenes appear to be poor ligands for the Co(II)-catalysed hydroVinylation of 1,3-dienes. An extensive survey of chiral ligands reveals that complexes of DIOP, BDPP and Josiphos ligands are quite effective for these reactions even at -45 degrees C and enantioselectivities in the range of 90-99% ee can be realized for a variety of 1,3-dienes. Cobalt(II)-complex of an electron-deficient Josiphos ligand is especially active, requiring only < 1 mol% catalyst to effect the reactions.Cobalt-catalysed asymmetric hydroVinylation of 1,3-dienes412015114#N/ATRUE
3723
c4sc00449c10.1039/c4sc00449cFALSEhttps://doi.org/10.1039/c4sc00449c
Korybut-Daszkiewicz, B
Chem. Sci.A novel, mechanically interlocked molecular device was obtained from unique supramolecular tectons -pi-deficient tetraazamacrocyClic complexes of copper(II) and nickel(II). We present the synthesis of the first rotaxanes based on donor-acceptor interactions involving transition metal complexes. While spontaneous shuttling manifests itself in the variability of the NMR spectra, voltammetric experiments reveal a surprising mode of potential-controlled molecular switching, which does not employ common co-conformational changes. Significantly, it relies on reversible folding/unfolding of the rotaxane. The process is driven by the interplay between electrostatic repulsion and cohesive pi-pi interaction - a tug of war with a critical point at 1.31 V. Although rotaxanes with equivalent stations are considered degenerate molecular shuttles, we show that this is not the case when an unusual mechanism of switching is involved.An electrochemically switchable foldamer - a surprising feature of a rotaxane with equivalent stationsElectrochemistry20201431#N/AFALSE
3724
c5sc00476d10.1039/c5sc00476dFALSEhttps://doi.org/10.1039/c5sc00476dDempsey, JLChem. Sci.A Ni(II) bisphosphine dithiolate compound degrades into an electrode-adsorbed film that can evolve hydrogen under reducing and protic conditions. An electrochemical study suggests that the degradation mechanism involves an initial concerted proton-electron transfer. The potential susceptibility of Ni-S bonds in molecular hydrogen evolution catalysts to degradation via C-S bond Cleavage is discussed.Electrode initiated proton-coupled electron transfer to promote degradation of a nickel(II) coordination complex41201564#N/ATRUE
3725
c5cc09840h10.1039/c5cc09840hFALSELuo, HABoosting one-step conversion of cyClohexane to adipic acid by NO2 and VPO composite catalysts2016#N/ATRUE
3726
c4cc08012b10.1039/c4cc08012bWang, FSControlled synthesis of high molecular weight poly(3-hexylthiophene)s via Kumada catalyst transfer polycondensation with Ni(IPr)(acac)(2) as the catalystx2015#N/AFALSE
3727
c5cc07455j10.1039/c5cc07455jFALSEOng, TGNickel-catalysed para-CH Activation of pyridine with switchable regioselective hydroheteroArylation of allylarenes2015#N/ATRUE
3728
c4cc05355a10.1039/c4cc05355aFALSEhttps://doi.org/10.1039/c4cc05355aAukauloo, AA nickel dimethyl glyoximato complex to form nickel based nanopartiCles for electrocatalytic H-2 productionx2014#N/AFALSE
3729
c5cc04389a10.1039/c5cc04389aFALSELu, YHigh-performance PdNi alloy structured in situ on monolithic metal foam for coalbed methane deoxygenation via catalytic combustion2015#N/ATRUE
3730
c5cc01932j10.1039/c5cc01932jFALSEhttps://doi.org/10.1039/c5cc01932jLimbach, MAcrylate formation from CO2 and ethylene: catalysis with palladium and mechanistic insight2015#N/ATRUE
3731
c4cc02919d10.1039/c4cc02919dFALSEhttps://doi.org/10.1039/c4cc02919dGottfried, JMCoordination reaction between tetraphenylporphyrin and nickel on a TiO2(110) surfacex2014#N/AFALSE
3732
c5cc00147a10.1039/c5cc00147aFALSEhttps://doi.org/10.1039/c9sc00174cDriess, MReductive Cleavage of P-4 by iron(I) centres: synthesis and structural characterisation of Fe-2(P-2)(2) complexes with two bridging P-2(2-) ligands2015#N/ATRUE
3733
c4cc02022g10.1039/c4cc02022gFALSEhttps://doi.org/10.1039/c4cc02022gNishihara, HOrdered alignment of a one-dimensional pi-conjugated nickel bis(dithiolene) complex polymer produced via interfacial reactionsx2014#N/AFALSE
3734
c4cc01286k10.1039/c4cc01286kFALSEhttps://doi.org/10.1039/c9sc05005aSong, SYIn situ assembly of well-dispersed gold nanopartiCles on hierarchical double-walled nickel silicate hollow nanofibers as an efficient and reusable hydrogenation catalystx2014#N/AFALSE
3735
c3sc52984c10.1039/c3sc52984cFALSEhttps://doi.org/10.1039/c3sc52984cGarcia-Fernandez, PTheoretical study of the magnetic anisotropy and magnetic tunnelling in mononuClear Ni(II) complexes with potential molecular magnet behaviorx2014#N/AFALSE
3736
c3sc52450g10.1039/c3sc52450gFALSEhttps://doi.org/10.1039/c3sc52450gChirik, PJChem. Sci.The reactivity of the disubstituted diazoalkane, N2CPh2 with a family of bis(imino)pyridine iron dinitrogen complexes was examined. For the most sterically protected member of the series, ((PDI)-P-iPr)Fe(N-2)(2) ((PDI)-P-iPr = 2,6-(2,6-(Pr2C6H3N)-Pr-i=CMe)(2)C5H3N), an S = 1 iron diazoalkane complex was obtained and structurally characterized. Reducing the size of the 2,6-Aryl substituents to ethyl or methyl groups resulted in isolation of bis(imino)pyridine iron carbene complexes. Magnetic measurements established S = 1 ground states, demonstrating rare examples of iron carbenes in a weak ligand field. Electronic structure determination using metrical parameters from X-ray diffraction as well as Mossbauer, XAS and computational data established high-spin iron(s) compounds engaged in antiferromagnetic coupling with redox-active bis(imino)pyridine and carbene radicals.Synthesis, electronic structure and reactivity of bis(imino)pyridine iron carbene complexes: evidence for a carbene radicalx56201465#N/AFALSE
3737
c4sc04002c10.1039/c4sc04002cFALSEhttps://doi.org/10.1039/c4sc04002cDikarev, EVChem. Sci.A novel series of mixed-valent, heteroleptic transition metal diketonates that can be utilized as prospective single-source precursors for the low-temperature preparation of oxide materials are reported. The first mixed-valent iron beta-diketonates with different Fe-III/Fe-II ratios have been synthesized by applying the mixed-ligand approach. Based on nearly quantitative reaction yields and analysis of iron-oxygen bonds, these compounds were formulated as [Fe-III(acac)(3)][Fe-II(hfac)(2)] (1) and [Fe-II(hfac)(2)][Fe-III(acac)(3)][Fe-II(hfac)(2)] (2). In the above heteroleptic complexes, the Lewis acidic, coordinatively unsaturated Fe-II centers chelated by two hfac (hexafluoroacetylacetonate) ligands with electron-withdrawing substituents maintain bridging interactions with oxygen atoms of electron-donating acac (acetylacetonate) groups that chelate the neighboring Fe-III atoms. Switching the ligands on Fe-III and Fe-II atoms in starting reagents resulted in the instant ligand exchange between iron centers and in yet another polynuClear homometallic diketonate [Fe-II(hfac)(2)][Fe-III(acac)(2)(hfac)][Fe-II(hfac)(2)] (3) that adheres to the same bonding pattern as in complexes 1 and 2. The proposed synthetic methodology has been extended to design heterometallic diketonates with different M : M' ratios. Homometallic parent molecules have been used as templates to obtain heterometallic mixed-valent [Fe-III(acac)(3)][Mn-II(hfac)(2)] (4) and [Ni-II(hfac)(2)] - [Fe-III(acac)(3)][Ni-II(hfac)(2)] (5) complexes. The combination of two different diketonate ligands with electron-donating and electron-withdrawing substituents was found to be crucial for maintaining the above mixed-valent heterometallic assemblies. Theoretical investigation of two possible isomers, [Fe-III(acac)(3)][Mn-II(hfac)(2)] (4) and [Mn-III(acac)(3)][Fe-II(hfac)(2)] (40) provided an additional support for the metal site assignment giving a preference of 9.78 kcal mol(-1) for the molecule 4. Heterometallic complexes obtained in the course of this study have been found to act as effective single-source precursors for the synthesis of mixed-transition metal oxide materials MxM2-xO3 and MxMi-xO. The title highly volatile precursors can be used for the low-temperature preparation of both amorphous and crystalline heterometallic oxides in the form of thin films or nanosized partiCles that are known to operate as efficient catalysts in oxygen evolution reaction.Mixed-valent, heteroleptic homometallic diketonates as templates for the design of volatile heterometallic precursors17201576#N/ATRUE
3738
c3sc51517f10.1039/c3sc51517fFALSEhttps://doi.org/10.1039/c3sc51517fHillhouse, GLChem. Sci.The synthesis and redox reactivity of unusual bent nickel-Arylimido complexes of the type L2Ni=NAr supported by a new chelating bis(N-heterocyClic carbene) ligand are described, inCluding experimental, structural, and computational data to validate this atypical binding motif. Upon oxidation the strongly bent imido complex undergoes C, C-coupling and dehydrogenation to afford a complex bearing an unusual diphenoquinonediimine ligand bridging two Ni(II) centers.Strongly bent nickel imides supported by a chelating bis(N-heterocyClic carbene) ligandx35201339#N/AFALSE
3739
c4sc02998d10.1039/c4sc02998dFALSEhttps://doi.org/10.1039/c4sc02998dRadius, UChem. Sci.Synthesis, characterization and investigations on the reactivity of the novel metal basic, yet isolable 14 VE NHC-complexes [M-0(iPr(2)Im)(2)] (M = Pd 3, Pt 4; iPr(2)Im = 1,3-di-isopropyl-imidazolin-2-ylidene; VE = valence electron; NHC = N-heterocyClic carbene) is reported and compared to the chemistry of the corresponding nickel complex. Quantum chemical analyses reveal that differences in the reactivity of group 10 NHC complexes are caused by differences in the rigidity and thus Activation strain associated with bending the corresponding d(10)-[M(NHC)(2)] fragments during reaction. These results should have implications for the understanding of the fundamental steps in catalytic cyCles, in which such complex fragments are employed.Bite-angle bending as a key for understanding group-10 metal reactivity of d(10)-[M(NHC)(2)] complexes with sterically modest NHC ligands20201583#N/ATRUE
3740
c4sc01089b10.1039/c4sc01089bFALSEhttps://doi.org/10.1039/c4sc01089bLee, YChem. Sci.Three distinct oxidation states of a nickel Carbonyl species, formally Ni(II), +1 and 0, (compounds 1, 2 and 3 respectively) have been realized using a (PNP) Ni scaffold (PNP- = N[2-(PPr2)-Pr-i-4-Me-C6H3](2-)). X-ray diffraction (XRD) studies of these Carbonyl complexes show a geometrical change about the nickel center from square planar (1) to pyramidal (2) and pseudotetrahedral (3). Interestingly, the Ni-C bond distance of 2 is longer than that of 1 and 3 due to the electron population of the antibonding d(x2-y2) orbital. A difference in the reactivity of these nickel Carbonyl species was Clearly observed. Reaction of the monovalent nickel Carbonyl species (2) with CH3I revealed the formation of (PNP)NiCOCH3 (4) via C-C bond coupling while the zerovalent congener (3) underwent an oxidative ligand substitution reaction.Transmethylation of a four-coordinate nickel(I) monoCarbonyl species with methyl iodide31201453#N/ATRUE
3741
c3sc50348h10.1039/c3sc50348hFALSEhttps://doi.org/10.1039/c8sc05677cYou, JSPd-catalyzed oxidative C-H/C-H cross-coupling of pyridines with heteroarenesx2013#N/AFALSE
3742
c3sc22242j10.1039/c3sc22242jFALSEhttps://doi.org/10.1039/c3sc22242jShi, ZJChem. Sci.A novel rhodium-catalyzed C-C bond formation was developed to construct biAryls through unreactive Aryl C-S bond Cleavage of thioethers with Aryl boroxines. This protocol provided a supplemental method of traditional Suzuki-Miyaura coupling.Cross coupling of thioethers with Aryl boroxines to construct biAryls via Rh catalyzed C-S Activationx65201398#N/AFALSE
3743
c3sc22173c10.1039/c3sc22173cFALSEhttps://doi.org/10.1039/c3sc22173cNam, WChem. Sci.MononuClear metal-dioxygen adducts, such as metal-superoxo and -peroxo species, are generated as key intermediates in the catalytic cyCles of dioxygen Activation by heme and non-heme metalloenzymes. We have shown recently that the geometric and electronic structure of the Ni-O-2 core in [Ni(n-TMC)(O-2)](+) (n = 12 and 14) varies depending on the ring size of the supporting TMC ligand. In this study, mononuClear Ni(II)-superoxo and Ni(III)-peroxo complexes bearing a common macrocylic 13-TMC ligand, such as [Ni-II(13-TMC)(O-2)](+) and [Ni-III(13-TMC)(O-2)](+), were synthesized in the reaction of [Ni-II(13TMC)( CH3CN)](2+) and H2O2 in the presence of tetramethylammonium hydroxide (TMAH) and triethylamine (TEA), respectively. The Ni(II)-superoxo and Ni(III)-peroxo complexes bearing the common 13-TMC ligand were successfully characterized by various spectroscopic methods, X-ray crystallography and DFT calculations. Based on the combined experimental and theoretical studies, we conClude that the superoxo ligand in [Ni-II(13-TMC)(O-2)](+) is bound in an end-on fashion to the nickel(II) center, whereas the peroxo ligand in [Ni-III(13-TMC)(O-2)](+) is bound in a side-on fashion to the nickel(III) center. Reactivity studies performed with the Ni(II)-superoxo and Ni(III)-peroxo complexes toward organic substrates reveal that the former possesses an electrophilic character, whereas the latter is an active oxidant in nuCleophilic reaction.MononuClear nickel(II)-superoxo and nickel(III)-peroxo complexes bearing a common macrocyClic TMC ligandx65201348#N/AFALSE
3744
c3sc22070b10.1039/c3sc22070bFALSEhttps://doi.org/10.1039/c3sc22070bDoyle, RPChem. Sci.We report highly unusual photophysical properties of a fac-Re(CO)(3)-bisthiazole complex, which is shown to break the Kasha-Vavilov rule. Herein, we show that such a complex has unusual emission wavelength variation due to the presence of photo-induced isomerisation from the stable, ground-state N,N-bound thiazole complex to S,N- and S,S-donation in the photo-induced excited state. A triple excitation, triple emission profile along with extensive DFT calculations support this theory to showcase an unusual circumstance of suulfur donation to the fac-Re(CO)(3) core upon luminescence. fac-Rhenium triCarbonyl complexes are extensively studied due to their fluorescent properties, high stability, and ready incorporation into conjugates with broad applicability in imaging and targeting. The spectroscopic features of the complex under study have broad fundamental interest while also offering potential for design of novel agents for use in biological imaging studies.Emission wavelength variation with changes in excitation in a Re(I)-bisthiazole ligand complex that breaks the Kasha-Vavilov rulex26201342#N/AFALSE
3745
c3sc22065f10.1039/c3sc22065fhttps://doi.org/10.1039/c3sc22065fFukuzumi, SChem. Sci.Lithium ion encapsulated [60]fullerene (Li+@C-60) is inCluded within a free base and nickel complex of a cyClic porphyrin dimer (M-CPDPy, M = H-4 and Ni-2) to afford supramolecules (Li+@C-60 subset of M-CPDPy) in a polar solvent (benzonitrile) with the association constants of 2.6 x 10(5) M-1 and 3.5 x 10(5) M-1, respectively. From the electrochemical analysis, the energies of the charge-separated (CS) states are estimated to be 1.07 eV for Li+@C-60 subset of H-4-CPDPy and 1.20 eV for Li+@C-60 subset of Ni-2-CPDPy. Both values are lower than the triplet excited energies of the fullerene and porphyrin. Upon the photoexcitation at the Q-band of the porphyrin chromophore of Li+@C-60 subset of H-4-CPDPy, electron transfer from the triplet excited state of the free base porphyrin to Li+@C-60 occurs to produce the CS state. Li+@C-60 subset of Ni-2-CPDPy also undergoes photoinduced electron transfer to produce the CS state. The lifetimes of the resulting CS states are 0.50 ms for Li+@C-60 subset of H-4-CPDPy and 0.67 ms for Li+@C-60 subset of Ni-2-CPDPy. These remarkably long CS lifetimes are the best values ever reported for non-covalent porphyrin-fullerene supramolecules in solution and are attributable to the lower CS energies than the triplet energy of each chromophore.Submillisecond-lived photoinduced charge separation in inClusion complexes composed of Li+@C-60 and cyClic porphyrin dimersPhotocatalyst44201388#N/AFALSE
3746
c4sc01065e10.1039/c4sc01065eFALSEhttps://doi.org/10.1039/c4sc01065eStrasser, PChem. Sci.A family of dealloyed metal-oxide hybrid (M1M2@M1Ox) core@shell nanopartiCle catalysts is demonstrated to provide substantial advances toward more efficient and less expensive electrolytic water splitting. IrNi@IrOx nanopartiCles were synthesized from IrNi chi precursor alloys through selective surface Ni dealloying and controlled surface oxidation of Ir. Detailed depth-resolved insight into chemical structure, composition, morphology, and oxidation state was obtained using spectroscopic, diffraction, and scanning microscopic techniques (XANES, XRD, STEM-EDX, XPS), which confirmed our structural hypotheses at the outset. A 3-fold catalytic activity enhancement for the electrochemical oxygen evolution reaction (OER) over IrO2 and RuO2 benchmark catalysts was observed for the core-shell catalysts on a noble metal mass basis. Also, the active site-based intrinsic turnover frequency (TOF) was greatly enhanced for the most active IrNi@IrOx catalyst. This study documents the successful use of synthetic dealloying for the preparation of metal-oxide hybrid core-shell catalysts. The concept is quite general, can be applied to other noble metal nanopartiCles, and points out a path forward to nanostructured proton-exchange-electrolyzer electrodes with dramatically reduced noble metal content.IrOx core-shell nanocatalysts for cost- and energy-efficient electrochemical water splitting188201454#N/ATRUE
3747
c3sc21822h10.1039/c3sc21822hFALSEhttps://doi.org/10.1039/c3sc21822hChe, CMChem. Sci.The synthesis, structures and photophysical properties of the charge-neutral Pt(II) complexes (1-6) and their Pd(II) (7) and Ni(II) (8) congeners supported by tetradentate dianionic bis[phenolate-(N-heterocyClic carbene)] ligands are described. The X-ray crystal structures of two solvatomorphs of 2, which has p-F substituents on the tetradentate ligand, have been determined. The photophysical properties of all the complexes were examined. In THF solutions, 1-4 display deep blue phosphorescence (lambda(max) = similar to 440-460 nm, Phi(e) - 3-18% and tau - 0.5-3.5 mu s). In solutions at room temperature, 5-8 show profoundly different luminescence properties from being virtually non-emissive (Phi(e) < 10(-3)) for 6-8 to highly emissive (Phi(e) = 15%) with much red-shifted phosphorescence (lambda(max) = similar to 530 nm) and a long emission lifetime (tau = 47.2 mu s) in the case of 5. Time-dependent density functional theory (TDDFT) calculations reveal that the tetradentate bis(phenolate-NHC) ligands in 1-4 provide a rigid scaffold for preserving a tightly bound Pt(II) in a square-planar coordination geometry in the T-1 as in the S-0 states and the blue emission is derived from the T1 state having predominant ligand (pi(Ar-O))-to-ligand (pi*(NHC)) charge transfer (LLCT) character. A switch of orbital parentage from LLCT to ligand-centred (LC) pi-pi* is responsible for the long emission lifetime and vibronically structured emission displayed by 5 when compared to that of 1-4 and 6. Both femtosecond time-resolved fluorescence (fs-TRF) and nanosecond time-resolved emission (ns-TRE) measurements were conducted on 2 and 4 to directly probe the excited-state dynamics after photoexcitation. Excellent thermal stability of the fluorine-free complex 4 and its higher emission quantum yield (relative to 1 and 3), and using 9-(4-tert-butylphenyl)-3,6-bis( triphenylsilyl)-9H-carbazole (CzSi) as host material, led to the fabrication of highly efficient deep blue OLEDs with peak current efficiency of 24 cd A(-1) and white organic light-emitting devices (WOLEDs) with peak current efficiency of 88 cd A(-1).Light-emitting platinum(II) complexes supported by tetradentate dianionic bis(N-heterocyClic carbene) ligands: towards robust blue electrophosphorsx1182013122#N/AFALSE
3748
c3sc00090g10.1039/c3sc00090ghttps://doi.org/10.1039/c3sc00090gMcNeil, AJChem. Sci.Small molecule competition experiments were performed to determine whether Ni-catalyzed Kumada cross-coupling reactions proceed through an intramolecular oxidative addition. Indeed, preferential intramolecular oxidative addition was observed for all four complexes when stoichiometric quantities of competitive agent were present. At higher concentrations of competitive agent, the intramolecular pathway was still preferred when bidentate, electron-rich ligands were utilized, suggesting that these ligands promote the formation and reactivity of the key intermediate. To determine whether a similar pathway is involved in the polymerizations, (4-bromo-2,5-bis(hexyloxy)phenyl)magnesium bromide was polymerized in the presence and absence of competitive agent. The number-average molecular weights were lower and the molecular weight distributions were broadened substantially when competitive agent was present, consistent with the presence of competing intermolecular pathways. Because bidentate, electron-rich ligands suppressed these undesired intermolecular reactions, these ligands should lead to improved polymerization catalysts.Evidence for a preferential intramolecular oxidative addition in Ni-catalyzed cross-coupling reactions and their impact on chain-growth polymerizationsx41201356#N/AFALSE
3749
c3sc00032j10.1039/c3sc00032jFALSEhttps://doi.org/10.1039/c3sc00032jLong, JRChem. Sci.A significant reduction in the energy costs associated with the cryogenic separation of ethylene-ethane and propylene-propane mixtures could potentially be realized through the use of selective solid adsorbents that operate at higher temperatures. The metal-organic frameworks M-2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobdc(4-) = 2,5-dioxido-1,4-benzenediCarbonylate) are of particular interest for this application, owing to their high density of coordinatively unsaturated M2+ cation sites that can selectively interact with unsaturated hydrocarbons. Here, we present gas adsorption data for ethylene, ethane, propylene, and propane at 45, 60, and 80 degrees C for the entire series. The means of sample preparation and Activation is found to be important for achieving high separation selectivities and capacities. While all of the compounds investigated show good performance characteristics, Fe-2(dobdc) and Mn-2(dobdc) exhibit the highest selectivities for the separation of ethylene-ethane and propylene-propane mixtures, respectively. Crystal structures determined from neutron powder diffraction data elucidate the binding of ethane, ethylene, and propylene in Mn2(dobdc) and Co-2(dobdc).Selective adsorption of ethylene over ethane and propylene over propane in the metal-organic frameworks M-2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Zn)x279201380#N/AFALSE
3750
c4sc00491d10.1039/c4sc00491dFALSEhttps://doi.org/10.1039/c4sc00491dMorokuma, KGraphene nuCleation on a surface-molten copper catalyst: quantum chemical molecular dynamics simulations2014#N/ATRUE
3751
c4sc00348a10.1039/c4sc00348aFALSEhttps://doi.org/10.1039/c4sc00348aKrautler, BChem. Sci.Non-fluorescent chlorophyll catabolites (NCCs) are ubiquitous, Colourless bilane-type natural products, first identified about 20 years ago. In various senescent leaves NCCs are oxidized, in part, to yellow chlorophyll catabolites (YCCs), which undergo further oxidation to unique pink chlorophyll catabolites (PiCCs). The present work presents the crystal structure of a PiCC, the first of a natural chlorophyll catabolite from a higher plant. The PiCC binds (divalent) zinc-, cadmium-, copper- and nickel-ions with high affinity. Binding of these metal ions to the PiCC is rapid at room temperature. The resulting deep blue complexes represent the first transition metal complexes of a burin-type chlorophyll catabolite. The structure of the metal complexes has been deduced from spectroscopic analyses, which has revealed an effective tridentate nature of the tetrapyrrolic PiCC ligand. The zinc and cadmium complexes show bright red luminescence, the nickel and copper complexes are non-luminescent. Binding of Zn- and Cd-ions to the PiCC 'lights-up' the intensive red fluorescence of the metal-complexes, which is detectable at nM levels of these Closed shell metal ions. Formation of transition metal complexes with PiCCs, and related chlorophyll catabolites, may thus also occur in the tissues of plants, notably of 'heavy metal (hyper)-accumulating' plants.Blue transition metal complexes of a natural bilin-type chlorophyll catabolite26201439#N/ATRUE
3752
c4cc08749f10.1039/c4cc08749fFALSEhttps://doi.org/10.1039/c4cc08749fMagdassi, SSelf-reduction of a copper complex MOD ink for inkjet printing conductive patterns on plastics2015#N/ATRUE
3753
c3cc45697h10.1039/c3cc45697hFALSEDuan, XSynthesis of supported Ni@(RhNi-alloy) nanocomposites as an efficient catalyst towards hydrogen generation from N2H4BH3x2013#N/AFALSE
3754
c4cc07578a10.1039/c4cc07578aFALSEhttps://doi.org/10.1039/c4cc07578aKonno, TProton-controlled formation and interconversion of (Au2NiII)-Ni-I trinuClear and (Au4Ni3II)-Ni-I heptanuClear complexes with mixed thiomalate and bis(diphenylphosphino)ethane2014#N/ATRUE
3755
c3cc43895c10.1039/c3cc43895cFALSEGong, JLSintering-resistant Ni-based reforming catalysts obtained via the nanoconfinement effectx2013#N/AFALSE
3756
c3cc43603a10.1039/c3cc43603aOhta, YScope of controlled synthesis via chain-growth condensation polymerization: from aromatic polyamides to pi-conjugated polymersx2013#N/AFALSE
3757
c4cc04800h10.1039/c4cc04800hFALSEhttps://doi.org/10.1039/c4cc04800hLee, YFormation of a nickel carbon dioxide adduct and its transformation mediated by a Lewis acid2014#N/ATRUE
3758
c3cc43212b10.1039/c3cc43212bFALSEhttps://doi.org/10.1039/c8sc03407aGao, EQUnusual composition dependence of magnetic relaxation for (Co1-xNixII)-Ni-II chain-based metal-organic frameworksx2013#N/AFALSE
3759
c4cc03135k10.1039/c4cc03135kFALSEFeng, XMEfficient synthesis of carbazolespirooxindole skeletons via asymmetric Diels-Alder reaction of 3-Vinylindoles and methyleneindolinones2014#N/ATRUE
3760
c4cc02809k10.1039/c4cc02809kFALSEhttps://doi.org/10.1039/c4cc02809kFeng, XMCatalytic hetero-ene reactions of 5-methyleneoxazolines: highly enantioselective synthesis of 2,5-disubstituted oxazole derivatives2014#N/ATRUE
3761
c2sc21489j10.1039/c2sc21489jFALSEhttps://doi.org/10.1039/c2sc21489jDilworth, JRChem. Sci.Complexes of Cu(II), Ni(II) and Zn(II) have been prepared with bis(thiosemicarbazonate) ligands bearing a pendant Bodipy fluorophore both with (ATSMBodipy) and without (GTSBodipy) backbone methyl groups. Biophysical analysis using steady state confocal laser scanning fluorescence images and excited state fluorescence lifetime imaging microscopy (FLIM) data obtained from live cells under aerobic uptake conditions has uniquely allowed both the spatial distribution and degree of dissociation of the complexes to be assessed. The CuATSMBodipy complex is virtually intact after 20 min and 1 h whereas the corresponding CuGTSBodipy complex is totally dissociated. The complexes ZnATSMBodipy and NiATSMBodipy show little evidence for dissociation. The relevance of this data to the biomedical applications of bis(thiosemicarbazonate) complexes for imaging applications and implications for the treatment of disease such as Alzheimer's and the PET imaging of hypoxia are discussed.Shining light on the stability of metal thiosemicarbazonate complexes in living cells by FLIMx24201342#N/AFALSE
3762
c2sc21345a10.1039/c2sc21345ahttps://doi.org/10.1039/c2sc21345aHillhouse, GLChem. Sci.The dimeric Ni(I)-Ni(I) N-heterocyClic carbene complex {(IPr)Ni(mu-Cl)}(2) (3; IPr = 1,3-(2,6-(Pr2C6H3)-Pr-i)(2)imidazolin-2-ylidene)) reacts with the lithium terphenylamides LiNHdmp and LiNHdippp (dmp = 2,6-di(mesityl)phenyl; dippp = 2,6-bis(2,6-di-iso-propylphenyl)phenyl) to give the monomeric Ni(I) amides (IPr)Ni(NHdmp) (4) and (IPr)Ni(NHdippp) (5), respectively. These nickel amides are 1-electron paramagnets, and crystallographic characterization indicates both are stabilized by Ni-C(ipso) interactions with a flanking Aryl group of the terphenyl fragment. This results in significant deviation from the linear C-NHC-Ni-N geometry typical for a two-coordinate transition-metal complex (112.17(9)degrees in 4, 116.41(9)degrees in 5). One-electron oxidation of 4 by ferrocenium results in intramolecular deprotonation at a terphenyl Benzylic position by the amide, giving the diamagnetic Ni(II) complex [(IPr)Ni(kappa(2)-C,N:NH2C6H3(Mes)C10H9)][B(Ar-F)(4)] (7). DFT calculations on oxidized 4 (i.e., 4(+)) indicate short amide N center dot center dot center dot CH3 interactions. One-electron oxidation of 5 by ferrocenium gives a new high-spin Ni(II) amide complex salt, [(IPr)Ni(NHdippp)][B(Ar-F)(4)] (9). The solid-state structure of 9 indicates it maintains the bent C-NHC-Ni-N core. Unlike three-coordinate cationic Ni(II) amides, 9 has not been observed to undergo smooth deprotonation (at N) to afford a two-coordinate imido complex.Single-electron oxidation of N-heterocyClic carbene-supported nickel amides yielding Benzylic C-H Activationx28201332#N/AFALSE
3763
c2sc21231e10.1039/c2sc21231eFALSEhttps://doi.org/10.1039/c2sc21231ePeters, JCChem. Sci.Heterobimetallic NiZn complexes featuring metal centers in distinct coordination environments have been synthesized using diimine-dioxime ligands as binuCleating scaffolds. A tetramethylfuran-containing ligand derivative enables a stable one-electron-reduced S = 1/2 species to be accessed using Cp2Co as a chemical reductant. The resulting pseudo-square planar complex exhibits spectroscopic and crystallographic characteristics of a ligand-centered radical bound to a Ni(II) center. Upon coordination of a pi-acidic ligand such as PPh3, however, a five-coordinate Ni(I) metalloradical is formed. The electronic structures of these reduced species provide insight into the subtle effects of ligand structure on the potential and reversibility of the Ni-II/I couple for complexes of redox-active tetraazamacrocyCles.Access to formally Ni(I) states in a heterobimetallic NiZn systemx23201346#N/AFALSE
3764
c2sc21214e10.1039/c2sc21214eFALSEhttps://doi.org/10.1039/c2sc21214eRoschenthaler, GVChem. Sci.A new synthetic pathway for the N-heterocyClic carbene adduct (NHCMe)SiCl4 (2) (NHCMe = 1,3-dimethylimidazolidin-2-ylidene) using silicochloroform is presented. Supported by DFT calculations, the energy for dissociation of 2 into the carbene and the SiCl4 fragment was found to be comparable to carbene transfer reagents based on silver(I) chloride. Compound 2 was used to transfer the NHC ligand to three different phosphorus(III) chloro compounds, resulting in the neutral complexes (NHCMe)PCl3 (3a), (NHCMe)PCl2Ph (3b) and (NHCMe)PCl2Me (3c). The sterically non-demanding NHC ligand allowed the phosphorus(III) in complex 3a to be oxidized to phosphorus(V) without loss of the NHC ligand, and afford (NHCMe)PF4H (4). Furthermore, bis-carbene complexes of Ni(II) (5) and Pd(II) (6) were obtained by reacting 2 with the respective metal chlorides.(NHCMe)SiCl4: a versatile carbene transfer reagent synthesis from silicochloroformx39201384#N/AFALSE
3765
c2sc20874a10.1039/c2sc20874ahttps://doi.org/10.1039/c2sc20874aReisner, EChem. Sci.A photoelectrochemical (PEC) cell for overall water splitting made of a Cu2O nanowire photocathode modified with a thin film of NiOx coupled to a WO3 nanosheet photoanode is presented. The photocathode was prepared by thermal annealing of Cu(OH)(2) nanowires on a Cu foil under N-2, followed by the deposition of a 10 nm NiOx film on the Cu2O nanowires (aspect ratio > 40). XPS spectra revealed that the surface species of NiOx is a mixture of NiO and Ni(OH)(2), which enhances charge separation in photoexcited Cu2O, as confirmed by electrochemical impedance spectroscopy. The optimized NiOx modified Cu2O electrode shows a photocurrent density up to -4.98 mA cm(-2) at -0.33 V and -0.56 mA cm(-2) at 0.1 V VS. the normal hydrogen electrode (NHE) under white-light irradiation (26 mW cm(-2)) in an aqueous electrolyte solution at pH 6 and 25 degrees C. The formation of H-2 gas was only observed by gas chromatography for NiOx-modified Cu2O and was not detectable for unmodified Cu2O electrodes during prolonged irradiation. The nanocomposite structure also resulted in a three-fold increase in photostability of Cu2O; 72 +/- 3% of the initial photocurrent density remained for the NiOx modified Cu2O electrode after 20 min irradiation at 0.1 V vs. NHE. The optimized photocathode was subsequently used in a two-electrode PEC cell with an n-type WO3 nanosheet photoanode for overall water splitting. The different band gap of Cu2O (2 eV) and WO3 (2.6 eV) permits for efficient and complementary light absorption and sunlight-driven water splitting. The p/n heterojunction PEC cell operates with a small output of electricity even in the absence of an external bias. We demonstrate that a Cu2O-based electrode for H-2 evolution can be prepared free of noble metals and we show its utilization in a PEC water splitting cell made solely from earth abundantCu2O vertical bar NiOx nanocomposite as an inexpensive photocathode in photoelectrochemical water splittingPhotocatalystx201201265#N/AFALSE
3766
c2sc20828h10.1039/c2sc20828hFALSEhttps://doi.org/10.1039/c2sc20828hBallav, NChem. Sci.Paramagnetic transition-metal complexes assembled on surfaces are of great interest for potential applications in organic spintronics. The magnetochemical interactions of the spin of the metal centers with both ferromagnetic surfaces and optional axial ligands are yet to be understood. We use a combination of X-ray magnetic circular dichroism (XMCD) and quantum-chemical simulations based on density functional theory (DFT + U) to investigate these metal-organic interfaces with chemically tunable magnetization. The interplay between an optional axial ligand (NO, spin S = 1/2 or NH3, S = 0) and Ni and Co ferromagnetic surfaces affecting the spin of Co(II) tetraphenylporphyrin (d(7), S = 1/2), Fe(II) tetraphenylporphyrin (d(6), S = 1), Mn(II) tetraphenylporphyrin (d(5), S = 5/2) and Mn(II) phthalocyanine (d(5), S = 3/2) is studied. We find that the structural trans effect on the surface rules the molecular spin state, as well as the sign and strength of the exchange interaction with the substrate. We refer to this observation as the surface spin-trans effect.On-surface coordination chemistry of planar molecular spin systems: novel magnetochemical effects induced by axial ligandsx78201249#N/AFALSE
3767
c3sc51711j10.1039/c3sc51711jFALSEhttps://doi.org/10.1039/c9cc00159jGray, HBEarth-abundant hydrogen evolution electrocatalysts2014#N/ATRUE
3768
c3sc50743b10.1039/c3sc50743bFALSEhttps://doi.org/10.1039/c3sc50743bLobkovsky, EBChem. Sci.Treatment of Ni(COD)(2) with Me2C(CH2N=CHpy)(2) (dmp(PI)(2)) afforded pseudo-square planar, diamagnetic {dmp(PI)(2)(2-)}Ni-II (Ni[0]), which contains radical anion pyridine-imine (PI) units bound to Ni(II). Ag+ oxidation of Ni[0] provided [{dmp(PI)(2)}Ni](+) (Ni[+]) whose assignment as Ni(I) or Ni(II) was made on the basis of ab initio calculations, and EPR spectroscopy. Upon crystallization, Ni[+] formed an asymmetric dimer, [{dmp(PI)(2)}(2)(NiNi0)-Ni-II](2+) (Ni[2+]Ni[0]), consisting of pseudo-octahedral Ni(II) and pseudo-tetrahedral Ni(0). Ferrocenium oxidation (2 equiv.) of Ni[0] provided [{dmp(PI)(2)}(MeCN)(2)Ni-II](2+) (Ni[2+]), while KC8 reduction provided [{dmp(PI)(2)(3-)}Ni-II](-)(K(THF)(2))(+) (Ni[-]) in polymeric form (K+ counterion) or as ion-pairs (with K+(crypt-2.2.2)). Excess K-0 or 2 equiv. Cs-0 and Ni[0] provided highly sensitive [{dmp(PI)(2)(4-)}Ni-II](2-) (Ni[2-]), which disproportionates with C=C bond formation and dehydrogenation to afford [{2-py,3-PI,4-Me-2-azacyClopent-2-ene(2-)}(2)Ni](2-) [K+(crypt-2.2.2)](2) (Ni[AcPP]) upon addition of crypt-2.2.2. All redox events may be construed as shuttling electrons in and out of the ligand scaffold. While radical character is implicated in the calculations of Ni[+], Ni[0], and Ni[-], the pseudo-square planar species are remarkably resilient to further reactivity, thereby highlighting the stability provided by this geometry.Exploring the limits of redox non-innocence: pseudo square planar [{kappa(4)-Me2C(CH2N=CHpy)(2)}Ni](n) (n=2+, 1+, 0,-1,-2) favor Ni(II)162013127#N/ATRUE
3769
c2sc20187a10.1039/c2sc20187aFALSEhttps://doi.org/10.1039/c2sc20187aSun, DFChem. Sci.Two chiral lead metal-organic nanotubes (CD-MONT-2 and CD-MONT-3) based on beta-cyClodextrin (beta-CD) and gamma-cyClodextrin (gamma-CD) were synthesized through a biphasic solvothermal reaction. The lead ions were connected by two beta-CD or gamma-CD molecules through their glycosidic oxygen atoms to generate a discrete metal-organic nanotube containing a {Pb-14} or {Pb-16} metallamacrocyCle, respectively. Guest solvents of cyClohexanol molecules were trapped in the cavity of the beta-CD-based nanotube, whereas there were no solvents in the cavity of the gamma-CD-based nanotube. These differences directly led to the formation of different 3D packing structures. Their properties inCluding temperature-dependent photoluminescence, adsorption of I-2 molecules and thermal-decomposition behaviors were studied.Pb(II) metal-organic nanotubes based on cyClodextrins: biphasic synthesis, structures and propertiesx56201269#N/AFALSE
3770
c3sc22051f10.1039/c3sc22051fFALSEhttps://doi.org/10.1039/c3sc22051fKrische, MJChem. Sci.The regioselective reductive coupling of paraformaldehyde to 2-substituted dienes at positions C1, C2 and C3 was achieved using metal catalysts based on nickel, cationic ruthenium and neutral ruthenium, respectively. Whilst C1 adducts predominate using dienes, silicon- or tin-substituted dienes exhibit C4 regioselectivity - the first time that this regioselectivity has been observed for the coupling of 2-substituted butadienes to aldehydes. Both nickel- and ruthenium-catalyzed processes avoid pyrophoric or mass intensive reducing agents, using paraformaldehyde or isopropanol, respectively. These couplings may be viewed as alternatives to diene hydroCarbonylation, for which regioselective formation of constitutionally isomeric products has not yet been achieved.Regiodivergent reductive coupling of 2-substituted dienes to formaldehyde employing ruthenium or nickel catalyst: hydrohydroxymethylation via transfer hydrogenation63201349#N/ATRUE
3771
c3cc48549h10.1039/c3cc48549hFALSEhttps://doi.org/10.1039/c8sc04500cThomas, FUnprecedented redox-driven ligand ejection in nickel(II)-diiminosemiquinonate radical complexes2014#N/ATRUE
3772
c3cc47170e10.1039/c3cc47170eFALSEhttps://doi.org/10.1039/c3cc47170eBattaglini, FSynthesis of atomic metal Clusters on nanoporous alumina2013#N/ATRUE
3773
c3cc46419a10.1039/c3cc46419aFALSEhttps://doi.org/10.1039/c3cc46419aChung, YKCopper nanopartiCle-catalyzed cross-coupling of Alkyl halides with Grignard reagents2013#N/ATRUE
3774
c2sc00005a10.1039/c2sc00005ahttps://doi.org/10.1039/c2sc00005aMcNeil, AJChem. Sci.The role of ligand-based electronic effects was investigated in the Ni-catalyzed polymerization of 4-bromo-2,5-bis(hexyloxy)phenylmagnesium chloride. The catalyst with the most electron-donating ligand outperformed the other catalysts by providing polymers with narrower molecular weight distributions. This result is attributed to both a suppression of competing reaction pathways (e. g., chain transfer and termination) as well as a relative acceleration of precatalyst initiation compared to propagation. Further studies revealed that, for all three catalysts, precatalyst initiation is slower than propagation, despite the fact that they exhibit the same rate-determining steps (i.e., reductive elimination) and have similar catalyst resting states. These results suggest that better control over the polymer molecular weight, end-functionality and sequence can be obtained with electron-rich catalysts, such as those described herein.Effect of ligand electronic properties on precatalyst initiation and propagation in Ni-catalyzed cross-coupling polymerizationsx39201255#N/AFALSE
3775
c2cc36965f10.1039/c2cc36965fFALSEhttps://doi.org/10.1039/c8sc03877eMinteer, SDEnhanced alcohol electrocatalysis with the introduction of magnetic composites into nickel electrocatalystsx2012#N/AFALSE
3776
c3cc45202f10.1039/c3cc45202fFALSEhttps://doi.org/10.1039/c3cc45202fHor, TSAAmbient Arylmagnesiation of alkynes catalysed by ligandless nickel(II)2013#N/ATRUE
3777
c2cc34560a10.1039/c2cc34560aFALSEhttps://doi.org/10.1039/c2cc34560aCaulton, KGProbing the redox non-innocence of dinuClear, three-coordinate Co(II) nindigo complexes: not simply beta-diketiminate variantsx2012#N/AFALSE
3778
c3cc43350a10.1039/c3cc43350aFALSEhttps://doi.org/10.1039/c3cc43350aKang, YMA novel co-precipitation method for one-pot fabrication of a Co-Ni multiphase composite electrode and its application in high energy-density pseudocapacitors2013#N/ATRUE
3779
c2cc32971a10.1039/c2cc32971aFALSEhttps://doi.org/10.1039/c8sc03385dTour, JMGraphene-Ni-alpha-MnO2 and -Cu-alpha-MnO2 nanowire blends as highly active non-precious metal catalysts for the oxygen reduction reactionx2012#N/AFALSE
3780
c3cc41399c10.1039/c3cc41399cFALSEhttps://doi.org/10.1039/c3cc41399cMochida, TThermochromic and solvatochromic Nafion films incorporating cationic metal-chelate complexes2013#N/ATRUE
3781
c2cc17302f10.1039/c2cc17302fFALSEhttps://doi.org/10.1039/c2cc17302fXu, QZIF-8 immobilized nickel nanopartiCles: highly effective catalysts for hydrogen generation from hydrolysis of ammonia boranex2012#N/AFALSE
3782
c2sc21754f10.1039/c2sc21754fFALSEhttps://doi.org/10.1039/c2sc21754fCardenas, DJChem. Sci.A novel Fe-NHC catalytic system allows the Alkyl-Alkyl cross-coupling reaction of Alkyl halides and Alkylmagnesium reagents has been developed. To our knowledge, this is the first Fe-catalysed Kumada-type coupling for the formation of C(sp(3))-C(sp(3)) bonds in the presence of functional groups. The process takes place under mild conditions, avoiding the formation of beta-elimination products. Mechanistic studies suggest the intermediacy of Fe(I) complexes, formed by reduction with the Grignard reagent, as the active species.Fe-catalysed Kumada-type Alkyl-Alkyl cross-coupling. Evidence for the intermediacy of Fe(I) complexes104201383#N/ATRUE
3783
C1SC00637A10.1039/C1SC00637AFALSEhttps://doi.org/10.1039/C1SC00637ABeale, AMChem. Sci.A combination of synchrotron mu-XRD-CT and mu-absorption-CT (CT = computed tomography) is demonstrated, providing a unique insight into the solid state changes occurring from within crystalline materials. Specifically, we examine here the solid state changes that occur in a millimetre-sized Ni/gamma-Al2O3 catalyst body in both 2D and 3D during calcination and CO methanation for the first time. The combination provides a unique insight into the spatial phase distribution of these materials and how these evolve via a series of solid state transformation processes. For example, initially, two Ni-ethylenediamine (en) complexes were observed on the impregnated and dried body; a hydrated and non-hydrated form, which 2D scans reveal possess an egg-shell and egg-yolk distribution, respectively. Furthermore, the mu-XRD data were of sufficient quality so as to be able to reveal that the partiCles within the 'egg-shell' were larger (similar to 35 nm) than those of the 'egg-yolk' (similar to 19 nm) and that there were more of them. On calcination, both precursors collapsed, yielding metallic fcc Ni partiCles with a surprisingly uniform average size distribution over the catalyst (similar to 4 nm). However, a comparison of the scattering at different stages of the experiment suggested that the crystalline structure of some of the Ni remained diffraction 'silent'. Calcination in oxygen lead to both Ni oxidation and partiCle sintering, mainly at the exterior, which on pre-reaction reduction (in H-2) yielded again fcc Ni partiCles (similar to 4 nm interior, similar to 6 nm exterior) with a significant reduction in the amorphous Ni component. The catalyst proved active for CO methanation and, during 2 h time on-stream, no change in the structure composition or shape was observed, leading us to conClude that nano-sized fcc Ni partiCles on gamma-Al2O3 are the active component in CO methanation. This work therefore demonstrates both the power of spatially resolved mu-XRD-CT/mu-absorption-CT measurement of catalytic systems and its advantage over more 'traditional' single point studies on small sieve fractions.Active phase evolution in single Ni/Al2O3 methanation catalyst bodies studied in real time using combined mu-XRD-CT and mu-absorption-CTx59201264#N/AFALSE
3784
c2sc20539d10.1039/c2sc20539dFALSEhttps://doi.org/10.1039/c2sc20539dHu, XLChem. Sci.Molybdenum sulfide materials have been shown as promising non-precious catalysts for hydrogen evolution. This paper describes the study of the promotional effects of certain transition metal ions on the activity of amorphous MoS3 films. Ternary metal sulfide films, M-MoS3 (M = Mn, Fe, Co, Ni, Cu, Zn), have been prepared by cyClic voltammetry of aqueous solutions containing MCl2 and (NH4)(2)[MoS4]. Whereas the Mn-, Cu-, and Zn-MoS3 films show similar or only slightly higher catalytic activity as the MoS3 film, the Fe-, Co-, and Ni-MoS3 films are significantly more active. The promotional effects of Fe, Co, and Ni ions exist under both acidic and neutral conditions, but the effects are more pronounced under neutral conditions. Up to a 12-fold increase in exchange current density and a 10-fold increase in the current density at an overpotential of 150 mV are observed at pH = 7. It is shown that Fe, Co, and Ni ions promote the growth of the MoS3 films, resulting a high surface area and a higher catalyst loading. These changes are the main contributors to the enhanced activity at pH = 0. However, at pH = 7, Fe, Co, and Ni ions appear to also increase the intrinsic activity of the MoS3 film.Fe, Co, and Ni ions promote the catalytic activity of amorphous molybdenum sulfide films for hydrogen evolution705201257#N/ATRUE
3785
c1sc00269d10.1039/c1sc00269dFALSEhttps://doi.org/10.1039/c1sc00269dEddaoudi, MChem. Sci.Systematic studies were conducted to gain a better understanding of the metal-organic cubes (MOCs) directed assembly and their crystallization under predetermined reaction conditions, i.e. charge and size of metal ions, solvent type, counter anions, pH, and temperature. Four novel metal-organic materials are constructed via solvothermal reactions of different metal ions and 2,2'-(1H-imidazole-4,5-diyl)di-1,4,5,6-tetrahydropyrimidine, namely [Co-8(C11N6H15)(12)]Cl-12 center dot 4H(2)O (1), [Ni-4(C11N6H15)(4)]-(NO3)(4)center dot 4DMF (2), {Cd(C11N6H15)(NO3)center dot DMF}(n) (3), and [In-8(C11N6H15)(12)](NO3)(12)center dot 4H(2)O (4). In addition, syntheses and crystal structures for compounds 1(a-f), constructed under deliberately modified reaction conditions of 1, are reported. In compounds 1(a-f), the Co-III-based cationic MOCs crystallize in various packing arrangements in the presence of different counter-ions. Discrete MOCs retain their structural integrity, when crystalline solid was dissolved in water, under various pH (2.03-8.07) and temperatures (298-333 K), as confirmed by solution NMR studies. The assembly of the discrete MOC, from its basic molecular building blocks under mild reaction conditions, is demonstrated and monitored through solution NMR and UV-vis studies.Insight into the construction of metal-organic polyhedra: metal-organic cubes as a case studyx31201169#N/AFALSE
3786
c2sc20343j10.1039/c2sc20343jFALSEhttps://doi.org/10.1039/c2sc20343jItami, KChem. Sci.The first size-selective synthesis of [9]-[11] and [13]cyCloparaphenylenes (CPP) has been achieved by strategically utilizing cis-1,4-diphenylcyClohexane-1,4-diyl as the key terphenyl-convertible L-shaped unit. To access the designed triangular or rectangular macrocyClic precursors, we utilized palladium-catalysed C-B/C-Br cross-coupling (Suzuki-Miyaura coupling) and/or nickel-mediated C-Br/C-Br coupling. We also established step-economical routes to [14] and [16]CPP using nickel-mediated C-Br/C-Br coupling. The final aromatization steps toward CPPs were accomplished with NaHSO4. Thus, combined with our previous size-selective synthesis of [12] and [14]-[16]CPP, we completed our size-selective synthesis of [9]-[16]CPP. The successful size-selective syntheses of [n]CPPs speak well for the flexibility and reliability of our strategy using a cyClohexane ring.Size-selective synthesis of [9]-[11] and [13]cyCloparaphenylenes108201235#N/ATRUE
3787
c1sc00233c10.1039/c1sc00233cFALSEhttps://doi.org/10.1039/c1sc00233cYu, SHLarge scale restructuring of porous Pt-Ni nanopartiCle tubes for methanol oxidation: A highly reactive, stable, and restorable fuel cell catalystx2011#N/AFALSE
3788
c1sc00069a10.1039/c1sc00069aFALSEhttps://doi.org/10.1039/c1sc00069aTeschner, DChem. Sci.In partial hydrogenation of highly unsaturated compounds, high-performance heterogeneous catalysts usually consist of multi-metallic systems providing enhanced selectivity. These materials often undergo complex segregation phenomena and to understand their function, a surface-sensitive in situ methodology is crucial. Recently, we reported a novel family of ternary Cu-Ni-Fe catalysts for propyne hydrogenation with exceptional selectivity to propene. Herein, we detail our study on the surface composition and electronic state of two representative samples (Cu(2.75)Ni(0.25)Fe and Cu(3)Fe) using in situ X-ray photoelectron (XPS) and X-ray absorption (XAS) spectroscopies. Surface segregation phenomena during Activation of the catalyst precursors (calcination and reduction) and hydrogenation reaction were evaluated. The multiple functions of nickel in the catalyst, which account for the extraordinary alkene selectivity, are unravelled.Surface state during Activation and reaction of high-performing multi-metallic alkyne hydrogenation catalystsx15201129#N/AFALSE
3789
c2sc20306e10.1039/c2sc20306eFALSEhttps://doi.org/10.1039/c2sc20306eDinca, MChem. Sci.The inorganic Clusters in metal-organic frameworks can be used to trap metal ions in coordination geometries that are difficult to achieve in molecular chemistry. We illustrate this concept by using the well-known basic Carbonylate Clusters in Zn4O(1,4-benzenediCarbonylate)(3) (MOF-5) as tripodal chelating ligands that enforce an unusual pseudo-tetrahedral oxygen ligand field around Ni2+. The new Ni-based MOF-5 analogue is characterized by porosity measurements and a suite of electronic structure spectroscopies. Classical ligand field analysis of the Ni2+ ion isolated in MOF-5 Classifies the Zn3O(Carbonylate)(6) tripodal ligand as an unusual, stronger field ligand than halides and other oxygen donor ligands. These results may inspire the widespread usage of MOFs as chelating ligands for stabilizing site-isolated metal ions in future reactivity and electronic structure studies.Lattice-imposed geometry in metal-organic frameworks: lacunary Zn4O Clusters in MOF-5 serve as tripodal chelating ligands for Ni2+131201248#N/ATRUE
3790
c1cc16109a10.1039/c1cc16109aFALSELubitz, WSpectroscopic characterization of the key catalytic intermediate Ni-C in the O-2-tolerant [NiFe] hydrogenase I from Aquifex aeolicus: evidence of a weakly bound hydridex2012#N/AFALSE
3791
c1cc14576b10.1039/c1cc14576bFALSEhttps://doi.org/10.1039/c1cc14576bTuna, FStructure and bonding in three-coordinate N-heterocyClic carbene adducts of iron(II) bis(trimethylsilyl) amidex2011#N/AFALSE
3792
c1cc13096j10.1039/c1cc13096jhttps://doi.org/10.1039/c1cc13096jTada, HNickel(II) oxide surface-modified titanium(IV) dioxide as a visible-light-active photocatalystPhotocatalystx2011#N/AFALSE
3793
c1cc12964c10.1039/c1cc12964cFALSELu, YMicrostructured Au/Ni-fiber catalyst for low-temperature gas-phase selective oxidation of alcoholsx2011#N/AFALSE
3794
c2sc01112c10.1039/c2sc01112cFALSEhttps://doi.org/10.1039/c2sc01112cReiher, MChem. Sci.Hydrogenases represent a heterogeneous group of enzymes consisting of three evolutionary unrelated Classes, i.e. [NiFe], [FeFe] and [Fe] hydrogenases. They allow the uni-cellular organisms in which they are expressed to use hydrogen as energy source or to reduce protons as a sink for excess reduction equivalents. Because of this capability there is growing interest in exploiting these enzymes in the field of sustainable energy generation. However, most hydrogenases which are appealing in this context are reversibly or irreversibly inhibited by dioxygen. Here, we summarize the current picture of oxygen-induced inhibition of the different Classes of hydrogenases and discuss possible avenues that might lead to tailored oxygen-robust enzyme variants.Hydrogenases and oxygen652012137#N/ATRUE
3795
c2sc01083f10.1039/c2sc01083fFALSEhttps://doi.org/10.1039/c2sc01083fChen, QYChem. Sci.The reductive Cleavage of the unactivated carbon-chlorine bond of 2-chloro-1,1,1-trifluoroethane (HCFC-133a) via a single electron transfer (SET) process using transition-metal-catalysis has been achieved. Ni(0) or Cu(0) catalytic systems afford 1,1,1-trifluoroethane (HFC-143a) or 1,1-difluoroethylene (VDF) with excellent yields respectively. The formation of VDF may be due to the beta-elimination of the 1,1,1-trifluoroethyl anion generated by SET between the corresponding radical and a Cu(I) intermediate.Ni(0) or Cu(0) catalyzed Cleavage of the unactivated C-Cl bond of 2-chloro-1,1,1-trifluoroethane (HCFC-133a) via a single electron transfer (SET) process17201248#N/ATRUE
3796
c0sc00464b10.1039/c0sc00464bFALSEHillhouse, GLSynthesis and carbene-transfer reactivity of dimeric nickel carbene cations supported by N-heterocyClic carbene ligandsx2011#N/AFALSE
3797
c2sc01033j10.1039/c2sc01033jFALSEhttps://doi.org/10.1039/c2sc01033jPeters, JCChem. Sci.The first examples of thermally stable molecular dihydrogen adducts of nickel were synthesized from their dinitrogen adduct precursors, which are themselves among the first examples of Ni(II)-N-2 complexes. The minimal Activation of the bound N-2 moieties suggests that these adducts are stabilized predominantly through sigma-donation from the adduct to the electrophilic metal center. We further show that the bound H-2 ligand can undergo heterolytic Cleavage to deliver hydride to the nickel center. The H-2 adducts are of particular interest in the context of hypotheses suggesting that Ni can serve as the site for H-2 binding and heterolytic Activation in [NiFe] hydrogenases.Thermally stable N-2 and H-2 adducts of cationic nickel(II)62201248#N/ATRUE
3798
c2sc00866a10.1039/c2sc00866aFALSEhttps://doi.org/10.1039/c2sc00866aMontgomery, JChem. Sci.A strategy for regiochemical reversal of reductive macrocyClizations of aldehydes and terminal alkynes has been developed. Using an advanced synthetic intermediate directed towards the methymycin/neomethymycin Class of macrolides, selective endocyClization provides the natural twelve-membered ring series, whereas ligand alteration enables selective exocyClization to provide access to the unnatural eleven-membered ring series. The twelve-membered ring adduct was converted to 10-deoxymethynolide, completing an efficient total synthesis of this natural product.Nickel-catalyzed regiodivergent approach to macrolide motifs32201246#N/ATRUE
3799
c2cc36375e10.1039/c2cc36375eFALSEhttps://doi.org/10.1039/c2cc36375eGao, GNovel bisimidazolium pincers as low loading ligands for in situ palladium-catalyzed Suzuki-Miyaura reaction in the ambient atmosphere2013#N/ATRUE
3800
c2cc33877g10.1039/c2cc33877gFALSEhttps://doi.org/10.1039/c2cc33877gSutter, JPFirst magnets based on thiocyanato-bridges2012#N/ATRUE
3801
c0cc04794e10.1039/c0cc04794eFALSEhttps://doi.org/10.1039/c0cc04794eFox, JMInterplay between the diamine structure and absolute helicity in Ni-salen metallofoldamersx2011#N/AFALSE
3802
c2cc31679j10.1039/c2cc31679jFALSEhttps://doi.org/10.1039/c2cc31679jLee, SA simple, fast, and easy assay for transition metal-catalyzed coupling reactions using a paper-based colorimetric iodide sensor2012#N/ATRUE
3803
c0cc03720f10.1039/c0cc03720fhttps://doi.org/10.1039/c0cc03720fTian, CESyntheses, structures and multi-photoluminescence images with confocal microscopy for three 5,5 '-azotetrazolate(AZT) based Zn(II) and Ni(II) complexesPhotocatalyst2011#N/AFALSE
3804
c2cc16221k10.1039/c2cc16221kFALSEhttps://doi.org/10.1039/c8sc00604kMurugesu, MA novel high-spin tridecanuClear Ni-II Cluster with an azido-bridged core exhibiting disk-like topology2012#N/ATRUE
3805
c0cc01879a10.1039/c0cc01879aFALSEhttps://doi.org/10.1039/c0cc01879aXu, QABimetallic nickel-iridium nanocatalysts for hydrogen generation by decomposition of hydrous hydrazinex2010#N/AFALSE
3806
c0cc00778a10.1039/c0cc00778aFALSEhttps://doi.org/10.1039/c0cc00778aWang, ZXMetal-catalyzed direct Alkylations of (hetero)arenes via C-H bond Cleavages with unactivated Alkyl halidesx2010#N/AFALSE
3807
c1sc00368b10.1039/c1sc00368bFALSEhttps://doi.org/10.1039/c1sc00368bXia, JBChem. Sci.Cross coupling of non-activated Alkyl halides is a potentially transformative methodology in organic synthesis. Herein we review the recent development of nickel-catalyzed coupling of non-activated Alkyl halides. The current understanding of the mechanism of these coupling reactions is highlighted. As the mechanism is ligand-dependant, the perspective is organized according to the types of ligands employed in the catalysis.Nickel-catalyzed cross coupling of non-activated Alkyl halides: a mechanistic perspective398201197#N/ATRUE
3808
c1sc00260k10.1039/c1sc00260kFALSEhttps://doi.org/10.1039/c1sc00260kDichtel, WRA mechanistic study of Lewis acid-catalyzed covalent organic framework formation2011#N/ATRUE
3809
c1sc00026h10.1039/c1sc00026hTRUEhttps://doi.org/10.1039/c1sc00026hDoyle, AGChem. Sci.A Ni(0) catalyst facilitates efficient C-C bond formation between a wide range of p-neutral and p-deficient Aryl boronic acids and N-acyliminium precursors derived from quinoline and isoquinoline. The reaction proceeds under mild conditions and is tolerant of common organic functional groups. In addition, a simple one-pot protocol amenable to the direct use of substituted quinolines is described. Consistent with preliminary data revealing a mild, organB(OH)2ronate-mediated racemization of enantioenriched N-acyliminium precursors, initial results indicate that a chiral phosphoramidite-ligated nickel catalyst promotes enantioselective Arylation of racemic substrate with no evidence of a kinetic resolution during catalysis.Transition metal-catalyzed cross coupling with N-acyliminium ions derived from quinolines and isoquinolinesCsp3-Csp2_arE-NuOBOEtB(OH)2AllylNo baseNo Base562011521/11/2022TRUE
3810
c1cc12619a10.1039/c1cc12619aFALSEhttps://doi.org/10.1039/c1cc12619aLiu, HHighly diastereo- and enantioselective synthesis of syn-beta-substituted tryptophans via asymmetric Michael addition of a chiral equivalent of nuCleophilic glycine and sulfonylindoles2011#N/ATRUE
3811
b916822b10.1039/b916822bFALSELercher, JAHydrodeoxygenation of bio-derived phenols to hydrocarbons using RANEY (R) Ni and Nafion/SiO2 catalystsx2010#N/AFALSE
3812
b916637h10.1039/b916637hFALSEYou, XZAssembling chirality into magnetic nanowires: cyano-bridged iron(III)-nickel(II) chains exhibiting slow magnetization relaxation and ferroelectricityx2009#N/AFALSE
3813
b915722k10.1039/b915722kFALSEhttps://doi.org/10.1039/b915722kNabeshima, THighly efficient regulation of cation recognition and promotion of self-assembly by metalation of a macrocyClic bis(N2O2) ligand with nickel(II)x2010#N/AFALSE
3814
c1cc12158h10.1039/c1cc12158hFALSEBendix, JA linear single-molecule magnet based on [Ru-III(CN)(6)](3-)2011#N/ATRUE
3815
c0sc00323a10.1039/c0sc00323aFALSEhttps://doi.org/10.1039/c0sc00323aSoldatov, AChem. Sci.Axial ligation mechanisms of a metalloporphyrin, nickel(II) tetramesitylporphyrin (NiTMP), were investigated by static and transient X-ray absorption spectroscopy at Ni K-edge (8.333 keV). A surprisingly broad (i.e. similar to 1.4 eV) linewidth for the Is -> 3d(x2-y2) transition in the ground state was attributed to strong geometry dependent 3d molecular orbital (MO) energies due to coexisting conformers in solution. The broad distribution of 3d MO energy levels enables transient degeneracy of the 3d(z2) and 3d(x2-y2) MOs to produce a temporary vacancy in the 3d(z2) MO which favors axial ligation. Photoexcitation also induces the vacancy in the 3d(z2) MO, leading to a more than two-fold enhancement in the axial ligated species. Therefore, a unified axial ligation mechanism for both the ground and excited state is proposed based on the elucidation of the excited state structural dynamics, which will have a broad impact in understanding and controlling axial ligation in enzymatic reactions and molecular catalysis involving transient axial ligation.X-ray snapshots for metalloporphyrin axial ligation34201049#N/ATRUE
3816
c0sc00269k10.1039/c0sc00269kFALSEhttps://doi.org/10.1039/c0sc00269kKurosawa, HChem. Sci.A series of bis-cyCloheptatrienyl triangular triplatinum complexes are synthesized as a novel Class of organoplatinum sandwich compounds. The tris-ethylene triplatinum sandwich complex and the monophenyl bis-ethylene sandwich complex of triangular triplatinum are structurally characterized by X-ray crystallographic analyses. The net assembling of three Pt-0 atoms between two tropylium cations is initiated by complexation of a Pt-0 moiety by a tropylium ligand, where the mononuClear cyCloheptatrienyl Pt-II intermediate is detectable in situ by NMR. It is revealed that the choice of added ligands is crucial to the efficient formation as well as conversion of the key mononuClear cyCloheptatrienyl Pt-II intermediate.Metallocenoids of platinum: Syntheses and structures of triangular triplatinum sandwich complexes of cyCloheptatrienyl39201155#N/ATRUE
3817
b904068d10.1039/b904068dFALSEhttps://doi.org/10.1039/b904068dGao, EQSolvent-modulated metamagnetism in a nickel(II) coordination polymer with mixed azide and Carbonylate bridgesx2009#N/AFALSE
3818
c0cc05805j10.1039/c0cc05805jFALSEhttps://doi.org/10.1039/c7sc02692gMatt, DHigh efficiency of cavity-based triAryl-phosphines in nickel-catalysed Kumada-Tamao-Corriu cross-coupling2011#N/ATRUE
3819
b815647f10.1039/b815647fFALSELi, HLElectrodeposited nickel hydroxide on nickel foam with ultrahigh capacitancex2008#N/AFALSE
3820
c0cc05608a10.1039/c0cc05608aFALSEAgapie, TTrinuClear first row transition metal complexes of a hexapyridyl, trialkoxy 1,3,5-triArylbenzene ligand2011#N/ATRUE
3821
c0cc04385k10.1039/c0cc04385kFALSEhttps://doi.org/10.1039/c0cc04385kOhe, KGallium (III)-catalysed bromocyanation of alkynes: regio- and stereoselective synthesis of beta-bromo-alpha,beta-unsaturated nitriles2011#N/ATRUE
3822
c0cc03064c10.1039/c0cc03064cFALSEWang, ZXRoom-temperature nickel-catalysed cross-couplings of Aryl chlorides with Arylzincs2011#N/ATRUE
3823
b801645c10.1039/b801645cFALSEhttps://doi.org/10.1039/b801645cVaccari, AHighly conductive Ni steam reforming catalysts prepared by electrodepositionx2008#N/AFALSE
3824
b700569e10.1039/b700569eFALSEhttps://doi.org/10.1039/b700569eBatten, SRMagnetic canting or not? Two isomorphous 3D Co-II and Ni-II coordination polymers with the rare non-interpenetrated (10,3)-d topological network, showing spin-canted antiferromagnetism only in the Co-II systemx2007#N/AFALSE
3825
c0cc00399a10.1039/c0cc00399aFALSEhttps://doi.org/10.1039/c0cc00399aDunbar, KRTrigonal bipyramidal magnetic molecules based on [Mo-III(CN)(6)](3-)2010#N/ATRUE
3826
c0cc00317d10.1039/c0cc00317dFALSEHolmes, SMA cyano-based octanuClear {(Fe4Ni4II)-Ni-III} single-molecule magnet2010#N/ATRUE
3827
c001675f10.1039/c001675fFALSEhttps://doi.org/10.1039/c001675fArtero, VA structural and functional mimic of the active site of NiFe hydrogenases2010#N/ATRUE
3828
b918626c10.1039/b918626cFALSEhttps://doi.org/10.1039/B918626CXia, JBCyanative alkene-aldehyde coupling: Ni(0)-NHC-Et2AlCN mediated chromanol synthesis with high cis-selectivity at room temperature2010#N/ATRUE
3829
b608297a10.1039/b608297aFALSEhttps://doi.org/10.1039/b608297aHolmes, SMSyntheses, structures, and magnetic characterization of dicyanometalate(II) building blocks: [NEt4][(Tp*)M-II(CN)(2)] [M-II = Cr, Co, Ni; Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate]x2006#N/AFALSE
3830
b915169a10.1039/b915169aFALSEhttps://doi.org/10.1039/c7sc04849aMagner, ETailored adsorption of His(6)-tagged protein onto nickel(II)-cyClam grafted mesoporous silica2010#N/ATRUE
3831
b511202h10.1039/b511202hhttps://doi.org/10.1039/c7cc09007bWaymouth, RMSynthesis, structure, and olefin polymerization with nickel(II) N-heterocyClic carbene enolatesx2005#N/AFALSE
3832
b914329g10.1039/b914329gFALSEhttps://doi.org/10.1039/b914329gYu, SHLamellar transition-metal molybdate-CTA mesostructured composites (metal = Ni, Co): one-pot synthesis and application in treatment of acid fuchsine2009#N/ATRUE
3833
b506465a10.1039/b506465aFALSECheng, PStructure and magnetic properties of a new ferrimagnet containing a paramagnetic [Cr(CN)(5)(NO)](3-) building blockx2005#N/AFALSE
3834
b912025d10.1039/b912025dFALSEhttps://doi.org/10.1039/b912025dHamachi, ISite-specific covalent labeling of His-tag fused proteins with a reactive Ni(II)-NTA probe2009#N/ATRUE
3835
b501520k10.1039/b501520kFALSELee, WYBenzene C-H Activation by platinum(II) complexes of bis(2-diphenylphosphinophenyl)amidex2005#N/AFALSE
3836
b900636b10.1039/b900636bFALSEhttps://doi.org/10.1039/b900636bZen, JMRuthenium-functionalized nickel hydroxide catalyst for highly efficient alcohol oxidations in the presence of molecular oxygen2009#N/ATRUE
3837
b813421a10.1039/b813421aFALSEStradiotto, M(kappa(2)-P,S)Pt(Benzyl) complexes derived from 1/3-(PPr2)-Pr-i-2-S-t Bu-indene: facile synthesis of carbanion- and borate-containing zwitterions2008#N/ATRUE
3838
b811831k10.1039/b811831kFALSEhttps://doi.org/10.1039/b811831kGu, YCSynthesis and reactions of the first fluoroAlkylated Ni(II) N-confused porphyrins2008#N/ATRUE
3839
b802454e10.1039/b802454eFALSEMezailles, NWhite phosphorus as single source of P in the synthesis of nickel phosphide2008#N/ATRUE
3840
b413433h10.1039/b413433hFALSESuarez-Varela, JRational design of azide-bridged bimetallic complexes. Crystal structure and magnetic properties of (FeMFeIII)-M-III (M = Ni-II and Cu-II) trinuClear speciesx2005#N/AFALSE
3841
b618401d10.1039/b618401dFALSEhttps://doi.org/10.1039/c7sc03912cLe Floch, PHighly efficient P-N nickel(II) complexes for the dimerisation of ethylene2007#N/ATRUE
3842
b613865a10.1039/b613865aFALSEBraunstein, PStructurally characterized intermediates in the stepwise insertion of CO-ethylene or CO-methyl acrylate into the metal-carbon bond of Pd(II) complexes stabilized by (phosphinomethyl)oxazoline ligands2007#N/ATRUE
3843
b613782b10.1039/b613782bFALSEChaudhuri, PA one-pot synthesis of a paramagnetic high-nuClearity nickel(II) Cluster: an octadecanuClear (Ni16Na2I)-Na-II metal aggregate2007#N/ATRUE
3844
b610751f10.1039/b610751fFALSEJohnson, MDSelf-exchange electron transfer in high oxidation state non-oxo metal complexes: amavadin2006#N/ATRUE
3845
b604502b10.1039/b604502bFALSEhttps://doi.org/10.1039/b604502bRay, DTetranuClear Cu(II) complex supported by a central mu(4)-1,1,3,3 azide bridge2006#N/ATRUE
3846
b509147k10.1039/b509147kFALSEhttps://doi.org/10.1039/b509147kFrolich, RStructural diversity in the assembly of helicate-type nickel(II) complexes with enantiopure bis(beta-diketonate) ligands2005#N/ATRUE
3847
b502850g10.1039/b502850gFALSEhttps://doi.org/10.1039/b502850gKepert, CJReversible hydrogen gas uptake in nanoporous Prussian Blue analogues2005#N/ATRUE
3848
b500581g10.1039/b500581gFALSEhttps://doi.org/10.1039/c7sc01239jWinpenny, REPSynthesis and characterisation of a {Ni-8} single molecule magnet and another octanuClear nickel cage2005#N/ATRUE
3849
b211395n10.1039/b211395nFALSEhttps://doi.org/10.1039/c7sc01239jMascharak, PKDioxygen Activation by a dinuClear nickel thiolate complex: structural characterization of the ligand oxidized productx2003#N/AFALSE
3850
b415838e10.1039/b415838eFALSEOyama, STA new type of nonsulfide hydrotreating catalyst: nickel phosphide on carbon2005#N/ATRUE
3851
b415431b10.1039/b415431bFALSEhttps://doi.org/10.1039/b415431bKitagawa, SA novel high-spin heterometallic Ni12K4 Cluster incorporating large Ni-azide cirCles and an in situ cyanomethylated di-2-pyridyl ketone2005#N/ATRUE
3852
b209053h10.1039/b209053hhttps://doi.org/10.1039/b209053hKumar, SPhotoactive chemosensors 3: a unique case of fluorescence enhancement with Cu(II)Photocatalyst2002#N/AFALSE
3853
b204851e10.1039/b204851eFALSEhttps://doi.org/10.1039/b204851eXu, ZQSynthesis and coordination chemistry of a water-soluble verdazyl radical. structures and magnetic properties of M(H2O)(2)(vdCO(2))(2)center dot 2H(2)O (M = Co, Ni; vdCO(2)=1,5-dimethyl-6-oxo-verdazyl-3-Carbonylate)x2002#N/AFALSE
3854
b413683g10.1039/b413683gFALSEhttps://doi.org/10.1039/b413683gBerreau, LMNeutral acetohydroxamic acid coordination to a mononuClear Ni(II) center stabilized by an intramolecular hydrogen-bonding interaction2005#N/ATRUE
3855
b203487p10.1039/b203487pFALSEhttps://doi.org/10.1039/b203487pRibas, JFirst tetrameric Ni-II Cluster with planar triangular topology exhibiting ferromagnetic pathwaysx2002#N/AFALSE
3856
b412338g10.1039/b412338gFALSEBalch, ALPyramidalization of Gd3N inside a C-80 cage. The synthesis and structure of Gd3N@C-802004#N/ATRUE
3857
b405695g10.1039/b405695gFALSEhttps://doi.org/10.1039/b405695gLough, AJIsolation and characterization of the first stable bicarbonato complex in a nickel(II) system: identification of unusual monodentate coordination2004#N/ATRUE
3858
b110747j10.1039/b110747jFALSEhttps://doi.org/10.1039/c6sc02456dMaestro, MSynthesis and characterization of [Cu(Me(2)oxpn)Ni(NO2)(tmen)](ClO4): a single ferrimagnetic dinuClear Cu-II-Ni-II complex acting as weak molecule-based magnetx2002#N/AFALSE
3859
b108162d10.1039/b108162dFALSEhttps://doi.org/10.1039/b108162dRaston, ClNi(II) N-4-macrocyCle grafted crown ether: caesium cobalt(III) bis(dicarbollide) coordination polymerx2002#N/AFALSE
3860
b107827p10.1039/b107827pFALSEhttps://doi.org/10.1039/c6sc02083fWelter, RBimetallic-induced tail-to-tail dimerization and C-H Activation of methyl acrylatex2001#N/AFALSE
3861
b104649g10.1039/b104649gFALSEhttps://doi.org/10.1039/b104649gChaudhuri, NRThe first metamagnetic one-dimensional molecular material with nickel(II) and end-to-end azido bridgesx2001#N/AFALSE
3862
b403876b10.1039/b403876bFALSEhttps://doi.org/10.1039/b403876bMcInnes, EJLSupertetrahedral decametallic Ni(II) Clusters directed by mu(6)-tris-alkoxides2004#N/ATRUE
3863
b009160j10.1039/b009160jFALSEhttps://doi.org/10.1039/b009160jCheetham, AKCatalytic conversion of butadiene to ethylbenzene over the nanoporous nickel(II) phosphate, VSB-1x2001#N/AFALSE
3864
b312716h10.1039/b312716hFALSETurner, PInherent helicity in an extended tris-bipyridyl molecular cage2004#N/ATRUE
3865
b310565b10.1039/b310565bFALSEhttps://doi.org/10.1039/b310565bTsuji, YCross-coupling reaction of thermally stable titanium(II)-alkyne complexes with Aryl halides catalysed by a nickel complex2003#N/ATRUE
3866
b300033h10.1039/b300033hFALSEHoffmann, RWKumada-Corriu coupling of Grignard reagents, probed with a chiral Grignard reagent2003#N/ATRUE
3867
b212861f10.1039/b212861fFALSEhttps://doi.org/10.1039/b212861fHashimoto, KIon-exchange synthesis and magneto-optical spectra of colored magnetic thin films composed of metal(II) hexacyanochromate(III)2003#N/ATRUE
3868
b000516i10.1039/b000516iFALSEhttps://doi.org/10.1039/b000516iThompson, LKA mixed-metal Cu(II)(2)Ni(II)(2) complex derived from a phenol-based heterotetranuCleating macrocyClic ligandx2000#N/AFALSE
3869
ar800138a10.1021/ar800138aFALSEhttps://pubs.acs.org/doi/10.1021/ar800138aWang, ZXCross-Coupling Reaction of Alkyl Halides with Grignard Reagents Catalyzed by Ni, Pd, or Cu Complexes with π-Carbon Ligand(s)Review AriCle291#N/A
3870
anie.20210898710.1002/anie.202108987https://doi.org/10.1002/anie.202108987Noel, TAngew. Chem.-Int. Edit.Herein, we report a photocatalytic procedure that enables the acylation/Arylation of unfunctionalized Alkyl derivatives in flow. The method exploits the ability of the decatungstate anion to act as a hydrogen atom abstractor and produce nuCleophilic carbon-centered radicals that are intercepted by a nickel catalyst to ultimately forge C(sp(3))-C(sp(2)) bonds. Owing to the intensified conditions in flow, the reaction time can be reduced from 12-48 hours to only 5-15 minutes. Finally, kinetic measurements highlight how the intensified conditions do not change the reaction mechanism but reliably speed up the overall process.Rapid and Direct Photocatalytic C(sp(3))-H Acylation and Arylation in Flowacylation; Arylation; flow chemistry; hydrogen atom transfer; TBADTPhotocatalyst0606/9/2022FALSE
3871
anie.20210895510.1002/anie.202108955FALSEhttps://doi.org/10.1002/anie.202108955Luo, JLAngew. Chem.-Int. Edit.The Co-based electrocatalyst is among the most promising candidates for electrochemical oxidation of 5-hydroxymethylfurfural (HMF). However, the intrinsic active sites and detailed mechanism of this catalyst remains unClear. We combine experimental evidence and a theoretical study to show that electrogenerated Co3+ and Co4+ species act as chemical oxidants but with distinct roles in selective HMF oxidation. It is found that Co3+ is only capable of oxidizing Carbonyl group to produce Carbonylate while Co4+ is required for the initial oxidation of hydroxyl group with significantly faster kinetics. As a result, the product distribution shows explicit dependence on the Co oxidation states and selective production of 5-hydroxymethyl-2-furanCarbonylic acid (HMFCA) and 2,5-furandiCarbonylic acid (FDCA) are achieved by tuning the applied potential. This work offers essential mechanistic insight on Co-catalyzed organic oxidation reactions and might guide the design of more efficient electrocatalysts.Understanding the Roles of Electrogenerated Co3+ and Co4+ in Selectivity-Tuned 5-Hydroxymethylfurfural Oxidation5-hydroxymethylfurfural; cobalt; electrochemistry; reaction mechanisms; selective oxidationx058#N/AFALSE
3872
anie.20210877010.1002/anie.202108770FALSEhttps://doi.org/10.1002/anie.202108770Shi, WDAngew. Chem.-Int. Edit.The fundamental understanding of the surface reconstruction induced by the applied potential is of great significance for enhancing the oxygen evolution reaction (OER). Here, we show that a previously overlooked discharge current in the low applied potential region also leads to in situ electrochemical Activation of a nitrogen-doped nickel oxyhydroxide surface. We exploit the fact that doping of heteroatoms weakens the surface structure, and hence, a weak discharge current originating from the capacitive nature of nickel oxyhydroxide has a strong structure-reforming ability to promote the formation of nitrogen and oxygen vacancies. The current density at 1.4 V (vs. Hg/HgO) can dramatically increase by as much as 31.3 % after discharge in the low applied potential region. This work provides insight into in situ enhancement of the OER and suggests that the low applied potential region must be a primary consideration in evaluating the origin of the activity of electrocatalysts.Discharge-Induced Enhancement of the Oxygen Evolution Reactiondischarge; doping; electrochemistry; oxygen evolution reaction; vacancyx059#N/AFALSE
3873
anie.20210858710.1002/anie.202108587https://doi.org/10.1002/anie.202108587Xue, DAngew. Chem.-Int. Edit.The Buchwald-Hartwig C-N coupling reaction has found widespread applications in organic synthesis. Over the past two decades or so, many improved catalysts have been introduced, allowing various amines and Aryl electrophiles to be readily used nowadays. However, there lacks a protocol that could be used to couple a wide range of chiral amines and Aryl halides, without erosion of the enantiomeric excess (ee). Reported in this artiCle is a method based on molecular Ni catalysis driven by light, which enables stereoretentive C-N coupling of optically active amines, amino alcohols, and amino acid esters with Aryl bromides, with no need for any external photosensitizer. The method is effective for a wide variety of coupling partners, inCluding those bearing functional groups sensitive to bases and nuCleophiles, thus providing a viable alternative to accessing synthetically important chiral N-Aryl amines, amino alcohols, and amino acids esters. Its viability is demonstrated by 92 examples with up to 99 % ee.Chiral Arylated Amines via C-N Coupling of Chiral Amines with Aryl Bromides Promoted by Lightchiral N-Aryl amines; chiral N-Aryl amino acids; chiral N-Aryl amino alcohols; C-N coupling; nickel catalysisPhotocatalyst062#N/AFALSE
3874
b211990k10.1039/b211990kFALSEhttps://doi.org/10.1039/b211990kDolphin, DInner C-cyanide addition and nuCleophilic addition to Ni(II) N-confused porphyrins2003#N/ATRUE
3875
anie.20210782010.1002/anie.202107820FALSEhttps://doi.org/10.1002/anie.202107820Baran, PSAngew. Chem.-Int. Edit.The formation of Aryl-Alkyl ether bonds through cross coupling of alcohols with Aryl halides represents a useful strategic departure from Classical S(N)2 methods. Numerous tactics relying on Pd-, Cu-, and Ni-based catalytic systems have emerged over the past several years. Herein we disClose a Ni-catalyzed electrochemically driven protocol to achieve this useful transformation with a broad substrate scope in an operationally simple way. This electrochemical method does not require strong base, exogenous expensive transition metal catalysts (e.g., Ir, Ru), and can easily be scaled up in either a batch or flow setting. Interestingly, e-etherification exhibits an enhanced substrate scope over the mechanistically related photochemical variant as it tolerates tertiary amine functional groups in the alcohol nuCleophile.Chemoselective, Scalable Nickel-Electrocatalytic O-Arylation of Alcoholschemoselectivity; coupling; electrochemistry; nickel catalysis; O-Arylation
Electrocatalytic
098#N/AFALSE
3876
b210327c10.1039/b210327cFALSEhttps://doi.org/10.1039/b210327cGudel, HUIncreasing the crystallisation temperature to access new spin Clusters: conversion of [Ni-8(cit)(6)(OH)(2)(H2O)(2)](10-) to [Ni-8(cit)(6)(OH)(2)](10-)2003#N/ATRUE
3877
b209270k10.1039/b209270kFALSEhttps://doi.org/10.1039/c6sc04819fBalch, ALCrystallographic characterization of Isomer 2 of Er-2@C-82 and comparison with Isomer 1 of Er-2@C-822002#N/ATRUE
3878
b203813g10.1039/b203813gFALSEhttps://doi.org/10.1039/b203813gDolphin, DDiels-Alder reactions of nickel(II) N-confused porphyrins as dienophiles2002#N/ATRUE
3879
b201337a10.1039/b201337aFALSEArmstrong, FADirect comparison of the electrocatalytic oxidation of hydrogen by an enzyme and a platinum catalyst2002#N/ATRUE
3880
anie.20210668210.1002/anie.202106682https://doi.org/10.1002/anie.202106682Chen, ClAngew. Chem.-Int. Edit.The practical synthesis of polar-functionalized polyolefins using transition-metal-catalyzed copolymerization of olefins with polar monomers is a challenge; the use of heterogeneous catalysts is little explored. Herein, we report the synthesis of heterogeneous naphthoquinone-based nickel (Ni/SiO2) and palladium (Pd/SiO2) catalysts through hydrogen bonding interactions of the ligands with the silica surface. Ni/SiO2 exhibits high activities (up to 2.65x10(6) g mol(-1) h(-1)) during the copolymerization of ethylene with 5-hexene-1-yl-acetate, affording high-molecular-weight (M-n up to 630 000) polar-functionalized semicrystalline polyethylene (comonomer incorporation up to 2.8 mol %), along with great morphology control. The resulting copolymers possess improved surface properties and great mechanical properties. Pd/SiO2 can mediate ethylene copolymerization with polar monomers with moderate activity to produce high-molecular-weight copolymers with tunable comonomer incorporation.Hydrogen-Bonding-Induced Heterogenization of Nickel and Palladium Catalysts for Copolymerization of Ethylene with Polar Monomersheterogenization; morphology; nickel; polar functionalization; polyolefinsx0202174#N/AFALSE
3881
anie.20210645910.1002/anie.202106459FALSEhttps://doi.org/10.1002/anie.202106459Huang, XQAngew. Chem.-Int. Edit.Over the past decades, despite the substantial efforts that have been devoted to the modifications of Pt nanopartiCles (NPs) to tailor their selectivities for hydrogenation reactions, there are still a lack of facile strategies for precisely regulation of the surface properties of NPs, especially for those with small sizes. In this work, we propose a top-down thermal annealing strategy for tuning the surface properties of Pt-based NPs (approximate to 4 nm) without the occurrence of aggregation. Compared to conventional bottom-up methods, the present top-down strategy can precisely regulate the surface compositions of Pt-Cd NPs and other ternary Pt-Cd-M NPs (M=Fe, Ni, Co, Mn, and Sn). The optimized Pt-Cd NPs exhibit excellent selectivity toward phenylacetylene and 4-nitrostyrene hydrogenations with a styrene selectivity and 4-aminophenyl styrene selectivity of 95.2 % and 94.5 %, respectively. This work provides a general strategy for the surface reconstructions of Pt-based NPs, and promotes fundamental research on catalyst design for heterogeneous catalysis.A Top-Down Strategy to Realize Surface Reconstruction of Small-Sized Platinum-Based NanopartiCles for Selective Hydrogenationcadmium; hydrogenation; platinum; surface reconstruction; top-down strategyx0202138#N/AFALSE
3882
b200131b10.1039/b200131bFALSEhttps://doi.org/10.1039/c6sc02123aLash, TDOrganometallic chemistry of carbaporphyrinoids: synthesis and characterization of nickel(II) and palladium(II) azuliporphyrins2002#N/ATRUE
3883
anie.20210624310.1002/anie.202106243FALSEhttps://doi.org/10.1002/anie.202106243Xie, KAngew. Chem.-Int. Edit.Dry reforming of CH4/CO2 provides a promising and economically feasible route for the large-scale carbon fixation; however, the coking and sintering of catalysts remain a fundamental challenge. Here we stabilize single-crystalline Ni nanopartiCles at the surface of porous single-crystalline MgO monoliths and show the quantitative production of syngas from dry reforming of CH4/CO2. We show the complete conversion of CH4/CO2 even only at 700 degrees C with excellent performance durability after a continuous operation of 500 hours. The well-defined and catalytically active Ni-MgO interfaces facilitate the reforming reaction and enhance the coking resistance. Our findings would enable an industrially and economically viable path for carbon reClamation, and the Nanocrystal On Porous Single-crystalline Monoliths technique could lead to stable catalyst designs for many challenging reactions.Dry Reforming of CH4/CO2 by Stable Ni Nanocrystals on Porous Single-Crystalline MgO Monoliths at Reduced Temperaturebasic site; interface; monolith; porous single crystal; reforming reactionx0202141#N/AFALSE
3884
anie.20210552310.1002/anie.202105523FALSEhttps://doi.org/10.1002/anie.202105523Zheng, GFAngew. Chem.-Int. Edit.Renewable energy-powered methane (CH4) conversion at ambient conditions is an attractive but highly challenging field. Due to the highly inert character of CH4, the selective Cleavage of its first C-H bond without over-oxidation is essential for transforming CH4 into value-added products. In this work, we developed an efficient and selective CH4 conversion approach at room temperature using intermediate chlorine species (*Cl), which were electrochemically generated and stabilized on mixed cobalt-nickel spinels with different Co/Ni ratios. The lower overpotentials for *Cl formation enabled an effective Activation and conversion of CH4 to CH3Cl without over-oxidation to CO2, and Ni3+ at the octahedral sites in the mixed cobalt-nickel spinels allowed to stabilize surface-bound *Cl species. The CoNi2Ox electrocatalyst exhibited an outstanding yield of CH3Cl (364 mmol g(-1) h(-1)) and a high CH3Cl/CO2 selectivity of over 400 at room temperature, with demonstrated capability of direct CH4 conversion under seawater working conditions.Electrocatalytic Methane Oxidation Greatly Promoted by Chlorine Intermediateschlorine intermediates; Co-Ni spinel; electrocatalysis; methane oxidation; selectivity
Electrocatalytic
0202143#N/AFALSE
3885
anie.20210549210.1002/anie.202105492FALSEhttps://doi.org/10.1002/anie.202105492Beller, MAngew. Chem.-Int. Edit.A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core-shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 degrees C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recyCling experiments.Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core-Shell Catalystalkenes; catalysis; deuteration; hydrogenation; nanopartiClesx0202146#N/AFALSE
3886
anie.20210535410.1002/anie.202105354FALSEhttps://doi.org/10.1002/anie.202105354Scheidt, KAAngew. Chem.-Int. Edit.Single-electron N-heterocyClic carbene (NHC) catalysis has gained attention recently for the synthesis of C-C bonds. Guided by density functional theory and mechanistic analyses, we report the light-driven synthesis of aliphatic and alpha-amino ketones using single-electron NHC operators. Computational and experimental results reveal that the reactivity of the key radical intermediate is substrate-dependent and can be modulated through steric and electronic parameters of the NHC. Catalyst potential is harnessed in the visible-light driven generation of an acyl azolium radical species that undergoes selective coupling with various radical partners to afford diverse ketone products. This methodology is showcased in the direct late-stage functionalization of amino acids and pharmaceutical compounds, highlighting the utility of single-electron NHC operators.Light-Driven Carbene Catalysis for the Synthesis of Aliphatic and alpha-Amino Ketonescarbene; catalysis; density functional theory; late-stage functionalization; photochemistryx02021111#N/AFALSE
3887
anie.20210487110.1002/anie.202104871FALSEhttps://doi.org/10.1002/anie.202104871Giri, RAngew. Chem.-Int. Edit.We disClose a nickel-catalyzed reaction, which enabled us to difunctionalize unactivated gamma,delta-alkenes in ketones with alkenyl triflates and Arylboronic esters. The reaction was made feasible by the use of 5-chloro-8-hydroxyquinoline as a ligand along with NiBr2DME as a catalyst and LiOtBu as base. The reaction proceeded with a wide range of cyClic, acyClic, endocyClic and exocyClic alkenyl ketones, and electron-rich and electron-deficient Arylboronate esters. The reaction also worked with both cyClic and acyClic alkenyl triflates. Control experiments indicate that Carbonyl coordination is required for the reaction to proceed.Nickel-Catalyzed Regioselective AlkenylArylation of gamma,delta-Alkenyl Ketones via Carbonyl Coordination8-hydroxyquinoline; alkenyl ketone; alkenylArylation; dicarbofunctionalization; nickel catalysisx0110#N/AFALSE
3888
anie.20210487110.1002/anie.202104871FALSEhttps://doi.org/10.1002/anie.202104871Giri, RAngew. Chem.-Int. Edit.We disClose a nickel-catalyzed reaction, which enabled us to difunctionalize unactivated gamma,delta-alkenes in ketones with alkenyl triflates and Arylboronic esters. The reaction was made feasible by the use of 5-chloro-8-hydroxyquinoline as a ligand along with NiBr2 center dot DME as a catalyst and LiOtBu as base. The reaction proceeded with a wide range of cyClic, acyClic, endocyClic and exocyClic alkenyl ketones, and electron-rich and electron-deficient Arylboronate esters. The reaction also worked with both cyClic and acyClic alkenyl triflates. Control experiments indicate that Carbonyl coordination is required for the reaction to proceed.Nickel-Catalyzed Regioselective AlkenylArylation of gamma,delta-Alkenyl Ketones via Carbonyl Coordination8-hydroxyquinoline; alkenyl ketone; alkenylArylation; dicarbofunctionalization; nickel catalysisx02021104#N/AFALSE
3889
b103050g10.1039/b103050gFALSEhttps://doi.org/10.1039/b103050gSteinfeld, GThe effect of N-methylation on the chemical reactivity of binuClear Ni amine-thiophenolate complexes2001#N/ATRUE
3890
anie.20210456410.1002/anie.202104564FALSEhttps://doi.org/10.1002/anie.202104564Cao, RAngew. Chem.-Int. Edit.The electrocatalytic conversion of CO2 into valueadded chemicals is a promising approach to realize a carbon-energy balance. However, low current density still limits the application of the CO2 electroreduction reaction (CO2RR). Metal-organic frameworks (MOFs) are one Class of promising alternatives for the CO2RR due to their periodically arranged isolated metal active sites. However, the poor conductivity of traditional MOFs usually results in a low current density in CO2RR. We have prepared conductive two-dimensional (2D) phthalocyanine-based MOF (NiPc-NiO4) nanosheets linked by nickel-catecholate, which can be employed as highly efficient electrocatalysts for the CO2RR to CO. The obtained NiPc-NiO4 has a good conductivity and exhibited a very high selectivity of 98.4% toward CO production and a large CO partial current density of 34.5 mAcm(-2), outperforming the reported MOF catalysts. This work highlights the potential of conductive crystalline frameworks in electrocatalysis.Conductive Two-Dimensional Phthalocyanine-based Metal-Organic Framework Nanosheets for Efficient Electroreduction of CO2CO; conductive metal-organic frameworks; electroreduction; phthalocyaninex1202181#N/AFALSE
3891
anie.20210455910.1002/anie.202104559https://doi.org/10.1002/anie.202104559Vicic, DAAngew. Chem.-Int. Edit.The acetonitrile-solvated [(MeCN)Ni(C2F5)(3)](-) was prepared in order to compare and contrast its reactivity with the known [(MeCN)Ni(CF3)(3)](-) towards organic electrophiles. Both [(MeCN)Ni(CF3)(3)](-) and [(MeCN)Ni(C2F5)(3)](-) successfully react with Aryl iodonium and diazonium salts as well as alkynyl iodonium salts to give fluoroAlkylated organic products. Electrochemical analysis of [(MeCN)Ni-II(C2F5)(3)](-) suggests that, upon electro-oxidation to [(MeCN)(n)Ni-III(C2F5)(3)], reductive homolysis of a perfluoroethyl radical occurs, with the concomitant formation of [(MeCN)(2)Ni-II(C2F5)(2)]. Catalytic C-H trifluoromethylations of electron-rich arenes were successfully achieved using either [(MeCN)Ni(CF3)(3)](-) or the related [Ni(CF3)(4)](2-). Stoichiometric reactions of the solvated nickel complexes reveal that ligandless nickel is exceptionally capable of serving as reservoir of CF3 groups under catalytically relevant conditions.Solvated Nickel Complexes as Stoichiometric and Catalytic PerfluoroAlkylation Agents**catalysis; fluorine; nickel; perfluoroAlkylation; trifluoromethylationx0202136#N/AFALSE
3892
anie.20210449410.1002/anie.202104494FALSEhttps://doi.org/10.1002/anie.202104494Chen, JAngew. Chem.-Int. Edit.Non-noble transition metal complexes have attracted growing interest as efficient electrocatalysts for oxygen reduction reaction (ORR) while their activities still lack rational and effective regulation. Herein, we propose a d-delta conjugation strategy for rough and fine tuning of ORR activity of TM-BTA (TM = Mn/Fe/Co/Ni/Cu, BTA = 1,2,4,5-benzenetetramine) coordination polymers. By first-principle calculations, we elucidate that the strong d-pi conjugation elevates the d(xz)/d(yz) orbitals of TM centers to enhance intermediate adsorption and strengthens the electronic modulation effect from substitute groups on ligands. Based on this strategy, Co-TABQ (tetramino benzoquinone) is found to approach the top of ORR activity volcano. The synthesized Co-TABQ with atomically distributed Co on carbon nanotubes exhibits a half-wave potential of 0.85 V and a specific current of 127 mA mg(metal)(-1) at 0.8 V, outperforming the benchmark Pt/C. The high activity, low peroxide yield, and considerable durability of Co-BTA and Co-TABQ promise their application in oxygen electro-catalysis. This study provides mechanistic insight into the rational design of transition metal complex catalysts.Regulating Electrocatalytic Oxygen Reduction Activity of a Metal Coordination Polymer via d-pi Conjugationd-pi conjugation effect; electrocatalyst; metal coordination polymer; oxygen reduction reaction
Electrocatalytic
x0202123#N/AFALSE
3893
b005338o10.1039/b005338oFALSEhttps://doi.org/10.1039/c6cc03901dJames, BRNickel bromide as a hydrogen transfer catalyst2000#N/ATRUE
3894
anie.20210414810.1002/anie.202104148FALSEhttps://doi.org/10.1002/anie.202104148Li, GRAngew. Chem.-Int. Edit.Metal-organic frameworks (MOFs) with Carbonylate ligands as co-catalysts are very efficient for the oxygen evolution reaction (OER). However, the role of local adsorbed Carbonylate ligands around the in-situ-transformed metal (oxy)hydroxides during OER is often overlooked. We reveal the extraordinary role and mechanism of surface-adsorbed Carbonylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs for OER electrocatalytic activity enhancement. The results of X-ray photoelectron spectroscopy (XPS), synchrotron X-ray absorption spectroscopy, and density functional theory (DFT) calculations show that the Carbonylic groups around metal (oxy)hydroxides can efficiently induce interfacial electron redistribution, facilitate an abundant high-valence state of nickel species with a partially distorted octahedral structure, and optimize the d-band center together with the beneficial Gibbs free energy of the intermediate. Furthermore, the results of in situ Raman and FTIR spectra reveal that the surface-adsorbed Carbonylate ligands as Lewis base can promote sluggish OER kinetics by accelerating proton transfer and facilitating adsorption, Activation, and dissociation of hydroxyl ions (OH-).Surface-Adsorbed Carbonylate Ligands on Layered Double Hydroxides/Metal-Organic Frameworks Promote the Electrocatalytic Oxygen Evolution ReactionCarbonylate ligands; catalytic mechanisms; electrocatalysis; layered double hydroxides
Electrocatalytic
2202166#N/AFALSE
3895
anie.20210405010.1002/anie.202104050FALSEhttps://doi.org/10.1002/anie.202104050Lu, CCAngew. Chem.-Int. Edit.Pincer-type nickel-aluminum complexes were synthesized using two equivalents of the phosphinoamide, [(PhNCH2PPr2)-Pr-i](-). The Ni-0-Al-III complexes, {((PAlP)-P-Mes)Ni}(2)(mu-N-2) and {((PAlP)-P-Mes)Ni}(2)(mu-COD), where (PAlP)-P-Mes is (Mes)Al((NPhCH2PPr2)-Pr-i)(2), were structurally characterized. The (PAlP)Ni system exhibited cooperative bond Cleavage mediated by the two-site Ni-Al unit, inCluding oxidative addition of Aryl halides, H-2 Activation, and ortho-directed C-H bond Activation of pyridine N-oxide. One intriguing reaction is the reversible intramolecular transfer of the mesityl ring from the Al to the Ni site, which is evocative of the transmetalation step during cross-coupling catalysis. The Aryl-transfer product,(THF)Al((NPhCH2PPr2)-Pr-i)(2)Ni(Mes), is the first example of a first-row transition metal-aluminyl pincer complex. The addition of a judicious donor enables the Al metalloligand to convert reversibly between the alane and aluminyl forms via Aryl group transfer to and from Ni, respectively. Theoretical calculations support a zwitterionic Ni delta--Al delta+ electronic structure in the nickel-aluminyl complex.Cooperative Bond Activation and Facile Intramolecular Aryl Transfer of Nickel-Aluminum Pincer-type Complexesaluminum; cooperative effects; Lewis acids; metal&#8211; metal interactions; nickelx2202172#N/AFALSE
3896
anie.20210388810.1002/anie.202103888FALSEhttps://doi.org/10.1002/anie.202103888Xie, WAngew. Chem.-Int. Edit.NiFe-based electrocatalysts have attracted great interests due to the low price and high activity in oxygen evolution reaction (OER). However, the complex reaction mechanism of NiFe-catalyzed OER has not been fully explored yet. Detection of intermediate species can bridge the gap between OER performances and catalyst component/structure properties. Here, we performed label-free surface-enhanced Raman spectroscopic (SERS) monitoring of interfacial OER process on Ni3FeOx nanopartiCles (NPs) in alkaline medium. By using bifunctional Au@Ni3FeOx core-satellite superstructures as Raman signal enhancer, we found direct spectroscopic evidence of intermediate O-O- species. According to the SERS results, Fe atoms are the catalytic sites for the initial OH- to O-O- oxidation. The O-O- species adsorbed across neighboring Fe and Ni sites experiences further oxidation caused by electron transfer to Ni-III and eventually forms O-2 product.Surface-Enhanced Raman Spectroscopic Evidence of Key Intermediate Species and Role of NiFe Dual-Catalytic Center in Water Oxidationintermediates; oxygen evolution reaction; superstructure; surface-enhanced Raman spectroscopyx063#N/AFALSE
3897
b003089i10.1039/b003089iFALSEhttps://doi.org/10.1039/b003089iLiao, DZA cyano-bridged molecular magnet with a novel two-dimensional brick wall structure2000#N/ATRUE
3898
anie.20210368610.1002/anie.202103686FALSEhttps://doi.org/10.1002/anie.202103686Marder, TBAngew. Chem.-Int. Edit.A novel protocol for the transition metal-free 1,2-addition of polyfluoroAryl boronate esters to aldehydes and ketones is reported, which provides secondary alcohols, tertiary alcohols, and ketones. Control experiments and DFT calculations indicate that both the ortho-F substituents on the polyfluorophenyl boronates and the counterion K+ in the carbonate base are critical. The distinguishing features of this procedure inClude the employment of commercially available starting materials and the broad scope of the reaction with a wide variety of Carbonyl compounds giving moderate to excellent yields. Intriguing structural features involving O-H...O and O-H...N hydrogen bonding, as well as arene-perfluoroarene interactions, in this series of racemic polyfluoroAryl carbinols have also been addressed.Transition Metal Catalyst-Free, Base-Promoted 1,2-Additions of Polyfluorophenylboronates to Aldehydes and Ketonesx02021128#N/AFALSE
3899
anie.20210355710.1002/anie.202103557FALSEhttps://doi.org/10.1002/anie.202103557Lu, GQAngew. Chem.-Int. Edit.Precisely regulating the electronic structures of metal active species is highly desirable for electrocatalysis. However, carbon with inert surface provide weak metal-support interaction, which is insufficient to modulate the electronic structures of metal nanopartiCles. Herein, we propose a new method to control the electrocatalytic behavior of supported metal nanopartiCles by dispersing single metal atoms on an O-doped graphene. Ideal atomic metal species are firstly computationally screened. We then verify this concept by deposition of Ru nanopartiCles onto an O-doped graphene decorated with single metal atoms (e.g., Fe, Co, and Ni) for hydrogen evolution reaction (HER). Consistent with theoretical predictions, such hybrid catalysts show outstanding HER performance, much superior to other reported electrocatalysts such as the state-of-the-art Pt/C. This work offers a new strategy for modulating the activity and stability of metal nanopartiCles for electrocatalysis processes.Exceptional Electrochemical HER Performance with Enhanced Electron Transfer between Ru NanopartiCles and Single Atoms Dispersed on a Carbon Substrateelectrocatalysis; electronic structures; hydrogen evolution; metal nanopartiCles; metal-carbon interactionsx1202160#N/AFALSE
3900
anie.20210339810.1002/anie.202103398FALSEChen, LTricyCloquinazoline-Based 2D Conductive Metal-Organic Frameworks as Promising Electrocatalysts for CO2 Reductionx2021#N/AFALSE
3901
b001513j10.1039/b001513jFALSEDunbar, KR{Mn(OH2)(2)[Mn(bpym)(OH2)](2)[Fe(CN)(6)](2)}(infinity): a two-dimensional ferrimagnet with a partial cubane motif2000#N/ATRUE
3902
b000791i10.1039/b000791iFALSEhttps://doi.org/10.1039/b000791iWalther, DDi- and oligo-nuClear nickel complexes with oxalic amidinato bridging ligands: syntheses, structures and catalytic reactions2000#N/ATRUE
3903
anie.20210315710.1002/anie.202103157FALSEhttps://doi.org/10.1002/anie.202103157Bonnet, SAngew. Chem.-Int. Edit.Finding photostable, first-row transition metal-based molecular systems for photocatalytic water oxidation is a step towards sustainable solar fuel production. Herein, we discovered that nickel(II) hydrophilic porphyrins are molecular catalysts for photocatalytic water oxidation in neutral to acidic aqueous solutions using [Ru(bpy)(3)](2+) as photosensitizer and [S2O8](2-) as sacrificial electron acceptor. Electron-poorer Ni-porphyrins bearing 8 fluorine or 4 methylpyridinium substituents as electron-poorer porphyrins afforded 6-fold higher turnover frequencies (TOFs; ca. 0.65 min(-1)) than electron-richer analogues. However, the electron-poorest Ni-porphyrin bearing 16 fluorine substituents was photocatalytically inactive under such conditions, because the potential at which catalytic O-2 evolution starts was too high (+1.23 V vs. NHE) to be driven by the photochemically generated [Ru(bpy)(3)](3+). Critically, these Ni-porphyrin catalysts showed excellent stability in photocatalytic conditions, as a second photocatalytic run replenished with a new dose of photosensitizer, afforded only 1-3 % less O-2 than during the first photocatalytic run.Ligand Controls the Activity of Light-Driven Water Oxidation Catalyzed by Nickel(II) Porphyrin Complexes in Neutral Homogeneous Aqueous Solutionshomogeneous photocatalysis; molecular catalysts; nickel; porphyrins; water oxidationPhotocatalyst3202160#N/AFALSE
3904
anie.20210298310.1002/anie.202102983https://doi.org/10.1002/anie.202102983Long, JLAngew. Chem.-Int. Edit.Single-atom metal-insulator-semiconductor (SMIS) heterojunctions based on Sn-doped Fe2O3 nanorods (SF NRs) were designed by combining atomic deposition of an Al2O3 overlayer with chemical grafting of a RuOx hole-collector for efficient CO2-to-syngas conversion. The RuOx-Al2O3-SF photoanode with a 3.0 nm thick Al2O3 overlayer gave a >5-fold-enhanced IPCE value of 52.0 % under 370 nm light irradiation at 1.2 V vs. Ag/AgCl, compared to the bare SF NRs. The dielectric field mediated the charge dynamics at the Al2O3/SF NRs interface. Accumulation of long-lived holes on the surface of the SF NRs photoabsorber aids fast tunneling transfer of hot holes to single-atom RuOx species, accelerating the O-2-evolving reaction kinetics. The maximal CO-evolution rate of 265.3 mmol g(-1) h(-1) was achieved by integration of double SIMS-3 photoanodes with a single-atom Ni-doped graphene CO2-reduction-catalyst cathode; an overall quantum efficiency of 5.7 % was recorded under 450 nm light irradiation.The Hole-Tunneling Heterojunction of Hematite-Based Photoanodes Accelerates Photosynthetic Reactionartificial photosynthesis; CO2 reduction; hematite; photoelectrocatalysis; SMIS heterojunctionsPhotocatalystx0202152#N/AFALSE
3905
anie.20210264710.1002/anie.202102647FALSEhttps://doi.org/10.1002/anie.202102647Song, WGAngew. Chem.-Int. Edit.Direct conversion of bulk metal or nanopartiCles into metal single atoms under thermal pyrolysis conditions is a highly efficient and promising strategy to fabricate single-atom catalysts (SACs). Usually, nitrogen-doped carbon is used as the anchoring substrate to capture the migrating metal ion species at high temperatures, and stable isolated SACs with nitrogen coordination are formed during the process. Herein, we report unexpected oxygen-coordinated metal single-atom catalysts (Fe-, Co-, Ni-, Mn-SACs) with high loadings (above 10 wt %) through direct transformation of metal oxide nanopartiCles (Fe-, Co-, Ni-, Mn-NPs) in an inert atmosphere at 750 degrees C for 2 h. The atomic dispersion of metal single atoms and their coordinated structures were confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption fine structures. In addition, the dynamic process of nanopartiCles to atoms was directly observed by in situ transmission electron microscopy. The as-prepared Fe SAC exhibited high activity and superior selectivity for catalytic oxidation of benzene to phenol with hydrogen peroxide.Direct Observation of Metal Oxide NanopartiCles Being Transformed into Metal Single Atoms with Oxygen-Coordinated Structure and High-Loadingsheterogeneous catalysis; high loading; oxidation; phenol; single-atom catalysisx0202151#N/AFALSE
3906
anie.20210795410.1002/anie.202107954FALSEhttps://doi.org/10.1002/anie.202107954Zhai, HBAngew. Chem.-Int. Edit.(+)-Mannolide C is a complex hexacyClic C-20 cephalotane-type diterpenoid featuring a highly strained 7/6/6/5 tetracyClic core containing eight consecutive stereocenters and two bridging lactones. The first asymmetric total synthesis of (+)-mannolide C has been accomplished by lipase-mediated resolution, Ru-complex-catalyzed double ring-Closing metathesis (RCM) reactions, Ni-II-catalyzed diastereoselective Michael addition, and Mn-III-catalyzed allylic oxidation as the key transformations.Asymmetric Total Synthesis of (+)-Mannolide C(+)-mannolide C; cephalotaxus diterpenoids; ring-Closing metathesis; total synthesis071#N/ATRUE
3907
anie.20210235910.1002/anie.202102359FALSEhttps://doi.org/10.1002/anie.202102359Qi, WAngew. Chem.-Int. Edit.Ni-promoted electrocatalytic biomass reforming has shown promising prospect in enabling high value-added product synthesis. Here, we developed a novel hybrid catalyst with Ni nanosheet forests anchored on carbon paper. The hybrid catalyst exhibits high efficiency in electrooxidation of HMF to FDCA coupling with H-2 production in high purity. The Ni nanosheets have small crystal grain sizes with abundant edges, which is able to deliver an efficient HMF oxidation to FDCA (selectivity >99 %) at low potential of 1.36 V-RHE with high stability. The post-reaction structure analysis reveals the Ni nanosheets would transfer electrons to carbon and readily turn into NiOx and Ni(OH)(x) during the reaction. DFT results suggest high valence Ni species would facilitate the chemical adsorption (Activation) of HMF revealing the reaction pathway. This work emphasizes the importance of the precise control of Ni activity via atomic structure engineering.Highly Efficient Electro-reforming of 5-Hydroxymethylfurfural on Vertically Oriented Nickel Nanosheet/Carbon Hybrid Catalysts: Structure-Function Relationships5-hydroxymethylfurfural; biomass valorization; electrocatalytic reforming; nickel catalysts; structure&#8211; function relationshipx1202163#N/AFALSE
3908
anie.20210758710.1002/anie.202107587FALSEhttps://doi.org/10.1039/c4sc03946gRoschenthaler, GVA Versatile Silver(I) Pentafluorooxosulfate Reagent for the Synthesis of OSF5 Compounds2021#N/ATRUE
3909
anie.20210221610.1002/anie.202102216FALSEhttps://doi.org/10.1002/anie.202102216Krossing, IAngew. Chem.-Int. Edit.130 years after Mond discovered the first homoleptic Carbonyl complex Ni(CO)(4), we report on a [Ni(CO)(4)](.+) salt as the first synthesis of any homoleptic nickel Carbonyl cation in the condensed phase. It was prepared by oxidation of nickel metal with the synergistic oxidant Ag[F{Al(ORF)(3)}(2)]/0.5 I-2 (R-F=C(CF3)(3)) in CO atmosphere. This D-2d-symmetric metalloradical represents the last missing entry among the structurally characterized homoleptic Carbonyl cations of Groups 6 to 11. Additionally, the nickel triCarbonyl-nitrosyl cation [Ni(CO)(3)(NO)](+) was obtained by usage of NO[F{Al(ORF)(3)}(2)] and all products were fully characterized by means of IR, Raman, NMR/EPR, single crystal and powder XRD.Chasing the Mond Cation: Synthesis and Characterization of the Homoleptic Nickel TetraCarbonyl Cation and its TriCarbonyl-Nitrosyl AnalogueCarbonyl ligands; nickel; transition metals; weakly coordinating anionsx0202184#N/AFALSE
3910
anie.20210214910.1002/anie.202102149FALSEhttps://doi.org/10.1002/anie.202102149Mosch-Zanetti, NCAngew. Chem.-Int. Edit.Reaction of [NiCl2(PnH)(4)] (1) (PnH=6-tert-butyl-pyridazine-3-thione) with NiCl2 affords the binuClear paddlewheel (PW) complex [Ni-2(Pn)(4)] (2). Diamagnetic complex 2 is the first example of a PW complex capable of reversibly binding and releasing NH3. The NH3 ligand in [Ni-2(Pn)(4)(NH3)] (2.NH3) enforces major spectroscopic and magnetic susceptibility changes, thus displaying vapochromic properties (lambda(max)(2)=532 nm, lambda(max)(2.NH3)=518 nm) and magnetochemical switching (2: S=0; 2.NH3: S=1). Upon repeated adsorption/desorption cyCles of NH3 the PW core remains intact. Compound 2 can be embedded into thin polyurethane films (2(P)) under retention of its sensing abilities. Therefore, 2 qualifies as reversible optical probe for ammonia. The magnetochemical switching of 2 and 2.NH3 was studied in detail by SQUID measurements showing that in 2.NH3, solely the Ni atom coordinated the NH3 molecule is responsible for the paramagnetic behavior.Vapochromism and Magnetochemical Switching of a Nickel(II) Paddlewheel Complex by Reversible NH3 Uptake and Releaseammonia; nickel complexes; paddlewheel complexes; spin-state switching; vapochromismx0202148#N/AFALSE
3911
anie.20210749210.1002/anie.202107492FALSEhttps://doi.org/10.1002/anie.202107492Oestreich, MAngew. Chem.-Int. Edit.A nickel/zinc-catalyzed cross-electrophile coupling of Alkyl electrophiles activated by an alpha-cyano group and chlorosilanes is reported. Elemental zinc is the stoichiometric reductant in this reductive coupling process. By this, a C(sp(3))-Si bond can be formed starting from two electrophilic reactants whereas previous methods rely on the combination of carbon nuCleophiles and silicon electrophiles or vice versa.Nickel-Catalyzed, Reductive C(sp(3))-Si Cross-Coupling of alpha-Cyano Alkyl Electrophiles and Chlorosilanescross-coupling; nickel; silicon; synthetic methods; zinc0202146#N/ATRUE
3912
anie.20210190610.1002/anie.202101906FALSEhttps://doi.org/10.1002/anie.202101906Ding, MNAngew. Chem.-Int. Edit.Motivated by in silico predictions that Co, Rh, and Ir dopants would lead to low overpotentials to improve OER activity of Ni-based hydroxides, we report here an experimental confirmation on the altered OER activities for a series of metals (Mo, W, Fe, Ru, Co, Rh, Ir) doped into gamma-NiOOH. The in situ electrical conductivity for metal doped gamma-NiOOH correlates well with the trend in enhanced OER activities. Density functional theory (DFT) calculations were used to rationalize the in situ conductivity of the key intermediate states of metal doped gamma-NiOOH during OER. The simultaneous increase of OER activity with intermediate conductivity was later rationalized by their intrinsic connections to the double exchange (DE) interaction between adjacent metal ions with various d orbital occupancies, serving as an indicator for the key metal-oxo radical character, and an effective descriptor for the mechanistic evaluation and theoretical guidance in design and screening of efficient OER catalysts.Double-Exchange-Induced in situ Conductivity in Nickel-Based Oxyhydroxides: An Effective Descriptor for Electrocatalytic Oxygen Evolutionactive metal d orbital; double-exchange interaction; in situ intermediates conductivity; Ni-based oxyhydroxides; oxygen evolution reaction
Electrocatalytic
1202162#N/AFALSE
3913
anie.20210187810.1002/anie.202101878FALSEhttps://doi.org/10.1002/anie.202101878Liu, JXAngew. Chem.-Int. Edit.We report the synthesis of two-dimensional metal-organic frameworks (MOFs) on nickel foam (NF) by assembling nickel chloride hexahydrate and 1,1 '-ferrocenediCarbonylic acid (NiFc-MOF/NF). The NiFc-MOF/NF exhibits superior oxygen evolution reaction (OER) performance with an overpotential of 195 mV and 241 mV at 10 and 100 mA cm(-2), respectively under alkaline conditions. Electrochemical results demonstrate that the superb OER performance originates from the ferrocene units that serve as efficient electron transfer intermediates. Density functional theory calculations reveal that the ferrocene units within the MOF crystalline structure enhance the overall electron transfer capacity, thereby leading to a theoretical overpotential of 0.52 eV, which is lower than that (0.81 eV) of the state-of-the-art NiFe double hydroxides.Ferrocene-Based Metal-Organic Framework Nanosheets as a Robust Oxygen Evolution Catalystelectrocatalysts; ferrocene; metal&#8211; organic frameworks; oxygen evolution reactionx0202144#N/AFALSE
3914
anie.20210177510.1002/anie.202101775https://doi.org/10.1002/anie.202101775Studer, AAngew. Chem.-Int. Edit.A three-component 1,2-aminoArylation of Vinyl ethers, enamides, ene-carbamates and Vinyl thioethers by synergistic photoredox and nickel catalysis is reported. 2,2,2-Trifluoroethoxy Carbonyl protected alpha-amino-oxy acids are used as amidyl radical precursors. anti-Markovnikov addition of the amidyl radical to the alkene and Ni-mediated radical/transition metal cross over lead to the corresponding 1,2-aminoArylation product. The radical cascade, which can be conducted under practical and mild conditions, features high functional group tolerance and broad substrate scope. Stereoselective 1,2-aminoArylation is achieved using a L-(+)-lactic acid derived Vinyl ether as the substrate, offering a novel route for the preparation of protected enantiopure alpha-Arylated beta-amino alcohols. In addition, 1,2-aminoacylation of Vinyl ethers is achieved by using an acyl succinimide as the electrophile for the Ni-mediated radical coupling.Three-Component AminoArylation of Electron-Rich Alkenes by Merging Photoredox with Nickel Catalysisamidyl radicals; aminoArylation; nickel catalysis; photoredox catalysis; synergistic catalysisPhotocatalyst1202183#N/AFALSE
3915
anie.20210670910.1002/anie.202106709FALSEhttps://doi.org/10.1002/anie.202106709Shi, ZJSite-Selective C-C Cleavage of BenzocyClobutenones Enabled by a Blocking Strategy Using Nickel Catalysis#N/ATRUE
3916
anie.20210166710.1002/anie.202101667https://doi.org/10.1039/c5sc00929dXu, YJCoupling Strategy for CO2 Valorization Integrated with Organic Synthesis by Heterogeneous PhotocatalysisPhotocatalyst#N/AFALSE
3917
anie.20210133510.1002/anie.202101335FALSEhttps://doi.org/10.1002/anie.202101335Kim, GAngew. Chem.-Int. Edit.Dry reforming of methane (DRM) is a feasible solution to address the reduction of greenhouse gases stipulated by the Paris Climate Agreement, given that it adds value by converting trivial gases, CO2 and CH4, simultaneously into useful syngas. However, the conventional Ni catalyst undergoes deActivation due to carbon coking and partiCle agglomeration. Here we demonstrate a highly efficient and durable DRM catalyst: exsolved Co-Ni-Fe ternary alloy nanopartiCles on the layered perovskite PrBaMn1.7Co0.1Ni0.2O5+delta produced by topotactic exsolution. This method readily allows the generation of a larger number of exsolved nanopartiCles with enhanced catalytic activity above that of Ni monometallic and Co-Ni bimetallic partiCles. The enhancement is achieved by the upshift of the d-band center of Co-Ni-Fe relative to those of Co-Ni and Ni, meaning easier charge donation to the adsorbate. Furthermore, the exsolved catalyst shows exceptional stability, with continuous DRM operation for about 350 hours.Enhancing Thermocatalytic Activities by Upshifting the d-Band Center of Exsolved Co-Ni-Fe Ternary Alloy NanopartiCles for the Dry Reforming of Methanealloy nanopartiCles; dry reforming of methane; exsolution; perovskites; topotactic exsolutionx0202140#N/AFALSE
3918
anie.20210670910.1002/anie.202106709FALSEhttps://doi.org/10.1002/anie.202106709Shi, ZJSite-Selective C-C Cleavage of BenzocyClobutenones Enabled by a Blocking Strategy Using Nickel Catalysis2021#N/ATRUE
3919
anie.20210626410.1002/anie.202106264FALSEhttps://doi.org/10.1002/anie.202106264Wang, XSAngew. Chem.-Int. Edit.Diverse Synthesis of Chiral Trifluoromethylated Alkanes via Nickel-Catalyzed Asymmetric Reductive Cross-Coupling FluoroAlkylation (vol 60, pg 9947, 2021)asymmetric trifluorofluoroAlkylation; late-stage fluoroAlkylation; nickel; reductive cross-coupling020211#N/ATRUE
3920
anie.20210103610.1002/anie.202101036FALSEhttps://doi.org/10.1002/anie.202101036van der Voort, PAngew. Chem.-Int. Edit.Covalent Organic Frameworks (COFs) have recently emerged as light-harvesting devices, as well as elegant heterogeneous catalysts. The combination of these two properties into a dual catalyst has not yet been explored. We report a new photosensitive triazine-based COF, decorated with single Ni sites to form a dual catalyst. This crystalline and highly porous catalyst shows excellent catalytic performance in the visible-light-driven catalytic sulfur-carbon cross-coupling reaction. Incorporation of single transition metal sites in a photosensitive COF scaffold with two-component synergistic catalyst in organic transformation is demonstrated for the first time.A Visible-Light-Harvesting Covalent Organic Framework Bearing Single Nickel Sites as a Highly Efficient Sulfur-Carbon Cross-Coupling Dual Catalystcross-coupling reactions; dual catalysts; single nickel sites; sulfur&#8211; carbon bonds; visible-light-driven photocatalysisx3202144#N/AFALSE
3921
anie.20210089710.1002/anie.202100897FALSEhttps://doi.org/10.1002/anie.202100897Huang, XQAngew. Chem.-Int. Edit.Two-dimensional (2D) metal-organic framework nanosheets (MOF NSs) play a vital role in catalysis, but the most preparation is ultrasonication or solvothermal. Herein, a liquid-liquid interfacial synthesis method has been developed for the efficient fabrication of a series of 2D Ni MOF NSs. The active sites could be modulated by readily tuning the ratios of metal precursors and organic linkers (R-M/L). The Ni MOF NSs display highly R-M/L dependent activities towards 2e oxygen reduction reaction (ORR) to hydrogen peroxide (H2O2), where the Ni MOF NSs with the R-M/L of 6 exhibit the optimal near-zero overpotential, ca. 98 % H2O2 selectivity and production rate of ca. 80 mmol g(cat)(-1) h(-1) in 0.1 M KOH. As evidenced by X-ray absorption fine structure spectroscopy, the coordination environment of active sites changed from saturation to unsaturation, and the partially unsaturated metal atoms are crucial to create optimal sites for enhancing the electrocatalysis.An Efficient Interfacial Synthesis of Two-Dimensional Metal-Organic Framework Nanosheets for Electrochemical Hydrogen Peroxide Productionhydrogen peroxide; interfacial synthesis; metal&#8211; organic framework nanosheets; oxygen reduction reactionx2202138#N/AFALSE
3922
anie.20210076710.1002/anie.202100767FALSEhttps://doi.org/10.1002/anie.202100767Chen, SZAngew. Chem.-Int. Edit.Temperature-programmed reduction of transition-metal phosphate precursors is the most commonly used method for the preparation of transition-metal phosphides (a new Class of versatile metal catalysts), but the reduction processes are still not Clear. Here we describe the construction of a temperature-programmed reduction-infrared spectroscopy apparatus (TPR-IR) to analyze the gas flows during the reduction of nickel, molybdenum, and tungsten phosphates. PH3 and Pn+ species already appeared in the gas flows at low temperature (ca. 200 degrees C), and PH3 was involved in the formation of phosphides. The emission of PH3 and Pn+ during the reduction of the molybdenum and tungsten phosphates was smaller than that of the nickel phosphate. Ni2P drastically accelerated the formation of the PH3 and Pn+. These results explain why excess phosphorus is needed for the preparation of Ni2P, and also demonstrate that the TPR-IR technique is an efficient method to understand the complex processes of catalyst preparation.Understanding the Reduction of Transition-Metal Phosphates to Transition-Metal Phosphides by Combining Temperature-Programmed Reduction and Infrared Spectroscopyinfrared; phosphate precursor; temperature-programmed reduction; transition-metal phosphidesx1202141#N/AFALSE
3923
anie.20210063110.1002/anie.202100631FALSEhttps://doi.org/10.1002/anie.202100631Strasser, PAngew. Chem.-Int. Edit.Layered double hydroxides (LDHs) are among the most active and studied catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. However, previous studies have generally either focused on a small number of LDHs, applied synthetic routes with limited structural control, or used non-intrinsic activity metrics, thus hampering the construction of consistent structure-activity-relations. Herein, by employing new individually developed synthesis strategies with atomic structural control, we obtained a broad series of crystalline alpha-M-A(II)M-B(III) LDH and beta-M-A(OH)(2) electrocatalysts (M-A=Ni, Co, and M-B=Co, Fe, Mn). We further derived their intrinsic activity through electrochemical active surface area normalization, yielding the trend NiFe LDH > CoFe LDH > Fe-free Co-containing catalysts > Fe-Co-free Ni-based catalysts. Our theoretical reactivity analysis revealed that these intrinsic activity trends originate from the dual-metal-site nature of the reaction centers, which lead to composition-dependent synergies and diverse scaling relationships that may be used to design catalysts with improved performance.Intrinsic Electrocatalytic Activity for Oxygen Evolution of Crystalline 3d-Transition Metal Layered Double Hydroxideselectrochemical surface area; hydrothermal synthesis; layered double hydroxides; oxygen evolution reaction; water splitting
Electrocatalytic
1202158#N/AFALSE
3924
anie.20210458610.1002/anie.202104586FALSEhttps://doi.org/10.1002/anie.202104586Zhang, LZAngew. Chem.-Int. Edit.Removal of non-biodegradable heavy metals has been the top priority in wastewater treatment and the development of green technologies remains a significant challenge. We demonstrate that phosphorylated nanoscale zero-valent iron (nZVI) is promising for removal of heavy metals (Ni-II, Cu-II, Cr-VI, Hg-II) via a boosted Kirkendall effect. Phosphorylation confines tensile hoop stress on the nZVI partiCles and breaks the structurally dense spherical nZVI to produce numerous radial nanocracks. Exemplified by Ni-II removal, the radial nanocracks favor the facile inward diffusion of Ni-II and the rapid outward transport of electrons and ferrous ions through the oxide shell for surface (Ni-II/electron) and boundary (Ni-II/Fe-0) galvanic exchange. Accompanied by a pronounced hollowing phenomenon, phosphorylated nZVI can instantly reduce and immobilize Ni-II throughout the oxide shell with a high capacity (258 mgNig(-1) Fe). For real electroplating factory wastewater treatment, this novel nZVI performs simultaneous Ni-II and Cu-II removal, producing effluent of stable quality that meets local discharge regulations.Kirkendall Effect Boosts Phosphorylated nZVI for Efficient Heavy Metal Wastewater Treatmentenvironmental control; heavy metal removal; Kirkendall effect; nanoscale zerovalent iron; phosphorylation0202139#N/ATRUE
3925
anie.20210045610.1002/anie.202100456FALSEhttps://doi.org/10.1002/anie.202100456Lah, MSAngew. Chem.-Int. Edit.MOF-74 is one of the most explored metal-organic frameworks (MOFs), but its functionalization is limited to the dative post-synthetic modification (PSM) of the monodentate solvent site. Owing to the nature of the organic ligand and framework structure of MOF-74, the covalent PSM of MOF-74 is very demanding. Herein, we report, for the first time, the covalent PSM of amine-tagged defective Ni-MOF-74, which is prepared by de novo solvothermal synthesis by using aminosalicylic acid as a functionalized fragmented organic ligand. The covalent PSM of the amino group generates metal binding sites, and subsequent post-synthetic metalation with Pd-II ions affords the Pd-II-incorporated Ni-MOF-74 catalyst. This catalyst exhibits highly efficient, size-selective, and recyClable catalytic activity for the Suzuki-Miyaura cross-coupling reaction. This strategy is also useful for the covalent modification of amine-tagged defective Ni-2(DOBPDC), an expanded analogue of MOF-74.Amine-Tagged Fragmented Ligand Installation for Covalent Modification of MOF-74covalent modification; fragmented ligands; heterogeneous catalysis; metal-organic frameworks; post-synthetic modificationx0202134#N/AFALSE
3926
anie.20210435210.1002/anie.202104352FALSEhttps://doi.org/10.1002/anie.202104352Font-Bardia, MAngew. Chem.-Int. Edit.A direct and asymmetric aldol reaction of N-acyl thiazinanethiones with aromatic aldehydes catalyzed by chiral nickel(II) complexes is reported. The reaction gives the corresponding O-TIPS-protected anti-aldol adducts in high yields and with remarkable stereocontrol and atom economy. Furthermore, the straightforward removal of the achiral scaffold provides enantiomerically pure intermediates of synthetic interest, which involve precursors for anti-alpha-amino-beta-hydroxy and alpha,beta-dihydroxy Carbonylic derivatives. Theoretical calculations explain the observed high stereocontrol.Direct and Enantioselective Aldol Reactions Catalyzed by Chiral Nickel(II) Complexesaldol reaction; asymmetric catalysis; direct reaction; nickel; thiazinanethiones020211#N/ATRUE
3927
anie.20210028810.1002/anie.202100288https://doi.org/10.1002/anie.202100288Puno, PTAngew. Chem.-Int. Edit.(-)-Isoscopariusin A was isolated from the aerial parts of Isodon scoparius. Chemical synthesis and spectroscopic analysis established its structure as an unsymmetrical meroditerpenoid bearing a sterically congested 6/6/4 tricyClic carbon skeleton with seven continuous stereocenters. A gram-scale synthesis was achieved in 12 steps from commercially available (+)-sClareolide. A cobalt catalyzed, hydrogen atom transfer-based olefin isomerization was used to prepare a trisubstituted alkene, which underwent stereoselective [2+2] cyCloaddition with a substituted keteniminium ion generated in situ from the corresponding amide. The cyClobutanone product was further elaborated into the fully substituted cyClobutane core through face-selective homologation, and the two side chains were installed by using nickel-catalyzed cross-electrophile coupling and carbodiimide-mediated esterification, respectively. (-)-Isoscopariusin A displayed selective inhibition of T-cell proliferation.(-)-Isoscopariusin A, a Naturally Occurring Immunosuppressive Meroditerpenoid: Structure Elucidation and Scalable Chemical Synthesisbioactivity; cyClobutane; natural products; scalable synthesis; structure elucidationPhotocatalyst3202199#N/AFALSE
3928
anie.20210027010.1002/anie.202100270https://doi.org/10.1002/anie.202100270Reiser, OAngew. Chem.-Int. Edit.The mainstream applications of visible-light photoredox catalysis predominately involve outer-sphere single-electron transfer (SET) or energy transfer (EnT) processes of precious metal Ru-II or Ir-III complexes or of organic dyes with low photostability. Earth-abundant metal-based (MLn)-L-n-type (M=metal, L-n=polydentate ligands) complexes are rapidly evolving as alternative photocatalysts as they offer not only economic and ecological advantages but also access to the complementary inner-sphere mechanistic modes, thereby transcending their inherent limitations of ultrashort excited-state lifetimes for use as effective photocatalysts. The generic process, termed visible-light-induced homolysis (VLIH), entails the formation of suitable light-absorbing ligated metal-substrate complexes ((MLn)-L-n-Z; Z=substrate) that can undergo homolytic Cleavage to generate Mn-1Ln and Z(.) for further transformations.Visible-Light-Induced Homolysis of Earth-Abundant Metal-Substrate Complexes: A Complementary Activation Strategy in Photoredox Catalysis3d transition metals; dissociative ligand-to-metal charge transfer; inner-sphere electron transfer; photoredox catalysis; visible-light-induced homolysisPhotocatalyst5173#N/AFALSE
3929
anie.20210007810.1002/anie.202100078https://doi.org/10.1002/anie.202100078Liu, SZAngew. Chem.-Int. Edit.Ferrihydrite (Fh) has been demonstrated as an effective interfacial layer for photoanodes to achieve outstanding photoelectrochemical (PEC) performance for water oxidation reaction owing to its unique hole-storage function. However, it is unknown whether such a hole-storage layer can be used to construct highly efficient photocathodes for hydrogen evolution reaction (HER). In this work, we report Fh interfacial engineering of amorphous silicon photocathode (with nickel as HER cocatalyst) achieving a photocurrent density of 15.6 mA cm(-2) at 0 V vs. the reversible hydrogen electrode and a half-cell energy conversion efficiency of 4.08 % in alkaline solution, outperforming most of reported a-Si based photocathodes inCluding multi-junction configurations integrated with noble metal cocatalysts in acid solution. Besides, the photocurrent density is maintained above 14 mA cm(-2) for 175 min with 100 % Faradaic efficiency for HER in alkaline solution. Our results demonstrate a feasible approach to construct efficient photocathodes via the application of a hole-storage layer.Hole-Storage Enhanced a-Si Photocathodes for Efficient Hydrogen Productionalkaline medium; amorphous silicon; ferrihydrite; hydrogen production; photoelectrochemicalPhotocatalyst0202172#N/AFALSE
3930
anie.20210001110.1002/anie.202100011FALSEhttps://doi.org/10.1002/anie.202100011Hou, YAngew. Chem.-Int. Edit.Electrocatalysts play a key role in accelerating the sluggish electrochemical CO2 reduction (ECR) involving multi-electron and proton transfer. We now develop a proton capture strategy by accelerating the water dissociation reaction catalyzed by transition-metal nanopartiCles (NPs) adjacent to atomically dispersed and nitrogen-coordinated single nickel (Ni-N-x) active sites to accelerate proton transfer to the latter for boosting the intermediate protonation step, and thus the whole ECR process. Aberration-corrected scanning transmission electron microscopy, X-ray absorption spectroscopy, and calculations reveal that the Ni NPs accelerate the adsorbed H (H-ad) generation and transfer to the adjacent Ni-N-x sites for boosting the intermediate protonation and the overall ECR processes. This proton capture strategy is universal to design and prepare for various high-performance catalysts for diverse electrochemical reactions even beyond ECR.Proton Capture Strategy for Enhancing Electrochemical CO2 Reduction on Atomically Dispersed Metal-Nitrogen Active Sites**dynamic understanding; electrochemical CO2 reduction; proton capture; single-atom catalystsx5202141#N/AFALSE
3931
anie.20201651110.1002/anie.202016511https://doi.org/10.1002/anie.202016511Reisner, EVisible-Light Promoted C-O Bond Formation with an Integrated Carbon Nitride-Nickel Heterogeneous PhotocatalystPhotocatalyst2021#N/AFALSE
3932
anie.20210382410.1002/anie.202103824FALSEhttps://doi.org/10.1002/anie.202103824Tuysuz, HPrinciples of Water Electrolysis and Recent Progress in Cobalt-, Nickel-, and Iron-Based Oxides for the Oxygen Evolution Reaction#N/ATRUE
3933
anie.20210326910.1002/anie.202103269FALSEhttps://doi.org/10.1002/anie.202103269Morandi, BAngew. Chem.-Int. Edit.We report an efficient and broadly applicable palladium-catalyzed iodination of inexpensive and abundant Aryl and Vinyl Carbonylic acids via in situ Activation to the acid chloride and formation of a phosphonium salt. The use of 1-iodobutane as iodide source in combination with a base and a deoxychlorinating reagent gives access to a wide range of Aryl and Vinyl iodides under Pd/Xantphos catalysis, inCluding complex drug-like scaffolds. Stoichiometric experiments and kinetic analysis suggest a unique mechanism involving C-P reductive elimination to form the Xantphos phosphonium chloride, which subsequently initiates an unusual halogen exchange by outer sphere nuCleophilic substitution.Palladium-Catalyzed DeCarbonylative Iodination of Aryl Carbonylic Acids Enabled by Ligand-Assisted Halide Exchangeiodination; ligand non-innocence; palladium; reaction mechanism; shuttle catalysis02021126#N/ATRUE
3934
anie.20210317010.1002/anie.202103170FALSEhttps://doi.org/10.1002/anie.202103170Meyer, KA Pair of Cobalt(III/IV) Terminal Imido Complexes2021#N/ATRUE
3935
anie.20201585110.1002/anie.202015851https://doi.org/10.1002/anie.202015851Herges, RAngew. Chem.-Int. Edit.Temperature can be used as Clinical marker for tissue metabolism and the detection of inflammations or tumors. The use of magnetic resonance imaging (MRI) for monitoring physiological parameters like the temperature noninvasively is steadily increasing. In this study, we present a proof-of-principle study of MRI contrast agents (CA) for absolute and concentration independent temperature imaging. These CAs are based on azoimidazole substituted Ni-II porphyrins, which can undergo Light-Driven Coordination-Induced Spin State Switching (LD-CISSS) in solution. Monitoring the fast first order kinetic of back isomerisation (cis to trans) with standard Clinical MR imaging sequences allows the determination of half-lives, that can be directly translated into absolute temperatures. Different temperature responsive CAs were successfully tested as prototypes in methanol-based gels and created temperature maps of gradient phantoms with high spatial resolution (0.13x0.13x1.1 mm) and low temperature errors (<0.22 degrees C). The method is sufficiently fast to record the temperature flow from a heat source as a film.Towards Photoswitchable Contrast Agents for Absolute 3D Temperature MR Imagingazo compounds; contrast agent; photoswitches; porphyrinoids; temperature MRIPhotocatalyst0202182#N/AFALSE
3936
anie.20201577310.1002/anie.202015773FALSEhttps://doi.org/10.1002/anie.202015773Wang, SYAngew. Chem.-Int. Edit.The nitrogenous nuCleophile electrooxidation reaction (NOR) plays a vital role in the degradation and transformation of available nitrogen. Focusing on the NOR mediated by the beta-Ni(OH)(2) electrode, we decipher the transformation mechanism of the nitrogenous nuCleophile. For the two-step NOR, proton-coupled electron transfer (PCET) is the bridge between electrocatalytic dehydrogenation from beta-Ni(OH)(2) to beta-Ni(OH)O, and the spontaneous nuCleophile dehydrogenative oxidation reaction. This theory can give a good explanation for hydrazine and primary amine oxidation reactions, but is insufficient for the urea oxidation reaction (UOR). Through operando tracing of bond rupture and formation processes during the UOR, as well as theoretical calculations, we propose a possible UOR mechanism whereby intramolecular coupling of the N-N bond, accompanied by PCET, hydration and rearrangement processes, results in high performance and ca. 100 % N-2 selectivity. These discoveries Clarify the evolution of nitrogenous molecules during the NOR, and they elucidate fundamental aspects of electrocatalysis involving nitrogen-containing species.Unveiling the Electrooxidation of Urea: Intramolecular Coupling of the N-N Bondcoupling reactions; dehydrogenation; electrocatalysis; nickel; ureax3202166#N/AFALSE
3937
anie.20210248110.1002/anie.202102481FALSEhttps://doi.org/10.1002/anie.202102481Wang, XSAngew. Chem.-Int. Edit.Monofluorinated Alkyl compounds are of great importance in pharmaceuticals, agrochemicals and materials. Herein, we describe a direct nickel-catalyzed monofluoromethylation of unactivated Alkyl halides using a low-cost industrial raw material, bromofluoromethane, by demonstrating a general and efficient reductive cross-coupling of two Alkyl halides. Results with 1-bromo-1-fluoroalkane also demonstrate the viability of monofluoroAlkylation, which further established the first example of reductive C(sp(3))-C(sp(3)) cross-coupling fluoroAlkylation. These transformations demonstrate high efficiency, mild conditions, and excellent functional-group compatibility, especially for a range of pharmaceuticals and biologically active compounds. Mechanistic studies support a radical pathway. Kinetic studies reveal that the reaction is first-order dependent on catalyst and Alkyl bromide whereas the generation of monofluoroAlkyl radical is not involved in the rate-determining step. This strategy provides a general and efficient method for the synthesis of aliphatic fluorides.Diversity-Oriented Synthesis of Aliphatic Fluorides via Reductive C(sp(3))-C(sp(3)) Cross-Coupling FluoroAlkylationlate-stage fluoroAlkylation; monofluoromethylation; nickel; reductive cross-coupling22021126#N/ATRUE
3938
anie.20210223310.1002/anie.202102233FALSEhttps://doi.org/10.1002/anie.202102233Oestreich, MAngew. Chem.-Int. Edit.A two-step sequence for the enantio- and diastereoselective synthesis of exClusively Alkyl-substituted acyClic allylic systems with a stereocenter in the allylic position is reported. The asymmetric induction and the site selectivity are controlled in an enantio- and regioconvergent nickel-catalyzed C(sp(3))-C(sp(3)) cross-coupling of regioisomeric mixtures of racemic alpha-/gamma-silylated allylic halides and primary Alkylzinc reagents. The silyl group steers the allylic displacement towards the formation of the Vinylsilane regioisomer, and the resulting C(sp(2))-Si bond serves as a linchpin for the installation of various C(sp(3)) substituents in a subsequent step.Enantio- and Regioconvergent Nickel-Catalyzed C(sp(3))-C(sp(3)) Cross-Coupling of Allylic Electrophiles Steered by a Silyl Groupcross-coupling; nickel; radical reactions; silicon; synthetic methods2202133#N/ATRUE
3939
anie.20210205310.1002/anie.202102053FALSEhttps://doi.org/10.1002/anie.202102053Fu, HGAngew. Chem.-Int. Edit.Dual-metal single-atom catalysts exhibit superior performance for oxygen reduction reaction (ORR), however, the synergistic catalytic mechanism is not deeply understood. Herein, we report a dual-metal single-atom catalyst consisted of Cu-N-4 and Zn-N-4 on the N-doped carbon support (Cu/Zn-NC). It exhibits high-efficiency ORR activity with an E-onset of 0.98 V and an E-1/2 of 0.83 V, excellent stability (no degradation after 10 000 cyCles), surpassing state-of-the-art Pt/C and great mass of Pt-free single atom catalysts. Operando XANES demonstrates that the Cu-N-4 as active center experiences the change from atomic dispersion to Cluster with the cooperation of Zn-N-4 during ORR process, and then turns to single atom state again after reaction. DFT calculation further indicates that the adjustment effect of Zn on the d-orbital electron distribution of Cu could benefit to the stretch and Cleavage of O-O on Cu active center, speeding up the process of rate determining step of OOH*.Operando Cooperated Catalytic Mechanism of Atomically Dispersed Cu-N-4 and Zn-N-4 for Promoting Oxygen Reduction Reactioncooperative catalysis; dual-metal single atom; mechanism; operando XANES; oxygen reduction reaction5202152#N/ATRUE
3940
anie.20201557110.1002/anie.202015571FALSEhttps://doi.org/10.1002/anie.202015571Li, JFAngew. Chem.-Int. Edit.Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion-exchange-membrane fuel cells. However, uncertainty remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface-enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OHad) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OHad species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum-alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.Spectroscopic Verification of Adsorbed Hydroxy Intermediates in the Bifunctional Mechanism of the Hydrogen Oxidation Reactionadsorbed hydroxy species; Au@PtNi core-shell nanopartiCles; hydrogen oxidation reaction; reaction mechanisms; surface-enhanced Raman spectroscopyx2202135#N/AFALSE
3941
anie.20210169810.1002/anie.202101698FALSEhttps://doi.org/10.1002/anie.202101698Strasser, PAngew. Chem.-Int. Edit.Water oxidation is a crucial reaction for renewable energy conversion and storage. Among the alkaline oxygen evolution reaction (OER) catalysts, NiFe based oxyhydroxides show the highest catalytic activity. However, the details of their OER mechanism are still unClear, due to the elusive nature of the OER intermediates. Here, using a novel differential electrochemical mass spectrometry (DEMS) cell interface, we performed isotope-labelling experiments in O-18-labelled aqueous alkaline electrolyte on Ni(OH)(2) and NiFe layered double hydroxide nanocatalysts. Our experiments confirm the occurrence of Mars-van-Krevelen lattice oxygen evolution reaction mechanism in both catalysts to various degrees, which involves the coupling of oxygen atoms from the catalyst and the electrolyte. The quantitative charge analysis suggests that the participating lattice oxygen atoms belong exClusively to the catalyst surface, confirming DFT computational hypotheses. Also, DEMS data suggest a fundamental correlation between the magnitude of the lattice oxygen mechanism and the faradaic efficiency of oxygen controlled by pseudocapacitive oxidative metal redox charges.Evidence of Mars-Van-Krevelen Mechanism in the Electrochemical Oxygen Evolution on Ni-Based Catalystsalkaline OER catalyst; differential electrochemical mass spectrometry; isotope O-18; lattice oxygen evolution1202146#N/ATRUE
3942
anie.20201465510.1002/anie.202014655FALSEhttps://doi.org/10.1002/anie.202014655Wei, MAngew. Chem.-Int. Edit.The development of efficient electrocatalysts for the CO2 reduction reaction (CO2RR) remains a challenge. Demonstrated here is a NiSn atomic-pair electrocatalyst (NiSn-APC) on a hierarchical integrated electrode, which exhibits a synergistic effect in simultaneously promoting the activity and selectivity of the CO2RR to formate. The NiSn atomic pair consists of adjacent Ni and Sn, each coordinated with four nitrogen atoms (N-4-Ni-Sn-N-4). The as-prepared NiSn-APC displays exceptional activity for the CO2RR to formate with a turnover frequency of 4752 h(-1), a formate productivity of 36.7 mol h(-1) g(Sn)(-1) and an utilization degree of active sites (57.9 %), which are superior to previously reported single-atomic catalysts. Both experimental data and density-functional theory calculations verify the electron redistribution of Sn imposed by adjacent Ni, which reduces the energy barrier of the *OCHO intermediate and makes this potential-determining step thermodynamically spontaneous. This synergistic catalysis provides a successful paradigm for rational design and preparation of atomic-pair electrocatalysts with enhanced performance.NiSn Atomic Pair on an Integrated Electrode for Synergistic Electrocatalytic CO2 Reductionelectrochemistry; carbon dioxide fixation; heterogeneous catalysis; reduction; structure elucidation
Electrocatalytic
8202163#N/AFALSE
3943
anie.20210132610.1002/anie.202101326FALSEhttps://doi.org/10.1002/anie.202101326Jaramillo, TFAngew. Chem.-Int. Edit.Understanding the differences between reactions driven by elevated temperature or electric potential remains challenging, largely due to materials incompatibilities between thermal catalytic and electrocatalytic environments. We show that Ni, N-doped carbon (NiPACN), an electrocatalyst for the reduction of CO2 to CO (CO2R), can also selectively catalyze thermal CO2 to CO via the reverse water gas shift (RWGS) representing a direct analogy between catalytic phenomena across the two reaction environments. Advanced characterization techniques reveal that NiPACN likely facilitates RWGS on dispersed Ni sites in agreement with CO2R active site studies. Finally, we construct a generalized reaction driving-force that inCludes temperature and potential and suggest that NiPACN could facilitate faster kinetics in CO2R relative to RWGS due to lower intrinsic barriers. This report motivates further studies that quantitatively link catalytic phenomena across disparate reaction environments.Bridging Thermal Catalysis and Electrocatalysis: Catalyzing CO2 Conversion with Carbon-Based Materialscarbon dioxide; catalysis; electrochemistry; nitrogen-doped carbon; reverse water-gas shift0202153#N/ATRUE
3944
anie.20210107610.1002/anie.202101076FALSEhttps://doi.org/10.1002/anie.202101076Wang, XSAngew. Chem.-Int. Edit.The trifluoromethyl group represents one of the most functional and widely used fluoroAlkyl groups in drug design and screening, while the drug candidates containing chiral trifluoromethyl-bearing carbons are still few due to the lack of efficient methods for the asymmetric introduction of trifluoromethyl group into organic molecules. Herein, we described a nickel-catalyzed asymmetric trifluoroAlkylation of Aryl iodides, for the first time, by utilizing reductive cross-coupling in enantioselective fluoroAlkylation. This novel method has demonstrated high efficiency, mild conditions, and excellent functional group tolerance, especially for substrates containing diverse pharmaceutical and bioactive molecules moieties. This strategy provided an efficient and facile way for diversity-oriented synthesis of chiral trifluoromethylated alkanes.Diverse Synthesis of Chiral Trifluoromethylated Alkanes via Nickel-Catalyzed Asymmetric Reductive Cross-Coupling FluoroAlkylationasymmetric trifluorofluoroAlkylation; late-stage fluoroAlkylation; nickel; reductive cross-coupling2202180#N/ATRUE
3945
anie.20210061010.1002/anie.202100610FALSEhttps://doi.org/10.1002/anie.202100610Zhang, BAngew. Chem.-Int. Edit.In electrochemical energy storage and conversion systems, the anodic oxygen evolution reaction (OER) accounts for a large proportion of the energy consumption. The electrocatalytic urea oxidation reaction (UOR) is one of the promising alternatives to OER, owing to its low thermodynamic potential. However, owing to the sluggish UOR kinetics, its potential in practical use has not been unlocked. Herein, we developed a tungsten-doped nickel catalyst (Ni-WOx) with superior activity towards UOR. The Ni-WOx catalyst exhibited record fast reaction kinetics (440 mA cm(-2) at 1.6 V versus reversible hydrogen electrode) and a high turnover frequency of 0.11 s(-1), which is 4.8 times higher than that without W dopants. In further experiments, we found that the W dopant regulated the local charge distribution of Ni atoms, leading to the formation of Ni3+ sites with superior activity and thus accelerating the interfacial catalytic reaction. Moreover, when we integrated Ni-WOx into a CO2 flow electrolyzer, the cell voltage is reduced to 2.16 V accompanying with approximate to 98 % Faradaic efficiency towards carbon monoxide.Regulating the Local Charge Distribution of Ni Active Sites for the Urea Oxidation Reactionelectrocatalysis; energy conversion; nickel; urea oxidation reaction1202132#N/ATRUE
3946
anie.20201430210.1002/anie.202014302FALSEhttps://doi.org/10.1002/anie.202014302Yu, GHAngew. Chem.-Int. Edit.To achieve the electrochemical nitrogen reduction reaction (NRR) for efficient and sustainable NH3 production, catalysts should exhibit high selectivity and activity with optimal adsorption energy. Herein we developed a three-dimensional (3D) amorphous BiNi alloy toward a significantly enhanced NRR compared with its crystalline and metal counterparts. Ni alloying enables the chemisorption of nitrogen and the lower free-energy change for the *NNH formation, and the 3D alloy electrocatalyst exhibits high catalytic activity for NH3 production with a yield rate of 17.5 mu g h(-1) mg(cat)(-1) and Faradaic efficiency of 13.8 %. The enhanced electron transfer and increased electrochemical surface area were revealed in the interconnected porous scaffold, affording it sufficiently efficient and stable activity for potential practical applications. This work offers new insights into optimizing the adsorption energy of reactants and intermediates combined with tuning the crystallinity of NRR electrocatalysts.Gel-Derived Amorphous Bismuth-Nickel Alloy Promotes Electrocatalytic Nitrogen Fixation via Optimizing Nitrogen Adsorption and Activationalloys; electrocatalysis; gels; heterogeneous catalysis; nitrogen fixation
Electrocatalytic
x5202150#N/AFALSE
3947
anie.20210043810.1002/anie.202100438FALSEhttps://doi.org/10.1002/anie.202100438Ray, KAngew. Chem.-Int. Edit.mu-1,2-peroxo-bridged diiron(III) intermediates P are proposed as reactive intermediates in various biological oxidation reactions. In sMMO, P acts as an electrophile, and performs hydrogen atom and oxygen atom transfers to electron-rich substrates. In cyanobacterial ADO, however, P is postulated to react by nuCleophilic attack on electrophilic carbon atoms. In biomimetic studies, the ability of mu-1,2-peroxo-bridged dimetal complexes of Fe, Co, Ni and Cu to act as nuCleophiles that effect deCarbonylation of aldehydes is documented. By performing reactivity and theoretical studies on an end-on mu-1,2-peroxodicobalt(III) complex 1 involving a non-heme ligand system, L1, supported on a Sn6O6 stannoxane core, we now show that a peroxo-bridged dimetal complex can also be a reactive electrophile. The observed electrophilic chemistry, which is induced by the constraints provided by the Sn6O6 core, represents a new domain for metal-peroxide reactivity.Ligand-Constraint-Induced Peroxide Activation for Electrophilic Reactivity0202186#N/ATRUE
3948
anie.20201421010.1002/anie.202014210FALSEhttps://doi.org/10.1002/anie.202014210Wang, JCAngew. Chem.-Int. Edit.The effective non-precious metal catalysts toward the oxygen evolution reaction (OER) are highly desirable for electrochemical water splitting. Herein, we prepare a novel glass-ceramic (Ni1.5Sn@triMPO(4)) by embedding crystalline Ni1.5Sn nanopartiCles into amorphous trimetallic phosphate (triMPO(4)) matrix. This unique crystalline-amorphous nanostructure synergistically accelerates the surface reconstruction to active Ni(Fe)OOH, due to the low vacancy formation energy of Sn in glass-ceramic and high adsorption energy of PO43- at the V-O sites. Compared to the control samples, this dual-phase glass-ceramic exhibits a remarkably lowered overpotential and boosted OER kinetics after surface reconstruction, rivaling most of state-of-the-art electrocatalysts. The residual PO43- and intrinsic V-O sites induce redistribution of electron states, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and promoting the OER activity.A Glass-Ceramic with Accelerated Surface Reconstruction toward the Efficient Oxygen Evolution ReactionDFT calculations; electrocatalysis; glass-ceramic; oxygen evolution reaction; surface reconstructionx10202157#N/AFALSE
3949
anie.20201414410.1002/anie.202014144FALSEhttps://doi.org/10.1002/anie.202014144Fang, JYAngew. Chem.-Int. Edit.Fabrication of 3d metal-based core@shell nanocatalysts with engineered Pt-surfaces provides an effective approach for improving the catalytic performance. The challenges in such preparation inClude shape control of the 3d metallic cores and thickness control of the Pt-based shells. Herein, we report a colloidal seed-mediated method to prepare octahedral CuNi@Pt-Cu core@shell nanocrystals using CuNi octahedral cores as the template. By precisely controlling the synthesis conditions inCluding the deposition rate and diffusion rate of the shell-formation through tuning the capping ligand, reaction temperature, and heating rate, uniform Pt-based shells can be achieved with a thickness of <1 nm. The resultant carbon-supported CuNi@Pt-Cu core@shell nano-octahedra showed superior activity in electrochemical methanol oxidation reaction (MOR) compared with the commercial Pt/C catalysts and carbon-supported CuNi@Pt-Cu nano-polyhedron counterparts.Synthesis of Core@Shell Cu-Ni@Pt-Cu Nano-Octahedra and Their Improved MOR Activitycore@shell; CuNi@Pt-Cu; MOR activity; nanocatalysts; nano-octahedrax3202151#N/AFALSE
3950
anie.20201385410.1002/anie.202013854https://doi.org/10.1002/anie.202013854Brookhart, MAngew. Chem.-Int. Edit.The reactivity of Ni-II and Pd-II olefin polymerization catalysts can be enhanced by introduction of electron-withdrawing substituents on the supporting ligands rendering the metal centers more electrophilic. Reported here is a comparison of ethylene polymerization activity of a Classical salicyliminato nickel catalyst substituted with the powerful electron-withdrawing 2,4,6-triphenylpyridinium (trippy) group to the -CF3 analogue. The trippy substituent is substantially more electron-withdrawing (sigma(meta)=0.63) than the trifluoromethyl group (sigma(meta)=0.43) which results in a ca. 8-fold increase in catalytic turnover frequency. An additional advantage of trippy is the high steric bulk relative to the trifluoromethyl group. This feature results in a four-fold increase in polymer molecular weight owing to enhanced retardation of chain transfer. A significant increase in catalyst lifetime is observed as well.2,4,6-Triphenylpyridinium: A Bulky, Highly Electron-Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalystshomogeneous catalysis; ligand design; nickel; polyolefinsx2202147#N/AFALSE
3951
anie.20201385210.1002/anie.202013852https://doi.org/10.1002/anie.202013852Rueping, MAngew. Chem.-Int. Edit.The formation of C-heteroatom bonds represents an important type of bond-forming reaction in organic synthesis and often provides a fast and efficient access to privileged structures found in pharmaceuticals, agrochemical and materials. In contrast to conventional Pd- or Cu-catalyzed C-heteroatom cross-couplings under high-temperature conditions, recent advances in homo- and heterogeneous Ni-catalyzed C-heteroatom formations under mild conditions are particularly attractive from the standpoint of sustainability and practicability. The generation of Ni-III and excited Ni-II intermediates facilitate the reductive elimination step to achieve mild cross-couplings. This review provides an overview of the state-of-the-art approaches for mild C-heteroatom bond formations and highlights the developments in photoredox and nickel dual catalysis involving SET and energy transfer processes; photoexcited nickel catalysis; electro and nickel dual catalysis; heterogeneous photoredox and nickel dual catalysis involving graphitic carbon nitride (mpg-CN), metal organic frameworks (MOFs) or semiconductor quantum dots (QDs); as well as more conventional zinc and nickel dual catalyzed reactions.Nickel-Catalyzed C-Heteroatom Cross-Coupling Reactions under Mild Conditions via Facilitated Reductive Eliminationcross-coupling; electrochemistry; nickel; photoredox; single electron transferPhotocatalyst11202179#N/AFALSE
3952
anie.20201634610.1002/anie.202016346FALSEhttps://doi.org/10.1002/anie.202016346Izumi, YEfficient and Selective Interplay Revealed: CO2 Reduction to CO over ZrO2 by Light with Further Reduction to Methane over Ni-0 by Heat Converted from Light2021#N/ATRUE
3953
anie.20201367810.1002/anie.202013678https://doi.org/10.1002/anie.202013678Verani, CNAngew. Chem.-Int. Edit.Two heterometallic photocatalysts were designed and probed for water reduction. Both [(bpy)(2)(RuNiII)-Ni-II(L-1)](ClO4)(2) (1) and [(bpy)(2)(RuNiII)-Ni-II(L-2)(2)Ru-II(bpy)(2)](ClO4)(2) (2) can generate the low-valent precursor involved in hydride formation prior to dihydrogen generation. However, while the bimetallic [(RuNiII)-Ni-II] (1) requires the presence of an external photosensitizer to trigger catalytic activity, the trimetallic [(RuNiRuII)-Ni-II-Ru-II] (2) displays significant coupling between the catalytic and light-harvesting units to promote intramolecular multielectron transfer and perform photocatalysis at the Ni center. A concerted experimental and theoretical effort proposes mechanisms to explain why 1 is unable to achieve self-supported catalysis, while 2 is fully photocatalytic.Reactivity and Mechanisms of Photoactivated Heterometallic [(RuNiII)-Ni-II] and [(RuNiRuII)-Ni-II-Ru-II] Catalysts for Dihydrogen Generation from Waterheterometallic complexes; hydrogen generation; photocatalysis; ruthenium photosensitizers; water reductionPhotocatalyst0202141#N/AFALSE
3954
anie.20201342710.1002/anie.202013427FALSEhttps://doi.org/10.1002/anie.202013427Hou, YAngew. Chem.-Int. Edit.Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M-N-4) to accelerate overall reaction dynamics of the electrochemical CO2 reduction reaction (CO2RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of the M-N-4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni-N-4-O/C). The Ni-N-4-O/C electrocatalyst exhibited excellent CO2RR performance with a maximum CO Faradic efficiency (FE) Close to 100 % at -0.9 V. The CO FE could be maintained above 90 % in a wide range of potential window from -0.5 to -1.1 V. The superior CO2RR activity is due to the Ni-N-4-O active moiety composed of a Ni-N-4 site with an additional oxygen atom that induces an axial traction effect.Dynamic Activation of Adsorbed Intermediates via Axial Traction for the Promoted Electrochemical CO2 Reductionaxial traction; dynamic understanding; electrochemical CO2RR; single-atom catalystsx11202138#N/AFALSE
3955
anie.20201621910.1002/anie.202016219FALSEhttps://doi.org/10.1002/anie.202016219Jiang, HLAngew. Chem.-Int. Edit.Single-atom catalysts (SACs) have attracted tremendous interests due to their ultrahigh activity and selectivity. However, the rational control over coordination microenvironment of SACs remains a grand challenge. Herein, a post-synthetic metal substitution (PSMS) strategy has been developed to fabricate single-atom Ni catalysts with different N coordination numbers (denoted Ni-N-x-C) on pre-designed N-doped carbon derived from metal-organic frameworks. When served for CO2 electroreduction, the obtained Ni-N-3-C catalyst achieves CO Faradaic efficiency (FE) up to 95.6 %, much superior to that of Ni-N-4-C. Theoretical calculations reveal that the lower Ni coordination number in Ni-N-3-C can significantly enhance COOH* formation, thereby accelerating CO2 reduction. In addition, Ni-N-3-C shows excellent performance in Zn-CO2 battery with ultrahigh CO FE and excellent stability. This work opens up a new and general avenue to coordination microenvironment modulation (MEM) of SACs for CO2 utilization.Rational Fabrication of Low-Coordinate Single-Atom Ni Electrocatalysts by MOFs for Highly Selective CO2 ReductionCO2 reduction; coordination environment; electrocatalysis; metal-organic frameworks; single-atom catalysts10202155#N/ATRUE
3956
anie.20201337310.1002/anie.202013373FALSEhttps://doi.org/10.1002/anie.202013373Kusamoto, TAngew. Chem.-Int. Edit.Developing tunable motifs for heterometallic interactions should be beneficial for fabricating functional materials based on cooperative electronic communications between metal centers. Reported here is the efficient formation of cyClic heterometallic interactions from a complex containing an artificial tripeptide with metal binding sites on its main chain and side chains. X-ray structural analysis and X-ray absorption spectroscopy revealed that the cyClic metal-metal arrangements arise from the amide groups connecting four square-planar Cu-II centers and four octahedral Ni-II centers in a cyClic manner. UV/Vis spectral studies suggested that this efficient formation was achieved by the selective formation of the square-planar Cu-II centers and a crystallization process. Magnetic measurements using SQUID Clarified that the cyClic complex represented the S=2 spin state at low temperatures due to effective antiferromagnetic interactions between the Ni-II and Cu-II centers.CyClic Heterometallic Interactions formed from a Flexible Tripeptide Complex Showing Effective Antiferromagnetic Spin Couplingheterometallic complexes; metal-metal interactions; peptides; structure elucidation; through-bond interactionx1202137#N/AFALSE
3957
anie.20201592110.1002/anie.202015921FALSEhttps://doi.org/10.1002/anie.202015921Zhang, XGAngew. Chem.-Int. Edit.A nickel-catalyzed highly gamma-regioselective Arylation and Carbonylative Arylation of 3-bromo-3,3-difluoropropene has been developed. The reaction proceeds under mild reaction conditions, providing the gem-difluoroalkenes with high efficiency and good functional group tolerance. The resulting gem-difluoroalkenes can serve as versatile building blocks for diversified synthesis. Preliminary mechanistic studies and density functional theory calculations reveal that both non-radical and radical pathways are possible for the reaction, and the radical pathway is more likely. The high gamma-regioselectivity results from the beta-bromide elimination of Alkylnickel(II) species or from the reductive elimination of nickel(III) species [(Aryl)(CF2=CHCH2)Ni-III(L-n)X]. The gamma-selective Carbonylation of 3-bromo-3,3-difluoropropene under 1 atm CO gas also provides a new way for nickel-catalyzed Carbonylation.Highly gamma-Selective Arylation and Carbonylative Arylation of 3-Bromo-3,3-difluoropropene via Nickel Catalysis3-bromo-3; 3-difluoropropene; Arylboronic acids; Carbonylation; gem-difluoroalkenes; nickel catalysis1202153#N/ATRUE
3958
anie.20201573810.1002/anie.202015738FALSEhttps://doi.org/10.1002/anie.202015738Menezes, PWAngew. Chem.-Int. Edit.Transition metal hydroxides (M-OH) and their heterostructures (X|M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption. Unfortunately, their poor electronic conductivity had been an issue of concern that significantly lowered its activity. Interesting advancements were made when heterostructured hydroxide materials with a metallic and or a semiconducting phase were found to overcome this pitfall. However, in the midst of recently evolving metal chalcogenide and phosphide based HER catalysts, significant developments made in the field of metal hydroxides and their heterostructures catalysed alkaline HER and their superiority have unfortunately been given negligible attention. This review, unlike others, begins with the question of why alkaline HER is difficult and will take the reader through evaluation perspectives, trends in metals hydroxides and their heterostructures catalysed HER, an understanding of how alkaline HER works on different interfaces, what must be the research directions of this field in near future, and eventually summarizes why metal hydroxides and their heterostructures are inevitable for energy-efficient alkaline HER.Strategies and Perspectives to Catch the Missing Pieces in Energy-Efficient Hydrogen Evolution Reaction in Alkaline Mediaelectrocatalysis; heterostructured materials; hydrogen evolution reaction; transition metal hydroxides; water splitting2151#N/ATRUE
3959
anie.20201573810.1002/anie.202015738FALSEhttps://doi.org/10.1002/anie.202015738Menezes, PWAngew. Chem.-Int. Edit.Transition metal hydroxides (M-OH) and their heterostructures (X vertical bar M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption. Unfortunately, their poor electronic conductivity had been an issue of concern that significantly lowered its activity. Interesting advancements were made when heterostructured hydroxide materials with a metallic and or a semiconducting phase were found to overcome this pitfall. However, in the midst of recently evolving metal chalcogenide and phosphide based HER catalysts, significant developments made in the field of metal hydroxides and their heterostructures catalysed alkaline HER and their superiority have unfortunately been given negligible attention. This review, unlike others, begins with the question of why alkaline HER is difficult and will take the reader through evaluation perspectives, trends in metals hydroxides and their heterostructures catalysed HER, an understanding of how alkaline HER works on different interfaces, what must be the research directions of this field in near future, and eventually summarizes why metal hydroxides and their heterostructures are inevitable for energy-efficient alkaline HER.Strategies and Perspectives to Catch the Missing Pieces in Energy-Efficient Hydrogen Evolution Reaction in Alkaline Mediaelectrocatalysis; heterostructured materials; hydrogen evolution reaction; transition metal hydroxides; water splitting22021150#N/ATRUE
3960
anie.20201301710.1002/anie.202013017FALSEhttps://doi.org/10.1002/anie.202013017Lipshutz, BHAngew. Chem.-Int. Edit.A new approach to C-S couplings is reported that relies on nickel catalysis under mild conditions, enabled by micellar catalysis in recyClable water as the reaction medium. The protocol tolerates a wide range of Het halides and thiols, inCluding Alkyl and heteroAryl thiols, leading to a variety of thioethers in good isolated yields. The method is scalable, results in low residual metal in the products, and is applicable to syntheses of targets in the pharmaceutical area. The procedure also features an associated low E Factor, suggesting a far more attractive entry than is otherwise currently available, especially those based on unsustainable loadings of Pd catalysts.Safe, Scalable, Inexpensive, and Mild Nickel-Catalyzed Migita-Like C-S Cross-Couplings in RecyClable Wateraqueous micellar catalysis; axitinib; designer surfactants; Migita cross-couplings; nickel catalysisx3202151#N/AFALSE
3961
anie.20201301410.1002/anie.202013014https://doi.org/10.1002/anie.202013014Lu, XQAngew. Chem.-Int. Edit.Depositing a transition-metal hydroxide (TMH) layer on a photoanode has been demonstrated to enhance photoelectrochemical (PEC) water oxidation. However, the controversial understanding for the improvement origin remains a key challenge to unlock the PEC performance. Herein, by taking BiVO4/iron-nickel hydroxide (BVO/FxN4-x-H) as a prototype, we decoupled the PEC process into two processes inCluding charge transfer and surface catalytic reaction. The kinetic information at the BVO/FxN4-x-H and FxN4-x-H/electrolyte interfaces was systematically evaluated by employing scanning photoelectrochemical microscopy (SPECM), intensity modulated photocurrent spectroscopy (IMPS) and oxygen evolution reaction (OER) model. It was found that FxN4-x-H acts as a charge transporter rather than a sole electrocatalyst. PEC performance improvement is mainly ascribed to the efficient suppression of charge recombination by fast hole transfer kinetics at BVO/FxN4-x-H interface.Insight into the Transition-Metal Hydroxide Cover Layer for Enhancing Photoelectrochemical Water Oxidationcharge transfer; interfaces; photoelectrochemistry; surface catalysis; transition-metal hydroxidesPhotocatalyst4202146#N/AFALSE
3962
anie.20201287710.1002/anie.202012877https://doi.org/10.1002/anie.202012877Xue, DAngew. Chem.-Int. Edit.A photochemical C-N coupling of Aryl halides with nitroarenes is demonstrated for the first time. Catalyzed by a Ni-II complex in the absence of any external photosensitizer, readily available nitroarenes undergo coupling with a variety of Aryl halides, providing a step-economic extension to the widely used Buchwald-Hartwig C-N coupling reaction. The method tolerates coupling partners with steric-congestion and functional groups sensitive to bases and nuCleophiles. Mechanistic studies suggest that the reaction proceeds via the addition of an Aryl radical, generated from a Ni-I/Ni-III cyCle, to a nitrosoarene intermediate.Light-Promoted C-N Coupling of Aryl Halides with Nitroarenesamination; Aryl halides; Aryl radicals; nickel catalysis; nitroarenesPhotocatalyst4202156#N/AFALSE
3963
anie.20201568010.1002/anie.202015680FALSEhttps://doi.org/10.1002/anie.202015680Wolf, RActivation of Di-tert-butyldiphosphatetrahedrane: Access to (tBuCP)(n) (n=2, 4) Ligand Frameworks by P-C Bond Cleavage2021#N/ATRUE
3964
anie.20201255010.1002/anie.202012550https://doi.org/10.1002/anie.202012550Yin, SFAngew. Chem.-Int. Edit.The introduction of oxygen vacancies (Ov) has been regarded as an effective method to enhance the catalytic performance of photoanodes in oxygen evolution reaction (OER). However, their stability under highly oxidizing environment is questionable but was rarely studied. Herein, NiFe-metal-organic framework (NiFe-MOFs) was conformally coated on oxygen-vacancy-rich BiVO4 (Ov-BiVO4) as the protective layer and cocatalyst, forming a core-shell structure with caffeic acid as bridging agent. The as-synthesized Ov-BiVO4@NiFe-MOFs exhibits enhanced stability and a remarkable photocurrent density of 5.3 +/- 0.15 mA cm(-2) at 1.23 V (vs. RHE). The reduced coordination number of Ni(Fe)-O and elevated valence state of Ni(Fe) in NiFe-MOFs layer greatly bolster OER, and the shifting of oxygen evolution sites from Ov-BiVO4 to NiFe-MOFs promotes Ov stabilization. Ovs can be effectively preserved by the coating of a thin NiFe-MOFs layer, leading to a photoanode of enhanced photocurrent and stability.Activity and Stability Boosting of an Oxygen-Vacancy-Rich BiVO4 Photoanode by NiFe-MOFs Thin Layer for Water OxidationBiVO4 photoanode; NiFe-MOFs; OER; oxygen vacancy; stabilityPhotocatalyst15202156#N/AFALSE
3965
anie.20201240010.1002/anie.202012400https://doi.org/10.1039/c3sc22051fHarth, ESwitching the Reactivity of Palladium Diimines with Ancillary Ligand to Select between Olefin Polymerization, Branching Regulation, or Olefin Isomerizationx2021#N/AFALSE
3966
anie.20201172210.1002/anie.202011722https://doi.org/10.1002/anie.202011722Lan, YQAngew. Chem.-Int. Edit.In this work, we rationally designed a series of crystalline and stable dioxin-linked metallophthalocyanine covalent organic frameworks (COFs; MPc-TFPN COF, M=Ni, Co, Zn) under the guidance of reticular chemistry. As a novel single-site catalysts (SSCs), NiPc/CoPc-TFPN COF exhibited outstanding activity and selectivity for electrocatalytic CO2 reduction (ECR; Faradaic efficiency of CO (FECO)=99.8(+/- 1.24) %/ 96.1(+/- 1.25) % for NiPc/CoPc-TFPN COF). More importantly, when coupled with light, the FECO and current density (j(CO)) were further improved across the applied potential range (-0.6 to -1.2 V vs. RHE) compared to the dark environment for NiPc-TFPN COF (j(CO) increased from 14.1 to 17.5 A g(-1) at -0.9 V; FECO reached up to ca. 100 % at -0.8 to -0.9 V). Furthermore, an in-depth mechanism study was established by density functional theory (DFT) simulation and experimental characterization. For the first time, this work explored the application of COFs as photo-coupled electrocatalysts to improve ECR efficiency, which showed the potential of using light-sensitive COFs in the field of electrocatalysis.Stable Dioxin-Linked Metallophthalocyanine Covalent Organic Frameworks (COFs) as Photo-Coupled Electrocatalysts for CO2 Reductioncovalent organic frameworks (COFs); CO2 reduction; electrocatalysis; metallophthalocyanine; photo-coupled electrocatalystsPhotocatalystx12202160#N/AFALSE
3967
anie.20201161410.1002/anie.202011614https://doi.org/10.1002/anie.202011614Jiang, HLAngew. Chem.-Int. Edit.Metal-organic frameworks (MOFs) have been shown to be an excellent platform in photocatalysis. However, to suppress electron-hole recombination, a Pt cocatalyst is usually inevitable, especially in photocatalytic H(2)production, which greatly limits practical application. Herein, for the first time, monodisperse, small-size, and noble-metal-free transitional-metal phosphides (TMPs; for example, Ni2P, Ni12P5), are incorporated into a representative MOF, UiO-66-NH2, for photocatalytic H(2)production. Compared with the parent MOF and their physical mixture, both TMPs@MOF composites display significantly improved H(2)production rates. Thermodynamic and kinetic studies reveal that TMPs, behaving similar ability to Pt, greatly accelerate the linker-to-Cluster charge transfer, promote charge separation, and reduce the Activation energy of H(2)production. Significantly, the results indicate that Pt is thermodynamically favorable, yet Ni2P is kinetically preferred for H(2)production, accounting for the higher activity of Ni2P@UiO-66-NH(2)than Pt@UiO-66-NH2.Incorporating Transition-Metal Phosphides Into Metal-Organic Frameworks for Enhanced Photocatalysiscocatalysts; hydrogen production; metal-organic frameworks; photocatalysis; transition-metal phosphidesPhotocatalystx20202073#N/AFALSE
3968
anie.20201466010.1002/anie.202014660FALSEhttps://doi.org/10.1002/anie.202014660Zhou, QHAngew. Chem.-Int. Edit.Reported here is a concise total synthesis of (-)-berkelic acid in eight linear steps. This synthesis features a Catellani reaction/oxa-Michael cascade for the construction of the isochroman scaffold, a one-pot deprotection/spiroacetalization operation for the formation of the tetracyClic core structure, and a late-stage Ni-catalyzed reductive coupling for the introduction of the lateral chain. Notably, four stereocenters are established from a single existing chiral center with excellent stereocontrol during the deprotection/spiroacetalization process. Stereocontrol of the intriguing deprotection/spiroacetalization process is supported by DFT calculations.A Concise Total Synthesis of (-)-Berkelic AcidCatellani reaction; natural products; reductive coupling; spiro-compounds; total synthesis1202160#N/ATRUE
3969
anie.20201436210.1002/anie.202014362FALSEhttps://doi.org/10.1002/anie.202014362Xie, YAngew. Chem.-Int. Edit.Electrochemical water splitting for H-2 production is limited by the sluggish anode oxygen evolution reaction (OER), thus using hydrazine oxidation reaction (HzOR) to replace OER has received great attention. Here we report the hierarchical porous nanosheet arrays with abundant Ni3N-Co3N heterointerfaces on Ni foam with superior hydrogen evolution reaction (HER) and HzOR activity, realizing working potentials of -43 and -88 mV for 10 mA cm(-2), respectively, and achieving an industry-level 1000 mA cm(-2) at 200 mV for HzOR. The two-electrode overall hydrazine splitting (OHzS) electrolyzer requires the cell voltages of 0.071 and 0.76 V for 10 and 400 mA cm(-2), respectively. The H-2 production powered by a direct hydrazine fuel cell (DHzFC) and a commercial solar cell are investigated to inspire future practical applications. DFT calculations decipher that heterointerfaces simultaneously optimize the hydrogen adsorption free energy (Delta G(H*)) and promote the hydrazine dehydrogenation kinetics. This work provides a rationale for advanced bifunctional electrocatalysts, and propels the practical energy-saving H-2 generation techniques.Artificial Heterointerfaces Achieve Delicate Reaction Kinetics towards Hydrogen Evolution and Hydrazine Oxidation Catalysisheterointerfaces; hydrazine electro-oxidation; hydrogen evolution; nickel; overall hydrazine splitting11202159#N/ATRUE
3970
anie.20201433110.1002/anie.202014331FALSEhttps://doi.org/10.1002/anie.202014331Driess, MAngew. Chem.-Int. Edit.Identifying novel Classes of precatalysts for the oxygen evolution reaction (OER by water oxidation) with enhanced catalytic activity and stability is a key strategy to enable chemical energy conversion. The vast chemical space of intermetallic phases offers plenty of opportunities to discover OER electrocatalysts with improved performance. Herein we report intermetallic nickel germanide (NiGe) acting as a superior activity and durable Ni-based electro(pre)catalyst for OER. It is produced from a molecular bis(germylene)-Ni precursor. The ultra-small NiGe nanocrystals deposited on both nickel foam and fluorinated tin oxide (FTO) electrodes showed lower overpotentials and a durability of over three weeks (505 h) in comparison to the state-of-the-art Ni-, Co-, Fe-, and benchmark NiFe-based electrocatalysts under identical alkaline OER conditions. In contrast to other Ni-based intermetallic precatalysts under alkaline OER conditions, an unexpected electroconversion of NiGe into gamma-(NiOOH)-O-III with intercalated OH-/CO32- transpired that served as a highly active structure as shown by various ex situ methods and quasi in situ Raman spectroscopy.Facile Access to an Active gamma-NiOOH Electrocatalyst for Durable Water Oxidation Derived From an Intermetallic Nickel Germanide Precursorelectroconversion; nickel germanide; oxygen evolution reaction; oxyhydroxide; renewable energy132021113#N/ATRUE
3971
anie.20201432810.1002/anie.202014328FALSEhttps://doi.org/10.1002/anie.202014328Ghadwal, RSAngew. Chem.-Int. Edit.Intramolecular 1,2-Dipp migration of seven mesoionic carbenes (iMIC(Ar)) 2 a-g (iMIC(Ar)=ArC{N(Dipp)}(2)CHC; Ar=Aryl; Dipp=2,6-iPr(2)C(6)H(3)) under nickel catalysis to give 1,3-imidazoles (IMDAr) 3 a-g (IMDAr=ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the Cleavage of an N-C-Dipp bond and the subsequent formation of a C-C-Dipp bond in 2, which is unprecedented in NHC chemistry. The use of 3 in accessing super-iMICs (5) (S-iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium (6), gold (7), and palladium (8) compounds. The quantification of the stereoelectronic properties reveals the superior sigma-donor strength of 5 compared to that of Classical NHCs. Remarkably, the percentage buried volume of 5 (%V-bur=45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5, which is consistent with their auspicious stereoelectronic features.Nickel-Catalyzed Intramolecular 1,2-Aryl Migration of Mesoionic Carbenes (iMICs)Aryl migration; C&#8722; N bond Activation; ligand design; mesoionic carbenes; nickel catalysis3202183#N/ATRUE
3972
anie.20201146210.1002/anie.202011462FALSEhttps://doi.org/10.1002/anie.202011462Jelinek, PAngew. Chem.-Int. Edit.Recently pi-d conjugated coordination polymers have received a lot of attention owing to their unique material properties, although synthesis of long and defect-free polymers remains challenging. Herein we introduce a novel on-surface synthesis of coordination polymers with quinoidal ligands under ultra-high vacuum conditions, which enables formation of flexible coordination polymers with lengths up to hundreds of nanometers. Moreover, this procedure allows the incorporation of different transition-metal atoms with four- or two-fold coordination. Remarkably, the two-fold coordination mode revealed the formation of wires constituted by (electronically) independent 12-membered antiaromatic macrocyCles linked together through two C-C single bonds.1D Coordination pi-d Conjugated Polymers with Distinct Structures Defined by the Choice of the Transition Metal: Towards a New Class of Antiaromatic MacrocyClescoordination polymers; macrocyCles; on-surface synthesis; &#960; &#8211; d conjugation; scanning probe microscopyx3202172#N/AFALSE
3973
anie.20201138810.1002/anie.202011388FALSEhttps://doi.org/10.1002/anie.202011388Hu, XLAngew. Chem.-Int. Edit.A bifunctional oxygen evolution reaction (OER) mechanism, in which the energetically demanding step of the attack of hydroxide on a metal oxo unit is facilitated by a hydrogen atom transfer to a second site, has the potential to circumvent the scaling relationship. However, the bifunctional mechanism has hitherto only been supported by theoretical computations. Here we describe an operando Raman spectroscopic and electrokinetic study of two highly active OER catalysts, FeOOH-NiOOH and NiFe layered double hydroxide (LDH). The data support two distinct mechanisms for the two catalysts: FeOOH-NiOOH operates by a bifunctional mechanism where the rate-determining O-O bond forming step is the OH- attack on a Fe=O coupled with a hydrogen atom transfer to a Ni-III-O site, whereas NiFe LDH operates by a conventional mechanism of four consecutive proton-coupled electron transfer steps. The experimental validation of the bifunctional mechanism enhances the understanding of OER catalysts.Spectroscopic and Electrokinetic Evidence for a Bifunctional Mechanism of the Oxygen Evolution Reaction**electrokinetics; nickel iron oxide; oxygen evolution reaction; Raman spectroscopy; reaction mechanismsx12202159#N/AFALSE
3974
anie.20201134710.1002/anie.202011347FALSEhttps://doi.org/10.1002/anie.202011347Xu, QAngew. Chem.-Int. Edit.Superstructures have attracted great interest owing to their potential applications. Herein, we report the first scalable preparation of a porous nickel-foam-templated superstructure of carbon nanosheets decorated with ultrafine cobalt phosphide nanopartiCles. Uniform two-dimensional (2D) Co-metal organic framework (MOF) nanosheets (Co-MNS) grow on nickel foam, followed by a MOF-mediated tandem (carbonization/phosphidation) pyrolysis. The resulting superstructure has a porous 3D interconnected network with well-arranged 2D carbon nanosheets on it, in which ultrafine cobalt phosphide nanopartiCles are tightly immobilized. A single piece of this superstructure can be directly used as a self-supported electrode for electrocatalysis without any binders. This one-piece porous superstructure with excellent mass transport and electron transport properties, and catalytically active cobalt phosphide nanopartiCles with ultrasmall size (3-4 nm), shows excellent trifunctional electrocatalytic activities for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR), achieving great performances in water splitting and Zn-air batteries.MOF-Mediated Fabrication of a Porous 3D Superstructure of Carbon Nanosheets Decorated with Ultrafine Cobalt Phosphide NanopartiCles for Efficient Electrocatalysis and Zinc-Air Batterieselectrocatalysis; metal phosphides; metal-organic frameworks (MOFs); water splitting; Zn-air batteriesx20202058#N/AFALSE
3975
anie.20201131810.1002/anie.202011318FALSEhttps://doi.org/10.1002/anie.202011318Song, BAngew. Chem.-Int. Edit.To ensure sustainable hydrogen production by water electrolysis, robust, earth-abundant, and high-efficient electrocatalysts are required. Constructing a hybrid system could lead to further improvement in electrocatalytic activity. Interface engineering in composite catalysts is thus critical to determine the performance, and the phase-junction interface should improve the catalytic activity. Here, we show that nickel diphosphide phase junction (c-NiP2/m-NiP2) is an effective electrocatalyst for hydrogen production in alkaline media. The overpotential (at 10 mA cm(-2)) for NiP2-650 (c/m) in alkaline media could be significantly reduced by 26 % and 96 % compared with c-NiP2 and m-NiP2, respectively. The enhancement of catalytic activity should be attributed to the strong water dissociation ability and the rearrangement of electrons around the phase junction, which markedly improved the Volmer step and benefited the reduction process of adsorbed protons.Phase-Junction Electrocatalysts towards Enhanced Hydrogen Evolution Reaction in Alkaline Mediaalkaline electrolytes; electrocatalysis; hydrogen evolution reaction; phase junctionsx8202160#N/AFALSE
3976
anie.20201424410.1002/anie.202014244TRUEhttps://doi.org/10.1002/anie.202014244Liu, TLAngew. Chem.-Int. Edit.Reported here is the redox neutral electrochemical C(sp(2))-C(sp(3)) cross-coupling reaction of bench-stable Aryl halides or beta-bromostyrene (electrophiles) and Benzylic trifluorB(OH)2rates (nuCleophiles) using nonprecious, bench-stable NiCl2.glyme/polypyridine catalysts in an undivided cell configuration under ambient conditions. The broad reaction scope and good yields of the Ni-catalyzed electrochemical coupling reactions were confirmed by 50 examples of Aryl/beta-styrenyl chloride/bromide and Benzylic trifluorB(OH)2rates. Potential applications were demonstrated by electrosynthesis and late-stage functionalization of pharmaceuticals and natural amino acid modification, and three reactions were run on gram-scale in a flow-cell electrolyzer. The electrochemical C-C cross-coupling reactions proceed through an unconventional radical transmetalation mechanism. This method is highly productive and expected to find wide-spread applications in organic synthesis.Nickel-Catalyzed Electrochemical C(sp(3))-C(sp(2)) Cross-Coupling Reactions of Benzyl TrifluorB(OH)2rate and Organic Halides**cross-coupling; electrochemistry; nickel; radicals; reaction mechanismsCsp2_ar-Csp3-ring(s)XXBF3KArylNo baseNo Base72021567/28/2022TRUE
3977
anie.20201109710.1002/anie.202011097FALSEhttps://doi.org/10.1002/anie.202011097Zhang, BAngew. Chem.-Int. Edit.Transition metal chalcogenides (TMCs) are efficient oxygen evolution reaction (OER) pre-electrocatalysts, and will in situ transform into metal (oxy)hydroxides under OER condition. However, the role of chalcogen is not fully elucidated after oxidation and severe leaching. Here we present the vital promotion of surface-adsorbed chalcogenates on the OER activity. Taking NiSe(2)as an example, in situ Raman spectroscopy revealed the oxidation of Se-Se to selenites (SeO32-) then to selenates (SeO42-). Combining the severe Se leaching and the strong signal of selenates, it is assumed that the selenates are rich on the surface and play significant roles. As expected, adding selenites to the electrolyte of Ni(OH)(2)dramatically enhance its OER activity. And sulfates also exhibit the similar effect, suggesting the promotion of surface-adsorbed chalcogenates on OER is universal. Our findings offer unique insight into the transformation mechanism of materials during electrolysis.Unveiling the Promotion of Surface-Adsorbed Chalcogenate on the Electrocatalytic Oxygen Evolution Reactionactive species; anion adsorption; electrochemical oxygen evolution reaction; in situ Raman spectroscopy; transition metal chalcogenides
Electrocatalytic
x26202048#N/AFALSE
3978
anie.20201106810.1002/anie.202011068Lu, TBTailoring Crystal Facets of Metal-Organic Layers to Enhance Photocatalytic Activity for CO2 ReductionPhotocatalyst2021#N/AFALSE
3979
anie.20201379210.1002/anie.202013792FALSEhttps://doi.org/10.1002/anie.202013792Kong, WQAngew. Chem.-Int. Edit.An unprecedented nickel-catalyzed domino reductive cyClization of alkynes and o-bromoAryl aldehydes is described. The reaction features broad substrate scope and is tolerant of a variety of functional groups, providing straightforward access to biologically significant indanones and spiroindanone pyrrolidine derivatives in good yields with excellent regio- and diastereoselectivity. Preliminary mechanistic studies have shown that indanones are formed by the cyClization of o-bromoAryl aldehydes and alkynes to form indenol intermediates, followed by hydrogen autotransfer.Synthesis of Indanones and Spiroindanones by Diastereoselective Annulation Based on a Hydrogen Autotransfer Strategydiastereoselectivity; domino reactions; hydrogen autotransfer; indanones; spiro compounds5202170#N/ATRUE
3980
anie.20201337610.1002/anie.202013376FALSEhttps://doi.org/10.1002/anie.202013376Sarkar, BAngew. Chem.-Int. Edit.We present herein anionic borate-based bi-mesoionic carbene compounds of the 1,2,3-triazol-4-ylidene type that undergo C-N isomerization reactions. The isomerized compounds are excellent ligands for Co-II centers. Strong agostic interactions with the C-H-groups of the cyClohexyl substituents result in an unusual low-spin square planar Co-II complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high-spin tetrahedral Co-II center, which is reactive towards external substrates inCluding dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single-crystal EPR spectroscopy. We conClusively show here that the structure and properties of these Co-II complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these Classes of anionic mesoionic carbene-based ligands.Isomerization Reactions in Anionic Mesoionic Carbene-Borates and Control of Properties and Reactivities in the Resulting Co-II Complexes through Agostic Interactionscobalt; ligand rearrangement; mesoionic carbene; reactivity; spin state1202180#N/ATRUE
3981
anie.20201069510.1002/anie.202010695https://doi.org/10.1002/anie.202010695Lan, YAngew. Chem.-Int. Edit.RETRACTION: Photoredox Catalysis Unlocks the Nickel-Catalyzed Cyanation of Aryl Halides under Benign Conditions (Retraction of Vol 59, Pg 17784, 2020)Photocatalyst11#N/AFALSE
3982
anie.20201058710.1002/anie.202010587FALSEhttps://doi.org/10.1002/anie.202010587Que, ELAngew. Chem.-Int. Edit.F-19 magnetic resonance (MR) based detection coupled with well-designed inorganic systems shows promise in biological investigations. Two proof-of-concept inorganic probes that exploit a novel mechanism for(19)F MR sensing based on converting from low-spin (S=0) to high-spin (S=1) Ni(2+)are reported. Activation of diamagneticNiL(1)andNiL(2)by light or beta-galactosidase, respectively, converts them into paramagneticNiL(0), which displays a single(19)F NMR peak shifted by >35 ppm with accelerated relaxation rates. This spin-state switch is effective for sensing light or enzyme expression in live cells using(19)F MR spectroscopy and imaging that differentiate signals based on chemical shift and relaxation times. This general inorganic scaffold has potential for developing agents that can sense analytes ranging from ions to enzymes, opening up diverse possibilities for(19)F MR based biosensing.Versatile Nickel(II) Scaffolds as Coordination-Induced Spin-State Switches for(19)F Magnetic Resonance-Based Detectionbiosensors; coordination chemistry; fluorine; magnetic resonance spectroscopy; nickelx5202060#N/AFALSE
3983
anie.20201334910.1002/anie.202013349FALSEhttps://doi.org/10.1002/anie.202013349Kubo, TAngew. Chem.-Int. Edit.Synthesis and properties of anthracene-based cyClic pi-Clusters which possess two and four anthracene units are discussed. The optimal cyClization conditions were determined based on a nickel(0)-mediated reaction that afforded a cyClic anthracene dimer as the major product. Bringing two anthracene planes in Close proximity in a face-to-face manner resulted in red-shifted absorption owing to the narrowing of the HOMO-LUMO gap. The cyClic anthracene dimer exhibits multi-stimuli responsiveness due to high pi-congestion. For example, photoirradiation on the anthracene dimer affords its photoisomer having C-C bonds that are longer than 1.65 angstrom, which can undergo thermal reversion under gentle heating. This enabled mechanochromism of the photoisomer (colorless) to the original anthracene dimer (red). Photoisomerization was also observed in the crystalline state, accompanied by crystal jumping or collapsing, that is, the photosalient effect.Synthesis of Anthracene-Based CyClic pi-Clusters and Elucidation of their Properties Originating from Congested Aromatic Planesanthracene; mechanochromism; photoisomerization; photosalient effect; pi-Clusters0202182#N/ATRUE
3984
anie.20201038610.1002/anie.202010386FALSEhttps://doi.org/10.1002/anie.202010386Zhu, SLAngew. Chem.-Int. Edit.A highly enantio- and regioselective hydroArylation process of Vinylarenes with Aryl halides has been developed using a NiH catalyst and a new chiral bis imidazoline ligand. A broad range of structurally diverse, enantioenriched 1,1-diArylalkanes, a structure found in a number of biologically active molecules, have been obtained with excellent yields and enantioselectivities under extremely mild conditions.Enantio- and Regioselective NiH-Catalyzed Reductive HydroArylation of Vinylarenes with Aryl Iodidesalkenes; asymmetric catalysis; hydroArylation; nickel; regioselectivityx23202090#N/AFALSE
3985
anie.20201311910.1002/anie.202013119FALSEhttps://doi.org/10.1002/anie.202013119Peters, JCAngew. Chem.-Int. Edit.M(NHx) intermediates involved in N-N bond formation are central to ammonia oxidation (AO) catalysis, an enabling technology to ultimately exploit ammonia (NH3) as an alternative fuel source. While homocoupling of a terminal amide species (M-NH2) to form hydrazine (N2H4) has been proposed, well-defined examples are without precedent. Herein, we discuss the generation and electronic structure of a Ni-III-NH2 species that undergoes bimolecular coupling to generate a Ni-2(II)(N2H4) complex. This hydrazine adduct can be further oxidized to a structurally unusual Ni-2(N2H2) species; this releases N-2 in the presence of NH3, thus establishing a synthetic cyCle for Ni-mediated AO. Distribution of the redox load for H2N-NH2 formation via NH2 coupling between two metal centers presents an attractive strategy for AO catalysis using Earth-abundant, late first-row metals.Hydrazine Formation via Coupling of a Nickel(III)-NH2 Radicalammonia oxidation; nickel; N&#8211; N bond formation; radicals1202146#N/ATRUE
3986
anie.20201018010.1002/anie.202010180FALSEhttps://doi.org/10.1002/anie.202010180Limberg, CAngew. Chem.-Int. Edit.The complexes [(LNi)-Ni-tBu(OCO-kappa O-2,C)]M-3[N(SiMe3)(2)](2) (M=Li, Na, K), synthesized by deprotonation of a nickel formate complex [(LNiOOCH)-Ni-tBu] with the corresponding amides M[N(SiMe3)(2)], feature a Ni-II-CO22- core surrounded by Lewis-acidic cations (M+) and the influence of the latter on the behavior and reactivity was studied. The results point to a decrease of CO2 Activation within the series Li, Na, and K, which is also reflected in the reactivity with Me3SiOTf leading to the liberation of CO and formation of a Ni-OSiMe3 complex. Furthermore, in case of K+, the {[K-3[N(SiMe3)(2)](2)}(+) shell around the Ni-CO22- entity was shown to have a large impact on its stabilization and behavior. If the number of K[N(SiMe3)(2)] equivalents used in the reaction with [(LNiOOCH)-Ni-tBu] is decreased from 3 to 0.5, the deprotonated part of the precursor enters a complex reaction sequence with formation of [(LNiI)-Ni-tBu(mu-OOCH)(NiLtBu)-L-I]K and [(LNi)-Ni-tBu(C2O4)NiLtBu]. The same reaction at higher concentrations additionally led to the formation of a unique hexanuClear Ni-II complex containing both oxalate and mesoxalate ([O2C-CO2-CO2](4-)) ligands.Selective Transformation of Nickel-Bound Formate to CO or C-C Coupling Products Triggered by Deprotonation and Steered by Alkali-Metal Ionsformate; Lewis acid; mesoxalate; nickel; oxalatex1202164#N/AFALSE
3987
anie.20201306910.1002/anie.202013069FALSEhttps://doi.org/10.1002/anie.202013069Jian, ZBAngew. Chem.-Int. Edit.An effective shielding of both apical positions of a neutral Ni-II active site is achieved by dibenzosuberyl groups, both attached via the same donors' N-Aryl group in a C-s-type arrangement. The key aniline building block is accessible in a single step from commercially available dibenzosuberol. This shielding approach suppresses chain transfer and branch formation to such an extent that ultrahigh molecular weight polyethylenes (5x10(6) g mol(-1)) are accessible, with a strictly linear microstructure (<0.1 branches/1000C). Key features of this highly active (4.3x10(5) turnovers h(-1)) catalyst are an exceptionally facile preparation, thermal robustness (up to 90 degrees C polymerization temperature), ability for living polymerization and compatibility with THF as a polar reaction medium.Efficient Suppression of Chain Transfer and Branching via C-s-Type Shielding in a Neutral Nickel(II) Catalystcoordination polymerization; C-s shielding; homogeneous catalysis; linear UHMWPE; nickel catalyst8202139#N/ATRUE
3988
anie.20200981410.1002/anie.202009814FALSEhttps://doi.org/10.1002/anie.202009814Peters, JCAngew. Chem.-Int. Edit.The prototypical reactivity profiles of transition metal dihydrogen complexes (M-H-2) are well-characterized with respect to oxidative addition (to afford dihydrides, M(H)(2)) and as acids, heterolytically delivering H(+)to a base and H-to the metal. In the course of this study we explored plausible alternative pathways for H(2)Activation, namely direct Activation through H-atom or hydride transfer from the sigma-H(2)adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutralS=1/2and an anionicS=0 Co-H(2)adduct, both supported by a trisphosphine borane ligand (P-3(B)). The thermally stable metalloradical, (P-3(B))Co(H-2), serves as a competent precursor for hydrogen atom transfer to Bu3ArO. What is more, its anionic derivative, the dihydrogen complex [(P-3(B))Co(H-2)](1) is a competent precursor for hydride transfer to BEt3, establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M-H(2)complexes known.Dihydrogen Adduct (Co-H-2) Complexes Displaying H-Atom and Hydride TransferH(2)Activation; H-atom transfer; hydricityx2202047#N/AFALSE
3989
anie.20200970010.1002/anie.202009700FALSEhttps://doi.org/10.1002/anie.202009700Wu, YEAngew. Chem.-Int. Edit.Herein, we report a negative pressure pyrolysis to access dense single metal sites (Co, Fe, Ni etc.) with high accessibility dispersed on three-dimensional (3D) graphene frameworks (GFs), during which the differential pressure between inside and outside of metal-organic frameworks (MOFs) promotes the Cleavage of the derived carbon layers and gradual expansion of mesopores. In situ transmission electron microscopy and Brunauer-Emmett-Teller tests reveal that the formed 3D GFs possess an enhanced mesoporosity and external surface area, which greatly favor the mass transport and utilization of metal sites. This contributes to an excellent oxygen reduction reaction (ORR) activity (half-wave potential of 0.901 V vs. RHE). Theoretical calculations verify that selective carbon Cleavage near Co centers can efficiently lower the overall ORR theoretical overpotential in comparison with intact atomic configuration.Negative Pressure Pyrolysis Induced Highly Accessible Single Sites Dispersed on 3D Graphene Frameworks for Enhanced Oxygen Reduction3D graphene frameworks; metal-organic frameworks; negative pressure; oxygen reduction reaction; single sitesx13202024#N/AFALSE
3990
anie.20201287610.1002/anie.202012876FALSEhttps://doi.org/10.1002/anie.202012876Nowicka, BAngew. Chem.-Int. Edit.Bistable and stimuli-responsive molecule-based materials are promising candidates for the development of molecular switches and sensors for future technologies. The CN-bridged {NH4[Ni(cyClam)][Fe(CN)(6)].5 H2O}(n) chain exists in two valence states: Ni-II-Fe-III (1(HT)) and Ni-III-Fe-II (1(LT)) and shows unique multiresponsivity under ambient conditions to various stimuli, inCluding temperature, pressure, light, and humidity, which generate measurable response in the form of significant changes in magnetic susceptibility and color. The electron-transfer phase transition 1(LT)<-> 1(HT) shows room-temperature thermal hysteresis, can be induced by irradiation, and shows high sensitivity to small applied pressure, which shifts it to higher temperatures. Additionally, it can be reversibly turned off by dehydration to the {NH4[Ni-II(cyClam)][Fe-III(CN)(6)]}(n) (1 d) phase, which features the Ni-II-Fe-III valence state over the whole temperature range, but responds to pressure by yielding Ni-III-Fe-II above 1.06 GPa.Room-Temperature Bistability in a Ni-Fe Chain: Electron Transfer Controlled by Temperature, Pressure, Light, and Humiditybistability; electron transfer; molecular switches; multiresponsivity; phase transitions3202184#N/ATRUE
3991
anie.20200944610.1002/anie.202009446FALSEhttps://doi.org/10.1002/anie.202009446Zhao, DAngew. Chem.-Int. Edit.Acetylene (C2H2) removal from ethylene (C2H4) is a crucial step in the production of polymer-grade C(2)H(4)but remains a daunting challenge because of the similar physicochemical properties of C(2)H(2)and C2H4. Currently energy-intensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metal-organic framework (MOF), Ni-3(pzdc)(2)(7 Hade)(2), is reported for efficient C2H2/C(2)H(4)separation. The MOF comprises hydrogen-bonded linked one-dimensional (1D) chains, and features high-density open metal sites (2.7 nm(-3)) and electronegative oxygen and nitrogen sites arranged on the pore surface as cooperative binding sites. Theoretical calculations, in situ powder X-ray diffraction and Fourier-transform infrared spectroscopy revealed a synergistic adsorption mechanism. The MOF possesses S-shaped 1D pore channels that efficiently trap trace C(2)H(2)at 0.01 bar with a high C(2)H(2)uptake of 60.6 cm(3) cm(-3)and C2H2/C(2)H(4)selectivity.Efficient Trapping of Trace Acetylene from Ethylene in an Ultramicroporous Metal-Organic Framework: Synergistic Effect of High-Density Open Metal and Electronegative Sitesadsorptive separation; electronegative sites; metal-organic frameworks; open metal sites; trace acetylene removalx23202060#N/AFALSE
3992
anie.20201158010.1002/anie.202011580FALSEhttps://doi.org/10.1002/anie.202011580Ajayaghosh, AAngew. Chem.-Int. Edit.Temperature is often not considered as a precision stimulus for artificial chemical systems in contrast to the host-guest interactions related to many natural processes. Similarly, mimicking multi-state volatile memory operations using a single molecular system with temperature as a precision stimulus is highly laborious. Here we demonstrate how a mixture of iron(II) chloride and bipyridine can be used as a reversible color-to-colorless thermochromic switch and logic operators. The generality of the approach was illustrated using Co-II and Ni-II salts that resulted in color-to-color transitions. DMSO gels of these systems, exhibited reversible opaque-transparency switching. More importantly, optically readable multi-state volatile memory with temperature as a precision input has been demonstrated. The stored data is volatile and is lost instantaneously upon withdrawal or change of temperature. Simultaneous read-out at multiple wavelengths results in single-input/multi-output sequential logic operations such as data accumulators (counters) leading to volatile memory states. The present system provides access to thermoresponsive materials wherein temperature can be used as a precision stimulus.Thermochromic Color Switching to Temperature Controlled Volatile Memory and Counter Operations with Metal-Organic Complexes and Hybrid Gelsgels; logic operation; metal&#8211; organic complex; thermochromism; volatile memory4202181#N/ATRUE
3993
anie.20200933110.1002/anie.202009331FALSEhttps://doi.org/10.1002/anie.202009331Wu, GAngew. Chem.-Int. Edit.Atomically dispersed and nitrogen coordinated single metal sites (M-N-C, M=Fe, Co, Ni, Mn) are the popular platinum group-metal (PGM)-free catalysts for many electrochemical reactions. Traditional wet-chemistry catalyst synthesis often requires complex procedures with unsatisfied reproducibility and scalability. Here, we report a facile chemical vapor deposition (CVD) strategy to synthesize the promising M-N-C catalysts. The deposition of gaseous 2-methylimidazole onto M-doped ZnO substrates, followed by an in situ thermal Activation, effectively generated single metal sites well dispersed into porous carbon. In particular, an optimal CVD-derived Fe-N-C catalyst exClusively contains atomically dispersed FeN(4)sites with increased Fe loading relative to other catalysts from wet-chemistry synthesis. The catalyst exhibited outstanding oxygen-reduction activity in acidic electrolytes, which was further studied in proton-exchange membrane fuel cells with encouraging performance.Chemical Vapor Deposition for Atomically Dispersed and Nitrogen Coordinated Single Metal Site Catalystschemical vapor deposition; electrocatalysis; Fe-N-C; oxygen reduction reaction; single metal sitesx20202069#N/AFALSE
3994
anie.20200926710.1002/anie.202009267FALSEhttps://doi.org/10.1002/anie.202009267Long, JLAngew. Chem.-Int. Edit.The design and synthesis of two semiconducting bis (4-ethynyl-bridging 1, 8-naphthalimide) bolaamphiphiles (BENI-COO- and BENI-NH3+) to fabricate supramolecular metal-insulator-semiconductor (MIS) nanostructures for biomimetic hydrogen evolution under visible light irradiation is presented. A H-2 evolution rate of ca. 3.12 mmol g(-1).h(-1) and an apparent quantum efficiency (AQE) of ca. 1.63 % at 400 nm were achieved over the BENI-COO--NH3+-Ni MIS photosystem prepared by electrostatic self-assembly of BENI-COO- with the opposite-charged DuBois-Ni catalysts. The hot electrons of photoexcited BENI-COO- nanofibers were tunneled to the molecular Ni collectors across a salt bridge and an Alkyl region of 2.2-2.5 nm length at a rate of 6.10x10(8) s(-1), which is five times larger than the BENI-NH3+ nanoribbons (1.17x10(8) s(-1)). The electric field benefited significantly the electron tunneling dynamics and compensated the charge-separated states insufficient in the BENI-COO- nanofibers.Electric-Field-Mediated Electron Tunneling of Supramolecular Naphthalimide Nanostructures for Biomimetic H-2 Productionelectron tunneling; H-2 production; MIS heterojunctions; molecular semiconductors; naphthalimidex2202158#N/AFALSE
3995
anie.20200889710.1002/anie.202008897https://doi.org/10.1002/anie.202008897Murakami, MAngew. Chem.-Int. Edit.A convenient method is reported to specifically acylate phenolic hydroxyl groups through a radical pathway. When a mixture of an aldehyde and a phenol in ethyl acetate is irradiated with blue light in the presence of iridium and nickel bromide catalysts at ambient temperature, phenoxyl and acyl radicals are transiently generated in situ and cross-couple to furnish an ester. Aliphatic hydroxy groups remain untouched under the reaction conditions.Photoinduced Specific Acylation of Phenolic Hydroxy Groups with Aldehydesaldehydes; nickel; phenols; photocatalysis; radical chemistryPhotocatalyst4202041#N/AFALSE
3996
anie.20201149410.1002/anie.202011494FALSEhttps://doi.org/10.1002/anie.202011494Meyer, FAngew. Chem.-Int. Edit.The dinickel(II) dihydride complex (1(K)) of a pyrazolate-based compartmental ligand with beta-diketiminato (nacnac) chelate arms (L-), providing two pincer-type {N-3} binding pockets, has been reported to readily eliminate H-2 and to serve as a masked dinickel(I) species. Discrete dinickel(I) complexes (2(Na), 2(K)) of L- are now synthesized via a direct reduction route. They feature two adjacent T-shaped metalloradicals that are antiferromagnetically coupled, giving an S=0 ground state. The two singly occupied local dx2-y2 type magnetic orbitals are oriented into the bimetallic Cleft, enabling metal-metal cooperative 2 e(-) substrate reductions as shown by the rapid reaction with H-2 or O-2. X-ray crystallography reveals distinctly different positions of the K+ in 1(K) and 2(K), suggesting a stabilizing interaction of K+ with the dihydride unit in 1(K). H-2 release from 1(K) is triggered by peripheral gamma-C protonation at the nacnac subunits, which DFT calculations show lowers the barrier for reductive H-2 elimination from the bimetallic Cleft.Ligand Protonation Triggers H-2 Release from a Dinickel Dihydride Complex to Give a Doubly T-Shaped Dinickel(I) MetallodiradicaldinuClear complexes; ligand protonation; magnetic properties; metalloradicals; nickel(I)4202141#N/ATRUE
3997
anie.20200878710.1002/anie.202008787FALSEhttps://doi.org/10.1002/anie.202008787Jiang, HLAngew. Chem.-Int. Edit.Single-atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and therefore, discerning differences in activity of diverse single-atom catalysts is not straightforward. Herein, a general strategy for synthesis of single-atom metals implanted in N-doped carbon (M-1-N-C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal-organic frameworks (MOFs). The M-1-N-C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single-atom metal species. When employed in electrocatalytic CO(2)reduction, Ni-1-N-C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe-1-, Co-1- and Cu-1-N-C. Remarkably, the best-performer, Ni-1-N-C, even demonstrated excellent CO FE at low CO(2)pressures, thereby representing a promising opportunity for the direct use of dilute CO(2)feedstock.Single-Atom Electrocatalysts from Multivariate Metal-Organic Frameworks for Highly Selective Reduction of CO(2)at Low PressuresCO(2)reduction; electrocatalysis; low pressure; metal-organic frameworksx31202065#N/AFALSE
3998
anie.20200849810.1002/anie.202008498https://doi.org/10.1002/anie.202008498Zhang, XGAngew. Chem.-Int. Edit.Efficient methods for the dicarbofuntionalization of the cyClic alkenes 2-pyrroline and 2-azetine are limited. Particularly, the dicarbofunctionalization of endocyClic enecarbamates to achieve fluorinated compounds remains an unsolved issue. Reported here is a nickel-catalyzedtrans-selective dicarbofunctionalization ofN-Boc-2-pyrroline andN-Boc-2-azetine, a Class of endocyClic enecarbamates previously unexplored for transition metal catalyzed dicarbofunctionalization. The reaction can be extended to six- and seven-membered endocyClic enamides. A variety of Arylzinc reagents and bromodifluoroacetate, and its derivatives, undergo the reaction, providing straightforward and efficient access to an array of pyrrolidine- and azetidine-containing fluorinated amino acids and oligopeptides, which may have applications in the life sciences.trans-Selective AryldifluoroAlkylation of EndocyClic Enecarbamates and Enamides by Nickel Catalysisalkenes; enecarbamates; fluorine; N-heterocyCles; nickelx15202078#N/AFALSE
3999
anie.20200842210.1002/anie.202008422FALSEChen, JA Universal Graphene Quantum Dot Tethering Design Strategy to Synthesize Single-Atom Catalystsx2020#N/AFALSE
4000
anie.20201149110.1002/anie.202011491FALSEhttps://doi.org/10.1002/anie.202011491Kambe, NAngew. Chem.-Int. Edit.A strategy for the formation of antimony-carbon bond was developed by nickel-catalyzed cross-coupling of halostibines. This method has been applied to the synthesis of various triAryl- and diArylAlkylstibines from the corresponding cyClic and acyClic halostibines. This protocol showed a wide substrate scope (72 examples) and was compatible to a wide range of functional groups such as aldehyde, ketone, alkene, alkyne, haloarenes (F, Cl, Br, I), and heteroarenes. A successful synthesis of Arylated stibine 3 a in a scale of 34.77 g demonstrates high synthetic potential of this transformation. The formed stibines (R3Sb) were then used for the palladium-catalyzed carbon-carbon bond forming reaction with Aryl boronic acids [R-B(OH)(2)], giving biAryls with high selectivity, even the structures of two organomoieties (R and R ') are very similar. Plausible catalytic pathways were proposed based on control experiments.Nickel- and Palladium-Catalyzed Cross-Coupling Reactions of Organostibines with OrganB(OH)2ronic AcidsbiAryl synthesis; nickel catalysis; oxidative cross-coupling; palladium catalysis; Sb&#8722; C bond formation3202169#N/ATRUE
4001
anie.20201148910.1002/anie.202011489FALSEhttps://doi.org/10.1002/anie.202011489Kohen, DBimetallic, Silylene-Mediated Multielectron Reductions of Carbon Dioxide and Ethylene2021#N/ATRUE
4002
anie.20200807110.1002/anie.202008071FALSEhttps://doi.org/10.1002/anie.202008071Evans, PAAngew. Chem.-Int. Edit.We have developed a highly regio- and diastereoselective rhodium-catalyzed allylic substitution of challenging Alkyl-substituted secondary allylic carbonates with Benzylzinc reagents, which are prepared from widely available Benzyl halides. This process utilizes rhodium(III) chloride as a commercially available, high-oxidation state and bench-stable pre-catalyst to provide a rare example of a regio- and diastereoselective allylic substitution in the absence of an exogenous ligand. This reaction tolerates electronically diverse Benzylzinc nuCleophiles and an array of functionalized and/or challenging aliphatic allylic electrophiles. Finally, the configurational fluxionality of the rhodium-allyl intermediate is exploited to develop a novel diastereoselective process for the construction of vicinal acyClic ternary/ternary stereogenic centers, in addition to a cyClic ternary/quaternary derivative.Regio- and Diastereoselective Rhodium-Catalyzed Allylic Substitution with Unstabilized Benzyl NuCleophilesBenzylzinc nuCleophiles; diastereoselective; hard nuCleophiles; regioselective; rhodium(III) chloridex2202159#N/AFALSE
4003
anie.20200768010.1002/anie.202007680https://doi.org/10.1002/anie.202007680Hu, WBAngew. Chem.-Int. Edit.Cu2O is a typical photoelectrocatalyst for sustainable hydrogen production, while the fast charge recombination hinders its further development. Herein, Ni(2+)cations have been doped into a Cu2O lattice (named as Ni-Cu2O) by a simple hydrothermal method and act as electron traps. Theoretical results predict that the Ni dopants produce an acceptor impurity level and lower the energy barrier of hydrogen evolution. Photoelectrochemical (PEC) measurements demonstrate that Ni-Cu2O exhibits a photocurrent density of 0.83 mA cm(-2), which is 1.34 times higher than that of Cu2O. And the photostability has been enhanced by 7.81 times. Moreover, characterizations confirm the enhanced light-harvesting, facilitated charge separation and transfer, prolonged charge lifetime, and increased carrier concentration of Ni-Cu2O. This work provides deep insight into how acceptor-doping modifies the electronic structure and optimizes the PEC process.Acceptor-Doping Accelerated Charge Separation in Cu2O Photocathode for Photoelectrochemical Water Splitting: Theoretical and Experimental Studiesdoping; charge transfer; copper; kinetics; water splittingPhotocatalyst17202050#N/AFALSE
4004
anie.20200766810.1002/anie.202007668Molander, GAStereoinduction in Metallaphotoredox CatalysisPhotocatalyst2021#N/AFALSE
4005
anie.20201123110.1002/anie.202011231FALSEhttps://doi.org/10.1002/anie.202011231Fang, XJAngew. Chem.-Int. Edit.A regiodivergent nickel-catalyzed hydrocyanation of a broad range of internal alkenes involving a chain-walking process is reported. When appropriate diastereomeric biAryl diphosphite ligands are applied, the same starting materials can be converted to either linear or branched nitriles with good yields and high regioselectivities. DFT calculations suggested that the catalyst architecture determines the regioselectivity by modulating electronic and steric interactions. In addition, moderate enantioselectivities were observed when branched nitriles were produced.Nickel-Catalyzed Migratory Hydrocyanation of Internal Alkenes: Unexpected Diastereomeric-Ligand-Controlled Regiodivergencechain-walking; diastereomeric ligands; nickel catalysis; regiodivergent catalysis; remote hydrocyanation32021118#N/ATRUE
4006
anie.20201084010.1002/anie.202010840FALSEhttps://doi.org/10.1002/anie.202010840Engle, KMAngew. Chem.-Int. Edit.A nickel-catalyzed regiodivergent hydroArylation and hydroalkenylation of unactivated alkenyl Carbonylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand-free conditions, with up to 99 % yield and >20:1 selectivity. Alternatively, anti-Markovnikov products can be accessed with a novel 4,4-disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining step induced by the optimal ligand. DFT calculations reveal that in the anti-Markovnikov pathway, repulsion between the ligand and the Alkyl group is minimized (by virtue of it being 1 degrees versus 2 degrees) in the rate- and regioselectivity-determining transmetalation transition state.Ligand-Controlled Regiodivergence in Nickel-Catalyzed HydroArylation and Hydroalkenylation of Alkenyl Carbonylic Acidsalkene functionalization; cross-coupling; hydrofunctionalization; nickel; regiodivergence13202089#N/ATRUE
4007
anie.20201073710.1002/anie.202010737FALSEhttps://doi.org/10.1002/anie.202010737Shu, XZCross-Electrophile C(sp(2))-Si Coupling of Vinyl Chlorosilanes2020#N/ATRUE
4008
anie.20201055910.1002/anie.202010559https://doi.org/10.1002/anie.202010559Nomura, KAngew. Chem.-Int. Edit.Remarkable effects of SiMe(3)and SiEt(3)para-substituents in the phenoxide-modified half-titanocenes, Cp*TiCl2(O-2,6-Pr-i(2)-4-R-C6H2) [R=SiMe3(6), SiEt3(7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9-decen-1-ol (DC-OH) have been demonstrated. The activities by6,7at 50 degrees C showed higher than those conducted at 25 degrees C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by7, which showed better DC-OH (HX-OH) incorporation at 50 degrees C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81x10(5) kg-polymer mol(-1)-Ti h, M-n=6.55-10.0x10(4), DC-OH 2.3-3.6 mol %).The Effect of SiMe(3)and SiEt(3)ParaSubstituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide-Modified Half-Titanocenes2202065#N/ATRUE
4009
anie.20200659310.1002/anie.202006593https://doi.org/10.1002/anie.202006593Wu, LZAngew. Chem.-Int. Edit.Inspired by the natural [NiFe]-H(2)ase, we designed mimic1, (dppe)Ni(mu-pdt)(mu-Cl)Ru(CO)(2)Cl to realize effective H(2)evolution under photocatalytic conditions. However, a new species2was captured in the course of photo-, electro-, and chemo- one-electron reduction. Experimental studies of in situ IR spectroscopy, EPR, NMR, X-ray absorption spectroscopy, and DFT calculations corrB(OH)2rated a dimeric structure of2as a Closed-shell, symmetric structure with a Ru(I)center. The isolated dimer2showed the real catalytic role in photocatalysis with a benchmark turnover frequency (TOF) of 1936 h(-1)for H(2)evolution, while mimic1worked as a pre-catalyst and evolved H(2)only after being reduced to2. The remarkably catalytic activity and unique dimer structure of2operated in photocatalysis unveiled a broad research prospect in hydrogenases mimics for advanced H(2)evolution.Identifying a Real Catalyst of [NiFe]-Hydrogenase Mimic for Exceptional H(2)Photogenerationartificial photosynthesis; heterobimetallic complexes; hydrogenase; photocatalytic H(2)evolution; photochemistryPhotocatalyst4202085#N/AFALSE
4010
anie.20200658610.1002/anie.202006586FALSEhttps://doi.org/10.1002/anie.202006586Leitch, DCAngew. Chem.-Int. Edit.Carbonylate esters have many desirable features as electrophiles for catalytic cross-coupling: they are easy to access, robust during multistep synthesis, and mass-efficient in coupling reactions. Alkenyl Carbonylates, a Class of readily prepared non-aromatic electrophiles, remain difficult to functionalize through cross-coupling. We demonstrate that Pd catalysis is effective for coupling electron-deficient alkenyl Carbonylates with Arylboronic acids in the absence of base or oxidants. Furthermore, these reactions can proceed by two distinct mechanisms for C-O bond Activation. A Pd(0/II)catalytic cyCle is viable when using a Pd(0)precatalyst, with turnover-limiting C-O oxidative addition; however, an alternative pathway that involves alkene carbopalladation and beta-Carbonyl elimination is proposed for Pd(II)precatalysts. This work provides a Clear path toward engaging myriad oxygen-based electrophiles in Pd-catalyzed cross-coupling.Palladium-Catalyzed Cross-Coupling of Alkenyl Carbonylatesalkenylation; C-O Activation; cross-coupling; heterocyCles; palladium catalysisx4202071#N/AFALSE
4011
anie.20200642210.1002/anie.202006422FALSEhttps://doi.org/10.1002/anie.202006422Huang, XQAngew. Chem.-Int. Edit.Herein, we developed a partially controlled pyrolysis strategy to create evenly distributed NiO nanopartiCles within NiFe-MOF nanosheets (MOF NSs) for electrochemical synthesis of H(2)O(2)by a two-electron oxygen reduction reaction (ORR). The elemental Ni can be partially transformed to NiO and uniformly distributed on the surface of the MOF NSs, which is crucial for the formation of the particular structure. The optimized MOF NSs-300 exhibits the highest activity for ORR with near-zero overpotential and excellent H(2)O(2)selectivity (ca. 99 %) in 0.1 mKOH solution. A high-yield H(2)O(2)production rate of 6.5 mol g(cat)(-1) h(-1)has also been achieved by MOF NSs-300 in 0.1 mKOH and at 0.6 V (vs. RHE). In contrast to completely pyrolyzed products, the enhanced catalytic activities of partially pyrolyzed MOF NSs-300 originates mainly from the retained MOF structure and the newly generated NiO nanopartiCles, forming the coordinatively unsaturated Ni atoms and tuning the performance towards electrochemical H(2)O(2)synthesis.Partially Pyrolyzed Binary Metal-Organic Framework Nanosheets for Efficient Electrochemical Hydrogen Peroxide Synthesiselectrocatalysis; hydrogen peroxide; metal-organic frameworks; oxygen reduction reaction; pyrolysisx19202039#N/AFALSE
4012
anie.20201024610.1002/anie.202010246FALSEhttps://doi.org/10.1002/anie.202010246Feng, SHAngew. Chem.-Int. Edit.Exfoliation of non-layered (structurally) bulk materials at the nanoscale is challenging because of the strong chemical bonds in the lattice, as opposed to the weak van der Waals (vdW) interactions in layered materials. We propose a top-down method to exfoliate epsilon-MnO(2)nanosheets in a family of charge-ordered La(1-x)AE(x)MnO(3)(AE=Ca, Sr, Ba) perovskites, taking advantage of the Jahn-Teller disproportionation effect of Mn(3+)and bond-strength differences. epsilon-MnO(2)crystallized into a nickel arsenide (NiAs) structure, with a thickness of 0.91 nm, displays thermal metastability and superior water oxidation activity compared to other manganese oxides. The exfoliation mechanism involves a synergistic proton-induced Mn(3+)disproportionation and structural reconstruction. The synthetic method could also be potentially extended to the exfoliation of other two-dimensional nanosheet materials with non-layered structures.Jahn-Teller Disproportionation Induced Exfoliation of Unit-Cell Scale epsilon-MnO2charge-ordered perovskite manganite; disproportionation reaction; Jahn-Teller effects; stochastic surface walking; vacancy-ordered 2D materials3202051#N/ATRUE
4013
anie.20200626910.1002/anie.202006269FALSEhttps://doi.org/10.1002/anie.202006269Mougel, VAngew. Chem.-Int. Edit.Electrocatalytic CO2 reduction to value-added products provides a viable alternative to the use of carbon sources derived from fossil fuels. Carrying out these transformations at reasonable energetic costs, for example, with low overpotential, remains a challenge. Molecular catalysts allow fine control of activity and selectivity via tuning of their coordination sphere and ligand set. Herein we investigate a series of cobalt(III) pyridine-thiolate complexes as electrocatalysts for CO2 reduction. The effect of the ligands and proton sources on activity was examined. We identified bipyridine bis(2-pyridinethiolato) cobalt(III) hexaflurophosphate as a highly selective catalyst for formate production operating at a low overpotential of 110 mV with a turnover frequency (TOF) of 10 s(-1). Electrokinetic analysis coupled with density functional theory (DFT) computations established the mechanistic pathway, highlighting the role of metal hydride intermediates. The catalysts deactivate via the formation of stable cobalt Carbonyl complexes, but the active species could be regenerated upon oxidation and release of coordinated CO ligands.Electroreduction of CO2 to Formate with Low Overpotential using Cobalt Pyridine Thiolate ComplexesCO2 reduction; cobalt thiolate complexes; electrocatalysis; formate; overpotentialx6202059#N/AFALSE
4014
anie.20200616210.1002/anie.202006162FALSEhttps://doi.org/10.1002/anie.202006162Lipshutz, BHAngew. Chem.-Int. Edit.Mild mono- and di-hydrodehalogenative reductions of gem-dibromocyClopropanes are described, providing an easy and green approach towards the synthesis of cyClopropanes. The methodology utilizes 0.5-5 mol % TMPhen-nickel as the catalyst, which, when activated with a hydride source such as sodium borohydride, Cleanly and selectively dehalogenates dibromocyClopropanes. Double reduction proceeds in a single operation at temperatures between 20-45 degrees C and at atmospheric pressure in an aqueous designer surfactant medium. At lower loading and either in the absence of ligand or in the presence of 2,2 '-bipyridine, this new technology can also be used to gain access to not only monobrominated cyClopropanes, interesting building blocks for further use in synthesis, but also mono- or di-deuterated analogues. Taken together, this base-metal-catalyzed process provides access to cyClopropyl-containing products and is achieved under environmentally responsible conditions.Nickel NanopartiCle Catalyzed Mono- and Di-Reductions ofgem-DibromocyClopropanes Under Mild, Aqueous Micellar Conditionsmicelles; nanopartiCles; nickel; reductions; water chemistryx2202048#N/AFALSE
4015
anie.20200999110.1002/anie.202009991FALSEhttps://doi.org/10.1002/anie.202009991Zhao, YFAngew. Chem.-Int. Edit.A zinc-based single-atom catalyst has been recently explored with distinguished stability, of which the fully occupied Zn2+ 3d(10) electronic configuration is Fenton-reaction-inactive, but the catalytic activity is thus inferior. Herein, we report an approach to manipulate the s-band by constructing a B,N co-coordinated Zn-B/N-C catalyst. We confirm both experimentally and theoretically that the unique N-2-Zn-B-2 configuration is crucial, in which Zn+(3d(10)4s(1)) can hold enough delocalized electrons to generate suitable binding strength for key reaction intermediates and promote the charge transfer between catalytic surface and ORR reactants. This exClusive effect is not found in the other transition-metal counterparts such as M-B/N-C (M=Mn, Fe, Co, Ni and Cu). Consequently, the as-obtained catalyst demonstrates impressive ORR activity, along with remarkable long-term stability in both alkaline and acid media. This work presents a new concept in the further design of electrocatalyst.Turning on Zn 4s Electrons in a N-2-Zn-B-2 Configuration to Stimulate Remarkable ORR Performanceco-doping; M-N-x-C; oxygen reduction; s-band manipulation; Zn single atoms18202138#N/ATRUE
4016
anie.20200613110.1002/anie.202006131FALSEhttps://doi.org/10.1002/anie.202006131Braunschweig, HAngew. Chem.-Int. Edit.The reductive coupling of an N-heterocyClic carbene (NHC) stabilized (dibromo)Vinylborane yields a 1,2-diVinyldiborene, which, although isoelectronic to a 1,3,5-triene, displays no extended pi conjugation because of twisting of the C2B2C2 chain. While this diVinyldiborene coordinates to copper(I) and platinum(0) in an eta(2)-B-2 and eta(4)-C2B2 fashion, respectively, it undergoes a complex rearrangement to an eta(4)-1,3-diborete upon complexation with nickel(0).Oxidation, Coordination, and Nickel-Mediated Deconstruction of a Highly Electron-Rich Diboron Analogue of 1,3,5-Hexatrienecarbenes; conjugation; density-functional calculations; rearrangements; structure elucidationx42020117#N/AFALSE
4017
anie.20200557910.1002/anie.202005579FALSEhttps://doi.org/10.1002/anie.202005579Ding, BAngew. Chem.-Int. Edit.The key to bringing the electrocatalytic nitrogen fixation from conception to application lies in the development of high-efficiency, cost-effective electrocatalysts. Layered double hydroxides (LDHs), also known as hydrotalcites, are promising electrocatalysts for water splitting due to multiple metal centers and large surface areas. However, their activities in the electrocatalytic nitrogen fixation are unsatisfactory. Now, a simple and effective way of phosphorus doping is presented to regulate the charge distribution in LDHs, thus promoting the nitrogen adsorption and Activation. The P-doped LDHs are further coupled to a self-supported, conductive matrix, that is, a carbon nanofibrous membrane, which prevents their aggregation as well as ensuring rapid charge transfer at the interface. By this strategy, decent ammonia yield (1.72x10(-10) mol s(-1) cm(-2)) and Faradaic efficiency (23 %) are delivered at -0.5 V vs. RHE in 0.1 m Na2SO4.Promoted Electrocatalytic Nitrogen Fixation in Fe-Ni Layered Double Hydroxide Arrays Coupled to Carbon Nanofibers: The Role of Phosphorus Dopingcarbon nanofibers; doping; electrocatalytic nitrogen fixation; layered double hydroxides; phosphorusx16202055#N/AFALSE
4018
anie.20200961210.1002/anie.202009612FALSEhttps://doi.org/10.1002/anie.202009612Wang, FAngew. Chem.-Int. Edit.High-performance electrocatalysts for the hydrogen evolution reaction (HER) have an important role to play in the development of renewable energy. Platinum remains the most efficient known HER electrocatalyst. Therefore, it is necessary to find ways to maximize Pt utilization in actual practical applications. Herein we demonstrate a facile strategy for synthesizing RuCeOx-supported, selectively loaded, atomic Pt (0.49 wt. %) (denoted Pt/RuCeOx-PA) by photoActivation at ambient temperature and pressure. Through the photoelectron transfer at the Mott-Schottky heterojunction in RuCeOx, Pt atoms became embedded into the RuO(2)lattice. The resulting selectively loaded Pt-O-Ru moieties in Pt/RuCeOx-PA give a stronger hydrogen spillover effect than Pt complexes randomly loaded by either chemical Activation or thermal Activation. As a result, Pt/RuCeOx-PA shows superior HER performance to the materials prepared by random loading and is even better than a commercial Pt/C catalyst with much higher Pt loading (20 wt. %) at high current densities (from 50-600 mA cm(-2)).Selective Loading of Atomic Platinum on a RuCeO(x)Support Enables Stable Hydrogen Evolution at High Current Densities15202052#N/ATRUE
4019
anie.20200940010.1002/anie.202009400FALSEhttps://doi.org/10.1002/anie.202009400Dou, SXAngew. Chem.-Int. Edit.Herein, we report a comprehensive strategy to synthesize a full range of single-atom metals on carbon matrix, inCluding V, Mn, Fe, Co, Ni, Cu, Ge, Mo, Ru, Rh, Pd, Ag, In, Sn, W, Ir, Pt, Pb, and Bi. The extensive applications of various SACs are manifested via their ability to electro-catalyze typical hydrogen evolution reactions (HER) and conversion reactions in novel room-temperature sodium sulfur batteries (RT-Na-S). The enhanced performances for these electrochemical reactions arisen from the ability of different single active atoms on local structures to tune their electronic configuration. Significantly, the electrocatalytic behaviors of diverse SACs, assisted by density functional theory calculations, are systematically revealed by in situ synchrotron X-ray diffraction and in situ transmission electronic microscopy, providing a strategic library for the general synthesis and extensive applications of SACs in energy conversion and storage.General Synthesis of Single-Atom Catalysts for Hydrogen Evolution Reactions and Room-Temperature Na-S Batterieselectrochemistry; hydrogen evolution reaction; RT Na-S batteries; single atoms11202056#N/ATRUE
4020
anie.20200496610.1002/anie.202004966FALSEhttps://doi.org/10.1002/anie.202004966Li, YDAngew. Chem.-Int. Edit.Atomic regulation of metal catalysts has emerged as an intriguing yet challenging strategy to boost product selectivity. Here, we report a density functional theory-guided atomic design strategy for the fabrication of a NiGa intermetallic catalyst with completely isolated Ni sites to optimize acetylene semi-hydrogenation processes. Such Ni sites show not only preferential acetylene pi-adsorption, but also enhanced ethylene desorption. The characteristics of the Ni sites are confirmed by multiple characterization techniques, inCluding aberration-corrected high-resolution scanning transmission electron microscopy and X-ray absorption spectrometry measurements. The superior performance is also confirmed experimentally against a Ni5Ga3 intermetallic catalyst with partially isolated Ni sites and against a Ni catalyst with multi-atomic ensemble Ni sites. Accordingly, the NiGa intermetallic catalyst with the completely isolated Ni sites shows significantly enhanced selectivity to ethylene and suppressed coke formation.Adsorption Site Regulation to Guide Atomic Design of Ni-Ga Catalysts for Acetylene Semi-Hydrogenationacetylene; heterogeneous catalysis; Ni-Ga intermetallic catalyst; semi-hydrogenation; site regulationx20202046#N/AFALSE
4021
anie.20200885410.1002/anie.202008854FALSEhttps://doi.org/10.1002/anie.202008854Fang, XJAngew. Chem.-Int. Edit.Metal-catalyzed chain-walking reactions have recently emerged as a powerful strategy to functionalize remote positions in organic molecules. However, a chain-walking protocol for nonconjugated dienes remains scarcely reported, and developments are currently ongoing. In this Communication, a nickel-catalyzed asymmetric hydrocyanation of nonconjugated dienes involving a chain-walking process is demonstrated. The reaction exhibits excellent regio- and chemoselectivity, and a wide range of substrates were tolerated, delivering the products in high yields and enantioselectivities. Deuterium-labeling experiments support the chain-walking process, which involves an iterative beta-H elimination and reinsertion processes. Gram-scale synthesis, regioconvergent experiments, and downstream transformations gave further insights into the high potential of this transformation.Enantioselective Nickel-Catalyzed Migratory Hydrocyanation of Nonconjugated Dieneschain-walking; nickel catalysis; nonconjugated dienes; regioconvergence; remote hydrocyanation142020132#N/ATRUE
4022
anie.20200490810.1002/anie.202004908FALSEhttps://doi.org/10.1002/anie.202004908Salgueirino, VAngew. Chem.-Int. Edit.Magnetically induced catalysis can be promoted taking advantage of optimal heating properties from the magnetic nanopartiCles to be employed. However, when unprotected, these heating agents that are usually air-sensitive, get sintered under the harsh catalytic conditions. In this context, we present, to the best of our knowledge, the first example of air-stable magnetic nanopartiCles that: 1) show excellent performance as heating agents in the CO(2)methanation catalyzed by Ni/SiRAlOx, with CH(4)yields above 95 %, and 2) do not sinter under reaction conditions. To attain both characteristics we demonstrate, first the exchange-coupled magnetic approach as an alternative and effective way to tune the magnetic response and heating efficiency, and second, the chemical stability of cuboctahedron-shaped core-shell hard CoFe2O4-soft Fe(3)O(4)nanopartiCles.Magnetically Induced CO(2)Methanation Using Exchange-Coupled Spinel Ferrites in Cuboctahedron-Shaped NanocrystalsCO(2)methanation; core-shell nanostructures; magnetic nanopartiCles; spinel ferritex3202036#N/AFALSE
4023
anie.20200484110.1002/anie.202004841FALSEhttps://doi.org/10.1002/anie.202004841Zhang, TRAngew. Chem.-Int. Edit.Carbon-supported Ni-II single-atom catalysts with a tetradentate Ni-N2O2 coordination formed by a Schiff base ligand-mediated pyrolysis strategy are presented. A Ni-II complex of the Schiff base ligand (R,R)-(-)-N,N '-bis(3,5-di-tert-butylsalicylidene)-1,2-cyClohexanediamine was adsorbed onto a carbon black support, followed by pyrolysis of the modified carbon material at 300 degrees C in Ar. The Ni-N2O2/C catalyst showed excellent performance for the electrocatalytic reduction of O-2 to H2O2 through a two-electron transfer process in alkaline conditions, with a H2O2 selectivity of 96 %. At a current density of 70 mA cm(-2), a H2O2 production rate of 5.9 mol g(cat.)(-1) h(-1) was achieved using a three-phase flow cell, with good catalyst stability maintained over 8 h of testing. The Ni-N2O2/C catalyst could electrocatalytically reduce O-2 in air to H2O2 at a high current density, still affording a high H2O2 selectivity (>90 %). A precise Ni-N2O2 coordination was key to the performance.High-Efficiency Oxygen Reduction to Hydrogen Peroxide Catalyzed by Nickel Single-Atom Catalysts with Tetradentate N2O2 Coordination in a Three-Phase Flow Cellelectrocatalysis; hydrogen peroxide; N2O2 coordination; Ni single atoms; three-phase flow cellx29202039#N/AFALSE
4024
anie.20200476310.1002/anie.202004763FALSEhttps://doi.org/10.1002/anie.202004763Jian, ZBAngew. Chem.-Int. Edit.Branched polyolefin microstructures resulting from so-called chain walking are a fascinating feature of late transition metal catalysts; however, to date it has not been demonstrated how desirable branched polyolefin microstructures can be generated thereby. We demonstrate how highly branched polyethylenes with methyl branches (220 Me/1000 C) exClusively and very high molecular weights (ca. 10(6) g mol(-1)), reaching the branch density and microstructure of commercial ethylene-propylene elastomers, can be generated from ethylene alone. At the same time, polar groups on the main chain can be generated by in-chain incorporation of methyl acrylate. Key to this strategy is a novel rigid environment in an alpha-diimine Pd(II)catalyst with a steric constraint that allows for excessive chain walking and branching, but restricts branch formation to methyl branches, hinders chain transfer to afford a living polymerization, and inverts the regioselectivity of acrylate insertion to a 1,2-mode.Ultrahigh Branching of Main-Chain-Functionalized Polyethylenes by Inverted Insertion Selectivityx31202058#N/AFALSE
4025
anie.20200840710.1002/anie.202008407FALSEhttps://doi.org/10.1002/anie.202008407Krautler, BAngew. Chem.-Int. Edit.The (formal) replacement of Co in cobalamin (Cbl) by Ni(II)generates nibalamin (Nibl), a new transition-metal analogue of vitamin B-12. Described here isNibl, synthesized by incorporation of a Ni(II)ion into the metal-free B-12 ligand hydrogenobalamin (Hbl), itself prepared from hydrogenobyric acid (Hby). The related Ni-II corrin nibyric acid (Niby) was similarly synthesized fromHby, the metal-free cobyric acid ligand. The solution structures ofHbl, andNibyandNibl, were characterized by spectroscopic studies.Hblfeatures two inner protons bound at N2 and N4 of the corrin ligand, as discovered inHby. X-ray analysis ofNibyshows the structural adaptation of the corrin ligand to Ni(II)ions and the coordination behavior of Ni-II. The diamagneticNibyandNibl, and corresponding isoelectronic Co(I)corrins, were deduced to be isostructural.Niblis a structural mimic of four-coordinate base-offCbls, as verified by its ability to act as a strong inhibitor of bacterial adenosyltransferase.Replacement of the Cobalt Center of Vitamin B(12)by Nickel: Nibalamin and Nibyric Acid Prepared from Metal-Free B-12 Ligands Hydrogenobalamin and Hydrogenobyric Acidcobalamins; porphyrinoids; transition metals; crystal structures; vitamins3202093#N/ATRUE
4026
anie.20200460310.1002/anie.202004603FALSEhttps://doi.org/10.1002/anie.202004603Wang, QAngew. Chem.-Int. Edit.Aqueous organic redox flow batteries (AORFBs) have received considerable attention for large-scale energy storage. Quinone derivatives, such as 9,10-anthraquinone-2,7-disulphonic acid (2,7-AQDS), have been explored intensively owing to potentially low cost and swift reaction kinetics. However, the low solubility in pH-neutral electrolytes restricts their application to corrosive acidic or caustic systems. Herein, the single molecule redox-targeting reactions of 2,7-AQDS anolyte are presented to circumvent its solubility limit in pH-neutral electrolytes. Polyimide was employed as a low-cost high-capacity solid material to boost the capacity of 2,7-AQDS electrolyte to 97 Ah L-1. Through in situ FTIR spectroscopy, a hydrogen-bonding mediated reaction mechanism was disClosed. In conjunction with NaI as catholyte and nickel hexacyanoferrate as the catholyte capacity booster, a single-molecule redox-targeting reaction-based full cell with energy density up to 39 Wh L(-1)was demonstrated.Single-Molecule Redox-Targeting Reactions for a pH-Neutral Aqueous Organic Redox Flow Batteryanthraquinone; energy storage; redox flow batteries; redox targeting; spectroelectrochemistryx4202049#N/AFALSE
4027
anie.202004441
https://doi.org/10.1002/anie.202004441
https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202004441Wei, H
Angew. Chem.-Int. Edit.
The utilizations of omnipresent, thermodynamically stable amides and aliphatic C(sp(3))-H bonds for various functionalizations are ongoing challenges in catalysis. In particular, the direct coupling between the two functional groups has not been realized. Here, we report the synergistic Activation of the two challenging bonds, the amide C-N and unactivated aliphatic C(sp(3))-H, via metallaphotoredox catalysis to directly acylate aliphatic C-H bonds utilizing amides as stable and readily accessible acyl surrogates. N-acylsuccinimides served as efficient acyl reagents for the streamlined synthesis of synthetically useful ketones from simple C(sp(3))-H substrates. Detailed mechanistic investigations using both computational and experimental mechanistic studies were performed to construct a detailed and complete catalytic cyCle. The origin of the superior reactivity of the N-acylsuccinimides over other more reactive acyl sources such as acyl chlorides was found to be an uncommon reaction pathway which commences with C-H Activation prior to oxidative addition of the acyl substrate.
Synergistic Activation of Amides and Hydrocarbons for Direct C(sp(3))-H Acylation Enabled by Metallaphotoredox Catalysis
Lee, GS; Won, J; Choi, S; Baik, MH; Hong, SH
Photocatalysty202020
Added by Imanuel
6/21/2022FALSE
4028
anie.20200430110.1002/anie.202004301FALSEhttps://doi.org/10.1002/anie.202004301Cui, CHAngew. Chem.-Int. Edit.A methanol economy will be favored by the availability of low-cost catalysts able to selectively oxidize methanol to formate. This selective oxidation would allow extraction of the largest part of the fuel energy while concurrently producing a chemical with even higher commercial value than the fuel itself. Herein, we present a highly active methanol electrooxidation catalyst based on abundant elements and with an optimized structure to simultaneously maximize interaction with the electrolyte and mobility of charge carriers. In situ infrared spectroscopy combined with nuClear magnetic resonance spectroscopy showed that branched nickel carbide partiCles are the first catalyst determined to have nearly 100 % electrochemical conversion of methanol to formate without generating detectable CO(2)as a byproduct. Electrochemical kinetics analysis revealed the optimized reaction conditions and the electrode delivered excellent activities. This work provides a straightforward and cost-efficient way for the conversion of organic small molecules and the first direct evidence of a selective formate reaction pathway.Selective Methanol-to-Formate Electrocatalytic Conversion on Branched Nickel Carbidebranched partiCles; formic acid; in situ infrared spectroscopy; methanol oxidation; nickel carbide
Electrocatalytic
8202049#N/AFALSE
4029
anie.20200426410.1002/anie.202004264FALSEhttps://doi.org/10.1002/anie.202004264Bal, WAngew. Chem.-Int. Edit.The amino-terminal copper and nickel/N-terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards Cu-II ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped-flow and microsecond freeze-hyperquenching (MHQ) techniques supported by steady-state spectroscopic and electrochemical data to demonstrate the formation of partially coordinated intermediate Cu-II complexes formed by glycyl-glycyl-histidine (GGH) peptide, the simplest ATCUN/NTS model. One of these novel intermediates, characterized by two-nitrogen coordination, t(1/2)approximate to 100 ms at pH 6.0 and the ability to maintain the Cu-II/Cu-I redox pair is the best candidate for the long-sought reactive species in extracellular copper transport.Key Intermediate Species Reveal the Copper(II)-Exchange Pathway in Biorelevant ATCUN/NTS Complexesamino-terminal copper and nickel (ATCUN) motif; copper; electrochemistry; EPR spectroscopy; peptidesx9202040#N/AFALSE
4030
anie.20200402410.1002/anie.202004024https://doi.org/10.1002/anie.202004024Chen, ClA Self-Supporting Strategy for Gas-Phase and Slurry-Phase Ethylene Polymerization using Late-Transition-Metal Catalystsx2020#N/AFALSE
4031
anie.20200402010.1002/anie.202004020FALSEhttps://doi.org/10.1002/anie.202004020Wolf, RAngew. Chem.-Int. Edit.The reaction of zerovalent nickel compounds with white phosphorus (P-4) is a barely explored route to binary nickel phosphide Clusters. Here, we show that coordinatively and electronically unsaturated N-heterocyClic carbene (NHC) nickel(0) complexes afford unusual Cluster compounds with P-1, P-3, P-5 and P-8 units. Using [Ni(IMes)(2)] [IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene], electron-deficient Ni3P4 and Ni3P6 Clusters have been isolated, which can be described as superhyperCloso and hyperCloso Clusters according to the Wade-Mingos rules. Use of the bulkier NHC complexes [Ni(IPr)(2)] or [(IPr)Ni(eta(6)-toluene)] [IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] affords a Closo-Ni3P8 Cluster. Inverse-sandwich complexes [(NHC)(2)Ni2P5] (NHC=IMes, IPr) with an aromatic cyClo-P-5(-) ligand were identified as additional products.Aggregation and Degradation of White Phosphorus Mediated by N-HeterocyClic Carbene Nickel(0) ComplexesCluster compounds; nickel; P-4 Activation; phosphorus; polyphosphidesx6202058#N/AFALSE
4032
anie.20200402010.1002/anie.202004020FALSEhttps://doi.org/10.1002/anie.202004020Wolf, RAngew. Chem.-Int. Edit.The reaction of zerovalent nickel compounds with white phosphorus (P-4) is a barely explored route to binary nickel phosphide Clusters. Here, we show that coordinatively and electronically unsaturated N-heterocyClic carbene (NHC) nickel(0) complexes afford unusual Cluster compounds with P-1, P-3, P-5 and P-8 units. Using [Ni(IMes)(2)] [IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene], electron-deficient Ni3P4 and Ni3P6 Clusters have been isolated, which can be described as superhyperCloso and hyperCloso Clusters according to the Wade-Mingos rules. Use of the bulkier NHC complexes [Ni(IPr)(2)] or [(IPr)Ni(eta(6)-toluene)] [IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] affords a Closo-Ni3P8 Cluster. Inverse-sandwich complexes [(NHC)(2)Ni2P5] (NHC=IMes, IPr) with an aromatic cyClo-P-5(-) ligand were identified as additional products.Aggregation and Degradation of White Phosphorus Mediated by N-HeterocyClic Carbene Nickel(0) ComplexesCluster compounds; nickel; P-4 Activation; phosphorus; polyphosphidesx6202058#N/AFALSE
4033
anie.20200383010.1002/anie.202003830FALSEhttps://doi.org/10.1002/anie.202003830Wang, CYAngew. Chem.-Int. Edit.Transition-metal-catalyzed hydroArylation of unactivated alkenes with strategic use of remote coordinating functional groups has received significant attention recently to address the issues of both low reactivity and poor selectivity. The bidentate 8-aminoquinoline amide group is the most successfully adopted in unactivated alkenes for Pd and Ni catalysis. We describe the first manganese-catalyzed hydroArylation of unactivated alkenes bearing diverse simple functionalities with Arylboronic acids. A series of delta- and gamma-Arylated amides, ketones, pyridines, and amines was accessed with excellent regioselectivity and in high yields. Hydroalkenylation of unactivated alkenes was also shown to be applicable under this manganese-catalysis regime. The method features earth-abundant manganese catalysis, easily available substrates, broad functional-group tolerance, and excellent regioselective control.Manganese-Catalyzed HydroArylation of Unactivated Alkenesalkenes; homogeneous catalysis; hydroalkenylation; hydroArylation; manganesex92020104#N/AFALSE
4034
anie.20200356010.1002/anie.202003560FALSEhttps://doi.org/10.1002/anie.202003560Weber, SAngew. Chem.-Int. Edit.We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long-lived triplet charge-transfer ((CT)-C-3) state, based on the electron spin control using spin-orbit charge transfer intersystem crossing (SOCT-ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT-ISC takes 8 ns to produce the (NI)-N-3* state. Then the slow secondary CS (125 ns) gives the long-lived (CT)-C-3 state (0.94 mu s in deaerated n-hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as (NI)-N-1*->(CT)-C-1 ->(NI)-N-3*->(CT)-C-3. With time-resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron-spin polarization pattern was observed for the naphthalimide-localized triplet state. Our spiro compact dyad structure and the electron spin-control approach is different to previous methods for which invoking transition-metal coordination or chromophores with intrinsic ISC ability is mandatory.Long-Lived Charge-Transfer State Induced by Spin-Orbit Charge Transfer Intersystem Crossing (SOCT-ISC) in a Compact Spiro Electron Donor/Acceptor Dyadcharge transfer; electron spin control; intersystem crossing; time-resolved EPR; triplet statex10202073#N/AFALSE
4035
anie.20200339010.1002/anie.202003390FALSEhttps://doi.org/10.1002/anie.202003390Rimer, JDAngew. Chem.-Int. Edit.Metal oxides exposing high-index facets are potentially impactful in catalysis and adsorption processes owing to under-coordinated ions and polarities that alter their interfacial properties compared to low-index facets. Here, we report molten-salt syntheses of NiO partiCles exposing a variety of crystal facets. We show that for a given anion (nitrate or chloride), the alkali cation has a notable impact on the formation of crystals exposing {311}, {611}, {100}, and {111} faces. Based on a parametric analysis of synthesis conditions, we postulate that the crystallization mechanism is governed by the formation of growth units consisting of Ni-II complexes whose coordination numbers are determined by temperature and the selection of anion (associated to the coordination sphere) and alkali cation (associated with the outer coordination sphere). Notably, our findings reveal that high-index facets are particularly favored in chloride media and are stable under prolonged periods of catalysis and steaming.Synthesis of NiO Crystals Exposing Stable High-Index Facetscrystal growth; crystal habit; flux-mediated method; molten-salt route; nickel oxidex6202057#N/AFALSE
4036
anie.20200335910.1002/anie.202003359FALSEhttps://doi.org/10.1002/anie.202003359Xue, DAngew. Chem.-Int. Edit.A highly effective C-O coupling reaction of (hetero)Aryl electrophiles with primary and secondary alcohols is reported. Catalyzed by a Ni-II-Aryl complex under long-wave UV (390-395 nm) irradiation in the presence of a soluble amine base without any additional photosensitizer, the reaction enables the etherification of Aryl bromides and Aryl chlorides as well as sulfonates with a wide range of primary and secondary aliphatic alcohols, affording synthetically important ethers. Intramolecular C-O coupling is also possible. The reaction appears to proceed via a Ni-I-Ni-III catalytic cyCle.Light-Promoted Nickel Catalysis: Etherification of Aryl Electrophiles with Alcohols Catalyzed by a Ni-II-Aryl ComplexAryl electrophiles; etherification; homogeneous catalysis; nickel; photocatalysis
Photocatalyst
17202071#N/AFALSE
4037
anie.20200298410.1002/anie.202002984FALSEhttps://doi.org/10.1002/anie.202002984Liu, BAngew. Chem.-Int. Edit.Single-atom catalysts (SACs) show great promise for electrochemical CO2 reduction reaction (CRR), but the low density of active sites and the poor electrical conduction and mass transport of the single-atom electrode greatly limit their performance. Herein, we prepared a nickel single-atom electrode consisting of isolated, high-density and low-valent nickel(I) sites anchored on a self-standing N-doped carbon nanotube array with nickel-copper alloy encapsulation on a carbon-fiber paper. The combination of single-atom nickel(I) sites and self-standing array structure gives rise to an excellent electrocatalytic CO2 reduction performance. The introduction of copper tunes the d-band electron configuration and enhances the adsorption of hydrogen, which impedes the hydrogen evolution reaction. The single-nickel-atom electrode exhibits a specific current density of -32.87 mA cm(-2) and turnover frequency of 1962 h(-1) at a mild overpotential of 620 mV for CO formation with 97 % Faradic efficiency.Atomically Dispersed Nickel(I) on an Alloy-Encapsulated Nitrogen-Doped Carbon Nanotube Array for High-Performance Electrochemical CO2 Reduction Reactioncarbon dioxide reduction reaction; electrocatalysis; nanoarrays; single-atom catalystsx24202049#N/AFALSE
4038
anie.20200265010.1002/anie.202002650https://doi.org/10.1002/anie.202002650Du, XWAngew. Chem.-Int. Edit.Developing highly efficient and low-cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into Clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel-cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble-metal co-catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so-called L-NiCo nanosheets with a nonstoichiometric composition and O2-/Co3+ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O2- and Co3+ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H-2 evolution rate of 1.7 mu mol h(-1) under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.A Hydrogen-Deficient Nickel-Cobalt Double Hydroxide for Photocatalytic Overall Water Splittingcobalt; laser ablation; nickel; photocatalysis; water splittingPhotocatalyst11202064#N/AFALSE
4039
anie.20200236410.1002/anie.202002364FALSEhttps://doi.org/10.1002/anie.202002364Hayton, TWAngew. Chem.-Int. Edit.The masked terminal Zn sulfide, [K(2.2.2-cryptand)][(LZn)-L-Me(S)] (2) (L-Me={(2,6-(Pr2C6H3)-Pr-i)NC(Me)}(2)CH), was isolated via reaction of [(LZnSCPh3)-L-Me] (1) with 2.3 equivalents of KC8 in THF, in the presence of 2.2.2-cryptand, at -78 degrees C. Complex 2 reacts readily with PhCCH and N2O to form [K(2.2.2-cryptand)][(LZn)-L-Me(SH)(CCPh)] (4) and [K(2.2.2-cryptand)][(LZn)-L-Me(SNNO)] (5), respectively, displaying both Bronsted and Lewis basicity. In addition, the electronic structure of 2 was examined computationally and compared with the previously reported Ni congener, [K(2.2.2-cryptand)][(LNi)-L-tBu(S)] (L-tBu={(2,6-(Pr2C6H3)-Pr-i)NC(Bu-t)}(2)CH).Synthesis of a Masked Terminal Zinc Sulfide and Its Reactivity with Bronsted and Lewis Acidsmultiple bonding; nitrogen oxides; protecting groups; sulfides; zincx2202054#N/AFALSE
4040
anie.20200807610.1002/anie.202008076FALSEhttps://doi.org/10.1002/anie.202008076Wang, HAngew. Chem.-Int. Edit.A series of largely pi-extended multichromophoric molecules inCluding cross-conjugated, half cross-conjugated, conjugation-interrupted and linearly conjugated systems were synthesized and characterized. These multichromophoric molecular systems revealed interesting structural-property relationships. Bisporphyrin-fused pentacenes Pen-1 band e linearly-conjugated bisporphyrin-fused pentacenes (Pen-1 band Pen-2 a) possess much narrower HOMO-LUMO gaps (1.65 and 1.42 eV redox, respectively) and higher HOMO energy levels than those of their pentacene analogues (2.23 and 2.01 eV redox, respectively), similar to those of much less stable hexacenes and heptacenes. An estimated half-life of >945 h was obtained for bisporphyrin-fused pentacene Pen-2 a, which is much longer than that of its pentacene analogue (BPE-P, half-life, 33 h).Nickel(II) Bisporphyrin-Fused Pentacenes Exhibiting Abnormal High Stabilitycharge separation; multichromophores; pentacene; stability; pi-extended porphyrin2202070#N/ATRUE
4041
anie.20200224010.1002/anie.202002240https://doi.org/10.1002/anie.202002240Idriss, HAngew. Chem.-Int. Edit.The major challenge in solar water splitting to H(2)and O(2)is in making a stable and affordable system for large-scale applications. We have designed, fabricated, and tested a photoelectrochemical reactor characterized as follows: 1) it comprises an integrated device to reduce the balance of the system cost, 2) it utilizes concentrated sunlight to reduce the photoabsorber cost, and 3) it employs and alkaline electrolyte to reduce catalyst cost and eliminate external thermal management needs. The system consists of an III-V-based photovoltaic cell integrated with Ni foil as an O(2)evolution catalyst that also protects the cell from corrosion. At low light concentration, without the use of optical lenses, the solar-to-hydrogen (STH) efficiency was 18.3 %, while at high light concentration (up to 207 suns) with the use of optical lenses, the STH efficiency was 13 %. Catalytic tests conducted for over 100 hours at 100-200 suns showed no sign of degradation nor deviation from product stoichiometry (H-2/O-2=2). Further tests projected a system stability of years.A Stable Integrated Photoelectrochemical Reactor for H(2)Production from Water Attains a Solar-to-Hydrogen Efficiency of 18 % at 15 Suns and 13 % at 207 Sunsconcentrated sunlight; hydrogen production; nickel oxide; OER catalyst stability; photoelectrochemistryPhotocatalyst6202040#N/AFALSE
4042
anie.20200756710.1002/anie.202007567FALSEhttps://doi.org/10.1002/anie.202007567Sun, SGAngew. Chem.-Int. Edit.Driven by the persisting poor understanding of the sluggish kinetics of the hydrogen evolution reaction (HER) on Pt in alkaline media, a direct correlation of the interfacial water structure and activity is still yet to be established. Herein, using Pt and Pt-Ni nanopartiCles we first demonstrate a strong dependence of the proton donor structure on the HER activity and pH. The structure of the first layer changes from the proton acceptors to the donors with increasing pH. In the base, the reactivity of the interfacial water varied its structure, and the Activation energies of water dissociation increased in the sequence: the dangling O-H bonds < the trihedrally coordinated water < the tetrahedrally coordinated water. Moreover, optimizing the adsorption of H and OH intermediates can re-orientate the interfacial water molecules with their H atoms pointing towards the electrode surface, thereby enhancing the kinetics of HER. Our results Clarified the dynamic role of the water structure at the electrode-electrolyte interface during HER and the design of highly efficient HER catalysts.Interfacial Structure of Water as a New Descriptor of the Hydrogen Evolution Reactionhydrogen evolution reaction (HER); interfacial water structure; nanopartiCles; pH-dependence; Raman spectroscopy8202059#N/ATRUE
4043
anie.20200136310.1002/anie.202001363FALSEhttps://doi.org/10.1002/anie.202001363Patra, AKAngew. Chem.-Int. Edit.According to the well-accepted mechanism, methyl-coenzyme M reductase (MCR) involves Ni-mediated thiolate-to-disulfide conversion that sustains its catalytic cyCle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni-ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of Ni-II complexes comprising a tridentate N2S donor thiol and its analogous N4S2 donor disulfide ligands. These complexes demonstrate reversible Ni-II-thiolate/Ni-II-disulfide (both bound and unbound disulfide-S to Ni-II) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cyCle.Nickel(II)-Mediated Reversible Thiolate/Disulfide Conversion as a Mimic for a Key Step of the Catalytic CyCle of Methyl-Coenzyme M Reductasemethanogenesis; methyl-coenzyme M reductase; nickel; thiolate; disulfide interconversion; thiyl radicalx2202064#N/AFALSE
4044
anie.20200114810.1002/anie.202001148https://doi.org/10.1002/anie.202001148Wang, LZAngew. Chem.-Int. Edit.Atomic co-catalysts offer high potential to improve the photocatalytic performance, of which the preparation with earth-abundant elements is challenging. Here, a new molten salt method (MSM) is designed to prepare atomic Ni co-catalyst on widely studied TiO2 nanopartiCles. The liquid environment and space confinement effect of the molten salt leads to atomic dispersion of Ni ions on TiO2, while the strong polarizing force provided by the molten salt promotes formation of strong Ni-O bonds. Interestingly, Ni atoms are found to facilitate the formation of oxygen vacancies (OV) on TiO2 during the MSM process, which benefits the charge transfer and hydrogen evolution reaction. The synergy of atomic Ni co-catalyst and OV results in 4-time increase in H-2 evolution rate compared to that of the Ni co-catalyst on TiO2 prepared by an impregnation method. This work provides a new strategy of controlling atomic co-catalyst together with defects for efficient photocatalytic water splitting.Molten-Salt-Mediated Synthesis of an Atomic Nickel Co-catalyst on TiO2 for Improved Photocatalytic H-2 Evolutionatomic co-catalysts; molten-salt method; nickel; oxygen vacancies; titanium dioxidePhotocatalyst35202037#N/AFALSE
4045
anie.20200707710.1002/anie.202007077FALSEhttps://doi.org/10.1002/anie.202007077Wang, DAngew. Chem.-Int. Edit.To boost the performance for various applications, a rational bottom-up design on materials is necessary. The defect engineering on nanopartiCle at the atomic level can efficiently tune the electronic behavior, which offers great opportunities in enhancing the catalytic performance. In this paper, we optimized the surface oxygen vacancy concentration and created the lattice distortion in rare-earth-based perovskite oxide through gradient replacement of the B site with valence alternated element. The dual defects make the electron spin state transit from low spin state to high spin state, thus decreasing the charge transport resistance. Furthermore, assembly the modified nanopartiCle subunits into the micro-sized hollow multishelled structures can provide porous shells, abundant interior space and effective contact, which enables an enhanced mass transfer and a shorter charge transport path. As a result, the systemic design in the electronic and nano-micro structures for catalyst has brought an excellent oxygen evolution performance.Dual-Defects Adjusted Crystal-Field Splitting of LaCo(1-x)Ni(x)O(3-delta)Hollow Multishelled Structures for Efficient Oxygen Evolutiondefects; hollow multishelled structures; oxygen evolution reaction; perovskite oxides; rare-earth compounds16202042#N/ATRUE
4046
anie.20200682610.1002/anie.202006826TRUEhttps://doi.org/10.1002/anie.202006826Amgoune, AAngew. Chem.-Int. Edit.The challenging nickel-catalyzed mono-alpha-Arylation of acetone with Aryl chlorides, pivalates, and carbamates has been achieved for the first time. A nickel/Josiphos-based catalytic system is shown to feature unique catalytic behavior, allowing the highly selective formation of the desired mono-alpha-Arylated acetone. The developed methodology was applied to a variety of (hetero)Aryl chlorides inCluding biologically relevant derivatives. The methodology has been extended to the unprecedented coupling of acetone with phenol derivatives. Mechanistic studies allowed the isolation and characterization of key Ni(0)and Ni(II)catalytic intermediates. The Josiphos ligand is shown to play a key role in the stabilization of Ni(II)intermediates to allow a Ni-0/Ni(II)catalytic pathway. Mechanistic understanding was then leveraged to improve the protocol using an air-stable Ni(II)pre-catalyst.Nickel-Catalyzed Mono-Selective alpha-Arylation of Acetone with Aryl Chlorides and Phenol DerivativesJosiphos ligands; mechanisms; nickel intermediates; oxidative addition; synthetic methodsCsp2_ar-Csp2E-NuOHOPivHArylCs2CO3Ionic-CO322020491/6/2022TRUE
4047
anie.20200672210.1002/anie.202006722FALSEhttps://doi.org/10.1039/b204851eCao, MHIdentifying the Transfer Kinetics of Adsorbed Hydroxyl as a Descriptor of Alkaline Hydrogen Evolution Reaction2020#N/ATRUE
4048
anie.20200069010.1002/anie.202000690FALSEhttps://doi.org/10.1002/anie.202000690Liu, ZQAngew. Chem.-Int. Edit.Herein, we highlight redox-inert Zn2+ in spinel-type oxide (ZnXNi1-XCo2O4) to synergistically optimize physical pore structure and increase the formation of active species on the catalyst surface. The presence of Zn2+ segregation has been identified experimentally and theoretically under oxygen-evolving condition, the newly formed V-Zn-O-Co allows more suitable binding interaction between the active center Co and the oxygenated species, resulting in superior ORR performance. Moreover, a liquid flow Zn-air battery is constituted employing the structurally optimized Zn0.4Ni0.6Co2O4 nanopartiCles supported on N-doped carbon nanotube (ZNCO/NCNTs) as an efficient air cathode, which presents remarkable power density (109.1 mW cm(-2)), high open circuit potential (1.48 V vs. Zn), excellent durability, and high-rate performance. This finding could elucidate the experimentally observed enhancement in the ORR activity of ZnXNi1-XCo2O4 oxides after the OER test.Surface Reorganization on Electrochemically-Induced Zn-Ni-Co Spinel Oxides for Enhanced Oxygen Electrocatalysisdefect chemistry; oxygen evolution reaction; oxygen reduction reaction; zinc-air batteriesx68202044#N/AFALSE
4049
anie.20200628510.1002/anie.202006285FALSEhttps://doi.org/10.1002/anie.202006285Coperet, CAngew. Chem.-Int. Edit.A silica-supported monomeric Alkylaluminum co-catalyst was prepared via surface organometallic chemistry by contacting tris(neopentyl)aluminum and partially dehydroxylated silica. This system, fully characterized by solid-state(27)Al NMR spectroscopy augmented by computational studies, efficiently activates ((Bu3P)-Bu-n)(2)NiCl(2)towards dimerization of ethene, demonstrating comparable activity to previously reported dimeric diethylaluminum chloride supported on silica. Three types of aluminum surface species have been identified: monografted tetracoordinated Al species as well as two types of bisgrafted Al species-tetra- and pentacoordinated. Of them, only the monografted Al species is proposed to be able to activate the ((Bu3P)-Bu-n)(2)NiCl(2)complex and generate the active cationic species.Silica-Grafted Tris(neopentyl)aluminum: A Monomeric Aluminum Solid Co-catalyst for Efficient Nickel-Catalyzed Ethene DimerizationAlkylaluminum; Al-27 solid-state NMR spectroscopy; co-catalysts; DFT computations; ethene oligomerization; nickel2202037#N/ATRUE
4050
anie.20200613510.1002/anie.202006135FALSEhttps://doi.org/10.1002/anie.202006135Fjellvag, HAngew. Chem.-Int. Edit.In this work we benefited from recent advances in tools for crystal-structure analysis that enabled us to describe an exotic nanoscale phenomenon in structural chemistry. The Mn0.60Ni0.40As sample of the Mn1-xNixAs solid solution, exhibits an incommensurate compositional modulation intimately coupled with positional modulations. The average structure is of the simple NiAs type, but in contrast to a normal solid solution, we observe that manganese and nickel segregate periodically at the nano-level into ordered MnAs and NiAs layers with thickness of 2-4 face-shared octahedra. The detailed description was obtained by combination of 3D electron diffraction, scanning transmission electron microscopy, and neutron diffraction. The distribution of the manganese and nickel layers is perfectly described by a modulation vectorq=0.360(3)c*. Displacive modulations are observed for all elements as a consequence of the occupational modulation, and as a means to achieve acceptable Ni-As and Mn-As distances. This modulated evolution of magnetic MnAs and non-magnetic NiAs-layers with periodicity at approximately 10 angstrom level, may provide an avenue for spintronics.Exotic Compositional Ordering in Manganese-Nickel-Arsenic (Mn-Ni-As) Intermetallicselectron diffraction; intermetallics; neutron diffraction; solid-state structures1202020#N/ATRUE
4051
anie.20200031810.1002/anie.202000318FALSEhttps://doi.org/10.1002/anie.202000318Gu, JAngew. Chem.-Int. Edit.Closing the anthropogenic carbon cyCle by converting CO(2)into reusable chemicals is an attractive solution to mitigate rising concentrations of CO(2)in the atmosphere. Herein, we prepared Ni metal catalysts ranging in size from single atoms to over 100 nm and distributed them across N-doped carbon substrates which were obtained from converted zeolitic imidazolate frameworks (ZIF). The results show variance in CO(2)reduction performance with variance in Ni metal size. Ni single atoms demonstrate a superior Faradaic efficiency (FE) for CO selectivity (ca. 97 % at -0.8 V vs. RHE), while results for 4.1 nm Ni nanopartiCles are slightly lower (ca. 93 %). Further increase the Ni partiCle size to 37.2 nm allows the H(2)evolution reaction (HER) to compete with the CO(2)reduction reaction (CO2RR). The FE towards CO production decreases to under 30 % and HER efficiency increase to over 70 %. These results show a size-dependent CO(2)reduction for various sizes of Ni metal catalysts.Size-Dependent Nickel-Based Electrocatalysts for Selective CO(2)ReductionCO selectivity; CO(2)reduction; DFT calculations; nickel; size dependencex13202052#N/AFALSE
4052
anie.20200022410.1002/anie.202000224https://doi.org/10.1002/anie.202000224Melchiorre, PAngew. Chem.-Int. Edit.Herein, we report a one-electron strategy for catalytic amide synthesis that enables the direct carbamoylation of (hetero)Aryl bromides. This radical cross-coupling approach, which is based on the combination of nickel and photoredox catalysis, proceeds at ambient temperature and uses readily available dihydropyridines as precursors of carbamoyl radicals. The method's mild reaction conditions make it tolerant of sensitive-functional-group-containing substrates and allow the installation of an amide scaffold within biologically relevant heterocyCles. In addition, we installed amide functionalities bearing electron-poor and sterically hindered amine moieties, which would be difficult to prepare with Classical dehydrative condensation methods.Amide Synthesis by Nickel/Photoredox-Catalyzed Direct Carbamoylation of (Hetero)Aryl Bromidesamides; cross-coupling; nickel catalysis; photoredox catalysis; radical chemistryPhotocatalyst21202056#N/AFALSE
4053
anie.20200498210.1002/anie.202004982FALSEhttps://doi.org/10.1002/anie.202004982Meek, SJAngew. Chem.-Int. Edit.A catalytic method for the site-selective and enantioselective synthesis of functionalized arenes by the intermolecular hydroArylation of terminal and internal 1,3-dienes with Aryl pinacolato boronates is reported. The reactions are promoted by 5.0 mol % of a readily available monodentate phosphoramidite-Ni complex in ethanol, affording a variety of enantioenriched products in up to 96 % yield and 99:1 er. Mechanistic studies indicate that Ni-allyl formation is irreversible and related to the nature of the Arylboronate.Enantioselective Synthesis of Functionalized Arenes by Nickel-Catalyzed Site-Selective HydroArylation of 1,3-Dienes with Aryl BoronatesBoronates; enantioselective; homogeneous catalysis; hydroArylation; nickel15202086#N/ATRUE
4054
anie.20191641910.1002/anie.201916419FALSEhttps://doi.org/10.1002/anie.201916419Chen, YTAngew. Chem.-Int. Edit.A universal nano-capillary based method for sample deposition on the silicon nitride membrane of liquid-cell transmission electron microscopy (LCTEM) chips is demonstrated. It is applicable to all substances which can be dispersed in a solvent and are suitable for drop casting, inCluding catalysts, biological samples, and polymers. Most importantly, this method overcomes limitations concerning sample immobilization due to the fragility of the ultra-thin silicon nitride membrane required for electron transmission. Thus, a straightforward way is presented to widen the research area of LCTEM to encompass any sample which can be externally deposited beforehand. Using this method, NixB nanopartiCles are deposited on the mu m-scale working electrode of the LCTEM chip and in situ observation of single catalyst partiCles during ethanol oxidation is for the first time successfully monitored by means of TEM movies.A Universal Nano-capillary Based Method of Catalyst Immobilization for Liquid-Cell Transmission Electron Microscopyelectrocatalysis; ethanol oxidation; liquid-cell TEM; nano electrochemistry; nickel boridex4202038#N/AFALSE
4055
anie.20191639810.1002/anie.201916398https://doi.org/10.1002/anie.201916398Nocera, DGAngew. Chem.-Int. Edit.Self-sustained Ni-I/III cyCles are established as a potentially general paradigm in photoredox Ni-catalyzed carbon-heteroatom cross-coupling reactions through a strategy that allows us to recapitulate photoredox-like reactivity in the absence of light across a wide range of substrates in the amination, etherification, and esterification of Aryl bromides, the latter of which has remained, hitherto, elusive under thermal Ni catalysis. Moreover, the accessibility of esterification in the absence of light is especially notable because previous mechanistic studies on this transformation under photoredox conditions have unanimously invoked energy-transfer-mediated pathways.General Paradigm in Photoredox Nickel-Catalyzed Cross-Coupling Allows for Light-Free Access to Reactivitycross-coupling; green chemistry; photoredox catalysis; sustainable chemistry; transition metalsPhotocatalyst19202068#N/AFALSE
4056
anie.20200498210.1002/anie.202004982FALSEhttps://doi.org/10.1002/anie.202004982Meek, SJAngew. Chem.-Int. Edit.A catalytic method for the site-selective and enantioselective synthesis of functionalized arenes by the intermolecular hydroArylation of terminal and internal 1,3-dienes with Aryl pinacolato boronates is reported. The reactions are promoted by 5.0 mol % of a readily available monodentate phosphoramidite-Ni complex in ethanol, affording a variety of enantioenriched products in up to 96 % yield and 99:1 er. Mechanistic studies indicate that Ni-allyl formation is irreversible and related to the nature of the Arylboronate.Enantioselective Synthesis of Functionalized Arenes by Nickel-Catalyzed Site-Selective HydroArylation of 1,3-Dienes with Aryl BoronatesBoronates; enantioselective; homogeneous catalysis; hydroArylation; nickel15202086#N/ATRUE
4057
anie.20191631410.1002/anie.201916314FALSEhttps://doi.org/10.1002/anie.201916314Hu, XLAngew. Chem.-Int. Edit.The hydroxide-exchange membrane fuel cell (HEMFC) is a promising energy conversion device. However, the development of HEMFC is hampered by the lack of platinum-group-metal-free (PGM-free) electrocatalysts for the hydrogen oxidation reaction (HOR). Now, a Ni catalyst is reported that exhibits the highest mass activity in HOR for a PGM-free catalyst as well as excellent activity in the hydrogen evolution reaction (HER). This catalyst, Ni-H-2-2 %, was optimized through pyrolysis of a Ni-containing metal-organic framework precursor under a mixed N-2/H-2 atmosphere, which yielded carbon-supported Ni nanopartiCles with different levels of strains. The Ni-H-2-2 % catalyst has an optimal level of strain, which leads to an optimal hydrogen binding energy and a high number of active sites.Efficient Hydrogen Oxidation Catalyzed by Strain-Engineered Nickel NanopartiClesalkaline fuel cells; electrocatalysts; hydrogen evolution reaction; hydrogen oxidation reaction; strain effectx13202042#N/AFALSE
4058
anie.20191603210.1002/anie.201916032FALSEhttps://doi.org/10.1002/anie.201916032Zeng, JAngew. Chem.-Int. Edit.It is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO2 methanation. Now, it is reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO2 methanation. The mass activity of fct-PdFe nanocrystals reached 5.3 mmol g(-1) h(-1), under 1 bar (CO2:H-2=1:4) at 180 degrees C, being 6.6, 1.6, 3.3, and 5.3 times as high as that of fcc-PdFe nanocrystals, Ru/C, Ni/C, and Pd/C, respectively. After 20 rounds of successive reaction, 98 % of the original activity was retained for PdFe intermetallic nanocrystals. Further mechanistic studies revealed that PdFe intermetallic nanocrystals enabled the maintenance of metallic Fe species via a reversible oxidation-reduction process in CO2 methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO2 into CO* as the intermediate, contributing to the enhanced activity.Surface Iron Species in Palladium-Iron Intermetallic Nanocrystals that Promote and Stabilize CO2 MethanationCO2 hydrogenation; intermetallic nanocrystals; iron; palladiumx9202049#N/AFALSE
4059
anie.20191587510.1002/anie.201915875FALSEhttps://doi.org/10.1002/anie.201915875Li, CJAngew. Chem.-Int. Edit.Controlling reaction selectivity is a permanent pursuit for chemists. Regioselective catalysis, which exploits and/or overcomes innate steric and electronic bias to deliver diverse regio-enriched products from the same starting materials, represents a powerful tool for divergent synthesis. Recently, the 1,2-Markovnikov hydroAlkylation of 1,3-dienes with simple hydrazones was reported to generate branched allylic compounds when a nickel catalyst was used. As part of the effort, shown here is that a complete switch of Markovnikov to anti-Markovnikov addition is obtained by changing to a ruthenium catalyst, thus providing direct and efficient access to homoallylic products exClusively. Isotopic substitution experiments indicate that no reversible hydro-metallation across the metal-pi-allyl system occurred under ruthenium catalysis. Moreover, this protocol is applicable to the regiospecific hydroAlkylation of the distal C=C bond of 1,3-enynes.Switch in Selectivity for Formal HydroAlkylation of 1,3-Dienes and Enynes with Simple Hydrazonesdienes; hydrazones; hydroAlkylation; regioselectivity; rutheniumx14202071#N/AFALSE
4060
anie.20200495010.1002/anie.202004950FALSEhttps://doi.org/10.1002/anie.202004950Xie, JA Highly Efficient Dimeric Manganese-Catalyzed Selective HydroArylation of Internal Alkynes2020#N/ATRUE
4061
anie.20200463910.1002/anie.202004639FALSEhttps://doi.org/10.1002/anie.202004639McDonald, ARAngew. Chem.-Int. Edit.In the search for highly reactive oxidants we have identified high-valent metal-fluorides as a potential potent oxidant. The high-valent Ni-F complex [Ni-III(F)(L)] (2, L=N,N '-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate) was prepared from [Ni-II(F)(L)](-) (1) by oxidation with selectfluor. Complexes 1 and 2 were characterized by using H-1/F-19 NMR, UV-vis, and EPR spectroscopies, mass spectrometry, and X-ray crystallography. Complex 2 was found to be a highly reactive oxidant in the oxidation of hydrocarbons. Kinetic data and products analysis demonstrate a hydrogen atom transfer mechanism of oxidation. The rate constant determined for the oxidation of 9,10-dihydroanthracene (k(2)=29 m(-1) s(-1)) compared favorably with the most reactive high-valent metallo-oxidants. Complex 2 displayed reaction rates 2000-4500-fold enhanced with respect to [Ni-III(Cl)(L)] and also displayed high kinetic isotope effect values. Oxidative hydrocarbon and phosphine fluorination was achieved. Our results provide an interesting direction in designing catalysts for hydrocarbon oxidation and fluorinationFast Hydrocarbon Oxidation by a High-Valent Nickel-Fluoride Complexfluorination; high-valent oxidants; metal-oxo species; oxidation catalysis; reactive intermediates42020121#N/ATRUE
4062
anie.20191567110.1002/anie.201915671https://doi.org/10.1002/anie.201915671Wang, LAngew. Chem.-Int. Edit.Increasing long-term photostability of BiVO4 photoelectrode is an important issue for solar water splitting. The NiOOH oxygen evolution catalyst (OEC) has fast water oxidation kinetics compared to the FeOOH OEC. However, it generally shows a lower photoresponse and poor stability because of the more substantial interface recombination at the NiOOH/BiVO4 junction. Herein, we utilize a plasma etching approach to reduce both interface/surface recombination at NiOOH/BiVO4 and NiOOH/electrolyte junctions. Further, adding Fe2+ into the borate buffer electrolyte alleviates the active but unstable character of etched-NiOOH/BiVO4, leading to an outstanding oxygen evolution over 200 h. The improved charge transfer and photostability can be attributed to the active defects and a mixture of NiOOH/NiO/Ni in OEC induced by plasma etching. Metallic Ni acts as the ion source for the in situ generation of the NiFe OEC over long-term durability.Towards Long-Term Photostability of Nickel Hydroxide/BiVO4 Photoanodes for Oxygen Evolution Catalysts via In Situ Catalyst Tuningbismuth vanadate; NiOOH; oxygen evolution; photoelectrochemical catalysis; plasma etchingPhotocatalyst40202033#N/AFALSE
4063
anie.20200231110.1002/anie.202002311FALSEhttps://doi.org/10.1002/anie.202002311Cao, RAngew. Chem.-Int. Edit.Several H-H bond forming pathways have been proposed for the hydrogen evolution reaction (HER). Revealing these HER mechanisms is of fundamental importance for the rational design of catalysts and is also extremely challenging. Now, an unparalleled example of switching between homolytic and heterolytic HER mechanisms is reported. Three nickel(II) porphyrins were designed and synthesized with distinct steric effects by introducing bulky amido moieties to ortho- or para-positions of the meso-phenyl groups. These porphyrins exhibited different catalytic HER behaviors. For these Ni porphyrins, although their 1e-reduced forms are active to reduce trifluoroacetic acid, the resulting Ni hydrides (depending on the steric effects of porphyrin rings) have different pathways to make H-2. Understanding HER processes, especially controllable switching between homolytic and heterolytic H-H bond formation pathways through molecular engineering, is unprecedented in electrocatalysis.Homolytic versus Heterolytic Hydrogen Evolution Reaction Steered by a Steric Effecthomolytic; heterolytic processes; hydrogen evolution; molecular catalysis; nickel porphyrins; steric effect16202071#N/ATRUE
4064
anie.20200214110.1002/anie.202002141FALSEhttps://doi.org/10.1002/anie.202002141Patil, NTAngew. Chem.-Int. Edit.Herein, we disClose the gold-catalyzed 1,2-diArylation of alkenes through the interplay of ligand-enabled Au-I/Au-III catalysis with the idiosyncratic pi-Activation mode of gold complexes. Unlike the Classical migratory-insertion-based approach to 1,2-diArylation, the present approach not only circumvents the formation of direct Ar-Ar ' coupling and Heck-type side products but more intriguingly demonstrates reactivity and selectivity complementary to those of previously known metal catalysis (Pd, Ni, or Cu). Detailed investigations to underpin the mechanistic scenario revealed oxidative addition of Aryl iodides to an Au-I complex to be the rate-limiting step owing to the non-innocent nature of the Aryl alkene.Gold-Catalyzed 1,2-DiArylation of Alkenesalkenes; cross-coupling; 1,2-difunctionalization; gold catalysis; pi-Activation24202090#N/ATRUE
4065
anie.20200114210.1002/anie.202001142FALSEhttps://doi.org/10.1002/anie.202001142Ye, MCAngew. Chem.-Int. Edit.A chiral aluminum complex controlled, enantioselective nickel-catalyzed domino reaction of Aryl nitriles and alkynes proceeding by C-CN bond Activation was developed. The reaction provides various indenes, bearing chiral all-carbon quaternary centers, under mild reaction conditions in yields of 32 to 91 % and ee values within the 73-98 % range. The reaction mechanism and aspects of stereocontrol were investigated by DFT calculations.Chiral Aluminum Complex Controls Enantioselective Nickel-Catalyzed Synthesis of Indenes: C-CN Bond Activationaluminum; cyClization; nickel; reaction mechanisms; synthetic methods152020123#N/ATRUE
4066
anie.20191496710.1002/anie.201914967FALSEhttps://doi.org/10.1002/anie.201914967Qiao, SZAngew. Chem.-Int. Edit.Vacancy engineering is an effective strategy to manipulate the electronic structure of electrocatalysts to improve their performance, but few reports focus on phosphorus vacancies (Pv). Herein, the creation of Pv in metal phosphides and investigation of their role in alkaline electrocatalytic hydrogen evolution reaction (HER) is presented. The Pv-modified catalyst requires a minimum onset potential of 0 mV vs. RHE, a small overpotential of 27.7 mV to achieve 10 mA cm(-2) geometric current density and a Tafel slope of 30.88 mV dec(-1), even outperforms the Pt/C benchmark (32.7 mV@10 mA cm(-2) and 30.90 mV dec(-1)). This catalyst also displays superior stability up to 504 hours without any decay. Experimental analysis and density functional theory calculations suggest Pv can weaken the hybridization of Ni 3d and P 2p orbitals, enrich the electron density of Ni and P atoms nearby Pv, and facilitate H* desorption process, contributing to outstanding HER activity and facile kinetics.Phosphorus Vacancies that Boost Electrocatalytic Hydrogen Evolution by Two Orders of Magnitudedensity functional calculations; electrocatalysis; material science; vacancy engineering; water splitting
Electrocatalytic
50202044#N/AFALSE
4067
anie.20200108310.1002/anie.202001083FALSEhttps://doi.org/10.1002/anie.202108587Dikarev, EVHeterotrimetallic Mixed-Valent Molecular Precursors Containing Periodic Table Neighbors: Assignment of Metal Positions and Oxidation States2020#N/ATRUE
4068
anie.20191474710.1002/anie.201914747https://doi.org/10.1002/anie.201914747Cui, DMAngew. Chem.-Int. Edit.Preparation of polyethylenes containing hydroxy groups has been already industrialized through radical copolymerization under harsh conditions followed by alcoholysis. By contrast, hydroxy-functionalized polypropylene has proven a rather challenging goal in polymer science. Propylene can't be polymerized through a radical mechanism, and its coordination copolymerization with polar monomers is frustrated by catalyst poisoning. Herein, we report a new strategy to reach this target. The coordination polymerization of allenes by rare-earth-metal precursors affords pure 1,2-regulated polyallenes, which are facilely transformed into poly(allyl alcohol) analogues by subsequent hydrB(OH)2ration/oxidation. Strikingly, the copolymerization of allenes and propylene gives unprecedented hydroxy-functionalized polypropylene after post-polymerization modification. Mechanistic elucidation by DFT simulation suggests kinetic rather than thermodynamic control.Access to Hydroxy-Functionalized Polypropylene through Coordination Polymerizationallenes; copolymerization; hydroxylated polypropylenes; polar monomers; rare-earth metalsx7202032#N/AFALSE
4069
anie.20191474210.1002/anie.201914742https://doi.org/10.1002/anie.201914742Harth, EAngew. Chem.-Int. Edit.We present a new strategy to regulate branching in chain-walking olefin polymerization by triggering a rapid isomerization of 1-alkene monomers into internal olefins by adding a Lewis acid. Polymerization of internal alkenes proceeds via chain-walking to give polymers with much higher branching than 1-alkene analogues. The utility of this approach is exemplified by synthesis of well-defined block copolymers with distinct branching characteristics per block by addition of Lewis acid midway through a reaction. We propose a novel mechanism whereby Lewis acid undergoes a counterion swap with the complex which favors isomerization as well as forming adducts with ancillary ligands, freeing coordination sites for internal alkene coordination polymerization.Branching Regulation in Olefin Polymerization via Lewis Acid Triggered Isomerization of Monomersblock copolymers; branching; chain-walking; Lewis acids; olefinsx4202037#N/AFALSE
4070
anie.20191471810.1002/anie.201914718FALSEhttps://doi.org/10.1002/anie.201914718Werncke, CGAngew. Chem.-Int. Edit.The 3d-metal mediated nitrene transfer is under intense scrutiny due to its potential as an atom economic and ecologically benign way for the directed amination of (un)functionalised C-H bonds. Here we present the isolation and characterisation of a rare, trigonal imido cobalt(III) complex, which bears a rather long cobalt-imido bond. It can Cleanly Cleave strong C-H bonds with a bond dissociation energy of up to 92 kcal mol(-1) in an intermolecular fashion, unprecedented for imido cobalt complexes. This resulted in the amido cobalt(II) complex [Co(hmds)(2)((NHBu)-Bu-t)](-). Kinetic studies on this reaction revealed an H atom transfer mechanism. Remarkably, the cobalt(II) amide itself is capable of mediating H atom abstraction or stepwise proton/electron transfer depending on the substrate. A cobalt-mediated catalytic application for substrate dehydrogenation using an organo azide is presented.C-H Bond Activation by an Imido Cobalt(III) and the Resulting Amido Cobalt(II) Complexamido cobalt complex; catalysis; C-H Activation; H atom transfer; imido cobalt complexx12202069#N/AFALSE
4071
anie.20191458710.1002/anie.201914587FALSEhttps://doi.org/10.1002/anie.201914587Yu, CZAngew. Chem.-Int. Edit.Amorphous metal-organic frameworks (aMOFs) are an emerging family of attractive materials with great application potential, however aMOFs are usually prepared under harsh conditions and aMOFs with complex compositions and structures are rarely reported. In this work, an aMOF-dominated nanocomposite (aMOF-NC) with both structural and compositional complexity has been synthesized using a facile approach. A ligand-competition amorphization mechanism is proposed based on experimental and density functional theory calculation results. The aMOF-NC possesses a core-shell nanorod@nanosheet architecture, inCluding a Fe-rich Fe-Co-aMOF core and a Co-rich Fe-Co-aMOF shell in the core-shell structured nanorod, and amorphous Co(OH)(2) nanosheets as the outer layer. Benefiting from the structural and compositional heterogeneity, the aMOF-NC demonstrates an excellent oxygen evolution reaction activity with a low overpotential of 249 mV at 10.0 mA cm(-2) and Tafel slope of 39.5 mV dec(-1).Amorphous Metal-Organic Framework-Dominated Nanocomposites with Both Compositional and Structural Heterogeneity for Oxygen Evolutionamorphization; complex structure; electrocatalysis; heterostructure; metal-organic frameworksx38202063#N/AFALSE
4072
anie.20191456510.1002/anie.201914565https://doi.org/10.1039/b203813gShi, JLElectron Configuration Modulation of Nickel Single Atoms for Elevated Photocatalytic Hydrogen EvolutionPhotocatalyst2020#N/AFALSE
4073
anie.20191454210.1002/anie.201914542FALSEhttps://doi.org/10.1002/anie.201914542Ho, CYAngew. Chem.-Int. Edit.Cross-dimerization of a methylenecyClopropane (1) and an unactivated alkene (2) with typical hydroalkenylation reactivity was observed for the first time by using a [NHC-Ni(allyl)]BArF catalyst (NHC=N-heterocyClic carbene). Results show that the C-C Cleavage of 1 did not involve a Ni-0 oxidative addition, which was crucial in former systems. Thus the method reported here emerges as a complementary method for attaining highly chemo- and regioselective synthesis of methylenecyClopentanes (3) with broad scope. An efficient NHC/Ni-II-catalyzed rearrangement of 1 leads to the convergent synthesis of 3 in the presence of 2.NHC/Nickel(II)-Catalyzed [3+2] Cross-Dimerization of Unactivated Olefins and MethylenecyClopropanesalkenes; hydroalkenylation; insertion; N-heterocyClic carbenes; nickelx4202057#N/AFALSE
4074
anie.20200106710.1002/anie.202001067FALSEhttps://doi.org/10.1002/anie.202001067Tsung, CKAngew. Chem.-Int. Edit.Controlling the surface composition of shaped bimetallic nanopartiCles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanopartiCle was designed, using multilayered Pd-Ni-Pt core-shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanopartiCle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low-temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape-controlled multimetallic nanopartiCles tailored to each potential application.Strain-Enhanced Metallic Intermixing in Shape-Controlled Multilayered Core-Shell Nanostructures: Toward Shaped Intermetallicsmultilayered core-shell nanostructures; shaped intermetallic nanopartiCles; strain-enhanced metallic intermixing6202064#N/ATRUE
4075
anie.20191417510.1002/anie.201914175https://doi.org/10.1002/anie.201914175Mao, JYAngew. Chem.-Int. Edit.A unique nickel/organic photoredox co-catalyzed asymmetric reductive cross-coupling between alpha-chloro esters and Aryl iodides is developed. This cross-electrophile coupling reaction employs an organic reductant (Hantzsch ester), whereas most reductive cross-coupling reactions use stoichiometric metals. A diverse array of valuable alpha-Aryl esters is formed under these conditions with high enantioselectivities (up to 94 %) and good yields (up to 88 %). alpha-Aryl esters represent an important family of nonsteroidal anti-inflammatory drugs. This novel synergistic strategy expands the scope of Ni-catalyzed reductive asymmetric cross-coupling reactions.Nickel/Photoredox-Catalyzed Asymmetric Reductive Cross-Coupling of Racemic alpha-Chloro Esters with Aryl Iodidesasymmetric reductive alpha-Arylation; Carbonylic acids; dual catalysis; nickel; organic photosensitizerPhotocatalyst27202081#N/AFALSE
4076
anie.20191406110.1002/anie.201914061https://doi.org/10.1002/anie.201914061Rueping, MAngew. Chem.-Int. Edit.Alkynes are an important Class of organic molecules due to their utility as versatile building blocks in synthesis. Although efforts have been devoted to the difunctionalization of alkynes, general and practical strategies for the direct hydroAlkylation and AlkylArylation of terminal alkynes under mild reaction conditions are less explored. Herein, we report a photoredox/nickel dual-catalyzed anti-Markovnikov-type hydroAlkylation of terminal alkynes as well as a one-pot ArylAlkylation of alkynes with Alkyl Carbonylic acids and Aryl bromides via a three-component cross-coupling. The results indicate that the transformations proceed via a new mechanism involving a single-electron transfer with subsequent energy-transfer Activation pathways. Moreover, steady-state and time-resolved fluorescence-spectroscopy measurements, density functional theory (DFT) calculations, and wavefunction analysis have been performed to give an insight into the catalytic cyCle.Regioselective HydroAlkylation and ArylAlkylation of Alkynes by Photoredox/Nickel Dual Catalysis: Application and Mechanismalkynes; ArylAlkylation; DFT calculations; hydroAlkylation; nickel; photoredox reactionsPhotocatalyst20202072#N/AFALSE
4077
anie.20200038310.1002/anie.202000383FALSEhttps://doi.org/10.1002/anie.202000383Bandarenka, ASAngew. Chem.-Int. Edit.Herein, we demonstrate an easy way to improve the hydrogen evolution reaction (HER) activity of Pt electrodes in alkaline media by introducing Ni-Fe Clusters. As a result, the overpotential needed to achieve a current density of 10 mA cm(-2) in H-2-saturated 0.1 m KOH is reduced for the model single-crystal electrodes down to about 70 mV. To our knowledge, these modified electrodes outperform any other reported electrocatalysts tested under similar conditions. Moreover, the influence of 1) Ni to Fe ratio, 2) Cluster coverage, and 3) the nature of the alkali-metal cations present in the electrolyte on the HER activity has been investigated. The observed catalytic performance likely originates from both the improved water dissociation at the Ni-Fe Clusters and the subsequent optimal hydrogen adsorption and recombination at Pt atoms present at the Ni-Fe/Pt boundary.Enhancing the Hydrogen Evolution Reaction Activity of Platinum Electrodes in Alkaline Media Using Nickel-Iron Clustersalkaline water electrolysis; electrocatalysis; hydrogen evolution reaction (HER); nickel-iron Clusters; platinum17202026#N/ATRUE
4078
anie.20200032310.1002/anie.202000323FALSEhttps://doi.org/10.1002/anie.202000323Chen, BLAngew. Chem.-Int. Edit.The separation of C2H2/CO2 is particularly challenging owing to their similarities in physical properties and molecular sizes. Reported here is a mixed metal-organic framework (M ' MOF), [Fe(pyz)Ni(CN)(4)] (FeNi-M ' MOF, pyz=pyrazine), with multiple functional sites and compact one-dimensional channels of about 4.0 angstrom for C2H2/CO2 separation. This MOF shows not only a remarkable volumetric C2H2 uptake of 133 cm(3) cm(-3), but also an excellent C2H2/CO2 selectivity of 24 under ambient conditions, resulting in the second highest C2H2-capture amount of 4.54 mol L-1, thus outperforming most previous benchmark materials. The separation performance of this material is driven by pi-pi stacking and multiple intermolecular interactions between C2H2 molecules and the binding sites of FeNi-M ' MOF. This material can be facilely synthesized at room temperature and is water stable, highlighting FeNi-M ' MOF as a promising material for C2H2/CO2 separation.Mixed Metal-Organic Framework with Multiple Binding Sites for Efficient C2H2/CO2 Separationacetylene; adsorption; gas separation; iron; metal-organic frameworks93202053#N/ATRUE
4079
anie.20191386510.1002/anie.201913865FALSEhttps://doi.org/10.1002/anie.201913865Chaudret, BEngineering Iron-Nickel NanopartiCles for Magnetically Induced CO2 Methanation in Continuous Flowx2020#N/AFALSE
4080
anie.20200012410.1002/anie.202000124FALSEhttps://doi.org/10.1002/anie.202000124Engle, KMAngew. Chem.-Int. Edit.We report that Ni(COD)(DQ) (COD=1,5-cyClooctadiene, DQ=duroquinone), an air-stable 18-electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel-catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert-atmosphere glovebox, as demonstrated across several case studies.Ni(COD)(DQ): An Air-Stable 18-Electron Nickel(0)-Olefin Precatalystcross-coupling; homogeneous catalysis; nickel; precatalysts19202042#N/ATRUE
4081
anie.20191370410.1002/anie.201913704FALSEhttps://doi.org/10.1002/anie.201913704Bhattacharyya, SAngew. Chem.-Int. Edit.Five-fold intertwined AgxNi1-x (x=0.01-0.25) heterogeneous alloy nanocrystal (NC) catalysts, prepared through unique reagent combinations, are presented. With only ca. 5 at % Ag (AgNi-5), Pt-like activity has been achieved at pH 14. To reach a current density of 10 mA cm(-2) the extremely stable AgNi-5 requires an overpotential of 24.0 +/- 1.2 mV as compared to 20.1 +/- 0.8 mV for 20 % Pt/C, both with equal catalyst loading of 1.32 mg cm(-2). The turnover frequency (TOF) is as high as 2.1 H-2 s(-1) at 50 mV (vs. RHE). Site-specific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Ag-rich, thereby exposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H-atom adsorption capability of the Ni centers as a function of their proximity to Ag atom.Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum-like Hydrogen Evolution Activitybimetallic catalysts; elemental analyses; heterogeneous catalysis; hydrogen evolution reaction; surfactantsx10202052#N/AFALSE
4082
anie.20191639110.1002/anie.201916391FALSEhttps://doi.org/10.1002/anie.201916391Skrydstrup, TAngew. Chem.-Int. Edit.An extensive range of functionalized aliphatic ketones with good functional-group tolerance has been prepared by a Ni-I-promoted coupling of either primary or secondary Alkyl iodides with NN2 pincer Ni-II-acyl complexes. The latter were easily accessed from the corresponding Ni-II-Alkyl complexes with stoichiometric CO. This Ni-mediated Carbonylative coupling is adaptable to late-stage carbon isotope labeling, as illustrated by the preparation of isotopically labelled pharmaceuticals. Preliminary investigations suggest the intermediacy of carbon-centered radicals.Direct Access to Isotopically Labeled Aliphatic Ketones Mediated by Nickel(I) ActivationCarbonylation; isotope labeling; ketones; ligand effects; nickel7202047#N/ATRUE
4083
anie.20191328410.1002/anie.201913284https://doi.org/10.1002/anie.201913284Lan, YQAngew. Chem.-Int. Edit.A series of stable heterometallic Fe2M Cluster-based MOFs (NNU-31-M, M=Co, Ni, Zn) photocatalysts are presented. They can achieve the overall conversion of CO2 and H2O into HCOOH and O-2 without the assistance of additional sacrificial agent and photosensitizer. The heterometallic Cluster units and photosensitive ligands excited by visible light generate separated electrons and holes. Then, low-valent metal M accepts electrons to reduce CO2, and high-valent Fe uses holes to oxidize H2O. This is the first MOF photocatalyst system to finish artificial photosynthetic full reaction. It is noted that NNU-31-Zn exhibits the highest HCOOH yield of 26.3 mu mol g(-1) h(-1) (selectivity of ca. 100 %). Furthermore, the DFT calculations based on crystal structures demonstrate the photocatalytic reaction mechanism. This work proposes a new strategy for how to design crystalline photocatalyst to realize artificial photosynthetic overall reaction.Stable Heterometallic Cluster-Based Organic Framework Catalysts for Artificial Photosynthesiscarbon dioxide reduction; heterometallic catalysts; metal-organic frameworks; photocatalystsPhotocatalyst43202031#N/AFALSE
4084
anie.20191584010.1002/anie.201915840FALSEhttps://doi.org/10.1002/anie.201915840Zhu, SLAngew. Chem.-Int. Edit.We report a NiH-catalyzed migratory defluorinative coupling between two electronically differentiated olefins. A broad range of unactivated donor olefins can be joined directly to acceptor olefins containing an electron-deficient trifluoromethyl substituent in both intra- and intermolecular fashion to form gem-difluoroalkenes. This migratory coupling shows both site- and chemoselectivity under mild conditions, with the formation of a tertiary or quaternary carbon center.NiH-Catalyzed Migratory Defluorinative Olefin Cross-Coupling: Trifluoromethyl-Substituted Alkenes as Acceptor Olefins to Form gem-DifluoroalkenesC-H Activation; cross-coupling; isomerization; nickel; regioselectivity25202087#N/ATRUE
4085
anie.20191311710.1002/anie.201913117https://doi.org/10.1002/anie.201913117Mecking, SAngew. Chem.-Int. Edit.In various nickel(II) salicylaldiminato ethylene polymerization catalysts, which are a versatile mechanistic probe for substituent effects, longer perfluoroAlkyl groups exert a strong effect on catalytic activities and polymer microstructures compared to the trifluoromethyl group. This effect is accounted for by a reduced electron density on the active sites, and is also supported by electrochemical studies. Thus, beta-hydride elimination, the key step of chain transfer and branching pathways, is disfavored while chain-growth rates are enhanced. This enhancement occurs to an extent that enables living polymerizations in aqueous systems to afford ultra-high-molecular-weight polyethylene for various chelating salicylaldimine motifs. These findings are mechanistically instructive as well as practically useful for illustrating the potential of perfluoroAlkyl groups in catalyst design.Remote PerfluoroAlkyl Substituents are Key to Living Aqueous Ethylene Polymerizationhomogeneous catalysis; fluorine; ligand design; nickel; polymersx18202049#N/AFALSE
4086
anie.20191308810.1002/anie.201913088https://doi.org/10.1002/anie.201913088Chen, ClAngew. Chem.-Int. Edit.Transition metal catalyzed ethylene copolymerization with polar monomers is a highly challenging reaction. After decades of research, the scope of suitable comonomer substrates has expanded from special to fundamental polar monomers and, recently, to 1,1-disubstituted ethylenes. Described in this contribution is a direct and tandem strategy to realize ethylene copolymerization with various 1,2-disubstituted ethylenes. The direct route is sensitive to sterics of both the comonomers and the catalyst. In the tandem route, ruthenium-catalyzed ethenolysis can convert 1,2-disubstituted ethylenes into terminal olefins, which can be subsequently copolymerized with ethylene to afford polar functionalized polyolefins. The one-pot, two-step tandem route is highly versatile and efficient in dealing with challenging substrates. This work is a step forward in terms of expanding the substrate scope for transition metal catalyzed ethylene copolymerization with polar-functionalized comonomers.Direct and Tandem Routes for the Copolymerization of Ethylene with Polar Functionalized Internal Olefinsmetathesis; olefins; palladium; polymerizations; synthetic methodsx39202061#N/AFALSE
4087
anie.20191580310.1002/anie.201915803FALSEhttps://doi.org/10.1002/anie.201915803Hu, XLAngew. Chem.-Int. Edit.Nickel iron oxyhydroxide is the benchmark catalyst for the oxygen evolution reaction (OER) in alkaline medium. Whereas the presence of Fe ions is essential to the high activity, the functions of Fe are currently under debate. Using oxygen isotope labeling and operando Raman spectroscopic experiments, we obtain turnover frequencies (TOFs) of both Ni and Fe sites for a series of Ni and NiFe layered double hydroxides (LDHs), which are structurally defined samples of the corresponding oxyhydroxides. The Fe sites have TOFs 20200 times higher than the Ni sites such that at an Fe content of 4.7% and above the Fe sites dominate the catalysis. Higher Fe contents lead to larger structural disorder of the NiOOH host. A volcano-type correlation was found between the TOFs of Fe sites and the structural disorder of NiOOH. Our work elucidates the origin of the Fe-dependent activity of NiFe LDH, and suggests structural ordering as a strategy to improve OER catalysts.Deciphering Iron-Dependent Activity in Oxygen Evolution Catalyzed by Nickel-Iron Layered Double Hydroxideactive sites; electrocatalysis; nickel iron oxyhydroxide; oxygen evolution reaction; Raman spectroscopy58202053#N/ATRUE
4088
anie.20191306210.1002/anie.201913062FALSEhttps://doi.org/10.1002/anie.201913062Engle, KMAngew. Chem.-Int. Edit.A nickel-catalyzed conjunctive cross-coupling of alkenyl Carbonylic acids, Aryl iodides, and Aryl/alkenyl boronic esters is reported. The reaction delivers the desired 1,2-diArylated and 1,2-Arylalkenylated products with excellent regiocontrol. To demonstrate the synthetic utility of the method, a representative product is prepared on gram scale and then diversified to eight 1,2,3-trifunctionalized building blocks using two-electron and one-electron logic. Using this method, three routes toward bioactive molecules are improved in terms of yield and/or step count. This method represents the first example of catalytic 1,2-diArylation of an alkene directed by a native Carbonylate group.Nickel-Catalyzed 1,2-DiArylation of Alkenyl Carbonylates: A Gateway to 1,2,3-Trifunctionalized Building BlocksCarbonylic acid; diArylation; nickel; trifunctionalizationx24202055#N/AFALSE
4089
anie.20191541810.1002/anie.201915418FALSEhttps://doi.org/10.1002/anie.201915418Rueping, MAngew. Chem.-Int. Edit.The first electrochemical approach for nickel-catalyzed cross-electrophile coupling was developed. This method provides a novel route to 1,1-diArylalkane derivatives from simple and readily available Alkyl and Aryl halides in good yields and excellent regioselectivity under mild conditions. The procedure shows good tolerance for a broad variety of functional groups and both primary and secondary Alkyl halides can be used. Furthermore, the reaction was successfully scaled up to the multigram scale, thus indicating potential for industrial application. Mechanistic investigation suggested the formation of a nickel hydride in the electroreductive chain-walking Arylation, which led to the development of a new nickel-catalyzed hydroArylation of styrenes to provide a series of 1,1-diAryl alkanes in good yields under mild reaction conditions.Nickel-Catalyzed Chain-Walking Cross-Electrophile Coupling of Alkyl and Aryl Halides and Olefin HydroArylation Enabled by Electrochemical Reduction1; 1-diArylalkanes; electrosynthesis; migratory cross-coupling; nickel; beta-hydride elimination38202094#N/ATRUE
4090
anie.20191278510.1002/anie.201912785FALSEhttps://doi.org/10.1002/anie.201912785Wu, YEAngew. Chem.-Int. Edit.A surface digging effect of supported Ni NPs on an amorphous N-doped carbon is described, during which the surface-loaded Ni NPs would etch and sink into the underneath carbon support to prevent sintering. This process is driven by the strong coordination interaction between the surface Ni atoms and N-rich defects. In the aim of Activation of C-H bonds for methane oxidation, those sinking Ni NPs could be further transformed into thermodynamically stable and active metal-defect sites within the as-generated surface holes by simply elevating the temperature. In situ transmission electron microscopy images reveal the sunk Ni NPs dig themselves adaptive surface holes, which would largely prevent the migration of Ni NPs without weakening their accessibility. The reported two-step strategy opens up a new route to manufacture sintering-resistant supported metal catalysts without degrading their catalytic efficiency.A Supported Nickel Catalyst Stabilized by a Surface Digging Effect for Efficient Methane Oxidationdigging effect; metal defect sites; methane oxidation; nickel; thermodynamic stabilityx20201927#N/AFALSE
4091
anie.20191538610.1002/anie.201915386FALSEhttps://doi.org/10.1002/anie.201915386Beller, MAngew. Chem.-Int. Edit.For the first time, the monoalkoxyCarbonylation of easily available 1,3-diynes to give synthetically useful conjugated enynes has been realized. Key to success was the design and utilization of the new ligand 2,2 '-bis(tert-butyl(pyridin-2-yl)phosphanyl)-1,1 '-binaphthalene (Neolephos), which permits the palladium-catalyzed selective Carbonylation under mild conditions, providing a general preparation of functionalized 1,3-enynes in good-to-high yields with excellent chemoselectivities. Synthetic applications that showcase the possibilities of this novel methodology inClude an efficient one-pot synthesis of 4-Aryl-4H-pyrans as well as the rapid construction of various heterocyClic, bicyClic, and polycyClic compounds.Tailored Palladium Catalysts for Selective Synthesis of Conjugated Enynes by MonoCarbonylation of 1,3-Diynes102020128#N/ATRUE
4092
anie.20191274510.1002/anie.201912745FALSEhttps://doi.org/10.1002/anie.202103686Meyer, FAn Adaptable N-HeterocyClic Carbene MacrocyCle Hosting Copper in Three Oxidation Statesx2020#N/AFALSE
4093
anie.20191271910.1002/anie.201912719FALSEhttps://doi.org/10.1002/anie.201912719Chen, JGGAngew. Chem.-Int. Edit.The electrochemical CO2 reduction reaction (CO2RR) to yield synthesis gas (syngas, CO and H-2) has been considered as a promising method to realize the net reduction in CO2 emission. However, it is challenging to balance the CO2RR activity and the CO/H-2 ratio. To address this issue, nitrogen-doped carbon supported single-atom catalysts are designed as electrocatalysts to produce syngas from CO2RR. While Co and Ni single-atom catalysts are selective in producing H-2 and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm(-2)) with CO/H-2 ratios (0.23-2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single-atom configurations for the H-2 and CO evolution. The results present a useful case on how non-precious transition metal species can maintain high CO2RR activity with tunable CO/H-2 ratios.Electrochemical Conversion of CO2 to Syngas with Controllable CO/H-2 Ratios over Co and Ni Single-Atom CatalystsCO2 electroreduction; density functional theory; high activity; selectivity control; syngas productionx49202030#N/AFALSE
4094
anie.20191497710.1002/anie.201914977FALSEhttps://doi.org/10.1002/anie.201914977Jiang, HLAngew. Chem.-Int. Edit.The general synthesis and control of the coordination environment of single-atom catalysts (SACs) remains a great challenge. Herein, a general host-guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal-organic framework. As an example, the introduction of Mg2+ in MgNi-MOF-74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single-atom Ni catalysts (named Ni-SA-N-x-C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the Ni-SA-N-2-C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h(-1)), far superior to those of Ni-SA-N-3-C and Ni-SA-N-4-C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single-atom Ni sites in Ni-SA-N-2-C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.Regulating the Coordination Environment of MOF-Templated Single-Atom Nickel Electrocatalysts for Boosting CO2 ReductionCO2 electroreduction; coordination environment; metal-organic frameworks; single-atom catalysts130202059#N/ATRUE
4095
anie.20191495010.1002/anie.201914950FALSEhttps://doi.org/10.1002/anie.201914950Weckhuysen, BMAngew. Chem.-Int. Edit.Ni contamination from crude oil in the fluid catalytic cracking (FCC) process is one of the primary sources of catalyst deActivation, thereby promoting dehydrogenation-hydrogenation and speeding up coke growth. Herein, single-partiCle X-ray fluorescence, diffraction and absorption (mu XRF-mu XRD-mu XAS) tomography is used in combination with confocal fluorescence microscopy (CFM) after thiophene staining to spatially resolve Ni interaction with catalyst components and study zeolite degradation, inCluding the processes of dealumination and Bronsted acid sites distribution changes. The comparison between a Ni-lean partiCle, exposed to hydrotreated feedstock, and a Ni-rich one, exposed to non-hydrotreated feedstock, reveals a preferential interaction of Ni, found in co-localization with Fe, with the gamma-Al2O3 matrix, leading to the formation of spinel-type hotspots. Although both partiCles show similar surface zeolite degradation, the Ni-rich partiCle displays higher dealumination and a Clear Bronsted acidity drop.Nickel Poisoning of a Cracking Catalyst Unravelled by Single-PartiCle X-ray Fluorescence-Diffraction-Absorption Tomographycatalyst deActivation; fluid catalytic cracking (FCC); heterogeneous catalysis; X-ray microscopy; zeolites11202050#N/ATRUE
4096
anie.20191255210.1002/anie.201912552https://doi.org/10.1002/anie.201912552Xu, RAngew. Chem.-Int. Edit.A simple solvent ligation effect was successfully used to disrupt the growth of a model compound, Fe[(OH)(O3P(CH2)(2)CO2H)]center dot H2O (MIL-37), into an extended 2D structure by replacing water with dimethylformamide (DMF) as the solvent during the synthesis. Owing to the lack of -OH group, which provides the corner-sharing (binding) oxygen atoms for the octahedra, an amorphous and porous structure is formed. When Fe3+ is partially replaced by Ni2+, the amorphous structure remains and the resultant binary metal catalyst displays excellent photocatalytic oxygen evolution activity with almost 100 % yield achieved under visible light irradiation using [Ru(bpy)(3)](2+) as the photosensitizer. This study opens up new possibilities of using the simple solvent effect to synthesize high surface area metal phosphonates for catalytic and other applications.Rational Synthesis of Amorphous Iron-Nickel Phosphonates for Highly Efficient Photocatalytic Water Oxidation with Almost 100 % Yieldiron; nickel; phosphonates; photocatalysis; water oxidationPhotocatalyst12202058#N/AFALSE
4097
anie.20191245810.1002/anie.201912458FALSEhttps://doi.org/10.1002/anie.201912458Lu, TBAngew. Chem.-Int. Edit.The reaction of precursors containing both nitrogen and oxygen atoms with Ni-II under 500 degrees C can generate a N/O mixing coordinated Ni-N3O single-atom catalyst (SAC) in which the oxygen atom can be gradually removed under high temperature due to the weaker Ni-O interaction, resulting in a vacancy-defect Ni-N-3-V SAC at Ni site under 800 degrees C. For the reaction of Ni-II with the precursor simply containing nitrogen atoms, only a no-vacancy-defect Ni-N-4 SAC was obtained. Experimental and DFT calculations reveal that the presence of a vacancy-defect in Ni-N-3-V SAC can dramatically boost the electrocatalytic activity for CO2 reduction, with extremely high CO2 reduction current density of 65 mA cm(-2) and high Faradaic efficiency over 90 % at -0.9 V vs. RHE, as well as a record high turnover frequency of 1.35x10(5) h(-1), much higher than those of Ni-N-4 SAC, and being one of the best reported electrocatalysts for CO2-to-CO conversion to date.Controlled Synthesis of a Vacancy-Defect Single-Atom Catalyst for Boosting CO2 ElectroreductionCO2 reduction; electrocatalysis; nickel; single atom catalysts; vacancy defectsx66202047#N/AFALSE
4098
anie.20191448010.1002/anie.201914480FALSEhttps://doi.org/10.1002/anie.201914480Osuka, AAngew. Chem.-Int. Edit.2,18-Bis(dicyanomethyl)-substituted Ni-II porphyrin 8 and Zn-II porphyrin 11 were prepared and subjected to oxidation with PbO2 in CH2Cl2 at 298 K to give cyClophane-type chlorin dimers (9)(2) and (12)(2) as a consequence of double recombination of biradicals 9 and 12, respectively. Dimer (9)(2) takes a syn-conformation of two distorted Ni-II chlorins but (12)(2) takes an anti-conformation of relatively planar Zn-II chlorins. At 298 K, dimer (9)(2) is stable and its H-1 NMR spectrum is sharp but becomes broad at high temperature, while the H-1 NMR spectrum of (12)(2) is considerably broad even at 298 K but becomes sharper at low temperature. These results indicate that the chlorin dimers dissociate to radical species, but the Activation barrier of the dissociation of (12)(2) is much less than that of (9)(2). The involvement of diradicals in dynamic covalent chemistry has been suggested by thermal scrambling of hetero dimer (16)(2) to give homo dimers (9)(2) and (15)(2).CyClophane-Type Chlorin Dimers from Dynamic Covalent Chemistry of 2,18-Porphyrinyl Dicyanomethyl Diradicalschlorin; cyClophane dimers; dicyanomethyl radical; dynamic covalent bonds; porphyrin1202037#N/ATRUE
4099
anie.20191199510.1002/anie.201911995FALSEhttps://doi.org/10.1002/anie.201911995Liu, BAngew. Chem.-Int. Edit.Designing effective electrocatalysts for the carbon dioxide reduction reaction (CO2RR) is an appealing approach to tackling the challenges posed by rising CO2 levels and realizing a Closed carbon cyCle. However, fundamental understanding of the complicated CO2RR mechanism in CO2 electrocatalysis is still lacking because model systems are limited. We have designed a model nickel single-atom catalyst (Ni SAC) with a uniform structure and well-defined Ni-N-4 moiety on a conductive carbon support with which to explore the electrochemical CO2RR. Operando X-ray absorption nearedge structure spectroscopy, Raman spectroscopy, and near-ambient X-ray photoelectron spectroscopy, revealed that Ni+ in the Ni SAC was highly active for CO2 Activation, and functioned as an authentic catalytically active site for the CO2RR. Furthermore, through combination with a kinetics study, the rate-determining step of the CO2RR was determined to be *CO2- + H+->*COOH. This study tackles the four challenges faced by the CO2RR; namely, activity, selectivity, stability, and dynamics.Elucidating the Electrocatalytic CO2 Reduction Reaction over a Model Single-Atom Nickel CatalystActive site; Electrochemistry; In situ reactions; Reaction mechanisms; Single-atom catalysts
Electrocatalytic
94202058#N/AFALSE
4100
anie.20191395110.1002/anie.201913951FALSEhttps://doi.org/10.1002/anie.201913951Hayward, MAAngew. Chem.-Int. Edit.Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion-exchange) is extremely challenging as these low-temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition-metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4-xNiRuO8 0.5<xx Sr4-xNiRuO4H4 phases. This is particularly noteworthy as the (Ni/Ru)H-2 sheets in the LaxSr4-xNiRuO4H4 phases are structurally analogous to the CuO2 sheets in cuprate superconductors and hole doping (Ni1+/2+, Ru2+) or electron doping (Ni2+, Ru1+/2+) yields materials with partial occupancy in Ni/Ru 3d/4dx2-y2-H 1s bands which are analogous to the partially occupied Cu 3dx2-y2-O 2p bands present in the CuO2 sheets of doped superconducting cuprates.Hole and Electron Doping of the 4d Transition-Metal Oxyhydride LaSr3NiRuO4H4anion-exchange reactions; solid-state reactions; topochemistry; transition-metal oxyhydrides; transition metals1202029#N/ATRUE
4101
anie.20191166010.1002/anie.201911660FALSEhttps://doi.org/10.1002/anie.201911660Rueping, MReviewDoes not have Nickel or CN keyword#N/AFALSE
4102
anie.20191391010.1002/anie.201913910FALSEhttps://doi.org/10.1002/anie.202107587Lu, SYA General Route to Prepare Low-Ruthenium-Content Bimetallic Electrocatalysts for pH-Universal Hydrogen Evolution Reaction by Using Carbon Quantum Dots2020#N/ATRUE
4103
anie.20191383510.1002/anie.201913835FALSEhttps://doi.org/10.1002/anie.201913835Mashima, KAngew. Chem.-Int. Edit.A highly E-selective cross-dimerization of terminal alkynes with either terminal silylacetylenes, tert-butylacetylene, or 1-trimethylsilyloxy-1,1-diphenyl-2-propyne in the presence of a dichlorocobalt(II) complex bearing a sterically demanding 2,9-bis(2,4,6-triisopropylphenyl)-1,10-phenanthroline, activated with two equivalents of EtMgX, gives a variety of (E)-1,3-enynes. A well-characterized diolefin/cobalt(0) complex, with diVinyltetramethyldisiloxane, acted as a catalytically active species without any Activation, Clearly indicating that a cobalt(0) species is involved in the catalytic cyCle.Cobalt-Catalyzed E-Selective Cross-Dimerization of Terminal Alkynes: A Mechanism Involving Cobalt(0/II) Redox CyClesalkynes; cobalt; dimerization; enynes; reaction mechanisms19202066#N/ATRUE
4104
anie.20191343510.1002/anie.201913435FALSEhttps://doi.org/10.1002/anie.201913435Giri, RAngew. Chem.-Int. Edit.We report a Ni-catalyzed regioselective alpha-CarbonylAlkylArylation of Vinylarenes with alpha-haloCarbonyl compounds and Arylzinc reagents. The reaction works with primary, secondary, and tertiary alpha-haloCarbonyl molecules, and electronically varied Arylzinc reagents. The reaction generates gamma,gamma-diArylCarbonyl derivatives with alpha-secondary, tertiary, and quaternary carbon centers. The products can be readily converted to Aryltetralones, inCluding a precursor to Zoloft, an antidepressant drug.Nickel-Catalyzed alpha-CarbonylAlkylArylation of Vinylarenes: Expedient Access to gamma,gamma-DiArylCarbonyl and Aryltetralone DerivativesAryltetralones; diArylCarbonyl compounds; dicarbofunctionalization; nickel catalysis; Vinylarenes13202073#N/ATRUE
4105
anie.20191087910.1002/anie.201910879FALSEhttps://doi.org/10.1002/anie.201910879Peng, YAngew. Chem.-Int. Edit.Reversible oxygen conversion is important for various green energy technologies. Herein we synthesize a series of bimetallic coordination polymers by varying the Ni/Co ratio and using HITP (HITP=2,3,6,7,10,11-hexaiminotriphenylene) as the ligand, to interrogate the role of metal centres in modulating the activity of the oxygen reduction reaction (ORR). Co3HITP2 and Ni3HITP2 are compared. Unpaired 3d electrons in Co3HITP2 result in less coplanarity but more radical character. Thus, despite of a reduced crystallinity and conductivity, the best ORR activity, comparable to 20 % Pt/C, is obtained for Co3HITP2, showing the 3d orbital configuration of the metal centre promotes ORR. Experimental and DFT studies show a transition of ORR pathway from four-electron for Co3HITP2 to two-electron for Ni3HITP2. Rechargeable zinc-air batteries using Co3HITP2 as the air cathode catalyst demonstrate excellent energy efficiency and stability.Unpaired 3d Electrons on Atomically Dispersed Cobalt Centres in Coordination Polymers Regulate both Oxygen Reduction Reaction (ORR) Activity and Selectivity for use in Zinc-Air Batteries3d orbital configuration; coordination polymers; oxygen reduction reaction (ORR); flexible electronics; zinc-air batteryx67202085#N/AFALSE
4106
anie.20191071610.1002/anie.201910716FALSEhttps://doi.org/10.1002/anie.201910716Xiong, JAngew. Chem.-Int. Edit.The oxygen evolution reaction (OER) has been explored extensively for reliable hydrogen supply to boost the energy conversion efficiency. The superior OER performance of newly developed non-noble metal electrocatalysts has concealed the identification of the real active species of the catalysts. Now, the critical active phase in nickel-based materials (represented by NiNPS) was directly identified by observing the dynamic surface reconstruction during the harsh OER process via combining insitu Raman tracking and exsitu microscopy and spectroscopy analyses. The irreversible phase transformation from NiNPS to alpha-Ni(OH)(2) and reversible phase transition between alpha-Ni(OH)(2) and gamma-NiOOH prior to OER demonstrate gamma-NiOOH as the key active species for OER. The hybrid catalyst exhibits 48-fold enhanced catalytic current at 300mV and remarkably reduced Tafel slope to 46mVdec(-1), indicating the greatly accelerated catalytic kinetics after surface evolution.Identification of Key Reversible Intermediates in Self-Reconstructed Nickel-Based Hybrid Electrocatalysts for Oxygen Evolutionin situ Raman tracking; oxygen evolution; oxyhydroxide intermediate; pre-catalysts; surface reconstructionx53201945#N/AFALSE
4107
anie.20191050510.1002/anie.201910505FALSEhttps://doi.org/10.1002/anie.201910505Wolf, RAngew. Chem.-Int. Edit.While tetrahedranes as a family are scarce, neutral heteroatomic species are all but unknown, with the only reported example being AsP3. Herein, we describe the isolation of a neutral heteroatomic X2Y2 molecular tetrahedron (X, Y=p-block elements), which also is the long-sought-after free phosphaalkyne dimer. Di-tert-butyldiphosphatetrahedrane, (tBuCP)(2), is formed from the monomer tBuCP in a nickel-catalyzed dimerization reaction using [(NHC)Ni(CO)(3)] (NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (IPr)). Single-crystal X-ray structure determination of a silver(I) complex confirms the structure of (tBuCP)(2). The influence of the N-heterocyClic carbene ligand on the catalytic reaction was investigated, and a mechanism was elucidated using a combination of synthetic and kinetic studies and quantum chemical calculations.Di-tert-butyldiphosphatetrahedrane: Catalytic Synthesis of the Elusive Phosphaalkyne Dimerdimerization; homogeneous catalysis; nickel; phosphaalkynes; phosphorusx12201958#N/AFALSE
4108
anie.20191049010.1002/anie.201910490FALSEhttps://doi.org/10.1002/anie.201910490Hu, XLAngew. Chem.-Int. Edit.A novel nickel pincer cofactor was recently discovered in lactate racemase. Reported here are three synthetic nickel pincer complexes that are both structural and functional models of the pincer cofactor in lactate racemase. DFT computations suggest the ipso-carbon atom of the pyridinium pincer ligands act as a hydride acceptor for lactate isomerization, whereas an organometallic pathway involving nickel-mediated beta-hydride elimination is less favored.Functional Models of the Nickel Pincer NuCleotide Cofactor of Lactate Racemasecofactors; enzymes; nickel; pincer ligands; reaction mechanismsx4201936#N/AFALSE
4109
anie.20191043610.1002/anie.201910436FALSEhttps://doi.org/10.1002/anie.201910436Morandi, BAngew. Chem.-Int. Edit.A nickel-catalyzed Aryl thioether metathesis has been developed to access high-value thioethers. 1,2-Bis(dicyClohexylphosphino)ethane (dcype) is essential to promote this highly functional-group-tolerant reaction. Furthermore, synthetically challenging macrocyCles could be obtained in good yield in an unusual example of ring-Closing metathesis that does not involve alkene bonds. In-depth organometallic studies support a reversible Ni-0/Ni-II pathway to product formation. Overall, this work not only provides a more sustainable alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information that are highly relevant to the further development and application of unusual single-bond metathesis reactions.Nickel-Catalyzed Inter- and Intramolecular Aryl Thioether Metathesis by Reversible ArylationmacrocyCles; reaction mechanisms; metathesis; nickel; thioethersx16202059#N/AFALSE
4110
anie.20191041410.1002/anie.201910414https://doi.org/10.1002/anie.201910414Wu, JAngew. Chem.-Int. Edit.Enantioenriched 1,4-diCarbonyl compounds are versatile synthons in natural product and pharmaceutical drug synthesis. We herein report a mild pathway for the efficient enantioselective synthesis of these compounds directly from aldehydes through synergistic cooperation between a neutral eosinY hydrogen atom transfer photocatalyst and a chiral rhodium Lewis acid catalyst. This method is distinguished by its operational simplicity, abundant feedstocks, atom economy, and ability to generate products in high yields (up to 99%) and high enantioselectivity (up to 99% ee).Asymmetric Synthesis of 1,4-DiCarbonyl Compounds from Aldehydes by Hydrogen Atom Transfer Photocatalysis and Chiral Lewis Acid CatalysisPhotocatalyst32201959#N/AFALSE
4111
anie.20191019710.1002/anie.201910197FALSEhttps://doi.org/10.1002/anie.201910197Takaya, JAngew. Chem.-Int. Edit.Rhodium complexes with an indium metalloligand were successfully synthesized by utilizing a pyridine-tethered cyClopentadienyl ligand as a support for an In-Rh bond. The indium metalloligand dramatically changes the electronic and redox properties of the rhodium metal, thereby enabling catalysis of sp(2)C-H bond Activation.Rhodium-Catalyzed C-H Activation Enabled by an Indium MetalloligandC-H Activation; indium; metalloligands; rhodium; Z-type ligandsx8201952#N/AFALSE
4112
anie.20191016810.1002/anie.201910168https://doi.org/10.1002/anie.201910168Melchiorre, PAngew. Chem.-Int. Edit.Photochemical enantioselective nickel-catalyzed cross-coupling reactions are difficult to implement. We report a visible-light-mediated strategy that successfully couples symmetrical anhydrides and 4-Alkyl dihydropyridines (DHPs) to afford enantioenriched alpha-substituted ketones under mild conditions. The chemistry does not require exogenous photocatalysts. It is triggered by the direct excitation of DHPs, which act as a radical source and as a reductant, facilitating the turnover of the chiral catalytic nickel complex.Photochemical Asymmetric Nickel-Catalyzed Acyl Cross-Couplingasymmetric catalysis; cross-coupling; nickel catalysis; photochemistry; radical chemistryPhotocatalyst282019876/1/2022FALSE
4113
anie.20191000210.1002/anie.201910002https://doi.org/10.1002/anie.201910002Chen, ClAngew. Chem.-Int. Edit.The nonpolar nature of polyolefins is one of their biggest limitations. Now, an efficient route to generate polar-functionalized, crosslinkable, self-healing, photoresponsive polyolefins with thermoplastic, elastomeric, and thermosetting properties is reported. Tunable amounts of Carbonylic acid and a cyClic comonomer are installed onto polyolefins by palladium-catalyzed terpolymerization reactions. The incorporated Carbonylic acid unit can alter the surface properties of polyolefins. The subsequently introduced Fe3+/citric acid combination induces dynamic crosslinking and enables self-healing. Under UV light irradiation, citric acid reduces Fe3+ to Fe2+ and decreases the crosslinking density. The Fe2+ moiety can be easily oxidized back to Fe3+, making the process reversible at the expense of citric acid. The incorporated cyClic comonomer modulates the crystallinity of polyolefins, provides elastic properties, and installs carbon-carbon double bonds for sulfur-induced vulcanization.Polar-Functionalized, Crosslinkable, Self-Healing, and Photoresponsive Polyolefinsphotoresponsive materials; polar functionalization; polyolefins; recyCling; self-healingPhotocatalystx46202065#N/AFALSE
4114
anie.20191325910.1002/anie.201913259FALSEhttps://doi.org/10.1002/anie.201913259Darensbourg, MYMetal-Templated, Tight Loop Conformation of a Cys-X-Cys Biomimetic Assembles a Dimanganese Complex2020#N/ATRUE
4115
anie.20191308010.1002/anie.201913080FALSEhttps://doi.org/10.1002/anie.201913080Zou, JJAngew. Chem.-Int. Edit.Ferric oxides and (oxy)hydroxides, although plentiful and low-cost, are rarely considered for oxygen evolution reaction (OER) owing to the too high spin state (e(g) filling ca. 2.0) suppressing the bonding strength with reaction intermediates. Now, a facile adsorption-oxidation strategy is used to anchor Fe-III atomically on an ultrathin TiO2 nanobelt to synergistically lower the spin state (e(g) filling ca. 1.08) to enhance the adsorption with oxygen-containing intermediates and improve the electro-conductibility for lower ohmic loss. The electronic structure of the catalyst is predicted by DFT calculation and perfectly confirmed by experimental results. The catalyst exhibits superior performance for OER with overpotential 270 mV @10 mA cm(-2) and 376 mV @100 mA cm(-2) in alkaline solution, which is much better than IrO2/C and RuO2/C and is the best iron-based OER catalyst free of active metals such as Ni, Co, or precious metals.Regulating the Spin State of Fe-III by Atomically Anchoring on Ultrathin Titanium Dioxide for Efficient Oxygen Evolution Electrocatalysiselectrocatalysis; iron; oxygen evolution reaction; spin states; titanium dioxide47202038#N/ATRUE
4116
anie.20190970710.1002/anie.201909707https://doi.org/10.1002/anie.201909707Lou, XWDispersed Nickel Cobalt Oxyphosphide NanopartiCles Confined in Multichannel Hollow Carbon Fibers for Photocatalytic CO2 ReductionPhotocatalystx2019#N/AFALSE
4117
anie.20191285710.1002/anie.201912857FALSEJaramillo, TFUnderstanding the Origin of Highly Selective CO2 Electroreduction to CO on Ni,N-doped Carbon Catalysts2020#N/ATRUE
4118
anie.20190963810.1002/anie.201909638FALSEhttps://doi.org/10.1002/anie.202100631Zhao, BRedox-State-Mediated Regulation of Cytochrome c Release in Apoptosis Revealed by Surface-Enhanced Raman Scattering on Nickel Substratesx2019#N/AFALSE
4119
anie.20191275310.1002/anie.201912753TRUEhttps://doi.org/10.1002/anie.201912753Mei, TSAngew. Chem.-Int. Edit.A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an Aryl halide and an Alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1-diArylalkanes.Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halidesarenes; cross-coupling; electrochemistry; nickel; reaction mechanismsCsp2_ar-Csp3XXXArylNo baseNo Base442020887/28/2022TRUE
4120
anie.20190907210.1002/anie.201909072https://doi.org/10.1002/anie.201909072MacMillan, DWCAngew. Chem.-Int. Edit.Here, we demonstrate that a metallaphotoredox-catalyzed cross-electrophile coupling mechanism provides a unified method for the alpha-Arylation of diverse activated Alkyl chlorides, inCluding alpha-chloroketones, alpha-chloroesters, alpha-chloroamides, alpha-chloroCarbonylic acids, and Benzylic chlorides. This strategy, which is effective for a wide variety of Aryl bromide coupling partners, is predicated upon a halogen atom abstraction/nickel radical-capture mechanism that is generically successful across an extensive range of Carbonyl substrates. The construction and use of Arylacetic acid products have further enabled two-step protocols for the delivery of valuable building blocks for medicinal chemistry, such as Aryldifluoromethyl and diArylmethane motifs.A Metallaphotoredox Strategy for the Cross-Electrophile Coupling of alpha-Chloro Carbonyls with Aryl HalidesCarbonylic acids; heterocyCles; nickel; photocatalysis; alpha-ArylationPhotocatalyst16201943#N/AFALSE
4121
anie.20191262910.1002/anie.201912629FALSEhttps://doi.org/10.1002/anie.201912629Hu, XLAngew. Chem.-Int. Edit.Nickel hydride (NiH) catalyzed hydrocarbonation has emerged as an efficient approach to construct new C-C bonds containing at least one C(sp(3)) center. However, the regioselectivity of this reaction is by far dictated by substrates. Described here is a strategy to achieve two different regioselectivites of hydroAlkylation of the same substrates by using ligand control. This strategy enables the first regiodivergent hydroAlkylation of 3-pyrrolines, yielding both 2- and 3-Alkylated pyrrolidines, valuable synthetic intermediates and common motifs in many bioactive molecules. This method demonstrates broad scope and high functional-group tolerance, and can be applied in late-stage functionalizations.Ligand-Controlled Regiodivergent HydroAlkylation of Pyrrolinesalkenes; heterocyCles; hydroAlkylation; nickel; reaction mechanisms24201970#N/ATRUE
4122
anie.20191258010.1002/anie.201912580FALSEhttps://doi.org/10.1002/anie.201912580Yan, NAngew. Chem.-Int. Edit.Chemical synthesis of amino acids directly from biomass feedstock is rare. Reported here is a one-step protocol to convert crude glycerol, from the biodiesel industry, into 43 % alanine over a Ru1Ni7/MgO catalyst. The multifunctional catalytic system promotes glycerol conversion into lactic acid, and then into alanine. X-ray absorption spectroscopy and scanning transmission electron microscopy revealed the existence of bimetallic RuNi species, whereas density-functional theory calculations suggested Ni-doped Ru substantially decreased the E-a of C-H bond dissociation of lactate alkoxide to form pyruvate, which is the rate-determining step. The catalytic route established in this work creates new opportunities for glycerol utilization and enriches the substrate scope of renewable feedstock to access value-added amino acids.Catalytic Production of Alanine from Waste Glycerolamino acids; biomass; glycerol; heterogeneous catalysis; surface chemistry22202039#N/ATRUE
4123
anie.20190872210.1002/anie.201908722FALSEhttps://doi.org/10.1002/anie.201908722Wang, SYAngew. Chem.-Int. Edit.2,5-FurandiCarbonylic acid was obtained from the electrooxidation of 5-hydroxymethylfurfural (HMF) with non-noble metal-based catalysts. Moreover, combining the biomass oxidation with the hydrogen evolution reaction (HER) increased the energy conversion efficiency of an electrolyzer and also generated value-added products at both electrodes. Here, the reaction pathway on the surface of a carbon-coupled nickel nitride nanosheet (Ni3N@C) electrode was evaluated by surface-selective vibrational spectroscopy using sum frequency generation (SFG) during the electrochemical oxidation. The Ni3N@C electrode shows catalytic activities for HMF oxidation and the HER. As the first in situ SFG study on transition-metal nitride for the electrooxidation upgrade of HMF, this work not only demonstrates that the reaction pathway of electrochemical oxidation but also provides an opportunity for nonprecious metal nitrides to simultaneously upgrade biomass and produce H-2 under ambient conditions.Electrochemical Oxidation of 5-Hydroxymethylfurfural on Nickel Nitride/Carbon Nanosheets: Reaction Pathway Determined by In Situ Sum Frequency Generation Vibrational Spectroscopybiomass; electrocatalysis; reaction mechanisms; surface chemistry; vibrational spectroscopyx66201942#N/AFALSE
4124
anie.20190827410.1002/anie.201908274FALSEhttps://doi.org/10.1002/anie.201908274Hu, WPAngew. Chem.-Int. Edit.pi-d Conjugated coordination polymers (CCPs) have attracted much attention for various applications, although the chemical states and structures of many CCPs are still blurry. Now, a one-dimensional (1D) pi-d conjugated coordination polymer for high performance sodium-ion batteries is presented. The chemical states of the obtained coordination polymer are Clearly revealed. The electrochemical process undergoes a three-electron reaction and the structure transforms from C=N double bonds and Ni-II to C-N single bonds and Ni-I, respectively. Our unintentional experiments provided visual confirmation of Ni-I. The existence of Ni-I was further corrB(OH)2rated by its X-ray absorption near-edge structure (XANES) and its catalytic activity in Negishi cross-coupling.A One-Dimensional pi-d Conjugated Coordination Polymer for Sodium Storage with Catalytic Activity in Negishi CouplingNegishi cross-coupling; organic sodium-ion batteries; pi-d conjugated coordination polymers; single-atom catalystsx43201985#N/AFALSE
4125
anie.20190825810.1002/anie.201908258FALSEhttps://doi.org/10.1002/anie.201908258Dobbek, HAngew. Chem.-Int. Edit.[NiFe] hydrogenases are complex model enzymes for the reversible Cleavage of dihydrogen (H-2). However, structural determinants of efficient H-2 binding to their [NiFe] active site are not properly understood. Here, we present crystallographic and vibrational-spectroscopic insights into the unexplored structure of the H-2-binding [NiFe] intermediate. Using an F-420-reducing [NiFe]-hydrogenase from Methanosarcina barkeri as a model enzyme, we show that the protein backbone provides a strained chelating scaffold that tunes the [NiFe] active site for efficient H-2 binding and conversion. The protein matrix also directs H-2 diffusion to the [NiFe] site via two gas channels and allows the distribution of electrons between functional protomers through a subunit-bridging FeS Cluster. Our findings emphasize the relevance of an atypical Ni coordination, thereby providing a blueprint for the design of bio-inspired H-2-conversion catalysts.X-ray Crystallography and Vibrational Spectroscopy Reveal the Key Determinants of Biocatalytic Dihydrogen CyCling by [NiFe] Hydrogenasesbiocatalysis; crystal structure; hydrogen Activation; [NiFe] hydrogenase; vibrational spectroscopyx11201947#N/AFALSE
4126
anie.20190819410.1002/anie.201908194FALSEhttps://doi.org/10.1002/anie.201908194Luo, WAngew. Chem.-Int. Edit.The search for highly efficient platinum group metal (PGM)-free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline electrolytes remains a great challenge in the development of alkaline exchange membrane fuel cells (AEMFCs). Here we report the synthesis of an oxygen-vacancy-rich CeO2/Ni heterostructure and its remarkable HOR performance in alkaline media. Experimental results and density functional theory (DFT) calculations indicate the electron transfer between CeO2 and Ni could lead to thermoneutral adsorption free energies of H* (Delta G(H*)). This, together with the promoted OH* adsorption strength derived from the abundance of oxygen vacancies in the CeO2 species, contributes to the excellent HOR performance with the exchange current density and mass activity of 0.038 mA cm(Ni)(-2) and 12.28 mA mg(Ni)(-1), respectively. This presents a new benchmark for PGM-free alkaline HOR and opens a new avenue toward the rational design of high-performance PGM-free electrocatalysts for alkaline HOR.Boosting Hydrogen Oxidation Activity of Ni in Alkaline Media through Oxygen-Vacancy-Rich CeO2/Ni HeterostructuresCeO2; hydrogen oxidation reaction; Ni; oxygen vacanciesx61201947#N/AFALSE
4127
anie.20191220510.1002/anie.201912205FALSEhttps://doi.org/10.1002/anie.201912205Nguyen, HAngew. Chem.-Int. Edit.For the in situ resource utilization (ISRU) of asteroids, the cost-mass conundrum needs to be solved, and technologies may need to be conceptualised from first principals. By using this approach, this Review seeks to illustrate how chemical process intensification can help with the development of disruptive technologies and business matters, how this might influence space-industry start-ups, and even industrial transformations on Earth. The disruptive technology considered is continuous microflow solvent extraction and, as another disruptive element therein, the use of ionic liquids. The space business considered is asteroid mining, as it is probably the most challenging resource site, and the focus is on its last step: the purification of adjacent metals (cobalt versus nickel). The key economic barrier is defined as the reduction in the amount of water used in the asteroid mining process. This Review suggests a pathway toward water savings up to the technological limit of the best Earth-based processes and their physical limits.Continuous-Flow Extraction of Adjacent Metals-A Disruptive Economic Window for In Situ Resource Utilization of Asteroids?asteroid mining; continuous-flow extraction; in&#8197; situ resource utilization; ionic liquids; space manufacturing42021174#N/ATRUE
4128
anie.20191166210.1002/anie.201911662FALSEhttps://doi.org/10.1002/anie.201911662Gabbai, FPAngew. Chem.-Int. Edit.Controlling the reactivity of transition metals using secondary, sigma-accepting ligands is an active area of investigation that is impacting molecular catalysis. Herein we describe the phosphine gold complexes [(o-Ph2P(C6H4)Acr)AuCl](+) ([3](+); Acr=9-N-methylacridinium) and [(o-Ph2P(C6H4)Xan)AuCl](+) ([4](+); Xan=9-xanthylium) where the electrophilic carbenium moiety is juxtaposed with the metal atom. While only weak interactions occur between the gold atom and the carbenium moiety of these complexes, the more Lewis acidic complex [4](+) readily reacts with chloride to afford a trivalent phosphine gold dichloride derivative (7) in which the metal atom is covalently bound to the former carbocationic center. This anion-induced Au-I/Au-III oxidation is accompanied by a conversion of the Lewis acidic carbocationic center in [4](+) into an X-type ligand in 7. We conClude that the carbenium moiety of this complex acts as a latent Z-type ligand poised to increase the Lewis acidity of the gold center, a notion supported by the carbophilic reactivity of these complexes.Stabilized Carbenium Ions as Latent, Z-type Ligandsalkynes; carbocations; gold; oxidative addition; Z-type ligands15201951#N/ATRUE
4129
anie.20191161710.1002/anie.201911617FALSEhttps://doi.org/10.1002/anie.201911617Jiang, LAngew. Chem.-Int. Edit.The development of high-efficiency electrocatalysts for large-scale water splitting is critical but also challenging. In this study, a hierarchical CoMoSx chalcogel was synthesized on a nickel foam (NF) through an in situ metathesis reaction and demonstrated excellent activity and stability in the electrocatalytic hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The high catalytic activity could be ascribed to the abundant active sites/defects in the amorphous framework and promotion of activity through cobalt doping. Furthermore, the superhydrophilicity and superaerophobicity of micro-/nanostructured CoMoSx/NF promoted mass transfer by facilitating access of electrolytes and ensuring fast release of gas bubbles. By employing CoMoSx/NF as bifunctional electrocatalysts, the overall water splitting device delivered a current density of 500 mA cm(-2) at a low voltage of 1.89 V and maintained its activity without decay for 100 h.An Engineered Superhydrophilic/Superaerophobic Electrocatalyst Composed of the Supported CoMoSx Chalcogel for Overall Water Splittingamorphous materials; chalcogels; overall water splitting; superaerophobicity; superhydrophilicity42202049#N/ATRUE
4130
anie.20191147010.1002/anie.201911470FALSEhttps://doi.org/10.1002/anie.201911470Yan, CHAngew. Chem.-Int. Edit.We report a novel modulation strategy by introducing transition metals into NiS2 nanosheets (NSs) to flexibly optimize the electronic configurations and atomic arrangement. The Co-NiS2 NSs exhibit excellent hydrogen evolution reaction (HER) performance with an overpotential of 80 mV at j=10 mA cm(-2) and long-term stability of 90 h in alkaline media. The turnover frequencies (TOFs) of 0.55 and 4.1 s(-1) at an overpotential of 100 and 200 mV also confirm their remarkable performance. DFT calculations reveal that the surface dopants abnormally sensitize surface Ni-3d bands in the long-range order towards higher electron-transfer activity, acting as the electron-depletion center. Meanwhile, the high lying surface S-sites possess substantially high selectivity for splitting the adsorbing H2O that guarantee the high HER performance within alkaline conditions. This work opens opportunities for enhancing water splitting by atomic-arrangement-assisted electronic modulation via a facile doping strategy.Atomic Arrangement in Metal-Doped NiS2 Boosts the Hydrogen Evolution Reaction in Alkaline Mediaatomic rearrangement; cobalt; electron configuration; hydrogen evolution reaction (HER); nanosheets57201966#N/ATRUE
4131
anie.20191110210.1002/anie.201911102FALSEhttps://doi.org/10.1002/anie.201911102Zeng, XQAngew. Chem.-Int. Edit.Alkynyl isocyanates have been postulated as highly reactive intermediates in synthetic chemistry. Herein, the parent molecule HC equivalent to CNCO is isolated for the first time. In sharp contrast to the previously reported short lifetime (ca. 15 s) at room temperature, we found that HC equivalent to CNCO has a lifetime of 55 h in the gas phase (2 mbar, 300 K) with a melting point of -79.5 degrees C and vaporization enthalpy (Delta H-vap) of 23.1(1) kJ mol(-1). Apart from the IR (gas, solid, and matrix), H-1 and C-13 NMR, and UV/Vis spectroscopic characterization, its photoisomerization with a acylnitrene HC equivalent to CC(O)N and cyanoketene NCC(H)CO has been observed.The Simplest, Isolable, Alkynyl Isocyanate HC equivalent to CNCO: Synthesis and Characterizationalkynes; heterocumulenes; isocyanates; isomers; photochemistry4201953#N/ATRUE
4132
anie.20190713610.1002/anie.201907136FALSEhttps://doi.org/10.1002/anie.202102481Bu, XHBi-Microporous Metal-Organic Frameworks with Cubane [M-4(OH)(4)] (M=Ni, Co) Clusters and Pore-Space Partition for Electrocatalytic Methanol Oxidation Reaction
Electrocatalytic
x2019#N/AFALSE
4133
anie.20190704510.1002/anie.201907045FALSEhttps://doi.org/10.1002/anie.201907045Hu, XLAngew. Chem.-Int. Edit.Metal hydride catalyzed hydrocarbonation reactions of alkenes are an efficient approach to construct new carbon-carbon bonds from readily available alkenes. However, the regioselectivity of hydrocarbonation remains challenging to be controlled. In nickel hydride (NiH) catalyzed hydrocarbonation, linear selectivity is most often obtained because of the relative stability of the linear Ni-Alkyl intermediate over its branched counterpart. Herein, we show that the boronic pinacol ester (Bpin) group directs a Ni-catalyzed hydrocarbonation to occur at its adjacent carbon center, resulting in formal branch selectivity. Both Alkyl and Aryl halides can be used as electrophiles in this hydrocarbonation, providing access to a wide range of secondary Alkyl Bpin derivatives, which are valuable building blocks in synthetic chemistry. The utility of the method is demonstrated by the late-stage functionalization of natural products and drug molecules, the synthesis of an anticancer agent, and iterative syntheses.Nickel-Catalyzed Regioselective HydroAlkylation and HydroArylation of Alkenyl Boronic Estersalkenes; boron compounds; hydroAlkylation; hydroArylation; nickel hydridesx34201981#N/AFALSE
4134
anie.20190990410.1002/anie.201909904FALSEhttps://doi.org/10.1002/anie.201909904Driess, MAngew. Chem.-Int. Edit.For the first time, the manganese gallide (MnGa4) served as an intermetallic precursor, which upon in situ electroconversion in alkaline media produced high-performance and long-term-stable MnOx-based electrocatalysts for water oxidation. Unexpectedly, its electrocorrosion (with the concomitant loss of Ga) leads simultaneously to three crystalline types of MnOx minerals with distinct structures and induced defects: birnessite delta-MnO2, feitknechtite beta-MnOOH, and hausmannite alpha-Mn3O4. The abundance and intrinsic stabilization of Mn-III/Mn-IV active sites in the three MnOx phases explains the superior efficiency and durability of the system for electrocatalytic water oxidation. After electrophoretic deposition of the MnGa4 precursor on conductive nickel foam (NF), a low overpotential of 291 mV, comparable to that of precious-metal-based catalysts, could be achieved at a current density of 10 mA cm(-2) with a durability of more than five days.Boosting Water Oxidation through In Situ Electroconversion of Manganese Gallide: An Intermetallic Precursor Approachelectrocorrosion; MnOx minerals; oxygen evolution reaction; renewable energy; water-splitting electrocatalysts23201963#N/ATRUE
4135
anie.20190669210.1002/anie.201906692https://doi.org/10.1002/anie.201906692Nevado, CAngew. Chem.-Int. Edit.The potential of merging photoredox and nickel catalysis to perform multicomponent alkene difunctionalizations under visible-light irradiation is demonstrated here. Secondary and tertiary Alkyl groups, as well as sulfonyl moieties can be added to the terminal position of the double bond with simultaneous Arylation of the internal carbon atom in a single step under mild reaction conditions. The process, devoid of stoichiometric additives, benefits from the use of bench-stable and easy-to-handle reagents, is operationally simple, and tolerates a wide variety of functional groups.Dual Photoredox/Nickel-Catalyzed Three-Component Carbofunctionalization of Alkenesalkenes; multicomponent reactions; nickel; photochemistry; reaction mechanismsPhotocatalyst51201988#N/AFALSE
4136
anie.20190668310.1002/anie.201906683FALSEhttps://doi.org/10.1002/anie.201906683Qiao, SZAngew. Chem.-Int. Edit.Heterogeneous electrocatalysis typically involves charge transfer between surface active sites and adsorbed species. Therefore, modulating the surface charge state of an electrocatalyst can be used to enhance performance. A series of negatively charged transition-metal (Fe, Co, Ni, Cu,and NiCo) phosphides were fabricated by designing strong electronic coupling with hydr(oxy)oxides formed in situ. Physicochemical characterizations, together with DFT computations, demonstrate that strong electronic coupling renders transition-metal phosphides negatively charged. This facilitates destabilization of alkaline water adsorption and dissociation to result in significantly improved H-2 evolution. Negatively charged Ni2P/nickel hydr(oxy)oxide for example exhibits a significantly low overpotential of 138 mV at 100 mA cm(-2), superior to that without strong electronic coupling and also commercial Pt/C.Negative Charging of Transition-Metal Phosphides via Strong Electronic Coupling for Destabilization of Alkaline Waterelectrocatalysis; H-2 evolution; strong coupling; water splittingx76201940#N/AFALSE
4137
anie.20190983210.1002/anie.201909832FALSEhttps://doi.org/10.1002/anie.201909832Peng, HSAngew. Chem.-Int. Edit.The electrocatalytic urea oxidation reaction (UOR) provides more economic electrons than water oxidation for various renewable energy-related systems owing to its lower thermodynamic barriers. However, it is limited by sluggish reaction kinetics, especially by CO2 desorption steps, masking its energetic advantage compared with water oxidation. Now, a lattice-oxygen-involved UOR mechanism on Ni4+ active sites is reported that has significantly faster reaction kinetics than the conventional UOR mechanisms. Combined DFT, O-18 isotope-labeling mass spectrometry, and in situ IR spectroscopy show that lattice oxygen is directly involved in transforming *CO to CO2 and accelerating the UOR rate. The resultant Ni4+ catalyst on a glassy carbon electrode exhibits a high current density (264 mA cm(-2) at 1.6 V versus RHE), outperforming the state-of-the-art catalysts, and the turnover frequency of Ni4+ active sites towards UOR is 5 times higher than that of Ni3+ active sites.A Lattice-Oxygen-Involved Reaction Pathway to Boost Urea Oxidationelectrocatalysis; kinetics; nickel; oxidation states; urea oxidation reaction33201926#N/ATRUE
4138
anie.20190637910.1002/anie.201906379FALSEhttps://doi.org/10.1002/anie.201906379Morin, JFAngew. Chem.-Int. Edit.The solution-phase synthesis is one of the most promising strategies for the preparation of well-defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect-free GNRs, cyCloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, inCluding alkyne benzannulation, photochemical cyClodehydrohalogenation, Mallory and Pd- and Ni-catalyzed reactions.Emerging Bottom-Up Strategies for the Synthesis of Graphene Nanoribbons and Related Structuresaromatization; carbon materials; graphene nanoribbons; nanographenes; polycyClic aromatic hydrocarbonsx192020131#N/AFALSE
4139
anie.20190634910.1002/anie.201906349FALSEKobayashi, SA Nickel-Diamine/Mesoporous Silica Composite as a Heterogeneous Chiral Catalyst for Asymmetric 1,4-Addition Reactionsx2019#N/AFALSE
4140
anie.20190967510.1002/anie.201909675FALSEhttps://doi.org/10.1002/anie.201909675Bourissou, DAngew. Chem.-Int. Edit.Metal-Lewis acid cooperation provides new opportunities in catalysis. In this work, we report a new type of palladium-borane cooperation involving anionic Pd-0 species. The air-stable DPB palladium complex 1 (DPB=diphosphine-borane) was prepared and reacted with KH to give the Pd-0 borohydride 2, the first monomeric anionic Pd-0 species to be structurally characterized. The boron moiety acts as an acceptor towards Pd in 1 via Pd -> B interaction, but as a donor in 2 thanks to B-H-Pd bridging. This enables the Activation of C-Cl bonds and the system is amenable to catalysis, as demonstrated by the hydro-/deutero-dehalogenation of a variety of (hetero)Aryl chlorides (20 examples, average yield 85 %).Palladium-Borane Cooperation: Evidence for an Anionic Pathway and Its Application to Catalytic Hydro-/Deutero-dechlorinationboranes; catalysis; dehalogenation; palladium18201964#N/ATRUE
4141
anie.20190947510.1002/anie.201909475FALSEhttps://doi.org/10.1002/anie.201909475Schuhmann, WAngew. Chem.-Int. Edit.Carbon corrosion at high anodic potentials is a major source of instability, especially in acidic electrolytes and impairs the long-term functionality of electrodes. In-depth investigation of carbon corrosion in alkaline environment by means of differential electrochemical mass spectrometry (DEMS) is prevented by the conversion of CO2 into CO32-. We report the adaptation of a DEMS system for online CO2 detection as the product of carbon corrosion in alkaline electrolytes. A new cell design allows for in situ acidification of the electrolyte to release initially dissolved CO32- as CO2 in front of the DEMS membrane and its subsequent detection by mass spectrometry. DEMS studies of a carbon-supported nickel boride (NixB/C) catalyst and Vulcan XC 72 at high anodic potentials suggest protection of carbon in the presence of highly active oxygen evolution electrocatalysts. Most importantly, carbon corrosion is decreased in alkaline solution.Online Monitoring of Electrochemical Carbon Corrosion in Alkaline Electrolytes by Differential Electrochemical Mass Spectrometrycarbon corrosion; cell design; DEMS; differential electrochemical mass spectrometry; electrocatalysis30202040#N/ATRUE
4142
anie.20190563510.1002/anie.201905635FALSEhttps://doi.org/10.1002/anie.201905635Daly, SRAngew. Chem.-Int. Edit.Bond distance is a common structural metric used to assess changes in metal-ligand bonds, but it is not Clear how sensitive changes in bond distances are with respect to changes in metal-ligand covalency. Here we report ligand K-edge XAS studies on Ni and Pd complexes containing different phosphorus(III) ligands. Despite the large number of electronic and structural permutations, P K-edge pre-edge peak intensities reveal a remarkable correlation that spectroscopically quantifies the linear interdependence of covalent M-P sigma bonding and bond distance. Cl K-edge studies conducted on many of the same Ni and Pd compounds revealed a poor correlation between M-Cl bond distance and covalency, but a strong correlation was established by analyzing Cl K-edge data for Ti complexes with a wider range of Ti-Cl bond distances. Together these results establish a quantitative framework to begin making more accurate assessments of metal-ligand covalency using bond distances from readily-available crystallographic data.Quantifying the Interdependence of Metal-Ligand Covalency and Bond Distance using Ligand K-edge XASbond distance; covalency; ionic radii; ligand K-edge XAS; metal-ligand bondx1201940#N/AFALSE
4143
anie.20190899810.1002/anie.201908998FALSEhttps://doi.org/10.1002/anie.201908998Wolf, RAngew. Chem.-Int. Edit.The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P5R2](+) cations with cyClopentadienyl metal complexes. The reaction of [(CpFe)-Fe-Ar(mu-Br)](2) (Cp-Ar=C-5(C6H4-4-Et)(5)) with [P5R2][GaCl4] (R=iPr and 2,4,6-Me3C6H2 (Mes)) afforded bicyClo[1.1.0]pentaphosphanes (1-R, R=iPr and Mes), showing an unsymmetric butterfly structure. The same products 1-R were formed from K[Cp-Ar] and [P5R2][GaCl4]. The cationic complexes [(CpCo)-Co-Ar(eta(4)-P5R2)][GaCl4] (2-R[GaCl4], R=iPr and Cy) and [((CpNi)-Ni-Ar)(2)(eta(3:3)-P5R2)][GaCl4] (3-R[GaCl4]) were obtained from [P5R2][GaCl4] and [(CpM)-M-Ar(mu-Br)](2) (M=Co and Ni) as well as by using low-valent (CpMI)-M-Ar sources. Anion metathesis of 2-R[GaCl4] and 3-R[GaCl4] was achieved with Na[BArF24]. The P-5 framework of the resulting salts 2-R[BArF24] can be further functionalized with nuCleophiles. Thus reactions with [Et4N]X (X=CN and Cl) give unprecedented cyano- and chloro-functionalized complexes, while organo-functionalization was achieved with CyMgX.Functionalization of Pentaphosphorus Cations by Complexationcobalt; coordination compounds; nickel; P ligands; phosphorus62019114#N/ATRUE
4144
anie.20190553310.1002/anie.201905533FALSEhttps://doi.org/10.1002/anie.201905533Feng, XMAngew. Chem.-Int. Edit.A highly enantioselective formal conjugate allyl addition of allylboronic acids to beta,gamma-unsaturated alpha-ketoesters has been realized by employing a chiral Ni-II/N,N '-dioxide complex as the catalyst. This transformation proceeds by an allylboration/oxy-Cope rearrangement sequence, providing a facile and rapid route to gamma-allyl-alpha-ketoesters with moderate to good yields (65-92 %) and excellent ee values (90-99 % ee). The isolation of 1,2-allylboration products provided insight into the mechanism of the subsequent oxy-Cope rearrangement reaction: substrate-induced chiral transfer and a chiral Lewis acid accelerated process. Based on the experimental investigations and DFT calculations, a rare boatlike transition-state model is proposed as the origin of high chirality transfer during the oxy-Cope rearrangement.Asymmetric Catalytic Formal 1,4-Allylation of beta,gamma-Unsaturated alpha-Ketoesters: Allylboration/Oxy-Cope Rearrangementallylic compounds; asymmetric catalysis; nickel; reaction mechanisms; rearrangementsx182019114#N/AFALSE
4145
anie.20190885010.1002/anie.201908850FALSEhttps://doi.org/10.1002/anie.201908850Murahashi, TAngew. Chem.-Int. Edit.The ligand-unsupported accommodation of extra metal moieties in a sandwich complex is reported. Although it has been considered that the metal-capacity of a metal sheet sandwich complex is strictly limited by the size of cyClic unsaturated hydrocarbon ligands, the M-M edge bonds in a metal sheet sandwich complex provide a ligand-unsupported docking site for extra metal moieties, allowing expansion of metal-capacity in sandwich complexes. The metal sheet sandwich complex [Pd-4(mu(4)-C8H8)(mu(4)-C9H9)](+), in which the ligand-based metal capacity is full in terms of the usage of all C=C moieties of the smaller carbocyClic ligand C8H8 in coordination, can accommodate extra M-0{P(OPh)(3)}(2) (M=Pd, Pt) moieties without coordinative assistance by either the C9H9 or the C8H8 ligand.Exceeding Metal Capacity in Sandwich Complexes: Ligand-Unsupported Docking of Extra Metal Moieties at Edges of a Metal Sheet Sandwich Complex4201959#N/ATRUE
4146
anie.20190543010.1002/anie.201905430FALSEhttps://doi.org/10.1002/anie.201905430Sun, YJAngew. Chem.-Int. Edit.The sluggish hydrogen oxidation reaction (HOR) under alkaline conditions has hindered the commercialization of hydroxide-exchange membrane hydrogen fuel cells. A low-cost Ni/NiO/C catalyst with abundant Ni/NiO interfacial sites was developed as a competent HOR electrocatalyst in alkaline media. Ni/NiO/C exhibits an HOR activity one order of magnitude higher than that of its parent Ni/C counterpart. Moreover, Ni/NiO/C also shows better stability and CO tolerance than commercial Pt/C in alkaline media, which renders it a very promising HOR electrocatalyst for hydrogen fuel cell applications. Density functional theory (DFT) calculations were also performed to shed light on the enhanced HOR performance of Ni/NiO/C; the DFT results indicate that both hydrogen and hydroxide achieve optimal binding energies at the Ni/NiO interface, resulting from the balanced electronic and oxophilic effects at the Ni/NiO interface.Enhanced Electrocatalytic Hydrogen Oxidation on Ni/NiO/C Derived from a Nickel-Based Metal-Organic Frameworkelectrocatalysis; hydrogen oxidation reaction; interface; metal-organic frameworks
Electrocatalytic
37201953#N/AFALSE
4147
anie.20190802910.1002/anie.201908029FALSEhttps://doi.org/10.1002/anie.201908029Morken, JPAngew. Chem.-Int. Edit.A hybrid transition-metal/radical process is described that results in the addition of organozinc reagents and Alkyl halides across alkenyl boron reagents in an enantioselective catalytic fashion. The reaction can be accomplished both intermolecularly and intramolecularly, providing useful product yields and high enantioselectivities in both manifolds.Enantioselective Radical Addition/Cross-Coupling of Organozinc Reagents, Alkyl Iodides, and Alkenyl Boron Reagentsboron; catalysis; cross-coupling; nickel; radical reactions352019101#N/ATRUE
4148
anie.20190464910.1002/anie.201904649FALSEhttps://doi.org/10.1002/anie.201904649Gong, JLAngew. Chem.-Int. Edit.Identification of the active structure under reaction conditions is of great importance for the rational design of heterogeneous catalysts. However, this is often hampered by their structural complexity. The interplay between the surface structure of Co3O4 and the CO2 hydrogenation is described. Co3O4 with morphology-dependent crystallographic surfaces presents different reducibility and formation energy of oxygen vacancies, thus resulting in distinct steady-state composition and product selectivity. Co3O4-0 h rhombic dodecahedra were completely reduced to Co-0 and CoO, which presents circa 85 % CH4 selectivity. In contrast, Co3O4-2 h nanorods were partially reduced to CoO, which exhibits a circa 95 % CO selectivity. The crucial role of the Co3O4 structure in determining the catalytic performance for higher alcohol synthesis over CuCo-based catalysts is demonstrated. As expected, Cu/Co3O4-2 h shows nine-fold higher ethanol yield than Cu/Co3O4-0 h owing to the inhibition for methanation.The Interplay between Structure and Product Selectivity of CO2 HydrogenationCO2 hydrogenation; Co3O4; crystallographic surfaces; methoxy; reducibilityx20201964#N/AFALSE
4149
anie.20190758410.1002/anie.201907584FALSEhttps://doi.org/10.1002/anie.201907584Hayashi, TAngew. Chem.-Int. Edit.Myoglobin reconstituted with Ni tetradehydrocorrin was investigated as a model of F430-containing methyl-coenzyme M reductase, which catalyzes anaerobic methane generation. The Ni-II tetradehydrocorrin complex has a Ni-II/Ni-I redox potential of -0.34 V vs. SHE and EPR spectroscopy indicates the formation of a Ni-I species upon reduction by dithionite. This redox potential is approximately 0.31 V more positive than that of F430. The Ni-I tetradehydrocorrin moiety is bound to the apo-form of myoglobin to yield the reconstituted protein. Methane gas is generated in the reaction of the model with methyl iodide in the presence of the reconstituted protein under reductive conditions, whereas the Ni-I complex itself does not produce methane gas. This is the first example of a protein-based functional model of F430-containing methyl-coenzyme M reductase.Myoglobin Reconstituted with Ni Tetradehydrocorrin as a Methane-Generating Model of Methyl-coenzyme M Reductaseenzyme models; heme proteins; metalloproteins; methyl-coenzyme M reductase; porphyrinoids7201933#N/ATRUE
4150
anie.20190747810.1002/anie.201907478FALSEhttps://doi.org/10.1002/anie.201907478Xiao, WJAngew. Chem.-Int. Edit.Chiral catalysts tolerating photochemical reactions are in great demand for the vast development of visible-light-induced asymmetric synthesis. Now, chiral octahedral complexes based on earth-abundant metal and chiral N-4 ligands are reported. One well-defined chiral Co-II-complex is shown to be an efficient catalyst in the visible-light-induced conjugated addition of enones by Alkyl and acyl radicals, providing synthetically valued chiral ketones and 1,4-diCarbonyls in 47->99 % yields with up to 97:3 e.r.Exploration of a Chiral Cobalt Catalyst for Visible-Light-Induced Enantioselective Radical Conjugate Addition36201972#N/ATRUE
4151
anie.20190424610.1002/anie.201904246https://doi.org/10.1002/anie.201904246Song, YFAngew. Chem.-Int. Edit.Although progress has been made to improve photocatalytic CO2 reduction under visible light (lambda>400 nm), the development of photocatalysts that can work under a longer wavelength (lambda>600 nm) remains a challenge. Now, a heterogeneous photocatalyst system consisting of a ruthenium complex and a monolayer nickel-alumina layered double hydroxide (NiAl-LDH), which act as light-harvesting and catalytic units for selective photoreduction of CO2 and H2O into CH4 and CO under irradiation with lambda>400 nm. By precisely tuning the irradiation wavelength, the selectivity of CH4 can be improved to 70.3 %, and the H-2 evolution reaction can be completely suppressed under irradiation with lambda>600 nm. The photogenerated electrons matching the energy levels of photosensitizer and m-NiAl-LDH only localized at the defect state, providing a driving force of 0.313 eV to overcome the Gibbs free energy barrier of CO2 reduction to CH4 (0.127 eV), rather than that for H-2 evolution (0.425 eV).Highly Selective Photoreduction of CO2 with Suppressing H-2 Evolution over Monolayer Layered Double Hydroxide under Irradiation above 600 nmCO2 photoreduction; defects; H-2 evolution; layered double hydroxides; visible light catalysisPhotocatalyst71201955#N/AFALSE
4152
anie.20190422410.1002/anie.201904224FALSEhttps://doi.org/10.1002/anie.201904224Ema, TAngew. Chem.-Int. Edit.Unique self- assembled macrocyClic multinuClear ZnII and NiII complexes with binaphthyl- bipyridyl ligands ( L) were synthesized. X- ray analysis revealed that these complexes consisted of an outer ring ( Zn3L3 or Ni3L3) and an inner core ( Zn2 or Ni). In the ZnII complex, the inner Zn2 part rotated rapidly inside the outer ring in solution on an NMR timescale. These complexes exhibited dual catalytic activities for CO2 fixations: synthesis of cyClic carbonates from epoxides and CO2 and temperature- switched N- Carbonylation/ N- methylation of amines with CO2 and hydrosilane.Unexpected MacrocyClic MultinuClear Zinc and Nickel Complexes that Function as Multitasking Catalysts for CO2 Fixationscarbon dioxide fixation; cyClic carbonates; multinuClear complexes; N; functionalization; self; assemblyx18201980#N/AFALSE
4153
anie.20190732210.1002/anie.201907322FALSEhttps://doi.org/10.1002/anie.201907322Yang, YProgrammable Exposure of Pt Active Facets for Efficient Oxygen Reduction2019#N/ATRUE
4154
anie.20190718510.1002/anie.201907185FALSEhttps://doi.org/10.1002/anie.201907185Zhu, SLAngew. Chem.-Int. Edit.The direct and selective functionalization of relatively simple and readily accessible precursors to produce highly functionalized Alkyl boronates is a synthetically useful process. Herein we report a NiH-catalyzed remote hydroArylation process that can, through a synergistic combination of chain walking and subsequent cross-coupling, introduce an Aryl group at the adjacent carbon atom of Alkyl boronates under mild conditions. By means of a preliminary experiment with moderate enantioselectivity, it was shown that an asymmetric version could also be realized.Rapid Access to Highly Functionalized Alkyl Boronates by NiH-Catalyzed Remote HydroArylation of Boron-Containing AlkenesArylation; C-H Activation; isomerization; nickel; regioselectivity35201995#N/ATRUE
4155
anie.20190379110.1002/anie.201903791https://doi.org/10.1002/anie.201903791Mori, AAngew. Chem.-Int. Edit.The unprecedented synthesis of regioregular head-to-tail-type poly(1,4-Arylene)s bearing different substituents at the 2- and 5-positions is described. They were prepared by the polymerization of 2,5-disubstituted bromo(chloro)Arylenes by selective halogen-metal exchange with a Grignard reagent and subsequent cross-coupling polymerization with a nickel catalyst [NiCl2(dppp)]. Formation of the regioregular poly(1,4-Arylene)s were confirmed by NMR spectroscopy, and showed remarkable differences to those polymers having uncontrolled regioregularity. Polymerization of bromo(chloro)Arylenes with a chiral alkoxy substituent also led to the regioregular head-to-tail-type polyArylene, which demonstrated circular dichroism, thus suggesting formation of a structure with higher-order regularity.Unprecedented Regioregular Poly(1,4-Arylene)s Prepared by Nickel(II)-Catalyzed Cross-Coupling Polymerization of 2,5-Disubstituted Bromo(chloro)AryleneArylenes; Cotton effect; halogen-metal exchange; nickel; polymersx3201935#N/AFALSE
4156
anie.20190363810.1002/anie.201903638FALSEhttps://doi.org/10.1002/anie.201903638Sanford, MSAngew. Chem.-Int. Edit.Described is a systematic comparison of factors impacting the relative rates and selectivities of C(sp(3))-C and C(sp(3))-O bond-forming reactions at high-valent Ni as a function of oxidation state. Two Ni complexes are compared: a cationic octahedral Ni-IV complex ligated by tris(pyrazolyl)borate and a cationic octahedral Ni-III complex ligated by tris(pyrazolyl) methane. Key features of reactivity/selectivity are revealed: 1) C(sp(3))-C(sp(2)) bond-forming reductive elimination occurs from both centers, but the Ni-III complex reacts up to 300-fold faster than the Ni-IV, depending on the reaction conditions. The relative reactivity is proposed to derive from ligand dissociation kinetics, which vary as a function of oxidation state and the presence/absence of visible light. 2) Upon the addition of acetate (AcO-), the Ni-IV complex exClusively undergoes C(sp(3))-OAc bond formation, while the Ni-III analogue forms the C(sp(3))-C(sp2) coupled product selectively. This difference is rationalized based on the electro-philicity of the respective M-C(sp(3)) bonds, and thus their relative reactivity towards outer-sphere S(N)2-type bond-forming reactions.Impact of Oxidation State on Reactivity and Selectivity Differences between Nickel(III) and Nickel(IV) Alkyl ComplexesC-C coupling; kinetics; nickel; reaction mechanisms; structure elucidationx9201954#N/AFALSE
4157
anie.20190678110.1002/anie.201906781FALSEhttps://doi.org/10.1002/anie.201906781Mejia, EAngew. Chem.-Int. Edit.On Lake Lucerne, 120 leading chemists gathered for the 54th time to discuss about the latest developments on medicinal chemistry, asymmetric synthesis, organo- and photocatalysis, organometallic chemistry, and green chemistry. The photograph shows a view of the lake from the entrance of the Burgenstock conference venue.A Celebration of Science amidst Nature: The 54th Burgenstock Conference02019117#N/ATRUE
4158
anie.20190665810.1002/anie.201906658FALSEhttps://doi.org/10.1002/anie.201906658Klein, JEMNAngew. Chem.-Int. Edit.Reductive elimination is an elementary organometallic reaction step involving a formal oxidation state change of -2 at a transition-metal center. For a series of formal high-valent Ni-IV complexes, Aryl-CF3 bond-forming reductive elimination was reported to occur readily (Bour et al. J. Am. Chem. Soc. 2015, 137, 8034-8037). We report a computational analysis of this reaction and find that, unexpectedly, the formal Ni-IV centers are better described as approaching a +II oxidation state, originating from highly covalent metal-ligand bonds, a phenomenon attributable to sigma-noninnocence. A direct consequence is that the elimination of Aryl-CF3 products occurs in an essentially redox-neutral fashion, as opposed to a reductive elimination. This is supported by an electron flow analysis which shows that an anionic CF3 group is transferred to an electrophilic Aryl group. The uncovered role of sigma-noninnocence in metal-ligand bonding, and of an essentially redox-neutral elimination as an elementary organometallic reaction step, may constitute concepts of broad relevance to organometallic chemistry.sigma-Noninnocence: Masked Phenyl-Cation Transfer at Formal Ni-IVcoinage metals; homolysis; ligand-field inversion; radicals; trifluoromethyl11201978#N/ATRUE
4159
anie.20190354510.1002/anie.201903545FALSEhttps://doi.org/10.1002/anie.201903545Schuth, FAngew. Chem.-Int. Edit.Supported catalysts are among the most important Classes of catalysts. They are typically prepared by wet-chemical methods, such as impregnation or co-precipitation. Here we disClose that dry ball milling of macroscopic metal powder in the presence of a support oxide leads in many cases to supported catalysts with partiCles in the nanometer size range. Various supports, inCluding TiO2, Al2O3, Fe2O3, and Co3O4, and different metals, such as Au, Pt, Ag, Cu, and Ni, were studied, and for each of the supports and the metals, highly dispersed nanopartiCles on supports could be prepared. The supported catalysts were tested in CO oxidation, where they showed activities in the same range as conventionally prepared catalysts. The method thus provides a simple and cost-effective alternative to the conventionally used impregnation methods.Milling Down to Nanometers: A General Process for the Direct Dry Synthesis of Supported Metal Catalystsball milling; catalysis; CO oxidation; mechanochemistry; supported catalystsx27201930#N/AFALSE
4160
anie.20190611110.1002/anie.201906111FALSEhttps://doi.org/10.1002/anie.201906111Zhang, XMAngew. Chem.-Int. Edit.A general and efficient rhodium-catalyzed asymmetric cyanide-free hydrocyanation of alkenes has been developed. Based on the asymmetric hydroCarbonylation/condensation/aza-Cope elimination sequences, a broad scope of substrates inCluding mono-substituted, 1,2-, and 1,1-disubstituted alkenes (involving natural product R- and S-limonene) were employed, and a series of valuable chiral nitriles are prepared with high yields (up to 95 %) and enantioselectivities (up to 98 % ee). Notably, the critical factor to achieve high enantioseletivies is the addition of catalytic amount of benzoic acid. This novel methodology provides an efficient and concise synthetic route to the intermediate of vildagliptin and anagliptin.Asymmetric Hydrocyanation of Alkenes without HCNasymmetric synthesis; hydrocyanation; hydroCarbonylation; nitriles; rhodium16201953#N/ATRUE
4161
anie.20190600510.1002/anie.201906005FALSEhttps://doi.org/10.1002/anie.201906005Diao, TNAngew. Chem.-Int. Edit.The incorporation of CO2 into organometallic and organic molecules represents a sustainable way to prepare Carbonylates. The mechanism of reductive Carbonylation of Alkyl halides has been proposed to proceed through the reduction of Ni-II to Ni-I by either Zn or Mn, followed by CO2 insertion into Ni-I-Alkyl species. No experimental evidence has been previously established to support the two proposed steps. Demonstrated herein is that the direct reduction of (tBu-Xantphos)(NiBr2)-Br-II by Zn affords Ni-I species. (tBu-Xantphos)Ni-I-Me and (tBu-Xantphos)Ni-I-Et complexes undergo fast insertion of CO2 at 22 degrees C. The substantially faster rate, relative to that of Ni-II complexes, serves as the long-sought-after experimental support for the proposed mechanisms of Ni-catalyzed Carbonylation reactions.Insertion of CO2 Mediated by a (Xantphos)Ni-I-Alkyl Speciescarbon dioxide; nickel; reaction mechanisms; reduction; structure elucidation15201953#N/ATRUE
4162
anie.20190282510.1002/anie.201902825FALSEhttps://doi.org/10.1002/anie.201902825Chen, JAngew. Chem.-Int. Edit.Bifunctional Au@Ni core-satellite nanostructures synthesized by a one-step assembly method were employed for in situ surface-enhanced Raman spectroscopic (SERS) monitoring of Ni-catalyzed C-C bond-forming reactions. Surprisingly, the reaction that was thought to be an Ullmann-type self-coupling reaction, was found to be a cross-coupling reaction proceeding by photoinduced aromatic C-H bond Arylation. In situ SERS monitoring enabled the discovery, and a series of biphenyl compounds were synthesized photocatalytically, and at room temperature, using cheap Ni nanopartiCle catalysts.C-H Arylation on Nickel NanopartiCles Monitored by In Situ Surface-Enhanced Raman SpectroscopyC-H Arylation; nanopartiCles; photocatalysis; self-assembly; surface-enhanced Raman spectroscopy (SERS)x20201947#N/AFALSE
4163
anie.20190555410.1002/anie.201905554FALSEQiao, SZNon-metal Single-Iodine-Atom Electrocatalysts for the Hydrogen Evolution Reaction2019#N/ATRUE
4164
anie.20190278510.1002/anie.201902785https://doi.org/10.1002/anie.201902785Seeberger, PHSemi-heterogeneous Dual Nickel/Photocatalysis using Carbon Nitrides: Esterification of Carbonylic Acids with Aryl HalidesPhotocatalyst2019#N/AFALSE
4165
anie.20190550110.1002/anie.201905501FALSEhttps://doi.org/10.1002/anie.201905501Koper, MTMAngew. Chem.-Int. Edit.Herein, the effect of the alkali cation (Li+, Na+, K+, and Cs+) in alkaline electrolytes with and without Fe impurities is investigated for enhancing the activity of nickel oxyhydroxide (NiOOH) for the oxygen evolution reaction (OER). CyClic voltammograms show that Fe impurities have a significant catalytic effect on OER activity; however, both under purified and unpurified conditions, the trend in OER activity is Cs+ > Na+ > K+ > Li+, suggesting an intrinsic cation effect of the OER activity on Fe-free Ni oxyhydroxide. In situ surface enhanced Raman spectroscopy (SERS), shows this cation dependence is related to the formation of superoxo OER intermediate (NiOO-). The electrochemically active surface area, evaluated by electrochemical impedance spectroscopy (EIS), is not influenced significantly by the cation. We postulate that the cations interact with the Ni-OO- species leading to the formation of NiOO--M+ species that is stabilized better by bigger cations (Cs+). This species would then act as the precursor to O-2 evolution, explaining the higher activity.Enhancement of Oxygen Evolution Activity of Nickel Oxyhydroxide by Electrolyte Alkali Cationscations; electrocatalysis; nickel oxyhydroxide; oxygen evolution reaction (OER); Raman spectroscopy52201952#N/ATRUE
4166
anie.20190486110.1002/anie.201904861FALSEhttps://doi.org/10.1002/anie.201904861Brown, MKAngew. Chem.-Int. Edit.A method for the construction of boron-substituted quaternary carbons or diArylquaternary carbons by Arylboration of highly substituted alkenylarenes is presented. A wide range of alkenes and Arylbromides can participate in this reaction thus allowing for a diverse assortment of products to be prepared. In addition, a solvent dependent regiodivergent Arylboration of 1,2-disubstituted alkenylarenes is presented, thus greatly increasing the scope of products that can be accessed.Nickel-Catalyzed Arylboration of Alkenylarenes: Synthesis of Boron-Substituted Quaternary Carbons and Regiodivergent Reactionsalkenes; Arylboration; boron; cross coupling; nickel20201957#N/ATRUE
4167
anie.20190244610.1002/anie.201902446FALSEhttps://doi.org/10.1002/anie.201902446Wang, QBAngew. Chem.-Int. Edit.Tuning the crystal phase of metal alloy nanomaterials has been proved a significant way to alter their catalytic properties based on crystal structure and electronic property. Herein, we successfully developed a simple strategy to controllably synthesize a rare crystal structure of hexagonal Close-packed (hcp) NiFe nanopartiCle (NP) encapsulated in a N-doped carbon (NC) shell (hcp-NiFe@NC). Then, we systemically investigated the oxygen evolution reaction (OER) performance of the samples under alkaline conditions, in which the hcp-NiFe@NC exhibits superior OER activity compared to the conventional face-centered cubic (fcc) NiFe encapsulated in a N-doped carbon shell (fcc-NiFe@NC). At the current densities of 10 and 100 mAcm(-2), the hcp-NiFe@NC with Fe/Ni ratio of approximate to 5.4% only needs ultralow overpotentials of 226 mV and 263 mV versus reversible hydrogen electrode in 1.0 M KOH electrolyte, respectively, which were extremely lower than those of fcc-NiFe@NC and most of other reported NiFe-based electrocatalysts. We proposed that hcp-NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER. This research provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.NiFe Alloy NanopartiCles with hcp Crystal Structure Stimulate Superior Oxygen Evolution Reaction Electrocatalytic Activitycrystal structure; electrocatalyst; metal alloy nanomaterial; NiFe alloy; oxygen evolution reactionx107201944#N/AFALSE
4168
anie.20190236110.1002/anie.201902361https://doi.org/10.1002/anie.201902361Long, JLHigh-Rate, Tunable Syngas Production with Artificial Photosynthetic CellsPhotocatalyst2019#N/AFALSE
4169
anie.20190198710.1002/anie.201901987https://doi.org/10.1002/anie.202011347Wei, WDPlasmonic Nickel-TiO2 Heterostructures for Visible-Light-Driven Photochemical ReactionsPhotocatalyst2019#N/AFALSE
4170
anie.20190193910.1002/anie.201901939FALSEhttps://doi.org/10.1002/anie.201901939Osuka, AAngew. Chem.-Int. Edit.meta- and para-Phenylenediamine-fused nickel(II) porphyrin dimers were synthesized by SNAr reaction of meso,beta,beta-trichloro nickel(II) porphyrin with meta- and para-phenylenediamines and subsequent Pd-catalyzed intramolecular C-H Arylation. Their tetrachlorinated dication diradicals are very stable, allowing SQUID magnetometry and revealing Clear open-shell characters for both meta and para isomers with ferro- and anti-ferromagnetic interactions, respectively. The nitrogen analogue of Thiele's hydrocarbon usually displays predominant Closed-shell nature but its hidden diradical characters increase either in a twisted conformation or upon insertion of an additional phenylene spacer. The observed distinct diradical nature of the para-congener indicates that diradical properties can be enhanced also by efficient spin delocalization.meta- and para-Phenylenediamine-Fused Porphyrin Dimers: Synthesis and Magnetic Interactions of Their Dication Diradicalscations; magnetic properties; porphyrinoids; radicals; structure elucidationx11201973#N/AFALSE
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anie.20190461410.1002/anie.201904614FALSEhttps://doi.org/10.1002/anie.202011097Dou, SXGeneral pi-Electron-Assisted Strategy for Ir, Pt, Ru, Pd, Fe, Ni Single-Atom Electrocatalysts with Bifunctional Active Sites for Highly Efficient Water Splitting2019#N/ATRUE
4172
anie.20190186610.1002/anie.201901866FALSEhttps://doi.org/10.1002/anie.201901866Mercado, BQAngew. Chem.-Int. Edit.A number of new transition metal catalyzed methods for the formation of C(sp(2))-C(sp(3)) bonds have recently been described. These reactions often utilize bidentate polypyridyl-ligated Ni catalysts, and paramagnetic Ni-I halide or Aryl species are proposed in the catalytic cyCles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl-ligated Ni halide and Aryl complexes through elementary reactions proposed in catalytic cyCles for C(sp(2))-C(sp(3)) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp(2))-C(sp(3)) coupling through stoichiometric studies and also explore their catalytic activity.Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp(2))-C(sp(3))Coupling Reactionscatalysis; cross-electrophile coupling; nickel(I) Complexes; polypyridyl ligands; reaction mechanismx34201946#N/AFALSE
4173
anie.20190430510.1002/anie.201904305FALSEhttps://doi.org/10.1002/anie.201904305Xiong, RGAngew. Chem.-Int. Edit.The X-site ion in organic-inorganic hybrid ABX(3) perovskites (OHPs) varies from halide ion to bridging linkers like HCOO-, N-3(-), NO2-, and CN-. However, no nitrite-based OHP ferroelectrics have been reported so far. Now, based on non-ferroelectric [(CH3)(4)N][Ni(NO2)(3)], through the combined methodologies of quasi-spherical shape, hydrogen bonding functionality, and H/F substitution, we have successfully synthesized an OHP ferroelectric, [FMeTP][Ni(NO2)(3)] (FMeTP=N-fluoromethyl tropine). As an unprecedented nitrite-based OHP ferroelectric, the well-designed [FMeTP][Ni(NO2)(3)] undergoes the ferroelectric phase transition at 400K with an Aizu notation of 6/mmmFm, showing multiaxial ferroelectric characteristics. This work is a great step towards not only enriching the molecular ferroelectric families but also accelerating the potential practical applications.A Nickel(II) Nitrite Based Molecular Perovskite Ferroelectricchemical design; molecular ferroelectrics; nitrite; organic-inorganic hybrid perovskites; piezoresponse force microscopy17201943#N/ATRUE
4174
anie.20190420710.1002/anie.201904207FALSEhttps://doi.org/10.1002/anie.201904207Cockroft, SLThe Energetic Significance of Metallophilic Interactions2019#N/ATRUE
4175
anie.20190396410.1002/anie.201903964FALSEhttps://doi.org/10.1002/anie.201903964Gabbai, FPAngew. Chem.-Int. Edit.With the intent to demonstrate that the charge of Z-type ligands can be used to modulate the electrophilic character and catalytic properties of coordinated transition metals, we are now targeting complexes bearing polycationic antimony-based Z-type ligands. Toward this end, the dangling phosphine arm of ((o-(Ph2P)C6H4)(3))SbCl2AuCl (1) was oxidized with hydrogen peroxide to afford [((o-(Ph2P)C6H4)(2)(o-Ph2PO)C6H4)SbAuCl2](+) ([2 a](+)) which was readily converted into the dicationic complex [((o-(Ph2P)C6H4)(2)(o-Ph2PO)C6H4)SbAuCl](2+) ([3](2+)) by treatment with 2 equiv AgNTf2. Both experimental and computational results show that [3](2+) possess a strong Au -> Sb interaction reinforced by the dicationic character of the antimony center. The gold-bound chloride anion of [3](2+) is rather inert and necessitates the addition of excess AgNTf2 to undergo Activation. The activated complex, referred to as [4](2+) [((o-(Ph2P)C6H4)(2)(o-Ph2PO)C6H4)SbAuNTf2](2+) readily catalyzes both the polymerization and the hydroamination of styrene. This atypical reactivity underscores the strong sigma-accepting properties of the dicationic antimony ligand and its activating impact on the gold center.An Antimony(V) Dication as a Z-Type Ligand: Turning on Styrene Activation at Goldantimony; gold; hydroamination; ligand design; olefins12201953#N/ATRUE
4176
anie.20190157510.1002/anie.201901575FALSEhttps://doi.org/10.1002/anie.201901575Zhao, CAngew. Chem.-Int. Edit.Polynary single-atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces. However, the fabrication and identification of such an active-site prototype remain elusive. Here we report isolated diatomic Ni-Fe sites anchored on nitrogenated carbon as an efficient electrocatalyst for CO2 reduction. The catalyst exhibits high selectivity with CO Faradaic efficiency above 90% over a wide potential range from -0.5 to -0.9V (98% at -0.7V), and robust durability, retaining 99% of its initial selectivity after 30hours of electrolysis. Density functional theory studies reveal that the neighboring Ni-Fe centers not only function in synergy to decrease the reaction barrier for the formation of COOH* and desorption of CO, but also undergo distinct structural evolution into a CO-adsorbed moiety upon CO2 uptake.Isolated Diatomic Ni-Fe Metal-Nitrogen Sites for Synergistic Electroreduction of CO2CO2 reduction; electrocatalysts; metal centers; single-atom catalystsx222201936#N/AFALSE
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anie.20190132710.1002/anie.201901327https://doi.org/10.1002/anie.201901327Rueping, MAngew. Chem.-Int. Edit.A dual catalytic protocol for the direct Arylation of non-activated C(sp(3))-H bonds has been developed. Upon photochemical excitation, the excited triplet state of a diAryl ketone photosensitizer abstracts a hydrogen atom from an aliphatic C-H bond. This inherent reactivity was exploited for the generation of Benzylic radicals which subsequently enter a nickel catalytic cyCle, accomplishing the Benzylic Arylation.The Dual Role of Benzophenone in Visible-Light/Nickel Photoredox-Catalyzed C-H Arylations: Hydrogen-Atom Transfer and Energy Transferatom transfer; benzophenone; C-H functionalization; energy transfer; metallaphotoredoxPhotocatalyst522019806/1/2022FALSE
4178
anie.20190356810.1002/anie.201903568FALSEhttps://doi.org/10.1002/anie.201903568Gaberscek, MAngew. Chem.-Int. Edit.Preparation of large quantities of high-performance supported Pt-alloy electrocatalysts is crucial for the faster development and implementation of low-temperature proton exchange membrane fuel cells (PEMFCs). One of the prospective nanofabrication synthesis methods is based on the galvanic displacement (GD) reaction. A facile, highly reproducible, gram scale, water-based double passivation GD method is now presented for the synthesis of carbon-supported Pt-M nanopartiCles (M=Cu, Ni, Co). It offers great flexibility over the catalyst design, such as the choice of the sacrificial metal (M), variation of the chemical composition of alloy, variation of total metal loading (Pt+M) on carbon support, or even variation of the carbon support itself. The obtained Pt-alloy catalysts are several times more active compared to a Pt reference and exhibits better stability during accelerated degradation tests performed at 60 degrees C.A Double-Passivation Water-Based Galvanic Displacement Method for Reproducible Gram-Scale Production of High-Performance Platinum-Alloy Electrocatalystsdouble passivation; galvanic displacement; oxygen reduction reaction; platinum alloys; proton exchange membrane fuel cell5201933#N/ATRUE
4179
anie.20190101010.1002/anie.201901010FALSEhttps://doi.org/10.1002/anie.201901010Sun, WPAngew. Chem.-Int. Edit.Heterostnictured nanomaterials, generally have physicochemical properties that differ from those of the individual components, and thus have potential in a wide range of applications. New platinum (Pt)/nickel bicarbonate (Ni(HCO3)(2)) heterostructures are designed for an efficient alkaline hydrogen evolution reaction (HER). Notably, the specific and mass activity of Pt in Pt/Ni(HCO3)(2) are substantially improved compared to the bare Pt nanopartiCles (NPs). The Ni(HCO3)(2) provides abundant water adsorption/dissociation sites and modulate the electronic structure of Pt, which determine the elementary reaction kinetics of alkaline HER. The Ni(HCO3)(2) nanoplales offer a platform for the uniform dispersion of Pt NPs, ensuring the maximum exposure of active sites. The results demonstrate that, Ni(HCO3)(2) is an effective catalyst promoter for alkaline HER.Platinum/Nickel Bicarbonate Heterostructures towards Accelerated Hydrogen Evolution under Alkaline Conditionselectrocatalysis; heterostructures; hydrogen evolution reaction; nickel bicarbonate; platinumx103201944#N/AFALSE
4180
anie.20190356510.1002/anie.201903565FALSEhttps://doi.org/10.1002/anie.201903565Ciurli, SAngew. Chem.-Int. Edit.Urease, the most efficient enzyme known, contains an essential dinuClear Ni-II Cluster in the active site. It catalyzes the hydrolysis of urea, inducing a rapid pH increase that has negative effects on human health and agriculture. Thus, the control of urease activity is of utmost importance in medical, pharmaceutical, and agro-environmental applications. All known urease inhibitors are either toxic or inefficient. The development of new and efficient chemicals able to inhibit urease relies on the knowledge of all steps of the catalytic mechanism. The short (microseconds) lifetime of the urease-urea complex has hampered the determination of its structure. The present study uses fluoride to substitute the hydroxide acting as the co-substrate in the reaction, preventing the occurrence of the catalytic steps that follow substrate binding. The 1.42 angstrom crystal structure of the urease-urea complex, reported here, resolves the enduring debate on the mechanism of this metalloenzyme.The Structure of the Elusive Urease-Urea Complex Unveils the Mechanism of a Paradigmatic Nickel-Dependent Enzymecatalytic mechanism; nickel; urea; urease; x-ray diffraction18201951#N/ATRUE
4181
anie.20190333010.1002/anie.201903330FALSEhttps://doi.org/10.1002/anie.201903330Hu, XLAngew. Chem.-Int. Edit.Ketones are an important Class of molecules in synthetic and medicinal chemistry. Rapid and modular synthesis of ketones remains in high demand. Described here is a nickel-catalyzed three-component reductive Carbonylation method for the synthesis of diAlkyl ketones. A wide range of both symmetric and asymmetric diAlkyl ketones can be accessed from Alkyl halides and a safe CO source, ethyl chloroformate. The approach offers complementary substrate scope to existing Carbonylation methods while avoiding the use of either toxic CO or metal Carbonyl reagents.From Alkyl Halides to Ketones: Nickel-Catalyzed Reductive Carbonylation Utilizing Ethyl Chloroformate as the Carbonyl SourceAlkyl halides; Carbonylation; ketones; nickel; synthetic methods23201945#N/ATRUE
4182
anie.20190320010.1002/anie.201903200FALSEhttps://doi.org/10.1002/anie.201903200Hu, XLAngew. Chem.-Int. Edit.Nickel iron oxide is considered a benchmark nonprecious catalyst for the oxygen evolution reaction (OER). However, the nature of the active site in nickel iron oxide is heavily debated. Here we report direct spectroscopic evidence for the different active sites in Fe-free and Fe-containing Ni oxides. Ultrathin layered double hydroxides (LDHs) were used as defined samples of metal oxide catalysts, and O-18-labeling experiments in combination with in situ Raman spectroscopy were employed to probe the role of lattice oxygen as well as an active oxygen species, NiOO-, in the catalysts. Our data show that lattice oxygen is involved in the OER for Ni and NiCo LDHs, but not for NiFe and NiCoFe LDHs. Moreover, NiOO- is a precursor to oxygen for Ni and NiCo LDHs, but not for NiFe and NiCoFe LDHs. These data indicate that bulk Ni sites in Ni and NiCo oxides are active and evolve oxygen via a NiOO- precursor. Fe incorporation not only dramatically increases the activity, but also changes the nature of the active sites.Oxygen Isotope Labeling Experiments Reveal Different Reaction Sites for the Oxygen Evolution Reaction on Nickel and Nickel Iron Oxidesactive site; electrocatalysis; nickel oxides; oxygen evolution reaction; Raman spectroscopy75201935#N/ATRUE
4183
anie.20190078710.1002/anie.201900787FALSEhttps://doi.org/10.1002/anie.201900787Dai, SAngew. Chem.-Int. Edit.High-entropy materials refer to a kind of materials in which five or more metal species were incorporated deliberately into a single lattice with random occupancy. Up to now, such a concept has been only restricted to hard materials, such as high-entropy alloys and ceramics. Herein we report the synthesis of hybrid high-entropy materials, polymetallic zeolitic imidazolate framework (also named as high-entropy zeolitic imidazolate framework, HE-ZIF), via entropy-driven room-temperature mechanochemistry. HE-ZIF contains five metals inCluding Zn-II, Co-II, Cd-II, Ni-II, and Cu-II which are dispersed in the ZIF structure randomly. Moreover, HE-ZIF shows enhanced catalytic conversion of CO2 into carbonate compared with ZIF-8 presumably a result of the synergistic effect of the five metal ions as Lewis acid in epoxide Activation.Entropy-Driven Mechanochemical Synthesis of Polymetallic Zeolitic Imidazolate Frameworks for CO2 Fixationcarbon dioxide fixation; high-entropy materials; mechanochemistry; metal-organic frameworks; zeolitic imidazolate frameworksx41201939#N/AFALSE
4184
anie.20190280510.1002/anie.201902805FALSESakai, NAcyl Fluorides in Late-Transition-Metal Catalysis2020#N/ATRUE
4185
anie.20190275110.1002/anie.201902751FALSEhttps://doi.org/10.1002/anie.201902751Hu, XLAngew. Chem.-Int. Edit.Hydroxide-exchange membrane fuel cells can potentially utilize platinum-group-metal (PGM)-free electrocatalysts, offering cost and scalability advantages over more developed proton-exchange membrane fuel cells. However, there is a lack of non-precious electrocatalysts that are active and stable for the hydrogen oxidation reaction (HOR) relevant to hydroxide-exchange membrane fuel cells. Here we report the discovery and development of Ni3N as an active and robust HOR catalyst in alkaline medium. A supported version of the catalyst, Ni3N/C, exhibits by far the highest mass activity and break-down potential for a PGM-free catalyst. The catalyst also exhibits Pt-like activity for hydrogen evolution reaction (HER) in alkaline medium. Spectroscopy data reveal a downshift of the Ni d band going from Ni to Ni3N and interfacial charge transfer from Ni3N to the carbon support. These properties weaken the binding energy of hydrogen and oxygen species, resulting in remarkable HOR activity and stability.Ni3N as an Active Hydrogen Oxidation Reaction Catalyst in Alkaline Mediumalkaline fuel cells; electrocatalysis; hydrogen evolution; hydrogen oxidation reaction; nickel69201955#N/ATRUE
4186
anie.20190251910.1002/anie.201902519FALSEhttps://doi.org/10.1002/anie.201902519Diao, TAngew. Chem.-Int. Edit.Nickel-Catalyzed Asymmetric Reductive DiArylation of Vinylarenes (vol 58, pg 3198, 2019)020191#N/ATRUE
4187
anie.20181463410.1002/anie.201814634https://doi.org/10.1002/anie.201814634Chen, ClAngew. Chem.-Int. Edit.Transition-metal-catalyzed copolymerization of olefins with polar monomers represents a challenge because of the large variety of substrate-induced side reactions. However, this approach also holds the potential for the direct synthesis of polar functionalized polyolefins with unique properties. After decades of research, only a few catalyst systems have been found to be suitable for this reaction. Some major advances in catalyst development have been made in the past five years. This Minireview summarizes some of the recent progress in the extensively studied Brookhart and Drent catalyst systems, as well as emerging alternative palladium and nickel catalysts.Emerging Palladium and Nickel Catalysts for Copolymerization of Olefins with Polar Monomersligand design; nickel; olefins; palladium; polymerizationx1332019122#N/AFALSE
4188
anie.20181449710.1002/anie.201814497https://doi.org/10.1002/anie.201814497Melchiorre, PAngew. Chem.-Int. Edit.We report a simple protocol for the photochemical Giese addition of C(sp(3))-centered radicals to a variety of electron-poor olefins. The chemistry does not require external photoredox catalysts. Instead, it harnesses the excited-state reactivity of 4-Alkyl-1,4-dihydropyridines (4-Alkyl-DHPs) to generate Alkyl radicals. Crucial for reactivity is the use of a catalytic amount of Ni(bpy)(3)(2+) (bpy=2,2'-bipyridyl), which acts as an electron mediator to facilitate the redox processes involving fleeting and highly reactive intermediates.A Redox-Active Nickel Complex that Acts as an Electron Mediator in Photochemical Giese Reactionsdihydropyridines; electron mediator; nickel catalysis; photochemistry; synthetic methodsPhotocatalyst41201949#N/AFALSE
4189
anie.20190192710.1002/anie.201901927FALSEhttps://doi.org/10.1002/anie.201901927Morken, JPAngew. Chem.-Int. Edit.beta-Boryl Carbonyl compounds are produced by a Ni-catalyzed cross-coupling of Vinylboron ate complexes and acid chloride or acid anhydride electrophiles. The reactions are efficient, being complete in as little as two minutes, and can be applied to a broad range of substrates.Catalytic Conjunctive Coupling of Carbonylic Acid Derivatives with 9-BBN-Derived Ate Complexesboron; catalysis; conjugative coupling; cross-coupling; nickel10201968#N/ATRUE
4190
anie.20181426510.1002/anie.201814265https://doi.org/10.1002/anie.201814265Reisner, EAngew. Chem.-Int. Edit.A precious-metal- and Cd-free photocatalyst system for efficient H-2 evolution from aqueous protons with a performance comparable to Cd-based quantum dots is presented. Rod-shaped ZnSe nanocrystals (nanorods, NRs) with a Ni(BF4)(2) co-catalyst suspended in aqueous ascorbic acid evolve H-2 with an activity up to 54 +/- 2 mmol(H2) g(ZnSe)(-1) h(-1) and a quantum yield of 50 +/- 4% (lambda=400nm) under visible light illumination (AM1.5G, 100 mWcm(-2), lambda > 400 nm). Under simulated full-spectrum solar irradiation (AM 1.5G, 100 mWcm(-2)), up to 149 +/- 22 mmol(H2) g(ZnSe)(-1) h(-1) is generated. Significant photocorrosion was not noticeable within 40 h and activity was even observed without an added co-catalyst. The ZnSe NRs can also be used to construct an inexpensive delafossite CuCrO2 photocathode, which does not rely on a sacrificial electron donor. Immobilized ZnSe NRs on CuCrO2 generate photocurrents of around -10 mu A cm(-2) in an aqueous electrolyte solution (pH 5.5) with a photocurrent onset potential of approximately +0.75V vs. RHE. This work establishes ZnSe as a state-of-the-art light absorber for photocatalytic and photoelectrochemical H-2 generation.ZnSe Nanorods as Visible-Light Absorbers for Photocatalytic and Photoelectrochemical H-2 Evolution in Waterdelafossite; hydrogen; photocatalysis; photocathode; zinc selenidePhotocatalystx56201967#N/AFALSE
4191
anie.20181423310.1002/anie.201814233https://doi.org/10.1002/anie.201814233Maseras, FAngew. Chem.-Int. Edit.The computational characterization of the full catalytic cyCle for the synthesis of indoline from the reaction between iodoacetanilide and a terminal alkene catalyzed by a nickel complex and a photoactive ruthenium species is presented. A variety of oxidation states of nickel, Ni-0, Ni-I, Ni-II and Ni-III, is shown to participate in the mechanism. Ni-0 is necessary for the oxidative addition of the C-I bond, which goes through a Ni-I intermediate and results in a Ni-II .species. The Ni-II species inserts into the alkene, but does not undergo the reductive elimination necessary for C-N bond formation. This oxidatively induced reductive elimination can be accomplished only after oxidation to Ni(III )by the photoactive ruthenium species. All the reaction steps are computationally characterized, and the barriers for the single-electron transfer steps calculated using a modified version of the Marcus Theory.Four Oxidation States in a Single Photoredox Nickel-Based Catalytic CyCle: A Computational StudycyClizations; density-functional calculations; nickel; photochemistry; reaction mechanismsPhotocatalyst13201968#N/AFALSE
4192
anie.20190186010.1002/anie.201901860FALSEhttps://doi.org/10.1002/anie.201901860Oestreich, MAngew. Chem.-Int. Edit.Robust procedures for two mechanistically distinct C(sp(3))-Ge bond formations from Alkyl electrophiles and germanium nuCleophiles are reported. The germanium reagents were made available as bench-stable solutions by lithium-to-magnesium and lithium-to-zinc transmetalation, respectively. The germanium Grignard reagent reacts with various primary and secondary Alkyl electrophiles by an ionic nuCleophilic displacement. Conversely, the coupling of the corresponding zinc reagent requires a nickel catalyst, which then engages in radical bond formations with primary, secondary, and even tertiary Alkyl bromides. Both methods avoid the regioselectivity issue of alkene hydrogermylation and enable the synthesis of a wide range of functionalized Alkyl-substituted germanes.Mechanistic Dichotomy of Magnesium- and Zinc-Based Germanium NuCleophiles in the C(sp(3))-Ge Cross-Coupling with Alkyl Electrophilesgermanium; magnesium; nuCleophilic substitution; radical cross-coupling; zinc5201935#N/ATRUE
4193
anie.20190181310.1002/anie.201901813FALSEhttps://doi.org/10.1002/anie.201901813Barpanda, PAngew. Chem.-Int. Edit.Sodium cobalt metaphosphate [NaCo(PO3)(3)] has CoO octahedra (CoO6) and shows superior oxygen evolution reaction (OER) activity in alkaline solution, comparable with the state-of-the-art precious-metal RuO2 catalyst. OER catalysts of this metaphosphate are prepared by combustion (Cb) and solid-state (SS) methods. The combustion-assisted method offers a facile synthesis and one-step carbon composite formation. Unusually high catalytic activity was observed in NCoM-Cb-Ar and could be due to chemical coupling effects between NaCo(PO3)(3) and partially graphitized carbon. This novel electrocatalyst exhibits very small overpotential of 340mV with high mass activity of 532Ag(-1). Good charge transfer abilities and chemical coupling between NaCo(PO3)(3) and amorphous carbon gives the OER activity in NCoM-Cb-Ar.Sodium Cobalt Metaphosphate as an Efficient Oxygen Evolution Reaction Catalyst in Alkaline Solution33201961#N/ATRUE
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anie.20190180110.1002/anie.201901801TRUEhttps://doi.org/10.1002/anie.201901801Guo, CAngew. Chem.-Int. Edit.Lewis-acid catalysis and electrochemistry represent two powerful fields that have found widespread application in organic chemistry. Reported herein is an asymmetric electrosynthesis in combination with a chiral Ni catalyst leading to an intermolecular Alkylation reaction in good yields with excellent enantioselectivities (up to 97% ee). Mechanistic studies suggest that the Lewis-acid-bound radical intermediate from a single-electron anodic oxidation selectively reacts with the Benzylic radical species to generate the desired adducts.Asymmetric Lewis Acid Catalyzed Electrochemical Alkylationasymmetric catalysis; electrochemistry; Lewis acids; nickel; radicalsCsp2-Csp3HHH
Carbonyl
No baseNo Base322019596/29/2022TRUE
4195
anie.20181270210.1002/anie.201812702https://doi.org/10.1002/anie.201812702Lloret-Fillol, JAngew. Chem.-Int. Edit.The chemical inertness of abundant and commercially available Alkyl chlorides preCludes their widespread use as reactants in chemical transformations. Presented in this work is a metallaphotoredox methodology to achieve the catalytic intramolecular reductive cyClization of unactivated Alkyl chlorides with tethered alkenes. The Cleavage of strong C(sp(3))-Cl bonds is mediated by a highly nuCleophilic low-valent cobalt or nickel intermediate generated by visible-light photoredox reduction employing a copper photosensitizer. The high basicity and multidentate nature of the ligands are key to obtaining efficient metal catalysts for the functionalization of unactivated Alkyl chlorides.Reductive CyClization of Unactivated Alkyl Chlorides with Tethered Alkenes under Visible-Light Photoredox CatalysiscyClizations; haloalkanes; photochemistry; reaction mechanisms; synthetic methodsPhotocatalyst22201963#N/AFALSE
4196
anie.20181260110.1002/anie.201812601https://doi.org/10.1002/anie.201812601Guo, LAngew. Chem.-Int. Edit.Electrochemical water splitting requires efficient, low-cost water oxidation catalysts to accelerate the sluggish kinetics of the water oxidation reaction. A rapid photocorrosion method is now used to synthesize the homogeneous amorphous nanocages of Cu-Ni-Fe hydr(oxy)oxide as a highly efficient electrocatalyst for the oxygen evolution reaction (OER). The as-fabricated product exhibits a low overpotential of 224mV on a glassy carbon electrode at 10mAcm(-2) (even lower down to 181mV when supported on Ni foam) with a Tafel slope of 44mVdec(-1) for OER in an alkaline solution. The obtained catalyst shows an extraordinarily large mass activity of 1464.5Ag(-1) at overpotential of 300mV, which is the highest mass activity for OER. This synthetic strategy may open a brand new pathway to prepare copper-based ternary amorphous nanocages for greatly enhanced oxygen evolution.Amorphous Nanocages of Cu-Ni-Fe Hydr(oxy)oxide Prepared by Photocorrosion For Highly Efficient Oxygen Evolutionamorphous materials; mass activity; nanocages; oxygen evolution reaction; ternary CuNiFePhotocatalystx66201925#N/AFALSE
4197
anie.20190106710.1002/anie.201901067FALSEhttps://doi.org/10.1002/anie.201901067Wang, CAngew. Chem.-Int. Edit.Reported is an asymmetric reductive dicarbofunctionalization of unactivated alkenes. Under the catalysis of a Ni/box system, various Aryl bromides, incorporating a pendant olefinic unit, were successfully reacted with an array of primary Alkyl bromides in the presence of Zn as a reductant, furnishing a series of benzene-fused cyClic compounds bearing a quaternary stereocenter in high enantioselectivities. Notably, this reaction avoids the use of pregenerated organometallics and demonstrates high tolerance of sensitive functionalities. The preliminary mechanistic investigations reveal that this Ni-catalyzed reaction proceeds as a cascade consisting of migratory insertion and cross-coupling with a nickel(I)-mediated intramolecular 5-exo cyClization as the enantiodetermining step.Nickel-Catalyzed Asymmetric Reductive ArylAlkylation of Unactivated Alkenesalkenes; annulations; asymmetric catalysis; nickel; synthetic methods64201956#N/ATRUE
4198
anie.20190098310.1002/anie.201900983FALSEhttps://doi.org/10.1002/anie.201900983Whitby, RJAngew. Chem.-Int. Edit.The endohedral fullerene CH4@C-60, in which each C-60 fullerene cage encapsulates a single methane molecule, has been synthesized for the first time. Methane is the first organic molecule, as well as the largest, to have been encapsulated in C-60 to date. The key orifice contraction step, a photochemical desulfinylation of an open fullerene, was completed, even though it is inhibited by the endohedral molecule. The crystal structure of the nickel(II) octaethylporphyrin/benzene solvate shows no significant distortion of the carbon cage, relative to the C-60 analogue, and shows the methane hydrogens as a shell of electron density around the central carbon, indicative of the quantum nature of the methane. The H-1 spin-lattice relaxation times (T-1) for endohedral methane are similar to those observed in the gas phase, indicating that methane is freely rotating inside the C-60 cage. The synthesis of CH4@C-60 opens a route to endofullerenes incorporating large guest molecules and atoms.First Synthesis and Characterization of CH4@C-60endohedral fullerene; mass spectrometry; NMR spectroscopy; synthetic methods; X-ray diffraction30201958#N/ATRUE
4199
anie.20181210010.1002/anie.201812100FALSEhttps://doi.org/10.1002/anie.201812100Jagadeesh, RVAngew. Chem.-Int. Edit.The preparation of nickel nanopartiCles as efficient reductive amination catalysts by pyrolysis of in situ generated Ni-tartaric acid complex on silica is presented. The resulting stable and reusable Ni-nanocatalyst enables the synthesis of functionalized and structurally diverse primary Benzylic, heterocyClic and aliphatic amines starting from inexpensive and readily available Carbonyl compounds and ammonia in presence of molecular hydrogen. Applying this Ni-based amination protocol, -NH2 moiety can be introduced in structurally complex compounds, for example, steroid derivatives and pharmaceuticals.Reusable Nickel NanopartiCles-Catalyzed Reductive Amination for Selective Synthesis of Primary Aminesammonia; Carbonyl compounds; nickel nanopartiCles; primary amines; reductive aminationx41201964#N/AFALSE
4200
anie.20181208110.1002/anie.201812081https://doi.org/10.1002/anie.201812081Domen, KAngew. Chem.-Int. Edit.Photoelectrochemical water splitting is regarded as a promising approach to the production of hydrogen, and the development of efficient photoelectrodes is one aspect of realizing practical systems. In this work, transparent Ta3N5 photoanodes were fabricated on n-type GaN/sapphire substrates to promote O-2 evolution in tandem with a photocathode, to realize overall water splitting. Following the incorporation of an underlying GaN layer, a photocurrent of 6.3 mA cm(-2) was achieved at 1.23 V vs. a reversible hydrogen electrode. The transparency of Ta3N5 to wavelengths longer than 600 nm allowed incoming solar light to be transmitted to a CuInSe2 (CIS), which absorbs up to 1100 nm. A stand-alone tandem cell with a serially-connected dual-CIS unit terminated with a Pt/Ni electrode was thus constructed for H-2 evolution. This tandem cell exhibited a solar-to-hydrogen energy conversion efficiency greater than 7 % at the initial stage of the reaction.Transparent Ta3N5 Photoanodes for Efficient Oxygen Evolution toward the Development of Tandem Cells(oxy)nitrides; photoelectrochemical tandem cell; photoelectrochemistry; solar energy conversion; water splittingPhotocatalyst34201950#N/AFALSE
4201
anie.20181192510.1002/anie.201811925FALSEhttps://doi.org/10.1002/anie.201811925Meyer, FAngew. Chem.-Int. Edit.Reductive coupling of nitric oxide (NO) to give N2O is an important reaction in the global nitrogen cyCle. Here, a dinickel(II) dihydride complex 1 that releases H-2 upon substrate binding and serves as a masked dinickel(I) scaffold is shown to reductively couple two molecules of NO within the bimetallic Cleft. The resulting hyponitrite complex 2 features an unprecedented cis-[N2O2](2-) binding mode that has been computationally proposed as a key intermediate in flavodiiron nitric oxide reductases (FNORs). NMR and DFT evidence indicate facile rotational fluxionality of the [N2O2](2-) unit, which allows to access an isomer that is prone to N2O release. Protonation of 2 is now found to trigger rapid N2O evolution and formation of a hydroxido bridged complex, reminiscent of FNOR reactivity. This work provides fundamental insight into the biologically relevant reductive coupling of two NO molecules and the subsequent trajectory towards N2O formation at bimetallic sites.Reductive Nitric Oxide Coupling at a Dinickel Core: Isolation of a Key cis-Hyponitrite Intermediate en route to N2O FormationdinuClear complexes; hyponitrite complexes; nickel; nitric oxide; small molecule Activationx20201930#N/AFALSE
4202
anie.20181154510.1002/anie.201811545https://doi.org/10.1002/anie.201811545Lin, ZNickel Metal-Organic Framework Monolayers for Photoreduction of Diluted CO2: Metal-Node-Dependent Activity and SelectivityPhotocatalyst2018#N/AFALSE
4203
anie.20181142010.1002/anie.201811420FALSEhttps://doi.org/10.1002/anie.201811420Ng, DKPAngew. Chem.-Int. Edit.Condensation of 1,8-diamino-3,6-dichlorocarbazole with a series of disubstituted 1,3-diiminoisoindolines, followed by treatment with BF3OEt2 led to the formation of the corresponding core-expanded boron(III) subphthalocyanine analogues. These air-stable pi-conjugated boron(III) carbazosubphthalocyanines possess two boron-containing seven-membered-ring units and a 16 pi-electron skeleton, and represent the first examples of antiaromatic boron(III) subphthalocyanine analogues as supported by spectroscopic and theoretical studies. The molecular structure of one of these compounds was unambiguously determined by single-crystal X-ray diffraction analysis. In contrast to typical boron(III) subphthalocyanines, which adopt a cone-shaped structure, the pi skeleton of this compound is almost planar.Boron(III) Carbazosubphthalocyanines: Core-Expanded Antiaromatic Boron(III) Subphthalocyanine Analoguesaromaticity; boron; magnetic circular dichroism; macrocyCles; structure elucidationx0201964#N/AFALSE
4204
anie.20190095610.1002/anie.201900956FALSEhttps://doi.org/10.1002/anie.201900956Mei, TSAngew. Chem.-Int. Edit.Transition-metal-catalyzed coupling reactions are useful tools for synthesizing Aryl sulfur compounds. However, conventional transition-metal-catalyzed thiolation of Aryl bromides and chlorides typically requires the use of strong base under elevated reaction temperature. Herein, we report the first examples of nickel-catalyzed electrochemical thiolation of Aryl bromides and chlorides in the absence of an external base at room temperature using undivided electrochemical cells.Nickel-Catalyzed Thiolation of Aryl Halides and HeteroAryl Halides through Electrochemistrynickel; electrocatalysis; electrosynthesis; thiolation; thiyl radicals672019112#N/ATRUE
4205
anie.20181121110.1002/anie.201811211https://doi.org/10.1002/anie.201811211Zheng, LSAngew. Chem.-Int. Edit.Heterometallic lanthanide-transition-metal (4f-3d) Clusters with well-defined crystal structures integrate multiple metal centers and provide a platform for achieving synergistic catalytic effects. Herein, we present a strategy for enhanced hydrogen evolution by loading atomically precise 4f-3d Clusters Ln(52)Ni(56) on a CdS photoabsorber surface. Interestingly, some Ni2+ ions in the Clusters Ln(52)Ni(56) were exchanged by the Cd2+ to form Ln(52)Ni(56-x)Cd(x)/CdS composites. Photocatalytic studies show that the efficient synergistic multipath charge separation and transfer from CdS to the Eu52Ni56-xCdx Cluster enable high visible-light-driven hydrogen evolution at 25353molh(-1)g(-1). This work provides the strategy to design highly active photocatalytic hydrogen evolution catalysts by assembling heterometallic 4f-3d Clusters on semiconductor materials.Integration of Lanthanide-Transition-Metal Clusters onto CdS Surfaces for Photocatalytic Hydrogen EvolutionClusters (4f-3d); hydrogen evolution; cadmium sulfide; photocatalysisPhotocatalyst58201833#N/AFALSE
4206
anie.20190079210.1002/anie.201900792FALSEhttps://doi.org/10.1002/anie.201900792Osuka, AAngew. Chem.-Int. Edit.A bis(Ni-II-porphyrinyl)aminyl radical with meso-C6F5 groups was prepared as a spin-delocalized stable aminyl radical with a doublet spin state. Upon addition of pyridine, both Ni-II centers became hexa-coordinated by accepting two axial pyridines, which triggered a spin-state change of the Ni-II centers from diamagnetic (S = 0) to paramagnetic (S = 1). The resulting high-spin Ni-II centers interact with the aminyl radical ferromagnetically to give rise to an overall sextet state (S = 5/2). Importantly, this coordination-induced spin-state switching can be conducted in a reversible manner, in that washing of the high-spin radical with aqueous hydrochloric acid regenerates the original doublet radical in good yield.Coordination-Induced Spin-State Switching of an Aminyl-Radical-Bridged Nickel(II) Porphyrin Dimer between Doublet and Sextet Statescoordination-induced spin-state switch; molecular magnetism; nickel; porphyrins; radicals8201945#N/ATRUE
4207
anie.20190065910.1002/anie.201900659FALSEhttps://doi.org/10.1002/anie.201900659Lautens, MAngew. Chem.-Int. Edit.A diastereoselective dearomative carboiodination reaction is reported. We report a novel metal-catalyzed approach to install reactive secondary Benzylic iodides. Utilizing the unique reactivity of nickel, we have expanded the carboiodination reaction to non-activated aromatic double bonds forming a previously unattainable Class of iodides. We also report a broadly applicable method to avoid the use of a metallic reducing agent by utilizing an Alkyl phosphite as the ligand. The reaction is thought to proceed through a syn intramolecular carbonickelation across a 2-substituted indole followed by a diastereoretentive reductive elimination of the carbon-iodine bond. The complex iodinated indolines generated in the reaction were obtained in moderate to good yields and good to excellent diastereoselectivity. The products were easily functionalized by a variety of synthetic methods.Forming Benzylic Iodides via a Nickel Catalyzed Diastereoselective Dearomative Carboiodination Reaction of Indolescarbohalogenation; dearomative reaction; diastereoselective catalysis; indoles; nickel40201964#N/ATRUE
4208
anie.20181094710.1002/anie.201810947https://doi.org/10.1002/anie.201810947Maes, BUWAngew. Chem.-Int. Edit.A new three-component reductive Arylation of amides with stable reactants (iPrOH and Arylboronate esters), making use of a 2-pyridinyl (Py) directing group, is described. The N-Py-amide substrates are readily prepared from Carbonylic acids and PyNH2, and the resulting N-Py-1-Arylalkanamine reaction products are easily transformed into the corresponding chlorides by substitution of the HN-Py group with HCl. The 1-Aryl-1-chloroalkane products allow substitution and cross-coupling reactions. Therefore, a general protocol for the transformation of Carbonylic acids into a variety of functionalities is obtained. The Py-NH2 by-product can be recyCled.Ruthenium-Catalyzed Reductive Arylation of N-(2-Pyridinyl)amides with Isopropanol and Arylboronate Estersamides; amines; Arylation; multicomponent reactions; rutheniumx11201959#N/AFALSE
4209
anie.20181077710.1002/anie.201810777FALSEhttps://doi.org/10.1002/anie.201810777Zhou, SHAngew. Chem.-Int. Edit.We report a facile and generic method for the synthesis of hollow mesoporous silica nanoreactors (HMSNs) with small-sized metal oxide nanopartiCles (NPs) inside their cavities. They were made by deposition of silica onto metal-containing charge-driven polymer micelles and subsequent calcination. The micelles consist of 1)negatively charged supramolecular polyelectrolyte chains of bis-ligand-bound metal ions, and 2)water-soluble, neutral/positive diblock copolymers. Owing to the facile coordination between transition-metal ion and the employed bidentate ligand, a series of HMSNs with <2nm MxOy NPs inside cavities (M=Mn, Co, Ni, Cu, or Zn) were obtained by simply varying the metal ions inside the micelles. The developed method circumvents the pre- and post-synthesis of metal oxide NPs; after calcination, hollow mesoporous nanostructures containing small-sized metal oxide NPs inside their cavities are directly obtained. The CoxOy-functionalized HMSNs catalyze the degradation of various dyes with H2O2.A Generic Method for Preparing Hollow Mesoporous Silica Catalytic Nanoreactors with Metal Oxide NanopartiCles inside Their Cavitiesdye degradation; heterogeneous catalysis; mesoporous materials; nanoreactors; transition-metal oxidesx31201840#N/AFALSE
4210
anie.20190022810.1002/anie.201900228FALSEhttps://doi.org/10.1002/anie.201900228Diao, TNAngew. Chem.-Int. Edit.A nickel-catalyzed asymmetric diArylation reaction of Vinylarenes enables the preparation of chiral alpha,alpha,beta-triArylated ethane scaffolds, which exist in a number of biologically active molecules. The use of reducing conditions with Aryl bromides as coupling partners obviates the need for stoichiometric organometallic reagents and tolerates a broad range of functional groups. The application of an N-oxyl radical as a ligand to a nickel catalyst represents a novel approach to facilitate nickel-catalyzed cross-coupling reactions.Nickel-Catalyzed Asymmetric Reductive DiArylation of Vinylarenesalkenes; Aryl bromides; asymmetric catalysis; diArylation; nickel83201969#N/ATRUE
4211
anie.20181052610.1002/anie.201810526https://doi.org/10.1002/anie.201810526Hashmi, ASKAngew. Chem.-Int. Edit.Herein we report a highly selective photoredox C(sp(3))-H Alkylation/Arylation of ethers through the combination of a photo-organocatalyst (benzaldehyde) and a transition-metal catalyst (nickel). This method provides a simple and general strategy for the C(sp(3))-H Alkylation/Arylation of ethers. A selective late-stage modification of (-)-ambroxide has also been conducted to demonstrate the applicability of the method.The Combination of Benzaldehyde and Nickel-Catalyzed Photoredox C(sp(3))-H Alkylation/ArylationAlkylation; Arylation; benzaldehyde; nickel catalysis; photoredox reactionPhotocatalyst392019416/1/2022FALSE
4212
anie.20181470110.1002/anie.201814701FALSEhttps://doi.org/10.1002/anie.201814701Itami, KAngew. Chem.-Int. Edit.2,2 '-Bipyridyls have been utilized as indispensable ligands in metal-catalyzed reactions. The most streamlined approach for the synthesis of 2,2 '-bipyridyls is the dehydrogenative dimerization of unfunctionalized pyridine. Herein, we report on the palladium-catalyzed dehydrogenative synthesis of 2,2 '-bipyridyl derivatives. The Pd catalysis effectively works with an Ag-I salt as the oxidant in the presence of pivalic acid. A variety of pyridines regioselectively react at the C2-positions. This dimerization method is applicable for challenging substrates such as sterically hindered 3-substituted pyridines, where the pyridines regioselectively react at the C2-position. This reaction enables the concise synthesis of twisted 3,3 '-disubstituted-2,2 '-bipyridyls as an underdeveloped Class of ligands.Dehydrogenative Synthesis of 2,2 '-Bipyridyls through Regioselective Pyridine Dimerization11201946#N/ATRUE
4213
anie.20181434010.1002/anie.201814340FALSEhttps://doi.org/10.1002/anie.201814340Oestreich, MAngew. Chem.-Int. Edit.An enantioselective C(sp(3))-C(sp(3)) cross-coupling of racemic alpha-silylated Alkyl iodides and Alkylzinc reagents is reported. The reaction is catalyzed by NiCl2/(S,S)-Bn-Pybox and yields alpha-chiral silanes with high enantiocontrol. The catalyst system does not promote the cross-coupling of the corresponding carbon analogue, corrB(OH)2rating the stabilizing effect of the silyl group on the Alkyl radical intermediate (alpha-silicon effect). Both coupling partners can be, but do not need to be, functionalized, and hence, even alpha-chiral silanes with no functional group in direct proximity of the asymmetrically substituted carbon atom become accessible. This distinguishes the new method from established approaches for the synthesis of alpha-chiral silanes.Enantioselective Construction of alpha-Chiral Silanes by Nickel-Catalyzed C(sp(3))-C(sp(3)) Cross-Couplingcross-coupling; nickel; radical reactions; silicon; synthetic methods17201950#N/ATRUE
4214
anie.20181420810.1002/anie.201814208FALSEhttps://doi.org/10.1002/anie.201814208Fu, GCAngew. Chem.-Int. Edit.Metal-catalyzed enantioconvergent cross-coupling reactions of Alkyl electrophiles are emerging as a powerful tool in asymmetric synthesis. To date, high enantioselectivity has been limited to couplings of electrophiles that bear a directing group or a proximal p/pi orbital. Herein, we demonstrate for the first time that enantioconvergent cross-couplings can be achieved with electrophiles that lack such features; specifically, we establish that a chiral nickel catalyst can accomplish Negishi reactions of racemic alpha-halosilanes with Alkylzinc reagents with good enantioselectivity under simple and mild conditions, thereby providing access to enantioenriched organosilanes, an important Class of target molecules.Enantioconvergent Cross-Couplings of Alkyl Electrophiles: The Catalytic Asymmetric Synthesis of OrganosilanesAlkylation; asymmetric catalysis; cross-coupling; nickel; silicon24201927#N/ATRUE
4215
anie.20180991910.1002/anie.201809919https://doi.org/10.1002/anie.201809919Molander, GAAngew. Chem.-Int. Edit.A regioselective, nickel-catalyzed photoredox allylation of secondary, Benzyl, and alpha-alkoxy radical precursors is disClosed. Through this manifold, a variety of linear allylic alcohols and allylated monosaccharides are accessible in high yields under mild reaction conditions. Quantum mechanical calculations [DET and DLPNO-CCSD(T)/support the mechanistic hypothesis of a Ni-0 to Ni-11 oxidative addition pathway followed by radical addition and inner-sphere allylation.Photoredox/Nickel-Catalyzed Single-Electron Tsuji-Trost Reaction: Development and Mechanistic Insightsallylic compounds; nickel; photochemistry; reaction mechanism; synthetic methodsPhotocatalyst372018666/15/2022FALSE
4216
anie.20181403410.1002/anie.201814034FALSEhttps://doi.org/10.1002/anie.201814034Boscher, NDAngew. Chem.-Int. Edit.Oxidative polymerization of nickel(II) 5,15-diphenyl porphyrin and nickel(II) 5,15-bis(di-3,5-tert-butylphenyl) porphyrin by oxidative chemical vapor deposition (oCVD) yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables one-step formation, deposition, and p-doping of conjugated poly(porphyrins) coatings without solvents or post-treatments. The decisive reactions and side reactions during the oCVD process are shown by high-resolution mass spectrometry. Owing to the highly conjugated structure of the fused tapes, the thin films exhibit an electrical conductivity of 3.6x10(-2)Scm(-1) and strong absorption in the visible to near-infrared spectral region. The formation of smooth conjugated poly(porphyrins) coatings, even on sensitive substrates, is demonstrated by deposition and patterning on glass, silicon, and paper. Formation of conductive poly(porphyrins) thin films could enable the design of new optoelectronic devices using the oCVD approach.Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approachchemical vapor deposition; oxidative coupling; polymerization; porphyrins; thin films14201940#N/ATRUE
4217
anie.20180985810.1002/anie.201809858FALSEhttps://doi.org/10.1002/anie.201809858Chen, JSAngew. Chem.-Int. Edit.As a new type of heterogeneous catalyst with homogeneous-like activity, single-site transition-metal materials are usually treated as integrated but separate active centers. A novel grouping effect is reported for single Ni N-4 sites in nitrogen-doped carbon (Ni/NC), where an effective ligand-stabilized polycondensation method endows Ni/NC nanocatalysts with a high content of single-site Ni up to 9.5 wt%. The enhanced electron density at each single Ni-N-4 site promotes a highly efficient hydrogen transfer, which is exemplified by the coupling of Benzyl alcohol and aniline into N-Benzylaniline with a turnover frequency (TOF) value of 7.0 mol(N-Benzylaniline)mol(metal)(-1) h(-1); this TOF outpaces that of reported stable non-noble-metal-based catalysts by a factor of 2.Grouping Effect of Single Nickel-N-4 Sites in Nitrogen-Doped Carbon Boosts Hydrogen Transfer Coupling of Alcohols and Aminesgrouping effect; hydrogen transfer; N-doped carbon; single-site nickelx24201838#N/AFALSE
4218
anie.20180978710.1002/anie.201809787FALSEhttps://doi.org/10.1002/anie.201809787Driess, MAngew. Chem.-Int. Edit.The synthesis of structurally ordered non-noble intermetallic cobalt stannide (CoSn2) nanocrystals and their utilization for high-performance electrocatalytic overall water-splitting is presented. The structurally and electronically beneficial properties of the tetragonal CoSn2 exhibit a considerably low overpotential for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on fluorine-doped tin oxide (FTO) and Ni foam (NF). Loss of Sn from the crystal lattices and oxidation of Co under strongly alkaline conditions furnishes highly disordered amorphous active CoOx(H), the catalytically active structure for OER. The Co-0 atoms in the CoSn2 act as active sites for HER and the presence of Sn provides efficient electrical conductivity. This intermetallic phase is a novel type of cost-effective and competitive bifunctional electrocatalysts and predestinated for overall water-splitting devices: A two-electrode electrolyzer with CoSn2 on NF delivers a cell voltage of merely 1.55 V at 10 mAcm(-2) maintaining long-term stability.Structurally Ordered Intermetallic Cobalt Stannide Nanocrystals for High-Performance Electrocatalytic Overall Water-Splittingcobalt stannide; intermetallic compounds; oxygen and hydrogen evolution; renewable energy; water-splitting electrocatalysisx51201841#N/AFALSE
4219
anie.20180949310.1002/anie.201809493https://doi.org/10.1002/anie.201809493Lin, WBAngew. Chem.-Int. Edit.Metal-organic frameworks (MOFs) have been extensively used for single-site catalysis and light harvesting, but their application in multicomponent photocatalysis is unexplored. We report here the successful incorporation of an Ir-III photoredox catalyst and a Ni-II cross-coupling catalyst into a stable Zr-12 MOF, Zr-12-Ir-Ni, to efficiently catalyze C-S bond formation between various Aryl iodides and thiols. The proximity of the Ir-III and Ni-II catalytic components to each other (ca. 0.6nm) in Zr-12-Ir-Ni greatly facilitates electron and thiol radical transfers from Ir to Ni centers to reach a turnover number of 38500, an order of magnitude higher than that of its homogeneous counterpart. This work highlights the opportunity in merging photoredox and organometallic catalysts in MOFs to effect challenging organic transformations.Merging Photoredox and Organometallic Catalysts in a Metal-Organic Framework Significantly Boosts Photocatalytic Activitiesheterogeneous catalysis; metal-organic frameworks; nickel; photochemistry; sulfidesPhotocatalyst42201845#N/AFALSE
4220
anie.20180943110.1002/anie.201809431https://doi.org/10.1002/anie.201809431Molander, GAAngew. Chem.-Int. Edit.The union of photoredox and nickel catalysis has resulted in a renaissance in radical chemistry as well as in the use of nickel-catalyzed transformations, specifically for carbon-carbon bond formation. Collectively, these advances address the longstanding challenge of late-stage cross-coupling of functionalized Alkyl fragments. Empowered by the notion that photocatalytically generated Alkyl radicals readily undergo capture by Ni complexes, wholly new feedstocks for cross-coupling have been realized. Herein, we highlight recent developments in several types of Alkyl cross-couplings that are accessible exClusively through this approach.Alkyl Carbon-Carbon Bond Formation by Nickel/Photoredox Cross-CouplingAlkyl radicals; cross-coupling; nickel; photocatalysis; single-electron transmetalationPhotocatalyst1792019148#N/AFALSE
4221
anie.20181318410.1002/anie.201813184FALSEhttps://doi.org/10.1002/anie.201813184Wang, XSAngew. Chem.-Int. Edit.A nickel-catalyzed 1,4-carbofluoroAlkylation of 1,3-enynes to access structurally diverse fluoroAlkylated allenes has been established. This method has demonstrated high catalytic reactivity, mild reaction conditions, broad substrate scope, and excellent functional-group tolerance. The key to success is the use of a nickel catalyst to generate different fluoroAlkyl radicals from readily available and structurally diverse fluoroAlkyl halides to access 1,4-difunctionalization of 1,3-enynes by a radical relay. This strategy provides facile synthesis of structurally diverse multisubstituted allenes, and offers a solution for batch production of various fluorinated bioactive molecules for drug discovery by further transformations.Nickel-Catalyzed CarbofluoroAlkylation of 1,3-Enynes to Access Structurally Diverse FluoroAlkylated Allenesallenes; carbofluoroAlkylation; nickel; radicals; synthetic methods492019116#N/ATRUE
4222
anie.20181258010.1002/anie.201812580FALSEhttps://doi.org/10.1002/anie.201812580Baran, PSAngew. Chem.-Int. Edit.Nickel-Catalyzed Barton DeCarbonylation and Giese Reactions: A Practical Take on Classic Transforms (vol 56, pg 260, 2017)120194#N/ATRUE
4223
anie.20181254510.1002/anie.201812545FALSEhttps://doi.org/10.1002/anie.201812545Huang, XQAngew. Chem.-Int. Edit.Perovskite-based electrocatalysts are one of the most promising materials for oxygen evolution reaction (OER), but their activity and durability are still far from desirable. Herein, we demonstrate that the double perovskite LaFexNi1-xO3 (LFNO) nanorods (NRs) can be adopted as highly active and stable OER electrocatalysts. The optimized LFNO-II NRs with Ni/Fe ratio of 8:2 achieve a low overpotential of 302 mV at 10 mA cm(-2) and a small Tafel slope of 50 mV dec(-1), outperforming those of the commercial Ir/C. The LFNO-II NRs also show high OER stability with slight current decrease after 20 h. The enhanced activity is explained by the improved surface area, tailored electronic structure as well as strong hybridization between O and Ni.Double Perovskite LaFexNi1-xO3 Nanorods Enable Efficient Oxygen Evolution Electrocatalysisdouble perovskite; electronic; Iron; LaNiO3; oxygen evolution reaction73201941#N/ATRUE
4224
anie.20181124110.1002/anie.201811241FALSEhttps://doi.org/10.1002/anie.201811241Zhang, BAngew. Chem.-Int. Edit.The oxygen evolution reaction (OER) is an important half reaction in many energy conversion and storage techniques. However, the development of a low-cost easy-prepared OER electrocatalyst with high mass activity and rapid kinetics is still challenging. Herein, we report the facile deposition of tannin-NiFe (TANF) complex film on carbon fiber paper (CP) as a highly efficient OER electrocatalyst. TANF gives rapid OER reaction kinetics with a very small Tafel slope of 28 mV dec(-1). The mass activity of TANF reaches 9.17 x 10(3) Ag-1 at an overpotential of 300 mV, which is nearly 200-times larger than that of NiFe double layered hydroxide. Furthermore, tannic acid in TANF can be electrochemically extracted under anodic potential, leaving the inorganic composite NixFe1-xOyHz as the OER-active species. This work may provide a guide to probing the electrochemical transformation and investigating the reactive species of other metal-organic complexes as heterogeneous electrocatalysts.In Situ Electrochemical Conversion of an Ultrathin Tannin Nickel Iron Complex Film as an Efficient Oxygen Evolution Reaction Electrocatalystactive species; NiFe electrocatalyst; oxygen evolution reaction; tannic complex; water splitting103201942#N/ATRUE
4225
anie.20180881810.1002/anie.201808818FALSEhttps://doi.org/10.1002/anie.201808818Boettcher, SWAngew. Chem.-Int. Edit.Iron cations are essential for the high activity of nickel and cobalt-based (oxy)hydroxides for the oxygen evolution reaction, but the role of iron in the catalytic mechanism remains under active investigation. Operando X-ray absorption spectroscopy and density functional theory calculations are used to demonstrate partial Fe oxidation and a shortening of the Fe-O bond length during oxygen evolution on Co(Fe)OxHy. Cobalt oxidation during oxygen evolution is only observed in the absence of iron. These results demonstrate a different mechanism for water oxidation in the presence and absence of iron and support the hypothesis that oxidized iron species are involved in water-oxidation catalysis on Co(Fe)OxHy.Operando X-Ray Absorption Spectroscopy Shows Iron Oxidation Is Concurrent with Oxygen Evolution in Cobalt-Iron (Oxy)hydroxide Electrocatalystselectrocatalysts; heterogeneous catalysis; oxygen evolution; water electrolysis; X-ray absorption spectroscopyx64201842#N/AFALSE
4226
anie.20180862910.1002/anie.201808629FALSEhttps://doi.org/10.1002/anie.201808629Zhao, CAngew. Chem.-Int. Edit.Nickel-heteroatoms bridge sites are important reaction descriptors for many catalytic and electrochemical processes. Herein we report the controllable surface modification of nickel-nitrogen (Ni-N) bridge sites on metallic Ni partiCles via a simplified vapor-assisted treatment approach. X-ray absorption spectroscopy (XAS) and Operando Raman spectroscopy verifies the interaction between Ni and surface-anchored N, which leads to distorted Ni lattice structure with improved wettability. The Ni-N bridge sites with appropriate N coverage level plays a critical role in the enhanced hydrogen evolution reaction (HER) and the optimized electrode (Ni-N-0.19) has demonstrated superior HER performances with low overpotential merely of 42 mV for achieving a current density of 10 mA cm(-2), as well as favorable reaction kinetics and excellent durability in alkaline electrolyte. DFT calculations revealed that the appropriate N-coverage level can lead to the most favorable Delta G(H*) kinetics for both adsorption of H* and release of H-2, while high N coverage (Ni-N-0.59) results in weaker H* adsorption, thus a decreased HER activity, corresponding well to our experimental observations. Furthermore, this generic synthetic approach can also be applied to prepare S-modified Ni HER catalyst by generating hydrogen sulfide vapor.Processable Surface Modification of Nickel-Heteroatom (N, S) Bridge Sites for Promoted Alkaline Hydrogen Evolutionbridge sites; hydrogen evolution; N surface modification; Ni-N catalystx53201924#N/AFALSE
4227
anie.20181098310.1002/anie.201810983FALSEhttps://doi.org/10.1002/anie.201810983Zelder, FAngew. Chem.-Int. Edit.F430 is a unique enzymatic cofactor in the production and oxidation of methane by strictly anaerobic bacteria. The key enzyme methyl coenzymeM reductase (MCR) contains a hydroporphinoid nickel complex with a characteristic absorption maximum at around 430nm in its active site. Herein, the three-step semisynthesis of a hybrid Ni-II-containing corrinoid that partly resembles F430 in its structural and spectroscopic features from vitamin B-12 is presented. A key step of the route is the simultaneous demetalation and ring Closure reaction of a 5,6-secocobalamin to metal-free 5,6-dihydroxy-5,6-dihydrohydrogenobalamin with cobaltocene and KCN under reductive conditions. Studies on the coordination chemistry of the novel compound support an earlier hypothesis why nature carefully selected a corphin over a corrin ligand in F430 for challenging nickel-catalyzed biochemical reactions.A Nickel(II)-Containing Vitamin B-12 Derivative with a Cofactor-F430-type pi-Systemcorrinoids; F430 cofactor; nickel; semisynthesis; vitamin B1215201842#N/ATRUE
4228
anie.20180821510.1002/anie.201808215FALSEhttps://doi.org/10.1002/anie.201808215Artero, VAngew. Chem.-Int. Edit.[NiFe]-hydrogenase enzymes are efficient catalysts for H-2 evolution but their synthetic models have not been reported to be active under aqueous conditions so far. Here we show that a Close model of the [NiFe]-hydrogenase active site can work as a very active and stable heterogeneous H-2 evolution catalyst under mildly acidic aqueous conditions. Entry in catalysis is a (NiFeII)-Fe-I complex, with electronic structure analogous to the Ni-L state of the enzyme, corrB(OH)2rating the mechanism modification recently proposed for [NiFe]-hydrogenases.Hydrogen Evolution from Aqueous Solutions Mediated by a Heterogenized [NiFe]-Hydrogenase Model: Low pH Enables Catalysis through an Enzyme-Relevant Mechanismelectrocatalysis; heterogeneous catalysis; hydrogen evolution; [NiFe]-hydrogenase; reaction mechanismx47201829#N/AFALSE
4229
anie.20181095010.1002/anie.201810950FALSEhttps://doi.org/10.1002/anie.201810950Schoenbeck, FAngew. Chem.-Int. Edit.While the TeCF3 moiety features promising properties and potential in a range of applications, no direct synthetic method exists for its incorporation into aromatic scaffolds. This report features the first direct catalytic method for the formation of C(sp(2))-TeCF3 bonds. The method relies on a Pd/Xantphos catalytic system and allows for the trifluoromethyl-tellurolation of Aryl iodides. Our computational and experimental mechanistic analyses shed light on the privileged activity of Xantphos in this transformation.Chemoselective Pd-Catalyzed C-TeCF3 Coupling of Aryl Iodidesdensity functional calculations; fluorine; homogeneous catalysis; palladium7201855#N/ATRUE
4230
anie.20180804910.1002/anie.201808049FALSEhttps://doi.org/10.1002/anie.201808049Wu, YAngew. Chem.-Int. Edit.The arrangement of the active sites on the surface of a catalysts can reduce the problem of mass transfer and enhance the atom economy. Herein, supported Ni metal nanopartiCles can be transformed to thermal stable Ni single atoms, mostly located on the surface of the support. Assisted by N-doped carbon with abundant defects, this synthetic process not only transform the nanopartiCles to single atoms, but also creates numerous pores to facilitate the contact of dissolved CO2 and single Ni sites. The proposed mechanism is that the Ni nanopartiCles could break surface C-C bonds drill into the carbon matrix, leaving pores on the surface. When Ni nanopartiCles are exposed to N-doped carbon, the strong coordination splits Ni atoms from Ni NPs. The Ni atoms are stabilized within the surface of carbon substrate. The continuous loss of atomic Ni species from the NPs would finally result in atomization of Ni NPs. CO2 electroreduction testing shows that the surface enriched with Ni single atoms delivers better performance than supported Ni NPs and other similar catalysts.InSitu Thermal Atomization To Convert Supported Nickel NanopartiCles into Surface-Bound Nickel Single-Atom CatalystsCO2 electroreduction; nickel; porous carbons; single-atom catalysts; thermal atomizationx142201848#N/AFALSE
4231
anie.20180771710.1002/anie.201807717FALSEhttps://doi.org/10.1002/anie.201807717Zhang, BAngew. Chem.-Int. Edit.For electrocatalytic water splitting, the sluggish anodic oxygen evolution reaction (OER) restricts the cathodic hydrogen evolution reaction (HER). Therefore, developing an alternative anodic reaction with accelerating kinetics to produce value-added chemicals, especially coupled with HER, is of great importance. Now, a thermodynamically more favorable primary amine (-CH2-NH2) electrooxidation catalyzed by NiSe nanorod arrays in water is reported to replace OER for enhancing HER. The increased H-2 production can be obtained at cathode; meanwhile, a variety of aromatic and aliphatic primary amines are selectively electrooxidized to nitriles with good yields at the anode. Mechanistic investigations suggest that Ni-II/Ni-III may serve as the redox active species for the primary amines transformation. Hydrophobic nitrile products can readily escape from aqueous electrolyte/electrode interface, avoiding the deActivation of the catalyst and thus contributing to continuous gram-scale synthesis.Boosting Hydrogen Production by Anodic Oxidation of Primary Amines over a NiSe Nanorod Electrodeelectrocatalysis; energy efficiency; hydrogen evolution reaction; nanostructures; primary amine oxidationx102201862#N/AFALSE
4232
anie.20180762910.1002/anie.201807629https://doi.org/10.1002/anie.201807629MacMillan, DWCAngew. Chem.-Int. Edit.Herein, we report a convenient and broadly applicable strategy for the difluoromethylation of Aryl bromides by metallaphotoredox catalysis. Bromodifluoromethane, a simple and commercially available Alkyl halide, is harnessed as an effective source of difluoromethyl radical by silyl-radical-mediated halogen abstraction. The merger of this fluoroAlkyl electrophile Activation pathway with a dual nickel/photoredox catalytic platform enables the difluoromethylation of a diverse array of Aryl and heteroAryl bromides under mild conditions. The utility of this procedure is show cased in the late-stage functionalization of several drug analogues.Metallaphotoredox Difluoromethylation of Aryl Bromidesdifluoromethylation; fluorine; heterocyCles; nickel; photoredox catalysisPhotocatalyst66201843#N/AFALSE
4233
anie.20180753410.1002/anie.201807534FALSEhttps://doi.org/10.1002/anie.201807534Futaki, SAngew. Chem.-Int. Edit.Endocytosis is an important route for the intracellular delivery of biomacromolecules, wherein their inefficient endosomal escape into the cytosol remains a major barrier. Based on the understanding that endosomal membranes are negatively charged, we focused on the potential of cationic lytic peptides for developing endosomolysis agents to release such entrapped molecules. As such, a venom peptide, MastoparanX, was employed and redesigned to serve as a delivery tool. Appending a tri-glutamate unit to the N-terminus attenuates the cytotoxicity of MastoparanX by about 40 fold, while introduction of a Ni-II-dipicolylamine complex enhances cellular uptake of the peptide by about 17 fold. Using the optimized peptide, various fluorescently labeled macromolecules were successfully delivered to the cytosol, enabling live-cell imaging of acetylated histones.Modular Redesign of a Cationic Lytic Peptide To Promote the Endosomal Escape of Biomacromoleculescytotoxicity; drug delivery; membranes; peptides; tridentate ligandsx11201847#N/AFALSE
4234
anie.20181055010.1002/anie.201810550FALSEhttps://doi.org/10.1002/anie.201810550Xiong, YJAngew. Chem.-Int. Edit.Quantum dots (QDs), a Class of promising candidates for harvesting visible light, generally exhibit low activity and selectivity towards photocatalytic CO2 reduction. Functionalizing QDs with metal complexes (or metal cations through ligands) is a widely used strategy for improving their catalytic activity; however, the resulting systems still suffer from low selectivity and stability in CO2 reduction. Herein, we report that doping CdS QDs with transition-metal sites can overcome these limitations and provide a system that enables highly selective photocatalytic reactions of CO2 with H2O (100% selectivity to CO and CH4), with excellent durability over 60h. Doping Ni sites into the CdS lattice leads to effective trapping of photoexcited electrons at surface catalytic sites and substantial suppression of H-2 evolution. The method reported here can be extended to various transition-metal sites, and offers new opportunities for exploring QD-based earth-abundant photocatalysts.Enabling Visible-Light-Driven Selective CO2 Reduction by Doping Quantum Dots: Trapping Electrons and Suppressing H-2 Evolutioncatalytic sites; CO2 reduction; doping; photocatalysis; quantum dots100201830#N/ATRUE
4235
anie.20181027010.1002/anie.201810270FALSEhttps://doi.org/10.1002/anie.201810270Ogo, SAngew. Chem.-Int. Edit.The development of hydrogen fuel cells is greatly hindered by the unwanted generation of H2O2 at the cathode. A non-Pt cathode catalyst is now shown to be capable of simultaneously reducing both O-2 and H2O2 thus rendering 1-1 H2O2, a useful part of the feed stream. The applicability of this unique catalyst is demonstrated by employing it in a fuel cell running on H-2/CO and O-2/H2O2.Multifunctional Catalysts for H2O2-Resistant Hydrogen Fuel Cellselectrocatalysis; fuel cells; hydrogen peroxide; nickel; ruthenium2201830#N/ATRUE
4236
anie.20180654110.1002/anie.201806541FALSEhttps://doi.org/10.1002/anie.201806541Zhang, ZAngew. Chem.-Int. Edit.Acquiring the kinetics of gas-nanopartiCle fast reactions under ambient pressure is a challenge owing to the lack of appropriate insitu techniques. Now an approach has been developed that integrates time-resolved insitu electron diffraction and an atmospheric gas cell system in transmission electron microscopy, allowing quantitative structural information to be obtained under ambient pressure with millisecond time resolution. The ultrafast oxidation kinetics of Ni nanopartiCles in oxygen was vividly obtained. In contrast to the well-accepted Wagner and Mott-Cabrera models (diffusion-dominated), the oxidation of Ni nanopartiCles is linear at the initial stage (<0.5s), and follows the Avrami-Erofeev model (n=1.12) at the following stage, which indicates the oxidation of Ni nanopartiCles is a nuCleation and growth dominated process. This study gives new insights into Ni oxidation and paves the way to study the fast reaction kinetics of nanopartiCles using ultrafast insitu techniques.Fast Gas-Solid Reaction Kinetics of NanopartiCles Unveiled by Millisecond InSitu Electron Diffraction at Ambient Pressurein situ electron diffraction; millisecond time resolution; nanopartiCles; nickel; oxidation kineticsx14201847#N/AFALSE
4237
anie.20180629810.1002/anie.201806298FALSEhttps://doi.org/10.1002/anie.201806298Schuhmann, WAngew. Chem.-Int. Edit.The electrochemical oxidation of the biorefinery product 5-(hydroxymethyl)furfural (HMF) to 2,5-furandiCarbonylic acid (FDCA), an important platform chemical for the polymer industry, is receiving increasing interest. FDCA-based polymers such as polyethylene 2,5-furandiCarbonylate (PEF) are sustainable candidates for replacing polyethylene terephthalate (PET). Herein, we report the highly efficient electrocatalytic oxidation of HMF to FDCA, using Ni foam modified with high-surface-area nickel boride (NixB) as the electrode. Constant potential electrolysis in combination with HPLC revealed a high faradaic efficiency of Close to 100% towards the production of FDCA with a yield of 98.5%. Operando electrochemistry coupled to ATR-IR spectroscopy indicated that HMF is oxidized preferentially via 5-hydroxymethyl-2-furanCarbonylic acid rather than via 2,5-diCarbonylfuran, which is in agreement with HPLC results. This study not only reports a low-cost active electrocatalyst material for the electrochemical oxidation of HMF to FDCA, but additionally provides insight into the reaction pathway.Electrocatalytic Oxidation of 5-(Hydroxymethyl)furfural Using High-Surface-Area Nickel BorideATR-IR; electrocatalysis; electrosynthesis; HMF oxidation; nickel boride
Electrocatalytic
x83201839#N/AFALSE
4238
anie.20180622110.1002/anie.201806221FALSEhttps://doi.org/10.1002/anie.201806221Xu, YJAngew. Chem.-Int. Edit.Ultrathin two-dimensional (2D) nanostructures have attracted increasing research interest for energy storage and conversion. However, tackling the key problem of lattice mismatch inducing the instability of ulreathin nanostructures during phase transformations is still a critical challenge. Herein, we describe a facile and scalable strategy for the growth of ultrathin nickel phosphide (Ni2P) nanosheets (NSs) with exposed (001) facets. We show that single-layer functionalized graphene with residual oxygen-containing groups and a large lateral size contributes to reducing the lattice strain during phosphorization. The resulting nanostructure exhibits remarkable hydrogen evolution activity and good stability under alkaline conditions.Stress-Transfer-Induced In Situ Formation of Ultrathin Nickel Phosphide Nanosheets for Efficient Hydrogen Evolutiongraphene; hydrogen evolution; nanosheets; nickel; stress transferx62201839#N/AFALSE
4239
anie.20180619410.1002/anie.201806194FALSEhttps://doi.org/10.1002/anie.201806194Gao, CBAngew. Chem.-Int. Edit.Although aqueous synthesis of nanocrystals is advantageous in terms of the cost, convenience, environmental friendliness, and surface Cleanness of the product, nanocrystals of Pt and non-noble metal alloys are difficult to obtain with controlled morphology and composition from this synthesis owing to a huge gap between the reduction potentials of respective metal salts. This huge gap could now be remedied by introducing a sulfite into the aqueous synthesis, which is believed to resemble an electroless plating mechanism, giving rise to a colloid of Pt-M (M=Ni, Co, Fe) alloy nanowires with an ultrasmall thickness (ca. 2.6 nm) in a high yield. The sulfite also leads to the formation of surface M-S bonds and thus atomic-level Pt/M-S(OH) interfaces for greatly boosted hydrogen evolution kinetics under alkaline conditions. An activity of 75.3 mA cm(-2) has been achieved with 3 mu g of Pt in 1 M KOH at an overpotential of 70 mV, which is superior to previously reported catalysts.Aqueous Synthesis of Ultrathin Platinum/Non-Noble Metal Alloy Nanowires for Enhanced Hydrogen Evolution Activityaqueous synthesis; bimetallic alloys; hydrogen evolution reaction; platinum; ultrathin nanowiresx64201836#N/AFALSE
4240
anie.20180604310.1002/anie.201806043FALSEhttps://doi.org/10.1002/anie.201806043Zeng, JAngew. Chem.-Int. Edit.Engineering electronic properties by elemental doping is a direct strategy to design efficient catalysts towards CO2 electroreduction. Atomically thin SnS2 nanosheets were modified by Ni doping for efficient electroreduction of CO2. The introduction of Ni into SnS2 nanosheets significantly enhanced the current density and Faradaic efficiency for carbonaceous product relative to pristine SnS2 nanosheets. When the Ni content was 5atm%, the Ni-doped SnS2 nanosheets achieved a remarkable Faradaic efficiency of 93% for carbonaceous product with a current density of 19.6 mAcm(-2) at -0.9V vs. RHE. A mechanistic study revealed that the Ni doping gave rise to a defect level and lowered the work function of SnS2 nanosheets, resulting in the promoted CO2 Activation and thus improved performance in CO2 electroreduction.Nickel Doping in Atomically Thin Tin Disulfide Nanosheets Enables Highly Efficient CO2 Reductionatomically thin nanosheets; CO2 electroreduction; nickel doping; tin disulfidex92201841#N/AFALSE
4241
anie.20181016110.1002/anie.201810161FALSEhttps://doi.org/10.1002/anie.201810161Kageyama, HAngew. Chem.-Int. Edit.Square-planar coordinate Ni2+ ions in oxides are exClusively limited to a low-spin state (S=0) owing to extensive crystal field splitting. Layered oxychalcogenides A(2)Ni(II)O(2)Ag(2)Se(2) (A=Sr, Ba) with the S=1 NiO2 square lattice are now reported. The structural analysis revealed that the Ni2+ ion is under-bonded by a significant tensile strain from neighboring Ag2Se2 layers, leading to the reduction in crystal field splitting. Ba2NiO2Ag2Se2 exhibits a G-type spin order at 130 K, indicating fairly strong in-plane interactions. The high-pressure synthesis employed here possibly assists the expansion of NiO2 square lattice by taking the advantage of the difference in compressibility in oxide and selenide layers.High-Pressure Synthesis of A(2)NiO(2)Ag(2)Se(2) (A=Sr, Ba) with a High-Spin Ni2+ in Square-Planar Coordinationhigh-pressure synthesis; oxychalcogenide; spin states; square lattice; strain9201928#N/ATRUE
4242
anie.20180572710.1002/anie.201805727FALSEhttps://doi.org/10.1002/anie.201805727Casini, AAngew. Chem.-Int. Edit.The binding modes and free-energy landscape of two Au-I/N-heterocyClic carbene complexes interacting with G-quadruplexes, namely a human telomeric (hTelo) and a promoter sequence (C-KIT1), are studied here for the first time by metadynamics. The theoretical results are validated by FRET DNA melting assays and provide an accurate estimate of the absolute gold complex/DNA binding free energy. This advanced in silico approach is valuable to achieve rational drug design of selective G4 binders.On the Mechanism of Gold/NHC Compounds Binding to DNA G-Quadruplexes: Combined Metadynamics and Biophysical Methodsanticancer; DNA; N-heterocyClic carbenes; G-quadruplexes; goldx28201832#N/AFALSE
4243
anie.20181010210.1002/anie.201810102FALSEhttps://doi.org/10.1002/anie.201810102Cheng, HSAngew. Chem.-Int. Edit.A palladium phosphide electrocatalyst supported on carbon black (PdP2@CB) shows efficient water splitting in both alkaline and neutral electrolytes. Significantly lower overpotentials are required for PdP2@CB (27.5 mV in 0.5 m H2SO4; 35.4 mV in 1m KOH; 84.6 mV in 1 m PBS) to achieve a HER electrocatalytic current density of 10mAcm(-2) compared to commercial Pt/CB (30.1 mV in 0.5 m H2SO4; 46.6 mV in 1 m KOH; 122.7 mV in 1 m PBS). Moreover, no loss in HER activity is detectable after 5000 potential sweeps. Only 270 mV and 277 mV overpotentials are required to reach a current density of 10mAcm(-2) for PdP2@CB to catalyze OER in 1m KOH and 1m PBS electrolytes, which is better OER activity than the benchmark IrO2 electrocatalyst (301 mV and 313 mV to drive a current density of 10 mA cm(-2)). 1.59V and 1.72 V are needed for PdP2@CB to achieve stable water splitting catalytic current density of 10mAcm(-2) in 1m PBS and 50 mA cm(-2) in 1m KOH for 10 h, respectively.Palladium Phosphide as a Stable and Efficient Electrocatalyst for Overall Water Splittinghydrogen evolution reaction; oxygen evolution reaction; palladium phosphide; water splitting104201851#N/ATRUE
4244
anie.20180988910.1002/anie.201809889FALSEhttps://doi.org/10.1002/anie.201809889Roesler, RNickel as a Lewis Base in a T-Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand2019#N/ATRUE
4245
anie.20180493210.1002/anie.201804932FALSEhttps://doi.org/10.1002/anie.201804932Soulantica, KAngew. Chem.-Int. Edit.The Fischer-Tropsch synthesis (FTS) is a structure-sensitive exothermic reaction that enables catalytic transformation of syngas to high quality liquid fuels. Now, monolithic cobalt-based heterogeneous catalysts were elaborated through a wet chemistry approach that allows control over nanocrystal shape and crystallographic phase, while at the same time enables heat management. Copper and nickel foams have been employed as supports for the epitaxial growth of hcp-Co nanowires directly from a solution containing a coordination compound of cobalt and stabilizing ligands. The Co/Cu-foam catalyst was tested for Fischer-Tropsch synthesis in a fixed-bed reactor, showing stability and significantly superior activity and selectivity towards C5+ compared to a Co/SiO2-Al2O3 reference catalyst under the same conditions.hcp-Co Nanowires Grown on Metallic Foams as Catalysts for Fischer-Tropsch Synthesiscobalt; Fischer-Tropsch synthesis; hcp structures; metallic foams; nanowiresx20201836#N/AFALSE
4246
anie.20180915210.1002/anie.201809152FALSEhttps://doi.org/10.1002/anie.201809152Munz, DAn Isolable Terminal Imido Complex of Palladium and Catalytic Implications2018#N/ATRUE
4247
anie.20180483210.1002/anie.201804832FALSEhttps://doi.org/10.1002/anie.201804832Mortensen, PMDual-Function Cobalt-Nickel NanopartiCles Tailored for High-Temperature Induction-Heated Steam Methane Reformingx2018#N/AFALSE
4248
anie.20180914610.1002/anie.201809146FALSEhttps://doi.org/10.1002/anie.201809146Schnick, WAngew. Chem.-Int. Edit.3d transition metal nitridophosphates (MP8N14)-P-II (M-II=Fe, Co, Ni) were prepared by high-pressure metathesis indicating that this route might give a systematic access to a structurally rich family of M-P-N compounds. Their structures, which are stable in air up to at least 1273K, were determined through powder X-ray diffraction and consist of highly condensed tetra-layers of PN4 tetrahedra and MN6 octahedra. Magnetic measurements revealed paramagnetic behavior of CoP8N14 and NiP8N14 down to low temperatures while, FeP8N14 exhibits an antiferromagnetic transition at T-N=3.5(1)K. Curie-Weiss fits of the paramagnetic regime indicate that the transition metal cations are in a oxidation state +II, which was corrB(OH)2rated by Mossbauer spectroscopy for FeP8N14. The ligand field exerted by the nitride ions in CoP8N14 and NiP8N14 was determined from UV/Vis/NIR data and is comparable to that of aqua-ligands and oxophosphates.Open-Shell 3d Transition Metal Nitridophosphates (MP8N14)-P-II (M-II = Fe, Co, Ni) by High-Pressure Metathesishigh-pressure chemistry; metathesis; nitrides; solid-state reactions; transition metals3201935#N/ATRUE
4249
anie.20180912210.1002/anie.201809122FALSEhttps://doi.org/10.1002/anie.201809122Lee, YAngew. Chem.-Int. Edit.The Carbonylation of a nickel(II) anilido species 2 led to the formation of a dinickel(0)-CO complex (P2P-PP2){Ni(CO)}(2) 3 with a P-P bond along with isocyanate generation. In this reaction, the central phosphide moiety of an anionic PPP ligand (PPP-=P-[2-(PPr2C6H4)-Pr-i](2)) acts as a single-electron donor to form a P radical. Alternatively, 3 can be synthesized from the reduction of (PPP)NiCl (1) in the presence of CO; thus, the reaction proceeds by radical coupling of a P-.-Ni-0-CO species. The reverse reaction occurred to generate 1 when 3 was treated with AgCl. Since the P-P bond is light-sensitive, its homolysis is possible and was explored by EPR spectroscopy and DFT analysis. Finally, various bond-Activation reactions of 3 occurred under visible-light conditions, thus indicating that a P-P bond can act as an active reaction site.A P-P Bond as a Redox Reservoir and an Active Reaction SiteCarbonylation; metal-ligand cooperation; metal radicaloids; nickel; phosphorus complexes5201844#N/ATRUE
4250
anie.20180892910.1002/anie.201808929FALSEhttps://doi.org/10.1002/anie.201808929Yu, SHAngew. Chem.-Int. Edit.Transition-metal phosphides have stimulated great interest as catalysts to drive the hydrogen evolution reaction (HER), but their use as bifunctional catalytic electrodes that enable efficient neutral-pH water splitting has rarely been achieved. Herein, we report the synthesis of ternary Ni0.1Co0.9P porous nanosheets onto conductive carbon fiber paper that can efficiently and robustly catalyze both the HER and water oxidation in 1M phosphate buffer (PBS; pH 7) electrolyte under ambient conditions. A water electrolysis cell comprising the Ni0.1Co0.9P electrodes demonstrates remarkable activity and stability for the electrochemical splitting of neutral-pH water. We attribute this performance to the new ternary Ni0.1Co0.9P structure with porous surfaces and favorable electronic states resulting from the synergistic interplay between nickel and cobalt. Ternary metal phosphides hold promise as efficient and low-cost catalysts for neutral-pH water splitting devices.A Janus Nickel Cobalt Phosphide Catalyst for High-Efficiency Neutral-pH Water Splittinghydrogen and oxygen evolution; nanosheets; overall water splitting; phosphides; transition metals114201833#N/ATRUE
4251
anie.20180462810.1002/anie.201804628FALSEhttps://doi.org/10.1002/anie.201804628Ritter, TAngew. Chem.-Int. Edit.A selective, nonchelation-assisted methylation of arenes has been developed. The overall transformation, which combines a C-H functionalization reaction with a nickel-catalyzed cross-coupling, offers rapid access to methylated arenes with high para selectivity. The reaction is amenable to late-stage methylation of small-molecule pharmaceuticals.Selective Methylation of Arenes: A Radical C-H Functionalization/Cross-Coupling Sequencearenes; C-H Activation; cross-coupling; methylation; nickelx17201868#N/AFALSE
4252
anie.20180850710.1002/anie.201808507https://doi.org/10.1002/anie.201808507Jia, LAngew. Chem.-Int. Edit.Zwitterionic structure is necessary for Ni-II complexes to catalyze Carbonylative polymerization (COP) of cyClic ethers. The cationic charge at the Ni-II center imparts sufficient electrophilicity to the Ni-acyl bond for it to react with cyClic ethers to give an acyl-cyClic ether oxonium intermediate, while the ligand-centered anionic charge ensures that the resultant oxonium cation is ion-paired with the Ni-0 nuCleophile. The current catalysts give non-alternating copolymers of carbon monoxide and cyClic ethers and are the most effective when both ethylene oxide and tetrahydrofuran are present as the cyClic ether monomers.Zwitterionic Design Principle of Nickel(II) Catalysts for Carbonylative Polymerization of CyClic EthersCarbonylation; carbon monoxide; catalysis; polymerization; zwitterions1201862#N/ATRUE
4253
anie.20180808510.1002/anie.201808085FALSEhttps://doi.org/10.1002/anie.201808085Ray, KAngew. Chem.-Int. Edit.The formation and detailed spectroscopic characterization of the first biuret-containing monoanionic superoxido-Ni-II intermediate [LNiO2](-) as the Li salt [2; L=MeN-[C(=O)NAr)(2); Ar=2,6-iPr(2)C(6)H(3))] is reported. It results from oxidation of the corresponding [Li(thf)(3)](2)[(LNiBr2)-Br-II] complex M with excess H2O2 in the presence of Et3N. The [LNiO2](-) core of 2 shows an unprecedented nuCleophilic reactivity in the oxidative deCarbonylation of aldehydes, in stark contrast to the electrophilic character of the previously reported neutral Nacnac-containing superoxido-Ni-II complex 1, [L'NiO2] (L'=CH(CMeNAr)(2)). According to density-functional theory (DFT) calculations, the remarkably different behaviour of 1 versus 2 can be attributed to their different charges and a two-state reactivity, in which a doublet ground state and a nearby spin-polarized doublet excited-state both contribute in 1 but not in 2. The unexpected nuCleophilicity of the superoxido-Ni-II core of 2 suggests that such a reactivity may also play a role in catalytic cyCles of Ni-containing oxygenases and oxidases.NuCleophilic versus Electrophilic Reactivity of Bioinspired Superoxido Nickel(II) Complexesdioxygen ligands; nickel; structure-activity relationships; structure elucidation; two-state reactivity10201840#N/ATRUE
4254
anie.20180746310.1002/anie.201807463FALSEhttps://doi.org/10.1002/anie.201807463Klotzer, BAngew. Chem.-Int. Edit.C-saturated Pd-0 nanopartiCles with an extended phase boundary to ZrO2 evolve from a (PdZr0)-Zr-0 precatalyst under CH4 dry reforming conditions. This highly active catalyst state fosters bifunctional action: CO2 is efficiently activated at oxidic phase boundary sites and PdxC provides fast supply of C-atoms toward the latter.Zirconium-Assisted Activation of Palladium To Boost Syngas Production by Methane Dry ReformingCO2 Activation; heterogeneous catalysis; methane dry reforming; photoelectron spectroscopy; X-ray diffraction22201850#N/ATRUE
4255
anie.20180403110.1002/anie.201804031FALSEhttps://doi.org/10.1002/anie.201804031Du, PWAngew. Chem.-Int. Edit.Herein we report the synthesis and photophysical and supramolecular properties of a novel three-dimensional capsule-like hexa-peri-hexabenzocoronene (HBC)-containing carbon nanocage, tripodal-[2] HBC, which is the first synthetic model of capped zigzag [12,0] carbon nanotubes (CNTs). Tripodal-[2]HBC was synthesized by the palladium-catalyzed coupling of triboryl hexabenzocoronene and L-shaped cyClohexane units, followed by nickel-mediated C-Br/C-Br coupling and subsequent aromatization of the cyClohexane moieties. The physical properties of tripodal-[2] HBC and its supramolecular host-guest interaction with C-70 were further studied by UV/Vis and fluorescence spectroscopy. Theoretical calculations revealed that the strain energy of tripodal-[2] HBC was as high as 55.2 kcal mol(-1).A Three-Dimensional Capsule-like Carbon Nanocage as a Segment Model of Capped Zigzag [12,0] Carbon Nanotubes: Synthesis, Characterization, and Complexation with C-70carbon nanotube segments; curved polyaromatic hydrocarbons; nanocages; nanocapsules; three-dimensional materialsx39201848#N/AFALSE
4256
anie.20180358710.1002/anie.201803587FALSEhttps://doi.org/10.1002/anie.201803587Lan, YQAngew. Chem.-Int. Edit.Despite wide applications of bimetallic electrocatalysis in oxygen evolution reaction (OER) owing to their superior performance, the origin of the improved performance remains elusive. The underlying mechanism was explored by designing and synthesizing a series of stable metal-organic frameworks (MOFs: NNU-21-24) based on trinuClear metal Carbonylate Clusters and tridentate Carbonylate ligands. Among the examined stable MOFs, NNU-23 exhibits the best OER performance; particularly, compared with monometallic MOFs, all the bimetallic MOFs display improved OER activity. DFT calculations and experimental results demonstrate that introduction of the second metal atom can improve the activity of the original atom. The proposed model of bimetallic electrocatalysts affecting their OER performance can facilitate design of efficient bimetallic catalysts for energy storage and conversion, and investigation of the related catalytic mechanisms.Exploring the Performance Improvement of the Oxygen Evolution Reaction in a Stable Bimetal-Organic Framework Systembimetallic electrocatalysts; Clusters; iron; metal-organic frameworks; oxygen evolution reactionx175201851#N/AFALSE
4257
anie.20180339610.1002/anie.201803396https://doi.org/10.1002/anie.201803396Schneider, SAngew. Chem.-Int. Edit.The endothermic reverse water-gas shift reaction (rWGS) for direct CO2 hydrogenation to CO is an attractive approach to carbon utilization. However, direct CO2 hydrogenation with molecular catalysts generally gives formic acid instead of CO as a result of the selectivity of CO2 insertion into M-H bonds. Based on the photochemical inversion of this selectivity, several synthetic pathways are presented for CO selective CO2 reduction with a nickel pincer platform inCluding the first example of a photodriven rWGS cyCle at ambient conditions.Photochemically Driven Reverse Water-Gas Shift at Ambient Conditions mediated by a Nickel Pincer ComplexCO2; hydrogenation; nickel; photochemistry; pincer ligandsPhotocatalyst16201843#N/AFALSE
4258
anie.20180732210.1002/anie.201807322FALSEhttps://doi.org/10.1002/anie.201807322McNally, AAngew. Chem.-Int. Edit.Coupling aromatic heteronuCleophiles to arenes is a common way to assemble drug-like molecules. Many methods operate via nuCleophiles intercepting organometallic intermediates, via Pd-, Cu-, and Ni-catalysis, that facilitate carbon-heteroatom bond formation and a variety of protocols. We present an alternative, unified strategy where phosphonium salts can replicate the behavior of organometallic intermediates. Under a narrow set of reaction conditions, a variety of aromatic heteronuCleophile Classes can be coupled to pyridines and diazines that are often problematic in metal-catalyzed couplings, such as where (pseudo)halide precursors are unavailable in complex structures with multiple polar functional groups.A Unified Approach to Couple Aromatic HeteronuCleophiles to Azines and Pharmaceuticalsheteroatom coupling; kinase inhibitors; phosphonium salts; pyridines25201847#N/ATRUE
4259
anie.20180322810.1002/anie.201803228FALSEhttps://doi.org/10.1002/anie.201803228Wang, XSAngew. Chem.-Int. Edit.A combinatorial nickel-catalyzed monofluoroAlkylation of Aryl halides with unactivated fluoroAlkyl halides by reductive cross-coupling has been developed. This method demonstrated high efficiency, mild conditions, and excellent fiinctional-group tolerance, thus enabling the late-stage monofluoroAlkylation of diverse drugs. The key to success was the combination of diverse readily available bidentate and monodentate pyridine-type nitrogen ligands with nickel, which in situ generated a variety of readily tunable catalysts to promote fluoroAlkylation with broad scope with respect to both coupling partners. This combinatorial catalysis strategy offers a solution for nickel-catalyzed reductive cross-coupling reactions and provides an efficient way to synthesize fluoroAlkylased druglike molecules for drug discovery.Nickel-Catalyzed Reductive Cross-Coupling of Aryl Halides with MonofluoroAlkyl Halides for Late-Stage MonofluoroAlkylationAryl halides; combinatorial catalysis; monofluoroAlkylation; nickel; reductive cross-couplingx48201881#N/AFALSE
4260
anie.20180578110.1002/anie.201805781FALSEhttps://doi.org/10.1002/anie.201805781Zhao, YXAngew. Chem.-Int. Edit.A formaldehyde-assisted metal-ligand crosslinking strategy is used for the synthesis of metal-phenolic coordination spheres based on sol-gel chemistry. A range of mono-metal (Co, Fe, Al, Ni, Cu, Zn, Ce), bi-metal (Fe-Co, Co-Zn) and multi-metal (Fe-Co-Ni-Cu-Zn) species can be incorporated into the frameworks of the colloidal spheres. The formation of coordination spheres involves the pre-crosslinking of plant polyphenol (such as tannic acid) by formaldehyde in alkaline ethanol/water solvents, followed by the aggregation assembly of polyphenol oligomers via metal-ligand crosslinking. The coordination spheres can be used as sensors for the analysis of nuCleic acid variants with single-nuCleotide discrimination, and a versatile precursor for electrode materials with high electrocatalytic performance.Sol-Gel Synthesis of Metal-Phenolic Coordination Spheres and Their Derived Carbon Compositescolloidal spheres; coordination polymers; electrocatalysis; plant polyphenol; sol-gel chemistry47201856#N/ATRUE
4261
anie.20180548610.1002/anie.201805486FALSEhttps://doi.org/10.1002/anie.201805486Knochel, PAngew. Chem.-Int. Edit.CoBr2 (5mol%) in the presence of 2,2-bipyridyl (5 mol%) enables electrophilic alkenylations between easily accessible alkenyl acetates or tosylates and various functionalized Aryl zinc pivalates at ambient temperature. This cobalt-catalyzed process was further applicable to alkenyl zinc pivalates to provide substituted 1,3-dienes.Cobalt-Catalyzed Cross-Couplings between Alkenyl Acetates and Aryl or Alkenyl Zinc Pivalates21201865#N/ATRUE
4262
anie.20180313610.1002/anie.201803136https://doi.org/10.1002/anie.201803136Thomas, AAngew. Chem.-Int. Edit.Pyrolysis of a bimetallic metal-organic framework (MIL-88-Fe/Ni)-dicyandiamide composite yield a Fe and Ni containing carbonaceous material, which is an efficient bifunctional electrocatalyst for overall water splitting. FeNi3 and NiFe2O4 are found as metallic and metal oxide compounds Closely embedded in an N-doped carbon-carbon nanotube matrix. This hybrid catalyst (Fe-Ni@NC-CNTs) significantly promotes the charge transfer efficiency and restrains the corrosion of the metallic catalysts, which is shown in a high OER and HER activity with an overpotential of 274 and 202mV, respectively at 10mAcm(-2) in alkaline solution. When this bifunctional catalyst was further used for H-2 and O-2 production in an electrochemical water-splitting unit, it can operate in ambient conditions with a competitive gas production rate of 1.15 and 0.57Ls(-1) for hydrogen and oxygen, respectively, showing its potential for practical applications.Bifunctional Electrocatalysts for Overall Water Splitting from an Iron/Nickel-Based Bimetallic Metal-Organic Framework/Dicyandiamide Compositebifunctional electrocatalyst; carbon nanotubes; metal-organic frameworks (MOFs); meso-; macroporous carbons; overall water splittingx155201836#N/AFALSE
4263
anie.20180309210.1002/anie.201803092FALSEhttps://doi.org/10.1002/anie.201803092Wang, XWAngew. Chem.-Int. Edit.Atomic layer deposition (ALD) of the pyrite-type metal disulfides FeS2, CoS2, and NiS2 is reported for the first time. The deposition processes use iron, cobalt, and nickel amidinate compounds as the corresponding metal precursors and the H2S plasma as the sulfur source. All the processes are demonstrated to follow ideal self-limiting ALD growth behavior to produce fairly pure, smooth, well-crystallized, stoichiometric pyrite FeS2, CoS2, and NiS2 films. By these processes, the FeS2, CoS2, and NiS2 films can also be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which thereby highlights the broad and promising applicability of these ALD processes for conformal film coatings on complex high-aspect-ratio 3D architectures in general.Atomic Layer Deposition of the Metal Pyrites FeS2, CoS2, and NiS2atomic layer deposition; conformal coating; metal sulfides; pyrite; thin filmsx51201843#N/AFALSE
4264
anie.20180539610.1002/anie.201805396FALSEhttps://doi.org/10.1002/anie.201805396Procter, DJAngew. Chem.-Int. Edit.An interrupted Pummerer/nickel-catalysed cross-coupling strategy has been developed and used in the elaboration of styrenes. The operationally simple method can be carried out as a one-pot process, involves the direct formation of stable alkenyl sulfonium salt intermediates, utilises a commercially available sulfoxide, catalyst, and ligand, operates at ambient temperature, accommodates sp-, sp(2)-, and sp(3)-hybridised organozinc coupling partners, and delivers functionalised styrene products in high yields over two steps. An interrupted Pummerer/cyClisation approach has also been used to access carbo- and heterocyClic alkenyl sulfonium salts for cross-coupling.An Interrupted Pummerer/Nickel-Catalysed Cross-Coupling Sequencecross-coupling; nickel catalysis; Pummerer reactions; sulfonium salts; sulfoxides51201892#N/ATRUE
4265
anie.20180265610.1002/anie.201802656https://doi.org/10.1002/anie.201802656Alcazar, JAngew. Chem.-Int. Edit.The merging of photoredox and transition-metal catalysis has become one of the most attractive approaches for carbon-carbon bond formation. Such reactions require the use of two organo-transition-metal species, one of which acts as a photosensitizer and the other one as a cross-coupling catalyst. We report herein an exogenous-photosensitizer-free photocatalytic process for the formation of carbon-carbon bonds by direct acceleration of the well-known nickel-catalyzed Negishi cross-coupling that is based on the use of two naturally abundant metals. This finding will open new avenues in cross-coupling chemistry that involve the direct visible-light absorption of organometallic catalytic complexes.Visible-Light-Induced Nickel-Catalyzed Negishi Cross-Couplings by Exogenous-Photosensitizer-Free PhotocatalysisC(sp(3))-C(sp(2)) coupling; flow chemistry; Negishi coupling; photocatalysis; visible lightPhotocatalyst33201839#N/AFALSE
4266
anie.20180488110.1002/anie.201804881FALSEhttps://doi.org/10.1002/anie.201804881Sun, XMAngew. Chem.-Int. Edit.Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel-iron layered double hydroxides (NiFe-LDHs) by partially substituting Ni2+ with Fe2+ to introduce Fe-O-Fe moieties. These Fe2+-containing NiFe-LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm(-2), which is among the best OER catalytic performance to date. In-situ X-ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe-O-Fe motifs could stabilize high-valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts.Introducing Fe2+ into Nickel-Iron Layered Double Hydroxide: Local Structure Modulated Water Oxidation Activityiron; layered double hydroxides; local structure; NiFe catalyst; oxygen evolution reaction (OER)127201836#N/ATRUE
4267
anie.20180228210.1002/anie.201802282https://doi.org/10.1002/anie.201802282Molander, GAAngew. Chem.-Int. Edit.The development of synthetic tools to introduce saccharide derivatives into functionally complex molecules is of great interest, particularly in the field of drug discovery. Herein, we report a new route toward highly functionalized, Arylated saccharides, which involves nickel-catalyzed cross-coupling of photoredox-generated sacchAryl radicals with a range of Aryl- and heteroAryl bromides, triggered by an organic photocatalyst. In contrast to existing methods, the mild reaction conditions achieve Arylation of saccharide motifs while leaving the anomeric carbon available, thus providing access to a Class of Arylated glycosides that has been underexplored until now. To demonstrate the potential of this strategy in late-stage functionalization, a variety of structurally complex molecules incorporating saccharide moieties were synthesized.Synthesis of Non-Classical Arylated C-Saccharides through Nickel/Photoredox Dual Catalysis1,4-dihydropyridines; glycosylation; homogeneous catalysis; nickel; photoredox chemistryPhotocatalyst61201862#N/AFALSE
4268
anie.20180481110.1002/anie.201804811FALSEhttps://doi.org/10.1002/anie.201804811Feng, XMAngew. Chem.-Int. Edit.A highly efficient asymmetric Diels-Alder/[3,3] sigmatropic rearrangement reaction of methyleneindolinones with 1-thiocyanatobutadienes has been realized by using a chiral N,N-dioxide/nickel(II) complex as the catalyst. A range of cyClohexenyl isothiocyanates were synthesized in high yields with excellent diastereo- and enantioselectivities. Based on mechanistic studies, a catalytic cyCle with possible transition-state models were proposed to explain the process.Catalytic Asymmetric Diels-Alder Reaction/[3,3] Sigmatropic Rearrangement Cascade of 1-Thiocyanatobutadienesasymmetric catalysis; cyCloaddition; isothiocyanates; nickel; rearrangements13201864#N/ATRUE
4269
anie.20180464810.1002/anie.201804648FALSEhttps://doi.org/10.1002/anie.201804648Shimizu, SAngew. Chem.-Int. Edit.5,15-Dioxaporphyrin was synthesized for the first time by a nuCleophilic aromatic substitution reaction of a nickel bis(,-dibromodipyrrin) complex with benzaldoxime, followed by an intramolecular annulation of the -hydroxy-substituted intermediate. This unprecedented molecule is a 20-electron antiaromatic system, in terms of Huckel's rule of aromaticity, because lone pair electrons of oxygen atoms are incorporated into the 18-electron conjugated system of the porphyrin. A theoretical analysis based on the gauge-inCluding magnetically induced current method confirmed its antiaromaticity and a dominant inner ring pathway for the ring current. The unique reactivity of 5,15-dioxaporphyrin forming a ,-linked dimer upon oxidation was also revealed.Rational Synthesis of Antiaromatic 5,15-Dioxaporphyrin and Oxidation into beta,beta-Linked Dimersaromaticity; dimers; heterocyCles; porphyrinoids; redox chemistry16201891#N/ATRUE
4270
anie.20180464410.1002/anie.201804644FALSEhttps://doi.org/10.1002/anie.201804644Osuka, AAngew. Chem.-Int. Edit.Trimethylenemethane (TMM) diradical is the simplest non-Kekule non-disjoint molecule with the triplet ground state (Delta E-ST = +16.1 kcal mol(-1)) and is extremely reactive. It is a challenge to design and synthesize a stable TMM diradical with key properties, such as actual aliphatic TMM diradical centers and the triplet ground state with a large positive Delta E-ST value, since such species provide detailed information on the electronic structure of TMM diradical. Herein we report a TMM derivative, in which the TMM segment is fused with three Ni-II meso-triArylporphyrins, that satisfies the above criteria. The diradical shows delocalized spin density on the propeller-like porphyrin pi-network and the triplet ground state owing to the strong ferromagnetic interaction. Despite the apparent TMM structure, the diradical can be handled under ambient conditions and can be stored for months in the solid state, thus allowing its X-ray diffraction structural analysis.A Stable Trimethylenemethane Triplet Diradical Based on a Trimeric Porphyrin Fused pi-Systemdiradicals; ferromagnetic interactions; fused-ring systems; porphyrinoids; trimethylenemethane22201867#N/ATRUE
4271
anie.20180159610.1002/anie.201801596FALSEhttps://doi.org/10.1002/anie.201801596Ghadwal, RSAngew. Chem.-Int. Edit.One-electron reduction of C2-Arylated 1,3-imidazoli(ni)um salts (IPrAr)Br (Ar=Ph, 3a; 4-DMP, 3b; 4-DMP=4-Me2NC6H4) and (SIPrAr)I (Ar=Ph, 4a; 4-Tol, 4b) derived from Classical NHCs (IPr=:C{N(2,6-iPr(2)C(6)H(3))}(2)CHCH, 1; SIPr=:C{N(2,6-iPr(2)C(6)H(3))}(2)CH2CH2, 2) gave radicals [(IPrAr)](center dot) (Ar=Ph, 5a; 4-DMP, 5b) and [(SIPrAr)](center dot) (Ar=Ph, 6a; 4-Tol, 6b). Each of 5a,b and 6a,b exhibited a doublet EPR signal, a characteristic of monoradical species. The first solid-state characterization of NHC-derived carbon-centered radicals 6a,b by single-crystal X-ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent Aryl group.Crystalline Radicals Derived from Classical N-HeterocyClic Carbenesdensity functional calculations; EPR spectroscopy; N-heterocyClic carbenes; radicals; X-ray diffractionx31201855#N/AFALSE
4272
anie.20180098910.1002/anie.201800989FALSEhttps://doi.org/10.1002/anie.201800989Hayward, MAAngew. Chem.-Int. Edit.The synthesis of the first 4d transition metal oxide-hydride, LaSr3NiRuO4H4, is prepared via topochemical anion exchange. Neutron diffraction data show that the hydride ions occupy the equatorial anion sites in the host lattice and as a result the Ru and Ni cations are located in a plane containing only hydride ligands, a unique structural feature with obvious parallels to the CuO2 sheets present in the superconducting cuprates. DFT calculations confirm the presence of S=1/2 Ni+ and S=0, Ru2+ centers, but neutron diffraction and SR data show no evidence for long-range magnetic order between the Ni centers down to 1.8K. The observed weak inter-cation magnetic coupling can be attributed to poor overlap between Ni3dz2 and H1s in the super-exchange pathways.LaSr3NiRuO4H4: A 4d Transition-Metal Oxide-Hydride Containing Metal Hydride Sheetsanion exchange reactions; metal hydrides; neutron diffraction; oxide-hydrides; transition metalsx11201819#N/AFALSE
4273
anie.20180095110.1002/anie.201800951https://doi.org/10.1002/anie.201800951Ong, TGOne-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single Palladium Carbodicarbene ComplexPhotocatalyst2018#N/AFALSE
4274
anie.20180074910.1002/anie.201800749https://doi.org/10.1002/anie.201800749MacMillan, DWCAngew. Chem.-Int. Edit.The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid Activation mode, has led to the development of an Arylation method for the selective functionalization of alcohol -hydroxy C-H bonds. This approach employs zinc-mediated alcohol deprotonation to activate -hydroxy C-H bonds while simultaneously suppressing C-O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn-based Lewis acids also deactivates other hydridic bonds such as -amino and -oxy C-H bonds. This approach facilitates rapid access to Benzylic alcohols, an important motif in drug discovery. A 3-step synthesis of the drug Prozac exemplifies the utility of this new method.Selective Hydrogen Atom Abstraction through Induced Bond Polarization: Direct alpha-Arylation of Alcohols through Photoredox, HAT, and Nickel Catalysisalcohols; heterocyCles; hydrogen atom transfer; nickel; photoredox catalysisPhotocatalyst702018416/1/2022FALSE
4275
anie.20180069910.1002/anie.201800699https://doi.org/10.1002/anie.201800699MacMillan, DWCAngew. Chem.-Int. Edit.Herein we report a highly efficient method for nickel-catalyzed C-N bond formation between sulfonamides and Aryl electrophiles. This technology provides generic access to a broad range of N-Aryl and N-heteroAryl sulfonamide motifs, which are widely represented in drug discovery. Initial mechanistic studies suggest an energy-transfer mechanism wherein C-N bond reductive elimination occurs from a triplet excited Ni-II complex. Late-stage sulfonamidation in the synthesis of a pharmacologically relevant structure is also demonstrated.Sulfonamidation of Aryl and HeteroAryl Halides through Photosensitized Nickel Catalysisenergy transfer; heterocyCles; nickel; photocatalysis; sulfonamidesPhotocatalysty62201830#N/AFALSE
4276
anie.20180434910.1002/anie.201804349FALSEhttps://doi.org/10.1002/anie.201804349Li, YDAngew. Chem.-Int. Edit.Developing an efficient single-atom material (SAM) synthesis and exploring the energy-related catalytic reaction are important but still challenging. A polymerization-pyrolysis-evaporation (PPE) strategy was developed to synthesize N-doped porous carbon (NPC) with anchored atomically dispersed Fe-N-4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe-N-4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn-air battery devices containing the Fe-N-4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.A Bimetallic Zn/Fe Polyphthalocyanine-Derived Single-Atom Fe-N-4 Catalytic Site:A Superior Trifunctional Catalyst for Overall Water Splitting and Zn-Air Batterieselectrochemistry; EXAFS; N-doped porous carbon; polymerization; pyrolysis195201832#N/ATRUE
4277
anie.20180431810.1002/anie.201804318FALSEhttps://doi.org/10.1002/anie.201804318Zhou, JSAngew. Chem.-Int. Edit.Enantioselective alpha-Arylation of racemic ketones containing existing alpha'-stereocenters is reported for the first time via base-induced dynamic kinetic resolution. Bridged bicyClic rings are formed in good ee values, which are difficult to obtain otherwise. Furthermore, reactions in DMSO-d(6) resulted in extensive deuteration of both alpha- and alpha' -positions in the products, thus supporting a pathway involving rapid, reversible deprotonation of ketones under catalytic conditions.Palladium-Catalyzed Enantioselective Arylation of Racemic Ketones to Form Bridged BicyCles via Dynamic Kinetic ResolutionArylation; deuterium; dynamic kinetic resolution; ketones; palladium20201860#N/ATRUE
4278
anie.20171342910.1002/anie.201713429FALSEhttps://doi.org/10.1002/anie.201713429Chen, JSAngew. Chem.-Int. Edit.Engineering the adsorption of molecules on active sites is an integral and challenging part for the design of highly efficient transition-metal-based catalysts for methanol dehydrogenation. A Mott-Schottky catalyst composed of Ni nanopartiCles and tailorable nitrogen-doped carbon-foam (Ni/NCF) and thus tunable adsorption energy is presented for highly efficient and selective dehydrogenation of gas-phase methanol to hydrogen and CO even under relatively high weight hourly space velocities (WHSV). Both theoretical and experimental results reveal the key role of the rectifying contact at the Ni/NCF boundaries in tailoring the electron density of Ni species and enhancing the absorption energies of methanol molecules, which leads to a remarkably high turnover frequency (TOF) value (356molmethanolmol(-1)Nih(-1) at 350 degrees C), outpacing previously reported bench-marked transition-metal catalysts 10-fold.Tuning the Adsorption Energy of Methanol Molecules Along Ni-N-Doped Carbon Phase Boundaries by the Mott-Schottky Effect for Gas-Phase Methanol Dehydrogenationadsorption energy; gas-solid reactions; heterogeneous catalysis; Mott-Schottky effect; nanostructuresx35201840#N/AFALSE
4279
anie.20171334610.1002/anie.201713346FALSEhttps://doi.org/10.1002/anie.201713346Ghadwal, RSAngew. Chem.-Int. Edit.Stable N-heterocyClic carbene analogues of Thiele and Chichibabin hydrocarbons, [(IPr)(C6H4)(IPr)] and [(IPr)(C6H4)(2)(IPr)] (4 and 5, respectively; IPr - C{N(2,6-iPr(2)C(6)H(3))}(2)CHCH), are reported. In a nickel-catalyzed double carbenylation of 1,4-Br2C6H4 and 4,4'-Br-2(C6H4)(2) with IPr (1), [(IPr)(C6H4)(IPr)](Br)(2) (2) and [(IPr)(C6H4)(2)(IPr)](Br)(2) (3) were generated, which respectively afforded 4 and 5 as crystalline solids upon reduction with KC8. Experimental and computational studies support the semiquinoidal nature of 5 with a small singlet-triplet energy gap Delta ES-T of 10.7 kcal mol(-1), whereas 4 features more quinoidal character with a rather large Delta ES-T of 25.6 kcal mol(-1). In view of the low Delta ES-T, 4 and 5 may be described as biradicaloids. Moreover, 5 has considerable (41%) diradical character.N-HeterocyClic Carbene Analogues of Thiele and Chichibabin HydrocarbonsChichibabin's hydrocarbons; diradicaloids; diradicals; N-heterocyClic carbenes; Thiele's hydrocarbonsx29201866#N/AFALSE
4280
anie.20180408010.1002/anie.201804080FALSEhttps://doi.org/10.1002/anie.201804080Feng, XMAngew. Chem.-Int. Edit.A highly enantioselective [2,3]Wittig rearrangement of oxindole derivatives was realized by using a chiral N,N-dioxide/Ni-II complex as the catalyst under mild reaction conditions. A strong chiral amplification effect was observed, and allowed access to chiral 3-hydroxy 3-substituted oxindoles bearing allenyl groups in high yields and enantioselectivities (up to 92% ee) by using a ligand with only 15% ee. A reasonable explanation was given based on the experimental investigations and X-ray crystal structures of enantiomerically pure and racemic catalysts. Moreover, the first catalytic kinetic resolution of racemic oxindole derivatives by a [2,3]Wittig rearrangement was realized with high efficiency and stereoselectivity.Nickel(II)-Catalyzed Asymmetric Propargyl [2,3]Wittig Rearrangement of Oxindole Derivatives: A Chiral Amplification Effectallenes; asymmetric catalysis; kinetic resolution; nickel; rearrangements21201876#N/ATRUE
4281
anie.20171273110.1002/anie.201712731FALSEhttps://doi.org/10.1002/anie.201712731Zhu, SLAngew. Chem.-Int. Edit.The terminal-selective, remote C(sp(3))-H Alkylation of alkenes was achieved by a relay process combining NiH-catalyzed hydrometalation, chain walking, and Alkylation. This method enables the construction of unfunctionalized C(sp(3))-C(sp(3)) bonds under mild conditions from two simple feedstock chemicals, namely olefins and Alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent Alkylation of isomeric mixtures of olefins at low catalyst loadings.NiH-Catalyzed Reductive Relay HydroAlkylation: A Strategy for the Remote C(sp(3))-H Alkylation of AlkenesAlkylation; C-H Activation; isomerization; nickel; regioselectivityx64201881#N/AFALSE
4282
anie.20171267910.1002/anie.201712679FALSEhttps://doi.org/10.1002/anie.201712679Schuhmann, WAngew. Chem.-Int. Edit.In order to design more powerful electrocatalysts, developing our understanding of the role of the surface structure and composition of widely abundant bulk materials is crucial. This is particularly true in the search for alternative hydrogen evolution reaction (HER) catalysts to replace platinum. We report scanning electrochemical cell microscopy (SECCM) measurements of the (111)-crystal planes of Fe4.5Ni4.5S8, a highly active HER catalyst. In combination with structural characterization methods, we show that this technique can reveal differences in activity arising from even the slightest compositional changes. By probing electrochemical properties at the nanoscale, in conjunction with complementary structural information, novel design principles are revealed for application to rational material synthesis.Local Surface Structure and Composition Control the Hydrogen Evolution Reaction on Iron Nickel Sulfideselectrocatalysis; hydrogen evolution reaction; iron nickel sulfides; SECCM; surfacesx59201830#N/AFALSE
4283
anie.20180335610.1002/anie.201803356FALSEhttps://doi.org/10.1002/anie.201803356Lu, CCAngew. Chem.-Int. Edit.Formal nickelate(-I) complexes bearing Group 13 metalloligands (M = Al and Ga) were isolated. These 17 e(-) complexes were synthesized by one-electron reduction of the corresponding Ni-0 -> M-III precursors, and were investigated by single-crystal X-ray diffraction, EPR spectroscopy, and quantum chemical calculations. Collectively, the experimental and computational data support: 1) the strengthening of the Ni-M bond upon one-electron reduction, and 2) the delocalization of the unpaired spin across the Ni and M atoms. An intriguing electronic configuration is revealed where three valence electrons occupy two sigma-type bonding interactions: Ni(3d(z2))(2)-> M and sigma-(Ni-M)(1). The latter is an unusual Ni-M sigma-bonding molecular orbital that comprises primarily the Ni 4p(z) and M np(z)/ns atomic orbitals.Formal Nickelate(-I) Complexes Supported by Group 13 IonsEPR spectroscopy; Group 13 elements; metalates; nickel; radicals22201866#N/ATRUE
4284
anie.20180318610.1002/anie.201803186FALSEhttps://doi.org/10.1002/anie.201803186Martin, RAngew. Chem.-Int. Edit.Driven by the inherent synthetic potential of CO2 as an abundant, inexpensive and renewable C-1 chemical feedstock, the recent years have witnessed renewed interest in devising catalytic CO2 fixations into organic matter. Although the formation of C-C bonds via catalytic CO2 fixation remained rather limited for a long period of time, a Close look into the recent literature data indicates that catalytic Carbonylation reactions have entered a new era of exponential growth, evolving into a mature discipline that allows for streamlining the synthesis of Carbonylic acids, building blocks of utmost relevance in industrial endeavors. These strategies have generally proven broadly applicability and convenient to perform. However, substantial challenges still need to be addressed reinforcing the need to cover metal-catalyzed Carbonylation area in a conceptual and concise manner, delineating the underlying new principles that are slowly emerging in this vibrant area of expertise.Transition-Metal-Catalyzed Carbonylation Reactions with Carbon Dioxidecarbon dioxide; Carbonylations; homogeneous catalysis; nickel; organometallic reagents2462018295#N/ATRUE
4285
anie.20171237210.1002/anie.201712372FALSEhttps://doi.org/10.1002/anie.201712372Zhou, HCAngew. Chem.-Int. Edit.Earth-abundant first-row transition-metal nanoClusters (NCs) have been extensively investigated as catalysts. However, their catalytic activity is relatively low compared with noble metal NCs. Enhanced catalytic activity of cobalt NCs can be achieved by encapsulating Co NCs in soluble porous coordination cages (PCCs). Two cages, PCC-2a and 2b, possess almost identical cavity in shape and size, while PCC-2a has five times more net charges than PCC-2b. Co2+ cations were accumulated in PCC-2a and reduced to ultra-small Co NCs in situ, while for PCC-2b, only bulky Co partiCles were formed. As a result, Co NCs@PCC-2a accomplished the highest catalytic activity in the hydrolysis of ammonium borane among all the first-row transition-metals NCs. Based on these results, it is envisioned that confining in the charged porous coordination cage could be a novel route for the synthesis of ultra-small NCs with extraordinary properties.Formation of a Highly Reactive Cobalt NanoCluster Crystal within a Highly Negatively Charged Porous Coordination Cageammonia-borane; first-row transition metals; hydrogen generation; metal-organic polyhedra; nanoClustersx48201861#N/AFALSE
4286
anie.20180315610.1002/anie.201803156FALSEhttps://doi.org/10.1002/anie.201803156Zhao, DBAngew. Chem.-Int. Edit.Described herein is the first intermolecular sigma-bond exchange reaction between the C-C bond of cyClopropenones and C-Si bond of (benzo)silacyClobutanes and it proceeds smoothly by treatment with either 1mol% of a palladium or 2mol% of a nickel catalyst. This reaction constitutes an unprecedented route for the synthesis of various sila(benzo)suberones. And it is also the first example of a sigma-bond exchange reaction involving cyClopropenones.Intermolecular sigma-Bond Cross-Exchange Reaction between CyClopropenones and (Benzo)silacyClobutanes: Straightforward Access towards Sila(benzo)cyCloheptenonesheterocyCles; palladium; ring expansion; silanes; strained molecules22201866#N/ATRUE
4287
anie.20180277910.1002/anie.201802779FALSEhttps://doi.org/10.1002/anie.201802779Itoh, SAngew. Chem.-Int. Edit.A bis(mu-oxido)dinickel(III) complex was synthesized and characterized by single crystal X-ray diffraction, resonance Raman, and ESI-mass measurements. Magnetic susceptibility measurements by SQUID and EPR spectroscopy reveal that the complex has a triplet ground state, which is unprecedented for high-valent metal (M) complexes with [M-2(mu-O)(2)] diamond core. DFT studies indicate ferromagnetic coupling of the nickel(III) centers. The complex exhibits hydrogen abstraction reactivity and oxygenation reactivity toward external substrates.A Bis(mu-oxido)dinickel(III) Complex with a Triplet Ground Statebis(mu-oxido) complexes; magnetic properties; nickel; oxidation; reactive intermediates7201845#N/ATRUE
4288
anie.20180249410.1002/anie.201802494FALSEhttps://doi.org/10.1002/anie.201802494Osuka, ASingly and Doubly 1,2-Phenylene-Inserted Porphyrin Arch-Tape Dimers: Synthesis and Highly Contorted Structures2018#N/ATRUE
4289
anie.20171137610.1002/anie.201711376FALSEhttps://doi.org/10.1002/anie.201711376Lang, JPAngew. Chem.-Int. Edit.Metal-organic frameworks (MOFs) are a Class of promising materials for diverse heterogeneous catalysis, but they are usually not directly employed for oxygen evolution electrocatalysis. Most reports focus on using MOFs as templates to in situ create efficient electrocatalysts through annealing. Herein, we prepared a series of Fe/Ni-based trimetallic MOFs (Fe/Ni/Co(Mn)-MIL-53 accordingly to the Material of Institute Lavoisier) by solvothermal synthesis, which can be directly adopted as highly efficient electrocatalysts. The Fe/Ni/Co(Mn)-MIL-53 shows a volcano-type oxygen evolution reaction (OER) activity as a function of compositions. The optimized Fe/Ni-2.4/Co-0.4-MIL-53 can reach a current density of 20 mA cm(-2) at low overpotential of 236 mV with a small Tafel slope of 52.2 mV dec(-1). In addition, the OER performance of these MOFs can be further enhanced by directly being grown on nickel foam (NF).Nanoscale Trimetallic Metal-Organic Frameworks Enable Efficient Oxygen Evolution Electrocatalysiselectrocatalysis; metal-organic frameworks; nickel; oxygen evolution reaction; porous materialsx314201849#N/AFALSE
4290
anie.20171122110.1002/anie.201711221FALSEhttps://doi.org/10.1002/anie.201711221Zhao, YSRuthenium(II)-Catalyzed C-H Difluoromethylation of Ketoximes: Tuning the Regioselectivity from the meta to the para Positionx2018#N/AFALSE
4291
anie.20180209010.1002/anie.201802090FALSEhttps://doi.org/10.1002/anie.201802090Baker, RTAngew. Chem.-Int. Edit.Alkene metathesis with directly fluorinated alkenes is challenging, limiting its application in the burgeoning field of fluoro-organic chemistry. A new nickel tris(phosphite) fluoro(trifluoromethyl)carbene complex ([P3Ni]=CFCF3) reacts with CF2=CF2 (TFE) or CF2=CH2 (VDF) to yield both metallacyClobutane and perfluorocarbene metathesis products, [P3Ni]=CF2 and CR2=CFCF3 (R=F, H). The reaction of [P3Ni]=CFCF3 with trifluoroethylene also yields metathesis products, [P3Ni]=CF2 and cis/trans-CFCF3=CFH. However, unlike reactions with TFE and VDF, this reaction forms metallacyClopropanes and fluoronickel alkenyl species, resulting presumably from instability of the expected metallacyClobutanes. DFT calculations and experimental evidence established that the observed metallacyClobutanes are not intermediates in the formation of the observed metathesis products, thus highlighting a novel variant of the Chauvin mechanism enabled by the disparate four-coordinate transition states.Nickel Fluorocarbene Metathesis with Fluoroalkenesalkene metathesis; Chauvin mechanism; fluoroalkenes; metallacyClobutanes; nickel carbenes7201834#N/ATRUE
4292
anie.20171110410.1002/anie.201711104https://doi.org/10.1002/anie.201711104Rueping, MAngew. Chem.-Int. Edit.An efficient photoredox/nickel catalyzed sulfonylation reaction of Aryl, heteroAryl, and Vinyl halides has been achieved for the first time. This newly developed sulfonylation protocol provides a versatile method for the synthesis of diverse aromatic sulfones at room temperature and shows excellent functional group tolerance. The electrophilic coupling partners are not limited to Aryl, heteroAryl, and Vinyl bromides and iodides, but also inCludes less reactive Aryl chlorides as suitable substrates for this transformation.Cross-Coupling of Sodium Sulfinates with Aryl, HeteroAryl, and Vinyl Halides by Nickel/Photoredox Dual CatalysisAryl halides; cross-coupling; nickel; photochemistry; sulfonePhotocatalyst93201898#N/AFALSE
4293
anie.20180196710.1002/anie.201801967FALSEhttps://doi.org/10.1002/anie.201801967Zhou, JSAngew. Chem.-Int. Edit.Intermolecular Alkylations of electron-deficient arenes proceed with good para selectivity. Palladium catalysts were used to generate nuCleophilic Alkyl radicals from Alkyl halides, which then directly add onto the arenes. The arene scope and the site of Alkylation are opposite to those of Classical Friedel-Crafts Alkylations, which prefer electron-rich systems.Palladium-Catalyzed para-Selective Alkylation of Electron-Deficient Arenes30201858#N/ATRUE
4294
anie.20171087710.1002/anie.201710877FALSEhttps://doi.org/10.1002/anie.201710877Lou, XWAngew. Chem.-Int. Edit.The oxygen evolution reaction (OER) is involved in various renewable energy systems, such as water-splitting cells and metal-air batteries. Ni-Fe layered double hydroxides (LDHs) have been reported as promising OER electrocatalysts in alkaline electrolytes. The rational design of advanced nanostructures for Ni-Fe LDHs is highly desirable to optimize their electrocatalytic performance. Herein, we report a facile self-templated strategy for the synthesis of novel hierarchical hollow nanoprisms composed of ultrathin Ni-Fe LDH nanosheets. Tetragonal nanoprisms of nickel precursors were first synthesized as the self-sacrificing template. Afterwards, these Ni precursors were consumed during the hydrolysis of iron(II) sulfate for the simultaneous growth of a layer of Ni-Fe LDH nanosheets on the surface. The resultant Ni-Fe LDH hollow prisms with large surface areas manifest high electrocatalytic activity towards the OER with low overpotential, small Tafel slope, and remarkable stability.Hierarchical Hollow Nanoprisms Based on Ultrathin Ni-Fe Layered Double Hydroxide Nanosheets with Enhanced Electrocatalytic Activity towards Oxygen Evolutioniron; layered double hydroxides; nanosheets; nickel; oxygen evolution reactionx308201857#N/AFALSE
4295
anie.20180196610.1002/anie.201801966FALSEhttps://doi.org/10.1002/anie.201801966Caro, JAngew. Chem.-Int. Edit.Co-MOF-74 rod like crystals with a length of several hundred micrometers are synthesized by a solvothermal procedure and their interaction with different gases is evaluated for selective gas sensing. We show strongly anisotropic absorption behavior of the Co-MOF-74 crystals when illuminated with polarized light. The interactions of guests (CO2, propane, propene, Ar, MeOH, H2O) with Co-MOF-74, is studied by various spectroscopic techniques. Vis/NIR shows peak shifts of Co-MOF-74 depending on the interaction with the guest. In the visible and the NIR the maximum absorbance is shifted selectively corresponding to the intensity of the Co-II-guest interaction. Even propene and propane could be distinguished at room temperature by their different interactions with Co-MOF-74. Raman spectroscopy was used to detect a modified vibrational behavior of Co-MOF-74 upon gas adsorption. We show that the adsorption of H2O leads to a characteristic shift of the peak maxima in the Raman spectra.The Interaction of Guest Molecules with Co-MOF-74: A Vis/NIR and Raman Approachgas sensing; metal-organic frameworks; MOF-guest interaction; Raman spectroscopy; UV; Vis spectroscopy29201843#N/ATRUE
4296
anie.20171073810.1002/anie.201710738https://doi.org/10.1002/anie.201710738Dong, SJFuel-Free Bio-photoelectrochemical Cells Based on a Water/Oxygen Circulation System with a Ni:FeOOH/BiVO4 PhotoanodePhotocatalystx2018#N/AFALSE
4297
anie.20180047910.1002/anie.201800479FALSEhttps://doi.org/10.1002/anie.201800479Pan, FAngew. Chem.-Int. Edit.The rechargeable aqueous metal-ion battery (RAMB) has attracted considerable attention due to its safety, low costs, and environmental friendliness. Yet the poor-performance electrode materials lead to a low feasibility of practical application. A hybrid aqueous battery (HAB) built from electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. Herein, we construct a high-voltage K-Na HAB based on K2FeFe(CN)(6) cathode and carbon-coated NaTi2(PO4)(3) (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160mAhg(-1) at a 0.5C rate. Considerable capacity retention of 94.3% is also obtained after 1000cyCles at even 60C rate. Meanwhile, high energy density of 69.6Whkg(-1) based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.Engineering Fast Ion Conduction and Selective Cation Channels for a High-Rate and High-Voltage Hybrid Aqueous Batterybatteries; energy-storage materials; fast ion conduction; ion selectivity; selective cation channels49201834#N/ATRUE
4298
anie.20171069810.1002/anie.201710698https://doi.org/10.1002/anie.201710698Xue, DAngew. Chem.-Int. Edit.A highly effective hydroxylation reaction of Aryl halides with water under synergistic organophotoredox and nickel catalysis is reported. The OH group of the resulting phenols originates from water, following deprotonation facilitated by an intramolecular base group on the ligand. Significantly, Aryl bromides as well as less reactive Aryl chlorides served as effective substrates to afford phenols with a wide range of functional groups. Without the need for a strong inorganic base or an expensive noble-metal catalyst, this process can be applied to the efficient preparation of diverse phenols and enables the hydroxylation of multifunctional pharmaceutically relevant Aryl halides.Synthesis of Phenols: Organophotoredox/Nickel Dual Catalytic Hydroxylation of Aryl Halides with WaterAryl halides; hydroxylation; nickel catalysis; phenols; photoredox catalysisPhotocatalyst49201867#N/AFALSE
4299
anie.20171058210.1002/anie.201710582FALSEhttps://doi.org/10.1002/anie.201710582Goicoechea, JMAngew. Chem.-Int. Edit.The reactivity of two paramagnetic nickel(I) compounds, CpNi(NHC) (where Cp = cyClopentadienyl; NHC = 1,3-bis(2,4,6-trimethylphenyl) imidazol-2-ylidene (IMes) or 1,3-bis(2,6-diisopropylphenyl) imidazol-2-ylidene (IPr)), towards [Na(dioxane)(x)][PnCO] (Pn = P, As) is described. These reactions afford symmetric bimetallic compounds (mu(2):eta(2),eta(2)-Pn(2)){Ni(NHC)(CO)}(2). Several novel intermediates en route to such species are identified and characterised, inCluding a compound containing the PCO- anion in an unprecedented mu(2) :eta(2),eta(2)-binding mode. Ultimately, on treatment of the (mu(2) :eta(2),eta(2)-Pn(2)){Ni(IMes)(CO)}(2) compounds with carbon monoxide, the Pn(2) units can be released, affording P-4 in the case of the phosphorus-containing species, and elemental arsenic in the case of (mu(2) :eta(2),eta(2)-As-2){Ni(IMes)(CO)}(2).Synthesis and Reactivity of Nickel-Stabilised mu(2):eta(2),eta(2)-P-2, As-2 and PAs Units2-arsaethynolate; 2-phosphaethynolate; arsenic; nickel(I) compounds; phosphorusx32201826#N/AFALSE
4300
anie.20171046310.1002/anie.201710463https://doi.org/10.1002/anie.201710463Alper, PBAngew. Chem.-Int. Edit.The photoinduced rearrangement pathways of simple 2,5-dienones and the natural product santonin were found to be effectively rerouted by amines, giving rise to unprecedented products. Either cis olefins or cyClobutenes were obtained from 4,4-disubstituted 2,5-dienone upon irradiation (365 nm) in the presence of various amines depending on the solvent. Previously undescribed [4.4.0] and [5.3.0] fused-ring-containing products were obtained when santonin was irradiated (365 nm) in the presence of methylamine. The amines present in these reactions were incorporated into the products by means of amide-group formation.Photoinduced Rearrangement of Dienones and Santonin Rerouted by Aminesdienones; natural products; photochemistry; rearrangement; santoninPhotocatalyst6201833#N/AFALSE
4301
anie.20180036310.1002/anie.201800363FALSEhttps://doi.org/10.1002/anie.201800363Lou, XWAngew. Chem.-Int. Edit.Complex nanostructures with multi-components and intricate architectures hold great potential in developing high-performance electrode materials for lithium-ion batteries (LIBs). Herein, we demonstrate a facile self-templating strategy for the synthesis of metal vanadate nanomaterials with complex chemical composition of NiCo2V2O8 and a unique yolk-double shell structure. Starting with the Ni-Co glycerate spheres, NiCo2V2O8 yolk-double shell spheres are synthesized through an anion-exchange reaction of Ni-Co glycerate templates with VO3- ions, followed by an annealing treatment. By virtue of compositional and structural advantages, these NiCo2V2O8 yolk-double shell spheres manifest outstanding lithium storage properties when evaluated as anodes for LIBs. Impressively, an extra-high reversible capacity of 1228 mAhg(-1) can be retained after 500 cyCles at a high current density of 1.0 Ag-1.Formation of NiCo2V2O8 Yolk-Double Shell Spheres with Enhanced Lithium Storage Propertieselectrode materials; energy storage materials; lithium-ion batteries; nanostructures; vanadates89201847#N/ATRUE
4302
anie.20171037610.1002/anie.201710376FALSEhttps://doi.org/10.1002/anie.201710376Wang, JAngew. Chem.-Int. Edit.While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. The design and operation of bioinspired synthetic nanomotors is presented. Chemical communication between nanomotors is possible and has an influence on propulsion behavior. A chemical message is sent from a moving activator motor to a nearby activated (receiver) motor by release of Ag+ ions from a Janus polystyrene/Ni/Au/Ag activator motor to the activated Janus SiO2/Pt nanomotor. The transmitted silver signal is translated rapidly into a dramatic speed change associated with the enhanced catalytic activity of activated motors. Selective and successive Activation of multiple nanomotors is achieved by sequential localized chemical communications. The concept of establishing chemical communication between different synthetic nanomotors paves the way to intelligent nanoscale rB(OH)2tic systems that are capable of cooperating with each other.Bioinspired Chemical Communication between Synthetic Nanomotorsbimetallic structures; bioinspired; chemical signals; self-diffusiophoresis; synthetic nanomotorsx27201835#N/AFALSE
4303
anie.20171015010.1002/anie.201710150FALSEhttps://doi.org/10.1002/anie.201710150Bao, SJAngew. Chem.-Int. Edit.Transition-metal phosphides (TMPs) have emerged as promising catalyst candidates for the hydrogen evolution reaction (HER). Although numerous methods have been investigated to obtain TMPs, most rely on traditional synthetic methods that produce materials that are inherently deficient with respect to electrical conductivity. An electrospinning-based reduction approach is presented, which generates nickel phosphide nanopartiCles in N-doped porous carbon nanofibers (Ni2P@NPCNFs) in situ. Ni2P nanopartiCles are protected from irreversible fusion and aggregation in subsequent high-temperature pyrolysis. The resistivity of Ni2P@NPCNFs (5.34 Omega cm) is greatly decreased by 10(4) times compared to Ni2P (> 10(4) Omega cm) because N-doped carbon NFs are incorporated. As an electrocatalyst for HER, Ni2P@NPCNFs reveal remarkable performance compared to other previously reported catalysts in acidic media. Additionally, it offers excellent catalytic ability and durability in both neutral and basic media. Encouraged by the excellent electrocatalytic performance of Ni2P@NPCNFs, a series of pea-like MxP@NPCNFs, inCluding Fe2P@NPCNFs, Co2P@NPCNFs, and Cu3P@NPCNFs, were synthesized by the same method. Detailed characterization suggests that the newly developed method could render combinations of ultrafine metal phosphides with porous carbon accessible; thereby, extending opportunities in electrocatalytic applications.Nanosized Metal Phosphides Embedded in Nitrogen-Doped Porous Carbon Nanofibers for Enhanced Hydrogen Evolution at All pH Valueshydrogen evolution reaction; nitrogen-doped; porous carbon; transition-metal phosphidesx174201838#N/AFALSE
4304
anie.20171296110.1002/anie.201712961FALSEhttps://doi.org/10.1002/anie.201712961Shinokubo, HAngew. Chem.-Int. Edit.Fused benzene rings to antiaromatic compounds generally improve their stability but attenuate their antiaromaticity. The opposite case is now reported. Ni-II benzonorcorroles were synthesized and the effect of benzo-fusion on the antiaromaticity was elucidated. The benzo-fusion resulted in significant decrease of the HOMO-LUMO gaps and enhancement of the paratropic ring current effect. Furthermore, the introduction of the benzo groups induced singlet diradical character in the antiaromatic porphyrinoid.Benzonorcorrole Ni-II Complexes: Enhancement of Paratropic Ring Current and Singlet Diradical Character by Benzo-Fusionantiaromaticity; diradicals; porphyrinoid; ring current16201871#N/ATRUE
4305
anie.20170957110.1002/anie.201709571https://doi.org/10.1002/anie.201709571Melchiorre, PAngew. Chem.-Int. Edit.We report herein that 4-Alkyl-1,4-dihydropyridines (Alkyl-DHPs) can directly reach an electronically excited state upon light absorption and trigger the generation of C(sp(3))-centered radicals without the need for an external photocatalyst. Selective excitation with a violet-light-emitting diode turns Alkyl-DHPs into strong reducing agents that can activate reagents through single-electron transfer manifolds while undergoing homolytic Cleavage to generate radicals. We used this photochemical dual-reactivity profile to trigger radical-based carbon-carbon bond-forming processes, inCluding nickel-catalyzed cross-coupling reactions.Radical-Based C-C Bond-Forming Processes Enabled by the Photoexcitation of 4-Alkyl-1,4-dihydropyridinescross-coupling; dihydropyridines; nickel catalysis; photochemistry; synthetic methodsPhotocatalyst98201743#N/AFALSE
4306
anie.20170955210.1002/anie.201709552
Fernandez-Garcia, M
Phase-Contact Engineering in Mono- and Bimetallic Cu-Ni Co-catalysts for Hydrogen Photocatalytic MaterialsPhotocatalyst2018#N/AFALSE
4307
anie.20170896110.1002/anie.201708961FALSEhttps://doi.org/10.1002/anie.201708961Frost, CGAngew. Chem.-Int. Edit.The para-selective C-H Alkylation of aniline derivatives furnished with a pyrimidine auxiliary is herein reported. This reaction is proposed to take place via an N-H-activated cyClometalate formed in situ. Experimental and DFT mechanistic studies elucidate a dual role of the ruthenium catalyst. Here the ruthenium catalyst can undergo cyClometalation by N-H metalation (as opposed to C-H metalation in meta-selective processes) and form a redox active ruthenium species, to enable site-selective radical addition at the para position.Ruthenium-Catalyzed para-Selective C-H Alkylation of Aniline Derivativesarenes; C-H Activation; homogeneous catalysis; reaction mechanisms; rutheniumx54201779#N/AFALSE
4308
anie.20171262410.1002/anie.201712624FALSEhttps://doi.org/10.1002/anie.201712624Goicoechea, JMAngew. Chem.-Int. Edit.The synthesis and characterization of a stable phosphaethynolatB(OH)2rane, [B]OCP (1, [B]=N,N-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl), is described. The increased triple bond character of the P-C bond in 1 relative to the free ion (PCO-) is probed in a series of reactivity studies. Compound 1 readily dimerises in donor solvents to afford a cyClic five-membered 6-aromatic compound, cyClo-P-2{C[B]}O{CO[B]} (2), which deCarbonylates on UV irradiation. By contrast the nickel-mediated dimerisation of 1 affords the isomeric diphosphacyClobutene [P(CO[B])](2). When 1 is reacted with organolithium reagents such as MesLi (Mes=2,4,6-trimethylphenyl), the boryl moiety shifts and the formation of the lithoxy-boryl-phosphaalkene [LiOC[B]P(Mes)](2) was observed. The reactivity of this species towards electrophiles is also described.An Isolable PhosphaethynolatB(OH)2rane and Its Reactivity1,3,2-diazaboroles; 1H-diphosphirenes; 2-phosphaethynolates; phosphalkenes; phosphorus32201880#N/ATRUE
4309
anie.20171254910.1002/anie.201712549FALSEhttps://doi.org/10.1002/anie.201712549Li, GRAngew. Chem.-Int. Edit.Iron-substituted CoOOH porous nanosheet arrays grown on carbon fiber Cloth (denoted as FexCo1-xOOH PNSAs/CFC, 0x0.33) with 3D hierarchical structures are synthesized by insitu anodic oxidation of -Co(OH)(2) NSAs/CFC in solution of 0.01m (NH4)(2)Fe(SO4)(2). X-ray absorption fine spectra (XAFS) demonstrate that CoO6 octahedral structure in CoOOH can be partially substituted by FeO6 octahedrons during the transformation from -Co(OH)(2) to FexCo1-xOOH, and this is confirmed for the first time in this study. The content of Fe in FexCo1-xOOH, no more than 1/3 of Co, can be controlled by adjusting the insitu anodic oxidation time. Fe0.33Co0.67OOH PNSAs/CFC shows superior OER electrocatalytic performance, with a low overpotential of 266mV at 10mAcm(-2), small Tafel slope of 30mVdec(-1), and high durability.Activating CoOOH Porous Nanosheet Arrays by Partial Iron Substitution for Efficient Oxygen Evolution Reaction269201850#N/ATRUE
4310
anie.20171212110.1002/anie.201712121FALSETakanabe, KA Permselective CeOx Coating To Improve the Stability of Oxygen Evolution Electrocatalysts2018#N/ATRUE
4311
anie.20170790610.1002/anie.201707906TRUEhttps://doi.org/10.1002/anie.201707906Baran, PSAngew. Chem.-Int. Edit.Along with amide bond formation, Suzuki cross-coupling, and reductive amination, the Buchwald-Hartwig-Ullmann-type amination of Aryl halides stands as one of the most employed reactions in modern medicinal chemistry. The work herein demonstrates the potential of utilizing electrochemistry to provide a complementary avenue to access such critical bonds using an inexpensive nickel catalyst under mild reaction conditions. Of note is the scalability, functional-group tolerance, rapid rate, and the ability to employ a variety of Aryl donors (Ar-Cl, Ar-Br, Ar-I, Ar-OTf), amine types (primary and secondary), and even alternative X-H donors (alcohols and amides).Electrochemically Enabled, Nickel-Catalyzed Aminationamination; Arylation; cross-coupling; electrochemistry; nickelElectrochemistryCsp2_ar-Csp3XHArylNo baseNo Base1412017877/28/2022FALSE
4312
anie.20170753810.1002/anie.201707538FALSEhttps://doi.org/10.1002/anie.201707538Rodriguez, JAAngew. Chem.-Int. Edit.Studies with a series of metal/ceria(111) (metal=Co, Ni, Cu; ceria=CeO2) surfaces indicate that metal-oxide interactions can play a very important role for the Activation of methane and its reforming with CO2 at relatively low temperatures (600-700 K). Among the systems examined, Co/CeO2(111) exhibits the best performance and Cu/CeO2(111) has negligible activity. Experiments using ambient pressure X-ray photoelectron spectroscopy indicate that methane dissociates on Co/CeO2(111) at temperatures as low as 300 K-generating CHx and COx species on the catalyst surface. The results of density functional calculations show a reduction in the methane Activation barrier from 1.07 eV on Co(0001) to 0.87 eV on Co2+/CeO2(111), and to only 0.05 eV on Co-0/CeO2-x(111). At 700 K, under methane dry reforming conditions, CO2 dissociates on the oxide surface and a catalytic cyCle is established without coke deposition. A significant part of the CHx formed on the Co-0/CeO2-x(111) catalyst recombines to yield ethane or ethylene.In Situ Investigation of Methane Dry Reforming on Metal/Ceria(111) Surfaces: Metal-Support Interactions and C-H Bond Activation at Low Temperaturecobalt; ceria; density functional theory; methane dissociation; XPSx68201731#N/AFALSE
4313
anie.20170747310.1002/anie.201707473FALSEhttps://doi.org/10.1002/anie.201707473Ji, XLAngew. Chem.-Int. Edit.Aqueous rechargeable batteries are promising solutions for large-scale energy storage. Such batteries have the merit of low cost, innate safety, and environmental friendliness. To date, most known aqueous ion batteries employ metal cation charge carriers. Here, we report the first rocking-chair NH4-ion battery of the full-cell configuration by employing an ammonium Prussian white analogue, (NH4)(1.47)Ni[Fe(CN)(6)](0.88), as the cathode, an organic solid, 3,4,9,10-perylenetetraCarbonylic diimide (PTCDI), as the anode, and 1.0 m aqueous (NH4)(2)SO4 as the electrolyte. This novel aqueous ammonium-ion battery demonstrates encouraging electrochemical performance: an average operation voltage of ca. 1.0 V, an attractive energy density of ca. 43 Wh kg(-1) based on both electrodes' active mass, and excellent cyCle life over 1000 cyCles with 67% capacity retention. Importantly, the topochemistry results of NH4+ in these electrodes point to a new paradigm of NH4+-based energy storage.Rocking-Chair Ammonium-Ion Battery: A Highly Reversible Aqueous Energy Storage Systemammonium-ion batteries; aqueous batteries; energy storage; Prussian white analoguesx85201731#N/AFALSE
4314
anie.20171175310.1002/anie.201711753https://doi.org/10.1002/anie.201711753Chen, ClAngew. Chem.-Int. Edit.The ability to carry out transition-metal-catalyzed copolymerizations of olefins with polar monomers is a great challenge in the field of olefin polymerization. Palladium has been the dominant player in this field, while its low-cost nickel counterpart has only achieved very limited success. We report the synthesis and evaluation of a highly versatile platform based on diphosphazane monoxide ligands. Both palladium and nickel catalysts bearing these ligands mediate the copolymerization of ethylene with a number of fundamental polar monomers.A Versatile Ligand Platform for Palladium- and Nickel-Catalyzed Ethylene Copolymerization with Polar Monomerscopolymers; olefins; nickel; palladium; polymerization114201870#N/ATRUE
4315
anie.20171166610.1002/anie.201711666FALSEhttps://doi.org/10.1002/anie.201711666Li, XGAngew. Chem.-Int. Edit.The hydrolysis reaction of aluminum can be decoupled into a battery by pairing an Al foil with a Pd-capped yttrium dihydride (YH2-Pd) electrode. This hydrolysis battery generates a voltage around 0.45V and leads to hydrogen absorption into the YH2 layer. This represents a new hydrogen absorption mechanism featuring electrical energy generation during hydrogen absorption. The hydrolysis battery converts 8-15% of the thermal energy of the hydrolysis reaction into usable electrical energy, leading to much higher energy efficiency compared to that of direct hydrolysis.Hydrolysis Batteries: Generating Electrical Energy during Hydrogen Absorptionaluminum; batteries; hydrogen storage; hydrolysis; yttrium8201831#N/ATRUE
4316
anie.20170703710.1002/anie.201707037FALSEhttps://doi.org/10.1002/anie.201707037Diau, EWGAngew. Chem.-Int. Edit.We synthesized and characterized methylammonium (MA) mixed tri-halide tin perovskites (MASnIBr(2-x)Cl(x)) for carbon-based mesoscopic solar cells free of lead and holetransporting layers. Varied SnCl2/SnBr2 ratios yielded tin perovskites with three halides (I, Br, and Cl) co-crystallized inside the tin-perovskite. When the SnCl2 proportion was >= 50% (x >= 1), phase separation occurred to give MAS-nI(3-y)Br(y) and MASnCl(3-z)Br(z) in the stoichiometric proportions of their precursors, confirmed by XRD. A device with MASnIBr(1.8)Cl(0.2) (SnCl2= 10%) showed the best photovoltaic performance: J(SC)= 14.0 mAcm(-2), V-OC= 380 mV, FF= 0.573, and PCE= 3.1%, and long-term stability. Electrochemical impedance spectra (EIS) show superior charge recombination and dielectric relaxation properties for the MASnIBr(1.8)Cl(0.2) cell. Transient PL decays showed the intrinsic problem of tinbased perovskites with average lifetimes less than 100 ps.Formation of Stable Tin Perovskites Co-crystallized with Three Halides for Carbon-Based Mesoscopic Lead-Free Perovskite Solar Cellscarbon electrodes; halides; perovskites; solar cells; tinx45201728#N/AFALSE
4317
anie.20171112810.1002/anie.201711128FALSEhttps://doi.org/10.1002/anie.201711128Wu, HAngew. Chem.-Int. Edit.Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO3 was frozen and dropped into a reductive NaBH4 solution at about 0 degrees C. The ultra-slow release of reactants was successfully achieved. An ice-melting process can be used to synthesize atomically dispersed metals, inCluding cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.Ice Melting to Release Reactants in Solution Synthesesatomically dispersed metals; ice melting; kinetic control; nuCleation; ultraslow release22201831#N/ATRUE
4318
anie.20170689610.1002/anie.201706896FALSEhttps://doi.org/10.1002/anie.201706896Wang, ZXAngew. Chem
A deaminative strategy for the visible-light-mediated generation of Alkyl radicals from redox-activated primary amine precursors is described. Abundant and inexpensive primary amine feedstocks, inCluding amino acids, were converted in a single step into redox-active pyridinium salts and subsequently into Alkyl radicals by reaction with an excited-state photocatalyst. The broad synthetic potential of this protocol was demonstrated by the Alkylation of a number of heteroarenes under mild conditions.
Deaminative Strategy for the Visible-Light-Mediated Generation of Alkyl RadicalsPhotocatalyst1852017Added by Yizhou#N/AFALSE
4319
anie.20171106810.1002/anie.201711068FALSEhttps://doi.org/10.1002/anie.201711068Billard, IAngew. Chem.-Int. Edit.The first instance of an acidic aqueous biphasic system (AcABS) based on tributyltetradecyl phosphonium chloride ([P-44414]Cl) and an acid is here reported. This AcABS exhibits pronounced thermomorphic behavior and is shown to be applicable to the extraction of metal ions from concentrated acidic solutions. Metal ions such as cobalt(II), iron(III), platinum(IV) and nickel(II) are found to partition preferentially to one of the phases of the acidic aqueous biphasic system and it is here shown that it successfully allows the difficult separation of Co-II from Ni-II, here studied at 24 and 508 degrees C.Ionic-Liquid-Based Acidic Aqueous Biphasic Systems for Simultaneous Leaching and Extraction of Metallic Ionshydrometallurgy; ionic liquids; metal recyCling; noble metals; sustainable chemistry46201826#N/ATRUE
4320
anie.20170658110.1002/anie.201706581FALSEhttps://doi.org/10.1002/anie.201706581Braunstein, PAngew. Chem.-Int. Edit.The imidazolium chloride [C3H3N(C3H6NMe2)N{C(Me)(=NDipp)}]Cl (1; Dipp = 2,6-diisopropyl phenyl), a potential precursor to a tritopic (NCNamine)-C-imine-N-NHC pincer-type ligand, reacted with [Ni(cod)(2)] to give the Ni-I-Ni-I complex 2, which contains a rare cod-derived eta(3)-allyl-type bridging ligand. The implied intermediate formation of a nickel hydride through oxidative addition of the imidazolium C-H bond did not occur with the symmetrical imidazolium chloride [C3H3N2{C(Me)(=NDipp)}(2)]Cl (3). Instead, a Ni-C(sp(3)) bond was formed, leading to the neutral (NCHNimine)-C-imine pincer-type complex Ni[C3H3N2{C(Me)(=NDipp)}(2)]Cl (4). Theoretical studies showed that this highly unusual feature in nickel NHC chemistry is due to steric constraints induced by the Nsubstituents, which prevent Ni-H bond formation. Remarkably, ethylene inserted into the C(sp(3))-H bond of 4 without nickel hydride formation, thus suggesting new pathways for the Alkylation of non-activated C-H bonds.Tritopic NHC Precursors: Unusual Nickel Reactivity and Ethylene Insertion into a C(sp(3))-H BondAlkylation; N-heterocyClic carbenes; nickel; oxidative addition; pincer ligandsx4201787#N/AFALSE
4321
anie.20170642310.1002/anie.201706423FALSEhttps://doi.org/10.1002/anie.201706423Schoenebeck, FAngew. Chem.-Int. Edit.We herein showcase the ability of NHC-coordinated dinuClear Ni-I-Ni-I complexes to override fundamental reactivity limits of mononuClear (NHC)Ni-0 catalysts in cross-couplings. This is demonstrated with the development of a chemoselective trifluoromethylselenolation of Aryl iodides catalyzed by a Ni-I dimer. A novel SeCF3-bridged Ni-I dimer was isolated and shown to selectively react with Ar-I bonds. Our computational and experimental reactivity data suggest dinuClear Ni-I catalysis to be operative. The corresponding Ni-0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3, over productive cross-coupling and is hence inactive.Divergent Reactivity of a DinuClear (NHC)Nickel(I) Catalyst versus Nickel(0) Enables Chemoselective Trifluoromethylselenolationcatalysis; chemoselectivity; density functional calculations; fluorine; nickelx53201751#N/AFALSE
4322
anie.20171083810.1002/anie.201710838FALSEhttps://doi.org/10.1002/anie.201911662Luterbacher, JSProtection Group Effects During alpha,gamma-Diol Lignin Stabilization Promote High-Selectivity Monomer Production2018#N/ATRUE
4323
anie.20170624910.1002/anie.201706249https://doi.org/10.1002/anie.201706249Chen, ClAngew. Chem.-Int. Edit.Transition-metal-catalyzed copolymerization reactions of olefins with polar-functionalized comonomers are highly important and also highly challenging. A second-coordination-sphere strategy was developed to address some of the difficulties encountered in these copolymerization reactions. A series of a-diimine ligands bearing nitrogen-containing second coordination spheres were prepared and characterized. The properties of the corresponding nickel and palladium catalysts in ethylene polymerizations and copolymerizations were investigated. In the nickel system, significant reduction in polymer branching density was observed, while lower polymer branching densities, as well as a wider range of polar monomer substrates, were achieved in the palladium system. Control experiments and computational results reveal the critical role of the metal-nitrogen interaction in these polymerization and copolymerization reactions.A Second-Coordination-Sphere Strategy to Modulate Nickel- and Palladium-Catalyzed Olefin Polymerization and Copolymerizationcopolymerization; olefin polymerization; palladium catalysts; polar monomers; second coordination spherex112201749#N/AFALSE
4324
anie.20170623710.1002/anie.201706237FALSEhttps://doi.org/10.1002/anie.201706237Nebra, NAngew. Chem.-Int. Edit.The robust, high-valent Ni-IV complex [(Py)(2)(NiF2)-F-IV(CF3)(2)] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 degrees C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric (NiCF3)-C-III complexes 2Py and 2 were identified as key intermediates, and their structures were unambiguously determined by EPR spectroscopy and X-ray diffraction. Preliminary kinetic studies in combination with the isolation of reaction intermediates confirmed that the C-H bond-breaking/C-CF3 bond-forming sequence can occur both at (NiCF3)-C-IV and (NiCF3)-C-III centers.C-H Bond Trifluoromethylation of Arenes Enabled by a Robust, High-Valent Nickel(IV) Complexfluorine; high-valent species; nickel; reaction mechanisms; trifluoromethylationx29201757#N/AFALSE
4325
anie.20171073510.1002/anie.201710735FALSEhttps://doi.org/10.1002/anie.201710735Zhou, QLAngew. Chem.-Int. Edit.A Ni-catalyzed hydroArylation of styrenes and 1,3-dienes with organB(OH)2ron compounds has been developed. The reaction offers a highly selective approach to diArylalkanes and allylarenes under redox-neutral conditions. In this hydroArylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni-H was developed. The Ni-catalyzed hydroArylation, combined with a Ir-catalyzed C-H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.Nickel(0)-Catalyzed HydroArylation of Styrenes and 1,3-Dienes with OrganB(OH)2ron Compoundsalkenes; coupling reactions; hydroArylation; nickel; organB(OH)2ron reagents82201837#N/ATRUE
4326
anie.20171046010.1002/anie.201710460FALSEhttps://doi.org/10.1002/anie.201710460Driess, MA Molecular Approach to Manganese Nitride Acting as a High Performance Electrocatalyst in the Oxygen Evolution Reaction2018#N/ATRUE
4327
anie.20170609010.1002/anie.201706090FALSEhttps://doi.org/10.1002/anie.201706090Zaworotko, MJAngew. Chem.-Int. Edit.Removal of CO2 from CO gas mixtures is a necessary but challenging step during production of ultra-pure CO as processed from either steam reforming of hydrocarbons or CO2 reduction. Herein, two hybrid ultramicroporous materials (HUMs), SIFSIX-3-Ni and TIFSIX-2-Cu-i, which are known to exhibit strong affinity for CO2, were examined with respect to their performance for this separation. The single-gas CO sorption isotherms of these HUMs were measured for the first time and are indicative of weak affinity for CO and benchmark CO2/CO selectivity (>4000 for SIFSIX-3-Ni). This prompted us to conduct dynamic breakthrough experiments and compare performance with other porous materials. Ultra-pure CO (99.99%) was thereby obtained from CO gas mixtures containing both trace (1%) and bulk (50%) levels of CO2 in a one-step physisorption-based separation process.Efficient CO2 Removal for Ultra<bold>-</bold>Pure CO Production by Two Hybrid Ultramicroporous MaterialsCO production; CO2 capture; gas separation; hybrid ultramicroporous materials; trace CO2 removalx28201867#N/AFALSE
4328
anie.20170585710.1002/anie.201705857FALSEhttps://doi.org/10.1002/anie.201705857Lavallo, VFusing Dicarbollide Ions with N-HeterocyClic Carbenesx2017#N/AFALSE
4329
anie.20170577810.1002/anie.201705778FALSEhttps://doi.org/10.1002/anie.201705778Goodenough, JBAngew. Chem.-Int. Edit.Electrocatalysts for both the oxygen reduction and evolution reactions (ORR and OER) are vital for the performances of rechargeable metal-air batteries. Herein, we report an advanced bifunctional oxygen electrocatalyst consisting of porous metallic nickel-iron nitride (Ni3FeN) supporting ordered Fe3Pt intermetallic nanoalloy. In this hybrid catalyst, the bimetallic nitride Ni3FeN mainly contributes to the high activity for the OER while the ordered Fe3Pt nanoalloy contributes to the excellent activity for the ORR. Robust Ni3FeN-supported Fe3Pt catalysts show superior catalytic performance to the state-of-the-art ORR catalyst (Pt/C) and OER catalyst (Ir/C). The Fe3Pt/Ni3FeN bifunctional catalyst enables Zn-air batteries to achieve a long-term cyCling performance of over 480 h at 10 mA cm(-2) with high efficiency. The extraordinarily high performance of the Fe3Pt/Ni3FeN bifunctional catalyst makes it a very promising air cathode in alkaline electrolyte.Ni3FeN-Supported Fe3Pt Intermetallic Nanoalloy as a High-Performance Bifunctional Catalyst for Metal-Air Batterieselectrocatalysis; intermetallic phases; oxygen evolution reaction; oxygen reduction reaction; Znair batteryx107201721#N/AFALSE
4330
anie.20170571510.1002/anie.201705715FALSEhttps://doi.org/10.1002/anie.201705715Chmielewski, PJAngew. Chem.-Int. Edit.A non-catalytic condensation of Ni-II beta-aminonorcorrole with Aryl aldehydes is shown to produce a family of pyrromethane dimers that undergo deaminative cyClization to yield pyridine-fused bis(norcorrole)s comprising two antiaromatic macrocyCles communicating by an aromatic moiety. The new compounds were characterized by spectroscopic, structural, and electrochemical methods supported by DFT calculations, all of which revealed unexpected antiaromaticity enhancement in the fused system.Pyridine-Fused Bis(Norcorrole) through Hantzsch-Type CyClization: Enhancement of Antiaromaticity by an Aromatic Bridgeantiaromaticity; dimerization; norcorrole; porphyrinoids; ring fusionx50201753#N/AFALSE
4331
anie.20171008910.1002/anie.201710089FALSEhttps://doi.org/10.1002/anie.201710089Skrydstrup, TAngew. Chem.-Int. Edit.An efficient catalytic protocol for the three-component assembly of Benzyl bromides, carbon monoxide, and Alkyl zinc reagents to give Benzyl Alkyl ketones is described, and represents the first nickel-catalyzed Carbonylative coupling of two sp(3)-carbon fragments. The method, which relies on the application of nickel complexed with an NN2-type pincer ligand and a controlled release of CO gas from a solid precursor, works well with a range of Benzylic bromides. Mechanistic studies suggest the intermediacy of carbon-centered radicals.Carbonylative Coupling of Alkyl Zinc Reagents with Benzyl Bromides Catalyzed by a Nickel/NN(2)Pincer Ligand ComplexCarbonylation; ketones; nickel; N ligands; reaction mechanisms32201850#N/ATRUE
4332
anie.20170892310.1002/anie.201708923FALSEhttps://doi.org/10.1002/anie.201708923Driess, MAngew. Chem.-Int. Edit.Facile oxygenation of the acyClic amido-chlorosilylene bis(N-heterocyClic carbene) Ni-0 complex [{N(Dipp)(SiMe3) ClSi -> Ni(NHC)(2)] (1; Dipp= 2,6-(Pr2C6H4)-Pr-i; N-hetero-cyClic carbene= C[(Pr-i) NC(Me)](2)) with N2O furnishes the first Si-metalated iminosilane, [DippN=Si(OSiMe3) Ni(Cl)(NHC)(2)] (3), in a rearrangement cascade. Markedly, the formation of 3 proceeds via the silanone (Si=O)-Ni p-complex 2 as the initial product, which was predicted by DFT calculations and observed spectroscopically. The Si=O and Si=N moieties in 2 and 3, respectively, show remarkable hydrB(OH)2ration reactivity towards H-B bonds of boranes, in the former case corrB(OH)2rating the proposed formation of a (Si=O)-Ni p-complex at low temperature.Synthesis of a Metallo-Iminosilane via a Silanone-Metal pi-ComplexhydrB(OH)2ration; nickel complexes; rearrangement; silicon; silyl complexes1220171#N/ATRUE
4333
anie.20170821210.1002/anie.201708212https://doi.org/10.1002/anie.201708212Chen, ClAngew. Chem.-Int. Edit.The transition-metal-catalyzed copolymerization of olefins with polar functionalized co-monomers represents a major challenge in the field of olefin polymerization. It is extremely difficult to simultaneously achieve improvements in catalytic activity, polar monomer incorporation, and copolymer molecular weight through ligand modifications. Herein we introduce a polyethylene glycol unit to some phosphine-sulfonate palladium and nickel catalysts, and its influence on ethylene polymerization and copolymerization is investigated. In ethylene polymerization, this strategy leads to enhanced activity, catalyst stability, and increased polyethylene molecular weight. In ethylene copolymerization with polar monomers, improvements in all copolymerization parameters are realized. This effect is most significant for polar monomers with hydrogen-bond-donating abilities.Influence of Polyethylene Glycol Unit on Palladium- and Nickel-Catalyzed Ethylene Polymerization and Copolymerizationcopolymerization; olefin polymerization; palladium; polar monomer; polyethylene glycol96201784#N/ATRUE
4334
anie.20170816910.1002/anie.201708169FALSEhttps://doi.org/10.1002/anie.201708169Konno, TAngew. Chem.-Int. Edit.Three oxidation states (+2, +3, +4) of an octahedral nickel center were stabilized in a newly prepared RhNiRh trinuClear complex, [Ni{Rh(apt)(3)}(2)](n+) (apt = 3-aminopropanethiolate), in which the nickel center was bound by six thiolato donors sourced from two redox-inert fac[Rh-III(apt)(3)] octahedral units. The three oxidation states of the octahedral nickel center were fully characterized by single-crystal X-ray crystallography, as well as spectroscopic, electrochemical, and magnetic measurements; all three were interconvertible, and the conversion was accompanied by changes in color, magnetism, and Jahn-Teller distortion.Valence Interconversion of Octahedral Nickel(II/III/IV) Centershigh oxidation states; nickel; redox chemistry; sulfur ligands10201742#N/ATRUE
4335
anie.20170723710.1002/anie.201707237FALSEhttps://doi.org/10.1002/anie.201707237Song, JXAngew. Chem.-Int. Edit.A powerful and concise synthesis of directly linked porphyrin-BODIPY hybrids has been demonstrated, which consists of condensation of directly linked meso-pyrroyl Ni-II-porphyrin with Arylaldehyde, oxidation with p-chloranil, and complexation with BF3Et2O. Synthesized hybrids inClude porphyrin dimer 6Ni, trimers 8Ni, 9Ni, tetramer 12Ni, pentamer 16Ni, hexamer 13Ni, and nonamers 17Ni and 18Ni. The structures of 6Ni, 9Ni and 12Ni were unambiguously confirmed by X-ray diffraction analysis. Some Ni-II porphyrins were effectively converted to the corresponding Zn-II porphryins. In these hybrids, the pigments are three-dimensionally arranged with a face-to-face dimeric porphyrin unit in a well-defined manner, featuring their potential as light-harvesting antenna and functional hosts.Strategic Construction of Directly Linked Porphyrin-BODIPY HybridsBODIPY; charge transfer; hybrid structures; nickel; porphyrinoids12201735#N/ATRUE
4336
anie.20170713410.1002/anie.201707134FALSEhttps://doi.org/10.1002/anie.201707134Zhou, JSAngew. Chem.-Int. Edit.A nickel-catalyzed asymmetric reductive Heck reaction of Aryl chlorides has been developed that affords substituted indolines with high enantioselectivity. Manganese powder is used as the terminal reductant with water as a proton source. Mechanistically, it is distinct from the palladium-catalyzed process in that the nickel-carbon bond is converted into a C-H bond to release the product through protonation instead of hydride donation followed by C-H reductive elimination on Pd.Nickel-Catalyzed Asymmetric Reductive Heck CyClization of Aryl Halides to Afford Indolinesasymmetric catalysis; cyClization; indolines; nickel; reductive Heck reaction73201786#N/ATRUE
4337
anie.20170692110.1002/anie.201706921FALSEhttps://doi.org/10.1002/anie.201706921Luo, JAngew. Chem.-Int. Edit.Single-atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential-cyCling method to synthesize a catalyst comprising single Pt atoms on CoP-based nanotube arrays supported bya Ni foam, termed PtSA-NT-NF. This binder-free catalyst is centimeter-scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA-NT-NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large-scale production strategy for binder-free Pt SAC electrodes for efficient HER in neutral media.Potential-CyCling Synthesis of Single Platinum Atoms for Efficient Hydrogen Evolution in Neutral Mediaelectrode materials; hydrogen evolution reaction; platinum; potential cyCling; single-atom catalysis235201754#N/ATRUE
4338
anie.20170661010.1002/anie.201706610FALSEhttps://doi.org/10.1002/anie.201706610Yan, QYAngew. Chem.-Int. Edit.Uniform Ni3C nanodots dispersed in ultrathin N-doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel cyanide coordination polymer precursors. The Ni3C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni3C based nanosheets exhibited outstanding electrocatalytic properties for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For example, 2 at % Fe (atomic percent) doped Ni3C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec(-1)) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec(-1) in KOH solution. Such nanodot-incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting.Fe-Doped Ni3C Nanodots in N-Doped Carbon Nanosheets for Efficient Hydrogen-Evolution and Oxygen-Evolution Electrocatalysisbifunctional electrocatalysts; HER; nanosheets; Ni3C nanodots; OER200201738#N/ATRUE
4339
anie.20170639810.1002/anie.201706398FALSEhttps://doi.org/10.1002/anie.201706398Masuda, JDAngew. Chem.-Int. Edit.The synthesis of the new m-terphenyl-substituted cyClopentadienyl ligand precursor 1-cyClopentadiene-2,6-bis(2,4,6-trimethylphenyl)benzene (Ter(Mes)CpH) is described. The synthesis proceeds through the reaction of Ter(Mes)Li with cobaltocenium iodide, followed by oxidation of the intermediate cobalt(I) species to give the corresponding cyClopentadiene as a mixture of isomers. The preparation and spectroscopic properties of the alkali-metal salts (Li-Cs) is described, as well as structural information obtained by X-ray diffraction studies for the lithium, potassium, and cesium analogues. Crystallographic data demonstrate the ability of these new ligands to act as monoanionic chelates by forming metal complexes with Cp-M-Ar bonding environments.A Bulky m-Terphenyl CyClopentadienyl Ligand and Its Alkali-Metal Complexesalkali metals; bulky ligands; chelates; crystallography; cyClopentadienyl ligands5201738#N/ATRUE
4340
anie.20170619610.1002/anie.201706196FALSEhttps://doi.org/10.1002/anie.201706196Driess, MAngew. Chem.-Int. Edit.A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 2,15 mV overpotential was achieved at a current density of 10 mA cm(-2), representing outstanding catalytic activity and stability because of Fe(OH)/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover; an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.From a Molecular 2Fe-2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splittingbioinspired complexes; energy conversion; hydrogen evolution; mixed valence; oxygen evolution100201762#N/ATRUE
4341
anie.20170613410.1002/anie.201706134FALSEhttps://doi.org/10.1002/anie.201706134Shinokubo, HAngew. Chem.-Int. Edit.The synthesis of a bowl-shaped antiaromatic molecule was achieved through the deformation of a planar antiaromatic porphyrinic -conjugation system by insertion of palladium into the small cavity of a metal-free norcorrole. The bowl-to-bowl inversion dynamics of the antiaromatic Pd-coordinated norcorrole was determined by variable-temperature (HNMR)-H-1 spectroscopy. The metal-free norcorrole was prepared from acid-induced demetalation of a copper norcorrole, which was obtained from the intramolecular coupling of a bis(diiododipyrrin) copper complex with copper thiopheneCarbonylate.Shaping Antiaromatic -Systems by Metalation: Synthesis of a Bowl-Shaped Antiaromatic Palladium Norcorrolearomaticity; bowl-shaped molecules; C-C coupling; porphyrinoids; strained molecules24201759#N/ATRUE
4342
anie.20170555110.1002/anie.201705551FALSEhttps://doi.org/10.1002/anie.201705551Broring, MAngew. Chem.-Int. Edit.10-Heterocorrole complexes with oxygen, sulfur, and selenium at position 10 of the macrocyCle and with the divalent ions of nickel, copper, and palladium were prepared and investigated. The focus was set on the size adaptation and matching mechanisms of cavity size versus ionic radius in corrole-type macrocyCles. A full set of single-crystal X-ray analytical data revealed that in all but one case the N-4 binding site of the ring-contracted tetrapyrrole was larger than necessary to bind the metal ion without deformation. In-plane size adaptation through M-N bond-length elongation by 2.5-3.2% was effective, as well as pronounced out-of-plane ruffling of the macrocyCle for those compounds with a more severe size mismatch. Such ruffling had been exCluded for corroles previously, but is apparently the most efficient mechanism to adapt to small central ions.Heterocorrole Conformations: Little Saddling, Much Rufflingconformation analysis; coordination compounds; heterocorroles; porphyrinoids; X-ray crystallography9201749#N/ATRUE
4343
anie.20170398910.1002/anie.201703989FALSEhttps://doi.org/10.1002/anie.201703989Hou, MHAngew. Chem.-Int. Edit.Small-molecule compounds targeting trinuCleotide repeats in DNA have considerable potential as therapeutic or diagnostic agents against many neurological diseases. Ni-II-(Chro)(2) (Chro=chromomycin A3) binds specifically to the minor groove of (CCG)(n) repeats in duplex DNA, with unique fluorescence features that may serve as a probe for disease detection. Crystallographic studies revealed that the specificity originates from the large-scale spatial rearrangement of the DNA structure, inCluding extrusion of consecutive bases and backbone distortions, with a sharp bending of the duplex accompanied by conformational changes in the Ni-II chelate itself. The DNA deformation of CCG repeats upon binding forms a GGCC tetranuCleotide tract, which is recognized by Ni-II(Chro)(2). The extruded cytosine and last guanine nuCleotides form water-mediated hydrogen bonds, which aid in ligand recognition. The recognition can be accounted for by the Classic induced-fit paradigm.Induced-Fit Recognition of CCG TrinuCleotide Repeats by a Nickel-Chromomycin Complex Resulting in Large-Scale DNA DeformationDNA deformation; induced-fit recognition; neurological disease; trinuCleotide repeats; X-ray crystallographyx14201738#N/AFALSE
4344
anie.20170552310.1002/anie.201705523FALSEhttps://doi.org/10.1002/anie.201705523Kishi, YAngew. Chem.-Int. Edit.Unified, efficient, and scalable syntheses of the halichondrin natural products are reported. A newly developed Zr/Ni-mediated one-pot ketone synthesis was used to couple the two halves of the final product at a late stage in the synthesis. With the use of a slight excess of the left halves, the desired ketones were isolated in yields of 80-90%. The halichondrins were obtained from these ketones in two steps, namely desilylation and [5,5]-spiroketal formation. The new synthetic route was effective for the total synthesis of all members in the homohalichondrin subgroup. The scalability of this process was demonstrated with halichondrin B; 150 mg of halichondrin B (68% overall yield) were obtained from 200 mg of the right-half precursor.Unified, Efficient, and Scalable Synthesis of Halichondrins: Zirconium/Nickel-Mediated One-Pot Ketone Synthesis as the Final Coupling Reactionhalichondrins; ketones; natural products; nickel catalysis; total synthesis19201725#N/ATRUE
4345
anie.20170361110.1002/anie.201703611https://doi.org/10.1002/anie.201703611Muniz, KAngew. Chem.-Int. Edit.An unprecedented method that makes use of the cooperative interplay between molecular iodine and photo-redox catalysis has been developed for dual light-activated intramolecular Benzylic C-H amination. Iodine serves as the catalyst for the formation of a new C-N bond by activating a remote C-sp3-H bond (1,5-HAT process) under visible-light irradiation while the organic photoredox catalyst TPT effects the reoxidation of the molecular iodine catalyst. To explain the compatibility of the two involved photochemical steps, the key N-I bond Activation was elucidated by computational methods. The new cooperative catalysis has important implications for the combination of non-metallic main-group catalysis with photocatalysis.Cooperative Light-Activated Iodine and Photoredox Catalysis for the Amination of C-sp3-H Bonds1,5-HAT processes; amination; cooperative catalysis; iodine catalysis; photoredox catalysisPhotocatalyst116201763#N/AFALSE
4346
anie.20170338010.1002/anie.201703380FALSEhttps://doi.org/10.1002/anie.201703380Lam, HWAngew. Chem.-Int. Edit.Enantioselective nickel-catalyzed Arylative cyClizations of substrates containing a Z-allylic phosphate tethered to an alkyne are described. These reactions give multisubstituted chiral aza- and carbocyCles, and are initiated by the addition of an Arylboronic acid to the alkyne, followed by cyClization of the resulting alkenylnickel species onto the allylic phosphate. The reversible E/Z isomerization of the alkenylnickel species is essential for the success of the reactions.Enantioselective Nickel-Catalyzed Intramolecular Allylic Alkenylations Enabled by Reversible Alkenylnickel E/Z Isomerizationallylic substitution; asymmetric catalysis; cyClization; isomerization; nickelx29201773#N/AFALSE
4347
anie.20170318310.1002/anie.201703183FALSEhttps://doi.org/10.1002/anie.201703183Hu, JSAngew. Chem.-Int. Edit.The exploration of new efficient OER electrocatalysts based on nonprecious metals and the understanding of the relationship between activity and structure of electrocatalysts are important to advance electrochemical water oxidation. Herein, we developed an efficient OER electrocatalyst with nickel boride (Ni3B) nanopartiCles as cores and nickel(II) borate (Ni-B-i) as shells (Ni-B-i@NB) via a very simple and facile aqueous reaction. This electrocatalyst exhibited a small overpotential of 302 mV at 10 mA cm(-2) and Tafel slope of 52 mV dec(-1). More interestingly, it was found that the OER activity of Ni-B-i@NB was Closely dependent on the crystallinity of the Ni-B-i shells. The partially crystalline Ni-B-i catalyst exhibited much higher activity than the amorphous or crystalline analogues; this higher activity originated from the enhanced intrinsic activity of the catalytic sites. These findings open up opportunities to explore nickel(II) borates as a new Class of efficient nonprecious metal OER electrocatalysts, and to improve the electrocatalyst performance by modulating their crystallinity.Crystallinity-Modulated Electrocatalytic Activity of a Nickel(II) Borate Thin Layer on Ni3B for Efficient Water Oxidationelectrolysis; nanohybrids; nickel borate; oxygen evolution reaction; water splitting
Electrocatalytic
167201763#N/AFALSE
4348
anie.20170552010.1002/anie.201705520FALSEhttps://doi.org/10.1002/anie.201705520Kishi, YAngew. Chem.-Int. Edit.A zirconium/nickel-mediated one-pot synthesis of ketones is reported. In the presence of Zn or Mn, Cp2ZrCl2 was found to dramatically accelerate the coupling and suppress side product formation via an I -> SPy displacement at the same time. Unlike Zn/Pd- and Fe/Cu-mediated one-pot ketone syntheses, the new method is effective for nuCleophiles bearing OR or equivalent functional groups at the alpha-position. A mechanism comprising a nickel catalytic cyCle, a zirconium catalytic cyCle, and Zr -> Ni transmetalation is proposed, and Cp2ZrCl2 and/or low-valent Zr species are suggested to play crucial dual roles.Zirconium/Nickel-Mediated One-Pot Ketone Synthesisketones; nickel; radical reactions; transition-metal catalysis; zirconium18201737#N/ATRUE
4349
anie.20170494810.1002/anie.201704948FALSEhttps://doi.org/10.1002/anie.201704948McNally, AAngew. Chem.-Int. Edit.HeterobiAryls are important pharmacophores that are challenging to prepare by traditional cross-coupling methods. An alternative approach is presented where pyridines and diazines are converted into heteroAryl phosphonium salts and coupled with Aryl boronic acids. Nickel catalysts are unique for selective heteroAryl transfer, and the reaction has a broad substrate scope that inCludes complex pharmaceuticals. Phosphonium ions also display orthogonal reactivity in cross-couplings compared to halides, enabling chemoselective palladium-and nickel-catalyzed coupling sequences.Phosphonium Salts as Pseudohalides: Regioselective Nickel-Catalyzed Cross-Coupling of Complex Pyridines and Diazinescross-coupling; diazines; nickel catalysis; phosphonium salts; pyridines38201738#N/ATRUE
4350
anie.20170491110.1002/anie.201704911FALSEhttps://doi.org/10.1002/anie.201704911Mu, SCAngew. Chem.-Int. Edit.Highly active, stable, and cheap Pt-free catalysts for the hydrogen evolution reaction (HER) are under increasing demand for future energy conversion systems. However, developing HER electrocatalysts with Pt-like activity that can function at all pH values still remains as a great challenge. Herein, based on our theoretical predictions, we design and synthesize a novel N, P dual-doped carbon-encapsulated ruthenium diphosphide (RuP2@NPC) nanopartiCle electrocatalyst for HER. Electrochemical tests reveal that, compared with the Pt/C catalyst, RuP2@NPC not only has Pt-like HER activity with small overpotentials at 10 mA cm(-2) (38 mV in 0.5m H2SO4, 57 mV in 1.0 M PBS and 52 mV in 1.0 m KOH), but demonstrates superior stability at all pH values, as well as 100% Faradaic yields. Therefore, this work adds to the growing family of transition-metal phosphides/heteroatomdoped carbon heterostructures with advanced performance in HER.RuP2-Based Catalysts with Platinum-like Activity and Higher Durability for the Hydrogen Evolution Reaction at All pH Valueselectrocatalysts; hydrogen evolution reaction; N,P dual-doped carbon; ruthenium diphosphide348201762#N/ATRUE
4351
anie.20170486210.1002/anie.201704862FALSEhttps://doi.org/10.1002/anie.201704862Nevado, CAngew. Chem.-Int. Edit.beta,beta-Disubstituted Vinyl sulfones were obtained with complete regio- and stereocontrol in a multicomponent reaction involving alkynes, organB(OH)2ronic acids, and sulfonyl chlorides in the presence of a nickel catalyst. The reaction proceeds via sulfonyl radicals generated in situ under mild reaction conditions.Nickel-Catalyzed Intermolecular Carbosulfonylation of Alkynes via Sulfonyl Radicalscarbosulfonylation; nickel; stereoselectivity; sulfonyl radicals; Vinyl radicals50201765#N/ATRUE
4352
anie.20170207910.1002/anie.201702079https://doi.org/10.1002/anie.201702079Doyle, AGAngew. Chem.-Int. Edit.We report a redox-neutral Carbonylation of Aryl chlorides that proceeds through selective 2-functionalization of 1,3-dioxolane through nickel and photoredox catalysis. This scalable benchtop approach provides a distinct advantage over traditional reductive Carbonylation in that no carbon monoxide, pressurized gas, or stoichiometric reductant is employed. The mild conditions give unprecedented scope from abundant and complex Aryl chloride starting materials.Mild, Redox-Neutral Carbonylation of Aryl Chlorides through the Photocatalytic Generation of Chlorine RadicalsC-H functionalization; Carbonylation; nickel; photocatalysis; redox reactionsPhotocatalyst76201733#N/AFALSE
4353
anie.20170198410.1002/anie.201701984FALSEhttps://doi.org/10.1002/anie.201701984Grimaud, AChemical Recognition of Active Oxygen Species on the Surface of Oxygen Evolution Reaction Electrocatalystsx2017#N/AFALSE
4354
anie.20170470410.1002/anie.201704704FALSEhttps://doi.org/10.1002/anie.201903545Sievers, CConversion of Methane into Methanol and Ethanol over Nickel Oxide on Ceria-Zirconia Catalysts in a Single Reactor2017#N/ATRUE
4355
anie.20170448710.1002/anie.201704487FALSEhttps://doi.org/10.1002/anie.201704487Lee, YAngew. Chem.-Int. Edit.A T-shaped Ni-I complex was synthesized using a rigid acridane-based pincer ligand to prepare a metalloradical center. Structural data displays a nickel ion is embedded in the plane of a PNP ligand. Having a sterically exposed half-filled d(x2-y2) orbital, this three-coordinate Ni-I species reveals unique open-shell reactivity inCluding the homolytic Cleavage of various sigma-bonds, such as H-H, N-N, and C-C.AT-Shaped Nickel(I) Metalloradical SpeciesC-C bond Activation; metalloradicals; nickel; radicals46201761#N/ATRUE
4356
anie.20170114910.1002/anie.201701149FALSEhttps://doi.org/10.1002/anie.201701149Lin, ZQAngew. Chem.-Int. Edit.Three-dimensional (3D) interconnected metal alloy nanostructures possess superior catalytic performance owing to their advantageous characteristics, inCluding improved catalytic activity, corrosion resistance, and stability. Hierarchically structured Ni-Cu alloys composed of 3D network-like microscopic branches with nanoscopic dendritic feelers on each branch were crafted by a facile and efficient hydrogen evolution-assisted electrodeposition approach. They were subsequently exploited for methanol electrooxidation in alkaline media. Among three hierarchically structured Ni-Cu alloys with different Ni/Cu ratios (Ni0.25Cu0.75, Ni0.50Cu0.50, and Ni0.75Cu0.25), the Ni0.75Cu0.25 electrode exhibited the fastest electrochemical response and highest electrocatalytic activity toward methanol oxidation. The markedly enhanced performance of Ni0.75Cu0.25 eletrocatalyst can be attributed to its alloyed structure with the proper Ni/Cu ratio and a large number of active sites on the surface of hierarchical structures.Highly Branched Metal Alloy Networks with Superior Activities for the Methanol Oxidation Reactionelectrocatalysis; electrodeposition; hierarchical structures; methanol oxidation; Ni-Cu alloyx92201742#N/AFALSE
4357
anie.20170094910.1002/anie.201700949FALSEhttps://doi.org/10.1002/anie.201700949Reisner, EAngew. Chem.-Int. Edit.Single-source precursor syntheses have been devised for the preparation of structurally similar graphitic carbon dots (CDs), with (g-N-CD) and without (g-CD) core nitrogen doping for artificial photosynthesis. An order of magnitude improvement has been realized in the rate of solar (AM1.5G) H-2 evolution using g-N-CD (7950 mu mol(H2) (g(CD))(-1) h(-1)) compared to undoped CDs. All graphitized CDs show significantly enhanced light absorption compared to amorphous CDs (a-CD) yet undoped g-CD display limited photosensitizer ability due to low extraction of photogenerated charges. Transient absorption spectroscopy showed that nitrogen doping in g-N-CD increases the efficiency of hole scavenging by the electron donor and thereby significantly extends the lifetime of the photogenerated electrons. Thus, nitrogen doping allows the high absorption coefficient of graphitic CDs to be translated into high charge extraction for efficient photocatalysis.Enhancing Light Absorption and Charge Transfer Efficiency in Carbon Dots through Graphitization and Core Nitrogen Dopingcarbon dots; doping; excited state dynamics; light harvesting; photocatalysisx112201736#N/AFALSE
4358
anie.20170432710.1002/anie.201704327FALSEhttps://doi.org/10.1002/anie.201905554Duan, CYControl of Redox Events by Dye Encapsulation Applied to Light-Driven Splitting of Hydrogen Sulfide2017#N/ATRUE
4359
anie.20170043610.1002/anie.201700436FALSEhttps://doi.org/10.1002/anie.201700436Winnik, FMAngew. Chem.-Int. Edit.Impurity-doping in nanocrystals significantly affects their electronic properties and diversifies their applications. Herein, we report the synthesis of transition metal (Mn, Ni, Co, Cu)-doped oleophilic silicon nanocrystals (SiNCs) through hydrolysis/polymerization of triethoxysilane with acidic aqueous metal salt solutions, followed by thermal disproportionation of the resulting gel into a doped-Si/SiO2 composite that, upon HF etching and hydrosilylation with 1-n-octadecene, produces free-standing octadecyl-capped doped SiNCs (diameter approximate to 3 to 8 nm; dopant < 0.2 atom %). Metal-doping triggers a red-shift of the SiNC photoluminescence (PL) of up to 270 nm, while maintaining high PL quantum yield (26% for Co doping).Transition-Metal-Doped NIR-Emitting Silicon Nanocrystalsdoping; nanocrystals; photoluminescence; silicon; thermal disproportionationx21201726#N/AFALSE
4360
anie.20170038810.1002/anie.201700388FALSEhttps://doi.org/10.1002/anie.201700388Fontecave, MAngew. Chem.-Int. Edit.To use water as the source of electrons for proton or CO2 reduction within electrocatalytic devices, catalysts are required for facilitating the proton-coupled multi-electron oxygen evolution reaction (OER, 2H(2)O -> O-2 + 4H(+) + 4e(-)). These catalysts, ideally based on cheap and earth abundant metals, have to display high activity at low overpotential and good stability and selectivity. While numerous examples of Co, Mn, and Ni catalysts were recently reported for water oxidation, only few examples were reported using copper, despite promising efficiencies. A rationally designed nanostructured copper/copper oxide electrocatalyst for OER is presented. This material derives from conductive copper foam passivated by a copper oxide layer and further nanostructured by electrodeposition of CuO nanopartiCles. The generated electrodes are highly efficient for catalyzing selective water oxidation to dioxygen with an overpotential of 290 mV at 10 mA cm(-2) in 1M NaOH solution.A Dendritic Nanostructured Copper Oxide Electrocatalyst for the Oxygen Evolution Reactioncopper oxide; electrocatalysis; electrodeposition; porous electrode; water oxidationx132201734#N/AFALSE
4361
anie.20170034110.1002/anie.201700341FALSEhttps://doi.org/10.1002/anie.201700341Stary, IAngew. Chem.-Int. Edit.A series of oxahelicenes composed of ortho/meta-annulated benzene/pyridine and 2H-pyran rings were synthesized on the basis of the cobalt(I)-mediated (or rhodium(I)- or nickel(0)-mediated) double, triple, or quadruple [2+2+2] cyCloisomerization of branched aromatic hexa-, nona-, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyClization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]-, [13]-, [17]- and [19] helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single-molecule conductivity was studied by the mechanically controllable break-junction method with a pyridooxa[9]helicene.Synthesis of Long Oxahelicenes by PolycyClization in a Flow Reactorasymmetric synthesis; chirality; conducting materials; helical structures; heterocyClesx36201751#N/AFALSE
4362
anie.20170009710.1002/anie.201700097https://doi.org/10.1002/anie.201700097Doyle, AGAngew. Chem.-Int. Edit.The enantioselective desymmetrization of cyClic meso-anhydrides with Benzyl trifluorB(OH)2rates under nickel-photoredox catalysis is described. The reaction tolerates a variety of sterically and electronically different trifluorB(OH)2rates, as well as structurally unique cyClic anhydrides. The trans isomer of the keto-acid products is also observed at varying levels dependent on the trifluorB(OH)2rate identity and relative catalyst loading. A mechanism involving deCarbonylation and Ni-C bond homolysis of a Ni-II adduct is proposed. This feature allows access to a trans keto-acid as the major product in high enantioselectivity from a cis meso anhydride.Dual Nickel- and Photoredox-Catalyzed Enantioselective Desymmetrization of CyClic meso-Anhydridesasymmetric synthesis; cross-coupling; desymmetrization; nickel; photoredox catalysisPhotocatalyst572017286/15/2022FALSE
4363
anie.20161242310.1002/anie.201612423https://doi.org/10.1002/anie.201612423Huang, BBAngew. Chem.-Int. Edit.The aluminum-based metal-organic framework (MOF) made from 2-aminoterephthalate is a photocatalyst for oxygen evolution. This MOF can be modified by incorporating Ni2+ cations into the pores through coordination to the amino groups, and the resulting MOF is an efficient photocatalyst for overall water splitting.Ni-II Coordination to an Al-Based Metal-Organic Framework Made from 2-Aminoterephthalate for Photocatalytic Overall Water Splittingmetal-organic frameworks; photocatalysis; water splittingPhotocatalyst99201742#N/AFALSE
4364
anie.20161223210.1002/anie.201612232FALSEhttps://doi.org/10.1002/anie.201612232Song, YFRobust Polyoxometalate/Nickel Foam Composite Electrodes for Sustained Electrochemical Oxygen Evolution at High pHx2017#N/AFALSE
4365
anie.20170425310.1002/anie.201704253FALSEhttps://doi.org/10.1002/anie.201704253Schmidt, TJAngew. Chem.-Int. Edit.Highly active and durable oxygen reduction catalysts are needed to reduce the costs and enhance the service life of polymer electrolyte fuel cells (PEFCs). This can be accomplished by alloying Pt with a transition metal (for example Ni) and by eliminating the corrodible, carbon-based catalyst support. However, materials combining both approaches have seldom been implemented in PEFC cathodes. In this work, an unsupported Pt-Ni alloy nanochain ensemble (aerogel) demonstrates high current PEFC performance commensurate with that of a carbon-supported benchmark (Pt/C) following optimization of the aerogel's catalyst layer (Cl) structure. The latter is accomplished using a soluble filler to shift the Cl's pore size distribution towards larger pores which improves reactant and product transport. Chiefly, the optimized PEFC aerogel cathodes display a circa 2.5-fold larger surface-specific ORR activity than Pt/C and maintain 90% of the initial activity after an accelerated stress test (vs. 40% for Pt/C).Unsupported Pt-Ni Aerogels with Enhanced High Current Performance and Durability in Fuel Cell Cathodesalloys; electrochemistry; energy conversion; fuel cells; nanostructures38201721#N/ATRUE
4366
anie.20170402710.1002/anie.201704027FALSEhttps://doi.org/10.1002/anie.201704027Ivanova, IIAngew. Chem.-Int. Edit.The novel approach based on S-33 isotope tracing is proposed for the elucidation of hydrodesulfurization (HDS) mechanisms and characterization of molybdenum sulfide catalysts. The technique involves sulfidation of the catalyst with S-33-isotope-labeled dihydrogen sulfide, followed by monitoring the fate of the S-33 isotope in the course of the hydrodesulfurization reaction by online mass spectrometry and characterization of the catalyst after the reaction by temperature-programmed oxidation with mass spectrometry (TPO-MS). The results point to different pathways of thiophene transformation over Co or Ni-promoted and unpromoted molybdenum sulfide catalysts, provide information on the role of promoter and give a key for the design of new efficient HDS catalysts.Sulfur-33 Isotope Tracing of the Hydrodesulfurization Process: Insights into the Reaction Mechanism, Catalyst Characterization and Improvementsulfur; heterogeneous catalysis; hydrodesulfurization; isotope tracing; mass spectrometry10201741#N/ATRUE
4367
anie.20161179610.1002/anie.201611796FALSEhttps://doi.org/10.1002/anie.201611796McEwen, JSAngew. Chem.-Int. Edit.The role of low concentrations of carbon complexes in hydrocarbon decomposition over transition metal surfaces has been a topic of much debate over the past decades. It is also a mystery as to whether or not electric fields can enhance hydrocarbon conversion in an electrochemical device at lower than normal reforming temperatures. To provide a bottom-up fundamental insight, C-H bond Cleavage in methane over Ni-based catalysts was investigated. Our theoretical results show that the presence of carbon or carbide-like species at the interface between the Ni Cluster and its metal-oxide support, as well as the application of an external positive electric field, can significantly increase the Ni oxidation state. Furthermore, the first C-H bond Cleavage in methane is favored as the local oxidation state of Ni increases. Thus, the presence of a low concentration of carbon species, or the addition of a positive electric field will improve the hydrocarbon Activation process.Catalytic Reaction Rates Controlled by Metal Oxidation State: C-H Bond Cleavage in Methane over Nickel-Based CatalystsC-H bond Activation; carbon species; electric fields; methane; nickelx28201739#N/AFALSE
4368
anie.20170402110.1002/anie.201704021FALSEhttps://doi.org/10.1002/anie.201704021Mayrhofer, KAngew. Chem.-Int. Edit.A fundamental understanding of the behavior of non-noble based materials toward the hydrogen evolution reaction is crucial for the successful implementation into practical devices. Through the implementation of a highly sensitive inductively coupled plasma mass spectrometer coupled to a scanning flow cell, the activity and stability of nonnoble electrocatalysts is presented. The studied catalysts comprise a range of compositions, inCluding metal carbides (WC), sulfides (MoS2), phosphides (Ni5P4, Co2P), and their base metals (W, Ni, Mo, Co); their activity, stability, and degradation behavior was elaborated and compared to the state-of-the-art catalyst platinum. The non-noble materials are stable at HER potentials but dissolve substantially when no current is flowing. Through pre-and post-characterization of the catalysts, explanations of their stability (thermodynamics and kinetics) are discussed, challenges for the application in real devices are analyzed, and strategies for circumventing dissolution are suggested. The precise correlation of metal dissolution with applied potential/current density allows for narrowing down suitable material choices as replacement for precious group metals as for example, platinum and opens up new ways in finding cost-efficient, active, and stable new-generation electrocatalysts.Stability and Activity of Non-Noble-Metal-Based Catalysts Toward the Hydrogen Evolution Reactionceramics; electrocatalysis; hydrogen evolution; non-noble metals; water splitting61201734#N/ATRUE
4369
anie.20161160510.1002/anie.201611605https://doi.org/10.1002/anie.201611605Driess, MAngew. Chem.-Int. Edit.Solar light harvesting by photocatalytic H-2 evolution from water could solve the problem of greenhouse gas emission from fossil fuels with alternative Clean energy. However, the development of more efficient and robust catalytic systems remains a great challenge for the technological use on a large scale. Here we report the synthesis of a sol-gel prepared mesoporous graphitic carbon nitride (sg-CN) combined with nickel phosphide (Ni2P) which acts as a superior co-catalyst for efficient photocatalytic H-2 evolution by visible light. This integrated system shows a much higher catalytic activity than the physical mixture of Ni2P and sg-CN or metallic nickel on sg-CN under similar conditions. Time-resolved photoluminescence and electron paramagnetic resonance (EPR) spectroscopic studies revealed that the enhanced carrier transfer at the Ni2P-sg-CN heterojunction is the prime source for improved activity.Boosting Visible-Light-Driven Photocatalytic Hydrogen Evolution with an Integrated Nickel Phosphide-Carbon Nitride Systemcarbon nitride; chemical energy storage; photocatalyst; semiconductor; water splittingPhotocatalyst181201754#N/AFALSE
4370
anie.20161157210.1002/anie.201611572FALSEhttps://doi.org/10.1002/anie.201611572Diao, TNAngew. Chem.-Int. Edit.Metal-metal bonds play a vital role in stabilizing key intermediates in bond-formation reactions. We report that binuClear benzo[h]quinoline-ligated Ni-II complexes, upon oxidation, undergo reductive elimination to form carbon-halogen bonds. A mixed-valent Ni(2.5+)-Ni(2.5+) intermediate is isolated. Further oxidation to Ni-III, however, is required to trigger reductive elimination. The binuClear Ni-III-Ni-III intermediate lacks a Ni- Ni bond. Each Ni-III undergoes separate, but fast reductive elimination, giving rise to Ni-I species. The reactivity of these binuClear Ni complexes highlights the fundamental difference between Ni and Pd in mediating bond-formation processes.BinuClear, High-Valent Nickel Complexes: Ni-Ni Bonds in Aryl-Halogen Bond FormationC-X bond formation; mixed-valent compounds; nickel-nickel bond; reaction mechanisms; reductive eliminationx33201755#N/AFALSE
4371
anie.20161153210.1002/anie.201611532FALSEhttps://doi.org/10.1002/anie.201611532Le Goff, AAngew. Chem.-Int. Edit.A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H-2/2H(+) interconversion from pH0 to 9, with catalytic preference for H-2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14mWcm(-2), only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers approximate to 2mWcm(-2), a new efficiency record for a hydrogen biofuel cell with base metal catalysts.Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cellsbiofuel cells; bio-inspired catalysts; H-2 oxidation; multicopper oxidases; nickel complexesx54201745#N/AFALSE
4372
anie.20161128210.1002/anie.201611282https://doi.org/10.1002/anie.201611282Diao, TNAngew. Chem.-Int. Edit.Single-crystal X-ray characterization of cationic (-diimine)Ni-ethyl and isopropyl -agostic complexes, which are key intermediates in olefin polymerization and oligomerization, are presented. The sharp Ni-C-C angles (75.0(3)degrees and 74.57(18)degrees) and short C-C distances (1.468(7) and 1.487(5)angstrom) provide unambiguous evidence for a -agostic interaction. An inverse equilibrium isotope effect (EIE) for ligand coordination upon Cleavage of the agostic bond highlights the weaker bond strength of Ni-H relative to the C-H bond. An Eyring plot for -hydride elimination-olefin rotation-reinsertion is constructed from variable-temperature NMR spectra with C-13-labeled agostic complexes. The enthalpy of Activation (H) for -H elimination is 13.2kcalmol(-1). These results offer important mechanistic insight into two critical steps in polymerization: ligand association upon Cleavage of the -agostic bonds and chain-migration via beta-H elimination.Structure and Isotope Effects of the beta-H Agostic (alpha-Diimine)Nickel Cation as a Polymerization Intermediatebeta-agostic interactions; inverse kinetic isotope effect; nickel; polymerization intermediatesx26201751#N/AFALSE
4373
anie.20161121410.1002/anie.201611214FALSEhttps://doi.org/10.1002/anie.201611214Feng, XMAngew. Chem.-Int. Edit.A highly efficient asymmetric cascade reaction between alkynyl esters and allylic alcohols has been realized. Key to success was the combination of a hydroalkoxylation reaction catalyzed by a pi-acidic gold(I) complex witha Claisen rearrangement catalyzed by a chiral Lewis acidic N,N'-dioxide-nickel(II) complex. A range of acyClic alpha-allyl beta-keto esters were synthesized in high yields (up to 99%) with good diastereoselectivities (up to 97:3) and excellent enantioselectivities (up to 99% ee) under mild reaction conditions. These products can be easily transformed into optically active beta-hydroxy esters, beta-hydroxy acids, or 1,3-diols.Gold(I)/Chiral N,N '-Dioxide-Nickel(II) Relay Catalysis for Asymmetric Tandem Intermolecular Hydroalkoxylation/Claisen Rearrangementasymmetric catalysis; Claisen rearrangement; gold; hydroalkoxylation; nickelx57201778#N/AFALSE
4374
anie.20170373110.1002/anie.201703731FALSEhttps://doi.org/10.1002/anie.201703731Driess, MAngew. Chem.-Int. Edit.A facile, one-pot synthesis of 1,Na(OC equivalent to As)-(dioxane)(x)] (x=2.3-3.5) in 78% yield is reported through the reaction of arsine gas with dimethylcarbonate in the presence of (NaOBu)-Bu-t and dioxane. It has been employed for the synthesis of the first arsaketenyl-functionalized germylene /LGeAsCO/ (2, L =CIIICMeN(Dipp)(2)],; Dipp = 2,6-(Pr2C6H3)-Pr-i) from the reaction with LGeCI (I). Upon exposure to ambient light, 2 undergoes CO elimination to form the 1,3-digerma-2,4-diarsacyClobtuadiene [L2Ge2As2] (3), which contains a symmetric Ge2As2 ring with ylide-like Ge=As bonds. Remarkably, the CO ligand located at the arsenic center of 2 can be exchanged with PPh3 or an N-heterocyClic carbene NI-IC donor ((NTIC)-N-iPr=L3-diisopropyl-4,5-dimethylimidazol-2-ylidene) to afford the novel germ ylidenylarsinidene complexes [LGe-AsPPh3] (4) and [LGe-As((NI)-N-iPr-IC)] (5), respectively, demonstrating transition-metal-like ligand substitution at the arsinidene-like As atom. The formation of 2-5 and their electronic structures have been studied by T)FT calculations.Facile Access to NaOC equivalent to As and Its Use as an Arsenic Source To Form Germylidenylarsinidene Complexesarsenic; arsinidene; germanium; germylene; main-group chemistry19201751#N/ATRUE
4375
anie.20170313910.1002/anie.201703139FALSEhttps://doi.org/10.1002/anie.201703139Osuka, AAngew. Chem.-Int. Edit.Alkynyl-substituted 3H-corrole 9a was converted to [3]cumulenic 2H-corrole 10a by treatment with trimethylsilyl chloride (TMSCl), and 1,3-butadiyne-bridged 3H-corrole dimer 11b was transformed into [5]cumulene-bridged 2H-corrole dimer 12b by oxidation with PbO2. Both 10a and 12b were metalated to form Zn-II complexes 10a-Zn and 12b-Zn. The structures of 10a-Zn and 12b-Zn show planar conformations with bond-length alternations that are analogous to those of tetraAryl [n]cumulenes. The cumulenic corrole dimers 12b and 12b-Zn display large NIR absorption bands in the range of 700-1400 nm (maximum epsilon approximate to 1.0 X 10(5) M-1 cm(-1)) owing to the effective pi-conjugation between the two corrole units through the [5]cumulene bridge.meso-Cumulenic 2H-Corroles from meso-Ethynyl-3H-corrolesaromaticity; bond-length alternation; corrole; cumulene; NIR absorption16201758#N/ATRUE
4376
anie.20161106610.1002/anie.201611066https://doi.org/10.1002/anie.201611066Cui, DMAngew. Chem.-Int. Edit.Styrene underwent unprecedented coordinationinsertion copolymerization with naked polar monomers (ortho-/ meta-/ para-methoxystyrene) in the presence of a pyridyl methylene fluorenyl yttrium catalyst. High activity (1.26 X 10(6) gmol(Y)(- 1)h (-1)) and excellent syndioselectivity were observed, and high-molecular-weight copolymers (24.6 X 10(4) gmol (-1)) were obtained. The insertion rate of the polar monomers could be adjusted in the full range of 0-100% simply by changing the loading of the polar styrene monomer. Strikingly, the copolymers had tapered, gradient, and even random sequence distributions, depending on the position of the polar methoxy group on the phenyl ring and thus on its mode of coordination to the active metal center, as shown by tracking the polymerization process and DFT calculations.Stereoselective Copolymerization of Unprotected Polar and Nonpolar Stryenes by an Yttrium Precursor:Control of Polar-Group Distribution and Mechanismpolar monomers; sequence regulation; styrene; syndioselective copolymerization; yttriumx59201744#N/AFALSE
4377
anie.20170277210.1002/anie.201702772FALSEhttps://doi.org/10.1002/anie.201702772Driess, MAngew. Chem.-Int. Edit.The first 16 valence electron [bis(NHC)]-(silylene)Ni-0 complex 1, [(L-TMS)ClSi:-> Ni(NHC)(2)], hearing the acyClic amido-chlorositylene (L-TMS)ClSi: (L-TMS=N-(SiMe3)Dipp; Dipp=2,6-(Pr2C6H4)-C-i) and two NHC ligands (N -heterocyClic carbene=:C[(Pr-i)NC(Me)](2)) was synthesized in high yield and structurally characterized. Compound 1 is capable of facile dihydrogen Activation under ambient conditions to give the corresponding 11Si-Nill complex 2. Most notably, 1 reads with catechol borane to afford the unprecedented hydrB(OH)2rylene-coordinated (chloro)(silyl)nickel(II) complex 3, ([cat(L-TMS)Si](Cl)Ni <-:BH(NHC)(2)], via the Cleavage of two B-O bonds and simultaneous formation o f two Si-O bonds. The mechanism for the formation of 3 was rationalized by means of DFT calculations highlight the powerful synergistic effects of the Si:-> Ni moiety in the breaking of incredibly strong B-O bonds.Silylene-Nickel Promoted Cleavage of B-O Bonds: From Catechol Borane to the HydrB(OH)2rylene Ligandagostic interactions; borane; hydrogen Activation; nickel; silicon16201763#N/ATRUE
4378
anie.20170257810.1002/anie.201702578FALSEhttps://doi.org/10.1002/anie.201702578Surendranath, YAngew. Chem.-Int. Edit.Polymer electrolyte membranes employed in contemporary fuel cells severely limit device design and restrict catalyst choice, but are essential for preventing short-circuiting reactions at unselective anode and cathode catalysts. Herein, we report that nickel sulfide Ni3S2 is a highly selective catalyst for the oxygen reduction reaction in the presence of 1.0M formate. We combine this selective cathode with a carbon-supported palladium (Pd/C) anode to establish a membrane-free, room-temperature formate fuel cell that operates under benign neutral pH conditions. Proof-of-concept cells display open circuit voltages of approximately 0.7 V and peak power values greater than 1 mW cm(-2), significantly outperforming the identical device employing an unselective platinum (Pt) cathode. The work establishes the power of selective catalysis to enable versatile membrane-free fuel cells.A Membrane-Free Neutral pH Formate Fuel Cell Enabled by a Selective Nickel Sulfide Oxygen Reduction Catalystelectrocatalysis; formate; fuel cells; heterogeneous catalysis; oxygen reduction27201742#N/ATRUE
4379
anie.20170240210.1002/anie.201702402FALSEhttps://doi.org/10.1002/anie.201702402Fu, GCAngew. Chem.-Int. Edit.Vicinal stereocenters are found in many natural and unnatural compounds. Although metal-catalyzed cross-coupling reactions of unactivated Alkyl electrophiles are emerging as a powerful tool in organic synthesis, there have been virtually no reports of processes that generate, much less control, vicinal stereocenters. In this investigation, we establish that a chiral nickel catalyst can mediate doubly stereoconvergent Alkyl-Alkyl cross-coupling, specifically, reactions of a racemic pyrrolidine-derived nuCleophile with cyClic Alkyl halides (as mixtures of stereoisomers) to produce vicinal stereocenters with very good stereoselectivity.Control of Vicinal Stereocenters through Nickel-Catalyzed Alkyl-Alkyl Cross-CouplingAlkylation; asymmetric synthesis; cross-coupling; nickel; zinc32201724#N/ATRUE
4380
anie.20170164210.1002/anie.201701642FALSEhttps://doi.org/10.1002/anie.201701642Takanabe, KAngew. Chem.-Int. Edit.The development of cost-effective and active water-splitting electrocatalysts that work at mild pH is an essential step towards the realization of sustainable energy and material circulation in our society. Its success requires a drastic improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. A simple electrochemical protocol has been developed to activate Ni electrodes, by which a stable NiOOH phase was formed, which could weakly bind to alkali-metal cations. The electrochemically activated (ECA) Ni electrode reached a current of 10 mA at <1.40V vs. the reversible hydrogen electrode (RHE) at practical operation temperatures (> 75 degrees C) and a mild pH of ca. 10 with excellent stability (> 24 h), greatly surpassing that of the state-of-the-art NiFeOx electrodes under analogous conditions. Water electrolysis was demonstrated with ECA-Ni and NiMo, which required an iR-free overall voltage of only 1.44 V to reach 10 mA cm(geo)(-2).Boosting the Performance of the Nickel Anode in the Oxygen Evolution Reaction by Simple Electrochemical Activationelectrochemistry; energy conversion; heterogeneous catalysis; oxygen evolution; water splitting29201747#N/ATRUE
4381
anie.20161010810.1002/anie.201610108FALSEhttps://doi.org/10.1002/anie.201610108Wang, WAngew. Chem.-Int. Edit.A simple Carbonylation reaction of Aryl halides, Aryl triflates, and Vinyl bromides under synergistic nickel- and organic-dye-mediated photoredox catalysis is reported. Distinct from widely used palladium-catalyzed Carbonylation processes, this reaction proceeds by a two-step mechanistic sequence involving initial insitu generation of the diethoxymethyl radical from diethoxyacetic acid by a 4CzIPN-mediated photoredox reaction. The Carbonyl-radical equivalent then undergoes nickel-catalyzed substitution reactions with Aryl halides and triflates and Vinyl bromides to form the corresponding aldehyde products. Significantly, besides Aryl bromides, less reactive Aryl chlorides and triflates and Vinyl halides serve as effective substrates for this process. Since the mild conditions involved in this reaction tolerate a plethora of functional groups, the process can be applied to the efficient preparation of diverse aromatic aldehydes.Visible-Light-Promoted Nickel- and Organic-Dye-Cocatalyzed Carbonylation Reaction of Aryl Halides and Triflates and Vinyl Bromides with Diethoxyacetic Acid as a Carbonyl Equivalentflow chemistry; Carbonylation; nickel catalysis; photoredox catalysis; synthetic methodsPhotocatalyst79201773#N/AFALSE
4382
anie.20161004710.1002/anie.201610047FALSEhttps://doi.org/10.1002/anie.201610047Ogoshi, SAngew. Chem.-Int. Edit.In the presence of Ni-0/PCy3, styrene was found to participate in oxidative cyClization with tetrafluoroethylene, thus leading to the corresponding nickelacyCle with a unique (3)--Benzyl structure. In addition, the flexibility of the coordination mode in the (3)-Benzyl moiety allowed the partially fluorinated nickelacyCle to undergo unprecedented amine-induced -fluorine elimination, thus leading to the construction of a fluorinated cyClobutyl skeleton.Nickel(0)-Mediated Transformation of Tetrafluoroethylene and Vinylarenes into Fluorinated CyClobutyl Compoundsamines; fluorine; nickel; reaction mechanisms; synthetic methodsx19201767#N/AFALSE
4383
anie.20170153310.1002/anie.201701533FALSEhttps://doi.org/10.1002/anie.201701533Huang, XQAngew. Chem.-Int. Edit.Trimetallic oxyhydroxides are one of the most effective materials for oxygen evolution reaction (OER) catalysis, a key process for water splitting. Herein, we describe a facile wet-chemical method to directly grow a series of coralloid trimetallic oxyhydroxides on arbitrary substrates such as nickel foam (NF) and carbon nanotubes (CNTs). The amount of iron in these oxyhydroxide sponges on NF and CNTs was precisely controlled, revealing that the electrocatalytic activity of the WCoFe trimetallic oxyhydroxides depends on the Fe amount in a volcano-like fashion. The optimized W0.5Co0.4Fe0.1/NF catalyst exhibited an overpotential of only 310 mV to deliver a large current density of 100 mAcm(-2) and a very low Tafel slope of 32 mVdec(-1). It also showed superior stability with negligible activity decay after use in the OER for 21 days (> 500 h). X-ray photoelectron spectroscopy revealed that the addition of Fe leads to an on average lower Co oxidation state, which contributes to the enhanced OER performance.Trimetallic Oxyhydroxide Coralloids for Efficient Oxygen Evolution Electrocatalysiscoralloid structures; electrocatalysis; oxygen evolution; trimetallic oxyhydroxides149201763#N/ATRUE
4384
anie.20170092710.1002/anie.201700927FALSEhttps://doi.org/10.1002/anie.201700927Sakai, KAngew. Chem.-Int. Edit.A nickel pyrazinedithiolate ([Ni(dcpdt)(2)](2-); dcpdt = 5,6-dicyanopyrazine-2,3-dithiolate), bearing a NiS4 core similar to the active center of [NiFe] hydrogenase, is shown to serve as an efficient molecular catalyst for the hydrogen evolution reaction (HER). This catalyst shows effectively low overpotentials for HER (330-400 mV at pH 4-6). Moreover, the turnover number of catalysis reaches 20000 over the 24h electrolysis with a high Faradaic efficiency, 92-100%. The electrochemical and DFT studies reveal that diprotonated one-electron-reduced species (i.e., [Ni-II(dcpdt)(dcpdtH(2))](-) or [Ni-II(dcpdtH)(2)](-)) forms at pH < 6.4 via ligand-based proton-coupled electron-transfer (PCET) pathways, leading to electrocatalytic HER without applying the highly negative potential required to generate low-valent nickel intermediates. This is the first example of catalysts exhibiting such behavior.A Nickel Dithiolate Water Reduction Catalyst Providing Ligand-Based Proton-Coupled Electron-Transfer Pathwaysartificial photosynthesis; hydrogen evolution; nickel complexes; proton-coupled electron transfer (PCET); pyrazine38201778#N/ATRUE
4385
anie.20161206510.1002/anie.201612065FALSEhttps://doi.org/10.1002/anie.201612065Shaik, SAngew. Chem.-Int. Edit.QM/MM calculations reveal that the nickel pincer complex in lactate racemase functions as a reversible single-center electrode that accepts and donates back an electron. In this way, it catalyzes the isomerization process D-lactate(->)L-lactate through successive proton-coupled electron-transfer steps.The Nickel-Pincer Complex in Lactate Racemase Is an Electron Relay and Sink that acts through Proton-Coupled Electron Transferenzyme mechanisms; lactate racemase; metalloenzymes; pincer complexes; QM/MM calculations13201738#N/ATRUE
4386
anie.20161186310.1002/anie.201611863FALSEhttps://doi.org/10.1002/anie.201611863Sun, LCHollow Iron-Vanadium Composite Spheres: A Highly Efficient Iron-Based Water Oxidation Electrocatalyst without the Need for Nickel or Cobalt2017#N/ATRUE
4387
anie.20160948010.1002/anie.201609480FALSEhttps://doi.org/10.1002/anie.201609480Schoenebeck, FAngew. Chem.-Int. Edit.Reported herein is the one-pot synthesis of trifluoromethylated amines at room temperature using the bench-stable (Me4N)SCF3 reagent and AgF. The method is rapid, operationally simple and highly selective. It proceeds via a formal umpolung reaction of the SCF3 with the amine, giving quantitative formation of thiocarbamoyl fluoride intermediates within minutes that can readily be transformed to N-CF3. The mildness and high functional group tolerance render the method highly attractive for the late-stage introduction of trifluoromethyl groups on amines, as demonstrated herein for a range of pharmaceutically relevant drug molecules.Efficient Synthesis of Trifluoromethyl Amines through a Formal Umpolung Strategy from the Bench-Stable Precursor (Me4N)SCF3x45201764#N/AFALSE
4388
anie.20160947710.1002/anie.201609477FALSEhttps://doi.org/10.1002/anie.201609477Chaudret, BAngew. Chem.-Int. Edit.The use of magnetic nanopartiCles to convert electromagnetic energy into heat is known to be a key strategy for numerous biomedical applications but is also an approach of growing interest in the field of catalysis. The heating efficiency of magnetic nanopartiCles is limited by the poor magnetic properties of most of them. Here we show that the new generation of iron carbide nanopartiCles of controlled size and with over 80% crystalline Fe2.2C leads to exceptional heating properties, which are much better than the heating properties of currently available nanopartiCles. Associated to catalytic metals (Ni, Ru), iron carbide nanopartiCles submitted to magnetic excitation very efficiently catalyze CO2 hydrogenation in a dedicated continuous-flow reactor. Hence, we demonstrate that the concept of magnetically induced heterogeneous catalysis can be successfully applied to methanation of CO2 and represents an approach of strategic interest in the context of intermittent energy storage and CO2 recovery.Magnetically Induced Continuous CO2 Hydrogenation Using Composite Iron Carbide NanopartiCles of Exceptionally High Heating Powerenergy storage; heterogeneous catalysis; iron carbide; magnetic properties; nanopartiClesx64201631#N/AFALSE
4389
anie.20160889910.1002/anie.201608899FALSEhttps://doi.org/10.1002/anie.201608899Sun, XPEnergy-Saving Electrolytic Hydrogen Generation: Ni2P Nanoarray as a High-Performance Non-Noble-Metal Electrocatalystx2017#N/AFALSE
4390
anie.20161176710.1002/anie.201611767FALSEhttps://doi.org/10.1002/anie.201611767Li, GRAngew. Chem.-Int. Edit.TiO2 Co nanotubes decorated with nanodots (TiO2 NDs/Co NSNTs-CFs) are reported as high-performance earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. TiO2 NDs/Co NSNTs can promote water adsorption and optimize the free energy of hydrogen adsorption. More importantly, the absorbed water can be easily activated in the presence of the TiO2-Co hybrid structure. These advantages will significantly promote HER. TiO2 NDs/Co NSNTs-CFs as electrocatalysts show a high catalytic performance towards HER in alkaline solution. This study will open up a new avenue for designing and fabricating low-cost high-performance HER catalysts.Efficient Hydrogen Evolution Electrocatalysis Using Cobalt Nanotubes Decorated with Titanium Dioxide Nanodotselectrocatalysts; hydrogen evolution reaction; nanosheets; nanotubes; renewable energies210201742#N/ATRUE
4391
anie.20161108510.1002/anie.201611085FALSEKato, MMethanol-Triggered Vapochromism Coupled with Solid-State Spin Switching in a Nickel(II)-Quinonoid Complex2017#N/ATRUE
4392
anie.20160761110.1002/anie.201607611FALSEhttps://doi.org/10.1002/anie.201607611Ray, KAngew. Chem.-Int. Edit.The strikingly different reactivity of a series of homo-and heterodinuClear [(MIII)(mu-O)(2)(M-III)'](2+) (M = Ni; M'= Fe, Co, Ni and M = M'= Co) complexes with beta-diketiminate ligands in electrophilic and nuCleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(M-III)(mu-O)(2)(M-III)'](2+) core. In particular, the unprecedented nuCleophilic reactivity of the symmetric [Ni-III(mu-O)(2)Ni-III](2+) complex and the decay of the asymmetric [Ni-III(mu-O)(2)Co-III](2+) core through aromatic hydroxylation reactions represent a new domain for high-valent bis(mu-oxido) dimetal reactivity.A New Domain of Reactivity for High-Valent DinuClear [M(mu-O)(2)M'] Complexes in Oxidation Reactionsdioxygen Activation; heterobimetallic complex; metal-oxo complexes; NIH shift; nuCleophilic oxidantx13201732#N/AFALSE
4393
anie.20161106910.1002/anie.201611069FALSEhttps://doi.org/10.1002/anie.201611069Driess, MAngew. Chem.-Int. Edit.To understand the molecular details of O-2-tolerant hydrogen cyCling by a soluble NAD(+)-reducing [NiFe] hydrogenase, we herein present the first bioinspired heterobimetallic S-oxygenated [NiFe] complex as a structural and vibrational spectroscopic model for the oxygen-inhibited [NiFe] active site. This compound and its non-S-oxygenated congener were fully characterized, and their electronic structures were elucidated in a combined experimental and theoretical study with emphasis on the bridging sulfenato moiety. Based on the vibrational spectroscopic properties of these complexes, we also propose novel strategies for exploring S-oxygenated intermediates in hydrogenases and similar enzymes.An S-Oxygenated [NiFe] Complex Modelling Sulfenate Intermediates of an O-2-Tolerant Hydrogenaseenzyme models; IR spectroscopy; [NiFe]hydrogenases; resonance Raman spectroscopy; spectroscopic models14201738#N/ATRUE
4394
anie.20160724310.1002/anie.201607243FALSEhttps://doi.org/10.1002/anie.201607243Schafer, LLAngew. Chem.-Int. Edit.Amidate-supported two-and three-coordinate Ni-I complexes were synthesized by reduction of the corresponding Ni-II precursors. A dramatic change in binding mode is observed upon reduction from Ni-II to Ni-I. The Ni-I derivatives inClude an unprecedented NiI bis(C-H) agostic complex and a two-coordinate Ni-I complex.Oxidation State Dependent Coordination Modes: Accessing an Amidate-Supported Nickel( I) delta-bis(C-H) Agostic Complexagostic complexes; AIM calculations; amidate; nickel; redox statesx18201669#N/AFALSE
4395
anie.20161099010.1002/anie.201610990FALSEhttps://doi.org/10.1002/anie.201610990Zhu, SLEnantioselective NiH/Pmrox-Catalyzed 1,2-Reduction of alpha,beta-Unsaturated Ketones2017#N/ATRUE
4396
anie.20161078410.1002/anie.201610784FALSEhttps://doi.org/10.1002/anie.201610784Murahashi, TAngew. Chem.-Int. Edit.A unique metal addition to the edge of a triangular palladium sandwich Cluster is reported. While the edge coordination sites of a parallel sandwich complex are narrow because of two sterically encumbering pi-ligands, association of an additional metal atom to a metal sheet gives a wider coordination site. It was proved that the additional metal atom plays a crucial role in binding of cyClopentadienyl by a Pd-3 sheet sandwich complex.Substrate Binding by a Parallel Metal Sheet Sandwich Complex: A Unique Role of an Additional Metal Atombenzene; Cluster compounds; coordination chemistry; palladium; sandwich complexes6201763#N/ATRUE
4397
anie.20161077610.1002/anie.201610776FALSEhttps://doi.org/10.1002/anie.201610776Sun, XPAngew. Chem.-Int. Edit.The topotactic conversion of cobalt phosphide nanoarray on Ti mesh into a cobalt phosphate nanoarray (Co-Pi NA) via oxidative polarization in phosphate-buffered water is presented. As a 3D oxygen evolution reaction (OER) catalyst electrode at neutral pH, the resulting Co-Pi NA/Ti shows exceptionally high catalytic activity and demands an overpotential of only 450 mV to drive a geometrical catalytic current density of 10 mA cm(-2). Notably, this catalyst also shows superior long-term electrochemical stability. The excellent catalytic activity can be attributed to that such 3D nanoarray configuration allows for the exposure of more active sites and the easier diffusion of electrolytes and oxygen.High-Performance Electrolytic Oxygen Evolution in Neutral Media Catalyzed by a Cobalt Phosphate Nanoarray264201765#N/ATRUE
4398
anie.20160651310.1002/anie.201606513https://doi.org/10.1002/anie.201606513Nishibayashi, YAngew. Chem.-Int. Edit.A combination of nickel and photoredox catalysts promoted novel cross-coupling reactions of Aryl halides with 4-Alkyl-1,4-dihydropyridines. 4-Alkyl-1,4-dihydropyridines act as formal nuCleophilic Alkylation reagents through a photoredox-catalyzed carbon-carbon (C-C) bond-Cleavage process. The present strategy provides an alternative to Classical carbon-centered nuCleophiles, such as organometallic reagents.Nickel- and Photoredox-Catalyzed Cross-Coupling Reactions of Aryl Halides with 4-Alkyl-1,4-dihydropyridines as Formal NuCleophilic Alkylation ReagentsC-C Cleavage; cross-coupling; dihydropyridines; nickel catalysts; photoredox catalystsPhotocatalyst101201683#N/AFALSE
4399
anie.20160645810.1002/anie.201606458https://doi.org/10.1002/anie.201606458Zhang, XGAngew. Chem.-Int. Edit.A nickel-catalyzed three-component reaction for the synthesis of difluoroAlkylated compounds through tandem difluoroAlkylation-Arylation of enamides has been developed. The reaction tolerates a variety of Arylboronic acids and widely available difluoroAlkyl bromides, and even the relatively inert substrate chlorodifluoroacetate. The significant advantages of this protocol are the low-cost nickel catalyst, synthetic convenience, excellent functional-group compatibility and high reaction efficiency.Tandem DifluoroAlkylation-Arylation of Enamides Catalyzed by Nickelboron; cross-coupling; fluorine; nickel; synthetic methodsx151201637#N/AFALSE
4400
anie.20160631310.1002/anie.201606313FALSEhttps://doi.org/10.1002/anie.201606313Xie, YAngew. Chem.-Int. Edit.The direct urea fuel cell (DUFC) is an important but challenging renewable energy production technology, it offers great promise for energy-sustainable developments and mitigating water contamination. However, DUFCs still suffer from the sluggish kinetics of the urea oxidation reaction (UOR) owing to a 6 e(-) transfer process, which poses a severe hindrance to their practical use. Herein, taking beta-Ni(OH)(2) nanosheets as the proof-of-concept study, we demonstrated a surface-chemistry strategy to achieve metallic Ni(OH)(2) nanosheets by engineering their electronic structure, representing a first metallic configuration of transition-metal hydroxides. Surface sulfur incorporation successfully brings synergetic effects of more exposed active sites, good wetting behavior, and effective electron transport, giving rise to greatly enhanced performance for UOR. Metallic nanosheets exhibited a much higher current density, smaller onset potential and stronger durability.Metallic Nickel Hydroxide Nanosheets Give Superior Electrocatalytic Oxidation of Urea for Fuel Cellsfuel cells; metallic transition-metal hydroxide; nanosheets; sulfur; urea oxidation reactionx199201633#N/AFALSE
4401
anie.20161051510.1002/anie.201610515FALSEhttps://doi.org/10.1002/anie.201610515Kitagawa, HAngew. Chem.-Int. Edit.The fabrication of so-called ghost-leg sheets and their electronic properties is reported. This unique sheet structure is composed of one-dimensional mixed-valence nickel chains, which are linked with one another by bis(aza-macrocyCle) ligands. They are also topologically unique Ni-II/Ni-III mixed-valence complexes, as confirmed by X-ray and optical measurements. Moreover, their magnetic susceptibilities indicated two-dimensional antiferromagnetic behavior following the Fisher 1D chain model with interchain interactions, where spins on Ni-III sites mutually interact antiferromagnetically in the sheets.Mixed-Valence Nickel Bis(azamacrocyCle) Compounds with Ghost-Leg-type Sheetslayered compounds; magnetic properties; mixed-valence compounds; nickel; supramolecular chemistry5201757#N/ATRUE
4402
anie.20160629010.1002/anie.201606290FALSEhttps://doi.org/10.1002/anie.201606290Huang, XQAngew. Chem.-Int. Edit.The design of high-performance electrocatalysts for the alkaline hydrogen evolution reaction (HER) is highly desirable for the development of alkaline water electrolysis. Phase- and interface-engineered platinum-nickel nanowires (Pt-Ni NWs) are highly efficient electrocatalysts for alkaline HER. The phase and interface engineering is achieved by simply annealing the pristine Pt-Ni NWs under a controlled atmosphere. Impressively, the newly generated nanomaterials exhibit superior activity for the alkaline HER, outperforming the pristine Pt-Ni NWs and commercial Pt/C, and also represent the best alkaline HER catalysts to date. The enhanced HER activities are attributed to the superior phase and interface structures in the engineered Pt-Ni NWs.Phase and Interface Engineering of Platinum-Nickel Nanowires for Efficient Electrochemical Hydrogen Evolutionhydrogen evolution reaction; nanowires; nickel; phase and interface control; platinumx207201631#N/AFALSE
4403
anie.20160554810.1002/anie.201605548https://doi.org/10.1002/anie.201605548Ley, SVAngew. Chem.-Int. Edit.We report herein a new method for the photoredox Activation of boronic esters. Using these reagents, an efficient and high-throughput continuous flow process was developed to perform a dual iridium- and nickel-catalyzed C(sp(2))-C(sp(3)) coupling by circumventing solubility issues associated with potassium trifluorB(OH)2rate salts. Formation of an adduct with a pyridine-derived Lewis base was found to be essential for the photoredox Activation of the boronic esters. Based on these results we were able to develop a further simplified visible light mediated C(sp(2))-C(sp(3)) coupling method using boronic esters and cyano heteroarenes under flow conditions.Visible Light Activation of Boronic Esters Enables Efficient Photoredox C(sp(2))-C(sp(3)) Cross-Couplings in Flowboronic esters; cross-coupling; flow chemistry; photoredox catalysis; synthetic methodsPhotocatalyst88201651#N/AFALSE
4404
anie.20160516210.1002/anie.201605162FALSEhttps://doi.org/10.1002/anie.201605162Martin, RAngew. Chem.-Int. Edit.A user-friendly, nickel-catalyzed reductive amidation of unactivated primary, secondary, and tertiary Alkyl bromides with isocyanates is described. This catalytic strategy offers an efficient synthesis of a wide range of aliphatic amides under mild conditions and with an excellent chemoselectivity profile while avoiding the use of stoichiometric and sensitive organometallic reagents.Nickel-Catalyzed Reductive Amidation of Unactivated Alkyl Bromidescross-coupling; nickel; reductive coupling; synthetic methodsx37201670#N/AFALSE
4405
anie.20160442910.1002/anie.201604429https://doi.org/10.1002/anie.201604429Johannes, JWAngew. Chem.-Int. Edit.A visible-light-promoted iridium photoredox and nickel dual-catalyzed cross-coupling procedure for the formation C-N bonds has been developed. With this method, various Aryl amines were chemoselectively cross-coupled with electronically and sterically diverse Aryl iodides and bromides to forge the corresponding C-N bonds, which are of high interest to the pharmaceutical industries. Aryl iodides were found to be a more efficient electrophilic coupling partner. The coupling reactions were carried out at room temperature without the rigorous exClusion of molecular oxygen, thus making this newly developed Ir-photoredox/Ni dual-catalyzed procedure very mild and operationally simple.Highly Chemoselective Iridium Photoredox and Nickel Catalysis for the Cross-Coupling of Primary Aryl Amines with Aryl Halidescross-coupling; nickel catalysis; photocatalysis; radical reactions; synthetic methodsPhotocatalyst83201652#N/AFALSE
4406
anie.20160979210.1002/anie.201609792FALSEhttps://doi.org/10.1002/anie.201609792Magdesieva, TVIndividual ((f,t)A)- and (C-f,C-t)-Fullerene-Based Nickel(II) Glycinates: Protected Chiral Amino Acids Directly Linked to a Chiral pi-Electron System2017#N/ATRUE
4407
anie.20160437210.1002/anie.201604372FALSEhttps://doi.org/10.1002/anie.201604372Fan, HJAngew. Chem.-Int. Edit.Electrochemical splitting of water to produce hydrogen and oxygen is an important process for many energy storage and conversion devices. Developing efficient, durable, low-cost, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) is of great urgency. To achieve the rapid synthesis of transition-metal nitride nanostructures and improve their electrocatalytic performance, a new strategy has been developed to convert cobalt oxide precursors into cobalt nitride nanowires through N-2 radio frequency plasma treatment. This method requires significantly shorter reaction times (about 1 min) at room temperature compared to conventional high-temperature NH3 annealing which requires a few hours. The plasma treatment significantly enhances the OER activity, as evidenced by a low overpotential of 290 mV to reach a current density of 10 mA cm(-2), a small Tafel slope, and long-term durability in an alkaline electrolyte.Rapid Synthesis of Cobalt Nitride Nanowires: Highly Efficient and Low-Cost Catalysts for Oxygen Evolutioncobalt nitride; electrocatalysis; nanostructures; oxygen evolution; water splittingx480201630#N/AFALSE
4408
anie.20160435510.1002/anie.201604355https://doi.org/10.1002/anie.201604355Reisner, EAngew. Chem.-Int. Edit.Carbon quantum dots (CQDs) are new-generation light absorbers for photocatalytic H-2 evolution in aqueous solution, but the performance of CQD-molecular catalyst systems is currently limited by the decomposition of the molecular component. Clean oxidation of the electron donor by donor recyCling prevents the formation of destructive radical species and non-innocent oxidation products. This approach allowed a CQD-molecular nickel bis(diphosphine) photocatalyst system to reach a benchmark lifetime of more than 5 days and a record turnover number of 1094 +/- 61 mol(H2)(mol(Ni))(-1) for a defined synthetic molecular nickel catalyst in purely aqueous solution under AM1.5G solar irradiation.Clean Donor Oxidation Enhances the H-2 Evolution Activity of a Carbon Quantum Dot-Molecular Catalyst Photosystemcarbon quantum dots; hydrogen evolution; molecular catalysis; photocatalysis; photosensitizersPhotocatalyst59201644#N/AFALSE
4409
anie.20160952610.1002/anie.201609526FALSEhttps://doi.org/10.1002/anie.201609526Limberg, CAngew. Chem.-Int. Edit.In metal-mediated O-2 Activation, nickel(II) compounds hardly play a role, but recently it has been shown that enzymes can use nickel(II) for O-2 Activation. Now a low-coordinate Lewis acidic nickel(II) complex has been synthesized that reacts with O-2 to give a nickel(II) organoperoxide, as proposed for the enzymatic system. Its formation was studied further by UV/Vis absorption spectroscopy, leading to the observation of a short-lived intermediate that proved to be reactive in both oxygen atom transfer and hydrogen abstraction reactions, while the peroxide efficiently transfers O atoms. Both for the enzyme and for the functional model, the key to O-2 Activation is proposed to represent a concomitant electron shift from the substrate/co-ligand.Activation of Dioxygen at a Lewis Acidic Nickel(II) Complex: Characterization of a Metastable Organoperoxide Complexdioxygen Activation; nickel; oxidation; oxygenases; peroxide23201752#N/ATRUE
4410
anie.20160402110.1002/anie.201604021FALSEhttps://doi.org/10.1002/anie.201604021Lee, STAngew. Chem.-Int. Edit.Ammonia-borane (AB) is an excellent material for chemical storage of hydrogen. However, the practical utilization of AB for production of hydrogen is hindered by the need of expensive noble metal-based catalysts. Here, we report CuxCo1-xO nanopartiCles (NPs) facilely deposited on graphene oxide (GO) as a low-cost and high-performance catalyst for the hydrolysis of AB. This hybrid catalyst exhibits an initial total turnover frequency (TOF) value of 70.0 (H-2) mol/(Cat-metal) mol.min, which is the highest TOF ever reported for noble metal-free catalysts, and a good stability keeping 94 % activity after 5 cyCles. Synchrotron radiation-based X-ray absorption spectroscopy (XAS) investigations suggested that the high catalytic performance could be attributed to the interfacial interaction between CuxCo1-xO NPs and GO. Moreover, the catalytic hydrolysis mechanism was studied by in situ XAS experiments for the first time, which reveal a significant water adsorption on the catalyst and Clearly confirm the interaction between AB and the catalyst during hydrolysis.CuxCo1-xO NanopartiCles on Graphene Oxide as A Synergistic Catalyst for High-Efficiency Hydrolysis of Ammonia-Boranegraphene oxide; heterogeneous catalysis; hydrogen storage; hydrolysis mechanism; nanopartiClesx126201628#N/AFALSE
4411
anie.20160951510.1002/anie.201609515FALSEhttps://doi.org/10.1002/anie.201609515Ozawa, FAngew. Chem.-Int. Edit.The Pt-0 complex [Pt(PPh3)(Eind(2)-BPEP)] with a pyridine-based PNP-pincer-type phosphaalkene ligand (Eind(2)-BPEP) has a highly planar geometry around Pt with Sigma(Pt)=358.6 degrees. This coordination geometry is very uncommon for formal d(10) complexes, and the Pd and Ni homologues with the same ligands adopt distorted tetrahedral geometries. DFT calculations reveal that both the Pt and Pd complexes are M-0 species with nearly ten valence electrons on the metals whereas their atomic orbital occupancies are evidently different from one another. The Pt complex has a higher occupancy of the atomic 6s orbital because of strong s-d hybridization due to relativistic effects, thereby adopting a highly planar geometry reflecting the shape and orientation of the partially unoccupied dx2-y2 orbital.A Square-Planar Complex of Platinum(0)phosphaalkene ligands; pincer complexes; platinum; relativistic effects; square-planar complexes11201621#N/ATRUE
4412
anie.20160948910.1002/anie.201609489FALSEhttps://doi.org/10.1002/anie.201609489Dong, GBAngew. Chem.-Int. Edit.Herein an intramolecular nickel-catalyzed (4+2) coupling between cyClobutanones and allenes, by C-C Cleavage, is reported. The reaction provides a distinct approach for accessing [3.2.2] bicyClic scaffolds which are challenging to prepare through conventional approaches. The reaction is efficient, chemoselective, and pH/redox neutral. Room temperature conditions and low catalyst loadings can be adopted. Excellent enantioselectivity is also achieved.Nickel-Catalyzed Chemo- and Enantioselective Coupling between CyClobutanones and Allenes: Rapid Synthesis of [3.2.2] BicyClesallenes; C-C Activation; cyCloaddition; nickel; small ring systems35201664#N/ATRUE
4413
anie.20160795910.1002/anie.201607959FALSEhttps://doi.org/10.1002/anie.201607959Gong, HGAngew. Chem.-Int. Edit.This work emphasizes the synthesis of substituted Vinyl arenes by reductive coupling of Aryl halides with Vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of Aryl halides, inCluding Hets, and Vinyl bromides were employed to yielding products in moderate to excellent yields with high functional- group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp(2))-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.Preparation of Vinyl Arenes by Nickel-Catalyzed Reductive Coupling of Aryl Halides with Vinyl Bromidesalkenes; arenes; cross-coupling; nickel; reaction mechanisms57201659#N/ATRUE
4414
anie.20160322310.1002/anie.201603223FALSEhttps://doi.org/10.1002/anie.201603223Yamauchi, YAngew. Chem.-Int. Edit.Deposition of Ni-based cyanide bridged coordination polymer (NiCNNi) flakes onto the surfaces of graphene oxide (GO) sheets, which allows precise control of the resulting lamellar nanoarchitecture by in situ crystallization, is reported. GO sheets are utilized as nuCleation sites that promote the optimized crystal growth of NiCNNi flakes. The NiCNNi-coated GO sheets then self-assemble and are stabilized as ordered lamellar nanomaterials. Regulated thermal treatment under nitrogen results in a Ni3C-GO composite with a similar morphology to the starting material, and the Ni3C-GO composite exhibits outstanding electrocatalytic activity and excellent durability for the oxygen reduction reaction.Self-Construction from 2D to 3D: One-Pot Layer-by-Layer Assembly of Graphene Oxide Sheets Held Together by Coordination Polymerscoordination polymers; hybrid materials; lamellar structures; layer-by-layer structures; metal carbidesx76201632#N/AFALSE
4415
anie.20160302210.1002/anie.201603022FALSEhttps://doi.org/10.1002/anie.201603022Huang, XQAngew. Chem.-Int. Edit.The development of superior non-platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen-reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu-based nanopartiCles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol-oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni.Ordered PdCu-Based NanopartiCles as Bifunctional Oxygen-Reduction and Ethanol-Oxidation Electrocatalystscopper; intermetallic phases; nanopartiCles; oxygen-reduction reaction; palladiumx193201636#N/AFALSE
4416
anie.20160280210.1002/anie.201602802FALSEhttps://doi.org/10.1002/anie.201602802He, JAngew. Chem.-Int. Edit.To address the urgent need for Clean and sustainable energy, the rapid development of hydrogen-based technologies has started to revolutionize the use of earth-abundant noble-metal-free catalysts for the hydrogen evolution reaction (HER). Like the active sites of hydrogenases, the cation sites of pyrite-type transition-metal dichalcogenides have been suggested to be active in the HER. Herein, we synthesized electrodes based on a Se-enriched NiSe2 nanosheet array and explored the relationship between the anion sites and the improved hydrogen evolution activity through theoretical and experimental studies. The free energy for atomic hydrogen adsorption is much lower on the Se sites (0.13 eV) than on the Ni sites (0.87 eV). Notably, this electrode benefits from remarkable kinetic properties, with a small overpotential of 117 mV at 10 mA cm(-2), a low Tafel slope of 32 mV per decade, and excellent stability. Control experiments showed that the efficient conversion of H+ into H-2 is due to the presence of an excess of selenium in the NiSe2 nanosheet surface.Selenium-Enriched Nickel Selenide Nanosheets as a Robust Electrocatalyst for Hydrogen Generationchalcogenides; electrocatalysis; hydrogen evolution reaction; nickel; seleniumx198201654#N/AFALSE
4417
anie.20160778910.1002/anie.201607789FALSEhttps://doi.org/10.1002/anie.201607789Rissanen, KAngew. Chem.-Int. Edit.Two [NI+N] halogen-bonded dimeric capsules using tetrakis(3-pyridyl)ethylene cavitands with different lower rim Alkyl chains are synthesized and analyzed in solution and the gas phase. These first examples of symmetrical dimeric capsules making use of the iodonium ion (I+) as the main connecting module are characterized by (HNMR)-H-1 spectroscopy, diffusion ordered NMR spectroscopy (DOSY), electrospray ionization mass spectrometry (ESI-MS), and ion mobility-mass spectrometry (TW-IMS) experiments. The synthesis and effective halogen-bonded dimerization proceeds through analogous dimeric capsules with [NAg+N] binding motifs as the intermediates as evidenced by the X-ray structures of (CH2Cl2)(2)@[3a(2)Ag(4)(H2O)(2)OTs4] and (CH2Cl2)(2)@[3a(2)Ag(4)(H2O)(4)OTs4], two structurally different capsules.[NI+N] Halogen-Bonded Dimeric Capsules from Tetrakis(3-pyridyl)ethylene Cavitandscavitands; dimeric capsules; halogen bonds; halonium ions; mass spectrometry56201630#N/ATRUE
4418
anie.20160254110.1002/anie.201602541FALSEhttps://doi.org/10.1002/anie.201602541Yang, JLAngew. Chem.-Int. Edit.Metal-nanopartiCle-catalyzed cutting is a promising way to produce graphene nanostructures with smooth and well-aligned edges. Using a multiscale simulation approach, we unambiguously identified a Pac-Man cutting mechanism, characterized by the metal nanopartiCle biting off edge carbon atoms through a synergetic effect of multiple metal atoms. By comparing the reaction rates at different types of edge sites, we found that etching of an entire edge carbon row could be triggered by a single zigzag-site etching event, which explains the puzzling linear dependence of the overall carbon-atom etching rate on the nanopartiCle surface area observed experimentally. With incorporation of the nanopartiCle size effect, the mechanisms revealed herein open a new avenue to improve controllability in graphene cutting.The NanopartiCle Size Effect in Graphene Cutting: A Pac-Man Mechanismdensity functional calculations; graphene; multiscale simulations; nanopartiCles; nickelx16201635#N/AFALSE
4419
anie.20160248910.1002/anie.201602489FALSEhttps://doi.org/10.1002/anie.201602489Rodriguez, JAAngew. Chem.-Int. Edit.Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanopartiCles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal-support interactions activate Ni for the dissociation of methane. The results of density-functional calculations show a drop in the effective barrier for methane Activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2-x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a Clean and efficient way.Dry Reforming of Methane on a Highly-Active Ni-CeO2 Catalyst: Effects of Metal-Support Interactions on C-H Bond Breakingceria; density functional theory; methane dissociation; nickel; X-ray photoelectron spectroscopyx137201634#N/AFALSE
4420
anie.20160746010.1002/anie.201607460FALSEhttps://doi.org/10.1002/anie.201607460O'Hagan, MAngew. Chem.-Int. Edit.. The The fastest synthetic molecular catalysts for H-2 production and oxidation emulate components of the active site of hydrogenases. The critical role of controlled structural dynamics is recognized for many enzymes, inCluding hydrogenases, but is largely neglected in designing synthetic catalysts. Our results demonstrate the impact of controlling structural dynamics on H-2 production rates for [Ni((P2N2C6H4R)-N-Ph)(2)](2+) catalysts (R=n-hexyl, n-decyl, n-tetradecyl, n-octadecyl, phenyl, or cyClohexyl) turnover frequencies correlate inversely with the rates of chair-boat ring inversion of the ligand, since this dynamic process governs protonation at either catalytically productive or non-productive sites. These results demonstrate that the dynamic processes involved in proton delivery can be controlled through modification of the outer coordination sphere, in a manner similar to the role of the protein architecture in many enzymes. As a design parameter, controlling structural dynamics can increase H-2 production rates by three orders of magnitude with a minimal increase in overpotential.Controlling Proton Delivery through Catalyst Structural Dynamicsartificial enzymes; electrocatalysis; homogeneous catalysis; hydrogen production; structural dynamics33201629#N/ATRUE
4421
anie.20160221510.1002/anie.201602215FALSEhttps://doi.org/10.1002/anie.201602215Corma, AAngew. Chem.-Int. Edit.A new family of stable layered organic-inorganic materials has been prepared, in one-step solvothermal process. They are based on an ordered nickel Cluster-type nanoribbons separated from each other by specific Alkyl (heptyl- or dodecyl-) Arylic mono-Carbonylate moieties acting as molecular spacers, perpendicular to the 1D inorganic chains. These organic spacers contain hydrocarbon tails with different length which control the separation level between inorganic 1D sub-units, inhibiting the 3D growth of conventional DUT-8-type metal-organic frameworks (MOFs). The lamellar nature of the materials formed was studied and confirmed by different characterization techniques, showing the structural location of individual organic and inorganic building units. They have been successfully used as a long-lasting biodegradable and water-proof materials for controlled release of chemicals, such as pheromones for sustainable treatment of insect plagues.Single-Layered Hybrid Materials Based on 1D Associated Metalorganic Nanoribbons for Controlled Release of Pheromonescontrolled release; layered structures; metalorganic nanosheets; organic-inorganic materials; pheromonesx9201636#N/AFALSE
4422
anie.20160697910.1002/anie.201606979FALSEhttps://doi.org/10.1002/anie.201606979Driess, MAngew. Chem.-Int. Edit.The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C](2)B10H10 (termed SiCCSi) is reported (NHSi=N-heterocyClic silylene; L=PhC(NtBu)(2)). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)(2) complexes. The CO stretching vibration modes of the latter indicate that the Si-II atoms in the SiCCSi ligand are even stronger sigma donors than the P-III atoms in phosphines and C-II atoms in N-heterocyClic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5mol% loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1-10mol%).A Bis(silylene)-Substituted ortho-Carborane as a Superior Ligand in the Nickel-Catalyzed Amination of Areneshomogeneous catalysis; N-heterocyClic silylenes; ligand design; nickel; o-carboranes82201681#N/ATRUE
4423
anie.20160209710.1002/anie.201602097FALSEhttps://doi.org/10.1002/anie.201602097Bao, XHAngew. Chem.-Int. Edit.The design of catalysts that are both highly active and stable is always challenging. Herein, we report that the incorporation of single metal active sites attached to the nitrogen atoms in the basal plane of graphene leads to composite materials with superior activity and stability when used as counter electrodes in dye-sensitized solar cells (DSSCs). A series of composite materials based on different metals (Mn, Fe, Co, Ni, and Cu) were synthesized and characterized. Electrochemical measurements revealed that CoN4/GN is a highly active and stable counter electrode for the interconversion of the redox couple I-/I-3(-). DFT calculations revealed that the superior properties of CoN4/GN are due to the appropriate adsorption energy of iodine on the confined Co sites, leading to a good balance between adsorption and desorption processes. Its superior electrochemical performance was further confirmed by fabricating DSSCs with CoN4/GN electrodes, which displayed a better power conversion efficiency than the Pt counterpart.A Graphene Composite Material with Single Cobalt Active Sites: A Highly Efficient Counter Electrode for Dye-Sensitized Solar Cellscobalt; composite materials; counter electrode; dye-sensitized solar cells; graphenex154201635#N/AFALSE
4424
anie.20160199110.1002/anie.201601991FALSEhttps://doi.org/10.1002/anie.201601991Stoltz, BMAngew. Chem.-Int. Edit.An efficient and exceptionally mild intramolecular nickel-catalyzed carbon-oxygen bond-forming reaction between Vinyl halides and primary, secondary, and tertiary alcohols has been achieved. Zinc powder was found to be an essential additive for obtaining high catalyst turnover and yields. This operationally simple method allows direct access to cyClic Vinyl ethers in high yields in a single step.Nickel-Catalyzed Intramolecular C-O Bond Formation: Synthesis of CyClic Enol Ethersalcohols; cross-coupling; ethers; heterocyCles; nickelx22201643#N/AFALSE
4425
anie.20160695510.1002/anie.201606955FALSEhttps://doi.org/10.1002/anie.201606955Senanayake, CHAngew. Chem.-Int. Edit.A nickel-catalyzed Heck cyClization for the construction of quaternary stereocenters is reported. This transformation is demonstrated in the synthesis of 3,3-disubstituted oxindoles, which are prevalent motifs seen in numerous biologically active molecules. The method shows broad scope, proceeds in synthetically useful yields, and provides a rare means to construct stereochemically complex frameworks by nonprecious-metal catalysis.Construction of Quaternary Stereocenters by Nickel-Catalyzed Heck CyClization ReactionscyClization; Heck reaction; heterocyCles; homogeneous catalysis; nickel34201661#N/ATRUE
4426
anie.20160683210.1002/anie.201606832FALSEhttps://doi.org/10.1002/anie.201606832Hu, XLAngew. Chem.-Int. Edit.The first efficient and non-precious nanopartiCle catalyst for alkene hydrosilylation with commercially relevant tertiary silanes has been developed. The nickel nanopartiCle catalyst was prepared in situ from a simple nickel alkoxide precatalyst Ni((OBu)-Bu-t)(2)center dot xKCl. The catalyst exhibits high activity for anti-Markovnikov hydrosilylation of unactivated terminal alkenes and isomerizing hydrosilylation of internal alkenes. The catalyst can be applied to synthesize a single terminal Alkyl silane from a mixture of internal and terminal alkene isomers, and to remotely functionalize an internal alkene derived from a fatty acid.An Easily Accessed Nickel NanopartiCle Catalyst for Alkene Hydrosilylation with Tertiary Silaneshydrosilylation; isomerization; nanopartiCles; nickel; tertiary silanes71201655#N/ATRUE
4427
anie.20160629310.1002/anie.201606293FALSEhttps://doi.org/10.1002/anie.201606293Osuka, AAngew. Chem.-Int. Edit.Doubly and quadruply quinoline-fused porphyrins were effectively synthesized through a reaction sequence consisting of Suzuki-Miyaura coupling of beta-borylated porphyrins with 2-iodoaniline and subsequent Pictet-Spengler cyClization. These quinoline-fused porphyrins display red-shifted absorption bands and higher electron-accepting abilities. This synthetic protocol also allowed the synthesis of phenanthroline-fused porphyrin dimers, which bound either a Ni-II or Zn-II cation. The resultant metal complexes displayed further red shifted absorption spectra and molecular twists to effect an almost perpendicular arrangement of the two porphyrins.Pictet-Spengler Synthesis of Quinoline-Fused Porphyrins and Phenanthroline-Fused DiporphyrinsheterocyCles; nickel; porphyrinoids; supramolecular chemistry; zinc19201645#N/ATRUE
4428
anie.20160440610.1002/anie.201604406FALSEhttps://doi.org/10.1002/anie.201604406Liao, XBAngew. Chem.-Int. Edit.A nickel-catalyzed methylation of Aryl halides with cheap and readily available CH3I or CD (3) I is described. The reaction is applicable to a wide range of substrates and allows installation of a CD3 group under mild reaction conditions without deuterium scrambling to other carbon atoms. Initial mechanistic studies on the stoichiometric and catalytic reactions of the isolated [(dppp)Ni(C6H4-4-CO2Et)Br] [dppp= 1,3-bis(diphenylphosphanyl)propane] suggest that a Ni-0/ Ni-II catalytic cyCle is favored.Nickel-Catalyzed Methylation of Aryl Halides with Deuterated Methyl Iodidearenes; cross-coupling; deuterium; methylation; nickel41201676#N/ATRUE
4429
anie.20160404010.1002/anie.201604040FALSEhttps://doi.org/10.1002/anie.201604040Zhang, XBAngew. Chem.-Int. Edit.Developing effective ways to recyCle rusted stainless steel and to promote the sluggish oxygen evolution reaction (OER), associated with water splitting and metal-air batteries, is important for a resource-sustainable and environment-friendly society. Herein, we propose a strategy to enable rusted stainless steel plate to be used as an abundant and low-cost OER catalyst, wherein a hydrothermal combined in situ electrochemical oxidation-reduction cyCle (EORC) method is developed to mimic and expedite the corrosion process, and thus activate stainless steel into free-standing OER electrodes. Benefiting from the plentiful electrolyte-accessible Fe/(Ni) oxyhydroxides, high conductivity and mechanical stability, this electrode exhibits remarkable OER performances inCluding low overpotential, fast kinetics, and long-term durability. The slight degradation in current after long-term use can be repaired immediately in situ by an EORC.In Situ Activating Ubiquitous Rust towards Low-Cost, Efficient, Free-Standing, and Recoverable Oxygen Evolution Electrodescorrosion; electrocatalysts; iron; oxygen evolution reaction; rust128201650#N/ATRUE
4430
anie.20160388210.1002/anie.201603882FALSEhttps://doi.org/10.1002/anie.201603882Shima, SAngew. Chem.-Int. Edit.All methanogenic and methanotrophic archaea known to date contain methyl-coenzymeM reductase (MCR) that catalyzes the reversible reduction of methyl-coenzymeM to methane. This enzyme contains the nickel porphinoidF(430) as a prosthetic group and, highly conserved, a thioglycine and four methylated amino acid residues near the active site. We describe herein the presence of a novel post-translationally modified amino acid, didehydroaspartate, adjacent to the thioglycine as revealed by mass spectrometry and high-resolution X-ray crystallography. Upon chemical reduction, the didehydroaspartate residue was converted into aspartate. Didehydroaspartate was found in MCRI andII from Methanothermobacter marburgensis and in MCR of phylogenetically distantly related Methanosarcina barkeri but not in MCRI andII of Methanothermobacter wolfeii, which indicates that didehydroaspartate is dispensable but might have a role in fine-tuning the active site to increase the catalytic efficiency.Didehydroaspartate Modification in Methyl-CoenzymeM Reductase Catalyzing Methane Formationdidehydroaspartate; enzyme catalysis; methyl-coenzyme M reductase; post-translational modification27201632#N/ATRUE
4431
anie.20160119910.1002/anie.201601199FALSEhttps://doi.org/10.1002/anie.201601199Zheng, LSAngew. Chem.-Int. Edit.Monodisperse metal Clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core-shell structure of the monodisperse molecule magnet of [Gd52Ni56(IDA)(48)(OH)(154)(H2O)(38)]@SiO2 (1a@SiO2) was prepared by encapsulating one high-nuClearity lanthanide-transition-metal compound of [Gd52Ni56(IDA)(48)(OH)(154)(H2O)(38)](NO3)(18)164H(2)O (1) (IDA=iminodiacetate) into one silica nanosphere through a facile one-pot microemulsion method. 1a@SiO2 was characterized using transmission electron microscopy, N-2 adsorption-desorption isotherms, and inductively coupled plasma-atomic emission spectrometry. Magnetic investigation of 1 and 1a revealed J(1)=0.25cm(-1), J(2)=-0.060cm(-1), J(3)=-0.22cm(-1), J(4)=-8.63cm(-1), g=1.95, and zJ=-2.0x10(-3)cm(-1) for 1, and J(1)=0.26cm(-1), J(2)=-0.065cm(-1), J(3)=-0.23cm(-1), J(4)=-8.40cm(-1)g=1.99, and zJ=0.000cm(-1) for 1a@SiO2. The zJ=0 in 1a@SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres.Magnetic Properties of a Single-Molecule Lanthanide-Transition-Metal Compound Containing 52 Gadolinium and 56 Nickel Atomscore-shell nanopartiCles; lanthanide-transition-metal compounds; magnetic properties; silica; single moleculesx45201659#N/AFALSE
4432
anie.20160379810.1002/anie.201603798FALSEhttps://doi.org/10.1002/anie.201603798Sun, YJAngew. Chem.-Int. Edit.As an environmentally friendly approach to generate H-2, electrocatalytic water splitting has attracted worldwide interest. However, its broad employment has been inhibited by costly catalysts and low energy conversion efficiency, mainly due to the sluggish anodic half reaction, the O-2 evolution reaction (OER), whose product O-2 is not of significant value. Herein, we report an efficient strategy to replace OER with a thermodynamically more favorable reaction, the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandiCarbonylic acid (FDCA), catalyzed by 3D Ni2P nanopartiCle arrays on nickel foam (Ni(2)PNPA/NF). HMF is one of the primary dehydration intermediates of raw biomass and FDCA is of many industrial applications. As a bifunctional electrocatalyst, Ni(2)PNPA/NF is not only active for HMF oxidation but also competent for H-2 evolution. In fact, a two-electrode electrolyzer employing Ni2P NPA/NF for simultaneous H-2 and FDCA production required a voltage at least 200 mV smaller compared with pure water splitting to achieve the same current density, as well as exhibiting robust stability and nearly unity Faradaic efficiencies.Simultaneous H-2 Generation and Biomass Upgrading in Water by an Efficient Noble-Metal-Free Bifunctional Electrocatalystbiomass upgrading; electrocatalysis; H-2 production; nickel phosphide198201669#N/ATRUE
4433
anie.20160079910.1002/anie.201600799FALSEhttps://doi.org/10.1002/anie.201600799Qin, YAngew. Chem.-Int. Edit.Ideal heterogeneous tandem catalysts necessitate the rational design and integration of collaborative active sites. Herein, we report on the synthesis of a new tandem catalyst with multiple metal-oxide interfaces based on a tube-in-tube nanostructure using template-assisted atomic layer deposition, in which Ni nanopartiCles are supported on the outer surface of the inner Al2O3 nanotube (Ni/Al2O3 interface) and Pt nanopartiCles are attached to the inner surface of the outer TiO2 nanotube (Pt/TiO2 interface). The tandem catalyst shows remarkably high catalytic efficiency in nitrobenzene hydrogenation over Pt/TiO2 interface with hydrogen formed in situ by the decomposition of hydrazine hydrate over Ni/Al2O3 interface. This can be ascribed to the synergy effect of the two interfaces and the confined nanospace favoring the instant transfer of intermediates. The tube-in-tube tandem catalyst with multiple metal-oxide interfaces represents a new concept for the design of highly efficient and multifunctional nanocatalysts.A Tandem Catalyst with Multiple Metal Oxide Interfaces Produced by Atomic Layer Depositionatomic layer depositon; heterogeneous catalysis; hydrogenation; metal-oxide interfaces; nanocatalysisx63201637#N/AFALSE
4434
anie.20160377710.1002/anie.201603777FALSEhttps://doi.org/10.1002/anie.201603777Ananikov, VPAngew. Chem.-Int. Edit.Environmental profiles for the selected metals were compiled on the basis of available data on their biological activities. Analysis of the profiles suggests that the concept of toxic heavy metals and safe nontoxic alternatives based on lighter metals should be re-evaluated. Comparison of the toxicological data indicates that palladium, platinum, and gold compounds, often considered heavy and toxic, may in fact be not so dangerous, whereas complexes of nickel and copper, typically assumed to be green and sustainable alternatives, may possess significant toxicities, which is also greatly affected by the solubility in water and biological fluids. It appears that the development of new catalysts and novel applications should not rely on the existing assumptions concerning toxicity/nontoxicity. Overall, the available experimental data seem insufficient for accurate evaluation of biological activity of these metals and its modulation by the ligands. Without dedicated experimental measurements for particular metal/ligand frameworks, toxicity should not be used as a selling point when describing new catalysts.Which Metals are Green for Catalysis? Comparison of the Toxicities of Ni, Cu, Fe, Pd, Pt, Rh, and Au Saltsbiological activity; green chemistry; sustainable chemistry; transition metals; toxicology1942016228#N/ATRUE
4435
anie.20160043110.1002/anie.201600431https://doi.org/10.1002/anie.201600431Lin, WBAngew. Chem.-Int. Edit.Metal-organic frameworks (MOFs) provide a tunable platform for hierarchically integrating multiple components to effect synergistic functions that cannot be achieved in solution. Here we report the encapsulation of a Ni-containing polyoxometalate (POM) [Ni-4(H2O)(2)(PW9O34)(2)](10-) (Ni4P2) into two highly stable and porous phosphorescent MOFs. The proximity of Ni4P2 to multiple photosensitizers in Ni4P2@MOF allows for facile multi-electron transfer to enable efficient visible-light-driven hydrogen evolution reaction (HER) with turnover numbers as high as 1476. Photophysical and electrochemical studies established the oxidative quenching of the excited photosensitizer by Ni4P2 as the initiating step of HER and explained the drastic catalytic activity difference of the two POM@MOFs. Our work shows that POM@MOF assemblies not only provide a tunable platform for designing highly effective photocatalytic HER catalysts but also facilitate detailed mechanistic understanding of HER processes.Hierarchical Integration of Photosensitizing Metal-Organic Frameworks and Nickel-Containing Polyoxometalates for Efficient Visible-Light-Driven Hydrogen Evolutionhydrogen evolution reaction; metal-organic frameworks; photocatalysis; polyoxometalatePhotocatalystx152201658#N/AFALSE
4436
anie.20160038710.1002/anie.201600387FALSEhttps://doi.org/10.1002/anie.201600387Qiao, SZAngew. Chem.-Int. Edit.A universal technique has been proposed to sort two-dimensional (2D) sub-nanometer thin crystals (manganese dioxide MnO2 and molybdenum disulfide MoS2) according to their lateral dimensions. This technique is based on tuning the zeta potential of their aqueous dispersions which induces the selective sedimentation of large-sized 2D crystals and leaves the small-sized counterparts in suspension. The electrocatalytic properties of as-obtained 2D ultrathin crystals are strongly dependent on their lateral size. As a proof-of-concept study, the small-sized MnO2 nanocrystals were tested as the electrocatalysts for the urea-oxidation reaction (UOR), which showed outstanding performance in both half reaction and full electrolytic cell. A mechanism study reveals the enhanced performance is associated with the remarkable structural properties of MnO2 inCluding ultrathin (ca. 0.95nm), laterally small-sized (50-200nm), and highly exposed active centers.Size Fractionation of Two-Dimensional Sub-Nanometer Thin Manganese Dioxide Crystals towards Superior Urea Electrocatalytic Conversionmanganese dioxide; size fractionation; two-dimensional nanocrystals; urea electrolysis; zeta potentialx182201633#N/AFALSE
4437
anie.20160024810.1002/anie.201600248FALSEhttps://doi.org/10.1002/anie.201600248Osuka, AAngew. Chem.-Int. Edit.Instead of using Aryl halides, Aryl sulfides, typically poisonous to transition-metal catalysts, were found to serve as Aryl electrophiles in the catalytic -Arylation of ketimines, a Class of Carbonyl derivatives. Low catalyst loadings (down to 0.5mol%) of a palladium-NHC complex are sufficient for efficient Arylation. -Arylated ketimine products are useful for the synthesis of various azaarenes, inCluding 2,3-diArylpyrroles, an indole, and pyrrolediones.alpha-Arylation of Ketimines with Aryl Sulfides at a Low Palladium Catalyst Loadingx24201687#N/AFALSE
4438
anie.20160268310.1002/anie.201602683FALSEhttps://doi.org/10.1002/anie.201602683Osuka, AAngew. Chem.-Int. Edit.The direct fusion of a diphenylmethane segment to a Ni-II 5,10,15-triArylporphyrin with three linkages furnished an air-and moisture-stable neutral radical through unexpected and spontaneous oxidation. This radical was demetalated by treatment with H2SO4 and CF3CO2H to provide the corresponding free-base radical. These porphyrin radicals are very stable owing to spin delocalization and have been fully characterized through UV/Vis/NIR absorption spectroscopy, X-ray crystallographic analysis, magnetic susceptibility measurements, electrochemical studies, laser-based ultrafast spectroscopic studies, and theoretical calculations. They were chemically oxidized and reduced to the corresponding cation and anion but did not react with hydrogen-atom donors.Spontaneous Formation of an Air-Stable Radical upon the Direct Fusion of Diphenylmethane to a TriArylporphyrinaromaticity; fused-ring systems; porphyrinoids; radical; redox chemistry37201640#N/ATRUE
4439
anie.20151202710.1002/anie.201512027https://doi.org/10.1002/anie.201512027Ackermann, LAngew. Chem.-Int. Edit.Room-temperature azole C-H Arylations were accomplished with inexpensive copper(I) compounds by means of photoinduced catalysis. The expedient copper catalysis set the stage for site-selective C-H Arylations of non-aromatic oxazolines under mild reaction conditions, and provides step-economical access to the alkaloid natural products balsoxin and texamine.Photoinduced Copper-Catalyzed C-H Arylation at Room TemperaturePhotocatalyst87201696#N/AFALSE
4440
anie.20151162110.1002/anie.201511621FALSEhttps://doi.org/10.1002/anie.201511621Masuda, HAngew. Chem.-Int. Edit.A novel nickel(II) complex [Ni(L)(2)Cl]Cl with a bidentate phosphinopyridyl ligand 6-((diphenylphosphino)methyl)pyridin-2-amine (L) was synthesized as a metal-complex catalyst for hydrogen production from protons. The ligand can stabilize a low Nioxidation state and has an amine base as a proton transfer site. The X-ray structure analysis revealed a distorted square-pyramidal Ni(II)complex with two bidentate L ligands in a transarrangement in the equatorial plane and a chloride anion at the apex. Electrochemical measurements with the Ni-II complex in MeCN indicate a higher rate of hydrogen production under weak acid conditions using acetic acid as the proton source. The catalytic current increases with the stepwise addition of protons, and the turnover frequency is 8400s(-1) in 0.1m [NBu4][ClO4]/MeCN in the presence of acetic acid (290equiv) at an overpotential of circa 590mV.Electrocatalytic Hydrogen Production by a Nickel(II) Complex with a Phosphinopyridyl Ligandelectrocatalysis; electrochemistry; hydrogen; hydrogenases; nickel
Electrocatalytic
60201628#N/AFALSE
4441
anie.20151144710.1002/anie.201511447FALSEhttps://doi.org/10.1002/anie.201511447Li, GRAngew. Chem.-Int. Edit.Herein, we developed FeOOH/Co/FeOOH hybrid nanotube arrays (HNTAs) supported on Ni foams for oxygen evolution reaction (OER). The inner Co metal cores serve as highly conductive layers to provide reliable electronic transmission, and can overcome the poor electrical conductivity of FeOOH efficiently. DFT calculations demonstrate the strong electronic interactions between Co and FeOOH in the FeOOH/Co/FeOOH HNTAs, and the hybrid structure can lower the energy barriers of intermediates and thus promote the catalytic reactions. The FeOOH/Co/FeOOH HNTAs exhibit high electrocatalytic performance for OER, such as low onset potential, small Tafel slope, and excellent long-term durability, and they are promising electrocatalysts for OER in alkaline solution.FeOOH/Co/FeOOH Hybrid Nanotube Arrays as High-Performance Electrocatalysts for the Oxygen Evolution Reactionelectrocatalysts; FeOOH; hybrid nanotubes; oxygen evolution reactionx407201674#N/AFALSE
4442
anie.20151143810.1002/anie.201511438https://doi.org/10.1002/anie.201511438Doyle, AGAngew. Chem.-Int. Edit.Using nickel and photoredox catalysis, the direct functionalization of C(sp(3))-H bonds of N-Aryl amines by acyl electrophiles is described. The method affords a diverse range of -amino ketones at room temperature and is amenable to late-stage coupling of complex and biologically relevant groups. C(sp(3))-H Activation occurs by photoredox-mediated oxidation to generate -amino radicals which are intercepted by nickel in catalytic C(sp(3))-C coupling. The merger of these two modes of catalysis leverages nickel's unique properties in Alkyl cross-coupling while avoiding limitations commonly associated with transition-metal-mediated C(sp(3))-H Activation, inCluding requirements for chelating directing groups and high reaction temperatures.Direct Acylation of C(sp(3))-H Bonds Enabled by Nickel and Photoredox Catalysisacylation; C-H Activation; cross-coupling; nickel; photochemistryPhotocatalyst1252016526/15/2022FALSE
4443
anie.20151133410.1002/anie.201511334https://doi.org/10.1002/anie.201511334Zhang, TRAngew. Chem.-Int. Edit.Metallic nickel nanostructures that were partially decorated by discrete nickel oxide layers were fabricated by insitu reduction of calcinated Ni-containing layered double hydroxide nanosheets, the structure of which was confirmed by extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The existence of the abundant interfaces between the surface Ni oxide overlayer and metallic Ni altered the geometric/electronic structure of the Ni nanopartiCles, making them apt for CO Activation under light irradiation. Most importantly, the unique structure favors the C-C coupling reaction on its surface, which confers the catalyst unexpected reaction power towards higher hydrocarbons at moderate reaction conditions. This study leads to a green and sustainable approach for the photocatalytic production of highly valuable chemical fuels.Oxide-Modified Nickel Photocatalysts for the Production of Hydrocarbons in Visible LightFischer-Tropsch synthesis; layered double hydroxides; nickel; photocatalysis; ultrathin nanosheetsPhotocatalyst142201631#N/AFALSE
4444
anie.20160223710.1002/anie.201602237FALSEhttps://doi.org/10.1002/anie.201602237Feng, XLAngew. Chem.-Int. Edit.To achieve sustainable production of H-2 fuel through water splitting, low-cost electrocatalysts for the hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) are required to replace Pt and IrO2 catalysts. Herein, for the first time, we present the interface engineering of novel MoS2/Ni3S2 heterostructures, in which abundant interfaces are formed. For OER, such MoS2/Ni3S2 heterostructures show an extremely low overpotential of ca. 218 mV at 10 mAcm(-2), which is superior to that of the state-of-the-art OER electrocatalysts. Using MoS2/Ni3S2 heterostructures as bifunctional electrocatalysts, an alkali electrolyzer delivers a current density of 10 mAcm(-2) at a very low cell voltage of ca. 1.56 V. In combination with DFT calculations, this study demonstrates that the constructed interfaces synergistically favor the chemisorption of hydrogen and oxygen-containing intermediates, thus accelerating the overall electrochemical water splitting.Interface Engineering of MoS2/Ni3S2 Heterostructures for Highly Enhanced Electrochemical Overall-Water-Splitting Activityelectrocatalysts; interface engineering; molybdenum disulfide; nickel sulfide; water splitting746201638#N/ATRUE
4445
anie.20151130510.1002/anie.201511305FALSEhttps://doi.org/10.1002/anie.201511305Astruc, DAngew. Chem.-Int. Edit.A ligand design is proposed for transition metal nanopartiCle (TMNP) catalysts in aqueous solution. Thus, a tris(triazolyl)-polyethylene glycol (tris-trz-PEG) amphiphilic ligand, 2, is used for the synthesis of very small TMNPs with Fe, Co, Ni, Cu, Ru, Pd, Ag, Pt, and Au. These TMNP-2 catalysts were evaluated and compared for the model 4-nitrophenol reduction, and proved to be extremely efficient. High catalytic efficiencies involving the use of only a few ppm metal of PdNPs, RuNPs, and CuNPs were also exemplified in Suzuki-Miyaura, transfer hydrogenation, and Click reactions, respectively.Highly Efficient Transition Metal NanopartiCle Catalysts in Aqueous Solutionsgreen chemistry; heterogeneous catalysis; ligand design; nitroarene reduction; transition metal nanopartiClesx99201674#N/AFALSE
4446
anie.20160220210.1002/anie.201602202FALSEhttps://doi.org/10.1002/anie.201602202Guo, YGAngew. Chem.-Int. Edit.Room-temperature sodium-ion batteries (SIBs) have shown great promise in grid-scale energy storage, portable electronics, and electric vehiCles because of the abundance of low-cost sodium. Sodium-based layered oxides with a P2-type layered framework have been considered as one of the most promising cathode materials for SIBs. However, they suffer from the undesired P2-O2 phase transition, which leads to rapid capacity decay and limited reversible capacities. Herein, we show that this problem can be significantly mitigated by substituting some of the nickel ions with magnesium to obtain Na0.67Mn0.67Ni0.33-xMgxO2 (0 <= x <= 0.33). Both the reversible capacity and the capacity retention of the P2-type cathode material were remarkably improved as the P2-O2 phase transition was thus suppressed during cyCling. This strategy might also be applicable to the modulation of the physical and chemical properties of layered oxides and provides new insight into the rational design of high-capacity and highly stable cathode materials for SIBs.Suppressing the P2-O2 Phase Transition of Na0.67Mn0.67Ni0.33O2 by Magnesium Substitution for Improved Sodium-Ion BatteriescyClability; electrochemistry; magnesium; phase transitions; sodium-ion batteries273201634#N/ATRUE
4447
anie.20160193510.1002/anie.201601935FALSEhttps://doi.org/10.1002/anie.201601935Strongin, DRAngew. Chem.-Int. Edit.We report a synthetic method to enhance the electrocatalytic activity of birnessite for the oxygen evolution reaction (OER) by intercalating Ni2+ ions into the interlayer region. Electrocatalytic studies showed that nickel (7.7 atomic %)-intercalated birnessite exhibits an overpotential (eta) of 400 mV for OER at an anodic current of 10 mA cm(-2). This eta is significantly lower than the eta values for birnessite (eta approximate to 700 mV) and the active OER catalyst beta-Ni(OH)(2) (eta approximate to 550 mV). Molecular dynamics simulations suggest that a competition among the interactions between the nickel cation, water, and birnessite promote redox chemistry in the spatially confined interlayer region.Nickel Confined in the Interlayer Region of Birnessite: an Active Electrocatalyst for Water Oxidationbirnessite; electrochemistry; nickel intercalation; oxygen evolution reaction; water splitting82201628#N/ATRUE
4448
anie.20160170310.1002/anie.201601703FALSEhttps://doi.org/10.1002/anie.201601703Coates, GWAngew. Chem.-Int. Edit.A dibenzobarrelene-bridged, alpha-diimine Ni-II catalyst (rac-3) was synthesized and shown to have exceptional behavior for the polymerization of ethylene. The catalyst afforded high molecular weight polyethylenes with narrow dispersities and degrees of branching much lower than those made by related a-diimine nickel catalysts. Catalyst rac-3 demonstrated living behavior at room temperature, produced linear polyethylene (T-m=135 degrees C) at -20 degrees C, and, most importantly, was able to copolymerize ethylene with the biorenewable polar monomer methyl 10-undecenoate to yield highly linear ester-functionalized polyethylene.Semi-Crystalline Polar Polyethylene: Ester-Functionalized Linear Polyolefins Enabled by a Functional-Group-Tolerant, Cationic Nickel Catalysthomogeneous catalysis; nickel; polymerization; polymers; renewable resources1382016104#N/ATRUE
4449
anie.20151059910.1002/anie.201510599FALSEhttps://doi.org/10.1002/anie.201807463Hu, YKFacile Preparation of Ni2P with a Sulfur-Containing Surface Layer by Low-Temperature Reduction of Ni2P2S6x2016#N/AFALSE
4450
anie.20151046010.1002/anie.201510460FALSEhttps://doi.org/10.1002/anie.201510460Han, SWAngew. Chem.-Int. Edit.A synthesis strategy for the preparation of ultrathin free-standing ternary-alloy nanosheets is reported. Ultrathin Pd-Pt-Ag nanosheets with a thickness of approximately 3 nm were successfully prepared by co-reduction of the metal precursors in an appropriate molar ratio in the presence of CO. Both the presence of CO and the interplay between the constituent metals provide fine control over the anisotropic two-dimensional growth of the ternary-alloy nanostructure. The prepared Pd-Pt-Ag nanosheets were superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics. This approach will pave the way for the design of multicomponent 2D nanomaterials with unprecedented functions.Ultrathin Free-Standing Ternary-Alloy Nanosheetsalloys; nanosheets; palladium; platinum; silverx130201641#N/AFALSE
4451
anie.20160146810.1002/anie.201601468FALSEhttps://doi.org/10.1002/anie.201601468Hoge, BAngew. Chem.-Int. Edit.The synthesis of the germylene phosphane adduct (C2F5)(2)GePMe3 is described. Starting from (C2F5)(3)GeH in an excess of PMe3, heating was applied, whereupon reductive elimination of C2F5H occurred. The molecular structure was ascertained by X-ray diffraction and compared with information obtained by quantum chemical methods. The ligand properties were derived by studying the IR spectrum of the nickel(0) complex [Ni(CO)(3){Ge(C2F5)(2)(PMe3)}] in the CO region. (C2F5)(2)GePMe3 turned out to be a -accepting ligand comparable to PMe3, in terms of Tolman's electronic parameter. Furthermore a [2+4] cyCloaddition reaction with 2,3-dimethyl-1,3-butadiene, and sigma-bond insertion reactions were recorded. Activation of the C-Cl bond in dichloromethane gives rise to the formation of the phosphonium ylide complex [(C2F5)(2)Cl2Ge-CH2PMe3], which was fully characterized by X-ray diffraction.The Bis(pentafluoroethyl)germylene Trimethylphosphane Adduct (C2F5)(2)GePMe3: Characterization, Ligand Properties, and Reactivityfluorine; fluorinated ligands; germanium; X-ray diffraction; structure elucidation7201626#N/ATRUE
4452
anie.20151007710.1002/anie.201510077https://doi.org/10.1002/anie.201510077Nozaki, KAngew. Chem.-Int. Edit.The replacement of precious metals in catalysis by earth-abundant metals is currently one of the urgent challenges for chemists. Whereas palladium-catalyzed copolymerization of ethylene and polar monomers is a valuable method for the straightforward synthesis of functionalized polyolefins, the corresponding nickel-based catalysts have suffered from poor thermal tolerance and low molecular weight of the polymers formed. Herein, we report a series of neutral nickel complexes bearing imidazo[1,5-a] quinolin-9-olate-1-ylidene (IzQO) ligands. The Ni/IzQO system can catalyze ethylene polymerization at 50-100 degrees C with reasonable activity in the absence of any cocatalyst, whereas most known nickel-based catalysts are deactivated at this temperature range. The Ni/IzQO catalyst was successfully applied to the copolymerization of ethylene with allyl monomers to obtain the corresponding copolymers with the highest molecular weight reported for a Ni-catalyzed system. SinceCopolymerization of Ethylene and Polar Monomers by Using Ni/IzQO Catalystsethylene; IzQO; nickel; polar monomers; polymerizationx86201672#N/AFALSE
4453
anie.20160138210.1002/anie.201601382FALSEhttps://doi.org/10.1002/anie.201601382Milstein, DAngew. Chem.-Int. Edit.Efficient iron-catalyzed homocoupling of terminal alkynes and cross-dimerization of Aryl acetylenes with trimethylsilylacetylene is reported. The complex [Fe(H)(BH4)(iPr-PNP)] (1) catalyzed the (cross-)dimerization of alkynes at room temperature, with no need for a base or other additives, to give the corresponding dimerized products with Z selectivity in excellent yields (79-99%).Z-Selective (Cross-)Dimerization of Terminal Alkynes Catalyzed by an Iron Complex67201651#N/ATRUE
4454
anie.20150936410.1002/anie.201509364FALSEhttps://doi.org/10.1002/anie.201509364Endres, FDendrite-Free Nanocrystalline Zinc Electrodeposition from an Ionic Liquid Containing Nickel Triflate for Rechargeable Zn-Based Batteriesx2016#N/AFALSE
4455
anie.20150919510.1002/anie.201509195FALSEhttps://doi.org/10.1002/anie.201509195Shimakawa, YAngew. Chem.-Int. Edit.Novel cubic perovskites SrFe1-xNixO3 (0 <= x <= 0.5) with unusual high-valence iron(IV) and nickel(IV) ions were obtained by high-pressure and high-temperature synthesis. Substantial magnetic moments of Ni-IV, which is intrinsically nonmagnetic with a nominal d(6) electron configuration, were induced by the large magnetic moments of Fe-IV through orbital hybridization with oxygen. As a result, ferromagnetism with the transition temperature (T-c) above room temperature could be induced.Ferromagnetism Induced by Substitution of the Iron(IV) Ion by an Unusual High-Valence Nickel(IV) Ion in Antiferromagnetic SrFeO3high-pressure chemistry; iron; magnetic properties; nickel; perovskite phasesx11201627#N/AFALSE
4456
anie.20150913310.1002/anie.201509133FALSEhttps://doi.org/10.1002/anie.201509133Hartwig, JFAngew. Chem.-Int. Edit.We report the chemo-and regioselective hydrogenolysis of the C-O bonds in di-ortho-substituted diAryl ethers under the catalysis of a supported nickel catalyst. The catalyst comprises heterogeneous nickel partiCles supported on activated carbon and furnishes arenes and phenols in high yields without hydrogenation. The high thermal stability of the embedded metal partiCles allows C-O bond Cleavage to occur in highly substituted diAryl ether units akin to those in lignin. Preliminary mechanistic experiments show that this catalyst undergoes sintering less readily than previously reported catalyst partiCles that form from a solution of [Ni(cod)(2)].Chemo- and Regioselective Hydrogenolysis of DiAryl Ether C-O Bonds by a Robust Heterogeneous Ni/C Catalyst: Applications to the Cleavage of Complex Lignin-Related FragmentsC-O Cleavage; diAryl ethers; heterogeneous catalysis; hydrogenolysis; nickel catalystsx85201663#N/AFALSE
4457
anie.20160135110.1002/anie.201601351FALSEhttps://doi.org/10.1002/anie.201601351Zhang, XGAngew. Chem.-Int. Edit.A nickel-catalyzed cross-coupling between (hetero)Arylborons and unactivated 1-bromo-1,1-difluoroalkanes has been developed. The use of two ligands (a bidentate bipyridine-based ligand, 4,4-ditBu-bpy, and a monodentate pyridine-based ligand, DMAP) offers a highly efficient nickel-based catalytic system to prepare difluoroAlkylated arenes which have important applications in medicinal chemistry.Nickel-Catalyzed DifluoroAlkylation of (Hetero)Arylborons with Unactivated 1-Bromo-1,1-difluoroalkanesarenes; cross-coupling; fluorine; ligand design; nickel74201644#N/ATRUE
4458
anie.20150870410.1002/anie.201508704FALSEhttps://doi.org/10.1002/anie.201803092Xie, YSolution-Liquid-Solid Synthesis of Hexagonal Nickel Selenide Nanowire Arrays with a Nonmetal Catalystx2016#N/AFALSE
4459
anie.20160129610.1002/anie.201601296FALSEhttps://doi.org/10.1002/anie.201601296Nevado, CAngew. Chem.-Int. Edit.Anickel-catalyzed three-component reaction involving terminal alkynes, boronic acids, and Alkyl halides is presented herein. Trisubstituted alkenes can be obtained in a highly regio- and stereocontrolled manner by the simultaneous addition of both Aryl and Alkyl groups across the triple bond in a radical-mediated process. The reaction, devoid of air- and moisture-sensitive organometallic reagents and catalysts, is operationally simple and offers a broad scope and functional-group tolerance.Nickel-Catalyzed Stereoselective Dicarbofunctionalization of AlkynesAlkyl halides; alkynes; boron; nickel; radicals70201651#N/ATRUE
4460
anie.20150835110.1002/anie.201508351FALSEhttps://doi.org/10.1002/anie.201508351Liaw, WFAngew. Chem.-Int. Edit.Despite extensive efforts, the electrocatalytic reduction of water using homogeneous/heterogeneous Fe, Co, Ni, Cu, W, and Mo complexes remains challenging because of issues involving the development of efficient, recyClable, stable, and aqueous-compatible catalysts. In this study, evolution of the de novo designed dinitrosyl iron complex DNIC-PMDTA from a molecular catalyst into a solid-state hydrogen evolution cathode, considering all the parameters to fulfill the electronic and structural requirements of each step of the catalytic cyCle, is demonstrated. DNIC-PMDTA reveals electrocatalytic reduction of water at neutral and basic media, whereas its deposit on electrode preserves exceptional longevity, 139 h. This discovery will initiate a systematic study on the assembly of [Fe(NO)(2)] motif into current collector for mass production of H-2, whereas the efficiency remains tailored by its molecular precursor [(L) Fe(NO)(2)].Development of a Dinitrosyl Iron Complex Molecular Catalyst into a Hydrogen Evolution Cathodeelectrocatalysis; hydrogen; iron; nitric oxide; water reductionx18201561#N/AFALSE
4461
anie.20150823210.1002/anie.201508232FALSEhttps://doi.org/10.1002/anie.201508232Hayton, TWAngew. Chem.-Int. Edit.The addition of 1 equiv of KSCPh3 to [(LNiCl)-Ni-R] (L-R ={(2,6-iPr(2)C(6)H(3))NC(R)}(2)CH; R=Me, tBu) in C6H6 results in the formation of [(LNi)-Ni-R(SCPh3)] (1: R=Me; 2: R=tBu) in good yields. Subsequent reduction of 1 and 2 with 2 equiv of KC8 in cold (-25 degrees C) Et2O in the presence of 2 equiv of 18-crown-6 results in the formation of masked terminal Ni-II sulfides, [K(18-crown-6)][(LNi)-Ni-R(S)] (3: R=Me; 4: R= tBu), also in good yields. An X-ray crystallographic analysis of these complexes suggests that they feature partial multiple-bond character in their Ni-S linkages. Addition of N2O to a toluene solution of 4 provides [K(18-crown-6)][(LNi)-Ni-tBu(SN= NO)], which features the first example of a thiohyponitrite (kappa(2)-[SN=NO](2-)) ligand.Synthesis of a Masked Terminal Nickel(II) Sulfide by Reductive Deprotection and its Reaction with Nitrous Oxidecoordination chemistry; nickel; nitrogen oxides; protecting groups; sulfidesx14201552#N/AFALSE
4462
anie.20160112610.1002/anie.201601126FALSEhttps://doi.org/10.1002/anie.201601126Kambe, NAngew. Chem.-Int. Edit.In the presence of a nickel catalyst, 1,3-butadiene undergoes selective dimerization and AlkylArylation with Alkyl fluorides and Aryl Grignard reagents to give 1,6-octadienes with Alkyl and Aryl groups at the 3- and 8-positions, respectively, by the consecutive formation of three carbon-carbon bonds. The formation of an anionic nickel complex plays an important role in forming C-C bonds with Alkyl fluorides.Nickel-Catalyzed Dimerization and AlkylArylation of 1,3-Dienes with Alkyl Fluorides and Aryl Grignard ReagentsAlkylation; dimerization; multicomponent reactions; nickel; regioselectivity30201678#N/ATRUE
4463
anie.20150810710.1002/anie.201508107FALSEhttps://doi.org/10.1002/anie.201508107Han, BXSynthesis of Supported Ultrafine Non-noble Subnanometer-Scale Metal PartiCles Derived from Metal-Organic Frameworks as Highly Efficient Heterogeneous Catalystsx2016#N/AFALSE
4464
anie.20150796510.1002/anie.201507965FALSEhttps://doi.org/10.1002/anie.201507965Johnson, MAAngew. Chem.-Int. Edit.We describe a systematic method for the preparation and spectroscopic characterization of a CO2 molecule coordinated to an activated bisphenoidal nickel(I) compound containing a tetraazamacrocyClic ligand in the gas phase. The resulting complex was then structurally characterized by using mass-selected vibrational predissociation spectroscopy. The results indicate that a highly distorted CO2 molecule is bound to the metal center in an h eta(2)-C,O coordination mode, thus establishing an efficient and rational method for the preparation of metal-activated CO2 for further studies using ion chemistry techniques.Capture of CO2 by a Cationic Nickel( I) Complex in the Gas Phase and Characterization of the Bound, Activated CO2 Molecule by Cryogenic Ion Vibrational Predissociation SpectroscopyCO2 Activation; infrared spectroscopy; mass spectrometry; nickelx41201635#N/AFALSE
4465
anie.20150791810.1002/anie.201507918FALSEhttps://doi.org/10.1002/anie.201507918Yashima, EAngew. Chem.-Int. Edit.The dynamic planar chirality in a peptide-bound Ni-II-salphen-based macrocyCle can be remotely controlled. First, a right-handed (P)-3(10)-helix is induced in the dynamic helical oligopeptides by a chiral amino acid residue far from the macrocyClic framework. The induced planar chirality remains dynamic in chloroform and acetonitrile, but is almost completely locked in fluoroalcohols as a result of the solvent-induced transition of the peptide chains from a 3(10)-helix to a wider a-helix, which freezes the rotation of the pendant peptide units around the macrocyCle.Remote Control of the Planar Chirality in Peptide-Bound MetallomacrocyCles and Dynamic-to-Static Planar Chirality Control Triggered by Solvent-Induced 3(10)-to-alpha-Helix Transitionschirality; macrocyCles; peptides; self-assembly; supramolecular chemistryx17201539#N/AFALSE
4466
anie.20150790210.1002/anie.201507902FALSEhttps://doi.org/10.1002/anie.201507902Mashima, KAngew. Chem.-Int. Edit.A salt-free procedure for the generation of a wide variety of metal(0) partiCles, inCluding Fe, Co, Ni, and Cu, was achieved using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza- 2,5-cyClohexadiene (1), which reduced the corresponding metal precursors under mild conditions. Notably, Ni partiCles formed in situ from the treatment of Ni(acac) 2 (acac = acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C - C bond-forming reactions of Aryl halides in the presence of excess amounts of 1. By examination of high-magnification transmission electron microscopy images and electron diffraction patterns, we conCluded that amorphous Ni nanopartiCles (Ni aNPs) were essential for the high catalytic activity.Salt- Free Reduction of Nonprecious Transition- Metal Compounds: Generation of Amorphous Ni NanopartiCles for Catalytic C-C Bond FormationC-C coupling; nanopartiCles; nickel; organosilicon compounds; reductive couplingx42201563#N/AFALSE
4467
anie.20160052510.1002/anie.201600525FALSEhttps://doi.org/10.1002/anie.201600525Lin, ZAngew. Chem.-Int. Edit.Bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte may improve the efficiency of overall water splitting. Nickel cobaltite (NiCo2O4) has been considered a promising electrode material for the OER. However, NiCo2O4 that can be used as an electrocatalyst in HER has not been studied yet. Herein, we report self-assembled hierarchical NiCo2O4 hollow microcuboids for overall water splitting inCluding both the HER and OER reactions. The NiCo2O4 electrode shows excellent activity toward overall water splitting, with 10 mA cm(-2) water-splitting current reached by applying just 1.65 Vand 20 mA cm(-2) by applying just 1.74 V across the two electrodes. The synthesis of NiCo2O4 microflowers confirms the importance of structural features for highperformance overall water splitting.Hierarchical NiCo2O4 Hollow Microcuboids as Bifunctional Electrocatalysts for Overall Water-Splittingelectrochemistry; NiCo2O4; solvothermal synthesis; water splitting521201636#N/ATRUE
4468
anie.20150738110.1002/anie.201507381FALSEhttps://doi.org/10.1002/anie.201507381Chen, MWAngew. Chem.-Int. Edit.Single-atom nickel dopants anchored to three-dimensional nanoporous graphene can be used as catalysts of the hydrogen evolution reaction (HER) in acidic solutions. In contrast to conventional nickel-based catalysts and graphene, this material shows superior HER catalysis with a low over-potential of approximately 50 mV and a Tafel slope of 45 mV dec(-1) in 0.5 M H2SO4 solution, together with excellent cyCling stability. Experimental and theoretical investigations suggest that the unusual catalytic performance of this catalyst is due to sp-d orbital charge transfer between the Ni dopants and the surrounding carbon atoms. The resultant local structure with empty C-Ni hybrid orbitals is catalytically active and electrochemically stable.Nanoporous Graphene with Single-Atom Nickel Dopants: An Efficient and Stable Catalyst for Electrochemical Hydrogen Productionelectrocatalysis; graphene; hydrogen evolution reaction; nanoporosity; nickel dopingx402201550#N/AFALSE
4469
anie.20160018510.1002/anie.201600185FALSEhttps://doi.org/10.1002/anie.201600185Ghosh, SKAngew. Chem.-Int. Edit.A three-dimensional water-stable cationic metal-organic framework (MOF) pillared by a neutral ligand and with Ni-II metal nodes has been synthesized employing a rational design approach. Owing to the ordered arrangement of the uncoordinated tetrahedral sulfate (SO42-) ions in the channels, the compound has been employed for aqueous-phase ion-exchange applications. The compound exhibits rapid and colorimetric aqueous-phase capture of environmentally toxic oxoanions (with similar geometries) in a selective manner. This system is the first example of a MOF-based system which absorbs both dichromate (Cr2O72-) and permanganate (MnO4-) ions, with the latter acting as a model for the radioactive contaminant pertechnetate (TcO4-).A Water-Stable Cationic Metal-Organic Framework as a Dual Adsorbent of Oxoanion Pollutantsadsorption; anions; environment chemistry; metal-organic frameworks; sensors214201680#N/ATRUE
4470
anie.20151132110.1002/anie.201511321FALSEhttps://doi.org/10.1002/anie.201511321Wang, XSAngew. Chem.-Int. Edit.The first example of nickel-catalyzed deCarbonylative fluoroAlkylation of ,-unsaturated Carbonylic acids has been developed with commonly available fluoroAlkyl halides. This novel transformation has demonstrated broad substrate scope, excellent functional-group tolerance, mild reaction conditions, and excellent stereoselectivity. Mechanistic investigations indicate that a fluoroAlkyl radical is involved in the catalytic cyCle.Nickel-Catalyzed DeCarbonylative DifluoroAlkylation of ,-Unsaturated Carbonylic AcidsfluoroAlkylation; nickel; olefins; radicals; synthetic methods100201695#N/ATRUE
4471
anie.20150642410.1002/anie.201506424FALSEhttps://doi.org/10.1002/anie.201506424Isobe, HAngew. Chem.-Int. Edit.The recent development of cyClo-para-phenylenes has demonstrated the feasibility of radial pi systems in nano-hoop structures, especially in the crystalline state. However, in contrast to macrocyClic molecules with benzene units, which have a several-decades-long history, macrocyCles composed solely of naphthylene units (the smallest acene) have been much less explored. Although two examples of cyClonaphthylenes have been reported to date, neither possesses a radial pi system. We herein report the first example of belt-shaped cyClonaphthylenes with curved pi systems. The molecule, [8]cyClo-amphi-naphthylene, is linked at the 2,6-positions of the naphthylene units, thus affording belt-shaped molecules. Although the molecular structures are flexible, which allows for rotation of the naphthylene units in solution, they can be rigidified with the aid of methylene bridges to afford persistent molecular structures in solution.Belt-Shaped CyClonaphthylenesarenes; atropisomerism; cyCloArylenes; macrocyCles; nanotubesx37201551#N/AFALSE
4472
anie.20150614710.1002/anie.201506147https://doi.org/10.1002/anie.201506147Molander, GAAngew. Chem.-Int. Edit.Direct access to complex, enantiopure Benzylamine architectures using a synergistic iridium photoredox/nickel cross-coupling dual catalysis strategy has been developed. New C(sp(3)) C(sp(2)) bonds are forged starting from abundant and inexpensive natural amino acids.alpha-Arylation/HeteroArylation of Chiral alpha-AminomethyltrifluorB(OH)2rates by Synergistic Iridium Photoredox/Nickel Cross-Coupling Catalysisamino acids; cross-coupling; heterocyCles; nickel; photochemistryPhotocatalyst85201644#N/AFALSE
4473
anie.20150604810.1002/anie.201506048FALSEhttps://doi.org/10.1002/anie.201713346Feng, XLLarge-Area, Free-Standing, Two-Dimensional Supramolecular Polymer Single-Layer Sheets for Highly Efficient Electrocatalytic Hydrogen Evolutionx2015#N/AFALSE
4474
anie.20151127110.1002/anie.201511271FALSEhttps://doi.org/10.1002/anie.201511271Uyeda, CAngew. Chem.-Int. Edit.DinuClear Ni complexes supported by naphthyridine-diimine (NDI) ligands catalyze the reductive cyClopropanation of alkenes with CH2Cl2 as the methylene source. The use of mild terminal reductants (Zn or Et2Zn) confers significant functional-group tolerance, and the catalyst accommodates structurally and electronically diverse alkenes. Mononickel catalysts bearing related Nchelates afford comparatively low cyClopropane yields (20%). These results constitute an entry into catalytic carbene transformations from oxidized methylene precursors.Reductive CyClopropanations Catalyzed by DinuClear Nickel Complexesalkenes; carbene transfer; cyClopropanation; nickel catalysis; reductive cyCloaddition48201640#N/ATRUE
4475
anie.20150580510.1002/anie.201505805FALSEhttps://doi.org/10.1002/anie.201505805Apeloig, YAngew. Chem.-Int. Edit.The thermally stable [(tBuMe(2)Si)(2)M] (M = Zn, Hg) generate R3Si center dot radicals in the presence of [(dmpe)Pt(PEt3)(2)] at 60-80 degrees C. The reaction proceeds via hexacoordinate Pt complexes, (M = Zn (2a and 2b), M = Hg (3a and 3b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR3 bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M = Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations.Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt-0 Complex, via Novel Pt-Zn and Pt-Hg Compoundsx4201544#N/AFALSE
4476
anie.20151074110.1002/anie.201510741FALSEhttps://doi.org/10.1002/anie.201510741Dobbek, HAngew. Chem.-Int. Edit.Quercetin 2,4-dioxygenase (quercetinase) from Streptomyces uses nickel as the active-site cofactor to catalyze oxidative Cleavage of the flavonol quercetin. How this unusual active-site metal supports catalysis and O-2 Activation is under debate. We present crystal structures of Ni-quercetinase in three different states, thus providing direct insight into how quercetin and O-2 are activated at the Ni2+ ion. The Ni2+ ion is coordinated by three histidine residues and a glutamate residue (E-76) in all three states. Upon binding, quercetin replaces one water ligand at Ni and is stabilized by a short hydrogen bond through E-76, the Carbonylate group of which rotates by 90 degrees. This conformational change weakens the interaction between Ni and the remaining water ligand, thereby preparing a coordination site at Ni to bind O-2. O-2 binds side-on to the Ni2+ ion and is perpendicular to the C2-C3 and C3-C4 bonds of quercetin, which are Cleaved in the following reaction steps.Quercetin 2,4-Dioxygenase Activates Dioxygen in a Side-On O-2-Ni Complexbiocatalysis; carbon monoxide; dioxygen Activation; dioxygenases; nickel superoxo complexes38201633#N/ATRUE
4477
anie.20150562510.1002/anie.201505625FALSEhttps://doi.org/10.1002/anie.201505625Zhou, HCAngew. Chem.-Int. Edit.Cooperative Cluster metalation and ligand migration were performed on a Zr-MOF, leading to the isolation of unique bimetallic MOFs based on decanuClear Zr6M4 (M=Ni, Co) Clusters. The M2+ reacts with the mu(3)-OH and terminal H2O ligands on an 8-connected [Zr6O4(OH)(8)(H2O)(4)] Cluster to form a bimetallic [Zr6M4O8(OH)(8)(H2O)(8)] Cluster. Along with the metalation of Zr-6 Cluster, ligand migration is observed in which a Zr-Carbonylate bond dissociates to form a M-Carbonylate bond. Single-crystal to single-crystal transformation is realized so that snapshots for cooperative Cluster metalation and ligand migration processes are captured by successive single-crystal X-ray structures. In3+ was metalated into the same Zr-MOF which showed excellent catalytic activity in the acetaldehyde cyClotrimerization reaction. This work not only provides a powerful tool to functionalize Zr-MOFs with other metals, but also structurally elucidates the formation mechanism of the resulting heterometallic MOFs.Cooperative Cluster Metalation and Ligand Migration in Zirconium Metal-Organic FrameworksCluster metalation; heterometallic MOFs; ligand migration; metal-organic frameworks; zirconiumx107201543#N/AFALSE
4478
anie.20151073410.1002/anie.201510734FALSEhttps://doi.org/10.1002/anie.201510734Matano, YAngew. Chem.-Int. Edit.The first examples of air-stable 20-electron 5,10,15,20-tetraAryl-5,15-diaza-5,15-dihydroporphyrins, their 18-electron dications, and the 19-electron radical cation were prepared through metal-templated annulation of nickel(II) bis(5-Arylamino-3-chloro-8-mesityldipyrrin) complexes followed by oxidation. The neutral 20-electron derivatives are antiaromatic and the cationic 18-electron derivatives are aromatic in terms of the magnetic criterion of aromaticity. The meso Natoms in these diazaporphyrinoids give rise to characteristic redox and optical properties for the compounds that are not typical of isoelectronic 5,10,15,20-tetraArylporphyrins.Redox-Switchable 20-, 19-, and 18-Electron 5,10,15,20-TetraAryl-5,15-diazaporphyrinoid Nickel(II) Complexesannulenes; aromaticity; heterocyClic compounds; porphyrinoids; redox chemistry41201633#N/ATRUE
4479
anie.20150533910.1002/anie.201505339FALSEhttps://doi.org/10.1002/anie.201505339Yu, LMAngew. Chem.-Int. Edit.The dissolution of platinum (Pt) has been one of the heart issues in developing advanced dye-sensitized solar cells (DSSCs). We present here the experimental realization of stable counter-electrode (CE) electrocatalysts by alloying Pt with transition metals for enhanced dissolution resistance to state-of-the-art iodide/triiodide (I-/I-3(-)) redox electrolyte. Our focus is placed on the systematic studies of dissolution engineering for PtM0.05 (M = Ni, Co, Fe, Pd, Mo, Cu, Cr, and Au) alloy CE electrocatalysts along with mechanism analysis from thermodynamical aspects, yielding more negative Gibbs free energies for the dissolution reactions of transition metals. The competitive reactions between transition metals with iodide species (I-3(-), I-2) could protect the Pt atoms from being dissolved by redox electrolyte and therefore remain the high catalytic activity of the Pt electrode.Dissolution Engineering of Platinum Alloy Counter Electrodes in Dye-Sensitized Solar Cellscatalytic activity; counter electrodes; dissolution resistance; dye-sensitized solar cells; electrocatalysisx135201522#N/AFALSE
4480
anie.20150523610.1002/anie.201505236FALSEhttps://doi.org/10.1002/anie.201505236Elbaz, LAngew. Chem.-Int. Edit.The future of affordable fuel cells strongly relies on the design of earth-abundant (non-platinum) catalysts for the electrochemical oxygen reduction reaction (ORR). However, the bottleneck in the overall process occurs therein. We have examined herein trivalent Mn, Fe, Co, Ni, and Cu complexes of beta-pyrrole-brominated corrole as ORR catalysts. The adsorption of these complexes on a high-surface-area carbon powder (BP2000) created a unique composite material, used for electrochemical measurements in acidic aqueous solutions. These experiments disClosed a Clear dependence of the catalytic activity on the metal center of the complexes, in the order of Co>Fe>Ni>Mn>Cu. The best catalytic performance was obtained for the Co-III corrole, whose onset potential was as positive as 0.81V versus the reversible hydrogen electrode (RHE). Insight into the properties of these systems was gained by spectroscopic and computational characterization of the reduced and oxidized forms of the metallocorroles.Metallocorroles as Nonprecious-Metal Catalysts for Oxygen Reductioncobalt; corroles; electrocatalysis; fuel cells; oxygen reduction reactionx91201547#N/AFALSE
4481
anie.20150513610.1002/anie.201505136FALSEhttps://doi.org/10.1002/anie.201505136Lipshutz, BHAngew. Chem.-Int. Edit.Nickel nanopartiCles, formed in situ and used in combination with micellar catalysis, catalyze Suzuki-Miyaura cross-couplings in water under very mild reaction conditions.Nanonickel-Catalyzed Suzuki-Miyaura Cross-Couplings in Watercross-couplings; green chemistry; micelles; nanopartiCles; nickelx61201533#N/AFALSE
4482
anie.20150496310.1002/anie.201504963https://doi.org/10.1002/anie.201504963Fensterbank, LAngew. Chem.-Int. Edit.This works introduces hypervalent bis-catecholato silicon compounds as versatile sources of Alkyl radicals upon visible-light photocatalysis. Using Ir[(dF(CF3)ppy)(2)(bpy)]-(PF6) (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine, bpy = bipyridine) as catalytic photooxidant, a series of Alkyl radicals, inCluding highly reactive primary ones can be generated and engaged in various intermolecular homolytic reactions. Based on cyClic voltammetry, Stern-Volmer studies, and supported by calculations, a mechanism involving a single-electron transfer from the silicate to the photoactivated iridium complex has been proposed. This oxidative photocatalyzed process can be efficiently merged with nickel-catalyzed C-sp2-C-sp3 cross-coupling reactions.Silicates as Latent Alkyl Radical Precursors: Visible-Light Photocatalytic Oxidation of Hypervalent Bis-Catecholato Silicon Compoundshypervalent compounds; oxidation; photocatalysis; radicals; silicatesPhotocatalyst154201561#N/AFALSE
4483
anie.20151040310.1002/anie.201510403FALSEhttps://doi.org/10.1002/anie.201510403Clark, KMAngew. Chem.-Int. Edit.To survey the noninnocence of bis(Arylimino) acenaphthene (BIAN) ligands (L) in complexes with early metals, the homoleptic vanadium complex, [V(L) 3] (1), and its monocation, [V(L) 3] PF6 (2), were synthesized. These complexes were found to have a very rich electronic behavior, whereby 1 displays strong electronic delocalization and 2 can be observed in unprecedented valence tautomeric forms. The oxidation states of the metal and ligand components in these complexes were assigned by using spectroscopic, crystallographic, and magnetic analyses. Complex 1 was identified as [V-IV(L-red)(L-center dot)(2)] (Lred = N, N'-bis(3,5-dimethylphenylamido)acenaphthylene; L-C= N, N'-bis(3,5-dimethylphenylimino) acenaphthenesemiquinonate). Complex 2 was determined to be [VV(Lred)(L-center dot)(2)]+ at T< 150K and [VIV(L-center dot)(3)]+ at T> 150 K. CyClic voltammetry experiments reveal six quasi-reversible processes, thus indicating the potential of this metal-ligand combination in catalysis or materials applications.Delocalization and Valence Tautomerism in Vanadium Tris(iminosemiquinone) Complexesmixed-valent compounds; noninnocent ligands; redox-active ligands; valence tautomerism; vanadium35201626#N/ATRUE
4484
anie.20150452410.1002/anie.201504524FALSEhttps://doi.org/10.1002/anie.201504524
Jacobi von Wangelin, A
Angew. Chem.-Int. Edit.Stable CO linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong CO bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 degrees C, 2h) with a ligand-free catalyst (1-2mol%).Iron-Catalyzed Cross-Coupling of Alkenyl Acetatesx83201564#N/AFALSE
4485
anie.20150446410.1002/anie.201504464FALSEhttps://doi.org/10.1002/anie.201504464Gates, DPPoly(p-phenylenediethynylene phosphane): A Phosphorus-Containing Macromolecule that Displays Blue Fluorescence Upon Oxidationx2015#N/AFALSE
4486
anie.20151000110.1002/anie.201510001FALSEhttps://doi.org/10.1002/anie.201510001Cao, RAngew. Chem.-Int. Edit.A nickel(II) porphyrin Ni-P (P=porphyrin) bearing four meso-C6F5 groups to improve solubility and activity was used to explore different hydrogen-evolution-reaction (HER) mechanisms. Doubly reduced Ni-P ([Ni-P](2-)) was involved in H-2 production from acetic acid, whereas a singly reduced species ([Ni-P](-)) initiated HER with stronger trifluoroacetic acid (TFA). High activity and stability of Ni-P were observed in catalysis, with a remarkable i(c)/i(p) value of 77 with TFA at a scan rate of 100 mVs(-1) and 20 degrees C. Electrochemical, stopped-flow, and theoretical studies indicated that a hydride species [H-Ni-P] is formed by oxidative protonation of [Ni-P](-). Subsequent rapid bimetallic homolysis to give H-2 and Ni-P is probably involved in the catalytic cyCle. HER cyCling through this one-electron-reduction and homolysis mechanism has been proposed previously but rarely validated. The present results could thus have broad implications for the design of new exquisite cyCles for H-2 generation.Singly versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen-Evolution Reactionbimetallic reactions; electrocatalysis; homolysis; hydrogen evolution; nickel porphyrins88201663#N/ATRUE
4487
anie.20150374910.1002/anie.201503749FALSEhttps://doi.org/10.1002/anie.201503749Qin, YAngew. Chem.-Int. Edit.To design highly efficient catalysts, new concepts for optimizing the metal-support interactions are desirable. Here we introduce a facile and general template approach assisted by atomic layer deposition (ALD), to fabricate a multiply confined Ni-based nanocatalyst. The Ni nanopartiCles are not only confined in Al2O3 nanotubes, but also embedded in the cavities of Al2O3 interior wall. The cavities create more Ni-Al2O3 interfacial sites, which facilitate hydrogenation reactions. The nanotubes inhibit the leaching and detachment of Ni nanopartiCles. Compared with the Ni-based catalyst supported on the outer surface of Al2O3 nanotubes, the multiply confined catalyst shows a striking improvement of catalytic activity and stability in hydrogenation reactions. Our ALD-assisted template method is general and can be extended for other multiply confined nanoreactors, which may have potential applications in many heterogeneous reactions.Multiply Confined Nickel Nanocatalysts Produced by Atomic Layer Deposition for Hydrogenation Reactionsatomic layer deposition; hydrogen spillover; hydrogenation reaction; interface; multiply confined catalystx74201537#N/AFALSE
4488
anie.20150893910.1002/anie.201508939FALSEhttps://doi.org/10.1002/anie.201508939Zhang, TRAngew. Chem.-Int. Edit.We report an effective and universal approach for the preparation of ultrathin single- or multiple-component transition-metal hydroxide (TMH) nanosheets with thickness below 5nm. The unique synthesis benefits from the gradual decomposition of the preformed metal-boron (M-B, M=Fe, Co, Ni, NiCo) composite nanospheres which facilitates the formation of ultrathin nanosheets by the oxidation of the metal and the simultaneous release of boron species. The high specific surface area of the sheets associated with their ultrathin nature promises a wide range of applications. For example, we demonstrate the remarkable adsorption ability of Pb-II and As-V in waste water by the ultrathin FeOOH nanosheets. More interestingly, the process can be extended simply to the synthesis of composite structures of metal alloy hollow shells encapsulated by TMH nanosheets, which show excellent catalytic activity in the Heck reaction.Controllable Synthesis of Ultrathin Transition-Metal Hydroxide Nanosheets and their Extended Composite Nanostructures for Enhanced Catalytic Activity in the Heck ReactionHeck reaction; nanostructures; transition-metal hydroxides; two-dimensional materials; nanosheets70201640#N/ATRUE
4489
anie.20150361210.1002/anie.201503612FALSEhttps://doi.org/10.1002/anie.201503612Cho, JAngew. Chem.-Int. Edit.The lack of high-efficient, low-cost, and durable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is currently one of the major obstaCles to commercializing the electrical rechargeability of zinc-air batteries. A nanocomposite CoO-NiO-NiCo bifunctional electrocatalyst supported by nitrogen-doped multiwall carbon nanotubes (NCNT/CoO-NiO-NiCo) exhibits excellent activity and stability for the ORR/OER in alkaline media. More importantly, real air cathodes made from the bifunctional NCNT/CoO-NiO-NiCo catalysts further demonstrated superior performance to state-of-the-art Pt/C or Pt/C+IrO2 catalysts in primary and rechargeable zinc-air batteries.Integrating NiCo Alloys with Their Oxides as Efficient Bifunctional Cathode Catalysts for Rechargeable Zinc-Air Batteriesbifunctional electrocatalysts; nickel-cobalt alloy; oxygen evolution reaction; oxygen reduction reaction; zinc-air batteriesx285201535#N/AFALSE
4490
anie.20150861310.1002/anie.201508613FALSEhttps://doi.org/10.1002/anie.201508613Guduru, PRThe Influence of Elastic Strain on Catalytic Activity in the Hydrogen Evolution Reaction2016#N/ATRUE
4491
anie.20150340710.1002/anie.201503407FALSEhttps://doi.org/10.1002/anie.201503407Sun, XPAngew. Chem.-Int. Edit.Active and stable electrocatalysts made from earth-abundant elements are key to water splitting for hydrogen production through electrolysis. The growth of NiSe nanowire film on nickel foam (NiSe/NF) insitu by hydrothermal treatment of NF using NaHSe as Se source is presented. When used as a 3D oxygen evolution electrode, the NiSe/NF exhibits high activity with an overpotential of 270mV required to achieve 20mAcm(-2) and strong durability in 1.0M KOH, and the NiOOH species formed at the NiSe surface serves as the actual catalytic site. The system is also highly efficient for catalyzing the hydrogen evolution reaction in basic media. This bifunctional electrode enables a high-performance alkaline water electrolyzer with 10mAcm(-2) at a cell voltage of 1.63V.NiSe Nanowire Film Supported on Nickel Foam: An Efficient and Stable 3D Bifunctional Electrode for Full Water Splittingbifunctional catalysts; nanowires; nickel; selenium; water splittingx1072201560#N/AFALSE
4492
anie.20150811310.1002/anie.201508113FALSEhttps://doi.org/10.1002/anie.201508113Fu, WFAngew. Chem.-Int. Edit.Ammonia-borane (AB) is a promising chemical hydrogen-storage material. However, the development of real-time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a challenge in the large-scale use of hydrogen as a long-term solution for future energy security. A new Class of low-cost catalytic system is presented that uses nanostructured Ni2P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia-borane with the initial turnover frequency of 40.4 mol((H2)) mol((Ni2P))(-1) min(-1) under air atmosphere and at ambient temperature. This value is higher than those reported for noble-metal-free catalysts, and the obtained Arrhenius Activation energy (E-a = 44.6 kJmol(-1)) for the hydrolysis reaction is comparable to Ru-based bimetallic catalysts. A Clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented.Nanostructured Ni2P as a Robust Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Boraneammonia-borane; heterogeneous catalysis; hydrogen storage; nickel phosphide; reaction mechanisms135201558#N/ATRUE
4493
anie.20150782210.1002/anie.201507822FALSEhttps://doi.org/10.1002/anie.201710582Osuka, ASynthesis of [n] CyClo-5,15-porphyrinylene-4,4'-biphenylenes Displaying Size-Dependent Excitation-Energy Hopping2015#N/ATRUE
4494
anie.20150320710.1002/anie.201503207FALSEhttps://doi.org/10.1002/anie.201503207Liu, XYAngew. Chem.-Int. Edit.The first Ni-0/bis(oxazoline)-catalyzed asymmetric denitrogenative transannulation of 1,2,3-benzotriazin-4(3H)-ones with bulky internal alkynes to form novel axially chiral isoquinolones in an atroposelective manner has been developed. This method provides direct asymmetric access to axially chiral isoquinolones with excellent functional-group tolerance in excellent yields and stereoselectivities from readily available starting materials under mild reaction conditions. These axially chiral isoquinolones exhibit high cytotoxicity against a number of human cancer cell lines. DFT calculations reveal the nature of the transition state in the key annulation step.Asymmetric Synthesis of Axially Chiral Isoquinolones: Nickel-Catalyzed Denitrogenative Transannulationannulations; chirality; density functional calculations; heterocyCles; nickelx51201580#N/AFALSE
4495
anie.20150727310.1002/anie.201507273FALSEhttps://doi.org/10.1002/anie.201507273Liu, HAngew. Chem.-Int. Edit.Structurally simple and inexpensive chiral tridentate ligands were employed for substantially advancing the purely chemical dynamic kinetic resolution (DKR) of unprotected racemic tailor-made -amino acids (TM--AAs), enabling the first DKR of TM--AAs bearing tertiary Alkyl chains as well as multiple unprotected functional groups. Owing to the operationally convenient conditions, virtually complete stereoselectivity, and full recyClability of the source of chirality, this method should find wide applications for the preparation of TM--AAs, especially on large scale.RecyClable Ligands for the Non-Enzymatic Dynamic Kinetic Resolution of Challenging -Amino Acidsamino acids; enantioselectivity; kinetic resolution; N ligands; nickel48201579#N/ATRUE
4496
anie.20150647510.1002/anie.201506475FALSEhttps://doi.org/10.1002/anie.201506475Krossing, IAngew. Chem.-Int. Edit.The straightforward synthesis of the cationic, purely organometallic Ni-I salt [Ni(cod)(2)](+)[Al(ORF)(4)] was realized through a reaction between [Ni(cod)(2)] and Ag[Al(ORF)(4)] (cod= 1,5-cyClooctadiene). Crystal-structure analysis and EPR, XANES, and cyClic voltammetry studies confirmed the presence of a homoleptic Ni-I olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic Ni-I complexes.[Ni(cod)(2)][Al(ORF)(4)], a Source for Naked Nickel(I) Chemistrycrystallography; cyClic voltammetry; density functional calculations; electron paramagnetic resonance; nickel(I) complexes25201593#N/ATRUE
4497
anie.20150273010.1002/anie.201502730FALSEhttps://doi.org/10.1002/anie.201502730Winpenny, REPAngew. Chem.-Int. Edit.An enormous family of heterometallic rings has been made. The first were Cr7M rings where M = Ni-II, Zn-II, Mn-II, and rings have been made with as many as fourteen metal centers in the cyClic structure. They are bridged externally by Carbonylates, and internally by fluorides or a penta-deprotonated polyol. The size of the rings is controlled through templates which have inCluded a range of ammonium or imidazolium ions, alkali metals and coordination compounds. The rings can be functionalized to act as ligands, and incorporated into hybrid organic-inorganic rotaxanes and into molecules containing up to 200 metal centers. Physical studies reported inClude: magnetic measurements, inelastic neutron scattering (inCluding single crystal measurements), electron paramagnetic resonance spectroscopy (inCluding measurements of phase memory times), NMR spectroscopy (both solution and solid state), and polarized neutron diffraction. The rings are hence ideal for understanding magnetism in elegant exchange-coupled systems.Heterometallic Rings: Their Physics and use as Supramolecular Building BlocksCarbonylate Clusters; heterometallic rings; metallocyCles; molecular magnets; supramolecular chemistryx622015107#N/AFALSE
4498
anie.20150593710.1002/anie.201505937FALSEhttps://doi.org/10.1002/anie.201505937Deng, LAngew. Chem.-Int. Edit.The synthesis, structural characterization, and reactivity of the first two-coordinate cobalt complex featuring a metal-element multiple bond [(IPr)Co(NDmp)] (4; IPr=1,3-bis(2',6'-diisopropylphenyl)imidazole-2-ylidene; Dmp=2,6-dimesitylphenyl) is reported. Complex 4 was prepared from the reaction of [(IPr)Co(eta(2)-vtms)(2)] (vtms=Vinyltrimethylsilane) with DmpN(3). An X-ray diffraction study revealed its linear C-Co-N core and a short Co-N distance (1.691(6) angstrom). Spectroscopic characterization and calculation studies indicated the high-spin nature of 4 and the multiplebond character of the Co-N bond. Complex 4 effected group-transfer reactions to CO and ethylene to form isocyanide and imine, respectively. It also facilitated E-H (E=C, Si) sigma-bond Activation of terminal alkyne and hydrosilanes to produce the corresponding cobalt(II) alkynyl and cobalt(II) hydride complexes as 1,2-addition products.A Two-Coordinate Cobalt(II) Imido Complex with NHC Ligation: Synthesis, Structure, and Reactivitycarbene ligands; cobalt; multiple bonds; N ligands; structure elucidation53201566#N/ATRUE
4499
anie.20150569910.1002/anie.201505699FALSEhttps://doi.org/10.1002/anie.201505699Vinyard, DJAngew. Chem.-Int. Edit.Ni-based precatalysts for the Suzuki-Miyaura reaction have potential chemical and economic advantages compared to commonly used Pd systems. Here, we compare Ni precatalysts for the Suzuki-Miyaura reaction supported by the dppf ligand in 3 oxidation states, 0, I and II. Surprisingly, at 80 degrees C they give similar catalytic activity, with all systems generating significant amounts of Ni-I during the reaction. At room temperature a readily accessible bench-stable Ni-II precatalyst is highly active and can couple synthetically important heterocyClic substrates. Our work conClusively establishes that Ni-I species are relevant in reactions typically proposed to involve exClusively Ni-0 and Ni-II complexes.Comparison of dppf-Supported Nickel Precatalysts for the Suzuki-Miyaura Reaction: The Observation and Activity of Nickel(I)cross-coupling; homogeneous catalysis; nickel; reaction mechanism; Suzuki-Miyaura coupling62201559#N/ATRUE
4500
anie.20150257710.1002/anie.201502577FALSEhttps://doi.org/10.1002/anie.201502577Liu, LFAngew. Chem.-Int. Edit.Nickel phosphide is an emerging low-cost, earth-abundant catalyst that can efficiently reduce water to generate hydrogen. However, the synthesis of nickel phosphide catalysts usually involves multiple steps and is laborious. Herein, a convenient and straightforward approach to the synthesis of a three-dimensional (3D) self-supported biphasic Ni5P4-Ni2P nanosheet (NS) array cathode is presented, which is obtained by direct phosphorization of commercially available nickel foam using phosphorus vapor. The synthesized 3D Ni5P4-Ni2P-NS array cathode exhibits outstanding electrocatalytic activity and long-term durability toward the hydrogen evolution reaction (HER) in acidic medium. The fabrication procedure reported here is scalable, showing substantial promise for use in water electrolysis. More importantly, the approach can be readily extended to synthesize other self-supported transition metal phosphide HER cathodes.One-Step Synthesis of Self-Supported Nickel Phosphide Nanosheet Array Cathodes for Efficient Electrocatalytic Hydrogen Generationelectrocatalysis; heterogeneous catalysis; hydrogen evolution; nanostructures; nickel phosphidex407201558#N/AFALSE
4501
anie.20150551810.1002/anie.201505518https://doi.org/10.1002/anie.201505518Power, PPAngew. Chem.-Int. Edit.The characterization of the unstable Ni-II bis(silylamide) Ni{N(SiMe3)(2)}(2) (1), its THF complex Ni{N(SiMe3)(2)}(2)(THF) (2), and the stable bis(pyridine) derivative trans-Ni{N(SiMe3)(2)}(2)(py)(2) (3), is described. Both 1 and 2 decompose at ca. 25 degrees C to a tetrameric Ni-I species, [Ni{N(SiMe3)(2)}](4) (4), also obtainable from LiN(SiMe3)(2) and NiCl2(DME). Experimental and computational data indicate that the instability of 1 is likely due to ease of reduction of Ni-II to Ni-I and the stabilization of 4 through dispersion forces.The Instability of Ni{N(SiMe3)(2)}(2): A Fifty Year Old Transition Metal Silylamide Mysterydispersion effects; magnetism; nickel; silylamide; steric effects21201541#N/ATRUE
4502
anie.20150481510.1002/anie.201504815FALSEhttps://doi.org/10.1002/anie.201504815Dai, HJAngew. Chem.-Int. Edit.The rising H-2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15% for light-driven water splitting using GaAs solar cells.Blending Cr2O3 into a NiO-Ni Electrocatalyst for Sustained Water Splittingchromium oxide; electrocatalysts; hydrogen-evolution reaction; sustainable chemistry; water splitting116201530#N/ATRUE
4503
anie.20150243810.1002/anie.201502438FALSEhttps://doi.org/10.1002/anie.201502438Shalom, MThe Synthesis of Nanostructured Ni5P4 Films and their Use as a Non-Noble Bifunctional Electrocatalyst for Full Water Splittingx2015#N/AFALSE
4504
anie.20150236410.1002/anie.201502364FALSEhttps://doi.org/10.1002/anie.201502364Rudiger, OAngew. Chem.-Int. Edit.The active site of hydrogenases has been a source of inspiration for the development of molecular catalysts. However, direct comparisons between molecular catalysts and enzymes have not been possible because different techniques are used to evaluate both types of catalysts, minimizing our ability to determine how far we have come in mimicking the enzymatic performance. The catalytic properties of the [Ni((P2N2Gly)-N-Cy)(2)](2+) complex with the [NiFe]-hydrogenase from Desulfovibrio vulgaris immobilized on a functionalized electrode were compared under identical conditions. At pH 7, the enzyme shows higher activity and lower overpotential with better stability, while at low pH, the molecular catalyst outperforms the enzyme in all respects. This is the first direct comparison of enzymes and molecular complexes, enabling a unique understanding of the benefits and detriments of both systems, and advancing our understanding of the utilization of these bio-inspired complexes in fuel cells.Direct Comparison of the Performance of a Bio-inspired Synthetic Nickel Catalyst and a [NiFe]-Hydrogenase, Both Covalently Attached to Electrodesenzyme catalysis; hydrogen oxidation; hydrogenases; molecular catalysis; surface-immobilized catalysisx47201536#N/AFALSE
4505
anie.20150406510.1002/anie.201504065FALSEhttps://doi.org/10.1002/anie.201504065Porschke, KROrganonickel(IV) Chemistry: A New Catalyst?2015#N/ATRUE
4506
anie.20150190810.1002/anie.201501908https://doi.org/10.1002/anie.201501908MacMillan, DWCMerging Photoredox and Nickel Catalysis: The Direct Synthesis of Ketones by the DeCarbonylative Arylation of -Oxo AcidsPhotocatalyst2015#N/AFALSE
4507
anie.20150370810.1002/anie.201503708https://doi.org/10.1002/anie.201503708Chen, ClAngew. Chem.-Int. Edit.A series of sterically demanding alpha-diimine ligands bearing electron-donating and electron-withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, inCluding high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow-chain-walking activity of these Pd complexes.Highly Robust Palladium(II) alpha-Diimine Catalysts for Slow-Chain-Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylatechain-walking polymerization; copolymerization; diimine ligands; palladium catalysis; polar monomers231201554#N/ATRUE
4508
anie.20150346110.1002/anie.201503461FALSEhttps://doi.org/10.1002/anie.201503461Martin, RAngew. Chem.-Int. Edit.The first catalytic intermolecular proximal C1C2 Cleavage of benzocyClobutenones (BCB) without prior Carbonyl Activation or employing noble metals has been developed. This protocol operates at room temperature and is characterized by an exquisite chemo-, regio- and diastereoselectivity profile, constituting a unique platform for preparing an array of elusive carbocyClic skeletons.Nickel-Catalyzed Chemo-, Regio- and Diastereoselective Bond Formation through Proximal C-C Cleavage of BenzocyClobutenonesbenzocyClobutenones; C-C Activation; nickel catalysis; ring strain63201573#N/ATRUE
4509
anie.20150159210.1002/anie.201501592FALSEhttps://doi.org/10.1002/anie.201501592Osuka, AAngew. Chem.-Int. Edit.Treatment of meso-chlorosubporphyrin with potassium hydroxide in DMSO followed by aqueous work up and recrystallization gave a cyClic trimer consisting of meso-hydroxysubporphyrin units linked between the central boron atoms and meso-hydroxy groups. Solutions of this trimer are nonfluorescent, but become fluorescent when exposed to acid or base, since hydrolytic Cleavage of the axial BO bonds generates the meso-hydroxysubporphyrin monomer or its oxyanion. Ring Cleavage of the trimer was also effected by reaction with phenylmagnesium bromide to produce meso-hydroxy-B-phenyl subporphyrin, which can be quantitatively oxidized with PbO2 to furnish a subporphyrin meso-oxy radical as a remarkably stable species as a result of spin delocalization over almost the entire molecule.meso-Hydroxysubporphyrins: A CyClic Trimeric Assembly and a Stable meso-Oxy Radicalboron; porphyrinoids; radicals; self-assembly; subporphyrinx37201548#N/AFALSE
4510
anie.20150143710.1002/anie.201501437https://doi.org/10.1002/anie.201501437van der Vlugt, JIAngew. Chem.-Int. Edit.Photochemical Activation of nickel-azido complex 2 [Ni(N-3)(PNP)] ((PNP)-P-H= 2,2'-di(isopropylphosphino)-4,4'-ditolylamine) in neat benzene produces diamagnetic complex 3 [Ni(Ph)((PNNH)-N-P)], which is crystallographically characterized. DFT calculations support photoinitiated N-2-loss of the azido complex to generate a rare, transient Ni-IV nitrido species, which bears significant nitridyl radical character. Subsequent trapping of this nitrido through insertion into the Ni - P bond generates a coordinatively unsaturated NiII imidophosphorane P= N donor. This species shows unprecedented reactivity toward 1,2-addition of a C-H bond of benzene to form 3. The structurally characterized chlorido complex 4 [Ni(Cl)-((PNNH)-N-P)] is generated by reaction of 3 with HCl or by direct photolysis of 2 in chlorobenzene. This is the first report of aromatic C-H bond Activation by a trapped transient nitrido species of a late transition metal.C-H Activation of Benzene by a Photoactivated Ni-II(azide): Formation of a Transient Nickel Nitrido Complexazides; C-H Activation; iminophosphoranes; nickel; nitridyl radicalPhotocatalyst40201549#N/AFALSE
4511
anie.20150104910.1002/anie.201501049FALSEhttps://doi.org/10.1002/anie.201501049Alexandrova, ANAngew. Chem.-Int. Edit.Surface carbides of cobalt and nickel are exceptionally stable, having stabilities competitive with those of graphitic C on these surfaces. The unusual structure of these carbides has attracted much attention: C assumes a tetracoordinate squareplanar arrangement, in-plane with the metal surface, and its binding favors a spontaneous p4g Clock surface reconstruction. A chemical bonding model for these systems is presented and explains the unusual structure, special stability, and the reconstruction. C promotes local two-dimensional aromaticity on the surface and the aromatic arrangement is so powerful that the required number of electrons is taken from the voidM4 squares, thus leading to Peierls instability. Moreover, this model predicts a series of new transition-metal and maingroup- element surface alloys: carbides, borides, and nitrides, which feature high stability, square-planar coordination, aromaticity, and a predictable degree of surface reconstruction.Origin of Extraordinary Stability of Square-Planar Carbon Atoms in Surface Carbides of Cobalt and Nickelalloys; aromaticity; bond energy; cobalt; density functional calculationsx41201554#N/AFALSE
4512
anie.20150329710.1002/anie.201503297FALSEhttps://doi.org/10.1002/anie.201503297Fu, GCAngew. Chem.-Int. Edit.Fluorinated organic molecules are of interest in fields ranging from medicinal chemistry to polymer science. Described herein is a mild, convenient, and versatile method for the synthesis of compounds bearing a perfluoroAlkyl group attached to a tertiary carbon atom by using an Alkyl-Alkyl cross-coupling. A nickel catalyst derived from NiCl(2)glyme and a pybox ligand achieves the coupling of a wide range of fluorinated Alkyl halides with Alkylzinc reagents at room temperature. A broad array of functional groups is compatible with the reaction conditions, and highly selective couplings can be achieved on the basis of differing levels of fluorination. A mechanistic investigation has established that the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) inhibits cross-coupling under these conditions and that a TEMPO-electrophile adduct can be isolated.Nickel-Catalyzed Alkyl-Alkyl Cross-Couplings of Fluorinated Secondary Electrophiles: A General Approach to the Synthesis of Compounds having a PerfluoroAlkyl Substituentcross-coupling; fluorine; homogeneous catalysis; nickel; zinc34201553#N/ATRUE
4513
anie.20150045310.1002/anie.201500453FALSEhttps://doi.org/10.1002/anie.201500453Roesler, RAngew. Chem.-Int. Edit.A Ni-0-NCN pincer complex featuring a six-membered N-heterocyClic carbene (NHC) central platform and amidine pendant arms was synthesized by deprotonation of its Ni-II precursor. It retained chloride in the square-planar coordination sphere of nickel and was expected to be highly susceptible to oxidative addition reactions. The Ni-0 complex rapidly activated ammonia at room temperature, in a ligand-assisted process where the carbene carbon atom played the unprecedented role of proton acceptor. For the first time, the coordinated (ammine) and activated (amido) species were observed together in solution, in a solvent-dependent equilibrium. A structural analysis of the Ni complexes provided insight into the highly unusual, non-innocent behavior of the NHC ligand.Ammonia Activation by a Nickel NCN-Pincer Complex featuring a Non-Innocent N-HeterocyClic Carbene: Ammine and Amido Complexes in Equilibriumammonia; bond Activation; N-heterocyClic carbenes; nickel; Nligandsx42201555#N/AFALSE
4514
anie.20150328810.1002/anie.201503288FALSEhttps://doi.org/10.1002/anie.201503288Kambe, NAngew. Chem.-Int. Edit.Copper complexes generated insitu from CuCl2, Alkyl Grignard reagents, and 1,3-dienes play important roles as catalytic active species for the 1,2-hydroAlkylation of 1,3-dienes by Alkyl fluorides through CF bond Cleavage. The Alkyl group is introduced to an internal carbon atom of the 1,3-diene regioselectively, thus giving rise to the branched terminal alkene product.Copper-Catalyzed Regioselective HydroAlkylation of 1,3-Dienes with Alkyl Fluorides and Grignard Reagents36201556#N/ATRUE
4515
anie.20150320410.1002/anie.201503204FALSEhttps://doi.org/10.1002/anie.201503204Han, LBAngew. Chem.-Int. Edit.Nickel-Catalyzed CO/CH Cross-Coupling Reactions for CC Bond Formationasymmetric catalysis; CH Activation; CO Activation; cross-coupling; nickel catalysis18201525#N/ATRUE
4516
anie.20150288210.1002/anie.201502882FALSEhttps://doi.org/10.1002/anie.201502882Zhang, XGAngew. Chem.-Int. Edit.The nickel-catalyzed fluoromethylation of Arylboronic acids was achieved with the industrial raw material fluoromethyl bromide (CH2FBr) as the coupling partner. The reaction proceeded under mild reaction conditions with high efficiency; it features the use of a low-cost nickel catalyst, synthetic simplicity, and excellent functional-group compatibility, and provides facile access to fluoromethylated biologically relevant molecules. Preliminary mechanistic studies showed that a single-electron-transfer (SET) pathway is involved in the catalytic cyCle.Facile Access to Fluoromethylated Arenes by Nickel-Catalyzed Cross-Coupling between Arylboronic Acids and Fluoromethyl BromideArylboronic acids; cross-coupling; fluoromethylation; fluoromethylbromide; nickel60201554#N/ATRUE
4517
anie.20150266610.1002/anie.201502666FALSEhttps://doi.org/10.1002/anie.201502666Shinokubo, HAngew. Chem.-Int. Edit.Treatment of antiaromatic nickel(II) norcorrole with potassium cyanide provided nickel(II) 3-cyanonorcorrole with perfect regioselectivity without the help of a catalyst. The reaction of the nickel(II) norcorrole with phenol or thiophenol in the presence of a base also yielded substitution products. The antiaromatic 16 pi conjugation system in the norcorrole core was preserved in the functionalized products. Introduction of phenylthio groups significantly decreased the HOMO-LUMO gap and enhanced the near IR absorption property.Regioselective NuCleophilic Functionalization of Antiaromatic Nickel(II) Norcorrolesaromaticity; electrophilic substitution; nickel; porphyrinoids; X-ray diffraction32201547#N/ATRUE
4518
anie.20150264410.1002/anie.201502644FALSEhttps://doi.org/10.1002/anie.201502644Drew, SCAngew. Chem.-Int. Edit.Accumulation of the -amyloid (A) peptide in extracellular senile plaques rich in copper and zinc is a defining pathological feature of Alzheimers disease (AD). The A1-x (x=16/28/40/42) peptides have been the primary focus of Cu-II binding studies for more than 15years; however, the N-truncated A4-42 peptide is a major A isoform detected in both healthy and diseased brains, and it contains a novel N-terminal FRH sequence. Proteins with His at the third position are known to bind Cu-II avidly, with conditional logK values at pH7.4 in the range of 11.0-14.6, which is much higher than that determined for A1-x peptides. By using A4-16 as a model, it was demonstrated that its FRH sequence stoichiometrically binds Cu-II with a conditional K-d value of 3x10(-14)M at pH7.4, and that both A4-16 and A4-42 possess negligible redox activity. Combined with the predominance of A4-42 in the brain, our results suggest a physiological role for this isoform in metal homeostasis within the central nervous system.A Functional Role for A in Metal Homeostasis? N-Truncation and High-Affinity Copper BindingAlzheimer's disease; amyloid; bioinorganic chemistry; copper; peptides67201528#N/ATRUE
4519
anie.20141168510.1002/anie.201411685FALSEhttps://doi.org/10.1002/anie.201411685Fellinger, TPAngew. Chem.-Int. Edit.A combination of ionothermal synthesis and hot-injection techniques leads to novel nanocarbons made from organic solvents. Controlled addition of commonly used organic solvents into a hot ZnX2 melt gives rise to spherical, sheetlike, and branched nanofibrous carbon nanopartiCles with surprisingly high carbon efficiency. When heteroatom-containing solvents were used, the doping levels reach up to 14 wt.% nitrogen and 13 wt.% sulfur. Materials with high surface areas and large pore volumes of solvent carbons as high as 1666 m(2)g(-1) and 2.80 cm(3) g(-1) in addition to CO2 adsorption capacities of 4.13 mmol g(-1) at 273K and 1 bar can be obtained. The new method works not only for pure carbon materials, but was also extended for the synthesis of carbon/inorganic nanocomposites. ZnS@C, Ni@C, and Co@C were successfully prepared with this straightforward procedure. The obtained Ni@C nanocomposites perform well in the electrocatalytic water oxidation, comparable with commercial noble-metal catalysts.Synthesis of Nanostructured Carbon through Ionothermal Carbonization of Common Organic Solvents and Solutionscarbon nanostructures; composite materials; electrocatalysts; hot injection; ionothermal synthesisx47201545#N/AFALSE
4520
anie.20150252910.1002/anie.201502529FALSEhttps://doi.org/10.1002/anie.201502529Limberg, CAngew. Chem.-Int. Edit.The hitherto most realistic low-molecular-weight analogue for the 1-aminocyClopropane-1-Carbonylic acid oxidase (ACCO) is reported. The ACCOs 2-His-1-Carbonylate iron(II) active site was mimicked by a TpFe moiety, to which the natural substrate ACC could be bound. The resulting complex [Tp(Me,Ph)FeACC] (1), according to X-ray diffraction analysis performed for the nickel analogue, represents an excellent structural model, featuring ACC coordinated in a bidentate fashion-as proposed for the enzymatic substrate complex-as well as a vacant coordination site that forms the basis for the first successful replication also of the ACCO function: 1 is the first known ACC complex that reacts with O-2 to produce ethylene. As a FeOOH species had been suggested as intermediate in the catalytic cyCle, H2O2 was tested as the oxidant, too, and indeed evolution of ethylene proceeded even more rapidly to give 65% yield.A Structural and Functional Model for the 1-AminocyClopropane-1-Carbonylic Acid OxidaseaminocyClopropane-1-Carbonylic acid; enzyme models; iron; oxidase; oxygen10201548#N/ATRUE
4521
anie.20150250210.1002/anie.201502502FALSEhttps://doi.org/10.1002/anie.201502502Xie, ZWAngew. Chem.-Int. Edit.A nickel-catalyzed Arylation at the carbon center of o-carborane cages has been developed, thus leading to the preparation of a series of 1-Aryl-o-carboranes and 1,2-diAryl-o-carboranes in high yields upon isolation. This method represents the first example of transition metal catalyzed C,C-diArylation by cross-coupling reactions of o-carboranyl with Aryl iodides.Nickel-Catalyzed Cross-Coupling Reactions of o-Carboranyl with Aryl Iodides: Facile Synthesis of 1-Aryl-o-Carboranes and 1,2-DiAryl-o-CarboranesArylation; CC formation; cross-coupling; homogeneous catalysis; nickel38201562#N/ATRUE
4522
anie.20150228510.1002/anie.201502285FALSEhttps://doi.org/10.1002/anie.201502285Furuta, HAngew. Chem.-Int. Edit.A contracted doubly N-confused dioxohexaphyrin derivative served as a dinuCleating metal ligand for unsymmetrical coordination. The complexation of two palladium(II) cations led to the formation of pi-radical species that were persistent in atmospheric air in the presence of moisture. Effective delocalization of an unpaired electron over the hexaphyrin backbone could contribute to the distinct chemical stability.Stable pi Radical from a Contracted Doubly N-Confused Hexaphyrin by Double Palladium Metalation37201537#N/ATRUE
4523
anie.20150177810.1002/anie.201501778FALSEhttps://doi.org/10.1002/anie.201501778Dobbek, HAngew. Chem.-Int. Edit.Ni, Fe-containing CO dehydrogenases (CODHs) use a [NiFe4S4] Cluster, termed Cluster C, to reversibly reduce CO2 to CO with high turnover number. Binding to Ni and Fe activates CO2, but current crystal structures have insufficient resolution to analyze the geometry of bound CO2 and reveal the extent and nature of its Activation. The crystal structures of CODH in complex with CO2 and the isoelectronic inhibitor NCO- are reported at true atomic resolution (d(min) <= 1.1 angstrom). Like CO2, NCO- is a mu(2), eta(2) ligand of the Cluster and acts as a mechanism-based inhibitor. While bound CO2 has the geometry of a Carbonylate group, NCO- is transformed into a carbamoyl group, thus indicating that both molecules undergo a formal two-electron reduction after binding and are stabilized by substantial pi backbonding. The structures reveal the combination of stable mu(2), eta(2) coordination by Ni and Fe2 with reductive Activation as the basis for both the turnover of CO2 and inhibition by NCO-.How the [NiFe4S4] Cluster of CO Dehydrogenase Activates CO2 and NCO-biocatalysis; carbon dioxide; CO dehydrogenase; cyanate; reductive Activation59201538#N/ATRUE
4524
anie.20141085710.1002/anie.201410857FALSEhttps://doi.org/10.1002/anie.201410857Shang, DJAngew. Chem.-Int. Edit.The development of the stereoselective rhodium-catalyzed [(3+2)+2] carbocyClization of alkynylidenecyClopropanes (ACPs) with substituted allenes is described. This work demonstrates that activated and unactivated allenes preferentially undergo carbometalation at the distal terminus to generate tri- and tetrasubstituted exocyClic olefins with a neutral rhodium catalyst. In addition, this method provides a strategy for the total synthesis of the guaiane family of sesquiterpenes, which are not directly accessible using alkynes as exogenous -components. Finally, the preparation of the bicyClo[5.4.0]undecane ring system using a homologated ACP tether serves to further illustrate the versatility of this approach.Rhodium-Catalyzed [(3+2)+2] CarbocyClization of AlkynylidenecyClopropanes with Substituted Allenes: Stereoselective Construction of Tri- and Tetrasubstituted ExocyClic Olefinsx31201538#N/AFALSE
4525
anie.20141070010.1002/anie.201410700FALSEhttps://doi.org/10.1002/anie.201410700Tang, WJAngew. Chem.-Int. Edit.The first asymmetric nickel-catalyzed intramolecular reductive cyClization of alkynones is reported. A P-chiral monophosphine and triethylsilane were used as the ligand and the reducing reagent, respectively, to form a series of tertiary allylic alcohols bearing furan/pyran rings in excellent yields and enantioselectivities. This reaction has a broad substrate scope and enabled the efficient synthesis of dehydroxycubebin and chiral dibenzocyClooctadiene skeletons.Highly Enantioselective Nickel-Catalyzed Intramolecular Reductive CyClization of Alkynonesalkynones; asymmetric catalysis; cyClization; nickel; Pligandsx45201584#N/AFALSE
4526
anie.20141069710.1002/anie.201410697FALSEhttps://doi.org/10.1002/anie.201410697
Ganduglia-Pirovano, MV
Angew. Chem.-Int. Edit.Water dissociation is crucial in many catalytic reactions on oxide-supported transition-metal catalysts. Supported by experimental and density-functional theory results, the effect of the support on O-H bond Cleavage activity is elucidated for nickel/ceria systems. Ambient-pressure O1s photoemission spectra at low Ni loadings on CeO2(111) reveal a substantially larger amount of OH groups as compared to the bare support. Computed Activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO2(111) compared with pyramidal Ni-4 partiCles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of this support effect is the ability of ceria to stabilize oxidized Ni2+ species by accommodating electrons in localized f-states. The fast dissociation of water on Ni/CeO2 has a dramatic effect on the activity and stability of this system as a catalyst for the water-gas shift and ethanol steam reforming reactions.In Situ and Theoretical Studies for the Dissociation of Water on an Active Ni/CeO2 Catalyst: Importance of Strong Metal-Support Interactions for the Cleavage of O-H Bondsceria; density functional calculations; nickel; water dissociation; X-ray photoelectron spectroscopyx133201536#N/AFALSE
4527
anie.20141067510.1002/anie.201410675FALSEhttps://doi.org/10.1002/anie.201410675Backvall, JEAngew. Chem.-Int. Edit.A method for determining lipase enantioselectivity in the transacylation of sec-alcohols in organic solvent was developed. The method was applied to a model library of Candida antarctica lipase A (CalA) variants for improved enantioselectivity (E values) in the kinetic resolution of 1-phenylethanol in isooctane. A focused combinatorial gene library simultaneously targeting seven positions in the enzyme active site was designed. Enzyme variants were immobilized on nickel-coated 96-well microtiter plates through a histidine tag (His(6)-tag), screened for transacylation of 1-phenylethanol in isooctane, and analyzed by GC. The highest enantioselectivity was shown by the double mutant Y93L/L367I. This enzyme variant gave an E value of 100 (R), which is a dramatic improvement on the wild-type CalA (E=3). This variant also showed high to excellent enantioselectivity for other secondary alcohols tested.Combinatorial Library Based Engineering of Candida antarctica Lipase A for Enantioselective Transacylation of sec-Alcohols in Organic Solventbiocatalysis; kinetic resolution; lipase A; protein engineering; secondary alcoholsx27201556#N/AFALSE
4528
anie.20141066810.1002/anie.201410668FALSEhttps://doi.org/10.1002/anie.201410668Yu, SHAngew. Chem.-Int. Edit.Resorcinol-formaldehyde (RF) and graphene oxide (GO) aerogels have found a variety of applications owing to their excellent properties and remarkable flexibility. However, the macroscopic and controllable synthesis of their composite gels is still a great challenge. By using GO sheets as template skeletons and metal ions (Co2+, Ni2+, or Ca2+) as catalysts and linkers, the first low-temperature scalable strategy for the synthesis of a new kind of RF-GO composite gel with tunable densities and mechanical properties was developed. The aerogels can tolerate a strain as high as 80% and quickly recover their original morphology after the compression has been released. Owing to their high compressibility, the gels might find applications in various areas, for example, as adsorbents for the removal of dye pollutants and in oil-spill Cleanup.Scalable Template Synthesis of Resorcinol-Formaldehyde/Graphene Oxide Composite Aerogels with Tunable Densities and Mechanical Propertiesaerogels; compressibility; graphene oxide; resorcinolx99201546#N/AFALSE
4529
anie.20141056910.1002/anie.201410569https://doi.org/10.1002/anie.201410569Hu, XLAngew. Chem.-Int. Edit.The splitting of water into hydrogen and oxygen molecules using sunlight is an attractive method for solar energy storage. Until now, photoelectrochemical hydrogen evolution is mostly studied in acidic solutions, in which the hydrogen evolution is more facile than in alkaline solutions. Herein, we report photoelectrochemical hydrogen production in alkaline solutions, which are more favorable than acidic solutions for the complementary oxygen evolution half-reaction. We show for the first time that amorphous molybdenum sulfide is a highly active hydrogen evolution catalyst in basic medium. The amorphous molybdenum sulfide catalyst and a Ni-Mo catalyst are then deposited on surface-protected cuprous oxide photocathodes to catalyze sunlight-driven hydrogen production in 1M KOH. The photocathodes give photocurrents of -6.3mAcm(-2) at the reversible hydrogen evolution potential, the highest yet reported for a metal oxide photocathode using an earth-abundant hydrogen evolution reaction catalyst.Photoelectrochemical Hydrogen Production in Alkaline Solutions Using Cu2O Coated with Earth-Abundant Hydrogen Evolution Catalystscuprous oxide; hydrogen evolution; photocatalysis; photoelectrochemistry; water splittingPhotocatalyst161201529#N/AFALSE
4530
anie.20150169110.1002/anie.201501691FALSEhttps://doi.org/10.1002/anie.201501691Pardo, EAngew. Chem.-Int. Edit.A single crystal to single crystal transmetallation process takes place in the three-dimensional (3D) metal-organic framework (MOF) of formula Mg-2(II){Mg-4(II)[Cu-2(II)(Me(3)mpba)(2)](3)}45H(2)O (1; Me(3)mpba(4-)=N,N-2,4,6-trimethyl-1,3-phenylenebis(oxamate)). After complete replacement of the Mg-II ions within the coordination network and those hosted in the channels by either Co-II or Ni-II ions, 1 is transmetallated to yield two novel MOFs of formulae Co-2(II){Co-4(II)[Cu-2(II)(Me(3)mpba)(2)](3)}56H(2)O (2) and Ni-2(II){Ni-4(II)[Cu-2(II)(Me(3)mpba)(2)](3)} 54H(2)O (3). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties.Postsynthetic Improvement of the Physical Properties in a Metal-Organic Framework through a Single Crystal to Single Crystal Transmetallationgas sorption; magnetic properties; metal-organic frameworks; transmetalation; X-ray diffraction78201552#N/ATRUE
4531
anie.20140998310.1002/anie.201409983FALSEhttps://doi.org/10.1002/anie.201409983Qing, FLAngew. Chem.-Int. Edit.An unprecedented reaction for the direct trifluoromethylthiolation and fluorination of Alkyl alcohols using AgSCF3 and nBu(4)NI has been developed. The trifluoromethylthiolated compounds and Alkyl fluorides were selectively formed by changing the ratio of AgSCF3/nBu(4)NI. This protocol is tolerant of different functional groups and might be applicable to late-stage trifluoromethylthiolation of alcohols.Direct Dehydroxytrifluoromethylthiolation of Alcohols Using Silver(I) Trifluoromethanethiolate and Tetra-n-butylammonium Iodidealcohols; chemoselectivity; fluorine; silver; synthetic methodsx119201581#N/AFALSE
4532
anie.20140973910.1002/anie.201409739FALSEhttps://doi.org/10.1002/anie.201409739Driess, MAngew. Chem.-Int. Edit.The Ni-II-mediated tautomerization of the N-heterocyClic hydrosilylcarbene (LSi)-Si-2(H)(CH2)NHC 1, where L-2 = CH(C=CH2)(CMe)(NAr)(2), Ar=2,6-iPr(2)C(6)H(3); NHC=3,4,5-trimethylimidazol-2-yliden-6-yl, leads to the first N-heterocyClic silylene (NHSi)-carbene (NHC) chelate ligand in the dibromo nickel(II) complex [(LSiD)-Si-1(CH2)(NHC)NiBr2] 2 (L-1 = CH(MeC=NAr)(2)). Reduction of 2 with KC8 in the presence of PMe3 as an auxiliary ligand afforded, depending on the reaction time, the N-heterocyClic silyl-NHC bromo Ni-II complex [L2Si(CH2)NHCNiBr(PMe3)] 3 and the unique Ni-0 complex [eta(2)(Si-H){(LSi)-Si-2(H)(CH2)NHC}Ni(PMe3)(2)] 4 featuring an agostic Si-H -> Ni bonding interaction. When 1,2-bis(dimethylphosphino) ethane (DMPE) was employed as an exogenous ligand, the first NHSi-NHC chelate-ligand-stabilized Ni-0 complex [(LSiD)-Si-1(CH2)NHCNi(dmpe)] 5 could be isolated. Moreover, the diCarbonyl Ni-0 complex 6, [(LSi:-)-Si-1(CH2)NHCNi(CO)(2)], is easily accessible by the reduction of 2 with K(BHEt3) under a CO atmosphere. The complexes were spectroscopically and structurally characterized. Furthermore, complex 2 can serve as an efficient precatalyst for Kumada-Corriu-type cross-coupling reactions.Synthesis of Mixed Silylene-Carbene Chelate Ligands from N-HeterocyClic Silylcarbenes Mediated by Nickelcross-coupling; homogeneous catalysis; main-group chemistry; N-heterocyClic carbenes; siliconx59201554#N/AFALSE
4533
anie.20150094210.1002/anie.201500942FALSEhttps://doi.org/10.1002/anie.201500942Li, FLAngew. Chem.-Int. Edit.Development of highly active, low cost, ecologically friendly, and durable homogenous catalysts for hydrogen generation from hydrolysis of borohydride is one of the most desirable pathways for future hydrogen utilization. The unexpected catalytic activities of inorganic ammonium species and the corresponding mechanisms underpinning them are studied. The catalytic activities of the ammonium species are higher than or comparable to those of mostly investigated noble-metal/transition-metal catalysts (such as Pd, Pt, Ni, and Co) but are considerably cheaper, more environmentally friendly, and more readily available. Quantum chemical calculations indicate that the unique ammonium-induced reaction pathway involved with a barrierless elementary reaction at the reaction entrance and the formation of the highly active intermediate BH3 are responsible for the unexpected catalytic activities and the significantly accelerated hydrogen generation.A Family of High-Efficiency Hydrogen-Generation Catalysts Based on Ammonium Speciesborohydride hydrolysis; catalytic activity; hydrogen generation; ammonium ions; metal-free catalysts37201534#N/ATRUE
4534
anie.20150014110.1002/anie.201500141FALSEhttps://doi.org/10.1002/anie.201500141Gade, LHAngew. Chem.-Int. Edit.Pincer-stabilized nickel(I) complexes readily react with molecular oxygen to form dinuClear 1,2--peroxo-bridged nickel(II) complexes, which are the major components of a dynamic equilibrium with the corresponding mononuClear superoxo species. The peroxo complexes further react with hydrogen peroxide to give the corresponding nickel(II) hydroperoxides. One of these hitherto elusive species was characterized by X-ray diffraction for the first time [O-O bond length: 1.492(2)angstrom].Structural Characterization of a Hydroperoxo Nickel Complex and Its Autoxidation: Mechanism of Interconversion between Peroxo, Superoxo, and Hydroperoxo Speciesautoxidation; hydroperoxides; nickel; peroxides; pincer ligand30201596#N/ATRUE
4535
anie.20141202610.1002/anie.201412026FALSEhttps://doi.org/10.1002/anie.201412026Wang, XSAngew. Chem.-Int. Edit.Nickel-Catalyzed Monofluoromethylation of Aryl Boronic AcidsAryl boronic acid; catalysis; monofluoromethylation; nickel; radicals63201577#N/ATRUE
4536
anie.20140942210.1002/anie.201409422FALSEhttps://doi.org/10.1002/anie.201409422Yu, LMAngew. Chem.-Int. Edit.The exploration of cost-effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye-sensitized solar cells (DSSCs). Transparent counter electrodes based on binary-alloy metal selenides (M-Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution-based method and employed in efficient bifacial DSSCs. Owing to superior charge-transfer ability for the I-/I-3(-) redox couple, electrocatalytic activity toward I-3(-) reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30% and 4.63% for Co0.85Se, 7.85% and 4.37% for Ni0.85Se, 6.43% and 4.24% for Cu0.50Se, 7.64% and 5.05% for FeSe, and 9.22% and 5.90% for Ru0.33Se in comparison with 6.18% and 3.56% for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels.Transparent Metal Selenide Alloy Counter Electrodes for High-Efficiency Bifacial Dye-Sensitized Solar Cellsalloys; electrocatalysis; energy conversion; metal selenides; solar cellsx188201441#N/AFALSE
4537
anie.20140885210.1002/anie.201408852FALSEhttps://doi.org/10.1002/anie.201408852Shinokubo, HAngew. Chem.-Int. Edit.3-Pyridyl-5,15-diazaporphyrin nickel(II) serves as a bidentate metalloligand for platinum(II), ruthenium(II), and rhenium(I) metal centers. Single-crystal X-ray diffraction analysis of these metal complexes unambiguously reveals the presence of a dative bond between the outer metal center and the meso-nitrogen atom. The UV/Vis absorption spectra of the complexes show substantially red-shifted bands which are perturbed by outer-metal coordination. This is due to the contribution of metal-to-ligand charge transfer interactions.A 3-Pyridyl-5,15-Diazaporphyrin Nickel(II) Complex as a Bidentate Metalloligand for Transition Metalscharge transfer; N ligands; platinum; porphyrinoids; rutheniumx17201458#N/AFALSE
4538
anie.20141198510.1002/anie.201411985FALSEhttps://doi.org/10.1002/anie.201705523Nitschke, JRGuest-Induced Transformation of a Porphyrin-Edged (Fe4L6)-L-II Capsule into a (CuFe2L4)-Fe-I-L-II Fullerene Receptor2015#N/ATRUE
4539
anie.20140851610.1002/anie.201408516https://doi.org/10.1002/anie.201408516
Jacobi von Wangelin, A
Angew. Chem.-Int. Edit.The synthesis of benzoates from Aryl electrophiles and carbon monoxide is a prime example of a transition-metal-catalyzed Carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative procedure that is free of any metal, ligand, and base. The method involves a redox reaction driven by visible light and catalyzed by eosin Y which affords Alkyl benzoates from arene diazonium salts, carbon monoxide, and alcohols under mild conditions. Tertiary esters can also be prepared in high yields. DFT calculations and radical trapping experiments support a catalytic photoredox pathway without the requirement for sacrificial redox partners.Metal-Free Carbonylations by Photoredox CatalysisCarbonylation; esters; organocatalysis; photoredox catalysis; redox reaction; visible lightPhotocatalyst124201559#N/AFALSE
4540
anie.20140826610.1002/anie.201408266FALSEhttps://doi.org/10.1002/anie.201408266Sun, LCAngew. Chem.-Int. Edit.The copper complex [(bztpen)Cu](BF4)(2) (bztpen=N-Benzyl-N,N,N-tris(pyridin-2-ylmethyl)ethylenediamine) displays high catalytic activity for electrochemical proton reduction in acidic aqueous solutions, with a calculated hydrogen-generation rate constant (k(obs)) of over 10000s(-1). A turnover frequency (TOF) of 7000h(-1)cm(-2) and a Faradaic efficiency of 96% were obtained from a controlled potential electrolysis (CPE) experiment with [(bztpen)Cu](2+) in pH2.5 buffer solution at -0.90V versus the standard hydrogen electrode (SHE) over two hours using a glassy carbon electrode. A mechanism involving two proton-coupled reduction steps was proposed for the dihydrogen generation reaction catalyzed by [(bztpen)Cu](2+).A Molecular Copper Catalyst for Electrochemical Water Reduction with a Large Hydrogen-Generation Rate Constant in Aqueous Solutioncopper; electrocatalysis; hydrogen; water reductionx127201438#N/AFALSE
4541
anie.20141185410.1002/anie.201411854FALSEhttps://doi.org/10.1002/anie.201411854Dinca, MAngew. Chem.-Int. Edit.The utility of metal-organic frameworks (MOFs) as functional materials in electronic devices has been limited to date by a lack of MOFs that display high electrical conductivity. Here, we report the synthesis of a new electrically conductive 2D MOF, Cu-3(HITP)(2) (HITP= 2,3,6,7,10,11-hex-aiminotriphenylene), which displays a bulk conductivity of 0.2 S cm(-1) (pellet, two-point-probe). Devices synthesized by simple drop casting of Cu-3(HITP)(2) dispersions function as reversible chemiresistive sensors, capable of detecting sub-ppm levels of ammonia vapor. Comparison with the isostructural 2D MOF Ni-3(HITP)(2) shows that the copper sites are critical for ammonia sensing, indicating that rational design/synthesis can be used to tune the functional properties of conductive MOFs.Cu-3(hexaiminotriphenylene)(2): An Electrically Conductive 2D Metal-Organic Framework for Chemiresistive Sensingammonia; conductivity; copper; metal-organic frameworks; sensors476201544#N/ATRUE
4542
anie.20141173710.1002/anie.201411737FALSEhttps://doi.org/10.1002/anie.201411737Alexanian, EJAngew. Chem.-Int. Edit.A stereoselective nickel-catalyzed [2+ 2] cyCloaddition of ene-allenes is reported. This transformation encompasses a broad range of ene-allene substrates, thus providing efficient access to fused cyClobutanes from easily accessed pcomponents. A simple and inexpensive first-row catalytic system comprised of [Ni(cod)(2)] and dppf was used in this process, thus constituting an attractive approach to synthetically challenging cyClobutane frameworks under mild reaction conditions.Stereoselective Nickel- Catalyzed [2+2] CyCloadditions of EneAllenesalkenes; allenes; carbocyCles; cyCloaddition; nickel32201530#N/ATRUE
4543
anie.20141107210.1002/anie.201411072FALSEhttps://doi.org/10.1002/anie.201411072Strasser, PAngew. Chem.-Int. Edit.Active and highly stable oxide-supported IrNiOx core-shell catalysts for electrochemical water splitting are presented. IrNix@IrOx nanopartiCles supported on high-surface-area mesoporous antimony-doped tin oxide (IrNiOx/Meso-ATO) were synthesized from bimetallic IrNix precursor alloys (PA-IrNix/Meso-ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNix/Meso-ATO as well as on the surface chemical state of the partiCle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core-shell partiCles. The core-shell IrNiOx/Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.Oxide-Supported IrNiOx Core-Shell PartiCles as Efficient, Cost-Effective, and Stable Catalysts for Electrochemical Water Splittingcore-shell nanopartiCles; oxide supports; oxygen evolution reaction; water splitting; X-ray photoelectron spectroscopy260201530#N/ATRUE
4544
anie.20141102510.1002/anie.201411025FALSEhttps://doi.org/10.1002/anie.201704911Wesemann, LNickel-Triad Complexes of a Side-on Coordinating Distannene2015#N/ATRUE
4545
anie.20140698310.1002/anie.201406983FALSEhttps://doi.org/10.1002/anie.201406983Lu, TBAngew. Chem.-Int. Edit.The development of an earth-abundant, first-row water oxidation catalyst that operates at neutral pH and low overpotential remains a fundamental chemical challenge. Herein, we report the first nickel-based robust homogeneous water oxidation catalyst, which can electrocatalyze water oxidation at neutral pH and low overpotential in phosphate buffer. The results of DFT calculations verify that the O-O bond formation in catalytic water oxidation prefers a HO-OH coupling mechanism from a cis-isomer of the catalyst.Homogeneous Electrocatalytic Water Oxidation at Neutral pH by a Robust MacrocyClic Nickel(II) Complexelectrocatalysis; homogeneous water oxidation; HO-OH coupling; nickel
Electrocatalytic
188201460#N/AFALSE
4546
anie.20140681110.1002/anie.201406811https://doi.org/10.1002/anie.201406811Reisner, EAngew. Chem.-Int. Edit.Solar-light-driven H-2 production in water with a [NiFeSe]-hydrogenase (H(2)ase) and a bioinspired synthetic nickel catalyst (NiP) in combination with a heptazine carbon nitride polymer, melon (CNx), is reported. The semibiological and purely synthetic systems show catalytic activity during solar light irradiation with turnover numbers (TONs) of more than 50000molH(2)(molH(2)ase)(-1) and approximately 155molH(2)(molNiP)(-1) in redox-mediator-free aqueous solution at pH6 and 4.5, respectively. Both systems maintained a reduced photoactivity under UV-free solar light irradiation (>420 nm).Photocatalytic Hydrogen Production using Polymeric Carbon Nitride with a Hydrogenase and a Bioinspired Synthetic Ni Catalystcarbon nitride; enzyme catalysis; hydrogen production; hydrogenases; photocatalysisPhotocatalystx136201468#N/AFALSE
4547
anie.20140657010.1002/anie.201406570FALSEhttps://doi.org/10.1002/anie.201406570Ding, FAngew. Chem.-Int. Edit.To improve the atomically controlled growth of graphene by chemical vapor deposition (CVD), understanding the evolution from various carbon species to a graphene nuCleus on various catalyst surfaces is essential. Experimentally, an ultrastable carbon Cluster on Ru(0001) and Rh(111) surfaces was observed, while its structure and formation process were still under debate. Using ab initio calculations and kinetic analyses, we disClose a specific type of carbon Cluster, composed of a C-21 core and a few dangling C atoms, which is exceptional stable in a size range from 21 to 27 C atoms. The most stable one of them, an isomer of C-24 characterized by three dangling C atoms attached to the C-21 core (denoted as C-21-3C), is the most promising candidate of the experimental observation. The ultrastability of C-21-3C originates from both the stable core and the appropriate passivation of the dangling carbon atoms by the catalyst surface.The Structure and Stability of Magic Carbon Clusters Observed in Graphene Chemical Vapor Deposition Growth on Ru(0001) and Rh(111) Surfacessupported carbon Clusters; chemical vapor deposition; density functional calculations; graphene; derivative of sumanenex29201450#N/AFALSE
4548
anie.20140649710.1002/anie.201406497FALSEhttps://doi.org/10.1002/anie.201406497Sun, SGAngew. Chem.-Int. Edit.The shape-controlled synthesis of multicomponent metal nanocrystals (NCs) bounded by high-index facets (HIFs) is of significant importance in the design and synthesis of high-activity catalysts. We report herein the preparation of Pt-Ni alloy NCs by tuning their shape from concave-nanocubic (CNC) to nanocubic and hexoctahedral (HOH). Owing to the synergy of the HIFs and the electronic effect of the Pt-Ni alloy, the as-prepared CNC and HOH Pt-Ni alloy NCs exhibited excellent catalytic properties for the electrooxidation of methanol and formic acid, as well as for the oxygen reduction reaction (ORR).Synthesis of Pt-Ni Alloy Nanocrystals with High-Index Facets and Enhanced Electrocatalytic Propertiesalloys; electrocatalysis; electrooxidation; oxygen reduction reaction; nanocrystalsx199201450#N/AFALSE
4549
anie.20141100910.1002/anie.201411009FALSEhttps://doi.org/10.1002/anie.201411009Xi, ZFAngew. Chem.-Int. Edit.Organolithium compounds can behave as reductants but never as oxidants in redox reactions. Reported herein is that 1,4-dilithio-1,3-butadienes reacted with [Ni(cod)(2)] (cod = 1,5-cyClooctadiene) to deliver dilithionickeloles. Single-crystal X-ray structural analysis revealed a coplanar structure of dilithionickeloles with an averaging of bond lengths. XPS data confirmed the oxidation state of Ni in dilithionickeloles was Ni2+. Li-7 NMR spectra of dilithionickeloles and theoretical calculations revealed a considerable aromatic character. In this redox reaction, the dilithio dianionic compounds behaved as formal oxidants, thus oxidizing Ni-0 into Ni2+. These results demonstrated that organolithium compounds with p-conjugation could be used as oxidants and could continue to accept extra electrons.Dianions as Formal Oxidants: Synthesis and Characterization of Aromatic Dilithionickeloles from 1,4-Dilithio-1,3-butadienes and [Ni(cod)(2)]aromaticity; lithium; nickel; oxidation; redox chemistry42201555#N/ATRUE
4550
anie.20141087510.1002/anie.201410875TRUEhttps://doi.org/10.1002/anie.201410875Stradiotto, MAngew. Chem.-Int. Edit.Structurally diverse (hetero)Aryl chloride, bromide, and tosylate electrophiles were employed in the Ni-catalyzed monoArylation of ammonia, inCluding chemoselective transformations. The employed JosiPhos/[Ni(cod)(2)]catalyst system enables the use of commercially available stock solutions of ammonia, or the use of ammonia gas in these reactions, thereby demonstrating the versatility and potential scalability of the reported protocol. Proof-of-principle experiments established that air-stable [(JosiPhos)NiCl2] precatalysts can be employed successfully in such transformations.Nickel-Catalyzed MonoArylation of Ammoniaamination; ammonia; Arylation; cross-coupling; nickelCsp2_ar-Nsp3E-NuOHOTsHHetNaOtBuIonic-OtBu742015821/5/2022TRUE
4551
anie.20141031610.1002/anie.201410316FALSEhttps://doi.org/10.1002/anie.201410316Wu, YTAngew. Chem.-Int. Edit.The syntheses, structures, and physical properties of dibenzozethrenes were explored. The results thus obtained were compared with those for zethrenes. Dibenzozethrenes were synthesized by the nickel-catalyzed cyClodimerization of 9-ethynyl-1-iodoanthracenes. The substituents in zethrene and dibenzozethrene twisted their backbones, and remarkably influenced their properties. Unlike Closed-shell disubstituted derivatives, the parent zethrene and dibenzozethrene are singlet open-shell biradicals, which were studied by variable-temperature (HNMR)-H-1, ESR, SQUID and computational methods. Since substituents were observed to affect significantly the biradical properties, the relevant mechanisms were analyzed. The nonlinear optical performance of each of these compounds depends on its -conjugation and biradical properties. Dibenzozethrenes have larger two-photon absorption cross-sections than zethrenes, as most strongly evidenced by the parent dibenzothrene [sigma(max)=4323GM at 530nm].Zethrene and Dibenzozethrene: Masked Biradical Molecules?density functional calculations; dimerization; macrocyCles; nickel; radicals21201536#N/ATRUE
4552
anie.20140519910.1002/anie.201405199FALSEhttps://doi.org/10.1002/anie.201405199Kersting, BAngew. Chem.-Int. Edit.The macrocyClic complex [Ni-2(L)(OAc)]ClO4 (1) adsorbs up to 17molar equivalents (>270wt%) of iodine, although it does not exhibit permanent porosity. Vibrational spectroscopic and crystallographic studies reveal that two I-2 molecules are captured by means of thiophenolateI(2) charge-transfer interactions, which enable the diffusion and sorption of further I-2 molecules in a polyiodide-like network. The efficient sorption and desorption characteristics make this material suitable for accommodation, sensing, and slow release of I-2.Adsorption of I-2 by MacrocyClic Polyazadithiophenolato Complexes Mediated by Charge-Transfer Interactionsadsorption; charge-transfer complexes; iodine; structure elucidation; thiophenolatesx11201438#N/AFALSE
4553
anie.20140966910.1002/anie.201409669FALSEhttps://doi.org/10.1002/anie.201409669Cramer, NAngew. Chem.-Int. Edit.The 1,6-annulated 2-pyridone motif is found in many biologically active compounds and its Close relation to the indolizidine and quinolizidine alkaloid core makes it an attractive building block. A nickel-catalyzed CH functionalization of 2-pyridones and subsequent cyClization affords 1,6-annulated 2-pyridones by selective intramolecular olefin hydroArylation. The switch between the exo- and endo-cyClization modes is controlled by two complementary sets of ligands. Irrespective of the ring size, the regioselectivity during the cyClization is under full catalyst control. Simple cyClooctadiene promotes an exo-selective cyClization, whereas a bulky N-heterocyClic carbene ligand results in an endo-selective mode. The method was further applied in the synthesis of the lupin alkaloid cytisine.Ligand-Controlled Regiodivergent Nickel-Catalyzed Annulation of PyridonesCH Activation; cyClization; heterocyCles; N-heterocyClic carbenes; nickel92201560#N/ATRUE
4554
anie.20140948210.1002/anie.201409482FALSEhttps://doi.org/10.1002/anie.201409482Karger, JAngew. Chem.-Int. Edit.Microimaging by IR microscopy is applied to the recording of the evolution of the concentration profiles of reactant and product molecules during catalytic reaction, notably during the hydrogenation of benzene to cyClohexane by nickel dispersed within a nanoporous glass. Being defined as the ratio between the reaction rate in the presence of and without diffusion limitation, the effectiveness factors of catalytic reactions were previously determined by deliberately varying the extent of transport limitation by changing a suitably chosen system parameter, such as the partiCle size and by comparison of the respective reaction rates. With the novel options of microimaging, effectiveness factors become accessible in a single measurement by simply monitoring the distribution of the reactant molecules over the catalyst partiCles.Microimaging of Transient Concentration Profiles of Reactant and Product Molecules during Catalytic Conversion in Nanoporous Materialsglasses; heterogeneous catalysis; reaction kinetics; reaction mechanisms; supported catalysts42201556#N/ATRUE
4555
anie.20140946910.1002/anie.201409469FALSEhttps://doi.org/10.1002/anie.201409469Driess, MAngew. Chem.-Int. Edit.The unusual reactivity of the newly synthesized -diketiminato cobalt(I) complexes, [((LCo)-Co-Dep)(2)] (2a, L-Dep=CH[C(Me)N(2,6-Et2C6H3)](2)) and [L(Dipp)Cotoluene] (2b, L-Dipp=CH[CHN(2,6-(Pr2C6H3)-Pr-i)](2)), toward white phosphorus was investigated, affording the first cobalt(I) complexes [((LCo)-Co-Dep)(2)((2):(4),(4)-P-4)] (3a) and [((LCo)-Co-Dipp)(2)((2):(4),(4)-P-4)] (3b) bearing the neutral cyClo-P-4 ligand with a rectangular-planar structure. The redox chemistry of 3a and 3b was studied by cyClic voltammetry and their chemical reduction with one molar equivalent of potassium graphite led to the isolation of [((LCo)-Co-Dep)(2)((2):(4),(4)-P-4)][K(dme)(4)] (4a) and [((LCo)-Co-Dipp)(2)((2):(4),(4)-P-4)][K(dme)(4)] (4b). Unexpectedly, the monoanionic Co2P4 core in 4a and 4b, respectively, contains the two-electron-reduced cyClo-P-4(2-) ligand with a square-planar structure and mixed-valent cobalt(I,II) sites. The electronic structures of 3a, 3b, 4a, and 4b were elucidated by NMR and EPR spectroscopy as well as magnetic measurements and are in agreement with results of broken-symmetry DFT calculations.A Neutral TetraphosphacyClobutadiene Ligand in Cobalt(I) Complexesbond Activation; cobalt; -diketiminates; phosphorus36201557#N/ATRUE
4556
anie.20140855210.1002/anie.201408552FALSEhttps://doi.org/10.1002/anie.201408552Hirota, SAngew. Chem.-Int. Edit.[NiFe] hydro@genase catalyzes the reversible Cleavage of H-2. The electrons produced by the H-2 Cleavage pass through three Fe-S Clusters in [NiFe] hydrogenase to its redox partner. It has been reported that the Ni-SIa, Ni-C, and Ni-R states of [NiFe] hydrogenase are involved in the catalytic cyCle, although the mechanism and regulation of the transition between the Ni-C and Ni-SIa states remain unrevealed. In this study, the FT-IR spectra under light irradiation at 138-198K show that the Ni-L state of [NiFe] hydrogenase is an intermediate between the transition of the Ni-C and Ni-SIa states. The transition of the Ni-C state to the Ni-SIa state occurred when the proximal [Fe4S4](p)(2+/+) Cluster was oxidized, but not when it was reduced. These results show that the catalytic cyCle of [NiFe] hydrogenase is controlled by the redox state of its [Fe4S4](p)(2+/+) Cluster, which may function as a gate for the electron flow from the NiFe active site to the redox partner.Control of the Transition between Ni-C and Ni-SIa States by the Redox State of the Proximal Fe-S Cluster in the Catalytic CyCle of [NiFe] Hydrogenasebiocatalysis; EPR spectroscopy; hydrogenases; iron-sulfur Clusters; IR spectroscopy30201444#N/ATRUE
4557
anie.20140794410.1002/anie.201407944FALSEhttps://doi.org/10.1002/anie.201407944Soloshonok, VAAngew. Chem.-Int. Edit.Reported herein is the first purely chemical method for the dynamic kinetic resolution (DKR) of unprotected racemic alpha-amino acids (alpha-AAs), a method which can rival the economic efficiency of the enzymatic reactions. The DKR reaction principle can be readily applied for S/R interconversions of alpha-AAs, the methodological versatility of which is unmatched by biocatalytic approaches. The presented process features a virtually complete stereochemical outcome, fully recyClable source of chirality, and operationally simple and convenient reaction conditions, thus allowing its ready scalability. A quite unique and novel mode of the thermodynamic control over the stereochemical outcome, inCluding an exciting interplay between axial, helical, and central elements of chirality is proposed.Chemical Dynamic Kinetic Resolution and S/R Interconversion of Unprotected alpha-Amino Acidsamino acids; chirality; diastereoselectivity; kinetic resolution; nickel63201460#N/ATRUE
4558
anie.20140788810.1002/anie.201407888FALSEhttps://doi.org/10.1002/anie.201407888Krische, MJAngew. Chem.-Int. Edit.Ruthenium-catalyzed reductive couplings of paraformaldehyde with dienes, alkynes, and allenes provide access to products of hydrohydroxymethylation that cannot be formed selectively under the conditions of hydroCarbonylation. In certain cases, the regioselectivity of the CC coupling can be inverted by using nickel catalysts. With iridium catalysts, methanol engages in redox-neutral regioselective hydrohydroxymethylations.Paraformaldehyde and Methanol as C1 Feedstocks in Metal-Catalyzed C-C Couplings of pi-Unsaturated Reactants: Beyond HydroCarbonylationindustrial chemistry; iridium; metal catalysis; nickel; ruthenium; transfer hydrogenation932015125#N/ATRUE
4559
anie.20140413310.1002/anie.201404133FALSEhttps://doi.org/10.1002/anie.201404133Patra, AKAngew. Chem.-Int. Edit.A functional model complex of nickel superoxide dismutase (NiSOD) with a non-peptide ligand which mimics the full catalytic cyCle of NiSOD is unknown. Similarly, it has not been fully elucidated whether NiSOD activity is a result of an outer-or inner-sphere electron-transfer mechanism. With this in mind, two octahedral nickel(II)/(III) complexes of a bistridentate N2S donor carboxamide ligand, N-2-phenylthiophenyl-2'-pyridinecarboxamide (HLPh), have been synthesized, structurally characterized, and their SOD activities examined. These complexes mimic the full catalytic cyCle of NiSOD. Electrochemical experiments support an outer-sphere electron-transfer mechanism for their SOD activity.Hexacoordinate Nickel(II)/(III) Complexes that Mimic the Catalytic CyCle of Nickel Superoxide Dismutaseelectrochemistry; enzyme models; nickel; outer-sphere electron transfer; X-ray diffractionx19201452#N/AFALSE
4560
anie.20140410310.1002/anie.201404103FALSEhttps://doi.org/10.1002/anie.201404103Gommes, CJAngew. Chem.-Int. Edit.A major cause of supported metal catalyst deActivation is partiCle growth by Ostwald ripening. Nickel catalysts, used in the methanation reaction, may suffer greatly from this through the formation of [Ni(CO)(4)]. By analyzing catalysts with various partiCle sizes and spatial distributions, the interpartiCle distance was found to have little effect on the stability, because formation and decomposition of nickel Carbonyl rather than diffusion was rate limiting. Small partiCles (3-4 nm) were found to grow very large (20-200 nm), involving local destruction of the support, which was detrimental to the catalyst stability. However, medium sized partiCles (8 nm) remained confined by the pores of the support displaying enhanced stability, and an activity 3 times higher than initially small partiCles after 150 h. Physical modeling suggests that the higher [Ni(CO)(4)] supersaturation in catalysts with smaller partiCles enabled them to overcome the mechanical resistance of the support. Understanding the interplay of partiCle size and support properties related to the stability of nanopartiCles offers the prospect of novel strategies to develop more stable nanostructured materials, also for applications beyond catalysis.NanopartiCle Growth in Supported Nickel Catalysts during Methanation Reaction-Larger is Bettercrystal growth; heterogeneous catalysis; nanopartiCles; nickel; supported catalystsx62201448#N/AFALSE
4561
anie.20140783710.1002/anie.201407837FALSEhttps://doi.org/10.1002/anie.201407837Hoveyda, AHAngew. Chem.-Int. Edit.A Multicomponent Ni-, Zr-, and Cu- Catalyzed Strategy for Enantioselective Synthesis of Alkenyl-Substituted Quaternary Carbons (vol 53, pg 1910, 2014)020141#N/ATRUE
4562
anie.20140709810.1002/anie.201407098FALSEhttps://doi.org/10.1002/anie.201407098Berben, LASynthesis of Square-Planar Aluminum(III) Complexes2014#N/ATRUE
4563
anie.20140346110.1002/anie.201403461FALSEhttps://doi.org/10.1002/anie.201403461Gao, PXMonolithically Integrated Spinel MxCo3-xO4 (M=Co, Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low-Temperature CH4 and CO Oxidationx2014#N/AFALSE
4564
anie.20140573810.1002/anie.201405738FALSEhttps://doi.org/10.1002/anie.201405738Neyman, KMAngew. Chem.-Int. Edit.Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H-sub, may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, Had, depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H-sub, especially on metal nanopartiCles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general.How Absorbed Hydrogen Affects the Catalytic Activity of Transition Metalsdensity functional calculations; heterogeneous catalysis; hydrogenations; nanopartiCles; surface chemistry59201427#N/ATRUE
4565
anie.20140292210.1002/anie.201402922TRUEhttps://doi.org/10.1002/anie.201402922Rueping, MAngew. Chem.-Int. Edit.The direct replacement of aromatic methoxy groups with activated carbon nuCleophiles would give rise to novel synthetic pathways for targeted and diversity-oriented syntheses. We demonstrate here that this transformation can be achieved in a one-step reaction involving a bifunctional organolithium nuCleophile in combination with a C-Ar-OMe bond-Cleaving nickel catalyst. The resulting products are stable, alpha-CH active, and suitable for various further modifications.Metal-Catalyzed Dealkoxylative C-Aryl-C-sp3 Cross-Coupling-Replacement of Aromatic Methoxy Groups of Aryl Ethers by Employing a Functionalized NuCleophileAryl ethers; C-O bond Cleavage; cross-coupling; methoxy functionalization; nickelxCsp2_ar-Csp3LiOMeLiArylNo baseNo Base9120148112/1/2021FALSE
4566
anie.20140230410.1002/anie.201402304FALSEhttps://doi.org/10.1002/anie.201402304Shaw, WJAngew. Chem.-Int. Edit.Hydrogenase enzymes use Ni and Fe to oxidize H-2 at high turnover frequencies (TOF) (up to 10 000 s(-1)) and low overpotentials (< 100 mV). In comparison, the fastest reported synthetic electrocatalyst, [Ni-II(P-Cy N-2(2)tBu)(2)](2+), oxidizes H-2 at 60 s(-1) in MeCN under 1 atm H-2 with an unoptimized overpotential of ca. 500 mV using triethylamine as a base.[1] Here we show that a structured outer coordination sphere in a Ni electrocatalyst enhances H-2 oxidation activity: [Ni-II(P-Cy N-2(2)Arg)(2)]8(+) (Arg = arginine) has a TOF of 210 s(-1) in water with high energy efficiency (180 mVoverpotential) under 1 atm H-2, and 144 000 s(-1) (460 mV overpotential) under 133 atm H-2. The complex is active from pH 0-14 and is faster at low pH, the most relevant condition for fuel cells. The arginine substituents increase TOF and may engage in an intramolecular guanidinium interaction that assists in H-2 Activation, while the COOH groups facilitate rapid proton movement. These results emphasize the critical role of features beyond the active site in achieving fast, efficient catalysis.Arginine-Containing Ligands Enhance H-2 Oxidation Catalyst Performanceamino acid catalysts; bioinspired catalysts; H-2 oxidation; homogeneous electrocatalysis; nickel complexx57201438#N/AFALSE
4567
anie.20140572610.1002/anie.201405726FALSEhttps://doi.org/10.1002/anie.201405726Mascarenas, JLAngew. Chem.-Int. Edit.At specific DNA sites, nickel(II) salts promote the assembly of designed components, namely a bis(histidine)-modified peptide that is derived from a bZIP transcription factor and a bis(benzamidine) unit that is equipped with a bipyridine. This programmed supramolecular system with emergent properties reproduces some key characteristics of naturally occurring DNA-binding proteins, such as bivalence, selectivity, responsiveness to external agents, and reversibility.Reversible Supramolecular Assembly at Specific DNA Sites: Nickel-Promoted Bivalent DNA Binding with Designed Peptide and Bipyridyl-Bis(benzamidine) ComponentsDNA recognition; minor-groove binders; peptides; self-assembly; supramolecular chemistry22201456#N/ATRUE
4568
anie.20140565310.1002/anie.201405653FALSEhttps://doi.org/10.1002/anie.201405653Zhang, XGAngew. Chem.-Int. Edit.Transition-metal-catalyzed difluoroAlkylation of aromatics remains challenging despite the importance of difluoroAlkylated arenes in medicinal chemistry. Herein, the first successful example of nickel-catalyzed difluoroAlkylation of Aryl boronic acids is described. The reaction allows access to a variety of functionalized difluoromethyl bromides and chlorides, and paves the way to highly cost-efficient synthesis of a wide range of difluoroAlkylated arenes. The notable features of this protocol are its high generality, excellent functional-group compatibility, low-cost nickel-catalyst, and practicality for gram-scale production, thus providing a facile method for applications in drug discovery and development.Nickel-Catalyzed Cross-Coupling of Functionalized Difluoromethyl Bromides and Chlorides with Aryl Boronic Acids: A General Method for DifluoroAlkylated Arenesboronic acids; cross coupling; fluorine; nickel; synthetic methods160201461#N/ATRUE
4569
anie.20140481610.1002/anie.201404816FALSEhttps://doi.org/10.1002/anie.201404816Kimura, MAngew. Chem.-Int. Edit.A nickel catalyst promotes the multicomponent coupling reaction of diketene, an alkyne, and Me2Zn to provide 3-methylene-4-hexenoic acids in excellent yields. Under similar conditions, the combination of the nickel catalyst and Et2Al(OEt) promotes a cyCloaddition reaction involving dimerization of an alkyne to furnish phenylacetic acids. In the presence of PPh3, a formal [2+2+1+1] cyCloaddition reaction proceeds to afford regioisomeric phenylacetic acids via Cleavage of the C=C bond.Efficient and Selective Formation of Unsaturated Carbonylic and Phenylacetic Acids from DiketeneCarbonylic acids; cyCloaddition; nickel; synthetic methods; zinc7201456#N/ATRUE
4570
anie.20131112810.1002/anie.201311128FALSEhttps://doi.org/10.1002/anie.201311128Fischer, RAMultifunctional, Defect-Engineered Metal-Organic Frameworks with Ruthenium Centers: Sorption and Catalytic Propertiesx2014#N/AFALSE
4571
anie.20140473410.1002/anie.201404734FALSEhttps://doi.org/10.1002/anie.201404734Tanaka, HAngew. Chem.-Int. Edit.Novel highly active electrocatalysts for hydrazine hydrate fuel cell application were developed, synthesized and integrated into an operation vehiCle prototype. The materials show in both rotating disc electrode (RDE) and membrane electrode assembly (MEA) tests the world highest activity with peak current density of 16 000 Ag-1 (RDE) and 450 mWcm(-2) operated in air (MEA).Anode Catalysts for Direct Hydrazine Fuel Cells: From Laboratory Test to an Electric VehiCle101201429#N/ATRUE
4572
anie.20140457710.1002/anie.201404577FALSEhttps://doi.org/10.1002/anie.201404577Tilley, TDAngew. Chem.-Int. Edit.Recently, the development of more sustainable catalytic systems based on abundant first-row metals, especially nickel, for cross-coupling reactions has attracted significant interest. One of the key intermediates invoked in these reactions is a Ni-III-Alkyl species, but no such species that is part of a competent catalytic cyCle has yet been isolated. Herein, we report a carbon-carbon cross-coupling system based on a two-coordinate Ni-II-bis(amido) complex in which a Ni-III-Alkyl species can be isolated and fully characterized. This study details compelling experimental evidence of the role played by this Ni-III-Alkyl species as well as those of other key Ni-I and Ni-II intermediates. The catalytic cyCle described herein is also one of the first examples of a two-coordinate complex that competently catalyzes an organic transformation, potentially leading to a new Class of catalysts based on the unique ability of first-row transition metals to accommodate two-coordinate complexes.Carbon-Carbon Cross-Coupling Reactions Catalyzed by a Two-Coordinate Nickel(II)-Bis(amido) Complex via Observable Ni-I, Ni-II, and Ni-III Intermediatescross-coupling; homogeneous catalysis; mechanism; metal amides; nickel57201441#N/ATRUE
4573
anie.20131048410.1002/anie.201310484FALSEhttps://doi.org/10.1002/anie.201310484Kruger, HJAngew. Chem.-Int. Edit.The influence of a coordinated pi-radical on the spin crossover properties of an octahedral iron(II) complex was investigated by preparing and isolating the iron(II) complex containing the tetradentate N, N'-dimethyl-2,11-diaza[3.3]-(2,6) pyridinophane and the radical anion of N, N'-diphenyl-acenaphtene-1,2-diimine as ligands. This spin crossover complex was obtained by a reduction of the corresponding low-spin iron(II) complex with the neutral diimine ligand, demonstrating that the reduction of the strong pi-acceptor ligand is accompanied by a decrease in the ligand field strength. Characterization of the iron(II) radical complex by structural, magnetochemical, and spectroscopic methods revealed that spin crossover equilibrium occurs above 240 K between an S = 1/2 ground state and an S = 3/2 excited spin state. The possible origins of the fast spin interconversion observed for this complex are discussed.How Does a Coordinated Radical Ligand Affect the Spin Crossover Properties in an Octahedral Iron(II) Complex?iron(II) complexes; magnetic properties; redox chemistry; spin crossover; pi-radical ligandsx24201435#N/AFALSE
4574
anie.20140433910.1002/anie.201404339https://doi.org/10.1002/anie.201404339Shishido, AAngew. Chem.-Int. Edit.A dipalladium complex with a double-decker structure catalyzes ethylene-acrylate copolymerization to produce the branched polymer containing the acrylate units in the polymer chain, not at the branch terminus. The cooperation of the two palladium centers, which are fixed in a rigid framework of the macrocyClic ligand, is proposed to have a significant din uClear effect on the copolymerization.Dipalladium Catalyst for Olefin Polymerization: Introduction of Acrylate Units into the Main Chain of Branched Polyethylenecopolymerization; homogeneous catalysis; palladium; polymers; reaction mechanism93201439#N/ATRUE
4575
anie.20131037410.1002/anie.201310374FALSEhttps://doi.org/10.1002/anie.201310374Shinokubo, HAngew. Chem.-Int. Edit.Although aromatic compounds occupy a central position in organic chemistry, antiaromatic compounds have demonstrated little practical utility. Herein we report the application of an antiaromatic compound as an electrode-active material in rechargeable batteries. The performance of dimesityl-substituted norcorrole nickel(II) complex (NiNC) as a cathode-active material was examined with a Li metal anode. A maximum discharge capacity of about 207mAhg(-1) was maintained after 100 charge/discharge cyCles. Moreover, the bipolar redox property of NiNC enables the construction of a Li metal free rechargeable battery. The high performance of NiNC batteries demonstrates a prospective feature of stable antiaromatic compounds as electrode-active materials.An Antiaromatic Electrode-Active Material Enabling High Capacity and Stable Performance of Rechargeable Batteriesantiaromaticity; electrochemistry; organic batteries; porphyrinoids; redox chemistryx89201429#N/AFALSE
4576
anie.20131033610.1002/anie.201310336FALSEhttps://doi.org/10.1002/anie.201310336Tanaka, KAngew. Chem.-Int. Edit.It has been established that a cationic rhodium(I)/(R)-tol-binap complex catalyzes the cross-cyClotrimerization of silylacetylenes, di-tert-butyl acetylenediCarbonylates, and acrylamides with excellent chemo-, regio-, and enantioselectivities. Unsymmetrical alkynoates can also be employed in place of di-tert-butyl acetylenediCarbonylate for this process, but with reduced chemoselectivity.Highly Chemo-, Regio-, and Enantioselective Rhodium-Catalyzed Cross-CyClotrimerization of Two Different Alkynes with Alkenesalkenes; alkynes; asymmetric catalysis; cyClotrimerization; multicomponent reactions; rhodiumx34201452#N/AFALSE
4577
anie.20140420810.1002/anie.201404208FALSEhttps://doi.org/10.1002/anie.201610047Geng, BYA Reliable Aerosol-Spray-Assisted Approach to Produce and Optimize Amorphous Metal Oxide Catalysts for Electrochemical Water Splitting2014#N/ATRUE
4578
anie.20140416110.1002/anie.201404161FALSEhttps://doi.org/10.1002/anie.201404161Sun, XPAngew. Chem.-Int. Edit.The development of effective and inexpensive hydrogen evolution reaction (HER) electrocatalysts for future renewable energy systems is highly desired. The strongly acidic conditions in proton exchange membranes create a need for acid-stable HER catalysts. A nanohybrid that consists of carbon nanotubes decorated with CoP nanocrystals (CoP/CNT) was prepared by the low-temperature phosphidation of a Co3O4/CNT precursor. As a novel non-noble-metal HER catalyst operating in acidic electrolytes, the nanohybrid exhibits an onset overpotential of as low as 40 mV, a Tafel slope of 54 mV dec(-1), an exchange current density of 0.13 mA cm(-2), and a Faradaic efficiency of nearly 100%. This catalyst maintains its catalytic activity for at least 18 hours and only requires overpotentials of 70 and 122 mV to attain current densities of 2 and 10 mA cm(-2), respectively.Carbon Nanotubes Decorated with CoP Nanocrystals: A Highly Active Non-Noble-Metal Nanohybrid Electrocatalyst for Hydrogen Evolution738201474#N/ATRUE
4579
anie.20140407810.1002/anie.201404078FALSEhttps://doi.org/10.1002/anie.201612065Peters, JCTwo-Coordinate Fe-0 and Co-0 Complexes Supported by CyClic (Alkyl)(amino) carbenes2014#N/ATRUE
4580
anie.20140355610.1002/anie.201403556FALSEhttps://doi.org/10.1002/anie.201611863Liu, HChemical Kinetic Resolution of Unprotected beta-Substituted beta-Amino Acids Using RecyClable Chiral Ligands2014#N/ATRUE
4581
anie.20140328810.1002/anie.201403288FALSEhttps://doi.org/10.1002/anie.201403288Osuka, AAngew. Chem.-Int. Edit.Operationally simple, efficient, and widely applicable Pummerer annulations of simple phenols with ketene dithioacetal monoxides, with the aid of trifluoroacetic anhydride, have been shown to provide a variety of benzofurans having a methylthio group at the 2-position. Subsequent and newly developed nickel-catalyzed Arylation at the methylthio group culminates in diversity-oriented synthesis of multisubstituted benzofurans. Our extended Pummerer annulation/cross-coupling sequence is powerful enough to synthesize biologically active natural products as well as highly fluorescent benzofuran derivatives.Practical, Modular, and General Synthesis of Benzofurans through Extended Pummerer Annulation/Cross-Coupling Strategyannulation; heterocyCles; nickel; rearrangement; synthetic methods94201474#N/ATRUE
4582
anie.20140102410.1002/anie.201401024FALSEhttps://doi.org/10.1002/anie.201401024Hofmann, PBis-NHC Chelate Complexes of Nickel(0) and Platinum(0)2014#N/ATRUE
4583
anie.20130922210.1002/anie.201309222FALSEhttps://doi.org/10.1002/anie.201309222Auffrant, AAngew. Chem.-Int. Edit.The oxidation of a Ni-II complex bearing a tetradentate phosphasalen ligand, which differs from salen by the presence of an iminophosphorane (P=N) in place of an imine unit, was easily achieved by addition of a silver salt. The site of this oxidation was investigated with a combination of techniques (NMR, EPR, UV/Vis spectroscopy, X-ray diffraction, magnetic measurements) as well as DFT calculations. All data are in agreement with a high-valent Ni-III center concentrating the spin density. This markedly differs from precedents in the salen series for which oxidation on the metal was only observed at low temperature or in the presence of additional ligands or anions. Therefore, thanks to the good electron-donating properties of the phosphasalen ligand, [Ni(Psalen)](+) represents a rare example of a tetracoordinated high-valent nickel complex in presence of a phenoxide ligand.A Tetracoordinated Phosphasalen Nickel(III) Complexhigh-valent metals; iminophosphoranes; nickel; one-electron oxidation; phosphasalensx22201446#N/AFALSE
4584
anie.20130889610.1002/anie.201308896FALSEhttps://doi.org/10.1002/anie.201308896Dai, LMAngew. Chem.-Int. Edit.A Class of 2D covalent organic polymers (COPs) incorporating a metal (such as Fe, Co, Mn) with precisely controlled locations of nitrogen heteroatoms and holes were synthesized from various N-containing metal-organic complexes (for example, metal-porphyrin complexes) by a nickel-catalyzed Yamamoto reaction. Subsequent carbonization of the metal-incorporated COPs led to the formation of COP-derived graphene analogues, which acted as efficient electro-catalysts for oxygen reduction in both alkaline and acid media with a good stability and free from any methanol-crossover/CO-poisoning effects.Highly Efficient Electrocatalysts for Oxygen Reduction Based on 2D Covalent Organic Polymers Complexed with Non-precious Metalscovalent organic polymers; electrocatalysts; graphene analogues; metal-organic frameworks; oxygen reduction reactionx323201432#N/AFALSE
4585
anie.20140075010.1002/anie.201400750FALSEhttps://doi.org/10.1002/anie.201400750Knochel, PAngew. Chem.-Int. Edit.We report a BF3-mediated direct alkynylation of pyridines at C(2) by using a variety of alkynyllithium reagents (oxidative cross-coupling). Moreover, we have developed a novel transition-metal-free cross-coupling method between Alkylmagnesium reagents and 4-substituted pyridines, such as isonicotinonitrile and 4-chloropyridine, by employing BF3.OEt2 as a promoter. The combination of these methods enabled us to efficiently prepare a range of di-, tri-, and tetrasubstituted pyridines.Transition-Metal-Free BF3-Mediated Oxidative and Non-Oxidative Cross-Coupling of Pyridinesalkynyllithium compounds; BF3; chloranil; cross-coupling; nitrogen heterocyCles35201444#N/ATRUE
4586
anie.20130817510.1002/anie.201308175FALSEhttps://doi.org/10.1002/anie.201308175Peters, JCA d(10) Ni-(H-2) Adduct as an Intermediate in H-H Oxidative Addition across a Ni-B Bondx2014#N/AFALSE
4587
anie.20130785110.1002/anie.201307851https://doi.org/10.1002/anie.201611069Garcia, HVisible-Light Photocatalytic Conversion of Carbon Monoxide to Methane by Nickel(II) OxidePhotocatalyst2013#N/AFALSE
4588
anie.20130774110.1002/anie.201307741https://doi.org/10.1002/anie.201307741Osakada, KAngew. Chem.-Int. Edit.Double-Decker-Type DinuClear Nickel Catalyst for Olefin Polymerization: Efficient Incorporation of Functional Co-monomerscopolymerization; homogeneous catalysis; nickel; polymerization; transition metalsx101201369#N/AFALSE
4589
anie.20140002310.1002/anie.201400023FALSEhttps://doi.org/10.1002/anie.201610990Ciriano, MATerminal Imido Rhodium Complexes2014#N/ATRUE
4590
anie.20130758110.1002/anie.201307581https://doi.org/10.1002/anie.201307581Shen, GZAngew. Chem.-Int. Edit.Integrated nanodevices with the capability of storing energy are widely applicable and have thus been studied extensively. To meet the demand for flexible integrated devices, all-solid-state asymmetric supercapacitors that simultaneously realize energy storage and optoelectronic detection were fabricated by growing Co3O4 nanowires on nickel fibers, thus giving the positive electrode, and employing graphene as both the negative electrode and light-sensitive material. The as-assembled integrated systems were characterized by an improved energy storage, enhanced power density (at least by 1860% enhanced) by improving the potential window from 0-0.6V to 01.5V, excellent photoresponse to white light, and superior flexibility of both the fiber-based asymmetric supercapacitor and the photodetector. Such flexible integrated devices might be used in smart and self-powered sensory, wearable, and portable electronics.Fiber-Based Flexible All-Solid-State Asymmetric Supercapacitors for Integrated Photodetecting Systemflexibility; integrated photodetector; nanofibers; nanotechnology; supercapacitorsPhotocatalyst335201443#N/AFALSE
4591
anie.20131099910.1002/anie.201310999FALSEhttps://doi.org/10.1002/anie.201310999Latos-Grazynski, LAngew. Chem.-Int. Edit.In the search for porphyrinoids with a built-in cyClopentadienyl moiety (true carbaporphyrins), a rational synthesis of carbathiaporphyrin, the synthons, has been elaborated. The donors (C,N,S,N) in the porphyrinic core of carbathiaporphyrinoids are potentially of fundamental importance for generating organometallic complexes, as exemplified through formation of the palladium(II) complex.Towards True Carbaporphyrinoids: Synthesis of 21-Carba-23thiaporphyrincarbaporphyrinoids; chlorin; NMR spectroscopy; palladium; porphyrinoids30201435#N/ATRUE
4592
anie.20131092810.1002/anie.201310928FALSEhttps://doi.org/10.1002/anie.201310928Ma, DWAngew. Chem.-Int. Edit.AspidophyllineA belongs to the akuammiline alkaloid family, the members of which possess intriguing cagelike structures and diverse biological activities. Herein we report a 15-step synthesis of this alkaloid from conveniently available starting materials. The key elements of the synthesis inClude an intramolecular oxidative coupling to create the tetracyClic furoindoline motif of the natural product and a [Ni(cod)(2)]-mediated cyClization to install its piperidine ring.Total Synthesis of the Monoterpenoid Indole Alkaloid (+/-)-Aspidophylline Amonoterpene indole alkaloids; natural products; nickel; oxidative coupling; total synthesis84201451#N/ATRUE
4593
anie.20131038610.1002/anie.201310386FALSEhttps://doi.org/10.1002/anie.201310386Zargarian, DAngew. Chem.-Int. Edit.We describe the results of a study on the stabilities of pincer-type nickel complexes relevant to catalytic hydroalkoxylation and hydroamination of olefins, CC and CX couplings, and fluorination of Alkyl halides. Complexes [(POCsp3OP)NiX] are stable for X=OSiMe3, OMes (Mes=1,3,5-Me3C6H2), NPh2, and CCH, whereas the O(tBu) and N(SiMe3)(2) derivatives decompose readily. The phenylacetylide derivative transforms gradually into the zero-valent species cis-[{(P),(C),(C)-(iPr(2)POCH(2)CHCH(2))}Ni{(2),(C),(C)-(iPr(2)P(O)CCPh)}]. Likewise, attempts to prepare [(POCsp3OP)NiF] gave instead the zwitterionic trinuClear species [{((3)-allyl)Ni}(2)-{,(P),(O)-(iPr(2)PO)(4)Ni}]. Characterization of these two complexes provides concrete examples of decomposition processes that can dismantle POCsp3OP-type pincer ligands by facile CO bond rupture. These results serve as a cautionary tale for the inherent structural fragility of pincer systems bearing phosphinite donor moieties, and provide guidelines on how to design more robust analogues.On the Stability of a POCsp3OP-Type Pincer Ligand in Nickel(II) ComplexesC-O bond Cleavage; nickel; pincer complexes35201457#N/ATRUE
4594
anie.20131024910.1002/anie.201310249FALSEhttps://doi.org/10.1002/anie.201310249Wu, LZMechanistic Insights into the Interface-Directed Transformation of Thiols into Disulfides and Molecular Hydrogen by Visible-Light Irradiation of Quantum Dots2014#N/ATRUE
4595
anie.20130998110.1002/anie.201309981FALSEhttps://doi.org/10.1002/anie.201610515Bendix, J[ReF6](2-): A Robust Module for the Design of Molecule-Based Magnetic Materials2014#N/ATRUE
4596
anie.20130992110.1002/anie.201309921FALSEhttps://doi.org/10.1002/anie.201309921Shinokubo, HAngew. Chem.-Int. Edit.The treatment of an antiaromatic norcorrole Ni-II complex with a kinetically stabilized silylene provided ring-expansion products in excellent yields through the highly regio- and stereoselective insertion into the - pyrrolic CC bonds. The resultant Ni-II porphyrinoid monoinsertion product exhibited relatively strong near-IR absorption bands due to the small HOMO-LUMO gap in spite of the disrupted cyClic -conjugation by the silicon atom.Near-IR Absorbing Nickel(II) Porphyrinoids Prepared by Regioselective Insertion of Silylenes into Antiaromatic Nickel(II) Norcorroleantiaromaticity; insertion; NIR absorption; porphyrinoids; silylenes33201442#N/ATRUE
4597
anie.20130986510.1002/anie.201309865FALSEhttps://doi.org/10.1002/anie.201309865Mori, HAngew. Chem.-Int. Edit.To introduce halogen-bond interactions between a cation and an anion, a novel Fe-III complex from iodine-substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and characterized. The compound exhibited the synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of -spins and played a crucial role in the synergistic magnetic transition between d- and -spins. In addition, the compound showed the light-induced excited spin state trapping effect.Synergistic Spin Transition between Spin Crossover and Spin-Peierls-like Singlet Formation in the Halogen-Bonded Molecular Hybrid System: [Fe(Iqsal)(2)][Ni(dmit)(2)]center dot CH3CN center dot H2Ohalogen bonds; iron complexes; nickel complexes; phase transitions; spin crossover55201424#N/ATRUE
4598
anie.20130349510.1002/anie.201303495FALSEhttps://doi.org/10.1002/anie.201303495Yu, SHAngew. Chem.-Int. Edit.Nickel/Nickel(II) Oxide NanopartiCles Anchored onto Cobalt(IV) Diselenide Nanobelts for the Electrochemical Production of Hydrogencobalt; electrocatalysis; electrochemistry; hydrogen evolution reaction; nickelx324201341#N/AFALSE
4599
anie.20130945610.1002/anie.201309456FALSEhttps://doi.org/10.1002/anie.201309456Hoveyda, AHAngew. Chem.-Int. Edit.The availability of enantiomerically enriched Carbonyl-containing compounds is essential to the synthesis of biologically active molecules. Since catalytic enantioselective conjugate addition (ECA) reactions directly generate the latter valuable Class of molecules, the design and development of such protocols represents a compelling objective in modern chemistry. Herein, we disClose the first solution to the problem of ECA of alkenyl groups to acyClic trisubstituted enones, an advance achieved by adopting an easily modifiable and fully catalytic approach. The requisite alkenylaluminum reagents are synthesized with exceptional site- and/or stereoselectivity by a Ni-catalyzed hydroalumination process, and the necessary enones are prepared through a site- and stereoselective zirconocene-catalyzed carboalumination/acylation reaction. The all-catalytic procedure is complete within four hours, furnishing the desired products in up to 77% overall yield and 99:1 enantiomeric ratio.A Multicomponent Ni-, Zr-, and Cu-Catalyzed Strategy for Enantioselective Synthesis of Alkenyl-Substituted Quaternary Carbonscarboalumination; conjugate additions; copper; N-heterocyClic carbenes; quaternary carbon center43201459#N/ATRUE
4600
anie.20130937410.1002/anie.201309374FALSEhttps://doi.org/10.1002/anie.201309374Oshio, HAngew. Chem.-Int. Edit.A bulky bidentate ligand was used to stabilize a macrocyClic [(Fe8Co6II)-Co-III] Cluster. Tuning the basicity of the ligand by derivatization with one or two methoxy groups led to the isolation of a homologous [(Fe8Co6II)-Co-III] species and a [(Fe6Fe2Co2Co2II)-Fe-III-Co-II-Co-III] complex, respectively. Lowering the reaction temperatures allowed isolation of [(Fe6Fe2Co2Co2II)-Fe-III-Co-II-Co-III] Clusters with all three ligands. Temperature-dependent absorption data and corresponding experiments with iron/nickel systems indicated that the iron/cobalt self-assembly process was directed by the occurrence of solution-state electron-transfer-coupled spin transition (ETCST) and its influence on reaction intermediate lability.Lability-Controlled Syntheses of Heterometallic Clusterscyanide bridges; ETCST; heterometallic complexes; mixed-valent compounds; self-assembly18201423#N/ATRUE
4601
anie.20130862010.1002/anie.201308620FALSEhttps://doi.org/10.1002/anie.201308620Hu, XLAngew. Chem.-Int. Edit.The direct formic acid fuel cell is an emerging energy conversion device for which palladium is considered as the state-of-the-art anode catalyst. In this communication, we show that the activity and stability of palladium for formic acid oxidation can be significantly enhanced using nickel phosphide (Ni2P) nanopartiCles as a cocatalyst. X-ray photoelectron spectroscopy (XPS) reveals a strong electronic interaction between Ni2P and Pd. A direct formic acid fuel cell incorporating the best Pd-Ni2P anode catalyst exhibits a power density of 550mWcm(-2), which is 3.5times of that of an analogous device using a commercial Pd anode catalyst.An Effective Pd-Ni2P/C Anode Catalyst for Direct Formic Acid Fuel Cellselectrocatalysis; formic acid; fuel cells; oxidation; nickel246201436#N/ATRUE
4602
anie.20130761810.1002/anie.201307618FALSEhttps://doi.org/10.1002/anie.201307618Maseras, FAngew. Chem.-Int. Edit.Pd and Ni dimers supported by PSiP ligands in which two hypervalent five-coordinate Si atoms bridge the two metal centers are reported. Crystallographic characterization revealed a rare square-pyramidal geometry at Si and an unusual asymmetric M2Si2 core (M=Pd or Ni). DFT calculations showed that the unusual structure of the core is also found in a model in which the phosphine and Si centers are not part of a pincer group, thus indicating that the observed geometry is not imposed by the PSiP ligand. NBO analysis showed that an asymmetric four-center two-electron (4c-2e) bond stabilizes the hypervalent Si atoms in the M2Si2 core.An Unusual Example of Hypervalent Silicon: A Five-Coordinate Silyl Group Bridging Two Palladium or Nickel Centers through a Nonsymmetrical Four-Center Two-Electron Bondelectronic structure; four-center two-electron bonds; hypervalent silicon; nickel; palladium31201470#N/ATRUE
4603
anie.20130706910.1002/anie.201307069TRUEhttps://doi.org/10.1002/anie.201307069Liu, LAngew. Chem.-Int. Edit.Nickel-Catalyzed Sonogashira Reactions of Non-activated Secondary Alkyl Bromides and Iodidesalkynes; cross-coupling; halides; nickel; synthetic methodsCsp1-Csp3E-NuHHBrAlkyneNo baseNo Base942013573/10/2022TRUE
4604
anie.20130690510.1002/anie.201306905FALSEhttps://doi.org/10.1002/anie.201604021Shinokubo, HSelective Synthesis of a [32]Octaphyrin(1.0.1.0.1.0.1.0) Bis(palladium) Complex by a Metal-Templated Strategy2013#N/ATRUE
4605
anie.20130658510.1002/anie.201306585FALSEhttps://doi.org/10.1002/anie.201306585Wiley, BJAngew. Chem.-Int. Edit.Optically Transparent Water Oxidation Catalysts Based on Copper Nanowires62201327#N/ATRUE
4606
anie.20130598710.1002/anie.201305987FALSEhttps://doi.org/10.1002/anie.201305987Masatake HarutaAngew. Chem.-Int. Edit.Chance and Necessity: My Encounter with Gold Catalysts98201450#N/ATRUE
4607
anie.20130534210.1002/anie.201305342FALSEhttps://doi.org/10.1002/anie.201305342Yao, KSAngew. Chem.-Int. Edit.Selective Reductive Cleavage of Inert Aryl C-O Bonds by an Iron Catalyst93201347#N/ATRUE
4608
anie.20130530810.1002/anie.201305308FALSEhttps://doi.org/10.1002/anie.201305308Robins, MJAngew. Chem.-Int. Edit.Luck, talent, and hard work: Currently, over a million tons of -olefins are manufactured per annum using the Shell Higher Olefin Process (SHOP). The discovery of the process was the result of correct model conceptions and lucky coincidence. W. Keim, one of the main participants in the development of SHOP, gives a personal account of the events.Oligomerization of Ethylene to alpha-Olefins: Discovery and Development of the Shell Higher Olefin Process (SHOP)210201325#N/ATRUE
4609
anie.20130399410.1002/anie.201303994FALSEhttps://doi.org/10.1002/anie.201303994Doyle, AGAngew. Chem.-Int. Edit.Nickel-Catalyzed Enantioselective Arylation of Pyridinium Ions: Harnessing an Iminium Ion Activation Modeasymmetric catalysis; cross-coupling; Negishi reaction; nickel; nitrogen heterocyCles48201340#N/ATRUE
4610
anie.20130280010.1002/anie.201302800FALSEhttps://doi.org/10.1002/anie.201302800Sutherland, AAngew. Chem.-Int. Edit.Nickel-Mediated Radioiodination of Aryl and HeteroAryl Bromides: Rapid Synthesis of Tracers for SPECT ImagingAryl bromides; halogen exchange; imaging agents; nickel; radioiodination27201326#N/ATRUE
4611
anie.20130261310.1002/anie.201302613FALSEhttps://doi.org/10.1002/anie.201302613Guan, HRAngew. Chem.-Int. Edit.A Robust Nickel Catalyst for Cyanomethylation of Aldehydes: Activation of Acetonitrile under Base-Free Conditionsaldol reaction; CH bond Activation; nickel; phosphane ligands; synthetic methods87201356#N/ATRUE
4612
anie.20130106610.1002/anie.201301066FALSEhttps://doi.org/10.1002/anie.201301066Zhang, XBAngew. Chem.-Int. Edit.An Efficient Three-Dimensional Oxygen Evolution Electrode255201349#N/ATRUE
4613
anie.20130086110.1002/anie.201300861FALSERay, KA High-Valent Heterobimetallic [Cu-III(mu-O)(2)Ni-III](2+) Core with NuCleophilic Oxo Groups2013#N/ATRUE
4614
anie.20120618610.1002/anie.201206186FALSEhttps://doi.org/10.1002/anie.201206186Ogoshi, SAngew. Chem.-Int. Edit.Synthesis of Five- and Six-Membered BenzocyClic Ketones through Intramolecular Alkene Hydroacylation Catalyzed by Nickel(0)/N-HeterocyClic Carbeneshomogeneous catalysis; hydroacylation; ketones; nickel; transition metalsx55201254#N/AFALSE
4615
anie.20121003010.1002/anie.201210030FALSEhttps://doi.org/10.1002/anie.201210030Weckhuysen, BMAngew. Chem.-Int. Edit.Correlating Metal Poisoning with Zeolite DeActivation in an Individual Catalyst PartiCle by Chemical and Phase-Sensitive X-ray Microscopycatalyst deActivation; fluid catalytic cracking; heterogeneous catalysis; X-ray microscopy; zeolites49201337#N/ATRUE
4616
anie.20120938410.1002/anie.201209384FALSEhttps://doi.org/10.1002/anie.201209384Han, BXAngew. Chem.-Int. Edit.Green Carbon Science: Scientific Basis for Integrating Carbon Resource Processing, Utilization, and RecyCling5022013255#N/ATRUE
4617
anie.20120874010.1002/anie.201208740FALSEhttps://doi.org/10.1002/anie.201208740Nitschke, JRAngew. Chem.-Int. Edit.Solvent-Dependent Host-Guest Chemistry of an Fe8L12 Cubic Capsule35201386#N/ATRUE
4618
anie.20120464610.1002/anie.201204646FALSEhttps://doi.org/10.1002/anie.201204646Tanaka, KAngew. Chem.-Int. Edit.Rhodium-Catalyzed Three-Component Cross-Addition of Silylacetylenes, Alkynyl Esters, and Electron-Deficient Alkenes or Isocyanatesx14201266#N/AFALSE
4619
anie.20120808210.1002/anie.201208082FALSEhttps://doi.org/10.1002/anie.201208082Schmalz, HGAngew. Chem.-Int. Edit.Enantioselective Nickel-Catalyzed Hydrocyanation of Vinylarenes Using Chiral Phosphine-Phosphite Ligands and TMS-CN as a Source of HCNasymmetric catalysis; nickel; nitriles; phoshite ligands; trimethylsilyl cyanide92201342#N/ATRUE
4620
anie.20120788010.1002/anie.201207880FALSEhttps://doi.org/10.1002/anie.201207880Hiyama, TAngew. Chem.-Int. Edit.Highly Chemoselective Carbon-Carbon sigma-Bond Activation: Nickel/Lewis Acid Catalyzed PolyfluoroArylcyanation of Alkynesalkynes; fluorides; insertion; nickel; nitriles63201343#N/ATRUE
4621
anie.20120784510.1002/anie.201207845FALSEhttps://doi.org/10.1002/anie.201207845Kaneda, KMetal-Ligand Core-Shell Nanocomposite Catalysts for the Selective Semihydrogenation of Alkynes2013#N/ATRUE
4622
anie.20120301410.1002/anie.201203014https://doi.org/10.1002/anie.201203014Vincent, JMCopper Catalyst Activation Driven by Photoinduced Electron Transfer: A Prototype Photolatent Click CatalystPhotocatalyst2012#N/AFALSE
4623
anie.20120742810.1002/anie.201207428FALSEhttps://doi.org/10.1002/anie.201207428Hartwig, JFAngew. Chem.-Int. Edit.Highly Reactive, Single-Component Nickel Catalyst Precursor for Suzuki-Miyuara Cross-Coupling of HeteroAryl Boronic Acids with HeteroAryl HalidesbiAryls; cross-coupling; homogeneous catalysis; nickel; synthetic methods124201238#N/ATRUE
4624
anie.20120676710.1002/anie.201206767FALSEhttps://doi.org/10.1002/anie.201206767Wesemann, LAngew. Chem.-Int. Edit.Side-On Coordinated Distannene: An Unprecedented Nickel(0) Complexcoordination chemistry; distannene; nickel; tin; xanthene16201267#N/ATRUE
4625
anie.20120634310.1002/anie.201206343FALSEhttps://doi.org/10.1002/anie.201206343Connon, SJAngew. Chem.-Int. Edit.The Thiolate-Catalyzed Intermolecular Crossed Tishchenko Reaction: Highly Chemoselective Coupling of Two Different Aromatic Aldehydes31201247#N/ATRUE
4626
anie.20120134910.1002/anie.201201349FALSEhttps://doi.org/10.1002/anie.201201349Carrier, XAngew. Chem.-Int. Edit.Surface Science Approach to the Solid-Liquid Interface: Surface-Dependent Precipitation of Ni(OH)(2) on alpha-Al2O3 Surfacesalumina; surface chemistry; X-ray absorption spectroscopyx18201229#N/AFALSE
4627
anie.20120069910.1002/anie.201200699FALSEAdzic, RRHydrogen-Evolution Catalysts Based on Non-Noble Metal Nickel-Molybdenum Nitride Nanosheetsx2012#N/AFALSE
4628
anie.20120621910.1002/anie.201206219FALSEhttps://doi.org/10.1002/anie.201206219Bach, UAngew. Chem.-Int. Edit.Highly Efficient p-Type Dye-Sensitized Solar Cells based on Tris(1,2-diaminoethane)Cobalt(II)/(III) Electrolytes151201332#N/ATRUE
4629
anie.20120621510.1002/anie.201206215FALSEhttps://doi.org/10.1002/anie.201206215Bercaw, JEAngew. Chem.-Int. Edit.Activator-Free Olefin Oligomerization and Isomerization Reactions Catalyzed by an Air- and Water-Tolerant Wacker Oxidation Intermediate15201225#N/ATRUE
4630
anie.20120596910.1002/anie.201205969FALSEhttps://doi.org/10.1002/anie.201205969Li, JHAngew. Chem.-Int. Edit.Nickel-Catalyzed Kumada Reaction of Tosylalkanes with Grignard Reagents to Produce Alkenes and Modified ArylketonesArylketones; cross-coupling; Kumada reaction; nickel; tosylalkanes44201274#N/ATRUE
4631
anie.20120516710.1002/anie.201205167FALSEhttps://doi.org/10.1002/anie.201205167Iwasawa, YAngew. Chem.-Int. Edit.The Active Phase of Nickel/Ordered Ce2Zr2Ox Catalysts with a Discontinuity (x=7-8) in Methane Steam Reformingmethane; nickel; solid solutions; steam reforming; XAFS26201242#N/ATRUE
4632
anie.20120484210.1002/anie.201204842FALSEhttps://doi.org/10.1002/anie.201204842Markovic, NMAngew. Chem.-Int. Edit.Enhancing the Alkaline Hydrogen Evolution Reaction Activity through the Bifunctionality of Ni(OH)2/Metal Catalystselectrocatalysis; electrochemistry; hydrogen; hydrogen evolution reaction; surface chemistry399201230#N/ATRUE
4633
anie.20110732910.1002/anie.201107329https://doi.org/10.1002/anie.201107329Eisenberg, RAngew. Chem.-Int. Edit.A Nickel Thiolate Catalyst for the Long-Lived Photocatalytic Production of Hydrogen in a Noble-Metal-Free Systemhomogeneous catalysis; hydrogen; nickel; photocatalysis; solar energyPhotocatalyst248201238#N/AFALSE
4634
anie.20120439510.1002/anie.201204395FALSEhttps://doi.org/10.1002/anie.201511621Shinokubo, HGram-Scale Synthesis of Nickel(II) Norcorrole: The Smallest Antiaromatic Porphyrinoid2012#N/ATRUE
4635
anie.20120427510.1002/anie.201204275FALSEhttps://doi.org/10.1002/anie.201204275Hu, XLAngew. Chem.-Int. Edit.Copper-Catalyzed Cross-Coupling of Functionalized Alkyl Halides and Tosylates with Secondary and Tertiary Alkyl Grignard Reagents74201257#N/ATRUE
4636
anie.20120352110.1002/anie.201203521FALSEhttps://doi.org/10.1002/anie.201203521Louie, JAngew. Chem.-Int. Edit.An Expeditious Route to Eight-Membered HeterocyCles By Nickel-Catalyzed CyCloaddition: Low-Temperature C-sp2-C-sp3 Bond Cleavageazetidinones; C?C Activation; cyCloaddition; dihydroazocines; nickel53201289#N/ATRUE
4637
anie.20120205510.1002/anie.201202055FALSEXu, QHighly Dispersed Surfactant-Free Nickel NanopartiCles and Their Remarkable Catalytic Activity in the Hydrolysis of Ammonia Borane for Hydrogen Generation2012#N/ATRUE
4638
anie.20120199910.1002/anie.201201999FALSEhttps://doi.org/10.1002/anie.201201999Stahl, SSAngew. Chem.-Int. Edit.Development of an O-2-Sensitive Fluorescence-Quenching Assay for the Combinatorial Discovery of Electrocatalysts for Water Oxidation54201254#N/ATRUE
4639
anie.20110443310.1002/anie.201104433FALSEhttps://doi.org/10.1002/anie.201104433Schwarz, HAngew. Chem.-Int. Edit.C-N and C-C Bond Formations in the Thermal Reactions of Bare Ni(NH2)(+) with C2H4: Mechanistic Insight on the Metal-Mediated Hydroamination of an Unactivated Olefinbond Activation; C?C bond formation; C?N coupling; density functional calculations; nickelx162012105#N/AFALSE
4640
anie.20120173710.1002/anie.201201737FALSEhttps://doi.org/10.1002/anie.201602202Zhang, TA Noble-Metal-Free Catalyst Derived from Ni-Al Hydrotalcite for Hydrogen Generation from N2H4 center dot H2O Decomposition2012#N/ATRUE
4641
anie.20120028010.1002/anie.201200280FALSEhttps://doi.org/10.1002/anie.201200280de Jong, KPAngew. Chem.-Int. Edit.Suppression of Carbon Deposition in the Iron-Catalyzed Production of Lower Olefins from Synthesis Gas68201226#N/ATRUE
4642
anie.20110261710.1002/anie.201102617FALSEhttps://doi.org/10.1002/anie.201102617
Jalowiecki-Duhamel, L
Angew. Chem.-Int. Edit.Highly Efficient and Stable CeNiHZOY Nano-Oxyhydride Catalyst for H-2 Production from Ethanol at Room Temperatureethanol; heterogeneous catalysis; hydrogen; metal oxides; sustainable chemistryx42201131#N/AFALSE
4643
anie.20120012010.1002/anie.201200120FALSEhttps://doi.org/10.1002/anie.201200120Chang, SAngew. Chem.-Int. Edit.A Versatile Rhodium(I) Catalyst System for the Addition of Heteroarenes to both Alkenes and Alkynes by a C?H Bond Activation118201272#N/ATRUE
4644
anie.20110835010.1002/anie.201108350TRUEhttps://doi.org/10.1002/anie.201108350Lei, AWAngew. Chem.-Int. Edit.Nickel-Catalyzed Heck-Type Alkenylation of Secondary and Tertiary a-Carbonyl Alkyl BromidesAlkyl bromides; a alkenylation; Heck reaction; nickel; radical reactionsCsp2-Csp3E-NuHHMgXVinylIonic-PO41522012463/10/2022TRUE
4645
anie.20110082810.1002/anie.201100828https://doi.org/10.1002/anie.201100828Girault, HHAngew. Chem.-Int. Edit.Interfacial Photoreduction of Supercritical CO2 by an Aqueous CatalystPhotocatalyst50201142#N/AFALSE
4646
anie.20110762010.1002/anie.201107620FALSEhttps://doi.org/10.1002/anie.201510077Mirkin, CACrystallographic Snapshots of the Bond-Breaking Isomerization Reactions Involving Nickel(II) Complexes with Hemilabile Ligands2012#N/ATRUE
4647
anie.20110736010.1002/anie.201107360FALSEhttps://doi.org/10.1002/anie.201107360Sato, YAngew. Chem.-Int. Edit.Nickel-Catalyzed Enantio- and Diastereoselective Three-Component Coupling of 1,3-Dienes, Aldehydes, and a Silylborane Leading to a-Chiral Allylsilanesaldehydes; asymmetric catalysis; dienes; nickel; silylborane48201274#N/ATRUE
4648
anie.20110713610.1002/anie.201107136FALSEhttps://doi.org/10.1002/anie.201107136Shi, ZJAngew. Chem.-Int. Edit.Extrusion of CO from Aryl Ketones: Rhodium(I)-Catalyzed C?C Bond Cleavage Directed by a Pyridine Group130201287#N/ATRUE
4649
anie.20100663910.1002/anie.201006639FALSEhttps://doi.org/10.1002/anie.201006639Schlogl, RDissolved Carbon Controls the Initial Stages of Nanocarbon Growthx2011#N/AFALSE
4650
anie.20110643310.1002/anie.201106433FALSEhttps://doi.org/10.1002/anie.201106433Ueno, MAngew. Chem.-Int. Edit.Chiral Zinc-Catalyzed Asymmetric a-Alkylallylation and a-Chloroallylation of Aldehydes35201183#N/ATRUE
4651
anie.20100542710.1002/anie.201005427FALSEhttps://doi.org/10.1002/anie.201005427Artero, VAngew. Chem.-Int. Edit.Noncovalent Modification of Carbon Nanotubes with Pyrene-Functionalized Nickel Complexes: Carbon Monoxide Tolerant Catalysts for Hydrogen Evolution and Uptakecarbon; heterogeneous catalysis; hydrogen; nanotubes; nickelx203201116#N/AFALSE
4652
anie.20110596410.1002/anie.201105964FALSEHu, XLCross-Coupling of Nonactivated Alkyl Halides with Alkynyl Grignard Reagents: A Nickel Pincer Complex as the Catalyst2011#N/ATRUE
4653
anie.20110580910.1002/anie.201105809FALSEhttps://doi.org/10.1002/anie.201105809Osuka, AAngew. Chem.-Int. Edit.Rearrangements of a [36]Octaphyrin Triggered by Nickel(II) Metalation: Metamorphosis to a Directly meso-beta-Linked Diporphyrindiporphyrin; metalation; octaphyrin; porphyrinoids; rearrangement25201145#N/ATRUE
4654
anie.20110460410.1002/anie.201104604FALSEhttps://doi.org/10.1002/anie.201104604Barnes, PAngew. Chem.-Int. Edit.Dynamic X-Ray Diffraction Computed Tomography Reveals Real-Time Insight into Catalyst Active Phase Evolution76201133#N/ATRUE
4655
anie.20110342810.1002/anie.201103428FALSEhttps://doi.org/10.1002/anie.201103428Yakovenko, AAAngew. Chem.-Int. Edit.Activated Phenacenes from Phenylenes by Nickel-Catalyzed Alkyne CyCloadditionsaromatic compounds; cyCloaddition; nickel; phenacenes; reaction mechanisms17201140#N/ATRUE
4656
anie.20110327110.1002/anie.201103271FALSEhttps://doi.org/10.1002/anie.201103271Schaus, SEAngew. Chem.-Int. Edit.Catalytic Diastereoselective Petasis Reactions52201145#N/ATRUE
4657
anie.20100193710.1002/anie.201001937FALSEhttps://doi.org/10.1002/anie.201001937Ishii, AAngew. Chem.-Int. Edit.Cleavage of C-S and O-H Bonds by Platinum(0) Complexes To Give Five-Membered 1,2-OxaplatinacyClesx17201050#N/AFALSE
4658
anie.20100192910.1002/anie.201001929https://doi.org/10.1002/anie.201001929Wu, YTAngew. Chem.-Int. Edit.Synthesis, Structure, and Photophysical Properties of Dibenzo[de,mn]naphthacenesPhotocatalyst72201059#N/AFALSE
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anie.19942330110.1002/anie.199423301FALSEhttps://doi.org/10.1002/anie.199423301VICKERS, DMAngew. Chem.-Int. Edit. Engl.SYNTHESIS AND CHARACTERIZATION OF THE FIRST COMPOUNDS CONTAINING A STABLE PHOSPHIRENYL CATION - CRYSTAL-STRUCTURE AND MOLECULAR-STRUCTURE OF [NI(ETA(3)-PC(2)TBU(2))(ETA(5)-P(3)C(2)TBU(2))W(CO)(5)]42199425#N/ATRUE
4824
anie.19942104110.1002/anie.199421041FALSEhttps://doi.org/10.1002/anie.199421041PRABHAKAR, BAngew. Chem.-Int. Edit. Engl.NIO/CAO-CATALYZED FORMATION OF SYNGAS BY COUPLED EXOTHERMIC OXIDATIVE CONVERSION AND ENDOTHERMIC CO2 AND STEAM REFORMING OF METHANE51199414#N/ATRUE
4825
anie.19920623110.1002/anie.199206231FALSEhttps://doi.org/10.1002/anie.199206231PAULUS, HAngew. Chem.-Int. Edit. Engl.The oxidative dehydrogenation of only one C-N bond in the [Ni(tetrahydrosalen)] complex 1 surprisingly affords the corresponding [Ni(dihydrosalen)] complex. This reaction is thus a rare example of the Activation of oxygen by nickel complexes. The Ni atom in 1 has an almost square-planar coordination geometry, and the two benzene rings are bent slightly upwards and downwards relative to the NiO2N2 plane.OXYGEN Activation ON NICKEL(II)TETRAHYDROSALEN COMPLEXES WITH THE FORMATION OF NICKEL(II)DIHYDROSALEN COMPLEXESx50199216#N/AFALSE
4826
anie.19920612110.1002/anie.199206121FALSEhttps://doi.org/10.1002/anie.199206121KUCHEN, WAngew. Chem.-Int. Edit. Engl.Against all previous experience for Ni(II) complexes chemistry, planarity is not necessarily linked with diamagnetism. An X-ray structure determination of the title complex 1 revealed that the Ni(II) center is in a strictly planar environment. Yet in the solid state and in solution. 1 shows Curie-Weiss behavior and has a magnetic moment, as expected for tetrahedral Ni(II) complexes.BIS(P,P-DI-TERT-BUTYLPHOSPHINIC-N-ISOPROPYLAMIDATO-N,O)NICKEL(II), A PARAMAGNETIC PLANAR COMPLEXx2019928#N/AFALSE
4827
anie.19942087110.1002/anie.199420871FALSEhttps://doi.org/10.1002/anie.201204395SOLANS, XTHE VERSATILITY OF THE AZIDO LIGAND - LINKAGE OF NI-II CENTERS TO FORM A CHAIN WITH ONE END-TO-END AND 3 END-ON BRIDGES IN ALTERNATION1994#N/ATRUE
4828
anie.19941879110.1002/anie.199418791FALSEhttps://doi.org/10.1002/anie.199418791SMITH, KMAngew. Chem.-Int. Edit. Engl.5,10,15,20-TETRA-TERT-BUTYLPORPHYRIN AND ITS REMARKABLE REACTIVITY IN THE 5-POSITION AND 15-POSITION121199415#N/ATRUE
4829
anie.19941373110.1002/anie.199413731FALSEhttps://doi.org/10.1002/anie.199413731GORLS, HAngew. Chem.-Int. Edit. Engl.BIS(TETRAMETHYLBUTYNEDIOL)NICKEL(0), THE FIRST PURE MONOALKYNE COMPLEX OF NICKEL AND ITS CHEMISTRY30199414#N/ATRUE
4830
anie.19941363110.1002/anie.199413631FALSEhttps://doi.org/10.1002/anie.199413631JAGER, EGAngew. Chem.-Int. Edit.CHANGE OF ORIENTATION OF AXIAL IMIDAZOLE LIGANDS IN A CYTOCHROME-B MODEL COMPLEX IN RESPONSE TO A CHANGE IN THE OXIDATION-STATE OF THE METAL CENTER11199433#N/ATRUE
4831
anie.19910961110.1002/anie.199109611FALSEhttps://doi.org/10.1002/anie.199109611BAYER, GMAngew. Chem.-Int. Edit. Engl.In its crude form, polyacetylene is black, insoluble, nonprocessible, and unstable. Now, ylide-nickel catalysts have opened up an approach to the preparation of novel polyacetylenes in a stabilizing polyacrylonitrile matrix. These were characterized by IR and UV spectroscopy. The composition of the polymers can be controlled; the degree of polyene' conjugation is dependent on the choice of ligand. Even for polyacetylene contents over 50%, the polymers are soluble and easily processed.ELECTRONIC-STRUCTURE AND REACTIVITY OF YLIDE SYSTEMS .17. POLYACETYLENE IN POLYACRYLONITRILE MATRIX - NOVEL SOLUBLE MATRIX POLYACETYLENES BY YLIDE-NICKEL CATALYSISx9199123#N/AFALSE
4832
anie.19940879110.1002/anie.199408791FALSEhttps://doi.org/10.1002/anie.199408791PORSCHKE, KRAngew. Chem.-Int. Edit. Engl.CYClOTRIMERIZATION OF ETHYNE ON THE COMPLEX FRAGMENT [(ETA(1)-TBU(2)PCH(2)PTBU(2))NI-0] WITH FORMATION OF AN ETA(6)-BENZENE-NICKEL(0) COMPLEX33199429#N/ATRUE
4833
anie.19910375110.1002/anie.199103751FALSEhttps://doi.org/10.1002/anie.199103751MAITLIS, PMAngew. Chem.-Int. Edit. Engl.Metallomesogens, metal complexes of organic ligands which exhibit liquid crystalline (mesomorphic) character, combine the variety and range of metal-based coordination chemistry with the extraordinary physical properties exhibited by liquid crystals. Thermotropic metallomesogens have been made incorporating many metals, inCluding representatives of s-, p-, d- and even f-block elements. Both rodlike (calamitic) and dislike (discotic) thermotropic metallomesogens are known, and examples of all the main mesophase types are found. Many different varieties of ligand can be used: monodentate (4-substituted pyridines), bidentate (beta-diketonates, dithiolenes, Carbonylates, cyClometalated aromatic amines), or polydentate (phthalocyanines, porphyrins). As with organic mesogens, molecular shape and intermolecular forces play an important role, i.e. the ligands are important in determining mesophase character. The chief requirement for a metallomesogen is a rigid core, usually unsaturated and either rod- or disklike in shape, bearing several long hydrocarbon tails. The metal atom is usually at or near the center of gravity of the molecule. In some cases the ligands are themselves mesogenic, but this is not requirement. The presence of one or more metals opens many exciting possibilities: new shapes, not easily generated by organic compounds, and hence new properties are then accessible. The incorporation of d-block metals brings with it features such as color and paramagnetism. Profound effects arise from the large and polarizable concentration of electron density that every metal atom possesses, since the molecular polarizability is a key factor in determining whether a molecule will form liquid crystals. Enhanced physical properties (e.g. high birefringencies), as well as new and unexpected ones, will result. A major requirement for metallomesogens to find applications in new device technology is that the metal-ligand bonds are strong and inert and the complexes stable; this can be accomplished with, for example, chelating ligands and the 5 d metals.METALLOMESOGENS - METAL-COMPLEXES IN ORGANIZED FLUID PHASESx5691991228#N/AFALSE
4834
anie.19930714110.1002/anie.199307141FALSEhttps://doi.org/10.1002/anie.199307141NUBER, BAngew. Chem.-Int. Edit. Engl.Six 0-H...0 contacts in the second coordination sphere are formed when the octahedral neutral complexes [M(III)L] (1, M = Cr, Fe: for L see the structural formula on the right) react in acetone with [M'II(OH2)6]2+ ions (M' = Mn. Co, Ni, Zn) to give the complexes [1 {M'II(OH2)6}1]2+. In contrast, [Co(III)L] coordinates in the first coordination sphere to give the complexes [LCoM'IICoL]2-.MOLECULAR RECOGNITION OF HEXAAQUA TRANSITION METAL(II) IONS20199312#N/ATRUE
4835
anie.19930429110.1002/anie.199304291FALSEhttps://doi.org/10.1002/anie.199304291STOLZENBERG, AMAngew. Chem.-Int. Edit. Engl.Under extremely mild conditions (room temperature) the hexahydroporphyrin 2 isomerizes to its tautomer 3. Complex 2 is the first metal complex with a 2,3,7,8,15,23-hexahydroporphyrin as ligand and is synthesized from 1 by reduction with sodium amalgam. [GRAPHICS]THE REDUCTIVE CHEMISTRY OF NICKEL HYDROPORPHYRINS .3. FACILE FORMATION OF HEXAHYDROPORPHYRIN COMPLEXES BY REDUCTION OF OCTAETHYLISOBACTERIOCHLORINNICKEL(II)10199321#N/ATRUE
4836
anie.19930388110.1002/anie.199303881FALSEhttps://doi.org/10.1002/anie.199303881HILDENBRAND, KAngew. Chem.-Int. Edit. Engl.Not a reductive rupture, but a strengthening of he result of the reduction of the dialane 1 with lithium. The salt isolated after addition of TMEDA contains the radical anion of 1, in which. as results of an X-ray structural analysis show, the Al-C bonds are distinctly longer (+ 0.06 angstrom) and the Al-Al bond considerably shorter (0.13 angstrom) than in 1 itself. These findings are in accord with results of MO calculations, which indicate a stabilization of the Al-Al bond by the additional electron. [GRAPHICS]AN AL-AL ONE-ELECTRON PI-BOND65199345#N/ATRUE
4837
anie.19930116110.1002/anie.199301161FALSEhttps://doi.org/10.1002/anie.199301161REIBENSPIES, JHAngew. Chem.-Int. Edit. Engl.Thanks to the unusual folding of the diazacyClooctane(~)ligand, which normally blocks an axial position of the metal center, the paramagnetic, blue nickel complex 1 containing a hexacoordinate central Ni atom could be synthesized. In the crystal the 0 atom of the Carbonyl group not coordinated to the Ni center participates in hydrogen bonding with water molecules to form a three-dimensional network.(~)[GRAPHICS]AXIAL LIGATION OF DIAZACYClOOCTANENICKEL AND DIAZACYClOOCTANEZINC COMPLEXES36199318#N/ATRUE
4838
anie.19930092110.1002/anie.199300921FALSEhttps://doi.org/10.1002/anie.199300921CRABTREE, RHAngew. Chem.-Int. Edit. Engl.At room temperature and ambient pressure,(~)the complex 1 catalyzes the reduction of methylviologen MV2+ with CO/H2O. The metal center and ligand coordination sphere suspected to be the active site of the enzyme CO dehydrogenase are present in 1; the catalytic activity of 1, like that of the biological system, is inhibited by CN- and Mel, and in the absence of MV2+ a Ni(I) complex is formed. Complex 1 also catalyzes the oxidation of CO to CO2 in air. [GRAPHICS]FUNCTIONAL-MODELING OF CO DEHYDROGENASE - CATALYTIC REDUCTION OF METHYLVIOLOGEN BY CO/H2O WITH AN N, O, S-LIGATED NICKEL-CATALYST2119939#N/ATRUE
4839
anie.19921343110.1002/anie.199213431FALSEhttps://doi.org/10.1002/anie.199213431WOCADLO, SMETAL-COMPLEXES OF HETEROARENES .4. TETRAKIS(ETA-1-PHOSPHABENZENE)NICKEL1992#N/ATRUE
4840
anie.19920401110.1002/anie.199204011FALSEhttps://doi.org/10.1002/anie.199204011Martin, RAngew. Chem.-Int. Edit. Engl.ON THE INFLUENCE OF HETEROATOMS IN ALPHA-FUNCTIONALIZED AND BETA-FUNCTIONALIZED Alkyl TRANSITION-METAL COMPOUNDS431992317#N/ATRUE
4841
anie.19880839110.1002/anie.198808391https://doi.org/10.1002/anie.198808391WITTE, JAngew. Chem.-Int. Edit. Engl.ACETYLENE POLYMERIZATION WITH YLIDE-NICKEL CATALYSTSx17198829#N/AFALSE
4842
anie.19880833110.1002/anie.198808331FALSEhttps://doi.org/10.1002/anie.198808331KRUGER, CAngew. Chem.-Int. Edit. Engl.MONONUClEAR AND DINUClEAR NICKEL(0) COMPLEXES OF BUTADIYNEx37198811#N/AFALSE
4843
anie.19920070110.1002/anie.199200701FALSEhttps://doi.org/10.1002/anie.199200701PENG, SMAngew. Chem.-Int. Edit. Engl.A tetraazamacrocyCle from three pyrrole units and a condensed furan ring-''furochlorophin''-surrounds the Ni(II) ion in 1. This 18-pi-electron system with a basic chlorin structure is formed surprisingly easily from the thermolysis of (octadehydrocorrinato)nickel(II) chloride. This synthesis will probably not only provide new impetus for corrinoid chemistry; but the absorption characteristics of the metal complex and the free base make these interesting compounds for applications in photodynamic cancer therapy.1ST EXAMPLE OF A CHLOROPHIN FROM AN UNEXPECTED OXIDATIVE RING-OPENING OF AN (OCTADEHYDROCORRINATO)NICKEL(II) SALT24199214#N/ATRUE
4844
anie.19911666110.1002/anie.199116661FALSEWILKE, GNICKEL(0)-CARBENE COMPLEXES1991#N/ATRUE
4845
anie.19870461110.1002/anie.198704611FALSEhttps://doi.org/10.1002/anie.198704611BREUER, OAngew. Chem.-Int. Edit. Engl.SURFACE-REACTIONS .8. DECarbonylATION ON CARBON-SUPPORTED NICKEL-CATALYSTSx16198724#N/AFALSE
4846
anie.19911158110.1002/anie.199111581FALSEhttps://doi.org/10.1002/anie.199111581MEYERSTEIN, DAngew. Chem.-Int. Edit. Engl.A distinctly negative reaction volume (-16.4 +/- 1.6 cm3 mol-1) characterizes reaction (a), which involves an almost pressure-independent bond formation and a highly pressure-decelerated bond breakage process. This indicates that pressure assists the formation of the cobalt-carbon sigma-bond by shifting the overall equilibrium to the right with increasing pressure. These results are discussed in terms of ligand substitution of Co(II) and homolysis of Co(III)-complexes, respectively (nta = nitrilotriacetate). [Co(II)(nta)(H2O)]2- + .CH3 reversible [Co(III)(nta)(H2O)(CH3)]- + H2O (a)PRESSURE-ASSISTED FORMATION OF A COBALT CARBON SIGMA-BOND - A HIGH-PRESSURE PULSE-RADIOLYSIS STUDY22199139#N/ATRUE
4847
anie.19910716110.1002/anie.199107161FALSEhttps://doi.org/10.1002/anie.199107161HERMOSO, JAAngew. Chem.-Int. Edit. Engl.A remarkable twelve-membered heterocyCle is present in the title complex anion 1. It is formed in the reaction of the NBu4 salt of the corresponding hydroxo-bridged anion with malonitrile in the molecular ratio 1:2. Catalytic amounts of the Ni compound, on the other hand, effect a cyClotrimerization of the malonitrile, leading to a highly functionalized pyridine derivative.NICKEL-CATALYZED CYClOTRIMERIZATION OF MALONONITRILE - THE DICYANOMETHANIDE-BRIDGED, ANIONIC NI-II COMPLEX [(NI(C5F5)2(MU-NCCHCN))2]2-36199115#N/ATRUE
4848
anie.19851001110.1002/anie.198510011https://doi.org/10.1002/anie.198510011FINK, GAngew. Chem.-Int. Edit. Engl.NOVEL POLYMERIZATION OF ALPHA-OLEFINS WITH THE CATALYST SYSTEM NICKEL AMINOBIS(IMINO)PHOSPHORANEx15919856#N/AFALSE
4849
anie.19901062110.1002/anie.199010621FALSEhttps://doi.org/10.1002/anie.199010621KASAI, NAngew. Chem.-Int. Edit. Engl.NICKEL-CATALYZED CYClODIMERIZATION OF HEXAPENTAENES - [4]RADIALENES AND [5]RADIALENONES WITH CUMULATED DOUBLE-BONDS16199015#N/ATRUE
4850
anie.19850599110.1002/anie.198505991https://doi.org/10.1002/anie.198505991WITTE, JAngew. Chem.-Int. Edit. Engl.HIGHLY-ACTIVE YLIDE-NICKEL CATALYSTS FOR THE POLYMERIZATION OF ETHYLENEx65198525#N/AFALSE
4851
anie.19900395110.1002/anie.199003951FALSEhttps://doi.org/10.1002/anie.199003951KUBIAK, CPAngew. Chem.-Int. Edit. Engl.[NI3(MU-3-CNME)(MU-3-I)(CNME)2(PH2PCH2PPH2)2]I, A TRIANGULO NICKEL ClUSTER WITH AN UNPRECEDENTED SYMMETRIC LINEAR MU-3-ETA-1 ISOCYANIDE LIGAND26199015#N/ATRUE
4852
anie.19900298110.1002/anie.199002981FALSEhttps://doi.org/10.1002/anie.199002981MICHAELIS, SAngew. Chem.-Int. Edit. Engl.ON A (1,4-DIAZABUTADIENE)BIS(ETHENE)NICKEL(0) COMPLEX AND RELATED-COMPOUNDS21199022#N/ATRUE
4853
anie.19900106110.1002/anie.199001061FALSEhttps://doi.org/10.1002/anie.199001061SCHWARZ, CAngew. Chem.-Int. Edit. Engl.OXYGEN Activation WITH TRANSITION-METAL COMPLEXES - NICKEL-CATALYZED OXIDATION OF A PENTACOORDINATED SUBSTRATE29199034#N/ATRUE
4854
anie.19850231110.1002/anie.198502311FALSEhttps://doi.org/10.1002/anie.198502311KUCHEN, WAngew. Chem.-Int. Edit. Engl.THE 1ST APPLICATION OF 2D-NMR TO THE SPECTRAL-ANALYSIS OF A PARAMAGNETIC COMPLEX - EXAMPLE - BIS[R-(+)-P,P-DIETHYLTHIOPHOSPHINIC ACID-N-ALPHA-METHYLBenzylAMIDO]NICKEL(II)x30198511#N/AFALSE
4855
anie.19891049110.1002/anie.198910491FALSEhttps://doi.org/10.1002/anie.198910491POLI, NAngew. Chem.-Int. Edit. Engl.N-ANALOGS OF METAL ACETYLACETONATES - BIS(1,2,6,7-TETRACYANO-3,5-DIIMINO-3,5-DIHYDRO-PYRROLIZINIDO)METAL(II), (METAL = FE, NI, CU, ZN) - CRYSTAL-STRUCTURE OF THE COPPER DERIVATIVE2519896#N/ATRUE
4856
anie.19890808110.1002/anie.198908081FALSEhttps://doi.org/10.1002/anie.198908081THOMAS, JMAngew. Chem.-Int. Edit.PROBING CHANGES IN THE STRUCTURE AND PERFORMANCE OF A LITHIUM NICKEL-OXIDE CATALYST BY INSITU X-RAY-DIFFRACTION DURING THE HIGH-TEMPERATURE OXIDATIVE COUPLING OF METHANE519897#N/ATRUE
4857
anie.19880941110.1002/anie.198809411FALSEhttps://doi.org/10.1002/anie.198809411
WICKRAMASINGHE, WA
Angew. Chem.-Int. Edit. Engl.STABILIZATION OF 1,2,4,5-TETRADEHYDROBENZENE BY COMPLEXATION AT 2 NICKEL(0) CENTERS14198816#N/ATRUE
4858
anie.19880414110.1002/anie.198804141FALSEhttps://doi.org/10.1002/anie.198804141BAUM, GMETAL PI-COMPLEXES OF BENZENE-DERIVATIVES .31. ELECTRON ELECTRON-SPIN SPIN LONG-RANGE INTERACTION AS STUDIED IN THE DIRADICAL DICATION [DI(BIS(DIMETHYLPHOSPHINO-ETA-6-BENZENE)CHROMIUM(I))-NICKEL(0)]1988#N/ATRUE
4859
anie.19870571110.1002/anie.198705711FALSEhttps://doi.org/10.1002/anie.198705711MILCHEREIT, AAngew. Chem.-Int. Edit. Engl.NICKEL(0)-CATALYZED PRODUCTION OF A FUNCTIONALIZED CYClOPENTANECarbonylIC ACID FROM 1,3-BUTADIENE AND CO25319879#N/ATRUE
4860
anie.19860753110.1002/anie.198607531FALSEhttps://doi.org/10.1002/anie.198607531RAO, CNRAngew. Chem.-Int. Edit. Engl.NATURE OF NI AND CU SPECIES IN REDUCED BIMETALLIC NI-CU/AL2O3 CATALYSTS319867#N/ATRUE
4861
anie.19830735110.1002/anie.198307351FALSEhttps://doi.org/10.1002/anie.198307351ESCHENMOSER, AAngew. Chem.-Int. Edit. Engl.ACID-CATALYZED DEMETALATION OF NICKEL-HYDROCORPHIN AND COBALT-CORRIN COMPLEXES WITH 1,3-PROPANEDITHIOLx20198323#N/AFALSE
4862
anie.19860640110.1002/anie.198606401FALSEhttps://doi.org/10.1002/anie.198606401WILKE, GAngew. Chem.-Int. Edit. Engl.NICKELACYClOBUTABENZENE COMPOUNDS BY OXIDATIVE ADDITION OF CYClOPROPABENZENE TO NICKEL(0) COMPOUNDS42198618#N/ATRUE
4863
anie.19850961110.1002/anie.198509611FALSEhttps://doi.org/10.1002/anie.198509611HERNANDEZ, EAngew. Chem.-Int. Edit. Engl.NICKEL(O)-CATALYZED SYNTHESIS OF SORBANILIDE FROM 1,3-PENTADIENE AND PHENYL ISOCYANATE2019857#N/ATRUE
4864
anie.19850496110.1002/anie.198504961FALSEhttps://doi.org/10.1002/anie.198504961WILKE, GAngew. Chem.-Int. Edit. Engl.AN INTERMEDIATE AND ITS SECONDARY PRODUCTS IN A NICKEL-CATALYZED SYNTHESIS OF [4]-RADIALENES2019859#N/ATRUE
4865
anie.19820214110.1002/anie.198202141FALSEhttps://doi.org/10.1002/anie.198202141Doyle, AGAngew. Chem.-Int. Edit. Engl.(A-]D) RING-ClOSURE TO THE NICKEL(II)-B,C,D-HEXADEHYDROCORRINATEX1919829#N/AFALSE
4866
anie.19850323110.1002/anie.198503231FALSEhttps://doi.org/10.1002/anie.198503231KRUGER, CAngew. Chem.-Int. Edit.ETHYNEBIS(TRIPHENYLPHOSPHANE)NICKEL(0)32198515#N/ATRUE
4867
anie.19850313110.1002/anie.198503131FALSEhttps://doi.org/10.1002/anie.198503131MYNOTT, RAngew. Chem.-Int. Edit. Engl.CONTROL OF METAL-CATALYZED REACTIONS .15. NICKEL-CATALYZED CYClO-DIMERIZATION OF 2-TERT-BUTYLSILYL-1,3-BUTADIENE AND 2-TRIMETHYLSILYL-1,3-BUTADIENE4198515#N/ATRUE
4868
anie.19840635110.1002/anie.198406351FALSEhttps://doi.org/10.1002/anie.198406351MERZWEILER, KAngew. Chem.-Int. Edit. Engl.THE REACTION OF [2,3-BIS(DIPHENYLPHOSPHINO)-N-METHYLMALEIMIDE]NICKEL(II) CHLORIDE WITH PHP(SIME3)2,PHAS(SIME3)219198414#N/ATRUE
4869
anie.19840460110.1002/anie.198404601FALSEhttps://doi.org/10.1002/anie.198404601YANG, ZYAngew. Chem.-Int. Edit. Engl.NICKEL-CATALYZED REDUCTION OF CARBON-MONOXIDE BY HEXAMETHYLDISILANE - A NEW REACTION LEADING TO A NOVEL SYNTHESIS OF SILOXANES7198420#N/ATRUE
4870
anie.19840368110.1002/anie.198403681FALSEhttps://doi.org/10.1002/anie.198403681RUF, FAngew. Chem.-Int. Edit. Engl.PARAMAGNETICALLY INDUCED NMR SHIFTS .10. DETECTION OF INTRAMOLECULAR LINKAGE ISOMERIZATION OF A (PSEUDO)TETRAHEDRAL NICKEL(II) BIS(CHELATE)4198410#N/ATRUE
4871
anie.19800221110.1002/anie.198002211https://doi.org/10.1002/anie.198002211KUNKELY, HAngew. Chem.-Int. Edit. Engl.PHOTO-OXIDATION OF THE LIGANDS OF BIS(ORTHO-SEMIQUINONEDIIMINE)NICKEL(II) AND BIS(ORTHO-SEMIQUINONEDIIMINE)PLATINUM(II)Photocatalyst2619805#N/AFALSE
4872
anie.19840061110.1002/anie.198400611FALSEhttps://doi.org/10.1002/anie.198400611PICKARDT, JNOVEL STRUCTURES CONTAINING GERMANIUM(II) - GERMANOCENE AND DIMERIC TRICarbonyl(DI-TERT-BUTOXYGERMYLENE)NICKEL(0)1984#N/ATRUE
4873
anie.19831006210.1002/anie.198310062FALSEhttps://doi.org/10.1002/anie.198310062SHELDRICK, GMAngew. Chem.-Int. Edit. Engl.[NI(S4)2]2(-), A HOMOLEPTIC TETRASULFIDO-NICKEL(II) COMPLEX3419836#N/ATRUE
4874
anie.19830991110.1002/anie.198309911FALSEhttps://doi.org/10.1002/anie.198309911KRUGER, CAngew. Chem.-Int. Edit. Engl.THE LEWIS ACIDITY OF NICKEL(0) .5. SYNTHESIS AND STRUCTURE OF [NA(TMEDA)2](+)[HNI2(C2H)4](-)2619839#N/ATRUE
4875
anie.19830547110.1002/anie.198305471FALSEhttps://doi.org/10.1002/anie.198305471KRUGER, CAngew. Chem.-Int. Edit. Engl.LITHIUMCARBAMOYL-BIS(ETHENE)NICKEL(0)1219836#N/ATRUE
4876
anie.19830503110.1002/anie.198305031FALSEhttps://doi.org/10.1002/anie.198305031KRUGER, CAngew. Chem.-Int. Edit. Engl.NOVEL NICKEL-OLIGOMERIZATION CATALYSTS WITH ARSENIC-OXYGEN CHELATE LIGANDS11319835#N/ATRUE
4877
anie.19820288210.1002/anie.198202882FALSEhttps://doi.org/10.1002/anie.198202882KNORR, RAngew. Chem.-Int. Edit. Engl.ORBITAL SYMMETRY ANALYSIS OF TRIPLET-SINGLET SPIN-FLIP DURING THERMAL-ISOMERIZATION OF TETRAHEDRAL TO PLANAR NICKEL(II) COMPLEXES819827#N/ATRUE
4878
anie.19820076210.1002/anie.198200762FALSEhttps://doi.org/10.1002/anie.198200762HOBERG, HAngew. Chem.-Int. Edit. Engl.OXANICKELACYClOPENTENE DERIVATIVES FROM NICKEL(0), CARBON-DIOXIDE, AND ALKYNES11019825#N/ATRUE
4879
anie.19810263110.1002/anie.198102631FALSEhttps://doi.org/10.1002/anie.198102631ESCHENMOSER, AAngew. Chem.-Int. Edit. Engl.CYClIZATION OF A SECO-PORPHYRINOGEN TO NICKEL(II) C,D-TETRADEHYDROCORRINATES21198121#N/ATRUE
4880
anie.19800927110.1002/anie.198009271FALSEhttps://doi.org/10.1002/anie.198009271HERRERA, AAngew. Chem.-Int. Edit. Engl.NICKELACYClOPENTENE DERIVATIVES FROM NICKEL(0), CARBON-MONOXIDE AND ALKYNE30198011#N/ATRUE
4881
anie.19800570110.1002/anie.198005701FALSEWEIMANN, BCONTROL OF METAL-CATALYZED REACTIONS .11. LIGAND-PROPERTY CONTROL IN THE NICKEL(0)-BUTADIENE-P-LIGAND CATALYTIC-SYSTEM - ELECTRONIC FACTORS IN THE CONTROL OF CYClODIMER DISTRIBUTION1980#N/ATRUE
4882
anie.19800569110.1002/anie.198005691FALSEWEIMANN, BCONTROL OF METAL-CATALYZED REACTIONS .10. LIGAND-PROPERTY CONTROL IN THE NICKEL(0)-BUTADIENE-P-LIGAND CATALYTIC-SYSTEM - DOMINANCE OF STERIC FACTORS IN THE CONTROL OF OLIGOMER DISTRIBUTION1980#N/ATRUE
4883
anie.19790488110.1002/anie.197904881FALSEhttps://doi.org/10.1002/anie.197904881PORSCHKE, KRAngew. Chem.-Int. Edit. Engl.NICKEL(0)-INDUCED SYNTHESIS OF ETHYLLITHIUM FROM LITHIUM, HYDROGEN, AND ETHYLENE11197911#N/ATRUE
4884
anie.19790469110.1002/anie.197904691FALSEhttps://doi.org/10.1002/anie.197904691SACCONI, LAngew. Chem.-Int. Edit. Engl.TETRAHEDRO-TETRAPHOSPHORUS AS MONODENTATE LIGAND IN A NICKEL(0) COMPLEX7319792#N/ATRUE
4885
anie.19790415210.1002/anie.197904152FALSEhttps://doi.org/10.1002/anie.197904152WUNDERLICH, HAngew. Chem.-Int. Edit. Engl.(-)579-BIS[(S)-(+)-O,O'(1,1'-BINAPHTHYL-2,2'-DIYL)-DITHIOPHOSPHATO]NICKEL(II) - 1ST DITHIOPHOSPHATO COMPLEX TO HAVE AXIAL CHIRALITY7197913#N/ATRUE
4886
anie.19790400110.1002/anie.197904001FALSEhttps://doi.org/10.1002/anie.197904001SCHENKLUHN, HAngew. Chem.-Int. Edit. Engl.CONTROL OF METAL-CATALYZED REACTIONS .6. LIGAND CONCENTRATION-CONTROL IN THE SYSTEM NICKEL(O)-TRIPHENYLPHOSPHANE-BUTADIENE1019799#N/ATRUE
4887
acscatal.9b0559810.1021/acscatal.9b05598https://doi.org/10.1021/acscatal.9b05598Konig, BACS Catal.The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible-light irradiation at room temperature affords the C(sp(2))-C(sp(3)) cross-coupling of Aryl halides and potassium Alkyl trifluorB(OH)2rates by single electron transmetallation. Like the homogeneously catalyzed protocol, the reaction is compatible with a variety of functional groups inCluding electron-donating and electron-withdrawing Aryl and heteroAryl moieties. Moreover, this protocol allows the installation of allyl groups onto (hetero)arenes, enlarging the scope of the method. The heterogeneous mpg-CN photocatalyst is easily recovered from the reaction mixture and reused several times, paving the way for larger-scale industrial applications of this type of photocatalytic bond-forming reactions.Photo-Ni-Dual-Catalytic C(sp(2))-C(sp(3)) Cross-Coupling Reactions with Mesoporous Graphitic Carbon Nitride as a Heterogeneous Organic Semiconductor PhotocatalystC(sp(2))-C(sp(3)) cross-coupling; heterogeneous photocatalyst; nickel catalysis; dual catalysis; single-electron transmetallationPhotocatalyst22202047#N/AFALSE
4888
acscatal.9b0554410.1021/acscatal.9b05544FALSEhttps://doi.org/10.1021/acscatal.9b05544Alexandrov, VACS Catal.The mechanistic interplay between the oxygen evolution reaction (OER) and material degradation during water electrolysis is not yet well understood even for the most studied OER electrocatalysts such as RuO2 and IrO2. It is still disputed whether the lattice oxygen mechanism (LOM) may be competitive with the conventional adsorbate evolving mechanism (AEM) of the OER in these materials and, if so, under what conditions. Herein, we employ density functional theory calculations to demonstrate that the LOM can give rise to higher OER activity than the AEM at the active sites involving structural defects, both intrinsic and extrinsic. Specifically, we show that, although the AEM is preferred for the perfect (110) and (211) surfaces, the formation of metal vacancies due to catalyst dissolution may lead to much lower OER overpotentials for the LOM. Also, by screening several metal impurities in RuO2, we reveal that dopants such as Ni and Co can promote the LOM over the AEM even for the perfectly structured surfaces. Overall, we demonstrate that defective IrO2 is less LOM active than RuO2 that should contribute to its superior stability under OER conditions.Role of Defects in the Interplay between Adsorbate Evolving and Lattice Oxygen Mechanisms of the Oxygen Evolution Reaction in RuO2 and IrO2density functional theory; lattice oxygen mechanism; oxygen evolution reaction; rutile; electrocatalysisx45202056#N/AFALSE
4889
anie.19780950110.1002/anie.197809501FALSEhttps://doi.org/10.1002/anie.197809501HOBERG, HAngew. Chem.-Int. Edit. Engl.2,2'-BIPYRIDINE(TETRAMETHYLCYClOBUTADIENE)NICKEL(0)819787#N/ATRUE
4890
acscatal.9b0551310.1021/acscatal.9b05513FALSEhttps://doi.org/10.1021/acscatal.9b05513McCrory, CClACS Catal.A series of Co complexes with bis(pyridylmonoimine)-based ligands with different degrees of structural flexibility have been prepared and studied for the electrocatalytic CO2 reduction reaction to CO. First, electrochemical kinetic studies of the structurally rigid [Co(L-L)] complex show that it undergoes a reductive dimerization upon reduction to the Co-I complex. This dimerization is facilitated by the planar geometry of the [Co(L-L)] complex. The dimer structure dissociates after reduction of the ligand, forming a monomer species that is active for CO2 reduction. The reductive dimerization can be sterically prevented either by adding the strong axially coordinating ligand such as triphenylphosphine (PPh3) or by distorting the square planarity of the Co geometry by modulating the flexibility of the ligand scaffold. The more flexible [Co(L-RL)] complexes prevent catalyst dimerization and operate with more positive catalytic onset potentials for CO2 reduction compared to the more rigid [Co(L-L)] complex but operate with lower overall activity in the presence of a proton source. CO-binding and inhibition studies provide evidence that the lower activity for CO2 reduction of the more flexible [Co(L-R-L)] complexes compared to [Co(L-L)] is due to CO poisoning because of the stronger binding affinity of the CO product to the flexible [Co(L-R-L)] complexes. This highlights an important trade-off in catalyst design for this Class of molecular electrocatalysts: Co bis(pyridylmonoimine) complexes with higher degrees of structural flexibility prevent dimerization and shift the onset of CO2 reduction catalysis to more positive potentials but decrease the maximum activity due to CO product inhibition.Electrocatalytic CO2 Reduction by Cobalt Bis(pyridylmonoimine) Complexes: Effect of Ligand Flexibility on Catalytic ActivityCO2 reduction; electrocatalysis; electrochemistry; ligand flexibility; product inhibition; CO inhibition; dimerization
Electrocatalytic
5202048#N/AFALSE
4891
acscatal.9b0549910.1021/acscatal.9b05499FALSEhttps://doi.org/10.1021/acscatal.9b05499Abruna, HDACS Catal.We have developed a facile and effective electrochemical dealloying strategy to enhance the electrocatalytic activity of Pd/M (M = Ni, Mn) nanopartiCles for the oxygen reduction reaction (ORR) in alkaline media. The enhancement arises from the higher atomic concentration of electrochemically active Pd exposed on the surface of the nanopartiCles as a result of the electrochemical dealloying process, which was verified by electron energy loss spectroscopy elemental mapping, X-ray photoelectron spectroscopy, and CO stripping. These dealloyed catalysts also showed a negligible decrease in the ORR activity after 4000 potential cyCles in alkaline media. In addition, after the degradation that resulted from extended potential cyCles in alkaline media, the ORR activity of the catalysts could be restored by repeating the dealloying procedures, with only a 14 mV decrease in the half-wave potential after 16,000 cyCles for dealloyed PdNi/C. Similar results were obtained for PdMn/C. These findings provide insights for the rational design of the composition and structure of electrocatalysts with higher atomic utilization of active materials and enhanced electrocatalytic activity, based on postsynthesis modification methods.Enhancing the Electrocatalytic Activity of Pd/M (M = Ni, Mn) NanopartiCles for the Oxygen Reduction Reaction in Alkaline Media through Electrochemical Dealloyingdealloying electrocatalyst; alkaline media; fuel cells; oxygen reduction reaction; palladium-nickel; palladium-manganese; enhanced ORR activityx14202043#N/AFALSE
4892
anie.19780466110.1002/anie.197804661FALSEhttps://doi.org/10.1002/anie.197804661KRUGER, CAngew. Chem.-Int. Edit. Engl.NOVEL COORDINATION OF (BENZOYLMETHYLENE)TRIPHENYLPHOSPHORANE IN A NICKEL OLIGOMERIZATION CATALYST416197813#N/ATRUE
4893
acscatal.9b0540410.1021/acscatal.9b05404https://doi.org/10.1002/anie.200804147Bernhard, SParallelized Screening of Characterized and DFT-Modeled Bimetallic Colloidal Cocatalysts for Photocatalytic Hydrogen EvolutionPhotocatalyst2020#N/AFALSE
4894
acscatal.9b0533310.1021/acscatal.9b05333FALSEhttps://doi.org/10.1021/acscatal.9b05333Perez-Ramirez, JACS Catal.The emergence of nickel single atoms on nitrogen-doped carbons as high-performance catalysts amenable to rationalization due to their well-defined structure could lead to applicable technologies for the electrocatalytic CO2 reduction reaction (eCO(2)RR). However, real materials are unlikely to display a uniform site structure, which limits the scope of current efforts focused on idealized models for future implementation. Here, we prepare distinct nickel entities (single atoms or nanopartiCles) on nitrogen-doped carbons and evaluate them in eCO(2)RR. Single atoms demonstrate a characteristic high selectivity to CO. However, this is not altered by the presence of metal nanopartiCles formed upon reducing the nitrogen content of the carrier. In contrast, nanopartiCles incorporated via a colloidal route promote the parasitic hydrogen evolution reaction. In these systems, the CO selectivity evolves upon repeated exposure to potential, reaching values comparable to single atoms. By introducing CO stripping voltammetry as a characterization tool for this Class of materials, we identify a decreased metallic surface, suggesting that the nanopartiCle surface is altered by CO. The findings highlight the critical role of dynamic effects in catalyst design for eCO(2)RR.Structure Sensitivity and Evolution of Nickel-Bearing Nitrogen-Doped Carbons in the Electrochemical Reduction of CO2electrocatalytic CO2 reduction; single-atom catalysis; nickel speciation; nitrogen-doped carbons; structure-activity relationshipsx6202054#N/AFALSE
4895
anie.19780132110.1002/anie.197801321FALSEhttps://doi.org/10.1002/anie.197801321BURKLE, WAngew. Chem.-Int. Edit. Engl.QUANTITATIVE RESOLUTION OF ENANTIOMERS OF TRANS-2,3-EPOXYBUTANE BY COMPLEXATION CHROMATOGRAPHY ON AN OPTICALLY-ACTIVE NICKEL(II) COMPLEX26197811#N/ATRUE
4896
anie.19770459110.1002/anie.197704591FALSEhttps://doi.org/10.1002/anie.197704591ESCHENMOSER, AAngew. Chem.-Int. Edit. Engl.(A-]D)-CYClIZATION OF A NICKEL(II) DELTA-18-DEHYDRO-1-METHYLIDENE-1,19-SECOCORRINATE19197721#N/ATRUE
4897
anie.19770253110.1002/anie.197702531FALSEhttps://doi.org/10.1002/anie.197702531TROXLER, EAngew. Chem.-Int. Edit. Engl.CONTROL OF NICKEL-CATALYZED COOLIGOMERIZATION OF BUTADIENE WITH SCHIFF-BASES BY CO-CATALYSTS419777#N/ATRUE
4898
acscatal.9b0513710.1021/acscatal.9b05137https://doi.org/10.1021/acscatal.9b05137Xia, JBACS Catal.We report here a Ni-catalyzed reductive coupling of aldehydes with widely available 1,3-dienes under visible-light photoredox dual catalysis. The homoallyic alcohols are obtained in broad scope with complete branched regioselectivity. Hantzsch ester is used as the hydrogen radical source to oxidize low-valent nickel salt affording Ni-H species. Preliminary mechanistic studies indicate a successive single-electron transfer (SET) pathway and the generation of a key pi-allylnickel intermediate via Ni-H insertion of 1,3-diene in this synergistic catalytic process.Photoredox Ni-Catalyzed Branch-Selective Reductive Coupling of Aldehydes with 1,3-Dienessynergistic catalysis; photoredox catalysis; nickel; reductive coupling; 1,3-dienePhotocatalyst15202079#N/AFALSE
4899
acscatal.9b0513310.1021/acscatal.9b05133FALSEhttps://doi.org/10.1021/acscatal.9b05133Sun, XLActive and Stable Pt-Ni Alloy Octahedra Catalyst for Oxygen Reduction via Near-Surface Atomical Engineeringx2020#N/AFALSE
4900
acscatal.9b0512010.1021/acscatal.9b05120FALSEhttps://doi.org/10.1021/acscatal.9b05120Mitsudome, TACS Catal.Although the development of metal nanopartiCle catalysts for organic synthesis has been widely studied, the catalytic potential of metal phosphide nanopartiCles has little been studied. Herein, we describe that nickel phosphide nanopartiCles (Ni2P NPs) act as a highly efficient heterogeneous catalyst for the selective transformation of biofuranic aldehydes into diketones, which is a useful biorefining technology. The biofuranic aldehydes are hydrogenated in water without any additives, giving the corresponding diketones in high yields. The catalytic performance of Ni2P NPs demonstrated here is significantly different from conventional Ni(0) and NiO NPs, and other metal phosphide NPs, which show no activity, indicating the unique catalysis of Ni2P NPs. Spectroscopic analyses showed that bifunctional Ni2P NP catalysis combining their hydrogen-activating ability and surface acidity plays a crucial role, leading to the transformations of selective biofuranic aldehydes.Unique Catalysis of Nickel Phosphide NanopartiCles to Promote the Selective Transformation of Biofuranic Aldehydes into Diketones in Waternickel phosphide; heterogeneous catalyst; hydrogenation; biofuranic aldehydes; diketonesx18202052#N/AFALSE
4901
acscatal.9b0509210.1021/acscatal.9b05092FALSEhttps://doi.org/10.1021/acscatal.9b05092Carter, EAACS Catal.Catalysts for electrochemical water oxidation or the oxygen evolution reaction (OER) are dominated by transition-metal (TM) complexes (homogeneous) and oxides (heterogeneous). For the latter Class of catalysts, iron-doped nickel oxyhydroxide (Ni1-xFexOOH) has shown promise for replacing precious-metal-based catalysts such as RuO2 and IrO2 for alkaline water electrolysis. Recently, we used first-principles quantum mechanics to illuminate the precise roles of Fe and Ni in this compound with respect to the mechanism of oxygen evolution. From periodic density functional theory using a screened-exchange hybrid exchange-correlation functional, we identified that the combined abilities of Fe to form an optimally metastable terminal oxo as Fe(IV)=O and Ni(III)'s relatively facile reduction to Ni(II) yield a very low overpotential OER In pursuit of other dopant(s) that can form other such optimal terminal oxos, here we assess the oxygen evolution mechanism and energetics when alternatively doping the beta-NiOOH((1) over bar2 (1) over bar1) surface, a catalytically active facet, with other first-row TMs, namely, V, Cr, Mn, and Co, and some second-row TMs, namely, Mo, Ru, and Rh. These dopants were chosen because their cations are known to form terminal oxos of varying strengths, and some are known to form oxides that are effective OER catalysts. Rather than finding an alternative dopant better than Fe, this study further confirms the unique chemistry of Fe that brings optimal OER activity. Co is found to be a competitive alternative to Fe, with only 0.07 V higher predicted thermodynamic overpotential. More importantly, this study also reveals the strong influence of Ni(III) on the oxidation state of the dopants, in that most dopants investigated could oxidize spontaneously to their respective high oxidation states, while lattice Ni(III) ion(s) reduce(s) concomitantly to Ni(II). Of note, V, Cr, Mo, Ru, and Rh could easily form +5, +6, +6, +7, and +5 TM-oxo groups, respectively. The enhanced stability of these high-oxidation-state cations due to the Ni(III)/Ni(II) redox render these dopants inactive toward reductive elimination of O-2, except for V, and thus we predict that they will be ineffective OER catalysts.Noninnocent Influence of Host beta-NiOOH Redox Activity on Transition-Metal Dopants' Efficacy as Active Sites in Electrocatalytic Water Oxidationwater splitting; oxygen evolution reaction; doped nickel oxyhydroxide; transition-metal doping; water oxidation catalyst; electrochemistry
Electrocatalytic
7202074#N/AFALSE
4902
anie.19770252210.1002/anie.197702522FALSEhttps://doi.org/10.1002/anie.197702522SCHENKLUHN, HAngew. Chem.-Int. Edit. Engl.CONTROL METAL-CATALYZED REACTIONS .2. CONTROL OF DIRECTION OF ADDITION IN NICKEL-CATALYZED 2=1-COOLIGOMERIZATION OF BUTADIENE WITH MONO-OLEFINS BY PERTURBATION OF MONO-OLEFIN619776#N/ATRUE
4903
acscatal.9b0491610.1021/acscatal.9b04916https://doi.org/10.1021/acscatal.9b04916Hu, XLACS Catal.Carbosilylation of alkenes can be an efficient approach to the synthesis of organosilicon compounds. However, few general methods of carbosilylation are known. Here, we introduce a strategy for Arylsilylation of electron deficient terminal alkenes by combining photoredox-catalyzed silyl radical generation, innate reactivity of silyl radical with alkene, and Ni-catalyzed Aryl-Alkyl cross-coupling. This cooperative photoredox and nickel catalysis operates under mild conditions. It employs readily available alkenes, Aryl bromides, and silane as reagents, and it produces useful synthetic building blocks in a modular manner.Arylsilylation of Electron-Deficient Alkenes via Cooperative Photoredox and Nickel Catalysisnickel catalysis; Arylsilylation; photoredox catalysis; cooperative catalysis; organosiliconPhotocatalyst16202076#N/AFALSE
4904
anie.19760768110.1002/anie.197607681FALSEhttps://doi.org/10.1002/anie.197607681KRAMOLOWSKY, RAngew. Chem.-Int. Edit. Engl.BIS(DIORGANYLPHOSPHINODITHIOFORMATO-S,P)NICKEL (II) COMPLEXES - NOVEL 4-MEMBERED RING CHELATES18197615#N/ATRUE
4905
anie.19760622110.1002/anie.197606221FALSEhttps://doi.org/10.1002/anie.197606221SCHIEFERSTEIN, LAngew. Chem.-Int. Edit. Engl.ANION PR2- AS SINGLE BRIDGE BETWEEN 2 NICKEL(0) COORDINATION CENTERS1419764#N/ATRUE
4906
anie.19760621110.1002/anie.197606211FALSEhttps://doi.org/10.1002/anie.197606211TSAY, YHAngew. Chem.-Int. Edit. Engl.CARBANION COMPLEXES OF NICKEL(0)3519767#N/ATRUE
4907
anie.19750567110.1002/anie.197505671FALSEhttps://doi.org/10.1002/anie.197505671WEISS, RAngew. Chem.-Int. Edit. Engl.INSERTION OF AN ETHOXYCarbonylMETHYLENE MOIETY INTO A NI-N BOND OF MESO-TETRAPHENYLPORPHINATONICKEL(II)2519754#N/ATRUE
4908
acscatal.9b0562110.1021/acscatal.9b05621FALSEhttps://doi.org/10.1021/acscatal.9b05621Abruna, HDACS Catal.Moving from proton exchange membrane fuel cells to anion exchange membrane fuel cells (AEMFCs) enables the use of non-Pt-group (NPG) metals as cathodes for the oxygen reduction reaction, since the oxygen reduction kinetics on NPG metals is significantly enhanced in alkaline media. These NPG metal catalysts are also stable under alkaline conditions and cost much less than Pt-group metals. However, in alkaline media, H-2 oxidation on Pt anodes is much more sluggish than in acidic media, and thus, more active H-2 oxidation catalysts are required to enable AEMFCs. Here we report on a family of H-2 oxidation catalysts: Ru alloys with Co, Ni, or Fe. A series of RuCo/C, RuNi/C, and RuFe/C alloy nanopartiCle catalysts have been synthesized via an impregnation method and characterized by atomic-scale scanning transmission electron microscopy. We find that Ru alloys with small amounts of Co, Ni, or Fe can significantly enhance H-2 oxidation (HOR), H-2 evolution (HER), O-2 reduction (ORR), and oxygen evolution (OER) reactions in alkaline media. They are much more active than pure Ru catalysts for the HOR, HER, ORR, and OER, and even more active than pure Pt catalysts for the HOR and HER, but they cost much less. In particular, Ru-0.95/Co-0.05/C is the most active among all studied Ru alloys catalysts for the HOR, HER, and ORR. Thus, they are promising catalysts for alkaline fuel cells and electrolyzers. The enhancement mechanism of Ru alloys has been elucidated by density functional theory calculations.Multifunctional Electrocatalysts: Ru-M (M = Co, Ni, Fe) for Alkaline Fuel Cells and ElectrolyzersRuCo alloy; RuNi alloy; RuFe alloy; alkaline fuel cell; alkaline electrolyzer; electrocatalysis14202046#N/ATRUE
4909
acscatal.9b0455510.1021/acscatal.9b04555FALSEhttps://doi.org/10.1021/acscatal.9b04555Muller, CRACS Catal.A key challenge in the catalytic conversion of CH4 and CO2 into a synthesis gas (CO and H-2) via the dry reforming of methane (DRM) is the development of stable catalysts. We demonstrate that the reductive exsolution of metallic Ru from fluorite-type solid solutions Sm2RuxCe2-xO7 (x = 0, 0.1, 0.2, 0.4) yields catalysts with high activity and remarkable stability for the DRM. The catalysts feature Ru(0) nanopartiCles about 1-2 nm in diameter that are uniformly dispersed on the surface of the resulting oxide support. The exsolved material was investigated by synchrotron X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS at Ru, Sm, and Ce K-edges), Raman spectroscopy, and transmission electron microscopy. In situ XAS-XRD experiments revealed that the exsolution of metallic ruthenium is accompanied by a rearrangement of the oxygen vacancies within the lattice. The catalysts derived through exsolution outperform (stable over 4 days) the reference catalysts prepared by wetness impregnation and sodium borohydride reduction. The superior performance of the exsolved catalysts is explained by their high resistance to sintering-induced deActivation owing to the stabilizing metal-support interaction in this Class of materials. It is also demonstrated that the Ru nanopartiCles can undergo redissolution (in air at 700 degrees C)-exsolution cyCles.Exsolution of Metallic Ru NanopartiCles from Defective, Fluorite-Type Solid Solutions Sm2RuxCe2-xO7 To Impart Stability on Dry Reforming Catalystsreductive exsolution; dry reforming of methane; X-ray absorption spectroscopy; Ru nanopartiCles; catalysisx132020101#N/AFALSE
4910
acscatal.9b0450510.1021/acscatal.9b04505FALSEhttps://doi.org/10.1021/acscatal.9b04505Tsuji, YACS Catal.We used a liquid phase reaction to synthesize a nickel (Ni) and iron (Fe)-containing layered double hydroxide (NiFe-LDH), having a lateral size less than 10 nm. A chelating agent introduced into the media was thought to increase the concentration of metal hydroxide nuClei and suppress excessive growth of the LDH crystal, resulting in the synthesis of nanometer-sized LDH. The NiFe-LDH catalyzed the oxygen evolution reaction (OER) at an overpotential of 247 mV and current of 10 mA cm(-2), which is superior to the performance of conventional iridium oxide (IrOx) catalysts. Notably, a membrane electrode assembly (MEA) for anion exchange membrane water electrolysis using NiFe-LDH as an anode catalyst exhibited an energy conversion efficiency of 74.7% for flowing 1.0 A cm(-2) in 1 M KOH at 80 degrees C. This efficiency is the highest among MEAs implemented with non-noble metal-based catalysts reported to date and offers a viable replacement for IrOx, anode catalysts.Single Nanometer-Sized NiFe-Layered Double Hydroxides as Anode Catalyst in Anion Exchange Membrane Water Electrolysis Cell with Energy Conversion Efficiency of 74.7% at 1.0 A cm(-2)layered double hydroxides; anion exchange membrane water electrolysis; electrocatalysts; oxygen evolution reaction; nanomaterialsx19202064#N/AFALSE
4911
acscatal.9b0551710.1021/acscatal.9b05517FALSEhttps://doi.org/10.1021/acscatal.9b05517DeBeer, SACS Catal.Herein, we report the synthesis of a gamma-Al2O3-supported NiCo catalyst for dry methane reforming (DMR) and study the catalyst using in situ scanning transmission X-ray microscopy (STXM) during the reduction (Activation step) and under reaction conditions. During the reduction process, the NiCo alloy partiCles undergo elemental segregation with Co migrating toward the center of the catalyst partiCles and Ni migrating to the outer surfaces. Under DMR conditions, the segregated structure is maintained, thus hinting at the importance of this structure to optimal catalytic functions. Finally, the formation of Ni-rich branches on the surface of the partiCles is observed during DMR, suggesting that the loss of Ni from the outer shell may play a role in the reduced stability and hence catalyst deActivation. These findings provide insights into the morphological and electronic structural changes that occur in a NiCo-based catalyst during DMR. Further, this study emphasizes the need to study catalysts under operating conditions in order to elucidate material dynamics during the reaction.In Situ X-ray Microscopy Reveals PartiCle Dynamics in a NiCo Dry Methane Reforming Catalyst under Operating Conditionsin situ; heterogeneous catalysis; nanoreactor; methane reforming; X-ray spectroscopy; microscopy6202067#N/ATRUE
4912
acscatal.9b0545810.1021/acscatal.9b05458FALSEhttps://doi.org/10.1021/acscatal.9b05458Liu, XBACS Catal.The steam is commonly supplied with H-2 to the anodes of Ni-based solid oxide fuel cells (SOFCs). Humidified H-2 is also widely used for emerging perovskite anodes of SOFCs, although the influences of H2O on the hydrogen oxidation reaction (HOR) on their surfaces have not been well understood yet. In this work, the effects of H2O on the HOR on Sr2Fe1.5 Mo0.5O6-delta (SF1.5M), La-0.5 Sr-1.5 Fe-1.5 Mo0.5O6-delta (LSFM), and Pr-0.5 Sr-1.5 Fe1.5Mo0.5O6-delta (PSFM) were systematically investigated using the electrochemical impedance spectroscopy (EIS) and electrical conductivity relaxation (ECR) methods. The EIS spectra suggested the possible promotional effect of H2O on decreasing the polarization resistance of SF1.5M. The ECR results confirmed that the presence of H2O in H-2 can significantly increase the oxygen exchange coefficients of SF1.5M, LSFM, and PSFM. To gain a mechanistic understanding of the role of H2O, the density functional theory-based calculations and thermodynamic modeling were performed to unravel the effect of H2O on the HOR on the SF1.5M (001) surfaces. Benefiting from the increment of the oxygen chemical potential and decrement of the free electron concentration upon increasing humidity, the plateau intermediate state in the HOR energy landscape, the step of H2O plus surface oxygen vacancy formation, is reduced on the SF1.5M (001) BO2 (B = Fe and Mo)-terminated surfaces, when decreasing the slab oxygen nonstoichiometry. Furthermore, by comparing the scenarios of the HOR on the dry and hydrated surfaces, the H2O plus surface oxygen vacancy formation energies are lower in the latter case. These two proposed factors, i.e., (i) change of electron chemical potential upon the change of near-surface delta and (ii) enhanced interaction of surface H species with the hydrated perovskite surfaces, contribute to the promoted HOR in the presence of H2O. This work provides important insights into the effects of H2O on the HOR for SOFCs.Positive Effects of H2O on the Hydrogen Oxidation Reaction on Sr2Fe1.5 Mo0.5O6-delta-Based Perovskite Anodes for Solid Oxide Fuel Cellssteam catalysis; hydrogen oxidation reaction kinetics; density functional theory; surface hydration; perovskite; solid oxide fuel cell5202057#N/ATRUE
4913
acscatal.9b0441910.1021/acscatal.9b04419FALSEhttps://doi.org/10.1021/acscatal.9b04419Guo, SJACS Catal.One-dimensional (1D) PtM (M = Fe, Co, Ni) nanowires (NWs), which represent a thriving Class of electrocatalysts for fuel cells, are experiencing a restriction in long-term durability because of the dissolving issue related to transition metals. Utilizing one-dimensional Pt3Co NWs as the basic catalyst model, here we have successfully demonstrated significant improvements in electrocatalytic durability and activity derived from doping of Ga atoms. The optimized surface energy caused by the doping of Ga atoms drives the resulting catalysts to exhibit good durability for oxygen reduction reaction (ORR) electrocatalysis. However, although oxygen binding energy (E-O) would rather deviate from the optimal value because of excessive Ga on the surface, the formation of proper Ga-O bonding can also promote oxygen binding to approach an optimal value, which results in an enhanced ORR activity. It can be therefore conCluded that doping of an appropriate amount of Ga atoms has a positive effect in improving the ORR performance of the catalyst, not only in terms of specific activity but also in durability. This interesting phenomenon was also further extended to improve the catalysis of methanol oxidation (MOR) and ethanol oxidation (EOR) reactions, thus reflecting multifunctionalities of lavender-like Ga-doped Pt3Co NWs on fuel cell reactions. This study highlights the great potential of Ga-doped strategies for surface and near-surface regulation, which can effectively address the poor durability of 1D Pt-based NWs for energy catalytic technology.Lavender-Like Ga-Doped Pt3Co Nanowires for Highly Stable and Active Electrocatalysisone-dimensional nanostructures; Ga-doped; Pt3Co; electrocatalysis; durabilityx21202054#N/AFALSE
4914
acscatal.9b0529410.1021/acscatal.9b05294FALSEhttps://doi.org/10.1021/acscatal.9b05294Tunon, IACS Catal.Orotate phosphoribosyltransferase (OPRTase) catalyzes the reaction between the ribose donor alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP) and orotate (OA) in the presence of Mg2+ ion to obtain pyrophosphate and pyrimidine nuCleotide orotidine 5'-monophosphate (OMP), a key precursor in de novo biosynthesis of pyrimidine nuCleotides. In this work, several structures of the dimeric Escherichia coli OPRTase (EcOPRTase) have been determined at high resolution, and kinetic measurements have been carried out to obtain the catalytic rate and Michaelis constants. Molecular dynamics (MD) simulations have been carried out, and structural analysis from the X-ray and MD simulation structures reveals conformational changes related to the flexible catalytic loop that establishes hydrogen bond interactions with the pyrophosphoryl group of PRPP. It is proposed that the OA substrate can be in equilibrium in its tautomeric forms. Starting from the most stable tautomeric form, all the plausible mechanisms have been explored by means of quantum mechanics/molecular mechanics (QM/MM) MD simulations using the adaptive string method. The most feasible mechanism consists of the proton transfer from the N1 atom of OA to a water molecule and from the water molecule to the alpha-phosphate O2A atom of PRPP. After that, the nuCleophilic attack of the Ni atom of OA to the Cl atom of PRPP proceeds to yield OMP and pyrophosphate. The free energy barrier obtained is in very good agreement with the experimental data reported. Analysis of some relevant distances between key residues and the substrates (OA and PRPP) at the reactant state and transition state (TS) of the rate-limiting step allows us to understand the role of some conserved residues (Lys73, Asp125, Lys103*, Arg99*, and Mg2+ ion) electrostatically stabilizing the TS and preserving the flexible catalytic loop in a Closed conformation during the enzymatic reaction.Elucidating the Catalytic Reaction Mechanism of Orotate Phosphoribosyltransferase by Means of X-ray Crystallography and Computational SimulationsX-ray structure; orotate phosphoribosyltransferase; pyrimidine metabolism; MD simulations; QM/MM methods; reaction mechanism; enzyme catalysis4202061#N/ATRUE
4915
acscatal.9b0421610.1021/acscatal.9b04216FALSEhttps://doi.org/10.1021/acscatal.9b04216Shanmugam, SACS Catal.Most reported catalysts for water oxidation undergo in situ electrochemical tuning to form the active species for their oxygen evolution reaction (OER). In general, the in situ electrochemical transformations of non-oxide catalysts are faster than those of the corresponding oxides, and they typically display improved OER activity. Although many approaches for tuning the active surfaces of catalysts as well as investigations into their roles in the mechanism of adsorption of OER intermediates have been reported, we still have a poor understanding of the dominant active sites formed during the OER. This review highlights current progress into the in situ electrochemical tuning with non-oxide catalysts (especially chalcogenides and pnictides) and offers a comprehensive summary of approaches for the enhancement of OER activity. We describe the non-oxide catalysts that have exhibited promising OER performance with strong in situ electrochemical tuning. We also discuss the preoxidation peak positions of the catalysts in alkaline electrolytes. Furthermore, we explore the probability of new active surface formation on non-oxide catalysts with modified OER mechanisms and the collections of available in situ and ex situ methods to identify the active sites in real-time. Finally, we discuss the challenges affecting the future detection of the active sites of the most promising OER catalysts.Surface Activation and Reconstruction of Non-Oxide-Based Catalysts Through in Situ Electrochemical Tuning for Oxygen Evolution Reactions in Alkaline Medianon-oxide catalysts; in situ electrochemical tuning; surface Activation; oxygen evolution reaction; alkaline water splittingx552020174#N/AFALSE
4916
acscatal.9b0526410.1021/acscatal.9b05264FALSEhttps://doi.org/10.1021/acscatal.9b05264Liao, JACS Catal.Hydrofluorination of simple alkenes is an attractive strategy to prepare fluorine-containing molecules. However, the catalytic asymmetric hydrofluorination remains an ongoing challenge. Here, we describe a palladium(II)-catalyzed enantioselective hydrofluorination of alkenylarenes, by employing sulfoxide phosphine (SOP) as a chiral ligand, triArylphosphine as a secondary ligand, Selectfluor as a fluorine source, and trihexylsilane as a hydride source. Under the optimal reaction conditions, a range of chiral Benzyl fluorides bearing different functional groups are obtained in good yields (up to 80%) with high enantiopurity (having an enantiomeric ratio of up to 94:6). Some mechanistic insight of this reaction is obtained using in situ one-and two-dimensional H-1-P-31 HMBC nuClear magnetic resonance spectroscopy and a catalytic cyCle is proposed.Enantioselective Palladium-Catalyzed Hydrofluorination of Alkenylarenesenantioselective; hydrofluorination; palladium-catalyzed; Pd-H species; in situ NMR11202078#N/ATRUE
4917
acscatal.9b0523110.1021/acscatal.9b05231FALSEhttps://doi.org/10.1021/acscatal.9b05231Hu, PACS Catal.Ethanol dry reformation (EDR) is a chemical process for syngas production, which consumes a greenhouse gas and reduces carbon footprint. We present a mechanistic study of EDR over Rh catalyst based on density functional theory (DFT) calculations and microkinetic analysis. Our results show that both the initial decomposition of C2H2OH and the later C-O bond formation are crucial steps on the reaction free energy landscape. The microkinetic model suggests that the alpha-dehydrogenation of ethanol is the rate-determining step, and the calculated reaction rate (r(H2)) is 8.23 x 10(3) s(-1). Moreover, factors behind catalyst deActivation were investigated and potential solutions were explored from both theoretical and experimental aspects. The results indicate that additional H-2 could potentially mitigate catalyst deActivation by methanation of coke deposited on the catalyst. These computational and experimental efforts further the understanding of the complicated catalytic process and inspire the rational design of EDR catalysts.CO2 Reforming of Ethanol: Density Functional Theory Calculations, Microkinetic Modeling, and Experimental Studiesethanol dry reforming; Rh catalyst; DFT calculations; microkinetic modeling; mechanistic study; mitigating catalyst deActivation1202073#N/ATRUE
4918
acscatal.9b0413810.1021/acscatal.9b04138FALSEhttps://doi.org/10.1021/acscatal.9b04138Sun, SGACS Catal.Li2CO3 is the cathodic discharge product of a LiCO2/O-2 battery and is difficult to electrochemically decompose. The accumulation of Li2CO3 leads to battery degradation and results in a short lifespan. Herein, a carbon nanotube supported Ru/NiO@Ni catalyst (Ru/NiO@Ni/CNT) is synthesized with Ru nanopartiCles (similar to 2.5 nm) anchored on the surface of core-shell structure NiO@Ni nanopartiCles (similar to 17 nm). We found strong interfacial interactions between Ru nanopartiCles and NiO. XRD and XPS analysis revealed that the presence of Ru could protect the Ni species from being deeply oxidized while the NiO species could modify the local electronic structure of Ru, inducing a higher oxidation state. When such a Ru/NiO@Ni/CNT catalyst is used as a cathode in Li-(CO2/O-2 (v:v = 4:1) batteries, a long cyCling life of 105 cyCles at a cutoff capacity of 1000 mAh g(-1) with an overpotential as low as 1.01 V was achieved, which is significantly better than 75 and 44 cyCles with Ru/CNT and NiO@Ni/CNT catalysts, respectively, and confirms the strong synergetic effect between the Ru and NiO species in the electrocatalytic decomposition of Li2CO3. Density functional theory (DFT) calculations of the electrochemical decomposition of Li2CO3 with the assistance of RuO2 indicates that the formation of O-2 is the rate-determining step. In addition, the formation and decomposition process of Li2CO3 was illuminated at a molecular level by in situ FTIR spectroscopy with Ru/NiO@Ni/CNT catalysts.Synergetic Effect of Ru and NiO in the Electrocatalytic Decomposition of Li2CO3 to Enhance the Performance of a Li-CO2/O-2 BatteryLi-CO2/O-2 battery; Ru/NiO@Ni/CNT catalyst; synergetic effect; in situ FTIR; DFT calculations
Electrocatalytic
12202044#N/AFALSE
4919
acscatal.9b0412810.1021/acscatal.9b04128FALSEhttps://doi.org/10.1021/acscatal.9b04128Lautens, MACS Catal.We report a Rh-catalyzed tandem isomerization-allylation sequence for the generation of alpha-quaternary aldehydes, starting from unsymmetrical diallyl carbonates. This reaction features a highly selective oxidative addition of the rhodium catalyst, leading to the discrimination of electrophilic and nuCleophilic elements of various diallyl carbonates. A rhodium-enolate and an allyl electrophile are produced catalytically in situ in a controlled fashion, enabling this reaction to occur with high chemoselectivity and regioselectivity. Mechanistic investigation via reaction progress kinetic analysis uncovered second-order kinetics in rhodium, suggesting that an unexpected dual metal pathway may be operative for the key C-C bond-forming step.Rhodium-Catalyzed Tandem Isomerization-Allylation: From Diallyl Carbonates to alpha-Quaternary Aldehydesallylation; allylic alcohol; isomerization; RPKA; rhodiumx5201944#N/AFALSE
4920
acscatal.9b0497510.1021/acscatal.9b04975FALSEhttps://doi.org/10.1021/acscatal.9b04975Liu, ZPACS Catal.The NiOOH catalyst as obtained dynamically from electrodeposition of Ni2+(aq) in the borate-containing electrolyte was observed to exhibit much higher oxygen evolution activity at a near-neutral pH range (7-9) compared to other NiOx-based materials. Here, we demonstrate that this intriguing high activity is owing to the high concentration of Ni cationic vacancy on the nascent ultra-small NiOOH partiCles (<3 nm). By using first-principles calculations, we compute the thermodynamics of Ni dissolution and Clarify the mechanism of oxygen evolution reaction (OER) on the gamma-NiOOH surface. We show that (i) similar to 4% Ni cations on the surface of gamma-NiOOH dissolve at pH = 7 and 1.73 V versus reversible hydrogen electrode; (ii) on the pristine gamma-NiOOH surface, OER proceeds via the lattice peroxide mechanism (*H2O -> *OH -> *O-(OH)-H-latt* -> O-O-latt -> O-2) with an overpotential of 0.70 V; (iii) in the presence of Ni cationic vacancies, OER proceeds via the hydroperoxide mechanism (*OH + *H2O -> *2OH -> *OOH -> O-2) with an overpotential of 0.40 V. Our electronic structure and geometrical structure analyses demonstrate that the structural flexibility at the four-coordinated Ni site nearby Ni vacancy, featuring the ability to bind two terminal oxo species, is key to boost the activity. Considering the presence of the active OOH intermediate, our theory thus implies that the ultra-small oxide nanoClusters with ample cation vacancies could be a paradigm in catalyst design for oxidation reactions.Oxygen Evolution Activity on NiOOH Catalysts: Four-Coordinated Ni Cation as the Active Site and the Hydroperoxide Mechanismoxygen evolution reaction; nickel oxyhydroxide; cationic vacancy; self-healing; DFT11202048#N/ATRUE
4921
acscatal.9b0410310.1021/acscatal.9b04103FALSEhttps://doi.org/10.1021/acscatal.9b04103Qiao, SZACS Catal.Exploring electrocatalysts with high activity is essential for the production of ammonia via an electrochemical routine. By employing density functional theory calculations, we investigated the electrochemical nitrogen reduction reaction (eNRR) activity on binary metal borides, a model system of metal borides. To elaborate the mechanisms, molybdenum borides (Mo2B, alpha-MoB, and MoB2) were first modeled; the results indicate that the crystal structures greatly impact the N-2 adsorption and therefore the electrocatalytic activity. Our electronic structure investigation suggests that boron p-orbital hybrids with dinitrogen pi*-orbital, and the population on p-pi*-orbital determine the N-2 adsorption strength. Therefore, the isolated boron site of Mo2B with less filled p(z)-orbital benefits the Activation of N-2 and weaken the triple bond of dinitrogen. This isolated boron sites concept was successfully extended to other metal borides in the form of M2B (M stands for Ti, Cr, Mn, Fe, Co, Ni, Ta, W). Mo2B, Fe2B, and Co2B were discovered as the most promising candidates with low limiting potentials due to appropriate adsorption strength of reaction intermediates led by moderate p(z), filling. This work provides insights for designing metal borides as promising eNRR electrocatalysts.Isolated Boron Sites for Electroreduction of Dinitrogen to Ammoniaelectrochemical nitrogen reduction; metal borides; density functional theory; electrocatalysis; nitrogen Activationx41202048#N/AFALSE
4922
acscatal.9b0490410.1021/acscatal.9b04904FALSEhttps://doi.org/10.1021/acscatal.9b04904Menage, SACS Catal.Artificial enzymes represent an attractive alternative to design abiotic biocatalysis. EcNikA-Rul, an artificial metalloenzyme developed by embedding a ruthenium-based catalyst into the cavity of the periplasmic nickel-binding protein NikA, was found to efficiently and selectively transform certain alkenes. The objective of this study was to provide a rationale on the enzymatic function and the unexpected substrate-dependent chemoselectivity of EcNikA-Rul thanks to a dual experimental/computational study. We observed that the de novo active site allows the formation of the terminal oxidant via the formation of a ruthenium aquo species that subsequently reacts with the hypervalent iodine of phenyl iodide diacetic acid. The oxidation process relies on a Ru-IV = 0 pathway via a two-step reaction with a radical intermediate, resulting in the formation of either a chlorohydrin or an epoxide. The results emphasize the impact of the protein scaffold on the kinetics of the reaction, through (i) the promotion of the starting oxidizing species via the exchange of a CO ligand with a water molecule; and (ii) the control of the substrate orientation on the intermediate structures, formed after the Ru-IV= 0 attack. When a C alpha attack is preferred, chlorohydrins are formed while an attack on C beta leads to an epoxide. This work provides evidence that artificial enzymes mimic the behavior of their natural counterparts.A Mechanistic Rationale Approach Revealed the Unexpected Chemoselectivity of an Artificial Ru-Dependent Oxidase: A Dual Experimental/Theoretical Approachartificial enzymes; catalysis-oxidation; hydroxychlorination; epoxidation; computational chemistry; reaction paths; spin flip2202073#N/ATRUE
4923
acscatal.9b0402910.1021/acscatal.9b04029FALSEhttps://doi.org/10.1021/acscatal.9b04029Stamatakis, MACS Catal.Highly dilute alloys of platinum group metals (PGMs: Pt, Rh, Ir, Pd, and Ni) with coinage metals (Cu, Au, and Ag) serve as highly selective and coke-resistant catalysts in a number of applications. The catalytic behavior of these materials is governed by the size and shape of the surface ensembles of PGM atoms. Therefore, establishing a means of control over the topological architecture of highly dilute alloy surfaces is crucial to optimizing their catalytic performance. In the present work, we use on-lattice Monte Carlo simulations that are parameterized by density functional theory-derived energetics to investigate the surface aggregation of PGM atoms under vacuum conditions and in the presence of CO. We study several highly dilute alloy surfaces at various PGM loadings, inCluding Pd/Au(1 1 1), Pd/Ag(1 1 1), Pt/Cu(1 1 1), Rh/Cu(1 1 1), Ir/Ag(1 1 1), and Ni/Cu(1 1 1). Under vacuum conditions, we observe a thermodynamic preference for dispersion of PGM as single atoms in the surface of the coinage metal host, on all examined alloy surfaces except Ir/Ag(1 1 1), where Ir atom aggregation and island formation is preferred. By evaluating the alloy surface structure in the presence of CO, we determine that the size and shape of PGM ensembles can be manipulated by tuning the partial pressure of CO (P-CO) on the Pd/Au(1 1 1), Pd/Ag(1 1 1), Ir/Ag(1 1 1), and Ni/Cu(1 1 1) surfaces. In contrast, we determine that Pt/Cu(1 1 1) and Rh/Cu(1 1 1) highly dilute alloys are unresponsive to changes in P-CO with Rh and Pt dispersing as isolated single atoms within the host matrix, irrespective of gaseous composition. Our findings suggest that it may be possible to fine-tune the surface architecture of highly dilute binary alloys for optimized catalytic performance.Engineering the Surface Architecture of Highly Dilute Alloys: An ab Initio Monte Carlo Approachnanoalloy; surface aggregation; surface restructuring; single atom alloys; highly dilute alloys; ab initio Monte Carlo simulationx13202073#N/AFALSE
4924
acscatal.9b0402810.1021/acscatal.9b04028https://doi.org/10.1021/acscatal.9b04028Mecking, SACS Catal.The influence of the labile ligand on the rate of beta-hydride elimination (BHE) for salicylaldiminato Ni(II) complexes is shown using a series of precatalysts which differ only in the labile ligand but produce polyethylenes with a range of molecular weights (M-n = 466 to 100 kg mol(-1)), degrees of branching (1.7 to 7.3 branches/1000 C), and melting temperatures (from 132 to 123 degrees C) under the same conditions. The use of a weakly coordinating solvent (diethyl ether) was able to suppress this increase in BHE. DFT studies on a related salicylaldiminato Ni(II) complex show that BHE can feasibly occur following recombination of the labile ligand with the catalyst.Ancillary Ligands Impact Branching Microstructure in Late-Transition-Metal Polymerization Catalysishomogeneous nickel(II) catalysts; ethylene insertion polymerization; mechanism; density functional theory; polyethylenex5201923#N/AFALSE
4925
acscatal.9b0398510.1021/acscatal.9b03985FALSEhttps://doi.org/10.1021/acscatal.9b03985Zhang, JLACS Catal.Mimicking of tunichlorin is of importance to correlate its biological function to the unusally similar structure to chlorophylls but with a nickel cofactor. Benefiting from the facile derivatization of porpholactones, we herein constructed a tunichlorin mimic 6 carrying a beta-hydroxyl group ([mesotetrakis(pentafluorophenyl)-3-hydroxy-2-oxaisobacteriochlorinato] nickel (II)), which exhibits significant hydrogen evolution reaction (HER) rate acceleration of ca. 56-fold compared to its porphyrin analogues. Importantly, in the presence of water, the TOF of 6 is up to 6.1 x 10(4) s(-1) with the lowest overpotential, ranking the best among the catalysts described. Coating catalyst 6 on a Ni foam electrode showed good HER performance in a two-electrode alkaline (1 M KOH) electrolyzer (eta(20) = 540 mV). The functional roles of the beta-hydroxyl group on the acceleration of electron transfer and the formation of the hydrogen bond network with water has been suggested in either chemical or electrochemical reductions and H/D kinetic isotope effects (KIEs), combined with DFT calculations. Interstingly, the DFT model suggested that the formation of the hydrogen bond renders more electron density on the Ni center (rho(Ni) = 0.91) in a one electron reduced intermediate [6(H2O)](-), which helps the stabilization of both one- or two-electron reduced intermediates and dramatically enhances the HER rates.Mimicking of Tunichlorin: Deciphering the Importance of a beta-Hydroxyl Substituent on Boosting the Hydrogen Evolution Reactiontunichlorin; nickel complexes; HER; electrocatalysis; beta-modification of porphyrinX6202049#N/AFALSE
4926
acscatal.9b0396810.1021/acscatal.9b03968FALSEhttps://doi.org/10.1021/acscatal.9b03968Dumesic, JAACS Catal.Catalysts consisting of transition metals (Ni, Co, Cu, and Ru) supported on molybdenum oxide synthesized by atomic layer deposition (ALD) on silica were studied for synthesis gas conversion at 523 K and a pressure of 580 psi. Transition-metal-promoted Mo-based catalysts (M/MoO3/SiO2) showed different selectivity patterns from the transition metal supported on silica (M/SiO2). All molybdenum-based catalysts displayed a similar selectivity pattern, consisting of 15-20% of CH4, 30-40% of C2+ hydrocarbons, and 35-40% of oxygenates. The addition of transition metals to molybdenum oxide promoted the catalytic activity by an order of magnitude. Temperature program reduction indicated hydrogen spillover from the transition metals to molybdenum species. H-2-D-2 exchange rate measurements showed that the addition of the transition metal enhanced the rate of H-2 dissociation on the catalyst. CO chemisorption measurements indicated that transition-metal-promoted molybdenum catalysts consist of a similar amount of strong adsorption sites, which may originate from the reduced transition metal, and weak adsorption sites, which may originate from reduced molybdenum oxides. A dual-site mechanism is suggested in which low-valent molybdenum species dissociate CO and generate CHx groups that are hydrogenated to hydrocarbons or react with adsorbed CO on higher-valent Mo sites to form higher alcohols. Ni, Co, and Ru are able to generate CHx groups and enhance the production of C2+ oxygenates, whereas all of the transition metals studied are able to provide sites for H-2 dissociation and H spillover to molybdenum oxide, leading to further enhancement in catalytic activity compared to MoOx/SiO2.Synthesis Gas Conversion Over Molybdenum-Based Catalysts Promoted by Transition Metalsatomic layer deposition (ALD); synthesis gas; higher alcohol; molybdenum oxide; transition metalx3202035#N/AFALSE
4927
acscatal.9b0478810.1021/acscatal.9b04788FALSEhttps://doi.org/10.1021/acscatal.9b04788Bron, MACS Catal.Nickel(II) hydroxide is a well-known material for the oxygen evolution reaction (OER) in alkaline media, particularly when iron is incorporated into its lattice. Moderate heat treatment of nickel(II) hydroxide (<= 700 degrees C) leads to the formation of nickel(II) oxide (nano)partiCles, which exhibit reduced OER activity the higher the heat treatment temperature was. In this work, we report that heat treatment of nickel(II) hydroxide in air at even higher temperatures (60 min at 900 degrees C) results in an oxide material with high OER activity superior to that of the nickel(II) hydroxide. Similarly, the stability of the nickel(II) oxide under electrochemical conditions is increased compared to nickel(II) hydroxide. Electrochemical in situ Raman measurements show the formation of surface nickel oxy-hydroxides (NiOOH) at positive potentials and are significantly affected by the initial heat treatment. From XPS, Raman, and XRD results, it is conCluded that a Ni3+-enriched phase, possibly a higher-valent mixed nickel oxide, is present at the surface of the nickel(II) oxide sample treated at 900 degrees C resulting in an increased OER activity compared to NiOOH. This basic understanding of high-temperature-treated nickel oxide may contribute to resolving the present stability issues of OER electrocatalysts and may help to leverage alkaline electrolysis as important key technology for a renewable energy supply.Higher-Valent Nickel Oxides with Improved Oxygen Evolution Activity and Stability in Alkaline Media Prepared by High-Temperature Treatment of Ni(OH)(2)oxygen evolution reaction; electrocatalysis; nickel oxide; in situ Raman spectroscopy; X-ray diffraction; X-ray photoelectron spectroscopy5202048#N/ATRUE
4928
acscatal.9b0382010.1021/acscatal.9b03820FALSEhttps://doi.org/10.1021/acscatal.9b03820Gonzalez-Elipe, ARACS Catal.In this work, we show that multilayer graphene forms by methanol decomposition at 280 degrees C on an electrochemically promoted nickel catalyst film supported on a K-beta Al2O3 solid electrolyte. In operando near ambient pressure photoemission spectroscopy and electrochemical measurements have shown that polarizing negatively the Ni electrode induces the electrochemical reduction and migration of potassium to the nickel surface. This elemental potassium promotes the catalytic decomposition of methanol into graphene and also stabilizes the graphene formed via diffusion and direct K-C interaction. Experiments reveal that adsorbed methoxy radicals are intermediate species in this process and that, once formed, multilayer graphene remains stable after electrochemical oxidation and back migration of potassium to the solid electrolyte upon positive polarization. The reversible diffusion of ca. 100 equivalent monolayers of potassium through the carbon layers and the unprecedented low-temperature formation of graphene and other carbon forms are mechanistic pathways of high potential impact for applications where mild synthesis and operation conditions are required.Graphene Formation Mechanism by the Electrochemical Promotion of a Ni Catalystgraphene formation; electrocatalysis; nickel electrode; potassium migration; NAP-XPS; methanol decomposition; EPOCx2201951#N/AFALSE
4929
acscatal.9b0380910.1021/acscatal.9b03809FALSEhttps://doi.org/10.1021/acscatal.9b03809Tan, YWACS Catal.The design and fabrication of efficient inexpensive electrocatalysts are critical for electrochemical energy conversion technologies. Control and understanding of electronic configuration at the active sites are of fundamental importance to achieve this goal. Herein, highly porous Ni1-xCuxO (p-Ni1-xCuxO) nanowire (NW) arrays grown on carbon fiber paper (CFP) were synthesized, characterized, and utilized as high-performance catalytic anode for catalyzing the ammonia-borane (AB) electrooxidation reaction (ABOR). This electrocatalyst shows exceptional electrocatalytic properties inCluding an extremely low onset potential (-0.316 V vs the reversible hydrogen electrode (RHE)), a high Faradaic efficiency (>98%), and long-term durability toward the ABOR, far outperforming the noble metal-based catalysts. Reaction free energies computed as a function of electrode potential by density-functional theory indicate that doping of Cu for Ni1-xCuxO is favorable for energetically decreasing the energy barriers in the multistep reaction pathways. The modulation of the electronic structure of bimetallic Ni1-xCuxO catalysts underlies the catalytic mechanism by the electronic coupling effect between Ni and Cu.Porous Ni1-xCuxO Nanowire Arrays as Noble-Metal-Free High-Performance Catalysts for Ammonia-Borane Electrooxidationelectrocatalysis; ammonia borane electrooxidation reaction; alkaline fuel cells; nickel copper oxide nanowires; bimetallic catalystsx4202048#N/AFALSE
4930
acscatal.9b0475010.1021/acscatal.9b04750FALSEhttps://doi.org/10.1021/acscatal.9b04750Sharman, JACS Catal.While extensive literature shows Pt alloy catalysts are a more active substitute for pure Pt catalysts at 0.9 V, high activity is also needed at high current densities if they are to be adopted for fuel cell application. We use a newly developed electrochemical technique to compare the performance of a range of catalysts with initial composition Pt4-xCox/C of different partiCle sizes at high current densities (similar to 0.65 V vs RHE) as well as the typical similar to 0.9 V vs RHE. Moving from 0.9 to 0.65 V, the current densities were found to increase by up to 80-fold for the Pt/C catalysts, with this factor decreasing as the amount of Co in the PtCo alloy increases. A kinetic model incorporating site blocking species at both high and low potentials has been used to explain this change. While the dealloyed catalysts were found to have a greater mass activity at low current densities (similar to 0.9 V vs RHE), they were no longer as active as 2.1 nm Pt partiCle catalyst at high current densities (similar to 0.65 V vs RHE). However, for equivalent partiCle sizes, the mass activity of the dealloyed Co-containing catalysts remains higher across the normal operating potentials of a fuel cell. Using this insight, we predict that at 0.65 V a catalyst composed of 3.8 nm CoPt@Pt1ML partiCles would give optimum mass activity performance. In addition, two peaks were observed during the cyClic voltammetry (CV) of the oxygen reduction reaction (ORR) on pure Pt nanopartiCles in the hydrogen adsorption region (0-0.4 V vs RHE). These peaks are associated with surface sites with different reactivities toward the ORR.Electrochemical Measurement of Intrinsic Oxygen Reduction Reaction Activity at High Current Densities as a Function of PartiCle Size for Pt4-xCox/C (x=0, 1, 3) Catalystsoxygen reduction reaction; fuel cells; electrocatalysis; platinum; cobalt13202064#N/ATRUE
4931
acscatal.9b0376010.1021/acscatal.9b03760FALSEhttps://doi.org/10.1021/acscatal.9b03760Lambert, RMACS Catal.Comprehensive Experimental and Theoretical Study of the CO+NO Reaction Catalyzed by Au/Ni NanopartiCles (vol 6, pg 4919, 2019)x020191#N/AFALSE
4932
acscatal.9b0467010.1021/acscatal.9b04670FALSEhttps://doi.org/10.1021/acscatal.9b04670Wu, GACS Catal.Ammonia (NH3) has proved to be an effective alternative to hydrogen in low-temperature fuel cells via its direct ammonia oxidation reaction (AOR). However, the kinetically sluggish AOR has prohibitively hindered the attractive direct ammonia fuel cell (DAFC) applications. Here, we report an efficient AOR catalyst, in which ternary PtIrNi alloy nanopartiCles well dispersed on a binary composite support consisting of porous silicon dioxide (SiO2) and Carbonyl-functionalized carbon nanotube (PtIrNi/SiO2-CNT-COOH) through a sonochemical-assisted synthesis method. The PtIrNi alloy nanopartiCles, with the aid of abundant OHad provided by porous SiO2 and the improved electrical conductivity by CNTs, exhibit remarkable catalytic activity for the AOR in alkaline media. It is evidenced by a lower onset potential (similar to 0.40 V vs reversible hydrogen electrode (RHE)) at room temperature than that of commercial PtIr/C (ca. 0.43 V vs RHE). Increasing NH3 concentrations and operation temperatures can significantly enhance AOR activity of this PtIrNi nanopartiCle catalyst. Specifically, the catalyst at the temperature of 80 degrees C exhibits a much lower onset potential (similar to 0.32 V vs RHE) and a higher peak current density, indicating that DAFCs operated at a higher temperature are favorable for increased performance. Constant-potential density functional theory (DFT) calculations showed that the Pt-Ir ensembles on {100}-terminated surfaces serve as the active site. The introduction of Ni raises the center energy of the density of states projected onto the group d-orbitals of surface sites and thus lowers the theoretical onset potential for *NH2 dehydrogenation to *NH compared to Pt and Pt3Ir alloy.Ternary PtIrNi Catalysts for Efficient Electrochemical Ammonia Oxidationelectrocatalysis; ammonia oxidation reaction; PtIrNi ternary alloy; DFT calculations; direct ammonia fuel cells21202060#N/ATRUE
4933
acscatal.9b0458610.1021/acscatal.9b04586FALSEhttps://doi.org/10.1021/acscatal.9b04586Liao, XBACS Catal.We report nickel-catalyzed cyanation and hydrocyanation methods to prepare Aryl nitriles and Vinyl nitriles from Aryl halides and alkynes, respectively. Using inexpensive and nontoxic 4-cyanopyridine N-oxide as the cyano shuttle, the methods provide an efficient approach to prepare Aryl cyanides and Vinyl nitriles under mild and operationally simple reaction conditions with a broad range of functional group tolerances. In hydrocyanation of alkynes, the method demonstrated good regioselectivity, producing predominantly E- or Z-alkenyl nitriles in a controlled manner and exClusively Markovnikov Vinyl nitriles when internal diAryl alkynes and terminal alkynes were applied as the substrates, respectively. The preliminary mechanistic investigation indicated that the C-CN bond Cleavage process is promoted by oxidative addition to the nickel(I) complex in the cyanation of Aryl halides, and further studies via a series of deuterium exchange experiments indicated that water serves as the hydrogen source for the hydrocyanation of alkynes.Nickel-Catalyzed Cyanation of Aryl Halides and Hydrocyanation of Alkynes via C-CN Bond Cleavage and Cyano Transfernickel catalysis; cyanation; hydrocyanation; C-CN bond Cleavage; Z/E selectivity; Markovnikov addition252020130#N/ATRUE
4934
acscatal.9b0363010.1021/acscatal.9b03630FALSEhttps://doi.org/10.1021/acscatal.9b03630Li, DQACS Catal.The catalytic upgrading of biomass-derived feedstocks to valuable chemicals generally requires catalysts with integrated active sites and tuned structures for selective Activation of their multifunctional groups. Herein, we fabricated different Cu-based catalysts with multiple interfaces by facile reduction of layered double hydroxides (LDHs), aimed at controlling the reaction pathway and product selectivity in the hydrogenation of 5-(hydroxymethyl)furfural (HMF), an important biomass-based platform molecule. These Cu catalysts were characterized by XRD, Raman, TPR, HAADF-STEM, and in situ XAFS. For Cu/MgAlOx, derived from CuMg5Al2-LDHs, Cu partiCles were partially encapsulated by a MgAlOx support, thus forming highly intimate Cu-MgAlOx interfaces. On Co@Cu/CoAlOx, derived from CuCoxAl2-LDHs, together with a Cu-CoAlOx interface, partially reduced ultrasmall Co Clusters were mounted around Cu partiCles to form a metallic Co-Cu interface, which is tunable by varying the Cu/Co ratio. As expected, Cu/MgAlO, was only active in C=O hydrogenation to produce 2,5-bis(hydroxymethyl)furan (DHMF) in a 92.7% yield, while Co@Cu/3CoAlO(x) sequentially catalyzed the C=O hydrogenation and C-OH hydrogenolysis to yield as high as 98.5% 2,5-dimethylfuran (DMF), in sharp contrast to Co@Cu/5CoAlO(x), which further broke the C=C bonds of DMF to yield 83.6% 2,5-dimethyltetrahydrofuran (DMTHF). The dependence of the reaction pathway and product selectivity on the composition and properties of the interface was revealed by identifying various intermediates using in situ IR. Specifically, HMF transformed into an O-bound intermediate on the Cu sites over the Cu-MgAlOx, while the unsaturated interfacial Cu-CoAlOx structure served as dual active sites to form a C,O-bound intermediate, thus leading to different products. In addition, the tunable Cu-Co interfacial sites remarkably influenced the adsorption modes of C=C bonds in the furan ring. This work provides a rationale for controlling the reaction pathway and product selectivity for complicated biomass reactions via the controllable construction of multiple interfaces.Interfacial Structure-Determined Reaction Pathway and Selectivity for 5-(Hydroxymethyl)furfural Hydrogenation over Cu-Based Catalystsx25202064#N/AFALSE
4935
acscatal.9b0362310.1021/acscatal.9b03623FALSEhttps://doi.org/10.1021/acscatal.9b03623Chen, ZFACS Catal.Transition-metal phosphides have been shown to be promising electrocatalysts in water for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To maximize reactivity toward both entails limiting the catalyst size while maintaining reactivity and avoiding aggregation. Frame-like hollow nanostructures (nanoframes) provide the required open structure with sufficient channels into the interior volume. We demonstrate here the design and synthesis of CoP nanoframes (CoP NFs) by a strategy involving precipitation, chemical etching, and low-temperature phosphidation steps. It results in impressive bifunctional catalytic activities for both HER and OER and consequently enables a highly efficient water electrolyzer with a current density of 10 mA cm(-2) driven by a cell voltage of only 1.65 V. The strategy has been generalized for the preparation of nanoframe Co dichalcogenides CoX2 NFs, with X = S, Se, and Te. The results of electrochemical measurements, supported by density functional theory calculations, show that HER catalytic activities for the series follow the sequence: CoP NFs > CoSe2 NFs > CoS2 NFs > CoTe2 NFs.CoP Nanoframes as Bifunctional Electrocatalysts for Efficient Overall Water Splittingcobalt phosphide; nanoframe; Prussian blue analogue; density functional theory; water splittingx89202039#N/AFALSE
4936
acscatal.9b0362010.1021/acscatal.9b03620FALSEhttps://doi.org/10.1021/acscatal.9b03620Ribas, XACS Catal.Nickel-catalyzed C-F Activations enabled chemodivergent C-C formation with alkynes by chelation assistance. The judicious choice of the alkyne electronic properties allowed the selective synthesis of double-insertion aromatic homologation or alkyne monoannulation products by C-F/C-H Activation. On the basis of the unambiguous crystallographic characterization of an unprecedented nine-membered nickelacyClic intermediate and extensive DFT studies, a plausible mechanistic rationale was established for the selective C-F Activation and the chemodivergent catalysis.Chemodivergent Nickel(0)-Catalyzed Arene C-F Activation with Alkynes: Uriprecedented C-F/C-H Double Insertionnickel catalysis; C-F Activation; aromatic homologation; directing group approach; DFTx11201950#N/AFALSE
4937
acscatal.9b0359610.1021/acscatal.9b03596https://doi.org/10.1021/acscatal.9b03596Huestis, MPACS Catal.A mild and direct strategy for the construction of Aryl aminooxetanes has been accomplished through the synergistic combination of photoredox and nickel catalysis. This approach represents a rare example of harnessing challenging tertiary radicals in photoredox/nickel cross-coupling. Oxetanes are often employed in medicinal chemistry as Carbonyl or gem-dimethyl bioisosteres, but their accessibility is hampered by the lack of practical synthetic methods. The strategy reported here utilizes a readily available oxetanyl amino acid building block in a cross-coupling manifold to rapidly access oxetane scaffolds with broad functional group tolerance. Computational studies reveal that a catalytic cyCle beginning with Ni(0)-Ni(II) oxidative addition, rather than radical addition to Ni(0), is operative for reactions with aminooxetanyl radicals. Consequently, for radical-based photoredox/nickel-catalyzed cross-couplings, the preferred mechanistic pathway has a fundamental dependence on the identity of the radical.Dual Photoredox/Nickel-Catalyzed Conversion of Aryl Halides to Aryl Aminooxetanes: Computational Evidence for a Substrate-Dependent Switch in Mechanismbioisostere; cross-coupling; density functional theory; mechanistic analysis; nickel catalysis; oxetane; photoredox catalysis; tertiary radicalPhotocatalyst5202044#N/AFALSE
4938
acscatal.9b0354410.1021/acscatal.9b03544FALSEhttps://doi.org/10.1021/acscatal.9b03544Nam, KTACS Catal.Although NiFeOxHy has attracted enormous attention as an alkaline water electrolyzer owing to its high performance in the oxygen evolution reaction (OER), it still requires further improvement in terms of catalytic activity, durability, and an underlying understanding of the mechanism. Here we report the fabrication of Zn-doped NiFeOxHy (Zn;NiFeOxHy) that has advanced electrocatalytic activity and stability in comparison to pure NiFeOxHy in the OER via simple chemical bath deposition and electrochemical Activation. The improvement with Zn;NiFeOxHy is due to the Zn2+ dopant, a strong Lewis acid that modulates its electronic property for better intermediate binding for the electrochemical process, resulting in the stabilization of the OER-active phase. This work opens up an opportunity to elucidate the detailed mechanism of NiFeOxHy-based electrocatalysts and improves our understanding of redox tuning through inductive effects, thereby leading to advanced OER catalyst developments.Chemically Deposited Amorphous Zn-Doped NiFeOxHy for Enhanced Water Oxidationwater oxidation; nickel; iron; zinc; dopant; Lewis acidx20202057#N/AFALSE
4939
acscatal.9b0445110.1021/acscatal.9b04451FALSEhttps://doi.org/10.1021/acscatal.9b04451Senanayake, SDACS Catal.The methane Activation and methane dry reforming reactions were studied and compared over 4 wt % Ni/CeO2 and 4 wt % Ni/CeZrO2 (containing 20 wt % Zr) catalysts. Upon the incorporation of Zr into the ceria support, the catalyst exhibited a significantly improved activity and H-2 selectivity. To understand the effects of the Zr dopant on Ni and CeO2 during the dry reforming of methane (DRM) reaction and to probe the structure-reactivity relationship underlying the enhanced catalytic performance of the mixed-oxide system, in situ time-resolved X-ray diffraction (TR-XRD), X-ray absorption fine structure (XAFS), and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) were employed to characterize the catalysts under reaction conditions. TR-XRD and AP-XPS indicate that ceria-zirconia supported Ni (Ni/CeZrO2) is of higher reducibility than the pure ceria supported Ni (Ni/CeO2) upon the reaction with pure CH4 or for the methane dry reforming reaction. The active state of Ni/CeZrO2 under optimum DRM conditions (700 degrees C) was identified as Ni, Ce3+/Ce4+, and Zr4+. The partiCle size of both nickel and the ceria support under reaction conditions was analyzed by Rietveld refinement and extended XAFS fitting. Zr in the ceria support prevents partiCle sintering and maintains small partiCle sizes for both metallic nickel and the partially reduced ceria support under reaction conditions through a stronger-metal support interaction. Additionally, Zr prevents Ni migration from the surface into ceria forming a Ce1-xNixO2-y solid solution, which is seen in Ni/CeO2, thus helping to preserve the active Ni-0 on the Ni/CeZrO2 surface.Effects of Zr Doping into Ceria for the Dry Reforming of Methane over Ni/CeZrO2 Catalysts: In Situ Studies with XRD, XAFS, and AP-XPSnickel; ceria; zirconia; CeZrO2 solid solution; XRD; XAFS; AP-XPS; dry reforming of methane21202055#N/ATRUE
4940
acscatal.9b0340210.1021/acscatal.9b03402FALSEhttps://doi.org/10.1021/acscatal.9b03402Laursen, SThe Origin of the Special Surface and Catalytic Chemistry of Ga-Rich Ni3Ga in the Direct Dehydrogenation of Ethanex2019#N/AFALSE
4941
acscatal.9b0335910.1021/acscatal.9b03359FALSEhttps://doi.org/10.1021/acscatal.9b03359Kucernak, AACS Catal.Carbon-supported MxPy (M = Ni, Co, W, Cr, and Mo) were prepared via pyrolysis using a very simple and scalable method utilizing nontoxic metal and phosphorus precursors. The electrochemical hydrogen evolution (HER), oxygen reduction (ORR), and oxygen evolution (OER) reactions and corrosion resistance under both acidic and alkaline conditions were examined for all these catalysts and compared to those for the benchmark catalysts Pt/C (HER/ORR) and IrO2 (OER). The highest activities were found in alkaline solutions for Co2P for HER and ORR and Ni2P for OER Good activity was also found in acid for some of these reactions, although the catalysts suffered from susceptibility to corrosion. Co2P was further studied in an alkaline environment, as it shows high catalytic activity toward the oxygen reduction reaction (ORR) without significant hysteresis. The onset potential (at 0.5 mA cm(-2)) obtained was 0.8 V vs RHE, and a Tafel slope value of 38 mV dec(-1) was found with a maximum kinetic mass activity of 2870 A g(Co)(-1) at 0.7 V vs RHE. Utilizing high-resolution transmission electron microscopy, it is possible to observe high-surface-area needle-like single-crystal cobalt oxide structures on the surface of the Co2P partiCles at the beginning of the ORR Hence the high rates of initial corrosion of the Co2P appear to be associated with the dissolution and precipitation of cobalt oxide on the partiCle surface. The as -synthesized Co2P/C also shows good performance in an 8-h stability test for the OER, carried out at 1.6 V vs RHE in alkaline conditions, with negligible drop in current density over time. Interestingly, in an acidic environment the catalyst is very active toward two-electron oxygen reduction, leading to H2O2 with high selectivity (85%). It is intriguing that the pH dependence of this catalyst toward the ORR is similar to that seen for gold.Supported Transition Metal Phosphides: Activity Survey for HER, ORR, OER, and Corrosion Resistance in Acid and Alkaline Electrolytesmetal phosphides; transition metals; hydrogen peroxide; oxygen reactions; single crystalx67201959#N/AFALSE
4942
acscatal.9b0442910.1021/acscatal.9b04429FALSEhttps://doi.org/10.1021/acscatal.9b04429Yang, BACS Catal.Dry reforming of methane (DRM) is an important reaction in the actual environmental and energy crisis context. It enables the production of syngas from CO2 and CH4 reforming. While Ni catalyst presents a high activity regarding this process, it often suffers from deActivation. It was found that the Sn-doped Ni catalyst can avoid carbon deposition, but a decrease in DRM reactivity was also observed. In this work, we used density functional theory calculations in combination with microkinetic modeling first to understand how Sn doping affects the resistance to carbon deposition and the surface catalytic activities of Ni. Based on the understandings, we found that an ideal dopant should give rise to a proper adsorption energy of carbon such that (i) the C* formation process, e.g., CH4 dissociation, is rate-controlling to improve the carbon resistance and (ii) relatively low dissociation barriers of CH4 and CO2 can be achieved to maintain a good activity. Therefore, the adsorption energy of carbon and the dissociation barriers of CH4 and CO2 can be utilized as descriptors for the stability and activity of Ni-based catalysts. Subsequently, we screened several metal dopants and found that the descriptors designed are capable of providing a consistent activity and stability trend with experiments reported in the literature. Therefore, our work could provide relevant guidelines to rationally design efficient catalysts for the DRM reaction.Descriptor Design in the Computational Screening of Ni-Based Catalysts with Balanced Activity and Stability for Dry Reforming of Methane Reactiondescriptor design; computational catalyst screening; dry reforming of methane; Ni-based catalyst; activity; stability21202077#N/ATRUE
4943
acscatal.9b0332210.1021/acscatal.9b03322https://doi.org/10.1021/acscatal.9b03322Bahnemann, DWVisible-Light-Mediated Photocatalytic Aerobic Dehydrogenation of N-heterocyCles by Surface-Grafted TiO2 and 4-amino-TEMPOPhotocatalyst2019#N/AFALSE
4944
acscatal.9b0324510.1021/acscatal.9b03245FALSEhttps://doi.org/10.1021/acscatal.9b03245He, JNi-0/Ni delta+ Synergistic Catalysis on a Nanosized Ni Surface for Simultaneous Formation of C-C and C-N Bondsx2019#N/AFALSE
4945
acscatal.9b0321210.1021/acscatal.9b03212FALSEhttps://doi.org/10.1021/acscatal.9b03212Duboc, CACS Catal.In nature, dihydrogen is catalytically produced or split by the [FeFe] and [NiFe] hydrogenases. Despite common structural features in their dinuClear active site, i.e., a thiolate-rich coordination sphere and CO/CN- ligation, the synergetic way, in which the two metal sites act during catalysis, is specific for each enzyme. With the aim of understanding the role of the nature of the metal (Fe vs Ni), we report on a homodinuClear FeFe complex, a parent of a previously reported NiFe complex, to compare their electrocatalytic activity for H-2 production. The di-iron complex [(CO)-(LFeII)-Fe-N2S2-Fe-II (CO)Cpr (with L-N2S2 = 2,2'-(2,2'-bipyridine-6,6'-diyObis(1,1-diphenylethanethiolate and Cp = cyClopentadienyl) has been synthesized and fully characterized. In the solid state, it contains two CO ligands: one bound to the {FeCp} moiety in a semibridging manner and one terminally bound to the {FeLN2S2} moiety. This dinuClear iron complex is thus not isostructural to [(LNiFeII)-Ni-N2S2-Fe-II(CO)Cp](+), which contains a single CO ligand terminally bound to the Fe site. However, at low concentrations in MeCN solutions, the CO ligand coordinated to the {FeLN2S2} moiety is removed and the CO ligand bound to the {FeCp} moiety becomes fully bridging between the two Fe sites. Under such conditions, the di-iron complex displays similar catalytic performances to the parent NiFe complex (a comparable overpotential, i = 730 and 690 mV, and TON = 15 and 16, respectively). CyClic voltammetry data give direct experimental evidence for an E[ECEC] mechanism, which was also previously proposed for the NiFe complex. However, the structure of the one-electron reduced species, the entry point of the catalytic cyCle, slightly differs for the two systems: in [(LNiI)-Ni-N2S2 (CO)(FeCp)-Cp-II], this is valence localized species on the site Ni and the CO ligand bridges the two metal ions, while in [(CO)L(N2S2F)eFeCp], this is a type II-III mixed-valence species with the CO terminally bound to the {FeLN2S2} unit.Role of the Metal Ion in Bio-Inspired Hydrogenase Models: Investigation of a HomodinuClear FeFe Complex vs Its HeterodinuClear NiFe AnalogueH-2 production; FeFe hydrogenase model; electrocatalysis; metal thiolate; mechanismx6202042#N/AFALSE
4946
acscatal.9b0320610.1021/acscatal.9b03206FALSEhttps://doi.org/10.1021/acscatal.9b03206Shao, MHImpact of Heat Treatment on the Electrochemical Properties of Carbon-Supported Octahedral Pt-Ni NanopartiClesx2019#N/AFALSE
4947
acscatal.9b0317510.1021/acscatal.9b03175FALSEhttps://doi.org/10.1021/acscatal.9b03175Qiu, JSACS Catal.Metal-doped zeolitic imidazolate framework-8 (ZIF-8)derived carbon materials are attractive for the electrocatalytic reduction of CO, into CO. In such carbon materials, due to the fusion and aggregation of ZIF-8 precursors during the high-temperature pyrolysis process, it is desirable yet still challenging to create a high specific surface area with more active sites available for reacting with reactants. Using SiO2 as a protective coating on the ZIF-8 surface, we synthesize Fe, N-co-doped porous carbon nanopartiCles (Fe-CNPs) which possess a hierarchical pore structure with a specific surface area as high as 1156.6 m(2) g(-1), much higher than the counterparts without a SiO2 coating (360.1 m(2) g(-1)). Over these highly porous Fe-CNPs, the total current densities are more than 3 times higher than those of the lowly porous ones for the electrochemical CO, reduction. More importantly, the maximum CO Faradaic efficiency for Fe-CNPs increases from ca. 75.0 to 98.8% in a concentrated KHCO3 solution (1 mol L-1). The porosity-induced high selectivity for COproduction is also revealed on Ni-doped and Co-doped ZIF-derived CNPs, suggesting a new pathway for designing high-performance carbon catalysts through engineering the porosity for the electrochemical CO2 reduction.Porosity-Induced High Selectivity for CO2 Electroreduction to CO on Fe-Doped ZIF-Derived Carbon Catalystszeolitic imidazolate framework; carbon dioxide reduction; electrocatalysis; carbon materials; porosityx23201954#N/AFALSE
4948
acscatal.9b0421710.1021/acscatal.9b04217FALSEhttps://doi.org/10.1021/acscatal.9b04217Zboril, RACS Catal.Carbon-based materials are widely employed as metal-free catalysts or supports in catalysis, energy, and ecological applications because of their interesting properties. Generally, their high surface areas, size, shape, porosity, and the possibility of incorporating additional moieties through chemical functional designs are believed to be essential for enriching the catalytic activity of carbon-containing materials. Lately, the new field of single-atom catalysts (SACs) has emerged as the finest alternative for not only homogeneous but also heterogeneous catalysts used in various kinds of catalytic applications. Among a variety of SACs, carbon-based SACs are widely investigated catalysts because of their extraordinary features such as tunable morphologies, ordered porosity, and effortless immobilization through various metals (noble and non-noble), making them highly efficient single-atom catalysts for numerous important catalytic applications. Herein, we intend to report on the progress achieved in researching carbon-based single-atom catalysts, inCluding primarily metals such as Co, Cu, Zn, Pd, Ni, Pt, among others, embedded in carbon matrices and applied to applications in organic catalysis, photocatalysis, and electrocatalysis. It is important to point out that the main focus of this Review is directed to the activity and applications of single atom catalysts, which are discussed in detail; thus, characterization and rationalization are exCluded. Finally, we provide a future perspective on the development and progress made on a carbon-based single metal atom for catalysis.Carbon-Based Single-Atom Catalysts for Advanced Applicationssingle-atom catalysts; single-site catalysts; synthesis; mechanistic aspects; organic synthesis; photocatalysis; electrocatalysis922020163#N/ATRUE
4949
acscatal.9b0419310.1021/acscatal.9b04193FALSEhttps://doi.org/10.1021/acscatal.9b04193Weckhuysen, BMACS Catal.Hydrogen is currently mainly produced via steam reforming of methane (SMR: CH4 + H2O -> CO + 3H(2)). An alternative to this process, utilizing carbon dioxide and thus potentially mitigating its environmentally harmful emissions, is dry methane reforming (DMR: CH4 + CO2 -> 2CO + 2H(2)). Both of these reactions are structure sensitive, that is, not all atoms in a catalytic metal nanopartiCle have the same activity. Mapping this structure sensitivity and understanding its mechanistic workings provides ways to design better, more efficient, and more stable catalysts. Here, we study a range of SiO2-supported Ni nanopartiCles with varying partiCle sizes (1.2-6.0 nm) by operando infrared spectroscopy to determine the active mechanism over Ni (carbide mechanism) and its kinetic dependence on Ni partiCle size. We establish that Ni partiCle sizes below 2.5 nm lead to a different structure sensitivity than is expected from and implied in literature. Because of the identification of CHxDx species with isotopically labeled experiments, we show that CH4 Activation is not the only rate-limiting step in SMR and DMR. The recombination of C and O or the Activation of CO is likely also an important kinetically limiting factor in the production of synthesis gas in DMR, whereas for SMR the desorption of the formed CO becomes more kinetically limiting. Furthermore, we establish the Ni partiCle size dependence of carbon whisker formation. The optimal Ni partiCle size both in terms of activity for SMR and DMR, at 500 and 600 degrees C, and 5 bar, was found to be approximately 2-3 nm, whereas carbon whisker formation was found to maximally occur at approximately 4.5 nm for SMR and for DMR increased with increasing partiCle size. These results have direct practical applications for tuning of activity and selectivity of these reactions, while providing fundamental understanding of their working.Structure Sensitivity in Steam and Dry Methane Reforming over Nickel: Activity and Carbon Formationsteam methane reforming; dry methane reforming; nickel; structure sensitivity; spectroscopy; Fourier transform infrared spectroscopy; nickel24202058#N/ATRUE
4950
acscatal.9b0303010.1021/acscatal.9b03030FALSEhttps://doi.org/10.1021/acscatal.9b03030Zhou, HQACS Catal.Molybdenum disulfide-based layered materials are promising electrocatalysts for hydrogen production from water electrolysis if their catalytic performance can be further improved by increasing the electrical conductivity and edge site density, and decreasing the contact resistance between the catalyst and its support. A suitable conductive scaffold can play a positive role in enhancing the relevant hydrogen evolution performance. Here we demonstrate that three-dimensional NiCoSe2 nanosheet arrays supported on Ni foam are effective as the conductive scaffold for enhancing the catalytic activity of layered MoS1.5Se0.5 partiCles. The resulting hierarchical MoS1.5Se0.5/NiCoSe2, hybrid electrocatalyst is highly efficient for hydrogen evolution in acid, yielding geometric current densities of 10, 50, and 100 mA cm(-2) at overpotentials as low as 57, 88, and 102 mV with good long-term durability at current densities up to 500 mA cm(-2) over 25 h. To the best of our knowledge, no MoS2-based electrocatalyst can realize both low overpotential affording a current density of 500 mA cm(-2) and good durability at a large current density (500 mA cm(-2)) except this report. In particular, the double-layer capacitance, turnover frequency measurements, and high normalized exchange current density indicate its possibly high intrinsic activity for hydrogen evolution in acid. It is among the most efficient earth-abundant catalysts exhibiting a low overpotential and simultaneous good intrinsic activity reported on a three-dimensional architecture thus far.Robust Hydrogen-Evolving Electrocatalyst from Heterogeneous Molybdenum Disulfide-Based Catalystelectrocatalyst; electronic coupling; hydrogen evolution; molybdenum disulfide; water electrolysisx23202053#N/AFALSE
4951
acscatal.9b0298410.1021/acscatal.9b02984https://doi.org/10.1021/acscatal.9b02984Reisner, EACS Catal.Dye-sensitized photoelectrochemical (DSPEC) cells are an emerging approach to producing solar fuels. The recent development of delafossite CuCrO2 as a p-type semiconductor has enabled H-2 generation through the coassembly of catalyst and dye components. Here, we present a CuCrO2 electrode based on a high surface-area inverse opal (IO) architecture with benchmark performance in DSPEC H-2 generation. Coimmobilization of a phosphonated diketopyrrolopyrrole (DPP-P) or perylene monoimide (PMI-P) dye with a phosphonated molecular Ni catalyst (NiP) demonstrates the ability of IO-CuCrO2 to photogenerate H-2. A positive photocurrent onset potential of approximately +0.8 V vs RHE was achieved with these photocathodes. The DPP-P-based photoelectrodes delivered photocurrents of -18 mu A cm(-2) and generated 160 +/- 24 nmol of H-2 cm(-2), whereas the PMI-P-based photocathodes displayed higher photocurrents of -25 mu A cm(-2) and produced 215 +/- 10 nmol of H-2 cm(-2) at 0.0 V vs RHE over the course of 2 h under visible light illumination (100 mW cm(-2), AM 1.5G, lambda > 420 nm, 25 degrees C). The high performance of the PMI-constructed system is attributed to the well-suited molecular structure and photophysical properties for p-type sensitization. These precious-metal-free photocathodes highlight the benefits of using bespoke IO-CuCrO2 electrodes as well as the important role of the molecular dye structure in DSPEC fuel synthesis.Inverse Opal CuCrO2 Photocathodes for H-2 Production Using Organic Dyes and a Molecular Ni Catalystdye-sensitized; molecular catalyst; photocatalysis; solar fuels; p-type semiconductor; delafossitePhotocatalyst14201998#N/AFALSE
4952
acscatal.9b0297810.1021/acscatal.9b02978FALSEhttps://doi.org/10.1021/acscatal.9b02978Yang, HGACS Catal.Single-atom catalysts have found considerable applications in the field of electrochemical CO2 reduction reaction (CO2RR) due to their unique coordination environments. However, during the preparation of single-atom catalysts, some metal nanopartiCles (NPs) are inevitably generated, which suffer from low selectivity in CO2RR. In this regard, complex postprocessing solution treatments are usually conducted to remove metal NPs using acid. Herein, we fabricated Ni(NC)-based catalysts composed of single Ni atoms and Ni NPs, both of which feature local Ni-N coordination via a simple Ni-metal organic framework (MOF)-assisted strategy. Based on X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy measurements, nitrogen species in N-doped carbon have been demonstrated to be coordinated with surface nickel species to form Ni-N motifs, which makes Ni at a low-valent state for efficient CO2RR. Consequently, the catalyst exhibited high performances toward CO2RR with CO Faradic efficiencies (FECO) maintained over 90% from -0.65 to -0.90 V vs reversible hydrogen electrode (RHE). More importantly, the FECO of 99% could be obtained at a considerable current density (j) of -160 mA cm(-2) in a flow cell configuration. These findings suggest that regulating the surface environment of Ni species can activate the original inert reaction sites into active reaction sites, providing a promising avenue to design high-performance electrocatalysts for CO2RR.Nitrogen-Stabilized Low-Valent Ni Motifs for Efficient CO2 ElectrocatalysisCO2 reduction reaction; nitrogen-modified Ni catalyst; operando XAFS; single-atom catalysis; electrocatalysisx19202041#N/AFALSE
4953
acscatal.9b0291310.1021/acscatal.9b02913FALSEhttps://doi.org/10.1021/acscatal.9b02913Lee, CFACS Catal.A nickel-catalyzed Aryl-aroyloxyl C(sp(2))-O radical cross-coupling reaction conducted using a redox active ester with Aryl zinc reagent was developed. This method demonstrates a new disconnection approach for formation of Aryl Aryl esters. In the one-pot sequential process, the readily available Aryl Carbonylic acids can be converted into functionalized Aryl Aryl esters and heteroAryl esters. This protocol is amenable to the gram-scale synthesis. The present method has a wide substrate scope and high functional group tolerance.Nickel-Catalyzed Cross-Coupling of Aryl Redoxactive Esters with Aryl Zinc Reagentsnickel; cross-coupling; redox-active esters; EPR study; single-electron transferx6201927#N/AFALSE
4954
acscatal.9b0284210.1021/acscatal.9b02842https://doi.org/10.1021/acscatal.9b02842Sun, YJACS Catal.Depolymerization of recalcitrant lignin is a crucial step in realizing the full potential of transforming biomass to value-added small organic molecules. Herein, we report a photocatalytic system consisting of ultrathin CdS nanosheets decorated with first-row transition metals (M/CdS) for the direct photoCleavage of lignin model compounds to small aromatic products. In the meantime, the reducing power of M/CdS is utilized to simultaneously generate another valuable product, H-2, hence eliminating the necessity of sacrificial reagents and maximizing the energy conversion efficiency. We further demonstrate that, by judiciously modulating the photocatalytic conditions, it is feasible to yield different products with very high selectivity using the same catalyst of Ni/CdS. A series of control experiments were performed to investigate the mechanistic steps of each reaction and highlight the important roles played by both solvent and base in the photoCleavage of the beta-O-4 bond in lignin valorization.Highly Selective Photocatalytic Valorization of Lignin Model Compounds Using Ultrathin Metal/CdSlignin valorization; photocatalysis; selective photoCleavage; ultrathin CdS; nickel cocatalystPhotocatalyst13201937#N/AFALSE
4955
acscatal.9b0418310.1021/acscatal.9b04183FALSEhttps://doi.org/10.1021/acscatal.9b04183Cao, PACS Catal.A modular synthesis of 2,8-dioxabicyClo[3.2.1]octane (2,8-DOBCO) ketals is realized by sequential catalysis. The key intermediates, epsilon-hydroxyl-beta,gamma-unsaturated ketones, are readily available by Ni-catalyzed three-component coupling of 1,3-dienes, aldehydes, and acylzirconocene reagents. These polyfunctionalized ketones can undergo a V-catalyzed cascade of epoxidation and ring rearrangement to provide access to 6-hydroxyl-2,8-DOBCOs. Mechanistic studies indicate that the V(V) species, generated under epoxidation conditions, promotes the ring rearrangement in a stereospecific manner. Meanwhile, the epsilon-hydroxyl-beta-gamma-unsaturated ketones are transformed into 6-amino-2,8-DOBCOs by a Cu-catalyzed cascade of aziridination and ring rearrangement. In the end, the one-pot approach toward 6-hydroxyl- or 6-amino-2,8-DOBCOs from 1,3-diene, aldehydes, and acylzirconocene reagents is more favorable.Modular Synthesis of 2,8-DioxabicyClo[3.2.1]octanes by Sequential Catalysis1,3-dienes; 2,8-dioxabicyClo[3.2.1]octane; modular synthesis; sequential catalysis; cyClization cascade4201973#N/ATRUE
4956
acscatal.9b0270110.1021/acscatal.9b02701FALSEhttps://doi.org/10.1021/acscatal.9b02701Lee, JSACS Catal.We report here a facile, one-step precipitating metal nitrate deposition (PMND) method to prepare amorphous metal oxyhydroxide films containing Fe, Co, and Ni as efficient electrocatalysts for water oxidation. The unique synthesis technique allows easy control of the metal composition over a wide range on various substrates. A series of unary and binary metal oxyhydroxides of 30 compositions are synthesized by PMND on fluorine-doped tin oxide (FTO) substrate as water oxidation electrocatalysts. The activity of the metal oxyhydroxide films is represented by a volcano plot as a function of a single experimental descriptor, i.e., the fraction of hydroxide in the surface oxygen species. The optimum compositions for binary metal oxyhydroxide (NiFe, NiCo, and CoFe) are determined on conductive substrates of FTO, nickel foam (NF), nickel mesh (NM), and carbon felt (CF), and the best NiFe (2:8) electrocatalyst on NF exhibits a water oxidation current density of 100 mA/cm(2) with only 280 mV of overvoltage, which outperforms conventional noble metal catalysts like IrOx and RuOx in an alkaline medium. Finally, we demonstrate a tandem PV-electrolysis system by using a c-Si PV module with a power conversion efficiency of 13.71% and an electrochemical cell composed of NiFe (2:8)/NF anode and a bare NF cathode with a conversion efficiency of 71.8%, which records a solar-to-hydrogen conversion efficiency of 9.84%.Precipitating Metal Nitrate Deposition of Amorphous Metal Oxyhydroxide Electrodes Containing Ni, Fe, and Co for Electrocatalytic Water Oxidationoxygen evolution reaction; electrocatalytic water splitting; precipitating metal nitrate deposition; PV-electrolysis; volcano plot
Electrocatalytic
x15201981#N/AFALSE
4957
acscatal.9b0259410.1021/acscatal.9b02594FALSEhttps://doi.org/10.1002/anie.200462569Jaouen, FVolcano Trend in Electrocatalytic CO2 Reduction Activity over Atomically Dispersed Metal Sites on Nitrogen-Doped Carbonx2019#N/AFALSE
4958
acscatal.9b0258010.1021/acscatal.9b02580FALSEhttps://doi.org/10.1021/acscatal.9b02580Halaoui, LIACS Catal.This work examines by electrochemical measurements a hypothesis that low-coordination Fe on the surface (surface-Fe) of NiFe-oxo/hydroxide promotes catalysis for the oxygen evolution reaction (OER) rather than Fe in the bulk structure (bulk-Fe) even in ultrathin films that are mostly surface. The effect of method of incorporation of Fe in Ni-oxo/hydroxide on the electrochemical behavior and OER activity is interrogated, and the sustainability of OER catalysis at NiFe-oxo/hydroxide is examined in the absence of Fe in solution. Ni(Fe)-oxo/hydroxide ultrathin films of a few monolayers and thicker films of tens of monolayers of Ni(OH)(2) were deposited at anodic bias from potassium borate buffer containing Ni nitrate or Ni and Fe nitrates at a 6:4 Ni:Fe ratio and were conditioned and studied in 1 M KOH containing Fe or purified from Fe. Fe was incorporated in NiFe-oxo/hydroxide during codeposition but removed from solution during conditioning and catalysis, was inCluded postdeposition during conditioning and catalysis in Fe-containing solution, or was incorporated postdeposition by conditioning in Fe-containing solution and then removed from solution during catalysis. Ultrathin and thicker NiOxHy and Ni0.6Fe0.4OxHy films exhibited high OER currents and low Tafel slopes in the range of 40 mV/dec in 1 M KOH after Activation that inCluded Fe from solution. However, ultrathin and thicker codeposited Ni0.6Fe0.4OxHy films exhibited low OER currents in Fe-purified KOH, which further decreased with the application of anodic bias, and exhibited high Tafel slopes of ca. 100 mV/dec or higher, in a behavior similar to that of NiOxHy in Fe-free KOH. Fe inCluded postdeposition or surface-Fe is therefore indicated to be responsible for high OER catalysis in ultrathin and thicker NiFe-oxo/hydroxide films. The sustainability of OER catalysis at postdeposition activated Ni(Fe)-oxo/hydroxide still required the presence of Fe in solution. NiOxHy films activated for OER postdeposition in Fe-containing electrolyte did not sustain their high OER catalysis in Fe-free KOH but were deactivated with potential cyCling. An exchange that causes surface-Fe to move into higher coordination bulk-Fe is proposed to cause the loss of OER activity of activated NiFe-oxo/hydroxide in Fe-free electrolyte.OER Catalysis at Activated and Codeposited NiFe-Oxo/Hydroxide Thin Films Is Due to Postdeposition Surface-Fe and Is Not Sustainable without Fe in SolutionOER catalysis; oxygen evolution reaction; nickel hydroxide; NiFe-oxo/hydroxide; Ni-Bi; electrocatalyst; water splittingx25202059#N/AFALSE
4959
acscatal.9b0255310.1021/acscatal.9b02553https://doi.org/10.1021/acscatal.9b02553Li, YLACS Catal.Growing greenhouse gas CO2 is driving the research on the chemical fixation of CO2. Here, the organic reaction of CO2 with Benzyl halogen for chemical CO2 fixation under ambient conditions with irradiation of ultraviolet light is successfully catalyzed by Cu-BDC nanosheet@macroporous-mesoporous-TiO2 (Cu-BDC@macro-meso-TiO2), which shows high photocatalytic activity for both Benzyl chloride and bromide reacting with CO2. Meanwhile, the prepared Cu-BDC@macro-meso-TiO2 possesses a three-scale porous structure, inCluding macropores, mesopores, and micropores. In the uniform hierarchical structure, the microporous Cu-BDC nanosheet is confined in the macropore of macroporous-mesoporous-TiO2, while the ordered mesoporous structure is in the macroporous walls. This multilevel porous distribution can significantly improve the active surface areas and mass transfer efficiency of Cu-BDC@macro-meso-TiO2. Therefore, this finding has opened a field of research on photocatalytic chemical CO2 fixation.Photocatalytic Chemical CO2 Fixation by Cu-BDC Nanosheet@Macroporous-Mesoporous-TiO2 under Mild ConditionsCu-BDC nanosheet; macroporous-mesoporous-TiO2; CO2; Carbonylation; ultraviolet lightPhotocatalyst9201956#N/AFALSE
4960
acscatal.9b0253810.1021/acscatal.9b02538FALSEhttps://doi.org/10.1021/acscatal.9b02538Tu, XACS Catal.A. better fundamental understanding of the plasma-catalyst interaction and the reaction mechanism is vital for optimizing the design of catalysts for ammonia synthesis by plasma-catalysis. In this work, we report on a hybrid plasma-enhanced catalytic process for the synthesis of ammonia directly from N-2 and H-2 over transition metal catalysts (M/Al2O3, M = Fe, Ni, Cu) at near room temperature (similar to 35 degrees C) and atmospheric pressure. Reactions were conducted in a specially designed coaxial dielectric barrier discharge (DBD) plasma reactor using water as a ground electrode, which could cool and maintain the reaction at near-room temperature. The transparency of the water electrode enabled operando optical diagnostics (intensified charge-coupled device (ICCD) imaging and optical emission spectroscopy) of the full plasma discharge area to be conducted without altering the operation of the reactor, as is often needed when using coaxial reactors with opaque ground electrodes. Compared to plasma synthesis of NH3 without a catalyst, plasma-catalysis significantly enhanced the NH3 synthesis rate and energy efficiency. The effect of different transition metal catalysts on the physical properties of the discharge is negligible, which suggests that the catalytic effects provided by the chemistry of the catalyst surface are dominant over the physical effects of the catalysts in the plasma-catalytic synthesis of ammonia. The highest NH3 synthesis rate of 471 mu mol g(-1) h(-1)was achieved using Ni/Al2O3 as a catalyst with plasma, which is 100% higher than that obtained using plasma only. The presence of a transition metal (e.g., Ni) on the surface of Al2O3 provided a more uniform plasma discharge than Al2O3 or plasma only, and enhanced the mean electron energy. The mechanism of plasma-catalytic ammonia synthesis has been investigated through operando plasma diagnostics combined with comprehensive characterization of the catalysts using N2 physisorption measurements, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), NH3-temperature-programmed desorption (TPD), and N-2-TPD. Four forms of adsorbed NHx (x = 0, 1, 2, and 3) species were detected on the surfaces of the spent catalysts using XPS. It was found that metal sites and weak acid sites could enhance the production of NH3 via formation of NH2 intermediates on the surface.Plasma-Enhanced Catalytic Synthesis of Ammonia over a Ni/Al2O3 Catalyst at Near-Room Temperature: Insights into the Importance of the Catalyst Surface on the Reaction Mechanismnonthermal plasmas; plasma-catalysis; nitrogen fixation; ammonia synthesis; reaction mechanismx46201965#N/AFALSE
4961
acscatal.9b0411210.1021/acscatal.9b04112FALSEhttps://doi.org/10.1021/acscatal.9b04112Wei, HACS Catal.A Ni-catalyzed 1,2-acyl migration triggered by C-C bond Cleavage was developed. The process of 1,2-acyl migration followed by olefin isomerization provides a convenient access to alpha,beta-unsaturated ketones, which are well-known building blocks in organic synthesis. Experimental and computational studies show that the selective beta-hydride elimination and Ni-hydride reinsertion play an essential role in this reaction.Ni-Catalyzed 1,2-Acyl Migration Reactions Triggered by C-C Bond Activation of KetonesNi catalysis; C-C bond Cleavage; 1,2-acyl migration; olefin isomerization; unsaturated ketones5202079#N/ATRUE
4962
acscatal.9b0248810.1021/acscatal.9b02488https://doi.org/10.1021/acscatal.9b02488Zhang, XGACS Catal.Nickel-catalyzed carbodifunctionalization of alkenes is an efficient strategy for the construction of C-C bonds. However, applications of the strategy in diAlkylation of alkenes remain underdeveloped due to the difficulties in suppressing competitive side reactions. We now describe a nickel-catalyzed tandem reaction by difluoroAlkylation-Alkylation of N-Vinyl 2-pyrrolidinone with difluoroAlkyl bromides and diAlkylzinc reagents. The reaction can also extend to N-Vinyloxazolidinone and N-Vinylacetamide. This carbodifunctionalization reaction proceeds smoothly under mild reaction conditions with good functional group tolerance, providing a straightforward access to gem-difluoroAlkylated 2-pyrrolidinone derivatives that are of interest in medicinal chemistry.Nickel-Catalyzed DifluoroAlkylation-Alkylation of EnamidesdiAlkylzinc reagent; cross-coupling fluorine; nickel; tandem reactionx38201947#N/AFALSE
4963
acscatal.9b0248310.1021/acscatal.9b02483FALSEhttps://doi.org/10.1021/acscatal.9b02483Li, CJACS Catal.HydroAlkylation of unsaturated hydrocarbons with unstabilized carbon nuCleophiles is difficult and remains a major challenge. The disClosed examples so far have mainly focused on the involvement of heteroatom and/or stabilized carbon nuCleophiles as efficient reaction partners. Reported here is an unprecedented regioselective nickel-catalyzed hydroBenzylation of 1,3-dienes with hydrazones, generated in situ from abundant Aryl aldehydes and ketones and acting as both the sources of unstabilized carbanion equivalent and hydride. With this strategy, both terminal and sterically hindered internal dienes are hydroAlkylated efficiently in a highly selective manner, thus providing a reliable catalytic method to construct challenging C(sp(3))-C(sp(3)) bonds.Nickel-Catalyzed Regioselective HydroBenzylation of 1,3-Dienes with HydrazoneshydroAlkylation; 1,3-diene; hydrazone; nickel catalysis; C(sp(3))-C(sp(3)) bondx19201953#N/AFALSE
4964
acscatal.9b0245810.1021/acscatal.9b02458https://doi.org/10.1021/acscatal.9b02458Molander, GAACS Catal.Herein, the introduction of oxa- and azabenzonorbornadienes into photoredox/nickel dual catalysis in a regioselective and diastereoselective transformation is disClosed. The inherent advantages of this dual catalytic system allow the use of Alkyl motifs forming exClusively cis-1,2-dihydro-1-naphthyl alcohol backbones using readily accessible 4-Alkyl-1,4-dihydropyridines (DHPs). Whereas previous studies have emphasized the use of nuCleophilic organometallic coupling partners, this protocol grants access to a rather unexplored core featuring Alkyl residues, while avoiding the use of highly reactive organometallic species (i.e., M = Al, Mg, Li, Zn, Zr). Density functional theory (DFT) calculations support an oxidative addition/reductive elimination mechanism, followed by a Curtin-Hammett scenario that controls the regioselectivity of the process, unlike previously reported transformations that proceed via a carbometalation/beta-oxygen elimination mechanism.Oxa- and Azabenzonorbornadienes as Electrophilic Partners under Photoredox/Nickel Dual Catalysisoxabenzonorbornadiene; Curtin-Hammett; photoredox/nickel dual catalysis; 4-Alkyldihydropyridines; cross-coupling; regioselectivePhotocatalyst112019716/15/2022FALSE
4965
acscatal.9b0403810.1021/acscatal.9b04038FALSEhttps://doi.org/10.1021/acscatal.9b04038Zhang, XGACS Catal.The nickel-catalyzed Carbonylation of aliphatic electrophiles with the most straightforward CO remains challenging. Here, we describe an example of the nickel-catalyzed Carbonylation of secondary Alkyl halides with Arylboronic acids under 1 atm of CO. The reaction exhibits high functional group tolerance and a broad substrate scope, inCluding trifluoromethylated, difluoromethylated, and difluoroacetylated secondary Alkyl iodides and secondary Benzyl bromides, providing a general and cost-efficient method to access Alkyl ketones, especially alpha-trifluoromethylated Alkyl ketones that are of great interest in medicinal chemistry. Preliminary mechanistic studies reveal that a bimetallic oxidative addition is likely involved in the reaction.Nickel-Catalyzed Carbonylation of Secondary Trifluoromethylated, Difluoromethylated, and Nonfluorinated Aliphatic Electrophiles with Arylboronic Acids under 1 atm of COAlkyl ketones; Carbonylation; CO; nickel; secondary aliphatic electrophiles16202044#N/ATRUE
4966
acscatal.9b0395510.1021/acscatal.9b03955FALSEhttps://doi.org/10.1021/acscatal.9b03955Yamanaka, IACS Catal.The direct dehydrogenative conversion of methane (DCM) to higher hydrocarbons has attracted much attention, because of the efficient utilization of natural gas. Ni catalysis of Activation of C-H bonds of methane to H-2 and C is well-known. We have tried to control the catalysis of Ni via the addition of second elements and found silica-supported nickel phosphide (Ni-P/SiO2) materials as active catalysts for the DCM reaction at 1173 K. The products inCluded C2H4 (ethylene), C2H6 (ethane), C2H2 (acetylene), C3H6 (propylene), C6H6 (benzene), C7H8 (toluene), and C10H8 (naphthalene). The formation of Ni2P on silica was determined using scanning electron microscopy and X-ray diffraction. Pure Ni2P material without support showed a fine catalytic activity for the DCM reaction. Almost the same Activation energies of the Ni2P (249 kJ mol(-1)) and Ni-P/SiO2 catalysts (251 kJ mol(-1)) were obtained in the conversion rate of methane, which were lower than that of SiO2 (365 kJ mol(-1)). This indicated that Ni2P was the activate phase for the DCM reaction. The Ni2P phase activates C-H bonds of methane and converts to ethane. Other higher hydrocarbons were produced from ethane in the gas phase at 1173 K.Direct Nonoxidative Conversion of Methane to Higher Hydrocarbons over Silica-Supported Nickel Phosphide Catalystmethane; direct conversion; higher hydrocarbons; nickel phosphide catalyst; coupling of methane10202026#N/ATRUE
4967
acscatal.9b0231610.1021/acscatal.9b02316FALSEhttps://doi.org/10.1021/acscatal.9b02316Handa, SACS Catal.Both Ni(0) complexes and nanopartiCles (NPs) are unstable in water, which poses a significant hindrance to their application in aqueous synthetic catalysis. To overcome these barriers, ligated Ni(0) nanopartiCles (diameter <1 nm) containing a minimum amount of Pd(0) in the microballs formed of amphiphile PS-750-M are developed and applied in the highly selective carbamate Cleavage. Selectivity and functional group tolerance are thoroughly investigated. Control experiments revealed the importance of an individual component of the nanocatalyst. Use of our proline-based amphiphile PS-750-M is critical for achieving microball architecture, the stability of nanopartiCles, and desired catalytic activity. Once formed, microballs can be isolated and stored at ambient temperature. Catalyst is thoroughly characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis, infrared, and cyClic voltammetry. For selective catalysis, zero oxidation state of both Ni and Pd is crucial. On the basis of catalyst characterization and control experiments, the plausible reaction mechanism is proposed.Microballs Containing Ni(0)Pd(0) NanopartiCles for Highly Selective Miceliar Catalysis in Watermicellar catalysis; organometallic catalyst; green chemistry; sustainability; chemistry in waterx14201932#N/AFALSE
4968
acscatal.9b0377210.1021/acscatal.9b03772FALSEhttps://doi.org/10.1021/acscatal.9b03772Machida, MMulticomponent Spinel Oxide Solid Solutions: A Possible Alternative to Platinum Group Metal Three-Way Catalysts2019#N/ATRUE
4969
acscatal.9b0370910.1021/acscatal.9b03709FALSEhttps://doi.org/10.1021/acscatal.9b03709Li, WZACS Catal.Dry reforming of methane (DRM) integrates resourceful utilization of unwanted CO2 using cheap methane and storage of renewable energy. High temperature favors the highly endothermic process, while catalyst thermal deterioration is a major obstaCle. Here we report a robust Ru/MgAl2O4 catalyst prepared via physical vapor deposition method that exhibits 1 or 2 orders of magnitude higher activity than conventional ruthenium or nickel catalysts. Importantly, instead of deActivation or coke deposition, the catalyst demonstrates a surprising activity increase by 1.5 times after reaction at 850 degrees C for 600 h. Ru initially was dispersed as isolated atoms on MgAl2O4, then condensed into unfaceted Clusters (1.1 nm), and finally retained as faceted nanopartiCles (NPs, 2.7 nm) upon testing, becoming more and more active by decreasing the barrier of breaking the C-H bond of methane. The low Ru content (0.15 wt %) and high space-time yield make it cost-competitive to regeneration-required nickel catalysts, paving a way to develop affordable commercial precious metal catalyst.Robust Ruthenium-Saving Catalyst for High-Temperature Carbon Dioxide Reforming of Methanecarbon dioxide; dry reforming; methane; ruthenium catalyst; magnesium aluminate spinel; physical vapor deposition10202032#N/ATRUE
4970
acscatal.9b0368710.1021/acscatal.9b03687FALSEhttps://doi.org/10.1021/acscatal.9b03687Penner, SACS Catal.Quantitative in situ X-ray diffraction in combination with catalytic tests in dry reforming of methane (DRM) has been performed to unveil the strong structural dynamics of LaNiO3 catalysts during the DRM reaction. Structure-activity correlations reveal polymorphic changes of the rhombohedral LaNiO3 structure first into cubic LaNiO3 and further into transient oxygen-deficient triClinic LaNiO2.7 and monoClinic LaNiO2.5. These changes occur up to 620 degrees C and already cause considerable DRM activity. Another intermediate structure, the Ruddlesden-Popper phase La2NiO4 with moderate DRM activity, is formed in parallel with the decomposition of monoClinic LaNiO2.5. The decay of La2NiO4 directly goes along with the appearance of crystalline metallic Ni and monoClinic La2O2CO3 and a drastic enhancement of DRM activity. The formation of monoClinic La2O2CO3 and decomposition of La2NiO4 proceed exactly alike up to 670 degrees C with the accumulation of metallic Ni. At 670 degrees C and up to 750 degrees C, monoClinic La2O2CO3 is directly transformed into hexagonal La2O2CO3, and no further Ni exsolution is observed. Only above 750 degrees C, hexagonal La2O3 is observed and apparently formed directly from a drastically accelerated decomposition of monoClinic La2O2CO3 alongside another small increase in metallic Ni. Our direct structure-activity correlation unambiguously shows that the active phase in DRM is a mixture of metallic Ni in contact with monoClinic La2O2CO3. The roles of the latter phase are twofold: acting as the CO2-activated species and stabilizing the metallic Ni partiCles. Naturally, this implies a perfect carbon removal ability of the metallic Ni/La2O2CO3 interface, which directly relates to an enhanced coking resistance and, most probably, long term stability. Heating LaNiO3 in hydrogen yields a similar sequence of structural transformations with the striking difference of the missing transient La2NiO4 structure, corrB(OH)2rating its crucial role in the formation of the DRM-active Ni/monoClinic La2O2CO3 interface. The final structural fate is a metallic Ni/hexagonal La2O3 phase mixture. Exemplified for the DRM reaction and the initial LaNiO3 structure, only the knowledge about the sheer complexity of the structural dynamics allows the unequivocal assignment of participating structures and phases to their respective catalytic performance, and therefore, allows definite conClusions about the formation and the properties of the final active phase.In Situ-Determined Catalytically Active State of LaNiO3 in Methane Dry Reformingperovskites; dynamics; phase diagram; polymorphism; in situ X-ray diffraction; in situ decomposition11202052#N/ATRUE
4971
acscatal.9b0223010.1021/acscatal.9b02230TRUEhttps://doi.org/10.1021/acscatal.9b02230Sevov, CSACS Catal.Despite significant efforts to replace Pd-based catalysts with those of Ni, the Ni-catalyzed Mizoroki-Heck coupling of Aryl halides and alkenes remains challenging. This work details the development of a Mizoroki-Heck reaction of Aryl halides and a broad range of alkenes that utilizes electrochemistry as a means to promote Ni-catalyzed coupling under mild conditions. Stoichiometric studies implicate low-valent Ni complexes as key intermediates in route to rapid reactions with even unactivated alkenes. As such, electrochemistry is employed to readily provide the reducing potentials necessary to access these reactive intermediates and render the transformation catalytic. CyClohexenone was found to be an unreactive substrate but a crucial additive that promotes facile electroreduction of the Ni catalyst and functionalization of other alkenes in high yields. Finally, preliminary mechanistic studies suggest that reactions proceed via an electron-chain transfer process that rapidly terminates but is reinitiated upon electroreduction.An Electrochemically Promoted, Nickel-Catalyzed Mizoroki-Heck Reactionelectrochemistry; Heck reaction; alkene functionalization; cyClic voltammetty; redox; catalysisElectrochemistryCsp2-Csp2_arHBrVinylNitrogenNitrogen(neutral)142019693/17/2022FALSE
4972
acscatal.9b0343010.1021/acscatal.9b03430FALSEhttps://doi.org/10.1021/acscatal.9b03430Peng, ZMTuning Electronic Structure and Lattice Diffusion Barrier of Ternary Pt-In-Ni for Both Improved Activity and Stability Properties in Oxygen Reduction Electrocatalysis2019#N/ATRUE
4973
acscatal.9b0217810.1021/acscatal.9b02178FALSEhttps://doi.org/10.1021/acscatal.9b02178Searles, DJACS Catal.Paired, single-atom catalysts have been shown to demonstrate synergistic effects computationally and experimen tally which enable them to outperform the benchmark catalyst, Pt/C, for electrochemical reactions. We explore the limit of these catalysts by screening different transition metal atoms (M = Co, Pt, Fe, Ni) in nitrogen-doped graphene for their ability to catalyze the oxygen reduction reaction (ORR). We employ density functional theory methods to explore the electronic factors affecting catalytic activity in an effort to rationalize trends in the performance of materials which are promising candidates for the next generation of electrocatalysts. It is found that CoPt@N8V4, composed of paired Co and Pt in a nitrogen- doped four-atom vacancy in graphene (N8V4), performs ideally for the ORR with an overpotential (eta) of 0.30 V, followed Closely by Co and Ni (eta = 0.35 V) and paired Co (eta = 0.37 V). The origin of activity is suggested to be the changing reduction potential of the active Co atom via the local distortion of the pore by the spectating metal partner. We utilize the ORR scaling relations and plot catalytic activity on a volcano plot, which we correlate with the degree of antibonding interactions with the O atom in the OH intermediate of the ORR. We establish that the local tuning of paired catalysts allows for the reactivity of metal atoms to be specifically modified for desirable reactivity.Evaluating the Catalytic Efficiency of Paired, Single-Atom Catalysts for the Oxygen Reduction Reactionelectrocatalysis; defects; oxygen reduction reaction; activity volcano; single-atom catalystsx45201945#N/AFALSE
4974
acscatal.9b0335210.1021/acscatal.9b03352TRUEhttps://doi.org/10.1021/acscatal.9b03352Osaka, IACS Catal.The C(sp(3))-C(sp3) Cross-Coupling of Alkyl halides with Alkyl tosylates has been developed by employing a combination of nickel and nuCleophilic cobalt catalysts in the presence of a manganese reductant. This method provides a straightforward route to a diverse set of not only secondary-primary but also primary-primary C(sp(3))-C(sp(3)) linkages under mild conditions without using Alkyl-metallic reagents. Mechanistic studies suggest the formation of Alkyl radicals from both Alkyl halides and Alkyl tosylates. Additionally, cross-coupling could be applied to the short-step synthesis of a histone deacetylase inhibitor, Vorinostat.Nickel/Cobalt-Catalyzed C(sp(3))-C(sp(3)) Cross-Coupling of Alkyl Halides with Alkyl TosylatesC(sp(3))-C(sp(3)) Cross-Coupling; nickel catalyst; cobalt catalyst; Alkyl tosylate; Alkyl halideCsp3-Csp3E-EOXOTsBrAlkylNo baseNo Base202019891/16/2022TRUE
4975
acscatal.9b0199510.1021/acscatal.9b01995FALSEhttps://doi.org/10.1021/acscatal.9b01995Sun, YQRoles of Surface-Active Oxygen Species on 3DOM Cobalt-Based Spinel Catalysts MxCO3-xO4 (M = Zn and Ni) for NOx-Assisted Soot Oxidationx2019#N/AFALSE
4976
acscatal.9b0317210.1021/acscatal.9b03172FALSEhttps://doi.org/10.1021/acscatal.9b03172Kong, WQACS Catal.Enantioselective Ni-catalyzed reductive Aryl monofluoroalkenylation of alkenes between Aryl bromides and gem-difluoroalkenes has been developed. The reaction proceeding under room temperature and base-free reaction conditions tolerates a wide range of functional groups on both coupling partners. Various synthetically useful oxindoles containing monofluoroalkenyl substituent are obtained in good yields with 85%-95% enantiomeric excess. In addition, the synthetic method can be further applied to the late-stage monofluoroalkenylation of complex biologically active compounds.Nickel-Catalyzed Enantioselective Reductive Aryl Fluoroalkenylation of AlkenesNi-catalyst; enantioselectivity; monofluoroalkenylation; reductive cross-coupling gem-difluoroalkenes; oxindole39201984#N/ATRUE
4977
acscatal.9b0312910.1021/acscatal.9b03129FALSEhttps://doi.org/10.1021/acscatal.9b03129Dauenhauer, PJACS Catal.Butadiene is an important monomer for rubbery and hard polymeric materials, and it can be produced efficiently from biomass-derived tetrahydrofuran (THF) using solid-acid zeolite catalysts. In this work, electronic structure calculations, kinetic experiments, and microkinetic modeling were applied to investigate the THF dehydra-decyClization reaction to butadiene as well as its retro-Prins fragmentation to the side product propene on a Bronsted acid site within H-ZSM5. A comprehensive reaction network consisting of 15 elementary surface reactions was investigated, and a microkinetic model was parametrized using computed energetics to compare with experimental kinetic data. Among the proposed reaction pathways, THF dehydra-decyClization primarily proceeds via an alkenol intermediate species, 2-buten-1-ol, while retro-Prins fragmentation to propene occurs through a direct pathway. Two other alkenol species that could be involved in the reaction network, 3-buten-1-ol and 3-buten-2-ol, do not substantially contribute to THF conversion. While multiple elementary steps were found to be kinetically relevant, the Bronsted acid-catalyzed ring opening of THF is the predominantly rate-limiting surface reaction. The apparent Activation energies (ca. 30 kcal mol(-1) for both butadiene and propene in the temperature range of 220-270 degrees C), reaction orders, and selectivity, as well as absolute rates predicted by the model are in agreement with experimental values, provided that the modeled entropy of Activation is calculated to account for translational freedom for transition states that exhibit complete proton transfer from the solid acid site.Dehydra-DecyClization of Tetrahydrofuran on H-ZSM5: Mechanisms, Pathways, and Transition State Entropytetrahydrofuran; butadiene; dehydra-decyClization; retro-Prins condensation; entropy11201937#N/ATRUE
4978
acscatal.9b0193510.1021/acscatal.9b01935FALSEhttps://doi.org/10.1021/acscatal.9b01935Du, XWACS Catal.Ni-Fe layered double hydroxides (LDHs) are promising for catalyzing the oxygen evolution reaction (OER) in alkaline media. However, the OER mechanism is highly debated, partially because of the lack of an ideal catalyst with 100% exposed active sites for unambiguous characterization. Herein, we develop an alcohol intercalation method to prepare ultrathin Ni-Fe LDH with a 1/3 unit-cell thickness and 100% exposed active sites. The ultrathin LDH catalyst exhibits an intrinsic activity similar to the bulk LDH and allows a direct and reliable characterization of the catalyst without any interference from bulk inactive species. Operando synchrotron X-ray analysis indicates that the metallic ions in ultrathin Ni-Fe LDH are fully oxidized into tetravalence states at low applied potentials and that the OER occurs on the tetravalent Ni and Fe ions following a decoupled proton/electron mechanism. Our findings demonstrate that a full oxidization of metal ions is crucial for highly active NiFe LDHs and that it can be accomplished by engineering ultrathin nanostructures.Fully Oxidized Ni-Fe Layered Double Hydroxide with 100% Exposed Active Sites for Catalyzing Oxygen Evolution Reactionoxygen evolution reaction; catalysts; operando analysis; synchrotron X-ray absorption spectroscopy; catalytic mechanism; layer double hydroxide; active sitex62201953#N/AFALSE
4979
acscatal.9b0274710.1021/acscatal.9b02747FALSEhttps://doi.org/10.1021/acscatal.9b02747Yin, GYACS Catal.As significant pharmacophores, 1,3-disubstituted cyClohexanes are widespread in natural products and synthetic bioactive molecules. In this work, we describe a palladium-catalyzed Arylboration of 1,4-cyClohexadienes, which allows expeditious access to an array of functionalized 1,3-disubstituted cyClohexanes from the readily available starting materials. Palladium catalysis enables the Arylboration to proceed in a reversed regioselectivity compared with earlier nickel catalysis. The most striking feature of this protocol lies in the 1,3-regioselectivity and exClusive cis-diastereoselectivity. Intriguingly, the success of this three-component reaction does not rely on the application of dative ligands but a cheap ammonium chloride salt instead. The synthetic utility of this method is highlighted by a series of downstream stereospecific transformations and a drug molecule synthesis.Stereoselective Palladium-Catalyzed 1,3-Arylboration of Unconjugated Dienes for Expedient Synthesis of 1,3-Disubstituted CyClohexanesalkenes; 1,3-Arylboration; palladium; metal migration; stereoselectivity10201961#N/ATRUE
4980
acscatal.9b0253210.1021/acscatal.9b02532FALSEhttps://doi.org/10.1021/acscatal.9b02532Zitoun, DACS Catal.The oxygen evolution reaction (OER) is an essential reaction for the sustainable synthesis of fuels from renewable feedstocks. In recent years, cathode materials for Li-ion batteries have been successfully utilized as OER electrocatalysts, and among them are the lithiated transition-metal phosphates possessing an olivine crystallographic phase. The LiMPO4 (M = Ni, Fe, Co) olivine materials display a potentially suitable overpotential for OER, which can be further enhanced by delithiation. Herein, we report the synthesis of olivine phases with both Li and Na as alkaline ions. The combination of alkaline ions stabilizes the olivine structure with low alkaline ion content, which is instrumental to reach low OER overpotential. The dual alkaline ion approach has been demonstrated for a single transition metal (Co) as well as different combinations of Co-Fe-Ni to form olivine solid solutions of the chemical formula Li(Na)Co(Fe,Ni)PO4. This screening of eight olivine materials revealed a trend in OER activity, and the Li0.6Na0.2Ni0.7Fe0.1PO4 solid solution displays an overpotential as low as 0.28 V versus RHE at 10 mA cm(-2), with a low Tafel slope of 30 mV dec(-1) and a stability tested over 20 h.Dual Alkaline Ion Route to Chemical De-insertion in Oxygen Evolution Olivine Electrocatalystselectrocatalysis; olivine; oxygen evolution reaction; water splitting; electrolysis2201938#N/ATRUE
4981
acscatal.9b0245710.1021/acscatal.9b02457FALSEhttps://doi.org/10.1021/acscatal.9b02457Ni, MACS Catal.As a highly appealing technology for hydrogen generation, water electrolysis inCluding oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode largely depends on the availability of efficient electrocatalysts. Accordingly, over the past years, much effort has been made to develop various electrocatalysts with superior performance and reduced cost. Among them, ruthenium (Ru)-based materials for OER and HER are very promising because of their prominent catalytic activity, pH-universal application, the cheapest price among the precious metal family, and so on. Herein, recent advances in this hot research field are comprehensively reviewed. A general description about water splitting is presented to understand the reaction mechanism and proposed scaling relations toward activities, and key stability issues for Ru-based materials are further given. Subsequently, various Ru-involving electrocatalysts are introduced and Classified into different groups for improving or optimizing electrocatalytic properties, with a special focus on several significant bifunctional electrocatalysts along with a simulated water electrolyzer. Finally, a perspective on the existing challenges and future progress of Ru-based catalysts toward OER and HER is provided. The main aim here is to shed some light on the design and construction of emerging catalysts for energy storage and conversion technologies.Recent Advances and Prospective in Ruthenium-Based Materials for Electrochemical Water Splittingruthenium-based materials; electrocatalysts; oxygen evolution reaction; hydrogen evolution reaction; water splitting1082019286#N/ATRUE
4982
acscatal.9b0233210.1021/acscatal.9b02332FALSEhttps://doi.org/10.1021/acscatal.9b02332Frei, EACS Catal.Among the Ni-based catalysts studied for CO2 Activation reactions, NixMg1-xO solid solutions present advantageous characteristics, mainly linked with the homogeneous distribution of the Ni species inside the MgO structure, leading to highly dispersed Ni-0 supported catalysts. In this work, we report on the preparation and characterization of NixMg1-xO precatalysts calcined at different temperatures. The resulting Ni-0/NixMg1-xO catalysts were tested for the methanation of CO2. Following the structural, morphological, and chemical changes during both the calcination and the reduction, we were able to observe Clear correlations between the reactivity of the catalysts and their physical properties, leading to a better understanding of the reaction mechanism and the respective contributions of the metal and the support. While no change was observed in the formation of CH4 over the range of temperature tested, the CO formation as byproduct Clearly changed with the increasing temperatures. Our results are consistent with the hypothesis that two different CO formation mechanisms are occurring, but depending on the temperature, one dominates over the other. This study illustrates the importance of the complex interplay of metal partiCles and oxidic support (at the interface), both actively participating in the CO2 hydrogenation mechanism.Highly Dispersed Ni-0/NixMg1-xO Catalysts Derived from Solid Solutions: How Metal and Support Control the CO2 HydrogenationNixMg1-xO solid solution; CO2 hydrogenation; methanation; metal-support interface; Ni catalysts17201968#N/ATRUE
4983
acscatal.9b0228610.1021/acscatal.9b02286FALSEhttps://doi.org/10.1021/acscatal.9b02286Huang, JCooperation of Ni and CaO at Interface for CO2 Reforming of CH4: A Combined Theoretical and Experimental Study2019#N/ATRUE
4984
acscatal.9b01620
https://doi.org/10.1021/acscatal.9b01620
https://pubs.acs.org/doi/10.1021/acscatal.9b01620Song, WFACS Catal.
The nickel-catalyzed intermolecular carboacylation of alkenes with amides and tetraArylborates is presented. BicyClic alkenes are readily functionalized with a variety of N-benzoyl-N-phenylbenzamides and triArylboranes, which are generated in situ from the corresponding tetraArylborates, to synthesize ketone products in up to 91% yield. Preliminary mechanistic studies suggest that migratory insertion precedes transmetalation and that reductive elimination is the turnover-limiting step. These reactions occur with excellent chemoselectivity and diastereoselectivity in the absence of a directing/chelating group and further demonstrate amides as practical acyl electrophiles for alkene dicarbofunctionalization reactions.
Ni-Catalyzed Three-Component Alkene Carboacylation Initiated by Amide C-N Bond Activation
Kadam, AA; Metz, TL; Qian, YQ; Stanley, LM
Addition reaction
y312019
Added by Imanuel
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4985
acscatal.9b0226410.1021/acscatal.9b02264FALSEhttps://doi.org/10.1021/acscatal.9b02264Peng, YACS Catal.Efficient water electrolysis for hydrogen production constitutes a key segment for the upcoming hydrogen economy, but has been impeded by the lack of high-performance and low-cost electrocatalysts for, ideally, simultaneously expediting the kinetics of both hydrogen and oxygen evolution reactions (HER and OER). In this study, the favored binding energetics of OER and HER reaction intermediates on iron-doped nickel phosphides are first predicted by density functional theory (DFT) simulations, and then experimentally verified through the fabrication of Fe-doped Ni2P nanopartiCles embedded in carbon nanotubes using metal-organic framework (MOF) arrays on nickel foam as the structural template. Systematic investigations on the effect of phosphorization and Fe doping reveal that while the former endows a larger benefit on OER than on HER, the latter enables not only modulating the electronic structure, but also tuning the micromorphology of the catalyst, synergistically leading to both enhanced HER and OER. As a result, extraordinary performances of constant water electrolysis are demonstrated requiring only a cell voltage of 1.66 V to afford a current density of 500 mA cm(-2), far outperforming the benchmark electrode couple composed of Pt/C and RuO2. Postelectrolysis characterizations combined with DFT inspection further reveal that while the Fe-doped Ni2P species are mostly retained after prolonged HER, they are in situ converted to Fe/P-doped gamma-NiOOH during OER, serving as the actual OER active sites with high activity.Morphological and Electronic Tuning of Ni2P through Iron Doping toward Highly Efficient Water Splittingelectrocatalysis; overall water splitting; transition-metal phosphides; metal-organic frameworks; iron doping71201962#N/ATRUE
4986
acscatal.9b0161610.1021/acscatal.9b01616FALSEhttps://doi.org/10.1021/acscatal.9b01616Savinova, ERNickel Metal NanopartiCles as Anode Electrocatalysts for Highly Efficient Direct Borohydride Fuel Cellsx2019#N/AFALSE
4987
acscatal.9b0224310.1021/acscatal.9b02243FALSEhttps://doi.org/10.1021/acscatal.9b02243Wang, YQACS Catal.The production of hydrogen from the aqueous-phase reforming (APR) of oxygenated hydrocarbons is promising. Herein, the performances of Pt loaded on NiAl2O4 spinel and gamma-Al2O3 were investigated in the APR of methanol. The conversion of methanol and the yield of hydrogen over Pt/NiAl2O4 reached 99.9% and 95.7%, respectively. In comparison with Pt/gamma-Al2O3 catalyst (26.5% and 23.3%, respectively), these values were enhanced by 4-fold. More importantly, Pt/NiAl2O4 had high stability with only 10% loss of its initial conversion after 600 h on stream. In situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) of the APR of methanol revealed that the reaction underwent the dehydrogenation of methanol and the sequential water-gas shift (WGS) reaction. These two reactions were then investigated independently, in which Pt/NiAl2O4 showed more efficient performance than Pt/gamma-Al2O3. Intensive characterization methods revealed that the chemical state of Pt played a pivotal role in the dehydrogenation of methanol to generate the adsorbed CO intermediate. For Pt/NiAl2O4 catalyst, the reduction of PtOx to metallic state Pt was easier because of the presence of the oxygen vacancy, leading to the higher catalytic performance in the dehydrogenation of methanol. Further studies with in situ DRIFTS-MS of WGS demonstrated a redox mechanism over Pt/NiAl2O4 catalyst, which was different from the associative route that occurred over Pt/gamma-Al2O3 and made the WGS reaction faster. The addition of Ni (NiAl2O4 spinel) creates oxygen vacancies, giving WGS which underwent a redox route. This work presents the deep understanding into the pathway and mechanism in the APR of methanol and is expected to have important implications for the future development of APR catalysts.NiAl2O4 Spinel Supported Pt Catalyst: High Performance and Origin in Aqueous-Phase Reforming of Methanolaqueous-phase reforming; Pt/NiAl2O4 catalyst; dehydrogenation; water-gas shift; oxygen vacancies19201965#N/ATRUE
4988
acscatal.9b0146010.1021/acscatal.9b01460FALSEhttps://doi.org/10.1021/acscatal.9b01460Berhault, GACS Catal.In the present study, different Al2O3-supported Ni-containing polyoxotungstates (POW) based on Keggin lacunary structures were synthesized in order to establish a correlation between the local conformation of the different Ni/POWs and the final catalytic performance of the corresponding supported NiW hydrodesulfiirization (HDS) catalysts. POWs containing various amounts of nickel (3, 4, or 9 Ni atoms per POW) were therefore prepared and supported on an Al2O3 support obtained by a sol-gel method using impregnation techniques in aqueous solutions at two different pH values (7 and 9). The as-obtained supported Ni-containing POWs were characterized after the drying (120 degrees C, 4 h) and calcination steps (400 degrees C, 4 h, air). The different solids were then sulfided using 10 mol % H2S in H-2 at 400 degrees C for 4 h and evaluated in the hydrodesulfurization of dibenzothiophene (DBT) at T = 300 degrees C and P = 30 bar H-2. Both the Ni localization inside the polyoxotungstate and the pH of the impregnation solution influence the degree of sulfidation and the intrinsic activity of the promoted phase, with Ni-3 POW/Al2O3 the most HDS active if impregnation occurs at pH 7. A direct correlation between the structure of the nickel-containing polyoxotungstate and the final HDS activity can be observed, opening the way for a rationalization of the preparation of this type of precursor.Nickel-Containing Polyoxotungstates Based on [PW9O34](9-) and [PW10O39](13-) Keggin Lacunary Anions Supported on Al2O3 for Dibenzothiophene Hydrodesulfurization ApplicationNi-W polyoxometalates; hydrodesulfurization; Ni-W catalysts; phosphorus; Keggin compoundsx6201976#N/AFALSE
4989
acscatal.9b0219710.1021/acscatal.9b02197FALSEhttps://doi.org/10.1021/acscatal.9b02197Ajayan, PMACS Catal.As CO2 emissions are sharply increasing, processes for converting CO2 into value-added products are becoming more desirable. Ruthenium-based catalysts are the most active for CO2 methanation; however, their substantially higher cost relative to transition metals makes them prohibitive for industrial application. In this study, we demonstrate porous hexagonal boron nitride (pBN) supports (an ideal support material for thermocatalysts due to the high thermal stability and conductivity) to improve the utilization of Ru and simultaneously enhance the catalytic activity and selectivity for CO2 methanation. A simple vacuum filtration process is proposed that allows the Ru precursor to quickly locate the defects of pBN, where atomic Ru can be restricted onto the defects via B, N coordination through an annealing treatment. The B and N coordinations reduce the valence state of atomic Ru. The as-prepared catalyst with low Ru loading (0.58 wt %) exhibits CH4 selectivity up to 93.5%, catalytic stability after 110 h, and a higher reaction rate [1.86 mmol(CO2)/(gcat s)] at 350 degrees C and 1.0 MPa compared to other nanopartiCle catalysts. Both atomic-scale size and low valence state of atomic Ru supported on pBN are responsible for the improvement of CH4 production rate as confirmed by density functional theory simulation.Atomic Ru Immobilized on Porous h-BN through Simple Vacuum Filtration for Highly Active and Selective CO2 Methanationatomic Ru; porous h-BN; vacuum filtration; CO2 methanation; high activity and selectivity17201972#N/ATRUE
4990
acscatal.9b0200610.1021/acscatal.9b02006FALSEhttps://doi.org/10.1021/acscatal.9b02006Bandarenka, ASACS Catal.Metal oxides are important functional materials with a wide range of applications, especially in the field of electro-catalysis. However, quick and accurate assessment of their real electroactive surface area (ECSA), which is of paramount importance for the evaluation of their performance, remains a challenging task. Herein, we present a relatively simple strategy for an accurate in situ determination of the ECSA of commonly used metal oxide catalysts, namely Ni-, Co-, Fe-, Pt-, and Ir-based oxides. Similar to the well -established practice in electrocatalysis, the method is based on the phenomenon of specific adsorption. It uses the fact that at electrode potentials Close to the onset of the oxygen evolution reaction, specifically adsorbed reaction intermediates manifest themselves through so called adsorption capacitance, which is unambiguously detectable using electrochemical impedance spectroscopy. We determined and calibrated these capacitances for common catalyst metal oxides using model thin films. Therefore, with simple impedance measurements, experimentalists can acquire the adsorption capacitance values and accurately estimate the real electroactive surface area of the above-mentioned oxide materials, inCluding nanostructured electrocatalysts. Additionally, as illustrative examples, we demonstrate the application of the method for the determination of the ECSA of oxide catalyst nanopartiCles.Determination of Electroactive Surface Area of Ni-, Co-, Fe-, and Ir-Based Oxide Electrocatalystselectrocatalysis; electrode surface area; oxide catalysts; ECSA determination; electrochemical impedance spectroscopy; iridium oxide; oxygen evolution reaction18201940#N/ATRUE
4991
acscatal.9b0128510.1021/acscatal.9b01285FALSEhttps://doi.org/10.1021/acscatal.9b01285Resasco, DEACS Catal.Catalysts based on earth-abundant elements, such as Ni and Mo, that can be used for the conversion of lignin-derived compounds are desirable. However, they usually exhibit low activity and/or selectivity toward the target reaction, hydrodeoxygenation (HDO). For example, conversion of m-cresol in H-2 over a typical Ni/SiO2 leads to ring hydrogenation at low temperatures and C-C hydrogenolysis to CH4 at high temperatures. Here, we report that a bimetallic Ni-Mo/SiO2 catalyst with Ni:Mo ratio approximate to 1 reduced at an optimized temperature can be very active and selective for HDO of m-cresol to toluene over a wide range of reaction temperatures (250-350 degrees C) and 1 atm of H-2. This behavior is explained in terms of the surface structure of Mo oxides on the surface of Ni nanopartiCles. Detailed characterization (XRD, Raman, TPR, EXAFS, and XPS) indicates that, after calcination, NiMoO4 is the predominant phase. However, after subsequent reduction, metallic Ni nanopartiCles segregate out of the partially reduced MoOx. Interestingly, while no significant structural/electronic modifications are detected for the bulk of the metallic Ni partiCles, the surface chemistry is Clearly altered (i.e., no hydrogenolysis/hydrogenation, weak CO/H-2 adsorption, and lower electron density in the d band of Ni). These results suggest that after reduction, in contrast to the formation of NiMo alloy, the Ni surface gets decorated by reduced MoOx moieties, a phenomenon similar to that previously observed on reducible oxides (so-called SMSI), which is essential for maximizing HDO and inhibiting hydrogenolysis.Enhancement of m-Cresol Hydrodeoxygenation Selectivity on Ni Catalysts by Surface Decoration of MoOx Speciesm-cresol; hydrodeoxygenation; Ni; MoOx; modified Ni; C-C hydrogenolysis; SMSIx27201955#N/AFALSE
4992
acscatal.9b0111010.1021/acscatal.9b01110https://doi.org/10.1021/acscatal.9b01110Hu, YHACS Catal.Thermo-photo catalytic water splitting, where the introduction of thermal energy increases the oxidation driving force for narrow-band-gap photocatalysts (with a low valence band potential), exhibited significantly advanced performance for hydrogen production as compared to general water splitting at room temperature. Herein, a low-cost NiOx-loaded TiO2 catalyst was reported for thermo-photo catalytic water splitting with methanol as the sacrificial agent. The catalyst with an optimal Ni ratio of 5 wt % achieved a hydrogen evolution rate of 53.7 mmol/h/g under simulated AM 1.5G sunlight at 260 degrees C, which was 2.5 times more than that without illumination, with apparent quantum efficiencies of 66.24%, 33.55%, 32.52%, and 15.35% at 380, 420, 450, and 500 nm, respectively. More impressively, under the irradiation of visible light (lambda > 420 nm) at this temperature, the photohydrogen yield could still reach 26.9 mmol/h/g, which was 5 orders of magnitude greater than that (0.0011 mmol/h/g) conducted at room temperature. Isotope tracer experiments demonstrated that the introduction of photoenergy promoted the hydrogen production mainly by enhancing hydrogen evolution from water splitting rather than methanol decomposition or reformation. Furthermore, the stepwise reaction mechanism was revealed with insights into the synergistic roles of thermo-energy and photoenergy for production of hydrogen from water. Those findings highlight the great promise of thermo-photo catalysis and should inspire more efforts for water splitting.Insights into the Thermo-Photo Catalytic Production of Hydrogen from Water on a Low-Cost NiOx-Loaded TiO2 Catalysthydrogen production; thermo-photo catalysis; visible light; nickel-based catalysts; titanium dioxidePhotocatalyst38201945#N/AFALSE
4993
acscatal.9b0196810.1021/acscatal.9b01968FALSEhttps://doi.org/10.1021/acscatal.9b01968Hensen, EJMACS Catal.Energy storage solutions are a vital component of the global transition toward renewable energy sources. The power-to-gas (PtG) concept, which stores surplus renewable energy in the form of methane, has therefore become increasingly relevant in recent years. At present, supported Ni nanopartiCles are preferred as industrial catalysts for CO2 methanation due to their low cost and high methane selectivity. However, commercial Ni catalysts are not active enough in CO2 methanation to reach the high CO2 conversion (>99%) required by the specifications for injection in the natural gas grid. Herein we demonstrate the promise of promotion of Ni by Mn, another low-cost base metal, for obtaining very active CO2 methanation catalysts, with results comparable to more expensive precious metal-based catalysts. The origin of this improved performance is revealed by a combined approach of nanoscale characterization, mechanistic study, and density functional theory calculations. Nanoscale characterization with scanning transmission electron microscopy-energy- dispersive X-ray spectroscopy (STEM-EDX) and X-ray absorption spectroscopy shows that NiMn catalysts consist of metallic Ni partiCles decorated by oxidic Mn2+ species. A mechanistic study combining IR spectroscopy of surface adsorbates, transient kinetic analysis with isotopically labeled CO2, density functional theory calculations, and microkinetics simulations ascertains that the MnO Clusters enhance CO2 adsorption and facilitate CO2 Activation. A macroscale perspective was achieved by simulating the Ni and NiMn catalytic activity in a Sabatier reactor, which revealed that NiMn catalysts have the potential to meet the demanding PtG catalyst performance requirements and can largely replace the need for expensive and scarce noble metal catalysts.Efficient Base-Metal NiMn/TiO2 Catalyst for CO2 MethanationCO2 hydrogenation; nickel; manganese; synergy; mechanism292019100#N/ATRUE
4994
acscatal.9b0096810.1021/acscatal.9b00968FALSEhttps://doi.org/10.1021/acscatal.9b00968Dai, SACS Catal.One of the grand challenges in industrial catalytic processes is the inevitable sintering and aggregation of conventional supported catalysts to large partiCles, leading to the decrease of activity and even deActivation with time. Herein, a surface spatial confinement strategy was employed to design high-performing catalysts for the dry reforming of methane (DRM). Specifically, active nickel (Ni) nanopartiCles (NPs) were confined on the surface of a dendritic mesoporous silica (DMS) in the form of the catalysts in coronas. The Ni/DMS catalyst exhibited a high catalytic performance Close to its equilibrium conversion (76% conversion for CH4 at 700 degrees C). More importantly, the prepared catalyst remained stable after 145 h time-on-stream at 700 degrees C without noticeable carbon deposition. This sintering and coking resistance was found to arise from the surface spatial confinement effect in which the three-dimensional dendritic layers in the corona posted a steric barrier against migration and aggregation of Ni NPs and size of Ni NPs was controlled below 5 nm, hence against sintering and coking. Meanwhile, the mesoporous feature of the layered wall facilitated mass transport of reactants to Ni species and further boosted catalysis. This strategy should be broadly applicable to a range of metal- and metal oxide-supported catalysts in high-temperature heterogeneous reactions, such as DRM, water gas shift reaction, and vehiCle emission control related reactions.Catalysts in Coronas: A Surface Spatial Confinement Strategy for High-Performance Catalysts in Methane Dry Reformingsurface spatial confinement; dendritic mesoporous silica; coking resistance; sintering resistance; dry reforming of methanex24201969#N/AFALSE
4995
acscatal.9b0086410.1021/acscatal.9b00864FALSEhttps://doi.org/10.1021/acscatal.9b00864Ordomsky, VVACS Catal.Selective synthesis of valuable primary amines is an important target in modern industry. Amination of alcohols with ammonia is an economically efficient and environmentally friendly process for primary amine synthesis. This consecutive reaction yields a mixture of primary, secondary, and tertiary amines. High selectivity to primary amines is an important challenge of alcohol amination. Carbon deposition on the catalyst surface is conventionally considered an undesirable process, which leads to poor catalytic performance. In this paper, carbon deposition produced by catalyst pretreatment with alcohols under the optimized conditions has been employed for major enhancement of the selectivity of alcohol amination to primary amines (from 30 to 50 to 80-90%). This extremely positive effect of carbon deposition on the amination selectivity arises from steric hindrance in hydrogenation of bulky secondary imines as intermediate products over partially carbon-decorated cobalt nanopartiCles.Catalyst DeActivation for Enhancement of Selectivity in Alcohols Amination to Primary Aminesamination; selectivity; primary amines; pretreatment; carbon depositionx12201965#N/AFALSE
4996
acscatal.9b0073310.1021/acscatal.9b00733FALSEhttps://doi.org/10.1021/acscatal.9b00733Gurlo, AACS Catal.The mechanism of multiwalled carbon nano-tube synthesis from methane chemical vapor deposition on a 5% Ni/MnO catalyst is studied at 873 and 1073 K by in situ transmission XRD using synchrotron radiation supported by Rietveld refinement and density functional theory calculations. Upon methane dissociative adsorption at the reaction temperature, the fcc nickel lattice initially expands above the temperature calibration experiment, as carbon dissolves interstitially and subsequently contracts upon graphite precipitation. At 1073 K, carbon dissolution in the fcc lattice of the MnO-supported nickel nanopartiCles results in three cubic nickel carbides that occur prior to graphite precipitation. At the two reaction temperatures, the atomic concentration of dissolved carbon exceeds the limit of solubility in nickel films due to the nanopartiCle effect. Nudged elastic band calculations display predominant surface diffusion and secondary subsurface bulk diffusion of carbon. Once catalysts are exposed to carbon dioxide, surface and subsurface carbon in nickel is easily oxidized by carbon dioxide and the nickel lattice returns to its original size. The mechanism described above explains the reaction pathway of the dry reforming of methane, confirming that the diffusing carbon species can act as reaction intermediates toward the generation of carbon monoxide, instead of deactivating the catalyst.Revealing the Mechanism of Multiwalled Carbon Nanotube Growth on Supported Nickel NanopartiCles by in Situ Synchrotron X-ray Diffraction, Density Functional Theory, and Molecular Dynamics Simulationsnanofiber; dissolved carbon; nickel carbide; nanopartiCle catalyst; subsurface carbon; dry reforming of methane; ReaxFF; NEBx8201956#N/AFALSE
4997
acscatal.9b0072110.1021/acscatal.9b00721FALSEhttps://doi.org/10.1021/acscatal.9b00721De Wispelaere, KACS Catal.The active site in ethene oligomerization catalyzed by Ni-zeolites is proposed to be a mobile Ni(II) complex, based on density functional theory-based molecular dynamics (DFT-MD) simulations corrB(OH)2rated by continuous-flow experiments on Ni-SSZ-24 zeolite. The results of the simulations at operating conditions show that ethene molecules reversibly mobilize the active site as they exchange with the zeolite as ligands on Ni during reaction. Microkinetic modeling was conducted on the basis of free-energy profiles derived with DFT-MD for oligomerization on these mobile [(ethene)(2)-Ni-Alkyl](+) species. The model reproduces the experimentally observed high selectivity to dimerization and indicates that the mechanism is consistent with the observed second-order rate dependence on ethene pressure.Ethene Dimerization on Zeolite-Hosted Ni Ions: Reversible Mobilization of the Active Siteadsorption; host-guest systems; molecular dynamics; agostic interactions; alkene oligomerization; homogeneous catalysisx12201943#N/AFALSE
4998
acscatal.9b0194010.1021/acscatal.9b01940FALSEMechler, AKFacile Protocol for Alkaline Electrolyte Purification and Its Influence on a Ni-Co Oxide Catalyst for the Oxygen Evolution Reaction2019#N/ATRUE
4999
acscatal.9b0190310.1021/acscatal.9b01903FALSEhttps://doi.org/10.1021/acscatal.9b01903Coperet, CACS Catal.Single-site Ni(II) catalytic centers supported on MCM-41-type materials were prepared via surface organo-metallic chemistry using tailored thermolytic molecular precursors. These materials catalytically convert ethene to propene, and their activity and stability strongly depend on the specific location of aluminum sites that are introduced in the catalyst either from the tailored Ni molecular precursor or doped in the support. The highest activity and stability are achieved when a Ni siloxide precursor is grafted on an Al-doped MCM-41 because this approach generates Ni(II) isolated sites and strong Bronsted acid sites that are both required for high catalytic performances.Specific Localization of Aluminum Sites Favors Ethene-to-Propene Conversion on (Al)MCM-41-Supported Ni(II) Single Sitesethene-to-propene conversion; nickel single sites; solid-state NMR spectroscopy; DNP SENS; pyridine11201954#N/ATRUE
5000
acscatal.9b0178510.1021/acscatal.9b01785FALSEhttps://doi.org/10.1021/acscatal.9b01785Reisman, SEACS Catal.An electrochemically driven enantioselective nickel-catalyzed reductive cross-coupling of alkenyl bromides and Benzyl chlorides is reported. The reaction forms products bearing allylic stereogenic centers with good enantioselectivity under mild conditions in an undivided cell. Electrochemical Activation and turnover of the catalyst mitigate issues posed by metal powder reductants. This report demonstrates that enantioselective Ni-catalyzed cross-electrophile couplings can be driven electrochemically.Enantioselective Electroreductive Coupling of Alkenyl and Benzyl Halides via Nickel Catalysisnickel; electrochemistry; enantioselective; cross-coupling; asymmetric catalysis53201927#N/ATRUE
5001
acscatal.9b0172010.1021/acscatal.9b01720FALSEhttps://doi.org/10.1021/acscatal.9b01720Shafaat, HSACS Catal.Secondary sphere interactions are known to significantly impact catalytic rates within biological systems as well as synthetic molecular catalysts. The [NiFe] hydrogenase enzymes oxidize and produce molecular hydrogen at high turnover rates within a complex coordination environment. Nickel-substituted rubredoxin (NiRd) has been developed as a functional, protein-based mimic of the [NiFe] hydrogenase, providing an opportunity to understand the influence of the secondary coordination environment on proton reduction activity. In this work, a rationally designed series of mutants was generated to study the effects of outer-sphere interactions on catalysis. This library was characterized using quantitative protein film electrochemistry, optical spectroscopy, X-ray crystallography, and molecular dynamics simulations. Changing the secondary sphere residues modulates the redox activity of the nickel- and iron-bound rubredoxin proteins, alters the hydrogen-bonding network, and perturbs solvent accessibility of the active site, which correlates with catalytic turnover frequency. The effects on reactivity are dependent on the site of mutation and, when coupled to crystallographic and computational analyses, implicate one of the nickel-coordinating cysteine residues as the mechanistically relevant site of protonation. Introduction of a Carbonylate residue, mimicking that found in the [NiFe] hydrogenase, significantly increases the overall catalytic rate, likely through installation of a proton transfer pathway into the active site. Apparent turnover frequencies within the mutant constructs range from 15 to 500 s(-1) without imparting significant variation in overpotential, and many mutants break the typical scaling relationship between catalytic rates and overpotential that is often seen in small-molecule systems. These results demonstrate the substantial impact of the coordination environment on the hydrogen-producing activity of the artificial metalloenzyme, NiRd, and highlight the importance of such interactions within molecular catalysts.Power of the Secondary Sphere: Modulating Hydrogenase Activity in Nickel-Substituted Rubredoxinhydrogen production; artificial metalloenzyme; protein film electrochemistry; outer-sphere effects; electrocatalysis12201997#N/ATRUE
5002
acscatal.9b0049210.1021/acscatal.9b00492FALSEhttps://doi.org/10.1021/acscatal.9b00492Kim, JHACS Catal.Here, a hierarchical nanostructure composed of Ni-doped alpha-FeOOH (Ni:FeOOH) nanosheets coupled with N-doped graphite foam (NGF) is demonstrated as a three-dimensional (3D) self-supported electrocatalyst for highly efficient and durable water oxidation. A facile, one-step directional growth of catalytically active Ni:FeOOH nanosheets on highly conducting 3D NGF results in a fully integrated, hierarchical, nanostructured electrocatalyst with (i) the high intrinsic activity of Ni:FeOOH, (ii) the outstanding electrical conductivity of NGF, and (iii) a well-defined porous structure with an enhanced active surface area. As a result, the self-supported 3D Ni:FeOOH/NGF electrocatalyst exhibits remarkable electrocatalytic activity for the oxygen evolution reaction (OER) in an alkaline solution with an overpotential of 214 mV at 10 mA/cm(2), a high stability for over 60 h, a low Tafel slope of 36.2 mV dec(-1), and a capability of delivering a high current density of 300 mA/cm(2) at an overpotential of 368 mV. In contrast to photodeposition, electrodeposition, and hydrothermal methods for the formation/integration of (oxy)hydroxides, this facile solution strategy for designing an attractive and efficient structure with a highly active metal (oxy)hydroxide and highly conducting NGF provides a pathway to develop other earth-abundant electrocatalysts for a multitude of energy-conversion-device applications.Hierarchically Coupled Ni:FeOOH Nanosheets on 3D N-Doped Graphite Foam as Self-Supported Electrocatalysts for Efficient and Durable Water Oxidationfacile electroless deposition; Ni-doped alpha-FeOOH (Ni:FeOOH); N-doped graphite foam (NGF); 3D self-supported electrocatalysts; electrochemical water oxidationx39201966#N/AFALSE
5003
acscatal.9b0167910.1021/acscatal.9b01679FALSEhttps://doi.org/10.1021/acscatal.9b01679Guo, YA Facile Way To Improve Pt Atom Efficiency for CO Oxidation at Low Temperature: Modification by Transition Metal Oxides2019#N/ATRUE
5004
acscatal.9b0040010.1021/acscatal.9b00400FALSEhttps://doi.org/10.1021/acscatal.9b00400Zhang, ZCACS Catal.The catalytic properties of physical mixtures of Ni partiCles (100-200 nm) with nanopartiCles of anatase TiO2 (TiO2-A), ZrO2, Al2O3, rutile TiO 2 (TiO2-R), and CeO2 were investigated for the hydrodeoxygenation (HDO) of guaiacol. High selectivities to phenolics were obtained only for Ni mixed with anatase TiO2 (Ni and TiO2-A), while saturated hydro- carbons were the main products for the mixtures with other supports. By thermal treatment in hydrogen gas only at 300 degrees C or higher and subsequently separating the large Ni partiCles from the TiO2-A partiCles with a magnet, it was further discovered that there was migration of TiO 2 from TiO2-A onto the large Ni partiCles, resulting in an amorphous TiO2 overlayer on the Ni partiCles as evidenced by high-resolution TEM, and vice versa, migration of Ni onto TiO2-A. The TiO2 overlayer rendered the Ni partiCles completely inactive as a hydrogenation/hydrodeoxygenation catalyst. Conversely, the small amounts of Ni (<1.5 wt %) migrated onto TiO2-A formed highly dispersed Ni, undetectable by high-resolution TEM (<2 nm), that were remarkably highly active for HDO of guaiacol, producing selectively phenolics. Such highly selective HDO catalysts could also be formed by incipient wetness impregnation of Ni in loadings above 2 wt % onto the TiO2-A, but it was essential to pretreat the sample in H-2 at 300 degrees C or higher. Pretreatment in H-2 at 200 degrees C generated catalysts that produced saturated ring products. The activity of the impregnated catalysts, as measured by guaiacol conversion, increased linearly with Ni loading below 0.5 wt %. The activity continued to increase with Ni loading but more slowly up to 2 wt %, beyond which there was little further change. The results suggested that two types of Ni species existed on the TiO2-A surface. One type consisted of a Cluster of Ni atoms that were dominant on larger Ni partiCles that were active in aromatic ring hydrogenation and hydrodeoxygenation. They were readily covered by reducible TiO2-A at 300 degrees C or higher due to the traditional strong metal support interaction (SMSI) effect and became inactive. Another type was Clusters of a very small number of Ni atoms, perhaps one atom, that were present as highly dispersed Ni Clusters interacting strongly with the defect sites of TiO2-A. The strong interaction of this type of Ni with the TiO2 defect deterred TiO, migration allowing surface exposed Ni atoms to catalyze the HDO of guaiacol with very high selectivities that were not characteristic of typical Ni partiCles.Selective Hydrodeoxygenation of Guaiacol to Phenolics by Ni/Anatase TiO2 Catalyst Formed by Cross-Surface Migration of Ni and TiO2guaiacol hydrodeoxygenation; phenol; SMSI or strong metal-support interaction; titania and nickel; ligninx24201954#N/AFALSE
5005
acscatal.9b0037510.1021/acscatal.9b00375https://doi.org/10.1021/acscatal.9b00375Guan, WACS Catal.Photoredox-mediated iridium/nickel dual catalysis has successfully triggered a series of traditionally challenging carbon-heteroatom cross-coupling reactions. However, detailed mechanisms, such as the catalytic cyCles for dual catalysts and the role of base additive, remain controversy in these reactions. In this study, a highly chemoselective C-S cross-coupling of thiols with heteroAryl iodides has been investigated by density functional theory (DFT) calculations and emission quenching experiments. Interestingly, the oxidation state modulation mechanism merging oxidative quenching (Ir-III-*Ir-III-Ir-IV-Ir-III) and nickel catalytic cyCles (Ni-II-Ni-I-Ni-III-Ni-I-Ni-II) is favorable. It is consisted of four major steps: pyridine mediated proton-coupled electron transfer, oxidative addition Ni(I)-halide complex, reductive elimination, and single-electron transfer. In contrast, the radical by reductive quenching of *Ir-III with thiols is impractical, because oxidative addition or sigma-bond metathesis from Ni(II)-thiolate intermediate is highly energy-demanding. This study will hopefully benefit the future understanding of such photoredox-mediated dual catalytic systems.How Does Iridium(III) Photocatalyst Regulate Nickel(II) Catalyst in Metallaphotoredox-Catalyzed C-S Cross-Coupling? Theoretical and Experimental InsightsC-S cross-coupling; photoredox catalysis; iridium; nickel; density functional calculationsPhotocatalyst10201969#N/AFALSE
5006
acscatal.9b0166810.1021/acscatal.9b01668FALSEhttps://doi.org/10.1021/acscatal.9b01668Shen, BJACS Catal.The SnSAPO-5 molecular sieve containing divalent tin in the framework was successfully synthesized and analyzed by XRD, XPS, XRF, N-2-asdorption desorption isotherms, NH3-TPD, Py-IR, and Al-27 and P-31 NMR. The results show that the trivalent aluminum is substituted by divalent tin in the framework of SnSAPO-5, generating a P((4-n)Al,nSn) (n = 1-4) environment, which increases the number of Lewis and Bronsted acid sites. The five catalysts (NiW/SAPA, NiW/SnSAPA, NiW/APA, NiW/SnAPA, and NiW/EPA) with the same content of active metals were obtained by the incipient wetness coimpregnation method. The catalyst NiW/SnSAPA with higher k(HDS) and TOF exhibited a much higher HDS rate of 4,6dimethyldibenzothiophene (4,6-DMDBT) (85%) at 280 degrees C, while the HDS rates over the other catalysts are less than 40% (24%, 34%, 37%, and 29%, respectively), which is attributed to the catalyst NiW/SnSAPA possessing more suitable acidic sites, a higher sulfidation degree of W species, and a higher stacking number of WS2 slabs. Futhermore, the catalyst NiW/SnSAPA has a much higher HDS rate (85%) for 4,6-DMDBT and exhibits a much higher performance of deep hydrodesulfurization in comparison to the catalyst NiW/EPA prepared with an industrial support (29%) at 280 degrees C. This finding has great practical significance for the development of ultradeep HDS industrial catalysts.Effect of Divalent Tin on the SnSAPO-5 Molecular Sieve and Its Modulation to Alumina Support To Form a Highly Efficient NiW Catalyst for Deep Hydrodesulfurization of 4,6-DimethyldibenzothiopheneSnSAPO-5; divalent tin; weak acid; 4,6-DMDBT; ultradeep HDS9201965#N/ATRUE
5007
acscatal.9b0033010.1021/acscatal.9b00330FALSEhttps://doi.org/10.1021/acscatal.9b00330Snyder, JDACS Catal.CO2 electrochemical reduction to formate has emerged as one of the promising routes for CO2 conversion to useful chemicals and energy storage. Palladium has been shown to make formate with a high selectivity at minimal overpotential. However, production of CO as a minor product quickly deactivates the catalyst during extended electrolysis. Here, we present nanoporous Pd alloys (np-PdX) formed by electrochemical dealloying of Pd15X85 alloys (X = Co, Ni, Cu, and Ag) as active free-standing electrocatalysts with high formate selectivity and CO poisoning tolerance. Rate of deActivation under constant potential electrolysis, due to CO passivation, is strongly correlated to the identity of the transition metal alloying component. We purport that this composition dependent behavior is due to the induced electronic changes in the active Pd surface, affecting both the CO adsorption strength and the near surface hydrogen solubility, which can impact the adsorption strength of active/inactive intermediates and reaction selectivity. Free-standing np-PdCo and np-PdNi are found to exhibit high areal formate partial current densities, >20 mA cm(-2), with high CO poisoning tolerance and minimal active area loss at cathodic potentials, demonstrating the utility of these materials for selective and stable CO2 electrolysis.Free Standing Nanoporous Palladium Alloys as CO Poisoning Tolerant Electrocatalysts for the Electrochemical Reduction of CO2 to Formatecarbon dioxide reduction; electrocatalysis; nanoporous metals; electrolysis; dealloyingx30201978#N/AFALSE
5008
acscatal.9b0029310.1021/acscatal.9b00293FALSEhttps://doi.org/10.1021/acscatal.9b00293Ma, HXACS Catal.The sluggish kinetics of the oxygen evolution reaction (OER) limits the practical applications of many important energy conversion systems such as electrolysis of water, metal-air batteries, solar fuel, and so on. Here, we report a highly efficient OER electrocatalyst that features (Co/Fe)(4)O-4 cubane motifs in an amorphous nanoring structure. The Co/Fe codopants in the cubane motifs can optimize the intermediates adsorption and significantly lower the overpotentials of the OER. In addition to finely tuning the adsorption of intermediates, the amorphous nanoring structures provide rapid ion channels and high surface area for the OER. Phosphorylation also increases the wettability of electrocatalysts. As a result, the nanorings exhibit highly catalytic activities for the OER with a low overpotential of 300 mV at 10 mA cm(-2) and a small Tafel slope of 36 mV dec(-1) in an alkaline solution. The long-term durability is demonstrated for at least 20 h at 10 mA cm(-2). In brief, we demonstrate a tuning strategy of Co/Fe codoped cubane motifs in amorphous phosphate nanorings and thus open up an avenue of structural tunability for advanced catalyst design.(Co/Fe)(4)O-4 Cubane-Containing Nanorings Fabricated by Phosphorylating Cobalt Ferrite for Highly Efficient Oxygen Evolution Reactionnanoring; amorphous structure; phosphorylation; catalyst; oxygen evolution reactionx23201961#N/AFALSE
5009
acscatal.9b0021410.1021/acscatal.9b00214FALSEhttps://doi.org/10.1021/acscatal.9b00214Taniike, TACS Catal.To study cooperative catalysis in ethylene polymerization, a series of polynorbornene (PNB)-supported half-titanocene catalysts were synthesized by grafting a half-titanocene complex to monodisperse PNB chains through Aryloxide ligands. Their performance in ethylene polymerization was extensively investigated to uncover the mechanism of cooperative catalysis among multiple Ti centers that are confined in a nanosized random coil of PNB chains. It was found that, under full Activation, the activity of the PNB-supported catalysts was consistently higher than that of the unsupported molecular catalyst. At a lower polymerization temperature, the cooperation effect prevailed and the activity tended to improve as the number of Ti centers per chain was increased. At a higher temperature, a smaller number of Ti centers per chain led to better activity due to the active-site isolation effect. On the basis of a kinetic examination, the cooperation at a lower temperature was attributed to the enhancement of the propagation rate constant, where confined active centers as monomer trapping sites plausibly suppressed the entropic loss in the pi complexation.Cooperative Catalysis by Multiple Active Centers of a Half-Titanocene Catalyst Integrated in Polymer Random Coilscooperative catalysis; polymer-supported catalyst; half-titanocene catalyst; ethylene polymerization; active centers per random coilx9201952#N/AFALSE
5010
acscatal.9b0161910.1021/acscatal.9b01619FALSEhttps://doi.org/10.1021/acscatal.9b01619Heyden, AACS Catal.Direct, catalytic oxidation of methane to methanol (MTM) with molecular oxygen is a highly desirable process to valorize methane. We propose that Rh-doped graphene (GR) supported on Ni(111) can be a promising catalyst for MTM with appreciable activity and selectivity. In the absence of the Ni(111) support, a MTM process is difficult. The catalytic activity of the Rh-doped GR is enabled by the Ni(111) support that covalently binds the Rh-doped GR and significantly modifies its properties, leading to facile O-2 Activation by the synergy of the Rh dopant and the neighboring carbon atom of GR The highly activated O-2 and the Rh dopant in turn activate CH4. Strikingly, the methane C-H bond breaking is preferred over methanol C-H bond breaking at 473 K. The strong interaction between TM-doped GR and Ni(111) is found to be a general mechanism for regulating the adsorption strength of various molecules, providing important insight for tuning the properties of single-atom catalysts.Direct Oxidation of Methane to Methanol Enabled by Electronic Atomic Monolayer-Metal Support Interactionmethane to methanol conversion; single atom catalyst; graphene; support interaction; DFT calculation11201953#N/ATRUE
5011
acscatal.9b0012910.1021/acscatal.9b00129https://doi.org/10.1021/acscatal.9b00129Mecking, SACS Catal.A combined experimental and theoretical study elucidates how Ni center dot center dot center dot O neighboring group interactions drastically switch catalytic properties toward ethylene. A range of salicylaldiminato complexes with Aryloxy groups in the 2,6-position of the N-phenyl group was found to dimerize and oligomerize ethylene to butenes and branched oligomers (C-4, C-6, C-8, C-10, ...) in pressure reactor experiments, while corresponding reference catalysts with Arylmethylene groups yield linear polyethylene with M-n of 100.000 g mol(-1) While both types of catalysts consume ethylene with similar high activities (10(5) turnovers h(-1)), the rate of ss-hydride elimination (BHE) is much increased for the case of Aryloxy substitution. Density functional theory (DFT) studies show that formation of the relevant cis agostic complex from which BHE occurs by displacement of ethylene from the cis-Alkyl olefin complex is promoted by an Ni center dot center dot center dot O interaction. This low energy pathway renders chain transfer competitive with insertion chain growth. The resulting Ni center dot center dot center dot O intermediate is rather stable and similar in energy to key species of catalysis (ss-agostic and Alkyl olefin complexes) but barely not yet an energetic sink that would impede catalysis.Tailored Strength Neighboring Group Interactions Switch Polymerization to Dimerization Catalysishomogeneous nickel(II) catalysts; ethylene insertion polymerization; secondary interactions; mechanism; density functional theoryx8201927#N/AFALSE
5012
acscatal.9b0004310.1021/acscatal.9b00043FALSEhttps://doi.org/10.1021/acscatal.9b00043Yan, NACS Catal.Development of heterogeneous catalysts for alcohol transformation into nitriles under oxidant-free conditions is a challenge. Considering the C-H Activation on alpha-carbon of primary alcohols is the rate-determining step, decreasing the Activation energy of C-H Activation is critical in order to enhance the catalytic activity. Several NiM/Al2O3 bimetallic catalysts were synthesized and scrutinized in catalytic transformation of 1-butanol to butyronitrile. Ni-Cu was identified as a suitable combination with the optimized Ni0.5Cu0.5/Al2O3 catalyst exhibiting 10 times higher turnover frequency than Ni/ Al2O3 catalyst. X-ray absorption spectroscopy (XAS) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) revealed that the NiCu partiCles in the catalyst exist in the form of homogeneous alloys with an average size of 8.3 nm, providing an experimental foundation to build up a catalyst model for further density functional theory (DFT) calculations. Calculations were done over a series of NiM catalysts, and the experimentally observed activity trend could be rationalized by the Bronsted-Evans-Polanyi (BEP) principle, i.e., catalysts that afford reduced reaction energy also feature lower Activation barriers. The calculated Activation energy (E-a) for C-H Activation with coadsorbed NH3 dropped from 63.4 kJ/mol on pure Ni catalyst to 49.9 kJ/mol on the most active NiCu-2 site in NiCu bimetallic catalyst, in good agreement with the experimentally measured Activation energy values. The Ni-0.5,Cu-0.5/Al2O3 catalyst was further employed to convert 11 primary alcohols into nitriles with high to near-quantitative yields, at a Ni loading 10 times less than that of the conventional Ni/Al2O3 catalyst.Identification of an Active NiCu Catalyst for Nitrile Synthesis from Alcoholalcohol; nitrile; ammonia; BEP; heterogeneous catalyst; NiCux22201973#N/AFALSE
5013
acscatal.8b0515410.1021/acscatal.8b05154FALSEhttps://doi.org/10.1021/acscatal.8b05154Lambert, RMACS Catal.The catalytic and structural properties of five different nanopartiCle catalysts with varying Au/Ni composition were studied by six different methods, inCluding in situ X-ray absorption spectroscopy and density functional theory (DFT) calculations. The as-prepared materials contained substantial amounts of residual capping agent arising from the commonly used synthetic procedure. Thorough removal of this material by oxidation was essential for the acquisition of valid catalytic data. All catalysts were highly selective toward N-2 formation, with 50-50 Au:Ni material being best of all. In situ X-ray absorption near edge structure spectroscopy showed that although Au acted to moderate the oxidation state of Ni, there was no Clear correlation between catalytic activity and nickel oxidation state. However, in situ extended X-ray absorption fine structure spectroscopy showed a good correlation between Au Ni coordination number (highest for Ni50Au50) and catalytic activity. Importantly, these measurements also demonstrated substantial and reversible Au/Ni intermixing as a function of temperature between 550 degrees C (reaction temperature) and 150 degrees C, underlining the importance of in situ methods to the correct interpretation of reaction data. DFT calculations on smooth, stepped, monometallic and bimetallic surfaces showed that N + N recombination rather than NO dissociation was always rate-determining and that the Activation barrier to recombination reaction decreased with increased Au content, thus accounting for the experimental observations. Across the entire composition range, the oxidation state of Ni did not correlate with activity, in disagreement with earlier work, and theory showed that NiO itself should be catalytically inert. Au-Ni interactions were of paramount importance in promoting N + N recombination, the rate-limiting step.Comprehensive Experimental and Theoretical Study of the CO plus NO Reaction Catalyzed by Au/Ni NanopartiClesBimetallic catalysts; in situ measurements; DFT; active species; effect of Au; reaction mechanismx7201928#N/AFALSE
5014
acscatal.8b0507010.1021/acscatal.8b05070https://doi.org/10.1021/acscatal.8b05070Idriss, HACS Catal.The main characteristics of noble metals on semiconductor photocatalysts within the context of hydrogen ions reduction are partiCles' size, electronic structure, and dispersion. In this work, we have systematically studied Au, Pd, and Pt partiCles on TiO2 with mean diameters of 5.2-5.8, ca. 2, and 1.2-1.5 nm, respectively, at different coverages. Ethanol photo-reforming with water was used as the example from which extraction of reaction rates per mass, per partiCle, and per atom has been analyzed. Irrespective of the metal nature, a narrow range for maximum catalytic performance was observed when the rate is normalized per unit mass or unit mole. Starting from a very low metal content (0.25 wt % for each metal), the H-2 production rates decreased with increasing number of Pd, Pt, or Au partiCles. However, the highest rate per partiCle is that of gold at any metal coverage. This rate exceeded by 2 orders of magnitude that of Pt and by 1 order of magnitude that of Pd. These results indicate that, unlike the case of thermal catalytic reaction, large partiCles perform better than small partiCles. Extraction of reaction rates from this study and from previous studies on Ni and Ag deposited on TiO2 indicated a direct relationship with the work function of the metals and a volcano-shape relationship with their d-band center position.Metal PartiCle Size Effects on the Photocatalytic Hydrogen Ion Reductionphotocatalysis; hydrogen production; metal partiCle size; work function; d-band center; reaction ratePhotocatalyst22201987#N/AFALSE
5015
acscatal.8b0502510.1021/acscatal.8b05025FALSEhttps://doi.org/10.1021/acscatal.8b05025Moret, MEACS Catal.Adaptive ligands, which can adapt their coordination mode to the electronic structure of various catalytic intermediates, offer the potential to develop improved homogeneous catalysts in terms of activity and selectivity. 2,2'-Diphosphinobenzophenones have previously been shown to act as adaptive ligands, the central ketone moiety preferentially coordinating reduced metal centers. Herein, the utility of this scaffold in nickel-catalyzed alkyne cyClotrimerization is investigated. The complex [((p-tol)L1)Ni(BPI)] ((p-tol)L1 = 2,2'-bis(di(para-tolyl)phosphino)-benzophenone; BPI = benzophenone imine) is an active catalyst in the [2 + 2 + 2] cyClotrimerization of terminal alkynes, selectively affording 1,2,4-substituted benzenes from terminal alkynes. In particular, this catalyst outperforms Closely related bi- and tridentate phosphine-based Ni catalysts. This suggests a reaction pathway involving a hemilabile interaction of the C=O unit with the nickel center. This is further borne out by a comparative study of the observed resting states and DFT calculations.Enhanced Catalytic Activity of Nickel Complexes of an Adaptive Diphosphine-Benzophenone Ligand in Alkyne CyClotrimerizationalkyne cyClotrimerization; nickel complexes; adaptive ligand; pi-acceptor ligand; hemilabile ligandx142019217#N/AFALSE
5016
acscatal.8b0488710.1021/acscatal.8b04887https://doi.org/10.1021/acscatal.8b04887Lan, YQACS Catal.The photocatalytic reduction of CO2 to energy carriers has emerged as one of the most promising strategies to alleviate the energy crisis and CO2 pollution, for which the development of catalyst was considered as the determining factor for the accomplishment of this conversion process. In this study, three stable and isostructural metal-organic frameworks (denoted as MOF-Ni, MOF-Co, and MOF-Cu) have been synthesized and used as heterogeneous catalysts in photocatalytic CO2 reduction reaction (CO2RR). It is worth noting that the MOF-Ni exhibited very high selectivity of 97.7% for photoreducing CO2 to CO, which has exceeded most of the reported MOF-based catalysts in the field. Significantly, the MOFs associated with a monometallic catalytic center offer a simple and precise structural model which allows us to understand more definitively the specific effects of different metal-ion species on photoreduction of CO2 as well as the reactive mechanism.Monometallic Catalytic Models Hosted in Stable Metal-Organic Frameworks for Tunable CO2 Photoreductionmetal-organic frameworks; isostructural; photocatalytic CO2 reduction; high selectivity; monometallic catalytic model; reactive mechanismPhotocatalystx156201960#N/AFALSE
5017
acscatal.8b0488310.1021/acscatal.8b04883FALSEhttps://doi.org/10.1021/acscatal.8b04883Stolten, DACS Catal.Direct methanol fuel cells (DMFCs) have the major advantage of the high energy density of the methanol (4.33 kWh/l) they use as a liquid fuel, although their costs remain too high due to the high quantity of Pt needed as a catalyst for oxygen reduction in the presence of methanol. Pt-Ni core-shell catalysts are promising candidates for improved oxygen reduction kinetics as shown in hydrogen fuel cells. The novelty in this work is due to the fact that we studied these catalysts in DMFC cathodes where oxygen must be reduced and membrane-permeating methanol oxidized at the same time. In spite of many attempts to overcome these problems, high amounts of Pt are still required for DMFC cathodes. During measurements over more than 3000 operating hours, the performance of the core-shell catalysts increased so substantially that a similar performance to that obtained with five times the amount of commercial platinum catalyst was achieved. While catalyst degradation has been thoroughly studied before, we showed here that these catalysts exhibit a self-protection mechanism in the DMFC cathode environment and prolonged operation is actually beneficial for performance and further stability due to the formation of a distinct Pt-rich shell on a PtNi core. The catalyst was analyzed by transition electron microscopy to show how the catalyst structure had changed during Activation of the core-shell catalyst.Dealloyed PtNi-Core-Shell Nanocatalysts Enable Significant Lowering of Pt Electrode Content in Direct Methanol Fuel Cellsdirect methanol fuel cell; Pt-Ni core-shell nanopartiCles; oxygen reduction reaction; scanning transmission electron microscopy; structural changex28201949#N/AFALSE
5018
acscatal.8b0484810.1021/acscatal.8b04848FALSEhttps://doi.org/10.1021/acscatal.8b04848Jaramillo, TFACS Catal.In2O3 has recently emerged as a promising catalyst for methanol synthesis from CO2. In this work, we present the promotional effect of Pd on this catalyst and investigate structure-performance relationships using in situ X-ray spectroscopy, ex situ characterization, and microkinetic modeling. Catalysts were synthesized with varying In:Pd ratios (1:0, 2:1, 1:1, 1:2, 0:1) and tested for methanol synthesis from CO2/H-2 at 40 bar and 300 degrees C. In:Pd(2:1)/SiO2 shows the highest activity (5.1 mu mol MeOH/g(Inpd)s) and selectivity toward methanol (61%). While all bimetallic catalysts had enhanced catalytic performance, characterization reveals methanol synthesis was maximized when the catalyst contained both In-Pd intermetallic compounds and an indium oxide phase. Experimental results and density functional theory suggest the active phase arises from a synergy between the indium oxide phase and a bimetallic In-Pd partiCle with a surface enrichment of indium. We show that the promotion observed in the In-Pd system is extendable to non precious metal containing binary systems, in particular In-Ni, which displayed similar composition-activity trends to the In-Pd system. Both palladium and nickel were found to form bimetallic catalysts with enhanced methanol activity and selectivity relative to that of indium oxide.Revealing the Synergy between Oxide and Alloy Phases on the Performance of Bimetallic In-Pd Catalysts for CO2 Hydrogenation to MethanolIn-Pd; In-Ni; In2O3; bimetallic; methanol synthesis; in situ characterization; CO2 utilization; intermetallicx73201995#N/AFALSE
5019
acscatal.9b0158210.1021/acscatal.9b01582FALSEhttps://doi.org/10.1021/acscatal.9b01582Cherevko, SACS Catal.Among the non-noble-metal electrocatalysts for the hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells (AEMFCs), Ni-based nanopartiCles have shown the highest reported activities. In this work, we investigated the chemical and electrochemical stability of representative Ni-based electrocatalysts. For this, carbon supported monometallic Ni and bimetallic Ni3M (M = Co, Fe, Cu, Mo) nanopartiCles were synthesized and tested using a set of complementary techniques. It was found that Mo suffers from intense dissolution due to thermodynamic instability. Cu was stable below 0.4 V-RHE, though it undergoes noticeable electrochemical transient dissolution if the potential range is extended to 0.5 V-RHE and higher. However, Ni, Co, and Fe showed negligible dissolution up to 0.7 V-RHE. Despite the absence of dissolution, all catalysts lose their HOR activity if they are cyCled to these high potentials. Physicochemical characterization of the aged catalysts revealed full oxidation of the metal nanopartiCles, which could be responsible for the performance deterioration. Although our results demonstrate that, besides Ni3Mo, all studied materials show high stability under operating potentials of AEMFCs, if fuel starvation in AEMFCs results in high anodic potentials, cell Activation and operation strategies are needed to prevent the passivation of the catalysts. These results present critical insights toward the design and development of affordable Ni-based electrocatalysts for AEMFCs as well as provide a better understanding of the operation strategies for the stability of AEMFCs.Stability Limits of Ni-Based Hydrogen Oxidation Electrocatalysts for Anion Exchange Membrane Fuel Cellsstability; anion exchange membrane fuel cell (AEMFC); nickel; electrocatalyst; hydrogen oxidation reaction (HOR)35201972#N/ATRUE
5020
acscatal.9b0131510.1021/acscatal.9b01315FALSEhttps://doi.org/10.1021/acscatal.9b01315Perez-Ramirez, JACS Catal.This artiCle investigates phosphates of transition metals (MPO, M = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) as catalysts for the selective transformation of propane via oxychlorination chemistry to propylene, a pivotal chemical commodity. The oxychlorination activity of the catalysts decreases in the order CuPO >> VPO > CoPO >> CrPO > FePO > MnPO approximate to NiPO approximate to TiPO, while the selectivity to propylene ranks as CrPO (95-98%) approximate to FePO (95-98%) > MnPO (67-85%) approximate to NiPO (65-85%) approximate to TiPO (66-75%) > CoPO (62-70%) > CuPO (33-45%) > VPO (30-42%) at 5-20% propane conversion. In-depth characterization using X-ray diffraction, Raman spectroscopy, and microscopy enables one to assess the structural and morphological stability of the phosphate samples. The most selective catalyst, CrPO, whose performance, crystal structure, and morphology are demonstrated stable for over 60 h on stream, enables one to reach propylene yields up to 50%, rivalling the best systems among any existing propane-to-propylene technology. Furthermore, the phosphate systems can be Classified into four categories, depending on which products they favor, as propylene (CrPO, FePO), cracking products (MnPO, NiPO, TiPO, CoPO), chlorinated hydrocarbons (CuPO), or carbon oxides (VPO). Finally, kinetic analysis of the oxychlorination, chlorination, and oxidation of propane as well as of propyl chloride dehydrochlorination and HCl oxidation over representative systems of each category rationalizes activity and selectivity patterns. In particular, the former is correlated to the material's ability to evolve chlorine, while a high selectivity toward propylene is a consequence of fast dehydrochlorination kinetics in combination with a hindered ability to evolve molecular chlorine to the gas phase and a low propensity toward propane cracking and combustion.Selective Propylene Production via Propane Oxychlorination on Metal Phosphate Catalystsheterogeneous catalysis; metal phosphates; natural gas; propane oxychlorination; propylene; selectivity12201943#N/ATRUE
5021
acscatal.8b0477810.1021/acscatal.8b04778FALSEhttps://doi.org/10.1021/acscatal.8b04778Grunwaldt, JDACS Catal.The reactive surface sites of MoS2 hydro treating catalysts (unpromoted as well as Co- and Ni-promoted) supported on MgA(2)O(4) spinel were investigated with respect to the substitution of sulfur by oxygen using in situ XAS coupled with modulation excitation spectroscopy (MES). Specifically, MES experiments were carried out by periodically cyCling between a H2O and H2S containing hydrogen gas mixture at 400 degrees C. Due to the low fraction of SO exchange, conventional XANES and EXAFS data hardly showed any changes when these catalysts were exposed to increasing ratios of H2O to H2S in an H-2 atmosphere. XANES and EXAFS data extracted at the Mo K-edge by MES analysis showed that for approximately 1% of the Mo atoms, sulfur atoms are replaced by oxygen atoms when exposed to H2O, causing partial oxidation of these active sites. The reaction is reversible and Mo returns to its initial sulfide phase when H2O is removed and H2S is supplied in the feed. In the case of Co- and Ni-promoted catalysts, the magnitude of S-O exchange was found to be reduced, indicating the beneficial effect of promotion. MES at the Ni K-edge showed that Ni was oxidized during H2O exposure, which in turn delayed the Mo oxidation in the Ni-promoted catalyst. The structures of these catalysts under S-O exchange were modeled using density functional theory (DFT) calculations, showing that the edge atoms are affected strongly. For all three catalysts, OH substitution is more favorable, while O substitution could be possible at high H2O pressure for unpromoted MoS2. Mo K-edge XANES spectra calculated using these simulated structures support the results obtained from the MES experiments. The presented approach using MES in combination with XAS and supported by DFT can be extended in general to catalysts under operando conditions and is thus a useful tool for determination of the active site on an atomic-scale.Probing the Active Sites of MoS2 Based Hydrotreating Catalysts Using Modulation Excitation SpectroscopyX-ray absorption spectroscopy; modulation excitation spectroscopy; hydrotreating; Ni/Co-promoted MoS2; phase sensitive detection; S-O exchangex18201974#N/AFALSE
5022
acscatal.8b0470710.1021/acscatal.8b04707https://doi.org/10.1021/acscatal.8b04707Mecking, SACS Catal.A possible involvement of radicals in catalytic insertion chain growth remains elusive, albeit it could account for thus far inconClusive experimental observations and enable yet unachieved synthetic reaction schemes. This work shows that radicals present, deliberately generated for this purpose, are incorporated as end groups in ethylene insertion polymerizations. Azo initiators (R-N = N-R' with R = C(CH3)(2)COOMe, Ph, 3,5-F2C6H3) added to pressure reactor Ni(II)salicylaldiminato-catalyzed ethylene polymerizations afforded initiator-derived Aryl or Alkyl end groups, respectively, as revealed by in-depth NMR studies of the polymer formed. The observation of additional solvent-derived Aryl end groups, originating from radical transfer to toluene, underlines that end groups are indeed formed from radicals. Evidence for incorporation as a chain-initiating as well as -terminating end group is discussed.Incorporation of Radicals during Ni(II)-Catalyzed Ethylene Insertion Polymerizationfree radicals; ethylene insertion polymerization; transfer to solvent; polymer end groups; nickel(II) catalystsx5201940#N/AFALSE
5023
acscatal.9b0129810.1021/acscatal.9b01298FALSEhttps://doi.org/10.1021/acscatal.9b01298Choi, JWACS Catal.The oxygen evolution reaction (OER) constitutes the key limiting process in water electrolysis, and various catalysts have recently been introduced to improve OER efficiency. Vacancy engineering in the crystal lattice is particularly promising in catalyst design, as vacancies could perturb the electronic properties of adjacent atoms to make them catalytically active. Noting that one of the well-adopted approaches to induce vacancies in a crystal structure is the mixing of elements with different valence states, herein, we investigate crystalline NiFe-V-M-O in comparison with NiO. Vacancies are naturally generated to meet charge neutrality when Ni2+ and Fe3+ are mixed via solid solution. As a result of vacancy formation, NiFe-V-M-O exhibits markedly enhanced catalytic performance for the OER. A combined in situ X-ray absorption fine structure and density functional theory analysis reveals that transition metal vacancies in NiFe-V-M-O distort the adjacent Ni's electronic structure toward weakening the interaction with the reaction intermediate *O, which is also associated with the enhanced structural flexibility of NiFe-V-M-O involving the transition metal vacancies. This study demonstrates the usefulness of the vacancy-local structure-electronic property relationship as a tool in manipulating the catalytic properties of OER electrocatalysts.Mixed Transition Metal Oxide with Vacancy-Induced Lattice Distortion for Enhanced Catalytic Activity of Oxygen Evolution Reactionelectrocatalysts; oxygen evolution reaction; transition metal vacancies; lattice distortion; in situ X-ray analysis; structure-property relationship35201970#N/ATRUE
5024
acscatal.8b0463310.1021/acscatal.8b04633FALSEhttps://doi.org/10.1021/acscatal.8b04633Pan, YACS Catal.This work describes a nickel-catalyzed Ullmann-type thiolation of Aryl iodidesunder mild electrochemical conditions. The simple undivided cell with graphene/nickel foam electrode setups offers excellent substrate tolerance, affording Aryl and Alkyl sulfides in good chemical yields. Furthermore, the mechanism for this electrochemical cross-coupling reaction has been investigated by cyClic voltammetry.Electrochemically Promoted Nickel-Catalyzed Carbon-Sulfur Bond Formationelectrochemistry; nickel; Ullmann coupling C-S bond; metal catalysis; thiolation; ArylationElectrochemistry45201950#N/AFALSE
5025
acscatal.8b0461210.1021/acscatal.8b04612FALSEhttps://doi.org/10.1021/acscatal.8b04612Bell, ATACS Catal.Ni-supported hydroxyapatite catalyst (Ni/HAP) was characterized and evaluated for propanol amination to propylamine at 423 K. The reaction proceeds via dehydroamination, a process that involves sequential dehydrogenation, condensation, and hydrogenation. Kinetic and isotopic studies indicate that alpha-H abstraction from propoxide species limits the rate of the dehydrogenation step and hence the overall rate of reaction. The rate of propanol dehydrogenation depends on the composition of the support and on the concentration of Ni sites located at the interface between Ni nanopartiCles and the support. Ni/HAP is an order of magnitude more active than Ni/SiO2 and displays a higher selectivity toward the primary amine. The superior performance of Ni/HAP is attributed to the high density of basic sites on HAP, which are responsible for stabilizing alkoxide intermediates and suppressing the disproportionation and secondary amination of amines.Propanol Amination over Supported Nickel Catalysts: Reaction Mechanism and Role of the Supporthydroxyapatite; HAP; dehydroamination; Alkylation; C-N couplingx20201944#N/AFALSE
5026
acscatal.8b0461110.1021/acscatal.8b04611FALSEhttps://doi.org/10.1021/acscatal.8b04611Lin, WBACS Catal.Herein we report that the Ti-8-BDC (MIL-125) (BDC is 1,4-benzeneCarbonylate) metal-organic framework (MOF) supports single-site solid Ni-II-hydride catalyst for the hydrogenolysis of Aryl ethers containing alpha-O-4, beta-O-4, and 4-O-5 linkages to exClusively afford hydrocarbons under mild conditions without the addition of a base. The catalytic activity of Ti-8-BDC-NiH is highly dependent on the reduction of Ti-8(mu(2)-O)(8)(mu(2)-OH)(4) nodes. Density functional theory (DFT) calculations revealed two key steps of a-bond metathesis in the catalytic cyCle of Ti-8-BDC-NiH catalyzed hydrogenolysis. This work highlights the potential of MOF-supported single-site catalysts in Aryl ether bond scission and other processes for the efficient production of biofuels and chemical feedstocks.Metal-Organic Framework Nodes Support Single-Site Nickel(II) Hydride Catalysts for the Hydrogenolysis of Aryl Ethersmetal organic frameworks; hydrogenolysis; single-site catalysts; nickel hydride catalysts; reduction of titanium; C-O Cleavagexy30201949#N/AFALSE
5027
acscatal.8b0451610.1021/acscatal.8b04516FALSEhttps://doi.org/10.1021/acscatal.8b04516Engle, KMACS Catal.We report a regioselective, nickel-catalyzed syn-1,2-carboamination of nonconjugated alkenyl Carbonyl compounds with O-benzoyl hydroxylamine (N-O) electrophiles and Aryl/Alkylzinc nuCleophiles to afford beta- and gamma-amino acid derivatives. This method enables preparation of products containing structurally diverse tertiary amine motifs, inCluding heterocyCles, and can also be used to form quaternary carbon centers. The reaction takes advantage of a tethered 8-aminoquinoline directing group to control the regiochemical outcome and suppress two-component coupling between the N-O electrophile and organozinc nuCleophile.Directed, Nickel-Catalyzed Umpolung 1,2-Carboamination of Alkenyl Carbonyl Compoundsnickel catalysis; C-N coupling; alkene; directing group; electrophilic nitrogenx30201963#N/AFALSE
5028
acscatal.9b0109310.1021/acscatal.9b01093FALSEhttps://doi.org/10.1021/acscatal.9b01093Hunt, AACS Catal.Transition metal oxides have gained attention as promising oxygen evolution reaction (OER) electrocatalysts in alkaline electrolytes, but heterogeneities in typical catalyst samples often obscure key structure-property relationships that are essential for developing higher performance materials. Here, we have combined ultrahigh vacuum surface science techniques, electrochemical measurements, and density functional theory (DFT) to quantify structure-dependent OER activity in a series of well-defined electrocatalysts. We describe a direct correlation between the population of Fe edge-site atoms and the OER activity of ultrathin Fe2O3 nanostructures (similar to 0.5 nm apparent height) grown on Au(111) substrates. Hydroxylated Fe atoms residing at edge-sites along the catalyst/support interface were spectroscopically identified as key reaction centers, and these Fe edge-site atoms were estimated to produce OER turnover frequencies approximately 150 times higher than that of Fe atoms on the catalyst surface at an applied potential of 1.8 V vs the reversible hydrogen electrode. Impressively, ultrathin Fe2O3/Au nanostructures with a high density of catalytically active Fe edge-site atoms outperformed an ultrathin IrOx/Au catalyst at moderate overpotentials. DFT calculations revealed more favorable OER at edge sites along the Fe2O3/Au interface, with lower predicted overpotentials due to beneficial modification of intermediate binding. Our results demonstrate how a combination of surface science, electrochemistry, and computational modeling can be used to identify key structure-property relationships in a well-defined electrocatalytic system.Edge-Enhanced Oxygen Evolution Reactivity at Ultrathin, Au-Supported Fe2O3 Electrocatalystsoxygen evolution reaction; well-defined catalysts; density functional theory; electrocatalysis; scanning tunneling microscopy; surface science; electrochemistry; structure-property relationships14201942#N/ATRUE
5029
acscatal.8b0442310.1021/acscatal.8b04423FALSEhttps://doi.org/10.1002/anie.199307141Cai, QTheoretical Insights of Ni2P (0001) Surface toward Its Potential Applicability in CO2 Conversion via Dry Reforming of Methanex2019#N/AFALSE
5030
acscatal.8b0411710.1021/acscatal.8b04117FALSEhttps://doi.org/10.1021/acscatal.8b04117Zeng, XCACS Catal.The development of a highly active and exceedingly durable electrocatalyst at low cost for the oxygen reduction reaction (ORR) is extremely desirable but remains to be a grand challenge. Over the past decade, the transitional metal (e.g., Fe, Co, Ni) and N codoped graphene materials have attracted most attention as the state-of-the-art nonprecious-metal-based effective electrocatalyst for ORR but still entail unsatisfactory issues such as moderate activity and life. Herein, the main-group-metal Al and N codoped graphene (ANG) is successfully fabricated via thermal annealing treatment of N-doped graphene with aluminum tri-(8-hydroxyquinoline). As a highly effective electrocatalyst for ORR, the as-prepared ANG exhibits not only high electrocatalytic activity that even outperforms the commercial Pt/C but also good durability in both three-electrode cell and Zn-air battery. Theoretical calculations show that the inhomogeneous charge density distribution and the interaction between Al and N are mainly responsible for the marked enhancement of ORR activity. The designed ANG electrocatalysts will provide a perspective application in energy storage and promote further exploration of main-group-element-based inexpensive, active, and durable electrocatalysts.Aluminum and Nitrogen Codoped Graphene: Highly Active and Durable Electrocatalyst for Oxygen Reduction ReactionAl-doped graphene; N-doped graphene; oxygen reduction reaction; electrocatalyst; noble-metal freex23201956#N/AFALSE
5031
acscatal.8b0410310.1021/acscatal.8b04103FALSEhttps://doi.org/10.1021/acscatal.8b04103Stevenson, KJACS Catal.The electrooxidation of urea continues to attract considerable interest as an alternative to the oxygen evolution reaction (OER) as the anodic reaction in the electrochemical generation of hydrogen due to the lower potential required to drive the reaction and the abundance of urea available in waste streams. Herein, we investigate the effect of Sr-substitution in a series of La2-xSrxNiO4+delta Ruddlesden-Popper catalysts on the electrooxidations of urea, methanol, and ethanol and conClude that activities toward the urea oxidation reaction increase with increasing Ni oxidation state. The 75% Sr-substituted La0.5Sr1.5NiO4+delta catalyst exhibits a mass activity of 588 mA mg(ox)(-1) and 7.85 A mg(-1) cm(ox)(-2) for the electrooxidation of urea in 1 M KOH containing 0.33 M urea, demonstrating the potential applications of Ni-based Ruddlesden-Popper materials for direct urea fuel cells and low-cost hydrogen production. Additionally, we find the same correlations between Ni oxidation state and activities for the electrooxidations of methanol and ethanol, as well as identify processes that result in catalyst deActivation for all three oxidations. This demonstration of how systematically increasing Ni - O bond covalency by raising the formal oxidation state of Ni above +3 serves to increase catalyst activity for these reactions will act as a governing principle for the rational design of catalysts for the electrooxidation of urea and other small molecules going forward.Enhanced Electrocatalytic Activities by Substitutional Tuning of Nickel-Based Ruddlesden-Popper Catalysts for the Oxidation of Urea and Small Alcoholselectrochemistry; Ruddlesden-Popper; perovskite; urea; electrooxidation; methanol; ethanol
Electrocatalytic
x37201946#N/AFALSE
5032
acscatal.8b0400310.1021/acscatal.8b04003FALSEhttps://doi.org/10.1021/acscatal.8b04003Choi, KSA Comparative Study of Nickel, Cobalt, and Iron Oxyhydroxide Anodes for the Electrochemical Oxidation of 5-Hydroxymethylfurfural to 2,5-FurandiCarbonylic Acidx2019#N/AFALSE
5033
acscatal.9b0064810.1021/acscatal.9b00648FALSEhttps://doi.org/10.1021/acscatal.9b00648Strasser, PACS Catal.Recent progress in the activity improvement of anode catalysts for acidic electrochemical water splitting is largely achieved through empirical studies of iridium-based bimetallic oxides. Practical, experimentally accessible, yet general predictors of catalytic OER activity have remained scarce. This study investigates iridium and iridium-nickel thin film model electrocatalysts for the OER and identifies a set of general ex situ properties that allow the reliable prediction of their OER activity. Well-defined Ir-based catalysts of various chemical nature and composition were synthesized by magnetron sputtering. Correlation of physicochemical and electrocatalytic properties revealed two experimental OER activity descriptors that are able to predict trends in the OER activity of unknown Ir-based catalyst systems. More specifically, our study demonstrates that the IrIII+- and OH-surface concentration of the oxide catalyst constitute Closely correlated and generally applicable OER activity predictors. On the basis of these predictors, an experimental volcano relationship of Ir-based OER electrocatalysts is presented and discussed.Experimental Activity Descriptors for Iridium-Based Catalysts for the Electrochemical Oxygen Evolution Reaction (OER)electrolysis; OER; electrolyzers; figures of merit; water splitting; catalyst design; volcano relationship; oxide formation and growth50201946#N/ATRUE
5034
acscatal.9b0060310.1021/acscatal.9b00603FALSEhttps://doi.org/10.1021/acscatal.9b00603Wang, DLACS Catal.Developing highly active as well as durable oxygen reduction reaction (ORR) electrocatalysts are still imperative for Clean and efficient energy conversion device, such as fuel cells and metal-air battery. For this purpose and maximize the utilization of noble Pt, we present here a facile, yet scalable strategy for the high-precise synthesis of 1-nm-thick Pt3Ni bimetallic alloy nanowires (Pt3Ni BANWs). The seed-mediated growth mechanism of Pt3Ni BANWs was identified subsequently. As expected, the Pt3Ni BANWs delivered enhanced mass activity (0.546 A mg(pt)(-1), exceeding the 2020 target of DOE) in comparison to Pt nanowires assembly (Pt NWA, 0.098 A mg(pt)(-1)) and Pt/C (Pt, 0.135 A mg(pt)(-1)), because of the rational integration of multiple compositional and structural advantages. Moreover, the Pt3Ni BANWs displayed enhanced durability (37% MA retention) than Pt NWA and Pt after 50 000 potential cyCles. All these results indicate that the ultrathin Pt3Ni BANWs are potential candidates for catalyzing ORR with acceptable activity and durability. The present work could not only provide a facile strategy but also a general guidance for the design of superb performance Pt-based nanowire catalysts for ORR.One-Nanometer-Thick Pt3Ni Bimetallic Alloy Nanowires Advanced Oxygen Reduction Reaction: Integrating Multiple Advantages into One Catalystoxygen reduction reaction; Pt-Ni alloy; ultrathin nanowires; seed-mediated growth; long-term durability54201940#N/ATRUE
5035
acscatal.8b0395310.1021/acscatal.8b03953FALSEhttps://doi.org/10.1021/acscatal.8b03953Llobet, AACS Catal.The present report uncovers the borderline between homogeneous and heterogeneous water oxidation catalysis using a family of Ni complexes containing oxamidate anionic type of ligands. In particular, the Ni complex [(L-1)Ni-II](2-)(1(2-); L-1 = o-phenylenebis(oxamidate)) and its modified analogues [(L-2)Ni-II](2-) ( 2(2-); L-2= 4,5-dimethyl-1,2-phenylenebis(oxamidate)) and [(L-3)Ni-II](2-) (3(2-); L-3 = 4-methoxy-1,2-phenylenebis-(oxamidate)) have been prepared and evaluated as molecular water oxidation catalysts at basic pH. Their redox features have been analyzed by means of electrochemical measurements revealing a crucial involvement of the ligand in the electron transfer processes. Moreover, the stability of those complexes has been assessed both in solution and immobilized on graphene-based electrodes at different potentials and pHs. The degradation of the molecular species generates a NiOx (Niguel oxides of general formula NixOyHz) layer, whose stability and activity as water oxidation catalyst have also been established. Electrochemical methods, together with surface characterization techniques, have shown the complex mechanistic scenario in water oxidation catalyzed by this family of Ni complexes, which consists of the coexistence of two catalytic mechanisms: a homogeneous pathway driven by the molecular complex and a heterogeneous pathway based on NiOx. The electronic perturbations exerted through the ligand framework have manifested a strong influence over the stability of the molecular species under turnover conditions. Finally, 1(2-) has been used as a molecular precursor for the formation of NiFeOx (Niquel/Iron oxides of general formula NixFe1-xOyHz) anodes that behave as extremely powerful water oxidation anodes.Can Ni Complexes Behave as Molecular Water Oxidation Catalysts?inorganic reaction mechanisms; water oxidation; water splitting; first row transition metal complexes; nickel catalyst; nickel oxidex26201942#N/AFALSE
5036
acscatal.8b0392110.1021/acscatal.8b03921FALSEhttps://doi.org/10.1021/acscatal.8b03921Wang, MACS Catal.The [FeFe]-hydrogenase model, [(mu-bdt)Fe-2(CO)(6)] (1, bdt = benzene-1,2-dithiolato), displays distinctive activity from its analogous complex, [(mu-edt)Fe-2(CO)(6)] (2, edt = ethane-1,2-dithiolato), for electrochemical CO2 reduction in acetonitrile with methanol or water as proton source. The maximum turnover frequency of 195 s(-1) estimated for 1 is more than 4800 times higher than that of 2. The influence of reaction conditions on faradaic yield and product selectivity was investigated. Controlled potential electrolysis experiments of 1 under optimal conditions gave a good faradaic yield of 88%, with formic acid as major product (selectivity, approximate to 81%) together with a small amount of CO (selectivity approximate to 11%) and H-2 (selectivity approximate to 8%). Density functional theory calculations suggest a mechanism of bimetal synergistic catalysis for electrochemical CO2 reduction by 1.Chemical Versatility of [FeFe]-Hydrogenase Models: Distinctive Activity of [mu-C6H4-1,2-(kappa(2)-S)(2)][Fe-2(CO)(6)] for Electrocatalytic CO2 Reductioncarbon dioxide reduction; carbon monoxide; diiron complex; electrocatalysis; formic acid; hydrogenase model
Electrocatalytic
10201972#N/AFALSE
5037
acscatal.9b0052110.1021/acscatal.9b00521TRUEhttps://doi.org/10.1021/acscatal.9b00521Wang, YACS Catal.A mild migratory reductive acyl cross-coupling has been achieved through NiH-catalyzed chainwalking and subsequent cross-coupling from two abundant starting materials, Alkyl bromides, and Carbonylic acids. This strategy allows the direct acylation of the Benzylic sp(3) C-H bond with high yield as a single regioisomer. As an alternative, the Alkyl bromide could be replaced by the proposed olefin intermediate and commercially available n-PrBr to achieve a remote hydroacylation process.Migratory Reductive Acylation between Alkyl Halides or Alkenes and Alkyl Carbonylic Acids by Nickel Catalysisacylation; C-H Activation; isomerization; migration; nickel; reductive cross-couplingCsp2-Csp3E-EOOHBr
Carbonyl
No baseNo Base2820191023/10/2022TRUE
5038
acscatal.8b0373710.1021/acscatal.8b03737https://doi.org/10.1021/acscatal.8b03737Xu, QJACS Catal.Earth-abundant nickel is a typical non-noble-metal cocatalyst used for photocatalytic hydrogen evolution (PHE). Ni nanopartiCles, however, tend to aggregate during the hydrogen production process, significantly lowering their PHE activity. To avoid aggregation, we used single atom form Ni and anchored them on vacancies in nitrogen-doped graphene (Ni-NG) as a cocatalyst for PHE. We demonstrated that Ni-NG is a robust and highly active cocatalyst for PHE from water. With only 0.0013 wt % of Ni loading, the PHE activity of composite Ni-NG/CdS photocatalyst improves by 3.4 times compared to that of NG/CdS, and it does not decay even after 10 rounds of 5-hour running. The quantum efficiency of Ni-NG/CdS for PHE reaches 48.2% at 420 nm, one of the highest efficiencies for non-noble-metal-based cocatalysts reported in the literature. Photoluminescence spectral analyses and electrochemical examinations indicated that Ni-NG coupled to CdS serves not only as an electron storage medium to suppress electronhole recombination but also as an active catalyst for proton reduction reaction. Density functional theory calculations show that the high activity of Ni-NG/CdS composite results from the single Ni atoms trapped in NG vacancies, which significantly reduces the Activation energy barrier of the hydrogen evolution reaction. This research may be valuable for developing robust and highly active noble metal free cocatalysts for solar hydrogen production.Single Nickel Atoms Anchored on Nitrogen-Doped Graphene as a Highly Active Cocatalyst for Photocatalytic H-2 Evolutionsingle Ni atom catalysts; non-noble-metal cocatalyst; photocatalytic hydrogen evolution; nitrogen-doped graphene; CdSPhotocatalyst86201848#N/AFALSE
5039
acscatal.8b0371710.1021/acscatal.8b03717FALSEhttps://doi.org/10.1021/acscatal.8b03717Chirik, PJACS Catal.A nickel-catalyzed method for the site-selective hydrogen isotope exchange (HIE) of C(sp(2)) H bonds in nitrogen heteroarenes is described and applied to the tritiation of pharmaceuticals. The alpha-diimine nickel hydride complex [((DI)-D-iPr)Ni(mu(2)-H)](2) ((DI)-D-iPr = N,N'-bis(2,6-diisopropylphenyl)-2,3-butanediimine) mediates efficient HIE when employed as a single component precatalyst or generated in situ from readily available and air-stable metal and ligand precursors (DI)-D-iPr, [(NEt3)Ni(OPiv)(2)](2) (Piv = pivaloyl) and (EtO)(3)SiH). The nickel catalyst offers distinct advantages over existing methods, inCluding: (i) high HIE activity at low D-2 or T-2 pressure; (ii) tolerance of functional groups, inCluding Aryl chlorides, alcohols, secondary amides, and sulfones; (iii) activity with nitrogen-rich molecules such as the chemotherapeutic imatinib; and (iv) the ability to promote HIE in sterically hindered positions generally inaccessible with other transition metal catalysts. Representative active pharmaceutical ingredients were tritiated with specific activities in excess of the thresholds required for drug absorption, distribution, metabolism, and excretion studies (1 Ci/mmol) and for protein receptor ligand binding assays (15 Ci/mmol). The activity and selectivity of the nickel-catalyzed method are demonstrated by comparison with the current state-of-the-art single-site (iridium and iron) and heterogeneous (Raney nickel and rhodium black) catalysts. A pathway involving C(sp(2)) H Activation by a alpha-diimine nickel hydride monomer is consistent with the experimentally measured relative rate constants for HIE with electronically disparate pyridines, the pressure-dependence of activity, positional selectivity preferences, and kinetic isotope effects.Site-Selective Nickel-Catalyzed Hydrogen Isotope Exchange in N-HeterocyCles and Its Application to the Tritiation of Pharmaceuticalsnickel; C-H Activation; tritium; pyridine; isotopex28201853#N/AFALSE
5040
acscatal.8b0370210.1021/acscatal.8b03702FALSEhttps://doi.org/10.1021/acscatal.8b03702Yang, YACS Catal.Understanding the synergism of bimetallic transition metal (TM)-based catalysts for oxygen evolution reaction (OER) is very difficult because it is complicated to identify the surface active sites in a bimetal system. Herein, we rationally designed Cu oxide (CuOx) nanoarray film (NF) as an example to investigate the synergism and doping effects of iron group metals on OER This is an advantage because CuOx is electrocatalytically inert and oxidatively stable, which is much better than carbon -based platforms. Especially, cobalt (Co) shows a much stronger synergism as compared with nickel (Ni) and iron (Fe). By introducing Co into the inert CuOx NFs, the Co active sites can be correlated to the OER activity by rationally regulating the morphology of CuOx NFs. In addition, the phase transformation from Cu2O to CuO occurs during the OER testing, further boosting the OER activity of Co-doped CuOx NF due to the hybridization change of Co active site. As a result, the Co-doped CuOx NF with 0.30 at. % Co (denoted as Co0.30CuOx) shows a remarkable OER activity (an overpotential of 0.29 V at 10 mA cm(-2)) in basic solution, superior to those of the state-of-the-art OER catalysts. Both experimental and computational studies indicate that the introduction of Co-dopant in CuOx changes the rate-limiting step from M-OHads -> M-O-ads to M-O-ads -> M-OOHads and decreases the theoretical onset potential by 0.31 V. The optimal concentration of Co-dopant in CuOx nanocrystals renders the favorable surface properties for the electron transfer, the adsorption, and desorption of OER-relevant intermediates. Moreover, the small size of CuOx nanocrystals contributes to the large electrochemically active surface area, which enables the sufficient Co active sites to the electrolyte.Understanding Synergism of Cobalt Metal and Copper Oxide toward Highly Efficient Electrocatalytic Oxygen Evolutioncobalt; doping effects; copper oxides; nanoarray film; oxygen evolution
Electrocatalytic
18201845#N/AFALSE
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acscatal.8b0366910.1021/acscatal.8b03669FALSEhttps://doi.org/10.1021/acscatal.8b03669Lee, KTACS Catal.Layered perovskite SrGdNixMn1-xO4 +/-delta phases were evaluated as new ceramic anode materials for use in solid oxide fuel cells (SOFCs). Hydrogen temperature-programmed reduction (H-2-TPR) analysis of the SrGdNixMn1-xO4 +/-delta (x = 0.2, 0.S, and 0.8) materials revealed that significant exsolution of Ni nanopartiCles occurred in SrGdNi0.2Mn0.8O4 +/-delta (SGNM28) in H-2 at over 650 degrees C. Consistently, the SGNM28 on the LSGM electrolyte showed low electrode polarization resistance (1.79 Omega cm(2)) in H-2 at 800 degrees C. Moreover, after 10 redox cyCles at 750 degrees C, the electrode area specific resistance of the SGNM28 anode in H-2 increased only 0.027 Omega.cm(2) per cyCle (1.78% degradation rate), indicating excellent redox stability in both reducing and oxidizing atmospheres. An LSGM-electrolyte-supported SOFC employing an SGNM28-Gd-doped ceria anode yielded a maximum power density of 1.26 W cm(-2) at 850 degrees C, which is the best performance among the SOFCs with Ruddlesden-Popper-based ceramic anodes to date. After performance measurement, we observed that metallic Ni nanopartiCles (similar to 25 nm) were grown in situ and homogeneously distributed on the SGNM28 anode surface. These exsolved nanocatalysts are believed to significantly enhance the hydrogen oxidation activity of the SGNM28 material. These results demonstrate that the SGNM28 material is promising as a high catalytically active and redox-stable anode for SOFCs.A Highly Active and Redox-Stable SrGdNi0.2Mn0.8O4 +/-delta Anode with in Situ Exsolution of Nanocatalystssolid oxide fuel cells; layered perovskite; ceramic anode; exsolution; redox stablex25201951#N/AFALSE
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acscatal.9b0049410.1021/acscatal.9b00494FALSEhttps://doi.org/10.1021/acscatal.9b00494Suib, SLACS Catal.A direct and effective approach is proposed to fabricate bimetallic phosphide Ni2P-Cu3P with controllable phase composition and distribution for catalytic hydrogen evolution reaction (HER). Unlike previously reported precursors, a porous Ni-Cu alloy incorporated with graphitic carbon (NiCuC) prepared via powder metallurgy is employed herein, and the generated Ni2P-Cu3P@NiCuC possesses a hierarchical porous structure and controllable phase composition due to the high porosity and tunable Ni/Cu ratio of the precursor. With an optimal Cu content of 30.0 wt %, the catalyst demonstrates the highest catalytic activity due to a synergistic interaction between different metallic phosphide sites and the facilitated mass transport. Meanwhile, density functional theory (DFT) calculation reveals that the atomic interaction of Ni2P-Cu3P substantially lower the Activation barrier for enhanced HER catalytic activity. The powder metallurgy provides an approach for the design of bimetallic phosphide electrocatalysts for HER and other catalytic applications.In Situ Growth of Ni2P-Cu3P Bimetallic Phosphide with Bicontinuous Structure on Self-Supported NiCuC Substrate as an Efficient Hydrogen Evolution Reaction Electrocatalystbimetallic phosphide; bicontinuous structure; Ni2P-Cu3P; hydrogen evolution reaction; catalyst45201950#N/ATRUE
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acscatal.9b0040110.1021/acscatal.9b00401FALSEhttps://doi.org/10.1021/acscatal.9b00401Bao, XHACS Catal.Strong metal-support interaction (SMSI) has been widely recognized for platinum-group metals on reducible oxide supports. Herein we report that the catalytic activity of Ni catalyst in CO2 methanation is significantly suppressed over conventional anatase (a-TiO2) support due to the SMSI-induced formation of a titania overlayer around the Ni nanopartiCles. Furthermore, CO is the only product . In contrast, the NH3-treatment and H-2-treatment of the a-TiO2 support enhance remarkably the activity of Ni, i.e., CO2 conversion increases by 1 order of magnitude and CO2 is hydrogenated almost exClusively to CH4. X-ray photoelectron spectroscopy (XPS), H-2 and CO chemisorption, and low temperature electron paramagnetic resonance (EPR) reveal that the enhanced CO2 methanation activity may be related with the Ti3+ species in the bulk that are generated by reduction treatment, which likely have altered the SMSI between Ni and a-TiO2 support. This simple reduction treatment approach may be applicable to modulate the SMSI of other reducible oxide-supported metal catalysts.Enhanced CO2 Methanation Activity of Ni/Anatase Catalyst by Tuning Strong Metal-Support InteractionsCO2; methanation; anatase; nickel-based supported catalyst; strong metal-support interactions19201957#N/ATRUE
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acscatal.8b0343510.1021/acscatal.8b03435FALSEhttps://doi.org/10.1021/acscatal.8b03435Regalbuto, JRACS Catal.In this work charge enhanced dry impregnation (CEDI), a hybrid method of supported nanopartiCle synthesis which combines the advantages of electrostatic adsorption small partiCle size and tight size distributions with the simplicity of incipient wetness impregnation, is demonstrated for four different metals (Pt, Pd, Co, and Ni) at multiple metal loadings over a common silica support. CEDI is achieved by basifying the impregnating solution sufficiently to charge the silica surface at the condition of incipient wetness. The electrostatic interactions induced between cationic ammine metal precursors and the deprotonated, negatively charged support result in smaller nanopartiCles with tighter size distribution in comparison to those for incipient wetness impregnation (or dry impregnation, DI) with no pH adjustment. The method works best when the balancing ion of the precursor salt is hydroxide, such as platinum tetraammine hydroxide, (NH3)(4)Pt(OH)(2). Using the corresponding chloride salts with CEDI results in larger metal partiCles, but these are still smaller than DI-derived partiCles. Washing out the chloride results in very small nanopartiCles without appreciable metal loss at metal loadings corresponding to one monolayer of precursor or below. Ammine complexes with nitrate as the counterion give small nanopartiCles at lower but still relevant metal loadings (1 or 2 wt %) with no washing; in this way the CEDI synthesis procedure is completely parallel to incipient wetness impregnation but gives much better metal dispersion.NanopartiCle Synthesis via Electrostatic Adsorption Using Incipient Wetness Impregnationcharged enhanced dry impregnation (CEDI); electrostatic adsorption; catalyst preparation; partiCle size; Pt; Pd; Co; Nix14201831#N/AFALSE
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acscatal.9b0036010.1021/acscatal.9b00360FALSEhttps://doi.org/10.1021/acscatal.9b00360Chakraborty, SACS Catal.We report the construction of an artificial hydrogenase (ArH) by reengineering a Cu storage protein (Csp1) into a Ni-binding protein (NBP) employing rational metalloprotein design. The hypothesis driven design approach involved deleting existing Cu sites of Csp1 and identification of a target tetrathiolate Ni binding site within the protein scaffold followed by repacking the hydrophobic core. Guided by modeling, the NBP was expressed and purified in high purity. NBP is a well-folded and stable construct displaying native-like unfolding behavior. Spectroscopic and computational studies indicated that NBP bound nickel in a distorted square planar geometry that validated the design. Ni(II)-NBP is active for photoinduced H-2 evolution following a reductive quenching mechanism. Ni(II)-NBP catalyzed H+ reduction to H-2 gas electrochemically as well. Analysis of the catalytic voltammograms established a proton-coupled electron transfer mechanism. Electrolysis studies confirmed H-2 evolution with quantitative Faradaic yields. Our studies demonstrate an important scope of rational metalloprotein design that allows imparting functions into protein scaffolds that have natively not evolved to possess the same function of the target metalloprotein constructs.Redesign of a Copper Storage Protein into an Artificial Hydrogenaseprotein design; artificial metalloenzymes; hydrogenases; spectroscopy; catalysis7201978#N/ATRUE
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acscatal.8b0333810.1021/acscatal.8b03338FALSEhttps://doi.org/10.1021/acscatal.8b03338Vlachos, DGACS Catal.Increasing the activity of non-noble catalysts for hydrogen oxidation is crucial in enhancing the efficiency of hydroxide exchange membrane fuel cells. Herein, we study the impact of graphene and nitrogen- and boron-doped graphene supports on the hydrogen oxidation reaction occurring on Ni, Cu, and Ag nanopartiCles using first-principles calculations and published experimental data. We find that doping of graphene leads to a stronger interaction between the nanopartiCle and the support, consequently weakening hydrogen adsorption. This leads to increased activity of supported Ni nanopartiCles, but decreased activity of supported Cu and Ag nanopartiCles. The dopant-induced changes in the hydrogen adsorption energies are quantitatively as important as the adsorption site. To describe adsorption energies for each supported nanopartiCle, principal component analysis is introduced to systematically identify molecular descriptors of adsorption energy. Finally, a size-dependent activity model is formulated to Close the size gap between first-principles calculations and experiments.Effect of Substitutionally Doped Graphene on the Activity of Metal NanopartiCle Catalysts for the Hydrogen Oxidation Reactionelectrocatalysis; hydrogen oxidation; density functional theory; nanopartiCle; support; graphene; size gapx12201951#N/AFALSE
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acscatal.9b0019110.1021/acscatal.9b00191FALSEhttps://doi.org/10.1021/acscatal.9b00191Delaunay, JJACS Catal.For the utilization of renewable energy resources to become widespread, efficient energy-storage devices must be developed. Electrocatalysts for the oxygen evolution reaction (OER) are needed for a wide variety of such devices, inCluding fuel cells, metal air batteries, and photoelectrochemical cells. Here we demonstrate a defect-rich NiCeOx layer, directly synthesized on a Ni substrate through a simple two-step dip-coating/annealing process, as a highly active and stable OER catalyst made from earth-abundant materials. With a low overpotential of 295 mV at 10 mA/cm(2) and a stability of over 200 h, NiCeOx boasts one of the best performances reported in the literature. This good performance is a result of the large number of oxygen vacancy defects introduced into NiCeOx by the diffusion of Ni from the Ni substrate into a deposited CeOx film during the annealing step. The oxygen vacancy defects not only supply an abundance of active sites but also decrease the mass-transfer resistance, resulting in the large electrochemically active surface area and high OER performance. This work demonstrates the potential of developing defect-rich Ce-containing materials as robust OER catalysts.Defect-Rich NiCeOx Electrocatalyst with Ultrahigh Stability and Low Overpotential for Water Oxidationoxygen evolution reaction; NiCeOx layer; Ni diffusion; defects; long-term stability35201942#N/ATRUE
5048
acscatal.8b0330110.1021/acscatal.8b03301FALSEhttps://doi.org/10.1021/acscatal.8b03301Ryoo, RACS Catal.Hydroisomerization of linear paraffins to branched isomers is an important petrochemical process, which commonly uses a microporous zeolite catalyst supported with Pt metal nanopartiCles. Although attempts were made in the past to find an alternative to costly Pt, replacement with low-cost metals was not successful for conventional bulk zeolites, due to the low metal dispersion resulting in poor catalytic performance. Here, we demonstrate that Ni can replace Pt when it is supported on zeolites with uniform mesopores. Ni-supported MFI-, *MRE-, and TON-type zeolites possessing mesopores showed the same or even better catalytic performance in comparison to that of Pt-supported conventional MFI, *MRE, and TON zeolites, respectively. The Ni-supported zeolites exhibited even better branched isomer yields, despite low Ni loading. This result is ascribed to the confinement or sandwiching effect of Ni nanopartiCles by the mesopore walls in the zeolites, which stabilizes the highly dispersed Ni nanopartiCles.Supporting Nickel To Replace Platinum on Zeolite Nanosponges for Catalytic Hydroisomerization of n-Dodecanemesoporous zeolites; zeolite nanosponges; supported Ni nanopartiCles; bifunctional catalysts; hydroisomerizationx27201840#N/AFALSE
5049
acscatal.8b0482810.1021/acscatal.8b04828FALSEhttps://doi.org/10.1021/acscatal.8b04828Hupp, JTACS Catal.Previous work has shown that introduction of hexafluoroacetylacetone (Facac) units as nonstructural ligands for the zirconia-like nodes of the eight-connected metal-organic framework (MOF), NU-1000, greatly alters the selectivity of node-supported oxy-nickel Clusters for ethylene dimerization vs oligomerization. Here we i explore a related concept: tuning of support/catalyst interactions, and therefore, catalyst activity, via parallel installation of organic modifiers on the support itself. As modifiers we focused on para-substituted benzoates (R-BA(-); R = -NH2, -OCH3, -CH3, -H, -F, and -NO2) where the substituents were chosen to present similar steric demand, but varying electron-donating or electron-withdrawing properties. R-benzoate-engendered shifts in the node-based aqua O-H stretching frequency for NU-1000, as measured by DRIFTS (diffuse-reflectance infrared Fourier-transform spectroscopy), together with systematic shifts in Ni 2p peak energies, as measured by X-ray photoelectron spectroscopy, show that the electronic properties of the support can be modulated. The vibrational and electronic peak shifts correlate with the putative electron-withdrawing vs electron-donating strength of the para-substituted benzoate modifiers. Subsequent installation of node-supported, oxy-Ni(II) Clusters for ethylene hydrogenation yield a compelling correlation between log (catalyst turnover frequency) and the electron donating or withdrawing character of the substituent of the benzoate units. Single crystal X-ray diffraction measurements reveal that each organic modifier makes use of only one of two available Carbonylate oxygens to accomplish grafting. The remaining oxygen atom is, in principle, well positioned to coordinate directly to an installed Ni(II) ion. We postulate that the unanticipated direct coordination of the catalyst by the node-modifier (rather than indirect modifier-based tuning of support(node)/catalyst electronic interactions) is the primary source of the observed systematic tuning of hydrogenation activity. We suggest, however, that regardless of mechanism for communication with active-sites of MOF-supported catalysts, intentional elaboration of nodes via grafted, nonstructural organic species could prove to be a valuable general strategy for fine-tuning supported-catalyst activity and/or selectivity.Introducing Nonstructural Ligands to Zirconia-like Metal-Organic Framework Nodes To Tune the Activity of Node-Supported Nickel Catalysts for Ethylene Hydrogenationmetal-organic framework; heterogeneous catalysis; ligand modification; zirconia-like node; ethylene hydrogenation; Hammett constant31201975#N/ATRUE
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acscatal.8b0320210.1021/acscatal.8b03202FALSEhttps://doi.org/10.1021/acscatal.8b03202Gounder, RACS Catal.The mechanistic origin of alkene dimerization on Ni sites supported on aluminosilicates has been ascribed to both coordination insertion (i.e., Cossee-Arlman) and metallacyCle-based cyCles; the latter is often invoked in the absence of externally supplied cocatalysts or activators that generate Ni-hydride or Ni-Alkyl species to initiate coordination insertion cyCles. Determining the prevalent reaction mechanism at Ni sites is often complicated by the formation and consumption of alkene dimer products via oligomerization and other parallel reactions (e.g., cracking, isomerization) that occur at Bronsted acid sites on supports. Here, ethene dimerization (453 K) was studied on Beta zeolites synthesized to contain predominantly exchanged Ni2+ sites according to site balances determined by cation exchange, and to Ni structure determined by CO infrared, UV-visible, and Ni K-edge X-ray absorption spectroscopies. The catalytic behavior of Ni2+ sites was isolated by suppressing contributions from residual H+ sites on support structures, either by selectively poisoning them with Li+ cations or NH4+ species, or by weakening them using a zincosilicate support. Bronsted acid sites form linear dimers (1-butene, cis-2-butene, trans-2-butene) in thermodynamically equilibrated ratios, in addition to their skeletal isomers (isobutene) and products of subsequent oligomerization-cracking cyCles; hence, isobutene formation rates serve as a kinetic marker for the presence of H+ sites. After residual H+ sites deactivate during initial reaction times or when they are suppressed prior to reaction, linear butene isomers form in nonequilibrated ratios that are invariant with ethene site-time, reflecting primary butene double-bond isomerization events catalyzed at Ni2+-derived active sites. Ni-zeolites pretreated in oxidative environments (5 kPa O-2, 773 K) show transient Activation periods during initial reaction times at dilute ethene pressures (<0.4 kPa) but not at higher ethene pressures (>0.4 kPa) or in the presence of co-fed hydrogen (5 kPa). This behavior is consistent with in situ ethene-assisted formation of [Ni(II)-H](+) intermediates, which isotopically scramble H-2-D-2 mixtures (453 K) and are quantified from surface H/D exchange reactions (453 K). Taken together, these findings provide unambiguous evidence for the coordination insertion mechanism as the dominant route for alkene dimerization at Ni2+ cations exchanged onto molecular sieves.Evidence for the Coordination-Insertion Mechanism of Ethene Dimerization at Nickel Cations Exchanged onto Beta Molecular Sievesalkene; coordination-insertion; dimerization; ethene; nickel; zeolitex202018100#N/AFALSE
5051
acscatal.8b0481710.1021/acscatal.8b04817FALSEhttps://doi.org/10.1021/acscatal.8b04817Mai, LQACS Catal.Unique interfacial properties within heterostructures play vital roles in enhancing hydrogen evolution reaction (HER) electrocatalysis. On the basis of the MoO2-Ni heterostructure, we hereby propose an upraised atomic orbital promoted catalytic mechanism for accelerating the HER kinetics. A controllable gradient-pyrolysis approach is adopted on molybdates to integrate Ni with MoO2, possessing numerous phase-separation-induced intimate interfaces. In situ characterizations demonstrate the formation process of MoO2-Ni interfaces and excellent compositional stability under alkaline conditions. The optimized MoO2-Ni catalyst delivers remarkable Pt-like HER activity and good stability with 50 h operation in 1 M KOH. An enhancement of 3 orders of magnitude on the exchange current density is achieved for MoO2-Ni in comparison to the simplex MoO2. Further experimental and theoretical analyses verify the existence of a concentrated surface charge at MoO2-Ni interfaces. Meanwhile, with the incorporation of Ni into MoO2, the most active sites dramatically change from Mo to O atoms at MoO2-Ni interfaces. The Ni contact upraises the O 2p orbital in MoO2, thus strengthening the hydrogen adsorption for enhanced HER kinetics.Upraising the O 2p Orbital by Integrating Ni with MoO2 for Accelerating Hydrogen Evolution Kineticsheterostructure; upraised orbital; enhanced hydrogen adsorption; hydrogen evolution reaction; catalytic mechanism62201967#N/ATRUE
5052
acscatal.8b0309210.1021/acscatal.8b03092FALSEhttps://doi.org/10.1021/acscatal.8b03092Hwang, BJACS Catal.Developing efficient and durable bifunctional electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) is highly desirable in energy conversion and storage systems. This study prepares nickel-ruthenium layered double hydroxide (NiRu-LDHs) nanosheets subjected to decoration with conductive silver nanopartiCles (Ag NP/NiRu-LDHs), which interestingly induce their multivacancies associated with catalytic site activity and populations. The as prepared Ag NP/NiRu-LDH shows excellent catalytic activity toward both OER and ORR features with low onset overpotentials of 0.21 V and -0.27 V, respectively, with a 0.76 V potential gap between OER potential at 10 mA cm(-2) and ORR potential at -3 mA cm(-2), demonstrating that it is the preeminent bifunctional electrocatalyst reported to date. Compared with pristine NiRu-LDHs, the resulting Ag NP/NiRuLDHs nanosheets require only an overpotential of 0.31 V to deliver 10 mA cm(-2) with excellent durability. The superb bifunctional performance of Ag NP/NiRu-LDH is ascribed to the formation of multivacancies, mutual benefits of synergistic effect between metal LDHs and silver nanopartiCles, and increased accessible active sites together with site activity are the key to the perceived performance. This work provides a new strategy to decorate LDHs and to engineer multivacancies to enhance site activity and populations simultaneously as ORR/OER bifunctional electrocatalysts.Site Activity and Population Engineering of NiRu-Layered Double Hydroxide Nanosheets Decorated with Silver NanopartiCles for Oxygen Evolution and Reduction Reactionsoxygen electrocatalyst; vacancies; site activity; site populations; layered double hydroxides; silver nanopartiClesx46201958#N/AFALSE
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acscatal.8b0464010.1021/acscatal.8b04640FALSEhttps://doi.org/10.1021/acscatal.8b04640Dutta, AACS Catal.The protein scaffold plays a key role during the enzymatic catalysis for metalloenzymes. Here we have rationally designed an enzyme-inspired outer coordination sphere in the form of protic functionalities, such as natural amino acid derived Carbonylic acid and phenolic -OH groups, on the fringe of the cobalt-salen like complexes. This inClusion has enabled electrocatalytic H-2 evolution for an otherwise inactive cobalt-salen like core. The complexes containing peripheral Carbonylic acid groups exhibited unique pH-switchable catalytic H-2 production that is connected with the pK(a) of the Carbonylic acid group (similar to 4.0), suggesting the crucial involvement of the Carbonylate group during the catalytic activity. The one- and two-dimensional NMR results of the complexes have indicated the presence of a possible hydrogen bonding network, generated by those protic groups in aqueous solution. These results highlight that an inactive metal complex can be activated for specific small molecule Activation via rational inClusion of outer coordination sphere functionalities.InClusion of Peripheral Basic Groups Activates Dormant Cobalt-Based Molecular Complexes for Catalytic H-2 Evolution in Waterelectrocatalytic H-2 production; cobalt-salen like complexes; pH-switchable outer coordination sphere; enzyme-inspired catalyst design; water-soluble H-2 production catalysts14201964#N/ATRUE
5054
acscatal.8b0295410.1021/acscatal.8b02954https://doi.org/10.1021/acscatal.8b02954Johannes, JWACS Catal.Medicinally relevant diArylamines are prepared through a photoredox-mediated dual catalytic nickel/ruthenium system from Aryl azides and Aryl electrophiles. Photoreduction of the Aryl azide is proposed to proceed through an Arylnickel-azide complex, which upon reduction and loss of nitrogen, generates a nickel(III) species capable of facile reductive elimination to afford the desired C-N bond formation. A variety of functionalized (hetero)Aryl electrophiles are shown to participate in the coupling, inCluding iodides, bromides, chlorides, and triflates. The reactions are simple to set up and are performed under ambient conditions, without the exClusion of oxygen or moisture.Nickel-Catalyzed Photoredox-Mediated Cross-Coupling of Aryl Electrophiles and Aryl Azidesphotoredox catalysis; nickel catalysis; cross-coupling; C-N bond formation; synthetic methodsPhotocatalyst192018267/6/2022FALSE
5055
acscatal.8b0292210.1021/acscatal.8b02922FALSEhttps://doi.org/10.1021/acscatal.8b02922Kubiak, CPACS Catal.Two heteroleptic nickel(II) complexes of the type [Ni(bis-NHC)(dRpe)](2+) (1, R = phenyl; 2, R = methyl; bis-NHC = 1,1':3,3'-bis(1,3-propanediyl)dibenzimidazolin-2,2'-diylidene) have been synthesized and characterized. The complexes exhibit reversible, two-electron reductions at -1.53 and -1.87 V versus Fc(+/0), respectively. Through the use of thermodynamic scaling relationships, hydricities for the corresponding nickel(II) hydride complexes 1H and 2H are estimated to be 45.6 and 37.8 kcal mol(-1), respectively. Experimental estimation of an upper bound for the hydricities (Delta G(H)degrees-(1H) < 50.3 kcal mol(-1) and Delta G(H)degrees-(2H) < 40.6 kcal mol(-1)) was determined by selection of an added weak acid such that the hydrogen evolution reaction (HER) becomes exergonic vs endergonic. Further electrochemical studies establish 2 as an efficient hydrogen evolution electrocatalyst, operating at low overpotential (eta = 0.4 V) and reasonable rates (TOF similar to 1000 s(-1)) using phenol as the Bronsted acid source. This demonstrates the utility of using ligand donor effects to impart noble-like, two-electron redox behavior at very negative potentials and increased hydride donor ability at nickel. This expands consideration of substrates suitable for hydrogen evolution at low overpotentials.Utilization of Thermodynamic Scaling Relationships in Hydricity To Develop Nickel Hydrogen Evolution Reaction Electrocatalysts with Weak Acids and Low Overpotentialshydricity; transition-metal hydride; nickel hydride; hydrogen evolution; catalyst designx15201834#N/AFALSE
5056
acscatal.8b0444710.1021/acscatal.8b04447FALSEhttps://doi.org/10.1021/acscatal.8b04447Sun, SGACS Catal.The instable structure of Pt-based high-indexed facets (HIFs) facile reconstructed is a key obstaCle for further practical applications because of its high surface energy and amounts of undercoordinated surface atoms. Herein, a strategy to advance the fundamental surface study on Pt-based HIFs materials is addressed by implanting non-noble metal or nonmetals as active auxiliaries into the near-surface of noble metal nanocrystals bounded with HIFs to engineer a stable structured catalyst. Then the Mo/Pt3Mn catalysts serving as proof-of-concept examples are designed and show enhanced catalytic performance of ethylene glycol (EG). According to the electrochemical in situ Fourier transform infrared spectroscopy results, the Mo modified Pt3Mn alloys with HIFs promote not only the C-C Cleavage of EG but also the direct conversion of COHx to CO2, without the formation of COL poison species. In this case, the Mo/Pt3Mn catalysts show the greatly significant increase of the catalytic activity in copamprison with Pt3Mn CNC and the commercial Pt/C, as well as the enhanced stability. The high-resolution transmission electron microscopy and X-ray photoelectron spectrum assisted by Ar surface etching experiments accompanied by density functional theory calculations are further used to explore the structure-performance relationship of Mo/Pt3Mn CNC for electro-oxidation of EG. This study addresses a promising strategy to fabricate a stable structured catalysts, which will elucidate a very promising methodology for developing Pt-based catalysts for further application of the fuel cell.Implanting Mo Atoms into Surface Lattice of Pt3Mn Alloys EnClosed by High-Indexed Facets: Promoting Highly Active Sites for Ethylene Glycol OxidationPt-based alloy catalysts; high-indexed facets; Mo decoration; electronic effect; ethylene glycol oxidation28201998#N/ATRUE
5057
acscatal.8b0283010.1021/acscatal.8b02830FALSEhttps://doi.org/10.1021/acscatal.8b02830Duboc, CACS Catal.Despite the report of several structural and functional models of the [NiFe]-hydrogenases, it is still unClear how the succession of electron and proton transfers during H-2 production catalysis are controlled in terms of both sequence (order of the chemical or redox steps) and sites (metal and/or ligand). To address this issue, the structure of the previously described bioinspired [NiFe]-hydrogenase complex [(LNiFII)-Ni-N2S2-F-II Cp(CO)](+) ((LNiFeCp)-Fe-II-Cp-II, with L-N2S2 = 2,2'-(2,2'-bipyridine-6,6'-diy1)bis(1,1'-diphenylethanethiolate) and Cp = cyClopentadienyl) has been fine-tuned by modifying exClusively the Fe site. In [(LNiFeCp)-Ni-N2S2-Fe-II-Cp-II* (CO)](+) ((LNiFeCp)-Fe-II-Cp-II*, with Cp* = pentamethylcyClopentadienyl), the Cp- ligand has been replaced by Cp*- to change both the redox and structural properties of the overall complex as a consequence of the steric hindrance of Cp*-. The (LNiFeCp)-Fe-II-Cp-II* complex acts as an efficient electrocatalyst to produce H-2. Density functional theory (DFT) calculations support a CEEC cyCle, following an initial reduction. The initial protonation leads to the Cleavage of one thiolate-iron bond and the next reduction to the generation of a bridging Fe-based hydride moiety. Interestingly, the second protonation step generates a species containing a terminal Ni-based thiol and a bridging hydride. In the presence of CO, the electrocatalytic activity of (LNiFeCp)-Fe-II-Cp-II* for H-2 production is markedly inhibited (about 90% of loss), while only a partial inhibition (about 30% of loss) is observed in the case of (LNIFeCp)-I-II-Cp-II. DFT calculations rationalized this effect by predicting that interactions of the one- and two-electron-reduced species for (LNiFeCp)-Fe-II-Cp-II* with CO are thermodynamically more favorable in comparison to those for (LNiFeCp)-Fe-II-Cp-II.Tuning Reactivity of Bioinspired [NiFe]-Hydrogenase Models by Ligand Design and Modeling the CO Inhibition Processbioinspired chemistry; hydrogenases; electrocatalysis; small-molecule Activation; H-2 production; nickel; ironx26201851#N/AFALSE
5058
acscatal.8b0282110.1021/acscatal.8b02821FALSEhttps://doi.org/10.1021/acscatal.8b02821Ma, DACS Catal.Dry reforming of methane (DRM) is an effective route to convert methane and carbon dioxide to syngas. Herein, we report an efficient nickel cobalt bimetallic catalyst with an activity of 4.97 mol(CH4) mol(Ni)(-1)s(-1) at 800 degrees C. It is active at low temperature as well, and near thermodynamic equilibrium conversion was achieved as low as 350 degrees C, with a high yield of H-2 implying inhibition of side reactions: i.e., a reverse water-gas shift (RWGS) reaction. The formation of Ni-Co alloy during the reaction was observed, and its lattice contraction was revealed by HAADF-STEM and EXAFS experiments. The lattice-strained Ni-Co alloy has good CO2 dissociation ability, which is responsible for its superior catalytic performance. Its weak chemisorption with H-2 results in inhibition of RWGS side reactions. This work is helpful in the design and development of other metal alloy materials with novel structures and/or electronic configurations for catalytic applications.Lattice Strained Ni-Co alloy as a High-Performance Catalyst for Catalytic Dry Reforming of Methanemethane; dry reforming; activity; Ni-Co alloy; lattice contractionx30201932#N/AFALSE
5059
acscatal.8b0400110.1021/acscatal.8b04001FALSEhttps://doi.org/10.1021/acscatal.8b04001Boettcher, SWACS Catal.Anion exchange membrane (AEM) electrolysis is a promising technology to produce hydrogen through the splitting of pure water. In contrast to proton-exchange-membrane (PEM) technology, which requires precious-metal oxide anodes, AEM systems allow for the use of earth-abundant anode catalysts. Here we report a study of first-row transition-metal (oxy)hydroxide/oxide catalyst powders for application in AEM devices and compare physical properties and performance to benchmark IrOx catalysts as well as typical catalysts for alkaline electrolyzers. We show that the catalysts' oxygen-evolution activity measured in alkaline electrolyte using a typical three-electrode cell is a poor indicator of performance in the AEM system. The best oxygen-evolution-reaction (OER) catalysts in alkaline electrolyte, NiFeOxHy oxyhydroxides, are the worst in AEM electrolysis devices where a solid alkaline electrolyte is used along with a pure water feed. NiCoOx-based catalysts show the best performance in AEM electrolysis. The performance can be further improved by adding Fe species to the partiCle surface. We attribute the differences in performance in part to differences in the electrical conductivity of the catalyst phases, which are also measured and reported.Earth-Abundant Oxygen Electrocatalysts for Alkaline Anion-Exchange-Membrane Water Electrolysis: Effects of Catalyst Conductivity and Comparison with Performance in Three-Electrode Cellsoxygen evolution reaction; water electrolysis; alkaline exchange membrane; electrocatalysts; electrolyzer; electrical conductivity46201955#N/ATRUE
5060
acscatal.8b0399110.1021/acscatal.8b03991FALSEhttps://doi.org/10.1021/acscatal.8b03991Ordomsky, VVACS Catal.Carbon monoxide hydrogenation over Co and Ni catalysts has provided important opportunities to, store energy and to manufacture alternative renewable transportation fuels. Catalyst deActivation is one of the most serious issues restricting application of this reaction. Hereby, we propose a simple and efficient way to enhance the stability of supported cobalt and nickel catalysts via their promotion with bismuth. In the promoted catalysts, bismuth is localized at the interface between metal nanopartiCles and the support covering the Co and Ni surface. Bismuth oxidation-reduction cyCling during carbon monoxide hydrogenation results in the removal of deposited carbon and catalyst self-regeneration. Formation of the bismuth layer at the metal nanopartiCles' surface protects them against sintering.Self-Regeneration of Cobalt and Nickel Catalysts Promoted with Bismuth for Non-deactivating Performance in Carbon Monoxide HydrogenationdeActivation; CO hydrogenation; Fischer-Tropsch; methanation; cobalt; nickel; coke; sintering6201932#N/ATRUE
5061
acscatal.8b0266510.1021/acscatal.8b02665FALSEhttps://doi.org/10.1021/acscatal.8b02665Dubau, LACS Catal.Hollow bimetallic nanostructures are perfect systems to unravel the aging mechanisms of both Pt-based alloys and highly defective nanostructures used in proton exchange membrane fuel cell (PEMFC) cathodes, since the mobility of their surface and bulk atoms leads to detectable chemical (i.e., Ni dissolution) and physical (i.e., decrease of the density of structural defects, collapse of the nanostructure, etc.) changes. In this study, we precisely and dynamically monitored these physicochemical changes on porous hollow PtNi/C nanopartiCles during an aging procedure composed of 5000 potential cyCles with linear ramps between 0.6 and 1.0 or 1.1 V vs RHE by using (i) synchrotron operando wide- and small-angle X-ray scattering (WAXS and SAXS), (ii) scanning transmission electron microscopy (STEM) in combination with X-ray energy dispersive spectroscopy (X-EDS), and (iii) electrochemical measurements. The synchrotron operando WAXS and SAXS results dynamically correlated the structural changes of the hollow NPs at both the atomic (Ni depletion, lattice parameter relaxation, variation in the density of structural defects, etc.) and nanometric (restructuring of the nanopartiCles/collapse of the hollow nanostructure) level. They revealed that the collapse of the hollow nanostructure was always accompanied by a significant loss of the Ni content. The 0.6-1.1 V vs RHE aging protocol resulted in a more severe depreciation of the ORR associated with a larger restructuring of the nanopartiCles in comparison to the 0.6-1.0 V vs RHE aging protocol, thus providing evidence that a critical potential exists for the stability of highly defective nanoalloys.Disentangling the Degradation Pathways of Highly Defective PtNi/C Nanostructures - An Operando Wide and Small Angle X-ray Scattering Studyoxygen reduction reaction; porous hollow PtNi/C nanopartiCles; structural defects; durability; operando wide- and small-angle X-ray scatteringx8201942#N/AFALSE
5062
acscatal.8b0258210.1021/acscatal.8b02582FALSEhttps://doi.org/10.1021/acscatal.8b02582Komatsu, TRemarkable Enhancement in Hydrogenation Ability by Phosphidation of Ruthenium: Specific Surface Structure Having Unique Ru Ensemblesx2018#N/AFALSE
5063
acscatal.8b0247610.1021/acscatal.8b02476FALSEhttps://doi.org/10.1021/acscatal.8b02476Sekine, YACS Catal.10wt%Ni-10wt%Mg-La0.1Zr0.9O2-x (LZO) catalyst shows high reforming activity of methane while suppressing methane combustion on tri-reforming of methane at low temperatures of 473 K in an electric field. On the basis of results of light-on and light-off tests for methane oxidation and temperature dependencies for catalytic methane steam reforming activity with or without the electric field, we found that Mg addition to 10wt%Ni-LZO catalyst suppresses methane combustion, while the methane steam reforming proceeds well by virtue of surface protonics in the electric field. Ni2+ on 10wt%Ni-10wt%Mg-LZO catalyst was more cationic than that on 10wt%Ni-LZO catalyst, and NiO-MgO solid solution formed on LZO support played an important role in combustion suppression.Ni-Mg Supported Catalysts on Tri-reforming of Methane with Low-Temperature Electrocatalytic Suppressed Oxidationmethane tri-reforming; oxidation suppression; Ni catalyst; steam reforming; XAFS measurements
Electrocatalytic
15201846#N/AFALSE
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acscatal.8b0236810.1021/acscatal.8b02368FALSEhttps://doi.org/10.1021/acscatal.8b02368Morokuma, KACS Catal.We present mechanistic details of the formation of a NiFe hydride complex and provide information on its electron-and hydride-transfer processes on the basis of density functional theory calculations and artificial-force induced-reaction studies. The NiFe hydride complex conducts three transfer reactions: namely, electron transfer, hydride transfer, and proton transfer. In a NiFe hydride complex, the hydride binds to Fe, which is different from the Ni-R state in hydrogenase where the hydride is located between Ni and Fe. According to our calculations, in reaction with the ferrocenium ion, electron transfer occurs from the NiFe hydride complex to the ferrocenium ion, followed by a hydrogen atom transfer (HAT) to the second ferrocenium ion. The oxidation state of Fe varies during the redox process, different from the case of NiFe hydrogenase, where the oxidation state of Ni varies. A single-step hydride transfer occurs in the presence of a 10-methylacridinium ion (AcrH(+)), which is more kinetically feasible than the HAT process. In contrast to the HAT and hydride-transfer process, the proton transfer occurs through a low barrier from a protonated diethyl ether. The revealed reaction mechanism guides the interpretation of the catalytic cyCle of NiFe hydrogenase and leads to the development of efficient biomimetic catalysts for H-2 generation and an electron/hydride transfer.Electron and Hydride Transfer in a Redox-Active NiFe Hydride Complex: A DFT StudyH-2 Activation; redox reaction; hydride complex; electron transfer; hydride transfer; metal oxidation state; sustainable energyx7201891#N/AFALSE
5065
acscatal.8b0376510.1021/acscatal.8b03765FALSEhttps://doi.org/10.1021/acscatal.8b03765Wang, GCACS Catal.In the present work, density functional theory calculations are performed to study mechanisms of ethanol steam reforming reactions on the Co-13/CeO2-x model. The related adsorption situations and reaction cyCles were Clarified. Ethanol will convert into CH3CO species through dehydrogenation steps on the Cox+ site, followed by coupling with hydroxyl from water dissociation on CeO2-x, yielding acetic acid on the interface. The acetic acid will spread to the Co-0 site to Cleave C-C and then convert to CO2 center dot H-2 forms on the Cox+ site. The coke formation is mainly caused by CH accumulation on the Co-0 site and could be released by CH oxidation on the Cox+ site. The oxidation state of Co on the surface affects the activity of ESR reactions. A higher oxidized Co site, featured with a lower ensemble size of Co, facilitates recombination reactions (e.g., H-2, acetic acid formation, and CH oxidation). On the contrary, a more reduced Co site favors dissociation reactions (e.g., C-C scission). The Cox+ site is the most favorable site for the dehydrogenation of ethanol into CH3CO center dot CeO2-x, will promote H2O dissociation via oxygen vacancy and lattice oxygen. On the hydroxylated CeO2-x surface, mobile O on CeO2-x has a higher tendency of oxidizing Co, while mobile OH is mainly responsible for releasing carbon deposition. In the experiment, keeping a high Co-0/Co2+ ratio can gain high proportions of Co-0 and Cox+ site, contributing to high ESR activity. Metal-oxide interaction should be strengthened to promote the spread of mobile OH. Enhancing metal-oxide interface formation is essential for CH3COOH formation. The redox property of CeO2 needs to be increased through doping with other elements, contributing to more oxygen vacancies. Adding O-2 could help release carbon deposition.The Mechanism of Steam-Ethanol Reforming on Co-13/CeO2-x: A DFT Studyethanol steam reform; reaction mechanism; coke formation; Co/CeO2-x; density functional theory calculations10201972#N/ATRUE
5066
acscatal.8b0221510.1021/acscatal.8b02215https://doi.org/10.1021/acscatal.8b02215Mul, GDACS Catal.Materials used for photocatalytic overall water splitting (POWS) are typically composed of light-absorbing semiconductor crystals, functionalized with so-called cocatalytic nanopartiCles to improve the kinetics of the hydrogen and/or oxygen evolution reactions. While function, quantity, and protection of such metal(oxide) nanopartiCles have been addressed in the literature of photocatalysis, the stability and transients in the active oxidation-state upon illumination have received relatively little attention. In this Perspective, the latest insights in the active state of frequently applied cocatalysts systems, inCluding Pt, Rh/Cr2O3, or Ni/NiOx, will be presented. While the initial morphology and oxidation state of such nanopartiCles is a strong function of the applied preparation procedure, significant changes in these properties can occur during water splitting. We discuss these changes in relation to the nature of the cocatalyst/semiconductor interface. We also show how know-how of other disciplines such as heterogeneous catalysis or electro-catalysis and recent advances in analytical methodology can help to determine the active state of cocatalytic nanopartiCles in photocatalytic applications.Driving Surface Redox Reactions in Heterogeneous Photocatalysis: The Active State of Illuminated Semiconductor-Supported NanopartiCles during Overall Water-Splittingphotocatalysis; cocatalysts; deActivation; interfaces; water splittingPhotocatalystx35201886#N/AFALSE
5067
acscatal.8b0357610.1021/acscatal.8b03576FALSEhttps://doi.org/10.1021/acscatal.8b03576Wu, XFACS Catal.Despite the general success of metal catalysts in modern organic chemistry, the exploration of natural available organic molecules as catalysts still has a strong appeal to scientists because of their green and sustainable advantages. Herein an intermolecular coupling reaction of cyClobutanone oximes with olefins promoted by biowaste gallic acid is reported. Both Alkylation and Carbonylative Alkylation reactions proceeded well in this system. Various cyClobutanone oximes and olefins can be transformed into the corresponding products in moderate to good yields. Detailed EPR investigations and control experiments are consistent with a single-electron transfer mechanism.Gallic Acid-Promoted SET Process for CyClobutanone Oximes Activation and (Carbonylative-)Alkylation of Olefinsgallic acid; cyClobutanone oximes; Carbonylation; Carbonylative coupling; radical process; domino reaction39201858#N/ATRUE
5068
acscatal.8b0217110.1021/acscatal.8b02171FALSEhttps://doi.org/10.1021/acscatal.8b02171Rhodes, CPACS Catal.Oxygen evolution reaction (OER) electrocatalysts with high activity, high stability, and low costs are needed for proton-exchange membrane (PEM) electrolyzers. Based on the high cost and limited supply of iridium, approaches that result in iridium-based OER catalysts with increased catalytic activity are of significant interest. We report a carbon-free, self-supported hydrous iridium nickel oxide two-dimensional nanoframe structure synthesized by thermal treatment of iridium-decorated nickel oxide nanosheets under reducing conditions and subsequent chemical leaching in acid. The catalyst nanoarchitecture contains an interconnected network of metallic iridium nickel alloy domains with hydrous iridium oxide and nickel oxide located in the surface region. The electrochemical oxidation step maintains the three-dimensional nanoarchitecture and results in a thin (similar to 5 angstrom) oxide/hydroxide surface layer. The temperature used for thermal reduction was found to strongly affect the catalyst surface structure and OER activity. Using a lower thermal reduction temperature of 200 degrees C was determined to provide a higher relative surface concentration of hydroxides and nickel oxide and result in higher OER activities compared with materials treated at 300 degrees C. The 200 degrees C-treated hydrous iridium nickel oxide electrocatalyst showed 15 times higher initial OER mass activity than commercial IrO2, and the activity remained 10 times higher than IrO, after accelerated durability testing. Density functional theory (DFT) calculations and analysis of the experimental Tafel slopes support that the second electron transfer step is the rate-limiting step for the reaction. The DFT calculations demonstrate that Ni substitution on the IrO, surface lowers the Activation energy for adsorbed intermediates of the second electron transfer step of the OER reaction. This work establishes that noble metal-decorated metal oxide nanosheets can be transformed into high surface area, carbon-free electrocatalyst nanostructures with high catalytic activities and molecular accessibility and reveals the importance of using controlled thermal reduction temperatures to alter the surface structure and OER activity.Self-Supported Hydrous Iridium-Nickel Oxide Two-Dimensional Nanoframes for High Activity Oxygen Evolution Electrocatalyststwo-dimensional materials; nanoframes; nanoarchitectures; electrocatalysts; oxygen evolution reaction; proton exchange membrane (PEM) electrolyzersx48201888#N/AFALSE
5069
acscatal.8b0211810.1021/acscatal.8b02118https://doi.org/10.1021/acscatal.8b02118Sundararaju, BACS Catal.A non-noble metal-free protocol has been developed for C-H bond functionalization at room temperature by merging cobalt-mediated catalysis with photo-catalysis. The reaction requires only oxygen as sole oxidant and operated at room temperature under redox-neutral conditions. Visible-light activated photoredox catalyst functions as an electron transfer reagent with oxygen as a terminal oxidant in the cobalt-mediated C-H and N-H bond annulation. The developed methodology allows annulations with various coupling partners. The concept demonstrated herein is expected to enhance the scope of cobalt catalysis as applied to sustainable fine chemical synthesis.Room-Temperature C-H Bond Functionalization by Merging Cobalt and Photoredox CatalysisPhotocatalyst72201878#N/AFALSE
5070
acscatal.8b0209110.1021/acscatal.8b02091FALSEhttps://doi.org/10.1021/acscatal.8b02091Zou, JJACS Catal.Nickel phosphide is a promising catalyst for hydrogenation of nitroarenes but suffers from sluggish H desorption and low chemoselectivity. Herein, we overcome these problems through reducing the Ni2P into subnanosized Clusters, tailoring the d-band center of Ni, and coupling them with P-doped carbon. Using density functional theory (DFT) calculations, we predicted that electron transfer from P-doped carbon to Ni2P Cluster results in downshift of d-band center of Ni that promotes H desorption on highly charged antibonding orbital of Ni-H, and reactant is preferentially adsorbed on P-doped carbon surface through nitro group due to the geometrical hindrance on Ni2P Clusters that leads to good selectivity. Then we developed a chemical anchoring method to fabricate Ni2P supported on P-doped carbon with high dispersion of 81.3%. The synthesized catalyst delivers high activity and selectivity chemo-selective hydrogenation of nitroarenes, and outperforms various noble- and transition-metal catalysts. Moreover, we revealed the origins of the superior performance of catalyst by characterizations, and confirmed the conClusion of DFT calculation. Such concept of tailoring d-band center and improving dispersion of active phase can provide insight for design of catalysts for hydrogenation and beyond.Ultradispersed Nickel Phosphide on Phosphorus-Doped Carbon with Tailored d-Band Center for Efficient and Chemoselective Hydrogenation of NitroarenesNi2P; d-band center; ultradispersion; synergistic effect; selective hydrogenationx60201847#N/AFALSE
5071
acscatal.8b0348910.1021/acscatal.8b03489FALSESun, SGInterfacial Interaction between FeOOH and Ni-Fe LDH to Modulate the Local Electronic Structure for Enhanced OER Electrocatalysis2018#N/ATRUE
5072
acscatal.8b0339610.1021/acscatal.8b03396FALSEhttps://doi.org/10.1021/acscatal.8b03396Liao, XBACS Catal.We present the anhydride-based deCarbonylative Alkylation of Aryl iodides catalyzed by nickel. This method of deCarbonylative coupling works with a broad scope of aliphatic Carbonylic anhydrides and tolerates synthetically useful aromatic substituents. Assisted by a redox system of pyridine N-oxide and zinc additives, the current reaction occurs under mild conditions and without the assistance of photocatalyst. Notably, this method features high chemoselectivity toward Alkyl migration with mixed aliphatic/aromatic anhydrides. Thus, it provides a powerful synthetic tool to modify high-valued aliphatic Carbonylic acids by converting them into mixed anhydrides using readily available Aryl Carbonylic acids such as p-toluic acid. We propose a catalytic cyCle that involves the key steps of free radical-based deCarbonylation and subsequent Alkyl transfer to nickel that precedes an oxidatively induced C C reductive elimination from Ni(III).Nickel-Catalyzed DeCarbonylative Alkylation of Aryl Iodides with AnhydridesdeCarbonylation; nickel catalysis; aliphatic acid anhydrides; cross-coupling; Alkylation7201857#N/ATRUE
5073
acscatal.8b0199910.1021/acscatal.8b01999https://doi.org/10.1021/acscatal.8b01999Jang, HWACS Catal.Converting solar energy by photoelectrochemical water splitting has been regarded as a promising way to resolve the global energy crisis and alleviate environmental pollution. Silicon, which is earth-abundant and has a narrow band gap, is an attractive material for photoelectrochemical water splitting. However, Si-based photoelectrodes suffer from photocorrosion, which leads to instability in electrolytes and high overpotential. Herein, we have fabricated a metalinsulatorsemiconductor structure of NiOx/Ni/n-Si photoanodes for highly efficient water splitting. NiOx/Ni nanopartiCles, which act as well-known oxygen evolution catalysts, are deposited on the surface of silicon by facile pulsed electrodeposition. Light absorption and catalytic activity are greatly affected by the coverage of Ni nanopartiCles, and the highly efficient NiOx/Ni catalyst structure is induced by simple annealing. The NiOx/Ni nanopartiCles show highly enhanced charge separation and transport efficiency, which are vital factors for photoelectrochemical water splitting, leading to similar to 100% Faradaic efficiency and incident photon-to-current efficiency. A low onset potential of 1.08 V versus a reversible hydrogen electrode for 1 mA/cm(2) and a high photocurrent density of 14.7 mA/cm(2) at 1.23 V are obtained.Tailored NiOx/Ni Cocatalysts on Silicon for Highly Efficient Water Splitting Photoanodes via Pulsed Electrodepositionphotoelectrochemical water splitting; Si photoanode; oxygen evolution reaction; cocatalyst; pulsed electrodepositionPhotocatalystx45201849#N/AFALSE
5074
acscatal.8b0197710.1021/acscatal.8b01977FALSEhttps://doi.org/10.1021/acscatal.8b01977Nath, MACS Catal.Designing high-efficiency electrocatalysts for water oxidation has become an increasingly important concept in the catalysis community due to its implications in Clean energy generation and storage. In this respect transition metal-doped mixed-metal selenides incorporating earth abundant elements such as Ni and Fe have attracted attention due to their unexpectedly high electrocatalytic activity toward the oxygen evolution reaction (OER) with low overpotential in alkaline medium. In this artiCle, quaternary mixed-metal selenide compositions incorporating Ni-Fe-Co were investigated through combinatorial electrodeposition by exploring the ternary phase diagram of Ni-Fe-Co systems. The OER electrocatalytic activity of the resultant quaternary and ternary mixed metal selenide compositions was measured in order to systematically investigate the trend of catalytic activity as a function of catalyst composition. Accordingly, the composition(s) exhibiting the best catalytic efficiency for the quaternary Fe-Co-Ni mixed-metal selenide was identified. It was observed that the quaternary selenide outperformed the binary as well as the ternary metal selenides in this Ni-Fe-Co phase space. The elemental composition and relative abundance of the elements in the catalyst film was ascertained from energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Mapping of the OER catalytic activity as a function of catalyst composition indicated that catalytic efficiency was more pronounced in the Fe rich region with moderate amounts of Ni and trace amounts of Co doping, and the best performance was exhibited by (Ni0.25Fe0.68Co0.07)(3)Se-4, which showed an overpotential of 230 mV (vs RHE) at 10 mA cm(-2) with stability exceeding 8 h for continuous oxygen generation. It was also observed that typically the quaternary metal selenide composition was Close to AB(2)Se(4), which shows a spinel structure type. Electrochemical measurements along with density functional theory (DFT) calculations were performed to correlate the enhancement of catalytic activity toward the Fe-rich region with composition. First principles DFT calculations were used to estimate the hydroxyl adsorption energy (E-ads) on the surface of the mixed-metal selenides with varying compositions. This adsorption energy could be directly correlated to the onset of OER activity, and the results matched very well with the experimentally observed trend with respect to onset overpotential. The knowledge of the trend of catalytic activity as a function of composition will be very important for catalyst design through targeted material synthesis. This work represents an example of a systematic phase exploration for quaternary metal selenides and provides a strong foundation which can be expanded to study other mixed-metal selenide combinations.Phase Exploration and Identification of Multinary Transition-Metal Selenides as High-Efficiency Oxygen Evolution Electrocatalysts through Combinatorial Electrodepositioncombinatorial electrodeposition; oxygen evolution reaction; water splitting; electrocatalyst; mixed-metal selenidex44201892#N/AFALSE
5075
acscatal.8b0196910.1021/acscatal.8b01969FALSEhttps://doi.org/10.1021/acscatal.8b01969Reisner, EACS Catal.Carbon nitrides (CNx) are a promising Class of photocatalyst for fuel and chemical synthesis as they are nontoxic and readily synthesized at a low cost. This study reports the enhanced photocatalytic activity for simultaneous alcohol oxidation and proton reduction when graphene oxide (GO) or reduced graphene oxide (RGO) is employed as an interlayer between a cyanamide-functionalized melon-type carbon nitride ((CNx)-C-NCN) and a phosphonated Ni-bis(diphosphine) H-2-evolution catalyst (NiP). Introduction of the GO/RGO enhanced the activity three times, reaching a specific activity of 4655 +/- 448 mu mol H-2 (g (CNx)-C-NCN)-1 h(-1) with a NiP-based turnover frequency of 116 +/- 3 h(-1). Mechanistic studies into this Closed photoredox system revealed that the rate of electron extraction from (CNx)-C-NCN is rate limiting. GO/RGO is commonly employed to improve the electron transfer dynamics on nanosecond time scales, but time-resolved photoluminescence and transient absorption spectroscopy reveal that these properties are not significantly affected in our (CNx)-C-NCN-GO hybrid on fast time scales (<0.1 s). However, long-lived trapped-electrons generated upon photoexcitation of (CNx)-C-NCN in the presence of organic substrates are shown by photoinduced absorption spectroscopy to be quenched faster with GO/RGO, supporting that GO/RGO improves electron transfer from (CNx)-C-NCN to NiP on time scales >0.1 s. The absorption profile of NiP in the presence of different GO loadings reveals that GO acts as a conductive interfacial binder between NiP and (CNx)-C-NCN. The enhancement in activity therefore does not primarily arise from changes in the photophysics of the (CNx)-C-NCN, but rather from GO/RGO enabling better electronic communication between (CNx)-C-NCN and NiP.Interfacial Engineering of a Carbon Nitride-Graphene Oxide-Molecular Ni Catalyst Hybrid for Enhanced Photocatalytic Activityphotocatalysis; carbon nitride; graphene oxide; interface; charge transfer; spectroscopyx292018122#N/AFALSE
5076
acscatal.8b0192910.1021/acscatal.8b01929FALSEhttps://doi.org/10.1021/acscatal.8b01929Linic, SACS Catal.Protective insulating layers between a semiconductor and an electrocatalyst enable otherwise unstable semiconductors to be used in photocatalytic water splitting. It is generally argued that in these systems the metal electrocatalyst must have work function properties that set a high inherent barrier height between the semiconductor and electrocatalyst and that the insulating layer should be as thin as possible. In this study we show that, for systems which suffer from inherently low barrier heights, the photovoltage can be significantly improved by tuning the thickness of the insulating layer. We demonstrate this in a case study of a system consisting of n-type silicon, a hafnium oxide protective layer (thickness 0-3 nm), and a Ni electrocatalyst. By optimizing the protective layer thickness, we observe increased efficiencies for photocatalytic oxygen evolution with a thick Ni electrocatalyst supported on n-Si. Our findings open avenues for the use of inexpensive electrocatalysts with favorable electrocatalytic and optical properties but poor work function characteristics.Maximizing Solar Water Splitting Performance by Nanoscopic Control of the Charge Carrier Fluxes across Semiconductor-Electrocatalyst Junctionswater splitting; MIS junction; oxygen evolution; photoelectrocatalysis; photoanodex15201840#N/AFALSE
5077
acscatal.8b0331910.1021/acscatal.8b03319FALSEhttps://doi.org/10.1021/acscatal.8b03319Yao, YGRevealing the Synergistic Effects of Rh and Substituted La2B2O7 (B = Zr or Ti) for Preserving the Reactivity of Catalyst in Dry Reforming of Methane2019#N/ATRUE
5078
acscatal.8b0186310.1021/acscatal.8b01863https://doi.org/10.1021/acscatal.8b01863Pan, YACS Catal.A photoredox and copper catalyzed asymmetric cyanoAlkylation reaction of alkenes has been developed, which uses Alkyl N-hydroxyphthalimide esters as Alkylation reagents. In this radical cyanoAlkylation reaction, the photoredox induced Alkyl radical adds to styrene, and the generated Benzylic radical couples with a chiral box/CuII cyanide complex to achieve the enantioselective cyanation. This reaction features mild conditions, operational simplicity, broad substrate scope, high yields, and high enantioselectivities, which represents an efficient method for the asymmetric radical difunctionalization of alkenes.Merging Photoredox and Copper Catalysis: Enantioselective Radical CyanoAlkylation of Styrenesasymmetric radical reaction; cyanoAlkylation; photoredox; Cu catalysis; difunctionalization of alkenePhotocatalyst70201871#N/AFALSE
5079
acscatal.8b0329810.1021/acscatal.8b03298FALSEhttps://doi.org/10.1002/anie.197904152Mavrikakis, MAnionic Single-Atom Catalysts for CO Oxidation: Support-Independent Activity at Low Temperatures2019#N/ATRUE
5080
acscatal.8b0182110.1021/acscatal.8b01821FALSEhttps://doi.org/10.1021/acscatal.8b01821Dou, SXACS Catal.Exploring economically efficient electrocatalysts with good electrocatalytic activity is essential for diverse electrochemical energy devices. Series of ultrathin metallic nickel-based holey nitride nanosheets were designed as bifunctional catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). They exhibit improved catalytic properties owing to the inherent advantages of their plentiful active reaction sites resulting from the complete exposure of the atoms in the large lateral surfaces and from the edges of pore areas, together with expanded lattice spacing distance. This obtained three-dimensional conductive integral architecture can not only accelerate the electron transportation by the highly orientated crystalline structure but also facilitate the diffusion of intermediate and gases. In terms of the OER electrocatalytic properties, a quite low overpotential (300 mV) is required for the holey two-dimensional (2D) Ni3Fe nitride nanosheets to deliver a current density of about 100 A g(-1) with an enhanced improvement over IrO2 by a factor of nearly 25 times. The holey 2D Ni3Fe nitride nanosheets also exhibit enhanced catalytic performance toward the HER, with a tiny overpotential (233 mV) to achieve a current density of about 100 A g(-1) with much better kinetic properties in comparison to those of highly active Pt/C.Ultrathin and Edge-Enriched Holey Nitride Nanosheets as Bifunctional Electrocatalysts for the Oxygen and Hydrogen Evolution Reactionstwo-dimensional; nitride electrocatalyst; LDH; oxygen evolution reaction; hydrogen evolution reactionx36201858#N/AFALSE
5081
acscatal.8b0182010.1021/acscatal.8b01820FALSEhttps://doi.org/10.1021/acscatal.8b01820Gurlo, AACS Catal.A 5% Ni/MnO catalyst has been tested for the dry reforming of methane at different temperatures and reactant partial pressures. Changing the reactant ratio with time on stream results in a decrease in the deActivation rate of the catalyst. Graphitic carbon growth and metal partiCle sintering have been observed by applying in situ transmission XRD using synchrotron radiation under actual reaction conditions. Both methane and carbon monoxide separately result in graphitic surface carbon, which can then be oxidized by carbon dioxide. The morphology of the surface carbon has been analyzed by TEM, and the reactions of both methane and carbon monoxide result in the same graphitic multiwalled carbon nanotubes. The present combination of catalytic experiments and in situ techniques suggests that surface carbon acts as an intermediate in the formation of CO and that catalyst deActivation happens via metallic partiCle sintering. These results enable a more rational choice of reaction conditions to ensure high catalyst activity and long-term stability. Future catalyst advances must aim to prevent metal partiCle sintering.Surface Carbon as a Reactive Intermediate in Dry Reforming of Methane to Syngas on a 5% Ni/MnO Catalystcarbon deposition; in situ XRD; synchrotron radiation; heterogeneous catalysis; DRM; nickel; surface carbonx26201847#N/AFALSE
5082
acscatal.8b0309510.1021/acscatal.8b03095FALSEhttps://doi.org/10.1021/acscatal.8b03095Lercher, JACS Catal.Nickel- and alkali-earth-modified LTA based zeolites catalyze the dimerization of 1-butene in the absence of Bronsted acid sites. The catalyst reaches over 95% selectivity to n-octenes and methylheptenes. The ratio of these two dimers is markedly influenced by the parallel isomerization of 1-butene to 2-butene, shifting the methylheptene/octene ratio from 0.7 to 1.4 as the conversion increases to 35%. At this conversion, the thermodynamic equilibrium of 90% cis- and trans-2-butenes is reached. Conversion of 2-butene results in methylheptene and dimethylhexene with rates that are 1 order of magnitude lower than those with 1-butene. The catalyst is deactivated rapidly by strongly adsorbed products in the presence of 2-butene. The presence of pi-allyl-bound butene and Ni-Alkyl intermediates was observed by IR spectroscopy, suggesting both to be reaction intermediates in isomerization and dimerization. Product distribution and apparent Activation barriers suggest 1-butene dimerization to occur via a 1'-adsorption of the first butene molecule and a subsequent 1'- or 2'-insertion of the second butene to form octene and methylheptene, respectively. The reaction order of 2 for 1-butene and its high surface coverage suggest that the rate-determining step involves two wealdy adsorbed butene molecules in addition to the more strongly held butene.Dimerization of Linear Butenes on Zeolite-Supported Ni2+linear alkenes; nickel Lewis acid zeolite; dimerization; nickel Alkyl and LTA zeolite17201960#N/ATRUE
5083
acscatal.8b0299210.1021/acscatal.8b02992FALSEhttps://doi.org/10.1021/acscatal.8b02992Campbell, CTEnergetics of Adsorbed Methanol and Methoxy on Ni(111): Comparisons to Pt(111)2018#N/ATRUE
5084
acscatal.8b0286910.1021/acscatal.8b02869FALSEhttps://doi.org/10.1021/acscatal.8b02869Milstein, DACS Catal.Homogeneous catalysis of organic transformations by metal complexes has been mostly based on complexes of noble metals. In recent years, tremendous progress has been made in the field of base-metal catalysis, mostly with pincer-type complexes, such as iron, cobalt, nickel, and manganese pincer systems. Particularly impressive is the explosive growth in the catalysis by Mn-based pincer complexes, the first such complexes being reported as recently as 2016. This review covers recent progress in the field of homogeneously catalyzed reactions using pincer-type complexes of cobalt and manganese. Various reactions are described, inCluding acceptorless dehydrogenation, hydrogenation, dehydrogenative coupling, hydrogen borrowing, hydrogen transfer, H-X additions, C-C coupling, alkene polymerization and N-2 fixation, inCluding their scope and brief mechanistic comments.Homogeneous Catalysis by Cobalt and Manganese Pincer Complexespincer ligand; homogenous catalysis; earth-abundant metal; cobalt; manganese122018228#N/ATRUE
5085
acscatal.8b0278410.1021/acscatal.8b02784FALSEhttps://doi.org/10.1021/acscatal.8b02784Wang, CACS Catal.In this protocol, we report an allylic defluorinative reductive cross-coupling reaction for C-C bond formation. Under the Ni-catalysis the challenging C(sp(3))-F bond Cleavage of trifluoromethyl-substituted alkenes was achieved with easily accessible primary, secondary and tertiary Alkyl halides as the coupling partners and Zn-powder as reducing agent. This process provides an efficient and convenient entry to gem-difluoroalkenes bearing various sensitive functional groups under mild reaction conditions. Moreover, this method proves to be suitable for late-stage functionalization of multifunctional complex molecules.Synthesis of gem-Difluoroalkenes via Nickel-Catalyzed Allylic Defluorinative Reductive Cross-Couplinggem-difluoroalkenes; C-F bond Activation; beta-F elimination; reductive cross-coupling; Ni-catalysis57201895#N/ATRUE
5086
acscatal.8b0159810.1021/acscatal.8b01598FALSEhttps://doi.org/10.1021/acscatal.8b01598Gorte, RJACS Catal.Conformal CaTiO3 films were deposited onto MgAl2O4 by atomic layer deposition (ALD) and then examined as intelligent catalyst supports for Ni in the steam and CO2 reforming of methane. CaTiO3 films (1 nm) were characterized by scanning transmission electron microscopy and XRD and shown to be stable to at least 1073 K. Catalysts with 1 and 20 wt % Ni were studied, and it was found that, following calcination at 1073 K, the Ni-CaTiO3/MgAl2O4 catalysts required high-temperature reduction to achieve activities comparable to that of their Ni/MgAl2O4 counterparts. However, the Ni-CaTiO3/MgAl2O4 catalysts exhibited dramatically improved tolerance toward carbon-whisker formation. The carbon content on the 1 wt % Ni catalyst on CaTiO3/MgAl2O4 was small even after heating the catalyst in a dry, 10% CH4-90% He mixture at 1073 K for 12 h. Possible mechanisms for the high carbon tolerance of the perovskite-containing catalysts are discussed.Improved Coking Resistance of Intelligent Ni Catalysts Prepared by Atomic Layer Depositionsteam methane reforming; dry methane reforming; atomic layer feposition (ALD); intelligent catalyst; coking resistance; Ni catalyst; CaTiO3x30201821#N/AFALSE
5087
acscatal.8b0267910.1021/acscatal.8b02679FALSEhttps://doi.org/10.1021/acscatal.8b02679Han, JWACS Catal.The high-temperature coelectrolysis system can be helpful to solve environmental issues by reducing carbon dioxide emissions. The technology is highly promising because of its high selectivity and conversion efficiency toward the products. In addition, the produced syngas can also be further converted into very useful synthetic fuels. In this study, we investigated the series of reactions on a wide range of transition metals to evaluate their ability to increase the activity of the conventional Ni catalysts used in the fuel electrode of solid oxide electrolyzer cells. We theoretically identified that the adsorption energies of O and H are the common descriptors of coelectrolysis of steam and carbon dioxide. We then combined microkinetic analysis with density functional theory calculations to derive a volcano plot to predict the activity of coelectrolysis on a variety of transition metals. We could successfully suggest good candidates of Ni-based bimetallic alloy catalysts with excellent activities in the coelectrolysis. Our result will provide insight into improving the electrode catalysts used in the high-temperature coelectrolysis system.Electrocatalysts with Increased Activity for Coelectrolysis of Steam and Carbon Dioxide in Solid Oxide Electrolyzer Cellssolid oxide electrolyzer cells; coelectrolysis; steam and carbon dioxide; electrocatalytic activity; density functional theory; microkinetic modeling12201981#N/ATRUE
5088
acscatal.8b0227710.1021/acscatal.8b02277FALSEhttps://doi.org/10.1021/acscatal.8b02277Liu, PACS Catal.Single-site catalysts (SSCs) have drawn considerable attention, because of their superior behaviors in catalysis. However, the origin of promoting the effect of a single site is not well understood. Here, we take the single-atom Ni-1/Mg(100) and single-site Ni-4/Mg(100) catalysts as a case study to elucidate their behaviors under the complex dry reforming of methane (DRM, CO2 + CH4 -> 2CO + 2H(2)) reaction by combining theoretical modeling (density functional theory and kinetic Monte Carlo simulation) and experimental studies. The synergy between single Ni atom and MgO is found to improve the binding property of MgO; yet, it is not enough to dissociate CO2 and CH4. It can be achieved by the single-site Ni-4/MgO(100) catalyst, enabling the formations of CO, H-2, and H2O under the DRM conditions. During this process, coking, as observed for bulklike Ni partiCles, is eliminated. By confining the reaction to occur at the isolated Ni sites in the SSC, the Ni-4/MgO(100) catalyst is able to balance the CO2 and CH4 Activations, which is identified as the key for tuning the DRM activity and selectivity of Ni/MgO catalysts. The theory-identified promotion introduced by increasing the size of MgO-supported Ni Clusters from Ni-1 to Ni-4 and the MgO-introduced site confinement of single-site catalysts are verified by corresponding experimental studies, highlighting the essential roles of confined sites in tuning the performance of SSCs during complex catalytic processes.Dry Reforming of Methane on Single-Site Ni/MgO Catalysts: Importance of Site Confinementsite confinement; dry reforming of methane; Ni/MgO; single-site catalyst; DFT; KMC; TEM46201878#N/ATRUE
5089
acscatal.8b0156410.1021/acscatal.8b01564FALSEhttps://doi.org/10.1021/acscatal.8b01564Sels, BFACS Catal.This contribution studies the steam-assisted deAlkylation of 4-npropylphenol (4-n-PP), one of the major products derived from lignin, into phenol and propylene over several micro- and mesoporous acidic aluminosilicates in gas phase. A series of acidic zeolites with different topology (e.g., FER, TON, MFI, BEA, and FAU) are studied, of which ZSM-5 outperforms the others. The catalytic results, inCluding zeolite topology and water stability effects, are rationalized in terms of thermodynamics and kinetics. A reaction mechanism is proposed by (i) analyzing products distribution under varying temperature and contact time conditions, (ii) investigating the deAlkylation of different regio- and geometric isomers of propylphenol, and (iii) studying the reverse Alkylation of phenol and propylene. The mechanism accords to the Classic carbenium chemistry inCluding isomerization, disproportionation, transAlkylation, and deAlkylation, as the most important reactions. The exceptional selectivity of ZSM-5 is attributed to a pore confinement, avoiding disproportionation/transAlkylation as a result of a transition state shape selectivity. The presence of water maintains a surprisingly stable catalysis, especially for ZSM-5 with low acid density. The working hypothesis of this stabilization is that water preCludes diphenyl ether(s) formation in the pores by reducing the lifetime of the phenolics at the active site due to the high heat of adsorption of water on H-ZSM-5, besides counteracting the equilibrium of the phenolics condensation reaction. The water effect is unique for the combination of (Alkyl)phenols and ZSM-5.Propylphenol to Phenol and Propylene over Acidic Zeolites: Role of Shape Selectivity and Presence of Steamcatalysis; lignin valorization; ZSM-5; deAlkylation; propylphenol and phenol; shape selectivityx262018101#N/AFALSE
5090
acscatal.8b0221210.1021/acscatal.8b02212FALSEhttps://doi.org/10.1021/acscatal.8b02212Wang, PACS Catal.Platinum (Pt) is well-known as the best-performing catalyst for the hydrogen evolution reaction (HER), but its practical application is severely hindered by its prohibitively high cost and problematic performance in alkaline electrolyte. Herein, we report that the issues of intrinsic activity and cost concern of Pt can be simultaneously addressed by employing a combination of concerted catalysis and nanoengineering strategies. Motivated by our density functional theory (DFT) calculations that the cooperative catalysis between Pt and NiO would lead to a better HER activity in comparison to Pt solely in alkaline solution, we successfully synthesized a Pt/NiO@Ni/NF nanocomposite catalyst by depositing highly dispersed Pt nanoClusters/nanopartiCles on a honeycomb-like NiO@Ni film supported on Ni foam (NF). The resulting Pt/NiO@Ni/NF catalyst outperforms the commercial Pt/C catalyst with a high and stable HER activity in alkaline solution and, more impressively, with an economical Pt content as low as similar to 0.1 mg cm(-2).Highly Dispersed Platinum on Honeycomb-like NiO@Ni Film as a Synergistic Electrocatalyst for the Hydrogen Evolution Reactionhydrogen evolution reaction; electrocatalyst; concerted catalysis; nanoengineering strategy; intrinsic activity73201846#N/ATRUE
5091
acscatal.8b0138010.1021/acscatal.8b01380FALSEhttps://doi.org/10.1021/acscatal.8b01380Zeng, XMACS Catal.The synthesis of aromatic ketones by chromium-catalyzed Kumada Arylation of secondary amides with organomagnesium reagents is described. This reaction was enabled by using low-cost chromium(III) salt as a precatalyst, combined with trimethylsilyl chloride as an additive, and presents a rare example of catalytic transformation of secondary amides to ketones at room temperature. It was shown that catalytically active low-valent chromium species might be responsible for the amide ketone exchange by mechanism involving the Activation of benzimidate intermediate.Kumada Arylation of Secondary Amides Enabled by Chromium Catalysis for Unsymmetric Ketone Synthesis under Mild Conditionschromium; homogeneous catalysis; Kumada reaction; amides; ketonesx39201851#N/AFALSE
5092
acscatal.8b0133210.1021/acscatal.8b01332FALSEhttps://doi.org/10.1021/acscatal.8b01332Dou, SXActive-Site-Enriched Iron-Doped Nickel/Cobalt Hydroxide Nanosheets for Enhanced Oxygen Evolution Reactionx2018#N/AFALSE
5093
acscatal.8b0119010.1021/acscatal.8b01190https://doi.org/10.1021/acscatal.8b01190Altomare, MACS Catal.Photocatalytic H-2 evolution reactions on pristine TiO2 is characterized by low efficiencies that are due to trapping and recombination of charge carriers and due to a sluggish kinetics of electron transfer. Noble-metal (mainly Pt, Pd, Au) nanopartiCles are typically decorated as co-catalysts on the TiO2 surface to reach reasonable photocatalytic yields. However, because of the high cost of noble metals, alternative metal co-catalysts are being developed. Here, we introduce an approach to fabricate an efficient noble-metal-free photocatalytic platform for H-2 evolution based on alloyed NiCu co-catalytic nanopartiCles at the surface of anodic TiO2 nanotube arrays. NiCu bilayers are deposited onto the TiO2 nanotubes by plasma sputtering. A subsequent thermal treatment is carried out that leads to dewetting, that is, because of surface diffusion, the Ni- and Cu-sputtered layers simultaneously mix with each other while splitting into NiCu nanopartiCles at the nanotube surface. The approach allows for a full control over key features of the alloyed nanopartiCles, such as their composition, work function, and co-catalytic ability toward H-2 generation. Dewetted-alloyed co-catalytic nanopartiCles composed of equal Ni and Cu amounts not only are significantly more reactive than pure Ni or Cu nanopartiCles, but also lead to H-2 generation rates that can be comparable to those obtained by conventional noble-metal (Pt) decoration of TiO2 nanotube arrays.Templated Dewetting Alloying of NiCu Bilayers on TiO2 Nanotubes Enables Efficient Noble-Metal-Free Photocatalytic H-2 Evolutiondewetting TiO2 nanotube; Ni Cu alloy; photocatalysis; H-2 evolutionPhotocatalystx41201845#N/AFALSE
5094
acscatal.8b0204410.1021/acscatal.8b02044FALSEhttps://doi.org/10.1021/acscatal.8b02044Lu, TBACS Catal.Syngas (CO and H-2) is an essential raw material for producing various chemicals in industry. The reduction of CO2 in a water-containing system can serve as a more sustainable pathway to obtain syngas than the transformation of fossil fuels, while the modulation of the H-2/CO ratios is a challenge. Herein a nickel(II) tripodal complex is employed as a homogeneous electrocatalyst for CO, and H2O reduction. With this catalyst, selective CO formation with negligible H-2 evolution can be accomplished in the presence of 5.0 M H2O in N,N'-dimethylformamide (DMF). By further varying the applied potentials, the H-2/CO ratio can be delicately tuned. The catalyst is appreciably robust with a high turnover number of 1.9 x 10(6) in 1 day operation with negligible deActivation, which can be attributed to the redox innocence of the used ligand. Based on the results of electrochemistry and DFT calculation, the catalytic mechanism is proposed.Syngas Production with a Highly-Robust Nickel(II) Homogeneous Electrocatalyst in a Water-Containing Systemcarbon dioxide reduction; water reduction; syngas; mononuClear nickel complex; electrocatalysis; high stability; redox innocence22201862#N/ATRUE
5095
acscatal.8b0116410.1021/acscatal.8b01164FALSEhttps://doi.org/10.1021/acscatal.9b05092Jiang, QDesign of Dual-Modified MoS2 with Nanoporous Ni and Graphene as Efficient Catalysts for the Hydrogen Evolution Reactionx2018#N/AFALSE
5096
acscatal.8b0108810.1021/acscatal.8b01088https://doi.org/10.1021/acscatal.8b01088Li, YSACS Catal.Several nickel complexes bearing sterically bulky phosphino-phenolate ([P,O]) ligands were synthesized and explored as catalysts for olefin (co)polymerization. In the absence of an activator, the complexes showed very high catalytic activities (up to 10(7) g mol(Ni)(-1) h(-1)) for ethylene polymerization even at 90 degrees C or with the addition of a large amount of a polar additive (such as ethyl alcohol, diethyl ether, acetone, or even water), affording linear polymers with high molecular weights (up to 6.53 x 10(5)). In contrast, most of the previously reported nickel catalysts suffer from severe activity suppression at elevated temperature. It is rare that a catalyst has so many good performances simultaneously, inCluding high catalytic activity, good tolerance for polar groups, strong thermal stability, and yielding high molecular weight linear polyethylene. Most importantly, these bulky nickel complexes used in this study also effectively copolymerized ethylene with challenging polar Vinyl monomers, inCluding commercially available acrylates and an acrylamide. As we expected, introducing a bulky substituent group on the phosphorus atom of the complex was vital for enhanced catalytic activity and the formation of high molecular weight linear copolymers. Microstructure analyses revealed that the polar functional units were mainly incorporated into the polymer main chain and also located at the chain end with insertion percentages of up to 7.4 mol %. The bulky [P,O] neutral nickel complexes reported herein are promising alternatives to the well-established palladium catalysts for direct copolymerization of olefins with commercially available polar Vinyl comonomers.Robust Bulky [P,O] Neutral Nickel Catalysts for Copolymerization of Ethylene with Polar Vinyl Monomersneutral nickel catalyst; bulky substituent; ethylene polymerization; copolymerization; polar Vinyl monomerx79201879#N/AFALSE
5097
acscatal.8b0202210.1021/acscatal.8b02022FALSEhttps://doi.org/10.1021/acscatal.8b02022Schmidt, TJACS Catal.The correlation between ex situ electronic conductivity, oxygen vacancy content, flat-band potential (E-fb), and the oxygen evolution reaction (OER) activity for a wide range of perovskite compositions [La1-xSrxCoO3-delta series (with x = 0, 0.2, 0.4, 0.6, 0.8), LaMO3-delta series (M = Cr, Mn, Fe, Co, Ni), Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF), and PrBaCo2O6-delta (PBCO)] are investigated experimentally and theoretically. It is found that all of these parameters can affect the OER activity; however, none of them alone play a crucial role in determining the electrocatalytic activity. The correlation of one single physicochemical property with the OER activity always presents deviation points, indicating that a limitation does exist for such 2-dimensional correlations. Nevertheless, these deviations can be explained considering other physicochemical properties and their correlation with the OER activity. Hence, this work aims in simultaneously linking the OER activity with several physicochemical materials properties. The concept of the OER/multidescriptor relationship represents a significant advancement in the search and design of highly active oxygen evolution catalysts, in the quest for efficient anodes in water electrolyzers.Oxygen Evolution Reaction on Perovskites: A Multieffect Descriptor Study Combining Experimental and Theoretical Methodselectrolyzers; water splitting; oxides; catalysts; activity descriptors38201851#N/ATRUE
5098
acscatal.8b0104510.1021/acscatal.8b01045FALSEhttps://doi.org/10.1021/acscatal.8b01045Rothenberg, GACS Catal.Multidoped carbons are often used for oxygen Activation catalysis, both in heterogeneous catalysis and electrocatalysis. Identifying their catalytic sites is crucial for developing better catalysts. We now report an in-depth study into O-2 Activation on an important Class of materials: carbons codoped by nitrogen and 10 different metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Pb). To identify catalytic sites, we studied their composition and structure (both bulk and surface) by a wide range of techniques, inCluding temperature programmed reduction, X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, and N-2 sorption porosimetry. The O-2 Activation step was studied by electrochemical oxygen reduction. To assign active sites, the electrocatalytic activity, selectivity, and stability were correlated to material composition and to known reactivity pathways. Two types of sites for O-2 Activation were identified and assigned for each multidoped material: (1) partiCles of partially reduced metal oxides and (2) metal-nitrogen Clusters embedded into the carbon matrix. The detailed assignment correlates to activity in alcohol oxidation through similar volcano plots and leads to practical suggestions for catalyst development.Understanding Oxygen Activation on Metal- and Nitrogen-Codoped Carbon Catalystscarbon-based catalysts; tandem catalysis; oxygen Activation; metal oxides; active site; oxygen reduction reaction; temperature-programmed reduction; cooperative catalysisx192018127#N/AFALSE
5099
acscatal.8b0103910.1021/acscatal.8b01039FALSEhttps://doi.org/10.1021/acscatal.8b01039Marin, GBACS Catal.We report a MgFexAl2-xO4 synthetic spinel, where x varies from 0 to 0.26, as support for Ni-based catalysts, offering stability and carbon control under various conditions of methane reforming. By incorporation of Fe into a magnesium aluminate spine!, a support is created with redox functionality and high thermal stability, as conCluded from temporal analysis of products (TAP) experiments and redox cyCling, respectively. A diffusion coefficient of 3 x 10(-17) m(2) s(-1) was estimated for lattice oxygen at 993 K from TAP experiments. X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) modeling identified that the incorporation of iron occurs as Fe3+ in the octahedral sites of the spinel lattice, replacing aluminum. Simulation of the X-ray absorption near edge structure (XANES) spectrum of the reduced support showed that 60 +/- 10% of iron was reduced from 3+ to 2+ at 1073 K, while there was no formation of metallic iron. A series of Ni/MgFexAl2-xO4 catalysts, where x varies from 0 to 0.26, was synthesized and reduced, yielding a supported Ni-Fe alloy. The evolution of the catalyst structure during H-2 temperature-programmed reduction (TPR) and CO2 temperature-programmed oxidation (TPO) was examined using time-resolved in situ XRD and XANES. During reforming, iron in both the support and alloy keeps control of carbon accumulation, as confirmed by O-2-TPO on the spent catalysts. By fine tuning the amount of Fe in MgFexAl2-xO4, a supported alloy was obtained with a Ni/Fe molar ratio of similar to 10, which was active for reforming and stable. By comparison of the performance of Ni-based catalysts with Fe either incorporated into or deposited onto the support, the location of Fe within the support proved crucial for the stability and carbon mitigation under reforming conditions.Fe-Containing Magnesium Aluminate Support for Stability and Carbon Control during Methane Reformingsyngas; Ni-Fe alloy; carbon; synthetic spinel; lattice oxygen; redox propertiesx37201868#N/AFALSE
5100
acscatal.8b0102210.1021/acscatal.8b01022FALSEhttps://doi.org/10.1021/acscatal.8b01022Daasbjerg, KACS Catal.Earth-abundant transition metal (Fe, Co, or Ni) and nitrogen doped porous carbon electrocatalysts (M-N-C, where M denotes the metal) were synthesized from cheap precursors via silica-templated pyrolysis. The effect of the material composition and structure (i.e., porosity, nitrogen doping, metal identity, and oxygen functionalization) on the activity for the electrochemical CO2 reduction reaction (CO2RR) was investigated. The metal-free N-C exhibits a high selectivity but low activity for CO2RR Incorporation of the Fe and Ni, but not CO2 sites in the N-C material is able to significantly enhance the activity. The general selectivity order for CO2-to-CO conversion in water is found to be Ni > Fe >> Co with respect to the metal in M-N-C, while the activity follows Ni, Fe >> Co. Notably, the Ni-doped carbon exhibits a high selectivity with a faradaic efficiency of 93% for CO production. Tafel analysis shows a change of the rate-determining step as the metal overtakes the role of the nitrogen as the most active site. Recording the X-ray photoelectron spectra and extended X-ray absorption fine structure demonstrates that the metals are atomically dispersed in the carbon matrix, most likely coordinated to four nitrogen atoms and with carbon atoms serving as a second coordination shell. Presumably, the carbon atoms in the second coordination shell of the metal sites in M-N-C significantly affect the CO2RR activity because the opposite reactivity order is found for carbon supported metal meso-tetraphenylporphyrin complexes. From a better understanding of the relationship between the CO2RR activity and the material structure, it becomes possible to rationally design high-performance porous carbon electrocatalysts involving earth-abundant metals for CO2 valorization.Selective CO2 Reduction to CO in Water using Earth-Abundant Metal and Nitrogen-Doped Carbon ElectrocatalystsCO2 reduction; carbon; iron/cobalt/nickel doping; electrocatalysis; structure-activity relationshipx116201841#N/AFALSE
5101
acscatal.8b0097210.1021/acscatal.8b00972FALSEhttps://doi.org/10.1021/acscatal.8b00972Chang, SZACS Catal.Four chain-like hybrid compounds based on mixed Carbonylic acid ligands-modified polyoxomolybdates, K2H[(H2O)(4)M] [AsMo6O21(Ala) (PHBA)(2)]center dot nH(2)O 1-4 (M = Co, Ni, Zn, Mn; Ala = alanine; PHBA = p-hydroxybenzonic acid), were prepared and characterized by elemental analysis, IR spectroscopy, solid diffuse reflective spectroscopy, TG analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Four isostructural compounds 1-4 not only represent the extended architectures constructed from two different organic ligands-modified polyoxometalates but also can rapidly catalyze the degradation of two chemical warfare agent simulants, 2-chloroethyl ethyl sulfide (GEES) and diethyl cyanophosphonate (DECP), at room temperature. The catalytic results were analyzed and confirmed by GC-FID, GC-MS, and (HNMR)-H-1 techniques. Within 5 min, CEES was high-selectively oxidized to the corresponding nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) using heterogeneous catalyst 1 with the oxidant H2O2 (conversion % = 98.5%, selectivity % > 99.9%). FTIR, PXRD techniques, and the following cyCles also ascertained the stability and structural integrity of 1 in the oxidation reaction. Within 10 min, DECP can be almost entirely hydrolyzed to the nontoxic products catalyzed by 1 (conversion % = 99.0%). To our knowledge, they are in the rank of highly active catalysts for the degradation of CEES and DECP to date, accompanied by the advantages of steady reuse.Rapid Destruction of Two Types of Chemical Warfare Agent Simulants by Hybrid Polyoxomolybdates Modified by Carbonylic Acid Ligandshybrid polyoxomolybdates; Carbonylic acids; catalysis; chemical warfare agents; destructionx32201851#N/AFALSE
5102
acscatal.8b0187410.1021/acscatal.8b01874FALSEhttps://doi.org/10.1021/acscatal.8b01874Kotora, MACS Catal.Catalytic C-C bond Cleavage processes followed by further transformations are some of the most fascinating reactions in chemistry and valuable organic synthesis tools. Herein, we demonstrate that the regioselectivity of C-C bond Cleavage in 1-azabiphenylene and its derivatives can be switched by using neutral or cationic transition metal catalysts. The use of the former leads to selective distal C-C bond Cleavage (with respect to the position of the nitrogen atom), whereas use of the latter leads to selective proximal bond Cleavage. This process enables synthesis of a variety of complex heterocyCles by regioselective C-C bond Cleavage switched on demand. Density functional theory calculations (SMD/M06/DGDZVP level of theory) show that the regioselectivity is a result of kinetically controlled oxidative addition into the C-C bond. In neutral complexes the transition states (TS) for distal Cleavage have lower energy, in agreement with experiments. For the cationic catalyst, the proximal TSs are stabilized presumably by relieving the Cl-N dipole dipole repulsion when the Rh-bound Cl is removed whereas the distal TSs remain largely unaffected.Catalyst-Counterion Controlled, Regioselective C-C Bond Cleavage in 1-Azabiphenylene: Synthesis of Selectively Substituted BenzoisoquinolinesC-C Activation; catalytic cyCloaddition; alkynes; regioselective catalysis; iridium; rhodium8201847#N/ATRUE
5103
acscatal.8b0183910.1021/acscatal.8b01839FALSEhttps://doi.org/10.1021/acscatal.8b01839Li, CAmorphous Multi-elements Electrocatalysts with Tunable Bifunctionality toward Overall Water Splitting2018#N/ATRUE
5104
acscatal.8b0086710.1021/acscatal.8b00867FALSEhttps://doi.org/10.1021/acscatal.8b00867da Silva, RGACS Catal.Allosteric modulation of catalysis is a common regulatory strategy of flux-controlling biosynthetic enzymes. The enzyme ATP phosphoribosyltransferase (ATPPRT) catalyzes the first reaction in histidine biosynthesis, the magnesium-dependent condensation of ATP and 5-phospho-alpha-D-ribosyl-1-pyrophosphate (PRPP) to generate N-1-(5-phospho-beta-D-ribosyl)-ATP (PRATP) and pyrophosphate (PP,). ATPPRT is allosterically inhibited by the final product of the pathway, histidine. Hetero-octameric ATPPRT consists of four catalytic subunits (HisG(s)) and four regulatory subunits (HisZ) engaged in intricate catalytic regulation. HisZ enhances HisG(s) catalysis in the absence of histidine while mediating allosteric inhibition in its presence. Here we report HisGs structures for the apoenzyme and complexes with substrates (PRPP, PRPP-ATP, PRPP-ADP), product (PRATP), and inhibitor (AMP), along with ATPPRT holoenzyme structures in complexes with substrates (PRPP, PRPP-ATP, PRPP-ADP) and product (PRATP). These 10 crystal structures provide an atomic view of the catalytic cyCle and allosteric Activation of Psychrobacter arcticus ATPPRT. In both ternary complexes with PRPP-ATP, the adenine ring is found in an anticatalytic orientation, rotated 180 degrees from the catalytic rotamer. Arg32 interacts with phosphate groups of ATP and PRPP, bringing the substrates in proximity for catalysis. The negative charge repulsion is further attenuated by a magnesium ion sandwiched between the alpha- and beta-phosphate groups of both substrates. HisZ binding to form the hetero-octamer brings HisG(s) subunits Closer together in a tighter dimer in the Michaelis complex, which poises ArgS6 from the adjacent HisG(s) molecule for cross-subunit stabilization of the PPi leaving group at the transition state. The more electrostatically preorganized active site of the holoenzyme likely minimizes the reorganization energy required to accommodate the transition state. This provides a structural basis for allosteric Activation in which chemistry is accelerated by facilitating leaving group departure.Catalytic and Anticatalytic Snapshots of a Short-Form ATP PhosphoribosyltransferaseATP phosphoribosyltransferase; allostery; HisG; HisZ; psychrophilic; catalytic Activation; histidine biosynthesisx5201847#N/AFALSE
5105
acscatal.8b0083510.1021/acscatal.8b00835FALSEhttps://doi.org/10.1021/acscatal.8b00835Tan, YSACS Catal.In heterogeneous catalysis, reactive gases often accelerate the growth of catalytically active metal nanopartiCles (NPs) by the formation of volatile metal-molecule intermediates, leading to undesired catalyst deActivation. This gas-enhanced partiCle growth is usually described by Ostwald ripening, in which the volatile metal-molecule intermediates are assumed to be transported from small metal NPs to large metal NPs. In this contribution, we demonstrated the strong steric hindrance effect of the adsorbed CO molecules on the transport of Ni(CO)(4) molecules between the Ni NPs during the early stage of CO hydrogenation reaction. Extensive analysis of the growth behaviors of different-sized Ni NPs revealed a critical concentration for the Ni(CO)(4) decomposition on the surface of Ni NPs, which was confirmed by Born-Oppenheimer molecular dynamics (BOMD) simulations. By considering the existence of the critical concentration, the modified Ostwald ripening model successfully described the main features of partiCle growth observed experimentally. In addition, the Ni(CO)(4) decomposition rate was found to be accelerated by the formation of Ni3C phase, because of the weak steric hindrance effect of CO molecules on these surfaces. The role of the adsorbed molecules found herein may provide an important prospective for understanding the growth behaviors of highly dispersed metal NPs in the presence of reactant gases.Insight into the NanopartiCle Growth in Supported Ni Catalysts during the Early Stage of CO Hydrogenation Reaction: The Important Role of Adsorbed CO MoleculespartiCle growth; supported metal catalysts; adsorbate coverage; Ni(CO)(4) supersaturation; Ostwald ripeningx12201827#N/AFALSE
5106
acscatal.8b0174610.1021/acscatal.8b01746FALSEhttps://doi.org/10.1021/acscatal.8b01746Vohs, JMACS Catal.Hydrodeoxygenation (HDO) of m-cresol to produce toluene over carbon-supported Pt and Pt-WOx catalysts was studied. In stark contrast to Pt/C that exhibits only modest selectivity and low stability for this reaction, Pt-WOx/C was found to be unusually active and selective to toluene with greater than 94% selectivity to this product while exhibiting little to no deActivation under a wide range of reaction conditions. Reactivity studies in combination with density functional theory (DFT) calculations for the adsorption and reaction of m-cresol on structurally optimized WOx-decorated Pt(111) structures indicate that the HDO reaction on Pt-WOx/C proceeds via a direct hydrogenolysis of the C-O bond in m-cresol adsorbed on oxygen vacancy (or redox) sites on WOx species. The DFT results also indicate that Pt helps stabilize the WOx film while facilitating oxygen vacancy formation.Mechanistic Study of the Direct Hydrodeoxygenation of m-Cresol over WOx-Decorated Pt/C Catalystshydrodeoxygenation; Pt-WOx/C catalyst; m-cresol; toluene; density functional theory; lignin41201869#N/ATRUE
5107
acscatal.8b0080310.1021/acscatal.8b00803FALSEhttps://doi.org/10.1021/acscatal.8b00803Gagliardi, LACS Catal.We have recently reported the heterobimetallic nickel gallium complex, NiGaL (where L represents the tris(phosphinoamido)amine ligand, [N(o-(NCH(2)Pi-Pr-2,) C6H4)(3)](3-)), which is the most active Ni-based molecular catalyst for CO2 hydrogenation to date. Understanding the reaction mechanism of this catalytic system and identifying the factors that govern its catalytic activity are important in order to design even more efficient base metal catalysts. Here, we present a computational study of possible reaction pathways for CO, hydrogenation catalyzed by NiGaL. The most favorable predicted pathway for formate production agrees well with key experimental observations and is defined by four elementary steps: (1) H, binding to the Ni center, (2) deprotonation of the H, adduct, (3) hydride transfer to CO2 to form a formate adduct, and (4) formate release to regenerate NiGaL. The overall catalytic process has two main time periods: an induction period, during which the deprotonation of the H-2 adduct by exogenous base is predicted to be rate-limiting, followed by a subsequent period where the produced formate assists in deprotonation by acting as a proton shuttle between the H-2 adduct and exogenous base. The barrier for H-2 adduct deprotonation is governed predominantly by the steric hindrance associated with the exogenous base and is found to be dramatically lowered by formate assistance. Once sufficient formate has been generated, the catalysis enters the steady-state period, during which hydride transfer to CO2 is predicted to become rate-limiting once sufficient formate has been generated and the reaction rate remains constant until the base is nearly consumed. For hydride transfer to CO2 the free energy of Activation was found to depend linearly on the thermodynamic hydricity for a series of bimetallic HM1M2L-complexes, providing a simple and efficient strategy for screening other bimetallic catalysts. Furthermore, the relative binding energies of H-2 and formate were analyzed to predict the ability of the bimetallics to facilitate the catalytic turnover. The predicted trends and structure activity relationships arising from these computational calculations can be further utilized for the rational design of more efficient catalysts for CO2 hydrogenation and other hydride transfer processes for which reactive M-H species are generated in the presence of a Lewis base.Rationalizing the Reactivity of Bimetallic Molecular Catalysts for CO2 Hydrogenationbimetallic complexes; H-2 deprotonation; CO2 hydrogenation; basicity; steric hindrance; hydricityx20201879#N/AFALSE
5108
acscatal.8b0171510.1021/acscatal.8b01715FALSEhttps://doi.org/10.1021/acscatal.8b01715Qiao, SZACS Catal.The replacement of precious-metal-based catalysts with earth-abundant alternatives for a diverse range of electrochemical applications is of great importance for next-generation energy technologies. Many self-supported earth-abundant nanoarrays have emerged as state-of-the-art electrocatalysts due to their fascinating structures and electrochemical properties. This Review presents recent advances made toward developing self-supported earth-abundant nanoarrays for a wide range of energy-conversion processes. We summarize the different synthetic methods used to construct nanoarrays and tune their compositions, morphologies, and structures. Then, we highlight their application and performance as catalysts for various energy-related reactions. We also discuss their ability to perform as bifunctional electrocatalysts in energy devices. Finally, we conClude with the challenges and prospects in this promising field, where further exploration into these materials will facilitate the development of next-generation energy technologies.Self-Supported Earth-Abundant Nanoarrays as Efficient and Robust Electrocatalysts for Energy-Related Reactions1802018190#N/ATRUE
5109
acscatal.8b0171010.1021/acscatal.8b01710FALSEhttps://doi.org/10.1021/acscatal.9b04216Jiao, FRole of Surface Oxophilicity in Copper-Catalyzed Water Dissociation2018#N/ATRUE
5110
acscatal.8b0169210.1021/acscatal.8b01692FALSEhttps://doi.org/10.1021/acscatal.8b01692Wang, XACS Catal.To investigate the Le doping effect on the structure and reactivity of NiO, a series of NiO catalysts doped by Li+ cations have been synthesized and probed by using CO oxidation as a model reaction. With a combination of experimental methods and DFT calculations, it has been revealed that the Li+ cations preferentially replace the lattice Ni2+ cations instead of directly refilling the Ni2+ vacancies in the cubic NiO lattice to form a solid solution structure below the lattice capacity. For samples possessing a pure solid solution phase, the Ni3+ cation amount increases with the increasing of lattice Li+ cation content, hence inducing the formation of larger quantities of surface mobile oxygen species. In addition, the surface reducibility and the CO adsorption and Activation ability can be enhanced, accompanying the easier formation of surface oxygen vacancies and Therefore, the intrinsic CO oxidation activity can be remarkably enhanced. In contrast, oxygen. by the addition of excess Li+ cations above the lattice capacity, Li+ is present as an additional surface Li2CO3 phase, which evidently degrades the activity of the catalysts because of the loss of lattice Ni3+ cations and active oxygen sites. It is conCluded in this paper that the best catalyst can be tailored at the atomic level by engineering the maximum amount of Ni3+ cations in the NiO lattice matrix with a pure solid solution phase by Li+ addition.Engineering Ni3+ Cations in NiO Lattice at the Atomic Level by Li+ Doping: The Roles of Ni3+ and Oxygen Species for CO OxidationLi+ doping effect; Ni3+ amount; surface active oxygen; experimental; DFT calculations46201839#N/ATRUE
5111
acscatal.8b0065010.1021/acscatal.8b00650FALSEhttps://doi.org/10.1021/acscatal.8b00650Wang, YACS Catal.The oxidative dehydrogenation of propane is an attractive reaction for propylene production, but the over oxidation leads to low propylene selectivity at considerable propane conversions. Here, we report the oxidative dehydrogenation of propane by oxygen in the presence of hydrogen chloride. CeO2 was found to be an efficient catalyst for the conversion of propane to propylene by (O-2 + HCl). The reaction was structure-sensitive, and the catalytic behavior depended on the exposed facet of CeO2 nanocrystals. The nanorod exposing {110} and {100} facets showed the highest activity, whereas the nanocube enClosed by {100} facets was the most selective for propylene formation. The modification of CeO2 nanorods by NiO increased both propane conversion and propylene selectivity. A propylene selectivity of 80% was achieved at propane conversion of 69% over an 8 wt % NiO-CeO2 catalyst at 773 K, offering a single-pass propylene yield of 55%. No significant catalyst deActivation was observed in 100 h of reaction. HCl played a pivotal role in the selective formation of propylene, and more than 95% of HCl could be recovered after the reaction. The structure-property correlation indicates that the surface oxygen vacancy and the surface chloride coverage are two crucial factors determining the activity and selectivity. The mechanistic studies suggest that the peroxide species (O-2(2-)) formed by adsorption of O-2 on surface oxygen vacancies may activate chloride, generating a radical-like active chlorine species. The active chlorine species accounts for the Activation of C-H bond of propane, forming propylene as a major product.Oxidative Dehydrogenation of Propane to Propylene in the Presence of HCI Catalyzed by CeO2 and NiO-Modified CeO2 Nanocrystalspropane; oxidative dehydrogenation; propylene; hydrogen chloride; cerium oxide; nickel oxide; oxygen vacancy; surface chloride coveragex52201878#N/AFALSE
5112
acscatal.8b0157210.1021/acscatal.8b01572FALSENishikata, TRadical-Organometallic Hybrid Reaction System Enabling Couplings between Tertiary-Alkyl Groups and 1-Alkenyl Groups2018#N/ATRUE
5113
acscatal.8b0156710.1021/acscatal.8b01567FALSEhttps://doi.org/10.1021/acscatal.9b04128Pan, FTuning Electronic Push/Pull of Ni-Based Hydroxides To Enhance Hydrogen and Oxygen Evolution Reactions for Water Splitting2018#N/ATRUE
5114
acscatal.8b0147710.1021/acscatal.8b01477FALSEhttps://doi.org/10.1021/acscatal.8b01477Hensen, EJMHighly Active and Stable CH4 Oxidation by Substitution of Ce4+ by Two Pd2+ Ions in CeO2(111)2018#N/ATRUE
5115
acscatal.8b0055410.1021/acscatal.8b00554FALSEhttps://doi.org/10.1021/acscatal.8b00554Ye, MCACS Catal.A redox-neutral Ni-catalyzed intramolecular hydroArylation of alkene with simple arene has been developed, in which DMF played a proton shuttle role in facilitating the intramolecular coupling, avoiding the use of additional reductants and oxidants. A series of oxindoles with a quaternary center were obtained in up to 99% yield.DMF-Promoted Redox-Neutral Ni-Catalyzed Intramolecular HydroArylation of Alkene with Simple Arenenickel; redox-neutral; hydroArylation; alkene; arenex13201859#N/AFALSE
5116
acscatal.8b0117210.1021/acscatal.8b01172FALSEhttps://doi.org/10.1021/acscatal.8b01172Kundu, SACS Catal.Copper and its oxides are among the best electrocatalysts for the electrochemical conversion of CO2 to value-added small organics because of its high hydrogen overvoltage, making the hydrogen evolution reaction (HER) a poor side reaction. Here we report an interesting finding that turned the nature of surface-oxidized Cu upside down in electrochemical H-2 evolution. It is commonly known that the electrochemical reactivity of a metal ion is highly sensitive to the anion to which it is coordinated in the electrolyte. In the case of Cu, when it is in the form of copper oxide, the hydrogen overvoltage is huge. Nonetheless, we found that when Cu is in coordination with Se2- ions as Cu2Se, the hydrogen overvoltage was shrunken by similar to 1 V, imparting ultralow charge transfer resistance (R-CT) that varied from 0.32 to 0.61 Omega depending on the means by which selenization was carried out. Selenization was done by two different methods. In one method, conventional stirring was employed to selenize Cu foam in a preheated NaHSe solution at 90 degrees C for 20 min. In another method, hydrothermal treatment was employed to selenize Cu foam with NaHSe solution at 120 degrees C for 1 h. The wet chemical method yielded honeycomb-like hierarchical arrays of Cu2Se sheets on Cu foam (designated as Cu2Se-ch/Cu), and the hydrothermal method yielded a uniform array of spiky rods of Cu2Se (designated as Cu2Se-ht/Cu). The HER electrocatalytic studies carried out in 0.5 M H2SO4 showed that Cu2Se-ch/Cu and Cu2Se-ht/Cu had similar kinetics, with Tafel slopes of 32 to 35 mV dec(-1), which is Closer to the state-of-the-art Pt/C. Interestingly, the Cu2Se-ch/Cu delivered a total kinetic current density of -1200 mA cm(-2) when polarized up to -0.85 V vs RHE, whereas Cu2Se-ht/Cu delivered a maximum of -780 mA cm(-2) only.Shrinking the Hydrogen Overpotential of Cu by 1 V and Imparting Ultralow Charge Transfer Resistance for Enhanced H-2 Evolutioncopper selenide; hydrogen overvoltage; hydrogen evolution reaction; water electrolysis; voltammetry; selenization24201869#N/ATRUE
5117
acscatal.8b0107610.1021/acscatal.8b01076FALSEhttps://doi.org/10.1021/acscatal.8b01076Yang, HGACS Catal.Developing efficient, low-cost, and biocompatible electrocatalysts toward hydrogen evolution reaction (HER) in neutral environments is vital to the development of a hybrid water splitting biosynthetic system to achieve high-efficiency solar-to-fuels conversion. We report here a strategy to improve the sluggish HER kinetics on 3d transition metal hydroxides by incorporating tungsten through a one-step electrodeposition method. The prepared amorphous CoW-(OH)(x) delivers high HER activity in neutral solution, which only requires overpotentials of -73.6 and -114.9 mV to achieve the current densities of -10 and -20 mA cm(-2) in 1.0 M phosphate buffer solution (PBS), respectively. The activity can be ascribed to the synergistic effects between Co and W, where Co sites facilitate H2O dissociation to generate H-ad intermediates and W sites could effectively convert H-ad to H-2. Meanwhile, the amorphous architecture features homogeneously dispersed Co and W atoms that avoid crystalline phase separation, further strengthening their collaborative interactions. Similar enhanced HER activity is also observed on the electrodeposited NiW(OH)(x) electrocatalyst, suggesting the universality of this strategy for accelerating HER in neutral environments.Accelerating Neutral Hydrogen Evolution with Tungsten Modulated Amorphous Metal Hydroxidestransition-metal hydroxides; tungsten modulation; amorphous; electrodeposition; neutral hydrogen evolution reaction39201834#N/ATRUE
5118
acscatal.8b0094910.1021/acscatal.8b00949FALSEhttps://doi.org/10.1021/acscatal.8b00949Wang, PACS Catal.The design and synthesis of high-performance hydrogen evolution reaction (HER) catalysts requires an overall consideration of intrinsic activity and number of active sites as well as electric conductivity. We herein report a facile synthesis of a cost-effective catalyst that can simultaneously address these key issues. A cobalt molybdenum oxide hydrate (CoMoO4 center dot nH(2)O) with a 3D hierarchical nanostructure can be readily grown on nickel foam using a hydrothermal method. Calcination treatment of this precursor material under a reductive atmosphere resulted in the formation of Co nanopartiCles on the Co2Mo3O8 surface, which worked in concert to act as active sites for the HER. In addition, the resulting Co2Mo3O8 from the dehydration and reduction reactions of CoMoO4 center dot nH(2)O showed remarkable increases in both active surface area and electrical conductivity. As a consequence of these favorable attributes, the catalyst exhibited electrocatalytic performance comparable to that of the commercial Pt/C catalyst for the HER in alkaline solution, which is promising for practical water-splitting applications.Cobalt Molybdenum Oxide Derived High-Performance Electrocatalyst for the Hydrogen Evolution Reactionelectrocatalysis; hydrogen evolution reaction; electroconductibility; intrinsic activity; nanostructure61201851#N/ATRUE
5119
acscatal.8b0015410.1021/acscatal.8b00154FALSEhttps://doi.org/10.1021/acscatal.8b00154Peng, ZMACS Catal.Carbon monoxide preferential oxidation (PROX) in an H-2-rich stream represents one promising H-2 purification technology but requires the development of active and selective catalysts to make the technology viable. We conducted density functional theory simulations of CO PROX catalysis on model Pt alloy systems to establish correlations between the catalyst parameters and the catalytic properties, which validated E-A,E-COOR and E-A,E-HOR as descriptors for CO oxidation and H-2 oxidation kinetics, Delta E-A as a descriptor for CO PROX selectivity, and epsilon(d) as a catalyst parameter descriptor for the Activation energy barriers. We discovered an interesting compromising relationship between the CO PROX activity and selectivity properties. Pt-Ni and Pt-Mn nanopartiCle catalysts were selected for synthesis on the basis of the computational data and tested for their properties, which matched well with the DFT calculations and verified the effectiveness of the computational findings. The use of computation-guided methods and the discovered catalyst parameter property relationships would establish a rational strategy to aid catalyst development and foster CO PROX research.Computation-Guided Development of Platinum Alloy Catalyst for Carbon Monoxide Preferential Oxidationcomputation-guided catalyst design; platinum; bimetallic catalysts; carbon monoxide; PROXx12201858#N/AFALSE
5120
acscatal.8b0006710.1021/acscatal.8b00067https://doi.org/10.1021/acscatal.8b00067Lopez, NACS Catal.Efficient lignin depolymerization is crucial for achieving a positive economical return in biorefineries. However, because of the complex cross-polymerized network formed by the aromatic lignols, catalysts that can work at low temperatures perform insufficiently in terms of both activity and selectivity. Recently, Ni-based catalysts have been reported to exhibit a superior catalytic behavior in lignin valorization, but the mechanism of the depolymerization remains unClear. In this study, we employed density functional theory to investigate lignin decomposition on pure and Ru-doped Ni(111) surfaces to unravel the key issues that limit performance. The reaction network was screened by using complex coniferyl dimer models containing different stereocenters to simulate the most abundant beta-O-4 linkages in lignin, thus presenting a better representation of the complexity of the parent compound. Our results show that on nickel, both adsorption geometries and the preferred reaction paths are different depending on the chirality of the dimer reactants. In addition, the rigidity of the beta-O-4 link is also responsible for the reactivity found. Finally, the presence of small amounts of Ru on the surface simplifies the reaction as they act as preferential points for beta-O-4 bond Cleavage via the weakened C-O bond that is induced by increasing metal-O bond strength.Chirality, Rigidity, and Conjugation: A First-Principles Study of the Key Molecular Aspects of Lignin Depolymerization on Ni-Based Catalystslignin; DFT; beta-O-4; chirality; rigidity; conjugation; Ni; Rux13201852#N/AFALSE
5121
acscatal.8b0001710.1021/acscatal.8b00017FALSEhttps://doi.org/10.1021/acscatal.8b00017Mhin, SACS Catal.The electrocatalytic performance of transition metal sulfide (TMS) graphene composites has been simply regarded as the results of high conductivity and the large surface/volume ratio. However, unavoidable factors such as degree of oxidation of TMSs have been hardly considered for the origin of this catalytic activity of TMS-graphene composites. To accomplish the reliable application of TMS-based electrocatalytic materials, a Clear understanding of the thermodynamic stability of TMS and effects of oxidation on catalytic activity is necessary. In addition, the mechanism of charge transfer at the TMS-graphene interface must be studied in depth to properly design composite materials. Herein, we report a comprehensive study of the physical chemistry at the junction of a Co1-xNixS2-graphene composite, which is a prototype designed to unravel the mechanisms of charge transfer between TMS and graphene. Specifically, the thermodynamic stability and the effects of oxidation of TMSs during the oxygen evolution reaction (OER) on the reaction mechanism are systematically investigated using density functional theory (DFT) calculations and experimental observations. Cobalt atoms anchored on pyridinic N sites in the graphene support form metal semiconductor (SC) junctions, and the internal band bending at these junctions facilitates electron transfer from TMSs to graphene. The junction enables fast sinking of the excess electron from OH- adsorbate. Partially oxidized amorphous TMS layers formed during the OER can facilitate adsorption and desorption of OH and H atoms, boosting the OER performance of TMS graphene nanocomposites. From the DFT calculations, the enhanced electrocatalytic activity of TMS graphene nanocomposites originates from two important factors: (i) increased internal band bending and (ii) parallelized OER pathways at the interface of pristine and oxidized TMSs.Parallelized Reaction Pathway and Stronger Internal Band Bending by Partial Oxidation of Metal Sulfide-Graphene Composites: Important Factors of Synergistic Oxygen Evolution Reaction Enhancementaerogel; cobalt nickel sulfide; graphene; water splittingx58201853#N/AFALSE
5122
acscatal.7b0446610.1021/acscatal.7b04466FALSEhttps://doi.org/10.1021/acscatal.7b04466Dismukes, GCClimbing the Volcano of Electrocatalytic Activity while Avoiding Catalyst Corrosion: Ni3P, a Hydrogen Evolution Electrocatalyst Stable in Both Acid and Alkali
Electrocatalytic
2018#N/AFALSE
5123
acscatal.8b0088110.1021/acscatal.8b00881FALSEhttps://doi.org/10.1021/acscatal.8b00881Stamatakis, MACS Catal.Doping isolated single atoms of a platinum-group metal into the surface of a noble-metal host is sufficient to dramatically improve the activity of the unreactive host yet also facilitates the retention of the hosts high reaction selectivity in numerous catalytic reactions. The atomically dispersed highly active sites in these single-atom alloy (SAA) materials are capable of performing facile bond Activations allowing for the uptake of species onto the surface and the subsequent spillover of adspecies onto the noble host material, where selective catalysis can be performed. For example, SAAs have been shown to activate C-H bonds at low temperatures without coke formation, as well as selectively hydrogenate unsaturated hydrocarbons with excellent activity. However, to date, only a small subset of SAAs has been synthesized experimentally and it is unClear which metallic combinations may best catalyze which chemical reactions. To shed light on this issue, we have performed a widespread screening study using density functional theory to elucidate the fundamental adsorptive and catalytic properties of 12 SAAs (Ni-, Pd-, Pt-, and Rh-doped Cu(111), Ag(111), and Au(111)). We considered the interaction of these SAAs with a variety of adsorbates often found in catalysis and computed reaction mechanisms for the Activation of several catalytically relevant species (H-2, CH4, NH3, CH3OH, and CO2) by SAAs. Finally, we discuss the applicability of thermochemical linear scaling and the Bronsted-Evans-Polanyi relationship to SAA systems, demonstrating that SAAs combine weak binding with low Activation energies to give enhanced catalytic behavior over their monometallic counterparts. This work will ultimately facilitate the discovery and development of SAAs, serving as a guide to experimentalists and theoreticians alike.Elucidating the Stability and Reactivity of Surface Intermediates on Single-Atom Alloy Catalystssingle-atom alloy; catalyst screening linear scaling; Bransted-Evans-Polanyi relation; bond Activation68201869#N/ATRUE
5124
acscatal.7b0438610.1021/acscatal.7b04386https://doi.org/10.1021/acscatal.7b04386Grave, DAACS Catal.Transparent Fe1-xNixOOH overlayers (similar to 2 nm thick) were deposited photoelectrochemically on (001) oriented heteroepitaxial Sn- and Zn-doped hematite (alpha-Fe2O3) thin film photoanodes. In both cases, the water photo-oxidation performance was improved by the cocatalyst overlayers. Intensity modulated photocurrent spectroscopy (IMPS) was applied to study the changes in the hole current and recombination current induced by the overlayers. For the Sn-doped hematite photoanode, the improvement in performance after deposition of the Fe1-xNixOOH overlayer was entirely due to reduction in the recombination current, leading to a cathodic shift in the onset potential. For the Zn-doped hematite photoanode, in addition to a reduction in recombination current, an increase in the hole current to the surface was also observed after the overlayer deposition, leading to a cathodic shift in the onset potential as well as an enhancement in the plateau photocurrent. These results demonstrate that Fe1-xNixOOH cocatalysts can play different roles depending on the underlying hematite photoanode. The effect of the cocatalyst is not always limited to changes in the surface properties but may also cause an increase in hole current from the bulk to the surface that indicates a possible cross-link between surface and bulk processes.Different Roles of Fe1-xNixOOH Cocatalyst on Hematite (alpha-Fe2O3) Photoanodes with Different DopantsPhotocatalyst36201838#N/AFALSE
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acscatal.8b0082010.1021/acscatal.8b00820FALSEhttps://doi.org/10.1021/acscatal.8b00820Mullins, CBACS Catal.InCluded among the many challenges regarding renewable energy technology are improved electrocatalysts for the oxygen evolution reaction (OER). In this study, we report a novel bifunctional electrocatalyst based on a highly dense CoOx catalyst by introducing CeOx The CoOx catalyst is fabricated by two-step electrodeposition, inCluding Co seed formation, to obtain a very dense, layered structure, and CeOx is also successfully deposited on the CoOx catalyst. CoOx is an active catalyst showing good activity (eta = 0.331 V at 10 mA cm(-2)) and also stability for the OER. Higher activity is observed with the CeOx/CoOx electrocatalyst (eta = 0.313 V at 10 mA cm(-2)). From mechanistic studies conducted with synchrotron-based photoemission electron spectroscopy and DFT calculations, Ce promotes a synergistic effect by perturbing the electronic structure of surface Co species (facile formation to CoOOH) on the CoOx catalyst and optimizes the binding energy of intermediate oxygenated adsorbates.Enhanced Activity Promoted by CeOx on a CoOx Electrocatalyst for the Oxygen Evolution Reactioncobalt; cerium; electrocatalyst; oxygen evolution reaction; synchrotron66201856#N/ATRUE
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acscatal.7b0430810.1021/acscatal.7b04308https://doi.org/10.1021/acscatal.7b04308Armstrong, FAACS Catal.Selective, visible-light-driven conversion of CO2 to CO with a turnover frequency of 20 s(-1) under visible light irradiation at 25 degrees C is catalyzed by an aqueous colloidal system comprising a pseudoternary complex formed among carbon monoxide dehydrogenase (CODH), silver nanoClusters stabilized by polymethacrylic acid (AgNCs-PMAA), and TiO2 nanopartiCles. The photocatalytic assembly, which is stable over several hours and for at least 250000 turnovers of the enzyme's active site, was investigated by separate electrochemical (dark) and fluorescence measurements to establish specific connectivities among the components. The data show (a) that a coating of AgNCs-PMAA on TiO2 greatly enhances its ability as an electrode for CODH-based electrocatalysis of CO2 reduction and (b) that the individual Ag nanoClusters interact directly and dynamically with the enzyme surface, most likely at exposed cysteine thiols. The results lead to a model for photocatalysis in which the AgNCs act as photosensitizers, CODH captures the excited electrons for catalysis, and TiO2 mediates hole transfer from the AgNC valence band to sacrificial electron donors. The results greatly increase the benchmark for reversible CO2 reduction under ambient conditions and demonstrate that, with such efficient catalysts, the limiting factor is the supply of photogenerated electrons.Fast and Selective Photoreduction of CO2 to CO Catalyzed by a Complex of Carbon Monoxide Dehydrogenase, TiO2, and Ag NanoClustersPhotocatalyst36201846#N/AFALSE
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acscatal.7b0429410.1021/acscatal.7b04294FALSEhttps://doi.org/10.1021/acscatal.7b04294Stradiotto, MACS Catal.With stricter ecological regulation and reduction of fossil feedstock, the research works have been oriented to renewable resources. Various bio-based molecules have been proposed for replacing the platform chemicals based on crude oil, but there are not yet well-established processes for producing these chemicals at large scale. As a result, in the short to midterm, a main impact will be expected from the production of bio-based bulk chemicals having identical structures as today's bulk chemicals, inCluding ethylene, which is a key intermediate for the production of platform molecules. The commercial method for producing ethylene is based on steam thermal cracking, but emerging methods using alternative sources (natural gas, coal, biomass) are very promising processes. For example, the high-volume production of ethylene by ethanol dehydration has become an economically feasible application. This perspective summarizes the advances in catalysts, processes, and fundamental understanding of reaction mechanisms in ethylene conversion to other high-value hydrocarbons, inCluding propylene, butenes, and BTX aromatics.Toward Platform Chemicals from Bio-Based Ethylene: Heterogeneous Catalysts and Processesethylene; ethanol; propylene; butene; aromatics; dimerization; metathesis; heterogeneous catalysisx402018169#N/AFALSE
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acscatal.7b0422610.1021/acscatal.7b04226FALSEhttps://doi.org/10.1021/acscatal.7b04226Shen, PKMo- and Fe-Modified Ni(OH)(2)/NiOOH Nanosheets as Highly Active and Stable Electrocatalysts for Oxygen Evolution Reactionx2018#N/AFALSE
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acscatal.8b0070610.1021/acscatal.8b00706FALSEhttps://doi.org/10.1021/acscatal.8b00706Frenkel, AIACS Catal.Alloy nanopartiCle catalysts are known to afford unique activities that can differ markedly from their parent metals, but there remains a generally limited understanding of the nature of their atomic (and likely dynamic) structures as exist in heterogeneously supported forms under reaction conditions. Notably unClear is the nature of their active sites and the details of the varying oxidation states and atomic arrangements of the catalytic components during chemical reactions. In this work, we describe multimodal methods that provide a quantitative characterization of the complex heterogeneity present in the chemical and electronic speciations of Pt-Ni bimetallic catalysts supported on mesoporous silica during the reverse water gas shift reaction. The analytical protocols involved a correlated use of in situ X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), complimented by ex-situ aberration corrected Scanning Transmission Electron Microscopy (STEM). The data reveal that complex reactions occur between the metals and support in this system under operando conditions. These reactions, and the specific impacts of strong metal-silica bonding interactions, prevent the formation of alloy phases containing Ni-Ni bonds. This feature of structure provides high activity and selectivity for the reduction of CO2 to carbon monoxide without significant competitive levels of methanation. We show how these chemistries evolve to the active state of the catalyst: bimetallic nanopartiCles possessing an intermetallic structure (the active phase) that are conjoined with Ni-rich, metal-silicate species.Identifying Dynamic Structural Changes of Active Sites in Pt-Ni Bimetallic Catalysts Using Multimodal Approachesbimetallic nanopartiCles; catalysis; platinum; nickel; reverse water gas shift; STEM; XAS; DRIFTS29201865#N/ATRUE
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acscatal.8b0068910.1021/acscatal.8b00689FALSEhttps://doi.org/10.1021/acscatal.8b00689Dekel, DRACS Catal.In the past 5 years, advances in anion conductive membranes have opened the door for the development of advanced anion-exchange membrane fuel cells (AEMFCs) as the next generation of affordable fuel cells. Several recent works have shown that AEMFCs currently achieve nearly identical beginning-of-life performance as state-of-the-art proton exchange membrane fuel cells. However, until now, these high AEMFC performances have been reached with platinum-group metal (PGM)-based anode and cathode catalysts. In order to fulfill the potential of AEMFCs, such catalysts should in the near future be free of PGMs and, eventually, free of critical raw materials. Although great progress has been achieved in the development of PGM-free catalysts for the oxygen reduction reaction in basic media, significantly less attention has been paid to the catalysis of the hydrogen oxidation reaction (HOR). The much lower HOR activity of Pt in basic media compared with that in acid was itself revealed only relatively recently. While several PGM-based composite materials have shown improved HOR activity in basic media, the HOR kinetics remains slower than necessary for an ideal nonpolarizable electrode. In addition, attempts to move away from PGMs have hitherto resulted in high anode overpotentials, significantly reducing the performance of PGM-free AEMFCs. This would be a major barrier for the large-scale deployment of this technology once the other technological hurdles (e.g., membrane stability) have been overcome. A fundamental understanding of the HOR mechanism in basic media and of the main energy barriers needs to be firmly established to overcome this challenge. This review presents the current understanding of the HOR electrocatalysis in basic media and critically discusses the most recent material approaches. Promising future research directions in the development of the HOR electrocatalysts for alkaline electrolytes are also outlined.Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolyteshydrogen oxidation reaction; anion exchange membrane fuel cell; alkaline media; electrocatalyst; platinum-group metal; non-noble1302018168#N/ATRUE
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acscatal.8b0066310.1021/acscatal.8b00663FALSEhttps://doi.org/10.1021/acscatal.8b00663Hulea, VACS Catal.In this study, we report that ethylene can be simultaneously and selectively converted into propylene and 1-butene through one-pot catalytic cascade reactions. In a single continuous-flow reactor and under identical mild conditions (60 degrees C, 3 MPa), without the use of cocatalyst, ethylene was first dimerized/isomerized over Ni-AlKIT-6 catalysts to form butenes, which reacted then with the excess of ethylene over ReOx/Al2O3 to produce propylene and 1-butene with more than 86% total selectivity. The selectivity for 1-butene was 97.4% in the C-4 fraction. The initial ethylene conversion was 73% and stabilized at 35% after 4 h on stream, with around 45% selectivity in propylene and 42% selectivity in 1-butene.Selective Production of Propylene and 1-Butene from Ethylene by Catalytic Cascade Reactionsheterogeneous catalysis; oligomerization; metathesis; ethylene; propylene; 1-butene14201841#N/ATRUE
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acscatal.8b0061910.1021/acscatal.8b00619FALSEhttps://doi.org/10.1021/acscatal.8b00619Sels, BFCatalytic Reductive Aminolysis of Reducing Sugars: Elucidation of Reaction Mechanism2018#N/ATRUE
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acscatal.8b0058410.1021/acscatal.8b00584FALSEhttps://doi.org/10.1021/acscatal.8b00584Hu, CWACS Catal.The activity of a ZrO2-supported nickel catalyst promoted by silica (Ni-Si/ZrO2) in CO2 dry reforming of methane was carried out at 400 and 450 degrees C. The catalysts were prepared by an impregnation method and characterized by H-2-TPR, XRD, TEM, TG-MS, Raman, XPS, and in situ XPS and DRIFTS. It was discovered that Ni-Si/ZrO2 showed higher initial conversion of CH4 (0.50 s(-1)) and CO2 (0.44 s(-1)), and stability for low temperature (400 degrees C) DRM reaction in comparison to an SiO2-supported nickel catalyst promoted by zirconia (Ni-Zr/SiO2) (0.32 s(-1) for both CO2 and CH4). The Ni-Si/ZrO2 catalyst featured the formation of active nickel partiCles with a small size of 6-9 nm and with slightly strong electronic donor ability, stabilization of the initial metal nickel state under the reaction conditions, and the formation of easily removed C-1 coke. However, for the 450 degrees C DRM reaction, the coke that formed on the Ni-Si/ZrO2 catalyst was mainly C-2 coke that was difficult to remove, because the CO2 preferred to combine with H species rather than react with the coke. For the Ni-Zr/SiO2 catalyst, the Ni species was oxidized to a NiO species under the reaction conditions at 400 degrees C and could not be restored, leading to its deActivation.Low-Temperature Catalytic CO2 Dry Reforming of Methane on Ni-Si/ZrO2 CatalystNi-based catalysts; low temperature; zirconium; methane; CO289201863#N/ATRUE
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acscatal.7b0396410.1021/acscatal.7b03964FALSEhttps://doi.org/10.1021/acscatal.7b03964Liu, BACS Catal.In traditional steam reforming of CH4, the CH4 conversion and its selectivity to CO and H-2 are thermodynamically limited. In this work, we designed a series of Ni Fe redox catalysts with varying Ni/Fe ratios. The Ni Fe redox catalysts could function as oxygen carriers to selectively convert CH4 to syngas via chemical looping. The selectivity to CO was dramatically enhanced via a selective conversion route of CH4 to C and H-2 in the reduction, followed by C gasification to syngas with hot steam. Taking the advantages of the highly reactive Ni species for CH4 Activation and Fe species for water splitting, together with the resulting NiFe alloy in the reduced catalyst for catalytic CH4 decomposition, high CH4 conversion up to 97.5% and CO selectivity up to 92.9% were achieved at 900 degrees C with productivity of CO and H-2 of 9.6 and 29.0 mol kg(catalyst)(-1), respectively, on equimolar Ni-Fe catalyst.High-Performance Ni-Fe Redox Catalysts for Selective CH4 to Syngas Conversion via Chemical LoopingNi-Fe redox catalyst; chemical looping; steam reforming of methane; carbon deposition; syngas productionx29201829#N/AFALSE
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acscatal.8b0057410.1021/acscatal.8b00574FALSEhttps://doi.org/10.1021/acscatal.8b00574Pentcheva, RACS Catal.Using density functional theory calculations with an on-site Hubbard term (DFT+U), we explore the effect of surface termination and cation substitution on the performance of the CoxNi1-xFe2O4(001) surface (x = 0.0, 0.5, 1.0) as an anode material in the oxygen evolution reaction (OER). Different reaction sites (Fe, Co, Ni, and an oxygen vacancy) were investigated at three terminations: the B-layer with octahedrally coordinated Co/Ni and with an additional half and full monolayer of Fe (0.5A and A-layer, respectively). Ni substitution with an equal concentration of Co and Ni (x = 0.5) reduces the overpotential over the end members for the majority of reaction sites. Surface Co cations are identified as the active sites and the ones at the A-layer termination for x = 0.5 exhibit one of the lowest theoretically reported overpotentials of 0.26 V. The effect of the additional iron layer on the active site modification is 2-fold: analysis of the electronic properties and spin densities indicates that the additional Fe layer stabilizes a bulk-like oxidation state of +2 for Co and Ni at the A-layer termination, whereas at the B-layer termination, they are oxidized to 3+. Moreover, the unusual relaxation pattern enables the formation of a hydrogen bond of the OOH intermediate to a neighboring surface oxygen that lowers the reaction free energy of this formerly rate-limiting step, leading to a deviation from the scaling relationship and almost equidistant reaction free-energy steps of intermediates. This renders an example of how a selective surface modification can result in a significant improvement of OER performance.Surface Termination and Composition Control of Activity of the CoxNi1-xFe2O4 Surface for Water Oxidation: Insights from DFT plus U Calculationsoxygen evolution reaction; water splitting; transition metal oxides; spinels; density functional theory26201878#N/ATRUE
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acscatal.7b0381710.1021/acscatal.7b03817FALSEhttps://doi.org/10.1021/acscatal.7b03817Kolen'ko, YVACS Catal.We report a simple low-cost concept for the preparation of water-oxidation electrocatalyst via modification of self-supported Ni5P4-Ni2P foam catalyst precursor with Al. As an anode for alkaline oxygen evolution reaction, this material exhibits an impressive Tafel slope of 27 mV dec(-1) and offers anodic current densities of 10, 100, and 300 mA cm(-2) at overpotentials of merely 180, 247, and 312 mV, respectively. Moreover, the anode demonstrates high operational stability, as reflected by a steady-state performance for more than 8 days. Combining state-of-the-art electron microscopy and photoelectron spectroscopy, we investigated the role of the Al dopant in the formation of active Ni(OH)(2)/NiO/Ni5P4-Ni2P nanocatalyst, which exhibits oxygen-evolving activity among the highest reported to date.Al-Induced In Situ Formation of Highly Active Nanostructured Water-Oxidation Electrocatalyst Based on Ni-PhosphideOER; sacrificial Al; nickel phosphide; in situ catalyst formation; PGM-free catalystx48201837#N/AFALSE
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acscatal.8b0054610.1021/acscatal.8b00546FALSEhttps://doi.org/10.1021/acscatal.8b00546Mercado, BQACS Catal.In this work, Ni(I) Aryl species that are directly relevant to cross-coupling have been synthesized. Transmetalation of (dppf)(NiX)-X-I (dppf = 1,1'-bis(diphenylphosphino)-ferrocene, X = Cl, Br) with Aryl Grignard reagents or Aryl boronic acids in the presence of base produces Fe Ni(I) Aryl species of the form (dppf)Ni-I(Ar) (Ar = Ph, o-tolyl, 2,6-xylyl, 2,4,6-mesityl, 2,4,6-(Pr3C6H2)-Pr-i). The stability of the Ni(I) Aryl species is inversely correlated to the steric bulk on the Aryl ligand. The most unstable Ni(I) Aryl species are the most active precatalysts for Suzuki-Miyaura reactions because they rapidly decompose to generate the active Ni(0) catalyst. This study shows that Ni(I) Aryl species are initially formed in the Activation of Ni(I) halide precatalysts for Suzuki-Miyaura reactions and establishes their stoichiometric and catalytic reactivity profile.Nickel(I) Aryl Species: Synthesis, Properties, and Catalytic Activitynickel; cross-coupling; mechanism; homogeneous catalysis; inorganic synthesis34201873#N/ATRUE
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acscatal.7b0379510.1021/acscatal.7b03795FALSEhttps://doi.org/10.1021/acscatal.7b03795Wang, TFACS Catal.Highly dispersed NiCo bimetallic alloy nanopartides have been successfully immobilized on the SiO2 frameworks by using heteronuClear metal organic frameworks (MOFs) as metal alloy precursors. Catalyst characterizations revealed that the average size of NiCo alloy partiCles was less than 1 nm, with a total metal loading of about 20 wt %. As compared to individual Ni or Co MOF-derived catalysts and the catalysts prepared by the conventional impregnation method, the ultrafine NiCo/SiO2-MOF catalyst showed a much better catalytic performance in the catalytic hydrogenation of furfuryl alcohol (FA) to tetrahydrofurfuryl alcohol (THFA) under mild conditions, giving 99.8% conversion of FA and 99.1% selectivity to THFA. It was found that a significant synergistic effect existed between Co and Ni within the subnanometer NiCo/SiO2-MOF catalyst, which was 2 and 20 times more active than Ni/SiO2-MOF and Co/SiO2-MOF, respectively.Supported Ultrafine NiCo Bimetallic Alloy NanopartiCles Derived from Bimetal-Organic Frameworks: A Highly Active Catalyst for Furfuryl Alcohol HydrogenationNiCo bimetallic catalyst; subnanometer; metal-organic framework; furfuryl alcohol; hydrogenation; tetrahydrofurfuryl alcoholx80201841#N/AFALSE
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acscatal.7b0378710.1021/acscatal.7b03787FALSEhttps://doi.org/10.1021/acscatal.7b03787Pivovar, BSACS Catal.Iridium-nickel (Ir-Ni) and iridium-cobalt (Ir-Co) nanowires have been synthesized by galvanic displacement and studied for their potential to increase the performance and durability of electrolysis systems. Performances of Ir-Ni and Ir-Co nanowires for the oxygen evolution reaction (OER) have been measured in rotating disk electrode half-cells and single-cell electrolyzers and compared with commercial baselines and literature references. The nanowire catalysts showed improved mass activity, by more than an order of magnitude compared with commercial Ir nanopartiCles in half-cell tests. The nanowire catalysts also showed greatly improved durability, when acid leached to remove excess Ni and Co. Both Ni and Co templates were found to have similarly positive impacts, although specific differences between the two systems are revealed. In single-cell electrolysis testing, nanowires exceeded the performance of Ir nanopartiCles by 4-5 times, suggesting that significant reductions in catalyst loading are possible without compromising performance.Iridium-Based Nanowires as Highly Active, Oxygen Evolution Reaction Electrocatalystselectrolysis; electrochemistry; nanostructures; iridium; oxygen evolutionx101201872#N/AFALSE
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acscatal.8b0024410.1021/acscatal.8b00244FALSEhttps://doi.org/10.1021/acscatal.8b00244Rahaim, RJACS Catal.Herein, we report the development of a dual catalytic approach for the cross-coupling of nitriles with Aryl- and aliphatic-bromides. A titanium(III) catalyst is used to activate nitriles enabling their coupling with organobromides through a nickel catalyst. The Ni/Ti system efficiently prepared unsymmetrical ketones with good chemoselectivity and could selectively couple a bromide in the presence of other functionalizable handles.Ni/Ti Dual Catalytic Cross-Coupling of Nitriles and Organobromides To Access Ketonescross-coupling; dual catalysis; nickel catalysis; titanium catalysis; and nitrile coupling12201856#N/ATRUE
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acscatal.8b0023010.1021/acscatal.8b00230FALSEhttps://doi.org/10.1021/acscatal.8b00230Nova, AACS Catal.This Perspective presents an overview on recent experimental and computational studies on the off-cyCle reactions of palladium and nickel-catalyzed cross-couplings. Several reactions entering or leaving the catalytic cyCle have been characterized, inCluding the Activation of Pd(II) precatalysts by H-shift and the deActivation of Ni(II) precatalysts by comproportionation. A fundamental difference between the off-cyCle chemistries of palladium and nickel is the larger diversity of species yielded by the latter, with a rich combination of different oxidation states, nuClearity, and ligand coordination modes. The molecular-level understanding of off-cyCle reactions has been exploited in catalyst design, inCluding the stereoelectronic fine-tuning of the ligands aimed at maximizing the Activation of the precatalyst meanwhile preventing its deActivation. Despite several challenges, which concern both experiments (e.g., isolation and characterization of transient species) and computations (e.g., comprehensive mapping of the potential energy surface), this approach has already been applied with success in the optimization of popular catalytic platforms (e.g., NHC-Pdally] precatalysts) and shows promise for the development of highly active and robust catalysts based on nickel.Designing Pd and Ni Catalysts for Cross-Coupling Reactions by Minimizing Off-CyCle Speciescatalysis; catalyst deActivation; cross-coupling Suzuki-Miyaura; palladium; nickel; DFT; precatalyst Activation482018171#N/ATRUE
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acscatal.7b0352910.1021/acscatal.7b03529FALSEhttps://doi.org/10.1021/acscatal.7b03529Behrens, MACS Catal.Cation substitution in transition-metal oxides is an important approach to improve electrocatalysts by the optimization of their composition. Herein, we report on phase-pure spinel-type CoV2-xFexO4 nanopartiCles with 0 <= x <= 2 as a new Class of bifunctional catalysts for the oxygen evolution (OER) and oxygen reduction reactions (ORR). The mixed-metal oxide catalysts exhibit high catalytic activity for both OER and ORR that strongly depends on the V and Fe content. CoV2O4 is known to exhibit a high conductivity, while in CoFe2O4 the cobalt cation distribution is expected to change due to the inversion of the spinel structure. The optimized catalyst, CoV1.5Fe0.5O4, shows an overpotential for the OER of similar to 300 mV for 10 mA cm(-2) with a Tafel slope of 38 mV dec(-1) in alkaline electrolyte. DFT+U+SOC calculations on cation ordering confirm the tendency toward the inverse spinel structure with increasing Fe concentration in CoV2-xFexO4 that starts to dominate already at low Fe contents. The theoretical results also show that the variations of oxidation states are related to the surface region, where the redox activity was found experimentally to be manifested in the transformation of V3+ -> V2+. The high catalytic activity, facile synthesis, and low cost of the CoV2-xFexO4 nanopartiCles render them very promising for application in bifunctional electrocatalysis.The Role of Composition of Uniform and Highly Dispersed Cobalt Vanadium Iron Spinel Nanocrystals for Oxygen Electrocatalysiscobalt vanadate; cobalt ferrite; mixed spinel oxides; composition; oxygen electrocatalysis; DFTx48201860#N/AFALSE
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acscatal.7b0441010.1021/acscatal.7b04410FALSEhttps://doi.org/10.1021/acscatal.7b04410Chen, JGGACS Catal.The oxygen evolution reaction (OER) has broad applications in electrochemical devices, but it often requires expensive and scarce Ir-based catalysts in acid electrolyte. Presented here is a framework to reduce Ir loading by combining core-shell iridium/metal nitride morphologies using in situ experiments and density functional theory (DFT) calculations. Several group VIII transition metal (Fe, Co, and Ni) nitrides are studied as core materials, with Ir/Fe4N core-shell partiCles showing enhancement in both OER activity and stability. In situ X-ray absorption fine structure measurements are used to determine the structure and stability of the core-shell catalysts under OER conditions. DFT calculations are used to demonstrate adsorbate binding energies as descriptors of the observed activity trends.Reducing Iridium Loading in Oxygen Evolution Reaction Electrocatalysts Using Core-Shell PartiCles with Nitride Coresacidic OER; core-shell partiCle; density functional theory; electrocatalysis; X-ray absorption spectroscopy54201833#N/ATRUE
5144
acscatal.7b0347510.1021/acscatal.7b03475https://doi.org/10.1021/acscatal.7b03475Wang, FACS Catal.Catalytic valorization of lignin is a sustainable way to provide aromatics for the human society, which depends on the electronic structure of catalytic sites. We herein report the preparation of a carbon-modified nickel catalyst via carbothermal reduction of Ni-doped layered double hydroxides. Lignosulfonate (LS), a lignin resource from the pulp industry, was used as a renewable carbon precursor. The carbon residues in the nickel surface layer changed the 3d electron distribution of nickel, which was highly selective for the C-O bond hydrogenolysis of lignin into aromatics, and 22 wt % total mass yields of aromatics were achieved from hydrogenolysis of oxidized birch lignin.Carbon Modification of Nickel Catalyst for Depolymerization of Oxidized Lignin to AromaticsC-O Cleavage; heterogeneous catalysis; nickel; lignin; supported catalystx68201871#N/AFALSE
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acscatal.7b0340610.1021/acscatal.7b03406FALSEhttps://doi.org/10.1021/acscatal.7b03406Qu, FLACS Catal.It is extremely important to develop earth-abundant and stable oxygen evolution reaction (OER) electrocatalysts with excellent performance in alkaline media. In this work, we describe the in situ electrochemical conversion of microrod array of Ni(tetracyanoquinodimethane), Ni(TCNQ)(2), into Ni(OH)(2) nanopartiCles embedded in a conductive TCNQ microrod array via anode oxidation. Such Ni(OH)(2)-TCNQ microarray shows OER activity needing over potentials of 322 and 354 mV to attain current densities of 50 and 100 mA cm(-2) in 1.0 M KOH, respectively. It is also extremely durable with its electrocatalytic performance being kept for at least 20 h. This work points out a stimulating approach to explore the utilization of TCNQ array as a conductive matrix for electrochemical applications.Ni(OH)(2) NanopartiCles Embedded in Conductive Microrod Array: An Efficient and Durable Electrocatalyst for Alkaline Oxygen Evolution ReactionTCNQ array; Ni(OH)(2) nanopartiCles; embedding; electrocatalysis; oxygen evolution reactionx97201853#N/AFALSE
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acscatal.7b0338810.1021/acscatal.7b03388FALSEhttps://doi.org/10.1021/acscatal.7b03388Yin, GYACS Catal.1,1-DiArylalkanes are important structural frameworks which are widespread in biologically active molecules. Herein, we report a reductive relay cross-coupling of Alkyl bromides with Aryl bromides by nickel catalysis with a simple nitrogen-containing ligand. This method selectively affords 1,1-diArylalkane derivatives with good to excellent yields and regioselectivity.Ligand-Controlled Nickel-Catalyzed Reductive Relay Cross-Coupling of Alkyl Bromides and Aryl BromidesAlkyl electrophiles; beta-hydride elimination; 1,1-diArylalkanes; migratory cross-coupling; high-valent nickelx60201842#N/AFALSE
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acscatal.7b0338310.1021/acscatal.7b03383FALSEhttps://doi.org/10.1021/acscatal.7b03383Fontecave, MACS Catal.Inspired by the metal active sites of formate dehydrogenase and CO-dehydrogenase, a nickel complex containing a NiS4 motif with two dithiolene ligands mimicking molybdopterin has been prepared and structurally characterized. During electroreduction, it converts to a good catalyst for the reduction of CO2 into formate as the major product, together with minor amounts of carbon monoxide and hydrogen, with reasonable overpotential requirement, good faradaic yield, and notable stability. Catalysis operates on a mercury electrode and dramatically less on a carbon electrode, as observed in the case of [Ni(cyClam)](2+) complexes. Density functional theory (DFT) computations indicate the key role of a Ni(III)-hydride intermediate and provide insights into the different reaction pathways leading to HCOOH, CO, and H-2. This study opens the route toward a new, yet unexplored, Class of mononuClear sulfur-coordinated Ni catalysts for CO2 reduction.A Bioinspired Nickel(bis-dithiolene) Complex as a Homogeneous Catalyst for Carbon Dioxide Electroreductiondithiolene ligands; homogeneous catalysis; CO2 reduction; nickel; density functional theoryx50201857#N/AFALSE
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acscatal.7b0437910.1021/acscatal.7b04379FALSEhttps://doi.org/10.1021/acscatal.7b04379Wiedner, ESACS Catal.A longstanding challenge in molecular electrocatalysis is to design catalysts that break away from the tradeoff between rate and overpotential arising from electronic scaling relationships. Here we report an inversion of the rate-over-potential correlation through system-level design of [Ni-((P2N2R')-N-R)(2)](2+) electrocatalysts for the production of H-2. The overpotential is lowered by an electron-withdrawing ligand, while the turnover frequency is increased by controlling the catalyst structural dynamics, using both ligand design and solvent viscosity. The cumulative effect of controlling each of these system components is an electrocatalyst with a turnover frequency of 70000 s(-1) and an overpotential of 230 mV, corresponding to a 100-fold rate enhancement and a 170 mV reduction in overpotential in comparison to the parent nickel catalyst. Molecular Tafel plot analysis reveals that the new catalysts reported here are substantially more efficient than other leading molecular electrocatalysts for the production of H-2.Reversing the Tradeoff between Rate and Overpotential in Molecular Electrocatalysts for H-2 Productionelectrocatalysis; hydrogen; scaling relation; overpotential; nickel; proton relay; viscosity44201869#N/ATRUE
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acscatal.7b0418310.1021/acscatal.7b04183FALSEhttps://doi.org/10.1021/acscatal.7b04183Ryoo, RACS Catal.High loading on a porous support is important for preparing high-performance metal catalysts, but the increased loading often results in a loss of dispersion and limited mass transfer. We approached this problem by supporting a large amount of metal or metal oxide on a hierarchically porous zeolite. The supported catalyst formed an embedded network of nanowires along the zeolite mesopores. Although tightly filled in the mesopores, the catalyst was readily accessible through microporous windows at the encasing mesopore walls. Cobalt, nickel, and TiO2, supported in this manner, exhibited high catalytic performance in Fischer-Tropsch synthesis, benzene hydrogenation, and furfural-to-gamma-valerolactone conversion, respectively.Confinement of Supported Metal Catalysts at High Loading in the Mesopore Network of Hierarchical Zeolites, with Access via the Microporous Windowshigh loading; supported catalyst; mesopore network; hierarchical zeolite; zeolite nanosponge24201823#N/ATRUE
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acscatal.7b0410510.1021/acscatal.7b04105FALSEhttps://doi.org/10.1021/acscatal.7b04105Wiest, OACS Catal.A combined computational and experimental study of the mechanism of a nickel-catalyzed alpha,beta-coupling of saturated ketones in the presence of an alkenyl halide is reported. The favored reaction mechanism, as determined using DFT calculations, differs from the previously proposed one and involves oxidative addition, transmetalation, and a direct beta-H transfer from the ketone to the alkenyl group. The beta-H transfer leads to a Ni-enone complex, reminiscent of a Saegusa oxidation, followed by a Michael addition to generate the final product. The beta-H transfer is the rate-determining step for the enone complex formation involving either a Ni-C species, with an enolate C-bound to Ni, or a Ni-O species, with an enolate O-bound to Ni. The Ni-C species beta-H transfer follows a more favorable, lower energy pathway. Experimental studies confirmed the Ni-enone species to be an intermediate in the reaction pathway and suggest that the enone dissociates from Ni before the final Michael reaction with a lithium enolate to give the a,alpha,beta-coupling product. The mechanism also rationalizes the selectivity between the previously reported enolate alkenylation and the presently studied alpha,beta-coupling reactions in the presence of PPh3 as a ligand. The alkenylation pathway with a PPh3 ligand is calculated to be 5.8 kcal/mol higher in free energy of Activation than that of the ketone coupling pathway, which is consistent with the experimental observation that no alkenylation products are formed when the reaction was performed under a,alpha,beta-coupling reaction conditions.Mechanistic Study of the Nickel-Catalyzed alpha,beta-Coupling of Saturated Ketonesnickel; ketone enolate; beta-H transfer; Saegusa oxidation; Michael addition; ligand-dependent selectivity10201841#N/ATRUE
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acscatal.7b0404110.1021/acscatal.7b04041FALSEhttps://doi.org/10.1021/acscatal.7b04041Campbell, CTACS Catal.Adsorbed hydroxyl is a common intermediate in many catalytic reactions on Ni catalysts. The heat of the dissociative adsorption of D2O onto an O-precovered Ni(111) surface producing adsorbed hydroxyls is measured here by single crystal adsorption calorimetry, with an average value of 67.3 kJ/mol up to 0.23 ML coverage. From this, the enthalpy of formation for adsorbed hydroxyl on Ni(111) and the bond energy of hydroxyl to Ni(111) were estimated to be -278.3 and 314.1 kJ/mol, respectively. The molecular adsorption of D2O on Clean Ni(111) gave an integral heat of 53.6 kJ/mol at 0.5 ML. In comparison to Pt(111), adsorbed hydroxyl binds to Ni(111) 67 kJ/mol more strongly and adsorbed D2O binds to Ni(111) similar to 2 kJ/mol more strongly. These energetics help Clarify the different catalytic properties of Ni versus Pt, and serve as benchmarks to evaluate the energy accuracy of quantum mechanical methods used in surface chemistry.Adsorbed Hydroxyl and Water on Ni(111): Heats of Formation by Calorimetryadsorbed hydroxyl; water adsorption; water dissociation; nickel; platinum; Ni(111); adsorption energy; calorimetry; heat of adsorption18201840#N/ATRUE
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acscatal.7b0319110.1021/acscatal.7b03191FALSEhttps://doi.org/10.1021/acscatal.7b03191Koel, BEACS Catal.Operando Raman spectroscopy and electrochemical techniques were used during the oxygen evolution reaction to identify the composition and local structure of electrodeposited CoOxHy and NiCoOxHy catalyst films. Before evaluation, the electrodeposited samples were subjected to a variety of thermal and electrochemical conditioning procedures, which generated unique initial catalyst structures and crystallinities. During oxygen evolution, Ni-modified CoOxHy films having lower initial crystallinity underwent substantial structural evolution that began with an irreversible transformation of a spinel local structure to an amorphous CoO structure at low anodic potentials (0.2 V vs Ag/AgCl). Increasing anodic polarization to greater than 0.3 V vs Ag/AgCl facilitated additional structural conversion from the amorphous CoO structure to a complex phase best described as an amalgamation of NiOOH and layered CoO2 motifs (NiOOH-h-CoO2) under elevated oxygen evolution rates. The formation of this NiOOH-h-CoO2 active structure was correlated with improved OER activity, which at 0.35 V overpotential is 100% greater than that of the catalyst where Ni was coordinated in a spinel structure. Independent of the initial cobalt oxide structure, the same NiOOH-h-CoO2 structure was formed during oxygen evolution, which suggests the active phase identified herein could be the universally active structure for NiCoOxHy materials.Reversible Structural Evolution of NiCoOxHy during the Oxygen Evolution Reaction and Identification of the Catalytically Active Phaseoperando Raman spectroscopy; oxygen evolution reaction; reversible structural evolution; spinel structure; amorphous cobalt oxide; layered delafossite; cobalt oxyhydroxide; Ni incorporationx72201859#N/AFALSE
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acscatal.7b0317710.1021/acscatal.7b03177FALSEhttps://doi.org/10.1021/acscatal.7b03177Xie, YACS Catal.The direct urea fuel cell (DUFC), as an efficient technology for generating power from urea, shows great potential for energy-sustainable development but is greatly hindered by the slow kinetics of the urea oxidation reaction (UOR). Herein, we highlighted a defect engineering strategy to design oxygen vacancy-rich NiMoO4 nanosheets as a promising platform to study the relationship between O vacancies and UOR activity. Experimental/theoretical results confirm that the rich O vacancies confined in NiMoO4 nanosheets successfully bring synergetic effects of higher exposed active sites, faster electron transport, and lower adsorption energy of urea molecules, giving rise to largely improved UOR activity. As expected, the r-NiMoO4/NF 3D electrode exhibits a higher current density of 249.5 mA cm(-2), which is about 1.9 and 5.0 times larger than those of p-NiMoO4/NF and Ni-Mo precursor/NF at a potential of 0.6 V. Our finding will be a promising pathway to develop non-noble materials as highly efficient UOR catalysts.Oxygen Vacancies Confined in Nickel Molybdenum Oxide Porous Nanosheets for Promoted Electrocatalytic Urea Oxidationoxygen vacancy; porous nanosheet; 3D configuration; urea oxidation; nickel molybdenum oxidex178201844#N/AFALSE
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acscatal.7b0397410.1021/acscatal.7b03974FALSEhttps://doi.org/10.1021/acscatal.7b03974Zimmerman, PMSpin-Switching Transmetalation at Ni Diimine Catalysts2018#N/ATRUE
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acscatal.7b0302410.1021/acscatal.7b03024https://doi.org/10.1021/acscatal.7b03024Ma, JACS Catal.Photoredox/transition-metal dual catalysis has become a hot research topic in the development of methodologies. Density functional theory (DFT) calculations have been performed to explore the detailed mechanism of photoredox/Ni-catalyzed carbon-nitrogen cross-coupling. The Ni(0) catalyst initiates the C-N cross-coupling, and the photocatalyst *[Ir(III)](+) engages the Ni(II) complex in single-electron transfer (SET). The pathway of the Ni(I) catalyst initiating the catalytic cyCle is prohibited due to the relatively high Activation barrier of the oxidative addition of the Aryl bromide to the Ni(I) catalyst. It is predicted that the Ni(II) salt is reduced by pyrrolidine through the mechanism of photoredox-catalyzed hydrogen atom transfer (HAT). The triplet triplet energy transfer (TTET) between the photocatalyst and the Ni(II) complex is less likely to occur due to the mismatched energy levels.Dual Role of a Photocatalyst: Generation of Ni(0) Catalyst and Promotion of Catalytic C-N Bond Formationmetallaphotoredox catalysis; C-N bond formation; reaction mechanism; DFT; SETPhotocatalyst32201885#N/AFALSE
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acscatal.7b0299110.1021/acscatal.7b02991FALSEhttps://doi.org/10.1021/acscatal.7b02991Yang, YACS Catal.A room-temperature synthesis of NiFe oxyfluoride (NiFeOF) holey film, using electrochemical deposition and anodic treatments, has been developed in this work. The developed room-temperature synthetic route can preserve the fine nanoporous structure inside the holey film, providing high surface area and abundant reaction sites for electrocatalytic reactions. Both computational and experimental studies demonstrate that the developed NiFeOF holey film with highly porous structure and metal residuals can be used as a high-efficiency and bifunctional catalyst for overall water splitting. Simulation result indicates that the exposed Ni atom on the NiFeOF surface serves as the active site for water splitting. Fe doping can improve the catalytic activity of the Ni active site due to the partial charge-transfer effect of Fe3+ on Ni2+. Electrochemical performance of the NiFeOF catalyst can be experimentally further enhanced through improved electrical conductivity by the residual NiFe alloy framework inside the holey film. The synergistic combination of NiFeOF holey film properties results in a highly efficient electrochemical catalyst, showing overall water splitting.Overall Water Splitting with Room-Temperature Synthesized NiFe Oxyfluoride Nanoporous FilmsNiFe oxyfluoride; nanoporous; room-temperature synthesis; bifunctional catalyst; water splittingx59201744#N/AFALSE
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acscatal.7b0297710.1021/acscatal.7b02977FALSEhttps://doi.org/10.1021/acscatal.7b02977Marinescu, SCACS Catal.Here, a cobalt dithiolene coordination polymer (CP) based on 9,10-dimethyl-2,3,6,7-anthracenetetrathiolate was synthesized via an interfacial reaction and was electrochemically characterized on glassy carbon (GCE) and graphite (GR) electrodes. Double-layer capacitance measurements, electrochemical impedance spectroscopy studies, and Tafel analyses were used to understand the role of electrochemically accessible active sites, electron and charge transfer, and electrical integration between the catalyst and the support in the resultant electrocatalytic hydrogen evolving activity. Overpotentials to achieve 10 mA/cm(2) ranging from 445 to 571 mV and from 388 to 527 mV for GCE vertical bar CP and GR vertical bar CP, respectively, were observed. Changes in the double-layer capacitance, which is related to electrochemically active surface area, and charge transfer resistance were determined to be the critical factors in the observed enhancement in catalytic activity, whereas bulk catalyst loading, which had been previously used to describe the hydrogen evolution reaction performance of CPs, was not the optimal indicator of catalytic activity.Understanding Variability in the Hydrogen Evolution Activity of a Cobalt Anthracenetetrathiolate Coordination Polymerx18201743#N/AFALSE
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acscatal.7b0287810.1021/acscatal.7b02878FALSEhttps://doi.org/10.1021/acscatal.7b02878Laasonen, KACS Catal.Among current technologies for hydrogen production as an environmentally friendly fuel, water splitting has attracted increasing attention. However, the efficiency of water electrolysis is severely limited by the large anodic overpotential and sluggish reaction rate of the oxygen evolution reaction (OER). To overcome this issue, the development of efficient electrocatalyst materials for the OER has drawn much attention. Here, we show that organometallic Ni(II) complexes immobilized on the sidewalls of multiwalled carbon nanotubes (MWNTs) serve as highly active and stable OER electrocatalysts. This Class of electrocatalyst materials is synthesized by covalent functionalization of the MWNTs with organometallic Ni bipyridine (bipy) complexes. The Ni-bipy-MWNT catalyst generates a current density of 10 mA cm(-2) at overpotentials of 310 and 290 mV in 0.1 and 1 M NaOH, respectively, with a low Tafel slope of similar to 35 mV dec(-1), placing the material among the most active OER electrocatalysts reported so far. Different simple analysis techniques have been developed in this study to characterize such a Class of electrocatalyst materials. Furthermore, density functional theory calculations have been performed to predict the stable coordination complexes of Ni before and after OER measurements.Functionalized Carbon Nanotubes with Ni(II) Bipyridine Complexes as Efficient Catalysts for the Alkaline Oxygen Evolution Reactioncarbon nanotubes; functionalization; bipyridine; organometallic Ni complex; oxygen evolution reactionx30201785#N/AFALSE
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acscatal.7b0279510.1021/acscatal.7b02795https://doi.org/10.1021/acscatal.7b02795Molander, GANickel/Photoredox-Catalyzed Amidation via Alkylsilicates and IsocyanatesPhotocatalyst2017#N/AFALSE
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acscatal.7b0278810.1021/acscatal.7b02788FALSEhttps://doi.org/10.1021/acscatal.7b02788Kegnaes, SACS Catal.The silylative pinacol coupling of Arylaldehydes catalyzed by an easily accessible, heterogeneous base-metal catalyst is demonstrated. Instead of using the Classical combination of catalyst, stoichiometric metal reductants, and chlorosilanes, the developed reaction only requires the use of a catalyst and a hydrosilane, which serves as both reductant and silylating agent. A rare mechanistic investigation in this field focusing on the organic reactants was undertaken using various techniques inCluding experimental rate orders, kinetic isotope effect, radical scavengers, and stoichiometric tests. The obtained results provided evidence for a reaction mechanism which is different from the Classical pinacol coupling pathway. We propose that the heterogeneous catalyst facilitates easy access to silyl radicals, thereby circumventing the usual need for explosive initiators to access these species. In addition, leaching tests and recyCling of the catalyst were performed, Clearly supporting the heterogeneous nature of the catalyst.Silylative Pinacol Coupling Catalyzed by Nitrogen-Doped Carbon-Encapsulated Nickel/Cobalt NanopartiCles: Evidence for a Silyl Radical Pathwayheterogeneous catalysis; nanopartiCles; nitrogen-doped carbon; mechanism; silyl radicalsx19201835#N/AFALSE
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acscatal.7b0276110.1021/acscatal.7b02761FALSEhttps://doi.org/10.1021/acscatal.7b02761Rappe, AMACS Catal.Optimizing catalysts for the hydrogen evolution reaction (HER) is a critical step toward the efficient production of H-2(g) fuel from water. It has been demonstrated experimentally that transition metal phosphides, specifically nickel phosphides Ni2P and Ni3P4, efficiently catalyze the HER at a small fraction of the cost of archetypal Pt-based electrocatalysts. However, the HER mechanism on nickel phosphides remains unClear. We explore, through density functional theory with thermodynamics, the aqueous reconstructions of Ni2P(0001) and Ni5P4(0001)/(000 (1) over bar), and we find that the surface P content on Ni2P(0001) depends on the applied potential, which has not been considered previously. At-0.21 V >= U >=-0.36 V versus the standard hydrogen electrode and pH = 0, a PHx-enriched Ni3P2 termination of Ni2P(0001) is found to be most stable, consistent with its P-rich ultrahigh-vacuum reconstructions. Above and below this potential range, the stoichiometric Ni3P2 surface is instead passivated by H at the Ni-3-hollow sites. On the other hand, Ni5P4(0001) does not favor additional P. Instead, the Ni4P3 bulk termination of Ni5P4(000-0 is passivated by H at both the Ni-3 and P-3-hollow sites. We also found that the most HER-active surfaces are Ni3P2+P+(7/3)H of Ni2P(0001) and Ni4P3+4H of Ni5P4(0001) due to weak H adsorption at P catalytic sites, in contrast with other computational investigations that propose Ni as or part of the active site. By looking at viable catalytic cyCles for HER on the stable reconstructed surfaces, and calculating the reaction free energies of the associated elementary steps, we calculate that the overpotential on the Ni4P3+4H surface of Ni5P4(0001) (-0.16 V) is lower than that of the Ni3P2+P+(7/3)H surface of Ni2P(0001) (-0.21 V). This is due to the abundance of P-3-hollow sites on Ni5P4 and the limited surface stability of the P-enriched Ni2P(0001) surface phase. The trend in the calculated catalytic overpotentials, and the potential-dependent bulk and surface stabilities explain why the nickel phosphides studied here perform almost as well as Pt, and why Ni5P4 is more active than Ni2P toward HER, as is found in the experimental literature. This study emphasizes the importance of considering aqueous surface stability in predicting the HER-active sites, mechanism, and overpotential, and highlights the primary role of P in HER catalysis on transition-metal phosphides.Active Role of Phosphorus in the Hydrogen Evolving Activity of Nickel Phosphide (0001) Surfaceselectrocatalysis; hydrogen evolution; metal phosphides; nickel phosphides; density functional theory; aqueous surface phase diagramx50201793#N/AFALSE
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acscatal.7b0397010.1021/acscatal.7b03970FALSEhttps://doi.org/10.1021/acscatal.7b03970Martinez, AACS Catal.Higher olefins produced via ethylene oligomerization are versatile commodity chemicals serving a vast range of industries with large global economic impact. Nickel aluminosilicates are promising candidates to replace the homogeneous catalysts employed in industrial ethylene oligomerization processes. The current poor understanding of the true nature of the active nickel centers and the nickel-mediated oligomerization mechanism in these materials, however, hampers the rational design of improved catalysts. Here we applied in situ time- and temperature-resolved FTIR spectroscopy with simultaneous MS analysis of products to disentangle these fundamental issues using nanocrystalline Ni-beta zeolite as catalyst. We elucidate that isolated Ni2+ cations grafted on acidic silanols are the most likely active species in the working catalysts rather than the generally accepted ion-exchanged nickel cations. On the basis of our results, a plausible initiation mechanism involving a nickel Vinyl hydride intermediate from which chain propagation proceeds similarly to the Cossee-Arlman pathway is proposed.Nature of Active Nickel Sites and Initiation Mechanism for Ethylene Oligomerization on Heterogeneous Ni-beta Catalystsethylene oligomerization; nickel-beta catalyst; in situ FTIR spectroscopy; active nickel sites; reaction mechanism46201862#N/ATRUE
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acscatal.7b0394910.1021/acscatal.7b03949FALSEhttps://doi.org/10.1021/acscatal.7b03949Chen, YACS Catal.Ultrathin transition-metal-based nanomeshes can perfectly combine the advantages of two-dimensional (2D) ultrathin nanosheets and porous nanostructures, which have wide applications in energy storage and conversion. In this work, we present an etch-free one-step approach to directly synthesize the ultrathin Co3O4 nanomeshes (Co-UNMs) by employing a CoCl2/K3Co(CN)(6) cyanogel as the reaction precursor. The 2D planar structural unit and solid properties of the cyanogel result in the preferential assembly of generated crystal nuClei at the solid-liquid interface (i.e., cyanogel-solution interface) in the 2D direction, which plays a key role in the formation of nanomeshes. The as-prepared Co-UNMs with 1.5 nm thickness and abundant pores have high surface area and numerous defect atoms, resulting in enhanced activity for the oxygen evolution reaction (OER) in alkaline media, such as a low overpotential of 307 mV at 10 mA cm(-2), a small Tafel slope of 76 mV dec(-1), and attractive durability in 1 M KOH electrolyte.Ultrathin Co3O4 Nanomeshes for the Oxygen Evolution Reactionnanomeshes; nanosheets; cyanogel; electrolysis; oxygen evolution reaction242201885#N/ATRUE
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acscatal.7b0271210.1021/acscatal.7b02712FALSEhttps://doi.org/10.1021/acscatal.7b02712Vegge, TACS Catal.Layered oxyhydroxides (ox-hys) of Ni and Co are among the most active catalysts for oxygen evolution in alkaline media. Their activities can be further tuned by delamination into single-layer oxide sheets or by means of doping. The active site for the reaction and how doping and delamination promote the intrinsic activity, however, remain elusive. To shed light on these open questions, we have undertaken a systematic analysis of the stability, catalytic activity, and electronic conductivity of Ni and Co ox-hys ranging from bulk (3D) to single-layer (2D) catalysts. In both cases, we investigate the role of terrace and edge sites and use stability, catalytic activity, and electronic conductivity as evaluation criteria to pinpoint the best catalysts. We arrive at several important conClusions: the ox-by surface is fully oxidized under oxygen evolution conditions, bulk terraces are ostensibly the most active sites, and Ni ox-hy sheets are more electronically conductive in comparison to their Co equivalents. Furthermore, we examine 25 different doped Co and Ni ox-hy nanosheets (V, Cr, Mn, Fe, Co/Ni, Cu, Ru, Rh, Pd, Ir, Pt, Ag, Al, Ga, In, Sn, Pb, Bi, Mg, Sc, Y, Ti, Nb, Zn, and Cd) to further tailor the catalytic performance. We establish the dependence of the electronic conductivity and activity on potential and find that it is more energetically favorable to dope Ni in comparison to Co ox-hys, with first-row transition and noble metals being the most stable dopants. Finally, we extend the analysis to inClude bulk terminations and reveal that most dopants, which are stable in the nanosheets, have a large propensity to segregate to the surface of bulk materials, and those that are less prone to segregation (Fe or Cr) are not electronically conductive in the bulk. Overall, we identify Rh-doped Ni ox-by to be the best catalyst material.From 3D to 2D Co and Ni Oxyhydroxide Catalysts: Elucidation of the Active Site and Influence of Doping on the Oxygen Evolution Activityoxygen evolution reaction; density functional theory; doping; Ni oxide; Co oxidex32201777#N/AFALSE
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acscatal.7b0266310.1021/acscatal.7b02663FALSEhttps://doi.org/10.1021/acscatal.7b02663Handa, SACS Catal.The efficacy of custom surfactant FI-750-M, designed to mimic polar solvents such as DMF and dioxane, has been demonstrated with the palladium-catalyzed sp(2)-sp(3) coupling of nitroalkanes to Aryl bromides using a heteroleptic palladium catalyst under unprecedentedly mild conditions. Optimized reaction conditions mostly provided good yields up to gram scale, with high selectivity and functional group tolerance for a wide scope of Aryl bromides. Use of surfactant FI-750-M makes water the gross reaction medium and enables in-flask recyCling. The behavior of the surfactant has been elucidated with DLS and cryo-TEM measurements, and mechanistic investigations have revealed the importance of the pi-allyl ligand in the catalytic cyCle.Micelle-Enabled Palladium Catalysis for Convenient sp(2)-sp(3) Coupling of Nitroalkanes with Aryl Bromides in Water Under Mild Conditionsmicellar catalysis; green chemistry; cross-couplings; E factor; amphiphilesx44201745#N/AFALSE
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acscatal.7b0264710.1021/acscatal.7b02647FALSEhttps://doi.org/10.1021/acscatal.7b02647Dinca, MACS Catal.Establishing catalytic structure function relationships introduces the ability to optimize the catalyst structure for enhanced activity, selectivity, and durability against reaction conditions and prolonged catalysis. Here we present experimental and computational data elucidating the mechanism for the O-2 reduction reaction with a conductive nickel-based metal organic framework (MOF). Elucidation of the O-2 reduction electrokinetics, understanding the role of the extended MOF structure in providing catalytic activity, observation of how the redox activity and pKa of the organic ligand influences catalysis, and identification of the catalyst active site yield a detailed O-2 reduction mechanism where the ligand, rather than the metal, plays a central role. More generally, familiarization with how the structural and electronic properties of the MOF influence reactivity may provide deeper insight into the mechanisms by which less structurally defined nonplatinum group metal electrocatalysts reduce O-2.Mechanistic Evidence for Ligand-Centered Electrocatalytic Oxygen Reduction with the Conductive MOF Ni-3(hexaiminotriphenylene)(2)O-2 reduction; electrocatalysis; metal organic framework; porous catalysts; 2D materialsx79201725#N/AFALSE
5167
acscatal.7b0380710.1021/acscatal.7b03807FALSEhttps://doi.org/10.1021/acscatal.7b03807Jaramillo, TFACS Catal.During CO2 electroreduction (CO2R), the hydrogen evolution reaction (HER) is a competing reaction. We present a combined experimental and theoretical investigation of the HER activity of transition metals under CO2R conditions. Experimental HER polarization curves were measured for six polycrystalline metal surfaces (Au, Ag, Cu, Ni, Pt, and Fe) in the presence of CO2 gas. We found that the HER activity of the transition metals is significantly shifted, relative to the CO2-free case. Density functional theory (DFT) calculations suggest that this shift arises from adsorbate adsorbate interactions between *CO and *H on intermediate and strong binding metals, which weakens the *H binding energy. Using a simple model for the effect of *CO on the *H binding energy, we construct an activity volcano for HER in the presence of CO, gas that is consistent with experimental trends. The significant changes in HER activity in the presence of CO2 gas is an important consideration in catalyst design and could help develop catalysts that are more selective for CO2R than the HER.Trends in the Catalytic Activity of Hydrogen Evolution during CO2 Electroreduction on Transition MetalsCO2; electroreduction; hydrogen evolution reaction; electrocatalysis; volcano plot; adsorbate-adsorbate interactions46201846#N/ATRUE
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acscatal.7b0257510.1021/acscatal.7b02575FALSEhttps://doi.org/10.1021/acscatal.7b02575Jin, SACS Catal.Highly efficient earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are of great importance for renewable energy conversion systems. Herein, guided by theoretical calculations, we demonstrate highly efficient water splitting in alkaline solution using quarternary mixed nickel iron phosphosulfide (Ni1-xFexPS3) nanosheets (NSs), even though neither NiPS3 nor FePS3 is a good HER (or OER) electrocatalyst. With tuned electronic structure and improved electrical conductivity induced by mixing appropriate amount of Fe into NiPS3, Ni09Fe0.1PS3 NSs display excellent HER activity (an overpotential of 72 mV vs reversible hydrogen electrode (RHE) at a geometric catalytic current density of -10 mA cm(-2) and a Tafel slope of 73 mV dec(-1)), which is among the best HER catalysts under alkaline conditions. Ni0.9Fe0.1PS3 NSs also show a good apparent OER activity (an overpotential of 329 mV vs RHE at a catalytic current density of 20 mA cm(-2) and a Tafel slope of 69 mV dec(-1)), although structural investigation indicates the formation of Ni(Fe)OOH and Ni(Fe)(OH), layers on the catalyst surface after OER reactions as likely the real active species. These mixed nickel iron phosphosulfide non-precious-metal electrocatalysts with enhanced intrinsic activity and long-term stability and durability should have great potential in overall water-splitting applications.Tuning Mixed Nickel Iron Phosphosulfide Nanosheet Electrocatalysts for Enhanced Hydrogen and Oxygen Evolutionnickel iron phosphosulfide; nanosheet; electrocatalysts; hydrogen evolution; oxygen evolutionx175201765#N/AFALSE
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acscatal.7b0256110.1021/acscatal.7b02561FALSEhttps://doi.org/10.1021/acscatal.7b02561Yeo, BSACS Catal.The electrocatalytic reduction of CO, and water splitting have received significant attention because recyCling CO, into fuels and chemical feedstock is a crucial step to Close the anthropogenic carbon cirCle, whereas splitting water produces H-2 gas, which is a valuable carbon-free energy carrier. The Clear identification of the catalytic-active sites and elucidation of the reaction mechanisms in these systems remain a grand challenge. It requires simultaneous characterizations of the catalysts under actual reaction conditions. Raman spectroscopy is among the handful of techniques that are suitable for the in situ/operando investigations of heterogeneous catalytic systems. This Perspective will highlight primarily recent works on the application of Raman spectroscopy in unraveling the structural changes of catalysts, their possible active sites, and the intermediates formed during water electrolysis and CO, electroreduction. Results from complementary techniques such as X-ray absorption spectroscopy, among others, will also be presented in order to provide a more holistic discussion. The outlook for future work is discussed.Characterization of Electrocatalytic Water Splitting and CO2 Reduction Reactions Using In Situ/Operando Raman Spectroscopyoperando; Raman spectroscopy; electrochemistry; oxygen evolution reaction; hydrogen evolution reaction; CO2 reduction reaction
Electrocatalytic
x802017123#N/AFALSE
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acscatal.7b0254010.1021/acscatal.7b02540https://doi.org/10.1021/acscatal.7b02540Szostak, MACS Catal.Direct C-H Arylation of nonacidic C(sp(2))-H bonds with primary amides as Arylating reagents via highly chemoselective C-H/C-N/C-C Cleavages has been accomplished for the first time. The key to the success is the cooperative combination of rhodium(I) catalysis and Lewis base catalysis, which can promote Activation of inert C-N bonds in generic primary amides after selective N-tertbutoxyCarbonyl Activation in a highly efficient manner. Notably, this report constitutes the first biAryl synthesis enlisting common primary amides by N-C bond Activation. This report also disCloses for the first time the potential of generic, acyClic secondary amides as Arylating reagents in directed C-H Arylation. Considering the fundamental importance of biAryls and the key role of primary amides in organic synthesis, we expect that this concept by synergistic catalysis for Aryl-Aryl coupling will unlock broad catalytic applications.Site-Selective C-H/C-N Activation by Cooperative Catalysis: Primary Amides as Arylating Reagents in Directed C-H ArylationC-H Activation; C-N Activation; amides; Arylation; Arylating reagents; cooperative catalysisxy62201786#N/AFALSE
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acscatal.7b0364010.1021/acscatal.7b03640FALSEhttps://doi.org/10.1021/acscatal.7b03640Senanayake, SDACS Catal.The Activation of methane and its dry reforming with CO2 was systematically studied over a series (2-30 wt %) of CO2 (similar to 5 nm in size) loaded CeO2 catalysts, with an effort to elucidate the interplay between Co and CeO2 during the catalytic process using in situ methods. The results of in situ time-resolved X-ray diffraction (TR-XRD) show a strong interaction of methane with the CoOx-CeO2 systems at temperatures between 200 and 350 degrees C. The hydrogen produced by the dissociation of C H bonds in methane leads to a full reduction of Co oxide, Co3O4 -> CoO -> Co, and a partial reduction of ceria with the formation of some Ce3+. Upon the addition of CO2, a catalytic cyCle for dry reforming of methane (DRM) was achieved on the CoOx-CeO2 powder catalysts at temperatures below 500 degrees C. A 10 wt % Co-CeO2 catalyst was found to possess the best catalytic activity among various cobalt loading catalysts, and it exhibits a desirable stability for the DRM with a accumulation. The phase transitions and the nature of active components in the catalyst were investigated under reaction conditions by in situ time-resolved XRD and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). These studies showed dynamic evolutions in the chemical composition of the catalysts under reaction conditions. CO2 attenuated the reducing effects of methane. Under optimum CO- and H-2-producing conditions, both XRD and AP-XPS indicated that the active phase involved a majority of metallic Co with a small amount of CoO, both supported on a partially reduced ceria (Ce3+/Ce4+). We identified the importance of dispersing Co, anchoring it onto the ceria surface sites, and then utilizing the redox properties of CeO2 for activating and then oxidatively converting methane while inhibiting coke formation. Furthermore, a synergistic effect between cobalt and ceria and likely the interfacial sitee are essential to successfully Close the catalytic cyCle.In Situ Elucidation of the Active State of Co-CeOx Catalysts in the Dry Reforming of Methane: The Important Role of the Reducible Oxide Support and Interactions with Cobalt43201862#N/ATRUE
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acscatal.7b0240210.1021/acscatal.7b02402FALSEhttps://doi.org/10.1021/acscatal.7b02402Yoo, SJACS Catal.A Rh-Sn nanopartiCle is achieved by combinatorial approaches for application as an active and stable electrocatalyst in the oxygen reduction reaction. Both metallic Rh and metallic Sn exhibit activities too low to be utilized for electrocatalytic reduction of oxygen. However, a Clean and active Rh surface can be activated by incorporation of Sn into a Rh nanopartiCle through the combined effects of lateral repulsion, bifunctional mechanism, and electronic modification. The corrosion-resistant property of Rh contributes to the construction of a stable catalyst that can be used under harsh fuel cell conditions. Based on both theoretical and experimental research, Rh Sn nanopartiCle designs with inexpensive materials can be a potential alternative catalyst in terms of the economic feasibility of commercialization and its facile and simple surfactant-free microwave-assisted synthesis.Rhodium-Tin Binary NanopartiCle-A Strategy to Develop an Alternative Electrocatalyst for Oxygen Reductionelectrocatalyst; oxygen reduction; fuel cells; rhodium-tin; nanomaterialx12201752#N/AFALSE
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acscatal.7b0359410.1021/acscatal.7b03594FALSEhttps://doi.org/10.1021/acscatal.7b03594Sun, XPPhosphorus-Doped Co3O4 Nanowire Array: A Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting2018#N/ATRUE
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acscatal.7b0231010.1021/acscatal.7b02310FALSEhttps://doi.org/10.1021/acscatal.7b02310Kao, HMACS Catal.In this study, ultrasmall Ni nanopartiCles (Ni NPs) were controllably supported in the cage-type mesopores of -COOH-functionalized mesoporous silica SBA-16 (denoted as Ni(x)@S16C, where x is the Ni loading) via wet impregnation under alkaline conditions, followed by thermal reduction. The partiCle sizes of the Ni NPs ranged from 2.7 to 4.7 nm, depending on the Ni loading. Under the appropriate alkaline conditions (i.e., pH 9) deprotonation of the Carbonylic acid groups on the cage type mesopore surfaces endowed the effective incorporation of Ni2+ precursors via favorable electrostatic interactions, and thus well-dispersed Ni NPs confined in the cage-type mesopores of SBA-16 were achieved. The combination of the cage-type mesopores and the surface functionality provided dual beneficial features to confine the immobilized Ni NPs and to tune their partiCle sizes. The remarkably enhanced catalytic activities of the Ni(x)@S16C materials for CO2 hydrogenation and CH4 formation were demonstrated. The cage-type SBA-16 support provided a positive effect for the Ni NPs to enrich the surface sites, which can strongly adsorb CO and CO2, thus leading to high catalytic rates for CO2, and CO hydrogenation. The reaction mechanism, catalytic kinetics, and active sites were investigated to correlate to the high reaction rate for CO2 hydrogenation to form CH4.Size-Tunable Ni NanopartiCles Supported on Surface-Modified, Cage-Type Mesoporous Silica as Highly Active Catalysts for CO2 Hydrogenationmesoporous silicas; SBA-16; Carbonylic acid functionalized mesoporous silica SBA-16; nickel nanopartiCles; CO2 hydrogenation; cage-type mesopore; Ni partiCles; carbon monoxide; methanex46201765#N/AFALSE
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acscatal.7b0350910.1021/acscatal.7b03509FALSEhttps://doi.org/10.1021/acscatal.7b03509Yeo, BSACS Catal.The oxygen evolution reaction (OER) is the bottleneck in the efficient production of hydrogen gas fuel via the electrochemical splitting of water. In this work, we present and elucidate the workings of an OER catalytic system which consists of cobalt oxide (CoOx) with adsorbed Fe3+ ions. The CoOx was electrodeposited onto glassy-carbon-disk electrodes, while Fe3+ was added to the 1 M KOH electrolyte. Linear sweep voltammetry and chronopotentiometry were used to assess the system's OER activity. The addition of Fe3+ significantly lowered the average overpotential (eta) required by the cobalt oxide catalyst to produce 10 mA/cm(2) O-2 current from 378 to 309 mV. The Tafel slope of the CoOx + Fe3+ catalyst also decreased from 59.5 (pure CoOx) to 27.6 mV/dec, and its stability lasted similar to 20 h for 10 mA/cm(2) O-2 evolution. CyClic voltammetry showed that oxidation of the deposited CoOx, from Co2+ to Co3+ occurred at a more positive potential when Fe3+ was added to the electrolyte. This could be attributed to interactions between the Co and Fe atoms. Comprehensive X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy were conducted. The in situ XANES spectra of Co sites in the CoOx, CoOx + Fe3+, and control Fe48Co52Ox ]catalysts were similar during the OER, which indicates that the improved OER performance of the CoOx + Fe3+ catalyst could not be directly correlated to changes in the Co sites. The XANES spectra of Fe indicated that Fe3+ adsorbed on CoOx did not further oxidize under OER conditions. However, Fes coordination number was notably reduced from 6 in pure FeOx to 3.7 when it was adsorbed on CoOx. No change in the Fe-O bond lengths/strengths was found. The nature and mechanistic role of Fe adsorbed on CoOx are discussed. We propose that Fe sites with oxygen vacancies are responsible for the improved OER activity of CoOx + Fe3+ catalyst.Enhanced Catalysis of the Electrochemical Oxygen Evolution Reaction by Iron(III) Ions Adsorbed on Amorphous Cobalt Oxideoxygen evolution reaction; synergistic effect; X-ray absorption near edge structure; extended X-ray absorption fine structure; iron active site; electrochemistry86201858#N/ATRUE
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acscatal.7b0329510.1021/acscatal.7b03295FALSEhttps://doi.org/10.1021/acscatal.7b03295Henseng, EJMACS Catal.Doping CeO2 with Pd atoms has been associated with catalytic CO oxidation, but current surface models do not allow CO adsorption. Here, we report a new structure of Pd-doped CeO2(111), in which Pd adopts a square planar configuration instead of the previously assumed octahedral configuration. Oxygen removal from this doped structure is favorable. The resulting defective Pd-doped CeO2 surface is active for CO oxidation and is also able to Cleave the first C-H bond in methane. We show how the moderate CO adsorption energy and dynamic features of the Pd atom upon CO adsorption and CO oxidation contribute to a low-barrier catalytic cyCle for CO oxidation. These structures, which are also observed for Ni and Pt, can lead to a more open coordination environment around the doped-transition-metal center. These thermally stable structures are relevant to the development of single-atom catalysts.Stable Pd-Doped Ceria Structures for CH4 Activation and CO OxidationPd-doped ceria; square planar PdO4; CH4 Activation; CO oxidation; DFT59201842#N/ATRUE
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acscatal.7b0214510.1021/acscatal.7b02145FALSEhttps://doi.org/10.1021/acscatal.7b02145Trudel, SACS Catal.The influence of calcium doping on the electrocatalytic activity of amorphous lanthanum cobaltite a-La1-yCayCoOx with respect to the oxygen evolution reaction in 0.1 M KOH is investigated. The introduction of calcium slightly decreases the activity and does not hamper the short-term stability very much. a-La0.7Ca0.3CoOx demonstrates the highest activity among the calcium-containing materials, which is ascribed to the higher concentration of Co3+ and lower film resistance as determined from ex situ X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy.Water Oxidation Catalysis: Tuning the Electrocatalytic Properties of Amorphous Lanthanum Cobaltite through Calcium Dopingwater splitting; amorphous materials; calcium-doped lanthanum cobaltite; oxygen evolution reaction; photochemical thin-film deposition; solar fuels; electrocatalysisx7201748#N/AFALSE
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acscatal.7b0213310.1021/acscatal.7b02133FALSEhttps://doi.org/10.1021/acscatal.7b02133Jaramillo, TFACS Catal.Molybdenum sulfides been identified as promising materials for catalyzing the hydrogen evolution reaction (HER) in acid, with active edge sites that exhibit some of the highest turnover frequencies among nonpreciousmetal catalysts. The thiomolybdate [Mo3S13](2-) nanoCluster catalyst contains a structural motif that resembles the active site of MoS2 and has been reported to be among the most active forms of molybdenum sulfide. Herein, we improve the activity of the [Mo3S13](2-) catalysts through catalyst support interactions. We synthesize [Mo3S13](2-) on gold, silver, glassy carbon, and copper supports to demonstrate the ability to tune the hydrogen binding energy of [Mo3S13](2-) using catalyst support electronic interactions and optimize HER activity.Investigating Catalyst-Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo3S13](2-) NanoClustershydrogen evolution reaction; molybdenum sulfide; electrochemistry; renewable energy; catalyst-support interactionsx46201753#N/AFALSE
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acscatal.7b0209610.1021/acscatal.7b02096FALSEhttps://doi.org/10.1021/acscatal.7b02096Sautet, PACS Catal.Understanding and predicting the nature of transition-metal surfaces under realistic pressure and temperature conditions is crucial for optimizing their catalytic, mechanical, or electronic properties. We focus here on the stability of transition metal surfaces submitted to a pressure of NH3 and H-2 and on the potential formation of metastable or stable surface nitrides. Our leading example is a Ni-based alcohol amination catalyst, studied by a combination of DFT, thermodynamic modeling, and experiments. Initial N-coverage on Ni nanopartiCles selectively occurs on (100) facets, which become the most stable terminations. Concomitantly, the equilibrium shape of the partiCle becomes modified under a realistic gas-phase environment of NH3 and H-2. Extreme conditions favor the genesis of metastable Ni3N nanopartiCles, mainly exposing (101) terminations. Transformation into Ni and gas-phase N-2, favored by thermodynamics, is kinetically hindered. H-2 controls the catalyst nitridation by the competition between H-covered and N-covered surfaces. Extension to 15 transition metals unveils a huge spectrum of nitridation behaviors arising from very reactive Mo to almost inert Au. Nonetheless, in several cases, a moderate H-2 pressure is sufficient to prevent nitridation under a pressure of NH3. The approach presented in this study gives insight into the surface nitridation behavior of transition metals, paving the way to in silico design under real conditions for applications in materials science and heterogeneous catalysis.Trends and Control in the Nitridation of Transition-Metal Surfacescatalysis; DFT; thermodynamics; amination; nitridationx11201853#N/AFALSE
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acscatal.7b0209110.1021/acscatal.7b02091FALSEhttps://doi.org/10.1021/acscatal.7b02091Coperet, CACS Catal.The conversion of methane and carbon dioxide into a synthesis gas, the so-called dry reforming of methane (DRM), suffers from a stability issue caused by coke formation at the surface of the Ni-based catalysts. Using a colloidal approach, we demonstrate that supported 3-4 nm bimetallic NiFe nanopartiCles with a Ni/Fe ratio of 3 have an enhanced stability compared to the corresponding pure Ni-based catalyst and a higher activity compared to conventional NiFe catalysts. The active sites for DRM are associated with Ni, while FeO, observed by operando XAS under DRM conditions, allows for an effective decoking of the metal centers.Supported Bimetallic NiFe NanopartiCles through Colloid Synthesis for Improved Dry Reforming Performancenickel iron colloids; dry reforming of methane; stability; segregated/alloy metal; XAS operandox34201740#N/AFALSE
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acscatal.7b0207910.1021/acscatal.7b02079FALSEhttps://doi.org/10.1021/acscatal.7b02079Wang, ZCACS Catal.Efficient water splitting demands highly active, low cost, and robust electrocatalysts. In this study, we report the synthesis of penroseite (Ni,Co)Se-2 nanocages anchored on 3D graphene aerogel using Prussian blue analogues as a precursor and further their applications in overall water splitting electrolysis. The synergy between the high activity of (Ni,Co)Se-2 and the good conductivity of graphene leads to superior performance of the hybrid toward the water splitting in basic solutions. The (Ni,Co)Se-2-GA only requires a low cell voltage of 1.60 V to reach the current density of 10 mA cm(-2), making the (Ni,Co)Se-2-GA hybrid a competitive alternative to noble metal based catalysts for water splitting.Prussian Blue Analogues Derived Penroseite (Ni,Co)Se-2 Nanocages Anchored on 3D Graphene Aerogel for Efficient Water SplittingPrussian blue analogues; penroseite (Ni,Co)Se-2 nanocages; graphene aerogel; OER; HERx148201753#N/AFALSE
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acscatal.7b0201510.1021/acscatal.7b02015FALSEhttps://doi.org/10.1021/acscatal.7b02015Beckham, GTACS Catal.Succinic acid is a biomass-derived platform chemical that can be catalytically converted in the aqueous phase to 1,4-butanediol (BDO), a prevalent building block used in the polymer and chemical industries. Despite significant interest, limited work has been reported regarding sustained catalyst performance and stability under continuous aqueous-phase process conditions. As such, this work examines Ru-Sn on activated carbon (AC) for the aqueous-phase conversion of succinic acid to BDO under batch and flow reactor conditions. Initially, powder Ru-Sn catalysts were screened to determine the most effective bimetallic ratio and provide a comparison to other monometallic (Pd, Pt, Ru) and bimetallic (Pt-Sn, Pd-Re) catalysts. Batch reactor tests determined that a similar to 1:1 metal weight ratio of Ru to Sn was effective for producing BDO in high yields, with complete conversion resulting in 82% molar yield. Characterization of the fresh Ru-Sn catalyst suggests that the sequential loading method results in Ru sites that are colocated and surface-enriched with Sn. Postbatch reaction characterization confirmed stable Ru-Sn material properties; however, upon a transition to continuous conditions, significant Ru-Sn/AC deActivation occurred due to stainless steel leaching of Ni that resulted in Ru-Sn metal crystallite restructuring to form discrete Ni-Sn sites. Computational modeling confirmed favorable energetics for Ru-Sn segregation and Ni-Sn formation at submonolayer Sn incorporation. To address stainless steel leaching, reactor walls were treated with an inert silica coating by chemical vapor deposition. With leaching reduced, stable Ru-Sn/AC performance was observed that resulted in a molar yield of 71% BDO and 15% tetrahydrofinan for 96 h of time on stream. Postreaction catalyst characterization confirmed low levels of Ni and Cr deposition, although early-stage islanding of Ni-Sn will likely be problematic for industrially relevant time scales (i.e., thousands of hours). Overall, these results (i) demonstrate the performance of Ru-Sn/AC for aqueous phase succinic acid reduction, (ii) provide insight into the Ru-Sn bimetallic structure and deActivation in the presence of leached Ni, and (iii) underscore the importance of compatible reactor metallurgy and durable catalysts.Ru-Sn/AC for the Aqueous-Phase Reduction of Succinic Acid to 1,4-Butanediol under Continuous Process ConditionsRu-Sn/AC; biobased chemical; lignocellulose; catalyst stability; leaching; restructuringx282017109#N/AFALSE
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acscatal.7b0199410.1021/acscatal.7b01994FALSEhttps://doi.org/10.1021/acscatal.7b01994Yang, XRACS Catal.The combinations of Earth-abundant materials with noble metals provide an orientation for developing highly active and stable catalysts toward hydrogen production with reduced noble metal loadings. Here, we designed carbon Cloth (CC)-supported Earth-abundant Co(OH)(2) nanosheets array (Co(OH)(2)/CC) as an ideal three-dimensional (3D) substrate for Pt electrodeposition (Pt-Co(OH)(2)/CC, Pt in Pt-Co(OH)(2): 5.7 wt %) to achieve top performance of a hydrogen evolution reaction (HER) under alkaline and neutral I conditions. The Pt-Co(OH)(2)/CC catalyst exhibits a near-zero onset over potential and a Tafel slope of 70 mV dec(-1), and it requires an overpotential of 32, 54, and 122 mV to deliver the geometrical current density of 10, 20, and 100 mA cm(-2), respectively, with catalytic activities exceeding to those of the commercial Pt/C decorated CC (Pt/C/CC). Furthermore, the HER activity of Co(OH)2 decorated with several transition metals (Ni, Co, and Fe) was demonstrated in experiments, further validating the high HER activity of the Pt-Co(OH)(2)/CC catalyst. In addition, this catalyst also offers enhanced catalytic performance and durability under neutral conditions. Impressively, based on the normalized HER current densities by electrochemical surface area, the HER activity of the Pt-Co(OH)(2)/CC catalyst is 4.8 and 2.6 times greater than that of the commercial Pt/C/CC in alkaline and neutral solution, respectively. The unprecedented catalytic performances of Pt-Co(OH)(2)/CC catalyst are attributed to the synergistic catalytic effects originating from the nanointerfaces between Co(OH)(2) and Pt.Ultrafine Pt NanopartiCle-Decorated Co(OH)(2) Nanosheet Arrays with Enhanced Catalytic Activity toward Hydrogen EvolutionCo(OH)(2); Pt nanopartiCles; reduced Pt loading; electrocatalyst; hydrogen evolution reactionx122201729#N/AFALSE
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acscatal.7b0197310.1021/acscatal.7b01973https://doi.org/10.1021/acscatal.7b01973Molander, GAACS Catal.A protocol for the aminomethylation of Aryl halides using alpha-silylamines via Ni/photoredox dual catalysis is described. The low oxidation potential of these silylated species enables facile single electron transfer (SET) oxidation of the amine followed by rapid desilylation. The resulting alpha-amino radicals can be directly funneled into a nickel-mediated cross-coupling cyCle with Aryl halides. The process accomplishes aminomethylation under remarkably mild conditions and tolerates numerous Aryl- and heteroAryl halides with an array of functional groups.Aminomethylation of Aryl Halides Using alpha-Silylamines Enabled by Ni/Photoredox Dual Catalysisaminomethylation; radicals; nickel/photoredox dual catalysis; visible light; cross-couplingPhotocatalyst42201759#N/AFALSE
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acscatal.7b0328210.1021/acscatal.7b03282FALSEhttps://doi.org/10.1021/acscatal.7b03282Wu, QACS Catal.The synthesis of polyethylenes with precise branching, especially long-chain branching (LCB), using ethylene monomer as a single feedstock is of a significant academic and industrial interest. On the basis of the ortho-Aryl effect, a series of adiimine nickel complexes with monoAryl-substituted anilines has been designed and prepared for the synthesis of the polyethylenes with controlled branching. The introduction of the ortho-Aryl on aniline moieties enhanced the branching control ability of the adiimine nickel catalysts. A different mechanistic model was proposed to interpret the presence of methyl and LCB but absence of other short branches in the obtained polyethylenes. LCB was formed by ethylene insertion into the primary Ni-Alkyl species originating from nickel migration to methyl terminal of the growing chain because of restricted ethylene insertion into secondary Ni-Alkyl species with an alpha-ethyl or a bulkier Alkyl group.Synthesis of Polyethylenes with Controlled Branching with alpha-Diimine Nickel Catalysts and Revisiting Formation of Long-Chain Branchingnickel catalyst; chain walking; ethylene; polyethylene; long-chain branching; controlled branching45201872#N/ATRUE
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acscatal.7b0195410.1021/acscatal.7b01954FALSEhttps://doi.org/10.1021/acscatal.7b01954Kolen'ko, YVACS Catal.An approach to significantly enhance the performance of the cost-effective nickel phosphide catalyst for electrochemical water oxidation has been developed via interfacing with Mg oxide-hydroxide. We have synthesized Ni2P nanopartiCles anchored on Mg2O(OH)(2)-like phase supported on carbon paper. During the oxygen evolution reaction, the well-defined Ni2P nanopartiCles serve as precursors for the immediate formation of active and stable nanostructured nickel hydroxide catalyst. As the anode for the oxygen evolution reaction in an alkaline electrolyte, the electrode shows a modest Tafel slope of 48 mV dec(-1) and a large turnover frequency of 0.05 s(-1) at an overpotential of 0.4 V. Microstructure and composition studies of the catalyst suggest that interfacial strain between Mg- and Ni-containing phases is responsible for high catalytic activity. A significant increase in catalytic activity upon the combination of magnesium compound and transition-metal phosphide suggests an interesting strategy for the controlled and reproducible preparation of active Earth-abundant oxygen-evolving catalysts.Interface Engineering in Nanostructured Nickel Phosphide Catalyst for Efficient and Stable Water OxidationOER; Ni2P; nanopartiCles; core-shell; strain; electrocatalysisx50201739#N/AFALSE
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acscatal.7b0195110.1021/acscatal.7b01951FALSEhttps://doi.org/10.1021/acscatal.7b01951Wei, MACS Catal.The modulation of strong metal-support interaction (SMSI) plays a key role and remains a challenge in achieving the desired catalytic performance in many important chemical reactions. Herein, we report a TiO2-x-modified Ni nanocatalyst with tunable Ni-TiO2-x interaction via a two-step procedure: preparation of Ni/Ti mixed metal oxide (NiTi-MMO) from NiTi-layered double hydroxide (NiTi-LDH) precursor, followed by a further reduction treatment at different temperatures. A combination study (XRD, TEM, H2-TPR, XPS, and in situ EXAFS) verifies that a high reduction temperature enhances the Ni-TiO2-x interaction, which results in an increased coverage degree of Ni nanopartiCles by TiO2-x as well as electron density of interfacial Ni (Nis-). Moreover, the creation of a Ni delta-,-O-v-Ti3+ interface site (O-nu denotes oxygen vacancy) induced by strong Ni-TiO2-x interaction serves as dual-active site to efficiently catalyze the water-gas shift reaction (WGSR). The optimized catalyst (Ni@TiO2-x(450)) via tuning Ni-TiO2-x interaction gives a TOF value of 3.8 s(-1) which is similar to 7 times larger than the conventional 15%Ni/TiO2(450) catalyst. Such a high catalytic efficiency is attributed to the interfacial site (Ni delta-,O-nu-Ti3+) with medium strength of metal-support interaction, as revealed by in situ diffuse reflectance Fourier transform infrared spectroscopy (in situ DRIFTS), which promotes the synergic catalysis between Ni delta- and oxygen vacancy toward WGSR.TiO2-x-Modified Ni Nanocatalyst with Tunable Metal-Support Interaction for Water-Gas Shift Reactionlayered double hydroxide; strong metal-support interaction; water-gas shift reaction; interface structure; structure-activity correlationx108201741#N/AFALSE
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acscatal.7b0189610.1021/acscatal.7b01896FALSEhttps://doi.org/10.1021/acscatal.7b01896Grunwaldt, JDACS Catal.A promising bimetallic 17 wt % Ni3Fe catalyst supported on gamma-Al2O3 was prepared via homogeneous deposition-precipitation for the application in the methanation of CO2 to gather more detailed insight into the structure and performance of the catalyst compared to state-of-the-art methanation systems. X-ray diffraction (XRD) analysis, detailed investigations using scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy analysis (EDX) of single partiCles as well as larger areas, high-resolution transmission electron microscopy (HRTEM) imaging, temperature-programmed reduction (H-2-TPR), and in-depth interpretation of Raman bands led to the conClusion that a high fraction of the Ni and Fe formed the desired Ni3Fe alloy resulting in small and well-defined nanopartiCles with 4 nm in size and a dispersion of 24%. For comparison, a monometallic catalyst with similar dispersion using the same preparation method and analysis was prepared. Using a fixed-bed reactor, the Ni3Fe catalyst showed better low-temperature performance compared to a monometallic Ni reference catalyst, especially at elevated pressures. Longterm experiments in a microchannel packed bed reactor under industrially relevant reaction conditions in competition with a commercial Ni-based methanation catalyst revealed an improved performance of the Ni3Fe system at 358 degrees C and 6 bar involving enhanced conversion of CO2 to 71%, selectivity to CH4 > 98%, and most notably a high stability. DeActivation occurred only at lower temperatures, which was related to carbon deposition due to an increased CO production. Kinetic measurements were compared with literature models derived for Ni/Al2O3 catalysts, which fit well but underestimate the performance of the Ni3Fe system, emphasizing the synergetic effect of Ni and Fe.Potential of an Alumina-Supported Ni3Fe Catalyst in the Methanation of CO2: Impact of Alloy Formation on Activity and StabilityNi3Fe alloy; CO2 methanation; high stability; long-term performance; kineticsx72201796#N/AFALSE
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acscatal.7b0188010.1021/acscatal.7b01880FALSEhttps://doi.org/10.1021/acscatal.9b00968Chen, WReactive Intermediates or Inert Graphene? Temperature- and Pressure-Determined Evolution of Carbon in the CH4-Ni(111) Systemx2017#N/AFALSE
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acscatal.7b0182310.1021/acscatal.7b01823https://doi.org/10.1021/acscatal.7b01823Zhang, BACS Catal.The development of a facile and general strategy to simultaneously enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities of bifunctional electrocatalysts is of great importance for practical applications. However, current strategies are usually restricted to monofunctional electrocatalysts owing to the opposite redox process at cathode and anode. Herein, we present a photo generated-carrier-driven strategy to enhance the electrocatalytic HER and OER activities of transition-metal/semiconductor bifunctional electrocatalysts. The Ni/NiO heterostructured ultrathin nanosheet array supported on Ni foam (denoted as Ni/NiO-NF) is chosen as the model metal/semiconductor bifunctional electrocatalyst and exhibits 10- and 2.6-fold enhancement of mass activity for HER and OER, respectively, after exposure to light irradiation. The increase in water-splitting activities can be attributed to the transfer of photogenerated electrons from excited NiO to HER-active Ni and the accelerating formation of OER-active Ni-III/IV, respectively.Photogenerated Carriers Boost Water Splitting Activity over Transition-Metal/Semiconducting Metal Oxide Bifunctional Electrocatalystsbifunctional electrocatalysts; Ni/NiO; photogenerated carriers; heterostructure; water electrolysisPhotocatalyst36201735#N/AFALSE
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acscatal.7b0321510.1021/acscatal.7b03215FALSEhttps://doi.org/10.1021/acscatal.7b03215Tlili, AACS Catal.The direct monoArylation of ammonia for the synthesis of aniline derivatives constitutes a significant challenge in modern synthetic chemistry. Over the past decade, major efforts have been made in order to develop highly active and selective catalyst systems for this transformation. More specifically, the application of various transition-metal catalysis has enabled substantial progress in substrate scope and reaction conditions as well as catalyst costs and availability. This review describes these advancements focusing on palladium-, copper-, and nickel-based catalyst systems that have been reported until mid-2017.Transition-Metal-Catalyzed MonoArylation of Ammoniaammonia; anilines; cross-coupling; transition metal; catalysis39201882#N/ATRUE
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acscatal.7b0179010.1021/acscatal.7b01790FALSEhttps://doi.org/10.1021/acscatal.7b01790Chen, PACS Catal.The development of cost-effective and highly efficient catalysts is of scientific importance and practical need in the conversion and utilization of Clean energy. One of the strategies fulfilling that demand is to achieve high exposure of a catalytically functional noble metal to reactants to maximize its utilization efficiency. We report herein that the single-atom alloy (SAA) made of atomically dispersed Pt on the surface of Ni partiCles (Pt is surrounded by Ni atoms) exhibits improved catalytic activity on the hydrolytic dehydrogenation of ammonia-borane, a promising hydrogen storage method for onboard applications. Specifically, an addition of 160 ppm of Pt leads to ca. 3-fold activity improvement in comparison to that of pristine Ni/CNT catalyst. The turnover frequency based on the isolated Pt is 12000 mol(H2) mol(pt)(-1) min(-1), which is about 21 times the value of the best Pt based catalyst ever reported. Our simulation results indicate that the high activity achieved stems from the synergistic effect between Pt and Ni, where the negatively charged Pt (Pt delta-) and positively charged Ni (Ni delta+) in the Pt-Ni alloy are prone to interact with H and OH of H2O molecules, respectively, leading to an energetically favorable reaction pathway.Atomically Dispersed Pt on the Surface of Ni PartiCles: Synthesis and Catalytic Function in Hydrogen Generation from Aqueous Ammonia-Boranesingle-atom alloy; Pt-Ni alloy; catalytic dehydrogenation; hydrogen storage; ammonia boranex99201763#N/AFALSE
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acscatal.7b0178610.1021/acscatal.7b01786FALSEhttps://doi.org/10.1021/acscatal.7b01786Li, FWACS Catal.The catalytic conversions of biomass and its derivatives into fuels and chemicals require active and stable catalysts. Non-noble-metal catalysts typically suffer from deActivation due to the leaching and sintering of the metal species in liquid-phase reactions. In this work, we report a facile synthesis of porous-carbon-coated Ni catalysts supported on carbon nanotubes (CNFx@Ni@CNTs) by atomic layer deposition for the reductive amination of levulinic acid (LA) with amines to pyrrolidones. Under the protection of porous carbon with a moderate thickness, the optimized CNF30@Ni@CNTs catalyst showed a 99% yield of pyrrolidones and recyClability of up to 20 runs without the leaching and sintering of Ni nanopartiCles. On the basis of verification experiments and density functional theory calculations, we determined that our Nicatalyzed reductive amination of LA with amines underwent an unconventional pathway via amides as the first intermediate, followed by tandem cyClization, intramolecular dehydration, and hydrogenation to the desired pyrrolidones. This pathway was completely different from the reported imine-intermediated route in Pt-catalyzed systems. This work provides insights into the design of active and stable heterogeneous catalysts for liquid-phase reactions as well as into switching reaction pathways to rea.lize the replacement of noble metals for the transformation of biobased multifunctional substrates.Highly Stable Porous-Carbon-Coated Ni Catalysts for the Reductive Amination of Levulinic Acid via an Unconventional Pathwayx51201764#N/AFALSE
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acscatal.7b0177510.1021/acscatal.7b01775FALSEhttps://doi.org/10.1021/acscatal.7b01775Zhang, JLACS Catal.It is undoubtedly desirable, albeit very challenging, to appropriately balance the catalytic activity, electrochemical durability, and noble-metal (NM) utilization when developing Pt-based catalysts for oxygen reduction reaction (ORR). Accordingly, in this work, a versatile and effective strategy that promises the nanostructure of both composition-graded core and mono- or multilayer shell is proposed to synthesize highly uniform, sub-10 nm PdxNi1-x@Pt nanospheres (NSs) as high-performance ORR electrocatalysts. Highly uniform and composition-graded PdxNi1-x NSs are previously obtained via a facile one-pot Ni-substitution-based process, and then Pt mono- or multilayer shells are coated onto them through Cu underpotential deposition coupled with Pt2+ galvanic displacement. Results show that carbon supported PdxNi1-x@Pt electrocatalysts possess both high catalytic activity and highly efficient NM utilization toward ORR The optimized Pd0.42Ni0.58@Pt/C exhibits 0.61 mA cm(-2), 0.42 A mg(Pd+pt)(-1), and 1.45 A mg(Pt)(-1) @ 0.9 V (vs RHE) in the area-specific, NM-mass specific, and Pt-mass-specific activity, respectively, reaching 2.8, 3.3, and 11.2 times relative to those of the commercial Pt/C. Moreover, Pd0.42Ni0.58@Pt/C also has a satisfactory electrochemical durability, preserving its high ORR catalytic activity even after 12 000 potential cyCles of the accelerated degradation test. The synthetic mechanism of PdxNi1-x NS core, Pt monolayer shell and their combined effects on the catalytic activity, electrochemical durability, and NM utilization of PdxNi1-x@Pt/C toward ORR are comprehensively investigated.Composition-Graded PdxNi1-x Nanospheres with Pt Monolayer Shells as High-Performance Electrocatalysts for Oxygen Reduction Reactioncomposition-graded; Pt monolayer shell; core@shell; nanospheres; electrocatalysts; oxygen reduction reaction; proton exchange membrane fuel cellx51201768#N/AFALSE
5195
acscatal.7b0177310.1021/acscatal.7b01773FALSEhttps://doi.org/10.1021/acscatal.7b01773Molander, GAACS Catal.The chemoselective functionalization of poly functional Aryl linchpins is crucial for rapid diversification. Although well-explored for C-sp(2) and c(sp) nuCleophiles, the chemoselective introduction of C-sp(3) groups remains notoriously difficult and is virtually undocumented using Ni catalysts. To fill this methodological gap, a haloselective cross-coupling process of arenes bearing two halogens, I and Br, using ammonium Alkylbis(catecholato)silicates, has been developed. Utilizing Ni/photoredox dual catalysis, C-sp(3)-C-sp(2) bonds can be forged selectively at the iodine-bearing carbon of bromo(iodo)arenes. The described high-yielding, base-free strategy accommodates various protic functional groups. Selective electrophile Activation enables installation of a second C-sp(3) center and can be done without the need for purification of the intermediate monoAlkylated product.Haloselective Cross-Coupling via Ni/Photoredox Dual Catalysisnickel/photoredox dual catalysis; bromo(iodo)arenes; hypervalent silicon; cross-coupling; selective functionalizationPhotocatalyst30201750#N/AFALSE
5196
acscatal.7b0168310.1021/acscatal.7b01683FALSEhttps://doi.org/10.1021/acscatal.7b01683Hoover, JMACS Catal.Oxidative deCarbonylative Arylation reactions are potentially attractive routes to generate biAryl structures from simple and readily available precursors; yet, they are underutilized, because of limitations in the Carbonylic acid scope. Here, we report a nickel catalyst system that enables the selective deCarbonylative Arylation of unactivated C-H bonds with a broad scope of (hetero)aromatic Carbonylate coupling partners. Preliminary mechanistic insights suggest that the efficiency and selectivity of this protocol originate from cooperation between Ni and Ag.Nickel-Catalyzed Oxidative DeCarbonylative (Hetero)Arylation of Unactivated C-H Bonds: Ni and Ag SynergydeCarbonylation; C-H Activation; nickel; silver; heteroArylx35201743#N/AFALSE
5197
acscatal.7b0168210.1021/acscatal.7b01682FALSEhttps://doi.org/10.1021/acscatal.7b01682Chen, JGGACS Catal.Selectively Cleaving the C=O bond of the aldehyde group in furfural is critical for converting this biomass-derived platform chemical to an important biofuel molecule, 2-methylfuran. This work combined density functional theory (DFT) calculations and temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) measurements to investigate the hydrodeoxygenation (HDO) activity of furfural on bimetallic surfaces prepared by modifying Pt(111) with 3d transition metals (Cu, Ni, Fe, and Co). The stronger binding energy of furfural and higher tilted degree of the furan ring on the Co-terminated bimetallic surface resulted in a higher activity for furfural HDO to produce 2-methylfuran in comparison to that on either Pt(111) or Pt-terminated PtCoPt(111). The 3d-terminated bimetallic surfaces with strongly oxophilic 3d metals (Co and Fe) showed higher 2-methylfuran yield in comparison to those surfaces modified with weakly oxophilic 3d metals (Cu and Ni). The effect of oxygen on the HDO selectivity was also investigated on oxygen-modified bimetallic surfaces, revealing that the presence of surface oxygen resulted in a decrease in 2-methylfuran yield. The combined theoretical and experimental results presented here should provide useful guidance for designing Pt-based bimetallic HDO catalysts.Understanding the Role of M/Pt(111) (M = Fe, Co, Ni, Cu) Bimetallic Surfaces for Selective Hydrodeoxygenation of Furfuralfurfural; hydrodeoxygenation; 2-methylfuran; bimetallic surfaces; oxophilicityx36201742#N/AFALSE
5198
acscatal.7b0319810.1021/acscatal.7b03198FALSEhttps://doi.org/10.1021/acscatal.7b03198Hu, XLACS Catal.The water-splitting reaction provides a promising mechanism to store renewable energies in the form of hydrogen fuel. The oxidation half-reaction, the oxygen evolution reaction (OER), is a complex four-electron process that constitutes an efficiency bottleneck in water splitting. Here we report a highly active OER catalyst, cobalt vanadium oxide. The catalyst is designed on the basis of a volcano plot of metal-OH bond strength and activity. The catalyst can be synthesized by a facile hydrothermal route. The most active pure-phase material (a-CoVOx) is X-ray amorphous and provides a 10 mA cm(-2) current density at an overpotential of 347 mV in 1 M KOH electrolyte when immobilized on a flat substrate. The synthetic method can also be applied to coat a high-surface-area substrate such as nickel foam. On this three-dimensional substrate, the a-CoVOx catalyst is highly active, reaching 10 mA cm(-2) at 254 mV overpotential, with a Tafel slope of only 35 mV dec(-1). This work demonstrates a-CoVOx as a promising electrocatalyst for oxygen evolution and validates M-OH bond strength as a practical descriptor in OER catalysis.Amorphous Cobalt Vanadium Oxide as a Highly Active Electrocatalyst for Oxygen Evolutionoxygen evolution reaction; cobalt vanadium oxide; electrocatalyst; volcano plot; amorphous materials113201832#N/ATRUE
5199
acscatal.7b0160010.1021/acscatal.7b01600FALSEhttps://doi.org/10.1021/acscatal.7b01600Shao-Horn, YACS Catal.Herein we investigate the reaction intermediates formed during CO oxidation on copper-substituted ceria nanopartiCles (Cu0.1Ce0.9O2-x) by means of in situ spectroscopic techniques and identify an activity descriptor that rationalizes a trend with other metal substitutes (M0.1Ce0.9O2-x M = Mn, Fe, Co, Ni). In situ X-ray absorption spectroscopy (XAS) performed under catalytic conditions demonstrates that O2- transfer occurs at dispersed copper centers, which are redox active during catalysis. In situ XAS reveals a dramatic reduction at the copper centers that is fully reversible under catalytic conditions, which rationalizes the high catalytic activity of Cu0.1Ce0.9O2-x Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) show that CO can be oxidized to CO32- in the absence of O-2. We find that CO32- desorbs as CO2 only under oxygen-rich conditions when the oxygen vacancy is filled by the dissociative adsorption of O-2. These data, along with kinetic analyses, lend support to a mechanism in which the breaking of copper oxygen bonds is rate-determining under oxygen-rich conditions, while refilling the resulting oxygen vacancy is rate determining under oxygen-lean conditions. On the basis of these observations and density functional calculations, we introduce the computed oxygen vacancy formation energy (E-vac) as an activity descriptor for substituted ceria materials and demonstrate that Evac successfully rationalizes the trend in the activities of M0.1Ce0.9O2-x catalysts that spans three orders of magnitude. The applicability of Evac as a useful design descriptor is demonstrated by the catalytic performance of the ternary oxide Cu0.1La0.1,Ce0.8O2-x, which has an apparent Activation energy rivaling those of state-of-the-art Au/TiO2 materials. Thus, we suggest that cost-effective catalysts for CO oxidation can be rationally designed by judicious choice of substituting metal through the computational screening of E-vac.In Situ Spectroscopy and Mechanistic Insights into CO Oxidation on Transition-Metal-Substituted Ceria NanopartiClescatalysis; mechanisms of reactions; in situ spectroscopy; ambient pressure XPS; nanotechnology; DFT; ceriax44201788#N/AFALSE
5200
acscatal.7b0159510.1021/acscatal.7b01595FALSEhttps://doi.org/10.1021/acscatal.7b01595Wang, JLTemplate-Grown MoS2 Nanowires Catalyze the Hydrogen Evolution Reaction: Ultralow Kinetic Barriers with High Active Site Densityx2017#N/AFALSE
5201
acscatal.7b0306310.1021/acscatal.7b03063FALSEhttps://doi.org/10.1021/acscatal.7b03063Muller, CACS Catal.To mitigate Climate change, the reduction of anthropogenic CO2 emissions is of paramount importance. CO2 capture and storage has been identified as a promising short- to midterm solution, yet the underground storage of CO2 faces often severe public resistance. In this regard, the conversion of the CO2 captured into useful chemicals or fuels is an attractive alternative. Here, we propose and experimentally demonstrate a process that directly integrates CO2 utilization into CO2 capture allowing for the full conversion of the CO2 captured and the selective production of a synthesis gas. The process is attractive both economically and from a process operation point of view as the coupled reactions are performed in a single reactor. The concentration of (unreacted) CO2 in the off-gas is below 0.08%, demonstrating the almost full conversion of the CO2 captured in a single, integrated step. Importantly, the process is demonstrated using a nonprecious metal catalyst and an inexpensive naturally occurring CO2 sorbent, viz., limestone.Integrated CO2 Capture and Conversion as an Efficient Process for Fuels from Greenhouse GasesCO2 capture and utilization; calcium looping; dry reforming of methane; Ni/MgO-Al2O3 DRM catalyst; limestone-derived CaO-based CO2 sorbent472018103#N/ATRUE
5202
acscatal.7b0149510.1021/acscatal.7b01495FALSEhttps://doi.org/10.1021/acscatal.7b01495Giambastiani, GACS Catal.Ammonia-borane (NH3 center dot BH3, AB), hydrazine (NH2NH2), lithium borohydride (Li(BH4)), and sodium alanate (Na(AlH4)) are popular chemical hydrogen storage inorganic solid materials featuring high gravimetric hydrogen contents (H wt %) and remarkable stability under ambient conditions. Ultrapure H-2 is formed from these compounds either via pyrolysis (i.e., a simple material heating) or via hydrolysis (chemical reaction with water). In both cases, a series of homogeneous and heterogeneous catalysts have been designed to assist the process. Among the latter, metal-organic frameworks (MOFs, crystalline 3D porous lattices made of metallic nodes and organic polytopic linkers) have rapidly emerged as versatile candidates for this role. The nanoconfinement of lightweight hydrides in MOFs produces a hydride@MOF composite material. Hydride coordination to MOF exposed metal sites or its reaction with functional groups on the organic linkers facilitates the thermal decomposition, lowering the hydrogen release temperature and increasing the hydrogen production rate. For hydrolysis, MOFs are used as templates for the preparation of metal(0) nanopartides (NPs) uniformly distributed through preliminary impregnation with a solution containing a metal salt followed by reduction. The NPs@MOF are the real active species that catalyze the reaction between the hydride and water, with concomitant H-2 evolution. This perspective highlights the most representative literature examples of MOFs as heterogeneous catalysts (or catalyst supports) for H-2 production from inorganic lightweight hydrides. Future trends in the field will also be discussed.Metal-Organic Frameworks as Heterogeneous Catalysts in Hydrogen Production from Lightweight Inorganic Hydridesmetal-organic frameworks; hydrogen; ammonia borane; hydrazine; borohydrides; alanatesx57201781#N/AFALSE
5203
acscatal.7b0143510.1021/acscatal.7b01435FALSEhttps://doi.org/10.1021/acscatal.7b01435Shao, MHACS Catal.Alloying Pt electrocatalysts with late transition metals (e.g., Ni, Co, and Fe) is an effective strategy to lower the catalyst cost and improve their tolerance toward CO in the anode of direct ethanol fuel cells. In this study, shape-controlled octahedral Pt-Ni/C nanocrystals with uniformly exposed (111) facets and an average edge length of 10 nm were synthesized. The octahedral Pt-Ni/C nanocatalyst was at least 4.6 and 7.7 times more active than conventional Pt-Ni/C and commercial Pt/C catalysts, respectively. In situ infrared spectroscopic results showed that the acetic acid/CO2 absorbance peak intensity on octahedral Pt-Ni/C was 7.6 and 1.4 times higher as compared to commercial Pt/C and conventional Pt-Ni/C, respectively, at 0.75 V. This result suggests that ethanol oxidation on octahedral Pt-Ni produces more acetic acid than on other surfaces. The synergistic electronic and facet effects may explain the superior ethanol oxidation reaction activity of octahedral Pt-Ni/C. Further surface modification with Ru significantly lowered the onset potential for CO, production by-100 mV and resulted in a higher selectivity on CO, as compared to unmodified surface, which further boosted the ethanol utilization efficiency.Pt-Ni Octahedra as Electrocatalysts for the Ethanol Electro-Oxidation ReactionPt alloy; ethanol electrooxidation; FTIR; reaction intermediates; adatomsx93201746#N/AFALSE
5204
acscatal.7b0118810.1021/acscatal.7b01188FALSEhttps://doi.org/10.1021/acscatal.7b01188Naldoni, AA Flexible Electrode Based on Al-Doped Nickel Hydroxide Wrapped around a Carbon Nanotube Forest for Efficient Oxygen Evolutionx2017#N/AFALSE
5205
acscatal.7b0275710.1021/acscatal.7b02757FALSEhttps://doi.org/10.1021/acscatal.7b02757Hensen, EJMACS Catal.The mechanism of CO hydrogenation to CH4 at 260 degrees C on a cobalt catalyst is investigated using steady-state isotopic transient kinetic analysis (SSITKA) and backward and forward chemical transient kinetic analysis (CTKA). The dependence of CHx residence time is determined by (CO)-C-12/H-2 -> (CO)-C-13/H-2 SSITKA as a function of the CO and H-2 partial pressure and shows that the CH, formation rate is mainly controlled by CH,, hydrogenation rather than CO dissociation. Backward CO/H-2 -> H-2 CTKA emphasizes the importance of H coverage on the slow CH, hydrogenation step. The H coverage strongly depends on the CO coverage, which is directly related to CO partial pressure. Combining SSITKA and backward CTKA allows determining that the amount of additional CH, obtained during CTKA is nearly equal to the amount of CO adsorbed to the cobalt surface. Thus, under the given conditions overall barrier for CO hydrogenation to CH4 under methanation condition is lower than the CO adsorption energy. Forward CTKA measurements reveal that O hydrogenation to H2O is also a relatively slow step compared to CO dissociation. The combined transient kinetic data are used to fit an explicit microkinetic model for the methanation reaction. The mechanism involving direct CO dissociation represents the data better than a mechanism in which H assisted CO dissociation is assumed. Microkinetics simulations based on the fitted parameters confirms that under methanation conditions the overall CO consumption rate is mainly controlled by C hydrogenation and to a smaller degree by O hydrogenation and CO dissociation. These simulations are also used to explore the influence of CO and H, partial pressure on possible rate-controlling steps.Mechanism of Cobalt-Catalyzed CO Hydrogenation: 1. Methanationcobalt; methanation; mechanism; SSITKA; rate-limiting step26201766#N/ATRUE
5206
acscatal.7b0109510.1021/acscatal.7b01095FALSEhttps://doi.org/10.1021/acscatal.7b01095Christopher, PACS Catal.5-(Hydroxymethyl)furfural (HMF) and furfural (FF) have been identified as valuable biomass-derived fuel precursors suitable for catalytic hydrodeoxygenation (HDO) to produce high octane fuel additives such dimethyl furan (DMF) and methyl furan (MF), respectively. In order to realize economically viable production of DMF and MF from biomass, catalytic processes with high yields, low catalyst costs, and process simplicity are needed. Here, we demonstrate simultaneous coprocessing of HMF and FF over Cu-Ni/TiO2 catalysts, achieving 87.5% yield of DMF from HMF and 88.5% yield of MF from FF in a one pot reaction. The Cu-Ni/TiO2 catalyst exhibited improved stability and regeneration compared to Cu/TiO2 and Cu/Al2O3 catalysts for FF HDO, with a similar to 7% loss in FF conversion over four sequential recyCles, compared to a similar to 50% loss in FF conversion for Cu/Al2O3 and a similar to 30% loss in conversion for Cu/TiO2. Characterization of the Cu-Ni/TiO2 catalyst by X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and H-2-temperature-programmed reduction and comparison to monometallic Cu and Ni on Al2O3 and TiO2 and bimetallic Cu-Ni/Al2O3 catalysts suggest that the unique reactivity and stability of Cu-Ni/TiO2 derives from support-induced metal segregation in which Cu is selectively enriched at the catalyst surface, while Ni is enriched at the TiO2 interface. These results demonstrate that Cu-Ni/TiO2 catalysts promise to be a system capable of integrating directly with a combined HMF and FF product stream from biomass processing to realize lower cost production of liquid fuels from biomass.Support Induced Control of Surface Composition in Cu-Ni/TiO2 Catalysts Enables High Yield Co-Conversion of HMF and Furfural to Methylated Furansfurfural; hydroxymethyl furfural; hydrodeoxygenation; bimetallic catalysts; biofuels; support effectsx932017100#N/AFALSE
5207
acscatal.7b0271810.1021/acscatal.7b02718FALSEhttps://doi.org/10.1021/acscatal.7b02718Shao, MHACS Catal.Hydrogen and oxygen evolution reactions (HER and OER) are important for many electrochemical systems. Besides traditional noble-metal-based catalysts, carbon-based materials have been found to be effective for catalyzing these reactions. Various carbon structures doped with heteroatoms (N, S, P, B, and transition metals) and graphitic-layer-encapsulated metal and compound partiCles have shown good activities toward HER and OER at universal pHs. In this Perspective, recent research on the development of carbon-based electrocatalysts for HER and OER, as well as their challenges and opportunities are discussed.Carbon-Based Electrocatalysts for Hydrogen and Oxygen Evolution Reactionswater splitting; electrolyzer; core-shell structure; nonprecious-metal electrocatalyst; metal organic framework2282017137#N/ATRUE
5208
acscatal.7b0099910.1021/acscatal.7b00999FALSEhttps://doi.org/10.1021/acscatal.7b00999Carter, EAACS Catal.NiOx has long been studied both as a battery cathode material and electrocatalyst for the oxygen evolution reaction (OER). Numerous investigations have demonstrated that Fe-doped nickel oxyhydroxide (NiOOH) is one of the most active OER catalysts in alkaline media. Despite extensive research, however, many unanswered questions pertaining to the OER mechanism on this material remain. Here, using density functional theory + U calculations, we compare several surfaces of beta-NiOOH studied for the OER and determine that unlike some earlier models selected, the (001) surface is the most stable surface under electrochemical conditions. We then examine several magnetic states of this material and predict that, unlike bulk beta-NiOOH, (001)-beta-NiOOH manifests a slight preference to be ferromagnetic. We then use the resulting structural model to compare in detail four commonly proposed OER mechanisms. In addition to exCluding a proposed mechanism involving hydrogen peroxide formation, we identify multiple binuClear mechanisms with slightly lower overpotentials than the commonly studied associative mechanism. All exhibit overpotentials that coincide well with measured values. However, the similarity in calculated overpotentials highlights the fact that several mechanisms are likely to be operative under electrochemical conditions on beta-NiOOH. This finding suggests that much of the complexity of studying the OER on NiOOH is due to multiple competing mechanisms occurring under given conditions, which should be accounted for in subsequent analyses.A Density Functional plus U Assessment of Oxygen Evolution Reaction Mechanisms on beta-NiOOHoxygen evolution reaction; nickel oxyhydroxide; density functional theory; transition metal oxides; electrocatalysisx642017107#N/AFALSE
5209
acscatal.7b0099610.1021/acscatal.7b00996FALSEhttps://doi.org/10.1021/acscatal.7b00996Strasser, PpH-Induced versus Oxygen-Induced Surface Enrichment and Segregation Effects in Pt-Ni Alloy NanopartiCle Fuel Cell Catalystsx2017#N/AFALSE
5210
acscatal.7b0097810.1021/acscatal.7b00978FALSEhttps://doi.org/10.1021/acscatal.7b00978Ess, DHACS Catal.HomodinuClear transition-metal catalysts with a direct metal metal bond have the potential to induce novel reaction mechanisms and selectivity compared with mononuClear catalysts. The dinuClear (i-PrNDI)Ni-2(C6H6) (NDI = naphthyridine-diimine) complex catalyzes selective cyClotrimerization of monosubstituted alkynes, whereas mononuClear Ni catalysts generally give cyClotetramerization of alkynes. Density functional theory calculations reveal that the homodinuClear Ni-Ni catalyst induces a spin crossover mechanism that involves metallacyClopentadiene and nonClassical bridging metallacyCloheptatriene intermediates. The cis configuration of the nonClassical bridging metallacyCloheptatriene Ni-Vinyl bonds results in alkyne cyClotrimerization by fast reductive elimination. This dinuClear mechanism differs from previously reported mononuClear Ni mechanisms and provides an explanation for cyClotrimerization versus cyClotetramerization selectivity and arene regioselectivity.Catalytic DinuClear Nickel Spin Crossover Mechanism and Selectivity for Alkyne CyClotrimerizationdinuClear; catalysis; density functional theory; nickel; alkyne cyClotrimerizationx202017119#N/AFALSE
5211
acscatal.7b0261710.1021/acscatal.7b02617FALSEhttps://doi.org/10.1021/acscatal.7b02617Apfel, UPACS Catal.Inspired by our recent finding that Fe4.5Ni4.5S8 rock is a highly active electrocatalyst for HER, we set out to explore the influence of the Fe:Ni ratio on the performance of the catalyst. We herein describe the synthesis of (FexNi1-x)(9)S-8 (x = 0-1) along with a detailed elemental composition analysis. Furthermore, using linear sweep voltammetry, we show that the increase in the iron or nickel content, respectively, lowers the activity of the electrocatalyst toward HER Electrochemical surface area analysis (ECSA) Clearly indicates the highest amount of active sites for a Fe:Ni ratio of 1:1 on the electrode surface pointing at an altered surface composition of iron and nickel for the other materials. Specific metal-metal interactions seem to be of key importance for the high electrocatalytic HER activity, which is supported by DFT calculations of several surface structures using the surface energy as a descriptor of catalytic activity. In addition, we show that a temperature increase leads to a significant decrease of the overpotential and gain in HER activity. Thus, we showcase the necessity to investigate the material structure, composition and reaction conditions when evaluating electrocatalysts.Influence of the Fe:Ni Ratio and Reaction Temperature on the Efficiency of (FexNi1-x)(9)S-8 Electrocatalysts Applied in the Hydrogen Evolution Reactioniron nickel sulfide; pentlandite; surface composition; hydrogen evolution; electrocatalysis; electrochemistry; HER61201854#N/ATRUE
5212
acscatal.7b0250110.1021/acscatal.7b02501FALSEhttps://doi.org/10.1021/acscatal.7b02501Wang, CACS Catal.Pt-bimetallic alloys involving 3d transition metals (Co, Ni, etc.) are promising electrocatalysts for the oxygen reduction reaction (ORR). Despite the enhanced catalytic activity versus Pt, the electrocatalytic performance of Pt-bimetallic catalysts is however limited by the lack of long-term durability, primarily due to the leaching of the non-noble element under harsh electrochemical conditions. Our study shows that the core-shell nanostructure comprising a Pt shell and a cobalt core (denoted as Co(alPt) could overcome this limitation, demonstrating similar to 10 times improvement in catalytic activity versus commercial Pt catalysts and no more than 13% of loss after 30000 potential cyCles. The evolutions of nanoscale and surface structures over the course of extensive potential cyCling were followed by combining electron microscopic elemental mapping and electrochemical studies of CO stripping. Atomistic simulations and density functional theory calculations suggest that the core-shell nanostructure could protect the non-noble cobalt from leaching under the electrochemical annealing conditions while maintaining the beneficial mechanisms of bimetallic systems for catalytic activity enhancement.Core-Shell Nanostructured Cobalt-Platinum Electrocatalysts with Enhanced Durabilitycobalt; platinum; core-shell nanopartiCles; electrocatalysts; oxygen reduction reaction; fuel cells41201847#N/ATRUE
5213
acscatal.7b0087610.1021/acscatal.7b00876FALSEhttps://doi.org/10.1021/acscatal.7b00876Sun, YJACS Catal.Water electrolysis to produce H-2 and O-2 with renewable energy input has been generally viewed as an attractive route to meet future global energy demands. However, the sluggish O-2 evolution reaction usually requires high overpotential and may yield reactive oxygen species (ROS) that can degrade the electrolyzer membrane and hence shorten the device lifetime. In addition, the potential gas crossover may result in an explosive H-2/O-2 mixture and hence safety risks. To address these issues, we herein report a general electrolysis strategy for the simultaneous H-2 production and alcohol oxidative upgrading (e.g., Benzyl alcohol, 4-nitroBenzyl alcohol, 4-methylBenzyl alcohol, ethanol, and 5-hydroxymethylfurfural), in which the thermodynamics of the latter is much easier than that of water oxidation. A facile and environmentally friendly template-free electrodeposition was used to obtain a 3D hierarchically porous nickel-based electrocatalyst (hp-Ni) for such an integrated electrolysis, requiring a voltage of similar to 220 mV smaller than that of water splitting to achieve 50 mA cm(-2) together with robust stability, high Faradaic efficiencies, and no formation of ROS, as well as production of valuable products at both the cathode (H-2) and anode (alcohol oxidation products). More importantly, we demonstrated that these diverse alcohol oxidations over hp-Ni exhibited similar onset potentials which were largely determined by the desirable oxidation potential of hp-Ni, irrespective of the different intrinsic thermodynamics of these alcohol oxidation reactions. This result provides a new direction for the rational design of heterogeneous transition-metal-based electrocatalysts with lower oxidation potential for more highly efficient electrocatalytic alcohol oxidation.Efficient H-2 Evolution Coupled with Oxidative Refining of Alcohols via A Hierarchically Porous Nickel Bifunctional Electrocatalystelectrocatalysis; alcohol oxidation; hydrogen evolution; water splitting; nickelx118201750#N/AFALSE
5214
acscatal.7b0077210.1021/acscatal.7b00772https://doi.org/10.1021/acscatal.7b00772Molander, GAACS Catal.Alkyl xanthate esters are perhaps best known for their use in deoxygenation chemistry. However, their use in cross-coupling chemistry has not been productive, which is due, in part, to inadequate xanthate Activation strategies. Herein, we report the use of O-Benzyl xanthate esters, readily derived from alcohols, as radical pronuCleophiles in Csp(3)-Csp(2) cross couplings under Ni/photoredox dual catalysis. Xanthate (C-O) Cleavage is found to be reliant on photogenerated (sec-butyl) radical for nickel-catalyzed cross-couplings. Mechanistic experiments support independently, and relative rates are carefully orchestrated, such that no activators to form new carbon-centered radicals primed the fact that the key radical components are formed cross reactivity is observed.O-Benzyl Xanthate Esters under Ni/Photoredox Dual Catalysis: Selective Radical Generation and Csp(3)-Csp(2) Cross-CouplingAlkyl xanthate esters; cross-coupling; selective radical generation; carbon-centered radicals; metal-catalyzed reactionsPhotocatalyst392017456/15/2022FALSE
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acscatal.7b0234710.1021/acscatal.7b02347FALSEhttps://doi.org/10.1021/acscatal.7b02347Yorimitsu, HACS Catal.Nickel-catalyzed Negishi-type cross-coupling of Aryl methyl sulfoxides with Arylzinc reagents has been developed. By consuming the catalyst-oxidizing methanesulfenate anion through oxidative homocoupling of the Arylzinc reagent, smooth catalyst turnover could be executed. Arylzinc reagents prepared from Arylmagnesium bromide, zinc bromide, and lithium bromide were optimal to afford the products in good to high yields, while Arylzinc reagents prepared through other procedures showed lower reactivities. The reactivity of Aryl methyl sulfoxide was compared with that of typical Aryl (pseudo)halides.Nickel-Catalyzed Cross-Coupling Reaction of Aryl Sulfoxides with Arylzinc Reagents: When the Leaving Group is an OxidantNegishi coupling nickel catalyst; Aryl sulfoxide; Arylzinc; alkanesulfenate anion28201754#N/ATRUE
5216
acscatal.7b0055610.1021/acscatal.7b00556FALSEhttps://doi.org/10.1021/acscatal.7b00556Ma, SMACS Catal.A three-component hydroCarbonylation of enynes with ZnEt2 and CO2 is realized. Highly selective cyClizative Carbonylation of the C-C triple bond was observed. Preliminary mechanistic studies indicated both the concerted cyClometalation mechanism and the stepwise C=C bond directed Carbonylation were possible in this reaction.Selectivities in Nickel-Catalyzed HydroCarbonylation of Enynes with Carbon Dioxidenickel; enyne; diethyl zinc; carbon dioxide; cyClic hydroCarbonylationx15201750#N/AFALSE
5217
acscatal.7b0222510.1021/acscatal.7b02225FALSEhttps://doi.org/10.1021/acscatal.7b02225Yu, JGACS Catal.Electrochemical water splitting to produce hydrogen bears a great commitment for future renewable energy conversion and storage. By employing an in situ chemical vapor deposition (CVD) process, we prepared a bimetal (Ni and Mo) sulfide-based hybrid nanowire (NiS2/MoS2 HNW), which was composed of NiS2 nanopartiCles and MoS2 nanoplates, and revealed that it is an efficient electrocatalyst for the hydrogen evolution reaction (HER) over a wide pH range due to the collective effects of rational morphological design and synergistic heterointerfaces. On a simple glassy carbon (GC) electrode, NiS2/MoS2 HNW displays over potentials at -10 mA cm(-2) catalytic current density (eta(10)) of 204, 235, and 284 mV with small Tafel slopes of 65, 58, and 83 mV dec(-1) in alkaline, acidic, and neutral electrolyte, respectively, exhibiting pH-universal-efficient electrocatalytic HER performance, which is comparable to the recently reported state-of-the-art sulfide-based HER electrocatalysts. Theoretical calculations further confirm that the advantage of all-pH HER activity of NiS2/MoS2 originates from the enhanced dissociation of H2O induced by the formation of lattice interfaces of NiS2-MoS2 heterojunctions. This work can pave a valuable route for designing and fabricating inexpensive and high-performance electrocatalysts toward HER over a wide pH range.In Situ Fabrication of Ni-Mo Bimetal Sulfide Hybrid as an Efficient Electrocatalyst for Hydrogen Evolution over a Wide pH Rangebimetal sulfide; NiS2/MoS2 HNW; hydrogen evolution reaction; wide pH range; lattice interfaces165201744#N/ATRUE
5218
acscatal.7b0043610.1021/acscatal.7b00436FALSEhttps://doi.org/10.1021/acscatal.7b00436Gong, JLACS Catal.Partially oxidizing methane into syngas via a two-step chemical looping scheme is a promising option for methane transformation. Providing the optimum lattice oxygen to selectively produce syngas represents the major challenge for the development of oxygen carrier materials in chemical looping processes. This paper describes the design of WO3-based oxygen carriers as the primary source of lattice oxygen with high melting points and attractive syngas selectivity. To further enhance the lattice oxygen availability and methane conversion capacity, NiO nanoClusters are introduced, considering the doping effect on chemical bonding disruption in both bulk and surface regions. For Ni0.5WOx/Al2O3, the nickel cations incorporated into the bulk of WO3 can strongly weaken the tungsten oxygen bond strength and increase the availability of lattice oxygen. The surface-grafted nickel species can effectively activate methane molecules and catalyze the partial oxidation reaction. Total methane conversion and syngas yield can be substantially increased by about 2.7-fold in comparison with unmodified WO3/Al2O3. This work demonstrates that the bulk and surface modifications are feasible to tailor the active lattice oxygen of oxygen-carrying materials in chemical looping processes.Enhanced Lattice Oxygen Reactivity over Ni-Modified WO3-Based Redox Catalysts for Chemical Looping Partial Oxidation of Methanechemical looping; partial oxidation; tungsten oxides; nickel partiCles; lattice oxygenx69201770#N/AFALSE
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acscatal.7b0214610.1021/acscatal.7b02146FALSEhttps://doi.org/10.1021/acscatal.7b02146Bocarsly, ABACS Catal.The transformation of CO, into chemical feedstocks or fuels is an attractive goal, but catalysts capable of generating useful, multicarbon products have been challenging to design. Here, thin films of the intermetallic Ni3Al on glassy carbon are found to be electrocatalytic for aqueous CO2 reduction. At-1.38 V vs Ag/AgC1, Ni3Al films produce a range of Cl, C2, and C3 oxygenated organic species inCluding 1-propanol and methanol at Faradaic efficiencies that are competitive with single-metal electrodes reported in the literature. To the best of our knowledge, Ni3Al on glassy carbon is the only noncopper-containing material shown to generate C3 products.Ni-Al Films on Glassy Carbon Electrodes Generate an Array of Oxygenated Organics from CO2CO2 reduction; electrocatalysis; nickel aluminum; Ni3Al; thin film; C3 production; 1-propanol; methanol29201736#N/ATRUE
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acscatal.7b0041110.1021/acscatal.7b00411FALSEhttps://doi.org/10.1021/acscatal.7b00411Lee, HACS Catal.Plasmonic metal nanopartiCles absorb light energy and release the energy through radiative or nonradiative channels. Surface catalytic reactions take advantage of the nonradiative energy relaxation of plasmons with enhanced activity. Particularly, binary nanopartiCles are interesting because diverse integration is possible, consisting of a plasmonic part and a catalytic part. Herein, we demonstrated ethanol dehydrogenation under light irradiation using Ag-Ni binary nanopartiCles with different shapes, snowman and core-shell, as plasmonic catalysts. The surface plasmon formed in the Ag part enhanced the surface catalytic reaction that occurred at the Ni part, and the shape of the nanopartiCles affected the extent of the enhancement. The surface plasmon compensated the thermal energy required to trigger the catalytic reaction. The absorbed light energy was transferred to the catalytic part by the surface plasmon through the nonradiative hot electrons. The effective energy barrier was greatly reduced from 41.6 kJ/mol for the Ni catalyst to 25.5 kJ/mol for the core-shell nanopartiCles and 22.3 kJ/mol for the snowman-shaped nanopartiCles. These findings can be helpful in designing effective plasmonic catalysts for other thermally driven surface reactions.Surface Plasmon Aided Ethanol Dehydrogenation Using Ag-Ni Binary NanopartiClesplasmonic catalyst; binary nanopartiCles; ethanol; dehydrogenation; effective energy barrierx23201767#N/AFALSE
5221
acscatal.7b0041010.1021/acscatal.7b00410FALSEhttps://doi.org/10.1021/acscatal.7b00410Maillard, FACS Catal.Because of their enhanced oxygen reduction reaction (ORR) kinetics (9 and 6 -fold) enhancement of specific activity and mass activity for the ORR relative to those of a commercial Pt/C catalyst, respectively), hollow PtNi/C nanopartiCles are attracting a growing level of interest. This catalytic enhancement arises from the synergetic combination of strain and ligand effects, the presence of structural defects, and their hollow morphology producing a convex and concave catalytic sites. However, preventing a loss of catalytic activity under practical proton exchange membrane fuel cell (PEMFC) cathode operating conditions on alloys of platinum with other transition metals (PtM alloys, M being a transition metal) or M-rich core@Pt-rich shell nanopartiCles remains highly challenging. A loss of performance is usually observed because of the dissolution of Pt and M under the harsh operating conditions of a PEMFC cathode, but the question remains unanswered for nanomaterials in which catalytic activity is not solely due to alloying effects. Herein, we have carefully investigated the changes in the ORR activity of solid and hollow PtNi/C nanopartiCles with identical chemical compositions but different nanostructures during an accelerated stress test simulating PEMFC cathode operation. By combining chemical, physical, and electrochemical techniques, we show that the dissolution of Ni atoms constitutes the primary reason for the loss of ORR catalytic activity but that the initial catalytic advantage of hollow over solid PtNi/C nanopartiCles is maintained in the long term. Hence, implementing structural disorder in PEMFC cathode electrocatalysts represents a promising direction for sustainably improving ORR kinetics.Implementing Structural Disorder as a Promising Direction for Improving the Stability of PtNi/C NanopartiCleshollow metal nanopartiCles; nanoscale Kirkendall effect; galvanic replacement; oxygen reduction reaction; degradation mechanismx36201778#N/AFALSE
5222
acscatal.7b0030010.1021/acscatal.7b00300FALSEhttps://doi.org/10.1021/acscatal.7b00300Liao, JACS Catal.An enantioselective Cu/Pd-catalyzed borylative coupling of styrenes with Aryl/alkenyl iodides was realized using a chiral sulfoxide-phosphine (SOP) ligand. Enantioenriched 1,1-diArylethyl and beta-Arylhomoallylic boronates are readily prepared. A streamlined procedure merging Arylboration and subsequent Pd-catalyzed Suzuki-Miyaura cross-coupling enables the modular assembly of enantioenriched 1,1,2-triArylethanes, inCluding two medicinally important chiral small-molecule targets.Modular Synthesis of Enantioenriched 1,1,2-TriArylethanes by an Enantioselective Arylboration and Cross-Coupling Sequencex76201786#N/AFALSE
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acscatal.7b0022510.1021/acscatal.7b00225FALSEhttps://doi.org/10.1021/acscatal.7b00225Yang, WMACS Catal.Metal cocatalysts are widely utilized for enhancing photocatalytic conversion. In TiO2-based photocatalysts, a wide range of metals dispersed on TiO2 surfaces were observed to be effective for photocatalytic hydrogen production. To Clarify the metal/oxide synergistic effect in photocatalysis and the insensitivity of photoactivity on metal types, here we investigate the mechanism of electron transfer from semiconductor to the cocatalyst by using ab initio molecular dynamics and hybrid density functional theory calculations. By determining the optimal geometry of a Pt-13 subnano Cluster on anatase TiO2(101) and quantifying the electron transfer energetics, we find that the electron transfer from oxide to the metal Cluster is significantly boosted (exothermic by more than 0.3 eV) by the adsorption of proton on the metal Cluster, which is otherwise endothermic without the presence of proton. This cooperative effect between oxide, subnano metal Cluster, and adsorbed proton is rationalized from electronic structure analyses. We show that the proton-promoted electron transfer phenomenon in photocatalysis appears to be universally present, as evidenced from theoretical calculations by replacing Pt with other metals, inCluding Co, Ni, Cu, Pd, and Rh. This mechanism differs fundamentally from the proton-coupled electron transfer frequently quoted in electrocatalysis and may assist the photocatalyst design toward highly efficient solar fuel production.Proton-Promoted Electron Transfer in Photocatalysis: Key Step for Photocatalytic Hydrogen Evolution on Metal/Titania Compositesproton-promoted electron transfer; proton-coupled electron transfer; photocatalytic hydrogen evolution; TiO2; metal cocatalyst; density functional theoryx36201756#N/AFALSE
5224
acscatal.7b0009410.1021/acscatal.7b00094FALSEhttps://doi.org/10.1021/acscatal.7b00094Molander, GAPhotoredox-Mediated Routes to Radicals: The Value of Catalytic Radical Generation in Synthetic Methods DevelopmentPhotocatalyst2017#N/AFALSE
5225
acscatal.7b0197110.1021/acscatal.7b01971FALSEhttps://doi.org/10.1021/acscatal.7b01971Wei, ZDACS Catal.The sluggish kinetics of the oxygen evolution reaction (OER) is the bottleneck of water electrolysis for hydrogen generation. Developing cost-effective OER materials with a high value of practical application is a prerequisite to achieve extreme performance in both activity and stability. Herein, we report a dual ligand synergistic modulation strategy to accurately tune the structure of transition-metal materials at atomic level, which finally achieves satisfactory results for the unity between robust stability and high activity. Remarkably, the elaborately designed S and OH dual-ligand NiCo2(SOH)(x) catalyst exhibits an excellent OER activity with a very small overpotential of 0.29 Vat a current density of 10 mA cm(-2) and a strong durability even after 30 h accelerated aging at a large current density of 100 mA cm(-2), both of which are superior to most of the state-of-the-art OER catalysts so far. The density functional theory (DFT) calculations disClose that the synergy of OH and S ligands on the surface of NiCo2(SOH)(x) can delicately tune the electronic structure of metal active centers and their chemical environment, which results in optimal binding energies of the OER intermediates (*OH, *O, and *OOH) and a strengthened binding energy between metal and anion ligands, thus leading to an excellent intrinsically enhanced OER activity and stability, respectively. Meanwhile, the special nonmagnetism of NiCo2(SOH)(x) can significantly weaken the resistance of O-2 desorption on the catalyst surface, thus facilitating the O-2 evolution proceedings.Dual-Ligand Synergistic Modulation: A Satisfactory Strategy for Simultaneously Improving the Activity and Stability of Oxygen Evolution Electrocatalystsoxygen evolution; electrocatalysis; dual-ligand modulation; DFT calculation; magnetism66201745#N/ATRUE
5226
acscatal.6b0366510.1021/acscatal.6b03665https://doi.org/10.1021/acscatal.6b03665Molander, GAACS Catal.An operationally simple, mild, redox-neutral method for the photoredox Alkylation of imines is reported. Utilizing an inexpensive organic photoredox catalyst, Alkyl radicals are readily generated from the single-electron oxidation of ammonium Alkyl bis(catecholato)silicates and are subsequently engaged in a C-C bond-forming reaction with imines. The process is highly selective, metal-free, and does not require a large excess of the Alkylating reagent or the use of acidic additives.Mild, Redox-Neutral Alkylation of !mines Enabled by an Organic Photocatalystvisible light; photocatalysis; imines; hypervalent silicon; radical AlkylationPhotocatalyst94201740#N/AFALSE
5227
acscatal.6b0366210.1021/acscatal.6b03662FALSEhttps://doi.org/10.1021/acscatal.6b03662Mul, GDACS Catal.Transients in the composition of Ni@NiOx core shell co -catalysts deposited on SrTiO3 are discussed on the basis of state-of-the-art continuous analysis of photocatalytic water splitting, and post-XPS and TEM analyses. The formation of excessive hydrogen (H-2:O-2 >> 2) in the initial stages of illumination demonstrates oxidation of Ni(OH)(2) to NiOOH (nickel oxyhydroxide), with the latter catalyzing water oxidation. A disproportionation reaction of Ni and NiOOH, yielding Ni(OH)(2) with residual embedded Ni, occurs when illumination is discontinued, which explains repetitive transients in (excess) hydrogen and oxygen formation when illumination is reinitiated.Transient Behavior of Ni@NiOx Functionalized SrTiO3 in Overall Water Splittingsolar water splitting; SrTiO3; Ni@NiOx co-catalysts; transient behavior; regenerationx50201718#N/AFALSE
5228
acscatal.6b0349710.1021/acscatal.6b03497FALSEhttps://doi.org/10.1021/acscatal.6b03497Zhao, CACS Catal.Surface wettability is very important for designing and developing. heterogeneous electrocatalysts that can be appliedin an aqueous environment. Here, by adjusting the surface wettability of the catalyst using a facile two-step strategy, a porous nanosheet electrocatalyst composed of NiFe hydroxide and NiFe phosphate (denoted as NiFe/NiFe:Pi), has been designed and developed. The two-step strategy not only allows us to successfully control the morphology but also provides an approach to modify the surface chemical property of a catalyst. After phosphorylation, the surface wettability of the NiFe/NiFe:Pi catalyst is significantly enhanced (contact angle 44 +/- 3 degrees) in comparison to that of NiFc hydroxide electrode without phosphorylation (contact angle 129 +/- 5 degrees). Serving as an oxygen evolution catalyst in 1 M KOH aqueous solution, the NiFe/NiFe:Pi electrode yields strong synergistic. oxygen evolution activity to deliver a current density of 10 mA cm(-2) with an overpotential merely of 290 mV. The catalyst also exhibits extraordinary high current densities of 300 mA cm(-2) at an extremely low overpotential of 340 mV, which is among the best Ni-based OER electrocatilysts to date. The well-maintained open, porous nanosheet structure, enhanced surface wettability, and increased charge transfer rate at the NiFe/NiFe:Pi catalyst, together with effective mass transport and enlarged catalytic active sites offered by the hierarchical porous structure, contribute to the extraordinary water oxidation performance.Enhancing Water Oxidation Catalysis on a Synergistic Phosphorylated NiFe Hydroxide by Adjusting Catalyst Wettabilitywettability; NiFe hydroxide; NiFe phosphate; phosphoglation; oxygen evolution reactionx167201745#N/AFALSE
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acscatal.7b0180010.1021/acscatal.7b01800FALSEhttps://doi.org/10.1021/acscatal.7b01800Kim, KSACS Catal.The persistently increasing energy consumption and the low abundance of conventional fuels have raised serious concerns all over the world. Thus, the development of technology for Clean-energy production has become the major research priority worldwide. The globalization of advanced energy conversion technologies like rechargeable metal-air batteries, regenerated fuel cells, and water-splitting devices has been majorly benefitted by the development of apposite catalytic materials that can proficiently carry out the pertinent electrochemical processes like oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and water hydrolysis. Despite a handful of superbly performing commercial catalysts, the high cost and low electrochemical stability of precursors have consistently discouraged their long-term viability. As a promising substitute of conventional platinum-, palladium-, iridium-, gold-, silver-, and ruthenium-based catalysts, various transition-metal (TM) ions (for example, Fe, Co, Mo, Ni, V, Cu, etc.) have been exploited to develop advanced electroactive materials to outperform the state-of-the-art catalytic properties. Among these TMs, nickel has emerged as one of the most hopeful constituents due to its exciting electronic properties and anticipated synergistic effect to dramatically alter surface properties of materials to favor electrocatalysis. This review artiCle will broadly confer about recent reports on nickel-based nanoarchitectured materials and their applications toward ORR, OER, HER, and whole water splitting. On the basis of these applications and properties of nickel derivatives, a futuristic outlook of these materials has also been presented.Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactionsnickel-based electrocatalysts; oxygen reduction reaction; oxygen evolution reaction; hydrogen evolution reaction; water splitting; bifunctional electrocatalysts4132017239#N/ATRUE
5230
acscatal.6b0339410.1021/acscatal.6b03394https://doi.org/10.1021/acscatal.6b03394Chen, CACS Catal.Use of palladium catalysts in olefin polymerization and copolymerization has evolved rapidly. In contrast, earth abundant and low-cost nickel catalysts generally suffer from drawbacks that inClude low thermal stability and generation of low molecular-weight polymers in the presence of polar monomers. By taking advantage of several design strategies, high-performance phosphine-sulfonate-based nickel catalysts were developed. These nickel catalysts demonstrated high activities and thermal stabilities to afford high-molecular-weight polyethylene. Most importantly, high-molecular-weight copolymers could be generated through the copolymerization of ethylene with a variety of polar monomers.Rational Design of High-Performance Phosphine Sulfonate Nickel Catalysts for Ethylene Polymerization and Copolymerization with Polar Monomersnickel catalysts; ligand design; olefin polymerization; polar monomer; copolymerizationx127201780#N/AFALSE
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acscatal.6b0334410.1021/acscatal.6b03344FALSEhttps://doi.org/10.1021/acscatal.6b03344Schoenebeck, FACS Catal.The direct introduction of the valuable SCF3 moiety into organic molecules has received considerable attention. While it can be achieved successfully for Aryl chlorides under catalysis with Ni degrees(cod)(2) and dppf, this report investigates the Ni-catalyzed functionalization of the seemingly more reactive Aryl halides Arl and ArBr. Counterintuitively, the observed conversion triggered by dppf/Ni degrees is ArCI > ArBr > Arl, at odds with bond strength preferences. By a combined computational and experimental approach, the origin of this was identified to be due to the formation of (dppf)Ni-1, which favors beta-F elimination as a competing pathway over the productive cross-coupling, ultimately generating the inactive complex (dppf)Ni(SCF2) as a catalysis dead end. The complexes (dppf)Ni-1-Br and (dppf)Ni-1-I were isolated and resolved by X-ray crystallography. Their formation was found to be consistent with a ligand-exchange-induced comproportionation mechanism. In stark contrast to these phosphine-derived Ni complexes, the corresponding nitrogen-ligand-derived species were found to be likely competent catalysts in oxidation state I. Our computational studies of N-ligand derived Ni-1 complexes fully support productive Ni-1/Ni-111 catalysis, as the competing beta-F elimination is disfavored. Moreover, N-derived Ni-1 complexes are predicted to be more reactive than their Ni counterparts in catalysis. These data showcase fundamentally different roles of Ni-1 in carbon-heteroatom bond formation depending on the ligand sphere.When Weaker Can Be Tougher: The Role of Oxidation State (I) in P-vs N-Ligand-Derived Ni-Catalyzed Trifluoromethylthiolation of Aryl Halidesnickel; cross-coupling; DFT; fluorine; mechanisms; ligandx50201774#N/AFALSE
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acscatal.6b0327710.1021/acscatal.6b03277https://doi.org/10.1021/acscatal.6b03277Garg, NKACS Catal.Amides have been widely studied for decades, but their synthetic utility has remained limited in reactions that proceed with rupture of the amide C-N bond. Using Ni catalysis, we have found that amides can now be strategically employed in several important transformations: esterification, transamidation, Suzuki-Miyaura couplings, and Negishi couplings. These methodologies provide exciting new tools to build C-heteroatom and C-C bonds using an unconventional reactant (i.e., the amide), which is ideally suited for use in multi-step synthesis. It is expected that the area of amide C-N bond Activation using nonprecious metals will continue to flourish and, in turn, will promote the growing use of amides as synthons in organic synthesis.Breaking Amides using Nickel Catalysisnickel; catalysis; cross-coupling; amides; nonprecious metalx2592017162#N/AFALSE
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acscatal.6b0321510.1021/acscatal.6b03215FALSEhttps://doi.org/10.1021/acscatal.6b03215Fu, YACS Catal.An iridium photoredox catalyst in combination with a phosphoric acid catalyzes the deCarbonylative alpha-aminoAlkylation of natural and unnatural alpha-amino acid-derived redox-active esters (N-hydroxyphthalimide esters) with a broad substrate scope of N-heteroarenes at room temperature under irradiation. Dipeptide- and tripeptide-derived redox-active esters are also amenable substrates to achieve deCarbonylative insertion of a N-heterocyCle at the C-terminal of peptides, yielding molecules that have potential medicinal applications. The key factors for the success of this reaction are the following: use of a photoredox catalyst of suitable redox potential to controllably generate alpha-aminoAlkyl radicals, without overoxidation, and an acid cocatalyst to increase the electron deficiency of N-heteroarenes.Photoredox/Bronsted Acid Co-Catalysis Enabling DeCarbonylative Coupling of Amino Acid and Peptide Redox-Active Esters with N-HeteroarenesPhotocatalyst172201757#N/AFALSE
5234
acscatal.6b0320510.1021/acscatal.6b03205FALSEhttps://doi.org/10.1021/acscatal.6b03205Martin, RACS Catal.A visible-light-mediated atom transfer radical cyClization of unactivated Alkyl iodides is described. This protocol operates under mild conditions and exhibits high chemoselectivity profile while avoiding parasitic hydrogen atom transfer pathways. Preliminary mechanistic studies challenge the perception that a canonical photoredox catalytic cyCle is being operative.Visible-Light-Promoted Atom Transfer Radical CyClization of Unactivated Alkyl Iodidesvisible light; Alkyl halide; photocatalysis; atom economy; radical cyClization
Photocatalyst
46201747#N/AFALSE
5235
acscatal.6b0320110.1021/acscatal.6b03201FALSEhttps://doi.org/10.1021/acscatal.6b03201Rinaldi, RACS Catal.Raney Ni is perhaps the most widely used catalyst for the transformation of biogenic molecules in industrial practice (e.g., as in the production of sugar alcohols and hardening of vegetable oils). Currently, Raney Ni has found another key application; the catalytic upstream biorefining (CUB) of lignocellulose in which the soluble products released from the lignocellulosic matrix undergo reductive processes, rendering depolymerized lignin oils in addition to high-quality holocellulosic pulps. Despite the industrial importance of Raney Ni, its surface chemistry is poorly understood. In this study, using the H-transfer reaction between 2-propanol (2-PrOH) and phenol as a model reaction, we studied the influence of various alcohols on the catalytic performance of Raney Ni. For the H-transfer hydrogenation of phenol to cyClohexanol, the inhibition of the catalyst increases in the order of secondary alcohols < primary alcohols < polyols at 130 degrees C. To better understand the observed inhibition, we also studied the molecular interactions of the various alcohols at the catalytic solid liquid interface using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. The in situ spectroscopic data revealed that 2-PrOH adsorbs on at least two chemically different sites on the surface of Raney Ni. One of these two adsorption sites was attributed to the Ni site responsible for the saturation of the phenolic ring. The ATR-IR spectroscopic data also shows that the adsorption of phenol involves its hydroxyl group. Notably, the phenolic ring was found to be tilted with respect to the surface. Competitive adsorption of various other alcohols was also investigated at the catalytic solid liquid interface. The presence of methanol inhibited the adsorption of 2-PrOH to a significantly greater degree than phenol. Therefore, it is proposed that hydrogen transfer hydrogenation of the phenolic ring is inhibited in the presence of additional alcohols mainly due to the competitive adsorption with 2-PrOH. Several polyols were found to interact through a bidentate interaction with the catalyst surface, which explains their stronger inhibition compared to primary alcohols. In a broader context, this study proposes the effect of hemicellulose sugars and sugar alcohols, formed in the CUB process, upon the product selectivity of CUB catalyzed by Raney Ni and using 2-PrOH as an H-donor.Liquid-Phase H-Transfer from 2-Propanol to Phenol on Raney Ni: Surface Processes and InhibitionRaney Ni; in situ ATR-IR spectroscopy; hydrogen transfer; lignin; biomassx23201745#N/AFALSE
5236
acscatal.6b0319210.1021/acscatal.6b03192FALSEhttps://doi.org/10.1021/acscatal.6b03192Gao, QSACS Catal.Exploring noble-metal-free electrocatalysts with high efficiency for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) holds promise for advancing the production of H-2 fuel through water splitting. Herein, one-pot synthesis was introduced for MoS2-Ni3S2 heteronanorods supported by Ni foam (MoS2-Ni3S2 HNRs/NF), in which the Ni3S2 nanorods were hierarchically integrated with MoS2 nanosheets. The hierarchical MoS2-Ni3S2 heteronanorods allow not only the good exposure of highly active heterointerfaces but also the facilitated charge transport along Ni3S2 nanorods anchored on conducting nickel foam, accomplishing the promoted kinetics and activity for HER, OER, and overall water splitting. The optimal MoS2-Ni3S2 HNRs/NF presents low overpotentials (eta(10)) of 98 and 249 mV to reach a current density of 10 mA cm(-2) in 1.0 M KOH for HER and OER, respectively. Assembled as an electrolyzer for overall water splitting, such heteronanorods show a quite low cell voltage of 1.50 V at 10 mA cm(-2) and remarkable stability for more than 48 h, which are among the best values of current noble-metal-free electrocatalysts. This work elucidates a rational design of heterostructures as efficient electrocatalysts, shedding some light on the development of functional materials in energy chemistry.MoS2-Ni3S2 Heteronanorods as Efficient and Stable Bifunctional Electrocatalysts for Overall Water Splittingheterointerfaces; metal sulfides; electrocatalysis; hydrogen evolution reaction; oxygen evolution reaction; overall water splittingx565201774#N/AFALSE
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acscatal.6b0316110.1021/acscatal.6b03161FALSEhttps://doi.org/10.1021/acscatal.6b03161Marinescu, SCACS Catal.The efficient reduction of water into hydrogen has emerged as an attractive strategy for the conversion of solar energy into chemical bonds. Hydrogenase enzymes efficiently catalyze this reaction. The [NiFeSe] hydrogenases, a subClass of the [NiFe] hydrogenases with a selenocysteine replacing a cysteine residue, display higher activities and O-2 tolerance than the conventional sulfur-only [NiFe] hydrogenases. Inspired by the enhanced activity upon replacement of sulfur with selenium seen in nature, we report here the syntheses and characterization of cobalt and nickel selenolate coordination polymers (CPs) based on benzene-1,2,4,5-tetraselenolate (BTSe), which are efficient catalysts for the hydrogen evolution reaction (HER) from water. To reach a current density of 10 mA/cm(2), the benchmarking metric for HER, both cobalt and nickel systems display overpotentials of only similar to 350 mV, displaying a reduction in overpotential in comparison to the previously reported cobalt and nickel CPs based on benzene-1,2,4,5-tetrathiolate (BTT). In addition, the cobalt selenolate polymer displays a 217 mV improvement in the overpotential in comparison to its sulfur-only analogue that arises from the ability to promote an alternative mechanism at high catalyst loadings that was not available for the cobalt BTT CP.Bioinspired Metal Selenolate Polymers with Tunable Mechanistic Pathways for Efficient H-2 Evolutionelectrocatalysis; [NiFeSe] hydrogenases; coordination polymers; HER mechanism; water; solar-to-fuel technologies; artificial photosynthesis; solar energy conversionx30201743#N/AFALSE
5238
acscatal.6b0313210.1021/acscatal.6b03132FALSEhttps://doi.org/10.1021/acscatal.6b03132Ren, ZFACS Catal.Exploring efficient and durable catalysts from earth-abundant and cost-effective materials is highly desirable for the sluggish anodic oxygen evolution reaction (OER), which plays a key role in water splitting, fuel cells, and rechargeable metal air batteries. First-row transition-metal (Ni, Co, and Fe)-based compounds are promising candidates as OER catalysts to substitute the benchmark of noble-metal based catalysts, such as IrO2, and RuO2. Although Fe is the cheapest and one of the most abundant transition-metal elements, there are seldom papers reported on Fe-only compounds with outstanding catalytic OER activities. Here we propose an interesting strategy by growing iron nitride (Fe3N/Fe4N) based nanoporous film on three-dimensional (3D) highly conductive graphene/Ni foam, which is demonstrated to be a robust and durable self-supported 3D electrode for the OER featuring a very low overpotential of 238 mV to achieve a current density of 10 mA/cm(2), a small Tafel slope of 44.5 mV/dec, good stability, and 96.7% Faradaic yield. The high OER efficiency is by far one of the best for single-metal (Fe, Co, and Ni)-based catalysts, and even better than that of the benchmark IrO2, which is attributed to the fast electron transfer, high surface area, and abundant active sites of the catalyst. This development introduces another member to the family of cost-effective and efficient OER catalysts.Three-Dimensional Nanoporous Iron Nitride Film as an Efficient Electrocatalyst for Water Oxidationiron nitride; oxygen evolution reaction; three-dimensional; nanoporous; water splittingx116201734#N/AFALSE
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acscatal.6b0312610.1021/acscatal.6b03126FALSEhttps://doi.org/10.1021/acscatal.6b03126Yano, JACS Catal.The oxygen evolution reaction (OER) is a critical component of industrial processes such as electrowinning of metals and the chlor-alkali process. It also plays a central role in the development of a renewable energy field for generation a solar fuels by providing both the protons and electrons needed to generate fuels such as H-2 or reduced hydrocarbons from CO2. To improve these processes, it is necessary to expand the fundamental understanding of catalytically active species at low overpotential, which will further the development of electrocatalysts with high activity and durability. In this context, performing experimental investigations of the electrocatalysts under realistic working regimes (i.e., under operando conditions) is of crucial importance. Here, we study a highly active quinary transition-metal-oxide-based OER electrocatalyst by means of operando ambient-pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy performed at the solid/liquid interface. We observe that the catalyst undergoes a Clear chemical-structural evolution as a function of the applied potential with Ni, Fe, and Co oxyhydroxides comprising the active catalytic species. While CeO2 is redox inactive under catalytic conditions, its influence on the redox processes of the transition metals boosts the catalytic activity at low overpotentials, introducing an important design principle for the optimization of electrocatalysts and tailoring of high-performance materials.An Operando Investigation of (Ni-Fe-Co-Ce)O-x System as Highly Efficient Electrocatalyst for Oxygen Evolution Reactionoxygen evolution reaction (OER); transiton metal oxides; operando techniques; ambient pressure; catalytic conditions; synchrotron radiation; electron spectroscopiesx782017100#N/AFALSE
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acscatal.6b0310510.1021/acscatal.6b03105FALSEhttps://doi.org/10.1021/acscatal.6b03105Ji, HBCore-Shell NiO@PdO NanopartiCles Supported on Alumina as an Advanced Catalyst for Methane Oxidationx2017#N/AFALSE
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acscatal.7b0164810.1021/acscatal.7b01648FALSEhttps://doi.org/10.1021/acscatal.7b01648Norskov, JKACS Catal.Bimetallic catalysts are promising for the most difficult thermal and electrochemical reactions, but modeling the many diverse active sites on polycrystalline samples is an open challenge. We present a general framework for addressing this complexity in a systematic and predictive fashion. Active sites for every stable low-index facet of a bimetallic crystal are enumerated and cataloged, yielding hundreds of possible active sites. The activity of these sites is explored in parallel using a neural-network-based surrogate model to share information between the many density functional theory (DFT) relaxations, resulting in activity estimates with an order of magnitude fewer explicit DFT calculations. Sites with interesting activity were found and provide targets for follow-up calculations. This process was applied to the electrochemical reduction of CO2 on nickel gallium bimetallics and indicated that most facets had similar activity to Ni surfaces, but a few exposed Ni sites with a very favorable on-top CO configuration. This motif emerged naturally from the predictive modeling and represents a Class of intermetallic CO2 reduction catalysts. These sites rationalize recent experimental reports of nickel gallium activity and why previous materials screens missed this exciting material. Most importantly these methods suggest that bimetallic catalysts will be discovered by studying facet reactivity and diversity of active sites more systematically.Machine-Learning Methods Enable Exhaustive Searches for Active Bimetallic Facets and Reveal Active Site Motifs for CO2 Reductiondensity functional theory; bimetallic facets; machine learning; catalysis; electrochemistry; CO2 reduction; machine learning; DFT; energy163201724#N/ATRUE
5242
acscatal.6b0298810.1021/acscatal.6b02988FALSEhttps://doi.org/10.1021/acscatal.6b02988Sawamura, MACS Catal.A polystyrene-cross-linking bisphosphine PSDPPBz was synthesized through radical emulsion copolymer-ization between 4-t-butylstyrene as a monomer and tetraviny-lated 1,2-bis(diphenylphosphino)benzene (DPPBz) as a 4-fold cross-linker. The location of the DPPBz bisphosphine moiety at the branching points of the cross-linked network organic polymer allowed controlled bisphosphine monochelation to transition metals under conditions where homogeneous ligands may form bischelated single metal complexes or multinuClear complexes. PS-DPPBz showed high ligand performance in first-row transition metal catalysis, enabling challenging molecular Alkyl transformations that were not possible through the screening of existing homogeneous ligands. In the Ni-catalyzed amination of Aryl chlorides with N-Alkyl-substituted primary amines, the substrate scope has been expanded to inClude 2,6-disubstituted Aryl chlorides and N-tertiary-Alkyl-substituted primary amines. PS-DPPBz was effective for the Ni-catalyzed C-H/C-O coupling between 1,3-azoles and monocyClic Aryl pivalates, which showed poor reactivity in the reported homogeneous catalytic system based on 1,2-bis(dicyClohexylphosphino)ethane (DCYPE). The usefulness of the polymer-cross-linking strategy was also demonstrated in alkene hydrB(OH)2ration reactions catalyzed by Cu or Co.A Polystyrene-Cross-Linking Bisphosphine: Controlled Metal Monochelation and Ligand-Enabled First-Row Transition Metal Catalysisimmobilized phosphines; polystyrene; bisphosphine; first-row transition metals; C-N coupling; C-H/C-Ocoupling; hydrB(OH)2rationx352017115#N/AFALSE
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acscatal.7b0158710.1021/acscatal.7b01587FALSEhttps://doi.org/10.1021/acscatal.7b01587McEwen, JSACS Catal.In this study, we approach several common problems with the Ni-catalyzed methane steam reformation reaction (MSR) using a two-pronged approach combining density functional theory (DFT) calculations with experimental work. Specifically, we look at the deActivation of a Ni catalyst due to coke formation, its high operating temperature requirements, and the high steam to methane (H2O/CH4) ratio needed for proper MSR operation. A DFTbased microkinetic model was developed in the presence and absence of electric fields, and the results were compared with experimental results. The microkinetic model shows that, under various electric fields, the most favorable MSR mechanism changed slightly. It also shows that the presence of a positive electric field decreases the surface coverage of carbon, increases the water coverage, accelerates the rate-limiting step of the C-H bond Cleavage in methane, and increases the desorption rates of the syngas product (CO + H-2) during MSR Consequently, for a given methane conversion, a positive electric field allows for significantly lower H2O/CH4 ratio and operating temperatures in comparison to systems without an electric field. These findings correspond well with experimental tests under a variety of operating conditions. In addition, improvement in the catalytic activity due to the presence of a positive electric field remained significant even at industrially relevant applied pressures-improving the hydrogen yield greatly. Overall, we find that an applied electric field can play a significant role in improving the catalytic activity of heterogeneous reactions. This information can guide the design of heterogeneous reactions in the presence of an electric field. By utilizing the electric field generated by various renewable energy sources, electric-field-assisted heterogeneous reactions can open up a paradigm in future energy research.Reducing Reaction Temperature, Steam Requirements, and Coke Formation During Methane Steam Reforming Using Electric Fields: A Microkinetic Modeling and Experimental Studyelectric-field-assisted catalysis; low-temperature methane Activation; methane steam reforming; low steam to carbon ratio; catalyst stability; first-principles-based microkinetic model21201776#N/ATRUE
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acscatal.7b0110910.1021/acscatal.7b01109FALSEhttps://doi.org/10.1021/acscatal.7b01109Batista, VSACS Catal.Dramatic enhancement of electrochemical CO2 conversion to CO, catalyzed by [Ni(cyClam)](PF6)(2) is observed on mercury/gold electrodes. We find that Hg provides favorable noncovalent dispersive interactions with the cyClam ligand. As a result, the Hg surface destabilizes the poisoned CO-bound form of the catalyst, leading to enhanced reaction kinetics. These findings are particularly relevant to the design of ligands that improve the electrocatalytic performance of transition-metal complexes on interaction with metallic surfaces under cell operating conditions.Electrode-Ligand Interactions Dramatically Enhance CO2 Conversion to CO by the [Ni(cyClam)](PF6)(2) CatalystCO2; electroreduction; adsorption; CO poisoning; dispersive interaction; nickel cyClam28201765#N/ATRUE
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acscatal.6b0279410.1021/acscatal.6b02794FALSEhttps://doi.org/10.1021/acscatal.6b02794Uchida, HHighly Active, CO-Tolerant, and Robust Hydrogen Anode Catalysts: Pt-M (M = Fe, Co, Ni) Alloys with Stabilized Pt-Skin Layersx2017#N/AFALSE
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acscatal.6b0275310.1021/acscatal.6b02753FALSEhttps://doi.org/10.1021/acscatal.6b02753Lercher, JAACS Catal.The mechanism of the deoxygenation of fatty acids on transition-metal sulfides was determined on the basis of kinetic data obtained with fatty acids, their reaction intermediates (aldehyde and alcohol), and reactants of restricted reactivity (adamantanyl-substituted Carbonylic acids). Deoxygenation on MoS2 proceeds exClusively via hydrogenolysis to aldehyde, followed by hydrogenation to the corresponding alcohol, consecutive dehydration to the olefin, and hydrogenation to the alkane. In contrast, the selectivity on Ni-MoS2 and on Ni3S2 substantially shifts toward carbon oxide elimination routes: i.e., direct production of Cn-1 olefins and alkanes. The carbon losses occur by deCarbonylation of a ketene intermediate, which forms only on sites associated with Ni. The rate determining steps are the Cleavage of the C-C bond and the removal of oxygen from the surface below and above, respectively, 2.5 MPa of H-2. The different reaction pathways catalyzed by MoS2 and Ni-MoS2 are attributed to a preferred deprotonation of a surface acyl intermediate formed upon the adsorption of the fatty acid on Ni-MoS2. The shift in mechanism is conCluded to originate from the higher basicity of sulfur induced by nickel.Carbon-Carbon Bond Scission Pathways in the Deoxygenation of Fatty Acids on Transition-Metal Sulfidesfatty acid; hydrodeoxygenation; deCarbonylation; reaction mechanism; transition metal sulfidesx23201770#N/AFALSE
5247
acscatal.6b0273510.1021/acscatal.6b02735FALSEhttps://doi.org/10.1021/acscatal.6b02735Mavrikakis, MACS Catal.Hydrodesulfurization is a process to produce ultralow-sulfur diesel fuel. Although promoted molybdenum sulfide (MoS2) catalysts have been used industrially for several decades, the active site requirements for selective hydrodesulfurization of organosulfur compounds with minimal inhibition by organonitrogen constituents of a real gasoil feed has not been resolved. Using molecular binding energy descriptors derived from plane wave density functional theory calculations for comparative adsorption of organosulfur and organonitrogen compounds, we analyzed more than 20 potential sites on unpromoted and Ni- and Co-promoted MoS2. We find that hydrogen sulfide and ammonia are simple descriptors of adsorption of sterically unhindered organosulfur and organonitrogen compounds such as dibenzothiophene and acridine, respectively. Further, organonitrogen compounds in gasoil bind more strongly than organosulfur compounds on all sites except on sites with exposed metal atoms on the corner and sulfur edges of promoted MoS2. Consequently, these sites are proposed as required for maximum-hydrodesulfurization minimum-inhibition catalysis.On the Preferred Active Sites of Promoted MoS2 for Hydrodesulfurization with Minimal Organonitrogen Inhibitionpromoted molybdenum sulfide; hydrodesulfurization; nitrogen inhibition; binding energy descriptors; density functional theory; active site identificationx45201789#N/AFALSE
5248
acscatal.6b0271410.1021/acscatal.6b02714FALSEhttps://doi.org/10.1021/acscatal.6b02714Watanabe, YACS Catal.A bimetallic catalyst of Au and Ni significantly increased the catalytic activity of the NO-CO reaction in comparison to monometallic Au and Ni catalysts. Unraveling the roles of Au and Ni atoms in the each of the NO-CO reaction steps occurring on the Au-Ni catalyst surface is crucial to reveal the origin of the increased activity. For this purpose, a well-defined Au/Ni(111) model catalyst was prepared, on which CO and NO adsorption, their coadsorption, NO dissociation, CO2 formation, and N-2 formation were investigated using infrared reflection absorption spectroscopy, temperature-programmed desorption/reaction, and density functional theory calculations. In the reaction process, the catalyst surface would be dominantly covered by N and O atoms, which would be removed from the surface by N-2 formation and CO2 formation. O atoms preferentially occupy the Ni hollow sites by segregating N atoms to the adsorption sites made up of Au and Ni atoms. Thus, only the N-2 formation step was affected by the Au atoms. The Activation energy for the N-2 formation step, which was assigned as a rate-limiting step, was significantly lowered by the Au atoms, and this effect will contribute to the decrease of the Activation energy of the overall NO-CO reaction. These results suggest that, by utilizing the adsorption site preferences among the coadsorbates on the bimetallic surface, the Activation energy of a rate-limiting step would be significantly decreased; this could be useful in the development of advanced NOx reduction catalysts.Synergistic Promotion of NO-CO Reaction CyCle by Gold and Nickel Elucidated using a Well-Defined Model Bimetallic Catalyst SurfaceNO reduction; CO oxidation; Au catalysis; alloy catalysis; automotive catalysisx17201759#N/AFALSE
5249
acscatal.7b0107010.1021/acscatal.7b01070FALSEhttps://doi.org/10.1021/acscatal.7b01070Jaramillo, TFACS Catal.We systematically investigate the effects of Au substrates on the oxygen evolution activities of cathodically electrodeposited nickel oxyhydroxide (NiOOH), nickel-iron oxyhydroxide (NiFeOOH), and nickel-cerium oxyhydroxide (NiCeOOH) at varying loadings from 0 to 2000 nmol of metal/cm(2). We determine that the geometric current densities, especially at higher loadings, were greatly enhanced on Au substrates: NiCeOOH/Au reached 10 mA/cm(2) at 259 mV overpotential, and NiFeOOH/Au achieved 140 mA/cm(2) at 300 mV overpotential, which were much greater than those of the analogous catalysts on graphitic carbon (GC) substrates. By performing a loading quantification using both inductively coupled plasma optical emission spectrometry and integration of the Ni2+/3+ redox peak, we show that the enhanced activity is predominantly caused by the stronger physical adhesion of catalysts on Au. Further characterizations using impedance spectroscopy and in situ X-ray absorption spectroscopy revealed that the catalysts on Au exhibited lower film resistances and higher number of electrochemically active metal sites. We attribute this enhanced activity to a more homogeneous electrodeposition on Au, yielding catalyst films with very high geometric current densities on flat substrates. By investigating the mass and site specific activities as a function of loading, we bridge the practical geometric activity to the fundamental intrinsic activity.Effects of Gold Substrates on the Intrinsic and Extrinsic Activity of High-Loading Nickel-Based Oxyhydroxide Oxygen Evolution Catalystssubstrate effects; oxygen evolution reaction; nickel oxyhydroxide; nickel cerium; nickel iron; loading dependence; conductivity; electrochemical impedance spectroscopy74201750#N/ATRUE
5250
acscatal.6b0265010.1021/acscatal.6b02650FALSEhttps://doi.org/10.1021/acscatal.6b02650Suib, SLACS Catal.The electrolysis of water provides a powerful pathway for the storage and conversion of Clean and renewable energy. Therefore, the development of earth-abundant, inexpensive, highly efficient electrocatalysts contributes a great deal to the overall efficiency of a water electrolytic system. Here, inspired by the low charge transfer resistance of mixed-valence cations, the favorable H atom binding energy of cobalt, and high electrical conductivity of graphene, we report a facile synthesis strategy to synthesize a spinel ternary oxide material consisting of nickel, manganese, and cobalt supported on reduced graphene oxide (rGO/NMC) with further conversion into a spinel ternary sulfide via a gaseous sulfurization protocol. The rGO/NMC-312 oxide material is found to be an efficient OER electrocatalyst with an overpotential as low as 320 mV for a current density of 10 mA cm(-2), which is comparable to that of the state of the art OER catalysts. In addition, when used as HER electrocatalysts, the as-converted rGO/NMC-312 sulfide materials exhibit a low overpotential of 151 mV to reach a current density of 10 mA cm(-2), a small Tafel slope of 52 mV/decade, and a remarkable long-term stability. Impressively, a voltage of 1.56 V is required to achieve a current density of 20 mA cm(-2) in an alkaline medium at room temperature by applying rGO/NMC-312 oxide and sulfide as an alkaline water electrolysis anode and cathode, respectively. Our work offers a strategy to apply spinel ternary oxides and sulfides as electrocatalysts in water electrolysis.Reduced Graphene Oxide Supported Nickel-Manganese-Cobalt Spinel Ternary Oxide Nanocomposites and Their Chemically Converted Sulfide Nanocomposites as Efficient Electrocatalysts for Alkaline Water Splittingwater electrolysis; oxygen evolution reaction; hydrogen evolution reaction; ternary oxide; sulfide; spinel; graphene oxidex60201765#N/AFALSE
5251
acscatal.6b0255210.1021/acscatal.6b02552FALSEhttps://doi.org/10.1021/acscatal.6b02552Greenleette, LFACS Catal.Iron-incorporated nickel-based materials show promise as catalysts for the oxygen evolution reaction (OER) half-reaction of water electrolysis. Nickel has also exhibited high catalytic activity for methanol oxidation, particularly when in the form of a bimetallic catalyst. In this work, bimetallic iron-nickel nanopartiCles were synthesized using a multistep procedure in water under ambient conditions. When compared to monometallic iron and nickel nanopartiCles, Fe-Ni nanopartiCles show enhanced catalytic activity for both OER and methanol oxidation under alkaline conditions. At 1 mA/cm(2), the overpotential for monometallic iron and nickel nanopartiCles was 421 and 476 mV, respectively, while the bimetallic Fe-Ni nanopartiCles had a greatly reduced overpotential of 256 mV. At 10 mA/cm(2), bimetallic Fe-Ni nanopartiCles had an overpotential of 311 mV. Spectroscopy characterization suggests that the primary phase of nickel in Fe-Ni nanopartiCles is the more disordered alpha phase of nickel hydroxide.Multi-Component Fe-Ni Hydroxide Nanocatalyst for Oxygen Evolution and Methanol Oxidation Reactions under Alkaline Conditionselectrocatalyst; nonprecious metal; core-shell nanopartiCles; oxygen evolution reaction; alcohol oxidation; fuel cellx902017109#N/AFALSE
5252
acscatal.6b0254110.1021/acscatal.6b02541FALSEhttps://doi.org/10.1021/acscatal.6b02541Hull, KLACS Catal.A rhodium-catalyzed oxidative amidation reaction has been developed with sterically hindered aldehydes and alcohols for the synthesis of amides containing a quaternary carbon at the alpha position. A variety of amine nuCleophiles, both aliphatic and aromatic, are employed and afford the corresponding amides in good to excellent yields. Finally, mechanistic studies are performed to gain insight into both catalytic cyCles.Rhodium-Catalyzed Oxidative Amidation of Sterically Hindered Aldehydes and Alcoholsrhodium; oxidation; amidation; hindered; amine; anilinex21201653#N/AFALSE
5253
acscatal.6b0253210.1021/acscatal.6b02532FALSEhttps://doi.org/10.1021/acscatal.6b02532Scott, SLPhenomena Affecting Catalytic Reactions at Solid-Liquid Interfacesx2016#N/AFALSE
5254
acscatal.7b0096410.1021/acscatal.7b00964FALSEIwasawa, YSimultaneous Improvements in Performance and Durability of an Octahedral PtNix/C Electrocatalyst for Next-Generation Fuel Cells by Continuous, Compressive, and Concave Pt Skin Layers2017#N/ATRUE
5255
acscatal.6b0247710.1021/acscatal.6b02477https://doi.org/10.1021/acscatal.6b02477Huang, YACS Catal.Direct homologation of aromatic amides with internal alkynes has been accomplished via a nickel-catalyzed sequential C-H Activation reaction. The use of a rigid chelating group and a strong aprotic polar solvent successfully divert the Classical [4 + 2] annulation to the [2 + 2 + 2] homologation pathway. This transformation is promoted by a simple nickel catalyst without the need of stoichiometric metal oxidants. Mechanistic studies support an unusual substrate-assisted ligand exchange process. NMR and X-ray data suggest a [5,5] Ni-bridged metallacyCle as the catalyst resting state. Substrate assisted directing group swap plays an important role for the subsequent meta-C-H insertion. In contrast, [4 + 2] annulation can be accomplished using a bulky, electron-rich phosphine ligand, which favors rapid reductive C-N elimination.Diverting C-H Annulation Pathways: Nickel-Catalyzed Dehydrogenative Homologation of Aromatic Amidesnickel catalysis; C-H Activation; dehydrogenative homologation; phosphine; directing groupxyy392016122#N/AFALSE
5256
acscatal.6b0244610.1021/acscatal.6b02446FALSEhttps://doi.org/10.1021/acscatal.6b02446Kobayashi, SACS Catal.The use of chiral ligand-modified metal nanopartiCles is a promising strategy for constructing active and robust asymmetric catalyst systems. A recent advance in such catalyst systems for C-C bond-forming reactions is highlighted, and the characteristics of the active species are discussed. Several studies suggested that a redox event between nanopartiCles and reagents might be a key to generating active species from nanopartiCles.Chiral Ligand-Modified Metal NanopartiCles as Unique Catalysts for Asymmetric C-C Bond-Forming Reactions: How Are Active Species Generated?metal nanopartiCle; asymmetric catalysis; heterogeneous catalyst; C-C bond-forming reactions; dual catalysis; bifunctional ligandx412016149#N/AFALSE
5257
acscatal.6b0239610.1021/acscatal.6b02396FALSEhttps://doi.org/10.1021/acscatal.6b02396Oyama, STACS Catal.Understanding the reactions of heteroatomic cyClic compounds is essential for developing good catalysts for the upgrading of bio-oils into liquid fuels. The present study presents the reaction network of 2-methyltetrahydrofuran (2-MTHF, C5H10O), a bio-oil model compound, on silica supported nickel phosphide at 0.1 MPa and 300 degrees C. Contact time experiments showed that 2-MTHF reacted to first form 1-pentanol and 2-pentanol, then n-pentanal, 2-pentanone, and 1- and 2-pentenes, and finally n-pentane. The observation is consistent with a reaction network in which adsorption of 2-MTHF is followed by rate-determining ring-opening steps on the more hindered side (path I) or the more open side (path II) to first produce adsorbed alcohols. The alcohols then transform into adsorbed aldehyde, ketone, and pentene species which can simply desorb or react to produce the final product n-butane (deCarbonylation of adsorbed n-pentanal) or n-pentane (hydrogenation of adsorbed pentenes). Kinetic modeling of the proposed reaction network gave good agreement with the experimental data and predicted that path I intermediates would be more numerous than path II intermediates on the surface. A series of in situ FTIR results gave further support for the mechanism with the presence of the C=O and C=C bands of the adsorbed aldehyde/ketone and alkene species. Transient experiments gave evidence for the model calculations that predicted more plentiful path I surface species.Kinetic and Infrared Spectroscopy Study of Hydrodeoxygenation of 2-Methyltetrahydrofuran on a Nickel Phosphide Catalyst at Atmospheric Pressurehydrodeoxygenation; kinetics; FTIR spectroscopy; 2-methyltetrahydrofuran; nickel phosphidex20201652#N/AFALSE
5258
acscatal.6b0236810.1021/acscatal.6b02368FALSEhttps://doi.org/10.1021/acscatal.6b02368Zhang, ZCACS Catal.Gold nanopartiCles on a number of supporting materials, inCluding anatase TiO2 (TiO2-A, in 40 nm and 45 pm), rutile TiO2 (TiO2-R), ZrO2, Al2O3, SiO2, and activated carbon, were evaluated for hydrodeoxygenation of guaiacol in 6.5 MPa initial H-2 pressure at 300 degrees C. The presence of gold nanopartiCles on the supports did not show distinguishable performance compared to that of the supports alone in the conversion level and in the product distribution, except for that on a TiO2-A-40 nm. The lack of marked catalytic activity on supports other than TiO2-A-40 nm suggests that Au nanopartiCles are not catalytically active on these supports. Most strikingly, the gold nanopartiCles on the least-active TiO2-A-40 nm support stood out as the best catalyst exhibiting high activity with excellent stability and remarkable selectivity to phenolics from guaiacol hydrodeoxygenation. The conversion of guaiacol (similar to 43.1%) over gold on the TiO2-A-40 nm was about 33 times that (1.3%) over the TiO2-A-40 nm alone. The selectivity of phenolics was 87.1%. The products are mainly phenolic compounds with no aromatics and saturated hydrocarbons such as cyClohexane. The gold partiCle size ranging from 2.7 to 41 nm and water content were found to significantly affect the Au/TiO2-A-40 nm catalyst activity but not the product selectivity. The reaction rates of 0.26 and 0.91 (min(-1) g-cat(-1) cm(3)) were determined for guaiacol hydrogenation and catechol hydrogenation, respectively. Bimolecular methylation was established as the dominant mechanism for methyl group transfer among the phenolics. Two major pathways of guaiacol hydrogenation to phenolics over the 0.4Au-19 nm/TiO2-A-40 nm are proposed: (1) direct hydrogenation of guaiacol to form phenol and methanol, (2) hydrodehydroxylation of catechol intermediate from the transmethylation between guaiacol and phenol.Anatase TiO2 Activated by Gold NanopartiCles for Selective Hydrodeoxygenation of Guaiacol to Phenolicsguaiacol hydrogenation; phenol; gold catalyst; anatase; ligninx42201764#N/AFALSE
5259
acscatal.6b0236010.1021/acscatal.6b02360FALSEhttps://doi.org/10.1021/acscatal.6b02360
Ganduglia-Pirovano, MV
ACS Catal.The results of core-level photoemission indicate that Ni-CeO2,(111) surfaces with small or medium coverages of nickel are able to activate methane at 300 K, producing adsorbed CHx and CO (x = 2, 3) groups. Calculations based on density functional theory predict a relatively low Activation energy of 0.6-0.7 eV for the Cleavage of the first C-H bond in the adsorbed methane molecule. Ni and O centers of ceria work in a cooperative way in the dissociation of the C-H bond at room temperature, where a low Ni loading is crucial for the catalyst activity and stability. The strong electronic perturbations in the Ni nanopartiCles produced by the ceria supports of varying natures, such as stoichiometric and reduced, result in a drastic change in their chemical properties toward methane adsorption and dissociation as well as the dry reforming of methane reaction. The coverage of Ni has a drastic effect on the ability of the system to dissociate methane and catalyze the dry re-forming process.Room-Temperature Activation of Methane and Dry Re-forming with CO2 on Ni-CeO2(111) Surfaces: Effect of Ce3+ Sites and Metal-Support Interactions on C-H Bond Cleavagemethane Activation; dry re-forming; ceria; nickel; supported catalysts; support effect; XPS; DFTx83201652#N/AFALSE
5260
acscatal.6b0235610.1021/acscatal.6b02356FALSEhttps://doi.org/10.1021/acscatal.6b02356Maillard, FACS Catal.The electrical performance of a proton exchange membrane fuel cell is limited by the slow oxygen reduction reaction (ORR) kinetics. Catalytic improvements for the ORR have been obtained on alloyed PtM/C or M-rich-core@Pt-rich-shell/C catalysts (where M is an early or late transition metal) in comparison to pure Pt/C, due to a combination of strain and ligand effects. However, the effect of the fine nanostructure of the nanomaterials on the ORR kinetics remains underinvestigated. Here, nanometer-sized PtNi/C electrocatalysts with low Ni content (similar to 15 atom %) but different nanostructures and different densities of grain boundary were synthesized: solid, hollow, or sea sponge PtNi/C nanoalloys, and solid Ni-core@Pt-shell/C nanopartiCles. These nanostructures were characterized by transmission and scanning transmission electron microscopy, X-ray energy dispersive spectroscopy, synchrotron wide-angle X-ray scattering (WAXS), atomic absorption spectroscopy, and electrochemical techniques. Their electrocatalytic activities for the ORR were determined and structure-activity relationships established. The results showed the following: (i) The compression of the Pt lattice by ca. 15 atom % Ni provides mild ORR activity enhancement in comparison to pure Pt/C. (ii) Highly defective PtNi/C nanostructures feature up to 9.3-fold enhancement of the ORR specific activity over a commercial Pt/C material with similar crystallite size. (iii) The enhancement of the ORR kinetics can be ascribed to the presence of structural defects, as shown by two independent parameters: the microstrain determined from WAXS and the average COads electrooxidation potential (mu(CO)(1)) determined from COads stripping measurements. This work indicates that, at fixed Ni content, ORR activity can be tuned by nanostructuring and suggests that targeting structural disorder is a promising approach to improve the electrocatalytic properties of mono- or bimetallic nanocatalysts.Beyond Strain and Ligand Effects: Microstrain-Induced Enhancement of the Oxygen Reduction Reaction Kinetics on Various PtNi/C Nanostructuresproton exchange membrane fuel cell; oxygen reduction reaction; structural defects; grain boundary; microstrainx80201793#N/AFALSE
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acscatal.6b0233110.1021/acscatal.6b02331FALSEhttps://doi.org/10.1021/acscatal.6b02331Bruckner, AACS Catal.Supported Ni catalysts have been studied during the dimerization of butenes by operando electron paramagnetic resonance (EPR) and in situ X-ray absorption spectroscopy (XAS) at 353 K and up to 16 bar. Single Ni-I/Ni-II shuttles were identified as active sites, whereby the conversion of initial Ni-I to Ni-II by oxidative addition of butene is obviously faster than the re-reduction of Ni-II to Ni-I by reductive elimination of the C8 product, rendering the equilibrium percentage of Nil small. At p <= 2 bar, Ni-I single sites form inactive Ni aggregates, while this is suppressed at higher pressure (similar to 12 bar). A reaction mechanism is proposed.Tracing Active Sites in Supported Ni Catalysts during Butene Oligomerization by Operando Spectroscopy under Pressureoperando EPR; in situ EXAFS/XANES; heterogeneous catalysis; butene dimerization; reaction mechanism; nickel catalystsx27201622#N/AFALSE
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acscatal.6b0231810.1021/acscatal.6b02318FALSEhttps://doi.org/10.1021/acscatal.6b02318McEwen, JSACS Catal.This work demonstrates the benefits of applying an external electric field to the methane steam reforming reaction (MSR) in order to tune the catalytic activity of Ni. Through combined DFT calculations and experimental work, we present evidence for the usefulness of an electric field in improving the efficiency of current MSR processes-namely by reducing coke formation and lowering the overall temperature requirements. We focus on the influence of an electric field on (i) the MSR mechanisms, (ii) the rate-limiting step of the most favorable MSR mechanism, (iii) the methanol synthesis reaction during the MSR reaction, and (iv) the formation of coke. Our computational results show that an electric field can change the most favorable MSR mechanism as well as alter the values of the rate constants and equilibrium constants at certain temperatures and, hence, significantly affect the kinetic properties of the overall MSR reaction. Both computational and experimental results also suggest that a positive electric field can impede the formation of coke over a Ni catalytic surface during the MSR reaction. Moreover, the presence of a negative electric field notably increases the rate constant and the equilibrium constant for the methanol synthesis reaction, which suggests a possible direct route from methane to methanol. Finally, a field-induced Bronsted-Evans-Polanyi (BEP) relationship was developed for C-H bond Cleavage, C-O bond Cleavage, and O-H bond formation over a Ni catalytic surface. Overall, this investigation strengthens our understanding of the effect of an electric field on the Ni-based MSR catalytic system and highlights the benefits of designing heterogeneous reactions under applied electric fields.Improving Ni Catalysts Using Electric Fields: A DFT and Experimental Study of the Methane Steam Reforming Reactionelectro-reforming; methane steam reforming; electric field-induced BEP correlations; transition state theory; coke formation; methanol synthesisx36201781#N/AFALSE
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acscatal.6b0226310.1021/acscatal.6b02263FALSEhttps://doi.org/10.1021/acscatal.6b02263Li, GRACS Catal.Herein, we develop strongly coupled Pd nanopartiCles/CoP nanosheets attached on the Cloth of carbon fibers (CFC) (Pd@CoP NSs/CFC) to enhance the catalytic activity and durability of Pd nanopartiCles by in situ nuCleation and growth of Pd nanopartiCles on the fabricated CoP nanosheets. In comparison with Pd/C and Pd/CFC catalysts, the Pd@CoP NSs exhibit not only high electroactivity but also excellent stability for the electrooxidation of ethanol in basic solution. The improved electrocatalytic activity of Pd@CoP NSs is due to the number increase and activity improvement of active sites, which can be attributed to the strong interactions between CoP nanosheets and Pd nanopartiCles. The high stability of Pd@CoP NSs is ascribed to the direct oxidation of intermediate species to carbonate by OHad that was produced from the intermediate species of Co(OH)(2). This study will open up exciting opportunities for the development of catalysts with enhanced electroactivity and stability via the fabrication of hybrids with strong electrical coupling between metal nanopartiCles and cocatalysts.Pd NanopartiCle/CoP Nanosheet Hybrids: Highly Electroactive and Durable Catalysts for Ethanol Electrooxidationelectrocatalyst; Pd nanopartiCle; CoP nanosheet; ethanol electrooxidation; synergic effectx68201678#N/AFALSE
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acscatal.6b0222110.1021/acscatal.6b02221FALSEhttps://doi.org/10.1021/acscatal.6b02221Schuth, FACS Catal.This study focuses on the synthesis and electrochemical performance (i.e, activity and stability) of advanced electrocatalysts for the oxygen reduction reaction (ORR), made of Pt-Ni nanopartiCles embedded in hollow graphitic spheres (HGS). The mechanism of the confined space alloying, that is, the controlled alloying of bimetallic precursors with different compositions (i.e., Pt3Ni, PtNi, and PtNi3) within the HGS mesoporous shell, was examined in detail. It was found that the presence of platinum during the reduction step, as well as the application of high annealing temperatures (at least 850 degrees C for 3.Sh in Ar), are necessary conditions to achieve the complete encapsulation and the full stability of the catalysts. The evolution of the activity, the electrochemical surface area, and the residual alloy composition of the Pt-Ni@HGS catalysts was thoroughly monitored (at the macro- and nanoscale level) under different degradation conditions. After the initial Activation, the embedded Pt-Ni nanopartiCles (3-4 nm in size) yield mass activities that are 2- to 3.5-fold higher than that of pure Pt@HGS (depending on the alloy composition). Most importantly, it is demonstrated that under the normal operation range of an ORR catalyst in PEM-FCs (potential excursions between 0.4 and 1.0 V-RHE) both the nanopartiCle-related degradation pathways (partiCle agglomeration) and dealloying phenomena are effectively suppressed, irrespectively of the alloy composition. Thus, the initial enhanced activity is completely maintained over an extended degradation protocol. In addition, owing to the peculiar configuration of the catalysts consisting of space-confined nanopartiCles, it was possible to elucidate the impact of the dealloying process (as a function of alloy composition and severity of the degradation protocols) separately from other parallel phenomena, providing valuable insight into this elusive degradation mechanism.Structure-Activity-Stability Relationships for Space-Confined PtxNiy NanopartiCles in the Oxygen Reduction Reactionoxygen reduction reaction; activity; stability; dealloying; nanopartiClesx38201670#N/AFALSE
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acscatal.7b0093710.1021/acscatal.7b00937FALSEhttps://doi.org/10.1021/acscatal.7b00937Xu, RACS Catal.Cobalt phosphate is considered to be one of the most active catalysts for the oxygen evolution reaction (OER) in neutral or near-neutral pH media, but only a few transition-metal phosphates are investigated in alkaline media, probably due to their poor intrinsic electrical conductivity and/or tendency to aggregate. Herein, in situ-formed cobalt phosphate decorated with N-doped graphitic carbon was prepared using phosphonate-based metal organic frameworks (MOFs) as the precursor. It can serve as a highly active OER catalyst in alkaline media, affording a current density of 10 mA cm(-2) at a small overpotential of 215 mV on the Ni foam. A combination of X-ray absorption spectroscopy and high-resolution XPS elucidates the origin of the high activity. Our observations unveil that cobalt diphosphate having the distorted metal coordination geometry with long Co-O and Co-Co distances is mainly responsible for the high OER activity. These results not only demonstrate the potential of a low-cost OER catalyst derived from phosphonate-based MOF but also open a promising avenue into the exploration of highly active and stable catalysts toward replacing noble metals as oxygen evolution electrocatalysts.Phosphonate-Based Metal-Organic Framework Derived Co-P-C Hybrid as an Efficient Electrocatalyst for Oxygen Evolution Reactionoxygen evolution; cobalt phosphate; electrocatalysis; N-doped graphitic carbon; metal-organic frameworks106201756#N/ATRUE
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acscatal.7b0061610.1021/acscatal.7b00616FALSEhttps://doi.org/10.1021/acscatal.7b00616Macgregor, SAACS Catal.The [Ni(0)(cod)(2)]/(PP)-P-boolean AND-catalyzed hydroalkoxylation of butadiene to form butenyl ethers is studied mechanistically, where (PP)-P-boolean AND = 1,4-bis(diphenylphosphino)butane (dppb) and 1,2-bis(diphenylphosphinomethyl)-benzene (dppmb). Experimental studies suggest the intermediacy of [(dppb)Ni(0)(butadiene)] and [(PP)-P-boolean AND)Ni(II)(ally1)] intermediates and rule out the involvement of Ni-H species. The related species [((PP)-P-boolean AND)Ni(0)(1,4-diphenylbutadiene)], 1, and [((PP)-P-boolean AND)Ni(II)(crotyl)(C1)] complexes 2 ((PP)-P-boolean AND = dppmb) and 3 ((PP)-P-boolean AND) = dppb) have been synthesized and characterized on the basis of VT NMR spectroscopy and X-ray crystallographic studies. Compounds 2 and 3 are shown to be catalytically competent for the hydroalkoxylation reaction. Computational studies on [(dppmb)Ni(0)(butadiene)] indicate a facile protonation that forms a cationic allylic intermediate Rdppmb)Ni(II)(eta-C4H7)]OMe. C-O bond formation then occurs via external attack by the solvent-stabilized methoxide nuCleophile. Hydroalkoxylation proceeds with modest computed barriers of ca. 18 kcal/mol, and the butenyl ether product formation is only marginally exergonic. Overall, the results are consistent with initial kinetic control leading to the major branched isomer followed by a reversible isomerization process operating under thermodynamic control.Deciphering the Mechanism of the Nickel-Catalyzed Hydroalkoxylation Reaction: A Combined Experimental and Computational Studyhydroalkoxylation; butadiene; nickel; mechanism; allyl13201752#N/ATRUE
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acscatal.6b0218110.1021/acscatal.6b02181https://doi.org/10.1021/acscatal.6b02181Robert, MACS Catal.Electrochemical and photochemical reduction of CO2, or a smart combination of both, are appealing approaches for the storage of renewable, intermittent energies and may lead to the production of fuels and of value-added chemicals. By using only earth-abundant metal (Cu, Ni, Co, Mn, Fe) complexes, cheap electrodes and/or cheap sacrificial electron donors and visible light sensitizers, systems functioning with molecular catalysts have been recently designed, showing promising results, in particular, for the two-electron reduction of the carbon dioxide. By combining experimental and mechanistic studies, key parameters controlling the catalysis efficiency have been deciphered, opening the way to the design of future, more efficient and durable catalysts, as well as to the development of electrochemical or photoelectrochemical cells, all being key steps for the emergence of applied devices. The most recent advances related to these issues are discussed in this review.Electrons, Photons, Protons and Earth-Abundant Metal Complexes for Molecular Catalysis of CO2 ReductionCO2 reduction; earth-abundant metals; molecular catalysis; electrochemical catalysis; photochemical catalysisPhotocatalyst3292017136#N/AFALSE
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acscatal.7b0050710.1021/acscatal.7b00507FALSEhttps://doi.org/10.1021/acscatal.7b00507Liu, WACS Catal.Exploitation of efficient water oxidation catalysts with cost effectiveness and high activity is a prerequisite to enable water splitting as an alternative pathway for a renewable energy source. Silicon has the potential for high efficiency oxygen evolution reaction (OER). However, an important factor, which is the doping concentration of the silicon influence on the OER performance, has not been studied. Our results show that the performance of the silicon photoanode is significantly influenced by its resistivity, which is directly related to the doping concentration. In combination with ultrathin NiFe alloy nanoflakes (2 nm thick) deposited by the electron beam evaporation method, a NixFe(1-x)/TiO2/n-Si photoanode for water oxidation has been demonstrated. Our results show that the prepared Ni80Fe20/TiO2/n-Si photoanode with Si resistivity of 0.5 Omega.cm(-1) exhibits high catalytic performance with a low onset potential of 1.06 V versus RHE (eta(0) = -0.17 V), which are comparable to the state-of-the-art photoanodes using Ir or Ru as a catalyst. In addition, the photocurrent density at the reversible potential for water oxidation (1.23 V versus RHE) is around 21.5 mA.cm(-2), which is higher than most of the metal/TiO2/n-Si photoanodes. Therefore, our Ni80Fe20/TiO2/n-Si (0.5) photoanode shows great potential to replace precious metals for highly efficient large-scale water splitting.Impact of Silicon Resistivity on the Performance of Silicon Photoanode for Efficient Water Oxidation Reactionoxygen evolution reaction (OER); photoanode; photoelectrochemical; resistivity; nickel iron alloy26201744#N/ATRUE
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acscatal.7b0042010.1021/acscatal.7b00420FALSEhttps://doi.org/10.1021/acscatal.7b00420Sun, LCACS Catal.The development of a highly active manganese-based water oxidation catalyst in the design of an ideal artificial photosynthetic device operating under neutral pH conditions remains a great challenge, due to the instability of pivotal Mn3+ intermediates. We report here defective and c-disordered layered manganese oxides (MnOx-300) formed on a fluorine-doped tin oxide electrode by constant anodic potential deposition and subsequent annealing, with a catalytic onset (0.25 mA/cm(2)) at an overpotential (eta) of 280 mV and a benchmark catalytic current density of 1.0 mA/cm(2) at an overpotential (eta) of 330 mV under neutral pH (1 M potassium phosphate). Steady current density above 8.2 mA/cm(2) was obtained during the electrolysis at 1.4 V versus the normal hydrogen electrode for 20 h. Insightful studies showed that the main contributing factors for the observed high activity of MnOx-300 are (i) a defective and randomly stacked layered structure, (ii) an increased degree of Jahn-Teller distorted Mn3+ in the MnO6 octahedral sheets, (iii) effective stabilization of Mn3+, (iv) a high surface area, and (v) improved electrical conductivity. These results demonstrate that manganese oxides as structural and functional models of an oxygen-evolving complex (OEC) in photosystem II are promising catalysts for water oxidation in addition to Ni/Co-based oxides/hydroxides.Defective and c-Disordered Hortensia-like Layered MnOx as an Efficient Electrocatalyst for Water Oxidation at Neutral pHartificial photosynthesis; electrocatalyst; layered manganese oxide; oxygen evolution; solar fuel; water oxidation42201778#N/ATRUE
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acscatal.7b0000710.1021/acscatal.7b00007FALSEhttps://doi.org/10.1021/acscatal.7b00007Ma, JTLateral-Size-Mediated Efficient Oxygen Evolution Reaction: Insights into the Atomically Thin Quantum Dot Structure of NiFe2O42017#N/ATRUE
5271
acscatal.6b0349510.1021/acscatal.6b03495FALSEhttps://doi.org/10.1021/acscatal.6b03495Shen, BJACS Catal.Extensive efforts have been devoted to developing desulfurization catalysts to effectively remove sulfur from fuel. Active phase metals inCluding cobalt, nickel, molybdenum, and tungsten have been extensively used in industry for hydrotreating/hydrodesulfurization catalysts for over 50 years. However, while it is desirable to use inexpensive materials to do the same job, it is a grand challenge. Herein, we report a Fe-based sulfide catalyst that is tuned by zinc with high activity for HDS, which shows an industrial application potential to replace industrial Mo-based catalysts. With an optimal configuration that has a Fe:Zn ratio Close to 1:1, the reaction rate constants of the dibenzothiophene (DBT) and 4,6-dimethydibenzothiophene (4,6-DMDBT) HDS are increased by 9.2 and 17.4 times, respectively, in comparison with the sums of those on the monoiron and zinc sulfides. HDS activity for the sterically hindered 4,6-DMDBT on the FeZn sulfide catalyst is even Close to that of Co-MoS2. The experimental results indicate that the addition of Zn greatly modifies the electronic properties of iron sulfide by transferring electrons from Zn to Fe, which tunes the d band center to modulate the adsorption behavior of DBT and 4,6-DMDBT. In combination with theoretical calculations, our experiments show that the addition of Zn dramatically tunes the formation of sulfur vacancies. We propose that the formation of sulfur vacancies is the critical factor for designing highly efficient Fe-based sulfide catalysts. This study provides the design principle of low-cost desulfurization catalysts for industrial refinery applications.Promotion of the Inactive Iron Sulfide to an Efficient Hydrodesulfurization Catalystiron sulfide; iron-zinc bimetallic sulfide; synergetic effect; sulfur vacancies; hydrodesulfurization29201764#N/ATRUE
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acscatal.6b0210110.1021/acscatal.6b02101FALSEhttps://doi.org/10.1021/acscatal.6b02101Williams, TJACS Catal.Di(carbene)-supported nickel species 1 and 2 are efficient catalysts for the room-temperature reduction of CO2 to methanol in the presence of sodium borohydride. The catalysts feature unusual stability, particularly for a base metal catalyst, enabling >1.1 million turnovers of CO2. Moreover, while other systems involve more expensive reducing reagents, sodium borohydride is inexpensive and easily handled. Furthermore, effecting reduction in the presence of water enables direct access to methanol. Preliminary mechanistic data collected are most consistent with a mononuClear nickel active species that mediates rate-determining reduction of a boron formate.Di(carbene)-Supported Nickel Systems for CO2 Reduction Under Ambient Conditionscarbon dioxide; methanol; nickel; catalyst; borohydridex33201644#N/AFALSE
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acscatal.6b0199710.1021/acscatal.6b01997FALSEhttps://doi.org/10.1021/acscatal.6b01997Campbell, CTACS Catal.The energetics of the reactions of water with metal oxide surfaces are of tremendous interest for catalysis, electrocatalysis, and geochemistry, yet the energy for the dissociative adsorption of water was only previously measured on one well-defined oxide surface, iron oxide. In the present paper, the enthalpy of the dissociative adsorption of water is measured on NiO(111)-2 x 2 at 300 K using single-crystal adsorption calorimetry. The differential heat of dissociative adsorption decreases with coverage from 170 to 117 kJ/mol in the first 0.25 ML of coverage. Water adsorbs molecularly on top of that, with a heat of similar to 92 kJ/mol. Density functional theory (DFT) calculations reproduce the measured energies well (all within 17 kJ/mol) and provide insight into the atomic-level structure of the surfaces studied experimentally. They show that the oxygen-terminated O-octo(2 X 2) structure is the most stable NiO(111)-2 X 2 termination and gives reaction energies with water that are more consistent with the calorimetry results than the metal-terminated surface. They show that water adsorbs dissociatively on this (2 x 2)-O-octo surface to produce a hydroxyl-covered surface with a heat of adsorption of 171 +/- 5 kJ/mol in the low-coverage limit (very Close to 170 kJ/mol experimentally) and an integral heat that decreases by 14 kJ/mol up to saturation (compared to similar to 30 kJ/mol experimentally). Sensitivity of this reaction's energy to choice of DFT method is tested using a variety of different exchange correlation functionals, inCluding HSE06, and found to be quite weak.Water Dissociative Adsorption on NiO(111): Energetics and Structure of the Hydroxylated Surfaceheat of adsorption; nickel oxide; surface hydroxyl; water dissociation; adsorption calorimetry; density functional theory; benchmarkx36201653#N/AFALSE
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acscatal.6b0187810.1021/acscatal.6b01878FALSEhttps://doi.org/10.1021/acscatal.6b01878Zdilla, MJWater Oxidation Catalyzed by Cobalt Oxide Supported on the Mattagamite Phase of CoTe2x2016#N/AFALSE
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acscatal.6b0183710.1021/acscatal.6b01837FALSEhttps://doi.org/10.1021/acscatal.6b01837Chen, ZFACS Catal.If an oxygen evolution reaction (OER) catalyst is expected to be more durable, especially under conditions of thin-layer catalysts or strong gas evolution, it will ideally function in a self-repair mode. In earlier studies, the electrochemical fabrications of Ni-Fe oxide catalysts were exClusively carried out by cathodic reduction of Ni(II) and Fe(III, II) in an individual solution that is different from the alkaline media commonly used for the OER. The procedure does not suggest that the dissolution/corrosion of the film catalysts could be countered by continual catalyst formation during the OER Herein, we report a highly active NiFeOx catalyst by in situ rapid (3-15 min) anodic deposition of Ni(II) and Fe(III,II) in concentrated carbonate solution. At a transparent indium tin oxide (ITO) electrode, the conformal deposition of NiFeOx, (7-11-atom layer) results in a very low optical loss (5-8%) with activity comparable to that of other planar NiFeOx films. Extension, to a 3D nickel foam produces a hierarchical coating of grasslike structure. With few added Ni(II) and Fe(III) atoms to counter the film dissolution/corrosion, the catalyst can deliver a stable current density of 100 mA/cm(2) at an overpotential of only 260 mV in alkaline media. This example of a NiFeOx catalyst forms during in situ OER and operates by a self-repair mode, highlighting a truly important feature for the practical application of this state of the art OER electrocatalyst.In Situ Rapid Formation of a Nickel-Iron-Based Electrocatalyst for Water OxidationNiFe oxide; in situ electrodeposition; transparent electrodes; water oxidation; electrocatalysisx79201642#N/AFALSE
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acscatal.6b0309610.1021/acscatal.6b03096FALSEhttps://doi.org/10.1021/acscatal.6b03096Moliner, VACS Catal.Cysteine proteases of the papain family are involved in many diseases, making them attractive targets for developing drugs. In this paper, different catalytic mechanisms of cruzain cysteine protease have been studied on the basis of molecular dynamics simulations within hybrid quantum mechanics/molecular mechanics potentials. The obtained free energy surfaces have allowed characterizing every single step along the mechanisms. The results confirm that the full process can be divided into an acylation and a deacylation stage, but important differences with respect to previous studies can be deduced from our calculations. Thus, our calculations suggest that the acylation stage takes place in a stepwise mechanism where a proton from a conserved His159 is transferred first to the Ni atom of the peptide and, after a transient intermediate is located, the Cys25 attacks the Carbonyl carbon atom. The stabilization of the activated Cys25 is achieved by an effect of the local environment through interactions with residues Trp26, Gly160, and His159, rather than by a less complex Cys25S(-)/His159H(+) ion pair. In contrast, the deacylation stage, which was proposed to occur via a general base-catalyzed reaction whereby His159 activates a water molecule that attacks the peptide, would take place through a concerted mechanism. In this stage, the role of some residues of the active site, such as Gln19, Asn175, and Trp181, appears to also be crucial. Interestingly, the local environment of His159 would be modulating its pK(a) value to act as an acid in the acylation stage and as a base in the following deacylation stage.Computational Study of the Catalytic Mechanism of the Cruzain Cysteine Proteasecysteine proteases; catalytic mechanism; QM/MM; molecular dynamics; PMF19201748#N/ATRUE
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acscatal.6b0168310.1021/acscatal.6b01683FALSEhttps://doi.org/10.1021/acscatal.6b01683Lunkenbein, TACS Catal.Dry reforming of methane (DRM) has been studied for many years as an attractive option to produce synthesis gas. However, catalyst deActivation by coking over nonprecious-metal catalysts still remains unresolved. Here, we study the influence of structural and compositional properties of nickel catalysts on the catalytic performance and coking propensity in the DRM. A series of bulk catalysts with different Ni contents was synthesized by calcination of hydrotalcite-like precursors NixMg0.67-xAl0.33(OH)(2)(CO3)(0.17)center dot mH(2)O prepared by constant-pH coprecipitation. The obtained Ni/MgAI oxide catalysts contain Ni nanopartiCles with diameters between 7 and 20 nm. High-resolution transmission electron microscopy (HRTEM) revealed a nickel aluminate overgrowth on the Ni partiCles, which could be confirmed by Fourier transform infrared (FTIR) spectroscopy. In particular, catalysts with low Ni contents (5 mol %) exhibit predominantly oxidic surfaces dominated by Ni2+ and additionally some isolated Ni-0 sites. These properties, which are determined by the overgrowth, effectively diminish the formation of coke during the DRM, while the activity is preserved. A large (TEM) and dynamic (microcalorimetry) metallic Ni surface at high Ni contents (50 mol %) causes significant coke formation during the DRM.High-Temperature Stable Ni NanopartiCles for the Dry Reforming of Methanemetal-support interaction; dynamic; overgrowth; heterogeneous catalysis; FTIR spectroscopy; microcalorimetry; transmission electron microscopy; carbon depositionx68201640#N/AFALSE
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acscatal.6b0156510.1021/acscatal.6b01565FALSEhttps://doi.org/10.1021/acscatal.6b01565Linic, SACS Catal.The oxygen reduction reaction is the limiting half reaction in hydrogen fuel cells. While Pt is the most active single component electrocatalyst for the reaction, it is hampered by high cost and low reaction rates. Most research to overcome these limitations has focused on Pt/3d alloys, which offer higher rates and lower cost. Herein, we have synthesized, characterized, and tested alloy materials belonging to a multilayer family of electrocatalysts. The multilayer alloy materials contain an AuCu alloy core of precise composition, surrounded by Au layers and covered by a catalytically active Pt surface layer. Their performance relative to that of the commercial Pt standards reaches up to 4 times improved area-specific activity. Characterization studies support the hypothesis that the activity improvement originates from a combination of Au-Pt ligand effects and local strain effects manipulated through the AuCu alloy core. The presented approach to control the strain and ligand effects in the synthesis of Pt-based alloys for the ORR is very general and could lead to promising alloy materials.Nanoscale Engineering of Efficient Oxygen Reduction Electrocatalysts by Tailoring the Local Chemical Environment of Pt Surface Sitesoxygen reduction; platinum alloy catalysts; core shell nanopartiCles; fuel cells; electrocatalysisx23201751#N/AFALSE
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acscatal.6b0155510.1021/acscatal.6b01555FALSEhttps://doi.org/10.1021/acscatal.6b01555Luo, JLACS Catal.The massive emission of carbon dioxide (CO2), the major portion of greenhouse gases, has negatively affected our ecosystem. Developing new technologies to effectively reduce CO2 emission or convert CO2 to useful products has never been more imperative. In response to this challenge, we herein developed novel in situ exsolved Fe-Ni alloy nanospheres uniformly socketed on an oxygen-deficient perovskite [La(Sr)Fe-(Ni)] as a highly stable and efficient catalyst for the. effective conversion of CO2 to carbon monoxide (CO) in a high temperature solid oxide electrolysis cell (HT-SOEC). The symmetry between the reduction and reoxidation cyCles of this catalyst indicates its good redox reversibility. The cathodic reaction kinetics for CO2 electrolysis is significantly improved with a polarization resistance as low as 0.272 Omega cm(2). In addition, a remarkably enhanced current density of 1.78 A cm(-2), along with a high Faraday efficiency (similar to 98.8%), was achieved at 1.6 V and 850 degrees C. Moreover, the potentiostatic stability test of up to 100 h showed that the cell was stable without any noticeable coking in a CO2/CO (70:30) flow at an applied potential of 0.6 V (vs OCV) and 850 degrees C. The increased oxygen vacancies together with the in situ exsolved nanospheres on the perovskite backbone ensures sufficiently active sites and consequently improves the electrochemical performance for the efficient CO2 conversion. Therefore, this newly developed perovskite can be a promising cathode material for HT-SOEC. More generally, this study points to a new direction to develop highly efficient catalysts in the form of the perovskite oxides with perfectly in situ exsolved metal/bimetal nanospheres.Highly Stable and Efficient Catalyst with In Situ Exsolved Fe-Ni Alloy Nanospheres Socketed on an Oxygen Deficient Perovskite for Direct CO2 ElectrolysisFe-Ni alloy; CO2 electrolysis; perovskite oxide; in situ exsolution; SOECx110201662#N/AFALSE
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acscatal.6b0146610.1021/acscatal.6b01466FALSEhttps://doi.org/10.1021/acscatal.6b01466Wadayama, TOxygen Reduction Reaction Activity for Strain-Controlled Pt-Based Model Alloy Catalysts: Surface Strains and Direct Electronic Effects Induced by Alloying Elementsx2016#N/AFALSE
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acscatal.6b0143310.1021/acscatal.6b01433FALSEhttps://doi.org/10.1021/acscatal.6b01433Shaw, WJACS Catal.Inspired by the contribution of the protein scaffold to the efficiency with which enzymes function, we used outer coordination sphere features to develop a molecular electrocatalyst for the reversible production/oxidation of H-2 at 25 degrees C: [Ni((P2N2Phe)-N-Cy)(2)](2+) (CyPhe; (P2N2R')-N-R = 1,5-diaza-3,7-diphosphacyClooctane, Cy = cyClohexyl, Phe = phenylalanine). Electrocatalytic reversibility is observed in aqueous, acidic methanol. The aromatic rings in the peripheral phenylalanine groups appear to be essential to achieving reversibility based on the observation that reversibility for arginine (CyArg) or glycine (CyGly) complexes is only achieved with elevated temperature (>50 degrees C) in 100% water. A complex with a hydroxyl group in the para-position of the aromatic ring, R' = tyrosine (CyTyr), shows similar reversible behavior. NMR spectroscopy and molecular dynamics studies suggest that interactions between the aromatic groups as well as between the Carbonylic acid groups limit conformational flexibility, contributing to reversibility. NMR spectroscopy studies also show extremely fast proton exchange along a pathway from the Ni-H through the pendant amine to the Carbonyl group. Further, a complex containing a side chain similar to tyrosine but without the Carbonyl group (CyTym; Tym = tyramine) does not display reversible catalysis and has limited proton exchange from the pendant amine, demonstrating an essential role for the Carbonylic acid and the proton pathway in achieving catalytic reversibility. This minimal pathway mimics proton pathways found in hydrogenases. The influence of multiple factors on lowering barriers and optimizing relative energies to achieve reversibility for this synthetic catalyst is a Clear indication of the intricate interplay between the first, second, and outer coordination spheres that begins to mimic the complexity observed in metalloenzymes.Achieving Reversible H-2/H+ Interconversion at Room Temperature with Enzyme-Inspired Molecular Complexes: A Mechanistic Studyreversible electrocatalysis; hydrogen production/oxidation; outer coordination sphere; renewable energy; enzyme mimicx39201672#N/AFALSE
5282
acscatal.6b0139310.1021/acscatal.6b01393FALSEhttps://doi.org/10.1021/acscatal.6b01393Head-Gordon, MACS Catal.Electrocatalytic reduction of CO2 to energy-rich hydrocarbons such as alkanes, alkenes, and alcohols is a very challenging task. So far, only copper has proven to be capable of such a conversion. We report density functional theory (DFT) calculations combined with the Poisson-Boltzmann implicit solvation model to show that single-atom alloys (SAAs) are promising electrocatalysts for CO2 reduction to C-1 hydrocarbons in aqueous solution. The majority component of the SAAs studied is either gold or silver, in combination with isolated single atoms, M (M = Cu, Ni, Pd, Pt, CO2 Rh, and Ir), replacing surface atoms. We envision that the SAA behaves as a one-pot tandem catalyst: first gold (or silver) reduces CO2 to CO2 and the newly formed CO is then captured by M and is further reduced to C-1 hydrocarbons such as methane or methanol. We studied 28 SAAs, and found about half of them selectively favor the CO2 reduction reaction over the competing hydrogen evolution reaction. Most of those promising SAAs contain M = CO2 Rh, or Ir. The reaction mechanism of two SAAs, Rh@Au(100) and Rh@Ag(100), is explored in detail. Both of them reduce CO2 to methane but via different pathways. For Rh@Au(100), reduction occurs through the pathway *CO -> *CHO -> *CHOH -> *CH + H2O(l) -> *CH2 + H2O(l) -> *CH3 + H2O(l) -> * + H2O(l) + CH4(g); whereas, for Rh@Ag(100), the pathway is *CO -> *CHO -> *CH2O ->*OCH3 -> *O + CH4(g) -> *OH + CH4(g) -> * + H2O(l) + CH4(g). The minimum applied voltages to drive the two electrocatalytic systems are -1.01 and -1.12 V-RHE for Rh@Au(100) and Rh@Ag(100), respectively, at which the Faradaic efficiencies for CO2 reduction to CO are 60% for gold and 90% for silver. This suggests that SAA can efficiently reduce CO2 to methane with as small as 40% loss to the hydrogen evolution reaction for Rh@Au(100) and as small as 10% for Rh@Ag(100). We hope these computational results can stimulate experimental efforts to explore the use of SAA to catalyze CO2 electrochemical reduction to hydrocarbons.Quantum Mechanical Screening of Single-Atom Bimetallic Alloys for the Selective Reduction of CO2 to C-1 HydrocarbonsCO2 reduction; single-atom alloys; one-pot tandem catalyst; electrocatalysis; density functional theoryx107201672#N/AFALSE
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acscatal.6b0288410.1021/acscatal.6b02884FALSEhttps://doi.org/10.1021/acscatal.6b02884Xie, YACS Catal.In this study, we systematically explore the connection between electrical conductivity and catalytic activity of OER catalysts and disClose the association between the structure of non-oxide-based catalysts and the corresponding OER activity, using a category of Ni-based materials as a model system: i.e., the serial Ni-based compounds NiO, NiSe, Ni3Se2, a and Ni with a wide range of continuously adjustable band gaps ranging from insulator to metallic state. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) revealed that structural rearrangement occurs (forming electrocatalytic active species) on the surface of these catalysts during electrochemical water oxidation. Extended X-ray absorption fine structure (EXAFS) curve fitting suggested the trend of surface oxidation facility for these investigated catalysts. Benefiting from the synergetic effect of intrinsic metallic state and more facile surface reorganization enabled by anions incorporated in a metal matrix, Ni3Se2 has a higher catalytic activity for electrochemical water oxidation in comparison with NiO, NiSe, and Ni. Our work suggests that both electrical transport and active species forming on the surface of precatalysts which are highly correlated with the structure of the precatalysts are critical factors determining the OER performance.Understanding Structure-Dependent Catalytic Performance of Nickel Selenides for Electrochemical Water Oxidationwater oxidation catalysis; nickel-based materials; non-oxide precatalysts; conductivity; surface oxidation72201747#N/ATRUE
5284
acscatal.6b0280610.1021/acscatal.6b02806FALSEhttps://doi.org/10.1021/acscatal.8b01564Laursen, STrends in the Surface and Catalytic Chemistry of Transition-Metal Ceramics in the Deoxygenation of a Woody Biomass Pyrolysis Model Compound2017#N/ATRUE
5285
acscatal.6b0135910.1021/acscatal.6b01359FALSEhttps://doi.org/10.1021/acscatal.6b01359Sun, CHACS Catal.DFT investigations have been carried out on the hydrogen evolution reaction (HER) mechanism followed by [NiFe] hydrogenases. Calculations on the active site of the [NiFe] hydrogenase from Desulfovibrio vulgaris str. Miyazaki F reveal that H-2 is formed as the final product through the singlet multiplicity pathway. Non-spontaneous reaction energies can be seen for both H+/e(-) additions to the reactive sulfur atom from the truncated cysteine residues, being the limiting steps of the whole reaction. In contrast, transfers toward the metal environment to produce the bridging hydride and the bonded H-2 molecule at the Ni-C and 12 steps, respectively, are spontaneous processes. Our DFT results highlight the role of the ligands attached to both the Ni and Fe centers. When the protein ligand environment is spatially confined, reaction energies for the HER are lower than those when the ligand carbons are able to freely adjust. In addition, larger changes can be seen on interchanging the [CN](-) and CO ligands on the Fe center; in particular, the energy profile dramatically changes as [CN](-) ligands are replaced by CO. These results may guide materials synthesis efforts toward optimized HER catalysts.Unraveling the Role of Ligands in the Hydrogen Evolution Mechanism Catalyzed by [NiFe] HydrogenasesH-2 production; spin effect; enzymatic catalysis; bimetallic enzymes; DFTx18201666#N/AFALSE
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acscatal.6b0127410.1021/acscatal.6b01274FALSEhttps://doi.org/10.1021/acscatal.6b01274Palmer, REACS Catal.This report focuses on a novel strategy for the preparation of transition metal MoS2 hybrid nanoClusters based on a one-step, dual-target magnetron sputtering, and gas condensation process demonstrated for Ni-MoS2. Aberration corrected STEM images coupled with EDX analysis confirms the presence of Ni and MoS2 in the hybrid nanoClusters (average diameter = 5.0 nm, Mo:S ratio = 1:1.8 +/- 0.1). The Ni-MoS2 nanoClusters display a 100 mV shift in the hydrogen evolution reaction (HER) onset potential and an almost 3-fold increase in exchange current density compared with the undoped MoS2 nanoClusters, the latter effect in agreement with reported DFT calculations. This activity is only reached after air exposure of the Ni-MoS2 hybrid nanoClusters, suggested by XPS measurements to originate from a Ni dopant atoms oxidation state conversion from metallic to 2+ characteristic of the NiO species active to the HER. Anodic stripping voltammetry (ASV) experiments on the Ni-MoS2 hybrid nanoClusters confirm the presence of Ni-doped edge sites and reveal distinctive electrochemical features associated with both doped Mo-edge and doped S-edge sites which correlate with both their thermodynamic stability and relative abundance.Enhancement of the Hydrogen Evolution Reaction from Ni-MoS2 Hybrid NanoClustersmolybdenum disulfide; nanoClusters; hydrogen evolution; doping; magnetron sputtering deposition; STEMx80201649#N/AFALSE
5287
acscatal.6b0123710.1021/acscatal.6b01237FALSEhttps://doi.org/10.1021/acscatal.6b01237Rodionov, VOACS Catal.The synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine is described. Hydrophobicity was identified as the key variable in mediating the catalytic competence of the complexes. The change in this parameter correlates with both the conformational mobility of the ligand core and the structural changes in the local solvent environment around the metal site. The optimal Co complex identified is hydrophobic, because of three semifluorinated side chains. It catalyzes water electro-oxidation efficiently at neutral pH, with an overpotential of 390 mV and a turnover frequency (TOF) of 1.83 s(-1) in the absence of soluble Co salts. The catalyst can be immobilized through physisorption, and it remains stable in prolonged electrolysis experiments.An Efficient and Stable Hydrophobic Molecular Cobalt Catalyst for Water Electro-oxidation at Neutral pHx39201646#N/AFALSE
5288
acscatal.6b0266610.1021/acscatal.6b02666FALSEhttps://doi.org/10.1021/acscatal.6b02666Driess, MACS Catal.A systematic structural elucidation of the near-surface active species of the two remarkably active nickel phosphides Ni(12)Ps and Ni2P on the basis of extensive analytical, microscopic, and spectroscopic investigations is reported. The latter can serve as complementary efficient electrocatalysts in the hydrogen (HER) versus oxygen evolution reaction (OER) in alkaline media. In the OER Ni12P5 shows enhanced performance over Ni2P due to the higher concentration of nickel in this phase, which enables the formation of an amorphous NiOOH/Ni(OH)(2) shell on a modified multiphase with a disordered phosphide/phosphite core. The situation is completely reversed in the HER, where Ni2P displayed a significant improvement in electrocatalytic activity over Ni12P5 owing to a larger concentration of phosphide/phosphate species in the shell. Moreover, the efficiently combined use of the two nickel phosphide phases deposited on nickel foam in overall electrocatalytic water splitting is demonstrated by a strikingly low cell voltage and high stability with pronounced current density, and these catalysts could be an apt choice for applications in commercial alkaline water electrolysis.Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splittingoverall water splitting; electrocatalysis; nickel phosphide; structural rearrangement; surface structure184201757#N/ATRUE
5289
acscatal.6b0122610.1021/acscatal.6b01226FALSEhttps://doi.org/10.1021/acscatal.6b01226Lu, YACS Catal.A Ni-foam-structured PdNi nanoalloy catalyst engineered from nano- to macro-scales has been successfully fabricated for the catalytic deoxygenation of coalbed methane (CBM). The catalyst was obtainable by embedment of Pd nanopartiCles onto Ni-foam substrate via a galvanic exchange reaction method and subsequent in situ Activation in the reaction, which was active at low temperature, selective (no CO formation), and oscillation free in this CH4-rich catalytic combustion process. Special Pd@NiO (Pd nanopartiCles partially wrapped by tiny NiO fragments) ensembles were formed in the galvanic deposition stage and could merely be transformed into PdNi nanoalloys in the real reaction stream at elevated temperatures (e.g., 450 degrees C or higher). Density functional theory (DFT) calculations were carried out to reveal the role of Ni decoration at Pd in PdNi nanoalloy catalyst for the CBM deoxygenation. By nature, the Pd Ni alloying modified the electronic structure of surface Pd and led to a decrease in the 0 adsorption energy, which can be taken as the activity descriptor for the CBM deoxygenation. A reaction kinetic study indicated that the Ni decoration at Pd by Pd Ni alloying lowered the apparent Activation energy in comparison to the pristine Pd catalyst, while leading to an increase of the reaction order of O-2 from 0.6 at Pd catalyst to 0.3. The foam-structured PdNi nanoalloy catalyst thus offered enhanced low-temperature activity and the elimination of oscillating phenomena as the result of a transient balance obtained between the cyCles of O-2 adsorption/Activation and CH4 oxidation.High-Performance PdNi Nanoalloy Catalyst in Situ Structured on Ni Foam for Catalytic Deoxygenation of Coalbed Methane: Experimental and DFT Studiesstructured catalyst; nanoalloy catalysis; foam; coalbed methane; catalytic combustion; reaction kinetics; DFT calculationsx30201660#N/AFALSE
5290
acscatal.6b0121110.1021/acscatal.6b01211FALSEhttps://doi.org/10.1021/acscatal.6b01211Jiang, DEACS Catal.The IT phase of transition-metal dichalcogenides (TMDs) has been demonstrated in recent experiments to display excellent catalytic activity for hydrogen evolution reaction (HER), but the catalytic mechanism has not been elucidated so far. Herein, using IT MoS2 as the prototypical TMD material, we studied the HER activity on its basal plane from periodic density functional theory (DFT) calculations. Compared to the nonreactive basal plane of 2H phase MoS2, the catalytic activity of the basal plane of IT phase MoS2 mainly arises from its affinity for binding H at the surface S sites. Using the binding free energy (Delta G(H)) of H as the descriptor, we found that the optimum evolution of H-2 will proceed at surface H coverage of 12.5% similar to 25%. Within this coverage, we examined the reaction energy and barrier for the three elementary steps of the HER process. The Volmer step was found to be facile, whereas the subsequent Heyrovsky reaction is kinetically more favorable than the Tafel reaction. Our results suggest that at low overpotential, HER can take place readily on the basal plane of IT MoS2 via the Volmer Heyrovsky mechanism. We further screened the dopants for the HER activity and found that substitutional doping of the Mo atom by metals such as Mn, Cr, Cu, Ni, and Fe can make IT MoS2 a better HER catalyst.Mechanism of Hydrogen Evolution Reaction on 1T-MoS2 from First PrinciplesIT MoS2; hydrogen evolution reaction; catalytic activity; basal plane; Volmer Heyrovsky mechanism; substitutional dopingx402201678#N/AFALSE
5291
acscatal.6b0117010.1021/acscatal.6b01170FALSEhttps://doi.org/10.1021/acscatal.6b01170Gewirth, AAObservation of an Inverse Kinetic Isotope Effect in Oxygen Evolution Electrochemistryx2016#N/AFALSE
5292
acscatal.6b0113410.1021/acscatal.6b01134FALSEhttps://doi.org/10.1021/acscatal.6b01134Chirik, PJACS Catal.Combination of the readily available alpha-diimine ligand, ((ArN=C(Me))(2) Ar = 2,6-Pr-i(2)-C6H3), ((DI)-D-iPr) with air stable nickel(II) bis(Carbonylates) generated a highly active catalyst exhibiting anti-Markovnikov selectivity for the hydrosilylation of alkenes with a variety of industrially relevant tertiary alkoxy- and siloxy-substituted silanes. A combination of the method of continuous variations with stoichiometric studies identified the formally Ni(I) hydride dimer, [((DI)-D-iPr)NiH](2) as the nickel compound formed following reduction of the Carbonylate ligands. For the hydrosilylation of 1-octene with (EtO)(3)SiH, a rate law of [Ni](1/2)[1-octene][(EtO)(3)SiH] in combination with deuterium-labeling studies establish dissociation of the nickel hydride dimer followed by fast and reversible alkene insertion into ((DI)-D-iPr)NiH, consistent with turnover-limiting C-Si bond formation. The hydrosilylation of 1-octene with triethoxysilane, a reaction performed commercially in the silicones industry on a scale of >5 000 000 kg/year, was conducted on a 10 g scale with 96% yield and >98% selectivity for the desired product. Silicone cross-linking, another major industrial application of homogeneous hydrosilylation, was also demonstrated using the air-stable nickel and ligand precursors.Alkene Hydrosilylation Using Tertiary Silanes with alpha-Diimine Nickel Catalysts. Redox-Active Ligands Promote a Distinct Mechanistic Pathway from Platinum Catalystsnickel; silicone; hydrosilylation; diimine; Carbonylate; hydride; mechanismx100201668#N/AFALSE
5293
acscatal.6b0247910.1021/acscatal.6b02479FALSEhttps://doi.org/10.1021/acscatal.6b02479Kundu, SACS Catal.Increasing demand for finding eco-friendly and everlasting energy sources is now totally depending on fuel cell technology. Though it is an eco-friendly way of producing energy for the urgent requirements, it needs to be improved to make it cheaper and more eco-friendly. Although there are several types of fuel cells, the hydrogen (H-2) and oxygen (O-2) fuel cell is the one with zero carbon emission and water as the only byproduct. However, supplying fuels in the purest form (at least the H-2) is essential to ensure higher life cyCles and less decay in cell efficiency. The current large-scale H-2 production is largely dependent on steam reforming of fossil fuels, which generates CO2 along with H-2 and the source of which is going to be depleted. As an alternate, electrolysis of water has been given greater attention than the steam reforming. The reasons are as follows: the very high purity of the H-2 produced, the abundant source, no need for high-temperature, high-pressure reactors, and so on. In earlier days, noble metals such as Pt (cathode) and Ir and Ru (anode) were used for this purpose. However, there are problems in employing these metals, as they are noble and expensive. In this review, we elaborate how the group VIII 3d metal sulfide, selenide, and phosphide nanomaterials have arisen as abundant and cheaper electrode materials (catalysts) beyond the oxides and hydroxides of the same. We also highlight the evaluation perspective of such electrocatalysts toward water electrolysis in detail.Recent Trends and Perspectives in Electrochemical Water Splitting with an Emphasis on Sulfide, Selenide, and Phosphide Catalysts of Fe, Co, and Ni: A Reviewwater splitting; hydrogen evolution; oxygen evolution; overpotential; Tafel analysis; metal chalcogenides; metal phosphides; electrolysis10682016259#N/ATRUE
5294
acscatal.6b0110610.1021/acscatal.6b01106FALSEhttps://doi.org/10.1021/acscatal.6b01106Maillard, FACS Catal.The catalytic performance of extended and nanometer-sized surfaces strongly depends on the amount and the nature of structural defects that they exhibit. However, whereas the effect of steps or adatoms may be unraveled with single crystals (surface science approach), implementing reproducibly in a controlled manner structural defects on nanomaterials remains hardly feasible. A case that deserves particular attention is that of bimetallic nanomaterials, which are used to catalyze the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). Point defects (vacancies), planar defects (dislocations and grain boundaries), and bulk defects (voids, pores) are likely to be generated in alloy or core@shell nanomaterials based on Pt and a transition metal due to the high lattice mismatch between the two elements. Here, we report the morphological and structural trajectories of hollow PtNi/C nanopartiCles during thermal annealing under vacuum, N-2 H-2 or air atmosphere by in situ transmission electron microscopy and synchrotron X-ray diffraction. We evidence atmosphere dependent restructuring kinetics, which enabled us to synthesize a set of catalysts with identical chemical compositions and elemental distributions but different morphologies, crystallite sizes, and lattice strain. By combining the results of Rietveld and pair-distribution function analyses and electrochemical measurements, we demonstrate that the structurally disordered areas located at the interface between individual crystallites are highly active for two reactions of interest for PEMFC devices: the electrochemical COads oxidation and the ORR. These results shed fundamental light on the effect of structural defects on the catalytic performance of bimetallic nanomaterials and should aid in the rational design of more efficient ORR electrocatalysts.Defects do Catalysis: CO Monolayer Oxidation and Oxygen Reduction Reaction on Hollow PtNi/C NanopartiClesproton exchange membrane fuel cell; oxygen reduction reaction; platinum nickel alloy; hollow nanopartiCles; structural defects; grain boundary; vacancyx79201694#N/AFALSE
5295
acscatal.6b0103310.1021/acscatal.6b01033FALSEhttps://doi.org/10.1021/acscatal.6b01033Nozaki, KACS Catal.The reactions of 2-methyltetrahydropyran (2-MTHP, C6H12O) on Ni2P/SiO2 provide insights on the interactions between a cyClic ether, an abundant component of biomass feedstock, with a transition-metal phosphide, an effective hydrotreating catalyst. At atmospheric pressure and a low contact time, conditions similar to those of a fast pyrolysis process, 70% of products formed from the reaction of 2-MTHP on Ni2P/SiO2 were deoxygenated products, 2-hexene and 2-pentenes, indicating a good oxygen removal capacity. Deprotonation, hydrogenolysis, dehydration, and deCarbonylation were the main reaction routes. The reaction sequence started with the adsorption of 2-MTHP, followed by ring-opening steps on either the methyl substituted side (Path I) or the unsubstituted side (Path II) to produce adsorbed alkoxide species. In Path I, a primary alkoxide was oxidized at the alpha-carbon to produce an aldehyde, which subsequently underwent deCarbonylation to 2-pentenes. The primary alkoxide could also be protonated to give a primary alcohol which could desorb or form the final product 2-hexene. In Path II, a secondary alkoxide was oxidized to produce a ketone or was protonated to a secondary alcohol that was dehydrated to give 2-hexene. The active sites for the adsorption of 2-MTHP and O-intermediates were likely to be Ni sites.Reactions of 2-Methyltetrahydropyran on Silica-Supported Nickel Phosphide in Comparison with 2-Methyltetrahydrofuranhydrodeoxygenation; 2-methyltetrahydropyran; nickel phosphide; contact time studies; reaction networkx18201663#N/AFALSE
5296
acscatal.6b0099510.1021/acscatal.6b00995FALSEhttps://doi.org/10.1021/acscatal.6b00995Garcia, HACS Catal.Adsorption of copper nanopartiCles (NPs) on preformed graphene (G) affords an efficient catalyst for the nuCleophilic addition of anilines to N,N'-diAlkylcarbodiimides to form the corresponding guanidines. Cu/G exhibits a wide scope in promoting guanylation of different substituted anilines and carbodiimides and outperforms Cu nanopartiCles supported on carbon nanotubes, active carbon, layered Clay, TiO2 and CeO2. Importantly, the performance of the catalyst could be increased by 3 orders of magnitude, reaching TONs of 5.95 x 10(4) and TOFs of 9.9 x 10(2) h(-1) by using as catalysts films of 1.1.1 facet oriented Cu nanoplatelets (3-4 nm thickness and 20-40 nm lateral dimensions) having a strong interaction with G. This enhancement of the catalytic activity derives from the preferential facet orientation of Cu nano platelets and their strong grafting on G. These catalytic results show the potential that G offers as support for metal NPs for the development of highly active recoverable heterogeneous catalysts.Isotropic and Oriented Copper NanopartiCles Supported on Graphene as Aniline Guanylation Catalystsheterogeneous catalysis; Cu nanopartiCles; graphene as support; oriented Cu nanopartiCles; catalytic guanylationx16201633#N/AFALSE
5297
acscatal.6b0220310.1021/acscatal.6b02203FALSEhttps://doi.org/10.1021/acscatal.6b02203Schuhmann, WACS Catal.We report metallic NiPS3@NiOOH core shell heterostructures as an efficient and durable electrocatalyst for the oxygen evolution reaction, exhibiting a low onset potential of 1.48 V (vs RHE) and stable performance for over 160 h. The atomically thin NiPS3 nanosheets are obtained by exfoliation of bulk NiPS3 in the presence of an ionic surfactant. The OER mechanism was studied by a combination of SECM, in situ Raman spectroscopy, SEM, and XPS measurements, which enabled direct observation of the formation of a NiPS3@NiOOH core shell heterostructure at the electrode interface. Hence, the active form of the catalyst is represented as NiPS3@NiOOH core shell structure. Moreover, DFT calculations indicate an intrinsic metallic character of the NiPS3 nanosheets with densities of states (DOS) similar to the bulk material. The high OER activity of the NiPS3 nanosheets is attributed to a high density of accessible active metallic-edge and defect sites due to structural disorder, a unique NiPS3@NiOOH core shell heterostructure, where the presence of P and S modulates the rface electronic structure of Ni in NiPS3, thus providing excellent conductive pathway for efficient electron-transport to the NiOOH shell. These findings suggest that good size control during liquid exfoliation may be advantageously used for the formation of electrically conductive NiPS3@ NiOOH core shell electrode materials for the electrochemical water oxidation.Metallic NiPS3@NiOOH Core-Shell Heterostructures as Highly Efficient and Stable Electrocatalyst for the Oxygen Evolution Reactionliquid exfoliation; metallic NiPS3 nanosheets; oxygen evolution; NiPS3@NiOOH core-shell heterostructure; electrocatalysis135201755#N/ATRUE
5298
acscatal.6b0084210.1021/acscatal.6b00842FALSEhttps://doi.org/10.1021/acscatal.6b00842Loffreda, DACS Catal.Polymer electrolyte membrane fuel cells have been studied for more than three decades as promising Clean energy converters for automotive applications. However, improving their durability and reducing the catalyst cost (platinum loading) are ongoing challenges. Alloys are often proposed as an alternative solution which combines a good catalytic activity toward the oxygen reduction reaction and a decreased platinum content. In this work, we address density functional theory calculations for the formation of water and hydrogen peroxide on three different Pt3Ni(111) alloy model surfaces: bulk-truncated, Pt-skin, and Pt-skeleton terminations, in comparison with Pt(111). From a low-coverage Gibbs free energy analysis, the prediction of the activity order between all the catalysts agrees with electrochemical measurements: Pt-skin > Pt-skeleton > Pt(111) > bulk-truncated Pt3Ni(111). The superior activity of Pt-skin has been explained in terms of thermodynamic and kinetic properties and through an energy decomposition analysis. A strong loss of stability for atomic oxygen and a significant decrease of the barrier to form hydroxyl induce more competitive transformation routes on this surface. The intermediate activity of Pt-skeleton has been linked to similar thermodynamic properties (at least for OH formation) and a rather moderate lowering of the Activation barriers of oxygen dissociation (morphology effect) and OH formation. Hence, the combined effects of coordination loss for surface Pt atoms (Pt skeleton) and the indirect effect of Ni (Pt-skin) are promoting the activity, with respect to Pt(111). In contrast, the direct effect from surface Ni atoms in the bulk-truncated surface is rather inhibiting. The expected selectivity to water is preferential, Pt skeleton being more selective than the three other surfaces.How Does the Surface Structure of Pt-Ni Alloys Control Water and Hydrogen Peroxide Formation?catalytic water formation; density functional theory; free energy; Activation energy; platinum; nickel; hydroxyl; hydrogen peroxidex6201662#N/AFALSE
5299
acscatal.6b0082210.1021/acscatal.6b00822FALSEhttps://doi.org/10.1021/acscatal.6b00822Coperet, CACS Catal.Due to the impact of anthropogenic CO2 emissions on global warming, the conversion of this molecule to useful products is of increasing interest. Therefore, further understanding of the CO2 Activation is needed. Ni-based catalysts are able to dissociate and convert CO2 into fuels, and although these systems are generally simulated using simple slab models, real catalysts are significantly more complex. They are generally composed of nanopartiCles supported on oxides, being gamma-Al2O3 one of the most widely used supports. In this study, we perform ab initio simulations in order to model the CO2 Activation on Ni nanopartiCles supported on gamma-Al2O3. Starting from ideal surface terminations, going to Ni nanopartiCles (0.5-1 nm) and up to gamma-Al2O3 supported Ni nanopartiCles, the role of terraces, steps, edges, and the support is evaluated for this chemical transformation. The metal oxide interface provides the most active sites for CO2 Activation, due to a synergistic effect between the nickel nanopartiCles and the Lewis acidic sites of gamma-Al2O3.CO2 Activation on Ni/gamma-Al2O3 Catalysts by First-Principles Calculations: From Ideal Surfaces to Supported NanopartiClesCO2 Activation; nickel; surfaces; nanopartiCles; alumina; support effects; DFT calculationsx53201660#N/AFALSE
5300
acscatal.6b0077810.1021/acscatal.6b00778FALSEhttps://doi.org/10.1021/acscatal.6b00778Dempsey, JLACS Catal.Proton-coupled electron transfer (PCET) reactions are at the heart of the catalytic processes involved in hydrogen evolution. In this Perspective, the state-of-the-art spectroscopic and electrochemical methods available to elucidate the mechanisms of PCET reactions of fuel-forming catalysts are presented. Through examples of our recent work, the applications of these methods are discussed with a focus on the type of information and the accuracy that can be obtained from each. Three case studies are presented to illustrate different possible origins for peak shifts observed in cyClic voltammograms.Reaction Pathways of Hydrogen-Evolving Electrocatalysts: Electrochemical and Spectroscopic Studies of Proton-Coupled Electron Transfer ProcessesPCET; electrocatalysis; cyClic voltammetry; stopped-flow; solar fuelsx812016157#N/AFALSE
5301
acscatal.6b0071510.1021/acscatal.6b00715FALSEhttps://doi.org/10.1021/acscatal.6b00715Yamashita, HACS Catal.Highly dispersed monometallic Ru nanopartiCles can be successfully synthesized on TiO2 supports for effective hydrogen production from ammonia-borane (NH3 center dot BH3; AB). The choice of support material and reduction methods were confirmed to significantly influence the size of the Ru nanopartiCles, and smaller sizes of Ru nanopartiCles with a mean diameter of 1.7 nm could be formed on a TiO2 support material by H-2 reduction at 200 degrees C. The catalytic activity of the Ru nanopartiCles can be significantly enhanced by alloying with Ni atoms, whereby a significantly high total turnover number (TTO) of approximately 153000 over 8 h was achieved with an excellent turnover frequency (TOF) of 914 min(-1) and an Activation energy of 28.1 kJ mol(-1). Detailed characterization by means of TEM, EDX, H-2-TPR, and in situ XAFS measurements revealed that a synergistic alloying effect originates from the random distribution of Ru-Ni nanopartiCles with a mean diameter of 2.3 nm and plays a crucial role in the exceptional catalytic performance. This catalytic system has particular potential for industrial application in fuel cells due to advantages such as the facile preparation method, the use of relatively cheap metals, and the exceptionally high catalytic activity.Ru and Ru-Ni NanopartiCles on TiO2 Support as Extremely Active Catalysts for Hydrogen Production from Ammonia-BoraneRu-Ni alloy; titania; dehydrogenation; ammonia-borane; hydrogenx193201647#N/AFALSE
5302
acscatal.6b0218810.1021/acscatal.6b02188FALSEhttps://doi.org/10.1021/acscatal.6b02188Bao, XHACS Catal.Encapsulation of metal nanopartiCles with porous oxide shells is a successful strategy to design catalysts with high catalytic performance. We suggest an alternative route to cover metal nanopartiCles with two-dimensional (2D) material shells such as hexagonal boron nitride (h-BN), in which active metal components are stabilized by the outer shells and meanwhile catalytic reactions occur at interfaces between cores and shells through feasible intercalation of the 2D material covers. As an illustration, Ni nanopartiCles encapsulated with few-layer h-BN shells were constructed and applied in syngas methanation. Ni@h-BN core-shell nanocatalysts exhibit enhanced methanation activity, higher resistance to partiCle sintering, and suppressed carbon deposition and Ni loss in reactions. Surface science studies in h-BN/Ni(111) model systems and chemisorption data confirm the occurrence of methanation reactions on Ni surfaces under h-BN cover. The confinement effect of h-BN shells improves Ni-catalyzed reaction activity and Ni catalyst stability.Enhanced Nickel-Catalyzed Methanation Confined under Hexagonal Boron Nitride Shellshexagonal boron nitride (h-BN); nickel; syngas methanation; core-shell; intercalation69201657#N/ATRUE
5303
acscatal.6b0217610.1021/acscatal.6b02176FALSEhttps://doi.org/10.1021/acscatal.6b02176Chen, JGGACS Catal.Dry reforming is a potential process to convert CO2 and light alkanes into syngas (H-2 and CO), which can be subsequently transformed to chemicals and fuels. In this work, PtNi bimetallic catalysts have been investigated for dry reforming of ethane and butane using both model surfaces and supported powder catalysts. The PtNi bimetallic catalyst shows an improvement in both activity and stability in comparison to the corresponding monometallic catalysts. The formation of PtNi alloy and the partial reduction of Ce4+ to Ce3+ under reaction conditions are demonstrated by in situ ambient-pressure X-ray photoemission spectroscopy (AP-XPS), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) measurements. A Pt-rich bimetallic surface is revealed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) following CO adsorption. Combined in situ experimental results and density functional theory (DFT) calculations suggest that the Pt-rich PtNi bimetallic surface structure would weaken the binding of surface oxygenate/carbon species and reduce the Activation energy for C-C bond scission, leading to an enhanced dry reforming activity.Dry Reforming of Ethane and Butane with CO2 over PtNi/CeO2 Bimetallic Catalystsdry reforming; bimetallic catalyst; synthesis gas; ethane; butane; CO260201640#N/ATRUE
5304
acscatal.6b0048710.1021/acscatal.6b00487FALSEhttps://doi.org/10.1021/acscatal.6b00487Stevenson, KJACS Catal.Urea electrooxidation has attracted considerable interest as an alternative anodic reaction in the electrochemical generation of hydrogen due to both the lower electrochemical potential required to drive the reaction and also the possibility of eliminating a potentially harmful substance from wastewater during hydrogen fuel production. Nickel and nickel-containing oxides have shown activities comparable to those of precious-metal catalysts for the electrooxidation of urea in alkaline conditions. Herein, we investigate the use of nanostructured LaNiO3 perovskite supported on Vulcan carbon XC-72 as an electrocatalyst. This catalyst exhibits an exceptionally high mass activity of ca. 371 mA mg(ox)(-1) and specific activity of 2.25 A mg(-1) cm(ox)(-2) for the electrooxidation of urea in 1 M KOH, demonstrating the potential applications of Ni-based perovskites for direct urea fuel cells and low-energy hydrogen production. While LaNiO3 is shown to be stable at low overpotentials, through in-depth mechanistic studies the catalyst surface was observed to restructure and there was apparent CO2 poisoning of the LaNiO3 upon extended cyCling, a result that may be extended to other Ni-based systems.Nanostructured LaNiO3 Perovskite Electrocatalyst for Enhanced Urea Oxidationperovskite; oxidation; electrocatalyst; urea; nickelx126201619#N/AFALSE
5305
acscatal.6b0048110.1021/acscatal.6b00481FALSEhttps://doi.org/10.1021/acscatal.6b00481Wang, YACS Catal.Oxygen evolution reaction (OER) is known to have a significant role in renewable energy. Herein, we report a low-cost, highly active, and superbly durable three-dimensional (3D) sandwiched NiFe/C arrays grown on Ni foam by a general procedure. This special structure, with both graphitized carbon and Ni foam, possesses a huge specific surface area, high electroconductivity, and a porous structure, effectively enhancing electrocatalytic activities for OER. Furthermore, the sandwiched structure with coupled graphitized carbon sheets encapsulating the outside can hinder active materials from agglomeration and falling off during long-term operation, leading to outstanding durability, even in large temperature ranges.Uniquely Monodispersing NiFe Alloyed NanopartiCles in Three-Dimensional Strongly Linked Sandwiched Graphitized Carbon Sheets for High-Efficiency Oxygen Evolution ReactionOER; sandwich-like; three-dimensional; NiFe; graphitized carbonx80201658#N/AFALSE
5306
acscatal.6b0045410.1021/acscatal.6b00454FALSEhttps://doi.org/10.1021/acscatal.6b00454Myers, DJACS Catal.Vertically aligned catalysts comprised of platinum nickel thin films on nickel nanorods (designated as Pt-Ni@Ni-NR) with varying ratios of Pt to Ni in the thin film were prepared by magnetron sputtering and evaluated for their oxygen reduction reaction (ORR) activity. A glancing angle deposition (GLAD) technique was used to fabricate the Ni nanorods (NRs) and a small angle deposition technique for growth of a thin conformal coating of Pt-Ni on the Ni-NRs. The Pt-Ni@Ni-NR structures were deposited on glassy carbon for evaluation of their ORR activity in an aqueous acidic electrolyte using the rotating disk electrode technique. The PtNi@Ni-NR catalysts showed superior area-specific and mass activities for ORR compared to those of Pt-Ni alloy nanorod catalysts prepared using the GLAD technique and compared to those of conventional large-surface area Pt and Pt-Ni alloy nanopartiCle catalysts.SAD-GLAD Pt-Ni@Ni Nanorods as Highly Active Oxygen Reduction Reaction Electrocatalystsmagnetron sputtering techniques; glancing angle deposition (GLAD); small angle deposition (SAD); nickel nanorods; Pt-Ni thin film catalysts; oxygen reduction reaction (ORR); polymer electrolyte fuel cell; polymer electrolyte membrane fuel cell (PEMFC)x16201662#N/AFALSE
5307
acscatal.6b0216210.1021/acscatal.6b02162FALSEhttps://doi.org/10.1021/acscatal.6b02162Yeo, BSACS Catal.The electrochemical reduction of carbon dioxide (CO2) to ethanol (C2H5OH) and ethylene (C2H4) using renewable electricity is a viable method for the production of these commercially vital chemicals. Copper (Cu) and its oxides are by far the most effective electrocatalysts for this purpose. However, the formation of ethanol using these catalysts is generally less favored in comparison to that of ethylene. In this work, we demonstrate that the selectivity of CO2 reduction toward ethanol could be tuned by introducing a cocatalyst to generate an in situ source of mobile CO reactant. Cu-based oxides with different amounts of Zn dopants (Cu, Cu10Zn, Cu4Zn, and Cu2Zn) were prepared and used as catalysts under ambient pressure in aqueous 0.1 M KHCO3 electrolyte. By varying the amount of Zn in the bimetallic catalysts, we found that the selectivity of ethanol versus ethylene production, defined by the ratio of their Faradaic efficiencies (FEethanol/FEethylene), could be tuned by a factor of up to similar to 12.5. Ethanol formation was maximized on Cu4Zn at -1.05 V vs RHE, with a remarkable Faradaic efficiency and current density of 29.1% and -8.2 mA/cm(2), respectively. The Cu4Zn catalyst was also catalytically stable for the production of ethanol for at least 5 h. The importance of Zn as a CO-producing site was demonstrated by performing CO2 reduction on Cu-Ni and Cu-Ag bimetallic catalysts. Operando Raman spectroscopy revealed that the as-deposited Cu-based oxide films were reduced to the metallic state during CO2 reduction, after which only signals belonging to CO adsorbed on Cu sites were recorded. This showed that the reduction of CO2 probably occurred on metallic sites rather than on metal oxides. A two-site mechanism to rationalize the selective reduction of CO2 to ethanol is proposed and discussed.Tuning the Selectivity of Carbon Dioxide Electroreduction toward Ethanol on Oxide-Derived CuxZn CatalystsCO2 reduction; copper-zinc; ethanol; ethylene; operando Raman spectroscopy258201655#N/ATRUE
5308
acscatal.6b0035710.1021/acscatal.6b00357FALSEhttps://doi.org/10.1021/acscatal.6b00357Chen, WACS Catal.We identify Ni-O phases as important intermediates in a modeled dry (CO2) reforming of methane catalyzed by Ni (111), based on results from in operando near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) experiments, corrB(OH)2rated by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) measurements. We find that, under a CO2 or CO2-CH4 atmosphere, the Ni-O phases exist in the forms of p(2 X 2)-structured chemisorbed oxygen (Chem-O), epitaxial NiO (111), or oxygen-rich NixOy (x < y, typically Ni2O3), depending on the chemical potential. The growth rates of the Ni-O phases have a negative correlation with temperature from 600 to 900 K, proving that their dynamic concentrations in the reaction are not limited by CO2 Activation, but by their thermal stability. Between 300 and 800 K (1:1 CH4 and CO, mixture), oxidation by CO, is dominant, resulting in a fully Ni-O covered surface. Between 800 and 900 K, a partially oxidized Ni (111) exists which could greatly facilitate the effective conversion of CH4. As CH4 is Activation-limited and dissociates mainly on metallic nickel, the released carbon species can quickly react with the adjacent oxygen (Ni-O phases) to form CO. After combining with carbon and releasing CO molecules, the Ni-O phases can be further regenerated through oxidation by CO. In this way, the Ni-O phases participate in the catalytic process, acting as an intermediate in addition to the previously reported Ni-C phases. We also reveal the carbon phobic property of the Ni-O phases, which links to the intrinsic coking resistance of the catalysts. The low dynamic coverage of surface oxygen at higher temperatures (>900 K) is inferred to be an underlying factor causing carbon aggregation. Therefore, solutions based on Ni-O stabilization are proposed in developing coking resisting catalysts.Dynamic Oxygen on Surface: Catalytic Intermediate and Coking Barrier in the Modeled CO2 Reforming of CH4 on Ni (111)NAP-XPS; surface oxygen; dry reforming; coking; methane; carbon dioxide; nickelx53201687#N/AFALSE
5309
acscatal.6b0029610.1021/acscatal.6b00296FALSEhttps://doi.org/10.1021/acscatal.6b00296Heeres, HJACS Catal.Sorbitol is an important commercially available chemical with a broad application range and is typically made by the catalytic hydrogenation of glucose. Here we report a high-yield synthesis of sorbitol from levoglucosan (1,6-anhydro-beta-D-glucopyranose) and cellobiose, two sugars present in pyrolysis liquids, using a mesoporous carbon-supported Ru catalyst (Ru/CMK-3). The hydrogenation reactions were performed in a batch autoClave setup under a hydrogen pressure of 50 bar and temperatures ranging from 120 to 180 degrees C in water. The hydrogenation of levoglucosan gave essentially quantitative yields of sugar alcohols, composed of 96.2 wt % of sorbitol and 3.8 wt % of mannitol (180 degrees C, 5 h). Ru/CMK-3 shows superior catalytic performance compared to a commercial Ru/C catalyst. A reaction pathway involving glucose as an intermediate and subsequent (hydrogenolysis) reactions of the desired sorbitol is proposed. Reactions with glucose and sorbitol were performed to define the reaction pathways and to highlight the differences between Ru/C and Ru/CMK-3. Disaccharides inCluding cellobiose and sucrose were also tested, yielding up to 95 wt % of C6 sugar alcohols at 180 degrees C in 5 h for both substrates. Detailed catalyst characterization studies (N-2 physisorption, TEM, XRD, NH3-TPD, H-2-TPD) revealed that Ru/CMK-3 contains considerable amounts of strong acid sites (NH3-TPD). Catalyst stability was tested by catalyst recyCling experiments using levoglucosan in batch. After three successive runs, the rate of the hydrolysis reaction of LG to glucose was about constant, though the subsequent hydrogenation reaction to sorbitol/mannitol was slightly retarded as evidenced from a slight increase in the remaining amounts of glucose at the end of reaction.A One-Step Synthesis of C6 Sugar Alcohols from Levoglucosan and Disaccharides Using a Ru/CMK-3 Catalystlevoglucosan; pyrolysis liquids; sorbitol; Ru/CMK-3; hydrogenationx18201669#N/AFALSE
5310
acscatal.6b0027610.1021/acscatal.6b00276FALSEhttps://doi.org/10.1021/acscatal.6b00276Fu, YACS Catal.By the combination of a Ni(II) salt, a bisphosphine ligand, and a catalytic amount of Carbonylic acid anhydride, atom-economic hydroCarbonylation of various alkynes with formic acid can be achieved with high selectivity and remarkable functional group compatibility, affording alpha,beta-unsaturated Carbonylic acids regio- and stereoselectively. Both terminal and internal alkynes are amenable substrates. A mechanism proceeding through carbon monoxide recyCling in a catalytic amount is demonstrated to be crucial for the success of this transformation.Nickel-Catalyzed Regio- and Stereoselective HydroCarbonylation of Alkynes with Formic Acid through Catalytic CO RecyClingnickel; hydroCarbonylation; formic acid; alkynes; carbon monoxidex40201648#N/AFALSE
5311
acscatal.6b0025910.1021/acscatal.6b00259FALSEhttps://doi.org/10.1021/acscatal.6b00259Baletto, FACS Catal.Elucidating the interplay between shape, chemical composition, and catalytic activity is an essential task in the rational nanocatalyst design process. We investigated the activity of MgO-supported PtNi nanoalloys of similar to 1.5 nm toward the oxygen reduction reaction using first-principles simulations. Cuboctahedral-shaped partiCles result to be more active than truncated octahedra of similar sizes, and alloying produces a quantitative improvement in the catalytic activity independent of the catalyst morphology. Our results suggest a practical recipe for catalyst nanoengineering controlling the chemical composition at the metal/oxide interface. Indeed, Ni atoms in contact with the oxide support reduce the binding energy of molecular oxygen at different adsorption sites.Get in Touch and Keep in Contact: Interface Effect on the Oxygen Reduction Reaction (ORR) Activity for Supported PtNi NanopartiClesORR; Pt; nanopartiCle; nanoalloy; core-shell; generalized coordination number; PEMFC; catalyst-by-designx30201640#N/AFALSE
5312
acscatal.6b0022110.1021/acscatal.6b00221FALSEhttps://doi.org/10.1021/acscatal.6b00221Weckhuysen, BMACS Catal.Understanding Fe deposition in fluid catalytic cracking (FCC) catalysis is critical for the mitigation of catalyst degradation. Here we employ soft X-ray ptychography to determine at the nanoscale the distribution and chemical state of Fe in an aged FCC catalyst partiCle. We show that both partiCle swelling due to colloidal Fe deposition and Fe penetration into the matrix as a result of precracking of large organic molecules occur. The application of ptychography allowed us to provide direct visual evidence for these two distinct Fe-based deActivation mechanisms, which have so far been proposed only on the basis of indirect evidence.Nanoscale Chemical Imaging of an Individual Catalyst PartiCle with Soft X-ray Ptychographyfluid catalytic cracking; chemical imaging; catalyst deActivation; iron and soft X-ray ptychographyx47201631#N/AFALSE
5313
acscatal.6b0009610.1021/acscatal.6b00096FALSEhttps://doi.org/10.1021/acscatal.6b00096Kozhevnikov, IVACS Catal.Deoxygenation and decomposition of ethers and esters, inCluding anisole, diisopropyl ether (DPE), and ethyl propanoate (EP), was investigated using bifunctional metal acid catalysis at a gas solid interface in the presence and absence of hydrogen. The bifunctional catalysts studied comprised Pt, Ru, Ni, and Cu as the metal components and Cs2.5H0.5PW12O40 (CspW), an acidic Cs salt of Keggin-type heteropoly acid (HPA) H3PW12O40, as the acid component, with the main focus on Pt CspW catalyst. It was found that bifunctional metal acid catalysis in the presence of H-2 is more efficient for ether and ester deoxygenation than the corresponding monofunctional metal and acid catalysis and that metal- and acid-catalyzed pathways play different roles in these reactions. With Pt-CspW, hydrodeoxygenation of anisole, a model for the deoxygenation of lignin, occurred with 100% yield of cyClohexane under very mild conditions (60-100 degrees C and 1 bar of H-2). This catalyst had the highest activity in anisole deoxygenation for a gas-phase catalyst system reported so far. The catalyst activity decreased in the order of metals: Pt >> Ru > Ni > Cu. For HPA-catalyzed DPE and EP decomposition, relationships between the turnover reaction rate (turnover frequency) and the HPA acid strength were found, which can be used to predict the activity of acid catalysts in these reactions.Deoxygenation of Ethers and Esters over Bifunctional Pt-Heteropoly Acid Catalyst in the Gas Phasedeoxygenation; anisole; diisoproplyl ether; ethyl propanoate; bifunctional catalysis; platinum; heteropoly acidx17201636#N/AFALSE
5314
acscatal.6b0001410.1021/acscatal.6b00014FALSEhttps://doi.org/10.1021/acscatal.6b00014Yang, XRACS Catal.The development of cost-effective hydrogen evolution reaction (HER) electrocatalysts based on 3d-transition metal is highly desired but still challenging. Herein, we report on the synthesis of the three-dimensional self supported nickel-oxide-coated cobalt manganese sulfide nanosheets array on carbon Cloth (CoMn-S@NiO/CC), which is used as an efficient electrocatalyst for HER in alkaline media. The performance of CoMn-S@NiO/CC is significantly improved through an in situ electrochemical reduction process. The electrochemically activated CoMn-S@NiO/CC (ECA CoMn-S@NiO/CC) drives 100 and 200 mA cm(-2) at overpotentials of 232 and 278 mV, respectively, with long-term stability for hydrogen production in 1.0 M KOH. Such high hydrogen evolution activity for ECA CoMn-S@NiO/CC is owed to the incorporation of Co ions, increase in electrochemically active surface area, and the newly formation of amorphous regions on its surface.In Situ Electrochemically Activated CoMn-S@NiO/CC Nanosheets Array for Enhanced Hydrogen Evolutionhydrogen evolution reaction; CoMn-S; NiO; nanosheets array; in situ electrochemical reductionx70201656#N/AFALSE
5315
acscatal.5b0292410.1021/acscatal.5b02924FALSEhttps://doi.org/10.1021/acscatal.5b02924Boettcher, SWEffects of Intentionally Incorporated Metal Cations on the Oxygen Evolution Electrocatalytic Activity of Nickel (Oxy)hydroxide in Alkaline Media
Electrocatalytic
2016#N/AFALSE
5316
acscatal.5b0290010.1021/acscatal.5b02900FALSEhttps://doi.org/10.1021/acscatal.5b02900Tao, FFACS Catal.Catalytic selectivity for producing an ideal product is a key topic for chemical transformations through heterogeneous catalysis. Tuning catalytic selectivity by integrating the second metal to form an alloy has been well demonstrated in the literature. Here we report a method to tune catalytic selectivity in oxidative catalysis on another category of heterogeneous catalysts, transition-metal oxides. By choosing the oxidative dehydrogenation (ODH) of ethane to ethylene as a probe reaction, we demonstrated that doping nonmetallic atoms to the surface lattice of catalyst of a transition-metal oxide can enhance catalytic selectivity through suppression of complete oxidation of the reactant molecules. Catalysts of Co3O4 with doped silicon atoms (Si-x-Co3O4) maintaining the spinel structure of pure Co3O4 exhibit much higher selectivity for the production of ethylene through ODH of ethane in comparison to pure Co3O4 at 600 degrees C by 40%. The suppression of activity of surface lattice oxygen atoms was evidenced by the observation that the surface lattice oxygen atoms of Si-x-Co3O4 cannot exchange oxygen atoms with gas-phase oxygen at low temperatures while pure Co3O4 can. The difference in releasing surface lattice oxygen atoms and dissociating molecular oxygen between pure Co3O4 and Si-x-Co3O4, was supported by DFT calculations. The calculated Activation barriers for dissociation of molecular O-2 and energy barriers for hopping surface oxygen vacancies of Si-x-Co3O4, are obviously higher than those of pure Co3O4, respectively. These experimental exploration and computational studies established a correlation between increase of catalytic selectivity and suppression of the activity of surface lattice oxygen atoms/oxygen vacancies. This correlation suggests an approach for increasing the catalytic selectivity of oxidative catalysis through suppressing activity of surface lattice oxygen atoms/vacancies via doping atoms of a nonmetallic element. This new approach was further confirmed by the observed higher catalytic selectivity for production of ethylene on Geol-Co3O4 in comparison to pure Co3O4.Tuning Catalytic Selectivity of Oxidative Catalysis through Deposition of Nonmetallic Atoms in Surface Lattice of Metal Oxidecatalytic selectivity; oxidative dehydrogenation; ethane; ethylene; surface lattice oxygen; oxygen vacancies; cobalt oxidex18201657#N/AFALSE
5317
acscatal.5b0288810.1021/acscatal.5b02888FALSEhttps://doi.org/10.1021/acscatal.5b02888Lewis, NSACS Catal.We report the electrocatalytic reduction of CO2 to the highly reduced C-2 products, ethylene and ethane, as well as to the fully reduced C-1 product, methane, on three different phases of nickel-gallium (NiGa, Ni3Ga, and Ni5Ga3) films prepared by drop-casting. In aqueous bicarbonate electrolytes at neutral pH, the onset potential for methane, ethylene, and ethane production on all three phases was found to be -0.48 V versus the reversible hydrogen electrode (RHE), among the lowest onset potentials reported to date for the production of C-2 products from CO2. Similar product distributions and onset potentials were observed for all three nickel gallium stoichiometries tested. The onset potential for the reduction of CO2 to C-2 products at low current densities catalyzed by nickel-gallium was >250 mV more positive than that of polycrystalline copper, and approximately equal to that of single crystals of copper, which have some of the lowest overpotentials to date for the reduction of CO2 to C-2 products and methane. The nickel-gallium films also reduced CO to ethylene, ethane, and methane, consistent with a CO2 reduction mechanism that first involves the reduction of CO2 to CO. Isotopic labeling experiments with (CO2)-C-13 confirmed that the detected products were produced exClusively by the reduction of CO2.Nickel-Gallium-Catalyzed Electrochemical Reduction of CO2 to Highly Reduced Products at Low OverpotentialsCO2 reduction; electrocatalysis; nickel gallium; NiGa; ethane; methane; low overpotential; C2 productionx156201645#N/AFALSE
5318
acscatal.5b0284410.1021/acscatal.5b02844FALSEhttps://doi.org/10.1021/acscatal.5b02844
de Lucas-Consuegra, A
ACS Catal.This paper reports a groundbreaking approach for simultaneous hydrogen production and storage that entails catalysis, electrochemistry, surface science, and materials synthesis. A novel electrocatalytic system is developed based on nickel nanocolumnar films of controlled microstructure prepared on K-beta Al2O3 solid electrolyte supports by oblique angle physical vapor deposition. The outstanding characteristics of this system are a hydrogen storage capacity of up to 19 g of H-2 (100 g of Ni)(-1), which is unparalleled in the literature and the possibility of controlling its release electrochemically, under fixed mild conditions (280 degrees C and normal pressure). H-2 is produced in situ by methanol steam reforming on the Ni catalyst, and it spills over onto graphene oxide aggregates formed during the catalytic process, as confirmed by SEM, FTIR, and Raman spectroscopy. The proposed storage mechanism considers a synergetic contribution of both Ni and graphene oxide, promoted by K+ ions, in enhancing the hydrogen storage capacity of the system.Electrocatalytic System for the Simultaneous Hydrogen Production and Storage from Methanolhydrogen storage; methanol re-forming; graphene oxide; alkali promotion; nickel nanorods; glancing angle deposition
Electrocatalytic
12201658#N/AFALSE
5319
acscatal.5b0280610.1021/acscatal.5b02806FALSEhttps://doi.org/10.1021/acscatal.5b02806Choi, JACS Catal.Efficient protocols for Rh-catalyzed intermolecular C-H silylation of unactivated arenes and heteroarenes are disClosed. The silylations are catalyzed by a Rh-complex (2 mol %) derived in situ from commercially available Rh(nbd)(2)BF4 and (S,S)-i-Pr-BPE (L3) with Et3SiH in the presence of hydrogen acceptor under either neat (excess of arene) or stoichiometric conditions. The regioselectivity is determined mainly by the steric bulk of the substituents and by the electronic effect as an ancillary factor. In addition, our preliminary result shows that the current protocol catalyzes the silylation of arenes in the absence of hydrogen acceptors.Intermolecular C-H Silylation of Arenes and Heteroarenes with HSiEt3 under Operationally Diverse Conditions: Neat/Stoichiometric and Acceptor/AcceptorlessC-H silylation; Rh-catalyzed silylation; intermolecular C-H silylation; silylation of unactivated arenes and heteroarenes; C-H bond Activation; acceptorless C-H silylationx26201661#N/AFALSE
5320
acscatal.5b0280410.1021/acscatal.5b02804FALSEhttps://doi.org/10.1021/acscatal.5b02804Takanabe, KTemperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide
Electrocatalytic
2016#N/AFALSE
5321
acscatal.5b0275010.1021/acscatal.5b02750FALSEhttps://doi.org/10.1021/acscatal.5b02750Mukerjee, SACS Catal.One of the major obstaCles to the commercialization of proton exchange membrane fuel cells (PEMFCs) is the usage of scarce platinum in the cathode for the oxygen reduction reaction (ORR). Although progress has been made in reducing Pt usage by alloying with transition metals M (M = Co, Ni, Cu, etc.), practical applications of Pt-M/C catalysts are impeded by their insufficient durability under the highly corrosive conditions at a PEMFC cathode. Herein, we reconcile the durability difficulty by demonstrating that the high mass activity of the dealloyed PtNi3/C catalyst with low nanoporosity further increases after 30k voltage cyCles in PEMFCs. A novel method has been developed to implement an in situ X-ray absorption spectroscopy study of these PEMFC-cyCled catalysts under operating conditions to understand the unusual activity trend. We reveal that the ORR activity of PtNi3/C catalysts with varied nanoporosities exhibits a Sabatier volcano curve as a function of the strain governed by Ni content, and the volcano is skewed toward the Pt-O weak binding leg owing to the asymmetric site-blocking effect. The Ni dissolution during PEMFC operation, which was previously believed to be detrimental, becomes beneficial for the solid PtNi3/C catalysts located on the Pt-O weak binding leg because it leads to the activity ascending toward the apex, and meanwhile the activity remains high throughout the long-term operation owing to the minimal site-blocking effect. More generally, the fundamental insights into the universal asymmetric volcano curve of redox catalysis will potentially guide the rational design of a broad variety of catalytic materials.Circumventing Metal Dissolution Induced Degradation of Pt-Alloy Catalysts in Proton Exchange Membrane Fuel Cells: Revealing the Asymmetric Volcano Nature of Redox Catalysisfuel cell degradation; oxygen reduction reaction; durability; strain effects; site-blocking effectx48201668#N/AFALSE
5322
acscatal.6b0212410.1021/acscatal.6b02124FALSEhttps://doi.org/10.1021/acscatal.6b02124Martin, RACS Catal.The recent years have witnessed the development of metal-catalyzed reductive Carbonylation of organic (pseudo)halides with CO2 as C1 source, representing potential powerful alternatives to existing methodologies for preparing Carbonylic acids, privileged motifs in a myriad of pharmaceuticals and molecules displaying significant biological properties. While originally visualized as exotic cross-coupling reactions, a Close look into the literature data indicates that these processes have become a fertile ground, allowing for the utilization of a variety of coupling partners, even with particularly challenging substrate combinations. As for other related cross-electrophile scenarios, the vast majority of reductive Carbonylation of organic (pseudo)halides are characterized by their simplicity, mild conditions, and a broad functional group compatibility, suggesting that these processes could be implemented in late-stage diversification. This perspective describes the evolution of metal-catalyzed reductive Carbonylation of organic (pseudo)halides from its inception in the pioneering stoichiometric work of Osakada to the present. Specific emphasis is devoted to the reactivity of these coupling processes, with substrates ranging from Aryl-, Vinyl-, Benzyl- to unactivated Alkyl (pseudo)halides. Despite the impressive advances realized, a comprehensive study detailing the mechanistic intricacies of these processes is still lacking. Some recent empirical evidence reveal an intriguing dichotomy exerted by the substitution pattern on the ligands utilized; still, however, some elementary steps within the catalytic cyCle of these reactions remain speculative, in many instances invoking a canonical cross-coupling process. Although tentative, we anticipate that these processes might fall into more than one distinct mechanistic category depending on the substrate utilized, suggesting that investigations aimed at unraveling the mechanistic underpinnings of these processes will likely bring new and innovative research grounds in this vibrant area of expertise.Metal-Catalyzed Carbonylation of Organic (Pseudo)halides with CO2catalysis; carbon dioxide; nickel; cross-coupling; Carbonylic acid1932016103#N/ATRUE
5323
acscatal.5b0263310.1021/acscatal.5b02633FALSEhttps://doi.org/10.1021/acscatal.5b02633Matranga, CACS Catal.The electrochemical oxygen evolution reaction (OER) is an important anodic process in water splitting and CO2 reduction applications. Precious metals inCluding Ir, Ru. and Pt are traditional OER catalysts, but recent emphasis has been placed on finding less expensive, earth-abundant materials with high OER activity. Ni-based materials are promising next-generation OER catalysts because they show high reaction rates and good long-term stability. Unfortunately, most catalyst samples contain heterogeneous partiCle sizes and surface structures that produce a range of reaction rates and rate-determining steps. Here we use a combination of experimental and computational techniques to study the OER at a supported organometallic nickel complex with a precisely known crystal structure. The Ni-6(PET)(12) (PET = phenylethyl thiol) complex out performed bulk NiO and Pt and showed OER activity comparable to Ir. Density functional theory (DFT) analysis of electrochemical OER at a realistic Ni-6(SCH3)(12) model determined the Gibbs free energy change (Delta G) associated with each mechanistic step. This allowed computational prediction of potential determining steps and OER onset potentials that were in excellent agreement with experimentally determined values. Moreover, DFT found that small changes in adsorbate binding configuration can shift the potential determining step within the OER mechanism and drastically change onset potentials. Our work shows that atomically precise nanocatalysts like Ni-6(PET)(12) facilitate joint experimental and computational studies because experimentalists and theorists can study nearly identical systems. These types of efforts can identify atomic-level structure-property relationships that would be difficult to obtain with traditional heterogeneous catalyst samples.Electrocatalytic Oxygen Evolution with an Atomically Precise Nickel Catalystelectrocatalysis; oxygen evolution reaction; water splitting density functional theory; atomically precise catalyst; nickel; organometallicx57201681#N/AFALSE
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acscatal.5b0262010.1021/acscatal.5b02620FALSEhttps://doi.org/10.1021/acscatal.5b02620Strasser, PACS Catal.We performed in situ transmission electron microscopy of phase-segregated octahedral Pt-Ni alloy fuel cell nanocatalysts under thermal annealing to study their morphological stability and surface compositional evolution. The pristine octahedral Pt-Ni nanopartiCles (NPs) showed Pt-rich comers/edges and slightly concave Ni-rich {111} facets. Time-resolved image series unequivocally revealed that upon annealing up to 500 degrees C, the Pt-rich surface atoms at the corners/edges diffused onto and subsequently covered the concave Ni-rich {111} surfaces, leading to perfectly flat Pt-rich 1111) surfaces with Ni-rich subsurface layers. This was further corrB(OH)2rated by in situ aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy. Our results propose a feasible approach to construct shaped Pt alloy nanopartiCles with Pt-rich 11111 surfaces and Ni-rich subsurface layers that are expected to be catalytically active and stable for the oxygen reduction reaction, thus providing important implications for rational synthesis of durably highly active shaped Pt alloy fuel cell electrocatalysts.Thermal Facet Healing of Concave Octahedral Pt-Ni NanopartiCles Imaged in Situ at the Atomic Scale: Implications for the Rational Synthesis of Durable High-Performance ORR Electrocatalystsoctahedral Pt-Ni nanopartiCles; concave nanopartiCles; surface composition; oxygen reduction reaction; thermal annealing; in situ TEMx64201620#N/AFALSE
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acscatal.5b0257110.1021/acscatal.5b02571FALSEhttps://doi.org/10.1021/acscatal.5b02571Chen, JFACS Catal.We report the preparation and use of the three-dimensionally ordered mesoporous Ni sphere arrays (3D-OMNiSA) as a highly effective OER catalyst in alkaline electrolyte. The 3D-OMNiSA is fabricated through lyotropic liquid crystal templating within a polymer inverse opal. The prepared 3D-OMNiSA catalyst exhibits a low overpotential of 254 mV at 10 mA cm(-2) and a small Tafel slope of 39 mV decade(-1), better than the commercial precious RuO2 catalyst. The mass activity (166.5 A g(-1)) and turnover frequency (0.0281 s(-1)) of 3D-OMNiSA are about 4.3 and 2.2 times that of RuO2, respectively. Additionally, this 3D-OMNiSA catalyst shows a high durability under harsh water oxidation cyCling test. The outstanding OER performance of the 3D-OMNiSA could be attributed to the large surface area, efficient mass and charge transport, and high structural stability arising from the unique 3D hierarchical porous structure of the 3D-OMNiSA consisting of ordered Close-packed mesoporous spheres.Ordered Mesoporous Nickel Sphere Arrays for Highly Efficient Electrocatalytic Water Oxidationordered mesoporous Ni spheres; templating; electrocatalyst; oxygen evolution reaction; durability
Electrocatalytic
82201654#N/AFALSE
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acscatal.5b0242610.1021/acscatal.5b02426https://doi.org/10.1021/acscatal.5b02426Chen, ClACS Catal.In this perspective, recent developments on palladium and nickel mediated chain walking olefin polymerization and copolymerization with polar functionalized comonomers are described. First, the chain walking polymerization mechanism is discussed followed by its implications in olefin polymerization and copolymerization. Then, recent advances in catalyst design are provided. Special attention is paid to the influence of ligand structures on the catalytic properties. Subsequently, the applications of these chain walking polymerization catalysts in the synthesis of functionalized hyperbranched polymers and copolymers are summarized. Finally, some recent developments and perspectives on very fast and very slow chain walking polymerization catalysts are discussed.Palladium and Nickel Catalyzed Chain Walking Olefin Polymerization and Copolymerizationchain walking; olefin polymerization; copolymerization; polar monomer; palladium catalysts; nickel catalysts; functionalized polyethylenex2942016165#N/AFALSE
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acscatal.6b0211410.1021/acscatal.6b02114FALSEhttps://doi.org/10.1021/acscatal.6b02114Backvall, JEACS Catal.alpha-Allenols are attractive and versatile compounds whose preparation can be a nontrivial task. In this Letter, we provide a method for the prompt synthesis of substituted alpha-allenols via a catalytic cross-coupling reaction which makes use of a nontoxic and cost-effective iron catalyst. The catalyst loading is typically as low as 1-5 mol %. The mild reaction conditions (-20 degrees C) and the short reaction time (15 min) allow for the presence of a variety of functional groups. Moreover, the reaction was shown to be scalable up to gram scale and the propargyl substrates are readily accessible by a one-pot synthesis.A Synthesis of Substituted alpha-Allenols via Iron-Catalyzed Cross-Coupling of Propargyl Carbonylates with Grignard Reagents21201649#N/ATRUE
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acscatal.5b0239510.1021/acscatal.5b02395FALSEhttps://doi.org/10.1021/acscatal.5b02395Ke, ZFACS Catal.A general mechanism for H-2 Activation by Lewis acid transition metal (LA-TM) bifunctional catalysts has been presented via density functional theory (DFT) studies on a representative nickel borane system, ((DPBPh)-D-Ph)Ni. There are four typical H-2 Activation modes for LA-TM bifunctional catalysts: (1) the cis homolytic mode, (2) the trans homolytic mode, (3) the synergetic heterolytic mode, and (4) the dissociative heterolytic mode. The feature of each Activation mode has been characterized by key transition state structures and natural bond orbital analysis. Among these four typical modes, ((DPBPh)-D-Ph)Ni catalyst most prefers the synergetic heterolytic mode (Delta G(double dagger) = 29.7 kcal/mol); however the cis homolytic mode cannot be totally disregarded (Delta G(double dagger) = 33.7 kcal/mol). In contrast, the trans homolytic mode and dissociative heterolytic mode are less feasible (Delta G(double dagger) = similar to 42 kcal/mol). The general mechanistic picture presented here is fundamentally important for the development and rational design of LA-TM catalysts in the future.General H-2 Activation Modes for Lewis Acid-Transition Metal Bifunctional CatalystsH-2 Activation; Lewis acid; Lewis base; transition metal; nickel; mechanism; density functional theory; homolytic; synergetic; heterolytic; hydrogenationx58201664#N/AFALSE
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acscatal.5b0236510.1021/acscatal.5b02365FALSEhttps://doi.org/10.1021/acscatal.5b02365Gewirth, AAACS Catal.Electrodeposition of Ni or NiFe films exhibiting fractal-like behavior from plating baths containing an inhibitor, such as 3,5-diamino-1,2,4-triazole (DAT), is found to yield oxygen evolution reaction (OER) catalysts for alkaline solutions exhibiting high current densities (100 mA/cm(2)), high mass activity (similar to 1200 A/g of catalyst), high stability (>72 h), and low overpotentials (similar to 300 mV). By changing electrodeposition time, the activity of the catalyst can be tuned, with longer times yielding higher activities. The electrodeposition method works with any conductive substrate yielding unprecedented performance and providing an easy route to high activity catalysts.High Activity Oxygen Evolution Reaction Catalysts from Additive-Controlled Electrodeposited Ni and NiFe Filmswater splitting; electrocatalyst; oxygen evolution; electrodeposition; NiFex109201642#N/AFALSE
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acscatal.6b0172110.1021/acscatal.6b01721FALSEhttps://doi.org/10.1021/acscatal.6b01721Yoshizawa, KACS Catal.Metal-exchanged zeolites are known to exhibit catalytic activity in the direct conversion of methane to methanol. The influence of different metals on this reaction has been theoretically investigated by using density functional theory (DFT) calculations on a periodic system of MO+-ZSM-5 zeolite (M = Fe, Co, Ni, Cu). The results indicate a high dependence of the reaction on the metals, where the reactivity toward C-H bond dissociation is predicted to increase in the order CoO+-ZSM-5 < NiO+-ZSM-5 < FeO+-ZSM-5 < CuO+-ZSM-5 and the selectivity of methanol is predicted to increase in the order FeO+-ZSM-5 < CoO+-ZSM-5 < NiO+-ZSM-5 < CuO+-ZSM-5. The role of ZSM-5 zeolite in the catalytic activity is also investigated by comparing our calculation results with those reported for the reaction by bare MO+ species in the gas phase. We found that the nanopores of ZSM-5 zeolite exert a confinement effect which destabilizes the adsorption of methane and lowers the Activation energy for the C-H bond dissociation. In addition to the conversion of methane, we investigated the direct conversion of ethane to ethanol by FeO+-ZSM-5 and found that this reaction proceeds with a lower C-H bond Activation energy and a higher product selectivity in comparison to the conversion of methane to methanol by the same catalyst.Direct Conversion of Methane to Methanol by Metal-Exchanged ZSM-5 Zeolite (Metal = Fe, Co, Ni, Cu)methane hydroxylation; methanol; transition metals; ZSM-5 zeolite; DFT calculation82201682#N/ATRUE
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acscatal.5b0229110.1021/acscatal.5b02291FALSEhttps://doi.org/10.1021/acscatal.5b02291Liang, YYACS Catal.Developing active, stable, and low-cost electrocatalysts which can promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is undoubtedly a vital progress toward a hydrogen economy. Herein, we report that such electrocatalysts can be easily prepared by pyrolyzing a precursor composed of nickel and iron salts with urea under inert atmospheres without any post-treatments. The obtained products are composed of metallic nickel-iron alloy nanopartiCles either encapsulated in or dispersed on nitrogen-doped bamboo-like carbon nanotubes (CNTs). This simple synthesis route could simultaneously realize nanostructuring, doping, and hybridizing with nanocarbon, which have been demonstrated as efficient strategies to optimize the catalytic activity of an electrocatalyst. The in situ formed hybrid catalysts exhibit good catalytic performances for both OER and HER under alkaline conditions, and the doping content of iron significantly affects the activities. When the best electrocatalyst is loaded on nickel foam with a loading of 2 mg cm(-2), a symmetric two-electrode cell can execute overall water splitting at a current density of 10 mA cm(-2) with only 1.58 V and shows negligible degradation after 24 h of operation. The excellent electrocatalytic activity and facile preparation method enable this hybrid electrocatalyst to be a promising candidate for future large-scale applications in water splitting.Facile Synthesis of Nickel-Iron/Nanocarbon Hybrids as Advanced Electrocatalysts for Efficient Water Splittingnickel-iron alloy nanopartiCles; carbon nanotubes; hybrid electrocatalyst; oxygen evolution reaction; hydrogen evolution reactionx201201651#N/AFALSE
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acscatal.5b0223010.1021/acscatal.5b02230https://doi.org/10.1021/acscatal.5b02230Hensen, EJMACS Catal.We investigated the role of Cu-Mg-Al mixed oxides in depolymerization of soda lignin in supercritical ethanol. A series of mixed oxides with varying Cu content and (Cu+Mg)/Al ratio were prepared. The optimum catalyst containing 20 wt % Cu and having a (Cu+Mg)/Al ratio of 4 yielded 36 wt % monomers without formation of char after reaction at 340 C for 4 h. Comparison with Cu/MgO and Cu--Al2O3 catalysts emphasized the excellent performance of Cu Mg Al oxides. These mixed oxides catalyze the reaction between formaldehyde and ethanol, which limits polymerization reactions between phenolic products and formaldehyde. The combination of Cu and basic sites catalyzes the associated Guerbet and esterification reactions. These reactions also protect lignin side-chains (e.g., aldehyde groups). Lewis acid sites of the catalyst, mainly Cu and Al cations, catalyze C- and O-Alkylation reactions that protect phenolic products and phenolic moieties in lignin oligomers. Hydrogen produced by dehydrogenation reactions is involved in hydrogenolysis reactions of the chemical bonds in lignin and also to deoxygenate the monomeric and oligomeric products. Careful investigation of the influence of the acid and base functionalities allows conCluding that Guerbet and esterification reactions are more important than Alkylation reactions in avoiding formation of heavy products such as char. These insights point out directions for rational design of catalysts for lignin conversion.Role of Cu-Mg-Al Mixed Oxide Catalysts in Lignin Depolymerization in Supercritical Ethanollignin; catalysis; supercritical ethanol; Alkylation; Guerbet reactionx101201558#N/AFALSE
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acscatal.5b0220410.1021/acscatal.5b02204TRUEhttps://doi.org/10.1021/acscatal.5b02204Zhang, JDonor-Acceptor Fluorophores for Visible-Light-Promoted Organic Synthesis:Photoredox/Ni Dual Catalytic C(sp(3))-C(sp(2)) Cross-Coupling
Photocatalyst
Csp2_ar-Csp3xCOOHArylNo baseNo Base20167/28/2022FALSE
5334
acscatal.5b0220110.1021/acscatal.5b02201FALSEhttps://doi.org/10.1021/acscatal.5b02201Liu, PACS Catal.The iridium-catalyzed Carbonyl-directed hydroArylation of monosubstituted alkenes developed by Bower and co-workers [Crisenza, G. E. M.; McCreanor, N. G.; Bower, J. F. J. Am. Chem. Soc. 2014, 136, 10258-10261] provides an efficient strategy for highly branched-selective hydroArylation of both Aryl- and Alkyl-substituted alkenes. Density functional theory calculations in the present study revealed that the unique regiochemical control in this reaction is due to an unconventional modified Chalk-Harrod-type mechanism. Instead of the commonly accepted Chalk-Harrod-type mechanism of transition metal-catalyzed hydroArylation that involves C-H oxidative addition, olefin migratory insertion into the Ir-H bond, and C-C reductive elimination, the Ir-catalyzed reaction occurs via migratory insertion of the olefin into the Ir-Aryl bond and C-H reductive elimination. The experimentally observed ligand-controlled selectivity is attributed to a combination of electronic and steric effects in the selectivity-determining olefin migratory insertion step. Ligand steric contour maps show that, in reactions with large-bite-angle bisphosphine ligands, such as d(F)ppb, the steric repulsions between the substrate and the Aryl substituents on the ligand lead to complete branched selectivity, and the linear selectivity in reactions with small-bite-angle ligands is due to electronic effects that favor 2,1-olefin migratory insertions.Mechanism and Origins of Ligand-Controlled Linear Versus Branched Selectivity of Iridium-Catalyzed HydroArylation of Alkenesiridium catalyst; hydroArylation; DFT calculations; mechanism; selectivityx732016126#N/AFALSE
5335
acscatal.5b0219310.1021/acscatal.5b02193FALSEhttps://doi.org/10.1021/acscatal.5b02193Sun, YJACS Catal.The development of high-performance nonprecious electrocatalysts with both H-2 and O-2 evolution reaction (HER and OER) activities for overall water splitting is highly desirable but remains a grand challenge. Herein, we report a facile two-step method to synthesize three-dimensional hierarchically porous urchin-like Ni2P microsphere superstructures anchored on nickel foam (Ni2P/Ni/NF) as bifunctional electrocatalysts for overall water splitting. The Ni2P/Ni/NF catalysts were prepared by template-free electro-deposition of porous nickel microspheres on nickel foam followed by phosphidation. The hierarchically macroporous E (V) superstructures with 3D configuration can reduce ion transport resistance and facilitate the diffusion of gaseous products (H-2 and O-2). The optimal Ni2P/Ni/NF exhibited remarkable catalytic performance and outstanding stability for both the HER and OER in alkaline electrolyte (1.0 M KOH). For the HER, Ni2P/Ni/NF afforded a current density of 10 mA cm(-2) at a low overpotential of only -98 mV. When it served as an OER electrocatalyst, Ni2P/Ni/NF was partially oxidized to nickel oxides/hydroxides/oxyhydroxides (mainly NiO) on the catalyst surface and exhibited excellent OER activity with small overpotentials of 200 and 268 mV to reach 10 and 100 mA cm(-2), respectively. Furthermore, when Ni2P/Ni/NF was employed as the electrocatalyst for both the cathode and anode, a water splitting electrolyzer was able to reach 10 and 100 mA cm(-2) in 1.0 M KOH at cell voltages of 1.49 and 1.68 V, respectively, together with robust durability. Various characterization techniques and controlled experiments indicated that the superior activity and strong stability of Ni2P/Ni/NF for overall water splitting originated from its electrochemically active constituents, 3D interconnected porosity, and high conductivity.Hierarchically Porous Urchin-Like Ni2P Superstructures Supported on Nickel Foam as Efficient Bifunctional Electrocatalysts for Overall Water Splittingsuperstructure; hydrogen evolution; oxygen evolution; water splitting; nickel phosphide; electrocatalysisx515201649#N/AFALSE
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acscatal.5b0212410.1021/acscatal.5b02124FALSEhttps://doi.org/10.1021/acscatal.5b02124Xu, BQACS Catal.Fabricating Pt-alloy and core-shell nanostructures with Au NPs in the cores are considered as two general approaches to improving the performance of Pt-based catalysts for the cathodic oxygen reduction reaction (ORR) in acidic electrolyte. These two approaches are combined herein to develop a heteroseed-mediated solvothermal method for synthesizing nearly monodisperse core-shell structured Au@NimPt2 nanopartiCles (NPs) of 5.0-6.5 nm (with the atomic ratio of Ni/Pt/Au = m/2/1) as ORR catalysts. With respect to controlling the amount and relative concentrations of the metal precursors in the starting solution, this method enables not only facile manipulation of the shell composition and thickness but also fine-tuning of the core-shell interaction and surface electronic structures of the resultant Au@NimPt2 NPs, endowing the Au@NimPt2 NPs with improved Pt activity and durability for ORR. Subjecting the Au@NimPt2 NPs to an ex situ pretreatment in flowing 2%CO/Ar at 300 degrees C is shown to result in further improved Pt activity. Data are also presented to correlate the intrinsic Pt activity with experimentally determined CO adsorption property (CO-stripping peak potential) of Pt for the Au@Ni(m)Pt2 samples, and to show the excellent electrochemical durability of the Au@NimPt2 NPs during 20 000 potential cyCles between 0.6 and 1.1 V (vs RI-IE) in O-2-saturated 0.1 M HClO4. Compared with the commercial E-TEK Pt/C catalyst, the most-active Au@Ni2Pt2 NPs exhibit 3-4- and 4-6-fold higher Pt activity at 0.9 V before and after the 20 000 potential cyCles, respectively. Factors relevant to the activity and durability control of the Au@NimPt2 catalysts for ORR are discussed.Core-Shell Nanostructured Au@NimPt2 Electrocatalysts with Enhanced Activity and Durability for Oxygen Reduction Reactionelectrocatalyst; multimetallic nanopartiCles; solvothermal synthesis; core-shell nanostructure; oxygen reduction reaction; catalyst design; electrochemical treatmentx54201646#N/AFALSE
5337
acscatal.5b0202110.1021/acscatal.5b02021https://doi.org/10.1021/acscatal.5b02021Chetcuti, MJACS Catal.The chemistry of nickel N-heterocyClic carbene species has blossomed at the beginning of this century with a particularly rapid acceleration in the last 5 years, as indicated by the fact that more than 65% of the discussed research artiCles in this comprehensive review date from the period 2010-2015. The rapid evolution of this chemistry has led to an increasing number of applications in the field of catalytic C-heteroatom bond formation, reduction, and oxidation where the heteroatom is nitrogen, sulfur, oxygen, or boron. Thus, in addition to the development of Aryl aminations, Aryl thiolations, alkyne hydrothiolations, and transfer hydrogenations, which are the most ancient reactions of this type known for these systems, the last five years have seen the appearance of a number of novel interesting Ni(NHC)-catalyzed transformations such as the dehydrogenative cross coupling of aldehydes and amines or alcohols, the hydroamination of alkenes, the hydroimination of alkynes, a one-step indoline synthesis, (cross-) Tishchenko reactions, the borylation of unsaturated C-C bonds and arenes, the borylative Cleavage of C-N bonds, the hydrosilylation of C-O and C-N multiple bonds, the reductive Cleavage of aromatic C-O bonds, and the anaerobic oxidation of alcohols. This rapid expansion calls for a review of the state of the art at this time with a special emphasis on mechanistic data to allow new insights into catalyst improvement.Nickel N-HeterocyClic Carbene-Catalyzed C-Heteroatom Bond Formation, Reduction, and Oxidation: Reactions and Mechanistic Aspectsnickel; N-heterocyClic carbene; catalysis; C-heteroatom bond; formation; reduction; oxidation; reaction mechanismPhotocatalyst1412016140#N/AFALSE
5338
acscatal.5b0200310.1021/acscatal.5b02003FALSEhttps://doi.org/10.1021/acscatal.5b02003Rojas, RSACS Catal.A cationic methallyl 2-pyridine-4,7-dimethoxybenzimidazole (L1) nickel precatalyst is highly selective in ethene dimerizations to 1-butene. The same catalyst isomerizes 1-butene and 1-octene to internal olefins. Co-catalytic additives of B(C6F5)(3) or BF3 center dot OEt2 coordinate to the catalyst and increase the reaction rates of ethene dimerization. ESI-MS was applied identifying a [L1NiH](+) cation as the catalytically active species.Lewis Acid Enhanced Ethene Dimerization and Alkene Isomerization-ESI-MS Identification of the Catalytically Active Pyridyldimethoxybenzimidazole Nickel(II) Hydride Speciesethene dimerization; nickel catalysis; olefin isomerization; microreactor; mass spectrometryx19201531#N/AFALSE
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acscatal.6b0137910.1021/acscatal.6b01379FALSEhttps://doi.org/10.1021/acscatal.6b01379Chen, YYACS Catal.Organic Carbonylates are readily available feedstock chemicals, and the Carbonylate group is a latent activating group which can be easily removed by deCarbonylation. The radical deCarbonylative functionalization by photoredox catalysis undergoes rapid development recently, with which many difficult transformations can be achieved by dual photoredox catalysis. We summarize radical deCarbonylative functionalizations via additional transition metal catalysts, thiol catalysts, or hypervalent iodine catalysts, which either activate the Carbonylates or enable new radical transformations.Radical DeCarbonylative Functionalizations Enabled by Dual Photoredox Catalysisphotoredox catalysis; deCarbonylation; dual catalysis; radical reaction; transition metal catalysis; thiol catalysis; hypervalent iodine catalysis115201650#N/ATRUE
5340
acscatal.5b0192610.1021/acscatal.5b01926FALSEhttps://doi.org/10.1021/acscatal.5b01926Esposito, DACS Catal.Lignin is one of the most important candidates for the procurement of renewable aromatics. The development of successful strategies for the production of building blocks from lignin implies the design of effective depolymmization protocols. Here we propose a continuous flow approach for the hydrogenolysis of Kraft lignin utilizing a TiN-Ni heterogeneous catalyst. The refining of commercial Kraft lignin was evaluated, showing that the catalyst can facilitate the partial depolymerization of this sulfur-containing material under very mild conditions and with short residence times. The process restitutes lignin in the form of oligomers in combination with an array of valuable single-ring aromatic compounds.Mild Continuous Hydrogenolysis of Kraft Lignin over Titanium Nitride-Nickel Catalystlignin; heterogeneous catalysis; titanium nitride; nickel; hydrogenationx57201663#N/AFALSE
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acscatal.5b0184610.1021/acscatal.5b01846FALSEhttps://doi.org/10.1021/acscatal.5b01846Corma, AACS Catal.The hydrogenation of nitro compounds is an industrial process that has experienced a renovated interest in the last 10 years due to the discovery of highly selective and environmentally friendly solid catalysts. Particularly, the performance of chemoselective reactions in the presence of very sensitive groups such as double and triple CC bonds, with H-2 as reductant and no soluble additives needed, had been elusive for decades. The discovery that gold nanopartides on solid supports could carry out such a reaction very selectively invigorated this area of research and Claimed gold as an outstanding catalyst beyond oxidation processes. Subsequent work, devoted to understand how gold catalysts operate, established a strong basis for the design of more efficient materials and the development of new routes for the synthesis of nitro derivatives. Here, we present three generations of materials that allowed improving the performance of the original gold catalysts. The relatively low activity of the initial Au/TiO2 catalysts could be first boosted, without practical loss of selectivity, by the design of a material that incorporated two catalytic functions on the support: small amounts of platinum to enhance H-2 dissociation and a greater amount of gold to activate the -NO2 group. Later, we learned how to control the catalytic structures and induce chemoselectivity to traditionally unselective metals such as platinum, ruthenium, and nickel nanopartiCles. Recently, Fe2O3 nanopartiCles surrounded by a nitrogen-doped carbon layer have erupted as a promising alternative. A remarkable outcome from all that work is that the final pool of catalytic alternatives has been markedly expanded. Diversity is important because different solutions may open new gates to different catalytic processes, and we summarize here how the scope of new reactions and products could be expanded by means of properly designed metal catalysts in which the support and metal work in a concerted way to direct the reaction toward the desired product. For example, whereas Au/TiO2 is a chemoselective catalyst that drives the reaction efficiently to the fully reduced reaction product (aniline), the reaction could be tuned to obtain azocompounds in high yields by using nanoparticulated ceria to support the gold nanopartiCles. On the other hand, whereas nitrobenzenes and aldehydes react in H-2 to afford ftnines in the presence of Au/TiO2, the product distribution can be switched toward a more oxidized condensation product (a nitrone) using a chemoselective Pt/C catalyst, or to produce cyClohexanone oxime directly from nitrobenzene by means of supported Au and Pd metal catalysts. These and other examples represent some notable achievements, which are possibly, just the tip of the iceberg.Transforming Nano Metal Nonselective Particulates into Chemoselective Catalysts for Hydrogenation of Substituted Nitrobenzenesgold catalysis; selective hydrogenation; reduction of nitro compounds; supported nanopartiCles design; green hydrogenation chemistry; strong metal-support interactions; cascade reactionsx152201556#N/AFALSE
5342
acscatal.5b0180710.1021/acscatal.5b01807FALSEhttps://doi.org/10.1021/acscatal.5b01807Zhang, TACS Catal.The direct hydrogenolysis of cellulose represents an attractive and promising route for green polyol production. Designing a catalyst system that could control the selectivity of polyols of this process is highly desirable. In this work, we realized the selectivity-switchable production of ethylene glycol (EG) and 1,2-propylene glycol (1,2-PG) by using Sn species with different valences in combination with Ni catalysts. The combination of Ni/AC and metallic Sn powders exhibited a superior activity toward EG (57.6%) with up to 86.6% total polyol yield, while the combination of Ni/AC and SnO favored the formation of 1,2-PG (32.2%) with a 22.9% yield of EG. The Sn species in NiSn alloy in situ formed from metallic Ni and Sn powders was found to be the active sites for the high selectivity of EG as evidenced by control experiments and characterizations inCluding X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy dispersive X-ray mapping, and Sn-119 Mossbauer spectroscopy. The effects of Sn loading, reaction temperature, reaction time, and the concentration of cellulose were investigated for Ni/AC + Sn powders. Because of the formation of NiSn alloy, the Ni-Sn catalyst showed good stability during repeated use. Experimental results disClosed that the Sn species with different valence possessed distinct catalytic functions. Both SnO and the alloyed Sn species could catalyze the retro-aldol condensation of glucose to glycolaldehyde, and meanwhile, SnO was also active for the isomerization of glucose to fructose. Therefore, controlling the glycol products distribution could be realized using SnO or the alloyed Sn species as catalysts.Selectivity-Switchable Conversion of Cellulose to Glycols over Ni-Sn Catalystscellulose; ethylene glycol; propylene glycol; nickel; tin; valencex44201648#N/AFALSE
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acscatal.5b0180610.1021/acscatal.5b01806FALSEhttps://doi.org/10.1021/acscatal.5b01806Hensen, EJMACS Catal.In this work, we have investigated the Activation process and structure of Ni-promoted MoxW(1-x)S2/Al2O3 hydrodesulfurization (HDS) catalysts. Conversion of Mo and W oxides to the catalytically active MS, (M = Mo, W) phase by sulfidation in gaseous H2S/1-12 proceeded via different pathways, as found by XPS and EXAFS. The slower sulfidation kinetics of W on the alumina support formed NiMoxWo_4 sulfides with a two-dimensional core shell structure. Mo was mostly located in the core and W in the shell, as evidenced by EXAFS. Increasing the H2S/H-2 pressure during sulfidation distributed Mo and W more homogeneously in the metal sulfide partiCles. This was attributed to the more favorable sulfidation of W under these conditions (i.e., below the temperature of MoS, formation). Catalytic testing was consistent with these findings and demonstrated that a core shell structure is the active phase in thiophene HDS (1 atm), whereas a homogeneously mixed MS, phase catalyzes the HDS of dibenzothiophene at 40 bar. This is the first example of a core shell structure in promoted MoxW(l-x)S, catalysts. Support interactions in the oxidic precursor, which affect the sulfidation kinetics, were determined to play a key role in the formation of these structures.Structure-Activity Correlations in Hydrodesulfurization Reactions over Ni-Promoted MoxW(1-x)/Al2O3 Catalystshydrodesulfurization; metal sulfides; alumina support; catalyst Activation; core shellx53201551#N/AFALSE
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acscatal.5b0176110.1021/acscatal.5b01761FALSEhttps://doi.org/10.1021/acscatal.5b01761Kolen'ko, YVACS Catal.An effective method to boost the electrocatalytic activity of nickel phosphides in H-2 evolution reaction is reported. The method took advantage of density functional theory calculations that allowed the design of a highly active material based on the combination of d-metal with p-metal within a phosphide structure. Furthermore, the principle is proven experimentally through successful synthesis of self-supported ternary Al-Ni-P foam electrocatalyst by alloying of Ni and Al followed by the gas transport phosphorization reaction. As a cathode for H-2 evolution reaction in acidic electrolyte, Al-Ni-P significantly outperforms pure Ni-P, and it has an exchange current density of 0.6 mA/cm(2) and a Tafel slope of 65 mV/decade.Design and Synthesis of Highly Active Al-Ni-P Foam Electrode for Hydrogen Evolution ReactionDFT; ELF; electrocatalysis; hydrogen evolution reaction; nickel phosphide; doping; Tafel slopex83201542#N/AFALSE
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acscatal.6b0137510.1021/acscatal.6b01375FALSEhttps://doi.org/10.1021/acscatal.6b01375Lefferts, LACS Catal.Nickel hairy foam, consisting of carbon nanofibers (CNFs) grown on the surface of nickel foam, were synthesized and tested for nitrite hydrogenation. The results showed that nickel hairy foam is catalytically active in the absence of any noble metal, which is attributed to the formation of nickel partiCles with high carbon content during CNF growth. These C-doped nickel partiCles showed catalytic properties similar to those of noble metals, but were easily deactivated as a result of oxidation treatments. This deActivation is partially attributed to nickel passivation, which is reversible by reducing with H-2 at room temperature in the gas or liquid phase. In addition, oxidation treatment also caused partial removal of the carbon dissolved in the nickel partiCles, causing irreversible deActivation. Increasing severity of the oxidation treatment induced slower reActivation via reduction, as well as lower steady-state activities after reActivation. This irreversible deActivation is attributed to the decreased concentration of dissolved carbon. Therefore, nickel hairy foam is a promising hydrogenation catalyst, provided it is protected against oxygen.Ni in CNFs: Highly Active for Nitrite Hydrogenationnitrite hydrogenation; nickel; carbon; dissolved C; hairy foam; carbon nanofiber; passivation18201657#N/ATRUE
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acscatal.5b0166610.1021/acscatal.5b01666FALSEhttps://doi.org/10.1021/acscatal.5b01666Dagle, RAACS Catal.Steam reforming of ethylene glycol (EG) over Mg,Al2O4 supported metal (15 wt % Ni, 5 wt % Rh, and IS wt % Co) catalysts was investigated using combined experimental and theoretical methods. Compared to highly active Rh and Ni catalysts with 100% conversion, the steam reforming activity of EG over the Co catalyst is comparatively lower with only 42% conversion under the same reaction conditions (500 degrees C, 1 atm, 119 000 h(-1), S/C = 3.3 mol). However, CH4 selectivity over the Co catalyst is remarkably lower. For example, by varying the gas hour space velocity (GHSV) such that complete conversion is achieved for all the catalysts, CH4 selectivity for the Co catalyst is only 8%, which is much lower than the equilibrium CH4 selectivity of similar to 24% obtained for both the Rh and Ni catalysts. Further studies show that varying H2O concentration over the Co catalyst has a negligible effect on activity, thus indicating zero-order dependence on H2O. These experimental results suggest that the supported Co catalyst is a promising EG steam reforming catalyst for high hydrogen production. To gain mechanistic insight for rationalizing the lower CH4 selectivity observed for the Co catalyst, the initial decomposition reaction steps of ethylene glycol via C-O, O-H, C-H, and C-C bond scissions on the Rh(111), Ni(111), and Co(0001) surfaces were investigated using density functional theory (DFT) calculations. Despite the fact that the bond scission sequence in the EG decomposition on the three metal surfaces varies, which leads to different reaction intermediates, the lower CH4 selectivity over the Co catalyst, as compared to the Rh and Ni catalysts, is primarily due to the higher barrier for CH4 formation. The higher S/C ratio enhances the Co catalyst stability, which can be elucidated by the facile water dissociation and an alternative reaction path to remove the CH species as a coking precursor via the HCOH formation.Steam Reforming of Ethylene Glycol over MgAl2O4 Supported Rh, Ni, and Co Catalystsethylene glycol; steam reforming; density functional theory; cobalt; rhodium; nickelx30201651#N/AFALSE
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acscatal.5b0165710.1021/acscatal.5b01657FALSEhttps://doi.org/10.1021/acscatal.5b01657Jin, SHigh-Performance Electrocatalysis for Hydrogen Evolution Reaction Using Se-Doped Pyrite-Phase Nickel Diphosphide Nanostructuresx2015#N/AFALSE
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acscatal.5b0164210.1021/acscatal.5b01642FALSEhttps://doi.org/10.1021/acscatal.5b01642Canty, AJACS Catal.Density functional theory (DFT) was used to study the reaction mechanism of cyanomethylation of aldehydes catalyzed by nickel pincer complexes under base-free conditions. The C-bound cyanomethyl complex, which was initially thought to be the active catalyst, is actually a precatalyst, and in order for the catalytic reaction to commence, it has to convert to the less-stable N-bound isomer. The carbon carbon bond formation then proceeds via direct coupling of the N-bound isomer and the aldehyde to give a zwitterionic intermediate with a pendant alkoxide function, which is further stabilized by hydrogen-bonding interaction with water molecules (or alcohol product). The N-bound alkoxide group of the zwitterionic intermediate is subsequently substituted by MeCN via an associative mechanism, followed by deprotonation of the coordinated MeCN to afford the final product. It was found that the transition structure for the exchange reaction (substitution of MeCN for the alkoxide group) is the highest energy point on the catalytic cyCle, and its energy crucially influences the catalyst efficiency. The Ni complexes ligated by bulky and weak trans-influencing pincer ligands are not appropriate catalysts for the cyanomethylation reaction due to the involvement of very-high-energy transition structures for the exchange reaction. In contrast, benzaldehydes with electron-withdrawing substituents are capable of stabilizing the exchange reaction transition structure due to the increased stability of the zwitterionic intermediate, leading to acceleration of the catalytic reaction.Theoretical Investigation into the Mechanism of Cyanomethylation of Aldehydes Catalyzed by a Nickel Pincer Complex in the Absence of Base Additivesdensity functional theory (DFT); catalytic reaction; nickel complexes; cyanomethylation; aldehydex14201656#N/AFALSE
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acscatal.5b0163810.1021/acscatal.5b01638FALSEhttps://doi.org/10.1021/acscatal.5b01638Calle-Vallejo, FACS Catal.The oxygen evolution reaction (OER) is one of the major bottlenecks hindering the implementation of a global economy based on solar fuels. It is known that Ni-based catalysts exhibit remarkable catalytic activities for the OER in alkaline media. In this joint theoretical-experimental study, we provide a thorough characterization of Ni-based double hydroxides with Cr, Mn, Fe, Co, Cu, and Zn at the atomic scale that not only explains the reasons for their high activity but also provides simple design principles for the enhancement of their electrocatalytic properties. Our approach, based on the local symmetry and composition of the active sites, helps rationalize the effect of dopants on the catalytic activity of Ni(OH)(2). In particular, NiFe, NiCr, and NiMn double hydroxides (DHs) have superior catalytic activity, which reduce the OER potential to reach 0.5 mA cm(-2) by 230, 190, and 160 mV, respectively, in comparison to IrO2 nanopartiCles, the state-of-the-art benchmarking catalysts, with 90% Faradaic efficiency for O-2 generation. The active species in NiFe and NiMn DHs are iron and manganese, while in NiCr DH, nickel is the active species.Guidelines for the Rational Design of Ni-Based Double Hydroxide Electrocatalysts for the Oxygen Evolution Reactionoxygen evolution reaction; nickel double hydroxides; transition-metal doping; cyClic voltammetry; rotating-disk electrode; electrocatalysis; density functional theory; volcano plotx345201549#N/AFALSE
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acscatal.6b0122710.1021/acscatal.6b01227FALSEhttps://doi.org/10.1021/acscatal.6b01227Sasai, HACS Catal.Professor Masakatsu Shibasaki's distinguished scientific accomplishments in the field of asymmetric catalysis are compiled here with particular emphasis on multimetallic cooperative catalysis. In 1992, he discovered revolutionary multimetallic chiral complexes composed of a rare earth metal, alkaline metals, and 1,1'-binaphthyl-2-binaphthols (BINOLs) that promoted a number of enantioselective reactions in a highly efficient and stereoselective manner. This finding resulted in chiral multimetallic catalysts that have significantly advanced the field of enantioselective catalysis.A Career in Catalysis: Masakatsu Shibasakimultimetallic complexes; rare earth metals; asymmetric catalysis; cooperative catalysis; C-C bond formation302016179#N/ATRUE
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acscatal.5b0160410.1021/acscatal.5b01604FALSEhttps://doi.org/10.1021/acscatal.5b01604Nguyen, STACS Catal.NU-1000-(bpy)Ni-II, a highly porous MOF material possessing well-defined (bpy)Ni-II moieties, was prepared through solvent-assisted ligand incorporation (SALI). Treatment with Et2AlCl affords a single-site catalyst with excellent catalytic activity for ethylene dimerization (intrinsic activity for butenes that is up to an order of magnitude higher than the corresponding (bpy)NiCl2 homogeneous analogue) and stability (can be reused at least three times). The high porosity of this catalyst results in outstanding levels of activity at ambient temperature in gas-phase ethylene dimerization reactions, both under batch and continuous flow conditions.Gas-Phase Dimerization of Ethylene under Mild Conditions Catalyzed by MOF Materials Containing (bpy)Ni-II Complexesmetal-organic framework; ethylene dimerization; gas-phase reaction; (bipyridyl)nickel complexes; catalysisx96201542#N/AFALSE
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acscatal.5b0155110.1021/acscatal.5b01551FALSEhttps://doi.org/10.1021/acscatal.5b01551Boettcher, SWACS Catal.One practical metric for electrocatalyst performance is current per geometric area at a given applied overpotential. An obvious route to increase performance is to increase the catalyst mass loading-as long as the intrinsic performance (i.e., specific activity or turnover frequency) of the catalyst is independent of loading, and other electrical, ionic, or masstransfer resistances are not severe. Here we report the geometric and intrinsic oxygen evolution reaction (OER) activities of Ni(Fe)OOH films, the fastest known water oxidation catalyst in basic media, as a function of mass loading from 0 to similar to 100 mu g cm(-2). We discuss practices for measuring and reporting intrinsic activities, highlighting experimental conditions where the film activity on a per-metal-cation basis can be accurately measured and where capacitance measurements of electrochemically active surface area fail. We find that the electrochemical reversibility of the (nominally) Ni2+/3+ redox wave correlates with the apparent intrinsic activity as a function of loading. We report a pulsed-electrodeposition method that dramatically improves the catalyst reversibility and performance at high loading compared to continuous electrodeposition, which we attribute to improved connectivity in the micro/nanostructure and better composition control. Pulse electrodeposited films are shown to have geometric performance similar to a number of advanced composite electrocatalyst structures and to maintain effective per-metal turnover frequencies of >0.4 s(-1) at 300 mV overpotential, even for loadings of similar to 100 mu g cm(-2).Pulse-Electrodeposited Ni-Fe (Oxy)hydroxide Oxygen Evolution Electrocatalysts with High Geometric and Intrinsic Activities at Large Mass Loadingsloading dependence; thickness dependence; electrochemically active surface area; turnover frequency; nickel iron oxyhydroxide; double-layer capacitance; conductivity; pulsed depositionx182201555#N/AFALSE
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acscatal.5b0154610.1021/acscatal.5b01546FALSEhttps://doi.org/10.1021/acscatal.5b01546Fabre, BACS Catal.The electrocatalytic reduction of CO2 to CO in hydroorganic medium has been investigated at illuminated (lambda > 600 nm; 20 mW cm(-2)) hydrogen-terminated silicon nanowires (SiNWs-H) photocathodes using three Mn-based Carbonyl bipyridyl complexes as homogeneous molecular catalysts ([Mn(L) (CO)(3)(CH3CN)](PF6) and [Mn(bpy) (CO)(3)Br) with L = bpy = 2,2'-bipyridine and dmbpy = 4,4'-dimethyl-2,2'-bipyridine). Systematic comparison of their cyClic voltammetry characteristics with those obtained at flat hydrogen-terminated silicon and traditional glassy carbon electrodes (GCE) enabled us to demonstrate the superior catalytic efficiency of SiNWs-H in terms of cathodic photocurrent densities and overpotentials. For example, the photocurrent densities measured at -1.0 V vs SCE for [Mn(bpy) (CO)(3)(CH3CN)](PF6) at SiNWs-H exceeded 1.0 mA cm(-2) in CO2-saturated CH3CN + 5% v/v H2O, whereas almost zero current was measured at this potential at GCE. Such characteristics have been supported by the energetic diagrams built for the different SiNWs vertical bar Mn-based catalyst interfaces. The fill factor FF and energy conversion efficiency eta calculated under catalytic conditions were higher for [Mn(bpy or dmbpy) (CO)(3)(CH3CN)](PF6) (FF = 0.35 and 0.34; eta = 3.0 and 2.0%, respectively). Further preparative-scale electrolysis at SiNWs-H photocathode with Mn-based complex catalysts in electrolytic solution evidenced the quantitative conversion of CO2 to CO with a higher stability of the [Mn(dmbpy) (CO)(3)(CH3CN)](PF6) complex. Finally, in order to develop technologically viable electrocatalytic devices, the elaboration of SiNWs-H photoelectrodes modified with a Mn-based complex has been successfully achieved from an electropolymerizable catalyst, and it was shown that the electrocatalytic activity of the complex was retained after immobilization.Selective Catalytic Electroreduction of CO2 at Silicon Nanowires (SiNWs) Photocathodes Using Non-Noble Metal-Based Manganese Carbonyl Bipyridyl Molecular Catalysts in Solution and Grafted onto SiNWselectrocatalytic reduction of CO2; silicon nanowires; photocathodes; Mn-Carbonyl-based complexes; modified electrodes; cyClic voltammebyx57201557#N/AFALSE
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acscatal.6b0113310.1021/acscatal.6b01133FALSEhttps://doi.org/10.1021/acscatal.6b01133Sievers, CACS Catal.The Pechini synthesis was used to prepare nickel aluminate catalysts with the compositions NiAl4O7, NiAl2O4, and Ni2Al2O5. The samples have been characterized by N-2 physisorption, temperature programmed reduction (TPR), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XFS), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Characterization results indicate unique structural properties and excellent regeneration potential of nickel aluminates. Prepared samples were tested when unreduced and reduced prior to reaction for methane dry reforming and methane steam reforming reactivity. NiAl2O4 in the reduced and unreduced state as well as NiAl4O7 in the reduced state are active and stable for methane dry reforming due to the presence of 4-fold coordinated oxidized nickel. The limited amount of metallic nickel in these samples minimizes carbon deposition. On the other hand, the presence of metallic nickel is required for methane steam reforming. Ni2Al2O5 in the reduced and unreduced states and NiAl2O4 in the reduced state are found to be active for methane steam reforming due to the presence of sufficiently small nickel nanopartiCles that catalyze the reaction without accumulating carbonaceous deposits.Differences in the Nature of Active Sites for Methane Dry Reforming and Methane Steam Reforming over Nickel Aluminate Catalystsspinel; synthesis gas; X-ray absorption spectroscopy; coordination number; regeneration71201663#N/ATRUE
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acscatal.5b0148110.1021/acscatal.5b01481FALSEhttps://doi.org/10.1021/acscatal.5b01481Mukerjee, SACS Catal.Ni-Fe and Ni-Fe-Co mixed-metal oxide (MMO) films were investigated as electrocatalysts for the oxygen evolution reaction (OER) in 0.1 M KOH. In an effort to optimize MMO morphology, aniline was used as a capping agent to produce high-surface-area Ni-Fe-Co films on Raney nickel supports. This catalyst exhibits enhanced mass activity in comparison to the Ni-Fe OER electrocatalysts reported to date. CyClic voltammetry shows changes in the potential of the Ni2+/(3+) transitions in Fe- or Co-containing MMO films. In situ X-ray absorption spectroscopy (XAS) analysis confirms that Fe acts to stabilize Ni in the 2+ oxidation state, while Co facilitates oxidation to the 3+ state. The results of this study support the recent Claims that Fe (not Ni) is the OER active site. The OER enhancement of the ternary Ni-Fe-Co catalyst results from two effects: (1) the charge-transfer effects of Co result in the formation of the conductive (NiOOH)-O-II phase at lower overpotential, thus activating the Fe sites which are otherwise inaccessible to electron transfer in the nonconductive Ni-II(OH)(2) host lattice, and (2) XAS analysis shows that the presence of Co effectively shrinks the Ni and Fe local geometry, likely resulting in an optimized Fe-OH/OOH bond strength. In addition, analysis of heat-treatment effects indicates that calcination at 400 degrees C improves the OER activity of Ni-Fe-Co but deactivates Ni-Fe. Annealing studies under argon show that MMO surfaces with a hydrated Ni(OH)(2) phase and a crystalline NiO phase exhibit nearly identical OER activities. Finally, the morphology of the MMO catalyst film on Raney Ni support provides excellent catalyst dispersion and should result in high active-site utilization for use in technologically relevant gas-diffusion electrodes.Charge-Transfer Effects in Ni-Fe and Ni-Fe-Co Mixed-Metal Oxides for the Alkaline Oxygen Evolution Reactionelectrochemistry; water electrolysis; alkaline oxygen evolution; nickel oxide; X-ray absorption spectroscopyx257201634#N/AFALSE
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acscatal.5b0127110.1021/acscatal.5b01271FALSEhttps://doi.org/10.1021/acscatal.5b01271Damsgaard, CDACS Catal.A nanodispersed intermetallic GaPd2/SiO2 catalyst is prepared by simple impregnation of industrially relevant high-surface-area SiO2 with Pd and Ga nitrates, followed by drying, calcination, and reduction in hydrogen. The catalyst is tested for CO2 hydrogenation to methanol at ambient pressure, revealing that the intrinsic activity of the GaPd2/SiO2 is higher than that of the conventional Cu/ZnO/Al2O3, while the production of the undesired CO is lower. A combination of complementary in situ and ex situ techniques are used to investigate the GaPd2/SiO2 catalyst. In situ X-ray diffraction and in situ extended X-ray absorption fine structure spectroscopy show that the GaPd2 intermetallic phase is formed upon Activation of the catalyst via reduction and remains stable during CO2 hydrogenation. Identical location-transmission electron microscopy images acquired ex situ (i.e., micrographs of exactly the same catalyst area recorded at the different steps of Activation and reaction procedure) show that nanopartiCle size and dispersion are defined upon calcination with no significant changes observed after reduction and methanol synthesis. Similar conClusions can be drawn from electron diffraction patterns and images acquired using environmental TEM (ETEM), indicating that ETEM results are representative for the catalyst treated at ambient pressure. The chemical composition and the crystalline structure of the nanopartiCles are identified by scanning TEM energy dispersive X-ray spectroscopy, selected area electron diffraction, and atomically resolved TEM images.Intermetallic GaPd2 NanopartiCles on SiO2 for Low-Pressure CO2 Hydrogenation to Methanol: Catalytic Performance and In Situ Characterizationmethanol synthesis; intermetallics; in situ characterization; XRD; TEM; EXAFSx87201557#N/AFALSE
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acscatal.5b0124810.1021/acscatal.5b01248FALSEhttps://doi.org/10.1021/acscatal.5b01248Maillard, FTuning the Performance and the Stability of Porous Hollow PtNi/C Nanostructures for the Oxygen Reduction Reactionx2015#N/AFALSE
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acscatal.5b0123110.1021/acscatal.5b01231FALSEhttps://doi.org/10.1021/acscatal.5b01231Shabaker, JWACS Catal.A dual catalyst system to implement in situ regeneration of ZnEt2, the Chain Transfer Agent (CTA) in Catalyzed Chain Growth of ethylene (CCG), has been demonstrated. As in typical CCG systems, an Fe homogeneous catalyst is used to grow oligomeric chains that transfer rapidly to ZnEt2. However, rather than liberating alkane products and destroying the expensive chain transfer agent via acid hydrolysis workup, a second Fe-Alkyl catalyst, (BiPy)(2)FeEt2, has been introduced to regenerate ZnEt2 via ethyl/Alkyl exchange and liberate the oligomer chains as alpha-olefins via beta-hydride elimination. This improvement reduces the ZnEt2 loading and leaves the chain growth catalyst competent, in contrast to Ni(acac)(2) shown to be unsuitable for in situ tandem catalysis. These findings greatly enhance the industrial viability of the chemistry.Iron-Catalyzed Chain Growth of Ethylene: In Situ Regeneration of ZnEt2 by Tandem Catalysiscatalyzed chain growth; chain transfer; alpha-olefins; ethylene polymerization; tandem catalysisx12201521#N/AFALSE
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acscatal.5b0122110.1021/acscatal.5b01221FALSEhttps://doi.org/10.1021/acscatal.5b01221Gong, JLACS Catal.Inexpensive group VIII metal (i.e., Fe, Co, and Ni)-based solid catalysts have been widely used in various energy transformation processes such as Fischer-Tropsch (F-T) synthesis, reforming, and water gas shift reactions. The emerging encapsulation strategy, which represents active metal species that are coated by a protective shell or matrix, has been demonstrated as a powerful means to promote the catalytic performance (i.e., activity, stability, and selectivity) of Fe-, Co-, and Ni-based catalysts due to synergic effects from the well-defined structures. This review describes recent progress on the design and synthesis of encapsulated group VIII base-metal nanomaterials developed for energy and environmental catalysis inCluding syngas conversion, CO2 dry reforming, steam reforming, methane conversion, and NH3 decomposition. We start with an introduction of the catalysts with different encapsulating structures (e.g., core@shell, yolk@shell, core@tube, mesoporous structures, and lamellar structures). Then, the synthetic methods of Fe-, Co-, and Ni-based catalysts with encapsulated structures are described in detail. The functions of encapsulation structures in catalysis, inCluding protecting metal nanopartiCles (NPs) from sintering, promoting the activity due to the confinement effect, and intensifying reaction processes in the form of multifunctional catalysts, are discussed, respectively. Our perspectives regarding the challenges and opportunities for future research in the field are also provided.Recent Advances on the Design of Group VIII Base-Metal Catalysts with Encapsulated Structuresgroup VIII base metal; iron; cobalt; nickel; encapsulation structure; antisintering; confinement effect; multifunctional catalysts; catalyst designx1082015222#N/AFALSE
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acscatal.5b0116510.1021/acscatal.5b01165FALSEhttps://doi.org/10.1021/acscatal.5b01165Sun, QACS Catal.Graphene-based materials are being hotly pursued for energy and environment applications. Inspired by the recent experimental synthesis of Fe-2 dimer supported on graphene (He, Z.; He, K.; Robertson, A. W.; Kirkland, A. I.; Kim, D.; Ihm, J.; Yoon, E.; Lee, G.-D.; Warner, J. H. Nano Lett. 2014, 14, 3766-3772), here using large-scale screening-based density functional theory and microkinetics modeling, we have identified that some transition metal dimers (Cu-2, CuMn, and CuNi), when supported on graphene with adjacent single vacancies (labeled as XY@2SV), perform better in CO2 electroreduction with reduced overpotental and enhanced current density. Specifically, Cu-2@2SV is catalytically active toward CO2 production, similar to Au electrodes but distinct from bulk Cu; MnCu@2SV is selective toward CH4 generation, while NiCu@2SV promotes CH3OH production because of the difference in oxophilicity between incorporated Mn and Ni. The advantages of the outstanding selectivity of products, the high dispersity of spatial distribution, and the reduced overpotentials allow these new systems to be promising catalysts, which will motivate more experimental research in this direction to further explore graphene-based materials for CO2 conversion.CO2 Electroreduction Performance of Transition Metal Dimers Supported on Graphene: A Theoretical StudyCO2 reduction; graphene-supported metal dimers; density functional theory; microkinetics modeling electrocatalysisx128201545#N/AFALSE
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acscatal.6b0091110.1021/acscatal.6b00911Nozaki, KElucidating the Key Role of Phosphine-Sulfonate Ligands in Palladium-Catalyzed Ethylene Polymerization: Effect of Ligand Structure on the Molecular Weight and Linearity of Polyethylene2016#N/ATRUE
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acscatal.5b0115110.1021/acscatal.5b01151FALSEhttps://doi.org/10.1021/acscatal.5b01151Mayrhofer, KJJACS Catal.We provide a comprehensive durability assessment dedicated to a promising Class of electrocatalysts for the oxygen reduction reaction (i.e., porous platinum nanopartiCles). The stability of these nanoengineered open structures is tested under two accelerated degradation test conditions (ADT), particularly selected to mimic the potential regimes experienced by the catalyst during the operative life of a fuel cell (i.e., load cyCles (up to 1.0 V-RHE) and start-up cyCles (up to 1.4 V-RHE)). To understand the evolution of the electrochemical performance, the catalyst properties are investigated by means of fundamental rotating disc electrode studies, identical location-transmission electron microscopy (IL-TEM) coupled with electron energy loss spectroscopy chemical mapping (IL-EELS), and post-use chemical analysis and online highly sensitive potential resolved dissolution concentration monitoring by scanning flow cell inductively coupled plasma-mass spectrometry (SFC-ICP-MS). The experimental results on the nanoporous Pt revealed distinctive degradation mechanisms that could potentially affect a wide range of other nanoengineered open structures. The study conCludes that, although providing promising activity performance, under the relevant operational conditions of fuel cells, the nanoporosity is only metastable and subjected to a progressive reorganization toward the minimization of the nanoscale curvature. The rate and pathways of this specific degradation mechanism together with other well-known degradation mechanisms like carbon corrosion and platinum dissolution are strongly dependent on the selected upper limit potential, leading to distinctly different durability performance.Stability of Dealloyed Porous Pt/Ni NanopartiClesporous metals; ORR; fuel cells; platinum alloys; stabilityx81201573#N/AFALSE
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acscatal.5b0108010.1021/acscatal.5b01080FALSEhttps://doi.org/10.1021/acscatal.5b01080Li, YWACS Catal.Hydrogenolysis of carbon oxygen bonds is a versatile synthetic method, of which hydrogenolysis of bioderived 5-hydroxymethylfurfural (HMF) to furanic fuels is especially attractive. However, low-temperature hydrogenolysis (in particular over non-noble catalysts) is challenging. Herein, nickel nanopartiCles (NPs) inlaid nickel phyllosilicate PS) are presented for efficient hydrogenolysis of HMF to yield furanic fuels at 130-150 degrees C, being much superior with impregnated Ni/SiO2 catalysts prepared from the same starting materials. NiSi-PS also shows a 2-fold HMF conversion intrinsic rate and 3-fold hydrogenolysis rate compared with the impregnated Ni/SiO2. The superior performance originated from the synergy of highly dispersed nickel NPs and substantially formed acid sites due to coordinatively unsaturated (II) sites located at the remnant nickel phyllosilicate structure, as revealed by detailed characterizations. The model reactions over the other reference catalysts further highlighted the metal acid synergy for hydrogenolysis reactions. NiSi-PS can also efficiently catalyze low-temperature hydrogenolysis of bioderived furfural and 5-methylfurfural, demonstrating a great potential for other hydrogenolysis reactions.Ni NanopartiCles Inlaid Nickel Phyllosilicate as a Metal-Acid Bifunctional Catalyst for Low-Temperature Hydrogenolysis Reactionshydrogenolysis; heterogeneous catalysis; nickel; silica; 5-hydroxymethylfurfuralx102201542#N/AFALSE
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acscatal.6b0067310.1021/acscatal.6b00673FALSEhttps://doi.org/10.1021/acscatal.6b00673Rosen, BAACS Catal.Shape-controlled LaNiO3 nanopartiCles were prepared by modified hydro thermal and precipitation routes resulting in cubes, spheres, and rods. The solid-phase crystallization of LaNiO3 into its active catalyst form, Ni/La2O3, was found to be highly dependent on the shape and structure of the parent nanopartiCle. Factors such as the crystallization pathway and Ni2+-ion depletion are considered as key factors influencing the final material. Catalysts derived from LaNiO3 spheres and rods were found to be free of carbon accumulation after 100 h of reforming, while those derived from cubes showed excessive carbon accumulation and signs of sintering. All three catalysts are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature -programmed reduction (TPR), and thermogravimetric analyses (TGA). The presence of defects, particularly stacking faults within the perovskite, may impact the reduction pathway and subsequent catalytic properties. Stable and active catalysts can therefore be designed and tuned by controlling the shape and structure of perovskite precursors.Influence of LaNiO3 Shape on Its Solid-Phase Crystallization into Coke-Free Reforming Catalystsperovskite; shape control; dry reforming of methane; solid-phase crystallization; carbon formation; defects53201624#N/ATRUE
5365
acscatal.5b0097910.1021/acscatal.5b00979FALSEhttps://doi.org/10.1021/acscatal.5b00979Yoon, KBACS Catal.Crystalline cobalt oxide nanopartiCles (nc-CoOx) supported on ITO glass or Ni foam doped with 5 mol % crystalline iridium oxide nanopartiCles (nc-IrOx) showed performances which are higher than those of nc-CoOx on ITO or Ni foam and nc-IrOx on a rotating glassy carbon disc electrode or Ni foam. The initial Co-III and Ir-IV become Co-IV and Ir-VI upon applying positive potentials. The nc-CoOx partiCles intrinsically carry (CoO5)-O-III centers which become (CoO6)-O-IV centers upon application of positive potentials. The O vacancy in (CoO5)-O-III is transferred to (IrO6)-O-VI upon application of positive potentials, giving rise to the formation of (IrO5)-O-VI centers, which are proposed to be the highly active catalytic centers for water oxidation.Cobalt Oxide Electrode Doped with Iridium Oxide as Highly Efficient Water Oxidation Electrodewater oxidation; crystalline cobalt oxide; crystalline iridium oxide; Tafel plot; XAS; EXAFS; oxygen vacancyx29201535#N/AFALSE
5366
acscatal.5b0086910.1021/acscatal.5b00869FALSEhttps://doi.org/10.1021/acscatal.5b00869Kleitz, FACS Catal.Efficient bimetallic nanocatalysts based on non-noble metals are highly desired for the development of new energy storage materials. In this work, we report a simple method for the synthesis of highly dispersed CuNi catalysts supported on mesoporous carbon or silica nanospheres using low-cost metal nitrate precursors. The mesoporous carbon-supported Cu0.5Ni0.5 nanocatalysts exhibit excellent catalytic performance for the hydrolysis of ammonia borane and decomposition of hydrous hydrazine with 100% hydrogen selectivity in aqueous alkaline solution at 60 degrees C. The chemical composition and size of the metal partiCles, which have a significant influence on the catalytic properties of the supported bimetallic CuNi materials, can readily be controlled by adjusting the metal loading and ratio of metal precursors. An exceedingly high turnover frequency of 3288 (mol(H2), mol(metal)(-1) h(-1)) and complete reaction within 1 mm in dehydrogenation of ammonia-borane were achieved over a tailored-made catalyst obtained through precise monitoring of metal partiCle size, composition, and support properties.Role of Metal-Support Interactions, PartiCle Size, and Metal-Metal Synergy in CuNi Nanocatalysts for H-2 Generationnanocatalysts; bimetallic CuNi; synergistic effect; hydrogen generation; ammonia-borane; mesoporous nanospheres; nanoporous carbonx105201570#N/AFALSE
5367
acscatal.5b0075610.1021/acscatal.5b00756FALSEhttps://doi.org/10.1021/acscatal.5b00756Nikolla, EACS Catal.Synthetically tuning the surface properties of many oxide catalysts to optimize their catalytic activity has been appreciably challenging, given their complex crystal structure. Nickelate oxides (e.g., La2NiO4+delta) are among complex, layered oxides with great potential toward efficiently catalyzing chemical/electrochemical reactions involving oxygen (oxygen reduction, ammonia oxidation). Our theoretical calculations show that the surface structure of La2NiO4+delta plays a critical role in its activity, with the (001)-Ni oxide-terminated surface being the most active. This is demonstrated through the effect on the energetics associated with surface oxygen exchange, a key process in reactions involving oxygen on these oxides. Using a reverse microemulsion method, we have synthesized La2NiO4+delta nanorod-structured catalysts highly populated by (001)-Ni oxide-terminated surfaces. We show that these nanostructures exhibit superior catalytic activity toward oxygen exchange/reduction as compared with traditional catalysts while maintaining stability under reaction conditions. The findings reported here pave the way for engineering complex metal oxides with optimal activity.Engineering Complex, Layered Metal Oxides: High-Performance Nickelate Oxide Nanostructures for Oxygen Exchange and Reductionnickelate oxide; solid oxide fuel cell; density functional calculations; oxygen exchange; catalysisx23201535#N/AFALSE
5368
acscatal.5b0072810.1021/acscatal.5b00728FALSEhttps://doi.org/10.1021/acscatal.5b00728Guo, HCNH3 Decomposition for H-2 Generation: Effects of Cheap Metals and Supports on Plasma-Catalyst Synergyx2015#N/AFALSE
5369
acscatal.5b0062710.1021/acscatal.5b00627FALSEhttps://doi.org/10.1021/acscatal.5b00627Rioux, RMACS Catal.The structures of ZnO-supported Ni catalysts were explored with in situ X-ray absorption spectroscopy, temperature-programmed reduction, X-ray diffraction, highresolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy, and electron energy loss spectroscopy. Calcination of nickel nitrate on a nanoparticulate ZnO support at 450 degrees C results in the formation of Zn-doped NiO (ca. Ni0.85Zn0.15O) nanopartiCles with the rock salt crystal structure. Subsequent in situ reduction monitored by X-ray absorption near edge structure (XANES) at the Ni K edge reveals a direct transformation of the Zn-doped NiO nanopartiCles to a face-centered cubic alloy, Ni1-xZnX at similar to 400 degrees C with x increasing with increasing temperature. Both in situ ?CANES and ex situ HRTEM provide evidence for intermetallic beta(1)-NiZn formation at similar to 550 degrees C. In comparison to a Ni/SiO2 catalyst, Ni/ZnO necessitates a higher temperature for the reduction of Ni-II to Ni-0, which highlights the strong interaction between Ni and the ZnO support The catalytic activity for acetylene removal from an ethylene feed stream is decreased by a factor of 20 on Ni/ZnO in comparison to Ni/SiO2. The decrease in catalytic activity of Ni/ZnO is accompanied by a reduced absolute selectivity to ethylene. H D exchange measurements demonstrate a reduced ability of Ni/ZnO to dissociate hydrogen in comparison to Ni/SiO2. These results of the catalytic experiments suggest that the catalytic properties are controlled, in part, by the zinc oxide support and stress the importance of reporting absolute ethylene selectivity for the catalytic setnihydrogenation of acetylene in excess ethylene.In Situ Spectroscopic Characterization of Ni1-xZnX/ZnO Catalysts and Their Selectivity for Acetylene Semihydrogenation in Excess Ethylenenickel; zinc oxide; X-ray absorption spectroscopy; reduction; acetylene; semihydrogenationx32201561#N/AFALSE
5370
acscatal.5b0055010.1021/acscatal.5b00550FALSEhttps://doi.org/10.1021/acscatal.5b00550Li, ZSimple and Efficient Immobilization of Extracellular His-Tagged Enzyme Directly from Cell Culture Supernatant As Active and RecyClable Nanobiocatalyst: High-Performance Production of Biodiesel from Waste Greasex2015#N/AFALSE
5371
acscatal.6b0066610.1021/acscatal.6b00666FALSEhttps://doi.org/10.1021/acscatal.6b00666Bruce, DAACS Catal.Increases in worldwide methane production from biological and fossil sources have led to an increased level of interest in the dry reforming of methane (DRM) to produce syngas. Experimental efforts have shown that select pyrochlore materials, such as the Rh-substituted lanthanum zirconate pyrochlore (LRhZ), are catalytically active for DRM, exhibit long-term thermal stability, and resist deActivation. This work seeks to allow further catalyst improvements by elucidating surface reaction kinetics via steady-state isotopic transient kinetic analysis (SSITKA) of dry reforming on the LRhZ pyrochlore. Isotopically labeled CH4 and CO2 were used in multiple SSITKA experiments to elucidate the migration of carbon atoms to product species. Short surface residence times at 650 and 800 degrees C (<0.6 s) were observed for DRM intermediates involved in reversible reactions, and the participation of all surface metal atoms as active sites for DRM, not only Rh, is suggested. Isotopic responses and kinetic isotope effects are explained using reaction mechanism details derived from density functional theory studies of the surface reactions.Dry Reforming of Methane on Rh-Doped Pyrochlore Catalysts: A Steady-State Isotopic Transient Kinetic Studydry reforming of methane; syngas; pyrochlore; steady-state isotopic transient kinetic analysis; reaction mechanism; DFT35201634#N/ATRUE
5372
acscatal.6b0037810.1021/acscatal.6b00378FALSEhttps://doi.org/10.1021/acscatal.6b00378Artero, VACS Catal.The perspective of integrating molecular catalysts for hydrogen evolution into operating devices requires the benchmarking of their activity preferentially in aqueous media. Within a series of cobalt complexes assessed in that way, cobalt diimine dioxime derivatives were shown to be the most active catalysts with onset overpotential for proton reduction as low as 260 mV in phosphate buffer (pH = 2.2) (McCrory et al. J. Am. Chem. Soc. 2012, 134, 3164-3170). Combining a set of analytical techniques (electrochemistry, gas chromatography, SEM, and XPS), we demonstrate here that the electrochemical wave previously assigned to H-2 evolution catalyzed by the molecular complex actually corresponds to low levels of catalytic hydrogen production (27% faradaic yield). Instead, we assign this wave to the reductive degradation of the molecular complex and to the formation of a nanoparticulate deposit at the electrode. Actually, this coating is responsible for the high faradaic yields for hydrogen evolution observed at more cathodic potentials. The catalytic nanoparticulate material is metastable and readily redissolves, so that rinse-test experiments were insufficient here to rule out the formation of solid-state materials. This point accounts for the previous misidentification of the active species in H2 evolution mediated by a cobalt diimine dioxime complex in aqueous phosphate buffer (pH = 2.2). Our finding, exemplified on a cobalt complex, may be extended to other molecular systems and suggests that the routine use of rinse test experiments may not be sufficient to ascertain the molecular nature of active water-splitting catalytic species.The Dark Side of Molecular Catalysis: Diimine-Dioxime Cobalt Complexes Are Not the Actual Hydrogen Evolution Electrocatalyst in Acidic Aqueous Solutionscobalt; nanopartiCle; cobaloximes; diimine-dioxime complexes; solar fuels; electrocatalysis; rotating ring disk electrode84201659#N/ATRUE
5373
acscatal.5b0035710.1021/acscatal.5b00357FALSEhttps://doi.org/10.1021/acscatal.5b00357Marin, GBACS Catal.A series of bimetallic Fe-Ni/MgAl2O4 catalysts with Fe/Ni ratios between 0 and 1.5 have been examined for methane dry reforming at 923-1073 K, atmospheric pressure, and a CH4/CO2 ratio of 1. The evolution of the catalyst structure during H-2 temperature-programmed reduction (TPR), CO2 temperature-programmed oxidation (TPO), and dry reforming is examined using time-resolved in situ X-ray diffraction (XRD). During H-2-TPR up to 973 K, Fe2O3 and NiO are reduced to Fe and Ni. Higher temperatures lead to Fe-Ni alloy formation. The alloy remains stable up to 900 K under CO2-TPO and is decomposed to Ni and Fe3O4 at higher temperatures. The Fe-Ni alloy is the active phase while Fe partially segregates from the alloy forming FeOx during dry reforming. This is beneficial as it reduces the surface carbon accumulation through interaction with FeOx lattice oxygen, producing CO. Alternate CH, and CO2 pulse experiments over Ni, Fe, and Ni-Fe samples showed that dry reforming over Fe-Ni catalysts can follow a Mars-van Krevelen mechanism. A molar Fe/Ni ratio of 0.7 provides the most active and least deactivated catalyst. All studied catalysts can be regenerated by CO2 carbon removal.Enhanced Carbon-Resistant Dry Reforming Fe-Ni Catalyst: Role of FeNi-based catalyst; effect of Fe; alloy; methane dry reforming; synthesis gas; in situ XRD; carbon formationx227201568#N/AFALSE
5374
acscatal.5b0022110.1021/acscatal.5b00221FALSEhttps://doi.org/10.1021/acscatal.5b00221Schneider, LACS Catal.The cheap stainless commodity steel AISI 304, which basically consists of Fe, Ni, and Cr, was surface-oxidized by exposure to Cl-2 gas. This treatment turned AISI 304 steel into an efficient electrocatalyst for water splitting at pH 7 and pH 13. The overpotential of the anodic oxygen evolution reaction (OER), which typically limits the efficiency of the overall water-splitting process, could be reduced to 260 mV at 1.5 mA/cm(2) in 0.1 M KOH. At pH 7, overpotentials of 500-550 mV at current densities of 0.65 mA/cm2 were achieved. These values represent a surprisingly good activity taking into account the simplicity of the procedure and the fact that the starting material is virtually omnipresent. Surface-oxidized AISI 304 steel exhibited outstanding long-term stability of its electro catalytic properties in the alkaline as well as in the neutral regime, which did not deteriorate even after chronopoteniometry for 150 000 s. XPS analysis revealed that surface oxidation resulted in the formation of Fe oxide and Cr oxide surface layers with a thickness in the range of a few nanometers accompanied by enrichment of Cr in the surface layer. Depending on the duration of the Cl-2 treatment, the purity of the Fe oxide/Cr oxide mixture lies between 95% and 98%. Surface oxidation of AISI 304 steel by chlorination is an easy and scalable access to nontoxic, cheap, stable, and efficient electrocatalysts for water splitting.Surface Oxidation of Stainless Steel: Oxygen Evolution Electrocatalysts with High Catalytic Activitysolar to fuel conversion; renewable energy sources; oxygen evolution electrocatalysis; stainless steel; surface oxidation; XPS spectroscopyx91201549#N/AFALSE
5375
acscatal.5b0271810.1021/acscatal.5b02718FALSEhttps://doi.org/10.1021/acscatal.5b02718Knochel, PACS Catal.This Perspective describes general methods for the preparation of polyfunctional zinc organometallics and their use in Negishi cross-coupling reactions. Recent advances inCluding new ligands and palladium catalysts are described. Related Negishi cross-coupling reactions involving Ni-, Cu-, Co-, and Fe-catalyzed cross-couplings are covered. The availability of a range of zinc organometallics combined with new efficient catalysts allows for efficient cross coupling reactions with various organic electrophiles under usually mild conditions.Recent Developments in Negishi Cross-Coupling ReactionsNegishi cross-coupling; zinc; palladium; nickel; copper; iron2102016140#N/ATRUE
5376
acscatal.5b0006510.1021/acscatal.5b00065FALSEhttps://doi.org/10.1021/acscatal.5b00065Wadayama, TACS Catal.A novel nanopartiCle-stacking thin film (NPSTF) of Pt-Ni alloy for highly active oxygen reduction reaction (ORR) electrocatalyst was synthesized. The Pt mass activity of the synthesized Pt-Ni NPSTF were 10-fold higher than commercial carbon-supported Pt catalysts. The remarkable ORR activity enhancement of the Pt-Ni NPSTF was attributed to the modified electronic properties of the surface Pt-enriched layers induced by underlying Ni atoms and to the increased active surface area achieved by stacking of Pt-Ni nanopartiCles.Pt-Ni NanopartiCle-Stacking Thin Film: Highly Active Electrocatalysts for Oxygen Reduction Reactionthin film catalysts; oxygen reduction reaction; Pt-based alloys; arc plasma deposition; proton exchange membrane fuel cellx34201528#N/AFALSE
5377
acscatal.5b0006010.1021/acscatal.5b00060FALSEhttps://doi.org/10.1021/acscatal.5b00060Semagina, NACS Catal.The crucial role of Ni mode addition to Pd catalysts for low-temperature wet methane combustion is addressed, resulting in excellent performance of ultralow-Ni-containing catalysts versus inactive nickel-alumina spinel. Traditional impregnation-calcination and colloidal techniques of bimetallic catalyst preparation yield monometallic Pd partiCles on a binary NiAl2O4 support and Pd and Ni nanopartiCles on the parent Al2O3 support, respectively. The catalyst is potentially valuable for natural gas catalytic combustion technologies because it decreases the required temperature for complete methane combustion in 5% water presence in the feed by 100 degrees versus monometallic Pd.100 degrees Temperature Reduction of Wet Methane Combustion: Highly Active Pd-Ni/Al2O3 Catalyst versus Pd/NiAl2O4palladium; nickel; spinel; bimetallic nanopartiCles; methane combustionx50201528#N/AFALSE
5378
acscatal.5b0004510.1021/acscatal.5b00045FALSEhttps://doi.org/10.1021/acscatal.5b00045Eisenberg, RACS Catal.A series of nickel bis(chelate) complexes having square planar coordination are studied for light-driven and electrocatalytic hydrogen production from water. The complexes Ni(abt)2 (abt = 2-aminobenzenethiolate), Ni(mp)(2) (mp = 2-mercaptophenolate) and Ni(mpo)(2) (mpo = 2-mercaptopyridyl-N-oxide) are found to be active catalysts under light-driven conditions, using fluorescein (Fl) as the photosensitizer (PS) and triethanolamine (TEOA) as the sacrificial electron donor in water under basic pH (pH = 9.8). These molecular systems achieve a turnover number (TON) of similar to 6000 (relative to catalyst) and are stable for more than 100 h under H-2-generating conditions. When water-soluble CdSe quantum dots with tripodal S-donor capping agents are employed as PS and ascorbic acid (AA) is used as the sacrificial electron donor at pH 4.5, an active and robust system is obtained for the light-driven generation of H-2 from aqueous protons. A TON of over 280 000 is achieved for the three active catalysts. These complexes are also examined electrochemically in organic solvents with weak organic acids as the proton source and in aqueous and aqueous/organic media for proton reduction. The most active photochemical catalysts also show excellent electrocatalytic activity in neutral pH water, achieving Faradaic yields Close to 100% under anaerobic conditions and similar to 80% under aerobic conditions.Nickel Complexes for Robust Light-Driven and Electrocatalytic Hydrogen Production from Waterphotochemistry; hydrogen evolution; molecular HER catalysis; Ni catalysts with redox active ligands; CdSe quantum dots; HER mechanism; fluorescein; heterocoupling
Electrocatalytic
156201569#N/AFALSE
5379
acscatal.1c0203110.1021/acscatal.1c02031FALSEhttps://doi.org/10.1021/acscatal.1c02031Long, MCACS Catal.Transition metal catalysts are known to activate persulfate, but the properties that govern the intrinsic activity of these catalysts are still unknown. Here, we developed a series of catalysts with transition metals anchored on carbon nanotubes (denoted M-N-CNTs, where M = Co, Fe, Mn, or Ni) containing single-atom M-N moieties, to activate peroxymonosulfate for the efficient nonradical oxidation of sulfamethoxazole. The spin state of M-N-CNTs strongly determined their catalytic activity. A large effective magnetic moment with a high spin state (e.g., Co-N) favored the overlap of d orbitals with oxygen-containing adsorbates (such as peroxo species) on metal active sites and promoted electron transfer, which facilitated peroxymonosulfate adsorption and enhanced the oxidation capacity of the reactive species. These findings advance the mechanistic understanding of transition metal-mediated persulfate Activation and inform the development of efficient spintronic catalysts for environmental applications.Spin-State-Dependent Peroxymonosulfate Activation of Single-Atom M-N Moieties via a Radical-Free Pathwayspin state; peroxymonosulfate Activation; intrinsic activity; single-atom catalysts; nonradical reactionx0202144#N/AFALSE
5380
acscatal.1c0180510.1021/acscatal.1c01805FALSEhttps://doi.org/10.1021/acscatal.1c01805Zheng, NFACS Catal.The development of highly active and stable earth-abundant electrocatalysts is crucial for the large-scale electrocatalytic hydrogen production. We report herein a crystal-phase heterostructured Ni catalyst with an interior backbone of the face-centered cubic phase covered by a thin surface layer of the hexagonal Close packing (hcp) phase. Systematic studies reveal that, upon oxidation, the surface hcp Ni is capable of forming a leaky oxidized layer with abundant Ni-0 sites buried underneath. Such underneath Ni-0 sites could act synergistically with the leaky surface (hydr)oxide layer from hcp Ni to promote H+ electroreductive formation of H-2. The unique surface chemical properties of hcp endow the as-prepared Ni catalyst with high hydrogen evolution activity (112 mV @ 100 mA cm(-2)) and incredible environment stability even under high current densities and high-concentration alkaline conditions (4-6 M KOH), making it a promising alternative to noble metal catalysts for practical applications in commercial alkaline electrolyzers.Hexagonal Nickel as a Highly Durable and Active Catalyst for Hydrogen Evolutionhexagonal Ni; crystal structure; surface properties; electrocatalysis; large-scale HERx0202143#N/AFALSE
5381
acscatal.5b0239910.1021/acscatal.5b02399FALSEhttps://doi.org/10.1021/acscatal.5b02399Ager, JWACS Catal.Carbon materials are frequently used as supports for electrocatalysts because they are conductive and have high surface area. However, recent studies have shown that these materials can contain significant levels of metallic impurities that can dramatically alter their electrochemical properties. Here, the electrocatalytic activity of pure graphite (PG), graphene oxide (GO), and carbon nanotubes (CNT) dispersed on glassy carbon (GC) are investigated for the electrochemical CO2 reduction reaction (CO2RR) in aqueous solution. It was observed that GO and CNT dispersed on GC all exhibit significant electrochemical activity that can be ascribed to impurities of Ni, Fe, Mn, and Cu. The level of Cu in GO can be particularly high and is the cause for the appearance of methane in the products produced over this material when it is used for the CO2RR. Washing these supports in ultrapure nitric acid is effective in removing the metal impurities and results in a reduction in the electrochemical activity of these forms of carbon. In particular, for GO, nearly all of the catalytically relevant metals can be removed. Electrochemical deposition of Cu on GO and PG supported on GC, and on GC itself, increased both the electrochemical activity of these materials and the production of methane via the CO2RR Particularly high rates of methane formation per unit of Cu mass were obtained for Cu electrodeposited on GO and PG supported on GC. We suggest that this high activity may be due to the preferential deposition of Cu onto defects present in the graphene sheets comprising these materials.Trace Levels of Copper in Carbon Materials Show Significant Electrochemical CO2 Reduction ActivityCO2 electroreduction; Faradaic efficiency; electrocatalytic activity; graphene oxide; carbon nanotubes102201637#N/ATRUE
5382
acscatal.1c0170210.1021/acscatal.1c01702FALSEhttps://doi.org/10.1021/acscatal.1c01702Jaouen, FMetal Oxide Clusters on Nitrogen-Doped Carbon are Highly Selective for CO2 Electroreduction to COx2021#N/AFALSE
5383
acscatal.5b0230810.1021/acscatal.5b02308FALSEhttps://doi.org/10.1021/acscatal.5b02308Deng, LCobalt Complex-Catalyzed Hydrosilylation of Alkenes and Alkynes2016#N/ATRUE
5384
acscatal.1c0160710.1021/acscatal.1c01607FALSEhttps://doi.org/10.1021/acscatal.1c01607Xu, ClACS Catal.The spinel Co3O4 has emerged as a promising alternative to noble-metal-based electrocatalysts for electrochemical water electrolysis in alkaline medium. However, pure Co3O4, despite having high activity in anodic water oxidation, remains inactive toward the hydrogen evolution reaction (HER). Here, a Ni-doped Co3O4 (Co3-xNixO4) prepared by a simple method exhibits favorable HER activity and stability (>300 h, whether in 1 M KOH or the realistic 30 wt % KOH solution) after in situ electrochemical Activation, outperforming almost all of the oxide-based electrocatalysts. More importantly, using the combination of in situ Raman spectroscopy and multiple high-resolution electron microscopy techniques, it is identified that the surface of Co3-xNixO4 crystals is reduced into intertwined CoyNi1-yO nanopartiCles with highly exposed {110} reactive planes. Density functional theory calculations further prove that the Ni- doped CoO component in CoyNi1-yO plays a major role during the alkaline HER, because the introduction of Ni atoms into Co-O octahedra can optimize the electrical conductivity and tailor the adsorption/desorption free energies of H-ad and OHad intermediates.In Situ Activated Co3-xNixO4 as a Highly Active and Ultrastable Electrocatalyst for Hydrogen Generationelectrocatalyst; electrochemical Activation; CoyNi1-yO; Co3-xNixO4; hydrogen evolution reactionx0202148#N/AFALSE
5385
acscatal.1c0160410.1021/acscatal.1c01604FALSEhttps://doi.org/10.1021/acscatal.1c01604Irigoyen, BACS Catal.Methane steam reforming (MSR) plays a key role in the production of syngas and hydrogen from natural gas. The increasing interest in the use of hydrogen for fuel cell applications demands development of catalysts with high activity at reduced operating temperatures. Ni-based catalysts are promising systems because of their high activity and low cost, but coke formation generally poses a severe problem. Studies of ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) indicate that CH4/H2O gas mixtures react with Ni/CeO2 (111) surfaces to form OH, CHx, and CHxO at 300 K. All of these species are easy to form and desorb at temperatures below 700 K when the rate of the MSR process is accelerated. Density functional theory (DFT) modeling of the reaction over ceria-supported small Ni nanopartiCles predicts relatively low Activation barriers between 0.3 and 0.7 eV for complete dehydrogenation of methane to carbon and the barrierless Activation of water at interfacial Ni sites. Hydroxyls resulting from water Activation allow for CO formation via a COH intermediate with a barrier of about 0.9 eV, which is much lower than that through a pathway involving lattice oxygen from ceria. Neither methane nor water Activation is a rate-determining step, and the OH-assisted CO formation through the COH intermediate constitutes a low-barrier pathway that prevents carbon accumulation. The interactions between Ni and the ceria support and the low metal loading are crucial for the reaction to proceed in a coke-free and efficient way. These results pave the way for further advances in the design of stable and highly active Ni-based catalysts for hydrogen production.Reaction Pathway for Coke-Free Methane Steam Reforming on a Ni/CeO2 Catalyst: Active Sites and the Role of Metal-Support Interactionsmethane; steam reforming; hydrogen; nickel; ceria; DFTx0202190#N/AFALSE
5386
acscatal.1c0156110.1021/acscatal.1c01561FALSEhttps://doi.org/10.1021/acscatal.1c01561Corma, AACS Catal.Non-noble bimetallic CoW nanopartiCles (NPs) partially embedded in a carbon matrix (cow@c) have been prepared by a facile hydrothermal carbon-coating methodology followed by pyrolysis under an inert atmosphere. The bimetallic NPs, constituted by a multishell core-shell structure with a metallic Co core, a W-enriched shell involving Co7W6 alloyed structures, and small WO3 patches partially covering the surface of these NPs, have been established as excellent catalysts for the selective hydrogenation of quinolines to their corresponding 1,2,3,4-tetrahydroquinolines under mild conditions of pressure and temperature. It has been found that this bimetallic catalyst displays superior catalytic performance toward the formation of the target products than the monometallic Co@C, which can be attributed to the presence of the CoW alloyed structures.Tuning the Catalytic Performance of Cobalt NanopartiCles by Tungsten Doping for Efficient and Selective Hydrogenation of Quinolines under Mild Conditionsnon-noble metal catalysts; CoW bimetallic alloys; heterogeneous catalysis; selective hydrogenation; quinolinesx02021122#N/AFALSE
5387
acscatal.5b0195710.1021/acscatal.5b01957FALSEhttps://doi.org/10.1021/acscatal.5b01957Olsbye, UACS Catal.Ni-containing porous aluminosilicates are promising heterogeneous catalysts for oligomerization of ethene, but little is known about the catalytic cyCle. In addition, it remains unClear why the aluminosilicates work without the Alkyl aluminum cocatalyst needed in homogeneous catalysis. As the first of its kind, this work uses density functional theory (DFT) to identify the most probable mechanism of oligomerization and active site formation. The periodic DFT calculations employed the BEEF-vdW functional to consider both short-range interactions involved in bond formation and long-range interactions with the zeolite framework. The calculations targeted Ni-containing SSZ-24 zeolite as a representative catalyst and considered Ni+, Ni2+ ions, and neutral nickel atoms as active sites. We investigated the catalytic cyCles of the metallacyCle and Cossee-Arlman mechanisms that have been proposed in the literature, in addition to a new proton transfer mechanism. Free energy profiles were derived at a typical experimental reaction temperature of 393 K and used to kinetically discriminate the mechanisms with the energetic span model. On the basis of the results, we predict the CosseeArlman mechanism known from homogeneous catalysts to prevail also in the zeolite catalyst. The calculated intrinsic enthalpy of Activation of 77 kJ/mol for ethene dimerization agrees well with available experimental data. We further propose a mechanism for formation of the active nickel-Alkyl species by reaction between ethene and isolated Ni2+ ions. The results hence provide a solid starting point for experimental investigations of the catalytic cyCle, to validate our predictions and ultimately determine the atom scale properties that control catalytic activity.Ethene Oligomerization in Ni-Containing Zeolites: Theoretical Discrimination of Reaction Mechanismsalkene; nickel; active site; proton transfer; metallacyCle; Cossee-Arlman; density functional theory56201674#N/ATRUE
5388
acscatal.5b0174810.1021/acscatal.5b01748FALSEhttps://doi.org/10.1021/acscatal.5b01748Toroker, MCACS Catal.Understanding the role of an overlayer material on a catalyst is crucial for improving catalytic activity. Iron(III) oxide (alpha-Fe2O3) is a widely studied catalyst commonly used for solar water splitting. Recently, the water splitting efficiency with alpha-Fe2O3 was enhanced by deposition of an alpha-Al2O3 overlayer. In order to understand the origin of this improvement, we perform first-principles calculations with density functional theory + U on the alpha-Fe2O3(0001) surface with an alpha-Al2O3 surface overlayer. We find catalysis is unfavorable directly over alpha-Al2O3 and rather takes place over a-Fe203 exposed areas. In agreement with experiment, we find that alpha-Al2O3 coverage decreases the overpotential required for water oxidation on alpha-Fe2O3. We explain this improvement through the decrease in the work function of alpha-Fe2O3 upon aAl(2)O(3) coverage that aids in extracting electrons during the water oxidation reaction. We suggest that selecting an overlayer with a smaller work function than that of the catalyst as a strategy for future development of better catalysts.A First-Principles Study on the Role of an Al2O3 Over layer on Fe2O3 for Water Splitting43201564#N/ATRUE
5389
acscatal.1c0141610.1021/acscatal.1c01416https://doi.org/10.1021/acscatal.1c01416Koh, MJACS Catal.The construction of C-C bonds through cross-coupling between two electrophiles in the absence of excess metallic reducing agents is a desirable objective in chemistry. Here, we show that N-Alkylpyridinium salts can be efficiently merged with Aryl or Alkyl halides in an intermolecular fashion, affording products in up to 92% yield at ambient temperature. These reactions harness the ability of N-Alkylpyridinium salts to form electron donor-acceptor complexes with Hantzsch esters, enabling photoinduced singleelectron transfer and fragmentation to afford Alkyl radicals that are subsequently trapped by a Ni-based catalytic species to promote C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bond formation. The operationally simple protocol is applicable to site-selective cross-coupling and tolerates diverse functional groups, inCluding those that are sensitive toward metal reductants.Photoinduced Nickel-Catalyzed Deaminative Cross-Electrophile Coupling for C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) Bond Formationphotochemistry; nickel catalysis; pyridinium salts; cross-electrophile coupling; EDA complexes; deaminationPhotocatalyst02021736/21/2022FALSE
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acscatal.1c0138610.1021/acscatal.1c01386FALSEhttps://doi.org/10.1021/acscatal.1c01386Lin, LACS Catal.Transfer hydrogenation (TH) of aldehydes/ketones with renewable and nontoxic ethanol is an attractive solution to produce alcohols. Here, we found that single-atom Ni-N-4 site catalysts bring high activity and selectivity for the reduction of hydroxymethyl-functionalized aldehydes/ketones using renewable and nontoxic ethanol as the hydrogen source. When biomass-derived 5-hydroxymethylfurfural was used as the substrate, a turnover frequency (TOF) value of 22 h(-1) for the as-prepared catalyst was achieved. Experiments and simulating computation revealed that pyridinic N of the Ni-N-4 site is the active center and the presence of single-atom Ni reduces the electron density of its coordinated pyridinic N and thus achieves the high catalytic activity, demonstrating the possibility of catalytic TH reactions over metal-free sites.Inducing Electron Dissipation of Pyridinic N Enabled by Single Ni-N-4 Sites for the Reduction of Aldehydes/Ketones with Ethanoltransfer hydrogenation; reduction of aldehydes; single site catalysts; hydrogen donor; 5-hydroxymethylfurfuralx0202146#N/AFALSE
5391
acscatal.1c0134710.1021/acscatal.1c01347FALSEhttps://doi.org/10.1021/acscatal.1c01347Wang, JHACS Catal.Classical strong metal-support interaction (SMSI) has attracted intensive attention in the heterogeneous catalysis field; however, its crystalline TiOx overlayer and reversible feature often curtail the effect of Classical SMSI on enhancing the catalytic performance of supported metal catalysts in oxidation reactions, especially at elevated temperatures. Here, we report the evidence that Pt nanopartiCles can be encapsulated by an amorphous and permeable TiOx cover layer in Pt/TiO2 catalysts under an oxidative atmosphere, where the keys are the utilization of melamine, followed by annealing in nitrogen flow and further calcination at 800 degrees C in air. More importantly, the formed overlayer is stabilized against re-oxidation at 400-600 degrees C in air, in sharp contrast to the retreat of the TiOx overlayer by subsequent oxidation treatment in Classical SMSI. Such an extraordinary strategy is further demonstrated on titania-supported Pd and Rh nanopartiCles, paving a promising way for designing supported platinum group metal-based catalysts with high activity and stability.Encapsulation of Platinum by Titania under an Oxidative Atmosphere: Contrary to Classical Strong Metal-Support Interactionsstrong metal-support interaction (smsi); platinum group metals; titania; encapsulation; oxidative atmospherex0202158#N/AFALSE
5392
acscatal.1c0129910.1021/acscatal.1c01299FALSEhttps://doi.org/10.1021/acscatal.1c01299Ma, XBACS Catal.A series of V-dopAed layered double hydroxide-derived Ni-x-V-MgAl catalysts were prepared and applied in the dry reforming of methane (DRM) reaction. The catalyst activity was enhanced with increasing amounts of a V promoter and was optimal at Ni/V = 10. Various characterizations showed that an appropriate amount of the V additive was doped in both the Ni sites and the MgAl mixed-oxide support. The addition of the V promoter not only improved the dispersion of Ni sites but also increased their electron Cloud density. The Activation energy of CH4 cracking to form CH3 and H species decreased from 72.1 kJ.mol(-1) on pure Ni(111) to 37.1 kJ.mol(-1) on V0.50Ni(111). Meanwhile, the adsorption and Activation abilities of CO2 were affected by the insertion of V species in the MgAl mixed-oxide support. In situ CO2 infrared spectrometry verified that the addition of the V promoter inhibited the formation of nonactivated multidentate carbonate and significantly increased the content of the monodentate carbonate species, which was considered as the intermediate of CO2 Activation. Thus, the enhanced CO2 Activation ability of the Ni-10-V-MgAl catalyst suppressed the generation of carbon deposits during the DRM reaction, thereby achieving excellent stability in long-term testing compared to undoped Ni-MgAl.Double-Site Doping of a V Promoter on Ni-x-V-MgAl Catalysts for the DRM Reaction: Simultaneous Effect on CH4 and CO2 Activationdry reforming of methane; V-doped LDH-derived Ni-x-V-MgAl catalysts; DFT; Activation of CH4 and CO2x0202159#N/AFALSE
5393
acscatal.1c0128410.1021/acscatal.1c01284FALSEhttps://doi.org/10.1021/acscatal.1c01284Jiang, LHACS Catal.Developing low-cost and robust hydrogen oxidation reaction (HOR) electrocatalysts is urgent for anion exchange membrane fuel cells (AEMFCs). Herein, we report an efficient Ni-based catalyst for HOR in alkaline electrolyte, which features an ultrafine Ni nanopartiCle (3.7 nm) core and an ultrathin N-doped carbon shell (0.36 nm). The optimized catalyst exhibits both excellent activity (24.4 A g(Ni)(-1) @ eta = 50 mV and exchange current density of 38 mu A cm(Ni)(-2)) and superior stability for the HOR. Theoretical calculations reveal that the d-band state of Ni encapsulated in ultrathin N-doped carbon shell is downshifted, with optimal binding energies of OHad and H-ad, leading to a low limiting energy pathway for HOR.Ultrafine Nickel NanopartiCles Encapsulated in N-Doped Carbon Promoting Hydrogen Oxidation Reaction in Alkaline Mediahydrogen oxidation reaction; anion exchange membrane fuel cell; Ni nanopartiCles; encapsulating; electrocatalystx0202146#N/AFALSE
5394
acscatal.1c0125510.1021/acscatal.1c01255FALSEhttps://doi.org/10.1021/acscatal.1c01255Hall, DGACS Catal.Catalytic Enantioselective Synthesis of a cis-beta-Boronyl CyClobutylcarboxyester Scaffold and Its Highly Diastereoselective Nickel/Photoredox Dual-Catalyzed Csp(3)-Csp(2) Cross-Coupling to Access Elusive trans-beta-Aryl/HeteroAryl CyClobutylcarboxyesters (vol 11, pg 404, 2021)Photocatalyst020213#N/AFALSE
5395
acscatal.1c0122310.1021/acscatal.1c01223FALSEhttps://doi.org/10.1021/acscatal.1c01223Sasmaz, EACS Catal.Herein, we report a highly carbon resistant nanotubular yolk-shell Pt-NiCe@SiO2 single-atom-alloy (SAA) catalyst for low-temperature dry reforming of methane (DRM). A synergetic combination of the confined yolk-shell morphology and Pt-Ni SAA structures prevents carbon formation and provides excellent catalyst stability. The confined morphology of the yolk-shell structures can impede carbon deposition due to the facile CO desorption from the surface. Carbon formation can be further minimized by 0.25 wt % Pt promotion, showing an excellent stability for 120 h during DRM at 500 degrees C. The enhanced stability of the Pe(0.25)-NiCe@SiO2 catalyst can be attributed to the atomically dispersed Pt on the yolks forming Pt-Ni SAA structures encapsulated by a nanotubular SiO2 shell. The Pt-Ni SAA facilitates Pt-Ni interactions and enhances the reducibility of the Ni species, which further suppresses carbon formation during DRM. The developed bifunctional catalyst exhibits excellent resistance to coking by decreasing the effect of both main carbon formation reactions: i.e., CO disproportionation and CH4 decomposition. When the Pt loading is increased above 0.25 wt %, Pt nanopartiCles form, leading to oligomerization of C-H species. Our results show that advantageous effects of both confined morphology and Pt-Ni SAA structures can lower the operating temperature of DRM without showing any catalyst deActivation.Yolk-Shell Pt-NiCe@SiO2 Single-Atom-Alloy Catalysts for Low-Temperature Dry Reforming of Methanesingle-atom alloy; yolk-shell; dry reforming of methane; syngas; catalystx0202173#N/AFALSE
5396
acscatal.5b0160810.1021/acscatal.5b01608FALSEhttps://doi.org/10.1021/acscatal.7b01495Zhong, CJComposition-Structure-Activity Relationships for Palladium-Alloyed Nanocatalysts in Oxygen Reduction Reaction: An Ex-Situ/In-Situ High Energy X-ray Diffraction Study2015#N/ATRUE
5397
acscatal.5b0149010.1021/acscatal.5b01490https://doi.org/10.1021/acscatal.5b01490Chen, ClACS Catal.The synthesis, characterization, and olefin (co)-polymerization studies of a series of palladium complexes bearing phosphine phosphonic amide ligands were investigated. In this ligand framework, substituents on three positions could be modulated independently, which distinguishes this Class of ligand and provides a great deal of flexibilities and opportunities to tune the catalytic properties. The palladium complex with an o-MeO-Ph substituent on phosphine is one of the most active palladium catalysts in ethylene polymerization, with 1 order of magnitude higher activity than the corresponding Classic phosphine-sulfonate palladium complex. Meanwhile, the polyethylene generated by this new palladium complex showed ca. 6 times higher molecular weight in comparison to that by the Classic phosphine-sulfonate palladium complex. In ethylene/methyl acrylate copolymerization, the new palladium complex showed lower activity, generating copolymer with similar methyl acrylate incorporation and much higher molecular weight. The new palladium complex was also able to copolymerize ethylene with other polar monomers, inCluding butyl Vinyl ether and allyl acetate, making it one of the very few catalyst systems that can copolymerize ethylene with multiple industrially relevant polar monomers.Ethylene Polymerization and Copolymerization with Polar Monomers by Cationic Phosphine Phosphonic Amide Palladium Complexesolefin polymerization; palladium; phosphine ligands; copolymerization; polar monomer108201563#N/ATRUE
5398
acscatal.1c0077810.1021/acscatal.1c00778https://doi.org/10.1021/acscatal.1c00778Mecking, SACS Catal.A direct comparison between neutral active sites and their corresponding cationic analogues is enabled by protonation of neutral bis(imino)phenoxy complexes, active for ethylene polymerization. The additional imine motif compared to parent salicylaldiminato catalysts does not influence the microstructure of the products in ethylene polymerization, but allows for the incorporation of a proton right next to the active center in an N center dot center dot center dot H+center dot center dot center dot O bridge yielding cationic complexes. These show an increased Ni-O bond length and a drastically reduced electron density on the Ni atom. In pressure reactor experiments, two different catalysts that produce linear HDPE or undergo extensive chain walking, respectively, in their neutral version, both produce short chain oligomers when the catalyst is charged cationically. A mechanistic analysis by DFT methods reveals an increased propensity for beta-hydride elimination compared to ethylene insertion chain growth for the cationic complexes. This results from a higher relative stability of beta-agostic species vs olefin-coordinated species.The Impact of Charge in a Ni(II) Polymerization Catalystethylene polymerization; protonation; neutral catalyst; cationic catalyst; charge; microstructurex0202143#N/AFALSE
5399
acscatal.5b0115210.1021/acscatal.5b01152FALSEhttps://doi.org/10.1021/acscatal.5b01152Raugei, SACS Catal.Design of fast, efficient electrocatalysts for energy production and energy utilization requires a systematic approach to predict and tune the energetics of reaction intermediates and the kinetic barriers between them as well as to tune reaction conditions (e.g., concentration of reactants, acidity of the reaction medium, and applied electric potential). Thermodynamics schemes based on the knowledge of pK(a) values, hydride donor ability, redox potentials, and other relevant thermodynamic properties have been demonstrated to be very effective for exploring possible reaction pathways. We seek to identify high-energy intermediates, which may represent a catalytic bottleneck, and low-energy intermediates, which may represent a thermodynamic sink. In this study, working on a well-established Ni-based bioinspired electrocatalyst for H-2 production, we performed a detailed kinetic analysis of the catalytic pathways to assess the limitations of our current (standard state) thermodynamic analysis with respect to prediction of optimal catalyst performance. To this end, we developed a microkinetic model based on extensive ab initio simulations. The model was validated against available experimental data, and it reproduces remarkably well the observed turnover rate as a function of the acid concentration and catalytic conditions, providing valuable information on the main factors limiting catalysis. Using this kinetic analysis as a reference, we show that indeed a purely thermodynamic analysis of the possible reaction pathways provides us with valuable information, such as a qualitative picture of the species involved during catalysis, identification of the possible branching points, and the origin of the observed overpotential, which are critical insights for electrocatalyst design. However, a significant limitation of this approach is understanding how these insights relate to rate, which is an equally critical piece of information. Taking our analysis a step further, we show that the kinetic model can easily be extended to different catalytic conditions by using linear free energy relationships for Activation barriers based on simple thermodynamics quantities, such as pKa values. We also outline a possible procedure to extend it to other catalytic platforms, making it a general and effective way to design catalysts with improved performance.Ab lnitio-Based Kinetic Modeling for the Design of Molecular Catalysts: The Case of H-2 Production Electrocatalystselectrocatalysis; H-2 production; ab initio calculations; molecular dynamics; free energy simulations; microkinetic modeling272015103#N/ATRUE
5400
acscatal.5b0107510.1021/acscatal.5b01075FALSEhttps://doi.org/10.1021/acscatal.5b01075Houk, KNComputational Exploration of Mechanism and Selectivities of (NHC)Nickel(II)hydride-Catalyzed Hydroalkenylations of Styrene with alpha-Olefins2015#N/ATRUE
5401
acscatal.5b0038310.1021/acscatal.5b00383FALSEhttps://doi.org/10.1021/acscatal.5b00383Hulea, VACS Catal.An original method for converting ethylene to propylene involving cascade oligomerization/isomerization/metathesis reactions over two robust and highly active heterogeneous catalysts is investigated. In a single flow reactor and under identical conditions, ethylene was first selectively dimerized/isomerized over Ni-AlSBA-15 catalyst to form 2-butenes, which reacted then with the excess of ethylene over MoO3-SiO2-Al2O3 to produce propylene. At 80 degrees C and 3 MPa, specific activities up to 48 mmol of propylene per gram of catalyst per hour were obtained.Ethylene to Propylene by One-Pot Catalytic Cascade Reactionstandem catalysis; heterogeneous catalysis; oligomerization; metathesis; Al-SBA-15; nonhydrolytic sol-gel31201537#N/ATRUE
5402
acscatal.1c0073110.1021/acscatal.1c00731https://doi.org/10.1021/acscatal.1c00731Bao, XGACS Catal.The construction of C(sp(3))-N bonds via direct radical-radical cross-coupling under benign conditions is a desirable but challenging approach. Herein, the cross-coupling of Alkyl and amidyl radicals to build aliphatic C-N bonds in a concise, mild, and oxidant-free manner is implemented by nickel/photoredox dual catalysis. In this protocol, the single electron transfer strategy is successfully employed to generate N- and C-centered radicals from sulfonyl azides/azidoformates and AlkyltrifluorB(OH)2rates, respectively. The photocatalyst-induced triplet-triplet energy-transfer mechanism, however, might not be applicable to this reaction. The oxidative quenching pathway of the excited photocatalyst (Ru-II/*Ru-II/Ru-III/Ru-II) combined with a possible Ni-I/Ni-II/Ni-III/Ni-I catalytic cyCle is proposed to account for the nickel/photoredox dual-catalyzed C(sp(3))-N bond formation based on synergistic experimental and computational studies.Nickel/Photoredox Dual Catalytic Cross-Coupling of Alkyl and Amidyl Radicals to Construct C(sp(3))-N Bondsphotoredox; nickel catalysis; radicals; amidation; mechanism; DFT calculationPhotocatalyst0202157#N/AFALSE
5403
acscatal.1c0053110.1021/acscatal.1c00531FALSEhttps://doi.org/10.1021/acscatal.1c00531Sigman, MSACS Catal.Multivariate linear regression (MLR) analysis is used to unify and correlate different categories of asymmetric Cubisoxazoline (box) catalysis. The versatility of Cu-box complexes has been leveraged for several types of enantioselective transformations inCluding cyClopropanation, Diels-Alder cyCloadditions, and difunctionalization of alkenes. Statistical tools and extensive molecular featurization have guided the development of an inClusive linear regression model, providing a predictive platform and readily interpretable descriptors. Mechanism-specific categorization of curated data sets and parameterization of reaction components allow for simultaneous analysis of disparate organometallic intermediates such as carbenes and Lewis acid adducts, all unified by a common ligand scaffold and metal ion. Additionally, this workflow permitted the development of a complementary linear regression model correlating analogous box-catalyzed reactions employing Ni, Fe, Mg, and Pd complexes. Comparison of ligand parameters in each model reveals the relevant structural requirements necessary for high selectivity. Overall, this strategy highlights the utility of MLR analysis in exploring mechanistically driven correlations across a diverse chemical space in organometallic chemistry and presents an applicable workflow for related ligand Classes.Linear Regression Model Development for Analysis of Asymmetric Copper-Bisoxazoline Catalysisasymmetric catalysis; copper; bisoxazoline; data science; carbene; Lewis acid; radicalx1202139#N/AFALSE
5404
acscatal.5b0036510.1021/acscatal.5b00365FALSEhttps://doi.org/10.1021/acscatal.5b00365Guo, GCACS Catal.The catalytic performances of supported Pd nanopartiCles (NPs) are strongly dependent on the support materials for CO oxidative coupling to dimethyl oxalate (DMO). Herein, hierarchical flower-like ZnO microspheres composed of porous nanosheets are employed as a new support material for a Pd catalyst, which exhibits excellent catalytic activity for CO oxidative coupling to DMO. The conversion of CO and the selectivity to DMO reach up to 67% and 98% at 130 degrees C, respectively. Unfortunately, the high activity of Pd/ZnO catalyst gradually deteriorates within 100 h. To resolve the poor stability, we further introduce Mg2+ ions into the ZnO support. It is exciting that the catalytic activity of the Mg2+-doped-ZnO-supported Pd nanocatalyst (Pd/Mg-ZnO) can be maintained for at least 100 h without obvious decay. Catalytic stability is greatly improved by the doping of Mg2+ ions. XRD, UV-visible diffuse reflectance spectra, and high-angle annular dark field scanning transmission electron microscopy characterizations demonstrate that a small portion of Mg2+ ions are successfully incorporated into the lattice of the ZnO support to form a Zn-Mg oxide solid solution. XPS, in situ diffuse reflectance Fourier transform infrared spectroscopy, and H-2-temperature-programmed reduction results reveal that the introduction of Mg2+ ions into the ZnO support leads to a strong metalsupport interaction caused by electron transfer from the ZnO substrate to the Pd NPs, which can effectively restrain the sintering of the active Pd NPs; retard the growth of Pd NPs; and thus, enhance the catalytic stability.Enhanced Stability of Pd/ZnO Catalyst for CO Oxidative Coupling to Dimethyl Oxalate: Effect of Mg2+ DopingMg2+ doping; Pd/ZnO; coal to ethylene glycol (CTEG); CO oxidative coupling; dimethyl oxalate50201556#N/ATRUE
5405
acscatal.1c0021810.1021/acscatal.1c00218FALSEhttps://doi.org/10.1021/acscatal.1c00218Shu, XZACS Catal.( )Earth-abundant transition metals, such as iron, nickel, copper, molybdenum, and vanadium, have been identified as essential constituents of the cellular gas metabolism in all kingdoms of life. Associated with biological macromolecules, gas-processing metalloenzymes (GPMs) are formed that catalyze a variety of redox reactions. This inCludes the reduction of O-2 to water by cytochrome c oxidase (complex IV), the reduction of N-2 to NH3 by nitrogenase, as well as the reversible reduction of protons to H(2 )by hydrogenase. GPMs perform at ambient temperature and pressure, in the presence of water, and often extremely low educt concentrations, thus serving as natural examples for efficient catalysis. Facilitating the design of biomimetic catalysts, biophysicist thrive to understand the reaction principles of GPMs making use of various techniques. In this Perspective, I will introduce Fourier-transform infrared spectroscopy in attenuated total reflection configuration (ATR FTIR) for the analysis of GPMs like cytochrome c oxidase, nitrogenase, and hydrogenase. Infrared spectroscopy provides information about the geometry and redox state of the catalytic cofactors, the protonation state of amino acid residues, the hydrogen-bonding network, and protein structural changes. I developed an approach to probe and trigger the reaction of GPMs by gas exchange and deuteration experiments exploring the reactivity of these enzymes with their natural reactants. This allows recording sensitive steady-state ATR FTIR (difference) spectra with seconds time resolution. Finally yet importantly, infrared spectroscopy is an electronically noninvasive technique that allows investigating protein samples under biologically relevant conditions, that is, at ambient temperature, ambient pressure, and in the presence of liquid water.In Situ Infrared Spectroscopy for the Analysis of Gas-processing MetalloenzymesFTIR spectroscopy; metalloenzymes; transition metals; biocatalysisx02021152#N/AFALSE
5406
acscatal.1c0021410.1021/acscatal.1c00214FALSEhttps://doi.org/10.1021/acscatal.1c00214Pentcheva, RACS Catal.Using density functional theory calculations with an on-site Hubbard U term, we study the oxygen evolution reaction (OER) at the Co3O4(001) surface. The stability of different surface terminations as a function of oxygen partial pressure as well as pH and applied voltage is compiled in a Pourbaix diagram. The termination with octahedral Co and O ions (B-layer) is found to have the lowest overpotential of 0.46 V for an octahedral Co reaction site, associated with its p-type conducting character and the higher oxidation state of the active site (+4) during OER Furthermore, we systematically investigated the effect of Fe and Ni doping on the overpotential. Our results indicate that Ni doping at an octahedral site in the surface layer reduces the overpotential from 0.46 to 0.34 V. Likewise, Fe doping at an octahedral site at the tetrahedral Co termination (A-layer) lowers eta from 0.63 to 0.37 V with octahedral Co remaining in the active site. We note that the potential determining step changes from *OH (B-layer) to *<b>OOH formation (A-layer). While implicit solvation increases the overpotential by 0.2 V (B-layer) and 0.4 V (A-layer), which is attributed to enhanced binding energies of the intermediates, the general trends with respect to doping remain unchanged. The scaling relationship of the binding energies of *OOH and *OH is overall satisfied, with the doped systems lying Close to the top of the volcano plot of the overpotential versus (Delta G*(b)(O) - Delta G*(b)(OH)). A further insight into the origin of this behavior is gained by analyzing the changes in oxidation states of surface ions and, in particular, the Co active site during OER.Influence of Fe and Ni Doping on the OER Performance at the Co3O4(001) Surface: Insights from DFT plus U Calculationscobalt oxide; oxygen evolution reaction; water splitting; density functional theory; implicit solvation; transition metal oxides; spinel surfaces; Pourbaix diagramx3202176#N/AFALSE
5407
acscatal.1c0020910.1021/acscatal.1c00209FALSEhttps://doi.org/10.1021/acscatal.1c00209Canivet, JACS Catal.Direct C-H functionalization catalyzed by a robust and recyClable heterogeneous catalyst is highly desirable for sustainable fine chemical synthesis. Bipyridine units covalently incorporated into the backbone of a porous organic polymer were used as a porous macroligand for the heterogenization of a molecular nickel catalyst. A controlled nickel loading within the porous macroligand is achieved, and the nickel coordination to the bipyridine (bpy) sites is assessed at the molecular level using IR and solid-state NMR spectroscopy. The heterogenized Ni-bpy catalyst was successfully applied to the direct and fully selective C2 Arylation of benzothiophenes, thiophene, and selenophene, as well as for the Arylation of free NH-indole. RecyClability of the catalyst was achieved by employing hydride activators to reach a cumulative turnover number of more than 300 after seven cyCles of catalysis, which corresponds to a total productivity of 12 g of 2-phenylbenzothiophene, chosen as model target biAryl, per gram of catalyst.Heterogenization of a Molecular Ni Catalyst within a Porous Macroligand for the Direct C-H Arylation of Heteroarenesporous polymers; macroligand; nickel complex; cross-coupling; heterobiAryl; C-H Arylation; LiHMDSx3202168#N/AFALSE
5408
acscatal.5b0014310.1021/acscatal.5b00143FALSEhttps://doi.org/10.1021/acscatal.5b00143Zhang, TACS Catal.Hydrous hydrazine is identified as a hydrogen reservoir owing to its high content of hydrogen (8.0 wt %). Its selective decomposition under mild conditions is the key for quick H-2 release. Modifying Ni nanopartiCles with a small amount of CeO2 (8.0 mol %) resulted in a 3-fold increase of turnover frequency (TOF) and an enhancement of H-2 selectivity from 67% to above 99%. This improvement was due to the modification of Ni with CeO2 nearby through strong metal-support interaction (e.g., Ni-O-Ce structure). Furthermore, this promoting effect was extended to other oxides which can form strong metal-support interaction with Ni, such as ZrO2, MgO, and La2O3.Cerium-Oxide-Modified Nickel as a Non-Noble Metal Catalyst for Selective Decomposition of Hydrous Hydrazine to Hydrogenhydrogen generation; hydrous hydrazine; non-noble metal Ni-CeO2; Ni-O-Ce97201552#N/ATRUE
5409
acscatal.1c0011010.1021/acscatal.1c00110FALSEhttps://doi.org/10.1021/acscatal.1c00110Waterhouse, GINACS Catal.Discovering highly active and stable electrocatalysts for the oxygen evolution reaction (OER) is critical to the commercial development of many next-generation energy conversion and storage devices, with Fe-doped nickel (oxy)hydroxide representing one of the most promising OER catalysts developed to date. However, the active sites and mechanism of OER on Fe-doped nickel (oxy)hydroxide catalysts remain unClear. To gain deeper insights into the role of metal dopants in enhancing OER activity, we explored here the role of Ir-doping in the OER performance of nickel (oxy)hydroxide catalysts, placing particular emphasis on the nature of the active site. Density functional theory calculations with Hubbard U correction revealed that Ir-doping of a beta-NiOOH(001) surface enhanced the electric conductivity while also activating an oxygen site involving three Ni atoms (Ni-3 site) to realize a remarkably low OER overpotential of only eta = 0.46 V, much lower than the overpotential on the oxygen site involving Ir + two Ni atoms (IrNi2 site, eta = 0.77 V) or the oxygen site involving three Ni atoms in pristine beta-NiOOH (eta = 0.66 V). Guided by the computational results, ultrathin Ir-doped Ni(OH)(2) nanosheets were then fabricated through a combination of hydrothermal assembly and liquid exfoliation, with the nanosheets transforming to Ir-doped NiOOH during OER and offering superior activity relative to pristine Ni(OH)(2) nanosheets or a commercial IrO2 catalyst, thereby validating the theoretical predictions. The computational and experimental results thus conClusively demonstrate that Ir-doping and nanosheet engineering are synergistic strategies for tuning the electronic and structural properties of nickel (oxy)hydroxides for improved oxygen evolution electrocatalysis.Structural and Electronic Engineering of Ir-Doped Ni-(Oxy)hydroxide Nanosheets for Enhanced Oxygen Evolution Activityiridium doping; nickel oxyhydroxide; oxygen evolution reaction; electrocatalyst; active sitex3202164#N/AFALSE
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acscatal.0c0569410.1021/acscatal.0c05694https://doi.org/10.1021/acscatal.0c05694Konig, BACS Catal.Graphitic carbon nitride materials have attracted significant interest in recent years and found applications in diverse light-to-energy conversions such as artificial photosynthesis, CO2 reduction, or degradation of organic pollutants. However, their utilization in synthetic photocatalysis, especially in the direct functionalization of C(sp(3))-H bonds, remains underexplored. Herein, we report mesoporous graphitic carbon nitride (mpg-CN as a heterogeneous organic semiconductor photocatalyst for direct Arylation of C(sp(3))-H bonds in combination with nickel catalysis. Our protocol has a broad synthetic scope (>70 examples inCluding late-stage functionalization of drugs and agrochemicals), is operationally simple, and shows high chemo- and regioselectivities. Facile separation and recyCling of the mpg-CN catalyst in combination with its low preparation cost, innate photochemical stability, and low toxicity are beneficial features overcoming typical shortcomings of homogeneous photocatalysis. Detailed mechanistic investigations and kinetic studies indicate that an unprecedented energy-transfer process (EnT) from the organic semiconductor to the nickel complex is operating.Photocatalytic (Het)Arylation of C(sp(3))-H Bonds with Carbon Nitrideheterogeneous photocatalysis; carbon nitride; hydrogen atom transfer; C(sp(3))-H Arylation; dual photo nickel; drug molecule functionalizationPhotocatalyst32021746/1/2022FALSE
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acscatal.0c0546810.1021/acscatal.0c05468FALSEhttps://doi.org/10.1021/acscatal.0c05468Wang, XACS Catal.Cr cation doping in the support of the Ru/CeO2 catalyst with a Cr/Ce molar ratio of 1:9 dramatically improved the CO2 methanation activity at low temperatures, with the turnover frequency value on Ru/Ce0.9Cr0.1Ox at 150 degrees C being 5.3 times higher than that on Ru/CeO2. X-ray diffraction and Raman spectroscopy results confirmed the Cr3+ doping in the lattice of the CeO2 support. Thus, more reactive surface oxygen formed on the Ce0.9Cr0.1Ox support, and the Ru/Ce0.9Cr0.1Ox catalyst contained more oxygen vacancies and hydroxyl groups during the reduction process than the Ru/CeO2 catalyst. In situ Fourier transform infrared spectroscopy and temperature-programed surface reaction revealed that CO2 methanation on both Ru/Ce0.9Cr0.1Ox and Ru/CeO2 catalysts followed the formate and CO* pathways, with the former being dominant at low temperatures. The formate pathway was identified, in which CO2 interacted with surface hydroxyl groups to produce adsorbed bicarbonates; then, the bicarbonates were further converted to formates, followed by the formation of CH4*. Cr3+ doping increased the number of surface oxygen vacancies and hydroxyl groups, thus increasing the amount of bicarbonates and formates. Consequently, Cr doping strongly promoted the formate pathway, greatly improving the activity of the Ru/Ce(0.9)Cr(0.1)O(x )catalyst at low temperatures.Facile Cr3+-Doping Strategy Dramatically Promoting Ru/CeO2 for Low-Temperature CO2 Methanation: Unraveling the Roles of Surface Oxygen Vacancies and Hydroxyl Groupsx0202152#N/AFALSE
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acscatal.0c0543710.1021/acscatal.0c05437FALSEhttps://doi.org/10.1021/acscatal.0c05437Cavazza, CACS Catal.Carbon monoxide dehydrogenase catalyzes the reversible oxidation of CO to CO2. The monofunctional enzyme from Rhodospirillum rubrum (RrCODH) has been extensively characterized in the past, although its use and investigation by bioelectrochemistry have been limited. Here, we developed a heterologous system yielding a highly stable and active recombinant RrCODH in one-step purification, with CO oxidation activity reaching a maximum of 26 500 U.mg(-1), making RrCODH the most active CODH under ambient conditions described so far. Electron paramagnetic resonance was used to precisely characterize the recombinant RrCODH, demonstrating the integrity of the active site. Selective CO2/CO interconversion with maximum turnover frequencies of 150 s(-1) for CO oxidation (1.5 mA cm(-2) at 250 mV overpotential) and 420 s(-1) for CO2 reduction (4.2 mA cm(-2) at 180 mV overpotential) is catalyzed by the recombinant RrCODH immobilized on MWCNT electrodes modified with 1-pyrenebutyric acid adamantyl amide (MWCNTADA), either in a Classic three-electrode cell or in specifically designed CO2/CO-diffusing electrodes. This functional device is stable for hours with a turnover number of at least 800 000. The performances of recombinant RrCODH-modified MWCNTADA are Close to the best metal-based and molecular-based catalysts. These results greatly increase the benchmark for bioelectrocatalysis of reversible CO2 conversion.Efficient Electrochemical CO2/CO Interconversion by an Engineered Carbon Monoxide Dehydrogenase on a Gas-Diffusion Carbon Nanotube-Based Bioelectrodex0202161#N/AFALSE
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acscatal.0c0515710.1021/acscatal.0c05157FALSEhttps://doi.org/10.1021/acscatal.0c05157Kakinuma, KACS Catal.We have examined the temperature dependence of the activities for the oxygen reduction reaction (ORR) at Pt catalysts supported on Nb-doped SnO2 (Pt/Nb-SnO2) in 0.1 M HClO4. The apparent rate constants (k(app)) for the ORR have been evaluated from 20 to 80 degrees C. The k(app) values increased with increasing temperature, and at each temperature, k(app) was also observed to increase with a higher loading amount of Pt on the Nb-SnO2 support (from 17.4 to 34.2 wt %). The Pt partiCles tended to coalesce and form nanorods with preferential growth of (111) planes when the Pt loading was increased. This is proposed to render the surface geometry favorable for the ORR, as explained by density functional theory (DFT) calculations. The high-weight-percent catalyst also showed higher Pt mass activity, making it possible to reduce the cathode Pt loading while maintaining high fuel cell performance. The apparent Activation energy of the ORR was found to be virtually independent of Pt loading on the Nb-SnO2, with values of 15-19 kJ mol(-1). The activity enhancement is explained by an increase in the pre-exponential factor of the Arrhenius equation, which could be related to the increased exposure of the (111)-like facets, which provide an optimum platform for O-2 adsorption, together with facile desorption of OHad. The durability was assessed in a high-temperature acid electrolyte, similar to that in an actual fuel cell. The test involved potential steps between 0.6 and 1.0 V in O-2-saturated 0.1 M HClO4 at 80 degrees C. The ORR mass activity (@0.9 V) of Pt/Nb-SnO2 (34.2 wt %-Pt) after 3000 cyCles showed only a small loss, 13%, and the retained value was 2.6 times higher than that of a commercial Pt/C catalyst, which experienced a much larger loss of 41%.Temperature Dependence of Oxygen Reduction Activity at Pt/Nb-Doped SnO2 Catalysts with Varied Pt Loadingfuel cell; cathode; tin oxide; electrocatalysis; oxygen reduction reactionx0202150#N/AFALSE
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acscatal.1c0171810.1021/acscatal.1c01718FALSEhttps://doi.org/10.1021/acscatal.1c01718Li, DQACS Catal.The efficiency of a heterogeneous catalyst depends on the nature and the number of catalytically active sites, but these are often inhomogeneous. One possible solution is to construct site-isolated catalysts in which most, if not all, of the sites are structurally uniform and well-defined. Metal phosphides and sulfides form with distinct crystal structures based on a range of component stoichiometries. Hence, incorporating active components (i.e., the catalytically active metal) into this structure can regulate geometric arrangements in a more reproducible manner where nonmetal atoms act as spacers around metal atoms to create isolated sites. A d-metal/p-block element strategy can provide several advantages compared with other methods which generate discrete active sites, inCluding convenient synthesis, good process economics, and improved catalyst stability. Interestingly, the metal atoms in these systems still show typical catalyst traits associated with the metal which opens up many possible catalytic applications. This Review presents several interesting synthesis methods for preparing metal phosphides and sulfides and aims to draw links between geometric structure/electronic properties and enhanced catalytic performance (i.e., enhanced activity, selectivity, and stability) for both petrochemical and fine chemical processes. With precise knowledge of metal phosphide and sulfide structures/active sites, we envision the development of practically useful d-metal/p-block element catalysts from powder formulations to more industrial type pellets. It should, however, be noted that these materials are not without additional complexities. For example, metal phosphides and sulfides can have complex surface chemistry and the operating environment can induce structural evolution. These factors also need to be carefully considered.Metal Phosphides and Sulfides in Heterogeneous Catalysis: Electronic and Geometric Effectssite isolation; d-metal/p-block elements; metal sulfides; metal phosphides; heterogeneous catalysis02021235#N/ATRUE
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acscatal.1c0164610.1021/acscatal.1c01646FALSEhttps://doi.org/10.1021/acscatal.1c01646Hosono, HC-2 Vacancy-Mediated N-2 Activation over Ni-Loaded Rare-Earth Dicarbides for Ammonia Synthesis2021#N/ATRUE
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acscatal.0c0489410.1021/acscatal.0c04894FALSEhttps://doi.org/10.1021/acscatal.0c04894Brueckner, AACS Catal.A series of supported Ni/SiO2-Al2O3 catalysts with the same Ni content but different ratios of Bronsted and Lewis acid sites resulting from different Al/Si ratios have been prepared by impregnation with Ni(Cp)(2) and analyzed by operando electron paramagnetic resonance (EPR) during dimerization of n-butenes under industrially relevant conditions as well as by in situ Fourier transform infrared (FTIR) spectroscopy of adsorbed pyridine and CO to derive relations between the surface acidic properties, the nature of the Ni sites, and the catalytic performance. 'While EPR monitored the formation of different Ni+ single sites as well as ferromagnetic Ni Clusters, it is silent for Ni2+. To compensate for this lack, FTIR spectroscopy of adsorbed CO was used to analyze the relative number and distribution of Ni single sites in both valence states of +1 and +2. This method was also used to analyze the relative number of Bronsted and Lewis acid sites exposed on the surface. Thus, a comprehensive picture on the formation of different Ni surface sites and their role for catalytic performance could be derived. It was found that Brmnsted sites have both a positive and negative effect: (1) they stabilize active Ni single species while Lewis sites do not play a significant role for catalytic performance; (2) they promote undesired branching of C-8 products. Thus, optimum catalysts should contain a maximum number of single Ni sites in the immediate vicinity of Bronsted surface sites, while an excess of the latter must be avoided to suppress isomerization.Role of Surface Acidity in Formation and Performance of Active Ni Single Sites in Supported Catalysts for Butene Dimerization: A View inside by Operando EPR and In Situ FTIR Spectroscopysupported Ni catalysts; butene dimerization; surface acidity; operando EPR; in situ FTIRx1202142#N/AFALSE
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acscatal.1c0145510.1021/acscatal.1c01455FALSEhttps://doi.org/10.1021/acscatal.1c01455Tao, FCoordination Number-Dependent Complete Oxidation of Methane on NiO Catalysts2021#N/ATRUE
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acscatal.1c0141910.1021/acscatal.1c01419FALSEhttps://doi.org/10.1021/acscatal.1c01419Machida, MACS Catal.This study aims to Clarify the effect of Ni addition on the enhancement of the NO reduction activity of Cu/Al2O3, which possesses high thermal durability, and to elucidate the associated structure-catalysis relationship. Thermal aging of Ni and Cu supported on gamma-Al2O3 at a high temperature (900 degrees C) induced the formation of a pseudo-spinel (NiCu)Al2O4 solid solution on the gamma-Al2O3 surface, which was observed using X-ray diffraction and high-angle annular dark-field scanning transmission electron microscopy techniques. Owing to the co-presence of Ni, the preferential occupation of octahedral sites by Ni increased the number of tetrahedrally coordinated Cu2+ ions, which played a key role in the reduction of NO in a stoichiometric NO-CO-C3H6-O-2 reaction. XPS analysis revealed that Cu active sites with electron-rich states were formed in pseudo-spinel (NiCu)Al2O4 owing to electron donation from Ni to Cu, which promoted NO adsorption on Cu+ and accelerated NO reduction. The tetrahedrally coordinated Cu formed on the pseudo-spinel oxide was structurally robust, and its local structure remained unchanged even after the redox cyCle occurred at a high temperature; this indicated that the formation of pseudo-spinel (NiCu)Al2O4 was effective for the enhancement of NO reduction activity and thermal durability.Enhanced Catalytic NO Reduction in NO-CO-C3H6-O-2 Reaction Using Pseudo-Spinel (NiCu)Al2O4 Supported on gamma-Al2O3nickel; copper; pseudo-spinel oxide; three-way catalyst; NO reduction0202141#N/ATRUE
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acscatal.1c0108810.1021/acscatal.1c01088FALSEhttps://doi.org/10.1021/acscatal.1c01088Kyriakidou, EAACS Catal.Catalytic oxidation of methane (CH4) over nonprecious Ni/CeO2 catalysts has received a lot of attention due to the large natural gas reserves found in North America and the prohibitive cost of palladium-based catalysts, commonly used for CH4 oxidation. However, the catalytic mechanism of CH4 oxidation over Ni/CeO2 still remains unClear. Moreover, the parameters affecting the reaction rates, the interaction between nickel and CeO2, and the reaction intermediates are still not well understood. Herein, kinetic model fitting, CH4 temperature-programmed reductionmass spectroscopy (CH4 TPR-MS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory (DFT) calculations were combined to elucidate the mechanism of complete oxidation of CH4 over Ni/CeO2. CH4 TPR-MS showed that the complete oxidation of CH4 over Ni/CeO2 requires 55-120 degrees C lower compared to bare CeO2 or Ni/quartz sand; complete oxidation of CH4 took place when the surface oxygen species were abundant, while partial oxidation products (CO, H-2) were formed when the oxygen species were depleted. In situ DRIFTS showed that CH3, CH2, CO, and CO2 were formed after CH4 Activation over Ni/CeO2, while CH3O species were not observed. Combining those findings with kinetic model fitting, a redox Mars-van Krevelen (MvK) mechanism showed the best description of the experimental observations. The MvK mechanism involves the reaction of dissociated oxygen species with gas-phase CH4 while water inhibits the reaction rate by adsorbing on the oxidized sites. Moreover, CH4 Activation leads to the reduction of the active sites and oxygen vacancy formation followed by reoxidation of the active sites by gas-phase O-2. A CH4 oxidation reaction pathway over Ni/CeO2 is proposed by DFT calculations. In summary, the findings shown here suggest that CH4 oxidation over Ni/CeO2 follows a redox MvK mechanism and provides guidance for the rational design of non-precious-metal catalysts for CH4 oxidation reactions.Mechanistic Understanding of Methane Combustion over Ni/CeO2: A Combined Experimental and Theoretical Approachmethane oxidation; nickel; ceria; kinetic study; DFT; Mars-van Krevelen0202154#N/ATRUE
5420
acscatal.0c0472510.1021/acscatal.0c04725https://doi.org/10.1021/acscatal.0c04725Zhao, JCACS Catal.Light-driven dual catalysis that combines photosensitizers and transition-metal complexes has become a powerful approach for diverse cross-coupling reactions. Heterogeneous photocatalysts recently have gained growing attention to build such catalytic system for controllable reaction kinetics and enhanced activity. Incorporating a metal catalyst into the framework of the photocatalyst could endow unique metallaphotoredox platforms. Herein, we assemble carbon nitride and nickel (C3N4-Ni) via direct coordination of Ni2+ to C3N4 nitrogen, for visible-light-driven carbon-oxygen cross-coupling. By operating with an imidazole auxiliary ligand, C3N4-Ni efficiently catalyzed etherification of a variety of Aryl bromides with alcohols or hydroxylation with water, exhibiting turnover numbers of >500. Ni maintained as isolated single site without aggregation after photoreaction and the recovered catalyst demonstrate sustained activity without additional Ni loading. Our work signifies the potential of uniting dual catalysis in well-designed sensitizer-metal architecture for complex organic transformations.Nickel-Coordinated Carbon Nitride as a Metallaphotoredox Platform for the Cross-Coupling of Aryl Halides with Alcoholsmetallaphotoredox catalysis; cross coupling; metalated carbon nitride; nickel catalysis; heterogeneous catalystPhotocatalyst3202065#N/AFALSE
5421
acscatal.0c0461510.1021/acscatal.0c04615FALSEhttps://doi.org/10.1021/acscatal.0c04615Tomishige, KACS Catal.Metal-alloyed atomic catalysts such as single-atom alloys have attracted much attention due to their high atom economy and their unique catalytic properties. Recently, we found that a SiO2 -supported Ni-Ir alloy (Ni-Ir/SiO2) was an effective heterogeneous catalyst for the hydrogenation of styrene and that the isolated Ni atom surrounded by k metal atoms, an Ir-alloyed Ni single atom, in the Ni-Ir alloy was the main active site, showing much higher activity in comparison with the monometallic Ir/SiO(2 )and Ni/SiO2 . Reports on such effective metal-alloyed non-noble-metal single-atom catalysts are limited, and their catalytic potential should be Clarified. In this study, bimetallic catalysts composed of non-noble metals and noble metals were comprehensively scrutinized in the hydrogenation of styrene as a model reaction. Among various combinations, Ni-IrSiO2 (introduced Ni/Ir molar ratio 1) showed the largest rate enhancement (7-fold) in comparison with the monometallic counterpart catalysts, while a SiO2 -supported Co-Ir alloy (Co-Ir/SiO2, introduced Co/Ir molar ratio 4) and Ni-Pt alloy (Ni-Pt/SiO2, introduced Ni/Pt molar ratio 0.25) were also effective. The activity orders were Co-Ir/SiO2 > Ir/SiO2 > Co/SiO(2 )and Ni-Pt/SiO2 > Pt/SiO2 > Ni/SiO2, and the (Co-k/SiO2 )/(Ir/SiO2) and (Ni-Pt/SiO2)/(Pt/SiO2 ) activity ratios were 3.5 and 2.5, respectively. Moreover, Ni-Ir/SiO2 showed higher activity for the hydrogenation of various olefins in comparison to the monometallic Ir/SiO2 and Ni/SiO2 . The reaction mechanism of styrene hydrogenation over the Ir-alloyed Ni single atom of Ni-Ir/SiO2 was proposed on the basis of spectroscopic studies such as FTIR, XPS, and XRD, kinetic studies such as the effect of substrate concentration and H-2 pressure, the isotopic effect of hydrogen, and the effect of the reaction temperature, and DFT calculations. The rate-determining step is the second hydrogenation of the half-hydrogenated styrene adspecies on an Ni atom by H species on Ir atoms in the Horiuti-Polanyi mechanism. The single Ni atom in Ir metal atoms has two roles: (1) formation of the reactive half-hydrogenated styrene adspecies on Ni atom and (2) formation of the reactive H species on Ir atoms by the electron transfer from an Ni atom to Ir atoms. These roles resulted in a low Activation energy, leading to a large rate enhancement in comparison to the monometallic counterpart catalysts.Comprehensive Study on Ni- or Ir-Based Alloy Catalysts in the Hydrogenation of Olefins and Mechanistic Insighthydrogenation; olefin; alloy; nickel; iridium; DFT calculationx1202186#N/AFALSE
5422
acscatal.0c0452010.1021/acscatal.0c04520https://doi.org/10.1021/acscatal.0c04520Hall, DGACS Catal.Chiral cyClobutanes are components of numerous bioactive natural products, and consequently, they have also gained significant attention in medicinal chemistry. Optically enriched cyClobutylboronates can serve as valuable synthetic intermediates for the synthesis of a broad variety of chiral cyClobutanes through exploiting the versatility of the boronyl functionality. Herein, by using a high-throughput ligand screening approach, an efficient method for the asymmetric conjugate borylation of a cyClobutene 1-carboxyester was optimized, leading to a highly enantioenriched cis-beta-boronyl cyClobutylcarboxyester scaffold (99% ee, >20:1 dr). Of the 118 ligands screened, the Naud family of phosphine-oxazoline ligands was found to be the most effective. Computational modeling of the possible preinsertion complexes shows a large preference for the pi-bound Cu(I)-alkene complex where the substrate's large Benzhydryl ester occupies a relatively unhindered quadrant of the chiral ligand in a spatially tight environment that is highly specific for the cyClobutenoate substrate and imparts much lower selectivity with larger ring substrates. The cis diastereoselectivity is proposed to arise from a sterically controlled, irreversible protodecupration step. A highly diastereoselective nickel/photoredox dual-catalyzed Csp(3)-Csp(2) cross-coupling of the corresponding trifluorB(OH)2rate salt with Aryl/heteroAryl bromides and cyCloalkenyl nonaflates was developed, providing access to a wide diversity of trans-beta-Aryl/heteroAryl and cyCloalkenyl cyClobutylcarboxyesters with an excellent diastereoselectivity and high retention of optical purity (91-99% ee, >20:1 dr). AzaheterocyClic halides, which are notoriously challenging substrates in Pd-catalyzed cross-coupling, are successful with this Ni/photoredox manifold. A stereoconvergent model based on steric factors is proposed for the key carbon-carbon bond forming step, leading to a high diastereoselectivity. Despite the radical nature of the cross-coupling conditions, the flanking carboxyester proved to be a reliable chirality relay group to maintain the stereochemical integrity of the organB(OH)2ron intermediate. Furthermore, mild oxidation of the carbon-boron bond and extension of the catalytic asymmetric conjugate borylation reaction to a three-component aldol reaction with an aldehyde afford valuable enantioenriched cyClobutane products.Catalytic Enantioselective Synthesis of a cis-beta-Boronyl CyClobutylcarboxyester Scaffold and Its Highly Diastereoselective Nickel/Photoredox Dual-Catalyzed Csp(3)-Csp(2) Cross-Coupling to Access Elusive trans-beta-Aryl/HeteroAryl CyClobutylcarboxyesterschiral ligands; conjugate borylation; cross-coupling; cyClobutanes; diastereoselectivity; enantioselective catalysis; heterocyClesPhotocatalyst1202150#N/AFALSE
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acscatal.0c0445010.1021/acscatal.0c04450https://doi.org/10.1021/acscatal.0c04450Li, YSACS Catal.A series of methyl nickel complexes with phosphino-naphtholate chelate ligands have been strategically designed, synthesized, and fully characterized. These catalysts showed extremely high activity toward ethylene polymerization and ethylene/unsaturated acid ester copolymerization without any activator under mild conditions. The catalytic activity for ethylene polymerization was up to 3.0 x 10(7) gPE mol(Ni)(-1) h(-1), which was the topmost among the neutral nickel catalysts previously reported. Besides, the catalytic activity for ethylene/methyl acrylate (MA) copolymerization was also outstanding (up to 3.7 x 10(5) g mol(Ni)(-1) h(-1)) among the representative Ni and Pd catalytic systems, which could mediate E/MA copolymerization. More remarkably, a very challenging 1,1-disubstituted difunctional ethylene comonomer, dimethyl itaconate, was copolymerized with ethylene by these catalysts to give end-difunctional polyethylene with double ester groups and molecular weight up to 10 700 directly.Robust and Reactive Neutral Nickel Catalysts for Ethylene Polymerization and Copolymerization with a Challenging 1,1-Disubstituted Difunctional Polar Monomerneutral nickel catalysts; ethylene polymerization; polar monomer copolymerization; 1,1-disubstituted difunctional ethylene; coordination-insertion copolymerizationx2202155#N/AFALSE
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acscatal.1c0079610.1021/acscatal.1c00796FALSEhttps://doi.org/10.1021/acscatal.1c00796Abakumov, AMACS Catal.The La0.6Ca0.4Fe0.7Ni0.3O2.9 perovskite was synthesized using a modified ultrasonic spray pyrolysis technique with sorbitol as the fuel and ozone as the oxidizer, resulting in chemically homogeneous hollow spheres with a specific surface area as high as similar to 15 m(2) g(-1). The crystal structure and the chemical composition were determined with powder X-ray diffraction, electron diffraction, aberration-corrected scanning transmission electron microscopy, energy-dispersive X-ray mapping, Fe-57 Mossbauer spectroscopy, iodometric titration, and X-ray photoelectron spectroscopy. Being employed as a catalyst for the oxygen evolution reaction (OER) in 1 M NaOH, La0.6Ca0.4Fe0.7Ni0.3O2.9 demonstrates a mass activity of similar to 400 A g(oxide)(-1) at 1.61 V vs RHE and a low 52 +/- 2.6 my dec(-1) Tafel slope without noticeable degradation. The superior activity of La0.6Ca0.4Fe0.7Ni0.3O2.9 compared to that of undoped LaFe0.7Ni0.3O3 was rationalized by the comparison of DFT-calculated electronic structures. The Ca doping increases Ni and Fe oxidation states, enhances covalency of the Ni/Fe-O bonds, shifts the center of the O 2p band Closer to the Fermi level thus decreasing formation energy of the oxygen vacancies, and activates the lattice oxygen mechanism of the OER, which enhances the catalytic activity. Yet, an optimal balance between stability and activity ensures that the thin and stable active layer of Ni-Fe (oxy)hydroxide is supported by the preserved perovskite structure.Mixed-Cation Perovskite La0.6Ca0.4Fe0.7Ni0.3O2.9 as a Stable and Efficient Catalyst for the Oxygen Evolution Reactionspray pyrolysis; oxygen evolution reaction; water splitting; perovskite; lattice oxygen mechanism0202143#N/ATRUE
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acscatal.0c0437910.1021/acscatal.0c04379FALSEhttps://doi.org/10.1021/acscatal.0c04379Manna, KACS Catal.The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal-organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of Aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(mu(2)-OH)(bpdc) (bpdc = 4,4'-biphenyldiCarbonylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H-2 and could be recyCled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon-oxygen bonds in Aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.Aluminum Metal-Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysisnickel-hydride catalyst; metal-organic frameworks; hydrogenation; hydrogenolysis; chemoselectivityx0202184#N/AFALSE
5426
acscatal.0c0429010.1021/acscatal.0c04290FALSEhttps://doi.org/10.1021/acscatal.0c04290Penner, SACS Catal.The influence of A- and/or B-site doping of Ruddlesden-Popper perovskite materials on the crystal structure, stability, and dry reforming of methane (DRM) reactivity of specific A(2)BO(4) phases (A = La, Ba; B = Cu, Ni) has been evaluated by a combination of catalytic experiments, in situ X-ray diffraction, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and aberration-corrected electron microscopy. At room temperature, B-site doping of La2NiO4 with Cu stabilizes the orthorhombic structure (Fmmm) of the perovskite, while A-site doping with Ba yields a tetragonal space group (I4/mmm). We observed the orthorhombic-to-tetragonal transformation above 170 degrees C for La2Ni0.9Cu0.1O4 and La2Ni0.8Cu0.2O4, slightly higher than for undoped La2NiO4. Loss of oxygen in interstitial sites of the tetragonal structure causes further structure transformations for all samples before decomposition in the temperature range of 400 degrees C-600 degrees C. Controlled in situ decomposition of the parent or A/B-site doped perovskite structures in a DRM mixture (CH4:CO2 = 1:1) in all cases yields an active phase consisting of exsolved nanocrystalline metallic Ni partiCles in contact with hexagonal La2O3 and a mixture of (oxy)carbonate phases (hexagonal and monoClinic La2O2CO3, BaCO3). Differences in the catalytic activity evolve because of (i) the in situ formation of Ni-Cu alloy phases (in a composition of >7:1 = Ni:Cu) for La2Ni0.9Cu0.1O4, La2Ni0.8Cu0.2O4, and La1.8Ba0.2Ni0.9Cu0.1O4, (ii) the resulting Ni partiCle size and amount of exsolved Ni, and (iii) the inherently different reactivity of the present (oxy)carbonate species. Based on the onset temperature of catalytic DRM activity, the latter decreases in the order of La2Ni0.9Cu0.1O4 similar to La2Ni0.8Cu0.2O4 >= La1.8Ba0.2Ni0.9Cu0.1O4 >= La2NiO4 > La1.8Ba0.2NiO4. Simple A-site doped La1.8Ba0.2NiO4 is essentially DRM inactive. The Ni partiCle size can be efficiently influenced by introducing Ba into the A site of the respective Ruddlesden-Popper structures, allowing us to control the Ni partiCle size between 10 nm and 30 nm both for simple B-site and A-site doped structures. Hence, it is possible to steer both the extent of the metal-oxide-(oxy)carbonate interface and its chemical composition and reactivity. Counteracting the limitation of the larger Ni partiCle size, the activity can, however, be improved by additional Cu-doping on the B-site, enhancing the carbon reactivity. Exemplified for the La2NiO4 based systems, we show how the delicate antagonistic balance of doping with Cu (rendering the La2NiO4 structure less stable and suppressing coking by efficiently removing surface carbon) and Ba (rendering the La2NiO4 structure more stable and forming unreactive surface or interfacial carbonates) can be used to tailor prospective DRM-active catalysts.Steering the Methane Dry Reforming Reactivity of Ni/La2O3 Catalysts by Controlled In Situ Decomposition of Doped La2NiO4 Precursor Structuresin situ decomposition; perovskite; Ruddlesden-Popper phase; in situ X-ray diffraction; copper; phase transformationx3202165#N/AFALSE
5427
acscatal.0c0426910.1021/acscatal.0c04269FALSEhttps://doi.org/10.1021/acscatal.0c04269Gunanathan, CACS Catal.A ruthenium-catalyzed reaction of HBpin with substituted organic ethers leads to the Activation of C-O bonds, resulting in the formation of alkanes and boronate esters via hydrB(OH)2ronolysis. A ruthenium precatalyst, [Ru (p-cymene)Cl](2)Cl-2 (1), is employed, and the reactions proceed under neat conditions at 135 degrees C and atmospheric pressure (ca. 1.5 bar at 135 degrees C). Unsymmetrical diBenzyl ethers undergo selective hydrB(OH)2ronolysis on relatively electron-poor C-O bonds. In ArylBenzyl or AlkylBenzyl ethers, C-O bond Cleavage occurs selectively on C-Bn-OR bonds (Bn = Benzyl); in Alkylmethyl ethers, selective deconstruction of C-Me-OR bonds leads to the formation of Alkylboronate esters and methane. CyClic ethers are also amenable to catalytic hydrB(OH)2ronolysis. Mechanistic studies indicated the immediate in situ formation of a mono-hydridobridged dinuClear ruthenium complex [{(eta(6)-p-cymene)RuCl}(2)(mu-H-mu-Cl)] (2), which is highly active for hydrB(OH)2ronolysis of ethers. Over time, the dinuClear species decompose to produce ruthenium nanopartiCles that are also active for this transformation. Using this catalytic system, hydrB(OH)2ronolysis could be applied effectively to a very large scope of ethers, demonstrating its great potential to Cleave C-O bonds in ethers as an alternative to traditional hydrogenolysis.Ruthenium-Catalyzed Selective HydrB(OH)2ronolysis of EthershydrB(OH)2ration; catalysis; hydroelementation; ethers; rutheniumx4202045#N/AFALSE
5428
acscatal.0c0424210.1021/acscatal.0c04242FALSEhttps://doi.org/10.1021/acscatal.0c04242Hu, JLACS Catal.Biomass-flare gas synergistic coprocessing is a novel energy conversion technology that aims at harnessing an abundant renewable energy source: biomass and mitigate shale gas flaring. p-Cresol is used to represent lignin- and biomass-derived oxygenates for performing experimental and molecular reaction engineering of methane-assisted hydrodeoxygenation (HDO), hydrogenolysis reforming. The reaction pathway was also demonstrated on complex feedstocks like lignin and biomass, which contain a wide range of oxygenates in their composition. Novel in situ catalyst synthesis using a biomass precursor was achieved through pyrolysis to yield graphene nanosheet (GNS)-supported transition metal (TM) and Mo2C nanopartiCles. Experimental work and density functional theory (DFT) modeling calculations were performed for methane-assisted p-cresol reforming using Fe, Ni, Mo2C, Fe-Mo2C, Ni-Mo2C, and Pd-Mo2C supported on GNS. Detailed mechanistic investigation of the methane-p-cresol synergistic reaction experimentally and through DFT-based molecular simulations helped ascertain the unique reaction pathway occurring on bifunctional (dual) active site-TM-doped beta-Mo2C. Without TM doping, Mo2C is equally effective as Fe-Mo2C-GNS and Ni-Mo2C-GNS for CH4 dissociation and p-cresol HDO but presents a significantly higher barrier for H-2 (1.7 eV vs 1.15, 1.13 eV) and CO (3.67 eV vs 2.87, 2.80 eV) gas-phase desorption. Dual active sites are required for hydrogen-rich syngas production through methane-assisted p-cresol reforming as validated by experiments, DFT calculations, and microkinetic modeling. Lignin and hardwood biomass both having a higher O/C weight ratio compared to p-cresol (0.46, 1.09 vs 0.19) were coprocessed with CH4 over Fe-Mo2C-GNS, Ni-Mo2C-GNS, and Pd-Mo2C-GNS catalysts. Fe-added Mo2C nanopartiCles dispersed in the graphene support were found to be highly active for simultaneous CH4 Activation and extensive HDO of p-cresol, lignin, and hardwood biomass. Higher HDO conversion and H-2/CO ratios were obtained from CH4-assisted lignin/biomass reforming over Fe-Mo2C-GNS. Up to 99% hydrogen present in lignin could be valorized as syngas with a concentration of >65%.Graphene-Supported Fe/Ni, beta-Mo2C NanopartiCles: Experimental and DFT Integrated Approach to Catalyst Development for Synergistic Hydrogen Production through Lignin-Rich Biomass Reforming and Reduced Shale Gas Flaringbiomass reforming; graphene nanocatalysts; flare gas mitigation; syngas; catalyst design; reaction engineering; reaction kineticsx0202167#N/AFALSE
5429
acscatal.1c0077310.1021/acscatal.1c00773FALSEhttps://doi.org/10.1021/acscatal.6b03205Strasser, PMolecular Understanding of the Impact of Saline Contaminants and Alkaline pH on NiFe Layered Double Hydroxide Oxygen Evolution Catalysts2021#N/ATRUE
5430
acscatal.1c0076810.1021/acscatal.1c00768FALSEhttps://doi.org/10.1021/acscatal.1c00768Ramani, VKACS Catal.Cost-effective and highly active borohydride oxidation reaction (BOR) electrocatalysts are crucial for the advancement of direct borohydride fuel cells (DBFCs). Noble-metal electrocatalysts, such as Pd, are used as benchmark electrocatalysts because of their superior BOR activity. However, Pd suffers from catalyst poisoning because of strong binding with BHx intermediates at a high BOR overpotential, making it unsuitable for high DBFC performance, whereas Ni exhibits a low degree of catalyst poisoning because of a relatively weak binding of BHx intermediates. Density functional theory (DFT) calculations indicate a lowering of H- and OH-binding energies on bimetallic PdNi surfaces in comparison to their individual counterparts, thereby freeing more sites for BH4 adsorption that is crucial for a high BOR rate. The as-synthesized bimetallic PdNi/C electrocatalyst exhibits higher current densities at a BH4 concentration range of 50-500 mM than Pd/C and Ni/C. A DBFC unit with a pH-gradientenabled microscale bipolar interface employing PdNi/C, Pt/C, and H2O2 as the anode, cathode, and oxidant, respectively, exhibits a power density of 466 +/- 1.5 mW/cm(2) at 1.5 V, a peak power density of 630 +/- 2 mW/cm(2) at 1.1 V, with an open-circuit voltage of 1.95 +/- 0.01 V. Our bimetallic alloy electrocatalyst shows high DBFC performance, providing a pathway for the development of suitable BOR electrocatalysts.Development of Bimetallic PdNi Electrocatalysts toward Mitigation of Catalyst Poisoning in Direct Borohydride Fuel Cellsbimetallic alloy electrocatalyst; direct borohydride fuel cell; pH-gradient microscale bipolar interface; catalyst poisoning; density functional theory0202178#N/ATRUE
5431
acscatal.1c0074710.1021/acscatal.1c00747FALSEhttps://doi.org/10.1021/acscatal.1c00747Kim, JACS Catal.The direct conversion of CO2 to methane, gasoline-to-diesel range fuels, methanol, and light olefins using sustainable hydrogen sources is considered a promising approach for mitigating global warming. Nevertheless, the direct conversion of CO2 to high value-added chemicals, such as acetic acid and propionic acid (AA and PA, respectively), has not been explored to date. Herein, we report a Ni-Zn intermetallic/Zn-rich NixZnyO catalyst that directly converted CO2 to AA and PA with an overall selectivity of 77.1% at a CO2 conversion of 13.4% at 325 degrees C. The surface restructuring of the ZnO and NiO phases during calcination and subsequent reduction led to the formation of a Ni-Zn intermetallic on the Zn-rich NixZnyO phase. Surface-adsorbed (*CHx)(n) species were formed via the reverse water gas shift reaction and subsequent CO hydrogenation. Afterward, monoCarbonylic acids were produced via the direct insertion of CO2 into the (*CHx)(n) species and subsequent hydrogenation. The synthesis of monoCarbonylic acid was highly stable up to 216 h on-stream over the Ni-Zn intermetallic catalyst, and the catalyst maintained its phase structure and morphology during long-term CO2 hydrogenation. The high selectivity toward monoCarbonylic acids and high stability of the Ni-Zn intermetallic demonstrated its high potential for the conversion of CO2 into value-added chemicals.Synthesis of MonoCarbonylic Acids via Direct CO2 Conversion over Ni-Zn Intermetallic CatalystsCO2; hydrogenation; acetic acid; propionic acid; Ni-Zn; intermetallic phase02021111#N/ATRUE
5432
acscatal.0c0407910.1021/acscatal.0c04079FALSEhttps://doi.org/10.1021/acscatal.0c04079Lenz, OACS Catal.[NiFe]-hydrogenases catalyze the reversible reac- tion H-2 reversible arrow 2Fr + 2e(.)(-) Their basic module consists of a large subunit, coordinating the NiFe(CO)(CN)(2) center, and a small subunit that carries electron-transferring iron-sulfur Clusters. Here, we report the in vitro assembly of fully functional [NiFe]-hydrogenase starting from the isolated large and small subunits. Activity assays complemented by spectroscopic measurements revealed a native-like hydrogenase. This approach was used to label exClusively the NiFe(CO)(CN)(2) center with Fe-57, enabling a Clear view of the catalytic site by means of nuClear resonance vibrational spectroscopy. This strategy paves the way for in-depth studies of [NiFe]-hydrogenase catalytic intermediates.In Vitro Assembly as a Tool to Investigate Catalytic Intermediates of [NiFe]-Hydrogenasemetalloenzyme; hydrogenase; hydrogen; nickel; iron; catalytic cyCle; spectroscopyx3202023#N/AFALSE
5433
acscatal.0c0402110.1021/acscatal.0c04021FALSEhttps://doi.org/10.1021/acscatal.0c04021Xin, HLACS Catal.Low platinum-group-metal (PGM) ordered intermetallic catalysts have been considered one of the most promising candidates for catalyzing the oxygen reduction reaction (ORR) in fuel cells, but achieving the desired performances in terms of activity, durability, and cost is still a grand challenge for the fuel cell research field. While the cubic- and tetragonal-ordered (L1(2) and L1(0) phases) low-PGM nanocatalysts have been investigated extensively and have shown considerably improved durability and activity toward the ORR, so far, little is known about rhombohedral ordered L1(1) catalysts. We report the synthesis of an L1(1)-ordered PtCu catalyst for the ORR. We demonstrate that by applying nitrogen (N) doping through a thermal treatment in an NH3 gas, the activity and stability of the N-doped, rhombohedral ordered PtCu catalyst can be further enhanced, and the ORR mass and specific activities achieve nearly 5-fold and 4-fold enhancement in acidic media, respectively, relative to those of commercial Pt/C. In situ synchrotron X-ray absorption and pair-distribution-function measurements reveal that both the formation of the ordered intermetallic structure and N-doping synergistically improve the corrosion resistance of the PtCu catalyst by lowering the Cu diffusivity and introduce a compressive strain effect regulating the adsorption of oxygenated species on the Pt surface, thus accounting for the improved ORR kinetics.Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reactionoxygen reduction reaction; rhombohedral ordered intermetallics; core shell; N-doping; PtCu nanocatalystx3202154#N/AFALSE
5434
acscatal.0c0402010.1021/acscatal.0c04020https://doi.org/10.1021/acscatal.0c04020Peng, YACS Catal.The development of redox-targeting co-catalysts is one of the important tasks in realizing hybrid photocatalytic systems for CO2 reduction reaction (CO2 RR), which has been sought after as a promising way to mitigate the energy and environmental crisis. In this study, hollow nickel hydroxide nanocages are successfully fabricated via an ion-assisted etching protocol using ZIF-8 as the structural template, and they are used as cocatalysts along with a molecular photosensitizer and sacrificial electron donor for reducing visible-light CO2. A remarkable CO evolution rate of 1.44 x 10(5) mu mol.g(co-cat)(-1).h(-1), a CO selectivity of 96.1%, and a quantum efficiency of 2.50% are achieved using the optimal cavernous structure with thin walls, attributing to the significantly improved light harvest owing to multiple light reflection and scattering, static electron transfer, abundant surface oxygen vacancies, as well as coherent energy flow among well-aligned band levels. This study highlights the design and development of hollow entities toward CO2 RR and provides insights into the structure-mediated photocatalytic response.Visible-Light Photocatalytic CO2 Reduction Using Metal-Organic Framework Derived Ni(OH)(2) Nanocages: A Synergy from Multiple Light Reflection, Static Charge Transfer, and Oxygen Vacanciesphotocatalysis; nanocages; CO2 reduction; nickel hydroxide; co-catalystPhotocatalystx2202173#N/AFALSE
5435
acscatal.0c0396510.1021/acscatal.0c03965FALSEhttps://doi.org/10.1021/acscatal.0c03965Wang, HACS Catal.Regulating electron density at the active site by integrating contributions from multiple channels is an effective strategy to accelerate the reaction rate. Herein, the hydrolysis of ammonia borane (AB) is systematically studied on the NiCu alloy-loaded carbon nitride nanosheets (NixCuy/CNS). The TOF of AB hydrolysis for NiCu/CNS catalyst under visible light irradiation was nearly 3.5 times higher than that in the dark. Photoelectrochemical characterizations indicate that the improved photocatalytic activities originate from a combination of alloying effect, Mott-Schottky junction at the metal-semiconductor interface as well as the localized surface plasmon resonance induced under the visible light irradiation, which synergistically increase the local electron density at the active Ni sites. More importantly, the infrared spectra and isotope labeling-mass spectrometry methods were used to establish the source of hydrogen and unravel the reaction mechanism. It is suggested that the Cleavages of B-H and O-H bonds are the initial steps of AB hydrolysis, which lead to the formation of intermediates M-H- (metal and electronegative H- from -BH3) and M-H+ (metal and electropositive H+ from H2O), respectively. The H-2 molecule could form through three main paths as (1) two H atoms from -BH3, (2) two H atoms from H2O, and (3) one H atom from -BH3 and another from H2O. Results of density functional theory (DFT) calculations are consistent with the formation of electron-rich Ni sites in the NiCu, and the Activation of H2O is a rate-limiting step (RLS). Redistribution of electrons in NiCu significantly enhances the adsorption of AB, the Activation of H2O molecules, and the associative desorption of H adatoms as well, which effectively promote the Cleavage of B-H and O-H bonds and release of H-2. This work gives a systematic mechanistic study on photocatalytic AB hydrolysis involving multichannel electron-transfer pathways, which will provide a powerful guidance for the rational design of active catalysts for AB hydrolysis through multipronged effects.Visible-Light-Driven Multichannel Regulation of Local Electron Density to Accelerate Activation of O-H and B-H Bonds for Ammonia Borane Hydrolysisvisible-light-driven; electronic regulation; Activation of O-H and B-H bonds; reaction mechanism analysis; ammonia borane hydrolysisx3202067#N/AFALSE
5436
acscatal.0c0395010.1021/acscatal.0c03950https://doi.org/10.1021/acscatal.0c03950Pieber, BACS Catal.The combination of nickel and photocatalysis has unlocked a variety of cross-couplings. These protocols rely on a few photocatalysts that can only convert a small portion of visible light (<500 nm) into chemical energy. The high-energy photons that excite the photocatalyst can result in unwanted side reactions. Dyes that absorb a much broader spectrum of light are not applicable because of their short-lived singlet excited states. Here, we describe a self-assembling catalyst system that overcomes this limitation. Immobilization of a nickel catalyst on dye-sensitized titanium dioxide results in a material that catalyzes carbon-heteroatom and carbon-carbon bond formations. The modular approach of dye-sensitized metallaphotocatalysts accesses the entire visible light spectrum and allows tackling selectivity issues resulting from low wavelengths strategically. The concept overcomes current limitations of metallaphotocatalysis by unlocking the potential of dyes that were previously unsuitable.Modular, Self-Assembling Metallaphotocatalyst for Cross-Couplings Using the Full Visible-Light Spectrummetallaphotocatalysis; dual catalysis; nickel catalysis; photoredox catalysis; dye-sensitized semiconductorPhotocatalyst3202021#N/AFALSE
5437
acscatal.1c0047610.1021/acscatal.1c00476FALSEhttps://doi.org/10.1021/acscatal.1c00476Vomiero, AACS Catal.Water splitting is considered one of the most promising approaches to power the globe without the risk of environmental pollution. The oxygen evolution reaction (OER) is even more challenging because the generation of only one oxygen molecule involves the transfer of four e(-) and removal of four H+ ions from water. Thus, developing highly efficient catalysts to meet industrial requirements remains a focus of attention. Herein, the prominent role of Sn in accelerating the electron transfer kinetics of Ni5P4 nanosheets in OER is reported. The post catalytic survey elucidates that the electrochemically induced Ni-Sn oxides at the vicinity of phosphides are responsible for the observed catalytic activity, delivering current densities of 10, 30, and 100 mA cm(-2) at overpotentials of only 173 +/- 5.2, 200 +/- 7.4, and 310 +/- 5.5 mV, respectively. The density functional theory calculation also supports the experimental findings from the basis of the difference observed in density of states at the Fermi level in the presence/absence of Sn. This work underscores the role of Sn in OER and opens a promising avenue toward practical implementation of hydrogen production through water splitting and other catalytic reactions.In Situ-Generated Oxide in Sn-Doped Nickel Phosphide Enables Ultrafast Oxygen Evolutionin situ-generated oxides; Ni5P4 nanosheets; Sn doping; phosphide vicinity; OER0202158#N/ATRUE
5438
acscatal.0c0388810.1021/acscatal.0c03888FALSEhttps://doi.org/10.1021/acscatal.0c03888Yamada, YMAACS Catal.A stable, reusable, and insoluble poly(4-Vinylpyridine) nickel catalyst (P4VP-NiCl2) was prepared through the molecular convolution of poly(4-Vinylpyridine) (P4VP) and nickel chloride. We proposed a coordination structure of the Ni center in the precatalyst based on elemental analysis and Ni K-edge XANES, and we confirmed that it is consistent with Ni K-edge EXAFS. The Suzuki-Miyaura-type coupling of Aryl halides and Arylboronic esters proceeded using P4VP-NiCl2 (0.1 mol % Ni) to give the corresponding biAryl compounds in up to 94% yield. Surprisingly, when the same reaction of Aryl halides and Arylboronic acid/ester was carried out in the presence of amides, the amidation proceeded predominantly to give the corresponding Arylamides in up to 99% yield. In contrast, the reaction of Aryl halides and amides in the absence of Arylboronic acid/ester did not proceed. P4VP-NiCl2 successfully catalyzed the lactamization for preparing phenanthridinone. P4VP-NiCl2 was reused five times without significant loss of catalytic activity. Pharmaceuticals, natural products, and biologically active compounds were synthesized efficiently using P4VP-NiCl2 catalysis. Nickel contamination in the prepared pharmaceutical compounds was not detected by ICP-MS analysis. The reaction was scaled to multigrams without any loss of chemical yield. Mechanistic studies for both Suzuki-Miyaura and amidation were performed.Switching from BiAryl Formation to Amidation with Convoluted Polymeric Nickel Catalysisreusable catalyst; nickel catalysis; heterogeneous catalysis; Suzuki-Miyaura coupling; amidation reactionx02020127#N/AFALSE
5439
acscatal.1c0016910.1021/acscatal.1c00169FALSEhttps://doi.org/10.1021/acscatal.1c00169Liu, XHACS Catal.Conversion of syngas into aromatics via the Fischer-Tropsch (FT) route provides a promising way to supply the value-added chemicals. However, it is still a great challenge to achieve controllable aromatics selectivity with good stability. Herein, we report the Na-mediated bimetallic Fe-Ni catalyst simply partiCle mixed with HZSM-5, which can boost the stable and selective production of aromatics from the syngas. In detail, FeNiOx(5:1)-0.41Na exhibits quite stable catalytic activity with notably higher selectivity to light alpha-olefins (C-2(=)-C-4(=)) compared to alpha-Fe2O3-0.75Na. Various characterizations suggest that an appropriate addition of Ni with Na substantially regulates iron carbide formation and suppresses carbon deposition owing to the electron donation of Fe to Ni reducing CO adsorption and dissociation. Interestingly, extra Na results in remarkably increased selectivity to C-1(o)-C-4(o), despite the fact that Na shows the ability to suppress hydrogenation. Both characterizations and density functional theory (DFT) calculations demonstrate that the addition of Na weakens the Fe-Ni interaction and reduces electron transfer from Fe to Ni, which promotes C-1(o)-C-4(o) formation as Ni tends to reflect its intrinsic catalysis. DFT calculations confirm that the adsorbed CH2 species at the Ni-Fe interface prefers to undergo coupling to form C2H4, and the formed C2H4 spontaneously desorbs from the surface, indicating that the formation of lower olefins is favorable and further chain growth is inhibited. This could be attributed to the fact that the accumulated electron at the Ni-Fe interface weakens the binding strength of CH2 and C2H4 species because of electronic repulsion. Furthermore, the effects of FT product distribution on aromatics formation were also investigated. FeMnOx(5:1)-0.40Na produces longer olefin-rich hydrocarbons in C5+ owing to oxygen vacancy-assisted CO dissociation, leading to highly branched monocydic aromatics and faster HZSM-5 deActivation because of increased coking from the isomerization-hydrocracking of long hydrocarbons. In contrast, FeNiOx (5:1)-0.41Na-HZSM-5 produces major light aromatics about 65.7% inCluding toluene, ethyl-benzene, and xylene in total aromatics with about 98.6% aromatics in the liquid phase, which benefits from the fact that FeNiOx(5:1)-0.41Na makes shorter hydrocarbons in C5+ and/or Ni metal has a strong ability of H-2 dissociation to provide atomic H spillover onto HZSM-5. Thus, HZSM-5 also shows improved stability. Note that the mixed catalysts with a high Na content indicate a substantial Na+ migration to increase light alpha-olefins in the gas phase owing to suppress H-transfer reaction. This study provides deep insights into how to develop stable and selective iron-based catalysts for the production of FT products and its further conversion into value-added light aromatics.Sodium-Mediated Bimetallic Fe-Ni Catalyst Boosts Stable and Selective Production of Light Aromatics over HZSM-5 ZeoliteFischer-Tropsch synthesis; Fe-Ni catalyst; HZSM-5; aromatics production; selectivity; stability1202176#N/ATRUE
5440
acscatal.0c0495610.1021/acscatal.0c04956FALSEhttps://doi.org/10.1021/acscatal.0c04956Lautens, MACS Catal.A scalable nickel-catalyzed carboiodination reaction generating 6-membered carbocyCles is reported. NiI2 and P(OEt)(3), as the ligand and reducing agent, provided decorated iodo-tetrahydronaphthalenes in up to 94% yield. The impact of varying electronic and steric parameters on the reaction are reported and a non-linear Hammett plot was obtained, supporting a change in the rate-determining step from oxidative addition to reductive elimination. Experimental and DFT studies suggest that the malonate group may stabilize a nickel oxidative-addition complex. A variety of heteroatom-containing nuCleophiles and medicinally relevant heterocyCles were easily incorporated into the products via simple S(N)2 chemistry.Synthesis of CarbocyClic Compounds via a Nickel-Catalyzed Carboiodination Reactionnickel; carbocyCles; iodides; Hammett study; malonates; DFT3202160#N/ATRUE
5441
acscatal.0c0385710.1021/acscatal.0c03857FALSEhttps://doi.org/10.1021/acscatal.0c03857Engle, KMACS Catal.1,2-DiArylation of alkenyl sulfonamides with Aryl iodides and Aryl boronic esters under nickel catalysis is reported. The developed method tolerates coupling partners with disparate electronic properties and substitution patterns. Di- and trisubstituted alkenes as well as alkenes distal from the directing group are all accommodated. Control experiments are consistent with a N-Ni coordination mode of the directing group, which stands in contrast to a previous report on amide-directed 1,2-diArylation, which involves Carbonyl coordination. The synthetic utility of the method arises from the dual function of the sulfonamide as both a directing group and a masked amine nuCleophile. This is highlighted by various product diversifications where complex amine compounds are synthesized in a two-step sequence of N-functionalization and deprotection of the sulfonyl group.Sulfonamide Directivity Enables Ni-Catalyzed 1,2-DiArylation of Diverse Alkenyl Aminesalkene; diArylation; nickel; sulfonamide; directing groupx4202042#N/AFALSE
5442
acscatal.0c0359710.1021/acscatal.0c03597FALSEhttps://doi.org/10.1021/acscatal.0c03597Zhu, YYACS Catal.The merger of photocatalysis and transition-metal catalysis is of particular interest to develop useful and challenging synthetic methodologies. The catalytic activities of conventional dual-catalytic systems, however, are limited by the low synergistic efficiency between discrete catalytic centers due to their long average distance in solution. Herein we carefully decorated Ir(III) photosensitizers and Ni(II) transition-metal catalyst into flexible polymers to afford two polymer-supported dual catalysts (P1-Ni and P2-Ni). These polyelectrolyte-type metallopolymers assembled into spherical polymer partiCles in some polar solvents. Their unique molecular and assembled structure contributed to shortening the distance between catalytic centers and increasing the local catalysts' concentration within the catalyst, thereby greatly facilitating their electron, energy, and organic radical transfers during the catalytic cyCles. The enhanced energy interaction and matched redox potential between two catalytic centers within the polymer were confirmed by steady- and transient-state luminescent spectra and cyClic voltammetry. These features enable them in catalyzing challenging organic transformations that involve efficiently incorporated photocatalytic and transition-metal catalytic cyCles. We demonstrated that these two catalysts were highly effective in catalyzing C-S cross-coupling, C-O functionalized, C-N cross-coupling, and C-C cross-coupling reactions with broad substrate scopes and low catalyst loadings with turnover numbers of similar to 3100, similar to 1500, similar to 1400, and similar to 500, respectively. This work provides a general methodology to merge photosensitizer and transition-metal catalyst in a flexible polymer for significantly boosting the catalytic activity.Boosting Photocatalytic Activities for Organic Transformations through Merging Photocatalyst and Transition-Metal Catalyst in Flexible Polymerspolymer-supported catalyst; photocatalytic organic transformation; dual catalysis; nickel; iridiumPhotocatalystx3202056#N/AFALSE
5443
acscatal.0c0491110.1021/acscatal.0c04911FALSEhttps://doi.org/10.1021/acscatal.0c04911Zhou, XGACS Catal.Dry methane reforming (DMR) is a promising technique aiming at converting two major greenhouse gases into useful chemical feedstocks. A major challenge in the commercialization of this process is to develop a suitable catalyst with long-term stability, strong catalytic activity, and low cost. In this work, a microkinetic analysis coupled with a descriptor-based approach is conducted to study the trend in the catalytic activity across eight transition metals, where the formation energies of adsorbed C and O are identified as two reactivity descriptors. The catalytic properties of the Close-packed (111) and stepped (211) surfaces are compared to show the structure sensitivity of the DMR reaction. The resultant activity map with adsorbate-adsorbate interactions taken into consideration shows that Rh, Ir, and Ni are among the most active elemental metals for this reaction. Then, 1482 A(3)B(1) and 741 A(1)B(1) alloys that contain 39 elements have been screened for the DMR catalyst based on their anticarbonization and antioxidation ability, catalytic activity, and cost, in which an unsupervised machine learning technique is employed to identify the thermodynamically stable alloys upon adsorption and thus to accelerate the screening process. The identification of 23 binary intermetallic compounds as potential DMR catalysts not only gives theoretical evidence in support of the experimentally reported combinations but also provides new guidelines for rationally designing alloy catalysts for the DMR reaction.High-Throughput Screening of Alloy Catalysts for Dry Methane Reformingdensity functional theory; rational catalyst design; microkinetic analysis; adsorbate-adsorbate interactions; dry methane reforming; machine learning0202192#N/ATRUE
5444
acscatal.0c0352310.1021/acscatal.0c03523FALSEhttps://doi.org/10.1021/acscatal.0c03523Sivula, KACS Catal.Metallic electrodes based on iron, nickel, and/or cobalt have re-emerged as promising cost-effective anodes for the alkaline oxygen evolution reaction (OER) due to their simplicity and their in situ formation of a highly active oxy-hydroxide surface catalyst layer, which exhibits state-of-the-art overpotentials for the OER. However, the effect of alloy composition has not been systematically studied. Herein, using metallic anodes with defined Fe-Ni-Co atomic ratios prepared via arc melting, we report the relationship between the initial alloy composition, the OER performance, and the emergent active catalyst composition. After 50 h operation at 0.5 A cm(-2) the most active initial alloys (having a moderate amount of cobalt <40 at. %, an iron proportion between 30 and 80 at. % and a nickel ratio below 60 at. %) gave average overpotentials for 10 mA cm(-2) ca. 300-320 mV and Tafel slopes of 35-50 mV dec(-1). Iron and nickel-rich alloys performed poorer. The oxyhydroxide OER catalyst formed on the anode surface generally showed an increased concentration of Co and Ni and a depletion of Fe compared to the initial metal composition, giving the most active OER catalyst at a composition of Ni and Co of ca. 40 at. % with Fe at ca. 20 at. %. However, the initial alloy composition of Fe12.5Co12.5Ni75, showed a nearly invariant surface metal composition, indicating this as the most stable composition. Further analysis of the surface identified no correlation of the mass of metals leached from the anode surface, the electrochemically active surface area, or the presence of active Ni2+/3+ redox surface sites to the OER performance suggesting these factors do not influence the results.Influence of Composition on Performance in Metallic Iron-Nickel-Cobalt Ternary Anodes for Alkaline Water Electrolysisoxygen evolution reaction; water oxidation; transition metal oxyhydroxide; alloy; surface composition; overpotentialx2202042#N/AFALSE
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acscatal.0c0482610.1021/acscatal.0c04826FALSEhttps://doi.org/10.1021/acscatal.0c04826Zhou, YInsights into the Nonthermal Effects of Light in Dry Reforming of Methane to Enhance the H-2/CO Ratio Near Unity over Ni/Ga2O32021#N/ATRUE
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acscatal.0c0335510.1021/acscatal.0c03355FALSEhttps://doi.org/10.1021/acscatal.0c03355Wang, YACS Catal.Water electrolysis is a promising technique to produce high-quality hydrogen. However, the design and synthesis of high-performance nonprecious metal catalysts for the hydrogen evolution reaction are still confronted with challenges because of their high overpotential and poor flexibility. We herein reported in situ formed bimetallic carbide Ni6Mo6C nanodot and NiMoOx nanosheet array hybrid electrocatalyst supported on activated carbon Cloth (Ni6Mo6C/NiMoOx/ACC), which is manufactured by controlling the diffusion of carbon atoms into precursor NiMoO4 nanosheets from activated carbon Cloth to produce active species bimetallic carbide during annealing in a H-2 atmosphere. The unique hierarchical structure of NiMoOx nanosheet arrays grown on ACC could significantly promote both mass transport and electric conductivity, and the embedded Ni6Mo6C with moderated hydrogen adsorption ability (Delta GH* = -0.13 eV) and low water dissociation barrier (Delta Gb = 0.27 eV) exhibited remarkable performance and durability for the hydrogen evolution reaction (HER). Optimal Ni6Mo6C/NiMoOx/ACC demonstrates zero onset overpotential and an overpotential of only 29 mV at a current density of 10 mA cm(-2) with long-term stability (60 h loss-free continuous operation) in 1.0 M KOH solution, even surpassing the benchmark Pt/C catalyst. Especially, the as-made electrocatalyst shows robust flexibility and its high electrocatalytic performance almost keeps constant under distorted states, thus meeting the requirements of flexible electrocatalysts such as bendability. These findings afford a new idea to integrally construct highly efficient flexible electrocatalysts.In Situ Formed Bimetallic Carbide Ni6Mo6C Nanodots and NiMoOx Nanosheet Array Hybrids Anchored on Carbon Cloth: Efficient and Flexible Self-Supported Catalysts for Hydrogen Evolutionbimetallic carbide; in situ formation strategy; flexible electrocatalyst; nonprecious metal catalyst; hierarchical structure; hydrogen evolution reactionx6202051#N/AFALSE
5447
acscatal.0c0473910.1021/acscatal.0c04739FALSEhttps://doi.org/10.1021/acscatal.0c04739Wen, XDACS Catal.At present, the catalytic conversion of carbon-containing resources remains a major challenge faced during the economic growth and energy mix adjustment around the world. The development of catalysts with high efficiency for the conversion of carbon-containing resources is one of the major solutions to the energy and environmental problems. During these conversion processes, carbon plays an essential role in the sense that it is not only the key element in the reactions but may also cause the modification of the chemical nature of the catalysts. Notably, comprehension of the structure-performance relationship of catalytic materials is the basis for catalyst development. In particular, the modulating role of carbon on the catalyst structures during the conversion of carbon-containing resources has attracted increasing attention. In the past five years, we have systematically studied the modulation of Fe-, Co-, Ni-, and Mo-based catalysts by carbon using theoretical approaches. In this review, with a focus on the active phases, morphologies, surface structures, electronic properties, and catalytic performances of transition-metal catalysts (Fe, Co, Ni, Mo, and other transition metals), the modulation of these catalysts by carbon will be summarized to shed light on the question of how to tune the behavior of carbon in terms of catalyst carburization and carbon-related surface reactions. This review provides systematic and fundamental information for the further design and development of catalysts for the conversion of carbon-containing resources.Theoretical Perspectives on the Modulation of Carbon on Transition-Metal Catalysts for Conversion of Carbon-Containing Resourcescarbon-containing resources; transition metals; heterogeneous catalysis; carbon chemical potential; carburization02021225#N/ATRUE
5448
acscatal.0c0334610.1021/acscatal.0c03346FALSEhttps://doi.org/10.1021/acscatal.0c03346Claeys, MACS Catal.Transition metal alloys are receiving considerable attention in heterogeneous catalysis as they hold promise to combine advantageous properties of the constituting metals and, therefore, provide attractive avenues for targeted catalyst design. The present study concerns the effect of Co and Ni substituents in the ferrite (Fe3O4) structure used as a catalyst precursor for medium-temperature Fischer-Tropsch (MTFT) synthesis, in anticipation of enhanced oxygenate selectivities. The ferrites were synthesized by co-precipitation and characterized in detail before and after exposure to MTFT conditions, employing both conventional ex situ and state of the art in situ techniques. The complex product spectrum from the MTFT was analyzed by combining off-line one-dimensional and on-line two-dimensional gas chromatography. The latter was used specifically to investigate the formation of minority species, such as oxygenates, which are often disregarded in literature. In situ XRD and magnetometry showed no notable change in the reduction behavior of the ferrites with a cobalt substituent, but substituting with Ni decreased the reduction temperature drastically from 315 to 250 degrees C, most likely due to the increased hydrogen dissociation activity of Ni. The activity, CO conversion, in MTFT increased in the order Fe << CoFe < NiFe < CoNiFe. Incorporation of Co and Ni in the catalysts makes them less prone to deposition of inactive carbon. The addition of Ni specifically, also results in a significant shift in selectivity toward a shorter average chain length, lower olefinicity and higher water-gas shift activity. Interestingly, these shifts are paralleled by a 76% or 170% increase in C2+ oxygenates selectivity or yield, respectively. The increase in hydrogenation activity of substituted (i.e., Co and/or Ni) Fe-based catalysts, plays a critical role in the Fischer-Tropsch synthesis activity and selectivity to the different product Classes (i.e., paraffins, olefins, and oxygenates) and the findings reported here provide valuable insights of key importance for further development and optimization of FT catalysts.Enhanced Oxygenates Formation in the Fischer-Tropsch Synthesis over Co- and/or Ni-Containing Fe Alloys: Characterization and 2D Gas Chromatographic Product Analysismedium-temperature Fischer-Tropsch; ferrites; alloys; GCxGC; oxygenate selectivityx02020125#N/AFALSE
5449
acscatal.0c0473310.1021/acscatal.0c04733FALSEhttps://doi.org/10.1021/acscatal.0c04733Krtil, PACS Catal.Rational optimization of the OER activity of catalysts based on LaNiO3 oxide is achieved by maximizing the presence of trivalent Ni in the surface structure. DFT investigations of the LaNiO3 catalyst and surface structures related to it predict an improvement in the OER activity for these materials to levels comparable with the top of the OER volcano if the La content is minimized while the oxidation state of Ni is maintained. These theoretically predicted structures of high intrinsic OER activity can be prepared by a templated sprayfreeze freeze-drying synthesis followed by a simple postsynthesis exfoliation-like treatment in acidic media. These nanocrystalline LaNiO3-related materials confirm the theoretical predictions, showing a dramatic improvement in OER activity. The exfoliated surfaces remain stable in OER catalysis, as shown by an in-operando ICP-OES study. The unprecedented OER Activation of the synthesized LaNiO3 based materials is related to a Close juxtaposition of the theoretical conception of ideal structural motifs and the ability to engender such motifs using a unique synthetic procedure, both principally related to stabilization and pinning of the Ni oxidation state within the local coordination environment of the perovskite structure.Engendering Unprecedented Activation of Oxygen Evolution via Rational Pinning of Ni Oxidation State in Prototypical Perovskite: Close Juxtaposition of Synthetic Approach and Theoretical Conceptionelectrocatalysis; oxygen evolution; rational catalyst design; DFT0202175#N/ATRUE
5450
acscatal.0c0330010.1021/acscatal.0c03300FALSEhttps://doi.org/10.1021/acscatal.0c03300Mitsudome, TACS Catal.While metal phosphides have begun to attract attention as electrocatalysts, they remain underutilized in the field of liquid-phase molecular transformations. Herein, we describe a supported cobalt phosphide nanoalloy (nano-Co2P) that functions as a highly efficient, reusable heterogeneous catalyst for the selective hydrogenation of furfural derivatives. The Carbonyl moieties of several furfural derivatives were selectively hydrogenated to produce the desired products in high yields. In contrast to conventional nonprecious metal catalysts, nano-Co2P uniquely exhibited air stability, which enabled easy and safe handling and preCluded the need for H-2 pretreatment. Infrared and density functional theory studies revealed that the highly efficient hydrogenation is due to the favorable Activation of the Carbonyl moiety of furfural derivatives through the backdonation to its pi* orbital from the Co d-electrons.Air-Stable and Reusable Cobalt Phosphide Nanoalloy Catalyst for Selective Hydrogenation of Furfural Derivativescobalt phosphide; nanoalloy; heterogeneous catalyst; hydrogenation; furfural derivativex6202133#N/AFALSE
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acscatal.0c0442910.1021/acscatal.0c04429FALSEhttps://doi.org/10.1021/acscatal.0c04429Chen, DACS Catal.By introducing Pt atoms into the surface of reduced hydrotalcite (HT)-derived nickel (Ni/HT) catalysts by redox reaction, we synthesized an enhanced active and stable Ni-based catalyst for methane dry reforming reaction. The bimetallic Pt-Ni catalysts can simultaneously enhance the catalyst activity, increase the H-2/CO ratio by suppressing reverse water-gas shift reaction, and enhance the stability by increasing the resistance to the carbon deposition during the reaction. Kinetic study showed that 1.0Pt-12Ni reduces the Activation energy for CH4 dissociation and enhances the catalytic activity of the catalyst and lowers the energy barrier for CO2 Activation and promotes the formation of surface O* by CO2 adsorptive dissociation. It is beneficial to enhance the resistance to the carbon deposition and prolong its service life in the reaction process. In addition, density-functional theory calculations rationalized the higher coke resistance of Pt-Ni catalysts where CH is more favorable to be oxidized instead of cracking into surface carbon on the Pt-Ni surface, compared with Ni(111) and Pt(111). Even if a small amount of carbon deposited on the Pt-Ni surface, its oxidation process requires a lower Activation barrier. Thus, it demonstrates that the bimetallic Pt-Ni catalyst has the best ability to resist carbon deposition compared with monometallic samples.Unraveling Enhanced Activity, Selectivity, and Coke Resistance of Pt-Ni Bimetallic Clusters in Dry Reformingmethane dry reforming; coke resistance; surface oxygen; Pt-Ni Cluster catalysts; DFT8202169#N/ATRUE
5452
acscatal.0c0421610.1021/acscatal.0c04216FALSEhttps://doi.org/10.1021/acscatal.6b02368Kim, JTrimetallic Cu-Ni-Zn/H-ZSM-5 Catalyst for the One-Pot Conversion of Levulinic Acid to High-Yield 1,4-Pentanediol under Mild Conditions in an Aqueous Medium2021#N/ATRUE
5453
acscatal.0c0316610.1021/acscatal.0c03166FALSEhttps://doi.org/10.1021/acscatal.0c03166Chen, JGGACS Catal.Ammonia synthesis by plasma catalysis has emerged as an alternative process for decoupling nitrogen fixation from fossil fuels. Plasma Activation can potentially circumvent the limitations of conventional thermocatalytic ammonia synthesis; however, the contribution of different reaction mechanisms to the production of ammonia at the catalyst surface remains unClear. Here, we identify the reaction intermediates adsorbed on gamma-Al2O3-supported Ni and Fe catalysts during plasma-activated ammonia synthesis under various temperatures and reactor configurations using FTIR spectroscopy, steady-state flow reactor experiments, and computational kinetic modeling. Ammonia yield can be influenced by plasma-derived intermediates and their interactions with catalyst surfaces, which lead to different reaction pathways: Ni/gamma-Al2O3 enhances plasma-promoted NH3 production and favors surface-adsorbed NHx species, while Fe/gamma-Al2O3 shows the presence of N2Hy and a lower overall concentration of N-containing adsorbates. Plasma-catalyst interactions are probed to reveal that elevated temperature and plasma irradiation of the surfaces promote NH3 desorption. The direct evidence of catalytic surface reactions occurring during a plasma-activated process provides mechanistic insight into plasma-activated ammonia synthesis.Identifying Surface Reaction Intermediates in Plasma Catalytic Ammonia Synthesisplasma catalysis; ammonia synthesis; in situ surface characterization; computational kinetic modeling; non-thermal plasmax7202056#N/AFALSE
5454
acscatal.0c0420010.1021/acscatal.0c04200FALSEhttps://doi.org/10.1021/acscatal.0c04200Yan, YSWater-Fed Hydroxide Exchange Membrane Electrolyzer Enabled by a Fluoride-Incorporated Nickel-Iron Oxyhydroxide Oxygen Evolution Electrode2021#N/ATRUE
5455
acscatal.0c0412410.1021/acscatal.0c04124FALSEhttps://doi.org/10.1021/acscatal.0c04124Engle, KMACS Catal.The decomposition of primary sodium alkoxide salts under ambient storage conditions and the effects of this phenomenon on commonly employed transition-metal-catalyzed cross-coupling reactions are described. By utilizing NMR, IR, and Raman spectroscopy, along with a modified Karl Fischer analysis, the main inorganic degradants were characterized, and CO2 in the air was found to be a critical reactant within the decomposition process. The effects of storage conditions on decomposition were evaluated, and preliminary experiments to understand the kinetics of this process were performed.An Under-Appreciated Source of Reproducibility Issues in Cross-Coupling: Solid-State Decomposition of Primary Sodium Alkoxides in AirCross-coupling; sodium alkoxide; palladium; nickel; solid-state chemistry0202139#N/ATRUE
5456
acscatal.0c0294910.1021/acscatal.0c02949https://doi.org/10.1021/acscatal.0c02949Do, LHACS Catal.Secondary metal cations, such as alkali and transition metal ions, have been shown to enhance the catalytic performance of nickel and palladium olefin polymerization catalysts. Their beneficial effects can manifest in different ways, such as increasing rates of polymerization, altering polymer microstructures, enhancing catalyst thermal stability, or a combination of these effects. We have systematically quantified secondary metal ion influences on nickel phenoxyphosphine polyethylene glycol (PEG) complexes. We demonstrate that cation tuning could readily achieve three-dimensional structures and electronic environments that are not easily accessible through conventional ligand tuning. This study led to the development of extremely active ethylene polymerization catalysts. For example, the nickel-lithium complex gave activity and turnover number as high as 7.0 x 10(4) kg PE/mol Ni.h and 2.5 x 10(6) mol ethylene/mol Ni, respectively, and the nickel-cesium complex showed unusual thermal stability up to 90 degrees C (activity = 2.3 x 10(4) kg/mol h, turnover number = similar to 4.1 x 10(5) mol ethylene/mol Ni, and M-n = 1.6 x 10(4) g/mol). We provide both experimental and computational data showing that secondary metals impact the relative stability of cis and trans isomers, which is a phenomenon not shown previously. Unlike in our earlier work, which was limited by poor nuClearity control and/or secondary metals that were too far from the catalyst center, the nickel phenoxyphosphine-PEG complex is an ideal platform for future studies of cation-controlled polymerization.Elucidating Secondary Metal Cation Effects on Nickel Olefin Polymerization Catalystsolefin polymerization; coordination insertion; nickel catalysts; cation tuning; polyethylenex62020104#N/AFALSE
5457
acscatal.0c0294410.1021/acscatal.0c02944FALSEhttps://doi.org/10.1021/acscatal.0c02944Shen, WACS Catal.Monolith catalysts of cobalt oxides grown on metal substrates exhibited good catalytic performance in the oxidation of volatile organic compounds (VOCs) and oxygen vacancies play a key role in activating. However, there is rarely a report about the increase in oxygen vacancies using a facile method in monolith catalysts. Besides, the corresponding mechanism of the promotional effects of oxygen vacancies over the monolith catalysts still remains elusive. In this work, Co3O4 nanowires with abundant oxygen vacancies in situ grown on the Ni foam (r-Co3O4 NW@Ni foam) were synthesized and used as high-performance monolith catalysts for catalytic oxidation of formaldehyde. The r-Co3O4 NW@Ni foam catalysts showed outstanding catalytic activity and stability. The T10 (temperature when HCHO conversion achieved 10%) of r-Co3O4 NW@Ni foam catalysts (75 degrees C) was lower than that of Co3O4 NW@Ni foam catalysts (100 degrees C) and Co3O4 NP catalysts (132 degrees C). More importantly, the r-Co3O4 NW@Ni foam catalysts have more active oxygen species because of the promotional effects of surface oxygen vacancies. In situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) results revealed that the formate species were reaction intermediates of HCHO catalytic oxidation reactions. However, the formate species on the surface of r-Co3O4 NW@Ni foam catalysts were more active thus could easily take part in catalytic reactions. Furthermore, combined with the calculation results, the abundant surface oxygen vacancies could weaken O-2 adsorption energy and make r-Co3O4 NW@Ni foam catalysts adsorb and store more active oxygen species, thus promoting more reaction intermediates to generate with a higher rate in redox cyCles. The present investigations in this work may lead to an alternative development of high-performance monolith catalysts for VOC catalytic oxidation.Insights into High-Performance Monolith Catalysts of Co3O4 Nanowires Grown on Nickel Foam with Abundant Oxygen Vacancies for Formaldehyde Oxidationformaldehyde oxidation; oxygen vacancy; monolith catalysts; Co3O4 nanowires; solvothermal reductionx1202050#N/AFALSE
5458
acscatal.0c0394910.1021/acscatal.0c03949FALSEhttps://doi.org/10.1021/acscatal.0c03949Wang, HMExperimental and Density Functional Theory Studies on the Zeolite-Based Fe-Ni-W Trimetallic Catalyst for High-Temperature NOx Selective Catalytic Reduction: Identification of Active Sites Suppressing Ammonia Over-oxidation2021#N/ATRUE
5459
acscatal.0c0290210.1021/acscatal.0c02902FALSEhttps://doi.org/10.1021/acscatal.0c02902Mavrikakis, MACS Catal.Hydrogen bonding accelerates many catalytic reactions by orienting intermediates, stabilizing transition states, and even opening reaction pathways. However, most mechanistic studies regarding the decomposition of formic acid (FA), a promising hydrogen storage material, neglect hydrogen-bonding interactions even though FA is a strong hydrogen-bond donor and acceptor. Here, we probe the formation of bimolecular hydrogen-bonded complexes between FA and formate (FA-HCOO complexes) adsorbed on metal surfaces and how these complexes affect HCOO* decomposition. Using first-principles density functional theory (DFT) calculations on 12 Close-packed (111)/(0001) and 8 open (100) surfaces of 12 transition metals-Ag, Au, Co, Cu, Ir, Ni, Os, Re, Pd, Pt, Rh, and Ru, we-show that FA-HCOO complexes are generally thermodynamically stable, even at elevated temperatures and pressures. We then illustrate that these complexes produce infrared spectroscopic signatures consistent with as yet unassigned experimental peaks. We last demonstrate that by stabilizing the dangling bond of monodentate HCOO*, these complexes significantly lower the barriers for rotation of HCOO* from a bidentate to a monodentate configuration, the rate-limiting step for HCOO* decomposition on many surfaces. FA thus acts as a cocatalyst for HCOO* decomposition. Our results may guide the community toward improved catalysts for reactions involving HCOO* such as FA decomposition, methanol steam reforming, and the water gas shift reaction. More broadly, our work highlights the ability of hydrogen bonding to modify the adsorbed structures of intermediates and lower the barriers for their reaction on heterogeneous catalysts. This phenomenon can be relevant for other reactions involving ammonia, alcohols, and Carbonylic acids.Formic Acid: A Hydrogen-Bonding Cocatalyst for Formate Decompositionhydrogen bonding; cocatalyst; formic acid decomposition; bimolecular mechanism; transition metals; density functional theoryx2202071#N/AFALSE
5460
acscatal.0c0289110.1021/acscatal.0c02891FALSEhttps://doi.org/10.1021/acscatal.0c02891Zhang, CACS Catal.Discovering efficient and promising non-noble catalysts toward the alkaline hydrogen evolution reaction (HER) is vital for a Clean energy system. Here, we design an efficient alkaline HER electrocatalyst, coating of WN nanowire core with a Ni(OH)(2) shell supported on a carbon fiber paper (WN-Ni(OH)(2)). In a 1 M KOH solution, the hierarchical electrocatalyst affords a current density of 20 mA cm(-2) at an overpotential of 170 mV and 100 mA cm(-2) at 245 mV. The enhanced performance of WN-Ni(OH)(2) in the HER is attributed to the synergy between WN and Ni(OH)(2): during water dissociation, hydroxyl groups are preferentially adsorbed on WN and hydrogen on Ni(OH)(2); meanwhile, Ni(OH)(2) could promote hydroxyl group desorption from WN. Thus, the full-surface Volmer reaction kinetics could be enhanced. As a consequence, the WN-Ni(OH)(2) has a reduced Activation energy of the HER and enhanced intrinsic activity performance. Meanwhile, the hybrid can reach a current density of 100 mA cm(-2) at an overpotential of 339 mV for the oxygen evolution reaction (OER), and an overpotential of 510 mV for the full water-splitting reaction. This interfacial cooperation offers a promising bifunctional electrocatalyst, as well as a hopeful strategy for fabricating efficient nitride-based electrocatalysts in alkaline media.Triple Functions of Ni(OH)(2) on the Surface of WN Nanowires Remarkably Promoting Electrocatalytic Activity in Full Water Splittingtungsten nitride; nickel hydroxide; synergistic effect; water dissociation; full water splittingx7202066#N/AFALSE
5461
acscatal.0c0387310.1021/acscatal.0c03873FALSEhttps://doi.org/10.1021/acscatal.0c03873Zhao, CConfinement of Ionic Liquids at Single-Ni-Sites Boost Electroreduction of CO2 in Aqueous Electrolytes2020#N/ATRUE
5462
acscatal.0c0283210.1021/acscatal.0c02832FALSEhttps://doi.org/10.1021/acscatal.0c02832Tang, XLACS Catal.Introducing oxygen vacancies into metal oxides is a promising strategy to promote their catalytic activity, which has been extensively studied in heterogeneous catalysis. Herein, transition metal (M = Fe, Co, and Ni) doping was used to introduce oxygen vacancies in CeO2 and promote activity for Carbonyl sulfide (COS) hydrolysis. Various techniques were performed to accurately characterize the catalyst structure and state. The transition metals successfully entered the crystal lattice of CeO2 and formed a solid solution structure. The metal-doped CeO2 (M/CeO2) showed improved reduction properties, more Ce3+ and oxygen vacancies in comparison with pure CeO2. The introduction of transition metal greatly enhanced activity of M/CeO2 for COS hydrolysis. Among them, the Co/CeO2 sample displayed the highest activity and H2S selectivity. The roles of metal doping in improving activity were explored on the basis of DFT calculations. The strong interaction between doped metals and CeO2 promotes the spontaneous formation of asymmetric oxygen vacancies in M/CeO2. These asymmetric oxygen vacancies facilitate the Activation and dissociation of H2O and generation of active hydroxyls, which contributes to the enhanced activity for COS hydrolysis. This work provides an attractive method for obtaining nonprecious metal catalysts for COS hydrolysis.Spontaneous Formation of Asymmetric Oxygen Vacancies in Transition-Metal-Doped CeO2 Nanorods with Improved Activity for Carbonyl Sulfide HydrolysisCOS catalytic hydrolysis; oxygen vacancy; H2O Activation; CeO2 nanorods; transition metal dopingx8202064#N/AFALSE
5463
acscatal.0c0278910.1021/acscatal.0c02789FALSEhttps://doi.org/10.1021/acscatal.0c02789Naldoni, ADirect Observation of Photoinduced Higher Oxidation States at a Semiconductor/Electrocatalyst Junctionx2020#N/AFALSE
5464
acscatal.0c0274510.1021/acscatal.0c02745FALSEhttps://doi.org/10.1021/acscatal.0c02745Wang, XACS Catal.N-2 electrolysis has been impeded by efficient catalysts for key reactions: cathodic nitrogen reduction reaction (NRR) and anodic oxygen evolution reaction (OER). A bifunctional nickel, iron-nanomesh array electrocatalyst has been developed characteristic of excellent structural features for favorable NRR and OER processes, inCluding highly exposed active sites originated from sub-nanometer-thick nanomeshes, hierarchical porosity resulting from the array-arranged nanolayers, and binary nickel, iron active sites. The electrode demonstrates excellent NRR activity with an ammonia yield of 16.89 mu g h(-1) mg(cat)(-1) and a faradaic efficiency (FE) of 12.50% at -350 mV (vs RHE), in addition to OER activity with a small overpotential of 191 mV to achieve 10 mA cm(-2). Consequently, a full N-2 electrolysis system has been constructed that exhibits remarkable ammonia production performance with an ammonia yield of 2.07 mu g h(-1) mg(cat)(-1) at 1.9 V, an FE of 9.87% at 1.6 V, and good durability for 30 h. Further mechanism study through density function theory shows that the NRR proceeds via an associative distal pathway, whereas the free energies for the N-2* -> NNH* intermediate step in the NRR as well as the OH* + H2O -> O* + H2O intermediate step in the OER can be reduced by tuning the catalysts electronic structure by the strong synergistic effect between nickel and iron.Two-Dimensional Nanomesh Arrays as Bifunctional Catalysts for N-2 Electrolysiselectrocatalysis; nitrogen fixation; bifunctional electrode; two-dimensional nanomesh arrayx7202035#N/AFALSE
5465
acscatal.0c0274310.1021/acscatal.0c02743FALSEhttps://doi.org/10.1021/acscatal.0c02743Takanabe, KACS Catal.A Ni-Mo composite functions as a promising non-noble metal electrocatalyst for the hydrogen evolution reaction (HER) in alkaline water. Despite its industrial relevance, the kinetic origin of the high catalytic activity remains under debate. The present report discusses a reaction mechanism of HER on Ni-Mo catalysts by combining experimental and theoretical studies. In contrast to a Ni catalyst, a Ni-Mo catalyst is insensitive to CO gas introduced during HER. In situ spectroscopic measurements inCluding Raman spectroscopy and electron paramagnetic resonance (EPR) show that Mo3+ prevails during HER catalysis. Density functional theory (DFT) simulations corrB(OH)2rate the thermodynamic stability and HER activity of Mo3+-containing centers on Ni(111) at HER potentials. Notably, Ni is demonstrated to play no direct role as a catalytic site but to effectively disperse and activate the oxidized catalytic Mo species. The results illustrate how to improve the electrocatalytic activity for alkaline HER.Role of Oxidized Mo Species on the Active Surface of Ni-Mo Electrocatalysts for Hydrogen Evolution under Alkaline Conditionsnickel; molybdenum; hydrogen evolution; alkaline; EPRx4202052#N/AFALSE
5466
acscatal.0c0386610.1021/acscatal.0c03866FALSEhttps://doi.org/10.1021/acscatal.0c03866Hutchings, GJACS Catal.Minimizing iridium loading in oxygen evolution reaction (OER) catalysts, without impairing electrocatalytic activity and stability is crucial to reduce the cost of water electrolysis. In this work, two Ir0.5Ni0.5Ox mixed oxide catalysts with layered and solid solution morphologies were prepared by modifying a facile hydrothermal methodology. The catalytic OER activity and stability of the Ir-Ni catalyst with a homogeneous distribution (IrNi-HD) was seriously compromised compared to pure IrOx due to the high concentration of surface nickel prone to corrosion under reaction conditions. However, the design of layered IrOx-Ni(OH)(x) (IrNi-LY) with Ir at the exposed surface allowed a 50% reduction in the molar concentration of the precious metal on the electrode compared to IrOx without impairing the catalytic activity or stability. As a result, IrNi-LY outperformed IrOx in activity when normalized to the Ir mass.Preparation of Solid Solution and Layered IrOx-Ni(OH)(2) Oxygen Evolution Catalysts: Toward Optimizing Iridium Efficiency for OERelectrocatalysis; oxygen evolution reaction; iridium oxide; amorphous iridium oxo-hydroxide; hydrothermal synthesis; iridium nickel mixed oxide3202053#N/ATRUE
5467
acscatal.0c0355510.1021/acscatal.0c03555FALSEhttps://doi.org/10.1021/acscatal.0c03555Lee, JACS Catal.In this study, boron-incorporated palladium catalysts supported on carbon (PdBInc./C) were synthesized; they exhibited considerably improved catalytic activity for the oxidation of formate (HCOO-). Boron-induced lattice expansion and electronic modification of Pd were observed in this catalyst through various physicochemical analyses. Furthermore, the effective electronic modification between Pd and B was found to overcome the limitation due to the lattice expansion of Pd and the modification was confirmed from the downshift and broadening of the d-band center. The direction of electron transfer was observed from B to Pd. Based on the experimental results, it is possible to infer that PdBInc./C significantly contributes to the weakening of the hydrogen adsorption, which is regarded as a rate-determining step for the oxidation of HCOO-. As an anode electrode, PdBInc./C also showed an outstanding performance in a direct formate fuel cell owing to its modified electronic structure, which is considered an important property to facilitate hygroscopic fuel accessibility in a practical system.Contribution of Interstitial Boron in a Boron-Incorporated Palladium Catalyst Toward Formate Oxidation in an Alkaline Direct Formate Fuel Cellformate; fuel cell; palladium; boron; alkaline media0202149#N/ATRUE
5468
acscatal.0c0242610.1021/acscatal.0c02426FALSEhttps://doi.org/10.1021/acscatal.0c02426Sievers, CACS Catal.Ceria-zirconia-supported Ni catalysts (Ni/Ce0.83Zr0.17O2 or Ni/CZ) are prepared by dry impregnation, strong electrostatic adsorption, coprecipitation (CP), and combustion synthesis (CS). The nature and abundance of Ni species in these samples are characterized by X-ray adsorption spectroscopy, temperature-programmed reduction, and CO chemisorption. The bulk synthesis methods (i.e., CP and CS) produce Ni cations that are incorporated into the CZ lattice forming mixed-metal oxides with Ni3+ species at low Ni content. The formation of mixed-metal oxides increases the reducibility of CZ and increases the abundance of active surface oxygen. All NiO/CZ catalysts are active for methane dry reforming and retain some of their activity at a steady state. The initial methane conversion correlates linearly with the fraction of accessible Ni after reduction. The predominant path of catalyst deActivation strongly depends on the structure of the catalyst and, thus, on the synthesis method used. All catalysts experience agglomeration of Ni partiCles under reaction conditions. Improving the Ni dispersion to isolated species embedded in a support does not improve resistance to Ni partiCle growth. Coke formation is inversely related to the concentration of active surface oxygen. The dominant deActivation mechanism for catalysts made by CS is the encapsulation of Ni partiCles by the support.Nickel Speciation and Methane Dry Reforming Performance of Ni/CexZr1-xO2 Prepared by Different Synthesis Methodsnickel catalyst; X-ray absorption spectroscopy; deActivation; sintering; coke formation; encapsulationx52020123#N/AFALSE
5469
acscatal.0c0230110.1021/acscatal.0c02301FALSEhttps://doi.org/10.1021/acscatal.6b01837Choi, SIFexNi2-xP Alloy Nanocatalysts with Electron-Deficient Phosphorus Enhancing the Hydrogen Evolution Reaction in Acidic Mediax2020#N/AFALSE
5470
acscatal.0c0226410.1021/acscatal.0c02264FALSEhttps://doi.org/10.1021/acscatal.0c02264McKone, JRACS Catal.We used in situ environmental transmission electron microscopy to image the formation of a Ni-Mo composite nanocatalyst via thermal reduction of NiMoO4 nanorods. Two Clear structural changes were observed as the temperature was increased from 25 to 500 degrees C in the presence of H-2(g): the first involved nuCleation of nanoscale Ni-rich partiCles and the second involved general collapse of the remaining oxide phase along with substantial coarsening of the alloy partiCles. The activity of the catalyst toward alkaline hydrogen evolution was found to reach a maximum in a narrow range of reduction temperatures from 375 to 425 degrees C. This resulted in the formation of a mixed-phase product comprising sub-10 nm Ni0.9Mo0.1 partiCles embedded in a porous Mo-rich oxide matrix. Thus, the most active Ni-Mo catalyst apparently requires intimate contact between the alloy component and the oxide phase, lending support to a catalytic mechanism involving metallic and oxidized surface sites.Direct Observation of Ni-Mo Bimetallic Catalyst Formation via Thermal Reduction of Nickel Molybdate Nanorodstransmission electron microscopy; in situ; ETEM; nickel; molybdenum; molybdate; nanorod; catalyst; hydrogenx2202078#N/AFALSE
5471
acscatal.0c0347110.1021/acscatal.0c03471FALSEhttps://doi.org/10.1021/acscatal.0c03471Han, YFACS Catal.The carbon dioxide (CO2) methanation reaction not only provides a solution for mitigating the excessive carbon dioxide emissions but also can potentially be employed for the storage and transportation of low-grade energies. A supported nickel-based catalyst is the most promising candidate for the CO2 methanation reaction. Additionally, understanding the role of the support is essential for the rational design of nickel-based CO2 methanation catalysts. Herein, we elaborated on the effect of the support on the catalyst structure, CO2 adsorption, CO2 Activation, methanation mechanism, and deActivation process. Future directions are suggested to elucidate the fundamental aspects of this catalytic system, inCluding the formation mechanism of preferentially exposed facets, the nature of strong metal-support interactions, the balance between support reducibility and basicity, and the CO2 methanation pathways over nickel-based catalysts with various supports.Essential Role of the Support for Nickel-Based CO2 Methanation Catalystssupport; CO2; methanation; heterogeneous catalysis; metal-support interaction42020120#N/ATRUE
5472
acscatal.0c0335110.1021/acscatal.0c03351FALSEhttps://doi.org/10.1021/acscatal.0c03351Bueno, JMCACS Catal.A spectroscopic and microscopic investigation was made of the dynamics of bimetallic nanopartiCles (NPs) in Co-Ni/MgAl2O4 catalysts used for the steam reforming of ethanol (SRE) reaction, considering the implications for catalytic performance, shedding light on the elusive effect of Co-Ni alloy in reforming reactions. X-ray absorption spectroscopy (XAS) analyses showed that contact with the reagent mixture led to major changes in the superficial structure of the Co-Ni nanopartiCles, which were strongly dependent on temperature and the metal partiCle size. At room temperature, contact between the Co-Ni NPs and the reactants (ethanol and H2O) led to the formation of a Co-Ni oxide film over the Co-Ni metal core, with CoO/NiO = 1. For smaller Co-Ni NPs (about 5 nm), the oxide film showed a dynamic composition according to temperature, with Co migrating to the surface while being oxidized up to around 350 degrees C. A structure with a core of (Co,Ni) and a shell rich in CoO was formed, which could be reduced above 350 degrees C. The surface CoO was mainly reduced upon heating in the reaction stream, with migration into the NP cores. For larger Co-Ni NPs (about 10 nm), the oxide film remained stable up to 200 degrees C, being reduced by the ethanol stream at higher temperatures. At operating temperatures in the range of 350-400 degrees C, the surface structure of the Ni-Co alloy showed (Ni,Co)-O species, while these metal oxide species decreased with increases of the thermal treatment temperature and the nanopartiCle size. At low temperatures, the Co-Ni nanopartiCles were covered by CoO/NiO and were active for the oxidative dehydrogenation of ethanol. With the increase of temperature, surface CoO was reduced and incorporated in the Co-Ni nanopartiCle core. These metal sites became active toward the reactant and catalyzed the dehydrogenation of ethanol, followed by C-C bond Cleavage, resulting in the formation of CH4, CO, and H-2. The presence of CoO at the surface of the smaller Co-Ni nanopartiCles suppressed carbon accumulation, compared to larger Co-Ni or Ni nanopartiCles that had highly reduced surfaces.Steam Reforming of Ethanol Using Ni-Co Catalysts Supported on MgAl2O4: Structural Study and Catalytic Properties at Different Temperaturesethanol; bimetallic catalyst; in situ XAS; nickel; cobalt0202179#N/ATRUE
5473
acscatal.0c0331310.1021/acscatal.0c03313FALSEhttps://doi.org/10.1021/acscatal.0c03313Schuhmann, WACS Catal.Complex solid solution (CSS) (often denoted as high-entropy alloy) electrocatalysts enable access to unique possibilities for tailoring active sites while overcoming ever-existing limitations in electrocatalysis by unique interactions of various elements in direct neighborhood. The challenge lies in the development of strategies, which allow for systematic design of element combination and composition optimization in the multinary composition space. This challenge is accompanied by a lack of a suitable analysis method of experimental activity measurements, which can cope with the complex surface structure of this catalyst Class. In this work, we propose the advantageous use of inflection points of voltammetric activity curves as activity descriptors enabling to correlate the potential of individual surface site groups to the respective peaks in the adsorption energy distribution pattern. This concept allows to methodologically gather information about the importance of each element in a CSS with respect to activity and stability of the relevant active sites and provides the basis for a guideline for systematic composition optimization. Further, the effect of phase stability on specific surface site groups as induced by degradation of the CSS phase or oxidation can be monitored. These concepts are experimentally evaluated using Cr-Mn-Fe-Co-Ni as a model system. NanopartiCles are synthesized with systematically varied compositions by means of scalable laser ablation synthesis using a multinary target. The composition is optimized with respect to the electrocatalytic activity for the oxygen reduction reaction (ORR) by varying its Mn content via laser ablation synthesis in ethanol. Subsequently, the concept is applied using rotating disk electrodes for ORR analysis in alkaline media.Comparing the Activity of Complex Solid Solution Electrocatalysts Using Inflection Points of Voltammetric Activity Curves as Activity Descriptorshigh-entropy alloy; complex solid solution; activity descriptor; oxygen reduction reaction; laser ablation4202146#N/ATRUE
5474
acscatal.0c0327210.1021/acscatal.0c03272FALSEhttps://doi.org/10.1021/acscatal.0c03272Wang, LACS Catal.In situ catalyst regeneration of NiFe-based oxygen evolution catalyst (OEC) has been recognized as one of the best approaches for photocorrosion inhibition on water splitting photoelectrodes. However, it generally suffers from laborious multistep procedures to obtain a controllable film. Herein, we use an electron density modulation to synthesize a stable NiFeY layered double hydroxide (LDH) OEC and then deposit this OEC on BiVO4 as photoanodes. The incorporation of Y modifies the chemical environment of Ni and reduces the bandgap of NiFe LDH, enhancing the electrocatalytic/photoelectrochemical performance. Importantly, Y insertion in NiFe LDH remarkably reduces the surface recombination of the BiVO4/cocatalyst system, thereby establishing a much high stability to the photocatalyst than in conventional NiFe OEC/BiVO4 approaches.Yttrium-Induced Regulation of Electron Density in NiFe Layered Double Hydroxides Yields Stable Solar Water Splittingbismuth vanadate; trimetallic NiFeY LDH; electron density; oxygen evolution catalyst; long-term stability10202033#N/ATRUE
5475
acscatal.0c0195010.1021/acscatal.0c01950FALSEhttps://doi.org/10.1021/acscatal.0c01950Chen, SWACS Catal.Single metal atoms embedded within select supporting matrices have shown great potential in the development of high-efficiency, low-cost electrocatalysts because of maximal atom utilization and mass activity. As the single metal atoms are stabilized by coordination bonds with the substrate, the strong metal-support interactions can be exploited for ready manipulation of the electrocatalytic activity and selectivity toward target reactions. However, most single-atom catalysts (SACs) are prepared by pyrolysis and contain a wide range of coordination structures. Resolving the atomic configurations of the metal coordination moieties represents a critical first step in the establishment of an unambiguous correlation between the SAC structure and activity. In this Review, we summarize recent progress in the studies of single-atom electrocatalysts, with a focus on the impacts of the coordination structure of the single-atom sites on the electrocatalytic activities toward a series of reactions that are important for various electrochemical energy technologies, such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, nitrogen reduction reaction, CO2 reduction reaction, and so on. The survey entails a wide range of SACs, from noble metals (e.g., Pt, Pd, Ru, Ir, Au, etc.) to non-noble metals (e.g., Fe, Co, Ni, Cu, etc.), supported on a variety of substrate materials (e.g., pristine and doped carbon, metal, metal oxide, metal sulfide, etc.). Finally, the Review conCludes with a perspective highlighting the promises and challenges in the further development of SACs within the context of coordination chemistry.Electrocatalysis of Single-Atom Sites: Impacts of Atomic Coordinationsingle-atom catalyst; coordination moiety; atomic configuration; electrocatalytic activity; noble metal; non-noble metalx482020254#N/AFALSE
5476
acscatal.0c0190910.1021/acscatal.0c01909FALSEhttps://doi.org/10.1021/acscatal.6b01433Lopez, NStability and Redispersion of Ni NanopartiCles Supported on N-Doped Carbons for the CO2 Electrochemical Reductionx2021#N/AFALSE
5477
acscatal.0c0185110.1021/acscatal.0c01851FALSEhttps://doi.org/10.1021/acscatal.0c01851Weckhuysen, BMACS Catal.A Na-S promoted Fe-based Fischer-Tropsch synthesis (FTS) catalyst converts a H-2/CO gas mixture into hydrocarbons with enriched C-2-C-4 olefin content. Above 300 degrees C, the carbon-depositing Boudouard reaction competes with the FTS reaction for CO as reactant. By making use of a combined in situ X-ray powder diffractometry (XRPD)/Raman spectroscopy setup, the simultaneous evolution of the FexOy/alpha-Fe/FexC phases and various formed carbon species has been monitored at 340 degrees C and 10 bar. CO carburized, Na-S promoted and unpromoted Fe(-Na-S)/alpha-Al2O3 catalysts were investigated. The various Fe phases present were quantified with Rietveld quantitative phase analysis (R-QPA) from the in situ collected XRPD patterns. The observed D- and G-bands in the in situ Raman spectra were analyzed for their relative intensities, band widths, and positions and compared to reference carbon materials. It was found that amorphous carbon with C sp(3) and C sp(2) in chain-like ordering evolved toward carbon nanofiber-like structures during FTS. Na-S promotion and initial CO carburization at temperatures >= 340 degrees C led to an increased amount of cyClic sixfold C sp(2) species. Preliminary carbon deposits present in the catalysts decreased the initial fast increase of the Raman band intensities, while Na-S promotion increased Raman band intensity growth after the initial fast increase period. The carbon species evolution was unaffected by the presence of specific Fe carbides or by carbide-to-carbide transitions. Na-S promotion aided in the reduction of Fe3O4 by (H-2:)CO to carbon-depositing Fe carbides. The results obtained add to our further understanding on the role of Fe and carbon species during a high-temperature FTS reaction.Combined In Situ X-ray Powder Diffractometry/Raman Spectroscopy of Iron Carbide and Carbon Species Evolution in Fe(-Na-S)/alpha-Al2O3 Catalysts during Fischer-Tropsch Synthesisheterogeneous catalysis; Fischer-Tropsch synthesis; iron carbides; Na-S promotion; X-ray powder diffractometry; Rietveld quantitative phase analysisx52020125#N/AFALSE
5478
acscatal.0c0321410.1021/acscatal.0c03214FALSEhttps://doi.org/10.1021/acscatal.0c03214Duan, XZACS Catal.Suppression of catalyst deActivation without compromising activity has been a long-standing yet elusive goal in heterogeneous catalysis. Herein, we report a remarkable achievement of both hydrogen generation activity and durability by atomically engineering Pt-PdO interfacial sites. A combination of kinetics (isotopic) analyses, multiple characterization techniques, molecular dynamics, and density functional theory calculations was employed to reveal the evolution of the Pt-Pd atomic structure where Pd segregates to the outer surface of Pt nanopartiCles, followed by partial oxidation, resulting in the structure of a Pt-rich core and a PdO-Pd-rich shell. The strong capability of PdO to activate H2O compensates for its adverse effects on Pt electronic properties and creates the Pt and PdO interfacial sites for ammonia borane and H2O Activation, respectively. Moreover, because of the strong electron repulsion and steric hindrance effects, these surface PdO sites strongly inhibit the adsorption of B(OH)(4)(-), thus protecting Pt active sites from poisoning. As a result, such a unique atomic structure with a Pt-Pd ratio of 1:1 is found to be the most promising catalyst at the apex of the volcano curve. The strategy developed here unambiguously Clarifies the activity and durability attributes of Pt-PdO interfacial sites for this reaction and sheds light on the design of a new type of highly active yet stable metal catalysts.Atomic Insights into Robust Pt-PdO Interfacial Site-Boosted Hydrogen GenerationPt-PdO interfacial sites; atomic insights; hydrogen generation; activity and durability; volcano curve3202052#N/ATRUE
5479
acscatal.0c0309410.1021/acscatal.0c03094FALSEhttps://doi.org/10.1021/acscatal.0c03094Kaya, SACS Catal.Developing active, durable, and inexpensive electrocatalysts is critical for hydrogen production to meet ever-growing sustainable energy needs. Nickel sulfides offer significant potential as electrocatalysts for a hydrogen evolution reaction (HER); however, the active phase governing the electrochemical conversion is still under debate. We show that mesoporous thin-film NiS2 synthesized by a novel soft-templating method without post-sulfurization exhibits superior HER activity in alkaline media after a preconditioning step that results in sulfur leaching, amorphization of the surface, and collapse of the mesoporous structure. A comparative analysis with crystalline NiS2 reveals that partial hydroxylation of the under-coordinated Ni sites is responsible for the superior HER activity.Mesoporous Thin-Film NiS2 as an Idealized Pre-Electrocatalyst for a Hydrogen Evolution ReactionNiS2; HER; mesoporous thin films; water splitting; stability1202073#N/ATRUE
5480
acscatal.0c0181310.1021/acscatal.0c01813FALSEhttps://doi.org/10.1021/acscatal.0c01813Cui, CHACS Catal.Transition-metal (oxy)hydroxides with an abundance of redox metal sites are important for the development of electrochromic devices, rechargeable metal-air batteries, pseudo-capacitors, and industrial electrolyzers. The robust charging reversibility of the redox metal sites ensures long-term durability of the devices but remains unachieved and usually ignored. Here, we use in situ UV-vis and Raman spectroscopies to track the redox states of a nickel hydroxide Ni(OH)(2) model catalyst for the oxygen evolution reaction (OER) during its lifetime in strong alkaline media. We show that at 200 mAcm(-2) in the 1.0 M KOH electrolyte, the reversible redox states of the catalytically active Ni sites gradually disappear when the catalyst converts into an irreversible and inactive phase. We found that after deActivation, the complete reduction of such oxidized Ni sites can not be achieved until a very negative reduction potential around 0.1 V RHE was applied owing to the structural amorphization/disordering of the layered Ni(OH)(2) catalyst. Our results suggest that the deactivated and unreduced Ni sites hardly re-hydrate/re-hydroxylate and thus obstruct the OER process. These findings provide direct evidence for elucidation of the origin of the oxygen evolution decay and contribute to a reference to extend the lifetime of 2D-layered transition-metal hydroxide catalysts by stabilizing the reversible redox metal sites.Spectroelectrochemical Tracking of Nickel Hydroxide Reveals Its Irreversible Redox States upon Operation at High Current Densityredox state; nickel hydroxide; spectroelectrochemistry; oxygen evolution reaction; stabilityx6202041#N/AFALSE
5481
acscatal.0c0176510.1021/acscatal.0c01765FALSEhttps://doi.org/10.1021/acscatal.0c01765Gan, LACS Catal.Thermal annealing is an indispensable process during the preparation and structural ordering of Pt alloy fuel cell catalysts, which exhibit superior electrocatalytic activities as compared to Pt catalysts and thus enable decreased Pt usage. However, thermal annealing usually induces detrimental partiCle sintering, which greatly offsets the performance enhancement. Although the mechanisms of partiCle sintering of monometallic Pt catalysts have been well studied, knowledge on the key factors controlling the partiCle sintering of Pt alloy catalysts is still very poor. Herein, we perform in situ heating (scanning) transmission electron microscopy of carbon-supported low-Pt alloy catalysts (PtFe3, PtCo3, and PtNi3) and reveal that the surface composition plays a key role in both the partiCle mobility and the coalescence process of the supported low-Pt nanopartiCles (NPs) under high temperatures. A surface enrichment of the less-noble transition metals not only induces a faster partiCle coalescence due to enhanced surface diffusion, but also causes a higher mobility of the NPs on the carbon support due to a strong chemical interaction between the less-noble transition metals and the carbon support. In contrast, the Pt richer surface results in a lower NP mobility as well as slower surface diffusion across contact NPs, which contributes to a higher antisintering capability. Our results suggest that controlling the surface composition, for example, by engineering the elemental growth kinetics during nanopartiCle synthesis, is critical for controlling the partiCle sintering of Pt alloy catalysts during thermal annealing.Revealing the Role of Surface Composition on the PartiCle Mobility and Coalescence of Carbon-Supported Pt Alloy Fuel Cell Catalysts by In Situ Heating (S)TEMPt alloy catalysts; oxygen reduction reaction; fuel cells; thermal stability; partiCle sintering; in situ transmission electron microscopyx1202029#N/AFALSE
5482
acscatal.0c0303310.1021/acscatal.0c03033FALSEhttps://doi.org/10.1021/acscatal.0c03033Drennan, ClACS Catal.The Wood-Ljungdahl pathway allows for autotrophic bacterial growth on carbon dioxide, with the last step in acetyl-CoA synthesis catalyzed by the bifunctional enzyme carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS). ACS uses a complex Ni-Fe-S metalloCluster termed the A-Cluster to assemble acetyl-CoA from carbon monoxide, a methyl moiety and coenzyme A. Here, we report the crystal structure of CODH/ACS from Moorella thermoacetica with substrate carbon monoxide bound at the A-Cluster, a state previously uncharacterized by crystallography. Direct structural characterization of this state highlights the role of second sphere residues and conformational dynamics in acetyl-CoA assembly, the biological equivalent of the Monsanto process.Crystallographic Characterization of the Carbonylated A-Cluster in Carbon Monoxide Dehydrogenase/Acetyl-CoA SynthaseCODH; ACS; Wood-Ljungdahl; acetogenesis; metalloenzymes; carbon monoxide; acetyl coenzyme A; X-ray crystallography2202035#N/ATRUE
5483
acscatal.0c0292910.1021/acscatal.0c02929FALSEhttps://doi.org/10.1021/acscatal.0c02929Duan, AJOriented Hydrocracking of Naphthalene into High-Value Light Aromatics over Difunctional Catalysts: Effect of Hydrogen Spillover and Utilization of Hydroreaction Characteristics for Different Active Metals2020#N/ATRUE
5484
acscatal.0c0156810.1021/acscatal.0c01568FALSEhttps://doi.org/10.1021/acscatal.0c01568Pylypenko, SACS Catal.Platinum-nickel (Pt-Ni) nanowires were developed as hydrogen evolving catalysts for anion exchange membrane electrolyzers. Following synthesis by galvanic displacement, the nanowires had Pt surface areas of 90 m(2) g(Pt)(-1). The nanowire specific exchange current densities were 2-3 times greater than commercial nanopartiCles and may benefit from the extended nanostructure morphology that avoids fringe facets and produces higher quantities of Pt{100}. Hydrogen annealing was used to alloy Pt and Ni zones and compress the Pt lattice. Following annealing, the nanowire activity improved to 4 times greater than the as-synthesized wires and 10 times greater than Pt nanopartiCles. Density functional theory calculations were performed to investigate the influence of lattice compression and exposed facet on the water-splitting reaction; it was found that at a lattice of 3.77 angstrom, the (100) facet of a Pt-skin grown on Ni3Pt weakens hydrogen binding and lowers the barrier to water-splitting as compared to pure Pt(100). Moreover, the Activation energy of water-splitting on the (100) facet of a Pt-skin grown on Ni3Pt is particularly advantageous at 0.66 eV as compared to the considerably higher 0.90 eV required on (111) surfaces of pure Pt or Pt-skin grown on Ni3Pt. This favorable effect may be slightly mitigated during further optimization procedures such as acid leaching near-surface Ni, necessary to incorporate the nanowires into electrolyzer membrane electrode assemblies. Exposure to acid resulted in slight dealloying and Pt lattice expansion, which reduced half-cell activity, but exposed Pt surfaces and improved single-cell performance. Membrane electrode assembly performance was kinetically 1-2 orders of magnitude greater than Ni and slightly better than Pt nanopartiCles while at one tenth the Pt loading. These electrocatalysts potentially exploit the highly active {100} facets and provide an ultralow Pt group metal option that can enable anion exchange membrane electrolysis, bridging the gap to proton exchange membrane-based systems.Platinum-Nickel Nanowires with Improved Hydrogen Evolution Performance in Anion Exchange Membrane-Based Electrolysislow-temperature electrolysis; anion exchange membrane; electrocatalysis; hydrogen evolution; extended surfacesx3202066#N/AFALSE
5485
acscatal.0c0149810.1021/acscatal.0c01498FALSEhttps://doi.org/10.1021/acscatal.0c01498Jin, SACS Catal.The electrochemical oxidation of abundantly available glycerol for the production of value-added chemicals, such as formic acid, could be a promising approach to utilize glycerol more effectively and to meet the future demand for formic acid as a fuel for direct or indirect formic acid fuel cells. Here we report a comparative study of a series of earth-abundant cobalt-based spinel oxide (MCo2O4 , M = Mn, Fe, Co, Ni, Cu, and Zn) nanostructures as robust electrocatalysts for the glycerol oxidation to selectively produce formic acid. Their intrinsic catalytic activities in alkaline solution follow the sequence of CuCo2O4 > NiCo2O4 > CoCo2O4 > FeCo2O4 > ZnCo2O4 > MnCo2O4 . Using the best-performing CuCo2O4 catalyst directly integrated onto carbon fiber paper electrodes for the bulk electrolysis reaction of glycerol oxidation (pH = 13) at the constant potential of 1.30 V vs reversible hydrogen electrode (RHE), a high selectivity of 80.6% for formic acid production and an overall Faradaic efficiency of 89.1% toward all value-added products were achieved with a high glycerol conversion of 79.7%. Various structural characterization techniques confirm the stability of the CuCo2O4 catalyst after electrochemical testing. These results open up opportunities for studying earth-abundant electrocatalysts for efficient and selective oxidation of glycerol to produce formic acid or other value-added chemicals.Electrocatalytic Oxidation of Glycerol to Formic Acid by CuCo2O4 Spinel Oxide Nanostructure Catalystsbiomass conversion; glycerol oxidation; spinel oxides; formic acid; electrocatalysis; fuel cellx21202068#N/AFALSE
5486
acscatal.0c0144110.1021/acscatal.0c01441FALSEhttps://doi.org/10.1021/acscatal.0c01441Truhlar, DGACS Catal.The surface structures at catalytic sites are critical factors for determining catalytic selectivity. Here, we use periodic density functional theory and microkinetic modeling to systematically investigate the effect of surface structures on the conversion of furfuryl alcohol (FA). We consider nine surface terminations of Ni with various coordination numbers representing terrace, step, and corner sites. We study three reaction paths for FA conversion on various surfaces and find that the surface structure impacts the adsorption configuration and causes significant differences in selectivity. Barrier height analysis shows that terrace sites favor hydrogenation to tetrahydrofurfuryl alcohol (THFA), whereas corner sites favor C-OH bond scission to produce 2-methylfuran (2-MF); step sites show similar barriers for the two reactions. We explain this by identifying three characteristics of the reactant adsorption structures that have a significant effect on selectivity, namely, that a shorter distance between the adsorbed hydrogen atom and the C3 carbon of FA favors hydrogenation to produce THFA, and more negative charge transfer to O-al(co)hol and a longer C-O-al(co)hol bond length favor C-O-al(co)hol bond scission to produce 2-MF. Since the reactions have similar barriers at a step site, microkinetic calculations are employed to calculate the product selectivity on a step site under experimental conditions. At lower temperatures and hiller generalized coordination number ((CN) over bar), THFA is the most favorable product, while the selectivity to 2-MF is higher at lower (CN) over bar and at higher temperature. This work provides guidance for the rational design catalysts to control the product distribution of FA conversion.Catalytic Conversion Furfuryl Alcohol to Tetrahydrofurfuryl Alcohol and 2-Methylfuran at Terrace, Step, and Corner Sites on Nibarrier heights; biomass; catalysis; furfural; hydrodeoxygenation; hydrogenation; microkinetic modeling; selectivityx6202061#N/AFALSE
5487
acscatal.0c0137310.1021/acscatal.0c01373FALSEhttps://doi.org/10.1021/acscatal.0c01373Altomare, MACS Catal.Cu- or Ni-decorated semiconductors represent a potential low-cost alternative to noble-metal-modified photocatalysts. Even more effective are bimetallic NiCu nanopartiCles, which can provide a remarkable photocatalytic H-2 evolution enhancement compared to single-element Cu or Ni systems. The main concern of such alloyed co-catalysts is their activity with respect to alteration of their elemental composition and oxidation state over reaction time. Ex situ characterization techniques provide controversial interpretations of the co-catalytic role of the individual elements. Hypotheses such as the in situ reduction of native Ni or Cu species during photocatalysis, the oxidation of metallic Cu or Ni into oxides or hydroxides, or the formation of p-n junctions or core/shell structures have been proposed. Herein, we present an operando X-ray absorption spectroscopy study of a NiCu-TiO2 system under UV light illumination in ethanol-water solutions, i.e., under photocatalytic H-2 evolution conditions. The experimental approach allows for monitoring in real time chemical changes that take place in the co-catalyst under intermittent illumination, i.e., under light on-off cyCles. We show that while Ni and Cu are partially oxidized in the as-formed NiCu co-catalyst (air-formed surface oxides or hydroxides) and undergo partial dissolution in the liquid phase under dark conditions, such Ni and Cu oxidized and dissolved species are reduced/redeposited as a bimetallic NiCu phase at the TiO2 surface under illumination. The dissolution/redeposition mechanism is triggered by TiO2 conduction band electrons. We not only prove a UV-light-induced healing of the NiCu co-catalyst but also unambiguously demonstrate that the species responsible for the strongly enhanced photocatalytic H-2 evolution of NiCu nanopartiCles are the metallic states of Ni and Cu.An Operando X-ray Absorption Spectroscopy Study of a NiCu-TiO2 Photocatalyst for H-2 Evolutionsolid-state dewetting; NiCu alloy nanopartiCles; TiO2 nanotubes; photocatalytic H-2 evolution; in situ XASx11202066#N/AFALSE
5488
acscatal.0c0288210.1021/acscatal.0c02882FALSEhttps://doi.org/10.1021/acscatal.0c02882Cui, CHACS Catal.Although much is known about the increased rate of a catalyst required for the oxygen evolution reaction (OER), the hole accumulation behaviors of the catalyst on both photo- and dark electrodes remain uncovered. We present a rational tuning of the hole-accumulation and hole-transfer ability of a catalyst by in situ deposition of IrOx on NiOx islands on model Si electrodes and we demonstrate a distinct hole accumulation behavior during the OER through electrochemical methods, in situ UV-vis and Raman spectroelectrochemistry. We find that the NiOx islands with <10% coverage on an n++-Si dark electrode demonstrate a 6-fold higher capacity of hole accumulation relative to that on an n-Si photoanode under illumination. A further in situ targeted deposition of soluble hexahydroxyiridate on the NiOx leads to the formation of NiOx/IrOx junctions, where the IrOx further depletes the extracted holes by NiOx from the n-Si photoanode decreasing the overpotential by similar to 260 mV at 20 mA cm(-2), yet the IrOx promotes the hole accumulation at the NiOx/IrOx on the dark electrodes presenting a similar decrease of the overpotential. In contrast to the dark-holes, an extremely lower charging level of photogenerated holes of the same catalyst at the identical current density reasoned a seemingly higher reactivity to drive the OER, and reasonably demonstrated a stronger oxidation/ corrosion to the Si electrode.Tuning Hole Accumulation of Metal Oxides Promotes the Oxygen Evolution Rateoxygen evolution reaction; dark-hole; hole accumulation; spectroelectrochemistry; solar fuel0202053#N/ATRUE
5489
acscatal.0c0127310.1021/acscatal.0c01273FALSEhttps://doi.org/10.1021/acscatal.0c01273Chen, GACS Catal.The rational design of oxygen evolution reaction (OER) catalysts from the perspective of electronic structure is highly desirable to optimize electrocatalytic activity. Monometallic phosphides such as Ni2P have been shown to be active toward OER, but their performance remains unsatisfactory. Herein, guided by the theoretical mechanism study of the intrinsic high electroactivity revealed in the d-band center (E-d) theory, the Fe-substituted Ni2P ((NixFe1-x)(2)P) nanosheets grown directly on NiFe foam are designed and synthesized. As OER electrocatalysts in alkaline media, the (NixFe1-x)(2)P nanosheets show an overpotential of 166 mV to deliver the current density of 10 mA cm(-2), which is superior to the Ni2P and most reported transition-metal-based catalysts. Combining DFT simulations with experiments reveals that the enhanced activity results from the moderate rise in E-d energy levels, which balances the adsorption and desorption capacities of the oxygen-containing intermediates (*O, *OH, and *OOH). This work supplies valuable insights for the rational design and construction of efficient doped electrocatalysts under the guidance of the d-band center theory.Tailoring the d-Band Centers Endows (NixFe1-x)(2)P Nanosheets with Efficient Oxygen Evolution Catalysisd-band center; Fe-substituted Ni2P; electrocatalysis; oxygen evolution reaction; DFT calculationsx20202052#N/AFALSE
5490
acscatal.0c0251410.1021/acscatal.0c02514FALSEhttps://doi.org/10.1021/acscatal.0c02514Nelson, DJACS Catal.The mechanism of the reactions between dppf-Ni-0 complexes and Alkyl halides has been investigated using kinetic and mechanistic experiments and DFT calculations. The active species is [Ni(kappa(2)-dppf)(kappa(1)-dppf)], which undergoes a halide abstraction reaction with Alkyl halides and rapidly captures the Alkyl radical that is formed. The rates of the reactions of [Ni(COD)(dppf)] with Alkyl halides and the yields of prototypical nickel-catalyzed Kumada cross-coupling reactions of Alkyl halides are shown to be significantly improved by the addition of free dppf ligand.Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0)nickel; homogeneous catalysis; cross-coupling; reaction mechanisms; organometallic chemistry1202050#N/ATRUE
5491
acscatal.0c0122910.1021/acscatal.0c01229FALSEhttps://doi.org/10.1021/acscatal.0c01229Kawi, SACS Catal.The partial substitution of Ni in LaNiO3 perovskite-derived catalysts by Fe has been shown to considerably improve the catalyst stability and coke resistance in dry reforming of methane (DRM). In this study, we have investigated the reaction mechanism of DRM on La0.9Sr0.1Ni0.5Fe0.5O3-derived catalysts and shown how it differs from that on La0.9Sr0.1NiO3. By using isotopically labeled reactants and in situ DRIFTS analysis, we observe that lanthanum oxycarbonates are active intermediates for CO2 Activation and oxidation of carbonaceous intermediates from methane on the La0.9Sr0.1NiO3 catalyst, whereas the oxidation of carbonaceous intermediates occurs solely through a MvK-type redox mechanism by support lattice oxygen in La0.9Sr0.1Ni0.5Fe0.5O3. The catalysts were thoroughly characterized by XRD, H-2-TPR, XAS, XPS, O-2- and CO2-TPD-MS, H-2 chemisorption, TGA-DTA, and TEM, and the catalyst properties were correlated with the proposed reaction mechanism. It was observed that in contrast to La0.9Sr0.1NiO3, which almost completely decomposed to form Ni/La2O3-xSrO after H-2 reduction pretreatment, La0.9Sr0.1Ni0.5Fe0.5O3 could partially retain a perovskite structure after reduction and in the DRM atmosphere. Detailed characterization of the La0.9Sr0.1Ni0.5Fe0.5O3 catalyst after reduction and exposure to reactant gases reveals that this perovskite phase is reversibly decomposed into La2O3 and metal (NiFe) upon exposure to CH4 and is reconstructed upon exposure to CO2 or CH4/CO2 mixture. The cyClic decomposition and formation of the perovskite phase is accompanied by the release and capture of oxygen from and into the perovskite lattice and the redox cyCling of Fe between Fe0 (in NiFe alloy) and Fe3+/Fe4+ (in perovskite) states. The La0.9Sr0.1NiO3, on the other hand, forms the lanthanum oxycarbonate phase in CO2 atmosphere, with no observable reconstruction of the perovskite phase. We attribute the reversibility of the formation of the stable La1-xSrxFeO3 perovskite phase under DRM conditions and its high oxygen storage/release capacity as the primary reason for the dominance of the redox mechanism and high coke resistance of La0.9Sr0.1Ni0.5Fe0.5O3.Effect of Partial Fe Substitution in La0.9Sr0.1NiO3 Perovskite-Derived Catalysts on the Reaction Mechanism of Methane Dry Reformingdry reforming of methane; perovskite; reaction mechanism; isotope study; in situ DRIFTSx3202060#N/AFALSE
5492
acscatal.0c0119910.1021/acscatal.0c01199TRUEhttps://doi.org/10.1021/acscatal.0c01199Doyle, AGACS Catal.A cross-electrophile coupling reaction of epoxides and (hetero)Aryl iodides that operates via the merger of three catalytic cyCles involving a Ni-, Ti-, and organic photoredox catalyst has been developed. Three distinct Classes of epoxides, styrene oxides, cyClic epoxides, and terminal aliphatic epoxides, all undergo coupling in moderate to good yield and high regioselectivity with the use of three different nitrogen-based ligands for Ni under otherwise identical reaction conditions. The mild reaction conditions accommodate a broad scope of abundant and complex coupling partners. Mechanistic studies suggest that when styrene oxides are employed radical intermediates are involved via Ti-radical ring-opening of the epoxide. Conversely, for terminal aliphatic epoxides, involvement of an iodohydrin intermediate enables the formation of the unexpected linear product.Regioselective Cross-Electrophile Coupling of Epoxides and (Hetero)Aryl Iodides via Ni/Ti/Photoredox Catalysisepoxides; Arylation; cross-electrophile coupling; photoredox catalysis; nickel catalysis; titanium catalysis; radical chemistry; photochemistryPhotocatalystCsp3-Csp2_ar
O(Ring-Opening)
XAlkylNitrogenNitrogen(neutral)102020646/15/2022FALSE
5493
acscatal.0c0246710.1021/acscatal.0c02467FALSEhttps://doi.org/10.1021/acscatal.0c02467Park, JYACS Catal.Platinum-based bimetallic catalysts exhibit surface atomic rearrangement in various adsorbate environments, which significantly impacts catalysis. A molecular-level understanding of intermediate structures created during catalysis is essential for developing high-performance bimetal catalysts. We show that intermediate Pt-NiO1-x interfacial structures drive the catalytic synergistic effect observed on Pt3Ni nanocrystals. Real-time microscopic observations at ambient pressure show the formation of oxygen-driven Ni oxide Clusters on the surface and provide direct evidence of Pt-NiO1-x interfacial structure formation. Spectroscopic analysis, inCluding ambient-pressure X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy, and catalytic measurements elucidate the role of Pt-NiO1-x interfacial structures and the catalytic reaction mechanism in CO oxidation. Our results indicate that metal-oxide interfacial intermediate structures in bimetal catalysts relate to the catalytic enhancement of the strong metal-support interaction (SMSI) effect.Catalytic Synergy on PtNi Bimetal Catalysts Driven by Interfacial Intermediate StructuresPtNi nanocrystal; CO conversion; bimetallic synergy; surface restructuring; operando micro/spectroscopy5202041#N/ATRUE
5494
acscatal.0c0109210.1021/acscatal.0c01092FALSEhttps://doi.org/10.1021/acscatal.0c01092Oliviero, LPromoter Location on NiW/Al2O3 Sulfide Catalysts: Parallel Study by IR/CO Spectroscopy and High-Resolution STEM-HAADF Microscopyx2020#N/AFALSE
5495
acscatal.0c0108510.1021/acscatal.0c01085FALSEhttps://doi.org/10.1021/acscatal.0c01085Rossmeisl, JACS Catal.In the past decade, the mass activity of catalysts for the oxygen reduction reaction (ORR) has been improved mainly via increasing the number of active sites. However, little progress has been made on the improvement of the intrinsic activity of ORR catalysts; consequently, the widespread use of fuel cells is still limited by low energy efficiency. In this Perspective, we provide an overview of the fundamentals underlying the ORR on platinumbased catalysts as well as metal-nitrogen-carbon nonprecious metal catalysts. We also report the diporphyrin complexes as promising catalysts with outstanding activity owing to structural advantages. In particular, diporphyrin anthracene (DPA) with optimized ligand coordination has a low barrier to dissociate O-2 molecules at the optimal oxygen adsorption energy region, which might unlock overpotentials of less than 0.2 V.Insights in the Oxygen Reduction Reaction: From Metallic Electrocatalysts to Diporphyrinsoxygen reduction reaction; O-2 dissociation; Bronsted-Evans-Polanyi relation; diporphyrins; density functional theoryx52020104#N/AFALSE
5496
acscatal.0c0221910.1021/acscatal.0c02219FALSEhttps://doi.org/10.1021/acscatal.0c02219Maurin, GACS Catal.Through density functional theory calculations, we unravel a microscopic picture of the catalytic NO oxidation activity of the MIL-100 MOF platform. By systematically varying the nature of the coordinatively unsaturated metal sites (Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ru), we demonstrate the relative energy of the metal-oxygen intermediate species to be a reliable descriptor to anticipate the catalytic activity of this family of MOFs. These conClusions are first validated by experimental data on MIL-100(Fe)/MIL-100(Fe,Mn) and further used as guidelines to develop a ruthenium-based MIL-100 with even better catalytic performance.Mechanistic Insight into the Catalytic NO Oxidation by the MIL-100 MOF Platform: Toward the Prediction of More Efficient CatalystsNO oxidation; metal-organic framework; coordinatively unsaturated metal sites; catalysis; molecular simulations; understanding of mechanism; rationalization; prediction0202046#N/ATRUE
5497
acscatal.0c0093410.1021/acscatal.0c00934FALSEhttps://doi.org/10.1021/acscatal.0c00934Dementin, SACS Catal.Ni-Fe CO-dehydrogenases (CODHs) catalyze the conversion between CO and CO2 using a chain of Fe-S Clusters to mediate long-range electron transfer. One of these Clusters, the D-Cluster, is surface-exposed and serves to transfer electrons between CODH and external redox partners. These enzymes tend to be extremely O-2-sensitive and are always manipulated under strictly anaerobic conditions. However, the CODH from Desulfovibrio vulgaris (Dv) appears unique: exposure to micromolar concentrations of O-2 on the minutes-time scale only reversibly inhibits the enzyme, and full activity is recovered after reduction. Here, we examine whether this unusual property of Dv CODH results from the nature of its D-Cluster, which is a [2Fe-2S] Cluster, instead of the [4Fe-4S] Cluster observed in all other characterized CODHs. To this aim, we produced and characterized a Dv CODH variant where the [2Fe-2S] D-Cluster is replaced with a [4Fe-4S] D-Cluster through mutagenesis of the D-Cluster-binding sequence motif. We determined the crystal structure of this CODH variant to 1.83-A resolution and confirmed the incorporation of a [4Fe-45] D-Cluster. We show that upon long-term O-2-exposure, the [4Fe-4S] DCluster degrades, whereas the [2Fe-2S] D-Cluster remains intact. Crystal structures of the Dv CODH variant exposed to O-2 for increasing periods of time provide snapshots of [4Fe-4S] D-Cluster degradation. We further show that the WT enzyme purified under aerobic conditions retains 30% activity relative to a fully anaerobic purification, compared to 10% for the variant, and the WT enzyme loses activity more slowly than the variant upon prolonged aerobic storage. The D-Cluster is therefore a key site of irreversible oxidative damage in Dv CODH, and the presence of a [2Fe-2S] D-Cluster contributes to the O-2-tolerance of this enzyme. Together, these results relate O-2-sensitivity with the details of the protein structure in this family of enzymes.The Solvent-Exposed Fe-S D-Cluster Contributes to Oxygen-Resistance in Desulfovibrio vulgaris Ni-Fe Carbon Monoxide DehydrogenaseCO-dehydrogenase; iron-sulfur Cluster; carbon monoxide; oxygen-sensitivity; oxidative damage; crystallography; protein film voltammetryx1202042#N/AFALSE
5498
acscatal.0c0091810.1021/acscatal.0c00918FALSEhttps://doi.org/10.1021/acscatal.0c00918Hirano, MPd/Cu-Catalyzed Dehydrogenative Coupling of Dimethyl Phthalate: Synchrotron Radiation Sheds Light on the Cu CyCle Mechanismx2020#N/AFALSE
5499
acscatal.0c0220310.1021/acscatal.0c02203FALSEhttps://doi.org/10.1021/acscatal.0c02203Wu, YACS Catal.Single atom catalysts (SACs) as a kind of bright star catalyst have attracted great attention, constituting a series of intriguing properties for catalytic reactions. Herein, a simple and ingenious strategy is developed for the fabrication of SACs via atomic filtration during a solid diffusion process under the assistance of graphene oxide membranes (GOMs). First, driven by the heat treatment, the Fe species (atoms, Cluster, or partiCles) are emitted from Fe foam diffused through the GOMs. By elaborately modulating the layer numbers of the GOM and their interlayer spacing, the GOM could exClude the Cluster and partiCles of the Fe species. Thus, the permeable single Fe atoms were trapped by defective N-rich sites, producing isolated Fe site catalyst (Fe SAs/N-C). The fabricated SACs exhibited an excellent catalytic performance for the oxygen reduction reaction (ORR). Furthermore, this strategy can be easily expanded to prepare other SACs, such as Co SAs/N-C and Ni SAs/N-C.Atomic Filtration by Graphene Oxide Membranes to Access Atomically Dispersed Single Atom Catalystssingle atom catalysts; graphene oxide membranes; atomic filtration; Fe SAs/N-C4202043#N/ATRUE
5500
acscatal.0c0090310.1021/acscatal.0c00903FALSEhttps://doi.org/10.1021/acscatal.0c00903Ordomsky, VVACS Catal.Supported cobalt and nickel nanopartiCles are commonly used as catalysts in the modern chemical industry. Traditional methods of catalyst preparation such as impregnation or precipitation lead to the formation of relatively large metal nanopartiCles (15-30 nm). The design of supported metal catalysts with higher dispersion is expected to result in major rate enhancement in many catalytic reactions. Hereby, we propose an efficient way to significantly increase the dispersion of metal catalysts by disassembling of supported metal nanopartiCles using in situ polycondensation of aldehydes produced during dehydrogenation of fatty alcohols. Bulky polymers behave as surfactants, facilitating budding of smaller metal nanopartiCles. Subsequent removal of carbon species by oxidative treatments results in smaller isolated metal nanopartiCles with the sizes of about 2-7 nm and 3-6 times higher catalytic activity in hydrogenation, amination, and oxidation reactions. This method opens up the possibility of metal redispersion in both freshly prepared and deactivated catalysts.Disassembly of Supported Co and Ni NanopartiCles by Carbon Deposition for the Synthesis of Highly Dispersed and Active CatalystsNPs; dispersion; carbon species; polymer; catalytic activityx0202036#N/AFALSE
5501
acscatal.0c0085610.1021/acscatal.0c00856FALSEhttps://doi.org/10.1021/acscatal.0c00856Yubero, FACS Catal.Herein we have developed nanostructured nickel-based electrode films for anion exchange membrane water electrolysis (AEMWE). The electrodes were prepared by magnetron sputtering (MS) in an oblique angle configuration and under various conditions aimed at preparing metallic, oxide, or oxyhydroxide films. Their electrochemical analysis has been complemented with a thorough physicochemical characterization to determine the effect of microstructure, chemical state, bilayer structure, and film thickness on the oxygen evolution reaction (OER). The maximum electrocatalytic activity was found for the metallic electrode, where analysis by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) demonstrated that the active catalytic phase at the surface after its electrochemical conditioning is a kind of oxidized nickel oxide/hydroxide layer with the thickness of a few nanometers. Electrochemical impedance spectroscopy analysis of these steady-state working electrodes supports that the enhanced performance of the metallic nickel anode vs other chemical states resides in the easier electron transfer through the electrode films and the various interlayers built up during their fabrication and Activation. The long-term steady-state operation of the anodes and their efficiency for water splitting was proved in a full-cell AEMWE setup incorporating magnetron-sputtered metallic nickel as the cathode. This work proves that MS is a suitable technique to prepare active, stable, and low-cost electrodes for AEMWE and the capacity of this technique to control the chemical state of the electrocatalytically active layers involved in the OER.Chemistry and Electrocatalytic Activity of Nanostructured Nickel Electrodes for Water Electrolysiselectrocatalytic activity; OER; HER; nickel electrodes; nickel oxide anodes; nanostructure; magnetron sputtering; water electrolyzersx7202082#N/AFALSE
5502
acscatal.0c0208910.1021/acscatal.0c02089FALSEhttps://doi.org/10.1021/acscatal.0c02089Chen, JGACS Catal.Machine learning is ideally suited for the pattern detection in large uniform data sets, but consistent experimental data sets on catalyst studies are often small. Here we demonstrate how a combination of machine learning and first-principles calculations can be used to extract knowledge from a relatively small set of experimental data. The approach is based on combining a complex machine-learning model trained on a computational library of transition-state energies with simple linear regression models of experimental catalytic activities and selectivities from the literature. Using the combined model, we identify the key C-C bond-scission reactions involved in ethanol reforming and perform a computational screening for ethanol reforming on monolayer bimetallic catalysts with architectures TM-Pt-Pt(111) and Pt-TM-Pt(111) (TM = 3d transition metals). The model also predicts four promising catalyst compositions for future experimental studies. The approach is not limited to ethanol reforming but is of general use for the interpretation of experimental observations as well as for the computational discovery of catalytic materials.Predicting the Activity and Selectivity of Bimetallic Metal Catalysts for Ethanol Reforming using Machine Learningethanol reforming; bimetallic catalysts; density-functional theory; transition states; machine learning; random forest regression; Gaussian process regression10202042#N/ATRUE
5503
acscatal.0c0197910.1021/acscatal.0c01979FALSEhttps://doi.org/10.1021/acscatal.0c01979Shang, RACS Catal.The development of transition metal (TM) catalysis for organic synthesis under visible light without recourse to typical photoredox catalysts has become a rapidly growing area of research and has been actively explored in the past several years. Distinct from the extensively developed photoredox catalysis, in which the photocatalyst generally does not directly participate in a bond-forming process, and photocatalyst/TM synergistic catalysis, in which the photocatalyst absorbs photon energy and transfers energy to the TM catalyst through a redox or energy transfer process, this Review focuses on summarizing the recent developments of photocatalytic reactions that use TM complexes to both absorb visible light and participate in catalytic bond formation involving a catalyst covalently bonded intermediate. The contents of this Review are categorized by the transition metal used (Pd, Cu, Co, Ni, Mn, Au, Rh, Fe, Ru), with a descending sequence according to the number of examples reported of each metal, and provide an overview of TM catalysis under visible light reported to April 2020. Future perspectives and personal opinions regarding this actively expanding research field are also discussed.Transition Metal-Catalyzed Organic Reactions under Visible Light: Recent Developments and Future Perspectivesphotocatalysis; transition metal catalysis; visible light; excited state; photoreactivity342020174#N/ATRUE
5504
acscatal.0c0184410.1021/acscatal.0c01844FALSEhttps://doi.org/10.1021/acscatal.0c01844Farha, OKACS Catal.Solid supports play an indispensable role in heterogeneous catalysis, as they can directly affect the catalytic activity and selectivity of supported catalysts. However, the specific roles of such supports remain to be demystified owing to the difficulties in obtaining precise structural information on supported catalysts. To understand the effects of MOF topology, pore environment, and metal identity of node supports on the catalytic activity, a Ni catalyst was supported on eight Zr- or Hf-MOFs based on 8-connected nodes: namely M-NU-1200, M-NU-1000, M-NU-1008, and M-NU-1010 (M = Zr, Hf). Single-crystal X-ray diffraction (SCXRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS) were employed to characterize the supported catalyst structures. To investigate the support effects on their activities, the supported Ni catalysts were evaluated by using ethylene hydrogenation as a model reaction. The results revealed that all Hf-based-MOF-supported Ni catalysts exhibited higher catalytic reactivity with TOF (turnover frequency) values at least double of those isostructural Zr counterparts. Additionally, MOFs with less congested metal anchoring sites, as a result of the topology and surrounding pore environment, yielded higher TOFs, suggesting the importance of supports in dictating both the catalyst accessibility and activity. Computational analysis complemented the experimental observations and provided insights into reaction barrier differences and their performance variation. This study demonstrates the essential role of the supports and provides a thought for selecting/designing suitable supports in heterogeneous catalysis.Insights into the Structure-Activity Relationships in Metal-Organic Framework-Supported Nickel Catalysts for Ethylene Hydrogenationethylene hydrogenation; support effect; Zr- and Hf-based MOFs; nickel catalyst; computational analysis2202048#N/ATRUE
5505
acscatal.0c0080210.1021/acscatal.0c00802https://doi.org/10.1021/acscatal.0c00802Hong, SACS Catal.Palladium complexes bearing abnormal imidazo-[1,5-a]pyridine (aImPy)-based N-heterocyClic carbene ligands were developed for the homopolymerization of olefins and the copolymerization of olefins and polar monomers. The highly electron-donating nature of these abnormal N-heterocyClic carbenes (aNHCs) embedded in the carbene-phenolate chelating ligand scaffold resulted in good catalytic activity, generating linear polyethylene with a high molecular weight (M-n = 237 000). aImPy-Pd complexes efficiently catalyzed propylene polymerization to afford polypropylene free of regio defects. These catalytic systems exhibit good tolerance of various polar monomers and afford the desired copolymers. Up to 3.0% of the polar monomers were incorporated into the main chain, as determined by H-1 and C-13 NMR analysis. Furthermore, methyl methacrylate (MMA), as a 1,1-disubstituted ethylene derivative, was successfully incorporated into the main chain of polyethylene. Computational studies indicated that ethylene insertion into a Pd-Alkyl bond by aImPy-Pd catalyst 6a is faster than that by the Pd catalyst bearing normal NHC analogues, which could be attributed to the high linearity and high molecular weight of polyethylene.Abnormal N-HeterocyClic Carbene-Palladium Complexes for the Copolymerization of Ethylene and Polar Monomersx82020155#N/AFALSE
5506
acscatal.0c0077710.1021/acscatal.0c00777FALSEhttps://doi.org/10.1021/acscatal.0c00777de Jong, KPACS Catal.Efficient and more sustainable production of transportation fuels is key to fulfill the ever-increasing global demand. In order to achieve this, progress in the development of highly active and selective catalysts is fundamental. The combination of bimetallic nanopartiCles and reactive support materials offers unique and complex interactions that can be exploited for improved catalyst performance. Here, we report on cobalt-nickel nanopartiCles on reducible metal oxides as support material for enhanced performance in the Fischer-Tropsch synthesis. For this, different cobalt to nickel ratios (Ni/(Ni + Co): 0.0, 0.25, 0.50, 0.75, or 1.0 atom/atom) supported on reducible (TiO2 and Nb2O5) or nonreducible (alpha-Al2O3) oxides were studied. At 1 bar, Co-Ni nanopartiCles supported on TiO2 and Nb2O5 showed stable catalytic performance, high activities and remarkably high selectivities for long-chain hydrocarbons (C5+, similar to 80 wt %). In contrast, catalysts supported on alpha-Al2O3 independently of the metal composition showed lower activities, high methane production, and considerable deActivation throughout the experiment. At 20 bar, the combination of cobalt and nickel supported on reducible oxides allowed for 25-50% cobalt substitution by nickel with increased Fischer-Tropsch activity and without sacrificing much C5+ selectivity. STEM-EDX and IR of adsorbed CO pointed to a cobalt enrichment of the nanopartiCle's surface and a weaker adsorption of CO in Co-Ni supported on TiO2 and Nb2O5 and not on alpha-Al2O3 , modifying the rate-determining step and the catalytic performance. Overall, we show the strong effect and potential of reducible metal oxides as support materials for bimetallic nanopartiCles for enhanced catalytic performance.Cobalt-Nickel NanopartiCles Supported on Reducible Oxides as Fischer-Tropsch Catalystsbimetallics; SMSI; Fischer-Tropsch synthesis; support effects; reducible oxides; metal-support interactionx6202090#N/AFALSE
5507
acscatal.0c0077410.1021/acscatal.0c00774https://doi.org/10.1021/acscatal.0c00774Corminboeuf, CACS Catal.The increasing urgency to make chemical processes more environmentally friendly while continuing to derive the chemicals required for modern society from renewable resources requires the development of a forthcoming generation of synthetic processes and the catalysts needed to facilitate these reactions. Recently, applications of machine-learning (ML) algorithms involving catalysis have begun to appear with increasing frequency, as they constitute an attractive pathway both for discovering prospective species and identifying trends surrounding catalytic behavior, principally because the number of potential catalysts that can be examined greatly exceeds those found in more traditional experimental or theoretical approaches. Here, we harness a data-driven approach powered by ML in tandem with molecular volcano plots to estimate the activity of over 143,000 homogeneous nickel catalysts bearing phosphine and N-heterocyClic carbene ligands for the reductive C(sp(2))-O Cleavage reaction in Aryl ether compounds, an important step in the degradation of biomass (lignin) into industrially useful feedstock chemicals. Our computational workflow reveals that a vast majority of Ni-phosphine and Ni-carbene catalysts are not ideally tuned to facilitate this reaction. An analysis of those species identified as being the most promising uncovers a Clear catalytic design strategy that can be exploited in an experimental setting to enhance the rate of reductive C(sp(2))-O Cleavage of Aryl ether compounds.Data-Driven Advancement of Homogeneous Nickel Catalyst Activity for Aryl Ether Cleavagehomogeneous catalysis; machine-learning; big data; lignin valorization; volcano plots; linear scaling relationships; ligand designdata analysisy10202069#N/AFALSE
5508
acscatal.0c0182810.1021/acscatal.0c01828FALSEhttps://doi.org/10.1021/acscatal.0c01828Tilley, TDACS Catal.The two-coordinate compound (IPr)Fe[N(SiMe3)-DIPP] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; DIPP = 2,6-diisopropylphenyl) catalyzes the cyClotrimerization of alkynes to arenes. Treatment of the Fe complex with 1 equiv of diphenylacetylene results in the formation of a bimetallic bridging alkyne complex, along with dissociation of IPr from Fe. At elevated temperatures, the bridging alkyne complex undergoes oxidative coupling to form a dimetallacyClopentadiene complex, formally by a one-electron oxidation at each metal center. Each complex catalyzes the cyClotrimerization of diphenylacetylene. Kinetic studies exhibit first-order dependence on the bimetallic complexes, providing further support for the presence of these species in the catalytic cyCle. DFT calculations support the experimental mechanistic data and suggest that the catalytic cyCle is completed by binding of an alkyne to the diene complex, followed by insertion to form a hexatriene species that then undergoes ring Closure to form an inverse sandwich complex, [DIPP(Me3Si)N]Fe(eta(6)-arene)Fe[N(SiMe3)DIPP]. The arene product is then displaced by alkyne to Close the catalytic cyCle.Bimetallic Mechanism for Alkyne CyClotrimerization with a Two-Coordinate Fe Precatalystcatalysis; two-coordinate; bimetallic; mechanism; alkyne cyClotrimerization2202048#N/ATRUE
5509
acscatal.0c0067910.1021/acscatal.0c00679FALSEhttps://doi.org/10.1021/acscatal.0c00679Perez-Ramirez, JACS Catal.The catalyzed semihydrogenation of dibromomethane (CH2Br2) to methyl bromide (CH3Br) is a key step in the bromine-mediated upgradation of methane. This study presents a cutting-edge strategy combining density functional theory (DFT), catalytic tests complemented with the extensive characterization of a wide range of metal catalysts (Fe, Co, Ni, Cu, Ru, Rh, Ag, Ir, and Pt), and statistical tools for a computer-assisted investigation of this reaction. The steady-state catalytic tests identified four Classes of materials comprising (i) poorly active (<8%) Fe/SiO2, Co/SiO2, Cu/SiO2, and Ag/SiO2; (ii) Rh/SiO2 and Ni/SiO2, which exhibit intermediate CH3Br selectivity (<60%); (iii) Ir/SiO2 and Pt/SiO2, which display great propensity to CH4 (>50%); and (iv) Ru/SiO2, which exhibits the highest selectivity to CH3Br (up to 96%). In-depth characterization of representative catalysts in fresh and used forms was done by X-ray diffraction, inductively coupled plasma optical emission spectroscopy, N-2 sorption, temperature-programmed reduction, Raman spectroscopy, electron microscopy, and X-ray photoelectron spectroscopy. The dimensionality reduction performed on the 272 DFT intermediate adsorption energies using principal component analysis identified two descriptors that, when employed together with the experimental data in a random forest regressor, enabled the understanding of activity and selectivity trends by connecting them to the energy intervals of the descriptors. In addition, a representative analytic model was found using the Bayesian inference. These findings illustrate the exciting opportunities presented by integrated experimental/computational screening and set the fundamental basis for the accelerated discovery of superior hydrodebromination catalysts and beyond.Performance of Metal-Catalyzed Hydrodebromination of Dibromomethane Analyzed by Descriptors Derived from Statistical Learningmethane Activation; dibromomethane; hydrodebromination; principal component analysis; random forest Classifier; statistical analysis; density functional theoryx7202075#N/AFALSE
5510
acscatal.0c0173310.1021/acscatal.0c01733FALSEhttps://doi.org/10.1021/acscatal.0c01733Liang, HYACS Catal.Efficient and low-cost electrocatalysts for oxygen evolution reaction (OER), particularly in neutral conditions, are of significant importance for renewable energy technologies such as CO2 reduction and seawater splitting electrolysis. High-valent transition-metal sites have been considered as OER active sites; however, the rational design and construction of these sites remain a big challenge. Here, we report a trimetallic NiFeCu oxyhydroxide electrocatalyst, in which high-valent Ni sites are promoted and stabilized by the atomically embedded Cu, as evidenced by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Through compositional optimization, Ni6Fe1Cu1 catalysts achieved an overpotential of 385 mV at 10 mA cm(-2), a Tafel slope of 164 mV dec(-1), and a stability of 100 h at pH = 7.2. Density function theory calculations demonstrated that the Cu-doping facilitates the formation of high-valent Ni and thus promotes OER electrocatalysis through modulating the d-band center of Ni and reducing the adsorption energy of oxygenated intermediates on the surface of the catalyst. This work paves a promising avenue for the construction of desired high-valent metal OER catalysts by embedding redox inactive metals.High-Valent Nickel Promoted by Atomically Embedded Copper for Efficient Water Oxidationoxygen evolution electrocatalysts; copper doping; high-valent nickel sites14202060#N/ATRUE
5511
acscatal.0c0035210.1021/acscatal.0c00352FALSEhttps://doi.org/10.1021/acscatal.0c00352Kauppinen, EIACS Catal.Mesoporous heteroatom-doped carbon-based nanomaterials are very promising as catalysts for electrochemical energy conversion and storage. We have developed a one-step catalytic chemical vapor deposition method to grow a highly graphitized graphene nanoflake (GF)-carbon nanotube (CNT) hybrid material doped simultaneously with single atoms of N, Co, and Mo (N-Co-Mo-GF/CNT). This high-surface-area material has a mesoporous structure, which facilitates oxygen mass transfer within the catalyst film, and exhibits a high electrocatalytic activity and stability in oxygen reduction and evolution reactions (ORR and OER) in alkaline media. We have shown that in this metal (M)-N-C catalyst, M (Co, Mo)-C centers are the main sites responsible for OER, while, for ORR, both M and N-C centers synergistically serve as the active sites. We systematically investigated tuning of the ORR and OER activity of the porous catalyst depending on the choice of the underlying substrate. The ORR kinetic current and OER activity for N-Co-Mo-GF/CNT were significantly enhanced when the catalyst was deposited onto a Ni substrate, resulting in an advanced electrocatalytic performance compared to the best bifunctional ORR/OER catalysts reported so far. Using a developed scanning electrochemical microscopy analysis method, we demonstrated that the higher OER reactivity on Ni was attributable to the formation of underlying catalyst/Ni interfacial sites, which are accessible due to the porous, electrolyte-permeable structure of the catalyst.Mesoporous Single-Atom-Doped Graphene-Carbon Nanotube Hybrid: Synthesis and Tunable Electrocatalytic Activity for Oxygen Evolution and Reduction Reactionssingle-atom electrocatalysis; heteroatom doping; graphene-carbon nanotube hybrid; mesoporous electrocatalyst; oxygen reduction/evolution reaction; substrate effect; scanning electrochemical microscopyx21202095#N/AFALSE
5512
acscatal.0c0033310.1021/acscatal.0c00333FALSEhttps://doi.org/10.1021/acscatal.0c00333Campbell, CTACS Catal.The morphology, interfacial bonding energetics, and charge transfer of Ni Clusters and nanopartiCles on slightly reduced CeO2-x(111) surfaces at 100-300 K have been studied using single-crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and density functional theory (DFT). The initial heat of adsorption of Ni vapor decreased with the extent of pre-reduction (x) of CeO2-x(111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies. On CeO1.95 (111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nuCleation of Ni Clusters on stoichiometric steps, followed by the Ni partiCles spreading onto less favorable terrace sites. At 100 K, the Clusters nuCleate on terraces due to slower diffusion. Adsorbed Ni monomers are in the +2 oxidation state, and they bind more strongly by similar to 45 kJ/mol to step sites than terraces. The measured heat of adsorption versus average partiCle size on terraces is favorably compared to DFT calculations. The Ce 3d XPS line shape showed an increase in Ce3+/Ce(4+ )ratio with Ni coverage, providing the number of electrons donated to ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing Cluster size for both experiments and DFT, and it shows large differences between Clusters at steps versus terraces. This charge is localized on the interfacial Ni and Ce atoms in their atomic layers Closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni/CeO2 catalysts, for which metal-oxide interactions play a very important role in the Activation of O-H and C-H bonds. The changes in these interactions with Ni partiCle size (metal loading) and the extent of reduction of ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details.Ni NanopartiCles on CeO2(111): Energetics, Electron Transfer, and Structure by Ni Adsorption Calorimetry, Spectroscopies, and Density Functional Theorycatalyst; nickel/ceria; nanopartiCles; size effect; metal adsorption; calorimetry; DFTx9202074#N/AFALSE
5513
acscatal.0c0168010.1021/acscatal.0c01680FALSEhttps://doi.org/10.1021/acscatal.5b02806Sagar, TVTiO2-Based Water-Tolerant Acid Catalysis for Biomass-Based Fuels and Chemicals2020#N/ATRUE
5514
acscatal.0c0028210.1021/acscatal.0c00282FALSEhttps://doi.org/10.1021/acscatal.0c00282Zhang, BPhotoimmobilized Ni Clusters Boost Photodehydrogenative Coupling of Amines to Imines via Enhanced Hydrogen Evolution Kineticsx2020#N/AFALSE
5515
acscatal.0c0020310.1021/acscatal.0c00203FALSEhttps://doi.org/10.1021/acscatal.0c00203Dorman, JAACS Catal.CeO2-ZrO2 (CZO) nanopartiCles (NPs) have applications in many catalytic reactions, such as methane dry reforming, due to their oxygen cyCling ability. Ni doping has been shown to improve the catalytic activity and produces active sites for the decomposition of methane. In this work, Ni:CZO NPs were synthesized via a two-step co-precipitation/molten salt synthesis to compare Ni distribution, oxygen vacancy concentration, and catalytic activity relative to a reference state-of-the-art catalyst prepared by a sol-gel-adsorptive deposition technique. To better understand the dispersion of Ni and oxygen vacancy formation in these materials, the Ni concentration, position, and reaction time were varied in the synthesis. X-ray diffraction (XRD) measurements show a homogeneous, cubic phase with little to no segregation of Ni/NiO. Catalytic activity measurements, performed via a differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA) method, displayed a 5-fold increase in the activity per surface area with an order of magnitude decrease in the coking rate for the partiCles synthesized by the molten salt method. Additionally, this approach resulted in an order of magnitude increase in oxygen vacancies, which is attributed to the high dispersion of Ni2+ ions in the NP core. This ability of controlling the oxygen vacancies in the lattice is expected to impact other such systems, which utilize the substrate redox cyClability to drive conversion via, e.g., a Mars-van Krevelen mechanism.Enhancing CexZr1-xO2 Activity for Methane Dry Reforming Using Subsurface Ni DopantsRaman spectroscopy; nanopartiCles; oxygen vacancies; cerium zirconium oxide; catalyst; methane dry reformingx122020101#N/AFALSE
5516
acscatal.0c0015110.1021/acscatal.0c00151FALSEhttps://doi.org/10.1021/acscatal.0c00151Furukawa, SACS Catal.Catalyst design based on a pseudobinary alloy concept was applied to develop a highly efficient catalytic system for alkane dehydrogenation. A series of Pt-based alloy catalysts supported on silica (Pt3M/SiO2, where M = Fe, Co, Cu, Zn, Ga, In, Sn, Pb) were prepared and tested for the dehydrogenation of methylcyClohexane, which has been an emerging topic in hydrogen carrier/production applications. Nanoparticulate intermetallic Pt3Fe exhibited high catalytic activity and durability. The Pt3Fe catalyst was further modified by substituting a part of the Fe with a series of metals (M = Co, Ni, Cu, Zn, Ga, In, Sn, Pb) to form a Pt-3(Fe-0.75,M-0.25) pseudobinary alloy. The partial substitution of Fe with Zn to form Pt-3(Fe0.75Zn0.25) resulted in outstandingly high catalytic activity, selectivity, and durability: a 2.7-fold higher turnover frequency (TOF) in comparison to that of Pt/SiO2 (the highest H-2 evolution rate ever reported), >99% toluene selectivity (methane concentration <500 ppm), and long-term durability with >99% MCH conversion for at least 50 h. A mechanistic study based on detailed characterization and theoretical calculations revealed that the Fe enhanced hydrogenation of CHx species (decoking) and Zn promoted toluene desorption by both ligand and ensemble effects. The adjacency of Pt, Fe, and Zn in at the atomic level allows construction of a multifunctional active site for effective C-H Activation, decoking, and toluene desorption.Active, Selective, and Durable Catalyst for Alkane Dehydrogenation Based on a Well-Designed Trimetallic Alloyalkane dehydrogenation; methylcyClohexane; intermetallic compound; Pt3Fe; pseudobinary alloy; decoking; DFT calculationx10202040#N/AFALSE
5517
acscatal.0c0131110.1021/acscatal.0c01311FALSEhttps://doi.org/10.1021/acscatal.0c01311Wachs, IEACS Catal.A series of copper-promoted iron-chromium oxide catalysts with various copper loadings are investigated for CO2 Activation (reverse water-gas shift reaction) to determine the nature of surface oxygen intermediates involved in this redox reaction. Using a series of in situ characterizations (XPS, HS-LEIS, DRIFTS, and EXAFS), H-2-TPR, and transient kinetic analysis, two reactive surface oxygen species with different reduction characteristics are identified for catalysts during the reaction. The more abundant and more active surface oxygen species are Closely related to the surface hydroxyls located at the Cu-Fe3O4 interfacial regions. A direct correlation of the CO2 hydrogenation reaction rate with both the number and reduction kinetics of the more active surface oxygen intermediates is established.Nature of Reactive Oxygen Intermediates on Copper-Promoted Iron-Chromium Oxide Catalysts during CO2 Activation7202042#N/ATRUE
5518
acscatal.0c0008210.1021/acscatal.0c00082FALSEhttps://doi.org/10.1021/acscatal.0c00082Florea, MACS Catal.Palladium is one of the most efficient metals for the hydrogenation of organic compounds. However, when molecules, such as nitroaromatics, with several reducible functionalities, are hydrogenated, Pd, like any other very active metal, such as nickel or platinum, often behaves unselectively. One strategy to render Pd more selective is to choose the proper support. Herein, we show that MAX phase powders of Ti3SiC2, Ti2AlC, or Ti3AlC2 can chemoselectively hydrogenate 4-nitrostyrene to 4-aminostyrene, with 100% selectivity, at around 3-4% conversion. To boost the latter, we loaded Ti3SiC2 with 0.0005 wt % Pd and increased the conversion to 100% while maintaining the 4-AS selectivity at >90%. By optimizing the Pd loading, we were also able to increase the turnover frequency 100-fold relative to previous literature results. The identification of this highly efficient and chemoselective system has broad implications for the design of cost-effective, earth-abundant, nontoxic, metal catalysts, with ultralow noble metal loadings.Highly Efficient Ultralow Pd Loading Supported on MAX Phases for Chemoselective HydrogenationMAX phase; 4-nitrostyrene; chemoselective hydrogenation; low noble metal amount; palladiumx4202044#N/AFALSE
5519
acscatal.0c0126110.1021/acscatal.0c01261FALSEhttps://doi.org/10.1021/acscatal.0c01261Laursen, SACS Catal.In this study, we present the use of compositionally and structurally well-defined, oxide-supported nanopartiCle Ni + Ga intermetallic compound (IMC) catalysts in the wet reforming of propane. The definition of the IMC catalysts allowed for more direct connections to be made between catalyst bulk and surface compositions and catalyst performance in wet reforming. We show that Ni + Ga catalysts exhibit comparable or better rates of reaction on a per-site basis and improved stability in comparison to other leading formulations. We also demonstrate excellent control over product selectivity as a function of Ni + Ga IMC bulk and surface compositions with nearly ideal selectivity toward CO2/H-2 or CO/H-2 achieved. Selectivity toward the production of smaller hydrocarbons could also be suppressed significantly due to uniquely limited rehydrogenation kinetics of the Ni + Ga IMCs. Our studies also shed light on the stability of Ni + Ga IMCs under reaction conditions and how high conversion in reactions that involve many strongly bound reaction intermediates can lead to IMC phase relaxation to the most stable phase with concomitant surface composition and catalytic performance changes. Correlations between surface chemistry and catalyst performance were afforded by both the well-defined nature of the IMCs and computational surface science studies.Controlling Selectivity and Stability in the Hydrocarbon Wet-Reforming Reaction Using Well-Defined Ni plus Ga Intermetallic Compound Catalystsmodel catalyst materials; non-noble metal catalysts; surface science; rational catalyst design; propane wet reforming1202083#N/ATRUE
5520
acscatal.0c0000710.1021/acscatal.0c00007FALSEhttps://doi.org/10.1021/acscatal.0c00007Yan, KACS Catal.Selective conversion of renewable sources is necessary for developing energy generation technology and protecting the environment. Herein, this work reports a one-step controllable synthesis of trimetallic NiCoFe-layered double hydroxides (NiCoFe-LDHs) nanosheets (1.36 nm) for both an efficient oxygen evolution reaction (OER) and highly selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMFOR) into value-added 2,5-furandiCarbonylic acid (FDCA). For comparison, two sets of bimetallic NiCo- and NiFe-LDHs were similarly synthesized and evaluated. In the OER process, the optimal NiCoFe-LDHs nanosheets exhibited the lowest necessary overpotential (288 mV) to reach 10 mA cm (-2) and the smallest Tafel slope of 92 mV dec(-1) compared with NiCo-LDHs (347 mV, 115 mV dec(-1)) and NiFe-LDHs (303 mV, 108 mV dec(-1)). The performance was also superior to most previously reported LDHs catalysts. Additionally, NiCoFe-LDHs nanosheets exhibited a much smaller charge transfer resistance (Rct) of 1.0 Omega and a larger C-dl value of 2.62 mF cm(-2) compared with NiCo-LDHs (2.1 Omega, 1.94 mF cm(-2)) and NiFe-LDHs (1.4 Omega, 2.22 mF cm(-2)), indicating fast catalytic kinetics. Furthermore, the NiCoFe-LDHs nanosheets possessed excellent durability over 10 h, much better than that of NiCo- and NiFe-LDHs. NiCoFe-LDHs catalysts also exhibited high performance in the oxidation of 5-hydroxymethylfurfural (HMF) to FDCA, which is a key precursor for the sustainable synthesis of polymers (e.g., polyethylene 2,5-furandiCarbonylate (PEF)). An ultralow overpotential of 280 mV was required to achieve 20 mA cm(-2), nearly 120 mV less than the activity in pure 1.0 M NaOH. The reaction intermediates and products were qualified by liquid chromatography-mass spectroscopy system (LC-MS) and LC, where 95.5% conversion of HMF and 84.9% yield of FDCA were obtained in 1 h. The reaction kinetics and possible pathways were further investigated. As a unique report utilizing trimetallic LDHs catalysts for OER and HMFOR, this study provides a promising perspective for energy conversion and electrocatalytic processing of biomass-derived monomers.Trimetallic NiCoFe-Layered Double Hydroxides Nanosheets Efficient for Oxygen Evolution and Highly Selective Oxidation of Biomass-Derived 5-Hydroxymethylfurfurallayered double hydroxides; nanosheets; oxygen evolution reaction; 5-hydroxymethylfurfural oxidation; activityx48202042#N/AFALSE
5521
acs.orglett.9b0173010.1021/acs.orglett.9b01730FALSEhttps://doi.org/10.1021/acs.orglett.9b01730Messaoudi, SNi/Photoredox-Dual-Catalyzed Functionalization of 1-Thiosugarsx2019#N/AFALSE
5522
acs.orglett.9b0109710.1021/acs.orglett.9b01097TRUEhttps://pubs.acs.org/doi/abs/10.1021/acs.orglett.9b01097Shi, ZJOrg. Lett
Described is a cross-electrophilic, deaminative coupling strategy harnessing Katritzky salts as a new species of electrophile in Ni/photoredox dual catalytic reductive cross-coupling reactions. Distinguishing features of this Arylation protocol inClude its mild reaction conditions, high chemoselectivity, and adaptability to a variety of complex substrates [i.e., pyridinium salts derived from amines and partners derived from (hetero)Aryl bromides].
Deaminative Reductive Arylation Enabled by Nickel/Photoredox Dual CatalysisPhotocatalystCsp2_ar-Csp3Br
Triphenylpyridinium+BF4-
ArylNo baseNo Base742019Added by Yizhou6/21/2022FALSE
5523
acs.orglett.9b0106610.1021/acs.orglett.9b01066FALSEhttps://doi.org/10.1021/acs.orglett.9b01066Shinokubo, HSynthesis of Hydroxyisooxophlorins by Oxidative Degradation of meso-Hydroxyporphyrinsx2019#N/AFALSE
5524
acscatal.0c0115910.1021/acscatal.0c01159FALSEhttps://doi.org/10.1021/acscatal.0c01159Fu, HGACS Catal.Modulation of the electronic structure of metal-based catalysts is a key to optimize the catalytic activity. Here, we have shown the electronic tuning of Ni by Mo species anchored on SAPO-11 (Ni-Mo/S-11) enabling the high-efficient hydroisomerization of n-alkanes comparable to commercial Pt/S-11, which is of great importance in producing fuel oils. The well-dispersed Ni partiCles intimately contacted with MoO2 are anchored on S-11 based on a vacuum-assisted route. There is the obvious presence of electron transfer from Mo species to Ni due to the intimate contact, which can increase the electron density around Ni and consequently promote H Activation and desorption on Ni catalyst. Also, the good dispersion of Ni-Mo species on S-11 is favorable to expose more Bronsted acid sites of S-11, being responsible for the skeletal isomerization. These characteristics endow enhanced activity of 3.0Ni-0.5Mo/S-11 for the hydroisomerization of n-hexadecane with a high isomer yield of 81.4%, being comparable to 81.0% for 0.5 wt % Pt/S-11. The analysis of products showed similar isomerization and cracking mechanisms over 3.0Ni-0.5Mo/S-11 catalyst to Pt catalyst. Further, the presence of Mo species can enhance the stability, with no obvious change after 100 h continuous catalytic reaction. Both the catalytic activity and stability are much superior to those of monometallic Ni/S-11 and the reported non-noble-metal catalyst. This work focuses on developing high-effective non-noble-metal-based catalysts.Electronic Tuning of Ni by Mo Species for Highly Efficient Hydroisomerization of n-Alkanes Comparable to Pt-Based Catalystshydroisomerization; Ni metals; MoOx species; synergistic interaction; non-noble-metal catalysis3202060#N/ATRUE
5525
acscatal.0c0098910.1021/acscatal.0c00989FALSEhttps://doi.org/10.1021/acscatal.0c00989Yan, WSACS Catal.For electrochemical energy conversion, highly efficient and inexpensive electrocatalysts are required, which are principally designed and synthesized by virtue of structural regulations. Herein, we propose a rational linker scission approach to induce lattice strain in metal-organic framework (MOF) catalysts by partially replacing multicoordinating linkers with nonbridging ligands. Strained NiFe-MOFs with 6% lattice expansion exhibit a superior catalytic performance for the oxygen evolution reaction (OER) under alkaline conditions; the overpotential is reduced to 230 mV (86.6 mV dec(-1)) from 320 mV (164.9 mV dec(-1)) for the unstrained NiFe-MOFs at a current density of 10 mA cm(-2). Operando studies by using synchrotron radiation X-ray absorption and infrared spectroscopy identified the emergence of a key *OOH intermediate on sites during OER, providing strong evidence that the Ni3+/4+ sites are the active sites and the formation of *OOH is the rate-limiting step. The first-principles calculations were performed to reveal the strain-induced electronic structure changes of the NiFe-MOFs and the Gibbs free energy profile during OER It is found that the optimized Ni 3d eg-orbital facilitates the formation of *OOH, thus enhancing the OER performance of the strained MOFs.Lattice Strain Induced by Linker Scission in Metal-Organic Framework Nanosheets for Oxygen Evolution ReactionMOFs; lattice strain; linker scission; oxygen evolution reaction; operando spectroscopy16202032#N/ATRUE
5526
acs.orglett.8b0094910.1021/acs.orglett.8b00949FALSEhttps://doi.org/10.1021/acs.orglett.8b00949Chen, TQPalladium-Catalyzed DeCarbonylative Alkynylation of Amidesx2018#N/AFALSE
5527
acs.orglett.7b03191
10.1021/acs.orglett.7b03191
Szostak, MOrg. Lett.
A general, highly selective method for the room temperature Suzuki-Miyaura cross-coupling of commonly encountered primary benzamides is reported. A combination of site-selective N,N-di-Boc-Activation (tert-butoxyCarbonyl Activation) of the amide nitrogen with practical air- and moisture-stable, well-defined, and highly reactive [Pd(NHC)(cin)Cl] (NHC = N-heterocyClic carbene; cin = cinnamyl) provides a highly effective route to biAryl ketones from primary amides in high yields. For the first time, a TON of > 1000 has been achieved in amide acyl cross-coupling.A general, highly selective method for the room temperature SuzukiMiyaura cross-coupling of commonly encountered primary benzamides is reported. A combination of site-selective N,N-di-Boc-Activation (tert-butoxyCarbonyl Activation) of the amide nitrogen with practical air- and moisture-stable, well-defined, and highly reactive [Pd(NHC)(cin)Cl] (NHC = N-heterocyClic carbene; cin = cinnamyl) provides a highly effective route to biAryl ketones from primary amides in high yields. For the first time, a TON of > 1000 has been achieved in amide acyl cross-coupling.
General Method for the Suzuki-Miyaura Cross-Coupling of Primary Amide-Derived Electrophiles Enabled by [Pd(NHC)(cin)Cl] at Room Temperature
x462017Added by Shihong#N/A
5528
acscatal.0c0090710.1021/acscatal.0c00907FALSEhttps://doi.org/10.1021/acscatal.0c00907Xiao, FSACS Catal.The empirical optimization of the preparation of catalytically active copper-containing catalysts is far more advanced than the fundamental understanding of the catalyst performance because of the structural complexity of the catalysts. Here, we demonstrate the interplay between the catalyst structure and CO2 hydrogenation on Cu catalysts boosted with nickel species. The nickel dispersion on copper markedly affects the CO2 dissociation activity and catalytic reaction pathways, thus resulting in distinctive catalytic activity and selectivity attributed to Ni. Specifically, the catalyst incorporating nickel alloyed in copper maximizes the synergy between the two metals and is characterized by conversions Close to the thermodynamic equilibrium to CO as a product-with switched off methanation-over a wide temperature range. Catalyst performance data, spectra characterizing the catalyst, and theoretical results demonstrate that surface copper with adjacent nickel atoms efficiently activates CO2 via a redox mechanism-with adsorption of CO being suppressed-so that methanation associated with deep hydrogenation of CO is inhibited. The results of this investigation highlight the importance of structures with copper-adjacent-nickel, which appear to offer appealing opportunities for tailoring efficient copper-containing catalysts for CO2 hydrogenation.Dispersed Nickel Boosts Catalysis by Copper in CO2 HydrogenationCO2 hydrogenation; copper catalyst; nickel; reverse water-gas shift; alloy6202052#N/ATRUE
5529
acs.orglett.7b00365
10.1021/acs.orglett.7b00365
Tian, SKOrg. Lett.
A one-pot protocol has been developed for sequential benzyne Activation and nuCleophilic substitution of enantioenriched tertiary Benzylic amines. In the presence of 2 (trimethylsilyl)phenyl triflate and CsF, a range-of enantioen-riched tertiary Benzylic amines were substituted by various nuCleophiles, delivering structurally diverse Benzylic-compounds in moderate to excellent yields with excellent retention of enantiopurity. Importantly, this operationally simple protocol permitted formation of various chiral C-S, C-Se, C-C, and C-N bonds with excellent enantiopurity under metal-free conditions.
Stereospecific NuCleophilic Substitution of Enantioenriched Tertiary Benzylic Amines via in Situ Activation with Benzynex412017Added by Shihong#N/A
5530
acscatal.0c0084710.1021/acscatal.0c00847FALSEhttps://doi.org/10.1021/acscatal.0c00847Xia, BYACS Catal.Electrochemical carbon dioxide (CO2) conversion is promising to balance the carbon cyCle for human society. However, an efficient electrocatalyst is the key to determine the selective conversion of CO2 toward valuable products. We report herein an efficient La2CuO4 perovskite catalyst for electrochemical CO2 reduction. A high Faradaic efficiency of 56.3% with a partial current density of 117 mA cm(-2) is achieved for methane production over this perovskite catalyst at -1.4 V (vs RHE). The results demonstrate that the structural evolution of La2CuO4 perovskite takes place simultaneously during the cathodic CO2 reduction process. Theoretical investigations further unravel that the emerging Cu/La2CuO4 interface accounts for the CO2 methanation behaviors. This work provides an effective perovskite electrocatalyst for ambient CO2 methanation and offers a valuable understanding of the structure evolution and surface reconstruction of precatalysts in catalytic reactions for energy-relevant technologies.Highly Selective Carbon Dioxide Electroreduction on Structure-Evolved Copper Perovskite Oxide toward Methane Production20202050#N/ATRUE
5531
acs.orglett.6b0214010.1021/acs.orglett.6b02140FALSEhttps://doi.org/10.1021/acs.orglett.6b02140Lee, DConformationally Distorted pi-Conjugation for Reaction-Based Detection of Nickel: Fluorescence Turn-on by Twist-and-Fragmentx2016#N/AFALSE
5532
acs.orglett.6b0132310.1021/acs.orglett.6b01323FALSEhttps://doi.org/10.1021/acs.orglett.6b01323Shinokubo, HSynthesis of Free-Base 10-Azacorrolesx2016#N/AFALSE
5533
acscatal.0c0084110.1021/acscatal.0c00841FALSEhttps://doi.org/10.1021/acscatal.0c00841Lautens, MACS Catal.This work reports the enantioselective formal transfer of a carbamoyl iodide across a 1,1-disubstituted styrene using Ni-catalysis. Employing an air-stable Ni(II) precatalyst and a commercially available chiral ligand ((S)-tBuPHOX), enantioen-riched 3,3-disubstituted iodooxindoles were obtained in up to 90% yield and up to 97:3 e.r. This methodology was applied to the total synthesis of (-)-esermethole and (-)-phenserine.Nickel-Catalyzed Enantioselective Carbamoyl Iodination: A Surrogate for Carbamoyl Iodidesnickel; enantioselective; carbamoyl-iodination reaction; oxindoles13202042#N/ATRUE
5534
acs.orglett.1c0171610.1021/acs.orglett.1c01716FALSEhttps://doi.org/10.1021/acs.orglett.1c01716Rasappan, RC-H Alkylation of Aldehydes by Merging TBADT Hydrogen Atom Transfer with Nickel CatalysisPhotocatalyst2021#N/AFALSE
5535
acs.orglett.1c0142010.1021/acs.orglett.1c01420FALSEhttps://doi.org/10.1021/acs.orglett.1c01420Xu, TDual Nickel- and Photoredox-Catalyzed Reductive Cross-Coupling to Access Chiral Trifluoromethylated AlkanesPhotocatalyst2021#N/AFALSE
5536
acscatal.0c0080510.1021/acscatal.0c00805FALSEhttps://doi.org/10.1021/acscatal.0c00805McFarland, EWACS Catal.Methane pyrolysis transforms CH4 into hydrogen and solid carbon without a CO2 byproduct. Using a high-temperature liquid catalyst in a bubble column reactor, deActivation from coking is avoided and the solid carbon removed. As an element with high electron affinity, liquid tellurium is an active methane pyrolysis catalyst with an apparent Activation energy of 166 kJ/mol. At the reaction temperature of approximately 1000 degrees C, Te has a high vapor pressure and the vapor is also found to be a catalyst with an apparent Activation energy of 178 kJ/mol. Contrary to results obtained for other molten alloy catalysts, dissolving Ni in molten tellurium lowers the pyrolysis activity. Quantum mechanical calculations were performed with accurate methods for the gas-phase reaction, and with ab initio, constant-temperature, molecular dynamics (MD) simulations with energies computed using density functional theory for the liquid phase.Catalytic Methane Pyrolysis with Liquid and Vapor Phase Telluriumheterogeneous catalysis; methane pyrolysis; tellurium; molten alloy; gas phase; carbon dioxide3202053#N/ATRUE
5537
acscatal.0c0074310.1021/acscatal.0c00743FALSEHeyden, APreferential Oxidation of CO in Hydrogen at Nonmetal Active Sites with High Activity and Selectivity2020#N/ATRUE
5538
acs.accounts.5b00223
10.1021/acs.accounts.5b00223
FALSEhttps://pubs.acs.org/doi/10.1021/acs.accounts.5b00223Percec, VStereospecific Nickel-Catalyzed Cross-Coupling Reactions of Benzylic Ethers and EstersReview170#N/A
5539
a905191k10.1039/a905191kFALSEhttps://doi.org/10.1039/a905191kMallah, TFerromagnetic order in a mu-cyano Cr-III-Mn-II assembly with an unusual branched architecturex1999#N/AFALSE
5540
a903788h10.1039/a903788hFALSEhttps://doi.org/10.1039/a903788hBochmann, MNew weakly coordinating counter anions for high activity polymerisation catalysts: [(C6F5)(3)B-CN-B(C6F5)(3)](-) and [Ni{CNB(C6F5)(3)}(4)](2-)x1999#N/AFALSE
5541
a901931f10.1039/a901931fFALSEhttps://doi.org/10.1039/a901931fSacchi, DA fluorescent molecular thermometer based on the nickel(II) high-spin/low-spin interconversionx1999#N/AFALSE
5542
a900500e10.1039/a900500eFALSEhttps://doi.org/10.1039/a900500eMcKee, VControlled synthesis of heterotetranuClear complexesx1999#N/AFALSE
5543
acscatal.0c0049010.1021/acscatal.0c00490FALSEhttps://doi.org/10.1021/acscatal.0c00490Grimaud, AACS Catal.Recent studies have revealed the critical role played by the electrolyte composition on the oxygen evolution reaction (OER) kinetics on the surface of highly active catalysts. While numerous works were devoted to understand the effect of the electrolyte composition on the physical properties of the catalysts' surface, very little is known yet about its exact impact on the OER kinetics parameters. In this work, we reveal that the origin for the electrolyte-dependent OER activity for Co-based catalysts originates from two different effects. Increasing the alkaline electrolyte concentration for La1-xSrxCoO3-delta perovskites with x > 0 and for amorphous CoOOH increases the pre-exponential factor, which can be explained either by an increase of the concentration of active sites or by a change in the entropy of Activation. However, changing the alkali cation results in a decrease of the apparent Activation enthalpy for Fe-containing amorphous films, traducing a change in intermediates' binding energies.Revealing the Impact of Electrolyte Composition for Co-Based Water Oxidation Catalysts by the Study of Reaction Kinetics ParametersCo-based electrocatalyst; kinetic parameter; Activation energy; pre-exponential factor; alkaline electrolyte; alkali-cation species9202054#N/ATRUE
5544
a707350j10.1039/a707350jFALSEhttps://doi.org/10.1039/a707350jZiessel, RStructural control of ferromagnetic interactions in nickel(II) complexes based on a tetradentate biradicalx1998#N/AFALSE
5545
a703797j10.1039/a703797jFALSEhttps://doi.org/10.1039/a703797jNixon, JFRemarkable 'edge' ligation of a triphosphacyClopentenyl ring system. Synthesis, crystal and molecular structure of [Ni(eta(5)-P3C2Bu2t){eta(2)-P3C2Bu2tCH(SiMe3)(2)Me}]x1997#N/AFALSE
5546
a703712k10.1039/a703712kFALSEhttps://doi.org/10.1039/a703712kGomezGarcia, CJIntercalation of decamethylferrocenium cations in bimetallic oxalate-bridged two-dimensional magnetsx1997#N/AFALSE
5547
a702788e10.1039/a702788eFALSEhttps://doi.org/10.1039/a702788eMcKee, VA tetranickel(II) macrocyClic complex incorporating five different bridging groupsx1997#N/AFALSE
5548
acscatal.0c0030410.1021/acscatal.0c00304FALSEhttps://doi.org/10.1021/acscatal.0c00304Lopez, NACS Catal.y The Pourbaix diagram of Ni electrodes under reaction conditions presents several metastable NiOxHy phases and Fe doping enlarges the stability area of oxyhydroxo species. For the Ni-only phase, water adsorption and intercalation can significantly lower both the surface and interface energies, and even introduce negative surface energy. Thus, water can exfoliate layers, leading to Fe ion adsorption on inner layers, as demonstrated by ab initio molecular dynamics. These single atoms have been carefully speciated (i.e., initially prepared as Fe2+ and Fe3+) and proton coupled electron transfer between the H2O-Fe and lattice oxygen ions has been observed in all ab initio molecular dynamics simulations, which is attributed to the Fe incorporation, since no proton coupled electron transfer occurs under free water conditions. Furthermore, 15 possible oxygen evolution reaction mechanisms near Fe ions show that the main active species corresponds to the Ni2+, which is reduced from Ni3+ via H transfer when a Fe2+ iron adsorbs nearby, and the overpotential can be significantly reduced to 0.23 V.The Role of Fe Species on NiOOH in Oxygen Evolution Reactionsfirst-principles; ab initio molecular dynamics; oxygen evolution reactions; proton coupled electron transfer; iron doping; Ni-based (oxy)hydroxide; exfoliation; dynamic oxidation states16202042#N/ATRUE
5549
9b0162010.1021/acscatal.9b01620https://doi.org/10.1021/acscatal.9b01620Stanley, LMACS Catal.The nickel-catalyzed intermolecular carboacylation of alkenes with amides and tetraArylborates is presented. BicyClic alkenes are readily functionalized with a variety of N-benzoyl-N-phenylbenzamides and triArylboranes, which are generated in situ from the corresponding tetraArylborates, to synthesize ketone products in up to 91% yield. Preliminary mechanistic studies suggest that migratory insertion precedes transmetalation and that reductive elimination is the turnover-limiting step. These reactions occur with excellent chemoselectivity and diastereoselectivity in the absence of a directing/chelating group and further demonstrate amides as practical acyl electrophiles for alkene dicarbofunctionalization reactions.Ni-Catalyzed Three-Component Alkene Carboacylation Initiated by Amide C-N Bond Activation#N/Ax26201945#N/AFALSE
5550
414625a10.1038/414625aFALSEhttps://doi.org/10.1038/414625aArakawa, HNatureThe photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially Clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting(1), or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide(2), were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light(3-7), which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium-tantalum-oxide with nickel yields a series of photocatalysts, In1-xNixTaO4 (x = 0-0.2), which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66%. Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'Clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.Direct splitting of water under visible light irradiation with an oxide semiconductor photocatalystx2863200115#N/AFALSE
5551
382703a010.1038/382703a0FALSEhttps://doi.org/10.1038/382703a0Maas, RNatureTHE late Archaean greenstone terranes of Western Australia contain abundant komatiites (high-MgO lavas) hosting magmatic sulphide deposits rich in nickel, copper and platinum-group elements, Thermal erosion and assimilation of sulphidic sea-floor sediments has been proposed as a mechanism by which the komatiites were brought to sulphide saturation(1-4), Such models have important implications not only for the genesis of these sulphide ores, but also for interpreting the magnitude and extent of isotopic heterogeneity in the Archaean mantle, Here we report that massive, matrix and disseminated sulphide ores and a komatiite from Western Australia yield a magmatic Re-Os isochron age of 2,706 +/- 36 Myr and a near-chondritic initial Os-187/Os-188 ratio of 0.10889 +/- 0.00035, whereas a proposed sulphidic sedimentary contaminant has an extremely radiogenic Os-187/Os-188 of 1.0983 at 2,706 Myr, These data demonstrate that the ore-forming komatiites were derived from the upper mantle without significant contamination by radiogenic crust either before eruption or during turbulent how at the surface, Thus, ground melting and assimilation of sulphidic sediments may not be as important in ore genesis as current theories suggest.Re-Os isotopic evidence for genesis of Archaean nickel ores from uncontaminated komatiitesx198199636#N/AFALSE
5552
379655a010.1038/379655a0FALSEhttps://doi.org/10.1038/379655a0Finley, DNatureTHE SUG1 gene of Saccharomyces cerevisiae encodes a putative ATPase. Mutations in SUG1 were isolated(1) as suppressors of a mutation in the transcriptional Activation domain of GAL4. Sug1 was recently proposed to be a subunit of the RNA polymerase II holoenzyme and to mediate the association of transcriptional activators with holoenzyme(2). We show here that Sug1 is not a subunit of the holoenzyme, at least in its purified form, but of the 26S proteasome(3,4), a large complex of relative molecular-mass 2,000K that catalyses the ATP-dependent degradation of ubiquitin-protein conjugates. Sug1 co-purifies with the proteasome in both conventional and nickel-chelate affinity chromatography. Our observations account for the reduced ubiquitin-dependent proteolysis in sug1 mutants(5) and suggest that the effects of sug1 mutations on transcription are indirect results of defective proteolysis.Identification of the gal4 suppressor Sug1 as a subunit of the yeast 26S proteasomex147199628#N/AFALSE
5553
365232a010.1038/365232a0FALSEhttps://doi.org/10.1038/365232a0WHEELER, JCNatureSUPERNOVA 1993J in the nearby galaxy M81 is one of the Closest-and hence brightest-supernovae to be witnessed this century. The early spectrum of SN1993J showed1-3 the characteristic hydrogen signature of type II supernovae, but its subsequent evolution is atypical for this Class of supernova. Here we present optical and infrared spectra of SN1993J up to 43 days after outburst, which reveal the onset of the helium absorption and emission features more commonly associated with hydrogen-free type Ib supernovae. Corresponding model spectra show that the progenitor star must have possessed an unusually thin (for type II supernovae) hydrogen-rich envelope overlying a helium-rich mantle. Moreover, the supernova ejecta must have remained compositionally stratified, with little transport of the hydrogen-rich material down into the underlying helium layer, or mixing of heavier elements (such as radioactive Ni-56) outwards. SN1993J therefore represents a transition object between hydrogen-dominated type II supernovae, and hydrogen-free, helium-dominated type Ib supernovae.SUPERNOVA-1993J AS A SPECTROSCOPIC LINK BETWEEN TYPE-II AND TYPE-IB SUPERNOVAEx62199324#N/AFALSE
5554
acscatal.0c0010110.1021/acscatal.0c00101FALSEhttps://doi.org/10.1021/acscatal.0c00101Chatenet, MACS Catal.Nickel is a very abundant transition metal in the Earth's crust, and it finds numerous applications in electrochemical processes where metallic Ni or its oxides are thermodynamically stable, particularly in alkaline environments. This contribution addresses electrocatalytic properties of Ni-based catalysts in reactions of fuel oxidation in alkaline media. It first details the electrochemical behavior of Ni in alkaline media and approaches to determine the active surface area of Ni electrodes. Second, the electrocatalytic activities of Ni-based electrocatalysts for the alkaline hydrogen oxidation reaction are described (an endeavor for the development of anion exchange membrane fuel cells), along with a detailed analysis of the strategies put forward to improve them. It is notably shown that the state of Ni surface (oxidized or reduced) largely determines its electrocatalytic activity. This state of the surface also conveys a pivotal importance regarding the activity of Ni for the oxidation of complex fuels (borohydride, boranes, and hydrazine). Finally, emphasis is made on the durability of Ni-based catalysts in alkaline environments. It is shown that, in such media, the material durability of Ni-based electrodes can be high, but this does not necessarily warrant stable electrocatalytic activity, because of possible deActivation following surface oxide or bulk hydride formation in operation.Recent Advances in the Understanding of Nickel-Based Catalysts for the Oxidation of Hydrogen-Containing Fuels in Alkaline Medianickel; hydrogen oxidation reaction (HOR); borohydride oxidation reaction (BOR); ammonia borane oxidation reaction (ABOR); hydrazine hydrate oxidation reaction (HHOR)212020251#N/ATRUE
5555
acscatal.0c0001910.1021/acscatal.0c00019FALSEhttps://doi.org/10.1021/acscatal.0c00019Xing, DACS Catal.We report a nickel/NHC-catalyzed branched-selective acrotylation of simple ketones using 1,3-butadiene as the Alkylation agent. This reaction is regioselective and operated under pH and redox-neutral conditions. Water was used as the sole additive, which significantly accelerates the transformation.Water-Accelerated Nickel-Catalyzed alpha-Crotylation of Simple Ketones with 1,3-Butadiene under pH and Redox-Neutral Conditionsnickel; 1,3-butadiene; crotylation; ketone; pH-neutral; atom-economy6202064#N/ATRUE
5556
356140a010.1038/356140a0FALSEhttps://doi.org/10.1038/356140a0GILLOW, JBNatureTHE presence of synthetic and naturally occurring chelating agents in nuClear and toxic-metal wastes is a major concern because of their potential to enhance mobilization of metal ions away from the disposal sites 1-3. Of particular interest is citric acid, which is present in low-level and transuranic radioactive wastes 4,5 and in domestic and industrial wastes (as washing fluids, for instance), as well as being found naturally. Citrate ions form multidentate, stable complexes with a variety of toxic metals and radionuClides; but biodegradation of these complexes, precipitating the metal ions as insoluble hydroxides, oxides or other salts, may retard migration. Here we report a study of the biodegradation of citrate complexes of Ca, Fe(II), Fe(III), Cd, Cu, Ni, Pb and U. Several of these complexes were not readily degraded by bacteria, and the biodegradability depended on the chemical nature of the complex, not on the toxicity of the metal to the bacteria. This resistance to biodegradation implies that citrate complexation may play an important part in migration of these hazardous wastes.BIODEGRADATION OF METAL CITRATE COMPLEXES AND IMPLICATIONS FOR TOXIC-METAL MOBILITYx234199226#N/AFALSE
5557
acs.orglett.8b0303910.1021/acs.orglett.8b03039FALSESvenda, JEnantioselective Conjugate Additions of 2-AlkoxyCarbonyl-3(2H)-furanones2018#N/ATRUE
5558
acs.orglett.8b0226710.1021/acs.orglett.8b02267FALSEhttps://doi.org/10.1021/acs.orglett.8b02267Qu, JHighly beta(Z)-Selective Hydrosilylation of Terminal Alkynes Catalyzed by Thiolate-Bridged Dirhodium Complexes2018#N/ATRUE
5559
acs.orglett.7b0158810.1021/acs.orglett.7b01588TRUEhttps://doi.org/10.1021/acs.orglett.7b01588Molander, GADirect Conversion of Carbonylic Acids to Alkyl KetonesCsp2-Csp3E-NuOOHBF3K
Carbonyl
No baseNo Base20176/9/2022TRUE
5560
acs.orglett.6b0278310.1021/acs.orglett.6b02783FALSEhttps://doi.org/10.1021/acs.orglett.6b02783Masu, HPyBidine-Ni(OAc)(2)-Catalyzed Michael/AIdoI Reaction of Methyleneindolinones and Thiosalicylaldehydes for Stereochemically Divergent Thiochromanyl-spirooxindoles2016#N/ATRUE
5561
1521-3773(20020715)41:14<2543::AID-ANIE2543>3.0.CO;2-W10.1002/1521-3773(20020715)41:14<2543::AID-ANIE2543>3.0.CO;2-Whttps://doi.org/10.1002/1521-3773(20020715)41:14<2543::AID-ANIE2543>3.0.CO;2-WFrohlich, RAngew. Chem.-Int. Edit.Formation of a butadienenickel-based zwitterionic single-component catalyst for ethylene polymerization: An alternative Activation pathway for homogeneous Ziegler-Natta catalysts of late transition metalsdiene ligands; homogeneous catalysis; nickel; polymerization; Ziegler-Natta catalysisx48200245#N/AFALSE
5562
1521-3773(20020703)41:13<2236::AID-ANIE2236>3.0.CO;2-310.1002/1521-3773(20020703)41:13<2236::AID-ANIE2236>3.0.CO;2-3https://doi.org/10.1002/1521-3773(20020703)41:13<2236::AID-ANIE2236>3.0.CO;2-3Reinartz, SAngew. Chem.-Int. Edit.Catalysts for the living insertion polymerization of alkenes: Access to new polyolefin architectures using Ziegler-Natta chemistryx5402002144#N/AFALSE
5563
acs.orglett.5b0078010.1021/acs.orglett.5b00780FALSEhttps://doi.org/10.1021/acs.orglett.5b00780Nguyen, HMScalable Synthesis of Fmoc-Protected GalNAc-Threonine Amino Acid and T-N Antigen via Nickel Catalysis2015#N/ATRUE
5564
acs.orglett.1c0040210.1021/acs.orglett.1c00402FALSEhttps://doi.org/10.1021/acs.orglett.1c00402Hirai, Gbeta-Glycosyl TrifluorB(OH)2rates as Precursors for Direct alpha-C-Glycosylation: Synthesis of 2-Deoxy-alpha-C-glycosides2021#N/ATRUE
5565
acs.orglett.0c0140210.1021/acs.orglett.0c01402FALSEhttps://doi.org/10.1021/acs.orglett.0c01402Shinokubo, HReactions of Antiaromatic Norcorrole Ni(II) Complex with Carbenes2020#N/ATRUE
5566
a802291g10.1039/a802291gFALSEhttps://doi.org/10.1039/a802291gWillis, ACRegiospecific synthesis of 2,3-naphthylenebis(diphenylphosphines) by double insertion of alkynylphosphines into nicker(0)-benzyne complexes1998#N/ATRUE
5567
1521-3773(20020104)41:1<144::AID-ANIE144>3.0.CO;2-J10.1002/1521-3773(20020104)41:1<144::AID-ANIE144>3.0.CO;2-JFALSEhttps://doi.org/10.1002/1521-3773(20020104)41:1<144::AID-ANIE144>3.0.CO;2-JGoodman, DWAngew. Chem.-Int. Edit.Characterization of C-2 (CxHy) intermediates from adsorption and decomposition of methane on supported metal catalysts by in situ INS vibrational spectroscopyx17200224#N/AFALSE
5568
a608148g10.1039/a608148gFALSEhttps://doi.org/10.1039/a608148gSato, SStructure of the centred icosahedral samarium Cluster formed by bis(L-prolinato)nickel(II) ligands1997#N/ATRUE
5569
364509a010.1038/364509a0FALSEhttps://doi.org/10.1038/364509a0ROSS, RRNatureSUPERNOVA 1993J in the spiral galaxy M81 is the brightest supernova since SN1987A and, like the latter, appears to be another 'peculiar' type II supernova. The available photometry1,2 of the supernova region before the explosion requires the presence of at least two supergiants (one of early spectral type and the other of late type), but the actual progenitor has yet to be identified. Here we show that the explosion of a late-type supergiant can explain the initial sharp peak in the supernova light curve, provided that the star had lost almost all of its hydrogen-rich envelope before the explosion. In our model, the secondary brightening of the supernova, approximately 10 days later, is then a consequence of the radioactive decay of Ni-56 and subsequently Co-56) produced in the explosion. The progenitor could have lost its hydrogen-rich envelope either in a strong stellar wind or, as seems more likely, through mass transfer to a companion star. In the latter case, the companion should reappear after the supernova photosphere has receded, the system having become a binary composed of a neutron star with a massive stellar companion.THE PROGENITOR OF SUPERNOVA-1993J - A STRIPPED SUPERGIANT IN A BINARY-SYSTEM178199316#N/ATRUE
5570
357065a010.1038/357065a0FALSEhttps://doi.org/10.1038/357065a0Panahi, FNatureEXPERIMENTAL studies have so far suggested that an insignificant amount of neutral nickel (Ni0) is soluble in silicate melts 1-4. This has led to difficulties in explaining the high concentrations of nickel in the modern Earth's mantle, because virtually all nickel (along with other siderophile elements such as cobalt and the noble metals) would have been removed from the mantle when the Earth's metallic core separated from it at low oxygen fugacity 1,2,5. Several models have been proposed to explain the Earth's siderophile element budget 1,6-8, each based on the belief that the solubility of neutral metal species in silicate melts is negligible. Here, however, I present experimental evidence indicating that the solubility of at least one neutral siderophile element, nickel, is not negligible. Because the presence of Ni0 will affect the partitioning of nickel between silicate melt and metal, and between silicate melt and crystalline silicate phases, these results have implications for our understanding of petrogenetic processes that take place in conditions of low oxygen fugacity, where Ni0 is an important part of total nickel. In particular, the Ni0 solubilities found in the present study are large enough to explain the anomalously high concentrations of nickel in the Earth's mantle if the temperature of the early mantle was sufficiently high (greater than or similar to 1,800-degrees-C).SOLUBILITY OF NEUTRAL NICKEL IN SILICATE MELTS AND IMPLICATIONS FOR THE EARTHS SIDEROPHILE ELEMENT BUDGET31199231#N/ATRUE
5571
1521-3773(20010817)40:16<3031::AID-ANIE3031>3.0.CO;2-#10.1002/1521-3773(20010817)40:16<3031::AID-ANIE3031>3.0.CO;2-#FALSEhttps://doi.org/10.1002/1521-3773(20010817)40:16<3031::AID-ANIE3031>3.0.CO;2-#Gao, SAngew. Chem.-Int. Edit.Ferromagnetic ordering in a diamond-like cyano-bridged (MnRuIII)-Ru-II bimetallic coordination polymerx90200128#N/AFALSE
5572
1521-3773(20010803)40:15<2831::AID-ANIE2831>3.0.CO;2-Z10.1002/1521-3773(20010803)40:15<2831::AID-ANIE2831>3.0.CO;2-ZFALSEhttps://doi.org/10.1002/1521-3773(20010803)40:15<2831::AID-ANIE2831>3.0.CO;2-ZCheetham, AKAngew. Chem.-Int. Edit.Nickel(II) phosphate VSB-5: A magnetic nanoporous hydrogenation catalyst with 24-ring tunnelsheterogeneous catalysis; hydrogenation; microporous materials; nickel; P ligands; zeolitesx298200122#N/AFALSE
5573
1521-3773(20010417)40:8<1513::AID-ANIE1513>3.0.CO;2-C10.1002/1521-3773(20010417)40:8<1513::AID-ANIE1513>3.0.CO;2-CFALSEhttps://doi.org/10.1002/1521-3773(20010417)40:8<1513::AID-ANIE1513>3.0.CO;2-CShi, ZJAngew. Chem.-Int. Edit.The first phosphine oxide ligand precursors for transition metal catalyzed cross-coupling reactions: C-C, C-N, and C-S bond formation on unactivated Aryl chloridesx436200176#N/AFALSE
5574
352225a010.1038/352225a0FALSEhttps://doi.org/10.1038/352225a0VERNON, PDFNatureINCREASING concern about world dependence on petroleum oil has generated interest in the more efficient use of natural gas 1-4. The conversion of methane to the common feedstock synthesis gas (carbon monoxide and hydrogen) by steam reforming is already well established 5, and we have shown recently that yields of synthesis gas in excess of 90% can be obtained at moderate temperatures and ambient pressure by partial oxidation, with air or oxygen, over supported transition-metal catalysts 6,7. The use of carbon dioxide as an oxidant for conversion of natural gas to synthesis gas is well established in steam reforming 5, and is also known in CO2 reforming (for example, the Calcor process 8,9), in which the use of excess CO2 yields mainly CO. In the present work, we describe an alternative catalytic strategy for CO2 reforming which gives excellent yields (90%) from a stoichiometric (1:1) feed of CO2 and CH4. Carbon deposition ('coking'), which is a hazard of CO2-reforming routes, is suppressed here by the use of catalysts based on platinum-group metals. We show that the exothermic partial oxidation of CH4 and the endothermic CO2- reforming reaction can be carried out simultaneously, thus introducing the possibility of tuning the thermodynamics of the process.PARTIAL OXIDATION OF METHANE TO SYNTHESIS GAS-USING CARBON-DIOXIDE721199122#N/ATRUE
5575
1521-3773(20021202)41:23<4487::AID-ANIE4487>3.0.CO;2-810.1002/1521-3773(20021202)41:23<4487::AID-ANIE4487>3.0.CO;2-8FALSEhttps://doi.org/10.1002/1521-3773(20021202)41:23<4487::AID-ANIE4487>3.0.CO;2-8Bensch, WAngew. Chem.-Int. Edit.Solvothermal synthesis, crystal structure, thermal stability, and Mossbauer spectroscopic investigation of the mixed-valent thioantimonate(III,V) [Ni(dien)(2)](2)Sb4S984200228#N/ATRUE
5576
1521-3773(20021018)41:20<3775::AID-ANIE3775>3.0.CO;2-210.1002/1521-3773(20021018)41:20<3775::AID-ANIE3775>3.0.CO;2-2FALSEhttps://doi.org/10.1002/1521-3773(20021018)41:20<3775::AID-ANIE3775>3.0.CO;2-2Weix, DJAngew. Chem.-Int. Edit.Asymmetric hydroVinylation: New perspectives through use of modular ligand systems59200245#N/ATRUE
5577
1521-3773(20010105)40:1<213::AID-ANIE213>3.0.CO;2-W10.1002/1521-3773(20010105)40:1<213::AID-ANIE213>3.0.CO;2-WFALSEhttps://doi.org/10.1002/1521-3773(20010105)40:1<213::AID-ANIE213>3.0.CO;2-WTanaka, MAngew. Chem.-Int. Edit.Isolation of dinuClear (mu-silylene)(silyl)nickel complexes and Si-Si bond formation on a dinuClear nickel frameworkx57200136#N/AFALSE
5578
1521-3773(20020802)41:15<2757::AID-ANIE2757>3.0.CO;2-Z10.1002/1521-3773(20020802)41:15<2757::AID-ANIE2757>3.0.CO;2-ZFALSEhttps://doi.org/10.1002/1521-3773(20020802)41:15<2757::AID-ANIE2757>3.0.CO;2-ZHu, YLAngew. Chem.-Int. Edit.Carbon-carbon double-bond formation from the reaction of organozinc reagents with aldehydes catalyzed by a nickel(II) complexaldehydes; alkenes; homogeneous catalysis; nickel; organozinc reagents48200227#N/ATRUE
5579
1521-3773(20001215)39:24<4492::AID-ANIE4492>3.3.CO;2-#10.1002/1521-3773(20001215)39:24<4492::AID-ANIE4492>3.3.CO;2-#FALSEhttps://doi.org/10.1002/1521-3773(20001215)39:24<4492::AID-ANIE4492>3.3.CO;2-#Ueda, HAromatic aminations by heterogeneous Ni-0/C catalysisx2000#N/AFALSE
5580
1521-3773(20020603)41:11<1879::AID-ANIE1879>3.0.CO;2-K10.1002/1521-3773(20020603)41:11<1879::AID-ANIE1879>3.0.CO;2-KFALSEhttps://doi.org/10.1002/1521-3773(20020603)41:11<1879::AID-ANIE1879>3.0.CO;2-KBeck, WAngew. Chem.-Int. Edit.Metal complexes of biologically important ligands, part 144. Selective alpha-carbon hydroxylation of glycine in nickel(II)-cyClotetrapeptide complexes by oxygen17200245#N/ATRUE
5581
1521-3773(20020503)41:9<1603::AID-ANIE1603>3.0.CO;2-D10.1002/1521-3773(20020503)41:9<1603::AID-ANIE1603>3.0.CO;2-DFALSEhttps://doi.org/10.1002/1521-3773(20020503)41:9<1603::AID-ANIE1603>3.0.CO;2-DChoi, SAngew. Chem.-Int. Edit.In situ enzymatic screening (ISES): A tool for catalyst discovery and reaction developmentallylic substitution; amino acids; catalyst screening; enzymes; nickel; transition metals32200272#N/ATRUE
5582
1521-3773(20020503)41:9<1521::AID-ANIE1521>3.0.CO;2-R10.1002/1521-3773(20020503)41:9<1521::AID-ANIE1521>3.0.CO;2-RFALSEhttps://doi.org/10.1002/1521-3773(20020503)41:9<1521::AID-ANIE1521>3.0.CO;2-RKempe, RAngew. Chem.-Int. Edit.Combinatorial libraries with p-functionalized aminopyridines: Ligands for the preparation of efficient C(Aryl)-Cl Activation catalysts63200262#N/ATRUE
5583
1521-3773(20000616)39:12<2141::AID-ANIE2141>3.0.CO;2-C10.1002/1521-3773(20000616)39:12<2141::AID-ANIE2141>3.0.CO;2-Chttps://doi.org/10.1002/1521-3773(20000616)39:12<2141::AID-ANIE2141>3.0.CO;2-CIrvine, DJAngew. Chem.-Int. Edit.Nickel-catalyzed generation of Schiff base aluminum enolate initiators for controlled methacrylate polymerizationaluminum; homogeneous catalysis; nickel; polymerizationsx36200038#N/AFALSE
5584
1521-3765(20020517)8:10<2239::AID-CHEM2239>3.0.CO;2-710.1002/1521-3765(20020517)8:10<2239::AID-CHEM2239>3.0.CO;2-7FALSEhttps://doi.org/10.1002/1521-3765(20020517)8:10<2239::AID-CHEM2239>3.0.CO;2-7Lin, ClControlled synthesis and magnetic properties of 2D and 3D iron azide networks (2)(infinity)[Fe(N-3)(2)(4,4 '-bpy)] and (3)(infinity)[Fe(N-3)(2)(4,4 '-bpy)]x2002#N/AFALSE
5585
1521-3773(20020118)41:2<343::AID-ANIE343>3.0.CO;2-110.1002/1521-3773(20020118)41:2<343::AID-ANIE343>3.0.CO;2-1FALSEhttps://doi.org/10.1002/1521-3773(20020118)41:2<343::AID-ANIE343>3.0.CO;2-1Jung, JAngew. Chem.-Int. Edit.Palladium-catalyzed regio- and diastereoselective tandem silastannylation/allyl addition of allene aldehydes and allene ketones: Synthesis of cis cyClopentanols and cyClohexanols62200221#N/ATRUE
5586
1521-3773(20011217)40:24<4734::AID-ANIE4734>3.0.CO;2-D10.1002/1521-3773(20011217)40:24<4734::AID-ANIE4734>3.0.CO;2-DFALSEhttps://doi.org/10.1002/1521-3773(20011217)40:24<4734::AID-ANIE4734>3.0.CO;2-DGoreshnik, EAAngew. Chem.-Int. Edit.A tetrameric nickel(II) chair with both antiferromagnetic internal coupling and ferromagnetic spin alignmentmagnetic properties; nickel; oximes38200125#N/ATRUE
5587
1521-3765(20011001)7:19<4253::AID-CHEM4253>3.0.CO;2-S10.1002/1521-3765(20011001)7:19<4253::AID-CHEM4253>3.0.CO;2-SFALSESiebert, DBinuClear complexes as building blocks for polynuClear complexes with high-spin ground states: Synthesis and structure of a tetranuClear nickel complex with an S=4 ground statex2001#N/AFALSE
5588
1521-3773(20011217)40:24<4671::AID-ANIE4671>3.0.CO;2-T10.1002/1521-3773(20011217)40:24<4671::AID-ANIE4671>3.0.CO;2-TFALSEhttps://doi.org/10.1002/1521-3773(20011217)40:24<4671::AID-ANIE4671>3.0.CO;2-TPapafilippopoulos, AAngew. Chem.-Int. Edit.Homoaromaticity in tris(ethylene)nickel(0) and tris(ethyne)nickel(0)aromaticity; electronic structure; magnetic properties; nickel; through-space interactions42200151#N/ATRUE
5589
1521-3765(20010504)7:9<1899::AID-CHEM1899>3.0.CO;2-510.1002/1521-3765(20010504)7:9<1899::AID-CHEM1899>3.0.CO;2-5FALSEhttps://doi.org/10.1002/1521-3765(20010504)7:9<1899::AID-CHEM1899>3.0.CO;2-5Sigel, HFormation of ternary complexes by coordination of (diethylenetriamine)platinum(II) to N1 or N7 of the adenine moiety of the antiviral nuCleotide analogue 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA): Comparison of the acid-base and metal-ion-binding properties of PMEA, (Dien)Pt(PMEA-N1), and (Dien)Pt(PMEA-N7)x2001#N/AFALSE
5590
1521-3773(20011119)40:22<4217::AID-ANIE4217>3.3.CO;2-L10.1002/1521-3773(20011119)40:22<4217::AID-ANIE4217>3.3.CO;2-LFALSEhttps://doi.org/10.1002/1521-3773(20011119)40:22<4217::AID-ANIE4217>3.3.CO;2-LHey-Hawkins, EAngew. Chem.-Int. Edit.Sodium tetra-tert-butylcyClopentaphosphanide: Synthesis, structure, and unexpected formation of a nickel(0) tri-tert-butylcyClopentaphosphene complex33200154#N/ATRUE
5591
1521-3765(20001016)6:20<3686::AID-CHEM3686>3.0.CO;2-F10.1002/1521-3765(20001016)6:20<3686::AID-CHEM3686>3.0.CO;2-FFALSEhttps://doi.org/10.1021/acscatal.1c00778Zanello, PMono-, di-, and trimetallic complexes of the nonalternating polycondensed pi-perimeter decacyClene, C36H18: Synthesis, structure, and spectroelectrochemistry of [{(eta(5)-Me4EtC5)Co}(2)(mu-eta(5):eta(4)-C36H18)]x2000#N/AFALSE
5592
1521-3773(20010401)40:7<1288::AID-ANIE1288>3.0.CO;2-610.1002/1521-3773(20010401)40:7<1288::AID-ANIE1288>3.0.CO;2-6FALSEhttps://doi.org/10.1002/1521-3773(20010401)40:7<1288::AID-ANIE1288>3.0.CO;2-6Hofmann, PAngew. Chem.-Int. Edit.Copper(I) carbenes: The synthesis of active intermediates in copper-catalyzed CS cyClopropanation114200121#N/ATRUE
5593
10.1021/ja902829p
10.1021/ja902829phttps://doi.org/10.1021/ja902829pRueping, MJ. Am. Chem. Soc.
The first observation of Cleavage of unactivated aromatic C−N bonds on a late-transition-metal center was achieved using o-acylanilines and a ruthenium complex. Use of olefins as additives dramatically improved the rate of C−N bond Cleavage. The carbon fragment remaining on the ruthenium after C−N bond Cleavage was coupled with a phenylboronate to form a biphenyl framework. The present results suggest that ruthenium-catalyzed C−C bond formation from o-acylaniline and organoboronate proceeds via direct C−N bond Cleavage on the ruthenium center.
Cleavage of C−N Bonds in Aniline Derivatives on a Ruthenium Center and Its Relevance to Catalytic C−C Bond Formationx1012009Added by Shihong#N/A
5594
10.1021/ja0713431
10.1021/ja0713431https://doi.org/10.1021/ja0713431Kalyani, DJ. Am. Chem. Soc.
The RuH2(CO)(PPh3)3-catalyzed reaction of 2-amino-6-methylacetophenone with phenylboronic acid 2,2-dimethyl-1,3-propanediol ester in refluxing toluene gave the corresponding phenylation product in 83% yield via Aryl carbon−nitrogen bond Cleavage. This reaction involves two notable features: (1) the coupling proceeds via the oxidative addition of an Aryl carbon−nitrogen bond in anilines to the ruthenium complex, and (2) C−C bond formation takes place via transmetalation between the Ru−NR2 species and organoboronates.
Ruthenium-Catalyzed Carbon−Carbon Bond Formation via the Cleavage of an Unreactive Aryl Carbon−Nitrogen Bond in Aniline Derivatives with Organoboronatesx1542007Added by Shihong#N/A
5595
(SICI)1521-3773(20000515)39:10<1842::AID-ANIE1842>3.0.CO;2-710.1002/(SICI)1521-3773(20000515)39:10<1842::AID-ANIE1842>3.0.CO;2-7FALSEhttps://doi.org/10.1002/(SICI)1521-3773(20000515)39:10<1842::AID-ANIE1842>3.0.CO;2-7Baranyai, KAngew. Chem.-Int. Edit.Confinement of [(H2O)(2) boolean AND ([18]crown-6)] in a disc-shaped cavity lined with six nickel(II) macrocyCle dimers acting as divergent receptor moleculesx1420008#N/AFALSE
5596
(SICI)1521-3773(20000502)39:9<1647::AID-ANIE1647>3.0.CO;2-M10.1002/(SICI)1521-3773(20000502)39:9<1647::AID-ANIE1647>3.0.CO;2-MFALSEhttps://doi.org/10.1002/(SICI)1521-3773(20000502)39:9<1647::AID-ANIE1647>3.0.CO;2-MEphritikhine, MSynthesis, crystal structure, and magnetic behavior of linear M-2(II)U(IV) complexes (M = Co, Ni, Cu, Zn)x2000#N/AFALSE
5597
1521-3773(20010401)40:7<1286::AID-ANIE1286>3.0.CO;2-I10.1002/1521-3773(20010401)40:7<1286::AID-ANIE1286>3.0.CO;2-IFALSEhttps://doi.org/10.1002/1521-3773(20010401)40:7<1286::AID-ANIE1286>3.0.CO;2-ICheng, CHAngew. Chem.-Int. Edit.Nickel-catalyzed highly regio- and stereoselective cyClization of oxanorbornenes with Alkyl propiolates: A novel method for the synthesis of benzocoumarin derivativesalkenes; coumarins; cyClization; nickel74200135#N/ATRUE
5598
1521-3773(20010216)40:4<763::AID-ANIE7630>3.0.CO;2-T10.1002/1521-3773(20010216)40:4<763::AID-ANIE7630>3.0.CO;2-TFALSEhttps://doi.org/10.1002/1521-3773(20010216)40:4<763::AID-ANIE7630>3.0.CO;2-TRao, KKAngew. Chem.-Int. Edit.The first example of Activation of molecular oxygen by nickel in Ni-Al hydrotalcite: A novel protocol for the selective oxidation of alcohols240200127#N/ATRUE
5599
1521-3773(20010105)40:1<177::AID-ANIE177>3.0.CO;2-X10.1002/1521-3773(20010105)40:1<177::AID-ANIE177>3.0.CO;2-XFALSEhttps://doi.org/10.1002/1521-3773(20010105)40:1<177::AID-ANIE177>3.0.CO;2-XRaabe, GAngew. Chem.-Int. Edit.Highly enantioselective isomerization of 4,7-dihydro-1,3-dioxepins catalyzed by Me-DuPHOS-modified dihalogenonickel complexes and determination of the absolute configuration of the isomerization products24200113#N/ATRUE
5600
1521-3773(20001103)39:21<3894::AID-ANIE3894>3.0.CO;2-K10.1002/1521-3773(20001103)39:21<3894::AID-ANIE3894>3.0.CO;2-Khttps://doi.org/10.1002/1521-3773(20001103)39:21<3894::AID-ANIE3894>3.0.CO;2-KReiss, GJAngew. Chem.-Int. Edit.Novel nickel(II) complexes for the catalytic copolymerization of ethylene and carbon monoxide: Polyketone synthesis in supercritical carbon dioxide43200014#N/ATRUE
5601
(SICI)1521-3773(20000103)39:1<191::AID-ANIE191>3.0.CO;2-F10.1002/(SICI)1521-3773(20000103)39:1<191::AID-ANIE191>3.0.CO;2-FFALSEhttps://doi.org/10.1002/(SICI)1521-3773(20000103)39:1<191::AID-ANIE191>3.0.CO;2-FStoeckli-Evans, HAngew. Chem.-Int. Edit.A metamagnetic two-dimensional molecular material with nickel(II) and azideazides; coordination chemistry; magnetic properties; nickel; N ligandsx140200017#N/AFALSE
5602
1521-3773(20001103)39:21<3772::AID-ANIE3772>3.0.CO;2-510.1002/1521-3773(20001103)39:21<3772::AID-ANIE3772>3.0.CO;2-5FALSEhttps://doi.org/10.1002/1521-3773(20001103)39:21<3772::AID-ANIE3772>3.0.CO;2-5Keim, WAngew. Chem.-Int. Edit.Ionic liquids - New solutions for transition metal catalysisbiphasic catalysis; homogeneous catalysis; ionic liquids; solvent effects59862000154#N/ATRUE
5603
1521-3773(20000901)39:17<3130::AID-ANIE3130>3.0.CO;2-I10.1002/1521-3773(20000901)39:17<3130::AID-ANIE3130>3.0.CO;2-IFALSEhttps://doi.org/10.1002/1521-3773(20000901)39:17<3130::AID-ANIE3130>3.0.CO;2-IIto, TAngew. Chem.-Int. Edit.A graphite-like complex with large cavities constructed with the complex ligand [Ni-II(bpca)(2)]92200034#N/ATRUE
5604
1521-3765(20011217)7:24<5343::AID-CHEM5343>3.0.CO;2-#10.1002/1521-3765(20011217)7:24<5343::AID-CHEM5343>3.0.CO;2-#FALSEPottgen, RA New(infinity)(1)[Ni-7] Cluster in LaNi7In6 and distorted bcc indium cubes in LaNiIn42001#N/ATRUE
5605
1521-3765(20011203)7:23<5041::AID-CHEM5041>3.0.CO;2-610.1002/1521-3765(20011203)7:23<5041::AID-CHEM5041>3.0.CO;2-6FALSEKessissoglou, DPHost-guest interaction of 12-MC-4, 15-MC-5, and fused 12-MC-4 metallacrowns with mononuClear and binuClear Carbonylato complexes: Structure and magnetic behavior2001#N/ATRUE
5606
1521-3765(20010702)7:13<2770::AID-CHEM2770>3.0.CO;2-#10.1002/1521-3765(20010702)7:13<2770::AID-CHEM2770>3.0.CO;2-#FALSEhttps://doi.org/10.1002/1521-3765(20010702)7:13<2770::AID-CHEM2770>3.0.CO;2-#Hampel, FSelf-assembly and crystal structure of a novel octadecametallic square box composed of 52 single components2001#N/ATRUE
5607
1521-3765(20010202)7:3<738::AID-CHEM738>3.0.CO;2-610.1002/1521-3765(20010202)7:3<738::AID-CHEM738>3.0.CO;2-6FALSEhttps://doi.org/10.1002/1521-3765(20010202)7:3<738::AID-CHEM738>3.0.CO;2-6Knoch, FCharge-transfer complexes of metal dithiolenes, part XXVII - Chiral metal-dithiolene/viologen ion pairs: Synthesis and electrical conductivity2001#N/ATRUE
5608
1521-3765(20000901)6:17<3254::AID-CHEM3254>3.0.CO;2-610.1002/1521-3765(20000901)6:17<3254::AID-CHEM3254>3.0.CO;2-6FALSEhttps://doi.org/10.1002/1521-3765(20000901)6:17<3254::AID-CHEM3254>3.0.CO;2-6Osuka, AThree-dimensionally arranged windmill and grid porphyrin arrays by Ag-I-promoted meso-meso block oligomerization2000#N/ATRUE
5609
(SICI)1521-3773(20000502)39:9<1602::AID-ANIE1602>3.0.CO;2-N10.1002/(SICI)1521-3773(20000502)39:9<1602::AID-ANIE1602>3.0.CO;2-NFALSEhttps://doi.org/10.1002/(SICI)1521-3773(20000502)39:9<1602::AID-ANIE1602>3.0.CO;2-NHerrmann, WAAngew. Chem.-Int. Edit.Nickel-catalyzed cross-coupling of Aryl chlorides with Aryl Grignard reagentsC-C coupling; combinatorial chemistry; homogeneous catalysis; N heterocyCles; nickel258200026#N/ATRUE
5610
(SICI)1521-3773(20000204)39:3<595::AID-ANIE595>3.0.CO;2-C10.1002/(SICI)1521-3773(20000204)39:3<595::AID-ANIE595>3.0.CO;2-CFALSEhttps://doi.org/10.1021/acscatal.1c01455Klemm, DNew building blocks for the design of oligonuClear copper complexes based on amino carbohydrates2000#N/ATRUE
5611
(SICI)1521-3773(20000204)39:3<558::AID-ANIE558>3.0.CO;2-G10.1002/(SICI)1521-3773(20000204)39:3<558::AID-ANIE558>3.0.CO;2-GFALSEhttps://doi.org/10.1002/(SICI)1521-3773(20000204)39:3<558::AID-ANIE558>3.0.CO;2-GOsuka, ADoubly meso-beta-linked diporphyrins from oxidation of 5,10,15-triAryl-substituted Ni-III- and Pd-II-porphyrins2000#N/ATRUE
5612
(SICI)1521-3773(20000117)39:2<344::AID-ANIE344>3.0.CO;2-110.1002/(SICI)1521-3773(20000117)39:2<344::AID-ANIE344>3.0.CO;2-1FALSEhttps://doi.org/10.1002/(SICI)1521-3773(20000117)39:2<344::AID-ANIE344>3.0.CO;2-1Rojo, TAngew. Chem.-Int. Edit.A dicubane-like tetrameric nickel(II) azido complexazides; Cluster compounds; magnetic properties; nickel110200036#N/ATRUE
5613
(SICI)1521-3773(19991115)38:22<3386::AID-ANIE3386>3.0.CO;2-W10.1002/(SICI)1521-3773(19991115)38:22<3386::AID-ANIE3386>3.0.CO;2-WFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19991115)38:22<3386::AID-ANIE3386>3.0.CO;2-WTamaru, YAngew. Chem.-Int. Edit.Nickel(0)-catalyzed three-component connection reaction of dimethylzinc, 1,3-dienes, and Carbonyl compoundsaldehydes; homogeneous catalysis; multicomponent reactions; nickel; zinc73199950#N/ATRUE
5614
(SICI)1521-3773(19991018)38:20<3018::AID-ANIE3018>3.0.CO;2-F10.1002/(SICI)1521-3773(19991018)38:20<3018::AID-ANIE3018>3.0.CO;2-FFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19991018)38:20<3018::AID-ANIE3018>3.0.CO;2-FYamaguchi, JAngew. Chem.-Int. Edit.Towards efficient and wide-scope metal-catalyzed Alkyl -Alkyl cross-coupling reactions118199922#N/ATRUE
5615
(SICI)1521-3765(19990702)5:7<2040::AID-CHEM2040>3.0.CO;2-410.1002/(SICI)1521-3765(19990702)5:7<2040::AID-CHEM2040>3.0.CO;2-4FALSEhttps://doi.org/10.1002/(SICI)1521-3765(19990702)5:7<2040::AID-CHEM2040>3.0.CO;2-4Floriani, Cmeso-Octaethylporphyrinogen displaying site selectivity in the stepwise synthesis of polymetallic aggregates with interesting redox properties: The pi-binding ability of metalla-porphyrinogensx1999#N/AFALSE
5616
(SICI)1521-3773(19990201)38:3<408::AID-ANIE408>3.0.CO;2-P10.1002/(SICI)1521-3773(19990201)38:3<408::AID-ANIE408>3.0.CO;2-PFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19990201)38:3<408::AID-ANIE408>3.0.CO;2-PMurray, KSAngew. Chem.-Int. Edit.[Co(2)(II)L(NCS)(2)(SCN)(2)]: The first cobalt complex to exhibit both exchange coupling and spin crossover effects95199925#N/ATRUE
5617
(SICI)1521-3765(19980904)4:9<1647::AID-CHEM1647>3.0.CO;2-Z10.1002/(SICI)1521-3765(19980904)4:9<1647::AID-CHEM1647>3.0.CO;2-ZFALSEhttps://doi.org/10.1002/(SICI)1521-3765(19980904)4:9<1647::AID-CHEM1647>3.0.CO;2-ZFox, MAAn Os-II-Ni-II-Pd-II trimetallic complex as an electro-switchable-photoinduced-electron-transfer devicePhotocatalyst1998#N/AFALSE
5618
(SICI)1521-3765(19980807)4:8<1384::AID-CHEM1384>3.3.CO;2-G10.1002/(SICI)1521-3765(19980807)4:8<1384::AID-CHEM1384>3.3.CO;2-GFALSERaston, ClMetal-containing rigid concave surfaces: An entry to the confinement of globular moleculesx1998#N/AFALSE
5619
(SICI)1521-3773(19990201)38:3<397::AID-ANIE397>3.0.CO;2-Y10.1002/(SICI)1521-3773(19990201)38:3<397::AID-ANIE397>3.0.CO;2-YFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19990201)38:3<397::AID-ANIE397>3.0.CO;2-YTamaru, YAngew. Chem.-Int. Edit.Nickel-catalyzed homoallylation of aldehydes and ketones with 1,3-dienes and complementary promotion by diethylzinc or triethylboranealdehydes; Alkylations; ketones; nickel; zinc132199916#N/ATRUE
5620
2812810.1038/28128FALSEhttps://doi.org/10.1038/28128Friend, RHNatureMetallic behaviour is well known in charge-transfer complexes that contain stacks of planar, partially oxidized (or reduced) pi-conjugated molecules. Electronic conduction occurs in the partially occupied, delocalized pi bands formed by intermolecular orbital overlap, and some of these materials exhibit superconductivity(1,2). Counter-ions, present to achieve charge neutrality, usually play a passive role, although in some cases they couple to the electronic structure, for example by imposing a new structural periodicity (a superlattice) by orientational ordering(1). The development of molecular solids that can simultaneously support the transport of both electrons and ions is important for several fields, inCluding the development of solid-state batteries(3,4), electroluminescent devices(5) and biomimetic systems(6,7). Crown ethers are promising components for such systems, as they provide cavities through which ion motion might occur. Here we report that the charge-transfer salt Li(0.6)(15-crown-5-ether) [Ni(dmit)(2)](2).H(2)O exhibits both electron and ion conductivity: the stacks of the nickel complex (dmit is an organic molecule) provide a pathway for electron conduction, and stacks of the crown ethers provide channels for lithium-ion motion. Evidence for the latter above 250 K is provided by NMR and conductivity studies. We also see evidence for coupling of the electron and ion motions. This compound might serve as a model for the development of other hybrid electronic/ionic conducting materials.A molecular metal with ion-conducting channelsx159199817#N/AFALSE
5621
(SICI)1521-3773(19990115)38:110.1002/(SICI)1521-3773(19990115)38:1/2<193::AID-ANIE193>3.0.CO;2-EFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19990115)38:1/2<193::AID-ANIE193>3.0.CO;2-EDo, YCanted ferromagnetism in a Ni-II chain with a single end-to-end azido bridge1999#N/ATRUE
5622
(SICI)1521-3773(19980918)37:17<2387::AID-ANIE2387>3.0.CO;2-M10.1002/(SICI)1521-3773(19980918)37:17<2387::AID-ANIE2387>3.0.CO;2-MFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980918)37:17<2387::AID-ANIE2387>3.0.CO;2-MKnochel, PAngew. Chem.-Int. Edit.An efficient nickel-catalyzed cross-coupling between sp(3) carbon centerscross-coupling; homogeneous catalysis; nickel; styrene; zinc153199821#N/ATRUE
5623
(SICI)1521-3773(19980918)37:17<2385::AID-ANIE2385>3.0.CO;2-Y10.1002/(SICI)1521-3773(19980918)37:17<2385::AID-ANIE2385>3.0.CO;2-YFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980918)37:17<2385::AID-ANIE2385>3.0.CO;2-YHaupt, KJAngew. Chem.-Int. Edit.Dichlorodinickel(I) complexes with mu(2)-CO or mu(2)-CS bridges and trimethylphosphane ligands: Homologous composition, but different frameworksfluxional systems; metal-metal interactions; nickel; P ligands519986#N/ATRUE
5624
(SICI)1521-3773(19980803)37:1310.1002/(SICI)1521-3773(19980803)37:13/14<1827::AID-ANIE1827>3.0.CO;2-CFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980803)37:13/14<1827::AID-ANIE1827>3.0.CO;2-CSelke, RAngew. Chem.-Int. Edit.Highly enantioselective complex-catalyzed reduction of ketones - Now with purely aliphatic derivatives too46199852#N/ATRUE
5625
(SICI)1521-3773(19980420)37:7<961::AID-ANIE961>3.0.CO;2-410.1002/(SICI)1521-3773(19980420)37:7<961::AID-ANIE961>3.0.CO;2-4FALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980420)37:7<961::AID-ANIE961>3.0.CO;2-4Wartchow, RAngew. Chem.-Int. Edit.Ni[In{C(SiMe3)(3)}(4)]: An organometallic nickel-indium compound analogous to [Ni(CO)(4)]73199842#N/ATRUE
5626
(SICI)1521-3773(19980316)37:5<657::AID-ANIE657>3.0.CO;2-L10.1002/(SICI)1521-3773(19980316)37:5<657::AID-ANIE657>3.0.CO;2-LFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980316)37:5<657::AID-ANIE657>3.0.CO;2-LMiller, JSAngew. Chem.-Int. Edit.[M-II(tcne)(2)].xCH(2)Cl(2) (M=Mn, Fe, Co, Ni) molecule-based magnets with T-c values above 100K and coercive fields up to 6500Oeiron; magnetic properties; radicals; tetracyanoethylene102199826#N/ATRUE
5627
(SICI)1521-3773(19980216)37:3<360::AID-ANIE360>3.3.CO;2-G10.1002/(SICI)1521-3773(19980216)37:3<360::AID-ANIE360>3.3.CO;2-GFALSEhttps://doi.org/10.1002/(SICI)1521-3773(19980216)37:3<360::AID-ANIE360>3.3.CO;2-GKruger, HJAngew. Chem.-Int. Edit.First isolation and structural characterization of a nickel(III) complex containing aliphatic thiolate donorshigh-valent metal ions; nickel; redox chemistry; S ligands70199816#N/ATRUE
5628
(SICI)1521-3765(20000417)6:8<1496::AID-CHEM1496>3.3.CO;2-#10.1002/(SICI)1521-3765(20000417)6:8<1496::AID-CHEM1496>3.3.CO;2-#FALSEhttps://doi.org/10.1002/(SICI)1521-3765(20000417)6:8<1496::AID-CHEM1496>3.3.CO;2-#Vogt, DApplication of P-stereogenic aminophosphine phosphinite ligands in asymmetric hydroCarbonylation2000#N/ATRUE
5629
(SICI)1521-3765(20000204)6:3<468::AID-CHEM468>3.3.CO;2-Y10.1002/(SICI)1521-3765(20000204)6:3<468::AID-CHEM468>3.3.CO;2-YFALSEhttps://doi.org/10.1021/acscatal.0c03950Janiak, CExperimental and theoretical investigations on the synthesis, structure, reactivity, and bonding of the stannylene-iron complex bis{{bis(2-tert-butyl-4,5,6-trimethyl-phenyl)}Sn}Fe(eta(6)-toluene) (Sn-Fe-Sn)2000#N/ATRUE
5630
(SICI)1521-3765(19980904)4:9<1731::AID-CHEM1731>3.0.CO;2-U10.1002/(SICI)1521-3765(19980904)4:9<1731::AID-CHEM1731>3.0.CO;2-UFALSEhttps://doi.org/10.1002/(SICI)1521-3765(19980904)4:9<1731::AID-CHEM1731>3.0.CO;2-UMiller, JSSources of naked divalent first-row metal ions: Synthesis and characterization of [M-II(NCMe)(6)](2+) (M = V, Cr, Mn, Fe, Co, Ni) salts of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate1998#N/ATRUE
5631
3504253410.1002/(SICI)1521-3765(19980904)4:9<1731::AID-CHEM1731>3.0.CO;2-UFALSEhttps://doi.org/10.1002/(SICI)1521-3765(19980904)4:9<1731::AID-CHEM1731>3.0.CO;2-UDotz, KHNatureTwo separate theories are often used to characterize the paramagnetic properties of ferromagnetic materials. At temperatures T well above the Curie temperature, T-C (where the transition from paramagnetic to ferromagnetic behaviour occurs), Classical mean-field theory(1) yields the Curie-Weiss law for the magnetic susceptibility: chi (T) proportional to 1/(T - Theta), where Theta is the Weiss constant. Close to T-C, however, the standard mean-field approach breaks down so that better agreement with experimental data is provided by critical scaling theory(2,3): chi (T) proportional to 1/(T -T-C)(gamma) , where gamma is a scaling exponent. But there is no known model capable of predicting the measured values of g nor its variation among different substances(4). Here I use a mean-field Cluster model(5) based on finite-size thermostatistics(6,7) to extend the range of mean-field theory, thereby eliminating the need for a separate scaling regime. The mean-field approximation is justified by using a kinetic-energy term to maintain the microcanonical ensemble(8). The model reproduces the Curie-Weiss law at high temperatures, but the Classical Weiss transition at T-C = Theta is suppressed by finite-size effects. Instead, the fraction of Clusters with a specific amount of order diverges at T-C, yielding a transition that is mathematically similar to Bose-Einstein condensation. At all temperatures above T-C, the model matches the measured magnetic susceptibilities of crystalline EuO, Gd, Co and Ni, thus providing a unified picture for both the critical-scaling and Curie-Weiss regimes.Mean-field Cluster model for the critical behaviour of ferromagnets75200032#N/ATRUE
5632
2594310.1038/25943FALSEhttps://doi.org/10.1038/25943Pihlaja, PNatureMicrometeorites-submillimetre-sized partiCles derived from asteroids and comets(1-5)-occur in significant quantities in deep sea sediments(1,2,4), and the ice sheets of Greenland(6,7) and Antarctica(8,9). The most abundant micrometeorites are cosmic spherules(3), which contain nickel-rich spinels(10) that were crystallized and oxidized during atmospheric entry, therefore recording the oxygen content in the uppermost atmosphere(10-12). But the use of micrometeorites for detecting past changes in the flux of incoming extraterrestrial matter, and as probes of the evolution of the atmosphere, has been hampered by the fact that most objects with depositional ages higher than 0.5 Mpr show severe chemical alteration(2). Here we report the discovery of unaltered cosmic spherules in a 1.4-Gyr-old(13-15) sandstone(16,17) (red bed) from Finland. From this we infer that red beds, a common lithology in the Earth's history, map contain substantial unbiased populations of fossil micrometeorites, The study of such populations would allow systematic research on variations in the micrometeorite flux from the early Proterozoic era to recent times(9) (a time span of about 2.5 Gyr), and could help to better constrain the time when the atmospheric oxygen content was raised to its present level(18-20)RETRACTED: Unaltered cosmic spherules in a 1.4-Gyr-old sandstone from Finland (Retracted ArtiCle. See vol 429, pg 322, 2004)17199829#N/ATRUE
5633
jo070944810.1021/jo0709448Not C-O ActivationLongFALSEhttps://pubs.acs.org/doi/10.1021/jo0709448Yang, LMJ. Org. Chem.trans-Haloarylbis(triphenylphosphine)nickel(II), a type of air- and moisture-stable Ni(II)−(σ-aryl) complex, was examined as catalyst precursor in the C−N coupling reaction. This type of Ni(II) pre-catalyst, associated with N-heterocyclic carbene ligands, is found to easily produce the catalytically active Ni(0) species in situ without the aid of external reductants and allows for the efficient amination of aryl chlorides with secondary cyclic amines and anilines under mild conditions.Ni(II)−(σ-Aryl) Complex: A Facile, Efficient Catalyst for Nickel-Catalyzed Carbon−Nitrogen Coupling Reactions1002007
5634
jacs.5b06255
10.1021/jacs.5b06255C-XFALSEhttps://pubs.acs.org/doi/10.1021/jacs.5b06255Hegui Gong1672015
5635
c3sc51098k10.1039/c3sc51098kNot C-O ActivationLongFALSEhttps://pubs.rsc.org/en/content/articlepdf/2013/sc/c3sc51098kGong, HGChem. Sci.The use of bis(pinacolato)diboron as the terminal reductant allows the efficient Ni-catalyzed coupling of unactivated secondary and primary alkyl halides, generating the C(sp3)–C(sp3) coupling products in good yields. The mild catalytic conditions display excellent functional group tolerance, and good chemoselectivities which require only 1.5 equiv. of primary bromides for the coupling with secondary bromides. Preliminary mechanistic studies suggest that an in situ organoborane/Suzuki process is not likely. It was identified that the base and ligand have more profound impact on selecting this reductive coupling pathway. The good chemoselectivity appears to be evoked by the formation of Ni–Bpin catalytic intermediates, which demands matched sizes and reactivities of the alkyl halide coupling partners for optimal coupling efficiency.Nickel-catalyzed cross-coupling of unactivated alkyl halides using bis(pinacolato)diboron as reductanty1042013
5636
c3cc49859j10.1039/c3cc49859jAdditionFALSEhttps://pubs.rsc.org/en/content/articlepdf/2014/cc/c3cc49859jHegui Gong
5637
jo00102a05910.1021/jo00102a059Shihonghttps://pubs.acs.org/doi/pdf/10.1021/jo00102a059ligand synthesis2151994
5638
s10562-013-0979-510.1007/s10562-013-0979-5C-S ActivationFALSEhttps://link.springer.com/content/pdf/10.1007/s10562-013-0979-5.pdfCATALYSIS LETTERSCATALYSIS LETTERSIn the present study, the nickel-catalyzed carbon carbon bond formation of a range of sulfur containing substrates with Grignard reagents via desulfurization has been explored. After investigation of different reaction parameters with a well-defined nickel complex an excellent and easy-accessible pre-catalyst was found. The obtained system was capable to convert a broad scope of substrates under mild reaction conditions.Nickel-catalyzed C(sp(2))-C(sp(2)) Cross Coupling Reactions of Sulfur-Functionalities and Grignard ReagentsC-S Activation332013
5639
anie.20150320410.1002/anie.201503204mini-reviewFALSEhttps://onlinelibrary.wiley.com/doi/10.1002/anie.201503204Chen, TQANGEWANDTE CHEMIE-INTERNATIONAL EDITIONNickel-Catalyzed CO/CH Cross-Coupling Reactions for CC Bond Formation
asymmetric catalysis; CH activation; CO activation; cross-coupling; nickel catalysis
mini-review192015
5640
jacs.1c0567010.1021/jacs.1c05670rearrangementFALSEhttps://pubs.acs.org/doi/10.1021/jacs.1c05670Shu, XZJOURNAL OF THE AMERICAN CHEMICAL SOCIETYCatalytic asymmetric dicarbofunctionalization of tethered alkenes has emerged as a promising tool for producing chiral cyclic molecules; however, it typically relies on aryl-tethered alkenes to form benzene-fused compounds. Herein, we report an enantioselective cross-electrophile divinylation reaction of nonaromatic substrates, 2-bromo-1,6-dienes. The approach thus offers a route to new chiral cyclic architectures, which are key structural motifs found in various biologically active compounds. The reaction proceeds under mild conditions, and the use of chiral t-Bu-pmrox and 3,5-difluoro-pyrox ligands resulted in the formation of divinylated products with high chemo-, regio-, and enantioselectivity. The method is applicable for the incorporation of chiral hetero- and carbocycles into complex molecules.Enantioselective Reductive Divinylation of Unactivated Alkenes by Nickel-Catalyzed Cyclization Coupling Reactionrearrangement42021
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FALSE#N/A
6088
FALSE#N/A
6089
FALSE#N/A
6090
FALSE#N/A
6091
FALSE#N/A
6092
FALSE#N/A
6093
FALSE#N/A
6094
FALSE#N/A
6095
FALSE#N/A
6096
FALSE#N/A
6097
FALSE#N/A
6098
FALSE#N/A
6099
FALSE#N/A
6100
FALSE#N/A
6101
FALSE#N/A
6102
FALSE#N/A
6103
FALSE#N/A
6104
FALSE#N/A
6105
FALSE#N/A
6106
FALSE#N/A
6107
FALSE#N/A
6108
FALSE#N/A
6109
FALSE#N/A
6110
FALSE#N/A
6111
FALSE#N/A
6112
FALSE#N/A
6113
FALSE#N/A
6114
FALSE#N/A
6115
FALSE#N/A
6116
FALSE#N/A
6117
FALSE#N/A
6118
FALSE#N/A
6119
FALSE#N/A
6120
FALSE#N/A
6121
FALSE#N/A
6122
FALSE#N/A
6123
FALSE#N/A
6124
FALSE#N/A
6125
FALSE#N/A
6126
FALSE#N/A
6127
FALSE#N/A
6128
FALSE#N/A
6129
FALSE#N/A
6130
FALSE#N/A
6131
FALSE#N/A
6132
FALSE#N/A
6133
FALSE#N/A
6134
FALSE#N/A
6135
FALSE#N/A
6136
FALSE#N/A
6137
FALSE#N/A
6138
FALSE#N/A
6139
FALSE#N/A
6140
FALSE#N/A
6141
FALSE#N/A
6142
FALSE#N/A
6143
FALSE#N/A
6144
FALSE#N/A
6145
FALSE#N/A
6146
FALSE#N/A
6147
FALSE#N/A
6148
FALSE#N/A
6149
FALSE#N/A
6150
FALSE#N/A
6151
FALSE#N/A
6152
FALSE#N/A
6153
FALSE#N/A
6154
FALSE#N/A
6155
FALSE#N/A
6156
FALSE#N/A
6157
FALSE#N/A
6158
FALSE#N/A
6159
FALSE#N/A
6160
FALSE#N/A
6161
FALSE#N/A
6162
FALSE#N/A
6163
FALSE#N/A
6164
FALSE#N/A
6165
FALSE#N/A
6166
FALSE#N/A
6167
FALSE#N/A
6168
FALSE#N/A
6169
FALSE#N/A
6170
FALSE#N/A
6171
FALSE#N/A
6172
FALSE#N/A
6173
FALSE#N/A
6174
FALSE#N/A
6175
FALSE#N/A
6176
FALSE#N/A
6177
FALSE#N/A
6178
FALSE#N/A
6179
FALSE#N/A
6180
FALSE#N/A
6181
FALSE#N/A
6182
FALSE#N/A
6183
FALSE#N/A
6184
FALSE#N/A
6185
FALSE#N/A
6186
FALSE#N/A
6187
FALSE#N/A
6188
FALSE#N/A
6189
FALSE#N/A
6190
FALSE#N/A
6191
FALSE#N/A
6192
FALSE#N/A
6193
FALSE#N/A
6194
FALSE#N/A
6195
FALSE#N/A
6196
FALSE#N/A
6197
FALSE#N/A
6198
FALSE#N/A
6199
FALSE#N/A
6200
FALSE#N/A
6201
FALSE#N/A
6202
FALSE#N/A
6203
FALSE#N/A
6204
FALSE#N/A
6205
FALSE#N/A
6206
FALSE#N/A
6207
FALSE#N/A
6208
FALSE#N/A
6209
FALSE#N/A